KR100816500B1 - Digital broadcasting transmitter/receiver using multiple transmission antennas - Google Patents

Abstract

A digital broadcast transmitting/receiving device is provided to improve a broadcasting receiving performance and increase service coverage within the same service area, by applying multiple transmission antennas, and space-time encoding, space-frequency encoding, or space-time-frequency encoding to a digital broadcast system. An encoding unit(110) generates a plurality of encoded symbol lines by applying encoding to an original symbol line. A first antenna(150) adds one of the encoded symbol lines to a data signal, and then transmits the data signal. At least one additive antenna(160) transmits the rest of the encoded symbol lines. A transmission power controller(130) controls the transmission power of the first antenna and the additive antenna.

Description

Digital Broadcasting Transmitter / Receiver using multiple transmission antennas

1 is a diagram schematically illustrating a digital broadcasting system using a multiple transmit antenna according to an embodiment of the present invention.

2 is a diagram schematically illustrating a digital multimedia broadcasting system using a multiple transmit antenna according to an embodiment of the present invention.

The present invention relates to a digital broadcast system, and more particularly, to a digital broadcast transceiver using multiple transmission antennas.

In general, a digital broadcast system transmits the same broadcast signal through all transmit antennas even when using a single transmit antenna or multiple transmit antennas. Through this, the receiver receives the broadcast signal and displays it on the screen.

On the other hand, a diversity technique has been developed to expand the coverage area of a wireless system by improving the error rate, data rate, or transmission capability of the wireless communication system. A paper entitled "A simple transmit diversity technique for wireless communications," by SM Alamouti, is published in IEEE journal of Selected Areas in Communications, vol. 16, no. 8, Oct. 1998, pp. 1451-1458. This paper presents orthogonal space-time coding for two transmit antennas and one receive antenna.

In this orthogonal space-time encoding, when the symbol string to be transmitted by the transmitter is {s ₁ , s ₂ , s ₃ , s ₄ , ...}, the symbol string transmitted through the first transmitting antenna is T _1. [1, 2, 3, 4, ...] = {s ₁ , s ₂ ^* , s ₃ , s ₄ ^* , ...}, and the heat transmitted through the second transmit antenna is T ₂ [1 , 2, 3, 4, ...] = {s ₂ , -s ₁ ^* , s ₄ , -s ₃ ^* , ...} When such a transmitted signal is received by one receiving antenna through different channels having channel gains h ₁ and h ₂ , signal components excluding noise or other interference among the received symbols are R [1, 2, 3, 4,. ..] = {h ₁ s ₁ + h ₂ s ₂ , h ₁ s ₂ ^* -h ₂ s ₁ ^* , h ₁ s ₃ + h ₂ s ₄ , h ₁ s ₄ ^* -h ₂ s ₃ ^* ,. ..}.

After obtaining information about the channel gains h ₁ and h ₂ through a channel estimation process at the receiver, the original transmit symbol string may be recovered by Equation 1 to obtain a transmit diversity gain.

When such space-time coding is applied to an existing digital broadcasting system, reception performance can be improved. However, when applied as it is, conventional receivers manufactured in consideration of the conventional single transmit antenna system have a problem in that normal operation is impossible.

Accordingly, an object of the present invention is to provide a digital broadcasting system using multiple transmission antennas in which space-time coding, space-frequency coding, or space-time frequency coding is applied to a digital broadcasting system.

In addition, another object of the present invention is to provide a digital broadcasting system using multiple transmission antennas for maintaining the existing reception performance almost the same for an existing receiver designed considering only a single transmission antenna.

To this end, a digital broadcast transmitter using a multiplex transmission antenna according to the present invention comprises: an encoder for generating an original symbol sequence and at least one additional symbol sequence by applying an encoding to an original symbol sequence; A first antenna for adding and transmitting the original symbol string to a data signal to be transmitted; And at least one additional antenna for transmitting the at least one additional symbol string.

In addition, the digital broadcast receiver using a multiplex transmission antenna for receiving a plurality of symbol strings through a plurality of channels with a single receiving antenna and restoring the original symbol string may determine whether the receiver supports predetermined encoding. When it is not possible to support the result of the determination, the transmission signal power of each of the plurality of symbol strings is compared to restore the signal of the largest symbol string to the original symbol string.

Meanwhile, by applying hierarchical modulation to a digital multimedia broadcasting system according to an embodiment of the present invention, digital multimedia broadcasting transmission using a multiplex transmission antenna for transmitting additional broadcast signals in addition to the original digital multimedia broadcasting signals simultaneously with the digital multimedia broadcasting signals. The method comprises: (a) performing a layer modulation on the digital multimedia broadcasting signal to output a base layer signal and an enhancement layer signal; (b) generating at least one additional base layer signal and an enhancement layer signal by applying encoding to both the output base layer signal and the enhancement layer signal; And (c) transmitting the base layer signal and the enhancement layer signal through a first antenna, and transmitting the at least one additional base layer signal and the enhancement layer signal through at least one additional antenna.

In addition, by applying hierarchical modulation to the digital multimedia broadcasting system according to an embodiment of the present invention, digital multimedia broadcasting transmission using a multiplex transmission antenna for transmitting additional broadcast signals in addition to the original digital multimedia broadcasting signal simultaneously with the digital multimedia broadcasting signal. The method comprises: (a) applying an encoding to an enhancement layer signal of the digital multimedia broadcast signal to generate an additional at least one encoded enhancement layer signal; (b) hierarchically modulating the additional at least one encoded enhancement layer signal and the base layer signal; And (c) transmitting the additional at least one encoded enhancement layer signal and the base layer signal through a first antenna and the additional at least one encoded enhancement layer signal through at least one additional antenna. Include.

Hereinafter, with reference to the accompanying drawings and embodiments will be described the present invention in detail. Like reference numerals refer to like or similar elements throughout the drawings.

FIG. 1 is a diagram briefly showing a digital broadcasting system using multiple transmission antennas according to an embodiment of the present invention. For convenience, a case in which two multiple transmission antennas are used will be described as an example.

As shown in FIG. 1, the system includes a transmitter 100 for space-time encoding and transmitting the original symbol sequence, and a receiver 200 for receiving the transmitted signal and restoring the original symbol sequence. The transmitter 100 and the receiver 200 are formed of at least one, and applied to a wireless system such as a base station and a terminal or a repeater and a terminal.

The transmitter 100 includes: an encoder 110 generating original symbol sequences and additional symbol sequences by applying space-time encoding to the original symbol sequences; A first antenna (150) for transmitting said one symbol sequence; And a second antenna 160 for transmitting said additional symbol strings. In addition, the pilot signal transmitter 120 for transmitting a pilot signal in a form that can be distinguished for each transmission antenna (150, 160) so that the receiver 200 can properly estimate the channel gain; A transmission power control unit 130 for controlling transmission power of the first antenna 150 and the second antenna 160; The apparatus further includes a control information transmitter 140 for transmitting relevant information for proper reception such as whether encoding is applied, transmitter antenna number information, encoding information, transmission power control information for each antenna, and the like through a control channel.

Although the receiver 200 may use an existing digital broadcast receiver, the following components are added according to the expansion of the space-time encoding application of the transmitter 100 described above. That is, the receiver 200 includes a pilot signal receiving unit 210 for receiving the above-described pilot signal to the existing receiver; The apparatus may further include a control information receiver 220 for receiving the related information received through the above-described control channel. In this case, the existing digital broadcast receiver includes a channel estimator 230 and a decoder 240.

The operation of the wireless communication transceiver to which the space-time encoding method according to the present invention configured as described above is applied will be described.

First, when a symbol string transmitted through the first antenna 150 is transmitted by adding {s ₁ , s ₂ , s ₃ , s ₄ , ...} to an existing wireless signal, the symbol string is transmitted to the second antenna 160. The symbol string transmitted through is {s ₂ ^* , -s ₁ ^* , s ₄ ^* , -s ₃ ^* , ...}.

At this time, these symbol strings are only an embodiment, and the present invention is not limited thereto. That is, if the symbol string added to the existing wireless signal is {s ₂ ^* , -s ₁ ^* , s ₄ ^* , -s ₃ ^* , ...}, the symbol string transmitted through the second antenna 160 is {s ₁ , s ₂ , s ₃ , s ₄ , ...}, and if the symbol sequence added to the existing radio signal is {s ₁ , s ₂ ^* , s ₃ , s ₄ ^* , ...}, the second antenna The symbol string transmitted through the 160 is {s ₂ , -s ₁ ^* , s ₄ , -s ₃ ^* , ...}, and the symbol string added to the existing radio signal is {s ₂ , -s ₁ ^* , s ₄ , -s ₃ ^* , ...}, the symbol string transmitted through the second antenna 160 may be {s ₁ , s ₂ ^* , s ₃ , s ₄ ^* , ...} have.

When such a transmitted signal is received by one receiving antenna 250 through different channels having channel gains h ₁ and h ₂ , signal components excluding noise or other interference among received symbols are R [1, 2, 3, 4, ...] = (h ₁ s ₁ + h ₂ s ₂ ^* , h ₁ s ₂ -h ₂ s ₁ ^* , h ₁ s ₃ + h ₂ s ₄ ^* , h ₁ s ₄ -h ₂ s ₃ ^*, ...} is the (in this case, to the two symbol streams for transmission via a first antenna 150 add _{{s 1, s 2, s} 3, s 4, ...} for the existing radio signal And a symbol string transmitted through the second antenna 160 is {s ₂ ^* , -s ₁ ^* , s ₄ ^* , -s ₃ ^* , ...}.

The information on the channel gains h ₁ and h ₂ may be obtained through the channel estimation process in the receiver 200, and then recovered by Equation 2 to obtain a transmission diversity gain.

,

,

, n = 1, 2, 3, ...

, n = 1, 2, 3, ...

 In this case, when the transmission data information is loaded only in the phase, since the denominator of each equation right term is not necessary in Equation 2, Equation 3 below.

, n=1, 2, 3, ...

, n = 1, 2, 3, ...

Meanwhile, since the transmission signal from the first antenna 150 and the transmission signal from the second antenna 160 are added to act as an interference signal to an existing receiver (that is, a conventional digital broadcast receiver), the above-described space-time encoding is performed. In order for existing receivers to operate while maintaining compatibility within the coverage area, the transmit power control unit 130 may transmit the transmit power from the second antenna 160 relatively sufficiently compared to the transmit power from the first antenna 150. It should be small. That is, in order to be compatible with the existing receiver, the α value shown in FIG. 1 must be made sufficiently small. This is because the existing receiver is only recognized that the channel gain h ₂ between the transmission signal from the second antenna 160 and the receiver is reduced by an α value, so that the receiver can receive the conventional method.

As such, after the initial system is configured with a small value of α, a terminal in a service area is gradually replaced by a receiver 200 that supports a space-time decoding function, or a receiver having an improved reception performance for an existing transmission scheme signal. As the prevalence rate increases, the α value is gradually increased, and finally, after all receivers in the service area are replaced by the receiver 200 supporting the space-time decoding function, the system value can be completed with the α value of 0.5. have. Alternatively, instead of the gradual upgrade as described above, the system changes the α value from the existing small value to 0.5 immediately after the completion of the space-time decoding function supporting receiver 200 in the service area is completed. You can also complete the upgrade.

In order for the digital broadcast receiver 200 according to the present invention to operate properly according to the above-described method, it is necessary to properly estimate the channel gain used in Equation 2 above. To this end, the pilot signal transmitter 120 of the transmitter should transmit a pilot signal for channel estimation in addition to the broadcast signal in a form in which the receiver 200 can separately receive each transmit antenna.

In addition, for proper reception operation of receivers in the service area, the control information transmitter 140 should appropriately provide relevant information to all receivers through the control channel. That is, the receivers in the service area normally receive information about whether the space-time coding is applied to the transmission signal and the space-time coding and the number of transmitting antennas to which the α value is applied when the space-time coding is applied. All receivers 200 should properly receive before.

Accordingly, the receiver 200 receives information on whether the above-described space-time coding is applied to the transmission signal, the space-time coding to which the α value is applied when the space-time coding is applied, and the number of transmitting antennas. Subsequently, it is determined whether the receiver 200 supports the space-time encoding, and when it does not support, only the symbol signal having the largest transmission power is restored, but when it supports, the decoding corresponding to the encoding is applied. That is, the original symbol string is restored through channel estimation as shown in Equation 2 above.

Example

Korean Patent Application No. 2005-90067 entitled "Transmitting and Receiving Method and Apparatus for High Quality Video Service in Digital Multimedia Broadcasting" for Improving Data Transmission Rate of Digital Multimedia Broadcasting (DMB) System The above-described space-time coding may be applied to the system disclosed in the present disclosure to further improve reception performance in a service area.

Hereinafter, a digital multimedia broadcasting transceiver using space-time encoding according to the present invention will be described based on this prior art.

First, as the first method, the above-described space-time encoding may be applied to the entire digital transmission signal generated as a result of hierarchically modulating the "enhanced layer signal" mentioned in the above-described conventional technology. . That is, in contrast to the configuration of FIG. 2 to be described later, when the layer modulation is performed prior to the space-time encoding, both the base layer signal and the enhancement layer signal are transmitted through the first antenna, and the above-described base layer signal and enhancement layer An additional signal for the signal (ie, a signal added according to the space-time encoding according to the invention) is transmitted via the second antenna. Since the following process is similar to that described based on FIG. 1, it is omitted.

As a second method, space-time coding may be applied only to an enhancement layer signal simultaneously transmitted through the same transmitting antenna together with an existing digital multimedia broadcasting signal. A conceptual diagram thereof is shown in FIG. 2.

2 is a diagram briefly illustrating a digital multimedia broadcasting system using a multiple transmit antenna according to an embodiment of the present invention. In this case, the base layer signal corresponding to the digital multimedia broadcasting signal is referred to as a high priority (HP) signal and an enhancement layer signal as a low priority (LP) signal.

As shown in FIG. 2, the system includes a digital multimedia broadcasting transmitter 300 and a digital multimedia broadcasting receiver 400, and applies space-time coding only to the enhancement layer signal LP described above. .

The digital multimedia broadcasting transmitter 300 includes the transmitter 100 of FIG. 1, the base layer signal (HP) symbol strings (S _A1 , S _A2 , S _A3 , S _A4 , ...) and the enhancement layer signal (LP) symbols. It further includes a hierarchical modulator 310 for modulating the columns S _B1 , S _B2 , S _B3 , S _B4 ,...

In the present embodiment, the digital multimedia broadcasting transmitter 300 includes a base layer signal (HP) symbol string (S _A1 , S _A2 , S _A3 , S _A4 , ...) and an enhancement layer hierarchically modulated through the first antenna 320. A signal LP symbol string S _B1 , S _B2 , S _B3 , S _B4 , ... is transmitted, and is spatially coded through the second antenna 330 A symbol layer S _B2 ^* , -S _B1 ^* , S _B3 ^* , -S _B4 ^* , ...) are transmitted.

The digital multimedia broadcasting receiver 400 further includes a hierarchical demodulator 410 which receives the broadcast signal through the receiving antenna 420 and separates and demodulates the base layer signal HP and the enhancement layer signal LP. The demodulated base layer signal HP is output as it is, and the space-time encoded enhancement layer signal LP is restored as described with reference to FIG. 1.

A digital multimedia broadcasting transceiver using multiple transmission antennas according to the present invention configured as described above will be described.

When the space-time encoding method is applied to the above-described enhanced layer signal (LP), the digital multimedia broadcasting transmitter 300 has sufficient transmission power of the LP signal compared to the HP signal to ensure backward compatibility with the digital multimedia broadcasting system. Should be small.

That is, when the power of the LP signal is expressed as P _B , the digital multimedia broadcasting transmitter 300 sets the power of the LP signal transmitted to the first antenna 320 along with the HP signal to P _B / 2 through hierarchical modulation. Instead, the additional LP signal generated by applying the orthogonal space-time coding to the LP signal is transmitted through the second antenna 330 at the same transmit power of P _B / 2.

Accordingly, the conventional digital multimedia broadcasting receiver, which does not include the hierarchical demodulator 410, recognizes only two LP signals as interference signals added to the HP signal and performs signal demodulation on the HP signal having a relatively high signal power. can do.

In addition, when the digital multimedia broadcasting receiver 400 including the hierarchical demodulator 410 does not support the space-time decoding function, the digital multimedia broadcasting receiver 400 may be connected to the HP signal like the digital multimedia broadcasting receiver without the hierarchical demodulator 410. Only demodulation can be performed. In this case, for the proper operation of the digital multimedia broadcasting receivers according to the present embodiment, whether or not hierarchical modulation is applied or hierarchical modulation parameter in the digital multimedia broadcasting transmitter 300, whether or not the space-time coding is applied and whether the application interval and the encoding and related parameters are used. Etc. information should be delivered to all digital multimedia broadcasting receivers 400 through a fast information channel (FIC) or a separate control channel.

Furthermore, in transmitting two LP symbol strings generated by applying space-time coding to the LP signal, the signal of the second antenna 330 is converted into the LP signal of the first antenna 320 similarly to FIG. 1. It can be made smaller than power. When the signal transmitted in this form is received by the receiver based on the prior art that does not support the space-time decoding function, it is possible to demodulate not only the HP signal received from the first antenna 320 but also the LP signal. .

When the space-time coding is introduced into such a digital multimedia broadcasting system, initially, the ratio of the space to the space-time coding is applied to one of the transmission frames is lowered, and then the receiver in the service area gradually performs the space-time decoding function. As the proportion of receivers replaced with supporting receivers, or receivers with improved reception performance over existing transmission signals, increases, the ratio gradually increases so that all receivers in the service area finally support the space-time decoding function. After being replaced by the receiver 400, the system upgrade can be completed by applying space-time encoding to one frame. Alternatively, the system upgrade may be completed by changing to apply the space-time encoding to the entire frame at a moment after the completion of the space-time decoding supporting receiver in the service area is completed, as described above. It may be.

As described above, in the present specification, a case in which orthogonal space-time coding is applied to two transmitting antennas and one receiving antenna is described as an example, but the space-frequency encoding that replaces the same concept by the frequency dimension instead of the time dimension or It is possible to apply the extended space-time frequency coding, including the space-time coding to the frequency dimension, to apply codes designed for various transmitter and receiver antenna numbers, and also to do not guarantee orthogonality. -orthogonal) may be applied.

While the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will recognize that various modifications or changes can be made without departing from the spirit and scope of the invention.

According to the present invention, by applying multiple transmit antennas and space-time, space-frequency or space-time-frequency coding to a digital broadcasting system, the receiver can improve reception performance and increase service coverage in the same service area. The effect can be obtained.

In addition, according to the present invention, since the transmission signal power ratio additionally generated by applying the encoding or the ratio of the interval to which the encoding is applied is gradually increased, there is an effect of preventing temporary overcost due to a system upgrade.

Claims (19)

An encoder which generates a plurality of encoded symbol strings by applying encoding to the original symbol strings; A first antenna for adding and transmitting one of the coded symbol strings to a data signal to be transmitted; At least one additional antenna configured to transmit a remaining symbol string among the encoded symbol strings; And And a transmission power control unit configured to control transmission powers of the first antenna and the additional antenna. delete The method of claim 1, The transmission power controller starts the transmission power from the additional antenna relatively less than the transmission power from the first antenna, and then until the ratio of the transmission power of the additional antenna and the first antenna is 1: 1. Digital transmission transmitter using a multiple transmit antenna, characterized in that for adjusting the transmission power of the first antenna and the additional antenna in stages. The method according to claim 1 or 3, A pilot signal transmitter for estimating a channel gain by transmitting a pilot signal in a form distinguishable for each antenna; And And a control information transmitter configured to transmit at least one of whether the encoding is applied, the antenna number information, the encoding information, and transmission power control information for each antenna through a control channel. Broadcast transmitter. The method according to claim 1 or 3, The coding is any one of space-time coding, space-frequency coding, and space-time-frequency coding. A digital broadcast receiver using a multiplex transmission antenna for receiving a plurality of symbol strings through a plurality of channels with one receiving antenna and restoring the original symbol string, It is determined whether the receiver supports a predetermined encoding, and if it cannot support the result of the determination, by comparing the power of the transmission signal of each of the plurality of symbol strings, the signal of the largest symbol string is restored to the original symbol string. Digital broadcast receiver using a multiplex transmission antenna. The method of claim 6, If it is determined that the encoding can be supported, at least one or more of the number of transmitting antennas, the encoding information, and transmission power control information for each antenna are received through a control channel, and channel gain information is obtained through channel estimation. And recovering the original symbol sequence by using the multiplex transmission antenna. The method of claim 7, wherein The first symbol string of the plurality of symbol strings is {s ₁ , s ₂ , s ₃ , s ₄ , ...} and the second symbol string is {s ₂ ^* , -s ₁ ^* , s ₄ ^* , -s _{If 3} ^* , ...} The plurality of symbol strings are received through different channels having channel gains h ₁ and h ₂ , excluding noise or interference among the received symbols, and channel information about the channel gains h ₁ and h ₂ . After acquiring through the estimation process, the plurality of symbol strings are restored by the following equation.

,

Where n is a natural number. The method of claim 8, When information about the symbol strings are transmitted only in phase, A digital broadcast receiver using a multiple transmit antenna, characterized in that to restore the plurality of symbol strings through the following equation.

,

Where n is a natural number. The method according to any one of claims 6 to 9, And the encoding is any one of space-time coding, space-frequency coding, and space-time-frequency coding. In the digital multimedia broadcasting transmission method using a multi-transmission antenna for applying a hierarchical modulation to the digital multimedia broadcasting system to transmit additional broadcast signals in addition to the original digital multimedia broadcasting signal simultaneously with the original digital multimedia broadcasting signal, (a) performing a layer modulation on the original digital multimedia broadcasting signal to output a base layer signal and an enhancement layer signal; (b) generating at least one additional base layer signal and an enhancement layer signal by applying encoding to both the output base layer signal and the enhancement layer signal; And (c) transmitting the base layer signal and the enhancement layer signal through a first antenna, and transmitting the at least one additional base layer signal and the enhancement layer signal through at least one additional antenna. Digital multimedia broadcasting transmission method using multiple transmission antennas. The method of claim 11, wherein step (b) comprises: And applying the encoding to the entire transmission frame of the digital multimedia broadcasting signal or to a part of the transmission frame. The method of claim 11, wherein step (c) comprises: The method of claim 1, wherein the signal power transmitted through the first antenna is relatively larger than the signal power transmitted through the additional antenna. The method of claim 11, wherein step (c) comprises: And a ratio of the signal power transmitted through the first antenna and the signal power transmitted through the additional antenna in a 1: 1 ratio. The method according to any one of claims 11 to 14, The encoding is any one of space-time coding, space-frequency coding, and space-time-frequency coding. In the digital multimedia broadcasting transmission method using a multi-transmission antenna for applying a hierarchical modulation to the digital multimedia broadcasting system to transmit additional broadcast signals in addition to the original digital multimedia broadcasting signal simultaneously with the original digital multimedia broadcasting signal, (a) generating an additional at least one encoded enhancement layer signal by applying encoding to an enhancement layer signal of the original digital multimedia broadcasting signal; (b) hierarchically modulating the additional at least one encoded enhancement layer signal and the base layer signal; And (c) transmitting the additional at least one encoded enhancement layer signal and the base layer signal through a first antenna and the additional at least one encoded enhancement layer signal through at least one additional antenna. Digital multimedia broadcasting transmission method using a multiple transmit antenna, characterized in that. The method of claim 16, wherein step (c) comprises: And transmitting power of the enhancement layer signal transmitted through the additional antenna is the same as the transmission power of the enhancement layer signal transmitted through the first antenna. The method according to claim 16 or 17, The encoding is any one of space-time coding, space-frequency coding, and space-time-frequency coding. The method of claim 1, The coded symbol string transmitted through the first antenna is {s ₁ , s ₂ , s ₃ , s ₄ , ...}, and the coded symbol string transmitted through the additional antenna is {s ₂ ^* ,- s ₁ ^* , s ₄ ^* , -s ₃ ^* , ...}.

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