JP2015216703A - Radio communication method, radio communication system, and radio base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately allocate a radio resource to downlink control information in an enhanced physical downlink control channel.SOLUTION: A radio base station includes: a transmission section for transmitting downlink control information by using an enhanced physical downlink control channel on which frequency division multiplexing with a downlink shared data channel is performed; and a mapping section for mapping the downlink control information to a plurality of physical resource block (PRB) pairs set for the enhanced physical downlink control channel. The downlink control information is constituted in units of enhanced channel control element (eCCE) constituted by a plurality of enhanced resource element groups (eREG). The mapping section grants index numbers differing from each other to a plurality of enhanced resource element groups (eREG) constituting one enhanced channel control element (eCCE), and performs mapping of the enhanced resource element groups to different physical resource block (PRB) pairs.

Description

  The present invention relates to a radio communication method, a radio communication system, and a radio base station in a next generation radio communication system.

  In a UMTS (Universal Mobile Telecommunications System) network, Long Term Evolution (LTE) has been studied for the purpose of further high data rate and low delay (Non-patent Document 1). LTE uses a multi-access scheme based on OFDMA (Orthogonal Frequency Division Multiple Access) for the downlink (downlink) and SC-FDMA (single carrier frequency division multiple access) for the uplink (uplink). Is used.

  In addition, a successor system of LTE (for example, sometimes referred to as LTE advanced or LTE enhancement (hereinafter referred to as “LTE-A”)) has been studied for the purpose of further broadbandization and higher speed from LTE. In LTE (Rel. 8) and LTE-A (Rel. 9, Rel. 10), MIMO (Multi Input Multi Output) technology is used as a wireless communication technology for transmitting and receiving data with a plurality of antennas and improving frequency utilization efficiency. It is being considered. In the MIMO technique, a plurality of transmission / reception antennas are prepared in a transceiver, and different transmission information sequences are transmitted simultaneously from different transmission antennas.

3GPP TR 25.913 “Requirements for Evolved UTRA and Evolved UTRAN”

  By the way, in LTE-A, which is a successor system of LTE, multi-user MIMO (MU-MIMO) transmission in which transmission information sequences are simultaneously transmitted to different users from different transmission antennas has been studied. This MU-MIMO transmission is also applied to Hetnet (Heterogeneous network) and CoMP (Coordinated Multi-Point) transmission.

  In a future system, it is assumed that the capacity of the downlink control channel for transmitting downlink control information is insufficient due to an increase in the number of users connected to the radio base station. For this reason, there is a possibility that the characteristics of the future system such as MU-MIMO transmission cannot be sufficiently exhibited by the conventional radio resource allocation method.

  As a determination method for solving such a problem, a method of transmitting more downlink control information by extending the radio resource area for the downlink control channel can be considered. In such a case, in the extended downlink control channel, how to allocate radio resources to the downlink control information, that is, how to map the downlink control information to the resource area for the extended control channel is a problem. It becomes.

  The present invention has been made in view of this point, and an object of the present invention is to provide a radio communication method, a radio communication system, and a radio base station that can appropriately allocate radio resources to downlink control information in an extended downlink control channel. And

  The radio base station of the present invention includes a transmitter that transmits downlink control information using an extended downlink control channel that is frequency-division multiplexed with a downlink shared data channel, and a plurality of physical resource blocks (PRBs) that are set for the extended downlink control channel. A mapping unit that maps downlink control information to a pair, and the downlink control information is configured in units of extended control channel elements (eCCE) configured by a plurality of extended resource element groups (eREGs). The mapping unit assigns different index numbers to a plurality of extended resource element groups (eREG) constituting one extended control channel element (eCCE) and maps them to different physical resource block (PRB) pairs. It is characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, a radio | wireless resource can be appropriately allocated to downlink control information in the extended downlink control channel.

It is the schematic of Hetnet to which MU-MIMO is applied. It is a figure which shows an example of the sub-frame by which downlink MU-MIMO transmission is performed. It is explanatory drawing of the sub-frame structure of extended PDCCH. It is explanatory drawing of the mapping method of extended PDCCH. It is a figure which shows an example of the dispersion | distribution mapping of extended PDCCH. It is a figure which shows an example of the allocation method of eCCE * eREG with respect to PRB. It is a figure which shows an example of the allocation method of the index of eREG. It is a figure which shows an example of allocation of the index of eREG. It is a figure which shows an example of the allocation method of eCCE with respect to eREG of multiple PRB. It is a figure which shows an example of allocation of eCCE with respect to eREG of multiple PRB. It is explanatory drawing of the system configuration | structure of the radio | wireless communications system which concerns on this Embodiment. It is explanatory drawing of the whole structure of the wireless base station which concerns on this Embodiment. It is explanatory drawing of the whole structure of the user terminal which concerns on this Embodiment. It is a functional block diagram which shows the baseband process part and some upper layer of the wireless base station which concern on this Embodiment. It is a function block diagram of the baseband process part of the user terminal which concerns on embodiment.

  FIG. 1 is a diagram illustrating an example of Hetnet to which MU-MIMO transmission is applied. The system shown in FIG. 1 is provided with a small base station (for example, RRH: Remote Radio Head) having a local coverage area within a coverage area of a radio base station (for example, eNB: eNodeB), and is hierarchically configured. Has been. In downlink MU-MIMO transmission in such a system, data for a plurality of user terminals UE (User Equipment) # 1 and # 2 are simultaneously transmitted from a plurality of antennas of a radio base station. Further, data for a plurality of user terminals UE # 3 and # 4 are simultaneously transmitted from a plurality of antennas of a plurality of small base stations.

  FIG. 2 is a diagram illustrating an example of a radio frame (for example, one subframe) to which downlink MU-MIMO transmission is applied. As shown in FIG. 2, in a system to which MU-MIMO transmission is applied, radio resources for a downlink control channel (PDCCH: Physical Downlink Control Channel) from the beginning to a predetermined OFDM symbol (maximum 3 OFDM symbols) in each subframe It is secured as a region (PDCCH region). Also, a radio resource area (PDSCH area) for a downlink shared data channel (PDSCH) is secured in radio resources after a predetermined symbol from the beginning of the subframe.

  Downlink control information (DCI: Downlink Control Information) for user terminals UE (here, UE # 1 to # 4) is allocated to the PDCCH region. DCI includes data allocation information for the user terminal UE in the PDSCH region. For example, in FIG. 2, the user terminal UE # 2 receives data for the user terminal UE # 2 assigned to the PDSCH region based on the DCI for the user terminal UE # 2 assigned to the PDCCH region.

  Moreover, in MU-MIMO transmission, data transmission to a plurality of user terminals UE can be performed at the same time and the same frequency. For this reason, in the PDSCH region of FIG. 2, it is conceivable to multiplex data for the user terminal UE # 1 and data for the user terminal UE # 5 in the same frequency region. Similarly, it is also conceivable to multiplex data for user terminal UE # 4 and data for user terminal UE # 6 in the same frequency domain.

  However, as shown in FIG. 2, even if data for user terminals UE # 1 to # 6 is allocated in the PDSCH region, DCI allocation regions for all user terminals UE # 1 to # 6 cannot be secured in the PDCCH region. There is. For example, in the PDCCH region of FIG. 2, DCI for user terminals UE # 5 and # 6 cannot be assigned. In this case, since the number of user terminals UE multiplexed in the PDSCH region is limited due to the lack of the PDCCH region to which DCI is allocated, there is a possibility that the effect of improving the use efficiency of radio resources by MU-MIMO transmission may not be obtained sufficiently. .

  As a method for solving such a shortage of PDCCH regions, the PDCCH allocation region is expanded from the beginning of the subframe to a control region other than a maximum of 3 OFDM symbols (the PDCCH region is expanded to an existing PDSCH region after 4 OFDM symbols). Can be considered. As a method for extending the PDCCH region, as shown in FIG. 3A, a method of time-division multiplexing PDSCH and PDCCH in the existing PDSCH region (TDM approach), as shown in FIG. 3B, PDSCH and PDCCH in the existing PDSCH region. And frequency division multiplexing (FDM approach).

  In the TDM approach shown in FIG. 3A, PDCCH is arranged over the entire system band in some OFDM symbols after 4 OFDM symbols in a subframe. On the other hand, in the FDM approach shown in FIG. 3B, PDCCH is arranged in a part of the system band in all OFDM symbols after 4 OFDM symbols in a subframe. The PDCCH frequency-division multiplexed with the PDSCH by this FDM approach can be demodulated using a demodulation reference signal (DM-RS: DeModulation-Reference Signal) which is a user-specific reference signal. For this reason, DCI transmitted on the PDCCH can obtain a beamforming gain, similarly to downlink data transmitted on the PDSCH, and is effective for increasing the capacity of the PDCCH. In the future, this FDM approach will be important.

  Hereinafter, the PDCCH frequency-division multiplexed with the PDSCH in the FDM approach is referred to as an enhanced PDCCH (enhanced PDCCH). This enhanced PDCCH may be referred to as an enhanced physical downlink control channel, ePDCCH, E-PDCCH, FDM type PDCCH, UE-PDCCH, or the like.

  In the extended PDCCH of the FDM approach as described above, the present inventors are examining the application of local mapping and distributed mapping as DCI mapping methods. FIG. 4 is a diagram illustrating an example of a DCI mapping method in the extended PDCCH. FIG. 4A shows an example of local mapping, and FIG. 4B shows an example of distributed mapping.

  As shown in FIGS. 4A and 4B, the extended PDCCH resource is configured by a predetermined number of resource block pairs (PRB (Physical Resource Block) pairs, hereinafter referred to as “PRB pairs”) distributed in the system band. The PRB pair is composed of two PRBs continuous in the time direction (first half slot and second half slot), and is identified by a PRB index given in the frequency direction. The plurality of PRB pairs constituting the extended PDCCH resource are determined by higher layers or specifications. The PRB index for identifying each of the plurality of PRB pairs is notified to the user terminal UE by higher layer signaling or the like.

  As shown in FIG. 4A, in the local mapping, 1DCI is locally mapped to a specific PRB pair constituting the enhanced PDCCH resource. Specifically, 1DCI is mapped within 1 PRB pair (for example, PRB pair with the best channel quality) based on the CQI fed back from the user terminal UE. In local mapping, frequency scheduling gain can be obtained by using CQI. In FIG. 4A, PDSCH may be mapped to a PRB pair to which DCI is not mapped among a plurality of PRB pairs constituting the extended PDCCH resource.

  As shown in FIG. 4B, in the distributed mapping, 1DCI is distributed and mapped to a plurality of PRB pairs constituting the extended PDCCH resource. Specifically, 1DCI is divided into a plurality of divided units, and each divided unit is distributed and mapped to the plurality of PRB pairs (may be all PRB pairs). In the dispersion mapping, frequency diversity gain can be obtained by dispersing 1DCI in the system band.

  As described above, in the distributed mapping, unlike the local mapping, each DCI is divided into a plurality of division units, and each division unit is distributed and mapped to a plurality of PRB pairs constituting the extended PDCCH resource.

  By the way, the downlink control information (DCI) allocated to the existing PDCCH arranged from the head of the subframe to the predetermined OFDM symbol is generated in units of control channel elements (CCE). The CCE is composed of nine resource element groups (REG: Resource Element Group), and each REG is composed of a set of four resource elements (RE: Resource Element).

  The present inventors are considering generating downlink control information (DCI) to be assigned to the extended PDCCH in units of predetermined control channel elements so that the existing CCE can be reused (for example, blind decoding). In the following description, a control channel element constituting downlink control information assigned to the extended PDCCH is referred to as an enhanced control channel element (eCCE: enhanced Channel Control Element).

  In this case, an extended control channel element (eCCE) can be composed of a plurality of resource element groups, and distributedly mapped in resource element group units to a plurality of PRB pairs for extended PDCCH. In the following description, a resource element group constituting an extended control channel element (eCCE) is referred to as an extended resource element group (eREG).

  FIG. 5 is a diagram illustrating an example of distributed mapping in the case where an extended PDCCH is provided. Here, a case is shown in which a system band is composed of 11 physical resource blocks (PRB pairs). The 11 PRB pairs are assigned PRB indexes (PRB # 0 to # 10) along the frequency direction. Here, the extended PDCCH is set to four PRB pairs # 1, # 4, # 8, and # 10 (see FIG. 5A). In FIG. 5A, the extended PDCCH is mapped in units of PRBs, but is not limited to this. For example, it may be performed in units of resource block groups (RBGs) composed of a plurality of continuous PRBs (for example, two or four PRB pairs).

  In FIG. 5A, when each PRB pair is composed of 4 eCCEs, the total number of eCCEs is 16. In this case, different eCCE index numbers # 0 to # 15 are assigned to the respective eCCEs (see FIG. 5B). Each eCCE is mapped to a PRB pair (see FIG. 5C) and then transmitted to the user terminal.

  In the mapping of eCCE, when distributed mapping is applied as shown in FIG. 4B, each eCCE is distributed to a plurality of PRB pairs (for example, PRB pairs # 1, # 4, # 8, and # 10). The mapping can be performed in units of division units (eREG) (see FIG. 5C). FIG. 5C shows a case where eCCE with index number 0 (eCCE # 0) is mapped to eREG (eREG # 0) with index number 0 of PRB # 1 and eREG # 4 with PRB # 8. That is, the two eREGs constituting the eCCE # 0 are mapped as eREG # 0 of PRB # 1 and eREG # 4 of PRB # 8.

  However, in this case, how to divide into multiple eREGs in each PRB pair (which eREG with different index numbers is set to which RE), how to map eCCE to eREGs in multiple PRB pairs , Not decided about.

  By the way, it has been studied to configure an eREG that is a mapping unit of eCCE for a PRB pair with a predetermined number of resource elements (RE). In one PRB pair in normal cyclic prefix (normal CP) and normal subframe (normal subframe), the number of REs that can be used as an extended PDCCH is defined as a predetermined value (for example, 144), and the number of REs of the predetermined value is Based on this, the number of eREG divisions (the number of eREGs included in one PRB pair) can be determined. When the number of REs that can be used as the extended PDCCH is defined as 144, the 144 corresponds to the total number of REs in one PRB pair (168) minus the number of REs in which DM-RSs are arranged (24). To do.

  For example, as shown in FIG. 6, when one PRB pair is divided into 8 eREGs (eREG # 0 to # 7), a method of providing eREG by dividing the PRB pair in a predetermined frequency / time axis direction is considered. It is done. In FIG. 6, when one PRB pair is divided into 8 eREGs (eREG # 0 to # 7), the eREG is provided by dividing into 4 in the frequency axis direction and 2 in the time axis direction (first half slot and second half slot). Shows the case. In this case, assuming that 1PRB is composed of 4 eCCEs (eg, 1eCCE is 36 REs), 1eCCE can be composed of 2 eREGs. That is, FIG. 6 shows a case where 1 eCCE composed of two eREGs is mapped to a PRB pair in units of eREG.

  As described above, when each eREG is provided in an area partitioned in the frequency axis direction and the time axis direction in one PRB pair, REs constituting the 1 eREG are collectively arranged in a predetermined area. That is, as shown in FIG. 6, the eREGs to which the respective index numbers are attached are provided collectively in areas divided in the frequency and time axis directions.

  In this case, there is a possibility that the number of REs that can be used for the extended PDCCH is different (non-uniform) between eREGs assigned different index numbers. This is because, as described above, the RE in the region where the DM-RS is arranged in one PRB pair cannot be used for the extended PDCCH. For example, in FIG. 6, in a PRB pair, when other than the RE in which DM-RS is arranged is used for the extended PDCCH, eREG # 3 includes 17 REs and eREG # 5 includes 19 REs. Therefore, depending on the combination of a plurality of eREGs, the sizes may be different (non-uniform) among the plurality of eCCEs.

  Further, when each eREG is provided in a predetermined area in one PRB pair, a large number of REs constituting the 1eREG are arranged in the same OFDM symbol. When the total power is limited within one OFDM symbol, if the eREGs are aggregated in a predetermined area, there is a possibility that the power utilization efficiency cannot be sufficiently achieved without averaging between the eREGs.

  Accordingly, the present inventors have mapped a plurality of REs constituting each eREG and / or a plurality of eREGs constituting each eCCE in a resource region (PRB, RBG, etc.) where the extended PDCCH is located. It has been found that downlink control information can be appropriately allocated to the resource region for the extended PDCCH by controlling the method.

  Specifically, it has been found that power utilization efficiency can be improved by dispersing a plurality of REs constituting 1eREG into a plurality of OFDM symbols in a resource region in which the extended PDCCH is arranged. In addition, at least in an existing LTE system (Rel. 8 to Rel10), a region where a control channel (existing PDCCH arranged in 1 to 3 OFDM symbols from the top of a subframe) is arranged, a reference signal (for example, CRS (Cell specific) The size of the eREGs is made uniform by uniformly allocating the REs constituting the eREGs of the respective index numbers to the REs in the regions in which the Reference Signal)) and the data channel (existing PDSCH) are arranged. I found out that

  Also, a plurality of eREGs constituting 1 eCCE are distributed to a plurality of resource regions where extended PDCCHs are arranged, and downlink control information (DCI) is mapped so that index numbers of the plurality of eREGs constituting 1 eCCE are different from each other. As a result, it has been found that the frequency diversity effect can be obtained and the size of the eCCE can be made uniform. Hereinafter, the present embodiment will be described in detail.

(EREG index assignment method)
With reference to FIG. 7, a method of assigning an eREG index to each RE (arrangement pattern control of a plurality of REs constituting each eREG) in a resource region where the ePDCCH is arranged will be described. In FIG. 7, the resource area is described by taking, as an example, a 1PRB pair in a normal cyclic prefix / normal subframe, but is not limited thereto.

  FIG. 7A shows a resource region (1PRB) in which ePDCCH is arranged. The resource region shown in FIG. 7 includes first to third regions that can be used for ePDCCH, and a fourth region in which DM-RSs are arranged and not used for ePDCCH. The first area, the second area, and the third area are allocated in the 1 to 3 OFDM symbols from the top of the PDSCH and subframe in the existing LTE system (or other resource areas in which ePDCCH is not allocated), respectively. This corresponds to an area where the existing PDCCH and the reference signal (CRS) are arranged.

  When the reference signal (CRS) is arranged in the resource area where the ePDCCH is arranged, when the first area and the second area are used for the ePDCCH and the reference signal and the existing PDCCH are arranged, The first area is used for ePDCCH. That is, in the resource region, the first region is the region most likely to be used for eCCE mapping.

  In the present embodiment, in such a resource region, mapping is performed so that the number of REs constituting different eREGs is uniform and a plurality of REs constituting one eREG are distributed over a plurality of OFDM symbols. Note that the uniform number of REs constituting different eREGs is not necessarily limited to the case where the number of REs is the same between different eREGs, and the difference in the number of REs between eREGs is made as small as possible (preferably different eREGs). The difference in the number of REs that constitute each is set to be within 1).

  For example, it is possible to make the sizes of the eREGs uniform by controlling the REs in the first to third regions so that the allocation of the respective eREG index numbers is equal. Further, by assigning each eREG index number to REs of different OFDM symbols, it is possible to distribute the REs constituting each eREG into a plurality of OFDM symbols. Below, an example of the allocation method of the eREG index number corresponding to each RE is demonstrated below.

<Step 1>
First, the REs in the regions (first region to third region) that can be used for ePDCCH are numbered (numbered) in order from the REs that are likely to be used for ePDCCH (see FIG. 7B). . For example, after numbering the REs in the first region, the regions (second region and third region) that may be used for other signals are numbered. Although FIG. 7B shows a case where the numbering is performed on the second area and then the numbering is performed on the third area, the numbering may be performed in the reverse order. Also, no numbering is performed on the RE in the fourth area where the DM-RS is arranged.

  For example, the numbering is performed in order along the frequency axis direction (vertical direction in FIG. 7B), starting from the RE in the region where the frequency and time are the smallest in the first region. Also, a cyclic shift may be applied for each OFDM symbol as shown in FIG. 7B so that REs constituting each eREG are dispersed as much as possible.

  In FIG. 7B, first, REs in the first area are numbered from 0 to 95. Subsequently, the REs in the second region are numbered from 96 to 127 along one OFDM symbol from the 3 OFDM symbol side, and then the REs in the third region are numbered from 128 to 143. .

<Step 2>
Next, a modulo operation is applied to the index assigned to each RE in step 1 using the number N of eREGs provided in the PRB pair. This case corresponds to the case where the PRB pair is divided into N eREGs.

  The number N of eREGs provided in the PRB pair can be selected from 8, 12, 16, 24, or 36, for example. This is because by selecting one of these numbers, the number of REs (144) that can be used for ePDCCH can be evenly allocated to each eREG. In particular, N is preferably 8, 16, or 36.

  FIG. 8A shows a case where a modulo operation of N = 8 is applied, and FIG. 8B shows a case where a modulo operation of N = 16 is applied. In the case of FIG. 8A, an index (eREG index number) of 0 to 7 is attached to an RE that can be used as ePDCCH. In this case, the eight eREGs with index numbers 0 to 7 are each composed of a maximum of 18 REs. In the case of FIG. 8B, an index (eREG index number) of 0 to 15 is attached to an RE that can be used as ePDCCH. In this case, the 16 eREGs with index numbers 0 to 15 are each composed of a maximum of 9 REs.

  In this way, after numbering the REs that can be used for ePDCCH in order, the RE number corresponding to each RE is determined by modulo calculation, thereby distributing a plurality of REs constituting one eREG into a plurality of OFDM symbols. It becomes possible. As a result, a large number of REs of eREGs having different index numbers can be arranged in the same OFDM symbol, and the power can be equalized between the OFDM symbols. Therefore, compared with the eREG allocation shown in FIG. The utilization efficiency of can be improved.

  In addition, by assigning numbers in order from the REs of the regions that are most likely to be used for ePDCCH among the regions (first region to third region) that can be used for ePDCCH, an index number is assigned to each region. REs of different eREGs can be equally arranged. As a result, even when a reference signal (CRS) and / or an existing PDCCH is arranged in a resource area allocated for ePDCCH, the sizes of the respective eREGs can be made substantially uniform.

(ECCE mapping method using eREG as an allocation unit)
Next, an eCCE mapping method for a plurality of resource areas will be described. In the present embodiment, a plurality of eREGs constituting one eCCE are distributed to a plurality of resource regions (here, PRB pairs) in which extended PDCCHs are arranged, and the index numbers of each eREG distributed to each resource region The downlink control information (DCI) is mapped so that each is different. Hereinafter, an example of a method for mapping eCCEs in units of eREGs to a plurality of resource regions (here, PRB pairs) that can be used as ePDCCH will be described with reference to FIG. In the following description, a case where 36 REs constituting an eCCE are defined (36 RE / 1 eCCE) will be described. However, in the present embodiment, the size of the eCCE is not limited to this.

  As described above, when the total number of REs that can be used as ePDCCH in one PRB pair is 144, assuming that 1 eCCE = 36 RE, a maximum of 4 eCCEs can be allocated to one PRB pair. In this case, the total number of eCCEs that can be used for downlink control information (DCI) transmitted using ePDCCH in the system band is the resource area × 4 arranged as ePDCCH. For example, as shown in FIG. 5A, when the extended PDCCH is set to four PRB pairs # 1, # 4, # 8, and # 10, the number of available eCCEs is 16.

  In this case, the number of eREGs constituting 1 eCCE can be obtained by “36 / (144 / N)”. That is, the value is obtained by dividing the number 36 of REs constituting 1 eCCE by the size of eREG (number of REs constituting 1 eREG). As described above, N corresponds to the number of eREGs provided in one resource region (for example, one PRB pair).

  For example, when eight eREGs are included in one PRB pair (N = 8), the number of eREGs constituting one eCCE is two. Further, when 16 eREGs are included in one PRB pair (N = 16), the number of eREGs constituting one eCCE is 4.

  FIG. 9A shows four resource areas in which the extended PDCCH is arranged (here, PRB pairs # 1 to # 4), and each PRB pair and a plurality of eREGs when the number N of eREGs allocated to one PRB pair is 16. The relationship with (eREG index) is shown. That is, eREG # 0 to # 15 are mapped to each PRB pair # 1 to # 4. As shown in FIG. 8B, the REs constituting each of the eREGs # 0 to # 15 can be distributed and arranged in each PRB pair.

  In addition, when the number of eCCEs allocated to one PRB pair is 4, the number of eREGs constituting one eCCE is 4. In this case, a plurality of eCCEs (here, 16 eCCEs # 0 to # 15) can be mapped to each PRB # 1 to # 4 as shown in FIG. 9B.

  In FIG. 9B, mapping is performed so that a plurality of eREGs constituting one eCCE are distributed to different PRB pairs and the index numbers of the plurality of eREGs distributed to different PRB pairs are different. That is, a plurality of eREGs constituting one eCCE are mapped to different PRB pairs with different eREG index numbers attached thereto.

  As described above, a frequency diversity effect can be obtained by mapping a plurality of eREGs constituting one eCCE to different PRB pairs. In addition, by configuring 1 eCCE with eREGs having different index numbers, it is possible to reduce non-uniform sizes between eCCEs.

  Specifically, the eCCE index is mapped in order to the eREG index of a plurality of PRB pairs. At this time, mapping is performed so that eCCEs having consecutive index numbers are assigned to different PRB pairs. For example, as shown in FIG. 9B, eCCEs # 0 to # 3 are allocated to eREG # 0 allocated to PRB pairs # 1 to # 4. Similarly, eCCEs # 4 to # 7 are assigned to eREG # 1 assigned to PRB pairs # 1 to # 4. The same procedure is performed until a plurality of eCCEs complete a cycle. As a result, eCCEs # 0 to # 15 are assigned to eREGs # 0 to # 3 assigned to the PRB pairs # 1 to # 4.

  Subsequently, after a plurality of eCCEs have been allocated, a cyclic shift is added and the allocation is performed in the same manner. For example, as shown in FIG. 9B, eCCEs # 0 to # 3 are allocated to eREG # 4 allocated to PRB pairs # 1 to # 4. However, in each eREG index, each eCCE is assigned in the order of PRB pairs # 2 to # 3, # 4, and # 1 (cyclic shift).

Thereby, a plurality of eREGs constituting one eCCE can be mapped to different PRB pairs. The cyclic shift amount can be determined by “the number of PRB pairs (N _PRB ) / the number of eREGs per eCCE (N _eREG )”. In this case, the cyclic shift amount is 1 (= 4/4).

  By repeatedly performing the above mapping method, a plurality of eCCEs can be mapped to each PRB pair in units of eREGs as shown in FIG. 9B. For example, four eREGs constituting eCCE # 0 having an eCCE index number of 0 are distributed and allocated to PRB # 1 to # 4, respectively. The four eREGs that make up eCCE # 0 are eREG # 0 (PRB pair # 1), eREG # 4 (PRB pair # 2), eREG # 8 (PRB pair # 3), eREG # 12 (PRB pair). # 4).

  As described above, by mapping a plurality of eREGs constituting one eCCE to different PRB pairs with different eREG index numbers attached thereto, it is possible to obtain a frequency diversity effect and to make the sizes of the eCCEs uniform. .

  In addition, eREGs mapped to each PRB pair can be distributed and arranged in REs of a plurality of OFDM symbols in one PRB as shown in FIG. As a result, it is possible to improve the power utilization efficiency and to effectively equalize the size between eREGs and between eCCEs.

  Next, FIG. 10A shows an eCCE mapping method when 4 PRB pairs are applied for extended PDCCH and 1 PRB pair is divided into 8 eREGs (N = 8). FIG. 10B shows an eCCE mapping method when a PRB pair is applied and one PRB pair is divided into 8 eREGs (N = 8). In FIG. 10, it is assumed that the number of eCCEs per 1 PBR is 4 (for example, 1 eCCE = 36 RE).

  10A and 10B, as shown in FIG. 9 above, a plurality of eREGs constituting one eCCE are mapped to different PRB pairs with different eREG index numbers. In the case shown in FIG. 10, the total number of eCCEs (16 in FIG. 10A and 32 in FIG. 10B) is larger than the number of eREGs included in one PRB pair. In this case, as shown in FIG. 9, the eCCE index is sequentially mapped to the eREG indexes of a plurality of PRB pairs, and as a result, eREGs of eCCEs having consecutive index numbers are assigned to different PRB pairs. .

  For example, eREGs constituting eCCE # 0 and eCCE # 1 are mapped to different PRB pairs. In this case, in FIG. 10A, two eREGs constituting eCCE # 0 are mapped to PRB pair # 1 (eREG # 0) and PRB pair # 3 (eREG # 4), and two eREGs constituting eCCE # 1 are mapped. eREG is mapped to PRB pair # 2 (eREG # 0) and PRB pair # 4 (eREG # 4). Thus, by mapping eREGs of eCCEs having consecutive index numbers to different PRB pairs, it is possible to obtain a frequency diversity effect even when the eCCE coupling level (aggregation level) is high.

  In addition, although this Embodiment demonstrated as each frequency resource unit which comprises an extended PDCCH set being a PRB pair, it is not restricted to this. Each frequency resource unit may be a PRB, an RBG (Resource Block Group) composed of PRBs continuous in the frequency direction, or the like.

  Hereinafter, the radio communication system according to the present embodiment will be described in detail.

(Configuration of wireless communication system)
FIG. 11 is an explanatory diagram of a system configuration of the wireless communication system according to the present embodiment. Note that the radio communication system shown in FIG. 11 is a system including, for example, an LTE system or a successor system. In this radio communication system, carrier aggregation in which a plurality of fundamental frequency blocks with the system band of the LTE system as a unit is integrated is used. Moreover, this radio | wireless communications system may be called IMT-Advanced, and may be called 4G.

  As shown in FIG. 11, the radio communication system 1 includes a radio base station 10 and a plurality of user terminals 20 that communicate with the radio base station 10. The radio base station 10 is connected to the upper station apparatus 30, and the upper station apparatus 30 is connected to the core network 40. The wireless base stations 10 are connected to each other by wired connection or wireless connection. Each user terminal 20 (20A, 20B) can communicate with the radio base station 10 in the cells C1, C2. The upper station device 30 includes, for example, an access gateway device, a radio network controller (RNC), a mobility management entity (MME), and the like, but is not limited thereto.

  Each user terminal 20 includes an LTE terminal and an LTE-A terminal. In the following, the description will proceed as a user terminal unless otherwise specified.

  In the radio communication system 1, OFDMA (Orthogonal Frequency Division Multiple Access) is applied to the downlink and SC-FDMA (Single Carrier-Frequency Division Multiple Access) is applied to the uplink as the radio access scheme. The wireless access method is not limited to this. OFDMA is a multi-carrier transmission scheme that performs communication by dividing a frequency band into a plurality of narrow frequency bands (subcarriers) and mapping data to each subcarrier. SC-FDMA is a single carrier transmission scheme that reduces interference between terminals by dividing a system band into bands each consisting of one or continuous resource blocks for each terminal, and a plurality of terminals using different bands. .

  Here, the communication channel will be described. The downlink communication channel includes PDSCH (Physical Downlink Shared Channel) as a downlink data channel shared by each user terminal 20, a downlink L1 / L2 control channel (PDCCH, PCFICH, PHICH), and an extended PDCCH obtained by extending PDCCH. And have. User data and higher control information are transmitted by the PDSCH. PDSCH and PUSCH scheduling information and the like are transmitted by PDCCH (Physical Downlink Control Channel). The number of OFDM symbols used for PDCCH is transmitted by PCFICH (Physical Control Format Indicator Channel). HARQ ACK / NACK for PUSCH is transmitted by PHICH (Physical Hybrid-ARQ Indicator Channel).

  PDSCH and PUSCH scheduling information and the like are transmitted by the extended PDCCH. The extended PDCCH is used to support a lack of PDCCH capacity using a resource region to which the PDSCH is allocated.

  The uplink communication channel includes a PUSCH (Physical Uplink Shared Channel) as an uplink data channel shared by each user terminal and a PUCCH (Physical Uplink Control Channel) that is an uplink control channel. User data and higher control information are transmitted by this PUSCH. Also, downlink radio quality information (CQI: Channel Quality Indicator), ACK / NACK, and the like are transmitted by PUCCH.

  FIG. 12 is an overall configuration diagram of the radio base station 10 according to the present embodiment. The radio base station 10 includes a plurality of transmission / reception antennas 101 for MIMO transmission, an amplifier unit 102, a transmission / reception unit 103, a baseband signal processing unit 104, a call processing unit 105, and a transmission path interface 106. Yes.

  User data transmitted from the radio base station 10 to the user terminal 20 via the downlink is input from the higher station apparatus 30 to the baseband signal processing unit 104 via the transmission path interface 106.

  The baseband signal processing unit 104 performs PDCP layer processing, user data division / combination, RLC layer transmission processing such as RLC (Radio Link Control) retransmission control transmission processing, MAC (Medium Access Control) retransmission control, for example, HARQ transmission processing, scheduling, transmission format selection, channel coding, inverse fast Fourier transform (IFFT) processing, and precoding processing are performed and transferred to each transmitting / receiving section 203. The downlink control channel signal is also subjected to transmission processing such as channel coding and inverse fast Fourier transform, and is transferred to each transceiver 103.

  Moreover, the baseband signal processing part 104 notifies the control information for communication in the said cell with respect to the user terminal 20 with an alerting | reporting channel. The information for communication in the cell includes, for example, the system bandwidth in the uplink or the downlink.

  Each transmission / reception unit 103 converts the baseband signal output by precoding for each antenna from the baseband signal processing unit 104 to a radio frequency band. The amplifier unit 102 amplifies the frequency-converted radio frequency signal and transmits the amplified signal using the transmission / reception antenna 101.

  On the other hand, for data transmitted from the user terminal 20 to the radio base station 10 via the uplink, radio frequency signals received by the respective transmission / reception antennas 101 are amplified by the amplifier units 102 and frequency-converted by the respective transmission / reception units 103. It is converted into a baseband signal and input to the baseband signal processing unit 104.

  The baseband signal processing unit 104 performs FFT processing, IDFT processing, error correction decoding, MAC retransmission control reception processing, RLC layer, and PDCP layer reception processing on user data included in the input baseband signal. The data is transferred to the higher station apparatus 30 via the transmission path interface 106. The call processing unit 105 performs call processing such as communication channel setting and release, status management of the radio base station 10, and radio resource management.

  FIG. 13 is an overall configuration diagram of the user terminal 20 according to the present embodiment. The user terminal 20 includes a plurality of transmission / reception antennas 201 for MIMO transmission, an amplifier unit 202, a transmission / reception unit (reception unit) 203, a baseband signal processing unit 204, and an application unit 205.

  For downlink data, radio frequency signals received by a plurality of transmission / reception antennas 201 are respectively amplified by an amplifier unit 202, frequency-converted by a transmission / reception unit 203, and converted into a baseband signal. The baseband signal is subjected to FFT processing, error correction decoding, retransmission control reception processing, and the like by the baseband signal processing unit 204. Among the downlink data, downlink user data is transferred to the application unit 205. The application unit 205 performs processing related to layers higher than the physical layer and the MAC layer. Also, broadcast information in the downlink data is also transferred to the application unit 205.

  On the other hand, uplink user data is input from the application unit 205 to the baseband signal processing unit 204. In the baseband signal processing unit 204, transmission processing for retransmission control (H-ARQ (Hybrid ARQ)), channel coding, precoding, DFT processing, IFFT processing, and the like are performed and transferred to each transmitting / receiving unit 203. The transmission / reception unit 203 converts the baseband signal output from the baseband signal processing unit 204 into a radio frequency band. Thereafter, the amplifier unit 202 amplifies the frequency-converted radio frequency signal and transmits the amplified signal using the transmitting / receiving antenna 201.

  FIG. 14 is a functional configuration diagram of the baseband signal processing unit 104 and some upper layers included in the radio base station 10 according to the present embodiment. Although FIG. 14 mainly shows a functional configuration for downlink (transmission), the radio base station 10 may include a functional configuration for uplink (reception).

  As illustrated in FIG. 14, the radio base station 10 includes an upper layer control information generation unit 300, a data generation unit 301, a channel encoding unit 302, a modulation unit 303, a mapping unit 304, a downlink control information generation unit 305, common control information. Generation unit 306, channel coding unit 307, modulation unit 308, control channel multiplexing unit 309, interleaving unit 310, measurement reference signal generation unit 311, IFFT unit 312, mapping unit 313, demodulation reference signal generation unit 314, weight multiplication Unit 315, CP insertion unit 316, and scheduling unit 317.

  The upper layer control information generation unit 300 generates upper layer control information for each user terminal 20. Further, the upper layer control information is control information that is subjected to upper layer signaling (for example, RRC signaling), and includes, for example, extended PDCCH set allocation information (described later). The data generation unit 301 generates downlink user data for each user terminal 20.

  The downlink user data generated by the data generation unit 301 and the higher layer control information generated by the higher layer control information generation unit 300 are input to the channel coding unit 302 as downlink data transmitted on the PDSCH. The channel coding unit 302 performs channel coding on the downlink data for each user terminal 20 according to a coding rate determined based on feedback information from each user terminal 20. The modulation unit 303 modulates the channel-coded downlink data according to a modulation scheme determined based on feedback information from each user terminal 20. The mapping unit 304 maps the modulated downlink data according to the instruction from the scheduling unit 317.

  The downlink control information generation unit 305 generates UE-specific downlink control information (DCI) for each user terminal 20. The UE-specific downlink control information includes PDSCH allocation information (DL assignment), PUSCH allocation information (UL grant), and the like. The common control information generation unit 306 generates cell-specific common control information.

  The downlink control information generated by the downlink control information generation unit 305 and the common control information generated by the common control information generation unit 306 are input to the channel coding unit 307 as downlink control information transmitted on the PDCCH or the extended PDCCH. The Downlink control information transmitted in PDCC can be generated in units of control channel elements (CCE), and downlink control information transmitted in extended PDCCH can be generated in units of extended control channel elements (eCCE). Note that the CCE and eCCE sizes (number of REs) may be different or the same.

  The channel coding unit 307 channel-codes the input downlink control information according to the coding rate instructed from the scheduling unit 317. Modulation section 308 modulates the channel-coded downlink control information according to the modulation scheme instructed from scheduling section 317.

  Here, downlink control information transmitted on the PDCCH is input from the modulation unit 308 to the control channel multiplexing unit 309 and multiplexed. The downlink control information multiplexed by the control channel multiplexing unit 309 is interleaved by the interleaving unit 310. The interleaved downlink control information is input to the IFFT unit 312 together with the measurement reference signal (CSI-RS: Channel State Information-Reference Signal, CRS: Cell specific Reference Signal, etc.) generated by the measurement reference signal generation unit 311. Is done.

  On the other hand, downlink control information transmitted on the extended PDCCH is input from the modulation unit 308 to the mapping unit 313. The mapping unit 313 maps the downlink control information in a predetermined allocation unit (for example, eREG unit) according to the instruction from the scheduling unit 317. The mapping unit 313 performs distributed mapping of eCCEs to which downlink control information is allocated for each resource region set for the extended PDCCH in units of eREGs. Also, the mapping unit 313 can switch between distributed mapping and localized mapping.

  For example, when performing distributed mapping, the mapping unit 313 distributes a plurality of eREGs constituting one eCCE to a plurality of resource regions (PRB pairs or RBGs) in which extended PDCCHs are arranged, and to each resource region. Mapping is performed so that the index numbers of the eREGs differ. For example, as shown in FIG. 9, a plurality of eREGs constituting one eCCE are assigned different eREG index numbers and mapped to different PRB pairs, thereby obtaining a frequency diversity effect and the size of the eCCEs. Uniformity can be achieved.

  Further, as shown in FIG. 8, mapping section 313 can disperse and arrange eREGs mapped to each PRB pair in REs of a plurality of OFDM symbols in one PRB. As a result, it is possible to improve the power utilization efficiency and to effectively equalize the size between eREGs and between eCCEs. The position (resource area) where the eREGs constituting each eCCE are mapped, the index number of the eREGs constituting each eCCE, the RE pattern corresponding to each eREG in the resource area, and the like are based on information from the scheduling unit 317. It may be set or determined in advance according to the specification.

  The mapped downlink control information includes downlink data transmitted on the PDSCH (that is, downlink data mapped by the mapping unit 304), and a demodulation reference signal (DM-RS) generated by the demodulation reference signal generation unit 314. At the same time, it is input to the weight multiplier 315. Weight multiplying section 315 multiplies downlink data transmitted by PDCSH, downlink control information transmitted by enhanced PDCCH, and a demodulation reference signal by a precoding weight specific to user terminal 20, and performs precoding.

  The precoded transmission data is input to the IFFT unit 312 and converted from a frequency domain signal to a time-series signal by inverse fast Fourier transform. A cyclic prefix (CP) functioning as a guard interval is inserted by the CP insertion unit 316 into the output signal from the IFFT unit 312 and output to the transmission / reception unit 103.

  The scheduling unit 317 performs scheduling of downlink data transmitted on the PDSCH, downlink control information transmitted on the enhanced PDCCH, and downlink control information transmitted on the PDCCH. Specifically, the scheduling unit 317 includes CSI (Channel State Information) including instruction information from the higher station apparatus 30 and feedback information from each user terminal 20 (for example, CQI (Channel Quality Indicator), RI (Rank Indicator), etc.). ) Etc.), radio resources are allocated.

  FIG. 15 is a functional configuration diagram of the baseband signal processing unit 104 included in the user terminal 20. 15 mainly shows a functional configuration for downlink (reception), but the user terminal 20 may have a functional configuration for uplink (transmission). The user terminal 20 includes a CP removing unit 401, an FFT unit 402, a demapping unit 403, a deinterleaving unit 404, a PDCCH demodulating unit 405, a PDSCH demodulating unit 406, an extended PDCCH demodulating unit 407, and a channel estimating unit as functional configurations for downlink. 408.

  The cyclic prefix (CP) is removed from the downlink signal received as reception data from the radio base station 10 by the CP removal unit 401. The downlink signal from which the CP is removed is input to the FFT unit 402. The FFT unit 402 performs fast Fourier transform (FFT) on the downlink signal to convert the signal in the time domain to the signal in the frequency domain, and inputs the signal to the demapping unit 403. The demapping unit 403 demaps the downlink signal. Note that the demapping process by the demapping unit 403 is performed based on higher layer control information input from the application unit 205. The downlink control information output from the demapping unit 403 is deinterleaved by the deinterleaving unit 404.

  PDCCH demodulation section 405 performs blind decoding, demodulation, channel decoding, etc. on downlink control information (DCI) output from deinterleaving section 404 based on the channel estimation result by channel estimation section 408. Specifically, PDCCH demodulation section 405 performs blind decoding on a search space candidate notified in advance from radio base station 10 or a predetermined search space candidate, and acquires downlink control information.

  The PDSCH demodulation unit 406 performs demodulation, channel decoding, and the like of downlink data output from the demapping unit 403 based on the channel estimation result from the channel estimation unit 408. Specifically, the PDSCH demodulator 406 receives the PDSCH assigned to the terminal based on the downlink control information demodulated by the PDCCH demodulator 405 or the extended PDCCH demodulator 407 (for example, downlink scheduling information such as DL grant). Demodulate and acquire downlink data (downlink user data and higher layer control information) addressed to the terminal itself.

  Enhanced PDCCH demodulation section 407 performs blind decoding, demodulation, channel decoding, and the like of enhanced PDCCH demodulation section 407 output from demapping section 403 based on the channel estimation result from channel estimation section 408.

  The channel estimation unit 408 performs channel estimation using a demodulation reference signal (DM-RS), a measurement reference signal (CRS, CSI-RS), and the like. Channel estimation section 408 outputs the channel estimation result based on the measurement reference signals (CRS, CSI-RS) to PDCCH demodulation section 405. On the other hand, channel estimation section 408 outputs the channel estimation result based on the demodulation reference signal (DM-RS) to PDSCH demodulation section 406 and enhanced PDCCH demodulation section 407. A beamforming gain can be obtained for the PDSCH and the extended PDCCH by demodulation using a demodulation reference signal (DM-RS) specific to the user terminal 20.

  As described above, according to the radio communication system 1 according to the present embodiment, the radio base station 10 generates downlink control information for each extended control channel element (eCCE) and is arranged for the extended downlink control channel. Downlink control information is mapped to a plurality of resource areas in units of eREG. In this case, the radio base station 10 distributes a plurality of eREGs constituting one eCCE in a plurality of resource areas, and performs mapping so that the index numbers of the eREGs distributed in the resource areas are different. In addition, the radio base station 10 arranges eREGs mapped to each PRB pair in a distributed manner in REs of a plurality of OFDM symbols in one PRB. As a result, it is possible to improve the frequency diversity effect and the power utilization efficiency, and to effectively equalize the size between eREGs and between eCCEs.

  Although the present invention has been described in detail using the above-described embodiments, it is obvious to those skilled in the art that the present invention is not limited to the embodiments described in this specification. The present invention can be implemented as modified and changed modes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention.

DESCRIPTION OF SYMBOLS 1 ... Wireless communication system 10 ... Wireless base station 20 ... User terminal 30 ... Host station apparatus 40 ... Core network 101 ... Transmission / reception antenna 102 ... Amplifier part 103 ... Transmission / reception part 104 ... Baseband signal processing part 105 ... Call processing part 106 ... Transmission Path interface 201 ... Transmission / reception antenna 202 ... Amplifier 203 ... Transmission / reception unit 204 ... Baseband signal processing unit 205 ... Application unit 300 ... Upper layer control information generation unit 301 ... Data generation unit 302 ... Channel encoding unit 303 ... Modulation unit 304 ... Mapping unit 305 ... Downlink control information generation unit 306 ... Common control information generation unit 307 ... Channel coding unit 308 ... Modulation unit 309 ... Control channel multiplexing unit 310 ... Interleaving unit 311 ... Measurement reference signal generation unit 312 ... IFFT unit 313 ... Mapping unit 314 ... Demodulation reference signal Generating unit 315... Weight multiplying unit 316. CP inserting unit 317. Scheduling unit 401... CP removing unit 402. Unit 408 ... channel estimation unit

Claims (7)

A transmitter for transmitting downlink control information on an extended downlink control channel that is frequency-division multiplexed with the downlink shared data channel;
A mapping unit that maps downlink control information to a plurality of physical resource block (PRB) pairs set for the extended downlink control channel;
The downlink control information is configured in units of extended control channel elements (eCCE) configured by a plurality of extended resource element groups (eREGs).
The mapping unit assigns different index numbers to a plurality of extended resource element groups (eREG) constituting one extended control channel element (eCCE) and maps them to different physical resource block (PRB) pairs. A wireless base station characterized by that.   The mapping unit assigns a number to an extended control channel element (eCCE), and assigns a plurality of extended resource element groups (eREGs) having different index numbers to the extended control channel element (eCCE) to which a predetermined number is assigned. The radio base station according to claim 1, wherein mapping is performed so as to correspond.   The mapping unit assigns the extended resource element group (eREG) to a resource element (RE) excluding a region to which a demodulation reference signal (DM-RS) is allocated for a plurality of resource elements constituting each PRB pair. The radio base station according to claim 1 or 2, wherein mapping is performed in a distributed manner.   The mapping unit extends an extended resource for a resource element (RE) to which a demodulation reference signal (DM-RS) is not allocated among a plurality of resource elements (RE) constituting the physical resource block (PRB) pair. The number corresponding to the index number of the element group (eREG) is distributed and given in the frequency and time directions, and each extended resource element group (eREG) is mapped to the resource element (RE) corresponding to the index number, The radio base station according to claim 3.   The radio base station according to any one of claims 1 to 4, wherein 16 physical resource block (PRB) pairs include 16 extended resource element groups (eREGs). A radio communication method of a radio base station that communicates with a user terminal using an extended downlink control channel that is frequency division multiplexed with a downlink shared data channel,
Transmitting downlink control information on an extended downlink control channel that is frequency division multiplexed with a downlink shared data channel;
Mapping downlink control information to a plurality of physical resource block (PRB) pairs set for the extended downlink control channel,
The downlink control information is configured in units of extended control channel elements (eCCE) configured by a plurality of extended resource element groups (eREGs).
A plurality of extended resource element groups (eREG) constituting one extended control channel element (eCCE) are assigned different index numbers and mapped to different physical resource block (PRB) pairs. Wireless communication method. A wireless communication system having a user terminal and a wireless base station that perform communication using an extended downlink control channel that is frequency division multiplexed with a downlink shared data channel,
The user terminal has a receiving unit for receiving downlink control information transmitted using an extended downlink control channel,
The radio base station includes a transmitter that transmits downlink control information using an extended downlink control channel that is frequency-division multiplexed with a downlink shared data channel, and a plurality of physical resource block (PRB) pairs that are set for the extended downlink control channel. And a mapping unit for mapping downlink control information,
The downlink control information is configured in units of extended control channel elements (eCCE) configured by a plurality of extended resource element groups (eREGs).
The mapping unit assigns different index numbers to a plurality of extended resource element groups (eREG) constituting one extended control channel element (eCCE) and maps them to different physical resource block (PRB) pairs. A wireless communication system.

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