U.S. patent number RE44,198 [Application Number 13/560,777] was granted by the patent office on 2013-05-07 for method of providing point-to-multipoint service in mobile communication system.
This patent grant is currently assigned to LG Electronics Inc.. The grantee listed for this patent is Jong Hoe An, Ki Jun Kim, Sang Gook Kim, Young Jun Kim, Chan Ho Kyung, Seok Woo Lee, Li-Hsiang Sun, Shu Wang, Young Cheul Yoon, Young Woo Yun. Invention is credited to Jong Hoe An, Ki Jun Kim, Sang Gook Kim, Young Jun Kim, Chan Ho Kyung, Seok Woo Lee, Li-Hsiang Sun, Shu Wang, Young Cheul Yoon, Young Woo Yun.
United States Patent |
RE44,198 |
An , et al. |
May 7, 2013 |
Method of providing point-to-multipoint service in mobile
communication system
Abstract
A method of providing a point-to-multipoint service in a mobile
communication system and transmission controlling method thereof
are disclosed, by which a better quality of a point-to-multipoint
service can be provided in a manner of coping with time-variable
channel situation variable adaptively. In a mobile communication
system providing a point-to-multipoint service, the present
invention includes the steps of receiving data for the
point-to-multipoint service from a base station, measuring a
reception quality for the received point-to-multipoint service
data, and transmitting reception quality information for the
point-to-multipoint service data to the base station.
Inventors: |
An; Jong Hoe (Anyang-si,
KR), Lee; Seok Woo (Anyang-si, KR), Yun;
Young Woo (Anyang-si, KR), Kim; Ki Jun
(Anyang-si, KR), Kim; Young Jun (Anyang-si,
KR), Kyung; Chan Ho (Anyang-si, KR), Yoon;
Young Cheul (San Diego, CA), Kim; Sang Gook (San Diego,
CA), Sun; Li-Hsiang (San Diego, CA), Wang; Shu (San
Diego, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
An; Jong Hoe
Lee; Seok Woo
Yun; Young Woo
Kim; Ki Jun
Kim; Young Jun
Kyung; Chan Ho
Yoon; Young Cheul
Kim; Sang Gook
Sun; Li-Hsiang
Wang; Shu |
Anyang-si
Anyang-si
Anyang-si
Anyang-si
Anyang-si
Anyang-si
San Diego
San Diego
San Diego
San Diego |
N/A
N/A
N/A
N/A
N/A
N/A
CA
CA
CA
CA |
KR
KR
KR
KR
KR
KR
US
US
US
US |
|
|
Assignee: |
LG Electronics Inc. (Seoul,
KR)
|
Family
ID: |
37813459 |
Appl.
No.: |
13/560,777 |
Filed: |
June 26, 2006 |
PCT
Filed: |
June 26, 2006 |
PCT No.: |
PCT/KR2006/002464 |
371(c)(1),(2),(4) Date: |
January 07, 2010 |
PCT
Pub. No.: |
WO2006/137720 |
PCT
Pub. Date: |
December 28, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
60698722 |
Jul 12, 2005 |
|
|
|
Reissue of: |
11993874 |
Jan 7, 2010 |
8000257 |
Aug 16, 2011 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Jun 24, 2005 [KR] |
|
|
10-2005-0055001 |
Jul 13, 2005 [KR] |
|
|
10-2005-0063245 |
Aug 16, 2005 [KR] |
|
|
10-2005-0074612 |
Sep 15, 2005 [KR] |
|
|
10-2005-0086564 |
|
Current U.S.
Class: |
370/252; 455/69;
370/312 |
Current CPC
Class: |
H04L
1/0002 (20130101); H04L 1/0027 (20130101); H04W
76/40 (20180201); H04L 1/0026 (20130101); H04L
2001/0093 (20130101); H04W 4/06 (20130101); H04W
72/005 (20130101); H04L 1/203 (20130101); H04W
72/08 (20130101); H04L 12/189 (20130101); H04W
92/10 (20130101) |
Current International
Class: |
H04L
1/00 (20060101); H04H 20/71 (20080101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1143635 |
|
Oct 2001 |
|
EP |
|
1363467 |
|
Nov 2003 |
|
EP |
|
2002/368684 |
|
Dec 2002 |
|
JP |
|
10-2004-0041289 |
|
May 2004 |
|
KR |
|
10-2004-0093498 |
|
Nov 2004 |
|
KR |
|
10-2005-0062359 |
|
Jun 2005 |
|
KR |
|
Primary Examiner: Han; Clemence
Attorney, Agent or Firm: Lee, Hong, Degerman, Kang &
Waimey
Parent Case Text
.Iadd.CROSS-REFERENCE TO RELATED APPLICATIONS.Iaddend.
.Iadd.This application is a reissue of U.S. Pat. No. 8,000,257,
which issued on Aug. 16, 2011, from U.S. application Ser. No.
11/993,874, filed on Jan. 7, 2010, which is the National Stage
filing under 35 U.S.C. 371 of International Application No.
PCT/KR2006/002464, filed on Jun. 26, 2006, which claims the benefit
of earlier filing date and right of priority to Korean Application
Nos. 10-2005-0055001, filed on Jun. 24, 2005, 10-2005-0063245,
filed on Jul. 13, 2005, 10-2005-0074612, filed on Aug. 16, 2005,
and 10-2005-0086564, filed on Sep. 15, 2005, and also claims the
benefit of U.S. Provisional Application Ser. No. 60/698,722, filed
on Jul. 12, 2005..Iaddend.
Claims
The invention claimed is:
1. A method of controlling a point-to-multipoint service
transmission in a mobile communication system, the method
comprising: receiving point-to-multipoint service data from a base
station; receiving control information from the base station, the
control information associated with reception quality information
of the received point-to-multipoint service data; measuring a
reception quality of the received point-to-multipoint service data;
and transmitting the reception quality information for the
point-to-multipoint service data to the base station according to
the control information, wherein the control information includes
an indicator of at least one mobile station that transmits the
reception quality information, wherein the control information
further includes information for a reception quality information
transmission mode, wherein the reception quality information
transmission mode corresponds to at least a periodic mode or a
threshold mode, wherein the control information further includes a
transmission period of the reception quality information if the
reception quality information transmission mode corresponds to the
periodic mode; wherein the control information further includes
threshold information for the reception quality information
transmission if the reception quality information transmission mode
corresponds to the threshold mode; and wherein the control
information further includes the transmission period of the
reception quality information and the threshold information for the
reception quality information transmission if the reception quality
information transmission mode corresponds to the periodic mode and
the threshold mode.
2. The method of claim 1, wherein the control information includes
information for a transmission condition of the reception quality
information, the transmission condition being to stop transmitting
the reception quality information during performance of a
handoff.
3. The method of claim 1, wherein: the reception quality
information is transmitted when a packet error rate or a signal to
noise ratio (SNR) exceeds a threshold and the reception quality
information transmission mode corresponds to the threshold mode;
and the reception quality information is transmitted to the base
station according to the transmission period if the reception
quality information transmission mode corresponds to the periodic
mode.
4. The method of claim 1, wherein measuring the reception quality
comprises checking the reception quality during a reception quality
measuring interval according to information in the control
information for a reception quality measurement starting point and
a reception quality measurement ending point.
5. The method of claim 4, wherein: the reception quality
measurement starting point is a timing point that meets
(SystemTime-MeasureStartTime) mod N=0; the information for the
reception quality measurement starting point is MeasureStartTime;
and N is a reception quality information transmission period.
6. The method of claim 5, wherein: the reception quality
measurement ending point is a timing point that meets
(SystemTime-MeasureEndTime) mod N=0; and the information for the
reception quality measurement ending point is MeasureEndTime.
7. The method of claim 5, wherein: the reception quality
measurement ending point is a timing point that meets
{SystemTime-(MeasureStartTime+MeasureDuration)} mod N=0; and the
information for the reception quality measuring interval is
MeasureDuration.
8. The method of claim 7, wherein the reception quality information
is transmitted at a pseudorandom timing point after the reception
quality measurement ending point with the transmission period.
9. The method of claim 4, wherein a unicast packet is not received
during the reception quality measuring interval.
10. A method of providing a point-to-multipoint service in a mobile
communication system, the method comprising: transmitting
point-to-multipoint service data to a plurality of mobile stations;
transmitting control information to the plurality of mobile
stations, the control information associated with reception quality
information of the point-to-multipoint service data to; receiving
the reception quality information for the point-to-multipoint
service data, the reception quality information transmitted from at
least one of the plurality of mobile stations according to the
control information; and controlling a quality of the
point-to-multipoint service according to the reception quality
information, wherein the control information includes an indicator
of at least one mobile station that shall transmit the reception
quality information, wherein the control information further
includes information for a reception quality information
transmission mode, wherein the reception quality information
transmission mode corresponds to at least a periodic mode or a
threshold mode, wherein the control information further includes a
transmission period of the reception quality information if the
reception quality information transmission mode corresponds to the
periodic mode; wherein the control information further includes
threshold information for the reception quality information
transmission if the reception quality information transmission mode
corresponds to the threshold mode; and wherein the control
information further includes the transmission period of the
reception quality information and the threshold information for the
reception quality information transmission if the reception quality
information transmission mode corresponds to the periodic mode and
the threshold mode.
11. The method of claim 10, wherein the control information
includes information for a transmission condition of the reception
quality information.
12. The method of claim 10, wherein controlling the quality of the
point-to-multipoint service comprises adjusting a data rate of the
point-to-multipoint service data.
Description
FIELD OF INVENTION
The present invention relates to a mobile communication system, and
more particularly, to a method of providing a point-to-multipoint
service in a mobile communication system and transmission
controlling method thereof.
BACKGROUND ART
Generally, a point-to-multipoint service in a mobile communication
system means a service provided to a plurality of user equipments
by a network through a point-to-multipoint connection between the
network and a plurality of the user equipments. The
point-to-multipoint connection can be compared to a point-to-point
connection that means a connection between a network and a user
equipment or between a pair of user equipments.
Recently, many efforts have been made to provide various multimedia
services via a mobile communication system, which mainly relates to
a point-to-multipoint service via broadcasting or multicasting.
Various names are used as a point-to-multipoint service according
to an associated mobile communication system. In particular, a
multimedia broadcast/multicast service (MBMS), a
broadcast/multicast (BCMC) service, a multicast broadcast service
(MBS) and the like are sorts of the point-to-multipoint
services.
In the following description, the broadcast/multicast service as a
sort of the point-to-multipoint service is mainly explained. Yet,
the same idea or explanation is applicable to other sorts of
point-to-multipoint services.
First of all, in a mobile communication system supporting a
broadcast/muiticast (hereinafter abbreviated BCMC), multimedia data
including video as well as audio is transmitted at a high data rate
to mobile stations located within an area.
In order to provide a BCMC service, a packet data channel of a
physical layer is able to support a high data rate. In a current
mobile communication system, BCMC data are transmitted via packet
data channels of a previously existing physical layer.
In a BCMC service, broadcast contents created by a base station or
contents delivered from another base station are transmitted to a
plurality of mobile stations within a base station area. For the
contents transmission using the BCMC, a protocol is agreed in
advance between a base station and a mobile station.
BCMC data is transmitted via a packet data channel. Since BCMC uses
a method of transmitting data to a plurality of mobile stations
from one base station, there exists no individual feedback for a
reception quality from each of a plurality of the mobile
stations.
For instance, in case that there exists an error in a received
packet, a mobile station does not feed back such a signal as an
acknowledgement (hereinafter abbreviated ACK) and a negative
acknowledgement (hereinafter abbreviated NACK) to a base
station.
So, in order to enable all mobile stations within a base station
area to receive data with a quality exceeding a prescribed level, a
base station providing a BCMC service decides a transmission data
rate by considering a payload size, the number of subpackets for
hybrid automatic repeat request (hereinafter abbreviated HARQ), a
modulation scheme and the like.
Namely, since there is no feedback from a receiving side in a BCMC
service, a base station is unable to change a transmission data
rate according to a channel environment but transmits a packet at a
decided data rate to all mobile stations within a base station
area. So, each base station decides a data rate to have a packet
error rate (hereinafter abbreviated PER) equal to or lower than a
reference value for all mobile stations within its area and then
transmits a packet at the decided data rate.
For instance, by considering a fading environment, an interference
environment or a cell radius and the like, a base station having a
good channel environment overall provides a BCMC service at a high
data rate or a base station having a poor channel environment
overall provides a BCMC service at a low data rate.
However, as mentioned in the foregoing description, if a BCMC
service is performed after deciding a data rate for each base
station, it is unable to cope with channel quality degradation due
to a subsequent situation. Hence, a service quality can be
degraded.
DISCLOSURE OF INVENTION
Accordingly, the present invention is directed to a method of
providing a point-to-multipoint service in a mobile communication
system and transmission controlling method thereof that
substantially obviate one or more problems due to limitations and
disadvantages of the related art.
An object of the present invention is to provide a method of
providing a point-to-multipoint service in a mobile communication
system and transmission controlling method thereof, by which a
better quality of a point-to-multipoint service can be provided in
a manner of coping with time-variable channel situation
adaptively.
Another object of the present invention is to provide a method of
providing a point-to-multipoint service in a mobile communication
system and transmission controlling method thereof, by which
quality information for a point-to-multipoint service provided by a
network can be effectively fed back.
Additional advantages, objects, and features of the invention will
be set forth in part in the description which follows and in part
will become apparent to those having ordinary skill in the art upon
examination of the following or may be learned from practice of the
invention. The objectives and other advantages of the invention may
be realized and attained by the structure particularly pointed out
in the written description and claims hereof as well as the
appended drawings.
To achieve these objects and other advantages and in accordance
with the purpose of the invention, as embodied and broadly
described herein, in a mobile communication system providing a
point-to-multipoint service, a method of controlling a
point-to-multipoint service transmission according to the present
invention includes the steps of receiving data for the
point-to-multipoint service from a base station, measuring a
reception quality for the received point-to-multipoint service
data, and transmitting reception quality information for the
point-to-multipoint service data to the base station.
In another aspect of the present invention, in a mobile
communication system providing a point-to-multipoint service, a
method of controlling a point-to-multipoint service transmission
includes the steps of receiving data for the point-to-multipoint
service from a base station, receiving control information
associated with reception quality information of the
point-to-multipoint service data from the base station, measuring a
reception quality for the received point-to-multipoint service
data, and transmitting the reception quality information for the
point-to-multipoint service data to the base station according to
the control information.
In another aspect of the present invention, a method of providing a
point-to-multipoint service in a mobile communication system
includes the steps of transmitting data for the point-to-multipoint
service to a plurality of mobile stations, receiving reception
quality information for the point-to-multipoint service data from
at least one of the plurality of mobile stations, and controlling a
quality of the point-to-multipoint service according to the
reception quality information.
In another aspect of the present invention, a method of providing a
point-to-multipoint service in a mobile communication system
includes the steps of transmitting data for the point-to-multipoint
service to a plurality of mobile stations, transmitting control
information associated with reception quality information of the
point-to-multipoint service data, receiving the reception quality
information for the point-to-multipoint service data, wherein the
reception quality information is transmitted from at least one of
the plurality of mobile stations according to the control
information, and controlling a quality of the point-to-multipoint
service according to the reception quality information.
In a further aspect of the present invention, in a mobile
communication system providing a point-to-multipoint service, a
method of controlling a point-to-multipoint service transmission
includes the steps of receiving a plurality of data packets for the
point-to-multipoint service from a base station, checking whether a
reception error rate for the plurality of data packets exceed a
prescribed threshold, and transmitting reception acknowledgement
information for the plurality of data packets according to the
checking result.
It is to be understood that both the foregoing general description
and the following detailed description of the present invention are
exemplary and explanatory and are intended to provide further
explanation of the invention as claimed.
BRIEF DESCRIPTION OF DRAWINGS
The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and
constitute a part of this application, Illustrate embodiment(s) of
the invention and together with the description serve to explain
the principle of the invention. In the drawings:
FIG. 1 is a diagram for explaining a zone-based service according
to one embodiment of the present invention;
FIG. 2 is a diagram of a cell having a different channel
environment within one zone according to one embodiment of the
present invention;
FIG. 3 is a diagram of a cell having a channel environment
different from that of a cell design according to one embodiment of
the present invention;
FIG. 4 is a flowchart of a method of controlling a data rate using
feedback information in a BCMC service according to one embodiment
of the present invention;
FIG. 5 is a flowchart of a method of controlling a feedback
information transmission in a BCMC service according to one
embodiment of the present invention; and
FIG. 6 is a diagram of a feedback timing point of BCMC service
quality information according to one embodiment of the present
invention.
FIG. 7 is a diagram of a feedback timing point of BCMC service
quality information according to another embodiment of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Reference will now be made in detail to the preferred embodiments
of the present invention, examples of which are illustrated in the
accompanying drawings. Wherever possible, the same reference
numbers will be used throughout the drawings to refer to the same
or like parts.
First of all, embodiments of the present invention explained in the
following description relate to a broadcast/multicast (BCMC)
service as a sort of a point-to-multipoint service. Yet, it is
apparent to those skilled in the art that the technical features of
the present invention is applicable to other kinds of
point-to-muitipoint services such as a multimedia
broadcast/multicast service (MBMS), a multicast broadcast service
(MBS) and the like.
FIG. 1 is a diagram for explaining a zone-based service according
to one embodiment of the present invention.
Referring to FIG. 1, a BCMC service can be performed by a zone
unit. In particular, one unit zone is configured with a plurality
of cells and a different BCMC flow service is transmitted to each
zone.
In case of performing a BCMC service by a zone unit, since all base
stations belonging to each zone transmitting data of the same
contents at a same timing point, a mobile station receives signals
transmitted from a plurality of base stations located within a same
zone and obtains a diversity gain by combining and decoding the
received signals.
Yet, since a base station belonging to a different zone at the same
timing point transmits data of different contents, a signal
transmitted from the base station belonging to the different zone
plays a role as interference.
So, In case of providing a zone unit service, a mobile station
located in the vicinity of a center of a zone is able to obtain a
diversity gain using the same signals transmitted from a plurality
of base stations. So, a channel status is good. Yet, a mobile
station located at an edge of the zone has a poor channel status
attributed to interference signals transmitted from base stations
belonging to a different zone.
FIG. 2 is a diagram of a cell having a different channel
environment within one zone according to one embodiment of the
present invention.
Referring to FIG. 2, a mobile station, which exists in a cell
located at such a central part of a zone as a cell A, is able to
obtain a diversity gain by receiving the same packets transmitted
from neighbor base stations.
Yet, a mobile station, which exists in a cell located at such a
peripheral part of the zone as a cell B, may have a poor channel
status since different packets transmitted from cells belonging to
a different zone cause interference.
Meanwhile, a mobile station, which exists in a cell located at such
a central part of the zone as a cell C, may have a poor channel
status due to environmental characteristics of the cell itself such
as geography, buildings and the like.
So, in such a cell having a good channel status as the cell A, it
is able to transmit a packet at a high data rate. Yet, in such a
cell having a poor channel status as the cell B and the cell C,
redundant information (redundancy) is attached to overcome the poor
channel environment and this needs to be transmitted several times.
So, it is unable to avoid transmitting a packet at a low data
rate.
Hence, a data rate of a BCMC service transmitted by each base
station is decided based on a channel situation tested in an
initial cell design. Yet, a channel situation of each cell may
differ from that of the initial cell design. So, a service quality
is degraded unless a data rate of a specific cell fits a current
channel situation.
FIG. 3 is a diagram of a cell having a channel environment
different from that of a cell design according to one embodiment of
the present invention.
Referring to FIG. 3, in case of a base station having a good
channel environment such as a cell D in designing a cell, a high
data rate is selected. In case of a base station having a poor
channel environment such as a cell B and a cell C in designing a
cell, a low data rate is selected.
Despite the good channel environment of the cell D in an Initial
cell design, the channel environment varies due to a new building
construction, a geographical change and the like. In this case, a
mobile station within the cell D receives a low quality of a BCMC
service because a high data rate was selected while the channel
status becomes poor now.
On the contrary, when a low data rate was selected due to a bad
channel environment in an initial cell design and then the channel
environment becomes better, a mobile station also receives the BCMC
service of the low quality despite the goon channel
environment.
Yet, a base station is unable to know the variation of the channel
status, thereby keeping providing the low quality of the BCMC
service.
Hence, a mobile station transmits feedback information indicating a
channel status to a base station. The base station then needs to
perform a BCMC service using the feedback information.
FIG. 4 is a flowchart of a method of controlling a data rate using
feedback information in a BCMC service according to one embodiment
of the present invention.
Referring to FIG. 4, a base station transmits information for a
data rate of a current BCMC service flow via a broadcast overhead
message (S41).
When reception quality is not good while receiving a BCMC service,
a mobile station transmits feedback information for the BCMC
service to the base station via a route update message (S42). In
this case, the mobile station is able to transmit a PER for the
current BCMC service flow, a signal to noise ratio (hereinafter
abbreviated SNR) or an indication signal indicating that a current
reception quality is low and the like.
In particular, the feedback Information transmitted by the mobile
station can be transmitted periodically or at a specific timing
point. And, the specific timing point can be requested by the base
station. Thus, in case that the feedback information is
periodically transmitted, a transmission period is notified to the
mobile station by the base station via signaling or can be set in
the mobile station itself from the beginning. The fed-back
information is reception quality Information that includes
information indicating an extent of erroneous packets among
received packets (e.g., PER) and channel status Information (e.g.,
SNR).
Meanwhile, the feedback information transmission period can be
varied according to a channel status. For instance, a transmission
period is elongated in case of a good channel status or shortened
in case of a poor channel status. So, a feedback information
transmission frequency is lowered in case of the good channel
status. And, the feedback information is more frequently
transmitted in case of the poor channel status.
Moreover, a condition for a feedback information transmission for a
BCMC service can be given. For instance, if a PER is equal to or
greater than a threshold or SNR is reduced equal to or lower than a
threshold, or if a number of packets decided as a reception error
as a result of reception increases equal to or greater than a
threshold, the feedback information can be transmitted.
As a detailed embodiment of the feedback information transmitted by
a mobile station to a base station, an On-Off Keying (OOK) scheme
can be taken Into consideration whereby `On` is for NACK and `Off`
is for ACK.
In particular, if a mobile station is able to decode a BCMC packet
received from a base station without error, `Off` (no signal) is
transmitted to mean an affirmative reception response (ACK) via the
ACK channel. In case that error occurs in the BCMC packet
reception, `On` is transmitted to mean a negative reception
response (NACK) via the ACK channel. Since the errorless case will
occur less frequently than the erroneous case, this method is able
to minimize interference and to save battery power of the mobile
station.
As a modified example of the ACK/NACK transmission method using the
OOK scheme, Instead of transmitting `ACK` or `NACK` for each BCMC
packet, `NACK` is transmitted if a rate of packets having reception
errors for BCMC packets received for a predetermined time or N
consecutively received BCMC packets exceeds a prescribed threshold.
Otherwise, `ACK` can be transmitted. For example, if the rate of
packets having reception errors for BCMC packets received for one
minute exceeds 1%, `NACK` can be transmitted.
As a similar embodiment, `ACK` or `NACK` can be transmitted with
reference to RS (Reed-Solomon) outer code blocks amounting to a
predetermined number (M). For example, if an average number of RS
block errors exceed 1%, `NACK` is transmitted. Otherwise, `ACK` is
transmitted.
In the above-explained embodiments, it is preferable that an offset
value on a time axis is assigned to each mobile station. In
transmitting the feedback information via the ACK channel. In case
that a plenty of mobile stations transmit feedback information at
the same time, self-interference or transmission failure is brought
about to interrupt another user's transmission.
FIG. 5 is a flowchart of a method of controlling a feedback
information transmission in a BCMC service according to one
embodiment of the present invention.
Referring to FIG. 5, a base station transmits a broadcast overhead
message. In this case, the broadcast overhead message includes
control Information associated with a feedback information
transmission. In particular, the broadcast overhead message
includes at least one of FeedbackTHEnable field, FeedbackPRDEnable
field, FeedbackTH field and FeedbackPRD field.
The FeedbackTHEnable field is a field that indicates whether
feedback information will be transmitted according to a threshold
mode. The FeedbackPRDEnable field is a field that indicates whether
feedback information will be transmitted according to a periodic
mode. The FeedbackTH field is a field that indicates a threshold in
a feedback information transmission according to the threshold
mode. And, the FeedbackPRD field is a field that indicates a
transmission period in the periodic mode.
The feedback information transmitting method according to the
threshold mode and the periodic feedback information transmitting
method according to the periodic mode can be independently set.
Meanwhile, a mobile station posses a pair of counters named
TotalPkt and ErrorPkt. The TotalPkt is the counter indicating a
total number of received packets. The TotalPkt is incremented by 1
each time a packet is received. And, the ErrorPkt is the counter
indicating a total number of packets failing in decoding. The
ErrorPkt is incremented by 1 each time a received packet decoding
falls.
Each of the counters TotalPkt and ErrorPkt is Initialized into 0.
An elapse of a specific time can be known through a count of the
counter TotalPkt. And, a PER can be calculated through a ratio
between the counters TotalPkt and ErrorPkt.
The mobile station transmits feedback information using the
information received via the broadcast overhead message in case
that FeedbackTHEnable is `1` (i.e., a case that feedback
Information is transmitted according to a threshold mode) and that
a value of the counter ErrorPkt becomes FeedbackTH (i.e., a case
that decoding falls over a specific threshold) or in case that
Feedback PRDEnable is `1 (i.e., a case that feedback information is
periodically transmitted according to a periodic mode) and that a
value of the counter TotalPkt becomes FeedbackPRD (i.e., a case of
a preset period).
The feedback information can be transmitted in a manner of
separately configuring a BCMC quality report message for a BCMC
service quality feedback.
Meanwhile, the feedback information can be transmitted by being
included in a route update message.
A procedure for deciding whether the value of the counter ErrorPkt
is identical to the FeedbackTH and a procedure for deciding whether
the value of the counter TotalPkt is identical to the FeedbackPRD
can be independently performed. Hence, one of the two cases is
selectively performed or both of the two cases can be performed
together.
The BCMC quality report message and the route update message can
have PER and SNR (or SIR) information as an example of feedback
information. In this case, the PER can be obtained by calculating
the Errorpkt/Totalpkt.
After the BCMC quality report message or the route update message
has been transmitted, each of the counters Totalpkt and ErrorPkt is
reset to zero.
If both values of FeedbackTHEnable and FeedbackPRDEnable received
via the broadcast overhead message are zero, the feedback
information transmission is not performed.
A base station is able to transmit control information for a BCMC
service quality Information feedback via a broadcast overhead
message. For instance, the base station is able to transmit the
control information using QualityReportMode and QualityReportCount
fields included in the overhead message.
Table 1 shows an example of information transmitted via
QualityReportMode field.
TABLE-US-00001 TABLE 1 Value Quality Report Mode 00 Quality report
is disabled 01 Quality report is enabled for all mobile stations
receiving broadcast content 10 Quality report is enabled for only
mobile station that is to receive broadcast content and is in bad
condition 11 Reserved
QualityReportMode field has information indicating which mobile
station will feed back BCMC service quality information to a base
station.
Referring to Table 1, if a base station conducts a transmission by
setting a QualityReportMode field value to `00`, a mobile station
having received this does not feed back the BCMC service quality
information to the base station.
if a base station conducts a transmission by setting a
QualityReportMode field value to `01`, all mobile stations
receiving a BCMC service feed back the BCMC service quality
information to the base station.
If a base station conducts a transmission by setting a
QualityReportMode field value to `10`, mobile stations having poor
BCMC service reception qualities feed back the BCMC service quality
information to the base station only.
For instance, mobile stations having PER over 1% feed back BCMC
service quality information to a base station. In this case, the
mobile station is able to periodically feed back the service
quality information to the base station.
Table 2 shows an example of information transmitted via
QualityReportCount field. The QualityReportCount field has
information for a feedback period.
TABLE-US-00002 TABLE 2 QualityReportCount QualityReportPeriod
(slots) `000` 2.sup.15 `001` 2.sup.16 `010` 2.sup.17 `011` 2.sup.18
`100` 2.sup.19 `101` 2.sup.20 `110` to `111` Reserved
Referring to Table 2, a feedback period is decided according to a
QualityReportCount value.
For instance, if a base station sets a QualityReportCount field
value to `101`, BCMC service quality information is fed back to the
base station by a period of 2.sup.20 slots. In particular, since
the feedback period is decided into QualityReportPeriodX1.66 ms,
the BCMC service quality information is fed back by a period of 29
minutes in case that the QualityReportCount field value is
`101`.
FIG. 6 is a diagram of a feedback timing point of BCMC service
quality information according to one embodiment of the present
invention.
Referring to FIG. 6, a first mobile station, a second mobile
station and a third mobile station receive a broadcast overhead
message at a same timing point.
Meanwhile, a mobile station has a timer named
BCMCSQualityReportTimer that operates by a predetermined time unit.
In the present embodiment, the timer operates by 1.66.. ms unit for
example.
An initial value of the BCMCSQualityReportTimer is set to a
pseudorandom value between zero and QualityReportPeriod*1.66.. ms.
Namely, the Initial value is set to a random value smaller than a
feedback period.
So, each of the mobile stations feeds back BCMC service quality
Information to a base station at a random timing point within the
feedback period from a timing point of receiving the broadcast
overhead message. In particular, the corresponding mobile station
periodically feeds back the BCMC service quality information with
reference to an initial feedback timing point.
Hence, the feedback information transmitting timing points of the
mobile stations are not mutually matched, whereby a reverse link
load according to the feedbacks of a plurality of the mobile
stations can be prevented from increasing.
A mobile station has a counter to calculate a PER. For instance, a
pair of counters named TotalPackets and ErrorPackets are explained
as follows.
First of all, the TotalPackets is the counter indicating a total
number of received packets. The TotalPackets is incremented each
time a packet is received.
The ErrorPackets is the counter indicating a total number of
packets failing in being decoded. The ErrorPackets is incremented
by 1 each time a decoding of the received packet fails.
Hence, the PER can be calculated through a ratio between the
ErrorPackets and the TotalPackets. And, each of the counters,
ErrorPackets and TotalPackets, are Initially set to zero.
A mobile station calculates a timer expiry value
QualityReportTimerMax according to Formula 1 and then stores the
calculated value.
QualityReportTimerMax=QualityReportPeriod.times.1.66..ms [Formula
1]
If a BCMCSQualityReportTimer value becomes Identical to the timer
expiry value QualityReportTimerMax, a mobile station feeds back
BCMC service quality information to a base station via
BCMCSQualityReport message. As the feedback information transmitted
through the BCMCSQualityReport, at least one of PER and SNR can be
used.
Table 3 shows an example of BCMCSQualityReport message.
TABLE-US-00003 TABLE 3 Field Length (bits) MessageID 8
ChannelQuality 5 BCMCSFlowFormat 1 BCMCSFlowIDLength 2 zero or one
occurrence of the following record: BCMCSFlowCount 6 BCMCSFlowCount
occurrence of the following three fields: BCMCSFlowID
(BCMCSFlowIDLength + 1) * 8 TotalPackets 20 ErrorPackets 10 zero or
one occurrence of the following record: ProgramCount 6 ProgramCount
occurrences of the remaining fields (expect Reserved field):
ProgramIDLSBLength 5 ProgramIDLSBs ProgramIDLSBLength
FlowDiscriminatorCount 6 FlowDiscriminatorLength 0 or 3
TotalPackets 20 ErrorPackets 10 FlowDiscriminateorCount occurrence
of the following three fields: FlowDiscriminator
FlowDiscriminatorLength TotalPackets 20 ErrorPackets 10 Reserved
0-7 (as needed)
In Table 3, MessageID field is an identifier indicating a type of
the present message and can be set to `0.times.05` for example.
ChannelQuality field is a field indicating channel status
information and can be represented as a signal to noise ratio (SNR)
using pilot signals of a base station. If a BCMC Flow Identifier
included in the message shown in Table 3 is specified to a Program
IdentifierFlowDiscriminator format, BCMCSFlowFormat field is set to
`1`. Otherwise, It is set to `0`.
Meanwhile, BCMCSFlowIDLength field is set to a value of
BCMCFlowLwngth received via a broadcast overhead message.
BCMClowCount field is omitted if BCMCSFlowFormat field has a value
of `1`. Otherwise, it is set to the number of BCMCS flow
Identifiers. BCMCSFlowID field indicates a BCMC flow identifier.
The BCMCSFlowID field is omitted if BCMCSFlowFormat field has a
value of `1`. TotalPackets field means the number of packets
received during a reception quality measuring interval. The
TotalPackets field is omitted if BCMCSFlowFormat field has a value
of 1'.
ErrorPackets field indicates the number of erroneous packets among
the packets received for the reception quality measuring interval.
The ErrorPackets field is omitted if BCMCSFlowField has a value of
`1`. ProgramIDLSBLength field is set to the number of LSB (least
significant bits) of ProgramID included in the present message. The
ProgramIDLSBLength field is omitted if BCMCSFlowFormat field has a
value of `1`. ProgramIDLSBs field is set to ProgramIDLSBLength LSB
(least significant bits) of ProgramID.
FlowDiscriminatorCount field means the number of flow
discriminators associated with a program to be registered by a
mobile station. The FlowDiscriminatorCount field is omitted if
BCMCSFlowFormat field has a value of FlowDiscriminatorLength field
represents a length of a flow discriminator. The
FlowDiscriminatorLength field is omitted if BCMCSFlowFormat field
has a value of `0` or if FlowDiscriminatorCount field has a value
of `000000`. FlowDiscriminator field indicates a flow
discriminator. The Flow Discriminator field is omitted if
BCMCSFlowFormat field has a value of `0`.
As shown in Table 3, one general information for a channel status
such as SIR is transmitted. Yet, TotalPackets information and
ErrorPackets information used in indicating PER corresponding to
each BCMCS flow are transmitted as many as the number of BCMCS
flows. After the SCMCSQualityReport message has been transmitted,
the BCMCSQualityReportTimer timer, TotalPackets counter and
ErrorPackets counter are reset to zero.
Meanwhile, a base station transmits a broadcast overhead message
including fields associated with the feedback information
transmission. For example, QialityReportMode field,
MeasureStartTime field and MeasureEndTime field can be used as the
fields representing the feedback associated information.
Referring to Table 1, if QualityReportMode field is set to `00`, it
means that a mobile station needs not to transmit the feedback for
a BCMC service. If QualityReportMode field is set to `01`, it means
that all mobile stations receiving the BCMC service need to
periodically transmit the feedback. If QualityReportMode field is
set to `10`, it means that prescribed mobile stations in poor
channel status (e.g., PER is over 1%) among a plurality of mobile
stations receiving the BCMC service need to transmit the feedback
information.
MeasureStartTime field and MeasureEndTime field have information
for an interval for measuring PER. MeasureStartTime is used In
deciding a starting point of a PER measurement. And, the starting
point of the PER measurement is decided as a timing point that
meets Formula 2 for example. (SystemTime-MeasureStartTime)mod N=0
[Formula 2]
In Formula 2, a unit of SystemTime or MeasureStartTime is slot
(1.66..ms) and `N` means a period for transmitting
BCMCSQualityReport to a base station.
MeasureEndTime is used in deciding an ending point of a PER
measurement. And, the ending point of the PER measurement is
decided as a timing point that meets Formula 3 for example.
(SystemTime-MeasureEndTime)mod N=0 [Formula 3]
In Formula 3, a unit of SystemTime or MeasureEndTime is slot
(1.66..ms) and `N` means a period for transmitting
BCMCSQualityReport to a base station.
In Formula 2 and Formula 3, a base station is able to decide and
transmit a value of N to a mobile station. Alternatively, a value
preset between a base station and a mobile station can be used as a
value of N. Preferably, the preset value is 218 slots (7.28
minutes). Thus, a mobile station measures PER from one timing point
meeting Formula 2 and to the other timing point meeting Formula
3.
So, a base station is able to accurately know the interval for
which a mobile station measures PER to recognize a distribution of
broadcast packets and unicast packets for the corresponding
measurement interval. Hence, the base station is able to compensate
inaccuracy of feedback information from the mobile station due to
the unicast packets.
Besides, in order to solve a problem caused by the mixed existence
of the broadcast and unicast packets, the base station is able to
restrict the broadcast packets to be transmitted only for a
specific interval for the generation of the feedback
information.
A base station may use MeasureStartTime and MeasureDuration fields
to transmit PER measurement interval information. In particular,
the base station uses MeasureStartTime to indicate a starting point
of measuring PER and MeasureDuration to indicate an interval for
measuring PER from the starting point. In this case, the starting
point of measuring PER is decided using Formula 2 and an ending
point of the PER measurement can be decided using Formula 4.
{SystemTime-(MeasureStartTime+MeasureDuration)} mod N=0 [Formula
4]
The PER measurement is executed until a timing point that
SystemTime meets Formula 4. In Formula 4, a unit of SystemTime,
MeasureStartTime or MeasureDuration is slot (1.66..ms) and `N`
means a period for transmitting BCMCSQualityReport to a base
station.
In Formula 4, a base station is able to decide and transmit a value
of N to a mobile station. Alternatively, a value preset between a
base station and a mobile station can be used as a value of N.
Preferably, the preset value is 218 slots (7.28 minutes). Thus, a
mobile station measures PER from one timing point meeting Formula 2
and to the other timing point meeting Formula 4.
A base station has a timer named BCMCSQualityReportTimer that
operated by a unit of slot (1.66..ms). The timer is set to a
pseudorandom value between 0 and
{N-(MeasureEndTime-MeasureStartTime)-1) mod N}.times.1.66..ms. The
timer is decreased by slot unit (1.66..ms). And, BCMCSQualityReport
message is transmitted at a timing point at which the timer becomes
zero. By enabling the timer set value to have a pseudorandom value,
it is able to prevent excessive loads from being given to a base
station if mobile stations transmit feedback Information
simultaneously.
FIG. 7 is a diagram of a feedback timing point of BCMC service
quality information according to another embodiment of the present
invention.
Referring to FIG. 7, a first mobile station (1.sup.st MS) measures
PER according to Formula 2 and Formula 3 and then transmits
BCMCSQuaityReport message according to the BCMCSQualityReportTimer
timer. A second mobile station (2.sup.nd MSS) measures PER
according to Formula 2 and Formula 3 and then transmits
BCMCSQualityReport message according to the BCMCSQualityReportTimer
timer. However, since the first and second mobile stations have
pseudorandom values as BCMCSQualityReportTimer set values,
respectively, they transmit the BCMCSQualityReport messages at
different timing points, respectively.
A mobile station sets a status indicator value and is then able to
perform the operation shown in FIG. 7 using the status indicator
value. For instance, a first status indicator
(RqualityReportEnabled), a second status indicator
(RqualityReportTimerEnabled) and a third status Indicator
(RqualityMeasureEnabled) can be used. The first status indicator
(RqualityReportEnabled) is set to `NO` only if a value of
QualityReportMode field is `00`. Otherwise, the first status
Indicator (RqualityReportEnabled) is set to `YES`.
If the first status indicator (RqualityReportEnabled) is `YES`, the
third status indicator (RqualityMeasureEnabled) is set to `YES`
each time. Formula 2 is met. If the first status indicator
(RqualityReportEnabled) is `YES`, the third status indicator
(RqualityMeasureEnabled) is set to `NO` each time Formula 3 or
Formula 4 is met. Meanwhile, if the first status indicator
(RqualityReportEnabled) is `NO`, the third status indicator
(RqualityMeasureEnabled) is set to `NO`.
If a value of the third status indicator (RqualityMeasureEnabled)
is changed into `NO` from `YES`, the second status indicator
(RqualityReportTimerEnabled) is set to `YES`. If BCMCSQuaiityReport
message is transmitted, the second status indicator
(RqualityReportTimerEnabled) is set to `NO`.
A mobile station is able to transmit feedback information if the
first status indicator (RqualityReportEnabled) is set to `YES`. A
mobile station is able to measure feedback information for an
interval during which the third status indicator
(RqualityMeasureEnabled) is set to `YES`. And, a mobile station
activates QualityReportTimer if the second status indicator
(RqualityReportTimerEnabled) is set to `YES`.
In case of transmitting the feedback information on an access
channel, the mobile station decides that the feedback is successful
if receiving transmission success information
(TransmissionSuccessful indication). In case of transmitting the
feedback information on a reverse traffic channel, the mobile
station decides that the feedback is successful by transmitting
BCMCSQuaiityReport message.
Meanwhile, in transmitting feedback information, a mobile station
is able to transmit its position Information as well as PER and
SNR. If a base station obtains the position information of the
mobile station as well as PER or SNR, the base station is able to
recognize an area having a poor channel situation. Hence, necessary
management can be provided to such an area.
Besides, if a predetermined condition is met for a mobile
communication terminal, it is able to stop the feedback information
transmission. For Instance, if a mobile station, which measures PER
and SNR and transmits feedback information, performs a handoff into
another cell area, a base station may be confused in understanding
whether the received feedback information it the information
corresponding to an old base station or a current serving base
station. So, in such a case, it is able to make the mobile station
stop the feedback information transmission.
As explained in the foregoing description, a base station having
received feedback information from a mobile station performs a BCMC
service transmission based on the received feedback
information.
In particular, according to the received feedback information, in
case that a channel status is not good, a transmission is performed
by lowering a data rate. If the channel status becomes better, the
transmission can be performed by raising the data rate. In the
example shown in FIG. 3, in case that a channel status is degraded
like the cell D, mobile stations within the cell transmit feedback
information. A base station controls reception quality of the BCMC
service based on the feedback information. The reception quality of
the BCMC service can be controlled by changing a transmission
format with which the BCMC service data is transmitted. The
transmission format means a combination of at least two
transmission parameters (e.g. a number of data bits included in a
frame, a modulation scheme, a channel coding rate, or a channel
coding scheme) with which the base station transmits the BCMC
service data to the mobile stations.
For example, if the number of mobile stations transmitting the
feedback information, which indicates that the channel status
becomes good, exceeds a first threshold, the data rate and the
coding rate can be raised. If the number of mobile stations
transmitting the feedback information, which indicates that the
channel status becomes poor, exceeds a second threshold, the data
rate and the coding rate can be lowered. Moreover, the data rate
can be raised only if the feedback information indicating that the
channel statuses of the entire mobile stations become good is
received. And, the data rate can be lowered only if the feedback
Information indicating that the channel statuses of the entire
mobile stations become poor is received.
Thus, in case that a base station decides a new data rate using
feedback information, the base station transmits the decided data
rate information to mobile stations within a cell via a broadcast
overhead message and then performs a BCMC service according to the
decided data rate.
Meanwhile, in aspect of a service provider, a smooth service can be
performed on an area, of which channel situation is decided poor
according to feedback information, by redesigning a cell or
installing a repeater additionally. And, the feedback information
can be used as a database for customer management. So, the customer
management can be enhanced in a manner of recognizing a user
failing to receive the BCMC service correctly using the feedback
information.
It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the spirit or scope of the inventions. Thus,
it is intended that the present invention covers the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
INDUSTRIAL APPLICABILITY
The present invention is applicable to a wireless communication
system such as a mobile communication system, a broadband wireless
access system, or a mobile internet system, etc.
* * * * *