Abstract: In a digital time-shared transmission system, a receiver receives a signal whose symbol rate is lower than the channel bandwidth of the system. A correlating and sampling circuit receives a baseband signal, samples the signal a number of times with each symbol time, performs channel correlation, generates a channel estimate and samples down the once sampled signal to an observed signal with two values for each symbol time. A channel equalizer executes a fractional viterbi algorithm which utilizes two delta-metric values for each state transition and generates estimated symbols. A channel estimating filter receives a symbol sequence of alternating zero-value symbols and the estimated symbols and generates an estimated signal. The channel estimating filter is adapted with the aid of an error signal and the filter delivers a channel estimate to the channel equalizer.

Abstract: According to method and apparatus for communication in a cellular TDMA mobile radio communication system with channel hopping, base and mobile stations transmit radio signal bursts in time slots of a plurality of radio channels in accordance with channel hopping schemes. All of the schemes used by a base and mobile stations in a cell are free from coincidence on any radio channel with any other of the schemes used for transmission within the same cell. A scheme used by a mobile station in one cell occasionally coincides on a radio channel with a scheme used by a mobile station in another cell. The major part of every channel shifting scheme used by a mobile station in a cell is free from coincidence on any radio channel with the major part of any channel hopping scheme used by a mobile station in another cell.

Abstract: Radio signals are transmitted over a fading radio channel and are filtered and sampled in a receiver to obtain a digital signal. A channel equalizer has an equalizing filter in which a channel estimate is formed with the aid of a known synchronizing sequence. A Viterbi analyzer decides symbols with the aid of the channel estimate. An estimated time derivative of the channel estimate is formed and adapted with the aid of the decided symbols. The channel estimate is adapted to the radio channel by the derivative estimate and the decided symbols. In the event of fading with rapidly varying signal strength, the channel estimate is adapted slowly and is predicted mainly through the derivative estimate which varies relatively evenly. The digital signal is stored in a memory and an initial value is formed for the derivative estimate as a difference between two known channel estimates divided by a time difference therebetween.

Abstract: An equalizer having an adaptive viterbi analyzer and channel estimation circuits connected to each a state of the viterbi analyzer. The equalizer receives a filtered and sampled signal which during its transmission has been subjected to time dispersion. For each state, the estimation circuits each estimate a partial impulse response for the communications channel. The iterative estimation process begins by determining transition error signals between a old and a new state with the aid of a preceding partial impulse response. The estimation circuits estimate the current partial impulse responses for the new state using the part partial impulse responses, the transition vectors, and the transition error signals selected by the viterbi analyzer. The partial impulse responses are used to estimate symbols included in the received signal.