54 research outputs found

    Application of SDMA with scheduling for MIMO MC-CDMA

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    Incoming Beyond 3G systems provides high data rates by using several techniques including Beamforming. Convenient DRA design is required to optimize the capabilities offered by smart antennas. This paper is to presents a DRA algorithm based on the HSDPA of UMTS, including scheduling that exploit SDMA technique that was implemented in the ambit of the IST 4MORE project. Results shown cell throughput gain of SDMA compared to sectorized cells about 76%, and that SDMA gain will increase with user diversity within the cell

    Resource Allocation in Ad Hoc Networks

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    Unlike the centralized network, the ad hoc network does not have any central administrations and energy is constrained, e.g. battery, so the resource allocation plays a very important role in efficiently managing the limited energy in ad hoc networks. This thesis focuses on the resource allocation in ad hoc networks and aims to develop novel techniques that will improve the network performance from different network layers, such as the physical layer, Medium Access Control (MAC) layer and network layer. This thesis examines the energy utilization in High Speed Downlink Packet Access (HSDPA) systems at the physical layer. Two resource allocation techniques, known as channel adaptive HSDPA and two-group HSDPA, are developed to improve the performance of an ad hoc radio system through reducing the residual energy, which in turn, should improve the data rate in HSDPA systems. The channel adaptive HSDPA removes the constraint on the number of channels used for transmissions. The two-group allocation minimizes the residual energy in HSDPA systems and therefore enhances the physical data rates in transmissions due to adaptive modulations. These proposed approaches provide better data rate than rates achieved with the current HSDPA type of algorithm. By considering both physical transmission power and data rates for defining the cost function of the routing scheme, an energy-aware routing scheme is proposed in order to find the routing path with the least energy consumption. By focusing on the routing paths with low energy consumption, computational complexity is significantly reduced. The data rate enhancement achieved by two-group resource allocation further reduces the required amount of energy per bit for each path. With a novel load balancing technique, the information bits can be allocated to each path in such that a way the overall amount of energy consumed is minimized. After loading bits to multiple routing paths, an end-to-end delay minimization solution along a routing path is developed through studying MAC distributed coordination function (DCF) service time. Furthermore, the overhead effect and the related throughput reduction are studied. In order to enhance the network throughput at the MAC layer, two MAC DCF-based adaptive payload allocation approaches are developed through introducing Lagrange optimization and studying equal data transmission period

    Cross-Layer Resource Allocation Protocols for Multimedia CDMA Networks

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    The design of mechanisms to efficiently allow many users to maintain simultaneous communications while sharing the same transmission medium is a crucial step during a wireless network design. The resource allocation process needs to meet numerous requirements that are sometimes conflicting, such as high efficiency, network utilization and flexibility and good communication quality. Due to limited resources, wireless cellular networks are normally seen as having some limit on the network capacity, in terms of the maximum number of calls that may be supported. Being able to dynamically extend network operation beyond the set limit at the cost of a smooth and small increase in distortion is a valuable and useful idea because it provides the means to flexibly adjust the network to situations where it is more important to service a call rather than to guarantee the best quality. In this thesis we study designs for resource allocation in CDMA networks carrying conversational-type calls. The designs are based on a cross-layer approach where the source encoder, the channel encoder and, in some cases, the processing gains are adapted. The primary focus of the study is on optimally multiplexing multimedia sources. Therefore, we study optimal resource allocation to resolve interference-generated congestion for an arbitrary set of real-time variable-rate source encoders in a multimedia CDMA network. Importantly, we show that the problem could be viewed as the one of statistical multiplexing in source-adapted multimedia CDMA. We present analysis and optimal solutions for different system setups. The result is a flexible system that sets an efficient tradeoff between end-to-end distortion and number of users. Because in the presented cross-layer designs channel-induced errors are kept at a subjectively acceptable level, the proposed designs are able to outperform equivalent CDMA systems where capacity is increased in the traditional way, by allowing a reduction in SINR. An important application and part of this study, is the use of the proposed designs to extend operation of the CDMA network beyond a defined congestion operating point. Also, the general framework for statistical multiplexing in CDMA is used to study some issues in integrated real-time/data networks

    Spreading factor optimization and random access stability control for IMT-2000.

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    Ho Chi-Fong.Thesis (M.Phil.)--Chinese University of Hong Kong, 2000.Includes bibliographical references (leaves 63-[64]).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Introduction --- p.1Chapter 1.2 --- The 2.5G Systems --- p.3Chapter 1.2.1 --- HSCSD --- p.3Chapter 1.2.2 --- GPRS --- p.3Chapter 1.2.3 --- EDGE --- p.4Chapter 1.2.4 --- IS-136 --- p.4Chapter 1.3 --- The Evolution from 2G/2.5G to 3G --- p.4Chapter 1.3.1 --- GSM Data Evolution --- p.4Chapter 1.3.2 --- TDMA Data Evolution --- p.5Chapter 1.3.3 --- CDMA Data Evolution --- p.6Chapter 1.4 --- UTRA --- p.7Chapter 1.4.1 --- UTRA FDD --- p.8Chapter 1.4.2 --- UTRA TDD --- p.18Chapter 1.4.3 --- Transport Channels --- p.25Chapter 2 --- Spreading Factor Optimization for FDD Downlink --- p.27Chapter 2.1 --- The Optimal Channel Splitting Problem --- p.28Chapter 2.2 --- Spreading Factor Optimization for FDD Downlink Dedicated Chan- nel --- p.30Chapter 3 --- Random Access Channel Stability Control --- p.33Chapter 3.1 --- Random Access Slotted Aloha --- p.33Chapter 3.1.1 --- System model --- p.33Chapter 3.1.2 --- Probability of Code-Collision --- p.34Chapter 3.1.3 --- Throughput Analysis of Random Access in TD/CDMA System --- p.37Chapter 3.1.4 --- Retransmission --- p.42Chapter 3.1.5 --- System Delay --- p.42Chapter 3.2 --- Random Access Channel Stability Control --- p.43Chapter 3.2.1 --- System Model --- p.43Chapter 3.2.2 --- Random Access Procedure --- p.44Chapter 3.3 --- Random Access Channel Stability Control Alogrithm --- p.47Chapter 3.3.1 --- Simulation --- p.49Chapter 3.4 --- Multi-class Model --- p.55Chapter 4 --- Conclusions and Topics for Future Study --- p.60Chapter 4.1 --- Thesis Conclusions --- p.60Chapter 4.2 --- Future Work --- p.61Chapter 4.2.1 --- Downlink and Uplink resource allocation in TDD --- p.61Chapter 4.2.2 --- Resource Unit Packing in TDD --- p.62Chapter 4.2.3 --- Other Topics --- p.62Bibliography --- p.6

    Realizing mobile multimedia systems over emerging fourth-generation wireless technologies

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    Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Includes bibliographical references (p. [161]-167) and index.by Pei-Jeng Kuo.M.Eng

    Radio resource management and metric estimation for multicarrier CDMA systems

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    On the performance and capacity of space-time block coded multicarrier CDMA communication systems

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    Ph.DDOCTOR OF PHILOSOPH

    Convergence of packet communications over the evolved mobile networks; signal processing and protocol performance

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    In this thesis, the convergence of packet communications over the evolved mobile networks is studied. The Long Term Evolution (LTE) process is dominating the Third Generation Partnership Project (3GPP) in order to bring technologies to the markets in the spirit of continuous innovation. The global markets of mobile information services are growing towards the Mobile Information Society. The thesis begins with the principles and theories of the multiple-access transmission schemes, transmitter receiver techniques and signal processing algorithms. Next, packet communications and Internet protocols are referred from the IETF standards with the characteristics of mobile communications in the focus. The mobile network architecture and protocols bind together the evolved packet system of Internet communications to the radio access network technologies. Specifics of the traffic models are shortly visited for their statistical meaning in the radio performance analysis. Radio resource management algorithms and protocols, also procedures, are covered addressing their relevance for the system performance. Throughout these Chapters, the commonalities and differentiators of the WCDMA, WCDMA/HSPA and LTE are covered. The main outcome of the thesis is the performance analysis of the LTE technology beginning from the early discoveries to the analysis of various system features and finally converging to an extensive system analysis campaign. The system performance is analysed with the characteristics of voice over the Internet and best effort traffic of the Internet. These traffic classes represent the majority of the mobile traffic in the converged packet networks, and yet they are simple enough for a fair and generic analysis of technologies. The thesis consists of publications and inventions created by the author that proposed several improvements to the 3G technologies towards the LTE. In the system analysis, the LTE showed by the factor of at least 2.5 to 3 times higher system measures compared to the WCDMA/HSPA reference. The WCDMA/HSPA networks are currently available with over 400 million subscribers and showing increasing growth, in the meanwhile the first LTE roll-outs are scheduled to begin in 2010. Sophisticated 3G LTE mobile devices are expected to appear fluently for all consumer segments in the following years
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