摘要:

AbstractVarious mobile satellite communication systems are being developed for providing integrated voice/data services over a shared satellite transponder which is power‐limited in nature. A common strategy is to use slotted ALOHA request channels to request channel assignments for voice/data calls from a network management station. To maximize efficiency in a system with a power‐limited satellite transponder, it is proposed that the bursty nature of voice sources be exploited by the NMS to ‘over‐assign’ channels. This may cause problems of inefficiency, potential instability as well as a degradation in the quality of service offered to the customers. Augmenting this with the introduction of simple state‐dependent control procedures provides systems which exhibit more desirable operational features. This approach is proposed and examined in

ISSN:0737-2884    

DOI:10.1002/sat.4600090102

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe frequency stability and reliability of the clocks are critical to the success of the GPS and GLONASS programs. We will show some of the similarities and differences between the clocks involved in these two systems. Because both systems plan to be operational in the next few years, the data leading up to this operational stage is of significant interest. On‐board clocks and the stability of the master control clocks for these systems are analysed.We will discuss the attributes of these two systems as time and frequency references. Their relationship to UTC will also be illustrated. More data over a longer period of time was available for the authors from GPS than from GLONASS. Even so it is obvious that both systems have matured. Though the GLONASS system was developed later, its overall clock performance has improved more rapidly. Some of the more recent GLONASS clock performance is at about the same level as that of the GPS clocks.The analysis has yielded some very interesting contrasts, comparisons and changes in these systems that should be of great interest for time and frequency users, as well as for clock vendors and receiver vendor

ISSN:0737-2884    

DOI:10.1002/sat.4600090103

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

年代:1991

数据来源: WILEY

摘要:

AbstractA previously proposed contention‐based TDMA protocol is modified to remain operational for a channel which is not noise free. The protocol is a mixture of random accessing and time division multiplexing and is suitable for data transmission through a channel which is characterized by non‐negligible round‐trip signal propagation delay. The effect of channel errors on the performance of the protocol is studied. Through numerical calculation it is observed that for the bit‐error‐rates encountered in practice the protocol remains stable. When the channel becomes rather noisy, error correcting codes can be imbedded to improve the performance. The validity of analysis has been verified by computer s

ISSN:0737-2884    

DOI:10.1002/sat.4600090104

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe architecture of an experimental payload with on‐board processing capabilities is described. Since the system is proposed as an experimental one it operates with only four beams in the 20/30 GHz frequency band. Special emphasis is put on the design of the switch and its associated control. The switch operates in a synchronous circuit‐switching manner and provides a throughput of 131 Mb/s. To derive the requirements for the on‐board controller, a process model is established. This model shows that an implementation in a finite state machine will not give enough flexibility. Therefore a microprocessor system is proposed for the contr

ISSN:0737-2884    

DOI:10.1002/sat.4600090105

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

年代:1991

数据来源: WILEY

ISSN:0737-2884    

DOI:10.1002/sat.4600090106

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

年代:1991

数据来源: WILEY

ISSN:0737-2884    

DOI:10.1002/sat.4600090101

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

年代:1991

数据来源: WILEY