Routing adaptable to electromagnetic conditions in a multihop network

1. A method for routing in a multihop network, comprising, for at least one node of the multihop network, the following steps:

a/ measuring a value of an intensity of an electromagnetic field over all of a frequency band, the electromagnetic field comprising signals attributable to messages transmitted in the multihop network and signals attributable to an electromagnetic environment of a neighborhood of the at least one node originating from outside the multihop network, said neighborhood comprising all nodes only one hop away from the at least one node, the frequency band comprising first frequencies relating to operating frequencies of the multihop network and second frequencies differing from said first frequencies, in the neighborhood of the at least one node,

b/ determining, using a computer processor, a ratio between said measured value and a predefined maximum electromagnetic field threshold value over said frequency band, and

c/ based on said ratio, selecting the at least one node as at least one routing node for at least one message in the multihop network so that the value of the intensity of the electromagnetic field at said at least one node does not exceed said predefined maximum electromagnetic field threshold value.

2. The method according to claim 1 , comprising, during the step a/,

receiving, for at least one remote sensor, a measurement of the intensity of the electromagnetic field in a neighborhood of said sensor,

and

evaluating the value of the intensity of the electromagnetic field in the neighborhood of the at least one node from the received measurement for each of the at least one remote sensor.

3. The method according to claim 2 , wherein, for at least one remote sensor, the measurement of the intensity of the electromagnetic field in the neighborhood of the at least one remote sensor is received directly from at least one remote sensor.

4. The method according to claim 2 , wherein, for at least one remote sensor, the measurement of the intensity of the electromagnetic field in the neighborhood of at least one remote sensor is received from a gateway device.

5. The method according to claim 2 , further comprising, during the step a/,

receiving a plurality of measurements of the intensity of the electromagnetic field in the neighborhood of a plurality of respective sensors,

selecting, from said plurality of received measurements, measurements corresponding to sensors situated at a predetermined maximum distance from the at least one node, and

obtaining the value of the intensity of the electromagnetic field in the neighborhood of the at least one node from the selected measurements.

6. The method according to claim 1 , further comprising, in step a/,

predicting the value of the intensity of the electromagnetic field in the neighborhood of the at least one node from at least one contextual parameter.

7. The method according to claim 1 , further comprising estimating a metric value from:

the ratio determined in step b/;

a previously determined ratio in step b/, and

wherein

during the step c/, said metric value is used for deciding whether or not said node can be selected as a routing node for at least one message in the multihop network.

8. The method according to claim 7 , wherein the metric value is estimated as follows:

c

t

=

1

α

·

M

t

+

(

1

-

α

)

·

M

t

-

1

,

where c t is the metric value,

0<α≦1,

M

t

=

max

⁡

(

E

t

E

M

,

B

t

B

M

)

,

and

⁢

⁢

M

t

-

1

=

max

⁡

(

E

t

-

1

E

M

,

B

t

-

1

B

M

)

where E M and B M are predetermined values,

E t is an electric field intensity value obtained in step a/, and

E t-1 is a previously obtained electric field intensity value,

B t is a magnetic field intensity value obtained in step a/, and

B t-1 is a previously obtained magnetic field intensity value.

9. The method according to claim 7 , wherein the ratio determined in step b/ and denoted M t is determined as follows:

M

t

=

max

⁡

(

E

t

E

M

,

B

t

B

M

)

,

and

⁢

⁢

M

t

-

1

=

max

⁡

(

E

t

-

1

E

M

,

B

t

-

1

B

M

)

where E M and B M are predetermined values,

E t is an electric field intensity value measured in step a/,

E t-1 is a previously measured electric field intensity value,

B t is a magnetic field intensity value measured in step a/, and

B t-1 is a previously measured magnetic field intensity value.

10. The method according to claim 7 , further comprising:

determining, for each candidate route of a set of candidate routes, comprising at least one node, a route parameter as a result of an adding operation on metric values of the nodes of said candidate route; and

choosing a route from among the candidate routes for which the route parameter thus determined is the highest.

11. A routing system for a multihop network comprising a plurality of nodes, said system comprising at least one computer configured to:

measure a value of an intensity of an electromagnetic field value over all of a frequency band, the electromagnetic field comprising signals attributable to messages transmitted in the multihop network and signals attributable to an electromagnetic environment of a neighborhood of at least one node originating from outside the multihop network, said neighborhood comprising all nodes only one hop away from the at least one node, the frequency band comprising first frequencies relating to operating frequencies of the multihop network and second frequencies differing from said first frequencies, in a neighborhood of the at least one node,

determine a ratio between said measured value and a predefined maximum electromagnetic field threshold value over said frequency band, and

select a route based on the determined ratio for deciding whether or not said at least one node can be selected as a routing node for at least one message in the multihop network so that the value of the intensity of the electromagnetic field at said at least one node does not exceed said predefined maximum electromagnetic field threshold value.

12. A node for a multihop network comprising a plurality of nodes, said node further comprising at least one computer configured to:

measure a value of an intensity of an electromagnetic field value over all of a frequency band, the electromagnetic field comprising signals attributable to messages transmitted in the multihop network and signals attributable to an electromagnetic environment of a neighborhood of said node originating from outside the multihop network, said neighborhood comprising all nodes only one hop away from said node, the frequency band comprising first frequencies relating to operating frequencies of the multihop network and second frequencies differing from said first frequencies, in said neighborhood of said node, and

determine a ratio between said measured value and a predefined maximum electromagnetic field threshold value over said frequency band, and

select a route based on the determined ratio for deciding whether or not said node can be selected as a routing node for at least one message in the multihop network so that the value of the intensity of the electromagnetic field at said node does not exceed said predefined maximum electromagnetic field threshold value.

13. The method of claim 12 wherein the node is a communication terminal of the multihop network.

14. An article of manufacture including computer readable media with instructions encoded and stored thereon, the stored instructions, when executed causes a processor to perform the steps of:

measuring a value of an intensity of an electromagnetic field value over all of a frequency band, the electromagnetic field comprising signals attributable to messages transmitted in a multihop network and signals attributable to an electromagnetic environment of a neighborhood of at least one node of the multihop network originating from outside the multihop network, said neighborhood comprising all nodes only one hop away from the at least one node, the frequency band comprising first frequencies relating to operating frequencies of the multihop network and second frequencies differing from said first frequencies, in said neighborhood of said at least one node,

determining, using a computer processor, a ratio between said measured value and a predefined maximum electromagnetic field threshold value over said frequency band, and

based on said ratio, selecting said at least one node as a routing node for at least one message in the multihop network so that the value of the intensity of the electromagnetic field at said at least one node does not exceed said predefined maximum electromagnetic field threshold value.

15. A method for routing in a multihop network, comprising, for at least one node of the multihop network, the following steps:

a/ measuring a value of an intensity of an electromagnetic field value in a neighborhood of the at least one node;

b/ determining, using a computer processor, a ratio between said measured value and a predefined electromagnetic field threshold value;

c/ based on said ratio, selecting the at least one node as at least one routing node for at least one message in the multihop network;

estimating a metric value from:

the value of the electromagnetic field measured in step a/;

a previously measured value of the electromagnetic field; and

the predefined electromagnetic field threshold value; and

wherein:

during the step c/, said metric value is used for deciding whether or not said node can be selected as a routing node for at least one message in the multihop network; and

the metric value is estimated as follows:

c

t

=

1

α

·

M

t

+

(

1

-

α

)

·

M

t

-

1

,

 where ct is the metric value,

0<α≦1,

M

t

=

max

⁡

(

E

t

E

M

,

B

t

B

M

)

,

and

⁢

⁢

M

t

-

1

=

max

⁡

(

E

t

-

1

E

M

,

B

t

-

1

B

M

)

where E M and B M are predetermined values,

E t is an electric field value obtained in step a/, and

E t-1 is a previously obtained electric field value,

B t is a magnetic field value obtained in step a/, and

B t-1 is a previously obtained magnetic field value.