JP4417324B2 - Wireless communication method - Google Patents

Description

  The present invention relates to a radio communication method and a radio communication system, and more particularly to a radio communication method and a radio communication system in a base station system that multiplexes channels for a plurality of terminals by a time division multiplexing method and has a beam direction variable antenna. About.

  The conventional time division multiplexing wireless communication system is basically based on suppressing crosstalk and interference between channels by transmitting signals for each terminal through channels using different time slots. Therefore, there is no interference under the same base station due to simultaneous transmission of signals for a plurality of terminals at the same time as in a code multiplex system, so that antenna directivity such as so-called smart antenna or adaptive antenna is being communicated. There has been little need for a system that concentrates on terminals and suppresses interference with other terminals.

In general, in a method for performing so-called best-effort communication by controlling communication channel modulation and coding parameters to optimum values in consideration of the level of observed interference noise (for example, Paul Bender, Peter Black , Matthew Grob, Roberto Padovani, Nagabhushana
Sindhushayana, and Andrew Vitervi, “CDMA / HDR: A Bandwidth-Efficient High-Speed
Wireless Data Service for Nomadic Users ”, IEEE Communications Magazine, Vol.
38, pp. 70-77, July, 2000. (Hereinafter referred to as HDR (High Data Rate) method), the data rate at which communication is possible is determined by the amount of interference noise observed at the terminal. In such a system, if the amount of interference noise is low, it becomes possible to perform communication at a higher data rate. Therefore, reducing the interference noise as much as possible is effective in improving the system performance. As long as the time division multiplexing method is used, the interference noise observed at this terminal is not a signal for other terminals transmitted from the same base station in communication, but is adjacent to another terminal or another terminal from another base station. This signal is sent at the same time.

  FIG. 23 is an explanatory diagram of the basic principle of the HDR method. In general, it is known that a signal for a terminal (hereinafter referred to as a downlink signal) transmitted from a base station attenuates power in inverse proportion to the 3.5th power of a distance in a large city, for example. As the distance increases, the received power gradually falls below the level of the signal transmitted from the adjacent base station or the interference signal constituted by thermal noise, etc., and normal reception at the terminal becomes difficult. The ratio between the received signal power and the interference signal power is referred to as C / I. When this C / I is sufficiently high in the vicinity of the base station, for example, the modulation method of the radio signal is set to 8-level multi-level modulation, and further, the radio wave quality is high, so that the error correction redundancy is reduced, and as a result Even if the same band is used, transmission at a high bit rate is possible. On the other hand, since the C / I decreases in an area far from the base station, it is necessary to use a binary modulation method that is less prone to errors and increase signal redundancy to improve error correction capability. As a result, the bit rate that can be transmitted decreases. In the HDR system, C / I is actually measured at a terminal before starting communication, and the maximum bit rate that can be received at that point is transmitted to the base station. As a result, a best-effort wireless transmission system is realized.

  Here, FIG. 24 shows an explanatory diagram of the multiplexing scheme in the HDR scheme downlink. FIG. 25 shows an explanatory diagram of an example of a general base station arrangement. FIG. 26 shows a timing diagram of a transmission signal in the HDR downlink.

  In the HDR method, as shown in FIG. 24, multiplexing of the downlink signal uses a so-called time division multiplexing method in which signals for different terminals are arranged in N time slots, for example. That is, when base stations are installed as shown in FIG. 25, each base station emits radio waves using time slots arbitrarily assigned in time as shown in FIG. As shown in the figure, for example, assuming that base stations (hereinafter referred to as BS) BS1 and BS2 are simultaneously emitting radio waves from time T1 to T2, a boundary region 3-1 between BS1 and BS2 indicated by hatching in FIG. Then, strong radio wave interference occurs. As a result, when observed at the terminal, the C / I of both the signal from BS1 and the signal from BS2 decreases, making it difficult to communicate at a high bit rate.

  FIG. 30 is an explanatory diagram of coverage (614.4 kbit / s) in the HDR downlink when conventional base stations are arbitrarily arranged in a square. This figure shows a bit rate of 614.4 kbit / s when a three-sector type HDR base station in which each sector is formed by a beam having an aperture angle of 90 degrees is arranged at the apex of a quadrangle with a side of 2 km. Service coverage is indicated by hatching. Here, the calculation is based on the assumption that radio waves are emitted in all time slots of all base stations. In the figure, in the area 20-5, the sector beam 20-1 of BS1 and the sector beam 20-2 of BS2 interfere with each other and cannot be serviced. On the other hand, in the area 20-6, since none of the sector beams of BS3 and BS4 are directed in this direction, the service cannot be performed. Further, in the region 20-8, the sector beams 20-1 and 20-7 of BS1 interfere with each other, and the unserviceable region is cut into a considerable vicinity of BS1. Similar notches are also observed in, for example, the region 20-9.

  FIG. 31 shows an explanatory diagram of coverage (204.8 kbit / s) in the HDR downlink when conventional base stations are arbitrarily arranged in a square. This figure shows the service area when the bit rate is lowered to 204.8 kbit / s under the same conditions, but there remains an area where service cannot be performed even if the bit rate is lowered so far.

In view of the above, the object of the present invention is to make it difficult to communicate at a sufficiently high bit rate because radio waves emitted from each base station interfere with each other particularly in the boundary region of a cell or sector in an HDR system. It is to provide a radio communication method and a radio communication system in a base station system that prevents the occurrence of the above. Another object of the present invention is to provide a radio communication method and a radio communication system capable of providing services in a wider area by reducing the area where the direction of the sector beam is not directed.
Another object of the present invention is to provide a radio communication method and a radio communication system capable of preventing as much as possible a situation in which an unserviceable area is cut off due to interference of a plurality of sector beams.

  Furthermore, another object of the present invention is, for example, the direction of radio waves emitted at the same time from each base station in the HDR downlink, the direction that is most unlikely to interfere with each other, wherever the terminal exists in the service area, It is always to receive a good radio signal with little interference. Accordingly, another object of the present invention is to maximize one of the features of HDR that enables high bit rate communication when radio wave interference is low.

In order to prevent radio waves from the base stations from interfering with each other as described above, the present invention does not radiate radio signals that interfere with each other at the same time, but radiates at different times. It is something to try to avoid. At this time, the time management at each base station is synchronized with high accuracy by utilizing a system capable of supplying absolute time with high accuracy in a wide area such as a GPS system, and the radio wave emission direction of each base station is set for each time. Switch to avoid interference.
According to the first solution of the present invention,
In each base station having a plurality of antenna elements, a method of wirelessly communicating with a wireless terminal,
Receives a signal from a wireless terminal via an antenna capable of realizing the antenna directivity of a predetermined beam pattern by combining a reception signal and a transmission signal by each antenna element,
Synthesize the signals from each antenna element with the antenna directivity of a predetermined beam pattern,
Based on the combined received signal of each directivity, select a received signal from the wireless terminal, determine transmission beam direction information for directing the beam in the selected direction,
Based on the determined transmission beam direction information and a table storing the relationship between the transmission beam direction and the time slot used when radiating in that direction, a transmission beam time slot is obtained,
Provided is a wireless communication method including transmitting a downlink signal by controlling an antenna using the obtained transmission beam time slot.
According to the second solution of the present invention,
Place multiple base stations in a square,
The antenna of each base station has a plurality of antenna elements, and is capable of realizing the antenna directivity of a predetermined beam pattern by combining the reception signal and the transmission signal by each antenna element. The beam pattern is installed in a direction in which the adjacent base stations shift the beam direction by 45 degrees or approximately 45 degrees from each other,
Receiving a signal from a wireless terminal via the antenna;
Synthesize the signals from each antenna element with the antenna directivity of a predetermined beam pattern,
Based on the combined received signal of each directivity, receive a signal from the wireless terminal,
Provided is a radio communication method between a radio terminal and a base station, which includes transmitting a downlink signal by controlling antenna directivity to a predetermined beam pattern.
According to the third solution of the present invention,
Multiple base stations are arranged in a triangle,
The antenna of each base station has a plurality of antenna elements, combines the reception signal and transmission signal by each antenna element to realize the antenna directivity of a predetermined beam pattern, and the same beam pattern of the antenna of each base station A wireless communication method between a base station and a terminal including dynamically or statically installing in the direction of the terminal is provided.
According to the fourth solution of the present invention,
Place multiple base stations in a square,
The antenna of each base station has a plurality of antenna elements, combines the reception signal and the transmission signal by each antenna element to realize the antenna directivity of a predetermined beam pattern, and sets the beam pattern of the antenna of each base station, Provided is a wireless communication method between a base station and a terminal, which includes dynamically or statically installing adjacent base stations in a direction in which the beam directions are shifted by 45 degrees or approximately 45 degrees from each other.
According to the fifth solution of the present invention,
A plurality of base stations are arranged in a triangular arrangement having a triangular positional relationship with each other in a plane.
The antenna of each base station is composed of 3 sector antennas,
Provided is a wireless communication method including combining a reception signal and a transmission signal by each antenna element.
According to the sixth solution of the present invention,
A plurality of base stations are arranged in a square arrangement that is a quadratic positional relationship with each other in a plane,
The antenna of each base station is composed of 4 sector antennas,
Provided is a wireless communication method including combining a reception signal and a transmission signal by each antenna element.
According to a seventh solution of the present invention,
A plurality of base stations are arranged in a square arrangement that is a quadrangular position in a plane,
The antenna of each base station is composed of antennas that can realize eight directivities every 45 °,
In each time slot, specify the antenna directivity so that the two directivities of the three directivity patterns are orthogonal to each other, and the other directivity is in the direction of 135 ° from these two directivities. A wireless communication method is provided.
According to the eighth solution of the present invention,
In a wireless communication system that performs wireless communication between a plurality of base stations and wireless terminals,
Each base station
An antenna that has a plurality of antenna elements, and that can synthesize a reception signal and a transmission signal by each antenna element to realize an antenna directivity of a predetermined beam pattern;
A circuit for receiving a signal from a wireless terminal via the antenna;
A circuit that synthesizes signals from each antenna element with the antenna directivity of a predetermined beam pattern;
A circuit that selects a received signal from a wireless terminal based on the combined received signal of each directivity and determines transmission beam direction information for directing the beam in the selected direction;
A circuit for generating a transmit beam time slot based on transmit beam direction information from the determining circuit and a table of information representing a relationship between the transmit beam direction and a beam time slot used when radiating in that direction;
There is provided a radio communication system including a circuit for controlling the antenna to transmit a downlink signal using the generated transmission beam time slot.

According to the present invention, as described above, radio waves emitted from the base stations interfere with each other, especially in the boundary region between cells and sectors in an HDR system, and communication at a sufficiently high bit rate becomes difficult. Can be prevented. Further, according to the present invention, it is possible to provide a service in a wider area by reducing the area where the direction of the sector beam is not directed. Further, according to the present invention, it is possible to prevent as much as possible that a non-serviceable area is cut off due to interference of a plurality of sector beams.
Furthermore, according to the present invention, for example, the direction of radio waves emitted from each base station at the same time on the HDR downlink is set to be the direction in which interference is least likely to interfere with each other. It is possible to receive a good radio signal with little noise. Thus, according to the present invention, one of the features of HDR that enables high bit rate communication when radio wave interference is low can be exhibited to the maximum.

  FIG. 1 is an explanatory diagram of service coverage (614.4 kbit / s) in an HDR downlink in which base stations according to the present invention are arranged in a triangle. This figure shows an optimal base station and a sector direction arrangement when a three-sector base station is used. Each base station shown in the figure is a three-sector antenna type HDR base station in which each sector is configured by an antenna having an opening angle of 90 degrees, and transmission of 614.4 kbit / s is performed using all time slots. Coverage when performing. As shown in the figure, transmission at this bit rate is difficult in the boundary area of the cell area of each base station, for example, 5-4. This is because the radio waves of the sector antenna 5-1 of BS1, the sector antenna 5-2 of BS2, and the sector antenna 5-3 of BS3 interfere with each other in space, making transmission at a rate of 614.4 kbit / s difficult. Yes. However, compared with the prior art FIG. 30, the difficult service area is greatly reduced. In FIG. 30, each base station is arranged in a square in which a square is laid out in a desired area and the base stations are arranged at the apexes thereof, whereas in the embodiment of FIG. 1, in the triangular shape in which the base stations are laid out This is because the base station is arranged in a triangular arrangement at the apex, and the sector directions of the base stations are arranged such that the radio wave interference is minimized. For this reason, for example, interference increases due to the crossing of beams that irradiate the same region at a short distance as shown in the case of the sector beam 20-1 of BS1 and the sector beam 20-2 of BS2 in FIG. Disappear.

  FIG. 2 is an explanatory diagram of service coverage (614.4 kbit / s) in an HDR downlink in which base stations according to the present invention are squarely arranged. In this figure, a half-value angle of 90 degrees, a 4-sector antenna, a bit rate of 614.4 kbit / s, and each base station uses all time slots. When a three-sector base station is used in a square arrangement, it is impossible to avoid the crossing of beams that interfere with each other in terms of geometry, as shown in FIGS. In the case of square arrangement, it is necessary to make the sector beam a 4-sector type as shown in FIG. Further, as shown in the figure, the adjacent base stations are tilted 45 degrees from each other as shown in the figure, so that the crossing of the beams can be minimized.

The above described the effect of the first embodiment of the present invention, but there still remains a region where service is impossible at the intermediate distance of each base station. For example, the region 5-4 in FIG. 1, the region 13-3 in FIG.
Further, FIG. 3 is an explanatory diagram of service coverage (1228.8 kbit / s) in an HDR downlink in which base stations according to the present invention are arranged in a triangle. In this figure, a half-sector angle of 90 degrees, a three-sector antenna, a bit rate of 1228.8 kbit / s, and all time slots are used. For example, if the bit rate is increased to 1228.8 kbit / s, the serviceable area is significantly reduced as shown. The difficult service area occurs in a cell boundary area with an adjacent base station and a sector boundary area in the same base station. That is, it may be difficult to eliminate the non-serviceable area only by the first embodiment that optimizes the number of sectors and the sector direction.

  Therefore, the service area is further expanded by utilizing the time division multiplexing method for the HDR downlink. In the example shown in FIG. 26, since BS2 stops emitting radio waves from time T2 to T3, the signal from BS1 can secure a high C / I even in hatching area 3-1 in FIG. Therefore, communication at a high bit rate is possible. That is, between cells / sectors that interfere with each other, it is possible to significantly reduce the amount of mutual interference by avoiding the emission of radio waves at the same time, and thus it is possible to expand the area where communication at a high bit rate is possible.

  In the second embodiment of the present invention, each base station in the system is provided with a function capable of switching the transmission directivity of the antenna, and the directivity switching is performed synchronously between the base stations, thereby enabling a specific terminal The main feature is to minimize the probability that signals transmitted from a plurality of base stations interfere with each other at the same time. As a result, each terminal can communicate at a communication time set for itself with the interference noise from adjacent or other base stations being extremely low, and the best effort function enables communication at the maximum bit rate. It becomes possible.

  FIG. 4 is an explanatory diagram of service coverage in an HDR downlink using a 30 degree sector antenna and time slot A (FIG. 24) according to the present invention. In this figure, the half-value angle is 30 degrees, three of the 12-sector antennas are used, the bit rate is 614.4 kbit / s, and the time slot is A. In the present embodiment, unlike the cases of FIGS. 1 and 3, the opening angle of each base station sector antenna is narrowed to 30 degrees. As shown in the figure, also in the boundary region 7-4 between BS1 and BS2, the coverage of each base station extends to an intermediate distance portion between both base stations. This is because, by narrowing the sector beam, for example, the signals radiated from the antennas in the areas 7-1 and 7-2 pass each other and are less likely to cause interference. However, since the beam has a narrow angle as it is, for example, an intermediate region of the beam as shown in the region 7-5 cannot be covered, and communication coverage may be limited to a narrow area.

  As shown in FIG. 24, each communication channel is temporally multiplexed in the HDR downlink. So, for example, in a sector base station composed of three 30 degree beam antennas, if the antenna radiation angle is shifted by 30 degrees for each time slot and radiated four times, the area around the base station is scanned. It is equivalent to rotating in such a manner that all directions can be included in the coverage. For example, assume that the state shown in FIG. 4 shows coverage in time slot A of FIG. 5, 6, and 7 are diagrams for explaining service coverage in an HDR downlink using a 30-degree sector antenna and time slots B, C, and D according to the present invention, respectively. As in FIG. 4, the half-value angle is 30 degrees, 3 sectors out of 12 sector antennas are used, and the bit rate is 614.4 kbit / s. As shown in the figure, the control of the radio wave radiation direction of each base station is changed in time synchronization in all time slots. This corresponds to using a 30-degree beam 12-sector antenna for 3 sectors per time slot. However, whether the system configuration is a 12-sector type, or each sector of 3 sectors is equally divided into four and the radio wave emission direction is changed for each time slot depends on traffic congestion, terminal geographical distribution characteristics, etc. Should be selected in.

  The direction of the radio wave emitted in each time slot is optimal as shown in FIGS. This direction will be described with reference to FIG. 5, for example. As shown in the figure, the base stations are classified into odd rows and even rows in the horizontal direction, and in time slot B in FIG. The sector directions are arranged in such a way that all base stations are directed in the same direction in even rows. On the other hand, in the time slot C shown in FIG. 6, all the odd-numbered base stations are now directed in the same direction, and the even-numbered base stations are in a direction in which the vertical relations are staggered.

  FIG. 8 is an explanatory diagram of service coverage (614.4 kbit / s) at the time of HDR downlink addition using a 30 degree sector antenna and time slots A, B, C, and D according to the present invention. This figure shows the result of adding coverage scanned in four time slots of bit rate 614.4 kbit / s, 3 sector base station, time slots A, B, C, and D. It can be seen that 614.4 kbit / s communication is possible in almost all areas as compared to the case of using the 90-degree fixed three-sector antenna shown in FIG.

  FIG. 9 is an explanatory diagram of service coverage (1228.8 kbit / s) at the time of HDR downlink addition using a 30-degree sector antenna and time slots A, B, C, and D according to the present invention. This figure shows the coverage at 1228.8 kbit / s calculated in a similar manner. Compared to the results of FIG. 3 calculated at the same bit rate, it can be seen that the coverage is clearly expanded.

  Next, a case where the second embodiment is applied to a base station arranged in a square will be described. FIGS. 10 to 13 are diagrams for explaining service coverage in the HDR downlink using the 90-degree sector antenna and time slots A, B, C, and D according to the present invention, respectively. In this figure, the half-value angle is 90 degrees, 3 sectors in an 8-sector antenna are used, and the bit rate is 614.4 kbit / s. In the case where the base stations are arranged in four corners in FIG. 2, an example is shown in which it is optimal that the sector has a four-sector configuration. For example, the sector direction relationship between the base stations as shown in FIG. No matter how the sector is rotated, for example, the area 13-3 corresponding to the intermediate area between BS1 and BS2 cannot be covered as a service area. This is because the beam 13-1 of BS1 and 13-2 of BS2 interfere with each other diagonally, and this diagonal interference is inevitable no matter how the four-sector antenna is rotated.

  10 to 13, in order to solve this problem, each base station is provided with a 90 degree beam type antenna capable of forming sectors in eight directions. Only three of them are used. As an example, of the three beams, two beams are in directions orthogonal to each other, and the other one beam is in a direction of 135 degrees from these two beams.

  FIG. 14 is an explanatory diagram of service coverage (614.4 kbit / s) at the time of HDR downlink addition using a 90-degree sector antenna and time slots A, B, C, and D according to the present invention. This figure shows a state in which all the beams in each of these time slots are added, but almost all areas can be service areas at a rate of 614.4 kbit / s as shown.

  The beam direction in the square arrangement is different from the case of the triangular arrangement shown in FIGS. 4 to 7, and the beam direction of each base station is optimal in all the time slots. However, out of the three beams emitted in each time slot, two beams are orthogonal to each other, but the remaining one beam needs to be emitted in a direction shifted by 135 degrees from the other two beams. Thereby, the beam emission directed diagonally in each time slot is always limited to one base station in each quadrangle, thereby preventing the occurrence of interference on the diagonal.

Next, a specific configuration for realizing the present invention will be described.
FIG. 15 is a block diagram showing the configuration of the base station according to the first embodiment of the present invention. This base station includes an antenna module 19-1, a duplexer (DUP) 19-2, a receiving high frequency circuit (RX) 19-3, an uplink fixed beam forming circuit (UL FBF) 19-4, and a demodulator (DEM). 19-5, decoder (DEC) 19-6, access line interface (LIF) 19-7, access line interface (LIF) 19-8, encoder (COD) 19-9, modulator (MOD) 19-10 Downlink fixed beam forming circuit (DL FBF) 19-11, transmitting high frequency circuit (TX) 19-12, weight controller (WC) 19-13, clock signal generating circuit (CLK) 19-14, GPS receiver (Global Positioning System Receiver) (GPS) 19-15.

  First, the uplink will be described. The antenna module 19-1 is configured by an antenna array that can form a beam pattern with sharp directivity such as 8 beams or 12 beams. The duplexer (DUP) 19-2 separates a transmission signal and a reception signal, and is configured by a band selection filter that selects each signal in a normal mobile communication system. The reception-side high-frequency circuit (RX) 19-3 realizes a predetermined sensitivity by performing amplification, frequency conversion, and the like on the signals from the antenna elements constituting each array. The output signal of the RX 19-3 is applied to an uplink fixed beam forming circuit (UL FBF) 19-4. The UL FBF 19-4 combines the signals received from the respective antenna elements in a vector manner to realize antenna directivity having, for example, an 8-beam or 12-beam radiation pattern (beam pattern) in the circulation direction.

FIG. 16 is a block diagram illustrating a detailed configuration of the UL FBF 19-4. Signals Ant # 1 to Ant # n in the figure are obtained by amplifying the output signals of the antenna modules output from RX 19-3 in FIG. These signals are appropriately weighted by the multipliers 23-11, 23-1n, 23-n1, 23-nn, and synthesized and added by the adders 23-21, 23-2n, respectively. Converted to Beam # 1 to Beam #n. The weighting factors W ₁₁ -W _nn applied to the multipliers generally use vector coefficients in order to change the amplitude and phase simultaneously. The arithmetic expression shown in the lower part of FIG. 16 shows signal processing performed in the UL FBF 19-4 in the form of a matrix arithmetic expression. The weighting factors W ₁₁ -W _nn can be easily set by a method such as simulation in order to form a beam having an appropriate aperture angle.

  Each directional reception signal synthesized by the UL FBF 19-4 is input to a demodulator (DEM) 19-5. FIG. 17 is a block diagram illustrating a detailed configuration of the DEM 19-5. In the DEM 19-5, the beam signals Beam # 1 to Beam # n output from the UL FBF 19-4 are sent from the desired terminal through channel separation circuits (DES) 24-1 to 24-n such as despreading circuits, respectively. The signal is separated and the subsequent switch 24-2 is used to select the appropriate beam. The signal of the selected beam is added with multipath by a rake receiver (RAKE) 24-3, for example, and demodulated into a baseband digital signal by a demodulator (DET) 24-4. A signal to be selected by the switch 24-2 is determined by a comparator (Comp) 24-5. For example, in order to select a signal to be received, this determination method is preferably selected so that the signal-to-interference noise ratio of the received signal is maximized. Therefore, for example, the switch 24-2 operates so as to select a signal having a larger amplitude from the multipath signals received by all the beams in order. The operation of the switch 24-2 is controlled by an uplink beam selection signal UL Beam Select. On the other hand, the beam to be selected in the downlink is determined by the downlink beam selection signal DL Beam Select. In the downlink, it is desirable to direct the beam in the direction in which the terminal physically exists. The direction in which the terminal is present can be known, for example, by identifying the beam direction that maximizes the amplitude of the received signal. The beam direction information selected by this identification is transmitted to the transmission side weight control circuit WC (19-13) as a DL Beam Select signal. The signal output from the DEM 19-5 is subjected to error correction decoding by a decoder (DEC) 19-6 at the next stage, and then connected to a wired communication network via an access line interface (LIF) 19-7. .

  In the downlink, the signal input from the access line interface (LIF) 19-8 is subjected to error correction coding by an encoder (COD) 19-9, and predetermined by an modulator (MOD) 19-10. Modulated by the modulation method. This signal is vector-synthesized into a beam pattern having directivity in the direction in which a radio wave should be emitted by a downlink fixed beam forming circuit (DL FBF) 19-11, and the transmitting side high frequency connected to each antenna element. It is applied to the circuit (TX) 19-12, performs processing such as amplification and frequency conversion, and is input to the antenna module 19-1 via the DUP 19-2. In which direction directivity is given in the downlink, DL Beam Select, which is transmission beam direction information based on the reception direction identified by the DEM 19-5 when receiving the uplink signal, is weight controlled. It is determined by inputting to the transmission side beam forming circuit 19-11 via the unit (WC) 19-13.

FIG. 18 is a block diagram illustrating a detailed configuration of the weight control circuit (WC) 19-13. In this circuit, in addition to the DL Beam Select signal, beam time slot table information defining the relationship between the beam direction in the downlink and the time slot to be used (in FIG. 15, signal 19- 18) is applied. Beam-Time Slot Table information is given from an upper station, a control station, etc., which will be described later. Instead, the own base station, other base stations, control stations, etc. are provided with storage means for storing the Beam-Time Slot Table that stores the time slot used corresponding to the downlink beam direction, and information is given from there. You may do it. As the weighting factors W ₁ -W _n for determining the beam direction in the downlink, a predetermined coefficient vector is selected based on the DL Beam Select information. With this weighting factor W ₁ -W _n , the beam pattern, the number of sectors, the beam direction, the beam angle, etc. of the antenna module 19-1 of each base station can be spatially controlled as shown in the above figures, Can be controlled in time as needed. On the other hand, in the WC 19-13, it is necessary to give the MOD 19-10 a time slot for emitting a downstream signal in the selected direction. The WC 19-13 refers to this time slot information based on the DL Beam Select information and refers to the Beam-Time Slot Table, thereby giving a time slot assign signal (shown as a signal 19-10 in FIG. 15). And given to MOD 19-10.

  FIG. 19 is a block diagram illustrating a detailed configuration of the MOD 19-10. The transmission signal transmitted from the transmission side encoder 19-9 is amplitude / phase modulated by the MOD 26-1, but the output is temporarily stored in the memory 26-2. The timing at which the signal stored in the memory is transmitted is determined by a Time Slot Assign signal 19-19 given from the weight control circuit WC19-13. Synchronization of the time slot to the absolute time is performed with reference to Timing CLK 19-14 provided from the synchronization signal generation circuit CLK.

FIG. 20 is a block diagram illustrating a detailed configuration of the downlink transmission side beam forming circuit DL FBF19-11. As shown in the figure, the signals are weighted by the vector coefficients W ₁ -W _n given from the weight control circuit WC19-13 and supplied to each antenna.

  The Timing CLK signal applied to the MOD 19-10 is generated by a clock signal generation circuit (CLK) 19-14. For the generation timing at this time, refer to the time signal transmitted from the GPS satellite by the GPS receiver 19-15. And synchronized to the absolute time. Therefore, accurate time information synchronized with each other can be obtained in all base stations, and using this time information, for example, the time slots A, B, C, and D shown in FIGS. It is possible to determine the stations in a synchronized manner. Using this time slot information, the antenna directivity can be changed in synchronism in all base stations.

  If the GPS receiver 19-15, the GPS antenna 19-16, or the GPS system itself becomes faulty and it becomes difficult to receive accurate absolute time information, it is built into the GPS receiver 19-15. A temporary clock signal is generated by a highly stable free-running clock generation circuit until a failure is recovered, or a clock signal is supplied to CLK19-14 via a signal 19-17 via a wired network to maintain an absolute time phase. It is possible to make it. In addition, the period by the signal 19-17 can also be mainly used without using a GPS system.

  FIG. 21 shows a flowchart of downlink beam control according to the embodiment of the present invention. As shown in the figure, at the beginning when the beam is not yet formed, it is unknown where the terminal exists, so the receiving side of the base station waits for transmission from the terminal with the antenna pattern set to be omnidirectional (S101). When the terminal starts transmitting using an appropriate signal, the receiving side of the base station receives the transmission from the terminal by the antenna module 19-1, DUP 19-2, RX 19-3 (S103). Here, the antenna directivity pattern is immediately switched to a narrow aperture angle beam using the UL FBF 19-4 (S105). At this time, the WC 19-13 uses the Beam-Time Slot Table to indicate the number of sectors, the beam direction, the beam angle, and the like of the antenna module 19-1 of each base station spatially and further as shown in each of the above drawings. Set the beam pattern appropriately. The signal strength that can be received by each direction beam is compared, and it is detected in which direction the receiving terminal is present (S107). Using this detection information, the weighting circuit WC19-13 determines the direction in which the downstream beam should be emitted (S109). On the other hand, in a centralized device, a control station, etc., a base station setting location and directional beam direction data are input (S111), and a Beam-Time Slot Table indicating a relationship between a transmission beam direction and a use time slot in each base station is provided. It is created (S113). After that, the WC 19-13 determines a time slot from which the downlink beam is to be emitted with reference to the Beam-Time Slot table that defines the relationship between the transmission beam direction and the use time slot prepared in advance (S115), and the MOD 19-10. To form an appropriate downstream signal (S117).

The Beam-Time Slot table can be manually created by a system designer using a map or the like in advance at the design stage for determining the base station installation location. The created table defining the relationship between the downlink beam direction and the time slot is converted into digital data and stored in a system management device connected to a centralized device of the system. Further, this Beam-Time Slot table may be stored inside each base station, or may be stored in a centralized device such as a mobile exchange so that it can be referred to as necessary. A table unique to each base station is downloaded to each base station as necessary. Further, when the table is provided in the central apparatus, the table information can be downloaded to the memory in the base station as necessary. When there is an additional change in the base station arrangement such as adding a new base station after the base station is installed, the table can be automatically corrected or newly created by a self-learning function described later. This Beam-Time Slot table shows the relationship between the beam radiation direction at each base station and the time slot used when radiating in that direction. In the weight control circuit (WC) 19-3 shown in FIG. When the direction information in which the downward radio wave is to be emitted is input, the time slot in which the radio wave is to be emitted is determined with reference to this Beam-Time Slot table, and the timing is transmitted to the memory 26-2 in FIG. This makes it possible to emit radio waves at an appropriate time.
FIG. 27 is a block diagram showing a base station control system according to another embodiment of the present invention. The system includes a plurality of base stations, a control station that constitutes the upper stations, and a backbone network (NW) of the upper stations. In FIG. 27, 19-20 ₁ ,..., 19-20 _n indicate the entire configuration of the base station shown in FIG. 15, and each base station includes antenna modules 19-1 _{1 to} 19-1 _n and an access circuit interface. (LIF) 19-7, weight controller (WC) 19-13, and access line interface (LIF) 19-8. Reference numeral 27-1 is installed for each of a plurality of base stations, and indicates an upper station, that is, a control station that controls them. Each upper station includes an uplink (UL) relay circuit 27-2, a circuit 27-3 for generating a table of beam timeslots to be notified to each base station, and a downlink (DL) relay circuit 27-4. Reference numeral 27-7 represents a backbone network (NW). The UL relay circuit 27-2 collects uplink signals transmitted from a plurality of base stations and connects them to the backbone NW, and the DL relay circuit 27-4 has a downlink terminal connected to a target terminal. Distribute to the base stations. Reference numeral 27-5 represents an uplink (UL) traffic information transmission signal.
In the circuit configuration of FIG. 27, the traffic statistical information that is aggregated at each base station and notified from the base station to the UL relay circuit 27-2 of the higher station on the uplink is obtained from the beam time slot table generation circuit 27-3. Will be notified. This traffic statistical information can be obtained by, for example, accumulating DL Beam Select information shown in FIG. 17 in time at each base station and measuring the traffic amount in each beam direction. This traffic statistical information is multiplexed with the uplink signal and notified to the upper station 27-1.
FIG. 28 shows a diagram illustrating a table of beam time slots used in the embodiment of the present invention. FIG. 28 shows an example of a beam time slot table for driving the base stations BS1, BS2 using the 30-degree sector antenna shown in FIGS. The figure shows the directional characteristics of each antenna at time slots A, B, C, and D in angle. Each time slot corresponds to the state shown in FIGS. The beam time slot generation circuit 27-3 notifies or instructs each base station of the table information shown in FIG.
As one embodiment, this beam time slot table is set in advance from geographical information when a base station is installed, and is used in a fixed manner. As another embodiment, the traffic for each antenna direction is observed over the long term, and the traffic unevenness for each radio wave emission direction at each base station is measured. Weighting is also possible that increases the frequency with which the beam is directed as compared to the direction of lower traffic demand.
In the traffic measurement for each slot, for example, DL Beam Select information shown in FIG. 17 can be accumulated for a long time to grasp the traffic uneven distribution situation for each direction. In order to increase the beam irradiation time rate in the high traffic direction, for example, FIG. 28 shows an example of using four time slots. However, by increasing the number of time slots, a plurality of time slots are set in the high traffic direction. Should be used.
FIG. 29 shows an example of a beam time slot table in which the frequency of beam irradiation in the high traffic direction is increased. For example, assume that high traffic occurs in the area 7-4 in FIG. This area is irradiated with beams from BS1 and BS2 in the time slots shown in FIGS. Therefore, as shown in FIG. 29, if time slots E and F are added and the same beam irradiation pattern as that of time slots A and D is generated by this addition, statistically, the traffic to the high traffic area is Beam irradiation frequency is improved.
If traffic in another direction rises, the beam pattern selection in this table can be changed. However, the frequency of this change depends on whether it is fast enough to withstand the instantaneous traffic rise or long-term observation results. There are two types of cases in which the change frequency is reduced using. The change time constant may be selected by observing actual traffic fluctuation characteristics.

  FIG. 22 is a block diagram showing the configuration of the second embodiment of the base station that implements the present invention. In this example, instead of the fixed beam forming circuits 19-4 and 19-11 shown in the first embodiment, a simple through circuit is used on the uplink side, and an antenna selection switch 20-1 is used on the downlink side. Yes. This selection switch 20-1 is selected by the weight controller 19-13, and it becomes possible to select an antenna directed in the direction in which the desired terminal exists. Originally, the beam forming circuits 19-4 and 19-11, for example, in the case of an uplink, perform vector synthesis on the output signal of each antenna element arranged in an array shape while controlling the phase and amplitude, so that an arbitrary half-value of the aperture is obtained. An antenna pattern having a corner is formed. However, when the antenna element itself has an aperture half-value angle characteristic that satisfies the object of the present invention, it is not necessary to perform vector synthesis by a beam forming circuit. This is because desired characteristics can be realized at this time.

  The description of the above embodiment is based on the premise that each base station is accurately arranged at the apex of a triangle or a quadrangle, and in which direction a radio wave should be emitted in each time slot in advance. It is a condition that it is set. However, it is often difficult to place an accurate triangle or quadrangle at the apex of an actual base station. Furthermore, when additional base stations are placed, the time slot and radio wave emission direction that were set at the beginning were set. It may be necessary to change the relationship. Assuming such a case, a method in which the base station determines the optimal radio wave emission direction while self-learning will be described below as a modification example.

  For example, in the embodiment shown in FIG. 15, a method for realizing the self-learning function will be described. As shown in the figure, in the uplink of the base station, a DEM 19-5 is used to select a reception beam with the best reception condition for an arbitrary terminal, that is, in which direction the corresponding terminal exists. Next, the terminal reports the downlink reception status at the location where the terminal exists to the terminal. That is, the terminal receives a pilot signal transmitted from each base station, and reports which base station can receive the signal received from the base station in the best condition. It is assumed that the relationship between the time slot and the radio wave emission direction has not yet been determined for the currently considered base station, but has already been determined for the surrounding base stations. In this case, since the neighboring base stations have already emitted radio waves in different directions for each time slot, the radio waves of other base stations can be received strongly when viewed from the terminal that is currently measuring the downlink quality. It is possible to distinguish and recognize time slots and less time slots. Therefore, the terminal can recognize which time slot is likely to receive interference from a strong neighboring base station where it is present, and conversely, the base station can determine which slot has relatively little interference. It becomes possible to report.

  The measurement of the interference radio wave intensity in each time slot may vary depending on the traffic state of the adjacent base station. Therefore, the base station that is currently self-learning observes the reports from each terminal for a certain period and obtains statistical information. It is possible to estimate whether the interference with other base stations is the least. It goes without saying that the table defining the relationship between the beam direction and the time slot stored in the central apparatus or base station is corrected based on the estimation result. In addition, the measurement of radio interference of other base stations can be realized by observing the radio wave intensity itself or how often an error occurs in communication using data.

Explanatory drawing of the service coverage (614.4 kbit / s) in the HDR downlink which arranged the base station by this invention in a triangle. Explanatory drawing of the service coverage (614.4 kbit / s) in the HDR downlink which squarely arranged the base station by this invention. Explanatory drawing of the service coverage (1228.8 kbit / s) in the HDR downlink which arranged the base station by this invention in a triangle. Explanatory drawing of the service coverage in the HDR downlink using the 30 degree | times sector antenna and time slot A by this invention. Explanatory drawing of the service coverage in the HDR downlink using the 30 degree | times sector antenna and time slot B by this invention. Explanatory drawing of the service coverage in the HDR downlink using the 30 degree | times sector antenna and time slot C by this invention. Explanatory drawing of the service coverage in the HDR downlink using the 30 degree | times sector antenna by this invention, and the time slot D. FIG. Explanatory drawing of the service coverage (614.4 kbit / s) at the time of the HDR downlink addition using the 30 degree | times sector antenna by this invention, and time slot A, B, C, D. FIG. Explanatory drawing of the service coverage (1228.8 kbit / s) at the time of the HDR downlink addition using the 30 degree | times sector antenna and time slot A, B, C, D by this invention. Explanatory drawing of the service coverage in the HDR downlink using the 90 degree sector antenna and time slot A by this invention. Explanatory drawing of the service coverage in the HDR downlink using the 90 degree sector antenna and time slot B by this invention. Explanatory drawing of the service coverage in the HDR downlink using the 90 degree | times sector antenna by this invention, and the time slot C. FIG. Explanatory drawing of the service coverage in the HDR downlink using the 90 degree sector antenna and time slot D by this invention. Explanatory drawing of the service coverage (614.4 kbit / s) at the time of the HDR downlink addition using the 90 degree sector antenna and time slot A, B, C, D by this invention. The block diagram which shows the structure of the base station by 1st embodiment of this invention. The block diagram which illustrates the detailed structure of UL FBF19-4. The block diagram which illustrates the detailed structure of DEM19-5. The block diagram which illustrates the detailed structure of a weight control circuit (WC). The block diagram which illustrates the detailed composition of MOD19-10. The block diagram which illustrates the detailed structure of downlink transmission side beam forming circuit DL FBF19-11. The flowchart of the downlink beam control by embodiment of this invention. The block diagram which shows the structure of the base station by 2nd embodiment of this invention. Explanatory drawing of the basic principle of HDR system. Explanatory drawing about the multiplexing system in a HDR system downlink. Explanatory drawing which shows the example of general base station arrangement | positioning. The timing diagram of the transmission signal in a HDR system downlink. The block diagram which shows the base station control system by other embodiment of this invention. The diagram which illustrates the table of the beam time slot used for embodiment of this invention. Explanatory drawing which shows an example of the beam time slot table which raised the beam irradiation frequency to a high traffic direction. Explanatory drawing of the service coverage (614.4 kbit / s) in the HDR downlink when the base station is arbitrarily arranged squarely in the past. Explanatory drawing of the service coverage (204.8 kbit / s) in the HDR downlink when the base station is arbitrarily arranged squarely in the past.

Explanation of symbols

19-1 Antenna Module 19-2 Duplexer (DUP)
19-3 Reception-side high-frequency circuit (RX)
19-4 Uplink fixed beam forming circuit (UL FBF)
19-5 Demodulator (DEM)
19-6 Decoder 19-7 Access Line Interface (LIF)
19-8 Access line interface (LIF)
19-9 Encoder (COD)
19-10 Modulator (MOD)
19-11 Downlink Fixed Beamforming Circuit (DL FBF)
19-12 Transmission-side high-frequency circuit (TX)
19-13 Weight Controller (WC)
19-14 Clock signal generation circuit (CLK)
19-15 Receiver (GPS)

Claims (1)

A plurality of base stations are arranged in a square arrangement that is a quadrangular position in a plane,
The antenna of each base station is composed of antennas that can realize eight directivities every 45 °,
In each time slot, specify the antenna directivity so that the two directivities of the three directivity patterns are orthogonal to each other, and the other directivity is the direction of 135 ° from these two directivities , And the radio | wireless communication method including making the antenna directivity of each base station the same in each time slot .

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