Hughes Aircraft Company

Hughes Electronics Corporation

Youngky Kim

Stanley Edward Kay

Yezdi F Antia

Michael I Parr

John D Kaewell

Ashok D Mehta

David M Cooley

Charles A Barnett

Long Huynh

John L Watson

Lou King

Andrew J Macdonald

Hiep Pham

A cellular base station (10) in a digital cellular system employs transmitting circuitry in which voice signals (15) are processed at a low frequency level (12) into two separate paths. A first of the low frequency signals is variably delayed (20), and the first and the other low frequency signals are upconverted to radio frequency level (16,22) for transmission over independent time-spaced transmission paths (26,28) to cellular receivers. A receiver downconverts and demodulates the radio frequency diversity signals, and then combines the demodulated diversity signals to generate an equalized combination diversity signal for receiver output processing.

Time division multiple access cellular communication system and method

A Digital Post-Detection (Post-Discriminator) FM spatial diversity combination circuit improves performance for fading channels typical of cellular radio operating environments. A feature of this system is its flexibility. The system can be configured to use signal quality information in a manner which is appropriate for a given radio environment. Also, the weighting information can be derived from various sources and then processed to accommodate various situations. This spatial combiner has the ability to perform as a 'hybrid' combiner. For example, this circuit can combine signals from various receivers based on soft weighting information, as in a maximal ratio combiner, or on hard weighting information, as in a switching combiner. The basic circuit includes a normalizing circuit (21, 22, 23) which receives the digitized received signal strength indicator samples from each of first and second receivers (11, 12) and generates first and second weighting signals. A first multiplier (24) multiplies the digitized discriminator samples from the first receiver by the first weighting signal to generate a first weighted output signal. A second multiplier (25) multiplies the digitized discriminator samples from the second receiver by the second weighting signal to generate a second weighted output signal. The first and second weighted output signals are combined in a post-detection, maximal ratio combining circuit (26).

Digital post-detection FM spatial diversity combination circuit

Demodulation is provided for a base station receiver in a cellular communication system by a demodulator having four data linked digital signal processors. An MLSE equalizer and maximal ratio combiner for diversity paths includes multiple components that are partitioned among the processors for pipelined execution with predetermined time ordering.

Multi-processor demodulator for digital cellular base station employing

A vestigial identification system is provided for transmitting information in a cellular communications network employing frequency reuse. The vestigial identification system enables a receiver to detect both bit errors and interfering messages to avoid call disruption. A composite parity check is produced by encoding message data and a site identifier via an encoder. A transmitter conveys a code word, formed at a code word generator by combining the composite parity check with the message data, to a receiver. At the receiver, an encoder forms an error detection parity check by encoding both the message data from the code word and the site identifier. An error detector compares the composite parity check from the transmitted code word to the error detection parity check, and generates an error if the parity checks are not identical to one another, enabling rejection of the message by the receiver.

Vestigial identification for co-channel interference in cellular

Cellular handoff is improved by tailing or adapting the measurement time based on the characteristics of the received signal intensity or power. More particularly, base stations typically measure mobile signal power in order to determine the necessity for handoff and the identity of a new cell. The measurement time must be of a duration which is sufficient to characterize the environment of the mobile. In accordance with the invention, the duration of the measurement time is determined from the received signal itself. Once the duration of the measurement time is determined, that data may be passed to a target cell along with other handoff data.

Sequential power estimation for cellular system handoff

A diversity combiner for use with the maximum likelihood sequence estimator is disclosed. First and second receive channels produce demodulated replicas Z.sub.1 (k) and Z.sub.2 (k) of the transmitted symbol data I(k). The two signals are processed in a Viterbi equalizer to obtain a single branch metric calculation based on the two signals Z.sub.1 (k) and Z.sub.2 (k) . The Viterbi equalizer provides an estimated value of I(k) based on this single branch metric calculation, which is used for channel estimator for both antennas.

Diversity combiner with MLSE for digital cellular radio

A lower order Viterbi system for estimating symbols being transmitted over a digital cellular channel. The received signal is oversampled at a rate at least twice the frequency of the symbol duration. The energy contained in the main and interference symbol signal is thus sampled and permits a superior BER to be obtained. The branch metric for the lower order Viterbi algorithm is calculated using both signal samples. Channel status information is individually estimated for both samples, further improving system BER. The channel status is obtained for both frequency offset errors, amplitude fading and phase occurring within the channel.

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N. Potomac, MD, United States of America

Youngky Kim