KR20050052816A - Method for solution of hidden station problem in wireless network - Google Patents

Abstract

The present invention provides a method for solving a hidden station problem in a wireless network, comprising: a first step of transmitting a CTS from a receiving node to the transmitting node and another node when transmitting a RTS from a transmitting node to a receiving node; And a second step of transmitting the CTS unicast from the receiving node after the first step so that communication with the transmitting node is performed, so that different transmitting nodes can simultaneously attempt to transmit to the receiving node in the wireless network. In this case, the collision that occurs can be prevented.

Description

Method for solution of hidden station problem in wireless network

The present invention relates to a method for solving a hidden station problem in a wireless network. In particular, the present invention relates to a wireless network suitable for preventing a collision occurring when different transmitting nodes simultaneously attempt to transmit to a receiving node in a wireless network. In this regard, the present invention relates to a solution of a hidden station problem.

In general, when a communication network for information transmission is largely classified into a wired network and a wireless network, a wired network is a low-speed data or image that requires a relatively low transmission rate from a voice service based on a public switched telephone network (PSTN). Through the narrowband communication service, the company is developing a broadband multimedia service that combines data, video, image, and video that require real-time and high-speed transmission.

Wireless networks include pagers, cordless phones that incorporate wireless concepts into existing landline phones, and cellular phones for car and mobile phones, which currently only provide voice services. As the demand for wireless communication increases, we seek to switch from analog system to digital system as a way to allocate communication lines economically and efficiently, reduce the size and weight of terminals, secure data, and improve the quality of data. It also enables the transmission of multimedia information such as video.

1 is a block diagram of a general wireless network.

As shown therein, a wireless operation apparatus 10 for performing wireless operation of a wireless network; A base station controller 20 connected to the wireless operation apparatus 10 to control a radio link and a wire link and perform a handoff function; It is configured to include a base station 30 is connected to the base station controller 20 and performs communication with the terminal using a protocol in a wireless section.

Here, the Institute of Electrical and Electronics Engineers (IEEE) 802.11 Medium Access Control (MAC) is composed of two parts: a distributed coordination function (DCF) and a point coordination function (PCF). DCF provides competition-based services, and PCF provides services without competition.

DCF is an access protocol, which is a basic medium access method of IEEE 802.11 MAC, and follows a carrier sense multiple access with collision avoidance (CSMA / CA) method.

CDMA / CA is a variation of Carrier Sense Multiple Access with Collision Detection (CSMA / CD) and is used with various radio access methods. The devices always detect the carrier on the network, and when the network is empty, they wait for a certain amount of time depending on their location on the list before sending data. Several methods are used to prioritize and reset the devices in the list. In some versions, a collision may occur, in which a collision detection procedure is performed.

In addition, this method is implemented in all terminals so that they can be applied in an IBSS (Infrared Background Signature Survey) or an infrastructure (Infrastructure) network structure.

2 is a flowchart illustrating a method of solving a hidden station problem by a conventional CSMA / CA method.

As shown therein, steps (ST11) (ST12) of determining whether the channel is idle by sensing the channel for a back off time; If the channel is idle, attempting to transmit (ST13); If the channel is not idle, attempting to transmit using the remaining backoff time in a contention period (ST14); Determining whether a channel has been acquired by the transmission attempt (ST15); If the channel is acquired, a step (ST16) of exchanging control frames of Request To Send (RTS) and Clear To Send (CTS) is performed.

A method for solving the conventional hidden station problem configured as described above will be described in detail with reference to the accompanying drawings.

First, the terminal detects the channel first and then continues to detect the channel while reducing the channel by the idle time in the randomly set backoff time to determine whether another terminal is transmitting before transmitting (ST11).

If the channel is idle until the backoff time becomes 0 (ST12) (ST13).

If the channel is not idle until the backoff time is 0, transmission is attempted using the remaining backoff time in the contention peerlead after the current transmission is completed (ST2) (ST13).

Therefore, the UE which successfully acquires the channel through the backoff process solves the hidden station problem by exchanging short control frames of the RTS and the CTS.

3 is a schematic diagram for explaining a general hidden station effect.

Thus, a hidden station (also called a hidden terminal) refers to a state in which A and C terminals do not receive communication with each other. This occurs due to an obstacle (see (a) of FIG. 3), a signal reduction, or a collision at the B terminal.

Therefore, in order to solve the hidden station effect, collision in the B terminal should be avoided (see (b) of FIG. 3).

Conventionally, collisions due to hidden terminals are avoided based on CSMA / CA in the same manner as in FIG. 2.

FIG. 4 is a frame diagram for explaining the RTS / CTS mechanism of FIG. 2.

This demonstrates the use of the RTS / CTS mechanism to prevent collisions caused by hidden station problems in IEEE 802.11.

Thus, the terminal that has obtained the right to transmit sends an RTS frame. The receiving terminal responds by sending a CTS frame.

In this process, other terminals generate and maintain NAV (Network Allocation Vector) and do not transmit during the corresponding time.

Then, when there is no error in the frame, the transmitting terminal sends an acknowledgment (ACK) frame to inform that the reception was successful.

In this case, when transmission is finished and no transmission occurs during DIFS (DCF Interface Spacing), UEs that want to transmit start to compete.

Since the RTS / CTS frame is smaller than the data frame, the recovery time can be shortened in case of an abnormal channel.

This prior art operation is described once again as a whole.

In the RTS / CTS frame used in the CSMA / CA method, there is a function to make a transmission reservation.

That is, the RTS / CTS frame has a duration area, which reserves how much I will use the shared resource in the future.

At this time, other terminals not involved in the communication set the NAV by interpreting the contents of the frame (that is, duration).

While the NAV remains, each terminal suppresses transmission.

That is, virtual carrier sensing is performed by the NAV. The use of RTS / CTS is determined by the No RTS parameter (minimum frame length not using RTS / CTS) of each terminal.

For example, a large-area local area network (LAN) can be used for communication to an access point (AP).

However, this conventional technology has the following problems.

The conventional CSMA / CA scheme using RTS / CTS and NAV is limited to use in a wider wireless network.

That is, when transmitting and receiving data in a series of RTS, CTS, DATA, and ACK formats, other wireless devices in the transmission queue can transmit after having a certain time back off. Therefore, there is no collision in transmission, but there is a problem in that it is applicable to a wide range of wireless networks because collision may occur at the receiving side.

Accordingly, the present invention has been proposed to solve the above conventional problems, and an object of the present invention is to wirelessly prevent collisions occurring when different transmitting nodes attempt to transmit to a receiving node at the same time in a wireless network. The present invention provides a solution to a hidden station problem in a network.

In order to achieve the above object, a method for solving a hidden station problem in a wireless network according to an embodiment of the present invention,

Transmitting the CTS from the transmitting node to the receiving node, transmitting the CTS from the receiving node to the transmitting node and another node; And a second step of performing communication with the transmitting node by transmitting the CTS unicast from the receiving node after the first step.

Hereinafter, an embodiment according to the present invention, a technical idea of a method for solving a hidden station problem in a wireless network will be described with reference to the accompanying drawings.

5 is a flowchart illustrating a method for solving a hidden station problem in a wireless network according to the present invention, and FIG. 6 is a signal flow diagram of FIG. 5.

As shown here, when the RTS is transmitted from the transmitting node C to the receiving node B, a first step of transmitting the CTS from the receiving node B to the transmitting node C and the other node A is performed. (ST21) (ST22); After the first step, the receiving node B transmits the CTS by unicast, so that communication with the transmitting node C is performed.

In the second step ST23 to ST26, when the other node A transmits a request to send response (RTSR) from the other node A to the receiving node B, the second node A receives the other node A from the receiving node B. A third step (ST23) (ST24) of informing that the receiving node (B) is communicating with the transmitting node (C) by transmitting a clear to send response (CTSR) to the receiver; A fourth step (ST25) (ST26) of transmitting an ACK from the receiving node (B) to the transmitting node (C) when the transmitting node (C) transmits the data to the receiving node (B) after the third step. To perform, including.

The operation of the method for solving the hidden station problem in the wireless network according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

First, the present invention is intended to prevent a collision that occurs when different transmitting nodes simultaneously attempt to transmit to a receiving node in a wireless network.

FIG. 7 is a schematic diagram illustrating a method of solving a hidden station problem to which FIG. 5 is applied.

Thus, as shown in FIGS. 5 to 7, the CTS is sent in the unicast format, not the broadcast format, in the exchange process between the RTS and the CTS.

And forms RTS / CTS / RTSR / CTSR / DATA / ACK.

Therefore, first, the access point of the transmitting node C transmits the RTS to the access point of the receiving node B in its cell in order to transmit data (ST21).

Then, the access point of the receiving node B transmits the CTS to the access point of the node A different from the access point of the transmitting node C (ST22).

At this time, RTS / CTS should not be used to solve the hidden station problem.

Thus, the CTS is transmitted from the receiving node B to unicast so that communication with the transmitting node C is performed.

That is, when the RTSR is transmitted from the access point of the other node A to the access point of the receiving node B (ST23), the CTSR is transmitted from the access point of the receiving node B to the other node A to receive the receiving node ( Informs that B) is communicating with the transmitting node C (ST24).

This solves the conflict problem.

Then, when DATA is transmitted from the access point of the transmitting node C to the access point of the receiving node B (ST25), by transmitting an ACK from the access point of the receiving node B to the transmitting node C, there is no conflict. It becomes possible to carry out communication.

As such, the present invention prevents collisions occurring when different transmitting nodes simultaneously attempt to transmit to a receiving node in a wireless network.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, the method for solving the hidden station problem in the wireless network according to the present invention has an effect of preventing a collision even when a collision occurs at the receiving side when there is no collision during transmission in the wireless network.

1 is a block diagram of a general wireless network,

2 is a flowchart illustrating a method of solving a hidden station problem by a conventional CSMA / CA method.

3 is a schematic diagram for explaining a general hidden station effect,

4 is a frame diagram for explaining the RTS / CTS mechanism of FIG.

5 is a flowchart illustrating a method of solving a hidden station problem in a wireless network according to the present invention;

6 is a signal flow diagram of FIG.

FIG. 6 is a schematic diagram illustrating a solution of a hidden station problem to which FIG. 5 is applied.

Explanation of symbols on the main parts of the drawings

10: Wireless operation device

20: base station controller

30: base station

Claims (2)

Transmitting the CTS from the transmitting node to the receiving node, transmitting the CTS from the receiving node to the transmitting node and another node; And a second step of transmitting the CTS by unicast from the receiving node to the communication with the transmitting node after the first step. The method of claim 1, wherein the second step, Transmitting, by the other node, the RTSR from the receiving node to the receiving node, transmitting a CTSR from the receiving node to the other node to indicate that the receiving node is in communication with the transmitting node; And a fourth step of transmitting an ACK from the receiving node to the transmitting node when transmitting data from the transmitting node to the receiving node after the third step. .