Packet detection and acquisition at low SINR in spread-spectrum based wireless communications

Abstract

A low signal to interference and noise ratio (SINR) wireless environment makes successful reception and accurate detection of packets a challenging task. We can combat a low SINR by using direct-sequence spread spectrum modulation with a sufficiently high processing gain, as well as by employing block codes for FEC on each packet. In this paper, we propose a packet detection and acquisition method for low SINR environments. The received waveform is processed using a non-linear filtering algorithm based on a maximum likelihood ratio calculation to detect the presence of transmitted packets. The algorithm uses the entire packet transmission for chip timing synchronization and code acquisition at the receiver. The performance of the algorithm is analyzed using simula- tions and real packet transmissions captured over the wireless medium. The algorithm is finally implemented on a FPGA which is a part of a wireless transceiver prototype. The experimental results are reported.