HK1249304B - Ack/nack signals for next generation lte devices and systems - Google Patents

Description

ACK/NACK Signaling for Next-Generation LTE Devices and Systems

Priority Declaration

This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 62/180,971, entitled “PHYSICAL LAYER DETAILS ON ACK/NACK CHANNEL DESIGN FOR 5G SYSTEM,” filed on June 17, 2015, which is incorporated herein by reference in its entirety.

Technical Field

Embodiments relate to radio access networks. Some embodiments relate to providing acknowledgments for transmissions in cellular networks, including 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) networks and LTE-Advanced (LTE-A) networks, as well as fourth generation (4G) networks and fifth generation (5G) networks.

Background Art

The use of 3GPP LTE systems has increased with the increase in the number of different types of devices communicating over the network to servers and other computing devices. In particular, as the number and complexity of UEs grows, the demand for an increased number and variety of services also grows. The goal of next-generation systems may be to meet the large number of different and sometimes conflicting performance constraints driven by these different services. When designing next-generation 5G systems, certain aspects of LTE communications may be modified to take into account the increased number of devices. In particular, among the various control signals, it may be desirable to provide flexibility for hybrid ARQ (HARQ) acknowledgement/negative acknowledgement (ACK/NACK) in next-generation networks.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which are not necessarily drawn to scale, like reference numerals may describe similar components in different views. Like reference numerals with different letter suffixes may represent different instances of similar components. The accompanying drawings generally illustrate various embodiments discussed in this document by way of example and not limitation.

FIG1 is a functional diagram of a wireless network according to some embodiments.

FIG2 illustrates components of a communication device according to some embodiments.

FIG3 illustrates a block diagram of a communication device according to some embodiments.

FIG4 illustrates another block diagram of a communication device according to some embodiments.

FIG5 illustrates a multiplexed uplink ACK/NACK channel according to some embodiments.

FIG6 illustrates another multiplexed uplink ACK/NACK channel according to some embodiments.

FIG7 illustrates a multiplexed downlink ACK/NACK channel according to some embodiments.

FIG8 illustrates another multiplexed downlink ACK/NACK channel in accordance with some embodiments.

FIG9 illustrates a time division duplex (TDD) special subframe according to some embodiments.

FIG10 illustrates another TDD special subframe according to some embodiments.

FIG11 illustrates a partial ACK/NACK transmission scheme according to some embodiments.

FIG12 illustrates a distributed ACK/NACK transmission scheme according to some embodiments.

FIG13 illustrates the generation of an ACK/NACK channel according to some embodiments.

14A-14C illustrate various resource mappings according to some embodiments.

DETAILED DESCRIPTION

The following description and accompanying drawings sufficiently illustrate the specific embodiments to enable those skilled in the art to practice them. Other embodiments may include structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in or replaced by portions and features of other embodiments. The embodiments set forth in the claims encompass all available equivalents of those claims.

Figure 1 shows an example of a portion of an end-to-end network architecture of a Long Term Evolution (LTE) network with various components of the network according to some embodiments. As used herein, LTE networks refer to LTE and Advanced LTE (LTE-A) networks, as well as other versions of LTE networks to be developed. Network 100 may include a radio access network (RAN) (e.g., E-UTRAN or Evolved Universal Terrestrial Radio Access Network as depicted) 101 and a core network 120 (e.g., shown as an Evolved Packet Core (EPC)) coupled together via an S1 interface 115. For convenience and brevity, only the core network 120 and a portion of the RAN 101 are shown in this example.

The core network 120 may include a mobility management entity (MME) 122, a serving gateway (serving GW) 124, and a packet data network gateway (PDN GW) 126. The RAN 101 may include an evolved Node B (eNB) 104 (which may operate as a base station) for communicating with a user equipment (UE) 102. The eNB 104 may include a macro eNB 104a and a low power (LP) eNB 104b. The eNB 104 and the UE 102 may employ the synchronization techniques described herein.

The MME 122 may be functionally similar to the control plane of a legacy Serving GPRS Support Node (SGSN). The MME 122 may manage mobility aspects of access, such as gateway selection and tracking area list management. The Serving GW 124 may terminate the interface toward the RAN 101 and route data packets between the RAN 101 and the core network 120. In addition, the Serving GW 124 may be a local mobility anchor point for inter-eNB handovers and may also provide an anchor point for inter-3GPP mobility. Other responsibilities may include lawful interception, charging, and some policy enforcement. The Serving GW 124 and the MME 122 may be implemented in one physical node or in separate physical nodes.

The PDN GW 126 can terminate the SGi interface toward the packet data network (PDN). The PDN GW 126 can route data packets between the EPC 120 and external PDNs and can perform policy enforcement and charging data collection. The PDN GW 126 can also provide an anchor point for mobile devices with non-LTE access. The external PDN can be an IP Multimedia Subsystem (IMS) domain as well as any type of IP network. The PDN GW 126 and the Serving GW 124 can be implemented in a single physical node or in separate physical nodes.

The eNB 104 (macro and micro eNBs) may terminate the air interface protocol and may be the first point of contact for the UE 102. In some embodiments, the eNB 104 may implement various logical functions for the RAN 101, including but not limited to RNC (Radio Network Controller) functions, such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. According to an embodiment, the UE 102 may be configured to communicate orthogonal frequency division multiplexing (OFDM) communication signals with the eNB 104 over a multi-carrier communication channel in accordance with OFDMA communication technology. OFDM signals may include multiple orthogonal subcarriers.

The S1 interface 115 may be an interface that separates the RAN 101 and the EPC 120. The S1 interface 115 may be divided into two parts: S1-U, which may carry traffic data between the eNB 104 and the Serving GW 124, and S1-MME, which may serve as a signaling interface between the eNB 104 and the MME 122. The X2 interface may be an interface between the eNBs 104. The X2 interface may include two parts, X2-C and X2-U. X2-C may be a control plane interface between the eNBs 104, while X2-U may be a user plane interface between the eNBs 104.

For cellular networks, LP cells 104b can typically be used to extend coverage to indoor areas where outdoor signals don't reach well, or to increase network capacity in densely populated areas. In particular, it may be desirable to use cells of different sizes (macrocells, microcells, picocells, and femtocells) to enhance the coverage of a wireless communication system to improve system performance. Cells of different sizes can operate on the same frequency band, or they can operate on different frequency bands, with each cell operating in a different frequency band, or with only cells of different sizes operating in different frequency bands. As used herein, the term LP eNB refers to any suitable lower power (LP) eNB for implementing smaller cells (smaller than macrocells) (e.g., femtocells, picocells, or microcells). Femtocell eNBs are typically provided by mobile network operators to their residential or enterprise customers. Femtocells are typically the size of a residential gateway or smaller and are typically connected to a broadband line. Femtocells can connect to the mobile operator's mobile network and provide additional coverage with a range of typically 30 to 50 meters. Thus, LP eNB 104b may be a femtocell eNB, as it is coupled via PDN GW 126. Similarly, a picocell may be a wireless communication system that typically covers a small area, such as within a building (office, shopping mall, train station, etc.), or more recently, within an airplane. A picocell eNB may typically be connected to another eNB (e.g., a macro eNB) via an X2 link through its base station controller (BSC) functionality. Thus, an LP eNB may be implemented using a picocell eNB, as it is coupled to macro eNB 104a via an X2 interface. A picocell eNB or another LP eNB (LP eNB 104b) may include some or all of the functionality of a macro eNB (LP eNB 104a). In some cases, this may be referred to as an access point base station or an enterprise femtocell.

Communications on an LTE network can be divided into 10ms frames, each of which can include ten 1ms subframes. Each subframe in a frame can include two 0.5ms time slots. Each subframe can be used for uplink (UL) communications from a UE to an eNB or downlink (DL) communications from an eNB to a UE. In one embodiment, the eNB can allocate a greater number of DL communications than UL communications in a particular frame. The eNB can schedule transmissions on various frequency bands ( _f1 and _f2 ). The resource allocation in a subframe used in one frequency band can be different from the resource allocation in a subframe used in another frequency band. Each time slot in a subframe can include 6-7 OFDM symbols, depending on the system used. In one embodiment, a subframe can include 12 subcarriers. A downlink resource grid can be used for downlink transmissions from an eNB to a UE, while an uplink resource grid can be used for uplink transmissions from a UE to an eNB or from a UE to another UE. A resource grid can be a time-frequency grid, which is the physical resource in each time slot in the downlink. The smallest time-frequency unit in a resource grid can be represented as a resource element (RE). Each column and each row of the resource grid may correspond to an OFDM symbol and an OFDM subcarrier, respectively. The resource grid may include resource blocks (RBs) that describe the mapping of physical channels to resource elements and physical RBs (PRBs). A PRB may be the smallest unit of resources that may be allocated to a UE. A resource block may be 180kHz wide in frequency and 1 slot long in time. In frequency, a resource block may be 12×15kHz subcarriers or 24×7.5kHz subcarriers wide. For most channels and signals, 12 subcarriers may be used per resource block, depending on the system bandwidth. In frequency division duplex (FDD) mode, both uplink and downlink frames may be 10ms, separated in frequency (full duplex) or time (half duplex). In time division duplex (TDD), both uplink and downlink subframes may be transmitted on the same frequency and multiplexed in the time domain. The duration of the resource grid 400 in the time domain corresponds to one subframe or two resource blocks. Each resource grid may include 12 (subcarriers)*14 (symbols)=168 resource elements.

Each OFDM symbol can include a cyclic prefix (CP) and a fast Fourier transform (FFT) period that can be used to effectively eliminate inter-symbol interference (ISI). The duration of the CP can be determined by the expected maximum delay spread. Although distortion from the previous OFDM symbol may exist within the CP, in the case of a CP with sufficient duration, the previous OFDM symbol will not enter the FFT period. Once the FFT period signal is received and digitized, the receiver can ignore the signal in the CP.

There may be several different physical downlink channels that are transmitted using such resource blocks, including the Physical Downlink Control Channel (PDCCH) and the Physical Downlink Shared Channel (PDSCH). Each subframe may be divided into the PDCCH and PDSCH. The PDCCH may normally occupy the first two symbols of each subframe and carry information regarding the transport format and resource allocation for the PDSCH channel, as well as H-ARQ information for the uplink shared channel. The PDSCH may carry user data and higher-layer signaling to the UE and occupies the remainder of the subframe. Typically, downlink scheduling (allocation of control and shared channel resource blocks to UEs within a cell) may be performed at the eNB based on channel quality information provided by the UE to the eNB. Downlink resource allocation information may then be sent to each UE on the PDCCH intended for (allocated to) the UE. The PDCCH may include downlink control information (DCI) in one of several formats, which instructs the UE how to locate and decode data sent on the PDSCH in the same subframe from the resource grid. The DCI format may provide details such as the number of resource blocks, resource allocation type, modulation scheme, transport block, redundancy version, coding rate, etc. Each DCI format may have a cyclic redundancy code (CRC) and be scrambled with a radio network temporary identifier (RNTI) that identifies the target UE for which the PDSCH is intended. The use of a UE-specific RNTI may restrict decoding of the DCI format (and thus the corresponding PDSCH) to only the intended UE.

To enable retransmission of lost or erroneous data units, a hybrid automatic repeat request (HARQ) scheme can be used to provide feedback to the transmitter on the success or failure of the decoding attempt after each received data block. When the eNB 104 sends PDSCH data to the UE 102 in a downlink transmission, the data packet can be sent along with an indicator in the PDCCH in the same subframe that informs the UE 102 about the PDSCH schedule, which includes the transmission time and other scheduling information about the data being transmitted. For each PDSCH codeword received by the UE 102, the UE 102 can respond with an ACK if the codeword was successfully decoded, or a NACK if the codeword was not successfully decoded. The eNB can expect ACK/NACK feedback a predetermined number of subframes after the subframe in which the PDSCH data was transmitted. When a NACK is received from the UE 102, the eNB can retransmit the transport block or skip retransmission if the number of retransmissions exceeds a maximum. The ACK/NACK for the corresponding PDSCH may be sent by UE 102 four subframes after receiving the PDSCH from the eNB. Depending on the number of codewords present, the HARQ-ACK information corresponding to the PDSCH may include, for example, 1 or 2 information bits (DCI formats 1a and 1b, respectively). The HARQ-ACK bits may then be processed according to the PUCCH.

The UE 102 may use the Physical Uplink Control Channel (PUCCH) to send uplink control information (UCI) to the eNB 104. The PUCCH may be mapped to an UL control channel resource defined by an orthogonal cover code and two RBs that are contiguous in time (possibly hopping at the boundary between adjacent time slots). The PUCCH may take several different formats, and the UCI includes information that depends on the format. Specifically, the PUCCH may include a scheduling request (SR), an acknowledgement response/retransmission request (ACK/NACK), or a channel quality indication (CQI)/channel state information (CSI). The CQI/CSI may indicate to the eNB 104 an estimate of the current downlink channel conditions as seen by the UE 102 to assist in channel-related scheduling, and may include MIMO-related feedback (e.g., precoding matrix indication, PMI) if the UE 102 is configured with a MIMO transmission mode. Uplink ACK/NACK feedback from the eNB 104 to the UE 102 may be provided in much the same manner as downlink ACK/NACK feedback using the PDCCH instead of the PUCCH.

The Physical Hybrid ARQ Indicator Channel (PHICH) can carry one or more HARQ ACK/NACKs for uplink communications. The PHICH can be located in the first OFDM symbol of each subframe. The PHICH can be carried by several resource element groups (REGs). Multiple PHICHs can share the same set of REGs, distinguished by orthogonal coverage. PHICHs sharing the same resources are called a PHICH group. A specific PHICH can be identified by two parameters: the PHICH group number and the orthogonal sequence index within the group. In the time domain, if an uplink transmission occurs in subframe n, the corresponding PHICH can be in subframe n+4. In the frequency domain, the PHICH can be indicated by an uplink resource allocation with DCI format 0, where the specific PHICH can be derived from the lowest uplink PRB index and demodulation reference signal (DMRS) cyclic shift in the first slot of the corresponding PUSCH transmission, as indicated in 3GPP TS 36.213 Section 9.1.2. DMRS can be used for channel estimation and coherent demodulation of PUSCH and PUCCH. If the DMRS is poor or not correctly decoded by the eNB 104, the PUSCH or PUCCH will not be decoded. The location of the DMRS in the PUCCH can vary according to the PUCCH format indicator; when in the PUSCH, the DMRS can be placed in the center symbol of the time slot (the 3rd symbol of time slot 0 and the 10th symbol of time slot 1).

Channel coding for HARQ ACK/NACK can use 3 bits: ACK can be indicated by 111, and NACK can be indicated by 000. The PHICH can use binary phase shift keying (BPSK) modulation, thus generating 3 modulation symbols for each ACK or NACK. The 3 modulation symbols can be multiplied by an orthogonal cover, which can have a spreading factor (SF) of 4 for a normal cyclic prefix (CP), resulting in a total of 12 symbols. Each REG can include 4 REs, and each RE can carry one modulation symbol, so 3 REGs are used for a single PHICH.

The REGs supporting the PHICH groups may be evenly distributed across the system bandwidth to provide frequency diversity. The Physical Control Format Indicator Channel (PCFICH) may also appear in the first symbol of each subframe and occupy four REGs, evenly distributed across the system bandwidth, regardless of the system bandwidth.

In some embodiments, a PHICH group can carry up to 8 PHICHs, as a total of 8 orthogonal sequences have been defined in 3GPP TS 36.211 Table 6.9.1-2. At least some of the information used to determine the number of PHICHs in a PHICH group (downlink bandwidth and parameters (Ng)) can be signaled using a master information block (MIB). The number of supported PHICH groups can be determined based on the network configuration as indicated in 3GPP TS 36.211 Section 6.9. For example, given a downlink channel bandwidth of 10 MHz and Ng = 1, a total of 7 PHICH groups will be available, the total number of PHICHs supported per subframe is 7 PHICH groups x 8 PHICHs per PHICH group = 56 PHICHs, and the total number of REs used is 7 PHICH groups x 3 REGs per PHICH group x 4 REs per REG = 84 REs.

A scheduling request (SR) allows a UE to request uplink resources for the physical uplink shared channel (PUSCH). In some embodiments, the UE does not send information bits to request uplink resources for sending PUSCH. However, the eNB can know when to expect a scheduling request from each UE in the cell because the resources for SR transmission for a given UE are allocated by the eNB and occur once every few subframes. Therefore, if PUCCH energy is detected, the eNB can identify it as a scheduling request from the corresponding UE. PUCCH formats 1, 1a, and 1b can use four SC-FDMA symbols of the seven OFDM symbols in each time slot to send HARQ-ACK information bits using a conventional CP, and can be modulated using BPSK and quadrature phase shift keying (QPSK), respectively. If a conventional CP is used, the remaining 3 symbols can be used for the PUCCH demodulation reference signal (DM-RS). If the sounding reference signal (SRS) overlaps with the PUCCH symbol, only three of the seven OFDM symbols can be used for HARQ-ACK information bit transmission in the second time slot of the subframe. The eNB may use the DM-RS symbols to perform channel estimation and allow coherent demodulation of the received signal. The DM-RS symbols may essentially be pilot symbols in LTE, used for channel estimation for demodulation of the data symbols of the subframe.

Periodic reference signaling messages including reference signals may occur between the eNB and the UE. Downlink reference signals may include cell-specific reference signals (CRS) and UE-specific reference signals. CRS may be used for scheduling transmissions to multiple UEs, channel estimation, coherent demodulation at the UE, and switching. Other reference signals may include a channel state information reference signal (CSI-RS) for measurement purposes, and a discovery reference signal (DRS) specific to an individual UE. CSI-RS is relatively sparse, present in the PDSCH, and is antenna-dependent.

The Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS) can be used by UEs to identify a cell using the cell ID, current subframe number, slot boundaries, and duplex mode. The PSS and SSS can be transmitted in the center 6 PRBs (1.08 MHz) of the system bandwidth used by the eNBs 104a, 104b. The PSS and SSS can be broadcast from the eNBs 104a, 104b to all UEs 102 in symbol periods 6 and 5, respectively, in each subframe 0 and 5 of each radio frame with a normal CP. Because the position of the PSS can be constant, the PSS can allow the UE 102 to synchronize to the network without any a priori knowledge of the allocated bandwidth. The PSS can include a sequence of length 62 symbols that is mapped to the center 62 subcarriers around the direct current (D.C.) subcarrier. The PSS can be composed of a frequency-domain Zadoff-Chu (ZC) sequence of length 63. The UE 102 can obtain the physical layer cell ID and achieve slot synchronization after detecting the PSS. The PSS and SSS can include a sequence of 62 symbols in length, which is mapped to the 62 subcarriers centered around the direct current (DC) subcarrier. The SSS sequence can be generated based on a maximum length sequence (M sequence), which can be created by looping through each possible state of a shift register of length n. The detection of the PSS and SSS can achieve time and frequency synchronization, provide the UE with the physical layer identifier and CP length of the cell, and inform the UE whether the cell uses FDD or TDD.

Thus, the above and other periodic messages not only provide information about the communication channel, but also enable tracking of the time and/or frequency of communications with the UE. The uplink reference signals may include a demodulation reference signal (DM-RS), which may be used to enable coherent signal demodulation at the eNB. The DM-RS may be time multiplexed with the uplink data and sent on the fourth or third symbol of the uplink timeslot using the same bandwidth as the data for the normal CP or extended CP, respectively. The sounding reference signal (SRS) may be used by UEs with different transmission bandwidths to enable channel-dependent uplink scheduling and may typically be sent in the last symbol of a subframe.

The embodiments described herein may be implemented in a system using any appropriately configured hardware and/or software. FIG2 illustrates components of a UE according to some embodiments. At least some of the components shown may be used in an eNB or MME (e.g., UE 102 or eNB 104 shown in FIG1 ). UE 200 and other components may be configured to utilize synchronization signals as described herein. UE 200 may be one of UE 102 shown in FIG1 and may be a fixed, non-mobile device or a mobile device. In some embodiments, UE 200 may include application circuitry 202, baseband circuitry 204, radio frequency (RF) circuitry 206, front-end module (FEM) circuitry 208, and one or more antennas 210, coupled together at least as shown. At least some of baseband circuitry 204, RF circuitry 206, and FEM circuitry 208 may form a transceiver. In some embodiments, other network elements, such as an eNB, may include some or all of the components shown in FIG2 . Other network elements (e.g., an MME) may include an interface, such as an S1 interface, to communicate with the eNB via a wired connection to the UE.

The application or processing circuitry 202 may include one or more application processors. For example, the application circuitry 202 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and specialized processors (e.g., graphics processors, application processors, etc.). The processor(s) may be coupled to and/or include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications and/or operating systems to run on the system.

The baseband circuitry 204 may include circuitry such as, but not limited to, one or more single-core processors or multi-core processors. The baseband circuitry 204 may include one or more baseband processors and/or control logic to process baseband signals received from the receive signal path of the RF circuitry 206 and generate baseband signals for the transmit signal path of the RF circuitry 206. The baseband processing circuitry 204 may interface with the application circuitry 202 to generate and process baseband signals and control the operation of the RF circuitry 206. For example, in some embodiments, the baseband circuitry 204 may include a second generation (2G) baseband processor 204a, a third generation (3G) baseband processor 204b, a fourth generation (4G) baseband processor 204c, and/or other baseband processor(s) 204d for other existing generations, generations under development, or generations to be developed in the future (e.g., fifth generation (5G), 6G, etc.). Baseband circuitry 204 (e.g., one or more of baseband processors 204a-d) may handle various radio control functions that enable communication with one or more radio networks via RF circuitry 206. Radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, and the like. In some embodiments, the modulation/demodulation circuitry of baseband circuitry 204 may include FFT, precoding, and/or constellation mapping/demapping functions. In some embodiments, the encoding/decoding circuitry of baseband circuitry 204 may include convolution, tail-biting, turbo, Viterbi, and/or low-density parity check (LDPC) encoder/decoder functions. Embodiments of the modulation/demodulation and encoder/decoder functions are not limited to these examples and may include other suitable functions in other embodiments.

In some embodiments, the baseband circuit 204 may include elements of a protocol stack, such as elements of an Evolved Universal Terrestrial Radio Access Network (EUTRAN) protocol, including, for example, physical (PHY) elements, medium access control (MAC) elements, radio link control (RLC) elements, packet data convergence protocol (PDCP) elements, and/or radio resource control (RRC) elements. The central processing unit (CPU) 204e of the baseband circuit 204 may be configured to execute elements of the protocol stack for signaling at the PHY, MAC, RLC, PDCP, and/or RRC layers. In some embodiments, the baseband circuit may include one or more audio digital signal processors (DSPs) 204f. The audio DSP(s) 204f may include elements for compression/decompression and echo cancellation, and in other embodiments may include other suitable processing elements. In some embodiments, the components of the baseband circuit may be appropriately combined in a single chip, a single chipset, or arranged on the same circuit board. In some embodiments, some or all of the components of the baseband circuit 204 and the application circuit 202 may be implemented together (e.g., on a system on a chip (SOC)).

In some embodiments, baseband circuitry 204 can provide communications compatible with one or more radio technologies. For example, in some embodiments, baseband circuitry 204 can support communications with the Evolved Universal Terrestrial Radio Access Network (EUTRAN) and/or other wireless metropolitan area networks (WMANs), wireless local area networks (WLANs), and wireless personal area networks (WPANs). Embodiments in which baseband circuitry 204 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry. In some embodiments, the device can be configured to operate in accordance with communication standards or other protocols or standards, including Institute of Electrical and Electronics Engineers (IEEE) 802.16 wireless technology (WiMax), IEEE 802.11 wireless technology (WiFi) including IEEE 802 ad operating in the 60 GHz millimeter wave spectrum, various other wireless technologies, such as Global System for Mobile Communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE Radio Access Network (GERAN), Universal Mobile Telecommunications System (UMTS), UMTS Terrestrial Radio Access Network (UTRAN), or other 2G, 3G, 4G, 5G, etc. technologies that have been developed or will be developed.

RF circuitry 206 can communicate with a wireless network using modulated electromagnetic radiation through a non-solid medium. In various embodiments, RF circuitry 206 can include switches, filters, amplifiers, and the like to facilitate communication with the wireless network. RF circuitry 206 can include a receive signal path that can include circuitry for down-converting RF signals received from FEM circuitry 208 and providing baseband signals to baseband circuitry 204. RF circuitry 206 can also include a transmit signal path that can include circuitry for up-converting baseband signals provided by baseband circuitry 204 and providing RF output signals to FEM circuitry 208 for transmission.

In some embodiments, RF circuitry 206 may include a receive signal path and a transmit signal path. The receive signal path of RF circuitry 206 may include mixer circuitry 206a, amplifier circuitry 206b, and filter circuitry 206c. The transmit signal path of RF circuitry 206 may include filter circuitry 206c and mixer circuitry 206a. RF circuitry 206 may also include synthesizer circuitry 206d to synthesize frequencies for use by mixer circuitry 206a in the receive and transmit signal paths. In some embodiments, mixer circuitry 206a in the receive signal path may be configured to downconvert the RF signal received from FEM circuitry 208 based on the synthesized frequency provided by synthesizer circuitry 206d. Amplifier circuitry 206b may be configured to amplify the downconverted signal, and filter circuitry 206c may be a low-pass filter (LPF) or a band-pass filter (BPF) configured to remove unwanted signals from the downconverted signal to generate an output baseband signal. The output baseband signal may be provided to baseband circuitry 204 for further processing. In some embodiments, the output baseband signal may be a zero-frequency baseband signal, but this is not required.In some embodiments, the mixer circuit 206a of the receive signal path may include a passive mixer, but the scope of the embodiments is not limited in this respect.

In some embodiments, mixer circuit 206a of the transmit signal path can be configured to upconvert an input baseband signal based on a synthesized frequency provided by synthesizer circuit 206d to generate an RF output signal for FEM circuit 208. The baseband signal can be provided by baseband circuit 204 and can be filtered by filter circuit 206c. Filter circuit 206c can include a low-pass filter (LPF), although the scope of the embodiments is not limited in this respect.

In some embodiments, the mixer circuit 206a of the receive signal path and the mixer circuit 206a of the transmit signal path may include two or more mixers and may be arranged for quadrature down-conversion and/or up-conversion, respectively. In some embodiments, the mixer circuit 206a of the receive signal path and the mixer circuit 206a of the transmit signal path may include two or more mixers and may be arranged for image suppression (e.g., Hartley image suppression). In some embodiments, the mixer circuit 206a of the receive signal path and the mixer circuit 206a of the transmit signal path may be arranged for direct down-conversion and/or direct up-conversion, respectively. In some embodiments, the mixer circuit 206a of the receive signal path and the mixer circuit 206a of the transmit signal path may be configured for superheterodyne operation.

In some embodiments, the output baseband signal and the input baseband signal may be analog baseband signals, but the scope of the embodiments is not limited in this respect. In some alternative embodiments, the output baseband signal and the input baseband signal may be digital baseband signals. In these alternative embodiments, RF circuitry 206 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry, and baseband circuitry 204 may include a digital baseband interface to communicate with RF circuitry 206.

In some dual-mode embodiments, separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.

In some embodiments, synthesizer circuit 206 d may be a fractional-N synthesizer or a fractional N/N+1 synthesizer, but the scope of the embodiments is not limited in this respect, as other types of frequency synthesizers may be suitable. For example, synthesizer circuit 206 d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer including a phase-locked loop with a frequency divider.

Synthesizer circuit 206d may be configured to synthesize an output frequency based on the frequency input and the divider control input for use by mixer circuit 206a of RF circuit 206. In some embodiments, synthesizer circuit 206d may be a divide-by-N/N+1 synthesizer.

In some embodiments, the frequency input may be provided by a voltage controlled oscillator (VCO), but this is not required. Depending on the desired output frequency, the divider control input may be provided by baseband circuitry 204 or application processor 202. In some embodiments, the divider control input (e.g., N) may be determined from a lookup table based on the channel indicated by application processor 202.

The synthesizer circuit 206d of the RF circuit 206 may include a frequency divider, a delay-locked loop (DLL), a multiplexer, and a phase accumulator. In some embodiments, the frequency divider may be a dual-modulus frequency divider (DMD), and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by N or N+1 (e.g., based on a carry output) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded tunable delay elements, a phase detector, a charge pump, and a D-type flip-flop. In these embodiments, the delay elements may be configured to decompose the VCO cycle into Nd equal phase groups, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

In some embodiments, the synthesizer circuit 206 d can be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency can be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with a quadrature generator and divider circuit to generate multiple signals at the carrier frequency with multiple different phases relative to each other. In some embodiments, the output frequency can be the LO frequency (f _LO ). In some embodiments, the RF circuit 206 can include an IQ/polarity converter.

FEM circuitry 208 may include a receive signal path that may include circuitry configured to operate on RF signals received from one or more antennas 210, amplify the received signals, and provide the amplified versions of the received signals to RF circuitry 206 for further processing. FEM circuitry 208 may also include a transmit signal path that may include circuitry configured to amplify signals provided for transmission by RF circuitry 206 for transmission by one or more of the one or more antennas 210.

In some embodiments, the FEM circuitry 208 may include a TX/RX switch to switch between transmit mode operation and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include a low noise amplifier (LNA) to amplify a received RF signal and provide the amplified received RF signal as an output (e.g., to the RF circuitry 206). The transmit signal path of the FEM circuitry 208 may include a power amplifier (PA) to amplify an input RF signal (e.g., provided by the RF circuitry 206) and may also include one or more filters to generate an RF signal for subsequent transmission (e.g., by one or more of the one or more antennas 210).

In some embodiments, as described in more detail below, UE 200 may include additional elements, such as memory/storage, displays, cameras, sensors, and/or input/output (I/O) interfaces. In some embodiments, UE 200 as described herein may be part of a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capabilities, a web tablet, a wireless phone, a smart phone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), or other devices that can wirelessly receive and/or send information. In some embodiments, UE 200 may include one or more user interfaces and/or peripheral component interfaces, wherein the one or more user interfaces are designed to enable user interaction with the system, and the peripheral component interface is designed to enable peripheral component interaction with the system. For example, the UE 200 may include one or more of the following: a keyboard, a keypad, a touchpad, a display, sensors, a non-volatile memory port, a universal serial bus (USB) port, an audio jack, a power interface, one or more antennas, a graphics processor, an application processor, a speaker, a microphone, and other I/O components. The display may be an LCD or LED screen including a touch screen. The sensors may include a gyroscope sensor, an accelerometer, a proximity sensor, an ambient light sensor, and a positioning unit. The positioning unit may communicate with components of a positioning network (e.g., global positioning system (GPS) satellites).

Antenna 210 may include one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas, or other types of antennas suitable for transmission of RF signals. In some multiple-input multiple-output (MIMO) embodiments, antennas 210 may be effectively separated to exploit spatial diversity and different channel characteristics that may result.

Although UE 200 is shown as having several separate functional elements, one or more of these functional elements may be combined and may be implemented by a combination of software-configured elements (e.g., a processing element comprising a digital signal processor (DSP)) and/or other hardware elements. For example, some elements may include one or more microprocessors, DSPs, field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), radio frequency integrated circuits (RFICs), and combinations of various hardware and logic circuits for performing at least the functions described herein. In some embodiments, a functional element may refer to one or more processes running on one or more processing elements.

Embodiments may be implemented in one of hardware, firmware, and software, or in a combination thereof. Embodiments may also be implemented as instructions stored on a computer-readable storage device, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transient mechanism for storing information in a machine (e.g., computer) readable form. For example, a computer-readable storage device may include a read-only memory (ROM), a random access memory (RAM), a magnetic disk storage medium, an optical storage medium, a flash memory device, and other storage devices and media. Some embodiments may include one or more processors and may be configured with instructions stored on a computer-readable storage device.

FIG3 is a block diagram of a communications device according to some embodiments. The device may be a UE or an eNB, such as the UE 102 or eNB 104 shown in FIG1 that may be configured to track a UE as described herein. Physical layer circuitry 302 may perform various encoding and decoding functions, which may include forming baseband signals for transmission and decoding received signals. The communications device 300 may also include medium access control (MAC) layer circuitry 304 for controlling access to the wireless medium. The communications device 300 may also include processing circuitry 306 (e.g., one or more single-core or multi-core processors) and a memory 308 configured to perform the operations described herein. The physical layer circuitry 302, MAC circuitry 304, and processing circuitry 306 may handle various radio control functions that enable communications with one or more radio networks compatible with one or more radio technologies. Radio control functions may include signal modulation, encoding, decoding, radio frequency shifting, and the like. For example, similar to the device shown in FIG2 , in some embodiments, communications may be implemented using one or more of a WMAN, a WLAN, and a WPAN. In some embodiments, the communication device 300 may be configured to operate in accordance with 3GPP standards or other protocols or standards, including WiMax, WiFi, GSM, EDGE, GERAN, UMTS, UTRAN, or other 2G, 3G, 4G, 5G, and other technologies that have been developed or will be developed. The communication device 300 may include a transceiver circuit 312 for implementing wireless communication with other external devices, and an interface 314 for implementing wired communication with other external devices. As another example, the transceiver circuit 312 may perform various transmission and reception functions, such as converting signals between a baseband range and a radio frequency (RF) range.

Antenna 301 may include one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas, or other types of antennas suitable for transmission of RF signals. In some MIMO embodiments, antennas 301 may be effectively separated to exploit spatial diversity and different channel characteristics that may result.

Although the communication device 300 is shown as having several separate functional elements, one or more of these functional elements can be combined and can be implemented by a combination of software-configured elements (e.g., processing elements including DSPs) and/or other hardware elements. For example, some elements may include one or more microprocessors, DSPs, FPGAs, ASICs, RFICs, and various hardware and logic circuits for performing at least the functions described herein. In some embodiments, a functional element may refer to one or more processes running on one or more processing elements. An embodiment may be implemented in one or a combination of hardware, firmware, and software. An embodiment may also be implemented as instructions stored on a computer-readable storage device that may be read and executed by at least one processor to perform the operations described herein.

Figure 4 shows another block diagram of a communication device according to some embodiments. In an alternative embodiment, the communication device 400 can operate as a standalone device or can be connected (e.g., networked) to other communication devices. In a networked deployment, the communication device 400 can operate as a server communication device, a client communication device, or both in a server-client network environment. In an example, the communication device 400 can be used as a peer communication device in a peer-to-peer (P2P) (or other distributed) network environment. The communication device 400 can be a UE, an eNB, a PC, a tablet PC, a STB, a PDA, a mobile phone, a smart phone, a network device, a network router, a switch or a bridge, or any communication device capable of executing instructions (sequentially or otherwise) for actions to be taken by a specified communication device. In addition, although only a single communication device is shown, the term "communication device" should also be considered to include any collection of communication devices that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methods discussed herein, such as cloud computing, software as a service (SaaS), and other computer cluster configurations.

Examples described herein may include logic or several components, modules or mechanisms, or may operate on logic or several components, modules or mechanisms. A module is a tangible entity (e.g., hardware) that can perform a specified operation and may be configured or arranged in a particular manner. In an example, a circuit may be arranged as a module (e.g., internally or relative to an external entity such as other circuits) in a specified manner. In an example, all or part of one or more computer systems (e.g., independent client or server computer systems) or one or more hardware processors may be configured by firmware or software (e.g., instructions, application parts or applications) to operate to perform a specified operation. In an example, software may reside on a communication device readable medium. In an example, software, when executed by the underlying hardware of a module, causes the hardware to perform a specified operation.

Thus, the term "module" is understood to include a tangible entity, i.e., an entity that is physically constructed, specifically configured (e.g., hardwired), or temporarily (e.g., transiently) configured (e.g., programmed) to operate in a specified manner or to perform part or all of any of the operations described herein. Considering an example where a module is temporarily configured, each of the modules need not be instantiated at all times. For example, where a module comprises a general-purpose hardware processor configured using software, the general-purpose hardware processor can be correspondingly configured as different modules at different times. Thus, software can configure a hardware processor to, for example, constitute a particular module at one instance in time and constitute another module at another instance in time.

The communication device (e.g., a computer system) 400 may include a hardware processor 402 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 404, and a static memory 406, some or all of which may communicate with each other via an interconnection (e.g., a bus) 408. The communication device 400 may also include a display unit 410, an alphanumeric input device 412 (e.g., a keyboard), and a user interface (UI) navigation device 414 (e.g., a mouse). In an example, the display unit 410, the input device 412, and the UI navigation device 414 may be a touch screen display. The communication device 400 may also include a storage device (e.g., a drive unit) 416, a signal generating device 418 (e.g., a speaker), a network interface device 420, and one or more sensors 421, such as a global positioning system (GPS) sensor, a compass, an accelerometer, or other sensors. The communication device 400 may include an output controller 428, such as a serial (e.g., universal serial bus (USB)), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate with or control one or more peripheral devices (e.g., a printer, a card reader, etc.).

The storage device 416 may include a communication device-readable medium 422 having stored thereon one or more sets of data structures or instructions 424 (e.g., software) that embody or are utilized by any one or more of the techniques or functionality described herein. The instructions 424 may also reside, completely or at least partially, within the main memory 404, completely or at least partially within the static memory 406, or completely or at least partially within the hardware processor 402 during execution by the communication device 400. In an example, one or any combination of the hardware processor 402, the main memory 404, the static memory 406, or the storage device 416 may constitute the communication device-readable medium.

Although the communication device readable medium 422 is shown as a single medium, the term “communication device readable medium” may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store one or more instructions 424.

The term "communication device readable medium" may include any medium capable of storing, encoding, or carrying instructions executed by the communication device 400 and causing the communication device 400 to perform any one or more of the techniques of the present disclosure, or any medium capable of storing, encoding, or carrying data structures used by or associated with such instructions. Non-limiting examples of communication device readable media may include solid-state memory, and optical and magnetic media. Specific examples of communication device readable media may include: non-volatile memory (such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices, magnetic disks (such as internal hard disks and removable disks), magneto-optical disks, random access memory (RAM), and CD-ROM and DVD-ROM disks. In some examples, the communication device readable medium may include non-transitory communication device readable media. In some examples, the communication device readable medium may include communication device readable media that is not a transient propagation signal.

The instructions 424 may also be sent and received over a communication network 426 using a transmission medium via the network interface device 420 utilizing any of a number of transport protocols (e.g., frame relay, Internet Protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), a mobile phone network (e.g., a cellular network), a plain old telephone (POTS) network, and a wireless data network (e.g., the so-called Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards, the so-called IEEE 802.16 family of standards), the IEEE 802.15.4 family of standards, the Long Term Evolution (LTE) family of standards, the Universal Mobile Telecommunications System (UMTS) family of standards, a peer-to-peer (P2P) network, etc. In an example, the network interface device 420 may include one or more physical jacks (e.g., Ethernet, coaxial, or telephone jacks) or one or more antennas to connect to the communication network 426. In an example, the network interface device 420 may include multiple antennas to communicate wirelessly using at least one of single-input multiple-output (SIMO), MIMO, or multiple-input single-output (MISO) technology. In some examples, the network interface device 420 may communicate wirelessly using multi-user MIMO technology. The term "transmission medium" should be taken to include any intangible medium capable of storing, encoding, or carrying instructions for execution by the communication device 400, including digital or analog communication signals or other intangible media to facilitate communication of such software.

As discussed above, due to the use of millimeter transmission wavelengths and the resulting enhanced use of beamforming, control signals may need to be redesigned for the upcoming 5G system. Among other things, the frame structure and position of the HARQ ACK/NACK signal may be advantageously adjusted to achieve good interference cancellation and mitigation performance. In particular, a symmetric downlink and uplink HARQ ACK/NACK design may be advantageous in simplifying receiver implementation, especially when considering device-to-device (D2D) communications. The control and data channels of the 5G system may be multiplexed using time division multiplexing (TDM) or frequency division multiplexing (FDM). In some embodiments, the ACK/NACK control channel may be multiplexed with other control channels and data channels using TDM.

As described above, for downlink transmissions, ACK/NACK feedback can be carried in the PUCCH, while for uplink transmissions, ACK/NACK feedback can be carried in the PHICH. Depending on the size of the aggregated ACK/NACK bits, different PUCCH formats can be used. The PUCCH resources are already located at the edge of the entire available spectrum and span 1 subframe. To provide frequency diversity, the frequency resources can be frequencies that hop across slot boundaries. Note that this PUCCH structure may not be suitable for TDM-based multiplexing schemes for control and data channels, and may not be preferred when considering supporting low-latency applications.

As described above, the PHICH can be located in the first OFDM symbol of each subframe of an FDD frame structure using a conventional PHICH duration. The PHICH can be carried by several REGs. PHICH groups of multiple PHICHs sharing the same set of REGs can be distinguished by an orthogonal cover. Therefore, a specific PHICH is identified by two parameters: the PHICH group number and the orthogonal sequence index within the group. A 3-bit repetition can be used for channel coding of HARQ ACK/NACK. The PHICH can use BPSK or QPSK modulation, so 3 modulation symbols can be generated for each ACK or NACK. The modulation symbols can be multiplied by an orthogonal cover, which can have a spreading factor (SF) of 4 for a conventional cyclic prefix, resulting in a total of 12 symbols. Each REG can include 4 REs and each RE can carry one modulation symbol, so 3 REGs can be used for a single PHICH.

On the other hand, the PUCCH can include one RB/transmission at one end of the system bandwidth, followed by another RB in the next slot (at the other end of the channel spectrum), which takes advantage of frequency diversity. The PUCCH control region includes every two such RBs. The PUCCH format is summarized in Table 1 below.

Table 1

In PUCCH format 1a/1b, 3 symbols are used as DMRS and 4 symbols are used for data by using BPSK or QPSK with coherent detection. UE 104 can detect the DMRS sequence, perform channel estimation using the DMRS sequence, and then perform data detection. Since there are only 3 DMRS symbols, the multiplexing capability may be limited by the DMRS. In some embodiments, the DL and UL ACK/ACK channel designs can be independent and omnidirectional transmission is used without considering beamforming. Frequency diversity can improve link robustness, and the use of symmetric DL/UL ACK/NACK transmissions can provide easier expansion of D2D communications and convergence of access and backhaul in the future. In addition, the ACK/NACK channel design can consider the use of beamforming, which can be used to compensate for the large path loss caused by the use of millimeter wave transmission.

In some embodiments, a unified DL/UL ACK/NACK channel design can be provided when the same physical structure is used for the ACK/NACK channel. Note that in some embodiments, the PDSCH and UL ACK/NACK may not be received by the UE at the same time. In some embodiments, the ACK/NACK channel can be time-division multiplexed with other control and data channels. For DL ACK/NACK transmission, both analog precoding and digital precoding can be used. The analog precoding weights can follow the PUSCH analog weights at the eNB 104 and UE 102. The digital precoding weights can be calculated using the channel estimate estimated from the UL DMRS. For UL ACK/NACK transmission, the analog precoding weights can be the same as the corresponding DL PDSCH. The digital precoding weights can be calculated using the channel estimated from the DL DMRS.

The unified DL/UL ACK/NACK channel design can use spreading codes and can use non-coherent detection of ACK/NACK. The DL/UL ACK/NACK channels can be beamformed using the same analog beamforming used for the corresponding PDSCH and PUSCH transmissions. This can provide a gain of more than 20dB in millimeter wave transmissions. The beamforming weights of the ACK/NACK channel can be dynamically adjusted following the data service being confirmed by the ACK/NACK transmission. Since Tx/Rx can be fixed based on HARQ timing, the UL ACK/NACK channel can be separated from the SR. Therefore, beamforming can be performed by following the previous data transmission.

FIG5 illustrates a multiplexed uplink ACK/NACK channel according to some embodiments. UL transmission 500 may include control information and data. The data may be provided in PUSCH 510. The control information may include SRS 502 and ACK/NACK 504 multiplexed with control information in PUCCH 506. Although not shown, PUCCH 506 may include scheduling requests, CSI reports, etc. ACK/NACK 504 occurs after SRS 502, thereby increasing the SINR of ACK/NACK 504 by allowing beamforming to occur before ACK/NACK 504 is received. In some embodiments, the UE Tx analog beam direction may be set based on the corresponding DL data traffic received; the eNB Rx analog beam direction may also be set using the same analog direction as the corresponding Tx direction in the DL data traffic.

FIG6 illustrates another multiplexed uplink ACK/NACK channel according to some embodiments. UL transmission 600 may include control information and data. The data may be provided in PUSCH 610. The control information may include SRS 602 and ACK/NACK 604 multiplexed with control information in PUCCH 606. In this embodiment, unlike the embodiment of FIG5 , the positions of SRS 602 and ACK/NACK 604 may be swapped. That is, ACK/NACK 604 occurs in the first symbol of the UL Transmission Time Interval (TTI) before SRS 602, thereby reducing the latency of ACK/NACK 604 by allowing ACK/NACK 604 to be received earlier. A TTI is the smallest unit of time in which an eNB can schedule a UE for uplink or downlink transmission.

In some embodiments, one or both of the SRS 502, 602 and the ACK/NACK 504, 604 may be provided at the end of the UL TTI after the PUSCH 510, 610, rather than at the beginning of the UL TTI as shown in Figures 5 and 6. In some embodiments, one or both of the SRS 502, 602 and the ACK/NACK 504, 604 may be provided before and adjacent to the PUSCH 510, 610. When the ACK/NACK 504, 604 is adjacent to the PUSCH 510, 610, if no ACK/NACK is used at the allocated resource block, the ACK/NACK resources 504, 604 may be used to transmit a PUSCH signal. In this case, a single bit switch can be added in the UL grant, where one value (e.g., value 0) can indicate that the PUSCH 510, 610 is not mapped to the ACK/NACK symbol 504, 604, while another value (e.g., value 1) can indicate that the PUSCH 510, 610 is mapped to the ACK/NACK symbol 504, 604. The meaning of the value can be predetermined in the standard or can be set by higher layer signaling. Similarly, in other embodiments, the ACK/NACK resources 504, 604 can be combined with the PUCCH 506, 606, where the indicator is provided in the UL grant. That is, the ACK/NACK resources 504, 604 can be sent together with other uplink control information (e.g., a CSI report in another PUCCH format). Note that although PUSCH and DL ACK/NACK are shown in FIG5 and FIG6 as being transmitted in the same subframe, if the UE does not have a UL grant from the eNB, the UE may transmit DL HARQ ACK/NACK but may not transmit PUSCH.

FIG7 illustrates a multiplexed downlink ACK/NACK channel according to some embodiments. DL transmission 700 may include control information and data. The data may be provided in PDSCH 710. The control information may include DMRS symbols 702 and ACK/NACK 704 multiplexed with control information in PDCCH 706. The eNB analog transmission weight for ACK/NACK 704 may be set to the same receive beam direction as the corresponding UL service (e.g., as shown in FIG5 or FIG6). The UE receive analog direction for ACK/NACK channel 500 may be set to the same as the UL data service Tx direction. The eNB may also apply digital precoding using the channel estimated from UL DMRS 702. The application of analog and digital precoding may be transparent to the UE. Note that while PDSCH and UL ACK/NACK are shown in FIG7 as being transmitted in the same subframe, in some embodiments, the PDSCH and UL ACK/NACK may not be transmitted simultaneously.

7 , ACK/NACK 704 may occur before and adjacent to DMRS 702. ACK/NACK 704 may also occur after PDCCH 706. In some embodiments, ACK/NACK 704 may occur between DMRS 702 and PDSCH 710.

FIG8 illustrates a multiplexed downlink ACK/NACK channel according to some embodiments. DL transmission 800 may include control information and data. The data may be provided in PDSCH 810. The control information may include DMRS symbols 802 and ACK/NACK 804 multiplexed with control information in PDCCH 806. The eNB analog transmission weight for ACK/NACK 804 may be set to the same receive beam direction as the corresponding UL traffic. The UE analog receive direction for ACK/NACK channel 500 may be set to the same as the UL data traffic Tx direction. The eNB may also apply digital precoding using the channel estimated from UL DMRS 802. The application of analog and digital precoding may be transparent to the UE. As shown in FIG8 , ACK/NACK 804 may occur before DMRS 802 and PDCCH 806. ACK/NACK 804 may also occur after PDCCH 806.

Similar to the above, when ACK/NACK feedback is not used, ACK/NACK resources 704, 804 can be used to send PDSCH 710, 810 or a reference signal. Whether the ACK/NACK resources 704, 804 send ACK/NACK symbols or send another signal can be configured via RRC signaling. A single bit switch can be added in the DL allocation, where one value (e.g., value 0) can indicate that the PDSCH 710, 810 is not mapped to the ACK/NACK symbols 704, 804, and another value (e.g., value 1) can indicate that the PDSCH 710 is mapped to the ACK/NACK symbols 704, 804. The meaning of the value can be predetermined in the standard or can be set by higher layer signaling. The downlink ACK/NACK resources 704, 804 can be merged with the PDCCH 706, 806, where an indicator is provided in the DL allocation.

Figure 9 shows a TDD special subframe according to some embodiments. The special subframe 900 (which may be preceded by a DL subframe) may include both a UL control region and a DL control region. As shown, the UL control region is allocated in the DL TTI in the special subframe 900. A guard period 912 may be reserved at the initiation of the special subframe 900 to allow the UE to switch from the receiver chain to the transmitter chain. Similar to Figure 5, the UL control region may include an SRS 902 for beamforming training of the eNB, an UL ACK/NACK 904, and a PUCCH 906. The special subframe 900 may also include DL control signals and DL data in the PDSCH 910. The DL control signals include DL ACK/NACK 914 and DCI allocation 908 for the same UE and/or different UEs as the UL ACK/NACK 904.

As shown in FIG9 , UL ACK/NACK 904 may occur between SRS 902 and PDCCH 906, while DL ACK/NACK 914 may occur between DCI allocation 908 and PDSCH 910. UL ACK/NACK 904 in the UL control region may occur at or near the beginning of a special subframe 900 to enable low-latency communication in DL-heavy traffic. In other embodiments, the location of UL/DL ACK/NACK 904 may be swapped with SRS 902 or DCI allocation 908.

FIG10 illustrates another TDD special subframe according to some embodiments. Similar to FIG9 , special subframe 1000 (which may be preceded by a UL subframe) may include both a UL control region and a DL control region. However, in FIG10 , the DL control region is allocated within the UL TTI within special subframe 1000. Special subframe 1000 may begin with the DL control region, which may include DL control signals including a DL ACK/NACK 1014 and a DCI allocation 1008 for the same UE and/or a different UE than the UL ACK/NACK 1004. A guard period 1012 may be reserved between the DL ACK/NACK 1014 and the UL control region, which begins with a PUCCH 1006 as shown. The UL control region may also include an SRS 1002 for beamforming training by the eNB and UL ACK/NACK 1004, where the UL ACK/NACK 1004 may be adjacent to the PUSCH 1010.

As shown in FIG10 , UL ACK/NACK 1004 may occur between SRS 1002 and PDCCH 1006, while DL ACK/NACK 1014 may occur between DCI allocation 1008 and PDSCH 1010. UL ACK/NACK 1004 in the UL control region may occur at or near the beginning of a special subframe 1000 to enable low-latency communication in DL-heavy traffic. In other embodiments, the location of UL/DL ACK/NACK 1004 may be swapped with SRS 1002 or DCI allocation 1008.

The physical structure of the ACK/NACK in any of the embodiments shown in Figures 5-10 can have various coding and spreading options to accommodate beamforming. The link budget of the ACK/NACK channel may be stricter than that of the data channel transmission to ensure reliability. Typically, in the LTE DL PHICH, an equivalent coding rate of 1/12 can be used. In the UL PUCCH, the sequence length of the DMRS can therefore be 12×3=36 samples long. In the ACK/NACK channel design of this article, the beamforming gain can be similar to the gain of the data service. This means that the spreading code of the ACK/NACK channel can ensure more reliable reception of the ACK/NACK channel. Due to the constraints of the analog beamforming weights, the minimum granularity of the ACK/NACK channel can be one symbol.

In one example, for a 500MHz bandwidth and 750KHz subcarrier spacing in DL transmission, there are a total of 600 subcarriers in one symbol. This can provide sufficient spreading gain for ACK/NACK transmission. Since the available UE transmit power is low, it may be desirable to carefully calculate the link budget for UL ACK/NACK transmission. In one example, a typical small cell may have a Tx power of 30dBm, while the UE has a Tx power of 20dBm. When the DL scheduling includes more than 4 UEs, the DL and UL powers can be balanced because the total UL Tx power from all UEs can be greater than 30dBm. The worst-case link budget occurs when the PDSCH is sent to only one UE. In this case, the UL ACK/NACK spreading gain should be much higher than 10dB. Since the UL uses one symbol to send ACK/NACK, the spreading gain is 10*log10(600)=27dB to meet the UL link budget.

In some embodiments, turning to ACK/NACK detection, non-coherent detection is used for ACK/NACK channel design. Due to the limitations of millimeter wave analog beamforming, the number of ACK/NACK bits may be limited. For single carrier (SC) waveforms, support for coherent detection uses at least one symbol for DMRS and at least one symbol for data. To support non-coherent detection, two sequences can be used for one ACK/NACK bit. Assigning ACK/NACK sequences to corresponding bits is for further study. The sequence can be a ZC sequence or selected from other random orthogonal sequences.

In order to maintain sequence orthogonality in the frequency selective channel, the entire frequency band can be divided into different sub-bands. Several options can be used to multiplex the ACK/NACK channels of multiple UEs to achieve robust detection or decoding execution for ACK/NACK feedback. These options include time division multiplexing (TDM), frequency division multiplexing (FDM) and code division multiplexing (CDM), and combinations of these. In some embodiments, a combination of frequency division multiplexing (FDM) and code division multiplexing (CDM) can be used, wherein the UEs are subjected to FDM on different sub-bands and CDM within each sub-band. In some embodiments, CDM can be used, wherein the sequence is repeated in different sub-bands to achieve a larger amount of frequency diversity. In some embodiments, orthogonal sequences, pseudo-random sequences or spreading codes can be used to separate ACK/NACK transmissions for different UEs.

ACK/NACK transmission can be performed using a localized or distributed transmission scheme. FIG11 illustrates a localized ACK/NACK transmission scheme according to some embodiments. When SC-FDMA or GI-DFT-s-OFDM waveforms are used for uplink ACK/NACK transmission, the channel design shown in FIG11 can be employed. As shown in FIG11 , the localized resource mapping scheme for ACK/NACK transmission can have a system bandwidth 1102 divided into L subbands 1104, where each subband 1104 includes K subcarriers, i.e.,

where N _sc is the total number of subcarriers within the system bandwidth 1102 .

In the example shown in FIG11 , the system bandwidth 1102 is divided into four contiguous subbands (L=4) 1104. However, other values for the subband size and number of subbands within the system bandwidth may be used. To minimize implementation cost and regulatory impact, the subband size may be fixed. In different embodiments, the number of subbands may be different for different system bandwidths, or the number of subbands may be fixed and independent of the system bandwidth.

FIG12 illustrates a distributed ACK/NACK transmission scheme according to some embodiments. When an OFDMA waveform is used for uplink ACK/NACK transmission, the channel design shown in FIG12 may be employed. As shown in FIG12 , the resource mapping scheme for ACK/NACK transmission may have a system bandwidth 1202 divided into L subbands 1204, where each subband 1204 includes M subcarrier blocks 1206, and each subcarrier block 1206 occupies N subcarriers. The number of subbands may be calculated as:

where N _sc is the total number of subcarriers within the system bandwidth 1202 .

In the example shown in FIG12 , similar to FIG11 , the system bandwidth 1202 is divided into four subbands 1204 (L=4). As shown, each subband 1204 occupies three subcarrier blocks 1206 (M=3). Unlike the embodiment shown in FIG11 , in which the subbands 1104 may be adjacent, in FIG12 , the subcarrier blocks 1206 of different subbands 1204 may be adjacent. In some embodiments, the frequency spacing between subcarrier blocks 1206 of the same subband 1204 may be the same for each subband 1204. In some embodiments, the frequency spacing between subcarrier blocks of the same subband may vary depending on the subband, may not be uniform within the same subband, and/or may not be uniformly distributed across the entire system bandwidth. For example, the frequency spacing between subcarrier blocks of one subband may be adjacent to each other (i.e., not separated by one or more subcarrier blocks of one or more other subbands), while other subcarrier blocks may be separated by one or more subcarrier blocks of one or more other subbands (and these other subbands may have different numbers of subcarrier blocks and/or different frequency spacing between subcarrier blocks). Other values for the subband size and number of subbands within the system bandwidth may be used.

A sequence-based or channel-based ACK/NACK channel design with modulated symbols can be used. When a sequence-based ACK/NACK channel design is used to minimize receiver complexity, non-coherent detection can be achieved. When a channel-based ACK/NACK channel design is used to enable correct channel estimation and coherent detection, reference symbols can be inserted within each subband or subcarrier block, or inserted within adjacent symbols.

For sequence-based ACK/NACK design, in some embodiments, ACK and NACK responses can be sent in two independent ACK/NACK resources for each UE. As described above, the resources used for ACK/NACK transmission can be defined as dedicated frequency resources or dedicated sequences, or a combination thereof. In one example, ACK/NACK transmission resource #1 can be defined as subband #1 and sequence #1, while ACK/NACK transmission resource #2 can be defined as subband #2 and sequence #1. In another example, ACK/NACK transmission resource #1 can be defined as subband #1 and sequence #1, while ACK/NACK transmission resource #2 can be defined as subband #1 and sequence #2.

In some embodiments, only ACK may be sent in the corresponding resource; no NACK may be sent. In this case, if no response is received, the receiver may assume that a NACK was sent.

At the transmitter, an ACK or NACK response can be sent via a dedicated sequence within a subband. This sequence can be based on, for example, a ZC sequence, an M sequence, a Hadamard sequence, or other sequences that satisfy the constant amplitude zero autocorrelation (CAZAC) property. The following ACK/NACK channel design is based on the use of a ZC sequence, however, similar design principles can be used for other sequences.

The sequence used for the ACK/NACK channel can be generated as follows:

where is the basic sequence used to transmit xTRS; u is the sequence group number, v is the sequence number; and α is the cyclic shift.

Note that u and v can be determined based on a physical cell identifier, a virtual cell identifier, or a slot/subframe/frame index. The virtual cell ID can be configured by a higher layer. In one example, u and v can be generated according to Release 13 of the LTE specification, where u is defined in Section 5.5.1.3 and v is defined in Section 5.5.1.4 of the 3GPP Technical Specification 36.211. Similarly, the basic sequence can be generated as defined in Section 5.5.1 of 3GPP TS 36.211. As defined, a ZC sequence can be used when the length is not less than 36, while a computer-generated sequence is used for 1 or 2 PRB allocations.

In another example, the sequence for the ACK/NACK channel can be generated by puncturing or cyclically extending a ZC sequence. The length of the ZC sequence is defined as _Nzc , and the subband size is defined as K. _Nzc can be a prime number in some embodiments. In one example, _Nzc can be defined as the largest prime number such that _Nzc <K or the smallest prime number such that _Nzc≥K .

When the ZC sequence length is less than the subband size, that is, N _zc < K, the base sequence can be generated by puncturing or cyclically extending the ZC sequence. In one option, the base sequence can be given by the cyclic extension of the ZC sequence x _u (n):

In another embodiment, a basic sequence may be given by puncturing a subcarrier in a subband:

The ZC sequence is generated by the following formula:

When the ZC sequence length is greater than the subband size, that is, N _zc ≥ K, the basic sequence can be generated by puncturing some elements in the ZC sequence.

In the above equation, the relationship between q and (u, v) can reuse the LTE specification defined in 3GPP TS 36.211 Section 5.5.1.1. Based on the above equation, multiple orthogonal sequences can be generated from a single base sequence by different values of cyclic shift α.

Figure 13 shows the generation of an ACK/NACK channel according to some embodiments. In operation 1302, the ACK/NACK bits may be encoded. That is, a repetition code of length Q may be applied to a 1-bit ACK/NACK. In some embodiments, bit "1" may be used to indicate ACK, and bit "0" may be used to indicate NACK. Q may be a fixed value for all UEs, or Q may have a UE-specific configuration. In an example of Q value selection, Q may be smaller for UEs with higher SINRs, and may have a larger value for UEs with lower SINRs. Q length selection may be configured via dedicated RRC signaling, or may be configured in a DCL. In another example, the Q value may be implicitly indicated by the CCE aggregation level or the modulation and coding scheme (MCS).

After being encoded, modulation may be applied to the encoded ACK/NACK bits at operation 1304. In some embodiments, BPSK or QPSK may be used for modulation.

A spreading code may be applied to the modulated symbols at operation 1306. As described above, the spreading code may be a ZC code, a Hadamard code, or an orthogonal code as defined in 3GPP TS 36.211 Section 6.9.1.

Subsequently, at operation 1308, cell-specific scrambling may be used to further randomize interference after the spreading code has been applied. More specifically, a scrambling seed may be defined as a function of the physical cell ID, virtual cell ID, and/or subframe/time slot/symbol index used to transmit the ACK/NACK. In one example, the scrambling seed may be given by:

where _ns is the slot index and is the cell ID.

After the ACK/NACK has been scrambled, the resulting modulated symbols may be mapped to appropriate resources at operation 1310. Resource mapping may be based on predetermined resource mapping rules. In some embodiments, resource mapping may start from the lowest frequency index within the allocated subband.

Figures 14A-14C illustrate various resource mappings according to some embodiments. Each of these figures shows resource mapping for one PRB 1400, which includes 12 symbols. Figures 14A-14C illustrate different mappings of data (ACK/NACK) symbols 1402A, 1402B, 1402C and reference symbols 1404A, 1404B, 1404C. Specifically, in Figure 14A, there may be a greater number of data symbols 1402A than reference symbols 1404A. The data symbols 1402A may be grouped together in pairs as shown, and the groups of data symbols 1402A may be separated by a single reference symbol 1404A. In some embodiments, each reference signal 1404A may be shifted by one or two symbols. In some embodiments, each reference signal 1404A may be shifted by one or two symbols.

In FIG14B , there may be a greater number of reference symbols 1404B than data symbols 1402B. Data symbols 1402B may be grouped together in pairs as shown, with groups of data symbols 1402B separated by a group of reference symbols 1404B. Each group of reference symbols 1404B may include the same number of reference symbols 1404B, or at least one group of reference symbols 1404B may have a different number of reference symbols 1404B, as shown.

In Figure 14C, there may be the same number of reference symbols 1404C as data symbols 1402C. Data symbols 1402C and reference symbols 1404C may be interleaved. Adjacent data symbols 1402C may be separated by a single reference symbol 1404C, and adjacent reference symbols 1404C may be separated by a single data symbol 1402C.

In some embodiments, reference symbols may be sent before the ACK/NACK channel. In this case, reference symbols may not be used in the symbols used for ACK/NACK transmission. In this case, the modulated ACK/NACK symbols may span the entire allocated subband.

The total number of resources depends on the spreading factor in each subband and the total number of subbands allocated to ACK/NACK transmission. In one example, in a sequence-based ACK/NACK channel design, the system bandwidth can be divided into 5 subbands, where each subband includes 120 subcarriers. The spreading factor or the number of orthogonal sequences within each subband can be 12. The total number of resources used for ACK/NACK transmission can therefore be 5*12=60. If independent resources are used to send ACK and NACK, the total capacity can be reduced to 30. In another example, for a channel-based ACK/NACK design, if the spreading factor is 8 based on the Hadamard sequence and the total number of subbands is 5, the total number of resources used for ACK/NACK transmission can be 5*8=40.

The resource index used for ACK/NACK transmission can be expressed in the form of a subband index ( _ISB ) and a spreading code index ( _ISF ). For sequence-based ACK/NACK channel design, the cyclic shift α can be considered as the spreading code index _ISF . Different embodiments can be used to determine the resource index ( _ISB , _ISF ) for each UE.

In some embodiments, the resource index used for ACK/NACK transmission can be obtained based on cell-specific parameters and/or UE-specific parameters. The cell-specific parameters (which can be physical cell IDs or virtual cell IDs) can be configured by MIB, SIB, or dedicated RRC signaling. The UE-specific parameters can be configured from the primary cell or serving cell via dedicated RRC signaling.

In one example, the resource index may be given by:

( _ISB , _ISF ) = f( _IAN )

Where I _AN is the UE-specific ACK/NACK resource index, which can be provided by UE-specific RRC signaling. For example, the resource index for transmitting ACK/NACK can be calculated as:

In another example, the resource index may be given by:

Where is the cell ID. For example, the resource index can be calculated as:

In some embodiments, the resource index for ACK/NACK transmission can be obtained based on cell-specific parameters, UE-specific parameters and/or parameters explicitly signaled in DCI format. The parameters signaled in DCI format for uplink grant or downlink allocation may include the subband index for ACK/NACK transmission and/or the DM-RS for PDSCH or PUSCH transmission. When using parameters signaled in DCI format, the determination of ACK/NACK transmission can follow equation (1), where I _AN is the parameter signaled in DCI format for uplink grant or downlink allocation. For adaptive retransmission users, the ACK/NACK resource index most recently sent in the same HARQ process can be used.

In another example, for sequence-based ACK/NACK channel design, the subband index I _SB can be explicitly signaled in the DCI format, and the cyclic shift α can be obtained based on the following formula:

Where K ₀ is the starting cyclic shift offset, n _DM-RS is the DM-RS sequence index used for PDSCH or PUSCH transmission, and N _SF is a constant, for example, N _SF = 12. _{K 0} may be predefined or configured by higher layer signaling via MIB, SIB, or dedicated UE-specific RRC signaling.

In another example, for both sequence-based and channel-based ACK/NACK designs, the resource index may be given by:

where c ₀ is a constant.

In some embodiments, the resource index for ACK/NACK transmission can be obtained based on the beamforming index, subframe/symbol/time slot index and/or PRB index used for PDSCH or PUSCH transmission. In addition, various combinations of the above parameters can be used to determine the resource index for transmitting ACK/NACK. In one example, the resource index for ACK/NACK transmission can be given by the following formula:

Where I _sym is the starting symbol index for transmitting PDSCH or PUSCH.

In another example, the resource index for ACK/NACK transmission may be given by:

Here, I _PRB is the starting PRB index used to transmit PDSCH or PUSCH.

In the above equation, for sequence-based ACK/NACK design, if separate resources are used for each ACK and NACK transmission, the resources used to transmit the NACK can be shifted by a constant from the resources used to transmit the ACK. The same design principle can be applied to the case of ACK/NACK feedback for the second transport block. The constant can be predefined or configured by higher layers via MIB, SIB, or dedicated UE-specific RRC signaling.

In one example, for the ACK/NACK feedback of the second transport block, the resource index may be given by:

where Δ is a constant.

In another example, the resource index may be given by:

In one example, when independent resources are used to transmit NACK, the cyclic shift may be given by:

Example 1 is an apparatus of a user equipment (UE), comprising: a transceiver arranged to communicate with an evolved Node B (eNB); and a processing circuit arranged to: configure the transceiver to receive a physical downlink shared channel (PDSCH) and an uplink (UL) hybrid automatic repeat request acknowledgment/negative acknowledgment (HARQ ACK/NACK) associated with the UE from the eNB; determine resources for downlink (DL) HARQ ACK/NACK in response to the PDSCH; and configure the transceiver to send DL HARQ ACK/NACK to the eNB, wherein the UL HARQ ACK/NACK and the DL HARQ ACK/NACK are symmetric.

In Example 2, the subject matter of Example 1 optionally includes: wherein, UL HARQ ACK/NACK is sent in a UL HARQ ACK/NACK channel, UL HARQ ACK/NACK for multiple UEs is multiplexed in the UL HARQ ACK/NACK channel in at least one of time division multiplexing (TDM), frequency division multiplexing (FDM) and code division multiplexing (CDM), and the UL HARQ ACK/NACK is down-converted to baseband through a mixer circuit before the resources are determined.

In Example 3, the subject matter of Example 2 optionally includes: wherein the UL HARQ ACK/NACK channel uses a localized transmission scheme in which the system bandwidth is divided into multiple subbands and each subband includes UL HARQ ACK/NACK for different UEs and includes multiple subcarriers.

In Example 4, the subject matter of any one or more of Examples 2-3 optionally includes: wherein the UL HARQ ACK/NACK channel uses a distributed transmission scheme, in which the system bandwidth is divided into multiple subbands, each subband includes UL HARQ ACK/NACK for different UEs, and is divided into multiple subcarrier blocks, each subcarrier block of a particular subband occupies multiple subcarriers and is separated from another subcarrier block of the particular subband by a subcarrier block of another subband.

In Example 5, the subject matter of any one or more of Examples 2-4 optionally includes: wherein the UL HARQ ACK/NACK channel uses a transmission scheme in which the system bandwidth is divided into multiple subbands and each subband includes UL HARQ ACK/NACK for different UEs, and uses a dedicated sequence selected from one of a Zadoff-Chu (ZC) sequence, an M sequence, a Hadamard sequence, and a sequence satisfying a constant amplitude zero autocorrelation (CAZAC) property.

In Example 6, the subject matter of Example 5 may optionally include: wherein the UL HARQ ACK/NACK of the UE includes separate ACK responses and NACK responses using independent resources.

In Example 7, the subject matter of any one or more of Examples 5-6 optionally includes: wherein the UE's UL HARQ ACK/NACK includes a single resource for both an ACK response and a NACK response, and the processing circuit is arranged to determine that a NACK response is indicated by a lack of an ACK response in the single resource.

In Example 8, the subject matter of any one or more of Examples 5-7 optionally includes: wherein the sequence includes a ZC sequence, the ZC sequence includes a basic sequence, and the basic sequence is determined based on at least one of a physical cell identifier, a virtual cell identifier, a time slot index of UL HARQ ACK/NACK, a subframe index of UL HARQ ACK/NACK, and a frame index of UL HARQ ACK/NACK.

In Example 9, the subject matter of any one or more of Examples 1-8 optionally includes: applying a repetition code of a predetermined length to the ACK/NACK bits to form repeated bits, modulating the repeated bits using one of binary phase shift keying (BPSK) and quadrature PSK (QPSK) to form modulated symbols, applying a spreading code to the modulated symbols to form spread symbols, applying cell-specific scrambling to the spread symbols to form scrambled symbols, a scrambling seed for the cell-specific scrambling being defined as a function of at least one of a physical cell identifier, a virtual cell identifier, a time slot index of the UL HARQ ACK/NACK, a subframe index of the UL HARQ ACK/NACK, and a frame index of the UL HARQ ACK/NACK, and the scrambled signal being mapped starting from a lowest frequency index within an allocated subband to form a modulated ACK/NACK symbol of the UL HARQ ACK/NACK.

In Example 10, the subject matter of any one or more of Examples 1-9 optionally includes: wherein an ACK/NACK resource for UL HARQ ACK/NACK is determined using a function of a subband index (I_SB) and a spreading code index (I_SF) for UL HARQ ACK/NACK, the resource index for UL HARQ ACK/NACK is a function of a cell-specific parameter, a UE-specific parameter, a parameter signaled in a DCI format, and at least one of the following items for one of PDSCH and a physical uplink shared channel (PUSCH): a beamforming index, a time slot index, a subframe index, a frame index, and a physical resource block index, and the cell-specific parameter is configured by a master information block (MIB), a system information block (SIB), or dedicated RRC signaling, the UE-specific parameter is configured from one of a primary cell and a serving cell via dedicated RRC signaling, and the parameter signaled in a DCI format is one of a subband index and a demodulation reference signal (DM-RS) for one of PDSCH and PUSCH.

In Example 11, the subject matter of any one or more of Examples 1-10 optionally includes at least one of the following items: DL HARQ ACK/NACK is time-division multiplexed with a physical uplink control channel (PUCCH) and sent in a beamformed DL HARQ ACK/NACK channel; and UL HARQ ACK/NACK is time-division multiplexed with a physical downlink control channel (PDCCH) and received in a beamformed UL HARQ ACK/NACK channel.

In Example 12, the subject matter of Example 11 optionally includes at least one of the following items: the beamforming weights of the DL HARQ ACK/NACK channel are dynamically adjusted to follow the beamforming of the PDSCH, so that the transmit analog beam direction of the DL HARQ ACK/NACK channel is based on the PDSCH; and the beamforming weights of the UL HARQ ACK/NACK channel are dynamically adjusted to follow the beamforming of the previous PUSCH, so that the transmit analog beam direction of the UL HARQ ACK/NACK channel is based on the previous PUSCH, and the digital precoding of the UL HARQ ACK/NACK channel is based on the channel estimate obtained from the UL demodulation reference signal (DMRS) sent by the UE.

In Example 13, the subject matter of any one or more of Examples 11-12 optionally includes at least one of the following items: for DL HARQ ACK/NACK: the DL HARQ ACK/NACK symbol is the first symbol of the UL Transmission Time Interval (TTI), the DL HARQ ACK/NACK symbol is adjacent to the PUSCH, and a sounding reference signal (SRS) and a DL HARQ ACK/NACK channel are allocated at the end of the UL TTI after the PUSCH; and for UL HARQ ACK/NACK: the UL HARQ ACK/NACK symbol is the first symbol of the DL TTI, the UL HARQ ACK/NACK symbol is adjacent to the PDSCH, and the UL HARQ ACK/NACK channel is arranged at the end of the DL TTI after the PDSCH.

In Example 14, the subject matter of Example 13 optionally includes at least one of the following items: a physical downlink control channel (PDCCH) received by the UE includes a UL grant for sending a PUSCH, and the UL grant includes an indicator indicating one of a plurality of values, one of which indicates that DL HARQ ACK/NACK resources for DL HARQ ACK/NACK symbols do not have a mapping of PUSCH to DL HARQ ACK/NACK resources, and another value indicates that the PUSCH is to be mapped to DL HARQ ACK/NACK resources; and the PDCCH includes a DL allocation, the DL allocation including an indicator indicating one of a plurality of values, one of which indicates that UL HARQ ACK/NACK resources for UL HARQ ACK/NACK symbols do not have a mapping of PDSCH to UL HARQ ACK/NACK resources, and another value indicates that the PDSCH is mapped to the UL HARQ ACK/NACK resources.

In Example 15, the subject matter of any one or more of Examples 11-14 may optionally include: wherein the DL HARQ ACK/NACK and the UL HARQ ACK/NACK are included in a special subframe.

In Example 16, the subject matter of any one or more of Examples 1-15 may optionally further include an antenna configured to provide communication between the transceiver and the eNB.

Example 17 is an apparatus of an evolved Node B (eNB), comprising: a transceiver arranged to communicate with a plurality of user equipments (UEs); and a processing circuit arranged to: configure the transceiver to receive a physical uplink shared channel (PUSCH) from each UE; determine, in response to the PUSCH, an uplink hybrid automatic repeat request acknowledgement/negative acknowledgement (UL HARQ ACK/NACK) channel of each UE multiplexed using at least one of time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM) in a UL HARQ ACK/NACK channel; and configure the transceiver to send the UL HARQ ACK/NACK channel to the UE.

In Example 18, the subject matter of Example 17 optionally includes: wherein the UL HARQ ACK/NACK channel uses the following transmission scheme, in which the system bandwidth is divided into multiple subbands, and each subband includes UL HARQ ACK/NACK for different UEs and occupies multiple subcarriers; each subband uses a dedicated sequence selected from one of a Zadoff-Chu (ZC) sequence, an M sequence, a Hadamard sequence, and a sequence satisfying a constant amplitude zero autocorrelation (CAZAC) property, the ZC sequence includes a basic sequence, and the basic sequence is determined according to at least one of the following items: a physical cell identifier, a virtual cell identifier, a time slot index of the UL HARQ ACK/NACK, a subframe index of the UL HARQ ACK/NACK, and a UL HARQ The frame index of ACK/NACK is determined, and one of the following is performed: a) the transmission scheme is a localized transmission scheme in which, for each subband, the subcarriers in the subband are adjacent to each other, and b) the transmission scheme is a distributed transmission scheme in which each subband is divided into a plurality of subcarrier blocks, and each subcarrier block is separated from another subcarrier block of the specific subband by a subcarrier block of another subband.

In Example 19, the subject matter of Example 18 optionally includes: wherein, for at least one of the UEs, one of the following items exists: the UL HARQ ACK/NACK includes separate ACK responses and NACK responses using independent resources; and the processing circuit is arranged to: determine whether the transceiver is to send an ACK response in the resources of the UL HARQ ACK/NACK, and in response to determining that the resources do not include an ACK response, send a UL HARQ ACK/NACK channel to the UE whose resources do not include an ACK response to indicate a NACK response to the PUSCH of at least one of the UEs.

In Example 20, the subject matter of any one or more of Examples 17-19 optionally includes: wherein, for at least one of the UEs, the processing circuit is further arranged to: apply a repetition code of a predetermined length to the ACK/NACK bits to form repeated bits, modulate the repeated bits using one of binary phase shift keying (BPSK) and quadrature PSK (QPSK) to form modulated symbols, spread the modulated symbols using a spreading code to form spread symbols, scramble the spread symbols using cell-specific scrambling to form scrambled symbols, a scrambling seed for the cell-specific scrambling being defined as a function of at least one of a physical cell identifier, a virtual cell identifier, a time slot index of the UL HARQ ACK/NACK, a subframe index of the UL HARQ ACK/NACK, and a frame index of the UL HARQ ACK/NACK, and map the scrambled signal starting from the lowest frequency index within the allocated subband to form a modulated ACK/NACK symbol of the UL HARQ ACK/NACK.

In Example 21, the subject matter of any one or more of Examples 17-20 optionally includes: for at least one of the UEs: UL HARQ ACK/NACK is time division multiplexed with a physical downlink control channel (PDCCH), and the beamforming weights of the UL HARQ ACK/NACK channel are dynamically adjusted to follow the beamforming of a previous PUSCH, so that the transmit analog beam direction of the UL HARQ ACK/NACK channel is based on the previous PUSCH, and the digital precoding of the UL HARQ ACK/NACK channel is based on a channel estimate obtained from a UL demodulation reference signal (DMRS) sent by the UE.

In Example 22, the subject matter of Example 21 optionally includes at least one of the following items: a) one of the following items: the UL HARQ ACK/NACK symbol is the first symbol of a DL transmission time interval (TTI), the UL HARQ ACK/NACK symbol is adjacent to a physical downlink shared channel (PDSCH), and the UL HARQ ACK/NACK channel is arranged at the end of the DL TTI after the PDSCH; and b) the PDCCH includes a DL allocation, the DL allocation includes an indicator, the indicator having one of multiple values, one value indicating that the UL HARQ ACK/NACK resources for the UL HARQ ACK/NACK symbol have no mapping of PDSCH to UL HARQ ACK/NACK resources, and another value indicating that the PDSCH will be mapped to the UL HARQ ACK/NACK resources.

Example 23 is a computer-readable storage medium storing instructions for execution by one or more processors of a user equipment (UE) to communicate with an evolved Node B (eNB), the one or more processors being configured to: receive a physical downlink shared channel (PDSCH) from the eNB, receive an uplink hybrid automatic repeat request acknowledgement/negative acknowledgement (UL HARQ ACK/NACK) channel, multiplexed with a UL HARQ ACK/NACK for another UE using at least one of time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM); determine resources for downlink (DL) HARQ ACK/NACK in response to the PDSCH; and send a DL HARQ ACK/NACK to the eNB in the DL HARQ ACK/NACK channel.

In Example 24, the subject matter of Example 23 optionally includes: wherein the DL HARQ ACK/NACK channel uses the following transmission scheme, in which the system bandwidth is divided into multiple subbands, and each subband includes DL HARQ ACK/NACK for different UEs and occupies multiple subcarriers; the subband of the UE uses a dedicated sequence selected from a Zadoff-Chu (ZC) sequence, an M sequence, a Hadamard sequence, and a sequence satisfying a constant amplitude zero autocorrelation (CAZAC) property, the ZC sequence includes a basic sequence, and the basic sequence is determined according to at least one of the following items: a physical cell identifier, a virtual cell identifier, a time slot index of the DL HARQ ACK/NACK, a subframe index of the DL HARQ ACK/NACK, and a DL HARQ The frame index of the ACK/NACK, and one of the following: a) the transmission scheme is a localized transmission scheme in which, for each subband, the subcarriers in the subband are adjacent to each other, and b) the transmission scheme is a distributed transmission scheme in which each subband is divided into a plurality of subcarrier blocks, and each subcarrier block is separated from another subcarrier block of the particular subband by a subcarrier block of another subband.

In Example 25, the subject matter of any one or more of Examples 23-24 optionally includes: wherein the DL HARQ ACK/NACK includes separate ACK responses and NACK responses using independent resources, and the one or more processors further configure the UE to: determine whether the transceiver is to send an ACK response in the resources of the DL HARQ ACK/NACK, and in response to determining that the resources do not include the ACK response, send a DL HARQ ACK/NACK channel to the eNB whose resources do not include the ACK response to indicate a NACK response to the PUSCH.

In Example 26, the subject matter of any one or more of Examples 23-25 optionally includes: wherein the UL HARQ ACK/NACK is time division multiplexed with a physical uplink control channel (PUCCH), and the beamforming weights of the DL HARQ ACK/NACK channel are dynamically adjusted to follow the beamforming of the PDSCH, so that the transmit analog beam direction of the DL HARQ ACK/NACK channel is based on the PDSCH.

In Example 27, the subject matter of any one or more of Examples 23-26 optionally includes at least one of the following items: a) one of the following items; the DL HARQ ACK/NACK symbol is the first symbol of a UL transmission time interval (TTI), the DL HARQ ACK/NACK symbol is adjacent to a physical uplink shared channel (PUSCH), and the DL HARQ ACK/NACK channel is arranged at the end of the UL TTI after the PDSCH; and b) a physical downlink control channel (PDCCH) received by the UE includes a UL grant for sending the PUSCH, and the UL grant includes an indicator that indicates one of multiple values, one value indicating that the DL HARQ ACK/NACK resources for the DL HARQ ACK/NACK symbol have no mapping of PUSCH to DL HARQ ACK/NACK resources, and another value indicating that the PUSCH will be mapped to the DL HARQ ACK/NACK resources.

Although the embodiments have been described with reference to specific example embodiments, it will be apparent that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the present disclosure. Accordingly, the description and drawings should be considered in an illustrative rather than a restrictive sense. The drawings forming a part hereof show, by way of illustration and not limitation, specific embodiments in which the subject matter may be practiced. The embodiments shown are described in sufficient detail to enable those skilled in the art to implement the teachings disclosed herein. Other embodiments may be utilized and derived therefrom so that structural and logical substitutions and changes may be made without departing from the scope of the present disclosure. Accordingly, this detailed description should not be regarded as having a restrictive meaning, and the scope of the various embodiments is limited only by the appended claims, together with the full scope of equivalents to which such claims are entitled.

Such embodiments of the subject matter of the present invention may be referred to herein individually and/or collectively by the term "invention", which is merely for convenience and is not intended to voluntarily limit the scope of this application to any single invention or inventive concept (if in fact more than one is disclosed). Therefore, although specific embodiments have been shown and described herein, it should be understood that any arrangement calculated to achieve the same purpose can replace the specific embodiments shown. This disclosure is intended to cover any and all modifications or variations of the various embodiments. Combinations of the above embodiments, as well as other embodiments not specifically described herein, will be apparent to those skilled in the art upon reading the above description.

In this document, the term "a or an" commonly used in patent documents is used to include one or more than one, which is independent of any other instance or use of "at least one" or "one or more". In this document, the term "or" is used to refer to a non-exclusive or, so that unless otherwise specified, "A or B" includes "is A but not B", "is B but not A", and "A and B". In this document, the terms "including" and "in which" are used as the plain English equivalents of the corresponding terms "comprising" and "wherein". In addition, in the appended claims, the terms "including" and "comprising" are open-ended, that is, a system, UE, article, composition, formula, or process that includes elements other than those listed after such a term in a claim is still considered to fall within the scope of the claim. In addition, in the appended claims, the terms "first", "second", and "third" are used merely as labels and are not intended to impose numerical requirements on their objects.

The Abstract of the Disclosure is provided to comply with the requirement of 37 C.F.R. Section 1.72(b) that the abstract will allow the reader to quickly ascertain the nature of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope of the claims. Additionally, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as reflected in the appended claims, the inventive subject matter lies in less than all the features of a single disclosed embodiment. Accordingly, the appended claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.

Claims (27)

1. An apparatus comprising: Transceiver, the transceiver being configured to communicate with an evolved Node B (eNB); and Processing circuitry, the processing circuitry being arranged to enable the user equipment (UE): The transceiver is configured to receive data from the eNB in the Physical Downlink Shared Channel (PDSCH) associated with the UE; In response to the PDSCH, resources for downlink (DL) hybrid automatic repeat request acknowledgment/negative acknowledgment (HARQACK/NACK) are determined; and The transceiver is configured to send the DL HARQ ACK/NACK to the eNB, wherein the DL HARQ ACK/NACK uses the same basic sequence but different cyclic shifts, the cyclic shifts depending on whether the received uplink (UL) HARQ ACK/NACK is UL HARQ ACK or UL HARQ NACK, wherein the cyclic shifts are determined based on an initial cyclic shift, a cell ID, and a predetermined constant shift function, and a modulo-12 operation performed on the function, the predetermined constant shift depending on whether the UL HARQ ACK/NACK is UL HARQ ACK or UL HARQ NACK, and wherein the initial cyclic shift is provided by a higher layer via dedicated UE-specific RRC signaling. 2. The apparatus according to claim 1, wherein: The UL HARQ ACK/NACK is transmitted in the UL HARQ ACK/NACK channel. The UL HARQ ACK/NACK for multiple UEs is multiplexed in the UL HARQ ACK/NACK channel in at least one of the time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM) modes. The UL HARQ ACK/NACK is down-converted to baseband by a mixer circuit before the resources are determined. 3. The apparatus according to claim 2, wherein: The UL HARQ ACK/NACK channel uses a local transmission scheme in which the system bandwidth is divided into multiple sub-bands, and Each subband includes UL HARQ ACK/NACK for different UEs, and each subband includes multiple subcarriers. 4. The apparatus according to claim 2, wherein: The UL HARQ ACK/NACK channel uses a distributed transmission scheme, in which the system bandwidth is divided into multiple subbands. Each subband includes UL HARQ ACK/NACK for different UEs, and each subband is divided into multiple subcarrier blocks. Each subcarrier block of a specific subband occupies multiple subcarriers, and each subcarrier block of the specific subband is separated from another subcarrier block of the specific subband by a subcarrier block of another subband. 5. The apparatus according to claim 2, wherein: The UL HARQ ACK/NACK channel uses a transmission scheme in which the system bandwidth is divided into multiple subbands, and Each subband includes UL HARQ ACK/NACK for different UEs, and each subband uses a dedicated sequence selected from one of the following sequences: Zadoff-Chu (ZC) sequence, M sequence, Hadamard sequence, and sequence that satisfies the constant amplitude zero autocorrelation (CAZAC) property. 6. The apparatus according to claim 5, wherein: The UL HARQ ACK/NACK of the UE includes separate ACK and NACK responses using independent resources. 7. The apparatus according to claim 5, wherein: The UL HARQ ACK/NACK of the UE includes a single resource for both the ACK response and the NACK response, and The processing circuitry is configured to determine that a NACK response is indicated by the absence of an ACK response in the single resource. 8. The apparatus according to claim 5, wherein: The ZC sequence includes a basic sequence determined to be a function of at least one of the following: physical cell identifier, virtual cell identifier, slot index of the UL HARQ ACK/NACK, subframe index of the UL HARQ ACK/NACK, and frame index of the UL HARQ ACK/NACK. 9. The apparatus according to any one of claims 1-8, wherein: A repeat code of predetermined length is applied to the ACK/NACK bits to form the repeat bits. The repeated bits are modulated using either binary phase shift keying (BPSK) or quadrature PSK (QPSK) to form modulated symbols. The spreading code is applied to the modulated symbols to form the spreading symbols. Cell-specific scrambling is applied to the spreading symbols to form scrambled symbols. The cell-specific scrambling seed is defined as a function of at least one of the following: physical cell identifier, virtual cell identifier, slot index of the UL HARQ ACK/NACK, subframe index of the UL HARQ ACK/NACK, and frame index of the UL HARQ ACK/NACK. The scrambled symbols are mapped starting from the lowest frequency index within the assigned sub-band to form the modulated ACK/NACK symbols of the ULHARQ ACK/NACK. 10. The apparatus according to any one of claims 1-8, wherein: The ACK/NACK resources for the UL HARQ ACK/NACK are determined using a function of the sub-band index ( _ISB ) and spreading code index ( _ISF ) for the UL HARQ ACK/NACK. The resource index for the UL HARQ ACK/NACK is a function of cell-specific parameters, UE-specific parameters, parameters transmitted in DCI format, and at least one of the following for one of the PDSCH and Physical Uplink Shared Channel (PUSCH): beamforming index, slot index, subframe index, frame index, and physical resource block index. The cell-specific parameters are configured by the Master Information Block (MIB), System Information Block (SIB), or dedicated RRC signaling. The UE-specific parameters are configured from one of the primary cell and the serving cell via dedicated RRC signaling, and the parameters transmitted in the DCI format are one of the subband index and demodulation reference signal (DM-RS) for one of the PDSCH and the PUSCH. 11. The apparatus according to any one of claims 1-8, wherein at least one of the following is performed: The DL HARQ ACK/NACK is time-division multiplexed with the Physical Uplink Control Channel (PUCCH) and transmitted in a beamformed DL HARQ ACK/NACK channel; and The UL HARQ ACK/NACK is time-division multiplexed with the Physical Downlink Control Channel (PDCCH) and received in a beamformed UL HARQ ACK/NACK channel. 12. The apparatus according to claim 11, wherein at least one of the following is performed: The beamforming weights of the DL HARQ ACK/NACK channel are dynamically adjusted to follow the beamforming of the PDSCH, such that the transmit analog beam direction of the DL HARQ ACK/NACK channel is based on the PDSCH; and The beamforming weights of the UL HARQ ACK/NACK channel are dynamically adjusted to follow the beamforming of the previous PUSCH, such that the transmit analog beam direction of the UL HARQ ACK/NACK channel is based on the previous PUSCH, and the digital precoding of the UL HARQ ACK/NACK channel is based on the channel estimate obtained from the UL demodulation reference signal (DMRS) transmitted by the UE. 13. The apparatus according to claim 11, wherein at least one of the following is performed: For the aforementioned DL HARQ ACK/NACK: The DL HARQ ACK/NACK symbol is the first symbol of the UL Transmission Time Interval (TTI). The DL HARQ ACK/NACK symbol is adjacent to the PUSCH, and The Sound Reference Signal (SRS) and the DL HARQ ACK/NACK channel are assigned after the PUSCH at the end of the ULTTI; and For the aforementioned UL HARQ ACK/NACK: The UL HARQ ACK/NACK symbol is the first symbol used by DL TTI. The UL HARQ ACK/NACK symbol is adjacent to the PDSCH, and The UL HARQ ACK/NACK channel is positioned after the PDSCH at the end of the DL TTI. 14. The apparatus according to claim 13, wherein at least one of the following is performed: The Physical Downlink Control Channel (PDCCH) received by the UE includes a UL grant for transmitting the PUSCH, and the UL grant includes an indicator indicating one of a plurality of values, one value indicating that there is no mapping of the PUSCH to the DL HARQ ACK/NACK resource for the DL HARQ ACK/NACK symbol, and another value indicating that the PUSCH will be mapped to the DL HARQ ACK/NACK resource; and The PDSCH includes a DL allocation, which includes an indicator indicating one of a plurality of values, one value indicating that the UL HARQ ACK/NACK resource for the UL HARQ ACK/NACK symbol has no mapping of the PDSCH to the UL HARQ ACK/NACK resource, and another value indicating that the PDSCH is mapped to the UL HARQ ACK/NACK resource. 15. The apparatus according to claim 11, wherein: The DL HARQ ACK/NACK and the UL HARQ ACK/NACK are included in a special subframe. 16. The apparatus according to any one of claims 1-8, further comprising: an antenna configured to provide communication between the transceiver and the eNB. 17. An apparatus comprising: A transceiver, the transceiver being configured to communicate with a plurality of user equipments (UEs); and Processing circuitry, the processing circuitry being arranged to enable the evolved Node B (eNB): Configure the transceiver to receive the Physical Uplink Shared Channel (PUSCH) from each UE; In response to the PUSCH, perform at least one of time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM) for each UE's UL HARQ ACK/NACK in the uplink hybrid automatic repeat request acknowledgment/negative acknowledgment (UL HARQ ACK/NACK) channel; The transceiver is configured to send the UL HARQ ACK/NACK to the UE in the UL HARQ ACK/NACK channel; The transceiver is configured to receive downlink (DL) HARQ ACK/NACK from a first UE, wherein the DL HARQ ACK/NACK uses the same basic sequence but different cyclic shifts, the cyclic shifts depending on whether the UL HARQ ACK/NACK for the first UE is a UL HARQ ACK or a UL HARQ NACK, wherein the cyclic shifts are determined based on an initial cyclic shift, a cell ID, and a predetermined constant shift function, and a modulo-12 operation performed on the function, the predetermined constant shift depending on whether the UL HARQ ACK/NACK is a UL HARQ ACK or a UL HARQ NACK, and wherein the initial cyclic shift is provided by a higher layer via dedicated UE-specific RRC signaling. 18. The apparatus according to claim 17, wherein: The UL HARQ ACK/NACK channel uses the following transmission scheme, in which the system bandwidth is divided into multiple subbands, and each subband includes UL HARQ ACK/NACK for different UEs and occupies multiple subcarriers; Each subband uses a dedicated sequence selected from one of the ZadofT-Chu (ZC) sequences, M sequences, Hadamard sequences, and sequences satisfying the constant amplitude zero autocorrelation (CAZAC) property. The ZC sequence includes a base sequence determined as a function of at least one of the following: physical cell identifier, virtual cell identifier, slot index of the UL HARQ ACK/NACK, subframe index of the UL HARQ ACK/NACK, and frame index of the UL HARQ ACK/NACK, and performs one of the following: The transmission scheme is a local transmission scheme, wherein, for each subband, the subcarriers in the subband are adjacent to each other, and The transmission scheme is a distributed transmission scheme, wherein each subband is divided into multiple subcarrier blocks, and each subcarrier block is separated from another subcarrier block in the multiple subcarrier blocks by a subcarrier block in another subband. 19. The apparatus of claim 18, wherein, for at least one of the UEs, one of the following is performed: The UL HARQ ACK/NACK includes separate ACK and NACK responses using independent resources; and The processing circuit is arranged as follows: Determine whether the transceiver should send an ACK response in the UL HARQ ACK/NACK resource, and In response to determining that the resource does not include the ACK response, the UL HARQ ACK/NACK channel indicating that the resource does not include the ACK response is sent to the UE to indicate a NACK response to the PUSCH of at least one of the UEs. 20. The apparatus according to any one of claims 17-19, wherein, for at least one of the UEs, the processing circuitry is further arranged as follows: A repeating code of a predetermined length is applied to the ACK/NACK bits to form repeating bits. The repeated bits are modulated using either Binary Phase Shift Keying (BPSK) or Quadrature PSK (QPSK) to form modulated symbols. The modulated symbols are spread using spreading codes to form spreading symbols. The spread spectrum symbols are scrambled using cell-specific scrambling to form scrambled symbols. The scrambling seed for the cell-specific scrambling is defined as a function of at least one of the following: physical cell identifier, virtual cell identifier, slot index of the UL HARQ ACK/NACK, subframe index of the UL HARQ ACK/NACK, and frame index of the UL HARQ ACK/NACK. The scrambled symbols are mapped starting from the lowest frequency index within the assigned sub-band to form the modulated ACK/NACK symbols of the ULHARQ ACK/NACK. 21. The apparatus according to any one of claims 17-19, wherein, for at least one of the UEs: The UL HARQ ACK/NACK is time-division multiplexed with the Physical Downlink Control Channel (PDCCH), and The beamforming weights of the UL HARQ ACK/NACK channel are dynamically adjusted to follow the beamforming of the previous PUSCH, such that the transmit analog beam direction of the UL HARQ ACK/NACK channel is based on the previous PUSCH, and the digital precoding of the UL HARQ ACK/NACK channel is based on the channel estimate obtained from the UL demodulation reference signal (DMRS) transmitted by the UE. 22. The apparatus of claim 21, wherein at least one of the following is performed: One of the following: the UL HARQ ACK/NACK symbol is the first symbol of the DL Transmission Time Interval (TTI), the UL HARQ ACK/NACK symbol is adjacent to the Physical Downlink Shared Channel (PDSCH), and the UL HARQ ACK/NACK channel is positioned after the PDSCH at the end of the DL TTI; and The PDSCH includes a DL allocation, which includes an indicator having multiple values, one of which indicates that the UL HARQ ACK/NACK resource for the UL HARQ ACK/NACK symbol does not have a mapping of the PDSCH to the UL HARQ ACK/NACK resource, and another value indicates that the PDSCH will be mapped to the UL HARQ ACK/NACK resource. 23. A computer-readable storage medium storing instructions for execution by one or more processors of a user equipment (UE) to communicate with an evolved Node B (eNB), the one or more processors configuring the UE to: Receive the Physical Downlink Shared Channel (PDSCH) associated with the UE from the eNB; In response to the PDSCH, resources for downlink (DL) hybrid automatic repeat request acknowledgment/negative acknowledgment (HARQACK/NACK) are determined; and The DL HARQ ACK/NACK is transmitted to the eNB in the DL HARQ ACK/NACK channel, wherein the DL HARQ ACK/NACK uses the same basic sequence but different cyclic shifts, the cyclic shifts depending on whether the received uplink (UL) HARQ ACK/NACK is UL HARQ ACK or UL HARQ NACK, wherein the cyclic shifts are determined based on an initial cyclic shift, a cell ID, and a predetermined constant shift function, and a modulo-12 operation performed on the function, the predetermined constant shift depending on whether the UL HARQ ACK/NACK is UL HARQ ACK or UL HARQ NACK, and wherein the initial cyclic shift is provided by a higher layer via dedicated UE-specific RRC signaling. 24. The medium according to claim 23, wherein: The DL HARQ ACK/NACK channel uses the following transmission scheme, in which the system bandwidth is divided into multiple subbands, and each subband includes DL HARQ ACK/NACK for different UEs and occupies multiple subcarriers; For the subband of the UE, a dedicated sequence is selected from one of the Zadoff-Chu (ZC) sequence, the M sequence, the Hadamard sequence, and a sequence that satisfies the constant amplitude zero autocorrelation (CAZAC) property. The ZC sequence includes a base sequence, which is determined to be a function of at least one of the following: physical cell identifier, virtual cell identifier, slot index of the DL HARQ ACK/NACK, subframe index of the DL HARQ ACK/NACK, and frame index of the DL HARQ ACK/NACK, and performs one of the following: The transmission scheme is a local transmission scheme, wherein, for each subband, the subcarriers in the subband are adjacent to each other, and The transmission scheme is a distributed transmission scheme, wherein each subband is divided into multiple subcarrier blocks, and each subcarrier block is separated from another subcarrier block in the multiple subcarrier blocks by a subcarrier block in another subband. 25. The medium according to claim 23 or 24, wherein: The DL HARQ ACK/NACK includes separate ACK and NACK responses using independent resources, and The one or more processors also configure the UE to: Determine whether the transceiver should send an ACK response in the DL HARQ ACK/NACK resource, and In response to determining that the resource does not include the ACK response, the DL HARQ ACK/NACK is sent to the eNB in the DL HARQ ACK/NACK channel where the resource does not include the ACK response, to indicate a NACK response to the PDSCH. 26. The medium according to claim 23 or 24, wherein: The UL HARQ ACK/NACK is time-division multiplexed with the Physical Uplink Control Channel (PUCCH), and The beamforming weights of the DL HARQ ACK/NACK channel are dynamically adjusted to follow the beamforming of the PDSCH, such that the transmit analog beam direction of the DL HARQ ACK/NACK channel is based on the PDSCH. 27. The medium according to claim 23 or 24, wherein at least one of the following is performed: One of the following: the DL HARQ ACK/NACK symbol is the first symbol of the UL Transmission Time Interval (TTI), the DL HARQ ACK/NACK symbol is adjacent to the Physical Uplink Shared Channel (PUSCH), and the DL HARQ ACK/NACK channel is allocated after the PDSCH at the end of the UL TTI; and The physical downlink control channel (PDCCH) received by the UE includes a UL grant for transmitting the PUSCH, and the UL grant includes an indicator indicating one of a plurality of values, one value indicating that there is no mapping of the PUSCH to the DL HARQ ACK/NACK resource for the DL HARQ ACK/NACK symbol, and another value indicating that the PUSCH will be mapped to the DL HARQ ACK/NACK resource.