WO2009145550A2

WO2009145550A2 - Apparatus for transmitting and receiving a signal and a method thereof

Info

Publication number: WO2009145550A2
Application number: PCT/KR2009/002786
Authority: WO
Inventors: Sang Chul Moon; Woo Suk Ko
Original assignee: Lg Electronics Inc.
Priority date: 2008-05-27
Filing date: 2009-05-26
Publication date: 2009-12-03
Also published as: EP2286532A4; EP2286532A2; WO2009145550A3

Abstract

In one aspect of the present invention, a method for receiving a signal is disclosed. The method includes receiving (S210) signals from multiple antennas, and demodulating the received signals, respectively; parsing (S220) signal frames of the demodulated signals; performing (S230) MIMO decoding on signals in the parsed signal frames and outputting the MIMO-decoded signals to multiple paths; calibrating (S240) power levels of the MIMO-decoded signals on the multiple paths, respectively; symbol-demapping (S250) the calibrated signals on the multiple paths to bit streams by using different symbol-demapping methods, respectively; and multiplexing (S260) the bit streams and error correction decoding the multiplexed bit streamapparatus for transmitting and receiving a signal and a method thereof

Description

APPARATUS FOR TRANSMITTING AND RECEIVING A SIGNAL AND A METHOD THEREOF

The present invention relates to an apparatus for transmitting and receiving a signal and a method thereof that may enhance data transmission efficiency

In order to enhance data transmission efficiency in broadcasting and telecommunication systems, interest in methods of using two or more transmitting and receiving antennas is growing. As one of the methods of using two or more transmitting and receiving antennas, the multi-input multi-output (MIMO) technology has already been adopted in telecommunication systems such as wireless broadband (Wibro) systems or 3rd generation partnership project (3GPP) systems. The MIMO technology broadly consists of spatial diversity, which reduces the transmission error rateso as to enhance the transmission efficiency, and spatial multiplexing, which transmits different data types from multiple antennas so as to enhance the transmission rate. It is also highly likely that the above-described MIMO technology will be adopted as the transmission method for the next generation digital broadcasting.

An object of the present invention devised to solve the problem lies on proposing an apparatus and method for transmitting and receiving signals that can enhance transmission efficiency of digital broadcast data by using the MIMO technology.

Another object of the present invention devised to solve the problem lies on proposing an apparatus and method for transmitting and receiving signals that can adjust a sub-divided transmission bit rate per unit time by using the MIMO technology.

To achieve the objects, methods for transmitting and receiving a signal in claims 1 and 3 are disclosed. The power levels may vary depending upon the symbol-mapping methods.

In another aspect, devices for transmitting and receiving a signal in claims 5 and 7 are disclosed.

The plurality of symbol mappers (330a, 330b) is further configured to symbol-map the demultiplexed bits in accordance with different symbol mapping methods.

The present invention is advantageous in that by using the MIMO technology the transmission efficiency of digital broadcast data may be enhanced, and that a transmission bit rate per unit time may be adjusted so as to be sub-divided.

FIG. 1 illustrates an exemplary transmitting system adopting the MIMO technology.

FIG. 2 illustrates an apparatus for receiving a signal according to an embodiment of the present invention.

FIG. 3 illustratesan apparatus for transmitting a signal according to another embodiment of the present invention.

FIG. 4 illustratesan apparatus for receiving a signal according to another embodiment of the present invention.

FIG. 5 illustrates an exemplary bit granularity per unit time, when symbols symbol-mapped by different symbol-mapping methods are transmitted by using MIMO spatial multiplexing technique.

FIG. 6 illustrates a method for transmitting a signal according to an embodiment of the present invention.

FIG. 7 illustrates a method for receiving a signal according to an embodiment of the present invention.

The possibility of adopting the multi-input multi-output (MIMO) technology, as a method of enhancing data transmission efficiency by using two or more transmitting and receiving antennas, also in digital broadcasting system is being researched.

FIG. 1 illustrates an exemplary transmitting system adopting the MIMO technology. The disclosed embodiment of the transmitting system includes an error correction encoding unit 110, a symbol mapper 120, an MIMO encoder 130, a first frame mapper 140a, a second frame mapper 140b, a first modulator 150a, and a second modulator 150b.

The error correction encoding unit 110 may error correction encode the data that are to be transmitted in appropriate units. The error correction encoding unit 110adds redundancy data so that the data that are to be transmitted can become robust against errors and, then, performs the error correction encoding process.

The symbol mapper 120 maps the error correction encoded data to symbols. For example, the error correction encoded bit data, may be mapped into symbols based upon a specific symbol-mapping method, such as quadrature phase shift keying (QPSK), quadrature amplitude modulation (QAM), and pulse amplitude modulation (PAM).

The MIMO encoder 130 distributes the mapped symbols to multiple antenna paths by using the MIMO technique. The MIMO encoder 130 distributes the inputted symbols to multiple transmission streams, so that the inputted symbols can be transmitted to each antenna path. In the example shown in this embodiment, the MIMO encoder 130 enables the data to be transmitted to two antenna paths.

The first frame mapper 140a and the second frame mapper 140b may map each transmission stream, which is to be transmitted to the respective antenna path, to a signal frame. The structure of the signal frame may vary depending upon the system to which the signal frame is to be transmitted. Therefore, an example of a specific signal frame structure will not be given herein.

The signal frame may be transmitted by being allocated to a single carrier or multiple carriers. Herein, an example of transmitting the signal frame by allocating the signal frame to multiple carriers will be described.

The first modulator 150a and the second modulator 150b respectively modulate the signal frame by using orthogonal frequency divisional modulation (OFDM). Thereafter, the first modulator 150a and the second modulator 150b may respectively transmit the modulated signal through each antenna.

FIG. 2 illustrates an apparatus for receiving a signal according to an embodiment of the present invention. The apparatus for receiving a signal according to the embodiment of the present invention includes a first synchronization unit (Sync) 210a, a second synchronization unit (Sync) 210b, a first demodulator 220a, a second demodulator 220b, a first frame parser 230a, a second frame parser 230b, a MIMO decoder 240, a symbol demapper 250, and an error correction decoding unit260. The apparatus for receiving a signal according to the embodiment of the present invention may receive signals from multiple antennas based upon the MIMO technique. This embodiment shows an example of receiving the signals through two antennas so that the signal transmitted from the embodiment of the FIG. 1 can be received.

The first synchronization unit (Sync) 210a and the second synchronization unit (Sync) 210b respectively acquire synchronization from the signal received through each antenna. The first synchronization unit 210a and the second synchronization unit 210b may respectively acquire and output time synchronization and frequency synchronization of the received signal.

The first demodulator 220a and the second demodulator 220b respectively perform demodulation of the synchronized signal.Herein, the demodulation method may be in accordance with the modulation method. In the example according to the embodiment of the present invention, the demodulation process may be performed by using the OFDM method with respect to the embodiment shown in FIG. 1. Furthermore, the first demodulator 220a and the second demodulator 220b may respectively equalize the channels of the signals received through two antenna paths.

The first frame parser 230a and the second frame parser 230b respectively parse the frames of the signals equalized through the corresponding antenna paths.

The MIMO decoder 240 performs MIMO decoding on the signals respectively parsed by the first frame parser 230a and the second frame parser 230b. The MIMO decoder 240 may output a resultant signal stream

The symbol demapper 250 symbol demaps the symbols included in the receiving stream into a bit stream by using the symbol demapping method.

The error correction decoding unit 260 error correction decodes the demapped bit stream, thereby acquiring the transmitted data.

However, when multiple path signals are transmitted by using the above-described spatial multiplexing MIMO, the symbol-mapping/-demapping method of the symbol mapper 120 and the symbol demapper 250 become the same. Therefore, a large difference in the bit granularity may occur depending upon the symbol mapping method. For example, when the symbol mapper 120 uses the QAM symbol-mapping method, data are transmitted a transmission data rate such as 4bps/Hz(QPSK+QPSK), 8bps/Hz(16QAM+16QAM), 12bps/Hz(64QAM+64QAM), 16bps/Hz(256QAM+256QAM), and so on. In this case, the bit granularities (or data transmission rate) of 6bps/Hz, 10bps/Hz, 14bps/Hz, and so on cannot be selected. Therefore, in order to transmit data, the system user is required to select a system having a bit granularity and a signal-to-noise ratio (SNR) unnecessarily larger than the data size that is intended to be transmitted.

More specifically, when using the MIMO technique, the difference in bit granularity based upon the mapping method becomes large. And, when data are transmitted through two or more transmission paths, the difference in bit granularity based upon the mapping method may become larger. Therefore, when transmitting signals through multiple paths by adopting the MIMO technique, the bit granularity may be controlled (or adjusted) by using different mapping methods for each transmission path. In other words, when MIMO encoding is performed with different mapping methods with respect to the input data for the MIMO encoding process, the transmission data rate per unit time may vary depending upon the symbol mapping method. Therefore, the system designer may be able to use the system based upon a specific bit granularity among subdivided bit granularities. Hereinafter, the corresponding embodiment will be described in detail.

FIG. 3 illustrates an apparatus for transmitting a signal according to another embodiment of the present invention. The disclosed apparatus for transmitting a signal according to this embodiment includes an error correction encodingunit 310, a demultiplexer 320, a first symbol mapper 330a, a second symbol mapper 330b, a first power calibration unit 340a, a second power calibration unit 340b, a MIMOencoder 350, a first frame mapper 360a, a second frame mapper 360b, a first modulator 370a, and a second modulator 370b.

The error correction encoding unit 310 performs error correction encoding on the data that are to be transmitted in accordance with a specific error correction encoding method.

The demultiplexer 320 divides the error correction encoded data into streams so that each data stream can be outputted to each of transmission paths. For example, when the error correction encoded data are transmitted to two antennas, the demultiplexer 320 demultiplexes the input data to two transmission paths.

The first symbol mapper 330a and the second symbol mapper 330b may respectively symbol-map the demultiplexed data. The symbol-mapping method may vary depending upon each symbol mapper. More specifically, the first symbol mapper 330a and the second symbol mapper 330b may use different symbol mapping methods. Thus, the data rate may be adjusted accordingly. Detailed description of the same will be presented later on.

The first power calibration unit 340a and the second power calibration unit 340b may control the power of the symbols, so that the symbols can be transmitted at optimum power levels in accordance with two different symbol mapping methods. For example, the symbols may also be transmitted at an average power level of the symbols being transmitted according to two different symbol mapping methods.

The MIMO encoder 350 receives each of the differently symbol-mapped symbols, as described above, thereby performing the MIMO encoding process. The MIMO encoder 350 outputs the MIMO-encoded data, which are to be transmitted to the transmission antenna, to the respective transmission paths.

The first frame mapper 360a and the second frame mapper 360b respectively configure a signal frame that is to be transmitted to each antenna path.

Finally, the first modulator 370a and the second modulator 370b respectively modulates each signal frame by using an orthogonal frequency divisional modulation (OFDM)method, thereby being able to transmitted the modulated signals to each antenna.

FIG. 4 illustrates an apparatus for receiving a signal according to another embodiment of the present invention. The apparatus for receiving a signal according to this embodiment of the present invention includes a first synchronization unit (Sync) 410a, a second synchronization unit (Sync) 410b, a first demodulator 420a, a second demodulator 420b, a first frame parser 430a, a second frame parser 430b, a MIMO decoder 440, a first power calibration unit 450a, a second power calibration unit 450b, a first symbol demapper 460a, a second symbol demapper 460b, a multiplexer 470, and an error correction decoding unit 480. The disclosed apparatus for receiving a signal according to this embodiment uses the MIMO technique so as to demap the signals received through multiple antennas based upon the respective symbol-demapping method.

The first synchronization unit (Sync) 410a and the second synchronization unit (Sync) 410b respectively acquire synchronization in the time and frequency domains of the signals received from each antenna.

The first demodulator 420a and the second demodulator 420b respectively perform demodulation using the OFDM method on the synchronization-acquired signals. Also, channel information for each signal received through 2 antenna paths are acquired, thereby performing channel equalization on each signal.

The first frame parser 430a and the second frame parser 430b respectively parse a signal frame from the signals received and equalized by each of the two antenna paths.

The MIMO decoder 440 receives a signal from each of the parsed signal frames, thereby performing MIMO decoding.

Then, the first power calibration unit 450a and the second power calibration unit 450bare calibrated so that the power level of the symbols that was changed during transmission can be return to its original level.

The first symbol demapper 460a and the second symbol demapper 460b perform symbol demapping based upon the respective symbol-mapping method. Herein, the symbol-demapping method corresponds to the symbol mapping method. And, accordingly, diverse bit granularity may be obtained by using different symbol-mapping methods or by using different symbol-demapping methods. Thefirst symbol demapper 460a and the second symbol demapper 460b respectively acquire likelihood ratio (LLR) of bit levels for the corresponding symbols, each having its power level adjusts in accordance with the respective transmission path. Thereafter, the first symbol demapper 460a and the second symbol demapper 460b use the acquired LLR to perform symbol-demapping.

The multiplexer 470 multiplexes the symbols symbol-mapped in accordance with the methods used in the first symbol demapper 460a and the second symbol demapper 460b into a single bit stream.

Furthermore, the error correction decoding unit 490 performs error correction decoding on the bit stream being outputted from the multiplexer 470.

Therefore, the number of symbol-mapping/-demapping methods used herein corresponds to the number of antenna paths transmitting and receiving data by using the MIMO technique. Accordingly, each of the mapped symbols adjust the power level, so that symbols mapped by different symbol-mapping methods can be transmitted with the appropriate accuracy.

FIG. 5 illustrates an exemplary bit granularity per unit time, when symbols symbol-mapped by different symbol-mapping methods are transmitted by using MIMO spatial multiplexing technique. In this drawing, Data1 indicates the symbol-mapping method used by the first symbol mapper, Data2 indicates the symbol-mapping method used by the second symbol mapper, and Capa(bps/Hz) indicates the respective bit granularity.

If the first symbol-mapping method and the second symbol-mapping method both correspond to the QPSK method, 4bps/Hz of data are transmitted. Alternatively, if the first symbol-mapping method corresponds to the QPSK method, and the second symbol-mapping method corresponds to the 16QAM method, 6bps/Hz of data are transmitted. If the first symbol-mapping method and the second symbol-mapping method both correspond to the 16QAM method, 8bps/Hz of data are transmitted. On the other hand, if the first symbol-mapping method corresponds to the 16QAM method, and the second symbol-mapping method corresponds to the 64QAM method, 10bps/Hz of data are transmitted.

If the first symbol-mapping method and the second symbol-mapping method both correspond to the 64QAM method, 12bps/Hz of data are transmitted. Alternatively, if the first symbol-mapping method corresponds to the 64QAM method, and the second symbol-mapping method corresponds to the 256QAM method, 14bps/Hz of data are transmitted. If the first symbol-mapping method and the second symbol-mapping method both correspond to the 256QAM method, 16bps/Hz of data are transmitted.

Therefore, since the bit granularity may differ depending upon the symbol-mapping method, the bit granularity may be adjusted with more accuracy even if the MIMO spatial multiplexing technique is applied herein.

FIG. 6illustrates a method for transmitting a signal according to an embodiment of the present invention. Error correction encoding is performed on the data that are to be transmitted, and then the error correction encoded data are demultiplexed to a number of paths corresponding to the number of transmission antenna (S110). The demultiplexed data are symbol-mapped by using different symbol-mapping methods (S120). Thereafter, the power levels for the symbols symbol-mapped in the paths are adjusted, respectively (S130). Herein, the power level of each symbol may be adjusted based upon the respective symbol-mapping method.

Subsequently, the symbols of which power level are adjusted based upon the respective symbol-mapping methods are MIMO-encoded, And the MIMO-encoded signals are outputted to the paths to the transmission antennas (S140). Then, the outputted signals are used to configure signal frames that are to be transmitted to the transmission antennas, respectively(S150). Finally, the signal frames that are to be transmitted to the transmission antennas are modulated and transmitted, respectively (S160). Therefore, when performing MIMO encoding, the bit granularity per unit time may be subdivided and adjusted by using each of the different symbol-mapping methods.

FIG. 7 illustrates a method for receiving a signal according to an embodiment of the present invention. Signals are received through multiple antennas, thereby demodulating the received signals, respectively (S210).During the demodulating process, channel information on the transmission paths for the signals received by the antennas may be acquired, respectively. Then, signal frames of the demodulated signals are parsed, respectively (S220). Thereafter, MIMO decoding is performed by using the parsed signal frames, thereby outputting the signals to multiple paths (S230).

The power levels of the symbols corresponding to the outputted signals are calibrated, respectively (S240). Thereafter, the symbols having the calibrated power levels are symbol-demapped by using different symbol-demapping methods (S250). Finally, the symbol-demapped bit streams are multiplexed, and then the multiplexed bit stream is error correction decoded (S250).

According to the above-described embodiment, the bit granularity may be efficiently adjusted by using different symbol-mapping methods for each input/output signal during the MIMO encoding/decoding process, and by performing power calibration on the symbols based upon different symbol-mapping methods. More specifically, by using the MIMO technique, the transmission efficiency of digital broadcast data may be enhanced, and the bit granularity per unit time may be adjusted so as to be subdivided.

A plurality of embodiments has been described based upon the best mode for carrying out the present invention.

The present invention may be industrially applied in the fields of broadcasting and telecommunication.

Claims

A method for transmitting a signal, comprising:

error correction encoding (S110)data that are to be transmitted, and demultiplexing the error correction encoded data to a number of paths corresponding to a number of transmission antennas;

symbol-mapping (S120) the data demultiplexed based upon the respective paths in accordance with different symbol-mapping methods to symbols, respectively ;

adjusting (S130) power levels for the symbols, respectively ;

performing (S140) multi-input multi-output (MIMO) encoding on the symbol of which power levels are adjusted, and outputting MIMO-encoded signals to be transmitted to the transmission antennas ;

configuring(S150) signal frames of the outputted MIMO-encoded signals, respectively; and

modulating and transmitting (S160) the signal frames through the transmission antennas, respectively .
The method of claim 1, wherein the power levels varies depending upon the symbol-mapping methods.
A method for receiving a signal, comprising:

receiving (S210) signals from multiple antennas, and demodulating the received signals, respectively ;

parsing (S220) signal frames of the demodulated signals ;

performing (S230) MIMO decoding on signals in the parsed signal frames and outputting the MIMO-decoded signals to multiple paths ;

calibrating (S240) power levels of the MIMO-decoded signals on the multiple paths, respectively ;

symbol-demapping (S250) the calibrated signals on the multiple paths to bit streams by using different symbol-demapping methods, respectively ; and

multiplexing (S260) the bit streams and error correction decoding the multiplexed bit stream .
The method of claim 3, wherein the power levels are calibrated depending upon the symbol-demapping methods.
An apparatus for transmitting a signal, comprising:

an error correction encoding unit (310) configured to error correction encode data that are to be transmitted;

a demultiplexer (320) configured to demultiplex the error correction encoded data to a number of paths corresponding to a number of transmission antennas

a plurality of symbol mappers (330a, 330b) configured to symbol-map the data demultiplexed based upon the respective paths in accordance with different symbol-mapping methods to symbols, respectively

a plurality of power calibration units (340a, 340b) configured to adjust power levels for the symbols, respectively

a MIMO encoder (350) configured to perform multi-input multi-output (MIMO) encoding on the symbol of which power levels are adjusted, and outputMIMO-encoded signals to be transmitted to the transmission antennas

a plurality of frame mappers (360a, 360b) configured to configure signal frames of the outputted MIMO-encoded signals, respectively and

a plurality of modulators (370a, 370b) configured to modulate and transmit the signal frames through the transmission antennas, respectively.
The apparatus of claim 5, wherein the power calibration units (340a, 340b) adjust the power levels in accordance with the symbol-mapping methods, respectively.
An apparatus for receiving a signal, comprising:

a plurality of demodulators (420a, 420b) configured to demodulate the received signals, respectively

a plurality of frame parsers (430a, 430b) configured to parsing signal frames of the demodulated signals, respectively

a MIMO decoder (440) configured to perform MIMO decoding on signals in the parsed signal frames and outputting the MIMO-decoded signals to multiple paths

a plurality of power calibration units (450a, 450b) configured to calibrate power levels of the MIMO-decoded signals on the multiple paths, respectively

a plurality of symbol demappers (460a, 460b) configured to symbol-demap the calibrated signals on the multiple paths to bit streams by using different symbol-demapping methods, respectively

a multiplexer (470) configured to multiplex the bit streams; and

an error correction decoding unit (480) configured to error correction decode the multiplexed bit streams.
The apparatus of claim 7, wherein the power calibration units (450a, 450b) adjust the power level in accordance with the symbol-mapping methods.