Adaptive High Throughput CDMA-based Wideband Waveform with Robust Timing and Frequency Synchronization for SDR-based Tactical Networks

Abstract

The future tactical systems require network based seamless communication with precise, ac- curate and reliable information. To achieve this end, a multi-mode high throughput CDMA- based wideband networking waveform for software de ned radio is proposed. The proposed waveform has several di erent modes of operation and the maximum achievable throughput of 17.2 Mbps. Novel algorithms for the waveform's physical layer transmitter and receiver including sampling clock recovery, burst detection, and carrier frequency o set estimation and compensation are proposed. For Sampling clock recovery, a novel three stage Mod- i ed Square Timing Recovery (MSTR) algorithm is proposed. For burst detection, two novel algorithms based on Time Domain Repetitive (TDR) and Di erentially Modulated (DM) training sequences are proposed. For carrier frequency o set estimation, a novel algorithm based on modi ed FFT and quadratic interpolation is proposed. A novel two stage carrier frequency o set estimator with improved performance is also proposed which consists of Maximum Likelihood Data Aided (MLDA) estimation and Sample-by-Sample Residual O set (S2RO) estimation stages. To reduce the packet re-transmissions overhead and achieve better throughput, a novel link adaptation technique is proposed, which is based on fuzzy inference system by considering Quality of Service and throughput requirement of user/application. The throughput adaptation is achieved by changing the modulation technique and the number of multicodes assigned to each user. The novelty of the pro- posed algorithms is selected by considering the implementation a nity. The performance improvement of the proposed algorithms is demonstrated by comparing them with a set of known existing methods. It is shown through simulation results that the proposed algorithms are superior in terms of performance, throughput and computational complexity. The pro- posed algorithms are implemented using Field Programmable Gate Array and Digital Signal Processor on SDR platform. Actual results from hardware are compared and veri ed with the simulation results to demonstrate the e ectiveness of the proposed techniques. This iv wideband SDR waveform based on the proposed algorithms nds many real world applica- tions in both the tactical and commercial scenarios. Some examples include biometrics, video conferencing, IP data, le transfer, situational awareness, messaging, voice push to talk, simultaneous voice and data transfer.