Distributed control methods for management of migrating data stations in a wireless communications network

• US 5,212,806 A
• Filed: 10/29/1990
• Issued: 05/18/1993
• Est. Priority Date: 10/29/1990
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Natarajan, Kadathur S.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): VO, NGUYEN THANH
• Application Number:
  US07/605,723
• Time in Patent Office: 932 Days
• Field of Search: 455/33.4, 455/33.2, 455/54.1, 455/54.2, 455/56.1, 379/59, 379/60
• US Class Current: 455/525
• CPC Class Codes: H04W 36/22 for handling the traffic
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 40/246 Connectivity information discovery
• CPC Class Codes: H04W 40/248 Connectivity information update
• CPC Class Codes: H04W 40/32 for defining a routing cluster membership

Abstract

In a wireless communications network having a plurality of header stations (12) in bidirectional wireless communication with one or more mobile communication units (10), a method of managing ownership of the mobile units. In accordance with the method the following steps are executed. A first step receives, with a mobile communication unit located at a position (44) that is served by two or more of the header stations, a transmission from each of the header stations. The received transmissions are received over the wireless communications network and each uniquely identify the transmitting header station. The method further includes a step of selecting, with the mobile communication unit, one of the header stations as a header station to manage future wireless communications for the mobile communications unit. A further step is performed if the selected header station is not a header station that is presently managing wireless communications for the mobile communications unit. This further step transmits a message over the wireless network from the mobile communications unit to the selected header station requesting that the mobile communications unit be assigned to the selected header station.

Claims

1. A method for managing ownership of one or more mobile communication units in a wireless communications network, the wireless communications network having a plurality of header stations in bidirectional wireless communication over the wireless communications network with one or more of the mobile communication units, the method comprising the steps of:

periodically transmitting a first message over the wireless communications network from each of the plurality of header stations, the transmitted first message including information for uniquely identifying the transmitting header station and also including information for specifying a number of mobile communication units for which the transmitting header station is presently managing wireless communications;

receiving, with a mobile communication unit located at a position that is served by two or more of the header stations, the transmitted first message from each of the header stations that serve the position occupied by the mobile communication unit, the transmitted first messages being received over the wireless communications network;

selecting, with the mobile communication unit in accordance with the received transmitted first messages from the two or more header station as, one of the header stations as a header station to manage future wireless communications for the mobile communication unit; and

if the selected header station is not a header station that is presently managing wireless communications for the mobile communication unit, transmitting a second message over the wireless communications network from the mobile communication unit to the selected header station, the transmitted second message requesting that wireless communications for the mobile communication unit be managed by the selected header station.

2. A method as set forth in claim 1 wherein the step of selecting includes the following steps:

determining if the received transmitted first message originated from a header station that is presently managing wireless communications for the mobile communication unit; and

, if so

determining if a strength of the received transmitted first message is above a predetermined threshold; and

, if so

retaining the header station that is presently managing wireless communications for the mobile communication unit.

3. A method as set forth in claim 2 wherein if the header station that is presently managing wireless communications for the mobile communication unit is not retained, the step of selecting further includes the steps of:

determining from the received transmitted first messages the number of other mobile communication units that are currently managed by each of the header stations that serve the position occupied by the mobile communication unit; and

selecting a header station that is managing wireless communications for the fewest number of other mobile units;

or

if all of the header stations that serve the position occupied by the mobile communication unit are determined to be managing a same number of other mobile communication units,

selecting the header station having a received signal strength that exceeds the received signal strengths of the other header stations by a predetermined amount;

or

if none of the header stations that serve the position occupied by the mobile communication unit are determined to have a received signal strength that exceeds that of the other header stations by the predetermined amount,

selecting one of the header stations at random.

4. A method as set forth in claim 1 and further comprising the steps of:

receiving at the selected header station the second message transmitted by the mobile communication unit; and

notifying the mobile communication unit that the selected header station has accepted the mobile communication unit for inclusion within a set of mobile communication units for which the selected header station is managing wireless communications.

5. A method as set forth in claim 1, wherein the second message includes information for identifying a header station, if any, that is currently managing wireless communications for the mobile communication unit, and further comprising the steps of:

receiving at the selected header station the second message transmitted by the mobile communication unit;

determining, with the selected header station, if wireless communications for the mobile communication unit was previously managed by another header station; and

, if so,

informing the other header station, from the selected header station, that the mobile communication unit is now managed by the selected header station.

6. A method as set forth in claim 5 and further comprising a step of notifying, with the selected header station, all other header stations that maintain a communications routing table that includes the mobile communication unit, that the mobile communication unit is now managed by the selected header station.

7. A method as set forth in claim 1 wherein the step of receiving occurs for a period of time determined to be sufficiently long so as to receive at least one transmitted first message from each of the header stations that serve the position occupied by the mobile communication unit.

8. A method as set forth in claim 1 wherein the step of receiving occurs for a period of time at least equal to (Δ

+ε

), where delta is a predetermined time interval and wherein epsilon is a variable time period, the period of time being sufficiently long so as to receive at least one transmitted first message from each of the header stations that serve the position occupied by the mobile communication unit.

9. A method as set forth in claim 1 wherein the step of transmitting the second message includes a step of transmitting a message including at least an identification of the mobile communication unit, an identification of a header station, if any, having a domain of which the mobile communication unit is currently a member, and an identification of the selected header station.

10. A method as set forth in claim 6 wherein the steps of informing and notifying each include a step of transmitting a message over a wired network that is coupled between the header station and others of the header stations.

11. A method as set forth in claim 1 wherein each of the header stations is bidirectionally coupled to a wired network, and wherein the selected header station records an identification of the second header station in response to a receipt of a message from the wired network that is directed to the mobile communication unit from a second header station.

12. A method as set forth in claim 11 wherein the selected header station, in response to a receipt of a message from the wired network from a third header station, the received message from the third header station indicating that the mobile communication unit has selected the third header station to manage wireless communications for the mobile communication unit, transmits a message over the wired network to the third header station, the message that is transmitted to the third header station including the identification of the second header station.

13. A method as set forth in claim 12 wherein the third header station, upon receipt of the message from the previously selected header station, transmits a message over the wired network to the second header station to inform the second header station that the third header station is managing wireless communications for the mobile communication unit.

14. A method as set forth in claim 13 wherein the second header station updates an internally maintained routing table in response to a receipt of the message from the third header station such that a subsequent message that is directed to the mobile communication unit is transmitted over the wired network from the second header station to the third header station.

15. A method as set forth in claim 12 wherein the third header station updates an internally maintained status table in response to a receipt of the message from the previously selected header station such that the third header station is enabled to determine what other header stations, if any, have previously directed a message to the mobile communication unit.

16. A wireless communications system having a plurality of header stations each serving a communication coverage area, the system further including at least one mobile communication unit, the mobile communication unit comprising:

means for receiving, when located at a position that is served by two or more of the header stations, a transmission from each of the header stations that serve the position occupied by the mobile communication unit, the received transmissions being received over the wireless communications network and each transmission including information for uniquely identifying the transmitting header station, each transmission further including other information for indicating a number of mobile communication units for which the transmitting header station is currently managing wireless communications;

means for selecting, in accordance with the received transmissions from the two or more header stations, one of the header stations as a header station to manage future wireless communications for the mobile communication unit; and

means for transmitting a message over the wireless communications network from the mobile communication unit to the selected header station, the transmitted message requesting that the mobile communication unit be assigned to the selected header station, said transmitting means operating in response to a determination by the mobile communication unit that the selected header station is not a header station that is presently managing wireless communications for the mobile communication unit, the transmitted message including information for identifying a header station, if any, that is currently managing wireless communications for the mobile communication unit.

17. A wireless communications system as set froth in claim 16 and further including a wired network for coupling together the plurality of header stations such that the header stations are enabled to communicate messages one to another, one type of message being transmitted over the wired network from the selected header station to a previously selected header station to inform the previously selected header station that the selected header station is now managing wireless communications for the mobile communication unit.

18. A wireless communications system as set forth in claim 16 wherein each of the header stations and the mobile communication unit include means for transmitting an infrared radiation signal to the wireless communications network and means for receiving an infrared radiation signal from the wireless communications network.

19. A wireless communications system as set forth in claim 16 wherein the mobile communication unit further includes:

means for storing a list of header stations that are determined by the mobile communication unit to be potential owners of the mobile communication unit; and

means for updating the list in response to the received transmissions;

and wherein each of the header stations includes means for storing a communications routing table associated with one or more mobile communication units that are owned by the header station.

20. A method for managing ownership of one or more mobile communication units in a wireless communications network, the wireless communications network having a plurality of header stations in bidirectional wireless communication with one or more of the mobile communication units, the method comprising the steps of:

receiving, with a mobile communication unit located at a position that is served by two or more of the header stations, a transmission from each of the header stations that serve the position occupied by the mobile communication unit, the received transmissions being received over the wireless communications network, each transmission uniquely identifying the transmitting header station;

selecting, with the mobile communication unit and in accordance with the received transmissions from the two or more header stations, one of the header stations as a header station to manage future wireless communications for the mobile communication unit; and

if the selected header station is not a header station that is presently managing wireless communications for the mobile communication unit, transmitting a message over the wireless communications network from the mobile communication unit to the selected header station requesting that the selected header station manage future wireless communications for the mobile communication unit;

wherein the selected header station, in response to a message directed to the mobile communication unit from a second header station, records an identification of the second header station; and

wherein

the selected header station, in response to a message from a third header station that indicates that the mobile communication unit has selected the third header station to manage wireless communications for the mobile communication unit, transmits a message to a a third header station, the message including the identification of the second header station.

21. A wireless data communications system, comprising:

a plurality of header stations, each of said header stations including means for transmitting information to a wireless network and means for receiving information for the wireless network, each of said header stations having a wireless communication cell associated therewith, each of said header stations further including means for bidirectionally coupling the header station to a wired network for transmitting information to the wired network and for receiving information from the wired network, wherein at least some of the information that is transmitted to the wired network is information that is first received from the wireless network, and wherein at least some of the information that is transmitted to the wireless network is information that is first received from the wired network; and

at least one mobile data station, said mobile data station including,

means for receiving, when located at a position where two or more wireless communications cells overlap, a transmission from each of the header stations associated with the overlapping wireless communications cells, each of the transmissions including information for uniquely identifying the transmitting header station, each transmission further including other information for indicating a number of mobile data stations for which the transmitting header station is currently managing wireless data communications;

means for selecting, in accordance with the received transmissions from the two or more header stations, one of the header stations as a header station to manage future wireless communications for the mobile data station; and

means for transmitting a message over the wireless communications network from the mobile data station, the transmitted message including information for uniquely identifying the mobile data station, information for specifying an identification of a header station, if any, that is currently managing wireless communications for the mobile data station, and information for specifying the identification of the selected header station, said transmitting means operating in response to a determination by the mobile communication unit that the selected header station is not a header station that is presently managing wireless communications for the mobile communication unit.

22. A wireless data communications system as set forth in claim 21 wherein each of the header stations and the mobile data station include means for transmitting an infrared radiation signal to the wireless communications network and means for receiving an infrared radiation signal for the wireless communications network.

23. A wireless data communications system as set forth in claim 21 wherein the mobile data station includes means for storing a list of header stations that are determined by the mobile data station to be potential owners of the mobile data station, and wherein each of the header stations includes means for storing a communications routing table having entries for at least each of the mobile data stations for which the header station is currently managing wireless data communications.