Ultra wideband-impulse radio (UWB-IR) systems transmit data by ultra short pulses. The UWB-IR systems can achieve a time diversity gain by transmitting some pulses for each information symbol. In L. Yang et al. (2002) the space time (ST)-UWB-IR system was proposed to achieve a space-time diversity gain by transmitting space-time block coded symbols with some antennas. In the ST-UWB-IR system, the transmit antennas transmit the same symbol over an ST code block simultaneously. If all the transmit antennas can transmit different symbols independently, that is, if it separates the symbols from each antenna, we can expect a higher transmission rate than the ST-UWB-IR system. Moreover, at the same transmission rate, we can expect a larger diversity gain by sending more pulses for each symbol. This paper proposes a space hopping (SH)-UWB-IR system. In the SH-UWB-IR system, to allow each user to transmit different symbols from different antennas, a unique time hopping sequence is assigned to each antenna, which is known to the receiver. In addition, to get the larger diversity gain in the SH-UWB-IR system, the transmitted symbols are interleaved over the transmit antennas. From the results of our computer simulation, we show that when the number of users is small, the bit error rate (BER) of the SH-UWB-IR system is superior to that of the ST-UWB-IR system at the same data rate.
['Takahiro Ezaki', 'Tomoaki Ohtsuki']
Performance evaluation of space hopping ultra wideband impulse radio (SH-UWB-IR) system