A Low Complexity Cyclostationary Detector for OFDM Signals

One of the key challenges for state of the art radio systems is enabling efficient utilisation of the Radio Frequency (RF) spectrum. Licensed frequency bands are often under-utilised in both time and geographical location and thus the opportunity exists for secondary users to transmit in these bands, provided that they do not interfere significantly with the operation of the primary licensed user. A proposed method for exploiting this opportunity is Cognitive Radio (CR) wherein the secondary user is able to modify its transmissions based on observation of the operating RF environment. Orthogonal Frequency Division Multiplexing (OFDM) is the enabling technology for many modern communications standards such as IEEE 802.11a (WiFi) and 4G Long Term Evolution (LTE). Therefore, facilitating robust and cost effective detection of OFDM signals is a key problem for the design of secondary user CR systems. In this paper, we derive and assess the performance of a low complexity detection scheme that exploits the inherent cyclostationarity of OFDM signals. We then present details of its implementation on a Xilinx Artix 7 FPGA and compare the resource cost of the proposed detector with another low complexity detection algorithm found in the literature.