JP3422945B2 - CDMA cellular radio base station - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA cellular radio base station, and more particularly to a CDMA cellular radio base station employing transmit antenna diversity. 2. Description of the Related Art When a plurality of receiving antennas are prepared and arranged so that the interval between the plurality of receiving antennas is equal to or longer than the wavelength of a used frequency, the correlation between received signal strengths decreases. For this reason, if the signal levels of the received signals at a plurality of receiving antennas are compared on the receiver side and the larger one is used on the receiver side, fading resistance can be improved. Such a scheme is called antenna diversity (in this case, in particular, "receiving antenna diversity").
This method is widely used for mobile communication antennas. [0003] Similar to the reception antenna diversity, even if a plurality of transmission antennas are prepared on the transmitter side, the same effect can be obtained (hereinafter, this configuration is referred to as "transmission diversity"). In such transmission diversity, a plurality of prepared transmission antennas are used by switching, but the reception signal levels before and after the switching of the transmission antennas are compared on the receiver side, and the antenna that transmits one of the higher signal levels is transmitted. Then, a control signal for switching the transmitting antenna is transmitted from the receiver to the transmitter so that the transmission is performed thereafter. [0004] In this case, since a plurality of antennas are provided on the transmitter side, only one antenna is required on the receiver side, which is significant when it is desired to reduce the size and weight of the receiver. [0005] In recent years, mobile communication terminals have been desired to be reduced in size and weight as well as to improve communication quality, and also to reduce power consumption so as to withstand long-term use. ing. For this reason, it is desirable that the above-described transmission diversity be adopted on the base station side in the mobile communication system, and the mobile communication terminal needs only one receiving antenna. However, when the above-mentioned transmission diversity is adopted, a control signal for switching the transmission antenna from the receiver must be transmitted to the base station.
For this reason, while fading resistance can be improved to improve the communication quality of the receiver, and the benefit of reducing the size and weight of the device can be enjoyed, there is a problem that it is difficult to reduce power consumption this time. Further, since a control signal for switching the transmitting antenna must be transmitted from the receiver side to the base station side, when employing the transmission diversity according to the above-described conventional technology in the mobile communication system, not only the base station but also the mobile station There is also a problem that renovation is required. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the power consumption of the receiver by adopting transmission diversity by modifying only the base station. It is to provide a possible CDMA cellular radio base station. [0008] To solve the above problems, the present invention provides a CDMA cellular radio base station,
Service area of the base station is divided into a plurality of sectors that are more cover A integrators Na, signal wirelessly transmitted from the A <br/> antenna to cover each sector, the mobile station between sectors
Mutual modulated signals simultaneously receiving and demodulating possible as the antenna when the handoff, two A even without least
Antenna is installed so as to cover the same sector, of identity
At least two antennas covering one sector
The line transmitted signal indicates whether the mobile stations are
These signals must also be modulated so that they can be received and demodulated simultaneously.
Allows the mobile station to signal from these antennas
Can be processed in the same way as signals from antennas in different sectors
Is modulated as follows. A radio base station according to the present invention employs a CDMA cellular radio communication system. In particular, a service area (cell) is divided into a plurality of sectors, and these sectors are covered by at least one antenna. The mobile stations can simultaneously receive and demodulate signals transmitted from antennas covering each sector, and hand off each other. In the radio base station according to the present invention, at least one sector is covered by at least two antennas. [0010] In this way, the mobile station located in the sector can simultaneously receive and demodulate signals transmitted from a plurality of antennas, and transmit from any of the antennas according to the received signal level. Signals can be selected, or signals transmitted from a plurality of antennas can be weighted and used. As a result, there is no need to transmit a control signal for switching the transmission antenna from the receiver side to the base station side, while employing transmission antenna diversity,
Power consumption of a receiver such as a mobile terminal can be reduced.
In addition, since the processing on the mobile station side is the same processing as the transmission antenna diversity and the handoff between sectors, it is necessary to adopt transmission diversity only with modification on the base station side without modifying the mobile station side in particular. Can be. Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows a CDM according to an embodiment of the present invention.
It is a figure showing the composition of A cellular radio base station. As shown in the figure, this base station is provided with two antennas 101a and 101b corresponding to the sector 102. These antennas 101a and 101b are also used for transmission and reception of a radio base station. The transmitting device 1 is provided to the antennas 101a and 101b.
03a and 103b are connected respectively. On the other hand, the signals received by the antennas 101a and 101b are distributed and input to the receiving devices 104a and 104b. Strictly speaking, the sector 102 includes a sector 102a covered by the antenna 101a and a sector 102b covered by the antenna 101b, and the antennas 101a and 101b are installed so that they are almost equal. Although not particularly shown in the figure, this base station has a service area (cell) divided into a plurality of sectors, one of which is a sector 102. That is, in this system, a plurality of antennas 101a and 101b are associated with one sector 102 in order to realize transmission antenna diversity and reception antenna diversity. When communication from the base station to the mobile station 105 (hereinafter referred to as “downlink”) is performed using the base station, the transmission information is spread-modulated by the transmitting apparatus 103a using the first spreading code. Then, the signal is transmitted to the mobile station 105 located in the sector 102 by the antenna 101a. At this time, the same transmission information is spread-modulated by the transmitting apparatus 103b using a second spreading code different from the first spreading code, and transmitted to the mobile station 105 located in the sector 102 also by the antenna 101b. Here, the first and second
Are selected as follows. That is, CDM
In the A cellular radio communication system, when the mobile station 105 performs a handoff between sectors, signals from each sector antenna can be simultaneously received and demodulated. In other words, the signal transmitted from the antenna of each sector is modulated with one of the predetermined spreading codes so that the mobile station 105 can simultaneously receive and demodulate. The first and second spreading codes may be determined from completely different code sequences, or may be the same code sequence but different code phases. The mobile station 105 has the antenna 101a
And those capable of simultaneously receiving and demodulating the signals transmitted from 101b and 101b. Therefore, for the mobile station 105, signals received from the antennas 101a and 101b can be processed in the same manner as signals received from antennas in different sectors. In this case, the mobile station 105 is connected to a conventional C
By including the RAKE receiver in the same manner as the DMA cellular receiver, the signal from the antenna 101a and the signal from the antenna 101b can be weighted and combined by the mobile station 105.
Even if the signal from any one of 101b is interrupted due to fading, the signal from the other can be received. Thus, transmission antenna diversity in the downlink is realized. In the mobile station 105,
Instead of using the RAKE receiver to weight and combine the signals from the antennas 101a and 101b, a signal from either one may be selectively received according to the signal level. Next, when performing communication from the mobile station 105 to the base station (hereinafter referred to as “uplink”), the mobile station 1
05 are transmitted from antennas 101a and 101b.
Are received together. Normally, a signal transmitted from the mobile station 105 is spread with a code corresponding to one of the sectors 102a or 102b or a code unique to the mobile station 105, and the receiving devices 104a and 104b respectively transmit antennas 101a and 104b. The signal received at 101b is despread with those codes. Then, the antennas 101a and 101b
A demodulation of the signal from the antenna 101 and weighting / synthesis or a selective use of the signal from one of the antennas 101a and 101b realizes the reception antenna diversity. The sector 102a covered by the antenna 101a and the sector 10 covered by the antenna 101b
2b are substantially equal, the receiving devices 104a, 104
4b may be omitted to simplify the configuration of the receiving system in the base station. Next, the configurations of the transmitting devices 103a and 103b and the receiving devices 104a and 104b will be described in detail. First, FIG. 2 is a diagram illustrating a configuration of the transmission device 103a. As shown in FIG. 1, the transmitting device 103a
Then, the transmission baseband signals Ita and Qta corresponding to the sector 102a are divided into information bits I and Q,
In multipliers 211i and 211q, sector 102
Are multiplied by the spreading codes Cai and Caq corresponding to. The outputs of the multipliers 211i and 211q are input to variable digital attenuators 201i and 201q, where the mobile station 10
5 based on information such as Eb / I0 (Eb: energy per information bit, I0: interference power per unit frequency) or received power Pr.
5 and digitally added to a signal for another mobile station 105. Variable digital attenuator 201i, 2
The output of 01q is then passed through roll-off filters 202i and 202q, respectively, having root Nyquist characteristics. And then, the digital / analog converter 203
i, 203q, where it is converted to an analog signal. The analog signal is input to the quadrature modulator 204,
It is QPSK modulated. This signal has an intermediate frequency (IF)
After being passed through a filter 205 and an IF amplifier 206, the output from a local oscillator 207 is multiplied by a mixer 208 and converted into a radio frequency (RF). After the RF signal is power-amplified by the transmission power amplifier 209, the RF signal is transmitted to the antenna 101a via the transmission / reception signal distributor 210,
It is transmitted to the mobile station 105 located in the sector 102 (sector 102a). The transmitting device 103b has the same configuration as the transmitting device 103a shown in FIG. In the figure, the characters in parentheses are for the transmitting device 103b.
In particular, the codes multiplied by the multipliers 211i and 211q are Cbi and Cbq, respectively, different from the transmitting device 103a. Cbi and Cbq may be assigned codes completely different from Cai and Caq, or may be assigned with different code phases. These Cbi, Cbq and Cai, Ca
If there is no strong correlation with q, the signal transmitted from antenna 101b does not have a strong correlation with the signal transmitted from antenna 101a. This is because even if there is a strong correlation in the unit of the spreading code 1 chip, the correlation generally becomes low in the unit of the information symbol composed of a plurality of chips. Therefore, in the sector 102 covered by both the antennas 101a and 101b,
Signals from 1a and 101b interfere with each other to prevent communication from becoming impossible. Thus, according to the CDMA cellular radio base station, effective transmission antenna diversity can be realized. FIG. 3 shows the structure of the receiving device 104a. In the receiving apparatus 104a shown in FIG. 3, a received signal input from the antenna 101a is input to the low noise amplifier 301 via the transmission / reception signal splitter 210, and then passes through the reception RF filter 302. The received signal is further multiplied by the output of the local oscillator 303 by the mixer 304 and converted into an IF frequency. This IF signal is
After passing through the F filter 305, the variable gain amplifier 306
Are controlled so that the baseband amplitude at the subsequent stage becomes constant, and the quadrature detector 307 controls the baseband signals Iri and Iri.
Converted to rq. This signal is shaped by the roll-off filters 308i and 308q having the root Nyquist characteristic, and then the analog / digital converter 309
The signal is converted into a digital signal at i, 309q. This digital signal is supplied to multipliers 310i and 310q for sector 1
02 or a code unique to the mobile station 105 and received as a base station channel or a channel unique to each mobile station. The receiving device 104b has the same configuration, but since the signal transmitted from the mobile station 105 is received by any of the antennas 101a and 101b, it is not always necessary to install both the receiving devices 104a and 104b. Therefore, resources of the receiving system in the base station can be saved. According to the CDMA cellular radio base station described above, the configuration of the conventional CDMA cellular mobile communication system having the sector configuration can be changed without greatly changing the configuration.
Transmit antenna diversity and receive antenna diversity can be realized on the base station side. Therefore, it is possible to improve the fading resistance of the system without providing a plurality of antennas in the mobile station 105, to reduce the size and weight of the mobile station 105 while maintaining communication quality, and to reduce power consumption. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an overall configuration of a CDMA cellular radio base station according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of a transmission device. FIG. 3 is a diagram illustrating a configuration of a receiving device. [Description of Signs] 101 antenna, 102 sector, 103 transmitting device, 104 receiving device, 105 mobile station, 201 variable digital attenuator, 202 roll-off filter, 203 digital / analog converter, 204 quadrature modulator, 205 IF filter, 206 IF amplifier,
207 local oscillator, 208 mixer, 209 transmission power amplifier, 210 transmission / reception signal distributor, 211, 31
0 Multiplier, 301 Low noise amplifier, 302 Receive RF
Filter, 303 local oscillator, 304 mixer,
305 IF filter, 306 Variable gain amplifier, 30
7 Quadrature detector, 308 roll-off filter, 309
Analog / digital converter.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B ^7/ 24-7/26 H04Q ⁷ /00-7/38

Claims (1)

(57) In the Patent Claims: 1. A CDMA cellular radio base station, the service area of the base station is divided into a plurality of sectors that are more cover A integrators Na, covering each sector antenna signal wirelessly transmitted from the mobile station is modulated signals from Anne <br/> antenna simultaneously receives and demodulates possible as when handing off to each other between sectors, two antennas even without least the same sector is installed so as to cover, at least two antennas that cover of identity one sector
The signals transmitted wirelessly from the
Signal is modulated so that it can be received and demodulated at the same time.
This allows the mobile stations to receive signals from their antennas.
Signal in the same way as signals from antennas in different sectors.
CDMA cellular radio base station characterized in that it is modulated in such a way that it can be modulated .