HK1150920A - Methods of reliably sending control signal - Google Patents

Abstract

Downlink PDCCH is communicated in a manner that mitigates a UE from decoding the PDCCH on multiple aggregation levels. Ambiguous payload sizes are identified and modified through zero padding with one or more bits based on the payload size. Aggregation level scrambling sequences can be generated such that a receiving UE can accurately identify the aggregation level on which to decode the PDCCH. Indicator bits that signal the aggregation level to a UE can also be included in the PDCCH.

Description

Method for reliably transmitting control signal

This patent application claims priority from a provisional application No. 61/040,823 entitled "method OF RELIABLY SENDING CONTROL SIGNALs (method OF RELIABLY SENDING CONTROL SIGNALs)" filed on 31/3/2008, a provisional application No. 61/053,347 entitled "method OF RELIABLY SENDING CONTROL SIGNALs (method OF RELIABLY SENDING CONTROL SIGNALs)" filed on 15/5/2008, and a provisional application No. 61/074,861 entitled "method OF RELIABLY SENDING CONTROL SIGNALs (method OF RELIABLY SENDING CONTROL SIGNALs)" filed on 23/6/2008. All of the above-mentioned provisional applications are assigned to the present assignee and are expressly incorporated herein by reference.

Technical Field

The following description relates generally to wireless communication systems, and more particularly to control signals.

Background

Generally, a wireless multiple-access communication system can simultaneously support communication for a plurality of wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-input single-output system, a multiple-input single-output system, or a multiple-input multiple-output (MIMO) system.

MIMO systems employing multiple (N)_T) Transmitting antenna and a plurality of (N)_R) The receiving antenna is used for data transmission. From N_TA transmitting antenna and N_RThe MIMO channel formed by the receiving antennas can be decomposed into N_SIndividual channels (which are also referred to as spatial channels), where N_S≤min{N_T，N_R}。N_SEach of the independent channels corresponds to a dimension. MIMO systems may provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.

MIMO systems support Time Division Duplex (TDD) and Frequency Division Duplex (FDD) systems. In a TDD system, the forward link transmission and the reverse link transmission are on the same frequency region, so that the reciprocity principle (reciprocity principle) allows the estimation of the forward link channel from the reverse link channel. This enables the access point to extract transmit beamforming gain on the forward link when multiple antennas are available at the access point.

In wireless communication systems, physical channels are typically further divided into dedicated channels and common channels depending on the entity being served. Dedicated channels are assigned to facilitate communication between a base station and a particular UE. A common channel is shared by different UEs and used by a base station to transmit signals, which are typically communicated to all users within a geographic area (cell) served by the base station. According to LTE technology, all allocations are signaled in a separately coded shared control channel. Thus, the downlink (or uplink) channel is divided into two separate parts, one for each of the control and data messages. The data part (PDSCH-physical downlink shared channel) carries downlink (or uplink) data for the simultaneously scheduled users, while the control Part (PDCCH) carries, among other things, allocation information for the scheduled users. Therefore, reliable exchange of control signals is essential for implementing an efficient wireless communication system.

Disclosure of Invention

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems.

According to an aspect, a transmission method that facilitates accurate decoding of PDCCH by a UE is disclosed. The method involves determining an aggregation level (aggregation level) of a downlink PDCCH for the UE. Analyzing a payload size of the PDCCH to determine whether it is ambiguous. In another aspect, the payload size n is ambiguous if it satisfies the condition n-m/k 24, where k, m are integers, m denotes the number of Control Channel Elements (CCEs) and k denotes the number of repetitions of the encoded block. In yet another aspect, if the maximum coding rate is x and 0 < x ≦ 1, then the corresponding maximum size of the ambiguous payload is 72 x (8-m) x. The ambiguous payload size is modified by zero-padding data packets of the downlink PDCCH with one or more bits and transmitting a payload with the zero-padded data packets. The number of bits used for zero padding may be based on the payload size.

Another aspect relates to a processor configured to facilitate accurate decoding of PDCCH by a UE. The processor can include a first module for determining whether a payload size of the PDCCH is ambiguous. In another aspect, if the payload size n is m/k 24 and the payload size n is less than 72 x (8-m) x, then n is ambiguous, where x is the maximum coding rate and 0 < x ≦ 1. The variables k, m are integers, m represents the number of CCEs and m is less than 8. The integer k represents the number of repetitions of the encoded block. For ambiguous payload sizes, a second module also included within the processor changes the size of the payload by zero-filling data packets of the downlink PDCCH with one or more bits for ambiguous payload sizes.

According to another aspect, a computer program product is disclosed that includes a computer-readable medium. The computer-readable medium includes a first set of codes for causing a computer to determine whether a payload size of a data packet of a downlink PDCCH is ambiguous. The medium may also include a second set of codes for causing the computer to include one or more bits in the data packet corresponding to the ambiguous payload size for zero padding. A third set of codes also included in the medium determines a number of bits for zero padding based at least on the payload size. According to yet another aspect, the payload size (n) is ambiguous if the payload size n is m/k 24, where k, m are integers. The variable m is less than 8, m representing the number of CCEs. The variable k represents the number of repetitions of the encoded block.

In another aspect, an apparatus for facilitating accurate decoding of PDCCH by a UE is disclosed. The apparatus includes means for determining a payload size of the PDCCH, and means for zero-filling data packets of the downlink PDCCH by including one or more bits for ambiguous payload sizes. After processing, the zero-padded payload is transmitted with a transmitting device also included in the apparatus.

In another aspect, a wireless communications apparatus is disclosed that includes a memory and a processor. The memory stores instructions for analyzing whether a data packet for transmission in a downlink PDCCH has a size in question. If the packet has a size in question, the memory further stores instructions for changing the size of such data packets by zero-filling such data packets with one or more bits based on the payload size. A processor coupled to the memory is configured to execute instructions stored in the memory.

In this aspect, a method of identifying a valid ACK/NACK from among a plurality of ACK/NACKs (acknowledgement/negative acknowledgements) received from a UE on different aggregation levels is disclosed. According to this aspect, it is initially determined whether more than one ACK/NACK is received from the UE. If multiple ACK/NACKs have been received, an aggregation level corresponding to a downlink PDCCH for which the UE has transmitted the multiple ACK/NACKs is also identified. Decoding all ACKs/NACKs received from a UE for all active aggregation levels less than or equal to the aggregation level of the downlink PDCCH. Attributes associated with each of the decoded ACK/NACKs are then analyzed, and a valid ACK/NACK from the plurality of ACK/NACKs is selected based at least on the analyzed attributes. In another aspect, the attribute may include SNR statistics and the ACK/NACK with the best SNR is identified as a valid ACK/NACK from the plurality of decoded ACK/NACKs. In another aspect, the attribute includes a transmit energy such that an ACK/NACK with the highest energy is identified as a valid ACK/NACK from the plurality of decoded ACK/NACKs.

According to another aspect, a wireless communications apparatus is disclosed that includes a memory and a processor. The memory stores instructions for determining attributes of a plurality of ACKs/NACKs received from a UE in response to a transmitted downlink PDCCH. Selecting a valid ACK/NACK from the plurality of ACK/NACKs based at least on attributes associated with the plurality of received ACK/NACKs. The processor is coupled to the memory and configured to execute instructions stored in the memory.

According to another aspect, a computer program product is also disclosed, comprising a computer-readable medium. The product includes a first set of codes for determining whether more than one ACK/NACK is received from a UE. Also included within the medium is a second set of codes for identifying an aggregation level corresponding to a downlink PDCCH for which the UE has transmitted the plurality of ACK/NACKs. Decoding all ACK/NACKs received from a UE for all active aggregation levels less than or equal to the aggregation level of the downlink PDCCH in accordance with a third set of codes in the medium. A fourth set of codes analyzes attributes associated with each of the decoded ACK/NACKs, and a fifth set of codes selects a valid ACK/NACK from the plurality of ACK/NACKs based at least on the analyzed attributes.

Another aspect relates to a method that facilitates accurate decoding of PDCCH. The method involves determining an aggregation level to be used for downlink PDCCH transmissions to a particular UE, and determining an offset based at least on the aggregation level. Mapping resources for uplink ACK/NACK for the UE with an offset determined based on the aggregation level. Resource assignment messages with aggregation-level dependent offsets are generated and transmitted to the UE in the downlink PDCCH.

According to another aspect, a wireless communications apparatus is disclosed that includes a memory and a processor. The memory stores instructions for generating a resource assignment message with an aggregation-level dependent offset to be transmitted in a downlink PDCCH. A processor coupled to the memory is configured to execute instructions stored in the memory.

Another aspect relates to a computer program product that includes a computer-readable medium. The medium includes a first set of codes for determining an aggregation level to be used for downlink PDCCH transmission to a particular UE. Also included in the medium is a second set of codes for mapping resources for uplink ACK/NACKs for a UE with an offset determined based on the aggregation level. Resource assignment messages with aggregation-level dependent offsets are generated and transmitted to the UE on a downlink PDCCH according to third and fourth sets of codes, respectively, also included in the medium.

According to yet another aspect, an apparatus that facilitates accurate decoding of a PDCCH is disclosed. Including means for determining, means for mapping resources, and means for generating a resource assignment message. The means for determining is for identifying an aggregation level to be used for downlink PDCCH transmissions to a particular UE. Thus, the mapping means maps the resources for uplink ACK/NACK for a UE with an offset determined based on the aggregation level, while generating means, also included within the apparatus, generates messages to be transmitted in a downlink PDCCH.

In yet another aspect, a method that facilitates accurate decoding of a PDCCH is disclosed. The method involves determining an aggregation level associated with a downlink PDCCH, and generating a sequence corresponding to the aggregation level of the PDCCH. Cyclic Redundancy Check (CRC) bits for the downlink PDCCH are scrambled with the generated sequence and transmitted in the downlink PDCCH.

Another aspect relates to a wireless communications apparatus. The apparatus includes: a memory storing instructions for scrambling Cyclic Redundancy Check (CRC) bits for a downlink PDCCH with a generated sequence corresponding to an aggregation level of the downlink PDCCH; and a processor coupled to the memory and configured to execute instructions stored in the memory.

According to this aspect, a computer program product is disclosed, comprising a computer-readable medium. The medium includes code for determining an aggregation level associated with a downlink PDCCH and generating a scrambling sequence corresponding to the aggregation level of the PDCCH. It further includes code for scrambling Cyclic Redundancy Check (CRC) bits for the downlink PDCCH with the generated scrambling sequence and transmitting the scrambled bits in the downlink PDCCH.

Another aspect relates to an apparatus that facilitates accurate decoding of PDCCH. The apparatus includes means for scrambling Cyclic Redundancy Check (CRC) bits for a downlink PDCCH with an aggregation level dependent sequence, and means for transmitting the scrambled CRC bits.

According to yet another aspect, a method of receiving a PDCCH is disclosed. The method includes receiving and decoding a downlink PDCCH including CRC bits scrambled with an aggregation level dependent sequence. It further comprises the following steps: the decoded bits are descrambled using a scrambling sequence to identify an aggregation level associated with the sequence, and a CRC is checked for the identified aggregation level.

Another aspect relates to a wireless communications apparatus. The apparatus includes a memory storing instructions for descrambling decoded Cyclic Redundancy Check (CRC) bits received on a downlink PDCCH. The CRC bits are descrambled with a generated sequence corresponding to an aggregation level of a downlink PDCCH. A processor coupled to the memory is configured to execute instructions stored in the memory.

In yet another aspect, a computer program product is also disclosed, comprising a computer-readable medium. The medium includes code for determining an aggregation level associated with a downlink PDCCH and generating a sequence corresponding to the aggregation level of the PDCCH. Cyclic Redundancy Check (CRC) bits for the downlink PDCCH are scrambled with the generated sequence and transmitted in the downlink PDCCH.

Another aspect relates to an apparatus that facilitates accurate decoding of PDCCH. The apparatus includes means for receiving CRC bits scrambled with an aggregation-level dependent scrambling sequence, and means for decoding a received downlink PDCCH on an associated aggregation level. The aggregation level is obtained by descrambling Cyclic Redundancy Check (CRC) bits received in a downlink PDCCH with the aggregation level dependent sequence.

According to yet another aspect, a transmission method that facilitates accurate decoding of PDCCH by multiple UEs is disclosed. According to this method, an aggregation level associated with a downlink PDCCH for each of the plurality of UEs is initially identified. Scrambling sequences corresponding to aggregation levels for each of the UEs are generated, and CRC bits for each of the UEs are scrambled using the respective scrambling sequences. Scrambled CRC bits are then transmitted to each of the UEs in the downlink PDCCH on the identified aggregation level.

Another aspect relates to a wireless communications apparatus that includes a memory that stores instructions for generating respective scrambling sequences corresponding to an aggregation level of a downlink PDCCH for each of a plurality of UEs. A processor coupled to the memory is configured to execute instructions stored in the memory.

According to this aspect, a computer program product is disclosed, comprising a computer-readable medium. The medium includes code for identifying an aggregation level associated with a downlink PDCCH for each of the plurality of UEs. Also included within the medium is a second set of codes for generating scrambling sequences corresponding to an aggregation level for each of the UEs. CRC bits for each of the UEs are scrambled using respective scrambling sequences in accordance with a third set of codes included in the medium, and the scrambled CRC bits are transmitted to each of the UEs in a downlink PDCCH on the identified aggregation level in accordance with a fourth set of codes included in the medium.

According to yet another aspect, an apparatus that facilitates accurate decoding of a PDCCH is disclosed. The apparatus includes means for generating scrambling sequences based on respective aggregation levels associated with downlink PDCCHs to be received by each of a plurality of UEs. It also includes means for encoding CRC bits to be transmitted to the plurality of UEs with aggregation-level dependent scrambling sequences, and means for transmitting a PDCCH with the encoded CRC bits to one or more of the plurality of UEs.

According to yet another aspect, a transmission method that facilitates a UE to accurately decode PDCCH is disclosed. The method includes identifying an aggregation level to be associated with a downlink PDCCH of a particular UE and including at least one bit within the downlink PDCCH to indicate the aggregation level. In another aspect, the bit is included if the payload size associated with the downlink PDCCH is an ambiguous payload size that causes the receiving UE to decode the downlink PDCCH on more than one aggregation level.

According to yet another aspect, a wireless communications apparatus is disclosed that includes a memory and a processor. The memory stores instructions for transmitting one or more bits indicating an aggregation level associated with a downlink PDCCH to a receiving UE. The processor is coupled to the memory and configured to execute instructions stored in the memory.

According to yet another aspect, a computer program product is disclosed that includes a computer-readable medium. The medium includes a first set of codes for identifying an aggregation level associated with a downlink PDCCH for a UE. A second set of codes is also included in the medium for including one or more bits within the PDCCH such that it indicates the aggregation level to the UE.

Another aspect relates to an apparatus that facilitates accurate decoding of PDCCH. The apparatus includes means for identifying an aggregation level associated with a downlink PDCCH for a particular UE. A PDCCH including one or more bits indicating an aggregation level is sent to a UE by a transmitting means also included within the apparatus.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed and this description is intended to include all such aspects and their equivalents.

Drawings

Fig. 1 is a schematic diagram of a multiple access wireless communication system, in accordance with one or more aspects.

FIG. 2 is a schematic diagram illustrating search spaces associated with different aggregation levels for various users.

Fig. 3 illustrates an example of a repetition of a particular payload size (48 bits).

Fig. 4 illustrates a method of transmission according to an aspect.

Fig. 5 details a transmission method that facilitates accurate decoding of PDCCH by a UE, according to an aspect.

Fig. 6 illustrates a reception method that accounts for consequences due to multiple CRC passes in accordance with an aspect.

Fig. 7 is a flowchart detailing a method of accurately identifying an ACK/NACK from a plurality of ACK/NACKs received from a UE on different aggregation levels.

Fig. 8 is a flow diagram detailing a method that facilitates accurate decoding of PDCCH by utilizing aggregation-level dependent rate matching.

Fig. 9 details another transmission method that uses an aggregation-level dependent Cyclic Redundancy Check (CRC) mask to assist in accurately decoding PDCCH.

Fig. 10 shows a method of transmitting a downlink PDCCH in a manner that assists a UE in receiving the downlink PDCCH to accurately decode the PDCCH without increasing the CRC false alarm rate.

Fig. 11 illustrates a transmission method that facilitates a UE to accurately decode PDCCH.

Fig. 12 illustrates another transmission method that facilitates a UE to accurately decode PDCCH.

Fig. 13 is a schematic diagram of an example system configured to transmit a downlink PDCCH in a wireless communication network, in accordance with one or more aspects.

Fig. 14 illustrates another example system configured to receive a downlink PDCCH in a wireless communication network, in accordance with one or more aspects.

Fig. 15 illustrates a multiple access wireless communication system according to one embodiment.

Fig. 16 is a block diagram of an embodiment of a transmitter system (also referred to as an access point) and a receiver system (also referred to as an access terminal) in a MIMO system.

Detailed Description

Various aspects are now described with reference to the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be evident, however, that such aspect(s) may be practiced without these specific details.

As used in this application, the terms "component," "module," "system," and the like are intended to include a computer-related entity, such as but not limited to hardware, firmware, a combination of hardware and software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components may reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. Further, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the internet with other systems by way of the signal).

Further, various aspects are described herein in connection with a terminal, which may be a wired terminal or a wireless terminal. A terminal can also be called a system, device, subscriber unit, subscriber station, mobile device, remote station, remote terminal, access terminal, user terminal, communication device, user agent, user device, or User Equipment (UE). A wireless terminal may be a cellular telephone, a satellite telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless connection capability, a computing device, or other processing device connected to a wireless modem. Moreover, various aspects are described herein in connection with a base station. A base station may be utilized for communicating with wireless terminal(s) and may also be referred to as an access point, a node B, or some other terminology.

The term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless specified otherwise or clear from context, the phrase "X employs a or B" is intended to mean any of the natural inclusive permutations. That is, any of the following examples satisfies the phrase "X employs a or B": x is A; x is B; or X employs both A and B. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form.

The techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other systems. The terms "system" and "network" are often used interchangeably. A CDMA system may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), CDMA2000, etc. UTRA includes wideband CDMA (wcdma) and other CDMA variants. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA system may implement a radio technology such as global system for mobile communications (GSM). The OFDMA system may implement radio technologies such as evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE802.16(WiMAX), IEEE 802.20, flash-OFDM, etc. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) is a version of UMTS that uses E-UTRA, which employs OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE and GSM are described in the literature from an organization named "third Generation partnership project" (3 GPP). In addition, cdma2000 and UMB are described in literature from an organization named "third generation partnership project 2" (3GPP 2). Moreover, such wireless communication systems may additionally include peer-to-peer (e.g., inter-mobile) ad-hoc network systems, which typically use unpaired unlicensed spectrum, 802.xx wireless LANs, bluetooth, and any other short-range or long-range wireless communication technologies.

Various aspects or features will be presented in terms of systems that may include a number of devices, components, modules, and the like. It is to be understood and appreciated that the various systems may include additional devices, components, modules, etc. and/or may not include all of the devices, components, modules etc. discussed in connection with the figures. Combinations of these methods may also be used.

Referring now to fig. 1, a multiple access wireless communication system 100 is illustrated in accordance with one or more aspects. The wireless communication system 100 may include one or more base stations in contact with one or more UEs. Although a single UE is shown, each base station 102 provides coverage for multiple UEs. UE104 is in communication with BS 102, and BS 102 transmits information to UE104 over forward link 106 and receives information from UE104 over reverse link 108. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations. Various data and control signals are transmitted by the BS 102 to the UE104 via common and dedicated communication channels. In particular, UE-specific control signals, such as information regarding uplink resources, are transmitted by BS 102 via the downlink PDCCH. The UE104 may not be able to accurately decode the PDCCH for various reasons, such as the size of the payload in question and the multiple locations of the PDCCH as described in further detail below. Thus, it cannot identify the resources allocated to it for uplink communication.

According to various aspects described in further detail below, the BS 102 or UE104 may implement various methods to address issues associated with PDCCH, thereby resulting in smoother communication. For example, according to an aspect, the BS 104 can be associated with an analysis component 110 and a processing component 112. While the analysis component 110 and the processing component 112 are illustrated as distinct components for clarity, it can be appreciated that the functions described herein can be performed by a single component. Analysis component 110 identifies whether the payload size of the downlink PDCCH is questionable or renders ambiguity in decoding the downlink PDCCH by the receiving UE. In an aspect, the payload size may include both information fields and CRC bits. The processing component 112 facilitates avoiding transmission payloads identified by the analysis component 110 as being associated with a size in question. According to another aspect, the processing component 112 may avoid problematic transmitted payloads by zero-padding. In a more detailed aspect, the processing component 112 may include an Artificial Intelligence (AI) component (not shown) that determines a number of bits for zero padding based on factors such as payload size. The payload so processed is transmitted to the UE104, thereby facilitating accurate identification of PDCCH locations in downlink transmissions. According to a different aspect, processing component 112 may accurately determine an ACK/NACK from multiple ACKs/NACKs received from UEs on different aggregation levels. It may be appreciated that various methods may be implemented as described in detail below, thereby reducing the chance of having two different aggregation levels decoded for one PDCCH.

As discussed above, various physical channels are utilized within the communication system for exchanging data and control signals between the BS and the UE. The Physical Downlink Control Channel (PDCCH) carries L1/L2 control information. Multiple PDCCHs may be transmitted in a subframe. In addition, the PDCCH supports multiple formats with different payload sizes. Downlink Control Information (DCI) transmitted within the PDCCH carries uplink grants, downlink scheduling, uplink power control commands, Random Access Channel (RACH) responses, and the like. DCI for multiple UEs is multiplexed into the first one, two, or three symbols of each subframe. Each PDCCH is mapped onto a Control Channel (CCH) which may be an aggregation of 1, 2, 4, or 8 Control Channel Elements (CCEs). Thus, the physical control channel is transmitted on an aggregation of one or several control channel elements. Each UE blindly searches its intended DCI from the common search space and the UE-specific search space. The starting CCE index of the UE-specific search space is given by a hash function, which may include the input parameters: UE ID, subframe number, total number of CCEs, and aggregation level.

According to the current E-UTRA specification, there are common and UE-specific search spaces defined according to aggregated CCEs at an aggregation level where the UE performs blind decoding of the PDCCH. CCEs in a set are contiguous and the set is spaced apart by a fixed number of CCEs. CCEs correspond to resource element sets such that one PDCCH may consist of 1, 2, 4,8 CCEs. Since the channel conditions with respect to a given BS may vary for different UEs, the BS transmits to these UEs at different power levels corresponding to the respective channel conditions. This is achieved via an aggregation level of CCEs such that level 1 is the most aggressive level requiring good channel conditions in order to transmit to a UE, while level 8 is the most conservative such that a UE can also receive BS signals transmitted on this level under poor channel conditions. However, at any given time, the UE needs to decode multiple locations, and within a particular location the UE must decode different aggregation levels to identify the PDCCH. Thus, for example, a UE may attempt six possible locations for control transmissions under aggregation levels 1 and 2, while the UE may attempt 2 possible locations for levels 4 and 8 in order to decode PDCCH. In addition, for each level, the PDCCH may have two potential control formats for different purposes. Therefore, the UE must attempt 32 different locations for identifying PDCCH transmissions. In addition, the search spaces may overlap or remain separate for different aggregation levels.

FIG. 2 is a schematic diagram illustrating search spaces associated with different aggregation levels for various users. The UE-specific search spaces associated with the three aggregation levels 1, 2 and 4 for four different users UE #1, UE #2, UE #3 and UE #4 are illustrated in this figure. The search space for UE #1 of aggregation level 1 extends from CCE index 10 to CCE index 15, for aggregation level 2 the search space extends from CCE index 4 to CCE index 7, and for aggregation level 4 the search space extends from CCE index 0 to CCE index 1. Thus, for UE #1, the search spaces corresponding to different aggregation levels do not overlap. The search space of aggregation level 1 of UE #2 spans from CCE index 1 to CCE index 6, the search space of aggregation level 2 spans from CCE index 1 to CCE index 4, and for aggregation level 4, the search space spans CCE index 1 and CCE index 2. Thus, the aggregation level 4 search space may contain some portion of the aggregation level 2 search space for UE # 2. Thus, if the control channel PDCCH is transmitted on level 4, UE #2 may be able to decode multiple PDCCHs for the downlink assignment. Thus, it can be speculated that the UE is decoding an assignment of another user or that the UE is decoding one PDCCH more than once, as illustrated in fig. 2 for UE # 2. The latter case may occur due to overlap of their search spaces when the UE decodes one PDCCH with different aggregation sizes. Search spaces of different aggregation levels may overlap due to certain specific payload sizes, as described in detail below. This overlap of search spaces of different aggregation levels leads to some ambiguity as to the resources used for uplink transmission. This is because the first CCE of the downlink PDCCH is used to determine the uplink ACK/NACK resource. Therefore, the first CCE must be unique to the uplink ACK/NACK resource mapping.

Another reason for the UE to detect PDCCH at multiple locations is the ambiguous payload size. As discussed above, the PDCCH includes an aggregation of CCEs, where each CCE includes 36 tones, also referred to as resource elements. Due to circular buffer based rate matching, for a given aggregation size (2, 4, or 8), the coded bits start to repeat themselves after the first CCE. For example, aggregation level 4 would involve 144 resource elements (36 x 4) and 72 encoded symbols. Fig. 3 illustrates an example of a repetition of a particular payload size (48 bits). As shown in the figure, aggregation size 4 involves two repetitions, while aggregation size 8 includes four repetitions such that each repetition starts at the same position in the circular buffer. Multiple aggregation sizes may be checked by Cyclic Redundancy Check (CRC) due to repetition of coded bits and overlap of search spaces between different aggregation sizes. Since the first CCE of PDCCH is linked to the uplink ACK/NACK resource for dynamic scheduling, the UE may send its ACK/NACK in different resources that are not recognized by the base station (multiple ACK/NACK resources are possible). In general, ten problematic payload sizes {28, 30, 32, 36, 40, 42, 48, 54, 60, 72} have been identified for LTE release 8 because the maximum PDCCH size is less than 80. It can be appreciated that payload sizes in question are identified herein as a means of illustration and not limitation. It can be further appreciated that as the system evolves, it will be able to transmit a larger payload and thus, the number of unambiguously identified payload sizes that give rise to PDCCH may increase. For example, according to LTE-advanced (release 9 and higher), the maximum payload size may be greater than 80. Thus, an additional ambiguous payload size of 96 bits can be identified for PDCCH when m-4, k-1, where m represents the number of CCEs and k represents the number of repetitions of the coded block.

Fig. 4 illustrates a transmission method 400 in accordance with an aspect. The method begins at 402, where a payload size is determined. At 404, a message is generated in a manner that avoids the problematic payload size. These messages are transmitted as shown at 406. With this approach, transmissions that cause payloads for multiple aggregation levels to be decoded for one PDCCH are mitigated. However, this approach depends on various factors such as bandwidth definition, carrier frequency, number of transmit antennas, and on whether the system implements time division multiplexing (TDD) or frequency division multiplexing (FDD). In addition, this approach increases processing complexity at the base station, as all possible aggregation level combinations should be tested to avoid a particular payload size.

As mentioned above, ten questionable or ambiguous payload sizes are identified. Based on factors such as the convolutional coding rate of 1/3, QPSK modulation, and the fact that each CCE corresponds to 36 resource elements, the payload size n in question should satisfy the following condition:

n 3/2 k m 36 or n m/k 24, where k and m are integers and m < 8

-n represents the payload size

-m represents the number of CCEs

-k represents the number of repetitions of the coded block

N should be less than (8-m) 36 x 2 x 72 x (8-m) x, wherein

x is maximum coding rate constraint and x is more than 0 and less than or equal to 1

If m is 7, then n < 54

If m is 6, then n < 108, and so on.

By way of example

·n＝48(m＝2，k＝1)

·n＝36(m＝3，k＝2)

N-32 (m-4, k-3), and so on.

According to yet another aspect, the coding rate may be less than 3/4 in order to facilitate the UE to decode PDCCH.

Fig. 5 details another transmission method 500 that facilitates accurate decoding of PDCCH by a UE, in accordance with an aspect. The method begins at 502, where it is determined whether a packet for downlink PDCCH corresponds to an ambiguous payload size identified above. If the data packet does not correspond to the ambiguous payload size described above, the method proceeds to 508, where the data packet is transmitted to the UE. If it is determined at 502 that the packet corresponds to one of ambiguous payload sizes, based on the packet size, a number of bits for zero padding may be determined as shown at 504. For example, if a payload of size 40 is filled with two bits, it results in a payload of size 42, which is another size in question. Thus, the number of bits used for zero padding may vary based at least on the payload size. At 506, the payload is processed to include the zero-filled bits as determined at 504. At 508, the packet so processed to include the padded bits is transmitted to the designated UE. This approach thereby avoids ambiguous payload sizes and assists the UE in accurately decoding the PDCCH, as it mitigates aggregation level overlap.

Fig. 6 illustrates a reception method 600 that accounts for consequences due to multiple CRC passes in accordance with an aspect. This approach does not require a change at the base station, but rather it is implemented by the UE to explicitly select the uplink ACK/NACK resource. According to this method, the UE decodes all possible aggregation sizes as shown at 602. At 604, it is determined whether the UE has decoded PDCCH on more than one aggregation level. If the UE decodes only one PDCCH, the method terminates at the end block because the uplink ACK/NACK resource is accurately identified. However, if it is determined at 604 that the UE has successfully decoded more than one PDCCH, the method proceeds to 606. At 606, the lowest CCE index (corresponding to the highest CCE passing aggregation level) among those valid PDCCHs is selected. At 608, an uplink ACK/NACK is transmitted utilizing the resources determined at step 606. The method then terminates at an end block. This approach thus facilitates explicitly identifying the resources for uplink ACK/NACK, but requires the UE to perform a full search of all PDCCHs that it can decode in order to identify the CCE with the lowest index.

Fig. 7 is a flow diagram 700 detailing a method of accurately identifying an ACK/NACK from multiple ACK/NACKs received from a UE on different aggregation levels. The method begins at 702, where a base station receives an uplink transmission from a UE. In accordance with this aspect, the uplink transmission may include an ACK/NACK associated with a previously transmitted downlink communication. At 704, it is determined whether multiple ACK/NACKs have been received. If it is determined at 704 that the base station has received only a single ACK/NACK corresponding to the uplink resources allocated to the UE, the process terminates at an end block. However, if it is determined at 704 that the base station has received more than one ACK/NACK from the UE, the method proceeds to 706, where the aggregation level g (k) corresponding to the downlink PDCCH for which the UE has transmitted the ACK/NACK is identified. At 708, all ACKs/NACKs received from the UE for all active aggregation levels less than or equal to g (k) are decoded. At 710, attributes associated with each of the decoded ACK/NACKs are determined and analyzed. At 712, a particular ACK/NACK is identified as a valid ACK/NACK for the downlink PDCCH based at least on the analyzed attributes. For example, energy in an ACK/NACK channel or a signal-to-noise ratio (SNR) of an uplink ACK/NACK transmission may be determined according to different aspects. Based at least on the determined attributes of the decoded ACK/NACK channel, a particular ACK/NACK is identified as the ACK/NACK that the UE transmitted in response to the downlink transmission. For example, the ACK/NACK channel with the most desirable SNR or highest power may be identified as the response of the UE to the received downlink transmission. This approach counteracts the effect of the UE decoding more than one PDCCH by identifying a valid ACK/NACK from among multiple ACK/NACKs sent by the UE in response to the received downlink PDCCH, rather than having the UE mitigate decoding more than one PDCCH. While this approach may increase decoding complexity at the base station, it is very robust and would not require any further implementation at the UE.

Fig. 8 relates to another aspect in which accurate decoding of PDCCH is facilitated by utilizing aggregation-level dependent rate matching. Different rate matching algorithms are implemented for different aggregation levels by shifting the resource mapping by an aggregation level dependent offset. The processes involved in bit collection, selection and transmission are detailed below in accordance with this aspect.

Length K is generated as follows_w＝3K_ΠThe circular buffer of (2):

for K ═ 0, · K_Π-1

For K ═ 0, · K_Π-1

For K ═ 0, · K_Π-1

The length of the rate-matched output sequence of this coded block is denoted by E, the rate-matched output bit sequence being E_kK is 0, 1, · and E-1. Define a (u), where u is a possible aggregation level for the control channel, i.e., u is 1, 2, 4,8

Setting k to 0 and j to 0

while{k＜E}

k＝k+1

j＝j+1

else

j＝j+1

end if

end while

The method 800 illustrated in fig. 8 begins at 802, where an aggregation level to be used for downlink PDCCH transmission to a particular UE is determined. The resources for the uplink ACK/NACK for the UE are mapped with an offset as shown at 804. According to another aspect, the offset is determined based on aggregation to be used for downlink PDCCH. At 806, a resource assignment message to be transmitted in the downlink PDCCH is generated such that it includes an aggregation-level dependent offset. At 808, the PDCCH is transmitted to the UE, thereby assisting it in accurately decoding the PDCCH. Upon receiving the PDCCH, the UE extracts information that accounts for aggregation-level dependent offsets.

Fig. 9 relates to yet another aspect in which aggregation-level dependent Cyclic Redundancy Check (CRC) masks are used to assist in accurately decoding PDCCH. This approach may assist in accurately decoding the downlink PDCCH without increasing the CRC false alarm rate. This is achieved by scrambling the CRC bits in a sequence determined by the aggregation level (e.g., 1, 2, 4, or 8). The CRC bits are calculated for the entire transport block of one PDCCH. At the receiver, for each aggregation level, the UE first descrambles the bits with an aggregation level dependent scrambling code. It then checks the CRC for one aggregation level corresponding to the scrambling sequence, thereby ensuring that only one aggregation level passes the CRC. The transmission methodology 900 begins at 902, wherein an aggregation level associated with a downlink PDCCH is initially determined. A sequence corresponding to an aggregation level of the PDCCH is generated at 904. At 906, CRC bits for the downlink PDCCH are scrambled with the generated sequence and the scrambled bits are transmitted in the downlink communication as shown at 908 before terminating at the end block.

Fig. 10 relates to another aspect associated with transmitting a downlink PDCCH in a manner that assists a UE in receiving the downlink PDCCH to accurately decode the PDCCH without increasing the CRC false alarm rate. According to this method, aggregation level dependent scrambling codes are applied to the PDCCH. One aspect relates to scrambling an entire transport block and corresponding CRC bits calculated based on the entire transport block. The receiver descrambles the decoded bits before checking the CRC. Another aspect relates to scrambling bits after channel coding or rate matching so that a receiver initially descrambles the received signal after decoding. By way of illustration and not limitation, one design for a 4CRC mask may be:

<0，0，0，0，0，0，0，0，0，0，0，0，0，0，0，0>

<1，1，1，1，1，1，1，1，1，1，1，1，1，1，1，1>

<0，1，0，1，0，1，0，1，0，1，0，1，0，1，0，1>

<1，0，1，0，1，0，1，0，1，0，1，0，1，0，1，0>

the methodology 1000 begins with identifying an aggregation level of downlink PDCCH to be used for a particular UE as shown at 1002. According to this aspect, if PDCCHs for different UEs are transmitted using different aggregation levels, different scrambling sequences corresponding to the respective aggregation levels are generated. Information to be transmitted on the downlink PDCCH for each UE is then scrambled using a scrambling sequence corresponding to the aggregation level of the PDCCH for each respective UE. Thus, a scrambling sequence corresponding to the aggregation level is generated as shown at 1004. The CRC bits are then scrambled with the generated sequence as shown at 1006. As mentioned above, this can be achieved in two ways: the entire transport block and the corresponding CRC bits calculated based on the transport block may be scrambled, or the bits may be scrambled after channel coding or rate matching. At 1008, CRC bits scrambled according to the generated sequence are transmitted in the downlink PDCCH, and the method terminates at an end block.

Fig. 11 illustrates another transmission methodology 1100 that facilitates a UE to accurately decode PDCCH. The methodology begins at 1102, wherein an aggregation level for a downlink PDCCH for a particular UE is determined. At 1104, bits are included in the PDCCH to indicate an aggregation level. In a more detailed aspect, two bits may be included to indicate any of the four aggregation levels (1, 2, 4, or 8). The PDCCH so modified with bits indicating the corresponding aggregation level is sent on the downlink to a particular UE as shown at 1106. The receiver may initially decode the indicator bits to identify the aggregation level on which it may receive PDCCH.

Fig. 12 illustrates another transmission methodology 1200 that facilitates a UE to accurately decode PDCCH. The method begins at 1202, where a payload size of a downlink PDCCH for a particular UE is determined. At 1204, it is further determined whether the payload size is one of the above-mentioned ambiguous payload sizes that cause confusion at the UE with respect to the aggregation level at which the downlink PDCCH is decoded. If the payload size does not cause ambiguity at the receiver, the method proceeds to 1208, where the packet is transmitted to the receiver. If the payload size is determined at 1204 to cause ambiguity at the receiver, a bit is included in the PDCCH as shown at 1206 to indicate the aggregation level. In a more detailed aspect, two bits may be included to indicate any of the four aggregation levels (1, 2, 4, or 8). The PDCCH so modified with bits indicating the corresponding aggregation level is sent on the downlink to a particular UE as shown at 1208. The receiver may initially decode the indicator bits to identify the aggregation level on which it may receive PDCCH. The above aspects regarding including aggregation level indicators in the downlink PDCCH may be applied to UL grants and DL power control (format 3/3a) to meet the requirement that formats 0/1a/3/3a should have the same size.

In different aspects, a combination of the methods described herein may be used to assist a UE in accurately decoding a PDCCH. This facilitates the UE to correctly identify resources for uplink ACK/NACK communication, thereby increasing efficiency and reducing interference within the wireless communication system.

Referring to fig. 13, an example system 1300 configured to transmit downlink PDCCH in a wireless communication network is illustrated, in accordance with one or more aspects. It is to be appreciated that system 1300 is represented as including functional blocks, which can be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware).

The system 1300 includes a logical grouping 1302 of electrical components that can function individually or in combination. Logical grouping 1302 may comprise means for determining that analyzes a size of a payload to be transmitted on a downlink PDCCH and determines whether the size is ambiguous. For example, the payload may be of a size such that it causes the receiving UE to decode PDCCH on two aggregation levels, thereby creating ambiguity at the UE. Also included in logical grouping 1302 is a means for processing a data packet 1306, the means 1306 changing the size of the payload determined to be ambiguous. According to different aspects, one or more bits may be included for zero padding the payload, thereby changing its size such that it causes the UE to decode the downlink PDCCH on only one aggregation level. The system may further include means for transmitting zero-padded data packets 1308.

According to certain aspects, the means for determining 1304 may also analyze communications received from the UE and determine whether more than one ACK/NACK is received from the UE. In accordance with this aspect, logical grouping 1302 further includes means for decoding all ANC/NACKs received from a UE for all active aggregation levels less than or equal to the aggregation level of the downlink PDCCH. Also included is means for analyzing attributes associated with each of the decoded ACK/NACKs, and means for selecting a valid ACK/NACK from the plurality of ACK/NACKs based at least on the analyzed attributes.

According to other aspects, the means for determining 1304 may also determine an aggregation level to be associated with the downlink PDCCH. Based at least on the aggregation level, an offset may further be determined such that uplink ACK/NACK resources are mapped in a downlink PDCCH utilizing the offset. In accordance with this aspect, including means for mapping in logical grouping 1302 enables resource assignment messages with aggregate-level dependent offsets to be generated. In this aspect, means for transmitting 1308 transmits a resource assignment message with an offset, thereby assisting the UE in receiving the downlink PDCCH to decode the PDCCH on one aggregation level and accurately identify uplink ACK/NACK resources. Another aspect relates to including one or more bits in the downlink PDCCH to indicate an aggregation level as determined by the means for determining 1304. This aspect relates to means 1308 for transmitting aggregation-level indicator bits to respective UEs. Another aspect may relate to transmitting aggregation level indicator bits only to UEs that receive data packets with ambiguous payload sizes on the downlink PDCCH.

In another aspect, grouping 1302 may also include means for scrambling CRC bits with aggregation level dependent sequences. In this aspect, the means for determining 1304 identifies an aggregation level corresponding to the UE-specific PDCCH. This aspect also includes means for generating an aggregation-level dependent sequence generator such that CRC bits are scrambled with this sequence. The means for transmitting 1310 transmits the scrambled CRC bits.

Another aspect relates to generating scrambling sequences based on respective aggregation levels associated with a plurality of UEs for receiving downlink PDCCH. In accordance with this aspect, means for encoding CRC bits to be transmitted to the plurality of UEs with aggregation level dependent scrambling sequences is included in logical grouping 1302.

Additionally, system 1300 can include a memory 1308 that retains instructions for executing functions associated with electrical components 1304 and 1306, or other components. While shown as being external to memory 1310, it is to be understood that one or more of electrical components 1304 and 1306 can exist within memory 1310.

Fig. 14 illustrates another example system 1400 configured to receive a downlink PDCCH in a wireless communication network, in accordance with one or more aspects. It is to be appreciated that system 1400 is represented as including functional blocks, which can be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware).

System 1400 includes a logical grouping 1402 of electrical components that can act separately or in combination. Logical grouping 1402 may include means for receiving a CRC bit scrambled with an aggregation-level dependent scrambling sequence 1404. Means for decoding 1406, also included within 1402, decodes the received downlink PDCCH on the associated aggregation level. An aggregation level is obtained by descrambling Cyclic Redundancy Check (CRC) bits received in the downlink PDCCH with the aggregation level dependent sequence.

Additionally, system 1400 can include a memory 1408 that retains instructions for executing functions associated with electrical components 1404 and 1406 or other components. While shown as being external to memory 1408, it is to be understood that one or more of electrical components 1404 and 1406 can exist within memory 1308.

Referring to fig. 15, a multiple access wireless communication system in accordance with one embodiment is illustrated. An access point 1500(AP) (also referred to as an e-NodeB or e-NB) includes multiple antenna groups, one including 1504 and 1506, another including 1508 and 1510, and an additional including 1512 and 1514. In fig. 15, only two antennas are shown for each antenna group, however more or fewer antennas may be utilized for each antenna group. An access terminal 1516(AT), also known as User Equipment (UE), is in communication with antennas 1512 and 1514, where antennas 1512 and 1514 transmit information to access terminal 1516 over forward link 1520 and receive information from access terminal 1516 over reverse link 1518. Access terminal 1522 is in communication with antennas 1506 and 1508, where antennas 1506 and 1508 transmit information to access terminal 1522 over forward link 1526 and receive information from access terminal 1522 over reverse link 1524. In a FDD system, communication links 1528, 1520, 1524 and 1526 may use different frequency for communication. For example, forward link 1520 may use a different frequency than that used by reverse link 1518.

Each group of antennas and/or the area in which they are designed to communicate is often referred to as a sector of the access point. In the embodiment, antenna groups each are designed to communicate to access terminals in a sector, of the areas covered by access point 1500.

In communication over forward links 1520 and 1526, the transmitting antennas of access point 1500 utilize beamforming in order to improve the signal-to-noise ratio of forward links for the different access terminals 1516 and 1524. Also, an access point that uses beamforming to transmit to access terminals scattered randomly through its coverage causes less interference to access terminals in neighboring cells than an access point that transmits through a single antenna to all its access terminals.

An access point may be a fixed station used for communicating with the terminals and may also be referred to as an access point, a node B, or some other terminology. An access terminal may also be called an access terminal, User Equipment (UE), a wireless communication device, terminal, or some other terminology.

Fig. 16 is a block diagram of an embodiment of a transmitter system 1610 (also referred to as an access point) and a receiver system 1650 (also referred to as an access terminal) in a MIMO system 1600. At transmitter system 1610, traffic data for a number of data streams is provided from a data source 1612 to a Transmit (TX) data processor 1614.

In an embodiment, each data stream is transmitted over a respective transmit antenna. TX data processor 1614 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream is then modulated (i.e., symbol mapped) based on a particular modulation scheme (e.g., BPSK, QSPK, M-PSK, or M-QAM) selected for that data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream can be determined by instructions performed by processor 1630 in conjunction with memory 1632.

The modulation symbols for all data streams are then provided to a TX MIMO processor 1620, which TX MIMO processor 1620 may further process the modulation symbols(e.g., for OFDM). TX MIMO processor 1620 then compares N_TA stream of modulation symbols is provided to N_TAnd Transmitters (TMTR)1622a through 1622 t. In certain embodiments, the TXMIMO processor 1620 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

Each transmitter 1622 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and frequency upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. N from transmitters 1622a through 1622t_TThe modulated signals are then respectively from N_TAnd a plurality of antennas 1624a through 1624 t.

At receiver system 1650, the transmitted modulated signal is represented by N_RA number of antennas 1652a through 1652r are received, and the received signal from each antenna 1652 is provided to a respective receiver (RCVR)1654a through 1654 r. Each receiver 1654 conditions (e.g., filters, amplifies, and frequency downconverts) a respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a respective "received" symbol stream.

RX data processor 1660 then receives the data from N_RN of receiver 1654_RA number of received symbol streams and processing the symbol streams based on a particular receiver processing technique to provide N_TA stream of "detected" symbols. RX data processor 1660 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by RX data processor 1660 is complementary to that performed by TX MIMO processor 1620 and TX data processor 1614 at transmitter system 1610.

A processor 1670 periodically determines which pre-coding matrix to use (discussed below). Processor 1670 formulates a reverse link message comprising a matrix index portion and a rank value portion.

The reverse link message may comprise various types of information regarding the communication link and/or the received data stream stored in memory 1672. The reverse link message is then processed by a TX data processor 1658, which also receives traffic data for a number of data streams from a data source 1656, modulated by a modulator 1680, conditioned by transmitters 1654a through 1654r, and transmitted back to transmitter system 1610.

At transmitter system 1610, the modulated signals from receiver system 1650 are received by antennas 1624, conditioned by receivers 1622, demodulated by a demodulator 1640, and processed by a RX data processor 1642 to extract the reserve link message transmitted by receiver system 1650. Processor 1630 then determines which pre-coding matrix to use for determining the beamforming weights and then processes the extracted message.

The various illustrative logics, logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Additionally, at least one processor may comprise one or more modules operable to perform one or more of the steps and/or actions described above.

The steps and/or actions of a method or algorithm described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium may be coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. Further, in some aspects, the processor and the storage medium may reside in an ASIC. Additionally, the ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal. Additionally, in some aspects, the steps and/or actions of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a machine readable medium and/or computer readable medium, which may be incorporated into a computer program product.

In one or more aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection may be termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc (disc), as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs usually reproduce data optically with light (with a laser). Combinations of the above should also be included within the scope of computer-readable media.

While the foregoing disclosure discusses illustrative aspects and/or embodiments, it should be noted that various changes and modifications could be made herein without departing from the scope of the described aspects and/or embodiments as defined by the appended claims. Furthermore, although elements of the described aspects and/or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise.

Claims (21)

1. A transmission method that facilitates accurate decoding of PDCCH by a UE, comprising:

determining an aggregation level of a downlink PDCCH for the UE;

determining whether a payload size of the PDCCH is ambiguous;

changing a size of a payload by zero-padding a data packet of the downlink PDCCH with one or more bits for an ambiguous payload size; and

transmitting a payload with the zero-padded data packet.

2. The method of claim 1, wherein a number of bits for zero padding is based at least on the payload size.

3. The method of claim 1, wherein the payload size n is ambiguous if the payload size n-m/k 24, where k, m are integers, m denotes a number of Control Channel Elements (CCEs) and k denotes a number of repetitions of an encoded block.

4. The method of claim 3, wherein m is less than 8 and x is the maximum coding rate, 0 < x ≦ 1 such that n is less than (8-m) 36 x 2 x.

5. At least one processor configured to facilitate accurate decoding of PDCCH by a UE, comprising:

a first module for determining whether a payload size of the PDCCH is ambiguous; and

a second module for changing a size of a payload by zero-filling a data packet of a downlink PDCCH with one or more bits for an ambiguous payload size.

6. The processor of claim 5, wherein the second module determines a number of bits for zero padding based at least on the payload size.

7. The processor of claim 5, wherein the first module identifies the payload size n as ambiguous if the payload size n is m/k 24, where k, m are integers, m represents a number of CCEs and k represents a number of repetitions of an encoded block.

8. The processor of claim 7, the first module further to identify n as ambiguous if m is less than 8 and n is less than 72 x (8-m) x, where x is a maximum coding rate and a value of x lies between 0 and 1.

9. A computer program product, comprising:

a computer-readable medium, comprising:

a first set of codes for causing a computer to determine whether a payload size of a data packet of a downlink PDCCH is ambiguous; and

a second set of codes for causing the computer to include one or more bits in the data packet corresponding to the ambiguous payload size for zero padding.

10. The computer program product of claim 9, further comprising a third set of codes that determines a number of bits to include into the data packet for zero padding based at least on the payload size.

11. The computer program product of claim 9, wherein the first set of codes determines the payload size (n) to be ambiguous if the payload size n-m/k-24, where k, m are integers, m represents a number of CCEs and k represents a number of repetitions of an encoded block.

12. The computer program product of claim 11, wherein the first set of codes determines the payload size (n) to be ambiguous if m is less than 8 and the payload size (n) is less than 72 x (8-m) x, where x is a maximum coding rate and 0 < x ≦ 1.

13. An apparatus for facilitating accurate decoding of PDCCH by a UE, comprising:

means for determining a payload size of the PDCCH;

means for processing a data packet of a downlink PDCCH by comprising one or more bits for an ambiguous payload size; and

means for transmitting a payload with zero-padded data packets.

14. A wireless communications apparatus, comprising:

a memory storing instructions for analyzing whether a payload of a transmission in a downlink PDCCH is associated with one of a problematic size and changing a size of a data packet by zero-padding the packet with one or more bits if the payload has a problematic size; and

a processor coupled to the memory, the processor configured to execute the instructions stored in the memory.

15. The wireless communications apparatus of claim 14, the memory further comprising instructions for determining a number of bits for zero padding the data packet based at least on the payload size.

16. A method of identifying a valid ACK/NACK from a plurality of ACK/NACKs received from a UE on different aggregation levels, comprising:

determining whether more than one ACK/NACK is received from the UE;

identifying an aggregation level corresponding to a downlink PDCCH for which the UE has transmitted multiple ACK/NACKs;

decoding all ACKs/NACKs received from the UE for all active aggregation levels less than or equal to the aggregation level of the downlink PDCCH;

analyzing attributes associated with each of the decoded ACK/NACKs; and

selecting a valid ACK/NACK from the plurality of ACK/NACKs based at least on the analyzed attribute.

17. The method of claim 16, wherein the attribute comprises SNR statistics and an ACK/NACK with best SNR is identified as a valid ACK/NACK from the plurality of decoded ACK/NACKs.

18. The method of claim 16, wherein the attribute comprises a transmission energy such that an ACK/NACK with a highest energy is identified as a valid ACK/NACK from the plurality of decoded ACK/NACKs.

19. A wireless communications apparatus, comprising:

a memory storing instructions for determining attributes of a plurality of ACK/NACKs received from a UE in response to a transmitted downlink PDCCH, and for selecting a valid ACK/NACK from the plurality of ACK/NACKs based at least on attributes associated with the plurality of received ACK/NACKs; and

a processor coupled to the memory, the processor configured to execute the instructions stored in the memory.

20. A computer program product, comprising:

a computer-readable medium, comprising:

a first set of codes for determining whether more than one ACK/NACK is received from the UE;

a second set of codes for identifying an aggregation level corresponding to a downlink PDCCH for which the UE has transmitted multiple ACK/NACKs;

a third set of codes for decoding all ACKs/NACKs received from the UE for all active aggregation levels less than or equal to the aggregation level of the downlink PDCCH;

a fourth set of codes for analyzing attributes associated with each of the decoded ACKs/NACKs; and

a fifth set of codes for selecting a valid ACK/NACK from the plurality of ACK/NACKs based at least on the analyzed attribute.

21. An apparatus for facilitating accurate decoding of PDCCH by a UE, comprising:

means for determining that a number of ACK/NACKs are received from the UE;

means for identifying an aggregation level corresponding to a downlink PDCCH for which the UE has transmitted multiple ACK/NACKs;

means for decoding all ACK/NACKs received from the UE for all active aggregation levels less than or equal to the aggregation level of the downlink PDCCH;

means for analyzing attributes associated with each of the decoded ACK/NACKs; and

means for selecting a valid ACK/NACK from the plurality of ACK/NACKs based at least on the analyzed attribute.