U.S. patent application number 13/058468 was filed with the patent office on 2011-07-28 for radio base station apparatus and mobile terminal.
This patent application is currently assigned to NTT DOCOMO, INC.. Invention is credited to Yoshihisa Kishiyama, Mamoru Sawahashi, Motohiro Tannno.
Application Number | 20110183673 13/058468 |
Document ID | / |
Family ID | 41668888 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110183673 |
Kind Code |
A1 |
Kishiyama; Yoshihisa ; et
al. |
July 28, 2011 |
RADIO BASE STATION APPARATUS AND MOBILE TERMINAL
Abstract
To provide a radio base station apparatus and mobile terminal
for enabling cell selection to be performed in a faster cell
switching period in handover, the radio base station apparatus of
the invention has a plurality of transmission/reception sections
capable of being extended to remote sites, an FCS application
determining section that determines whether to apply fast cell
selection in handover based on information from the mobile
terminal, and a multi-cell scheduling control section that controls
transmission/non-transmission of the first and second
transmission/reception sections when the FCS application
determining section determines that FCS is applied.
Inventors: |
Kishiyama; Yoshihisa;
(Kanagawa, JP) ; Tannno; Motohiro; (Kanagawa,
JP) ; Sawahashi; Mamoru; (Kanagawa, JP) |
Assignee: |
NTT DOCOMO, INC.
Tokyo
JP
|
Family ID: |
41668888 |
Appl. No.: |
13/058468 |
Filed: |
July 27, 2009 |
PCT Filed: |
July 27, 2009 |
PCT NO: |
PCT/JP2009/063321 |
371 Date: |
April 15, 2011 |
Current U.S.
Class: |
455/436 |
Current CPC
Class: |
H04W 36/24 20130101;
H04W 72/042 20130101; H04W 36/0061 20130101; H04B 7/022
20130101 |
Class at
Publication: |
455/436 |
International
Class: |
H04W 36/00 20090101
H04W036/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 11, 2008 |
JP |
2008-207505 |
Claims
1. A radio base station apparatus comprising: a
transmission/reception section configured to have a plurality of
transmission/reception elements capable of being extended from a
main apparatus to remote sites; a fast cell selection determining
section configured to determine whether to apply fast cell
selection in handover of a mobile terminal based on information
from the mobile terminal; and a control section configured to
control transmission/non-transmission for each of the plurality of
transmission/reception sections when the fast cell selection
determining section determines that fast cell selection is
applied.
2. The radio base station apparatus according to claim 1, further
comprising: a notification section configured to notify the mobile
terminal of fast cell selection information, when the fast cell
selection determining section determines that the fast cell
selection is applied.
3. The radio base station apparatus according to claim 1, further
comprising: a reference signal generating section configured to
generate a terminal specific reference signal in addition to a cell
specific reference signal, when the fast cell selection determining
section determines that the fast cell selection is applied.
4. The radio base station apparatus according to claim 1, further
comprising: a control signal generating section configured to
generate a control signal including identification information of
the transmission/reception element to perform transmission, when
the fast cell selection determining section determines that the
fast cell selection is applied.
5. The radio base station apparatus according to claim 4, wherein
the control signal generating section generates the control signal
including transmission power information.
6. The radio base station apparatus according to claim 4, wherein
the control signal generating section generates the control signal
including information of the presence or absence of the terminal
specific reference signal.
7. A mobile terminal comprising: a channel estimation section
configured to perform channel estimation using a cell specific
reference signal from a radio base station apparatus; and a
communication environment information generating section configured
to generate communication environment information obtained in the
channel estimation section, wherein when fast cell selection is
applied, the communication environment information generating
section generates the communication environment information
concerning adjacent cells.
8. The mobile terminal according to claim 7, wherein the
communication environment information concerning adjacent cells
includes the communication environment information of each
cell.
9. The mobile terminal according to claim 7, wherein the
communication environment information concerning adjacent cells
includes identification information of a cell with the best
communication conditions, and the communication environment
information of the cell with the best communication conditions.
10. The mobile terminal according to claim 7, wherein the
communication environment information concerning adjacent cells
includes the communication environment information concerning a
particular cell, and a relative value of the communication
environment information of the other adjacent cells to the
communication identification information of the particular
cell.
11. The mobile terminal according to claim 7, wherein when the fast
cell selection is applied, the mobile terminal receives fast cell
selection information from the radio base station apparatus.
12. The mobile terminal according to claim 7, wherein when the fast
cell selection is applied, the channel estimation section performs
channel estimation using a terminal specific reference signal in
addition the cell specific reference signal.
13. The radio base station apparatus according to claim 2, further
comprising: a reference signal generating section configured to
generate a terminal specific reference signal in addition to a cell
specific reference signal, when the fast cell selection determining
section determines that the fast cell selection is applied.
14. The radio base station apparatus according to claim 2, further
comprising: a control signal generating section configured to
generate a control signal including identification information of
the transmission/reception element to perform transmission, when
the fast cell selection determining section determines that the
fast cell selection is applied.
15. The radio base station apparatus according to claim 3, further
comprising: a control signal generating section configured to
generate a control signal including identification information of
the transmission/reception element to perform transmission, when
the fast cell selection determining section determines that the
fast cell selection is applied.
16. The radio base station apparatus according to claim 13, further
comprising: a control signal generating section configured to
generate a control signal including identification information of
the transmission/reception element to perform transmission, when
the fast cell selection determining section determines that the
fast cell selection is applied.
17. The radio base station apparatus according to claim 14, wherein
the control signal generating section generates the control signal
including transmission power information.
18. The radio base station apparatus according to claim 15, wherein
the control signal generating section generates the control signal
including transmission power information.
19. The radio base station apparatus according to claim 16, wherein
the control signal generating section generates the control signal
including transmission power information.
20. The radio base station apparatus according to claim 14, wherein
the control signal generating section generates the control signal
including information of the presence or absence of the terminal
specific reference signal.
21. The radio base station apparatus according to claim 15, wherein
the control signal generating section generates the control signal
including information of the presence or absence of the terminal
specific reference signal.
22. The radio base station apparatus according to claim 16, wherein
the control signal generating section generates the control signal
including information of the presence or absence of the terminal
specific reference signal.
23. The mobile terminal according to claim 8, wherein when the fast
cell selection is applied, the mobile terminal receives fast cell
selection information from the radio base station apparatus.
24. The mobile terminal according to claim 9, wherein when the fast
cell selection is applied, the mobile terminal receives fast cell
selection information from the radio base station apparatus.
25. The mobile terminal according to claim 10, wherein when the
fast cell selection is applied, the mobile terminal receives fast
cell selection information from the radio base station
apparatus.
26. The mobile terminal according to claim 8, wherein when the fast
cell selection is applied, the channel estimation section performs
channel estimation using a terminal specific reference signal in
addition the cell specific reference signal.
27. The mobile terminal according to claim 9, wherein when the fast
cell selection is applied, the channel estimation section performs
channel estimation using a terminal specific reference signal in
addition the cell specific reference signal.
28. The mobile terminal according to claim 10, wherein when the
fast cell selection is applied, the channel estimation section
performs channel estimation using a terminal specific reference
signal in addition the cell specific reference signal.
29. The mobile terminal according to claim 11, wherein when the
fast cell selection is applied, the channel estimation section
performs channel estimation using a terminal specific reference
signal in addition the cell specific reference signal.
30. The mobile terminal according to claim 23, wherein when the
fast cell selection is applied, the channel estimation section
performs channel estimation using a terminal specific reference
signal in addition the cell specific reference signal.
31. The mobile terminal according to claim 24, wherein when the
fast cell selection is applied, the channel estimation section
performs channel estimation using a terminal specific reference
signal in addition the cell specific reference signal.
32. The mobile terminal according to claim 25, wherein when the
fast cell selection is applied, the channel estimation section
performs channel estimation using a terminal specific reference
signal in addition the cell specific reference signal.
Description
TECHNICAL FIELD
[0001] The present invention relates to a radio base station
apparatus and mobile terminal in the next-generation mobile
communication system.
BACKGROUND ART
[0002] Generally, in cellular mobile communications, when a mobile
terminal moves from a cell to another cell, the mobile terminal
performs handover for switching between radio base station
apparatuses as a communicating party. With respect to the handover
function in the data link layer and lower layers, required QoS
(Quality of Service) in the data link layer and lower layers is
guaranteed by macro diversity between cells. In handover between
cells, when high-speed packet scheduling and ARQ (Automatic Repeat
Request) is considered, it is desired that the cell switching
period is 100 ms.
[0003] Meanwhile, in UMTS (Universal Mobile Telecommunications
System) networks, for the purpose of improving spectral efficiency
and further improving data rates, by adopting HSDPA (High Speed
Downlink Packet Access) and HSUPA (High Speed Uplink Packet
Access), it is performed exploiting maximum features of the system
based on W-CDMA (Wideband Code Division Multiple Access). For the
UMTS network, for the purpose of further increasing high-speed data
rates, providing low delay and the like, Long Term Evolution (LTE)
has been considered (Non-patent Document 1). Further, in the UMTS
network, for the purpose of further increasing the wide-band and
high speed, next-generation systems to LTE have been considered
(for example, LTE Advancement (LTE-A), IMT Advance (IMT-A)).
CITATION LIST
Non-Patent Literature
Non-Patent Literature 1
[0004] 3GPP, TR25. 912 (V7.1.0), "Feasibility study for Evolved
UTRA and UTRAN", September 2006
SUMMARY OF THE INVENTION
Technical Problem
[0005] In the next-generation mobile communication systems as
described above, it is required to achieve a faster cell switching
period in macro diversity in handover, however, under present
circumstances, there is no method for enabling cell selection in a
faster cell switching period to be achieved.
[0006] The present invention was made in view of the respect, and
it is an object of the invention to provide a radio base station
apparatus and mobile terminal for enabling cell selection to be
performed in a faster cell switching period in handover.
Solution to Problem
[0007] A radio base station apparatus of the invention is
characterized by having a transmission/reception section configured
to have a plurality of transmission/reception elements capable of
being extended from a main apparatus to remote sites, a fast cell
selection determining section configured to determine whether to
apply fast cell selection in handover of a mobile terminal based on
information from the mobile terminal, and a control section
configured to control transmission/non-transmission for each of the
plurality of transmission/reception sections when the fast cell
selection determining section determines that fast cell selection
is applied.
Technical Advantage of the Invention
[0008] In the invention, the radio base station apparatus
determines whether to apply fast cell selection in handover based
on information from the mobile terminal, and controls
transmission/non-transmission of at least one of the
transmission/reception elements. For this control of
transmission/non-transmission, it is possible to collectively
control the transmission/reception elements extended to remote
sites and the transmission/reception element provided in the main
apparatus, and it is thereby possible to perform cell selection in
a faster cell switching period in macro diversity in handover.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a diagram illustrating a radio base station
apparatus and mobile terminal according to Embodiment 1 of the
invention;
[0010] FIG. 2 is a diagram illustrating a schematic configuration
of the radio base station apparatus according to Embodiment 1 of
the invention;
[0011] FIGS. 3(a) to 3(c) are diagrams illustrating formats of
downlink control information;
[0012] FIG. 4 is a diagram illustrating a schematic configuration
of the mobile terminal according to Embodiment 1 of the
invention;
[0013] FIGS. 5(a) to 5(c) are diagrams illustrating formats for
feedback of communication environment information to the radio base
station apparatus;
[0014] FIGS. 6(a) and 6(b) are diagrams illustrating application of
FCS of control channel and data channel;
[0015] FIG. 7 is a diagram illustrating a schematic configuration
of a radio base station apparatus according to Embodiment 2 of the
invention; and
[0016] FIG. 8 is a diagram illustrating a schematic configuration
of a mobile terminal according to Embodiment 2 of the
invention.
DESCRIPTION OF EMBODIMENTS
[0017] Embodiments of the invention will specifically be described
below with reference to accompanying drawings.
Embodiment 1
[0018] FIG. 1 is a diagram illustrating a radio base station
apparatus and mobile terminal according to the Embodiment of the
invention. In a radio communication system comprised of the radio
base station apparatus and mobile terminal, as a multiplexing
scheme, OFDMA (Orthogonal Frequency Division Multiple Access) is
used in downlink, while SC-FDMA (Single Carrier Frequency Division
Multiple Access) is used in uplink.
[0019] The radio base station apparatus according to the invention
has the configuration as shown in FIG. 1. The radio base station
apparatus has a transmission/reception element 1a provided in the
main apparatus 1, and at least one of transmission/reception
elements 1b, is extended to remote sites by optical fibers 3. The
radio base station apparatus has all of processing sections
(baseband processing section, call control processing section,
etc.) for the cell of the transmission/reception element 1a,
processing sections (baseband processing section, call control
processing section, etc.) for the cell of the
transmission/reception element 1b and of processing sections
(baseband processing section, call control processing section,
etc.) for the cell of the transmission/reception element 1c
provided in the main apparatus 1, and is further provided with a
multi-cell scheduling control section, described later, for
collectively performing scheduling to perform
transmission/non-transmission for respective cells of the
transmission/reception elements 1a, 1b, 1c and a FCS (Fast Cell
Selection) determining section, described later, for determining
whether to apply fast cell selection. Further, the
transmission/reception elements 1b, 1c are extended to remote sites
by the optical fibers 3.
[0020] In the configuration as shown in FIG. 1 i.e. the
configuration in which the main apparatus 1 has at least one of
transmission/reception elements 1b, 1c extended to remote sites by
optical fibers 3, the processing sections of each of the
transmission/reception elements 1b, 1c are provided in the main
apparatus 1, and the multi-cell scheduling control section and the
FCS determining section are collected in the main apparatus 1,
since processing sections for downlink to adjacent cells are
collected in the main apparatus 1, it is possible to collectively
perform scheduling of transmission signals for downlink to each of
the adjacent cells. Further, The main apparatus 1 may collect, via
the optical fibers 3, the communication environment information
(communication environment information, etc.) between each of the
transmission/reception sections 1a, 1b,1c and the mobile terminal 2
using an uplink signal received in each of the
transmission/reception sections 1a, 1b, 1c. Therefore, it is
possible to determine whether to apply FCS based on above
information. It is possible to make such an FCS application
determination and scheduling of downlink signals to each cell, and
it is thereby possible to perform faster cell selection. In
addition, it is not always necessary to extend the
transmission/reception elements 1b, 1c to remote sites, and it is
also possible to provide a plurality of transmission/reception
elements inside the main apparatus 1. Alternately, it is possible
to provide a configuration that the transmission/reception element
1a is not provided inside the apparatus 1. Further, it is possible
to use cables connecting between the main apparatus 1 and the
extended transmission/reception elements 1b, 1c except optical
cables.
[0021] In the configuration, in handover between cells, it is
determined whether it is necessary to apply FCS i.e. the mobile
terminal 2 exits at the cell edge, based on the communication
environment information from the mobile terminal 2. When the mobile
terminal 2 exits at the cell edge, it is necessary to apply FCS,
FCS is applied (FCS mode). In the FCS mode, the radio base station
apparatus transmits downlink signals from the cell
(transmission/reception element) with the best communication
environment among the adjacent cells, while halting transmission
from the other cells (transmission/reception elements).
[0022] The determination (cell edge identification) whether it is
necessary to apply FCS i.e. whether the mobile terminal 2 exists at
the cell edge is preferably made, for example, using identification
information (cell ID) of the adjacent cell, reference signal
received power (RSRP) of the cell, etc. In this case, the RSRP of
adjacent cells (for example, handover source and handover target)
is obtained, and compared with each other, and the determination is
made by determining whether the difference is in a predetermined
range. This is because when the difference in RSRP between the
cells is in a predetermined range, it is considered that the mobile
terminal 2 is not close to one of the transmission/reception
elements, and is located at some distance from both of the
transmission/reception elements i.e. exists at the cell edge.
[0023] FIG. 2 is a diagram illustrating the configuration of the
radio base station apparatus according to the Embodiment of the
invention. The radio base station apparatus as shown in FIG. 2 is
an apparatus for generating only a cell specific reference signal.
The radio base station apparatus as shown in FIG. 2 is principally
comprised of processing sections (cell #1 processing section, cell
#2 processing section and cell #3 processing section) of a
plurality of adjacent cells (herein, three cells), transmission
amplifiers 109a, 109b, 109c respectively for cell #1, cell #2 and
cell #3, an FCS determining section 111 that determines whether to
apply FCS, and a multi-cell scheduling control section 110 that
collectively performs transmission/non-transmission to each of the
cell #1, cell #2 and cell #3. The transmission amplifiers 109a,
109b, 109c are included in the above-mentioned
transmission/reception elements (transmission/reception sections
1a, 1b, 1c in FIG. 1), and are used to transmit cell #1
transmission signal, cell #2 transmission signal, and cell #3
transmission signal, respectively. Further, transmission amplifiers
109b, 109c are installed in the transmission reception elements
that are extended using optical fibers and that are located at
remote sites as shown in FIG. 1. In addition, the processing
sections of the cells include respective processing section of
reception-systems (not shown).
[0024] Each of the processing sections is principally comprised of
a downlink control information generating section 101 that
generates control information (control signal) to transmit to a
mobile terminal, a downlink control information coding/modulation
section 102 that performs coding and modulation on the downlink
control signal, a downlink RS sequence generating section 103 that
generates a reference signal (RS) sequence (cell specific reference
signal sequence) used for channel estimation in the mobile
terminal, a downlink transmission data generating section 104 that
generates data to transmit to the mobile terminal, a downlink
transmission data coding/modulation section 105 that performs
coding and modulation on the downlink transmission data, a downlink
channel multiplexing section 106 that multiplexes the coded
modulated downlink control signal and downlink data and the
downlink RS sequence, an IFFT (Inverse Fast Fourier Transform)
section 107 that performs IFFT computing on the channel multiplexed
signal, and a CP adding section 108 that adds CP (Cyclic Prefix) to
the IFFT-computed signal. In FIG. 2, each processing block as
mentioned above is described in the processing section of cell #1,
and the each processing block as mentioned above is similarly
included in the processing section of cell #2 and the processing
section of cell #3.
[0025] The FCS application determining section 111 is notified,
from the mobile terminal, of information (for example, information
of whether the mobile terminal exists at the cell edge (for
example, whether the difference of RSRP is in the predetermined
range)) required for FCS application determination which is
obtained from the received signal in the mobile terminal. This
notification is made using signaling in the upper layer, for
example. The FCS application determining section 111 outputs the
FCS application information (determination result) determined in
the section 111 i.e. information of whether to apply FCS and when
required, a target cell of FCS, to the downlink control information
generating section 101 and downlink transmission data generating
section 104 in the processing section of each cell, and the
multi-cell scheduling control section 110. In other words, when the
FCS application determining section 111 is notified of the
information required for the FCS application determination, the
section 111 makes the determination whether to apply FCS
(determines application of FCS when the mobile terminal exists at
the cell edge), and outputs the information indicative of
application of FCS to the downlink control information generating
section 101 of each cell, while further outputting the information
to the multi-cell scheduling control section 110 to perform fast
cell selection.
[0026] The FCS application information may be notified to the
mobile terminal. By notifying the mobile terminal of the FCS
application information, the mobile terminal is capable of
acquiring all of the communication environment information of the
adjacent cells, identifying a cell with the best communication
environment, or obtaining the relative relationship of the
communication environment between cells, and notifying the radio
base station apparatus of the communication environment
information, cell information and/or the relative relationship of
the communication environment as feedback. The notification of the
FCS application information may be performed using signaling in the
upper layer, or may be transmitted to the mobile terminal using a
dedicated control channel.
[0027] Further, by notifying the mobile terminal of the FCS
application information, the mobile terminal is capable of
performing channel estimation using the cell specific reference
signal (common reference signal) in addition to the terminal
specific reference signal (dedicated reference signal). In other
words, the mobile terminal is capable of recognizing a change in
the cell to transmit from the FCS application information, and
therefore, is capable of performing channel estimation for each
cell using the cell specific reference signal based on a format for
each cell. Thus, by performing channel estimation using the cell
specific reference signal in addition to channel estimation of the
terminal specific reference signal, it is possible to perform
channel estimation with high accuracy, and accuracy increases in
the communication environment information required for the FCS
application determination.
[0028] In addition, when the FCS application information is not
notified to the mobile terminal, the mobile terminal notifies the
radio base station apparatus of the communication environment
information based on channel estimation using the terminal specific
reference signal as feedback, and the radio base station apparatus
makes the FCS application determination based on the communication
environment information based on the single cell.
[0029] As described above, the FCS application information is
output from the FCS application determining section 111 to the
downlink control information generating section 101. At the normal
time (except the time of FCS application), the downlink control
information includes the user ID (terminal identification
information), radio resource allocation information, etc. When the
mobile terminal receives the downlink control information, the
mobile terminal checks the user ID, and only the mobile terminal
corresponding to the user ID is capable of decoding the radio
resource allocation information (blind decoding).
[0030] At the time of applying FCS, the FCS information is output
to the downlink control information generating section 101. The
downlink control information generating section 101 adds the cell
identification (cell identifier), which corresponds to the
transmission/reception element that performs transmission, to the
downlink control information. For example, the downlink control
information generating section 101 may generate a control signal
including the identification information of the cell that performs
transmission when FCS is applied. In other words, the section 101
may generate a downlink control signal using the format as shown in
FIG. 3(a). The mobile terminal receiving such downlink control
information is capable of decoding the cell identification
information by blind decoding, and is thereby capable of
identifying the cell to perform transmission. Therefore, the mobile
terminal is capable of recognizing the cell of the cell specific
reference signal (the cell of the format), and thereby performing
channel estimation using the cell specific reference signal.
[0031] Further, the downlink control information generating section
101 may generate a control signal including transmission power
information. In other words, as shown in FIG. 3(b), by thus adding
the transmission power information, the mobile terminal is capable
of being notified of the transmission power in FCS application, and
it is thereby possible to transmit signals with the higher
transmission power at the FCS application time than at the normal
time. Furthermore, the downlink control information generating
section 101 may generate a control signal including information of
the presence or absence of the terminal specific reference signal.
In other words, as shown in FIG. 3(c), the section 101 may add the
information of the presence or absence of the terminal specific
reference signal as well as the cell identification information. By
thus adding the information of the presence or absence of the
terminal specific reference signal, it is possible to notify the
mobile terminal of use of the terminal specific reference signal,
and the mobile terminal is thereby capable of performing channel
estimation also using the terminal specific reference signal that
is additionally used.
[0032] Upon receiving the FCS application information from the FCS
application determining section 111, the multi-cell scheduling
(fast cell selection) control section 110 performs scheduling for
multiple cells for performing transmission to the mobile terminal
via the transmission/reception element (cell) with the best
communication environment, while not performing transmission to the
mobile terminal via the other transmission/reception elements
(cells). In other words, in the FCS mode, the multi-cell scheduling
control section 110 specifies a cell with the best communication
environment based on the communication environment information (for
example, CQI (Channel Quality Indicator) of the adjacent cells and
PMI) transmitted from the mobile terminal, and instructs the
downlink signal generating sections 101, 104 of the processing
section of the cell to generate the signal (multi-cell scheduling).
By this means, transmission is performed only from the
transmission/reception element of the cell with the best
communication environment, and transmission is halted from the
transmission/reception elements of the other cells. The multi-cell
scheduling control section 110 collectively performs scheduling
corresponding to a plurality of cells including control of the
transmission cell and non-transmission cells.
[0033] FIG. 4 is a diagram illustrating the configuration of the
mobile terminal that performs radio communications with the radio
base station apparatus as shown in FIG. 2. The mobile terminal as
shown in FIG. 4 is principally comprised of a CP removing section
201 that removes CP from a signal transmitted from the radio base
station apparatus, an FFT section 202 that performs FFT computing
on the received signal, a downlink channel demultiplexing section
203 that demultiplexes the FFT-computed signal into control
information, reference signal and data, a downlink control
information receiving section 204 that performs predetermined
reception processing on the demultiplexed downlink control
information, a channel estimation sections 205 that performs
channel estimation using the demultiplexed reference signal, a
channel estimation cell selecting section 206 that selects a
transmission cell to perform the reception processing based on the
channel estimation result, a downlink transmission data receiving
section 207 that performs predetermined reception processing on the
demultiplexed downlink transmission data, a communication
environment information estimating sections 208 that estimate the
communication environment (CQI and PMI) based on the channel
estimation result, and a multi-cell communication environment
information generating section 209 that generates the communication
environment information from the communication environment
information of each cell. The channel estimation sections 205 and
the communication environment information estimating sections 208
are provided corresponding to cells.
[0034] In the mobile terminal with such a configuration, when the
FCS application information is notified from the radio base station
apparatus, the FCS application information is output to the
downlink control information receiving section 204 and the
multi-cell communication environment information generating section
209.
[0035] Upon receiving the FCS application information, the
multi-cell communication environment information generating section
209 generates the status of communication environments of adjacent
cells (multi-cell communication environment information) using the
communication environment information (for example, CQI and PMI) of
the adjacent cells to report the radio base station apparatus
(feedback to the radio base station apparatus). By this means, the
radio base station apparatus is capable of recognizing which cell
is with the best communication environment among the adjacent
cells.
[0036] When the mobile terminal notifies the radio base station
apparatus of the communication environment information as feedback,
there are various methods. For example, by including the
communication environment information concerning each cell as the
communication environment information concerning the adjacent cells
i.e. using the format as shown in FIG. 5(a), the mobile terminal
reports all the communication environment information of the
adjacent cells. Alternately, by including the identification
information of the cell with the best communication conditions, and
the communication environment information of the cell with the best
communication conditions as the communication environment
information concerning the adjacent cells i.e. using the format as
shown in FIG. 5(b), the mobile terminal compares the communication
environment information of the cells with one another, specifies
the best cell, and reports the identification information of the
cell and the communication environment information of the cell.
Otherwise, by including the communication environment information
on a particular cell, and a relative value of the communication
environment information of the other adjacent cells to the
communication environment information of the particular cell as the
communication environment information concerning the adjacent cells
i.e. using the format as shown in FIG. 5(c), the mobile terminal
reports the communication environment information of the particular
cell (for example, the source cell of handover) and the relative
value to the communication environment information.
[0037] The downlink control information receiving section 204
performs the predetermined reception processing e.g. blind decoding
on the downlink control information. By this means, the section 204
is capable of recognizing that the information is data to the
mobile terminal. When the section 204 recognizes that the
information is the data to the mobile terminal, the information is
output to the downlink transmission data receiving section 207, and
the downlink transmission data receiving section 207 performs the
predetermined reception processing, e.g. demodulation and decoding,
on the downlink transmission data.
[0038] When the downlink control information receiving section 204
is notified of the FCS application information, the reception
format for FCS is varied to perform reception or the number of
cells to perform reception is increased. For example, when FCS is
applied, considered are the case of performing FCS only on the data
channel (PDSCH) as shown in FIG. 6(a), and the case of performing
FCS on both of the data channel (PDSCH) and the control channel
(PDCCH) as shown in FIG. 6(b). In the case as shown in FIG. 6(b),
the data channel and the control channels are transmitted from the
same cell, and the cell to perform reception is a single cell. In
the case as shown in FIG. 6(a), the data channel and the control
channel may be transmitted from different cells. In the case, it is
necessary to receive signals from two cells, and the downlink
control information receiving section 204 increases the number of
cells to perform reception.
[0039] Described next is the case of applying FCS in the radio base
station apparatus as shown in FIG. 2 and the mobile terminal as
shown in FIG. 4. Herein, described is the case of performing
channel estimation using only the cell specific reference
signal.
[0040] First, the mobile terminal notifies the information (for
example, whether the difference of RARP is in the predetermined
range) required for FCS application determination obtained from the
received signal in the mobile terminal. This notification is made
using signaling in the upper layer, for example. Upon receiving the
information required for the FCS application determination, the FCS
application determining section 111 in the radio base station
apparatus determines whether to apply FCS. When the FCS application
determining section 111 determines that FCS is applied, the FCS
application information is output to the downlink control
information generating section 101 of the processing section of
each cell and the multi-cell scheduling control section 110.
[0041] The communication environment information (CQI and PMI) is
transmitted from the mobile terminal to the multi-cell scheduling
control section 110. The multi-cell scheduling control section 110
selects a cell with the best communication environment based on the
communication environment information, and performs scheduling. In
this case, the mobile terminal transmits the communication
environment information using the format as shown in FIGS. 5(a) to
5(c). The scheduling information is output to the downlink control
information generating section 101 and downlink transmission data
generating section 104 of the processing section of the cell (the
scheduled cell) with the best communication environment. Then, the
downlink control information generating section 101 and downlink
transmission data generating section 104 of the cell with the best
communication environment generate the control information and
transmission data based on the scheduling information, and the
generated control information and transmission data is transmitted
through the corresponding transmission amplifier. For example, when
the cell with the best communication environment is cell #2, the
downlink control information generating section 101 and downlink
transmission data generating section 104 of cell #2 generate the
control information and transmission data, and the control
information and transmission data is transmitted from the
transmission amplifier 109b installed at the remote site via the
optical fiber.
[0042] The mobile terminal receives the FCS application information
from the radio base station apparatus to output to the downlink
control information receiving section 204 and multi-cell
communication environment information generating section 209.
Further, in the mobile terminal, the downlink control information
receiving section 204 performs blind decoding, and identifies
whether the information is the control information to the mobile
terminal. The identification information is output to the downlink
transmission data receiving section 207. Meanwhile, the mobile
terminal performs channel estimation in the channel estimation
section 205, using the cell specific reference signal included in
the downlink signal from the radio base station apparatus. The
obtained channel estimation value is used in the reception
processing in the downlink transmission data receiving section 207.
Thus, the downlink transmission data is obtained.
[0043] In addition, as shown in FIG. 6(a), when the data channel
and the control channel are transmitted from different cells, since
the downlink control information receiving section 204 increases
the number of cells to perform reception, the number of cells to
perform channel estimation increases. Therefore, the identification
information obtained in the downlink control information receiving
section 204 is output to the channel estimation cell selecting
section 206. Then, using the identification information, the
channel estimation cell selecting section 206 selects a channel
estimation value for use in the reception processing of the
downlink transmission data from a plurality of channel estimation
values from the channel estimation sections 205.
[0044] The channel estimation value for each cell obtained in the
channel estimation section 205 is output to the communication
environment information estimating section 208, and the
communication environment is estimated for each cell. Then, the
communication environment information for each cell is output to
the multi-cell communication environment information generating
section 209. The multi-cell communication environment information
generating section 209 generates the communication environment
information to transmit to the radio base station apparatus as
feedback from the communication environment information for each
cell. For example, using the format as shown in FIGS. 3(a) to 3(c),
the communication environment information is transmitted to the
radio base station apparatus as feedback. Then, the multi-cell
scheduling control section 110 in the radio base station apparatus
selects the cell with the best communication environment based on
the communication environment information to perform
scheduling.
[0045] Thus, in the system of this Embodiment, the radio base
station apparatus determines whether to apply FCS in handover based
on the information from the mobile terminal, and when determining
that FCS is applied, controls transmission/non-transmission in at
least one of transmission/reception elements extended to the remote
sites by optical fibers and the transmission/reception element
provided in the main apparatus. The control of
transmission/non-transmission is collectively performed on the
transmission/reception elements extended to the remote sites by
optical fibers and transmission/reception element provided in the
main apparatus, and it is thereby possible to perform cell
selection in the faster cell switching period in macro diversity in
handover.
Embodiment 2
[0046] This Embodiment describes the case of performing channel
estimation using a terminal specific reference signal in addition
to the cell specific reference signal. FIG. 7 is a diagram
illustrating a configuration of a radio base station apparatus
according to Embodiment 2. In addition, in FIG. 7, the same parts
as those in FIG. 2 are assigned the same reference numerals, and
specific descriptions thereof are omitted. The radio base station
apparatus as shown in FIG. 7 is provided with an dedicated RS
sequence generating section 112 that generates a terminal specific
reference signal (dedicated RS). The FCS application information is
input to the dedicated RS sequence generating section 112 from the
FCS application determining section 111, and the section 112
generates the dedicated RS, when the FCS application information is
input to the section 112. The generated dedicated RS is output to a
downlink channel multiplexing section 106 and multiplexed as a
downlink signal.
[0047] FIG. 8 is a diagram illustrating a configuration of a mobile
terminal according to Embodiment 2. In addition, in FIG. 8, the
same parts as those in FIG. 4 are assigned the same reference
numerals as in FIG. 4, and specific descriptions thereof are
omitted. The mobile terminal as shown in FIG. 8 is provided with an
dedicated RS channel estimation section 210 that performs channel
estimation using the terminal specific reference signal (dedicated
RS), and is further provided with a channel estimation cell
selecting/combining section 211 that combines or selects the
channel estimation value obtained by using the cell specific
reference signal (common RS) and a channel estimation value
obtained by using the dedicated RS, as a substitute for the channel
estimation cell selecting section 206.
[0048] The FCS application information is input to the channel
estimation cell selecting/combining section 211 from the FCS
application determining section 111, and when the FCS application
information is input thereto, the channel estimation cell
selecting/combining section 211 selects using a channel estimation
value based on the terminal specific reference signal or using a
channel estimation value based on the cell specific reference
signal, or combines the channel estimation value based on the
terminal specific reference signal and the channel estimation value
based on the cell specific reference signal.
[0049] Thus, by performing channel estimation using the terminal
specific reference signal in addition to the cell specific
reference signal, accuracy of the channel estimation value is
increased, and it is possible to enhance the reception quality of
downlink transmission data.
[0050] Described next is the case where FCS is applied in the radio
base station apparatus as shown in FIG. 7 and the mobile terminal
apparatus as shown in FIG. 8. Described herein is the case of
performing channel estimation using the terminal specific reference
signal in addition to the cell specific reference signal.
[0051] First, the mobile terminal notifies the information required
for the FCS application determination (for example, information
indicating whether the difference of RSRP is in the predetermined
range) obtained from a received signal in the mobile terminal. This
notification is made, for example, using signaling in the upper
layer. Upon receiving the information required for the FCS
application determination, the FCS application determining section
111 in the radio base station apparatus determines whether to apply
FCS. When the FCS application determining 111 determines that FCS
is applied, the FCS application information is output to the
downlink control information generating section 101 and dedicated
RS sequence generating section 112 of the processing section of
each cell, and the multi-cell scheduling control section 110.
[0052] The communication environment information (CQI and MPI) is
transmitted to the multi-cell scheduling control section 110 from
the mobile terminal. The multi-cell scheduling control section 110
selects a cell with the best communication environment based on the
communication environment information to perform scheduling. In
this case, the mobile terminal transmits the communication
environment information using the format as shown in FIGS. 5(a) to
5(c). The scheduling information is output to the downlink control
information generating section 101 and downlink transmission data
generating section 104 of the processing section of the cell (the
scheduled cell) with the best communication environment. Then, the
downlink control information generating section 101 and downlink
transmission data generating section 104 of the cell with the best
communication environment generate the control information and
transmission data based on the scheduling information, and the
generated control information and transmission data is transmitted
through the corresponding transmission amplifier. For example, when
the cell with the best communication environment is cell #2, the
downlink control information generating section 101 and downlink
transmission data generating section 104 of cell #2 generate the
control information and transmission data, and the control
information and transmission data is transmitted from the
transmission amplifier 109b installed at the remote site via the
optical fiber. In addition, when the FCS application information is
output to the dedicated RS sequence generating section 112, the
terminal specific reference signal is generated, and is multiplexed
into the downlink signal.
[0053] The mobile terminal receives the FCS application information
from the radio base station apparatus to output to the downlink
control information receiving section 204 and multi-cell
communication environment information generating section 209.
Further, in the mobile terminal, the downlink control information
receiving section 204 performs blind decoding, and identifies
whether the information is the control information to the mobile
terminal. The identification information is output to the downlink
transmission data receiving section 207. Meanwhile, the mobile
terminal performs channel estimation in the channel estimation
section 205, using the cell specific reference signal included in
the downlink signal from the radio base station apparatus. Further,
the dedicated RS channel estimation section 210 performs channel
estimation using the terminal specific reference signal. These
channel estimation values are output to the channel estimation cell
selecting/combining section 211. Then, the channel estimation cell
selecting/combining section 211 selects or combines the channel
estimation values. The channel estimation value is used in the
reception processing in the downlink transmission data receiving
section 207. Thus, the downlink transmission data is obtained.
[0054] In addition, as shown in FIG. 6(a), when the data channel
and the control channel are transmitted from different cells, since
the downlink control information receiving section 204 increases
the number of cells to perform reception, the number of cells to
perform channel estimation increases. Therefore, the identification
information obtained in the downlink control information receiving
section 204 is output to the channel estimation cell
selecting/combining section 211. Then, using the identification
information, the channel estimation cell selecting/combining
section 211 selects a channel estimation value for use in the
reception processing of the downlink transmission data from a
plurality of channel estimation values from the channel estimation
sections 205.
[0055] The channel estimation value for each cell obtained in the
channel estimation section 205 is output to the communication
environment information estimating section 208, and the
communication environment is estimated for each cell. Then, the
communication environment information for each cell is output to
the multi-cell communication environment information generating
section 209. The multi-cell communication environment information
generating section 209 generates the communication environment
information to transmit to the radio base station apparatus as
feedback from the communication environment information for each
cell. For example, using the format as shown in FIGS. 3(a) to 3(c),
the communication environment information is transmitted to the
radio base station apparatus as feedback. Then, the multi-cell
scheduling control section 110 in the radio base station apparatus
selects the cell with the best communication environment based on
the communication environment information to perform
scheduling.
[0056] Thus, also in the system of this Embodiment, the radio base
station apparatus determines whether to apply FCS in handover based
on the information from the mobile terminal, and when determining
that FCS is applied, controls transmission/non-transmission in at
least one of transmission/reception elements extended to the remote
sites by optical fibers and the transmission/reception element
provided in the main apparatus. The control of
transmission/non-transmission is collectively performed on the
transmission/reception elements extended to the remote sites by
optical fibers and transmission/reception element provided in the
main apparatus, and it is thereby possible to perform cell
selection in the faster cell switching period in macro diversity in
handover.
[0057] The present invention is not limited to the above-mentioned
Embodiments, and is capable of being carried into practice with
various modifications thereof as appropriate. For example, the
number of cells, the numbers of processing sections, processing
procedures and parameters indicating the communication environment
in the above-mentioned descriptions are capable of being carried
into practice with modifications thereof as appropriate without
departing from the scope of the invention. Further, the invention
is capable of being carried into practice with modifications
thereof as appropriate without departing from the scope of the
invention.
* * * * *