NeTS-WN: COGNET: Cognitive Radio Networks based on OFDM

认知无线电网络能够与授权用户共享无线频谱，但由于频谱的波动特性以及多样化的服务质量(Qos)要求，认知无线电网络带来了挑战。为了应对这些挑战，提出了一种基于正交频分复用(Ofdm)的频谱感知认知无线电网络(Cognet)。在Cognet中，主要研究了五个方面的研究方向：(1)首先，开发了一种频率捷变、宽带模拟/射频前端技术，该技术对非线性(射频/模拟IC设计)具有鲁棒性。(2)为了检测许可用户的存在，利用多用户网络固有的空间分集(频谱感知)，提出了一种快速检测方案；(3)为了选择最佳信道，提出了综合考虑信道信息、许可用户活动和应用需求的新决策方法(频谱决策)。(4)提出了一种双模频谱共享框架，使得认知无线电用户能够接入现有网络并进行协作(频谱共享)。(5)提出了一种频谱移动性管理框架，以实现认知用户在检测到许可用户(频谱移动性)时在信道之间切换时的高效操作。基于这些研究课题，开发了一个测试床来演示认知无线电收发信机上开发的协议。虽然Cognet最初被建议用于基础设施和adhoc网络，但由于预算的削减，关于adhoc网络的研究课题(用于Cognet自组织接入的协作频谱感知和用于Cognet自组织接入的频谱自适应路由恢复)将不被研究。

Cognitive radio networks enable the sharing of the wireless spectrum with licensed users, but impose challenges due to the fluctuating nature of the spectrum as well as the diverse quality-of-service (QoS) requirements. To address these challenges, a spectrum-aware COGnitive radio NETwork (COGNET) based on orthogonal frequency division multiplexing (OFDM) is proposed.In COGNET, five major research directions are investigated: (1) First, a frequency agile, wideband analog/RF front-end technology is developed, which is robust to non-linearity (RF/analog IC design). (2) To detect the presence of licensed users, a fast detection scheme is developed by exploiting the spatial diversity inherent to multi-user networks (spectrum sensing), (3) To select the best channel, novel decision methods are proposed that consider channel information, licensed user activities, and application requirements (spectrum decision). (4) A dual-mode spectrum sharing framework is proposed, which enables access to existing networks as well as coordination between cognitive radio users (spectrum sharing). (5) A spectrum mobility management framework is proposed to achieve efficient operations as cognitive users switch between the channels when a licensed user is detected (spectrum mobility). Based on these research topics, a testbed is developed to demonstrate the protocols developed on cognitive radio transceivers.Although COGNET was originally proposed for both infrastructure and ad hoc networks, due to the budget cut, research topics on ad hoc networks ("cooperative spectrum sensing for COGNET ad-hoc access" and "spectrum-adaptive route recovery for COGNET ad hoc access") will not be investigated.