SAFE (Smart Access Frequency Exploitation) Radio Field Experiment Results

This paper describes field experiments of an 802.16-based radio that has an innovative cognitive radio technology that significantly increases the link range, increases battery life, or reduces a radios´ RF signature. The SAFE (Smart Access Frequency Exploitation) radio combines Dynamic Spectrum Access (DSA) and channel sounding capabilities simultaneously. This enables spectrum sharing on a noninterference basis with other users and selects the radios´ operating frequency that has minimal link (antenna and propagation) loss, and uses a transmit power control algorithm to reduce the transmit power level. There are multiple frequency dependent factors that determine link loss (multi-path, reflection coefficients, antenna gain, power amplifier gain, foliage/wall penetration, atmospheric refraction, etc.). SAFE exploits these propagation factors, and provides 10-20 dB less link loss compared to a conventional, fixed tuned radio. This provides a significant improvement in link range, increased battery life or a reduction in the radio´s signature. The SAFE radios were separated by a long (non-line of sight) distance in an outdoor, hilly area. The link distance, the obstacles, and the radio transmit power are selected so that the radios was near its maximum range. The link range distances (1 km to 4.5 km) were found empirically based on the terrain blockage. The field tests validate the 10-20 dB link loss reduction.