Software-defined Radio Testbed Research Articles

A CFO-Assisted Algorithm for Wireless Time-Difference-of-Arrival Localization Networks: Analytical Study and Experimental Results

Localization of wireless transmitters is traditionally done using Radio Frequency (RF) sensors that measure the propagation delays between the transmitter and a set of anchor receivers. One of the major challenges of wireless localization systems is the need for anchor nodes to be time-synchronized to achieve accurate localization of a target node. Using a reference transmitter is an efficient way to synchronize the anchor nodes Over-The-Air (OTA), but such algorithms require multiple periodic messages to achieve tight synchronization. In this paper, we propose a new synchronization method that only requires a single message from a reference transmitter. The main idea is to use the Carrier Frequency Offset (CFO) from the reference node, alongside the Time of Arrival (ToA) of the reference node messages, to achieve tight synchronization. The ToA allows the anchor nodes to compensate for their absolute time offset, and the CFO allows the anchor nodes to compensate for their local oscillator drift. Additionally, using the CFO of the messages sent by the reference nodes and the target nodes also allow us to estimate the speed of the targets. The error of the proposed algorithm is derived analytically and is validated through controlled laboratory experiments. Finally, the algorithm is validated by realistic outdoor vehicular measurements with a software-defined radio testbed.

Experimental Validation of Timing, Frequency and Phase Correction of Received Signals Using Software Defined Radio Testbed

Recently, almost all the wireless devices are being designed for the fast evolving technology of software-defined radios, which is a radio access technology that most of the signal processing components are implemented digitally in software rather than in hardware to redefine the functionality of components, reduce the cost and complexity of the systems. This paper presents a low cost, portable, and flexible frequency hopping signal record and playback system based on a general purpose software radio front end, the Universal Software Radio Peripheral N210 devices. Further, this paper addresses the different issues such as timing recovery, phase recovery and frequency correction. In addition to that various GNU schematics are created to show the effect of different signal processing blocks on a modulated signal and their corresponding outputs are presented in the view of time domain, frequency domain and waterfall sink.

On the effects of spreading sequence pairs over MIMO-STS systems

Previous studies have found that the Multiple Access Interference (MAI) effect is strongly associated with which sequence pairs are spread over Multiple-Input Multiple-Output Space-Time Spreading (MIMO-STS) systems. An improved method of determining which sequence pairs are to be spread is proposed. The choice of these pairs from the selected spreading code families results in a number of ways to mitigate the MAI effects. A Software Defined Radio (SDR) test bed system has been developed to evaluate the selected spreading sequences, in an attempt to mitigate the MAI effects over 2 × 1 MIMO-STS systems. The SDR test bed results reveal that, for a number of the spreading sequence families, improved transmission properties for asynchronous transmission can be achieved.

Cooperative Stepwise Relaying and Combining for Multihop Vehicular Wireless Communication

Vehicular ad hoc networks (VANETs) require cooperation among vehicles in exchanging information, which improves traffic efficiency and safety. Cooperative communication among these vehicles can significantly improve wireless communication performance. This paper proposes a novel cooperative scheme named cooperative stepwise relaying and combining (CSRC) for multihop VANETs, which utilizes low-order demodulations to partially demodulate high-order modulated signals cooperatively at intermediate relay vehicular nodes. Bit error rate (BER) probability is analyzed. The performance comparison among the proposed CSRC and conventional cooperative schemes is conducted through simulation and a software-defined radio testbed. The experiment results show that CSRC significantly improves the multihop VANETs' performance with cooperative communication.

Concatenated Coding in OFDM for Wimax Using USRP N210 and GNU Radio

A software Defined Radio (SDR) device employs a reconfigurable hardware (Universal Software Radio Peripheral-USRP) that may be programmed over-the-air or software (GNU Radio) to function under different Wireless standards. This paper analyzes the effect of various parameters such as channel noise, frequency offset, timing offset, timing beta, FLL (Frequency Lock Loop) bandwidth, Costas loop (phase) bandwidth, filter roll off factor and multiply const on OFDM signal in WiMAX physical layer with concatenated coding using SDR test bed. Concatenated coding is performed by suggesting RM coder and Convolutional coders as inner code and outer codes respectively. Moreover, bit error rate and symbol error rates performance are analyzed by varying bits per symbol, window size and modulation scheme. Results proved that BER and SER values are improved as modulation scheme size (M) is increased. OFDM signal transmission and reception is performed using USRP N210 and configured by GNU radio in the laboratory environment.