Software Defined Radio Implementation of the Dual Link Algorithm in TDD Mode using USRP E310

Zhe Feng; Xing Li; Victor Palacios; Peter Mathys; Youjian Liu; Mingda Zhau; Xinming Huang; Xin Cai

Zhe Feng Department of Electrical, Computer, and Energy Engineering, University of Colorado at Boulder
Xing Li Department of Electrical, Computer, and Energy Engineering, University of Colorado at Boulder
Victor Palacios Department of Electrical, Computer, and Energy Engineering, University of Colorado at Boulder
Peter Mathys Department of Electrical, Computer, and Energy Engineering, University of Colorado at Boulder
Youjian Liu Department of Electrical, Computer, and Energy Engineering, University of Colorado at Boulder
Mingda Zhau Department of Electrical and Computer Engineering, Worcester Polytechnic Institute
Xinming Huang Department of Electrical and Computer Engineering, Worcester Polytechnic Institute
Xin Cai ISN Lab, Xidian University

Abstract

This paper presents challenges and the progress of implementing the Dual Link Algorithm in the fairly new USRP E310 software defined radio (SDR) in time division duplex (TDD) mode. The dual link algorithm that we designed previously aims to solve the interference problem in future dense cellular networks. The algorithm performs joint beam-forming matrix design for transmit signals of multiple transmitters, which are equipped with multiple antennas. The receivers can also be equipped with multiple antennas. The algorithm is the most efficient one we know to find a locally optimal solution to the weighted sum rate maximization problem. Our experiment uses four E310s to model two pairs of interfering users with two antennas at each transmitter and each receiver. In TDD mode, the distributed version of the dual link algorithm is an iterative algorithm with iterations between forward link and reverse link transmissions. The algorithm takes advantage of channel reciprocity to reduce complexity. Therefore, it requires that the same antennas are used for both transmission and reception, as well as a compensation for the differences in transmit and receive RF chains. This paper shares our experience with GNU Radio on using the two TRX ports in each E310 to transmit and then receive signals in network mode, where the signal processing is performed on computers.