Research On Outdoor Networking Technology For Conducting Fusion System

In recent years,with the development and maturity of communication technology and Internet technology,Location Based Service(LBS)has gradually become inseparable from people’s daily life,and various application scenarios based on location information cover all aspects of life.The Time&Code Division-Orthogonal Frequency Division Multiplexing(TC-OFDM)system discussed in this article is a ground positioning system that can realize the integration of communication and navigation,and can achieve high-precision indoor and outdoor Sewing positioning.In the TC-OFDM system,the positioning signal multiplexes the frequency resources of the communication signal and the hardware equipment such as the base station to co-site and broadcast on the same frequency,which can realize the normal operation of the communication network and precise navigation and positioning at the same time.In the outdoor wide-area positioning scenario,the TC-OFDM system may have problems such as interference between communication signals and positioning signals,auto-correlation interference of spreading codes,multiple coverage of base stations,and insufficient number of spreading codes.In this paper,aiming at the needs of outdoor large-scale base station networking in the TC-OFDM system,a new cellular positioning networking model is proposed,and a greedy algorithm based on secondary optimization is proposed to select a spreading code with better performance.For multiplexing between cellular networking modules.Depth-first and breadth-first algorithms are designed to allocate the selected spreading codes in the networking module.The main work and research results of the thesis are divided into the following parts:1.Starting from the characteristics of the co-band system,this article explains the positioning principle and main application scenarios of the TC-OFDM system.Based on the characteristics of the spreading code signal,this article deeply explores the generation process of the TC-OFDM spreading code.It also analyzes the various indexes that affect the positioning performance of spreading codes,including balance,autocorrelation and cross-correlation.It also analyzes and discusses the principle of TDOA positioning and multiple important indicators for evaluating positioning performance.2.Aiming at outdoor wide-area positioning scenarios,this paper proposes a new cellular networking scheme suitable for TC-OFDM systems.In the networking plan,the characteristics of the communication and conduction fusion system are fully considered.By controlling the upper and lower bounds of the side length of the cellular network,multiple coverage of the positioning signal is achieved,and the cross-correlation interference of the positioning signal in the area is eliminated.By controlling the power difference between the communication signal and the positioning signal,the positioning performance and the communication performance can be satisfied at the same time.Then,the Okumura-Hata path loss transmission model is used to theoretically analyze the constructed cellular network model and perform simulation verification.3.A new screening algorithm is proposed to optimize the spreading codes,and the selected spreading code groups that meet the performance are used for multiplexing among network modules.The balance,auto-correlation,and cross-correlation of spreading codes have a greater impact on the positioning performance.These three indicators are optimized through the idea of divide and conquer.The complexity of cross-correlation screening is exponential,so this article focuses on the algorithm and process of cross-correlation screening.When using the cross-correlation criterion to screen spreading codes,by abstracting the spreading codes into multiple vertices in graph theory,the cross-correlation screening problem is abstracted into the problem of finding connected subsets in graph theory,and a second optimization based Greedy algorithm to filter spreading codes.After selecting a sufficient number of spreading code groups,the spreading codes need to be assigned to each base station of the networking module in turn.In this paper,the allocation process is modeled as a traversal problem in graph theory,and spreading codes are allocated through the traversal algorithm,which improves the system’s anti-multiple access capability.After simulation verification and experimental testing,the cellular network model proposed in this paper can well meet the requirements of the outdoor wide-area communication and conduction fusion positioning system,and the cellular base station layout structure has a good regular ductility,compared to other layouts.The method precision factor and positioning performance are better.The area with GDOP below 50 has a significant increase compared with other layouts,reaching 79%.The greedy algorithm based on secondary optimization proposed in this paper can select the spread spectrum code group that meets the conditions,and compared with the existing algorithm,the overall running time is shorter and it has better performance.In the two spread-spectrum code allocation algorithms proposed in this paper,the average values of the cross-correlation values of neighboring base stations reach-30.99dB and-30.87dB respectively,which are better than the average value of the cross-correlation values of the spread-spectrum codes.