Robust Cognitive-Radio-Based OFDM Architecture With Adaptive Traffic Allocation in Time and Frequency

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.