On-line Arithmetic for Detection in Digital Communication Receivers

This paper demonstrates the advantages of using on-line arithmetic for traditional and advanced detection algorithms for communication systems. Detection is one of the core computationallyintensive physical layer operations in a communication receiver and determines the communication data rates. Detection algorithms typically involve hard decisions (sign based testing) to find the sign of the transmitted information bit. This implies extraneous computations in a conventional number system as the sign is obtained only at the end due to the Least Significant Digit First (LSDF) nature of computations. On-line arithmetic, based on a signed digit number representation, provides Most Significant Digit First (MSDF) computation. Hence, the computations can stop after the first non-zero MSD (sign) is computed and additional computations for the successive digits can be avoided. The need of back-conversion to a conventional number system is also not required as the sign of the digit represents the detected bit. A comparison of a radix-4 serial digit on-line detector with a 8-bit parallel conventional arithmetic detector shows a decrease in latency by 1.9X, a 3X increase in throughput and possible savings in area. We show that similar benefits are also possible with on-line arithmetic for decoding algorithms in communication receivers.