On Satellite Path Diversity for GSM Rate Compatible TDMA Big LEOs

  • Tor E. Wisløff
Part of the The Kluwer International Series in Engineering and Computer Science book series (SECS, volume 366)


The mobile link of the proposed non-geostationary satellite systems is subject to multipath fading and shadowing of the required line-of-sight path, resulting in link-outage. This paper explains how satellite path diversity can be employed to overcome this link-outage in a TDMA based non-geostationary satellite communications system. The GSM halfrate TDMA format is used as an example. Timing and implementation issues related to dynamic satellite path diversity are considered. Two TDMA structures are derived. Both accommodate diversity, but differ in the assumed usage of diversity. Neither of the structures necessitate a duplicated receiver chain nor a duplexer in the mobile terminal. The diversity schemes divide the 16 timeslot halfrate GSM TDMA frame in different slots for communicating with different satellites. The slots represent how much the timing adjustment at the mobile terminal can be changed before timing constraints are violated. The paper also considers mechanisms to determine whether a call should be set-up with diversity, and whether the diversity state should be allowed to toggle during a connection’s lifetime. It is demonstrated how diversity toggling can be used to achieve a seamless handover, and message sequence charts are shown for both handover and diversity toggling.


Elevation Angle Mobile Terminal Earth Station Path Delay Timing Adjustment 
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Copyright information

© Kluwer Academic Publishers, Boston 1996

Authors and Affiliations

  • Tor E. Wisløff
    • 1
  1. 1.Department of Computer Systems and TelematicsNorwegian University of Science and TechnologyTrondheimNorway

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