Mobile communication apparatus and method including base station and mobile station having multi-antenna

A mobile communication apparatus including a base station and at least two mobile stations, having multiple antennas, respectively is provided. In the mobile communication apparatus, the base station restores from feedback signals transmitted from the mobile stations weight information determined in the mobile stations, generates from the restored weight information downlink control information ensuring maximum throughput to each of the mobile stations, and selects from among data of all of the mobile stations data of a desired mobile station(s) to be transmitted, based on the downlink control information. Each of each of the mobile stations has at least one mobile station antenna, the base station has at least two base station antennas, and the downlink control information includes mobile station selection information, an optimal basis matrix index, and optimal gain indices. As a result, nominal peak throughput in multi-antenna mobile communications can be efficiently achieved at low costs.

FIELD OF THE INVENTION

The present invention relates to mobile communications, and more particularly, to a mobile communication apparatus including multi-antenna base station and mobile stations, which maximizes throughput in a multi-user communication environment based on high-speed downlink wireless packet access, and a mobile communication method therefor.

DESCRIPTION OF THE RELATED ART

Various technologies are used to maximize throughput in mobile communications. As such, logical improvements using new wireless access and physical improvements using, for example, multiple antennas, have attracted more attention than other methods.

First, as an example of a new wireless access based logical improvement, next-generation mobile communication system standardization associations have proposed in recent years new standard packet access technologies enabling high-speed packet transmission via downlinks. The 3rdGeneration Partnership Project (3GPP), an asynchronous standardization association led by Europe and Japan, works for the standardization of high-speed downlink packet access (HSDPA) technology, and the 3GPP2, a synchronous standardization association led by the U.S. works for the standardization of 1× Evolution Data Only/Voice (1×EV-DO/V) technology. The HSDPA and 1×EV-DO/V technologies suitable for-web-based Internet 25 services are based on high-speed downlink packet access for wireless packet transmission. Since high-speed downlink packet access is optimized for peak throughput as well as average throughput, it can achieve peak throughput in an intermittent wireless packet transmission environment. The implementation of such a high-speed downlink packet access technology basically requires an adaptive modulation & coding (AMC) technology, a hybrid automatic request (HARQ) technology, and a multi-user diversity scheduling technology. Basic technologies for high-speed downlink packet access are described in an European IMT-2000 standard, the 3GPP specification available at www.3gpp.org, the 3GPP2 specification available at www.3gpp2.org, and the article “CDMA/HDR: A Bandwidth Efficient High Speed Wireless Data Service for Nomadic Users” by P. Bender, P. Black, M. Grob, R. Padovani, N. Sindhushayana, and A. Viterbi, IEEE Communications, Vol. 38(7), 70-78, July, 2000.

Second, unlike the wireless access improvement method enabling the efficient use of bandwidths within a given range, a physical improvement method using multiple antennas increases bandwidth resources using more spatial resources to maximize throughput. Recently, Lucent Technologies verified through intensive research into BLAST (Bell Labs LAyered Space Time) that the bandwidth is increased min(N,M) times when using N base station antennas and M mobile station antennas compared to when using a single base station antenna and a single mobile station antenna. Here, min(N,M) means the minimum of N and M. This research ensured the effectiveness of using multiple antennas for peak throughput. The principle of increasing the channel capacity using multiples antennas in a base station and mobile stations can be explained based on a matrix rank criterion. The number of paths is determined by the rank characteristic of the matrix H of channel downlink characteristics of multiple base station and mobile station antennas. A rich scatter environment for mobile communications can be created by a number of uncritical obstacles. In such a rich scatter communication environment, the theoretical maximum capacity CMAXof a multi-antenna communication system including a base station and a single mobile station is expressed as equation (1) below based on Shannon's channel capacity bound principle.

CMAX=log2⁢det⁡[I+1σn2⁢HH⁢PH](1)
where I denotes an identity matrix, P denotes a diagonal matrix of power allocation parameters, and σn2denotes the variance of noise. Shannon's channel capacity bound principle and Lucent's BLAST technology are described in the article entitled “On Limits of Wireless Communications in a Fading Environment When Using Multiple Antennas,” by G. J Foschini and M. J. Gans, Wireless Personal Communications, Vol. 6, 311-335, August 1998.

In particular, Lucent's BLAST technology provides maximum channel capacity based on equation (1) in an environment where one base station corresponds to one mobile station; Since the BLAST technology does not require channel information feedback, no problems arise from channel information feedback delay and channel information feedback errors. However, in a multi-antenna system based on Lucent's BLAST technology, in which data is transmitted via only one channel between the base station and the mobile station, and no channel information is fed back, it is impossible to apply a nulling method, which forms a principle of multi-antenna systems, and to achieve peak throughput in a multi-user, multi-antenna system environment. In addition, there is a structural limitation in that more mobile station antennas than base station antennas are required. The concept of the nulling principle for multi-antennal systems is described in the article entitled “Applications of Antenna Arrays to Mobile Communications, Part I: Performance Improvement, Feasibility, and System Considerations,” by LAL C. GODARA, Proceedings of the IEEE, Vol. 85, No. 7, 1031-1097, July 1997 (refer to D. Null Beamforming on page 1041).

In the above-described physical improvement method using multiple antennas, channel information cannot be fed back in a low-speed Doppler environment including low-speed mobile stations, in which channel switching rarely occurs, or in a high-power environment ensuring minimal channel feedback errors, so that peak throughput cannot be achieved. The problem of poor throughput is more serious because information fed back from a plurality of mobile stations cannot be considered concurrently.

SUMMARY OF THE INVENTION

The present invention provides a mobile communication apparatus including a base station and at least two mobile stations, in which each of the base and mobile stations has multiple antennas. In the mobile communication apparatus, the downlink characteristics of each of the mobile stations as well as the channel downlink characteristics of spatial, sub-channels in each of the antennas are considered for optimal beamforming and multi-stream data transmission via the base station antennas, thereby achieving nominal throughput in multi-user, multi-antenna systems.

The present invention also provides a mobile communication method performed in the above mobile communication apparatus, which includes a base station having multiple antennas and at least two mobile stations having multiple antennas.

In accordance with one aspect of the present invention, there is provided a mobile communication apparatus including a base station having multiple antennas and at least two mobile stations having multiple antennas, wherein the base station restores from feedback signals transmitted from the mobile stations weight information determined in the mobile stations, generates from the restored weight information downlink control information ensuring maximum throughput to each of the mobile stations, and selects from among data of all of the mobile stations data of desired mobile stations to be transmitted, based on the downlink control information. Each of the mobile stations has at least one mobile station antenna, the base station has at least two base station antennas, and the downlink control information includes mobile station selection information, an optimal basis matrix index, and optimal gain indices.

In the mobile communication apparatus, the base station may perform a predetermined signal process on the data of the desired mobile station, which are selected based on the downlink control information, matrix-multiply the processed data by a basis matrix having the optimal basis matrix index in the downlink control information to generate data signals, add mobile station bit size information and the pilot channel signals to the data signals, and transmit the added results to the desired mobile station on a frame by frame basis.

According to a specific embodiment of the present invention, the base station may comprise: a feedback information restoration unit which restores from the feedback signals received from the mobile stations the weight information of each of the mobile stations and outputs the restored weight information; a downlink control information generation unit which generates the downlink control information based on the restored weight information received from the feedback information restoration unit and outputs the generated downlink control information; and a mobile station data selection unit which selects from among the data of all of the mobile stations the data of the desired mobile station based on the mobile station selection information, extracts an amount of data from the selected data based on a predetermined bit size, and combines the extracted data into frames, each of which has the predetermined bit size, for transmission to the desired mobile station.

In another embodiment, each of the mobile stations may comprise: a channel characteristics measurement unit measures the channel downlink characteristics based on the pilot channel signals received via the at least one mobile station antenna; a channel information determination unit which determines the weight information ensuring maximum throughput to each of the mobile stations based on the channel downlink characteristics; and an information feedback unit which converts the weight information input from the channel information determination unit into the feedback signal and transmits the feedback signal via the at least one mobile station antennas to the base station.

In accordance with another aspect of the present invention, there is provided a method of mobile communications between a base station having multiple antennas and at least two mobile stations having multiple antennas, the method comprising step (a) of: the base station restoring feedback signals transmitted from the mobile stations weight information determined in the mobile stations, generating from the restored weight information downlink control information ensuring maximum throughput to each of the mobile stations, and selecting from among data of all of the mobile stations data of a desired mobile station to be transmitted, based on the downlink control information, wherein each of the mobile stations has at least one mobile station antenna, the base station has at least two base station antennas, and the downlink control information includes mobile station selection information, an optimal basis matrix index, and optimal gain indices.

DETAILED DESCRIPTION OF THE INVENTION

Korean Patent Application No. 10-2002-004107, filed on Jul. 10, 2002, in the Korean Intellectual Property Office, and entitled: “MOBILE COMMUNICATION APPARATUS AND METHOD INCLUDING BASE STATION AND MOBILE STATION HAVING MULTI-ANTENNA,” is incorporated by reference herein in its entirety.

The structure and operation of a mobile communication apparatus utilizing multiple base station and mobile station antennas and a mobile communication method therefor according to the present invention will be described in detail with reference to the appended drawings.

As shown inFIG. 1, which is a block diagram of a mobile communication apparatus according to an embodiment of the present invention, the mobile communication apparatus includes a base station10, a first mobile station20, a second mobile station22, . . . , and a Kthmobile station24. The base station10has at least two antennas, and each of the mobile stations20through24has at least one antenna.

FIG. 2is a flowchart illustrating a mobile communication method according to an embodiment of the present invention, which is performed in the mobile communication apparatus ofFIG. 1. The mobile communication method includes determining and transmitting weight information and detecting high-speed downlink shared channel (HS-DSCH) signals (step30) and adding first control signals and pilot channel (PICH) signals to data signals generated based on the weight information restored from feedback signals and transmitting the added results (step32).

InFIG. 2, the first mobile station20, the second mobile station22, . . . , and the Kthmobile station24, where K is an integer of 2 or greater, have the same function. According to the present invention, each of the mobile stations20,22, . . . , and24includes M(k) mobile station antennas where M(k) is an integer of 1 or greater, and k denotes mobile station number and 1≦k≦K. The number of mobile stations, M(k), may be smaller than or equal to the number of base station antennas, N, where N is an integer of 2 or greater, which is expressed as 1≦M(k)≦N. The number of mobile stations, M(k), may be greater than or equal to the number of base station antennas, N, which is expressed as N≦M(k).

The base station10ofFIG. 1restores from feedback signals received from the first through Kthmobile stations20through24, which are based on the channel downlink characteristics of the multiple base station and mobile station antennas (hereinafter, referred to as first characteristics H(k), where H(k) is a matrix with 1≦k≦K, weight information determined in each of first through Kthmobile stations20through24. Hereinafter, capital bold letters indicate matrices, small bold letters indicate vectors, and non-bold symbols indicate scalars. The base station10also generates from the restored weight information of each of the mobile stations downlink control information ensuring maximum throughput, selects data of a desired mobile station for transmission from among data of all of the mobile stations based on the downlink control information, modulates and codes the selected data, adjusts the gains of the selected data, and spreads the bandwidths of the selected data. The base station10multiplies the bandwidth-spread data by a basis matrix selected based on the downlink control information, adds a first control signal, which indicates the bit size of data to be transmitted to each of the mobile stations, and pilot channel signals PICHi, where i is an integer from 1 to N, to the products and transmits the added results to each of the first through Kthmobile stations20through22on a frame by frame basis (step32).

In the above description, the downlink control information includes mobile station selection information, the indices of an optimal basis matrix (hereinafter, optimal basis matrix indices), and the indices of optimal gain values (hereinafter, optimal gain indices), as described later. The first characteristics H(k) means the phase and magnitude of a signal transmitted via a channel from the base station10to an arbitrary mobile station20,22, . . . , or24. The matrix of the first characteristics H(k) consists of channels for base station antennas in columns and channels for mobile station antennas in rows. In other words, the column components of the matrix of the first characteristics H(k) are obtained in the base station antenna space, and the row components thereof are obtained in the mobile station antenna space. The pilot channel signals PICHimay be common pilot channel (CPICH) signals, dedicated common pilot channel (DCPICH) signals, secondary common pilot channel (SCPICH) signals, etc. Although the data of the desired mobile station selected based on the downlink control information are processed by modulation and coding, gain adjustment, and bandwidth spreading in the above, other various processing methods can be applied to the selected data without limitation.

The first through Kthmobile stations20through24can be implemented in any structure as far as they can ensure the above operations to the base station10. For example, it is necessary for each of the mobile stations20through24to determine the weight information based on the first characteristics H(k) for each antenna. In particular, each of the mobile stations20through24measures the first characteristics H(k) based on the PICH signals transmitted from the base station10, determines the weight information ensuring peak throughout to each base/mobile station antenna, converts the determined weight information into feedback signals, transmits the feedback signals to the base station10, and detects a high-speed downlink shared channel (HS-DSCH) signal in units of a frame based on the first characteristics H(k) and based on the first control signal and data signals, which are received from the base station10(step30).

Each of the mobile stations20through24analyzes the first control signal received through the mobile station antennas to determine whether the first control signal transmitted from the base station 10 is correctly addressed thereto. The HS-DSCH signal reflects the second and third characteristics of the channels. The second characteristics show that the transmission of data through a channel is completed without channel switching because the length of a data frame, i.e., the unit of data transmission, is much shorter than the channel coherence time due to a general Doppler effect. The third characteristics are related to the non-continuous, burst transmission of data through a channel commonly owned by all of the mobile stations20through24belonging to the base station10.

For the convenience of understanding the present invention, embodiments of the first, second, . . . , or Kthmobile station20,22, . . . , or24and step30inFIG. 2will be described first, followed by descriptions on embodiments of the base station10and step32inFIG. 2.

FIG. 3is a flowchart illustrating an embodiment30A of step30ofFIG. 2according to the present invention, which includes transmitting the weight information determined based on the first characteristics H(k) to the base station10(steps40through44) and selecting and combining desired data information from among data information restored based on data signals transmitted from the base station10(steps46through52).

FIG. 4is a block diagram of an embodiment of the first, second, . . . , or Kthmobile station20,22, . . . ,24ofFIG. 1, which includes an antenna array60, a channel characteristics measurement unit70, a channel information determination unit72, an information feedback unit74, a control information restoration unit76, a data information restoration unit78, a data information selection unit80, and a data information combination unit82.

In particular, the antenna array60ofFIG. 4includes M(k) mobile antennas62,64, . . . , and66. The antenna array60receives PICH signals, data signals, and a first control signal transmitted from the base station10. The channel characteristics measurement unit70measures the first characteristics H(k) based on the PICH signals received via the antenna array60from the base station10and outputs the measured first characteristics H(k) to the channel information determination unit72, the control information restoration unit76, and the data information restoration unit78(step40).

After step40, the channel information determination unit72determines the weight information enabling maximum throughput based on the first characteristics H(k) and using a set of basis matrices set {T} and a set of gain values {p} and outputs the determined weight information to the information feedback unit74(step42). The weight information includes basis matrix indices IT(i) and gain indices IP(i). When a basis matrix with a particular index is denoted as T(IT) and a gain value with a particular index is denoted as P(IP) in equation (2) below, the maximum capacity C′MAXof the mobile communication apparatus for multiple users, which includes multiple base station/mobile station antennas, is expressed as equation (3) below based on Shannon's channel capacity bound principle.
P(IP)=diag[p(IP(1))p(Ip(2)) . . .p(IP(N))]T(2)
where diag means a diagonal matrix.

CMAX′=MAXP⁡(IP),T⁡(IT)⁢⁢log2⁢det⁡[I+ρ⁢⁢P⁡(IP)⁢T⁡(IT)H⁢HH⁢HT⁡(IT)⁢P⁡(IP)](3)
where ρ denotes a signal to interference and noise ratio. Since the number of mobile station antennas, M(k), is greater than or equal to 1 and less than or equal to N, the basis matrix vector size and the gain size are less than or equal to N. This is conceptually the same as when some of the gain values become null (=0) according to the first characteristics, i.e., downlink channel characteristics, of the multiple base station and mobile station antennas. In the two cases, the indices of zero gains are selected without setting the basis matrix vector size and the gain size to N.

After step42, the information feedback unit74converts the weight information IT(i) and IP(i) input from the channel information determination unit72into feedback signals for transmission to the base station10by general communication signal processing and transmits the converted feedback signals via the antenna array60to the base station10(step44). In particular, the information feedback unit74formats the weight information IT(i) and IP(i) input from the channel information determination unit72, time-division-multiplexes the formatted results, and transmits the time-division-multiplexed results as the feedback signals via the antenna array60to the base station10. Alternatively, the information feedback unit74may process the formatted weight information into the feedback signals by code division multiplexing or frequency division multiplexing, instead of time division multiplexing.

After step44, the control information restoration unit76compensates for distortion in the first control signal received via the antenna array60from the base station10based on the first characteristics H(i) input from the channel characteristics measurement unit70, restores a second control signal from the restored first control signal, and outputs the restored second control signal to the data information selection unit80(step46). The second control signal includes information on whether the data signals are received through a desired sub-channel and information on the bit size of the data signals. The second control signal may be restored from the first control signal through general multi-antennal signal, processes as in step48described later.

After step46, the data information restoration unit78restores the data information received via all the sub-channels based on the data signals received from the base station10via the antenna array60and the first characteristics H(i) provided from the channel characteristics measurement unit70and outputs the restored data information of all the sub-channels to the data information selection unit80(step48). The data signals received from the base station70are expressed as r(k) in equation (4) below and can be modelled using equation (5) below.
r(k)=[r(1,k)r(2,k) . . .r(N,K)]T(4)
where r(n,k) denotes a data signal received via the nthantenna of the Kthmobile station.
r(k)=H(k)s+n(k)=U(k)Σ(k)VH(k)s+n(k)  (5)
where n(k) denotes a noise component, and U(k)Σ(k) VH(k) means singular value decomposition (SVD), which is a kind of common matrix operation, using the first characteristics H(k), and s is modeled as equation (6) below. SVD in multi-antenna systems is described in an article entitled “Fading Correlation and Its effect on the Capacity of Multielement Antenna Systems” by Da-Shan Shiu, Gerard J. Foschini, Michael J. Gans, and Joseph M Kahn, IEEE Transactions on Comm. Vol. 48, No. 3, 502-513, March 2003.
s=TPd  (6)
where T and P denotes the optimal basis matrix and the optimal gain value determined in the base station, respectively, and particularly, P is a diagonal matrix of optimal gain values expressed as diag[p].

A data signal r(n)where n is an integer from 1 to min(N,K), which transmitted from the base station10as multiple streams after beamforming for each of the mobile stations and received in the mobile station20,22, . . . , or24, is expressed as equation (7) below using multiple-weight information. The above-described equation (5) is established based on the following assumption.

d~⁡(k)=UH⁡(k)⁢r⁡(k)=UH⁡(k)⁢(H⁡(k)⁢s+n⁡(k))⁢⁢=UH⁡(k)⁢(U⁡(k)⁢∑(k)⁢VH⁡(k)⁢s+n⁡(k))⁢⁢=∑(k)⁢VH⁡(k)⁢TPd+UH⁡(k)⁢n⁡(k)⁢=∑(k)⁢Pd+n^⁡(k)⁢(8)
where U(k) and V(k) denote right and left unitary matrices, respectively, Σ(k) denotes a diagonal matrix of singular values. To solve equation (3) above, the following conditions are required: T=V(k), and theoretical gain values PNode-Bshould be optimized for peak throughput in a multi-user channel environment. According to the present invention, in the base station10, the gain values P of a desired mobile station20,22, . . . , or24are optimally combined into the optimal gain values PNode-B. For example, a matrix of singular values ΣUEis received from the desired mobile station20,22, . . . , or24and combined together to form a matrix of singular values ΣNode-Bfor the base station10, which is expressed as equation (9) below, and PNode-Bis obtained from the matrix of the singular values ΣNode-Busing a water-filling method. The water-filling method is described in a book entitled “Digital Baseband Transmission and Recording” by Jan W. M. Bergmans, Kluwer Academic Press, Boston, 1996. The above unitary matrix V may be a theoretical basis matrix.

After step48, the data information selection unit80selects data information received a desired sub-channel from among the data information received from the data information restoration unit78, which is transmitted via all of the sub-channels, according to the second control signal input from the control information restoration unit76, and outputs Ne(k) selected data information where 0≦Ne(k)≦N, which are received via the desired sub-channel, to the data information combination unit82(step50).

After step50, the data information combination unit82combines the selected data information received from the data information selection unit80over a predetermined period TBLOCKcorresponding to the length of a frame and outputs the combined result as a high-speed downlink shared channel signal HS-DSCH(i)′ of the corresponding mobile station (step52).

Embodiments of the base station10ofFIG. 1and step32ofFIG. 2according to the present invention will now be described with reference toFIGS. 5 and 6.

FIG. 5is a flowchart illustrating an embodiment32A of step32ofFIG. 2according to the present invention, which includes generating the downlink control information based on the restored weight information (steps100and102), selecting data of a desired mobile station (steps104through110), processing the selected data to generate data signals (steps112through118), and adding the first control signal and pilot channel signals to the data signals and transmitting the added results to the corresponding mobile station (step120).

FIG. 6is a block diagram of an embodiment10A of the base station10ofFIG. 1according to the present invention, which includes an antenna array128, a feedback information restoration unit136, a lookup table (LUT)138, a downlink control information generation unit140, an adaptive modulation and power control unit142, a mobile station control information generation unit144, an antenna signal processing unit146, a mobile station data selection unit148, an adaptive modulation and coding (AMC) unit150, first and second multiplication units152and154, a basis multiplication unit156, and an addition unit158.

The antenna array128ofFIG. 6includes N base station antennas130,132, . . . ,134. The antenna array128receives the feedback signals transmitted from the first through Kthmobile stations20through24as uplink dedicated physical control channel signals (HS-DPCCH) and transmits the result of adding the first control signal and pilot channel signals to the data signals, which are spatially processed HS-DSCH signals, to the first through Kthmobile stations20through24.

In particular, after step30inFIG. 2, the feedback information restoration unit136restores the weight information from the feedback signal received from each of the first through Kthmobile stations20through24and outputs the restored weight information to the downlink control information generation unit140(step100). The restored weight information includes restored basis matrix indices, such as IT(1), IT(2), . . . , and IT(K), and restored gain indices, such as IP(1), IP(2), . . . , and IP(K). The restored basis matrix indices, which are generalized as IT(k), indicate the indices of individual basis matrices T1, T2, . . . , and TJof a basis matrix set {T}, where J denotes the number of basis matrices in the set {T}. The gain indices, which are generalized collectively as IP(K), consist of [IP(1,k) IP(2,k) . . . IP(N,k)]T. IP(n,k), where n denotes the number of the basis antenna and 1≦n≦N, indicates the indices of the individual gain values p(1), p(2), . . . , and p(Jp) of a gain value set {p} where Jpdenotes the gain size of the set {p}.

When the information feedback unit74ofFIG. 4generates the feedback signals by time division multiplexing, the feedback information restoration unit136restores the weight information by time division demultiplexing. Alternatively, when the information feedback unit74generates the feedback signals by code division multiplexing or frequency division multiplexing, the feedback information restoration unit136may restore the weight information by code division demultiplexing or frequency division demultiplexing.

After step100ofFIG. 5, the downlink control information generation unit140generates the downlink control information based on the restored weight information input from the feedback information restoration unit136and outputs the generated downlink control information (step102). Among the downlink control information output from the downlink control information generation unit140, mobile station selection information IUSERis output to the mobile station data selection unit148and the mobile'station control information generation unit144, an optimal basis matrix index IT,TXis output to the basis multiplication unit156, and optimal gain indices IP,TXare output to the adaptive modulation and power control unit142. The mobile station selection information IUSERincludes IUSER(1), IUSER(2), . . . , and IUSER(3). The optimal gain indices IP,TXinclude IP,TX(1), IP,TX(2), . . . , and IP,TX(N). The optimal basis matrix index IT,TXincludes IT,TX(1), IT,TX(2), . . . , and IT,TX(N).

Embodiments of step102ofFIG. 5and the downlink control information generation unit140ofFIG. 6according to the present invention will now be described in detail with reference toFIGS. 7 and 8.

FIG. 7is a flowchart illustrating an embodiment102A of step102ofFIG. 5according to the present invention, which includes generating the downlink control information based on the restored weight information (steps238through244).

FIG. 8is a block diagram of an embodiment140A of the downlink control information generation unit140ofFIG. 6according to the present invention, which includes a weight information extension portion258, a basis matrix-based classification portion260, first through Jthmaximum value selection portions262through266, and a transmission order determination portion268.

After step100ofFIG. 5, the gain indices in the restored weight information are analyzed to find gain values including a null, null basis matrices are generated using the found gain values and the basis matrix index in the restored weight information, and gain indices are duplicated and generated as many as the number of generated null basis matrices (step238). In a null basis matrix, basis vectors other than the basis vector corresponding to a gain value including null have the same value to other basis vectors of other null basis matrices. For example, when a null basis matrix consists of first through Nthbasis vectors and the first basis vector has null gain, the second through Nthbasis vectors have common values to other null basis matrices.

In step238, the weight information extension portion258analyzes the gain indices IP(1), IP(2), . . . , and IP(K) in the restored weight information input from the feedback information restoration unit136to find the gain values including a null, generates the indices of the null basis matrices based on the found gain values including a null and the basis matrix indices IT(1), IT(2), . . . , and IT(K) in the restored weight information, and duplicates and generates the number of gain indices as many as the number of generated null basis matrices, and outputs the indices of the generated null basis matrices and the generated number of gain indices to the basis matrix-based classification portion260.

After step238, the generated gain indices for indices of the null basis matrices are distributed or concentrated (step240). To this end, the basis matrix-based classification portion260allows the generated gain indices for indices of the null basis matrices input from the weight information extension portion285to be distributed or concentrated, and outputs the distributed gain indices having the number of a mobile station to one or more first through Jthmaximum value selection portions262through266so that the gain indices are classified according to the indices of the generated null basis matrices. Alternatively, the concentrated gain indices may be output to only one of the first through Jthmaximum value selection portions262through266without the distribution according to the indices of the generated null basis matrices.

A determination as to whether to distribute or concentrate the gain indices to one or more first through Jthmaximum value selection portions262through266is made based the indices of the generated null basis matrices. For example, when the generated null basis matrix T is a first basis matrix T1with IT(k)=1, the gain indices IP(k) are output to the first maximum value selection portion262. In particular, a first gain index IP(1,k) among the gain indices IP(k) is output to a 11thmaximum value selector280, a second gain index IP(2,k) is output to a 12thmaximum value selector282, and an Nthgain index IP(N,k) is output to a 1Nthmaximum value selector284. When the generated null basis matrix T is a second basis matrix T2with IT(k)=2, the gain indices IP(k) are output to the second maximum value selection portion264. In particular, the first gain index IP(1,k) among the gain indices IP(k) is output to a 21stmaximum value selector290, the second gain index Ip(2,k) is output to a 22ndmaximum value selector292, and the Nthgain index IP(N,k) is output to a 2Nthmaximum value selector294. When the generated null basis matrix T is a Jthbasis matrix TJwith IT(k)=J, the gain indices IP(k) are output to the Jthmaximum value selection portion266. In particular, the first gain index Ip(1,k) among the gain indices IP(k) is output to a J1stmaximum value selector300, the second gain index IP(2,k) is output to a J2ndmaximum value selector302, and the Nthgain index IP(N,k) is output to a JNthmaximum value selector304.

After step240inFIG. 7, for each of J basis matrices, the index of the largest gain value (“maximum gain index”) is selected for each of first through Nthbasis vectors of the corresponding basis matrix from among the distributed or concentrated gain indices which correspond to a mobile station k(step242). To this end, each of the first through Jthmaximum value selection portions262through266, i.e., a jthmaximum value selection portion where 1 j J, selects the maximum gain index from among the gain indices, which are received via the basis-matrix classification portion260, for each of the first through Nthbasis vectors, and outputs the selected maximum gain index, the value of j indicating the current maximum value selection portion, the number of the basis vector having the largest gain value, and the number of the mobile station corresponding to the maximum gain index, to the transmission order determination portion268. For example, the first maximum value selection portion262, where j=1, selects the maximum gain index from among the gain indices, which are received via the basis matrix-based classification portion260, for each of the first through Nthbasis vectors, and outputs the selected maximum gain index, the value of j (=1), the number of the basis vector having the selected maximum gain index, and the number of the mobile station corresponding to the selected maximum gain index to the transmission order determination portion268.

For step240, the jthmaximum value selection portion includes j1stthrough jNthmaximum value selectors. For example, the first maximum value selection portion262includes the 11ththrough 1Nthmaximum value selectors208through284, the second maximum value selection portion264includes the 21stthrough 2Nthmaximum value selectors20through294, and the Jthmaximum value selection portion266includes the J1stthrough JNthmaximum value selectors300through304. Each of the J1stthrough JNthmaximum value selectors300through304, i.e., a jthmaximum value selection portion, selects the maximum gain index from among Kegain indices where 0≦Ke≦K, which are received via the basis matrix-based classification portion260, for each of the basis vectors, and outputs the selected maximum gain index, the value of j, and the number (n) of the basis vector having the largest gain value, and the number (k) of the mobile station corresponding to the selected maximum gain index to the transmission order determination portion268. Accordingly, the transmission order determination portion268can recognize from which one of the first through jthmaximum value selection portions262through266the maximum gain index is received from the input value of j, can recognize which maximum value selector in the corresponding maximum value selection portion has the maximum gain index from the input value of n, and can recognize which mobile station corresponds to the maximum gain index from the input value of k. The maximum gain index output from the jnthmaximum value selector of the jthmaximum value selection portion, which corresponds to the kthmobile station, can be expressed as equation (10) below.
IP,TX(n)|[IT(k)=j]=min{IP,TX(n,k)|[IT(k)=j]}  (10)
where the right term of operator | shows the conditions for the left term.

According to the present invention, when gain values are indexed starting with the largest one in ascending index order, the maximum value selectors inFIG. 8select the smallest index having the largest gain value.

After step242, the transmission order determination portion268selects an optimal basis matrix index IT,TXfrom among J basis matrix indices IT(k) using a predetermined determination method, selects the optimal gain indices IP,TXcorresponding to the optimal basis matrix index IT,TXfrom among the maximum gain indices received from the first through Jthmaximum value selection portions262through266, selects as mobile station selection information IUSERthe number of the mobile station corresponding to the optimal basis matrix index IT,TXfrom among the numbers of the mobile stations received from the first through Jthmaximum value selection portions262through266, and outputs the selected optimal gain indices IP,TX, the selected optimal basis matrix index IT,TX, and the selected mobile station selection information IUSER(step244). The transmission order determination portion268outputs the optimal gain indices IP,TXin a predetermined order with reference to the values of n's received from the first through Jthmaximum value selection portions262through266with reference to the number (n) received from the first through Jthmaximum value selection portions262through266.

The above predetermined determination method may include a round robin method of selecting one of the basis matrix indices in sequential order as the optimal basis matrix IT,TXand a Max C/I method of selecting as the optimal basis matrix IT,TXone of the basis matrix indices in an order in which the sum of corresponding gain values increases. The round robin and Max C/I methods are described in an article entitled “CDMA/HDR: a bandwidth efficient high speed wireless data service for nomadic users”, IEEE Communications Magazine, Vol. 38(7), 70-78, July 2000, and an article entitled “CDMA 2000: High rate packet data air interface specification”, TIA/EIA IS-866, November 2000, by P. Bender, P. Black, M. Grob, R. Padovani, N. Sindhushayana, and A. Viterbi. When the weight information fed back in consideration of feedback error ratio and delay rate is determined to be significantly reliable, the Max C/I method, in which one of the basis matrix indices is selected as the optimal basis matrix index IT,TXin an order in which the sum of corresponding gain values increases, is applied.

After step102ofFIG. 5, modulation and coding orders are selected based on the optimal gain indices IP,TXa required bit size is selected based on the modulation and coding orders, and a set of gain values having the optimal gain indices IP,TXis selected (step104). Step104is implemented using the LUT138and the adaptive modulation and power control unit142. The LUT138stores one or more sets of gain values {p} and one or more sets of basis matrices {T}. The adaptive modulation and power control unit412calculates modulation and coding orders m1, m2, . . . , and mNbased on the optimal gain indices IP,TXinput from the downlink control information generation unit140, calculates the required bit size {n1, n2, . . . , and nN} of a data frame based on the modulation and coding orders m1, m2, . . . , and mN, and reads a set of the gain values having the optimal gain indices IP,TXfrom the LUT138, and outputs the gain values p1, p2, . . . , and pNto the first multiplication unit152. A modulation and coding order mnis proportional to the gain value having the corresponding optimal gain index IP,TX.

For example, when the number of data frame symbols is 100, 16-quadrature amplitude modulation (QAM) (4 bits/symbol) is used, and the code rate is ½, the bit size of each data frame is 200 (=100*4*(½)). Here, since the number of data frame symbols, which is equal to 100, is previously set in the mobile station and the base station, the required bit size nncan be calculated using the modulation and coding order mn, which corresponds to “4” and “½” in the above example.

Alternatively, the adaptive modulation and power control unit142may further include a LUT (not shown) storing the modulation and coding orders m1, m2, . . . , and mNand the required bit size {n1, n2, . . . , and nN}. In this case, the LUT in the adaptive modulation and power control unit142is accessed based on the optimal gain indices IP,TXand the number of frame symbols to read a modulation and coding order mnand a bit size nnfrom the corresponding address of the LUT.

After step104ofFIG. 5, the mobile station control information generation unit144outputs to the antenna signal processing unit146the bit size {n1, n2, . . . , and nN}, which are input from the adaptive modulation and power control unit142, and the mobile station selection information IUSER, which is input from the downlink control information generation unit140, as mobile station bit size information CUE(step106). In other words, the mobile station bit size information CUEincludes information on the selected mobile station and the bit size {n1, n2, . . . , and nN} required for each of the mobile stations. The mobile station bit size information CUEis expressed as equation (11) below.
CUE=[cUE(1)cUE(2) . . . cUE(K)]  (11)
where cUE(k) can be expressed as equation (12) below:
cUE(k)=[c(1,k)c(2,k) . . .c(n,k)]  (12)
where c(n,k) can be expressed as equation (13) below:

As presented in equation (13), for any n and k satisfying IT(k)=IT,TX, nn(k) is substituted for c(n,k), otherwise 0 is substituted for c(n,k).

After step106ofFIG. 5, the antenna signal processing unit146converts the mobile station bit size information CUEinput from the mobile station control information generation unit144into wireless signals and outputs the wireless signals to the addition unit158as first control signals (step108).

After step108, the mobile station data selection unit148selects data of desired mobile stations from among data of all of the mobile stations HS-DSCH(1), HS-DSCH(2), . . . , and HS-DSCH(K) based on the mobile station selection information IUSER, extracts from the selected data of the desired mobile stations an amount of data based on the bit size {n1, n2, . . . , and nN} input from the adaptive modulation and power control unit142, combines the extracted data of the desired mobile stations into data frames, respectively, each of which has the bit size {n1, n2, . . . , and nN}, and outputs the data of the frames to the AMC unit150(step110).

After step110, the AMC unit150modulates and codes the data input from the mobile station data selection unit148in units of a frame based on the modulation and coding orders m1, m2, . . . , and mNinput from the adaptive modulation and power control unit142, and outputs the modulated and coded results to the first multiplication unit150(step112). To this end, the AMC unit150may be implemented with first, second, . . . , and Nthadaptive AMC sub-units170,172, . . . , and174. Each of the first through NthAMC sub-units170,172, . . . , and174, i.e., an nthAMC sub-unit, modulates and codes a data frame output from the mobile station data selection unit148based on the corresponding modulating and coding order mninput from the adaptive modulation and power control unit142and outputs the modulated and coded result. The AMC is described in an article entitled “Channel coding for 4G systems with adaptive modulation and coding” by K. L. Baum, P. J. Sartor, and V. Desi, Proceedings of 3G wireless '2001, 496-501, May 30-Jun. 2, 2001, San Francisco, U.S.A.

After step112, the gains of the modulated and coded results are adjusted (step114). To this end, the first multiplication unit152multiplies the modulated and coded results input from the adaptive modulating and coding unit150by the gain values p1, p2, . . . , and pNinput from the adaptive modulation and power control unit142and outputs the products to the second multiplication unit154. The first multiplication unit152may be implemented with first, second, and Nthmultipliers190,192, . . . , and194. Each of the first through Nthmultipliers190through194, i.e., an nthmultiplier, multiplies the modulated and coded result input from the nthAMC coding sub-unit190,192, . . . , or194by the gain value pnand outputs the product.

After step114, the bandwidths of the gain-adjusted results are spread (step116). To this end, the second multiplication unit154multiplies the products input from the first multiplication unit152by spread/scramble signal streams and outputs the products to the basis multiplication unit156. Here, the spread/scramble signal streams refer to the products CspCscof multiplying scramble signal streams Cscand spread signal streams Csp. The scramble/spread signal streams may be previously stored in the base station10A or may be externally input as illustrated inFIG. 6.

After step116, the bandwidth-spread results are matrix-multiplied by a basis matrix having the optimal basis matrix index IT,TXand outputs the products as data signals for transmission to the mobile stations20,22, . . . , and24(step118). To this end, the basis multiplication unit156reads from the LUT138a set of basis matrices {T} corresponding to the optimal basis matrix index IT,TXinput from the downlink control information generation unit140, selects from the set of the basis matrices a basis matrix having the optimal basis matrix index IT,TX, matrix-multiplies the products input from the second multiplication unit154by the selected basis matrix, and outputs the products of the matrix multiplication as the data signals to the addition unit158. Here, the matrix multiplication refers to multiplying N basis vectors that belong to the selected basis matrix by N products input from the second multiplication unit154, respectively and adding the multiplied results.

After step118, the first control signals and the pilot channel signals are added to the data signals, and the added results are transmitted to the mobile stations20,22, . . . , and24on a frame by frame basis (step120). Step120is performed using the addition unit158and the base station antenna array128. The addition unit158adds the first control signals and the externally input pilot channel signals PICH1, PICH2, . . . , and PICHNto the data signals input from the basis multiplication unit156and outputs the added results to the base station antenna array128. To this end, the addition unit158may be implemented with first, second, . . . , and Nthadders210,212, . . . , and214. Each of the first through Nthadders210through214, i.e., an nthadder, adds the first control signals input from the antenna signal processing unit146and pilot channel signals PICH1to PICHnto the data signals input from the basis multiplication unit156and outputs the added result to the corresponding antenna130,132, . . . , or134of the base station antenna array128. The added result input to the base station antenna array128from the addition unit158is transmitted to the mobile station20,22, . . . , or24.

As described above, in a mobile communication apparatus using multiple base station and mobile station antennas and a mobile communication method therefor according to the present invention, downlink characteristic information transmitted to a base station from each of the mobile stations is fully reflected for optimal beamforming and data transmission. In addition, the first control signal transmitted from the base station to each of the mobile stations enables the mobile station to receive data in units of a frame on a basis vector basis, so that nominal peak throughput in multi-antenna mobile communications can be efficiently achieved at low costs.