The effect of time synchronization errors on the performance of cooperative MISO systems

We consider a wireless sensor network scenario where closely packed nodes can he grouped into clusters. Although each node might have only a single antenna, nodes within a cluster can cooperate during transmission or reception, thereby forming a cooperative multiple input multiple output (MIMO) system. Much of the work in the area of cooperative MIMO has assumed perfect synchronization between the nodes in the network and the associated benefits have been investigated. We examine this assumption in a system where a cluster of nodes cooperatively transmits to a single receive node over a flat fading channel. We evaluate the effect of clock jitter between nodes on the performance of this cooperative multiple input single output (MISO) system. The clock jitter at the transmit nodes results in the lack of a reference clock at the receive node and causes inter-symbol interference (ISI). This leads to a performance degradation in the system. However, simulation results indicate that jitters as large as 10% of the bit time do not have much effect on the BER performance of the system. We also show that when the channel is not undergoing fading, the power penalty due to the clock jitter is independent of the number of transmit nodes and the penalty increases as the SNR increases.