Abstract: Systems (1600) and methods (1500) for frame synchronization. The methods involve: extracting bit sequences S0 and S1 from a Bit Stream (“BS”) of a Data Burst (“DB”); decoding S0 and S1 to obtain decoded bit sequences S?0 and S?1; using S?0 and S?1 to determine Bit Error Rate (“BER”) estimates (516, 518); combining the BER estimates to obtain a combined BER estimate; modifying S0 and S1 so that each includes at least one bit of BS which is not included in its current set of bits and so that it is absent of at least one of the bits in the current set of bits; iteratively repeating the decoding, using, combining and modifying steps to obtain more combined BER estimates; analyzing the combined BER estimates to identify a minimum combined BER estimate; and using the minimum combined BER estimate to determine a location of a vocoder voice frame within DB.

Abstract: A security system for a digital trunked radio system having a digital control channel and a plurality of working channels, wherein said working channels are assigned for temporary use of individual radio units by digital control signals transmitted over said control channel, said control channel carrying digital control signals between a base site and said radio units, comprising a digital key, said key used to limit access to the system equipment and system control channel transmissions.

Abstract: A method for reliable communication within a digital trunked radio system having a digital control channel and a plurality of working channels, wherein said working channels are assigned for temporary use by a subset of radio units by digital control signals transmitted over said control channel, said control channel carrying outbound digital control signals from a base site to said radio units, said outbound digital control signals having a fixed transmission time slot, said method comprising the steps of: (a) transmitting a first message and a second message, each 28 bits in length, within said time slot; (b) defining at least one first message type identifier field within said first message; (c) defining a group identifier in said first message, said group identifier comprising from greater than 11 up to 16 bits; (d) defining at least one second message type identifier field within said second message; (e) defining a logical identifier in said second message, said logical identifier comprising from greater

Abstract: A security system for a digital trunked radio system having a digital control channel and a plurality of working channels, wherein said working channels are assigned for temporary use of individual radio units by digital control signals transmitted over said control channel, said control channel carrying digital control signals between a base site and said radio units, comprising a digital key, said key used to limit access to the system equipment and system control channel transmissions.

Abstract: Method and processor for determining loading of a communications system shared by a plurality of user-terminals are provided. The method allows a respective terminal for monitoring a control channel including logical messages therein. The monitoring of the messages in the control channel is performed regardless of whether or not the logical messages therein are specifically addressed to that terminal. The method further allows for estimating a parameter indicative of system loading based on information in the monitored logical messages.

Abstract: Hybrid subband coding and decoding (using different encloding/decoding algorithms in at least one subband channel) and subband time delay compensation at a point of maximum digital bandwidth compression are effected so as to reduce required DSP on-chip memory requirements. At the same time a special digital signal format is employed so as to provide enhanced data frame synchronization, enhanced cryptographic synchronization and selective signalling ability within a cryptographic digital signal transceiver. The ability to successfully accomplish late entry (or to re-establish synchronization once lost) into an ongoing received message is provided.

Abstract: Method and apparatus are disclosed for transceiving digital control and cryptographically encoded data signals in a unique format. The format includes frame synchronization, cryptographic synchronization and selective signalling (addressing) information both in a preamble portion to an entire message and recurrently at regular intervals throughout a message of encrypted digital voice signals. This arrangement permits successful late entry and/or synchronization recovery (both frame and cryptographic synchronization recovery) in an addressable selective signalling type of private radio communication system even if such synchronization is never acquired from the preamble (e.g. because of a long radio transmission channel fade or the like) or in the event such synchronization is temporarily lost after the preamble has already occurred.