Multipoint communication system having polling and reservation schemes

A communication system for a central station and a plurality of groups of terminal stations, comprising:

• first means for estabalishing a multiple access channel from each of said terminal stations to said central station and a time-division multiplexed broadcast channel from said central station to said terminal stations;
• second means for transmitting first polling signals in succession on said broadcast channel to said terminal stations without waiting for a reply therefrom, said first polling signals being addressed respectively to said groups asking a request for reservation from the terminal stations of each of the addressed groups;
• third means for transmitting a reservation signal on said multiple access channel from one or more of the terminal stations of said addressed groups which wish to send a data signal;
• fourth means for transmitting a second polling signal in response to said reservation signal and reserving said multiple access channel for a period of time variable in accordance with said reservation signal;
• and
• fifth means for transmitting said data signal on said reserved multiple access channel during said time period in response to said second polling signal.

A data communication method for a network having a multiple access channel established from each of a plurality of terminal stations to a central station and a time-division multiplexed broadcast channel established from said central station to said terminal stations, comprising the steps of:

• (a) sequentially transmitting on said broadcast channel first polling signals from said central station for respectively addressing said terminal stations;
• (b) respectively receiving said first polling signals at said terminal stations and transmitting on said multiple access channel a reservation signal if a data signal is present in one of said terminal stations;
• (c) receiving said reservation signals at said central station and reserving a time slot in said multiple access channel in accordance with the received reservation signal and transmitting on said broadcast channel a second polling signal addressing the terminal station from which said reservation signal is received, said second polling signal indicating the length of said reserved time slot;
• (d) receiving said second polling signal at said addressed terminal station and transmitting said data signal in said reserved time slot if no more data signal is present or transmitting said data signal along with a second reservation signal in said reservation time slot if a further data signal is present;
• and
• (e) receiving said second reservation signal at said central station and reserving a second time slot in said multiple access channel in accordance with the received second reservation signal and transmitting on said broadcast channel a third polling signal addressing the terminal station from which said second reservation signal is received, said third polling signal indicating the length of said reserved second time slot.