Research On Neighbor Discovery And Resource Allocation In Directed Ad Hoc Networks

Network has become an indispensable part of various fields in recent years.Due to the characteristics of no need to set up basic communication facilities,flexible mobile,fast networking,and no center,wireless ad hoc networks as a representative type of network are widely used in modern military,emergency communications and other scenarios.Different from omnidirectional antenna,directional antenna has the ability to resist interference and monitoring while increasing network capacity and channel bandwidth utilization.Therefore,directional ad hoc network is necessary to be used in scenarios with higher requirements for security and network capacity.The purpose of directional ad-hoc network is to allocate resources including time slot and channel through neighbor discovery,topology control,routing algorithm and other technologies,so that each node in the network can realize fast networking and timely communication.Among them,the neighbor discovery technology is the prerequisite and necessary condition of the entire directional ad hoc network process,and the use of resource allocation technology to obtain node resources is the fundamental purpose of the directional ad hoc network.Most of the existing neighbor discovery algorithms are based on the full blindness of the two-dimensional plane and are separated from the research of subsequent technologies such as resource allocation.To this end,the thesis studies he neighbor discovery technology and resource allocation technology based on narrow-beam directional antennas in single-beam mode and the two main contributions are as follows:Firstly,the thesis proposes a directional neighbor discovery algorithm suitable for two-dimensional plane and three-dimensional space under semi-blind conditions.The semi-blind situation refers to the situation in which rough location information of some nodes has been obtained in advance,which can greatly reduce the number of sectors that need to be scanned during the neighbor discovery process.The semi-blind directional neighbor discovery algorithm proposed in this thesis solves the problem of the performance degradation of the directional neighbor discovery algorithm caused by the sharp increase in the number of sectors and the inability to use opposite sectors to improve the performance of the algorithm.The thesis analyzes the performance of the semi-blind directional neighbor discovery algorithm in terms of maximum time-to-discovery(MTTD)and average time-to-discovery(ATTD).In the algorithm,a specific coding method is used to generate a receiving and sending sequence for the node and a sector scanning sequence with a mixture of determinism and randomness is designed which can make any two sectors in the network need to be scanned with N and M respectively be ensured that all possible sectors can be aligned one by one within the maximum discovery time interval(MTTD)and the average discovery time interval(ATTD)is lower than MTTD.In this thesis,the semi-blind neighbor discovery algorithm is simulated by MATLAB to verify the superiority of the algorithm.Secondly,the thesis proposes a resource allocation mechanism to assist neighbor discovery.This mechanism utilizes the powerful anti-interference and spatial multiplexing characteristics of narrow beam directional antennas and the one-factor decomposition theory of the complete graph to design a fairness in the semi-blind case and fully space division multiplexing in each time slot which can allocate the time slot and channel resources of the nodes in the network.In this mechanism,the neighbor discovery process and the resource allocation process alternate according to a certain ratio and a mechanism to assist neighbor discovery is designed which allows any two nodes to exchange their neighbor location information during the practice of sector alignment.If two nodes have indirectly learned the location information of each other,they can align the sectors in the pre-allocated time slots for resource allocation to complete each other's neighbor discovery while communicating.Through this method of inter-node cooperation,opportunistic neighbor discovery is linked with deterministic resource allocation which can makesure the timely communication between nodes.Besides,it can also ensure the node fairness and network throughput while reducing the need for neighbor discovery.The thesis uses MATLAB to simulate the resource allocation mechanism which assists neighbor discovery to verify the superiority of the mechanism.