Method to bootstrap into a frequency agile ad hoc network of radios that use a non-deterministic frequency pattern
View Patent ↗A method to facilitate late entry of a late entrant node into an ad-hoc radio network involves accessing from a memory at the late entrant node an initial frequency hopping sequence for the ad-hoc radio network. The late entrant node uses at least the initial frequency hopping sequence to determine a first frequency to monitor during a communication epoch corresponding to one of the frequency hops. The late entrant node thereafter monitors the first frequency to detect the presence of a beacon signal transmitted by a participating node of the network. Subsequently, the late entrant node determines a second frequency included in the current hopping sequence of the network based on information contained in the beacon signal.
1. A method for facilitating late entry of a late entrant node into an ad-hoc radio network in which a network hopping sequence changes over time in a non-deterministic manner in response to a spectral environment, comprising:
accessing from a memory at the late entrant node an initial frequency hopping sequence for said ad-hoc radio network, said initial frequency hopping sequence specifying a plurality of frequencies, each respectively assigned to one of a plurality of defined frequency hops of said frequency hopping sequence, said initial frequency hopping sequence specifying a sequence of frequency hops used by the ad-hoc network at a time corresponding to initiation of the ad-hoc network;
at a time after said initiation when the initial frequency hopping sequence has migrated in a non-deterministic way to a current frequency hopping sequence different from the initial frequency hopping sequence, and unknown by the late entrant node, discovering the current frequency hopping sequence by exclusively monitoring at least a first frequency specified by the initial frequency hopping sequence;
if the presence of a signal transmitted by a participating node of said ad-hoc network is not detected on at least the first frequency as a result of the exclusive monitoring, iteratively monitoring one or more alternate frequency values in accordance with an ordered list respectively specified for at least the first frequency until detecting the presence of the signal, said signal comprising
(1) first information concerning at least one “next+M” hop frequency of the current hopping sequence of said ad-hoc network, where M is an integer having a value equal to or greater than zero, and
(2) second information useful for determining a time when the at least one next+M hop frequency will be used by nodes of said ad-hoc network; and
determining a second frequency included in said current hopping sequence of said network based on the first information contained in said signal.
2. The method according to claim 1 , further comprising specifying with said ordered list an order in which said alternate frequencies are to be monitored by said late entrant node.
3. The method according to claim 1 , further comprising monitoring at least the first frequency specified in said initial hopping sequence for a defined frequency hop and, if said signal is not detected, then monitoring at least one said alternate frequency for said defined frequency hop.
4. The method according to claim 3 , further comprising monitoring in a sequential order each of said alternate frequencies for said defined frequency hop until said signal is detected.
5. The method according to claim 4 , further comprising specifying said sequential order with said ordered list.
6. The method according to claim 1 , further comprising continuing to monitor said first frequency during at least a second communication epoch, and determining a third frequency included in said current hopping sequence of said network based on information contained in said signal.
7. The method according to claim 6 , wherein said third frequency specified in said signal is chosen for inclusion in said signal in accordance with a pseudorandom selection scheme.
8. The method according to claim 6 , wherein said third frequency is selected from the group consisting of a next frequency and a next+1 frequency in said current hopping sequence.
9. The method according to claim 1 , further comprising:
detecting the presence of a second signal by monitoring said second frequency; and
determining a third frequency included in said current hopping sequence of said network based on information contained in said second signal.
10. The method according to claim 1 , further comprising monitoring during each of said defined frequency hops a corresponding one of said plurality of frequencies included in said initial frequency hopping sequence.
11. The method according to claim 10 , further comprising determining said first frequency for a plurality of said defined frequency hops by accessing an ordered list which specifies a plurality of alternate frequencies for each of said defined frequency hops.
12. The method according to claim 1 , further comprising monitoring at least one frequency included in said initial frequency hopping sequence for at least N+1 hops where N is the total number of hops in said initial frequency hopping sequence.
13. The method according to claim 12 , further comprising iteratively monitoring each frequency included in said initial frequency hopping sequence for at least N+1 hops until said signal is detected.
14. The method according to claim 1 , wherein a timing of said communication epoch is determined in accordance with a stable source of timing information, and said late entrant node accesses said stable source of timing information to determine a timing of said epoch.
15. The method according to claim 14 , wherein said stable source of timing information is a GPS signal.
16. A communication transceiver for an ad-hoc radio network, comprising:
a computer processing device configured to
access from a memory at the communication transceiver an initial frequency hopping sequence for said ad-hoc radio network, said initial frequency hopping sequence specifying a plurality of frequencies, each respectively assigned to one of a plurality of defined frequency hops of said frequency hopping sequence, said initial frequency hopping sequence specifying a sequence of frequency hops used by the ad-hoc network at a time corresponding to initiation of the ad-hoc network;
discover the current frequency hopping sequence by exclusively monitoring at least a first frequency specified by the initial frequency hopping sequence at a time after said initiation, when the initial frequency hopping sequence has migrated in a non-deterministic way to a current frequency hopping sequence different from the initial frequency hopping sequence, and unknown by the late entrant node;
if the presence of a signal transmitted by a participating node of said ad-hoc network is not detected on at least the first frequency as a result of the exclusive monitoring, iteratively monitor one or more alternate frequency values in accordance with an ordered list respectively specified for at least the first frequency until detecting the presence of the signal, said signal comprising
(1) first information concerning at least one “next+M” hop frequency of the current hopping sequence of said ad-hoc radio network, where M is an integer having a value equal to or greater than zero, and
(2) second information useful for determining a time when the next+M hop frequency will be used by nodes of said ad-hoc radio network; and
determine a second frequency included in said current hopping sequence of said ad-hoc radio network based on information contained in said signal.
17. The communication transceiver according to claim 16 , wherein said ordered list specifies an order in which said alternate frequencies are to be monitored by said communication transceiver.
18. The communication transceiver according to claim 16 , wherein said computer processing device is further configured to cause said communication transceiver to monitor at least the first frequency specified in said initial hopping sequence for a defined frequency hop and, if said signal is not detected, then monitor at least one said alternate frequency for said defined frequency hop.
19. The communication transceiver according to claim 18 , wherein said computer processing device is further configured to cause said communication transceiver to monitor in a sequential order each of said alternate frequencies for said defined frequency hop until said signal is detected.
20. The communication transceiver according to claim 19 , wherein said sequential order is specified with said ordered list.
21. The communication transceiver according to claim 16 , wherein said computer processing device is further configured to cause said communication transceiver to continue to monitor said first frequency during at least a second communication epoch, and determines a third frequency included in said current hopping sequence of said network based on information contained in said signal.
22. The communication transceiver according to claim 21 , wherein said third frequency specified in said signal is determined for inclusion in said signal in accordance with a pseudorandom selection scheme.
23. The communication transceiver according to claim 21 , wherein said third frequency is selected from the group consisting of a next frequency and a next+1 frequency in said current hopping sequence.
24. The communication transceiver according to claim 16 , wherein said computer processing device is further configured to:
detect the presence of a second signal by monitoring said second frequency; and determine a third frequency included in said current hopping sequence of said network based on information contained in said second signal.
25. The communication transceiver according to claim 16 , wherein said computer processing device is further configured to cause said communication transceiver to monitor during each of said defined frequency hops a corresponding one of said plurality of frequencies included in said initial frequency hopping sequence.
26. The communication transceiver according to claim 25 , wherein said computer processing device is further configured to determine said first frequency for a plurality of said defined frequency hops by accessing an ordered list which specifies a plurality of alternate frequencies for each of said defined frequency hops.
27. The communication transceiver according to claim 16 , wherein said computer processing device is further configured to cause said communication transceiver to monitor at least one frequency included in said initial frequency hopping sequence for at least N+1 hops where N is the total number of hops in said initial frequency hopping sequence.
28. The communication transceiver according to claim 16 , wherein said computer processing device is further configured to cause said communication transceiver to iteratively monitor each frequency included in said initial frequency hopping sequence for at least N+1 hops until said signal is detected.
29. The communication transceiver according to claim 16 , wherein said computer processing device is further configured to determine a timing of said communication epoch in accordance with a stable source of timing information.
30. The communication transceiver according to claim 29 , wherein said stable source of timing information is a GPS signal.