Impact of electromagnetic noise from PCs on performance of multiband-OFDM UWB systems

Since personal computers (PCs) radiate radio noise in a wide frequency range, wireless devices added to PCs may be subjected to interference from PC noise. Investigations were carried out on what impact clock harmonics radiating from a PC had on the bit error rate (BER) of multiband OFDM (MB-OFDM) UWB devices. The results indicated that clock harmonics cause considerable BER degradation in UWB devices especially those operated in high-bitrate communication modes. It was also found that the frequency modulation of a PC clock signal, i.e., so-called spread spectrum clocking (SSC), had no effect on mitigating BER degradation, even though SSC techniques are commonly used in PCs for reducing the power spectral density of radiated noise. Discussions were further made on a possible scheme of mitigating interference by using Viterbi decoding with channel state information (CSI) that is obtained by estimating the instantaneous frequency of clock signal directly provided by the PC to the UWB device.