Claiming priority based on 35U.S.C. § 119
The present application claims priority to a provisional application entitled "METHOD AND APPARATUS FOR PREAMBLE CONFIGURATION IN WIRELESS COMMUNICATION SYSTEMS", serial No. 60/834,118, filed on 28.7.2006, assigned to the present assignee and expressly incorporated herein by reference
Detailed Description
The transmission techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA and SC-FDMA systems. The terms "system" and "network" are often used interchangeably. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), and so on. cdma2000 covers IS-2000, IS-95 and IS-856 standards. UTRA includes wideband CDMA (W-CDMA) and Low Code Rate (LCR). TDMA systems may implement wireless technologies such as global system for mobile communications (GSM). OFDMA systems may implement, for example, evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE802.16(WiMAX), IEEE 802.20, Flash-Etc. wireless technologies. These various wireless technologies and standards are well known in the art. UTRA, E-UTRA, and GSM are described in documents entitled "third Generation partnership project" (3GPP) organization. Under the name "third generation partnershipCdma2000 is described in a document of the organization of project 2 "(3 GPP 2).
For clarity, certain aspects of the transmission technique are described below for a High Rate Packet Data (HRPD) system implementing IS-856. HRPD is also known as evolution-data optimized (EV-DO), Data Optimized (DO), High Data Rate (HDR), etc. For clarity, HRPD terminology is used in much of the description below.
Fig. 1 illustrates a wireless communication system 100 having multiple receiving points 110 and multiple access terminals 120. An access point is typically a fixed station that communicates with the access terminals and may also be referred to as a base station, a node B, etc. Each access point 110 provides communication coverage for a particular geographic area 120 and supports communication for access terminals located within the coverage area. The access points 110 may be coupled to a system controller 130, which system controller 130 coordinates and controls the access points. System controller 130 may include one or more network entities such as a Base Station Controller (BSC), a Packet Control Function (PCF), a Packet Data Serving Node (PDSN), and the like.
The access terminals 120 may be dispersed throughout the system, and each access terminal may be fixed or mobile. An access terminal may also be called a terminal, mobile station, user equipment, subscriber unit, station, or the like. An access terminal may be a cellular telephone, Personal Digital Assistant (PDA), wireless device, handheld device, wireless modem, laptop computer, or the like. In HRPD, an access terminal may receive a data transmission on the forward link from one access point and may send a data transmission on the reverse link to one or more access points at any given moment. The forward link (or downlink) refers to the communication link from the access points to the access terminals, and the reverse link (or uplink) refers to the communication link from the access terminals to the access points.
Fig. 2 shows a slot structure 200 for transmission on the forward link. The transmission timeline may be partitioned into multiple time slots. Each time slot may have a predetermined duration. In one design, each slot has a duration of 1.667 milliseconds (ms) and spans 2048 chips, with each chip having a duration of 813.8 nanoseconds (ns) for a chip rate of 1.228 mega chips per second (Mcps). Each time slot may be divided into two identical half-time slots. Each half-slot may include (i) an overhead section consisting of a pilot segment in the middle of the half-slot and two Medium Access Control (MAC) segments on either side of the pilot segment, and (ii) two traffic segments on either side of the overhead section. The traffic segments may also be referred to as traffic channels, data segments, data fields, etc. The pilot segment may have a duration of 96 chips and may carry a pilot, which may be used to initiate acquisition, frequency and phase recovery, timing recovery, channel estimation, wireless combining, and so on. Each MAC segment may have a duration of 64 chips and may carry signaling such as Reverse Power Control (RPC) information, channel structure, frequency, transmit power, coding and modulation, and so on. Each traffic segment may have a duration of 400 chips and may carry traffic data (e.g., unicast data for a particular access terminal, broadcast data, etc.) and/or signaling.
It may be desirable to use Orthogonal Frequency Division Multiplexing (OFDM) and/or single carrier frequency division multiplexing (SC-FDM) for the traffic segments. OFDM and SC-FDM partition the system bandwidth into multiple orthogonal subcarriers, which are also referred to as frequency bins, etc. Each subcarrier may be modulated with data. Typically, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. OFDM and SC-FDM have certain desirable features, such as the ability to prevent inter-symbol interference (ISI) caused by frequency selective fading. OFDM can also efficiently support multiple-input multiple-output (MIMO) and Spatial Division Multiple Access (SDMA), which can be used on each subcarrier individually. For clarity, the following describes the use of OFDM to transmit data and signaling in a traffic segment.
It is also desirable to support OFDM while maintaining backward compatibility with early HRPD releases. In HRPD, the pilot and MAC segments can be demodulated at all times by all active terminals, while the traffic segments are demodulated only by the terminals being served. Backward compatibility is achieved by maintaining the pilot and MAC segments and modifying the traffic segment.
Fig. 2 shows a design to support OFDM using an HRPD slot structure. In this design, R OFDM symbols may be transmitted in one slot, or R/4 OFDM symbols may be transmitted per traffic segment, where R may be any suitable integer value. In general, OFDM symbols may be generated based on various OFDM symbol algorithms. Each OFDM symbol algorithm is associated with specific values for relevant parameters such as OFDM symbol duration, number of subcarriers, cyclic prefix length, etc. Table 1 lists three OFDM symbol algorithms according to one design and gives the parameter values for each algorithm.
TABLE 1
In the design shown in table 1, each slot may include a total of T1440 tones. One tone may correspond to one subcarrier in one symbol period and may be used to transmit one modulation symbol. Tones may also be referred to as resource elements, transmission units, etc. Some of the T tones may be reserved for pilot while the remaining tones may be used for data and/or signaling.
An access point may transmit data to one or more access terminals in each time slot. The access point may also send signaling in each time slot. The signaling may also be referred to as a preamble, scheduling information, control information, overhead information, etc. In general, the signaling may include any information used to support data transmission on the forward link and/or the reverse link. The signaling may be for any number of access terminals and may include any type of information.
In one design, the signaling may include information indicating which access terminals are scheduled for data transmission on the forward link in a given time slot. The signaling may also include information regarding parameters used by the scheduled terminals to receive data transmissions sent on the forward link. For example, the signaling may include information related to a data rate for the scheduled access terminal. The access terminal may estimate the forward link channel quality of the access point and may determine a data rate for data transmission sent to the access terminal based on the estimated channel quality and/or other factors. The access terminal may transmit the data rate to the access point on a Data Rate Control (DRC) channel. The access point may use the data rate transmitted by the access terminal or may select another data rate. The access point may send a rate adjustment that may indicate a difference, if any, between the data rate selected by the access point and the data rate provided by the access terminal. Rate adjustment may cause the access point to overwrite the DRC feedback from the access terminal. Rate adjustment may also provide the access terminal with the actual data rate used by the access point so that the access terminal can avoid having to decode different possible data rates for data transmission.
In one design, the scheduled signaling for the access terminal may include the following:
● 8-bit MAC _ AD of the scheduled access terminal,
● scheduled 2-bit rate adjustment of the access terminal.
Access terminals communicating with the access point may be assigned a unique MAC _ AD. Each access terminal may then be identified by its MAVC AD. The access terminal may also be identified based on other types of identifiers.
In another design, the scheduled signaling for the access terminal may include the following:
● 8-bit MAC _ AD of the scheduled access terminal,
● scheduled 2 bit rate adjustment of the access terminal,
● 2 bits to allocate a size indicator,
● 1 bit sticky allocation indicator.
A variable amount of resources may be allocated for scheduled access terminals for data transmission. The allocation size indicator may represent the amount of resources allocated to the access terminal for data transmission. In one design, resources may be granted in block units, where each block (tile) includes a predetermined number of tones. For example, a slot may be partitioned into 6 blocks, and each block may include 240 tones. An access terminal may be allocated 1, 2, 4, or 6 chunks, which may be represented by a 2-bit allocation size indicator. The particular zone allocated to an access terminal may be determined based on the location of the signaling and/or indicated by other means. The sticky allocation indicator may be set to 1 to indicate that the current resource allocation is ongoing or set to 0 to indicate that the current resource allocation terminates after the current time slot. The use of sticky allocation indicators may avoid the need to send the same signaling for the same consecutive resource allocation in each time slot.
The signaling of the scheduled access terminals may be transmitted in various manners. In one design, signaling may be sent in an OFDM symbol during a traffic segment. The signaling may be sent on tones distributed across the system bandwidth to achieve frequency diversity and/or over multiple symbol periods to achieve time diversity.
Fig. 3 shows a design of a tone structure 300 for signaling according to the 200-chip algorithm 2 in table 1. In this design, signaling for the access terminal may be sent on a set of K tones, which may be distributed over the entire system bandwidth and over one "half-slot". In general, the set of tones may include any number of tones, and K may be any value. The number of tones (K) may be selected based on a trade-off between signaling overhead and signaling reliability. In one design, the set of tones may include K-32 tones, where algorithm 1 may be set to eight tones per symbol period for 200 chips in table 1 (as shown in fig. 3), or four tones per symbol period for 100 chip algorithm 2, or 16 tones per symbol period for 400 chip algorithm 3. These tones may occupy different subcarriers in different OFDM symbol periods to increase frequency diversity, as shown in fig. 3. Generally, sending signaling earlier in a slot causes the access terminal to receive the signaling sooner and begin preparing to process a data transmission sooner. Thus, signaling is sent in the first OFDM symbol, the first traffic segment, the first "half slot," etc.
Fig. 4A shows a design of a signaling tone structure using 4 x 4 blocks. Each 4 x 4 block may consist of two 4 x 2 blocks occupying the same four subcarriers in two traffic segments. In this design, the signaling for the access terminal may be sent on 32 tones located in two 4 x 4 blocks of two "half slots".
Fig. 4B shows a design of a signaling tone structure using 8 x 2 blocks. In this design, the signaling for the access terminal may be sent on 32 tones located in two 8 x 2 blocks of two "half slots". Each tile may include eight subcarriers and span the first two symbol periods in a "half-slot".
Fig. 4C shows a design of a signaling tone structure using 16 x 1 blocks. In this design, the signaling for the access terminal may be sent on 32 tones located in two 16 x 1 blocks of two "half slots". Each tile may include 16 subcarriers and span the first symbol period in one "half-slot".
Fig. 4D shows a design of a signaling tone structure using 1 x 1 blocks. In this design, the signaling for the access terminal may be sent on 32 tones located in 32 1 × 1 blocks of two "half slots". Each tile may include one subcarrier and span one symbol period.
Fig. 3-4D illustrate some example tone structures for signaling on K-32 tones. Other tone structures may also be specified for signaling on a different number of tones (e.g., K16, 64, 128, etc.) and/or with a different distribution of K tones in frequency and time. Placing the K tones closely together in frequency and time may improve orthogonality between multiple possible codewords sent for signaling, thereby improving decoding performance. Distributing the K tones over frequency and time may improve diversity. Signaling may be sent based on any tone structure selected for use.
In one design, the signaling for the scheduled access terminal may be sent on a designated set of tones among all tones allocated to the access terminal for data transmission. The designated tone block set may be fixed for a given time slot, but may vary from time slot to time slot.
In another design, the signaling for the scheduled access terminal may be sent on one of multiple sets (S) of tones. The S-group tones may be defined in terms of all tones used to send signaling (e.g., all tones allocated to a terminal for data transmission). The S groups of tones may be disjoint such that each tone belongs to at most one group. The number of groups (S) may depend on the number of available tones and the number of tones in each group (K). In one design, S-16 sets of tones may be formed for the left half-slot based on the algorithm shown in table 1, where each set includes K-32 tones. One of the S groups of tones may be selected for use based on the first portion of the signaling and the selected group of tones may be used to transmit the remaining portion of the signaling. The signaling may puncture (or replace) data on the selected tone group.
Fig. 5 shows a block diagram of a design of access point 110x and access terminal 120x of one of the plurality of access points and plurality of access terminals in fig. 1. For simplicity, only the processing units for transmission on the forward link are shown in fig. 5. Also for simplicity, access point 110x and access terminal 120x are each shown with one antenna. In general, each entity may be equipped with any number of antennas.
At access point 110x, a transmit processor 510 may receive traffic data for one or more scheduled access terminals and signaling for the scheduled terminals. Transmit processor 510 may process (e.g., encode, interleave, and symbol map) traffic data, pilot, and signaling and provide data symbols, pilot symbols, and signaling symbols, respectively. Data symbols are symbols for traffic data, pilot symbols are symbols for pilot, signaling symbols are symbols for signaling, and symbols are typically complex values. An OFDM modulator (Mod)520 may receive data, pilot, and signaling symbols from transmit processor 510, perform OFDM modulation on the symbols, and provide OFDM output samples. Transmit processor 512 may receive and process traffic data, pilot, and/or overhead information to be transmitted with CDM. CDM modulator 522 may perform CDM modulation on the output of transmit processor 512 and provide CDM output samples. A multiplexer (Mux)524 may multiplex the output samples from modulators 520 and 522, provide the output samples from OFDM modulator 520 during a period in which an OFDM symbol is transmitted (or an OFDM period), and provide the output samples from CDM modulator 522 during a period in which CDM data is transmitted (or a CDM period). A transmitter (TMTR)526 may process (e.g., analog convert, amplify, filter, and upconvert) the output samples from multiplexer 524 and generate a forward link signal, which may be transmitted via an antenna 528.
At access terminal 120x, an antenna 552 can receive the forward link signal from access point 110x and provide a received signal to a receiver (RCVR) 554. Receiver 554 may process (e.g., filter, amplify, downconvert, and digitize) the received signal and provide received samples. A demultiplexer (Demux)556 may provide received samples in the OFDM period to an OFDM demodulator (Demod)560 and may provide received samples in the CDM period to a CDM demodulator 562. OFDM demodulator 560 may perform OFDM demodulation on the received samples and provide received signaling symbols and received data symbols, which are estimates of the signaling symbols and data symbols sent by access point 110x to access terminal 120 x. Receive processor 570 can process the received signaling symbols to obtain detected signaling for access terminal 120 x. Receive processor 570 can further process the received data symbols to obtain decoded data for access terminal 120 x. CDM demodulator 562 may perform CDM demodulation on the received samples. A receive processor 572 may process the output of CDM demodulator 562 to recover the information sent by access point 110x to access terminal 120 x. In general, the processing for access terminal 120x is complementary to the processing for access point 110 x.
Controllers/processors 530 and 580 may manage the operation at access point 110x and access terminal 120x, respectively. Memories 532 and 582 may store program codes and data for access point 110x and terminal 120x, respectively.
Fig. 6 shows a block diagram of a design of transmit processor 510 and OFDM modulator 520 at access point 110x of fig. 5. Within transmit processor 510, a signaling processor 610 may process signaling for one or more scheduled access terminals and provide signaling symbols. The traffic processor 620 may process traffic data for the scheduled access terminals and provide data symbols. A pilot processor 630 may process the pilot and provide pilot symbols. A tone mapper 640 may receive signaling, data, and pilot symbols and map these symbols to the appropriate tones. In each symbol period, tone mapper 640 may provide N symbols of the N subcarriers to OFDM modulator 520.
Within OFDM modulator 520, an Inverse Discrete Fourier Transform (IDFT) unit 650 may perform an N-point IDFT on the N symbols for the N subcarriers and provide a useful portion containing N time-domain samples. Cyclic prefix generator 652 may add a cyclic prefix by copying the last C samples of the useful portion and adding these C samples to the front end of the useful portion. Windowing/pulse-shaping filter 654 may filter the samples from generator 652 and provide an OFDM symbol comprised of N + C samples, where N and C are dependent upon the algorithm selected for use.
For clarity, the signaling process for one scheduled access terminal (e.g., access terminal 120x) is described below. The signaling may include P bits, where P may be any integer value. In one design, the signaling may include P-10 bits and consist of 8-bit MAC _ AD and 2-bit rate adjustment. In another design, the signaling may include P ═ 13 bits and consist of an 8-bit MAC _ AD, a 2-bit rate adjustment, a 2-bit allocation size indicator, and a 1-bit sticky allocation indicator.
Fig. 7 shows a block diagram of transmit processor 510a (which is a design of transmit processor 510 in fig. 6). In this design, the signaling for access terminal 120x may be split into two parts and sent on two subsets of tones. One subset may include K1One tone and the other subset may include K2A subset of K1+K2. Within signaling processor 610, which is one design of signaling processor 610 in fig. 6, block encoder 710a may utilize (K)1M) Block codes encode the M Most Significant Bits (MSBs) of the signaling and provide K1A code bit. For example, symbol mapper 712a may map K based on BPSK1Mapping of individual code bits to K1And a modulation symbol. Gain unit 714a may be for K1Scaling the modulation symbols to obtain the required signalling transmission power and providing K1A signaling symbol. The block encoder 710b may utilize (K)2L) Block codes encode L Least Significant Bits (LSBs) of the signaling and provide K2A code bit. Symbol mapper 712b may map K to K2Mapping of individual code bits to K2And a modulation symbol. Gain unit 714b may be for K2Scaling the modulation symbols to obtain the required signalling transmission power and providing K2A signaling symbol. In one design, M ═ L ═ 5, K1＝K2And each block encoder 710 may implement a (16, 5) block code. For M, L, K1And K2Other values may also be used.
In one design, orthogonal codes may be used for signaling and B-bit signaling values may be mapped to 2BA bit codeword. For example, a Walsh code may map four possible 2-bit signaling values to 0000, 0101, 0011, and 0110 codewords. In another design, a biorthogonal code may be used for signaling and B-bit signaling values may be mapped to 2B-1A bit codeword. For example, a bi-orthogonal code may map four possible 2-bit signaling values to 00, 11, 01, and 10 codewords. The B-bit biorthogonal code may use all codewords in the (B-1) -bit orthogonal code as well as complementary codewords. As described below, can also be used forOther codes are used for signaling.
When encoding with orthogonal or bi-orthogonal codes, splitting the signaling into portions may reduce the number of tones used to transmit the signaling. For example, an orthogonal code may map 10-bit signaling values to 1024-bit codewords. The 10-bit signaling may be split into two 5-bit portions, each 5-bit portion may be mapped to a 32-bit codeword, and a total of 64 bits may be generated for the 10-bit signaling value. The signaling may be partitioned into multiple portions based on various factors, such as the number of signaling bits sent, the number of tones used for signaling, the coding gain required, detection performance, etc.
Within traffic processor 620, an encoder 720 may encode traffic data for a scheduled access terminal 120x based on a data rate selected for the access terminal and provide code bits. A symbol mapper 722 may map the code bits to modulation symbols based on a modulation scheme determined by the selected data rate. Gain unit 724 may scale modulation symbols to obtain a desired traffic data transmit power and provide data symbols. Within pilot processor 630, a pilot generator 730 may generate pilot symbols. Gain unit 734 may scale the symbols from generator 730 to obtain the desired pilot transmit power and provide pilot symbols. A tone mapper 640a may map 32 signaling symbols from processor 610a to 32 tones for signaling, data symbols from processor 620 to tones for traffic data, and pilot symbols from processor 630 to tones for pilot.
The signaling may also be split into more than two portions, independently coded, and sent on more than two subsets of tones. In one design, the 13-bit signaling for access terminal 120x may be split into three parts: a first portion of 4 bits, which may be encoded with a (8, 4) block code and mapped to 8 tones; a second portion of 4 bits, which may also be encoded with a (8, 4) block code and mapped to another 8 tones; and a third portion of 5 bits, which may be encoded with a (16, 5) block code and mapped to another 16 tones. In another design, the 13-bit signaling may be split into four parts: a first portion of 3 bits, which may be encoded with a (4, 3) block code and mapped to 4 tones; a second portion of 3 bits, which may also be encoded with a (4, 3) block code and mapped to another 4 tones; a third portion of 3 bits, which may also be encoded with a (4, 3) block code and mapped to another 4 tones; and a fourth 4-bit section that may be encoded with an (8, 4) block code and mapped to another 8 tones. Signaling may also be encoded with a single block code and transmitted on a set of tones.
Fig. 8 shows a block diagram of transmit processor 510b (which is another design of transmit processor 510 in fig. 6). In this design, signaling for access terminal 120x may be sent on one of a set of possible S groups of tones, where each group of tones includes K tones, where S and K may be any integer value. Within signaling processor 610b, which is another design of signaling processor 610 of fig. 6, block encoder 810 may encode the L LSBs of signaling with a (K, L) block code and provide K code bits. The symbol mapper 810 may map the K code bits to K modulation symbols. Gain unit 814 may scale the K modulation symbols and provide K signaling symbols. Selector 816 may receive the M MSBs of signaling and select one of the possible S groups of tones based on the M MSBs, where S ≧ 2M. Tone mapper 640b may map K signaling symbols from processor 610b to K tones in the selected tone group and may map data and pilot symbols to tones for traffic data and pilot, respectively.
Table 2 presents some example designs of signaling processor 610b in fig. 8. These designs assume that the signaling includes P-10 bits, a total of 512 tones may be used to transmit the signaling, and BPSK is used for the signaling. Other values for S, K, M and/or L may be used for other signaling sizes, other modulation schemes, etc. For example, QPSK may be used instead of BPSK, and the number of tones may be reduced by half.
TABLE 2
| Set size | Number of tone groups S | Number of tones K per group | Number M of MSBs | Number of LSBs L | Block code (K, L) |
| 256 tone group | 2 | 256 | 1 | 9 | (256，9) |
| 128 tone group | 4 | 128 | 2 | 8 | (128，8) |
| 64 tone group | 8 | 64 | 3 | 7 | (64，7) |
| 32 tone group | 16 | 32 | 4 | 6 | (32，6) |
| 16 tone group | 32 | 16 | 5 | 5 | (16，5) |
| 8 tone group | 64 | 8 | 6 | 4 | (8，4) |
| 4 tone group | 128 | 4 | 7 | 3 | (4，3) |
Sending signaling on one of the sets of tones may provide certain advantages. Some signaling bits may be sent via a selected designated tone group used, while the remaining signaling bits may be sent on the selected tone group. The number of groups of tones and the number of tones in each group may be selected based on various factors such as the number of signaling bits transmitted, the number of tones available for signaling, the coding gain required, detection performance, and the like.
Fig. 9 shows a block diagram of transmit processor 510c (which is another design of transmit processor 510 in fig. 6). In this design, signaling for access terminal 120x may be sent on one of the possible S groups of tones, where each group of tones includes K tones. Within signaling processor 610c, which is another design of signaling processor 610 in fig. 6, block encoder 910 may encode the L LSBs of signaling using block coding and provide a plurality of code bits. Symbol mapper 912 may map the code bits to K modulation symbols. A Discrete Fourier Transform (DFT) unit 914 may transform the K modulation symbols with a K-point DFT and provide K frequency domain symbols. Unit 914 may also be replaced with some other unitary transform (with non-zero terms) that can spread each modulation symbol over all or many tones. Gain unit 916 may scale the frequency domain symbols and provide K signaling symbols. Selector 918 may receive the M MSBs of the signaling and select one of the S groups of tones based on the M MSBs. Tone mapper 640d may map K signaling symbols from processor 610c to K tones of the selected tone group and may map data and pilot symbols to tones for traffic data and pilot, respectively.
The DFT processing of unit 914 may provide frequency diversity for the L LSBs of signaling. Equalization may be used at the receiver to improve performance.
In the designs shown in fig. 8 and 9, the MAC _ ID may be sent in the MSB portion of the signaling. In this case, each access terminal may be mapped to one of the possible S groups of tones based on its MAC _ ID. Each access terminal then detects signaling only on its assigned tone group.
Fig. 10 shows a block diagram of transmit processor 510d (which is another design of transmit processor 510 in fig. 6). In this design, signaling for access terminal 120x may be sent on a set of K tones. Within signaling processor 610d, which is another design of signaling processor 610 in fig. 6, a Cyclic Redundancy Check (CRC) generator 1010 may generate a CRC for the signaling. The CRC may be used by access terminal 120x for error detection. Convolutional encoder 1012 may encode the CRC and signaling and provide code bits. Puncturing unit 1014 may puncture or delete some code bits to obtain a desired number of code bits. Symbol mapper 1016 may map the code bits from unit 1014 to K modulation symbols. Gain unit 1018 may scale the modulation symbols and provide K signaling symbols. A tone mapper 640d may map K signaling symbols from processor 610d to K tones of the selected tone group and data and pilot symbols to tones for traffic data and pilot, respectively.
In one design, CRC generator 1010 may generate a 10-bit CRC for 10-bit signaling. Convolutional encoder 1012 may append 8 tail bits (tail bits) and then encode a total of 28 bits with a rate 1/3 convolutional code to obtain 84 code bits. Puncturing unit 1014 may puncture 20 of the 84 code bits to provide 64 code bits. The symbol mapper 1016 may map 64 code bits to 32 QPSK modulation symbols, and may map 32 QPSK modulation symbols to K-32 tones. Other values may also be used for signaling 610 d.
Fig. 11 shows a block diagram of a transmit processor 510e (which is another design of transmit processor 510 in fig. 6). In this design, signaling for access terminal 120x may be sent on K tones, which are pseudo-randomly selected from all tones assigned to access terminal 120 x.
Within signaling processor 610e, which is another design of signaling processor 610 in fig. 6, block encoder 1110 may encode the L LSBs of signaling using block coding and provide multiple code bits. Symbol mapper 1112 may map the plurality of code bits to K modulation symbols. Gain unit 1114 may scale the K modulation symbols and provide K signaling symbols. Tone selector 1116 may receive the signaled M MSBs, as well as possibly other information such as cell _ ID, slot index, etc. Selector 1116 may pseudo-randomly select K tones among all tones assigned to access terminal 120x based on the input. A tone mapper 640e may map K signaling symbols from processor 610e to K pseudo-randomly selected tones and data and pilot symbols to tones for traffic data and pilot, respectively.
In the design shown in fig. 11, signaling may be sent using a "flash" technique, which sends information on a smaller number of tones with higher transmit power (e.g., 6dB or more) than the traffic transmit power. By sending the signaling for each access terminal on the tones assigned to that access terminal, collisions between signaling for different access terminals within the same cell can be avoided. By pseudo-randomly selecting tones, collisions between signaling of different access terminals in different cells may be reduced. In one design, the M MSBs may include an 8-bit MAC _ ID and the L LSBs may include the remainder of the signaling. For the 10-bit signaling design described above, the L LSBs may include a 2-bit rate adjustment, and K — 2 tones may be pseudorandomly selected and used for signaling. For the 13-bit signaling design described above, the L LSBs may include a 2-bit rate adjustment, and K-5 tones may be pseudorandomly selected and used for signaling. The tones may also be selected from a designated set of tones, from all tones in a time slot, and so on.
Fig. 7 through 11 illustrate some example designs of signaling processor 610 in fig. 6. Signaling processor 610 may also be implemented using other designs.
In some of the designs described above, all or a portion of the signaling may be encoded with one or more block encoders to generate code bits. In one design, signaling may be encoded using one or more static block encoders. The static block encoder has a predetermined codebook and maps each possible signaling value to a specific codeword or output value. The static block encoder may implement any block code known in the art, such as an orthogonal code, a bi-orthogonal code, a hamming code, a Reed-Muller code, a Reed-Solomon code, a repetition code, and the like.
In another design, the signaling may be encoded using one or more dynamic block encoders. The dynamic block encoder has a time-varying codebook that varies over time. For example, the codebook may vary from slot to slot, and a given signaling value may be mapped to different codewords in different slots. A dynamic block encoder may implement a pseudo-random codebook, which may be derived based on a pseudo-random number (PN) sequence. Each access terminal may be assigned a unique 48-bit PN sequence that may be updated at the beginning of each time slot. 16 length-32 codewords may be defined based on a 48-bit PN sequence, for example, the mth codeword may include m to m +31 bits of the PN sequence, where m is 0, 1. Due to the pseudo-random nature of the PN sequence, the correlation between any two codewords in the pseudo-random codebook may be small. Different codebooks may be used for different access terminals and generated based on their different PN sequences. Further, the codebook for each access terminal may vary over time based on the PN sequence for that access terminal. These codebooks may be generated simply by the access point and each access terminal. In some channel conditions, the use of a pseudorandom codebook may reduce false positives. A false positive is a codeword representation when no transmission is taking place or signaling is targeted to other access terminals.
The signaling for access terminal 120x may be sent in an adaptive manner based on channel conditions to ensure that access terminal 120x can reliably receive the signaling. In one design, signaling may be sent in different numbers of tones, where the number of tones may be determined based on channel conditions. For example, channel conditions can be determined based on DRC feedback from access terminal 120 x. In general, more tones may be used for poor channel conditions (e.g., low SNR) and fewer tones may be used for better channel conditions (e.g., high SNR). In one design, signaling may be sent on 8, 16, 32, 64, 128, 256, or 512 tones depending on channel conditions, e.g., DRC feedback. The signaling may be sent at a fixed signaling to pilot transmit power ratio.
In another design, signaling for access terminal 120x may be sent in a fixed number of tones, but the transmit power of the signaling may vary based on channel conditions. In general, greater transmit power (or higher signaling gain) may be used for poor channel conditions, while less transmit power (or lower signaling gain) may be used for better channel conditions. The signaling transmit power may be determined based on the DRC feedback.
The signaling for access terminal 120x may be sent from one or more antennas at the access point. In one design, signaling may be sent from one antenna even when multiple transmit antennas are available. In another design, signaling may be precoded (or spatially processed) with transmit steering vectors and transmitted from multiple antennas. In this design, signaling may be sent from one virtual antenna constructed using a transmit steering vector. In another design, signaling may be space-time block coded and transmitted from multiple antennas, e.g., from two antennas using space-time transmit diversity (STTD). The signaling may be precoded in a similar manner as the traffic and pilot.
Fig. 12 shows a block diagram of a design of OFDM demodulator 560 and receive processor 570 at access terminal 120x in fig. 5. Within OFDM demodulator 560, a cyclic prefix removal unit 1210 may obtain N + C received samples in each OFDM symbol period, remove the cyclic prefix, and provide N received samples for the useful portion. DFT unit 1212 may perform an N-point DFT on the N received samples and provide N received symbols for the N subcarriers. Demultiplexer 1214 can provide received symbols for traffic data and signaling to a data demodulator 1216 and received symbols for pilot to a channel estimator 1218. Channel estimator 1218 may derive a channel estimate based on the received symbols for the pilot. Data demodulator 1216 may perform data detection (e.g., matched filtering, equalization, etc.) on the received symbols for traffic data and signaling using the channel estimates from channel estimator 1218 and provide received data symbols and received signaling symbols.
Within receive processor 570, tone demapper 1220 may provide received signaling symbols to a signaling detector 1230 and received data symbols to a Receive (RX) traffic processor 1240. Tone demapper 1220 may determine the tones used for signaling in the same manner as access point 110x, e.g., based on all or part of the MAC _ ID of access terminal 120x of the design shown in fig. 8, 9, and 11, based on a predetermined set of tones of the design shown in fig. 7 and 10. Signaling detector 1230 can detect signaling sent to access terminal 120x based on received signaling symbols and provide detected signaling. Within the signaling detector 1230, a matrix calculation unit 1232 calculates a matrix for each codeword that may be signaled. Codeword detector 1234 may determine whether to transmit any codeword to access terminal 120x based on the matrix, and if a codeword is transmitted, codeword detector 1234 may provide information associated with the codeword in accordance with the detected signaling. Within RX traffic processor 1240, a unit 1242 may calculate log-likelihood ratios (LLRs) for the code bits based on the detected signaling (e.g., rate adjustments) from signaling detector 1230. Decoder 1244 may decode the LLRs based on the detected signaling and provide decoded data for access terminal 120 x.
The received signaling symbol at access terminal 120x may be expressed as:
formula (1)
Wherein s iskIs a signaling symbol sent on tone k,
ckis soundThe composite channel gain of k is adjusted,
Ekis the transmit power of the signaling symbol sent on tone k,
nknoise of tone k, and
rkis the received signaling symbol for tone k.
In one design, unit 1232 may calculate a matrix Q for each possible codeword m for the signaling as followsm：
Formula (2)
WhereinIs an estimate of the channel gain for tone k,
sk，mis the signaling symbol for tone k of the mth codeword,
Ntis the noise variance, which may be estimated, an
"+" denotes the complex conjugate, and "Re" denotes the real part.
The matrix in equation (2) may provide good detection performance in terms of false positives of signaling from other access terminals.
In another design, unit 1232 may calculate a matrix Q for each possible codeword m as followsm：
Formula (3)
The matrix in equation (3) may provide good detection performance in terms of false positives for traffic data and signaling from other access terminals and when received codewords are not orthogonal.
Signaling detector 1230 can detect signaling for each of the different possible resource allocations for access terminal 120 x. For each possible resource allocation, unit 1232 may calculate a matrix Q for each possible codewordmEach possible codeword may be sent to the signaling interfaceAnd into terminal 120 x. Detector 1234 may compare the matrix computed for each codeword to a threshold value and publish the detected codeword if the matrix exceeds the threshold value. A single threshold value may be used for all channel scenarios, e.g., different power delay characteristics, high and low geometry/SNR, high and low mobility/doppler characteristics, etc. Alternatively, different threshold values may be used for different channel scenarios. The threshold values may be selected to achieve the desired false positive and detection probabilities.
Fig. 12 shows a design of a signaling detector 1230 for signaling sent with block codes as shown in fig. 7, 8 and 11. Block decoding may also be performed in other ways. If signaling is sent with DFT precoding, such as that shown in fig. 9, the signaling detector may perform IDFT prior to block decoding. If the signaling is transmitted using convolutional coding such as shown in fig. 10, the signaling detector may perform Viterbi decoding.
Fig. 13 shows a design of a process 1300 for sending data and signaling. Process 1300 may be performed by an access point for downlink transmission or by an access terminal for uplink transmission. Signaling for data transmission may be processed, e.g., encoded based on a block code, a convolutional code, etc. (block 1312). The block code may be an orthogonal code, a bi-orthogonal code, a static block code, a dynamic block code, a pseudo-random block code, or the like. The pseudo-random block code may be based on a PN sequence of or assigned to a receiver (e.g., an access terminal) to which the data transmission is transmitted. The signaling may also be split into multiple parts and each part of the signaling may be encoded with a respective code. The signaling may also be processed using a DFT or some other transformation to spread each signaling symbol over multiple tones. The signaling may include an identifier of a receiver (e.g., an access terminal), information indicating a data rate for data transmission, information indicating a resource allocation for data transmission, and so on. Data for the data transmission may be processed, e.g., encoded, interleaved, and symbol mapped (block 1314).
Signaling for the data transmission may be mapped to a first set of tones in a slot (block 1318). Data for the data transmission may be mapped to a second set of tones in the slot (block 1316). The first and second sets of tones may be among a plurality of tones allocated for data transmission. The tones in the first set may be (i) distributed over the system bandwidth and/or (ii) distributed over the time slot or located in an earlier portion of the time slot. All signaling may be sent in the first set of tones, e.g., as shown in fig. 7 and 10. Alternatively, the signaling may include first and second portions, the first set of tones may be selected based on the first portion of the signaling, and the second portion of the signaling may be sent on the first set of tones, e.g., as shown in fig. 8, 9, and 11.
The number of tones in the first set and/or the transmit power used for signaling may be selected based on channel conditions for data transmission. A slot may include one or more traffic segments time multiplexed with one or more overhead segments. The first and second sets of tones may be located in a traffic segment.
FIG. 14 shows a design of a process 1400 for sending signaling. Process 1400 may also be performed by an access point or an access terminal. The signaling may be partitioned into multiple portions, including a first portion and a second portion (block 1412). The signaling may include any information for data transmission, and each portion may be of any size. For example, the first portion of the signaling may include all or part of an identifier of a receiver (e.g., access terminal) used for data transmission.
A set of tones may be selected from the plurality of tones based on the first portion of the signaling (block 1414). The plurality of tones may be tones allocated for data transmission or tones that may be used to send signaling. The set of tones may be selected from a plurality of sets of tones based on the first portion of the signaling. The set of tones may also be pseudo-randomly selected from the plurality of tones based on the first portion of the signaling, an identifier of a transmitter (e.g., an access point or cell) sending the data transmission, an index of a time slot sending the data transmission, and so on.
The second portion of the signaling may be encoded based on a static block code, a time-varying block code, a pseudo-random block code, a convolutional code, or the like. The second part of the signaling may also be processed based on a DFT or some other transformation. A second portion of the signaling may be transmitted on the selected tone group (block 1416). The second portion of the signaling may be sent with a higher transmit power than the data transmit power to improve reliability.
Fig. 15 shows a design of a process 1500 for receiving data and signaling. Process 1500 may be performed by an access terminal for downlink transmission or by an access point for uplink transmission. The received symbols for the first set of tones in the slot may be obtained, for example, by performing OFDM demodulation on the received samples (block 1512). The received symbols for the first set of tones may be processed to obtain detected signaling (block 1514). A first set of tones may be determined from a plurality of sets of tones based on an identifier of a receiver (e.g., an access terminal). The first set of tones may also be determined among a plurality of tones that may be allocated for data transmission based on an identifier of a receiver (e.g., an access terminal), an identifier of a transmitter (e.g., an access point or a cell), a slot index, and/or the like. For block 1514, a matrix may be computed for each of a plurality of codewords based on the received symbols. Whether a codeword is transmitted may be determined based on the calculated matrix for each codeword. The detection signaling may be obtained based on the codeword determined to have been transmitted.
A determination may be made whether to process a second set of tones in the time slot for data transmission based on the detected signaling (block 1516). If it is determined that the codeword was not sent, the detected signaling may indicate that no data transmission was sent to the receiver. If the detected signaling indicates that a data transmission was sent, the received symbols for the second set of tones may be processed to recover the sent data. The second set of tones, the data rate of the data transmission, and/or other information may be obtained based on the detected signaling.
Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, electromagnetic fields or particles, optical fields or particles, or any combination thereof.
Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The example logic blocks, modules and circuits described in connection with the embodiments disclosed herein may be implemented or performed with the following components: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.