Method and apparatus for efficient data transmissions in half-duplex communication systems with large propagation delays

Abstract

Methods and apparatus for efficient transmission of data by half-duplex transceivers in satellite communication systems are provided. Time reference for the return link is skewed or time-lagged relative to the time reference for the forward link to reduce the amount of guard time required to separate return link transmission from forward link reception by the half-duplex transceiver of a user terminal. The guard time is determined based on a maximum differential round-trip propagation delay and transition times of the half-duplexer transceiver to switch between transmit and receive modes. In a satellite communication system in which a large number of active user terminals are present in a beam coverage, random time offsets are applied to spread approximately equal traffic loads across the time offsets.

What is claimed is: 
     
         1 . A method of determining a forward link time duration and a guard time duration in a half-duplex frame in a satellite communication system, the method comprising:
 allocating a forward link time segment in a special subframe of the half-duplex frame;   allocating a guard time segment in the special subframe;   determining the forward link time duration in the half-duplex frame based on the forward link time segment in the special subframe; and   determining the guard time duration in the half-duplex frame based on the guard time segment in the special subframe.   
     
     
         2 . The method of  claim 1 , wherein the half-duplex frame further comprises a forward link subframe preceding the special subframe and a guard subframe succeeding the special subframe. 
     
     
         3 . The method of  claim 2 , wherein determining the forward link time duration in the half-duplex frame comprises adding the forward link time segment in the special subframe to the forward link subframe. 
     
     
         4 . The method of  claim 2 , wherein determining the guard time duration in the half-duplex frame comprises adding the guard time segment in the special subframe to the guard subframe. 
     
     
         5 . The method of  claim 1 , wherein the method is performed by an adaptive special subframe (SSF) scheduler. 
     
     
         6 . The method of  claim 5 , wherein the adaptive SSF scheduler is in a gateway. 
     
     
         7 . The method of  claim 1 , wherein the satellite communication system includes at least one ground station. 
     
     
         8 . The method of  claim 1 , wherein the satellite communication system includes a satellite that is a non-geosynchronous satellite. 
     
     
         9 . An apparatus configured to determine a forward link time duration and a guard time duration in a half-duplex frame in a satellite communication system, the apparatus comprising:
 at least one processor; and   at least one memory coupled to the at least one processor, the at least one processor and the at least one memory being configured to:   allocate a forward link time segment in a special subframe of the half-duplex frame;   allocate a guard time segment in the special subframe;   determine the forward link time duration in the half-duplex frame based on the forward link time segment in the special subframe; and   determine the guard time duration in the half-duplex frame based on the guard time segment in the special subframe.   
     
     
         10 . The apparatus of  claim 9 , wherein the half-duplex frame further comprises a forward link subframe preceding the special subframe and a guard subframe succeeding the special subframe. 
     
     
         11 . The apparatus of  claim 10 , wherein determining the forward link time duration in the half-duplex frame comprises adding the forward link time segment in the special subframe to the forward link subframe. 
     
     
         12 . The apparatus of  claim 10 , wherein determining the guard time duration in the half-duplex frame comprises adding the guard time segment in the special subframe to the guard subframe. 
     
     
         13 . The apparatus of  claim 15 , wherein the apparatus comprises an adaptive special subframe (SSF) scheduler. 
     
     
         14 . The apparatus of  claim 13 , wherein the adaptive SSF scheduler is in a gateway. 
     
     
         15 . The apparatus of  claim 9 , wherein the satellite communication system includes at least one ground station. 
     
     
         16 . The apparatus of  claim 9 , wherein the satellite communication system includes a satellite that is a non-geosynchronous satellite. 
     
     
         17 . An apparatus for determining a forward link time duration and a guard time duration in a half-duplex frame in a satellite communication system, the apparatus comprising:
 means for allocating a forward link time segment in a special subframe of the half-duplex frame;   means for allocating a guard time segment in the special subframe;   means for determining the forward link time duration in the half-duplex frame based on the forward link time segment in the special subframe; and   means for determining the guard time duration in the half-duplex frame based on the guard time segment in the special subframe.   
     
     
         18 . The apparatus of  claim 17 , wherein the half-duplex frame further comprises a forward link subframe preceding the special subframe and a guard subframe succeeding the special subframe. 
     
     
         19 . The apparatus of  claim 18 , wherein determining the forward link time duration in the half-duplex frame comprises adding the forward link time segment in the special subframe to the forward link subframe. 
     
     
         20 . The apparatus of  claim 18 , wherein determining the guard time duration in the half-duplex frame comprises adding the guard time segment in the special subframe to the guard subframe. 
     
     
         21 . The apparatus of  claim 17 , wherein the apparatus comprises an adaptive special subframe (SSF) scheduler. 
     
     
         22 . The apparatus of  claim 21 , wherein the adaptive SSF scheduler is in a gateway. 
     
     
         23 . The apparatus of  claim 17 , wherein the satellite communication system includes at least one ground station. 
     
     
         24 . The apparatus of  claim 17 , wherein the satellite communication system includes a satellite that is a non-geosynchronous satellite. 
     
     
         25 . A non-transitory computer-readable medium comprising at least one instruction for causing a computer or processor to perform a method to determine a forward link time duration and a guard time duration in a half-duplex frame in a satellite communication system, the at least one instruction comprising instructions to:
 allocate a forward link time segment in a special subframe of the half-duplex frame;   allocate a guard time segment in the special subframe;   determine the forward link time duration in the half-duplex frame based on the forward link time segment in the special subframe; and   determine the guard time duration in the half-duplex frame based on the guard time segment in the special subframe.   
     
     
         26 . The non-transitory computer-readable medium of  claim 25 , wherein the half-duplex frame further comprises a forward link subframe preceding the special subframe and a guard subframe succeeding the special subframe. 
     
     
         27 . The non-transitory computer-readable medium of  claim 26 ,
 wherein determining the forward link time duration in the half-duplex frame comprises adding the forward link time segment in the special subframe to the forward link subframe,   wherein determining the guard time duration in the half-duplex frame comprises adding the guard time segment in the special subframe to the guard subframe, or   any combination thereof.   
     
     
         28 . The non-transitory computer-readable medium of  claim 25 , wherein an apparatus comprising the computer or processor comprises an adaptive special subframe (SSF) scheduler. 
     
     
         29 . The non-transitory computer-readable medium of  claim 28 , wherein the adaptive SSF scheduler is in a gateway. 
     
     
         30 . The non-transitory computer-readable medium of  claim 25 ,
 wherein the satellite communication system includes at least one ground station,   wherein the satellite communication system includes a satellite that is a non-geosynchronous satellite, or   any combination thereof.