HK1171294B - Extension of ue-rs to dwpts - Google Patents

Description

Extension of UE-RS to DWPTS

Cross Reference to Related Applications

This application claims priority TO us provisional patent application No.61/231,294 entitled "extenson ofeu-RS TO DWPTS IN LTE" filed on 8, 4.2009. The above application is incorporated by reference herein in its entirety.

Technical Field

The following description relates generally to wireless communications, and more specifically to using a UE-specific reference signal (UE-RS) design that depends on a number of symbols used for downlink transmission in a wireless communication system.

Background

Wireless communication systems have been widely deployed to provide various types of communication content such as voice, data, and so on. A typical wireless communication system may be a multiple-access system capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth, 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, Orthogonal Frequency Division Multiple Access (OFDMA) systems, and the like. Additionally, these systems may conform to specifications such as third generation partnership project (3GPP), 3GPP Long Term Evolution (LTE), Ultra Mobile Broadband (UMB), multicarrier wireless specifications such as evolution-data optimized (EV-DO), one or more modified versions thereof, and so forth.

Generally, a wireless multiple-access communication system can simultaneously support communication for multiple User Equipments (UEs). Each UE may communicate 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 UEs, and the reverse link (or uplink) refers to the communication link from the UEs to the base stations. Further, communication between the UE and the base station may be established through a single-input single-output (SISO) system, a multiple-input single-output (MISO) system, a multiple-input multiple-output (MIMO) system, or the like. Further, the UE may communicate with other UEs (and/or base stations with other base stations) in a peer-to-peer wireless network configuration.

To facilitate coherent demodulation and decoding of transmissions sent over a wireless channel, channel estimation may be used. The channel response may be estimated, for example, by embedding a known reference signal in the transmission. The reference signal may be analyzed by a receiver to facilitate estimating a channel response, which may approximate the variation caused to the transmitted symbols due to channel conditions. This variation in approximation can assist the receiver during symbol identification, demodulation, and decoding.

Disclosure of Invention

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

In accordance with one or more embodiments and corresponding disclosure thereof, various aspects are described herein in connection with facilitating transmission and/or reception of user equipment-specific reference signals (UE-RSs) in a wireless communication environment. The UE-RS pattern may be selected, generated, etc., based on the number of symbols in the subframe used for downlink transmission. At least one time domain component of the UE-RS pattern can vary according to a number of symbols in a subframe utilized for downlink transmission. For example, the at least one time domain component may be punctured, time shifted, and/or the like. Further, the UE-RS can be mapped to resource elements of the subframe according to a UE-RS pattern. Further, the UE may use the UE-RS pattern to detect for UE-RS on resource elements of a subframe. In addition, the UE can estimate the channel according to the UE-RS.

According to related aspects, a method that facilitates transmitting reference signals for channel estimation in a wireless communication environment is described herein. The method comprises the following steps: a number of symbols in a subframe for downlink transmission is identified. In addition, the method further comprises: selecting a user equipment-specific reference signal (UE-RS) pattern according to a number of symbols in the subframe for downlink transmission, wherein at least one time domain component of the UE-RS pattern varies according to the number of symbols in the subframe for downlink transmission. In addition, the method further comprises: mapping UE-RSs to resource elements of the subframe according to the UE-RS pattern.

Another aspect relates to a wireless communications apparatus. The wireless communications apparatus includes a memory that retains instructions related to performing operations comprising: identifying a number of symbols in a subframe for downlink transmission; selecting a user equipment-specific reference signal (UE-RS) pattern according to a number of symbols in the subframe for downlink transmission, wherein at least one time domain component of the UE-RS pattern varies according to the number of symbols in the subframe for downlink transmission; mapping UE-RSs to resource elements of the subframe according to the UE-RS pattern. The wireless communications apparatus can further include a processor, coupled to the memory, configured to execute the instructions retained in the memory.

Another aspect relates to a wireless communications apparatus that enables reference signal transmission in a wireless communication environment. The wireless communication apparatus includes: means for identifying a number of symbols in a subframe for downlink transmission. Further, the wireless communication apparatus further includes: means for selecting a user equipment-specific reference signal (UE-RS) pattern based on a number of symbols in the subframe for downlink transmission, wherein at least one time domain component of the UE-RS pattern varies based on the number of symbols in the subframe for downlink transmission. Further, the wireless communication apparatus further includes: means for mapping UE-RSs to resource elements of the subframe according to the UE-RS pattern.

Another aspect relates to a computer program product that includes a computer-readable medium. The computer readable medium includes: code for identifying a number of symbols in a subframe for downlink transmission. Further, the computer-readable medium further comprises: code for selecting a user equipment-specific reference signal (UE-RS) pattern based on a number of symbols in the subframe for downlink transmission, wherein at least one time domain component of the UE-RS pattern varies based on the number of symbols in the subframe for downlink transmission. Further, the computer-readable medium further comprises: code for mapping UE-RSs to resource elements of the subframe according to the UE-RS pattern.

According to another aspect, a wireless communications apparatus includes a processor that can be configured to identify a number of symbols in a subframe for downlink transmission. Further, the processor may be further configured to: selecting a user equipment-specific reference signal (UE-RS) pattern according to a number of symbols in the subframe for downlink transmission, wherein at least one time domain component of the UE-RS pattern varies according to the number of symbols in the subframe for downlink transmission. Further, the processor may be further configured to: mapping UE-RSs to resource elements of the subframe according to the UE-RS pattern.

According to other aspects, a method that facilitates estimating a channel in a wireless communication environment is described. The method comprises the following steps: the number of symbols allocated for downlink transmission in a subframe is identified. In addition, the method further comprises: identifying a user equipment-specific reference signal (UE-RS) pattern according to a number of symbols allocated for downlink transmission in the subframe, wherein at least one time domain component of the UE-RS pattern varies according to the number of symbols allocated for downlink transmission in the subframe. In addition, the method further comprises: detecting a UE-RS on a resource element in a subframe specified by the UE-RS pattern. In addition, the method further comprises: estimating a channel according to the UE-RS.

Another aspect relates to a wireless communications apparatus. The wireless communications apparatus includes a memory that retains instructions related to performing operations comprising: identifying a number of symbols allocated for downlink transmission in a subframe; identifying a user equipment-specific reference signal (UE-RS) pattern according to a number of symbols allocated for downlink transmission in the subframe, wherein at least one time domain component of the UE-RS pattern varies according to the number of symbols allocated for downlink transmission in the subframe; detecting a UE-RS on a resource element in a subframe specified by the UE-RS pattern; estimating a channel according to the UE-RS. The wireless communications apparatus can further include a processor, coupled to the memory, configured to execute the instructions retained in the memory.

Another aspect relates to a wireless communications apparatus that enables estimating a channel in a wireless communication environment. The wireless communication apparatus includes: means for identifying a number of symbols allocated for downlink transmission in a subframe. Further, the wireless communication apparatus further includes: means for identifying a user equipment-specific reference signal (UE-RS) pattern based on a number of symbols allocated for downlink transmissions in the subframe, wherein at least one time domain component of the UE-RS pattern varies based on the number of symbols allocated for downlink transmissions in the subframe. Further, the wireless communication apparatus further includes: means for detecting a UE-RS on resource elements in a subframe specified by the UE-RS pattern. Further, the wireless communication apparatus further includes: means for estimating a channel according to the UE-RS.

Another aspect relates to a computer program product that includes a computer-readable medium. The computer readable medium includes: code for identifying a number of symbols allocated for downlink transmission in a subframe. Further, the computer-readable medium further comprises: code for identifying a user equipment-specific reference signal (UE-RS) pattern based on a number of symbols allocated for downlink transmissions in the subframe, wherein at least one time domain component of the UE-RS pattern varies based on the number of symbols allocated for downlink transmissions in the subframe. Further, the computer-readable medium further comprises: code for detecting a UE-RS on a resource element in a subframe specified by the UE-RS pattern. Further, the computer-readable medium further comprises: code for estimating a channel based on the UE-RS.

According to another aspect, a wireless communications apparatus includes a processor that can be configured to identify a number of symbols allocated for downlink transmission in a subframe. Further, the processor may be further configured to: identifying a user equipment-specific reference signal (UE-RS) pattern according to a number of symbols allocated for downlink transmission in the subframe, wherein at least one time domain component of the UE-RS pattern varies according to the number of symbols allocated for downlink transmission in the subframe. Further, the processor may be further configured to: detecting a UE-RS on a resource element in a subframe specified by the UE-RS pattern. Further, the processor may be further configured to: estimating a channel according to the UE-RS.

To the accomplishment of the foregoing and related ends, the one or more embodiments 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 aspects of the one or more embodiments. These aspects are indicative, however, of but a few of the various ways in which the principles of various embodiments may be employed and the described embodiments are intended to include all such aspects and their equivalents.

Drawings

Fig. 1 illustrates a wireless communication system in accordance with various aspects described herein.

Fig. 2 illustrates an example wireless network that facilitates downlink channel estimation using UE-RSs in accordance with various aspects.

FIG. 3 depicts an example system that maps UE-RSs to REs in a subframe in a wireless communication environment.

Fig. 4 depicts an example subframe that can be employed in a wireless communication environment.

Fig. 5 depicts an example time-shifted UE-RS pattern, in accordance with various aspects.

Fig. 6 depicts an example punctured UE-RS pattern, in accordance with various aspects.

Fig. 7 depicts an example partial time shifted UE-RS pattern, in accordance with various aspects.

Fig. 8 depicts an example time-shifted UE-RS pattern, in accordance with various aspects.

Fig. 9 depicts an example subframe that can be utilized in a legacy wireless communication environment.

Fig. 10 illustrates an example methodology that facilitates transmitting reference signals for channel estimation in a wireless communication environment.

Fig. 11 illustrates an example methodology that facilitates estimating a channel in a wireless communication environment.

Fig. 12 illustrates an example system that enables transmitting reference signals in a wireless communication environment.

Fig. 13 illustrates an example system that enables estimating a channel in a wireless communication environment.

14-15 depict example systems that can be employed to implement various aspects of the functionality described herein.

Fig. 16 depicts an example wireless communication system that can be employed in conjunction with the various systems and methods described herein.

Detailed Description

Various aspects of the present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. 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. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more aspects.

As used in this application, the terms "component," "module," "system," and the like are intended to refer to a computer-related entity, either 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 integrated circuit, 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 can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable storage media having various data structures 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).

The various techniques described herein may be used for various wireless communication systems such as Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and other such 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, and so on. UTRA includes wideband CDMA (W-CDMA) and other variants of CDMA. CDMA2000 covers IS-2000, IS-95 and IS-856 standards. TDMA systems may implement wireless technologies such as global system for mobile communications (GSM). OFDMA systems may implement wireless technologies such as evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.12(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, flash OFDM, and so on. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) is an upcoming release of UMTS that uses E-UTRA, which uses OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE, and GSM are described in documents from an organization named "third Generation partnership project" (3 GPP). In addition, CDMA2000 and UMB are described in documents from an organization named "third generation partnership project 2" (3GPP 2). Further, these wireless communication systems may additionally include peer-to-peer (e.g., mobile-to-mobile) ad hoc network systems that typically use unpaired unlicensed spectrum, 802.xx wireless LANs, BLUETOOTH, and any other short-range or long-range wireless communication technologies.

Single carrier frequency division multiple access (SC-FDMA) uses single carrier modulation and frequency domain equalization. SC-FDMA has similar performance and substantially the same overall complexity as OFDMA systems. The SC-FDMA signal has a low peak-to-average power ratio (PAPR) due to its inherent single carrier structure. For example, SC-FDMA may be used for uplink communications where a lower PAPR greatly benefits the UE in terms of transmit power efficiency. Thus, SC-FDMA is implemented as an uplink multiple access scheme in 3GPP Long Term Evolution (LTE) or evolved UTRA.

Moreover, various aspects are described herein in connection with a User Equipment (UE). A UE may refer to a device that provides voice and/or data connectivity. The UE may be connected to a computing device such as a laptop computer or desktop computer, or it may be a self-contained device such as a Personal Digital Assistant (PDA). A UE can also be called a system, subscriber unit, subscriber station, mobile, remote station, remote terminal, mobile device, user terminal, wireless communication device, user agent, user device, or access terminal. A UE may be a cellular 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. Various aspects are described herein in connection with a base station. A base station may be utilized for communicating with the UEs and may also be referred to as an access point, a node B, an evolved node B (eNodeB, eNB), or some other terminology. A base station may refer to a device in an access network that communicates over the air-interface, through one or more sectors, with UEs. The base station may act as a router between the wireless terminal and the rest of the access network, including an Internet Protocol (IP) network, by converting received air-interface frames to IP packets. The base station may also coordinate the management of attributes for the air interface.

Furthermore, the term "or" means an inclusive "or" rather than an exclusive "or". That is, the phrase "X employs A or B" means any normal or permutation, unless stated otherwise or clear from context. That is, if X employs A; b is used as X; or X employs A and B, then the phrase "X employs A or B" is satisfied in any of the above instances. 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.

Furthermore, the various functions described herein may be implemented in hardware, software, firmware, or any combination thereof. When 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. Further, any connection is properly 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 (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 (BD), where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

This application is intended to present aspects in the context of a system that includes 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 one or more of the devices, components, modules etc. discussed in connection with the figures. Combinations of these approaches may also be used.

Referring now to FIG. 1, a system 100 is depicted in accordance with various aspects presented herein. System 100 includes a base station 102 that can have multiple antenna groups. For example, one antenna group can include antennas 104 and 106, another group can include antennas 108 and 110, and an additional group can include antennas 112 and 114. Two antennas are shown for each antenna group; however, more or fewer antennas may be used for each group. Base station 102 can additionally include a transmitter chain and a receiver chain, each of which can in turn comprise a plurality of components associated with signal transmission and reception (e.g., processors, modulators, multiplexers, demodulators, demultiplexers, antennas, etc.), as will be appreciated by one skilled in the art.

Base station 102 may communicate with one or more User Equipments (UEs) such as UE 116 and UE 122; however, it should be appreciated that base station 102 may communicate with virtually any number of UEs similar to UE 116 and UE 122. For example, UE 116 and UE122 may be cellular phones, smart phones, laptops, handheld communication devices, handheld computing devices, satellite radios, global positioning systems, PDAs, and/or any other suitable device for communicating over system 100. As shown, UE 116 is in communication with antennas 112 and 114, where antennas 112 and 114 transmit information to UE 116 over a forward link 118 and receive information from UE 116 over a reverse link 120. In addition, UE122 is in communication with antennas 104 and 106, where antennas 104 and 106 transmit information to UE122 over a forward link 124 and receive information from UE122 over a reverse link 126. In a Frequency Division Duplex (FDD) system, forward link 118 can utilize a different frequency band than that used by reverse link 120, and forward link 124 can employ a different frequency band than that employed by reverse link 126. Further, in a Time Division Duplex (TDD) system, forward link 118 and reverse link 120 can utilize a common frequency band and forward link 124 and reverse link 126 can utilize a common frequency band.

Each antenna group and/or the area in which they are designated to communicate can be referred to as a sector of base station 102. For example, antenna groups can be designed to communicate to UEs in a sector of the areas covered by base station 102. In communication over forward links 118 and 124, the transmitting antennas of base station 102 may use beamforming to improve signal-to-noise ratio of forward links 118 and 124 for UE 116 and UE 122. Moreover, when base station 102 uses beamforming to transmit to UEs 116 and 122 scattered randomly through an associated coverage, UEs in neighboring cells can be subject to less interference as compared to a base station transmitting through a single antenna to all its UEs.

System 100 can employ UE-specific reference signals (UE-RSs) to facilitate downlink channel estimation. In particular, base station 102 may identify a number of symbols in a subframe for downlink transmission. The number of symbols in a subframe used for downlink transmission varies according to: whether the subframe is a regular subframe (e.g., all symbols of the subframe are used for downlink transmission.), whether the subframe includes a downlink pilot time slot (DwPTS), whether the subframe is used for downlink transmission to a relay station (where one or more symbols in the subframe are reserved as gap symbols), and so on. For example, if the subframe includes a DwPTS, the subframe may be a mixed subframe from a radio frame having a frame structure type 2 for TDD. Continuing the example, one or more symbols in the hybrid subframe may be allocated for a guard period or an uplink pilot time slot (UpPTS); thus, these one or more symbols from the mixed subframe are not used for DwPTS and thus not for downlink transmission. Further, base station 102 can map the UE-RS to Resource Elements (REs) of the subframe according to a UE-RS pattern corresponding to a number of symbols in the subframe utilized for downlink transmission.

For example, for a regular subframe, the base station 102 can map the UE-RS to REs in the subframe according to a first UE-RS pattern. Moreover, when a smaller number of symbols of a subframe are used for downlink transmission than a regular subframe (e.g., at least one symbol in the subframe is not used for downlink transmission.), base station 102 may map UE-RSs to REs in the subframe according to a second UE-RS pattern. The first UE-RS pattern may include a plurality of frequency domain components and a plurality of time domain components. Changing at least one of the plurality of time domain components from the first UE-RS pattern in the second UE-RS pattern. For example, in the second UE-RS pattern, one of the multiple time domain components from the first UE-RS pattern can be time shifted. For example, as another example, multiple time domain components from a first UE-RS pattern can be time shifted in a second UE-RS pattern. Continuing with the example, the plurality of time domain components from the first UE-RS pattern are time-shifted by a common number of symbols or by different numbers of symbols, respectively. According to another example, one of the plurality of time domain components from the first UE-RS pattern is punctured in the second UE-RS pattern. Further, the second UE-RS pattern has the same frequency domain components as the first UE-RS pattern.

Turning now to fig. 2, an example wireless network 200 that facilitates downlink channel estimation using UE-RSs is depicted in accordance with various aspects. Wireless network 200 includes wireless device 202 and wireless device 220 that communicate with each other over a wireless network. By way of example, wireless device 202 and/or wireless device 220 can be an access point (e.g., a macrocell access point, femtocell or picocell access point, eNB, mobile base station, and portions thereof) and/or virtually any device or apparatus that provides access to a wireless network. In another example, wireless device 202 and/or wireless device 220 can be a mobile device (e.g., a UE and portions thereof) and/or virtually any device or apparatus that receives access to a wireless network.

Wireless device 202 may include multiple communication layers to facilitate transmitting/receiving data with wireless device 220. For example, wireless device 202 can include a Packet Data Convergence Protocol (PDCP) module 206 that compresses packet headers and facilitates ciphering and integrity protection of data. The wireless device 202 may also include a Radio Link Control (RLC) module 208, a Medium Access Control (MAC) module 210, and a physical layer module 212, where the RLC module 208 implements segmentation/concatenation, retransmission processing, and in-order delivery to higher layers, the MAC module 210 implements logical channel multiplexing, hybrid automatic repeat request (HARQ) retransmission, and scheduling, and the physical layer module 212 manages encoding/decoding, modulation/demodulation, and antenna/resource mapping. Likewise, the wireless device 220 may include a PDCP module 224, an RLC module 226, a MAC module 228, and a physical layer module 230 that provide the same or similar functionality.

According to one example, wireless device 202 transmits an Internet Protocol (IP) packet 204 to wireless device 220 over a wireless channel. The wireless channel may be a downlink channel or an uplink channel. Higher layers (not shown) of wireless device 202 generate IP packets 204 or receive IP packets 204 for transmission to one or more devices. Higher layers may include an application layer, an IP layer, and the like. The PDCP module 206 can receive IP packets 204 from higher layers and generate one or more PDCP Service Data Units (SDUs). The PDCP module 206 may perform IP header compression on the IP packet 204. In addition, the PDCP module 206 can cipher the IP packet 204 and/or provide integrity protection for the IP packet 204. The PDCP module 206 can also generate PDCP Protocol Data Units (PDUs) by combining the compressed and ciphered IP packets 204 (e.g., PDCP SDUs) with a PDCP header that includes at least a sequence number associated with the PDCP SDUs. The PDCP PDUs can be provided to an RLC module 208, which segments or concatenates one or more PDCP PDUs into an RLC PDU and an RLC header. For example, a particular amount of data is selected for transmission from an RLC buffer managed by the RLC module 208 based on a resource scheduling decision, wherein the RLC module 208 segments or concatenates one or more PDCP PDUs to generate an RLC PDU.

The RLC module 208 provides RLC PDUs to the MAC module 210, where the MAC module 210 provides MAC layer services (e.g., multiplexing, HARQ retransmissions, scheduling, etc.) in the form of logical channels to the RLC module 208. The logical channels may be characterized according to the type of information carried. For example, the logical channels provided by the MAC module 210 may include: a Broadcast Control Channel (BCCH) carrying system information from the wireless network to the mobile devices, a Paging Control Channel (PCCH) for paging the mobile devices, a Common Control Channel (CCCH) carrying control information for random access, a Dedicated Control Channel (DCCH) carrying control information to and/or from the mobile devices, a Dedicated Traffic Channel (DTCH) for user data to and/or from the mobile devices, a Multicast Control Channel (MCCH) used to carry control information for a Multicast Traffic Channel (MTCH) carrying a transmission of multimedia broadcast multicast traffic.

The MAC module 210 may map logical channels to transport channels, where the transport channels represent services provided by the physical layer module 212. Data on the transport channels is organized into transport blocks. One or more transport blocks are transmitted over the radio interface for a given Transmission Time Interval (TTI). In one example, the MAC module 210 multiplexes RLC PDUs into one or more transport blocks.

The transport blocks may be provided to a physical layer module 212 that facilitates coding, modulation, multi-antenna processing, and/or mapping of signals to physical time-frequency resources (e.g., REs. -). According to an example, the physical layer module 212 can introduce a Cyclic Redundancy Check (CRC) to the transport block to facilitate error detection. In addition, the physical layer module 212 may include an encoding module 214 that encodes bits of the transport block. For example, the encoding module 214 may use Turbo coding. The physical layer module 212 may include a modulation module 216 that modulates the coded bits to generate symbols. The physical layer module 212 may configure the antennas using the mapping module 218 to provide different multi-antenna transmission schemes, such as transmit diversity, beamforming, and/or spatial multiplexing. In addition, the mapping module 218 may map the symbols to physical resource units to enable transmission over the air.

Wireless device 202 may use one or more antennas 240 to send IP packet 204 to wireless device 220, where wireless device 220 receives the transmission through antenna 250. Although fig. 2 depicts two antennas associated with wireless device 202 and wireless device 220, respectively, it should be understood that wireless device 202 and wireless device 220 may include nearly any number of antennas. After receiving the IP packet 204 from the wireless device 202, the wireless device 220 may use the physical layer module 230 to decode and demodulate the transmission. For example, the physical layer module 230 may include a demapping module 236 that demaps the REs to recover a set of symbols. The physical layer module 230 may also use a demodulation module 234 that demodulates the set of symbols to recover a set of coded bits. Further, a decoding module 232 is included in the physical layer module 230 to decode the set of encoded bits to generate a transport block. The transport block is provided to the MAC module 228 to manage HARQ retransmissions if needed due to errors (e.g., decoding errors, transmission errors..) to facilitate MAC demultiplexing to generate one or more RLC PDUs. The one or more RLC PDUs may be provided to the RLC module 226 for group reporting. For example, the RLC PDUs may include one or more RLC SDUs and/or portions thereof. Accordingly, the RLC module 226 reconstructs RLC SDUs from these RLC PDUs. The reassembled RLC SDUs can be processed by the PDCP module 224, wherein the PDCP module 224 decrypts and decompresses the RLC SDUs to recover one or more data packets (e.g., IP packet 222).

It is to be appreciated that wireless device 220 can employ similar functionality and/or similar modules as wireless device 202 to transmit data packets to wireless device 202. Further, wireless device 202 may receive transmissions from a different device (e.g., wireless device 220) using similar modules and/or functionality as described above for wireless device 220.

According to an example in which the wireless device 202 transmits the IP packet 204 to the wireless device 220, the wireless device 220 can use the estimate of the downlink channel to facilitate coherent demodulation of the downlink physical channel used to transmit the IP packet 204. To enable channel estimation, wireless device 202 can include a reference signal in a transmission to wireless device 220. For example, when the transmission is an OFDM transmission, the wireless device 202 can include a reference signal. For example, wireless device 202 can use physical layer module 212 and/or mapping module 218 to map reference signals to resource elements in a TTI corresponding to a transmission to wireless device 220. In an aspect, the reference signal may be a cell-specific reference signal (CRS), wherein the CRS is transmitted in multiple downlink subframes and may span the entire bandwidth of the downlink. The reference signals may also be UE-RS, where the UE-RS is transmitted in subframes and resource blocks for a particular receiving device or group of receiving devices.

Also, reference is made to the example where wireless device 202 transmits a signal to wireless device 220. To enable the wireless device 220 to generate channel estimates for the transmission, the UE-RS is incorporated and beamformed in a manner similar to data transmission. By way of example, wireless device 202 can employ physical layer module 212 to generate UE-RS, and mapping module 218 can insert UE-RS at particular REs according to a UE-RS pattern.

According to one example, a UE-RS pattern may span a pair of Resource Blocks (RBs) (e.g., a set of REs) included in one subframe. The pair of RBs may be provided to have a duration of one subframe (e.g., 1 ms.,.) and a time-frequency grid (time-frequency grid) spanning 12 subcarriers. One subframe may include two slots, where each slot has six or seven symbols in length, depending on the cyclic prefix used. In this regard, a pair of RBs may include 12x12 bins or 12x14 bins of REs. However, it should be understood that other RB conventions may be provided and that the UE-RS patterns described below may be applicable to different RB conventions.

In another aspect, a UE-RS pattern for downlink transmission depends on a number of symbols in a subframe used for downlink transmission. According to an example, a first UE-RS pattern can be used when a regular subframe is used for downlink transmission. Continuing with the example, the first UE-RS pattern may be used when all symbols of one subframe are used for downlink transmission (e.g., a normal subframe, fourteen symbols in the subframe are used for downlink transmission when a normal cyclic prefix is used). As another example, a second UE-RS pattern may be used when one or more symbols of a subframe are not used for downlink transmission. According to this example, when the subframe includes a DwPTS, one or more symbols of the subframe are not used for downlink transmission. Alternatively, when a subframe is used for downlink transmission to a relay station, one or more symbols of the subframe are not used for downlink transmission, wherein one or more symbols in the subframe are reserved for use as gap symbols. For example, when a normal cyclic prefix is used, a second UE-RS pattern may be used when less than fourteen symbols in a subframe are used for downlink transmission.

The second UE-RS pattern for the subframe is different from the first UE-RS pattern for a regular subframe, wherein the subframe has at least a subset of symbols not used for downlink transmission. For example, the second UE-RS pattern takes into account the number of symbols used for downlink transmission; however, it should be understood that the invention is not so limited. According to another example, the second UE-RS pattern used in the case where at least a subset of the symbols of the subframe are not used for downlink transmission may be based on the first UE-RS pattern used for the regular subframe. Continuing with the example, a first UE-RS pattern for a regular subframe may be time shifted and/or punctured to obtain a second UE-RS pattern for the subframe in which at least a subset of symbols are not used for downlink transmissions.

As further depicted in the system 200, the wireless device 202 can include a processor 217 and/or a memory 219, wherein the processor 217 and/or the memory 219 can be utilized to implement some or all of the functionality of the PDCP module 206, the RLC module 208, the MAC module 210, and the physical layer module 212. Likewise, fig. 2 depicts the wireless device 220 further comprising a processor 237 and/or memory 239, wherein the processor 237 and/or memory 239 may be used to implement some or all of the functionality of the PDCP module 224, the RLC module 226, the MAC module 228, and the physical layer module 230. By way of example, the memories 219 and/or 239 may store computer program products for enabling use of the UE-RS as described herein.

Referring next to fig. 3, a system 300 that facilitates mapping UE-RSs to REs in a subframe in a wireless communication environment is illustrated. The system 300 includes a base station 302 that communicates with a UE 304. Although base station 302 and UE304 are depicted in fig. 3, it should be appreciated that system 300 can include any number of base stations and/or UEs. In accordance with an aspect, base station 302 can transmit information to UE304 over a forward link or downlink channel, and UE304 can transmit information to base station 302 over a reverse link or uplink channel. It should be understood that system 300 may operate in an OFDMA wireless network, a CDMA network, a 3GPP LTE or LTE-A wireless network, a 3GPP2 CDMA2000 network, an EV-DO network, a WiMAX network, and so forth.

Base station 302 can include a scheduler 306 that schedules and allocates radio resources to one or more UEs (e.g., UE 304) to provide uplink and downlink transmissions. For example, scheduler 306 may allocate one or more resource blocks to UE304 for downlink transmission. The one or more resource blocks may be located in the same subframe or in different subframes.

The scheduler 306 may allocate radio resources from various types of subframes to the UE304 for downlink transmission. For example, scheduler 306 may allocate radio resources from regular subframes to UE 304; thus, radio resources on all symbols in a regular subframe allocated to the UE304 may be used for downlink transmission. According to another example, the scheduler 306 may allocate radio resources in subframes that include the DwPTS to the UE 304. Continuing with the example, radio resources from a subset of symbols in a subframe that includes the DwPTS may be used for downlink transmissions while radio resources from the remaining portion of symbols in the subframe are not used for downlink transmissions (e.g., instead for a guard period or uplink transmissions as part of the UpPTS).

Although not shown, it is also contemplated that system 300 may include a relay station, according to another example. On the downlink, base station 302 transmits a signal to a relay station, which transmits a signal to a UE associated with the relay station. Likewise, on the uplink, the UE associated with the relay station transmits a signal to the relay station, which in turn transmits a signal to the base station 302. In general, a relay station is not capable of transmitting and receiving signals simultaneously (e.g., during a common subframe, etc.). Thus, if base station 302 transmits a packet on the downlink that is part of a given subframe, relay stations may receive the packet transmitted by base station 302 (e.g., after a delay). Thereafter, the relay station transmits the packet to a UE associated with the relay station on a downlink that is part of a later subframe. Thus, the relay station may listen for the packet during the first subframe and then switch to transmission of the packet during the second subframe. However, the transition from listening to transmitting takes time, so the last one or two (or more) symbols from the first subframe may be reserved as gap symbols to support the backhaul relay connection. Thus, scheduler 306 may allocate radio resources for downlink transmission in a subframe to a relay station, wherein one or more symbols in the subframe are reserved as gap symbols; thus, radio resources from a subset of the symbols in the subframe may be used for downlink transmission, while radio resources from the remainder of the symbols in the subframe are reserved as gap symbols.

In addition, the base station 302 can include a mode selection module 308 and a dedicated reference signal module 310. The dedicated reference signal module 310 can generate a UE-RS and insert the UE-RS on radio resources in a subframe allocated by the scheduler 306 for transmission to the UE 304. The dedicated reference signal module 310 may generate a UE-RS and/or map the UE-RS to one or more REs according to the UE-RS pattern selected by the pattern selection module 308.

The mode selection module 308 can select a UE-RS mode to be used by the dedicated reference signal module 310. The mode selection module 308 can select the UE-RS mode based on the number of symbols from the subframe allocated by the scheduler 306 for downlink transmission. For example, the UE-RS pattern selected by the pattern selection module 308 for subframes that include DwPTS is different from the UE-RS pattern selected by the pattern selection module 308 for regular subframes. The DwPTS spans only a fraction of a subframe, and downlink transmission may use symbols included in the DwPTS. According to another example, mode selection module 308 considers the number of symbols of a subframe for the DwPTS (e.g., as managed by scheduler 306). The following table gives the number of symbols comprising the DwPTS in both the normal Cyclic Prefix (CP) subframe and the extended Cyclic Prefix (CP) subframe (e.g., for release 8.,) for different configurations (conf). It should be noted that for a DwPTS of 3 symbols, there is no Physical Downlink Shared Channel (PDSCH) transmission and therefore a scenario with a DwPTS greater than 3 symbols may be considered.

According to an example, the UE-RS pattern selected or generated by the mode selection module 308 for the DwPTS can be based on the UE-RS pattern used for the regular subframe. Thus, the mode selection module 308 may obtain the UE-RS pattern for the DwPTS by time shifting and/or puncturing the UE-RS pattern for regular subframes. For example, puncturing the UE-RS pattern for the regular subframes refers to preserving the time domain components of the UE-RS pattern for the regular subframes (e.g., which belong to the symbol..) as part of the DwPTS. Further, time shifting the UE-RS pattern of the regular subframe refers to shifting the time domain component of the UE-RS pattern of the regular subframe by a given value (e.g., number of symbols). According to an example, all time domain components of the UE-RS pattern of a regular subframe can be time shifted by a given value. According to further examples, a subset of time domain components of the UE-RS pattern of the regular subframe may be time shifted by a given value, while other time domain components of the UE-RS pattern of the regular subframe are not time shifted, time shifted by a different value, and so forth. Thus, for example, the mode selection module 308 may obtain the UE-RS pattern for subframes that include the DwPTS by time shifting and/or puncturing the UE-RS pattern for regular subframes. The simplifications and conventional structures of the above operations implemented by the mode selection module 308 may be used to simplify the implementation of the system 300.

Further, the maximum number of control symbols in the DwPTS may be two. Thus, when generating a subframe including the DwPTS, the mode selection module 308 may shift the UE-RS pattern for the regular subframe toward the edge of the subframe including the DwPTS. Further, the mode selection module 308 can shift the UE-RS pattern of the regular subframe according to the number of configured control symbols. According to another example, the mode selection module 308 can use a fixed UE-RS pattern that is independent of the number of control symbols configured in the regular subframe.

The puncturing and time shifting operations implemented by the mode selection module 308 may be applied to UE-RS patterns of RBs that may have collisions with different signals and channels (e.g., Primary Synchronization Signal (PSS), Physical Broadcast Channel (PBCH), Secondary Synchronization Signal (SSS), etc.). Moreover, puncturing and time shifting operations implemented by the mode selection module 308 can be used to design a UE-RS pattern for a backhaul relay connection, in which case it is desirable to reserve one or two (or more) last symbols of a subframe as gap symbols. It should be understood, however, that the invention is not limited by the foregoing description.

Continuing with the example of system 300 that includes a relay station, when the relay station transitions from downlink reception from base station 302 to downlink transmission to a UE associated with the relay station, the relay station may lose the last one or two (or more) symbols from a subframe, where the one or two (or more) symbols are reserved as gap symbols. Thus, on normal subframes of the relay station and UE304 scheduled by base station 302 (e.g., by scheduler 306...), mode selection module 308 can use a first UE-RS pattern (e.g., a regular UE-RS pattern.,...) for UE304 and a second UE-RS pattern (e.g., punctured, time-shifted....) for the relay station. Thus, the mode selection module 308 can select a UE-RS mode depending on whether a downlink transmission is sent to the UE or the relay station.

Radio resources from subframes with incorporated UE-RSs may be transmitted to the UE 304. The UE304 may include an allocation analysis module 312 that identifies one or more resource blocks in one or more subframes allocated to the UE 304. Allocation analysis module 312 may analyze control information included on a control channel (e.g., a Physical Downlink Control Channel (PDCCH)) to identify the one or more resource blocks. Further, the allocation analysis module 312 can identify a number of symbols of a subframe for downlink transmission to the UE 304.

After receiving the one or more resource blocks, the UE304 can use the reference signal evaluation module 314 to extract the UE-RS from the one or more resource blocks. For example, the reference signal evaluation module 314 can identify the UE-RS inserted in the one or more resource blocks by knowledge of the UE-RS pattern used by the base station 302. The UE-RSs are provided to a channel estimation module 316, which generates channel estimates to facilitate demodulation of data in one or more resource blocks associated with the UE-RSs.

Referring to fig. 4-8, illustrated are UE-RS patterns for use in accordance with various aspects described herein. For simplicity of illustration, these UE-RS patterns are shown and described in the context of a pair of resource blocks, where each resource block includes twelve subcarriers in the frequency domain and one slot with seven symbols in the time domain. It is to be understood and appreciated that these UE-RS patterns are not limited by the constraints of the described resource block pairs, as some resource block pairs include different dimensions (e.g., different numbers of subcarriers and/or different durations (number of symbols)) in accordance with one or more embodiments. Further, the resource block pairs described and depicted herein are numbered in the frequency domain by an index corresponding to each subcarrier. As shown in fig. 4-8, the subcarriers are numbered from 1 to 12, starting with the top or higher frequency subcarriers. Further, in the time domain, the resource block pairs are numbered by an index corresponding to each symbol (e.g., OFDM symbol,...) in the subframe from 1 to 14, starting at the beginning of the subframe. It should be understood that these structures are not limited to the numbering conventions depicted herein, and that other conventions may also be used. For example, those of ordinary skill in the art will understand and appreciate that resource block pairs may be represented by other labeling conventions for resource blocks. Furthermore, it should be understood that the structures described in fig. 4-8 are intended to encompass equivalent structures derived by shifting the reference symbol positions in the time and/or frequency domain.

Turning to fig. 4, an example subframe 400 that can be employed in a wireless communication environment is depicted. The subframe 400 may be used for a normal Cyclic Prefix (CP). It should be understood that the subframe 400 is provided as an example, and the present invention is not limited thereto.

Subframe 400 may have a duration of 1ms, which may include two slots (e.g., each slot having a duration of 0.5 ms.). In the depicted example, in the case of a normal CP length, one slot of the subframe 400 includes seven symbols; thus, subframe 400 includes fourteen symbols. As another example, it is contemplated that a subframe (not shown) using extended CP may include two slots, each of which may include six symbols. It should be understood, however, that the present invention is not limited by the foregoing examples.

In the frequency domain, the resources of subframe 400 may be grouped in units of twelve subcarriers (e.g., 180 kHz.). A unit of twelve subcarriers having a duration of one slot (e.g., 0.5 ms.,..) may be referred to as one Resource Block (RB) (e.g., one example is RB 402.,..). The subframe 400 includes a pair of RBs. The smallest unit of resource may be referred to as a Resource Element (RE), which may be one subcarrier for one symbol in duration (e.g., one example is RE 404,. included in RB 402). For the normal CP, one RB includes 84 REs (or for the extended CP, one RB includes 72 REs).

According to one example, subframe 400 may be a regular subframe. Continuing with this example, up to the first three symbols of subframe 400 may be control symbols (e.g., the first one, two, or three symbols of subframe 400 may be control symbols, and the remaining symbols may be for data.). According to another example, the subframe 400 may be a subframe including a DwPTS; thus, up to the first two symbols of the subframe 400 may be control symbols. It should be noted that the UE-RS is transmitted in the data portion of the subframe.

REs in subframe 400 may carry CRS and UE-RS. For example, CRS (e.g., one example is CRS 406.,) may be mapped to REs on the first, second, fifth, eighth, ninth, and twelfth symbols of subframe 400. However, it should be understood that the present invention is not limited by this example, as other mapping manners of the CRS also fall within the scope of the claims appended to the present application.

Further, the UE-RS can be mapped to REs according to a UE-RS pattern as described herein. A UE-RS pattern for multiple layers can be specified. The multiple layers in the UE-RS mode may be multiplexed using a combination of Code Division Multiplexing (CDM)/Frequency Division Multiplexing (FDM) and/or Time Division Multiplexing (TDM). For example, the UE-RS pattern may support up to two layers. Thus, a UE-RS pattern may include multiple CDM groups, where one CDM group maps to two temporally consecutive REs (e.g., one example is CDM group 408). Therefore, the pilots of the two layers can be orthogonally multiplexed on two time-consecutive REs. Each layer is assigned a spreading sequence, which may be spread over the RE set shared by the other layers using the spreading sequence assigned by the UE-RS for each layer. In addition, the assigned spreading sequences may be selected to be orthogonal, thereby minimizing cross-interference.

Fig. 4 depicts a UE-RS pattern for a regular subframe. The UE-RS pattern of a regular subframe includes a frequency domain component and a time domain component. The frequency domain components refer to all CDM groups on the same subcarrier; thus, the depicted UE-RS pattern for a regular subframe includes three frequency domain components (e.g., three displays in frequency). Furthermore, the time domain component refers to all CDM groups on the same set of symbols. The described UE-RS pattern for a regular subframe includes two time domain components (e.g., two displays in time.. department), where one time domain component includes three CDM groups on symbols 6 and 7 from subframe 400 and the other time domain component includes three CDM groups on symbols 13 and 14 from subframe 400. Accordingly, the UE-RS pattern of a regular subframe may include all six CDM groups, which may mitigate the impact due to channel changes in frequency and time.

Referring now to fig. 5, an example time shifted UE-RS pattern is depicted in accordance with various aspects. Fig. 5 depicts a UE-RS pattern 500 and a time shifted UE-RS pattern 502 for a regular subframe. For example, when the subframe includes a DwPTS, a time shifted UE-RS pattern 502 may be used. Thus, no downlink transmission is sent on a subset of symbols of the end portion of the subframe, wherein the number of symbols comprised in the subset depends on the DwPTS configuration. Much of the following discussion in relation to fig. 5-8 follows this example, i.e., in this example, a subset of symbols is not used for downlink transmission since the subframe includes a DwPTS. However, it should be understood that at least a portion of the following may extend to subframes used in connection with downlink transmissions to a relay station, where one or more symbols in the subframe are reserved as gap symbols (e.g., according to the number of control symbols).

Similar to the UE-RS pattern in fig. 4, the UE-RS pattern 500 includes two time domain components: namely a time domain component 504 and a time domain component 506. To generate the time-shifted UE-RS pattern 502, the time domain component 504 and the time domain component 506 are time-shifted by a common number of symbols. Specifically, time domain component 504 and time domain component 506 are each shifted by three symbols, resulting in a time shifted UE-RS pattern 502 with time domain component 508 and time domain component 510. Time domain component 508 includes three CDM groups on symbols 3 and 4, and time domain component 510 includes three CDM groups on symbols 10 and 11.

According to one example, when the DwPTS includes seven or twelve symbols, the time-shifted UE-RS pattern 502 may be used and, thus, the last two or three symbols (e.g., symbols 12-14 or symbols 13-14). Furthermore, the time-shifted UE-RS pattern 502 provides the same pilot spacing as compared to the UE-RS pattern 500, since the UE-RS pattern 500 is uniformly shifted in time. For subframes that include DwPTS, a time shifted UE-RS pattern 502 may be used because at most two control symbols (e.g., the previous one or two symbols..) are included in the control domain of the subframe compared to a conventional subframe that includes at most three control symbols (e.g., the previous one, two, or three symbols..) in the control domain. Furthermore, the frequency domain components between the UE-RS pattern 500 and the time shifted UE-RS pattern 502 remain unchanged.

Referring to fig. 6, an example punctured UE-RS pattern is depicted in accordance with various aspects. Fig. 6 depicts a UE-RS pattern 600 and a punctured UE-RS pattern 602 for a regular subframe. As described herein, the UE-RS pattern 600 includes two time domain components: namely a time domain component 604 and a time domain component 606. To generate the punctured UE-RS pattern 602, the time domain component 606 (e.g., the second time domain component of the punctured UE-RS pattern 602..) is punctured (e.g., deleted.). Thus, the punctured UE-RS pattern 602 includes a time domain component 608 (which includes three CDM groups on symbols 3 and 4), and has no second time domain component. When the DwPTS includes nine, ten, eleven, or twelve symbols, the punctured UE-RS pattern 602 may be used and thus the last two, three, four, or five symbols (e.g., symbols 10-14, 11-14, 12-14, or 13-14). Furthermore, the frequency domain components between the UE-RS pattern 600 and the punctured UE-RS pattern 602 remain unchanged.

Turning to fig. 7, an example partial time shifted UE-RS pattern is depicted in accordance with various aspects. Fig. 7 depicts a UE-RS pattern 700 and a partially time shifted UE-RS pattern 702 for a regular subframe. As described herein, the UE-RS pattern 700 includes two time domain components: namely a time domain component 704 and a time domain component 706. To generate a partially time shifted UE-RS pattern 702, a portion of the UE-RS pattern 700 is time shifted. Specifically, the time domain component 706 may be shifted by three symbols without shifting the time domain component 704. The above-described operations result in a UE-RS pattern 702 with a partial time shift of the time domain component 708 and the time domain component 710. Time domain component 708 includes three CDM groups on symbols 6 and 7, and time domain component 710 includes three CDM groups on symbols 10 and 11. Thus, the interval between time domain component 704 and time domain component 706 in UE-RS pattern 700 is not the same as the interval between time domain component 708 and time domain component 710 in partially time shifted UE-RS pattern 702. When the DwPTS includes seven or twelve symbols, the partially time shifted UE-RS pattern 702 may be used and thus the last two or three symbols (e.g., symbols 12-14 or symbols 13-14..) are not used for downlink transmission. Furthermore, the frequency domain components between the UE-RS pattern 700 and the partially time shifted UE-RS pattern 702 remain unchanged.

For example, the partially time shifted UE-RS pattern 702 may be used for a relay station. For a relay station, up to the first three symbols may be configured as control symbols. Thus, the partially time shifted UE-RS pattern 702 avoids the first three symbols. Further, the partially time shifted UE-RS pattern 702 avoids the last few (e.g., one or more,..) symbols that the relay may use as gap periods.

Referring to fig. 8, an exemplary time shifted UE-RS pattern is depicted in accordance with various aspects. Fig. 8 depicts a UE-RS pattern 800 and a time shifted UE-RS pattern 802 for a regular subframe. As described herein, the UE-RS pattern 800 includes two time domain components: namely a time domain component 804 and a time domain component 806. To generate the time-shifted UE-RS pattern 802, the time domain component 804 and the time domain component 806 are time-shifted by different numbers of symbols, respectively. For example, time domain component 804 may be shifted by three symbols and time domain component 806 by seven symbols, which results in a UE-RS pattern 802 with a time shift of time domain component 808 and time domain component 810. Time domain component 808 includes three CDM groups on symbols 3 and 4, and time domain component 810 includes three CDM groups on symbols 6 and 7. Thus, the interval between time domain component 804 and time domain component 806 in UE-RS pattern 800 is not the same as the interval between time domain component 808 and time domain component 810 in time shifted UE-RS pattern 802. When the DwPTS includes nine, ten, eleven, or twelve symbols, a time-shifted UE-RS pattern 802 may be used and, thus, the last two, three, four, or five symbols (e.g., symbols 10-14, 11-14, 12-14, or 13-14). Furthermore, the frequency domain components between the UE-RS pattern 800 and the time shifted UE-RS pattern 802 remain unchanged.

Turning to fig. 9, an example subframe 900 that can be employed in a legacy wireless communication environment is depicted. Subframe 900 may carry Dedicated Reference Signals (DRSs), where DRSs are mapped to REs according to a legacy DRS mode. For example, the legacy DRS mode may be used for a release 8 wireless communication environment.

Fig. 9 is provided to highlight the differences between the puncturing described in the present application and the puncturing in the context of the conventional DRS mode. Since the time-domain CDM group is used for the UE-RS patterns described herein (e.g., the UE-RS patterns described in fig. 4-8), the pilots (e.g., UE-RS) on symbols 13 and 14 are deleted (e.g., punctured), for a subframe having thirteen symbols, although symbol 13 is still used for downlink transmission. Therefore, when puncturing, all CDM groups are deleted.

In contrast, the legacy DRS mode of subframe 900 may be used for rank 1 (one layer) transmission. The legacy DRS mode may be punctured if the subframe 900 is a DwPTS subframe. For example, for a sub-frame having 10-12 symbols, the first three displays in time are kept, while the fourth display in time is punctured. According to another example, for a sub-frame having 7-9 symbols, the first two displays in time are kept, while the next two displays in time are punctured. It should be understood, however, that the present invention is not limited to the example described in connection with fig. 9.

Referring to fig. 10-11, methodologies relating to utilizing a UE-RS in a wireless communication environment are illustrated. While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts may, in accordance with one or more embodiments, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with one or more embodiments.

With reference to fig. 10, illustrated is a methodology 1000 that facilitates transmitting reference signals for channel estimation in a wireless communication environment. At 1002, a number of symbols in a subframe for downlink transmission is identified. The number of symbols in the subframe for downlink transmission may be identified, for example, by an assignment. For example, if the subframe is identified as a regular subframe, all symbols from the subframe are identified for downlink transmission. According to another example, if the subframe is identified as including a downlink pilot time slot (DwPTS), the number of symbols for downlink transmission may be the number of symbols included in the DwPTS as configured. As another example, if the subframe is used to send a downlink transmission to a relay station, it is identified that one or more symbols in the subframe are reserved as gap symbols.

At 1004, a user equipment-specific reference signal (UE-RS) pattern can be selected based on a number of symbols in the subframe for downlink transmission. For example, at least one time domain component of the UE-RS pattern may be changed according to the number of symbols used for downlink transmission in the subframe. The time domain component of the UE-RS pattern includes Code Division Multiplexing (CDM) sets on the same set of symbols. Furthermore, the frequency domain components of the UE-RS pattern do not change according to the number of symbols used for downlink transmission in the subframe. At 1006, the UE-RS is mapped to Resource Elements (REs) of the subframe according to the UE-RS pattern.

According to one example, at least one time domain component of the UE-RS pattern can be changed by time shifting the at least one time domain component according to a number of symbols in a subframe utilized for downlink transmission. For example, a set of time domain components of the UE-RS can be time-shifted by a common number of symbols. According to another example, a set of time domain components of the UE-RS can be time-shifted by different numbers of symbols, respectively. As another example, one time domain component of the UE-RS pattern can be time shifted while a different time domain component of the UE-RS pattern does not change in time. As another example, at least one time domain component of the UE-RS pattern can be changed by puncturing one time domain component of the UE-RS pattern based on a number of symbols in a subframe utilized for downlink transmission. According to another example, the UE-RS pattern can be selected based on whether a downlink transmission is sent to the relay or the UE.

Turning to fig. 11, illustrated is a methodology 1100 that facilitates estimating a channel in a wireless communication environment. At 1102, a number of symbols allocated for downlink transmission in a subframe is identified. For example, if the subframe is identified as a regular subframe, all symbols from the subframe are identified as allocated for downlink transmission. According to another example, if the subframe is identified as including a downlink pilot time slot (DwPTS), the number of symbols allocated for downlink transmission may be the number of symbols included in the DwPTS as configured.

At 1104, a user equipment-specific reference signal (UE-RS) pattern is identified based on a number of symbols allocated for downlink transmission in the subframe. For example, at least one time domain component of the UE-RS pattern may be changed according to the number of symbols allocated for downlink transmission in the subframe. The time domain component of the UE-RS pattern includes Code Division Multiplexing (CDM) sets on the same set of symbols. Furthermore, the frequency domain components of the UE-RS pattern do not change according to the number of symbols used for downlink transmission in the subframe. At 1106, UE-RSs are detected on Resource Elements (REs) of a subframe specified by the UE-RS pattern. At 1108, the channel is estimated from the UE-RSs.

According to one example, at least one time domain component of the UE-RS pattern can be changed by time shifting the at least one time domain component according to a number of symbols in a subframe utilized for downlink transmission. For example, a set of time domain components of the UE-RS can be time-shifted by a common number of symbols. According to another example, a set of time domain components of the UE-RS can be time-shifted by different numbers of symbols, respectively. As another example, one time domain component of the UE-RS pattern can be time shifted while a different time domain component of the UE-RS pattern does not change in time. As another example, at least one time domain component of the UE-RS pattern can be changed by puncturing one time domain component of the UE-RS pattern based on a number of symbols in a subframe utilized for downlink transmission.

It is to be appreciated that, in accordance with one or more aspects described herein, inferences can be made regarding transmitting and/or receiving UE-RSs in a wireless communication environment. As used herein, the term to "infer" or "inference" refers generally to the process of reasoning about or inferring states of the system, environment, and/or user from a set of observations as captured via events and/or data. Inference can be employed to identify a specific context or action, or can generate a probability distribution over states, for example. The inference can be probabilistic-that is, the computation of a probability distribution over states of interest based on a consideration of data and events. Inference can also refer to techniques employed for composing higher-layer events from a set of events and/or data. Such inference results in the construction of new events or actions from a set of observed events and/or stored event data, whether or not the events are correlated in close temporal proximity, and whether the events and stored event data come from one or several event and data sources.

With reference to fig. 12, illustrated is a system 1200 that enables transmitting reference signals in a wireless communication environment. For example, system 1200 can reside at least partially within a base station. It is to be appreciated that system 1200 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 1200 includes a logical grouping 1202 of electrical components that can act in conjunction. For example, logical grouping 1202 may include: an electrical component for identifying a number of symbols in a subframe for downlink transmission 1204. Moreover, logical grouping 1202 may also include: an electrical component for selecting a user equipment-specific reference signal (UE-RS) pattern based on a number of symbols in the subframe for downlink transmission 1206, wherein at least one time domain component of the UE-RS pattern varies based on the number of symbols in the subframe for downlink transmission. Moreover, logical grouping 1202 may also include: an electrical component 1208 for mapping UE-RSs to resource elements of the subframe according to the UE-RS pattern. Additionally, system 1200 can include a memory 1210 that retains instructions for executing functions associated with electrical components 1204, 1206, and 1208. While electrical components 1204, 1206, and 1208 are illustrated as being external to memory 1210, it is to be understood that one or more of electrical components 1204, 1206, and 1208 may exist within memory 1210.

With reference to fig. 13, illustrated is a system 1300 that enables estimating a channel in a wireless communication environment. System 1300 can reside within a UE, for instance. 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). System 1300 includes a logical grouping 1302 of electrical components that can act in conjunction. For example, logical grouping 1302 may include: an electrical component 1304 for identifying a number of symbols allocated for downlink transmission in a subframe. Moreover, logical grouping 1302 may also include: an electrical component 1306 for identifying a user equipment-specific reference signal (UE-RS) pattern as a function of a number of symbols allocated for downlink transmissions in the subframe, wherein at least one time domain component of the UE-RS pattern varies as a function of the number of symbols allocated for downlink transmissions in the subframe. Moreover, logical grouping 1302 may also include: an electrical component for detecting the UE-RS on Resource Elements (REs) in a subframe specified by the UE-RS pattern 1308. Moreover, logical grouping 1302 may also include: an electrical component 1310 for estimating a channel from the UE-RS. Additionally, system 1300 can include a memory 1312 that retains instructions for executing functions associated with electrical components 1304, 1306, 1308, and 1310. While shown as being external to memory 1312, it is to be understood that one or more of electrical components 1304, 1306, 1308 and 1310 can exist within memory 1312.

FIG. 14 depicts a system 1400 that can be employed to implement various aspects of the functionality described herein. System 1400 includes a base station 1402 (e.g., base station 302). Base station 1402 may receive signals from one or more UEs 1404 via one or more receive (Rx) antennas 1406 and transmit signals to one or more UEs 1404 via one or more transmit (Tx) antennas 1408. Moreover, base station 1402 can comprise a receiver 1410 that receives information from receive antenna 1406. According to an example, receiver 1410 can be operatively associated with a demodulator (Demod)1412 that demodulates received information. Demodulated symbols can be analyzed by a processor 1414. The processor 1414 can be coupled to the memory 1416, which can store data to be transmitted to or received from the UE1404 and/or any other suitable protocols, algorithms, information, etc., related to performing the various actions and functions described herein. For example, base station 1402 can employ processor 1414 to perform methodology 1000 and/or other similar and appropriate methodologies. Base station 1402 can additionally include a modulator 1418 that can multiplex the signal for transmission by transmitter 1420 through antenna(s) 1408.

Processor 1414 can be a processor dedicated to analyzing information received by receiver 1410, a processor dedicated to generating information for transmission by transmitter 1420, or a processor dedicated to controlling one or more modules of base station 1402. According to another example, processor 1414 can analyze information received by receiver 1410, generate information for transmission by transmitter 1420, and control one or more modules of base station 1402. For example, the one or more modules of base station 1402 can include a PDCP module, an RLC module, a physical layer module, a coding module, a modulation module, a mapping module, a scheduler, a mode selection module, and/or a dedicated reference signal module. Further, although not shown, it is contemplated that one or more of the modules of base station 1402 can be part of processor 1414 or a plurality of processors (not shown).

FIG. 15 depicts an example system 1500 that can be employed to implement various aspects of the functionality described herein. System 1500 includes a UE1502 (e.g., UE 304). The UE1502 can receive signals from one or more base stations 1504 and/or transmit signals to one or more base stations 1504 via one or more antennas 1506. In addition, UE1502 can comprise a receiver 1508 that receives information from antenna 1506. According to an example, the receiver 1508 can be operatively associated with a demodulator (Demod)1510 that demodulates received information. The demodulated symbols can be analyzed by a processor 1512. Processor 1512 can be coupled to memory 1514, which can store data to be transmitted to and received from base station 1504, and/or any other suitable protocols, algorithms, information, and/or the like, related to performing various acts and functions described herein. For example, the UE1502 can employ the processor 1512 to perform the methodology 1100 and/or other similar and appropriate methodologies. UE1502 can also include a modulator 1516 that can multiplex a signal for transmission by a transmitter 1518 via antenna 1506.

Processor 1512 can be a processor dedicated to analyzing information received by receiver 1508, a processor dedicated to generating information for transmission by transmitter 1518, or a processor dedicated to controlling one or more modules of UE 1502. According to another example, the processor 1512 can analyze information received by the receiver 1508, generate information for transmission by the transmitter 1518, and control one or more modules of the UE 1502. For example, the one or more modules of the UE1502 can include a PDCP module, an RLC module, a physical layer module, a coding module, a modulation module, a mapping module, an allocation analysis module, a reference signal evaluation module, and/or a channel estimation module. Further, although not shown, it is contemplated that one or more modules of the UE1502 can be part of the processor 1512 or multiple processors (not shown).

Fig. 16 illustrates an exemplary wireless communication system 1600. For simplicity, the wireless communication system 1600 depicts one base station 1610 and one UE 1650. However, it is to be appreciated that system 1600 can include more than one base station and/or more than one UE, wherein the other base stations and/or UEs can be substantially similar or different from example base station 1610 and UE1650 described below. Moreover, it is to be appreciated that base station 1610 and/or UE1650 can employ the systems (fig. 1-3 and 12-15) and/or methods (fig. 10-11) described herein to facilitate wireless communication there between.

At base station 1610, traffic data for a number of data streams can be provided from a data source 1612 to a Transmit (TX) data processor 1614. According to an example, each data stream can be transmitted over a respective antenna. TX data processor 1614 formats, codes, and interleaves the traffic data stream based on a particular coding scheme selected for that data stream to provide coded data.

The coded data for each data stream can be multiplexed with pilot data using Orthogonal Frequency Division Multiplexing (OFDM) techniques. Additionally or alternatively, the pilot symbols may be Frequency Division Multiplexed (FDM), Time Division Multiplexed (TDM), or Code Division Multiplexed (CDM). In general, the pilot data is a known data pattern that is processed in a known manner and can be used by the UE1650 to estimate the channel response. The multiplexed pilot and coded data for each data stream can be modulated (e.g., symbol mapped) based on a particular modulation scheme (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), etc.) selected for that data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions performed or provided by processor 1630.

The modulation symbols for the data streams can be provided to a TX MIMO processor 1620, which TX MIMO processor 1620 can further process the modulation symbols (e.g., for OFDM). TX MIMO processor 1620 then forwards to N_TA transmitter (TMTR)1622a through 1622t provides N_TA stream of modulation symbols. In various embodiments, TX MIMO 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 upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. In addition, from N respectively_TAntennas 1624a through 1624t transmit N from transmitters 1622a through 1622t_TA modulated signal.

At UE1650, by N_RThe transmitted modulated signals are received by antennas 1652a through 1652r 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 downconverts) a respective signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

RX data processor 1660 from N_RA receiver 1654 receives N_RA received symbol stream is processed according to a particular receiver processing technique to provide N_TA "detected" symbol stream. RX data processor 1660 can demodulate, deinterleave, and decode 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 of base station 1610.

As described above, the processor 1670 may periodically determine which available technology to use. Further, processor 1670 can formulate 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. The reverse link message may be processed by a TX data processor 1638, modulated by a modulator 1680, conditioned by transmitters 1654a through 1654r, and transmitted back to base station 1610, where TX data processor 1638 also receives traffic data for a number of data streams from a data source 1636.

At base station 1610, the modulated signals from UE1650 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 reverse link message transmitted by UE 1650. Further, processor 1630 can process the extracted message to determine which precoding matrix to use for determining the beamforming weights.

Processors 1630 and 1670 can direct (e.g., control, coordinate, manage, etc.) operation at base station 1610 and UE1650, respectively. Processors 1630 and 1670 can be associated with memory 1632 and 1672, respectively, that store program codes and data. Processors 1630 and 1670 can also perform computations to derive frequency and impulse response estimates for the uplink and downlink, respectively.

It is to be understood that the aspects described herein may be implemented in hardware, software, firmware, middleware, microcode, or any combination thereof. For a hardware implementation, the processing units may be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.

When the embodiments are implemented in software, firmware, middleware or microcode, program code or code segments, they may be stored in a machine-readable storage medium, such as a storage component. A code segment may be represented by a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.

For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.

What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned aspects, but one of ordinary skill in the art may recognize that many further combinations and permutations of various aspects are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in a claim.

Claims (36)

1. A method that facilitates transmitting reference signals for channel estimation in a wireless communication environment, comprising:

identifying a number of symbols in a subframe for downlink transmission;

selecting a user equipment-specific reference signal (UE-RS) pattern as a function of a number of symbols in the subframe for the downlink transmission, wherein at least one time domain component of the UE-RS pattern is changed by time-shifting the at least one time domain component according to the number of symbols in the subframe for the downlink transmission; and

mapping UE-RSs to resource elements of the subframe according to the UE-RS pattern.

2. The method of claim 1, wherein the subframe is a regular subframe and all symbols from the subframe are identified for the downlink transmission.

3. The method of claim 1, wherein the subframe comprises a downlink pilot time slot (DwPTS) and the number of symbols from the subframe for the downlink transmission is identified as a number of symbols included in the configured DwPTS.

4. The method of claim 1, wherein the subframe is transmitted to a relay station and comprises one or more symbols reserved for gap symbols.

5. The method of claim 1, wherein a time domain component of the UE-RS pattern comprises Code Division Multiplexing (CDM) sets on a same set of symbols.

6. The method of claim 1, wherein a frequency domain component of the UE-RS pattern does not change according to a number of symbols from the subframe used for the downlink transmission.

7. The method of claim 1, wherein a set of time domain components of the UE-RS pattern are time-shifted by a common number of symbols.

8. The method of claim 1, wherein a set of time domain components of the UE-RS pattern are time-shifted by different numbers of symbols, respectively.

9. The method of claim 1, wherein the at least one time domain component of the UE-RS pattern is time shifted and at least one different time domain component does not change in time.

10. The method of claim 1, wherein the at least one time domain component of the UE-RS pattern is varied by puncturing one time domain component of the UE-RS pattern as a function of a number of symbols from the subframe utilized for the downlink transmission.

11. The method of claim 1, wherein the UE-RS pattern is selected based on whether the downlink transmission is transmitted to one of a relay or a user equipment.

12. A wireless communications apparatus, comprising:

a scheduler (306) for allocating symbols for downlink transmission in a subframe;

a mode selection module (308) for selecting a user equipment-specific reference signal (UE-RS) mode as a function of a number of symbols from the subframe for the downlink transmission, wherein at least one time domain component of the UE-RS mode is changed by time shifting the at least one time domain component of the UE-RS mode as a function of the number of symbols from the subframe for the downlink transmission; and

a dedicated reference signal module (310) for mapping UE-RSs to resource elements of the subframe according to the UE-RS pattern.

13. The wireless communications apparatus of claim 12, wherein the subframe is one of: a regular subframe, a subframe including a downlink pilot time slot (DwPTS), or a subframe including one or more symbols reserved for gap symbols transmitted to a relay station.

14. The wireless communications apparatus of claim 12, wherein a time domain component of the UE-RS pattern includes Code Division Multiplexing (CDM) groups on a same set of symbols.

15. The wireless communications apparatus of claim 12, wherein frequency domain components of the UE-RS pattern do not change as a function of a number of symbols from the subframe utilized for the downlink transmission.

16. The wireless communications apparatus of claim 12, wherein the mode selection module (308) time-shifts a set of time domain components of the UE-RS pattern by a common number of symbols.

17. The wireless communications apparatus of claim 12, wherein the mode selection module (308) time-shifts a set of time domain components of the UE-RS pattern by different respective numbers of symbols.

18. The wireless communications apparatus of claim 12, wherein the mode selection module (308) time shifts the at least one time domain component of the UE-RS pattern and at least one disparate time domain component does not change in time.

19. The wireless communications apparatus of claim 12, wherein the mode selection module (308) varies the at least one time domain component of the UE-RS pattern by puncturing one time domain component of the UE-RS pattern as a function of a number of symbols from the subframe utilized for the downlink transmission.

20. The wireless communications apparatus of claim 12, wherein the mode selection module (308) selects the UE-RS mode based on whether the downlink transmission is transmitted to one of a relay or a user equipment.

21. A wireless communications apparatus that enables transmitting reference signals in a wireless communication environment, comprising:

means for identifying a number of symbols in a subframe for downlink transmission;

means for selecting a user equipment-specific reference signal (UE-RS) pattern as a function of a number of symbols from the subframe for the downlink transmission, wherein at least one time domain component of the UE-RS pattern is changed by time shifting the at least one time domain component of the UE-RS pattern as a function of the number of symbols from the subframe for the downlink transmission; and

means for mapping UE-RSs to resource elements of the subframe according to the UE-RS pattern.

22. The wireless communications apparatus of claim 21, wherein the time domain component of the UE-RS pattern includes Code Division Multiplexing (CDM) groups on a same set of symbols.

23. The wireless communications apparatus of claim 21, wherein the at least one time domain component of the UE-RS pattern is varied based upon a number of symbols from the subframe utilized for the downlink transmission by puncturing one time domain component of the UE-RS pattern.

24. A method that facilitates estimating a channel in a wireless communication environment, comprising:

identifying a number of symbols from a subframe allocated for downlink transmission;

identifying a user equipment-specific reference signal (UE-RS) pattern as a function of a number of symbols from the subframe allocated for the downlink transmission, wherein at least one time domain component of the UE-RS pattern is changed by time shifting the at least one time domain component of the UE-RS pattern as a function of the number of symbols from the subframe allocated for the downlink transmission;

detecting a UE-RS on a resource element of the subframe specified by the UE-RS pattern; and

estimating a channel according to the UE-RS.

25. The method of claim 24, wherein a time domain component of the UE-RS pattern comprises Code Division Multiplexing (CDM) groups on a same set of symbols.

26. The method of claim 24, wherein a frequency domain component of the UE-RS pattern does not change according to a number of symbols from the subframe utilized for the downlink transmission.

27. The method of claim 24, wherein a set of time domain components of the UE-RS pattern are time-shifted by a common number of symbols.

28. The method of claim 24, wherein a set of time domain components of the UE-RS pattern are time-shifted by different numbers of symbols, respectively.

29. The method of claim 24, wherein the at least one time domain component of the UE-RS pattern is time shifted and at least one different time domain component does not change in time.

30. The method of claim 24, wherein the at least one time domain component of the UE-RS pattern is varied by puncturing one time domain component of the UE-RS pattern as a function of a number of symbols from the subframe utilized for the downlink transmission.

31. The method of claim 24, wherein the subframe is one of: a regular subframe, a subframe including a downlink pilot time slot (DwPTS), or a subframe including one or more symbols reserved for gap symbols transmitted to a relay station.

32. A wireless communications apparatus, comprising:

an allocation analysis module (312) for identifying a number of symbols from a subframe allocated for downlink transmission;

a reference signal evaluation module (314) to identify a user equipment-specific reference signal (UE-RS) pattern based on a number of symbols from the subframe allocated for the downlink transmission, wherein at least one time domain component of the UE-RS pattern is changed by time shifting the at least one time domain component according to the number of symbols from the subframe allocated for the downlink transmission, and a UE-RS is detected on resource elements of the subframe specified by the UE-RS pattern; and

a channel estimation module (316) for estimating a channel according to the UE-RS.

33. The wireless communications apparatus of claim 32, wherein the time domain component of the UE-RS pattern includes Code Division Multiplexing (CDM) groups on a same set of symbols.

34. The wireless communications apparatus of claim 32, wherein the at least one time domain component of the UE-RS pattern is varied based upon a number of symbols from the subframe utilized for the downlink transmission by puncturing one time domain component of the UE-RS pattern.

35. A wireless communications apparatus that enables estimating a channel in a wireless communication environment, comprising:

means for identifying a number of symbols from a subframe allocated for downlink transmission;

means for identifying a user equipment-specific reference signal (UE-RS) pattern as a function of a number of symbols from the subframe allocated for the downlink transmission, wherein at least one time domain component of the UE-RS pattern is changed by time shifting the at least one time domain component of the UE-RS pattern as a function of the number of symbols from the subframe allocated for the downlink transmission;

means for detecting a UE-RS on resource elements of the subframe specified by the UE-RS pattern; and

means for estimating a channel according to the UE-RS.

36. The wireless communications apparatus of claim 35, wherein the modification of the at least one time domain component of the UE-RS pattern as a function of a number of symbols from the subframe utilized for the downlink transmission is achieved by puncturing one time domain component of the UE-RS pattern.