Method of resolving media contention in radio communication links

• US 5,471,469 A
• Filed: 02/08/1994
• Issued: 11/28/1995
• Est. Priority Date: 02/08/1994
• Status: Expired due to Term

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Metricom, Inc.
• Inventors: Galloway, Brett D., Flammer, III, George H.
• Primary Examiner(s): Kizou, Hassan
• Application Number:
  US08/193,338
• Time in Patent Office: 658 Days
• Field of Search: 370/50, 370/85.2, 370/85.3, 370/85.8, 370/94.1, 370/94.2, 370/95.2, 370/18, 375/1, 375/58, 375/202, 375/285, 455/166.1, 455/63, 380/33, 380/34
• US Class Current: 370/346
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04L 1/1607 Details of the supervisory signal
• CPC Class Codes: H04W 72/044 based on the type of the allocated resource
• CPC Class Codes: H04W 74/06 using polling
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]

Abstract

In a wireless packet communication system having a plurality of nodes, each having a transmitter and a receiver, the receiver at each node is assigned a specific frequency hopping band plan on which to receive signals, and the transmitter of any source node desiring to communicate with a target node changes frequency to the frequency of the target node according to the band plan. Thereupon, the source node transmits a poll packet which polls the target node to determine whether the target node is able and willing to accept a specified number of packets, at a specified level of priority. A failure to receive an acknowledgement on the source node'"'"'s receive channel is a prompt to the source node either to retransmit a polling packet later, to change the polling packet or to redirect the polling packet to another target. In the event the target node returns an acknowledgement, the target node reserves access to itself for the polling station at a determined time for a determined duration. The source node then transmits its data packet on the target node receive channel and waits for an acknowledgement on its own receive channel. The source node and the target node exchange information on the agreed upon data exchange channel, even though the expected receive channel according to the frequency hopping band play of the target node may have changed in the meantime.

Claims

1. In a communications network having a plurality of nodes each capable of transmitting and or receiving data over any one of a plurality of shared channels, a method for enabling any transmitting node to transmit data to any receiving node without contention from any other transmitting node comprising the steps of:

assigning to each receiving node a channel hopping band plan that is known to any node in the network wishing to transmit data to said receiving node and enabling said receiving node to follow said channel hopping band plan;

monitoring for silence at a transmitting node an expected channel of a receiving node according to said receiving node'"'"'s channel hopping band plan in order to determine if said receiving node is idle;

transmitting from a transmitting node a polling packet to a receiving node at an expected channel according to said receiving node'"'"'s channel hopping band plan;

receiving at said transmitting node from said receiving node an acknowledgement packet if said receiving node is available to receive data packets; and

,

transmitting data from said transmitting node to said receiving node on a channel which is different from the expected channel for said receiving node according to said receiving node'"'"'s channel hopping band plan.

2. The method according to claim 1 wherein said channel which is different from the expected channel for said receiving node is the channel at which the acknowledged polling packet was transmitted.

3. The method according to claim 1 wherein failure to receive an acknowledgement packet at said transmitting node from said receiving node causes said transmitting node to either wait a determined amount of time before transmitting a new polling packet to said receiving node at said receiving node'"'"'s then expected channel or to select an alternative receiving node and transmit a polling packet on said alternative receiving node'"'"'s expected channel.

4. The method according to claim 1 further comprising the step of switching said receiving node back to its expected channel according to its channel hopping band plan once data transmission is complete.

6. The method according to claim 1 wherein said plurality of nodes are enabled to transmit and receive data via radio signals and wherein said channels are radio frequency bands.

7. The method according to claim 1 wherein said data is comprised of digital data packets.

8. The method according to claim 1 wherein said communications network is a wireless local area network.

9. The method according to claim 7 wherein said polling packet contains a request for said receiving node to accept a specified number of data packets at a specified priority.

10. The method according to claim 7 wherein said receiving node hops between channels at a specified interval of time.

11. The method according to claim 1 further comprising the step of determining if the total time it will take to complete transmitting data will exceed a certain predetermined allowed time interval and if said transmitting will exceed said allowed time interval, hopping to another channel different from the expected channel for said receiving node in order to continue transmitting data.

5. A communications network comprising:

a shared medium with a plurality of channels; and

a plurality of channel-agile nodes each capable of transmitting and or receiving on the plurality of channels of said shared medium wherein each of said nodes capable of receiving is assigned and follows a channel hopping band plan that is known to each of the nodes wishing to transmit to said node capable of receiving;

whereby a first node wishing to transmit data to a second node switches to the expected channel of said second node according to said second node'"'"'s channel hopping band plan and then after detecting silence transmits a polling packet and whereby on receipt and successful acknowledgement of said polling packet said first node transmits data to said second node on a channel which is different from the expected channel of said second node according to said second node'"'"'s frequency hopping band plan.

12. The communications network according to claim 5 wherein said plurality of channel-agile nodes are enabled to transmit and receive data via radio signals and wherein said channels are radio frequency bands.

13. The communications network according to claim 5 wherein said data is comprised of digital data packets.

14. The communications network according to claim 5 wherein said communications network is a wireless local area network.

15. The communications network according to claim 14 wherein said polling packet contains a request for said receiving node to accept a specified number of data packets at a specified priority.

16. The communications network according to claim 5 wherein said channel-agile nodes hop between channels at a specified interval of time.