计算机系统应用  2018, Vol. 27 Issue (9): 236-242 PDF

Research on MAC Protocol for Cognitive Radio Networks
LI Xiao-Yan, ZHANG Yong, CHEN Lei
School of Electronic Information Engineering, Xi’an Technological University, Xi’an 710021, China
Foundation item: Research Plan Project of Bureau of Education of Shaanxi Province (2016JK1387); The General Program of National Natural Science Foundation of China (61271362)
Abstract: Following some rules, the Cognitive Radio Networks (CRNs) can be divided into several clusters, each cluster has a Common Control Channel (CCC) to exchange control information. The cluster-based CCC is one of the solutions to the problem of spectrum sharing on MAC protocol for CRNs. In order to validate the clustering structure, we propose a MAC protocol based on clustering. In our protocol, channel access time is divided into a sequence of superframes. Each period in superframes is corresponding to the operation of cluster node. This mechanism can make the cluster structure more robust to the primary users’ activities. Simulation results reveal that our proposed MAC protocol can achieve higher throughput and lower delay in high traffic conditions.
Key words: cognitive radio     MAC protocol     spectrum sharing     superframe

1 系统模型

 图 1 分簇的认知无线电网络

2 基于分簇的MAC层协议 2.1 MAC层超级帧结构

 图 2 超级帧结构

(1) 信标时段(Beacon period)

 图 3 信标时段在BC发送信标信息

① 时间同步信息, 例如时间戳;

② 簇和簇首节点的ID;

③ 为簇内各节点分配对应的时隙, 用于交换节点的控制信息;

④ 簇内CCC的信道安排以及其他的一些簇内控制信息.

 图 4 信标时段在CCC发送信标信息

(2) 频谱感知时段(Spectrum sensing period)

 图 5 频谱感知的时段结构

(3) 簇内通信时段(Intra-communication period)

 图 6 族内通信时段的结构

(4) 簇间-簇内通信时段(Inter-intra-communication period)

(5) 数据传输时段(Data transmission period)/邻居节点发现(Neighbor discovery)

2.2 MAC协议流程

 图 7 MAC协议流程

3 经验数据库及参数

C_xy 节点的地理位置;

Ci 信道i成为簇内CCC的次数;

ti信道i被节点用于数据传输的总时长;

Wi在信道i上传输的总的比特数;

tm 该条记录被修改的时间.

 ${t_i} = \sum\limits_{k \in T} {{t_k}}$ (1)
 ${W_i} = \sum\limits_{k \in T} {{w_k}}$ (2)

4 仿真分析

 图 8 在不同负载下的网络吞吐量

 图 9 在不同负载下的传输时延

5 结束语