U.S. patent application number 11/546971 was filed with the patent office on 2007-02-08 for dsch power control method for wcdma.
This patent application is currently assigned to LG Electronics Inc.. Invention is credited to Seung Hoon Hwang, Bong Hoe Kim.
Application Number | 20070032257 11/546971 |
Document ID | / |
Family ID | 27350562 |
Filed Date | 2007-02-08 |
United States Patent
Application |
20070032257 |
Kind Code |
A1 |
Kim; Bong Hoe ; et
al. |
February 8, 2007 |
DSCH power control method for WCDMA
Abstract
In the DSCH power control method for mobile communication system
according to the present invention, the cell transmitting DSCH
receives a signal from an UE, determines whether a cell
transmitting DSCH to be set as primary or non-primary based on the
received signal, and controls DSCH transmit power according to a
result of the determination. The cell decreases DSCH transmit power
when the cell is set as primary and increases DSCH transmit power
when the cell is set as non-primary. In the DSCH transmit power
control method of the present invention the cell transmitting DSCH
sets its state as non-primary when the received signal quality is
bad, such that it is possible to prevent the cell transmitting the
DSCH from reducing the DSCH transmit power even when the received
signal quality is bad, unlike in the typical SSDT.
Inventors: |
Kim; Bong Hoe; (Kyungki-do,
KR) ; Hwang; Seung Hoon; (Seoul, KR) |
Correspondence
Address: |
FLESHNER & KIM, LLP
P.O. BOX 221200
CHANTILLY
VA
20153
US
|
Assignee: |
LG Electronics Inc.
|
Family ID: |
27350562 |
Appl. No.: |
11/546971 |
Filed: |
October 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10359099 |
Feb 6, 2003 |
|
|
|
11546971 |
Oct 13, 2006 |
|
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Current U.S.
Class: |
455/522 |
Current CPC
Class: |
H04W 52/38 20130101;
H04W 52/143 20130101 |
Class at
Publication: |
455/522 |
International
Class: |
H04B 7/00 20060101
H04B007/00; H04Q 7/20 20060101 H04Q007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2002 |
KR |
07776/2002 |
Aug 10, 2002 |
KR |
47369/2002 |
Aug 20, 2002 |
KR |
49268/2002 |
Claims
1. A DSCH power control method in a mobile communication system
comprising: (a) receiving a signal from an UE; (b) determining
whether a cell transmitting DSCH to be set as primary or
non-primary based on the received signal; and (c) adjusting DSCH
transmit power according to a result of the determination, wherein
(b) includes, (1) determining whether or not a primary cell ID code
contained in the received signal matches a cell ID code of the
cell, and setting the cell as primary if the cell ID code matches
the primary cell ID code, (2) if the cell ID code matches the
primary cell ID code, determining whether the received signal is
encoded in normal mode or compressed mode, and if the received
signal is encoded in the compressed mode, determining whether or
not the number of bits punctured from the total number of bits
N.sub.ID in the primary cell ID code is less than .left
brkt-bot.N.sub.ID/3.right brkt-bot., and setting the cell as
non-primary when the number of punctured bits is not greater than
.left brkt-bot.N.sub.ID/3.right brkt-bot., and in all other
situations, setting the cell as primary.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation Application of prior U.S.
patent application Ser. No. 10/359,099 filed Feb. 6, 2003, which
claims priority under 35 U.S.C. .sctn.119 to Korean Application
Nos. 07776/2002 filed on Feb. 9, 2002, 47369/2002 filed on Aug. 10,
2002, and 49268/2002 filed on Aug. 20, 2002, whose entire
disclosures are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a wireless communication
and, more particularly, to a method for controlling transmit power
of a downlink shared channel (DSCH) in third generation mobile
communication system.
[0004] 2. Description of the Background Art
[0005] A universal mobile telecommunications system (UMTS) is a
third generation mobile communication system that has evolved from
a standard known as Global System for Mobile communications (GSM).
This standard is a European standard which aims to provide an
improved mobile communication service based on a GSM core network
and wideband code division multiple access (W-CDMA) technology. In
December, 1998, the ETSI of Europe, the ARIB/TTC of Japan, the T1
of the United States, and the TTA of Korea formed a Third
Generation Partnership Project (3GPP) for the purpose of creating
the specification for standardizing the UMTS.
[0006] The work towards standardizing the UMTS performed by the
3GPP has resulted in the formation of five technical specification
groups (TSG), each of which is directed to forming network elements
having independent operations. More specifically, each TSG
develops, approves, and manages a standard specification in a
related region. Among them, a radio access network (RAN) group
(TSG-RAN) develops a specification for the function, items desired,
and interface of a UMTS terrestrial radio access network (UTRAN),
which is a new RAN for supporting a W-CDMA access technology in the
UMTS.
[0007] The TSG-RAN group includes a plenary group and four working
groups. Working group 1 (WG1) develops a specification for a
physical layer (a first layer). Working group 2 (WG2) specifies the
functions of a data link layer (a second layer) and a network layer
(a third layer). Working group 3 (WG3) defines a specification for
an interface among a base station in the UTRAN, a radio network
controller (RNC), and a core network. Finally, Working group 4
(WG4) discusses requirements desired for evaluation of radio link
performance and items desired for radio resource management.
[0008] FIG. 1 shows a structure of a 3GPP UTRAN. This UTRAN 110
includes one or more radio network sub-systems (RNS) 120 and 130.
Each RNS 120 and 130 includes a RNC 121 and 131 and one or more
Nodes B 122 and 123 and 132 and 133 (e.g., a base station) managed
by the RNCs. RNCs 121 and 131 are connected to a mobile switching
center (MSC) 141 which performs circuit switched communications
with the GSM network. The RNCs are also connected to a serving
general packet radio service support node (SGSN) 142 which performs
packet switched communications with a general packet radio service
(GPRS) network.
[0009] Node Bs are managed by the RNCs, receive information sent by
the physical layer of a terminal 150 (e.g., mobile station, user
equipment and/or subscriber unit) through an uplink, and transmit
data to a terminal 150 through a downlink. Nodes B, thus, operate
as access points of the UTRAN for terminal 150.
[0010] The RNCs perform functions which include assigning and
managing radio resources. An RNC that directly manages a Node B is
referred to as a control RNC (CRNC). The CRNC manages common radio
resources. A serving RNC (SRNC), on the other hand, manages
dedicated radio resources assigned to the respective terminals. The
CRNC can be the same as the SRNC. However, when the terminal
deviates from the region of the SRNC and moves to the region of
another RNC, the CRNC can be different from the SRNC. Because the
physical positions of various elements in the UMTS network can
vary, an interface for connecting the elements is necessary. Nodes
B and the RNCs are connected to each other by an Iub interface. Two
RNCs are connected to each other by an Iur interface. An interface
between the RNC and a core network is referred to as Iu.
[0011] FIG. 2 shows a structure of a radio access interface
protocol between a terminal which operates based on a 3GPP RAN
specification and a UTRAN. The radio access interface protocol is
horizontally formed of a physical layer (PHY), a data link layer,
and a network layer and is vertically divided into a control plane
for transmitting control information and a user plane for
transmitting data information. The user plane is a region to which
traffic information of a user such as voice or an IP packet is
transmitted. The control plane is a region to which control
information such as an interface of a network or maintenance and
management of a call is transmitted.
[0012] In FIG. 2, protocol layers can be divided into a first layer
(L1), a second layer (L2), and a third layer (L3) based on three
lower layers of an open system interconnection (OSI) standard model
well known in a communication system.
[0013] The first layer (L1) operates as a physical (PHY) layer for
a radio interface and is connected to an upper medium access
control (MAC) layer through one or more transport channels. The
physical layer transmits data delivered to the physical (PHY) layer
through a transport channel to a receiver using various coding and
modulating methods suitable for radio circumstances. The transport
channel between the PHY layer and the MAC layer is divided into a
dedicated transport channel and a common transport channel based on
whether it is exclusively used by a single terminal or shared by
several terminals.
[0014] The second layer L2 operates as a data link layer and lets
various terminals share the radio resources of a W-CDMA network.
The second layer L2 is divided into the MAC layer, a radio link
control (RLC) layer, a packet data convergence protocol (PDCP)
layer, and a broadcast/multicast control (BMC) layer.
[0015] The MAC layer delivers data through an appropriate mapping
relationship between a logical channel and a transport channel. The
logical channels connect an upper layer to the MAC layer. Various
logical channels are provided according to the kind of transmitted
information. In general, when information of the control plane is
transmitted, a control channel is used. When information of the
user plane is transmitted, a traffic channel is used. The MAC layer
is divided two sub-layers according to performed functions. The two
sub-layers are a MAC-d sub-layer that is positioned in the SRNC and
manages the dedicated transport channel and a MAC-c/sh sub-layer
that is positioned in the CRNC and manages the common transport
channel.
[0016] The RLC layer forms an appropriate RLC protocol data unit
(PDU) suitable for transmission by the segmentation and
concatenation functions of an RLC service data unit (SDU) received
from an upper layer. The RLC layer also performs an automatic
repeat request (ARQ) function by which an RLC PDU lost during
transmission is re-transmitted. The RLC layer operates in three
modes, a transparent mode (TM), an unacknowledged mode (UM), and an
acknowledged mode (AM). The mode selected depends upon the method
used to process the RLC SDU received from the upper layer. An RLC
buffer stores the RLC SDUs or the RLC PDUs received from the upper
layer exists in the RLC layer.
[0017] The packet data convergence protocol (PDCP) layer is an
upper layer of the RLC layer which allows data items to be
transmitted through a network protocol such as the IPv4 or the
IPv6. A header compression technique for compressing and
transmitting the header information in a packet can be used for
effective transmission of the IP packet.
[0018] The broadcast/multicast control (BMC) layer allows a message
to be transmitted from a cell broadcast center (CBC) through the
radio interface. The main function of the BMC layer is scheduling
and transmitting a cell broadcast message to a terminal. In
general, data is transmitted through the RLC layer operating in the
unacknowledged mode.
[0019] The PDCP layer and the BMC layer are connected to the SGSN
because a packet switching method is used, and are located only in
the user plane because they transmit only user data. Unlike the
PDCP layer and the BMC layer, the RLC layer can be included in the
user plane and the control plane according to a layer connected to
the upper layer. When the RLC layer belongs to the control plane,
data is received from a radio resource control (RRC) layer. In the
other cases, the RLC layer belongs to the user plane. In general,
the transmission service of user data provided from the user plane
to the upper layer by the second layer (L2) is referred to as a
radio bearer (RB). The transmission service of control information
provided from the control plane to the upper layer by the second
layer (L2) is referred to as a signaling radio bearer (SRB). As
shown in FIG. 2, a plurality of entities can exist in the RLC and
PDCP layers. This is because a terminal has a plurality of RBs, and
one or two RLC entities and only one PDCP entity are generally used
for one RB. The entities of the RLC layer and the PDCP layer can
perform an independent function in each layer.
[0020] The RRC layer positioned in the lowest portion of the third
layer (L3) is defined only in the control plane and controls the
logical channels, the transport channels, and the physical channels
in relation to the setup, the reconfiguration, and the release of
the RBs. At this time, setting up the RB means processes of
stipulating the characteristics of a protocol layer and a channel,
which are required for providing a specific service, and setting
the respective detailed parameters and operation methods. It is
possible to transmit control messages received from the upper layer
through a RRC message.
[0021] Transport channels are services offered by the Layer 1 to
the higher layers. A transport channel is defined by how and with
what characteristics data is transferred over the air interface.
The transport channels can be classified into Dedicated channels
and Common channels. There exists only one type of dedicated
transport channel, the Dedicated Channel (DCH). On the other hand,
there are six types of common transport channels, i.e., Broadcast
Channel (BCH), Forward Access Channel (FACH), Paging Channel (PCH),
Random Access Channel (RACH), Common Packet Channel (CPCH), and
Downlink Shared Channel (DSCH).
[0022] Among them DSCH is a downlink transport channel shared by
several UEs. The DSCH is associated with one or several downlink
DCH and is transmitted over the entire cell or over only a part of
the cell using beamforming antennas.
[0023] FIG. 3 shows frame structure for downlink shared channel
(DSCH). As shown in FIG. 3, each frame has a length of 10 ms and is
split into 15 slots. Each of the slots has a length T.sub.slot=2560
chips.
[0024] A DSCH is shared by several UEs through time division
scheduling which is carried out at the single frame level (10 ms)
or over several frames. Thus, DSCH enables multiple UEs with
relatively low activity and bursty traffic to share a high data
rate channel employing a common channelization code resource.
[0025] The primary way of sharing the channelization code resource
is to allocate the code resource to a single UE at a time in the
time domain. Despite this, a limited degree of code multiplexing,
i.e, more than one user transmitting DSCH data at the same time
using distinct parts of the set of codes allocated for the DSCH, is
useful to increase the granularity in supported payload sizes. In
other words, DSCH is a code multiplexed and time multiplexed
channel. Accordingly, power control for the DSCH is performed in
association with the UEs occupied the DSCH.
[0026] The UEs are identified by root channelization codes of
spreading factor allocated to the DSCH. For example, when the
spreading factor (SF) of DSCH are 4, 8, 16, 32, and 64, there are
respective 4, 8, 16, 32, and 64 root channelization codes. The high
rate channelization code is generated by splitting a low rate
channelization code.
[0027] The DSCH is associated with one or several downlink DCH.
That is, the UE occupied DSCH has one DCH. In view of power
control, UE measures the power level of the DCH transmitted from
the base station, generates a transmit power control (TPC) command
based on the measured power level, and transmits the TPC to the
base station. The base station adjusts the power level of the DCH
according to the TPC received from the UE. Also, the base station
can update the power level of the DSCH in association with the DCH
without additional TPC for DSCH. The reason why the power level of
the DSCH is associated with the power level of DCH is because the
DSCH is shared by several UEs and can be occupied by only one UE.
The DCH is allocated per UE occupying the DSCH for periodically
transmitting Pilot for Fast Power Control and transmitting control
information on the DSCH, which is called an associated DCH.
[0028] Since the DSCH is associated with the DCH, the data
transmission from the base station to UEs via the DSCH can be
performed. Each UE to which data can be transmitted on the DSCH has
an associated downlink dedicated physical channel (DPCH). The
associated downlink DPCH is used to carry control commands for the
associated uplink DPCH and, if needed, other services, e.g.,
circuit-switched voice.
[0029] FIG. 4 shows a frame structure for downlink DPCH. As
explained above, DCH is a transport channel between the PHY layer
and the MAC layer, and the DPCH is a physical channel between a
transmitter and receiver.
[0030] As shown in FIG. 4, each frame has a length of 10 ms and is
split into 15 slots (slot#0.about.slot#14). Each slot has a length
T.sub.slot=2560 chips, corresponding to one power control period.
Within one downlink DPCH, dedicated data generated at Layer 2 and
above, i.e., the dedicated transport channel (DCH), is transmitted
in time multiplex with control information generated at Layer 1,
i.e., pilot bits, TPC commands, and an optional TFCI. The downlink
DPCH can thus be seen as a time multiplex of a downlink Dedicated
Physical Data Channel (DPDCH) and a downlink Dedicated Physical
Control Channel (DPCCH). In FIG. 5, the parameter k determines the
total number of bits per downlink DPCH slot. It is related to the
spreading factor (SF) of the physical channel as SF=512/2.sup.k.
Thus the SF ranges from 512 to 4. The number of bits of the
downlink DPCH fields (N.sub.data1, N.sub.TPC, N.sub.TFCI,
N.sub.data2, N.sub.pilot) vanes according to a slot format to used.
The Transport Format Combination Indicator (TFCI) field includes
channel quality information such as data rate and coding scheme of
the associated channel.
[0031] In case that data for one UE is transmitted on the DSCH, the
channel information of the DSCH should be transmitted as well as
that of the DCH through TFCI field of the DPCCH. For this reason,
the TFCI field per slot may be divided into two parts, one for the
DCH and the other for the DSCH.
[0032] There are two methods for encoding the information on the
DCH and DSCH. The first method is to encode the TFCI information of
the DCH and DSCH into one codeword using the second order
Reed-Muller coding, which is called Logical Split Mode.
[0033] The second method is to encode the TFCI information of the
DCH and TFCI information of the DSCH into respective two codewords
using the first order Reed-Muller coding and scramble the bits of
the codewords, which is called Hard Split Mode.
[0034] The second TFCI coding method can be used in case that the
DCHs are transmitted from different RNCs. That is, the second TFCI
coding method supports the transmission of TFCI information of the
DSCH from some of RNCs.
[0035] The TPC of DPCCH is a transmit power control command for
controlling transmit power of the uplink channel such that the UE
adjust the transmit power according to the TPC. The associated
channel condition is measured using the pilot field.
[0036] The problem comes from the fact that DCH may be in soft
handover and the DSCH is not because the DSCH is shared several UEs
in time domain in one cell. That is, only one cell can communicate
with one UE through the DSCH such that if the UE moves to a new
cell it should occupy the DSCH of the associated cell. Accordingly,
in case that the DCH is in the soft handover state, i.e. connected
to more than one cell and DSCH is connected to one base station,
another power control method is required.
[0037] Unlike the DCH for which the UE generates TPC of the uplink
DPCCH based on the sum of the powers transmitted from plural cells,
the DSCH can be provided by only one cell such that it is difficult
to expect reliable power control of the DSCH based on the TPC
associated with the DCH.
[0038] The 3GPP standard specifies a Site Selection Diversity
Transmit (SSDT) signaling as another macro diversity method in soft
handover mode. This method is optional in UTRAN.
[0039] The SSDT operates in such a way that the UE selects one of
the cells from its active set to be `primary`, all other cells are
classed as `non-primary.` In order to select a primary cell, each
cell is assigned a temporary identification (ID) and UE
periodically informs a primary cell ID to the connecting cells. The
non-primary cells selected by UE switch off the transmission power.
The primary cell ID is delivered by UE to the active set via uplink
FBI field. SSDT activation, SSDT termination and ID assignment are
all carried out by higher layer signaling.
[0040] In SSDT, to avoid the channel is broken due to failure of
primary cell selection when the channel quality is bad, conditions
for being a non-primary cell is critical.
[0041] The UE periodically sends the primary cell ID code via a
portion of the uplink FBI field assigned for SSDT use. A cell
recognizes its state as non-primary if the following conditions are
fulfilled simultaneously:
[0042] (1) The received ID code does not match with the own ID
code.
[0043] (2) The received uplink signal quality satisfies a quality
threshold, Qth, a parameter defined by the network.
[0044] (3) If uplink compressed mode is used, and less than
N.sub.ID/3 bits are lost from the ID code (as a result of uplink
compressed mode), where N.sub.ID is the number of bits in the ID
code (after puncturing if puncturing has been done).
[0045] Otherwise the cell recognizes its state as primary.
[0046] In SSDT, only the primary cell transmits DPDCH. Since the
cell of which the ID code is identical with the primary cell ID
code transmitted by the UE is set as a primary cell, DPDCH is not
transmitted to the UE when the channel quality is so bad that the
cell to be primary fails to recognize its state as primary. To
avoid this situation, the conditions for being a non-primary cell
are very critical.
[0047] Also, SSDT is used for transmitting power control of the
DSCH. In this case, the cell, in the active set, transmitting DSCH
decodes the primary cell ID code transmitted from the UE so as to
determine whether it is primary or non-primary, while the other
cells in the active set does not activate SSDT. The cell sets its
state as primary reduces the DSCH transmitting power as much as a
power offset for the primary cell.
[0048] In SSDT, the cell may recognize its state as primary in two
situations, i.e., when the uplink channel quality is good so as to
recognize its state based on the primary cell ID code transmitted
by the UE and when the channel quality is bad so as not to rely on
the primary cell ID code due to decoding performance degradation.
In the latter situation, the cell transmitting DSCH sets its state
as primary regardless of the primary cell ID code for overcoming
shortage of the SSDT, i.e., all of the cells become
non-primary.
[0049] However, the above DSCH power control using SSDT has a
drawback in that since the cell transmitting DSCH sets its state as
primary and reduces DSCH transmit power even when the channel
quality is bad, resulting in degradation of DSCH performance.
SUMMARY OF THE INVENTION
[0050] The present invention has been made in an effort to solve
the above problems.
[0051] It is an object of the present invention to provide a DSCH
power control method capable of preventing the cell transmitting
DSCH from setting its status as primary regardless of the primary
cell ID code transmitted by the UE when the uplink channel quality
is bad.
[0052] It is another object of the present invention to provide a
DSCH power control method capable of efficiently controlling the
DSCH transmit power by modifying conditions for setting a cell as
primary to be more critical.
[0053] To achieve the above objects, the DSCH power control method
according to the present invention includes the steps of: (a)
receiving a signal from an UE, (b) determining whether a cell
transmitting DSCH to be set as primary or non-primary based on the
received signal, and (c) adjusting DSCH transmit power according to
a result of the determination.
[0054] In one aspect of the present invention, the cell determines
whether or not a received signal quality is greater than a quality
threshold (Qth) so as to set its state as non-primary when the
received signal quality is not greater than the quality threshold.
On the other hand when the received signal quality is greater than
the quality threshold, the cell determines whether or not a primary
cell ID code contained in the received signal matches with a cell
ID code of the cell so as to set its state as non-primary when the
cell ID code does not match with the primary cell ID code and set
its state as primary when the cell ID code matches with the primary
cell ID code.
[0055] In another aspect of the present invention, the cell further
determines whether the received signal is encoded in a normal or
compressed mode when the cell ID code matches with the primary cell
ID code so as to set the cell as primary when the received signal
is encoded in the normal mode and determines whether or not bits
punctured from number of bits (N.sub.ID) of the primary cell ID
code is less than N.sub.ID/3 when the received signal is encoded in
the compressed mode. The cell sets its state as non-primary when
the bits punctured from number of bits (N.sub.ID) of the cell ID
code is greater than or equal to N.sub.ID/3 and as non-primary when
the bits punctured from number of bits (N.sub.ID) of the cell ID
code is less than N.sub.ID/3.
[0056] In another aspect of the present invention, the cell firstly
determines whether or not a primary cell ID code contained in the
received signal matches with a primary cell ID code of the cell so
as to set its state as non-primary when the cell ID code does not
match with the primary cell ID code and as primary when the cell ID
code matches with the primary cell ID code. The cell further
determines whether the received signal is encoded in a normal or
compressed mode when the primary cell ID code matches with the cell
ID code, such that the cell sets its state as primary when the
received signal is encoded in the normal mode and determines
whether or not bits punctured from number of bits (N.sub.ID) of the
cell ID code is less than N.sub.ID/3 when the received signal is
encoded in the compressed mode. Sequentially, the cell sets its
state as non-primary when the bits punctured from number of bits
(N.sub.ID) of the cell ID code is greater than or equal to
N.sub.ID/3 and as non-primary when the bits punctured from number
of bits (N.sub.ID) of the cell ID code is less than N.sub.ID/3.
[0057] In still another aspect of the present invention, the cell
firstly determines whether the received signal is encoded in a
normal or compressed mode so as to perform a normal mode pressures
when the received signal is encoded normal mode and a compressed
mode procedures according to a result of the determination. In the
normal mode procedure, the cell determines whether or not a primary
cell ID code contained in the received signal matches with a cell
ID code of the cell so as to set the cell as primary when the
primary cell ID code matches with the primary cell ID code and as
non-primary when the primary cell ID code does not match with the
primary cell ID code. In the compressed procedure, the cell
determines whether or not bits punctured from number of bits
(N.sub.ID) of the primary cell ID code is less than N.sub.ID/3 so
as to set its state as non-primary when the bits punctured from the
number of bits (N.sub.ID) of the primary cell ID code is greater
than or equal to N.sub.ID/3 and determines whether or not a primary
cell ID code contained in the received signal matches with a cell
ID code of the cell when the bits punctured from number of bits
(N.sub.ID) of the primary cell ID code is less than N.sub.ID/3.
Sequentially, the cell sets its state as primary when the primary
cell ID code matches with the primary cell ID code and as
non-primary when the primary cell ID code does not match with the
primary cell ID code.
[0058] In the DSCH power control method of the present invention,
the cell decreases DSCH transmit power when the cell is set as
primary and increase DSCH transmit power when the cell is set as
non-primary.
BRIEF DESCRIPTION OF THE DRAWINGS
[0059] The invention will be described in detail with reference to
the following drawings in which like reference numerals refer to
like elements wherein:
[0060] FIG. 1 is a conceptual view showing a structure of a UMTS
radio access network (UTRAN) of a 3GPP;
[0061] FIG. 2 is a conceptual view for showing a protocol structure
of a radio interface adapted to the UTRAN of FIG. 1;
[0062] FIG. 3 is a drawing illustrating frame structure for
downlink shared channel (DSCH);
[0063] FIG. 4 is a drawing illustrating frame structure for
downlink dedicated physical channel (DPCH);
[0064] FIG. 5 is a flowchart illustrating a DSCH power control
method according to a first embodiment of the present invention;
and
[0065] FIG. 6 is a flowchart illustrating a DSCH power control
method according to a second embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0066] The present invention will be described hereinafter with
reference to the accompanying drawings.
[0067] In the present invention, a primary cell is determined using
the SSDT uplink signaling. To control the DSCH transmit power a
primary cell is firstly selected from an active set of associated
UE. In order to select a primary cell, each cell is assigned a
temporary identification (ID) and UE periodically informs a primary
cell ID to the connecting cells via a portion of the uplink FBI
field assigned for SSDT use. A cell recognizes its state as primary
when the received ID code from the UE matches with its own ID
code.
[0068] The primary cell selection is performed in consideration of
the transmit power level of the UE. When the received signal
quality is less than a predetermined level, errors may occur while
decoding the received signal. In this case the cell transmitting
DSCH sets its state as non-primary unlike the typical SSDT
procedure in which the cell maintains its state as primary.
[0069] FIG. 5 is a flowchart illustrating a method for controlling
the DSCH transmitting power according to a first embodiment of the
present invention.
[0070] In FIG. 5, once the cell transmitting DSCH receives a signal
from a UE at step S501, the cell determines whether or not the
received uplink signal quality is greater than or equal to an
uplink quality threshold (Qth) at step S502. If the received signal
quality is greater than or equal to the uplink quality threshold,
the cell determines whether or not its own ID code matches with a
primary cell ID code transmitted by the UE at step S503. If the
cell ID code matches with the primary cell ID code, the cell
determines whether or not an uplink compressed mode is used at step
S504. If the uplink compressed mode is used, the cell determines
whether or not less than .left brkt-bot.N.sub.ID/3.right brkt-bot.
bits are punctured from the ID code, where N.sub.ID is the number
of bits in the cell ID code, at step S505. If less than .left
brkt-bot.N.sub.ID/3.right brkt-bot. bits are punctured, the cell
sets its state as primary at step S506 and the algorithm returns to
step S501. At step S504, if it is determined that the uplink
compressed mode is not used, the cell sets its state as primary
with skipping the step S505.
[0071] On the other hand, if the received signal quality is less
than the uplink quality threshold (Qth) at step S502, if the cell
ID code does not match with the primary cell ID code from the UE at
step S503, or more than or equal to .left brkt-bot.N.sub.ID/3.right
brkt-bot. bits are punctured from the primary cell ID code, the
cell sets its state as non-primary at step S507 and the algorithm
returns to step S501.
[0072] The received uplink signal quality can be ignored because
whether or not the primary cell exists is not important for DSCH
power control. In this case the cell sets its state as primary when
the two conditions are satisfied, i.e., when the cell ID code
matches with the primary cell ID code and less than .left
brkt-bot.N.sub.ID/3.right brkt-bot. bits are punctured from the ID
code in the uplink compressed mode.
[0073] FIG. 6 is a flowchart illustrating a method for controlling
the DSCH transmitting power according to a second embodiment of the
present invention.
[0074] In FIG. 6, once the cell transmitting DSCH receives a signal
from a UE at step S601, the cell determines whether or not the
uplink compressed mode is used at step S602. If the uplink
compressed mode is not used, the cell determines whether or not its
own cell ID code matches with the primary cell ID code received
from the UE at step S603. Consequently, the cells sets its state as
primary at step S604 if the cell ID code matches with the primary
cell ID code and sets its state as non-primary at step S606 if the
cell ID code does not match with the primary cell ID code.
[0075] On the other hand, at step S602 if it is determined that the
uplink compressed mode is used, the cell determines whether or not
less than .left brkt-bot.N.sub.ID/3.right brkt-bot. bits are
punctured from the ID code at step S605. If it is determined that
less than .left brkt-bot.N.sub.ID/3.right brkt-bot. bits are
punctured from the ID code, the cell performing the step S603. If
it is determined that greater than or equal to .left
brkt-bot.N.sub.ID/3.right brkt-bot. bits are punctured from the ID
code, the cell sets its state as non-primary at step S606.
[0076] Once the cell transmitting DSCH sets its state as primary in
accordance with the methods of the first and second embodiments,
the cell decreases DSCH transmit power as much as a predetermined
power offset for the primary cell. That the primary cell is
selected means that the uplink channel quality is good.
[0077] On the other hand, when the cell transmitting DSCH is set as
non-primary one, the cell increases DSCH transmit power by adding a
predetermined power offset to the TFCI field of the DCH.
[0078] As described above, in the DSCH transmit power control
method of the present invention the cell transmitting DSCH sets its
state as non-primary when the received signal quality is bad, such
that it is possible to prevent the cell transmitting the DSCH from
reducing the DSCH transmit power even when the received signal
quality is bad, unlike in the typical SSDT.
[0079] Also, since the DSCH transmit power decreases when the cell
transmitting DSCH is set as primary and increases when the cell
transmitting DSCH is set as non-primary in the DSCH power control
method of the present invention, the DSCH transmit power is
efficiently controlled according to the received signal
quality.
[0080] While this invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not
limited to the disclosed embodiments, but, on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *