Abstract: A turbo decoder in which a sliding-block MAP decoder pipelines the forward-propagating and backward-propagating computations.

Abstract: The frequency hopping pattern of a first wireless communication device is modified such that each transmission (73) to a second wireless communication device is on a frequency (MSj+1) that the second device's normal frequency hopping pattern specifies for one of the second device's next several transmissions to the first device. This permits the second device to make quality measurements (54) on a frequency that the second device will soon use (51) for transmission to the first device.

Abstract: In one form of the invention, a process of sending real-time information from a sender computer (103) to a receiver computer (105) coupled to the sender computer (103) by a packet network (100) wherein packets (111,113) sometimes become lost, includes steps of directing (441) packets (111) containing the real-time information from the sender computer (103) by at least one path (119) in the packet network (100) to the receiver computer (105), and directing packets (113) containing information dependent on the real-time information from the sender computer (103) by at least one path diversity path (117) in the packet network (100) to the same receiver computer (105).

Abstract: A transceiver (100) such as used in Discrete Multitone (DMT) modulation of digital signals for communication, such as in a DSL modem communications system, is described. The transceiver (100) includes a function (119) by way of which unloaded subchannels are encoded with a clip prevention signal. The clip prevention signal is derived to avoid clipping by an amplifier (18) after modulation into the time domain, upsampling, and filtering. The effects of the upsampling and filtering are considered in deriving the clip prevention signal, by considering the upsampling and filtering as a polyphase combination, and using the filter response for each phase. Frequency domain and time domain update alternatives are disclosed.

Abstract: The interference cancellation (IC) system (500) includes a plurality of IC units, for which IC is applied. Each IC unit has its spread spectrum code generator, delay devices, correlators or matched filters (MF), spreading circuits and subtracting and adding devices. The IC process in accordance with the invention includes using a bank of MF to despread the received signal at every time instant corresponding to every identified multipath of every user's transmitted signal. Based on the despread signals, an initial decision for the present information symbol of every user can be made using a single-user receiver such as, for example, the conventional Rake receiver or an equalizer. Based on the initial decisions, IC regenerates the multipath signals for each user using timed versions of the spread spectrum code, the delays of the multipaths, and the corresponding channel medium estimates.

Abstract: In one form of the invention, a process of sending real-time information from a sender computer (103) to a receiver computer (105) coupled to the sender computer (103) by a packet network (100) wherein packets (111,113) sometimes become lost, includes steps of directing (441) packets (111) containing the real-time information from the sender computer (103) by at least one path (119) in the packet network (100) to the receiver computer (105), and directing packets (113) containing information dependent on the real-time information from the sender computer (103) by at least one path diversity path (117) in the packet network (100) to the same receiver computer (105).

Abstract: The interference cancellation (IC) system (500) includes a plurality of IC units, for which IC is applied. Each IC unit has its spread spectrum code generator, delay devices, correlators or matched filters (MF), spreading circuits and subtracting and adding devices. The IC process in accordance with the invention includes using a bank of MF to despread the received signal at every time instant corresponding to every identified multipath of every user's transmitted signal. Based on the despread signals, an initial decision for the present information symbol of every user can be made using a single-user receiver such as, for example, the conventional Rake receiver or an equalizer. Based on the initial decisions, IC regenerates the multipath signals for each user using timed versions of the spread spectrum code, the delays of the multipaths, and the corresponding channel medium estimates.

Abstract: A wireless receiver (UST). The receiver comprises at least one antenna (ATU) for receiving a plurality of frames (FR) in a form of a plurality of paths. Each of the plurality of frames comprises a plurality of time slots (SLN), and each of the plurality of time slots comprises a plurality of symbols. Further, each of the plurality of paths has a corresponding sample position, wherein the plurality of symbols comprise a primary synchronization code symbol (PSC). The receiver further comprises circuitry (52) for correlating a primary synchronization code across a group of the plurality of symbols and circuitry (52) for identifying a plurality of path positions within the group. Each of the plurality of path positions corresponds to a respective one of a plurality of largest-amplitude paths represented within the group as detected in response to the circuitry for correlating. The receiver further comprises circuitry (56) for defining a plurality of sub-windows.

Abstract: A wireless receiver (UST). The receiver comprises at least one antenna (ATU) for receiving a plurality of frames (FR) in a form of a plurality of paths. Each of the plurality of frames comprises a plurality of time slots (SLN), and each of the plurality of time slots comprises a plurality of symbols. Further, each of the plurality of paths has a corresponding sample position, wherein the plurality of symbols comprise a primary synchronization code symbol (PSC). The receiver further comprises circuitry (52) for correlating a primary synchronization code across a group of the plurality of symbols, and circuitry for identifying a plurality of path positions within the group. Each of the plurality of path positions corresponds to a respective one of a plurality of largest-amplitude paths represented within the group as detected in response to the circuitry for correlating.

Abstract: A circuit for detecting a transmit diversity signal comprises a first circuit (706) arranged to receive a first synchronization code. The first synchronization code is modulated by a data signal. The first circuit produces a first output signal. A second circuit (732) is arranged to receive a plurality of predetermined signals. The second circuit produces a channel estimate. A detection circuit (710, 712) is arranged to receive the first output signal and the channel estimate. The detection circuit produces a signal corresponding to the data signal.

Abstract: A modem comprises circuitry for receiving an analog signal from a line and circuitry for converting the analog signal to a digital signal. The digital signal comprises a plurality of ideal sample points (P0-P3), each separated in time by a period T, and the plurality of ideal sample points comprises a sync sequence (14). The modem further comprises circuitry (34) for detecting the sequence comprising an integer number S of sampling circuits (38, 40), wherein S is two or greater. Each of the sampling circuits comprises circuitry for taking a sample corresponding to each of the plurality of ideal sample points at least once per the period T. Each of the sampling circuits also comprises circuitry for comparing a plurality of taken samples to a correlation sequence. Finally, each of the sampling circuits comprises circuitry for outputting a sync detected signal (SYNC0, SYNC1) in response to a sufficient match between the plurality of taken samples and the correlation sequence.

Abstract: An improved interference cancellation technique is disclosed. Digital baseband circuitry (40) includes user and symbol detection circuitry (50) for performing a Gibbs sampler type of interference cancellation, either embodied in custom hardware (44) or in software. Random initial guesses for a signal sample (either a symbol or chip) are made for each user. Interference cancellation is performed on a user-by-user basis, using the then-current data decision values for the other, interfering users. A soft data decision is used to derive a probability distribution function for the actual data decision for the sample for the user. A randomly selected value is applied against the probability distribution function to generate the next data decision value for that user, and the process is repeated until convergence. Following convergence, a statistic is used to select a final data decision value for each user, from the set of intermediate data decision values stored in memory.

Abstract: A Viterbi decoder system is provided in accordance with the present invention. The decoder system includes a State Metric Update unit including a state metric memory and a cascaded Add/Compare/Select (ACS) unit. The cascaded ACS unit comprises a plurality of serially coupled ACS stages for performing a plurality of ACS operations in conjunction with the state metric memory. An ACS stage is operable to identify a plurality of path decisions and communicate the identified path decisions to a next ACS stage coupled thereto. A Traceback unit is provided for storing a set of accumulated path decisions in a traceback memory associated therewith, and performing a traceback on the set of accumulated path decisions. The path decisions associated with the ACS stage and the next ACS stage are accumulated as a set during the ACS operations before being written to the traceback memory, thereby minimizing accesses to the traceback memory.

Abstract: In one form of the invention, a process of sending real-time information from a sender computer (103) to a receiver computer (105) coupled to the sender computer (103) by a packet network (100) wherein packets (111,113) sometimes become lost, includes steps of directing (441) packets (111) containing the real-time information from the sender computer (103) by at least one path (119) in the packet network (100) to the receiver computer (105), and directing packets (113) containing information dependent on the real-time information from the sender computer (103) by at least one path diversity path (117) in the packet network (100) to the same receiver computer (105).

Abstract: The operation of a line card in the local exchange of a point-to-point switched telephone network is modified to increase the data rate of voiceband modem transmission by increasing the sampling rate and providing controlled intersymbol interference using partial response techniques.

Abstract: A multiplier (12) is disclosed that includes an encoder (36), a hierarchy of compressors (40, 42, 44, 50, 52, 60 and 70), a bit detector (130) and a switch (134). The encoder (36) is operable to receive a first and second encoder input. The compressors (40, 42, 44, 50, 52, 60 and 70) are coupled to the encoder (36). The compressors (40,42, 44, 50, 52, 60 and 70) are operable to receive a first number of inputs and to generate a second number of outputs, with the second number being less than the first number. The bit detector (130) is operable to monitor the first encoder input to determine whether the first encoder input is in a reduced precision range (28). The bit detector (130) is also operable to deactivate a subset of the compressors (40 and 50) when the bit detector (130) determines that the first encoder input is in the reduced precision range (28). The switch (134) is coupled to a specified one of the compressors (42).

Abstract: This invention provide parallel interference cancellation for wireless communication base stations. Received user inputs symbols are spread by means of pseudo-noise sequences to form user input chip vectors. These are added together and interpreted to form chip vectors of interference samples. These chip vectores are despread to form interference output symbols by means of said pseudo-noise sequences. The interference output signals are subtracted from the received user input symbols to obtain a first estimate of transmitted symbols. This process may be continued for two or more iterations to obtain better interference cancellation.

Abstract: A programmable co-processor system comprising a datapath, a microprogram, and a microcontroller is provided. The datapath includes one or more datapath elements operable to receive input signals. The microprogram memory includes a microprogram operable to control the datapath in order to process the input signals. The microcontroller is operable to modify the microprogram based on a modification command.

Abstract: Quasi-parallel read/write interleaver architecture for data blocks by sequential spreading of variable size data subblocks into memory banks with bank address contention initiating the next data subblock. Iterative Turbo decoders with MAP decoders use such quasi-parallel interleavers and deinterleavers.

Abstract: MAP decoder with cascade architecture. Iterative Turbo decoders can use two such cascade MAP decoders with feedback in conjunction with interleaver and deinterleaver where the MAP decoders generate extrinsic information for iterations.