IEEE TRANS. AEROSP. ELECTRON. SYST., VOL. 43, NO. 4, PP. 1617-1624, OCT. 2007 1617 Terrain-Based Simulation of IEEE 802.11a and b Physical Layers on the Martian Surface Anirudh Daga, Gaylon R. Lovelace, Deva K. Borah, Member, IEEE, and Phillip L. De Leon, Senior Member, IEEE Abstract This paper presents results concerning the use of IEEE 802.11a and b wireless local area network (WLAN) standards for proximity wireless networks on the Martian surface. The radio frequency (RF) environment on the Martian surface is modeled using high-resolution digital elevation maps (DEMs) of Gusev Crater and Meridiani Planum (Hematite) as sample sites. The resulting propagation path loss models are then used in a physical layer (PHY) simulation. Our results show that Martian terrain as represented by the sites studied, can create multipath conditions which in turn affect 802.11a and b PHY performance. However, with a few tens of milliwatts of radiated power and antenna heights within 1–2 m, orthogonal frequency division multiplexing (OFDM)-based 802.11a can have very good PHY performance in terms of bit- and packet-error rates for distances up to a few hundred meters; 802.11b, which is based on direct-sequence spread spectrum (DSSS), is found to be much more adversely affected in the multipath environment. The DEM-based simulation methodology presented here may be more useful to mission planners than generic statistical models. Index Terms Wireless LAN, Communication system performance. I. I NTRODUCTION N ASA’S long-term goals for the exploration of Mars include the use of rovers and sensors which intercommunicate through proximity wireless networks. These networks are designed to have a short range, relatively low cost, and short lifespan and are obviously required to be reliable, robust, and power efficient. Of considerable interest is the applicability of wireless local area network (WLAN) standards such as IEEE 802.11a, b, and g for such planetary surface networks. However, since these standards were primarily developed for indoor use, there are many factors in the outdoor environment that can limit network performance and thus need to be studied before consideration for application in a planetary exploration mission. In particular, lack of man-made structures and vegetation, a negligible atmosphere, and the presence of unique terrain features on the Martain surface raise questions about the exact behavior of WLAN technology on that planet. A methodology to address questions such as how much transmission power is needed for a reliable link, how the distance affects receiver’s performance, and the effect of antenna heights on communications can provide valuable guidelines for future mission planners. Numerous publications have considered many of the steps toward such a study of WLAN performance in an outdoor environment, albeit for Earth. These steps include channel modeling and performance analysis of the physical layer (PHY) in the multipath environment. With respect to channel modeling at the 2.4 and 5 GHz WLAN frequencies, most studies have focused either on the indoor office environment or outdoor urban environment [1], [2], [3]. In [1], the authors considered IEEE 802.11a and g and simulated path loss, coverage, and medium access control (MAC) throughput in a corporate office environment using detailed models of the building and ray-tracing methods to carefully simulate the indoor multipath propagation. It is well known that such methods which take into account detailed models of the propagation environment provide more accurate channel models than other simple statistical models. Their work demonstrates the utility of using environment-based radio frequency (RF) modeling in order to evaluate PHY and MAC performance but is limited to the indoor environment. In [2], the authors develop empirical channel models for the outdoor urban environment based on measured data. They demonstrate that in the outdoor urban environment, large man-made objects are a major source of long multipaths and significant rms delay spreads and take this in account when developing their channel models. With respect to performance analysis of the PHY in an outdoor multipath environment, several studies have focussed on the application of WLAN standards for cellular telephony. In [4], the authors examined the use of 802.11b (1 Mbps) for an outdoor cellular network and in particular, investigated the impact of multipath on bit error rate (BER) performance by assuming a simple multipath channel model with rms delay spreads of 250 ns, 1 μs, and 3 μs. Their work demonstrates that higher delay spreads associated with the outdoor environment led to poorer 802.11b PHY performance. In [5], the authors tested 802.11a outdoors in a city environment and measured network throughput as a function of user mobility. This work was presented in part at the 2005 and 2006 IEEE Aerospace Conference, Big Sky, MT. This work was supported by NASA Grant NAG3-2864. A. Daga is with Motorola. D. K. Borah, P. L. De Leon, and G. R. Lovelace, are with the Klipsch School of Electrical and Computer Engineering, New Mexico State University, Las Cruces, NM 88003 USA. * Direct all correspondence regarding this manuscript to Dr. Phillip De Leon (pdeleon@nmsu.edu).