Timing synchronization for IEEE 802.11a-based non-regenerative wireless relay networks

This paper addresses the problem of timing synchronization at the destination node of a non-regenerative wireless relay network which employs the IEEE 802.11a standard for data transmission. The two-hop relay network consists of an IEEE 802.11a-compliant source and destination pair, each equipped with a single antenna, aided by a relay node equipped with two antennas, which operate in half-duplex mode. The source-to-relay link remains a point-to-point system and perfect timing synchronization can be assumed at the relay. The relay performs cyclic prefix (CP) removal and re-insertion operations on the received signal to restore the cyclic structure of the amplified and forwarded signal and also introduces transmit diversity, in the form of cyclic delay diversity (CDD), into the forwarded signal. The maximum likelihood (ML) timing synchronization cost function for the received signal at the destination node of the system is derived to show that the ML solution cannot be implemented in practice due to the high computational complexity involved. The use of correlation-based timing synchronization algorithms is then studied. In addition to the probability of achieving timing synchronization, the packet error rate (PER) performance is used as an additional measure of the performance of the different timing synchronization algorithms. It is seen that the use of a correlation-based timing synchronization algorithm does not result in significant PER performance loss compared to the PER achieved by ML methods. In addition, the introduction of CDD in the forwarded signal, which is transparent to the destination node, is shown to achieve an improvement in the PER performance over a relay which performs conventional amplify-and-forward (A & F) relaying.