METHODS OF SCHEDULING A CARRIER COMPONENT
FIELD OF THE INVENTION
The present invention relates to a wireless communication technology, and more
particularly, to a technology of cross-scheduling of multiple carrier components in a carrier
aggregation scenario.
BACKGROUND OF THE INVENTION
In LTE-A, wider bandwidth, up to 100 MHz, is used to satisfy higher data rate
requirement. For backward compatibility, the 100 MHz bandwidth is separated into
multiple carrier components, each of which has the maximum width of 20 MHz.
Therefore, each user may support up to 5 carrier components. For each user equipment
(UE), there is one primary carrier component (PCC) and optionally one or more secondary
carrier components (SCC), with the former always keeping active. Another related
concept is primary cell (Pcell) and secondary cell (Scell) adopted by 3GPP, wherein a
primary cell refers to a downlink/uplink PCC pair, and a secondary cell refers to a
downlink/uplink SCC pair or a single downlink carrier. A primary cell is established by
R8 radio resource control (RRC) connection procedure, and a secondary cell is
established by new Release- 10 secondary cell adding message. It has been agreed that
each secondary cell will be assigned with one cell index to identify its corresponding
downlink and uplink carrier components or corresponding downlink carrier.
Cross-scheduling has been agreed for LTE-A carrier aggregation so that physical
downlink control channel (PDCCH) in one carrier component can indicate resource
information of other carrier component(s). For this purpose, a carrier identification field
(CIF) is inserted into PDCCH to indicate target carrier component(s) at which the resource
information is located. One basic consensus on CIF is that CIF and cell index should be defined
separately. Another consensus is that the downlink/uplink carrier components of the same cell
linked by system information block 2 (SIB2) should be scheduled by the same downlink carrier
component. And it is still inconclusive about CIF assignment and scheduling.
A solution of adopting implicit CIF assignment for each carrier component has been
proposed. For example, the CIF is determined on the basis of the cell index of a carrier
component or frequency information of a carrier component. Such kind of implicit assignment
helps to save signaling overhead, but the gain is very small since at most 15 bits can be saved
even in a case where a UE is configured with 5 carrier components. On the other hand, this
implicit CIF assignment based on cell index violates the current consensus that CIF and cell
index should be defined separately. Another drawback is that this solution may probably cause
specification complexity when the CIF of a carrier component is reconfigured (e.g., the CIF of a
carrier component is reconfigured from one PDCCH of a downlink carrier component to another)
and also restrict reconfiguration flexibility (e.g., the network may need to assign a particular CIF
value for a carrier component, instead of any cell order or frequency order). Another drawback
of this solution is that potential loss of synchronization may happen with the CIF of the carrier
components between an evolved Node B (eNB) and a UE. For example, one possibility for
primary cell index assignment is to reserve a default value for the primary cell. Hence for
primary cell change due to reconfiguration where the current primary cell is changed into a
new secondary cell, the cell index of the primary cell needs to be changed, and its CIF should
also be changed according to this implicit solution, thereby giving the chance of mismatch of
CIF value of carrier components between the eNB and the UE. In addition, this implicit
assignment method must further define a specific mapping strategy between CIF and cell index
or frequency information, thereby increasing specification complexity is caused.
SUMMARY OF THE INVENTION
To solve the aforementioned problems in the prior art, the present invention provides
solutions of scheduling a carrier component between a base station and a user equipment by
assigning a CIF.
In one embodiment of the present invention, a method, in a base station, of scheduling a
carrier component for a user equipment is provided. The method includes: transmitting a
configuration message to configure cells of the user equipment, wherein the configuration
message includes respective first information for carrier identification of each cell.
In another embodiment of the present invention, a method, in a base station, of scheduling a
carrier component for a user equipment is provided. The method includes: transmitting a
handover command for the handover of the user equipment, wherein the handover command
includes an information element carrying first information of each cell, the first information
being utilized for carrier identification.
In yet another embodiment of the present invention, a method, in a base station, of
scheduling a carrier component for a user equipment is provided. The method includes:
transmitting a RRC layer message relating to primary cell change of the user equipment, wherein
the RRC layer message includes: a first information to indicate a carrier identification of a cell;
and at least one of a second information to indicate the index(es) of the cell(s) served by the cell
and a third information to indicate an index of a cell serving the cell.
The technical solutions provided by the present invention can guarantee the flexibility of
carrier component configuration, avoid the need for a specific CIF mapping strategy, and reduce
specification complexity.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features, objectives and advantages of the present invention will become more
apparent after reading the following detailed description of non-limiting embodiments, with
reference to the accompanying drawings, wherein below:
FIG. 1 is a block diagram illustrating a system according to an embodiment of the present
invention;
FIG. 2 is a structural diagram illustrating an information element for a carrier component
pair according to an embodiment of the present invention;
FIG. 3 is a flowchart illustrating a method, in a base station, of scheduling a carrier
component for a user equipment according to an embodiment of the present invention;
FIG. 4 is a flowchart illustrating a method, in a base station, of scheduling a carrier
component for a user equipment according to another embodiment of the present invention;
FIG. 5 is a flowchart illustrating a method, in a base station, of scheduling a carrier
component for a user equipment according to yet another embodiment of the present invention;
and identical or similar reference signs refer to corresponding features throughout the
drawings.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the present invention, some terms are defined as follows:
Cell: a downlink/uplink carrier component pair between a base station and a user
equipment.
Primary cell: a downlink/uplink primary carrier component pair.
Secondary cell: a downlink/uplink secondary carrier component pair.
FIG. 1 is a block diagram illustrating a system according to an embodiment of the present
invention. As shown, the mobile communication system includes a base station 10 and a user
equipment 20. As shown, one primary cell and one or more secondary cells are included
between the base station 10 and the user equipment 20.
FIG. 2 is a structural diagram illustrating an information element for a carrier component
pair according to an embodiment of the present invention. The information element shown is
usually assigned to each cell in some control messages to indicate configuration of the cell. A
first information is utilized to carry CIF information, i.e., information for carrier identification.
A second information is utilized to indicate cell index(es) of secondary cell(s) that a certain cell
is intended to serve. And a third information is utilized to indicate the cell index of a cell serving
a certain cell. The second and third information is invalid for the configuration of a
self-scheduling cell. The second and third information is needed only for the configuration of a
cross-scheduling cell. And those skilled in the art can understand that the information element
structure shown in FIG. 2 is exemplary rather than restrictive, and that in different
implementations, the first information, the second information, and the third information in the
information element may employ any permutation and combination, depending on the
requirements of specific applications. Because the CIF here is defined in each cell, the
downlink/uplink carrier components of a cell linked by SIB2 share the same CIF. Therefore,
only one information element is needed for each cell, and there is no need to design information
elements separately for the downlink carrier component and the uplink carrier component. This
helps to optimize the size of carrier component management messages.
FIG. 3 is a flowchart illustrating a method, in a base station, of scheduling a carrier
component for a user equipment according to an embodiment of the present invention.
Description will be given in connection with FIGs. 1-3 as follows.
As shown, the flowchart of the method includes a step S11.
When the base station 10 schedules a carrier component for the user equipment 20, in the
step SI 1, the base station 10 transmits a configuration message to configure cells of the user
equipment 20, wherein the configuration message includes respective first information for
carrier identification of each cell.
Based on the value of the first information of a certain cell, the user equipment 20 may get
to know whether the resource is allocated to this cell or other cell(s). Resource allocation to the
cell itself corresponds to self-scheduling, and resource allocation to other cell(s) corresponds to
cross-scheduling. Specifically, the first information may employ 3 bits to indicate which cell a
corresponding resource pertains to.
If the primary cell is configured to serve other secondary cell(s), the first information of the
primary cell is mandatory; otherwise, it is dispensable. Hence it is dispensable to assign CIF
value for a primary cell during its setup procedure. The reason is that primary cell setup is based
on LTE-A Release-8 RRC connection setup procedure, and thus backward compatibility of the
system can be guaranteed without introducing new information element such as the first
information into primary cell setup procedure.
In one embodiment of the present invention, the configuration message transmitted from
the base station 10 to the user equipment 20 to reconfigure a primary cell includes a first
information and a second information of the primary cell. The first information includes a carrier
identification of the primary cell to indicate that corresponding resource pertains to the primary
cell. And the second information is utilized to indicate cell index(es) of secondary cell(s) that the
primary cell is intended to serve.
In one embodiment of the present invention, the configuration message transmitted from
the base station 10 to the user equipment 20 to add or update a secondary cell includes a first
information of the secondary cell, and at least one of a second information and a third
information thereof. The first information is utilized to indicate that the secondary cell is a
cross-scheduling cell. When the secondary cell is intended to serve other secondary cell(s), the
configuration message further includes a second information of the secondary cell to indicate
cell index(es) of the other secondary cell(s) that the secondary cell is intended to serve. When
the secondary cell is served by other cell(s), the configuration message further includes a third
information of the secondary cell to indicate cell index(es) of the other cell(s) serving the
secondary cell. If the third information is empty, the secondary cell is scheduled by its own
downlink carrier component. If the second information is empty, the secondary cell doesn't
serve other secondary cell(s). And if both the second information and the third information is
empty, the first information is dispensable.
According to the above description, the first information assignment of a primary cell may
be achieved via the following options:
Option 1: a default first information value is reserved for the primary cell.
Option 2: the first information of the primary cell is assigned in the configuration message
used to reconfigure the primary cell when the primary cell is configured to serve other secondary
cell(s).
Option 3: when the primary cell is configured to serve other secondary cell(s), the first
information of the primary cell is assigned in the configuration message used to add or update
the secondary cell(s).
And the first information assignment of a secondary cell may be achieved via the following
options:
Option 1: when a secondary cell is added, the first information of the secondary cell is
assigned in the configuration message used to add the secondary cell.
Option 2: when a secondary cell is configured to serve other secondary cell(s), the first
information of the secondary cell is assigned in the configuration message used to update the
secondary cell.
Option 3: when other cell(s) (a primary cell or other secondary cell(s)) is/are configured to
serve a secondary cell, the first information of the secondary cell is assigned in the configuration
message relating to the other cell(s).
For primary cell reconfiguration message possibly used to configure the primary cell to
serve other secondary cell(s), two types of information element are needed:
A first information is utilized to assign a CIF value for the primary cell; and
A second information is utilized to identify a list of secondary cell(s) that the primary cell is
intended to serve, wherein the list includes index information of the secondary cell(s) that the
primary cell is intended to serve.
If the second information is empty, the first information may be empty too.
For secondary cell adding/updating message used to add a new secondary cell or to
reconfigure a currently configured secondary cell, the following information elements are
needed:
A first information is utilized to assign a CIF value for the secondary cell. If the CIF of the
secondary cell was assigned previously, or the secondary cell is scheduled by itself and doesn't
serve any other secondary cell, the first information may be empty.
A second information is utilized to identify a list of other secondary cell(s) that the
secondary cell is intended to serve.
A third information is utilized to identify information of downlink carrier component(s)
scheduled by the secondary cell, i.e., information of downlink carrier component(s) serving the
secondary cell, including cell index(es) of the primary cell or secondary cell(s). If the third
information is empty, the secondary cell is scheduled by itself.
A fourth information is utilized to assign a CIF value for a primary cell if the primary cell is
intended to serve the secondary cell. If the CIF of the primary cell was assigned previously, the
fourth information element may be empty.
Accordingly, the CIF of a secondary cell may be assigned by the following options:
Option 1: the CIF value of the secondary cell is assigned in a secondary cell adding
message.
Option 2: the CIF value of the secondary cell is assigned in a secondary cell
adding/updating message when the secondary cell is scheduled by other secondary cell(s).
Option 3: the CIF value of the secondary cell is assigned in a secondary cell
adding/updating message when the secondary cell is intended to serve other secondary cell(s).
Option 4: the CIF value of the secondary cell is assigned in a primary cell reconfiguration
message when a primary cell is intended to serve the secondary cell.
FIG. 4 is a flowchart illustrating a method, in a base station, of scheduling a carrier
component for a user equipment according to another embodiment of the present invention.
Description will be given in connection with FIGs. 1-4 as follows.
As shown in FIG. 4, the flowchart of the method includes a step S21.
When the base station 10 schedules a carrier component for the user equipment 20, in the
step S21, the base station 10 transmits a handover command for the handover of the user
equipment 20, wherein the handover command includes an information element carrying first
information of each cell, and the first information is utilized for carrier identification. In general,
this corresponds to a scenario where the access service of the user equipment 20 is handed-over
from another base station to the base station 10.
In one embodiment of the present invention, the handover command transmitted from the
base station 10 for the handover of the user equipment 20 includes the first information of a
cross-scheduling cell. And the first information of remaining cross-scheduling cell(s) is
deducible according to the first information of the cross-scheduling cell.
In the handover scenario, one important issue is that a base station may include information
of a primary cell and optionally information of one or more secondary cells. In general, there are
two options for CIF assignment in the handover scenario: one is to assign the CIF value in the
handover command; the other is to assign the CIF value after the handover command and before
transmission/reception operation. Regarding the second option, the method in the embodiment
shown in FIG. 3 may be employed to assign the CIF value.
Regarding the first option above, the CIF may be assigned for a primary cell and configured
secondary cell(s) by the following solution.
An information element of first information of the primary cell and each configured
secondary cell is included in the handover command.
If a default value is employed as the CIF value of the primary cell, the first information
element may be empty.
When the primary cell is configured to serve other secondary cell(s), the first information
element is mandatory.
For a configured secondary cell, when the secondary cell is scheduled by other cell(s)
(secondary cell(s) or the primary cell) or is intended to serve other secondary cell(s), the first
information element is mandatory. And when the secondary cell is neither scheduled by other
cell(s) nor intended to serve other secondary cell(s), the first information element may be empty.
Specifically, CIF value may be assigned for only one cell, and CIF value of other cells may
be calculated according to that CIF value.
More specifically, the handover command may include the first information element of
only the primary cell for its CIF value assignment. And the CIF value of other configured
secondary cells may be calculated according to the CIF value of the primary cell.
Alternatively, the handover command may include the first information element of only the
first secondary cell for its CIF value assignment. And the CIF value of the primary cell and other
configured secondary cells may be calculated according to the CIF value of the first secondary
cell.
When the primary cell is configured to serve other secondary cell(s), the handover
command further includes a secondary information element of the primary cell to include a list
of configured secondary cell(s) that the primary cell is intended to serve.
When a secondary cell is configured to serve other secondary cell(s), the handover
command further includes a secondary information element of the secondary cell to indicate the
other secondary cell(s) that the secondary cell is intended to serve.
When a certain cell is configured to be scheduled by other cell(s), the handover command
further includes a third information element of the secondary cell to indicate its scheduling cell.
Another important issue associated with the design of CIF assignment is primary cell
change without handover. FIG. 5 is a flowchart illustrating a method, in a base station, of
scheduling a carrier component for a user equipment according to yet another embodiment of the
present invention. Description will be given in connection with FIGs. 1-5 as follows.
As shown in FIG. 5, the flowchart of the method includes a step S31.
When the base station 10 schedules a carrier component for the user equipment 20, in the
step S31, the base station 10 transmits a RRC layer message relating to primary cell change of
the user equipment 20. The RRC layer message includes: a first information to indicate a carrier
identification of a cell; and at least one of a second information to indicate the index(es) of the
cell(s) served by the cell and a third information to indicate an index of a cell serving the cell.
In one embodiment of the present invention, a cross-scheduling primary cell of the user
equipment 20 is changed to a newly configured secondary cell, and the RRC layer message
transmitted by the base station 10 and relating to primary cell change of the user equipment 20
includes: the first information to indicate the carrier identification of the newly configured
secondary cell; and at least one of the second information to indicate the index(es) of the cell(s)
served by the newly configured secondary cell and the third information to indicate the index of
the cell serving the newly configured secondary cell.
If the CIF was assigned for the newly configured secondary cell previously, the CIF may be
reused and the first information element is dispensable.
If the newly configured secondary cell is scheduled by itself and doesn't schedule any other
secondary cell, the first information element may be empty. In other words, the newly
configured secondary cell isn't configured with cross-scheduling function.
In one embodiment of the present invention, a cross-scheduling secondary cell of the user
equipment 20 is changed to a new primary cell, and the RRC layer message transmitted by the
base station 10 and relating to primary cell change of the user equipment 20 includes: the first
information of the new primary cell to indicate the carrier identification of the new primary cell;
and the second information of the primary cell to indicate the index(es) of the cell(s) served by
the new primary cell.
Unless a default value is employed, the first information element of the new primary cell is
utilized to assign the CIF for the new primary cell.
In one embodiment of the present invention, a newly configured cell of the user equipment
20 is changed to a new primary cell, and the RRC layer message transmitted by the base station
10 and relating to primary cell change of the user equipment 20 includes: the first information of
the new primary cell to indicate the carrier identification of the new primary cell; and the second
information of the new primary cell to indicate the index(es) of the cell(s) served by the new
primary cell.
In a variation example where the CIF was assigned for the new primary cell previously, the
cell may reuse the previously assigned CIF and the first information in the above RRC layer
message may be empty.
In one embodiment of the present invention, the information element for each cell includes
a fourth information to indicate whether the first information of the corresponding cell is
mandatory or optional. Those skilled in the art can understand that the base station 10 may add
the fourth information to the aforementioned configuration message utilized to configure the
cells of the user equipment 20, the handover command for the handover of the user equipment
20, and the RRC layer message relating to primary cell change of the user equipment 20.
When the fourth information received by the user equipment 20 indicates that the
corresponding first information is mandatory, the user equipment 20 monitors the corresponding
first information on the PDCCH, and configures or updates the CIF value of the corresponding
cell according to the monitored first information.
When the fourth information received by the user equipment 20 indicates that the
corresponding first information is optional, the user equipment 20 may not monitor the first
information in the same downlink frame.
In one embodiment of the present invention, the CIF assignment is valid in all configured
cells. In other words, the CIF of each cell should be unique among all configured cells, and the
life period of the CIF is valid until the cell is released. The advantage of this option is that when
a downlink carrier component reconfiguration is scheduled, there is no need to assign other CIFs,
thereby corresponding RRC layer messages is reduced.
In another embodiment of the present invention, the CIF assignment is valid in the cells
scheduled by the same downlink carrier component. In other words, the CIF of each cell is
unique among the cells scheduled by the same downlink carrier component. The life period of
the CIF continues until the scheduling downlink carrier component is reconfigured. This means
that when a scheduling downlink carrier component of a cell is reconfigured, its CIF must be
reconfigured to avoid collision with other cells scheduled by the same downlink carrier
component.
Those skilled in the art can understand that the above embodiments are exemplary rather
than restrictive. Combination of the different technical features in the different embodiments can
be made to achieve an adventurous effect. Other variations to the disclosed embodiments can
be understood and implemented by those skilled in the art, from a study of the drawings,
the disclosure, and the appended claims. In the claims, any form of the word "comprise"
does not exclude other elements or steps; the indefinite article "a" or "an" does not
exclude a plurality; and the words "first" and "second" are utilized to identify a name and
not to mean any particular order. Any reference signs in the claims should not be
construed as limiting the scope. A single hardware or software module may fulfill the
functions of several items recited in the claims. The mere fact that certain technical
features are recited in mutually different dependent claims does not indicate that a
combination of these features cannot be made to achieve an adventurous effect.
Claims
1. A method, in a base station, of scheduling a carrier component for a user equipment,
comprising:
transmitting a configuration message to configure cells of the user equipment, wherein the
configuration message comprises respective first information for carrier identification of each
cell.
2. The method of claim 1, wherein the cells of the user equipment comprise a
cross-scheduling primary cell, and the configuration message comprises a second information of
the primary cell to indicate cell index(es) of secondary cell(s) that the primary cell is intended to
serve.
3. The method of claim 1, wherein the cells of the user equipment comprise a
cross-scheduling secondary cell, and the configuration message further comprises a third
information to indicate the cell index of a cell serving the secondary cell.
4. The method of claim 1, wherein the cells of the user equipment comprise a
cross-scheduling secondary cell, and the configuration message further comprises a second
information of the secondary cell to indicate cell index(es) of other secondary cell(s) that the
secondary cell is intended to serve.
5. The method of any of claims 1-4, wherein the configuration message further comprises
a fourth information to indicate whether the first information is mandatory or optional.
6. A method, in a base station, of scheduling a carrier component for a user equipment,
comprising:
transmitting a handover command for the handover of the user equipment, wherein the
handover command comprises an information element carrying first information of each cell, the
first information being utilized for carrier identification.
7. The method of claim 6, wherein the handover command comprises the first information
of a cross-scheduling cell, and the first information of remaining cross-scheduling cell(s) is
deducible according to the first information.
8. The method of claim 6 or 7, wherein the handover command comprises a fourth
information of each cell to indicate whether the first information of a corresponding cell is
mandatory or optional.
9. A method, in a base station, of scheduling a carrier component for a user equipment,
comprising:
transmitting a RRC layer message relating to primary cell change of the user equipment,
wherein the RRC layer message comprises:
a first information to indicate a carrier identification of a cell; and
at least one of a second information to indicate the index(es) of the cell(s) served by the
cell and a third information to indicate an index of a cell serving the cell.
10. The method of claim 9, wherein a cross-scheduling primary cell of the user equipment
is changed to a reconfigured secondary cell, and the RRC layer message comprises:
the first information to indicate the carrier identification of the reconfigured secondary
cell; and
at least one of the second information to indicate the index(es) of the cell(s) served by
the reconfigured secondary cell and the third information to indicate the index of the cell serving
the reconfigured secondary cell.
11. The method of claim 9, wherein a cross-scheduling secondary cell of the user
equipment is changed to a new primary cell, and the RRC layer message comprises:
the first information to indicate the carrier identification of the new primary cell; and
the second information to indicate the index(es) of the cell(s) served by the new primary
cell.
12. The method of claim 9, wherein a reconfigured cell of the user equipment is changed
to a new primary cell, and the RRC layer message comprises:
the first information to indicate the carrier identification of the new primary cell; and
the second information to indicate the index(es) of the cell(s) served by the new primary
cell.
13. The method of any of claims 9-12, wherein the RRC layer message further comprises a
fourth information of the cell to indicate whether the first information of the cell is mandatory or
optional.
14. The method of any of claims 1-13, wherein the first information of each cell is unique
among all configured cells, or among the cells scheduled by the same downlink carrier
component.