Uniformly distributed control burst structure for the uplink of a processing satellite communication system

#The present invention relates to satellite communication systems. More specifically, the invention relates to a uniformly distributed synchronization burst structure for the uplink of a processing satellite communication system.

#Today, satellite systems commonly transmit and receive communications signals to and from user terminals. Such satellite based communications systems may utilize a constellation of satellites to relay communications signals to and from the user terminals (fixed or mobile). Each satellite includes at least one antenna which defines the satellite's coverage region on the earth called its footprint. The satellite antenna(s) may divide the footprint into multiple beam spots called cells, or the footprint may be a single cell. Each cell is assigned one or more frequency bands (subbands), in which communications signals travel between the satellite and each user terminal within that cell.

#The user terminals communicate along preassigned communications channels in the subband. The transmission of information along a preassigned communications channel from an earth station to a satellite occurs on the uplink, and the transmission of information along a preassigned communications channel from a satellite to an earth station occurs on the downlink.

#FIG. 1 illustrates a prior implementation at a synchronization burst structure.

#FIG. 2 illustrates a uniformly distributed synchronization burst structure in accordance with the present invention.

#FIG. 3 illustrates a detailed drawing of a single control burst field.

#Turning first to FIG. 2, that Figure illustrates a uniformly distributed control burst structure in accordance with the present invention. As shown in the embodiment of FIG. 2, a superframe 200 may be divided, for example, into 10 traffic burst fields (202, 204, 206, 208, 210, 212, 214, 216, 218, 220) and 10 control burst fields (221, 223, 225, 227, 229, 231, 233, 235, 237, 239). As explained above, each control burst field may contain control information from several different user terminals. It is noted that, although the following detailed description proceeds primarily with reference to sync bursts, the invention applies to other synchronization and control information as well, including, for example, orderwire information.

#As explained above with respect to FIG. 1, past synchronization methods dedicated a single segment 111 of the superframe 100 to control burst access, and all terminals launched their control bursts during this dedicated period 111. Thus, in accordance with past synchronization methods, several traffic burst fields 101-110 elapsed between control burst fields 111 and 112, creating irregular cadence and cell delay variation.

#FIG. 3 shows a control burst field 300 (e.g., a single one of the control burst fields (221, 223, 225, 227, 229, 231, 233, 235, 237, 239) shown in FIG. 2) with 25 control time slots 302 (labeled S1-S25 in FIG. 3). Each control time slot 302 represents a period of time during which a user terminal may transmit, for example, a sync burst. As explained above, in a satellite communications system, each terminal in either a standby state or a state of active transmission is allocated at least one dedicated control time slot during which the terminal launches a control burst periodically on an uplink.