Digital-carrier multi-band user codes for baseband UWB multiple access

The growing interest towards ultra-wideband (UWB) radios stems from their attractive features that include low-power low-complexity baseband operation, rich multipath diversity, and the potential of enhanced user capacity. Existing baseband spreading codes are not flexible in handling narrowband interference (NBI), which emerges when UWB radios overlay co-existing systems. In this paper, we introduce two novel spreading codes, for baseband UWB multiple access. Utilizing a single or multiple digital subcarriers (SC or MC), these codes give rise to multi-band UWB systems. In addition to providing flexibility in handling NBI, SC- and MC-UWB codes also enable full multipath diversity, and maximum coding gains. Equally attractive is their capability to reduce the number of interfering users, with simple matched filter operations.