U.S. patent number 9,271,152 [Application Number 14/197,753] was granted by the patent office on 2016-02-23 for heterogeneous cellular network.
This patent grant is currently assigned to Hitachi, Ltd.. The grantee listed for this patent is HITACHI, LTD.. Invention is credited to Dongxu Cao, Chunguang Liu, Mika Mizutani, Zhisheng Niu, Peng Yang, Sheng Zhou.
United States Patent |
9,271,152 |
Cao , et al. |
February 23, 2016 |
Heterogeneous cellular network
Abstract
Provided is a micro base station to be used in a heterogeneous
cellular network. The micro base station has resources including
frequency bands and time slots and being available for a user to
use. The heterogeneous cellular network includes a plurality of
base stations including a macro base station and the micro base
station. The micro base station includes: an information acquiring
part configured to acquire configuration information and load
information of the micro base station, and to acquire configuration
information and load information of a neighboring base station
adjacent to the micro base station from the neighboring base
station; and a resource selection part configured to select a part
of the resources from the resources to provide the selected part of
the resources to the user based on the configuration information
and the load information of the micro base station and the
neighboring base station.
Inventors: |
Cao; Dongxu (Beijing,
CN), Liu; Chunguang (Beijing, CN), Zhou;
Sheng (Beijing, CN), Yang; Peng (Beijing,
CN), Niu; Zhisheng (Beijing, CN), Mizutani;
Mika (Beijing, CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
HITACHI, LTD. |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
51488410 |
Appl.
No.: |
14/197,753 |
Filed: |
March 5, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20140256329 A1 |
Sep 11, 2014 |
|
Foreign Application Priority Data
|
|
|
|
|
Mar 11, 2013 [CN] |
|
|
2013 1 0076449 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
16/08 (20130101) |
Current International
Class: |
H04W
36/20 (20090101); H04W 16/08 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Appiah; Charles
Assistant Examiner: Pierre; Robenson
Attorney, Agent or Firm: Mattingly & Malur, PC
Claims
What is claimed is:
1. A micro base station to be used in a heterogeneous cellular
network, the micro base station having resources including
frequency bands and time slots and being available for a user to
use, the heterogeneous cellular network comprising a plurality of
base stations including a macro base station and the micro base
station, the micro base station comprising: an information
acquiring part configured to acquire configuration information and
load information of the micro base station, and to acquire
configuration information and load information of a neighboring
base station adjacent to the micro base station from the
neighboring base station; and a resource selection part configured
to select a part of the resources from the resources to provide the
selected part of the resources to the user based on the
configuration information and the load information of the micro
base station and the neighboring base station, which are acquired
by the information acquiring part, wherein: all of the resources
possessed by the micro base station are divided into N resource
blocks, and that M resource blocks is selected from the N resource
blocks as the part of the resources to be provided to the user,
where N and M are positive integers and satisfy N.gtoreq.M; the
resource selection part calculates a system parameter c based on
the transmitting powers of the macro base station and the micro
base station, and calculates a value of the M resource blocks in
accordance with the following equations,
.beta..times..times..times..times..rho..rho..lamda..times..times..rho..rh-
o..times..times..lamda. ##EQU00002## .times..times..beta.
##EQU00002.2## where um represents the user rate requirement of the
micro base station, uM represents the user rate requirement of the
macro base station, .rho.m represents the micro base station
density, .rho.M represents the macro base station density, .lamda.m
represents the user density of the micro base station, and .lamda.M
represents the user density of the macro base station.
2. The micro base station to be used in a heterogeneous cellular
network according to claim 1, wherein: the configuration
information includes positions of the base stations and
transmitting power; the load information includes user rate
requirement and user density; the information acquiring part
further acquires micro base station density and macro base station
as configuration information density from the heterogeneous
cellular network; the resource selection part selects the part of
the resources from the resources to provide the selected part of
the resources to the user, based on the configuration information
and the load information of the micro base station and the
neighboring base station, and the micro base station density and
the macro base station density, which are acquired by the
information acquiring part.
3. The micro base station to be used in a heterogeneous cellular
network according to claim 1, wherein the resource selection part
determines an amount of the selected part of the resources and
randomly selects the amount of resources from the resources to
provide the part of the resources to the user.
4. A resource selection method for a micro base station to be used
in a heterogeneous cellular network, the micro base station having
resources including frequency bands and time slots and being
available for a user to use, the heterogeneous cellular network
comprising a plurality of base stations including a macro base
station and the micro base station, the resource selection method
comprising: an information acquiring step of acquiring
configuration information and load information of the micro base
station, and of acquiring configuration information and load
information of a neighboring base station adjacent to the micro
base station from the neighboring base station; and a resource
selection step of selecting the part of the resources from the
resources to provide the selected part of the resources to a user,
based on the configuration information and the load information of
the micro base station and the neighboring base station, and the
micro base station density and the macro base station density,
which are acquired by the information acquiring step, wherein: all
of the resources possessed by the micro base station are divided
into N resource blocks, and that M resource blocks is selected from
the N resource blocks as the part of the resources to be provided
to the user, where N and M are positive integers and satisfy
N.gtoreq.M; the resource selection step calculates a system
parameter c based on the transmitting powers of the macro base
station and the micro base station, and calculates a value of the M
resource blocks in accordance with the following equations,
.beta..times..times..times..times..rho..rho..lamda..times..times..rho..rh-
o..times..times..lamda. ##EQU00003## .times..times..beta.
##EQU00003.2## where um represents the user rate requirement of the
micro base station, uM represents the user rate requirement of the
macro base station, .rho.m represents the micro base station
density, .rho.M represents the macro base station density, .lamda.m
represents the user density of the micro base station, and .lamda.M
represents the user density of the macro base station.
5. The resource selection method for a micro base station to be
used in a heterogeneous cellular network according to claim 4,
wherein, the configuration information includes positions of the
base stations and transmitting power; the load information includes
user rate requirement and user density; the information acquiring
step further comprises acquiring micro base station density and
macro base station density as configuration information from the
heterogeneous cellular network; the resource selection step
comprises selecting the part of the resources from the resources to
provide the selected part of the resources to a user, based on the
configuration information and the load information of the micro
base station and the neighboring base station, and the micro base
station density and the macro base station density, which are
acquired by the information acquiring step.
6. The resource selection method for a micro base station to be
used in a heterogeneous cellular network according to claim 4,
wherein the resource selection step determines an amount of the
selected part of the resources and randomly selects the amount of
resources from the resources to provide the part of the resources
to the user.
7. A heterogeneous cellular network, comprising a plurality of base
stations including a macro base station and a micro base station,
the macro base station and the micro base station each having
resources including frequency bands and time slots and being
available for a user to use, the macro base station comprising: an
information acquiring part configured to acquire configuration
information and load information of the macro base station; and a
resource allocation part configured to allocate the resources
possessed by the macro base station to a user, the micro base
station comprising: an information acquiring part configured to
acquire configuration information and load information of the micro
base station, and to acquire configuration information and load
information of a neighboring base station from the base station
adjacent to the micro base station; and a resource selection part
configured to select a part of the resources from the resources to
provide the selected part of the resources to the user based on the
configuration information and the load information of the micro
base station and the neighboring base station, which are acquired
by the information acquiring part, and further configured to
allocate the part of the selected resources to the user, wherein:
all of the resources possessed by the micro base station are
divided into N resource blocks, and that M resource blocks is
selected from the N resource blocks as the part of the resources to
be provided to the user, where N and M are positive integers and
satisfy N.gtoreq.M; the resource selection part of the micro base
station calculates a system parameter c based on the transmitting
powers of the macro base station and the micro base station, and
calculates a value of the M resource blocks in accordance with the
following equations,
.beta..times..times..times..times..rho..rho..lamda..times..times..rho..rh-
o..times..times..lamda. ##EQU00004## .times..times..beta.
##EQU00004.2## where um represents the user rate requirement of the
micro base station, uM represents the user rate requirement of the
macro base station, .rho.m represents the micro base station
density, .rho.M represents the macro base station density, .lamda.m
represents the user density of the micro base station, and .lamda.M
represents the user density of the macro base station.
8. The heterogeneous cellular network according to claim 7,
wherein, the configuration information includes positions of the
base stations and transmitting power; the load information includes
user rate requirement and user density; the information acquiring
part of the micro base station further acquires micro base station
density and macro base station density as configuration information
from the heterogeneous cellular network; the resource selection
part of the micro base station selects the part of the resources
from the resources to provide the selected part of the resources to
the user, based on the configuration information and the load
information of the micro base station and the neighboring base
station, and the micro base station density and the macro base
station density, which are acquired by the information acquiring
part.
9. The heterogeneous cellular network according to claim 7, wherein
the resource selection part of the micro base station determines an
amount of the selected part of the resources and randomly selects
the amount of resources from the resources to provide the part of
the resources to the user.
Description
CLAIM OF PRIORITY
The present application claims priority from Chinese patent
application No. 201310076449.1 filed on Mar. 11, 2013, the content
of which is hereby incorporated by reference into this
application.
BACKGROUND
This invention relates to a heterogeneous cellular network.
Currently, a conventional cellular network (hereinafter sometime
referred to as homogeneous cellular network) including only one
type of base station is widely used. A cellular network
(hereinafter also referred to as "heterogeneous cellular network")
including many types of base stations has also been researched and
developed, and is being gradually applied and popularized.
FIG. 9 is a block diagram illustrating a configuration of the
heterogeneous cellular network. In the heterogeneous cellular
network illustrated in FIG. 9, there are four macro base stations
(Macro BS) MBS and eight micro base stations mBS. Here, the micro
base station is a generic term for mini type base stations, which
are different from the macro base station, including, for example,
femto base stations (Femto BS), pico base stations (pico BS), micro
base stations (Micro BS), and the like. Further, MC (also referred
to as "macro cell") represents a cell covered by the macro base
station MBS, and mC (also referred to as "micro cell") represents a
cell covered by the micro base station mBS.
Usually, the transmitting power of the micro base station is much
lower than that of the macro base station, the coverage area of the
micro cell is much smaller than that of the macro cell, and a
probability that the number of users of the micro cell is smaller
than that of the macro cell is high. However, in the related art,
same frequency bands may be allocated to the micro base station and
the macro base station, or in order to reduce interference between
cells, different frequency bands may also be allocated to the micro
base station and the macro base station. In addition, the frequency
bands to be allocated to the micro base station and the macro base
station are often in either state of being used up completely or
being completely off.
Thus, when the same frequency bands are allocated to the micro base
station and the macro base station, the micro base station
allocates all of the frequency bands to the users in the micro
cell. As a result, there is a fear of providing the so-called
excess service of more than a required number of frequency bands
for the users. For that reason, there exist problems in that not
only the resources are wasted due to providing the excess service,
but also the interference between cells becomes stronger because
the micro base station and the neighboring base station use the
same frequency bands, resulting in reducing the network
capacity.
In order to reduce the interference, US2012/0157108A1 discloses a
technology of a fractional frequency reuse mechanism for a
heterogeneous cellular network. The mechanism is a direct extension
of the fractional frequency reuse mechanism in the traditional
homogeneous cellular network, i.e., allocating resources based on
the user's position information. Further, WO2012/106987A1 discloses
a solution of reducing the interference, in which the base station
and the micro node in a heterogeneous cellular network use
different position information.
SUMMARY
As described above, most of the homogeneous cellular networks use
the full frequency reuse mechanism for 3G and future standards.
However, the heterogeneous cellular network slightly differs from
the homogeneous cellular network in that the heterogeneous cellular
network includes different types of coverage capacities, and uses
different types of base stations. As a result, the differences
between the base stations and between the cells make the full
frequency reuse mechanism be no longer the optimal reuse mechanism
of the heterogeneous cellular network.
Thus, it is desired to reduce the same frequency interference
between cells in a heterogeneous cellular network, thereby
enhancing the network capacity.
An aspect of the invention is a micro base station to be used in a
heterogeneous cellular network. The micro base station has
resources including frequency bands and time slots and being
available for a user to use. The heterogeneous cellular network
includes a plurality of base stations including a macro base
station and the micro base station. The micro base station
includes: an information acquiring part configured to acquire
configuration information and load information of the micro base
station, and to acquire configuration information and load
information of a neighboring base station adjacent to the micro
base station from the neighboring base station; and a resource
selection part configured to select a part of the resources from
the resources to provide the selected part of the resources to the
user based on the configuration information and the load
information of the micro base station and the neighboring base
station, which are acquired by the information acquiring part.
An aspect of the invention allows reduction of the same frequency
interference between cells in a heterogeneous cellular network,
thereby enhancing the network capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a block diagram schematically illustrating a
configuration of a micro base station in a heterogeneous cellular
network of the embodiment.
FIGS. 1B to 1D are schematic diagrams illustrating selections of
resources of the micro base station of the embodiment, which are
available for users to use.
FIG. 2 is a block diagram schematically illustrating a
configuration of a macro base station in the heterogeneous cellular
network of the embodiment.
FIG. 3 is a flowchart illustrating a resource selection method for
a micro base station in the heterogeneous cellular network of the
embodiment.
FIG. 4 is a flowchart illustrating a resource allocation method for
a macro base station in the heterogeneous cellular network of the
embodiment.
FIG. 5 is a message signaling diagram during an exchange of
configuration information between the base stations of the
embodiment.
FIG. 6 is a message signaling diagram of the embodiment when the
micro base station of this invention acquires load information from
the macro base station.
FIG. 7 is a diagram illustrating a format of the message signaling
of FIGS. 5 and 6.
FIG. 8 is a diagram illustrating a processing of the micro base
station of the embodiment randomly selecting M resource blocks from
N resource blocks to provide the selected M resource blocks to the
users.
FIG. 9 is a block diagram illustrating a configuration of the
heterogeneous cellular network.
DETAILED DESCRIPTION OF EMBODIMENTS
Now, description is made of an embodiment of the invention. The
embodiment descries a heterogeneous cellular network based on a
fractional frequency reuse mechanism and a micro base station to be
used therein and a resource selection method for the micro base
station, which may reduce the same frequency interference between
cells, thereby enhancing the network capacity.
The embodiment presents a distributed type fractional frequency
reuse mechanism, and the reuse mechanism may adjust self-adaptively
with change of a network load. In particular, the fractional
frequency reuse mechanism may be applied for the cases where the
loads of respective cells are unbalanced (e.g., hot spot area) and
the user requirements of the respective cells are different, and
may also adjust self-adaptively to activation and hibernation of
the base station.
The heterogeneous cellular network of the embodiment includes a
plurality of base stations including two types of base stations
including a macro base station and the micro base station, and the
macro base station and the micro base station each have resources
available for users to use. The "resources" referred herein include
frequency bands and time slots.
The macro base station includes an information acquiring part
configured to acquire configuration information and load
information of the macro base station itself, and a resource
allocation part configured to allocate the resources possessed by
the macro base station itself to a user.
The micro base station includes an information acquiring part
configured to acquire configuration information and load
information of the micro base station itself, and to acquire
configuration information and load information of a neighboring
base station from the base station adjacent to the micro base
station, and a resource selection part configured to select a part
of the resources from the resources to provide the selected part of
the resources to the user based on the configuration information
and the load information of the micro base station itself and the
neighboring base station, which are acquired by the information
acquiring part.
The micro base station may select a part of the resources as little
as possible from all of the resources including frequency bands and
time slots to provide the selected part of the resources to the
user. Thus, the idle resources may be increased and the same
frequency interference between cells may be reduced while ensuring
the user requirements, thereby being capable of enhancing the
network capacity. The "neighboring cell (or neighboring base
station)" used herein refers to a neighboring cell (or neighboring
base station) having its boundary connecting to or an area
intersecting with the cell covered by the base station.
Further, the "configuration information" used herein means
information on a configuration of a base station, including, for
example, a position of a base station, transmitting power (Pm, PM),
micro base station density (.rho.m), and macro base station density
(.rho.M). Characters including m represent value of micro base
stations and characters including M represent values of macro base
stations.
In addition, the "load information" used herein refers to
information on users within a cell covered by a base station,
including, for example, rate requirement (um, uM) of a single user
within the cell (hereinafter abbreviated as "user rate
requirement"), user density (.lamda.m, .lamda.M) within the
cell.
When the micro base station cannot acquire the load information of
its own cell due to load measurement, or the like, a predetermined
value can be used as its replacement. When the micro base station
cannot acquire the load information of the neighboring cell due to
information exchange, or the like, the load information of the
neighboring cell can be estimated by utilizing the information
measured by the micro base station itself, and can be assumed that
uM=um, .lamda.M=.lamda.m.
Embodiments of the invention are described below with reference to
the drawings, but these embodiments are only examples for
illustrating specific operations of the above-mentioned embodiments
of the invention, and are not intended to limit the scope of claim
of the invention. Therefore, according to a gist of the
embodiments, new technical solution may be formed through addition
or deletion of the component thereof.
A configuration of the micro base station of the embodiment is
illustrated below with reference to FIGS. 1A to 1D.
FIG. 1A is a block diagram schematically illustrating a
configuration of a micro base station in a heterogeneous cellular
network of the embodiment, and FIGS. 1B to 1D are schematic
diagrams illustrating selections of resources of the micro base
station of the embodiment, which are available for users to
use.
As illustrated in FIG. 1A, the micro base station mBS in the
heterogeneous cellular network includes a sending module 101, a
receiving module 102, a storage module 103, an automatic
configuration module 110, a neighbor finding module 111, an
information exchange module 112, a load measurement module 113, a
short cycle update module 114, a long cycle update module 115, and
a resource selection module 120. Of those, the resource selection
module 120 includes a calculation module 121 and an M-RB (M random
resource blocks) generation module 122. These modules may be
configured by a processor operable according to programs and/or
dedicated hardware circuits.
The sending module 101 is used to send message signals, and the
like including data and information, to outside users, other base
stations, and the like within the heterogeneous cellular
network.
The receiving module 102 is used to receive message signals, and
the like including data and information, sent from outside users
and other base stations, and the like within the heterogeneous
cellular network.
The storage module 103 is used to store various data, information,
and the like.
The automatic configuration module 110 is used to acquire
configuration information such as ID, position, and transmitting
power Pm of the micro base station itself, and further acquire
configuration information such as macro base station density .rho.M
and micro base station density .rho.m from a heterogeneous cellular
network.
The neighbor finding module 111 is used to find neighboring base
stations including a neighboring micro base station(s) and a
neighboring macro base station(s). For example, from a user roamed
from a neighboring cell, the information of the base station to
which the neighboring cell belongs, for example, ID of the base
station, is acquired.
The information exchange module 112 is used to exchange various
kinds of information, for example configuration information and
load information, with a neighboring base station. Of course, when
the other base station does not need (does not require) those
information, there is no need to send those information, and is
only required to receive and acquire those information.
The load measurement module 113 is used to estimate a size of the
micro cell covered by the micro base station, and to measure an
actual load of the micro cell, to thereby acquire the load
information of the micro base station. For example, the user
density .lamda.m within the micro cell and the user rate
requirement um of the micro cell are calculated.
The short cycle update module 114 is used to newly select the
resources to be provided for users to use within a relatively short
cycle by the M-RB generation module 122, and in this case, it is
not required to update the system parameter. In this case, a length
of the short cycle is not particularly limited, and the length may
be set as needed. Moreover, an operation of the short cycle update
can be triggered by a given time or a given event.
The long cycle update module 115 is used to newly select the
resources provided for users to use within a relatively long cycle
by the calculation module 121 and the M-RB generation module 122,
and in this case, it is required to update the system parameter. In
this case, a length of the long cycle is also not particularly
limited, the length may only be set to be longer than that of the
short cycle. Moreover, an operation of the long cycle update can be
triggered by a given time or a given event.
The resource selection module 120 is used to select a part of the
resources (M, N.gtoreq.M) to provide the selected part of the
resources to the users from all resources (e.g., N) that are
available for users to use, according to the acquired configuration
information and the load information of the micro base station
itself and a neighboring base station. M represents the selected
amount of resources. In this selection, the optimal resources may
be precisely selected. In this case, however, the interference may
be further reduced, but the process is very complicated and time
consuming. Accordingly, the selection is carried out at random so
that the process may be made simple.
Now, while describing the calculation module 121 and the M-RB
generation module 122, a specific processing for resource selection
is described, but it is not limited thereto, it suffices that as
much idle resources as possible can be remained while the user
requirements are ensured.
The calculation module 121 is used to perform calculations. For
example, the values of .beta. and M are calculated according to
Equations (1) to (3).
.alpha..times..times..beta..times..times..times..times..rho..rho..lamda..-
times..times..rho..rho..times..times..lamda..times..times..times..times..b-
eta..times..times. ##EQU00001##
where:
c represents a system parameter, and is determined depending on
transmitting powers of the macro base station and the micro base
station;
Pm represents a transmitting power of the micro base station;
PM represents a transmitting power of the macro base station;
.alpha. represents a path loss factor, which is usually a constant,
typically 3.7, 4, etc.;
um represents a user rate requirement of a single user within the
micro cell;
uM represents a user rate requirement of a single user within the
macro cell;
.rho.m represents a micro base station density, indicating a number
of active micro base stations per unit area, excluding the dormant
micro base stations, etc.;
.rho.M represents a macro base station density, indicating a number
of active macro base stations per unit area, excluding the dormant
macro base stations, etc.;
.lamda.m represents a user density within a micro cell, indicating
a number of the users having service requests per unit area,
excluding standby or dormant users;
.lamda.M represents a user density within a macro cell, indicating
a number of the users having service requests per unit area,
excluding standby or dormant users;
.lamda.M represents an average value of the user densities of a
plurality of macro cells;
N represents a total number of the resource blocks in which the
resources available for users to use is divided;
M represents a number of a part of the resource blocks selected
from N resource blocks to be provided for the users to use.
When Equation (2) is expressed by .beta.=min{A, B}, it means that
.beta. equals to the smaller number among A and B. When .beta.,
which is calculated by Equation (2), equals to 1, it means that the
micro base station is required to select all the resource blocks to
provide the selected part of the resources to the user, and when
.beta. is less than 1, the smaller the value of .beta. is, the less
resource blocks are selected, and the more idle resource blocks
there are.
M and N are both integers, N.beta. is rounded up when N.beta. is
not an integer. For example, if N.beta.=2. 3, then M=3. Because
.beta. is less than or equal to 1, M is also less than or equal to
N.
The M-RB generation module 122 randomly selects M resource blocks
from N resource blocks to provide the selected M resource blocks to
the users. In the description below, the process will be described
in details with reference to FIG. 8.
In the above-mentioned description, description is made of an
example of calculating the values of .beta. and M by Equation (1)
to (3), and then selecting M resource blocks from N resource blocks
to provide the selected M resource blocks to the users. However,
the embodiment is not limited thereto, it suffices that the number
of the selected resources can be reduced as much as possible while
the user requirements are ensured.
For example, it is needless to say that the calculating equations
(Equation (1) and Equation (2)) of .beta. can use the other load
information and configuration information. Further, the number of
blocks (M) of the selected resource blocks does not necessarily
need to directly use the M value calculated by Equation (3), but
can be obtained according to the M value. For example, there can be
obtained by multiplying M by a factor greater than one, or by
adding a given value (e.g., 1, 2) to M. In this case, it results in
selecting more resources. However, a certain room may be provided
for the user requirements, thereby being capable of satisfying more
the user requirements.
FIGS. 1B to 1D each illustrate the selection solutions of the
resources available for users to use, and in this case, N=16 and
M=6. Specifically, the micro base station can provide a total of 16
resource blocks for the users, within which 6 resource blocks are
selected to provide for the users to use. Accordingly, the number
of the idle resource blocks becomes 16-6=10, and hence the
frequency interference between cells can be greatly reduced to
enhance the network capacity.
Next, the configuration of the macro base station of the embodiment
is illustrated with reference to FIG. 2.
FIG. 2 is a block diagram schematically illustrating a
configuration of a macro base station in the heterogeneous cellular
network of t the embodiment.
As illustrated in FIG. 2, the macro base station MBS in the
heterogeneous cellular network includes a sending module 201, a
receiving module 202; a storage module 203, an automatic
configuration module 210, a neighbor finding module 211, an
information exchange module 212, a load measurement module 213, a
short cycle update module 214, a long cycle update module 215 and a
resource allocation module 220. These modules may be configured by
a processor operable according to programs and/or dedicated
hardware circuits.
The sending module 201 is used to send message signals, and the
like including data and information to outside users and other base
stations of the heterogeneous cellular network, and the like.
The receiving module 202 is used to receive message signals, and
the like including data and information sent from outside users and
the other base stations of the heterogeneous cellular network, and
the like.
The storage module 203 is used to store various data, information,
and the like.
The automatic configuration module 210 is used to acquire the
configuration information such as ID, position, and transmitting
power PM of the macro base station itself, and further acquire the
configuration information such as macro base station density
.rho.M, micro base station density .rho.m, and the like from a
heterogeneous cellular network.
The neighbor finding module 211 is used to find neighboring base
stations including a neighboring micro base station(s) and a
neighboring macro base station(s). For example, from a user roamed
from a neighboring cell, the information of the base station to
which the neighboring cell belongs, such as ID of the base station,
is acquired.
The information exchange module 212 is used to exchange various
kinds of information, for example configuration information and
load information, with a neighboring base station. Of course, when
the macro base station does not need the information, there is no
need to request the neighboring base station to send those
information, and is required to only send those information.
The load measurement module 213 is used to estimate a size of the
macro cell covered by the macro base station, and to measure an
actual load of the macro cell, to thereby acquire the load
information of the macro base station. For example, the user
density .lamda.M within the macro cell and the user rate
requirement uM of the macro cell are calculated.
The short cycle update module 214 is used to newly allocate the
resources for users to use within a relatively short cycle by the
resource allocation module 220. In this case, a length of the short
cycle is not particularly limited.
The long cycle update module 215 is used to newly select the
resources provided for users to use within a relatively long cycle
by the resource allocation module 220, and in this case, it is
required to update the system parameter. In this case, a length of
the long cycle is also not particularly limited as in the case of
the short cycle.
The resource allocation module 220 is used to allocate resources to
the users for use.
As described above, the micro base station differs from the macro
base station in regard to the allocations of resources to users.
The macro base station directly allocates all resources to users
for use. However, the micro base station first selects a part of
the resources from all resources, and then allocates the selected
part of the resources to users for use. Thus, the other part of
resources becomes an idle state, thereby being capable of reducing
the interference between cells to enhance the network capacity.
Further, the processing of the micro base station configured to
select a part of the resources from all the resources can be
randomly repeated within a given cycle, thus the selected resource
blocks and the number of the selected resource blocks will also
change. Accordingly, when the resources such as frequency bands
with very strong interference, and the like, exist, there is no
case where the frequency bands with very strong interference are
continuously used.
Now, description is made of the resource allocation method for a
micro base station of the embodiment with reference to FIG. 3.
FIG. 3 is a flowchart illustrating a resource selection method for
a micro base station in the heterogeneous cellular network of the
embodiment.
As illustrated in FIG. 3, first, the micro base station carries out
the automatic configuration processing, acquires the configuration
information such as ID, position, and transmitting power of the
micro base station itself, and further acquires the micro base
station density .rho.m and the macro base station density .rho.M
from the heterogeneous cellular network (Step S301).
After that, from a related user roamed from a peripheral cell to a
current cell covered by the micro base station itself, ID of the
base station, to which the peripheral cell belongs, is acquired,
thereby finding the neighboring base station (also referred to as
adjacent base station) (Step S302). Needless to say; the
neighboring base station may be a macro base station, or may also
be a micro base station, but for convenience of the description, it
is assumed herein that the micro base station is only adjacent to
other macro base stations.
Next, the configuration information such as position of a base
station and transmitting power is interchanged with the found base
station (Step S303).
After that, based on the strongest signal access standard, an area
of the current cell is estimated (Step S304).
After that, the traffic load of the current cell is measured. For
example, the numbers of the users having service requests at
different points of time within a given period of time are sampled,
and a mean value thereof is calculated. Further, based on the area
estimated in Step S304, the user density .lamda.m within the micro
cell is calculated. In addition, the user rate requirement um of
the micro cell may be acquired from the service types of the user
requests (Step S305).
Next, the load information is exchanged with the peripheral macro
base station again, to thereby acquire the load information such as
the user rate requirement uM, and the user density .lamda.M of the
found neighboring macro base station (Step S306). In this case,
when the neighboring macro base station does not require the load
information, the load information of the micro base station itself
may not be sent to the neighboring macro base station.
After that, the value of .beta. is calculated according to the
above-mentioned Equation (1) and Equation (2), and the value of M
is calculated according to the above-mentioned Equation (3) (Step
S307).
After that, M resource blocks are randomly selected from all of the
N resource blocks to be provided for users to use (Step S308). In
the following description, the random selection method for M
resource blocks is described in detail with reference to FIG.
8.
After that, the M random resource blocks generated are allocated to
users for use (Step S309). In this case, the related art may be
used.
The update of the resource allocation includes a long cycle update
and a short cycle update. When the long cycle update is carried
out, it is necessary to newly calculate the values of .beta. and M,
and hence Step S305 to Step S309 are repeatedly carried out. When
the short cycle update is carried out, the values of .beta. and M
are not newly calculated, and the value of M calculated before is
directly used. By repeatedly carry out only Step S308 to Step S309,
the frequency band selection becomes more rapid and more
convenient.
Now, description is made of a resource allocation method for a
macro base station of the embodiment with reference to FIG. 4.
FIG. 4 is a flowchart illustrating a resource allocation method for
a macro base station in the heterogeneous cellular network of the
embodiment. In this case, for convenience of the description, it is
assumed that the macro base station does not need to acquire the
load information of the neighboring base station.
As illustrated in FIG. 4, first, the macro base station carries out
the automatic configuration processing to acquire the configuration
information such as ID, position, and transmitting power of the
macro base station itself and the micro base station density .rho.m
and the macro base station density .rho.M from the network (Step
S401).
After that, from a related user roamed from a peripheral cell to
the current cell covered by the macro base station itself, ID of
the base station to which the peripheral cell belongs is acquired,
thereby finding the neighboring base station. The neighboring base
station may be a macro base station, or may also be a micro base
station (Step S402).
Next, the configuration information such as position of base
station, and transmitting power is interchanged with the found base
station (Step S403).
After that, based on the strongest signal access standard, an area
of the current cell is estimated (Step S404).
After that, the traffic load of the current cell is measured. For
example, the numbers of the users having service requests at
different points of time during a given period of time are sampled,
and a mean value thereof is calculated. Further, based on the area
estimated in Step S404, the user density .lamda.M within the macro
cell is calculated. In addition, the user rate requirement uM of
the macro cell may be acquired from the service types of the user
requests (Step S405).
Next, from all resources, resources provided for the users to use
are allocated to the users (Step S406). In this case, the related
art may be used.
The update of the resource allocation includes a long cycle update
and a short cycle update. When the long cycle update is carried
out, Step S405 to Step S406 are repeatedly carried out. When the
short cycle update is carried out, only Step S406 is repeatedly
carried out.
Now, descriptions are made of the specific processes of Step S303
of FIG. 3 and Step S403 of FIG. 4 of the embodiment with reference
to FIG. 5.
FIG. 5 is a message signaling diagram during an exchange of
configuration information between the base stations of the
embodiment. Of those, the particular base station and the
neighboring base station may be macro base stations, or may also be
micro base stations. The format of the message signaling concerning
various requests, responses, acknowledgements, and the like is
described later in detail with reference to FIG. 7.
First, after the particular base station acquires ID of the
neighboring base station (refer to Step S302, Step S402), the
particular base station sends a link establishment request
including ID of the neighboring base station to the neighboring
base station, and requests the neighboring base station to
establish a link with the neighboring base station (Step S501). The
neighboring base station responds to the request, and sends an ACK
(acknowledgement) message to the particular base station (Step
S502). With this, a link between the particular base station and
the neighboring base station is established.
After that, the particular base station sends a configuration
information sending request, to the neighboring base station, for
requesting the configuration information such as position of the
base station, and transmitting power of the neighboring base
station (Step S503). The neighboring base station responds to the
request, and sends the configuration information such as position
of the base station, and transmitting power of itself to the
particular base station (Step S504). After receiving the
configuration information, the particular base station sends an
information receiving acknowledgement, to the neighboring base
station, for acknowledging the receipt of the configuration
information (Step S505).
Next, the neighboring base station sends a configuration
information sending request, to the particular base station, for
requesting the configuration information such as position of the
base station, and transmitting power of the particular base station
(Step S506). The particular base station responds to the request,
and sends the configuration information such as position of the
base station, and transmitting power of itself to the neighboring
base station (Step S507). After receiving the configuration
information, the neighboring base station sends an information
receiving acknowledgement, to the particular base station, for
acknowledging the receipt of the configuration information (Step
S508).
After that, the particular base station sends a message to the
neighboring base station indicating that the information exchange
is completed (Step S509). The neighboring base station sends an ACK
(acknowledgement) message to the particular base station (Step
S510).
As described above, after passing through Step S501 to Step S510,
the configuration information exchange (refer to Step S303, Step
S403) between the particular base station and the neighboring base
station is completed.
Now, description is made of the specific process of Step S306 of
FIG. 3 of the embodiment with reference to FIG. 6.
FIG. 6 is a message signaling diagram when the micro base station
of the embodiment acquires load information from the macro base
station. The format of the message signaling concerning various
requests, responses, and acknowledgements is described later in
detail with reference to FIG. 7.
First, after the particular micro base station acquires ID of the
neighboring macro base station (refer to Step S302), the particular
micro base station sends a link establishment request including ID
of the neighboring macro base station, to the neighboring macro
base station, for requesting establishment of a link with the
neighboring macro base station (Step S601). The neighboring macro
base station responds to the request, and sends an ACK
(acknowledgement) message to the particular micro base station
(Step S602). With this, a link between the particular micro base
station and the neighboring macro base station is established.
After that, the particular micro base station sends a load
information sending request, to the neighboring macro base station,
for requesting the load information such as user density and user
rate requirement of the neighboring macro base station (Step S603).
The neighboring macro base station responds to the request, and
sends the load information such as user density and user rate
requirement of itself to the particular, micro base station (Step
S604). After receiving the load information, the particular micro
base station sends an information receiving acknowledgement, to the
neighboring macro base station, for acknowledging the receipt of
the load information (Step S605).
Next, the particular micro base station sends a message to the
neighboring macro base station indicating that the information
exchange has been completed (Step S606). The neighboring macro base
station sends an ACK (acknowledgement) message to the particular
micro base station (Step S607).
Thus, after passing through Step S601 to Step S607, the particular
micro base station acquires the load information of the neighboring
macro base station.
Now, description is made of the format of various message signaling
illustrated in FIGS. 5 and 6 with reference to FIG. 7.
FIG. 7 is a diagram illustrating a format of the message signaling
of FIGS. 5 and 6.
As illustrated in FIG. 7, the messages such as the link
establishment request, the link establishment acknowledgement, the
information sending request, the information sending response, and
the information receiving acknowledgement include those four
domains of sequence number 701, flag 702, checksum 703, and data
704.
Of those, the serial number 701 is used to designate a serial
number to the message.
The flag 702 indicates that the message type is any one of
"request", "response", "acknowledgement (ACK)", and "end
(END)".
The checksum 703 is used to indicate whether a verifying head has
already been damaged.
The data 704 is used to record the content of the message and the
length thereof is variable. When the flag 702 is a "request", the
data 704 contains a specific content of the request. When the flag
702 is a "response", the data 704 contains a serial number of the
response to the request and the content of the response. When the
flag 702 is an "acknowledgement", the data 704 contains the serial
number of the acknowledgement. When the flag 702 is an "end", the
data 704 is blank.
Now, description is made of the specific process of Step S308 of
FIG. 3 of the embodiment with reference to FIG. 8.
FIG. 8 is a diagram illustrating a processing of the micro base
station of the embodiment randomly selecting M resource blocks from
N resource blocks to provide the selected M resource blocks to the
users. In the equation, N and M are positive integers and satisfy
N.gtoreq.M.
As illustrated in FIG. 8, first, a pseudo-random number of from 1
to N is assigned to each resource block of N resource blocks (Step
S801). Next, the N pseudo-random numbers acquired in Step S801 are
sorted in an ascending order, and the M.sub.th small pseudo-random
number is determined to be a threshold value (Step S802). Finally,
traversing the pseudo-random numbers corresponding to the N
resource blocks, and comparing to the threshold value determined in
Step S802, M resource blocks having a comparison result of "less
than or equal to the threshold value" are selected from the N
resource blocks (Step S803).
The invention is not limited to the above-described embodiments but
includes various modifications. The above-described embodiments are
explained in details for better understanding of this invention and
are not limited to those including all the configurations described
above. A part of the configuration of one embodiment may be
replaced with that of another embodiment; the configuration of one
embodiment may be incorporated to the configuration of another
embodiment. A part of the configuration of each embodiment may be
added, deleted, or replaced by that of a different
configuration.
The above-described configurations, functions, and processors, for
all or a part of them, may be implemented by hardware: for example,
by designing an integrated circuit. The above-described
configurations and functions may be implemented by software, which
means that a processor interprets and executes programs providing
the functions. The information of programs, tables, and files to
implement the functions may be stored in a storage device such as a
memory, a hard disk drive, or an SSD (Solid State Drive), or a
storage medium such as an IC card, or an SD card.
* * * * *