Zero-Crossing Modulation for Wideband Systems Employing 1-Bit Quantization and Temporal Oversampling: Transceiver Design and Performance Evaluation

Abstract

Next-generation wireless communications systems are anticipated to utilize the vast amount of available spectrum in the millimeterwave and sub-terahertz bands above 100 GHz to meet the ever-increasing demand for higher data rates. However, the analog-todigital converter (ADC) power consumption is expected to be a major bottleneck if conventional system designs are employed at these frequencies. Instead, shifting the ADC resolution from the amplitude domain to the time domain by employing 1-bit quantization and temporal oversampling w.r.t. the Nyquist rate is expected to be more energy-efficient.Hence, we consider a system employing 1-bit quantization and temporal oversampling at the receiver, which operates on a wideband line-of-sight channel. We present a practical transceiver design for a zero-crossing modulation waveform, which combines faster-than-Nyquist signaling and runlength-limited (RLL) transmit sequences. To this aim, we derive four fixed-length finite-state machine RLL encoders enabling efficient transmit signal construction and soft-demapping at the receiver. Moreover, we propose a soft-output equalizer, which approximates maximum a posteriori RLL symbol detection. We evaluate the system performance in terms of peak-to-average-power ratio, coded block error rate, and a lower bound on the spectral efficiency (SE) w.r.t. a fractional power containment bandwidth. Our numerical results show that SEs of up to 4 bit/s/Hz are achievable with the presented transceiver design.

State Machine-based Waveforms for Channels With 1-Bit Quantization and Oversampling With Time-Instance Zero-Crossing Modulation

“…To obtain the autocorrelation function, the TI ZX modulation system is converted to a finite-state machine where the current output values are determined only by its current state which corresponds to an equivalent Moore machine [18]. For M Rx = 3, one symbol in terms of two bits is mapped in one output pattern, so ̺ = 4 and n s = 8 different states are presented.…”

Comparing Iterative and Least-Squares Based Phase Noise Tracking in Receivers with 1-bit Quantization and Oversampling

“…The stream of the complex valued transmit symbols x[l] is formed by using such RLL sequences for the real and the imaginary component separately. The minimum runlength constraint is chosen as d = Mtx−1 [11]. Note that the choice of Mtx defines the grid on which zero-crossings of the transmit signal can be placed.…”

“…To evaluate if the additional step of utilizing iterative algorithms is worth the computational effort and the increase in latency, the influence of the phase estimation on the system performance needs to be evaluated. For this we employ a system nearly identical to the one described in [11] using finite-state machine based RLL codes with a minimal run-length of d = Mtx − 1. The presented algorithms are used to track the phase, which is corrected in the analog domain.…”

“…The presented algorithms are used to track the phase, which is corrected in the analog domain. Then a lower bound on the achievable spectral efficiency (SE) is evaluated by empirically estimating the mutual information between the RLL encoder input bits and the log-likelihood ratios at the RLL decoder output as in [11,Section V].…”

On Information Rates over a Binary-Input Filtered Gaussian Channel

“…Those systems are usually implemented by some form of Pulse Width Modulation (PWM), Pulse Position Modulation (PPM), or similar schemes, operating over Gaussian noise channels [1], [2], [3]. Communication systems with binary transmitted signals are of recent practical interest in millimeter-wave wide-band applications, e.g., [4], [5].…”