The Impact of Bandwidth on the Performance of DSSS Signals in Indoor Office Environments

This letter presents an empirical analysis of the impact of spreading bandwidth on fading performance of direct-sequence spread spectrum signals. Over 20000 measurements were recorded in an indoor office environment at chip rates of 25 MHz, 100 MHz, 225 MHz, 400 MHz, and 500 MHz. A continuous wave signal was also used to characterize the fading of narrowband signals. Three particular effects are examined as chip rate (i.e., bandwidth) increases: energy splintering due to temporal dispersion, reduction in the fading of the total received energy due to reduced multipath interaction and the fading reduction per resolvable component. The effects are characterized for line-of-sight and non-line-of-sight environments and are used to determine the BER performance of a BPSK system when operating in the presence of all three effects. The results are also compared with the theoretical relationship between signal energy variation and chip rate. The analysis demonstrates that the use of a chip rate greater than 225 MHz (or bandwidth greater than approximately 200 MHz) provides only minor improvements in fading performance in these environments.