Distributed cognitive radio network architecture, SDR implementation and emulation testbed

This paper presents a distributed cognitive radio network architecture for joint routing and spectrum access, its implementation with software-defined radios (SDRs), and its evaluation in a high-fidelity emulation testbed. CREATE-NEST, a comprehensive cognitive radio system, is built as an experimental prototype that provides a Cognitive Radio nEtworking ArchiTecturE (CREATE) for distributed support of cross-layer optimization in cognitive radio networks, and the Network Emulator Simulator Testbed (NEST) capability for plug-and-play cognitive network implementation with USRP N210 radios. CREATE deploys a full protocol stack with distributed coordination (no common control channel) and local network state information, and integrates neighborhood discovery, spectrum sensing and channel estimation with joint routing and channel access implemented with backpressure algorithm. The high fidelity, controllable and repeatable wireless testbed platform, NEST, supports USRP N210 radios communicating with each other through RFnest, a high fidelity wireless network emulation tool. RFnest provides realistic physical channel environments under various path loss, fading, delay, and mobility scenarios for cognitive networks and provides protocol design verification and evaluation over realistic RF channels with digitally controlled channel impulse responses. The CREATE-NEST implementation is distributed with plug-and-play devices running identical codes and scales up seamlessly. Extensive emulation testbed results are provided to verify the CREATE-NEST implementation.

I. Introduction

Spectrum resources are scarce but they are not efficiently utilized with static spectrum allocation. Cognitive radio paradigm answers this need by opportunistically discovering and using spectrum opportunities across time, space, and frequency. In a multi-hop communication setting, spectrum occupancy is time and location-dependent and therefore joint design of routing and spectrum access is needed with distributed implementation instead of using a common control channel (both a bottleneck and a single point of failure).