Configurable pilot signals in wireless communication system

TECHNICAL FIELD OF THE INVENTION

The present disclosure relates generally to communication, and more specifically to pilot transmission in a wireless communication system.

BACKGROUND

In a wireless communication transmitter typically processes (e.g., encodes and symbol maps) traffic data to generate data symbols, which are modulation symbols for data. For a coherent system transmitter multiplexes pilot symbols with the data symbols, processes the multiplexed data symbols and pilot signal to generate a modulated signal and transmits this signal wirelessly. The wireless channel distorts the transmitted signal due to the channel response and further degrades the signal due to noise and interference.

The receiver receives the transmitted signal and processes the received signal to obtain received data symbols and the pilot signal. For coherent data detection, the receiver estimates wireless channel characteristics based on received pilot symbols and obtains a channel estimate. The receiver then performs data detection (e.g., equalization) on the received data symbols with the channel estimate to obtain data symbol estimates, which are estimates of the data symbols transmitted by the transmitter. The receiver then processes (e.g., demodulates and decodes) the data symbol estimates to obtain decoded data.

The quality of the channel estimate has a large impact on data detection performance and affects the quality of the estimates of the data symbols and the reliability of the decoded data. Typically, the channel estimate obtained by the receiver, the better, the more pilot signals transmitted by the transmitter. However, increasing the number of pilot signals increases overhead, which reduces the efficiency of the system.

Therefore, there exists a need for effective methods for pilot transmission in order to achieve high performance while reducing the overhead of the pilot processing.

SUMMARY OF THE INVENTION

Described herein are methods for transferring configurable pilots in a wireless communication system. In one aspect, the arrangement of pilot signals are determined based on the resource assignment for transmission. For different resource assignments using different placement of pilots, which may correspond to a different number of frames, the number of interlaces different H-ARQ, a different number of subcarriers, etc. The pilot signals transmitted in the position in time and frequency dimensions, determined by the layout of the pilot signals. Each pilot may be transmitted on one or more subcarriers in one or multiple symbol periods.

Resource assignment may be for one or more consecutive frames. Next, the arrangement of pilot signal (s) in each frame can be determined based on the placement of pilot (s) in the preceding (s) frame (s), if it exists. Assignment may also be designed for one or more interlaces H-ARQ. Next, the arrangement of pilot signal (s) in each interlace H-ARQ can be determined based on the number of interlaces H-ARQ administering, placing the pilot signal (s) in the previous (their) interlace (s) H-ARQ, if it exists, etc. Placing pilot signals can be identified by one or more pilot patterns. For different resource assignments can use different pilot patterns. At least one pilot pattern may be selected for use based on resource assignment.

The pilot signals may be pilot signals, time division multiplexed (TDM) and / or pilot signals of any other type. Pilot signals may be transmitted using various multiplexing schemes such as IFDMA, LFDMA, EFDMA, OFDMA, etc. Pilot signals and data can be transmitted using the same or different multiplexing schemes.

Various aspects and embodiments of the invention are further described below in more detail.

BRIEF DESCRIPTION OF DRAWINGS

The features and nature of the present invention will become more apparent from the detailed description given below in conjunction with the drawings identify correspondingly throughout.

1 - block diagram of a transmitter and a receiver.

2A - the transfer of H-ARQ.

2B - interleaving multiple H-ARQ.

3A, 3B and 3C - three exemplary subcarrier structures.

4A - exemplary pilot pattern for interleaving one H-ARQ.

4B - using a pilot pattern 4A for two interlaces H-ARQ.

5A - 2-frame pilot pattern for two interlaces H-ARQ.

5B - 3-frame pilot pattern for three interlaces H-ARQ.

6A - dynamic pilots for pulse transmission of two frames.

6B - dynamic pilots for pulse transmission of three frames.

7 - the process of transmitting or receiving configurable pilots.

8 - a device that supports configurable pilots.

9 - a process of receiving configurable pilots.

10 - the device receiving configurable pilots.

Detailed description

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

1 shows a block diagram of a transmitter 110 and a receiver 150 in a wireless communication system 100. For the forward link (or downlink), transmitter 110 may be part of a base station, and receiver 150 may be part of a terminal. For the reverse link (or uplink), transmitter 110 may be part of a terminal, and receiver 150 may be part of a base station. The base station is a station that communicates with the terminals. The base station can also be called a base transceiver system (BTS), an access point, Node B, or some other network entity, and may contain some or all of their functionality. A terminal may be stationary or mobile and may also be called an access terminal (AT), a mobile station (MS), user equipment (UE), and / or any other object, and may contain some or all of their functionality. The terminal can be a wireless device, a cellular phone, a personal digital assistant (PDA), a wireless modem, a handheld device, etc.

At transmitter 110, processor 120 transmit (TX) data and pilot signal processes (e.g., encodes, interleaves, and symbol maps) the traffic data and signaling and generates data symbols. Processor 120 also generates pilot symbols and multiplexes the data symbols and pilot symbols. In general, a data symbol is a modulation symbol for data, a pilot symbol is a modulation symbol for pilot, and a modulation symbol is a complex value phasor diagram of the signal points (e.g., for PSK or QAM), and a symbol is a complex value. The pilot signal is a data transmission / beforehand known / th transmitter and receiver. Modulator 130 modulates the data symbols and pilot in accordance with one or more multiplexing schemes / radio technologies and generates output chips. A transmitter (TMTR) 132 processes (e.g., converts to analog, amplifies, filters, and upconverts) the output chips (chips), and generates a modulated radio frequency signal (RF), which is transmitted via an antenna 134.

At receiver 150, an antenna 152 receives the RF modulated signal from transmitter 110 and provides a received signal to a receiver (RCVR) 154. Receiver 154 processes (e.g., filters, amplifies, downconverts, and digitizes) the received signal and provides samples. The demodulator 160 demodulates samples and obtains received data symbols and received pilot symbols. Evaluation unit / channel processing 162 can display various types of information of the channel (e.g., channel estimation, estimate the received signal quality, noise estimation, etc.) based on the received pilot symbols. Then, the demodulator 160 performs data detection (e.g., equalization or matched filtering) on ​​the received data symbols with the channel information and provides data symbol estimates. Processor 170 receives (Rx) data processor (e.g., symbol demaps, deinterleaves, and decodes) the data symbol estimates and provides decoded data. In general, the processing at receiver 150 is complementary to the processing at transmitter 110.

Controllers / processors 140 and 180 direct the operation of various processing units at transmitter 110 and receiver 150, respectively. The memory units 142 and 182 store program codes and data for transmitter 110 and receiver 150, respectively.

System 100 may use a scheme of the hybrid automatic repeat request (H-ARQ). In the H-ARQ transmitter sends one or multiple transmissions for a data packet until the packet is decoded correctly by the receiver or until a maximum number of transmissions sent. H-ARQ improves reliability of data transmission and support automatic speed control data packets in the presence of changes in channel conditions.

2A shows the transmission of H-ARQ. The transmitter processes (e.g., encodes and modulates) a data packet (packet A) and generates multiple (D) data blocks. A data packet may also be called a codeword and so on A data block may also be called a subpacket transmission of H-ARQ, etc. Each data block for the packet may contain sufficient information to allow the receiver to correctly decode the packet under favorable channel conditions. D data blocks typically contain different redundancy information for the packet. Each data block may be transmitted in the frame, which may be any duration of time. D blocks of data are transferred one by one, until the package is not complete, and block transfer are separated by Q frames, where Q> 1.

The transmitter transmits the first data block (block A1) for packet A in frame n. The receiver receives and processes (e.g., demodulates and decodes) Block A1, determines that Packet A is decoded in error, and sends a negative acknowledgment (NAK) to the transmitter in frame n + q, where q - delay feedback and 1≤q <Q . The transmitter receives the NAK and transmits the second block of data (block A2) for packet A in frame n + Q. The receiver receives Block A2, processes Blocks A1 and A2, determines that Packet A is decoded in error, and sends a NAK in frame n + Q + q. The block transmission and NAK response may continue to D again. In the example shown in Figure 2A, the transmitter transmits a third block of data (block A3) for packet A in frame n + 2Q. The receiver receives Block A3, processes Blocks A1-A3, determines that Packet A is decoded correctly, and sends a positive acknowledgment (ACK) in frame n + 2Q + q. The transmitter receives the ACK and terminates the transmission of packet A. The transmitter then processes the next data packet (packet B), and transmits the data blocks for the packet B in a similar manner.

According 2A new data block is transmitted every Q frames. To improve the efficiency of channel utilization, the transmitter may transmit up to Q packets in interleaved mode.

2B shows an embodiment of multiple (Q) interlaces H-ARQ. In this embodiment, the H-ARQ interlace 1 includes frames n, n + Q, etc., H-ARQ interlace 2 includes frames n + 1, n + Q + 1, etc., and H-ARQ interlace Q includes frames n + Q-1, n + 2Q-1, etc. Q H-ARQ interlaces are offset from one another by one frame. For example, if Q = 2, the H-ARQ interlace 1 may include odd-numbered frames, and H-ARQ interlace 2 may include even-numbered frames. In general, the retransmission delay Q H-ARQ feedback and the delay q are typically selected to provide sufficient processing time for both transmitter and receiver. The transmitter may transmit up to Q packets on the Q interlaces H-ARQ.

System 100 may use various multiplexing schemes / radio technologies, such as multiple access technology, frequency division on a single carrier (SC-FDMA), a multiple access orthogonal frequency division (OFDMA), code division multiple access (CDMA), a multiple access time- division (TDMA), multiple access, frequency division (FDMA), etc. SC-FDMA includes interleaved FDMA with (IFDMA), localized FDMA with (LFDMA), and enhanced FDMA (EFDMA). IFDMA is also called distributed FDMA, and LFDMA also called narrowband FDMA or classical FDMA. Data and pilot may be transmitted on (1) the subcarriers uniformly distributed across the system bandwidth, by IFDMA, (2) a group of adjacent subcarriers by LFDMA, or (3) multiple groups of adjacent subcarriers by EFDMA. OFDMA utilizes a multiplexing scheme, an orthogonal frequency division (OFDM). In general, modulation symbols are sent in the time domain via SC-FDMA and in the frequency domain by means of OFDMA. The main disadvantage of OFDMA is a high ratio of peak to average power ratio (PAPR), in the sense that the ratio of peak power to average power of the OFDM waveform can be high. PAPR signal SC-FDMA signal points determined by a vector diagram of a signal selected for use (e.g., PSK or QAM), and a lower PAPR than OFDM signal.

System 100 may utilize one or more multiplexing schemes for the forward and reverse links. For example, system 100 may utilize (1) SC-FDMA for the forward and reverse links, (2) one version of SC-FDMA (e.g., LFDMA) for one link and another version of SC-FDMA (e.g., IFDMA) for the other link connection (3) OFDMA for the forward and reverse links, (4) SC-FDMA for one link (e.g., uplink), and OFDMA for the other link (e.g., forward link), or (5) kakuyu- any other combination of multiplexing schemes. It may be desirable to use SC-FDMA (e.g., IFDMA) for the reverse link to achieve lower PAPR and to use OFDMA on the forward link to allow the increase in system capacity.

3A illustrates a structure 300 subcarriers that can be used for IFDMA and OEDMA. The system bandwidth of BW MHz is divided into multiple (K) orthogonal subcarriers that are given indices of 1 through K, where K may be any integer but is typically a power of two. The subcarriers may also be called tones, bins, etc. The spacing between adjacent subcarriers is BW / K MHz. For simplicity, the following description assumes that all K subcarriers may be used for transmission. For subcarrier structure 300, the set of K sub-organized into S non-overlapping sets, with each set containing N subcarriers that are uniformly distributed across the K subcarriers together where K = S · N. Consecutive subcarriers in each set are separated by S subcarriers. Thus, set s contains subcarriers s, S + s, 2S + s, ..., (N-1) × S + s, for s∈ {1, ..., S}.

3B illustrates the structure of subcarrier 310 which can be used for LFDMA and OFDMA. For subcarrier structure 310, the K subcarriers collection is organized into S non-overlapping sets, with each set contains N consecutive subcarriers, where K = S × N. Thus, set s contains subcarriers (s-1) × N + 1 to s × N, s∈ to {1, ..., S}.

3C shows the structure 320 subcarriers that can be used for the EFDMA and OFDMA. For subcarrier structure 320, the set of K sub-organized into S non-overlapping sets, with each set contains N subcarriers that are arranged into G groups of L consecutive subcarriers, where K = S × N and N = G × L. The totality of the K subcarriers may be distributed on the S sets as follows. The set of K subcarriers first partitioned into multiple frequency ranges, with each frequency range containing K '= S × L consecutive subcarriers. Each frequency range is further partitioned into S groups, with each group includes L adjacent subcarriers. For each frequency range of the first group from L subcarriers is allocated a set of 1, the next group from L subcarriers is allocated a set of 2, and so on, and the last group from L subcarriers is allocated a set S. Set s, for s∈ {1, ..., S} contains subcarriers whose indexes are k satisfy: (s-1) × L <(k mod K ') ≤s × L.

In general, the subcarrier structure may include any number of sets, and each set may contain any number of subcarriers. The kits may contain the same or different numbers of subcarriers and the number of subcarriers in each set may or may not be an integer divisor of K. The subcarriers in each set may be arranged in any manner, for example distributed uniformly or non-uniformly across the system bandwidth. The modulation symbols may be transmitted on one or more sets of subcarriers in the time domain or by SC-FDMA, a frequency domain by means of OFDMA.

SC-FDMA symbol may be generated for one subcarrier set in one symbol period as follows. N modulation symbols to be transmitted by N subcarriers are transformed to the frequency measurement via an N-point fast Fourier transform (FFT) to obtain N values ​​in the frequency domain. These N values ​​are displayed in the frequency domain at the N subcarriers used for transmission, and zero values ​​are displayed in the remaining subcarriers KN. Then, a K-point inverse FFT (IFFT) on the K frequency domain values ​​and zero values ​​to obtain a sequence of K samples in the time domain. The last C samples of the sequence are copied to the beginning of the sequence to form a symbol SC-FDMA, which contains K + C samples. The C copied samples are often called a cyclic prefix or a guard interval, and C is the cyclic prefix length. The cyclic prefix is ​​used to combat intersymbol interference (ISI), due to the frequency selective fading.

The OFDM symbol may be generated for one symbol period as follows. The modulation symbols mapped to subcarriers used for transmission and zero symbols with signal value of zero are displayed on the remaining subcarriers. Then K-point IFFT is performed on the K modulation symbols and zero symbols to obtain a sequence of K samples in the time domain. The last C samples of the sequence are copied to the start of the sequence to form the OFDM symbol, which contains K + C samples.

Transmit symbol may be an OFDM symbol or symbol SC-FDMA. SC-FDMA symbol may be a symbol of IFDMA, LFDMA symbol or character EFDMA. K + C samples of a transmission symbol are transmitted in K + C sample periods. Period symbol - is the duration of one transmission symbol and is equal to K + C sample periods.

The techniques described herein for transmitting a pilot signal can be used for the forward and reverse links. These methods can also be used for p azlichnyh multiplexing schemes such as SC-FDMA and OFDMA. For simplicity, some aspects and embodiments of the methods described in connection with IFDMA.

To transfer one H-ARQ interlace may be assigned a set of N subcarriers. If each frame takes T symbol periods in each frame of the assigned H-ARQ interlaces available T · N transmission units, wherein transmission unit is one subcarrier in one symbol period. Each frame interlace H-ARQ can transmit only N · T symbols. In OPDMA for pilot transmission may be any transmission units from P N · T of transmission units, and these units of transmission P P can transmit the pilot symbols. The SC-FDMA pilot signals may be transmitted in TDM mode, to maintain a low PAPR. In this case, each symbol period, N pilot symbols may be transmitted on N subcarriers used for pilot transmission. Alternatively, the pilot symbols may be transmitted on some subcarriers and the data symbols may be transmitted on the remaining subcarriers in a given symbol period. This multiplexing of pilot and data in the same symbol period leads to increased PAPR.

In general, it is desirable to transmit a sufficient number of pilot signals that the receiver can derive a good enough channel estimate. The pilot signals should be allocated in frequency and time to record changes in the channel in frequency and time. For SC-FDMA and OFDMA increasing the number of pilot symbols may improve channel estimation performance. However, because of the reduced number of transmission units available for transmitting data. In this case, can be reduced or the bit rate of transmission, or the coding efficiency error correcting code, which can lead to a reduction in coverage and / or increase the probability of decoding errors. Since pilot signals are associated with overhead, it is desirable to minimize the number of pilot signals, but to achieve the goals.

For simplicity, the following description uses the following embodiment. The system has K = 16 total subcarriers that are arranged into S = 4 subcarrier sets. Each subcarrier set includes N = 4 subcarriers that are uniformly distributed across 16 subcarriers. The system also has Q≥3 interlaces H-ARQ. Each frame holds T = 8 symbol periods, and the transmission symbol (e.g., IFDMA symbol or OFDM symbol) can be transmitted in each symbol period. The system uses a frequency hopping sequence of characters, allowing for transmission in each symbol period, you can use a separate set of subcarriers. A specific set of subcarriers to be used in each symbol period may be determined by a frequency hopping pattern, which is known to both the transmitter and receiver. Frequency hopping may increase the frequency diversity.

4A shows an embodiment of template 400 of the pilot signal that can be used to transmit on one set of subcarriers in one interlace H-ARQ. The template 400 pilot TDM pilot signals are transmitted in the first and last symbol periods in each frame interlace assigned H-ARQ. Each TDM pilot is composed of pilot symbols that are transmitted on all assigned subcarriers in a symbol period. The TDM maintain low PAPR for transmission which is performed using SC-FDMA. Transfer each TDM pilot on all K subcarriers allows the receiver to record changes in frequency channel and estimate the channel response across the system bandwidth. Transfer TDM pilots in the first and last symbol periods allows the receiver to record the time variation in the channel. In general, TDM pilot signals should be (1) sufficiently spaced apart to register the channel variations in time, but (2) must not be spaced too far to be able to provide enough "representative" channel characteristic. Placing pilot signal shown in Figure 4A, it can be useful for quickly varying channel such as a channel with a strong Doppler effect due to movement of the vehicle. If TDM pilots are used according to Figure 4A, the variations in the design may limit the number TDM pilots, to be transferred and the location of the TDM pilots in the time axis.

In general, a pilot pattern may include any number of pilot signals that can be transmitted in any unit of a transmission frame. Different pilot patterns may be evaluated, with each pilot pattern has a separate arrangement of pilot signals in the frame. Pilot pattern that provides the best performance may be selected for use.

Template 400 pilot may provide superior performance, when the transmission is carried out periodically, for example every Q frames on the assigned interlace H-ARQ, as shown in Figure 4A. Since the frames assigned H-ARQ interlace are spaced apart in time, the time variation in the channel can lead to the fact that the pilot observations in one frame are irrelevant or obsolete for another frame. Thus, each frame should include a sufficient number of pilot signals that the receiver can derive a good channel estimation for that frame.

4B illustrates the use of template 400 for pilot transmission on two successive alternations H-ARQ. In this example, the assigned H-ARQ interlaces 1 and 2, and the TDM pilot is transmitted in the first and last symbol periods of each frame in each assigned H-ARQ interlace. 4B TDM pilot signal, transmitted in the last symbol period of frame 1 H-ARQ interlace 1, located immediately to the right of TDM pilot signal, transmitted in the first symbol period of the frame 1 H-ARQ interlace 2. These pilot signals are TDM substantially redundant, and are associated with the inefficient use of system resources. 4A and 4B, pilot pattern 400 may be suitable for transmission on a single interlace H-ARQ, but not effective to transmit on multiple interlaces consecutive H-ARQ.

In one aspect, the number of pilots and arrangement of pilot signals determines the assignment of resources for transmission. In an embodiment, different pilot patterns are used for different purposes resources that can correspond to a different number of frames, the number of interlaces different H-ARQ, a different number of subcarriers, etc. One or more pilot pattern can be used for each individual resource assignment may be designed to provide high performance while reducing the overhead of the pilot processing.

5A shows an embodiment of a 2-frame pilot pattern 500 of the signal that can be used to transmit on one set of subcarriers in interlaces two consecutive H-ARQ. Multi-frame pilot pattern may be considered as multiple, single compound pilot patterns. The template 500 pilot TDM pilot signals are transmitted in the first and last symbol periods of frame 1 H-ARQ interlace 1 (or 1.1 in the frame), and the TDM pilot is transmitted in symbol periods of the frame from the second to the last alternation 1 H -ARQ 2 (or block 1.2). Channel estimates for the frame 1.1 can be derived based on the pilot TDM, transmitted in the first and last period of the symbols of the frame. Channel estimates for the frame 1,2 can be deduced on the basis of TDM pilot signal, transmitted in the last symbol period of Frame 1,1 and the TDM pilot, the transmitted symbol periods in the frame with a 1.2 second to last. The TDM pilot in the first symbol period of Frame 1,2 is replaced by data. The TDM pilot in the frame 1.2 can be rearranged to improve performance.

5B shows an embodiment of three-frame pattern 510 of the pilot signal that can be used to transmit on one set of three consecutive subcarriers in interlaces H-ARQ. For pattern 510, a pilot signal, the TDM pilot is transmitted in the second symbol period of the frame 1 H-ARQ interlace 1 (or 1.1 in the frame), the TDM pilot is transmitted in the first and last symbol periods of frame 1 H-ARQ interlace 2 ( or block 1.2), and the TDM pilot is transmitted in symbol periods of the frame from the second to the last one H-ARQ interlace 3 (or in block 1.3). Channel estimates for the frame 1,1 can be deduced on the basis of TDM pilot signal, transmitted in the second symbol period of the frame and the TDM pilot signal, transmitted in the first symbol period of Frame 1,2. Channel estimates for the frame 1.2 can be derived based on the pilot TDM, transmitted in the first and last period of the symbols of the frame. Channel estimates for the frame 1,3 can be deduced on the basis of TDM pilot signal, transmitted in the last symbol period of Frame 1,2 and the TDM pilot, the transmitted symbol periods in the frame with a 1.3 second to last.

5A and 5B show exemplary pilot patterns for two and three consecutive H-ARQ interlaces, respectively. These pilot patterns maintain a uniform spacing of 7 symbol periods between consecutive TDM pilots. For transmission also possible to define and use other pilot patterns.

In an embodiment, the one-frame various pilot patterns can be used for different frames based on a resource assignment, for example, as shown in Figures 5A and 5B. In this embodiment, the pilot patterns for different frames can have the TDM pilots, located in different symbol periods. According to the embodiment shown in Figure 5A, the TDM pilot for Frame 1,2 is moved one symbol period ago to improve the performance channel estimation for that frame. According to the embodiment shown in Figure 5B, the TDM pilot for Frame 1,1 is moved one symbol period ahead, and the TDM pilot for Frame 1,3 is moved one symbol period ago to improve channel estimation performance for these frames .

In another embodiment, the same pilot pattern is used for each frame, but redundant TDM pilot data can be exchanged. 5A, the TDM pilot may be transmitted in the last symbol period (instead of the symbol periods of the second to last) frame 1.2. According 5B TDM pilot may be transmitted in the first symbol period (and not in the second symbol period) of the frame 1,1 and the TDM pilot may be transmitted in the last symbol period (instead of the symbol periods of the second to last) frame 13. The TDM pilot in the last symbol period of frame or TDM pilot in the first symbol period of the next frame can be replaced with data.

In general, any set of pilot patterns which provides high performance, can be used for each individual purpose H-ARQ.

Single-frame pilot pattern may be used to assign one interlace H-ARQ, 2-frame pilot pattern may be used to assign two interlaces H-ARQ, 3-frame pilot pattern may be used to assign the three interlaces H-ARQ, etc. .d. Each pilot pattern can be designed to provide high performance for a corresponding number of interlaces H-ARQ. Available pilot patterns may be known in advance to the transmitter and receiver, so that both know the specific pilot pattern to be used for transmission, depending on the purpose of H-ARQ.

5A and 5B show the cases where the resource assignment can be static and known in advance. For each destination can select a proper pilot pattern is used for the entire transmission. For example, a pattern 500 of the pilot signal if two successive interlace assigned H-ARQ, and can use the template 510 pilot if three successive alternations assigned H-ARQ. Another pilot pattern can be selected every time you change the destination, which can occur frequently or infrequently.

Resource assignments can be dynamic, can change rapidly over time and can be known in advance. In this case it may be impossible to select a specific pilot pattern to be used for an extended period of time because the selected pilot pattern may not be compatible with different destinations. For example, the package can be transferred to this alternation of H-ARQ, until the package is finished, and you can then transmit a new packet on this alternation of H-ARQ. The multiple access system, the available H-ARQ interlaces may be shared by all users, and new packets may be transmitted whenever the H-ARQ interlaces are available. Uncertainty as to when we can transmit new packets as well as alternations of H-ARQ, used to transmit these packets can lead to unpredictable and dynamic resource assignments.

According to an embodiment of the pilot patterns is dynamically selected based on current and previous assignments. Selection of the pilot pattern can be performed for each transmission pulse which is continuous in the transfer of one or more consecutive frames. The duration of each pulse transmission may be not known beforehand. For example, whether the next frame is assigned, it may not be known until the end of the current frame. Pilot pattern for each frame can be selected based on the template (s) of the pilot signal used (s) for the preceding (s) frame (s), if any, in the current transmission pulse.

6A shows an embodiment of pilot placement 600 for a transmission pulse signal of two frames. In this embodiment, the first frame pulse transmission pattern 610, the one-frame pilot signal is selected to provide high performance for this frame, without reliance on any of the pilot signals in the previous frame does not exist. Template 610 pilot signal includes TDM pilots in the first and last symbol periods of the frame. For the second block transmission pulse pattern 612, the one-frame pilot signal is selected to provide high performance for this frame with pilot pattern 610 for the previous frame signal. Template 612 pilot signal includes TDM pilot symbol in a frame period from the second to the last. Placement of the TDM pilot in pilot pattern 612 determines the location of the signal TDM pilots in pilot pattern 610 of the signal used in the previous frame.

6B shows an embodiment of pilot placement 602 for a transmission pulse signal of three frames. In this embodiment, the template 610 a pilot signal is used for transmission of the first frame pulse and 612 template pilot signal is used for the second frame as described above. The third one-frame picture pattern 614 pilot signal is selected to provide high performance for this frame with pilot pattern 612 for the second frame signal. Template 614 pilot signal includes TDM pilot symbol in a frame period from the third to the last. Placement of the TDM pilot in pilot pattern 614 may be determined by placing the signal TDM pilots in pilot pattern 612 of the signal used in the previous frame, or the templates 610 and 612, the pilot signal in the previous two frames.

6A and 6B show embodiments in which the pilot patterns maintain a uniform spacing of 7 symbol periods between consecutive TDM pilots. This embodiment can be extended to the appointment of more than three consecutive frames. The TDM pilot for each successive frame may be transmitted by one symbol period earlier to maintain the same spacing. For transmission also possible to use other pilot patterns.

The transmitter and receiver can know in advance the specific pilot patterns to be used for dynamic resource assignment. This avoids the need to transmit signaling to transfer pilot pattern to be used. If each resource assignment related to a specific pilot pattern, for transferring the signaling resource assignment can be regarded as explicit signaling of the corresponding pilot pattern. Alternatively, signaling can be transmitted explicitly to transfer pilot pattern to be used.

According to the embodiments shown in Figures 5A-6B, the receiver may store surveillance pilot signal of the current and previous frames is possible to be used for channel estimation in subsequent frames. Using observations from the pilot signal of one frame for channel estimation in another frame allows to re-optimize the location of the pilot signal, and also reduce the processing overhead of the pilot signal in successive frames. Thus, we can improve the efficiency of the whole system without affecting performance.

4A-6B shows an embodiment in which each symbol period have the same duration. The TDM pilot may also be transmitted in symbol period, which is shorter or longer than the symbol period for the data. For example, shorter TDM pilot is approximately half the length can be generated by performing P-point FFT on the P pilot symbols, by displaying P values ​​in the frequency domain in the P assigned sub-carriers, inserting zero values ​​for K / 2-P remaining subcarriers carrying K / 2-point IFFT, and cyclic prefix appending. Each subcarrier in a shorter TDM pilot would occupy two consecutive subcarriers in the regular TDM pilot.

For clarity, the techniques for transmitting a pilot signal has been described with reference to the TDM pilot signals, transmitted on subcarriers uniformly distributed. These TDM pilots may be generated in different ways for IFDMA and OFDMA, as described above. Methods for pilot transmission may also be used for LFDMA and EFDMA, OFDMA and for other subcarrier structures. In general, a pilot signal to be distributed over the frequency range of interest, and to incorporate changes in the channel in frequency and time. The frequency range of interest, typically covers the frequency range used for the transmission of data, which may be an entire system bandwidth or a portion of the system bandwidth.

For subcarrier structure 300, shown in Figure 3A, and subcarrier structure 320 shown in Figure 3C, each sub-carrier set occupies the whole system bandwidth. TDM pilot signal, transmitted on one subcarrier set may then be used to estimate the channel response across the system bandwidth. Thus, one can achieve a reduction in number of TDM pilots, as described above, regardless of whether the applied frequency hopping.

For subcarrier structure 310, shown in Figure 3B, each set of sub-carriers occupies only part of the system bandwidth. TDM pilot signal, transmitted on one subcarrier set may then be used for estimating the channel response on the part of the system bandwidth. If frequency hopping is not applied, and the same set of subcarriers used in different frames, it is possible to achieve a reduction in number of TDM pilots, as described above. If frequency hopping is used, and different subcarrier sets are used in different frames, the pilot observations for one frame may not be applicable to another frame if these frames occupy different frequency bands. Thus, one can achieve a reduction in number of TDM pilots whenever the pilot observations for one frame may be used for another frame.

For SC-FDMA and OFDMA TDM pilot may be transmitted as described above, wherein TDM pilots provide a lower PAPR for SC-FDMA. For SC-FDMA and OFDMA may also be multiplexed pilot symbols and data on different subcarriers in the same symbol period, albeit with a higher PAPR for SC-FDMA. Multiplexing the pilot data and may provide increased flexibility while reducing the overhead of the pilot processing. For example, if one set of subcarriers assigned, then pilot may be transmitted on subcarriers in the last half of the symbol period of one frame and the first half of the subcarrier symbols of the next frame period. If multiple sets of subcarriers assigned, then pilot may be transmitted on one set of subcarriers, and the data can be transmitted to other set of subcarriers.

The pilot signals transmitted by the transmitter, the receiver can be used to derive various types of channel information. The receiver may derive an estimate of channel response in the frequency domain and / or measurement of the channel impulse response in the time domain based on the received pilot signals. The receiver may also estimate the received signal quality for the transmitter based on the received pilot signals. The signal quality can be quantitatively expressed by the signal / noise ratio (SNR), signal / noise ratio + noise (SINR), a carrier / noise ratio (C / I), the ratio of energy symbol / noise ratio (Es / No), etc. The received signal quality can be moved by a report channel quality indication (CQI), a packet format and data rate, etc. The receiver may also derive an estimate of the interference based on the received pilot signals. Methods for output of these various estimates are known in the art and are not described here.

Described herein are methods for transmitting a pilot signal can be used for various multiplexing schemes, and different types of pilot, as described above. The methods are of particular advantage for systems that use TDM pilots, for example, to maintain a low PAPR for IFDMA, LFDMA, and EFDMA. Using TDM pilots limits the degree of freedom while reducing the overhead of the pilot processing. The methods allow to reduce the overhead of the pilot signal for the TDM pilots, as well as other types of pilot signals while maintaining high performance.

7 shows an embodiment of a process 700 for transmitting or receiving configurable pilots. Process 700 may be performed by the transmitter or receiver. Determines the assignment of resources for transmission in a wireless communication system (block 712). For different purposes different resources used by placing the pilot signals. Then determines the location of the pilot signal for transmission on the basis of the resource assignment (block 714). The pilot signals transmitted by the transmitter (and received by a receiver) at positions in time and frequency dimensions, determined by the layout of the pilot signals (block 716).

The appointment may relate to one or more consecutive frames. You can then determine the location of the at least one pilot in each frame based on placement of at least one pilot in at least one previous frame. For example, at least one symbol period to be used for at least one pilot signal in the current frame can be determined on the basis of at least one symbol period used for at least one pilot signal in the previous frame. The pilots can be placed on the frames uniformly or in other ways.

The appointment may relate to one or more interlaces H-ARQ. Can then determine the location of the at least one pilot in each H-ARQ interlace based on the number of H-ARQ interlaces in the assignment, the placement of at least one pilot signal in a preceding H-ARQ interlace, etc.

Assignment of resources may be static and used for the entire transmission. In this case, the placement of the pilot signal may be static and known in advance based on the purpose. Alternatively, the resource assignment can be dynamic and change during the transmission. For example, if the next frame is assigned may not be known until the current frame. Placing pilot can also be dynamic and may be refined as additional resource assignment.

Placing pilot signals can be identified by one or more pilot patterns. For different resource assignments can use different pilot patterns. At least one pilot pattern may be selected for use based on the destination. If the designation contains several consecutive frames, the pilot pattern to be used for each frame can be determined based on a pilot pattern used for the previous frame.

In general, each pilot signal may be transmitted on one or more subcarriers in one or multiple symbol periods. The pilot signals may be pilot signals TDM, each TDM pilot is transmitted on all assigned subcarriers in a predetermined time interval, for example one symbol period. Placement of each of the TDM pilot may be determined based on the destination. Pilot signals may be transmitted using various multiplexing schemes such as IFDMA, LFDMA, EFDMA, OFDMA, etc. Pilot signals and data can be transmitted using the same or different multiplexing schemes.

Figure 8 shows an embodiment of an apparatus 800 supporting configurable pilots. The apparatus 800 includes one or more processors for determining resource assignment for transmission in a wireless communication system (block 812), one or more processors for determining placement of pilots for the transmission based on the resource assignment (block 814), and one or more processors to transmit (or receive) the pilot signals at positions of time and frequency dimensions, determined by the layout of the pilot signals (block 816).

9 shows an embodiment of a process 900 receiving configurable pilots. Process 900 may be performed by the receiver. Placing at least one pilot in the current transmission is determined based on placement of at least one pilot in at least one previous transmission (block 912). The pilot signals received in the current transmission and the at least one previous transmission is processed to obtain channel information (block 914). Various placement pilot may be used for different assignments of resources. Then placing the pilot signal in the current and the previous transmission can be determined based on the assignment of resources. Current and previous transmission can be received in consecutive frames at different H-ARQ interlaces, etc. Each transmission can be a transmission in a frame on the H-ARQ interlace, etc. The channel information may comprise a channel frequency response estimate, estimate the channel impulse response estimate received signal quality, noise estimation, some other measurements or a combination thereof.

10 shows an embodiment of an apparatus 1000 receiving configurable pilots. Apparatus 1000 includes one or more processors for determining placement of at least one pilot in the current transmission based on placement of at least one pilot in at least one previous transmission (block 1012), and one or more processors for processing the pilot signals received in the current transmission and the at least one previous transmission to obtain channel information (block 1014).

Described herein are methods for transmitting a pilot signal may be implemented by various means. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the processing units used for channel estimation may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing (DSPD), programmable logic devices (PLDs), field programmable gate arrays user (FPGA), processors, controllers, microcontrollers, microprocessors, other electronic units designed to perform the functions described herein, or combinations thereof.

For a firmware and / or software implementation, the techniques may be implemented with instructions (commands) (e.g., procedures, functions, etc.) that one or more processors can be used to perform the functions described herein. The firmware and / or software instructions may be stored in memory (e.g., memory 142 or 182 in Figure 1) and executed by one or more processors (e.g., processor 140 or 180). Memory may be implemented within the processor or external to the processor.

The above description of the disclosed embodiments is provided to enable a person skilled in the art could apply the present invention. One skilled in the art can be various modifications of these embodiments and use the generic principles defined herein to other embodiments without departing from the spirit and scope of the invention. Thus, the present invention is not subject to limitation the embodiments shown herein but is to encompass the widest scope consistent with the principles disclosed herein, and novel features.