Field trials with IEEE 802.11b-based UHF tactical wideband radio

The intention of the system described in this paper is to provide wideband none line-of-sight (NLOS) communications for tactical users. The ultra high frequency (UHF) band 1 (225 - 400 MHz) seems to be a good compromise giving acceptable range and coverage with acceptable bandwidth. The paper reports on adapting commercial-based technology for military applications. It describes a solution for UHF 225 - 400 MHz wideband ad hoc tactical wireless local area network (TWLAN) based on the IEEE 802.11b standard in order to emphasize on commercial developments of wireless radios. The ad hoc routing protocol used is the optimized link state routing (OLSR) protocol. Two systems are presented. One system based on a modified D-link IEEE 802.11b WLAN card were frequency was converted to 323 MHz, output power at 3 W but without rate reduction. The other system was similar but with the bandwidth reduced by a factor of four giving 250, 500, 1375 and 2750 kbit/s. Two versions of this radio were used: a small "soldier version" at 1 Watt output power and one "vehicle mounted version" at 3 Watts output power. The radios are used between vehicles in a squadron and also between the soldiers within a unit and through the unit's vehicle back to head quarter. Calculations indicate 2.5 kilometers transmission range within 50% probability according to Egli (1957). The measurements show that communication limited by attenuation is possible within a few kilometers with high probability but the signal is susceptible to multipath fading. Since there is no forward error correction (FEC) implemented in 802.11b, adaptive FEC would probably improve performance at the two lower bit rates that uses BPSK and QPSK modulation.