The Resolution Mechanism Of Hidden Terminal In Broadcast Based On Analog Network Coding

In multi-hop wireless networks, wireless broadcast protocols are basic primitivemethods of communication and cornerstone of a variety of other wireless networksprotocols such as routing discovery topology confirm and ARP etc, which play animportant role in all network environments. The broadcast protocols are quite simple,which start with a node that has the information transmit to all nodes in networks. Butthe simple protocols are unreliability. Because of the lack of acknowledge mechanismand RTS-CTS handshake mechanism in wireless broadcast protocols, the hiddenterminal problem can’t be avoided or restored in wireless networks, which candeteriorate the entire networks performance, and bring a unpredictable disaster tonetworks.This paper basis on the above-mentioned matter and first introduces the causes ofthe hidden terminal problem and several kinds of classic algorithms which resolve thehidden terminal problem and the basic idea of reliable broadcast. Then this paperfocus on the theory of network coding which is a recent rising of network technologyand utilize analog network coding to solve the problem of packet collisions andpropose two hidden terminal resolution mechanisms which adapting to differentwireless network environments.(1) For the multi-hop wireless mesh networks whose nodes have unlimitedenergy and large memory space, we use the repetitive of the packet received correctlyand propose HB-CODE. The method utilizes that the node which has received apacket will produce a copy of the packet and then uses a special mechanism toconfirm that whether the packet in collision packets has been received. If the packethave been received then using network coding method decodes packet collisions, thenrestoring the original packet. Our evaluation shows that compared with the floodingprotocol, HB-CODE reduces the max delay of15%, an average of25%packet loss,improved broadcast network reliability and throughput.(2) For the hidden terminal problem in multi-hop wireless ad-hoc networks inwhich the nodes storage capacity is limited, because in HB-CODE only the one ofcollision packet has been received correctly, the node can recover them. so theHB-CODE requires a large amount of storage space. To further improve the packetloss rate, this paper propose NACK-CODE which initiatively creates coding opportunities and base on the idea of ZigZag and use NACK to solve the hiddenterminal in broadcast. The algorithm first manages the node which occurs packetscollision and has it send a NACK to nodes which are the last hop of collision packets,then has the nodes which are the last hop of collision packets have priority toretransmit the collision pocket, which ensures that the retransmit occur collision incollision node and the collision packets are same with the first collision packets. thecollision node can decode the collision packets and recover them with ZigZagalgorithm. Our evaluation shows that compared with the flooding protocol,NACK-CODE greatly reduce the packet loss rate, and the average packet loss ratereduce to50%, and greatly improves the reliability of the broadcast networks.