Performance Analysis of IEEE 802.15.4a BPSK/BPPM UWB Transmission

The IEEE 802.15.4a standard uses coded impulse-radio ultra-wideband (UWB) transmission with combined binary phase-shift keying/binary pulse-position modulation (BPSK/BPPM) and direct-sequence spreading with time hopping as physical layer. In this paper, semi-analytical expressions are derived to evaluate the bit-error rate (BER) performance for such a UWB system. Thereby, two different methods for generating reliability information (i.e., decoding metrics) for decoding of the convolutional code at the receiver, the use of time-varying spreading sequences, and suboptimal multipath combining employing a selective RAKE (SRAKE) front-end are included in the analysis. The presented numerical results show that (i) the devised BER approximations are very tight over a wide range of BERs, (ii) symbol-wise metrics are clearly advantageous over bit-wise metrics for decoding, and (iii) SRAKE combining with about 5-10 fingers is sufficient to closely approach the optimal performance for highly dispersive UWB transmission channels.