JP2002094393A - Digital broadcast system and its transmission station and relay station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital broadcast system that enhances the reception quality for a specific application channel, without decreasing channel multiplex number. SOLUTION: When there is a specific channel, such as a pilot channel, a pay broadcast channel and a channel for broadcast emergency information through which reception stations MS1-MSm have to receive information with high quality, a weight control section 40A gives a weight coefficient which is larger than others to a weight multiplier section, corresponding to the specific channel to enable the weight multiplier section to multiply the coefficient by transmission data, so as to set the transmission power of the specific channel to a value higher than the transmission power of other channels only for a required period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a digital broadcasting system employing a code division multiplexing (CDM) system and a transmitting station apparatus thereof.

[0002]

2. Description of the Related Art In recent years, digital broadcasting systems employing the CDM system have attracted attention. Systems using the CDM method use spread spectrum technology.
For example, the configuration is as follows.

[0003] That is, a transmitting station first performs primary modulation of digitalized audio data and image data for each channel by a digital modulation method such as a phase modulation method. Next, the modulated transmission data is converted into a broadband transmission signal by performing spectrum spreading using a different spreading code for each channel, and the wideband transmission signal is synthesized and converted into a radio frequency signal. Send.
On the other hand, the receiver performs spectrum despreading on the received radio frequency signal using a spreading code corresponding to a desired channel. Then, the received signal separated by the despreading is subjected to primary demodulation by a digital demodulation method such as a phase demodulation method to reproduce received data.

[0004] The CDM system has an advantage that it is easy to maintain a high reception quality against a change in a radio environment such as fading by using a spread spectrum technique.

[0005] In this type of system, it is necessary to increase the number of multiplexed channels in order to transmit more information in a predetermined transmission band, that is, to increase the frequency utilization efficiency. However, when the number of multiplexed channels is increased, cross-correlation of spreading codes causes interference between channels, which tends to cause deterioration in reception quality. This problem is not particularly preferable in a channel for broadcasting important information such as emergency information, and a countermeasure is eagerly desired.

[0006]

As described above, the digital broadcasting system adopting the CDM system has an advantage that it is resistant to changes in the radio environment, but is liable to cause inter-channel interference when the number of multiplexed channels is increased. Therefore, there is a problem that the reception quality is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a digital broadcasting system in which the reception quality of a channel for a specific application is improved without reducing the number of multiplexed channels. It is to provide the transmitting station and the relay station.

[0008]

In order to achieve the above object, a first invention multiplexes information of a plurality of channels by performing spreading processing with different spreading codes, and multiplexes the multiplexed signal into a plurality of channels. In a digital broadcasting transmitting station that performs radio transmission to a receiving station, transmission power control means for individually and variably setting the transmission power for each channel according to the use of each channel is provided.

As the control contents of the transmission power control means, for example, the following can be considered. (1) When a pilot channel used by each receiving station to establish spreading code synchronization is included in a plurality of channels, the transmission power control means reduces the transmission power of this pilot channel to that of another channel. Make it larger than the transmission power.

(2) When the free broadcast channel and the pay broadcast channel are included in the plurality of channels, the transmission power of the pay broadcast channel is reduced by the transmission power control means from the transmission power of the free broadcast channel. Enlarge.

(3) A first channel for transmitting information having a predetermined importance among a plurality of channels, and a second channel for transmitting information having a higher importance than the information transmitted by the first channel. When the second channel is included, the transmission power of the second channel is made larger than the transmission power of the first channel by the transmission power control means. At this time, the transmission power control means sets the transmission power of the second channel to be higher than the transmission power of the first channel only during the period of transmitting information of high importance.

(4) The transmission power control means monitors the presence or absence of information to be transmitted for each channel, and sets the transmission power of the channel to a minimum power value during a period when there is no information to be transmitted.

Therefore, according to the present invention, for a channel that requires a receiving station to receive information with high quality according to the use of the channel, the channel is transmitted with a higher transmission power than other channels. For this reason, even if the number of multiplexed channels is increased and inter-channel interference is likely to occur, the receiving station can use a channel for a specific application, such as a pilot channel necessary for establishing synchronization, a pay broadcast channel, or emergency information. Reception quality of a channel for broadcasting important information can be improved.

Further, a power normalizing means is provided, and the transmission power of the multiplexed signal is kept constant based on the transmission power control result for each channel by the transmission power control means. By doing so, the transmission power of the transmitting station is always kept within an allowable range.

The transmitting station includes not only a broadcasting station but also a relay station that performs CDM multiplexing of information distributed from the broadcasting station and transmits the multiplexed information.

On the other hand, in the second invention, information indicating a channel being received or scheduled to be received is notified from each receiving station to the transmitting station, and each of the transmitting stations determines each channel based on the information notified from each receiving station. The reception rate, that is, the viewing rate or the listening rate for each channel is obtained, and the transmission power of a channel having a high reception rate is controlled to be larger than the transmission power of a channel having a lower reception rate based on the reception rate. is there.

Therefore, according to the present invention, the transmission power of a channel having a high reception rate is set to a higher value than other channels. For this reason, more receiving station users among the preceding receiving station users can perform high quality reception.

According to a third aspect of the present invention, in each receiving station, the receiving quality of the receiving channel is detected, and the detection result is notified to the transmitting station, and the transmitting station detects the received quality notified from each of the receiving stations. Based on the result, a ratio (also referred to as a location ratio) of receiving stations satisfying a predetermined reception quality is obtained for each channel, and the transmission power of a channel having a low reception quality satisfaction ratio is determined based on the reception quality satisfaction ratio. The reception quality satisfaction rate is controlled so as to be larger than the transmission power of the higher channel.

Therefore, according to the present invention, for a channel in which the ratio of receiving stations satisfying the reception quality is lower than the reference value, the transmission power is set to a high value, and instead, the reception power satisfying the reception quality is set. The transmission power is reduced for channels in which the proportion of stations exceeds the reference value. That is, the transmission power of each channel is optimized according to the proportion of receiving stations that satisfy the reception quality. For this reason, it is possible to prevent extreme degradation of reception quality in a specific channel and reduce variation in reception quality between channels.

Further, the fourth invention comprises a relay station, and multiplexes information of a plurality of channels distributed from a broadcasting station by performing spreading processing with different spreading codes, and covers the multiplexed signal by itself. In a digital broadcasting system for performing radio transmission to a plurality of receiving stations existing in a service area, each of the plurality of receiving stations indicates information indicating a channel being received or scheduled to be received, or indicates reception quality of a received channel. The information is notified to the relay station that is the transmission source of the reception channel. On the other hand, each of the plurality of relay stations calculates the reception rate for each channel based on the information notified from each reception station, or determines each channel based on the information indicating the notified reception quality. The ratio of receiving stations satisfying a predetermined reception quality is calculated for each of the cases. Then, based on the calculated reception rate of each channel, control is performed to set the transmission power of the channel with the higher reception rate to a value larger than the transmission power of the channel with the lower reception rate,
Alternatively, based on the calculated reception quality satisfaction rate of each channel, control is performed to set the transmission power of the channel having the lower reception quality satisfaction rate to a value larger than the transmission power of the channel having the higher reception quality satisfaction rate. It was made.

Therefore, according to the present invention, for example, in a system having a relay station for a gap filler, a predetermined reception quality is satisfied according to a reception rate, that is, a viewing rate or a listening rate, for each channel, or for each channel. In the relay station, the transmission power for each channel is individually variably controlled in accordance with the ratio of receiving stations. For this reason, even in a system using a relay station, optimal transmission power can be performed according to the audience rating or listening rate for each channel or according to the reception quality satisfaction rate.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention relates to the use of a channel in a broadcasting station, for example, whether it is a channel for transmitting a pilot signal or a pay broadcast channel. Alternatively, the transmission power of each channel is individually variably set according to whether the channel transmits important information.

FIG. 1 is a schematic configuration diagram showing a first embodiment of a digital broadcasting system according to the present invention. The broadcasting station BS multiplexes information of a plurality of channels by CDM, and wirelessly transmits the digital multiplexed signal to a service area BE covered by the broadcasting station BS. Multiple receiving stations MS1 to M
Sm receives the digital multiplexed signal transmitted by the broadcasting station BS in the service area SE. Then, after separating the received digital multiplexed signal for each channel, the user selects and reproduces and outputs a channel desired to be viewed or listened.

The digital multiplexed signal can be broadcasted from the broadcasting station BS by terrestrial broadcasting,
It is also possible to broadcast from S via a broadcasting satellite or a communication satellite. Each of the receiving stations MS1 to MSm includes a type that is fixedly installed indoors and outdoors, a type that is mounted on a vehicle, and a type that is carried by a user.

Incidentally, the broadcasting station BS and each receiving station M
S1 to MSm are configured as follows. FIGS. 2A and 2B are circuit block diagrams each showing a main configuration thereof.

First, the broadcasting station BS includes a plurality of CDM modulators 2.
0 to 2N, and these CDM modulators 20 to 2
A pilot signal generated from the pilot signal generator 10 and broadcast data of a plurality of broadcast channels Ch # 1 to Ch # N generated from a program generator not shown are input to N. The pilot signals are received at the receiving stations MS1 to MS
Sm is a known signal used to establish the synchronization of the spreading code, and for example, is composed of a signal pattern of all "1". The broadcast data of each of the channels Ch # 1 to Ch # N includes one consisting of images and sounds, one consisting only of sounds, and one consisting of character data. The types of these data depend on channels or time zones. Selected.

Each of the CDM modulators 20 to 2N performs primary modulation on the inputted pilot signal and broadcast data of each channel by a digital modulation system such as a QPSK (Quadrature Phase Shift Keying) system, and then performs each channel. PN (Pseudo random No)
ise) Multiplies the code to spread the band. As the PN code, a code obtained by multiplying a long code such as an M sequence having a long cycle in which synchronization of spreading codes is easily established with an orthogonal code such as a Walsh code for ensuring orthogonality between channels is used. For pilot signals, all "0"
Walsh codes are used.

The data modulated by the CDM modulators 20 to 2N are input to weight multipliers 30 to 3N, respectively. The weight multiplying units 30 to 3N correspond to the CDM modulating units 20 to
The modulation data output from the 2N is multiplied by the weight coefficient given from the weight control unit 40A. Weight control unit 40A
Sets a weight coefficient for each channel in accordance with weight control data given from a main control unit (not shown), and gives the weight coefficient to each of the weight multipliers 30 to 3N. At the same time, normalization information is given to the power normalization unit 60 so as to keep the total power after all channels multiplexed, which increases or decreases according to the weight set for each channel, constant.

The multiplexing unit 50 includes an adder, adds the weighted modulated data output from the weight multiplying units 30 to 3N, and outputs the added CDM modulated data to the power normalizing unit 60. The power normalizing unit 60 controls the power (amplitude) of the CDM modulated data output from the multiplexing unit 50 according to the normalization information given from the weight control unit 40A.
Is normalized to be a constant level.

The radio section (RF section) 70 converts the CDM modulated data output from the power normalizing section 60 into a radio carrier frequency, limits the band, and transmits the band from the antenna 80 to the service area.

On the other hand, the receiving stations MS1 to MSm are configured as follows. That is, the radio carrier signal arriving from the broadcast station BS is received by the antenna 110 and then input to the radio unit (RF unit) 111A. The RF unit 111A
After band-limiting the received radio frequency signal, the frequency is converted to a baseband signal, and the received baseband signal is input to the CDM demodulation unit 112 and the code synchronization unit 113, respectively.

The code synchronization section 113 extracts a pilot signal transmitted by a pilot channel from the received baseband signal using a matched filter, establishes a PN code synchronization timing based on the extraction result, and The synchronization timing is instructed to the CDM demodulation unit 112.

The CDM demodulation section 112 has a PN code generator, and generates a PN code corresponding to a desired reception channel selected and designated by the channel selection section 114 on a one-to-one basis. Then, the PN code is despread by multiplying the reception baseband signal at the synchronization timing instructed by the code synchronization unit 113. Then, the primary modulation scheme of the transmitting station is applied to the despread reception data. For example, perform QPSK demodulation corresponding to
As a result, demodulated data of the desired reception channel is obtained.

The demodulated data is converted into a predetermined display format or audio format by the conversion unit 115 depending on the data type, that is, whether it is an image or audio, or character data. It is supplied to the display 117 and the speaker 116 to be displayed and loudspeaked and output.

Next, the operation of the broadcasting station BS of the system configured as described above will be described. First, the service area S
If E is a location where the occurrence of multipath is relatively small, such as a rural area, the main control unit (not shown) of the broadcasting station BS sets the transmission power of each channel to the same value. The weight control information is provided to the weight control unit 40A. Therefore, in this case, the weight control unit 40A gives the same value of the weight coefficient to all the weight multiplication units 30 to 3N including those for the pilot channel. For this reason, the pilot signal and the broadcast data of each channel are multiplied by the same weighting factor,
As a result, the pilot signal and each broadcast data are CDM-multiplexed at the same transmission power and transmitted.

On the other hand, if the service area SE has many occurrences of multipath, such as an urban area, and is likely to lose synchronization of the PN code at the receiving station, the main control unit (not shown) Provides weight control information for increasing the transmission power of the pilot channel to the transmission power of the other broadcast channels to the weight control unit 40A. Therefore, in this case, weight control section 40A sets the weight coefficient given to weight multiplier section 30 for the pilot channel to a value larger than the weight coefficient given to weight multiplier sections 31 to 3N of the other channels. For this reason, the power value (amplitude) of the pilot signal is set to a larger value than the broadcast data of other channels, and the CDM
It is multiplexed and transmitted.

Therefore, even if the receiving stations MS1 to MSm in the service area SE are located in a place where a large number of multipaths occur, the multipath resolution is kept high and the synchronization with the PN code is reliably established and maintained. It is possible to do.

When there is a pay broadcast channel among the plurality of broadcast channels, the main control unit performs weight control on the weight control information for increasing the transmission power of the pay broadcast channel over other free broadcast channels. To the unit 40A.
Therefore, a larger weighting factor is given to each of the weight multiplying units 31 to 3N for the broadcast channel from the weight control unit 40A only to the weight multiplying unit 3i for the pay broadcast channel than the others.
As a result, the pay broadcast channel is transmitted with higher transmission power than the other free broadcast channels.

Therefore, even when the receiving stations MS1 to MSm are relatively far from the broadcasting station BS or in a place where the reception quality is likely to deteriorate such as in a building or the like, at least with respect to the pay broadcasting channel, the receiving stations MS1 to MSm are good. It is possible to receive with high quality.

Further, when it becomes necessary to broadcast emergency information relating to a disaster or the like, the main control unit performs weight control for increasing the transmission power of the broadcast channel over other channels only during the period of transmitting the emergency information. Weight control unit 4
Give to 0A. Therefore, the weight control section 40A sends the broadcast channel weight multiplication sections 3j to 3N only during the emergency information transmission period to the broadcast channel weight multiplication section 3j.
Is given a larger weighting factor than the others. For this reason, only during the transmission period of the emergency information, the broadcast channel is transmitted with higher transmission power than the other broadcast channels.

Therefore, even when the receiving stations MS1 to MSm are relatively far from the broadcasting station BS or in a place where the reception quality is likely to deteriorate such as in a building or the like, at least the emergency information can be transmitted in good quality. , It is possible to reliably receive the data.

When there is a broadcast channel having a non-broadcast time zone such as at night, weight control information for setting the transmission power of the broadcast channel in the non-broadcast time zone to the minimum power value (for example, zero) Is given from the main control unit to the weight control unit 40A. Therefore, in the non-broadcast time zone, the transmission power of the broadcast channel is set to zero. Accordingly, during the non-broadcasting time slot, the substantial number of multiplexed broadcasting channels of the system can be reduced, thereby improving the reception quality of each broadcasting channel.

As described above, in the first embodiment, it is necessary to specify the receiving stations MS1 to MSm to receive information with high quality, such as a pilot channel, a pay broadcast channel, a channel for broadcasting emergency information, and the like. When there is a channel, the weight control unit 40A gives a weight multiplication unit corresponding to the specific channel a weighting coefficient larger than that of the other channel to multiply the transmission data, thereby increasing the transmission power of the specific channel for another required period. It is set to a value larger than the transmission power of the channel. Therefore, the reception quality of a channel for a specific application can be improved without reducing the number of multiplexed channels.

(Second Embodiment) In a second embodiment of the present invention, each receiving station notifies the broadcasting station of the number of the channel being received or scheduled to be received, and the broadcasting station reports the number of the channel being received. Determine the reception rate for each channel, that is, the audience rating or listening rate based on the channel number being selected for reception,
Based on this reception rate, weight control is performed so that the transmission power of a channel having a high reception rate is larger than the transmission power of a channel having a lower reception rate.

FIGS. 3A and 3B show the second embodiment of the present invention.
FIG. 2 is a circuit block diagram showing a configuration of a broadcasting station and a receiving station of the digital broadcasting system according to the embodiment. 2A and 2B are denoted by the same reference numerals, and detailed description thereof will be omitted.

First, the receiving stations MS1 to MSm include a modulation section 118B and an RF section 111B provided with a transmission system in order to notify the number of the currently selected channel to the broadcasting station BS at the time of channel selection or periodically. Have. Modulator 118B
Modulates the notification data including the currently selected channel number output from the channel selection unit 114 by a digital modulation method such as the QPSK method, and supplies the modulated signal to the RF unit 111B. The RF unit 111B converts the frequency of the modulated signal into a predetermined radio carrier frequency for an uplink channel, amplifies the signal, and transmits the amplified signal to the broadcasting station BS from the antenna 110. In addition, as the uplink channel, for example, a mobile phone system or a PHS (Personal Handyphone Sy
stem) communication channel may be used.

On the other hand, the broadcasting station BS has the receiving stations MS1 to M
In order to receive notification data from Sm, an RF unit 70B having a receiving system and a demodulation unit 90 are provided. RF unit 70
B receives the radio frequency signals arriving via the upstream channel from each of the receiving stations MS1 to MSm, converts the frequency to an intermediate frequency signal or a baseband signal, and inputs the converted received signal to the demodulation unit 90. . The demodulation unit 90 reproduces the notification data by QPSK demodulating the received signal.

The broadcasting station BS includes a channel reception rate calculation section 100 and a weight control section 4 which operates according to the calculation result.
0B. The channel reception rate calculation unit 100 calculates the number of receiving stations that have selected to receive this broadcast channel for each broadcast channel based on the selected channel number notified by the notification data from each of the receiving stations MS1 to MSm. Then, a rating or a listening rate, that is, a receiving rate for each broadcast channel is calculated from the value.

The weight control unit 40B increases the transmission power of a broadcast channel with a large number of currently selected receiving stations in accordance with the result of calculating the reception rate, and instead increases a broadcast channel with a small number of currently selected receiving stations. , A weighting factor is set for each broadcast channel, and the weighting factor is given to the weight multipliers 31 to 3N. At the same time, normalization information is given to the power normalization unit 60 in order to keep the total power after multiplexing all channels increased or decreased by the set weight.

With such a configuration, each receiving station MS
When the user performs a channel selection operation in 1 to MSm, notification data including the selected channel number is input from the channel selection unit 114 to the modulation unit 118B, and QPSK-modulated by the modulation unit 118B.
1B is transmitted to the broadcasting station BS via an uplink channel.

On the other hand, in the broadcasting station BS, the receiving stations MS1 to MS
When a radio frequency signal arrives from m, the radio frequency signal is received by the RF unit 70B, then demodulated by the demodulation unit 90 to reproduce the notification data, and input to the channel reception rate calculation unit 100. Each time the notification data arrives from the receiving stations MS1 to MSm, the channel reception rate calculation unit 100 recalculates the reception rate for each channel based on the channel number inserted in the notification data. The calculation result of the rate is notified to the weight control unit 40B.

The weight control unit 40B calculates a new weight coefficient for each channel based on the calculation result of the reception rate. For example, it is assumed that the reception rate of the broadcast channel Ch # i has increased significantly and the reception rate of the broadcast channel Ch # j has decreased. Then, the weight control unit 40B sets the broadcast channel C
The weight coefficient is changed to a large value to increase the transmission power of h # i, and conversely, the weight coefficient is changed to a small value to reduce the transmission power of broadcast channel Ch # j.

As described above, each broadcast channel Ch # 1 to Ch #
When the weight coefficient of #N is changed, each broadcast channel C output from the weight multipliers 31 to 3N according to the weight coefficient is changed.
The power value (amplitude) of the modulation data of h # 1 to Ch # N is varied. Then, the modulated data whose power value has been changed is multiplexed by the multiplexing unit 50 and normalized by the power normalizing unit 60 so that the total power becomes constant.
B is transmitted to the service area SE.

Therefore, according to the second embodiment, according to the reception rate of each broadcast channel, that is, the viewing rate or the listening rate,
Channels with higher reception rates have higher transmission powers, while channels with lower reception rates have relatively lower transmission powers, so even if the number of multiplexed channels is large and inter-channel interference cannot be avoided. Therefore, many receiving station users can receive broadcast data with high quality.

If there is a broadcast channel with no receiving station being received, that is, a broadcast channel with a reception rate of “0”, the weight coefficient for the broadcast channel is set to “0” in the weight control unit 40B, As a result, the transmission power of the broadcast channel becomes “0”. Therefore, it is possible to increase the transmission power of other broadcast channels accordingly,
The reception quality of the receiving station receiving these broadcast channels can be improved.

(Third Embodiment) In a third embodiment of the present invention, each receiving station detects the reception quality of the channel whose reception is selected, notifies the broadcast station of the detection result, and the broadcast station performs Based on the reception quality detection result notified from each of the reception stations, the ratio of the reception stations satisfying the predetermined reception quality for each channel, that is, the reception quality satisfaction rate is obtained, and based on this reception quality satisfaction rate, Thus, the transmission power of a channel having a low reception quality satisfaction rate is controlled to be larger than the transmission power of a channel having a higher reception quality satisfaction rate.

FIGS. 4A and 4B show a third embodiment of the present invention.
FIG. 2 is a circuit block diagram showing a configuration of a broadcasting station and a receiving station of the digital broadcasting system according to the embodiment. In the figure, the same parts as those in FIGS. 3A and 3B are denoted by the same reference numerals, and detailed description is omitted.

First, the receiving stations MS1 to MSm measure a bit error rate (BER) by a BER measuring unit 11
9 to notify the broadcasting station BS of the measured BER together with the channel number selected for reception.
8C and an RF unit 111C having a transmission system.

The modulation section 118C is provided with the BER measurement section 11
9 is modulated by a digital modulation scheme such as the QPSK scheme, and the modulated data is transmitted to the RF section 111C. Supply.
The RF unit 111C converts the frequency of the modulated signal into a predetermined radio carrier frequency for an uplink channel, amplifies the signal, and transmits the amplified signal to the broadcasting station BS from the antenna 110. In addition,
As the uplink channel, for example, as in the third embodiment, for example, a mobile phone system or a PHS (Personal Handy)
phone System).

On the other hand, the broadcasting station BS has the receiving stations MS 1 to M
In order to receive notification data from Sm, an RF unit 70C including a receiving system and a demodulation unit 90 are provided. RF unit 70
C receives the radio frequency signal arriving from each of the receiving stations MS1 to MSm via the upstream channel, converts the frequency to an intermediate frequency signal or a baseband signal, and inputs the converted received signal to the demodulation unit 90. . The demodulation unit 90 reproduces the notification data by QPSK demodulating the received signal.

The broadcast station BS includes a reception quality satisfaction rate calculation unit 101 and a weight control unit 4 that operates according to the calculation result.
0C. The reception quality satisfaction rate calculation unit 101 satisfies a predetermined reception quality for each broadcast channel based on the channel number selected for reception notified by the notification data from each of the receiving stations MS1 to MSm and its BER. The ratio of receiving stations, that is, the reception quality satisfaction rate is obtained.

The weight control unit 40C increases the transmission power of the broadcast channel whose reception quality satisfaction rate is lower than the reference value in accordance with the above calculation result of the reception rate, and conversely, sets the reception quality satisfaction rate to a certain margin than the reference value. Control is performed so that the transmission power of the high broadcast channel is set to a small value. Also with it
In order to keep the total power after all channels multiplexed increased or decreased by the set weight constant, normalization information is given to the power normalization unit 60.

With such a configuration, each receiving station MS
In 1 to MSm, the BER measured by the BER measuring unit 119 during reception is inserted into the notification data together with the channel number being received and input to the modulation unit 118C, and after QPSK modulation by the modulation unit 118C, the RF unit 111C Is transmitted to the broadcast station BS via the uplink channel.

On the other hand, in the broadcasting station BS, the receiving stations MS1 to MS
When a radio frequency signal arrives from m, the radio frequency signal is received by the RF unit 70C, then demodulated by the demodulation unit 90 to reproduce notification data, and input to the reception quality satisfaction rate calculation unit 101. Each time notification data arrives from the receiving stations MS1 to MSm, the reception quality satisfaction rate calculation section 101 calculates the reception quality satisfaction rate for each channel based on the BER inserted in the notification data and the channel number. Is calculated, and the calculation result of the reception quality satisfaction rate is calculated by the weight control unit 40C.
Will be notified.

The weight control unit 40C calculates a new weight coefficient for each broadcast channel based on the calculation result of the reception quality satisfaction rate. For example, it is assumed that the reception quality satisfaction rate of the broadcast channel Ch # i has dropped below the reference value. Then, weight control section 40C changes the weight coefficient to a large value to increase the transmission power of broadcast channel Ch # i. On the other hand, it is assumed that the reception quality satisfaction rate of broadcast channel Ch # j is higher than a certain margin. In this case, the weight coefficient is changed to a small value in order to reduce the transmission power of broadcast channel Ch # j.

As described above, each of the broadcast channels Ch # 1 to Ch #
When the weight coefficient of #N is changed, each broadcast channel C output from the weight multipliers 31 to 3N according to the weight coefficient is changed.
The power value (amplitude) of the modulation data of h # 1 to Ch # N is varied. Then, the modulated data whose power value has been changed is multiplexed by the multiplexing unit 50 and normalized by the power normalizing unit 60 so that the total power becomes constant.
C is transmitted to the service area SE.

Therefore, in the service area SE, the transmission power of a broadcast channel having many receiving stations that are not satisfied with the reception quality is increased, and as a result, the reception quality of the broadcast channel is improved.

Also in this embodiment, for a broadcast channel having no receiving station during reception, the weight control unit 40
In C, the weight coefficient for the broadcast channel is “0”
, And as a result, the transmission power of the broadcast channel becomes “0”. Therefore, the transmission power of other broadcast channels can be increased accordingly, and the reception quality of the receiving station receiving these broadcast channels can be improved.

(Fourth Embodiment) In a fourth embodiment of the present invention, a plurality of relay stations constituting a cell are provided, and information of a plurality of channels distributed from a broadcasting station is spread by different spreading codes. By multiplexing this CDM
In a digital broadcasting system for wirelessly transmitting a multiplexed signal to a plurality of receiving stations present in a cell covered by the own station, each of the plurality of receiving stations transfers its own position to a relay station via an uplink channel. In addition to the registration, the reception quality of the channel selected for reception is detected, and the detection result is notified to the relay station, and the relay station uses the reception quality detection result notified from each reception station for each channel. The ratio of the receiving stations satisfying the predetermined reception quality, i.e., the reception quality satisfaction rate is obtained, and the transmission power of the channel having the low reception quality satisfaction rate is determined based on the reception quality satisfaction rate. This is controlled so as to be larger than the transmission power of the channel.

FIG. 5 is a schematic configuration diagram of a digital broadcasting system according to a fourth embodiment of the present invention. In the service area covered by the system, a plurality of relay stations (three stations are shown in the figure) RS1 to RS3 are distributed and arranged. Each of these relay stations RS1 to RS3 is connected to the broadcast master station BSS via a wired line, and receives data of the same broadcast channel distributed from the broadcast master station BSS. Then, the data of these broadcast channels is CDM-multiplexed together with the pilot signal, and transmitted to the respective relay service areas RE1 to RE3 formed by itself. Each of the receiving stations MS1 to MSm selectively receives a broadcast signal having the highest reception quality among broadcast signals arriving from each of the relay stations RS1 to RS3.

The broadcast master station BSS and each of the relay stations RS1 to RS1
It is also possible to connect to the RS 3 via a wireless line other than the wired line.

FIGS. 6A and 6B are circuit block diagrams showing the main parts of the relay stations RS1 to RS3 and the receiving stations MS1 to MSm, respectively. The receiving stations MS1 to MS
In the configuration of Sm, the same portions as those in FIG. 5B are denoted by the same reference numerals, and detailed description will be omitted.

First, the relay stations RS1 to RS3 are
Like the broadcasting station BS described in (a), the broadcasting station BS has a plurality of CDM modulators 220 to 22N.
To 20 to 22N, a pilot signal generated from pilot signal generation section 210 and broadcast data of a plurality of broadcast channels Ch # 1 to Ch # N received from broadcast master station BSS are input, respectively. The pilot signal is received by the receiving station M
S1 to MSm are known signals used to establish synchronization of spread codes, and include, for example, all "1" signal patterns. The broadcast data of each of the channels Ch # 1 to Ch # N includes one consisting of images and sounds, one consisting only of sounds, and one consisting of character data. The types of these data depend on channels or time zones. Selected.

Each of the CDM modulators 220 to 22N performs primary modulation on the inputted pilot signal and broadcast data of each channel by a digital modulation method such as the QPSK method, and then performs P modulation for each channel.
The band is spread by multiplying the N code. As a PN code, a long code such as an M-sequence having a long cycle that can easily establish synchronization of a spread code is used to ensure orthogonality between channels.
A code obtained by multiplying an orthogonal code such as a Walsh code is used.
For pilot signals, Wals of all "0"
The h code is used.

The data modulated by the CDM modulators 220 to 22N are input to weight multipliers 230 to 23N, respectively. The weight multiplication units 230 to 23N
The modulation data output from the modulation units 220 to 22N is multiplied by the weight coefficient given from the weight control unit 240.

Multiplexing section 250 is composed of an adder, adds the weighted modulated data output from weight multiplying sections 230 to 23N, and outputs the added CDM modulated data to power normalizing section 260. The power normalization unit 260
According to the normalization information provided from the weight control section 240, the power (amplitude) of the CDM modulated data output from the multiplexing section 250 is normalized so as to be at a constant level.

The radio section (RF section) 270 converts the CDM modulated data output from the power normalization section 260 into a radio carrier frequency, performs band limitation, and then performs antenna limiting.
Transmit from 0 to the service area.

Incidentally, the relay stations RS1 to R
S3 includes an RF unit 270 and a demodulation unit 290 having a reception system for receiving notification data from the reception stations MS1 to MSm. The RF unit 270 is connected to each receiving station MS1.
ＭＳMSm, receives the radio frequency signal arriving via the above up channel, converts the frequency to an intermediate frequency signal or a baseband signal, and demodulates the received signal after this conversion.
Enter 0. Demodulation section 290 converts the received signal to QPS
The notification data is reproduced by performing K demodulation.

The relay stations RS1 to RS3 each include a reception quality satisfaction rate calculation unit 300 and a weight control unit 240 that operates according to the calculation result. Receiving quality satisfaction rate calculator 3
00 is based on the channel number currently selected for reception notified by the notification data from the receiving station that is receiving the broadcast channel of the own station among the receiving stations MS1 to MSm and the BER thereof.
The ratio of receiving stations satisfying a predetermined reception quality for each broadcast channel, that is, a reception quality satisfaction rate is obtained.

The weight control section 240 increases the transmission power of the broadcast channel whose reception quality satisfaction rate is lower than the reference value according to the calculation result of the reception quality satisfaction rate, and conversely, the reception quality satisfaction rate is more constant than the reference value. Is controlled so that the transmission power of a broadcasting channel higher than the margin of the transmission channel is set to a small value. At the same time, in order to keep the total power after all channels multiplexed increased or decreased by the set weight constant, the power normalizing section 260
Is given normalization information.

Further, each of the relay stations RS1 to RS3 includes a receiving station registration control unit 310. Receiving station registration control section 310
Is based on the identification number of the source receiving station included in the notification data received from the receiving stations MS1 to MSm via the uplink channel, and based on the relay service areas RE1 to RE1 of the own station.
A list of the receiving stations existing in No. 3 is created. This list is used by the reception quality satisfaction rate calculation section 300 to calculate the reception quality satisfaction rate by the receiving station receiving the broadcast channel of the own station.

The receiving station registration control section 310 also has a function of notifying the receiving stations MS1 to MSm of their own identification numbers. That is, the notification data pilot signal generator 2
10 is given its own identification number, whereby the identification number of its own station is inserted into a part of the pilot signal and transmitted.

On the other hand, the receiving stations MS1 to MSm measure the BER of the broadcast channel being received.
And a registration control unit 120. Registration control unit 12
0 is the transmission source relay station RS from the pilot signal having the highest reception level detected by the code synchronization section 113.
Extract and hold the identification number of i. Then, in order to register the own station with the currently receiving relay station RSi, the extracted identification number of the relay station and the identification number of the own station are combined with the modulating unit 11.
Give to 8D.

The modulation section 118D is connected to the BER measurement section 11
9, the channel number currently selected for reception output from the channel selection unit 114, and the relay station RS
And notification data including the identification number of the own station. The notification data is modulated by a digital modulation method such as the QPSK method, and the signal after the modulation is R
It is supplied to the F section 111D. The RF unit 111D converts the frequency of the modulated signal into a predetermined uplink channel radio carrier frequency, amplifies the signal, and transmits the amplified signal from the antenna 110 to the receiving relay station RSi.

With such a configuration, each receiving station MS
1 to MSm, the BER measurement unit 1 starts receiving or during reception of a broadcast channel from an arbitrary relay station RSi.
19 measures the BER of the broadcast channel being received. Then, the measured BER value is inserted into the notification data together with the number of the broadcast channel being received, and
8D, QPSK-modulated by the modulator 118D, and transmitted from the RF unit 111D to the relay station RSi via the uplink channel. At this time, the identification number of the relay station RSi being received and the identification number of its own station extracted by the registration control unit 120 are inserted into the notification data and transmitted.

On the other hand, in the relay station RSi, the receiving station MS
When a radio frequency signal arrives from 1 to MSm, the radio frequency signal is received by the RF unit 270 and then demodulated by the demodulation unit 290 to reproduce the notification data. The reception quality satisfaction rate calculation unit 300 and the reception station registration control unit 310 are input. The receiving station registration control unit 310 extracts the number of the relay station as the transmission destination and the identification number of the receiving station of the transmission source from the notification data arriving from each receiving station. Then, based on these identification numbers, a list of receiving stations currently receiving the broadcast channel transmitted by the own station is created.

Each time the notification data arrives, the reception quality satisfaction rate calculation unit 300 determines whether the transmission source of the notification data is a receiving station that is receiving the broadcast channel transmitted by the own station. The determination is made based on the list created by the reception registration control unit 310. Then, if the transmission source of the notification data is a receiving station receiving the broadcast channel transmitted by the own station, the BER inserted in the notification data and the number of the channel are used to determine the channel for each channel. The reception quality satisfaction rate is calculated, and the result of the calculation of the reception quality satisfaction rate is notified to the weight control unit 240.

The weight control section 240 calculates a new weight coefficient for each broadcast channel based on the calculation result of the reception quality satisfaction rate. For example, it is assumed that the reception quality satisfaction rate of the broadcast channel Ch # i has dropped below the reference value. Then, weight control section 240 changes the weight coefficient to a large value so as to increase the transmission power of broadcast channel Ch # i. On the other hand, it is assumed that the reception quality satisfaction rate of broadcast channel Ch # j is higher than a certain margin. In this case, the weight coefficient is changed to a small value in order to reduce the transmission power of broadcast channel Ch # j.

As described above, each broadcast channel Ch # 1 to Ch
When the weight coefficient of #N is changed, the power value (amplitude) of the modulation data of each of the broadcast channels Ch # 1 to Ch # N output from the weight multipliers 231 to 23N is changed according to the weight coefficient. . Then, the modulated data whose power value has been changed is multiplexed by the multiplexing unit 250 and the power normalizing unit 26
After being normalized so that the total power is constant at 0, RF
The data is transmitted from the unit 270 to the relay service area REi.

Therefore, each relay service area RE1
For each RE3, the transmission power of a broadcast channel with many receiving stations that do not satisfy the reception quality is increased, and as a result, the reception quality of the broadcast channel is improved.

The present invention is not limited to the above embodiments. For example, in the fourth embodiment,
Each of the relay stations RS1 to RS3 calculates the reception quality satisfaction rate of each channel by each reception station receiving the broadcast channel from the relay station, and based on the reception quality satisfaction rate, the transmission power of each broadcast channel. Has been described above. However, not limited to this, each relay station RS1
To RS3, calculate the reception rate of each broadcast channel by each receiving station receiving the broadcast channel from the own station, and variably control the transmission power of each broadcast channel based on this reception rate. Is also good.

Also, each relay station R shown in the fourth embodiment
In each of S1 to RS3, when there is a specific channel that requires receiving stations MS1 to MSm to receive information with high quality, such as a pilot channel, a pay broadcasting channel, a channel for broadcasting emergency information, etc., weight control is performed. The unit 240 gives the weight multiplication unit corresponding to the specific channel a weighting factor larger than the others to multiply the transmission data, thereby setting the transmission power of the specific channel to a value larger than the transmission power of the other channels only for a necessary period. You may make it.

In addition, the circuit configurations of the broadcasting station, the relay station, and the receiving station, the transmission power control procedure for each channel and the contents thereof can be variously modified without departing from the gist of the present invention.

[0094]

As described in detail above, according to the present invention, information of a plurality of channels is multiplexed by performing spreading processing with different spreading codes, and the multiplexed signal is wirelessly transmitted to a plurality of receiving stations. In the transmitting station for digital broadcasting, transmission power control means individually and variably sets the transmission power for each channel according to the use of each channel.

Therefore, according to the present invention, it is possible to provide a digital broadcasting system capable of improving the reception quality of a channel for a specific application without reducing the number of multiplexed channels, and a transmission station and a relay station thereof.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a digital broadcasting system according to a first embodiment of the present invention.

FIG. 2 is a circuit block diagram showing a main configuration of a broadcasting station and a receiving station of the system shown in FIG. 2;

FIG. 3 is a circuit block diagram showing a main configuration of a broadcasting station and a receiving station according to a second embodiment of the present invention.

FIG. 4 is a circuit block diagram showing a main configuration of a broadcasting station and a receiving station according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a digital broadcasting system according to a fourth embodiment of the present invention.

FIG. 6 is a circuit block diagram showing a main configuration of a broadcasting station and a receiving station of the system shown in FIG. 5;

[Explanation of symbols]

 BS: Broadcasting station BE: Service area MS1 to MSm: Receiving station BSS: Broadcasting master station RS1 to RS3: Relay station RE1 to RE3: Relay service area 10, 210: Pilot signal generator 20 to 2N, 220 to 22N: CDM modulation Units 30 to 3N, 330 to 33N: Weight multiplication units 40A, 40B, 40C, 240 ... Weight control units 50, 250 ... Multiplex units 60, 260 ... Power normalization units 70A, 70B, 70C, 270 ... RF units 80, 280 ... Antenna 90,290 ... Demodulation unit 101,300 ... Reception quality satisfaction rate calculation unit 110 ... Reception station antenna 111A ... RF unit 112 ... CDM demodulation unit 113 ... Code synchronization unit 114 ... Channel selection unit 115 ... Conversion unit 116 ... Speaker 117: display unit 118B, 118C, 118D: modulation unit 119: BER measurement unit 120 Registration control unit 310 ... receiving station registration control

Claims (15)

[Claims] 1. A digital broadcasting transmitting station that multiplexes information of a plurality of channels by performing spreading processing with different spreading codes, and wirelessly transmits the multiplexed signal to a plurality of receiving stations. A transmission station for digital broadcasting, comprising transmission power control means for individually and variably setting transmission power for each channel according to the use of the channel. 2. When the plurality of channels include a pilot channel used by each of the receiving stations to establish spreading code synchronization, the transmission power control means may include a transmission power of the pilot channel. 2. The transmitting station for digital broadcasting according to claim 1, wherein the transmission power is set to be larger than the transmission power of another channel. 3. When the plurality of channels include a free broadcast channel and a pay broadcast channel, the transmission power control means converts the transmission power of the pay broadcast channel to the transmission power of the free broadcast channel. 2. The digital broadcasting transmitting station according to claim 1, wherein the transmitting station is set larger. 4. A first channel for transmitting information having a predetermined importance among the plurality of channels, and a first channel for transmitting information having a predetermined importance.
And a second channel for transmitting information of higher importance than the information transmitted by the channel of the second channel, the transmission power control means sets the transmission power of the second channel to that of the first channel. 2. The digital broadcasting transmitting station according to claim 1, wherein the transmitting power is higher than the transmitting power. 5. The transmission power control means sets the transmission power of the second channel to be higher than the transmission power of the first channel only during the period of transmitting the information of high importance. The transmitting station for digital broadcasting according to claim 1. 6. The transmission power control means monitors presence or absence of information to be transmitted for each channel, and sets transmission power of the channel to a minimum power value during a period when there is no information to be transmitted. The transmitting station for digital broadcasting according to claim 1. 7. A power normalizing means further comprising a power normalizing means for keeping a transmission power of a multiplexed signal constant based on a control result of transmission power for each channel by said transmission power control means. A transmitting station for digital broadcasting according to any one of claims 1 to 6. 8. A digital broadcasting system in which information of a plurality of channels is multiplexed in a transmitting station by performing spreading processing with different spreading codes, and the multiplexed signal is wirelessly transmitted to a plurality of receiving stations. Each of the plurality of receiving stations includes a receiving channel notifying unit that notifies the transmitting station of information indicating a channel that is being received or scheduled to be received, and the transmitting station is configured to transmit the information based on the information notified from each of the receiving stations. Receiving rate calculating means for determining a receiving rate for each channel; and transmitting power of a channel having a higher receiving rate based on the receiving rate of each channel calculated by the receiving rate calculating means. A transmission power control unit for performing control for setting the value to a larger value. 9. A digital broadcasting transmitting station that multiplexes information of a plurality of channels by performing spreading processing with different spreading codes, and wirelessly transmits the multiplexed signal to a plurality of receiving stations. Receiving rate calculating means for calculating a receiving rate for each channel based on the information indicating the channel being received or scheduled to be received, and receiving based on the receiving rate of each channel calculated by the receiving rate calculating means. A transmission station for digital broadcasting, comprising: transmission power control means for performing control for setting transmission power of a channel with a high rate to a value larger than transmission power of a channel with a lower reception rate. 10. A digital broadcasting system in which information of a plurality of channels is multiplexed at a transmitting station by performing spreading processing with different spreading codes, and the multiplexed signal is wirelessly transmitted to a plurality of receiving stations. Each of the plurality of receiving stations includes reception quality notifying means for detecting the reception quality of the received channel and notifying the transmission station of the detection result, wherein the transmission station has a reception quality notified from each of the reception stations. Receiving quality satisfaction rate calculating means for calculating a ratio of receiving stations satisfying a predetermined receiving quality for each channel based on the detection result; and receiving quality of each channel calculated by the receiving quality satisfaction rate calculating means. Control for setting the transmission power of a channel having a lower reception quality satisfaction rate to a value larger than the transmission power of a channel having a higher reception quality satisfaction rate based on the satisfaction rate Digital broadcasting system characterized by comprising a transmission power control means for performing. 11. A digital broadcasting transmitting station that multiplexes information of a plurality of channels by performing spreading processing with different spreading codes, and wirelessly transmits the multiplexed signal to a plurality of receiving stations. A reception quality satisfaction rate calculating means for calculating a ratio of receiving stations satisfying a predetermined reception quality for each channel based on the received reception quality detection result of the received channel; and a reception quality satisfaction rate calculation means. Based on the calculated reception quality satisfaction rate of each channel, the transmission power for performing control for setting the transmission power of the channel having the lower reception quality satisfaction rate to a value larger than the transmission power of the channel having the higher reception quality satisfaction rate A transmitting station for digital broadcasting, comprising: a control unit. 12. A broadcast station for distributing information of a plurality of channels, and information of the plurality of channels distributed from the broadcast station are multiplexed by performing spreading processing with different spreading codes, respectively. Digital broadcasting system comprising: a plurality of relay stations for wirelessly transmitting to a service area covered by a plurality of relay stations; and a plurality of receiving stations for receiving multiplexed signals wirelessly transmitted by the relay stations and reproducing information of a desired channel. Wherein each of the plurality of receiving stations includes a receiving channel notifying unit for notifying a relay station serving as a transmission source of the receiving channel of information indicating a channel being received or scheduled to be received, A receiving rate calculating means for obtaining a receiving rate for each channel based on the information notified from each of the receiving stations; and each channel calculated by the receiving rate calculating means. Transmission power control means for performing control for setting the transmission power of a channel having a higher reception rate to a value larger than the transmission power of a channel having a lower reception rate based on the reception rate of Digital broadcasting system. 13. Multiplexing is performed by spreading information of a plurality of channels distributed from a broadcasting station by different spreading codes, and multiplexing the multiplexed signal to a plurality of receiving stations existing in a service area covered by the own station. A digital broadcast relay station that transmits radio waves to a receiving station, receiving rate calculating means for obtaining a receiving rate for each channel based on information indicating channels being received or scheduled to be received notified from the receiving stations; Based on the reception rate of each channel calculated by the calculation means, transmission power control means for performing control for setting the transmission power of the channel with a high reception rate to a value greater than the transmission power of the channel with a lower reception rate; A relay station for digital broadcasting, comprising: 14. A broadcast station that distributes information of a plurality of channels, and information of the plurality of channels distributed from the broadcast station is multiplexed by performing spreading processing with different spreading codes, respectively. Digital broadcasting system comprising: a plurality of relay stations for wirelessly transmitting to a service area covered by a plurality of relay stations; and a plurality of receiving stations for receiving multiplexed signals wirelessly transmitted by these relay stations and reproducing information of a desired channel Wherein each of the plurality of receiving stations includes a reception quality notifying unit that detects reception quality of a received channel and notifies a detection result to a relay station that is a transmission source of the reception channel, Each of the relay stations, based on the reception quality detection result notified from each of the reception stations, is a reception product that calculates a ratio of reception stations that satisfy a predetermined reception quality for each channel. Based on the reception quality satisfaction rate of each channel calculated by the reception quality satisfaction rate calculation means, the transmission power of the channel having the lower reception quality satisfaction rate is calculated for the channel having the higher reception quality satisfaction rate. A transmission power control unit for performing control for setting the transmission power to a value larger than the transmission power. 15. Multiplexing is performed by spreading information of a plurality of channels distributed from a broadcasting station by different spreading codes, and multiplexing the multiplexed signal to a plurality of receiving stations existing in a service area covered by the own station. A digital broadcast relay station that performs radio transmission for the receiving station, based on a detection result of the channel reception quality notified from each of the reception stations, and calculates a ratio of reception stations that satisfy a predetermined reception quality for each channel. Based on the reception quality satisfaction rate of each channel calculated by the reception quality satisfaction rate calculation means, the transmission power of the channel having the lower reception quality satisfaction rate is calculated for the channel having the higher reception quality satisfaction rate. And a transmission power control means for performing control for setting the transmission power to a value larger than the transmission power.