WO2013045864A1

WO2013045864A1 - Data processing for the allocation of radio resources

Info

Publication number: WO2013045864A1
Application number: PCT/FR2012/052222
Authority: WO
Inventors: Jérôme GALTIER; Jean-Marc Kelif
Original assignee: France Telecom
Priority date: 2011-09-30
Filing date: 2012-10-01
Publication date: 2013-04-04
Also published as: FR2980950A1

Abstract

Method of data processing for carrying out an allocation of radio resources in a packet mode cellular radio network, said cellular radio network comprising a base station (1) and a set of user equipment (UE) configured to exchange useful data streams with the base station, the method being implemented in the base station and comprising the following steps: a) assignment of a number of units of radio resources to the transmission of control data as a function of at least one quality of service constraint relating to the useful data streams while waiting to be served by said base station; b) determination, as a function of said number of units of radio resources allotted for the transmission of control data, of a number of units of radio resources available for the transmission of useful data streams; c) allocation of the units of radio resources available for the transmission in the course of a determined time interval of data of at least one subset of the useful data streams waiting to be served.

Description

Data processing for radio resource allocation

The present invention is directed to data processing for allocating radio resources to terminals in a packet radio network. In particular, the present invention is applicable to a cellular network using LTE (Long Term Evolution) technology and / or using the Orthogonal Frequency-Division Multiple Access (OFDMA) technique.

LTE technology increases user throughput up to 100 Mbps downlink and 50 Mbps uplink for 20MHz bandwidth. The LTE technology also makes it possible to reduce the RRT (Round Trip Time) time below 10ms.

LTE technology uses Orthogonal Frequency Division Multiplex (OFDM) modulation to share radio resources among users. In addition, in an uplink, the allocation must be carried out so that, in a given sub-frame of 1ms, the spectrum assigned to a user is contiguous. In particular, control data should not be inserted into the bandwidth assigned to a user, and the bandwidth allocated to two users should not be interleaved.

In a network using LTE technology, the planning of the allocation of radio resources is carried out by the transmission of control data, which consumes up to three OFDM symbols out of a total number of symbols of twelve or fourteen, ie ie up to 25% of radio resources.

In some LTE systems, the size of this planning space can be reduced to only 8% of radio resources, but such systems can only serve a limited number of terminals per time slot.

For this purpose, the invention proposes a data processing method for realizing a radio resource allocation in a packet radio cellular network, said cellular radio network comprising a base station and a set of user equipments configured for exchanging data. useful data streams with the base station, the method being implemented by the base station and comprising the following steps:

a) assigning a number of radio resource units to control data transmission based on at least one quality of service constraint on useful data streams waiting to be served by said base station, b) determining, based on said number of radio resource units allocated for the transmission of control data, a number of radio resource units available for the transmission of useful data streams,

c) allocating available radio resource units for transmission over a specified time interval of data of at least a subset of the useful data streams waiting to be served.

The resource allocation method proposed in this invention minimizes bandwidth devoted to resource planning while maintaining, at all times, a planning bandwidth adapted to the number of present terminals and their quality constraints. on duty.

This process will be named in the rest of this document indifferently "data processing method" or "resource allocation method".

According to one embodiment of the method according to the invention, step a) comprises the steps of:

assign a first number of radio resource units for the transmission of control data,

- test whether it is possible to transmit, by means of the radio resource units assigned to the transmission of control data, all the control data necessary to address all the priority useful data streams to be used,

if not, assigning a second number of radio resource units to the transmission of control data, the second number being greater than the first number.

This method makes it possible to limit the number of radio resource units allocated to the transmission of control data to what is actually needed to serve priority priority data streams waiting to be served.

According to one embodiment of the method according to the invention, step c) comprises

a determination of the maximum number Fmax of flows that may be served during said time interval taking into account the number of radio resource units allocated to the transmission of control data; a determination of the minimum number Fmin2 of non-priority flows to be used during said time interval, according to a minimum period defined to serve the non-priority flows of a given priority level;

a determination of the maximum number Fmax1 of priority streams that may be served during said time interval, as a function of said maximum number Fmax of flows that may be served and said minimum number Fmin2 of non-priority streams to be served,

a determination of the number FSnp of non-priority flows to be used and the number FSp of priority streams to be served during said time interval, as a function of said minimum number Fmin2 of non-priority streams to be served and of the maximum number Fmaxl of priority streams likely to serve; to be served;

- an identification of FSnp non priority flows to be used in priority and FSp priority flows to serve and

- an allocation of radio resource units for these FSnp non-priority flows and FSp identified priority flows.

This ensures that a minimum number of radio resource units will be allocated to the transmission of control data and that the number of resource units allocated to the payloads is as high as possible. This maximizes the bandwidth consumed, while taking into account a maximum of priority flows and ensuring that the transmission of non-priority flows will not be blocked in favor of priority streams alone.

According to one embodiment of the method according to the invention, step c) comprises a determination of the maximum number of non-priority streams that may be served during said time interval, as a function of said maximum number of priority streams likely to be served during said time interval.

This makes it possible to serve a maximum of non-priority flows, taking into account the resource units consumed by the priority flows.

According to one embodiment of the method according to the invention,

when all the priority streams can not be served during said time interval, the priority streams to be prioritized are selected among the priority streams waiting to be served for the longest, when all the priority streams can not be served during the same time interval, the priority flows to be used are selected among the non-priority flows that are waiting to be served the longest.

In a simple way and in the respect of the constraints of quality of service, the selection of the flows to be treated in priority is carried out.

According to one embodiment of the method according to the invention, step c) comprises for the useful data stream (s) of a given priority level x to be used during said time interval:

obtaining a distribution parameter representing a distribution mode of the bandwidth between the different streams of said priority level;

determining a number of radio resource units to allocate to each stream of the priority level x so as to maximize a utilization rate of the available bandwidth taking into account said distribution parameter.

This gives the best possible performance taking into account the available bandwidth and a mode of distribution of this bandwidth between the different flows.

According to a preferred implementation, the various steps of the method according to the invention are implemented by software or computer program, this software comprising software instructions intended to be executed by a data processor of a base station and being designed to control the execution of the different steps of this process.

The invention also proposes a computer program comprising instructions for implementing the method according to the invention when this program is executed by a processor.

The invention also proposes a base station configured to perform a radio resource allocation in a packet radio cellular network comprising a set of user equipment configured to exchange useful data streams with the base station, the base station. comprising:

a module for assigning a number of radio resource units to the transmission of control data as a function of at least one quality of service constraint concerning the useful data streams waiting to be served by said station basic , a determination module, based on said number of radio resource units allocated for the transmission of control data, of a number of radio resource units available for the transmission of useful data streams,

a module for allocating the radio resource units available for transmission during a given time interval of data of at least one subset of the useful data streams waiting to be served.

The invention is implemented by a base station by means of software and / or hardware components. In this context, the term "module" may correspond in this document to both a software component, a hardware component or a set of hardware and / or software components, capable of implementing a function or a set of functions, as described below for the module concerned.

The base station thus comprises modules or software and / or hardware components for implementing and executing the various steps of the method according to the invention (data processing method / resource allocation method) as defined and described in this document, in its various embodiments.

The invention also proposes a cellular radio network comprising at least one base station as described above and a set of user equipment configured to exchange data with the base station.

Other features and advantages of the invention will become apparent on reading the description which follows. This is purely illustrative and should be read in conjunction with the attached drawings in which:

- Figure 1 is a block diagram showing a cellular radio network according to one embodiment of the invention;

Figure 2 is a block diagram showing a base station of the cellular radio network of Figure 1;

FIG. 3 is a flowchart illustrating the steps of a method for allocating radio resources according to one embodiment of the invention, this flow chart possibly representing the general algorithm of the computer program within the meaning of the invention;

FIG. 4 is a graph illustrating the performances obtained by using the radio resource allocation method; Figure 5 is a diagram illustrating certain aspects of the allocation method; and

FIG. 6 is a flowchart illustrating the substeps of a step of the radio resource allocation method.

FIG. 1 represents a cellular radio network comprising a base station 1 and a set of UE UE UE ₂ and UE ₃ UEs configured to exchange data with the base station 1. The cellular radio network uses a communication technology allowing dynamic planning, such as LTE (Long Term Evolution) technology.

FIG. 2 represents the base station 1, which comprises a transmission-reception module 10 configured to enable the exchange of data with network equipment, in particular with the user equipment UEi, UE ₂ and UE ₃ . The data exchanged between the user equipment UEi, UE ₂ and UE ₃ and the base station 1 include control data, defining a resource allocation, and useful data.

The base station 1 further comprises a processing module 11 configured to process received data and data to be transmitted. In particular, the processing module 11 is configured to perform data modulation and to allocate available radio resources. The allocation of radio resources is done in Orthogonal Frequency - Division Multiple Access (OFDMA).

The allocation of radio resources is performed periodically, the time interval defining the allocation periodicity is named "Transmission Time Interval" (TTI) in the LTE standard and is currently set to 1 ms. The available total frequency range is divided into a predefined number (equal to 12 or 14 for example) of frequency bands that can be allocated. Each frequency band can be allocated:

either to the transmission of control data,

- or to one or more equipment, for the transmission of useful data that this equipment must send or receive.

A frequency band thus constitutes a radio resource unit. Allocating such a radio resource unit to a device means that that equipment will be allowed to transmit in the frequency band that defines that radio resource unit.

FIG. 5 schematically represents a radio resource unit allocation matrix for eight time slots T1 to T8 and seven frequency bands B1 to B7: each column of the matrix corresponds to a time interval TTI, each line of the matrix corresponds to a frequency band. The control data is transmitted by the base station to one or more devices via a downlink control channel called PDCCH (Physical Downlink Control Channel) in the LTE standard.

For each time slot, the processing module 11 allocates the available radio resource units.

The processing module 11 is configured to dynamically determine the number of radio resource units to be allocated to the transmission of control data. The control data can consume a variable number of radio resource units, this number being, in the case of example of the LTE standard, between one and three.

The processing module 11 is further configured to determine a number of radio resource units available for the transmission of payload data, taking into account the number of radio resource units allocated to the transmission of control data.

The processing module 11 is also configured to allocate, to the user equipment having data to be transmitted or received, radio resource units available for the transmission of useful data.

Each allocation results in an allocation table that is used to define how the different radio resource units are allocated. When the total number of radio resource units to be allocated is equal to C, an allocation table defines a set of C values Ci, where Q:

- identify the equipment to which the radio resource unit i is allocated,

indicates that the unit i is allocated to the control data.

Thus, an allocation table defines a possible allocation configuration.

The processing module 11 is also configured to determine, for a given allocation / allocation configuration table - which corresponds to an allocation made or envisaged - a performance parameter characterizing this allocation from the point of view of the rate of utilization of the allocation. bandwidth, and to look for the allocation configuration that maximizes the performance parameter.

The processing module 11 is also configured to allocate one or more radio resource units to at least one subset of the set of user equipments according to the optimal configuration found. FIG. 3 represents steps of an OFDMA radio resource allocation method according to one embodiment of the invention. The method is for example implemented in the base station 1.

In step S1, base station 1 allocates a number of radio resource units for transmission of control data. The assignment is performed by applying a predetermined attribution rule.

The allocation rule to be applied is chosen from a set of several predetermined allocation rules, for example according to at least one quality of service criterion and / or desired performance: to maximize the bit rate or to reduce the transmission delay of non-priority data, known as "best effort" data.

For example, the rule set includes three predetermined attribution rules.

A first allocation rule RI defines that a minimum number of radio resource units must be allocated for the transmission of control data, thereby increasing the available bandwidth for the payload.

A second allocation rule R2 defines that a maximum number of radio resource units must be allocated for the transmission of control data, which makes it possible to reduce the transmission delay of non-priority useful data, called "best" data. effort ".

A third allocation rule R3 defines that an intermediate number of radio resource units must be allocated for the transmission of control data, so as to obtain a compromise between the available bandwidth for the payload and the transmission delay. non-priority useful data.

As an alternative or in combination, the allocation rule to be applied is chosen according to at least one quality of service criterion, in particular as a function of the quantity of data to be transmitted and / or the number of user equipment having data. to transmit or receive. For example, the number of radio resource units for the transmission of control data can be reduced (in this case, the first rule will be chosen first) when the quantity of data to be transmitted is greater than a predetermined threshold, to have a sufficient flow rate, and can be increased (in this case, the second rule will be chosen first) when the number of user equipment exceeds a predetermined threshold, so that all the requests (or at least all the requests considered as priorities) can be addressed by the control data. In step S1, base station 1 then tests whether it is possible to transmit, by means of the assigned radio resource units for the transmission of control data, all the control data necessary to send all the useful data to pass.

When all the control data, which are necessary to address the useful data to be transmitted, can not be transmitted, the base station 1 increases the number of radio resource units allocated to the transmission of control data: it assigns a new number of radio resource units for transmission of control data, the new number being greater than the initial number of radio resource units for transmission of control data.

When the maximum number of radio resource units attributable to the transmission of control data does not make it possible to transmit all the control data necessary to address all the useful data to be transmitted, the base station 1 rejects certain useful data to be transmitted, for example useful data associated with equipment with which data has already been exchanged recently.

The allocation is thus performed dynamically according to a current state of the network.

According to one embodiment of the invention, the useful data comprise priority useful data and non-priority useful data. For example, according to LTE technology, useful data can be classified into two categories:

- the priority payloads to be scheduled during the next TTI time interval, without delay, and

- the non-priority useful data (or "best effort") that may or may not be scheduled during the next TTI time interval.

The priority useful data is for example used for the transmission of the voice, or for any type of transmission which requires minimizing a transmission delay and / or a time shift between different data streams. Useful data can also be considered as a priority when associated with a customer who has subscribed to a subscription guaranteeing a good quality of service.

Non-priority useful data allows for greater flexibility and can be processed using different planning policies, for example as described in R. Combes, Z. Altman and E. Altman. "On the use of packet scheduling in self-optimization processes: application to coverage-capacity optimization", WiOpt, pages 11-20, 2010. When the payloads comprise priority payloads and non-priority payloads, priority payloads should be processed first. The useful data to be transmitted then comprise:

- all priority payloads, or at least some of the priority payloads, where all priority payloads can not be transmitted in the same time interval; or

all the priority payloads as well as all the non-priority payloads or at least part of the non-priority payloads when all priority and non-priority payloads can not be transmitted in the same time interval.

In the rest of the description, the user equipment having priority user data to be sent or received will be called "priority user equipment", the user equipment having non-priority useful data to be sent or receive "non-priority user equipment".

The number of radio resource units allocated to control data transmission automatically limits the number of useful data streams that may be served during a TTI time interval.

Thus, when the base station 1 tests whether it is possible to transmit, by means of the assigned radio resource units for the transmission of control data, all the control data necessary to address all the useful data to be transmitted, it determines beforehand, which of the useful data should be transmitted, given the priority or otherwise of this useful data. The logic is here:

- to try to transmit as much priority data as possible, and, when all the priority useful data can not be transmitted during the same time interval, to serve priority priority user equipment that is waiting to be served since the longest,

- when all the priority useful data can be transmitted, to try to transmit as much non-priority data as possible, and in the event of saturation, to give priority to non-priority user equipment that is waiting to be served for the longest time .

In addition, a minimum period for serving the non-priority streams is defined, corresponding to a time interval TTI, or N time slots TTI, with N equal to 2 or 3 for example. It is then necessary to serve, during this minimum period, at least one non priority. Thus, if the time interval TTI is equal to 1ms, at least one non-priority stream will be served every 1ms, or every 2ms, or every 3ms, for example. This ensures that the priority streams are processed with a minimum rate, and at the same time guarantees that the bandwidth is not entirely consumed by the priority streams. This avoids penalizing certain flows to the detriment of others and respecting the logic inherent in the method proposed here of taking into account the state of the network, including the quality of service needs of the different streams to be transmitted.

In step S2, the base station 1 then determines a number of radio resource units available for the transmission of useful data to be transmitted.

The total number of radio resource units available for transmission of control and payload data, ie the maximum number of radio resource units that can be allocated per time slot, is "pr". TTI.

"Pctrl" is the number of radio resource units allocated for the transmission of control data. The number C of radio resource units available for the transmission of useful data to be transmitted is therefore equal to:

C = pr - Pctrl

In step S2, the base station 1 allocates the number C of radio resource units available for the transmission of useful data in the downward and / or upward direction.

The number of radio resource units allocated to a user equipment i is called A _{ over a given time interval TTI. The sum of the numbers À _{ must be such that:

The bandwidth assigned to the user equipment i is then equal to

= λ _ί o (i),

where o (i) designates the number of bytes to be transmitted to the user equipment i (in the case of a downstream flow) or by the user equipment i (in the case of a upstream flow) per unit radio resource. In the case of using the Multiple-Input Multiple-Output (MIMO) technique for a user equipment i, the parameter o (i) takes into account the total number of bytes to be transmitted or received by the user equipment i , all antennas combined.

The base station 1 determines for each user equipment, the number of bytes o (i) is estimated taking into account a gain factor F, representative of the surrounding conditions in which the transmission of the bytes concerned, and the technology of antenna used by the user equipment (MIMO, beam forming, etc.).

The gain factor F of a user equipment in a radio environment can be modeled by the equation:

1

F ^{= ~} ^ "ff 'shadowing where:

r is the distance between the equipment and the base station,

η is a propagation loss factor,

ff is a fast fading factor, and

"Shadowing" is a shading factor.

It is assumed here that the shading factor does not depend on the frequency, and remains constant for a period of time k ms, where k is an integer.

The performance of a radio resource allocation can be estimated by the sum S measuring the bandwidth utilization rate:

where a is a real, positive or zero.

The higher the sum S, the more efficient the allocation of resources, in particular the higher the amount of allocated bandwidth. The parameter OC is a distribution parameter representing a distribution mode of the bandwidth between the different flows of said priority level. This parameter OC is a real coefficient, common to the different user equipments, which is applied according to the formula above to the value representing the bandwidth assigned to the user equipment i, in order to determine the distribution mode of the bandwidth between the different streams of a priority level. Maximize the sum S under the constraint ^ Â _{ <C is the best distribution of the number

C of radio resource units between the different streams, that is to say to allocate to each equipment a number of resource units so as to maximize the utilization rate of the available bandwidth taking into account the parameter of O distribution, ie of the distribution mode chosen.

When a = 0, this sum S represents the sum of the bandwidths allocated to the different user equipments. In this case, maximizing the sum S makes it possible to maximize the bandwidth consumed and thus to ensure optimal use of this bandwidth.

When a = 1 or OC tends to 1, this sum S represents the product of the bandwidths allocated to the different user equipments. In this case, maximizing the sum S makes it possible to ensure that an infrequently served user is served by more packets. We can speak here of proportional equity between the different user equipments.

When the value of OC is high, for example greater than 10, at the limit when OC tends towards infinity, this sum S represents a criterion of equity of the type "MAX MIN", that is to say with maximization the minimum bandwidth allocated. In this case, maximizing the sum S makes it possible to optimize the smallest bandwidth: it is therefore ensured that each user equipment will benefit from a minimum of bandwidth.

Like Γί

o (i), the performance parameter S to be maximized is equal to:

_S -Σ ^ <* ^■ <* · ""

The base station chooses the value of OC according to the nature of the expected performance during the time interval TTI for which it performs the allocation. Then the base station uses an optimization algorithm to look for the values λί which make it possible to maximize the sum S corresponding to the chosen value of OC. An example of such an algorithm can be found in the patent document FR 04 13 887, concerning a method for allocating resources of a telecommunications cellular network.

The values λί obtained by such an optimization algorithm being real values, generally not integers, they must be converted into integer values before the allocation can be performed. In addition, the LTE standard requires that the number λί of radio resource units allocated to user equipment i during a TTI time interval take a value in a predetermined set of VLs of integer values. For example, for the upward direction, this set includes the integer values 1, 2, 3 and 5. For the downward direction, this set includes all integer values between 1 and 12. In order to respect this constraint, the base station 1 calculates, for each user equipment i, an indicator L such that:

where \ _Â _i J is equal to: - the value λ _ί obtained by the optimization algorithm when this value λ _ί is an integer value, and otherwise

at the integer value, chosen from the values of the set VL which are strictly smaller than the value λ _ί; which is the closest to the real value λ _ί obtained by the optimization algorithm; and or

is equal to: the value λ _ί obtained by the optimization algorithm when this value λ _ί is an integer value, and if not,

at the integer value, chosen from the values of the set VL which are strictly greater than the value λ _ί; which is the closest to the real value λ _ί obtained by the optimization algorithm;

This indicator L represents the difference in bandwidth consumption for the equipment i according to whether the actual value λ _ί is rounded up to the lower integer value \ _Â _i J or to the higher integer value \ λ _ί ^~ | .

Then, the base station 1 classifies the calculated indicators L, for example in increasing order.

Then, the base station 1 selects as configuration to maximize the performance parameter configuration assigning the number \ λ _ί ^~ | radio resource units at user equipment i having the highest L indicators, and the number | _ l _; J of radio resource units to user equipment i having the lowest L indicators.

Thus, the user equipment i of a first sub-group of user equipment respectively have a number

of radio resource units, and the user equipment i of a second sub-group of user equipment respectively have a number | _ l _; J of radio resource units. The number of user equipment in each subgroup is determined such that the total number of allocated radio resource units does not exceed the number C of assignable radio resource units. For example, we arbitrarily take a number of user equipment in the first subgroup equal to half the total number of user equipment. Then, if the total number of radio resource units allocated with this subgroup decomposition is strictly greater than the number C of attributable radio resource units, the user equipment i having the lowest L indicator is searched for. equipment for which the number of radio resource units allocated and assigned to that user equipment the number i \ _i J _A radio resource units. This operation is iterated until the total number of radio resource units allocated in this manner is less than or equal to the number C of assignable radio resource units.

In the end, for each user equipment i is

of radio resource units. We denote Li the number | _ l _; J or

assigned to a user equipment i at the end of step S2.

In step S3, the base station 1 allocates the C radio resource units still available - i.e., not allocated to the transmission of the control data - to the user equipment having priority payload data to be received / transmitted. based on Li values obtained in step S2 for these user equipment.

For the direction going back to the base station, the allocation of radio resources is for example carried out considering the user equipment i by decreasing values of Li. For the upstream direction, the LTE standard provides that the frequency ranges corresponding to different Resource units that are allocated to a given UE during a TTI time interval must be consecutive. There must therefore be no frequency range, allocated to another equipment or control data, which is found between two frequency ranges allocated to the same user equipment.

Thus, for each time interval TTI, the base station 1 ranks the numbers Li by decreasing value. Then, the base station 1 allocates the radio resource units starting with the user equipments to which is assigned a higher Li number, and then proceeding in decreasing order of Li value, allocating progressively a number of units. consecutive resources to each user equipment.

At each allocation, the available radio resource units not necessarily being all consecutive, because the allocation to the control data of some of the radio resource units, the Li radio resource units which are assigned to a user equipment i are selected from the remaining radio resource units that are still available and the following way. The base station 1 identifies the groups of consecutive radio resource units not yet allocated and classifies these groups by increasing size, the size of a group of radio resource units being defined as the number of radio resource units that contains this group. The base station allocates to the user equipment i a group of consecutive radio resource units of size Li, first assigning the largest radio resource unit group, and ensuring, when the size of this group is higher than the number Li, the remaining radio resource units in this group of units are all consecutive to each other: which amounts to allocating the corresponding Li radio resource units:

- either the highest frequency bands among the frequency bands represented by the group of units concerned,

- either the lowest frequency bands among the frequency bands represented by the group of units considered.

The groups of consecutive radio resource units not yet allocated are then classified by increasing size, before proceeding to the allocation for the next user equipment i, in order of decreasing value Li.

If this allocation method does not allocate to allocating the radio resource units to the priority payload streams, the value of C is decreased by 1 or more and the steps S2 and S3 are repeated. The search for the value of C for allocating the radio resource units to the priority payload streams can be done by dichotomy.

If necessary, in order to better manage the frequency hopping that is recommended in the LTE standard, the base station 1 can also, when two radio resource unit groups, forming two adjacent frequency ranges, have been assigned to two pieces of equipment. user, perform a swap of the radio resource units assigned to these two user equipments: the one of the two to which the lower frequency bands had initially been assigned is assigned the highest frequency bands and viceversa, and this without however, modify the number of radio resource units - that is the number of frequency bands - assigned to each of these two devices.

For example, using the notations used in FIG. 5, if a first frequency range comprising the two frequency bands B1 and B2 is assigned to the user equipment 1 and a second frequency range comprising the three frequency bands B3 to B5 is assigned to the user equipment 2, the permutation amounts to assigning the frequency bands B1 to B3 to the user equipment 2 and the frequency bands B4 and B5 to the user equipment 1. For the downlink, it is not necessary that consecutive frequency bands are allocated to the same user equipment. The radio resources are therefore allocated to the user equipment i by ranking the numbers Li by decreasing value, then assigning the radio resource units starting with the user equipment to which is assigned a higher Li number and proceeding in order of Li value decreasing.

If necessary, in the same way as for the upstream direction, in order to better manage the frequency hopping that is recommended in the LTE standard, the base station 1 can also, when two groups of radio resource units, form two ranges of adjacent frequency, have been assigned to two different user equipment, perform a switch of the radio resource units assigned to these two user equipment. The permutations here are simpler than for the uplink, since the constraint on the consecutive frequency bands does not exist: it is therefore possible to exchange the two priority user equipment to which two units of any radio resource are allocated.

In step S4, when the useful priority data has been processed, the base station 1 allocates the remaining radio resource units (not yet allocated to control data or priority payload data) to the non-wanted payload data. priority.

For this, the base station 1 determines a number C2 of radio resource units available for the transmission of the non-priority payload data from the number of radio resource units allocated for the transmission of control data and the number of priority_traffic "of radio resource units used for the transmission of priority payload data:

C2 = pr - control - priority _ traffic

Then, the base station 1 re-executes steps S2 and S3 to allocate resource units to the user equipment having non-priority payload data to be transmitted / received so as to generate a unit number Li of radio resources for each user equipment i having non-priority useful data to be transmitted or received. In the execution of steps S2 and S3, C is replaced by C2 when it is a question of processing the allocation of non-priority flows.

When it is not possible to use during the same time interval TTI all the users equipment having non-priority useful data to transmit / receive, a Round Robin method (selection with circular permutation) can be used to select at each time interval the user equipment that will be served: in this case, a Li value will be calculated only for the user equipment selected for a time interval.

The number of non-priority user equipment selected at each time interval TTI can be low: in this case, we will serve only a few non-priority user equipment at a time, but it will be possible to allocate them more resources.

The assignment of the radio resources still available to the different user equipments then proceeds in the same way as for the priority streams (see step S3): in particular by firstly assigning the radio resources to the upstream flows.

For each subsequent time slot, other user equipment having non-priority payload data to be transmitted / received will be selected, in accordance with the Round Robin method, according to the resource units still available after allocation of priority flows and steps S2. and S3 repeated for these non-priority user equipment.

Methods of prioritization other than Round Robin are of course usable to select the non-priority user equipment that will be served during a given time interval.

The allocation method has been described in the case where there are two priority levels for the payload data: priority or non-priority payloads. This method is easily generalized to any number of levels from priority 1 to X (whole X, strictly greater than 2): the allocation of the radio resources is carried out by proceeding by priority level, and repeating for each priority level the steps S2 and S3 with radio resource units not yet allocated. In the execution of steps S2 and S3, C will then be replaced by the number Cx of radio resource units allocated to the priority level data x when it is necessary to process the allocation of the priority level streams x .

The logic here is always:

to serve as many priority streams as possible in view of the number Pctrl of radio resource units allocated to the transmission of control data, and, when all the priority streams can not be served during the same time interval, to prioritize priority flows that are waiting to be served for the longest time,

- when all priority flows can be served, to serve as many non-priority flows as possible, and, where all non-priority flows can not be served during the same interval of time, to serve first priority non-priority flows that are waiting to be served for the longest time.

In addition, Cx values are calculated to ensure a minimum quality of service for each priority level. For non-priority flows, that is, for x greater than or equal to 2, a minimum period Px for serving the priority level streams x is defined, equal to a time interval TTI, or to Nx intervals of time TTI, with Nx equal to 2 or 3 for example. It is then necessary to serve, during this minimum period Px, at least one priority level stream x (or a predetermined minimum number Fx, strictly greater than 1, of priority level stream x). This ensures that the priority level x flows are processed with a minimum rate Px, and it is simultaneously ensured that the bandwidth is not entirely consumed by the priority streams, that is to say by the flows priority level 1. This avoids penalizing certain flows to the detriment of others and respecting the logic inherent in the method proposed here to take into account the state of the network, including the quality of service needs of the different streams to be transmitted. .

In practice, for the selection of the streams to be served during a given time interval carried out during step S1, the following method, illustrated in FIG. 6, is applied.

Then, in step 600, the total number Fp of priority streams waiting to be served and the total number Fnp of non-priority streams waiting to be served are obtained.

In step 610, the minimum number Fmin2 of non-priority streams to be used during said time interval is determined according to a minimum period defined to serve non-priority streams; this determination is made for each level of priority different from level 1, the number Fmin2 of non-priority streams to be used being the sum of the priority flow numbers Fx to serve at least during said time interval on all the different priority levels x Level 1:

x

F min 2 = Fx

In step 620, the number Pctrl of radio resource units assigned to the transmission of control data is determined, taking into account an allocation rule R, R2, or R3 chosen beforehand. The method described above is applicable. For example, Pctrl = 2.

In step 630, the maximum number Fmax of flows that may be served during said time interval is determined taking into account the number Pctrl of radio resource units allocated to the transmission of flow control data. In step 640, the number Fmax1 of priority streams that may be served during said time interval is determined as a function of the difference between the maximum number Fmax of flows that may be served and the minimum number Fmin2 of flows. non-priority to serve:

F max 1 = F max- F min 2

Then, in step 650, the number Fmax1 of priority streams that can be served is compared with the total number Fp of priority streams waiting to be used to determine the number FSp of priority streams that will actually be served and the number FSnp. non-priority flows that will actually be served during the time interval considered. One of the steps 651, 652 or 653 is executed according to the result of the comparison.

If max l> p (step 651), then all the priority streams can be served: the number FSp of priority flows that will actually be served during the time interval considered will be equal to Fp. In addition to the Fmin2 priority streams to be served, an additional number of streams of non-priority streams that can be served is equal to F max 1 - Fp. The number Fmax2 of non-priority streams that may be served is in this case equal to F max 1 - Fnp + F min 2. Thus the number FSnp of non-priority streams that will actually be served during the time interval considered will be equal to

min (max 1 - Fnp + F min 2, Fnp) The final step 660 is then executed following step 651.

If F max 1 = Fp (step 652), then all the priority streams can be served: the number FSp of priority streams that will actually be served during the time interval considered will be equal to Fp. The number FSnp of non-priority flow streams that will actually be served is equal and limited to the determined value Fmin2.

The final step 660 is then executed following step 652.

If F max l <Fp (step 653), then all the priority streams can not be served: the number FSp of priority streams that will actually be served during the time interval considered will be equal to Fmaxl. The number FSnp of non-priority flow streams that will actually be served is equal and limited to the determined value Fmin2. In such a situation, it is compared (test of step 655) the number Pctrl of radio resource units allocated to the transmission of control data to the maximum number (3 in general in LTE) of radio resource units capable of be assigned to the transmission of control data.

If these two numbers are identical, the values of FSp and FSnp are unchanged, then the final step 660 is executed following step 655.

In the opposite case, if the number Pctrl of radio resource units allocated to the transmission of control data is strictly less than the maximum number of radio resource units that can be allocated to the transmission of control data, then the in step 656 the number Pctrl of radio resource units allocated to the transmission of control data, for example of 1 unit:

Pctrl = Pctrl +1

Then, step 630 and the following ones are executed again according to the logic described above, until reaching the final step 660.

In the final step 660, the number FSp of priority flows that will actually be served and the number FSnp of non-priority flow streams that will actually be served are known. We then identify the flows to be served effectively, according to the waiting time of each candidate stream waiting to be served, and then allocate the radio resources to the identified flows.

The identification of the flows is carried out for example in the following manner. If FSp <Fp, priority is given to priority Fsp streams that are waiting to be served for the longest time. If FSnp <Fnp, priority is given to FSnp priority flows that are waiting to be served for the longest time.

The allocation method that has just been described makes it possible to dynamically adapt the allocation of radio resources to a current state of the network. The method makes it possible in particular to reduce as much as possible the bandwidth devoted to the transmission of control data while at the same time maintaining a bandwidth adapted to the number of terminals present and to the needs of these terminals in bandwidth or, more generally, as a service.

The allocation method also makes it possible to maximize the bandwidth consumed while ensuring an equitable distribution between the users, in that it makes it possible to allocate more bandwidth to non-priority or low-bandwidth flows, made : on the one hand, the dynamic allocation method, which supports the quality of service constraints of the different devices at a given instant, which is applied to allocate radio resource units to control data and on the other hand , optimization performed on the allocation of radio resource units to priority payloads.

These two measures make it possible to retain for the non-priority payload a significantly larger bandwidth than with the known method.

Simulations for comparing an allocation performed using the resource allocation method described above with statically determined resource allocations are described below.

The maximum output power of base station 1 is set at 20W, the surrounding white noise at 5E-14dB, the typical cell size at 1000m, the propagation loss factor at 3, the maximum power of d a user equipment at 200mW.

It is further considered that the shading factor follows a normal logarithmic law with an average of 6 dB, and the fast fading factor an exponential law with K = 1. The coding of the signal is assumed to be able to exploit 80% of Shannon's capacity, and a MIMO factor of 1.8 is used.

The LTE parameters include a long cyclic prefix, up and down frequency ranges of 3MHz, and a maximum number of radio resource units of 6, 18, and 30 for a radio resource unit number (PDCCH) allocated to the data. of control equal to 1,2 and 3 respectively.

The network is loaded with the following data streams:

Type Priorit Numbe Uplink Uplink Uplink Downlin Downlin Downlin y of frequency minimu maximu k k k

Such package of packet size and packet size packets

(per s.) size (Bytes) packets size size

(Bytes) (per s.) (Bytes) (Bytes)

Call Video 1 4 30 200 50000 30 200 50000

Call Voice 1 60 50 20 160 50 20 160 Video

monitoring 1 4 30 700 7000 / / / e

interactive

1 4 50 20 20 50 20 200 game

Music 2 2 / / / 1 400 5000

Web

2 4 / / / 1500 1500 surfing

Figure 4 shows the results obtained for this simulation, with:

a variable number of radio resource unit allocated to the control data (curve Ci),

a number equal to 2 (curve C ₂ ) and

a number equal to 3 (curve C ₃ ).

The gain obtained by using the resource allocation method with a minimum number of radio resource units allocated to the control data (for the duration of the tests, therefore, the first rule RI is used for determining the number of 'radio resource units allocated to control data), is 5% and 16% of the bandwidth for web feeds versus the use of a fixed number of radio resource units allocated to equal control data 2 and 3 respectively. The method thus makes it possible to increase the bandwidth allocated to user equipment transmitting or receiving web streams.

We also note that other streams (including voice streams, video) are very little impacted: no additional delay, a slight change in quality in some configurations but without overall degradation.

As a result, the allocation method preserves performance for priority streams (voice, typically) and / or large bandwidth consumers (typically video), while significantly improving performance for non-priority streams and low bandwidth consumers such as web feeds. The available bandwidth is therefore allocated more optimally.

Claims

A data processing method for realizing radio resource allocation in a packet radio cellular network, said cellular radio network comprising a base station (1) and a set of user equipment (UE) configured to exchange streams useful data with the base station, the method being implemented in the base station and comprising the following steps:

a) assigning a number of radio resource units to control data transmission based on at least one quality of service constraint on useful data streams waiting to be served by said base station,

b) determining, based on said number of radio resource units allocated for the transmission of control data, a number of radio resource units available for the transmission of useful data streams,

The method of claim 1, wherein step a) comprises:

The method of claim 1 or 2, wherein step c) comprises

4. The method according to claim 3, wherein step c) comprises a determination of the maximum number of non-priority flows that may be served during said time interval, as a function of said maximum number of priority streams that can be served during said time interval.

The method of claim 4, wherein

when all the priority streams can not be served during said time interval, the priority streams to be prioritized are selected among the priority streams waiting to be served for the longest,

when all the priority streams can not be served during the same time interval, the priority flows to be used are selected among the non-priority flows that are waiting to be served the longest.

The method of claim 1, wherein step c) comprises, for the one or more useful data streams of a given priority level x to be served during said time interval:

obtaining a distribution parameter representing a distribution mode of the bandwidth between the different streams of said priority level; determining a number of radio resource units to allocate to each stream of the priority level x so as to maximize a utilization rate of the available bandwidth taking into account said distribution parameter.

7. Computer program comprising instructions for implementing the method according to any one of the preceding claims when the program is executed by a processor.

A base station (1) configured to perform radio resource allocation in a packet radio cellular network having a set of user equipments (UEs) configured to exchange useful data streams with the base station, the station Basic comprising:

a module for assigning a number of radio resource units to the transmission of control data as a function of at least one quality of service constraint concerning the useful data streams waiting to be served by said station basic ,

a determination module, based on said number of radio resource units allocated for the transmission of control data, of a number of radio resource units available for the transmission of useful data streams,

9. cellular radio network comprising at least one base station according to claim 8 and a set of user equipment configured to exchange data with the base station.