Research On The Key Technologies Of Cognitive Radio And Its Application In Home Base Station

Wireless communication technology plays an important role and has rapid development in recent years. However, the shortage of spectrum resources impacts on all kinds of wireless technology. In order to solve this problem, the cognitive radio technology has been studied extensively. The cooperative sensing in cognitive radio can overcome problems such as hidden terminal and unreliable performance effectively. Nevertheless, it still has to face several serious challenges that addressed as following:(1) the cooperative spectrum sensing needs reliable feedback channel, which is not consistent with the original intention. Minimize the needs of feedback channel and maximize the utilization have important research value;(2) the spectrum imbalances are prevalent in the typical cognitive radio systems. Due to the different conditions in different locations, cooperative sensing may not improve the performance but lead to the decline of the spectrum sensing accuracy. And also for spectrum sensing technology, there is another challenge:(3) spectrum sensing technology does not have any practical applications because of the policy, management and other restrictions. Therefore, how to apply these frontier technologies in the practical system is also one of the important points that worth to pay attention to. And this paper will aim to solve these three challenges that addressed as above.1. According to the usage of feedback channel resources, this paper includes the research of two aspects:reducing the amount of feedback data and improving the utilization of feedback channel. Firstly, this paper analysises the structure of optimal data fusion rule and the distribution of weighting factors. And then user reject algorithm is proposed:we try to reduce the consumption of the feedback channel resources through rejecting the unreliable users in cooperative sensing with the optimal data fusion rule. This algorithm would not induce little performance loss with rejecting part of users:about20%users are rejected, which means20%feedback data is reduced, if90%performance of the optimal data fusion rule is acceptable. Than, this paper focuses on the optimal data fusion rule designing when the feedback quantization bits number for each user is difference which is called differentiated feedback due to the relativity between feedback information quantization and the sensing performance. And we conclude some useful principle for the weighting factor calculation in optimal data fusion rule. Compared to traditional cooperation sensing, the cooperative sensing system adopts differentiated feedback would improve the performance significantly with the same feedback channel resources, especially under the low signal to noise ratio condition.2. To overcome the spectrum unbalance phenomenon, this paper proposes two cognitive radio user clustering algorithms. These algorithms try to utilize the spectrum unbalance phenomenon to improve the reliability of sensing. The first one utilizes the spectrum sensing data as the clustering basis and clusters according to the distribution function analysis. The clustering algorithm has very high adaptive aility as it clusters the users based on the spectrum sensing data. After the first algorithm feasibility of clustering based on coorelation between the spectrum conditions of different users, we proposed the second clustering algorithm which utilizes the information theoretic criteria. In addition to the advantages of the first algorithm, this algorithm could complete the clustering without any artificial settings and improve the clustering performance.3. We try to find the new applications of cognitive radio and spectrum sensing technology in the home base station, which is the most recommended indoor coverage approach. Nevertheless, this device is also facing a lot of interference problems while it provides good indoor coverage. Firstly, we analyze the complex interference scenarios of home base station, which is different from cognitive radio system. And the computer simulation proves the interference too. Based on the interference analysis, two home base station interference avoidance schemes have been proposed, which using spectrum sensing technology as the key technology. The both schemes take full advantage of information avialable to increase the capacity and avoid the inference. Compared to power control algorithm which is very popular, the proposed schemes have great comprehensive advantages in inference and capacity two aspects.