Abstract: The IEEE 802.22 WRAN is the first standard which is based on the cognitive radio network. WRAN basically uses unused or white spaces within the television bands between 54 and 862 MHz, especially within rural areas where usage may be lower. One of the major challenges for WRAN is how to efficiently schedule both the spectrum sensing and data transmission simultaneously. This problem for signal transmission is termed as coexistence. In this paper we give an overview of WRAN and discuss some techniques to reduce coexistence.

Keywords: Cognitive radio Network (CRN), white space, spectrum sensing, coexistence.