Non-Coherent Signal Detection and Bit Error Rate for an Ambient Backscatter Link under Fast Fading

Abstract

This paper is focused on the non-coherent detection in ambient backscatter communication, which is highly appealing for systems where the trade-off between signaling overhead and the actual data transmission is very critical. Modeling the time-selective fading channel as a first-order autoregressive (AR) process, we consider two data encoding schemes at the transmitter and propose a new receiver architecture based on the direct averaging of the received signal samples for detection, which departs significantly from the energy averaging-based receivers considered in the literature. For the proposed setup, we characterize the exact asymptotic bit error rate (BER) for both single and multi antenna receivers. Our results demonstrate that while the direct interference received from the ambient power source leads to a BER floor in the single antenna receiver, the multi-antenna receiver can efficiently remove this interference by estimating the angle of arrival (AoA) of the direct link from the power source. A key intermediate result of our analysis is a new concentration result for a general sum sequence (including the asymptotic growth rates of its expectation and variance) that is central to the derivation of the conditional distributions of the signal at the receiver. Index TermsAmbient backscatter, non-coherent detection, auto-regressive model, time-selective fading, bit error rate.

Large-Scale Wireless-Powered Networks With Backscatter Communications—A Comprehensive Survey

“…Among these, non-coherent detection is commonly adopted due to its simplicity because it can be used without the knowledge of channel state information. It is suitable for ASK and FSK [28], [44], [88], [89]. A diagram of binary amplitude demodulation based on envelope detection is shown in Fig.…”

Manchester Encoding for Non-coherent Detection of Ambient Backscatter in Time-Selective Fading

“…However, unlike the direct OOK modulation used in [10], the transmitter in this case sends out codewords [0 1] and [1 0], known as Manchester coding, using the OOK modulation for message (b) bits 0 and 1, respectively. For completeness, note that a preliminary study of Manchester encoding appears in our conference paper [13], which is limited to a dual-antenna receiver and assumed independent fading across the ambient symbols. For a fair comparison with the direct OOK modulation, we assume that each codeword of Manchester encoding is sent within a single symbol duration of the backscatter data instead of the time duration of two symbols.…”

“…It is important to highlight the advantages of Manchester encoding over the direct OOK modulation. The decision rule, given in (13), for Manchester encoding is just a function of the relative magnitudes of the two RVs Z 0 and Z 1 . On the other hand, the decision rule of the direct OOK modulation is based on the comparison of the magnitude of a single TS Z (evaluated over all the N samples) with a threshold, which can be expressed as follows:…”

“…Hence, the conditional joint PDFs of Z 0 and Z 1 are given by: N are the variances of the MA receiver as derived in [10] for the direct OOK modulation. The optimal decision rule once again turns out to be (13), from which the conditional BER can be derived as:…”