The combination of cooperative communication and Space-Time-Frequency-Codes (STFCs) has been recently proposed in the literature for Multiband OFDM Ultra-Wideband
(MB-OFDM UWB) to improve the bit error performance, system capacity, data rate and wireless communications range. This paper proposes a cooperative communication design using Order-4 Orthogonal STFCs in MB-OFDM UWB systems, which is referred
to as Order-4 Orthogonal Cooperative Communication Scheme (4-OCCS). It will be shown that 4-OCCS improves significantly the diversity and error performance of the MB-OFDM
UWB system, compared to the conventional MB-OFDM UWB (without STFCs) as well as our Order-2 Orthogonal Cooperative Communication Scheme using Alamouti STFCs (2-OCCS) proposed previously, with the same data rate and without any increase of transmission power.