JPH09247168A - Multimedia radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To most efficiently transmit an ATM cell for executing multimedia communication. SOLUTION: A network is accessed by a TDMA multi-carrier system and user stations 2a-2c execute communication with public line network communication equipment connected to a gateway station 4 through a radio communication line with a satellite station. The user stations 2a-2c are provided with middle- speed modulators 42a-42c. The gateway station 4 is provided with middle-speed demodulators 44a-44n for the portion of the number of commuication channels and outputs a burst to the designated communication channel once to a frame cycle at the time of basic rate transmission. At the time of n × basic rate transmission, the burst is outputted to the designated communication channel (n) times to the frame cycle. When the transmission power of the user stations 2a-2c, the respective device scales and signal processing scales of the middle- speed modulators 42a-42c and the middle-speed demodulators 44a-44c of the gateway station 4 are compared with those in FDMA single carrier/multi-carrier systems and a TDMA single carrier system, most efficient access to ATM cell transmission is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multimedia wireless communication system for transmitting ATM cells when performing multimedia communication using bit rate data having a plurality of different transmission rates.

[0002]

2. Description of the Related Art In recent years, in the field of communication, multimedia has been developed for transmitting voice data, communication data, moving image data and the like. The transmission rates of these data differ greatly in bit rate data. Therefore, it is necessary to widely support the transmission speed of the subscriber terminal device in multimedia communication from low speed to high speed.

As a transmission system for realizing such multimedia communication, for example, an asynchronous transfer mode (ATM) shown in the satellite communication system of Japanese Patent Application Laid-Open No. 5-48509 is known. ATM can support transmission speeds from low speed to high speed, and a high-speed transmission line (UNI: 155/622 Mbps) that uses an optical fiber between a subscriber's house and a switching node.
The connection is made in order to perform high-speed data communication.

In this case, data transmission from a low speed to a high speed is uniformly performed to both a user who performs a small amount of data communication (small user) and a user who performs a large amount of data communication (large user) through a transmission line of 155/622 Mbps. To perform multimedia communication. Actually the transmission speed is 64
At Mbps, one cell is transmitted every 6 ms. In addition, when the transmission rate is 2 Mbps, it is 1 every 188 μs.
Transmit cells. If this transmission data does not exist, a blank cell with a blank mark is transmitted.

On the other hand, a wireless communication system is easier to construct a communication system than a wired communication system, and
Since the construction cost is low, the wireless communication system is expected as one of the means for realizing the multimedia communication network. However, since the wireless communication system has a finite frequency band, it is not possible to always set up a wide band high-speed transmission system between the subscriber's house and the switching node, unlike the wired communication system. Therefore, demand assignment (DAMA) for setting a communication channel (ch) according to a request is required.

As a demand assign type multimedia wireless communication system which has been put into practical use, a satellite communication distributed network system (SPA) in Intelsat is used.
DE) is known. In this SPADE, the frequency band 36 MHz is divided into 800 communication channels.
In this SPADE, after the user station on the ground makes a call,
A communication channel allocation request is transmitted to a control station that performs frequency allocation and system monitoring. The control station that has received this allocation request allocates an idle communication channel to the user station, and the user station performs communication using this allocated communication channel.

[0007]

As described above, in the demand assign type wireless communication network of the above-mentioned conventional example, the allocated frequency band is fixed, and in the Ittelsat SPADE, the frequency band of 1 ch of audio data is 4
It is 5 KHz. Therefore, in a narrow fixed frequency band, it is difficult to transmit wideband data in multimedia. In other words, there is a drawback that multimedia communication having a transmission speed from low speed to high speed cannot be efficiently performed.

The present invention solves the problems in the prior art as described above, and is capable of most efficiently transmitting an asynchronous transfer mode (ATM) cell for performing multimedia communication having a transmission speed from low speed to high speed. An object is to provide a media wireless communication system.

[0009]

In order to achieve the above object, the invention according to claim 1 is a multimedia for transmitting bit rate data at a plurality of different transmission rates including voice data, communication data and moving image data. In a wireless communication system, a TDMA multi-carrier method using N frequencies is used to access a network and transmit ATM cells.

According to a second aspect of the present invention, in the multimedia wireless communication system according to the first aspect, TDMA is performed.
A data terminal for performing data communication by a multicarrier method, and a connection station for connecting the data terminal and a communication network are provided, and the terminal device has a medium speed modulation means for modulating transmission data at a medium speed, and The connection station is provided with a medium speed demodulating means for demodulating a received signal at a medium speed.

According to a third aspect of the present invention, in the multimedia wireless communication system according to the second aspect, when the medium-speed modulator of the data terminal performs the basic rate transmission by the TDMA multi-carrier system, one per frame cycle is used.
The burst is output to the specified communication channel once, and n times the frame cycle is transmitted at the time of n × basic rate transmission.
Once, the burst is output to the designated communication channel.

According to a fourth aspect of the present invention, the multimedia wireless communication system according to the first or second aspect is applied to a satellite communication system, and a terrestrial user station as a data terminal and a gateway station as a connection station are provided. The two are connected by a satellite station wireless communication line.

The multimedia wireless communication system having the above-described structure uses the TDMA multi-carrier system when performing multimedia communication for transmitting bit rate data having different transmission rates including voice data, communication data and moving image data. Access network by AT
It is transmitting M cells. In this TDMA multi-carrier multimedia wireless communication system, a data terminal performs medium-speed modulation using a medium-speed modulation means, and the connecting station uses the medium-speed demodulation means for the number of communication channels to demodulate the medium speed. It is carried out. Moreover, this multimedia wireless communication system is applied to a satellite communication system.

In this case, the transmission power of the data terminal (user station), the device scale and signal processing scale of the medium speed modulation means, and the device scale and signal processing scale of the medium speed demodulation means of the connecting station (gateway station) are set as follows. For example, when compared with the FDMA single carrier / multi-carrier method and the TDMA single carrier method, the access method is the most efficient access method for ATM cell transmission. That is, an ATM for performing multimedia communication having a transmission speed from low speed to high speed.
The cells are transmitted most efficiently.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a multimedia wireless communication system of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a multimedia wireless communication system of the present invention. FIG. 1 is an example in which a multimedia wireless communication system is applied to a satellite communication system, and satellite stations 1 and user stations 2a, 2b, 2c that communicate with each other through a wireless communication line Wa between the satellite stations 1.
And a control station 3 that performs frequency allocation and system monitoring for the satellite station 1 through the control / signal line Wb. Further, a gateway station 4 for connecting the user stations 2a to 2c to a communication device connected to a public line through a wireless communication line Wa with the satellite station 1, and a public line network 5 connected to the gateway station 4. And have.

An FDMA (Frequency Divisio) is used as a network access method in such a satellite communication system.
n multiple access), TDMA (Time Division multipl)
e Access) and a CDMA (Code Division Multiple Access) method that is resistant to interference and interference but inferior in frequency utilization efficiency are known.

Further, as an access process for allocating a frequency band according to a request from the user stations 2a to 2c, FD
There are MA single carrier system, FDMA multi carrier system, TDMA single carrier system, and TDMA multi carrier system.

FIG. 2 is a block diagram showing the configuration of the user stations 2a to 2c and the gateway station 4 in the FDMA single carrier system. In FIG. 2, user stations 2a-2
c includes variable rate modulators 12a, 12b, 12c,
The gateway station 4 includes variable rate demodulators 14a, 14b, 14c ... 14n-1, 14n for the number of communication channels.

FIG. 3 is a block diagram showing the configuration of the user stations 2a to 2c and the gateway station 4 in the FDMA multicarrier system. In FIG. 3, user stations 2a to 2c
Is equipped with multi-carrier modulators 22a, 22b, 22c, and the gateway station 4 includes low-speed demodulators 24a, 24b, 24c ... 24f for unit channels corresponding to the number of communication channels.
... is equipped with 24n.

FIG. 4 is a block diagram showing the configuration of the user stations 2a to 2c and the gateway station 4 in the TDMA single carrier system. In FIG. 4, user stations 2a-2
c has high-speed modulators 32a, 32b, 32c, and the gateway station 4 has one high-speed demodulator 34.

FIG. 5 is a block diagram showing the configuration of the user stations 2a to 2c and the gateway station 4 in the TDMA multicarrier system. In FIG. 5, user stations 2a to 2c
Is provided with medium speed modulators 42a, 42b, 42c, and the gateway station 4 has a medium speed demodulator 44 for the number of communication channels.
a, 44b ... 44n.

Next, the operation of this embodiment will be described. In the satellite communication system of FIG. 1, the user stations 2a to 2c
Communicate with a communication device in the public network 5 connected to the gateway station 4 through a wireless communication line with the satellite station. Note that, hereinafter, description of communication between the user stations 2a to 2c using a wireless communication line with the satellite station 1 will be omitted.

In FIG. 2, the user stations 2a to 2c of the FDMA single carrier system are variable rate modulators 1.
2a to 12c perform variable rate modulation, and the variable rate demodulators 14a to 14n of the gateway station 4 perform the variable rate demodulation. In this case, the number of communication channels is 1000 here, and the basic rate transmission rate, for example, 64
In the case of kbps, carriers for one communication channel are output. In addition, during n × basic rate transmission, carriers for n communication channels are output.

In FIG. 3, the number of communication channels is 1000 in this FDMA multicarrier system. User stations 2a-2c are multi-carrier modulators 22a-22
multi-carrier modulation with c, the gateway station 4
Low-speed demodulation is performed by the low-speed demodulators 24a to 24n for the number of communication channels, here 1000 unit channels. In this example, a carrier for one communication channel is output during the basic rate transmission. In addition, during n × basic rate transmission, n carriers for one communication channel are output.

In FIG. 4, the number of bursts per frame cycle is 1 in this TDMA single carrier system.
000 and the high speed modulators 32a to 32a of the user stations 2a to 2c.
32 c performs high-speed modulation, and the gateway station 4 uses one high-speed demodulator 34 to perform high-speed demodulation. in this case,
During basic rate transmission, one burst is output per frame cycle. In the case of n × basic rate transmission, bursts are output n times in a frame cycle.

In FIG. 5, in this TDMA multicarrier system, the number of communication channels is 10, and the number of bursts per frame cycle is 100. The user stations 2a to 2c perform medium speed modulation by the medium speed modulators 42a to 42c, and the gateway station 4 performs medium speed demodulation by the number of communication channels, here, 10 medium speed demodulators 44a to 44n. ing. In this case, during the basic rate transmission, a burst is output to the designated communication channel once every frame cycle. In the case of n × basic rate transmission, burst is output to the designated communication channel n times in the frame cycle.

Hereinafter, these FDMA single carrier / multi-carrier system and TDMA single carrier /
The multi-carrier method will be described in comparison. Table 1 is shown in FIG.
From the FDMA single carrier system shown in FIG.
Transmission power amplifiers (HPAs) (not shown) up to the DMA multi-carrier system, variable rate modulators 12a to 12c of user stations 2a to 2c to medium speed modulator 42a to.
42c and variable rate demodulator 1 of gateway station 4
4a to 14n to the medium speed demodulators 44a to 44n are compared with each other, and this superior sequence is represented by numerical values in five stages.

[0028]

[Table 1]

In Table 1, when the transmission powers of the transmission power amplifiers (HPA) of the user stations 2a to 2c are compared,
In the order that favors its low transmit power, F shown in FIG.
The DMA single carrier method is the best, and next,
The TDMA multi-carrier system shown in FIG. 5 is excellent, the FDMA multi-carrier system shown in FIG. 3 is further adopted, and finally the TDMA single-carrier system shown in FIG. 4 is adopted.

The third TDMA single carrier system from the top of Table 1 is the high speed modulator 32a to 32c shown in FIG.
Is used, and the maximum speed modulation is used, so high power transmission is performed. The FDMA multicarrier system shown in FIG. 3 which is the second from the top of Table 1 is the multicarrier modulators 22a to 2c for the user stations 2a to 2c which transmit a plurality of carriers from one station.
It is necessary to provide 2c. In this case, intermodulation is likely to occur. The fourth TDMA multi-carrier scheme shown in FIG. 5 is not as fast as the modulation rate of the third TDMA single-carrier scheme shown in FIG.
The A single carrier method is lower.

Next, when comparing the device scale and the signal processing scale of each modulator of the user stations 2a to 2c in which the simplicity is superior, the TDMA multi-carrier system shown in FIG. 5 is the best, Next, the FDMA single carrier system shown in FIG. 2 is excellent, the TDMA single carrier system shown in FIG. 4 becomes the last, and finally the FDMA multi carrier system shown in FIG.

The FDMA shown in FIG. 3 which is the second from the top in Table 1
The multi-carrier method requires the multi-carrier modulators 22a to 22c in the user stations 2a to 2c, the circuit configuration is complicated, and the device scale and the signal processing scale increase. In the TDMA single carrier system shown in FIG. 4 which is the third from the top of Table 1, the high speed modulators 32a to 3c are provided to the user stations 2a to 2c.
2c is required. Therefore, since the modulation is performed at the highest speed, the device scale and the signal processing scale are increased. The first FDMA single carrier system shown in FIG. 2 requires variable rate modulators 12a to 12c (1000 in the example shown in FIG. 2) in the user stations 2a to 2c, and the fourth from the top in FIG. The device scale and processing scale are more complicated than those of the TDMA multi-carrier system shown in FIG.

Next, in Table 1, when comparing the device scale and the processing scale of the demodulator of the gateway station 4 in which the simplicity is superior, the TDMA single carrier system shown in FIG. 4 is the best. Next, the TDMA multi-carrier system shown in FIG. 5 is excellent, further the FDMA multi-carrier system shown in FIG. 3 is obtained, and finally the FDMA single-carrier system shown in FIG. 2 is obtained.

The FDMA shown in FIG. 2 which is the first from the top of Table 1
In the single-carrier system, the gateway station 4 has an extremely large number of variable rate demodulators 14a to 1 for the number of communication channels.
4n is required, and the device scale and the processing scale are complicated. The second FDMA multi-carrier system shown in FIG. 3 requires low-speed demodulators 24a to 24n (1000 units in the example shown in FIG. 3) for the number of communication channels (for unit channels), and the device scale and signal processing scale are large. In addition, intermodulation is likely to occur.

The fourth TDMA from the top of Table 1 shown in FIG.
In the multi-carrier system, medium speed demodulators 44a to 44n
(10 in the example of FIG. 5) is required. Further, the TDMA single carrier system shown in FIG. 4 which is the third from the top of Table 1 is capable of high speed demodulation, and one high speed demodulator 34
Only provided.

Therefore, from the result of examination of the superiority in the 5-step evaluation, it was found that the multi-carrier TDMA method is the most efficient access method for the transmission of ATM cells.

[0037]

As is apparent from the above description, according to the multimedia wireless communication system of claims 1 to 4, when performing multimedia communication for transmitting bit rate data at different transmission rates, ATM by accessing the network by the TDMA multi-carrier system
Since the cell is transmitted, the transmission power of the data terminal,
When comparing the device size and signal processing size of modulation, and the device size and signal processing size of demodulation of the connecting station with, for example, the FDMA single carrier / multi-carrier system and the TDMA single carrier system, the most suitable for the transmission of ATM cells. ATM for multimedia communication with efficient access method and transmission speed from low speed to high speed
The cells can be transmitted most efficiently.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a multimedia wireless communication system of the present invention.

FIG. 2 is a block diagram showing a configuration of an FDMA single carrier system in the embodiment.

FIG. 3 is a block diagram showing a configuration of an FDMA multicarrier system in the embodiment.

FIG. 4 is a block diagram showing a configuration of a TDMA single carrier system in the embodiment.

FIG. 5 is a block diagram showing a configuration of a TDMA multicarrier system in the embodiment.

[Explanation of symbols]

 1 Satellite station 2a-2c User station 3 Control station 4 Gateway station 5 Public line network 12a-12c Variable rate modulator 14a-14n Variable rate demodulator 22a-22c Multi-carrier modulator 24a-24n Low speed demodulator 32a-32c High speed modulation Device 34 High-speed demodulator 42a-42c Medium-speed modulator 44a-44n Medium-speed demodulator

Claims (4)

[Claims] 1. A multimedia wireless communication system for transmitting bit rate data at different transmission rates including voice data, communication data and moving image data, wherein N
A multimedia wireless communication system, characterized in that a TDMA multi-carrier method using a plurality of frequencies is used to access a network to transmit ATM cells. 2. The multimedia wireless communication system according to claim 1, further comprising: a data terminal that performs data communication by a TDMA multicarrier method, and a connection station that connects the data terminal and a communication network. A multimedia wireless communication system characterized in that the device has a medium speed modulation means for modulating transmission data at a medium speed, and the connection station has a medium speed demodulation means for demodulating a received signal at a medium speed. . 3. The multimedia wireless communication system according to claim 2, wherein when the medium speed modulator of the data terminal performs the basic rate transmission by the TDMA multi-carrier method, the designated communication is performed once every frame cycle. A multimedia wireless communication system, which outputs a burst to a channel and outputs the burst to a designated communication channel n times in a frame cycle during n × basic rate transmission. 4. The multimedia radio communication system according to claim 1 or 2 is applied to a satellite communication system, and a satellite station is provided between a terrestrial user station as a data terminal and a gateway station as a connecting station. A multimedia wireless communication system characterized by being connected by a wireless communication line.