Phase compensation communication technique against time reversal for ultra‐wideband channels

Abstract

Phase compensation (PC) prefiltering is experimentally investigated for multipath channels over the frequency band spanning 2-12 GHz, a topic which to the best of the authors knowledge has not been studied in the literature on ultrawideband (UWB) communications. The authors emphasis is to assess the capabilities of PC compared to time reversal (TR) prefilters over indoor UWB channels regarding multipath suppression, channel hardening, noise sensitivity and high-speed data transmission. Experiments were carried out for PC and TR prefilters in both line-of-sight (LOS) and non-LOS (NLOS) environments. The multipath compression effectiveness is characterised by computing the root-mean-square delay spread and peak-to-average power ratio for actual measured channels and for the IEEE 802.15.4(a) UWB model. The authors study suggests PC outperforms TR considerably in mitigating the multipath channel dispersion. Bit-error-rate (BER) curves have been simulated for data rates in the range of 125-4000 Mbps based on the measured channel responses. The BER simulations suggest that while the TR performance is prohibitively saturated by its residual intersymbol interference for data rates of 500 Mbps and above (especially in NLOS), PC can be used for high-speed data transmissions as fast as 2 Gbps in both LOS and NLOS environments.

Photonic-Assisted Error-Free Wireless Communication With Multipath Precompensation Covering 2–18 GHz

“…By employing a phase compensation (PC) algorithm, we achieve error-free wireless transmission at 250 Mb/s data rate over a strong multipath channel (the bit error rate is bounded at 8 × 10 −6 or below by the PN-sequence length equal to 2 17 − 1). Our work, the first to compare the performance of TR and PC directly in data transmission experiments, confirms the prediction [12] that PC provides substantial superiority over TR in terms of ISI suppression. A preliminary description of our work covering PC only was reported in [13].…”

“…However, the output signal now contains a squared spectral magnitude. As pointed out in [12], this squaring operation increases the spectral intensity variation evident for example in Fig. 3(b), leading to higher sidelobe levels in pulse compression and aggravating ISI.…”

“…The close resemblance between the simulation and experimental results and the fact that the average received positive peak voltage is ∼6.7 times the STD clearly demonstrates the substantial ISI suppression. According to the simulations of [12], the excellent performance of our system in mitigating ISI should allow scaling to several Gbits/s data rate if a higher repetition rate optical pulse source becomes available.…”

“…As in our group's previous work [12], [22], in the current experiments the received sounding waveform at the receiver (Rx) is communicated back to the transmitter (Tx) through Ethernet cable or wireless LAN for channel impulse response analysis. In this case, both the sounding waveform and the data-encoded pre-compensation waveform (to be discussed in Section IV) are transmitted from Tx to Rx.…”

“…Through canceling the frequency-dependent phase variation of the transmission channel, the PC algorithm generates a pre-distorted waveform which self-compresses while propagating and arrives at the receiver with a strong peaking effect. Compared to TR, PC is more effective at sidelobe reduction and thus improves ISI suppression [12]. If we denote the impulse and frequency response of the system by h sys (t) and H sys (f ), respectively, the phasecompensated waveform can be expressed as…”