A bit error rate (BER) estimation-based adaptive space-time-frequency coded (STFC) multiband orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) wireless body area network (WBAN) system is proposed in this paper. It is designed to improve the average BER performance for high data rate applications while maintaining a reasonably high throughput in body-to-externallinks of a WBAN. The performance improvement fundamentally translates to power saving at the transmitter and/or receiver, thus reducing battery requirements and size of WBAN devices. Two novel blocks, namely the BER estimation-based adaptive algorithm which controls the set of modulation, STFC coding rate, and power of signal constellations, and the linearly interpolated CM4 WBAN channel model are implemented in the proposed adaptive STFC MB-OFDM UWB WBAN system. Three sets of adaptive schemes are defined, each of which is determined by two BER thresholds, i.e. the lower and upper thresholds, which are in turns calculated from the non-adaptive average BER performance as the benchmark. Simulation results show a significant improvement in the performance and/or Tx/Rx power saving, with the cost of a slight reduction in the throughput.