| Since2007, the global mobile communications data showing explosive growth. According to statistics, from2008to2010, global mobile data services grew by522%. And according to authorities predict that in2016global mobile data traffic will grow18times to2011. The rapid growth of its high-speed and broadband wireless communication services feature allows the growing demand for spectrum resources, but also makes the problem of supply and demand of spectrum resources become increasingly prominent. According to the trend of rapid development of wireless mobile communication system, the next5-10years will face a large amount of spectral gap. To ensure the efficient use of spectrum resources, the need for use of the band between the effectiveness of broadband mobile services and broadcasting, satellite, weather, location, and other services were fully assessed, exploring the methods applicable to broadband mobile services in the band. Therefore, this article as a starting point to systems coexist, the main research based on the adjacent frequency band with different communication technologies and the same frequency band with the same communication technology:LTE wireless communication network and Wi-Fi wireless communication network and their spectrum utilization efficiency and propose targeted suggestions for improvement.In the scenario of adjacent frequency band with different communication technologies, this paper chose to work at1980MHz-2010MHz MSS bands (Mobile Satellite System) system and the possible future deployment of the2010-2020MHz TDD-LTE (Time Division Long Term Evolution) system to study the losses of LTE system capacity with two systems in the adjacent channel conditions, and then get the spectrum utilization efficiency of the band, in particular:Firstly, based on the traditional macro-cell structure, using Monte Carlo simulation method to build a LTE system-level simulation platform. Then, through the analysis to MSS system, based on the LTE system platform adds beam satellite communications earth terminal models. Finally, based on the above model, with the different density of MSS terminals, the different coverage patterns, and LTE system users under different terminals transmit power (including cellular edge users and regular users), we got spectrum utilization situation, and made specific suggestions for improvement.In the scenario of the same frequency band with the same communication technology, in this paper, we study both work in the2.4GHz band portable Wi-Fi devices and metro CBTC (Communication Based Train Control) system. Specifically:paper first get two communication devices coexist scene through analysis, and as a basis for the establishment of coexistent system model. Thereafter, through theoretical derivation we obtained the key factors that affect Metro CBTC system downlink communication-DCF (Distributed Coordination Function) protocol, and by controlling the number of variables method to quantify the affect to CBTC system with the number of Wi-Fi devices in the car and data frame length of Wi-Fi devices, the simulation results show that with the increase in the growth of portable Wi-Fi device data frames and the number of Wi-Fi devices in the car, CBTC system will have a high probability of interference due to severe forced outage. Based on simulation results and theoretical analysis, this paper puts forward a dynamic collision reduction back-off window DCF (Distributed Coordination Function) algorithm and a multi-channel real-time dynamic monitoring approach. The simulation results show that the algorithm greatly reduces the likelihood of the subway outage, and greatly improving the efficiency of spectrum use.In summary, this paper studies around the scenarios with the adjacent frequency band with different communication technologies and the same frequency band with the same communication technology with the problem that how to make efficient use of the frequency with MSS, LTE and Wi-Fi devices and metro CBTC systems coexist in scenarios. From the point of frequency selection that covers two adjacent channel and co-channel interference scenarios; from the standard view, covering the cellular communication systems, satellite communication systems, wireless local area network communication systems and specialty equipment these four categories; network types, the LTE cellular network covering this centralized networking architecture and portable Wi-Fi devices such a distributed network. Therefore, this paper implements a more comprehensive study of the spectral efficiency of common scenarios, and propose targeted improvement program, which provides a good opportunity for follow-up studies spectral efficiency. |
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