Wim A. Th. Kotterman

Over-the-Air Testing of Cognitive Radio Nodes in a Virtual Electromagnetic Environment

This paper provides an overview of ongoing research in over-the-air (OTA) testing for next-generation communication and data transmission devices with special consideration of cognitive radio (CR). Existing state-of-the-art techniques and their merits and limitations are discussed. We identify the requirements and issues for the OTA test in a virtual electromagnetic environment (OTAinVEE) which needs to address the more complex scenario of future networks, where interference emulation becomes a highly challenging task. A complex interference scenario arises due to the attempt to simultaneously utilize several opportunity dimensions such as frequency, time, direction (space), and polarization, in a dynamic manner in a multiuser scenario. Although MIMO-OTA testing addresses many limitations of single antenna-conducted test systems, more dimensions and parameters to be addressed in the new scenarios imply further increase in cost and complexity. Closed-loop OTA test setups for CR evaluation are discussed along with an overview of other test scenarios.

Over-the-air test strategy and testbed for cognitive radio nodes

In this paper, an over-the-air test strategy for evaluating cognitive radio nodes is presented. This technique allows to emulate the activities of primary and secondary users with respect to received power spectral densities, and the spatial structures of their radio channels. This enables an experimental evaluation of cognitive devices with directional and spectral sensitivity. This type of testing is more realistic than conducted tests, as it includes all antenna effects involved in the perception of the radio environment. A multi-level test procedure is proposed, which implements different levels of complexity in terms of the operation of the device-under-test, the synthetic radio environment, and the required complexity of the test setup. A proof of principle based on an experiment is presented.

Emulation of virtual radio environments for realistic end-to-end testing for intelligent traffic systems

We consider two approaches for real-time end-to-end over-the-air testing for intelligent traffic systems using virtual radio environments. One approach is based on coherent wavefield synthesis, while the other aims at emulating the essential features of a realistic radio channel in vehicular ad-hoc networks. Due to finite hardware resources, the former is limited to electrically small systems-under-test, while the latter is suited for typical vehicle-to-vehicle scenarios. Three major aspects of the emulation of radio environments in our facilities in Ilmenau, Germany, are described: 1. Emulation hardware, 2. Channel sounding, modeling, and feature extraction, 3. Emulation methods.