WO2016169047A1

WO2016169047A1 - Method and network node for pdcch resource allocation

Info

Publication number: WO2016169047A1
Application number: PCT/CN2015/077382
Authority: WO
Inventors: Kunpeng Qi; Anders Johansson; Bjorn Nordstrom; Ping Wu; Wei Zhao
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2015-04-24
Filing date: 2015-04-24
Publication date: 2016-10-27

Abstract

The present disclosure provides a method (100) for PDCCH resource allocation for a plurality of Scheduling Entities (SEs) in a control region. The method (100) comprises: determining (S110), for each of the plurality of SEs, a search space consisting a number of PDCCH candidates each including at least one Control Channel Element (CCE); assigning (S120), at least for each of other SEs than a first SE having a highest scheduling priority among the plurality of SEs, a SE weight associated with the SE to each CCE in the search space for the SE; calculating (S130), at least for each CCE in the search space for the first SE, a CCE weight by summing up the SE weights assigned to the CCE over at least the other SEs; selecting (S140), for the first SE, one PDCCH candidate based on the CCE weights calculated for the respective CCEs in the search space for the first SE.

Description

METHOD AND NETWORK NODE FOR PDCCH RESOURCE ALLOCATION

TECHNICAL FIELD

The disclosure relates to communication technology， and more particularly， to a method and a network node for Physical Downlink Control Channel (PDCCH) resource allocation.

BACKGROUND

In the Long Term Evolution (LTE) standard， Orthogonal Frequency Division Multiplexing (OFDM) technique has been adopted in downlink (DL) . In the time domain， one DL subframe has duration of 1ms and is divided into 12 or 14 OFDM symbols， depending on the subframe configuration. In the frequency domain， one OFDM symbol consists of a number of sub-carriers， depending on channel bandwidth and configuration. One OFDM symbol on one sub-carrier is referred to as a Resource Element (RE) .

In LTE， no dedicated data channel is used. Instead， shared channel resources are used in both DL and uplink (UL) . These shared channel resources， including DL-SCH (Downlink Shared Channel) and UL-SCH (Uplink Shared Channel) ， are controlled by a scheduler that allocates different portions of DL and UL shared channels to different User Equipments (UEs) for reception and transmission respectively.

The allocations of the shared channel resources are signaled in a control region covering a few OFDM symbols at the beginning of each DL subframe. The DL-SCH is transmitted in a data region covering the remaining OFDM symbols in each DL subframe. The size of the control region is typically one， two or three OFDM symbols and is set per subframe.

Physical Downlink Control Channel (PDCCH) carries control information and is transmitted in the control region of each subframe. A PDCCH can be transmitted over an aggregation of one or more consecutive Control Channel Elements (CCEs) . One CCE corresponds to nine Resource Element Groups (REGs) each containing four REs. Accordingly， the number of REGs in the control region that are not allocated to Physical Control Format Indicator Channel (PCFICH) or Physical Hybrid Automatic Repeat Request (HARQ) Indicator Channel (PHICH) is denoted as N_REG. The CCEs available in the control region are numbered from 0 to N_CCE-1， where

PDCCH supports multiple formats as listed in Table 1 below. A PDCCH consisting of n consecutive CCEs may only start with a CCE having an index i mod n ＝ 0， where 0≤i＜N_CCE. Multiple PDCCHs can be transmitted in a subframe.

Table 1-PDCCH Formats

A UE shall monitor a set of PDCCH candidates on one or more serving cells as configured via higher layer signaling for control information in each non-DRX (Discontinuous Reception) subframe by attempting to decode each of the PDCCH candidates in the set with all PDCCH formats.

The set of PDCCH candidates to be monitored constitute a search space， denoted as

where k represents a subframe index and L ∈ {1， 2， 4， 8} represents Aggregation Level (AL) ， i.e.， the number of CCEs included in a PDCCH candidate. There are two types of search spaces， UE-specific search space and common search space. An example of PDCCH candidates are listed in Table 2 below.

Table 2-PDCCH Candidates

For each serving cell on which PDCCH is monitored， the indices of the CCEs included in a PDCCH candidate having an index m in the search space

are given by：

where i＝0， …， L-1 and：

-for common search spaces：

Y_k＝0，

m′＝ m， m ＝ 0， …， M^(L)-1， M^(L) denotes the number of PDCCH candidates in the search space

and

-for UE-specific search spaces：

Y_k＝ (A·Y_k-1) mod D， Y_-1＝n_RNTI≠0， A＝39827， D＝65537 and

n_s is slot number within a radio frame， n_RNTI is the value of Radio Network Temporary Identifier (RNTI) of the UE，

m′＝ m +M^(L)·n_CI， if the UE is configured with a carrier indicator field， where n_CI is the value of the carrier indicator field； or otherwise m′＝ m， m ＝ 0， …， M^(L)-1， M^(L) denotes the number of PDCCH candidates in the search space

Resource allocations for PDCCHs are organized with respect to Scheduling Entities (SEs) . In this context， the term “SE” refers to a UE or a common control channel， corresponding to the above UE-specific search space and common search space， respectively. Resources (CCEs) can be allocated to an SE in accordance with the above Equation (1) . When it is desired to allocate resources to two or more SEs in a single subframe， these SEs’ search spaces may overlap， i.e.， collide with， each other. One or more SEs may not be allocated with resources successfully due to such collision and have to wait in a scheduling queue to be scheduled in subsequent subframes.

Each SE may have its scheduling priority， depending on e.g.， its traffic type and/or how long it has waited in the scheduling queue. Conventionally， the SE having the highest scheduling priority first selects a PDCCH candidate (e.g.， the one having the lowest CCE indices) from its search space， regardless of the search spaces of the remaining SEs’ in the scheduling queue.

Table 3 shows an exemplary PDCCH resource allocation. It is assumed here that there are three SEs， SE1， SE2 and SE3， to be scheduled in one single subframe and that SE1 has a higher scheduling priority than SE2， which in turn has a higher scheduling priority than SE3.

Table 3-Example of PDCCH resource allocation

As shown in Table 3， the search space for SE1 contains two PDCCH candidates C1-1 and C1-2 each having AL＝8， the search space for SE2 contains six PDCCH candidates C2-1 ～ C2-6 each having AL＝1 and the search space for SE3 contains six PDCCH candidates C3-1 ～ C3-6 each having AL＝2. According to the conventional PDCCH resource allocation scheme as discussed above， SE1 selects C1-1 first， which makes CCEs having indices 0 ～ 7 unavailable. Thus， SE2 will not be allocated with any PDCCH resource since its entire search space has been occupied by SE1. Then， SE3 selects C3-1 for its PDCCH transmission.

It can be seen from the above example shown in Table 3 that the conventional PDCCH resource allocation scheme cannot achieve the optimal resource utilization since SE2 is not allocated with any PDCCH resource. Further， it does not allow an SE having a higher scheduling priority (e.g.， SE2) to preempt another SE having a lower scheduling priority (e.g.， SE3) .

There is thus a need for an improved solution for PDCCH resource allocation.

SUMMARY

It is an object of the present disclosure to provide a method and a network node for PDCCH resource allocation， capable of achieving improved resource utilization.

In a first aspect， a method for Physical Downlink Control Channel (PDCCH) resource allocation for a plurality of Scheduling Entities (SEs) in a control region is provided. The method comprises： determining， for each of the plurality of SEs， a search space consisting a number of PDCCH candidates each including at least one Control Channel Element (CCE) ； assigning， at least for each of other SEs than a first SE having a highest scheduling priority among the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE； calculating， at least for each CCE in the search space for the first SE， a CCE weight by summing up the SE weights assigned to the CCE over at least the other SEs； selecting， for the first SE， one PDCCH candidate based on the CCE weights calculated for the respective CCEs in the search space for the first SE.

In an embodiment， the SE weight associated with each SE is dependent on at least one of a size of the search space for the SE and a scheduling priority of the SE.

In an embodiment， the SE weight associated with an SE having a smaller size of search space is higher than that associated with an SE having a larger size of search space. The step of selecting comprises： selecting， for the first SE， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for the first SE.

In an embodiment， the SE weight associated with each SE is further modified by a factor dependent on a scheduling priority of the SE. The factor for modifying the SE weight of an SE having a higher scheduling priority is larger than the factor for modifying the SE weight of an SE having a lower scheduling priority.

In an embodiment， the SE weight associated with an SE having a higher scheduling priority is higher than that associated with an SE having a lower scheduling priority. The step of selecting comprises： selecting， for the first SE， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for the first SE.

In an embodiment， the method further comprises： removing the first SE from the plurality of SEs and removing the CCEs included in the selected one PDCCH candidate from the control region.

In an embodiment， the method further comprises： calculating， for each of the remaining CCEs in search space for a second SE having a highest scheduling priority among the remaining SEs， a CCE weight by summing up the weights assigned to the CCE over the remaining SEs or over the remaining SEs other than the second SE.

In an embodiment， the step of calculating comprises： calculating， for each CCE in the control region， a CCE weight by summing up the SE weights assigned to the CCE over the other SEs. The method further comprises： updating the CCE weight for each of the remaining CCEs in the control region by subtracting from the CCE weight the SE weight associated with a second SE having a highest scheduling priority among the remaining SEs.

In an embodiment， the step of assigning comprises： assigning， for each of the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE. The step of calculating comprises： calculating， for each CCE in the control region， a CCE weight by summing up the SE weights assigned to the CCE over the plurality of SEs. The method further comprises： updating the CCE weight for each of the remaining CCEs in the control region by subtracting from the CCE weight the SE weight associated with the first SE.

In an embodiment， each SE is associated with a User Equipment (UE) or a common control channel. The step of determining comprises： determining for each UE a UE-specific search space； or determining for each common control channel a common search space.

In a second aspect， a network node for Physical Downlink Control Channel (PDCCH) resource allocation for a plurality of Scheduling Entities (SEs) in a control region is provided. The network node comprises： a determining unit configured to determine， for each of the plurality of SEs， a search space consisting a number of PDCCH candidates each including at least one Control Channel Element (CCE) ； an assigning unit configured to assign， at least for each of other SEs than a first SE having a highest scheduling priority among the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE； a calculating unit configured to calculate， at least for each CCE in the search space for the first SE， a CCE weight by summing up the SE weights assigned to the CCE over at least the other SEs； a selecting unit configured to select， for the first SE， one PDCCH candidate based on the CCE weights calculated for the respective CCEs in the search space for the first SE.

The above embodiments of the first aspect are also applicable for the second aspect.

With the embodiments of the present disclosure， an SE weight is introduced into resource allocation for a plurality of SEs in a control region. In an example， an SE weight can be assigned to each CCE in the search space for each SE. Then， a CCE weight can be calculated for each CCE in the search space for an SE having a highest scheduling priority based on the assigned SE weights. Finally， a PDCCH candidate is selected for that SE based on the calculated CCE weights. In this way， when selecting the PDCCH candidate for the SE having the highest scheduling priority， the SE weights of the other SEs can be considered to increase the probability that the other SEs will be allocated with PDCCH resources， thereby improving the resource utilization in the control region.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects， features and advantages will be more apparent from the following description of embodiments with reference to the figures， in which：

Fig. 1 is a flowchart illustrating a method for PDCCH resource allocation according to an embodiment of the present disclosure；

Fig. 2 is a block diagram of a network node for PDCCH resource allocation according to an embodiment of the present disclosure； and

Fig. 3 is a block diagram of a network node for PDCCH resource allocation according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

The embodiments of the disclosure will be detailed below with reference to the drawings. It should be noted that the following embodiments are illustrative only， rather than limiting the scope of the disclosure.

Fig. 1 is a flowchart illustrating a method 100 for PDCCH resource allocation according to an embodiment of the present disclosure. The method 100 can be applied in a network node (e.g.， an evolved NodeB (eNB) ) to allocate PDCCH resources for a plurality of SEs in a control region of a subframe. It is to be noted here that， in the context of the present disclosure， the term “PDCCH” may refer to the conventional PDCCH or the evolved PDCCH (ePDCCH) . Accordingly， the term “CCE” as used herein may refer to the conventional CCE or the evolved CCE (eCCE) .

Without loss of generality， it is assumed in the following that there are three SEs， SE1， SE2 and S3， as in the above Table 3. Again， it is assumed that SE1 has a higher scheduling priority than SE2， which in turn has a higher scheduling priority than SE3.

The method 100 will be explained with reference to the following exemplary schemes.

Scheme I

The method 100 according to this scheme includes the following steps.

At step S110， it is determined， for each of SE1， SE2 and SE3， a search space consisting a number of PDCCH candidates each including at least one CCE. The determination can be made in accordance with the above Equation (1) . Here， when an SE is associated with a UE， a UE-specific search space can be determined for the UE. Alternatively， when an SE is associated with a common control channel， a common search space can be determined for the common control channel.

In the following， it is assumed that the search spaces for SE1， SE2 and SE3 are the same as those shown in the above Table 3.

At step S120， for each of SE1， SE2 and SE3， an SE weight associated with that SE is assigned to each CCE in the search space for that SE.

In an example， the SE weight associated with each SE can be dependent on a size of the search space for the SE. For example， the SE weight associated with an SE having a smaller size of search space can be higher than that associated with an SE having a larger size of search space， or vice versa. In the example shown in the above Table 3， the sizes of the search spaces for SE1， SE2 and SE3 are 16， 6 and 12， respectively. Hence， as an example， the SE weights associated with SE1， SE2 and SE3 can be 1， 4 and 2， respectively.

At step S130， for each CCE in the search space for the SE having the highest scheduling priority among the plurality of SEs (i.e.， SE1) ， a CCE weight is calculated by summing up the SE weights assigned to the CCE over SE1， SE2 and SE3， as shown in Table 4 below.

Table 4-Example of CCE weights

At step S140， one PDCCH candidate is selected for SE1 based on the CCE weights calculated for the respective CCEs in the search space for SE1.

In the above example shown in Table 4， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE1 can be selected in the step S140. Since the sum of CCE weights for C1-2 is 3+3+3+3+3+3+3+3＝24， which is smaller than that for C1-1 (1+5+5+5+5+5+5+1＝32) ， C1-2 will be selected for SE1.

It is to be noted here that， if in the step S120 the SE weight associated with an SE having a smaller size of search space is lower than that associated with an SE having a larger size of search space， one PDCCH candidate with a largest sum of CCE weights among the PDCCH candidates in the search space for SE1 would be selected in the step S140. The same also applies to the schemes described hereinafter.

After being allocated with the PDCCH resource C1-2 in accordance with the rules discussed above， SE1 can be removed from the list of SEs that are to be allocated with PDCCH resources in the control region and the CCEs included in the selected PDCCH candidate C1-2 can be removed from the control region. Then， for each of the remaining CCEs in search space for the SE having the highest scheduling priority among the remaining SEs (i.e.， SE2) ， a CCE weight is calculated by summing up the weights assigned to the CCE over the remaining SEs (i.e.， SE2 and SE3) . This is shown in Table 5 below.

Table 5-Example of CCE weights

Then， similarly to the above step S140， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE2 can be selected. Here， since each of the PDCCH candidates C2-1 ～ C2-6 has the same CCE weight of 4， any one of them can be selected， e.g.， randomly， for SE2. For example， the PDCCH candidate with the lowest CCE index (i.e.， C2-1) can be selected.

Next， SE2 can be removed and the CCEs included in the selected PDCCH candidate C2-1 can be removed from the control region. In this case， the only remaining SE is SE3. This is shown in Table 6 below.

Table 6-Example of CCE weights

Then， similarly to the above step S140， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE3 can be selected. Here， since each of the PDCCH candidates C3-5 ～ C3-6 has the same CCE weight of 2， any one of them can be selected， e.g.， randomly， for SE3. For example， the PDCCH candidate with the lowest CCE index (i.e.， C3-5) can be selected.

With this scheme， SE1， SE2 and SE3 are allocated with PDCCH candidates C1-2， C2-1， C3-5， respectively. When compared with the conventional scheme discussed above in connection with Table 3， the resource utilization is improved as all the SEs have been allocated with PDCCH resources. Since an SE having a smaller size of search space is assigned with a higher SE weight and a PDCCH candidate with a smallest sum of CCE weights is selected (or vice versa) ， the probability that more SEs will be allocated with PDCCH resources can be increased.

Scheme II

The general principle of this scheme is substantially the same as the above Scheme I. Only the difference between this scheme and Scheme I will be described below.

It can be seen from the above Scheme I that the SE weight of SE1 does not affect the result of the selection. That is， it is equally applicable if the calculation of the CCE weights does not involve the SE weight of SE1. In this case， for each CCE in the search space for SE1， a CCE weight can be calculated by summing up the SE weights assigned to the CCE over SE2 and SE3 only， resulting in the following example as shown in Table 7 below.

Table 7-Example of CCE weights

In the above example shown in Table 7， the sum of CCE weights for C1-2 is 2+2+2+2+2+2+2+2＝16， which is smaller than that for C1-1 (0+4+4+4+4+4+4+0＝24) ， again C1-2 will be selected for SE1.

Since in this scheme the SE weight for SE1 is not considered in the calculation of the CCE weights， it is possible that the SE weight for SE1 is not assigned to each CCE in the search space for SE1. That is， in the step S120， only for each of SE2 and SE3， a SE weight associated with the SE is assigned to each CCE in the search space for the SE. In this case， it is even possible that SE1 does not have its associated SE weight.

After being allocated with the PDCCH resource C1-2 in accordance with the rules discussed above， SE1 can be removed from the list of SEs that are to be allocated with PDCCH resources in the control region and the CCEs included in the selected PDCCH candidate C1-2 can be removed from the control region. Then， for each of the remaining CCEs in search space for the SE having the highest scheduling priority among the remaining SEs (i.e.， SE2) ， a CCE weight is calculated by summing up the weights assigned to the CCE over the remaining SE other than SE2 (i.e.， SE3) . This is shown in Table 8 below. The example is only for generality that the search spaces of SE2 and SE3 are not partly overlapping. However， in practice， the larger the number of SEs to be allocated with PDCCH resources in a single control region is， the higher the possibility of potential collision will be because of at least partly overlapping of the search spaces for these SEs. Accordingly， if there are more SEs (e.g.， SE4， SE5， ...) in Table 8 below， the CCE weight for each CCE in the search space of SE2 would possibly be affected by the SE weight of SE4 or SE5 which has its search space at least partly overlapped with the search space of SE2.

Table 8-Example of CCE weights

Then， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE2 can be selected. Here， since each of the PDCCH candidates C2-1 ～ C2-6 has the same CCE weight of 0 (in this case， since no SE weight for SE3 is assigned to CCE 1 ～ 6， this SE weight can be considered as 0) ， any one of them can be selected for SE2. For example， the PDCCH candidate with the lowest CCE index (i.e.， C2-1) can be selected.

Next， SE2 can be removed and the CCEs included in the selected PDCCH candidate C2-1 can be removed from the control region. In this case， the only remaining SE is SE3. This is shown in Table 9 below.

Table 9-Example of CCE weights

Then， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE3 can be selected. Here， since each of the PDCCH candidates C3-5 ～ C3-6 has the same CCE weight of 0 (in this case， since there is no other remaining SE， the CCE weight can be considered as 0) ， any one of them can be selected for SE3. For example， the PDCCH candidate with the lowest CCE index (i.e.， C3-5) can be selected.

Scheme III

The general principle of this scheme is similar to the above Scheme I. The major difference between this scheme and Scheme I will be described below.

In the step S130， for each CCE in the control region， a CCE weight is calculated by summing up the SE weights assigned to the CCE over SE1， SE2 and SE3， as shown in Table 10 below. The difference from Scheme I is that the CCE weights of CCE 16 ～ 19 are calculated (as opposed to Table 4) .

Table 10-Example of CCE weights

In the step S140， one PDCCH candidate is selected for SE1 based on the CCE weights calculated for the respective CCEs in the search space for SE1.

In the above example shown in Table 10， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE1 can be selected in the step S140. Since the sum of CCE weights for C1-2 is 3+3+3+3+3+3+3+3＝24， which is smaller than that for C1-1 (1+5+5+5+5+5+5+1＝32) ， C1-2 will be selected for SE1.

After being allocated with the PDCCH resource C1-2 in accordance with the rules discussed above， SE1 can be removed from the list of SEs that are to be allocated with PDCCH resources in the control region and the CCEs included in the selected PDCCH candidate C1-2 can be removed from the control region. Then， the CCE weight for each of the remaining CCEs in the control region can be updated by subtracting from the CCE weight the SE weight associated with SE1. This is shown in Table 11 below. It can be seen that Table 11 differs from Table 5 in that the CCE weight has been calculated for each of the remaining CCEs， including CCEs 0， 7 and 16 ～ 19.

Table 11-Example of CCE weights

Then， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE2 can be selected. Here， since each of the PDCCH candidates C2-1 ～ C2-6 has the same CCE weight of 4， any one of them can be selected for SE2. For example， the PDCCH candidate with the lowest CCE index (i.e.， C2-1) can be selected.

Next， SE2 can be removed and the CCEs included in the selected PDCCH candidate C2-1 can be removed from the control region. In this case， the only remaining SE is SE3. This is shown in Table 12 below.

Table 12-Example of CCE weights

Then， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE3 can be selected. Here， since each of the PDCCH candidates C3-5 ～ C3-6 has the same CCE weight of 2， any one of them can be selected for SE3. For example， the PDCCH candidate with the lowest CCE index (i.e.， C3-5) can be selected.

Scheme IV

The general principle of this scheme is similar to the above Scheme III. The major difference between this scheme and Scheme III will be described below.

It can be seen from the above Scheme III that the SE weight of SE1 does not affect the result of the selection. That is， it is equally applicable if the calculation of the CCE weights does not involve the SE weight of SE1. In this case， for each CCE in the control region， a CCE weight can be calculated by summing up the SE weights assigned to the CCE over SE2 and SE3 only， resulting in the following example as shown in Table 13 below.

Table 13-Example of CCE weights

In the above example shown in Table 13， the sum of CCE weights for C1-2 is 2+2+2+2+2+2+2+2＝16， which is smaller than that for C1-1 (0+4+4+4+4+4+4+0＝24) ， again C1-2 will be selected for SE1.

After being allocated with the PDCCH resource C1-2 in accordance with the rules discussed above， SE1 can be removed from the list of SEs that are to be allocated with PDCCH resources in the control region and the CCEs included in the selected PDCCH candidate C1-2 can be removed from the control region. Then， the CCE weight for each of the remaining CCEs in the control region can be updated by subtracting from the CCE weight the SE weight associated with SE2. This is shown in Table 14 below.

Table 14-Example of CCE weights

Then， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE2 can be selected. Here， since each of the PDCCH candidates C2-1 ～ C2-6 has the same CCE weight of 0， any one of them can be selected for SE2. For example， the PDCCH candidate with the lowest CCE index (i.e.， C2-1) can be selected.

Next， SE2 can be removed and the CCEs included in the selected PDCCH candidate C2-1 can be removed from the control region. The CCE weight for each of the remaining CCEs in the control region can be updated by subtracting from the CCE weight the SE weight associated with SE3. This is shown in Table 15 below.

Table 15-Example of CCE weights

Then， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE3 can be selected. Here， since each of the PDCCH candidates C3-5 ～ C3-6 has the same CCE weight of 0， any one of them can be selected for SE3. For example， the PDCCH candidate with the lowest CCE index (i.e.， C3-5) can be selected.

Scheme V

This scheme is similar to the above Scheme I， except that the SE weight associated with each SE is dependent on a scheduling priority of the SE.

For example， the SE weight associated with an SE having a higher scheduling priority can be higher than that associated with an SE having a lower scheduling priority， or vice versa. As an example， the SE weights associated with SE1， SE2 and SE3 can be 4， 2 and 1， respectively. In this case， for each CCE in the search space for the SE having the highest scheduling priority among the plurality of SEs (i.e.， SE1) ， a CCE weight can be calculated as shown in Table 16 below.

Table 16-Example of CCE weights

In the above example shown in Table 16， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE1 can be selected in the step S140. Since the sum of CCE weights for C1-2 is 5+5+5+5+5+5+5+5＝40， which is smaller than that for C1-1 (4+6+6+6+6+6+6+4＝44) ， C1-2 will be selected for SE1.

After being allocated with the PDCCH resource C1-2 in accordance with the rules discussed above， SE1 can be removed from the list of SEs that are to be allocated with PDCCH resources in the control region and the CCEs included in the selected PDCCH candidate C1-2 can be removed from the control region. Then， for each of the remaining CCEs in search space for the SE having the highest scheduling priority among the remaining SEs (i.e.， SE2) ， a CCE weight is calculated by summing up the weights assigned to the CCE over the remaining SEs (i.e.， SE2 and SE3) . This is shown in Table 17 below.

Table 17-Example of CCE weights

Then， similarly to the above step S140， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE2 can be selected. Here， since each of the PDCCH candidates C2-1 ～ C2-6 has the same CCE weight of 2， any one of them can be selected for SE2. For example， the PDCCH candidate with the lowest CCE index (i.e.， C2-1) can be selected.

Next， SE2 can be removed and the CCEs included in the selected PDCCH candidate C2-1 can be removed from the control region. In this case， the only remaining SE is SE3. This is shown in Table 18 below.

Table 18-Example of CCE weights

Then， similarly to the above step S140， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for SE3 can be selected. Here， since each of the PDCCH candidates C3-5 ～ C3-6 has the same CCE weight of 1， any one of them can be selected for SE3. For example， the PDCCH candidate with the lowest CCE index (i.e.， C3-5) can be selected.

With this scheme， SE1， SE2 and SE3 are allocated with PDCCH candidates C1-2， C2-1， C3-5， respectively. When compared with the conventional scheme discussed above in connection with Table 3， the resource utilization is improved as all the SEs have been allocated with PDCCH resources. Furthermore， since an SE having a higher scheduling priority is assigned with a higher SE weight and a PDCCH candidate with a smallest sum of CCE weights is selected (or vice versa) ， the probability that an SE having a higher scheduling priority is allocated with PDCCH resources can be increased when compared with an SE having a lower scheduling priority.

Alternatively， the SE weight associated with each SE can be dependent on both a size of the search space for the SE and a scheduling priority of the SE. For example， in the above Scheme I where the SE weight associated with an SE having a smaller size of search space is higher than that associated with an SE having a larger size of search space， the SE weight associated with each SE can be further modified by a factor dependent on a scheduling priority of the SE. The factor for modifying the SE weight of an SE having a higher scheduling priority is larger than the factor for modifying the SE weight of an SE having a lower scheduling priority. In this way， if two SEs have the same size of search space but different scheduling priority， the probability that an SE having a higher scheduling priority is allocated with PDCCH resources can be increased when compared with an SE having a lower scheduling priority.

The above Schemes II， III and IV also apply to the situation where the SE weight associated with each SE is dependent on any one or both of a size of the search space for the SE and a scheduling priority of the SE.

Correspondingly to the method 100 as described above， a network node is provided. Fig. 2 is a block diagram of a network node 200 for PDCCH resource allocation for a plurality of SEs in a control region according to an embodiment of the present disclosure. The network node 200 can be e.g.， an eNB.

As shown in Fig. 2， the network node 200 includes a determining unit 210 configured to determine， for each of the plurality of SEs， a search space consisting a number of PDCCH candidates each including at least one Control Channel Element (CCE) . The method node 200 further includes an assigning unit 220 configured to assign， at least for each of other SEs than a first SE having a highest scheduling priority among the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE. The method node 200 further includes a calculating unit 230 configured to calculate， at least for each CCE in the search space for the first SE， a CCE weight by summing up the SE weights assigned to the CCE over at least the other SEs. The method node 200 further includes a selecting unit 240 configured to select， for the first SE， one PDCCH candidate based on the CCE weights calculated for the respective CCEs in the search space for the first SE.

In an embodiment， the SE weight associated with an SE having a smaller size of search space is higher than that associated with an SE having a larger size of search space. The selecting unit 240 is configured to select， for the first SE， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for the first SE.

In an embodiment， the SE weight associated with an SE having a higher scheduling priority is higher than that associated with an SE having a lower scheduling priority. The selecting unit 240 is configured to select， for the first SE， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for the first SE.

In an embodiment， the calculating unit 230 is further configured to remove the first SE from the plurality of SEs and remove the CCEs included in the selected one PDCCH candidate from the control region.

In an embodiment， the calculating unit 230 is further configured to calculate， for each of the remaining CCEs in search space for a second SE having a highest scheduling priority among the remaining SEs， a CCE weight by summing up the weights assigned to the CCE over the remaining SEs or over the remaining SEs other than the second SE.

In an embodiment， the calculating unit 230 is further configured to calculate， for each CCE in the control region， a CCE weight by summing up the SE weights assigned to the CCE over the other SEs， and to update the CCE weight for each of the remaining CCEs in the control region by subtracting from the CCE weight the SE weight associated with a second SE having a highest scheduling priority among the remaining SEs.

In an embodiment， the assigning unit 220 is configured to assign， for each of the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE. The calculating unit 230 is configured to calculate， for each CCE in the control region， a CCE weight by summing up the SE weights assigned to the CCE over the plurality of SEs， and to update the CCE weight for each of the remaining CCEs in the control region by subtracting from the CCE weight the SE weight associated with the first SE.

In an embodiment， each SE is associated with a User Equipment (UE) or a common control channel. The determining unit 210 is configured to determine for each UE a UE-specific search space， or to determine for each common control channel a common search space.

Each of the units 210-240 can be implemented as a pure hardware solution or as a combination of software and hardware， e.g.， by one or more of： a processor or a micro processor and adequate software and memory for storing of the software， a Programmable Logic Device (PLD) or other electronic component (s) or processing circuitry configured to perform the actions described above， and illustrated， e.g.， in Fig. 1.

Fig. 3 is a block diagram a block diagram of a network node 300 according to another embodiment of the present disclosure. The network node 300 is e.g.， an eNB.

The network node 3300 includes a transceiver 310， a processor 320 and a memory 330. The memory 330 contains instructions executable by the processor 320 whereby the network node 300 is operative to allocate Physical Downlink Control Channel (PDCCH) resource for a plurality of Scheduling Entities (SEs) in a control region by： determining， for each of the plurality of SEs， a search space consisting a number of PDCCH candidates each including at least one Control Channel Element (CCE) ； assigning， at least for each of other SEs than a first SE having a highest scheduling priority among the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE； calculating， at least for each CCE in the search space for the first SE， a CCE weight by summing up the SE weights assigned to the CCE over at least the other SEs； selecting， for the first SE， one PDCCH candidate based on the CCE weights calculated for the respective CCEs in the search space for the first SE.

The present disclosure also provides at least one computer program product in the form of a non-volatile or volatile memory， e.g.， an Electrically Erasable Programmable Read-Only Memory (EEPROM) ， a flash memory and a hard drive. The computer program product includes a computer program. The computer program includes： code/computer readable instructions， which when executed by the processor 320 causes the network 300 to perform the actions， e.g.， of the procedure described earlier in conjunction with Fig. 1.

The computer program product may be configured as a computer program code structured in computer program modules. The computer program modules could essentially perform the actions of the flow illustrated in Fig. 1.

The processor may be a single CPU (Central processing unit) ， but could also comprise two or more processing units. For example， the processor may include general purpose microprocessors； instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuit (ASICs) . The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a computer readable medium on which the computer program is stored. For example， the computer program product may be a flash memory， a Random-access memory (RAM) ， a Read-Only Memory (ROM) ， or an EEPROM， and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories.

The disclosure has been described above with reference to embodiments thereof. It should be understood that various modifications， alternations and additions can be made by those skilled in the art without departing from the spirits and scope of the disclosure. Therefore， the scope of the disclosure is not limited to the above particular embodiments but only defined by the claims as attached.

Claims

A method (100) for Physical Downlink Control Channel (PDCCH) resource allocation for a plurality of Scheduling Entities (SEs) in a control region， comprising：

-determining (S110) ， for each of the plurality of SEs， a search space consisting a number of PDCCH candidates each including at least one Control Channel Element (CCE) ；

-assigning (S120) ， at least for each of other SEs than a first SE having a highest scheduling priority among the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE；

-calculating (S130) ， at least for each CCE in the search space for the first SE， a CCE weight by summing up the SE weights assigned to the CCE over at least the other SEs；

-selecting (S140) ， for the first SE， one PDCCH candidate based on the CCE weights calculated for the respective CCEs in the search space for the first SE.
The method (100) of claim 1， wherein the SE weight associated with each SE is dependent on at least one of a size of the search space for the SE and a scheduling priority of the SE.
The method (100) of claim 2， wherein the SE weight associated with an SE having a smaller size of search space is higher than that associated with an SE having a larger size of search space， and said selecting (S140) comprises：

-selecting， for the first SE， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for the first SE.
The method (100) of claim 3， wherein the SE weight associated with each SE is further modified by a factor dependent on a scheduling priority of the SE， and wherein the factor for modifying the SE weight of an SE having a higher scheduling priority is larger than the factor for modifying the SE weight of an SE having a lower scheduling priority.
The method (100) of claim 2， wherein the SE weight associated with an SE having a higher scheduling priority is higher than that associated with an SE having a lower scheduling priority， and said selecting (S140) comprises：

-selecting， for the first SE， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for the first SE.
The method (100) of any of claims 1-5， further comprising：

-removing the first SE from the plurality of SEs and removing the CCEs included in the selected one PDCCH candidate from the control region.
The method (100) of claim 6， further comprising：

-calculating， for each of the remaining CCEs in search space for a second SE having a highest scheduling priority among the remaining SEs， a CCE weight by summing up the weights assigned to the CCE over the remaining SEs or over the remaining SEs other than the second SE.
The method (100) of claim 6， wherein said calculating (S130) comprises： calculating， for each CCE in the control region， a CCE weight by summing up the SE weights assigned to the CCE over the other SEs， and

the method further comprises：

-updating the CCE weight for each of the remaining CCEs in the control region by subtracting from the CCE weight the SE weight associated with a second SE having a highest scheduling priority among the remaining SEs.
The method (100) of claim 6， wherein said assigning (S120) comprises： assigning， for each of the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE，

said calculating (S130) comprises： calculating， for each CCE in the control region， a CCE weight by summing up the SE weights assigned to the CCE over the plurality of SEs， and

the method further comprises：

-updating the CCE weight for each of the remaining CCEs in the control region by subtracting from the CCE weight the SE weight associated with the first SE.
The method (100) of any of claims 1-9， wherein each SE is associated with a User Equipment (UE) or a common control channel， and said determining (S110) comprises：

-determining for each UE a UE-specific search space； or

-determining for each common control channel a common search space.
A network node (200) for Physical Downlink Control Channel (PDCCH) resource allocation for a plurality of Scheduling Entities (SEs) in a control region， comprising：

-a determining unit (210) configured to determine， for each of the plurality of SEs， a search space consisting a number of PDCCH candidates each including at least one Control Channel Element (CCE) ；

-an assigning unit (220) configured to assign， at least for each of other SEs than a first SE having a highest scheduling priority among the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE；

-a calculating unit (230) configured to calculate， at least for each CCE in the search space for the first SE， a CCE weight by summing up the SE weights assigned to the CCE over at least the other SEs；

-a selecting unit (240) configured to select， for the first SE， one PDCCH candidate based on the CCE weights calculated for the respective CCEs in the search space for the first SE.
The network node (200) of claim 11， wherein the SE weight associated with each SE is dependent on at least one of a size of the search space for the SE and a scheduling priority of the SE.
The network node (200) of claim 12， wherein the SE weight associated with an SE having a smaller size of search space is higher than that associated with an SE having a larger size of search space， and the selecting unit (240) is configured to select， for the first SE， one PDCCH candidate with a smallest sum of CCE weights among the PDCCH candidates in the search space for the first SE.
The network node (200) of claim 13， wherein the SE weight associated with each SE is further modified by a factor dependent on a scheduling priority of the SE， and wherein the factor for modifying the SE weight of an SE having a higher scheduling priority is larger than the factor for modifying the SE weight of an SE having a lower scheduling priority.
The network node (200) of claim 12， wherein the SE weight associated with an SE having a higher scheduling priority is higher than that associated with an SE having a lower scheduling priority， and the selecting unit (240) is configured to select， for the first SE， one PDCCH candidate with a smallest sum of CCEweights among the PDCCH candidates in the search space for the first SE.
The network node (200) of any of claims 11-15， wherein the calculating unit (230) is further configured to remove the first SE from the plurality of SEs and remove the CCEs included in the selected one PDCCH candidate from the control region.
The network node (220) of claim 16， wherein the calculating unit(230) is further configured to calculate， for each of the remaining CCEs in search space for a second SE having a highest scheduling priority among the remaining SEs， a CCE weight by summing up the weights assigned to the CCE over the remaining SEs or over the remaining SEs other than the second SE.
The network node (200) of claim 16， wherein the calculating unit (230) is further configured to calculate， for each CCE in the control region， a CCE weight by summing up the SE weights assigned to the CCE over the other SEs， and to update the CCE weight for each of the remaining CCEs in the control region by subtracting from the CCE weight the SE weight associated with a second SE having a highest scheduling priority among the remaining SEs.
The network node (200) of claim 16， wherein the assigning unit (220) is configured to assign， for each of the plurality of SEs， a SE weight associated with the SE to each CCE in the search space for the SE， and

the calculating unit (230) is configured to calculate， for each CCE in the control region， a CCE weight by summing up the SE weights assigned to the CCE over the plurality of SEs， and to update the CCE weight for each of the remaining CCEs in the control region by subtracting from the CCE weight the SE weight associated with the first SE.
The network node (200) of any of claims 11-19， wherein each SE is associated with a User Equipment (UE) or a common control channel， and the determining unit (210) is configured to determine for each UE a UE-specific search space， or to determine for each common control channel a common search space.