Research On Some Key Technologies Of Aeronautical Ad Hoc Networks

As the future direction of aeronautical communication systems,aeronautical ad hoc network(AANET)has got extensive concerns in industry and academia.AANET is mainly comprised of aircraft in the airspace,and is a new sort of mobile ad hoc network(MANET)whose airborne nodes move fleetly and corresponding topology changes rapidly.Besides the characteristics of MANET,i.e.,the network is self-organized without central control points and every node is equal,AANET has some unique attributes including large-scale,high dynamic topology,limited bandwidth,strict quality of service(Qo S)requirements,time-varying channel,frequent blackouts and high link error rates.Thus,compared with general wireless networks,it is more challenging to provide aeronautical communication service with Qo S guarantees in AANET.In order to resolve the challenges posed by AANET,this dissertation studies some technologies of AANET which include topology control,medium access control(MAC)protocol,transport protocol and distributed bandwidth allocation.The main contents of this dissertation can be summarized as follows:(1)The state of the art and future trends for aeronautical communication systems in military and civil aviation are summarized.Through analyzing application scenarios in the future airborne networks with AANET technology,some key technologies of AANET are summarized.(2)AANET suffers from frequent network partitioning in the highly-dynamic environment,which may affect the operation of network applications.A topology control algorithm is proposed to realize the network fault-tolerant against link or node failures.In the algorithm,additional relay nodes are required for constructing such a fault-tolerant network.As airborne nodes move,relay nodes need to move as well in order to re-establish the topology as quickly as possible.Relay movement control problem is abstracted as a minimum cost feasible moving matrix(MCFM)problem.Based on the MCFM problem,relay nodes' velocities are calculated such that the network can keep fault-tolerance and have a certain level of reliability and survivability during the running time.(3)Due to the rapid-changing topology and limited spectrum allocated to AANET,a spatial reuse TDMA(STDMA)based MAC protocol is proposed for AANET.The protocol is an extension of TDMA where the capacity is increased by spatial reuse of the time slots,i.e.,a time slot can be shared by radio units geographically separated so that small interference is obtained.The protocol dose not need central control points and runs in parallel at every node in a distributed manner.The result shows that the protocol can work well in the highly-dynamic aeronautical environment.(4)AANET has some unique attributes including instable channels,frequent blackouts and high link error rates.To satisfy the communication requirements in AANET,a fountain code-based multipath transport protocol is proposed for it.Fountain code is employed as packet-level forward error correction(FEC)code to recover from data loss and avoid retransmissions.Aircraft commonly have two or more heterogeneous network interfaces which offer an opportunity to form multiple communication paths between any two nodes in AANET.The proposed protocol counters the volatility of a single path by transmitting data across different paths intelligently and leverage diversity among paths to yield stable and high goodput.(5)Most of traffics generated in AANET are non-elastic traffics which are typically sensitive to assigned bandwidth and transmission delays.As a distributed network,AANET does not have central control points.Thus,a Qo S-based distributed bandwidth allocation mechanism is proposed for AANET.The mechanism is implemented in transport layer and uses additive-increase multiplicative-decrease(AIMD)congestion control approach.By adjusting AIMD parameters of the flows based on their bandwidth requirements,the mechanism can implement the bandwidth allocation at the sender side and no central node is needed.