LTE系统自适应软频率复用技术研究

提高小区边缘用户性能是蜂窝移动通信系统的经典难题.下一代蜂窝移动通信系统3GPP LTE通过有效的小区间干扰协调以及频率资源分配来改善小区边缘用户性能.提出一种自适应软频率复用算法，根据系统负载情况自适应地为各小区分配主、副载波及其发射功率，在实现系统吞吐量优化的同时保证小区中心和边缘区域速率需求.算法首先通过穷尽搜索和贪婪递减策略，获得单小区最优资源分配，然后在不同小区间迭代执行单小区算法直到系统吞吐量不变为止.仿真结果表明，算法通过多次迭代后，系统吞吐量保持不变并输出一种优化的资源分配方案.与同类频率分配算法相比，可以有效提升小区边缘用户的吞吐量，同时获得更高的系统容量，更适用于高速率的LTE系统.

An Adaptive Soft Frequency Reuse Scheme for LTE Systems

Enhancing cell edge user performance is an important and challenging issue for cellular mobile communication systems. The next generation cellular mobile system, 3GPP long term evolution (LTE), aims at improving cell edge user performance through effective inter-cell interference coordination (ICIC) and spectrum resource allocation schemes. An adaptive soft frequency reuse (ASFR) algorithm is proposed, aiming at optimizing the system throughput while guaranteeing the minimum data rate requirements for both cell center and cell edge regions. The ASFR algorithm can adaptively adjust the major and minor subcarriers, and their respective transmit power in each cell according to the system traffic loads. In the ASFR, the optimal resource allocation in each single cell is first determined by using exhaustive search and greedy descending methods. Then the single cell resource allocation is repeated iteratively among all cells until the system throughput does not change any more. Simulation results show that the ASFR algorithm yields an SFR resource allocation after a number of internal iterations. It is also shown that the ASFR algorithm improves the cell edge user throughput and achieves higher system throughput compared with several traditional frequency allocation schemes. These advantages reveal that the proposed algorithm is more preferred for the LTE system.