In a data communication system capable of variable rate transmission, high rate packet data transmission improves utilization of the forward link and decreases the transmission delay. Data transmission on the forward link is time multiplexed and the base station transmits at the highest data rate supported by the forward link at each time slot to one mobile station. The data rate is determined by the largest C/I measurement of the forward link signals as measured at the mobile station. Upon determination of a data packet received in error, the mobile station transmits a NACK message back to the base station. The NACK message results in retransmission of the data packet received in error. The data packets can be transmitted out of sequence by the use of sequence number to identify each data unit within the data packets.

Method and apparatus for high-rate packet data transmission

The high quality PCS communications are enabled in environments where adjacent PCS service bands operate with out-of-band harmonics that would otherwise interfere with the system's operation. The highly bandwidth-efficient communications method combines a form of time division duplex (TDD), frequency division duplex (FDD), time division multiple access (TDMA), orthogonal frequency division multiplexing (OFDM), spatial diversity, and polarization diversity in various unique combinations. The method provides excellent fade resistance. The method enables changing a user's available bandwidth on demand by assigning additional TDMA slots during the user's session.

Method for frequency division duplex communications

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

Two or more antenna elements are arranged in the vertical direction to give vertical spatial adaptivity to a wireless discrete multitone spread spectrum communications system. The system is based on a combination of Discrete Multitone Spread Spectrum (DMT-SS) and multi-element adaptive antenna array technologies. This enables the automatic positioning of a beam in the vertical direction to position nulls where interferers are located on the same azimuth but are separated in elevation.

Vertical adaptive antenna array for a discrete multitone spread spectrum communications system

A method and apparatus for pilot-symbol aided channel estimation in a wireless digital communication system which transmits packets of N OFDM data blocks, each data block comprising a set of K orthogonal carrier frequencies. At the transmitter, pilot symbols are inserted into each data packet at known positions so as to occupy predetermined positions in the time-frequency space. At the receiver, the received signal is subject to a two-dimensional inverse Fourier transform, two-dimensional filtering and a two-dimensional Fourier transform to recover the pilot symbols so as to estimate the channel response.

Pilot-aided channel estimation for OFDM in wireless systems

A CDMA demodulating apparatus with an improved interference canceling effect when there are a large number of communicators. A reception signal having a frame configuration in which a pilot signal of a known pattern is inserted between information signals is received from a plurality of communicators. Transmission data of each communicator is demodulated, an interference canceler for estimating is provided in a plurality of stages, in each channel of each stage, a variation of transmission path is estimated in each path to achieve data demodulation and estimation of interference replica. The later the stage, the more error of interference signal replica can be reduced, thereby improving the interference canceling effect. An even better effect can be obtained when interference canceling is performed after detecting a reception level of each channel by summation of reception power of each path of each channel, and channel ranking is determined in the order of higher reception level.

Cdma demodulating apparatus

A CDMA demodulator which can follow fast fading, and reduce interference components from other users in the same cell. A received input spread signal is despread by an orthogonal filer (103). The orthogonal filer provides the input spread signal with successive delays each of an amount of 1/m of the chip interval of a spreading code, multiplies the delayed signals by tap coefficients, and sums up the products, thereby outputting the despread signal. Pilot symbols in the despread signal are compared with known pattern pilot symbols by an absolute phase estimator/phase error compensator (107) to obtain phase fluctuations of the received pilot symbols. The phase fluctuations are interpolated to each information symbol, and each information symbol is phase compensated. The phase compensated information symbols are decided by a decision block (108). The tap coefficients are calculated by a tap coefficient controller (110) so that the mean square error of differences between signals before and after the decision is kept minimum, and the calculated values are fed back to the orthogonal filter.

CDMA demodulator and demodulation method

A CDMA demodulation circuit which can reduce interference wave components from another user in the cell and can follow up high-speed fading. The frequency band of the received inputted spread-spectrum signals are compressed back by means of an orthogonalizing filter (103). The filter (103) successively gives a delay of 1/m of the chip period of the spread codes to the inputted spread-spectrum signals and outputs compressed-back signals by multiplying the inputted spread-spectrum signals by a tap factor and summing up the multiplied results. An absolute phase estimating and phase error compensating section (107) compares the pilot symbols in the compressed-back signals with the pilot symbols of a known pattern and finds the phase shifts of the received pilot symbols. The section (107) compensates the phase of each information symbol by interpolating the phase shifts in the respective information symbols. An identifying and judging section (108) identifies the phase-compensated information symbols. A tap factor control section (110) calculates the tap factor so that the mean square error of the errors of signals before and after the identification may be the minimum and feeds back the calculated tap factor to the filter (103).

CDMA demodulation circuit and demodulation method

PURPOSE: To shorten the convergence time of the tap coefficient of an adaptive control orthogonalizing filter used in the demodulation circuit used for demodulation in a radio reception part in the CDMA system. CONSTITUTION: The output of a phase error compensation part 107 is outputted with a pilot symbol period and is held for a time of several symbols by a timing adjusting function part 110. An error generation circuit 109 uses the held phase compensation value to generate an error vector for each information symbol in accordance with the signal vector after discrimination and decision and that before the discrimination and decision. The error vector is successively inputted to a tap coefficient control part 111 with the symbol period. This part 111 updates the tap coefficient of the orthogonalizing filter with the symbol period. Since the value of the tap coefficient can be quickly converged to an optimum value, the time when the service quality is degraded is shortened even if the state of an interference wave is changed by call originating or terminating of another user on the way of service.

Cdma demodulation circuit

PURPOSE: To constitute down channels of one pilot channel consisting of a pilot signal having a known pattern and plural communication channels for transmission of information data signals and control data signals. CONSTITUTION: The variance of a transmission line is estimated by a matched filter 103 for pilot channel and a pilot channel phase variance estimation part 104 which averages the reception phase of the pilot signal in plural symbols. The variance in reception phase is inversely converted while being compensated based on this estimation by a communication channel orthogonalizing filter 105 and a communication channel phase variance compensation part 106 which compensates the variance in reception phase. The output signal of the communication channel phase variance compensation part is re stored to the original signal by a discrimination and decision part 107. The tap coefficient of the orthogonalizing filter 105 is controlled by a tap coefficient control part 108 so that an average square error of the error vector obtained by an error vector generation part 109 is minimum. COPYRIGHT: (C)1996,JPO

Hidehiro Andou

Papers

Cdma demodulating apparatus

CDMA demodulator and demodulation method

CDMA demodulation circuit and demodulation method

Cdma demodulation circuit

Cdma signal receiver