KR100459133B1 - Apparatus and method for transmitting signal in multiple input multiple output system - Google Patents

Abstract

The present invention relates to a mobile communication system, and more particularly, to an apparatus and method for transmitting signals in a multiple input multiple output system. The apparatus for transmitting signals in the MIMO system according to the present invention includes M antennas arranged at equal intervals, M signal processors for encoding input sub data streams, and sub data streams encoded by the signal processors. A plurality of transmission blocks including delay generation means for generating different transmission delay times to the respective antennas; A preprocessing encoder which divides an input data stream into the sub data streams and adds an indicator for identifying the plurality of transmission blocks for each sub data stream; And demuxing means for inputting the sub data stream output from the preprocessor to each signal processor of the plurality of transmission blocks.

Description

Apparatus and method for transmitting signal in multiple input multiple output system}

The present invention relates to a mobile communication system, and more particularly, to an apparatus and method for transmitting signals in a multiple input multiple output system.

In general, a multiple input multiple output (MIMO) system includes a conventional single input single output (SISO) communication scheme and a single input multiple output (SIMO) system. Evolved from communication schemes, it has been developed for use in technologies that require high capacity data transmission. The MIMO system transmits information through M antennas and receives information through N antennas, and is considered as an essential element in a fourth generation communication system that requires high frequency efficiency.

1 is a view showing an example of a MIMO system according to the prior art.

Referring to FIG. 1, a transmitter divides an information source (or an information stream or a data stream) into M sub-streams and performs signal processing, and modulates the processed signal to M antennas. And a demodulator (103) for receiving and demodulating the signals transmitted from the transmitter with N antennas, and receiving multiple inputs for signal-processing the demodulated signals to restore the original information stream. It consists of multiple output processors 104.

2 is a diagram illustrating an example of a transmitter of a D-BLAST MIMO system according to the prior art.

3 is a diagram illustrating an example of a receiver for receiving a signal from the transmitter illustrated in FIG. 2.

2 and 3 illustrate a MIMO system using four transmit and receive antennas having a distance between antennas of 1.5 lambda and a diagonal-bell labs' layered space time (hereinafter, D). -BLAST) MIMO system.

First, the information stream to be transmitted is divided into M sub data streams having the same ratio by the demux 203 and encoded in the signal processor 202, respectively, and the encoded signal is transmitted to the ternary cyclic shifter 202. Is periodically connected to each antenna and transmitted to the receiver.

The signal processor 202 applies symbols generated by encoding the same information to the antenna with different transmission delay times. That is, the signals transmitted through each antenna include symbols encoded from the same information.

That is, the cyclic shifter 202 periodically changes the connection of the signal-processed sub-stream and the transmission antenna. After τ seconds, the connection of the signal-processed sub-stream and the transmission antenna is periodically changed and transmitted. By doing so, the transmitter employs a delay diversity scheme, in which the M signaled substreams transmitted on the fading channel are received by all N receive antennas. Here, since M transmit signals are received at all receive antennas, any one of the transmit signals is received without being seriously affected by the worst channel environment that may occur when passing through the multipath.

Thus, the symbols of the signal received at the receiver are detected diagonally at each spatial layer (identified by the receiving antenna) of the detector 301. That is, M symbols are received, symbols already detected from the received symbols are canceled, and undetected symbols are nulled to detect a desired symbol value. This process detects a desired symbol value along a diagonal line as many as the number of transmit antennas.

The nulling detects the desired symbol by removing the weakest signal from the detection of the strongest signal, and the canceling is a method of smoothing the detection of the remaining weak symbol by removing the already detected signals from the original received symbol.

The detected data symbols are then combined by the mux 302 to produce one data stream in each spatial layer, and finally the data streams of all antennas are combined at the maximum ratio in combiner 203.

The maximum ratio combining scheme is a reception scheme that maximizes the value of the output signal-to-interference ratio by multiplying each channel by a gain proportional to the square root of the signal-to-interference ratio (SNR) of each channel. The signal-to-interference ratios of these channels are added together to represent one signal-to-interference ratio.

4 is a view showing another example of a transmitter of the V-BLAST MIMO system according to the prior art.

FIG. 5 is a diagram illustrating an example of a receiver for receiving a signal from the transmitter illustrated in FIG. 4.

4 and 5 illustrate a MIMO system using four transmit and receive antennas with a distance between 4 antennas and a vertical-bell labs' layered space time (hereinafter, V-). BLAST) MIMO system.

4 and 5 have a configuration similar to that of FIGS. 2 and 3, respectively.

However, in FIG. 4, the signal processor 401 simplifies the encoding process by performing a vector encoding process that converts a simple bit into a symbol. The signal processor 401 encodes a plurality of sub data streams divided from one information. That is, in the signal transmitted through each antenna, M coded symbols divided from the same information are divided and transmitted through the plurality of antennas.

In addition, the detector 501 aligns the received M symbols according to the magnitude of the signal-to-interference ratio (SNR), and detects a desired symbol from among the aligned symbols with a good reception state.

Although the frequency efficiency of the system used in FIGS. 4 and 5 is lower than the frequency efficiency of the MIMO system used in FIGS. 2 and 3, it is advantageous in that the reception circuit can be implemented with a simplified receiver circuit.

That is, since the symbols transmitted in FIGS. 2 and 3 can cause fatal errors as they travel through the channel, the receiver fails to recover the original information stream from these symbols. And, the receiver becomes complicated and there are restrictions when applying channel coding. On the other hand, the frequency utilization efficiency is high.

On the other hand, although alternatively shown in Figures 4 and 5 can be implemented using a simplified receiving circuit, there is a disadvantage that the frequency utilization efficiency is low, and the antenna array spacing must be very wide. This is because there is a correlation of 10λ between each antenna so that there is no correlation, and at least 4λ can be practically ignored. (80% capacity when there is no correlation)

Therefore, it is necessary to devise a MIMO system scheme that takes advantage of the D-BLAST shown in FIGS. 2 and 3 and supplements the weak points of V-BLAST shown in FIGS. 4 and 5.

Accordingly, an object of the present invention is to provide a signal transmission apparatus and method in a multiple input multiple output system having high frequency utilization efficiency.

It is also an object of the present invention to provide an apparatus and method for transmitting signals in a multiple input multiple output system in which the arrangement of each antenna is efficiently arranged in a limited space.

The present invention also provides an apparatus and method for transmitting signals in a multiple input multiple output system with simple implementation.

In one aspect of the present invention, a signal transmission apparatus in a MIMO system according to the present invention includes M antennas arranged at equal intervals, M signal processors for encoding an input sub data stream, and each signal processor. A plurality of transmission blocks including delay generation means for generating different transmission delay times in the encoded sub data streams and applying them to the respective antennas; A preprocessing encoder which divides an input data stream into the sub data streams and adds an indicator for identifying the plurality of transmission blocks for each sub data stream; And demuxing means for inputting the sub data stream output from the preprocessor to each signal processor of the plurality of transmission blocks. In another aspect of the present invention, there is provided The apparatus for transmitting signals in a MIMO system includes: N antenna groups including a plurality of antennas arranged at equal intervals and arranged at different intervals from the same interval; A demultiplexer for dividing a data stream to be transmitted into N sub data streams including an indicator of an antenna group of the group; And a signal processor for signal processing the sub data streams, and for i increasing from 1 to N, a different transmission delay time is given to the i th signaled sub data stream through respective antennas of the i th group. In another aspect of the present invention, a signal transmission method in a MIMO system according to the present invention includes a plurality of antennas arranged at equal intervals, and is arranged at different intervals from the same interval. A multi-input multi-output system including N antenna groups, comprising: signal processing a data stream to be transmitted divided into N sub data streams including an indicator of a corresponding antenna group; And transmitting a different transmission delay time to the i th signal-processed sub data stream through each of the antennas of the i th group with respect to i increasing from 1 to N.

1 is a view showing an example of a MIMO system according to the prior art.

2 is a diagram illustrating an example of a transmitter of a D-BLAST MIMO system according to the prior art.

3 shows an example of a receiver for receiving a signal from the transmitter shown in FIG.

4 illustrates another example of a transmitter of a V-BLAST MIMO system according to the prior art.

FIG. 5 shows an example of a receiver for receiving a signal from the transmitter shown in FIG. 4; FIG.

6 is a diagram illustrating an example (four antennas) of a transmitter of a hybrid MIMO system according to the present invention.

7 shows an example of a receiver for receiving a signal from the transmitter shown in FIG. 6;

8A is a diagram showing a mutual polarization structure of a general V-BLAST.

8b is a diagram illustrating a dual polarization structure of a general V-BLAST.

8C illustrates a mutual polarization structure in a hybrid MIMO system according to the present invention.

8D illustrates a dual polarization structure in a hybrid MIMO system according to the present invention.

* Description of the symbols for the main parts of the drawings *

601 binary binary shifter

602: Signal Processor

603: Demux

604 preprocessor encoder

The present invention proposes a hybrid MIMO transmission / reception system that compensates for the disadvantages of V-BLAST while using high frequency efficiency and narrow transmission antenna spacing which are advantages of D-BLAST.

In addition, the system proposed in the present invention is a system in which the transmitting end does not directly know the state of the channel, and only the receiving end knows the state of the channel, that is, a system composed of an open loop.

Hereinafter, a configuration and an operation according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

6 is a diagram illustrating an example (four antennas) of a transmitter of the hybrid MIMO system according to the present invention.

FIG. 7 is a diagram illustrating an example of a receiver for receiving a signal from the transmitter illustrated in FIG. 6.

6 and 7 show a case where the number of transmitting and receiving antennas is the same and the simplest uses four. In addition, a D-BLAST transmitter having two antennas is considered as one structural unit, and the structural units follow the configuration of V-BLAST.

Here, the spacing of the antennas constituting the D-BLAST transmitter is 1.5 lambda as in the prior art. The antenna spacing of the plurality of D-BLAST transmitters constituting the V-BLAST is 4λ, as in the related art, using the D-BLAST transmitter as one structural unit. That is, in order to implement the V-BLAST MIMO system, 12 lambda is required when arranging four antennas, but only 7 lambda is required in a hybrid MIMO structure.

First, the data stream is appended with a header or indicator for distinguishing the D-BLAST structural units in the preprocessing encoder 604. This is to distinguish each D-BLAST unit of the transmitting end when receiving M signals from the receiving antenna. Signals transmitted through the antennas of the same D-BLAST component unit among the M signals have the same header or indicator.

The data stream to which the header or indicator is added is divided into M sub data streams of equal ratio by the mux 603 and provided to the signal processors 602a and 602b. Two signal processors arranged in parallel encode these sub data streams.

Each of the signal processors 602a and 602b encodes a plurality of sub data streams divided from one information. In detail, either signal processor 602a or 602b encodes the specific sub data stream divided as described above to have different transmission delay times. Signals according to these different transmission delay times are transmitted to the receiver through antennas included in the same D-BLAST component unit.

The binary cyclic shifter 601a or 601b periodically connects signals encoded in the same D-BLAST component unit with each antenna so that the signals are transmitted to the receiver through the corresponding antenna.

At the receiver, any one of the pre-processing decoders 701a checks the header or the identifier of the transmitted signal, so that the signal transmitted from the antenna of the same D-BLAST component unit is connected to at least two muxes 703a and 703b. The corresponding symbols are detected by the detector 702a.

The detector 702a is composed of a plurality of D-BLAST detectors (two examples in FIG. 7), and performs a function of detecting respective signals according to the transmission delay difference at the transmitting end. Here, the D-BLAST detectors constituting either detector (eg, 702a) are connected to different muxes 703a or 703b.

That is, the preprocessing decoders 701a to 701d are provided with the number of B-BLAST structural units, and the plurality of D-BLAST detectors provide signals having the same transmission delay among the detected signals to the same mux 703a or 703b. Similarly, the mux 703a or 703b is also provided by the number of D-BLAST structural units at the transmitting end.

Thus, either mux 703a or 703b muxes the signals with the same transmission delay to produce one bitstream, which provides this bitstream to combiner 704.

The combiner 704 combines signals with different transmission delays at a maximum ratio.

In addition, the configuration when polarization diversity is applied to the hybrid MIMO system proposed in the present invention is illustrated in FIGS. 8A to 8D in comparison with the general technology.

This configuration illustrates a configuration when polarization diversity is applied to an open loop hybrid MIMO system.

In general, polarization diversity includes a co-polarized structure and a dual-polarized structure. The former transmits the same polarization (e.g., transmits vertical polarization, respectively) at each antenna, and the latter transmits two polarizations of different vertical components (e.g., the first antenna is vertically polarized). And the second antenna is horizontally offset, wherein the first antenna is tilted at 45 ° and the second antenna is -45 °, respectively.

8A is a diagram illustrating a mutual polarization structure of a general V-BLAST.

Here, in order to reduce the distance between antennas, the signal is transmitted with only 80% of transmission capacity when there is no correlation, and instead the distance is reduced from 10λ to 4λ. Thus, a total of 6 lambda is used to arrange four antennas, thereby making it possible to construct a more dense antenna structure than the method using only spatial diversity.

8B is a diagram illustrating a dual polarization structure of a general V-BLAST.

Here, a total of 6 lambda is used to arrange four transmit antennas, thereby making it possible to construct a more dense antenna structure than the method using only spatial diversity.

8C illustrates a mutual polarization structure in a hybrid MIMO system according to the present invention.

Here, four antennas are configured because each pair has an antenna spacing of 1.5λ and each pair has a spacing of 4λ according to transmission characteristics (each pair sends the same signal, one of which has one symbol delay). 7λ is used to do this.

8D illustrates a dual polarization structure in a hybrid MIMO system according to the present invention.

That is, in FIG. 8D, antennas of the same D-BLAST unit are arranged at the same interval, and transmit signals having different transmission delay times and different phases (in the present invention, examples of vertical polarizations transmitting mutually orthogonal signals). do. In addition, the antennas of the same D-BLAST unit are disposed at an angle of 45 degrees with respect to the reference axis.

In this case, the total length of the same D-BLAST unit is arranged, even if the antenna of the same D-BLAST unit transmits the same phase signal (for example, 7λ) 1/2 times (3.5λ) of the total length Suffice.

Therefore, it can be arranged at a minimum interval, and may be arranged at a further interval for a better transmission rate. In detail, it can be seen that each pair has a transmitter structure for the simplest D-BLAST and is a V-BLAST transmitter structure as a whole.

In addition, in addition to the compactness of the antenna array space, polarization diversity provides another advantage, which is combined with spatial diversity to provide a reception gain when the spatial correlation is high in a wireless channel.

Therefore, it plays a role of reducing the deterioration of transmission capacity in the weak condition of MIMO system.

As described above, the present invention has the following effects.

First, the use of polarization diversity can reduce the base station antenna spacing by 50% by configuring a more compact system.

Second, there is an effect that can mitigate the reception gain resulting from the diversity effect of the fundamental performance degradation of the MIMO system that occurs when the channel state changes from uncorrelated state to correlation state due to the constantly changing channel change.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (7)

M antennas arranged at equal intervals to transmit mutually orthogonal signals, M signal processors encoding the input sub data streams, and different transmission delay times are generated in the sub data streams encoded by the signal processors. A plurality of transmission blocks including delay generation means applied to each of the antennas; A preprocessing encoder which divides an input data stream into the sub data streams and adds an indicator for identifying the plurality of transmission blocks for each sub data stream; And And demuxing means for inputting the sub data stream output from the preprocessor to each signal processor of the plurality of transmission blocks. delete The apparatus of claim 1, wherein the antennas are disposed at an angle of 45 degrees with respect to a reference axis. 2. The apparatus of claim 1, wherein an interval between antennas in each transmission block is smaller than an interval between each transmission block. 2. The apparatus of claim 1, wherein an interval between antennas in each transmission block is smaller than an interval between each transmission block. N antenna groups including a plurality of antennas arranged at equal intervals and arranged at different intervals from the same interval; A demultiplexer for dividing a data stream to be transmitted into N sub data streams including an indicator of an antenna group of the group; And a signal processor for signal processing the sub data streams, Signal transmission in a multi-input multiple output system for i, which increases from 1 to N, is transmitted by giving different transmission delay times to the i-th signaled sub data stream through each antenna of the i-th group. Device. In the multiple input multiple output system comprising a plurality of antennas arranged at equal intervals, and comprising N antenna groups arranged at different intervals from the same interval, Dividing the data stream to be transmitted into N sub data streams including an indicator of a corresponding antenna group and performing signal processing; And Signal transmission in a multi-input multiple output system comprising transmitting, by i, a different transmission delay time to the i-th signaled sub data stream through each antenna of the i-th group, for i increasing from 1 to N Way.