IEE Proceedings - Communications
Volume 149, Issue 3, June 2002
Volumes & issues:
Volume 149, Issue 3
June 2002
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- Author(s): R.J. Higgs and J.F. Humphreys
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 129 –131
- DOI: 10.1049/ip-com:20020316
- Type: Article
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p.
129
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A formula is found in terms of the syndromes for finding the locations of two errors in a received word of an e error-correcting quadratic residue code with e≥2. This formula is independent of the characteristic of the underlying field. All quadratic residues codes for which the formula is applicable are described. - Author(s): M.A. Kousa and A.H. Mugaibel
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 132 –138
- DOI: 10.1049/ip-com:20020230
- Type: Article
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p.
132
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The authors address various important issues related to punctured turbo codes. A modified technique for finding the transfer function of punctured turbo codes is developed. This modified technique provides a means of deterministic evaluation of the weight distribution of the code, as well as a possibility of studying various puncturing patterns. These advantages are shown with some illustrative examples. Moreover, the paper explains some characteristics of the puncturing pattern, and arrives at useful guidelines for the design of a good puncturing matrix. - Author(s): H. Che ; H. Che ; S. Zheng ; X. Hong
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 139 –146
- DOI: 10.1049/ip-com:20020317
- Type: Article
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p.
139
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A framework is developed for performance analysis of an integrated model of multiple class-of-service Internet. An Internet service provider is considered who provides premium, assured and best-effort services to end-users. Various aspects of the model are studied including link bandwidth allocation/sharing policies, user behaviours and service price-quality structure design. An analytic Markov model is developed and equilibrium performance measures are derived. Based on the analytical model, numerical analysis demonstrates the importance of trunk reservation in providing service protection and bandwidth sharing and the effects of user behaviours on service price and quality design. To get more insight on service price and quality design, two service quality declaration mechanisms are studied, i.e. static and dynamic service quality declarations under the assumption of static pricing. Simulation results show that the dynamic service quality declaration offers better performance when traffic level/pattern varies. - Author(s): H.-H. Liu ; J.-L.C. Wu ; W.-Y. Chen
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 147 –151
- DOI: 10.1049/ip-com:20020205
- Type: Article
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p.
147
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To enhance the system capacity of the IEEE 802.11 wireless local area networks (WLANs), a frame-based adaptive multirate transmission scheme is envisaged. The medium access control (MAC) operation and the selection of parameters, such as the thresholds of request to send (RTS) and fragmentation, are discussed. The original virtual carrier sense mechanism in the IEEE 802.11 WLAN standard is no longer suitable because the transmission rate is adaptively selected such that it is prone to allocate a wrong network allocation vector (NAV) to jam or inhibit the radio transmission that degrades the performance. A modification of the NAV reservation scheme must be made to adopt this change. The authors have performed simulations to illustrate the performance improvement to the modification of the NAV reservation scheme. Simulations are based on a time-correlated multipath fading channel model and a movable mobile station assumption, where the station may be out of range from certain mobile stations. - Author(s): X. Fang
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 152 –156
- DOI: 10.1049/ip-com:20020312
- Type: Article
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p.
152
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The proliferating demands for mobile services propel the development of increasingly sophisticated techniques to overcome wireless radio resource limitations. With the introduction of cell splitting and sectorisation in cellular communications systems, system capacity can be significantly increased. Space division multiple access (SDMA) technology along these lines has therefore gained a great deal of attention recently; intensive research on resource allocation for SDMA systems has been undertaken in the last few years. In the paper, the author carries out a realistic performance analysis for some resource allocation schemes in SDMA systems and obtains more accurate analytical results for blocking probability. - Author(s): S.-C. Lin
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 157 –165
- DOI: 10.1049/ip-com:20020311
- Type: Article
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p.
157
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Research is presented which provides fast and accurate performance analysis for optimum diversity combining and equalisation with quadrature amplitude modulation (QAM) over mobile radio channels with frequency-selective fading. The performance of optimum diversity combining and equalisation over a noise-limited channel has been presented previously, but the error rate calculation was based on the upper bound method. The accurate performance of such a diversity receiver has not been evaluated completely. An analysis is present in which the upper bound method for each individual run is replaced by the moment method in a quasi-analytical (QA) Monte Carlo simulation. Simulation techniques are first used to evaluate the residual ISI after equalisation, and then moments of this ISI are calculated using a very fast and accurate recursive method of computation. Based on these moments, the author uses the series expansion to obtain the error rate of the system. The multipath channel is treated as quasistatic and the system, including the channel, is assumed to be linear. Minimum mean-square-error (MMSE) equalisation techniques with linear and decision-feedback structures are considered and compared in the analysis. A method is defined for finding the transfer function of the infinitely long decision feedback equaliser, which requires greater computational complexity. Numerical results show that by using the moment method the performance can be improved significantly in comparison to the upper bound approach. - Author(s): A.H. Ulusoy ; H.A. Amca ; K. Hacıoǧlu ; A. Rizaner
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 167 –170
- DOI: 10.1049/ip-com:20020309
- Type: Article
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p.
167
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The conventional multipath–decorrelating receiver performance depends on the number of resolvable paths. The conventional multipath–decorrelating receiver uses as many branches as the number of resolvable paths of the channel to improve the performance of the system. However, using all of the resolvable paths of the channel in the receiver increases the system complexity and the decorrelating filter implemented by the use of all the resolvable paths produces high noise enhancement. The authors propose a scheme that adaptively selects a subset of the paths reducing both system complexity and noise enhancement. Analytical results that show the tradeoff between noise enhancement and multipath-induced multiple-access interference for better performance are provided. - Author(s): J.P. Cances and V. Meghdadi
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 171 –178
- DOI: 10.1049/ip-com:20020299
- Type: Article
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p.
171
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The authors present a multicarrier asynchronous direct sequence code division multiple access (DS-CDMA) system which uses an adaptive blind algorithm for the optimum combining of the desired signal contributions from different carriers. The output of the transmitter convolutional encoder modulates multiple band-limited DS-CDMA waveforms which are parallel transmitted with different carrier frequencies. The performance of this system is compared to that of a conventional single-carrier DS-CDMA system with a RAKE receiver and a RAKE receiver with a sliding window decorrelator filter. In this latter case, the RAKE receiver uses pilot symbols to track the channel impulse response time variations. Results demonstrate a performance similar to that of a decorrelating detector in the context of a severe near–far situation while exhibiting lower complexity. - Author(s): M. Faulkner
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 179 –184
- DOI: 10.1049/ip-com:20020263
- Type: Article
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p.
179
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DC offsets cause interference in homodyne receivers, caused by nonlinearity and imbalances in the receiving amplifier and mixing circuits, as well as local oscillator (LO) leakage into the RF input port and RF leakage into the LO port. The latter causes a squaring action (hence, second order intermodulation distortion (IM2)) in the mixer which generates a DC offset (low frequency) that varies with the amplitude of any high power RF interfering (jamming) signal, whatever its applied frequency. A method for removing this DC offset is described. The signal immediately after the mixer is squared to obtain a distortion estimate of the jamming signal, and then subtracted from the main signal path to remove the interference from the desired signal. The experimental results indicate an 11.5 dB improvement in jamming margin for systems with 30 kHz RF bandwidth. In the experiment an adaptive equaliser is used to equalise the two paths and improve the dynamic response. - Author(s): D. Li and X. Jia
- Source: IEE Proceedings - Communications, Volume 149, Issue 3, p. 185 –188
- DOI: 10.1049/ip-com:20020204
- Type: Article
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p.
185
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The authors discuss the optimal allocation of wavelength converters in shared-per-link structure in WDM networks. In particular, they consider the following two cases: given the total number of converters available in the system, or given the number of converters available at each node in the system, allocate them properly at the outgoing links of the nodes, such that the total sum of traffic of connections getting through the system is maximised. An optimisation algorithm is proposed to solve the first case, and a heuristic algorithm is developed to find an approximate solution for the second case. Simulation results have shown the effectiveness of the solutions.
Two-error-location for quadratic residue codes
Puncturing effects on turbo codes
Integrated model for performance analysis of multiple class-of-service Internet
New frame-based network allocation vector for 802.11b multirate wireless LANs
More realistic analysis for blocking probability in SDMA systems
Accurate error rate estimate using moment method for optimum diversity combining and MMSE equalisation in digital cellular mobile radio
Decorrelating detector for asynchronous CDMA channels with adaptive path selection
Blind adaptive receiver for coded multicarrier DS-CDMA systems in multipath fading channels
DC offset and IM2 removal in direct conversion receivers
Allocating wavelength converters in shared-per-link structure in WDM networks
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