Bit density based signal and jamming detection in 1-bit quantized MIMO systems.

A conceptual schematic diagram of pilot attack in the uplink of a 1-bit quantized massive MIMO system. We equip the BS with a sufficient number of adapted 1-bit window comparators to facilitate detection, followed by a very low-complexity binary hypothesis detector, where its operation is mainly based on counting the number of 1's in the observed binary sequence to decide on the presence or absence of a potential jamming signal. In the asymptotic sense, the proposed 1-bit window comparator allows the BS to partition the space of observed sequences into two distinct typical sets; null and alternative sets, which is not possible using a traditional 1-bit quantizer. This paper studies the problem of deciding on the absence (i.e., null hypothesis, H 0) or presence (i.e., alternative hypothesis, H 1) of an unknown signal embedded in the received signal in a multiple-input, multiple-output (MIMO) receiver, employing 1-bit quantization. The originality of our solution lies in quantizing the received signal by an adapted 1-bit window comparator, rather than a traditional 1-bit quantizer. This enables us to divide the space of observed binary sequences into two typical sets (w.r.t. the distribution of the no. of 1's in a sequence) asymptotically, where the first set corresponds to H 0 and the second to H 1. As a result, we reduce the detection problem to determining the highly probable set for an observed sequence. Thus, a very low-complexity binary hypothesis detector is proposed and its probability of detection is given. To show the high efficacy of the proposed 1-bit receiver structure, we consider two wireless applications; jamming detection in a massive MIMO system, and probing a non-stationary low-power transmitter in a wireless sensor network (WSN), assuming unknown Rayleigh-fading channels. Compared with an unquantized system employing a chi-square test, it is shown that the performance loss can be roughly as large as 10% in massive MIMO and this gap diminishes as sequence length or/and jamming power increases. For WSN, we show that compared with an unquantized system, the performance gap becomes smaller when the observation interval is extended over a few symbols. [ABSTRACT FROM AUTHOR]