JPH11252030A - Radio signal transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio signal transmitter without degrading present distortion characteristics even at the time of sharing the signals of an existing frequency band and the signals of the other new frequency band. SOLUTION: A first antenna 36a receives the radio signals (first signals) of a first frequency band to which transmission power control is not performed and a second antenna 36b receives the radio signals (second signals) of a second frequency band to which the transmission power, control is performed. The received first and second signals are receptively inputted through circulators 35a and 35b to second and third amplification parts 34a and 34b and the second and third amplification parts 34a and 34b respectively amplify the inputted signals so as to make the level of the second signals after amplification lower than the level of the first signals after the amplification and output them to a signal multiplex part 37. The signal multiplex part 37 frequency-multiplexes the respective signals outputted from the second and third amplification parts 34a and 34b and the frequency/multiplexed signals are converted to optical signals in an electric/optic conversion part 33 and then, outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio signal transmission apparatus, and more particularly, to a radio signal transmission apparatus that receives radio signals of two or more different frequency bands and multiplexes and transmits them.

[0002]

2. Description of the Related Art Conventionally, mobile phones and PHSs (Personal
As a wireless signal transmission device represented by a mobile communication system such as a Handy-phone System, there is, for example, a device as shown in FIG.

[0003] In FIG. 4, in a conventional radio signal transmission apparatus, a master station 100 and a slave station 300 are connected by optical fibers 201 and 202. The optical fiber 201 is used when transmitting an optical signal from the master station 100 to the slave station 300 (hereinafter, referred to as a downstream system). The optical fiber 202 is
From the slave station 300 to the master station 100 (hereinafter referred to as uplink system)
Used when transmitting optical signals. The slave station 300 includes an optical / electrical converter 301, an electrical / optical converter 303, and a first
, A second amplifier 304, a circulator 305, and an antenna 306.

First, downlink signal transmission will be described. The optical signal transmitted from the master station 100 is transmitted to the slave station 300 located at a remote place via the optical fiber 201.
In the slave station 300, the optical / electrical conversion unit 301 includes the master station 1
It receives the optical signal transmitted from 00 and converts it into a wireless modulation signal that is an electric signal. This wireless modulation signal is amplified by the first amplifying unit 302 and then radiated from the antenna 306 via the circulator 305. The circulator 305 is a device having a function of outputting an input from a certain terminal only to an adjacent terminal in a specific direction, and outputs an input from the first amplifying unit 302 to the antenna 306, while an input from the antenna 306 Is output to the second amplification unit 304 (indicated by an arrow in FIG. 4). Radio modulated signals radiated from antenna 306 are received by mobile terminals (not shown) within the area.

Next, uplink signal transmission will be described. Radio modulated signals of different frequencies transmitted from each mobile terminal in the area are received by the antenna 306 and frequency-multiplexed. The frequency-multiplexed radio modulation signal is input to the second amplification unit 304 via the circulator 305. The second amplification unit 304 amplifies the input wireless modulation signal and outputs the amplified signal to the electrical / optical conversion unit 303. The electrical / optical converter 303 converts the wireless modulation signal input from the second amplifier 304 into an optical signal and outputs the optical signal. The optical signal output after being converted in the electric / optical conversion unit 303 is transmitted to the master station 100 at a remote place via the optical fiber 202.

[0006] Here, in the configuration of the slave station 300 as described above, there is a large difference in the received power received by the antenna 306 due to the difference in the distance from each mobile terminal to the slave station 300. For this reason, in the conventional wireless signal transmission device, in consideration of the difference in the received power, an extremely wide dynamic range is used for the uplink signal, and the optical modulation degree per wave is set high.

An example of the system design of the slave station 300 is described in Sanada et al., "Optical transmission equipment for slave station" (National TECHNICAL REPORT, Aug, 1993).
In this document by Sanada et al., The optical modulation factor m of the upstream system is 10.7% ≦ m ≦ 2, assuming that the upstream system has two carriers.
It is 1.2%. The lower limit and upper limit of the optical modulation factor m are determined by the carrier-to-noise ratio (CNR) characteristic and the distortion characteristic, respectively. FIG. 5 shows the degree of light modulation, CNR and distortion (in this case, the third-order distortion “distortion IM
3) shows the relationship with the quantity.

As can be seen from FIG. 5, the CNR increases with an increase in the degree of light modulation, and the distortion IM3 deteriorates with an increase in the degree of light modulation. First, the lower limit of light modulation is CNR = 8.
It is determined by a value satisfying 0 dB, and the value of the light modulation degree at this time is 10.7%. On the other hand, the upper limit of light modulation is
The distortion is determined by a value satisfying IM3 = −84 dBc, and the light modulation degree at this time is 21.2%. However, this distortion IM3 = −84 dBc is the amount of distortion that can be tolerated by a semiconductor laser diode (LD) module used as an optical / electrical conversion unit in an optical transmitter when the distortion characteristic of the entire transmission device is −80 dBc. It is.

In the above-mentioned document by Sanada et al., Performance evaluation is performed in the case of two carriers, but in an actual system, uplink carriers are multicarriers. The literature by Sanada et al. Also assumes a maximum of 32 carriers. Therefore, the evaluation of distortion characteristics performed on two carriers will be performed on a multicarrier. In the case of multicarrier transmission, the distortion characteristics of the composite triple beat (CTB) must be considered instead of the distortion IM3 for each wave. The distortion CTB at the time of multicarrier transmission is given by the number of composites, which is the number of third-order distortions occurring at the same frequency, and the distortion IM3.

The relationship between the number of composites and the number of carriers is described in Westcott, R .; J. Authored document "Inve
stigation of multiple f.
m. / F. d. m. carriers through
a satellite t. w. t. operation
ing near to saturation "(Pr
oc.IEE, Vol. 114, no. 6, 1967),
It is obtained by the following equation (1). Nc = M * (N−M + 1) / 2 + ((N−3) ² −5) − (1−
(−1)) − ^N * (− 1) ^{N + M} ‥‥ (1) In the above equation (1), N is the number of carriers, M is the Mth frequency band among N carriers, and Nc is the Mth frequency band. It represents the number of composites in the frequency band. FIG. 6 shows the result of calculating the relationship between the number of carriers and the number of composites using the above equation (1).
Shown in

The distortion IM3 and distortion CTB in the same frequency band
Is related to the case where the distortion IM3 generated when transmitting two carriers having the optical modulation degree m2 [%] is D2 [dBc], and N carriers with the optical modulation degree mN [%] are transmitted in the same transmission system. When the resulting distortion CTB is DN [dBc], D
N is estimated by the following equation (2) using the number of composites Nc. DN = D2 + 10 * log (Nc) + 2 * 20 * log
(mN / m2) ‥‥ (2)

Then, mN = 10.7% and 21.2
%, M2 = 20%, the value D2 of the distortion IM3 is -85.
Assuming dBc, the relationship between the amount of distortion DN and the number of composites at mN = 10.7% and 21.2% can be obtained from the above equation (2). This relationship is shown in FIG. FIG. 7 shows the specifications of the distortion characteristics DN of the LD module.
When the number of composites satisfying 84 dBc is obtained, mN
= 10.7%, "15", and mN = 21.2%, "1". Further, the number of carriers can be obtained from the relationship between the number of composites and the number of carriers shown in FIG. 6, and the number of carriers is “8” when the modulation factor is 10.7%.
When the carrier has a modulation factor of 21.2%, the carrier is “3”.

The number of carriers is the number of mobile terminals transmitting at a location closest to the slave station 300 within a certain area. Within this range of the number of carriers, a range in which the third-order distortion caused by the combination of carriers has an effect on the signal transmitted at the location farthest from the slave station 300 (the reception level at the antenna 306 is the smallest) is also acceptable. It has become.

[0014]

However, the above-mentioned conventional radio signal transmission apparatus requires an extremely wide dynamic range for an upstream signal as described above, and sets a high optical modulation degree per one wave. ing. For this reason, in the above-mentioned conventional wireless signal transmission device, when a communication system using another frequency band is shared, a problem arises that the distortion characteristic is deteriorated.

[0015] Therefore, an object of the present invention is to provide a radio signal transmission device which maintains the current performance and realizes an increase in the number of transmission carriers at low cost.

[0016]

Means for Solving the Problems and Effects of the Invention The first invention is a radio signal (hereinafter referred to as a first radio signal) which is in a first frequency band and whose transmission power is not limited.
A plurality of slave station devices for transmitting and receiving both a radio signal (hereinafter, referred to as a second radio signal) in a second frequency band different from the first frequency band and subjected to transmission power restriction,
A wireless signal transmission device in which one master station device is connected via a transmission path, wherein the slave station device transmits and receives a first wireless signal, and transmits and receives a second wireless signal. And a first antenna received by the first antenna.
A first amplifying means for amplifying the first wireless signal to a predetermined level; and a second amplifying means for amplifying the first wireless signal output from the first amplifying means. At least a second amplifying means for amplifying to a predetermined level smaller than the level, and a frequency multiplexing means for frequency multiplexing the first and second radio signals respectively amplified by the first and second amplifying means. .

As described above, according to the first aspect, the second aspect
The signal whose transmission power is controlled is used for the wireless signal.
For this reason, regarding the processing of the uplink signal in the slave station device, a wide dynamic range is not required for the second wireless signal, and transmission at an optical modulation degree that is much smaller than that of the first wireless signal becomes possible. . Therefore, the number of transmission carriers can be increased without substantially changing the transmission characteristics of the two systems from the transmission characteristics of the conventional one system.
Further, since only a slight change in the slave station is required, the cost associated with the introduction of a new system can be significantly reduced.

According to a second aspect, in the first aspect, the second aspect is provided.
Is characterized by being a code division multiplexed signal.

As described above, according to the second aspect, a code division multiplexed signal is used as the second radio signal whose transmission power is controlled. Accordingly, since the distortion signal generated from the second radio signal has a wide band and very low peak power, the first radio signal is not affected even when distortion occurs in the first radio frequency band. .

According to a third aspect, in the first and second aspects, the master station device and the slave station device are connected by an optical fiber.

As described above, in the third invention, the transmission path of the wireless signal transmission device in the first and second inventions is an optical fiber.

According to a fourth aspect of the present invention, there is provided a wireless signal (hereinafter referred to as a first wireless signal) which is in a first frequency band and whose transmission power is not limited, and a second signal which is different from the first frequency band.
A second wireless signal that is transmitted and received in the frequency band of the second wireless signal (hereinafter, referred to as a second wireless signal), and transmits and receives the first wireless signal.
Antenna, a second antenna for transmitting and receiving a second wireless signal, and a first wireless signal received by the first antenna,
The first amplifying means for amplifying to a predetermined level and the second wireless signal received by the second antenna become lower than the level of the amplified first wireless signal output from the first amplifying means. At least a second amplifying means for amplifying to a predetermined level and a frequency multiplexing means for frequency multiplexing the first and second radio signals amplified by the first and second amplifying means, respectively, are provided.

According to a fifth aspect, in the fourth aspect, the second aspect is provided.
Is characterized by being a code division multiplexed signal.

As described above, the fourth and fifth aspects of the present invention
The present invention relates to only the slave station device in the first and second inventions. Therefore, the effects of the fourth and fifth inventions are the same as those of the first and second inventions.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a wireless signal transmission device according to an embodiment of the present invention. In the wireless signal transmission device shown in FIG. 1, a master station 10 and slave stations 30 are connected by optical fibers 21 and 22. The slave station 30 includes an optical / electrical converter 31, an electrical / optical converter 33, a first amplifier 32, and a second amplifier 34a.
, A third amplifying unit 34b, and a first circulator 35
a, the second circulator 35b, and the signal multiplexing unit 37
And a first antenna 36a and a second antenna 36b.

Here, the second amplifying unit 34a, the first circulator 35a, and the first antenna 36a
(A frequency band used in a conventional wireless communication service). In addition, when the signal of the first frequency band is transmitted from the first mobile terminal, power control is not performed. On the other hand, the third amplifying unit 34b, the second circulator 35b, and the second antenna 36b process signals in a second frequency band (a frequency band used for performing a new wireless communication service). The power of the signal in the second frequency band is controlled when the signal is transmitted from the second mobile terminal.
Note that the second frequency band may be different from the first frequency band, and there is no particular limitation in assigning. FIG. 2 shows an example of the relationship between the frequency of the signal received by the first antenna 36a and the second antenna 36b and the received power.

First, downlink signal transmission will be described. The optical signal transmitted from the master station 10 is the optical fiber 2
1 to the remote station 30 located at a remote place. Slave station 3
At 0, the optical / electrical conversion unit 31 receives the optical signal transmitted from the master station 10 and converts the optical signal into a wireless modulation signal that is an electric signal. The first amplifying unit 32 amplifies and outputs the wireless modulation signal. The amplified radio modulated signal is the first
Is radiated from the antenna 36a via the circulator 35a, and is radiated from the antenna 36a through the circulator 35a, and is radiated from the antenna 36a through the circulator 35a. If it is abbreviated as a signal), it is radiated from the antenna 36b via the circulator 35b. First and second radiations radiated from antennas 36a and 36b
Are respectively received by corresponding first and second mobile terminals (not shown) in the area.

Next, uplink signal transmission will be described. The first wireless modulation signal transmitted from each first mobile terminal in the area is frequency-multiplexed after being received by the first antenna 36a. Here, as described above, the first
Since the power control is not performed when the wireless modulated signal is transmitted from the first mobile terminal, the received power varies due to the difference in the distance between each first mobile terminal and the slave station 30. The frequency-multiplexed first wireless modulation signal is input to the second amplifier 34a via the circulator 35a. The second amplifying unit 34 a amplifies the input first wireless modulation signal and outputs the amplified signal to the signal multiplexing unit 37.

On the other hand, the second radio modulation signal transmitted from each second mobile terminal in the area is received by the second antenna 36b and then frequency-multiplexed. Here, as described above, since the power control is performed when the second wireless modulation signal is transmitted from the second mobile terminal, the distance between each second mobile terminal and the slave station 30 is determined. The received power at the slave station 30 is at a constant level without depending on the difference. The frequency-multiplexed second wireless modulation signal is input to the third amplifier 34b via the circulator 35b. The third amplifying unit 34b amplifies the input second wireless modulation signal and outputs the amplified signal to the signal multiplexing unit 37. At this time, the third amplifier 34b
Is amplified so that the level of the amplified second wireless modulation signal is lower than the level of the first wireless modulation signal amplified by the second amplifying unit 34a.

The signal multiplexing unit 37 includes a first radio modulation signal output from the second amplification unit 34a and the third amplification unit 34.
multiplexed with the second wireless modulation signal output from b, and output to the electrical / optical conversion unit 33. The electrical / optical converter 33 is
The multiplexed radio modulation signal is input, converted into an optical signal, and output. The optical signal output after being converted in the electrical / optical converter 33 is transmitted to the master station 10 located at a remote place via the optical fiber 22.

As described above, when the communication system of another frequency band is shared with the communication system of the existing frequency band,
A signal for controlling transmission power is used as a signal used in a communication system in another frequency band. When the transmission power of the signal is controlled, the dynamic range can be reduced as compared with the case where the conventional transmission power control is not performed. For this reason, the degree of optical modulation when controlling the transmission power can be set smaller than when not controlling the transmission power. Even if two communication systems are shared, the transmission characteristics of the entire communication system can be reduced. Is almost the same as in the case of one conventional communication system, and the number of transmission carriers can be increased.

The above will be verified by using equations (1) and (2) described in the above-mentioned conventional technique.

In the conventional radio signal transmission apparatus, since the transmission power is not controlled, a dynamic range as large as 60 dB is required. In the case of a signal providing a new service this time, the transmission power from each mobile terminal (second mobile terminal) is controlled, so that a dynamic range as wide as 60 dB is not required. For example, assuming that the dynamic range of a new service is 20 dB, the signal level can be reduced by 40 dB as compared with the case of 60 dB, and the optical modulation degree at this time is 1/100 of that when the transmission power is not controlled. Become.

The number of carriers N is assumed to be “8”, which is the number of mobile terminals in the conventional radio signal transmission apparatus, in which simultaneous communication was possible at a place close to the slave station 300. The calculation of the distortion characteristics when frequency-multiplexing the band signals was performed. FIG. 3 shows the calculation results. As is clear from FIG. 3, even if the signal of the second frequency band is frequency-multiplexed with the signal of the first frequency band, the distortion characteristic is not deteriorated,
The number of carriers that can transmit a signal in the frequency band of as many as 700.

As described above, according to the radio signal transmission apparatus according to the embodiment of the present invention, the transmission characteristics of the two communication systems as a whole can be reduced by a small change in the slave station 30 as compared with the conventional one.
It can be realized with little change from the transmission characteristics of only one communication system. Therefore, the number of transmission carriers can be increased, and the cost associated with the introduction of a new communication system can be significantly reduced.

The signal transmitted from the second mobile terminal is, for example, CDMA (coded multiple multiple a).
In the case where a signal subjected to code division multiplexing according to the ccess) method is used, the following effects are further produced. Since the code-division multiplexed signal has a characteristic that the band is wide and the peak power is low, the distortion signal generated from the second wireless modulation signal also has a wide band and a very low peak power. Therefore, the first
Even when distortion occurs in the frequency band of the wireless modulation signal of
It does not affect the wireless modulation signal of Therefore, by using the code-division multiplexed signal, the influence on the first wireless modulation signal by frequency-multiplexing the second wireless modulation signal with the first wireless modulation signal can be further reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a wireless signal transmission device according to an embodiment of the present invention.

FIG. 2 shows a first antenna 36a and a second antenna 36b.
FIG. 7 is a diagram showing an example of the relationship between the frequency of the signal received at step (1) and the received power.

FIG. 3 is a diagram illustrating a relationship between the number of carriers in a second frequency band and distortion CTB.

FIG. 4 is a block diagram illustrating an example of a configuration of a conventional wireless signal transmission device.

FIG. 5 is a diagram showing the relationship between the degree of light modulation and CNR and distortion.

FIG. 6 is a diagram showing the relationship between the number of carriers and the number of composites.

FIG. 7 is a diagram showing the relationship between the number of composites and the amount of distortion DN.

[Description of Signs] 10, 100: master station 21, 22, 201, 202: optical fiber 30, 300: slave station 31, 301: optical / electrical converter 32, 34a, 34b, 302, 304: amplifier 33, Numeral 303: electrical / optical converters 35a, 35b, 305: circulators 36a, 36b, 306: antenna 37: signal multiplexing unit

Claims (5)

[Claims] A wireless signal (hereinafter referred to as a first wireless signal) which is in a first frequency band and has no transmission power limitation, and a transmission signal which is in a second frequency band different from the first frequency band. Restricted radio signals (hereinafter referred to as the second
A wireless signal transmission device in which a plurality of slave station devices that transmit and receive both of the slave station devices and one master station device are connected via a transmission path. A first antenna for transmitting and receiving a first wireless signal; a second antenna for transmitting and receiving the second wireless signal; and the first wireless signal received by the first antenna,
First amplifying means for amplifying to a predetermined level, and the second radio signal received by the second antenna,
A second amplifying means for amplifying to a predetermined level smaller than a level of the amplified first radio signal output from the first amplifying means, and amplifying by the first and second amplifying means, respectively. A frequency multiplexing unit for frequency-multiplexing the first and second radio signals. 2. The wireless signal transmission device according to claim 1, wherein the second wireless signal is a code-division multiplexed signal. 3. The wireless signal transmission device according to claim 1, wherein the master station device and the slave station device are connected by an optical fiber. 4. A radio signal which is in a first frequency band and whose transmission power is not limited (hereinafter referred to as a first radio signal), and which has a transmission power in a second frequency band different from the first frequency band. Restricted radio signals (hereinafter referred to as the second
A radio signal that transmits and receives the first radio signal, a first antenna that transmits and receives the first radio signal, a second antenna that transmits and receives the second radio signal, The first radio signal received by the first antenna,
First amplifying means for amplifying to a predetermined level, and the second radio signal received by the second antenna,
A second amplifying means for amplifying to a predetermined level smaller than a level of the amplified first radio signal output from the first amplifying means, and amplifying by the first and second amplifying means, respectively. And a frequency multiplexing means for frequency multiplexing the first and second radio signals. 5. The slave station device according to claim 4, wherein the second wireless signal is a code-division multiplexed signal.