JP2002290317A - Transmission diversity communication unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission diversity communication unit that stably controls transmission diversity with less pilot signal total transmission power independently of increase in number of transmission antennas. SOLUTION: In a base station unit of a mobile communication system where a mobile station receives/analyzes a prescribed pilot signal sent from a base station via a plurality of antennas, transmits obtained feedback information to an incoming channel of the base station and the base station controls a transmission signal of an outgoing channel of the base station on the basis of the feedback information from the mobile station, a plurality of antennas #1-#N are divided into a plurality of groups, and the pilot signal is transmitted only through the antennas #1, #j or the like being references of the groups with low fading correlation. Furthermore, the pilot signal is transmitted from all the antennas in a specific group with high fading correlation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission diversity communication apparatus, and more particularly, a mobile station receives and analyzes a predetermined pilot signal transmitted from a base station via a plurality of antennas, and obtains feedback information obtained. The present invention relates to a transmission diversity communication apparatus (a base station apparatus and a mobile station apparatus) of a mobile communication system that transmits an uplink channel of a base station and controls a transmission signal of a downlink channel of the base station based on feedback information from the mobile station.

WC which is a third generation mobile communication system
In a diversity scheme in DMA, a closed loop transmission diversity scheme using two transmission antennas is employed. When a closed-loop transmission diversity scheme using two transmission antennas is applied to a radio base station of a cellular mobile communication system, after signals from each transmission antenna undergo independent fading, ideally, the signals are transmitted at the reception antenna position of the mobile station. Are combined in phase, so that a diversity gain according to the number of transmitting antennas, and further, an improvement in gain by in-phase combining can be obtained. Therefore, the reception characteristics are improved, and the number of users that can be accommodated in one cell can be increased. In addition, if the number of transmitting antennas is increased, an increase in in-phase combined gain can be expected. At present, the case of using four transmitting antennas has been actively researched and developed.

[0003]

2. Description of the Related Art FIG. 8 is a diagram for explaining the prior art, and shows a system configuration of a closed-loop transmission diversity system using two transmission antennas. In the figure, reference numeral 80 denotes a base station; 81, two transmission antennas (# 1 and # 2) for transmitting downlink channel transmission signals; 82, a pilot signal generation unit for generating pilot signals; A feedback information extracting unit for extracting feedback information from the antenna, an amplitude / phase control unit 84 for controlling the amplitude / phase of a downlink channel transmission signal based on the feedback information, 89 a receiving antenna, 90 a mobile station, 91 a receiving antenna thereof , 92 are control amounts (amplitude, phase) of the transmission signal of the base station 10 based on the downlink channel pilot signal.
, A multiplexing unit that multiplexes the obtained control amount (feedback) information with the uplink transmission data, 9
9 is a transmitting antenna.

The base station 80 has two transmitting antennas # 1, #
2, the pilot signals P ₁ and P ₂ orthogonal to each other are transmitted. The mobile station 90 receives the pilot signals P ₁ ′,
By correlating P ₂ ′ with the known pilot signals P ₁ and P ₂ , the channel impulse response vector <h of the path from the transmitting antennas # 1 and # 2 of the base station 80 to the receiving antenna 91 of the mobile station 90 is obtained. _1>, determine the <h _2>. Furthermore,
Using these channel estimates, the power P shown in equation (1)
And the amplitude and phase control vector (weight vector) of the base station transmitting antennas # 1 and # 2 (w) = [w
₁ , w ₂ ], is quantized, multiplexed on the uplink channel, and transmitted (feedback) to the base station 80. However, it is not necessary to transmit both w ₁ and w ₂ , and the weight coefficient w
Only the value of w ₂ (= a + jb) when ₁ = 1 is required to be transmitted.

[0005]

(Equation 1)

Here, <h ₁ > and <h ₂ > are channel impulse response vectors from transmitting antennas # 1 and # 2, respectively. The subscript of the shoulder of H ^H or <w> ^H indicates that the Hermitian conjugate of H or <w> is taken. Assuming that the length of the impulse response is L, the vector <h _i > is expressed by equation (3).

[0007]

(Equation 2)

At the time of soft handover, a control vector <w> that maximizes the power P in equation (4) is obtained instead of equation (1).

[0009]

(Equation 3)

Here, H _k is the channel impulse response of the pilot signal from the k-th base station. Base station 8
At 0, the control amount w ₂ (where w ₁ = 1) is extracted from the received signal of the uplink channel, and this is extracted as the transmission antenna #
2 is multiplied by the transmission signal. Thus, the transmitting antenna #
The amplitude and phase of the data signals transmitted from # 1 and # 2 can be corrected in advance on the base station 80 side.

[0011] In W-CDMA, two methods, a mode 1 for quantizing the weight coefficient w ₂ to 1 bit and a mode ₂ for quantizing the weight coefficient w ₂ to 4 bits, are defined. Mode 1
In this case, since control is performed by transmitting 1-bit feedback information for each slot, the control speed is high, but the quantization of the control amount is coarse, so that accurate control cannot be performed. On the other hand, in mode 2, since control is performed with 4-bit information, more accurate control can be performed. On the other hand, since one-word feedback information is transmitted in four slots, it cannot follow a high fading frequency. , Characteristics are degraded. Therefore, in a situation where the transmission rate of the uplink channel is limited, there is a trade-off between the control accuracy and the speed of following the fading.

Also, the Release-99 standard of W-CDMA does not consider a case where the number of transmission antennas is more than two in order to avoid a decrease in uplink channel transmission efficiency due to feedback information transmission. It is the current situation. However, if the increase in the feedback information and the decrease in the update speed can be suppressed, the number of feedback information can be actually increased to three or more.

[0013]

However, one of the important problems when increasing the number of transmitting antennas is the influence of a common pilot signal. That is, in estimating the channel impulse response required for generating feedback information, it is necessary to keep the transmission power of the common pilot signal from each transmission antenna sufficiently high to obtain sufficient accuracy. With the increase, the total transmission power of the common pilot signal from all the transmitting antennas increases. Therefore, when the orthogonality of each data signal or control signal is broken by multipath, the common pilot signal is given to the data signal. There is a problem that the amount of interference increases.

On the other hand, if the total transmission power of the common pilot signal is kept constant irrespective of the number of transmission antennas in order to keep the influence of such interference constant, the common transmission power per transmission antenna increases with the number of transmission antennas. Since the transmission power of the pilot signal decreases, the estimation accuracy of the channel impulse response decreases.

[0015] From this, in an environment where a mobile station compatible with the closed-loop transmission diversity system using three or more transmission antennas and a mobile station compatible with the closed-loop transmission diversity system using two transmission antennas coexist in the same cell, Since the total transmission (reception) power of the common pilot signal that can be used is different from each other, there is a problem that the increase in the number of transmission antennas is disadvantageous for the latter mobile station.

The present invention has been made in view of the above-mentioned problems of the prior art. It is an object of the present invention to perform stable transmission diversity control with a small total pilot signal transmission power regardless of an increase in the number of transmission antennas. It is an object of the present invention to provide a diversity communication device that can perform the communication. For other purposes,
It is an object of the present invention to provide a transmission diversity communication apparatus capable of maintaining compatibility between a plurality of mobile stations supporting transmission diversity schemes having different numbers of channels.

[0017]

The above-mentioned problem is solved, for example, by referring to FIG.
Is solved. That is, the base station apparatus 10 of the present invention (1) receives and analyzes a predetermined pilot signal transmitted from the base station via a plurality of antennas at the mobile station,
In the base station device of the mobile communication system that transmits the obtained feedback information to the uplink channel of the base station and controls the transmission signal of the downlink channel of the base station based on the feedback information from the mobile station, a plurality of antennas # 1 to
#N is divided into a plurality of groups, and pilot signals are transmitted only from antennas # 1, #j, etc., which serve as references for each group.

According to the present invention (1), the number of pilot signal transmission channels (total transmission power) is suppressed to a predetermined important transmission channel regardless of the increase in the number of transmission antennas (channels) of the base station 10. Thus, stable transmission diversity control can be performed efficiently. The diversity control (phase control) of each antenna in each group can be realized by using, for example, an arrival direction estimating means for estimating the arrival direction of radio waves in the uplink channel.

Preferably, in the present invention (2), in the above-mentioned present invention (1), the base station apparatus 10 is provided with antennas in each group close to each other so that fading correlation is high, and Are provided apart from each other so as to reduce fading correlation.

Therefore, with a small number of pilot signal transmission channels (total transmission power), transmission diversity control of antenna groups between groups having low fading correlation can be efficiently performed.

Preferably, in the present invention (3),
In the present invention (2), the base station apparatus 10 further transmits pilot signals from all antennas in a specific group.

According to the present invention (3), stable transmission diversity control for all transmission antennas can be efficiently performed only by further increasing the number of pilot signal transmission channels (total transmission power) in a specific group.

The mobile station apparatus 30 of the present invention (4) receives and analyzes a predetermined pilot signal transmitted from the base station via a plurality of antennas at the mobile station, and transmits the obtained feedback information to the uplink of the base station. In a mobile station device of a mobile communication system that transmits to a channel and controls a downlink channel transmission signal of a base station based on feedback information from the mobile station, a base station in which a plurality of antennas # 1 to #N are divided into a plurality of groups. The station 10 receives and analyzes pilot signals from the antennas # 1, #j, etc., which serve as references for each group of the station 10, and also uses the reference antennas #j, etc. for other groups based on the reference antenna # 1 of a specific group. The control amount is obtained, feedback information is formed, and the control information is returned to the base station 10.

Therefore, stable transmission diversity control can be efficiently performed with a small amount of feedback information processing.
Which pilot signal of the downlink channel is processed and fed back can be flexibly dealt with in relation to the base station 10 to be connected. Therefore, even a normal (conventional) mobile station that processes pilot signals of all downlink channels can be connected to the base station 10 of the present invention simply by selecting (decreasing) the downlink pilot channel to be processed. .

Preferably, in the present invention (5), in the present invention (4), the mobile station device 30
The pilot signals from all the antennas # 1 and the like in the specific group are further received and analyzed, and the control amounts of all the other antennas in the same group based on the reference antenna # 1 in the specific group are obtained. Thus, the feedback information is formed and returned to the base station 10.

According to the present invention (5), the processing of the base station 10 for pilot signals of a specific group is simply increased.
Stable transmission diversity control can be efficiently received for all channels.

FIG. 1 and FIG. 2 are diagrams (1) and (2) showing the basic configuration of the present invention. In the transmitter of the base station, the same transmission data signal is applied to the same transmission data signal based on feedback information from the mobile station. After performing different amplitude and phase control, transmission is performed using a plurality of different antennas, and the mobile station side determines the amplitude and phase control amounts using downlink pilot signals, and the amplitude and phase control amounts are determined. 2 shows an example of application to a closed-loop transmission diversity system in which feedback information indicating is multiplexed into an uplink channel signal and transmitted to the base station side. FIG. 1 shows the basic system configuration of the transmission diversity system, and FIG. 2 shows the configuration of the transmission antenna of the base station 10.

In FIG. 1, generally, amplitude and phase control vectors (weight vectors) <w> = [w _{1 of} base station transmitting antennas # 1 to #N that maximize power P when the number of channels is N , W ₂ ,..., W _N ] are obtained by equation (5).

[0029]

(Equation 4)

At the time of soft handover, a control vector <w> that maximizes the power P in equation (8) is obtained instead of equation (5).

[0031]

(Equation 5)

However, in the present invention, efficient transmission diversity control as described below is realized by using a part of the transmission antennas of the base station 10.

Referring to FIG. 2, base station 10 divides all transmitting antennas # 1 to #MK into a plurality of groups 1 to M including a plurality of antennas # 1 to #K. The transmission antennas are arranged close to each other so that the fading correlation is high, and the transmission antennas of each of the groups 1 to M are spaced apart from each other so that the fading correlation is low. I have. Here, N is the number of all transmitting antennas, M is the number of antenna groups, and K = N / M is the number of antennas for each group.

Signals from the transmitting antennas in the same group in the base station 10 have almost the same fading because of high fading correlation, but the mobile station 30 has a phase difference corresponding to the angle of the mobile station 30 with respect to the base station 10. It reaches 30 receiving antennas 31. Therefore, the impulse channel responses from the transmitting antennas in the same group of the base station 10 have a phase difference corresponding to the angle of the mobile station 30 with respect to the base station 10, and these values are affected by the movement of the mobile station 30. It changes along with it, but has the property of changing more slowly than fading fluctuation.

In particular, in a macro cell system having a somewhat large cell radius, the angles of the mobile station 30 with respect to each antenna group in the base station 10 are substantially equal. _{1, m} (m = 2,..., M) and an antenna control amount G _{m, k} (m = 1,..., M, k = 2,.
K), the amount of antenna control in a specific group can be used as the amount of antenna control in each of the other groups.

Therefore, the antenna control amount G in a certain specific group (for example, group 1) of the base station 10 is substantially obtained.
_{1, k} (k = 2,..., K), the reference antenna # 1 of the specific group and the reference antennas # (k
+1) to # (M−1) k + 1, the mobile station 30 obtains the inter-group antenna control amount F _{1, m} (m = 2,..., M), quantizes this, and sends it up as feedback information. If multiplexed with channel signals and transmitted to the base station 10 side, regardless of the increase in the number of transmission antennas (channels),
The control of the amplitude and the phase of all the transmitting antennas # 1 to #MK can be performed accurately and efficiently while the increase in the total transmission power of the common pilot signal is sufficiently suppressed.

Next, the operation of the transmission diversity according to the present invention will be described with reference to FIGS. In the base station 10, all antennas # in a specific (eg, first) group 1
, #K, and other groups, reference antennas # (K + 1) and # (2K
+1),..., # {(M−1) K + 1} and mutually orthogonal common pilot signals P ₁ (t), P ₂ (t) _,.
(T) and P _{k + 1} (t), P _{2k + 1} (t),..., P
_{(M-1) k + 1} (t) is transmitted. Each pilot signal undergoes amplitude and phase fluctuations due to fading, and these combined signals are transmitted to the receiving antenna 31 of the mobile station 30.
Is input to

The control amount calculation unit 35 of the mobile station 30 calculates the correlation between each received pilot signal and each pilot signal known in the mobile station 30, thereby obtaining the base station 1
0 <h ₁ >, <h ₂ >,..., <H _K >, and the channel impulse response vectors <h _{K +1} from the reference antennas of the other groups. >, < _{H2K + 1} >, ...,
<H _{(M-1) K + 1} > is estimated.

Further, the channel impulse response
Each address in the specific group 1 of the base station 10 is
For the antenna, the electric power P shown in the equation (9)_{intra_group}To
Transmit antenna amplitude and phase control vector to maximize
Torr (weight vector) <w_{in tra_group}> = [W₁,
w_Two, ..., w_K], And the standard antenna between each group
The power P shown in equation (11)_{inter_group}The most
Large transmit antenna amplitude and phase control vector
(Weight vector) <w_{inter_group}> = [W₁,
w _{k + 1}, ..., w_{(M-1) K + 1}] Is calculated. However, in this case
But weight coefficient w₁= 1.

[0040]

(Equation 6)

Furthermore, these <w_{intra_group}〉 ＝
[W₁, W_Two, ..., w_K] And <w_{inter_gr oup}〉 ＝
[W₁, W_{k + 1}, ..., w_{(M-1) K + 1}] And each glue
Antenna control amount F_{1, m}, And within specific group 1
Antenna control amount G_{1, k}Is given by Equations (13) and (14)
Desired.

[0042]

(Equation 7)

As described above, according to the present invention, the base station 1
0, the antenna control amount G _{1, k} in the specific group 1
Is used as an antenna control amount in each of the other groups 2 to M, the mobile station 30 may perform channel response estimation from some of the transmission antennas of the base station 10. On the other hand, the base station 10 can reduce the number of antennas for transmitting pilot signals.

Therefore, when the number of transmission antennas of base station 10 is increased and the transmission power of the common pilot signal per transmission antenna is constant, the increase in the total transmission power of the common pilot signal becomes gentle. Therefore, it is possible to suppress the amount of interference that the common pilot signal gives to the data signal in a multipath environment. Further, when the total transmission power of the common pilot signal is constant, the decrease in the transmission power of the common pilot signal per transmission antenna becomes gentle, so that a decrease in the estimation accuracy of each channel response can be suppressed.

The number of antennas K of each group (> 2)
, In any same group m, the channel response from the reference antenna # (m−1) K + 1 is
When comparing the phase differences of the channel responses from the other antennas, this value depends on the distance between the antennas being compared. Therefore, G _{m, k} (k = 3,..., G _{m, 2)}
K) can be easily calculated. By doing so, the amount of antenna control in each group to be transmitted as feedback information may be only the amount of antenna control G _1,2 in a group for a specific group 1, and the other G _{1, k} (k =
3,..., K) can be further reduced.

However, the above-described method of using the antenna control amount for a certain antenna as the antenna control amount for another antenna uses a plurality of transmitting antennas (circuits) of the base station.
Work ideally when they have the same circuit characteristics. However, since these antennas are actually circuits of different systems, there are variations in circuit characteristics, that is, deviations in phase and amplitude. Therefore, the above method is effective when a calibration technique for compensating for the phase / amplitude deviation of each antenna is applied.

[0047]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that
Throughout the drawings, the same reference numerals indicate the same or corresponding parts. FIG. 3 is a diagram showing a configuration of the transmission diversity system according to the first embodiment, and shows a case where the number of transmission antennas N = 4 and the number of transmission antenna groups M = 2.

In FIG. 3, reference numeral 10 denotes a base station, 11 denotes four transmission antennas (# 1 to # 4), 12 denotes a pilot signal generator for generating a pilot signal, and 13 denotes feedback information from an uplink channel received signal. The feedback information extracting unit 14 extracts the amplitude / phase for controlling the amplitude / phase of the transmission signal of the downlink channel based on the feedback information.
Phase control unit, 19 is a receiving antenna, 30 is a mobile station, 31
Is the receiving antenna, 32 is the data channel despreading unit,
33 is a pilot channel despreading unit, 34 is a channel estimating unit that obtains an impulse response of each downlink channel based on correlation calculation between a received pilot signal and a known pilot signal, and 35 is a transmission signal of the base station 10 based on the obtained impulse response. A control amount calculating unit for calculating the control amount (amplitude and phase) of the control signal; 36, a multiplexing unit for multiplexing the obtained control amount (feedback) information on the uplink transmission data; 37, a spreading unit for the uplink channel signal; is there.

The transmission antennas # 1 and # 1 at the base station 10
Between # 2 and between transmission antennas # 3 and # 4, they are arranged at a distance of, for example, one wavelength (λ), so that the fading correlation becomes higher. Also, between the transmitting antennas # 1 and # 3 and between the transmitting antennas # 2 and # 4, each is separated by a length of, for example, 20 wavelengths (20λ) so that the fading correlation becomes sufficiently low (no correlation). Are located. Here, transmission antennas # 1 and # 2
Are group 1 and transmission antennas # 3 and # 4 are group 2. Also, transmitting antennas # 1 and # 3 are grouped into groups 1 and 2.
Are the respective reference antennas. Further, transmission antenna # 1 is used as a reference antenna for all groups.

In the base station 10, the pilot signal generator 1
2, three types of orthogonal pilot signals P
₁ (t), P ₂ (t), and P ₃ (t) are generated and transmitted from transmission antennas # 1, # 2, and # 3, respectively. Each pilot signal receives amplitude and phase fluctuations due to fading, and reaches the receiving antenna 31 of the mobile station 30.

In mobile station 30, a signal from base station 10 is received by receiving antenna 31, and a pilot channel despreading section 33 despreads the received pilot signal. Further, in the channel estimating section 34, the received pilot signals P ₁ (t) ′, P
₂ (t) of known and ', P ₃ (t)' pilot signals P
₁ (t), P ₂ (t), and P ₃ (t) are correlated and averaged, so that each of the transmitting antennas # 1, #
2, the channel response vector <h ₁ > from # 3,
<H ₂ > and <h ₃ > are obtained. Further, in the control amount calculation unit 35, the obtained channel response vector H = [<h ₁ >,
Based on <h ₂ >, <h ₃ >], a weight vector <w> = [w ₁ , w ₃ ] that maximizes the power P of the above equation (5) is obtained by a known method, and this is calculated. It is transferred to the multiplexing unit 36 as feedback information. This feedback information is multiplexed into the uplink transmission data signal by the multiplexing unit 36, and its output is spread by the spreading unit 37 and transmitted from the transmission antenna 39.

In the base station 10, the signal from the mobile station 30 is received by the receiving antenna 19, and the feedback information is extracted by the feedback information extracting unit 13. The extracted feedback information is input to the amplitude / phase control unit 14 to generate a weighting factor w ₂ (= w ₁ ) from the weighting factors w ₁ and w ₃ included in the feedback information, and to generate these for each corresponding antenna. Multiply the downlink transmission data signal. Then, each transmission data is transmitted from transmission antennas # 1 to # 4.

In the mobile station 30, the signal from the base station 10 is received by the receiving antenna 31 and the data channel despreading section 3
In step 2, the downlink received data signal is despread, and a data receiving unit (not shown) RAKE-combines the signal of each data channel according to the channel estimation result, and finally decodes the signal.

Next, a case will be described in which, when the weighting factor w _i = a _i e ^j φ _i is expressed, a _i = 1 (i = 1, 2, 3) and only the phase control amount φ _i is controlled. . The mobile station 30 obtains a phase control amount φ ₁ (equivalent to w ₁ ) of the antenna # 2 based on the antenna # 1 and a phase control amount φ ₃ (equivalent to w ₃ ) of the antenna 3 based on the antenna # 1. Quantize,
These are transmitted to the base station 10 as feedback information. When quantizing each with one bit, for example, the following is performed.

[0055]

(Equation 8)

[0056] In addition, φ ^Q feedback information in the case of _{i = 0 b i = 0,} φ Q i = feedback information in the case of π b _i =
Let it be 1.

The phase control amounts φ ₁ and φ ₂ depend on the direction of the mobile station 30 with respect to the base station 10 and the phase control amount φ ₂ can be replaced by φ ₁ , so that the feedback information in this case is the phase control amount φ ₃ The transmission speed of b ₃ corresponding to the phase control amount φ
₁ so as to be higher than the transmission rate of b ₁ corresponding to the (phi doubles as a _2), multiplexes the upstream channel, the base station 10
To be transmitted.

FIG. 4A shows an example of the transmission format of the feedback information in this case. For example, a W-CDMA frame format (1 frame of 10 ms length is 15 frames)
In the case where 1-bit feedback information is transmitted in each slot,
Every 5 slots bits b _1, the other slot for transmitting the bit b _3. Note that the transmission rate of the feedback information bits only needs to have a relationship of b ₃ > b ₁ and is not necessarily limited to the example of FIG. FIG. 4B shows another example of the transmission format of the feedback information. Here, two bits b ₁ are transmitted per frame.

Returning to FIG. 3, in the base station 10, the amplitude / phase control unit 14 determines the phase of each transmitting antenna for each slot based on the feedback information b ₁ , b ₃ (corresponding to w ₁ , w ₃ ) received on the uplink channel. Perform control. At this time, w ₂ (= w ₁ )
Is generated.

For example, based on the feedback information b ₁ received in the immediately preceding reception slot, the corresponding antenna # 2,
The weight coefficients w ₁ and w ₂ (= w ₁ ) of # 4 are directly controlled.
Also controls the antenna # weighting coefficient w ₃ of 3 (# including 4) corresponding on the basis of the feedback information b ₃ received in the immediately preceding reception slot directly. In this case, for an antenna that is not the control target (timing), the latest feedback information is stored and used for control.

Alternatively, the effect of transmission errors and quantization errors may be reduced by performing filtering processing on each of the feedback information b ₁ and b ₃ input in time series. For example, the control amount w ₁ of an average value of two and the controlled variable w ₁ by the control amount w ₁ and earlier temporally recent of the feedback information by the feedback information received in the immediately preceding reception slot, actually used Is considered.

In W-CDMA, when synchronous detection is performed by the mobile station 30, channel response estimation values from each transmitting antenna of the base station 10 are used. To determine this value, a common pilot signal common to all users or an individual pilot signal unique to each user is used. In general, a common pilot signal having relatively high transmission power is often used. By the way, in the first embodiment, when the mobile station 30 performs synchronous detection using the common pilot signal, the common pilot signal is not transmitted from some antennas (for example, transmission antenna # 4). However, channel response estimation values from these antennas can be obtained from channel response estimation values from other antennas and antenna control amounts. Therefore, synchronous detection can be appropriately performed even in this method.

Next, a case where the control amount obtained by the mobile station 30 is quantized by a plurality of bits (words) will be described. FIG. 5 (A)
The b ₁ to 3 bits _{b 1 (2), b 1} (1), b 1 (0), b
₃ is 4 bits b ₃ (3), b ₃ (2), b ₃ (1), b
₃ shows an example of a transmission format in the case of quantizing each with (0). As for b ₁ (2), b ₁ (1), and b ₁ (0), for example, as shown in FIG. 5D, between antennas # 1 and # 2 (and antennas # 3 and # 4) having a high fading correlation. Used for phase control. On the other hand, b ₃ (3), b
_{As for 3} (2) and b ₃ (1), for example, as shown in FIG.
Used for phase control between the two. The b ₃ (0) bit is used for phase control between the antenna groups 1 and 2 having the same low fading correlation, for example, as shown in FIG.

FIG. 6 is a diagram showing the configuration of the transmission diversity system according to the second embodiment, in which the base station 10 uses the result of estimating the direction of arrival of the uplink channel for antenna control information (phase control information) in a group. Is shown. In the figure, reference numeral 15 denotes an arrival direction estimating unit for estimating the arrival direction of an uplink radio wave, 16 denotes an uplink channel signal reception processing unit, and 18
Is an array antenna for both transmission and reception. Here, it should be noted that the pilot signal P ₂ has not been sent. Other configurations may be the same as those described with reference to FIG.

As the arrival direction estimating unit 15, a known beam forming method or subspace method (MUSIC: Multiple
Signal Classification) can be adopted. The beamforming method is to sweep the direction (main lobe) having the largest reception gain of the antenna to the left and right, and estimate the arrival direction of the uplink channel by measuring the reception power. In addition, the MUSIC method uses a unique structure of a covariance matrix of a received signal, and is widely used as a highly accurate method of estimating a direction of arrival. Since the arrival direction of the received wave strongly depends on the angle of the mobile station 30 with respect to the base station 10, a method of setting the direction of the downlink transmission beam to the arrival direction of the uplink reception signal is also known.

In array antenna 18, group 1
As the transmission antennas # 1 and # 2 and the transmission antennas # 3 and # 4 of the group 2, a plurality of antenna elements arranged at intervals of one wavelength λ are used. On the other hand, as the receiving antennas (antenna groups 1 and 2) for estimating the arrival direction of the received wave, if necessary according to the arrival direction estimation method, for example, a plurality of antenna elements arranged at an interval of λ / 2 can be used. The direction-of-arrival estimating unit 15 receives the reception group 1
Or 2 based on the single measurement results, or groups 1, 2
The arrival direction of the received wave is estimated based on the average value of the two measurement results.

The base station 10 estimates the direction of arrival from the uplink received signal received by the array antenna 18. In the second embodiment, phase difference information within a group is calculated from the arrival direction estimation result of the uplink channel, and the inter-group phase difference information of the uplink feedback information is used for the inter-group antenna control information. In the mobile station 30, in order to obtain feedback information in this case, the common pilot signals P ₁ and P ₃ from the transmission antennas # 1 and # _{3 are obtained.}
Since only the processing needs to be performed, only the base station 10 in this case can reduce the number of antennas for transmitting the common pilot signal to two, which is even smaller than the three in the first embodiment.

FIG. 7 is a diagram showing the configuration of the transmission diversity system according to the third embodiment. In base station 10, antenna control information (phase difference information) in a group is used as feedback information of the uplink channel and arrival direction of the uplink channel. The case where control is performed using both of the estimation result information is shown.
Here, the pilot signal P ₂ is also transmitted. Other configurations may be the same as those described with reference to FIG.

Several methods are conceivable for controlling using both the feedback information of the uplink channel and the arrival direction estimation result information. For example, the control amount phi ₁ of uplink feedback information about the group in the phase difference information is, if not within a predetermined range around the control amount θ by DOA Estimation of the uplink channel, the amount of control by the arrival direction estimation result θ Control is performed using only

Alternatively, if the variance when monitoring the control amount φ ₁ based on the uplink feedback information of the intra-group phase difference information in a time series is larger than a predetermined value, the control is performed using only the control amount θ of the arrival direction estimation result. I do. Therefore, according to the third embodiment, it is possible to further increase the accuracy of the intra-group antenna control information.

In the above embodiment, an example of application to a common pilot signal common to all users has been described, but the present invention is not limited to this. The invention is also applicable to individual pilot signals specific to each user.

Further, in the above-described embodiment, a case has been described where the mobile station 30 includes the channel estimation unit 34 of a necessary minimum (three or two) scale. However, the present invention is not limited to this. For example, the mobile station 30 can include a channel estimator 34 for four downlink pilot channels, and such a mobile station 30 can be connected to the base station 10 according to the present invention by simple software switching control. Or it can be connected to a base station of another type, i.e. all downlink pilot channels are used for transmit diversity control.

Although the above embodiment has been described with specific numerical examples, the present invention is not limited to these numerical examples.

Although a plurality of embodiments suitable for the present invention have been described, it is to be understood that various changes in the configuration, control, processing, and combinations thereof can be made without departing from the spirit of the present invention. Not even.

(Supplementary Note 1) A predetermined pilot signal transmitted from the base station via a plurality of antennas is received and analyzed by the mobile station, and the obtained feedback information is transmitted to the uplink channel of the base station. In a base station apparatus of a mobile communication system that controls a downlink channel transmission signal based on feedback information from a mobile station, a plurality of antennas are divided into a plurality of groups, and a pilot signal is transmitted only from a reference antenna of each group. A base station device characterized by the above-mentioned.

(Supplementary Note 2) The antennas in each group are provided close to each other so that the fading correlation is high.
2. The base station apparatus according to claim 1, wherein antenna groups between the groups are provided apart from each other so as to reduce fading correlation.

(Supplementary note 3) The base station apparatus according to supplementary note 2, wherein pilot signals are further transmitted from all antennas in a specific group.

(Supplementary note 4) The base station apparatus according to supplementary note 1 or 3, wherein each pilot signal is spread by code patterns orthogonal to each other.

(Supplementary Note 5) An arrival direction estimating means for estimating the arrival direction of the radio wave of the uplink channel is provided, and the phase of the transmission signal of the downlink channel in each group is determined based on the information of the arrival direction estimated by the arrival direction estimating means. 3. The base station device according to supplementary note 2, wherein the base station device performs control.

(Supplementary Note 6) An arrival direction estimating means for estimating the arrival direction of the radio wave of the uplink channel is provided, and the phase of the transmission signal of the downlink channel in each group is estimated by the feedback information of the uplink channel and the arrival direction estimating means. 3. The base station apparatus according to claim 3, wherein the control is performed based on both the information on the incoming direction.

(Supplementary note 7) The base station apparatus according to supplementary note 6, characterized in that a downlink channel transmission signal is controlled based on a result of filtering of one or more pieces of feedback information at present and at the past.

(Supplementary Note 8) A predetermined pilot signal transmitted from the base station via a plurality of antennas is received and analyzed by the mobile station, and the obtained feedback information is transmitted to the uplink channel of the base station. In a mobile station device of a mobile communication system that controls a downlink channel transmission signal based on feedback information from a mobile station, a pilot signal from an antenna serving as a reference for each group of a base station in which a plurality of antennas is divided into a plurality of groups is provided. A mobile station apparatus that receives and analyzes, calculates feedback amounts of reference antennas of other groups with reference to a reference antenna of a specific group, forms feedback information, and returns the feedback information to a base station.

(Supplementary Note 9) The pilot signals from all the antennas in the specific group of the base station are further received and analyzed, and the pilot signals of all the other antennas in the same group with respect to the reference antenna in the specific group are further referred to. The mobile station apparatus according to claim 8, wherein feedback information is formed by obtaining a control amount, and the feedback information is returned to the base station.

(Supplementary Note 10) Control information between groups is
Calculate faster than the control information in a specific group,
The mobile station apparatus according to supplementary note 9, wherein the mobile station apparatus transmits these as feedback information to the base station side.

[0085]

As described above, according to the present invention, by increasing the number of diversity antennas, it is possible to improve the diversity effect of the mobile communication system and the reception diversity combining gain at the mobile station, and to perform the closed loop transmission diversity control. By reducing the number of antennas for transmitting the pilot signal to be used, if the transmission power of the pilot signal per transmission antenna is constant, the amount of interference that the pilot signal gives to the data signal in a multipath environment is reduced. Effectively suppressed. Alternatively, when the total transmission power of the pilot signal is constant, a decrease in the estimation accuracy of the impulse response in each downlink channel can be effectively suppressed. Furthermore, compatibility of a mobile station can be easily maintained in a closed-loop transmission diversity type mobile communication system using an arbitrary number of transmission antennas.

[Brief description of the drawings]

FIG. 1 is a diagram (1) showing a basic configuration of the present invention.

FIG. 2 is a diagram (2) showing a basic configuration of the present invention.

FIG. 3 is a diagram illustrating a configuration of a transmission diversity system according to the first embodiment.

FIG. 4 is a diagram (1) illustrating an example of a transmission format of feedback information according to the embodiment;

FIG. 5 is a diagram (2) illustrating an example of a transmission format of feedback information according to the embodiment;

FIG. 6 is a diagram illustrating a configuration of a transmission diversity system according to a second embodiment.

FIG. 7 is a diagram illustrating a configuration of a transmission diversity system according to a third embodiment.

FIG. 8 is a diagram illustrating a conventional technique.

[Explanation of symbols]

 Reference Signs List 10 base station 11 transmission antenna (# 1 to # 4) 12 pilot signal generation unit 13 feedback information extraction unit 14 amplitude / phase control unit 15 arrival direction estimation unit 16 reception processing unit 18 array antenna 19 reception antenna 30 mobile station 31 reception antenna 32 data channel despreading unit 33 pilot channel despreading unit 34 channel estimating unit 35 control amount calculating unit 36 multiplexing unit 37 spreading unit 39 transmitting antenna

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshinori Tanaka 4-1-1, Kamikodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa F-term within Fujitsu Limited (reference) 5K059 CC02 DD10 DD31 EE02 5K067 CC10 CC24 DD27 EE02 EE10 GG08 HH21 KK03

Claims (5)

[Claims] 1. A mobile station receives and analyzes a predetermined pilot signal transmitted from a base station via a plurality of antennas,
In the base station apparatus of the mobile communication system, which transmits the obtained feedback information to the uplink channel of the base station and controls the transmission signal of the downlink channel of the base station based on the feedback information from the mobile station, And transmitting a pilot signal only from an antenna serving as a reference for each group. 2. An antenna in each group is provided close to each other so as to increase fading correlation, and an antenna group between groups is provided apart from each other so as to reduce fading correlation. Item 2. The base station device according to item 1. 3. The base station apparatus according to claim 2, wherein pilot signals are further transmitted from all antennas in a specific group. 4. A mobile station receives and analyzes a predetermined pilot signal transmitted from a base station via a plurality of antennas,
A mobile station device of a mobile communication system that transmits the obtained feedback information to an uplink channel of a base station and controls a transmission signal of a downlink channel of the base station based on feedback information from the mobile station. In addition to receiving and analyzing pilot signals from the reference antennas of each group of the base station, the feedback information is obtained by obtaining the control amounts of the reference antennas of the other groups with respect to the reference antennas of the specific group. A mobile station device formed and returned to a base station. 5. A pilot signal from all antennas in a specific group of base stations is further received and analyzed, and a control amount of all other antennas in the same group with respect to a reference antenna in the specific group is controlled. The mobile station apparatus according to claim 4, wherein feedback information is formed by obtaining the feedback information, and the feedback information is returned to the base station.