Method of evaluating the quality of radio links for a wireless body area network, method of transmitting messages for a wireless body area network, and devices for implementing those methods

• US 9,363,098 B2
• Filed: 03/13/2012
• Issued: 06/07/2016
• Est. Priority Date: 04/01/2011
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Hamida, Elyes Ben, Benoit, Denis
• Primary Examiner(s): Kassim, Khaled
• Assistant Examiner(s): Yang, Zhaohui
• Application Number:
  US13/419,095
• Publication Number:
  US 20120250546A1
• Time in Patent Office: 1,547 Days
• Field of Search: 370225-228
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/0028 Body tissue as transmission medium, i.e. transmission systems where the medium is the human body
• CPC Class Codes: H04L 43/00 Arrangements for monitoring or testing data switching networks
• CPC Class Codes: H04L 43/08 Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
• CPC Class Codes: H04L 43/0852 Delays
• CPC Class Codes: H04L 43/0894 Packet rate
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

A method for evaluating quality of radio links for a wireless body area network includes first and second wireless devices forming a body area network and configured to communicate with each other. One of the two wireless devices is mobile relative to the other, The method includes exploiting messages received by one of the wireless devices to measure instantaneous quality of a corresponding radio link and to estimate times during and between which a radio link is reliable, calculating an estimated times reliability indicator, and classifying the radio links as a function of the reliability indicator into at least first and second categories. One of these categories is a category relating to intermittently reliable radio links taking into account the mobility of the wireless devices of the body area network.

Claims

1. A method for evaluating quality of radio links for a wireless body area network comprising at least first and second wireless devices positioned on parts of a body forming a body area network and configured to communicate with each other, at least one of the two wireless devices being mobile relative to the other, said method comprising exploiting messages received by at least one of the wireless devices to measure instantaneous quality of a corresponding radio link and to estimate times during and between which a radio link is reliable, calculating an estimated times reliability indicator, and classifying the radio links as a function of said reliability indicator into at least first and second categories, one of which is a category relating to intermittently reliable radio links taking into account the mobility of the wireless devices of the body area network, and routing or relaying messages via an intermittently reliable radio link during periods in which the intermittently reliable radio link is considered reliable and not during periods when the intermittently reliable radio link is considered not reliable;

wherein a radio link is considered reliable when a logical link is established between said at least first and second wireless devices and a radio link is considered not reliable when a logical link is not established between said at least first and second wireless devices; and

wherein the reliability of the intermittently reliable radio link varies due to the at least first and second wireless devices being mobile relative to each other caused by the mobility of the parts of the body on which the at least first and second wireless devices are positioned.

2. The method of claim 1, further comprising selecting the messages from the group consisting of service messages, data messages, and a combination of service messages and data messages.

3. The method of claim 1, wherein the messages are exchanged periodically.

4. The method of claim 1, wherein the messages are exchanged at a variable frequency.

5. The method of claim 1, further comprising evaluating the instantaneous quality of the radio links by measuring at least one radio indicator.

6. The method of claim 5, wherein, at a given time t, at least one of a connectivity parameter representative of an instantaneous quality of a radio link between two distinct nodes i and j and the radio indicator representative of an instantaneous quality of a radio link between two distinct nodes i and j is defined by a binary variable L_i,j^[t]={0,1}.

7. The method of claim 6, wherein the binary variable is set to a first value if the link is active and a second value if the link is inactive.

8. The method of claim 7, wherein classifying the radio links as a function of said reliability indicator into at least first and second categories comprises determining, from at least one of the connectivity parameter and the radio indicator for two devices, contact and inter-contact times and the presence of repetitive patterns of intermittent contact.

9. The method of claim 8, further comprising calculating the contact time Ĉ

_i,j^[t] at a time t between two distinct nodes i and j to be a duration of a binary sequence L_N+M={L_i,j^[1], L_i,j^[2], . . . , L_i,j^[N+M]}ε

{1}^N and {0}^M such that

10. The method of claim 9, further comprising calculating the inter-contact time at a time t between two distinct nodes i and j, Î

_i,j^[t] as being the duration of a binary sequence L_N+M={L_i,j^[1], L_i,j^[2], . . . , L_i,j^[N+M]}ε

{1}^N and {0}^M such that N≦

γ

_UP, where γ

_UP is the maximum number of occurrences of an inactive link tolerated during the inter-contact period.

11. The method of claim 10, further comprising calculating final contact and inter-contact times from the formulas C_i,j^[t](α

_CT)=α

_CT ×

C_i,j<sup>[t−

1]</sup>+(1−

α

_CT)×

Ĉ

_i,j^[t] and I_i,j^[t](α

_CT)=α

_CT×

I_i,j<sup>[t−

1]</sup>+(1−

α

_CT)×

Î

_i,j^[t] where Ĉ

_i,j^[t] is an instantaneous estimate of contact time, Î

_i,j^[t] is an instantaneous estimate of inter-contact time, C_i,j^[t] is a final estimate of contact time, I_i,j^[t], is a final estimate of inter-contact time, and α

_CT is a forget factor.

12. The method of claim 11, further comprising calculating a moving coefficient of variation V_i,j^[t] over a window of size W_V that is defined as being a ratio between standard deviation and mean of estimates over a moving window of size W_V, comparing the moving coefficient to a threshold γ

_V, and classifying a link as being one of intermittently reliable and reliable based on a result of said comparison.

13. The method of claim 6, wherein the binary variable is set to a first value if the radio indicator is less than a threshold and to a second value otherwise.

14. The method of claim 5, wherein the radio indicator is selected from the group consisting of RSSI, LQI or SNR.

15. The method of claim 1, further comprising evaluating the instantaneous quality of the radio links by measuring a connectivity parameter.

16. The method of claim 1, further comprising, for each wireless device, storing the reliability of the radio links associated with the device in a table of neighbors.

17. The method of claim 1, further comprising selecting an intermittently reliable radio link for transmission of a message to optimize at least one parameter selected from the group consisting of energy consumption, latency, and data delivery rate.

18. The method of claim 17, further comprising measuring distances between wireless devices based on a schedule that accounts for predicted appearance and disappearances of intermittently reliable links.

19. A system for evaluating quality of radio links for a wireless body area network, comprising at least first and second wireless devices positioned on parts of a body forming a body area network and configured to communicate with each other, at least one of the two wireless devices being mobile relative to the other, at least one of the wireless devices includes a first device configured to measure instantaneous quality of a corresponding radio link and to estimate times during and between which said radio link is reliable, said first device configured to calculate an estimated times reliability indicator and classify the radio links as a function of said reliability indicator into at least first and second categories, one of which is a category relating to intermittently reliable radio links taking into account the mobility of the wireless devices of the body area network;

the at least one of the wireless device further includes a second device configured to route or relay messages via the intermittently reliable radio link during a period in which the intermittently reliable radio link is considered reliable and not during periods when the intermittently reliable radio link is considered not reliable;

wherein a radio link is considered reliable when a logical link is established between said at least first and second wireless devices and a radio link is considered not reliable when a radio link is not established between said at least first and second wireless devices; and

wherein the reliability of the intermittently reliable radio link varies due to the at least first and second wireless devices being mobile relative to each other caused by the mobility of the parts of the body on which the at least first and second wireless devices are positioned.

20. An apparatus for transmitting messages across a wireless body area network, said apparatus comprising a first device configured to evaluate a quality of radio links in the wireless body area network for communication between wireless devices, and a second device configured to route messages via an intermittently reliable radio link during a period during which the intermittently reliable radio link is considered reliable.