Third International Conference on 3G Mobile Communication Technologies
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- Location: London, UK
- Conference date: 8-10 May 2002
- ISBN: 0 85296 749 7
- Conference number: CP489
- The following topics are dealt with: trials and implementation aspects; IP based networks; handover and roaming; coverage and capacity planning; power control and interference; modulation and coding; performance modelling; QoS techniques; receiver techniques; system planning; security; location and positioning; services and applications; WLAN, Bluetooth and TDD; smart antennas and MIMO; 3G evolution and beyond; software radio; resource management and optimisation
1 - 20 of 110 items found
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Europe's first 3G network: a case study in design and implementation
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This paper outlines the work undertaken in the design and implementation of a 3rd generation mobile telephone network in the Isle of Man. From the very beginning the Manx Telecom 3G project adopted an applications-centric design philosophy. That is, all design and planning decisions were based on consideration of the desired end user experience, considering network quality, service coverage and performance of new data applications. The project has allowed new and valuable lessons to be learned about IP performance over a radio interface.
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3G shared infrastructure
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The paper gives an overview of the network sharing options open to 3G network operators. The drivers for network sharing are mainly economic and the need to roll out infrastructure quickly. Network sharing may always be the preferred implementation strategy in sparsely populated areas. Some of the technical issues are outlined, particularly in the areas of antenna sharing and network management, which are considered to be the main challenges in sharing 3G networks. The regulatory framework is introduced. The paper concludes with a brief look at the future of network sharing.
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IP header and signalling compression for 3G systems
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IP header compression techniques have evolved to meet the challenges of cellular networks. The scope has also broadened. Solutions are being developed for voice traffic transport, SIP and protocols such as TCP, which covers the major traffic volumes. All of these standards are currently under development in accordance with the working group charter and IETT process. With these solutions, 2.5G and 3G networks will be a ubiquitous way of obtaining IP connectivity, even for multimedia applications. The integration of these techniques into the protocol architecture is being done within other standards activities, for example 3GPP. Many aspects of compression schemes (such as BNF grammars for specific content) have been left as implementation decisions, reflecting a principle of the ROHC group: to enable the deployment of sophisticated compression without standardising every aspect of their use.
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Session establishment over satellite-UMTS
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As part of the roll out of Universal Mobile Telecommunication Systems (UMTS), a satellite component has been identified, aiming at providing a seamless communication. Since an all IP architecture has been defined by the Third Generation Partnership Project (3GPP) for the terrestrial component in Release 5 and beyond, an integration of satellite in the IP network is needed. Thus this paper aims to present a possible architecture for a seamless integration of an IP-based terrestrial/satellite network. We describe how sessions based on session initiation protocol (SIP) can be established between the mobile terminal (UE) under the coverage of Satellite-UMTS with other end users. The impact of random access delay and SIP message lengths on the session setup delay are analysed and demonstrated via performance evaluation in OPNET.
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An iterative multiuser detection receiver for 3GPP with antenna arrays: performance in terms of BER, cell size and capacity
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This paper discusses the implementation of a very powerful but computationally efficient, iterative multi-user detector, intended for use as the base station physical layer receiver for wideband CDMA. This multiuser detector is unique in that it is fully compliant with the release '99 3GPP standard, a result that has not been shown before. The transmitter chain is discussed before the channel model used is introduced. The receiver design approach is then discussed. Special consideration is given to show how channel estimation is integrated into the receiver. We show single cell performance results that indicate a capacity increase of approximately three times over the "conventional" receiver implementation is possible (with and without antenna arrays). Results are then shown using a cell dimensioning simulation tool to indicate the overall gain in terms of increase in cell size. Here we can show that a gain of approximately 50% of the cell size is possible with such a multi-user detection approach. The dimensioning tool is also used to show the increase in capacity for a fixed cell size. Here we can show that a gain in the order of 330% is possible, compared to a conventional receiver approach.
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Resource allocation algorithms and power control for cellular systems
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Multiband (or multi-carrier) CDMA is a promising approach to increasing the capacity of CDMA systems, while maintaining compatibility with existing systems. This paper surveys three different power control based resource allocation algorithms and proposes a modified joint band allocation, beamforming and load sharing algorithm. This algorithm will solve the problem of degradation in performance at high loads.
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An efficient algorithm for distributed power control in cellular radio systems
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In most modern cellular radio systems, efficient interference management aims at acceptable carrier-to-interference (CIR) ratios in all active communication links in the system. Power control is an integral technique in the design and operation of such cellular radio systems. It can be used to reduce cochannel interference and hence the near-far effects. Two main approaches have been adopted for power control, which are known as centralized and distributed. Centralised power control requires knowledge of the information of all link gains between base stations and mobiles, which is very difficult to implement for large real-time systems. We consider distributed power control algorithms, which are based only on local information at the base station. A new technique, based on the method of projection onto convex sets (POCS), is developed and is used to obtain the minimum protection ratio. Simulation results show that the POCS method achieves much faster convergence and improved outage probability than other conventional methods.
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Predictive power control for S-UMTS based on least-mean-square algorithm
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In order to exploit the presence of non-zero autocorrelation between consecutive samples of channel variations, predictive schemes based on a recursive least squares (RLS) adaptive algorithm have been proposed. The main motivation for using RLS is its fast convergence property. The RLS algorithm places enormous computational burden on the transmit power control system. In slow power control, however, the fast convergence property is not a stringent requirement. Therefore, we propose a predictive power control scheme based on a least-mean-square (LMS) algorithm. Unlike the RLS algorithm, the LMS algorithm is simple to implement and has low computational complexity. Furthermore, the LMS algorithm has better tracking properties than the RLS algorithm in a nonstationary environment. We demonstrate, through simulation, that a performance gain of up to 0.5 dB in terms of the standard deviation of transmit power control error, over the conventional closed-loop transmit power control, can be achieved through the use of the LMS algorithm. Furthermore, we optimise the performance of the closed-loop power control based on parameters of the LMS predictor, namely adaptation constant and predictor order.
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Performance of space-time coding for 3GPP HSDPA service under flat and frequency selective fading conditions
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There is little doubt that an important feature of third generation (3G) mobile systems is going to be the ability to send and receive large volumes of data at high speed. The Third Generation Partnership Project (3GPP) is currently considering suitable systems for high-speed downlink packet access (HSDPA) services to provide the required data throughput. One of the systems currently under consideration is a space-time coding (STC) architecture using the vertical Bell Labs layered space-time (VBLAST) system on the downlink-shared channel (DSCH) to allow simultaneous transmissions over multiple channels destined for a single user. Although link level results for flat fading channels indicate significant performance advantages over conventional single antenna systems, it is only under frequency selective fading conditions that we are able to make a realistic analysis. We simulate the system and obtain its performance in frequency selective fading environments. Our results show severe system performance degradation in comparison to flat fading channels. This loss in performance is due to the loss of orthogonality between spreading codes induced by such channels. This leads us to the conclusion that changes in the structure of the system are necessary in order to overcome this issue.
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On signalling issues for the high speed downlink packet access in UMTS
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The high-speed downlink packet access (HSDPA) adopted in UMTS aims to support, integrated on the same carrier, voice on the dedicated channel (DCH) and high-speed data on the high-speed downlink shared channel (HS-DSCH). Taking account of some noticeable deficiencies in the system, the paper examines different signalling approaches for the HSDPA, based on a two-step signalling scheme. In this scheme, the downlink signalling control information associated with the HS-DSCH is carried by shared control channels (SCCH-HS). A high-speed indicator (HI) is provided by the dedicated physical channel (DPCH). We analyse the impact of using the uncoded HI on the power consumption and overall efficiency of the system. Based on that, we propose some channel coding schemes for protecting the HI and improving the deficiencies. In particular, we recommend a very similar code to the previous one for encoding the information of the transport format combination indicator (TFCI). This new coding scheme can provide protection for the HI with high error-control capacity and have good error performance for both Gaussian and fading channels.
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Zero correlation zone sequences for multi-carrier DS-CDMA systems
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A multi-carrier DS-CDMA system is proposed that employs zero correlation zone (ZCZ) sequences as spreading sequences to reduce the multipath interference. Bit error rates (BER) and frame error rates (FER) for a range of Eb/N0 values are presented. It is demonstrated that the proposed scheme can improve the BER and FER performance, in the frequency selective fading channel evaluated, when a single correlator receiver is used on each sub-carrier.
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Implementation of an improved reconfigurable SOVA/log-MAP turbo decoder in 3GPP
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SOVA (soft-output Viterbi algorithm) and log-MAP turbo decoding algorithms share common operations, making feasible a reconfigurable SOVA/log-MAP turbo decoder for reduced power consumption. We show that the improved reconfigurable SOVA/log-MAP turbo decoder is suitable for implementation in 3GPP systems. Simulations of turbo coding and decoding have been done using the parameters of 3GPP with AWGN and uncorrelated Rayleigh fading channels, and an outer block interleaver-deinterleaver. We concentrate on the dedicated transport channel (DCH) and use a pipeline turbo decoder architecture with 8 decoding iterations. We examine two typical bit rates, and for each we consider four different service classes (as possible service examples) using suitable turbo interleaver lengths. Considering the BER and latency constraints for SOVA and log-MAP, it is shown that there is an optimum decoding algorithm for each possible implementation scenario.
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Orthogonality of UMTS codes in indoor channels
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UMTS (Universal Mobile Telecommunications System) spreading codes are only truly orthogonal in the absence of multipath delay and time offsets. In all practical channels the loss of orthogonality will result in the generation of non-zero cross-correlation products that can compromise the error performance of code division multiple access (CDMA) systems. The practical level of cross-correlation produced in the uplink of multiuser applications at the base-station site and the effect of this interference on the RAKE receiver is investigated by means of wideband dual polar channel measurements from a field trials campaign, taken within the UMTS time division duplex (TDD) uplink (1910-1915 MHz). The results showed that 75% of the measurements in an indoor channel had normalised correlations less than 0.25.
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Adaptive modulation switching level control in high speed downlink packet access transmission
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In Release 5 of the UMTS systems, adaptive modulation and coding (AMC) plays a key role in boosting the peak rate of packet transmission up to 10 Mbps. One of the key challenges for the AMC scheme is the selection of the AMC switching levels. This is a challenging issue due to dissimilar sensitivity of the modulation schemes to Doppler velocity or multipath channel impairment. Furthermore, given the wide range of receiver and transmitter technologies, a scheme is required that adaptively estimates the optimal switching point which will maximize the system throughput. We present an adaptive mechanism utilizing the fast hybrid ARQ feedback signal that is available in R5 of the UMTS system. Conceptually, the proposed threshold adjustment algorithm (TAA) is somewhat similar to the outer loop power control scheme that is already adopted in R99. The switching level is adjusted in such a way that the link performance, in terms of block error rate, maintains a target value. Performance of the proposed scheme is also demonstrated using a link level simulation.
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Modified non-coherent sequential acquisition scheme of DS/SS signals
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The paper proposes a modified noncoherent sequential detection decision logic based on continuous accumulation in order to achieve fast PN code acquisition. In most reports on sequential schemes, the decision process is based on independent and identically distributed random variables, which requires the integrator to be reset periodically. This introduces loss in the effective signal-to-noise ratio. In this paper, on the contrary, the sequential scheme use continuous integration. To simplify the design and analysis, we deduce the equivalent relationship between the likelihood ratio of the current sample and that of all the previous samples. The scheme is proved to be an optimum sequential detection under certain assumptions. In addition, because the average sample number (ASN) can not be calculated through the methods applied to conventional sequential detection, an algorithm is also provided, which can estimate both the probability density function (PDF) and the upper threshold of ASN. The desired probability of false alarm and detection, as well as faster PN code acquisition compared to conventional sequential detection can be achieved by employing this structure. The correctness and advantage of the scheme was also verified by computer simulation. The performances of the proposed schemes were obtained and they suggested that the proposed non-coherent sequential detection is more desirable.
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Implementation of COST259 channel models using tapped delay line for multiple antenna receivers
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In this paper, the implementation of COST 259 channel models in macrocells, using a stochastic approach in terms of tapped delay line (TDL) models is presented. The implementation of this wideband channel is very important for link level simulation in future wireless systems that exploit space-time processing techniques using multiple antenna elements. Major channel effects are discussed and incorporated into existing channel models. The temporal correlation is realised by using a power spectrum shaping filter whereas the spatial correlation is achieved by invoking a canonical Gaussian approach. Furthermore, antenna effects as well as array geometries can be taken into consideration for the development of compact antenna arrays at the user's terminal. The array implementation is focused at the mobile station (MS) point of view.
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Network planning considerations for network sharing in UMTS
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The objective of the paper is to illustrate the potential impacts on operating costs associated with a variety of different 'UMTS network sharing' scenarios such as sharing site locations, RNS (radio network subsystem) equipment, transmission, core network, national roaming and MVNO (mobile virtual network operators). Comparisons are made between a generic reference network design, obtained using simplified dimensioning tools (see Kromer, J., ibid., p.281-8), and a number of network sharing options currently under consideration in the market place. In addition to covering areas such as sharing sites, node B equipment, RNC (radio network controller), core network and transmission costs, installation and operation issues are also considered. Regulatory and standards issues related to network sharing are included in the analysis. The relative merits of each network sharing scenario are presented and sharing recommendations for the different phases of network deployment are provided.
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Link-level simulation of W-CDMA satellite-UMTS random access channel
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In this paper, link level simulation for the W-CDMA Satellite-UMTS RACH (radio access channel) has been presented. Simulation results show improvements in detection using a longer preamble with differential accumulation. For a longer preamble, coherent processing suffers large losses in the presence of Doppler. Efficient channel estimation algorithms and pre-Doppler compensation are required if a coherent approach is used. The reduced sensitivity of coherent detection in the presence of Doppler could be compensated by adopting a differential approach even though this solution increases the complexity at the receiver. It can be seen that the modified ETSI proposal does not degrade the performance compared to the ETSI proposal in terms of detection probability. Hence, we can expect improvements in the RACH throughput efficiency and delay since there are more available signatures and so the probability that more than one user chooses the same signature that results in collision is lower. Also, to achieve a one-shot-acquisition for the random access burst, the performance of preamble detection and message detection must be aligned, i.e. at an Ec/N0, where the preamble detection is likely, the RACH message BLER (block error rate) must be adequately low. The alignment is done by adjusting the preamble detection performance setting the threshold of the received energy of the matched filter at the receiver. From the simulation results, it was shown that with the used threshold, the probability of detection corresponds to more than 0.9 at the required Eb/N0 for a BLER of 10-1 for the message part.
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Spatio-temporal investigation of UTRA FDD channels
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Smart antennas promise to provide range extension and capacity enhancements crucial to the successful deployment of Universal Mobile Telecommunications System (UMTS) networks. The frequency offset between the uplink and downlink in the frequency division duplex (FDD) air interface gives rise to a frequency dependency in the channel responses and potential problems in downlink beamforming. In order to investigate this, a highly novel dual-band, dual-polarised channel sounding trial was performed in the UMTS FDD bands by the University of Bristol. The wideband measurements were conducted in the City of Bristol, encompassing urban city and sub-urban residential scenarios and subsequent post processing was performed to extract channel parameters across the two bands. This paper presents the results and analysis done for the single polarisation static measurements. It was observed that in most instances, there was a higher degree of scattering in the higher frequency band, resulting in larger angular spreads and delay spreads. The channels also exhibited a strong degree of de-correlation when viewed from the spatial and temporal domains.
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Blind adaptive single user detection with adjustable step size for DS/CDMA communication over a Rayleigh fading mobile channel
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An adaptive single user algorithm with adjustable step size has been proposed for use in DS/CDMA based communications. In addition, the adaptive step size algorithm has been incorporated into two multipath combiners in the forms of the RAKE receiver and the general sidelobe canceller architecture for use in a Rayleigh fading channel. The frame error rate results obtained by means of computer simulation illustrate the superior multiple access interference resistance of the proposed detectors compared to the conventional RAKE receiver. Furthermore, the results also reflect the enhanced convergence speed of the detectors and their ability to adjust the step sizes according to the rate of change of the received signal. Joint blind detection and blind channel parameter estimation and the robustness of the gradient adaptive step size constant modulus algorithm to imperfect channel estimation are the topics of future study by the authors.
