Wireless coupling of devices to wired network

• US 5,276,680 A
• Filed: 05/01/1991
• Issued: 01/04/1994
• Est. Priority Date: 04/11/1991
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Telesystems SLW, Inc. (Zebra Technologies Corporation)
• Inventors: Messenger, Steven
• Primary Examiner(s): Chin, Wellington
• Application Number:
  US07/694,401
• Time in Patent Office: 979 Days
• Field of Search: 370/85.1, 370/85.7, 370/85.8, 370/94.1, 370/94.2, 370/95.1, 370/95.2, 370/95.3, 370/85.15, 370/16, 370/13, 455/32.1, 455/33.1, 455/33.2, 455/34.1, 455/34.2, 455/38.3, 455/53.1, 455/54.1, 455/56.1, 340/825.08, 340/825.54, 340/825.06, 340/825.07, 379/58, 379/59, 379/60, 379/63, 371/11.1, 371/11.2, 371/8.2, 371/8.1
• US Class Current: 370/311
• CPC Class Codes: H04L 45/7453 using hashing
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04W 48/14 using user query or user detection
• CPC Class Codes: H04W 60/00 Affiliation to network, e.g. registration; Terminating affiliation with the network, e.g. de-registration
• CPC Class Codes: H04W 76/10 Connection setup
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 92/02 Inter-networking arrangements
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Spaced-apart communication controllers connected to a cable-based network place a portable device in communication with the network for transfer of data packets. Each controller communicates with the portable device with packet transmissions through air, and requires registration of the portable device before offering packet transferring services. The registration process involves transmitting a packet from the portable unit requesting a response from controllers, transmitting a response packet from each controller receiving the request, selecting one of the responding controllers at the portable unit according to criteria that enhance data transfer, and transmitting from the portable unit a packet identifying the selected controller to complete registration. The selected controller transmits to other controllers via the network cable a packet confirming the registration. A controller with which the portable device was previously registered responds by de-registering the device and transmitting any stored packets addressed to the device via the cable to the newly selected controller. A power saving protocol is implemented for a battery-operated portable device and adjusted continually to accommodate the rate at which transmissions to the device occur. The power saving arrangement includes disabling the receiving section of the device.

Claims

1. In a network comprising a cable medium conveying packets between predetermined nodes, a portable unit capable of transmitting and receiving packets through air, and a plurality of communication controllers in a predetermined spaced-apart arrangement, each of the plurality of controllers being capable of transmitting and receiving packets through air within a limited area and being coupled to the cable medium for transfer of packets to and from the cable medium, each of the plurality of controllers requiring registration of the portable unit with the controller before transferring packets between the portable unit and the cable medium, a method of placing and maintaining the portable unit in wireless communication with the cable medium for transfer of packets via the cable medium to and from the portable unit, comprising:

registering the portable unit with one of the plurality of controllers with a registration process comprising;

(a) transmitting through air from the portable unit a packet requesting a response from each of the plurality of controllers;

(b) responding to the request for response at each of the controllers that receives the packet from the portable unit, the responding comprising transmitting through air a response packet identifying the controller and indicating that the controller may register the portable unit;

(c) responding at the portable unit to receipt of one or more controller response packets by selecting one of the responding controllers and transmitting through air from the portable unit a selection packet indicating the selected controller;

(d) responding at the selected controller to receipt of the selection packet by registering the portable unit with the selected controller;

(e) transmitting via the cable medium from the selected controller upon its registration of the portable unit a registration-indicating packet indicating that the selected controller has registered the portable unit;

(f) responding to receipt of the registration-indicating packet at another of the controllers with which the portable unit had been registered prior to registration with the selected controller by de-registering the portable unit from the other controller; and

,

monitoring transmission of packets between the portable unit and the selected controller at the portable unit after registration of the portable unit with the selected controller thereby to detect transmission faults and re-initiating the registration process at the portable unit in response to transmission faults.

2. The method of claim 1 in which each of the controllers is adapted to store packets addressed to the portable device and received by the controller prior to transmission of such packets by the controller through air to the portable unit, the method being adapted to recover any undelivered packets stored by the other controller with which the portable unit had been registered, the registration process further comprising:

responding to the registration-indicating packet at the other controller by transmitting the undelivered packets via the cable medium to the selected controller; and

,

receiving and storing the transmitted undelivered packets at the selected controller for transmission through air to the portable unit.

3. The method of claim 1 comprising detecting at any one of the controllers with which the portable unit is registered a predetermined condition indicating that further transfer of packets between the portable unit and controller is not required and de-registering the portable unit from the controller in response to detection of such a condition.

4. The method of claim 3 in which the predetermined condition at the any one of the controllers is one of (a) expiry of a predetermined period of time without receipt of a packet through air from the portable unit and (b) receipt via the cable medium of a packet indicating that the portable unit has registered with another of the controllers.

5. The method of claim 1 in which the portable unit is operated with a battery that delivers electric current required for operation of a packet-receiving block of the portable unit, the method further comprising:

storing packets received by the selected controller and addressed to the portable unit in a buffer associated with the selected controller;

transmitting at intervals through air from the portable unit a polling packet;

enabling delivery of the required electric current for a predetermined period of time following transmission of each polling packet from the portable unit and so disabling delivery of the required electric current between transmission of polling packets that current demands on the battery are reduced;

transmitting stored packets addressed to the portable unit through air from the selected controller only in response to receipt of polling packets from the portable unit and only within a preselected period of time following receipt of each polling packet from the portable unit, the preselected period corresponding substantially to the predetermined period during which delivery of the required current to the packet-receiving block is enabled; and

,

decreasing the interval between transmission of successive polling packets incrementally toward a predetermined lower limit in response to receipt at the portable unit of each stored packet addressed to the portable unit and transmitted through air by the selected controller.

6. The method of claim 5 further comprising:

transmitting a predetermined response packet addressed to the portable unit in response to each polling packet received by the selected controller from the portable unit in the event that the buffer of the selected controller contains no stored packet addressed to the portable unit; and

,

increasing the interval between transmission of successive polling packets incrementally toward a predetermined upper limit in response to receipt at the portable unit of each predetermined response packet addressed to and received by the portable unit.

7. In a network comprising a cable medium conveying packets between predetermined nodes, a portable unit capable of transmitting and receiving packets through air, and a plurality of communication controllers in a predetermined spaced-apart arrangement, each of the plurality of controllers being capable of transmitting and receiving packets through air within a predetermined area and being coupled to the cable medium for transfer of packets to and from the cable medium, the portable unit being operated with a battery that delivers electric current required for operation of a packet-receiving block of the portable unit, the portable unit being registered with one of the plurality of controllers during transfer of packets between the portable unit and the cable medium, a method of reducing current demands on the battery of the portable unit, comprising:

storing packets received by the one controller and addressed to the portable unit in a buffer associated with the one controller;

transmitting at intervals through air from the portable unit a polling packet;

enabling delivery of the required electric current for a predetermined period of time following transmission of each polling packet from the portable unit and so disabling delivery of the required electric current between transmission of polling packets that current demands on the battery are reduced;

transmitting stored packets addressed to the portable unit through air from the one controller only in response to receipt of polling packets from the portable unit and only within a preselected period of time following receipt of each polling packet from the portable unit, the preselected period corresponding substantially to the predetermined period during which delivery of the required current to the packet-receiving block is enabled; and

,

decreasing the interval between transmission of successive polling packets incrementally toward a predetermined lower limit in response to receipt at the portable unit of each stored packet addressed to the portable unit and transmitted through air by the selected controller.

8. The method of claim 7 further comprising:

transmitting a predetermined response packet addressed to the portable unit in response to each polling packet received by the selected controller from the portable unit in the event that the buffer of the selected controller contains no stored packet addressed to the portable unit; and

,

increasing the interval between transmission of successive polling packets incrementally toward a predetermined upper limit in response to receipt at the portable unit of each predetermined response packet addressed to and received by the portable unit.

9. The method of claim 7 adapted to recover undelivered packets addressed to the portable unit and stored in the buffer of the one controller in response to registration of the portable unit with another of the plurality of controllers, comprising:

transmitting from the other controller via the cable medium upon its registration of the portable unit a registration-indicating packet indicating that the other controller has registered the portable unit;

responding to the registration-indicating packet at the one controller by transmitting the undelivered packets via the cable medium to the other controller; and

receiving the transmitted undelivered packets at the other controller and storing the undelivered packets in a buffer associated with the other controller for transmission to the portable unit.

10. In a network comprising a cable medium for conveying packets between predetermined nodes, a portable unit capable of transmitting and receiving packets through air, and a plurality of communication controllers in a predetermined spaced-apart arrangement, each of the plurality of controllers being capable of transmitting and receiving packets through air within a limited area and being coupled to the cable medium for transfer of packets to and from the cable medium, each of the plurality of controllers requiring registration of the portable unit with the controller before transferring packets between the portable unit and the cable medium, the portable unit being registered with one of the plurality of controllers, a method of reducing loss of packets during registration of the portable unit with another of the plurality of controllers in response to a transmission fault to or from one controller, comprising:

storing packets addressed to the portable unit and received by the one controller for transmission to the portable unit in a buffer of the one controller while the portable unit is registered with the one controller;

transmitting from the other controller via the cable medium upon registration of the portable unit with the other controller a registration-indicating packet indicating that the controller has registered the portable unit;

responding at the one controller to receipt of the registration-indicating packet by transmitting via the cable medium any undelivered packets addressed to the portable unit and stored in the buffer of the one controller; and

,

receiving the transmitted undelivered packets at the other controller and storing the undelivered packets in a random access buffer of the other controller for transmission through air to the portable unit.

11. The method of claim 10 further comprising de-registering the portable unit from the one controller in response to receipt of the registration-indicating packet.

12. A communication controller for placing a portable unit capable of transmitting and receiving packets through air in communication with a cable medium of a network for transfer of packets via the cable medium to and from the portable unit, comprising:

means for transmitting and receiving packets through air;

means for transferring packets to and from the cable medium;

a buffer;

control means for registering the portable unit with the controller in response to receipt of a packet transmitted through air by the portable unit and requesting registration of the portable unit with the controller, the control means being adapted to store packets received by the controller via the cable medium and addressed to the portable unit in the buffer for transmission to the portable unit upon registration of the portable unit with the controller;

the control means being adapted to respond to a packet received from another controller of the network and indicating registration of the portable unit with the other controller by transmitting any undelivered ones of the stored packets stored by the controller via the cable medium to the other controller.

13. The communication controller of claim 12 in which the controller means are adapted to de-registered the portable unit from the controller in response to receipt by the controller of the registration-indicating packet from the other controller.

14. The controller of claim 13 in which the control means are adapted to transmit via the cable medium upon registration of the portable unit with the controller a packet indicating registration of the portable unit with the controller thereby to initiate transmission of undelivered packets addressed to the portable unit and stored in any controller with which the portable unit was previously registered.