【摘要】：通信技術(shù)和移動(dòng)業(yè)務(wù)廣泛而成功的發(fā)展運(yùn)行,導(dǎo)致了包括3G、4G、WLAN、Wi MAX、LTE-A等各種無(wú)線通信技術(shù)被異構(gòu)融合部署形成異構(gòu)無(wú)線網(wǎng)絡(luò)。并且異構(gòu)網(wǎng)絡(luò)因其可以顯著提高單一網(wǎng)絡(luò)的服務(wù)保障和接入能力,近年來(lái),也被廣泛關(guān)注和研究應(yīng)用。再加上選擇接入某個(gè)網(wǎng)絡(luò)是用戶終端與該網(wǎng)絡(luò)建立連接前的首要步驟和關(guān)鍵準(zhǔn)備工作,是確定用戶發(fā)起業(yè)務(wù)呼叫后將使用何種網(wǎng)絡(luò)完成通信需求的重要行為和決定環(huán)節(jié)。故用戶依賴一個(gè)各方面性能突出而智能的網(wǎng)絡(luò)選擇策略,幫助他們完成接入網(wǎng)絡(luò)的選擇,成為異構(gòu)網(wǎng)絡(luò)環(huán)境中要解決的關(guān)鍵問(wèn)題之一。本文首先針對(duì)現(xiàn)有異構(gòu)網(wǎng)絡(luò)選擇策略很少將用戶特性和網(wǎng)絡(luò)特性全面聯(lián)合起來(lái)去設(shè)計(jì)選網(wǎng)算法這一現(xiàn)狀,研究了高移動(dòng)速度用戶和低移動(dòng)速度用戶在由宏基站和微基站構(gòu)成的雙層異構(gòu)網(wǎng)絡(luò)上的基于用戶終端的網(wǎng)絡(luò)選擇策略。因?yàn)橐苿?dòng)性是用戶最本質(zhì)的屬性,所以對(duì)高移動(dòng)速度用戶網(wǎng)絡(luò)選擇策略的設(shè)計(jì),會(huì)因?yàn)榧纫苊獠缓侠淼念l繁切換,又要綜合整個(gè)系統(tǒng)吞吐量性能的優(yōu)劣而復(fù)雜難求。再加上已有研究總是將基站位置建模為傳統(tǒng)正六邊形,忽略了實(shí)際覆蓋情景。面對(duì)這些問(wèn)題,本文結(jié)合隨機(jī)幾何理論建模異構(gòu)網(wǎng)絡(luò)場(chǎng)景,研究了微蜂窩上駐留時(shí)間可能會(huì)很小的高移動(dòng)速度用戶,和要連接至宏蜂窩上卻位于微蜂窩覆蓋區(qū)內(nèi)的一部分高移速用戶,他們?cè)诮尤脒x擇時(shí)的帶寬預(yù)留和帶寬分配問(wèn)題。該策略先用系統(tǒng)接入高移速和低移速終端的網(wǎng)絡(luò)容量減去網(wǎng)絡(luò)切換開(kāi)銷,得到關(guān)于全網(wǎng)絡(luò)收益的效用函數(shù),然后證明該效用函數(shù)的最優(yōu)解是關(guān)于限制條件的一個(gè)凸優(yōu)化問(wèn)題,并用梯度下降法的迭代過(guò)程,得到高移速和低移速用戶在宏、微蜂窩上接入選擇時(shí)的預(yù)留帶寬、分配帶寬和接入概率的最優(yōu)解。另一方面,考慮到傳統(tǒng)馬爾科夫決策模型在進(jìn)行重疊區(qū)域中實(shí)時(shí)/非實(shí)業(yè)務(wù)的垂直切換決策時(shí),通常會(huì)忽略業(yè)務(wù)QoS差異而導(dǎo)致整個(gè)網(wǎng)絡(luò)的資源利用不充分這一問(wèn)題,本文針對(duì)實(shí)時(shí)業(yè)務(wù)的垂直切換行為,給出其馬爾科夫決策過(guò)程中行動(dòng)集合的改進(jìn)結(jié)果,并將改進(jìn)后的馬爾科夫決策過(guò)程與我們重新設(shè)計(jì)的帶寬預(yù)留機(jī)制結(jié)合,提出一種基于全網(wǎng)絡(luò)的聯(lián)合呼叫接入選擇策略。仿真結(jié)果表明:本文研究的針對(duì)用戶終端的和全網(wǎng)絡(luò)的呼叫選擇策略優(yōu)化方案,在新呼叫阻塞率、切換掉線率、全網(wǎng)絡(luò)容量收益這幾個(gè)方面均有良好的表現(xiàn)和改進(jìn)。
[Abstract]:The extensive and successful development and operation of communication technology and mobile services lead to heterogeneous wireless networks such as 3GN 4G WLAN Wi MAX,LTE-A and other wireless communication technologies. Heterogeneous networks have been widely studied and applied in recent years because they can significantly improve the service security and access capability of a single network. In addition, choosing to access a network is the first step and the key preparation work before the user terminal establishes the connection with the network. It is also an important behavior and decision link to determine which network will be used to fulfill the communication requirements after the user initiates the service call. Therefore, users rely on an intelligent network selection strategy with outstanding performance in various aspects to help them complete the selection of access networks, which has become one of the key problems to be solved in heterogeneous network environments. In this paper, first of all, we focus on the fact that the existing heterogeneous network selection strategies seldom combine user characteristics with network characteristics to design network selection algorithms. The network selection strategies based on user terminals for high mobile speed users and low mobile speed users on a two-layer heterogeneous network composed of a macro base station and a microbase station are studied in this paper. Because mobility is the most essential attribute of users, the design of high mobile speed user network selection strategy will be complex and difficult because of avoiding unreasonable frequent switching and integrating the throughput performance of the whole system. In addition, previous studies always model the base station position as the traditional hexagonal, ignoring the actual coverage scenario. In view of these problems, this paper combines stochastic geometry theory to model heterogeneous network scenarios, and studies the high mobile speed users whose residence time on microcellular may be very small. And a portion of high speed users who are connected to a macro cell but are located in the microcellular coverage area, and their bandwidth reservation and bandwidth allocation problems in access selection. In this strategy, the network capacity of high and low speed terminals is used to subtract the network switching overhead, and the utility function of the whole network income is obtained. Then, it is proved that the optimal solution of the utility function is a convex optimization problem with restricted conditions. By using the gradient descent method, the optimal solutions of reserved bandwidth, allocated bandwidth and access probability for users with high and low moving speeds in macro and microcellular access are obtained. On the other hand, when traditional Markov decision models make vertical handoff decisions for real-time / non-real services in overlapped regions, the differences in service QoS are usually ignored, which leads to the insufficient utilization of resources in the whole network. In this paper, for the vertical handoff behavior of real-time services, the improved results of the action set in the Markov decision process are given, and the improved Markov decision process is combined with the bandwidth reservation mechanism redesigned by us. A joint call access selection strategy based on the whole network is proposed. The simulation results show that the optimization scheme of call selection strategy for user terminals and the whole network has good performance and improvement in the aspects of new call blocking rate, handoff drop rate and total network capacity income.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN929.5

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本文編號(hào)：2380339