摘要:

AbstractThe problem of diversity reception ofM‐arydifferential phase shift keying modulated, signals in the presence of additive white Gaussian noise and Nakagami‐distributed slow and non‐selective fading is addressed. N‐branch selection diversity and maximal ratio combiners are considered. The average symbol error rate is analytically evaluated in terms of integral expressions, which can be easily computed via numerical integration routines. Numerical results are presented that allow one to point out those operational situations where diversity systems can operate successfully to mitigate the degrading effects of short‐te

ISSN:1124-318X    

DOI:10.1002/ett.4460070202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe PLL frequency synthesizer with anN‐stage cycle swallower (NSCS) is one of the fastest frequency switching synthesizers. The synthesizer, however, requires many stages in theNSCSto obtain accurate output frequencies. In this paper, to obtain both more accurate output frequencies with a few stages and a higher speed acquisition time, we propose two methods for improvingNSCSswitching operation. First, by allowing theNSCSoutput frequency to be variable a large range of choices in the division ratios becomes available in theNSCS. The proposed synthesizer has the output frequency of deviation within 0.0003 ppm when the 3‐stage cycle swallower is employed. Second, by temporarily increasing the expected amount of the variation in the output frequency, the acquisition time of theNSCSsynthesizer can be improved. Experimental results confirm that the proposed technique results in a shortened acquisition t

ISSN:1124-318X    

DOI:10.1002/ett.4460070203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThis work considers asynchronous DS‐CDMA systems with single‐user receivers. The focus is on chip pulse shaping and combined error control/PN sequence spreading. It is shown that pulse shaping can significantly reduce the effects of cross‐talk interference. A criterion which measures the ability of a chip waveform to reduce cross‐talk interference is derived, taking into account, the signal bandwidth. This work also shows that the best performance is achieved when all the bandwidth expansion is accomplished by error control coding. instead of PN sequences. Comparisons of CDMA systems using different pulse shapes are presented, taking into account the bandwidth of each pulse. Finally CDMA is compared to orthogonal multiple access (TDMA/FDMA) in an interference free environment. It is shown that for the same bandwidth (99% energy containment bandwidth), CDMA with suitable chip waveforms and coding yields the same performance as binary orthogonal multiple access with raised cosine shaping of 70% excess ba

ISSN:1124-318X    

DOI:10.1002/ett.4460070204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractWe present frequency hopped spread‐spectrum multiple‐access (FH‐SSMA) employing bandwidth‐efficient modulations that are phase‐continuous during each hop. The particular cases of minimum‐shift keying (MSK), and Gaussian minimum‐shift keying (GMSK) are studied in detail. Noncoherent sequence estimation on a hop‐by‐hop basis is considered. System performance has been evaluated in selective Rayleigh fading with additive white Gaussian noise (AWGN) and the presence of multiple‐access cellular interference. This system performance is better than the performance of FH‐SSMA with noncoherent binary FSK modulation. The effects of power control, different fading covariance functions and different power bandwidth definit

ISSN:1124-318X    

DOI:10.1002/ett.4460070205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractWe consider a cellular satellite system conceived to enhance the capabilities of the pan‐European terrestrial system (GSM). This adopts EHF band and highly‐inclined orbits. We present a preliminary assessment of system capacity based on asynchronous direct‐sequence spread‐spectrum multiple access (DS‐SSMA). Performance is measured in terms of error probability achieved byKusers simultaneously accessing the system with a given signal‐to

ISSN:1124-318X    

DOI:10.1002/ett.4460070206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractAbstract A suitable and often used stochastical model for the description of the fading behaviour of a time variant and frequency‐selective channel is the wide sense stationary uncorrelated scattering (WSSUS) model. Usually, the wide sense stationary process is assumed to be a zero mean Gaussian process. In such a case, the WSSUS model is completely determind by the so called scattering function. In order to approximate a desired scattering function of a WSSUS model by a simulation model, it is well known that Monte Carlo based methods cm be used for the computation of the simulation model parameters (discrete echo delays and discrete Doppler frequencies). In this paper, we present a new method, which results always in a better approximation of a prescribed scattering function of a WSSUS model than the Monte Carlo principle. We show that the statistical behaviour of the resulting fading channel model ‐ in particular the level‐crossing rate and the average duration of fades ‐ is not only independent of a random realization of the discrete echo delays and discrete Doppler frequencies, but is also extremely close to the statistical behaviour as it was to be expected from the

ISSN:1124-318X    

DOI:10.1002/ett.4460070207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractPartially coherent detection is studied as a problem of detection over diversity channels with unknown amplitudes, and known or perfectly estimated phases. The optimum composite hypothesis receiver is derived for binary, uniformly orthogonal signaling. Because of the high corn plexity of this optimum receiver, two suboptimal structures are considered a Linear equal gain combiner (LEGC) receiver and a quadratic coherent combiner, which is also a generalized likelihood ratio test (GLRT) receiver for this case. We examine the combiner output signal‐to‐noise ratio (SNR) for the two suboptimal receivers and show that this measure cannot be a performance comparison criterion for receivers of different orders. The exact performance of the GLRT receiver is evaluated in terms of the conditional, average and asymptotic bit error rates (BER), and graphical results are presented. An interesting result is that theseBERexpressions are obtained, for even and odd diversity orders, via different routes and that quadratic noncoherent detection represents a degenerate case of quadratic coherent detection with even diversity. The averageBERof LEGC is exactly evaluated for dual diversity. LEGC and quadratic coherent combining are compared with respect to the asymptoticBEAand the exactBERfor dual diversity. It is shown that LEGC is better in terms of the averageBERin fading, while quadratic coherent combining is conditionally better whenever the signals received over different links have significantly different streng

ISSN:1124-318X    

DOI:10.1002/ett.4460070208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe performance of a receiver which uses fading prediction technique in conjunction. with a channel coding/interleaving scheme is determined for Ridan non‐selective fading channels., The essence of the proposed technique is based on predicting the fading process and designing the receiver accordingly. The novel receiver employs a combination of a prediction technique and Reed Solomon (RS) codes/interleaving scheme using phase shift keying (PSK) modulation scheme. The obtained computer simulation results of the bit error rate (BER) performance show that the proposed prediction/coding/interleaving technique greatly reduces theBERdegradation caused by the multi path fadin

ISSN:1124-318X    

DOI:10.1002/ett.4460070209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractA class of binary‐input discrete‐time channels with symmetric distribution of the output with respect to the input is considered and the channel capacity is analytically evaluated. The Gaussian and Rayleigh fading channel belong to this class and their capacities are numerically obtained for different quantization of the output. The asymptotic capacities for low signal‐to‐noise ratio (SNR) are compared and it is shown that the Rayleigh fading channel loses abo

ISSN:1124-318X    

DOI:10.1002/ett.4460070210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractIn the past five years practical multi‐channel AM‐VSB optical fibre links have moved from the R&D labs into real world applications. In this paper, we focus on the design and performance capabilities of current commercialized systems using distributed feedback lasers (DFB), single mode optical fibres and PIN optical receivers. We first discuss fundamental concepts used in IM‐DD communication links. The noise and distortions sources are identified and their influence on the systems performances are presented. The use of Erbium Doped Fibre Amplifiers (EDFA) at 1550 nm is envisaged and their influence on the power budget of the CATV network is ana

ISSN:1124-318X    

DOI:10.1002/ett.4460070211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY