CN101778396B - Method for detecting cognitive user in opportunity spectrum sharing system - Google Patents

Abstract

The invention discloses a method for detecting a cognitive user in an opportunity spectrum sharing system, which relates to a design method for detecting a master user and sending data information frame length by the cognitive user (secondary user) in a system based on an opportunity spectrum access (OSA) technique in a cognitive network. The method comprises the following steps of: firstly, analyzing the testing frequency based the signal interference noise ratio of the secondary user; and secondly, defining the frame length of data transmission of the secondary user based on the testing frequency and the spectral optimization. A control channel is needed to be added in a single-channel multi-user scene, the selection and the scheduling of users are performed first, and then a method for detecting a single user is implemented. The basic thought of the method that the occupation condition of an authorized channel by the master user and the influence on the signal interference noise ratio (SINR) of the secondary user by the master user are analyzed, and thus the detection frequency and the transmission frame length of the secondary user are designed, and an optimizing and compromising scheme is found between the throughput of the secondary user and the collision probability with the master user.

Description

The detection method of cognitive user in opportunity spectrum sharing system

Technical field

The present invention relates generally in a kind of cognition network and insert the method for designing that cognitive user (inferior user) detected and sent the data message frame length in (OSA) technological system to main user based on opportunistic spectrum.The basic thought of this method is to analyze main user the influence to inferior subscriber signal interference-to-noise ratio (SINR) is appearred in the occupancy and the main user of authorization channel; And design time user with this and detect frequency and transmission frame length, inferior user throughput and and main user's collision probability between find and optimize and the scheme of compromise.

Background technology

Opportunistic spectrum access (OSA) technology is meant and need not cooperation between the primary and secondary user that inferior user acts according to circumstances and uses main user's frequency spectrum resource.Main user need not to know time user's existence, brings additional overhead can for main user.Inferior user at first intercepts local frequency spectrum, searching idle channel before access; If there is idle channel, just inferior user inserts; If temporarily do not have, just inferior user waits for that main user discharges channel; In inferior telex network process, in case main user need take the channel that time user is using, inferior user this channel of rapid release at the appointed time supplies main user to use.Therefore; In the OSA system; Inferior user need detect main user in time, and inferior user's detection time, the frame length that detects frequency and inferior user data transmission all have fundamental influence to inferior user's transmission quality itself and to main user's interference and transmission quality.

If detection time is long, frequency is high, the detection probability of cognitive nodes is high, just can protect authorized user better.Simultaneously, this can bring time user to transmit the increase of interruption frequency, and the throughput of inferior user service data transmission reduces, and brings time delay thus.Therefore, as far as inferior user, hope to have a rational transmission time and detection frequency, feasible time user can have as far as possible more chances of transmitting data continuously, transmits more business datum, and try one's best minimizing and main user's collision.

Same problem is present in single user's single channel applied environment and the multi-user competes the single channel environment, and the basic thought of the design under the different scenes is consistent, but between the multi-user, need carry out necessary scheduling and coordination.

Summary of the invention

Technical problem: the purpose of this invention is to provide the detection method of a kind of cognitive user in opportunity spectrum sharing system; This method is to insert the method for designing that cognitive user (inferior user) detected and sent the data message frame length in (OSA) technological system to main user based on opportunistic spectrum in the cognition network; This method addresses the above problem and/or shortcoming, and the detection method that time user takes into account the increase throughput, reduces interference and conflict in a kind of cognition network is provided.

Technical scheme: the detection method of cognitive user of the present invention in opportunity spectrum sharing system is based on above consideration; Solution is in wireless cognition network; Between inferior user or inferior user, main user detected the design of frequency and time user's transmission frame length, reach time user throughput and and main user's collision probability between optimization and compromise.

This method comprises two parts: the one, detect frequency from inferior subscriber signal interference-to-noise ratio angle analysis; The 2nd, from detecting the frame length of frequency and frequency spectrum optimization viewpoint definition time user data transmission; In single channel multi-user scene, needing increases control channel, at first carries out user's selection and scheduling, implements the detection method of unique user again, is specially:

1). single channel list user scene

Step 1: inferior user detects main user in the time at i, judges whether to exist main user, if exist main user to continue the detection of next i time; If do not exist time user according to main user to channel take rule and the channel conditions of self calculates its frame length T;

Step 2: based on Mathematical Modeling and the probabilistic method of main user to channel occupancy; Calculate the average time user of time user when bumping Signal Interference and Noise Ratio SINR with main user, and the average SINR of inferior user when not bumping with main user;

Step 3: calculate the average boundary that can reach maximum throughput when time user and main user do not bump based on the average SINR of inferior user when not bumping with main user;

Step 4:, obtain the optimum time user's frame length that obtains from the spectrum efficiency optimal angle according to optimization criterion;

Step 5: according to the average SINR of inferior user when bumping with main user, and the average SINR of inferior user when not bumping with main user, in conjunction with the second-order statistics of SINR, calculate the inferior user who obtains from the SINR statistical property and detect frequency;

Step 6: detect at optimum the user's frame length that obtains from the spectrum efficiency optimal angle with from the inferior user that the SINR statistical property obtains and to get minimum value between frequency and obtain final inferior user's frame length T; After calculating T, carry out transfer of data in the time at T-i; After the transfer of data of a frame is intact, judge whether time user's data has been transmitted, if transmitted, inferior user sends CTS message to authorization channel, withdraws from this authorization channel; If inferior user data has not transmitted, then repeat above detection and transmission course,

2). single channel multi-user scene

In single channel multi-user scene, the practical implementation step of inferior user's detection method is:

Step 7: distribute time slot i by control channel; N time user who exists in the current system in time at i carries out joint-detection to authorization channel; And the result fed back to control channel; Carry out data fusion and judge whether main user exists by control channel, if exist then proceed joint-detection in the next i time; If do not exist; Control channel is selected best access time user i according to optimizing utility function

, and sends RTS/CTS message to i;

Step 8: selected inferior user carries out the detection step in single user's scene after receiving the message of control channel, inferior user i according to main user to channel take rule and the channel conditions of self calculates its frame length T _i, and at T _iThe data of transmission time user i in the-i;

Step 9: when a frame data end of transmission, system judges whether all data of time user i have been transmitted, if transmitted; Inferior user sends CTS message to control channel; Withdraw from this authorization channel, control channel upgrades user's combination, and gets into new round detection and transmission course; If inferior user data has transmitted, then continue above detection of repetition and transmission course.

Beneficial effect: experimental result proves, this scheme has realized that the effective collision between inferior user and main user suppresses, frequency spectrum share efficiently, and between inferior user, realized the fairness and the low probability conflict of competition.And the scheme that the present invention proposes does not have extra increase primary and secondary user's expense, only need increase a control channel in multi-user's scene, realizes that cost and complexity are low.

Description of drawings

Through below in conjunction with the accompanying drawing and the detailed description of carrying out, it is clearer that above and other objects of the present invention, characteristics and advantage will become, wherein;

Fig. 1 shows single CU authorization channel and detects the frame structure case of authorization channel.

Fig. 2 shows the frame structure case that the multi-user takies authorization channel and detects authorization channel.

Fig. 3 shows scheme flow chart among Fig. 1.

Fig. 4 shows scheme flow chart among Fig. 2.

Embodiment

Fig. 1 shows that single main CU authorization channel and single user detect authorization channel and in the frame structure case of authorization channel transmission data.With reference to Fig. 1, main user takies index of coincidence on-off discharge model to authorization channel.Main CU channel in this model, the average duration of promptly opening is β ₀Main user is busy channel not, and the average duration of promptly closing is β _i, main user is t by busy channel to discharging the used time of channel, its obeys index distribution.Suppose that time user's frame length is T, the t millisecond time is used for the detection to main subscriber channel before the transmission data.When detecting main user and not existing, transmit time user data in the time at T-i, in the transmission data procedures, main user can occur at any time, and the primary and secondary user data package can bump and made time user's data packet loss this moment.Frame length T has not only determined inferior user to transmit data length (inferior user throughput) but also has determined the frequency (collision probability) that inferior user detects main user.Fig. 2 shows single authorization channel multi-user's case.With reference to Fig. 2, also there is race problem between time user simultaneously in the same problem of confirming frame length T that exists.

At first, here the term definition of definition is following:

SINR: inferior user's Signal Interference and Noise Ratio

γ：SINR

β ₀: the average duration of main CU channel

β _i: main user discharges the average duration of channel

T: main user by busy channel to discharging the used time of channel

Tt: main user is by discharging channel to the used time of busy channel

I: inferior user is to main user's detection time

T: inferior user's frame length

I: i time user

T _i: the frame length of inferior user i

P ₀: main user is in the received power of inferior user's receiving terminal

P _s: inferior user is in the received power of inferior user's receiving terminal

N: system is number of users last time

N ₀: AWGN power

N _j: the SINR level passes through SINR thresholding γ _jLevel crossing rate

P (): probability density function

F (): exponential distribution function

B: the channel width of authorization channel

γ _c(T, τ, P _s, P ₀): time user's instantaneous SINR when bumping with main user

Time user's average SINR when

bumps with main user

γ _Nc(T, τ, P _s, P ₀): time user's instantaneous SINR when not bumping with main user

average SINR of time user when not bumping with main user

when not bumping with main user time user can reach the on average lower bound of throughput

when not bumping with main user i user when optimum frame length, can reach the on average lower bound of throughput

T ^*: the inferior user's that the optimization throughput obtains optimum frame length

T _i ^*: i time user's that the optimization throughput obtains optimum frame length

DF (P _s, P ₀): the inferior user's who obtains according to second-order statistics frame length

f _D: the maximum doppler frequency of fading channel

The average SINR of

fading channel

RTS/CTS: request transmission/clear to send

The design that inferior user detected and sent the data message frame length is following:

1. single user's single channel scenario:

With reference to Fig. 1, in the time, when main user occurred, inferior user's SINR was expressed as at T

Because t obeys following exponential distribution

Average SINR when bumping at this moment, is expressed as

Likewise, in the time, when main user did not occur, inferior user's SINR was expressed as at T

Tt obeys following exponential distribution

$f\left(\mathrm{tt}\right)=\frac{1}{{\mathrm{\β}}_1}\exp (-\frac{\mathrm{tt}}{{\mathrm{\β}}_1})\mathrm{dt}$

Average SINR when not bumping at this moment, is expressed as

The corresponding time user of this SINR can reach one of throughput on average lower bound, promptly

Inferior user is in the wireless authorization channel, and its characteristic of channel is consistent with the fading channel characteristic, and under the fading channel condition, the second-order statistics of inferior user SINR comprises two important parameters of the level crossing rate and the average duration of fading.

Inferior user's frame length T is by following formula definition

T＝min(T ^*，DF(P _s，P ₀))

T ^*Obtain by following optimization

DF (P _s, P ₀) obtain by following formula

At this,

$N_j=\sqrt{\frac{2\mathrm{\π}{\mathrm{\γ}}_j}{\stackrel{\‾}{\mathrm{\γ}}}}{f}_D{e}^{-{\mathrm{\γ}}_j/\stackrel{\‾}{\mathrm{\γ}}}$

2. multi-user's single channel scenario

Each time user's frame length is definite consistent with single user's single channel scenario in multi-user's single channel scenario, and different is scheduling and the distribution that between inferior user, has increased MAC, to avoid the collision between time user.For this reason, need a control channel.With reference to Fig. 2; Participate in the individual time joint detection of users authorization channel of N of application authorization channel in time and testing result is sent to control channel at i; Control channel obtains the result to main user's detection through data fusion, if main user does not occur, according to the utility function of the maximization availability of frequency spectrum

$\underset{i}{\arg \max }{\left(\stackrel{\‾}{R_{\min }}\left(T_i^{*}\right)\right)}_i$

Select the best channel time user i that uses, and through send the RTS/CTS order to inferior user i.When the frame length end of transmission of inferior user i, above process repeats, and selects the use time user and the corresponding frame length of next frame.

Preferential embodiment of the present invention is here described below with reference to accompanying drawings.Because known function and structure make the present invention fuzzy in unnecessary details, therefore they are described no longer in the specification below.

A. single channel list user scene

With reference to Fig. 3, the practical implementation step of time user's detection scheme is in single channel list user scene:

In step 310, inferior user detects main user in the time at i.In step 312, judge whether to have main user, if having main user then return step 310; If do not exist then time user carries out transfer of data at the T-i that calculates in the time.After the transfer of data of a frame is intact, judge in step 316 whether all data of time user have been transmitted, get into step 318 if transmitted, inferior user sends CTS message to authorization channel, withdraws from this authorization channel.If inferior user data has not transmitted, then get into step 310, repeat above the detection and transmission course.

B. single channel multi-user scene

With reference to Fig. 4; The practical implementation step of time user's detection scheme is in single channel multi-user scene: in step 410; Distribute time slot i by control channel; N time user who exists in the current system in time at i carries out joint-detection to authorization channel, and the result is fed back to control channel, carried out data fusion and judged in step 412 whether main user exists by control channel.If exist then return step 410; If do not exist; In step 414; Control channel is selected best access time user i according to utility function , and sends RTS/CTS message to i.After receiving message, inferior user i is according to the corresponding frame length T of state computation of oneself _i, and in Ti-i the data of transmission time user i.Whether all data of in step 418, judging time user i have been transmitted, and get into step 420 if transmitted, and inferior user sends CTS message to control channel, withdraws from this authorization channel, and control channel upgrades user's combination in step 422, and gets into step 410 again.If inferior user data has not transmitted, then get into step 410, repeat above the detection and transmission course.

Claims (1)

1. the detection method of a cognitive user in opportunity spectrum sharing system is characterized in that this method comprises two parts: the one, detect frequency from cognitive user Signal Interference and Noise Ratio angle analysis; The 2nd, from detecting the frame length of frequency and frequency spectrum optimization viewpoint definition cognitive user transfer of data; In single channel multi-user scene, needing increases control channel, at first carries out user's selection and scheduling, implements the detection method of unique user again, is specially:

1). single channel list user scene

Step 1: cognitive user detects main user in the time at t, judges whether to exist main user, if exist main user to continue the detection of next t time; If do not exist cognitive user according to main user to channel take rule and the channel conditions of self calculates its frame length T;

Step 2: based on Mathematical Modeling and the probabilistic method of main user to channel occupancy; Calculate the Signal Interference and Noise Ratio SINR of the average cognitive user of cognitive user when bumping with main user, and the average SINR of cognitive user when not bumping with main user;

Step 3: calculate the average boundary that can reach maximum throughput when cognitive user and main user do not bump according to the average SINR of cognitive user when not bumping with main user;

Step 4:, obtain the optimum cognitive user frame length that obtains from the spectrum efficiency optimal angle according to optimization criterion;

Step 5: the average SINR of cognitive user when bumping with main user, and the average SINR of cognitive user when not bumping with main user, in conjunction with the second-order statistics of SINR, calculate the cognitive user that obtains from the SINR statistical property and detect frequency;

Step 6: obtain getting minimum value between cognitive user detection frequency at the optimum cognitive user frame length that obtains from the spectrum efficiency optimal angle with from the SINR statistical property and obtain final cognitive user frame length T; After calculating T, carry out transfer of data in the time at T-t; After the transfer of data of a frame is intact, judge whether the data of cognitive user have been transmitted, if transmitted, cognitive user is sent CTS message to authorization channel, withdraws from this authorization channel; If the cognitive user data have not been transmitted, then repeat above detection and transmission course,

2). single channel multi-user scene

In single channel multi-user scene, the practical implementation step of cognitive user detection method is:

Step 7: distribute time slot t by control channel; N cognitive user in that t existed in the current system in the time carried out joint-detection to authorization channel; And the result fed back to control channel; Carry out data fusion and judge whether main user exists by control channel, if exist then proceed joint-detection in the next t time; If do not exist; Control channel is selected best access cognitive user i according to optimizing utility function

, and sends RTS/CTS message to i;

is: i cognitive user can reach the on average lower bound of throughput when not bumping with main user when optimum frame length;

Step 8: selected cognitive user is carried out the detection step in single user's scene after receiving the message of control channel, cognitive user i according to main user to channel take rule and the channel conditions of self calculates its frame length T _i, and at T _iThe data of transmitting cognitive user i in the-t;

Step 9: when a frame data end of transmission, system judges whether all data of cognitive user i have been transmitted, if transmitted; Cognitive user is sent CTS message to control channel; Withdraw from this authorization channel, control channel upgrades user's combination, and gets into new round detection and transmission course; If the cognitive user data have been transmitted, then continue above detection of repetition and transmission course.

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