Handoff method and apparatus for mobile wireless workstation

• US 5,181,200 A
• Filed: 10/29/1990
• Issued: 01/19/1993
• Est. Priority Date: 10/29/1990
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Harrison, Colin G.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Chin, Wellington
• Application Number:
  US07/605,720
• Time in Patent Office: 813 Days
• Field of Search: 370/85.1, 370/85.2, 370/85.3, 370/85.4, 370/85.13, 370/85.14, 370/85.15, 370/94.1, 370/94.2, 370/95.1, 370/95.3, 340/825.44, 455/33, 455/34, 455/53, 455/54, 455/56, 455/33.1, 455/33.2, 455/34.1, 455/53.1, 455/54.1, 455/54.2, 455/56.1
• US Class Current: 370/468
• CPC Class Codes: H04W 36/02 Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection

Abstract

In response to a data processor (10) breaking a wireless link with a first, original, link adapter (12) a first step deletes the data processor from an active group of the first link adapter and re-directs network datagrams intended for the data processor to a spooler. In response to the data processor subsequently establishing a link with a second, new, link adapter a next step adds the data processor to the active group associated with the second link adapter and transmits stored datagrams in a First In/First Out order from the spooler to the second link adapter for transmission to the data processor. In response to the storage device transmitting all of the stored datagrams to the second link adapter the method includes the further steps of terminating the re-direction of datagrams from the first link adapter to the storage device and, receiving, from the network with the second link adapter, further datagrams addressed to the data processor.

Claims

1. A method for providing an appearance of a continual connection of a data processor means to a wired network of the type having a plurality of wireless link adapter means each of which bidirectionally passes data to and from the network over a wireless link, the data being transmitted to or received from data processor means having means for coupling to the wireless link, comprising the steps of:

in response to the data processor means breaking the wireless link with a first link adapter means of the plurality of wireless link adapter means,

re-directing to network storage means, with the first link adapter means, any data received from the network that is intended for the data processor means;

in response to the data processor means establishing a link with a second link adapter means of the plurality of wireless link adapter means,

transmitting stored data from the network storage means to the second link adapter means;

receiving with the second link adapter means the data from the storage means; and

sending the received data from the second link adapter means to the data processing means;

in response to the network storage means transmitting all of the stored data to the second link adapter means,

terminating the re-direction of data from the first link adapter means to the storage means; and

receiving from the network, with the second link adapter means, any further data addressed to the data processing means.

2. A method as set forth in claim 1 wherein, in response to the data processor means breaking the wireless link with the first link adapter means and then reestablishing the wireless link with the first link adapter means, the method includes the steps of:

transmitting stored data from the network storage means to the first link adapter means;

receiving with the first link adapter means the data transmitted from the storage means; and

sending the received data from the first link adapter means to the data processing means.

3. A method as set forth in claim 1 wherein the step of redirecting includes a step of maintaining, with the first link adapter means, a first record for identifying the data re-directed to the storage means.

4. A method as set forth in claim 3 wherein the step of receiving the data from the storage means includes a step of maintaining, with the second link adapter means, a second record for identifying the data received from the storage means.

5. A method as set forth in claim 4 wherein the step of terminating includes a step of transmitting the first record from the first link adapter means to the second link adapter means, and wherein the method includes a further step of comparing the received first record to the second record to determine if all stored data has been received from the storage means.

6. A method as set forth in claim 1 wherein the step of sending includes a step of transmitting the data with an infrared radiation medium.

7. A method as set forth in claim 1 wherein the step of sending includes a step of transmitting the data with a radio frequency medium.

8. A method for providing an appearance of a continual connection of a data processor means to a wired network of the type having a plurality of wireless link adapter means, individual ones of the plurality of link adapter means directing data from the wired network over a wireless link to one or more data processor means belonging to an associated active group of data processor means, where a data processor means is enabled, at any given time, to be a member of only one active group that is associated with one of said plurality of link adapter means, comprising the steps of:

in response to the data processor means breaking the wireless link with a first link adapter means, the data processor means being a member of the active group of the first link adapter means,

deleting the data processor means from the active group of the first link adapter means; and

re-directing data, that is intended for the data processor means, from the first link adapter means over the wired network to a storage means selected from one or more storage means that are coupled to the wired network;

in response to the data processor means establishing a link with a second link adapter means,

adding the data processor means to the active group associated with the second link adapter means;

transmitting stored data in a First In/First Out order from the storage means to the second link adapter means;

receiving the data from the storage means; and

sending the received data from the second link adapter means to the data processing means;

in response to the storage means transmitting all of the stored data to the second link adapter means,

terminating the re-direction of data from the first link adapter means to the storage means; and

receiving, from the network, further data addressed to the data processing means, the further data being received with the second link adapter means.

9. A method as set forth in claim 8 wherein the step of adding the data processing means to the active group includes a step of:

interrogating the data processing means to determine an identity of the first link adapter means.

10. A method as set forth in claim 8 wherein the step of redirecting includes a step of maintaining a first log that identifies the data re-directed to the storage means.

11. A method as set forth in claim 10 wherein the step of receiving the data from the storage means includes a step of maintaining a second log that identifies the data received from the storage means.

12. A method as set forth in claim 11 wherein the step of terminating includes a step of transmitting, over the wired network, the first log from the first link adapter means to the second link adapter means, and wherein the method includes a further step of comparing the received first log to the second log to ensure that all stored data has been received from the storage means.

13. A method as set forth in claim 8 wherein the step of receiving the data addressed to the data processing means with the second link adapter means includes an initial step of informing a network bridge means that the second link adapter means is associated with a second network.

14. A method as set forth in claim 8 wherein the step of sending includes a step of transmitting the data with an infrared radiation medium.

15. A method as set forth in claim 8 wherein the step of sending includes a step of transmitting the data with a radio frequency medium.

16. A method as set forth in claim 9 wherein the step of interrogating the data processing means includes a step of transmitting information over a first infrared radiation link having a first bandwidth, wherein the step of sending the received data from the second link adapter means to the data processing means includes a step of transmitting data over a second infrared radiation link having a second bandwidth, and wherein the first bandwidth is less than the second bandwidth.

20. A method as set forth in claim 9 wherein the step of adding the data processing means to the active group includes a step of:

interrogating the identified first link adapter means with the second link adapter means to determine an identity of the storage means to which the data is being redirected by the first link adapter means.

17. Apparatus for providing an appearance of a continual connection of a data processor means to a wired network of the type having a plurality of wireless link adapter means each of which bidirectionally passes data to and from the network over a wireless link, the data being transmitted to or received from data processor means having means for coupling to the wireless link, comprising:

data storage means bidirectionally coupled to the network;

means, responsive to the data processor means breaking the wireless link with a first link adapter means of the plurality of link adapter means, for re-directing to the data storage means any data received from the network that is intended for the data processor means;

means, responsive to the data processor means establishing a link with a second link adapter means of the plurality of link adapter means, for initiating the transmission of stored data from the data storage means to the second link adapter means;

means for receiving the data from the data storage means; and

means for sending, over the wireless link, the received data from the second link adapter means to the data processing means.

18. Apparatus as set forth in claim 17 and further comprising means, responsive to the data storage means transmitting all of the stored data to the stored link adapter means, for terminating the re-direction of data from the first link adapter means to the data storage means, the second link adapter means further including means for receiving from the network any further data addressed to the data processing means.

19. Apparatus as set forth in claim 17 wherein each of the link adapter means and the data processing means include means for transmitting and for receiving control information over a first infrared radiation link having a first bandwidth, and means for transmitting and receiving the data over a second infrared radiation link having a second bandwidth, and wherein the second bandwidth is greater than the first bandwidth.