Collision free access scheduling in cellular TDMA-CDMA networks

A method for scheduling an access channel in a cellular telephony system, said system based on CDMA techniques wherein individual coding sequences are substantially orthogonal to one another and are respectively assigned to the mobile stations for spread-spectrum modulating a common carrier in uplink, and de-spreading demodulating the downlink carrier, in order to make them distinguishable at the air interface, the system adopting a two step procedure for managing the mobile stations' network access, comprising the steps of:

• selecting a signature burst from a plurality of orthogonal coding sequences;
• transmitting said signature burst from said mobile station to said network, said transmission occurring over a first configured physical channel;
• pausing for a select time interval;
• after said step of pausing, transmitting an acknowledgement message from said network to said mobile station, said message being transmitted over a second configured physical channel, said second channel being one of directly and indirectly correlated to said first channel;
• transmitting to said network from said mobile station an access request message on a third configured physical channel, said third configured channel being one of directly and indirectly correlated to at least one of said second and first channels;
• assigning a set of signatures and an acknowledgement message into a cell;
• calculating first time intervals at said mobile stations, said first time intervals indicative of when said signature bursts are transmitted;
• calculating second time intervals at said mobile stations, said second time intervals indicative of a wait for arrival of said acknowledgement message from said network;
• and
• minimizing collisions in said third configured physical channels between said access request messages sent from other mobiles stations via said first and second calculated time intervals depending on both a duration of said respective access request messages and delays in issuing said request messages.