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Communications, IEE Proceedings-

Issue 2 • Date 8 April 2005

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Displaying Results 1 - 20 of 20
  • Efficient one-time proxy signatures

    Page(s): 129 - 133
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1908 KB)  

    Proxy signatures allow a signer to delegate signing ability to a proxy signer. Many schemes have been proposed for proxy signatures under typical security requirements. The authors propose a proxy signature model with extended security requirements. Based on Shamir's online/offline signature scheme, a proxy signature scheme is proposed for the model. In addition to the typical requirements, the proposed scheme satisfies other very important security requirements. It is shown that the scheme can provide signature indistinguishability, restrict the proxy signing power, provide signature unlinkability, resolve internal disputes, and is more efficient. View full abstract»

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  • Dynamic security analysis of group key agreement protocol

    Page(s): 134 - 137
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1914 KB)  

    Group key agreement is a fundamental building block for the increasing number of collaborative applications. The protocol is more complicated than peer-to-peer communication owing to its dynamic characteristics, but the research to date on group key agreement protocols (GKAP) mainly focuses on static security, the most distinctively dynamic characteristic of GKAP being difficult to analyse by existing methods. The paper attempts to extend the strand space theory to analyse the dynamic security of GKAP. With the aid of the theory, the AT-GDH protocol is taken as an example to discuss the general conditions of security retention in dynamic cases. A new scheme is proposed of updating the session key when some member leaves the group; it is based on SA-GDH.2 protocol to avoid the single-point weakness. View full abstract»

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  • Provably secure three-party password-based authenticated key exchange protocol using Weil pairing

    Page(s): 138 - 143
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1931 KB)  

    The Weil Diffie-Hellman problem discovered by A. Joux (see Proc. ANTS 4, Lect. Notes in Comp. Sci., vol.1838, p.385-94, 2000) is a new primitive in cryptography. The authors propose the first provably secure three-party password-based authenticated key exchange protocol based on the Weil Diffie-Hellman problem. In the protocol, two communication entities can authenticate each other and establish a session key through the assistance of an authentication server. The proposed protocol requires only four communication steps, which is more efficient than previous solutions. The security of the proposed scheme has been proven in the random oracle model. In addition, the communication steps of the proposed protocol can be reduced to three rounds of transmissions. View full abstract»

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  • Soft-decision decoding of Reed-Muller codes based on simple multi-step SISO module

    Page(s): 144 - 150
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1962 KB)  

    The paper proposes a new multi-step soft-decision decoding for the generic Reed-Muller (RM) code family, which is based on a simple multi-step soft-input soft-output (SISO) module and the inherent merits of the RM codes. In an AWGN channel, the simulation results show that, for RM codes of different code rates and lengths, the introduced approach can offer pronounced performance gains over other soft-decision sub-optimal approaches and a conventional hard majority logic decoder. The results also indicate that the new algorithm can achieve a performance very close to that provided by a maximum likelihood decoder under the same conditions. View full abstract»

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  • FFT-based fast Reed-Solomon codes with arbitrary block lengths and rates

    Page(s): 151 - 156
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1935 KB)  

    By puncturing Reed-Solomon codes with the block lengths of 2m, it is possible to design systematic and nonsystematic codes with arbitrary block lengths and rates that can be decoded using FFT. Because Reed-Solomon (RS) codes are maximum distance separable (MDS), the resultant codes keep this property as well. The codes are constructed over prime fields as opposed to the conventional practice of extension fields, and hence additions and multiplications are simple mod operations and there is no need to use polynomials and look-up tables. View full abstract»

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  • Distance spectrum of right-regular low-density parity-check codes: derivation and discussion of numerical results

    Page(s): 157 - 166
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2887 KB)  

    The asymptotic distance distribution of regular low-density parity-check (LDPC) codes derived by Litsin and Sherlev (2002) is generalised for the case of irregular LDPC codes with constant check node degree. Numerical analysis of simple irregular LDPC codes with weight-two variable nodes shows that their minimum Hamming distance can be increased linearly with the code length when the maximum variable node degree of the code is kept below a critical value. This result is consistent with the stability condition of the LDPC codes, at least for the simple irregular case. View full abstract»

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  • Notion of cost and quality in telecommunication networks: an abstract approach

    Page(s): 167 - 171
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1910 KB)  

    With the advent of complex, integrated networks providing a variety of services, the notion of quality becomes an important factor in the design and usage of such networks. An abstract approach toward understanding the notion of cost in the context of providing services with differentiated levels of quality is presented. Several interesting results are presented that challenge the deeply entrenched notion of telescopically varying rates to 'larger' users of services. The authors also present a means whereby compensating levels of prices can be set for users of different classes. View full abstract»

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  • Efficient entry-reduction algorithm for TCAM-based IP forwarding engine

    Page(s): 172 - 176
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1914 KB)  

    Ternary content-addressable memory has been widely used to perform fast routing lookups. It is able to accomplish the best matching prefix searching in O(1) time without considering the number of prefixes and their lengths. As compared to software-based solutions, ternary content-addressable memory can offer sustained throughput and simple system architecture. However, it also comes with several shortcomings, such as a limited number of entries, and enormous cost and power consumption. Accordingly, an efficient algorithm is proposed to reduce the required size of ternary content-addressable memory. The proposed scheme can eliminate 98% of ternary content-addressable memory entries by adding comparatively little DRAM and, thus, is attractive for IPv6 routing lookup. View full abstract»

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  • Joint local delivery and congestion control framework for reliable multicast

    Page(s): 177 - 184
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1958 KB)  

    The use of a server-based loss recovery technique for reliable multicast can significantly improve the system performance in terms of loss recovery latency and bandwidth consumption. Appropriate congestion control mechanisms are necessary to provide fairness and to maintain a high network throughput and link utilisation. In reliable multicast protocol design, the loss recovery associated with data delivery and congestion control are not independent issues and should be addressed simultaneously. This suggests that a server-based loss recovery technique, allied with congestion control, could have potential in addressing the challenges of scalability and heterogeneity for reliable multicast in a best-effort network. The authors propose a new framework which jointly performs local delivery and congestion control (LDCC). In this framework, delivery and control servers (DCSs), collocated with routers, perform LDCC functions. Each DCS and its serving receivers form a local DCS region according to a tree topology. With proper acknowledgment processing and buffer management, packet loss can be efficiently recovered locally. Also, the overall throughput degradation caused by the interference of neighbouring regions can be minimised by local congestion control. NS-2 simulations are used to demonstrate that the framework can achieve a significantly lower loss recovery latency without sacrificing network throughput, compared to existing approaches such as AER/NCA. It is also shown, by using fairness tests, that the proposed framework is TCP-compatible. View full abstract»

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  • Minimal Web patch generation for incremental Web caching

    Page(s): 185 - 190
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1930 KB)  

    The principle of Web caching is to keep frequently requested items close to where they are needed. The cache may reside in local computers, dedicated cache proxies, or clients that share their local caches. Frequent updates on the original Web server shorten the useful lifetime of cache contents. If the update is minor, the stale cache still contains valuable information. An incremental update and delivery scheme, which allows the client to fetch a patch from the original Web server to update the stale cache, can improve the caching performance. The paper focuses on the minimal patch generation problem. Web objects are transformed into ordered labelled trees, and the patch is generated in tree space. The paper models the Web patch problem as a minimal set cover problem with dynamic weights. This problem can be solved using available solutions of the fixed weighted minimal set cover problem by imposing appropriate conditions. View full abstract»

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  • Colour-aware rate/coverage-controlled DS/CDMA downlink transmission for DiffServ

    Page(s): 191 - 196
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2056 KB)  

    To improve the quality-of-service (QoS) support over cellular DS/CDMA systems with IP transport, rate/coverage-controlled downlink transmission schemes that utilise the QoS information from the IP layer of the differentiated services (DiffServ) architecture are proposed. The rate/coverage is controlled depending on the packet-drop precedence (packet colour) of the assured forwarding class in DiffServ and the traffic load at the base station. The out-of-profile packets are given less priority in the physical rate allocation or provided with less coverage compared with the in-profile packets. Simulations verify the advantages of the DiffServ-aware schemes and show that the coverage control scheme outperforms the rate control scheme. View full abstract»

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  • Exact error probability for space-time block-coded MIMO systems over Rayleigh fading channels

    Page(s): 197 - 201
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1940 KB)  

    Existing analysis on the error performance of space-time block codes has focused on deriving error-rate upper bounds for a general system or exact error probabilities for some special cases. The authors introduce a general method to calculate the exact error probability for orthogonal space-time block codes in multiple-input multiple-output systems which employ coherent and differentially coherent phase shift keying (PSK) modulation over flat Rayleigh fading channels. These results enable one to evaluate the performance of space-time block-coded systems with different coding rates and an arbitrary number of transmit and receive antennas. View full abstract»

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  • Capacity of space-time block-coded CDMA systems: comparison of unitary and complementary codes

    Page(s): 203 - 214
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2074 KB)  

    Two major categories of CDMA signature codes, namely unitary codes and complementary codes, are of interest. All currently available 2-3G CDMA systems make use of the unitary codes, such as Gold codes, m-sequences, Walsh-Hadamard sequences and OVSF codes, all of which work on a one-code-per-channel basis. On the other hand, a CDMA system based on complementary codes works on a flock-of-codes basis. Each user in such a CDMA system is assigned a flock of codes which should be sent to a receiver via different carriers to reconstruct perfect autocorrelation and crosscorrelation functions. A comprehensive analytical study of a STBC-CDMA system using different spreading codes is given and their bit error rate performance is evaluated and compared with both analysis and simulation under Rayleigh fading and multiple-access interference. The results reveal that a STBC-CDMA system based on complementary codes offers a capacity similar to that achievable in a noise-limited system, while a STBC-CDMA system based on traditional unitary codes suffers serious interference-limited problems even with full STBC diversity gain. View full abstract»

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  • Performance of a VSF-OFCDM system using a symbol relocated scheme during retransmission

    Page(s): 215 - 220
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1958 KB)  

    A symbol-relocated (SR) scheme has been proposed for variable spreading factor orthogonal frequency code-division multiplex systems to achieve frequency diversity during retransmission. The performance has been evaluated for two combining schemes of hybrid auto repeat request, namely chase combining and incremental redundancy. The results show that the proposed SR scheme achieves significant improvement in terms of system throughput over conventional schemes. This effect is more significant for chase combining because the rotated mechanism is more effective when the same packet is transmitted during the retransmission. It is also found that the SR scheme is not sensitive to Doppler frequency variation, which makes it an attractive candidate for fast-fading channels. Further investigation also suggests the suitability of an SR scheme for smaller spreading factors (in the frequency domain) and larger coding rates. View full abstract»

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  • Differential detection of GMSK signals with postdetection MRC over correlated and unbalanced Nakagami-m fading channels

    Page(s): 221 - 228
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1990 KB)  

    Differential detection with postdetection diversity reception of Gaussian minimum shift keying (GMSK) signals has become increasingly important owing to its widespread use in wireless communications. Its error analysis, however, is not available in the literature. The authors derive a bit-error probability expression for the differential detection of GMSK signals with post-detection maximal ratio combing (MRC) in additive white Gaussian noise and slow frequency-nonselective arbitrarily correlated and unbalanced Nakagami-m fading channels, in which the diversity branches can have unequal signal-to-noise ratios (SNRs) as well as different severity parameter m. The effects of arbitrary values of the fading severity parameter m and the arbitrary correlation between the unbalanced L diversity channels are considered. The derived expression can be easily computed via numerical integration routines, and hence, can be usefully exploited in the performance evaluation of digital mobile radio systems. View full abstract»

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  • Using UWB Gaussian pulses for inter-vehicle communications

    Page(s): 229 - 234
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1942 KB)  

    Ultra-wideband (UWB) radio is a candidate technology for future wireless communications. It uses very short pulses, so that the spectrum of the emitted signals may spread over several GHz. An inter-vehicle communication system based on UWB technology is studied. Two waveforms are compared: Gaussian and monocycle pulses. A 2 GHz pulse generator is associated with an antipodal (AP) modulator in the first case and with a binary phase shift keying (BPSK) modulator in the second case. The numerical receiver and the detection algorithm are described. The performance of the matched filter receiver is evaluated in the case of multipath propagation with additive white Gaussian noise (AWGN). The European Telecommunication Systems Institute (ETSI) rural area (RA) channel has also been considered. The bit error rate (BER) values are calculated for the two UWB waveforms and the time jitter problem is also addressed. It is shown that the AP-coded Gaussian pulses waveform is the best signalling waveform among those studied here, with the supplementary advantages of a very low sensitivity to multipath effects and to jitter, together with much lower error rates. View full abstract»

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  • High-rate transmission scheme for pulse-based ultra-wideband systems over dense multipath indoor channels

    Page(s): 235 - 240
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1981 KB)  

    A new high-rate transmission scheme is proposed for pulse-based ultra-wideband (UWB) systems over dense multipath channels. In contrast to the existing UWB schemes that transmit one short-duration pulse each pulse-repetition interval, the proposed scheme transmits a series of N (N≥1) consecutive pulses (a burst) each burst-repetition interval. The author then develops a successive, a zero-forcing (ZF), and a high-performance ZF-based successive receiver for effective detection in the presence of intersymbol interference within a burst. To lower complexity, an efficient algorithm for the ZF-based successive receiver is also derived. The error performance of these receivers, assuming the availability of perfect channel estimates over lognormal fading channels, is studied. Comparison is made between the proposed scheme and the conventional pulse amplitude-modulation scheme, when the transmission rate, the total transmitted power, and the channel delay spread are kept the same. Impacts of imperfect channel estimation are also studied by simulation. The proposed scheme could achieve a much higher throughput than the conventional scheme in dense multipath channels. View full abstract»

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  • Optimum sequence design and performance evaluation of channel estimation techniques for ultra-wideband systems

    Page(s): 241 - 245
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1930 KB)  

    Unstructured approaches for the estimation of ultra-wideband (UWB) channels are investigated, namely optimal maximum likelihood (ML) estimation, suboptimal least squares (LS) estimation, and the so-called pilot symbol assisted modulation (PSAM) estimation techniques. Moreover, closed form expressions for the maximum likelihood for a UWB system and an optimum sequence design technique for the LS scheme are derived. Performance analysis in terms of the minimum squared error (MSE) and accuracy in terms of the Cramer-Rao lower bound (CRLB) are provided. The trade-off between performance and complexity is shown for each reported estimation technique. View full abstract»

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  • Data transmission for implantable microsystems using magnetic coupling

    Page(s): 247 - 250
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1944 KB)  

    The authors consider design issues associated with the use of high-frequency inductive coupling, in the context of miniaturised, embedded electronic systems in medical diagnosis, environmental monitoring and other industrial applications. Recent developments in system-on-chip and lab-on-a-chip technologies have made the implementation of such miniaturised systems feasible, and pose an interesting set of problems with respect to low-power, short-range wireless communications. The design of a compact transmitter that maximises the magnetic component of the field is discussed and some early results are presented. View full abstract»

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  • Bandwidth efficient transmission through sparse channels using a parametric channel-estimation-based DFE [decision-feedback equaliser]

    Page(s): 251 - 256
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2047 KB)  

    A novel equalisation scheme, based on parametric channel estimation, is presented. The proposed scheme is appropriate for channels with a long and sparse impulse response, such as those encountered in high-definition digital video-transmission systems. The main feature of the channel estimation is that instead of seeking the whole channel impulse response only the unknown time delays and attenuation factors of the physical channel multipath components are efficiently estimated. The equalisation consists of an adaptive decision-feedback equaliser (DFE), whose initialisation is properly designed for sparse channels. The information needed in the initialisation procedure is provided by the channel estimation part. The DFE converges much faster compared to a conventional DFE, and the whole scheme utilises a very short training sequence and hence a significant saving in bandwidth is achieved. View full abstract»

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