Communication system with fast control traffic

Abstract

A method and system for conducting rapid control traffic in a time division multiple access (TDMA) communication system comprises a base station communicating with a plurality of user stations in assigned time slots of a time frame. For bearer traffic, time slots are assigned to particular user stations for an extended duration. In unassigned time slots, the base station transmits a general polling message indicating availability of the time slot. A user station desiring to hand off communication from one base station to another uses multiple available time slots at the target base station for exchanging control traffic messages with the target base station. The next available time slot is indicated by a slot pointer in the header of each general polling message to facilitate rapid exchange of control traffic messages. During handover, the user station may establish a new link with the target base station before relinquishing the existing communication link with the old base station.

What is claimed is:  
     
         1 . In a time division multiple access communication system having a base station and a plurality of user stations, a method of communicating between the base station and a user station, comprising the steps of: 
 establishing a series of time frames, each time frame comprising a plurality of time slots; and    transmitting a plurality of messages from the base station to the user station, each of said messages comprising an information element indicating a location of a subsequent time slot available for communication.    
     
     
         2 . The method of  claim 1 , wherein said plurality of messages comprise control traffic messages, and wherein said step of transmitting a plurality of messages from the base station to the user station comprises the step of completing a control traffic transaction.  
     
     
         3 . The method of  claim 1 , further comprising the step of completing a handshake transaction between said base station and said user station so as to establish a communication channel, and thereafter exchanging bearer traffic messages between said user station and said base station over said established communication channel.  
     
     
         4 . The method of  claim 1 , wherein said step of transmitting said plurality of messages comprises the step of spread spectrum encoding said messages.  
     
     
         5 . The method of  claim 1 , further comprising the step of transmitting a plurality of messages from the user station to the base station, each of said plurality of messages transmitted in the time slot indicated by the information element of the preceding message from the base station.  
     
     
         6 . In a communication system comprising at least one base station capable of communicating with a plurality of user stations, a method of communication comprising the steps of: 
 transmitting a first message from the base station, said first message comprising an information element indicating a relative time position for a subsequent communication;    receiving said first message at a user station;    transmitting, according to said relative time position, a second message from said user station to said base station; and    receiving said second message at said base station.    
     
     
         7 . The method of  claim 6  wherein said step of transmitting said first message comprises the step of spread spectrum encoding said first message, and wherein said step of transmitting said second message comprises the step of spread spectrum encoding said second message.  
     
     
         8 . The method of  claim 6  wherein 
 said base station and said user station communicate according to a time division multiple access protocol in which a series of time frames are each divided into a plurality of time slots, and  
 wherein said information element indicates said relative time position by reference to a designated one of said time slots.  
 
     
     
         9 . A message structure for use in a time division multiple access communication system, said time division multiple access communication system operating according to a communication protocol by which a series of time frames are each divided into a plurality of time slots, said message structure comprising: 
 a data segment; and    a header segment, said header segment comprising a next slot pointer.    
     
     
         10 . The message structure of  claim 9  wherein said next slot pointer identifies a subsequent time slot available for communication.  
     
     
         11 . The message structure of  claim 10 , wherein said slot pointer comprises a numerical value indicating a relative number of time slots until said subsequent time slot available for communication.  
     
     
         12 . The message structure of  claim 10 , wherein said slot pointer comprises a numerical value indicating a position of said subsequent time slot available for communication relative to a starting point of a time frame.  
     
     
         13 . In a time division multiple access communication system wherein a base station is capable of communicating with a plurality of user stations, a method of communicating comprising the steps of: 
 transmitting a first plurality of control traffic messages from a user station to a base station in a first plurality of time slots, at least two of said first plurality of time slots within a single time frame;    receiving said first plurality of control traffic messages at said base station;    transmitting a second plurality of control traffic messages from said base station to said user station in a second plurality of time slots, at least two of said second plurality of time slots within a single time frame; and    receiving said second plurality of control traffic messages at said user station.    
     
     
         14 . The method of  claim 13  wherein said step of transmitting said first plurality of control traffic messages comprises the step of spread spectrum encoding said first plurality of control traffic messages, and wherein said step of transmitting said second plurality of control traffic messages comprises the step of spread spectrum encoding said second plurality of control traffic messages.  
     
     
         15 . The method of  claim 13  wherein at least one of the control traffic messages in said second plurality of control traffic messages comprises a next slot pointer.  
     
     
         16 . The method of  claim 15  wherein said next slot pointer indicates a relative position of a subsequent time slot for transmitting a control traffic message of said first plurality of control traffic messages.  
     
     
         17 . The method of  claim 13  wherein said first plurality of control traffic messages and said second plurality of control traffic messages are transmitted over the same frequency band.  
     
     
         18 . In a time division multiple access communication system having a series of time frames each divided into a plurality of time slots, said time slots collectively comprising a plurality of user transmission intervals and a plurality of base transmission intervals, a method of communication comprising the steps of: 
 transmitting, over a designated frequency band and in a first base transmission interval, a general poll message from a base station;    receiving said general poll message at a user station;    transmitting in response to said general poll message, over said designated frequency band and in a first user transmission interval, a general response message from said user station to said base station;    receiving said general response message at said base station;    transmitting in response to said general response message, over said designated frequency band and in a second base transmission interval, a specific poll message from said base station to said user station; and    receiving said specific poll message at said user station;    wherein said general poll message, said general response message, and said specific poll message are all transmitted within the time span of a single time frame.    
     
     
         19 . The method of  claim 18 , wherein each time slot is duplex and comprises a user transmission interval followed by a base transmission interval.  
     
     
         20 . The method of  claim 18  wherein said first user transmission interval and said second base transmission interval are located within the same time slot.  
     
     
         21 . The method of  claim 18  further comprising the steps of: 
 transmitting, over said designated frequency band and in a second user transmission interval, a user control traffic message from said user station to said base station;  
 receiving said user control traffic message at said base station;  
 transmitting, over said designated frequency band and in a third base transmission interval, a base control traffic message from said base station to said user station; and  
 receiving said base control traffic message at said user station.  
 
     
     
         22 . The method of  claim 18 , wherein: 
 said general poll message is transmitted in a first time slot;    said general response message is transmitted in a second time slot; and    said general poll message comprises a next slot pointer identifying to the user station a slot position of said second time slot.    
     
     
         23 . The method of  claim 18  wherein said specific poll message comprises a next slot pointer identifying to the user station a slot position of a subsequent time slot for communication between the base station and the user station.  
     
     
         24 . The method of  claim 18  wherein said steps of transmitting said general poll message, transmitting said general response message, and transmitting said specific poll message each comprise the step of transmitting a spread spectrum signal.  
     
     
         25 . The method of  claim 18  further comprising the steps of: 
 connecting a call from a network to said base station;  
 completing said call from said base station to said user station; and  
 thereafter exchanging bearer traffic messages between said user station and said base station during said call.  
 
     
     
         26 . A multiple-user communication system, comprising: 
 a base station, said base station generating a series of time frames, each of said time frames comprising a plurality of time slots; and    a plurality of user stations;    wherein said base station transmits control traffic messages during selected ones of said time slots, each control traffic message comprising a next slot pointer identifying a subsequent time slot available for communication; and    wherein a user station responding to one of said control traffic messages does so in the time slot identified by the next slot pointer of that control traffic message.    
     
     
         27 . The multiple-user communication system of  claim 26 , wherein each of said time slots comprises a first interval during which a user message may be transmitted by a user station to which the time slot is assigned, and a second interval during which the base station may transmit a base message.  
     
     
         28 . The multiple-user communication system of  claim 27  wherein said user message and said base message are each transmitted in a spread spectrum format.  
     
     
         29 . The multiple-user communication system of  claim 27  wherein said base message comprises a base header segment, and wherein said next slot pointer is contained within said base header segment.  
     
     
         30 . In a time division multiple access communication system in which a time frame is divided into a plurality of time slots, a method of communication comprising the steps of: 
 communicating between a mobile station and a first base station; and    handing off communication from said first base station to a second base station, said step of handing off communication comprising the step of exchanging a plurality of control traffic messages between said mobile station and said second base station during multiple time slots of a single time frame.    
     
     
         31 . The method of  claim 30 , further comprising the step of establishing a duplex communication link between said mobile station and said second base station as a result of said step of exchanging said plurality of control traffic messages.  
     
     
         32 . The method of  claim 31 , further comprising the step of assigning a time slot for bearer communication to said mobile station as a result of said step of exchanging said plurality of control traffic messages.  
     
     
         33 . The method of  claim 32 , further comprising the step of exchanging bearer traffic messages between said mobile station and said second base station during said time slot assigned for bearer communication.  
     
     
         34 . The method of  claim 30 , wherein said step of exchanging a plurality of control traffic messages between said mobile station and said second base station during multiple time slots of a single time frame comprises the step of transmitting a next slot pointer in each control traffic message transmitted from said second base station to said mobile station.