摘要:

AbstractIn this paper we analyze the structure and the performance of a digital modem for band‐limited spread‐spectrum signals to be employed in a radio communication network with asynchronous code‐division multiple access and constant‐envelope continuous‐phase modulation. After a description of the modem structure and the evaluation of its bit error rate in the presence of co‐channel interference, we tackle the key point of code synchronization. In particular, we present a detailed analysis of the code acquisition strategy, assessing its performance in terms of false alarm probability, missed detection probability and mean acquisition time. Furthermore, we address the problem of code chip timing recovery, describing the performance of three different code tracking loops in terms of the steady‐state RMS chip timing error jitter. The analytical approach we present can be applied to any Continuous Phase Modulation (CPM) format that can be approximated by an Offset‐QAM signal, such as Gaussian‐filtered Minimum‐

ISSN:1124-318X    

DOI:10.1002/ett.4460070302

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

年代:1996

数据来源: WILEY

摘要:

AbstractLarge families of ≈pQ(pprime,Q= 2, 3, 4.,) polynomial phase sequences are presented. Thep‐arysequences are of lengthp. Their correlation magnitudes are upper bounded by ≈Q√p. The families are suitable for application in asynchronous CDMA

ISSN:1124-318X    

DOI:10.1002/ett.4460070303

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

年代:1996

数据来源: WILEY

摘要:

AbstractA method of spread spectrum radar polyphase code design based on the code elements' symmetry and nonlinear programming is presented. The main features of the synthesized code are the very low sidelobes in the compressed pulse and noncoherent processing. The comparison to the well‐known classes of polyphase codes is mad

ISSN:1124-318X    

DOI:10.1002/ett.4460070304

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

年代:1996

数据来源: WILEY

摘要:

AbstractIt is shown that the TCM scheme with 8‐D rectangular constellation designed by Tretter [1] based on a well known method invented by Wei [2]can support an opportunistic channel which can transmit 300 bits/

ISSN:1124-318X    

DOI:10.1002/ett.4460070305

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

年代:1996

数据来源: WILEY

摘要:

AbstractOrthogonal Frequency Division Multiplexing (OFDM) is considered as an effective technique in high speed digital transmission under multipath fading. In this paper we theoretically analyze the behaviour of a coherent pilot‐symbol aided M‐QAM‐OFDM system in presence of time selective multipath channel. In the analyzed scheme, pilot symbols are periodically inserted to monitor the channel characteristics. The fading process experienced by the pilot symbols is used to estimate the fade characteristics at symbol‐rate through interpolation. The estimated channel is used to compensate for the random phase variation caused by the Doppler spread, so that the signal can be coherently demodulated. The bit error rate (BER) performance of this coherent OFDM modulation scheme is derived. The obtained results show that, with a reasonable amount of redundancy (frequency of the pilot symbols) introduced, the system performance approaches that of the ideal coherent demodulation, as long as a suitable channel estimate procedure is

ISSN:1124-318X    

DOI:10.1002/ett.4460070306

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

年代:1996

数据来源: WILEY

摘要:

AbstractThis paper (1) describes the structure and the performance of a band‐limited spread‐spectrum transmission system suited for short‐range terrestrial inter‐vehicle or vehicle‐to‐beacon radio links that features Generalized MSK as modulation format and asynchronous direct‐sequence code‐division multiple access. The Bit Error Rate (BER) performance of such a system is evaluated over a recently proposed 60 GHz short‐range mobile radio channel model. In particular, the sensitivity to a number of relevant link parameters (such as the distance between transmit and receive antennas and the receiver speed) is investigated, and the impact of code tracking errors and of differential encoding/detection of the spreading code chips on system performance

ISSN:1124-318X    

DOI:10.1002/ett.4460070307

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

年代:1996

数据来源: WILEY

摘要:

AbstractDue to the adoption in high capacity Digital Radio Relay Systems of transmission techniques such as low redundancy error‐correcting codes, trellis coded modulations, Viterbi receivers, etc., the errors tend to be clustered in bursts. Up to now, a model used to describe the burst error distribution was the Neyman‐A contagious model. This model was conceived to be applied in entomology and bacteriology, but it is also used in telecommunications. So, according to this model, the bursts and the number of errors in bursts are both supposed to be Poisson distributed. However, this distribution does not represent accurately the real situation, so, in order to derive a new probability distribution function, that improves the accuracy of the description of a burst error distribution a new model is required. In this paper a new model based on Erlang distribution for the number of errors in bursts, is described by using the Neyman appro

ISSN:1124-318X    

DOI:10.1002/ett.4460070308

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe maximum achievable rate of an error‐correcting runlength‐limited code is considered. Runlength‐limited codes find wide applications in magnetic and optical recording, baseband. pulse transmission, and fiber optic communications. When a runlength‐limited code is used on a noisy channel, error‐correction control is often needed in order to obtain the desired system reliability. It is well‐known that the error‐correcting capability of a code is closely related to its distance properties. In this paper, asymptotic upper bounds for the maximum achievable rate of a runlength‐limited code are derived as a function of the code's minimum H

ISSN:1124-318X    

DOI:10.1002/ett.4460070309

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

年代:1996

数据来源: WILEY

摘要:

AbstractA novel modulating scheme is presented that allows optimal echo path modelling using, real time least mean square (LMS) system identification techniques. The systems of interest are usually based on a class of digital adaptive filters (DAFs). The modelling convergence rate derived from the optimal Wiener weights defines the performance criterion. A novel chaotic based modulation regime utilising the logistic mapping is exploited to whiten the speech power spectral density (PSD) whilst preserving the signal bandwidth requirements. The whitened signal optimises the convergence rate and allows adaptation times to be calculated without a‐priori knowledge of the speech signal's second order statistics. Software simulations are reported for an ensemble of conversational speech realisations and it is shown that the described modulation scheme significantly improves the convergence rate and guarantees optimal modelling independent of the input speech signal statistics. Furthermore, the noise whitened input signal circumvents control supervisory problems usually associated with uncoded speech input

ISSN:1124-318X    

DOI:10.1002/ett.4460070310

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

年代:1996

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460070311

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

年代:1996

数据来源: WILEY