KR100964376B1 - Method for communication in a mobile communication system - Google Patents

Abstract

The present invention relates to a communication method in a mobile communication system.

In order to provide a multimedia broadcasting service, the present invention modulates broadcast content at different data rates by applying a hierarchical modulation method, and transmits the generated signal to a terrestrial auxiliary device and a terminal. Accordingly, the transmission rate of the mobile communication system is increased, thereby increasing the available service channel for multimedia broadcasting. And, it is possible to provide a high quality service to the user.

Hierarchical modulation technique, terrestrial auxiliary, satellite communications, base layer, enhancement layer

Description

Method for communication in a mobile communication system

The present invention relates to a communication method in a mobile communication system.

The present invention is derived from the research conducted as part of the IT source technology development project of the Ministry of Information and Communication and the Ministry of Information and Communication Research and Development (Task Management Number: 2005-S-014-03, Task name: Satellite IMT2000 + technology development).

Satellite DMB is a mobile satellite communication system that uses a terrestrial component (CTC) such as a repeater, a complementary ground component (CGC), or an ancillary terrestrial component (ATC) to communicate between the satellite and the terminal. (Digital Multimedia Broadcasting) system, DVB-SH (Digital Video Broadcasting Satellite services to Handhelds) system, and terrestrial satellite integrated system.

The satellite DMB system, which already provides a service, uses a terrestrial system that uses a co-channel repeater (gapfiller) together with satellites to provide high-quality audio and multimedia signals to service users. Here, the co-channel repeater is used to effectively eliminate the coverage of the shadow area. In order to provide such services, the frequency bands used by satellites and the frequency bands used in terrestrial systems are optimized for 2630 to 2655 MHz bands.

The satellite DMB system consists of a feeder link earth station, a broadcasting satellite, a terrestrial repeater, and a terminal for receiving a service. The signal transmitted from the terminal is transmitted to the satellite through the feeder circuit earth station, and in this case, a band for fixed satellite service (FSS) (for example, 14 GHz) is used as an uplink. The satellite converts the received signal into a signal of 2.6 GHz band, and the converted signal is amplified to a preset size by an amplifier in the satellite repeater and broadcasted to a terminal located in a service area.

The terminal should be able to receive the signal transmitted from the satellite through a small antenna having a low directivity. To this end, the terminal must have an effective isotropic radiated power of sufficient size. Therefore, the satellite must have a large transmitting antenna and a high power repeater is required.

In addition, when the satellite transmits a signal of 2.6 GHz band, a shadowing problem occurs due to a direct pathway obstacle from the satellite. To overcome this, it is necessary to add a repeater to retransmit satellite signals at the system design stage. This repeater allows the signal to be transmitted to the part where the signal transmitted from the satellite cannot be reached by a band obstacle such as a building, and is divided into a direct amplification repeater and a frequency conversion repeater.

The direct amplified repeater simply amplifies the 2.6 GHz signal from the satellite. The direct amplification repeater uses a low gain amplifier to prevent unnecessary divergence due to signal interference between the receive and transmit antennas. This direct amplified repeater covers a narrow area from the repeater to 500m based on the line of sight (LoS).

On the other hand, the frequency conversion repeater is responsible for a wide area up to 3km, and converts the signal of the 2.6GHz band transmitted from the satellite to another frequency band (for example, 11GHz) and transmits it to the terminal. In such an environment in which two types of repeaters exist, multipath fading occurs in which two or more signals are received by the terminal.

Another mobile satellite communication system, DVB-SH system, aims to provide a service to a terminal using satellite in nationwide coverage and a service to a terminal using CGC in indoor environment and terrestrial coverage. have. The DVB-SH system intends to provide a mobile TV service in the 15 MHz bandwidth of the S band based on the DVB-H. Here, the DVB-SH system intends to use a band close to a band used in terrestrial International Mobile Telecommunication (IMT) of the S band. Therefore, it is easy to integrate with the terrestrial IMT and the network reuse with the terrestrial system can be easy to reduce the installation cost.

In addition, the DVB-SH system considers a hybrid broadcast structure with the terrestrial system. Also, in order to solve the signal interference problem between satellite and CGC and to use frequency efficiently, reuse factor is 1 for CGC cells in one satellite spot beam and 3 is for satellite spot beam. Consider the structure. In such a case, nine TV channels can be broadcast in nationwide coverage through satellite spot beams, and 27 channels can be broadcasted through a terrestrial repeater in urban or indoor environments.

Lastly, the terrestrial satellite integrated system is a GEO (Geostationary Orbit) based mobile satellite communication system. In order to provide MSVs with ubiquitous wireless wide area communication services such as Internet access service and voice call service in L band and S band, (Mobile Satellite Ventures) and Terrestar. The system uses a hybrid wireless network structure that combines satellites and ATC to provide voice or high-speed packet service through ATC, or terrestrial systems, in urban or densely populated areas, and via satellites in rural or off-shore areas that ATC cannot cover. Has a structure to service Since ATC uses the same air interface as satellites, ATC is developing satellite services without increasing the complexity of terrestrial terminals.

The satellite mobile communication system developed in the future aims to provide a service using a satellite in rural areas or rural areas where a visible distance is secured, and a ground assist device in an urban or indoor environment where satellite signals are not secured. . Therefore, it is necessary to maximize the frequency use by increasing the spectrum use efficiency in consideration of the characteristics of the service providing environment through the ground assist device and the service environment through the satellite.

The present invention provides a communication method capable of providing a multimedia broadcasting service using a hierarchical modulation technique in a satellite mobile communication system having a terrestrial auxiliary device.

In a mobile communication system which is a feature of the present invention for achieving the technical problem of the present invention, a communication method for providing a signal corresponding to the content to the terminal, the terminal,

Receiving a hierarchical modulated signal generated by modulating content to be transmitted to a terminal at a different data rate; And amplifying and transmitting the hierarchical modulated signal to the terminal.

In another aspect of the present invention, there is provided a communication method for providing a content to a terminal by a mobile communication system.

Modulating content to be provided to a terminal at a different data rate and generating a signal including a hierarchical modulated signal; Transmitting the hierarchical modulated signal to a first terminal; And amplifying and transmitting the hierarchical modulated signal to a second terminal.

According to an embodiment of the present invention, when a signal is transmitted by applying a hierarchical modulation method, a signal transmission rate of a system is increased to increase an available service channel for multimedia broadcasting.

And, it is possible to provide a high quality service to the user.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have.

In the present specification, a terminal is a mobile station (MS), a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), a user equipment (User Equipment). It may also refer to a user equipment (UE), an access terminal (AT), and the like, and may include all or some functions of a mobile terminal, a subscriber station, a portable subscriber station, a user device, and the like.

In the present specification, a base station (BS) is an access point (AP), a radio access station (Radio Access Station, RAS), a Node B (Node B), a base transceiver station (Base Transceiver Station, BTS), MMR ( Mobile Multihop Relay) -BS and the like, and may include all or part of functions such as an access point, a radio access station, a Node B, a base transceiver station, and an MMR-BS.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

First, an embodiment of a communication system will be described with reference to FIG. Herein, an embodiment of the present invention will be described using a satellite mobile communication system having the most commonality with the terrestrial system among various communication systems as an example. Further, embodiments of the present invention are different from connection standards such as orthogonal frequency division multiplexing (OFDM), code division multiple access (CDMA), or time division multiple access (TDMA). Regardless, it can be applied to the satellite mobile communication system using the ground assist device.

1 is an exemplary diagram of a satellite mobile communication system according to an embodiment of the present invention.

As shown in FIG. 1, the satellite mobile communication system according to an exemplary embodiment of the present invention provides a service to a terminal 300 or 300 ′ using one satellite or several Governance Earth Orbit (GEO) satellite groups. To provide. At this time, the satellite 100 narrows the communication area of the transmitting beam to cover only a small area with a large amount of communication, and uses a single spot beam or a multi-spot used to widen a narrow communication area to concentrate power. Signals are sent using any one of multi-spot beams.

Terminals 300 and 300 ′ that receive signals transmitted through the satellite 100 are located in one spot. When the user uses a roaming service, the spot is set to several spots as a group, and the terminals 300 and 300 'are located in the spot. The terminals 300 and 300 'are connected to a network generated through one satellite or multiple satellites through a gateway (not shown) located between the terminals 300 and 300' and the satellite 100. Here, the gateway refers to any one gateway included in a group of centralized gateways or geographically distributed gateways according to a service provider's request.

The gateway transmits signals transmitted from the terminals 300 and 300 'to the satellite base station and the satellite control station. The satellite base station and the satellite control station perform the same functions as those of the base station and the control station used in the terrestrial system 400 and may exist inside or outside the gateway. Here, the terrestrial system 400 includes a base station 410, a base station controller 420, and a core network 430, and when a signal is transmitted from the core network 430 to the base station controller 420, the terminal uses the terrestrial network. Enable communication. On the contrary, when the core network 430 transmits a signal to the satellite gateway, the terminal may perform communication through the satellite.

In addition, the system according to the embodiment of the present invention includes the ground auxiliary apparatus 200 in consideration of the signal transmitted from the satellite 100 is not transmitted to the shaded area formed by the building or the mountain. Here, the ground auxiliary apparatus 200 amplifies a signal transmitted from the satellite and transmits the signal from the satellite to the shadow area for coverage continuity in the shadow area.

In such a system environment, the satellite 100 and the ground assisting device 200 may both provide a broadcast service to the terminals 300 and 300 '. At this time, the broadcast service is provided through the satellite (100) in the national coverage, such as rural areas and rural areas where the visible distance is secured, and in the urban or indoor environment where satellite signals are difficult to reach due to the large number of buildings or buildings, The broadcast service is provided through.

Therefore, since the repeater does not provide voice and data communication services to the terminal, only the downlink transmission is considered, and when the terrestrial auxiliary device needs information for a broadcast service, the repeater transmits the information through the terrestrial system 400. However, when the broadcast service is provided through the satellite 100, the information for the broadcast service is provided by the terminal to the satellite through an uplink formed between the satellite 100 and the terminals 300 and 300 ′. Here, the information for the broadcast service means information about a broadcast service that the user wants to receive the service.

Next, in the system environment according to an embodiment of the present invention to provide voice and data communication services to the terminals (300, 300 '), providing a communication service to all users in the satellite beam having a wide coverage with limited frequency resources It is impossible. Therefore, only a small number of users in areas not covered by the terrestrial system 400 provide a communication system including voice service and data service via satellite.

In other words, as shown in FIG. 1, the terminal 300 ′ located in an area not covered by the terrestrial system 400 receives voice and data services through the satellite 100. Thereafter, when the terminal enters into the coverage that the terrestrial system 400 can cover, a vertical handover, which receives a service through the terrestrial system 400 with high transmission efficiency, is generated.

Therefore, the terminals 300 and 300 'should be able to receive both the signal transmitted from the terrestrial system 400 and the signal transmitted from the satellite. In this case, when the terrestrial system 400 and the satellite 100 require heterogeneous terminal specifications for communication, an overhead of a communication chip embedded in the terminal increases. Therefore, the terminal according to the embodiment of the present invention uses a satellite air interface having the maximum in common with the terrestrial system 400.

In addition, the embodiment of the present invention considers a case in which a broadcasting and multimedia broadcasting service (MBMS) is provided to terminals 300 and 300 'through a satellite and a terrestrial auxiliary apparatus in a satellite mobile communication system. In this case, the ground assisting device considers both an on-frequency ground assisting device (hereinafter referred to as 'same frequency terrestrial assisting device') and a frequency conversion terrestrial assisting device (hereinafter referred to as 'frequency converting terrestrial assisting device').

Here, the same frequency terrestrial auxiliary apparatus is a terrestrial auxiliary apparatus that performs a function of simply amplifying a signal transmitted from the satellite 100 and transmitting the signal to the terminal 300. This is used when the frequency band of the signal sent from the satellite 100 to the terrestrial auxiliary device 200 and the frequency band of the signal sent from the terrestrial auxiliary device 200 to the terminal 300 are the same.

In addition, the frequency conversion terrestrial auxiliary apparatus performs a function of frequency conversion, signal processing, and sending the signal transmitted from the satellite 100 to the terminal 300. This is used when the frequency band of the signal transmitted from the satellite 100 to the terrestrial auxiliary device 200 and the signal from the terrestrial auxiliary device 200 to the terminal 300 are used differently.

Next, a satellite mobile communication system having the terrestrial auxiliary device 200 described with reference to FIG. 1 will be described. First, a satellite mobile communication system using the same frequency terrestrial auxiliary device will be described with reference to FIG. 2. .

2 is an exemplary diagram of a satellite mobile communication system according to a first embodiment of the present invention.

As shown in FIG. 2, the satellite 100 transmits layered modulation signals to the terminal 300 ′ and the terrestrial assistance device 200 located outside the coverage of the terrestrial assistance device 200. The auxiliary device 200 simply amplifies the satellite signal received from the satellite 100 and transmits the amplified satellite signal to a terminal within the coverage of the terrestrial auxiliary device 200. The terminal 300 'out of coverage of the terrestrial auxiliary device 200 demodulates a basic layer modulated signal among the layered modulation signals, and the terminal 300 in terrestrial auxiliary device coverage modulates an enhancement layer. Demodulate the signal.

According to the first embodiment of the present invention, the terrestrial auxiliary device 200 that receives a signal through a carrier used by the satellite 100 to provide a broadcast service may transmit a signal to the terminal 300 using the same carrier. Use frequency bands to ensure In this case, since the terrestrial auxiliary apparatus 200 only has a function of simply amplifying the received signal, no baseband signal processing is required, and thus the terrestrial auxiliary apparatus 200 may be simply installed.

In addition, since a satellite signal and a single frequency network (SFN) form a terminal, the terminal may receive both a satellite signal and a terrestrial auxiliary signal on one carrier. Thus, diversity gain can be obtained.

In addition, since the terrestrial auxiliary apparatus 200 uses only one subcarrier to send one broadcast content to the terminal, spectrum use efficiency is high. In this transmission method, since the satellite signal and the terrestrial auxiliary signal form a single frequency network, it is important for the terminal to synchronize the satellite signal and the signal received from the terrestrial auxiliary device.

When a service is provided to a terminal through a general satellite DMB system, the terminal receives a signal having the same data rate from the signal transmitted from the satellite and the signal transmitted from the terrestrial auxiliary device. Therefore, both the terminal outside the coverage of the terrestrial assistance apparatus and the terminal in the coverage of the terrestrial assistance apparatus are provided with the same service from the satellite.

In this case, the signal transmitted from the terrestrial auxiliary device to the terminal has a better channel condition than a satellite signal having a large path loss due to a long distance. Therefore, it can be transmitted to the terminal with a higher data rate than the satellite signal. However, given the high data rate, it can be said that the frequency spectrum is not effectively used.

Therefore, in the first exemplary embodiment of the present invention, it is considered that a signal transmitted from the terrestrial auxiliary apparatus 200 to the terminal 300 is better than a signal transmitted directly from the satellite 100 to the terminal 300 '. Therefore, in the coverage of the terrestrial assistance device 200 transmits a signal having a higher transmission rate than the satellite signal out of coverage. Accordingly, in the coverage of the terrestrial assisting device 200, the broadcast service that provides a greater amount of broadcast services, that is, a greater number of channels than the broadcast service provided to the terminal 300 'outside the coverage, or provides high quality A method of providing a broadcast service is used.

As shown in FIG. 2, in order to provide the terminal 300 with a higher number of broadcast channels or a higher-quality broadcast service within the coverage of the terrestrial assisting device 200, the satellite 100 is a terminal outside the coverage of the terrestrial assisting device 200. The signal must be transmitted to the terrestrial auxiliary device 200 using a transmission rate higher than that transmitted to 300 '. However, in the first embodiment of the present invention, the same frequency terrestrial assistance apparatus is considered. Therefore, when the satellite 100 transmits a signal having a high data rate to the terrestrial auxiliary device 200, a signal having a high data rate is also transmitted to the terminal 300 ′ that is outside the coverage of the terrestrial auxiliary device. This is because the terminal 300 ′ out of coverage of the terrestrial assistance device cannot receive signals from the satellites, so the satellite 100 uses a communication method of transmitting signals using hierarchical modulation.

In other words, the satellite 100 transmits not only the broadcast content provided to the terminal 300 ′ out of coverage of the terrestrial assisting device 200, but also broadcast content serviced only by the terrestrial assisting device 200. In this case, since the satellite 100 needs to transmit more content to the terrestrial auxiliary apparatus 200 and the terminal 300 'than a general system, the satellite 100 transmits a signal using a high level modulation technique used by the terrestrial auxiliary apparatus 200. It must be tampered with. In this case, the broadcast content for the terminal 300 ′ located outside the coverage of the terrestrial assisting device. The modulation is transmitted to the terminal 300 'at a higher level than the modulation provided previously. Therefore, in the case of the terminal 300 'in which only the signal from the satellite 100 is transmitted without transmitting the signal of the terrestrial auxiliary apparatus 200, the terminal 300' cannot receive the satellite broadcasting content.

Therefore, embodiments of the present invention modulate the content using a hierarchical modulation technique. That is, the satellite 100 transmits a signal using a higher level modulation method than the existing system, but modulates and broadcasts the broadcast content for the terminal 300 'that is outside the coverage of the terrestrial auxiliary apparatus at the same level as a general system. .

For example, suppose that a general system transmits broadcast content to a terminal 300 ′ out of coverage of a terrestrial auxiliary apparatus and transmits it to QPSK, and the terrestrial auxiliary apparatus 200 may process data through 16 QAM modulation. In this case, the satellite 100 transmits a signal processed by a higher order modulation technique through hierarchical modulation rather than a QPSK signal. At this time, the signal for the terminal 300 'out of coverage of the ground assist device is transmitted as shown in FIG.

3 is a signal transmission flowchart according to a first embodiment of the present invention.

As shown in FIG. 3, the satellite 100 generates a signal to be transmitted to the terrestrial assistance device 200 and the terminal 300 ′ (S100). Here, the signal is a signal generated by modulating the broadcast content at the data rate of the base layer and the data rate of the enhancement layer. In this case, a signal generated by modulating broadcast content at the data rate of the base layer is referred to as a first layer modulated signal, and a signal generated by modulating broadcast content at a data rate of the enhancement layer is referred to as a second layer modulated signal. It doesn't happen.

The satellite transmits the generated signal to the terrestrial auxiliary device and the first terminal (S110 and S115). Here, the first terminal refers to the terminal 300 ′ located outside the coverage of the ground assist device. The satellite 100 simultaneously transmits the generated signal to the terrestrial auxiliary device 200 and the first terminal 300 ', but for convenience of explanation, the satellite 100 transmits the signal generated by the satellite 100 to the terrestrial auxiliary device. It is shown as transmitting sequentially to the device 200 and the first terminal (300 '). However, this does not mean that signals are transmitted sequentially.

The first terminal 300 ′ receiving the signal transmitted from the satellite 100 demodulates a second layer modulated signal among the received signals (S125) and uses broadcast content included in the signal. After receiving the signal transmitted from the satellite 100, the terrestrial auxiliary apparatus 200 performs signal processing for simply amplifying the received hierarchical modulated signal (S120) and transmits the signal to the second terminal (S130). Here, the second terminal refers to the terminal 300 located within the coverage of the ground assisting device 200.

After receiving the signal including the hierarchical modulation signal from the terrestrial auxiliary device 200, the second terminal 300 demodulates the received hierarchical modulation signal (S140) and uses broadcast content included in the corresponding signal. If the signal modulated at the first layer data rate and the signal modulated at the second layer data rate are signals generated by modulating the same broadcast content, the second terminal 300 may be provided with high quality broadcast content. In addition, if the first layer modulated signal and the second layer modulated signal are signals generated by modulating different broadcast contents, the second terminal 300 may be provided with a large amount of broadcast services.

In this case, the first hierarchical modulated signal and the second hierarchical modulated signal may be modulated by a modulation scheme having various data rates. Next, signal constellations according to the modulation scheme will be described with reference to FIGS. 4 and 5.

4 is an exemplary diagram of a signal constellation according to hierarchical modulation according to an embodiment of the present invention.

4 shows a signal constellation diagram for hierarchical modulation of the first base layer and the first enhancement layer. Here, the first base layer is described as an example of the QPSK layer and the first enhancement layer is described as an example of the QPSK layer, but is not necessarily limited thereto.

The broadcast content for the out-of-coverage terminal 300 'of the terrestrial assist device is transmitted to the terminal 300' through the QPSK base layer, among constellations similar to those of 16 QAM in which the QPSK enhancement layer is added to the QPSK base layer. The effect of transmitting a signal with QPSK can be obtained. In addition, the local broadcast content serviced only by the terrestrial auxiliary apparatus 200 may be transmitted through the QPSK enhancement layer so that the terrestrial auxiliary apparatus 200 may process data corresponding to 16 QAM modulation, and thus, the terrestrial auxiliary apparatus 200 may exist. Increase efficiency of spectrum use in urban areas.

Similarly, since the diversity gain can also be obtained in the same manner, it is possible to increase the total coverage capacity of the terrestrial assistance device 200 without degrading performance. This increased capacity may increase the number of broadcast service channels of terrestrial auxiliary device coverage as mentioned above, and may provide high quality broadcast services with the same number of channels.

Symbols modulated according to hierarchical modulation according to an embodiment of the present invention may be represented by α, β, or θ according to input bits, or may be represented by Equation 1 below. Here, if 'α / β = 1/2' and 'θ = 10', it is the same as the 16QAM constellation.

Next, an example of a signal constellation according to another hierarchical modulation will be described with reference to FIG. 5.

5 is an exemplary diagram of a signal constellation according to hierarchical modulation according to another embodiment of the present invention.

In FIG. 5, the satellite 100 transmits a signal through the QPSK base layer among constellations similar to those of 64 QAM in which the second base layer and the second enhancement layer are added, thereby obtaining the effect of transmitting to QPSK. Here, the second base layer will be described with QPSK and the second enhancement layer with 16 QAM layers as an example, but the present invention is not necessarily limited thereto.

Local broadcast content serviced only by the terrestrial auxiliary apparatus 200 may be transmitted through a 16 QAM enhancement layer, and the terrestrial auxiliary apparatus 200 may perform data processing corresponding to 64 QAM modulation. In addition, it is possible to increase the spectrum use efficiency in the city center where the terrestrial assistance device 200 exists.

The diversity gain obtained in such a system can also be obtained in the same manner as the spectrum utilization efficiency described above, so that the total coverage of the terrestrial assistance device can be increased without degrading performance.

Symbols modulated according to the second hierarchical modulation according to an embodiment of the present invention may be represented by α, β, and θ according to input bits as mentioned in FIG. 3. In addition, modulated symbols for input bits may be expressed as in Equation 2 below.

In this case, if 'α / β = 1/4' and 'θ = 0', it is the same as the 64QAM constellation, which is already known and will not be described in detail in the embodiments of the present invention.

In addition to the above-described method, it is assumed that a signal is transmitted through a 16 QAM base layer among constellations similar to 64 QAM in which a third enhancement layer is added to the third base layer. Here, the third base layer is described with 16 QAM layers and the third enhancement layer with QPSK layers as an example, but is not necessarily limited thereto.

If the signal is transmitted in this way, the effect of transmitting at 16 QAM can be obtained. In addition, local broadcast content, which is only serviced by terrestrial auxiliary devices, can be transmitted through the QPSK enhancement layer so that terrestrial auxiliary devices can perform data processing corresponding to 64 QAM modulation, thereby improving spectrum usage efficiency in urban areas where terrestrial auxiliary devices exist. have.

Next, a satellite mobile communication system in the case of using a frequency conversion terrestrial assist device, which is another form of the terrestrial assist device, will be described with reference to FIG. 6.

6 is an exemplary diagram of a satellite mobile communication system according to a second embodiment of the present invention.

As shown in FIG. 6, the terrestrial auxiliary apparatus 200 according to the second embodiment of the present invention includes a frequency band of a signal transmitted from the satellite 100 and a frequency transmitted from the terrestrial auxiliary apparatus 200 to the terminal 300. Since the bands are different, the signal transmitted from the satellite 100 is subjected to frequency conversion and signal processing. At this time, the signal transmitted from the satellite 100 is a signal generated by modulating the broadcast content to be provided to the terminal to the data rate of the data rate of the base layer plus the data rate of the enhancement layer, and modulates the broadcast content to the data rate of the base layer It is divided into generated signals.

The satellite 100 transmits the layered modulation signal to the terminal 300 'out of the coverage of the terrestrial auxiliary apparatus, and transmits the terrestrial auxiliary apparatus 200 to the terrestrial auxiliary apparatus 200 in a different frequency band by using another radio interface. Send the content. In addition, the terrestrial auxiliary apparatus 200 generates a layered modulated signal transmitted from the satellite 100 in the same manner to the terminal by using the same air interface that transmits the satellite signal received from the satellite 100 from the satellite to the terminal. send.

Then, the terminal 300 'outside the coverage of the terrestrial auxiliary device demodulates a signal generated by modulating at the data rate of the base layer among the layered modulation signals, and the terminal 300 in the coverage of the terrestrial auxiliary device is modulated at the data rate of the enhancement layer. Demodulate the generated signal. As described above, when the signal is transmitted according to the second embodiment of the present invention, the frequency of the signal transmitted from the satellite 100 to the terrestrial auxiliary device 200 and the signal transmitted to the terminal 300 'outside the terrestrial auxiliary device coverage are different. .

For this reason, the signal transmitted from the satellite 100 to the terminal 300 'is transmitted late in consideration of the delay time that the terrestrial auxiliary device 200 receives from the satellite 100 and transmits the signal to the user in the coverage. Accordingly, the terminal can easily synchronize the satellite signal with the terrestrial auxiliary signal. In addition, since the signal transmitted from the satellite 100 to the terminal 300 'outside the coverage of the terrestrial apparatus and the signal transmitted from the terrestrial assistance apparatus 200 to the terminal 300 within the coverage are the same as described with reference to FIG. Hierarchical modulation can be used as-is, increasing spectral efficiency by the same amount.

A method of transmitting a signal using the satellite mobile communication system according to the second embodiment of the present invention will be described with reference to FIG. 7.

7 is a signal transmission flowchart according to a second embodiment of the present invention.

As shown in FIG. 7, the satellite 100 generates a signal including a hierarchical modulated signal to be transmitted to the terrestrial auxiliary apparatus and the terminal (S200). Here, the hierarchical modulated signal means a signal generated by modulating broadcast content to be provided to the terminal at the data rate of the base layer and the data rate of the enhancement layer. In this case, a signal obtained by modulating broadcast content at a data rate of a base layer is referred to as a first hierarchical modulation signal, and a signal modulated at broadcast rate by a data rate of an enhancement layer is referred to as a second layer modulated signal, but is not necessarily limited thereto.

The satellite 100 transmits the generated signal to the ground auxiliary apparatus 200 and the first terminal (S210 and S215). Here, the first terminal refers to the terminal 300 ′ located outside the coverage of the ground assist device. The satellite 100 simultaneously transmits the generated signal to the terrestrial auxiliary device 200 and the first terminal 300 ', but for convenience of explanation, the satellite 100 transmits the signal generated by the satellite to the terrestrial auxiliary device and the first terminal 300'. It is shown as transmitting sequentially to one terminal. However, this does not mean that signals are transmitted sequentially.

The first terminal 300 ′ receiving the signal transmitted from the satellite 100 demodulates the first layer modulated signal among the received layer modulated signals (S225) and uses broadcast content included in the signal. After receiving the signal transmitted from the satellite 100, the terrestrial auxiliary apparatus 200 performs signal processing for amplifying the received hierarchical modulated signal after frequency conversion (S220) and transmits the signal to the second terminal (S230). Here, the second terminal 300 refers to a terminal located within the coverage of the terrestrial assistance apparatus, and the frequency of the signal transmitted by the satellite to the terrestrial assistance apparatus 200 and the signal transmitted to the terminal 300 'outside the coverage of the terrestrial assistance apparatus. Since is different, frequency conversion is required.

After receiving the hierarchical modulation signal from the terrestrial auxiliary apparatus 200, the second terminal 300 demodulates the received hierarchical modulation signal (S240) and modulates the broadcast content modulated at the base layer data rate and the broadcast content modulated at the enhancement layer data rate. Use

The embodiments of the present invention described above are not only implemented by the apparatus and method but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, The embodiments can be easily implemented by those skilled in the art from the description of the embodiments described above.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is an exemplary diagram of a satellite mobile communication system according to an embodiment of the present invention.

2 is an exemplary diagram of a satellite mobile communication system according to a first embodiment of the present invention.

3 is a signal transmission flowchart according to a first embodiment of the present invention.

4 is an exemplary diagram of a signal constellation according to hierarchical modulation according to an embodiment of the present invention.

5 is an exemplary diagram of a signal constellation according to hierarchical modulation according to another embodiment of the present invention.

6 is an exemplary diagram of a satellite mobile communication system according to a second embodiment of the present invention.

7 is a signal transmission flowchart according to a second embodiment of the present invention.

Claims (9)

A communication method in which a terrestrial auxiliary device provides a signal corresponding to content to a terminal in a mobile communication system using a satellite, The hierarchical modulation signal generated by the terrestrial auxiliary device to be transmitted to the terminal at a different data rate. Receiving; And Transmitting, by the terrestrial auxiliary device, the hierarchical modulation signal to a terminal; Communication method comprising a. The method of claim 1, A frequency band used by the terrestrial auxiliary device to receive a signal, and a frequency band used by the terrestrial auxiliary device to transmit a signal to the terminal. The method of claim 1, The step of transmitting to the terminal, Performing frequency conversion of the hierarchical modulated signal More, And a frequency band different from that used by the terrestrial auxiliary apparatus to receive a signal and a frequency band used by the terrestrial auxiliary apparatus to transmit a signal to the terminal. The method of claim 3, The terminal is a terminal located within the coverage of the terrestrial assistance device. The method of claim 1, The signal modulated at the data rate of the first layer is transmitted to the terminal without passing through the terrestrial auxiliary device, where the terminal is a terminal not located within the coverage of the terrestrial auxiliary device. In a communication method for providing a content to a terminal by a mobile communication system using a satellite, Generating a signal including a hierarchical modulated signal by modulating content to be provided to a terminal at a different data rate by the mobile communication system; Transmitting, by the mobile communication system, the hierarchical modulated signal to a first terminal not located within the coverage of the terrestrial auxiliary device; And Amplifying the hierarchical modulation signal by the mobile communication system and transmitting the amplified signal to a second terminal located within the coverage of the terrestrial auxiliary device; Communication method comprising a. The method of claim 6, The hierarchical modulated signal is a signal generated by modulating the content at a data rate of a first layer and a data rate of a second layer. The method of claim 7, wherein And a data rate of the hierarchical modulated signal demodulated by the first terminal has a data rate lower than that of the hierarchical modulated signal demodulated by the second terminal. delete

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