Abstract: A wireless multiple access method allows multiple transmitters to access the same channels so that substantial interference occurs. The transmitters use low rate turbo coding and the receiver uses multi-user detection to separate and decode the transmissions. Different propagation and/or transmission characteristics between the transmitters help to distinguish the transmissions at the receiver. The transmitters may add random variation to their transmission timing, power and/or frequency to assist with decoding.

Abstract: In a frame sync method, a receiver searches for the presence of an N-symbol long unique word pattern. For each possible frame sync detected, the receiver proceeds to demodulation and FEC processing. After each iteration of the FEC decoder, the detected unique word pattern is compared to the expected one and the frame sync is detected if the number of unique word errors has decreased.

Abstract: In a wireless communications system, transceivers transmit short bursts to a base station, which determines timing corrections from the time of receipt of the burst and transmits the timing corrections to the respective transceivers. In one aspect, the base station indicates to the transceivers a plurality of time slots, each transceiver selects one of the time slots at random, formats a burst including an indicator of the selected time slot and transmits the burst in that slot. In another aspect, the base station transmits to each transceiver a timing uncertainty value, which determines how the timing correction will be modified by the tranceiver as the interval since last receiving a timing correction increases. Data bursts are transmitted in a format comprising a first unique word, a content field and a second unique word, in that order. The bursts are transmitted in a TDMA channel format which can accommodate both short and long bursts in a block format of constant periodicity.

Abstract: In a frame sync method, a receiver searches for the presence of an N-symbol long unique word pattern. For each possible frame sync detected, the receiver proceeds to demodulation and FEC processing. After each iteration of the FEC decoder, the detected unique word pattern is compared to the expected one and the frame sync is detected if the number of unique word errors has decreased.

Abstract: In a frame sync method, a receiver searches for the presence of an N-symbol long unique word pattern. For each possible frame sync detected, the receiver proceeds to demodulation and FEC processing. After each iteration of the FEC decoder, the detected unique word pattern is compared to the expected one and the frame sync is detected if the number of unique word errors has decreased.

Abstract: In a wireless communications system, transceivers transmit short bursts to a base station, which determines timing corrections from the time of receipt of the burst and transmits the timing corrections to the respective transceivers. In one aspect, the base station indicates to the transceivers a plurality of time slots, each transceiver selects one of the time slots at random, formats a burst including an indicator of the selected time slot and transmits the burst in that slot. In another aspect, the base station transmits to each transceiver a timing uncertainty value, which determines how the timing correction will be modified by the tranceiver as the interval since last receiving a timing correction increases. Data bursts are transmitted in a format comprising a first unique word, a content field and a second unique word, in that order. The bursts are transmitted in a TDMA channel format which can accommodate both short and long bursts in a block format of constant periodicity.

Abstract: A wireless communication system uses an adaptive air interface in which burst parameters are variable on a burst-by-burst basis, based on the reception quality of previous bursts and/or properties of the receiver or receivers of the burst. The parameter values are selected as sets which represent only some of the possible combinations of parameter values, to avoid redundancy in performance characteristics. Coding rates are selected to give a substantially constant increment in gain. Each burst may contain multiple FEC blocks with different coding rates. A unique word indicates the FEC coding rate of the first block and the first block identifies the coding rate of each of the subsequent blocks.

Abstract: In a wireless communications system, transceivers transmit short bursts to a base station, which determines timing corrections from the time of receipt of the burst and transmits the timing corrections to the respective transceivers. In one aspect, the base station indicates to the transceivers a plurality of time slots, each transceiver selects one of the time slots at random, formats a burst including an Indicator of the selected time slot and transmits the burst in that slot. In another aspect, the base station transmits to each transceiver a timing uncertainty value, which determines how the timing correction will be modified by the tranceiver as the interval since last receiving a timing correction increases. Data bursts are transmitted in a format comprising a first unique word, a content field and a second unique word, in that order. The bursts are transmitted in a TDMA channel format which can accommodate both short and long bursts in a block format of constant periodicity.

Abstract: A radio frequency paging service has one or more TDMA return channels (R) in which terminals (14) acknowledge receipt of messages having an acknowledge flag set. In one alternative, slots are allocated in the return channel (R) by a slot allocation field in the respective messages. In another alternative, each terminal (14) monitors the messages addressed to other terminals (14) to determine which of them require a response, and determines, from the order of a message addressed to itself among the messages requiring a response, which slot to use for acknowledgement. The TDMA return channels (R) include unreserved slots which terminals (14) access on a contention basis. The frequencies of transmissions in the slots are randomized within a predefined limit to reduce the probability of interference between different terminals (14) in the same unreserved slot. The predefined limit is based on the maximum differential Doppler shift between terminals (14).

Abstract: In a frame sync method, a receiver searches for the presence of an N-symbol long unique word pattern. For each possible frame sync detected, the receiver proceeds to demodulation and FEC processing. After each iteration of the FEC decoder, the detected unique word pattern is compared to the expected one and the frame sync is detected if the number of unique word errors has decreased.

Abstract: Data is transmitted in a signal comprising a data signal D.sub.m at a frequency within a range B of discrete frequency tones D.sub.0 to D.sub.m-1 representing a predetermined range of digital values, and a pilot signal (36, 37). The signal is received by a circuit comprising a transformer (44 to 54) which transforms the received signal into a set of frequency samples of the pilot signal and a set of frequency samples of the data signal. The samples are input to a correlator (58) which correlates the set of frequency samples of the pilot signal with the set of frequency samples of the data signal at each of the discrete frequency tones in order to identify the discrete frequency tone to which the frequency of the data signal corresponds. In this way, the digital value represented by the data signal can be identified. The circuit is suitable for use in a radio pager for receiving data signal transmissions from a distant source which may be transmitted from a satellite.