Abstract: A slot selection algorithm for use in a multi-slot TDMA communications system which has provision for transmissions requiring a single time slot or a double time slot. The algorithm requires that whenever possible a transmission requiring a single time slot is allocated to an acceptable, but not necessarily the best, inactive time slot which is located adjacent to an active time slot in a TDMA frame. By so doing the number of inactive time slots available for double time slot transmissions may be increased.

Abstract: In a code excited linear prediction (CELP) analog signal coding system sequences from a master codebook (40), which may be a one dimensional codebook, are filtered (42) and then stored in slave codebooks (70,72). Input analog siganls (20)are filtered (34,36) and compared orthogonally (66,78,80) with sequences from the slave codebooks and an optimum pair of sequences are selected. Reduced length sequences from the master codebook may be compared with orthogonalized analog signals since orthogonalized siganls contain some redundancy.

Abstract: A speech coding system of the code excited linear prediction (CELP) type includes apparatus (24,26) for filtering digitized speech samples to form perceptually weighted speech samples. Entries in a one-dimensional codebook (110) comprising frame length sequences are filtered in a perceptually weighted synthesis filter (28) to form a one-dimensional filtered codebook. The filtered codebook entries are compared with the perceptually weighted speech signals to obtain a codebook index which gives the minimum perceptually weighted error when the speech is resynthesized. Using a one-dimensional codebook (110) reduces the amount of computation which is required compared to the use of a two-dimensional codebook.