OFDMA网络中基于用户协作的负载均衡机制

User cooperation-based load balancing scheme for OFDMA networks

在蜂窝小区中,利用用户在不同小区之间的切换实现负载均衡可以提高系统频率利用率,减小用户中断率。但是,高负载小区的边缘用户切换到低负载小区时信噪比会降低。提出了一种基于用户协作的负载均衡机制,在均衡小区间负载的同时,解决了小区边缘用户切换后信噪比降低的问题。所提机制中,轻负载小区的某个用户作为中继节点与重负载小区的被切换用户进行协作通信。被切换的边缘用户通过选择合适的"用户中继",保证了切换后的信噪比性能。推导了选择用户作为中继的必要条件,提出了最大化系统容量的用户中继选择方案。数值仿真结果表明,所提机制可以有效的提高被切换用户的吞吐量,从而证明被切换用户的信噪比性能没有损失。

In cellular networks handover-based load balance is a commonly used scheme for balancing the unevenly distributed traffic among different cells in order to improve the spectrum utilization. However, edge users shifted from the heavy-loaded cell to the light-loaded cell usually suffer from SNR degradation. This paper proposed a user relaying assisted load balance scheme to overcome this problem. In the scheme, the shifted user could select another user in the light-loaded cell as the relay node for cooperative transmis- sion. By selecting the appropriate ＂user relay＇, the SNR degradation could be effectively avoided. Further- more, we developed an analytical model, in which the necessary condition of the cooperative user selection was analyzed and the optimal user selection criteria for capacity maximization were derived, too. Numerical results showed that the derived cooperative user selection criteria could increase the shifted users＂ maximum throughput,which indicated the SNR degradation problem was solved.