CN101364847A - Cooperative communication method in cognitive radio - Google Patents

Abstract

The invention relates to a cooperative communication method in cognitive wireless network of the communication technical field. If a main user and a secondary user work in a non-cooperative mode, the main user can access a channel at any time, and the secondary user can only use the channel when the channel is idle. If only one secondary user is present in the cognitive wireless network, the throughput increasing rate of the secondary user is determined whether or not to reach a set threshold according to the channel quality, and the secondary user carries out cooperative communication with the main user by adopting a TDMA-AF protocol technique if the throughput increasing rate is larger than or equal to the set threshold, otherwise, the secondary user does on participate in the communication with the main user. If a plurality of secondary users exist in the cognitive wireless network, the secondary user with the largest throughput increasing amount is selected as a relay user to carry out cooperative communication. The throughput of the secondary user can be improved by 8% to 20%.

Description

Collaboration communication method in the cognitive radio

Technical field

The present invention relates to a kind of method of communication technical field, specifically is the collaboration communication method in a kind of cognitive radio.

Background technology

Be extensive use of along with wireless, taking of frequency spectrum makes frequency spectrum resource rare further.And requirements of different users will cause the space that utilizes of certain frequency spectrum.Cognitive radio utilizes spectrum opportunities just, maximally utilises frequency spectrum thereby insert channel.In cognitive radio networks, generally be divided into main users and secondary user (also claiming secondary user's).Main users is an authorized user, has the ownership to channel, momentarily access channel and can not be subjected to any interference.Secondary user is a unauthorized user, only just can take when main users is not used channel, thereby that is to say that chance formula ground busy channel obtains maximum throughput.In the cognition wireless telecommunication, secondary user must wait for that main users is finished using could access channel, and main users is when using channel, and secondary user can only monitor and can not produce interference.Collaboration communication is a kind of new technology of utilizing the cooperation diversity to overcome the wireless channel fading characteristic.In 3 communication patterns, relay nodes is sent to destination node again by accepting the information of source node after the processing.Collaboration type communication is that radio has brought the cooperation diversity, has reduced the transmission interruption rate effectively.

Find by prior art documents, H.-P.Shiang etc. are at " IEEE Transactions onMultimedia, vol.10, no.5, pp.896-909, Aug.2008 " (institute of electrical and electronic engineers multimedia field periodical, publish in August, 2008, the 10th volume, the 5th phase, the 896-909 page or leaf). on " Queuing-Based Dynamic Channel Selection for Heterogeneous MultimediaApplications Over Cognitive Radio Networks " (being chosen in application in the cognitive radio multi-media network) of delivering based on the dynamic channel of formation, this article has proposed a kind of method of using based on formation, and be applied in the cognitive radio, but the method that this article proposes is an approximate solution, is not enough to accurately explain the phenomenon in the cognitive radio.

Also find by retrieval, O.Simeone etc. are at " IEEE Transactions on Communications, vol.55, no.12, pp.2351-2360, Dec.2007 " (institute of electrical and electronic engineers communications field periodical, publish in December, 2007, the 55th volume, the 12nd phase, the 2351-2360 page or leaf) " the Stable Throughput ofCognitive Radios With and Without Relaying Capability " that delivers on (the steady-state throughput performance of cognitive radio under the relay situation), this article has proposed the application of collaboration communication at cognitive radio, but do not propose concrete relay agreement, and only limit to study the phenomenon under the limit, be not enough to explain fully the application of collaboration type communication in cognitive radio.

Summary of the invention

The present invention is directed to above-mentioned the deficiencies in the prior art, collaboration communication method in a kind of cognitive radio is provided, make under concrete relay agreement, when secondary user uses channel in main users, the communication of cooperation main users, the main users resource of can finishing using as early as possible, thus for secondary user provides new spectrum opportunities, the throughput of final secondary user gets a promotion.

The present invention is achieved by the following technical solutions, the present invention includes following steps:

Step 1, main users and secondary user constitute cognitive radio networks, main users and secondary user work under no collaboration mode, main users is access channel at any time, if secondary user is using channel, then secondary user must withdraw from channel is returned in main users, and secondary user only could use when channel idle;

Step 2, if only have a secondary user in the cognitive radio networks, whether the throughput raising rate of judging this secondary user according to channel quality information reaches preset threshold, if select this secondary user to adopt TDMA-AF (time division multiplexing-forward direction amplifies) protocol technology and main users to carry out collaboration communication more than or equal to preset threshold, otherwise do not participate in the communication of main users; If have a plurality of secondary users in the cognitive radio networks, select the secondary user of throughput raising amount maximum to carry out collaboration communication as the relay user.Finish a collaboration communication and comprise two time slots: at first time slot, main users sends information, and relay station and secondary user receive information simultaneously, at second time slot, main users and secondary user send information simultaneously, and relay station receives both information simultaneously.

Described main users and secondary user, its information all is base unit with the bag, the entering of bag according to Poisson distribution, the length of bag is to distribute arbitrarily.

Described main users and secondary user, its throughput is respectively:

${\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="A200810200427E00122.png,A200810200427E00131.png"\; state="\{\{state\}\}">U</figure-callout>}}_0=\frac{{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="A200810200427E00122.png,A200810200427E00131.png"\; state="\{\{state\}\}">L</figure-callout>}}_0}{\frac{{\mathrm{\&rho;}}_0^2}{2(1-\mathrm{\&rho;}0)}+\frac{{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="A200810200427E00122.png,A200810200427E00131.png"\; state="\{\{state\}\}">L</figure-callout>}}_0+L_{\mathrm{oh}}}{R_0(1-P_0)}}$ Formula one

$\begin{array}{cc}{U}_i=\frac{L_i}{\frac{{\mathrm{\&Sigma;}}_{k=0}^N{\mathrm{\&rho;}}_{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="A200810200427E00122.png"\; state="\{\{state\}\}">k</figure-callout>}}^2}{2(1-{\mathrm{\&rho;}}_0)(1-{\mathrm{\&Sigma;}}_{k=0}^N){\mathrm{\&rho;}}_k}+\frac{L_i+L_{\mathrm{oh}}}{R_i(1-P_i)}}& i=\mathrm{1,2},...,N\end{array}$ Formula two

Wherein, subscript 0 is represented main users, and subscript i represents secondary user's (allowing a plurality of secondary users here), and L represents average packet long, ρ that represent traffic load capacity, and R represents physical layer transmission rate, P represents Packet Error Ratio.

Described TDMA-AF agreement, it works under the semiduplex mode, and the forward direction amplifying technique can directly use hardware to realize, is easy to implement in actual applications.

In described first time slot, main users sends information, and relay station and secondary user receive information simultaneously, and secondary user only will receive information storage in buffering area at first time slot, and stay next time slot and send,

Wherein, main users with the input/output relation of communicating by letter of relay station is:

$y_{D,1}=\sqrt{E_{\mathrm{SD}}}{h}_{\mathrm{SD}}{x}_1+n_{D,1},$

In the formula, subscript S, D represent main users and relay station, y respectively _{D, 1}Represent the received information of relay station, x ₁The information of representing main users to send, E _SdBe average received energy in a time slot, represented large scale decay (path attenuation and shielding), h _SdBe the random complex variable of unitization, represent channel gain to that is to say the small scale decay, noise component(s) n represents white Gaussian noise, and variance is N ₀

The input/output relation of main users and secondary user is:

$y_{R,1}=\sqrt{E_{\mathrm{SR}}}{h}_{\mathrm{SR}}{x}_1+n_{R,1},$

Meaning of parameters in the input/output relation of communicating by letter of the meaning of parameters in the formula and main users and relay station is identical, subscript difference just, and subscript S, R represent main users and secondary user respectively in the formula.

In described second time slot, main users and secondary user send information simultaneously, and relay station receives both information simultaneously, and the information that receives is amplified by secondary user Doubly make transmitting power maximize, relay station is finished collaboration communication with the information separated from two users that receives simultaneously,

Wherein, the signal input/output relation of relay station reception main users and secondary user is:

$y_{D,2}=\sqrt{E_{\mathrm{SD}}}{h}_{\mathrm{SD}}{x}_2+\sqrt{E_{\mathrm{RD}}}{h}_{\mathrm{RD}}\frac{y_{R,1}}{\sqrt{\mathrm{\&epsiv;}\left\{{\left|y_{R,1}\right|}^2\right\}}}+n_{D,2}$

Wherein, subscript R represents secondary user, x ₂Be that main users is at second information that time slot sent, y _{D, 2}Be that relay station is second information that time slot is received.

Described secondary user, it does not use any encoding and decoding or demodulation function during as relay nodes in the forward direction amplifying technique, only the signal that receives is carried out linear amplification.

The threshold value of described throughput raising rate is 5%, and this is because if the raising amount of secondary user is less, DeGrain increases the power loss of secondary user on the contrary.

Described collaboration communication in first time slot, has two nodes in reception information; At second time slot, two nodes are arranged in transmission information, each time slot has all made full use of each node,, therefore maximized the cooperation diversity.

Described main users, it is using this collaboration communication agreement, and small scale decays under the situation of rayleigh distributed, and the upper bound of interruption rate is:

$P(I<\mathrm{\&eta;})\&le;{\left(\frac{2^{2\mathrm{\&eta;}}-1}{\mathrm{\&beta;}}\right)}^2$

Wherein

$\mathrm{\&beta;}=\min \{(1+\frac{1}{{\mathrm{\&omega;}}^2})\frac{{\mathrm{<figure-callout\; id="0"\; label="E\; SD\; N"\; filenames="A200810200427E00122.png,A200810200427E00131.png"\; state="\{\{state\}\}">E</figure-callout>}}_{\mathrm{SD}}}{N_{}},\frac{1}{{\mathrm{\&omega;}}^2}\frac{E_{\mathrm{SR}}{E}_{\mathrm{RD}}}{(E_{\mathrm{SR}}+N_0)N_0}\}$

${\mathrm{\&omega;}}^2=1+\frac{E_{\mathrm{RD}}}{E_{\mathrm{SR}}+{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="A200810200427E00122.png,A200810200427E00131.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}$

E represents power gain, and subscript S, R, D represent main users, secondary user and relay station respectively.N ₀Represent average noise power.

Compared with prior art, the present invention has following beneficial effect: in cognitive radio, because the low priority of secondary user, often can't obtain comparatively ideal throughput, the present invention proposes a kind of concrete cognitive radio collaboration type communication means, after adopting collaboration type communication, the throughput of secondary user can obtain 8%～20% raising.

Description of drawings

The structural representation of Fig. 1 embodiments of the invention collaboration type cognitive radio.

The three-dimension curved surface schematic diagram of main users and secondary user's throughput when Fig. 2 embodiments of the invention are communicated by letter at no collaboration type;

Wherein: (a) being the throughput schematic diagram of main users about Packet Error Ratio and bag arrival rate, (b) is the throughput schematic diagram of secondary user about Packet Error Ratio and bag arrival rate.

Fig. 3 be embodiments of the invention under collaboration communication, main users performance schematic diagram;

Wherein: (a) be the schematic diagram data of main users channel Packet Error Ratio, (b) be the schematic diagram data of secondary user's throughput about the main users signal to noise ratio about signal to noise ratio.

Fig. 4 be embodiments of the invention under collaboration communication, the curved line relation schematic diagram between the recruitment of secondary user's throughput and the main users bag arrival rate.

Embodiment

Below in conjunction with accompanying drawing embodiments of the invention are elaborated: present embodiment is being to implement under the prerequisite with the technical solution of the present invention, provided detailed execution mode and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

As shown in Figure 1, be the structural representation of using the collaboration type cognitive radio of present embodiment method, a main users and a plurality of secondary user's (secondary user's is a secondary user) insert relay station simultaneously and have constituted cognitive radio networks.The bag that each user need send enters respectively in the transmit queue, and wherein the transmit queue priority of main users is the highest, and the priority of secondary user is minimum.At the transmit queue of main users is empty, and when also being the main users channel idle, the bag that secondary user could incite somebody to action in the formation separately sends out.When main users had bag to arrive, secondary user was deprived the channel right to use at once, and secondary user does not send the bag that finishes as yet and puts back in this user's the formation, and main users is used channel.In Fig. 1, secondary user 1 carries out collaboration communication as relay nodes according to TDMA-AF (time division multiplexing-forward direction amplifies) protocol technology and main users.

The environmental parameter of present embodiment is:

Main users: the channel spectrum utilance is 0.2, physical layer rate 1Mbps, the long 1KBytes of average packet, Packet Error Ratio 0.1,30 per seconds of bag arrival rate, channel average power gain 0dB.

Secondary user: the channel spectrum utilance is 0.2, physical layer rate 1Mbps, the long 1KBytes of average packet, Packet Error Ratio 0.1,10 per seconds of bag arrival rate, main users-Secondary Users' channel average power gain 30dB, Secondary Users-relay station channel average power gain 30dB.

Present embodiment comprises following concrete steps:

Step 1, main users and secondary user constitute cognitive radio networks, main users and secondary user work under no collaboration mode, main users is access channel at any time, if secondary user is using channel, then secondary user must withdraw from channel is returned in main users, and secondary user only could use when channel idle;

Utilize formula one and formula two, the throughput that obtains main users and secondary user is respectively 0.75Mbps, 0.613Mbps, Fig. 2 (a) is that main users is 1Mbps in physical layer rate, average packet is long under the 1KByte, and about the throughput schematic diagram of Packet Error Ratio and bag arrival rate, Fig. 2 (b) is that secondary user is 0.1 at Packet Error Ratio, physical layer rate is grown under the situation identical with main users, about the throughput schematic diagram of Packet Error Ratio and bag arrival rate with average packet.

Step 2, if only have a secondary user in the cognitive radio networks, whether the throughput raising rate of judging this secondary user according to channel quality information reaches preset threshold, if select this secondary user to adopt TDMA-AF (time division multiplexing-forward direction amplifies) protocol technology and main users to carry out collaboration communication more than or equal to preset threshold, otherwise do not participate in the communication of main users; If have a plurality of secondary users in the cognitive radio networks, select the secondary user of throughput raising amount maximum to carry out collaboration communication as the relay user.Finish a collaboration communication and comprise two time slots: at first time slot, main users sends information, and relay station and secondary user receive information simultaneously, at second time slot, main users and secondary user send information simultaneously, and relay station receives both information simultaneously.

In described first time slot, main users sends information, and relay station and secondary user receive information simultaneously, secondary user only will receive information storage in buffering area at first time slot, stay next time slot and send, wherein, main users with the input/output relation of communicating by letter of relay station is:

$y_{D,1}=\sqrt{E_{\mathrm{SD}}}{h}_{\mathrm{SD}}{x}_1+n_{D,1},$

In the formula, subscript S, D represent main users and relay station, y respectively _{D, 1}Represent the received information of relay station, x ₁The information of representing main users to send, E _SdBe average received energy in a time slot, represented large scale decay (path attenuation and shielding), h _SdBe the random complex variable of unitization, represent channel gain to that is to say the small scale decay, noise component(s) n represents white Gaussian noise, and variance is N ₀

The input/output relation of main users and secondary user is:

$y_{R,1}=\sqrt{E_{\mathrm{SR}}}{h}_{\mathrm{SR}}{x}_1+n_{R,1},$

Meaning of parameters in the input/output relation of communicating by letter of the meaning of parameters in the formula and main users and relay station is identical, subscript difference just, and subscript S, R represent main users and secondary user respectively in the formula.

In described second time slot, main users and secondary user send information simultaneously, and relay station receives both information simultaneously, and the information that receives is amplified by secondary user Doubly make transmitting power maximize, relay station is finished collaboration communication with the information separated from two users that receives simultaneously,

Wherein, the signal input/output relation of relay station reception main users and secondary user is:

$y_{D,2}=\sqrt{E_{\mathrm{SD}}}{h}_{\mathrm{SD}}{x}_2+\sqrt{E_{\mathrm{RD}}}{h}_{\mathrm{RD}}\frac{y_{R,1}}{\sqrt{\mathrm{\&epsiv;}\left\{{\left|y_{R,1}\right|}^2\right\}}}+n_{D,2}$

Wherein, subscript R represents secondary user, x ₂Be that main users is at second information that time slot sent, y _{D, 2}Be that relay station is second information that time slot is received.

Fig. 3 (a) is the schematic diagram data of main users channel Packet Error Ratio about signal to noise ratio, and Fig. 3 (b) is the schematic diagram data of secondary user's throughput about the main users signal to noise ratio.Owing to only have a secondary user, only need judge whether throughput raising amount surpasses minimum, the error rate of main users channel drops to 0.0454 from 0.138 as calculated, and the throughput of secondary user rises to 0.667Mbps at this moment.

Fig. 4 for a change after the bag arrival rate of main users, can reach a conclusion by observing by the performance schematic diagram of the recruitment of secondary user's throughput, and when main users bag arrival rate was adjusted into for 63.58 bag/seconds, the throughput of secondary user obtained the maximum raising.

Claims (9)

1, the collaboration communication method in a kind of cognitive radio is characterized in that, comprises the steps:

Step 1, main users and secondary user constitute cognitive radio networks, main users and secondary user work under no collaboration mode, main users is access channel at any time, if secondary user is using channel, then secondary user must withdraw from channel is returned in main users, and secondary user only could use when channel idle;

Step 2, if only have a secondary user in the cognitive radio networks, whether the throughput raising rate of judging this secondary user according to channel quality information reaches preset threshold, if select this secondary user to adopt TDMA-AF protocol technology and main users to carry out collaboration communication more than or equal to preset threshold, otherwise do not participate in the communication of main users; If have a plurality of secondary users in the cognitive radio networks, select the secondary user of throughput raising amount maximum to carry out collaboration communication as the relay user, finish a collaboration communication and comprise two time slots: at first time slot, main users sends information, relay station and secondary user receive information simultaneously, at second time slot, main users and secondary user send information simultaneously, and relay station receives both information simultaneously.

2, the collaboration communication method in the cognitive radio according to claim 1 is characterized in that, described TDMA-AF agreement, and it works under the semiduplex mode, and its forward direction amplifying technique directly uses hardware to realize.

3, the collaboration communication method in the cognitive radio according to claim 1, it is characterized in that, in described first time slot, main users sends information, relay station and secondary user receive information simultaneously, secondary user only will receive information storage in buffering area at first time slot, stay next time slot and send

Wherein, main users with the input/output relation of communicating by letter of relay station is:

$y_{D,1}=\sqrt{E_{\mathrm{SD}}}{h}_{\mathrm{SD}}{x}_1+n_{D,1},$

In the formula, subscript S, D represent main users and relay station, y respectively _{D, 1}Represent the received information of relay station, x ₁The information of representing main users to send, E _SdBe average received energy in a time slot, represented large scale decay (path attenuation and shielding), h _SdBe the random complex variable of unitization, represent channel gain to that is to say the small scale decay, noise component(s) n represents white Gaussian noise, and variance is N ₀

The input/output relation of main users and secondary user is:

$y_{R,1}=\sqrt{E_{\mathrm{SR}}}{h}_{\mathrm{SR}}{x}_1+n_{R,1},$

Meaning of parameters in the input/output relation of communicating by letter of the meaning of parameters in the formula and main users and relay station is identical, subscript difference just, and subscript S, R represent main users and secondary user respectively in the formula.

4, the collaboration communication method in the cognitive radio according to claim 1 is characterized in that, in described second time slot, main users and secondary user send information simultaneously, and relay station receives both information simultaneously, and the information that receives is amplified by secondary user

Doubly make transmitting power maximize, relay station is finished collaboration communication with the information separated from two users that receives simultaneously,

Wherein, the signal input/output relation of relay station reception main users and secondary user is:

$y_{D,2}=\sqrt{E_{\mathrm{SD}}}{h}_{\mathrm{SD}}{x}_2+\sqrt{E_{\mathrm{RD}}}{h}_{\mathrm{RD}}\frac{y_{R,1}}{\sqrt{\mathrm{\&epsiv;}\left\{{\left|y_{R,1}\right|}^2\right\}}}+n_{D,2}$

Wherein, subscript R, D represent secondary user and relay station, x respectively ₂Be that main users is at second information that time slot sent, y _{D, 2}Be that relay station is at second information, y that time slot is received _{D, 1}Represent the received information of relay station.

5, the collaboration communication method in the cognitive radio according to claim 1 is characterized in that, the threshold value of described throughput raising rate is made as 5%.

6, the collaboration communication method in the cognitive radio according to claim 1 is characterized in that, described main users and secondary user, and its information all is base unit with the bag, the entering of bag according to Poisson distribution, the length of bag is to distribute arbitrarily.

7, according to the collaboration communication method in claim 1 or the 6 described cognitive radios, it is characterized in that, described main users and secondary user, its throughput is respectively:

$U_0=\frac{L_0}{\frac{{\mathrm{\&rho;}}_0^2}{2(1-{\mathrm{\&rho;}}_0)}+\frac{L_0+L_{\mathrm{oh}}}{R_0(1-P_0)}},$

$\begin{array}{cc}{U}_i=\frac{L_i}{\frac{{\mathrm{\&Sigma;}}_{k=0}^N{\mathrm{\&rho;}}_k^2}{2(1-{\mathrm{\&rho;}}_0)(1-{\mathrm{\&Sigma;}}_{k=0}^N{\mathrm{\&rho;}}_k)}+\frac{L_i+L_{\mathrm{oh}}}{R_i(1-P_i)}}& i=\mathrm{1,2},...,N\end{array},$

Wherein, subscript 0 is represented main users, and subscript i represents secondary user, and L represents average packet long, ρ that represent traffic load capacity, and R represents physical layer transmission rate, P represents Packet Error Ratio.

8, according to the collaboration communication method in claim 1 or the 6 described cognitive radios, it is characterized in that, described secondary user, it only carries out linear amplification with the signal that receives in the forward direction amplifying technique.

9, according to the collaboration communication method in claim 1 or the 6 described cognitive radios, it is characterized in that, described main users, it is using this collaboration communication agreement, and small scale decays under the situation of rayleigh distributed, and the upper bound of interruption rate is:

$P(I<\mathrm{\&eta;})\&le;{\left(\frac{2^{2\mathrm{\&eta;}}-1}{\mathrm{\&beta;}}\right)}^2,$

Wherein:

$\mathrm{\&beta;}=\min \{(1+\frac{1}{{\mathrm{\&omega;}}^2})\frac{E_{\mathrm{SD}}}{N_0},\frac{1}{{\mathrm{\&omega;}}^2}\frac{E_{\mathrm{SR}}{E}_{\mathrm{RD}}}{(E_{\mathrm{SR}}+N_0)N_0}\}$

${\mathrm{\&omega;}}^2=1+\frac{E_{\mathrm{RD}}}{E_{\mathrm{SR}}+N_0}$

E represents power gain, and subscript S, R, D represent main users, secondary user and relay station, N respectively ₀Represent average noise power.

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