2.5 Predicting the Performance of M-ary Codes in an Unknown Multipath Environment

Wireless communication is a critical link in our global military communication system. In scenarios ranging from the battlefield to the White House, we must be able to send information reliably without a cumbersome infrastructure. Wireless environments typically contain a large amount of multipath interference. Therefore, a waveform that is transmitted through a wireless channel must be robust to multipath. With this in mind, Harris Corporation and Lucent Corporation proposed the complementary code keying (CCK) waveform for the high data rate IEEE 802.11 WLAN standard. The CCK waveform has proven to be robust in a harsh multipath environment. Harris Corporation is implementing this waveform in their PRISM chip which will be deployed by Harris GCSD in a number of military applications including interand intra-ship communication and military telemedicine and telemaintenance. This paper presents a new performance measure based on the distance between M-ary codes in a multipath environment. Significantly, this measure does not depend on knowledge of the multipath environment. Consequently, this measure is well suited for evaluating codes to be used in the many scenarios envisioned for wireless LANs. In the paper, this measure is described and then used to compare a number of M-ary codes. The results of this performance measure as well as performance simulations show that the CCK waveform performs well in a variety of multipath environments.