KR20050087551A - Method for transmitting a radio signal using channel information - Google Patents

Abstract

The present invention relates to a wireless signal transmission using channel information, and the wireless signal transmission method according to the embodiment of the present invention comprises the steps of (a) extracting wireless channel information from the received first wireless signal, and the extracted wireless channel (B) determining whether the first antenna that transmits the first wireless signal from the information is located on a line-of-sight; and the method of transmitting the first wireless signal according to the determination result. And (c) transmitting the second wireless signal to the antenna.

Description

Method for transmitting a radio signal using channel information {Method for transmitting a radio signal using channel information}

The present invention relates to a wireless signal transmission method using channel information, and more particularly, to a method for determining a wireless signal transmission method by checking whether a line-of-sight environment from the channel information.

With the proliferation and development of digital products, digital technology is demanding the development of high speed wireless local area network (WLAN) over 100Mbits / sec. One of the candidates for the high speed technology of next-generation wireless LAN that can meet such development needs is the Multiple Input Multiple Output (MIMO) technology.

In relation to the MIMO, the multiple transmit / receive antenna technology uses a multiple antenna for a transmitter and a receiver, and simultaneously transmits different data at the same time. It is divided into " Spatial Diversity " technology for obtaining transmission diversity by transmitting the same data through multiple transmission antennas.

Among these, the “Spatial Multiplexing” technology is an adaptive array antenna technology that uses plural antennas to electrically control directivity. Doubling. At this time, the frequency and transmission timing used by each antenna are the same.

In a conventional single input single output (SEE) -based wireless LAN (IEEE 802.11 or 802.11a) system, the so-called link adaptation (Link adaptation) to change the transmission method according to the communication situation between stations The adaptation method is used for more efficient transmission by reflecting the data transmission of the current transmitter by using the wireless channel state as a factor. The link adaptation as described above Adaptation method is also applied to MIMO system.

1 is an exemplary diagram illustrating a relationship between a MAC layer and a physical layer in the IEEE 802.11 standard.

The MAC layer exchanges data with the upper layer LLC layer using MAC SAP (MAC Service Access Point) (not shown), and the PHY layer (PHY) with PHY SAP (Physical Service Access Point (not shown)). Receive.

Although not shown in FIG. 1, the PHY layer may be divided into two sublayers, namely, a PLCP layer (Physical Layer Convergence Procedure Sublayer) and a PMD (Physical Medium Dependent Sublayer). The PLCP and PMD sublayers send and receive data through the PMD SAP (not shown).

The PLCP sublayer is a layer defined to ensure that the IEEE 802.11 MAC layer has minimal association with the PMD sublayer. That is, the service generated in the MAC layer is converted into an orthogonal frequency division multiplexing (OFDM) physical layer or a signal in the OFDM physical layer into a signal suitable for the service in the MAC layer. Is a block that can operate independently regardless.

On the other hand, the PMD sublayer is a layer providing a method for the OFDM physical layer to send and receive signals. That is, it is closely related to the OFDM physical layer, and serves to change the service in the IEEE 802.11 MAC to be suitable for the OFDM physical layer operation.

The physical layer of the receiving station, more specifically the PLCP sublayer, delivers the RXVECTOR to the MAC layer via the PHY SAP (not shown), where parameters such as Received Signal Strength Indicator (RSSI) are present. In addition, the MAC layer of the transmitting station transmits TXVECTOR to the PLCP sublayer through the PHY SAP (not shown), which includes a data rate, power, etc. of data transmitted through signal modulation in the PHY layer. There are parameters of.

That is, when data to be transmitted in the MIMO system is generated, the MAC layer accepts an MSDU (MAC Service Data Unit) corresponding to the data, which is determined by the link adaptation module at the moment when the channel license is acquired in an appropriate manner. TxPower and TxRate information is attached to the MPDU (MAC Protocol Data Unit) and transmitted to the PHY layer, and the PHY layer transmits the TxPower and TxRate in the form of a PPDU (PLCP Protocol Data Unit).

 When the PPDU is received at the PHY layer, the RxRate, Received Signal Strength Indicator (RSSI), etc. obtained when the PPDU is received are attached to the MPDU and transmitted to the MAC layer. This is reflected when selecting the next tx method.

FIG. 2A is an exemplary diagram illustrating a function applied to TXVECTOR and its parameters, and FIG. 2B is an exemplary diagram illustrating a function applied to RXVECTOR and its parameters.

TXVECTOR is used as an argument of the PHY-TXSTART.request function, and RXVECTOR is used as an argument of the PHY-RXSTART.indicate function.

As a parameter of TXVECTOR, "LENGTH" indicates the number of data octets that the current MAC layer intends to transmit through the physical layer, and has a value in the range of 1-4095. "DATARATE" refers to the transmission rate of the signal to be transmitted in the WLAN. This value has a transmission rate supported by IEEE 802.11a, which is 6, 9, 12, 18, 24, 36, 48, And 54 (unit Mbps) can be selected. However, 6, 12, and 24 are necessary transmission rates.

SERVICE consists of seven null bits for the initialization of the scrambler and nine null bits left for future use. Also, 'TXPWR_LEVEL' is used to determine the power of a transmission signal to be used in the current transmission, and has a value of 1-8.

As a parameter of the RXVECTOR, "LENGTH" means a value that the LENGTH field has in the received PLCP header, and has a value between 1-4095 as in the TXVECTOR 70. RSSI detects the energy of the signal observed from the antenna receiving the current data and indicates its strength, and determines when receiving the PLCP preamble. And, "DATARATE" refers to the transmission rate of the currently received data, and may have the same value as in TXVECTOR, and "SERVICE" is determined to be null as in TXVECTOR.

In general, if only the line of sight (hereinafter referred to as 'LOS') is transmitted only in the MIMO method, the transmission rate is lower than that of the SISO method in the LOS environment. Therefore, in the LOS situation, it is necessary to transmit data in the SISO method rather than the MIMO method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of operating in a SISO by determining whether a corresponding channel is LOS while operating in a MIMO system.

In order to achieve the above object, the wireless signal transmission method using the channel information according to an embodiment of the present invention comprises the steps of (a) extracting the radio channel information from the received first radio signal, and (B) determining whether the first antenna that has transmitted the first wireless signal is located in a line-of-sight, and transmitting the second signal to the first antenna by varying the wireless signal transmission method according to the determination result. (C) transmitting a wireless signal.

Advantageously, said first radio signal comprises a radio signal modulated by an Orthogonal FDM method.

Preferably, the radio channel information includes matrix information of at least two subcarriers constituting the first radio signal modulated by an orthogonal frequency division multiplex (FDM) method. In this case, step (b) preferably compares a result of calculating at least two elements constituting a matrix for each of the subcarriers and a first threshold value (b)- (B)-determining whether the first antenna is located on a line-of-sight using the comparison results of the number of subcarriers obtained from step 1 and step (b)- Includes two steps. Preferably, the result of computing at least two elements constituting a matrix for each of the subcarriers is a determinant for the matrix, an inverse of the determinant for the matrix, or two It includes the ratio to the element.

Preferably, in the step (c), when the first antenna is located in line-of-sight, the second wireless signal is transmitted through one second antenna and the first antenna is transmitted. If the antenna is not located line-of-sight, transmitting the second wireless signal through at least two of the second antennas.

Specific details of other embodiments are included in the detailed description and the drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and only the embodiments make the disclosure of the present invention complete, and those of ordinary skill in the art to which the present invention belongs. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

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

3 is an exemplary diagram illustrating a relationship between a MAC layer and a physical layer according to an embodiment of the present invention.

The PHY layer extracts channel information through channel measurement while receiving a preamble, and determines whether the corresponding channel is an LOS through the extracted channel information. Then, the LOS information is attached to the PSDU (PLCP Service Data Unit) or MPDU (MAC Protocol Data Unit) extracted from the received frame and transmitted to the MAC layer. In the MAC layer, LOS information is updated in a space for storing status information of a station distinguished by a source address of a received MPDU. When transmitting the MPDU to the corresponding station, the MAC layer utilizes LOS information in the state information of the station and attaches information on whether the transmission method is MIMO or SIMO to the PHY layer according to the LOS. The PHY layer transmits the PSDU (PLCP Service Data Unit) in a manner that is received.

4A is an exemplary diagram illustrating a function and a parameter applied to a TXVECTOR according to an embodiment of the present invention, and FIG. 4B is an exemplary diagram illustrating a function and a parameter applied to an RXVECTOR according to an embodiment of the present invention. That is, by adding the 'SISO' factor to the conventional TXVECTOR, and the 'LOS' factor to the conventional RXVECTOR can perform the operation as shown in FIG.

FIG. 5 is a flowchart illustrating a method of determining an LOS using channel information according to an embodiment of the present invention. FIG.

In the MIMO system, when a radio signal modulated by an orthogonal FDM method is received (S510), each matrix information of 48 subcarriers is obtained through a fast fourier transform (FFT) process. It may be (S520). In this case, the matrix information indicates information about a channel between the reception antenna and the transmission antenna, which will be referred to as an 'H matrix'. The H matrix is stored in the MIMO system (S530), the elements constituting the stored H matrixes are operated according to a predetermined method (S540), and the threshold value is determined by the calculated result value. value (S550) to determine whether the LOS (S560).

At this time, as a preferred embodiment of the operation, the inverse of the determinant or determinant for each H matrix is obtained, and the inverse of each determinant or determinant is a predetermined threshold. If LOS is small or large compared to the threshold value, for example, LOS is small in comparison with the threshold value, it is set to 1 in this case and 0 otherwise. Then, if a value of 1 or 0 is assigned to the H matrix for all 48 subcarriers, all of the values are added, and when the sum exceeds a predetermined value, the LOS is finally determined to be LOS. will be.

In this case, as another embodiment of the operation, two arbitrary elements constituting the H matrix for each subcarrier may be selected, and the ratio between the selected elements may be compared with a predetermined threshold. It is also possible to select as many elements as to perform other types of operations.

On the other hand, the LOS determination process using the channel information as described above is preferably made in the PHY layer, the determination of which of the MIMO method or the SISO method to transmit data by using the LOS determination result in the MAC layer Can be done.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited to drawing.

According to the embodiment of the present invention, the performance of the MIMO system can be improved by using the method of identifying the LOS environment and transmitting the data in a relatively fast MIMO method when there are few LOS components, and transmitting the data in a relatively stable SISO method when there are many LOS components. There is an effect to improve.

1 is an exemplary diagram illustrating a relationship between a MAC layer and a physical layer in the IEEE 802.11 standard.

2A is an exemplary diagram illustrating a function applied to a TXVECTOR and its parameters.

2B is an exemplary diagram illustrating a function applied to RXVECTOR and its parameters.

3 is an exemplary diagram illustrating a relationship between a MAC layer and a physical layer according to an embodiment of the present invention.

4A is an exemplary diagram illustrating a function applied to a TXVECTOR and its parameters according to an embodiment of the present invention.

4B is an exemplary diagram illustrating a function and parameters thereof applied to an RXVECTOR according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating a method of determining an LOS using channel information according to an embodiment of the present invention. FIG.

Claims (8)

(A) extracting radio channel information from the received first radio signal; (B) determining whether a first antenna that transmits the first radio signal is located in a line-of-sight from the extracted radio channel information; And (c) transmitting a second radio signal to the first antenna by varying a radio signal transmission method according to the determination result. The method of claim 1, And the first radio signal is a radio signal modulated by an orthogonal frequency division multiplex (FDM) method. The method of claim 1, And the radio channel information is matrix information for at least two subcarriers constituting the first radio signal modulated by an orthogonal frequency division multiplex (FDM) method. The method of claim 3, (B) step (b) -1 comparing the result of calculating at least two elements constituting a matrix for each of the subcarriers and a first threshold value; And (b) -2 determining whether the first antenna is located in line-of-sight using the comparison result of the number of subcarriers obtained from step (b) -1. Wireless signal transmission method. The method of claim 4, wherein And a resultant value of calculating at least two elements constituting a matrix for each of the subcarriers is a determinant for the matrix. The method of claim 4, wherein And calculating a result of calculating at least two elements constituting a matrix for each of the subcarriers, being a reciprocal of a determinant for the matrix. The method of claim 4, wherein And a result of calculating at least two elements constituting a matrix for each of the subcarriers is a ratio with respect to two elements. The method of claim 1, In the step (c), when the first antenna is located in line-of-sight, the step (c) transmits the second radio signal through one second antenna, and the first antenna is visible. transmitting the second wireless signal through at least two or more second antennas when not located in line-of-sight.