Cisco Technology, Inc.

Leland Stanford Junior University

At&t Wireless Services, Inc.

Cingular Wireless Ii, LLC

Derek Gerlach

Gregory G Raleigh

Vincent Knowles Jones, Iv

David Sheldon Stephenson

David B Gibbons

Elliott Hoole

Brian G Agee

David J Ryan

Mary Jesse

Robert G Mechaley, Jr

James Timothy Golden

Robert Lee Maxwell

David J Nix

Robert Ray Naish

Matthew Bromberg

Vincent K Jones

Minnie Ho

James M Gardner

Arogyaswami J Paulraj

Michael A Pollack

Richard W Koralek

Ali Raissinia

Bretton Lee Douglas

Vincent K Jones Iv

Santosh Anikhindi

Minnic Ho

David James Ryan

Minni Ho

Robert G Mechaley

Systems and methods for precisely controlling the amount of redundancy introduced by a turbo encoding process. Bits having predetermined values are introduced into the turbo encoding input stream and then deleted from the turbo encoding output stream. At the receiver end, the bits having predetermined values are reintroduced into the encoded information stream as having been received with a maximum confidence level. Coding rate may be varied by varying the number of bits having predetermined values which are inserted at the encoder input. This scheme permits the amount of redundancy to be varied according to system requirements.

Coding rate reduction for turbo codes

A discrete multitone stacked-carrier spread spectrum communication method is based on frequency domain spreading including multiplication of a baseband signal by a set of superimposed, or stacked, complex sinusoid carrier waves. In a preferred embodiment, the spreading involves energizing the bins of a large Fast Fourier transform (FFT). This provides a considerable savings in computational complexity for moderate output FFT sizes. Point-to-multipoint and multipoint-to-multipoint (nodeless) network topologies are possible. A code-nulling method is included for interference cancellation and enhanced signal separation by exploiting the spectral diversity of the various sources. The basic method may be extended to include multielement antenna array nulling methods for interference cancellation and enhanced signal separation using spatial separation. Such methods permit directive and retrodirective transmission systems that adapt or can be adapted to the radio environment. Such systems are compatible with bandwidth-on-demand and higher-order modulation formats and use advanced adaptation algorithms. In a specific embodiment the spectral and spatial components of the adaptive weights are calculated in a unified operation based on the mathematical analogy between the spectral and spatial descriptions of the airlink.

Highly bandwidth-efficient communications

Systems and methods for optimally combining signals from multiple antennas to ameliorate the effects of noise and/or interference on OFDM communications are provided. In one embodiment, an initial spatial statistical characterization of interference and/or noise is based on training symbols received via each antenna. Because the transmitted values of the training symbols are already known, there is no need to estimate their transmitted value to form this initial statistical characterization. The data symbol values received via the multiple antennas are combined based on the initial spatial statistical characterization. The result of this combination step is then used to form a refined spatial statistical characterization of noise and/or interference. The received data symbol values are then recombined based on the refined spatial statistical characterization.

OFDM interference cancellation based on training symbol interference

Improved adjustment of transmission power in a communication system is provided. In one embodiment, in a point to multipoint communication system, transmission power of a subscriber unit is controlled based on power measurements made at a central access point. Power measurement information based on transmissions occurring at irregular intervals may be combined in a beneficial manner to control transmission output power. In one embodiment, a power regulation process determines a series of difference values indicating the differences between desired received power level at the central access point and measured received power level. A smoothing process is applied to the difference values. One or more parameters of the smoothing process vary with elapsed time since a last available power measurement.

Power regulation using multi-loop control

Improved receiver automatic gain control for OFDM-based communication systems is provided, thus realizing the full potential of OFDM systems to handle rapid variation in channel characteristics. The improved automatic gain control technique can also accommodate reception of multiple OFDM signals having disparate power levels via the same analog receiver chain and analog to digital converter while minimizing the arithmetic precision necessary for optimal digital processing. By reducing the necessary arithmetic precision, the cost of implementing the receiver with integrated circuit technology is greatly reduced.

Automatic digital scaling for digital communication systems

A spatial processor that exploits signals that arrive via multiple outputs of a communication channel to provide soft decision values useful to a trellis or Viterbi decoder. A spatial processor may take into account a statistical characterization of interference as received via the multiple channel outputs. Spatial processor operation may also be optimized to operate in conjunction with orthogonal frequency division multiplexing (OFDM).

System for interference cancellation

Systems and methods for augmenting the performance of iterative soft decision-in soft decision-out decoding of block codes with extrinsic information based on multiple parity equations inherent to the block codes. Cyclic shifting of codewords may be applied in the context of iterative soft decision-in soft decision-out decoding to maximize the usefulness of a parity equation corresponding to any particular codeword bit. Soft decisions are determined on a bit-by-bit basis in response to multi-bit symbol measurements. This allows the use of relatively inexpensive bit-based decoders for decoding of multi-bit symbols.

Iterated soft-decision decoding of block codes

A chirp waveform is employed in establishing timing synchronization between nodes of a data communication network. In one embodiment, the chirp waveform is combined with a waveform modulated with data to form a synchronization waveform. The receiver of the synchronization waveform determines an alignment of the chirp waveform to a template chirp waveform to synchronize timing between nodes.

Subscriber unit ranging in a point to multipoint system

Priority messaging method for a discrete multitone spread spectrum communications system

Growing community of inventors

Mountain View, CA, United States of America

Derek Gerlach