TR201905196T4 - Localized radiated signal transmission for wireless communication. - Google Patents

Abstract

The invention relates generally to communication and more particularly to techniques used to transmit signals in a wireless communication system.

Description

DESCRIPTION LOCALIZED SPREAD SIGNAL TRANSMISSION FOR WIRELESS COMMUNICATIONS This application claims priority under provisional application Serial No. 60/843,366 filed September 8, 2006, which is assigned to the assignee of this application and is hereby incorporated by reference. BACKGROUND OF THE INVENTION This notice of patent right relates generally to communications and more particularly to techniques used to transmit signals in a wireless communications system. ll. Background Wireless communication systems are widely used to provide a variety of communication services such as voice, video, packet data, messaging, broadcasting, etc. These systems can be multiple access systems that can support communications for multiple users by sharing available system resources. Examples of such multiple access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA) systems, and Single Carrier FDMA (SC-FDMA) systems. A wireless communication system can contain any number of base stations capable of supporting communication for any number of terminals. Each base station can transmit data and signals to the terminals it serves. Each terminal can, in turn, transmit data and signals to the base station that serves it. It is desirable for a transmitter to transmit its signals in a manner that ensures reliable reception by a designated receiver. This can be achieved by encrypting and/or repeating the signal and transmitting the encrypted and/or repeated signal through dedicated radio resources. This transmission of signals can improve detection performance. However, there may be situations where the radio resources allocated to the signal are more interference than normal and the signal is received incorrectly. Therefore, the subtleties of the technique require that signals be well received when interference variations are present. The invention addresses the division of a control channel used to transmit control data into multiple subchannels operating at a speed. It describes a signal modulator capable of generating data signals from one and M frequency subbands for transmitting control data from an access point to the respective user terminal, for each of one or more user terminals, the M frequency subbands being selected from among N frequency subbands available for transmission, and both M and N being greater than one, and M being less than or equal to N. Summary of the Invention According to the present invention, a method and equipment for localized spread signal transmission for wireless communication, as set forth in the individual claims, are provided. Preferred embodiments are described in the dependent claims. Techniques for localized spread signal transmission that will provide good detection performance are described herein. In one embodiment, a transmitter (e.g., a base station) may spread multiple signal symbols to obtain multiple output symbols. The multiple signal symbols may include acknowledgement (ACK) symbols and/or other types of signal symbols. The transmitter may obtain each set of output symbols by spreading multiple signals with a spreading matrix. In this case, a transmitter may map multiple sets of output symbols to multiple time frequency blocks, such that each time frequency block corresponds to a set of output symbols. In this manner, the spreading may be localized for each time frequency block. A receiver (e.g., a terminal) may perform complementary summing to collect one or more desired signal symbols. In another design, a transmitter can scale multiple signal symbols with multiple gains (which may be aimed at different receivers) based on the required transmit power for those signal symbols. The transmitter can mix each scaled signal symbol with a corresponding scrambling sequence to obtain multiple scrambling symbols for that signal symbol. The transmitter can generate multiple sets of scrambling symbols, and each set can have a scrambling symbol for each multiple signal symbol. The transmitter can spread each set of scrambling symbols through a spreading matrix to obtain a corresponding set of output symbols. The transmitter can then map each set of output symbols to its corresponding time-frequency block. The receiver can then perform complementary summing to receive one or more desired signal symbols. Various aspects and features related to notification are described in more detail below. Brief Description of Drawings FIGURE 1 shows a wireless communications system. FIGURE 2 shows an example transmission structure. FIGURE 3 shows an example transmission of four ACK bits. FIGURE 4 shows localized spreading for each of multiple tiles. FIGURE 5 shows localized spreading recovery for each tile. FIGURE 6 shows the transmission of ACK signals by localized spreading. FIGURE 7 shows the mapping of output symbols for ACK signals to three tiles. FIGURE 8 shows the reception of ACK signals sent by localized spreading. FIGURES 9 and 10 show a process and equipment for transmitting signals by localized spreading, respectively. FIGURES 11 and 12 show another process and equipment for transmitting signals by localized spreading. FIGURES 13 and 14 show a process and equipment for receiving signals sent by localized spreading. FIGURES 15 and 16 show another process and another equipment for receiving signals sent by localized propagation. FIGURE 17 shows a block diagram of a base station and a terminal. Detailed Description FIGURE 1 shows a wireless communication system 100 with multiple base stations 110 and multiple terminals 120. A base station is a station that communicates with the terminals. A base station may also be referred to as an access point, a Node B, an evolved Node B, etc. Each base station 110 provides communication coverage for a specific geographic area 102. The term "cell" may refer to a base station and/or its coverage area, depending on the context. To improve system capacity, a base station's coverage area may be divided into multiple smaller areas, each of which may be served by a specific base station subsystem. It may refer to the subsystem serving the area. Terminals 120 may be distributed throughout the system, and each terminal may be fixed or mobile. A terminal may also be referred to as an access terminal, mobile station, user equipment, subscriber unit, station, etc. A terminal may be a cellular phone, personal digital assistant (PDA), walkie-talkie, wireless modem, handheld device, laptop computer, etc. A terminal may be communicating with zero, one, or multiple base stations at any given time, in forward and/or backward links. The forward link (or downlink) is the communication link from base stations to terminals, and the backward link (or uplink) is the communication link from terminals to base stations. In this text, "terminal" and The techniques described here can be used in various wireless communication systems, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA systems. A CDMA system uses Code Division Multiplexing (CDM) and sends transmissions using different orthogonal codes. A TDMA system uses Time Division Multiplexing (TDM) and sends transmissions in different time slots. An FDMA system uses Frequency Division Multiplexing (FDM) and sends transmissions on different intermediate carriers. An OFDMA system uses Orthogonal Frequency Division Multiplexing (OFDM), while an SC-FDMA system uses Single Carrier Frequency Division Multiplexing (SC-FDM). OFDM and SC-FDM divide the system bandwidth into multiple orthogonal intermediate carriers, referred to as tones, boxes, and so on. Each intermediate carrier may be modulated with data. Generally, modulation symbols are sent in the frequency domain using OFDM and in the time domain using SC-FDM. For wireless communication systems, techniques that use a combination of multiplexing schemes can also be used, such as CDMA and OFDM, or OFDM and SC-FDM, etc. For a better understanding, some aspects of the techniques are described below for a system using OFDM in the forward link. Some aspects of the techniques are also described in detail in the "Physical Layer Specification for Ultra Mobile Broadband (UMB) Air Interface" for a system using Ultra Mobile Broadband (UMB) radio technology. The techniques described here can also be used for various types of signals. For example, these techniques can be used for acknowledgments (ACKs) and negative acknowledgments (NAKs) in packets, for power control commands, and so on. For a better understanding, some aspects of the techniques are described below for ACK/NAK signals. Figure 2 shows the design of a transmission structure 200 that can be used for forward link. The transmission timeline can be divided into slots, called physical layer (PHY) slots, time slots, etc. Each slot can cover a specific time interval and can be fixed or adjustable. Each slot can cover T symbol periods, where T 2 is 1 and in one design, T = 8. The symbol period is the duration of one OFDM symbol. The system bandwidth can be partitioned into multiple (K) orthogonal intercarriers. All K intercarriers may be used for transmission. Alternatively, only a subset of all K intercarriers can be used for transmission, with the remaining intercarriers serving as security intercarriers, ensuring that the spectral mask requirements of the system are met. In a design, the spacing between intermediate carriers is fixed, and the number of intermediate carriers (K) available for system bandwidth forwarding may be divided into tiles, which may be called time-frequency blocks, resource blocks, etc. A tile may contain eight intermediate carriers in T symbol periods, where T is generally 8 2 1 and T 2 1. In one design, a tile may contain 16 intermediate carriers in 8 symbol periods. In other designs, a tile may have other dimensions of 8 x T. The eight intermediate carriers in a tile may be consecutive intermediate carriers or may be spread out throughout the system bandwidth. A tile has an S-T resource unit, which can be used to send symbols up to S-T. A resource unit is an intermediate carrier within a symbol period and may also be called a resource element, intermediate carrier-symbol, etc. For a given tile, some resource units may be used for pilot symbols and the remaining resource units for data and/or signal symbols. As used here, a data symbol is a symbol for data traffic, a signal symbol is a symbol for signal, a pilot symbol is a symbol for pilot, and a symbol is a complex number. A pilot is data known a priori to both transmitter and receiver. One or more signal channels may be defined and partitioned into a sufficient number of tiles. For example, a Forward Link Control Segment (FLCS) may be defined and may consist of a number of signaling/control channels, such as a Forward Acknowledgement Channel (F-ACKCH). To provide diversity, the FLCS may be partitioned across time and frequency units. Within tiles allocated to the FLCS, different control channels may be partitioned across different resource units. The signal for each control channel may be sent over resource units allocated to control channel 0. A control channel, such as F-ACKCH, may carry a single signal symbol or a single piece of information for a user in a given transmission. A signal bit has one of two possible values (e.g., 0 or 1), while a signal symbol can have one of two possible real or complex values. To provide diversity and improve reliability, the signal symbol or information bit may be repeated and sent over multiple resource units, distributed across a number of intermediate carriers and/or symbol periods. FIGURE 2 shows an example of the transmission of an ACK bit for a user. In this example, the ACK bit is repeated and sent across three resource units in three tiles in the FLCS. Sending the ACK bit at a frequency-wide rate can provide frequency diversity. Within-tile interference variations can be observed in the resource units used for the ACK bit; these are variations in the interference within a tile. Within-tile interference variations can correspond to the interference intensity on the pilot symbols in one tile not being the same as the interference intensity on the other symbols in the tile. Within-tile interference variations can be caused by strong control channels in adjacent tiles and can negatively impact performance. To reduce within-tile interference variations, the ACK bit can be spread across and sent across more resource units; this allows for greater averaging of the interference variations. To maintain the same processing overhead (e.g., three resource units for one ACK bit in the example shown in Figure 2), multiple ACK bits can be spread together with a spreading matrix to produce output symbols, which can be sent over the resource units. Figure 3 shows a design for transmitting a vector of four ACK bits for four different users or for four packets belonging to one or more users. In this design, the four ACK bits can be spread out with a 12 x 4 spreading matrix to produce 12 output symbols, which can be sent over the 12 resource units. In the design shown in Figure 3, the first four output symbols can be sent over the four resource units in the first tile, the second four output symbols can be sent in the second tile, and the last four output symbols can be sent in a third tile. In this case, each ACK bit can be sent over 12 resource units and is therefore less prone to performance degradation due to within-tile interference variations. In general, a transmitter can spread any (L) number of signal symbols and obtain any (Q) number of output symbols. In one design, Q is an integer multiple of L, or Q = L - M, so that L output symbols can be sent to each of M tiles. A receiver can perform complementary summing to receive one or more desired signal symbols. Spreading by the transmitter and complementary summing by the receiver can average out the interference variations within a tile. In this way, the effect of within-tile interference variations can be reduced. The transmitter can perform spreading in a way that improves detection performance and simplifies processing by the receiver. By choosing an arbitrary spreading matrix Q x L, each signal symbol is spread in a different spreading sequence of length Q. In this case, the receiver can perform equalization across all Q resource units used to transmit the Q output symbol to compensate for variations in channel response across these Q resource units. Equalization can be based on minimum mean square error (MMSE), least squares (LS), or some other technique. In a highly frequency-selective channel, large variations in channel response can lead to a significant loss of orthogonality across the L spreading sequence in the Q x L spreading matrix. This loss of orthogonality can affect performance even with equalization. On one hand, multiple signal symbols can be spread to combat interference variations. Spreading can be localized to each tile used to transmit signal symbols to reduce performance degradation due to synchronization loss and to simplify processing by the receiver. In one design, spreading is based on a spreading matrix composed of smaller invertible matrices. In one design, a total spreading matrix S of Q x L can be formed by concatenating M smaller L x L base spreading matrices. With M base spreading matrices, M sets of output symbols can be obtained and sent over M different tiles. In one design, a single type of base spreading matrix is used, and the total spreading matrix 8 consists of M copies of this base spreading matrix. The base spreading matrix can be a discrete Fourier transform (DFT) matrix, a Walsh matrix (also called a Hadamard matrix), a unitary matrix, and so on. In another design, the total spreading matrix could be composed of eight different types of base spreading matrices. For example, the L signal symbol might be spread with a DFT matrix and transmitted in one tile, and the same L signal symbol might be spread with a Walsh matrix and transmitted in another tile. Figure 4 shows a signal transmission design with localized spreading for each tile. For M emitters 410a to 410m, a vector of the L signal symbol, a=[A1...AL]T, can be provided, where T represents a transpose. Each emitter 410 can spread L signal symbols with its associated base spreading matrix Sm, producing a vector of L output symbols, Zm = [Zlm...ZLm]T, where m 6 {l,..., M}. The L output symbols from each emitter 410 can be mapped to the L resource unit in the corresponding tile. In this way, each signal symbol M can be sent to the ML resource unit in the tile. Each signal symbol can be spread through the L resource unit in each tile, depending on the spreading sequence for the signal symbol for that tile. The spreading for the L signal symbol vector can be expressed as: Equation (1) where Sm for 6 {1 M } is the base spreading matrix for tile m and; Zm for 6 {1 M } is the vector of output symbols for tile m. The base spreading matrix for each tile m can be a unitary matrix with the following property: 1! _ :1 _ S S -Sm S -' - Equation (2) where " H " denotes a conjugate transpose and I is the unitary matrix. Equation (2) indicates that the columns of the basis span matrix are orthogonal to each other and each column is a unit power. The span for each tiling m can be expressed as: .WE 21.. M 1 - for Z" _ b'" a ` Equation (3) Equation (3) can be expanded as: Zliri S1 in 1 J› 'SILiii 'Sil Zlm Sîlr. 5 r 15_ l m 4_ Zi .'r. `çi lm ISl _ 5" Il!' _ `IL Equation (4) where Ai for l e {1,..., L} is the lth signal symbol in vector a, Sklm is the element in the kth row and fth column of the spreading matrix Sm, and Zkm for k 6 {1,..., L} is the output symbol for the kth source unit of tile m. With localized spreading, a receiver can obtain L recovered symbols for each tile by inverting the base spreading matrix for that tile. The recovered symbols are initial estimates of the signal symbols. For each signal symbol, M recovered symbols can be obtained from M tiles and combined to obtain a final estimate of that signal symbol. Alternatively, the receiver can equalize, for example, based on MMSE or LS. In this case, the loss due to equalization is calculated for each tile, rather than for all M tiles. This may be due to channel variations within a tile. The synchronization loss can be smaller due to this localized spreading than if the spreading were across all M tiles. Figure 5 shows the reception design for a signal sent with localized spreading for each tile. An L received symbol vector, rm = [R1m...RLm]T, can be obtained from each tile used to send the L signal symbol. M received symbol vectors, r1 to r1v, can be obtained from the M tiles and transmitted to M aggregators (510a) to (510m), respectively. Each aggregator (510) can aggregate its received symbol vector rm, based on its respective base spreading matrix Sm, and provide a vector bm of L aggregated symbols. A combiner (520) can aggregate the L received symbol vectors, b1 to b1n, from the M tiles. The combiner 520 can receive the M accumulated symbol vectors from the combiners 510a to 510m, respectively. The combiner 520 expands and combines these M accumulated symbol vectors to obtain a vector of L signal symbol estimation, %1 = [A1...ALF. The accumulation for each tile m can be expressed as: b, *Sil ro' ` ›i o› ,. Equation (5) where 8m '1 is a accumulation matrix for tile m and is the inverse of matrix Sm. The receiver can only deal with a subset of the L signal symbols sent by the transmitter. The receiver can then accumulate for a given signal symbol Ai in each tile m as follows: Bfni : [Slim: SEVIM SLI.`m] ; ' RL* Equation (6) where Rkm is the kth vector in vector rm is the received symbol, S'kim is the element in the mth row and lth column of the recovery matrix, and Blm is the lth recovered symbol in vector bm, which is the recovered symbol from tile m for signal symbol Ai. The receiver can perform symbol defragmentation for signal symbol Ai across M tiles as follows: [Equation (7)] where Wlm is a tile m weight for signal symbol Ai, and Ai is the final estimate for signal symbol Ai. The Wlm weight for each tile can be determined based on the received signal quality for tile 0. The received signal quality needs to be quantified by a signal-to-noise ratio (SNR) or some other metric. More weight can be given to recovered symbols from tiles with higher received signal quality. Alternatively, the same weight can be applied to recovered symbols from all M tiles. Figure Figure 6 shows a block diagram of a transmit (TX) signal processor 600 design for sending an ACK signal with localized spreading. In this design, four ACK symbols can be spread and sent in three tiles, with the spreading localized to each tile. In one design, there are four possible values that an ACK symbol can take, which can be given as follows: Ü _ . elm" for an ACK value of 0 * " e_,«4.ç..43 for an ACK value of 2 Equation (8) An ACK value of 0 could correspond to a NAK that may have been sent by mistake for a packet decoder. An ACK value of 1 could indicate a packet that was correctly decrypted and could inform the user to maintain the current resource allocation. An ACK value of 2 could indicate a packet that was correctly decrypted. The ACK symbol can indicate a decoded packet and inform the user to abandon the current resource assignment. An ACK value of 3 can inform the user to abandon the current resource assignment. Again, an ACK symbol can be defined to have one of two possible values (e.g., 0 and 1) or based on another set of possible values. The scaling unit 610 can receive and scale four ACK symbols. The ACK symbols can be sent to different users with different geometries or SNRs. The ACK symbol for each user can be scaled with an appropriate gain to achieve the desired SNR for the ACK symbol. The scaling unit 610 can present four scaled ACK symbols, A'o to A'3, to four scramblers 612a to 612d, respectively. Each scrambler (Yio, Yii, and Yi2) can generate three scramble values from a scramble sequence for the user to which it is sent. Different scrambling sequences can be assigned to different users, which can be created based on parameters such as the MAC ID for the user, the sector ID for the transmission sector, etc. The scrambling can provide scrambled symbol signals to different users with different MAC IDs from different sectors. Each spreader 614 can receive four scrambled symbols for four ACK symbols from four scramblers 612a to 612d. Each spreader 614 can spread its four scrambled symbols through a spreading matrix (e.g., a 4 x 4 DFT matrix) and generate four output symbols. Each mapper 616 can map the four output symbols to four source units in the corresponding tile. Mapper 616a sends the output symbols to tile 1, mapper 616b sends the output symbols to tile 2, and mapper 616b sends the output symbols to tile 3. symbols to tile 2 and the mapper (6160) can map the output symbols to tile 3. The transmitter operating for each tile can be expressed as: 2 = DM- G 3 '- Equation (9) where 3 = [A0 A1 A2 A3 ]T is a 4 x 1 vector of four ACK symbols, G is a 4 x 4 diagonal matrix with four gains for the four ACK symbols and zero values elsewhere, Ym is a 4 x 4 diagonal matrix with four gains for the four ACK symbols of tile m, D is a 4 x 4 DFT matrix used for spreading in a tile. and Zm = [Zom Z1m 22m Z3m]T is a vector of four gains for the output symbols of tile m. It is a 4x1 vector. The processing for each ACK symbol Ai can be expressed as: Zklm = DkIYIm GiAi for k = 0,..., 3 and m = 0,... 2. Equation (10) where Gi = x/Ptxi, is the gain, PTXI is the transmit power for ACK symbol Ai, Ylm is the scrambling value for ACK symbol Ai in tile m, Dkl is the element in the kth row and 1st column of the DFT matrix D, and Zklm is an output symbol for ACK symbol Ai for the kth source unit in tile m. Equation (10) shows that the ACK symbol Ai can be scaled with the gain Gi to obtain the desired transmit power for ACK symbol Ai. The scaled ACK symbol can then be scrambled with three scrambling values to obtain three scrambled symbols. Each scrambled symbol can be represented as four elements in one column of the DFT matrix. By spreading by , four output symbols can be sent in one tile for that scrambled symbol. A total of 12 output symbols can be obtained for the ACK symbol Ai. The output symbols for all four ACK symbols can be combined as follows: where Zkm is the output symbol to be sent over the kth resource unit in tile m. Figure 7 shows a design for transmitting 12 output symbols for four ACK symbols in three tiles. In this design, each tile covers 16 intermediate carriers within an 8-symbol period. In each tile, 18 resource units are reserved for pilot symbols, and the remaining resource units can be used to send other symbols. In one design, the four output symbols ZOm, Z1m, Z2m, and Z3m are mapped to a set of four adjacent resource units in tile m. Sending four output symbols close together in frequency and time can cause these output symbols to experience fewer channel changes, resulting in less orthogonality loss. As shown in Figure 7, output symbols can be mapped to different symbol periods across three tiles. This can allow for better power sharing among symbols sent on different intermediate carriers. Transmitting output symbols over multiple sets within the same pair of symbol periods can result in using excessive power for these output symbols and leaving less power for the remaining symbols in that pair of symbol periods. Output symbols can also be mapped to source units in different ways. Figure 8 shows a block diagram of the design of a receive (RX) signal processor 800 for receiving an ACK signal sent by localized spreading. More For clarity, FIGURE 8 shows the process for receiving an AiACK symbol. Each demapper 810 can receive acknowledgment symbols from the three tiles used for ACK signaling. Each demapper 810 can spread the four columns of the four acknowledgment matrices from the four source units used to send the ACK signal in that tile. Each demapper 812 can then re-spread the four acknowledgment symbols with the four elements in the 1st column of an inverse DFT (IDFT) matrix, which do not correspond to the 1st column of the DFT matrix used to spread the ACK symbol Ai to be recovered. The demapper 814 can receive symbols in turn. The demapper 814 can multiply the three recovered symbols by the three scramble values Yio, Yi1, and Yi2 for the ACK symbol Ai, yielding three demapped symbols. (816) can scale three descrambled symbols with three weights applied to three tiles and then combine the three scaled symbols, as shown in Equation (7), to obtain the ACK symbol estimate A1. This process can be repeated for each desired ACK symbol. The ACK symbol Ai can also be summed by equalizing (e.g., based on MMSE or LS) and descramming. In general, any gain value Gi can be used for each ACK symbol Ai. For a flat fading channel, the four spread ACK symbols remain orthogonal at the receiver, and each ACK symbol can be summed by summing the acknowledged symbols. For a frequency-selective channel, channel changes can cause loss of orthogonality, resulting in each ACK symbol causing noise in the remaining ACK symbols. An ACK symbol transmitted at high power This can cause excessive interference to a low-power ACK symbol, which in turn degrades detection performance for a low-power ACK symbol. To mitigate this effect, the ratio of the highest gain to the lowest gain among the four ACK symbols can be limited to a threshold value or below. This ensures that the highest-power ACK symbol does not cause excessive interference to the lowest-power ACK symbol. The threshold value can be selected according to various factors, such as the expected loss in orthogonality due to channel changes, the desired detection performance, etc. ACK symbols for different users can also be divided into groups so that each group contains ACK symbols with similar transmit power. The operations shown in FIGURES 6 and 8 can also be performed in other ways or in different orders. For example, jamming can be performed before spreading (as shown in FIGURE 6). (e.g., ) or after spreading. Scaling can be done first (as shown in FIGURE 6), after scrambling, or at another point. It is also possible to not perform scaling and/or scrambling. For better understanding, the techniques for ACK signaling are explained above. The techniques can also be used for other types of signals. For example, the techniques can be used for power control commands, other-sector-interference (OSI) indications, access permissions, resource assignments, pilot quality indicators, start of packet indications, reverse activity bits, etc. Figure 9 shows the design of process 900 for signal transmission with localized spreading. The process 900 can be performed by a transmitter, such as a base station, etc. Multiple signal symbols can be spread to obtain multiple sets of output symbols, each set of output symbols being a spread of multiple signal symbols. The multiple sets of output symbols can be mapped to multiple time-frequency blocks or tiles (block 914). For example, each set of output symbols can be mapped to a contiguous set of resource units contained in a time-frequency block. The multiple signal symbol can consist of ACK symbols and/or other types of signal symbols. Figure 10 shows a design for equipment 1000 that transmits signals by localized spreading. The equipment 1000 has the capability to spread multiple signal symbols to obtain multiple sets of output symbols, and each set of output symbols is obtained by spreading multiple signal symbols with a spreading matrix (module 1012); the equipment also has the capability to map these multiple sets of output symbols to multiple time-frequency blocks (module 1014). Figure 11 shows the design of process 1100 for signal transmission by localized spreading. The process 1100 may be implemented by a transmitter such as a base station, etc. Multiple signal symbols (e.g., ACK symbols) may be scaled by multiple gains, which are determined by the transmit power of these signal symbols (block 1112). The ratio of the largest gain to the smallest gain may be limited to be below a predetermined value. Each of the scaled signal symbols may be mixed with the corresponding mixing sequence to obtain a multiple mixed symbol for the 0 signal symbol (block 1114). Multiple sets of mixed symbols may be created, and each set may include one mixed symbol for each multiple signal symbol (block 1116). Multiple sets of mixed symbols may be propagated (e.g., with a DFT matrix or a Walsh matrix) to obtain multiple sets of output symbols, such that there is a set of output symbols for each set of mixed symbols (block 1118). Multiple sets of output symbols may be mapped to multiple time frequency blocks, such that there is a set of output symbols for each time frequency block (block 1120). Each set of output symbols may be mapped to a set of adjacent source units in a time frequency block. The processing shown in Figure 11 can also be performed in different orders. It is also possible to omit some parts of the processing (e.g., scaling and/or blending). Other operations can also be performed on the signal symbols. Figure 12 shows the design of equipment 1200 for signal transmission with localized propagation. Equipment 1200 has the ability to scale multiple signal symbols with multiple gains, which gains are determined by the transmission power of these signal symbols (module 1212); The equipment also has a facility for obtaining multiple scrambled symbols for a signal symbol by scrambling each multiple scaled signal symbol with its corresponding scrambling sequence (module 1214); for generating multiple sets of scrambled symbols such that each set contains one scrambled symbol for each multiple signal symbol (module 1216); for obtaining multiple sets of output symbols by spreading multiple sets of scrambled symbols such that there is a set of output symbols for each set of scrambled symbols (module 1218); and for mapping multiple sets of output symbols to multiple time frequency blocks such that each time frequency block receives a set of output symbols (module 1220). This can be accomplished by a receiver such as a terminal, etc. Multiple sets of acknowledgment symbols can be obtained from multiple time-frequency blocks used to send multiple signal symbols (e.g., ACK symbols) by spreading (block 1312). Multiple sets of acknowledgment symbols can be accumulated (e.g., based on a decomposition matrix such as an IDFT matrix or a Walsh matrix) to obtain multiple decomposed symbols (block 1314). The signal symbol estimate for one of the multiple signal symbols can be derived based on the multiple decomposed symbols (block 1316). The process can be repeated for each desired signal symbol. Figure 14 shows the design for equipment 1400 that transmits signals by spreading. The equipment 1400 has the capability to obtain multiple sets of acknowledgement symbols from multiple time frequency blocks used to send multiple signal symbols by spreading (module 1412), to accumulate multiple sets of acknowledgement symbols to obtain multiple recovered symbols (module 1414), and to derive a signal symbol estimate based on the multiple recovered symbols for one of the multiple signal symbols (module 1416). This can be performed by a receiver such as a terminal, etc. Multiple sets of acknowledgement symbols can be obtained from multiple time frequency blocks, with one set of acknowledgement symbols from each time frequency block (block 1512). Each set of acknowledgement symbols can be accumulated based on a decomposition matrix, thereby obtaining a decomposed symbol (block 1514). Multiple descrambled symbols can be obtained for multiple sets of received symbols, and these can be descrambled to obtain multiple descrambled symbols (block 1516). Multiple descrambled symbols can be combined to obtain signal symbol estimation for one of the multiple signal symbols (block 1518). For block 1518, for example, multiple weights can be determined for multiple time frequency blocks, depending on the received signal qualities for these time frequency blocks. Multiple descrambled symbols can be scaled with multiple weights, resulting in multiple scaled symbols. The multiple scaled symbols can then be combined to obtain signal symbol estimation. The processing performed by the receiver may depend on the processing performed by the transmitter. Figure 16 shows the design for equipment 1600 that receives a signal transmitted by localized propagation. The equipment 1600 has the capability to obtain multiple sets of acknowledgement symbols from multiple time frequency blocks, with one set of acknowledgement symbols from each time frequency block (module 1612), to obtain a descrambled symbol by descrambled each set of acknowledgement symbols based on a descramble matrix (module 1614), to obtain multiple descrambled symbols by descrambled multiple descrambled symbols (module 1616), and to obtain signal symbol estimation for one of the multiple signal symbols by combining multiple descrambled symbols (module 1618). The modules in Figures 10, 12, 14, and 16 may consist of processors, electronic devices, hardware devices, electronic components, logic circuits, memories, etc., or any combination thereof. Figure 17 shows a block diagram of the design of a base station 110 and a terminal 120, which are one of the base stations and one of the terminals in Figure 1. In the base station 110, TX data and signal processors 1710 can receive data traffic from a data source (not shown) and/or signals from the controller/processor 1740. Processor 1710 can process data traffic and signals (e.g., format, encrypt, add blank pages, or perform symbol matching) and process data and signal symbols signals and pilot symbols (e.g., for OFDM) and provide output chips. The transmitter (TMTR) 1722 can process the output chips (e.g., convert to analog, expand, filter, and boost) and generate a forward link signal to be transmitted through the antenna 1724. It can receive the forward link signals and provide the acknowledgement signal to the receiver (RCVR) 1754. The receiver 1754 can condition the acknowledgement signal (e.g., filter, expand, down-regulate, and digitize) and provide acknowledgement samples. The demodulator (DEMOD) 1760 can perform mode decoding on the acknowledgement samples (e.g., for OFDM) and provide acknowledgement symbols. The RX data and signal processor 1770 can process the received symbols (e.g., by decoding, removing blank pages, or by decoding) to obtain the decoded data and signals sent to the terminal 120. In the reverse connection, at the terminal 120, the data traffic and signals to be sent by the terminal 120 can be processed by the TX data and signal processor 1790, modulated by the modulator 1792, conditioned by the transmitter 1794, and transmitted via the antenna 1752. At the base station 110, backward link signals from terminal 120, and perhaps other terminals as well, may be received by antenna 1724, conditioned by a receiver 1730, demodulated by a demodulator 1732, and processed by RX data and signal processor 1734 to receive data traffic and signals from the terminals. The operations for backward link transmission may be similar to or different from the operations for forward link transmission and may store data and program codes for terminal 120. The scheduler 1744 may schedule forward and/or backward link transmissions of the terminals and may provide for the allocation of resources (e.g., tiles) for scheduled user equipment and may perform other operations for the techniques described. For signal reception, processor 1734 and/or 1770 may perform the operations shown in FIGS. 5 or 8, or the operation shown in FIG. 13. The techniques described herein may be implemented in a variety of ways. For example, these techniques may be implemented in hardware, firmware, software, or any combination thereof. For hardware implementation, the processing units used to implement the techniques on an entity (e.g., a base station or a terminal) may be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, control units, microcontrollers, microprocessors, electronic devices, other electronic units that perform the functions described herein, a computer, or a combination thereof. For a firmware and/or software application, the techniques can be implemented with modules that perform the functions described herein (e.g., procedures, functions, etc.). The firmware and/or software instructions/code can be stored in memory (e.g., FIGS. 1740 or 1780). The memory can be executed within or outside the processor. The firmware and/or firmware instructions/code may be stored in a computer/processor-readable medium, such as a random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), FLAS memory, soft disk, compact disk (CD), digital versatile disk (DVD), magnetic or optical data storage device, etc. The instructions/code may be executed by one or more processors and may cause the processor(s) to perform some aspect of the functions described herein. The foregoing explanation of this patent right notice is intended to enable any person skilled in the art to make and use this patent right notice. Various modifications of this patent right notice, It will be readily apparent to those skilled in the art; the general principles described herein may be applied to variations without departing from the spirit and scope of this disclosure. Therefore, this patent notice is not intended to be limited to the examples and designs described herein, but is to be understood in the broadest possible context consistent with the principles and new features described herein.TR TR TR TR TR

Claims (1)

1.