Philips Electronics North America Corporation

Ati Technologies Inc.

Koninklijke Philips Corporation N.v.

U.S. Philips Corporation

North American Philips Corporation

Nxtwave Communications, Inc.

Other

Sarnoff Digital Communications

Philips Electronics North America Corporatioin

Samir N Hulyalkar

Christopher H Strolle

Troy A Schaffer

Thomas J Endres

Anand M Shah

Chiu Yeung Ngo

Yonggang Du

Carlo Basile

Monisha Ghosh

David A Bryan

Christoph Herrmann

Karl R Wittig

Peter May

Zhi-Yuan Guan

Raul Alejandro Casas

Gerrit J Keesman

Jeffrey S Hamilton

Stephen L Biracree

Haosong Fu

Leon Steiner

Hari Thirumoorthy

Aldo G Cugnini

A robust data extension, added to a standard 8VSB digital television signal, is used to improve the performance of a digital television receiver. Robust data packets are encoded at a 1/3-trellis rate as compared to normal data packets that are encoded at a 2/3-trellis rate. In addition to delivery of robust data for mobile applications, the redundant robust data packets also improve the performance of the receiver in the normal tier of service. In particular, the robust data packets improve the performance of the receiver equalizer filter in the presence of rapidly changing transient channel conditions such as dynamic multipath for both robust data packets and normal data packets. The robust data packets improve the performance of the carrier recovery loop and the symbol timing recovery loop. Backward compatibility with existing receivers is maintained for 1) 8VSB signaling, 2) trellis encoding and decoding, 3) Reed Solomon encoding and decoding, and 4) MPEG compatibility.

Receiver for robust data extension for 8VSB signaling

Centrally controlled wireless networks require reliable communications between the central controller and each of the stations within the wireless networks. The structure of a wireless network is often dynamic, or ad-hoc, as stations enter and exit the network, or are physically relocated. The selection of the central controller for the network may also be dynamic, either because the current central controller desires to exit the network, or because the communication between the current central controller and one or more of the stations is poor. This invention discloses a method and apparatus for assessing the quality of the communication paths among all stations in the network. This assessment is useful as a continual monitor of the quality of the network, and can be utilized to select an alternative central control station based upon the quality of communication paths to and from this station. Additionally, the quality assessment can be utilized to establish relay communication paths, as required.

Apparatus and method for peer-to-peer link monitoring of a wireless network with centralized control

An equalizer for use in a communication receiver includes an infinite impulse response (IIR) feedback filter operated in acquisition and tracking feedback modes on a sample by sample basis to form a hybrid Decision Feedback Equalizer (DFE) architecture. In acquisition mode, soft decision samples from the filtered received signal are input to the IIR filter. In the tracking mode, hard decision samples from a slicer are input to the IIR filter. Acquisition and tracking operating modes are selected in accordance with a set of decision rules on a sample by sample basis based on the quality of the current hard decision. If the current hard decision is low quality, then the soft decision sample (acquisition mode) is used. If the current hard decision is high quality, then the hard decision sample (tracking mode) is used. In such manner, the DFE is operated in a hybrid mode, i.e., using both soft and hard decisions on a sample by sample basis. Furthermore, the decision rules that are responsive to signal reliability to select acquisition and tracking modes are adaptive.

Hybrid soft and hard decision feedback equalizer

A multiple channel diversity receiver includes joint automatic gain control (AGC) signal processing wherein the first and second channels of the multiple channel diversity receiver share at least one joint AGC loop. The maximum difference between the AGC feedback signal in the control loop for the first channel and the AGC feedback control signal in the control loop for the second channel is limited to a selectable maximum differential. The AGC control loop with the stronger first RF signal thus limits the maximum amount that the weaker signal is amplified in the AGC control loop with the weaker second RF signal. By limiting the AGC feedback signal in the control loop of the second channel to a maximum differential with respect to the AGC feedback signal in the control loop of the first channel, the weaker signal is not overly amplified thereby avoiding the undue amplification of noise in the second channel.

Diversity receiver with joint automatic gain control signal processing

Original RF carriers are recovered for first and second channels in a diversity receiver and used to de-rotate (demodulate) each of the first and second received signals. The pilot loop filters of each channel are cross coupled to create a joint pilot loop between both channels. The channel with the stronger signal provides a dominant influence on the frequency of the synthesized recovered RF carrier in the channel with the weaker signal. The phase locked pilot loops in both channels will tend to be frequency locked to the frequency of the stronger signal, leaving the respective phase locked pilot loops to make an individual phase adjustment for each channel.

Diversity receiver with joint phase locked loop filter

First and second RF signals in the respective first and second channels of a multiple channel diversity receiver are processed jointly in a joint timing loop filter for baud clock recovery. The channel with the stronger signal determines the frequency of the baud clock for the channel with the weaker signal, leaving the respective PLL's to make individual phase adjustments for each channel. The first and second channels also share a skew corrector for baud clock recovery when the multipath delay between the first and second RF signals is greater than one whole baud clock period. The whole baud skew corrector computes the correlation between the first and second received signals, and if the correlation is low, shifts the first and second signals by one whole baud and recomputes the correlation. The process of shifting the first and second received signals and computing the correlation function is repeated for various whole baud shifts in accordance with a search strategy to find the best (highest) correlation.

Diversity receiver with joint baud clock recovery

The system transmits data between terminals of a wireless network. In the system, a base station/central controller (&ldquo;BS/CC&rdquo;) controls transmission of data from a transmitting terminal to plural receiving terminals, where the data is ordered in slots of a control data frame (&ldquo;CDF&rdquo;), and where each slot is reserved for a data transmission between the transmitting terminal and a specific receiving terminal. Specifically, the BS/CC divides the plural receiving terminals into a set of power-saving terminals and a set of non-power-saving terminals, and then reserves a set of slots in the CDF for data transmission between the transmitting terminal and the power-saving terminals, and another set of slots in the CDF for data transmission between the transmitting terminal and the non-power-saving terminals. The BS/CC then issues a message over the wireless network instructing the power-saving terminals when to switch between a low-power mode and a data-receiving mode based on a location of the set of slots in the frame reserved for data transmission between the transmitter and the power-saving terminals.

Data transmission system for reducing terminal power consumption in a wireless network

A digital communication receiver includes a blind equalizer using the Constant Modulus Algorithm (CMA) to compensate for channel transmission distortion in digital communication systems. Improved CMA performance is obtained by using a partial trellis decoder to predict 1 bit or 2 bits of the corresponding 3-bit transmitted symbol. The predicted bits from the partial trellis decoder are used to reduce the effective number of symbols in the source alphabet, which reduces steady state jitter of the CMA algorithm. Specifically, the received input signal to the CMA error calculation is shifted up or down by a computed delta (&Dgr;), in accordance with the predicted bit(s). In addition, a different constant gamma (&ggr;), for the CMA error calculation is selected in accordance with the predicted bit(s). The disclosed technique is applicable to trellis and non-trellis codes in which at least one bit of the present symbol can be predicted in advance and used to reduce the effective number of symbols in the source alphabet.

Equalizer method and apparatus using constant modulus algorithm blind equalization and partial decoding

A diversity receiver is coupled to a composite antenna having first and second antennas physically configured to provide one or more forms of diversity reception. The multiple channel diversity receiver includes first and second RF channels with joint signal processing. First and second RF signals are processed jointly in the multiple channel diversity receiver with respect to tuning, automatic gain control (AGC), baud clock recovery, RF carrier recovery and forward equalization. The multiple channels of the diversity receiver are linked or cross coupled to each other through respective joint processing circuitry. In particular, first and second RF tuners share a common local oscillator and a common AGC feedback loop. First and second front ends share a common baud timing loop and a common pilot carrier recovery loop. Finally, first and second diversity receiver channels share a common sparse equalization filter. By processing first and second signals jointly in the diversity receiver, the receiver provides equal or superior performance to a single receiver processing only the best signal.

Diversity receiver with joint signal processing

A prioritized buffer for the Medium Access Control (MAC) layer for multimedia applications, in particular wireless Asynchronous Transfer Mode (ATM) in which reservation based TDMA is performed on the basis of control data frames (CDFs), is formed by an addressable memory system which is divided into sequential equal-sized pages for storing respective data packets or ATM cells having the same number of bytes. The memory system includes a tag register for storing tags associated with the respective pages, each tag indicating whether the associated page is empty or full, a shadow register for storing conflict-free updates from the tag register, and a page register for storing pointers to the lowest free or unoccupied page. Sequential buffer addresses of memory locations in the memory system, which control sequential writing into the buffer of bytes contained in data packets, are generated from summing a first address component responsive to the contents of the page register and a second address component which is a byte count of a current packet being received from a stream data source. A succession of byte addresses is produced which jumps over addresses within pages which are full, thereby bypassing and avoiding overwriting pages which are full.

Prioritized-buffer management for fixed sized packets in multimedia application

An adaptive equalizer for use in blind equalization systems to compensate for transmission channel distortion and noise in a digital communication system uses multiple quantization levels for implementation of the Constant Modulus Algorithm (CMA). Different quantization levels are used in different regions of the CMA error function for both passband and baseband equalizers. In one embodiment, a quantizer with a step rise having logarithmic scale is used to digitize the CMA error function. In particular, a quantizer with a step rise in which each level of the quantizer step rise is a power of 2 is used to digitize the CMA error function. In another embodiment, a quantizer with a step rise in which each level of the quantizer step rise is the sum of two or more logarithmic scales is used to digitize the CMA error function. In particular, a quantizer with a step rise wherein each level of the quantizer step rise is the sum of two or more numbers each of which is a power of 2 is used to digitize the CMA error function. The use of logarithmic scales, the sum of logarithmic scales, powers of 2, or the sum of powers of 2 for the quantizer step rise size to digitize the CMA error function make efficient use of shift and add operations to achieve multiplication in the adaptation process.

Adaptive equalizer with enhanced error quantization

An adaptive equalizer for use in blind equalization systems to compensate for transmission channel distortion and noise in a digital communication system quantizes the input signal samples to generate a quantized implementation of the Constant Modulus Algorithm (CMA). To quantize the input signal samples, a nearest-element decision device (a slicer), that is typically present in a digital receiver, is used to pre-compute the quantized CMA error function. The number of unique values for the CMA error term is thereby reduced, and the reduced number of CMA error term values are stored in a lookup table. By greatly reducing the number of received signal values used in the CMA error calculation a relatively small lookup table can be used to compute the CMA error function. Passband implementation is accommodated by incorporating the signal de-rotation factor into the lookup table entries. In one embodiment the CMA multiply operation is replaced with shifts and adders. To make efficient use of shift and add operations to achieve multiplication in the adaptation process, the lookup table values are selected to be either a power of 2 or a minimal sum of powers of 2.

Adaptive equalizer with decision directed constant modulus algorithm

A protocol, method, and apparatus for managing network communications which are particularly well suited for ATM communications across a wireless medium. Contiguous time slots within a frame are allocated to each node having traffic to send. Each node is assured a nominal bandwidth, and excess bandwidth is distributed by demand. The allocation of excess bandwidth can be dependent upon the size of the buffer at each node, as well as the time-criticality of each message. Nodes communicate their requests for allocation by appending such control information to the first of their transmitted packets. The allocation, of each node's transmit and receive time slots, is transmitted to all the nodes at the beginning of each frame. Thereafter, each node need not participate on the network until their allocated time periods, thereby allowing portable devices to enter inactive states to conserve power. The network is operated in a connection mode; connections are established in a relatively non-interfering manner by the use of periodically occurring beacons. Inactive, unconnected, nodes need only monitor the network during these beacon periods, further allowing for power conservation.

Growing community of inventors

Plainsboro, NJ, United States of America

Samir N Hulyalkar