On measuring memory length of the error rate process in wireless channels

Bit errors are orders of magnitude more frequent in wireless channels than in wired channels. Design of network protocols and other architectural components of wireless networking systems entail a better understanding of the process that introduces errors into transmissions. A key characteristic of the error process operating on a channel is its memory length which determines the degree of similarity and clustering of errors. In this paper we demonstrate the inadequacy of correlation coefficient based analysis used in determining memory length of bit level errors to the packet-level bit error rate (BER) process. To overcome this problem we propose an alternate means of measuring channel memory, called the relative mutual information (RMI) and a lower complexity variant, the pairwise RMI. We demonstrate the use of RMI and pairwise RMI to sets of residual bit-error traces collected in IEEE 802.15.4 low rate-wireless personal area network (LR-WPAN) and IEEE 802.11b wireless local area network (WLAN) channels.