Online ISSN
1751-8636
Print ISSN
1751-8628
IET Communications
Volume 1, Issue 5, October 2007
Volumes & issues:
Volume 1, Issue 5
October 2007
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- Author(s): H.C. Chao ; C.M. Huang ; M. Guizani ; S.Y. Kuo ; A.F.G. Skarmeta ; W. Seah
- Source: IET Communications, Volume 1, Issue 5, p. 819 –820
- DOI: 10.1049/iet-com:20079028
- Type: Article
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- Author(s): L. Le ; E. Hossain ; T. Le-Ngoc
- Source: IET Communications, Volume 1, Issue 5, p. 821 –830
- DOI: 10.1049/iet-com:20060193
- Type: Article
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A complete queueing model for radio link layer performance analysis is developed assuming adaptive modulation and coding (AMC) at the physical layer and truncated automatic repeat request (ARQ)-based error control at the link layer. From the model, queue length distribution and average queueing delay can be calculated. The average queueing delay is then used to estimate transmission control protocol (TCP) throughput performance using a fixed-point approach. Using the model, we are able to choose signal-to-noise ratio thresholds of different transmission modes for AMC at the physical layer for different persistence levels of ARQ at the link layer so that TCP throughput is maximized. We observe that channel correlation negatively impacts the TCP throughput performance. Also, throughput enhancement of TCP NewReno over TCP Reno is observed to be non-negligible only if no ARQ-based error recovery is employed at the link layer. - Author(s): H. Hu ; H.-H. Chen ; K. Guo ; M. Weckerle
- Source: IET Communications, Volume 1, Issue 5, p. 831 –837
- DOI: 10.1049/iet-com:20060220
- Type: Article
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Orthogonal frequency division multiplex (OFDM) has become one of the most popular air-link technologies for future broadband wireless communications. To further improve its bandwidth efficiency and system performance, adaptive resource allocation and smart antenna techniques have been widely used in the OFDM system. However, the use of fully adaptive beamforming in an OFDM system significantly increases the complexity of the medium access control layer design and thus affects the implementation of adaptive resource allocation. A novel cross-layer adaptive resource allocation strategy with hybrid adaptive array and switched-beam smart antennas suitable for the OFDM systems has been proposed. With the help of different smart antennas schemes based on different users' quality of service requirements, the strategy effectively reduces the complexity of adaptive resource allocation in an OFDM system, while still maintaining a satisfactory system performance. - Author(s): A. Mohamed and H. Alnuweiri
- Source: IET Communications, Volume 1, Issue 5, p. 838 –845
- DOI: 10.1049/iet-com:20060224
- Type: Article
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Multicast-based data communication is an efficient communication scheme especially in multihop ad hoc networks where the MAC layer is based on one-hop broadcast from one source to multiple receivers. The problem of resource allocation for a set of homogeneous multicast sessions over multihop wireless network is addressed. An iterative algorithm is proposed that achieves the optimal rates for a set of multicast sessions such that the aggregate utility for all sessions is maximised. The authors demonstrate analytically and through simulations that the algorithm achieves optimal resource utilisation while guaranteeing fairness among multicast sessions. The algorithm in network environments with asynchronous distributed computations has been further analysed. Two implementations for the algorithm based on different network settings are presented and show that the algorithm not only converges to the optimal rates in all network settings but it also tracks network changing conditions, including mobility and dynamic channel capacity. - Author(s): Y.-C. Lin and W.K. Lai
- Source: IET Communications, Volume 1, Issue 5, p. 846 –857
- DOI: 10.1049/iet-com:20060231
- Type: Article
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In infrastructure wireless networks, the wireless hop can be considered as another hop of the transmission path. With the rapid growth of wireless traffics, the future wireless network is expected to provide services for heterogeneous data traffics with different quality of service (QoS) requirements. Most proposed schemes do not have adaptive mechanisms to deal with the environment changes. In real situation, bandwidths, error rates and loss rates of wireless links vary frequently. We will base on the differentiated service model and propose a wireless differentiation (WD) scheme for user datagram protocol (UDP) flows and a wireless differentiation with prioritised ACK scheme for connections with transmission control protocol (TCP) flows. Both schemes provide QoS support for IEEE 802.11b and do not change the basic access mechanism of IEEE 802.11b. - Author(s): C. Wang ; T. Lin ; J-L. Chen
- Source: IET Communications, Volume 1, Issue 5, p. 858 –865
- DOI: 10.1049/iet-com:20060264
- Type: Article
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The authors address the problem of providing fair multimedia quality-of-service (QoS) in IEEE 802.11 distributed co-ordination function-based wireless local area networks in the infrastructure mode where mobile hosts experience heterogeneous channel conditions due to mobility and fading effects. It was observed that unequal link qualities can pose significant unfairness of channel sharing, which may thereby lead to the degradation of multimedia QoS performed in adverse conditions. A cross-layer adaptation scheme that provides fair QoS by online adjusting the multidimensional medium access control layer backoff parameters in accordance with the application-layer QoS requirements as well as the physical-layer channel conditions was proposed. The solution is based on an optimisation approach, which utilises neural networks to learn the cross-layer function. Simulation results demonstrate that the proposed adaptation scheme can tackle heterogeneous channel conditions and random joining (or leaving) of hosts to achieve fair QoS in terms of throughput and packet delay. - Author(s): C.-M. Huang and J.-W. Li
- Source: IET Communications, Volume 1, Issue 5, p. 866 –874
- DOI: 10.1049/iet-com:20060236
- Type: Article
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The 3G mobile data network provides always-on and ubiquitous connectivity for subscribers. Although the service coverage area in wireless local area network (WLAN) is much smaller than that in a 3G mobile data network, the data transmission rate in WLAN can be from 2 to 54 Mbps, which is much faster than 3G mobile network. Obviously, the relationship between the 3G mobile data network and WLAN is complementary in terms of service coverage and data transmission rate. Therefore integration of 3G mobile network and WLAN can offer subscribers higher speed wireless service in hot spots and ubiquitous connectivity in 3G mobile data network. An authentication mechanism over the loose coupled integration mechanism using a cross-layer bootstrap is proposed. The benefits of the proposed mechanism are (a) integrating Universal Mobile Telecommunication System network and WLAN using the existing protocols defined in 3GPP, IETF and IEEE 802.11i, (b) the use of the Extension Authentication Protocol authentication method is flexible, (c) reduction of the authentication signalling when a subscriber roams from one access point (AP) to another AP and (d) user identity privacy protection. - Author(s): R.S. Chang and C.F. Lin
- Source: IET Communications, Volume 1, Issue 5, p. 875 –879
- DOI: 10.1049/iet-com:20060244
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This paper studies link layer throughput maximisation for mobile ad hoc network routing algorithms. We analyse the transmission rates and take into account the interference effects to propose a theoretical model of throughput maximisation called Throughput Aware Link Selection (TALS). TALS can easily be infused into other routing protocols. Simulations show performances increases when compared with other methods. The results demonstrate that TALS helps to increase network throughput. - Author(s): Y.C. Lai ; A. Chang ; J. Liang
- Source: IET Communications, Volume 1, Issue 5, p. 880 –886
- DOI: 10.1049/iet-com:20060245
- Type: Article
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The proportional delay differentiation (PDD) is one of the most well-known quality of service (QoS) models and has drawn much attention because of its ‘controllable’ and ‘predictable’ characteristics. How to provide PDD in a wireless LAN (WLAN) is addressed and a cross-layer fine-tuning scheduling (CFS) scheme with the goal to maintain PDD among all wireless stations is proposed, while improving performance in a WLAN. CFS additionally considers the time-varying channel capacity to schedule packets, finely tunes the contention window and properly arbitrates the backoff time. Also, it operates in a fully distributed manner among all stations and in a cross-layer approach in each station. The simulation results demonstrate that the CFS scheme can provide more satisfactory PDD and higher performance in a WLAN, compared with 802.11e. - Author(s): Y.-M. Huang ; M.-H. Tsai ; T.-C. Chiang ; T.-W. Hou
- Source: IET Communications, Volume 1, Issue 5, p. 887 –892
- DOI: 10.1049/iet-com:20060252
- Type: Article
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The conventional layered protocols in ad hoc networks tend to suffer from the inability to distinguish between losses due to route failures and congestion because of the inflexible structure. Recently, in efforts to overcome the challenges of dynamic environment, there have been increased interests in protocols that rely on interactions between different layers. The authors propose a cross-layer multicasting scheme based on the concept of local backtracking groups and adequate buffer equipped within nodes to avoid undesired retransmission from the source and further to improve the efficiency of source-to-receivers delivery with the aid of buffer. While encountering route failure, a node can quickly restore its routing paths to multicast subscribers by exploiting the precise notification from the MAC layer and the parent group then opportunely provides it with an unacknowledged packets conserved in the buffer. It is obviously benefic that retransmission packets are issued from the parent group rather than from the source. The authors present both analytic models and simulation results that substantiate the efficiency and robust of our approach based on realistic mobility scenarios. - Author(s): J. Villalón ; P. Cuenca ; L. Orozco-Barbosa ; Y. Seok ; T. Turletti
- Source: IET Communications, Volume 1, Issue 5, p. 893 –902
- DOI: 10.1049/iet-com:20060249
- Type: Article
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Multicast is an efficient paradigm for transmitting data from a sender to a group of receivers. According to the IEEE 802.11 standard, the multicast service is defined as an unreliable service, that is, it does not include the use of ACK frames. Furthermore, different to the unicast service, the multicast service makes use of a single rate out of the various rates included in the basic service set defined by the IEEE 802.11 standard. Even though various proposals have recently appeared in the literature addressing these issues, none of them has come out with a structured set of control mechanisms taking into account the varying conditions characterising the wireless channels as well as the requirements of various applications. A novel cross-layer auto rate selection multicast mechanism for multi-rate wireless LANs, namely auto rate selection for multicast, capable of adapting the data transmission to the varying conditions of the channel and taking into account the characteristics of various applications, is introduced. The simulation results show that our proposal outperforms the IEEE 802.11 standard and the mechanisms recently proposed in the literature. - Author(s): J.-W. Dai and L.-F. Chiang
- Source: IET Communications, Volume 1, Issue 5, p. 903 –908
- DOI: 10.1049/iet-com:20060247
- Type: Article
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Within the MultiProtocol Label Switching (MPLS) network, packets with the same forwarding equivalent class can easily be identified by their attached label value. The cross-layer topology associates with access protocol and IP mobility agents. The necessity of agent discovery is reduced and an approach to enhance handoff efficiency proposed. This efficient handoff scheme is performed by a foreign tracking agent (FTA) that plays a role as an administrator of a hierarchy that consists of some foreign agents (FAs) to localise the routing operation of forwarded packets. To analyse the performance of a hierarchical mobile MPLS network, the system is modelled as an M/G/1 system with capacity c, where c represents the number of FAs that can be administered for an FTA. The mean delay time of the FTA to process the forwarding of packets is analysed using M/M/1 with capacity c queueing model. The minimum number of FAs that can be administered for an FTA is derived to improve network performance by minimising mean delay time. - Author(s): V. Friderikos ; K. Papadaki ; D. Wisely ; H. Aghvami
- Source: IET Communications, Volume 1, Issue 5, p. 909 –914
- DOI: 10.1049/iet-com:20060260
- Type: Article
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The problem of multi-rate power-controlled collision-free scheduling in spatial time division multiple access (STDMA) wireless mesh networks is formulated as a mathematical program utilising cross layer information. As these mixed integer linear programs are intractable (${\cal NP}$-hard problems), optimal collision-free schedules can be found only for topologies consisting of a few nodes. To this end, approximation algorithms that are based on linear programming relaxation and randomised rounding are studied. The proposed framework, which aims to maximise the spatial timeslot reuse under predefined signal-to-interference noise ratio thresholds, is suitable for providing centralised scheduling in the mesh mode of the IEEE 802.16 standard. Performance aspects of the approximation algorithms under different scenarios are investigated. - Author(s): H.-Z. Chou ; S.-C. Wang ; S.-Y. Kuo ; I.-Y. Chen ; S.-Y. Yuan
- Source: IET Communications, Volume 1, Issue 5, p. 915 –923
- DOI: 10.1049/iet-com:20060262
- Type: Article
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Peer-to-peer (P2P) communications have attracted a great deal of attention from the network research community in recent years. However, due to the fundamental limitations of wireless environments, providing reliable data availability for P2P applications over wireless ad hoc networks is still a major challenge. To address the problem, a distributed and randomised scheme based on self-avoiding walks is proposed. The scheme concatenates disparate network layers, with the goal of recovering from routing failures that disrupt P2P data accessibility. In addition, a probabilistic approach is presented that explores the tradeoffs between several system parameters. Some new analysis tools, such as path coupling, are utilised which provide a better understanding of the system's operations. That the proposed concepts and techniques make a significant contribution to the design of effective and efficient P2P applications in wireless ad hoc networks is believed. - Author(s): R.-C. Wang and R.-S. Chang
- Source: IET Communications, Volume 1, Issue 5, p. 924 –932
- DOI: 10.1049/iet-com:20060298
- Type: Article
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Mobility support in Internet Protocol version 6 (IPv6) is a de facto standard for allowing nodes to remain connected while moving around in the IPv6 networks. To provide better handoff latency and performance, numerous optimisation techniques were developed. Some of them are single-layer optimisation such as the Hierarchical Mobile IPv6 architecture, which aims at reducing the registration time in network layer. Others are cross-layer optimisation such as the Fast Handover mechanism, which tries to reduce the address resolution time in network layer based on the data-link layer detection. Most of these techniques are focused on data-link and network layer optimisation. The authors propose a cross-layer mechanism, which uses the standard binding update packet in Mobile IPv6 handoff to enhance the overall transmission control protocol performance in transmission. The theoretical analysis and simulations show promising performance enhancements.
Editorial: Wireless mobile networks: cross-layer communication
Interaction between radio link level truncated ARQ, and TCP in multi-rate wireless networks: a cross-layer performance analysis
Cross-layer adaptive resource allocation for OFDM systems with hybrid smart antennas
Cross-layer distributed approach for optimal rate allocation for homogeneous wireless multicast
Adaptive bandwidth sharing mechanism for quality of service administration in infrastructure wireless networks
A cross-layer adaptive algorithm for multimedia QoS fairness in WLAN environments using neural networks
Authentication mechanism over the integrated UMTS network and WLAN platform using the cross-layer bootstrap
Using link layer throughput maximisation in ad hoc network routing algorithms
Provision of proportional delay differentiation in wireless LAN using a cross-layer fine-tuning scheduling scheme
Reliable cross-layer multicast with local backtracking for improving transmission control protocol performance in ad hoc networks
ARSM: a cross-layer auto rate selection multicast mechanism for multi-rate wireless LANs
Hierarchical wireless mobile MPLS mechanism using foreign tracking agent based on M/G/1 with capacity c queueing model
Multi-rate power-controlled link scheduling for mesh broadband wireless access networks
Randomised and distributed methods for reliable peer-to-peer data communication in wireless ad hoc networks
Cross-layer binding update for TCP performance enhancement over Mobile IPv6 networks
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- Author(s): Y. Zhang ; P. Fan ; M. Lee
- Source: IET Communications, Volume 1, Issue 5, p. 933 –936
- DOI: 10.1049/iet-com:20045084
- Type: Article
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The non-trivial errors in the calculation of the mean and variance of intercell interference in a recently published paper, [Wang, L. Aghvami, A.H. and Chambers, W.G.: ‘Capacity of a wideband multirate CDMA system with multiservice in the presence of fading and power-control error’, IEE Proc., Commun., 2003, 150, (1), pp. 59–63.] are pointed out. Because of these errors, the main numerical result in the above work is incorrect but it has been corrected. - Author(s): S.Z. Pinter and X.N. Fernando
- Source: IET Communications, Volume 1, Issue 5, p. 937 –944
- DOI: 10.1049/iet-com:20045143
- Type: Article
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Radio-over-fibre (ROF) has received increasing attention for its ability to enable broadband wireless access. This fibre-based wireless access scheme meets the demand for broadband service by integrating the high capacity of optical networks with the flexibility of radio networks (the optical and wireless channels are concatenated with one another). There are, however, impairments that come with this appealing technology. The nonlinear distortion of the optical link and the multipath dispersion of the wireless channel are two of the major factors. In order to limit the effects of these distortions, estimation, and subsequently equalisation, of the concatenated fibre-wireless channel needs to be done. An estimation algorithm for the fibre-wireless uplink in a multiuser code division multiple access (CDMA) environment is presented using pseudonoise training sequences. It has already been shown by Fernando et al. (2001) that identification of the fibre-wireless uplink is possible in a single user CDMA environment. However, the more difficult task of identification in a multiuser spread spectrum environment, which is more realistic, is shown. In the multiuser case, the cumulative effect of multiuser interference, multipath dispersion, nonlinear distortion and noise should all be handled together which makes it more challenging. Numerical evaluations of the developed algorithm show that a good estimation of both the linear and nonlinear systems is possible in the presence of 16 independent users and an signal-to-noise ratio (SNR) of 22 dB. The estimation accuracy increases with the length of the PN sequence. - Author(s): X. Dai
- Source: IET Communications, Volume 1, Issue 5, p. 945 –953
- DOI: 10.1049/iet-com:20045301
- Type: Article
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Time- and frequency-selective fading of propagating channels degrades the performance of multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/OFDM) systems extensively by introducing double convolutions in both time-domain and frequency-domain. The author addresses the problem of linearly time-varying (LTV) channel estimation of MIMO/OFDM systems. First, the time-varying coefficients of the LTV channel are modelled by complex exponential basis expansions. Secondly, the LTV channel is estimated and the optimal pilot symbols are derived following the minimum mean square error criterion. It is shown that the optimal pilot strategy is to group consecutive pilot tones together as a pilot cluster and to distribute uniformly all pilot clusters in frequency-domain. In addition, the LTV channel estimation is further improved by imposing a window function on received signals. Finally, through simulations, it is shown that the new channel estimator can provide a considerable performance improvement in estimating MIMO-LTV channels, especially for the rapidly time-varying channel of a large Doppler frequency. - Author(s): K. Kang ; Y. Cho ; J. Cho ; H. Shin
- Source: IET Communications, Volume 1, Issue 5, p. 954 –961
- DOI: 10.1049/iet-com:20060163
- Type: Article
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Multimedia services over a CDMA2000 broadcast network face a challenge from the unreliable and error-prone nature of the radio channel. Reed–Solomon (RS) coding, integrated with the MAC protocol, is used to cope with this problem. However, performance analysis of RS coding under varying channel conditions shows that it is not always effective, especially for slow-moving nodes which experience relatively long error bursts. Therefore a more efficient scheme is proposed that uses a RS code with reduced parity overhead, and freeing bandwidth can be used flexibly for retransmission. The packets to be retransmitted are prioritised by a utility function derived from the map of the error control block at each mobile node and the number of mobile nodes that require the lost packet. Simulation results show that the gain of retransmission exceeds the loss incurred by reducing the parity, leading to an improvement in the playback quality of MPEG-4 video streams. As a result, service area for high-quality multimedia can be expanded. - Author(s): H.M. Wang ; X.Q. Gao ; B. Jiang ; X.H. You ; W. Hong
- Source: IET Communications, Volume 1, Issue 5, p. 962 –969
- DOI: 10.1049/iet-com:20060581
- Type: Article
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Low complexity channel estimation for single-carrier block transmission systems over multiple-input multiple-output time varying frequency-selective channels is investigated. A time slot structure that uses Golay complementary sequences with perfect periodic autocorrelations as two-sided pilot blocks is presented. Employing this strucutre, optimal least square estimate in the minimum mean square error (MMSE) sense is achieved. Furthermore, a computationally efficient algorithm which is named as fast periodic Golay correlation is proposed based on the specific generator and the properties related to circulant matrices. Finally, the simulation results show the MMSE performance of the proposed scheme and algorithm. - Author(s): Z. Li ; L. Sun ; E.C. Ifeachor
- Source: IET Communications, Volume 1, Issue 5, p. 970 –976
- DOI: 10.1049/iet-com:20060289
- Type: Article
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Efficient mobility metrics are necessary for mobile ad hoc networks to measure the impact of node mobility on performance. Normally, measuring mobility requires the use of complex localisation systems. A new mobility metric for performance measurements, the intra-vicinity dependency, is proposed. Its main novelty is that it can fully capture the relative motions between a node and its vicinity in a 2D plane, in real-time, using simple triangulation. Variants of this metric are proposed for predicting the performance of networks that follow group and random mobility models (e.g. inter-group inter-meeting times and packet delivery rate). To make the proposed mobility metrics more robust in noisy environments, a calibration method is also proposed for improving accuracy. Experimental results show that, without the help of any localisation systems, the proposed metrics enable a more accurate approximation of the average relative speed between mobile nodes/groups than existing methods. It is also shown that the proposed metrics yield excellent performance when they are used to predict the inter-group inter-meeting times for networks that follow the Rereence Point Group Mobility model and to estimate the packet delivery rate for those that follow the Random Way Point model. - Author(s): B. Hu and N.C. Beaulieu
- Source: IET Communications, Volume 1, Issue 5, p. 977 –981
- DOI: 10.1049/iet-com:20060337
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A precise analysis is derived for calculating the bit error probability of a direct-sequence ultra-wideband system accounting for the multiuser interference on additive white Gaussian noise (non-frequency selective) channels. The exact solution is validated by simulation and used to determine the accuracy of a recently published approximation based on a simplified receiver decision statistic, as well as to assess the inaccuracy of the Gaussian approximation. It is established that the Gaussian approximation may only be accurate for an impractically large number of simultaneous users. - Author(s): V. Zarimpas ; B. Honary ; M. Darnell
- Source: IET Communications, Volume 1, Issue 5, p. 982 –989
- DOI: 10.1049/iet-com:20060355
- Type: Article
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The presence and availability of several independent wired and wireless networks within a communication environment has led to the channel adaptive multiple I/O (CAMIO) protocol being developed as an appropriate and novel technique for data transmission. The proposed system utilises an intelligent multiplexing technique that enables the transmission/reception of multiple data sources via several wired/wireless networks simultaneously. Real-time configuration and adaptation capabilities when data sources/channels are dynamically added/deleted/modified are described. Data prioritisation methods, combined with traffic control and congestion-reactive techniques, are presented. Simulation results demonstrate that the use of the CAMIO protocol over multiple transmission/reception channels increases the overall data transmission rate, handles the delivery of time-sensitive packets and maintains the quality of service, especially in situations where one or more communication channels fail to operate. - Author(s): Z.B. Krusevac ; P.B. Rapajic ; R.A. Kennedy
- Source: IET Communications, Volume 1, Issue 5, p. 990 –998
- DOI: 10.1049/iet-com:20060477
- Type: Article
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This paper looks at capacity achieving detection strategies for information transfer over time-varying channels. The time-varying binary symmetric channel (TV-BSC) is identified as the basic binary state-space model. Separation of entropies principles and the TV-BSC model-based state-space approach are used to determine the performance bounds for coherent and non-coherent detection over time-varying communication channels. The mutual information rate over the TV-BSC, assuming channel estimation in the presence of channel noise, is shown to be below the channel information capacity because of lack of perfect channel knowledge. Furthermore, it is shown that TV-BSC model-based differential detection has a fundamental advantage over the channel estimation based detection since it theoretically preserves the TV-BSC information capacity when the observation interval approaches infinity. Simulation analysis corroborates the theoretical results, showing that multiple-symbol differential detection practically achieves the TV-BSC capacity in just a few symbol observation times. - Author(s): M. Peng ; Y. Wang ; W. Wang
- Source: IET Communications, Volume 1, Issue 5, p. 999 –1006
- DOI: 10.1049/iet-com:20060519
- Type: Article
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Infrastructure wireless mesh network, also named as mesh router, is one key topology for the next generation wireless networking. In this work, the performance optimisation for the infrastructure wireless mesh network is presented and the sub-optimum solution mechanism is investigated. A cross-layer design for tree-type routing, level-based centralised scheduling and distributed power control theme is proposed as the sub-optimum solution strategy. The cross-layer design relies on the channel information and the distributed transmission power control in the physical layer, and the wireless scheduling in the medium access control (MAC) layer, as well as the routing selection mechanism in the MAC upper layer. In this work, a modified distributed power control algorithm is proposed first. In addition, a tree-type routing construction algorithm for centralised scheduling is presented to improve the network throughput by jointly considering interference and hop-count to construct the routing tree. Simulation results show that the proposed cross-layer design strategy can effectively improve the network throughput performance, decrease the power consumption and achieve better performances. - Author(s): J. Yang ; M.E. Aydin ; J. Zhang ; C. Maple
- Source: IET Communications, Volume 1, Issue 5, p. 1007 –1014
- DOI: 10.1049/iet-com:20060495
- Type: Article
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Radio networks of universal mobile telecommunication system (UMTS) need accurate planning and optimisation, and many factors not seen in second generation (2G) networks must be considered. However, planning and optimisation of UMTS radio networks are often carried out with static simulations, for efficiency and to save time. To obtain a good trade-off between accuracy and computational load, link-level performance factors need to be taken into account. The authors propose a mathematical model for UMTS radio network planning taking into consideration fast power control, soft handover and pilot signal power in both uplink and downlink. Optimisation strategies are investigated based on three meta-heuristics: genetic algorithm, simulated annealing (SA) and evolutionary-SA. The base station location problem is modelled as a simplified p-median problem, and parameter tuning of these meta-heuristics are presented. Extensive experimental results are used to compare the performance of different algorithms in terms of statistical measurements. - Author(s): I. Pehlivan and Y. Uyaroğlu
- Source: IET Communications, Volume 1, Issue 5, p. 1015 –1022
- DOI: 10.1049/iet-com:20070131
- Type: Article
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Diffusionless Lorentz equations a simplified one-parameter version of the well-known Lorentz model. Also, it was attained in the limit of high Rayleigh and Prandtl numbers, physically corresponding to diffusionless convection. A simplified, one-parameter version of the Lorentz model called diffusionless Lorentz is proposed, which is suitable for chaotic synchronisation and masking communication circuits using Matlab–Simulink and PSpice programmes. It is also suitable for a real electronic experimental circuit. - Author(s): V. Bozantzis ; F.H. Ali ; E. Stipidis
- Source: IET Communications, Volume 1, Issue 5, p. 1023 –1030
- DOI: 10.1049/iet-com:20060546
- Type: Article
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A new vector encoder–decoder (VED) design that is jointly adaptive to source statistics and optimised for noisy channels is proposed. The vector encoder consists of a source-adaptive vector quantiser (AVQ) and a structured index assignment with embedded redundancy (IAER) scheme to provide error-protection capability for noisy channels. The AVQ and IAER processes are combined together resulting in a very effective source-adaptive and channel-optimised VED design. The joint algorithm is designed and evaluated for the non-stationary Wiener process, modelling the source, and for two noisy channels, the binary symmetric channel and the more practical wireless flat-fading Rayleigh channel. It is shown that the proposed technique gives substantial signal-to-noise ratio gains over the separate design of the source AVQ and the IAER in both channel conditions without any additional online computational complexity. In addition, it is suitable for different applications of varying source and channel environments. - Author(s): V. Ponnampalam and P.B. Darwood
- Source: IET Communications, Volume 1, Issue 5, p. 1031 –1038
- DOI: 10.1049/iet-com:20060550
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Short spreading sequences facilitate efficient multiuser detectors and have hence been incorporated into practical code division multiple access systems such as 3rd Generation Partnership Project UTRA-TDD. However, as the number of users approaches the spreading code length, the asymptotic performance and the numerical stability of linear multiuser detection algorithms degrade. Given some simplifications such as synchronous users, it is shown that receive diversity effectively mitigates these degradations and allows the system to be operated with a high load. A lower bound on the mean asymptotic multiuser efficiency is presented and the numerical stability of linear multiuser detection algorithms for systems with receive diversity is analysed. It is further shown that the performance variability is significantly reduced by receive diversity. - Author(s): M. Esmaeili and A. Kakhbod
- Source: IET Communications, Volume 1, Issue 5, p. 1039 –1041
- DOI: 10.1049/iet-com:20070076
- Type: Article
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A source ={s1, s2, …} having a binary Huffman code with code-word lengths satisfying l1=1, l2=2, … is called an anti-uniform source. If l1=1, l2=2, … , li=i, then the source is called an i-level partially anti-uniform source. The redundancy, expected codeword length and entropy of anti-uniform sources are dealt here. A tight upper bound is derived for the expected codeword length L of anti-uniform sources. It is shown that L does not exceed $\surd{5}+3/2$. For each $1\lt L\le \lpar \surd{5}+3\rpar /2$, an anti-uniform distribution achieving maximum entropy H(P)max=L log L−(L−1)log(L−1) is introduced. This shows that the maximum entropy achieved by anti-uniform distributions does not exceed 2.512. It is shown that the range of redundancy values for i-level partially anti-uniform sources with distribution {pi} is an interval of length ∑j=i+1pj. This results in a realistic approximation for the redundancy of these sources. - Author(s): C.-H. Cheng ; J.-Y. Lin ; J.-H. Wen
- Source: IET Communications, Volume 1, Issue 5, p. 1042 –1047
- DOI: 10.1049/iet-com:20060587
- Type: Article
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A convenient signalling scheme, called orthogonal on–off (O3), together with a simple one-shot linear decorrelating detector (LDD) and a RAKE bank, is adopted in asynchronous ultra-wideband (UWB) systems. The performance of the proposed system is evaluated over multipath fading channels. This investigation also analyses mathematically the effect of the maximal-ratio combining diversity technique on the O3UWB LDD performance over lognormal fading channels. The analytical and simulation results indicate that the diversity technique significantly improves the performance of the O3UWB LDD scheme over fading channels, and the proposed receiver still demonstrates a better near–far-resistant property than a conventional UWB receiver. - Author(s): J. Dunlop and M. Mzyece
- Source: IET Communications, Volume 1, Issue 5, p. 1048 –1055
- DOI: 10.1049/iet-com:20060606
- Type: Article
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The incremental redundancy mechanism defined for enhanced general packet radio service (EGPRS) (also known as type-II hybrid ARQ) is considered here. The optimum packet combining strategy is identified and is then used to assess the performance of transmission control protocol/internet protocol in the transmission of bulk data over an EGPRS system. The influence of other key system operating parameters is also assessed and a set of optimal operating parameters is derived and discussed. - Author(s): M.H. Xia ; Y.P. Zhou ; W.K. Wen
- Source: IET Communications, Volume 1, Issue 5, p. 1056 –1060
- DOI: 10.1049/iet-com:20060629
- Type: Article
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To avoid poor efficiency of the power amplifiers, the opportunistic cophasing communication system randomises only the phase of beamforming vector elements, instead of randomising both amplitude and phase. The opportunistic cophasing system with multi-beam transmission is focused. The cophasing matrix with a rotation matrix is first constructed. Then, the upper and lower bounds of asymptotic system throughput are analytically derived, based on the theory of order statistics. Finally, simulation results demonstrate the effectiveness of the proposed method in terms of system throughput. - Author(s): J. Kim ; J. Kim ; H. Park ; B. Kim ; S. Park
- Source: IET Communications, Volume 1, Issue 5, p. 1061 –1066
- DOI: 10.1049/iet-com:20060632
- Type: Article
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Using a variable scaling factor (VSF), a modified enhanced max-log-maximum a posteriori (EMLMAP) algorithm is proposed to improve the performance of the conventional EMLMAP algorithm which uses a fixed SF. The VSF, maximising the mutual information exchanged between component decoders in a turbo decoder, is adaptively varied with a priori information of each component decoder. For a large size of interleaver, it is shown that the proposed algorithm improves the bit error rate performance and speed of decoding convergence of the conventional EMLMAP algorithm. The improved speed of the decoding convergence reduces the average number of iterations and results in low-power implementations of a turbo decoder. - Author(s): X. Shao ; J. Yuan ; Y. Shao
- Source: IET Communications, Volume 1, Issue 5, p. 1067 –1074
- DOI: 10.1049/iet-com:20070037
- Type: Article
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Linear precoding (LP) techniques for a multiuser multiple-input-multiple-output broadcast channel is investigated and analytical results of the achievable sum capacity and error performance for zero forcing (ZF) linear precoders is presented. It is shown that the detection signal-to-noise ratio of ZF-LP can be accurately approximated by a shrinking Chi-square distribution. The symbol error rate and its achievable diversity gain of ZF-LP are given. Then, an improved linear precoder based on the minimum mean-square error (MMSE) criterion is derived. Its error performance and sum capacity are analysed and compared with that of the ZF-LP. It is shown that the MMSE-LP can achieve much better error performance and a high sum capacity than the existing ZF-LP. - Author(s): L. Chu ; J. Yuan ; Z. Chen
- Source: IET Communications, Volume 1, Issue 5, p. 1075 –1081
- DOI: 10.1049/iet-com:20060680
- Type: Article
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In this paper, a coded beamforming scheme is considered for frequency-flat multiple-input-multiple-output (MIMO) fading channels. With channel state information (CSI) available at the transmitter, this scheme combines coded modulation (CM) with downlink transmission beamforming to exploit both diversity and coding advantages. In order to identify the appropriate code design criteria, the exact pairwise error probability and bit error rate upper bounds are derived for both frequency-flat slow and fast MIMO Rayleigh fading channels. It is shown that the minimum squared Euclidean distance of the code should be maximised in slow-fading channels, whereas the minimum effective code length and the product distances should be maximised in fast-fading scenarios. This conclusion indicates that the conventional Ungerboeck's trellis-coded modulation codes originally designed for additive white Gaussian noise channels and single-antenna Rayleigh fading channels could be directly utilised in the proposed scheme for slow and fast MIMO fading channels, respectively. This eliminates the need for complicated code design. Simulation results are provided to substantiate the theoretical analysis. For an example, it is demonstrated that a trellis-coded beamforming scheme can outperform the published space-time trellis coded beamforming schemes by up to 4 dB, although it has a simpler encoder structure and requires no specific code design. Interference free is assumed in the analysis, while the impact of the imperfect CSI and antenna correlation on the system error performance is evaluated. - Author(s): W. Wang ; R. Jin ; J. Geng
- Source: IET Communications, Volume 1, Issue 5, p. 1082 –1087
- DOI: 10.1049/iet-com:20070011
- Type: Article
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The minimum symbol error rate (SER) precoder design for spatial multiplexing (SM) system with zero forcing detector over correlated channel is investigated. With the knowledge of channel correlation at the transmitter, a precoder scheme that combines eigen-beamforming with power allocation (PA) is proposed. A closed-form expression for optimal PA on the eigenbeams is presented to minimise the overall average SER through an approximate SER analysis. When compared with the minimum mean-square error (MMSE) waterfilling precoder, the pre-processing is very simple in that it avoids loop or iteration operation in waterfilling algorithm. Both the analytical and simulation results have confirmed the effectiveness of the precoder. Moreover, when the number of receive antennas is larger than that of the transmit antennas, the performance of this proposal can approximate or even exceed that of MMSE waterfilling precoder at higher signal-to-noise ratio.
Comments on ‘capacity of a wideband multirate CDMA system with multiservice in the presence of fading and power-control error’
Concatenated fibre-wireless channel identification in a multiuser CDMA environment
Optimal training design for linearly time-varying MIMO/OFDM channels modelled by a complex exponential basis expansion
Error recovery in video transmission over CDMA2000 broadcast networks
Efficient MIMO channel estimation using complementary sequences
GPS-free mobility metrics for mobile ad hoc networks
Precise performance analysis of DS-UWB systems on additive white Gaussian noise channels in the presence of multiuser interference
Channel adaptive multiple I/O protocol for mixed wireless and wired channels
Basic binary state-space model for time-varying communication channels: uncertainty and information capacity
Cross-layer design for tree-type routing and level-based centralised scheduling in IEEE 802.16 based wireless mesh networks
UMTS base station location planning: a mathematical model and heuristic optimisation algorithms
Simplified chaotic diffusionless Lorentz attractor and its application to secure communication systems
Joint source-adaptive vector quantisation and index assignment with embedded redundancy
Diversity reception in short-code CDMA
On information theory parameters of infinite anti-uniform sources
Orthogonal on–off-based near–far-resistant detection with diversity technique in UWB systems
Influence of incremental redundancy on the performance of TCP in enhanced general packet radio service
Throughput of the opportunistic cophasing communication system with multi-beam transmission
Modified enhanced max-log-maximum a posteriori algorithm using variable scaling factor
Error performance analysis of linear zero forcing and MMSE precoders for MIMO broadcast channels
A coded beamforming scheme for frequency-flat MIMO fading channels
Minimum symbol error rate precoder design for spatial multiplexing over correlated channels
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