| 摘要: |
| 解决ad hoc网络中隐藏节点问题、暴露节点问题的最终目的是减少节点间的冲突,提高网络空间复用率,从而提高网络吞吐量.现有MAC协议在解决隐藏节点问题时着重于彻底消除网络中的隐藏节点,忽略了网络空间复用率,即使能够彻底解决隐藏节点问题,也不能有效提高网络吞吐量.同样,现有协议在解决暴露节点问题时着重于如何允许暴露节点并行发送数据,忽略了暴露节点接收数据的问题,也影响了网络空间复用率.提出了一种高效的MAC协议e-MAC,协议采用两种方法提高网络空间复用率:首先,协议中接收节点根据接收到发送节点的信号强度动态调整忙音发射功率,使忙音恰好覆盖所有的隐藏节点,在彻底解决隐藏节点问题的同时,提高网络空间复用率;其次,隐藏节点接收到RTS消息后,通过判断RTS消息信号强度与信道中干涉信号的强度之比来决定是否接收数据,允许满足信噪比要求的接收节点接收数据,进一步提高网络空间复用率.仿真结果验证了协议的有效性,在任意拓扑结构下,e-MAC协议的平均吞吐量比DUCHA(dual channel access)协议高87%. |
| 关键词: Ad Hoc网络 隐藏节点问题 网络空间复用率 网络吞吐量 e-MAC |
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| 基金项目:Supported by the National High-Tech Research and Development Plan of China under Grant No.2005AA121130 (国家高技术研究发展计划(863)); the National Key Technology R&D Program of China under Grant No.2008BAH37B04 (国家科技支撑计划) |
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| e-MAC: A High Throughput MAC Protocol for Ad Hoc Networks |
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ZHANG Ke-Wang,PAN Yu,ZHANG Qiong,ZHANG De-Yun
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| Abstract: |
| Collision avoidance and spatial reuse are two important approaches to improving the throughput of ad hoc networks, and many MAC protocols are proposed to achieve these goals. In most MAC protocols, collisions are reduced by solving the hidden terminal problems, but the spatial reuse remains un-optimized in these protocols, which affects network throughput dramatically. Moreover, reception of exposed terminals is not allowed in current MAC protocols even if they can receive packets successfully, which leads to lower spatial reuse. In this paper, a high throughput MAC protocol named e-MAC is proposed. To improve the network throughput, two approaches are used in e-MAC. First, a power controlled busy tone is used to eliminate hidden terminals. The receiver adjusts the transmission power of busy tone, according to a received signal strength from the transmitter, so that the spatial reused is optimized while all hidden terminals are covered by a busy tone. Second, exposed terminals are allowed to receive when the ratio between signal strength of RTS (ready-to-send) and interference satisfies the SINR (signal to interference and noise ratio) requirements, which further improves the spatial reuse. Simulation results show that the average throughput of e-MAC outperforms that of DUCHA (dual channel access) by 87%. |
| Key words: ad hoc network hidden terminal problem spatial reuse throughput e-MAC |
