Abstract: For use with a multiple-input, multiple-output (MIMO) transmitter, a signal field controller, a method of controlling signal fields and a MIMO transmitter incorporating the controller or the method. In one embodiment, the controller includes: (1) a primary signal field mode indicator configured to cause a primary signal field to indicate a presence of a supplemental signal field and provide the primary signal field to the MIMO transmitter for transmission thereby and (2) a supplemental signal field generator coupled to the primary signal field mode indicator and configured to provide a supplemental signal field to the MIMO transmitter for further transmission thereby only when the primary signal field indicates the presence.

Abstract: Modularized clock decoupling and signal delay management is provided for the purpose of reducing simultaneous binary signal switch-induced inductive voltage transients in lower voltage synchronous semiconductor devices. The voltage levels in low-voltage devices must be tightly maintained for proper transistor logic operations. Signal switching results in current changes on the power net of an IC. Current changes produce inductive voltage transients which propagate throughout the device and which can interfere with signal transmission and device operation. Relatively independent functioning circuits of an integrated circuit are isolated from the chip clock and each isolated circuit module is provided with its own independent, same-frequency, but slightly out-of-phase clock signal. Signal switching within any module is thus occurring out-of-phase with that of all other modules and, as a result, switch-associated voltage transients are limited to those associated with one module's circuits at a time.

Abstract: A method and apparatus to reduce the amount of required memory and instruction cycles when implementing Fast Fourier Transforms (FFTs) on a computer system is described. The invention optimizes FFT software using in-place bit reversal (IPBR) implemented on a processor capable of bit reversed incrementation. Alternative embodiments implement the invention for out of place bit reversal (OOPBR) and on processors that do not support special instructions for bit reversed incrementation. The invention only generates unique bit-reversed address pairs and avoids generation of self-reversed addresses. To optimize the invention for in place bit reversal, every non-self bit reversed address in the input array is generated only once, while making simple, computationally efficient increments away from the previous pair of bit reversed addresses. The address pair generator can independently advance only one address in each address pair, and bit reversal of one address uniquely defines the other address.

Abstract: A system for transmitting modern signals across a packet network with improved resistance to bursty network packet loss that includes a first and a second processor, which connect a first and second V.32 and above modem to a first and a second side of the packet network and which provide a modified V.42 error correction using a Link Access Procedure for Modems (LAPM). The first and second processors provide a local interface to the V.32 and above moderns, demodulate a first and second data stream from the corresponding V.32 modems into bits, packetize the bits for transport over the packet network according to an Internet Protocol (IP), and remodulate data streams received from a remote end. The modified V.42 error correction includes a staggered redundancy of packet data, in which the staggered redundancy attaches data from a packet n1 to a subsequent packet nL, where L>2.

Abstract: A method of initializing an ITU Recommendation G.729 Annex B compliant voice activity detection (VAD) device is disclosed, having the steps of (1) determining a first set of running average background noise characteristics in accordance with Recommendation G.729B; (2) determining a second set of running average background noise characteristics; and (3) substituting the second set of running average background noise characteristics for the first set when a specific event occurs. The specific event is a divergence between the first and second sets of running average background noise characteristics.

Abstract: A wireless local area network (LAN) adapter (20) that optimizes the length of message packets, for example according to the IEEE 802.11 standard, and in an environment having interfering transmissions (BL1 et seq.), is disclosed. The disclosed adapter (20) executes an adaptive process by way of which an adjustment to the packet length is derived based upon rate measures for the most recent two trial packet lengths. The rate measure corresponds to a packet success rate for that packet length, determined either from an estimating function or by actual measurements, multiplied by a ratio of the data portion of each packet to a total packet length including interpacket spacing. Upon convergence as the adjustment becomes smaller, the optimized packet length for best data rate given the present interference. A method of determining the need for packet length optimization is also disclosed, in which the actual packet error rate is compared against an expected packet error rate based upon signal-to-noise ratios.

Abstract: A system and method is provided for monitoring interference in a wireless communication system. The system and method monitor error statistic data at one or more devices in a wireless communication system. The error statistic data can be utilized to determine the location of the interference. If any unusual error statistic data is present at the one or more of the devices, raw unprocessed data is provided from the devices experiencing unusual error activity. The raw unprocessed data can be utilized to characterize the interference. For example, the raw unprocessed data can be compared to one or more interference templates to determine an interference type. The raw unprocessed data can be compared between devices in the wireless communication system to determine the location of the interference with increased precision.

Abstract: A method of initializing an ITU Recommendation G.729 Annex B voice activity detection (VAD) device is disclosed, having the steps of (1) extracting a set of parameters from a signal that characterize the signal; (2) calculating an energy measure of the signal from the set of parameters; (3) comparing the energy measure with a reference value; (4) determining an initial value for an average of a noise characteristic of the signal; and (5) counting the number of times the energy measure equals or exceeds the reference level. Also disclosed is a method of converging an ITU Recommendation G.

Abstract: Disclosed are methods of selecting a multi-dimensional signal constellation in relation to impairments in a communication system having a data frame consisting of a fixed number of symbols. The methods make use of impairments detected from a Digital Impairment Learning sequence (DIL) and channel impairments, such as POE and SNR. Signal points are individually assigned to each symbol in a data frame in relation to that symbol's particular digital impairments and a pre-selected minimum performance level and maximum power constraints.

Abstract: A digital input signal is analyzed by a peak detector (210) configurable to trigger a first logic signal (260) if the peak detector detects the digital input signal level crossing a certain threshold. The threshold value can be modified by an overhead. The amplifier (250) employs a plurality of supply rails of differing voltages (253, 255) as a function of the logic signals. A digital signal delay element (220) may delay the signal to allow sufficient time for the amplifier to switch between supply sources. A logic delay element (280) may delay transmittal of the first logic signal by the peak detector to compensate for signal delay caused by a filter. A hold element (270) ensures that the first logic signal is applied to the output amplifier for a given amount of time.

Abstract: A multi-client ADSL modem network (10) that can be configured for a home or office network when multiple ADSL client modems (18) are installed in different communication terminals (22). One ADSL modem (14) at a central office (12) coordinates the remote multi-client modems (18) for communication over a single twisted pair loop carrier phone line (16), allowing the connected modems (18) to communicate not only with the CO modem (14), but also with each other by sharing frames, tones, or by code division techniques on upstream channels. The CO modem (14) operates as a network hub and/or arbitrator, and facilitates one ADSL modem to become the master modem and maintain a superframe. The present invention provides home network ADSL service without extra wiring or equipment, thus providing a low cost approach for home networking of ADSL service.

Abstract: A method for deriving coefficients for a time domain equalizer function (24) as implemented by a digital signal processor (35) in a DSL modem (20) is disclosed. A transmitting modem (10), such as at a central office, issues a pseudo-random training sequence that is received by the receiving modem (20). Correlation matrices are derived by the digital signal processor (35), from which sets of eigenvalues and eigenvectors are derived. A flatness constraint on the frequency response of the time domain equalizer is established, and included with a flatness scaling factor (?) into a minimization cost function. One or more values of the flatness scaling factor (?), preferably between minimum and maximum eigenvalues, are evaluated in the cost function, to derive the optimum filter for the time-domain equalizer. The flatness constraint ensures that the time-domain equalizer is not subject to near null conditions and large variations in its frequency response.

Abstract: A method is disclosed for providing data for automatically estimating channel performance if different parameters of a Reed-Solomon (RS) code are used in a communication system while transmission is occurring in the communication system without changing the current Reed-Solomon (RS) code parameters.

Abstract: A network switch system (10) is disclosed, in which a plurality of switch fabric devices (20) are interconnected according to a ring arrangement, each of the switch fabric devices (20) including therein switch interfaces (22) coupled to corresponding network switches (14, 16). Each switch fabric device includes a plurality of ring paths (24), each of which is associated with a receive ring interface (26R) and a transmit ring interface (26X). Each ring path (24) includes a circular buffer (44) having a plurality of entries, each of which is associated with valid logic (50). The valid logic (50) for each entry presents valid signals on valid lines (WV, RV) to the receive and transmit domains of the ring path (24), and receives signals on write and read word request lines (WRW, RDW) therefrom.

Abstract: A central office modem (50) that includes the capability of single-ended loop testing (SELT) is disclosed. The modem (50) includes a digital signal processor (54), a codec (56), line driver and receiver circuitry (58), and a hybrid circuit (60), by way of which a subscriber loop (LOOP) can be driven and sensed. The line driver and receiver circuitry (58) may include a transformer (74a, 74b) for driving the loop (LOOP), or the output may be capacitively coupled. The line driver and receiver circuitry (58) includes active termination, by way of operational amplifiers (80a, 80b). Switches (82a, 82b; 84a, 84b) are provided to selectively enable and disable the active termination function, and to selectively bypass or include the hybrid circuit (60). This control of the line driver and receiver circuitry (58) provides the ability to calibrate out its own characteristics, providing high precision SELT measurements of the load impedance type, and of frequency domain reflectometry, and time domain reflectometry.

Abstract: A method for constellation design in a telecommunications network using pulse code modulation to transmit data signals upstream between client and server voice-band modems. The invention selects a constellation for transmission over an analog channel of an equivalence class of data points using pulse code modulation based on the presence or absence of robbed bit signaling and interference from echo levels. The constellation is designed by determining noise in a PCM channel using a cumulative distribution function for echo, determining the extent of said noise for an array of possible constellation points, and selecting constellation points such that the largest negative noise of a first point remains above the largest positive noise level of a neighboring second point. Constellations are created off-line and stored for retrieval during modulation depending on the level of the echo.

Abstract: Methods and systems for performing iterative soft slicing methods are disclosed. A data signal is received and processed into individual data tones. A noise estimator provides noise estimates for each data tone. A beamformer utilizes the noise estimates to provide first and second components of a constellation point estimate. A ratio of the first and second components corresponds to the constellation point estimate. A soft slicer uses outputs from the beamformer and noise estimator to determine weighted constellation points without dividing the first component by the second component.

Abstract: A receiver window design algorithm (210) is developed which minimizes the noise power of the demodulated multicarrier signal. The windows are effective on a variety of different channels and noise sources. Receiver windowing is a computationally efficient technique for reducing noise spreading in multicarrier communication systems.

Abstract: A distributed conferencing system has a plurality of conferencing nodes to connect groups of participants to a conference. Each of the conferencing nodes provides for the connection of one or more participants to the conference. Each node includes a DSP for distributed signal processing. The node DSP includes: A signal measuring device for measuring features of the signals from each of the participants such as power, zero crossing rate and short term energy. The nodes include voice activity determination and a communication device for communicating the measured signal characteristics for a plurality of participant input signals to all other conferencing nodes. Muting means for muting individual participant input signals so that only selected signals are transmitted over the conference bus to the other participants.

Abstract: A method of providing an automatic repeat request (ARQ) that employs a selective repeat, enabling a transmitting medium access control (MAC) entity at a transmitting station to retransmit those MAC data whose previous transmissions have failed is described. The MAC data is organized into fixed-sized ARQ blocks, with said ARQ blocks being the building blocks of MAC service data units (MSDUs) or MSDU fragments; The transmitting MAC entity assigns a local number and a global number to each ARQ block to be transmitted and identifies ARQ blocks contained in a transmitted MAC protocol data unit (MPDU) by including into the MPDU the local and global numbers of the first ARQ block in that MPDU. A receiving MAC entity at a receiving station determines and acknowledges the reception status of the ARQ blocks received or anticipated.