KR101087280B1 - The Wireless Communication Method For Based Orthogonal Frequency Division Multiple Access and The Apparatus Thereof - Google Patents

Abstract

A wireless communication method and apparatus based on orthogonal frequency division multiple access is disclosed. In the wireless communication method based on the orthogonal frequency division multiple access method, when there is a frequency collision, the base station determines a frequency different from the frequency allocated to the base station among the allocated frequencies on the network as the hopping frequency and the base station takes the hopping. And communicating with the terminal by applying the multiple access method adaptively based on the characteristics of the frequency. Thus, even in an environment in which the base station moves and jamming exists, the base station can provide services to the terminal quickly and continuously.

Frequency hopping, assigned frequency, OFDMA

Description

Wireless communication method based on orthogonal frequency division multiple access and its device {The Wireless Communication Method For Based Orthogonal Frequency Division Multiple Access and The Apparatus Thereof}

The present invention relates to a wireless communication method and apparatus based on an orthogonal frequency division multiple access method, and more particularly, to a method and apparatus for frequency hopping when there is a frequency collision in a wireless network based on an orthogonal frequency division multiple access method. It is about.

As a data communication scheme, there is a frequency division multiple access (FDMA) scheme based on orthogonal frequency division multiplex (OFDM). Wireless communication systems using such orthogonal frequency division multiple access include IEEE 802.16e (Mobile WiMax), WiBro, and IEEE 802.22.

IEEE 802.16e additionally selects various parameters of the physical layer to support mobility of lower terminals in addition to the existing IEEE 802.16 standard for fixed wireless access, and introduces a handoff function and a power saving function of a terminal. IEEE 802.16e operates in a time division duplex (TDD) mode, where uplink and downlink exist at different times within the same allocated frequency, and a frame structure is configured as shown in FIG. The frame length is 5ms and contains 42 time axis symbols.

WiBro is a Korean standard of IEEE 802.16e. It is not technically different except IEEE 802.16e and diversity channel and AMC (Adaptive Modulation and Coding) channel, and it is designed to be compatible with IEEE 802.16e. While IEEE 802.16e has a frequency band of 2 to 11 GHz and a variable allocation frequency bandwidth of 1.25 to 28 MHz, WiBro has a frequency of 2.3 to 2.4 Ghz and an allocated frequency bandwidth of 10 MHz. In particular, WiBro is different from that of IEEE 802.16e having 256 to 2048 variable subcarriers while WiBro has 1024 fixed subcarriers.

The prior arts show a limitation in that no proper measures can be taken for frequency collisions in consideration of an environment in which a base station moves and an environment in which malicious jamming exists.

In addition, IEEE 802.22 is a wireless communication scheme standard based on cognitive radio, and is designed to establish a wireless network in a local area, and has a frame structure similar to IEEE 802.16e as shown in FIG. The main difference is that the IEEE 802.22 network must operate without interfering with the primary service, and because multiple IEEE 802.22 base stations must be able to operate in adjacent areas, it includes dynamic spectrum detection and dynamic spectrum hopping functions. There is an additional section.

In IEEE 802.22, both the base station and the lower terminals perform frequency detection. In order to detect a signal of the primary service, as shown in FIG. 3, fast / fine detection (Fast / Fine Sensing) is supported through a periodic Quiet Period (QP). Quick detection is performed for a short time (1ms) and is used to analyze the occupancy status of the assigned frequency, and fine detection requires a long time (up to 25ms) to identify specific signal characteristics of the primary service.

Since IEEE 802.22 applies radio recognition technology, appropriate measures can be taken for frequency collisions with primary services and other IEEE 802.22 base stations. However, periodic dormant intervals are vulnerable to jamming. In other words, when the period of the QP is exposed to the malicious enemy, it can be mistaken as a specific allocated frequency is occupied by emitting the jamming signal only during the idle period. Therefore, there is a disadvantage that jamming to a specific band at a low cost.

An object of the present invention is to provide a frequency hopping and a multiple access method at a leap frequency in a wireless communication system based on an orthogonal frequency division multiple access scheme to solve the above problems.

In particular, by solving a frequency collision problem that may occur in an environment in which some base stations move or jamming, attempts to hop in frequency to provide fast and seamless service to the lower terminals of the base station. The purpose is.

In addition, even when there is no empty frequency, the frequency of the base station occupying the existing allocated frequency is leased and used for a predetermined time to provide an opportunity to transmit the necessary traffic to or from the lower terminals of the base station. have.

It is yet another object of the present invention to improve the antijamming and low pit detection ability from malicious enemies in frequency searching.

In the wireless communication method based on the orthogonal frequency division multiple access method according to the present invention for achieving the above object, if there is a frequency collision, the base station is a frequency different from the frequency assigned to the base station among the allocated frequencies on the network Determining the hopping frequency; And the base station communicating with the terminal by adaptively applying the orthogonal frequency division multiple access method based on the characteristic of the hopping frequency.

The communicating may include: when the hopping frequency is not used by another base station, the base station communicates with the terminal using the entire frame period of the hopping frequency, and the base station having a different hopping frequency is used. If the frequency is in use, it is preferable that the base station communicates with the terminal using a frame interval except for the time required for transmitting the necessary traffic of the other base station.

In addition, the first frame transmitted to the terminal is a preamble area for synchronizing the physical layer, a frame control header (FCH) area containing frame configuration and physical layer information, and synchronization with the terminal; It is preferably configured as a ranging channel (Ranging channel) area for receiving a data transmission request message.

The determining of the hopping frequency may include: determining a hopping frequency from among allocated frequencies on a network using a radio recognition technology; And determining, by the base station, the hopping frequency as one of the hopping frequencies when there is a frequency collision.

The determining of one hopping frequency as the hopping frequency may include determining the empty frequency as the hopping frequency when there is an empty frequency that is not used by another base station among the hopping frequencies. desirable.

The determining of one frequency among the hopping frequencies as the hopping frequency may include: when all of the hopping frequencies are frequencies used by other base stations, the frequency of the base station having the smallest amount of transmission traffic is set as the hopping frequency. It is desirable to decide.

In the determining of the hopping frequency, it is preferable that the allocation frequency on the network is detected by randomly detecting the detection time and the frequency to be detected to determine the hopping frequency.

And, the frequency collision is preferably generated by the movement or jamming of the base station.

On the other hand, the wireless communication apparatus based on the orthogonal frequency division multiple access method according to the present invention for achieving the above object, when there is a frequency collision, is different from the frequency assigned to itself among the allocated frequencies on the wireless communication system A hopping frequency determiner configured to determine a frequency as a hopping frequency; And an adaptor adapted to communicate with a terminal by applying the orthogonal frequency division multiple access scheme based on the characteristic of the hopping frequency.

The adaptor may communicate with the terminal using the entire frame interval of the hopping frequency when the hopping frequency is not used by another base station, and when the hopping frequency is a frequency used by another base station. In addition, it is preferable to communicate with the terminal using a frame interval except for the time required for transmission of the required traffic of the other base station.

The apparatus may further include a frequency detector configured to determine a hopping frequency among the allocated frequencies using a radio recognition technology.

Preferably, the frequency detector detects an allocated frequency on the wireless communication system by randomly detecting a detection time and a frequency to be detected to determine a frequency that can be leaped.

According to the present invention, if the present invention is applied to a wireless communication system based on an orthogonal frequency division multiple access scheme, a base station can provide a service to a terminal quickly and continuously even in an environment where a base station moves and jamming exists. . Specifically, the effects obtained through the frequency hopping and the multiple access method at the hopping frequency are as follows.

First, the mobile base station and the base station jammed to the assigned frequency can support a fast and continuous wireless communication service to the lower terminals. In the current wireless communication system that receives the allocated frequency and uses it without frequency hopping, the mobile station cannot support the services of the lower stages as soon as jamming is received. There was a problem not to do this, the present invention has the effect of solving the above problems.

Second, it can increase the throughput of the entire network and reduce the transmission delay time. According to the present invention, after the base station, which has a frequency collision due to movement and jamming, performs frequency hopping and leasing as quickly as possible, the frequency collision time is shortened by receiving synchronization and data transmission request messages with the lower terminal in a short time. And it can continue to provide services to the lower terminal. Thus, overall network throughput and transmission latency can be shortened.

Third, even if there is no empty frequency, it is possible to transmit essential traffic essential in the battlefield situation such as HOT-Line. If the neighboring base stations are using all assigned frequencies, the reliability of the required traffic and the survivability of the network can be achieved because mobile base stations and base stations that have lost communication due to jamming can support the necessary traffic that must be transmitted through the lease frequency multiple approach. Can improve.

Fourth, anti-jamming and low pit detection ability can be improved in frequency detection. By using a random detection interval allocation method in the time and frequency axis proposed in the present invention, the ability to avoid malicious jamming can be improved because the detection interval is not easily exposed to the enemy.

Hereinafter, with reference to the drawings will be described the present invention in more detail.

The present invention is not limited to the exemplary embodiments described below, but can be carried out in various ways without departing from the gist of the present invention in various ways. If you grow up, you can easily understand. If such improvement, change, substitution or addition is carried out within the scope of the appended claims, the technical spirit should also be regarded as belonging to the present invention.

4 is a diagram illustrating a wireless communication system according to an embodiment of the present invention. Each base station in a wireless communication system communicates with terminals using an Orthogonal Frequency Division Multiple Access (OFDMA). The base station receives one of one or more limited Frequency Assignment (FA) and communicates with the lower terminal using the assigned frequency. Thus, when the base station enters the initial network, it is desirable to be allocated a frequency where there is no interference or the interference can be minimized to avoid collisions with neighboring base stations.

On the other hand, some base stations may be moved or the communication between the base station and the terminal may be hindered by jamming of the malicious terminal or node.

For example, the first base station 410 and the second base station 420 communicate with each other by receiving the first frequency FA 1, and the third base station 430 communicates with the third frequency FA 3. . However, when the first base station 410 moves so that the frequency region of the first base station 410 and the frequency region of the second base station 420 overlap, the signal of the first base station communicates with the second base station. It interferes with one terminal and causes a problem in the communication in the second base station.

Thus, either one of the first base station 410 and the second base station 420 needs to make a frequency hopping. Preferably, the first base station 410, which is a mobile base station, makes the frequency hopping.

In this case, the base station that attempts frequency hopping is called a secondary base station, and a base station that has been assigned and used a frequency is called a primary base station, and the priority of the allocated frequency is assigned to the primary base station. It is desirable to have.

When the first base station 410 hops in frequency, the first base station 410 preferably hops at a frequency that can avoid a frequency collision with not only the second base station 420 but also the surrounding third base station 430. .

In addition, as shown in FIG. 4, when the fourth base station 440 is disturbed due to jamming, frequency hopping may be performed. Even when the fourth base station 440 makes a frequency hopping, it is preferable to make the frequency hopping while avoiding collision with the frequency used for the neighboring base stations.

5 is a block diagram of an orthogonal frequency division multiple access communication apparatus for frequency hopping according to an embodiment of the present invention, and FIG. 6 is a wireless communication system of an orthogonal frequency division multiple access method according to an embodiment of the present invention. Is a flow chart illustrating a frequency hopping and frequency multiple access method.

As illustrated in FIGS. 5 and 6, the frequency detector 510 detects an allocated frequency on a network using a radio recognition technology and determines a frequency that can be leaped among the allocated frequencies (S610). The frequency detector 510 preferably has anti-jamming and low pit detection performance.

FIG. 7 is a diagram illustrating a method of allocating a frequency detection interval having anti-jamming and low detect performance according to an embodiment of the present invention. Assume that there are a total of N assigned frequencies in the entire network. The base station communicates with the lower terminal using one assigned frequency, and communication is preferably performed in units of frames.

On the other hand, the frequency detector 510 of the base station detects a total of N assigned frequencies by using a detection interval allocation method that randomly detects a detection time and a detection frequency in order to recognize a frequency collision due to the movement or jamming of the base station. Perform continuously

The frequency detector 510 performs frequency detection immediately before transmitting a frame to the terminal. The hopping frequency detector 510 preferably detects one frequency, transmits a random number of frames with the terminal, and detects another frequency again. In addition, the frequency detector 510 detects only one frequency when performing frequency detection, and selects a frequency to be randomly detected when there are N assigned frequencies on the network. However, the frequencies to be detected are preferably selected with the same probability.

If frequency detection is performed at regular frame intervals and sequential frequency intervals, the frame intervals can be easily exposed, and interference signals for all assigned frequencies can be generated through malicious jamming signals. Therefore, it is preferable to perform frequency detection randomly as shown in FIG.

The frequency detector 510 may detect a hopping frequency using an energy detection technique. In addition, the signal-to-noise ratio (SNR), signal-to-interference and noise ratio (SIGNAL-TO-INTERFERENCE-PLUSE-NOISE-RATIO: SINR) can also be used to detect hopping frequencies. In detail, the frequency detector 510 determines that the frequency can be leap if the SNR or SINR of the detected frequency is equal to or greater than a set threshold. For example, in FIG. 4, the hopping frequency determined by the first base station 410 may be a frequency excluding the first frequency and the third frequency.

The frequency that can be jumped is divided into a frequency not used by the base station (hereinafter, referred to as an empty allocated frequency) and a frequency used by the primary base station (hereinafter, referred to as a non-empty assigned frequency). In other words, an empty allocated frequency may be referred to as a first hopping frequency, and a non-empty allocated frequency may be referred to as a second hopping frequency. If it is greater than or equal to 1 threshold, it may be determined that the allocated allocation frequency is empty. If the SNR or SINR of the detected frequency is less than the first threshold, it may be determined that the allocated frequency is not empty.

When there is a frequency collision (S620-Y), the hopping frequency determiner 530 determines a frequency to hop to using the detected result (S630). In detail, when the communication with the terminal is impossible, the hopping frequency determiner 530 determines the hopping frequency from among the hopping frequencies. In this case, the communication between the base station and the terminal means that the frequency collision occurs due to the movement of the base station or the frequency collision occurs due to the jamming signal.

The hopping frequency determiner 530 determines one of the empty allocation frequencies as the hopping frequency when the hopping frequency has an empty allocation frequency. However, if all of the frequencies that can be hopped are allocated non-empty frequencies, the hopping frequency determiner 530 determines one of the non-empty frequencies as the hopping frequency.

When the empty frequency is determined as the hopping frequency, it is preferable to determine the empty frequency according to the statistical method or the received signal strength. In other words, it is desirable to determine a frequency having a large received signal strength. When determining the non-empty frequency as the hopping frequency, it is preferable to determine the frequency of the base station having the smallest amount of transmission traffic as the hopping frequency. Here, the statistical method is to average the information detected before the collision with respect to each assigned frequency, the threshold value with the largest value among the empty frequencies, or the longest threshold value based on the present based on previously detected information. This means that the assigned frequency that maintains the abnormality is determined as the hopping frequency.

In the present invention, the frequency is not limited to the above-described embodiments, but may be variously improved, changed, replaced, or added to without departing from the gist of the present invention.

The frequency detector 510 is performed before the frequency collision, and the hopping frequency determiner 530 is preferably performed after the frequency collision. However, the present invention is not limited thereto, and both the frequency detector 510 and the hopping frequency determiner 530 may be performed after the frequency collision.

The adaptor 550 communicates with the terminal by adaptively applying orthogonal frequency division multiple access based on the determined characteristic of the hopping frequency (S640).

Specifically, when there is no primary base station in the determined hopping frequency, that is, when the hopping frequency is empty, the hopping frequency multiple access method for supporting a service to the lower terminal through frequency hopping is applied. However, when the primary base station exists in the determined hopping frequency, that is, when the determined hopping frequency is a non-empty frequency, a lease frequency multiple access method that supports service to the lower terminal through frequency leasing is applied.

The following describes the hopping frequency multiple access method and the lease frequency multiple access method in detail.

8 illustrates a hopping frequency multiple access method according to an embodiment of the present invention. As shown in FIG. 8, the adaptor 550 communicates with the lower terminal using the entire frame period of the hopping frequency. However, when the adaptation unit 550 hops at the determined hopping frequency, the base station is in a state of not receiving synchronization and data transmission request messages from all lower terminals.

Thus, in the first frame transmitted to the terminal after the frequency hopping, the adaptation unit 550 is a control message (FCH) containing a preamble area, frame configuration and physical layer information for rough synchronization of the physical layer. All of the frames except the header area are used as a ranging channel area for receiving synchronization and data transmission request messages with the lower terminal. The preambles, FCHs, and ranging channels mentioned herein serve the same as the preambles, FCHs, and ranging channels mentioned in IEEE 802.16 and IEEE 802.22.

If the first frame is configured as described above, even after the frequency hopping, the base station receives the synchronization and data transmission request message within a short time, thereby enabling fast and seamless communication with the lower terminal.

Subsequent frames, as shown in FIG. 8, are the same as the frame structure applied to the conventional orthogonal frequency division multiple access method.

9 is a diagram illustrating a rental frequency multiple access method according to an embodiment of the present invention. As shown in FIG. 9, if the primary base station is already serving the lower terminals of the primary base station using the hopping frequency, the adaptor 550 rents and uses the allocated frequency of the primary base station.

In detail, before the frequency hopping, the adaptation unit 550 transmits a lease request message to the primary base station through the ranging channel of the primary base station, similarly to the lower terminal of the primary base station. In addition, the primary base station transmits the remaining frame interval except the time required for transmitting the required traffic of the primary base station among the frame interval to the adaptor 550 of the secondary base station. Then, the adaptor 550 uses the remaining frame period for the necessary traffic transmission of the secondary base station. The frame remaining after transmitting the required traffic of the primary base station is called a lease frame.

And, when transmitting the lease request message to the primary support station, the secondary base station may request as many consecutive M frames as necessary for transmitting necessary traffic of the secondary base station.

In addition, in the lease frequency multiple access method, the first lease frame is used as the ranging channel except for the preamble and the control message (FCH). After that, the orthogonal frequency division multiple access method such as IEEE 802.16 and IEEE 802.22 is applied to the lease frame in the same manner as the aforementioned hop frequency multiple access method.

On the other hand, if the lease frame time is very short, essential traffic is transmitted in order of high priority according to the priority of the traffic. This mandatory traffic can be limited to the transmission of very high priority traffic that must be transmitted, such as HOT-LINE traffic used in tactical environments.

When the present invention is applied to a wireless communication system based on an orthogonal frequency division multiple access scheme, a base station can provide a service to a terminal quickly and continuously even in an environment where a base station moves and jamming exists. Specifically, the effects obtained through the frequency hopping and the multiple access method at the hopping frequency are as follows.

First, the mobile base station and the base station jammed to the assigned frequency can support a fast and continuous wireless communication service to the lower terminals. In the current wireless communication system that receives the allocated frequency and uses it without frequency hopping, the mobile station cannot support the services of the lower stages as soon as jamming is received. There was a problem not to do this, the present invention has the effect of solving the above problems.

Second, it can increase the throughput of the entire network and reduce the transmission delay time. According to the present invention, after the base station, which has a frequency collision due to movement and jamming, performs frequency hopping and leasing as quickly as possible, the frequency collision time is shortened by receiving synchronization and data transmission request messages with the lower terminal in a short time. And it can continue to provide services to the lower terminal. Thus, overall network throughput and transmission latency can be shortened.

Third, even if there is no empty frequency, it is possible to transmit essential traffic essential in the battlefield situation such as HOT-Line. If the neighboring base stations are using all assigned frequencies, the reliability of the required traffic and the survivability of the network can be achieved because mobile base stations and base stations that have lost communication due to jamming can support the necessary traffic that must be transmitted through the lease frequency multiple approach. Can improve.

Fourth, anti-jamming and low pit detection ability can be improved in frequency detection. By using a random detection interval allocation method in the time and frequency axis proposed in the present invention, the ability to avoid malicious jamming can be improved because the detection interval is not easily exposed to the enemy.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

1 is a diagram illustrating a frame structure of a conventional IEEE 802.16e.

2 is a diagram illustrating a frame structure of the conventional IEEE 802.22;

3 is a view for explaining a detection section in the conventional IEEE 802.22,

4 illustrates a wireless communication system according to an embodiment of the present invention;

5 is a block diagram of a communication apparatus of an orthogonal frequency division multiple access method for frequency hopping according to an embodiment of the present invention;

6 is a flowchart illustrating a frequency hopping and a frequency multiple access method in a wireless communication system having an orthogonal frequency division multiple access method according to an embodiment of the present invention;

7 is a view for explaining a method for allocating a frequency detection interval having anti-jamming and low-detection capability according to an embodiment of the present invention;

8 is a diagram illustrating a hopping frequency multiple access method according to an embodiment of the present invention.

9 is a diagram illustrating a rental frequency multiple access method according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

510: frequency detector 530: hopping frequency determiner

550: adaptation unit

Claims (12)

A wireless communication method based on orthogonal frequency division multiple access, If there is a frequency collision, determining, by the base station, a hopping frequency, a frequency different from a frequency previously allocated to the base station among the allocated frequencies on the network; And And after the base station hops to the hopping frequency, communicating with the terminal by adaptively applying the orthogonal frequency division multiple access method based on the characteristic of the hopping frequency. The method of claim 1, The communicating step, If the hopping frequency is a frequency not used by another base station, the base station communicates with the terminal using the entire frame period of the hopping frequency, If the hopping frequency is a frequency used by another base station, the base station communicates with the terminal using a frame period except for the time required for transmission of the required traffic of the other base station. 3. The method of claim 2, The first frame transmitted to the terminal is a preamble area for synchronizing the physical layer, a frame control header (FCH) area containing frame configuration and physical layer information, and synchronization with the terminal; And a ranging channel region for receiving a data transmission request message. The method of claim 1, Determining the hopping frequency, Determining a hopping frequency from among allocated frequencies on a network using a radio recognition technology; And And a base station, if there is a frequency collision, determining one frequency among the hoppable frequencies as the hopping frequency. The method of claim 4, wherein Determining one of the hopping frequencies as the hopping frequency, And when there is an empty frequency that is not used by another base station among the hopping frequencies, determining the empty frequency as the hopping frequency. The method of claim 4, wherein Determining one of the hopping frequencies as the hopping frequency, And when all of the hopping frequencies are frequencies used by other base stations, determining the frequency of the base station having the smallest amount of transmission traffic as the hopping frequency. The method of claim 4, wherein Determining the hopping frequency, And detecting an allocated frequency on the network by irregularly detecting a detection time and a frequency to be detected to determine a frequency that can be hopped. The method of claim 1, Wherein said frequency collision is caused by movement or jamming of said base station. A wireless communication apparatus based on orthogonal frequency division multiple access, A hopping frequency determiner for determining a hopping frequency from a frequency different from the frequency allocated to the frequency among the allocated frequencies on the wireless communication system when there is a frequency collision; And And an adaptor adapted to communicate with a terminal by adaptively applying the orthogonal frequency division multiple access scheme based on the characteristic of the hopping frequency after hopping at the hopping frequency. The method of claim 9, The adaptation unit, If the hopping frequency is a frequency not used by another base station, the frame period of the hopping frequency is used to communicate with the terminal using the whole, And if the hopping frequency is a frequency used by another base station, communicating with the terminal using a frame period except for the time required for transmitting the required traffic of the other base station. The method of claim 9, And a frequency detector for determining a hopping frequency from among the allocated frequencies using a radio recognition technology. The method of claim 11, The frequency detector, And randomly detecting a detection time and a frequency to be detected to detect an allocated frequency on the wireless communication system to determine a hopping frequency.

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