Research On Spectrum Occupancy Modeling And Access Schemes In Cognitive Radio

Cognitive radio has been recognized as one of the core technologies which can solve the problem of spectrum scarcity. Moreover, the study of spectrum usage model focuses on feature extraction from the spectrum usage of licensed users, and can provide support for the research of resource sharing strategies, performance evaluation of system and so on, which are based on cognitive radio. However, in the recent literatures, there was a lack of systematic and comprehensive study about spectrum usage model. As well, the research of cognitive radio was based on the assumption that the primary user model was already known, which was lack of measurements and verifications. In the context of cognitive radio, this article has studied the spectrum usage model based on measurement, and resource-sharing access strategy based on measurement and verification, which combines the air measurement of spectrum resource, the spectrum usage model of primary system and the access strategies in spectrum sharing context together, and completes the tasks of measurement, verification, modification and application of spectrum usage model. According to this main clue, we have finished that:(1)Design and configure the accurate measurement scheme. Measure the GSM downlink band which is widespread and representative continuously for a whole day. Analyze the usage of the target band in the target area. The measurement results show that the spectrum efficiency of the target band is high in the daytime and low in the nighttime. The maximum occupation rate is less than 44% in the time domain, and 36% in the frequency domain, which means that this band is very suitable for cognitive radio.(2)According to the analyses of the measurement data, some spectrum usage models whose characteristics are consistent with the spectrum usage pattern of the target band are studied and tested, including the queuing-based model, the ON-OFF model, the discrete-time Markov model and so on. Meanwhile, the measurement data provides supports to modify the model. The testing results show that, all the models above(with the modified ones) can describe the features of the spectrum usage from different angles more accurately.(3)The tested queuing-based model is chosen as the primary model to explore the spectrum sharing access schemes based on channel reservation. On the strength of the traditional approaches, our work expands the channel reservation schemes from integer to fractional. The simulation results show that, the two fractional channel reservation schemes we proposed act better than integral ones in flexibility and system performance. Identically, the fractional reservation schemes for hand-off users performs better than for primary users.Through the combination of measurement, spectrum usage modeling and application of the model, we have realized the following three tasks: the spectrum usage modeling based on measurement, the usage model modification based on measurement analysis and access schemes design based on accurate primary user model.