Method and apparatus for low power mobile unit for cellular communications system

• US 6,058,289 A
• Filed: 09/26/1995
• Issued: 05/02/2000
• Est. Priority Date: 09/26/1995
• Status: Expired due to Term

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Pacific Communication Sciences , Inc. (Cirrus Logic Incorporated)
• Inventors: Petranovich, James E., Hardin, Carl Thomas, Gardner, Steven Holmsen
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Ferguson, Keith
• Application Number:
  US08/533,682
• Time in Patent Office: 1,680 Days
• Field of Search: 379/59, 379/60, 379/58, 370/95.3, 370/95.1, 370/311, 370/459, 455/33.1, 455/54.1, 455/33.2, 455/432, 455/434, 455/436, 455/437, 455/438, 455/439, 455/574, 455/572, 455/31.2, 455/31.3, 455/38.3, 455/515, 455/550, 455/426, 340/825.44, 340/825.47
• US Class Current: 340/7.32
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/0245 according to signal strength
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method and apparatus for efficient use of both power and bandwidth in a cellular communications system in which a Mobile Unit preferably enters Sleep-Mode when no communications have occurred between the Mobile Unit and the Base Station over a predetermined amount of time measured by an "Idle Timer". Upon expiry of a Wake Timer, the Mobile Unit awakes from Sleep-Mode to determine whether a message is pending. Concurrently, the Base Station transmits a "TEI-Notification" message directed to all Mobile Units to notify each Mobile Unit that has data pending. A system parameter determines the intervals at which the Base Station will transmit these notifications. Upon waking to receive a TEI-Notification message, the Mobile Unit determines whether the quality of the transmission is at least sufficient to allow the Mobile Unit to decipher the TEI-Notification message. If this minimal requirement is met, and the TEI-Notification message does not indicate that data is pending for the Mobile Unit, the Mobile Unit returns to sleep, even though the Mobile Unit may reside in a cell other than the cell associated with the Base Station currently assigned by the IS to communicate with the Mobile Unit. The Mobile Unit of the present invention does not monitor the forward channels on a regular basis, but rather waits until either the signal quality of the forward channel over which the Mobile Unit is receiving has degraded such that the TEI-Notification message can no longer be deciphered, or the TEI-Notification message indicates that a message is pending.

Claims

1. A low power mobile unit for receiving on a forward channel and transmitting on a reverse channel over a wireless cellular communication network, the low power mobile unit comprising;

(a) a receiver for receiving over forward channels, the receiver for periodically receiving notification messages from a current forward channel and for periodically measuring signal quality of at least the current forward channel of the forward channels;

(b) a transmitter for transmitting over reverse channels; and

(c) a management entity coupled to the receiver and the transmitter, the management entity of the low sower mobile unit for;

(1) periodically receiving notification messages from the receiver, the notification messages including client numbers client numbers having been received from a current, each such client number in the notification messages being associated with a mobile unit for which data is pending, the low power mobile unit determining if its client number is within the notification message;

(2) periodically receiving from the receiver an indication of the signal quality of the current forward channel;

(3) (i) periodically comparing the signal quality of the current forward channel with the signal quality of at least one other forward channel, (ii) periodically identifying a new forward channel having the highest signal quality, and (iii) if the receiver receives a notification message with the client number associated with the low power mobile unit or if the management entity determines that the signal quality of the current forward channel is below a minimum quality level, then providing the transmitter with a cell transfer message to be transmitted over a reverse channel associated with the new forward channel to change communication channels, otherwise, the management entity continuing to have the low power mobile unit communicate with the cellular network over the current forward channel.

2. A mobile unit, for use in a cellular communications network having a plurality of base stations, each base station being associated with a cell, the mobile unit comprising:

a. a receiver for receiving over forward channels from a plurality of base stations and for periodically receiving notification messages over a forward channel;

b. a management entity, coupled to the receiver, for;

i. requesting that the receiver attempt to receive notification messages periodically at predetermined intervals from a particular base station, regardless of whether the mobile unit remains within the cell associated with that base station;

ii. upon failing to successfully receive a notification message at a predetermined interval over the first selected forward channel, scanning for a forward channel being transmitted from a base station associated with the cell in which the mobile unit is located and attempting to receive the notification messages over a forward channel being transmitted from the base station;

iii. upon successfully receiving a notification message, determining whether a code associated with the mobile unit is encoded within the notification message and if so, acknowledging receipt of the code through the base station associated with the cell in which the mobile unit is currently located; and

,

wherein the mobile unit continues to receive notification messages from a particular base station after leaving the cell associated with that particular base station until the mobile unit is incapable of successfully receiving a notification message from that base station or until one of the notification messages includes the code associated with the mobile unit.

3. The mobile unit of claim 2, further including:

a. an idle timer; and

b. a wake timer;

wherein the management entity and the receiver enter sleep mode upon expiry of the idle timer and awake to receive and process a notification message upon expiry of the wake timer, whereafter the management entity and receiver enter sleep mode once again if the notification message has been successfully received and does not include a code associated with the mobile unit.

4. The mobile unit of claim 2, wherein the management entity causes the mobile unit to scan for the best available forward channel upon initial application of power to the mobile unit.

5. The mobile unit of claim 2, wherein the mobile unit is assigned a unique code upon initial application of power to the mobile unit.

6. The mobile unit of claim 2, wherein the management entity requests the receiver to scan for a better forward channel in response to the quality of the channel dropping below a predetermined threshold.

7. The mobile unit of claim 2, wherein the management entity requests the receiver to scan for a better forward channel a predetermined amount of time after the last attempt to find a better forward channel.

8. The mobile unit of claim 2, wherein the management entity causes the mobile unit to enter a power conservation mode after each successful attempt to receive a notification message in which no code associated with the mobile unit was encoded.

9. The mobile unit of claim 8, further including a timer for indicating when the next notification message is to be received.

10. A method for communicating between a base station within a cellular communications system and a mobile unit, the method comprising:

scanning the available forward channels to determine in which cell a mobile unit initially is located;

establishing an airlink between the mobile unit and an initial base station associated with the cell in which the mobile unit is initially located; and

attempting to receive messages from the initial base station after the mobile unit leaves the cell associated with the initial base station, unless;

i. the mobile unit is to respond to a received message;

or

ii. messages sent by the initial base station are no longer being successfully received within the mobile unit; and

establishing an airlink between the mobile unit and the base station associated with the cell in which the mobile unit is currently located if;

i. the mobile unit is to respond to a received message from the initial base station;

or

ii. messages sent by the initial base station are no longer being successfully received within the mobile unit.

11. The method of claim 10, wherein if the mobile unit is to respond to the received message, then the step of establishing an airlink comprises:

scanning the available forward channels prior to responding to determine in which cell the mobile unit currently is located.

12. The method of claim 10, wherein if the messages being sent by the base station associated with the cell in which the mobile unit was initially located are no longer being successfully received, then the method further comprises:

scanning the available forward channels to determine in which cell the mobile unit currently is located; and

transmitting the response to the base station associated with the cell in which the mobile unit is located.

13. The method of claim 10, further comprising the mobile unit scanning to establish an air link with the cell in which the mobile unit is currently located at predetermined intervals.

14. The method of claim 10, further comprising:

scanning for a forward channel which is being transmitted by a base station associated with the cell in which the mobile unit is currently located if the signal quality of the message signals falls below a predetermined threshold;

establishing an airlink to the base station which is associated with the cell in which the mobile unit is currently located over a current forward channel; and

receiving notification messages over the current forward channel until;

i. the current forward channel signal quality falls below the predetermined threshold;

ii. the mobile unit leaves the cell associated with the base station which is transmitting the current forward channel and the notification messages can no longer be successfully received;

or

iii. the mobile unit leaves the cell associated with the base station which is transmitting the current forward channel and the notification message received requires a response.

15. A method of conserving power in a mobile paging unit operating in a cellular communication system, the method comprising:

a. providing the mobile paging unit, the mobile paging unit including a receiver, a transmitter, and a processor for controlling the receiver and the transmitter,

b. resisting changing channels in the mobile unit from a current channel to another channel when moving from a first cell associated with the current channel to another cell associated with the another channel, resisting changing channels in the mobile unit in order to conserve power;

c. periodically deactivating the receiver and the transmitter of the mobile paging unit after a first predetermined period of time elapses with no communication by the mobile paging unit in a cell, periodically deactivating the receiver and the transmitter of the mobile pading unit in order to conserve power; and

,

d. periodically activating the receiver to receive a notification message after a second predetermined period of time elapses with the receiver and the transmitter being deactivated.

16. The method of claim 15 for conserving power in a mobile paging unit operating in a cellular communication system, the method further comprising:

if the notification message is not received after periodically activating the receiver to receive a notification message, scanning for the best forward channel of the current cell over which to receive the notification message; and

selecting the best forward channel of the forward channels of the current cell and executing a cell transfer command to communicate within the cell using the best forward channel.

17. The method of claim 15 for conserving power in a mobile paging unit operating in a cellular communication system, the method further comprising:

if the notification message is received after periodically activating the receiver to receive a notification message and if the notification message has no code associated with the mobile paging unit therefore indicating that no messages are pending for the mobile paging unit, deactivating the receiver to conserve power.

18. The method of claim 15 for conserving power in a mobile paging unit operating in a cellular communication system, the method further comprising:

if the notification message is received after periodically activating the receiver to receive a notification message and if the notification message has a code associated with the mobile paging unit therefore indicating that messages are pending for the mobile paging unit, keeping the receiver activated to receive a message for the mobile paging unit and briefly activating the transmitter to transmit an acknowledgment signal indicating the message for the mobile paging unit was received.