Patent ID: 6977969

Claim:
A digital data receiver for recovering at least one message word signal included in a received digital data frame which consists of a plurality of sub-frames, each sub-frame including a given dotting sequence signal, a given word sync signal and a message word signal in which each signal is represented by a plurality of symbols and modulated by frequency in a mobile communication system, wherein a dotting sequence signal of the first sub-frame is longer than dotting sequence signals of the rest of the sub-frames, and the word sync signal and message word signal of each sub-frame consist of the same length and pattern, the digital data receiver comprising; a digital FM demodulator for receiving frequency modulated signals, and for demodulating a dotting sequence signal, a word sync signal and a message word signal of each sub-frame included in said digital data frame; a dotting signal detector, which is provided with symbols of said signals demodulated by said digital FM demodulator, for detecting a dotting sequence signal of at least one sub-frame by determining whether the symbols corresponding to the dotting sequence signal are continuously detected more than a specific value that is shorter than the length of each dotting sequence signal; a word sync detector, which is provided with symbols of said demodulated signals, for detecting the word sync signal of each sub-frame; a frame end counter for counting the symbols received and determining termination of the received digital data frame by increasing or decreasing a counting number whenever each of the symbols is detected until the counting number reaches a predetermined number, and for resetting to a initial number if the word sync signal is detected prior to reaching the predetermined number; and a message processor means including a message word accumulator that detects and stores at least one message word signal of the sub-frame from the demodulated signals, for recovering the at least one message word signal from message word signals stored in said message word accumulator until receiving of the digital data frame is terminated.