On Key Technologies And System Performance Evaluation In Evolution For UTRA FDD HSPA+

An exponential growth driven from the fields of telecommunication, Internet and indevidial communication is currently making a thicker catalogue containing a variety of newfangle traffic categories, which has motivated most of academic and industry researchers to search more new routes on how to improve service performance in a cost-efficient way. In order to extract satisfaction of being in a fast-paced growth of traffic requirements in market at present, international standard organizations are energetically promoting the development of next mobile communication technologies including UTRA FDD HSPA+(Universal Terrestrial Radio Access Frequency Division Duplexing High Speed Packet Access Evolution) featured by faster data rate, larger spectral efficiency, shorter latency, greater capacity as well as wider coverage which make it become an important rule in a boom of future mobile communication. This dissertation will be covering enhancement and optimization for part of key technologies in UTRA FDD HSPA+evolution along with the evaluation for the critical performance metrics. The target of this dissertation is to deeply understand these crucial technologies in UTRA FDD HSPA+evolution as well as to get an extra enhancement in order to get the better performance.The main body of this dissertation puts a premium on discussions and optimizations on three novel critical technologies in process of UTRA FDD HSPA+standardization evolution. We aim at enhancing and optimizing these key technologies to improve the system performance. The main contributions and contents of this dissertation are enumerated as follows:Firstly, closed loop transmit diversity in HSPA+uplink. This sub-section first gives a careful analysis on existing issues in current diversity resource allocation schemes. One of the notable problems is how to choose diversity resource to ensure a satisfactory performance. In the existing schemes, the diversity resource will be selected if it is able to provide the maximum effective gain on useful signal from target user to its serving base station, but ignoring the potential interference cost that will be brought to other users rather than the target user. If the diversity resource on which the impact of introduced interference is greater than that of effective gain on useful signal is chosen to implement diversity transmission, the whole system performance will predictably be lowered down. Therefore, we propose an improved scheme of allocating diversity resources which comprehensively considers the affect of both effective gain and introduced interference to reduce the interference level as well as enhance the system performance. When implementing it, we propose a modification to the existing rule for the allocation of diversity resources. That is to say, in addition to the effect of useful signal in the current rule, we further consider the effect of potential interference introduced by the usage of different diversity resources. After comprehensively evaluating the two-fold impact and reasonability, we accordingly give an optimized rule for diversity resource allocation, and further define the detailed parameters in this rule on the basis of different type of diversity resources. Through system-level simulation, we find that our scheme can lower the interference level, save the transmit power and improve the throughout performance, which illustrates the advantages of our scheme.Secondly, multi-flow transmission in HSPA+. This sub-section first explores some importance of implementing cross-cell coordination in multi-flow transmission. Lack of cross-cell coordination will account for unexpected cross-cell interference brought by the extra transmit flow to other users in serving area and limiting the anticipant performance gain from multi-flow operation. An effective cross-cell coordination scheme is developed to maximize system sum-rate as well as minimize packet sum-delay in multi-carrier multi-flow HSDPA network. The proposed scheme is able to carry out cross-cell coordination more reasonably and conveniently, which can achieve the expected performance under a relatively lower complexity. In order to enhance multi-factor concurrently, we first try to model this problem as a multi-objective optimization problem simultaneously maximizing sum-rate and minimizing sum-delay of data packet in system rather than only considering the rate-maximization. During implementing the cross-cell coordination, power allocation and cross-cell scheduling have been mainly considered in which there are two serial steps:intra-cell scheduling and inter-cell scheduling. Thereafter, considering the complexity of realization, we attempt to develop a heuristic method based on the theory of flow network and Minimum Cost Maximum Flow algorithm to solve the whole cross-cell scheduling with a relatively lower computation complexity. The simulation results show that the proposed cross-cell coordination scheme can improve performance of both sum-rate and sum-delay of packet with a reasonable tradeoff between the performance and complexity.Thirdly, co-channel heterogenous network in HSPA+. This sub-section first analyzes uplink-downlink imbalance and interference issues in HSPA+co-channel heterogenous network. Furthermore, range expansion skill by which uplink-downlink imbalance can be mitigated as well as a derived interference problem driven from range expansion is particularly introduced. Considering the network framework of HSPA+, we develop a distributed interference coordination scheme based on non-cooperative game and energy-efficiency requirement as well as user QoS constraint. Within our proposal, every decision entity makes a final decision on scheduling and power allocation to maximize its own utility only according to some local information in a distributed fashion. The proposed scheme can reduce power consumption, lower interference level as well as save energy within the whole system. We clarify the existence and uniqueness of the equilibrium for this game. Then, a closed-form best response of this game is derived. Meanwhile, we also propose a feasible implementation to realize our scheme in practice. The simulation results illustrate that our proposed scheme can prettily lower the interference level in HSPA+co-channel heterogenous network, enhance the efficiency of resource utilization and improve the average throughput of overall as well as edge users.