JP4426356B2 - Radio apparatus and beam pattern control method - Google Patents

Description

  The present invention relates to a radio apparatus and a beam pattern control method.

  In general, in a wireless communication system, since the distance between a transmitting station and a receiving station is not uniform, a transmission signal arranged on a complex plane by a modulation method such as QPSK is received with phase rotation at the receiving station. In particular, in a mobile communication system, the amount of phase rotation changes significantly due to multipath fading. In order to solve this problem, in a mobile communication system, a mobile station generally uses a pilot channel for transmitting a known signal in broadcast format for detection of a location from a base station to a mobile station. Receive synchronization processing.

  FIG. 4 is a diagram for explaining the principle of reception synchronization processing using a pilot channel. In FIG. 4, the base station transmits a known signal (only the real part) on the pilot channel. In addition, transmission data (complex number) is transmitted through the data channel. These transmission signals are received by the mobile station in response to phase rotation α due to fading on the radio propagation path. The mobile station calculates the phase rotation α on the complex plane from the known signal transmitted through the pilot channel and the received signal of the pilot channel (known signal that has received the phase rotation α). Then, the complex conjugate number of the phase rotation α is obtained and multiplied by the data channel reception signal (transmission data subjected to the phase rotation α). As a result, the phase rotation α is corrected for the reception signal of the data channel, and the reception data after this correction can be demodulated to obtain the reception data with high accuracy.

  Further, a beam control technique for adaptively controlling a beam pattern by using an array antenna composed of a plurality of antenna elements is known. In this beam control technique, an arbitrary beam pattern can be formed by multiplying a signal input / output to / from each antenna element by a coefficient called an array weight for adjusting the amplitude and phase of each signal. The beam control technique adaptively controls the beam pattern so that a high gain beam is formed in the desired station direction and a null is formed in the undesired station direction. Each orthogonal beam pattern can be formed. This enables multiple access (space division multiple access (SDMA)) using a space (beam pattern) independent of time and frequency.

  In a mobile communication system, when the transmission beam pattern is adaptively controlled by the beam control technique described above, it is generally applied to the data channel described above, but not to the pilot channel. This is because the data channel is an individual channel for each mobile station, and the SDMA of the data channel can be performed by forming an individual transmit beam pattern for each mobile station, whereas the pilot channel is used for all mobile stations. This is because it is a common channel and it is not necessary to form individual transmit beam patterns for each mobile station. A transmission beam pattern having uniform directivity, for example, an omni pattern or a sector pattern is applied to the pilot channel. For this reason, the transmission channel weight for forming the transmission beam pattern is different between the pilot channel and the data channel. As a result, since the phase amount characteristics of the transmission beam patterns differ between the pilot channel and the data channel, a problem arises in the reception synchronization processing of the mobile station described above. That is, since the phase rotation amount differs between the pilot channel and the data channel, correct correction cannot be performed even if the data channel reception signal is corrected based on the phase rotation of the pilot channel reception signal. As a result, the received signal is not demodulated normally and the received data is incorrect.

In order to solve this problem, conventionally, a separate pilot channel is provided for each mobile station apart from a pilot channel common to all mobile stations. For transmission of this dedicated pilot channel, a transmission beam pattern using the same transmission array weight as that of the data channel is formed and transmitted simultaneously with the data channel at a frequency different from that of the data channel (see, for example, Patent Document 1). ).
Japanese Patent Application Laid-Open No. 2002-314481

  However, in the conventional technique described above, since a dedicated pilot channel is newly provided, it is necessary to change the specifications of the mobile station, and there is a problem that the existing mobile station terminal cannot be used. Also, the burden of developing a terminal for a new mobile station is large. Further, since a frequency for the dedicated pilot channel is required, the frequency utilization efficiency is lowered. For this reason, there is no need to newly provide a dedicated pilot channel as in the prior art described above, and it is possible to divert an existing mobile station terminal, which does not cause a decrease in frequency utilization efficiency. New solutions are desired.

  FIG. 5 is a diagram for explaining a conventional influence due to a difference in transmission beam patterns between a pilot channel and a data channel. In FIG. 5, an omni pattern is formed for transmission of a pilot channel common to all mobile stations, and a transmission beam pattern (adaptive beam pattern) by adaptive control is formed for transmission of individual data channels for each mobile station. The As shown in FIG. 5, the phase amount characteristic of the omni pattern is uniform regardless of the radiation direction, but the phase amount characteristic of the adaptive beam pattern varies depending on the radiation direction. Further, the phase amount in the mobile station direction differs between the omni pattern and the adaptive beam pattern, that is, the initial phase of the transmission beam pattern differs between the pilot channel and the data channel. This difference in the initial phase causes a correction shift in the reception synchronization processing of the mobile station. Therefore, if the initial phase of the transmission beam pattern can be matched between the pilot channel and the data channel, the correction deviation can be eliminated, and the reception synchronization processing of the mobile station can be performed with high accuracy.

  The present invention has been made in view of such circumstances, and its purpose is to use a channel (for example, a data channel) to be transmitted by an adaptive beam pattern and a beam pattern (for example, an omni pattern) different from the adaptive beam pattern. An object of the present invention is to provide a radio apparatus and a beam pattern control method capable of matching the initial phase of each transmission beam pattern with a channel to be transmitted (for example, a pilot channel).

In order to solve the above problems, a radio apparatus according to the present invention, the array antenna including a plurality of antenna elements, for forming a first transmit beam pattern of the array antenna, each of said antenna elements A first transmission array weight calculating means for adaptively calculating a first transmission array weight vector composed of elements corresponding to each receiving station, and a second transmission beam pattern for the array antenna , The second transmission array weight calculation means for calculating a second transmission array weight vector composed of elements corresponding to each of the antenna elements, and the radiation characteristic measurement data of each antenna element of the array antenna are vectorized. A steering vector comprising elements corresponding to each of the antenna elements, including information on relative amplitude and phase between the antenna elements. Le, each radial direction, acquires a radiation characteristic storage means for storing in advance a receiving station direction estimating means for estimating the direction of the receiving station, the steering vector of the estimated received station direction from the radiation characteristic storage means A vector product of the obtained steering vector and the first transmission array weight vector is performed, and a phase component (first initial phase) of a complex scalar value obtained by the vector product is extracted. A vector product of a steering vector and the second transmission array weight vector is performed, a phase component (second initial phase) of a complex scalar value obtained by the vector product is extracted, and the first initial phase and the calculating a difference amount of phase and second initial phase, the initial phase correction means for only phase rotation said difference amount of phase the phase component of the first transmission array weight vector It is characterized by comprising a.

A beam pattern control method according to the present invention is a vectorization of an array antenna composed of a plurality of antenna elements and radiation characteristic measurement data of each antenna element of the array antenna. A beam pattern control method in a radio apparatus comprising storage means for storing in advance , for each radiation direction, steering vectors comprising elements corresponding to each of the antenna elements including information on relative phases , Adaptively calculating, for each receiving station, a first transmit array weight vector composed of elements corresponding to each of the antenna elements to form a first transmit beam pattern; and a second of the array antenna for forming a transmit beam pattern, each feed of the second consisting of the corresponding element of the antenna element A step of calculating an array weight vector, the steps of estimating the direction of the receiving station, wherein the steps of steering vectors of the estimated received station direction acquired from the storage unit, transmits with the acquired steering vector the first Performing a vector product with the array weight vector, extracting a phase component (first initial phase) of the complex scalar value obtained by the vector product , the same steering vector and the second transmission array weight vector, And extracting a phase component (second initial phase) of a complex scalar value obtained by the vector product, and a differential phase amount between the first initial phase and the second initial phase as a feature comprising the steps of calculating, the process of only phase rotation said difference amount of phase the phase component of the first transmission array weight vector, to include a That.

  According to the present invention, since the initial phase shift of each of the first transmission beam pattern and the second transmission beam pattern by adaptive control is corrected, for example, the transmission beam patterns for the data channel and the pilot channel, respectively. The initial phase can be adjusted. Thereby, in the mobile station, it is possible to correct the data channel reception signal correctly based on the phase rotation of the pilot channel reception signal, and the mobile station reception synchronization processing can be accurately performed. can get.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a wireless device according to an embodiment of the present invention. In this embodiment, a base station radio apparatus of a mobile communication system will be described as an example.
In FIG. 1, an array antenna 1 is composed of a plurality of antenna elements 1a. The RF unit 2 transmits and receives an RF band radio signal via each antenna element 1a. The RF unit 2 outputs the RF band reception signal of each antenna element 1a to the adaptive control unit 3 after converting it into a baseband signal and digitizing it. In addition, the baseband transmission signal of each antenna element 1a is received from the adaptive control unit 3, and after being converted into an RF band signal and converted into an analog signal, the antenna element 1a is wirelessly transmitted.

  The adaptive control unit 3 adaptively controls the beam pattern of the array antenna 1 and performs adaptive reception and adaptive transmission for each mobile station. In adaptive reception, a reception beam pattern is formed by adaptive control for each mobile station, and a data channel for each mobile station is received. The received data is output to the reception channel processing unit 4 and processed.

  Further, in adaptive transmission, transmission beam patterns are formed by adaptive control for each mobile station, and data channels for individual mobile stations are transmitted. The transmission data of this data channel is input from the transmission channel processing unit 5. Further, the adaptive control unit 3 forms a transmission beam pattern for a pilot channel and transmits a pilot channel common to mobile stations. The transmission data of the pilot channel is input from the transmission channel processing unit 5.

  The adaptive control unit 3 may be realized by dedicated hardware. The adaptive control unit 3 includes a memory and an arithmetic processing unit such as a DSP (digital signal processor). The function may be realized by loading a program for realizing the function of the control unit 3 into a memory and executing the program.

FIG. 2 is a block diagram showing a configuration relating to a transmission function provided in the adaptive control unit 3 of FIG.
In FIG. 2, a pilot channel transmission array weight calculation unit 11 calculates a transmission array weight vector Wp for forming a transmission beam pattern for a pilot channel. The transmission array weight vector Wp includes elements corresponding to each of the antenna elements 1a, that is, elements corresponding to the number of antenna elements 1a.
When a transmission beam pattern having uniform directivity, such as an omni pattern or a sector pattern, is used as the transmission beam pattern for the pilot channel, a predetermined transmission array weight vector Wp (fixed value) is stored. A memory may be provided.

  The data channel transmission array weight calculation unit 12 adaptively calculates a transmission array weight vector Wd for forming a data channel transmission beam pattern for each mobile station. The transmission array weight vector Wd includes elements corresponding to each of the antenna elements 1a, that is, elements corresponding to the number of antenna elements 1a.

  The mobile station direction estimation unit 13 estimates the direction in which the mobile station is located, and outputs this direction estimation value φ to the transmission array weight phase correction unit 15. For example, the direction in which the mobile station is located is obtained based on a reception beam pattern formed by adaptive reception.

The array antenna element radiation characteristic data storage unit 14 stores radiation characteristic data A of the array antenna 1 in advance for each radiation direction. This radiation characteristic data A is a vector obtained by vectorizing radiation characteristic data of each antenna element 1a (steering vector), and includes elements corresponding to each of the antenna elements 1a, that is, elements corresponding to the number of antenna elements 1a. The radiation characteristic data A includes information on relative amplitude and relative phase between antenna elements.
Note that actual measurement data and simulation data are used as radiation characteristic data of the antenna element 1a alone. For example, the data measured using the transmission frequency of the RF band in the state where it is actually assembled as the array antenna 1 is used. Alternatively, data simulated under simulation conditions equivalent to the measurement conditions is used.

  The transmission array weight phase correction unit 15 forms a transmission array for forming a transmission beam pattern for the data channel so that the initial phases of the transmission beam pattern for the pilot channel and the transmission beam pattern for the data channel are equal to each other. The weight vector Wd is corrected. The corrected transmission array weight vector Wd ′ is output to the transmission beam forming unit 16.

  The transmission beam forming unit 16 multiplies the transmission array weight vector Wd ′ and the data channel data by the multiplier 17, and outputs the data channel transmission signal resulting from the multiplication to the RF unit 2. Thereby, a transmission beam pattern for the data channel of the array antenna 1 is formed. Further, the transmission channel weight vector Wp for the pilot channel and the pilot channel data are multiplied by the multiplier 17, and the pilot channel transmission signal resulting from the multiplication is output to the RF unit 2. Thereby, a transmission beam pattern for the pilot channel of the array antenna 1 is formed.

Next, the operation of the transmission array weight phase amount correction unit 15 in FIG. 2 will be described with reference to FIG. FIG. 3 is a processing flowchart of the transmission array weight phase correction unit 15 shown in FIG.
In FIG. 3, first, the transmission array weight phase amount correction unit 15 uses the radiation characteristic data A (steering vector) in the radiation direction corresponding to the direction estimation value φ of the desired station that is the data channel transmission target, as the array antenna element radiation characteristic. Obtained from the data storage unit 14 (step S1).

  Next, the initial phase of each transmission beam pattern for each channel is calculated from the acquired steering vector and each transmission array weight vector Wp, Wd related to the desired station (step S2). In this initial phase calculation process, the vector product of the transmission array weight vector Wp and the steering vector is performed, and the phase component of the resulting complex scalar value is extracted. This phase component represents the initial phase of the transmission beam pattern for the pilot channel. Similarly, the vector product of the transmission array weight vector Wd and the steering vector is performed, and the phase component of the resulting complex scalar value is extracted. This phase component represents the initial phase of the transmit beam pattern for the data channel.

  Next, a difference phase amount of each initial phase is calculated by calculating a difference between these phase components (step S3). Next, the phase component of the transmission array weight vector Wd is rotated by the difference phase amount (step S4). In this phase rotation process, the phase components of all elements of the transmission array weight vector Wd, that is, all elements corresponding to each of the antenna elements 1a are shifted by the difference phase amount. Thereby, the initial phase of each transmission beam pattern becomes equal for the data channel and the pilot channel. Even if the phase rotation processing is performed, the relative phase and the relative amplitude between the elements of the transmission array weight vector Wd do not change, so that a transmission beam pattern for a desired data channel can be obtained.

  As described above, according to the present embodiment, since the initial phase shift between the transmission beam pattern for the pilot channel and the transmission beam pattern for the data channel is corrected, the phase of the received signal of the pilot channel is corrected in the mobile station. Based on the rotation, the reception signal of the data channel can be corrected correctly, and the reception synchronization process of the mobile station can be accurately performed.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.
For example, the present invention can be similarly applied to a case where a transmission beam pattern for a pilot channel is formed for each mobile station. Further, the present invention can be similarly applied when correcting the initial amplitude of the transmission beam pattern.
In addition, the present invention can be applied to various wireless devices provided with an array antenna.

It is a block diagram which shows the structure of the radio | wireless apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure which concerns on the transmission function with which the adaptive control part 3 of FIG. 1 is equipped. FIG. 3 is a process flow diagram of a transmission array weight phase amount correction unit 15 shown in FIG. 2. It is a figure for demonstrating the principle of the reception synchronous process using a pilot channel. It is a figure for demonstrating the conventional influence by the difference in the transmission beam pattern of a pilot channel and a data channel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Array antenna, 1a ... Antenna element, 2 ... RF part, 3 ... Adaptive control part, 4 ... Reception channel processing part, 5 ... Transmission channel processing part, 11 ... Transmission array weight calculation part for pilot channels, 12 ... Data channel Transmission array weight calculation unit, 13 ... mobile station direction estimation unit, 14 ... array antenna element radiation characteristic data storage unit, 15 ... transmission array weight phase amount correction unit, 16 ... transmission beam forming unit.

Claims (2)

An array antenna composed of a plurality of antenna elements;
A first transmission array weight for adaptively calculating, for each receiving station, a first transmission array weight vector composed of elements corresponding to each of the antenna elements for forming a first transmission beam pattern of the array antenna. A calculation means;
Second transmission array weight calculating means for calculating a second transmission array weight vector comprising elements corresponding to each of the antenna elements for forming a second transmission beam pattern of the array antenna;
Radiation characteristic measurement data of each antenna element of the array antenna is vectorized and includes a steering vector composed of elements corresponding to each of the antenna elements including information on relative amplitude and phase between the antenna elements. Radiation characteristic storage means for storing in advance for each direction ;
Receiving station direction estimating means for estimating the direction of the receiving station;
The estimated steering vector in the direction of the receiving station is acquired from the radiation characteristic storage means , a vector product of the acquired steering vector and the first transmission array weight vector is performed, and a complex scalar obtained by this vector product A phase component of the value (first initial phase) is extracted, and a vector product of the same steering vector and the second transmission array weight vector is performed, and a phase component of the complex scalar value obtained by the vector product (Second initial phase) is extracted, a differential phase amount between the first initial phase and the second initial phase is calculated, and a phase component of the first transmission array weight vector is calculated by the differential phase amount. Initial phase correction means for rotating the phase;
A wireless device comprising: An array antenna composed of a plurality of antenna elements and radiation characteristics measurement data of each antenna element of the array antenna are vectorized and include information on relative amplitude and relative phase between the antenna elements. A beam pattern control method in a radio apparatus comprising storage means for storing in advance a steering vector composed of elements corresponding to each, for each radiation direction ,
Adaptively calculating, for each receiving station, a first transmit array weight vector composed of elements corresponding to each of the antenna elements to form a first transmit beam pattern of the array antenna;
Calculating a second transmit array weight vector comprising elements corresponding to each of the antenna elements to form a second transmit beam pattern of the array antenna;
A step of estimating the direction of the receiving station,
Obtaining the estimated steering vector in the direction of the receiving station from the storage means;
Performing a vector product of the acquired steering vector and the first transmission array weight vector, and extracting a phase component (first initial phase) of a complex scalar value obtained by the vector product ;
Performing a vector product of the same steering vector and the second transmit array weight vector, and extracting a phase component (second initial phase) of a complex scalar value obtained by the vector product ;
Calculating a differential phase amount between the first initial phase and the second initial phase;
Rotating the phase component of the first transmit array weight vector by the differential phase amount;
A beam pattern control method.

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