Maintenance link using active/standby request channels

Abstract

Multiple field units in a CDMA system are synchronized for communication with a base station using shared forward and reverse link channels. In an illustrative embodiment, each field unit is assigned a time slot in a forward link channel to receive messages from the base station. Likewise, each field unit is assigned a time slot on a common reverse link channel for transmitting messages to the base station. Timing alignment and power level control among each of many field units and the base station is achieved by analyzing messages received at the base station in a corresponding time slot as transmitted by each field unit. Thereafter, a message is transmitted from the base station in a corresponding time slot to a particular field unit for adjusting its timing or power level so that future messages transmitted from the field unit are received in the appropriate time slot at the base station at a desired power level. In this way, minimal resources are deployed to maintain communication and precise synchronization between a base station and each of multiple users, minimizing collisions between field units transmitting in adjacent time slots on the reverse link. This method reduces the frequency a field unit must rely on the use of a slotted aloha random access channel according to IS-95.

1 . A method of supporting wireless communications, the method comprising: 
 assigning a first coded channel to a plurality of transmitters to support communications from the plurality of transmitters, the first coded channel having a first portion for transmitting a first type of information from the plurality of transmitters and a second portion for transmitting a second type of information from the plurality of transmitters;    receiving the first type of information from a first transmitter in the plurality of transmitters in the first portion of the first coded channel; and    receiving the second type of information from a second transmitter in the plurality of transmitters in the second portion of the first coded channel.    
   
   
       2 . A method as defined in  claim 1  wherein the first type of information is a reference signal.  
   
   
       3 . A method as defined in  claim 1  wherein the second type of information is link quality information that indicates a quality of a wireless link to the first transmitter.  
   
   
       4 . A method as defined in  claim 1  wherein the first coded channel contains a plurality of time slots wherein each time slot is assigned to a particular transmitter in the plurality of transmitters.  
   
   
       5 . A method as defined in  claim 4  further comprising: 
 receiving a message from a transmitter in the plurality of transmitters; and    analyzing the message to determine a timing adjustment that needs to be made by the transmitter to synchronize the transmitter to transmit a successive message in the transmitter's assigned time slot.    
   
   
       6 . A method as defined in  claim 5  further comprising: 
 generating a feedback message containing the timing adjustment; and transmitting to the transmitter.    
   
   
       7 . A method as defined in  claim 5  wherein the timing adjustment indicates whether the transmitter should advance or retard timing of message transmissions.  
   
   
       8 . A method as defined in  claim 1  further comprising: 
 assigning a second coded channel to the plurality of transmitters to support indications from the transmitters to allocate one or more traffic channels for the transmission of data from the transmitters.    
   
   
       9 . A method as defined in  claim 8  wherein the second coded channel contains a plurality of time slots wherein each time slot is assigned to a particular transmitter in the plurality of transmitters.  
   
   
       10 . A method as defined in  claim 9  wherein an indication from a transmitter in the plurality of transmitters is a transmission by the transmitter in a time slot assigned to the transmitter that is contained in the second coded channel.  
   
   
       11 . A method as defined in  claim 8  wherein an indication from a transmitter is a pseudo random noise (PN) code.  
   
   
       12 . A method as defined in  claim 8  further comprising: 
 receiving an indication in the second coded channel from a transmitter that indicates the transmitter is to be set into an active mode; and    allocating a traffic channel for use by the transmitter to transmit data.    
   
   
       13 . An apparatus comprising: 
 a processor configured to:    (a) assign a first coded channel to a plurality of transmitters to support communications from the plurality of transmitters, the first coded channel having a first portion for transmitting a first type of information from the plurality of transmitters and a second portion for transmitting a second type of information from the plurality of transmitters; and    a receiver configured to:    (a) receive the first type of information from a first transmitter in the plurality of transmitters in the first portion of the first coded channel, and    (b) receive the second type of information from a second transmitter in the plurality of transmitters in the second portion of the first coded channel.    
   
   
       14 . An apparatus as defined in  claim 13  wherein the first coded channel contains a plurality of time slots wherein each time slot is assigned to a particular transmitter in the plurality of transmitters.  
   
   
       15 . An apparatus as defined in  claim 14  wherein the receiver is further configured to receive a message from a transmitter in the plurality of transmitters, and the processor is further configured to analyze the message to determine a timing adjustment that needs to be made by the transmitter to synchronize the transmitter to transmit a successive message in the transmitter's assigned time slot.  
   
   
       16 . An apparatus as defined in  claim 13  wherein the processor is further configured to assign a second coded channel to the plurality of transmitters to support indications from the transmitters to allocate one or more traffic channels for the transmission of data from the transmitters.  
   
   
       17 . A base station as defined in  claim 16  wherein the receiver is configured to receive an indication in the second coded channel from a transmitter that indicates the transmitter is to be set into an active mode and, the processor is further configured to allocate a traffic channel for use by the transmitter to transmit data.  
   
   
       18 . An apparatus comprising: 
 means for assigning a first coded channel to a plurality of transmitters to support communications from the plurality of transmitters, the first coded channel having a first portion for transmitting a first type of information from the plurality of transmitters and a second portion for transmitting a second type of information from the plurality of transmitters;    means for receiving the first type of information from a first transmitter in the plurality of transmitters in the first portion of the first coded channel; and    means for receiving the second type of information from a second transmitter in the plurality of transmitters in the second portion of the first coded channel.    
   
   
       19 . An apparatus as defined in  claim 18  wherein the first coded channel contains a plurality of time slots wherein each time slot is assigned to a particular transmitter in the plurality of transmitters.  
   
   
       20 . An apparatus as defined in  claim 19  further comprising: 
 means for receiving a message from a transmitter in the plurality of transmitters; and    means for analyzing the message to determine a timing adjustment that needs to be made by the transmitter to synchronize the transmitter to transmit in its assigned time slot.    
   
   
       21 . An apparatus as defined in  claim 20  further comprising: 
 mean for transmitting a feedback message containing the timing adjustment to the transmitter.    
   
   
       22 . An apparatus as defined in  claim 18  further comprising: 
 means for assigning a second coded channel to the plurality of transmitters to support indications from the transmitters to allocate one or more traffic channels for the transmission of data from the transmitters.    
   
   
       23 . An apparatus as defined in  claim 21  further comprising: 
 means for receiving an indication in the second coded channel from a transmitter that indicates the transmitter is to be set into an active mode; and    means for allocating a traffic channel for use by the transmitter to transmit data.