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With the limited wireless spectrum and the ever-increasing demand for wireless services, two issues are pressing and difficult: efficient spectrum utilization and heterogeneous traffic management. Throughput and utility maximization problems are proposed to quantify these two issues. To exploit the wireless spatial multiplex gain, concurrent transmissions, if controlled appropriately, can lead to overall higher network throughput as well as utility. The optimal scheduling and power control for concurrent transmissions in rate-adaptive wireless networks is a very challenging NPhard problem. In the thesis, we propose efficient power allocation and scheduling algorithms for concurrent transmissions which can improve network throughput and utility with fairness consideration. We first formulate the optimal power allocation and scheduling problem for network throughput and utility maximization individually, and convert the original non-convex problems into a series of convex problems using a two-phase approximation. Then, we propose power and channel allocation with fairness for network throughput maximization (PCAF-NTM) and for network utility maximization (PCAF-NUM) algorithms to solve the converted problems. Extensive simulation results show the substantial improvement in terms of both network throughput and utility, comparing to the previous scheduling algorithms. / Graduate

Abstract Wideband-CDMA (WCDMA) is a kind of third-generation wireless communication system. It can provide multi-rate services and fast transmission with wideband technology. To improve the solution of no enough wireless bandwidth currently, the 3G communication systems have been researched and developed in several leading countries recently. WCDMA adopts a kind of new spreading codes named Orthogonal Variable Spreading Factor codes (OVSF codes) that have advantages of dynamically variable rates and keeping orthogonality. OVSF codes can provide different data transmission rates by assigning codes with different lengths. By building a code tree, we can discuss some better schemes to assign available data rate. In this paper, we propose an efficient channel assignment scheme that can decrease the call blocking rate and complexity of channel reassignment procedure. Based on the properties of the binary code tree, we use code merge scheme to decrease channel reassignment rate and call blocking rate. This will efficiently improve the performance of channel assignment and spectral efficiency. Simulation results show that the proposed scheme has expected results.

This dissertation presents and develops the Intelligent Picocell as a solution for high bit rate, efficient bandwidth indoor wireless communication. The research has examined different aspects of the indoor radio propagation environment and system implementation in order to highlight key benefits of the proposed architecture. Explosive growth in demand for indoor wireless communications motivates research into this novel radio architecture. The architecture should be capable of tailoring capacity and coverage to the needs of the specific indoor environment, while maximising spectral efficiency. The Intelligent Picocell is based on an evolution of the distributed antenna concept to provide macrodiversity, microdiversity and interference cancellation. The architecture is fully scalable to large numbers of users and can provide plug-and-play operation, with no need for detailed system planning beyond the antenna locations. The research examines different aspects of picocell system performance and design, including: Investigation on the indoor radio environment. Through measurements, the effects of building features on path loss and shadowing are analysed and propagation models are proposed for simulating picocell systems. Analysis of the Intelligent Picocell architecture, two algorithms are proposed for interference reduction, one based on a distributed narrowband optimum combiner and the other on a dynamic channel assignment and allocation scheme. Through simulation, it was demonstrated that the mobile transmitted power for an Intelligent Picocell is lower than the power required in a distributed antennas system. It was also shown that the capacity of the system depends on the number of antennas distributed in the building. Key words: Intelligent picocell, adaptive antennas, diversity, distributed antennas, dynamic channel allocation, propagation measurements.

Efficient channel allocation in GSM communication is difficult and believed to be a performance bottleneck. This thesis is dedicated to studying the performance of GSM/EDGE networks in modern usage scenarios (surfing the web, chatting and streaming services) under the assumption that explicit channel allocation is not needed. Users are able to be (re-)allocated at any time without explicit signaling and the typically associated delay. The radio hardware of these users is identical to that of typically used devices and the theoretical peak performance is not affected. This allows the network to use the radio channels in a more efficiently way and the delays from signaling are reduced or eliminated. The thesis studies this problem by statistically modeling such usage scenarios and the resulting channel utilization patterns. The study finds that the latency can be reduced by 40-70% for typical radio hardware, and that network throughput can be improved by up to 20%. However, further studies are needed on the subject.

Pico-Cellular architecture fully reuses frequency to increase network capacity. However, it will increase the occurance of Handoff due to the small range of cell. Previous works in channel allocations can reduce blocking probability of handoff call, but it may increase blocking probability of new call. As a result, channel utilization is decreased because they can not adapt to network changes. In this thesis, we present a Dynamic Channel Allocation Mechanism with priority support. All channels and calls are divided into high and low priority. If there is no high_priority channel for high_priority call, high_priority call may downgrade its priority by sacrificing some QoS to utilize low_priority channels. We define two new array for network information status, one is next_cell state, and the other is the transition probability. Next_cell state is used to save prior M Cell_Ids where handoff calls may move to. Transition probability is used to save the probabilities for active calls moving to other neighboring cells. According to next_cell state and transition probability, we can accurately predict the probabilities for mobile hosts moving to other neighboring cells. Therefore, we can dynamically adjust bandwidth reservation requests sending to neighboring cells by the latest transition probability and the number of active calls in this cell. We analyze the proposed mechanism through a mathematical model. In the model, we build a four-dimension Markov Chain and use MATLAB[41] tool to evaluate blocking probability, channel throughput and utilization. We found out that blocking probability of handoff call can be decreased and channel utilization can be increased through the proposed channel allocation mechanisms with high and low priority support.

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In cellular networks, channels should be allocated efficiently to support communication betweenmobile hosts. In addition, in cellular networks, base stations may fail. Therefore, designing a faulttolerantchannel allocation algorithm is important. That is, the algorithm should tolerate failuresof base stations. Many existing algorithms are neither fault-tolerant nor efficient in allocatingchannels.We propose channel allocation algorithms which are both fault-tolerant and efficient. In theproposed algorithms, to borrow a channel, a base station (or a cell) does not need to get channelusage information from all its interference neighbors. This makes the algorithms fault-tolerant,i.e., the algorithms can tolerate base station failures, and perform well in the presence of thesefailures.Channel pre-allocation has effect on the performance of a channel allocation algorithm. Thiseffect has not been studied quantitatively. We propose an adaptive channel allocation algorithmto study this effect. The algorithm allows a subset of channels to be pre-allocated to cells. Performanceevaluation indicates that a channel allocation algorithm benefits from pre-allocating allchannels to cells.Channel selection strategy also inuences the performance of a channel allocation algorithm.Given a set of channels to borrow, how a cell chooses a channel to borrow is called the channelselection problem. When choosing a channel to borrow, many algorithms proposed in the literaturedo not take into account the interference caused by borrowing the channel to the cells which havethe channel allocated to them. However, such interference should be considered; reducing suchinterference helps increase the reuse of the same channel, and hence improving channel utilization.We propose a channel selection algorithm taking such interference into account.Most channel allocation algorithms proposed in the literature are for traditional cellular networkswith static base stations and the neighborhood relationship among the base stations is fixed.Such algorithms are not applicable for cellular networks with mobile base stations. We proposea channel allocation algorithm for cellular networks with mobile base stations. The proposedalgorithm is both fault-tolerant and reuses channels efficiently.KEYWORDS: distributed channel allocation, resource planning, fault-tolerance, cellular networks,3-cell cluster model.

In this thesis, we investigate several radio resourcemanagement (RRM) techniques and concepts in an indoorenvironment with a dense infrastructure. Future wireless indoorcommunication networks will very likely be implemented atplaces where the user concentration is very high. At these hotspots, the radio resources must be used efficiently. The goalis to identify efficient RRM techniques and concepts that aresuitable for implementation in an indoor environment. Handling the high level of co-channel interference is shownto be of paramount importance. Several investigations in thethesis point this out to be the key problem in an indoorenvironment with a dense infrastructure. We show that a locallycentralized radio resource management concept, the bunchconcept, can give a very high performance compared to othercommonly used RRM concepts. Comparisons are made withdistributed systems and systems using channel selection schemeslike CSMA/CA. The comparisons are primarily made by capacityand throughput analysis which are made by system levelsimulations. Results show that the centralized concept can give85 percent higher capacity and 70 percent higher throughputthan any of the compared systems. We investigate several RRM techniques to deal with thechannel interference problem and show that beamforming cangreatly reduce the interference and improve the systemperformance. Beamforming, especially sector antennas, alsoreduce the transmitter powers and the necessary dynamic range.A comparison is made between the use of TD/CDMA and pure TDMAwhich clearly shows the performance benefits of usingorthogonal channels that separates the users and reduces theco-channel interference. Different channel selection strategiesare studied and evaluated along with various methods to improvethe capability of system co-existence. We also investigate several practical measures to facilitatesystem implementation. Centralized RRM is suitable forguaranteeing QoS but is often considered too complex. With thestudied centralized concept the computational complexity can bereduced by splitting the coverage area into smaller pieces andcover them with one centralized system each. This reduces thecomplexity at the prize of lost capacity due to theuncontrolled interference that the different systems produce.Our investigations show that sector antennas can be used toregain this capacity loss while maintaining high reduction incomplexity. Without capacity loss, the computational complexitycan be reduced by a factor of 40 with sectoring. Theimplementation aspects also include installation sensitivity ofthe indoor architecture and the effect of measurement errors inthe link gains. The robustness against installation errors ishigh but the bunch concept is quite sensitive to largemeasurement errors in the studied indoor environment. Thiseffect can be reduced by additional SIR-margins of the radiolinks. The studied bunch concept is shown to be promising for usein future wireless indoor communication systems. It provideshigh performance and is feasible to implement. Keywords:Radio resource management, indoorcommunication, the bunch concept, centralized RRM, dynamicchannel allocation, channel selection, co-channel interference,power control, feasibility check, capacity, throughput, qualityof service, beamforming, downtilting, sector antennas,co-existence, computational complexity, sensitivity analysis,measurement errors, infrastructure, system implementation,WLAN, HiperLAN/2, IEEE 802.11.