Synchronization at Low SINR in Asynchronous Direct-Sequence Spread-Spectrum Communications

Currently deployed asynchronous wireless networks, e.g., 802.11a/b/g, have a limited spatial range and low reliability due to their inability to operate at low signal to interference and noise ratio (SINR). Low SINR operation can be achieved using a direct-sequence spread-spectrum (DSSS) based communication with a high spreading gain. The reception at low SINR is limited by the inability to synchronize at a low SINR. In this paper, we present the design of a synchronization block which enables a receiver to synchronize to an incoming packet at a low SINR with a high reliability. It leverages an algorithm for code acquisition in asynchronous packet-based reception described in [1]. The design of this block also consists of novel algorithms for code tracking, frame synchronization and multipath search for RAKE combining. A payload based on binary orthogonal signaling is attached to the packet header to complete an asynchronous packet-based system. The simulation results show that each of the synchronization algorithms as well as the entire synchronization block operate reliably at low SINR at the input of the receiver.