Abstract: In a wireless communication receiver (31) of a wireless communication system that utilizes transmit diversity and turbo coding, symbol decisions are based at least in part on a posteriori probabilities (47, 48) produced by SISO decoders (35, 36). These probabilities are produced iteratively in alternating fashion to support the symbol decision process. The SISO decoder associated with the weakest (92) wireless communication channel goes first (93) in the iterative process.

Abstract: This invention describes implementation approaches for sliding window turbo decoders. Sliding windows are used for both the beta and alpha state metric calculations. Initialization of the beta/alpha prolog sections with data from a previous iteration is employed in conjunction with a reduced length prolog section. For subsequent sliding windows the trellis values of the prolog sections are dynamically initialized based upon data derived from the signal to noise ratio of the calculated extrinsic data or the difference between the two most probable trellis states.

Abstract: A cable modem (20) including a demodulator (25) having an improved carrier recovery circuit (35) is disclosed. The cable modem (20) demodulates phase-modulated signals, including phase and amplitude modulated signals such as quadrature amplitude modulation (QAM) information. The carrier recovery circuit (35) includes a phase detection function (40), preferably realized by way of programs executed by a digital signal processor, that generates a derivative signal (g(x″)) based upon a summation of a complex function of a corrected input signal (x″) over some or all of the possible points in the modulation constellation. In one embodiment of the invention, the derivative signal is an exact evaluation, considered over the sum of all points in the constellation; in another embodiment of the invention, only four small magnitude points, at relative quadrature phases, are included in the summation.

Abstract: Operands (90) that are represented in two's complement format are prepared for use in binary arithmetic. For each operand, it is determined (91, 93) whether an original value thereof is within a predetermined proximity of a maximum positive/maximum negative value boundary associated with the two's complement format. If any of the original operand values is within the predetermined proximity, all of the original operand values are adjusted (95) to produce respectively corresponding adjusted operand values (96) for use in a binary arithmetic operation.

Abstract: A modem (12) including a least-significant bit convolutional coding scheme is disclosed. In the transmit side of the modem (12), an encoder (28) is included, within which convolutional coders (35I, 35Q) are used to each encode one bit of each symbol applied to a phase and amplitude modulation constellation, preferably the least significant bits, such that the encoded bits select one of a plurality of sub-constellations in the modulated signal. Each of the coders (35, 35′) are arranged as finite state machines, of either thirty-two or sixty-four states. The minimum Hamming distance (dfree) provided by the codes is four, such that the resulting coding gain of the modem is improved over conventional encoding schemes.

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 frequency band for use in wireless communication is selected by passively monitoring at least one of a plurality of available frequency bands (13) to determine whether the at least one frequency band is acceptable for a desired wireless communication. If the at least one frequency band is determined to be acceptable, it is then selected (19) for the desired wireless communication.

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: A linecard (175) permits an increased rate connection between a subscriber (15) and a service provider (40) over the PSTN (50) includes an analog interface (152) a digital interface (165) coupled to the digital backplane (170) to the service provider's host server (34), a conversion circuit (258) interspersed between the analog interface (152) and the digital interface (165), and a linecard microcontroller (300) configured to request bandwidth on the backplane (170) A linecard (175) incorporates a codec (250) with a code recognition mechanism (200) to monitor the Pulse Code Modulated (PCM) input from the provider. The code recognition mechanism (200) provides a way to dynamically allocate and deallocate timeslots on the backplane (170).

Abstract: In one form of the invention, a process of sending real-time information from a sender computer to a receiver computer coupled to the sender computer by a packet network wherein packets sometimes become lost, includes steps of directing packets containing the real-time information from the sender computer by at least one path in the packet network to the receiver computer, and directing packets containing information dependent on the real-time information from the sender computer by at least one path deversity path in the packet network to the same receiver computer.

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: In an equalizer filter unit, the filter is divided into a plurality of sequential segments. While all the components of the equalizer unit multiply data signal groups by the a coefficient signal group, in only one segment are the coefficient signal groups updated. The data and the coefficient signal groups are periodically transferred to the next sequential filter segment while the filter segments are reconfigured in the original sequential order. In this manner, the each data signal group interacts with a coefficient signal group in the original sequential order. Because the coefficients are updated in only one of the filter segments, the amount of apparatus required for processing signal groups is reduced.

Abstract: In a wireless communication system, coded bits (Yt) and an interleaved version of the coded bits (Xt) are separately modulated and transmitted. On the receiver side, a priori output probabilities produced by a probability generator (34) are combined (112) and then input to a SISO decoder (111). Combined a posteriori output probabilities (115) produced by the SISO decoder are split (113) and then fed back to the probability generator.

Abstract: A communications device (100) with an extended filter (74) provides more bandwidth for V.34, V.90 and other data communications protocols. The device (100) permits voice and data communications over the same twisted pair connection (22) to a central office facility (35) and allows an increased data rate between a subscriber (15) and the central office linecard (50). A variable frequency filter (74) capable of switching between “voice” mode and “data” mode is used. In “data” mode, the bandwidth of filter (74) is extend to provide more bandwidth which can be utilized to transfer data. A line monitoring mechanism (102) is provided which monitors the PCM data flowing over a digital backplane (60) as well as requests from a subscriber for an increased data rate connection. A micro-controller (104) can be provided to adjust the bandwidth of the filter (74) and cause it to enter “data” mode.

Abstract: A method and a system for performing memory-based convolutional interleaving are disclosed. According to the disclosed method, delay lines (DL) are paired with one another within rows of a memory, where the pairing is effected so that the sum of the delay of the paired delay lines is constant over the rows. Both in transmission and in receipt of the interleaved data packets, one or more data packets are read from the oldest location of one of the paired delay lines, with one or more data packets from a received vector being written into this delay line; this reading and writing is repeated for each of the rows of the memory, advancing in a first direction. The process of reading and writing is then repeated for the other delay line in each of the rows of the memory, advancing in the opposite direction. The pairing of the delay lines (DL) in each row of the memory permits efficient implementation of convolutional interleaving, with a minimum of overhead processing required.

Abstract: A linecard codec (250) permitting an increased throughput connection between a subscriber modem (20) and a service provider coupled to a digital backplane (150). The linecard codec (250) includes an analog interface (152) to the Public Switched Telephone Network, a digital interface (119) to the digital backplane (150), conversion circuits (258, 280) interspersed between the analog interface (152) and the digital interface (119), and a controller (340) having a network interface (350) and configured to format requests for bandwidth and transmit them to a network administrator of the digital backplane (150). A code recognition mechanism (272) is used to monitor the Pulse Code Modulated (PCM) signals from service providers and in combination with control logic (300) and the controller (340) provides a way to allocate and deallocate timeslots on the digital backplane (150).

Abstract: A linecard (175) permits an increased rate connection between a subscriber (15) and a service provider (40) over the PSTN (50) includes an analog interface (152) a digital interface (165) coupled to the digital backplane (170) to the service provider's host server (34), a conversion circuit (258) interspersed between the analog interface (152) and the digital interface (165), and a linecard microcontroller (300) configured to request bandwidth on the backplane (170) A linecard (175) incorporates a codec (250) with a code recognition mechanism (200) to monitor the Pulse Code Modulated (PCM) input from the provider. The code recognition mechanism (200) provides a way to dynamically allocate and deallocate timeslots on the backplane (170).

Abstract: A linecard codec (250) eliminates limitations of companded code disclosed which increases data rates over a public switched telephone network. The network links a plurality of subscribers and services providers through a central office facility (25) which includes at least one digital backplane (150). The codec (250) comprises an analog interface (152) to the network and a converter (258) coupled to the analog interface and configured to convert analog signals from subscribers to linear coded data (259). A RAM table (262) is used to map the linear coded data (259) to a predetermined coding scheme based on the values stored in the RAM table (262). The RAM table (262) stores mapping values that determine a mapping function between data transmitted by a service provider on the digital backplane (150) and data transmitted to a subscriber.

Abstract: A concentrator (11) coupled to a wired network (13) also acts as a master device relative to each of a plurality of ad hoc wireless communication networks (15), thereby permitting wireless communication devices in the ad hoc networks to access the wired network. The concentrator utilizes antenna array processing and beamforming techniques when communicating with the devices of the various networks, in order to advantageously reduce communication interference between the networks.

Abstract: A concentrator (11) coupled to a wired network (13) also acts as a master device relative to each of a plurality of ad hoc wireless communication networks (15), thereby permitting wireless communication devices in the ad hoc networks to access the wired network. The concentrator utilizes antenna array processing and beamforming techniques when communicating with the devices of the various networks, in order to advantageously reduce communication interference between the networks.