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Performance of Cognitive Radio Systems Based on Multiple Orthogonal Sequences

다중 직교 시퀀스를 이용한 인지 무선 시스템의 성능

  • Lee, Kyung-Sun (Department of Wireless Communications Engineering, Kwangwoon University) ;
  • Kim, Yoon-Hyun (Department of Wireless Communications Engineering, Kwangwoon University) ;
  • Kim, Jin-Young (Department of Wireless Communications Engineering, Kwangwoon University)
  • Received : 2011.12.02
  • Accepted : 2012.07.31
  • Published : 2012.08.31

Abstract

Ad hoc networks can be used under difficult conditions, where it is difficult to construct infrastructures, such as shadowing areas, disaster areas, war area, and so on. In order to support to considerable and various wireless services, more spectrum resources are needed. However, efficient utilization of the frequency resource is difficult because of spectrum scarcity and the conventional frequency regulation. Ad-hoc networks employing cognitive radio(CR) system that guarantee high spectrum utilization provide effective way to increase the network capacity. However, there is a problem that all CR user do not fairly use the primary user's idle bandwidth which has been sensed. In this paper, to solve this problem, we propose the spectrum sharing algorithm which uses the multiple orthogonal sequences based on the code division multiple access(CDMA). From the proposed algorithm, it is expected that system performance of CR based ad-hoc network is improved significantly and it can be applied to the implementation of CR based ad-hoc network system.

Ad-hoc 네트워크는 음영지역, 재난지역, 전쟁 시와 같은 통신 인프라가 구축되기 어려운 상황에서 유용하게 사용될 수 있다. 그러나 음성 및 데이터 서비스 등과 같은 무선 서비스의 제공을 위해 많은 양의 네트워크 용량이 필요하게 되지만, 기존의 제한된 주파수 자원에 따른 주파수 부족 상황 및 주파수 자원 정책의 규제에 따라 원활한 주파수 사용이 어려운 상황이다. 이에 따라 높은 주파수 활용을 제공하는 인지 무선 시스템을 ad-hoc 네트워크에 적용하여 보다 다양하고 확장된 네트워크 서비스를 제공할 수 있다. 하지만 인지 무선 시스템을 통해 센싱한 1차 사용자의 유휴 대역을 모든 CR 사용자들이 공평하게 사용할 수 없다는 문제점이 있다. 이러한 문제점을 해결하고자 본 논문에서는 CDMA 방식의 다중 orthogonal sequence를 이용하여, 하나의 주파수 대역 내에서도 여러 명의 CR user가 간섭 없이 효율적인 주파수 대역을 활용할 수 있는 기법을 제안하였으며, 이를 통해 인지 무선 시스템에서의 성능 향상을 보여 준다.

Keywords

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