Abstract
This article addresses the impact of forward error correction when applied to the report channel transmissions of a centralized decision fusion cooperative spectrum sensing scheme designed to detect idle orthogonal frequency division multiple access (OFDMA) subchannels. The OFDMA signal is transmitted over slow frequency-selective multipath Rayleigh fading channels and sensed using the maximum eigenvalue detection test statistic. The decisions on the OFDMA subchannel occupancy are transmitted to a fusion center over report channels represented by a shadowed fading model combining a three-dimensional spatially correlated shadowing with a slow and flat multipath Rayleigh fading. Binary Bose-Chaudhuri-Hochquenghem (BCH) and Repetition codes are used to protect these decisions. Results show that shadowing correlation severely deteriorates the overall spectrum sensing performance and that error correction may not be able to protect the report channel transmissions. It can be even worse with respect to the system performance especially at low signal-to-noise regimes. In the situations in which error correction is effective, the Repetition code is capable of outperforming the BCH, meaning that the diversity gain may be more relevant than the coding gain when the spectrum sensing decisions are subjected to correlated shadowing.
Highlights
The scarcity of radio-frequency spectrum due to the unprecedented increased demand for new wireless communication systems and services has become a problem of paramount importance, especially in the case of wide-band communications
This article addresses the performance of a centralized decision fusion cooperative spectrum sensing (CSS) scheme designed for detecting idle orthogonal frequency division multiple access (OFDMA) subchannels in secondary user (SU) networks
Transmitter activity of 50% (PH0 = PH1 = 0.5); perform, in each SU, the local spectrum sensing over all OFDMA subchannels by means of the maximum eigenvalue detection (MED) test statistic computed from J = 120 received samples collected in each subcarrier, and for a predefined local decision threshold γ; report the coded or uncoded SUs decisions to the fusion center (FC) via orthogonal spatially correlated shadowed fading channels; perform channel decoding and make the global decision on a single OFDMA subchannel; compute false alarm and detection rates, which are the estimates of the associated probabilities
Summary
The scarcity of radio-frequency spectrum due to the unprecedented increased demand for new wireless communication systems and services has become a problem of paramount importance, especially in the case of wide-band communications. Typical logic operations are AND, OR, and majority-voting (hereafter denoted by MAJ) [8,9] In both centralized schemes, the global decision is informed back to the SUs, and the access algorithm adopted by the secondary network takes place. The three-dimensional (3D) spatially correlated shadowed fading channel model proposed in [14,15] is adopted in this article to encompass such impairments, and to yield a realistic assess of the spectrum sensing performance.
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