Method and apparatus relating to spectrum sensing
The invention presents methods and corresponding devices for improving cooperative spectrum initiating sensing. A device ( 61;61.1 ) first receives an invitation ( 17;35 ) to participate in cooperative spectrum sensing. The device performs an autonomous decision ( 19 ) on whether or not to participate in the cooperative spectrum sensing in response to the invitation. If it is determined to participate in the cooperative spectrum sensing to which the invitation relates, spectrum sensing is then performed ( 21;45 ). With the invention, sensor selection becomes “distributed”, i.e. it is up to the device itself to decide on participation in the cooperative sensing, rather than having, for example, a central entity determining what devices should act as sensors in the cooperative spectrum sensing. One advantage is that the amount of signalling required for sensor selection can be kept at a minimum, thereby saving communication resources.
1. A method for operating a device, the method comprising:
receiving an invitation to participate in cooperative spectrum sensing;
in response to the invitation, determining autonomously based on a random procedure whether or not to participate in the cooperative spectrum sensing; and
performing spectrum sensing in response to the determination to participate in the cooperative spectrum sensing,
wherein the random procedure causes the device to have a probability of participating in cooperative spectrum sensing that is responsive to participation probability.
2. The method according to claim 1 , further comprising obtaining the specified participation probability, wherein
the random procedure comprises:
generating a random number in accordance with a predetermined probability distribution;
comparing the random number with the obtained participation probability; and
determining whether or not to participate in the cooperative spectrum sensing based on the step of comparing.
3. The method according to claim 2 , wherein:
the predetermined probability distribution is a uniform distribution on the interval from zero to one; and
the step of comparing involves checking whether the generated random number is less than the obtained participation probability.
4. The method according to claim 2 , wherein the specified participation probability is obtained by evaluating a mathematically defined probability function.
5. The method according to claim 4 , further comprising selecting the probability function.
6. The method according to claim 5 , wherein the step of selecting comprises selecting the probability function from a predetermined collection of probability functions.
7. The method according to claim 5 , wherein the step of selecting comprises selecting the probability function at least in part based on information from an entity that transmitted the invitation to participate in the cooperative spectrum sensing.
8. The method according to claim 5 , wherein the step of selecting comprises selecting the probability function based on a need parameter that indicates a need for participation in cooperative spectrum sensing relative to one or more previous occasions of cooperative spectrum sensing.
9. The method according to claim 5 , wherein the step of selecting comprises selecting the probability function based on a desired number of participants in the cooperative spectrum sensing.
10. The method according to claim 9 , wherein the step of selecting comprises selecting the probability function based on a constraint requiring that a statistically expected number of participants in the cooperative spectrum sensing should equal the desired number of participants in the cooperative spectrum sensing.
11. The method according to claim 9 , wherein the step of selecting comprises selecting the probability function based on a constraint requiring that a probability that a number of participants in the cooperative spectrum sensing is greater than or equal to the desired number of participants in the cooperative spectrum sensing fulfils a predetermined relationship with respect to a predetermined probability threshold value.
12. The method according to claim 1 , further comprising reporting information relating to a result of having performed the cooperative spectrum sensing.
13. A device comprising:
a communication unit configured for receiving an invitation to participate in cooperative spectrum sensing;
a decision unit configured to take an autonomous decision based on a random procedure on whether or not to participate in the spectrum sensing in response to the invitation; and
a sensing unit configured to perform the cooperative spectrum sensing in response to the decision being made to participate in the cooperative spectrum sensing has been taken,
wherein the decision unit is configured to perform the random procedure to cause the device to have a probability of participating in the cooperative spectrum sensing that is responsive to a specified participation probability.
14. The device according to claim 13 , wherein:
the decision unit is configured to obtain the specified participation probability; and wherein
the decision unit is configured responsive to the random procedure to:
generate a random number in accordance with a predetermined probability distribution;
compare the random number with the obtained participation probability; and
determine whether or not to participate in the cooperative spectrum sensing based on the comparison between the random number and the participation probability.
15. The device according to claim 14 , wherein:
the predetermined probability distribution is a uniform distribution on the interval from zero to one; and
the decision unit is configured to check whether the generated random number is less than the obtained participation probability.
16. The device according to claim 14 , wherein the decision unit is configured to obtain the specified participation probability by evaluation of a mathematically defined probability function.
17. The device according to claim 13 , wherein the communication unit is configured to transmit a report containing information relating to a result of having performed the cooperative spectrum sensing.