双忙音媒体接入协议中的隐藏节点问题及其改进

Hidden Terminals in Dual Busy Tone Multiple Access and an Improved Solution

针对双忙音媒体接入(DBTMA)协议只能防止发送距离范围内隐藏节点的问题,提出了一种增强的DBTMA改进(EDBTMA)协议,以彻底消除大规模ad hoc网络中的隐藏节点问题.ED-BTMA协议特点有二,一是采用了双收发器结构,其中的一个物理信道(数据信道)为高带宽信道,可利用现有802.11a/g无线设备,二是采用了忙音自适应功率控制机制,这样接收节点根据发送节点的信号强度可动态调整忙音的发射功率,以完全覆盖接收节点周围所有的隐藏节点,并在接收数据的过程中保证接收节点不受隐藏节点的干涉.仿真结果表明,在改进协议下的网络吞吐量平均提高了48%.

DBTMA （dual busy tone multiple access） protocol is designed to solve both hidden and exposed terminal problems, but hidden terminals outside the transmission range of the receiver are out of control in the protocol. An enhanced protocol named EDBTMA is proposed, which can eliminate hidden terminals in large-scale ad hoc network. There are two key enhancements in EDBTMA different from DBTMA. Firstly, the dual transceiver is adopted in EDBTMA and the 802. 11a/g device is used for high-speed data channel. Secondly, the adaptive busy-tone power control scheme is used in EDBTMA. The receiver adjusts the transmission power of busy-tone according to received signal strength of the sender. All hidden terminals are covered by the busytone and no collisions occur during the reception of data packet. Simulation results show that EDBTMA solves the hidden terminals problem better than DBTMA and achieves 48% additional network throughput.