Abstract: In an OFDM system, a transmitter broadcasts a first TDM pilot on a first set of subbands followed by a second TDM pilot on a second set of subbands in each frame. The subbands in each set are selected from among N total subbands such that (1) an OFDM symbol for the first TDM pilot contains at least S1 identical pilot-1 sequences of length L1 and (2) an OFDM symbol for the second TDM pilot contains at least S2 identical pilot-2 sequences of length L2, where L2>L1, S1·L1=N, and S2·L2=N. The transmitter may also broadcast an FDM pilot. A receiver processes the first TDM pilot to obtain frame timing (e.g., by performing correlation between different pilot-1 sequences) and further processes the second TDM pilot to obtain symbol timing (e.g., by detecting for the start of a channel impulse response estimate derived from the second TDM pilot).

Abstract: Techniques for multiplexing and transmitting multiple data streams are described. Transmission of the multiple data streams occurs in “super-frames”. Each super-frame has a predetermined time duration and is further divided into multiple (e.g., four) frames. Each data block for each data stream is outer encoded to generate a corresponding code block. Each code block is partitioned into multiple subblocks, and each data packet in each code block is inner encoded and modulated to generate modulation symbols for the packet. The multiple subblocks for each code block are transmitted in the multiple frames of the same super-frame, one subblock per frame. Each data stream is allocated a number of transmission units in each super-frame and is assigned specific transmission units to achieve efficient packing. A wireless device can select and receive individual data streams.

Abstract: A demultiplexer for channel interleaving in communications systems with multiple carriers and/or transmitter diversity includes a distribution module that distributes data bits in succession to successive transmitter antennas, and a switching module coupled to the distribution module. The distribution module routes one data bit to each antenna such that no data bit is routed to the same antenna as the previous data bit. The switching module controls the distribution module to skip an antenna in the routing process once each time a predefined number of data bits have been routed. Alternatively, the switching module may control the distribution module to repeat an antenna in the routing process once each time a predefined number of data bits have been routed. The transmitter antennas may, in the alternative, be different carrier frequency bands.

Abstract: A demultiplexer for channel interleaving in communications systems with multiple carriers and/or transmitter diversity includes a distribution module that distributes data bits in succession to successive transmitter antennas, and a switching module coupled to the distribution module. The distribution module routes one data bit to each antenna such that no data bit is routed to the same antenna as the previous data bit. The switching module controls the distribution module to skip an antenna in the routing process once each time a predefined number of data bits has been routed. Alternatively, the switching module may control the distribution module to repeat an antenna in the routing process once each time a predefined number of data bits has been routed. The transmitter antennas may, in the alternative, be different carrier frequency bands.

Abstract: Techniques to adjust the setpoint of a power control loop in a wireless communication system. The setpoint may be adjusted based on frame status indicative of erased/good decoded frames, one or more (typically soft) metrics indicative of the confidence in the decoded results, power surplus/deficit indicative of the difference between the received signal quality and the setpoint, setpoint surplus/deficit indicative of the difference between the setpoint and a threshold Eb/Nt needed for the desired level of performance, or a combination thereof. The metrics may include re-encoded symbol error rate, re-encoded power metric, modified Yamamoto metric, minimum or average LLR among decoded bits, number of decoding iterations, and possibly others. The setpoint may be adjusted in different manners and/or by different amounts depending on the above-noted factors. The techniques may be employed for forward and/or reverse links in CDMA systems.

Abstract: Techniques for transmitting data from a transmitter unit to a receiver unit in a multiple-input multiple-output (MIMO) communication system. In one method, at the receiver unit, a number of signals are received via a number of receive antennas, with the received signal from each receive antenna comprising a combination of one or more signals transmitted from the transmitter unit. The received signals are processed to derive channel state information (CSI) indicative of characteristics of a number of transmission channels used for data transmission. The CSI is transmitted back to the transmitter unit. At the transmitter unit, the CSI from the receiver unit is received and data for transmission to the receiver unit is processed based on the received CSI.

Abstract: A method and apparatus for wireless communications wherein a base station transmits a signal to sending data to a subscriber station through a signal beam that sweeps through the coverage area of the base station. User data addressed to the subscriber station is buffered until the signal beam angle of the signal beam allows efficient transmission. The base station may alter the beam sweep speed or the shape of the beam's radiation pattern over time to maximize system efficiency and capacity.

Abstract: Techniques for transmitting data from a transmitter unit to a receiver unit in a multiple-input multiple-output (MIMO) communication system. In one method, at the receiver unit, a number of signals are received via a number of receive antennas, with the received signal from each receive antenna comprising a combination of one or more signals transmitted from the transmitter unit. The received signals are processed to derive channel state information (CSI) indicative of characteristics of a number of transmission channels used for data transmission. The CSI is transmitted back to the transmitter unit. At the transmitter unit, the CSI from the receiver unit is received and data for transmission to the receiver unit is processed based on the received CSI.

Abstract: Techniques to adjust the setpoint of a power control loop in a wireless communication system. The setpoint may be adjusted based on frame status indicative of erased/good decoded frames, one or more (typically soft) metrics indicative of the confidence in the decoded results, power surplus/deficit indicative of the difference between the received signal quality and the setpoint, setpoint surplus/deficit indicative of the difference between the setpoint and a threshold Eb/Nt needed for the desired level of performance, or a combination thereof. The metrics may include re-encoded symbol error rate, re-encoded power metric, modified Yamamoto metric, minimum or average LLR among decoded bits, number of decoding iterations, and possibly others. The setpoint may be adjusted in different manners and/or by different amounts depending on the above-noted factors. The techniques may be employed for forward and/or reverse links in CDMA systems.

Abstract: An optimum combiner that reduces the amount of interference imposed upon a first base station by transmissions of other base stations within the same communication system. Two antennas are used to receive transmissions within a receiving station. A rake receiver is coupled to each antenna. By optimally combining the signals that are received by each independent finger of the rake receiver, interference that is correlated between a finger associated with the first antenna and a finger associated with the second antenna can be minimized with respect to the desired signal. Optimum combining requires determination of optimum combining coefficients.

Abstract: According to one aspect of the invention, a method for determining a power control set point is provided. In one embodiment, the power control set point is determined based on one or more factors including a first factor corresponding to a pilot bit error rate, a second factor corresponding to a normalized signal variance, and a third factor corresponding to an average number of fingers in lock.

Abstract: An optimum combiner that reduces the amount of interference imposed upon a first base station by transmissions of other base stations within the same communication system. Two antennas are used to receive transmissions within a receiving station. A rake receiver is coupled to each antenna. By optimally combining the signals that are received by each independent finger of the rake receiver, interference that is correlated between a finger associated with the first antenna and a finger associated with the second antenna can be minimized with respect to the desired signal. Optimum combining requires determination of optimum combining coefficients. A max-ratio combining algorithm may be substituted for the optimal combining algorithm depending upon interference characteristics.

Abstract: Apparatus for a transmitter and a receiver which enhance the performance of a system coherent demodulation by utilizing non-pilot sub-channels to enhance the accuracy of estimates of amplitude and phase noise inherent in the transmission channel is described. This enhancement is accomplished by utilizing the corrected received data on a fundamental channel to enhance a pilot channel estimate, which is subsequently utilized by a dot product module in demodulating a supplementary data channel.

Abstract: Techniques for puncturing symbols in a communications system are disclosed. S symbols are received for a frame having a capacity of N symbols, with S being greater than N. P symbols need to be punctured so that remaining symbols fit into the frame. A number of puncture distances, D1 through DN, are computed based on S and P. A particular number of symbol punctures is determined for each computed puncture distance. P1 through PN symbol punctures are then performed at the distances of D1 through DN, respectively. For a more even distribution of the symbol punctures, each of the distances D1 through DN can be selected to be greater than or equal to a minimum puncture distance Dmin defined as Dmin=└S/P┘, where └ ┘ denotes a floor operator. The symbol punctures at each computed distance can be performed together or distributed with symbol punctures at other distances.

Abstract: A turbo code interleaver using linear congruential sequences may be employed as a two-dimensional interleaver in a turbo coder that also includes first and second constituent encoders. The interleaver and the first encoder are each configured to receive input bits. The first encoder produces output symbols therefrom. The interleaver receives the input bits sequentially by row. A linear congruential sequence recursion algorithm within the interleaver serves to pseudo-randomly rearrange, or shuffle, the bits within each row of the interleaver. The bits are then output from the interleaver sequentially by column. The second encoder is configured to receive the interleaved bits from the interleaver. The second encoder produces output symbols therefrom. The two streams of output symbols are multiplexed together, with appropriate puncturing. If desired, the linear congruential recursion sequence can be generated in reverse.

Abstract: A method and apparatus for wireless communications wherein a base station transmits a signal to sending data to a subscriber station through a signal beam that sweeps through the coverage area of the base station. User data addressed to the subscriber station is buffered until the signal beam angle of the signal beam allows efficient transmission. The base station may alter the beam sweep speed or the shape of the beam's radiation pattern over time to maximize system efficiency and capacity.

Abstract: The present invention is a novel and improved method and apparatus for performing closed loop power control. A method of implementing reverse link outer loop using only pilot signal is described. Such a method is especially useful when the data signals are only present in short burst such that packet or frame error rates (PER or FER) cannot be estimated accurately. Moreover, since this method provides a mechanism for accurate set point adjustment even without a PER (FER) estimate, it can also be used to improve the accuracy of outer loop performance when such estimate becomes available. The present invention estimates a “pilot bit error rate” (PBER), where each pilot “bit” consists of a number pilot chips distributed over a frame. In addition, it estimates the normalized variance of the signal energy (or C/I) for each packet. In addition, in the preferred embodiment, the average number of fingers in lock is also used to determine the power control set point.

Abstract: Techniques for puncturing symbols in a communications system. S symbols are received for a frame having a capacity of N symbols, with S being greater than N. P symbols need to be punctured so that remaining symbols fit into the frame. A number of puncture distances, D1 through DN, are computed based on S and P. A particular number of symbol punctures is determined for each computed puncture distance. P1 through PN symbol punctures are then performed at the distances of D1 through DN, respectively. For a more even distribution of the symbol punctures, each of the distances D1 through DN can be selected to be greater than or equal to a minimum puncture distance Dmin defined as Dmin=└S/P┘, where └ ┘ denotes a floor operator. The symbol punctures at each computed distance can be performed together or distributed with symbol punctures at other distances.

Abstract: A method and apparatus for efficient candidate frequency search while initiating a handoff in a code division multiple access communication system. The method includes when the pilot signal is transmitted by the mobile station that is power controlled to a target receive level, the traffic channel power level is increased relative to the pilot channel to improve receiver performance. An improved feature is that the received pilot received at the base station stays the same while the receiver receives extra energy in the redundant traffic symbols received to enhance the probability of correctly decoding the received frame. The base station detects the absence of the mobile station transmitted signal from the frequency of interest. If the base station is aware of the starting time and duration of the absence, it can focus its detection during this predetermined time period. The performance can be improved if the absence of the signal is spread across two frames at the frame boundary.

Abstract: A receive filter receives signals from a communication channel. The received signals correspond to original Walsh covered chip sequences transmitted by a transmit filter through the communication channel to the receive filter. The received signals are processed by an equalizer to generate a soft estimate of chip sequences corresponding to the original Walsh covered chip sequences. An N chip Walsh decover is then utilized to generate a soft estimate of code symbols corresponding to the soft estimate of the chip sequences. A number of symbol slicers are then used in parallel to produce a hard estimate of the code symbols corresponding to the soft estimate of code symbols generated by the N chip Walsh decover. Thereafter an N chip Walsh cover is used as part of a scheme to generate a hard estimate of chip sequences corresponding to the hard estimate of the code symbols generated by the symbol slicers.