ISSN:1124-318X    

DOI:10.1002/ett.4460020502

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

年代:1991

数据来源: WILEY

摘要:

AbstractCellular radio channels suffer from signal outages due to multipath fading and shadowing. Analytical expressions are given for the probability that the instantaneousC/I‐ratio drops below a required protection ratio. A radio signal from a mobile subscriber exhibits outages at different base station sites with relatively low correlation. The quality of communication over a mobile telephone circuit can be improved by appropriately combining voice segments received at various base stations. The probability of dropping a voice segment for an end‐to‐end «up‐link» circuit (mobile‐to‐PSTN) in an interference‐limited cellular network with discontinuous voice transmission and macro diversity is evaluated mathematically. Asymptotic expressions of the signal outage probability for high averageC/I‐ratios are present

ISSN:1124-318X    

DOI:10.1002/ett.4460020503

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

年代:1991

数据来源: WILEY

摘要:

AbstractPacket radio has recently gained great interest in the wider context of mobile communications. In this scenario, the signal worsening due to real transmission conditions (linear and nonlinear distortion, fading, interferences, noise) deeply affect the network performance. It is then necessary to verify whether it is feasible, and if so, how to dimension the transmission system supporting the network itself, in order to respect a fixed quality condition.In this work we suggest the introduction of a quality criterion which seems particularly suitable to set up a relationship between transmission and network parameters, and therefore to solve the problem previously submitted. We determine this relationship with reference to a star topology network, where the slotted Aloha protocol is employed in conjunction with a narrowband modulation scheme; independent, non‐selective and slowly varying fading conditions on every link of the network are also assumed.The treatment developed is then applied to a significant example of packet radio network, and many numerical results are reporte

ISSN:1124-318X    

DOI:10.1002/ett.4460020504

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe Packet Reservation Multiple Access (PRMA) is analysed using a Markov chain model for speech/data transmission to a central base station. The effect of the number of users on the speech packet dropping probability is investigated including consideration of transmission permission probability.

ISSN:1124-318X    

DOI:10.1002/ett.4460020505

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

年代:1991

数据来源: WILEY

摘要:

AbstractIt is well‐known that the simulation of analog filters must be based on thesimulation theorem, which refers to a digital model of the filter to be simulated. Here we show the relationships between the DFT simulation techniques and this theorem, and how to extract the digital model implicitly contained in a filtering process based on DFT. As the simulation results depend on the quality of the digital model, we propose to introduce a parameter able to measure the difference between the actual model and the ideal one. Here we define aquality coefficient, related to the mean square error between the actual model and the ideal one, with some interesting characteristics: it can be very easily software implemented, depends only on the digital model, can be evaluated at the beggining of the simulation process (before filtering), gives the user a very simple criterion to estimate the quality of the digital mode

ISSN:1124-318X    

DOI:10.1002/ett.4460020506

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper presents a classification of ortho‐mode transducers (OMTs). The OMTs are classified into five main groups. The first four contain OMTs based on waveguide‐to‐waveguide transitions. The basis for this classification is symmetrical properties which affect both the isolation and the matching capacities. A systematic analysis of the generation of symmetrical and odd symmetrical higher‐order modes including their influence on the isolation and matching conditions is also included. The last group of OMTs consists of devices with waveguide‐to‐coax transitions. These are denoted

ISSN:1124-318X    

DOI:10.1002/ett.4460020507

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe abstract representation of the scalar wave equation of optics is extended from the time‐dependent wave equation to the stationary wave equation via the fundamental action integral. It is demonstrated that the stationary wave equation together with general initial conditions is not equivalent with the corresponding time‐dependent equation, because with the transition one has lost physical information. The consequences thereof are discussed. Subsequently the modes of the stationary wave equation are defined and their attributes, which follow from missing losses of the physical system, are given. Finally the mode coupling method for the stationary wave equation is derived by geometrical reflections. Two examples illustrate the considerati

ISSN:1124-318X    

DOI:10.1002/ett.4460020508

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe purpose of this note is to establish the equivalence of two distinct definitions of forced‐response stability used in the literatur

ISSN:1124-318X    

DOI:10.1002/ett.4460020509

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn burst transmission spread spectrum systems it is advantageous to effect receiver synchronization by passive correlation, i.e. by matched filtering, and to detect the message by active correlation which means multiplication by a reference signal and integration in the time domain. If the number of available active correlation circuits is limited, a certain percentage of the arriving telegrams cannot be processed and will be lost. In conventional analog burst spread spectrum systems the loss can be calculated with the Erlang loss formula. For modern digital burst spread spectrum systems the Erlang loss formula is only an approximation which maiy give unaccurate results. In this paper an exact loss formula for digital spread spectrum systems will be presented and compared with the Erlang loss formula. The formula will be applied to minimize the loss of a practical system.

ISSN:1124-318X    

DOI:10.1002/ett.4460020510

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn this paper a generalized procedure to extract the noise parameters of GaAs MESFETs is presented. The average quadratic error between the measured values of optimum noise figure and the calculated ones is minimized in order to obtain the optimum admittance value at the amplifier input. The hypothesis of device unilaterality is assumed. A comparison between the proposed method and the previous ones has been carried out. A consequent more simplified analytical approach to evaluate the optimum noise source impedance of a GaAs MESFET amplifier allows the proposed procedure to be easly implemented in the most popular CAD tools.

ISSN:1124-318X    

DOI:10.1002/ett.4460020511

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

年代:1991

数据来源: WILEY