摘要:

The optimum diversity receiver in arbitrary non-Gaussian noise and Rayleigh fading statistics is derived for binary narrowband correlated symmetric incoherent signalling in the threshold regime, i.e. for small signals and independent noise samples. Its performance is obtained in terms of the error probabilityPefor various values of a specific signal crosscorrelation coefficient ρ and multichannel order, when fading in the channel is assumed to be slow, nonselective Rician or Rayleigh. This expression forPeis shown to be a generalisation of a recent performance result in optimum threshold detection of incoherent narrowband signals in narrowband non-Gaussian noise. It is graphically demonstrated that the best signalling in Rayleigh fading is orthogonal (ρ = 0) and that performance significantly improves as the diversity order increases for fixed sample sizeN(≥≥ 1) and second-order noise statisticL(2)(≥ 1). A novel by-product of the analysis is the error probability expression of the single-channel threshold incoherent receiver with Rician fading, which is used to graphically demonstrate that the signalling scheme which optimises, i.e. gives the minimum possible value of,Peis also orthogonal.

DOI:10.1049/ip-i-2.1989.0034

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper describes techniques for reducing the adjacent channel interference that could be caused to a wanted, in-channel, amplitude-modulated (AM) signal. The interference is that due to the detected modulation of the unwanted signal as well as by the beats between the sidebands and carriers of both signals. The techniques include those based upon extraction of one or both signal carriers and their replacement and/or elimination before subsequent detection. Important features of the extraction techniques are that more precise analysis of the resultant effects are possible and the replaced carriers are added rather than multiplied with the original signal; the latter feature leads to an acceptable performance being obtained even when no extraction can be carried out. Some very powerful reduction techniques emerge through extraction of the unwanted signal carrier, but it is concluded that this raises some economic and operating problems with respect to the receiver; except, perhaps, for specialised purposes.

DOI:10.1049/ip-i-2.1989.0035

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The timing recovery performance of partial-response class-4 signalling is experimentally determined as a function of transmit filter bandwidth, transmit filter rolloff and tuned circuit misalignment in the timing recovery circuit of a baseband transmission system operating at the ISDN basic access rate. The implications for echo cancellation are briefly discussed and some general properties of partial-response class 4 signalling are presented.

DOI:10.1049/ip-i-2.1989.0036

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The principles of a new real-time channel evaluation (RTCE) technique applicable to digital communication channels are described. At the transmitter, the statistical properties of the data are specified by appropriate source coding. At the receiver, the corresponding statistical properties of the received data are monitored continuously. Discrepancies between the specified transmitted data statistics and those actually observed at the receiver are then analysed to yield information on channel state. An implementation of the technique employing variable-rateT-codes for source coding is described, together with its performance over an additive white Gaussian noise (AWGN) channel and a channel with memory. It is shown that SRTCE techniques are particularly applicable to communication channels where the effect of noise is severe.

DOI:10.1049/ip-i-2.1989.0037

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper calculates limits to the performance of low-rate block-oriented coding and coded modulation schemes, such as spherical coding. The method is appropriate to fairly lowrate communication systems, in terms of bit rate per unit bandwidth. An approach based onn-dimensional geometry is used to derive an ideal geometric structure for such codes based on the form of a regular polytope with simplex cells. This structure is in general unrealisable, but its performance would give a limit to the performance of any practical code. Its performance in terms of the coding gain achievable is therefore calculated in order to find that limit. Maximum coding gain is found to be dependent on code length (equivalent to number of dimensions) and to a lesser extent on code rate. For a code length of 24 and rate 0.5 a coding gain of nearly 5 dB is possible, and in general the coding gain increases by 1 to 1.5 dB for every doubling of the number of dimensions.

DOI:10.1049/ip-i-2.1989.0038

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper shows how to convert the order-8 cosine transforms into a family of integer cosine transforms (ICTs) using the theory of dyadic symmetry. The new transforms can be implemented using simple integer arithmetic. It was found that performance close to that of the DCT can be achieved with an ICT that requires only 4 bits for representation of its kernel component magnitude. Better performance can be achieved by some ICTs whose kernel components require longer bit lengths for representation. ICTs that require 3 bits or less for representation of their component magnitude are available but with degraded performance. The availability of many ICTs provides an engineer the freedom to tradeoff performance for simple implementation in designing a transform codec.

DOI:10.1049/ip-i-2.1989.0039

出版商:IEE    

年代:1989

数据来源: IET

摘要:

In the paper we describe a model (ARCOS) for dynamic planning of small- and medium-size urban telephone networks. The main innovative feature of the method is the fact that, by exploring the spatial decomposition of a simplified initial network, we are led to a network of tractable size in the sense that it is possible to schedule ‘K-best’ network expansions in time, represented on a decision graph obtained according to some heuristic simplifications. For the purpose of defining the network expansions from the decision graph we used adequate versions of theK-shortest-paths algorithm and of a dynamic programming algorithm. That is, in ARCOS we seek to improve a type of algorithm for primary cable network planning as presented by Rapp by introducing a new heuristic method that seeks to optimise the dynamic evolution of the network topology together with the equipments capcity expansions. The actual version of the ARCOS model and its application to particular urban networks is described. The advantages and difficulties of the method are also discussed.

DOI:10.1049/ip-i-2.1989.0040

出版商:IEE    

年代:1989

数据来源: IET

摘要:

An expression is derived for the symbol error probability (SEP) of coherentM-ary phaseshift-keyed (PSK) signals (M> 4) transmitted through a bandlimited nonlinear channel. The bandpass nonlinearity (BPNL) considered exhibits AM/AM and AM/PM distortions. Additive white Gaussian noise (AWGN) on both up- and downlinks, and intersymbol interference (ISI) on up-link only have been taken as system impairments. SEPs are computed for an onboard TWTA and a phase-compensating receiver. The use of a softlimiter lineariser (SL-LRZ) to compensate the nonlinearities is also presented.

DOI:10.1049/ip-i-2.1989.0041

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The performance of a recently proposed efficient anti-jam communication system is examined. The system employs frequency hopping,MFSK modulation, diversity, Reed-Solomon (RS) coding and parallel error-erasure-correction decoding. It has previously been shown to be very effective in partial band noise jamming, and is one of the best known systems against jamming. In the paper, the performance of the system in multitone jamming is evaluted. An exact method is used rather than a bounding technique. The worst case jamming parameter is determined. In the worst case of multitone jamming, the conclusion is twofold. When the redundancy is not large, from the jammer's point of view, multitone jamming tends to be more effective than partial band noise jamming for nonbinary FSK. However, when large redundancy can be provided by diversity and RS coding, the worst case multitone jamming, one jamming tone perM-ary band, can be nullified with a properly designed system. The optimum design of the system under worst case jamming is presented in terms of the combination ofMFSK, diversity and RS coding. This forces the jammer to consider using multiple jamming tones perM-ary band. For a system having low redundancy, the design is locally optimised. These results provide detailed information on the design of a robust system.

DOI:10.1049/ip-i-2.1989.0042

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Many types of satellite tracking system have been suggested in recent years, and most have found applications in either the civil or military telecommunications sectors. However, all systems so far proposed have advantages and disadvantages, and hence considerable effort is still being directed towards the design of systems which are more economical but still offer high performance. One such system, utilising an electronic beam-control technique, is detailed here with particular reference to the design and characterisation of an optimum tracking receiver, and the new problems which the system poses in this. The system is described with an identification of the factors in existing receivers which limit the performance of the electronic tracking technique. By means of a computer simulation, a fundamental understanding of the physical processes involved is presented and some experimental results are included to validate the conclusions and proposed solutions.

DOI:10.1049/ip-i-2.1989.0043

出版商:IEE    

年代:1989

数据来源: IET