System and method of adaptive frequency hopping with look ahead interference prediction

• US 20090257396A1
• Filed: 04/09/2008
• Published: 10/15/2009
• Est. Priority Date: 04/09/2008
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Tsfati, Yossi, Eliezer, Oren E.
• Granted Patent: US 8,218,487 B2
• Time in Patent Office: Days
• US Class Current: 370/330
• CPC Class Codes: H04B 1/036 Cooling arrangements

Abstract

A novel and useful adaptive frequency hopping scheme for wireless devices and networks operating in a congested environment of similar devices, where capacity maximization is desired. The hopping sequence of each wireless link is dynamically adapted such that the impact of the surrounding interference is minimized and the interference induced onto the coexisting systems is also minimized. The scheme detects the repetitive presence of interference on a particular channel and comprises a replacement mechanism for swapping the interfered frequency-channel with one that would be clear for that particular time-slot. The mechanism detects interference during a redundant portion of the transmission (i.e. header or trailer) without having to experience packet failures (i.e. data loss). If the interference impact (e.g. corrupted header bits) exceeds a predefined threshold, that frequency channel is declared temporarily unusable for that time slot and is replaced with another in accordance with a frequency replacement policy. Periodic interference at a particular frequency, originating from a coexisting system of similar operating parameters, may also be detected at instances that are distant from the timeslots for which that particular frequency is to be used, such that frequency replacement in the hopping sequence can be scheduled ahead of time and collisions would be avoided altogether.

Claims

1. A method of adapting a periodic frequency hopping sequence in a frequency hopping communication system having fixed slot timing, said method comprising the steps of:

detecting the presence of repeated interference at a particular frequency having specific timing with respect to time slots at which that particular frequency is periodically used by said system; and

replacing the potentially interfered frequency of said time slot with a replacement frequency.

2. The method according to claim 1, wherein said step of detecting the presence of repeated interference comprises the steps of:

detecting an impact on a received packet causing corruption of one or more bits in a redundant portion of said received packet; and

declaring said particular frequency channel unusable if said impact exceeds a predefined threshold.

3. The method according to claim 2, wherein said redundant portion of said received packet comprises one or more trailer bits.

4. The method according to claim 2, wherein said redundant portion of said received packet comprises one or more header bits.

5. The method according to claim 1, wherein said step of detecting the presence of repeated interference comprises the steps of:

detecting the presence of periodic transmissions from neighboring coexisting systems occurring at said frequency assigned to a time slot having specific timing with respect to said time slots at which this frequency is used by said system;

determining a drift in the relative timing between said periodic transmissions and the timing at which said system periodically uses said frequency; and

declaring said particular frequency unusable if the detected level of said periodic transmissions exceeds a predefined threshold.

6. The method according to claim 5, wherein said periodic potential interference is detected before it causes any loss of payload data in said system.

7. A method of adapting a frequency hopping sequence in a frequency hopping communication system having a plurality of frequency channels, said method comprising the steps of:

detecting an impact on a transmitted packet causing corruption of one or more bits in a redundant portion of said transmitted packet;

declaring said particular channel unusable if said impact exceeds a threshold; and

replacing the frequency of an unusable channel with an alternate frequency.

8. The method according to claim 7, wherein said redundant portion of said transmitted packet comprises one or more header/trailer bits which appear either before or after the payload in a packet.

9. The method according to claim 7, wherein potential periodic interference is detected without any loss of payload data.

10. A method of adaptive frequency hopping for use in a frequency hopping communication system, said method comprising the steps of:

maintaining a channel frequency counter for each individual frequency in a hopset;

incrementing said channel frequency counter associated with a particular frequency upon occurrence of a predetermined event; and

if the value of a channel frequency counter associated with a particular frequency exceeds a threshold, replacing an interfered channel corresponding thereto with a clear channel.

11. The method according to claim 10, further comprising the step of adding a penalty to the channel frequency counter associated with the particular frequency in response to the occurrence of a predetermined event to expedite frequency replacement.

12. The method according to claim 11, wherein said predetermined event comprises the occurrence of two or more consecutive detections of on-channel interference.

13. The method according to claim 10, further comprising the step of subtracting a decrement value from the channel frequency counter associated with the particular frequency when a packet is successfully received.

14. The method according to claim 10, wherein only a single frequency is replaced at a time.

15. The method according to claim 10, wherein additional adjacent frequencies potentially suffering interference due to their proximity are replaced.

16. The method according to claim 10, wherein said step of replacing comprises sending a frequency replacement message to a communication device at an opposite end of a link, said frequency replacement message comprising a ‘

bad frequency’

indication corresponding to said interfered channel and a ‘

new frequency’

indication corresponding to said clear channel.

17. A mobile communications device for use in a frequency hopping communication system having a plurality of frequency channels, comprising:

a frequency hopping based radio transceiver;

a processor coupled to said transceiver, said processor operative to;

detect the presence of repeated interference at a particular frequency having specific timing with respect to time slots at which that particular frequency is periodically used by said transceiver; and

replace the potentially interfered frequency of said time slot with a replacement frequency.

18. The mobile communications device according to claim 17, wherein said frequency hopping based transceiver comprises a Bluetooth transceiver.

19. The mobile communications device according to claim 17, wherein said step of detecting the presence of interference comprises the steps of:

detecting the interference impact in a received packet through its corruption of one or more bits in a redundant portion of said packet; and

declaring said particular frequency channel unusable if said interference impact exceeds a predefined threshold.

20. The mobile communications device according to claim 17, wherein said step of detecting the presence of potential interference comprises the steps of:

detecting the presence of periodic bursty transmissions from other coexisting systems occurring at said frequency at specific timing with respect to said time-slots at which this frequency is used by said system;

determining the drift in the relative timing between said periodic transmissions and the timing at which said system periodically uses said frequency; and

declaring said particular frequency channel unusable if the detected level of said periodic transmissions, which can potentially create interference once their timing drifts into that at which said frequency is used by the system, exceeds a predefined threshold.

21. The mobile communications device according to claim 17, wherein the presence of said repeated interference is detected before it causes any loss of payload data in said device.

22. A method of adapting a periodic frequency hopping sequence in a frequency hopping communication system having fixed slot timing, said method comprising the steps of:

detecting the presence of potential periodic interference from transmissions by neighboring coexisting systems occurring at a frequency assigned to a time slot to occur in the future in the potentially interfered system and having specific timing with respect to time slots at which the frequency is used by said system;

determining a drift in relative timing between said periodic transmissions and the timing at which said system periodically uses said frequency; and

declaring said particular frequency unusable if the detected level of said periodic transmissions repeatedly exceeds a first predefined threshold, and replacing said unusable frequency with a replacement frequency.

23. The method according to claim 22, wherein said potential periodic interference is detected before it causes any loss of payload data in said system.

24. The method according to claim 22, further comprising the step of detecting the presence of potential periodic interference from transmissions by neighboring coexisting systems occurring at said replacement frequency, such that the potentially interfered frequency would not be replaced with another potentially interfered frequency.

25. The method according to claim 24, further comprising the step of selecting a second replacement frequency if the level of periodically detected interference at said second replacement frequency exceeds a second predefined threshold.