定向发送和定向接收的Ad Hoc 网络具有传输距离远、隐蔽性好等优势，但将传统
的网络层广播机制应用于该类Ad Hoc 网会产生广播包传输时延过大的问题. 针对该问题，提
出利用MAC 层D-TDMA 协议的预约子帧来缩短广播包传输时间的广播机制. 节点一旦与其
邻居交换改进的握手消息就可得知广播包传输的信息，直接与邻居节点预约广播包转发时间，
避免了因等待从父节点接收到广播包后再预约所带来的长时延问题. 仿真结果表明，相比于传
统网络层广播机制，所提出的MAC层广播机制能将广播包更快地传递给网络中所有节点，使
占用的时隙数更少.
Using directional antennas for both transmission and reception provides many
benefits for Ad Hoc networks such as longer transmission range and lower probability of
being detected. However, applying traditional broadcast mechanisms for network layers
to Ad Hoc networks will cause long delay problem. To deal with this problem, a broadcast
mechanism is proposed, which uses the reservation sub-frame in the D-TDMA MAC
protocol to reduce the time for delivering broadcast packets. Nodes make reservation for
forwarding broadcast packets after exchanging modified handshaking messages with their
neighbors. This can avoid long delay caused by waiting for receiving broadcast packets
from their parent nodes. Simulation shows that, compared to the performance of planting
traditional network layer broadcast mechanism into an Ad Hoc network, broadcast packets
can be transmitted to all nodes more quickly by occupying smaller slots by using the
proposed mechanism.
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