Abstract: An interleaver receives incoming data frames of size N. The interleaver indexes the elements of the frame with an N1×N2 index array. The interleaver then effectively rearranges (permutes) the data by permuting the rows of the index array. The interleaver employs the equation I(j,k)=I(j,&agr;jk+&bgr;j)modP) to permute the columns (indexed by k) of each row (indexed by j). P is at least equal to N2, &bgr;j is a constant which may be different for each row, and each &agr;j is a relative prime number relative to P. After permuting, the interleaver outputs the data in a different order than received (e.g., receives sequentially row by row, outputs sequentially each column by column).

Abstract: Construction of a Turbo code interleaver for blocks of any size is facilitated by partitioning the block into co-sets of predetermined size, permuting each co-set with an interleaver whose parameters are selected and optimized for the predetermined size, and recombining the elements of the permuted co-sets according to a predetermined order. Partitioning of the block into co-sets is accomplished by choosing a value n for the number of co-set, and assigning to each co-set those positions of the block having a common value for modulo-n of the block size. The permuted output may be punctured to maintain a desired ratio.

Abstract: Systems and methods for interleaving codes includes a processor that acts on a data frame received and stored in a memory. The processor separates portions of the data frame and permutes the portions, achieving maximum data scattering by using equations based on number theory.

Abstract: A demodulator, within a receiver attached to a single antenna, that cancels co-channel interference within a time division multiple access (TDMA) communication system is disclosed. The demodulator takes as input a series of received signals comprising an information signal and a co-channel interference signal, both using the &pgr;/4-differential quadrature phase shift keying (DQPSK) modulation protocol. During a training period, in which the information signals corresponds to a known SYNC word, the demodulator estimates the fading coefficients corresponding to the information and interference signals. After the completion of the training period, the demodulator uses these estimates to generate accurate estimations for future information and interference signals corresponding to future data received signals.

Abstract: A maximal correlation symbol estimation (MCSE) method for estimating the symbols that are modulating an information signal component of a received signal, which can be applied to received signals that additionally contain an interference signal component, is disclosed. The method is achieved by correlating the received signal with all possible reference signals, each reference signal being one of a closed set of all possible information signals recognized by the given digital modulation scheme, and selecting as an estimate of the information signal the reference signal whose correlation with the received signal most closely resembles a weighted average of correlations between previously estimated information signals and their corresponding received signals. Demodulators that implement this method are adapted to perform many functions, including the estimation of symbols modulating frequency modulated (FM) received signals prior to the signals being FM demodulated.