Method and device for determining time and frequency resources from amongst time and frequency resources of wireless communications network

1. A method for determining time and frequency resources from amongst time and frequency resources of a wireless communications network to be used for performing K individual transmissions over N successive frames in said wireless communications network, the time and frequency resources to be used for performing the K individual transmissions defining respective individual sequences T 1 , . . . , T K over the N successive frames, one time and frequency resource having to be allocated to one of the K individual transmissions per frame,

wherein the time and frequency resources of the wireless communications network are represented by a grid with time resources on one dimension and frequency resources on another dimension, the grid defining possible time and frequency resources sequences such that one transmission among the K individual transmissions being allowed per time resource,

wherein the method is performed by a managing device in charge of allocating time and frequency resources to perform transmissions within the wireless communications network, the method comprising:

computing a figure of merit G(A, T 1 , . . . , T K ) for each possible set of the individual sequences T 1 , . . . , T K over the N successive frames on which respective frequency hopping sequences [A 1 , . . . , A N ]=A apply, the figure of merit G(A, T 1 , . . . , T K ) being representative of transmission robustness to interference and/or noise and/or path loss, and being determined under a constraint such that the frequency hopping sequences A 1 , . . . , A N are defined among a predefined set of allowable frequency hopping sequences which is a subset of all the time and frequency resources sequences made possible by said grid;

selecting the set of individual sequences T 1 , . . . , T K showing the best figure of merit G(A, T 1 , . . . , T K ) according to a predefined criteria relative to the computed figures of merit G(A, T 1 , . . . , T K );

dynamically defining the frequency hopping sequences A 1 , . . . , A N jointly with the set of individual sequences T 1 , . . . , T K ; and

determining signalling information intended to be broadcasted in the wireless communications network to provide information representative of each frequency hopping sequence A 1 , . . . , A N to be applied to the respective N successive frames, said signalling information consisting of a code in a codebook representing an alphabet of said predefined set of allowable frequency hopping sequences, the alphabet having a size limited by a maximum size of the signalling information.

2. The method according to claim 1 , wherein the figure of merit G(A, T 1 , . . . , T K ) is representative of a probability of occurrence of any individual transmission stop and is defined as follows:

G

⁡

(

A

,

T

1

,

…

⁢

,

T

K

)

=

∑

k

=

1

K

⁢

-

log

⁡

(

1

-

P

k

⁡

(

A

,

T

k

)

)

wherein k is an index for parsing the K individual transmissions, P k is a probability that the individual transmission designated by the index k stops in view of the frequency hopping sequences A 1 , . . . , A N and of the set of individual sequences T 1 , . . . , T K ;

and in that the managing device selects the set of individual sequences T 1 , . . . , T K minimizing the figure of merit G(A, T 1 , . . . , T K ).

3. The method according to claim 2 , wherein, allocating time and frequency resources being performed thanks to a search tree approach on the basis of a sliding window having a size equal to N frames, said method relies on a per branch investigation comprising:

selecting a time and frequency resource of the N-th frame of the sliding window for one individual transmission k among the K individual transmissions, according to said predefined set of allowable frequency hopping sequences, wherein selecting said time and frequency resource corresponds to a branch of the search tree;

computing a cumulative distance CD[k] as follows:

CD[k]=CD[k− 1]−log(1 −P k ( A′,T′ k ))

wherein k=1, . . . , K is an index for parsing the K individual transmissions, CD[0] is null, and wherein A′=[A 1 , . . . , A′ N ], with A′ N being the frequency hopping sequence for the N-th frame considered when selecting the time and frequency resource to be tested, and wherein T′ k is the individual sequence for the individual transmission k which is an aggregation of the time and frequency resources allocated to said individual transmission k in the N−1 first frames of the sliding window and of the selected time and frequency resource for the N-th frame of the sliding window;

and in that the method further comprises:

moving forward in the investigation of the branch by considering the individual transmission represented by the index k+1 when the computed cumulative distance CD[k] is lower than, or equals to, a best cumulative distance BD computed during a preceding investigation of another branch in which all K individual transmissions have been considered; and

starting investigating another branch when the computed cumulative distance CD[k] is greater than the best cumulative distance BD.

4. The method according to claim 3 , wherein, when the search tree approach is prematurely interrupted, the frequency hopping sequence A N is defined as the frequency hopping sequence A′ N corresponding to the best cumulative distance BD computed so far and the individual sequences T 1 , . . . , T K are defined as the individual sequences T′ 1 , . . . , T′ K also corresponding to the best cumulative distance BD computed so far.

5. The method according to claim 2 , wherein, the probability for one individual transmission among the K individual transmissions to stop is identical from one time resource to another in the N-th frame of a sliding window having a size equal to N frames, said method comprises:

computing, for each individual transmission k among the K individual transmissions, a partial figure of merit G″ for all possible frequency resources, the partial figure of merit G″ being defined as follows:

G ″( k,F m )=(1 −P k ( F m ))

wherein F m represents a considered frequency resource and P k (F m ) represents a probability that the individual transmission k stops when using the frequency resource F m ;

sorting, for each individual transmission k among the K individual transmissions, the frequency resources in increasing order of the partial figures of merit G″;

selecting, for each individual transmission k among the K individual transmissions, the frequency resource F m appearing first among the sorted frequency resources;

and, for each individual transmission k, the K individual transmissions being considered in decreasing order of the partial figures of merit G″ respectively associated with the frequency resources F m selected for the K individual transmissions:

determining a list of allowable frequency hopping sequences such that said allowable frequency hopping sequences match the frequency resources F m selected for the K individual transmissions, and when the list becomes empty, selecting the frequency resource F m appearing next among the sorted frequency resources F m for the individual transmission k;

and in that the method further comprises:

selecting an allowable frequency hopping sequence from said list of allowable frequency hopping sequences, the selected allowable frequency hopping sequence then being the frequency hopping sequence A N to be applied to the N-th frame of the sliding window; and

allocating time resources to the K individual transmissions, according to the selected allowable frequency hopping sequence.

6. The method according to claim 2 , wherein, the probability for one individual transmission among the K individual transmissions to stop is identical from one time resource to another in the N-th frame of a sliding window having a size equal to N frames, said method comprises:

computing, for each individual transmission k among the K individual transmissions, a partial figure of merit G″ for all possible frequency resources, the partial figure of merit G″ being defined as follows:

G ″( k,F m )=(1 −P k ( F m ))

wherein F m represents a considered frequency resource and P k (F m ) represents a probability that the individual transmission k stops when using the frequency resource F m ;

sorting, for each individual transmission k among the K individual transmissions, the frequency resources in increasing order of the partial figures of merit G″, in order to obtain for each individual transmission k an initial sorted list of the frequency resources;

selecting, for each individual transmission k among the K individual transmissions, the frequency resource F m appearing first among the sorted frequency resources;

sorting the K individual transmissions in decreasing order of the partial figures of merit G″ respectively associated with the frequency resources F m selected for the K individual transmissions;

and, for each individual transmission k, a processing phase of:

determining a list of allowable frequency hopping sequences such that said allowable frequency hopping sequences match the frequency resources F m selected for the K individual transmissions, and when the list becomes empty, modifying the selected frequency resource F m for the individual transmission k by selecting the frequency resource F m appearing next among the sorted frequency resources F m for the individual transmission k;

determining the figure of merit G(A, T 1 , . . . , T K ) for each allowable frequency hopping sequence in the list of allowable frequency hopping sequences;

and, when the selected frequency resource F m has been modified for at least one individual transmission:

re-sorting the K individual transmissions in decreasing order of the partial figures of merit G″ respectively associated with the frequency resources F m selected, or modified when applicable, for the K individual transmissions, in order to obtain a re-sorted list of the K individual transmissions;

reiterating the processing phase on the basis of the initial sorted list of the frequency resources and on the basis of the re-sorted list of the K individual transmissions;

and in that the method further comprises:

selecting the allowable frequency hopping sequence from said list of allowable frequency hopping sequences which shows the best figure of merit G(A, T 1 , . . . , T K ), the selected allowable frequency hopping sequence then being the frequency hopping sequence A N to be applied to the N-th frame of the sliding window; and

allocating time resources to the K individual transmissions, according to the selected allowable frequency hopping sequence.

7. The method according to claim 2 , wherein the signalling information imposes having blocks of consecutive time resources used in conjunction with a same frequency resource, the probability for one individual transmission among the K individual transmissions to stop is identical from one time resource to another in the N-th frame of a sliding window having a size equal to N frames,

wherein a frequency assignment vector FAV is intended to indicate, for each block of consecutive time resources, what frequency resource is associated with, the frequency assignment vector FAV having a quantity of dimensions equal to the quantity of blocks in each frame;

wherein a transmission assignment counter TAC intended to indicate, for each block of consecutive time resources, how many individual transmissions among the K individual transmissions are assigned to the frequency resource associated with said block, the transmission assignment counter TAC having a quantity of dimensions equal to the quantity of blocks in each frame;

and in that said method comprises:

computing, for each individual transmission k among the K individual transmissions, a partial figure of merit G″ for all possible frequency resources, the partial figure of merit G″ being defined as follows:

G ″( k,F m )=(1 −P k ( F m ))

wherein F m represents a considered frequency resource and P k (F m ) represents a probability that the individual transmission k stops when using the frequency resource F m ;

sorting, for each individual transmission k among the K individual transmissions, the frequency resources in increasing order of the partial figures of merit G″;

selecting, for each individual transmission k among the K individual transmissions, the frequency resource F m appearing first among the sorted frequency resources;

sorting the K individual transmissions in decreasing order of the partial figures of merit G″ respectively associated with the frequency resources F m selected for the K individual transmissions;

and, for each individual transmission k, a processing phase of:

checking whether there exists a block i such that FAV[i] equals to the frequency resource F m selected for the individual transmission k;

incrementing by one unit TAC[i], when there exists such a block i and when TAC[i] has not reached a maximum quantity of time resources in the block i;

and, when such a block i doesn't exist, or when such a block i exists and TAC[i] has reached the maximum quantity of time resources in the block i:

checking whether there exists a block j such that FAV[j] is null;

assigning the frequency resource F m selected for the individual transmission k to the block j by assigning said frequency resource F m to FAV[j] and incrementing by one unit TAC[j], when there exists such a block j;

selecting the frequency resource F m appearing next among the sorted frequency resources F m for the individual transmission k, when such a block j doesn't exist and reiterating the processing phase for said individual transmission k;

and in that the method further comprises:

allocating the frequency hopping sequence A N for the N-th frame of the sliding window and the individual sequences T 1 , . . . T K which correspond to the frequency assignment vector FAV.

8. The method according to claim 2 , wherein, considering the N-th frame of a sliding window having a size equal to N frames, said method comprises:

obtaining initial frequency hopping sequences [A 1 , . . . , A N−1 , A′ N ]=A′ and a set of initial individual sequences T′ 1 , . . . , T′ K , for the respective K individual transmissions, over the sliding window, wherein the initial frequency hopping sequences A 1 , . . . , A N−1 result from time and frequency resources allocation for the N−1 first frames of the sliding window and wherein the time and frequency resources of the individual sequences T′ 1 , . . . , T′ K for the N−1 first frames of the sliding window result from the time and frequency resources allocation for said N−1 first frames;

computing a partial figure of merit G o for each individual transmission k of the K individual transmissions, as follows:

G o ( k,TS m ,F m )=(1 −P k ( TS m ,F m ))

wherein F m represents the frequency resource that has been attributed to the individual transmission k for the N-th frame in the initial individual sequences T′ k , TS m represents the time resource that has been attributed to the individual transmission k for the N-th frame in the initial individual sequences T′ k and P k (TS m , F m ) represents a probability that the individual transmission k stops when using the time and frequency resource (TS m , F m );

determining the figure of merit G(A′, T′ 1 , . . . , T′ K ) according to the initial frequency hopping sequences [A 1 , . . . , A N−1 , A′ N ]=A′ and the set of initial individual sequences T′ 1 , . . . , T′ K ;

and, for each individual transmission k among the K individual transmissions, considered for each allowable frequency hopping sequence for the N-th frame of the sliding window, in decreasing order of the partial figures of merit G o :

determining possible permutations, according to the frequency hopping sequence A′ N , between the time and frequency resource attributed to the selected individual transmission for the N-th frame in the initial individual sequences T′ k and another time and frequency resource attributed to another individual transmission for the N-th frame;

determining the figure of merit G for each determined possible permutation;

and in that the method further comprises, once a predefined time period has elapsed:

allocating the frequency hopping sequence A N for the N-th frame of the sliding window and the individual sequences T 1 , . . . , T K which led to the best figure of merit G according to said predefined criteria.

9. The method according to claim 1 , wherein the figure of merit G(A, T 1 , . . . , T K ) is representative of a probability of non-occurrence of any individual transmission stop and is defined as follows:

G

⁡

(

A

,

T

1

,

…

⁢

,

T

K

)

=

∏

k

=

1

K

⁢

(

1

-

P

k

⁡

(

A

,

T

k

)

)

wherein k is an index for parsing the K individual transmissions, P k is a probability that the individual transmission designated by the index k stops in view of the frequency hopping sequences A 1 , . . . , A N and of the set of individual sequences T 1 , . . . , T K ;

and in that the managing device selects the set of individual sequences T 1 , . . . , T K maximizing the figure of merit G(A, T 1 , . . . , T K ).

10. A method for determining time and frequency resources from amongst time and frequency resources of a wireless communications network to be used for performing K individual transmissions over N successive frames in said wireless communications network, the time and frequency resources to be used for performing the K individual transmissions defining respective individual sequences T 1 , . . . , T K over the N successive frames, one time and frequency resource having to be allocated to one of the K individual transmissions per frame,

wherein the time and frequency resources of the wireless communications network are represented by a grid with time resources on one dimension and frequency resources on another dimension, the grid defining possible time and frequency resources sequences such that one transmission among the K individual transmissions being allowed per time resource,

wherein the method is performed by a managing device in charge of allocating time and frequency resources to perform transmissions within the wireless communications network, the method comprising:

computing a figure of merit G(A, T 1 , . . . , T K ) for each possible set of the individual sequences T 1 , . . . , T K over the N successive frames on which respective frequency hopping sequences [A 1 , . . . , A N ]=A apply, the figure of merit G(A, T 1 , . . . , T K ) being representative of transmission robustness to interference and/or noise and/or path loss, and being determined under a constraint such that the frequency hopping sequences A 1 , . . . , A N are defined among a predefined set of allowable frequency hopping sequences which is a subset of all the time and frequency resources sequences made possible by said grid:

selecting the set of individual sequences T 1 , . . . , T K showing the best figure of merit G(A, T 1 , . . . , T K ) according to a predefined criteria relative to the computed figures of merit G(A, T 1 , . . . , T K );

wherein the figure of merit G(A, T 1 , . . . , T K ) is representative of a probability of non-occurrence of any individual transmission stop and is defined as follows:

G

⁡

(

A

,

T

1

,

…

⁢

,

T

K

)

=

∏

k

=

1

K

⁢

(

1

-

P

k

⁡

(

A

,

T

k

)

)

wherein k is an index for parsing the K individual transmissions, P k is a probability that the individual transmission designated by the index k stops in view of the frequency hopping sequences A 1 , . . . , A N and of the set of individual sequences T 1 , . . . , T K ;

and in that the managing device selects the set of individual sequences T 1 , . . . , T K maximizing the figure of merit G(A, T 1 , . . . , T K ).

11. A method for determining time and frequency resources from amongst time and frequency resources of a wireless communications network to be used for performing K individual transmissions over N successive frames in said wireless communications network, the time and frequency resources to be used for performing the K individual transmissions defining respective individual sequences T 1 , . . . , T K over the N successive frames, one time and frequency resource having to be allocated to one of the K individual transmissions per frame,

wherein the time and frequency resources of the wireless communications network are represented by a grid with time resources on one dimension and frequency resources on another dimension, the grid defining possible time and frequency resources sequences such that one transmission among the K individual transmissions being allowed per time resource,

wherein the method is performed by a managing device in charge of allocating time and frequency resources to perform transmissions within the wireless communications network, the method comprising:

computing a figure of merit G(A, T 1 , . . . , T K ) for each possible set of the individual sequences T 1 , . . . , T K over the N successive frames on which respective frequency hopping sequences [A 1 , . . . , A N ]=A apply, the figure of merit G(A, T 1 , . . . , T K ) being representative of transmission robustness to interference and/or noise and/or path loss, and being determined under a constraint such that the frequency hopping sequences A 1 , . . . , A N are defined among a predefined set of allowable frequency hopping sequences which is a subset of all the time and frequency resources sequences made possible by said grid;

selecting the set of individual sequences T 1 , . . . , T K showing the best figure of merit G(A, T 1 , . . . , T K ) according to a predefined criteria relative to the computed figures of merit G(A, T 1 , . . . , T K );

wherein the frequency hopping sequences A 1 , . . . , A N are statically defined.

12. A device for determining time and frequency resources from amongst time and frequency resources of a wireless communications network to be used for performing K individual transmissions over N successive frames in said wireless communications network, the time and frequency resources to be used for performing the K individual transmissions defining respective individual sequences T 1 , . . . , T K over the N successive frames, one time and frequency resource having to be allocated to one of the K individual transmissions per frame,

wherein the time and frequency resources of the wireless communications network are represented by a grid with time resources on one dimension and frequency resources on another dimension, the grid defining possible time and frequency resources sequences such that one transmission among the K individual transmissions being allowed per time resource,

the device comprising:

processing circuitry

to compute a figure of merit G(A, T 1 , . . . , T K ) for each possible set of the individual sequences T 1 , . . . , T K over the N successive frames on which respective frequency hopping sequences [A 1 , . . . , A N ]=A apply, the figure of merit G(A, T 1 , . . . , T K ) being representative of transmission robustness to interference and/or noise and/or path loss, and being determined under a constraint such that the frequency hopping sequences A 1 , . . . , A N are defined among a predefined set of allowable frequency hopping sequences which is a subset of all the time and frequency resources sequences made possible by said grid;

to select the set of individual sequences T 1 , . . . , T K showing the best figure of merit G(A, T 1 , . . . , T K ) according to a predefined criteria relative to the computed figures of merit G(A, T 1 , . . . , T K );

dynamically defining the frequency hopping sequences A 1 , . . . , A N jointly with the set of individual sequences T 1 , . . . , T K ; and

determining signalling information intended to be broadcasted in the wireless communications network to provide information representative of each frequency hopping sequence A 1 , . . . , A N to be applied to the respective N successive frames, said signalling information consisting of a code in a codebook representing an alphabet of said predefined set of allowable frequency hopping sequences, the alphabet having a size limited by a maximum size of the signalling information.