摘要:

AbstractIn this paper non—data—aided(NDA), maximum likelihood(ML) algorithms are derived for the carrier frequency and phase offset, separately, for OFDM systems employing M—PSK modulation scheme. NDA ML estimation algorithm for frequency offset estimation exploits the redundant information contained in the cyclic prefix proceeding the OFDM symbols, thus reducing the need for pilots. Its mean—squared performance is obtained analytically and compared with simulation results. It is observed that the resulting algorithm generates very accurate estimation even when the offset is high. It is also shown that the frequency estimator may be used in a tracking mode. The ML algorithm derived for the carrier phase estimation is also a non—data—aided(NDA) and maximizes the lowSNRlimit of the likelihood function averaged over M—PSK signal constellation. It is shown that for sufficiently smallSNRthe ML phase estimator obtained reduces to the familiar M/th order power synchronizer which belongs to the class of NDA feedforward carrier synchronizers introduced earlier in the literature. Its mean—squared performance is obtained analytically and compared with simulation results. We observe that the resulting algorithm generates very accurate estimation even when the phase offset is high, that the self noise is absent and the performance of the algorithm is basically the same as die Cramer—Rao bound for moderate to highSNR.Finally we note mat me error variance derived for the mean—squared performance of this NDA ML synchronizer is an extension of the approximate variance formula appeared in Reference 20,equ

ISSN:1124-318X    

DOI:10.1002/ett.4460120202

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

年代:2001

数据来源: WILEY

摘要:

AbstractThe problem of transmitting a wideband signal through a narrowband channel is considered. A new solution to this problem is proposed in which the wideband signal is divided into two parts: a first part which occupies exactly the spectrum that the channel can carry and a second— the rest of the signal. It is proposed to transmit the first part without any coding (in analog form) while the second part is sampled and quantized and the resulting data stream is transmitted simultaneously with the first part via the same channel. An alternative approach, based on the separation theorem, is to optimally quantize the whole signal using an optimal source encoder at the rate equal to the channel capacity and then to transmit the signal (digitally) using an optimal channel encoder. Such double optimality yields the best achievable MSE performance. It is shown that if the double optimality assumptions are applied to the second part of the signal, in the proposed case, than the MSE performance equals that which follows from the separation theorem. If, however at least one of these optimal encoders can not be achieved, the proposed method has a better MSE performance than that based on the separation theorem when applied to the whole signa

ISSN:1124-318X    

DOI:10.1002/ett.4460120203

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

年代:2001

数据来源: WILEY

摘要:

AbstractTransmission of 4—DPSK signals over an additive white Gaussian noise channel with an unknown phase rotation is considered, together with block detection [1] and Reed—Solomon encoding. The combination of the block detection's length and RS code parameters is analy

ISSN:1124-318X    

DOI:10.1002/ett.4460120204

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

年代:2001

数据来源: WILEY

摘要:

AbstractThe paper presents an analysis of the investment costs associated with broadband' upgrades in various residential areas in which there is an existing twisted pair infrastructure. Upgrade strategies— based on a combination of optical fibre systems and digital subscriber line (DSL) technologies are examined. The analysis highlights the significant differences in investment levels expected in downtown, urban, suburban and rural areas for the ranges of DSL capacities from 2 Mbit/s to 26 Mbit/s. The paper reports work performed in the EURESCOM2project P614, Implementation Strategies for Advanced Access Networks*. The methodology and tool initially developed by the RACE32087/TITAN4project, and now under further development in the ACTS5226 OPTIMUM6project has been applied in the techno—economic analy

ISSN:1124-318X    

DOI:10.1002/ett.4460120205

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

年代:2001

数据来源: WILEY

摘要:

AbstractThe performance of a baseband adaptive predistortion system to linearize memoryless high power amplifier (HPA) are analyzed in the presence of an Orthogonal Frequency Division Multiplexing (OFDM) signal. The predistortion scheme adopted is based on a digital signal processing microprocessor and a memory look—up table to predistort the baseband drive signal. Stability of the adaptation algorithm, rate of convergence and effect of quantization are assessed through simulation. The curves of Total Degradation versus the Output Back—off have been calculated for QPSK, 16QAM and 64QAM constellations. Starting from these results, the improvement brought by the use of the predistorter and the degradation caused by the quantization has been asses

ISSN:1124-318X    

DOI:10.1002/ett.4460120206

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

年代:2001

数据来源: WILEY

摘要:

AbstractThe development of sophisticated multimedia applications requires accurate performance evaluation tools to efficiently design and manage future high bandwidth networks. These tools have to be accurate, in order to closely match the statistical characteristics of network traffic, easy to implement, and efficient. VBR compressed video traffic is expected to represent most of the multimedia traffic loading networks in the immediate future, and the MPEG coding scheme will be the most widely used standard for many types of applications. Although many works in literature present models of video traffic, little effort has been devoted up to now to capturing one of the most important characteristics of MPEG video traffic: intra—GoP correlation. In this paper, after demonstrating that this correlation strongly affects the performance of a network loaded by MPEG video traffic, an accurate, fast and easy generation algorithm is proposed. The algorithm allows a sequence to be generated, imposing the Short Range Dependence (SRD), the Long Range Dependence (LRD) behavior and the probability density function of any given MPEG video sequenc

ISSN:1124-318X    

DOI:10.1002/ett.4460120207

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

年代:2001

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460120208

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

年代:2001

数据来源: WILEY

摘要:

AbstractOutage analysis is one of the primary objectives in the design and operation of the 3rd Generation (3G) micro— and pico— cellular mobile radio systems in order to increase spectrum efficiency and to control the Quality of Service (QoS) and Grade of Service (GoS) demands. This paper presents an alternative direct formulation of the outage probability for Nakagami fading channels in the presence of multiple L Nakagami interferers with arbitrary parameters. This formulation can be used with and—without a constraint of a minimum signal power. Computer simulation results are also presented to illustrate the proposed formul

ISSN:1124-318X    

DOI:10.1002/ett.4460120209

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

年代:2001

数据来源: WILEY

摘要:

AbstractWhile hysteresis alleviates the ping—pong effect in a cellullar handoff, it also introduces severe outage degradation. In this letter, the handoff triggering condition as well as the unavailability to handoff completion are studied in terms of mobile location and hysteresis factor. It is shown how hysteresis favors high dropped—call probability zones within the service area. The proposed methodology is applicable to both forward and reverse channel analysis. Numerical results are presented and discus

ISSN:1124-318X    

DOI:10.1002/ett.4460120210

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

年代:2001

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460120201

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

年代:2001

数据来源: WILEY