摘要:

AbstractThe availability of good software tools is vital to simulation practitioners. The objective of the OSISIM project (open system integrated simulator) is to set up an environment which integrates facilities and tools to build a communication system, and to study its performance. The environment is called AMS : atelier for modelling and simulation. Using it, the network architect, i.e. the user of the atelier, can quickly construct, in a graphical environment, a concise system from models of several standard networks available in a specific library, and execute the system in an efficient manner. Starting with an outline of the components of the atelier, we describe the AMS prototype, and the internal structure of basic models to be included in it. Moreover, a concrete example of a communication system including a satellite backbone is provided to illustrate how AMS is used to simulate such a system.

ISSN:0737-2884    

DOI:10.1002/sat.4600130302

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

年代:1995

数据来源: WILEY

摘要:

AbstractMobile satellite communication systems atKa/Kband (30/20 GHz) are attractive because of their large bandwidth availability and potentiality to support smaller earth‐stations and satellite antennas compared withL‐band (1·6/1·5 GHz) systems. In this paper, multiple‐symbol Viterbi decoding and dual‐space equal‐gain diversity reception for trellis‐coded differentialM‐ary phase‐shift‐keying (DPSK) modulation are investigated as two mitigation techniques for severe channel impairments expected from a land mobile satellite communication channel atKband and, for comparison purposes, atLband. The multiple‐symbol Viterbi decoder (MSVD) is a modified Viterbi decoder with inputs from multiple differential detectors. The channel is modelled as Rayleigh distributed multipath fading with a lognormally distributed line‐of‐sight (LOS) component due to shadowing. Four trellis‐coded modulation (TCM) schemes are studied. The dependency of the system performance improvement on the decoder structure, the TCM scheme, and the system RF

ISSN:0737-2884    

DOI:10.1002/sat.4600130303

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

年代:1995

数据来源: WILEY

摘要:

AbstractRecently many companies and consortia have considered launching LEO satellites for such projects as remote sensing, transportation and mining operations. When the multiple low Earth orbit (LEO) satellites are transmitting they can interfere with existing terrestrial microwave and satellite earth‐stations in the fixed and mobile service. The interference problem is related to the number of proposed LEOs and the altitude and consequently the time to orbit the earth. These systems usually consist of many small satellites, and each satellite stays in the beam of a terrestrial station for up to 72 seconds in each 222 minute orbit. Earth coverage could be obtained by 48 (LEO) satellites 1500 km above the earth in polar orbit, and hence at least one LEO would always be interfering with terrestrial networks. A technical evaluation would then be required to determine the resultant BER (bit error rate) effecting existing terrestrial services. A determination can then be made to support such a LEO system or object via official channels such as the IT

ISSN:0737-2884    

DOI:10.1002/sat.4600130304

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

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents a quantitative analysis by computer simulation of the active set update (ASU) handover algorithm for a shadowed low earth orbit (LEO) land mobile satellite (LMS) environment. As a precursor to the handover analysis, the mutual visibility statistics for a 66 satellite polar and 48 satellite rosette‐type constellation are presented. These results show the statistical nature of the levels of satellite diversity and mobile‐to‐satellite elevation angles (to the highest satellite) within each network and also indicate the influence of the channel characteristics on the handover strategy. A two‐state Markov modulated channel model is assumed in the handover analysis, and this enables the assessment of increased levels of power and time hysteresis on the quality of service and network signalling load in a shadowed land mobile satellite environment. In particular, attention is given to the different modes of ASU operation for hard handover, switch diversity and soft h

ISSN:0737-2884    

DOI:10.1002/sat.4600130305

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper, the design and results are presented of an experimental study which was conducted in order to assess subjectively the impact of transmission delay in audiovisual communications. This study was undertaken using two 64 kb/s videotelephones which were connected over links incorporating simulated one‐way circuit propagation delays of 0 ms, 250 ms and 500 ms. From the results obtained it was concluded that audiovisual communication is weakly affected by propagation delay. In general, performance degradation between terrestrial and single‐hop satellite connections was minimal and in most cases statistically insignificant. A subsidiary conclusion is that the presence of the visual cues appears to mitigate the impact of transmission delay in audiovisual communicat

ISSN:0737-2884    

DOI:10.1002/sat.4600130306

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

年代:1995

数据来源: WILEY

摘要:

AbstractFor the prospective personal satellite communications in the early 21st century, this paper presents a general exploration of aKa‐band DBPSK/DQPSK land‐mobile satellite channel model and its BER performance from system design, modelling and simulation. A forward‐link (i.e. outbound from the hub) channel design is introduced in brief. A complete model of channel multipath fading and shadowing is proposed for the first time, including a basic model and various derivative submodels corresponding to different actual propagation environments. Computer simulation results are given for a Rician channel model, a shadowed channel model and different combinational‐fading channel models by complete curve sets of BER performance, which coincide with the results of the analysis, and could be used as valuable references in further research and impleme

ISSN:0737-2884    

DOI:10.1002/sat.4600130307

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

年代:1995

数据来源: WILEY

ISSN:0737-2884    

DOI:10.1002/sat.4600130301

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

年代:1995

数据来源: WILEY