Fallthrough Correlation Techniques for Arbitrary-Phase Spread Spectrum Waveforms

Abstract

The use of practically non-repeating spreading codes to generate sequence-based spread spectrum waveforms is a strong method to improve transmission security, by limiting an observer's opportunity to cross-correlate snapshots of the signal into a coherent gain. Such time-varying codes, particularly when used to define multi-bit resolution arbitrary-phase waveforms, present significant challenges to the intended receiver, who must synchronize acquisition processing to match the time-varying code each time it changes. This paper presents a series of options for optimizing the traditional brute-force matchedfilter preamble correlator for burst-mode arbitrary-phase spread spectrum signals, achieving significant computational gains and flexibility, backed by measurable results from hardware prototypes built on an Intel Arria 10 Field Programmable Gate Array (FPGA). The most promising of which requires no embedded multipliers and reduces the total hardware logic by more than 76%. Extensions of the core fallthrough correlator techniques are considered to support low-power asynchronous reception, underlay-based physical layer firewall functions, and Receiver-Assigned Code Division Multiple Access (RA-CDMA) protocols in Internet of Things (IoT)-caliber devices.

Evaluating HPA Effects on Chaotic Sequence Spread Spectrum Detectability

“…11 is how the composition of predistortion and amplifier distortion impact the quality of the intended receiver. Related work in [56] explores how mismatched filter reception (i.e., a non-matched filter) degrades the overall system performance for arbitrary-phase spread spectrum. The net impact is extremely low given the despreading process that consolidates a statistical selection of chips to a soft symbol estimate.…”

“…11, while phase distortions are more impactful, yet the composite effects of the AM-PM LUT and amplifier distortion are expected to be a near zero phase deviation. No receiver was employed as part of this experiment, yet extrapolation of results in [56] suggests a performance loss of less than 0.1 dB on the intended link.…”