Study On Hybrid TDOA/AOA Location Algorithms Of The Mobile Terminal In Mobile Communication Network

With the development of communication technology, the wireless location technique in wireless cellular network has obtained more and more attention. Through the location system, people can get information about the position of a MS operating in a geographical are and process that information to form a location estimate. There are several potential applications of wireless location system, such as public safety, location-sensitive billing, cellular system design and resource management and intelligent transportation system.In July 1996 US Federal Communication Commission(FCC) issued the E-911 mandate stating that all carriers of mobile communication must provide the geolocation of an emergency 911 caller to the appropriate public safety answering point. In Oct. 1999 the FCC issued the E-911 Third report and Order, which adopt the revised standards for Phase 11 location accuracy For network-based solutions:100 meters for 67% of callers, 300 meters for 95% of caller。But in cellular environments, because of the influence of several adverse factors, such as multipath, non-line-of-sight propagation, noise, interference and channel frequency characteristics, the measurements attained from methods at present inevitably have errors, the performance of location algorithm may be significantly degraded and the position estimation of MS is biased. So it becomes the focus on how to utilize existing network resource to achieve locate mobile station by low cost.By analyzing the previous research in wireless location extensively, aimed at the core question of improve the accuracy of MS location, many methods are discussed in detail. The TDOA technique is one of the most promising position location techniques for cellular-type wireless communication system, which can provide accurate position location information using the existing cellularinfrastructure without requiring additional hardware and software implementationwithin the mobile unit. So this thesis aim at the research of wireless location algorithm based on time-related measurements in Wire Cellular Network.First of all, the thesis introduce the development of TDOA arithmetic and TDOA arithmetic. And mainly expatiate the broad sense mutual TDOA parameter estimating arithmetic and MUSIC_LIKE AOA parameter estimating arithmetic. The thesis also prove the advantage of the arithmetic in terms of theory. And indroduce the new TDOA estimating module in different wireless channel environment. The new module analyze the Stat characteristic of the NLOS error and deduce the formula of the Stat characteristical variable. The new method can deal with TDOA measuring value simplely and weaken the NLOS influence. This can improve the precision of orientation.Whereafter the thesis put forward the maths model of TDOA hyperbola equation. And mainly introduce two kinds of TDOA orientation arithmetic: Taylor method and Chan method. And introduce the other arithmetic briefly. The thesis emulate the arithmeticse during different base stations and get the capability evaluation. Test prove Taylor and Chan arithmetic have better precision and can be carried out easily. But the arithmetics have themselvise shortage in different base stations. So we need improve the orientation arithmetic for fulfiling the E-911 request.Because single orientation arithmetic has its localization. So we use TDOA/AOA hybrid orientation arithmetic. The arithmetic only needs two base stations complish orientation. But because TDOA and AOA measuring value are often unexact. So the thesis put forward three or more base station orientation arithmetic. The thesis analyze Chan ,Taylor and Kalman arithmetic and put forwatd two kinds of hybrid orientation arithmetic. Proving their advantage in term of theory.One kind of arithmetic is Kalman TDOA/AOA hybrid orientation arithmetic. It needs the initial value of the mobile station and repeatedly calculates the location value in term of Kalman filter. Finally get the exact location. This arithmetic needs consume more time and can get better location result in less NLOS influence. When AOA value is more precise, the operation time will decrease more and the orientation result will be more precise.The other kind of arithmetic is Chan TDOA/AOA hybrid orientation arithmetic in term of attenuation gene. Because the true channel environment is NLOS. So for reducing error influence, we add the steepest grad arithmetic to Chan TDOA/AOA hybrid orientation arithmetic. In calculation we setup the gene's least value and renew the attenuation gene equation ceaselessly. Thereby get exacter TDOA value and mobile station location. This arithmetic can combine the advantage of Chan and attenuation gene arithmetic. It use twice WLS and don't need the original location value. Emulation prove it can better reduce the influence of NLOS comparing to other TDOA/AOA hybrid orientation arithmetic and get better orientation precision.After emulating the two kinds of hybrid orientation arithmetic, we find their precision is better than Taylor arithmetic. When AOA measuring value is exacter, TDOA/AOA hybrid orientation arithmetic can have better orientation precision and successful probability comparing to single TDOA arithmetic and make use of the resource of beehive network sufficiently.