Study Of LTE Network Dynamic Spectrum Management Under The Condition Of Spectrum Coexistence

With the development of modern technologies and the progress of the times, the quality of life for many people has also improved rapidly.Due to the popularity of mobile end, the mobile traffic has been increasing fast. It has put an enormous pressure on the cellular mobile communication system. Because of the scarce resource of licensed spectrum, those operators have to satisfy the user needs by constantly improving the utilization rate of licensed spectrum and frequency range for a long time. The technology has the disadvantage of high cost and low efficiency. If the rich spectrum resources can be applied to the cellular system, it will not only reduce the cost but also offer better services.Hence, many people start to pay much attention to the unlicensed frequency range with rich spectrum resources. It should be noted that the operation of wireless access technology in the unlicensed frequency range is faced with the problems of irrational allocation of channel resource and same-frequency interference. The first urgent problem to be solved for the operation of unlicensed frequency range in the LTE system is to realize the harmoniums coexistence between LTE system and the network system as well as improve the utilization rate of spectrum resource.Aimed at the problem of spectrum coexistence between the LTE of unlicensed frequency range and original network, this paper has researched the spectrum sensing algorithm based on the transmitter and interference, the collaborative spectrum sensing algorithm and the spectrum sensing algorithm based on fractal box dimension. The advantage and disadvantage of each algorithm have been also analyzed.Besides having the advantage of simple algorithm and small amount of calculation work, the spectrum sensing algorithm based on fractal box dimension can be applied to the detection of spread spectrum signal.Moreover, the time for calculation can satisfy the need for real-time determination of CCA Slot in the Listen-Before-Talk mechanism. Hence,the spectrum sensing algorithm based on fractal box dimension has been chosen in this paper.In addition, the multi-channel and multi-system spectrum allocation strategy has been also researched. After researching the spectrum allocation algorithm based on graph theory, this paper has also proposed the two-round parallel allocation algorithm which can realize the two-layer parallel allocation. The self-adaptive adjustment strategy has been adopted to suit the network feature. The combination of channel-based parallel algorithm and parallel algorithm based on the maximal interference set can ensure the effectiveness and stability of the algorithm.Lastly, the single-channel and multi-system spectrum allocation strategy has been researched. The LTE self-adaptive backoff system based on spectrum aggregation has been proposed. Based on the features of network coexistence, spectrum coexistence and self-load, the self-adaptive backoff system can adjust the backoff time and maximal time of data transmission of LTE system dynamically. By realizing the fair sharing of license-free spectrum resource between LTE and the network in coexistence, it can achieve the spectrum coexistence under complicated environments of network coexistence and different loads.