CA2593385A1 - Apparatus and method for controlling transmit antenna array for physical downlink shared channel in a mobile communication system - Google Patents

Abstract

In a mobile communication system, if a UE enters a SHO (Soft Handover) region, the UE
determines weight information for a DPCH and a PDSCH depending on DPCH signals and PDSCH signals received from Node Bs, and transmits the determined weight information to the Node Bs. The Node Bs then determine weights of the PDCH
signals and the PDSCH signals to be transmitted to the UE depending on the feedback information received from the UE, and transmit the determined weights to the UE along with the DPCH signals and the PDSCH signals, respectively.

Description

APPARATUS AND METHOD FOR CONTROLLING TRANSMIT ANTENNA ARRAY
FOR PHYSICAL DOWNLINK SHARED CHANNEL IN A MOBILE COMMUNICATION
SYSTEM

BACKGROUND OF THE INVENTION

This is a divisional application of Canadian Patent Application Serial No. 2, 394, 093 filed on October 11, 2001.

1. Field of the Invention The present invention relates generally to a mobile communication system, and in particular, to an apparatus and method for controlling a transmit antenna array (TxAA) for a physical downlink shared channel (PDSCH) in a soft handover (SHO) region.

It should be understood that the expression "the invention" and the like encompasses the subject-matter of both the parent and the divisional applications.

2. Description of the Related Art In general, a physical downlink shared channel (PDSCH) used in an asynchronous W-CDMA (Wideband Code Division Multiple Access) mobile communication system, a type of a 3'd generation mobile communication system, refers to a channel shared by a plurality of UEs (User Equipments). The PDSCH is a channel assigned to transmit packet data or high-rate data to the UEs in a lOms radio frame unit, and is commonly used by a plurality of the UEs. The PDSCH can vary a data rate of transmission data in a frame unit, and can also perform weight adjustment on a transmit antenna array and power control in a slot unit, like a dedicated channel (DCH) established between a Node B and a UE in the W-CDMA system. The radio frame, a basic unit for transmitting signals in the W-CDMA system, has a length of l Oms, and each radio frame is comprised of 15 slots. In addition , the PDSCH is a channel for transmitting user data only. When the PDSCH is assigned to the UE from power control on the PDSCH, a downlink dedicated physical channel (DL-DPCH) is assigned to the UE
in association with the PDSCH. Here, the DL-DPCH becomes a channel for power control on the PDSCH. The PDSCH can be continuously transmitted to one UE over a plurality of frames. Altetnatively, the PDSCH can be transmitted to the -la-UE over only one frame. In addition, the time to transmit the frames to a plurality of the UEs is determined by scheduling in an upper layer.

A structure of the PDSCH and a structure of the DL-DPCH assigned to the UE in association with the PDSCH will be described with FIGs. lA and FIG. 1B. FIG.
lA
illustrates a structure of the PDSCH used in a mobile communication system, and FIG.
1B illustrates a structure of the DL-DPCH assigned to the UE in association with the PDSCH.

Referring to FIG. 1 A, a radio frame 101 of the PDSCH is lOms in length, and is comprised of 15 slots Slot#t0-S1ot414. Each slot, e_g., a slot Slot#i (103), has a length of 2560 chips, and an amount of information transmitted over the S1ot#i 103 is in inverse proportion to a spreading factor (SF) used for the PDSCH slots. The SF has a value of 4 to 256, and transmission information data is spread according to the SF value. Only the user data is transmitted over the PDSCH.

Next, referring to FIG. l B, when the PDSCH shown in FIG. IA is used, the DL-DPCH associated with the PDSCH is assigned to the corresponding UE by the Node B. A radio frame 111 of the DL-DPCH is also comprised of 15 slots Slot#0-Slot414, and each slot, as shown in FIG. IB, is comprised of Datal bits 112, TPC (Transmit Power Control) bits 113, TFCI (Transmit Format Combination Indicator) bits 114, Data2 bits 115, and Pilot bits 116.
Each slot of the DL-DPCH can have various structures according to the lengths of Datal, TPC, TFCI, Data2 and Pilot.

The Datal bits 112 and the Data2 bits 115 are transmitted over a downlink dedicated physical data channel (DL-DPDCH), and the DL-DPDCH transmits user data and signaling information from the upper layer. The TPC 113, the TFCI 114, and the Pilot 116 are transmitted over a downlink dedicated physical control channel (DL-DPCCH). The TPC 113 is a field for transmitting a command for controlling t~ran.smission power of uplink channels transmitted from the UE to the Node B; the TFCI 114 is a field for transmitting a codeword indicating that transport channels having different data rates are transmitted over the DL-DPCH;
and the Pilot 116 is a field for enabling the UE to measure transmission power of a downlink signal for power control on the received downlink signal. Here, the "lransport channel" refers to a channel serving to connect a physical channel for actually transmitting the data to the upper layer In the W-CDMA system, for a closed-loop transmit antenna array for the PDSCH, the UE receiving the DL-DPCH 111 transmits, to the Node B, weight information acquired by measuring a common pilot channel (CPICH) received from the Node B. That is, upon receiving the CPICH transmitted from the Node B, the UE compensates for its phase difference thereby to detect a weight proper for the maximum receiving power level. The weight information created depending on the detected weight is transmitted to the Node B, and the Node B
applies corresponding weights to respective antennas for the DL-DPCH transmitted to the UE, depending on the weight information of the DL-DPCH and/or PDSCH received from the UE, before transmission.

With reference to FIG_ 2, a description will be made of the downlink and uplink signal flows for the case where the UE receiving the PDSCH is located in a soft handover (or hando$) region. FIG. 2 illustrates downlink and uplink signal flows for the case where a UE receiving a PDSCH is located in a soft handover region, wherein for sirnplicity, only two Node Bs are considered.

In a soft handover (SHO) process, when a UE moves away from a current Node B I
in communication with the UE, and at the same time moves to an area where it can receive signals from an adjacent new Node B2, the UE receives the signals not only from the current Node B I
but also from the new Node B2. In this state, if a quality (or level) of the signal received from the Node BI is less than a predetermined threshold, the UE releases the channei established to the Node B1, and then establishes a new channel to the Node B2 providing high-quality signals, thus performing the handover process. By doing so, it is possible to maintain a call without interruption.

Referring to FIG. 2, a Node B 1 201; which is currently communicated with a UE
211, transmits a PDSCH and a DL-DPCH associated with the PDSCH to the UE 211.
However, a Node B2 203 transmits only the DL-DPCH to the UE 211 when the UE 211 moves to an SHO
region between the Node B 1 201 and the Node B2 203. A set of all the Node Bs set to transmit signals to the UE 211 existing in the SHO region is called an "active set".
That is, the Node B 1 201 transmits both the DL-DPCH and the PDSCH to the UE 211, and Node B2 203 is newly admitted to the active set and transmits only a DL-DPCH to the UE 211_ The UE

broadcasts the UL-DPCHto Node BI 201 and Node B2 203 indiscriminately. In the prior azt, when the UE 211 enters an SHO region, the UE 211 receives CPICHs from node BI
201 and node B2 203 together and measures the signal strengths of the CPICHs to select a primary node B among the Node Bs. The UE 211 transmits the temporary ID of a node B
designated as a primary Node B in the feedback infoanation (FBI) field of a UL DCH. The FBI is 2 fields in length as shown in FIG. IC. Referring to FIG. 1 C, reference numera1501 denotes an S field of the FBI that the UE 211 transmits to the node B when SSDT (Site Selection Diversity Transmission) is employed. Reference numeral 503 denotes a D field of the FBI
that the UE
211 transmits to a Node B when transmission antenna diversity is employed. The S field 501 consists of 0, 1 or 2 bits. If the S field consists of 0 bit, this implies that the SSDT is not used.
If the SSDT is used, the FBI field transmits a codeword representing the temporary ID of a primary Node B_ The D field -503 consists of 0, 1, or 2 bits. Ifthe D field 503 consists of 0 bit, this implies that the transmission antenna diversity is not used. In the case of 1 bit, the transmission antenna diversity is used together with the SSDT, and in the case of 2 bits, ornly the transmission antenna diversity is adopted_ When the UE 211 receiving the PDSCH from the Node Bi 201 exists in the SHO
region, a problem occurs in that the UE 211 receives both the PDSCH and the DL-DPCH from the Node B1 201 but receives only the DL-DPCH from the Node B2 203. Here, the typical reason that the PDSCH does not support the SHO is because compared with the DL-DPCH, the PDSCH transmits data at a relatively high data rate, thus consvming an increased number of channel resources of the Node B. As a result, system capacity is affected. In addition, the W-CDMA mobile communication system may have a timing problem due to non-synchronization between the Node Bs. hz order to support the SHO, the PDSCH shared by a plurality of the UEs requires elaborate scheduling for the time points where it is used by the respective UEs. In light of the scheduling, it is difficult to embody transmissi- -- of the PDSCH from the new Node B to 1 > the UE.

The DL-DPCHs transmitted from the Node BI 201 and the Node B2 203 are received at the UE 211, and then subjected to soft combining. Here, "soft combining"
refers to combining the signals received at the UE through different paths. Therefore, by calculating a phase difference between the CPICHs received from the Node Bs and then compensating for the phase difference, it is possible to reduce the influence of fading and noise, which affect the signals received at the UE 211. Soft combining is available only when the UE
211 receives the same information from the different Node Bs. However, when the UE 211 receives different infonnation from the Node Bs, the received information, though subjected to soft combining, will be recognized as a noise component, restilting in an inciease in the noise component of the signal.

In the process of analyzing the DL-DPCH, the downlink signals transrnitted to the UE
211 from the respective Node Bs, i.e., the Node BI 201 and the Node B2 203, are subjected to soft combining except for the TPC bits 113 shown in FIG IB. The reason that the TPC 113 is analyzed separately rather than being analyzed by soft combining is because the TPCs received at the UE 211 from the respective Node Bs may be different from each other, since the signal received at the Node B1 201 from the UE 211 is high in level while the signal received at the Node B2 203 from the UE 211 is low in Ievel, or vice versa, due to movement of the UE 211.
Tberefore, the TPC 113 is analyzed through a separate TPC analysis algorithm for a plurality of ihe Node Bs, rather than being subjected to soft combining.

With reference to FIG. 2, a description has been made of the downlink and the uplink signals for the case where the UE is located in the SHO region. Next, an operation of a transmit antenna array (TxAA) supporting the SHO will be described with reference to FIG. 3.

FIG. 3 illustrates an operation of a transmit antenna array using the conventional soft handover scheme. Referring to FIG. 3, when a UE 311 is located in an SHO
region during a call, a Node Bl 301 and a Node B2 303 transmitting signals to the UE 311 decrease their transmission power, for soft handover of the call service, and at the same time, the UE 311 calculates weights depending on a phase difference between the CPICHs transmitted from both of the Node Bs so as to maximize SINR (Signal to-Interference+Noise Ratio), and then feeds the weights back to the Node B1 301 and the new Node B2 303 over the DL-DPCH
and the PDSCH of the Node B1 301 and the new Node B2 303_ The UE 311 soft-combines the signals received from the Node B 1 301 and the Node B2 303 with the weights transmitted to the Node Bs over a FBI (Feedback Information) field of an uplink dedicated physical channel (UL-DPCH) shown in FIG. 3, and then, determines the weights so as to maximize the SINR of the soft-combined received signals. That is, since the UE 311 soft-combines the signals received from the Node B1 301 and the Node B2 303 and determines the feedback weights of the received signals so as to mamimize the SINR, a conventional method for applying an optimal weight for the PDSCH, in which only one Node B
in the SHO region, e.g., the Node BI 301 having the highest received signal level should transmit the signals, has the following disadvantages:
If the UE 311 is located in a non-SHO region, the transmit antenna weights for the PDSCH and the DL-DPCH transmitted to the UE 311 are identical to each other.
In other words, the transmit antenna array weight for the PDSCH is determined in association with the DL-DPCH. A change in a ratio of the phase and size of the two antennas for the DL-DPCH causes an equivalent change in the weights, since thePDSCH is transmitted over the same channel. For this reason, for the weight for thePDSCH, the weight for the associated DL-DPCH is used.
However, if the UE 311 is located in the SI-10 region, the transmit antenna arrays for the DL-DPCH ancd, the PDSCH are equally determined using the weights determined by measuring a phase difference between the CPICHs from not only the Node B
transmitting the PDSCH to the UE 311 but also other Node Bs registered in the active set.
Specifically describing this with reference to FIG. 3, the transmit antenna array weight for the PDSCH is determined considering a channel environment between the UE 311 and the Node B
having the highest received signal level, i.e., the Node B1 301, while the transmit antenna array weight for the DL-DPCH is determined considering the channel environment to not only the Node B1 301 having the highest received signal level but also the Node B2 303 in the active set of the UE 311.
As described above, since the transmit antenna weight for the PDSCH according to the conventional SHO scheme is proposed to have the same value as the transmit antenna weight for the DL-DPCH, the above problem occitrs. That is, in the SHO region, the weights transmitted from the Node Bs to the UE 311 are determined considering not only the channel environment between the UB 311 and the Node BI 301 but also the channel environment between the UE 311 and the Node B2 303. Thus, if the intact weights are applied, the PDSCH
will be provided with a weight difference from a weight for the acWal transmit antenna array.
Therefore, the method for applying the same weight to the transmit antenna arrays, as used for the DL-DPCH and the PDSCH in the non-SHO region, cannot be used in the SHO
region.
Accordingly, there has been a demand for an apparatus and method for properly controlling a transmit antenna array for the PDSCH in the SHO region.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide an apparatus and method for controlling a transmit antenna array for a PDSCH by a UE in an SHO region.

It is another object of the present invention to provide an apparatus and method for controlling a transmit antenna array for a PDSCH by determining an optimal weight for a PDSCH diversity scheme by a UE in an SHO region.

It is further another object of the present invention to provide an apparatus and method for controlling a transmit antenna array for a PDSCH using an FBI D-field of a UL-DPCCH by a UE receiving the PDSCH in an SHO region.

It is yet another object of the preserrt invention to provide an apparatus and method for controlling a PDSCH transmit antenna array using different transmit antenna diversity schemes for the PDSCH so as not to be associated with a DL-DPCH by a UE receiving the PDSCH in an SHO region.

It is sthll another object of the present invention to provide an apparatus and method wherein in an SHO region, a Node B transmitting both a PDSCH and a DL-DPCH
uses a transmit antenna array, and other Node Bs transmitting only the DL-DPCH use an open loop transmit antenna diversity scheme such as STTD (Space-Time block coding based Transmit antenna Diversity; open loop transmit diversity).

It is still another object of the present invention to provide an apparatus and method wherein in an SHO region, a Node B transmitting both a PDSCH and a DL-DPCH
uses a transmit antenna array, and other Node Bs transmitting only the DL-DPCH use a smgle antenna without a transmit antenna diversity scheme.

It is sill another object of the present invention to provide a method for switching a transmit antenna diversity mode according to Node Bs when a UE receiving a PDSCH is subject to PDSCH handover in an SHO region_ It is still another object of the present invention to provide a method for transmitting feedback information for aPDSCH and feedback information for a DPCCH over separate UL-DPCCHs when a UE receiving the PDSCH is located in an SHO region.

It is still another object of the present invention to provide a method for properly controlling an E-PDSCH (Enhanced PDSCH) by determining whether data is received over the E-PDSCH from the same Node B on a time-sequence basis in an SHO region.
It is still another object of the present invention to provide a method for previously recognizing a transmission time of aPDSCH, and separately applying a weight to a Node B
transmitting thePDSCH so that the Node B transmitting thePDSCH operates in a transmit antenna array mode in an SHO region.
To achieve the above and other objects, there is provided a Node B apparatus having at least two antennas, for controlling a diversity of data transmitted through the antennas. The apparatus comprises a first spreader for spreading first data and outputting a first spread signal;
a second spreader for spreading second data and outputting a second spread signal; a first multiplier for multiplying a first weight for a first antenna by the first spread signal output from the first spreader, and outputting a first weighted spread signal; a second multiplier for multiplying a second weight for a second antenna by the first spread signal output from the first spreader, and outputting a second weighted spread signal; a third multiplier for multiplying a third weight for the first antenna by the second spread signal output from the second spreader, and outputting a third weighted spread signal; a fourth multiplier for multiplying a fourth weight for the second antenna by the second spread signal output from the second spreader, and outputting a fourth weighted spread signal; a first adder for adding the first weighted spread signal to the third weighted spread signal, and transmitting the added signal through the first antenna; a second adder for adding the second weighted spread signal to the fourth weighted spread signal, and transmitting the added signal through the second antenna; and a weight generator for determining the first to fourth weights from feedback information received from a UE (User Equipment), and providing the determined first to fourth weights to the first to fourth multipliers, respectively.

According to an aspect of the present invention there is provided a Node B
apparatus having at least two antennas, for controlling a diversity of data transmitted through the antennas, comprising a first spreader for spreading first data and outputting a first spread signal, wherein the first data is dedicated physical channel (DPCH) data, a second spreader for spreading second data and outputting a second spread signal, wherein the second data is physical downlink shared channel (PDSCH) data, a first multiplier for multiplying a first weight for a first antenna by the first spread signal output from the first spreader, and outputting a first weighted spread signal, a second multiplier for multiplying a second weight for a second antenna by the first spread signal output from the first spreader, and outputting a second weighted spread signal, a third multiplier for multiplying a third weight for the first antenna by the second spread signal output from the second spreader, and outputting a third weighted spread signal, a fourth multiplier for multiplying a fourth weight for the second antenna by the second spread signal output from the second spreader, and outputting a fourth weighted spread signal, a first adder for adding the first weighted spread signal to the third weighted spread signal, and transmitting the added signal through the first antenna, a second adder for adding the second weighted spread signal to the fourth weighted spread signal, and transmitting the added signal through the second antenna, and a weight generator for determining the first to fourth weights from feedback information received from a UE (User Equipment), and 8a providing the determined first to fourth weights to the first to fourth multipliers, respectively.
According to another aspect of the present invention there is provided an apparatus for controlling a diversity of data transmitted from a Node B in a UE which is on a soft handover process between a first Node B which transmits a downlink shared channel signal and a dedicated channel signal and a second Node B, which transmits the dedicated channel signal, comprising a first.despreader for despreading a signal received from the first Node B with a first spreading code and outputting a first despread signal, a second despreader for despreading the signal received from the second Node B
with a second spreading code and outputting a second despread signal, a transmit antenna array (TxAA) weight generator for generating a TxAA weight for applying to th2 downlink shared channel and the dedicated channel by receiving the first despread signal and the second despread signal wherein, the TxAA weight is determined more by the first Node B than by the second Node B, and a transmitter for generating feedback information including the TxAA weight and transmitting the generated feedback information to the first Node B and the second Node B.
According to another aspect of the invention there is provided a method for controlling a transmit antenna array for a Physical Downlink Shared Channel, PDSCH, in a mobile communication system, the system having a first Node B (401), a second Node B (403) and a User Equipment, UE (411), the first Node B (401) transmitting the PDSCH
signal and a Dedicated Physical Channel, DPCH, signal and the second Node B
(403) transmitting the DPCH signal, comprising the steps of:
if the UE (411) is on the soft handover process between the first Node B(401) currently in communication with the UE (411) and the second Node B (403), transmitting a DownLink Dedicated Physical Channel, DL-DPCH, established to the UE (411) from the second Node B (403) to the UE (411) in a Space Time block coded Transmit Diversity, STTD, mode or a Single Antenna, SA, mode; and determining, by the UE (411), weights by receiving a common pilot channel, CPICH, signal from the first Node B (401), and transmitting the determined weights as weight information of an uplink dedicated physical channel, UL-DPCH, for the first Node B (401).
According to a further aspect of the invention there is provided a method for controlling a transmit antenna array for a Physical Downlink Shared Channel, PDSCH, in 8b a mobile communication system, the system having a first Node B (421), a second Node B (423) and a User Equipment, UE (431), the first Node B(421) transmitting the PDSCH
signal and a Dedicated Physical Channel, DPCH, signal and the second Node B
(423) transmitting the DPCH signal, comprising the steps of:
if the UE (431) is on the soft handover process between the first Node B(421) currently in communication with the UE (431) and the second Node B (423), transmitting Downlink Dedicated Physical Channels, DL-DPCHs, from the first and second Node Bs (421, 423) to the UE (431) in a Space Time block coded Transmit Diversity, STTD, mode or a Single Antenna, SA, mode;
transmitting a PDSCH signal from the first Node B(421) to the UE (431) in a Transmit Antenna Array, TxAA, mode; and determining, by the UE (431) , weights by receiving the PDSCH signal from the first Node B (421), and transmitting the determined weights as weight information of an Uplink Dedicated Physical Channel, UL-DPCH, for the first Node B(42I ).
According to a further aspect of the invention there is provided a method for controlling a transmit antenna array for a Physical Downlink Shared Channel, PDSCH, in a mobile communication system, the system having a first Node B (441), a second Node B (443) and a User Equipment, UE (451), the first Node B(441) transmitting the PDSCH
signal and a Dedicated Physical Channel, DPCH, signal the second Node B (443) transmitting the DPCH signal, comprising the steps of:
if the UE (451) is on the soft handover process between the first Node B(441) currently in communication with the UE (451) and the second Node B (443), transmitting a PDSCH established to the UE (451) from the first Node B(441) to the UE (443) in an Space Time block Transmit Diversity, STTD, mode or a Single Antenna, SA, mode;
transmitting Downlink Dedicated Physical Channels, DL-DPCHs, established to the UE (451) from the first and second Node Bs (441, 443) to the UE (451) in a Transmit Antenna Array, TxAA, mode;
determining, by the UE (451), weights of Uplink Dedicated Physical Channels, UL-DPCHs, for the first and second Node Bs (441, 443) depending on a phase difference between a first Common Pilot Channel, CPICH, signal received from the first Node B
(441) and a second CPICH signal received from the second Node B (443), and transmitting the determined weight information as weight information of the UL-DPCHs for the first and second Node Bs (441, 443).

8c According to a further aspect of the invention there is provided a method for controlling a transmit antenna array for a Physical Downlink Shared Channel, PDSCH, in a mobile communication system, the system having a first Node B (461), a second Node B (463) and a User Equipment, UE (471), the first Node B (461) transmitting the PDSCH
signal and a Dedicated Physical Channel, DPCH, signal the second Node B (463) transmitting the DPCH signal, comprising the steps of:
if the UE (471) is on the soft handover process between the first Node B (461) currently in communication with the UE (471) and the second Node B (463), transmitting a PDSCH established to the UE (471) from the first Node B (461) to the UE
(463) in an Transmit Antenna Array, TxAA, mode;
transmitting Downlink Dedicated Physical Channels, DL-DPCHs, established to the UE (471) from the first and second Node Bs (461, 463) to the UE (471) in the TxAA
mode;
determining, by the UE (471), weights for DPCHs of the first and second Node Bs (461, 463) depending on a phase difference between a first Common Pilot Channel, CPICH, signal received from the first Node B (461) and a second CPICH signal received from the second Node B (463), and weights for the PDSCH by receiving the PDSCH
signal from the first Node B (461);
transmitting, by the UE (471), the determined weights for the PDSCH as weight information for the PDSCH through a Feedback Information, FBI, field of a first Uplink Dedicated Physical Control Channel, UL-DPCCH; and transmitting, by the UE (471), the determined weights for DPCHs as weight information for the UL-DPCHs of the.first and second Node Bs (461, 463) through a FBI
field of a second UL-DPCCH.
According to a further aspect of the invention there is provided a method for controlling a transmit antenna array for a Physical Downlink Shared Channel, PDSCH, in a mobile communication system, the system having a first Node B (481), a second Node B (483) and a User Equipment, UE (491), the first Node B(48I) transmitting the PDSCH
signal and a Dedicated Physical Channel, DPCH, signal and the second Node B
(483) transmitting the DPCH signal, comprising the steps of:

if the UE (491) is on the soft handover process between the first Node B (481) currently in communication with the UE (491) and the second Node B(483), 8d determining, by the UE (491), weight information by summing up Downlink Dedicated Physical Channel, DL-DPCH, signals received from the first and second Node Bs (481, 483);
comparing, by the UE (491), pilot signal levels of Common Pilot Channels, CPICHs, received respectively from the first and second Node Bs (481, 483), and determining a primary Node B depending on the compared results;
transmitting an Identification, ID, of the determined primary Node B from the UE
(491) to other Node Bs except the primary Node B; and applying, by the primary Node B, a Transmit Antenna Array, TxAA, mode to the UE (491) in the same manner as when the UE (491) is located in a nonsoft handover, non-SHO, region.
According to a further aspect of the invention there is provided a method for controlling a transmit antenna array for a Physical Downlink Shared Channel, PDSCH, in a mobile communication system, the system having a first Node B (461), a second Node B (463) and a User Equipment, UE (471), the first Node B(461) transmitting the PDSCH
signal and a Dedicated Physical Channel, DPCH, signal and the second Node B
(463) transmitting the DPCH signal, comprising the steps of:
if the UE (471) is on the soft handover process between the first Node B (461) currently in communication with the UE (471) and the second Node B (463), newly establishing, by the UE (471), a second Uplink Dedicated Physical Control Channel, UL-DPCCH, to the first Node B (461) in addition to a first UL-DPCCH previously established to the first Node B(461);
transmitting weight information of a Downlink Dedicated Physical Channel, DL-DPCH, through a Feedback Information, FBI, field of the first UL-DPCCH (465) by the UE (471); and transmitting weight information of a PDSCH through an FBI field of the second UL-DPCCH (467) by the UE (471).
According to a further aspect of the invention there is provided a method for controlling a transmit antenna array for a Physical Downlink Shared Channel, PDSCH, in a mobile communication system, the system having Node Bs and a User Equipment, UE, being on the soft handover region, comprising the steps of_ determining (913), by a UE, whether an Enhanced PDSCH, PDSCWE-DSCH, signal is received in a Transmit Antenna Array, TxAA, mode;

8e upon receipt of the PDSCH/E-DSCH signal, selecting a Node B having a best channel condition, and assigning a weight for the selected Node B;
upon receipt of data from the same Node B on a time-sequence basis, controlling (915) a TxAA feedback information register operation mode;

after controlling the TxAA feedback information register operation mode, additionally creating (919) the PDSCH/E-DSCH depending on result data before the data is received, and feeding back the created PDSCH/E-DSCH; and switching (911) the operation mode back to the TxAA mode, if receiving the PDSCH/E-DSCH from the Node B is completed.
According to a further aspect of the invention there is provided a method for controlling a transmit antenna array for a Physical Downlink Shared Channel, PDSCH, in a mobile communication system, the system having Node Bs and a User Equipment, UE, being on the soft handover region between a serving Node B currently in communication with the UE and other Node Bs in an active set, the serving Node B
transmitting the PDSCH signal and a Dedicated Physical Channel, DPCH, signal and the other Node Bs transmitting the DPCH signal, comprising the steps of:
transmitting information on a transmission start point of the PDSCH over a specific channel from the serving Node B to the UE, a predetermined number of slots ahead of the transmission start point of the PDSCH;

upon receipt of the specific channel, by the UE, detecting (913) the PDSCH
transmission start information and creating weights for a PDSCH of the serving Node B;
by the UE, feeding back (919) Uplink Dedicated Physical Control Channel, UL-DPCCH signals to respective Node Bs in the active set depending on received PDSCH
and DPCH signals; and maintaining (911), by the serving Node B, a Transmit Antenna Array, TxAA, mode depending on the UL-DPCCH signal fed back from the UE.
According to a further aspect of the present invention there is provided a method for controlling Node B having at least two antennas and controlling a diversity of data transmitted through the antennas, comprising the steps of determining first to fourth weights from feedback information received from a UE, generating a first spread signal by spreading first data, wherein the first data is dedicated physical channel (DPCH) data, generating a second spread signal by spreading second data, wherein the second data is 8f physical downlink shared channel (PDSCH) data, generating a first weighted spread signal by multiplying a first weight for a first antenna by the first spread signal, generating a second weighted spread signal by multiplying a second weight for a second antenna by the first spread signal, generating a third weighted spread signal by multiplying a third weight for the first antenna by the second spread signal, generating a fourth weighted spread signal by multiplying a fourth weight for the second antenna by the second spread signal, adding the first weighted spread signal to the third weighted spread signal, and transmitting the added signal through the first antenna, and adding the second weighted spread signal to the fourth weighted spread signal, and transmitting the added signal through the second antenna.

According to a further aspect of the present invention there is provided a UE
for controlling a diversity of data transmitted from a Node B in a UE which is on a soft handover process between a first Node B which transmits a downlink shared channel signal and a dedicated channel signal and a second Node B which transmits the dedicated channel signal, comprising the steps of despreading a signal received from the first Node B with a first spreading code and outputting a first despread signal, despreading the signal received from the second Node B with a second spreading code and outputting a second despread signal, generating a TxAA weight for applying to the downlink shared channel and the dedicated channel by receiving the first despread signal and the second despread signal, wherein the TxAA weight is determined more by the first Node B than by the second Node B, and generating feedback information including the TxAA
weight and transmitting the generated feedback information to the first Node B and the second Node B.

According to another aspect of the present invention there is provided an apparatus for controlling a diversity of data transmitted from a Node B in a UE which is on a soft handover process between a first Node B which transmits a downlink shared channel signal and a dedicated channel signal and a second Node B which transmits the dedicated channel signal, comprising:

a first despreader for dispreading a signal received from the first Node B
with a first spreading code and outputting=a first despread signal;
a second despreader for dispreading the signal received from the second Node B
with a second spreading code and outputting a second despread signal;
a transmit antenna array (TxAA) weight generator for generating a TxAA weight for 8g applying to the downlink shared channel and the dedicated channel by receiving the first despread signal and the second despread signal, wherein the TxAA weight is determined by the first Node B; and a transmitter for generating feedback information including the TxAA weight and transmitting the generated feedback information to the first Node B and the second Node B.
According to another aspect of the invention there is provided a UE control method for controlling a diversity of data transmitted from a Node B in a UE
which is on a soft handover process between a first Node B which transmits a downlink shared channel signal and a dedicated channel signal and a second Node B which transmits the dedicated channel signal, comprising the steps of:
despreading a signal received from the first Node B with a first spreading code and outputting a first despread signal;
despreading the signal received from the second Node B with a second spreading code and outputting a second despread signal;
generating a TxAA weight for applying to the downlink shared channel and the dedicated channel by receiving the first despread signal and the second despread signal, wherein the TxAA weight is determined by the first Node B; and generating feedback information including the TxAA weight and transmitting the generated feedback information to the first Node B and the second Node B.

BRIEF DESCRIPTION OF THE DRAWINGS
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:
FIG 1 A illustrates a structure of the PDSCH used in a mobile communication system;
FIG. 1 B illustrates a structure of the DL-DPCH assigned to the UE in association with the PDSCH;
FICz 2 illustrates downlink and uplink signal flows for the case in which a UE
receiving a PDSCH is located in a soft handover region;

8h FIG. 3 illustrates an operation of a transmit antenna array using the conventional soft handover scheme, FIG 4A illustrates a transmit diversity control process according to a first embodiment of the present invention;
FIG. 4B illustrates a transmit diversity control process according to a second embodiment of the present invention;
FIG. 4C illustrates a transmit diversity control process according to a third embodiment of the present invention;
FIG. 4D illustrates a transmit diversity control process according to a fourth embodiment of the present invention;
FIG 4E illustrates a transmit diversity control process according to a fifth embodiment of the present invention;
FIG. 4F illustrates an internal structure of a transmit antenna array channel measurer for perforniing the different embodiments of the process of the present invention;
FIG. 5 illustrates a flow chart of a procedure for the transmit diversity control process shown in FIG. 4A;
FIG. 6 illustrates a structure of a. UE for performing the transmit diversity control process shown in FIG. 4A;
FIG. 7 illustrates a structure of a UE for performing the transmit diversity control process shown in FIG. 4D;
FIG. 8 illustrates a structure of a Node B for performing the transmit diversity control process shown in FIG. 4D; and FIG. 9 illustrates a flow chart of a procedure for transmitting PDSCH/E-DSCH
on the basis of a transmission time point according to a seventh embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

FIG. 4A illustrates a transmit diversity control process according to a first embodiment of the present invention. FIG. 4B illustrates a transmit diversity control process according to a second embodiment of the present invention_ FIG. 4C illustrates a transmit diversity control process according to a third embodiment of the present invention. FIG. 4D
illustrates a transmit diversity control process according to a fourth embodiment of the present invention. FIG. 4E illustrates a transmit diversity control process according to a fifth embodiment of the present invention. FIG. 4F illustrates an intemal structure of a transmit antenna array channel measurer for performing different embodiments of the present invention.
In descnbing FIGs. 4A to 4F, the number of Node Bs registered in the active set is shown as 2, for simplicity. The Node B used in the asynchronous W-CDMA system has the same operation as a BTS (Base station Transceiver Subsystem) in the synchronous CDMA-2000 system.

Referring to FIG. 4A, a Node B 1 401, a Node B currently communicating with a UE
411, transmits both a DL-DPCH and a PDSCH to the UE 411. A Node B2 403, a Node B newly added to an active set of the UE 411, transmits only the DL-DPCH to the UE 411 when the UE
411 is located in an SHO region. The UE 411 receives both thePDSCH and the DL-DPCH from the Node B1 401, but it receives only the DL-DPCH from the Node B2 403. The UE

transmits FBI (Feedback information) included in the UL-DPCH to the Node B1 In FIG. 4A, the UE 411 is located in the SHO region, and enables a new Node B, i.e., the Node B2 403 in the active set to transmit the DL-DPCH signal in a STTD
(Space-Time block coded Transmit Diversity) mode or a single-antenna (SA) mode, even though a transmit antenna array (TxAA) mode is available.

The STTD, a type of open loop antenna diversity scheme, is not subject to a feedback operation, so that there is noPDSCH signal loss due to soft combining on the CPICHs from both of the Node Bs. In addition, since the SA uses a single antenna, it does not use diversity. Among the DL-DPCCH information, TxAA weight information on an FBI D-field is actually valid only for the Node B1 401. Therefore, the weight information is calculated depending on the CPICH
transmitted from the Node B 1 401. This is because in the conventional SHO
scheme, the UE
411 enables both the current Node B1 401 and the Node B2 403, newly added to the active set, to perform TxAA transmission, calculates weights from the information determined by combining the information received from the Node B1 401 and the Node B2 403, and applies the calculated weights asPDSCH weights of the Node BI 401. Therefore, the present invention can resolve the problem that in the conventional system, the TxAA operation for thePDSCH
does not show proper performance in the SHO region due to a difference between the actual weights and the calculated weights, when thePDSCH, the transmit antenna weight of which is set to the same value of those of the DL-DPCH, is equally used in both the Node B 1 401 and the Node B2 403.

Therefore, when thePDSCH being transmitted from the Node B1 401 has been completely handed over to the Node B2 403, the DL-DPCH from the Node B2 403 is transmitted in the TxAA mode along with thePDSCH as shown in FIG_ 4A, and the DL-DPCH
left in the Node BI 401 is switched from the TxAA mode to the STTD or SA mode_ Meanwhile, if the SA mode and the STTD mode can be used together in the same Node B, it is preferable to use the STTD mode rather than the SA mode_ This is because the STTD scheme has a diversity effect equal to or better than that of the TxAA scheme, unless the data rate is extremely low.

-II-Even though the data rate is low, the S1TD scheme, compared with the TxAA
scheme, suffers from a decrease in SINR of a maximum of 2dB, but has a simpler hardware structnre.

Meanwhile, in the first embodiment of the present invention, as illustrated in Table 1 in which a switching operation of the UE 411 is shown by table information at a PDSCH
receiving point in the SHO region, the DPCHs of the Node Bs other than thePDSCH serving cell transnut signals in the STTD or SA mode, while tbePDSCH and DPCH of thePDSCH
serving cell continue to operate in the TxAA mode. That is, the UE 411 receives TFCI of the DPCH, the TFCI including thePDSCH transmission start information from thePDSCH
serving cell, 5 slots before thePDSCH is transmitted. Upon receiving the TFCI from thePDSCH serving cell, the UE 411 can recognize that thePDSCH will be received prior to its transmission.
Therefore, the UE 411 separately creates weights proper only for thePDSCH
serving cell, at predetermined time slots before thePDSCH is received, and then feeds back the created weights using the FBI of the UL-DPCH.
More specifically, the UE in the SHO red on receives the DPCH, or the DPCH
with the PDSCH according to the transmission condition. Upon receiving the PDSCH
along with the DPCH from the Node B, the UE feeds back the FBI of the UL-DPCH to the respective Node Bs in the active set. Then, the Node B transmitting the DPCH including thePDSCH
continues to operate in the TxAA mode using the FBI information, while the other Node Bs simply transmitting only the DPCH do not use the FBI information and enable their DPCHs to operate in the STTD or SA mode. The SA mode inchides the TxAA mode where the diversity gain is not obtained by disregarding the FBI or using the previous value. In addition, after transnission of thePDSCH is completed, a mode of the non-DSCH serving cell having been operating in the STTD or SA mode retums to the TxAA mode, and the UE returns to a pre-DSCH
transmission state where the UE calculates weights using the phase difference between the CPICHs transmitted from the Node Bs and then feeds back the calculated weights to the Node Bs_ Table I
Transmission Determination of PDSCH DPCH in the DPCH in the non-Condition FBI PDSCH cell PDSCH cell PDSCH+DPC PDSCH cell FBI is FBI is used. STTD/SA
H used.
Only DPCH AII cells FBI is used_ Here, the STTD scheme is a type of open loop-mode antenna transit diversity scheme, and if STI'D encoding is performed on a da#a signal A having a format constructed such that symbols Sl and S-, are sequentially input in transmit diversity encoding periods TI and T2, respective, then the consecutive symbols SISZ are output as S1S2 through a first antenna and as -SZ*S,* through a second antenna. The-above-stated symbol STTD encoding will be described again in a channel bit unit_ As described in the STTD encoding, if it is assumed that the symbols S1 and S2 received in the transnut diversity encoding periods are created with channel bits bpbl and b2b3, respectively, then the received symbols S,SZ become the channel bits bablb2b3. After the channel bits boblb2b3 are subject to the STTD encoding, the channel bits boblb2b3 (S1S2) are output through the first antenna and the channel bits -bZb3bo bt (-SZ*Si*) are output through the second antenna. Herein, the first antenna is a reference antenna and the second antenna is a diversity antenna_ Referring to FIG. 4B, if a UE 431, to which a downlink channel includin.g the PDSCH
is connected, enters the SHO region, the DL-DPCH is transmitted in the STTD or SA mode in both a Node BI 421 and a Node B2 423. ThePDSCH being transmitted by only the Node B1 421 is transmitted in the TxAA mode. That is, by using the TxAA only for thePDSCH used for data transmission despite performance degradation of the DL-DPCH, an overall loss of thePDSCH signal is decreased, malang it possible to ensure reliable data transmission. Here, a dedicated pilot channel included in the DL-DPCH from the Node B2 421 should additionally include information forPDSCH demodulation. As for the dedicated pilot channel, a method for additionally including the infoiination for thePDSCH demodulation includes TDM
(Time Division Muttiplexing)/CDM (Code Division Multiplea-ing)/FDM (Frequency Division Multiplexing)/Space Time Coded-DM/additional or field modifying methods. It is preferable to consider using the TDM, given that the UE receiving thePDSCH has a low data rate.

In the second embodiment of the present invention, as i7lustrated in Table 2 in which a switching operation of the UE 431 is shown by table information at aPDSCH
receiving point in the SHO region, the DL-DPCH is ttansmitted in the STTD or SA mode in both the Node B1 421 and the Node B2 423, while thePDSCH being transmitted by only the Node BI
421 is transmitted in the TxAA mode using the FBI of the UL-DPCH. Here, the UB 431 receives TFCI
including the transmission start information from thePDSCH serving ceIl, 5 slots before thePDSCH is transmitted, and then recognizes that thePDSCH will be received pnor to its transmission. Therefore, the UE 411 creates weights proper only for thePDSCH
serving cell, at predetermined time slots before thePDSCH is receivect and then feeds back the created weights.

In addition, if only the DPCH is received after completion of transmitting thePDSCH, the UE
returns to a pre-DSCH transmission state.

Table 2 Transmission Determination of PDSCH DPCH in the DPCH in the non-Condition FBI PDSCH cell PDSCH cell PDSCH+DPC PDSCH cell FBI is STID/SA
H used.
DPCH All cells FBI is used.
Referring to FIG. 4C, if a UE 451 receiving the PDSCH from a Node Bl 441 enters the SHO region, the Node BI 441 transmittuig thePDSCH is set to operate in the STTD or SA
mode, even though thePDSCH has operated in the TxAA mode. Of course, in this case, the DL-DPCH operates in the TxAA mode in both the Node BI 441 and the Node B2 443.
ThePDSCH
will show better performance in the TxAA mode than in the STTD or SA mode.
However, in the SHO region, since the TxAA scheme applies the weights calculated from the two Node Bs, i.e., the Node B1 441 and the Node B2 443, the weights are different from the weights to be actually applied, thus ca.using an improper weight application problem, and additionally there occurs a feedback error and delay error, decreasing the performance compared with the SA
scheme. Therefore, it is preferable to operate the PDSCH in the STTD or SA
mode rather than in the TxAA mode. In this case, however, by using the TxAA for the DPCH, it is possible to obtain better performance for the DPCH having the high throughput and QoS
(Quality of Service).

In the third embodiment of the present invention, as illustrated in Table 3 in which a switching operation of the UE 451 is shown by table information at a PDSCH
receiving point in the SHO region, the DL-DPCH is transmitted in the TxAA mode in both the Node B1 441 and the Node B2 443, while thePDSCH being transnutted by only the Node B 1 441 is transmitted in the STTD or SA mode. Here, the UE 451 calculates weights depending on a phase difference between the CPICHs transmitted from the Node Bs in the same manner. In addition, if only the DPCH is received after completion of transmitting the PDSCH, the UE returns to a pre-DSCH
transmission state_ Table 3 Transmission Determination of PDSCH DPCH ui the DPCH in the non-Condition FBI PDSCH cell PDSCH cell PDSCH+DPC All cells STTA/S FBI is used_ H A
DPCH All cells FBI is used.

Referring to FIG. 4D, if a UE 471 enters the SHO region, the UE 471 creates an additional separate FBI field#2 for thePDSCH in the UL-DPCCH and transmits the created FBI
field##2 to the Node BI 461. That is, the UE 471 calculates two different weights and transmits the created weights with FBI field#1 for the DPCH and FBI field42 for thePDSCH
in the UL-DPCH. The method for additionally creating the FBI field includes TDM/CDM/FDM/additional or field modifying methods. It is preferable to use TDM, given that the UE
receiving thePDSCH
has a low data rate.

The method for separating the FBI field into the FBI field41 and the FBI
field#2 by TDM multipleiting is shown in Table 5. In the conventional method shown in Table 4, one FBI field is used, so that I and Q values of the weight symbols are alternately transmitted on a t-vvo-slot unit basis. However, in Table 6 according to an embodiment of the present invention, two symbols are continuously transmitted in a manner of lo, II, Qo, Ql.
Herein, Io+Qo is a TxAA
weight symbol for the DL-DPCH, and 11+Q1 is a TxAA weight symbol for the PDSCH. It is assumed in Table 5 that a ratio of weight information of the DL-DPCH to weight information of the PDSCH is 1:1. The ratio can be changed according to the operation mode and the channel environment. In addition, Table 6 shows a slot format used when the weights of the different Node Bs are sent using the FBI field of the PDSCH. In this case, it is necessary to additionally set a field for transmitting the TxAA weights in the UL-DPCCH. The additional field is implemented by using an SSDT field (S field of the FBI) or a pilot field.

Table 4 Slot D

Fiel Io Q. Io Q. lo Qo 1o Q. 1o Qo lo Qo lo Qo Io d Table 5 Slot D

Fiel Io 1i Qo Q, 10 1i Qo Qi l0 1i Qo Qt l0 1i Qo d Table 6 Slot D, Fiel Io Qo 1o Qo Io Qo Io Qo lo Qo 1o Qo lo Qo lo d D, Fiel Ii Q- li Q, 11 Q, 1i Qi 11 Q, 11 Q, 11 Qi li d In the fourth embodiment of the present invention, as illustrated in Table 7 in which a switching operation of the UE 471 is shown by table information at a PDSCH
receiving point in the SHO region, FBII for the DL-DPCH transmitted by both the Node B 1461 and the Node B2 463 and FBI2 for the PDSCH transmitted by only the Node BI 461 are additionally fed back usmg the TDM/CDiV1/FDM/additional or field modifying method. In addition, if only the DPCH
is received after completion of transmitting the PDSCH, the UE returns to a pre-DSCH
transmission state.

Table 7 Transmission Determination of FBI PDSCH DPCH in the DPCH in the non-Case PDSCH cell PDSCH cell PDSCH+ FBII: PDSCH cell FBI1 is FBI2 is used_ DPCH FBI,: All cells used DPCH FBI: All cells FBI is used.

Referring to FIG. 4E, if a UE 491 enters the SHO region, i.e., if thePDSCH
transmitted by a Node B1 481 enters the SHO region, a method for applying a transmit weight for thePDSCH operates in the same manner as the conventional method, but it identifies a primary. Node B using SSDT signaling and then determines whether to increase or maintainPDSCH transmission power before transnission. Of course, the weights for the transmit diversity are used by the PDSCH as well as the DL-DPCH in the two Node Bs in t.he same manner as the conventional method.

The SSDT signaling should be used not only when the SSDT is used but also when the DL-DPCH including thePDSCH enters the SHO region. Upon receiving primary cell information through the SSDT signaling, the Node BI 481 transmits thePDSCH
without additionally increasing the transmission power. Upon receiving non-primary cell information, the Node B 1 481 applies a power offset to thePDSCH before transmission. For the transmission power offset, a transnussion power offset hi-gher than when thePDSCH uses the TxAA scheme is used. In conchision, a transmit diversity offset for the SA scheme, a transmission power offset for the STTD scheme and a transmission power offset for the TxAA scheme should be set to have independent values according to the transmit diversity mode of thePDSCH.

An operating principle of the SSDT will be described below. In the SSDT , the UE
491 located in the SHO region assigns temporary IDs (identifications) to the respective Node Bs in its active set, i_e., the Node B1 481 and the Node B2 483, and then, selects a Node B capable of better satisfying the received signal quality of the UE 491 among the Node Bs. Only the selected Node B, e.g., the Node B1 481, transmits the DL-DPDCH to the UE 491, and the Node B2 483 except the selected Node B 1 481 transmits only the DL-DPCCH to the UE
491, thereby reducing interference signals generated when all the Node Bs in the active set operate an operation for supporting the SHO. In the SSDT, the Node B transmitting the DL-DPDCH is called a primary Node B, and the primary Node B is periodically updated depending on information measured by the UE 491. To update the primary Node B, the UE 491 transmits the temporary ID of the primary Node B to the other Node Bs in the active sets.

The method for controlling transmission power of PDSCH to which the transmit diversity scheme is applied using the SSDT signaling will be described again in detail with reference to FIG. 4E. Upon receiving CPICHs transmitted from the Node BI 481 and the Node B2 483, the UE 491 compares pilot signal levels of the received CPICHs and determines the primary Node B depending on the compared results. Further, the UE 491 transmits the temporary ID previously set for the determined primary Node B to the other Node Bs, i.e_, the Node B2 483 _ In FIG. 4E, the Node BI 481 is a Node B transmitting the DL-DPCH
and the PDSCH to the UE 491, and the Node B2 483 is a Node B newly added to the active set, which transniits only the DL-DPCH to the UE 491.

If the UE 491 transmits the temporary ID for the primary Node B, the Node B1 determines the transmission power of the PDSCH by applying the TPC bits of the DL-DPCH, and transmits the signals at the normal transmission power considering that an influence due to the TxAA weights is minimized. That is, whether to increase or decrease the transmission power of the PDSCH is determined depending on the TPC bits transmitted by the UE 491. As a result, when the Node B 1 481 becomes the primary Node B, a transmission power control operation including the TxAA operation of the PDSCH is performed in the same manner as when the UE 491 is located in the non-SHO region.
If the Node B 1 481 having been serving as the primary Node B is redefined as a secondary Node B and the Node B2 483 having been servi.ng as the secondary Node B is redefined as the primary Node B, the Node B 1 481 estimates that the distance from the UE 491 has increased or the channel environment is bad, applies a fixed transmission power offset to the transmission power of the PDSCH and transmits it to the UE 491. Thereafter, in the period where information on the primary Node B is updated, the Node B controls transniission power of thePDSCH depending on the TPC bits transmitted by the UE 491. However, it should be noted that when the TxAA scheme is used for thePDSCH in the SHO region, different values must be used for the fixed transmission power offset according to the diversity modes.
Next, a transmit diversity control method according to a sixth embodiment of the present invention will be described. In the sixth embodiment of the present invention, if the UE
receiving the PDSCH exists in the SHO region and the Node B transinitting the PDSCH
transmits the PDSCH using the closed-loop transmit antenna diversity, the UE
additionally assigns a new UL-DPCCH. Here, the UL-DPCCH transmitted to the Node B when the UE first uses thePDSCH will be referred to as "UL-DPCCHI" and the additional UL-DPCCH
newly added when the IJE is located in the SHO region will be referred to as "'UL-DPCCH2".

Under the 3rd generation mobile communication standard, a W-CDMA standard, the UL-DPCCHs used by the UE are spread with the first OVSF (Orthogonal Variable Spreading Factor) code, i.e., an OVSF code having all 1-coded bits, among 256 SF=256 OVSF codes having a length of 256, and is transnutted by the UE through the Q channel by necessity. The reason that the UL-DPCCH is transmitted over the Q channel is to continuously transmit the UL-DPCCH even when the UE has no uplink data to transmit after a call setup, under the W-CDMA standard, and thus prevent discontinuous transmission of the uplink signal, thereby - 1g-preventing electromagnetic interference. The UL-DPDCH transmitted along with the UL-DPCCH can use a spreading factor of 4 to 256. It is possible to transmit a maximum of 6 UL-DPDCHs. When the 6 UL-DPDCHs are all used, a spreading factor SF=4 is used: 3 UL-DPDCHs are transtnitted through the I cbannel and the remaining 3 UL-DPDCHs are transmitted through the Q channel. Since the data received over the I channel and the data received over Q channels can be independently analyzed at the receiver, there is no interference between the UL-DPDCHs caused by using the same OVSF code in the I channel and the Q
channel. In using the new additional UL-DPCCH, the UE can determine the OVSF
code to be used for the UL-DPCCH in various ways.
As a first example, when the current UL-DPCCH, i_e., the UL-DPCCHI, is established, an SF=256 OVSF code baving all 1-coded bits, a basically used OVSF code, is assigned to the newly assigned UL-DPCCH, i_e_, the UL-DPCCH2 and then transmitted through the I channel. As a second example, one of the OVSF codes created in the same OVSF branch as the UL-DPCCH currently used by the UE is selected as the OVSF code to be used for the newly assigned [JL-DPCCH2. As a third example, the SF of the OVSF code to be used for the newly assigned UL-DPCCH2 is changed to 128.

As described above, when the UE receiving the PDSCH communicates with the Node B transmitting the downlink channels using the closed-loop antenna diversity scheme which uses 2 UL-DPCCHs, the conununication between the UE and the Node B is performed as follows. The UE transmits feedback information for controlling a closed-loop antenna gain of the DL-DPCHs transmitted by the Node Bs in the active set of the UE, created as the UE enters the SHO region, through the FBI field of the UL-DPCCH previously used before the UE is located in the SHO region, i.e., the UL-DPCCHI, and the UE transmits the feedback information only for thePDSCH to the Node B transmitting thePDSCH, over the FBI field of the newly used UL-DPCCH, i.e., the UL-DPCCH2, thereby properly controlling the respective antenna transmission gains for thePDSCH. As a result, the UE can obtain a sufficient closed-loop antenna diversity gain while receiving thePDSCH. As described above, the UL-DPCCHI
can be used in transmitting the feedback information for controlling an antenna transmit parameter of the DL-DPCH. Alternatively, it is also possible to transmit feedback information for controlling an antenna transmit parameter of the DL-DPCH over the FBI
field of the newly used UL-DPCCH2.

When the feedback information for the PDSCH and the feedback information for the DL-DPCH are separately transmitted as stated above, the feedback information for thePDSCH
can be created by measuring the CPICH from the Node B transrnitting thePDSCH, measuiing the pilot field of the DL-DPCH, or directly measuring thePDSCH; and the feedback information for the DPCH can be created based on an optimal antenna gain parameter by suinming up the CPICH signals transmitted from the respective Node Bs in the active set of the UE.

Referring next to FIG. 4F, when a Node B1 to which the PDSCH is currently connected is a primary Node B, weights applied to the TxAA scheme are determined depending on a receiving power level of the CPICH received from the Node B1, so that weight factors al and a2 are all set to '1'_ When the Node B1 is not the'primary Node B, the CPICH values are weighted with weight factors al and a2 (where al>a2) in order to increase reliability of the TxAA weights used for thePDSCH, and then provided to a TxAA weight decision device 495.
The TxAA weight decision device 495 differently creates the weights to be provided to aIl the cell in the active set according to the circumstances. A TxAA channel measurement operation by the UE receiving thePDSCH using the proposed TxAA scheme can be represented by, P= (ajIIHjwjj)Z+(aifjH,wjE)z ...........(1) In Equation (1), H, (where i denotes an ID number of the Node B) indicates a channel matrix, w indicates an antenna weight, and a; indicates a weight factor for the Node B;.

FIG. 5 illustrates a flowchart for the transnYit diversity control process shown in FIG.
4A. Referring to FIG. 5, in a state where the UE 411 communicates with the Node BI 401, i_e., where the UE 411 performs normal communication in a non-SHO region (Step 500), the UE
411 determines whether the DL-DPCH with the PDSCH and thePDSCH received from the Node B1 401 operate in the TxAA mode (Step 503). If it is determined that thePDSCH and the DL-DPCH do not operate in the TxAA mode, the UE 411 returns to Step 500.
However, if thePDSCH and the DL-DPCH operate in the TxAA mode, the UE 411 determines whether it is located in the SHO region (Step 505). If it is determined that the UE 411 is located in a non-SHO region, the UE 411 returns to Step 500. If, however, it is determined that the UE 411 is located in the SHO region, the UE 411 determines whether the DL-DPCH of the Node B2 403, i.e., the other Node B except the current Node B1 401 is added to the active set (Step 507).

If it is determined that the DL-DPCH of the Node B2 403 is not added to the active set, the UE 411 proceeds to Step 513. Otherwise, if it is determined that the DL-DPCH of the Node B2 403 is added to the active set, the UE 411 determines whether the Node B
whose DL-DPCH
is added to the active set can operate in the TxAA mode (Step 509). If it is determined that the Node B whose DL-DPCH is added to the active set cannot operate in the TxAA
mode, the UE
411 proceeds to Step 513. If, however, it is determined that the Node B whose DL-DPCH is added to the active set can operate in the TxAA mode, the UE 411 aIlows the Node B whose DL-DPCH is added to the active set to use the STTD or SA mode instead of the TxAA mode (Step 511). Next, the UE 411 determines whether the PDSCH is handed over (Step 513). If it is determined that thePDSCH is not handed over, the UE 411 proceeds to Step 519_ Otherwise, if it is determined that thePDSCH is handed over, the UE 411 determines whether the Node BI
401 uses the TxAA mode (Step 515).

If it is determined that the Node BI 401 does not use the TxAA mode, the UE
proceeds to Step 519. However, if it is determined that the Node B 1 401 uses the TxAA mode, the UE 411 switches the TxAA mode of the Node B1 401 to the STTD or SA mode (Step 517).
Thereafter, the UE 411 determines whether the Node B2 403 can use the TxAA
mode (Step 519). If it is determined that the Node B2 403 canuot use the TxAA mode, the UE 411 retams to Step 500. However, if it is determined that the Node B2 403 can use the TxAA
mode, the UE
411 enables the TxAA mode of the Node B2 403 and then ends the operation (Step 521).

FIG. 6 illustrates a structure of a UE for performing the transmit diversity control process shown in FIG_ 4A. Referring to FIG. 6, an input signal of the UE 411 is received through an antenna 701 and then provided to a down-converter 702. The down-converter 702 down-converts the received signal by mixing it with a composite frequency f.
and provides the dovkm-converted signal to a lowpass fdter (LPF) 703. The lowpass filter 7031owpass-fihers the down-converted signal output from the down-converter 702 and provides the filtered baseband signal to an analog to-digital (A/D) converter 704. The A/D converter 704 converts the analog baseband signal output from the lowpass filter 703 to a digital signal and provides the converted digital signal to a finger# 1.

3 0 In the finger# I, a common processor 705 commonly processes the digital signal output from the A/D converter 704 in the TxAA mode and the STTD mode and provides its output to a switch 706. The switch 706, under the control of a transmit diversity mode selection controller (or transmit diversity mode selection controller for DL-DPCH/PDSCH
during SHO) 710, switches the output of the common processor 705 to a TxAA mode processor 707 or an STTD/SA mode processor 708, and then the switched signals output from the TxAA
mode processor 707 and the STTD/SA mode processor 708 are provided to a digital signal processor (DSP) 709. Here, the transmit diversity mode selection controller 710 operates in accordance with an algorithm shown in FIG. 5. In FIG. 6, a finger#2 and a finger-43 have the same operation as that of the finger# 1_ The DSP 709 processes the digital data for a service required by the UE
411 using the results output from the TxAA mode processor 707 or the STTD/SA
mode processor 708, and transmits the processed data to an upper layer.

FIG. 7 illustrates a structure of a UE for performing the transmit diversity control process shown in FIG. 4D. Referring to FIG. 7, a radio signal in the air is received through an antenna 801 and then provided to a down-converter 802. The down-converter 802 down-converts the received radio signal by multiplying with a predetermined composite frequency f.
and provides its output signal to an LPF 803 _ The LPF 803 lowpass-filters the signal output from the down-converter 802 and provides the lowpass-filtered analog signal to an A/D
converter 804. The A/D converter 804 converts the analog signal output from the LPF 803 to a digital signal and provides the converted digital signal a first finger Finger# 1 and a second finger Finger#2. Here, the first finger is for processing the signals received from the Node B 1 461, while the second is for processing the signals received from the Node B2 463 of FIG. 4D.

In the fingerl, a descramber 805 descrambles the output signal of the A/D
converter 804 by multiplying with a scrambling code C~ 1 for the Node B I 461. A
despreader 806 despreads the output signal of the descrainbler 805 by multiplying it by a spreading code Cpl for the Node B1 461. An accumulator 807 accumulates the output signal of the despreader 806 and provides the accumulated signal to a weight generator 811. The weight generator 811 calculates a weight wA argma~ I wThj ( 2 for ma.~amizing SINR depending on the signal output from the accumulator 807.

In the finger2, a descrambler 808 descrambles the output signal of the A/D
converter 804 by multiplying with a scrambling code CSc~_ for the Node B2 463. A second despreader 809 despreads the output signal of the descrambler 808 by multiplying it by a spreading code C~,Z
for the Node B2 463. An accumulator 810 accumulates the output signal of the second despreader 809 and provides the accumulated signal to an adder 812. The adder 812 adds the output signal of the accumulator 807 to the output signal of the accumulator 810, and provides its output to a weight generator 813. The weight generator 813 calculates a weight wõ"=argmaxl I wrhj 1 2 for maximizing SINR depending on the signal output from the adder 812.

, , . .

FIG_ 8 illustrates a structure of a Node B for perforining the transmit diversity control process shown in FIG. 4D. Referring to FIG. 8, radio signals in the air received from the UE
471 through a first antenna (ANTI) 859 and a second antenna (ANT2) 860 are provided to a demultiplexer (DEMUX) 852. The DEMUX 852 detects feedback information (FBI) from DPCCH signals of the radio signals received through the first and second antennas 859 and 860, and provides the detected feedback information to a weight generator 851. The weight generator 851 generates weights w= I w I exp(j) of complex floating points, i.e., w,,, w12, w21 and w,,, by properly combining the input bits based on the feedback information from the DEMUX 852, and provides the generated weights wD, w12i w21 and w22 to multipliers 855, 856, 863 and 864, respectively.

Meanwhile, a multiplexer (MUX) 853 multiplexes a DPDCH signal and a DPCCH
signal into a DPCH (Dedicated Physical Channel) signal, and provides the DPCH
signal to a multiplier 854. The multiplier 854 multiplies the DPCH signal output from the MUX 853 by a spreading and scrambling code for the Node B1 461, and provides its output signal to the multiplier 855 and the multiplier 856. The multiplier 855 multiplies the weight w], output from the weight generator 851 by the output signal of the multiplier 854, and provides its output to a summer 857. The multiplier 856 multiplies the weight wlZ output from the weight generator 851 by the output signal of the multiplier 854, and provides its output to a summer 85 8.

Further, a multiplier 862 multiplies a PDSCH signal by a spreading and scrambling code for the Node B1 461 and provides its output to the multiplier 863 and the multiplier 864.
The multiplier 863 multiplies the weight %, output from the weight generator 851 by the output signal of the multiplier 862, and provides its output to the summer 857. The multiplier 864 multiplies the weight w2, output from the weight generator 851 by the output signal of the multiplier 862, and provides its output to the summer 858.

The snimner 857 sums up the output signal of the multiplier 855, the output signal of the multiplier 863 and a first common pilot channel signal (CPICHI), and transmits the summed signal through the first antenna 859. The summer 858 sums up the output signal of the multiplier 856, the output signal of the multiplier 864 and a second common pilot channel signal (CPICH2), and transmits the summed signal through the second antenna 860.
Accordingly, it is possible to apply different weights to the DL-DPCH signal and the PDSCH signal based on the feedback information of the UP-DPCCH signal received from the UE 471.

= ~

- ?3 -Meanwhile, in FIGs. 4A to 4F, if the mode switching is performed using FCS
(Fast Cell Selection) information, the enhanced PDSCH (E-PDSCH) supporting the FCS
will operate as follows. Here, the FCS determines from which Node B the UE is to receive data, and provides the Node B with the corresponding information. Therefore, if the UE
determines the Node B which will transmit the E-PDSCH, based on the FCS, then the UE creates weights proper for the E-PDSCH serving cell, and then transmits the created weights to the E-PDSCH
serving cell using the FBI. That is, in the SHO region, the UE previously recognizes an anival time of the E-PDSCH by receiving the TFCI bits inc}uding infonnation on the transmission start point from the E-PDSCH serving cell, and thus switches to the above-stated modes, i.e., the modes of FIGs. 4A to 4F. In other words, the target Node B calculating the weights is dynamically changed according to the Node B determined by the UE.

For example, when E-PDSCH data of two or more frames is consecutively received from the same Node B by consulting the FCS information, the UE can transmit FSM (Finite States Machine, a type of shift register) bit information of the TxAA FBI, beginning at a next bit of the previous bit position, not at the initial bit_ If the UE changed the cell or failed to receive the just previous frame, the UE retransmits the FSM bits from the initial bit.
However, when the UE simply transmits the FMS bit information in the same format like in Mode#1 of 3GPP (or UMTS W-CDMA), it is possible to continuousl.y transmit the FSM bits of the FBI
regardless of whether the cell is determined based on the FCS. In addition, when both the E-PDSCH and the normalPDSCH use the information transrnitted by the E-PDSCH and thePDSCH in the SHO
region, the E-PDSCH and thePDSCH must operate in accordance with the number of slots for transmitting the FBI, required by the TxAA.
FIG. 9 iIlustrates a procedure for transmitting PDSCH/E-PDSCH on the basis of a transmission time point according to a seventh embodiment of the present invention. Referring to FIG. 9, in the SHO region between the Node Bs supporting the TxAA mode, the UE
performs a general DPCH TxAA mode (Step 911). When the UE enters the SHO
region, the UE
determines whether thePDSCH/E-DSCH is received from the Node B in the DPCH
TxAA
mode (Step 913)_ If it is determined that thePDSCH/E-DSCH is not received from the Node B, the UE performs the general DPCH TxAA mode (Step 911). However, if it is determined that thePDSCH/E-DSCH is received from the Node B, the UE repeatedly selects a Node B having a good channel condition'depending on the FCS, thereby increasing the reliability and niinimizing the determination time. That is, in the SHO region, the UE repeatedly selects a Node B having the best channel condition among a plurality of Node Bs from which signals are received, using the FCS, thereby selecting the Node B having the best channel condition. Upon receiving thePDSCH/E-DSCI-I, the UE determines whether data is received from the same Node B on a time-sequence basis (Step 915). If it is detennined that the data is received from the same Node B on a time-sequence basis, the UE maintains a TxAA FBI FSM index in Mode# I
using 2 bits, and initializes the TxAA FBI FSM index to '0' in Mode#2 using 4 bits (Step 917). If the data is received from the same Node B on a time-sequence basis, the UE applies the new data output on the basis of the previous result. However, if the data is not received from the same Node B or received with time delay, the UE applies a new value on the basis of a predetermined offset or the result which was previously applied to another Node B, and then performs PDSCH/E-DSCH
addition, creation and feedback, orPDSCH/E-DSCH mode switching between the TxAA mode and the STTD/SA mode (Step 919)_ Thereafler, the UE detennines whether transmission/reception of thePDSCH/E-DSCH is completed (Step 921). If it is determined that transmission/reception of thePDSCH/E-DSCH is completed, the UE changes its operation mode from the STTD or SA mode to the DPCH TxAA mode (Step 911). Otherwise, if it is detennined that transmission/reception of thePDSCH/E-DSCH is not completed, the UE
determines again whether thePDSCH/E-DSCH is received from the Node B (Step 913).

As descnbed above, in the SHO region, the UE can control a transmit antenna arra.y for the PDSCH, making it possible to apply proper transmit antenna diversity weights. In addition, in the SHO region, the UE can control the transmit antenna array for the E-PDSCI-I/PDSCH, making it possible to apply the proper transmit antenna weights. Further, in the SHO region, the UE can separately apply a transmit antenna weight for the PDSCH and a transmit antenna weight for the DL-DPCH, thereby resolving the problem caused by the conventional SHO scheme that the applied weights are different from the proper transmit antennas weights due to the use of the same transmit antenna weights for the DPSCH and the DL-DPCH.

While the invention has been shown and descnbed 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.

Claims (4)

1. An apparatus for controlling a diversity of data transmitted from a Node B
in a UE which is on a soft handover process between a first Node B which transmits a downlink shared channel signal and a dedicated channel signal and a second Node B
which transmits the dedicated channel signal, comprising:
a first despreader for dispreading a signal received from the first Node B
with a first spreading code and outputting a first despread signal;
a second despreader for dispreading the signal received from the second Node B
with a second spreading code and outputting a second despread signal;
a transmit antenna array (TxAA) weight generator for generating a TxAA weight for applying to the downlink shared channel and the dedicated channel by receiving the first despread signal and the second despread signal, wherein the TxAA weight is determined by the first Node B; and a transmitter for generating feedback information including the TxAA weight and transmitting the generated feedback information to the first Node B and the second Node B.

2. The apparatus as claimed in claim 1, wherein the first despread signal is a DPCH
signal and the second despread signal is a PDSCH signal.

3. A UE control method for controlling a diversity of data transmitted from a Node B in a UE which is on a soft handover process between a first Node B which transmits a downlink shared channel signal and a dedicated channel signal and a second Node B
which transmits the dedicated channel signal, comprising the steps of:
despreading a signal received from the first Node B with a first spreading code and outputting a first despread signal;
despreading the signal received from the second Node B with a second spreading code and outputting a second despread signal;
generating a TxAA weight for applying to the downlink shared channel and the dedicated channel by receiving the first despread signal and the second despread signal, wherein the TxAA weight is determined by the first Node B; and generating feedback information including the TxAA weight and transmitting the generated feedback information to the first Node B and the second Node B.

4. The UE control method as claimed in claim 3, wherein the first despread signal is a DPCH signal and the second despread signal is a PDSCH signal.