Maintenance link using active/standby request channels
View Patent ↗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 for supporting wireless communications between a transmitter and a receiver, the method comprising the steps of:
allocating both a first coded channel and a second coded channel in a common direction to support synchronized communications from the transmitter to the receiver;
assigning a time segment in which the transmitter communicates an indication to the receiver by generating a reference signal over a selected one of the first coded channel or the second coded channel;
maintaining transmissions on the first coded channel and the second coded channel in a time segment by analyzing the reference signal on the first coded channel or the second coded channel at the receiver; and
adjusting timing of the transmitter by sending a message from the receiver to the transmitter indicating whether to advance or retard timing so that subsequently generated reference signals on the first coded channel or the second coded channel fall within a corresponding time segment,
wherein the message indicating whether to advance or retard timing at the transmitter includes a single bit indicating whether to advance or retard timing, the timing is advanced or retarded a predefined time depending on a logic level of the single bit and
the timing is advanced or retarded based on a second predefined time if the single bit is in a same state for a predetermined number of periods in a row, the second predefined time being greater than the first predefined time.
2. A method for supporting wireless communications, the method comprising the steps of:
allocating a coded channel to support synchronized communications from each of multiple transmitters to a receiver;
assigning a first portion of the coded channel for use by a first transmitter to transmit a reference signal to the receiver; and
assigning a second portion of the channel for use by a second transmitter to transmit a message to the receiver, the first portion and the second portion of the coded channel transmitting different types of information between the multiple transmitters and the receiver.
3. A method as in claim 2 , wherein the reference signal transmitted over the coded channel is a timing signal used to synchronize the first transmitter with the receiver.
4. A method as in claim 2 , wherein the signal transmitted by the first transmitter does not include forward error correction information.
5. A method as in claim 2 , wherein the reference signal transmitted over the first portion of the coded channel does not include a data payload.
6. A method as in claim 2 , wherein the reference signal is analyzed at the receiver and a feedback message is sent to the transmitter for adjusting its timing.
7. A method as in claim 2 , wherein the feedback message indicates to the first transmitter whether to advance or retard its timing.
8. A method as in claim 2 , wherein the coded channel is divided into time slots.
9. A method as in claim 2 , wherein the second transmitter generates a message including forward error correction information.
10. A method for supporting wireless communications between a transmitter and a receiver, the method comprising the steps of:
allocating both a first coded channel and a second coded channel in a common direction to support synchronized communications from the transmitter to the receiver;
assigning a time segment in which the transmitter communicates an indication to the receiver by generating a signal at an adjusted power level over a selected one of the first coded channel or the second coded channel;
maintaining transmissions on the first coded channel and the second coded channel in a time segment by analyzing a power level of a transmission on the first coded channel or the second coded channel; and
adjusting a power transmission level of the transmitter by sending a message from the receiver to the transmitter indicating whether to increase or decrease its power level so that subsequently generated signals on the first coded channel or the second coded channel can be detected at the receiver,
wherein the message indicating whether to increase or decrease power level transmissions at the transmitter includes a single bit indicating whether to increase or decrease its power level of the signal transmitted over the first coded channel or the second coded channel, the timing is increased or decreased a predefined amount depending on a logic level of the single bit and
the power level of the signal is increased or decreased based on a second predefined amount if the single bit is in a same state for a predetermined number of periods in a row, the second predefined amount being greater than the first predefined amount.