Method and apparatus for selecting a communication channel in a communication network

• US 6,185,423 B1
• Filed: 05/28/1999
• Issued: 02/06/2001
• Est. Priority Date: 05/28/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Brown, John Richard, Elliott, Steve Oliver
• Primary Examiner(s): Tsang, Fan
• Assistant Examiner(s): Nguyen, Simon
• Application Number:
  US09/321,647
• Time in Patent Office: 620 Days
• Field of Search: 455/450, 455/451, 455/452, 455/455, 455/464, 455/434, 455/509, 455/507, 455/513, 455/515, 455/516, 455/4.1, 455/574, 455/561, 455/62
• US Class Current: 455/434
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 52/0245 according to signal strength
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method and apparatus for reducing power consumption in a roaming portable communication device is described. Various embodiments include optimizing a channel acquisition scan, or pre-scan, and a background scan in order to delay the reaction to a suspected loss of coverage to prevent unnecessary roaming and the associated power consumption. A list of received signal strengths is generated for a number of possible channels. Only those channels with a received signal strength above a threshold level are retained. The received signal strength of the remaining possible channels is retested. The selected channel is determined from the remaining possible channels by comparing the received signal strength of the last channel used, the last channel attempted (if available), and a best channel having the highest received signal strength. In this manner, a method and apparatus of analyzing and organizing base station channel strengths for subsequent channel acquisitions based on the power consumption costs for acquisition of a new channel is provided.

Claims

1. A method of selecting a communication channel from a group of communication channels using a communication device, comprising:

accessing a first list comprising a plurality of communication channels;

scanning and measuring a first received signal strength of each channel in the first list;

forming a second list comprising the channels of the first list having the first received signal strength equal to or greater than a first threshold signal strength;

scanning and measuring a second received signal strength of each channel in the second list;

ordering the second list in response to the second received signal strength;

selecting a communication channel by comparatively evaluating a last used channel, a last attempted channel and a best channel according to the corresponding second received signal strength, wherein the last attempted channel is a previously selected channel selected for communication but for which communication is not established, wherein the best channel has the highest received signal strength in the second list; and

performing a background scan during at least one evaluation period, the background scan comprising scanning and measuring the channels of a currently used channel list, monitoring for one sweep cycle communication channels of the currently used channel list having a received signal strength equal to or greater than a received signal strength of the selected channel plus a fourth threshold signal strength, and monitoring for two sweep cycles communication channels of the currently used channel list having a received signal strength equal to or greater than the received signal strength of the selected channel plus a better base threshold signal strength.

2. The method of claim 1, wherein the selecting comprises:

determining that the last used channel is in the second list;

selecting the last used channel as the channel for communication when the last used channel is determined to be the best channel; and

selecting a first new channel for communication when the first new channel has a received signal strength that exceeds the received signal strength of the last used channel by a second threshold signal strength.

3. The method of claim 1, wherein the selecting comprises:

determining that the last used channel is absent from the second list;

selecting the last attempted channel for communication when it is determined that the last attempted channel is in a first position of the second list;

moving a second new channel into the first position of the second list when the second new channel has a received signal strength that exceeds the received signal strength of the last attempted channel by a third threshold signal strength; and

selecting the channel in the first position in the second list.

4. A method of prolonging battery life in a mobile communication device, comprising:

acquiring at least one signal comprising at least one list of communication channels;

selecting a communication channel for use from the at least one list, wherein selecting comprises optimizing the at least one list by eliminating channels having a received signal strength less than a first threshold and organizing the remaining channels according to the received signal strength and comparatively evaluating a last used channel and a last attempted channel and a best channel;

background scanning channels, wherein channels having a received signal strength equal to or greater than a received signal strength of the selected channel plus at least one threshold signal strength are background scanned for a number of cycles, the number of cycles determined by a magnitude of the at least one threshold; and

selectively controlling changes by the mobile communication terminal among the communication channels using the optimized list.

5. The method of claim 4, wherein selecting a communication channel comprises:

accessing a first list comprising a plurality of communication channels;

scanning and measuring a first received signal strength of each channel in the first list;

forming a second list comprising the channels of the first list having the first received signal strength equal to or greater than a first threshold signal strength;

scanning and measuring a second received signal strength of each channel in the second list;

ordering the second list in response to the second received signal strength; and

selecting a channel for communication by comparatively evaluating a last used channel and a last attempted channel and a best channel according to the second received signal strength, wherein the last attempted channel is a channel selected for communication over which communication is not established, wherein the best channel has the highest received signal strength in the second list.

6. The method of claim 5, wherein selecting a communication channel comprises:

determining that the last used channel is in the second list;

selecting the last used channel as the channel for communication when the last used channel is determined to be the best channel; and

selecting a first new channel for communication when the first new channel has a received signal strength that exceeds the received signal strength of the last used channel by a second threshold signal strength.

7. The method of claim 5, wherein selecting a communication channel comprises:

determining that the last used channel is absent from the second list;

selecting the last attempted channel for communication when it is determined that the last attempted channel is in a first position of the second list;

moving a second new channel into the first position of the second list when the second new channel has a received signal strength that exceeds the received signal strength of the last attempted channel by a third threshold signal strength; and

selecting the second new channel for communication.

8. The method of claim 5, wherein background scanning channels comprises:

scanning and measuring the channels of a currently used channel list;

monitoring for one sweep cycle communication channels of the currently used channel list having a received signal strength equal to or greater than a received signal strength of the selected channel plus a fourth threshold signal strength; and

monitoring for two sweep cycles communication channels of the currently used channel list having a received signal strength equal to or greater than the received signal strength of the selected channel plus a better base threshold signal strength.

9. A computer readable medium containing executable instructions which, when executed in a processing system, causes the system to select a communication channel from a group of channels, the selection comprising:

accessing a first list comprising a plurality of communication channels;

scanning and measuring a first received signal strength of each channel in the first list;

forming a second list comprising the channels of the first list having the first received signal strength equal to or greater than a first threshold signal strength;

scanning and measuring a second received signal strength of each channel in the second list;

ordering the second list in response to the second received signal strength;

selecting a channel for communication by comparatively evaluating a last used channel and a last attempted channel and a best channel according to the second received signal strength, wherein the last attempted channel is a channel selected for communication over which communication is not established, wherein the best channel has the highest received signal strength in the second list; and

performing a background scan during at least one evaluation period, the background scan comprising scanning and measuring the channels of a currently used channel list, monitoring for one sweep cycle communication channels of the currently used channel list having a received signal strength equal to or greater than a received signal strength of the selected channel plus a fourth threshold signal strength, and monitoring for two sweep cycles communication channels of the currently used channel list having a received signal strength equal to or greater than the received signal strength of the selected channel plus a better base threshold signal strength.

10. The computer readable medium of claim 9, wherein selecting further comprises:

determining that the last used channel is in the second list;

selecting the last used channel as the channel for communication when the last used channel is determined to be the best channel; and

selecting a first new channel for communication when the first new channel has a received signal strength that exceeds the received signal strength of the last used channel by a second threshold signal strength.

11. The computer readable medium of claim 9, wherein selecting further comprises:

determining that the last used channel is absent from the second list;

selecting the last attempted channel for communication when it is determined that the last attempted channel is in a first position of the second list;

moving a second new channel into the first position of the second list when the second new channel has a received signal strength that exceeds the received signal strength of the last attempted channel by a third threshold signal strength; and

selecting the second new channel for communication.

12. A portable device that selects a communication channel from a group of channels, the device comprising at least one processor coupled to a memory, a display, and at least one radio modem, the at least one processor capable of selecting a communication channel from a group of channels by:

receiving a first list comprising a plurality of communication channels;

scanning and measuring a first received signal strength of each channel in the first list;

forming a second list comprising the channels of the first list having the first received signal strength equal to or greater than a first threshold signal strength;

scanning and measuring a second received signal strength of each channel in the second list;

ordering the second list in response to the second received signal strength;

selecting a channel for communication by comparatively evaluating a last used channel and a last attempted channel and a best channel according to the second received signal strength, wherein the last attempted channel is a channel selected for communication over which communication is not established, wherein the best channel has the highest received signal strength in the second list; and

performing a background scan during at least one evaluation period by scanning and measuring the channels of a currently used channel list, monitoring for one sweep cycle communication channels of the currently used channel list having a received signal strength equal to or greater than a received signal strength of the selected channel plus a fourth threshold signal strength, and monitoring for two sweep cycles communication channels of the currently used channel list having a received signal strength equal to or greater than the received signal strength of the selected channel plus a better base threshold signal strength.

13. The portable device of claim 12, wherein the at least one processor is capable of selecting by:

determining that the last used channel is in the second list;

selecting the last used channel as the channel for communication when the last used channel is determined to be the best channel; and

selecting a first new channel for communication when the first new channel has a received signal strength that exceeds the received signal strength of the last used channel by a second threshold signal strength.

15. The portable device of claim 12, wherein the portable device is selected from a group comprising hand-held computers, portable electronic assistants, and cellular telephones.

14. The portable device of claimed, wherein the at least one processor is capable of selecting by:

determining that the last used channel is absent from the second list;

selecting the last attempted channel for communication when it is determined that the last attempted channel is in a first position of the second list;

moving a second new channel into the first position of the second list when the second new channel has a received signal strength that exceeds the received signal strength of the last attempted channel by a third threshold signal strength; and

selecting the second new channel for communication.

16. An apparatus for communicating among a network of base stations, the apparatus comprising at least one processor coupled to a memory, a display, and at least one radio modem, the apparatus further comprising:

means for receiving a first list comprising a plurality of communication channels;

means for scanning and measuring a first received signal strength of each channel in the first list;

means for forming a second list comprising the channels of the first list having the first received signal strength equal to or greater than a first threshold signal strength;

means for scanning and measuring a second received signal strength of each channel in the second list;

means for ordering the second list in response to the second received signal strength;

means for selecting a channel for communication by comparatively evaluating a last used channel and a last attempted channel and a best channel according to the second received signal strength, wherein the last attempted channel is a channel selected for communication over which communication is not established, wherein the best channel has the highest received signal strength in the second list; and

means for performing a background scan during at least one evaluation period by scanning and measuring the channels of a currently used channel list, monitoring for one sweep cycle communication channels of the currently used channel list having a received signal strength equal to or greater than a received signal strength of the selected channel plus a third threshold signal strength, and monitoring for two sweep cycles communication channels of the currently used channel list having a received signal strength equal to or greater than the received signal strength of the selected channel plus a better base threshold signal strength.

17. The apparatus of claim 16, further comprising:

means for determining whether the last used channel is in the second list;

means for selecting the last used channel as the channel for communication when the last used channel is determined to be the best channel;

means for selecting a first new channel for communication when the first new channel has a received signal strength that exceeds the received signal strength of the last used channel by a second threshold signal strength;

means for selecting the last attempted channel for communication when it is determined that the last attempted channel is in a first position of the second list;

means for moving a second new channel into the first position of the second list when the second new channel has a received signal strength that exceeds the received signal strength of the last attempted channel by a third threshold signal strength; and

means for selecting the second new channel for communication.

18. The apparatus of claim 16, wherein the apparatus communicates using frequency modulated signals along with Gaussian minimum shift keying modulation.

19. The apparatus of claim 16, wherein the apparatus is selected from a group comprising hand-held computers, portable electronic assistants, and cellular telephones.

20. An electromagnetic medium containing executable instructions which, when executed in a processing system, causes the system to select a communication channel from a group of channels, the selection comprising:

accessing a first list comprising a plurality of communication channels;

scanning and measuring a first received signal strength of each channel in the first list;

forming a second list comprising the channels of the first list having the first received signal strength equal to or greater than a first threshold signal strength;

scanning and measuring a second received signal strength of each channel in the second list;

ordering the second list in response to the second received signal strength;

selecting a channel for communication by comparatively evaluating a last used channel and a last attempted channel and a best channel according to the second received signal strength, wherein the last attempted channel is a channel selected for communication over which communication is not established, wherein the best channel has the highest received signal strength in the second list; and

performing a background scan during at least one evaluation period, the background scan comprising scanning and measuring the channels of a currently used channel list, monitoring for one sweep cycle communication channels of the currently used channel list having a received signal strength equal to or greater than a received signal strength of the selected channel plus a second threshold signal strength, and monitoring for two sweep cycles communication channels of the currently used channel list having a received signal strength equal to or greater than the received signal strength of the selected channel plus a better base threshold signal strength.

21. A system comprising a plurality of base stations using a group of channels, the base stations communicating with at least one portable device that selects a communication channel from the group of channels, the portable device comprising at least one processor coupled to a memory, a display, and at least one radio modem, the at least one processor capable of selecting a communication channel from the group of channels by:

receiving a first list comprising a plurality of communication channels;

scanning and measuring a first received signal strength of each channel in the first list;

forming a second list comprising the channels of the first list having the first received signal strength equal to or greater than a first threshold signal strength;

scanning and measuring a second received signal strength of each channel in the second list;

ordering the second list in response to the second received signal strength;

selecting a channel for communication by comparatively evaluating a last used channel and a last attempted channel and a best channel according to the second received signal strength, wherein the last attempted channel is a channel selected for communication over which communication is not established, wherein the best channel has the highest received signal strength in the second list; and

performing a background scan during at least one evaluation period by scanning and measuring the channels of a currently used channel list, monitoring for one sweep cycle communication channels of the currently used channel list having a received signal strength equal to or greater than a received signal strength of the selected channel plus a fourth threshold signal strength, and monitoring for two sweep cycles communication channels of the currently used channel list having a received signal strength equal to or greater than the received signal strength of the selected channel plus a better base threshold signal strength.

22. The system of claim 21, wherein the at least one processor is further capable of selecting by:

determining that the last used channel is in the second list;

selecting the last used channel as the channel for communication when the last used channel is determined to be the best channel; and

selecting a first new channel for communication when the first new channel has a received signal strength that exceeds the received signal strength of the last used channel by a second threshold signal strength.

23. The system of claim 21, wherein the at least one processor is further capable of selecting by:

determining that the last used channel is absent from the second list;

selecting the last attempted channel for communication when it is determined that the last attempted channel is in a first position of the second list;

moving a second new channel into the first position of the second list when the second new channel has a received signal strength that exceeds the received signal strength of the last attempted channel by a third threshold signal strength; and

selecting the second new channel for communication.

24. A method for reducing power consumption in a roaming portable communication device, comprising:

generating a list of received signal strengths for at least one possible channel;

identifying channels with a received signal strength above a threshold level;

resampling received signal strengths of the identified channels;

selecting a communication channel from the identified channels by comparing the received signal strength of a last used channel, an available last attempted channel, and a best channel having the highest resampled received signal strength of the identified channels; and

performing a background scan during at least one evaluation period, the background scan comprising scanning and measuring channels of a currently used channel list, monitoring for one sweep cycle communication channels of the currently used channel list having a received signal strength equal to or greater than a received signal strength of the selected channel plus a first threshold signal strength, and monitoring for two sweep cycles communication channels of the currently used channel list having a received signal strength equal to or greater than the received signal strength of the selected channel plus a better base threshold signal strength.