OUTAGE CAPACITY ANALYSIS OF MC-CDMA BASED ON COGNITIVE RADIO NETWORK

Abstract

Cognitive Radio Networks (CRN) are aimed at efficiently utilizing the spectrum to solve the spectrum surge generated by large wireless node deployments. Such networks allow users to operate within the best frequency band available, ensuring smooth connectivity requirements during spectrum transitions. The spectrum can be used by both licensed (also called primary) and unlicensed (also called secondary) users. However, unlicensed users vacate the spectrum whenever demanded by the licensed users. This study presents the performance assessment of the Multi-Carrier Code Division Multiple Access (MCCDMA) based cooperative CRN over Rayleigh fading channel. The proposed network scenario consists of Primary Transmitter (PT) and Primary Receiver (PR) pairs as well as a group of Secondary Transmitters (STs) and Secondary Receivers (SRs). A PT communicate with PR using inactive ST/SR and only one active ST may transmit data at the same time slot using the licensed channel of the PT, if the transmitted power of ST does not exceed predefined interference threshold. Analyses are carried out in order to obtain the expressions for the Signal to Noise plus Interference Ratio (SNIR) expressions of MC-CDMA systems. Based on the analytical models, a closed-form expression for the outage capacity as well as the outage probability over Rayleigh fading channel was derived. The analysis is further extended to derive SNIR of cooperative systems using Amplify and Forward (AF) or Decode and Forward (DF) relaying system. Finally, the performance of the proposed system is evaluated, showing changes in performance over state-of-the-art systems. In outage probability analysis, a close match has been found between simulation and numerical results and it depends primarily on the number of antennas being used in the PT/PR and ST/SR, and max interference temperature limit. The outage probability reduces (more than 3 dB) if the number of antennas increases (from 2x2 to 4x4) and interference temperature reduces. As selected ST/SR nodes are identified between PT and PR, the power analysis demonstrates efficiency improvement. If the active ST is situated farther away from the PR, the outage capacity of PU over Direct Link (DL) transmission as well as the cooperative relay link increases as a result.