Effect of baseband filter bandwidth in fractional sampling orthogonal frequency division multiplexing on indoor channel model with measured impulse responses

In the IEEE 802.11a WLAN standard, orthogonal frequency division multiplexing (OFDM) modulation is employed. Diversity techniques are effective way to overcome multipath fading in the OFDM systems. A fractional sampling (FS) scheme is one of the diversity techniques with a single antenna. Through FS it is possible to separate multipath components and obtain diversity gain in OFDM. Though FS has been analysed numerically, the experiment of FS on actual indoor channels with real filter characteristics has not been carried out. In addition, though it has been suggested that in FS diversity a sharp filter limits the diversity gain, this limitation has not been confirmed especially with measurements. Therefore we investigate the effect of filter bandwidth in FS through simulation and an experiment. Numerical results through the simulation and the experiment indicate that the FS can achieve path diversity and improves the performance by about 2 dB if the bandwidth of the baseband filter is larger than the minimal bandwidth.