Robust Cognitive‐Radio‐Based OFDM Architecture with Adaptive Traffic Allocation in Time and Frequency

• Published in: ETRI journal Vol. 30; no. 1; pp. 21 - 32
• Main Authors: Kim, Nak‐Myeong, Kim, Mee‐Ran, Kim, Eun‐Ju, Shin, Su‐Jung, Yu, Hye‐In, Yun, Sang‐Boh
• Format: Journal Article
• Language: English
• Published: 한국전자통신연구원 01.02.2008
• Subjects: Cognitive radio; data repetition over frequency; orthogonal frequency division multiplexing (OFDM); time spreading; 전자/정보통신공학
• ISSN: 1225-6463; 2233-7326
• DOI: 10.4218/etrij.08.0106.0253

Cognitive radio (CR) has been proposed as an effective technology for flexible use of the radio spectrum. The interference between primary users and CR users, however, becomes a critical problem when they are using adjacent frequency channels with different transmission power levels. In this paper, a robust CR orthogonal frequency division multiplexing (OFDM) architecture, which can effectively suppress interference to nearby primary users and overcome adjacent channel interference (ACI) to the CR user, is proposed. This new approach is characterized by adaptive data repetition for subcarriers under heavy ACI, and adaptive time spreading for subcarriers near the borders of the CR user's spectrum. The data repetition scheme provides extra power gain against the ACI coming from primary users. Time spreading guarantees an acceptable interference level to nearby primary users. By computer simulation, we demonstrate that, under a CR environment, the proposed CR OFDM architecture outperforms conventional OFDM systems in terms of throughput and BER performance.