Abstract: A TDD antenna array S-CDMA system for increasing the capacity and quality of a wireless communications is disclosed. By simultaneous exploiting the spatial and code diversities, high performance communications between a plurality of remote terminals and a base station is achieved without sacrificing system flexibility and robustness. The time-division-duplex mode together with the inherent interference immunity of S-CDMA signals allow the spatial diversity to be exploited using simple and robust beamforming rather than demanding nulling. Measurements from an array of receiving antennas at the base station are utilized to estimate spatial signatures, timing offsets, transmission powers and other propagation parameters associated with a plurality of S-CDMA terminals. Such information is then used for system synchronization, downlink beamforming, as well as handoff management.

Abstract: A method for estimating symbol sequences from multiple transmitters which communicate with common receivers sharing the same medium is disclosed. This invention can be used in wireless communications and wireline communications such as in cable modem sys terms and digital subscriber loops to speed up joint detection of symbol sequences of multiple transmitters to achieve low error probability. For convenience, only applications of this invention to wireless communications employing multiple antennas are described herein. The requirement for matrix operations like matrix inverses increase with the logarithm of the number of symbols instead of the number of symbols as with techniques based on Cholesky decomposition.

Abstract: In a synchronous code division multiple access (SCDMA) time division duplex (TDD) communication system, a remote terminal uses both open loop and closed loop techniques for synchronization with a base station. The timing of reception of information by tile remote terminal is performed with an open loop technique, while the timing of transmissions from the terminal is performed with a closed loop technique. Furthermore, a clock locked loop in the terminal compensates for differences between clocks of the terminal and the base station. The clock locked loop responds to signals from both the aforesaid open loop and closed loop techniques.

Abstract: A code division multiple access time division duplex communication system having an adaptive antenna array station communicates beamformed orthogonal code channels to a remote station. The remote station determines the amplitude and phase components of the received code channels and communicates the information back to the adaptive antenna array station which uses the information plus the beamform of the received signal in an adaptive antenna array station calibration process. By varying one of the beamforms received by the remote station, sufficient data points may be gathered to facilitate accurate calibration. The calibration procedure may be performed while voice or other digital information is communicated between the remote station and the adaptive antenna array station.

Abstract: A communication system having an adaptive antenna array subsystem generates calibration information for the adaptive array subsystem by measuring the amplitude and phase of modulated signals within the subsystem at the antenna array mount and at the back plane mount for the transmit and receive array. The calibration information is used to more accurately perform beamforming for both received an transmitted information signals. The communication system uses a time diversity duplex (TDD) synchronous code division multiple access (SCDMA) protocol for wireless communication between remote terminals and a base station. The calibration means uses a combination combiner and splitter having matched micro strip lines incorporated into a printed circuit board in either the antenna array mount or the back plane.

Abstract: A code division multiple access time division duplex communication system having an adaptive antenna array station communicates beamformed orthogonal code channels to a remote station. The remote station determines the amplitude and phase components of the received code channels and communicates the information back to the adaptive antenna array station which uses the information plus the beamform of the received signal in an adaptive antenna array station calibration process. By varying one of the beamforms received by the remote station, sufficient data points may be gathered to facilitate accurate calibration. The calibration procedure may be performed while voice or other digital information is communicated between the remote station and the adaptive antenna array station.

Abstract: A wireless communication system has a protocol enabling synchronous code division multiple access (CDMA) communication on a time division duplex (TDD) frequency, and provides for a smart antenna system as an integral component of the system. The protocol has downlink time slots (DTS) which provide for synchronization and paging of all remote terminals from a base station on a omnidirectional code channel and while providing for traffic signals on directional traffic channels. The protocol has uplink time slots (DTS) which enable rapid link requests by remote terminals, as well as enabling improved spacial estimation, synchronization and power control of remote terminals by the base station.

Abstract: An improved system and method for determining and tracking the carrier offset in a communications system. In an exemplary implementation, sampled spread spectrum digital signals are compensated with an expected carrier offset and stripped of pseudo-noise codes to produce demodulated signals. The demodulated signals are applied to a carrier offset estimator. The carrier offset estimator divides pairs of demodulated signals with a predetermined interval to produce results containing phase change information. The results are then averaged, and the average is normalized with respect to the predetermined interval to yield a new estimate of the carrier offset. The expected carrier frequency is adjusted based on the new offset estimate for frequency compensation in subsequent reception and transmission operations.

Abstract: A method and apparatus for increasing the capacity and quality of code-division-multiple-access (CDMA) communications in a near-far and frequency-selective fading environment is disclosed. The invention can be utilized in both synchronous and asynchronous CDMA systems. For convenience, only applications of this invention to synchronous CDMA are described herein. Unique to this invention is that using measurements from a receiver and multiple receivers at the base station, propagation channel parameters associated with a plurality of subscribers are determined without the use of training sequences. The channel parameters are used to calculate any individual user's signature waveform and reconstruct its transmitted signal from the received data. This invention can also be implemented at base stations with multiple antennas or/and fractionally spaced measurements to further improve signal quality by incorporating spatial and temporal diversities.

Abstract: A system and method for modulating synchronous CDMA (S-CDMA) signals in antenna array wireless system. By taking advantage of the symmetric property of Walsh code words utilized in S-CDMA perform modulation of signals intended for a plurality of users. The system includes a Fast Hadamard Transform (FHT) Processor that realizes baseband operations including spreading and digital combining in one step. In addition to significant reduction in computations and storage over prior methods, the invention also provides substantial advantages in hardware implementation. While the exemplary embodiment is described in the context of antenna array CDMA systems, the disclosed techniques have general applications in CDMA systems with arbitrary symbol values.