Power-saving arrangement and method for mobile units in communications network

• US 6,002,918 A
• Filed: 11/08/1996
• Issued: 12/14/1999
• Est. Priority Date: 06/29/1989
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Werback, Andrew, Shiba, Michael, Heiman, Frederic, Pinard, Patrick
• Primary Examiner(s): WOLFE JR, WILLIS RAY
• Application Number:
  US08/747,034
• Time in Patent Office: 1,131 Days
• Field of Search: 455/412, 455/414, 455/31.2, 455/31.3, 455/38.3, 455/38.4, 455/466, 455/503, 455/507, 455/517, 455/526, 455/566, 455/434, 455/343, 455/574, 455/500
• US Class Current: 340/7.38
• CPC Class Codes: G06K 17/0022 arrangements or provisions for transferring data to distant stations, e.g. from a sensing device "transfer between computer elements G06F13/00 "; data-transmission H04L
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: H04B 1/7156 Arrangements for sequence synchronisation
• CPC Class Codes: H04B 2001/71563 Acquisition
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: H04W 88/02 Terminal devices
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A communications network comprising a cellular local area wireless network includes a plurality of access points connected to a housed computer and each other, and a plurality of mobile units each mobile unit being arranged for association with an access point. The mobile units are arranged to periodically scan for and identify the most eligible access point for association on the basis of the criteria of best quality signal strength and loading factor. In order to identify when mobile units are being removed from a predetermined area, access points having directional antennae are situated adjacent exit points to detect when mobile units are in a vicinity. Each mobile unit may include paging facilities, including the capability of transmitting information in a coded form known both to the unit and to a host, and power-saving facilities.

Claims

1. An arrangement for maximizing battery life in each of a plurality of portable, battery-powered, mobile units, each of the mobile units being in wireless communication with a plurality of spaced-apart, stationary access points of a communications network, the arrangement comprising:

a) a radio in each of the mobile units, the radio having a transceiver for transmitting data to and from the access points within a predetermined working range in a powered mode of network operation;

b) a processor in each of the mobile units, the processor having a controller operatively connected to the transceiver; and

c) a timer in each of the mobile units, for powering the radio only during the powered mode of network operation, and for reducing power to the radio to prevent data transmission by the transceiver during a power-saving mode of operation.

2. In a communications network including a plurality of spaced-apart stationary access points each of the access points being capable of wireless communication with portable, battery-powered, mobile units when within a working range from the access points, an arrangement for maximizing battery life in each of the mobile units, the arrangement comprising:

a) a radio section in each of the mobile units, the radio section having a transceiver for transmitting data to and from the access points in a powered mode of network operation;

b) a processor section in each of the mobile units, the processor section having electronic components including a control processor operatively connected to the transceiver; and

c) a timer in each of the mobile units, for powering the radio section only during the powered mode of network operation.

3. The arrangement according to claim 2, wherein the control processor reduces battery power to the processor section in a suspended mode, and wherein the control processor controls the timer to reduce battery power to the transceiver when the processor section is in the suspended mode.

4. The arrangement according to claim 2, wherein the timer is operative for reducing power to the transceiver to prevent the transceiver from transmitting data in a power-saving mode of operation.

5. The arrangement according to claim 4;

and further comprising an interface between the radio and processor sections of each of the mobile units, the transceiver of a respective radio section being operation for transmitting control data to and from the control processor via the interface.

6. The arrangement according to claim 5, wherein the network includes a host computer, each of the mobile units desiring access to the host computer being operative for selecting a most eligible access point from among the access points based on the control data received by the transceiver of the respective radio section.

7. The arrangement according to claim 6, wherein the mobile unit desiring access to the host computer transmits a probe message to the access points, receives response messages from the access points, and selects the most eligible access point based on the received response messages;

and wherein the timer powers the radio section to the power-saving mode for each mobile unit not associated with an access point.

8. The arrangement according to claim 4, wherein one of the electronic components is a clock for timing the control processor, and wherein the timer is operative for halting the clock in the power-saving mode.

9. The arrangement according to claim 4, wherein each access point repeatedly transmits a broadcast beacon at predetermined intervals, and wherein the control processor controls the timer to power the radio section back to the powered mode upon receipt of the beacon.

10. The arrangement according to claim 9, wherein the radio section is powered to the powered mode upon receipt of every beacon.

11. The arrangement according to claim 9, wherein the radio section is powered to the powered mode upon receipt of every other beacon.

12. The arrangement according to claim 9, wherein the radio section is powered to the powered mode upon receipt of a predetermined number of beacons.

13. The arrangement according to claim 9, wherein the radio section is powered to the powered mode based on the number of transmissions of the data in a given time period.

14. The arrangement according to claim 9, wherein the radio section is powered to the powered mode upon elapse of a fixed time interval after receipt of the beacon.

15. The arrangement according to claim 9, wherein the radio section is powered to the powered mode upon elapse of a variable time interval after receipt of the beacon.

16. In a communications network including a plurality of spaced-apart stationary access points each of the access points being capable of wireless communication with portable, battery-powered, mobile units when within a working range from the access points, a method maximizing battery life in each of the mobile units, the method comprising the steps of:

a) transmitting data to and from the access points in a powered mode of network operation by providing a transceiver in each of the mobile units;

b) providing a processor section in each of the mobile units, the processor section having electronic components including a control processor, and operatively connecting the control processor to the transceiver; and

c) powering the radio section with a timer only during the powered mode of network operation.

17. The method according to claim 16, wherein the control processor reduces battery power to the processor section in a suspended mode, and further comprising the step of controlling the timer to reduce battery power to the transceiver when the processor section is in the suspended mode.

18. The method according to claim 16, wherein the powering step is performed by reducing power to the transceiver to prevent the transceiver from transmitting data in a power-saving mode of operation.

19. The method according to claim 18, and further comprising the step of transmitting control data to and from the control processor via an interface provided between the radio and processor sections of each of the mobile units.

20. The method according to claim 19, wherein the network includes a host computer, each of the mobile units desiring access to the host computer being operative for selecting a most eligible access point from among the access points.

21. The method according to claim 20, wherein the mobile unit desiring access to the host computer transmits a probe message to the access points, and receives response messages from the access points, and selects the most eligible access point based on the received response messages, and further comprising the step of powering the radio section to the power-saving mode for each mobile unit not associated with an access point.

22. The method according to claim 18, wherein one of the electronic components is a clock for timing the control processor, and further comprising the step of halting the clock in the power-saving mode.

23. The method according to claim 18, wherein each access point repeatedly transmits a broadcast beacon at predetermined intervals, and further comprising the step of controlling the timer to power the radio section back to the powered mode upon receipt of the beacon.

24. The method according to claim 23, and further comprising the step of powering the radio section to the powered mode upon receipt of each beacon.

25. The method according to claim 23, and further comprising the step of powering the radio section to the powered mode upon receipt of every other beacon.

26. The method according to claim 23, and further comprising the step of powering the radio section to the powered mode upon receipt of a predetermined number of beacons.

27. The method according to claim 23, and further comprising the step of powering the radio section to the powered mode based on the number of transmissions of the data in a given time period.

28. The method according to claim 23, and further comprising the step of powering the radio section to the powered mode upon elapse of a fixed time interval after receipt of the beacon.

29. The method according to claim 23, and further comprising the step of powering the radio section to the powered mode upon elapse of a variable time interval after receipt of the beacon.