MXPA06008335A - Method and apparatus for setting, transmitting and receiving data for virtual carrier sensing in wireless network communication - Google Patents

Abstract

Methods and apparatuses for setting, transmitting, and receiving virtual carrier sensing information in wireless network communications are provided. A receiving station in a wireless communications network receives a frame transmitted according to various modulation schemes and extracts information concerning virtual carrier sensing from a portion of the frame modulated using a basic modulation scheme, so that virtual carrier sensing is achieved using the extracted virtual carrier sensing information.

Description

For two-lener codes and other abbreviations. refer to the "Guidance Notes on Codes and Abbreviations" appearing to the ihe begin-ning ofeach regular issue of the PCT Gazette.

METHOD AND APPARATUS FOR SETTING, TRANSMITTING AND RECEIVING DATA FOR DETECTION OF VIRTUAL CARRIERS IN NETWORK COMMUNICATION WIRELESS FIELD OF THE INVENTION The present invention relates to a wireless communication method, and more particularly, to the detection of virtual bearers in a network - of communications using various data transmission speeds, and a method of wireless communications. -cas-that uses it. BACKGROUND OF THE INVENTION Recently, there is a -increasing demand for ultra high-speed communication networks due to the widespread public use of the Internet and a rapid increase in multimedia data. Since the emergence of local area networks (LAN, for its acronym in English) in the late eighties, the speed of data transmission over the Internet has increased dramatically from about 1 Mbps to about 100 Mbps today. Therefore, high-speed Ethernet transmission has gained popularity and is in widespread use today. So far, intensive research has been under way in the area of Ethernet at gigabit speeds. A growing interest in connections and network communications " Ref .: 17448"wireless has promoted the research and implementation of wireless local area networks (WLAN). Now, there is a growing availability of WLAN to consumers. Although the use of WLAN can be obstructed due to deterioration in performance in terms of lower transmission speeds and poorer stability compared to wired LANs, WLANs have several advantages, including wireless network transmission capacity, greater mobility, etc. Subsequently, the WLAN markets have been growing. Due to the need for higher transmission speeds and the development of wireless transmission technology, the initial IEEE 802 standard; 11, which specifies a transfer speed of 1-2 Mbps, has evolved into more advanced standards including 602. llb, 802. llg and 802.11a. Recently, conferences have been organized to establish the new standard. IEEE, 8O2.11g. The IEEE 802.11 standard, which specifies a transmission speed of 6-54 Mbps in the National Information Infrastructure band < NII) of 5-GHz, uses orthogonal frequency division multiplexing. { OFDM, for its acronym in English) as transmission technology. With a growing public interest in the transmission of OFDM and - the use of the 5 GHz band, the IEEE 802.11a has been given much more attention than the other inal LAN standards. - Recently, wireless Internet services using WLAN have been launched, called "Nespot", and offered by Korea Telecommunication (KT) Corporation, Korea. The Nespot service provides access to the Internet using a WLAN in compliance with IEEE 802.11b, commonly referred to as Wi-Fi that refers to wireless fidelity. Communication standards for wireless data communication systems, which have been completed and enacted or that have been under investigation and discussion, include WCDMA (Broad Code Division Wide Access), IEEE 802-.llx, Bluetooth, IEEE 802.15 .2, eto. , known as 3G communication standards - (third generation). The most common and widely known wireless data communication standard is IEEE 802.11b, a series of IEEE 802. llx. An IEEE 802.11b WLAN standard provides data transmission at a minimum speed of 11 Mbps and uses the Industrial, Scientific, and Medical (ISM) band of 2.4 GHz, which can be used under an electrical field. default electric without permission. With the recent widespread use of IEEE 802.11a as WLAN, which provides a maximum data rate of 54 Mbps in the 5 GHz band using OFDM, IEEE 802. llg developed as an extension to IEEE 802.11-n for MIMO (multiple input multiple output) is being investigated intensively.

The ethernet and the WLAN, which are currently being widely used, both use a multiple carrier-sensing access method (CSMA, for its acronym in English). The CSMA method is used to determine if a channel is in use or not. When it is determined that the channel is not in use, that is, when the channel is inactive, then data is transmitted. If the channel is busy, data retransmission is attempted after a predetermined period of time. A multiple carrier detection access with a collision detection method (CSMA / CD) is an enhancement of the CSMA method, which is used in a wired LAN, while a multiple carrier detection access with a collision cancellation method (CSMA / CA) is used in packet-based wireless data communications. In the CSMA / CD method, a station suspends signal transmission when a collision is detected during transmission. Unlike the CSMA method which checks again whether a channel is busy or not before transmitting data, in the CSMA / CD method, the station suspends the transmission of signals when a collision is detected during the transmission of signals and transmits a congestion signal to another station to report the occurrence of the collision. After the transmission of the congestion signal, the station must wait for a period of random withdrawal and then restart by transmitting the signals. In the CSMA / CA method, the station does not transmit data immediately after the channel becomes inactive but must wait for a period of random withdrawal after a predetermined duration before transmission to avoid collision of the signals. If a signal collision occurs during transmission, the duration of the random withdrawal period is doubled to decrease the probability of collision (interference). Figures 1 and 2 illustrate a conventional process of transmitting and receiving a frame in a containment period. A frame is received in a station under the assumption that the received frame has been transmitted to another station as a receiving station. First, with reference to Figure 1, a frame transmitted through a channel is received by a station without error. A station can not transmit a frame through a channel while the frame is being received at another station: this method is called physical bearer detection. A media access control (MAC) header of the received frame contains duration information. This duration information contains a length of time taken from the transmission of a frame by a transmitting station to the reception of an acknowledgment frame (ACK) of a receiving station. The receiving station receives the transmitted frame from a transmitting station and transmits the ACK frame after a short duration, known as interframe short space (SIFS), to the transmitting station. A station establishes a network allocation vector (NAV) using duration information. This method is called virtual bearer detection. In order to -each station transmits a frame to another station, the station waits for a distributed frame spacing (DIFS) after the lapse of a NAV time period, and then performs a random recall , and finally transmits the plot. However, when the carrier is detected in a medium while performing the random withdrawal, the station suspends the random withdrawal, and waits until the channel is empty. Afterwards, the station waits for a DIFS, and performs the random withdrawal. With reference to Figure 2, a station can not receive a frame transmitted through a channel. A station can not use a channel while a frame is being transmitted through the channel, which is called physical carrier detection. When a frame transmitted through a channel can not be received due to the occurrence of an error, the station can not establish a NAV value because the NAV value is provided as information loaded in the frame. Therefore, before the transmission of a frame, the station. that is unable to establish a NAV value must wait for the duration of an extended frame spacing (EIFS), which is longer than a DIFS, and then perform a random recall. In Figure 2, when the channel becomes inactive due to a failure in receiving a frame, the station waits for an EIFS. An ACK frame corresponding to the frame is transmitted through the channel before the. EIFS, that is, immediately after a SIFS. If the station can not receive even the ACK frame, the station must wait for another EIFS which starts after the duration of the ACK frame and finally performs a random withdrawal when the channel is inactive, in order to transmit the plot. In other words, when the station can not perform a virtual bearer detection due to a failure to obtain a value of? AV, the station has to wait longer than when the frame is received without error. Due to this, the probability that the station loses in the containment of the frame transmission could increase, thus negatively affecting the data transmission efficiency. The occurrence of such an error may be more distinguishable in a communication environment in which various modulation schemes and coding rates are used, as in IEEE 802.11a communications. In other words, when the frames are transmitted to a station at a rate that is not supported by the station, the station can not interpret the transmitted frame so that the duration information can not be obtained from a MAC header of the frame. Consequently, the detection of the virtual bearer of a frame transmitted at a rate not available for reception by a station can not be achieved, resulting in the deterioration of the performance of the station. BRIEF DESCRIPTION OF THE INVENTION Technical Problem In more detail, the problems associated with the detection of conventional virtual bearer will be described with reference to FIGS. 1 and 2. In contrast to physical bearer detection, virtual bearer detection (VCS, its acronym in English) assumes that a medium is occupied for a predetermined duration. While physical bearer detection is achieved based on actual wireless media measurements, the virtual bearer detection is performed in such a way that a predetermined selected value is established between received / transmitted data, the duration of the occupation of a medium is determined. estimated using the selected default value, and then the data transmission begins after the estimated duration has elapsed. That is, unlike physical carrier detection, virtual bearer detection can not be performed properly when the data is not received successfully. In a normal virtual bearer detection operation, as shown in Figure 1, when a network allocation vector (NAV), as information necessary for virtual bearer detection, is normally received, it is possible to identify how much will be occupied ( active) the medium, reading the value of NAV. On the other hand, when an error occurs, that is, when there is an error in reading a received frame, as shown in Figure 2, a NAV value of the frame can not be read. Therefore, the station has to wait for more than one NAV period, for example, an EIFS (Extended Framespace) in accordance with IEEE 801.11a. Now, the reasons why the problems posed above have been generated will be described with reference to Figure 3. Figure 3 illustrates a conventional carrier detection, which supports two types of carrier detection structures: physical bearer detection and virtual bearer detection. With respect to the physical detection structure, the information stored in a physical layer 210 has a structure 212. A physical layer convergence procedure preamble (PLCP) 214 is a PLCP synchronization signal for the purpose of informing in advance what data in the physical layer 21 will be transmitted, A signal 216, as indicated by the SIGNAL, is preceded by the preamble PLCP 214, a SIGNAL is modulated by a basic modulation scheme, and carries information that is necessary to receive a next data field 218, as indicated by DATA. The SIGNAL 216 will be described later in detail with reference to Figures 8 to 10. The information contained in the SIGNAL 216 has a segment, as indicated by TASA, corresponding to a modulation scheme used in the transmission of DATA 218. This information allows the transmission / reception of data using various modulation schemes. As shown in Figure 3, the physical carrier detection is implemented based on the question of whether or not the medium receives a certain signal. Upon receiving the PLCP preamble 214, the physical layer 210 informs a media access control layer (MAC) 220 that the physical layer 210 is busy, by a busy signal 222. Also, at a time when the data reception terminates, that is, when the channel becomes inactive as indicated by the reference number 228, the physical layer 210 informs the MAC layer 220 that terminates the use of the physical layer 210. In the detection of physical bearer, however, the transmission of data to an arbitrary station may not be accepted by another station. In this case, it is necessary to perform virtual bearer detection. In the virtual bearer detection, a duration value (NAV) in an MPDU of the DATA 218 is read by the MAC layer 220 to recognize whether the medium is busy for a corresponding duration. Here, the MPDU, which is an abbreviation for MAC protocol data unit, refers to data adopted by a MAC to transmit to another MAC connected to the network. However, the NAV value can be read only when a data field is normally received. Therefore, if a receiving station is only capable of receiving a signal field but is not able to read the modulated data field using various schemes, a NAV value set in the data field can not be read. What is needed is a communication method capable of improving the performance of a station by ensuring the detection of virtual channels using frames transmitted at various speeds. Technical solution The present invention has been proposed in accordance with the needs described above. One aspect of the present invention is to provide a virtual carrier detection method in wireless network communications that supports multiple speeds and a wireless communication method using them. Another aspect of the present invention provides a method of detecting virtual bearer in MIMO communications and a wireless communication method and apparatus, which employs the same. According to an exemplary embodiment of the present invention, there is provided a method for establishing virtual carrier detection data in wireless network communications, the method comprising receiving a transmitted frame using various modulation schemes and extraction data for carrier detection virtual of a modulated segment of the frame based on a basic modulation esguema, and establishing the detection, of carrier, -virtual using the. extracted data. . Preferably, in the reception of the frame, the modulation scheme used comprises multiplexing of. orthogonal frequency division .. - .. In the reception of the frame, the data for the virtual bearer detection is preferably added in the modulated segment of the frame based on the basic modulation scheme that has a data rate that is supported by a stanchion, preceded by. a synchronization signal. The extraction of the data is preferably carried out after verifying whether there is an error in the modulated segment of the frame based on the basic modulation scheme. . The establishment of virtual bearer detection data may comprise transmitting the. data to a layer. physical.

The method of establishing virtual carrier detection data in wireless network communications may further comprise storing the data as a vector parameter of a physical layer virtual bearer detection indicator (PHy-RXINlCIO.indicator) and transmitting the same to the physical layer. The value of? AV stored in a signal segment is also stored in a data segment to be received in a next step. In other words, the same NAV value in the data segment is stored in the signal segment. BRIEF DESCRIPTION OF THE FIGURES The foregoing and other features and advantages of the present invention will be more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying figures in which: Figures 1 and 2 illustrate conventional processes of transmission and reception of a plot in a period of contention; Figure 3 illustrates examples of conventional physical bearer detection and virtual bearer detection frame structures and corresponding frame formats; Figure 4 illustrates a data transmission method for virtual bearer detection in accordance with an exemplary embodiment of the present invention; Figures 5 to 7 illustrate conventional virtual bearer detection and virtual bearer detection in accordance with an exemplary embodiment of the present invention; Figures 8 to 10 illustrate a PDDU (PLCP Protocol Data Unit) frame format as defined by IEEE 802.11a, and modified PDDU frame formats of example in accordance with the present invention; Figure 11 shows a table of information related to modulation schemes in an IEEE 802.11a wireless network communication; Fig. 12 is a flow diagram illustrating a virtual bearer detection method in accordance with an exemplary embodiment of the present invention; Figure 13 illustrates a difference between a conventional signal reception method and a PLCP reception method in accordance with the present invention; Fig. 14 is a flow chart illustrating the data transmission method in accordance with an exemplary embodiment of the present invention; Figure 15 illustrates a difference between the conventional signal transmission method and a transmission method in accordance with the present invention. Figure 16 illustrates the virtual bearer detection method in accordance with another example embodiment of the present invention; and Figure 17 illustrates a MIMO PPDU structure in accordance with an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION The present invention is described below in the context of an orthogonal frequency division multiplexing modulation (OFDM) via a WLAN communication. IEEE 802.11a. However, it will be appreciated that the teachings of the invention discussed herein are not limited thereto. That is, the invention is applicable to any wireless communication system using - several modulation schemes. To find a solution for delay problems caused by conventional virtual bearer detection technology, the present invention proposes a new virtual bearer detection method, which will now be described with reference to Figure 4: As described above , in order for all stations to establish their respective NAVs, duration information 324 is included in a signal that is transmitted by a basic modulation scheme. Therefore, a physical layer 310 can transmit the value of? AV (duration) 324 to a MAC 320 layer. PHY-RXINICIO. indication ', which provides information relating to the reception of the NAV value of the physical layer 319 by the MAC 320 layer, may have a vector value. For this purpose, the values of previous vectors must be changed, which will be described later with reference to Figures 13 and 15. As in the conventional method, the NAV value can also be stored in a data field. In accordance with the present invention, the NAV value can be transmitted regardless of the reception speed of a station,. even in a wireless network communication environment that uses several modulation schemes. Figures 5 to 7 illustrate a method of virtual bearer detection in accordance with an exemplary embodiment of the present invention, in which the NAV value can be read even when a continuous frame is not received. In detail, Figure 5 illustrates that a frame is normally received by a receiving station. When the reception of the frame ends, a station can read a NAV value of the received frame, and the station then waits for a duration of NAV 450 for a virtual bearer detection. After a span of a period of Distributed Frame Spacing (DIFS) 420 and a random withdrawal period 440, the next frame may be transmitted. In some cases, • where a receiving station does not support an appropriate data reception speed, a frame can not be • received: • by the receiving station and not-a NAV value can be read from the frame, as shown in Figure 6. In such a case, the receiving station must wait for a period of Extended Frame Spacing (EIFS) 430, which is longer than the duration corresponding to the NAV value. Then, after the lapse of a random withdrawal period, the data can be transmitted, which has already been described with reference to Figure 1. In the present invention, data not received by a station is described with reference to the figure 7. Although data can not be received by the receiving station, data transmission can take place after the lapse of a NAV period and a period of DIFS 460, as shown in Figure 7. The NAV period obtained from a known NAV value stored in a signal segment. As a result, a waiting period can be shortened due to a reception error. Figures 8 to 10 illustrate a conventional PPDU frame format (PLCP Protocol Data Unit) as defined by IEEE 802.11a, and modified example PPDU formats for representation of the present invention. The PPDU is a complete PLCP (Physical Layer Convergence Procedure) frame, which includes a PLCP header, a PSDU, queue bits and attenuation bits. First, PLCP will be briefly described. A relatively complicated physical layer (PHY) is required when using radio waves in it. A physical layer in compliance with IEEE 802.11a includes a PLCP and a PDM system (Dependent on the Physical Environment). The PLCP, which is a top layer portion of the physical layer in an IEEE 82.11 network, matches a frame of a MAC layer with a medium. Each physical layer has its own PLCP, which provides an auxiliary frame to the MAC layer. The PMD system is responsible for the transmission of a radio frequency (RF) signal to another station in order to transmit the MAC layer frame. The PLCP header in accordance with an illustrative embodiment of the present invention stores basic information required for the interaction between the PHY layer and the MAC layer. A conventional frame format will be described below. The SIGNAL shown in Figure 8 is modulated by • a basic modulation scheme, ie, binary phase shift transmission (BPSK) with r = 1/2, and transmitted as an OFDM symbol, denoted by 520. The reason for using the basic modulation scheme is to allow any station to read the SIGNAL because the SIGNAL provides very important information for the next frame to be received. The information stored in the SIGN (an OFDM symbol) 520 includes a 4-bit RATE, that is, a modulation speed to read data that will be applied in a next stage.

Reserved 1 bit, LONGITUDE 510 of 12 bits, and Tail of 6 bits. A service bit field, denoted by SERVICE, is included in the PLCP header but is carried in combination with the DATA due to an OFDM symbol characteristic based on BPSK, ie, only 24 bits are transmitted by the symbol of OFDM. The data rate, the coding rate, and data bits per OFDM symbol, including a basic modulation scheme, BPSK with R = 1/2, are shown in Figure 11, as indicated by the reference numbers 610, 630 and 66O, respectively. The SIGNAL is transmitted at the rate of 'lowest coding of € Mbit / s (610 shown in Figure 11), and a total of 24 bits of data per symbol can be transmitted at the lowest coding rate, ie R- = 1/2, or which allows all stations to read the SIGNAL. • The encoding speed (R) 630 is -referred- to a relation between bits that carry information for error verification and bits that carry information that will actually be transmitted. Half of a total of 48 bits encoded by OFDM symbol, ie 24 bits, are transmitted as real data, as indicated by the reference number 660. In accordance with example frame formats of the present invention, as shown in Figures 9 and 10, each signal field, as indicated by SIGNAL, includes two OFDM symbols, which is to store in it the NAV value described above. Also, for compatibility with conventional protocols, a reserved one-bit field is set for transmission. The number of duration bits (duration information) 530, 550 is set to be equal to the value of NAV stored in the DATA. Also, the SIGNAL is transmitted as two symbols, indicated by the reference numbers 540 and 560, where one of the two symbols is for storing the duration information. Therefore, when using BPSK with r = 1/2, whereby a total of 24 data bits per symbol can be transmitted, a total of 48 bits of data can be transmitted using the frame formats shown in FIGS. and 10, with the addition of 8 attenuation bits. When using other wireless communications protocols, a NAV value can be added. According to the conditions of the various embodiments of the present invention, the value of? AV can be stored in the DATA, which is modulated using the basic modulation scheme, or both in DATA and in SIGNAL.

As described above, a NAV value can be established by modifying a conventional PPEU frame structure. It is also possible to set a value of? AV with the conventional IEEE 802.11a standard PPDU frame format (Figure 8). This will be described with reference to Figure 1: 6. Next, the establishment of a value of? AV, that is, duration information, in a signal using a basic modulation scheme in transmission and reception stations will be described. Fig. 12 is a flow chart illustrating a virtual bearer detection procedure in a receiving station. With reference to Figure 12, a particular signal, that is, a PLCP preamble, as shown in Figures 8-10, which is indicative of the reception of information by the receiving station through a wireless medium, is detected in step S110, and the following basic information, i.e., a first signal symbol, is received on a second side, i.e., the receiving station, in step S120. In this case, a particular field of the reserved bits of the basic information is provided separately in such a way that the number of reserved bits of a symbol is set to one (1), thereby indicating the transmission of new data, and the NAV value information is extracted from the information transmitted using a basic modulation scheme. In step S130, it is determined whether a new PPDU exists. The parity bit is verified to determine if the received data is correct. It is determined if a frame received through the above processes is based on a new modulation scheme. If it is determined that the frame is not based on a new modulation scheme, it is determined that the frame is based on a conventional scheme and is processed - then by the conventional scheme. In this case, it is determined whether a data rate is supported by the receiving station in step S160. If a data rate is supported by the receiving station, the following symbols are received at the data rate, a NAV value of the symbols in step S170 is read. However, if the data rate is not supported by the receiving station, a NAV value can not be read, such that an EIFS duration is expected, instead of the NAV value in step S180. In step S130, if it is determined that a new PPDU exists, a second signal sibling is received in step S140. Then, a NAV value read from the signal symbol is set as a duration value of a signal field in step S150. That is, regardless of the reception capacity of the receiving station, the NAV value can be obtained from the SIGNAL. Consequently, the receiving station can transmit data immediately after the duration of NAV, regardless of its data rate range supported in Figure 12. Steps S130, S140 and S150 shown in Figure 12 represent an example mode of the present invention, as defined by IEEE 802.11a. In this case, regardless of the normal reception of the frame, the NAV value can be read accurately without an error. When virtual bearer detection is achieved in accordance with the present invention, each standby expects to transmit data up to the span of a NAV period and a DIFS period, and the station can transmit data after a containment channel such as a window containment, which is shown in Figure 13. Figure 13 illustrates differences between a conventional signal reception procedure, as defined by IEEE 802.11a, by way of example, and a PLCP reception method in accordance with this invention. In detail, unlike the conventional method in which a signal of one (1) OFDM symbol is received, in the present invention, a signal of 2 -OFDM symbols is received, as indicated by the reference number. 820. The same format of signal 560 as- is shown in Figure 10-, that is, 2 symbols of OFDM, also applies to the case of the present invention, as indicated by reference number 830 in the figure 13. To transmit a NAV value obtained from the SIGNAL to a MAC layer of a PHY layer, the vector value is corrected, as indicated by the reference number 810, as follows: PHY-RXINICIO.ind (RXVECTOR) where RXVECTOR =. { LENGTH, RSSI, DATA SPEED, SERVICE, DURATION} In other words, to transmit the value of NAV (DURATION), obtained from the symbol of the PHY layer, to the MAC layer, the conventional RXVECTOR values are corrected.

Figure 14 shows an example of the transmission of a frame for a new virtual bearer detection that highlights where a NAV-value is stored in a field corresponding to the PLCP header in the conventional transmission method. A PLCP preamble is generated in the e-chip S210, and a PPDU frame including the PLCP preamble is generated in the step "S220." In order to generate the PPDU frame in the step S220, it is necessary to set the number of bits to 1 and set the parity bits to verify errors in the data to be transmitted.

S230, a station examines whether a channel is available. If a channel is determined to be available, the PPDU frame is transmitted in step S240, and the mode changes to a reception mode in step S290. However, if it is determined in step S240 that a channel is busy, it is determined whether a previously received PPDU frame includes duration information, i.e., a value of NAV, in "step 250. If the PPDU frame received previously it includes the value of NAV -, - the frame is transmitted through a channel connection after the lapse of a duration corresponding to the value of NAV, in step S260.Otherwise, the frame is transmitted through the channel of containment after the lapse of an estimated EIFS, in step S270. In figure 15 information is shown between the MAC layer and the PHY layer for the frame transmission .. To transmit - the NAV value (DURATION) generated in the layer MAC to the physical layer, the following correction is made, as indicated by the reference number 1010: PHY-TXINICO request (TXVECTOR) where TXVECTOR = {LENGTH, DATA SPEED, SERVICE, TXPWR_NIVEL, DURATION.}. of DURATION transmitted is ported by a signal of 2 OFDM symbols 1020, as described above, and as indicated by reference numeral 1030. The same frame format of SIGNAL 560 is also applied to the illustrative mode, as shown in FIG. 10. Figure 16 illustrates the virtual carrier detection method in accordance with another example embodiment of the present invention. In this example embodiment, a structure of the frame is the same as the structure of the previous frame, but the former allows a receiving station to perform virtual bearer detection with information included in the data length. For the virtual carrier detection by the receiving station, a transmitting station records the value obtained by adding the length of the data portion in the frame and intervals between frames (SIFS, DIFS, etc.), and the length and signal of the preamble of another frame and the length of data. The receiving station detects the PLCP preamble of a frame transmitted through a wireless means S310. The station that has detected the PLCP preamble is in a state of being capable of receiving OFDM symbols. The station that has detected the preamble PLCP receives a symbol signal from the frame S320. The signal symbol includes information thereon about speed and length. After having received the symbol signal, the receiving station determines whether a virtual NAV value is established in the frame S330. In an exemplary embodiment of the present invention, if the value of the virtual NAV is established in the frame, it is determined based on the reserved bit value. For example, when a reserved bit is set to x 0 'the received frame refers to a previous frame to which the virtual NAV value is not set. When the reserved bit is set as? 1 ', the received frame refers to a frame to which the virtual NAV value is established. In another example mode, whatever the virtual NAV value established in the frame is determined by the rate. The rate refers to a total of 4 bits, and is defined by counting with a total of 8 bits under IEEE 802.11a as illustrated in Figure 11. The transmitting station informs the receiving station if the virtual NAV value is set in the plot, by using eight reserved rates. When the received frame refers to a frame to which the virtual NAV value is set, the receiving station calculates the value of NAV S34O. The value of NAV can be calculated by the speed and length of data. That is, the receiving station divides the data length. by speed in order to calculate the NAV value. The receiving station that has calculated the value of NAV establishes the value of NAV as the value obtained through calculation S350. . - When the received frame refers to the previous frame, the receiving station determines whether the obtained speed of the signal symbol can support itself S360. When the speed can be supported by the receiving station, the receiving station can obtain an MPDU and set the NAV value with the. duration of the S370 MPU. When the speed can not be supported by the receiving station, the receiving station estimates the duration to set the NAV value to the EIFS S380. EIFS covers the time from the state that does not have physical carrier detection to the SIFS and ACK frames of the lowest speed, and DIFS and random withdrawal. Next, a method of the station including NA value information on length and speed will be described with reference to Figure 5. With reference to this figure, the PPDU frame rate of the IEEE 802.11a standard comprises 4 bits, thus designating a total of 15 tates. The length comprises 12 bits, indicating with it-a total of 4,096 bytes-maximum. In this example mode, the value. of NAV for the detection of virtual bearer is set in length. However, the indication of the length unit with byte (s) is only an example, and therefore, the unit of length may be indicated by the number of OFDM symbols or time, and, for example, one microsecond. For example, if the speed is 54 Mbps and the data is 150 bytes, the length will be calculated as follows. The OFDM symbol is transmitted during the time of 4 microseconds, and an OFDM symbol can transmit information of 216 bytes when the speed is of 54 Mbps. On the other hand, the SIFS is of 16 microseconds and the data ACK frame comprises a preamble of 16 microseconds, a signal of 4 microseconds, and data (MPDU) of 16 bytes (1 OFDM symbol). SIFS corresponds to 4 symbols of OFDM, that is 864 bytes (216 x 4). Consequently, the transmitting station records 3,660 bytes (1,500 + 864 + 1,296) in the field of frame length. If the speed is 6 Mbps and the data is 1500 bytes, the length can be calculated as follows. The OFEM symbol corresponds to 24 bytes. Therefore, 1,740 bytes are recorded <; 1,500 + 24 x 4 + 24 x 6) in the length field. The virtual bearer detection of a physical layer can also be applied to a wireless communication using MIMO. The virtual bearer detection of the physical layer in the WLAN using MIMO will be described with reference to Figure 17.

Figure 17 illustrates a MIMO PPDU structure in accordance with an exemplary embodiment of the present invention. MIMO PPDU should comprise a plurality of preambles. The example mode of Figure 17 illustrates a MIMO PPDU structure that uses two antennas. In the MIMO frame of this mode, a preamble for a second antenna is placed next to the signal in order to allow the existing SISO stations to receive the signals. The data frame includes the first preamble of PLCP 1210, a signal 1220, a second preamble of PLCP 1230 and data 1240. The transmitting station records a value obtained by converting the second preamble of PLCP 120 in bytes to the length of signal 1220, a value obtained by converting the number of bytes of data 1240 and the SIFS into bytes, and a value obtained by converting an ACK frame into bytes. Industrial Applicability As described above, a method and apparatus for transmitting and receiving information, and a method and apparatus for establishing information in wireless network communications in accordance with the invention provide the following effects. First, even when there is an error in receiving frames transmitted in accordance with various modulation schemes, virtual bearer detection data can be obtained and the delay time is reduced. Second, even in a wireless network communication without virtual bearer detection data, the NAV value can be appropriately converted and transmitted to avoid collisions and reduce delays. Third, by using reserved bit data, the methods and apparatus in accordance with the present invention can be made compatible with conventional techniques by using "AV" values. Fourth, the information for the detection of virtual bearer in a physical layer can be provided without changing the structure of the conventional frame.

Numerous alterations and modifications of the present invention described herein will be presented by themselves to those skilled in the art. It will be understood that the above embodiments described are for illustration purposes only and will not be considered in a limited sense. Therefore, it is intended that the appended claims, instead of the detailed description of the present invention, encompass such modifications or modalities. All those modifications that do not depart from the spirit of the invention are intended to be included within the scope of the appended claims. In particular, the embodiments of the present invention described above with reference to the modulation of OFDM in accordance with IEEE 802.11a are provided for illustration only and are not intended to limit the scope of the present invention. The present invention can be applied to any wireless network communication using various modulation schemes. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (11)

1. CLAIMS Having described the foregoing invention, the content of the following claims is claimed as property: 1. A method of establishing virtual carrier detection data in wireless network communications, characterized in that the method comprises: receiving a transmitted frame using a plurality of modulation schemes and extracting data for the virtual bearer detection of a modulated segment of the frame based on a basic modulation scheme; and establish a virtual bearer using the extracted data.
2. 2. The method according to claim 1, characterized in that one of the modulation schemes is orthogonal frequency division multiplexing. The method according to claim 1, characterized in that the data for the virtual bearer detection is preceded by synchronization data. 4. The method according to claim 1, characterized in that the basic modulation scheme has a data rate that is supported by any station. 5. The method according to claim 1, characterized in that the extraction of the data is performed after verifying if there is an error in the modulated segment of the frame based on the basic modulation esguema. 6. The method according to claim 1, characterized in that the establishment of the virtual bearer detection additionally comprises transmitting the extracted data to a media access control layer (MAC). The method according to claim 6, characterized in that it additionally comprises establishing the extracted data as a vector parameter (physical PHY-RX.HOME indicator) of physical layer virtual carrier detection and sending that vector to the control layer of the physical layer. access to media. The method according to claim 1, characterized in that the data for the virtual bearer detection have the same bit size and the same value as the virtual bearer detection data received in a next step after the modulated segment of the plot based on the basic modulation scheme. The method according to claim 1, characterized in that it additionally comprises the frame after expiry of a time duration corresponding to the virtual bearer detection. The method according to claim 1, characterized in that the information for virtual bearer detection includes a value obtained by converting a section for virtual bearer detection into bytes. 11. A method of transmitting data for the detection of virtual bearer in wireless network communications for a plurality of modulated frames, characterized in that the method comprises: adding virtual bearer detection data to a modulated segment of a frame based on a scheme of basic modulation; and transmit that modulated segment. The method according to claim 11, characterized in that the basic modulation scheme is the orthogonal frequency division multiplexing. The method according to claim 11, characterized in that the data for the detection of virtual bearer are preceded by synchronization signal. The method according to claim 11, characterized in that the basic modulation scheme has a data rate that is supported by any station. 15. The method according to claim 11, characterized in that the addition of the data is performed after establishing a parity bit to verify errors in the modulated segment of the frame based on the basic modulation scheme. 16. The method according to claim 11, characterized in that the addition of the data further comprises transmitting the virtual bearer detection data of a media access control layer (MAC) to a physical layer. 17. The method according to claim 16, characterized in that it additionally comprises storing the virtual carrier detection data of a physical layer virtual bearer detection indicator vector (PHY-RX.HOME.indicator) and transmitting that vector to the physical layer. 18. The method according to claim 11, characterized in that the data for the virtual bearer detection have the same bit size and the same value as the virtual bearer detection data included in the next transmitted segment which is a segment modulation of the frame based on the basic modulation axes. 19. The method according to claim 11, characterized in that the information for the virtual bearer detection includes a value obtained by the conversion of a section for the detection of virtual bearer. in bytes. 20. An apparatus for wireless network communications, characterized in that it comprises: a frame receiving unit, which receives a frame transmitted using a plurality of modulation schemes and extracts virtual carrier detection data from a modulated segment of the frame modulated by a basic modulation scheme, - a frame generating unit, which adds virtual bearer detection data to the frame; and a transmitter unit, which transmits the frame with the virtual bearer detection data added to it. The apparatus according to claim 20, characterized in that the frame is transmitted based on the extracted virtual bearer detection data to avoid a collision. The apparatus according to claim 21, characterized in that the frame receiving unit sends data for virtual bearer detection interpreted by a physical layer to a media access control layer < MAC). 23. The apparatus according to claim 21, characterized in that the frame receiving unit sends the data for virtual bearer detection generated by an access control means (MAC) to a physical layer. 24. The apparatus according to claim 23, characterized in that the information for virtual bearer detection includes a value obtained by converting a section for virtual bearer detection to a byte. 25. A recording medium, characterized in that a program for executing a method according to claim 1 is recorded thereon. 26. A recording medium, characterized in that a program for executing a method according to the invention is recorded thereon. claim 11.