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Communications, IEE Proceedings-

Issue 3 • Date Jun 1994

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Displaying Results 1 - 15 of 15
  • Coded modulation based on rings of integers modulo-q. 1. Block codes

    Page(s): 129 - 136
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    The authors aim to present an alternative multilevel (nonbinary) coding method, based on a ring of integers modulo-q (q is a nonprime integer number) which is suitable for coded modulation schemes. Some new concepts and definitions are introduced in order to build up a theoretical framework which allows a search for good multilevel codes. Such classes of block codes are also presented together with their interesting properties. Such codes can be used not only in q-PSK modulations, but also in q-QAM modulations by making a simple adaptation View full abstract»

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  • Hybrid threshold soft decision decoding algorithm

    Page(s): 126 - 128
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    A hybrid threshold soft decision decoding scheme which combines a Chase 2 algorithm with a bit-by-bit decision decoding algorithm is presented. For higher signal-to-noise ratios (SNRs), its behaviour is not inferior to that of the corresponding bit-by-bit decoding algorithm. This scheme can overcome the exponential increase of the test patterns used in the Chase 2 algorithm, as d (the minimum Hamming distance of code) increases View full abstract»

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  • Effective erasure node algorithm for slot reuse in DQDB

    Page(s): 196 - 202
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    The distributed queue dual bus (DQDB) protocol, which has been specified by the IEEE 802.6 as the metropolitan area networks (MANs) standard, has an undesirable feature in that already received (i.e. read) busy slots continue to propagate downstream unnecessarily. The use of special nodes, known as erasure nodes, allows conversion of read slots to empty, so that downstream nodes may reuse these slots. This should result in an increase of the total throughput of the network. The authors introduce and evaluate the performance of an erasure node algorithm. The algorithm keeps track of past activities on both buses to effectively balance the slot erasure and the request cancellation functions. It is shown that this algorithm possesses a number of features which make it superior to existing algorithms View full abstract»

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  • Soft decision decoding techniques for a class of runlength-limited error control codes

    Page(s): 118 - 125
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    Two soft decision decoding algorithms for a new class of runlength-limited error control codes with maximum runlength constraints 2, 6 and 14 are presented. Software simulation results for illustrative codes of block length 16 and 64 provide a comparison with the general soft decision decoders proposed by Chase (1972) View full abstract»

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  • Private-key encryption based on concatenation of codes

    Page(s): 105 - 110
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Public-key algebraic encryption (PUAE) has certain advantages that make it attractive in some applications. Variants of PUAE for private-key algebraic encryption (PRAE); have been proposed subsequently. PRAE is proven to be insecure under chosen plaintext attack. In the paper, some invariants of PRAE are studied, and a private-key cryptosystem based on concatenation of codes is proposed and analysed. The new system is, composed of short-length codes and is designed to avoid the weaknesses in other PRAE systems. The system looks secure against known attacks. Some methods to improve the system information rate and security are also suggested View full abstract»

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  • Algorithms suitable for low complexity implementation of at class of runlength-limited error control codes

    Page(s): 111 - 117
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    Encoding and decoding procedures which exploit the cyclic-like properties of a class of runlength-limited error control-codes are presented. These algorithms enable simple encoding and decoding circuits consisting of only a few basic circuit elements to be designed. A comparison with conventional syndrome decoding shows that they provide comparable error performance although requiring considerably less circuitry View full abstract»

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  • Some digital receivers for the GSM pan-European cellular communication system

    Page(s): 168 - 176
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    The Global System for Mobile Communications (GSM) provides the European Community countries with a common digital mobile radio structure for overland communications. The authors describe some new digital receivers that utilise coherent detection for the GSM system. Of the receivers described, that with the classical Viterbi processor, while notably robust, has high implementation complexity for a mobile environment. Some simplified receiver structures have been devised whose algorithms reduce implementation complexity, albeit at the expense of the error probability. With a channel simulator suitable for mobile communications, the performance of the simplified receivers has been evaluated. Through suitable parameter choices, the bit error probability increase can be maintained sufficiently low, while a marked reduction in the computation complexity is achieved View full abstract»

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  • Performance analysis of the knockout switch with input buffers

    Page(s): 183 - 189
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Since the asynchronous transfer mode (ATM) has been strongly promoted as the transport structure for broadband integrated services digital networks, a variety of ATM switching architectures have been proposed. The knockout switch, which is one of the well known ATM switches, has a single-stage architecture and adopts an output buffering method. It has excellent traffic performance (cell loss probability, maximum throughput and delay, etc.), but needs many switch elements and buffers. The authors propose an ATM switch, called a knockout switch with input buffers. The proposed switch has almost the same traffic performance as the existing knockout switch but needs fewer switch elements and buffers than the existing knockout switch. The authors analyse the traffic performance and complexity (i.e. the number of switch elements and buffers required) of the proposed architecture by discrete-time Markov chain models and compare them with those of the existing knockout switch. It is found that the proposed architecture could reduce the need for over 40% of the switch elements and over 30% of the buffers while satisfying the given loss requirements View full abstract»

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  • Trellis coded Q2PSK signals. 2. Land mobile satellite fading channels

    Page(s): 159 - 167
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    Utilisation of Q2PSK signals is analysed on the land mobile satellite channel. Trellis codes design criteria for coherent, differentially coherent and noncoherent detection procedures are derived. The implementation model of the transmitter-channel-receiver structure, where block interleaving/deinterleaving is utilised, is presented. New Q2PSK MTCM systems are designed following construction criteria for optimum performance on fading channels. Also, four different four-dimensional Q2PSK MTCM with different number of states and diversity factors are designed. Double 8-PSK MTCM are also combined with decoupled Q2PSK signals to construct bandwidth efficient TCs for optimum performance an the fading channel. Finally, the new Q2PSK MTCM and some of the Q2PSK TCs codes presented in Part 1 are evaluated on fading channels, where various levels of shadowing have been tested, from the Rayleigh channel to the AWGN channel View full abstract»

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  • Performance analysis of a multicast packet switch with capacity m

    Page(s): 177 - 182
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    A multicast packet switch provides an efficient transport method which can connect any input port to any subset of output ports. Each input packet of the switch which is copied and destined to a subset of output ports usually experiences contention with other copy packets. So, the offered load to output ports increases as the mean number of copy packets generated by one input packet increases in a multicast switch, thus requiring some scheme for speeding up the switch. The authors study the performance of an input buffered multicast packet switch with capacity m. The study indicates that the service time involved by packets at the head of input queues becomes a phase-type process for a large switch size. With this service time distribution, the authors analyse the saturation throughput of the switch, input queue length distribution and mean delay using the matrix-geometric solution method. Their numerical and simulation results indicate that the switch capacity 2 is sufficient for adequate multicase switch performance View full abstract»

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  • Performance analysis of an ATM statistical multiplexer with batch arrivals

    Page(s): 190 - 195
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    The authors propose a method for evaluating the impact of bursty traffic sources on the performance of an ATM multiplexer which can handle packetised voice, data and video traffic. The multiplexer is modelled as a single-server queue with batch phase type Markov renewal input. The authors describe an analytical approach to the solutions of such queueing systems with finite capacity using the matrix analytic method. The methodology was chosen because its ability to model exactly complex nonMarkovian models having correlated, nonrenewal input processes. It is nearly impossible to obtain exact expressions using the classical method of generating functions. A study of different mixed traffic assumptions indicates that bursty traffic does have a very significant effect on the loss performance View full abstract»

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  • Fibre-based local area network with priority access

    Page(s): 203 - 208
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    A new-local area network based on a multiaccess unidirectional fibre bus is described. Communication between network stations is by means of objects and can be point-to-point, multicast or broadcast: Each communication object is unique, with an inherent priority embedded in its frame structure. It is impossible for objects of the same priority to attempt media access at the same time, and collisions between objects of different priority are always resolved in favour of the highest-ranked object without the need for a backoff interval. The access protocol is simple, robust and fair in as much as the physical position of stations does not adversely affect their probability of accessing the media or the station queueing delays. The network is ideal for real-time applications and electrically hostile environments, which are characteristic of manufacturing cells. Similar networks are briefly reviewed and the new distributed access protocol is described. It is shown that throughput is high, irrespective of the number of active nodes or the physical length of the media View full abstract»

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  • Coded modulation based on rings of integers modulo-q. 2. Convolutional codes

    Page(s): 137 - 142
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    The authors presents a coded modulation method based on multilevel convolutional codes defined over finite rings of integers. A previously developed theory is applied to multilevel convolutional codes. Some tables of convolutional codes defined over rings of integers modulo-q are obtained. Curves of soft- and hard-decision decoding performance are also shown View full abstract»

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  • Some new rotationally invariant TCM schemes for multidimensional M-PSK

    Page(s): 143 - 150
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    Trellis codes for multidimensional constellations offer a number of advantages which cannot be obtained with bidimensional constellations. Some new trellis codes for multidimensional M-PSK constellations are presented. They are all completely rotationally invariant. The performance of these codes is discussed and compared with that exhibited by Ungerboeck codes for bidimensional phase modulation with the same effective rate View full abstract»

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  • Trellis coded Q2PSK signals. I. AWGN and nonlinear satellite channels

    Page(s): 151 - 158
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    Suitable bandwidth efficient coding techniques, to be combined with Q2PSK signals, are derived and analysed on AWGN and nonlinear channels. Five new Q2PSK TCs are presented. First, an expanded Q2PSK signal constellation has been used to design new 4D RI Q2PSK TCs. Partition of the 4D expanded Q 2PSK signal space into 2D subspaces has allowed the utilisation of any 8-PSK TC to be implemented along Q2PSK signals. This novel division of the Q2PSK signal space has been utilised to implement double 8-PSK TCs designed by Ungerboeck and double convolutional codes over ring modulo-8 along Q2PSK signals. Finally, an unexpanded Q2PSK signal has been considered to implement and design 2/4 and 3/4 rate Q2PSK trellis codes. Performance evaluation of coded and uncoded Q2PSK signals on nonlinear satellite channels is reported, and the results obtained from computer simulations of coded and uncoded Q2PSK on nonlinear channels are presented, where different amplifier working situations have been considered View full abstract»

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