FIELD OF THE INVENTION

The invention concerns a method and device to associate telecommunication at least one user equipment to component carriers.

One filed of the invention is wireless communication systems, and for example, Long Term Evolution (LTE) system as defined by the 3GPP (3rd Generation Partnership Project) with carrier aggregation techniques.

BACKGROUND OF THE INVENTION

One of the target searched by International Mobile Telecommunications (IMT)-Advanced system is the enhanced peak data rates to support advanced services and applications (100 Mbit s for high mobility and 2 Gbit/s for low mobility were established as targets for research), as provided in [1 ] 3GPP TR 36.913 V8.0.0, "requirements for Further Advancements for E-UTRA (LTE-Advanced)", Release 8, June 2008. Therefore, the LTE-Advanced system requires wider system bandwidth, e.g. up to 100 MHz, to achieve such high target peak data rates.

Carrier aggregation (CA) is a known approach to defining new bandwidth modes in fulfilling this requirement. Carrier aggregation has the advantages of not requiring extensive changes to the LTE physical layer structure, providing for bandwidth scalabilty and maintaining backwards compatibility, as provided in [2] 3GPP TSG-RAN WG1 Meeting #53b, R1 -082448, "Carrier aggregation in Advanced E- UTRA", Huawei and in [3] 3GPP TSG-RAN WG1 Meeting #53b, R1-082468, "Carrier aggregation in Advanced E-UTRA", Ericsson. In CA systems, multiple component carriers (CC) are aggregated to cover the desired LTE-Advanced system bandwidth. These component carriers are either LTE- Rel-8 compatible or are designed specially to support new LTE-Advanced features. An LTE Rel-8 terminal can transmit data one of these component carriers, while an LTE-Advanced terminal can simultaneously transmit data on multiple component carriers.

Two user equipments scheduling approaches in carrier aggregation system are studied in] 3GPP

TSG-RAN WG1 Meeting #57, R1-091828, "System Simulation Results on Carrier Aggregation for Bursty Traffic", CMCC, namely independent carrier (IC) and carrier aggregation (CA).

In a first approach, known as independent carrier (IC), no change on the user equipments is required, i.e. the user equipments can receive data only on one of the carrier at a time and changing the carrier associated to the user equipment is a slow procedure. When a new user equipment attaches itself to a eNodeB (evolved Node B), the eNodeB assigns a suitable carrier to the new user equipment according to different criteria. The user equipment transmits data in the associated carrier frequency for a relatively long period of time until intra-frequency handover is performed.

One drawback of the IC approach is that it does not mention how to associate a user equipment to a component carrier. Furthermore, when large frequency gaps exist between the component carriers, the IC approach encounters difficulties in serving users equipment with optimal component carrier.

In a second approach, known as carrier aggregation (CA), a user equipment can simultaneously transmit on multiple carriers and no intra-frequency handover is required. The resource blocks which can be allocated on all the component carriers are allocated to the user equipments as a large resource pool. The user equipments can be scheduled to their best resources irrespective of whether or not these resources are within the same one or multiple component carriers(s).

One drawback of the CA approach is that is involves high scheduling complexity and requires multiple component carriers process ability on the user equipments side.

SUMMARY OF THE INVENTION

One of the goals of the invention is to improve the method and device to associate at least one telecommunication user equipment to component carriers.

According to an aspect of the invention, there is provided a method to associate at least one user equipment to a plurality of component carriers,

characterized in that

a carrier-to-interference ratios is calculated for each of component carriers available for the user equipment,

differences between the calculated carrier-to-interference ratios are calculated, with each difference being associated to a different one of the component carriers intervening in said difference, the component carriers being ordered in the decreasing order of their carrier frequency, the user equipment is associated with the component carrier having the lowest difference.

Thanks to the invention, the throughput of the telecommunication user equipments is enhanced. The invention proposes a method to associate telecommunication user equipments to proper component carriers in a carrier aggregation system with multiple component carriers of different propagation characteristics. The larger the frequency gap between the carrier frequencies of the component carriers, the more gains the allocation according to the invention acquires. The invention provides higher throughput than randomly associated component carriers in the CA approach. The enhanced throughput is obtained by the invention for proportional fair (PF) scheduling, as well as for round robin (RR) scheduling.

According to an embodiment of the invention, there is a number m of telecommunication user equipments, whose bandwidths are included in a bandwidth of said component carrier. According to an embodiment of the invention, m is proportional to the bandwidth of said component carrier divided by the sum of the required bandwidths of said telecommunication user equipments.

According to an embodiment of the invention, N being the number of carrier components, N-1 differences D _{1 ik} ' are calculated and associated to N-1 respective component carriers CC _k , which are other than the component carrier CC^ of lowest carrier frequency, for k going from 2 to N, as follows:

wherein CIR/ is the carrier-to-interference ratio of said component carrier CC^ of lowest carrier frequency,

wherein CIR _k ' are the carrier-to-interference ratios of said N-1 respective component carriers

CC _k for k going from 2 to N and for each telecommunication user equipment UEi for i going from 1 to P, wherein P is the number of telecommunication user equipments in said plurality of telecommunication user equipments.

According to an embodiment of the invention, N-1 differences D _k-1ik ' are calculated and associated to N-1 respective component carriers CC _k , which are other than the component carrier CC^ of lowest carrier frequency, for k going from 2 to N, as follows:

D _k -i , _k ' = CIR _k _i ' - CIR _k '

wherein CIR _k ' are the carrier-to-interference ratios of said N-1 respective component carriers CC _k for k going from 2 to N and for each telecommunication user equipment UEi for i going from 1 to P, wherein P is the number of telecommunication user equipments in said plurality of telecommunication user equipments.

According to an embodiment of the invention, k in the N carrier-to-interference ratios is ordered for each i according to the ascending order of the carrier frequency of the N component carriers for each of the telecommunication user equipments transmitting respectively on the N component carriers.

According to an embodiment of the invention, the N carrier-to-interference ratios are ordered according to the ascending order of the carrier frequency of the N component carriers for each of the telecommunication user equipments transmitting respectively on the N component carriers.

According to an embodiment of the invention, if all the component carrier except the component carrier of lowest carrier frequency are associated to telecommunication user equipments and if it remains at least one unassociated telecommunication user equipment, said at least one remaining telecommunication user equipment is associated to the component carrier of lowest carrier frequency with a maximum of m telecommunication user equipment for said component carrier of lowest carrier frequency.

According to another aspect of the invention, there is provided a device to associate at least one user equipment to a plurality of component carriers,

characterized in that the device comprises : first means to calculate a carrier-to- interference ratios for each of component carriers available for the user equipment,

second means to calculate differences between the calculated carrier-to-interference ratios, with each difference being associated to a different one of the component carriers intervening in said difference,

means to associate, the user equipment with the component carrier having the lowest difference, the component carriers being ordered in the decreasing order of their carrier frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the method and device according to the invention will be clear from the reading of the description hereafter of a non-limiting example, with reference to the accompanying drawings, wherein :

- Figure 1 shows schematically a telecommunication user equipments and component carriers in a telecommunication environment, in which the method and device according to the invention are carried out,

- Figure 2 shows an example of flow chart of the method according to the invention,

- Figure 3 shows an example of allocation according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In figure 1 , a plurality of telecommunication user equipments UEi, for example a number P of telecommunication user equipments UE1 , UE2, UEi, ... UEP is provided, with i being an integer going from 1 to P, and P being an integer with P > 2. A telecommunication user equipment is generally called user equipment UEi hereinafter, and indicia i in the following description designates a telecommunication user equipment. The telecommunication user equipment may comprise for example wireless terminals such as mobiles telephones or mobile equipments. Any user equipment UEi has his own frequency bandwidth UEBWi in which it transmits and receives signals. For example, the telecommunication user equipments UEi transmit and receive signals to and from a node B, which is also called E-UTRAN NodeB in the state in the art. Node B is the first node encountered for communication with the telecommunication user equipments UEi.

Also, a number N of component carriers CC^ , CC ₂ , ... CC _k , CC _N , with k being an integer going from 1 to N, and N being an integer with N > 2, is provided. Each component carrier CC _k has a frequency bandwidth BW _k and a center frequency. The bandwidths BW _k of each carrier component CC _k are separated one from another, i.e. for example they cover each at least one carrier frequencies range having no common intersection range with the other bandwidths, or having only a carrier frequency limit in common with the other bandwidths. It is considered that the component carriers CC _k may have propagation characteristics which may be different one from another. It is also considered that the component carriers CC _k having similar propagation characteristics will be treated as one component carrier group. In the following, the term component carrier CC _k designates both a component carrier CC _k and a component carrier group and will be called component carrier CC _k . Consequently, in an embodiment, the bandwidth BW _k of each component carrier CC _k comprises at least one range of carrier frequencies. In an embodiment, the bandwidth BW _k of each component carrier CC _k comprises one range of carrier frequencies or several ranges of carrier frequencies, which are separated one from another.

For example, for k going from 1 to N, the bandwidths BW _k cover carrier frequencies ranges ordered in the ascending order. For example, for k going from 1 to N-1 , the bandwidth BW _k covers a carrier frequencies range which is situated at lower carrier frequencies than the bandwidth BW _k+1 .

For example, for k going from 1 to N, each bandwidth BW _k is in a carrier frequencies range going from A _k to B _k with < ≤ A ₂ < B ₂ < ... < A _k < B _k < A _k+1 < B _k+1 < ... < A _N < B _N or with < < A ₂ < B ₂ < ... < A _k < B _k < A _k+1 < B _k+1 < ... < A _N < B _N , as shown for example on Figure 1 showing the bandwidths depending on the frequency on the ascendant vertical axis f.

The method and device according to the invention are used for example in a carrier aggregation system.

According to the invention, there is provided a method to associate at least one user equipment UEi to a plurality of component carriers CC _k ,

a carrier-to-interference ratios CIR _k ' is calculated for each of component carriers CC _k available for the user equipment UEi,

differences D _k between the calculated carrier-to-interference ratios CIR _k ' are calculated, with each difference D _k being associated to a different one of the component carriers CC _k intervening in said difference D _k ,

the component carriers CC _k being ordered in the decreasing order of their carrier frequency, the user equipment UEi is associated with the component carrier CC _k having the lowest difference D _k .

According to the invention, there is provided a device to associate at least one user equipment

UEi to a plurality of component carriers CC _k ,

characterized in that the device comprises :

first means to calculate a carrier-to-interference ratios CIR _k ' for each of component carriers CC _k available for the user equipment UEi,

second means to calculate differences D _k between the calculated carrier-to-interference ratios

CIR _k ', with each difference D _k being associated to a different one of the component carriers CC _k intervening in said difference D _k ,

means to associate, the user equipment UEi with the component carrier CC _k having the lowest difference D _k , the component carriers CC _k being ordered in the decreasing order of their carrier frequency.

According to the carrier aggregation scheme, one or several bandwidth UEBWi of one or several telecommunication user equipment UEi is comprised in the signal communication bandwidth BW _k of any one of the component carriers CC _k . Consequently, the bandwidth UEBWi of each telecommunication user equipment UEi is less wide than or as wide as the signal communication bandwidths BW _k of each component carrier CC _k . The signal communication bandwidth BW _k of any one of the component carriers CC _k is used by the node B for communication (transmission and reception of signals as described above) with one or several telecommunication user equipment UEi. Consequently, signal communication bandwidth BW _k can be divided into several bandwidth UEBWi of several telecommunication user equipment UEi, which is then called association of these telecommunication user equipment UEi to this component carrier CC _k .

A method and device to associate a plurality of P telecommunication user equipments UEi to N component carriers CC _k according to an embodiment of the invention is explained hereunder in reference to Figure 2.

In a first step S1 , N carrier-to-interference ratios CIR _k ' are calculated for each of the telecommunication user equipments UEi transmitting respectively on the N component carriers CC _k . The N carrier-to-interference ratios CIR _k ' are calculated for each of the telecommunication user equipments UEi transmitting respectively on the N component carriers CC _k , for k going from 1 to N. Consequently, for i going from 1 to P and for k going from 1 to N, there are N.P carrier-to-interference ratios CIR _k ' which are calculated.

For example, each telecommunication user equipment UEi calculates the N carrier-to- interference ratios CIR _k ' for this telecommunication user equipment UEi transmitting respectively on the N component carriers CC _k . First means to calculate the N carrier-to-interference ratios CIR _k ' for each of the telecommunication user equipments UEi transmitting respectively on the N component carriers CC _k are embedded in each user equipment UEi and/or in the node B.

In an embodiment, the N carrier-to-interference ratios CIR _k ' are ordered according to the ascending order of the carrier frequency of the N component carriers CC _k for each of the telecommunication user equipments UEi transmitting respectively on the N component carriers CC _k .

For example, k in the N carrier-to-interference ratios CIR _k ' is ordered for each i according to the ascending order of the carrier frequency of the N component carriers CC _k for each of the telecommunication user equipments UEi transmitting respectively on the N component carriers CC _k .

Then, for example, the N carrier-to-interference ratios CIR/ , CIR ₂ ' , CIR _k ' , CIR _k+1 ' , ... , CIR _N ' correspond respectively to the order of CCi, CC ₂ , ... , CC _k , CC _k+1 , CC _N, which correspond itself to the ascending order of BWi, BW ₂ , ... , BW _k , BW _k+1 , BW _N mentioned above.

For example, each user equipment UEi calculates on all the available component carriers CC _k the carrier-to-interference ratios CIR _k ' which depend on the location of the user equipment UEi, the pathloss model, shadow fading, penetration loss and so on.

In a second step S2, differences D _k between the carrier-to-interference ratios CIR _k ' of each telecommunication user equipment UEi are calculated. Each difference D _k is associated to a different one of the component carriers CC _k intervening in said difference D _k . Each difference D _k depends also on the telecommunication user equipment UEi and then depends on i, which means that D _k = D _k (i). Second means to calculate the differences D _k between the carrier-to-interference ratios CIR _k ' of each telecommunication user equipment UEi are provided, for example in the telecommunication user equipment UEi and/or in the node B.

The differences D _k are then reported to the first node B.

In a first embodiment, the differences D _k are calculated by subtracting one carrier-to-interference ratio from the other carrier-to-interference ratios.

For example, in the first embodiment, D _k = D _{1 k} ' as described below :

wherein CIR/ is the carrier-to-interference ratio of said component carrier CC^ of lowest carrier frequency,

wherein CIR _k ' are the carrier-to-interference ratios of said N-1 respective component carriers CC _k for k going from 2 to N and for each telecommunication user equipment UEi for i going from 1 to P.

Then, N-1 differences D _{1 k} ' are calculated and associated to N-1 respective component carriers CC _k , which are other than the component carrier CC^ of lowest carrier frequency, for k going from 2 to N.

In a second embodiment, the differences D _k are calculated by subtracting the successive carrier- to-interference ratios successively one from another.

For example, in the second embodiment, D _k = D _k . _{1 k} ' as described below :

D _k -i , _k ' = CIR _k _i ' - CIR _k '

wherein CIR _k ' are the carrier-to-interference ratios of said N-1 respective component carriers CC _k for k going from 2 to N and for each telecommunication user equipment UEi for i going from 1 to P.

Then, N-1 differences D _k . _{1 k} ' are calculated and associated to N-1 respective component carriers CC _k , which are other than the component carrier CC^ of lowest carrier frequency, for k going from 2 to N.

In a third step S3, it is determined that the bandwidth of each component carrier CC _k is able to cover a number m=m _k of telecommunication user equipments UEi. Consequently m depend on the component carrier CC _k and on indicia k. The number m _k of telecommunication user equipments UEi which each component carrier CC _k is able to cover is calculated. Third means to determine the number m of telecommunication user equipments UEi that each component carrier CC _k is able to cover, are provided for example in the node B and/or in the telecommunication user equipments UEi.

For example, m=m _k is the number of telecommunication user equipments UEi, whose bandwidths UEBWi are separately included in the bandwidth BW _k of said component carrier CC _k .

For example, m=m _k is proportional to the bandwidth BW _k of said component carrier CC _k divided by the sum of the required bandwidths UEBWi of said telecommunication user equipments UEi. The second step S2 can be carried out before the third step S3 as shown on Figure 2, but could also be carried out after the third step S3 or at the same time as the third step S3.

It is not compulsory that the number m of telecommunication user equipments UEi that a component carrier CC _k is able to cover, is strictly proportional to the bandwidth BW _k of the component carrier CC _k .

In a fourth step S4, the component carriers CC _k being ordered in the decreasing order of their carrier frequency, a number q of telecommunication user equipments UEi having the q lowest differences D _k for each associated component carrier CC _k are selected to be associated to said component carrier CC _k , with q < m or q < m _k .. Then the fourth step is carried out in the decreasing order of the carrier frequency of the component carriers CC _k . The telecommunication user equipments UEi are sorted according to the differences D _k , in the ascending order of these differences D _k . Fourth means to select, for the component carriers CC _k being ordered in the decreasing order of their carrier frequency, a number q of telecommunication user equipments UEi having the q lowest differences D _k for each associated component carrier CC _k with q < m, in order to associate said selected telecommunication user equipments UEi to said associated component carrier CC _k , are provided, for example in the node B and/or in the telecommunication user equipments UEi.

Consequently, the association begins with the component carrier CC _N having the highest carrier frequency (between A _N and B _N ). For the component carrier CC _N , q telecommunication user equipments UEi are selected and associated. For example, q < m _N for the component carrier CC _N . The q telecommunication user equipments UEi which are selected are the telecommunication user equipments UEi having the q lowest differences D _N , with k=N as described above.

Then the q telecommunication user equipments UEi associated to the component carrier CC^ are no more considered for the other associations to the other component carriers.

Suppose the current component carrier to be associated is component carrier CC _k , all the telecommunication user equipments UEi which have not been associated to any component carrier are reordered according to the smallest differences D _k = D _k (i), which means in the ascending order of the differences D _k = D _k (i), with i being variable (except the already associated user equipments UEi) and k being constant for this current component carrier CC _k . It means that the smaller differences D _k = D _k (i) come first.

If, for the current component carrier CC _k of highest carrier frequency, the number of telecommunication user equipments UEi left to be associated is u _k , then the sorted differences D _k = D _k (i) are differences D _k = {D _k (n1 ) < D _k (n2)≤ ... , < D _k (nu _k )} with D _k (ni) < D _k (ni+1 ), where πί is the user equipment index satisfying 1 < πί < u _k , and πί≠ nj when i≠ j.

Then, in the first embodiment mentioned above, if, for the current component carrier CC _k of highest carrier frequency, the number of telecommunication user equipments UEi left to be associated is u _k , then the sorted differences D _k = D _k (i) = D ' are differences D _k = {0 ₁ ^π < 0 ₁ ^π < < D _{1 k} ™ _k } with Di _, ™≤ D^™ ^*1 , where πί is the user equipment index satisfying 1 < πί < u _k , and πί≠ nj when i≠ j.

Then, in the second embodiment mentioned above, if, for the current component carrier CC _k of highest carrier frequency, the number of telecommunication user equipments UEi left to be associated is u _k , then the sorted differences D _k = D _k (i) = D _k . _{1 k} ' are differences D _k = {D^ ^ ¹ < D _k-1, ≤ ... , < D _k . i _,k ™ with D _k -Lk"' < D _k -i. _k "' ^*1 , where πί is the user equipment index satisfying 1 < πί < u _k , and πί≠ nj when i≠ j.

It is not compulsory that the number of telecommunication user equipments UEi that is associated to a component carrier CC _k or to each component carrier CC _k , is strictly proportional to the bandwidth BW _k of the component carrier CC _k , if it can't be satisfied.

In a fifth step S5, the q selected telecommunication user equipments UEi are associated to said component carrier CC _k as mentioned above for the fourth step. If all the component carriers CC _k except the component carrier CC^ of lowest carrier frequency are associated to telecommunication user equipments UEi and if it remains at least one unassociated telecommunication user equipment UEi, said at least one remaining telecommunication user equipment UEi is associated to the component carrier CC^ of lowest carrier frequency.. The association is then completed and ends. If there is at least one component carrier CC _k which is not associated, then step 4 is carried out again for this component carrier CC _k .

Steps S4 and S5 are carried out for example by the node B. Then node B divides the telecommunication user equipments UEi into groups, the number of which is equal to the number of component carriers CC _k or to the number of groups CC _k of component carriers. The telecommunication user equipments UEi will transmit and receive signals on the corresponding associated component carriers CC _k for a period of time, for example as in the independent carrier scheme (IC).

Figure 3 illustrates an example of the method of association according to the invention. For example, there are N=3 component carriers CC^, CC ₂ and CC ₃ of different propagation characteristics, all with the same bandwidth BWi, BW ₂ , BW ₃ . The component carrier CC^ has a carrier frequency fl lower than the carrier frequency f2 of component carrier CC ₂ , which itself has a carrier frequency f2 lower than the carrier frequency f3 of component carrier CC ₃ .

In the first step, the 3 carrier-to-interference ratios CIR/ , CIR ₂ ' , CIR ₃ ' are calculated for each of the telecommunication user equipments UEi = UE1 , UE2, UE3, UE4, UE5, UE6, UE7, UE8, UE9 transmitting respectively on the 3 component carriers CC^ , CC ₂ and CC ₃ .

In the second step, the differences D _1ik ' = CIR/ - CIR _k ' in the first embodiment are calculated, for k going from 1 to 3 (component carriers CC^ , CC ₂ and CC ₃ ) and for i going from 1 to 9.

In the third step, the number m = 3 telecommunication user equipments UEi is determined for each of the component carriers CCi, CC ₂ and CC ₃ . In the fourth step, for CC ₃ having the highest carrier frequency, which means k=3, all the telecommunication user equipments UEi are sorted in the first embodiment in an ascending order of D _{1 i3} ' = CIR - CIR ₃ ' and the first m = 3 first user equipments UEi are associated to CC ₃ , for example UE4, UE6 and UE2 as shown on Figure 3, for which respectively D _{1 3} ⁴ < D _{1 3} ⁶ < D _{1 3} ² .

Then, for the next component carrier CC ₂ having the highest carrier frequency, which means k=2, the left telecommunication user equipments UEi, except UE4, UE6 and UE2 which are associated to CC ₃ , are reordered in an ascending order of D _1i2 ' = CIR/ - CIR ₂ ' and the first m = 3 first user equipments UEi are associated to CC ₂ , for example UE3, UE1 and UE7 as shown on Figure 3, for which respectively D _{1 i3} ³ < D _1i3 ¹ < D _1i3 ⁷ .

At last, some remaining telecommunication user equipments UEi, which are for example UE5,

UE9 and UE8 are associated to component carriers CC^ .

In the invention, telecommunication user equipments that have higher carrier-to-interference ratio in low band than high band will get more reliable transmission in low band, so they will be associated to low component carrier, e.g. CC^ in Figure 3. And those with high carrier-to-interference ratio both in low band and high band will achieve similar result in either band, and therefore the allocation of them to the high band is reasonable. It is considered that fast fading is not considered in the allocation of user equipments.

It is also provided according to the invention a computer program comprising instructions for executing the method mentioned above, when said computer program is executed by a processor.

It is also provided according to the invention a non-transitory storage medium storing the computer program.