6th IEE International Conference on 3G and Beyond (05/11182)
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- Location: London, UK
- Conference date: 7-9 Nov. 2005
- ISBN: 0 86341 572 5
- Conference number: CP512
- The following topics were dealt with: MIMO; OFDM systems; multihop networks; multimedia; advanced signal processing; IP-based systems; MC-CDMA; QoS issues; detection, equalisation and acquisition; location and resource management; frequency hopping multiple access systems; WLAN; mobility management; DS-CDMA ad hoc networks; 4G mobile networks; 3G wireless networks; WiMax; WCDMA; homodyne receiver; advanced networks; media streaming; HSDPA; smart antennas; and cellular coverage, costs and charging.
1 - 20 of 95 items found
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MIMO-OFDM: basic relations between coding, spreading, multicarrier and single-carrier transmission
- Author(s): J. Lindner
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Summary form only given. This contribution considers the basic relations between coding, spreading, multicarrier and single-carrier transmission against the background of MIMO-OFDM. MIMO-OFDM is taken, because it can be regarded as a scheme which contains many others as special cases, and also because of its increasing relevance for future wireless communication. It is shown that spreading plays a central role: spreading in space, time and frequency can be considered as the most general form of linear space-time-frequency-coding. Additionally it is demonstrated that spreading can be used to transform multicarrier transmissions into single-carrier transmissions. Moreover, fading channels can be transformed in nonfading ones. This will be demonstrated for the case of Rayleigh fading channels with additive Gaussian noise, which become simple Gaussian channels. After an introduction and a short description of MIMO-OFDM, the concept of spreading and despreading is explained. It is shown, how spreading produces diversity which can be exploited at the receiving side. If no knowledge about the MIMO channel is available at the transmit side, i.e. if no backward channel can be used, this is an excellent means to cope with frequency- and/or time-selective channels. It is also shown what conventional channel coding can do in this context and what this means at the receiving side. Coding at the transmit side is concatenated with spreading and the MIMO channel. This results in a potential, that can be exploited by iterative detection schemes (turbo equalization/decoding). Simulation results are presented to underline the relevance of theoretical derivations. The main intention of this contribution is to give some new insights which can help in future realizations of close-to-optimum performance MIMO-OFDM systems.
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IPv6-based architecture for fast and cost-effective micro-mobility management
- Author(s): Q. Wang and M.A. Abu-Rgheff
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To improve mobility management in all IPv6-based wireless networks, optimisation work on mobile IPv6 (MIPv6) is being standardised. The hierarchical MIPv6 (HMIPv6) and the fast handovers for MIPv6 (FMIPv6) have emerged as the two most promising protocols. However, the optimal integration of both schemes, together with mobility-aware QoS (quality of service) management, remains an open research issue. Furthermore, the current standard IPv6 address auto-configuration is not optimised for mobility contexts and thus is the bottleneck to real fast handoffs. In addition, out-of-order packets are generated at a mobile host when both FMIPv6 and HMIPv6 are applied jointly, degrading the QoS of ongoing sessions. To solve these problems, we propose IPv6-based micro-mobility architecture, where HMIPv6 and FMIPv6 are enhanced effectively and integrated efficiently. The simulation results demonstrate that the proposed architecture is the most cost-effective solution among three schemes based on the combination of HMIPv6 and FMIPv6, and can achieve faster handoffs compared with FMIPv6.
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TCP performance over UMTS dedicated channels with finite RLC buffer size
- Author(s): W. Featherstone ; J.P. Wallington ; F. Schneider
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In this paper, simulation results are presented to demonstrate the effects on the performance of a TCP connection over a UMTS dedicated channel when the size of the acknowledged mode radio link control (AM-RLC) data buffer at the radio network controller is finite. The consequence of this restriction is that buffer overflow can occur. The TCP flavour (Tahoe, Reno, New Reno or SACK), FTP file size, RLC buffer size and DCH data rate are varied independently to map the effects of buffer size on the link throughput. The results are used to demonstrate how small changes in the RLC buffer size can have a significant impact on TCP throughput and that this impact varies considerably with TCP flavour. Explanations for the differing behaviours are examined in detail throughout the paper, before summarising with the overall conclusions.
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Inter-operator cooperation challenges in SIP-based service architecture of IP multimedia subsystem of UMTS
- Author(s): A. Gouya and N. Crespi
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One of the benefits of the evolution of the third generation mobile systems such as UMTS (Universal Mobile Telecommunications System) toward the all-IP network architecture is to provide functionalities to support real-time multimedia services. Simple and efficient multimedia session handling characteristics of the session initiation protocol (SIP), candidates it by 3GPP (Third Generation Partnership Project) for the signalling protocol of IP multimedia subsystem (IMS) of UMTS. An important issue in IMS is the fact that service control procedures of the subscribers are performed in the home network. In this paper we review the SIP-based service registration and session establishment procedures in IMS and we study the challenges for providing a SIP-based cooperative mechanism between network operators of different subscribers in IMS in order to prevent extending of service control procedures of roamers to home network and to optimize the session establishment procedure by performing service control procedures of roamers in the visited network.
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VoIP applications over WLAN with multistage interference cancellation smart antennas
- Author(s): Hsin-Chin Liu
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In order to improve the transmission quality of wireless local area network (WLAN), incorporation of emerging technologies is required. Smart antennas, as one of the key technologies in future communications, can significantly improve the signal-to-interference-plus-noise ratio (SINR) and hence reduce the transmission errors. Because WLAN uses the unlicensed industrial, scientific, and medical (ISM) radio bands, strong cochannel interference (CCI) sources from systems other than WLAN can significantly degrade the throughput of WLAN and result in various transmission problems, such as latency, jitter, and packet loss. These problems usually render performance degradation of voice over IP (VoIP) services. The CCI from uncoordinated sources also lead to slow convergence of smart antennas using data-dependent adaptive algorithms. This work demonstrates that applying low cost multistage interference cancellation smart antennas (MICSA) to WLAN conducts superior interference suppression and better performance improvement of VoIP services compared with using conventional single stage smart antennas to WLAN.
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Slow frequency hopping assisted MC DS-CDMA using large area synchronism spreading sequences
- Author(s): H. Wei ; L.L. Yang ; L. Hanzo
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The family of multi-carrier direct-sequence CDMA (MC DS-CDMA) systems exhibits numerous attractive properties, which render them attractive candidates for next-generation wireless communications. We demonstrate that spreading codes exhibiting a so-called interference-free window (IFW) are capable of outperforming classic spreading codes, when the interfering multi-user and multipath components arrive within this IFW. The best possible quasi-synchronous timing of the spreading sequences has to be adjusted with the aid of accurate adaptive timing advance control, which has to be significantly more accurate than that used in the lower-bit-rate second-generation GSM system. Fortunately, the IFW duration may be extended with the advent of multi-carrier DS-CDMA proportionately to the number of subcarriers. Hence the resultant MC DS-CDMA system is capable of exhibiting a near-single-user performance without employing a multi-user detector. A deficiency of the resultant system is that the number of spreading codes exhibiting a certain IFW is limited and so is the IFW duration. This contribution sets out to mitigate the above-mentioned shortcomings so that when the users' delays are in the range of the IFW, we separate them with the aid of the unique, user-specific LAS spreading codes. By contrast, when the users roam at a high distance from the base-station and hence their received signal arrive outside the range of the IFW, we separate them using their unique frequency hopping patterns.
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Exploiting multiuser diversity for MIMO cellular systems using packet scheduling and the VBLAST receiver
- Author(s): C. Floros ; S. McLaughlin ; J.S. Thompson
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Several packet scheduling techniques for the downlink of a multiple-input multiple-output (MIMO) cellular system are investigated. The system capacity for three scheduling algorithms, the conventional round robin scheduling (RRS), the antenna-assisted round robin (AA-RRS) and a novel VBLAST AA-RRS, are evaluated. Computer simulations are used to compare these scheduling schemes in terms of the expected and outage capacities. The novel scheme has proven to be beneficial for the system performance.
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Turbo-coded OFCDM systems for 4G mobile communications
- Author(s): Y.Q. Zhou ; J. Wang ; M. Sawahashi
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In this paper, a hybrid multicode interference cancellation (MCI) and minimum mean square error (MMSE) detection scheme is presented for the turbo-coded orthogonal frequency and code division multiplexing (OFCDM) systems. The weights of hybrid detection are derived theoretically and an effective method to generate the weights in practical applications is proposed. By means of computer simulation, it is shown that to carry out interference regeneration for the hybrid detection, the conventional turbo decoding algorithm should be extended to decode parity bits as well. Moreover, two iterations in turbo decoding are sufficient to provide good performance for the system with the multistage hybrid detection. Finally, the proposed method for MMSE weight estimation works well with properly chosen parameters.
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A proposal of multicarrier CDMA system for combating channel blocking in frequency-selective Rayleigh fading MIMO channel
- Author(s): T. Fujino and J. Nakamura
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We propose a scheme for mobile communications to combat the channel blocking. The scheme is of the MIMO-STBC for the downlink MC-CDMA, which enables receivers to extract all the signals even when they encounter the blocking.
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Combining space frequency coding with a pre-filtering technique for TDD downlink MC-CDMA systems in a beyond 3G context
- Author(s): A. Silva and A. Gameiro
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This paper deals with downlink space-frequency block coding with a joint pre-filtering and spreading technique for time division duplex MC-CDMA. We consider the use of antenna arrays at the base station (BS) and a single antenna at the mobile terminal (MT). The space-frequency block codes allow that the spatial diversity be efficiently exploited and the linear multi-user pre-filtering technique allows to format the transmitted signals so that the multiple access interference and channel distortions at mobile terminals are completely removed, keeping the MT at low complexity. Simulations results are carried out in scenarios with both perfect and imperfect channel estimates and using the channel turbo code specified for current UMTS system, to demonstrate the effectiveness of the proposed SFBC with a linear multi-user pre-filtering approach.
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Performance of the smart antenna aided generalized multicarrier DS-CDMA downlink using both time-domain spreading and steered space-time spreading
- Author(s): Bin Hu ; Lie-Liang Yang ; L. Hanzo
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In this contribution a generalized MC DS-CDMA system invoking smart antennas for improving the achievable performance in the downlink of the system is studied, which is capable of minimizing the downlink interference inflicted upon co-channel mobiles, while achieving frequency, time and spatial diversity. In the MC DS-CDMA system considered the transmitter employs multiple antenna arrays and each of the antenna arrays consists of several antenna elements. More specifically, the space-time transmitter processing scheme considered is based on the principles of steered space-time spreading (SSTS). Furthermore, the generalized MC DS-CDMA system employs time and frequency (TF)-domain spreading, where a user-grouping technique is employed for reducing the effects of multiuser interference.
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A link adaptation scheme to support relative DiffServ QoS over CDMA radio systems
- Author(s): Lin Wang ; V. Friderikos ; M. Iwamura ; N. Nafisi ; A.H. Aghvami ; M. Dohler
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A link adaptation schemes is proposed to improve the efficiency to support relative DiffServ QoS traffic over CDMA air interface. To differentiate the resource allocation between DiffServ PHBs and between the in/out profile packets within each AF class, two-level differentiation is done in the proposed scheme: inter-class differentiation and intra-class differentiation. In the inter-class resource differentiation, an adaptation based on delta modulation is proposed to allocate the resource based on their relative QoS parameters. The intra-class scheme is carried out priority queuing and rate adaptation in order to give further differentiation on the in/out packets and make full use of resource allocated through inter-class resource differentiation Then each class's delay in the current frame is feedback to the proposed delta modulation scheme at the inter-class level for resource in the following frame. Thus through this interaction between the two levels, a better QoS balance between classes is achieved and therefore a higher capacity is gained as shown by our numerical evaluation.
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Performance aspects of enhanced radio resource management with QoS differentiation in UMTS network
- Author(s): J. Singh
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Supporting multiple traffic classes with different quality of service (QoS) constraints in UMTS System is a tough problem due to the limited bandwidth available on the air interface and over subscribed resources. In order to meet the QoS specification of the different traffic classes, the network resources have to be allocated appropriately and radio resource management (RRM) strategies with user/service differentiation have to be realised in order to exploit the spectrum in an efficient way under loaded multi service scenario. This paper proposes and analyses RRM strategies for resource allocation and mechanism for QoS differentiation in a mixed service scenario. In particular the effect of prioritization between users/services with different QoS profile is studied in terms of call admission probabilities, dropping and blocking probabilities. It is demonstrated that RRM schemes incorporating QoS differentiation provides enhanced flexibility and control in meeting the QoS targets and thus results in better overall performance under loaded multi service scenarios. Moreover proposed RRM algorithms with QoS differentiation are inherently suited to handle emergency calls during catastrophic events and preserve the ongoing call during handovers.
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Connection setup delay for packet switched services
- Author(s): C. Johnson ; H. Holma ; I. Sharp
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The connection establishment procedure for packet switched data services uses a combination of signalling protocols. This paper describes the messages associated with these signalling protocols and identifies the relationship between them. RNC databuild parameters related to connection establishment are identified and discussed. A set of measurements are used to illustrate the dominant phases of connection establishment. The dominant phases are discussed in terms of reducing setup delays while minimising the impact upon other aspects of system design. The paper concludes by suggesting a number of ways in which setup delays can be refined.
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A prioritized uplink call admission control algorithm for 3G WCDMA cellular systems with multi-services
- Author(s): S. Al-Qahtani and A. Mahmoud
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The 3G cellular mobile systems which are based on WCDMA technology are expected to be interference limited. Soft capacity is one of the main characteristics of 3G (i.e, UMTS) and it requires new radio resource management strategies to serve diverse quality of service requirements. In this paper, a WCDMA prioritized uplink call admission control (CAC) algorithm for UMTS, which combines QoS negotiation and service differentiation by priority, is studied. This CAC scheme gives preferential treatment to high priority calls, such as soft handoff calls, by reserving some bandwidth margin (soft guard channel) to reduce handoff failures. In addition, queuing is also used to enhance the handoff success probability. The algorithm uses the effective load as an admission criterion and applies different thresholds for new and handoff calls. Finally, the study considers two types of services: voice and data calls. Results indicate that this algorithm reduces the drop handoff calls and increases the total system capacity; hence the GoS and the system performance can significantly be improved especially in case of high mobility environments.
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Effective PN code acquisition in Global Positioning Systems for new generation wireless networks and services
- Author(s): F. Benedetto ; G. Giunta ; A. Neri ; L. Vandendorpe
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The ability to support position location within wireless networks provides network operators with additional value added services, as well as users with a host of new applications. This contribution addresses algorithms for the PN code acquisition and synchronization for a Global Positioning System (GPS) signal, such as the one used by position location techniques in the 3rd generation wireless networks (UMTS). In this work, we present a method exploiting local phase coherence (inspired by the Pisarenko harmonic decomposition, PHD) allowing global frequency estimation in the presence of random phase noise. Moreover, we match the conventional power detector testing method for the presence of a synchronization code signal. Several computer simulations have been accomplished to validate the proposed PHD method. In particular, the numerical results obtained from our simulation trials show that the proposed technique is somewhat superior to the non-coherent one. Moreover, the real cost of the proposed method is practically the same, because the same structure of block correlators (implemented by matched filters) needs to be used.
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A novel frequency domain turbo-equalizer for STBICM over MIMO ISI channel
- Author(s): R. Visoz ; A.O. Berthet ; S. Chtourou
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This paper presents a novel frequency domain block turbo-equalizer for single-carrier transmission over MIMO broadband wireless channel. This turbo-equalizer treats intersymbol interference and multi-antenna interference separately, enabling to choose different criteria for their resolution. This functional split introduces an additional degree of freedom to adapt the turbo-equalizer structure to specific transmission scenarios. As an example, a point-to-point MIMO scenario where a single-user employs a space-time bit-interleaved coded modulation is considered. Simulations show that the proposed turbo-equalizer is sometimes able to outperform the conventional approach inspired by Wang and Poor's seminal paper (on multiuser turbo-detection for CDMA) at the price of an additional but manageable complexity.
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Evaluation of the capacity of multiple-access MIMO schemes with feedback in a small outdoor cell
- Author(s): M.W. Webb ; M. Hunukumbure ; M.A. Beach ; A.R. Nix
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Three algorithms to exploit the multi-user MIMO channel are examined and their system capacity evaluated in the uplink of a small urban cell scenario using measured channel data. An iterative scheme to determine transmit weights that achieve the system-wide Nash equilibrium (NE) is compared to schemes achieving block-diagonalization (BD) of the overall system channel matrix and successive diagonalization (SD) among users. The BD scheme is shown to noticeably outperform the NE at high SNR - by as much as 9.7 bps/Hz (44%) at 20 dB SNR, whilst the SD yields as little as 33% of the capacity of BD. SD is, however, completely non-iterative which could be important in rapidly changing environments. The NE is found to sometimes yield a higher system capacity with more users; the setup examined here shows a rise of about 2 bps/Hz in the system capacity when going from 3 users to 4. We also find that NE converges quickly, usually in fewer than 6 iterations, and reliably, more than 99% of the time, but BD can have serious slow-convergence problems.
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High-rate irregular-LDPC coded OFDM BLAST systems
- Author(s): Yuanliang Huang ; Jiangzhou Wang ; K. Higuchi ; M. Sawahashi
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This paper is focused on the study of high coding rate irregular low-density parity-check (LDPC) coded orthogonal frequency division multiplexing (OFDM) Bell Laboratories layered space-time (BLAST) [G.J. Foschini, 1996] systems for high-speed wireless transmission. One modified LDPC-coded OFDM BLAST scheme is proposed. To generate high coding rate irregular LDPC codes, three construction rules are adopted to obtain low encoding complexity with little loss of decoding performance. The list sphere decoding is adopted for BLAST detection [B.M. Hochwald and S.T. Brink, Mar. 2003]. The simulation results show that with sphere decoding for BLAST detection and LDPC as channel code, this proposed OFDM BLAST scheme can jointly exploit the available spatial, frequency and temporal diversity as effectively as the OFDM-based BLAST applying coding across the whole data stream [B. Vucetic and Jinhong Yuan, 2003], and reduce the code length and processing rate for LDPC construction and the implementation of LDPC encoder and decoder as much as the OFDM-based BLAST assuming independent coding within each sub-stream [B. Vucetic and Jinhong Yuan, 2003].
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OS estimation and IC equalization in BICM-ID with mapping optimization
- Author(s): A. Ghaith and Y. Yuan-Wu
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In this paper, we extend the iterative demapping technique to observation separation (OS), which is an iterative channel estimation and symbol detection procedure. We consider a BICM-ID on a multipath channel with coded packet oriented transmission system with 16-QAM. We propose here to analyse the influence of mapping in a turbo equalization. Then we proposed an optimized binary mapping of 16-QAM constellation in order to increase coding gain which can be used for some practically important cases.
