FR3081668A1 - WIRELESS COMMUNICATION DEVICES, SYSTEMS, AND METHODS FOR DECODING DATA PACKETS FOR ESTABLISHING CRITICAL LATENCY SERVICES - Google Patents

Abstract

Provided are wireless communication devices (110, 120), systems (100) and methods (200, 300) for decoding data packets for establishing latency critical services. The general principle of the invention is based on two aspects. First, each mobile station transmits multiple copies of the same data packet over a contention-based multiple access uplink channel without prior resource reservation. Then, for a given mobile station, copies of a data packet are transmitted over identified channel resources in a known sequence of the base station. Thus, for each mobile station, the base station knows which resources of the channel to look for to make its decoding easier.

Description

Title: Wireless communication devices, systems and methods for decoding data packets for establishing latency critical services

Description

Technical Field [001] The present invention relates to the field of decoding data packets transmitted over resources of a multiple access uplink radio channel based on contention without prior reservation of resources. More specifically, it relates to wireless communication devices, systems and methods for establishing latency critical services.

PRIOR ART The IMT-2020 standard defines the structure of the fifth generation of mobile networks.

This standard is intended to revolve around several major uses including critical latency services such as so-called ultra-reliable and low latency communications (URLLC for "ultra-Reliable Low Latency Communication" in English). Critical latency services include all applications requiring extremely high reactivity as well as a very strong guarantee of packet transmission. These needs are mainly found in transport (for example, autonomous vehicles, drones), in medicine (for example, telesurgery via medical robots) and, in general, in the fields of industrial digitization.

In practice, a latency of only 1 ms may be required for critical latency services. For comparison, the latency on a fourth generation mobile network is around 50 to 100 ms. As a reminder, latency corresponds to the delay time which can be attributed to the cellular network itself between two sources.

It is envisaged that such critical latency services established between a base station and many mobile stations can be implemented via a multiple access radio channel based on contention without prior reservation of the channel resources.

In this case, the base station must be able to decode the data packets associated with these numerous mobile stations, while respecting the latency constraints of the critical latency services. However, to date, the latency constraints of critical latency services do not allow a large number of mobile stations to be supported. Indeed, some current systems require supporting a very low load, for example, by limiting the number of mobile stations or by limiting their transmission rate. On the other hand, other systems are inefficient, in that they require the use of a very large number of resources.

-2 [006] Thus, it is advisable to propose a solution making it possible to facilitate decoding by the base station within the framework of the establishment of critical latency services, while supporting a high number of mobile stations.

Summary of the invention [007] The present invention therefore aims to solve the aforementioned problem.

For this, in a first aspect of the invention, there is proposed a wireless communication system comprising at least a first base station. The system also includes a plurality of mobile stations, each mobile station being configured to establish a critical latency service with the first base station. Finally, the system also includes a multiple access uplink channel based on contention without prior reservation of resources, the uplink channel comprising a plurality of resources. According to the invention, the communication system is configured so that each mobile station is associated with its own sequence, each sequence defining part of the plurality of resources of the uplink channel. Furthermore, each mobile station is further configured to transmit to the first base station, a plurality of copies of a data packet according to the associated sequence. Finally, the first base station is configured to decode, for each mobile station, at least one resource as a function of the associated sequence.

An advantage of the invention is that thanks to the knowledge of the resources in which each mobile station will transmit, it is possible to facilitate the decoding operation of the base station, while respecting the constraints of latency of critical latency services. In addition, the invention makes it possible to comply with the latency constraints of the critical latency services in systems where the load is high.

According to a first implementation of the first aspect of the invention, each mobile station comprises a first memory storing the associated sequence, the associated sequence being predetermined. In addition, the first base station includes a second memory storing the sequence associated with each mobile station.

With such an implementation, it is possible to directly use all of the mobile stations and a first base station when the system is put into service.

According to a second implementation of the first aspect of the invention, the first base station is, moreover, configured to determine, for each mobile station, the associated sequence, and to transmit, to each mobile station, the associated sequence. Furthermore, each mobile station is further configured to receive, from the first base station, the associated sequence.

With such an implementation, it is possible to dynamically define the sequences according to the environment of the system.

-3 In a first example of the second implementation of the first aspect of the invention, the first base station is also configured to randomly determine the sequence associated with each mobile station.

With such an implementation, it is possible to increase the probability of decoding the first base station.

In a second example of the second implementation of the first aspect of the invention, the first base station is configured to determine the sequence associated with each mobile station according to a sequence determination method meeting at least one condition in which a single resource is common between two sequences.

Thus, compliance with this condition to determine the sequences specific to the mobile stations, makes it possible to minimize the probability that the emissions of the mobile stations according to their respective sequence collide.

In a third example of the second implementation of the first aspect of the invention, the system further comprises a second base station of the same type as the first base station. Furthermore, the system is further configured so that, when transferring the uplink channel between the first base station and the second base station, for at least one mobile station, the first communication station the base is further configured to transmit the sequence associated with the mobile station to the second base station.

With such an implementation, it is possible, for a mobile station, to use the same sequence after a cell change in the system.

According to a third implementation of the first aspect of the invention, the system is further configured so that the first base station is further configured to be synchronized with the plurality of mobile stations. Furthermore, the plurality of mobile stations is further configured to define a predetermined cyclic transmission time.

With such an implementation, it is possible to plan the decoding at the end of each transmission cycle.

According to a fourth implementation of the first aspect of the invention, each mobile station is, moreover, configured to define an acyclic transmission time. Furthermore, the system is further configured so that each mobile station is further configured to perform the transmission of the plurality of copies of the data packet as part of a plurality of time intervals having a predetermined duration. Thereafter, the first base station is further configured to store the data packets received on all of the resources of the uplink channel, and to perform decoding, in a current time interval, from the data packets received during the predetermined period preceding the current time interval.

- 4 With such an implementation, it is possible to take into account unordered transmissions from mobile stations.

According to a fifth implementation of the first aspect of the invention, the system is further configured so that resources of the uplink channel are reserved. Furthermore, the first base station is further configured to receive, from the plurality of mobile stations, on the reserved resources of the uplink channel, at least one transmission code, and to determine, from the received transmission code, the mobile station for which subsequent transmission is planned. Thereafter, each mobile station is further configured to transmit to the first base station, on the reserved resources of the uplink channel, before the transmission of the plurality of copies of the data packet, the transmission code received .

With such an implementation, it is possible to prevent the first base station from the occurrence of future transmissions.

According to a sixth implementation of the first aspect of the invention, the system is further configured so that the first base station is further configured to decode, for each mobile station, a combination of all or part of the resources of the associated sequence.

With such an implementation, it is possible to use several copies of the same data packet to successfully decode it.

According to a sixth implementation of the first aspect of the invention, the system is further configured so that the first base station is further configured to apply an interference cancellation technique successive as a function of the associated sequence, after decoding.

With such an implementation, it is possible to subtract from the colliding resources the data packets which have been successfully decoded.

In a second aspect of the invention, a base station is proposed for establishing a critical latency service with a plurality of mobile stations, each mobile station being configured to communicate with the base station via a multiple access uplink channel based on contention without prior resource reservation, the uplink channel comprising a plurality of resources. According to the invention, the base station comprises a calculation unit for decoding, for each mobile station, at least one resource as a function of an associated own sequence. In particular, the associated sequence defines, part of the plurality of uplink channel resources, and the resources on which each mobile station is further configured to transmit to the base station, a plurality of copies of an data packet.

According to a first implementation of the second aspect of the invention, the base station further comprises a memory storing the sequence associated with each mobile station.

According to a second implementation of the second aspect of the invention, the calculation unit is, moreover, configured to determine, for each mobile station, the associated sequence, and the base station further comprises , a transmission unit for transmitting the associated sequence to each mobile station.

According to a particular mode of the second aspect of the invention, the calculation unit is, moreover, configured to determine the sequence associated with each mobile station according to a sequence determination method respecting at least one condition in which a only resource is common between two sequences.

In a third aspect of the invention, a mobile station is proposed for establishing a critical latency service with a base station via a multiple access uplink channel based on contention without prior reservation resource, the uplink channel comprising a plurality of resources. According to the invention, the mobile station comprises a transmission unit for transmitting to the base station, a plurality of copies of a data packet according to an associated own sequence, the associated sequence defining part of the plurality of uplink channel resources.

In a fourth aspect of the invention, there is proposed a wireless communication method, implemented by a base station, for establishing a critical latency service with a plurality of mobile stations, each the mobile station being configured to communicate with the base station via a contention-based multiple access uplink channel without prior reservation of resources, the uplink channel comprising a plurality of resources. According to the invention, the following steps are implemented:

- associate each mobile station with its own sequence defining part of the plurality of uplink channel resources,

- receive, from each mobile station, a plurality of copies of a data packet according to the associated sequence, and

- decode, for each mobile station, at least one resource according to the associated sequence.

According to a particular embodiment, a sequence specific to each mobile station is determined according to a method for determining sequences respecting at least one condition in which a single resource is common between two sequences.

Thus, the sequences are determined so that the probability that the emissions from mobile stations according to their respective sequence collide is minimized.

In an exemplary embodiment of such a sequence determination, the sequence determination method determines a number n1 * n2 of sequences by the combination of a first set of n1 sequences comprising s resources chosen from a number m = n / k of resources and respecting the condition in which a single resource is common between two sequences, to a second set of n2 = k * k sequences comprising s resources among a number k * s of resources for composing

- 6 of the sequences comprising s resources among n resources, where k is a prime number greater than or equal to s-1.

This method makes it possible to obtain, in a simple manner, a large number of proper sequences for a large number of resources and respecting the condition in which a single resource is common between two sequences.

Brief description of the drawings Other characteristics and advantages of the invention will be better understood on reading the description which follows and with reference to the accompanying drawings, given by way of illustration and in no way limiting.

Figure 1 shows a system according to the invention.

Figure 2 shows an implementation of the uplink channel resources of Figure 1, and four resource sequences.

FIG. 3 represents a flow chart of a method according to the invention.

Figures 4a, 4b and 4c illustrate an example of determination of proper sequences according to a method of determining sequences of an embodiment of the invention [0045] For reasons of clarity, the elements shown are not at scale with respect to each other, unless otherwise stated.

Description of the embodiments The general principle of the invention is based on two aspects. First, each mobile station transmits multiple copies of the same data packet over a contention-based multiple access uplink channel without prior resource reservation. Then, for a given mobile station, the copies of a data packet are transmitted over identified resources of the channel, according to a sequence known to the base station. Thus, for each mobile station, the base station knows in which resources of the channel to look in order to carry out its decoding in an easier manner.

In the description, the invention will be described with reference to URLLC communications ("ultra-Reliable Low Latency Communication" in English) as envisaged in the fifth generation of mobile networks. However, the invention is also applicable more generally to critical latency services.

Figure 1 illustrates a wireless communication system 100 according to the invention. The system 100 comprises a base station 110, several mobile stations 120 and an uplink radio channel 130 with multiple access based on contention without prior reservation of resources. In a particular implementation, the system 100 includes several base stations 110.

In the example of FIG. 1, the base station 110 comprises at least one transmission unit 111 and a reception unit 112. In one example, the transmission unit 111 is a radio transmitter and the reception unit 112 is a radio receiver.

- 7 In the example of Figure 1, each mobile station 120 comprises at least one transmission unit 121 and a reception unit 122. In one example, the transmission unit 121 is a radio transmitter and l the receiving unit 122 is a radio receiver.

In addition, each mobile station 120 is configured to establish a critical latency service with the base station 110.

In the example of Figure 1, the uplink channel 130 includes a plurality of radio resources. In one example, the resources of the channel are two-dimensional time-frequency resources comprising a plurality of symbol duration in a time dimension and a plurality of subcarriers in a frequency dimension. In another example, the resources are carrier frequencies, time intervals or orthogonal codes.

In Figure 1, when the system 100 is in operation, the latter is configured so that each mobile station 120 is associated with a resource sequence of the uplink channel 130, which is specific to it. In addition, each sequence defines a part of the plurality of resources of the uplink channel 130. The specific nature of the sequence of resources associated with a mobile station 120 implies that each mobile station 120 is associated with a particular sequence of resources. In addition, it also covers the fact that several mobile stations 120 are associated with the same particular sequence of resources.

FIG. 2 illustrates an example of resources 200 of the uplink channel 130 and four sequences of resources S1, S2, S3 and S4, defined according to the invention. The sequence S1 comprises the resources 0, 3, 5, 6, 10 and 13. The sequence S2 comprises the resources 1, 3, 8, 10, 12, 15 and 22. The sequence S3 comprises the resources 6, 8 and 12. Finally, the sequence S4 comprises the resources 12, 15, 18, 21 and 23. In the example of FIG. 2, it is noted that the sequences S1, S2, S3 and S4 do not include the same number of resources. However, in a particular implementation, all or part of the sequences includes the same number of resources. Furthermore, in the example of FIG. 2, it is noted that certain resources are in common between the sequences. This is, for example, resource 6 which is found in sequences S1 and S3, or even resource 15 which is found in sequences S2 and S4. However, in a particular implementation, when the number of resources allows, each sequence defines a unique list of resources.

In a first particular implementation of the invention, the sequence associated with each mobile station 120 is predetermined. For example, the sequence associated with each mobile station 120 is predetermined during the commissioning of the mobile station 120 and / or the base station 110. In this first implementation, each mobile station 120 includes a first memory 123 storing the associated sequence. In addition, the base station 110 comprises a second memory 113 storing the sequence associated with each mobile station 120.

-8 [0056] [0057] [0058] [0059] [0060]

In a second particular implementation of the invention, the sequence associated with each mobile station 120 is determined by the base station 110. In this implementation, the base station 110 comprises a calculation unit 114 for determining, for each mobile station 120, the associated sequence. In one example, the computing unit 114 is a processor. In addition, the transmission unit 111 of the base station 110 is configured to transmit, to each mobile station 120, the associated sequence. Furthermore, the reception unit 122 of each mobile station 120 is, moreover, configured to receive, from the base station 110, the associated sequence.

In an example of the second particular implementation, the calculation unit 114 of the base station 110 is, moreover, configured to randomly determine the sequence associated with each mobile station 120.

In another example of the second implementation, the calculation unit 114 of the base station 110 is also configured to determine the sequence associated with each mobile station 120 according to a sequence determination method respecting at least one condition in which a single resource is common between two sequences. Such a sequence determination method is described later with reference to FIGS. 4a to 4c.

In another example of the second particular implementation, we consider the case where the system 100 is a cellular communication system, in which a process is provided whereby a mobile station 120 can change radio channel maintaining a call in progress. Such a channel transfer process is commonly called "handover" in English. In this case, the system 100 comprises at least two base stations 110 which are interconnected, for example, via a network interface of the system 100. Furthermore, the system 100 is further configured so that, during a transfer of the uplink channel 130 between a first base station 110 and a second base station 110, for at least one mobile station 120, the first base station 110 is, in addition configured, to transmit to the second base station 110, the sequence associated with mobile station 120.

Returning to FIG. 1, each mobile station 120 is, moreover, configured to transmit to the base station 110, a plurality of copies of a data packet according to the associated sequence. In an example, with reference to FIG. 2, a mobile station 120 associated with the sequence S2 will transmit at least two copies of a data packet on at least two resources among the resources 1,3, 8, 10, 12, 15 and 22. In an implementation of this example, the mobile station 120 associated with the sequence S2 will transmit seven copies of a data packet using the set of resources 1,3, 8, 10, 12, 15 and 22 .

In FIG. 1, the base station 110 is configured to decode, for each mobile station 120, at least one resource 200 as a function of the associated sequence. In the example mentioned above, the base station 110 knows that a mobile station 120 is

-9 [0062] [0064] [0065] associated with the sequence S2, so that the base station 110 will decode at least one of the resources 1, 3, 8, 10, 12, 15 and 22. Thus, for the mobile station 120 of the example, it will not be necessary to decode all of the resources 200 of the uplink channel 130.

In a particular implementation, the base station 110 is, moreover, configured to decode, for each mobile station 120, a combination of all or part of the resources 200 of the associated sequence. This implementation may be necessary when the sequence resources associated with a mobile station 120 are in collisions with data packets from other mobile stations 120. This means that it has not been possible to decode the data packet from one of the resources mentioned in the sequence associated with a mobile station 120.

In another particular implementation, the base station 110 is also configured to apply a successive interference cancellation technique as a function of the associated sequence, after decoding. Thus, when a data packet from a mobile station 120 is decoded, the copies of the data packet are subtracted from the resources in which they were transmitted. It is then possible to unblock cases of collisions on one or more of these resources.

In the invention, it is also envisaged the cases where the mobile stations 120 transmit the copies of data packets in a cyclic transmission mode or in an acyclic transmission mode.

In the case where the transmission is cyclic, the base station 110 is further configured to be synchronized with the mobile stations 120. In one example, the base station 110 and the mobile stations 120 are synchronized to a clock of the system 100. Furthermore, the mobile stations 120 are further configured to define a predetermined cyclic transmission time. Thus, at each transmission cycle, the mobile stations 120 are authorized to transmit the copies of their data packets. In one example, the predetermined cyclic transmission time corresponds to a plurality of unit transmission times, the duration of a unit time being chosen from 0.125 ms; 0.25 ms; 0.5 ms or 1 ms. However, other values can be considered, as long as they are consistent with establishing critical latency services. In the case where the transmission is acyclic, each mobile station 120 is, moreover, configured to carry out the transmission of the plurality of copies of the data packet within the framework of a plurality of time intervals (TTI for " transmission time interval "in English) with a predetermined duration. In one example, the duration of the plurality of time intervals is chosen from 2 to 5 TTI. However, other values can be considered, as long as they are consistent with establishing critical latency services. Furthermore, the base station 110 is further configured to store the data packets received on all of the resources of the uplink channel 130. Finally, the base station 110 is further configured to perform the decoding, in a current time interval, from the received data packets

- 10 [0067] [0068] [0069] [0070] [0071] [0072] during the predetermined duration preceding the current time interval. Thus, it is possible, thanks to a sliding decoding mechanism, to take into account the acyclic transmissions of the mobile stations 120.

The invention also provides an additional mechanism to facilitate decoding, in the cyclic transmission mode as in the acyclic transmission mode.

In the mechanism according to the invention, each mobile station 120 uses a unique transmission code which identifies a subsequent transmission from the mobile station 120. The unique transmission code is transmitted to the base station on reserved resources of the uplink channel 130. To implement this mechanism, each mobile station 120 is, moreover, configured to transmit to the base station 110, on the reserved resources of the uplink channel 130, before the transmission of the copies of the data packet, the transmission code received. Furthermore, the base station 110 is further configured to receive, from the mobile stations 120, on the reserved resources of the uplink channel 130, at least one transmission code. Finally, the base station 110 is further configured to determine, from the received transmission code, the mobile station 120 for which subsequent transmission is planned. Thereafter, the decoding is carried out as mentioned above. In a first particular implementation of the mechanism, the transmission code associated with each mobile station 120 is predetermined. For example, the transmission code associated with each mobile station 120 is predetermined during commissioning (“commissioning” in English) of the mobile station 120 and the base station 110. In this first implementation, the first memory 123 of each mobile station 120 stores the associated transmission code. In addition, the second memory 113 of the base station 110 stores the transmission code associated with each mobile station 120.

In a second particular implementation of the mechanism, the transmission code associated with each mobile station 120 is determined by the base station 110. In this implementation, the calculation unit 114 of the base station 110 is configured to determining, for each mobile station 120, the associated transmission code. In addition, the transmission unit 111 of the base station 110 is configured to transmit, to each mobile station 120, the associated transmission code. Furthermore, the reception unit 122 of each mobile station 120 is, moreover, configured to receive, from the base station 110, the associated transmission code.

FIG. 3 illustrates a method 300 of wireless communication, according to the invention.

The method 300 consists first of all in providing at step 310, at least one base station 110.

Next, in step 320, a plurality of mobile stations 120 are provided, in which each mobile station 120 is configured to establish a critical service in latency with the first base station.

- 11 [0074] [0075] [0076] [0077] [0078] [0079] [0080] [0081] [0082]

Furthermore, in step 330, an uplink channel 130 with multiple access based on contention without prior reservation of resources is provided, the uplink channel 130 comprising a plurality of resources 200.

Thereafter, in step 340, each mobile station is associated with its own sequence defining part of the plurality of resources of the uplink channel, as mentioned above.

Then, in step 350, a plurality of copies of a data packet are transmitted by each mobile station to the base station according to the associated sequence, as mentioned above. The base station therefore receives from each mobile station, a plurality of copies of a data packet according to their associated sequence.

Finally, in step 360, at least one resource is decoded by the base station for each mobile station as a function of the associated sequence.

FIGS. 4a, 4b and 4c illustrate the steps of an exemplary embodiment of a method for determining sequences specific to each mobile station. In one embodiment of the invention, this method is implemented by the base station to determine its own sequence per mobile station in order to transmit it to them.

In another embodiment, these sequences are predetermined using this method, and are stored in their respective mobile station and in the base station.

This sequence determination method determines a number n1 * n2 of sequences by the combination of a first set of n1 sequences comprising s resources chosen from a number m = n / k of resources and respecting the condition in which a single resource is common. between two sequences, to a second set of n2 = k * k sequences comprising s resources among a number k * s of resources to compose sequences comprising s resources among n resources, where k is a prime number greater than or equal to s-1 .

Thus, in a first step, a set P1 = {sO, ..., sn1 -1} of n1 sequences can be defined by exhaustively choosing sequences of length s chosen (s being the number of resources per sequence) respecting at least one condition in which a single resource is common between two sequences. This set P1 can be formed from a small number of resources. This sequence P1 can also be determined by proceeding in the same way as to construct the set of sequences P2 as explained below.

In the example illustrated in FIG. 4a, 7 sequences s0 to s6 (SQs) are defined on a number of resources aO to a6 (RSs) equal to 7. We choose a sequence length equal to 3 (s = 3) in this example of realization. These sequences s0 to s6 of the set P1 are chosen so that a single resource is common between two sequences of P1.

The “1s” represented in the table of FIG. 4a represent the positions of the resources of each sequence. For sO for example, we see vertically that the 3

- 12 resources associated with the sequence are the resources aO, a1 and a2. For s3, the associated resources are a1, a3 and a5.

In a second step, a prime number k is chosen, greater than or equal to s-1 to define a second set P2 of resources respecting the condition in which a single resource is common between two sequences. For this set of sequences P2 = {t0, ..., tn2-1], the number of sequences of length s is equal to n2 = k * k. The s resources of each sequence are chosen from k2 = k * s resources from n resources.

The n2 P2 sequences are determined as follows:

The k * s resources are grouped into s groups, denoted gO to gs-1 of k resources. Any sequence of P2 is such that its l-th element is chosen from the group gl (with I going from 0 to s-1). A sequence of P2 therefore occupies one and only one resource in each of the groups of k resources. In addition, a P2 sequence must also respect the condition in which a single resource is common between two sequences. A sequence tj = (bjO, ..., bjs-1) has its first element in group 0 in position bjO between 0 and k-1, its next element in group 1 in position bj1, between k and 2 * k -1, etc ..., its l-th element in position bjl between l * k and l * k + l-1.

The k * k P2 sequences can be composed as follows.

Let the j-th sequence of P2 with j = x * k + y and 0 <= j <= k * k-1 and where x and y take their values between 0 and k-1. The lth element of the jth sequence of P2, I between 0 and s-1, is equal to:

x (taking the values from 0 to k-1), if l = 0 k + y (y taking the values from 0 to k-1), if 1 = 1 l * k + ((x + (l-1) * y ) modulo k), for I between 2 and s-1 where h modulo k is the remainder of the Euclidean division of h by k. k being a prime number, the sequences thus defined have one and only one resource in common.

Indeed, the following demonstration shows that if two elements are equal between two sequences, it means that they are the same sequence. We can therefore have only one common element between two sequences.

To demonstrate this, we verify that if two distinct elements, 11 and I2, are equal between two sequences j and j ', defined respectively by x and y, x' and y ', then these two sequences are equal, that is that is, x = x 'and y = y'. Recall that (a modulo k) = (b modulo k) if and only if k divides a-b. Furthermore since k is prime then k divides a * b if and only if k divides a or k divides b. Finally if k divides a with the absolute value of a less than k, then a = 0.

We consider four cases:

- 11 = 0 and 12 = 1:

in this case x = x ’and k + y = k + y’ so y = y ’and therefore j = j’.

- H = 0etl2> 1

- 13 in this case x = x ’and k divides x + (l2-1) * y- (x’ + (l2-1) * y ’) = (l2-1) * (y-y’). Since k is prime, k must divide either (12-1) or (y-y ’). These two numbers being of absolute value smaller than k, so either 12-1 = 0 or y-y ’= 0. Since I2> 1, y-y ’= 0 and therefore j = j’.

- 11 = 1 and I2> 1 in this case y = y ’and k divides x + (l2-1) * y- (x’ + (l2-1) * y ’) = x-x’. Since k is prime, k must divide x-x ’. This difference being of absolute value smaller than k, then x-x ’= 0 and therefore jri’ ·

- 11> 1 and I2> 1 in this case k divides x + (l1 -1) * y- (x '+ (l1 -1) * y') and k divides x + (l2-1) * y- (x ' + (L2-1) * y '). So k divides their difference (11 -I2) * y- (I1 -I2) * y ’= (l1 -I2) * (y-y’). Since k is prime, k must divide either (11-12) or (y-y ’). These two numbers being of absolute value smaller than k, then either 11-12 = 0 or y-y ’= 0. Since 11 and I2 are distinct, then y-y ’= 0 and therefore y = y’. Now k divides x + (l2-1) * y- (x ’+ (l2-1) * y’) = x-x ’· Since k is prime, k must divide x-x’. This difference being of absolute value smaller than k, then x-x ’= 0 and therefore j = j’.

This shows that if two elements are equal in two sequences, then these two sequences are one and the same sequence. Thus two distinct sequences have at most one element in common.

As an example illustrated in FIG. 4b, k is defined with a value equal to 2. We therefore have a set P2 of n2 = k * k = 4 sequences, represented vertically. As for the set P1 illustrated in FIG. 4a, s representing the number of resources per sequence is equal to 3. The values at "1" in a column give the positions of the resources of the corresponding sequence.

It can thus be seen that the first element of the sequence tO is positioned at the value x = 0, that is to say at bO in the group gO corresponding to l = 0.

The second element of the sequence tO is positioned at the value k + y with y = 0, therefore at the value 2, i.e. at the resource b2 in the group g1 corresponding to 1 = 1.

From one sequence to another, the value of x can vary every k sequences while the value of y varies from one sequence to another at each sequence, therefore diagonally as shown in Figure 4b.

For the third element of the sequence tO in figure 4b, it is positioned at the value l * k + ((x + (l-1) * y) modulo k), that is to say here (with l = 2 , k = 2, x = 0 and y = 0) at the value 4, ie the resource b4.

From the sets of sequences P1 and P2 respecting the condition in which a single resource is common between two sequences, it is then possible to form n1 * n2 sequences of a number s of resources respecting this same condition. From each of the n1 sequences if = (ai0, ..., ais-1) of P1 and of the n2 sequences tj = (bjO, ..., bjs-1) of P2, we create n1 * n2 sequences uij, of s resources among n, such as u ij = (ai O * k + bj 0, ..., ail * kl * k + bjl, ..., ais-1 * k- (s-1) * k + bjs-1).

- 14 [0087] [0088] [0089] [0090] [0091] [0092] [0093]

Thus, the l-th element of uij, ail * kTk + bjl, is positioned in an ail-th subgroup of k elements of the n resources. With m = n / k, m groups of k elements are thus considered and noted from gO to gm-1.

Thus, the n1 * n2 new sequences of s resources among n verify the desired condition of a single common resource between two sequences. Indeed, two sequences thus obtained can only have one subgroup in common. The resources used in common can only be in this subgroup and these sequences use only one resource per subgroup. They can therefore only have one resource at most in common.

Figure 4c illustrates the combination of the n1 sequences in Figure 4a and the n2 sequences in Figure 4b. We thus have n1 * n2 = 7 * 4 = 28 sequences (U0 to U27) verifying the desired condition. The number of resources m for the set of sequences P1 is such that m = n / k. With k = 2, the n resources (rO to r13) used to define the 28 sequences are then the number of n = m * k = 7 * 2 = 14.

It can be seen in FIG. 4c that the combination of n1 and n2 sequences according to the sequence determination process of this embodiment amounts to integrating each of the 3 groups gO to g2 defined in P2 in the 3 positions of the resources defined in P1 for a sequence. We thus extend the number of sequences by a factor of 4 (= k * k) horizontally for a number of extended resources by a factor of 2 (= k).

This extension process can be repeated by combining the sequences defined by this new set ΡΊ of n1 * n2 sequences with again the set P2 of sequences defined as explained above.

We thus obtain (n1 * n2) * n2 sequences for n * k resources which always verify the condition of a single common resource between two sequences.

Using the same numerical examples as those illustrated in Figures 4a to 4c, we can then have (n1 * n2) * n2 = 28 * 4 = 112 sequences of s = 3 resources among n * k = 14 * 2 = 28 resources .

This method therefore makes it possible to find a large number of sequences in a simple manner verifying the property of a single common resource between two sequences for a large number of resources.

The present invention has been described and illustrated in the present detailed description and in the figures. However, the present invention is not limited to the embodiments presented. Thus, other variants and embodiments can be deduced and implemented by the person skilled in the art on reading this description and the appended figures.

For example, the method 300 can be implemented from hardware and / or software elements. It can in particular be implemented as a computer program comprising instructions for its execution. The computer program can be recorded on a recording medium readable by a processor. The support can be electronic, magnetic, optical or electromagnetic.

In particular, the invention can be implemented by devices comprising a processor and a memory. The processor can be a generic processor, a specific processor, an application-specific integrated circuit (also known as ASIC for “Application-Specific Integrated Circuit”) or a network of in situ programmable doors (also known as the English name of FPGA for "FieldProgrammable Gate Array").

The device can use one or more dedicated electronic circuits or a general-purpose circuit. The technique of the invention can be carried out on a reprogrammable calculation machine (a processor or a microcontroller for example) executing a program comprising a sequence of instructions or on a dedicated calculation machine (for example, a set of logic gates such as an FPGA or ASIC, or any other hardware module).

According to one embodiment, the device comprises at least one computer-readable storage medium (RAM, ROM, EEPROM, flash memory or another memory technology, CD-ROM, DVD or another optical disk medium, magnetic cassette, magnetic tape, magnetic storage disk or other storage device, or other non-transient computer-readable storage medium) encoded with a computer program (i.e., several executable instructions) which, when executed on a processor or several processors, performs the functions of the embodiments of the invention, described above.

Claims (18)

claims 1. Wireless communication system (100), comprising: - at least a first base station (110), - a plurality of mobile stations (120), each mobile station being configured to establish a critical latency service with the first base station, and - an uplink channel (130) with multiple access based on contention without prior reservation of resources, the uplink channel comprising a plurality of resources, in which: the communication system is configured so that each mobile station is associated with its own sequence (S1, S2, S3, S4), each sequence defining part of the plurality of resources of the uplink channel, each mobile station is, further configured to transmit to the first base station a plurality of copies of a data packet in accordance with the associated sequence, and the first base station is configured to decode, for each mobile station, at least one resource depending on the associated sequence. 2. Wireless communication system according to claim 1, in which: each mobile station comprises a first memory (123) storing the associated sequence, the associated sequence being predetermined, and - The first base station includes a second memory (113) storing the sequence associated with each mobile station. 3. Wireless communication system according to claim 1, in which: the first base station is, moreover, configured to determine, for each mobile station, the associated sequence, and transmit, to each mobile station, the associated sequence, each mobile station is further configured to receive the associated sequence from the first base station. The wireless communication system according to claim 3, wherein the first base station is further configured to randomly determine the sequence associated with each mobile station. 5. Wireless communication system according to claim 3, in which the first base station is further configured to determine the sequence associated with each mobile station according to a sequence determination method respecting at least one condition in which only one resource is common between two sequences. 6. Wireless communication system according to any one of claims 3 to 5, further comprising a second base station of the same type as the first radio station. - 17base, and in which: - the system is further configured so that, when the uplink channel is transferred between the first base station and the second base station, for at least one mobile station, the first base station is , further configured, to transmit to the second base station, the sequence associated with the mobile station. 7. Wireless communication system according to any one of claims 1 to 6, further configured so that: the first base station is further configured to be synchronized with the plurality of mobile stations, and - the plurality of mobile stations is further configured to define a predetermined cyclic transmission time. 8. Wireless communication system according to any one of claims 1 to 6, in which each mobile station is, moreover, configured to define an acyclic transmission time, the system being, moreover, configured so that: each mobile station is further configured to transmit the plurality of copies of the data packet within the framework of a plurality of time intervals having a predetermined duration, and - the first base station is further configured to store the data packets received on all the resources of the uplink channel, and to carry out the decoding, in a current time interval, from the data packets received during the predetermined period preceding the current time interval. 9. Wireless communication system according to any one of claims 1 to 8, further configured so that resources of the uplink channel are reserved and that: - the first base station is, moreover, configured to receive, from the plurality of mobile stations, on the reserved resources of the uplink channel, at least one transmission code, and determine, from the transmission received, the mobile station for which subsequent transmission is planned, each mobile station is further configured to transmit to the first base station, on the reserved resources of the uplink channel, before the transmission of the plurality of copies of the data packet, the transmission code received. 10. Wireless communication system according to any one of claims 1 to 9, furthermore configured so that: the first base station is further configured to decode, for each mobile station, a combination of all or part of the resources of the associated sequence. 11. Wireless communication system according to any one of claims 1 to 10, further configured so that: - the first base station is also configured to apply a successive interference cancellation technique as a function of the associated sequence, after decoding. 12. Base station (110) for establishing a latency critical service with a plurality of mobile stations (120), each mobile station being configured to communicate with the base station via an uplink channel (130) multiple access based on contention without prior reservation of resources, the uplink channel comprising a plurality of resources, the base station comprising: - a calculation unit (114) for decoding, for each mobile station, at least one resource as a function of an associated own sequence (S1, S2, S3, S4), the associated sequence defining, part of the plurality of resources of the uplink channel, and the resources on which each mobile station is further configured to transmit to the base station, a plurality of copies of a data packet. 13. The base station according to claim 12, in which the calculation unit is further configured to determine, for each mobile station, the associated sequence, the base station further comprising a transmission unit (111 ) to transmit the associated sequence to each mobile station. 14. Base station according to claim 13, in which the calculation unit is further configured to determine the sequence associated with each mobile station according to a sequence determination method respecting at least one condition in which a single resource is common between two sequences. 15. Mobile station (120) for establishing a latency critical service with a base station (110) via an uplink channel (130) with multiple access based on contention without prior reservation of resources, the channel uplink comprising a plurality of resources, the mobile station comprising: - a transmission unit (121) for transmitting to the base station, a plurality of copies of a data packet according to an associated own sequence, the associated sequence defining part of the plurality of resources of the link channel uplink. 16. Method (300) of wireless communication, implemented by a base station, for establishing a critical latency service with a plurality of mobile stations (120), Each mobile station being configured to communicate with the base station via an uplink channel (130) with multiple access based on contention without prior reservation of resources, the uplink channel comprising a plurality of resources, the method comprising following steps : - associate (340) each mobile station with its own sequence defining part of the plurality of resources of the uplink channel, - receive (350), from each mobile station, a plurality of copies of a data packet according to the associated sequence, and - decode (360), for each mobile station, at least one resource as a function of the associated sequence. 17. The method of claim 16, wherein a sequence specific to each mobile station is determined according to a sequence determination method respecting at least one condition in which a single resource is common between two sequences. 18. The method of claim 17, wherein the sequence determination method determines a number n1 * n2 of sequences by the combination of a first set of n1 sequences comprising s resources chosen from a number m = n / k of resources and respecting the condition in which a single resource is common between two sequences, to a second set of n2 = k * k sequences comprising s resources among a number k * s of resources to compose sequences comprising s resources among n resources, where k is a prime number greater than or equal to s-1.