Design and Performance Analysis of Non-Coherent Detection Systems with Massive Receiver Arrays

Harvesting the gain of a large number of antennas in a mmWave band has mainly been relying on the costly operation of channel state information (CSI) acquisition and cumbersome phase shifters. Recent works have started to investigate the possibility to use receivers based on energy detection (ED), where a single data stream is decoded based on the channel and noise energy. The asymptotic features of the massive receiver array lead to a system where the impact of the noise becomes predictable due to a noise hardening effect. This in effect extends the communication range compared to the receiver with a small number of antennas, as the latter is limited by the unpredictability of the additive noise. When the channel has a large number of spatial degrees of freedom, the system becomes robust to imperfect channel knowledge due to channel hardening. We propose two detection methods based on the instantaneous and average channel energy, respectively. Meanwhile, we design the detection thresholds based on the asymptotic properties of the received energy. Differently from existing works, we analyze the scaling law behavior of the symbol-error-rate (SER). When the instantaneous channel energy is known, the performance of ED approaches that of the coherent detection in high SNR scenarios. When the receiver relies on the average channel energy, our performance analysis is based on the exact SER, rather than an approximation. It is shown that the logarithm of SER decreases linearly as a function of the number of antennas. Additionally, a saturation appears at high SNR for PAM constellations of order larger than two, due to the uncertainty on the channel energy. Simulation results show that ED, with a much lower complexity, achieves promising performance both in Rayleigh fading channels and in sparse channels

Enhancing the bit error rate performance of ultra wideband systems using time-hopping pulse position modulation in multiple access environments

Ultra-Wide Band (UWB) technology is one of the possible solutions for future short-range indoor data communication with uniquely attractive features inviting major advances in wireless communications, networking, radar, imaging, and positioning systems. A major challenge when designing UWB systems is choosing a suitable modulation technique. Data rate, transceiver complexity, and BER performance of the transmitted signal are all related to the employed modulation scheme. Several classical modulation schemes can be used to create UWB signals, some are more efficient than others. These schemes are namely, Pulse Position Modulation (PPM), Pulse Amplitude Modulation (PAM), Binary Phase Shift Keying (BPSK), and On-Off Keying (OOK) are reviewed. In the thesis, the performance of PPM system, combined with Time Hopping Spread Spectrum (THSS) multiple access technique is evaluated in an asynchronous multiple access free space environment. The multiple access interference is first assumed to be a zero mean Gaussian random process to simulate the scenario of a multi user environment. An exact BER calculation is then evaluated based on the characteristic function (CF) method, for Time Hopping-Pulse Position Modulation Ultra Wide Band (TH-PPM UWB) systems with multiple access interference (MAI) in AWGN environment. The resulting analytical expression is then used to assess the accuracy of the MAI Gaussian Approximation (GA) first assumed. The GA is shown to be inaccurate for predicting BERs for medium and large signal-to-noise ratio (SNR) values. Furthermore, the analysis of TH-PPM system is further extended to evaluate the influence of changing and optimising some of the system or signal parameters. It can be shown how the system is greatly sensitive to variations in some signal parameters, like the pulse shape, the time-shift parameter associated with PPM, and the pulse length. In addition, the system performance can be greatly improved by optimising other system parameters like the number of pulses per bit, Ns, and the number of time slots per frame, Nh. All these evaluation are addressed through numerical examples. Then, we can say that, by improving signal or system parameters, the BER performance of the system is greatly enhanced. This is achieved without imposing exact complexity to the transceiver and with moderate computational calculations