A scanning method for receiving a signal in a frequency hopped communication system that transmits a packet having N segments that are encoded with an error correction code that allows recovery of a packet even if e segments are erasures. A receiving station continuously scans the first p (1.ltoreq.p.ltoreq.e+1) channels, testing each channel for the existence of a transmission. If detected, a segment is received, and then the receiving station sequences through the remaining channels, receiving the segments if possible, and then applying error correction to the complete transmission. This technique of scanning the first several channels, receiving the first unimpaired segment, and thereby gaining the ability to recover all unimpaired segments enables the full theoretical power of a coded, slow frequency hopped system to be realized.
A frequency hopping system comprises a transmitting station and a receiving station, both stations storing a frequency hopping sequence comprising a predetermined sequence of N frequencies, where N is an integer greater than 2. In order for the receiving station to acquire synchronization with the transmitter which is continuously hopping through the sequence of frequencies, the receiver initiates a search by tuning to one of the N frequencies and checking if that frequency corresponds to the currently transmitted frequency during that hop period. If it does not correspond, the receiver eliminates the phase of hopping sequence associated with that frequency and tunes to another of the N frequencies with the exception of the next frequency in the eliminated phase and checks for correspondence. If there is not correspondence then the phase of the hopping sequence associated with that frequency is also eliminated from the search. The search is continued with the progressive elimination from the search of those phases found to be unacceptable until a phase which matches the transmitted phase is found and the search is terminated.
An error correcting code including of basic data and a BCH-based parity code appended thereto is divided into smaller packets. An error detecting code is appended to each of the thus-divided packets, so that transmission basic data is formed. When the transmission basic data is received, the basic data and a BCH-based parity code are derived from the transmission basic data. Error correcting is carried out with respect to the overall transmission basic data. An error detecting operation is carried out with respect to each packet using the error detecting code. If a packet is found to contain errors, a request for retransmission of that packet will be sent to the sending side.
A signaling protocol for an infrastructureless short range communication system uses slow frequency hopping compatible with the industrial/scientific/medical (ISM) frequency spectrum. The signaling protocol utilizes a multi-tiered structure having an acknowledgment request frame (200), ping frame (300), connect frame (400) and voice frame (500). These frames are used to determine an appropriate allocation of frequency spectrum from an initiating station (11') to at least one other non-initiating station (11). The signaling protocol allows an initiating station (11') to rapidly identify other stations (11) within a talk group (13) and resolve actual and/or potential collisions to establish clear and reliable infrastructureless communication.
A method for coded transmission of data is disclosed. A first code word interleaved in a first plurality of burst transmissions is recovered for further processing. The recovered code word is decoded to correct and identify any errors within the code word. Using the results of the above-decoding, bad burst transmissions are identified and erased. Subsequently, a second code word interleaved within a second plurality of burst transmissions is recovered. The second plurality of burst transmissions includes the erased burst transmissions from the first plurality of burst transmissions. The received second code word is then errors and erasures decoded.
