【摘要】：新一代以O(shè)FDM(Orthogonal Frequency Division Multiplexing)和MIMIO(Multiple-Input Multiple-Output)技術(shù)為核心的LTE-Advanced通信系統(tǒng)對(duì)通信網(wǎng)絡(luò)的傳輸能力提出了更高的要求,因此需要提升單位傳輸帶寬上的數(shù)據(jù)傳輸速率,即提高系統(tǒng)的頻譜效率。另一方面,通信行業(yè)高速發(fā)展所帶來(lái)的高能耗問(wèn)題也引起了社會(huì)的廣泛關(guān)注。未來(lái)移動(dòng)通信與網(wǎng)絡(luò)技術(shù)的發(fā)展必須要面對(duì)能量消耗的挑戰(zhàn),要求在優(yōu)化網(wǎng)絡(luò)資源的同時(shí)降低單位業(yè)務(wù)量的能量消耗,實(shí)現(xiàn)綠色通信。如何降低移動(dòng)通信網(wǎng)絡(luò)所消耗的能量,提高移動(dòng)通信系統(tǒng)的能量效率(Energy Efficiency,EE),用盡可能少的能量傳輸盡可能多的數(shù)據(jù),已成為了當(dāng)前移動(dòng)通信研究領(lǐng)域一個(gè)新的熱點(diǎn)問(wèn)題。由于傳統(tǒng)的宏基站成本高,能耗大,而在蜂窩網(wǎng)絡(luò)中重疊部署一些低功率節(jié)點(diǎn)如中繼、微微基站、毫微微基站使得網(wǎng)絡(luò)異構(gòu)化,能夠增加網(wǎng)絡(luò)的覆蓋范圍,提高系統(tǒng)容量。異構(gòu)網(wǎng)絡(luò)中由于低功率節(jié)點(diǎn)能耗低,較之于部署宏基站能夠減少系統(tǒng)的能量消耗;而小基站一般部署在熱點(diǎn)區(qū)域或者蜂窩網(wǎng)絡(luò)的盲區(qū),距離用戶較近,信號(hào)傳輸?shù)膿p耗小,能夠提高用戶的服務(wù)質(zhì)量(QoS)。因此,部署異構(gòu)網(wǎng)絡(luò)將宏小區(qū)的流量卸載到小基站中是提高系統(tǒng)能量效率的可行方法。然而,新加入的網(wǎng)絡(luò)元素在傳統(tǒng)的蜂窩網(wǎng)絡(luò)中產(chǎn)生了新的小區(qū),宏小區(qū)和低功率節(jié)點(diǎn)小區(qū)、低功率節(jié)點(diǎn)小區(qū)之間形成許多小區(qū)邊緣,使得網(wǎng)絡(luò)中的干擾分布情形變得復(fù)雜。系統(tǒng)中用戶的接入小區(qū)選擇成為最基本的挑戰(zhàn),一方面運(yùn)營(yíng)商希望更多的用戶接入到低功率節(jié)點(diǎn),最大限度地利用小節(jié)點(diǎn),減少系統(tǒng)的能量消耗,提高系統(tǒng)容量;另一方面,由于低功率節(jié)點(diǎn)發(fā)射功率低,距離較遠(yuǎn)的用戶受到宏小區(qū)的嚴(yán)重干擾。因此,在異構(gòu)網(wǎng)絡(luò)中,需要提出一個(gè)有效的接入選擇方案來(lái)提高異構(gòu)網(wǎng)絡(luò)系統(tǒng)的能量效率。本文在宏基站和微微基站聯(lián)合部署的異構(gòu)網(wǎng)絡(luò)下,研究用戶的選擇接入策略對(duì)系統(tǒng)的性能影響,提出優(yōu)化系統(tǒng)性能的接入方案,設(shè)計(jì)基于動(dòng)態(tài)規(guī)劃、遺傳算法等優(yōu)化算法的接入機(jī)制,為異構(gòu)網(wǎng)絡(luò)場(chǎng)景下用戶的接入選擇提供有效的策略方案。在異構(gòu)網(wǎng)絡(luò)中,低功率節(jié)點(diǎn)分擔(dān)宏小區(qū)的流量的現(xiàn)象我們稱之為流量卸載(Traffic Offloading)。本文首先提出了在宏小區(qū)-微微小區(qū)聯(lián)合部署場(chǎng)景下易于實(shí)現(xiàn)的流量卸載算法——TO(Traffic Offloading)算法。TO算法是基于用戶的測(cè)量參數(shù)RSRP(Reference Signal Received Power)的接入選擇算法,該算法的主要思想是將宏小區(qū)用戶卸載到滿足RSRP和小區(qū)負(fù)載條件的微微小區(qū)中。由于在新型網(wǎng)絡(luò)中增加了很多的小區(qū)邊緣,小區(qū)邊緣的干擾較為嚴(yán)重,本文將部分頻譜復(fù)用技術(shù)(FFR,Fractional Frequency Reuse)與TO算法相結(jié)合,提出了TOFFR(Traffic Offloading based on Fractional Frequency Reuse)流量卸載算法。仿真結(jié)果表明,兩種流量卸載算法都能有效地提高系統(tǒng)的能量效率,而TOFFR算法性能更佳。動(dòng)態(tài)的流量卸載是本文接下來(lái)考慮的情形,基于此,本文將動(dòng)態(tài)的流量卸載分為即時(shí)流量卸載和延時(shí)流量卸載,并且依據(jù)用戶的卸載模型,對(duì)動(dòng)態(tài)流量卸載進(jìn)行動(dòng)態(tài)規(guī)劃問(wèn)題建模,將整體能效優(yōu)化目標(biāo)轉(zhuǎn)化成多階段接入決策的最優(yōu)化子問(wèn)題進(jìn)行求解。在該方案中,考慮了不同的時(shí)延參數(shù),利用用戶速率限制條件減少算法復(fù)雜度。仿真結(jié)果顯示,與基于RSRP的流量卸載算法相比較,基于動(dòng)態(tài)規(guī)劃的流量卸載算法能夠有效地提高系統(tǒng)的能量效率和流量卸載效率。頻譜效率(SE,Spectral Efficiency)也是衡量系統(tǒng)優(yōu)劣的主要指標(biāo)之一。本文將系統(tǒng)的能量效率和頻譜效率作為優(yōu)化目標(biāo),提出了SE-EE聯(lián)合優(yōu)化的接入方案。對(duì)于SE-EE的多目標(biāo)優(yōu)化問(wèn)題,首先利用層次分析法分析優(yōu)化目標(biāo)SE和EE的判斷準(zhǔn)則的相對(duì)重要性,計(jì)算得到SE和EE的相對(duì)歸一化權(quán)重系統(tǒng),從而將SE和EE的雙目標(biāo)問(wèn)題轉(zhuǎn)化為一個(gè)多項(xiàng)式的單一優(yōu)化問(wèn)題。然后利用遺傳算法求解得到系統(tǒng)能量效率和頻譜效率聯(lián)合優(yōu)化。仿真實(shí)驗(yàn)證實(shí),與最大化頻譜效率和最大化能量效率相比較,本文提出的SE-EE聯(lián)合優(yōu)化方案能有效地進(jìn)行能量效率和頻譜效率的折中。
[Abstract]:The new generation of the LTE-Advanced communication system based on the OFDM (Orthogonal Frequency Division Multiplexing) and the MIMIO (Multiple-Input Multiple-Output) technology has higher requirements on the transmission capability of the communication network, and therefore it is necessary to improve the data transmission rate on the unit transmission bandwidth, that is, to improve the spectral efficiency of the system. On the other hand, the high energy consumption caused by the high-speed development of the communication industry has also attracted wide attention from the society. In the future, the development of mobile communication and network technology must face the challenge of energy consumption, and it is required to reduce the energy consumption of unit traffic while optimizing network resources and realize the green communication. How to reduce the energy consumed by the mobile communication network, improve the energy efficiency (EE) of the mobile communication system, and transmit as much data as possible with as little energy as possible has become a new hot issue in the current research field of mobile communication. Because the traditional macro base station cost is high and the energy consumption is large, some low power nodes such as relay, pico base station and femto base station are overlapped and deployed in the cellular network so that the network is isomerized, the coverage of the network can be increased, and the system capacity can be improved. In the heterogeneous network, because the energy consumption of the low power node is low, the energy consumption of the system can be reduced compared with the deployment of the macro base station, and the small base station is generally deployed in the blind area of the hot spot area or the cellular network, the distance is close to the user, the loss of the signal transmission is small, and the service quality (QoS) of the user can be improved. Thus, deploying heterogeneous networks to offload traffic from a macro cell to a small base station is a feasible way to improve system energy efficiency. However, the newly added network elements create new cells in the traditional cellular network, and a number of cell edges are formed between the macro cell and the low power node cell and the low power node cell, so that the interference distribution situation in the network is complicated. the access cell of the user in the system is selected to be the most basic challenge, on the one hand, the operator wants more users to access the low power node, the small node is utilized to the maximum extent, the energy consumption of the system is reduced, the system capacity is improved, and on the other hand, the low power node transmitting power is low, The user farther from the distance is seriously disturbed by the macro cell. Therefore, in the heterogeneous network, a valid access selection scheme is needed to improve the energy efficiency of the heterogeneous network system. In this paper, under the heterogeneous network of the joint deployment of the macro base station and the pico base station, the influence of the user's access strategy on the performance of the system is studied, the access scheme for optimizing the system performance is put forward, and the access mechanism based on the optimization algorithm such as the dynamic programming and the genetic algorithm is designed. And provides an effective strategy scheme for the access selection of a user in a heterogeneous network scene. In a heterogeneous network, the phenomenon of the low power node sharing the traffic of the macro cell is referred to as Traffic Offloading. In this paper, the traffic offload algorithm, which is easy to implement in macro-cell-picocell joint deployment scenario, is proposed. The TO algorithm is an access selection algorithm based on the user's measurement parameter RSRP (Reference Signal Received Power), the main idea of which is to unload the macro cell user into the picocell meeting the RSRP and the cell loading conditions. In this paper, due to the addition of many cell edges in the new network, the interference of the edge of the cell is serious. In this paper, partial frequency spectrum multiplexing (FFR, Fractional Frequency Reuse) is combined with the TO algorithm, and the traffic offload algorithm of the TFFFR (Traffic Offloading based on Frequency Reuse) is put forward. The simulation results show that the two kinds of flow unloading algorithms can effectively improve the energy efficiency of the system, and the TOFD algorithm is better in performance. The dynamic traffic offload is the case to be considered in this paper. Based on this, the dynamic traffic offload is divided into real-time flow unloading and time-delay flow unloading, and the dynamic traffic offload is modeled according to the user's unloading model. And solving the optimization problem of the overall energy efficiency optimization target to the multi-stage access decision. In this scheme, different time delay parameters are considered, and the complexity of the algorithm is reduced by using the user rate limiting condition. The simulation results show that the dynamic programming-based traffic offload algorithm can effectively improve the energy efficiency and discharge efficiency of the system compared with the RSRP-based traffic offload algorithm. The spectral efficiency (SE) is one of the main indexes to measure the quality of the system. In this paper, the energy efficiency and spectral efficiency of the system are used as the optimization targets, and the access scheme of SE-EE joint optimization is put forward. In order to solve the multi-objective optimization problem of SE-EE, first, the relative importance of the decision criterion of the objective SE and EE is analyzed by the analytic hierarchy process, and the relative normalized weight system of SE and EE is calculated, so that the double-objective problem of SE and EE is converted into a single optimization problem of a polynomial. And then using the genetic algorithm to solve the joint optimization of the system energy efficiency and the spectrum efficiency. The simulation experiments confirm that the SE-EE joint optimization scheme proposed in this paper can effectively compromise the energy efficiency and spectral efficiency compared with the maximum spectral efficiency and the maximum energy efficiency.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN929.5

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