Mitigation of wideband interference on UWB-IR transmission using multi-carrier templates

Abstract

Ultra wideband (UWB) wireless systems are highly susceptible to interference from other services. To reduce the effect of interference from co-existing sources such as the WLAN standard IEEE 802.11a on UWB Communication, the construction of a modified template waveform using multi-carrier sinusoids is proposed in Ohno and Ikegami (2003), Ohno et al. (2004), Ikegami (2006), andNikookar (2007). However, the work in Ohno and Ikegami (2003), Ohno et al. (2004), Ohno and Ikegami (2006), and Lakshmanan and Nikookar (2007) considers a free space propagation channel model with no treatment of the frequency dependence of the path loss. In this paper, we broaden the study by taking into consideration a frequency-dependent path loss environment. The novelty of the work is in the investigation of the effect of frequency dependency of the path loss on the performance of interference mitigation schemes.Keywords: Impulse radio, Interference mitigation, Multi-carrier type pulses, Template waveforms, Frequency-dependent path loss I . I N T R O D U C T I O NUltra-wideband (UWB) communication systems have received significant attention from industry, media, and academia alike. The reason for all these excitements is that this technology promises to deliver both high data rate personal-area network wireless connectivity as well as longerrange, low data rate communication, with efficient utilization of scarce radio bandwidth in realistic multi-path environments, all while consuming very little power and silicon area. It is expected that UWB devices will provide low cost solutions that can satisfy the consumer's insatiable appetite for data rates spawning new consumer market segments.Ultra wideband impulse radio (UWB-IR) makes use of ultrashort (,1 ns) base band pulses to communicate, thereby spreading the energy of the radio signal very thinly over extremely large frequency bandwidths [1]. Given their very large bandwidth, the UWB-IR systems must share the spectrum with other users as well as with the existing communication systems. Even though UWB systems have high processing gain, and operate at very low power (due to regulations), they are highly susceptible to interference. And performance degradation of UWB communication due to interference from other co-existing services is a major issue. By using template waveforms derived from multi-carrier sinusoids at the transceiver, the interference power can to a large extent be mitigated [2][3][4][5]. The template waveforms are constructed by representing the UWB transmission waveform with multi-carrier sinusoids and by selectively removing those sub-carriers whose spectral footprints fall near the interference spectrum. This way the UWB signal spectrum is sculpted to avoid the regions of interference. Through simulation studies it is proven that such an interference mitigation technique is effective, allowing for coexistence with different wideband systems.However, these efforts employ a free space propagation model with no consideration for the frequency dependence of the UWB signal...