Architecture and Implementation of Fading Compensation for Dynamic Spectrum Access Wireless Communication Systems

This paper proposes an efficient architecture and implementation of fading compensation dedicated to dynamic spectrum access (DSA) wireless communication. Since pilot subcarrier arrangements are adaptively determined in wireless communication systems with DSA, the proposed architecture employs piecewise linear interpolation to the channel response estimation for data subcarriers in order to increase the channel estimation accuracy. The fading compensation for an orthogonal frequency-division multiplexing (OFDM) symbol is performed within the time for one OFDM symbol to make increase of latency smaller. The proposed architecture guarantees real-time processing with 76？MHz or higher clock frequency. The FPGA implementation of the proposed architecture occupies 1,577 slices and works up to 121？MHz. 1. Introduction In ambient information society, the ICT infrastructure interacts with each person in order to make the one’s surrounding space more comfortable. In this kind of interaction, various types of information are exchanged, ranging from small size such as the control data of air conditioners and room lights to large size of data like video streaming. Here, wireless mesh networks that use unlicensed radio frequency bands have been the focus of attention as one of the ambient networks. Among various wireless mesh networks, IEEE 802.11 WLAN series and ZigBee using carrier sense multiple access with collision avoidance (CSMA/CA) are expected to achieve popularity due to their capabilities to interconnect. However the following problem arises by using the technique of CSMA/CA. Let us assume that there are two nodes, and , that use IEEE 802.11g [1] for the former and ZigBee [2] for the latter, and the radio resource that has requested partially overlaps with that of . In this situation, even if the node uses far fewer radio resources than node requests, the node judges that the band are not available in case the node performs transmission and does not start to transmit data despite the presence of many unused radio resources. This causes the degradation of total transmission performance of the heterogeneous wireless infrastructure. In order to solve this problem, the so-called cognitive radio systems have been proposed [3, 4], which introduce various techniques with dynamic spectrum access (DSA). These techniques are based on the concept of exploiting spatial and temporal spectrum white space. Among them, [4] proposed dynamic subcarrier selection technique based on CSMA/CA with orthogonal frequency division multiplexing (OFDM). In this technique, wireless