Study On Frequency Hopping Channel Allocation Algorithm In Cognitive Radio Networks

The new generation wireless communication technology should provide many kinds of services including data, speech, video services, which makes the enhancement of frequency efficiency necessary. In the current mobile communication systems, frequency spectrum resource allocation mainly adopts the fixed method whose structure is simple, and thereby easy to realize. However, it has a severe limitation that its frequency efficiency is quite low. The cognitive radio is one kind of sharing frequency spectrum resources intelligent sensation technologies. It can allocate the sensed frequency spectrum resources, including both the licensed and unlicensed frequency bands, which can obviously increase the potential frequency spectrum efficiency.Compared with the conventional frequency spectrum resource allocation approach, the cognitive radio frequency spectrum resource allocation approach can allocate frequency spectrum resources among the primary users (PUs) as well as the secondary users (SUs). If a secondary user can find the unlicensed idle frequency spectrum, it can be allowed to use the licensed channel to communicate, without affecting the original PU communications. Therefore, the cognitive radio frequency spectrum resource allocation algorithm can improve the overall frequency efficiency in an expanded mobile communication system.In the existing SU channel selection algorithms mostly use the stochastic algorithm, which have the possibility to take the unlicensed bad-conditioned channel and deteriorate the quality of SU. In order to solve this problem, this thesis proposed a new SU channel selection algorithm based on frequency hopping(FH) in the wide frequency band. This algorithm can guarantee that SU always chooses the best-state channel to communicate. The procedure of the algorithm is as follows: firstly, SU should sensate spectrum resources in a wider frequency band, then sort the available channel and transmit to the cognitive radio resources allocation center. The cognitive radio resources allocation center allocates SU the radio channel according to the FH pattern. The proposed SU channel selection algorithm not only uses the cognitive radio frequency spectrum resource allocation technique to increase the spectral efficiency, but also uses the FH technique to improve the signal to noise ratio (SNR) performance in fading channels. Based on the system model of combining cognitive radio and FH technique, this thesis derives the bit-error-rate (BER) performance analysis and throughput formula. The simulation results indicate that the proposed channel selection algorithm in cognitive radio networks can increase the overall spectral efficiency as well as improve the BER performance.