A new class of binary iteratively decodable codes with good decoding performance is presented. These codes, called braided block codes (BBCs), operate on continuous data streams and are constructed by interconnection of two component block codes. BBCs can be considered as convolutional (or sliding) version of either Elias' product codes or expander codes. In this paper, we define BBCs, describe methods of their construction, analyze code properties, and study asymptotic iterative decoding performance.

Potentially large storage requirements and long initial decoding delays are two practical issues related to the decoding of low-density parity-check (LDPC) convolutional codes using a continuous pipeline decoder architecture. In this paper, we propose several reduced complexity decoding strategies to lessen the storage requirements and the initial decoding delay without significant loss in performance. We also provide bit error rate comparisons of LDPC block and LDPC convolutional codes under equal processor (hardware) complexity and equal decoding delay assumptions. A partial syndrome encoder realization for LDPC convolutional codes is also proposed and analyzed. We construct terminated LDPC convolutional codes that are suitable for block transmission over a wide range of frame lengths. Simulation results show that, for terminated LDPC convolutional codes of sufficiently large memory, performance can be improved by increasing the density of the syndrome former matrix.

We consider construction and realization aspects of encoders and decoders for braided block codes (BBCs), which are a powerful class of iteratively decodable codes. An efficient encoder is proposed as well as a pipeline decoder realization. Also, upper and lower bounds on the free distance of BBCs are derived

We present a class of convolutional codes defined by a low-density parity-check matrix and an iterative algorithm for decoding these codes. The performance of this decoding is close to the performance of turbo decoding. Our simulation shows that for the rate R=1/2 binary codes, the performance is substantially better than for ordinary convolutional codes with the same decoding complexity per information bit. As an example, we constructed convolutional codes with memory M=1025, 2049, and 4097 showing that we are about 1 dB from the capacity limit at a bit-error rate (BER) of 10/sup -5/ and a decoding complexity of the same magnitude as a Viterbi decoder for codes having memory M=10.

Coherent reception of quadrature phase-shift keying (QPSK) modulated signals in an uplink channel of a direct-sequence code-division multiple access (DS-CDMA) system is considered. The receivers, commonly referred as the conventional matched-filter receiver and the RAKE receiver, are analyzed when the transmission of data is performed over the additive white Gaussian noise (AWGN) channel and the multipath slow Rayleigh fading channel, respectively. Both analyses take into account inaccuracies in the carrier phase estimations resulting from a carrier phase estimator.