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Communications, IET

Issue 15 • Date October 16 2012

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Displaying Results 1 - 25 of 30
  • Balanced counting bloom filters: a space-efficient synoptic data structure for a high-performance network

    Page(s): 2259 - 2266
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    A Bloom filter is a simple space-efficient randomised data structure allowing membership queries over data sets. It is widely utilised in peer-to-peer network, traffic measurement and distributed systems. Aiming at the deficiencies of the naïve counting Bloom filters (NCBFs), a novel data structure called balanced counting Bloom filters (BCBFs) is presented. In order to achieve space-efficient storage and effective query, the BCBF adopts the following methods: introducing hash fingerprints, partitioning bucket vectors into equally sized segments and storing elements with the least load bucket. Analytical expressions are deduced in detail based on the theory of differential equations and probability. Besides, simulations are conducted based on the data produced by computer and real network trace. The results demonstrate that the BCBF cannot only serve the same functionality as the NCBF using much less space, but also becomes a valuable tool in hardware to scale the high-speed link. View full abstract»

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  • Improved transmitted reference pulse cluster scheme for ultra wideband communication systems

    Page(s): 2267 - 2273
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (779 KB)  

    In this study, from a more practical point of view, the authors develop an improved transmitted reference pulse cluster (iTRPC) scheme. Based on a recently proposed transmitted reference pulse cluster (TRPC) structure, each pulse cluster is broken into reference pulse clusters (RPCs) and data pulse clusters (DPCs). It is observed that by inserting a number of zeros at the end of each RPC and each DPC, inter pulse interference can be dramatically reduced. This also results in more multi-path delayed power being captured for data detection. The performance of the proposed iTRPC scheme is analysed and compared with that of traditional TR and the original TRPC (oTRPC) system. Simulations verify that this iTRPC scheme, with quite low-complexity and not extra energy requirements, achieves more than 7 dB performance improvement over the oTRPC scheme. View full abstract»

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  • Data rate selection for efficient broadcasting in ad hoc networks

    Page(s): 2274 - 2277
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (415 KB)  

    The required transmission time decreases as the data rate increases on a single link. When broad-casting in an ad hoc radio network, this may not be so, as the number of retransmissions may grow as the data rate increases because of decreased transmission range. Moreover, there is often a non-trivial optimum. To resolve the problem of selecting an appropriate rate in such a network, the authors propose a novel method that is theoretically optimal under certain simplifying conditions. When compared with other rate selection methods under more realistic assumptions, the authors have found it to perform better. It is also easy to implement in a real system. View full abstract»

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  • Game-theoretic approach for interference management in heterogeneous multimedia wireless personal area networks

    Page(s): 2278 - 2286
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (610 KB)  

    Emergence of new wireless technologies has facilitated the way to higher data rates and more robust communication links. Ultra wideband (UWB) is one of these promising technologies that, despite its several outstanding benefits, can cause interference to other networks operating in the same frequency range because of its large bandwidth. In this study, the authors introduce a solution for interference management in heterogeneous UWB networks. The analysis can be generalised for other coexistence scenarios where we have wireless networks with different specifications. Game theory is used to study the joint power and rate control problem under mutual interference between two UWB standards, namely, multiband orthogonal frequency division multiplexing UWB and direct-sequence UWB. A non-cooperative joint rate and power control game with pricing (NRPGP) in which each node seeks to choose its possible transmit power and rate in order to maximise its own utility while satisfying its target signal-to-interference-and-noise ratio as quality-of-service requirement is introduced. Simulation results are provided to evaluate the performance of the proposed game, NRPGP. View full abstract»

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  • QoS-guaranteed IP mobility management for fastmoving vehicles with multiple network interfaces

    Page(s): 2287 - 2295
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    In this study, the authors present a quality-of-service (QoS)-guaranteed IP mobility management scheme for fast-moving vehicles with multiple wireless network interfaces. The idea of the proposed mechanism consists of two things. One is that new wireless connections are established to available wireless channels whenever the measured data rate at the mobile node drops below to the required data rate of the user requirement. The other is that parallel distribution packet tunnels between an access router and the mobile node are dynamically constructed using multiple wireless network interfaces in order to guarantee the required data rate during the mobile node's movement. By doing these methods, the required data rate of the mobile node can be preserved while eliminating the possible delay and packet loss during handover operation, thus resulting in the guaranteed QoS. The architecture of the Internet engineering task force standard hierarachical mobile IPv6 (HMIPv6) has been extended to realise the proposed scheme, and detailed algorithms for the extension of HMIPv6 has been designed. Finally, simulation has been done for performance evaluation, and the simulation results show that the proposed mechanism demonstrates guaranteed QoS during the handover with regard to the handover delay, packet loss and throughput. View full abstract»

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  • Phase locked loop assisted phase tracking in asynchronous-code division multiple access systems over slow fading and time-varying channels using simplified expression for improved Gaussian approximation

    Page(s): 2296 - 2305
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1104 KB)  

    In this study, a simplified expression for improved Gaussian approximation is considered to model multiple access interference in an A-code division multiple access system. Punctured convolutional codes, which are one of the subclasses of convolutional codes, are employed to provide error protection to the information transmitted over the wireless channel. A detailed theoretical analysis is carried out initially and then compared with the simulated results for the various code rates. The simulated performance of the codes is then compared for different power levels and different number of interferers of the desired user. No phase information is assumed to be available for the information signal of the desired user throughout this study. View full abstract»

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  • Transmit precoding scheme for inter-carrier interference suppression and path diversity in fractional sampling-orthogonal frequency division multiplexing (OFDM)

    Page(s): 2306 - 2313
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (555 KB)  

    Fractional sampling (FS) has been investigated to achieve path diversity with a single antenna in an OFDM system. However, in the FS-OFDM system, it is necessary to oversample a received signal and it leads to large power consumption in a small terminal. To shift the signal processing burdens for FS from a receiver to a transmitter, a precoded transmit path diversity scheme in OFDM has been proposed. It achieves path diversity without oversampling the received signal at the receiver side on time invariant channels. However, it has not taken time variant channels into consideration. On time variant channels, inter-carrier interference (ICI) deteriorates the bit-error-rate (BER) performance. In this study, the precoding for both ICI suppression and path diversity combining at the transmitter side has been proposed. Computer simulation shows that both the conventional scheme and the proposed scheme can achieve transmit path diversity. On a two path Rayleigh fading channel, the BER performance of the proposed scheme is better than that of the conventional scheme by about 1 dB. On ultra wideband (UWB) channels, the performance of the proposed scheme is 7-10 dB better at BER 10-2 than that of the conventional scheme. It can achieve ICI suppression and path diversity without any specific signal processing at the receiver. The effect of the ICI suppression is more significant as the number of the multipath is larger. View full abstract»

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  • Different perspective and approach to implement adaptive normalised belief propagation-based decoding for low-density parity check codes

    Page(s): 2314 - 2325
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (558 KB)  

    In this study, the authors propose an improved version of the min-sum algorithm for low-density parity check code decoding, which the authors call `adaptive normalised BP-based` algorithm. Their decoder provides a compromise solution between belief propagation and the min-sum algorithms by adding an exponent offset to each variable node`s intrinsic information in the check node update equation. The extrinsic information from the min-sum decoder is then adjusted by applying a negative power of the two scale factor, which can be easily implemented by right shifting the min-sum extrinsic information. The difference between their approach and other adaptive normalised min-sum decoders is that the authors select the normalisation scale factor using a clear analytical approach based on the underlying principles. The simulation results show that the proposed decoder outperforms the min-sum decoder and performs very close to the BP decoder with lower complexity. View full abstract»

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  • Theoretical framework for quality of service analysis of differentiated traffic in 802.11 wireless local area networks

    Page(s): 2326 - 2334
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (578 KB)  

    In this study, the authors provide an analytical framework to assess network-level quality of service (QoS) measures for differentiated, non-saturated traffic in infrastructure-mode 802.11 wireless local area networks using the distributed coordination function access mechanism. The authors build on a general analytical framework that takes into account the medium access control (MAC) access mechanism, the MAC layer packet buffer and the characteristics of the offered load to obtain the probability of a collision with M classes of traffic. The authors then derive analytical expressions for the throughput, the end-to-end packet delay and the packet delay outage probability for differentiated traffic. A case study of voice-over-IP (VoIP) traffic in 802.11b/g networks is used to validate the theoretical framework. The analytical results are in good agreement with the simulation results, showing that although the collision probability for packets transmitted at the access point (AP) is lower than for packets transmitted from the clients, the end-to-end delay in the downlink is much longer than that in the uplink because of the large queuing delay because of the multiplexing of several VoIP connections at the AP. The authors also compare the maximum number of VoIP connections that can be admitted in an 802.11 network while respecting their QoS constraints; these were computed with the proposed theoretical model, an ns-2 simulation model and other schemes previously proposed in the literature. The results indicate that their approach is more accurate over a wide range of parameter values, thus demonstrating the validity, the flexibility and the robustness of the proposed theoretical framework. View full abstract»

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  • Beamforming and positioning-assisted handover scheme for long-term evolution system in high-speed railway

    Page(s): 2335 - 2340
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (247 KB)  

    As the railway industry expands and trains speed-up, the reliability and efficiency of wireless communication systems in high-speed railway have to face the severe challenges. The high-speed brings about more severe Doppler effect, the postponement of handover triggering location and more frequent handover. Therefore the influence caused by the high-speed decreases the reliability of wireless communication network. In this study, considering the decision of `global system for mobile communication for railway` evolution to long-term evolution for railway (LTE-R) by International Union of Railways, a scheme based on the beamforming and positioning information is proposed to improve the system handover performance for the LTE system which is being applied to the high-speed railway. In the overlapping region, both the current serving eNodeB and the target eNodeB start to use beamforming with different gain factors to improve handover success probability. The results have shown that the proposed scheme increases the handover success probability effectively. View full abstract»

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  • Doubly multistage decoding of low-density parity-check codes over Z2m

    Page(s): 2341 - 2350
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    A doubly multistage decoder (DMD) for low-density parity-check codes over Z2m, m>;1, which fuses the multistage decoding approaches of Armand et al. and Varnica et al., is proposed. Two variants of the DMD are considered. The first (respectively, second) performs belief-propagation (BP) [respectively, offset min-sum (OMS)] decoding in each decoding stage and is referred to as DMD - BP (respectively, DMD - OMS). For the moderate-length codes considered in this study, the computer simulations show the DMD - BP (respectively, DMD - OMS) achieving coding gains of up to 0.43 dB (respectively, 0.67 dB) over standard BP decoding at a bit error rate of 10-6 on an additive-white-Gaussian-noise channel, while requiring significantly less computational power. Remarkably, DMD - OMS outperforms DMD - BP, yet has lower computational complexity than DMD - BP. Snapshots of the log-likelihood ratio densities of the decoded bits midway through the decoding process explain the superiority of the DMD over standard BP decoding. View full abstract»

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  • Parallel interference cancellation with different linear equalisation and rake receiver for the downlink MC-CDMA systems

    Page(s): 2351 - 2360
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1477 KB)  

    The multi-carrier code division multiple access (MC-CDMA) is becoming a very attractive multiple access technique for high-rate data transmission in the future wireless communication systems. MC-CDMA systems transmitting over multipath channels suffer from inter-symbol interference (ISI) and multiple access interference (MAI). Recently, MC-CDMA with equalisation has attracted much attention for its ability to obtain an excellent performance even in strong frequency-selective fading channels. In this study, the proposed architecture uses the minimum mean-square error (MMSE) with parallel interference cancellation (PIC) for downlink MC-CDMA system and compared with another system based on the rake receiver with PIC for downlink MC-CDMA system. A comparison between such architectures is presented. The effect of the tentative decision functions and the effect of the loading users on the performance of the two proposed receivers are discussed and presented in this study. Simulation results show that the combination of tentative decisions with PIC and equalisation provides an efficient solution to suppress the MAI and ISI in downlink MC-CDMA systems over frequency-selective fading channels. View full abstract»

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  • Additive statistical modelling of land mobile satellite channels in three-dimensional scattering environment

    Page(s): 2361 - 2370
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (699 KB)  

    A new channel model with additive complex envelope process for land mobile satellite channel is proposed. The two fading processes, small-scale fading and shadow fading, are represented with Nakagami-q and lognormal distribution, respectively. Exact analytical expressions of first- and second-order statistics are derived for the proposed model. For the purpose of normalisation of second-order statistics with respect to maximum Doppler frequency, a three-dimensional scattering model is taken. A special case of the authors' proposed channel model gives rise to a new distribution, 'extended Nakagami-q distribution', and the same is reported with its statistics. The dependence of second-order statistics on different parameters is analysed with the computed results obtained from derived expressions. The results computed from the analytical expressions are also in good resemblance with the corresponding measurement results in a suburban propagation environment. View full abstract»

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  • Block diagonalisation-based multiuser multiple input multiple output-aided downlink relaying

    Page(s): 2371 - 2377
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (382 KB)  

    A novel block diagonalisation (BD)-based Multiuser multiple input multiple output (MU-MIMO)-aided relaying scheme is proposed for downlink transmissions, which does not require any channel state information at the base station (BS) and decomposes a MU-MIMO-aided relaying system into several parallel single-user MIMO-assisted relaying schemes. Furthermore, based on the proposed algorithm the optimal linear processing matrix designed for the maximum achievable capacity is derived, which significantly outperforms the so-called naive weighting matrix. View full abstract»

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  • Phase ambiguity mitigation for per-cell codebookbased limited feedback coordinated multi-point transmission systems

    Page(s): 2378 - 2386
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    Limited feedback techniques, that employ codebook-based quantisation, are used in coordinated multi-point (CoMP) transmission to convey the channel direction information between the mobile user and each base station in the cooperative set and also among the cooperating base stations. However, unlike single-cell multiple-user multiple input multiple output (MU-MIMO) systems, CoMP systems face additional challenges in this codebook design. Among these challenges are the huge feedback overhead and the need for dynamic codebook size. These problems are solved when CoMP uses the so-called per-cell codebook, in which the channel to each cell is quantised separately. However, this results in a further problem, that is having random phase values between the quantised per-cell channels of the same user. In this study, the phase ambiguity problem is explained and its effect on performance degradation is quantified. A new quantisation technique is proposed where the quantisation of each of the real and the imaginary parts is performed independently using the same real codebook. This novel solution prevents the phase ambiguity problem instead of trying to mitigate its effects, in addition to simplifying the codebook design. The proposed quantisation technique outperforms two recently introduced solutions in the literature. The first solution is to quantise phase ambiguity as part of channel state information (CSI), whereas the other avoids phase ambiguity by an iterative selection procedure. Mathematical validations and simulations are provided to verify these findings. View full abstract»

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  • Capacity and power allocation for spectrum sharing in cognitive radio systems under unknown channel state information and imperfect spectrum sensing

    Page(s): 2387 - 2394
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (510 KB)  

    Cognitive radio is a technology with tremendous potential for more efficient utilisation of the radio spectrum. Based on the available network side information to the secondary user, three transmission models are proposed in the literature: the `underlay` method, the `overlay` method and the `hybrid` method. The authors study here the capacity and power allocation for the hybrid method. In particular, the authors investigate the ergodic capacity of the secondary user under joint average transmission power and average interference to the primary user receiver constraints when no channel state information is available to the secondary user except its probability density function. An algorithm based on the barrier method is proposed to achieve this. Finally, simulation results are presented and analysed to validate the authors` theoretical results. View full abstract»

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  • Device-free localisation with wireless networks based on compressive sensing

    Page(s): 2395 - 2403
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (515 KB)  

    A compressive sensing-based approach to solve the problem of tracking targets in the deployment area of the wireless networks without the need of equipping the target with a wireless device has been proposed. We present a dynamic statistical model for relating the change of the received signal strength between the node pairs to the spatial location of the target. On the basis of the model, the problem is formulated as a sparse signal reconstruction problem, and we propose a novel Bayesian greedy matching pursuit (BGMP) algorithm to tackle the signal reconstruction problem even from a small set of measurements. The BGMP iteratively seeks the contribution of each pixel for multi-times to compensate for the inaccuracy of the measurement matrix, and builds the enumeration region based on the past estimations to speed up the algorithm and improve its reconstruction performance simultaneously. Experimental results demonstrate the effectiveness of our approach and confirm that the BGMP algorithm could achieve satisfactory localisation and tracking results. View full abstract»

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  • Characterisation of highly absorbent and highly reflective radio wave propagation environments in industrial applications

    Page(s): 2404 - 2412
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    Experience has shown that Bluetooth, Wireless LAN (WLAN), Digital Enhanced Cordless Telecommunications (DECT) and other Industrial, Scientific and Medical (ISM) frequency band wireless technologies developed for office use, have encountered problems when used in critical industrial applications. The development of more reliable wireless solutions requires extensive knowledge of industrial environments with regards to both electromagnetic interference and wave propagation. This study presents the results of the analysis of two important classes of industrial environments having opposite characteristics, one being highly absorbent and the other being highly reflective, with respect to radio wave propagation. The analysis comprises both multipath and path loss characterisation. The results show that wireless solutions with different fundamental properties must be chosen for each of these environments to ensure high reliability. The conclusions of this work can be used as an important reference for further research in this area, as well as the design of new standards and guidelines for selecting wireless solutions in similar industrial environment classes. View full abstract»

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  • Capacity maximisation in eigen-multiple-input multiple-output using adaptive modulation and Reed-Solomon coding

    Page(s): 2413 - 2424
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (622 KB)  

    Eigen-multiple-input multiple-output (MIMO) with water-filling gives the maximum information-theoretic capacity, but realising this maximisation is not straightforward because practical factors are omitted. Adaptive modulation and error coding are combined for finding the maximum practicable capacity (throughput of correctly detected bits) in eigen-MIMO. Quadrature amplitude modulation (QAM) is the logical choice of modulation and here Reed-Solomon (RS) coding is used. RS coding has the advantages of algorithmic simplicity, low-memory requirements, and decoder complexity, and its unique closed-form error probability makes it possible to obtain an optimal power allocation, signal constellation size(s), and code rate(s) on the eigenchannels, for the maximum practicable capacity. The proposed adaptive scheme is applied to two architectures for the encoders/decoders (CODECs): outer coding, where a single CODEC is deployed for the overall serial data; and inner coding, where there is a CODEC for each eigenchannel. The optimal power allocation is different to the water-filling used for the information-theoretic capacity. Also, simple and accurate approximations are found for the bit-error rate (BER) of a single Rayleigh channel and of a 2-2 system. Finally, a selection procedure between different system configurations is presented for obtaining the highest practicable capacity subject to either average or instantaneous output BER. View full abstract»

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  • Performance analysis of two-dimensional optical code-division multiple-access systems using novel multi-code pulse-position modulation

    Page(s): 2425 - 2431
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (539 KB)  

    Previous works show that pulse-position modulation (PPM) is an effective signalling method for mitigating multiple-access interference, and hence is able to increase the number of users in two-dimensional (2-D) optical code-division multiple-access (OCDMA) systems. However, in order to achieve high bit-rates, 2-D OCDMA systems using PPM signalling require very high transmitted power because of the negative impact of dispersion. In this study, the authors propose a novel modulation technique of multi-code PPM (MCPPM), which is the combination of the PPM and multi-code modulation (MCM). As the proposed technique inherits advantages from both MCM (in mitigating the dispersion) and PPM, 2-D OCDMA systems using MCPPM signalling are able to support higher user bit-rates for a larger number of users at low transmitted powers. Numerical results show that 2-D OCDMA systems using 4-4-MCPPM can support 60 users with 5 Gbps per user at the transmitted power of 7 dBm. The power gain in this case is 11 dB compared to 2-D OCDMA systems using 4-PPM signalling. The proposed systems using 4-2-MCPPM can support as many as 36 users with the bit-rate of 10 Gbps per user and transmitted power is 2 dBm. View full abstract»

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  • Design of low peak-to-average power ratio transceiver with enhanced link quality for coded single-carrier frequency division multiple access system

    Page(s): 2432 - 2441
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1358 KB)  

    A new low peak-to-average power ratio (PAPR) transceiver is proposed for the coded single-carrier frequency division multiple access (SC-FDMA) system over frequency selective fading channels. By exploiting the constant envelope of the Chu-sequence in both frequency and time domains, the parallel spreading scheme and M-ary cyclic shift mapping technique can support the coded SC-FDMA system with a low PAPR for transmission at a high data rate. Interleaved time and frequency domain orthogonal modulation can increase the frequency diversity gain through the frequency domain equaliser and the time domain despreader. Moreover, the maximum likelihood rule is designed to detect the M-ary mapping data, which can provide M-ary gain to improve system performance. Simulation results reveal that the proposed high-rate coded SC-FDMA system can provide a lower PAPR and a better bit error rate (BER) performance than the conventional interleaved SC-FDMA system. View full abstract»

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  • Transmission scheme for a K-way relay multiple-input multiple-output channel

    Page(s): 2442 - 2447
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    In the multiple-input multiple-output Gaussian K-users relay interference channel, each user intends to convey a multicast message to all the other users while receiving K-1 independent messages from the other users via an intermediate relay. An encoding and decoding strategy is proposed which is inspired from cryptography theory. The proposed encoding and decoding strategy involves a signal space alignment for an encryption message for multiple access phases and zero forcing with successive network code decoding for the broadcast phase. Then, the investigation of the antenna configuration conditions is an initial step for addressing the degrees of freedom of the above channel. It presents a new modified high-order pulse amplitude modulation that enables us to use the computationally efficient binary channel coding under a physical-layer network coding. It is shown that the proposed signalling scheme significantly outperforms the conventional non-binary code and is slightly worse than the lattice code. View full abstract»

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  • Singular value decomposition-based multiuser multiple-input multiple-output vector perturbationaided downlink transmitter and lattice-reductionassisted uplink receiver pair

    Page(s): 2448 - 2454
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    A full-duplex uplink/downlink (UL/DL) system having a UL transmitter/receiver (transceiver) pair and a DL transceiver is considered. Both the UL and DL are improved. The DL is enhanced by a novel vector perturbation (VP)-aided singular value decomposition (SVD)-based precoding scheme, which is capable of exploiting the different-quality SVD eigenbeams and substantially reduces the overall average transmit power requirement of the traditional zero-forcing (ZF) precoder. By contrast, the UL is enhanced by a lattice reduction (LR)-aided receiver scheme designed for SVD-based multiuser multiple-input multiple-output (MU MIMO) UL transmission, when different modulation schemes are employed for different-quality eigenbeams. This new UL scheme avoids the noise-enhancement problem of the classic ZF UL receiver. The authors demonstrate that the proposed VP-aided DL and LR-assisted UL constitute a powerful full-duplex system, which achieves an ~15~dB signal to noise ratio (SNR) gain for both SVD-based MU-MIMO DL and UL transmissions over the traditional ZF-aided schemes at a bit error rate (BER) of 10-3. View full abstract»

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  • Analytical modelling of a cognitive IEEE 802.11 wireless local area network overlaid on a cellular network

    Page(s): 2455 - 2464
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (462 KB)  

    In this study, the authors propose an analytical model to evaluate the maximum stable throughput and average delay of a cognitive IEEE 802.11-based wireless local area network (WLAN) overlaid on uplink band of a cellular network. The main feature of the proposed model is to include different status of the cognitive users, that is, different spectrum opportunities for different secondary users, as the result of dynamic nature of primary users as well as different locations of the cognitive users relative to primary ones. The proposed model has been founded on an open queueing network comprised of several queueing nodes equivalent to different states of a typical secondary user. By mapping the details of MAC scheme of the cognitive WLAN and dynamic nature of spectrum opportunities onto suitable parameters of the proposed analytical model and writing the corresponding traffic equations, the authors are able to find the maximum stable throughput, that is, the maximum rate of packet generation at the cognitive nodes guaranteeing the stability of all nodes. Below this rate, that is, at the rate when all cognitive nodes are in non-saturation mode, with resort to the proposed analytical model the authors are able to evaluate the average delay comprised of the queueing delay as well as the transmission delay. The authors also show the applicability of our approach in evaluating the effect of different parameters of the cognitive network scenario, for example, the number of users, activity factors etc., onto the maximum stable throughput and non-saturation average delay. Simulation results confirm the validity of the authors analytical approach. View full abstract»

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  • Performance of general network coding nodes with stop-and-wait automatic repeat request transmission

    Page(s): 2465 - 2473
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    The steady-state performance of general network coding node is investigated, when data are transmitted in packets based on the stop-and-wait automatic repeat request error-control scheme. The general network coding node considered has H number of incoming links that provide packets for forming the coded packets transmitted by one outgoing link. Each of the incoming and outgoing links is assumed to have some buffers for temporarily storing the data packets. The state transition of the general network coding node is modelled by a finite state machine, and its steady-state performance is derived based on the properties of discrete-time Markov chain. Specifically, the throughput, blocking probability and the distribution of contents are analysed, when the general network coding node is operated in the steady state. The performance of the general network coding node is investigated either by simulations or by evaluation of the formulas derived in this study. The performance results show that the analytical formulas obtained can be well justified by the simulation results. Furthermore, it can be shown that the packet error rate, the capacity of buffer and the number of incoming links may impose significant impact on the performance of general network coding node. View full abstract»

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