Adjacent Frequency Coding Technique for Decreasing MB-OFDM UWB Interference to Other Radio Services

Multiband OFDM (MB-OFDM) ultrawideband radio will have to coexist with numerous narrowband radio services that operate over the 3.1 - 10.6 GHz band. In order to coexist with other radio systems without becoming a harmful source of interference, MB-OFDM radio designers are actively developing methods to protect those portions of the band that are being used by other, actively transmitting, radios. This requires the ability to notch segments of the transmitted spectrum so that the impact to other services is minimal. In this paper, we present the Adjacent Frequency Coding method, which uses weighted sub- carrier pairs to shape the MB-OFDM spectrum so that it has a steeper roll-off, and thus a better ability to notch. This technique, which increases the achievable notch depth by ~ 10 dB when compared to simple tone dropping (i.e. sub-carrier nulling without spectral shaping), requires only a modest modification to the current MB-OFDM PHY specification.