Pulse parity modulation for impulse radio UWB transmission based on non-coherent detection

Abstract

To enhance the error performance of impulse radio UWB transceivers, we introduce in this manuscript a novel modulation scheme based on exploiting the symmetry properties of transmitted waveforms. Parity Modulation utilizes odd versus even pulses to represent binary data, while the detector relies on a time reverser and non-coherent cross correlator. The analytical expression of power spectral density has been derived; then, considering different orders of Gaussian derivatives as pulse waveforms, the spectral characteristics have been optimized to comply with the UWB emission regulation. The bit error rate formula in an AWGN channel has been developed, while our simulation measurements showed a significant performance gain for 2 Gbps Parity over 1 Gbps Pulse Position Modulation and 2 Gbps On Off Keying. A reference-based parity scheme has been eventually proposed to enhance robustness against multi-path effects, interesting results have been achieved in terms of error probability in a realistic channel, with a compromise between data rate and complexity.

Introduction

In recent years, Ultra Wide Band (UWB) radio technology has been a central investigation topic for many researchers in wireless community. Thanks to the extremely broad bandwidth, UWB has certain potential advantages like high transmission rate capability, very good time and spatial resolution, communication security, robustness against multi-path effects, in addition to the low power dissipation [1], [2], [3], [4], [5], [6], [7]. These salient features make UWB an appropriate candidate for numerous application scenarios, such as local and wide area networks, vehicular radar, biomedical engineering, sensor networks, and indoor communications [8], [9], [10], [11], [12], [13]. UWB free-space propagation is limited to short distances, due to the power and spectral constraints of the Federal Communication Commission (FCC) [14], [15]. The latter has authorized UWB operation in the [3.1,10.6] GHz frequency range, where the emitted power must not exceed −41.3 dBm/MHz, in order to ensure a non-problematic coexistence with other wireless devices [15]. Impulse Radio (IR) is a particular UWB technique, based on transmitting nanosecond pulses occupying the desired frequency band; IR is a carrier-free scheme which reduces the system cost and complexity [16], [17], [18], [19], [20], [21], [22], [23], [24]. Several IR modulation options have been investigated in the literature, mainly the Pulse Amplitude Modulation (PAM), Pulse Position Modulation (PPM), On Off Keying (OOK), Binary Phase-Shift Keying (BPSK), and Pulse Shape Modulation (PSM), besides combining different techniques [2], [25], [26], [27]. Non-coherent impulse radio approach is gaining popularity, as associated with a simple transceiver architecture and no need for a channel estimation [28], [29], [30], [31], [32]. OOK and PPM are mostly employed with IR, the former can operate at a high data rate and acceptable bit error rate (BER); whereas the latter is associated with a better error performance, but the time shifting required has a main drawback against bit rate, which is actually half that for OOK [2]. In this manuscript, we explore a new modulation concept which enhances the error performance without significantly degrading the symbol rate. The novelty of our work originates from taking advantage of an opposite parity, so as to modulate binary data. By employing even and odd pulses belonging to Gaussian Derivative family, we obtain a substantial reduction in the probability of error compared to OOK and PPM non-coherent alternatives, while achieving a higher transmission speed than PPM.