Method for communicating in mobile system
The present invention relates to a method for communicating from a primary station to a plurality of secondary station, comprising the step of at the primary station allocating a resource to the secondary stations over the time on the basis of a hash function, wherein the hash function is such that the probability that two secondary stations are allocated common resources in two sub frames substantially equals the product of the probability that the two secondary stations are allocated a common resource in the first subframe and the probability that the two secondary stations are allocated a common resource in the second subframe.
1. A method for communicating between a primary station and a plurality of secondary stations, comprising the steps
(a) each, secondary station is configured to search at least one of a plurality of search spaces, each search space comprising at least one resource set, where at least one resource set might be used to transmit a message to the considered secondary station,
(b) the search space of a given secondary station is determined on the basis of a hash function, wherein the hash function is such that the probability that two secondary stations are configured to have common resources in the search spaces in both of any two subframes substantially equals the product of the probability that the two secondary stations are configured to have a common resource in the first subframe and the probability that the two secondary stations are configured to have a common resource in the second subframe,
(c) at each secondary station, searching in the configured at least one search space for a control message from the primary station addressed to the considered secondary station, and receiving the control message.
2. The method of claim 1 , wherein the hash function results in a substantially uniform probability of configuring each of the available resources to a given secondary station in a given subframe.
3. The method of claim 1 , wherein for two distinct subframes, s and t, the outputs of the hash functions are substantially independent from each other.
4. The method of claim 1 , wherein the hash function has the form:
f ( x,s )=( h ( x )mod g ( s ))mod M,
where x is a parameter of each secondary station, s is the subframe number, h is a function dependent on x, g is a function dependent on s, M is a constant, and mod is the modulo function.
5. The method of claim 4 , wherein h is a constant, multiplier.
6. The method of claim 4 , wherein the parameter of the secondary station is an identifier of the secondary station.
7. The method of claim 4 , wherein for each value of s, g(s) is a prime number.
8. A primary station comprising means for communicating with a plurality of secondary stations, the primary station further comprising
allocating means to allocate at least one resource set to a given secondary station into at least one of a plurality of search spaces, each search space comprising at least one resource set, wherein the search space of the given secondary station is determined on the basis of a hash function, wherein the hash function is such that the probability that two secondary stations are configured to have common resources in the search spaces in both of any two subframes substantially equals the product of the probability that the two secondary stations are configured to have a common resource in the first subframe and the probability that the two secondary stations are configured to have a common resource in the second subframe.
9. A secondary station comprising means for communicating with a primary, the secondary station further comprising
control means configured to search at least one of a plurality of search spaces, each search space comprising at least one resource set, where at least one resource set might be used to transmit a message to the considered secondary station, wherein the search space of the secondary station is determined on the basis of a hash function, wherein the hash function is such that the probability that two secondary stations are configured to have common resources in the search spaces in both of any two subframes substantially equals the product of the probability that the two secondary stations are configured to have a common resource in the first subframe and the probability that the two secondary stations are configured to have a common resource in the second subframe; wherein the control means are configured for searching in the configured at least one search space for a control message from the primary station addressed to the considered secondary station, and receiving the control message.