KR101401111B1 - Apparatus and method for adaptive transmission based on interference termperature cognition in the cognitive radio system - Google Patents

Abstract

The present invention provides a method for ensuring an optimal transmission rate for a CR user while minimizing interference to a main user in a cognitive radio (CR) communication system. The CR user performs spectral idle detection at all times, selects a channel having the lowest interference temperature level, calculates a distance from the main user based on the interference temperature level measured at the CR user's receiver in a given channel environment , Calculates a transmission power of a CR user by performing a power control process, and performs adaptive modulation to obtain an optimal transmission rate performance by obtaining an interference signal power (SINR: Signal-to-Interference and Noiser Ratio) Determine the modulation scheme. Then, a signal is finally transmitted using the determined transmission power and modulation scheme.

Cognitive Radio, Interference Temperature, Transmit Power Control, Adaptive Modulation, SINR

Description

[0001] APPARATUS AND METHOD FOR ADAPTIVE TRANSMISSION BASED ON INTERFERENCE TERMERATIVE COGNITION IN THE COGNITIVE RADIO SYSTEM [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission / reception technique of a communication system, and more particularly to a technique of transmitting / receiving a signal to / from a main user in a cognitive radio (hereinafter referred to as " CR ") communication system The present invention relates to an adaptive transmission scheme capable of providing an optimum transmission rate to a CR user in a non-influential line.

Due to the rapid development of wireless communication systems and the introduction of various services, the demand for wireless resources is increasing day by day. However, due to the fact that almost all commercially available frequency bands are allocated, a frequency resource for a new wireless platform is extremely short. If you look at the current frequency usage, there is little room available for the several GHz band, especially the low frequency band. In order to solve this frequency shortage problem, CR communication system based on CR method has been proposed. The CR communication system senses a frequency band that is allocated to a frequency but is not actually used, and can efficiently share and use the frequency band. Such a CR communication system is a communication system that can be used in connection with a next-generation communication system currently being studied.

The CR system actively recognizes a given channel environment through a radio sensor or the like and uses a learning algorithm and adaptation capability based on the perceived environment information to not affect the main user Means a technique capable of adaptively providing transmission parameters and networks that are most suitable for the environment given to the CR user in the range. This CR technology recognizes the frequency idle by the context awareness ability and can reuse the limited frequency resources according to time, space, and region, so it can improve the frequency resource use efficiency, It is possible to actively cope with a given environment by using the CR system, and it is advantageous in the next generation wireless communication field because it has a merit that it can guarantee the highest quality of service (QoS) in a given environment situation to a user using the CR system .

Research areas of CR can be roughly divided into spectrum sensing, resource management, and wireless adaptive transmission technology. Spectrum sensing technology is a technology that can recognize the idle frequency band in time, space, and region in order to avoid interference with the main user's system. Resource management technology is a technology in which a control channel for CR system does not exist And a MAC technology including a protocol for allowing the base station and the terminal to recognize a frequency idle degree perceived through spectrum sensing. The wireless adaptive transmission technology can optimize the data transmission by setting the system parameter that is best suited to the given environment considering the environment information perceived by the spectrum sensing and the interference temperature including the channel state information (CSI) . Therefore, it is necessary to study all three fields in order to construct the completed CR system. However, to date, research on CR has not only been at the level of initial approach in the field of spectrum sensing and resource management technology, but research on wireless adaptive transmission technology for CR system has been in progress, Relatively inferior.

Meanwhile, the present invention uses an interference temperature model as a method for grasping interference between a main user and a CR user in a CR system model. Interference Temperature (IT) is a concept that emerged as part of a new frequency policy for efficient management of frequency resources in the US Federal Communications Commission (FCC). It is a quantification index of all interferences from other users in a wireless channel Is used. Unlike the conventional radio interference avoidance method, which defines and sources the interference source as a transmitter, the interference temperature model is defined to support an open frequency management policy that manages the radio environment in consideration of the mutual operation of the transceivers. This means that the paradigm of the frequency management policy has shifted from the center of the transmitter to the center of the receiver.

Therefore, an object of the present invention is to provide a CR adaptive transmission scheme based on interference temperature awareness that can guarantee an optimal transmission rate for a CR user while minimizing interference effects to a main user in a given channel state.

In order to achieve the above object, a cognitive radio communication system according to the present invention is a cognitive radio (CR) communication system using a frequency band used by a main user communication system,

A transmission / reception unit for receiving spectrum sensing information on a frequency band of a main user communication system; An analysis module for analyzing the spectrum sensing information and analyzing whether there is an idle band in the frequency band; A measurement module for measuring an interference temperature for the frequency band when there is no idle band; A first calculation module for calculating a channel capacity using the measured interference temperature and selecting a channel having the lowest interference with respect to the main user communication system; A second calculation module for calculating a distance between the main user and the CR user using the measured interference temperature; Calculates a SINR for a main user's communication system by using the main user calculated by the second calculation module and the interference temperature measured by the measurement module, And a third calculation module for calculating the transmission power of the signal to be used by the communication system and for determining the modulation method for the signal of the CR user communication system.

According to another aspect of the present invention, there is provided a method of adaptively transmitting a CR user signal in a cognitive radio (CR) communication system,

를 측정하는 단계와; (B) 상기 측정된 주 사용자와의 거리에 기초하여 상기 주 사용자에게 간섭 영향을 미치지 않도록 상기 CR 사용자가 사용할 신호의 전송전력(P _max , _CR )을 결정하는 단계와; (C) 상기 결정된 전송전력과 상기 측정된 간섭 온도 값를 이용하여 신호 대 간섭 및 잡음비(SINR: Signal-to-Interference and Noise)를 계산하는 단계와; (D) 상기 SINR을 이용하여 상기 CR 사용자가 사용할 신호의 최적 변조 방식을 결정하는 단계를 포함하는 것을 특징으로 한다.(A) a distance between the CR user and the main user based on the interference temperature value (IT value) for the frequency band of the main user measured and calculated using the spectrum sensing algorithm

; ≪ / RTI > (B) determining the transmit power (P _{max, CR)} of the signal CR users to use so as not to interfere with the effect on the primary user on the basis of the measured distance and the primary user; (C) calculating a signal-to-interference and noise ratio (SINR) using the determined transmission power and the measured interference temperature value; (D) determining an optimal modulation scheme of a signal to be used by the CR user using the SINR.

Preferably, the step (A)

Calculating an interference temperature value (IT value) using Equation (2) and a power spectrum density measured through a spectrum sensing algorithm; Calculating a channel capacity of each channel in the frequency band of the main user using the calculated interference temperature value; And measuring a distance between the CR user and the main user using Equation (4) based on the interference temperature value and the information of Equation (3).

이고, Preferably, Equation (2)

ego,

이고,Equation (3)

ego,

인 것을 특징으로 한다.Equation (4)

.

Preferably, the step (B)

Determining an SINR, which ensures that bit error rate (BER) performance of the main user system does not suffer deterioration, using Equation (6); and

And determining a transmission power value that can provide the maximum transmission efficiency to the CR user using Equation (5).

이고, 상기 수학식 6은

인 것을 특징으로 한다.Preferably, Equation (5)

, And the equation (6)

.

Preferably, the step (D)

( T _I , _CR ) for the maximum transmission power ( P _max , _CR ) of the _CR user and the signal s ( t ) received from the main user in the frequency band of the main user and outputs the interference temperature value Calculating a SINR value ( SINR _CR ) given to the user; And adaptively selecting a modulation scheme capable of ensuring an optimal transmission rate for a CR user based on the calculated SINR value.

Preferably, if the SINR _CR satisfies the required SINR value of each modulation scheme to obtain a desired BER performance, the modulation scheme that provides the highest data rate among the modulation schemes satisfying the required SINR is selected.

The method and the procedure of the present invention are largely composed of four steps. In step 1 and step 2, the CR user is aware of the situation. In steps 3 and 4, the CR user's adaptive transmission is handled. Each of these steps will be described in detail below.

In step 1, the CR user performs spectral sensing for the entire frequency range under consideration, and selects a channel exhibiting the lowest interference temperature (IT) value through the perceived information . That is, this is a procedure for selecting a channel capable of providing the maximum transmission capacity in a given environment to a CR user.

In step 2, the CR user estimates the position of the main user, that is, the distance between the CR user and the main user, through the sensing information on the channel determined in step 1 as a step of 'distance to the main user'.

Step 3 is a step of adjusting the transmission power between CR users, and determines the maximum available transmission power of the CR user based on the distance to the main user recognized in step 2. This minimizes interference effects on the primary user, the primary goal of the CR system, while at the same time providing the maximum transmission power for CR users.

Step 4 is a step of determining the modulation scheme of the CR user. In step 4, the CR user determines the maximum transmission power available for the CR user and the interference level generated by the main user, that is, the interference level (IT) To determine the most appropriate modulation technique.

The present invention minimizes the interference effect to the main user (the main system or the main system terminal) by adjusting the transmission power of the CR user by recognizing the distance from the main user based on the interference temperature information measured in a given channel state. Then, by determining the determined transmission power, the SINR value for interference and noise, and determining the modulation scheme of a signal to be transmitted, an optimal transmission rate can be guaranteed for a CR user (subsystem, subsystem terminal) in a given channel state.

The present invention is applied to a cognitive radio (CR) communication system. However, the present invention is not limited thereto, but may be applied to all communication systems and communication systems to which the technical idea of the present invention can be applied.

In the present invention, the 'main user' refers to the main system or the user (or terminal) of the main system. The term 'CR user' refers to a sub system or a user (or terminal) of a sub system that uses the same frequency band (channel) as the main user. In other words, it is the CR user that wants to use the specific frequency band without interfering with the main user, and it is the main user having the license of the specific frequency band. In terms of the network, the network of the primary user and the network of the CR user may be networks of the same communication method, or may be networks of different communication methods.

The basic concept of the present invention is to use an interference temperature model to minimize interference to a main user's communication system using a specific frequency channel, And transmits a signal on the specific frequency channel at the optimum transmission rate.

Hereinafter, a flowchart of a process procedure of a CR adaptation transmission method according to the present invention will be described in detail with reference to the accompanying drawings. In the following description, only parts necessary for understanding the operation according to the present invention will be described, and the description of other parts will be omitted so as not to disturb the present invention.

The present invention proposes a CR adaptive transmission scheme based on interference temperature awareness that can guarantee an optimal throughput for a CR user while minimizing interference effects to a main user in a given channel state. The adaptive transmission scheme for the proposed CR system should be based on the license of the main user in the situation where the main user exists in the same frequency band and minimizing the influence of the interference to the main user should be a top priority, The user should be able to provide the maximum transmission rate in a given communication environment condition. Therefore, the present invention provides an optimal transmission rate for a CR user within a range that does not cause interference to a main user by using an interference temperature model in a given channel environment.

The present invention is largely divided into a 'cognitive procedure' and an 'adaptive transmission procedure' in accordance with the process procedure of the CR adaptive transmission scheme described above. The cognitive procedure consists of a first stage of spectrum idle state and a second stage main user , The adaptive transmission procedure consists of three stages: the CR user's transmission power control and the 4th modulation level determination. Fig. 1 shows a processing flowchart for this procedure. Hereinafter, the CR adaptive transmission scheme according to the present invention will be described in detail.

Referring to FIG. 1, step 1 includes steps (S110) to (S150). First, the receiving end of the CR user (i.e., the receiving end of the CR user terminal that can use the CR communication system) performs the spectrum idle detection (S110) using the spectrum sensing algorithm. Next, it is determined whether there is an idle band based on information obtained through recognition of the current spectrum idle state (S120). If there is an idle band, the idle band is selected as the optimum channel (S150). If the current idle band does not exist, the interference temperature measurement for each channel is performed (S130). The interference temperature is expressed as Equation (1).

이다. 따라서, T _I(f _c , B)와 P _I(f _c , B)는 각각 중심 주파수f _c 에서 대역폭이 B일 경우에 대한 IT 값(즉, 간섭온도 값)과 평균 간섭전력 값을 의미한다. 한편, 수학식 1의 간섭온도를 전력스펙트럼밀도 (Power Spectral Density) 함수를 이용하여 표현하면 수학식 2와 같다.In Equation (1), f _c and B denote the center frequency and bandwidth of the considered frequency band respectively, P _I denotes the average interference power in the corresponding band, k denotes a Boltzman constant,

to be. Therefore, T _I ( f _c , B ) and P _I ( f _c , B ) mean the IT value (that is, the interference temperature value) and the average interference power value for the bandwidth B at the center frequency f _c . Meanwhile, the interference temperature of Equation (1) can be expressed by Equation (2) using a power spectral density function.

Where S ( f ) represents the power spectral density for the interference in the frequency band under consideration. In an actual system, the interference temperature can be calculated using Equation 2 as the power spectral density measured through the spectrum sensing algorithm.

Next, the channel capacity of each channel is calculated based on the measured interference temperature information (S140). In operation S150, an optimal channel is selected based on the channel capacity information for each channel (i.e., the channels allocated to the frequency band used by the main user). The formula for calculating the channel capacity is obvious to those skilled in the art, and a detailed description of the calculation of the channel capacity is omitted.

In step S260, a step of recognizing the distance between the CR user and the main user is performed prior to determining the maximum transmission power of the CR user in step S370. The CR user calculates the interference temperature value for the channel band selected in step 1 and uses this information to estimate the distance from the main user. That is, assuming that the main signal the user is transmitted on the selected channel band signal path loss and additive white Gaussian noise (AWGN: Additive White Gaussian Noise, hereinafter referred to as 'AWGN' referred) n (t) by the CR The user is received in the form of Equation (3).

In Equation (3), PL denotes an amount of attenuation according to the distance between the CR user and the main user, and this value is calculated by the following Equation (4).

는 경로손실 지수를 나타낸다. 따라서, CR 사용자는 식 수학식 3의 정보를 기반으로 수학식 4를 이용하여 주 사용자와의 거리

를 추정하게 된다.In Equation (4), d ₀ denotes a reference distance, and d ₁ denotes a distance between a main user and a CR user. PL ₀ is the reference path loss value for d ₀ ,

Represents the path loss index. Therefore, the CR user can calculate the distance from the main user using Equation (4) based on the information of Equation (3)

.

값을 통해 CR 사용자가 사용 가능한 최대 전송전력을 결정한다. CR 사용자는 추정된

값을 이용하여 신호를 전송할 때 주 사용자 시스템의 비트오율 (BER: Bit Error Rate, 이하 ‘BER’이라 칭하기로 한다) 성능에 열화를 끼치지 않을 정도의 신호 대 간섭 및 잡음비 (SINR: Signal-to-Interference and Noise Raio, 이하 ‘SINR’이라 칭하기로 한다)를 보장할 수 있어야 되며, 동시에 CR 사용자에게는 최대 전송효율을 제공할 수 있는 전송전력 값을 설정하게 된다. 따라서, 주 사용자의 시스템 에 보장되어야 될 SINR과 CR 사용자가 사용할 수 있는 최대 전송전력 값은 하기의 수학식 5와 6처럼과 같이 계산될 수 있다.In step 3, the transmission power control step 170,

The value determines the maximum transmit power available to the CR user. The CR user

(SINR: Signal-to-Noise Ratio) which does not cause deterioration in bit error rate (BER) performance of the main user system when transmitting a signal using a value -Interference and Noise Raio (hereinafter referred to as SINR), and at the same time, the CR user sets a transmission power value that can provide the maximum transmission efficiency. Therefore, the SINR to be guaranteed to the primary user's system and the maximum transmission power value that can be used by the CR user can be calculated as shown in Equations (5) and (6) below.

값을 이용하여, 수학식 3을 통해 CR 사용자의 최대 전송전력 P _max , _CR 을 결정할 수 있게 된다. 이때, 결정된 P _max , _CR 에 의해 주 사용자의 SINR 값은 수학식 6과 같이 계산될 수 있다. IU and CR indicated by the subscript in the above Equation 5 and 6 shows the main user and the CR user, respectively, T _{I, IU} means the interference temperature measurement value obtained by the main user. That is, the distance estimation CR user is sure of the state of the user T _{L, IU}

The maximum transmission power P _max , _CR of the CR user can be determined using Equation (3). At this time, the SINR value of the main user can be calculated according to the determined P _max , _CR as shown in Equation (6).

In step 4, the adaptive modulation is performed in step S180, the maximum transmission power P _max , _CR of the CR user determined in step 3 (S170) is received from the main user (i.e., the main user's communication system) The interference temperature value T _I , _CR for the signal s (t) can be calculated to calculate the SINR value SINR _CR given to the CR user. Then, the modulation scheme that can guarantee the optimal transmission rate to the CR user is adaptively selected through the calculated SINR value. When the SINR _CR satisfies the required SINR value of each modulation scheme to obtain a desired BER performance, a modulation scheme that provides the highest data rate among the modulation schemes satisfying the required SINR is selected and applied. After the adaptive modulation is performed, the CR user finally transmits a signal (S 190).

In summary, the present invention uses the same frequency band to estimate the distance from a main user at a specific distance using an interference temperature model, and determines the maximum transmission power within a range that does not cause interference to the main user through this information . In addition, the optimal modulation scheme can be selected in consideration of the determined maximum transmission power and the amount of interference received from the main user. Therefore, the proposed CR adaptive transmission scheme can provide an optimum transmission rate to CR users without causing almost interference to the main user using the same frequency band.

2 is a schematic block diagram of a CR communication system according to the present invention. A transmission / reception unit 210 for receiving spectrum sensing information on a frequency band of a main user transmitted by a terminal of the CR communication system 200; An analysis module 220 for analyzing the spectrum sensing information and analyzing whether there is an idle band in the frequency band; A measurement module (230) for measuring an interference temperature for the frequency band when there is no idle band; A first calculation module 240 for calculating a channel capacity using the measured interference temperature and selecting a channel (or a frequency band) having the lowest interference with respect to the communication system of the main user; A second calculation module 250 for calculating a distance between the main user and the CR user using the measured interference temperature; A CR user communication is performed so as not to give signal interference to the main user by using the main user calculated by the second calculation module and the interference temperature measured by the measurement module (i.e., the interference temperature with respect to the frequency band of the main user) A third computation module 260 for computing the transmit power of the signal to be used by the system and for determining an optimal modulation method for the signal of the CR user communication system.

Meanwhile, the first to third operation modules may be constituted by one integrated operation module or may be constituted by separate operation modules. The first to third calculation modules may be referred to as a control unit or a processing unit.

The functions and operations of each component of the CR communication system 200 correspond to the contents described with reference to FIG.

The technical idea of the present invention described above can be implemented by a combination of software and hardware having the software. Further, the terms " module ", " module ", as used in the embodiment of the present invention means a hard air component such as software or FPGA or ASIC, and the module performs certain roles and functions. However, the module is not limited to software or hardware. The module may be configured to reside on an addressable storage medium, or may be configured to play one or more of its processors.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope of the present invention . Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

1 is a flowchart illustrating a flow of a CR user performing adaptive transmission in a CR system according to an embodiment of the present invention.

2 is a schematic block diagram of a CR communication system according to the present invention.

Claims (8)

1. A cognitive radio (CR) communication system using a frequency band used by a main user communication system, A transmission / reception unit for receiving spectrum sensing information on a frequency band of a main user communication system; An analysis module for analyzing the spectrum sensing information and analyzing whether there is an idle band in the frequency band; A measurement module for measuring an interference temperature for the frequency band when there is no idle band; A first calculation module for calculating a channel capacity using the measured interference temperature and selecting a channel having the lowest interference with respect to the main user communication system; A second calculation module for calculating a distance between the main user and the CR user using the measured interference temperature; Using the main user calculated by the second calculation module and the distance and the interference temperature measured by the measurement module Calculates the SINR for the primary user's communication system, The transmission power of the signal to be used by the CR user communication system is calculated so that signal interference does not occur to the main user, And a third computation module for determining a modulation scheme for the signal of the CR user communication system. A method for a CR user adaptively transmitting a signal in a cognitive radio (CR) communication system, (A) a distance between the CR user and the main user based on the interference temperature value (IT value) for the frequency band of the main user measured and calculated using the spectrum sensing algorithm

; ≪ / RTI > (B) determining the transmit power (P _{max, CR)} of the signal CR users to use so as not to interfere with the effect on the primary user based on a distance from the said measured primary user; (C) calculating a signal-to-interference and noise ratio (SINR) using the determined transmission power and the measured interference temperature value; (D) determining an optimal modulation scheme of a signal to be used by the CR user using the SINR. 3. The method of claim 2, wherein step (A) Calculating an interference temperature value (IT value) using Equation (2) and a power spectrum density measured through a spectrum sensing algorithm; Calculating a channel capacity of each channel in the frequency band of the main user using the calculated interference temperature value; And measuring the distance between the CR user and the main user using Equation (4) based on the value of the interference criterion temperature and the information of Equation (3) Equation (2)

ego, Equation (3)

ego, Equation (4)

Wherein the adaptive transmission method comprises the steps of: delete 3. The method of claim 2, wherein step (B) Determining an SINR that ensures that bit error rate (BER) performance of the main user system does not suffer deterioration using Equation (6); And determining a transmission power value capable of providing a maximum transmission efficiency to the CR user using Equation (5) Equation (5)

ego, Equation (6)

Wherein the adaptive transmission method comprises the steps of: delete 3. The method of claim 2, wherein step (D) ( T _I , _CR ) for the maximum transmission power ( P _max , _CR ) of the _CR user and the signal s ( t ) received from the main user in the frequency band of the main user and outputs the interference temperature value Calculating a SINR value ( SINR _CR ) given to the user; And adaptively selecting a modulation scheme capable of ensuring an optimal transmission rate for a CR user based on the calculated SINR value. 8. The method of claim 7, Characterized in that if the SINR _CR satisfies the required SINR value of each modulation scheme to obtain a desired BER performance, the modulation scheme which provides the highest transmission rate among the modulation schemes in which the required SINR is satisfied is selected. Transmission method.

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