Redundant radio frequency network having a roaming terminal communication protocol

• US 5,673,031 A
• Filed: 07/05/1994
• Issued: 09/30/1997
• Est. Priority Date: 08/04/1988
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Norand Corporation (Baker Hughes Company)
• Inventors: Meier, Robert C.
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Hill, Andrew
• Application Number:
  US08/270,533
• Time in Patent Office: 1,183 Days
• Field of Search: 340/825.08, 340/825.44, 455/38.1, 455/38.2, 455/58.1, 455/67.1, 455/67.4, 455/54.2, 370/85.3, 370/85.8, 370/95.2, 379/59
• US Class Current: 340/2.4
• CPC Class Codes: G06F 1/1626 with a single-body enclosure integrating a flat display, e.g. Personal Digital Assistants [PDAs]
• CPC Class Codes: G06F 1/163 Wearable computers, e.g. on a belt
• CPC Class Codes: G06F 1/1632 External expansion units, e.g. docking stations
• CPC Class Codes: G06F 1/28 Supervision thereof, e.g. detecting power-supply failure by out of limits supervision
• CPC Class Codes: G06K 17/0022 arrangements or provisious 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 7/10574 Multiple sources
• CPC Class Codes: G06K 7/10584 Source control
• CPC Class Codes: G06K 7/10702 Particularities of propagating elements, e.g. lenses, mirrors G06K7/10831 takes precedence
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/10881 constructional details of hand-held scanners
• CPC Class Codes: G06K 7/1093 sensing, after transfer of the image of the data-field to an intermediate store, e.g. storage with cathode ray tube
• CPC Class Codes: G06K 7/1098 the scanning arrangement having a modular construction
• CPC Class Codes: G06Q 10/08 Logistics, e.g. warehousing, loading or distribution; Inventory or stock management
• CPC Class Codes: G06Q 20/343 Cards including a counter
• CPC Class Codes: G07F 7/02 by keys or other credit registering devices
• CPC Class Codes: G07G 1/0045 with a code reader for reading of an identifying code of the article to be registered, e.g. barcode reader or radio-frequency identity [RFID] reader
• CPC Class Codes: G08C 17/02 using a radio link
• CPC Class Codes: G08C 2201/20 : Binding and programming of remote control devices
• CPC Class Codes: H01Q 1/007 : specially adapted for indoor communication
• CPC Class Codes: H02J 9/005 : using a power saving mode for copiers G03G15/5004
• CPC Class Codes: H04B 1/3883 : Arrangements for mounting batteries or battery chargers
• CPC Class Codes: H04B 17/0085 : using test signal generators
• CPC Class Codes: H04B 17/318 : Received signal strength
• CPC Class Codes: H04B 2001/3894 : Waterproofing of transmission device
• CPC Class Codes: H04L 1/0025 : Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0032 : Without explicit signalling
• CPC Class Codes: H04L 12/403 : with centralised control, e.g. polling
• CPC Class Codes: H04L 45/00 : Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04L 69/14 : Multichannel or multilink protocols
• CPC Class Codes: H04L 69/18 : Multiprotocol handlers, e.g. single devices capable of handling multiple protocols
• CPC Class Codes: H04W 40/12 : based on transmission quality or channel quality
• CPC Class Codes: H04W 40/24 : Connectivity information management, e.g. connectivity discovery or connectivity update
• CPC Class Codes: H04W 40/36 : due to handover
• CPC Class Codes: H04W 52/029 : reducing the clock frequency of the controller
• CPC Class Codes: H04W 52/343 : taking into account loading or congestion level
• CPC Class Codes: Y02D 30/70 : in wireless communication networks

Abstract

A redundant network and communication protocol is disclosed having host computers, RF base stations and roaming terminals. In one embodiment, this network utilizes a polling communication protocol which, under heavy loaded conditions, requires that a roaming terminal wishing to initiate communication must first determine that the channel is truly clear by listing for an entire interpoll gap time. Thus, when a "hidden" terminal is communicating, the roaming terminal can conclude that such communication is taking place upon receiving a polling frame directed to that "hidden" terminal from the normally silent base station. In a further embodiment, a criterion used by the roaming terminals for attaching to a given base station reduces conflicts in the overlapping RF regions of adjacent base stations. Also, in another embodiment, inherent redundancy techniques are used with a spanning tree approach for determining the most efficient pathways from a source to a destination for ensuring that the network adapts to spatial changes or break downs within the network.

Claims

1. A method utilized by each of a plurality of sending devices for beginning and conducting a data exchange over an RF communication channel to a polling device wherein at least one of the plurality of sending devices cannot always detect transmissions originated by the other of the plurality of sending devices, said method comprising the steps of:

(a) after identifying data to be exchanged with a polling device, converting such identified data into a series of data segments;

(b) identifying a period of time that is at least as long as a predetermined time period during which no communication can be detected on RF communication channel;

(c) transmitting a request for poll frame to the polling device; and

(d) sequentially exchanging the series of data segments as prompted by a corresponding series of poll frames transmitted by the polling device, wherein each two consecutive poll frames transmitted are separated by the predetermined time period with one of the series of data segments transmitted therebetween.

2. The method of claim 1 wherein, in step (b), if the beginning of the period of time during which no communication is detected coincides with a detected end of a transmission, attempting to avoid collisions by delaying a random period before executing step (c).

3. The method of claim 1 wherein the last of the series of poll frames transmitted in step (d) indicates that the data exchange has completed.

4. The method of claim 3 wherein, in step (b), if a series of poll frame transmissions is detected, performing the additional steps of:

(i) waiting for the last of the series of poll frames to be transmitted;

(ii) waiting a random back-off period; and

(iii) branching to step (c).

5. The method of claim 1 wherein the polling device acknowledges each data segment that is successfully received through a corresponding one of the series of poll frames.

6. A method utilized by a sending device for beginning a data exchange over an RF communication channel with a polling device wherein the polling device maintains a predetermined time period of fixed duration between consecutive poll frames, comprising the steps of:

(a) converting data to be exchanged into a series of data segments;

(b) determining whether traffic on the RF communication channel is below a predetermined level;

(c) if the traffic is below the predetermined level, branching to step (e);

(d) identifying a period of time which is at least as long as the predetermined time period during which no communication can be detected on the RF communication channel; and

(e) transmitting a request for poll frame.

7. The method of claim 6 wherein, in step (c), if the traffic is below the predetermined level, branching to step (e) only when the sending device does not sense a carrier on the RF communication channel.

8. The method of claim 6 comprising the further step of sequentially exchanging the series of data segments as prompted by a corresponding series of poll frames transmitted by the polling device.

9. A method of conducting a data exchange from each of a plurality of sending devices to a destination device over a wireless communication channel, wherein each of the plurality of sending devices occasionally collect data to be exchanged with the destination device, and at least one of the plurality of sending devices cannot always detect data transmissions originated by the other of the plurality of sending devices, said method comprising the steps of:

(a) identifying, by one of the plurality of sending devices having data to be exchanged, a period of time that is at least as long as a predetermined time period during which no communication can be detected on the wireless communication channel;

(b) attempting, by the one of the plurality of sending devices, to initiate communication to a destination terminal; and

(c) if the attempt in step (b) proves successful, transmitting, by the destination device, a series of packets wherein each two consecutive packet transmissions are separated by no more than the predetermined time period; and

(d) transmitting, by the one of the plurality of sending devices, between each two consecutive packet transmissions the data to be exchanged in segments.

10. The method of claim 9 wherein the series of packets contain acknowledge messages whenever the segments of the data to be exchanged have been successfully received by the destination device.

11. The method of claim 10 wherein the destination device comprises a polling device.

12. The method of claim 9 wherein, in step (a), if the beginning of the period of time during which no communication is detected coincides with the end of a detected transmission, attempting to avoid collisions by delaying a random period before executing step (b).

13. The method of claim 9 wherein the last of the series of packets transmitted in step (c) indicates that the data exchange has completed.

14. The method of claim 13 wherein, in step (a), if a series of packets being transmitted is detected, performing the additional steps of:

(i) waiting for the last of the series of packets to be transmitted;

(ii) waiting a random back-off period; and

(iii) branching to step (b).

15. The method of claim 9 which comprises, before the step (a), a further step of branching to step (b) if traffic on the wireless communication channel is below a predetermined level.

16. The method of claim 9 which comprises, before the step (a), a further step of branching to step (b) when the sending device does not sense activity on the wireless communication channel, if traffic on the wireless communication channel is below a predetermined level.

17. A method of beginning and conducting data exchanges from one of a plurality of sending devices over a wireless communication channel to a destination device wherein the one of the plurality of sending devices cannot directly detect transmissions from others of the plurality of sending devices to the destination device, comprising the steps of:

(a) identifying, by the one of the plurality of sending devices, a period during which the destination device does not transmit for at least a predetermined duration;

(b) concluding, by the one of the plurality of sending devices, that because of the identification in step (a), the wireless communication is not being used by other of the plurality of sending devices to communicate to the destination device;

(c) transmitting, by the one of the plurality of sending devices, a portion of data to be exchanged to the destination device wherein the transmission time does not exceed the predetermined duration;

(d) initiating and concluding transmission, by the destination device, of a packet after receiving the portion of data to be exchanged;

(e) receiving, by the one of the plurality of sending devices, the packet transmitted by the destination device;

(f) transmitting, by the one of the plurality of sending devices, another portion of the data be exchanged to the destination device wherein the transmission time does not exceed the predetermined duration;

(g) initiating and concluding transmission, by the destination device, of another packet, wherein such initiation occurs no later than the predetermined duration since the initiation of transmission of the previously transmitted packet that was received in step (e); and

(h) repeating steps (e) through (g) until all portions of the data to be exchanged have been transmitted to the destination device.

18. The method of claim 17 which comprises before the step (a) a further step of branching to step (c) if traffic on the wireless communication channel is below a predetermined level.

19. The method of claim 17 which comprises, before the step (a), a further step of branching to step (c) when the sending device does not sense activity on the wireless communication channel, if traffic on the wireless communication channel is below a predetermined level.

20. The method of claim 17 wherein the destination device comprises a polling device, and the packets sent by the destination device comprise polling messages.

21. A method of managing data transmissions originating from a plurality of sending devices over a wireless communication channel, wherein each of the plurality of sending devices can detect transmissions from a control device, but at least one of the plurality of sending devices cannot always detect transmissions from the other of the plurality of sending devices, said method comprising the steps of:

(a) attempting, by one of the plurality of sending devices having data to be exchanged, to identify a period of time that is at least as long as a predetermined time period during which no communication can be detected on a wireless communication channel;

(b) requesting, by the one of the plurality of sending devices, assistance from a control device; and

(c) transmitting, by the control device, a bracket of frames which can be detected by each of the plurality of sending devices, and the bracket of frames providing the one of the plurality of sending devices an opportunity to transmit the data to be exchanged in a corresponding series of segments within the bracket of frames, wherein each of the transmission of one of the segments has a duration no longer than the predetermined time period.