U.S. patent application number 11/083845 was filed with the patent office on 2005-12-01 for method and system for transmitting reverse data in a mobile communication system.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Bae, Beom-Sik, Han, Jin-Kyu, Jung, Jung-Soo, Kim, Dong-Hee, Kim, Youn-Sun, Kwon, Hwan-Joon.
Application Number | 20050265236 11/083845 |
Document ID | / |
Family ID | 34975948 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050265236 |
Kind Code |
A1 |
Kwon, Hwan-Joon ; et
al. |
December 1, 2005 |
Method and system for transmitting reverse data in a mobile
communication system
Abstract
Disclosed is a method for controlling a reverse data rate by a
mobile station in a mobile communication system supporting
high-rate packet data transmission. The method includes receiving
average loading information (FRAB) from a particular base station
when the mobile station attempts an initial access to the base
station; setting the received average loading information as
average loading information for the base station; and upon
receiving reverse activity information (RAB) from the base station,
controlling a rate of reverse data using the received reverse
activity information and the set average loading information.
Inventors: |
Kwon, Hwan-Joon;
(Hwaseong-gun, KR) ; Kim, Youn-Sun; (Scangnam-si,
KR) ; Han, Jin-Kyu; (Suwon-si, KR) ; Kim,
Dong-Hee; (Seoul, KR) ; Jung, Jung-Soo;
(Seoul, KR) ; Bae, Beom-Sik; (Suwon-si,
KR) |
Correspondence
Address: |
DILWORTH & BARRESE, LLP
333 EARLE OVINGTON BLVD.
UNIONDALE
NY
11553
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
34975948 |
Appl. No.: |
11/083845 |
Filed: |
March 18, 2005 |
Current U.S.
Class: |
370/235 |
Current CPC
Class: |
H04L 1/0002 20130101;
H04W 36/18 20130101; H04W 28/22 20130101; H04L 1/0026 20130101 |
Class at
Publication: |
370/235 |
International
Class: |
H04L 012/26 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2004 |
KR |
18587/2004 |
Claims
What is claimed is:
1. A method for controlling a reverse data rate by a mobile station
in a mobile communication system supporting high-rate data
transmission, the method comprising: receiving average loading
information (FRAB) from a particular base station when the mobile
station attempts an initial access to the base station; setting the
received average loading information as average loading information
for the base station; and upon receiving reverse activity
information (RAB) from the base station, controlling a rate of
reverse data using the received reverse activity information and
the set average loading information.
2. The method of claim 1, further comprising upon receiving the
reverse activity information from the base station, updating the
average loading information.
3. The method of claim 1, wherein the average loading information
indicates long term sector loading.
4. The method of claim 1, wherein the average loading information
is real number between +1 and -1.
5. The method of claim 1, further comprising: receiving reverse
activity information from respective base stations in an active
set; and storing the average loading information for the respective
base stations in the active set using the reverse activity
information received from the respective base stations.
6. The method of claim 5, further comprising, upon occurrence of a
need for handoff to one of the base stations in the active set,
setting a maximum value among the average loading information for
the respective base stations in the active set as average loading
information for a target base station to which the mobile station
will perform handoff.
7. A method for controlling a reverse data rate upon handoff during
reverse communication in a mobile communication system supporting
high-rate packet data transmission, the method comprising: upon
occurrence of a need for handoff to a target base station, setting,
by a mobile station, average loading information having a maximum
value among average loading information provided for at least one
base stations in an active set, as average loading information for
the target base station; and upon receiving reverse activity
information from the base station, controlling, by a mobile
station, the reverse data rate using the received reverse activity
information and the set average loading information.
8. The method of claim 7, further comprising, upon receiving the
reverse activity information from the base station, updating the
average loading information.
9. The method of claim 7, wherein the average loading information
indicates long term sector loading.
10. The method of claim 7, wherein the average loading information
is real number between +1 and -1.
11. The method of claim 7, wherein the average loading information
is Filtered Reverse Activity Bit (FRAB).
12. A method for providing rate control information for reverse
packet data to an initially accessed mobile station by a base
station in a mobile communication system supporting high-rate
packet data transmission, the method comprising: generating average
loading information (FRAB) to be transmitted to the mobile station
into a predetermined message; and transmitting the generated
message through a predetermined forward channel.
13. The method of claim 12, wherein the average loading information
is a value generated from reverse activity information transmitted
by the base station for a predetermined time.
14. The method of claim 12, wherein the predetermined forward
channel is a signaling channel.
15. An apparatus for providing rate control information for reverse
packet data to an initially accessed mobile station by a base
station in a mobile communication system supporting high-rate
packet data transmission; wherein the base station generates
average loading information to be transmitted to the mobile station
into a predetermined message and transmits the generated message
through a predetermined forward channel.
16. The apparatus of claim 15, wherein the average loading
information is a value generated from reverse activity information
transmitted by the base station for a predetermined time.
17. A mobile station apparatus for controlling a reverse data rate
in a mobile communication system supporting high-rate packet data
transmission; wherein when the mobile station attempts an initial
access to a predetermined base station, the mobile station receives
average loading information (FRAB) from the base station, sets the
received average loading information as average loading information
for the base station, and upon receiving reverse activity
information (RAB) from the base station, controlling a reverse data
rate using the received reverse activity information and the set
average loading information.
18. The mobile station apparatus of claim 17, wherein upon
receiving the reverse activity information from the base station,
the mobile station updates the average loading information.
19. The mobile station apparatus of claim 17, wherein the average
loading information is received from the base station through a
signaling channel.
20. The mobile station apparatus of claim 17, wherein the mobile
station receives reverse activity information from respective base
stations in an active set, and stores average loading information
for the respective base stations using the reverse activity
information received from the respective base stations in the
active set.
21. The mobile station apparatus of claim 20, wherein upon
occurrence of a need for handoff to one of base stations in the
active set, the mobile station sets a maximum value among the
average loading information for the base stations in the active
set, as average loading information for a target base station to
which the mobile station will perform handoff.
22. A mobile station apparatus for controlling a reverse data rate
upon handoff by the mobile station in reverse communication in a
mobile communication system supporting high-rate packet data
communication; wherein upon occurrence of a need for handoff to a
target base station, the mobile station sets average loading
information having a maximum value among average loading
information provided for at least one base stations in an active
set, as average loading information for the target base station,
and upon receiving reverse activity information from the target
base station, determines the reverse data rate using the received
reverse activity information and the set average loading
information.
23. The mobile station apparatus of claim 22, wherein upon
receiving reverse activity information from the base station, the
mobile station updates the average loading information.
24. The apparatus of claim 22, wherein the average loading
information indicates long term sector loading.
25. The apparatus of claim 22, wherein the average loading
information is real number between +1 and -1.
26. The apparatus of claim 22, wherein the average loading
information is Filtered Reverse Activity Bit(FRAB).
27. A mobile station apparatus for determining a reverse data rate
upon handoff in a mobile communication system supporting high-rate
packet data communication; a receiver for receiving reverse
activity information from a target base station; and a controller
for setting average loading information having a maximum value
among average loading information provided for at least one base
stations in an active set, as average loading information for the
target base station and determining the reverse data rate using the
received reverse activity information and the set average loading
information upon occurrence of a need for handoff to a target base
station.
28. A mobile station apparatus for controlling a reverse data rate
upon handoff by the mobile station in a mobile communication system
supporting high-rate packet data communication comprising: a
controller; and a memory having a program stored thereon to direct
the controller; wherein upon occurrence of a need for handoff to
one of base stations in an active set, the mobile station
controller sets average loading information having a maximum value
among average loading information provided for the respective base
stations in the active set, as average loading information for a
target base station to which the mobile station will perform
handoff, and upon receiving reverse activity information from the
target base station, determines a reverse data rate using the
received reverse activity information and the set average loading
information.
29. A mobile station apparatus for controlling a data rate in a
mobile communication system supporting high-rate packet data
transmission comprising: a controller; and a memory having a
program stored thereon to direct the controller to: receive average
loading information (FRAB) from the base station, set the received
average loading information as average loading information for the
base station, and, upon receiving reverse activity information
(RAB) from the base station, controlling a rate of reverse data
using the received reverse activity information and the set average
loading information.
Description
PRIORITY
[0001] This application claims priority under 35 U.S.C. .sctn. 119
to an application entitled "Method and System for Transmitting
Reverse Data in a Mobile Communication System" filed in the Korean
Intellectual Property Office on Mar. 18, 2004 and assigned Serial
No. 2004-18587, the contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a method and
system for transmitting data in a mobile communication system, and
in particular, to a method and system for controlling a rate of
data transmitted in a reverse direction.
[0004] 2. Description of the Related Art
[0005] Generally, 2.sup.nd generation (2G) Code Division Multiple
Access (CDMA) mobile communication systems provide voice service
with low-speed data service through a traffic channel in forward
and reverse directions. With the rapid progress of wireless
technology, increased amounts of data need to be transmitted at
high speeds to provide users with multimedia content and Internet
access in addition to simple voice service. To meet user demand,
mobile communication systems are developing into advanced systems
capable of providing both high-speed data service and
voice-oriented service.
[0006] The 3.sup.rd generation (3G) mobile communication system
aims at providing high-speed service with a special focus on
data-oriented multimedia service.
[0007] For example, a 1.times. Evolution-Data Only (EV-DO)
standard, also known as High Data Rate (HDR), has been established
by 3.sup.rd Generation Partnership Project 2 (3GPP2) which is a
standardization camp for a synchronous system with the intent to
provide a CDMA2000 1.times. data service. During forward
transmission, a 1.times. EV-DO system transmits packet data to a
particular mobile station only. Therefore, the 1.times. EV-DO
system can transmit packet data to the particular mobile station
with maximum power at high speed.
[0008] A description will now be made of the 1.times. EV-DO system.
For a forward link of the 1.times. EV-DO system, an access network
(AN) or a base station (BS) serves as a transmitter while an access
terminal (AT) or a mobile station (MS) serves as a receiver. A
physical layer of the 1.times. EV-DO system adopting a link
adaptation scheme adaptively uses various modulation schemes such
as Quadrature Phase Shift Keying (QPSK), 8-ary Phase Shift Keying
(8PSK) and 16-ary Quadrature Amplitude Modulation (16QAM), with
various data rates according to a channel environment. In addition,
the 1.times. EV-DO system supports multimedia service using the
same frequency band, and in the system, a plurality of mobile
stations can simultaneously transmit data to a base station. In
this case, identification of the mobile stations is achieved
through spreading codes uniquely allocated to the mobile
stations.
[0009] In the 1.times. EV-DO system, data transmission in a reverse
direction from a mobile station to a base station is achieved
through a reverse packet data channel (R-PDCH) per physical layer
packet (PLP), with a fixed packet length. The data rate for each
packet is variable, and is based on the power of the receiving
mobile station to which a corresponding packet is transmitted, the
total amount of data to be transmitted to the mobile station, and
information provided from a base station.
[0010] While a mobile station attempts to change its connection
from a current base station (or serving base station) to a new base
station (or target base station) to perform handoff or to set up
initial communication, the mobile station cannot receive rate
control information from the target base station because the
connection to the target base station is not established.
Therefore, the mobile station has difficulty in efficiently
controlling the rate of transmission for each data packet according
to channel conditions.
SUMMARY OF THE INVENTION
[0011] It is, therefore, an object of the present invention to
provide a reverse rate control method and system in which a mobile
station determines its data rate at the time when it first
initiates communication with a base station or initiates
communication with a new base station to perform handoff.
[0012] It is another object of the present invention to provide a
method and system in which when a mobile station first initiates
communication with a base station or initiates communication with a
new base station to perform handoff, the mobile station controls
its data rate by determining a system loading condition using base
station's loading information provided from the base station.
[0013] To achieve the above and other objects, there is provided a
method for controlling a reverse data rate by a mobile station in a
mobile communication system supporting high-rate packet data (HRPD)
transmission, the method including receiving filtered Reverse
Activity Bit (FRAB) which indicates long term sector loading from a
particular base station when the mobile station attempts an initial
access to the base station; setting the received average loading
information as average loading information for the base station;
and upon receiving reverse activity information (RAB) from the base
station, controlling a rate of reverse data using the received
reverse activity information and the set average loading
information.
[0014] To achieve the above and other objects, there is provided an
apparatus for providing rate control information for reverse packet
data to an initially accessed mobile station by a base station in a
mobile communication system supporting high-rate packet data (HRPD)
transmission; wherein the base station generates average loading
information to be transmitted to the mobile station into a
predetermined message and transmits the generated message through a
predetermined forward channel; wherein when the mobile station
attempts an initial access to a predetermined base station, the
mobile station receives average loading information (FRAB) from the
base station, sets the received average loading information as
average loading information for the base station, and upon
receiving reverse activity information (RAB) from the base station,
controlling a rate of reverse data using the received reverse
activity information and the set average loading information.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description when taken in conjunction with the
accompanying drawings in which:
[0016] FIG. 1 is a block diagram illustrating a structure of a
mobile communication system according to an embodiment of the
present invention;
[0017] FIG. 2 is a flowchart illustrating an operation of
receiving, by a mobile station, system loading information from a
base station according to an embodiment of the present invention;
and
[0018] FIG. 3 is a flowchart illustrating an operation of setting,
by a mobile station, an initial FRAB value for a new base station
depending on FRAB values for its old base stations according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] A preferred embodiment of the present invention will now be
described in detail with reference to the annexed drawings. In the
following description, a detailed description of known functions
and configurations incorporated herein has been omitted for
conciseness.
[0020] Herein, a description of the present invention will be made
with reference to a 1.times. Evolution-Data Only (EV-DO) system
using Code Division Multiple Access (CDMA). A description will now
be made of controlling the data rate of each packet transmitted in
a reverse direction in the 1.times. EV-DO mobile communication
system.
[0021] In the 1.times. EV-DO system, the data rate for each packet
transmitted in the reverse direction is controlled based on power
of the mobile station to which the corresponding packet is
transmitted, the total amount of transmission data, and a system
loading condition. That is, a base station generates a Reverse
Activity Bit (RAB) which is information determined considering
system loading conditions.
[0022] Thereafter, the base station transmits the generated RAB to
mobile stations through a forward channel. The RAB has a value `+1`
or `-1`. A RAB=+1 indicates that the system is busy, and a RAB=-1
indicates that the system is not busy. Each base station transmits
the RAB to all mobile stations located in its cell or sector to
provide system loading information to the mobile stations. The
mobile stations control their reverse data rates according to the
system loading condition. Herein, the RAB is transmitted per
specific time, for example, every 1.67 ms, also referred to as a
slot.
[0023] A detailed description will now be made of a process in
which a mobile station controls its data rate based on the RAB.
[0024] When a mobile station controls a reverse data rate using the
received RAB, it uses two parameters of a Quick RAB (QRAB) and a
Filtered RAB (FRAB) received from the base station, as well as the
RAB. The QRAB, a parameter indicating a reverse loading condition
of a base station at a specific time, is a value determined by
filtering RABs continuously received from the base station for a
relatively short time interval (e.g., 1.67 ms*4). A value of the
QRAB is determined by performing hard decision to +1 or -1 on the
values filtered in the foregoing manner. The FRAB, a parameter
indicating a reverse loading condition of a base station for a long
time, which means long term sector loading, is a value determined
by filtering RABs continuously received from the base station for a
relatively long time interval (e.g., 1.67 ms*256). The FRAB value
is a real number between -1 and +1. So, as the FRAB value becomes
smaller at a specific time, it indicates that the base station has
more frequently transmitted a RAB=-1, indicating the average system
loading condition is low.
[0025] As the FRAB value becomes larger at a specific time, it
indicates that the base station has more frequently transmitted a
RAB=+1, and that the average system loading condition is high.
[0026] The mobile station controls its reverse data rate using the
QRAB and the FRAB. That is, the mobile station determines whether
to increase or decrease its data rate according to whether the QRAB
value is -1 or +1. If the QRAB value is +1 at a specific time,
indicating that the current system loading condition is high, the
mobile station attempts to decrease its data rate. On the contrary,
if the QRAB value is -1 at a specific time, indicating that the
current system loading condition is low, the mobile station
attempts to increase its data rate.
[0027] Once the mobile station has determined whether to decrease
or increase its data rate according to whether the QRAB value is +1
or -1 at a specific time, the mobile station determines how much it
will decrease or increase its data rate according to the FRAB
value. The FRAB value is used because it indicates a reverse system
loading condition for a relatively long time, as described above.
For example, assuming that a mobile station attempts to increase
its data rate determining that the QRAB value is -1 at a particular
time, if the FRAB value is very small, the mobile station is
allowed to increase its data rate by a relatively high level
without increasing a load on the system. On the contrary, if the
FRAB value is very large even though the QRAB value is still -1,
the mobile station increases its data rate by a relatively low
level.
[0028] In the system, a time constant value of a filter, used for
generating the QRAB and the FRAB, is provided from a base station
to mobile stations through a signaling message. For example, if a
base station provides a mobile station with information indicating
that a time constant value of a filter used for generating a FRAB
is 256*1.67 ms, the mobile station generates a FRAB by averaging
and filtering RABs received from the base station for the time of
256*1.67 ms, and uses the generated FRAB value in controlling its
data rate.
[0029] In a typical cellular system, there are several base
stations neighboring a particular base station. In this situation,
each base station transmits its own RAB. Therefore, a mobile
station in handoff operation receives RABs from several base
stations. In this case, the mobile station generates and manages
the QRAB and FRQB values separately for each base station. As
described above, the FRAB is an average value for RABs received
from a base station for a relatively long time interval, and is
information indicating an average system loading condition.
However, the mobile station cannot determine the FRAB at the time
when it initially starts communication with a base station and the
time when it starts communication with a new base station to
perform handoff. Therefore, an embodiment of the present invention
will provide a method for initializing a FRAB value for controlling
a reverse system load to determine a data rate at the time when the
mobile station first starts communication with a base station and
the time when the mobile station starts communication with a new
base station to perform handoff. A description will now be made of
a structure of a mobile communication system according to an
embodiment of the present invention.
[0030] FIG. 1 is a block diagram illustrating the structure of a
mobile communication system for controlling a reverse rate
according to an embodiment of the present invention. Referring to
FIG. 1, a mobile communication system includes a mobile station
(MS) 10 and a base station system, or a base station (BS) 20, and
the base station 20 includes a base station transceiver system
(BTS) 21 performing communication with the mobile station 10, and a
base station controller (BSC) 22 for controlling the base station
transceiver system 21. Herein, the base station system will be
referred to as the base station (BS) 20. The mobile station 10 may
include a memory, a receiver and a controller (not shown).
Software, or a program, residing on the memory, controls the
controller, and thereby, the mobile station, to perform the
specific functions described herein.
[0031] The mobile station 10 transmits packet data to the base
station 20 through a reverse packet data channel (R-PDCH). The
mobile station 10 receives a RAB from the base station 20. The
mobile station 10 generates average loading information FRAB using
the RABs continuously received for a predetermined time (for
example, 1.67 ms*256), or using FRAB values for old base stations
(not shown) at initial access to a target base station after
performing handoff from a serving base station, and then updates
the generated FRAB value as average loading information FRAB to be
used in the current base station.
[0032] The base station 20 generates a system loading information
RAB using a method for measuring a Rise-of-Thermal (RoT) that
indicates a ratio of a thermal noise to the total reverse reception
power. Alternatively, the base station 20 may use a method using
the total load. After generating the RAB, it is transmitted to the
mobile station 10 through a forward channel.
[0033] Preferably, when the base station 20 is initially connected
to the mobile station 10 and/or when it is initialized to perform
handoff, the base station 20 sets an initial FRAB value at the
initialization time and transmits the initial FRAB value to the
mobile station 10. Then the mobile station 10 sets the FRAB value
received from the base station 20 to a FRAB to be used later, and
determines an increasing/decreasing step for its reverse data rate
using received RAB and QRAB.
[0034] A description will now be made of a method in which a mobile
station controls a data rate by initializing a FRAB value at the
time when it first accesses a base station and the time when it
attempts to access a new base station to perform handoff.
[0035] An initialization method for the FRAB value can be roughly
divided into two methods. The first method transmits an initial
FRAB value through a signaling message to a mobile station
initiating communication either with a base station or a new base
station to perform a handoff. The second method is for a mobile
station initiating communication with a new base station to perform
handoff. In this method, the mobile station sets an initial FRAB
value for the new base station by itself, depending on FRAB values
for its old base stations.
[0036] A detailed description will now be made of the two methods.
With reference to the accompanying drawing, a description will now
be made of the first FRAB initialization method according to a
first embodiment of the present invention.
[0037] FIG. 2 is a flowchart illustrating an operation of receiving
system loading information from a base station according to an
embodiment of the present invention in a mobile station. Referring
to FIG. 2, in step 101, a mobile station attempts an initial access
to a system or attempts handoff to a new base station. At this
point, the mobile station has no QRAB and FRAB for reverse
communication with the new base station. In step 102, the mobile
station receives an initial FRAB value from a target base station
through a signaling message. The base station can randomly set the
initial FRAB value, or transmit RABs to a mobile station so that
the mobile station can set the initial FRAB value by averaging the
RABs transmitted from the base station. Alternatively, the initial
FRAB value can be generated using a separate algorithm. As a
further alternative, the initial FRAB value can be previously set
through a parameter message during initial call setup.
[0038] In step 103, the mobile station sets a FRAB value received
from the base station as an initial value, and determines how much
it will increase or decrease the current data rate according to the
received FRAB value. Thereafter, in step 104, the mobile station
receives from the base station a RAB indicating current business of
the base station or system loading information. The mobile station
determines, in step 105, whether a time constant value of a filter
has been received from the base station. Upon failure to receive
the time constant value, the mobile station returns to step
104.
[0039] If, however, the time constant value is received, the mobile
station proceeds to step 106 where it generates a FRAB by averaging
RABs received for the time constant value received from the base
station, for example, 256*1.67 ms as described above, and updates
the generated FRAB value as a FRAB for the corresponding base
station. Thereafter, the mobile station returns to step 104.
Although it is shown that the mobile station receives the time
constant value in step 105, the mobile station may skip step 105 in
the case where the time constant value is preset in the mobile
station.
[0040] Next, with reference to the accompanying drawing, a
description will be made of the second FRAB initialization method
according to a second embodiment of the present invention.
[0041] The second method is for a mobile station initiating
communication with a new base station to perform handoff, and in
this method, the mobile station sets an initial FRAB value for the
new base station depending on FRAB values for its old base
stations.
[0042] FIG. 3 is a flowchart illustrating an operation of setting,
by a mobile station, an initial FRAB value for a new base station
depending on FRAB values for its old base stations according to an
embodiment of the present invention. Referring to FIG. 3, in step
201, a mobile station attempts handoff to a new base station. In
step 202, the mobile station sets FRAB values for its old base
stations as an initial FRAB value for the new base station to set a
FRAB value for the target base station.
[0043] Thereafter, in step 203, the mobile station determines how
much it will increase or decrease a current data rate using the set
initial FRAB value. In step 204, the mobile station receives a RAB
from the base station. Thereafter, the mobile station determines in
step 205 whether a time constant value of a filter has been
received from the base station. Upon failure to receive the time
constant value, the mobile station returns to step 204. Upon
receiving the time constant value, the mobile station proceeds to
step 206 where it generates a FRAB by filtering the RAB for a time
corresponding to the received time constant value, for example,
256*1.67 ms. In addition, the mobile station updates the generated
FRAB value as a FRAB value for the base station, and then returns
to step 204. Although it is shown that the mobile station receives
the time constant value in step 205, the mobile station may skip
step 205 in the case where the time constant value is preset in the
mobile station.
[0044] A detailed description will now be made of three methods for
setting, in step 203, an initial FRAB value for a new base station
using FRAB values for its old base stations.
[0045] In the first method, the mobile station can use an average
value of FRABs of its old base stations with which it has
previously communicated, as an initial FRAB value for a new base
station. For example, assume a mobile station performs handoff from
a base station A and a base station Bto a new base station C. If
the FRAB value for the base station A is -0.5 and the FRAB value
for the base station B is -0.4, the mobile station sets an initial
FRAB value for the new base station C to -0.45, the average of the
two FRABs. This method using an average value available when
several base stations have similar reverse load conditions.
[0046] In the second method, the mobile station uses a minimum
value among FRAB values for its old base stations as an initial
FRAB value for a new base station. For example assume a mobile
station performs handoff from a base station A and a base station
Bto a new base station C. If the FRAB value for the base station A
is -0.5 and the FRAB value for the base station B is -0.4, the
mobile station sets an initial FRAB value for the new base station
C to -0.5, the minimum value of the two FRABa. This method is
aggressive because the mobile station initializes a reverse load
level of the newly added base station to a relatively low
value.
[0047] In the third method, the mobile station uses a maximum value
among FRAB values for its old base stations as an initial FRAB
value for a new base station. For example, assume a mobile station
performs handoff from a base station A and a base station Bto a new
base station C. If the FRAB value for the base station A is -0.5
and the FRAB value for the base station B is -0.4, the mobile
station sets an initial FRAB value for the new base station C to
-0.4, the greater FRAB of the two. This method is stable because
the mobile station initializes a reverse load level of the newly
added base station to a relatively high value.
[0048] As can be understood from the foregoing description,
according to the present invention, a mobile station sets an
initial FRAB value indicating average loading information of a base
station at the time when it initially attempts to start
communication with a base station, or at the time when it attempts
communication with a new base station when performing a handoff. In
this manner, the mobile station can correctly determine a system
loading condition in determining its data rate, making it possible
to efficiently control a reverse system load.
[0049] While the invention has been shown and described with
reference to certain preferred embodiments thereof, it will be
understood by those skilled in the art that various changes in form
and details may be made therein without departing from the spirit
and scope of the invention as defined by the appended claims.
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