CN102869018B - Channel and power joint distribution method for guaranteeing communication continuity in cognitive radio - Google Patents

Abstract

The invention discloses a channel and power joint distribution method for guaranteeing communication continuity in cognitive radio. The method includes that S1, a cognitive user periodically perceives radio environment, and a cognitive base station obtains sub-channel state information; S2, a cognitive user sends a communication request to the cognitive base station and informs the cognitive base station of amount of information required to be transmitted, and simultaneously the cognitive base station acquires service quality demand information of the cognitive user; S3, the cognitive base station distributes optimum channel and power of an initial phase for the cognitive user through solving an optimization problem, and the cognitive user starts to communicate; S4, when the communication of the initial phase is finished, the sub-channel state information and the service quality demand information are updated; S5, the cognitive base station performs the optimal joint distribution of channel and power of i<th> phase; and S6, the cognitive user continues to periodically perceiving surrounding radio environment, and the optimal distribution of the channel and power of subsequent phases is achieved. The method can guarantee the communication continuity of the cognitive user at different resource distribution phases.

Description

In cognitive radio, ensure channel and the power combined allocation method of continuity

Technical field

The channel and the power combined allocation method that the present invention relates to ensure in a kind of cognitive radio continuity, belong to wireless communication field.

Background technology

Radio Spectrum Resource is a kind of non-renewable resources of preciousness.Along with the development of wireless communication technology, the shortage of frequency spectrum resource becomes one of subject matter that the current communications field faces.On the one hand, the rise of the radio network techniques such as WLAN (wireless local area network), wireless personal area network and wireless MAN, makes people growing to the demand of radio spectrum resources, the contradiction of frequency spectrum supply and demand; On the other hand, many frequency ranges of having distributed are not in most of the cases fully utilized.The data that FCC (FCC) provides at the inquiry agency of 2003 show, the utilance of the frequency spectrum having distributed is only 15% ~ 85%.Under this background, cognitive radio technology arises at the historic moment.Cognitive radio technology is as a kind of dynamic spectrum technology of sharing of intelligence, can cognitive radio communication environment, according to certain study and dispatching algorithm, real-time adaptive ground changes the running parameter of system, detection of dynamic and effectively utilize idle frequency spectrum, improves in itself frequency spectrum resource utilization rate, solves frequency spectrum resource shortage problem.In cognitive radio networks, due to time, the spatial variations characteristic of radio spectrum resources, and cognitive user moves and causes network topology change etc., therefore must meet the requirement of dynamic self-adapting to the distribution of resources in network (channel, power etc.).Dynamic resource allocation method obtains channel condition information by periodically detecting wireless network environment, according to the QoS demand of current business, for the most suitable transmission channel of user assignment and through-put power, fully improve the utilance of wireless frequency spectrum and the throughput of network.

Application number is that the patent document of " 201110274437.0 " discloses " a kind of channel for cognitive radio networks and power combined allocation method ", the method emphasis is considered and what ensure is rate requirement and the user fairness of cognitive user, finally, by the theoretical assignment problem that solves of cooperative game, realize the fair allocat of resource.Application number is that the patent document of " 200910034228.1 " discloses " channel based on interference temperature in cognitive radio and power combined allocation method ", what the method emphasis was considered is under the restriction of authorized user interference temperature, the fairness assignment problem of channel and power resource, what the maximum interference temperature allowing according to authorized user in community was extrapolated cognitive user can transmitted power, and introduces poverty line and ensure the fairness of each user channel allocations.

In the channel and power combined allocation method of above-mentioned cognitive radio, although considered the interference of cognitive user to primary user and the service quality problem of cognitive user, but the channel that what these methods solved is all under a certain specific radio environment state and the assignment problem of power resource, and do not consider multistage channel and power co-allocation problem; And all there is no considering cognition user's continuity problem, under these distribution mechanisms, cognitive user, at each spectrum allocation may stage switching channels continually, has not only consumed energy, the continuity of communication before and after also cannot ensureing.Therefore study and in cognitive radio, ensure that the channel of continuity and power combined allocation method tool are of great significance.

Summary of the invention

The object of the invention is to, the channel and the power combined allocation method that in a kind of cognitive radio, ensure continuity are provided, can ensure the continuity of cognitive user at different resource allocated phase.

For solving the problems of the technologies described above, the present invention adopts following technical scheme: the channel and the power combined allocation method that in a kind of cognitive radio, ensure continuity, a random distribution N cognitive user (SU) in the cognitive radio networks of centralized configuration, a cognitive base station (BS) is set in the center of network, in network, usable spectrum is divided into the individual orthogonal subchannel of M (M > N), the bandwidth of every sub-channels is W, comprises the following steps:

S1, cognitive user is cognitive radio electrical environment periodically, and cognitive base station adopts certain merging criterion, and the data message that N cognitive user collected merges, and obtains sub-channel information by the method for cooperative detection, uses vectorial I={I _m| I _m∈ { 0,1}} _{m × 1}represent, wherein, I _m=1 represents that subchannel m is taken by primary user (PU), I _m=0 represents the subchannel m free time; " certain merging criterion " and " method of cooperative detection " all adopts known technology.

S2, cognitive user sends communication request to cognitive base station, and informs the amount of information size (unit is bit) that need to transmit cognitive base station, uses vectorial R={R _n| R _n>=0} _{n × 1}represent R _n=0 represents that cognitive user n is without communication requirement, and meanwhile, cognitive base station gathers the QoS requirement information of each cognitive user, and QoS requirement information is weighed by signal to noise ratio, with vectorial γ={ γ _n} _{n × 1}represent;

S3, optimum channel and the power resource of starting stage, according to sub-channel information and QoS requirement information, distributed for cognitive user in cognitive base station by solving an optimization problem with Prescribed Properties, and cognitive user starts to communicate;

S4, in the time of the sign off of starting stage, upgrades sub-channel information and QoS requirement information, is carrying out next stage,, before the channel and power resource allocation in i (i > 1) stage, need complete following steps:

S41, before the channel in i stage and the distribution of power resource, need pass through be that formula (1) detects each cognitive user and whether completes i-1 phase communication; Wherein represent the amount of information that i-1 stage cognitive user n need to transmit; represent the rate of information throughput of i-1 stage cognitive user n, c _{m, n}=1 represents that subchannel m distributes cognitive user n to use, p _{m, n}represent the transmitted power of cognitive user n on subchannel m, h _m,nrepresent the channel gain of cognitive user n on subchannel m, N ₀represent noise power spectral density; T represents in each stage that cognitive user is for transmitting the time of data;

S42, if formula (1) is set up, represents that cognitive user n has completed the transmission of i-1 session information amount, otherwise represents that cognitive user n does not complete the transmission of i-1 session information amount;

S43, has judged whether the channel that the cognitive user of communication was assigned with in the i-1 stage is all taken by primary user in the i stage, if occupied, this cognitive user is put under to set Ψ ₂, otherwise put under set Ψ ₁;

S44, if having new cognitive user to send communication request to cognitive base station in the i stage, puts this cognitive user under set Ψ ₂;

S5, obtains gathering Ψ by step S4 ₁and Ψ ₂after, cognitive base station carries out the channel in i stage and the optimal joint of power distributes, wherein:

(1) for set Ψ ₁in the cognitive user that does not complete i-1 phase communication, cognitive base station allows them to hold over subchannel that the i-1 stage is assigned with and that do not taken by primary user in the current generation to communicate;

(2) suppose to distribute to set Ψ in the i-1 stage ₁in user and the set of the subchannel that do not taken by primary user in the current generation be ∏, in the optimization problem described in step S3, add a restrictive condition: m ∈ ∏, n ∈ Ψ ₁, wherein, c _{m, n}=1 represents that subchannel m distributes to cognitive user n and uses, and becomes channel and the optimization problem corresponding to power co-allocation in i stage, by solving the optimization problem adding after restrictive condition, is set Ψ ₂in user assignment preferred channels, and for set Ψ ₁and Ψ ₂in user assignment optimal power; This restrictive condition can make the cognitive user of communication take identical channel resource at different allocated phases, has avoided channel switching process frequently, has ensured the continuity of cognitive user in different allocated phase communications.

S6, complete after the channel in i stage and the distribution of the optimal joint of power, cognitive user continues periodically perception radio environment around, upgrades sub-channel information and QoS requirement information, realizes the optimum allocation of channel and the power resource of follow-up phase.

In aforesaid cognitive radio, ensure in the channel and power combined allocation method of continuity, the cycle of cognitive user cognitive radio electrical environment is determined by system protocol, in one-period, cognitive user is τ for the time of cognitive radio electrical environment, is T for transmitting the time of data.

In aforesaid cognitive radio, ensure in the channel and power combined allocation method of continuity, in step S1, cognitive base station takes the frequency spectrum sensing method of cooperation to detect the situation that takies of subchannel, obtains sub-channel information.Suppose that the signal that cognitive user n receives is y _n, cooperative frequency spectrum sensing method is exactly that the data message each cognitive user being received by cognitive base station merges, if take equal gain combining criterion, the information that cognitive base station obtains is Y=∑ y _n; If adopt weighting merging criterion, the information that cognitive base station obtains is Y=∑ w _ny _n, wherein w _nrepresent weight factor, adopt cooperative frequency spectrum sensing method to improve and detect performance.

In aforesaid cognitive radio, ensure that in the channel and power combined allocation method of continuity, the optimization problem in described step S3 comprises:

(a) target function

Taking maximum system throughput as target function, its expression formula is:

$\underset{C,P}{\max }\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{c}_{m,n}W{\log }_2(1+\frac{p_{m,n}{\left|h_{m,n}\right|}^2}{N_{0}W}),$

Wherein C and P represent respectively channel allocation matrix and power division matrix, c _{m, n}=1 represents that subchannel m distributes to cognitive user n and uses, p _{m, n}represent the transmitted power of cognitive user n on subchannel m, h _m,nrepresent the channel gain of cognitive user n on subchannel m, N ₀represent noise power spectral density;

(b) constraints

I. when cognitive user sends when communication request, cognitive base station is just its allocated channel, and only available free subchannel is just used to distribute to cognitive user use, and every sub-channels can only use by a cognitive user, therefore needs to meet c _{m, n}=0, n ∈ { n|R _n=0}, c _{m, n}=0, m ∈ { m|I _m=1}, with m ∈ { m|I _m=0};

II. for fear of the interference to primary user, must the transmitted power on each sub-channels limit cognitive user, need to meet wherein, P _mrepresent the interference power upper limit of primary user on subchannel m;

III. in order to reach the quality of service requirement of cognitive user, signal to noise ratio when each cognitive user is carried out transfer of data on subchannel need meet wherein, γ _nrepresent to ensure the lowest signal-to-noise requirement of cognitive user n telecommunication service quality;

Therefore, the optimization problem of channel and power co-allocation is described as:

$\underset{C,P}{\max }\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{c}_{m,n}W{\log }_2(1+\frac{p_{m,n}{\left|h_{m,n}\right|}^2}{N_{0}W})$

s.t.c _m，n∈{0,1}

c _m，n＝0, n∈{n|R _n＝0},

c _m,n＝0, m∈{m|I _m＝1},

$\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{c}_{m,n}=1,$ m∈{m|I _m＝0}

$\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{c}_{m,n}{p}_{m,n}{\left|h_{m,n}\right|}^2\&le;P_m,\&ForAll;m$

$\frac{\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{c}_{m,n}{p}_{m,n}{\left|h_{m,n}\right|}^2}{N_{0}W}\&GreaterEqual;{\mathrm{\&gamma;}}_n,\&ForAll;n$

By solving this optimization problem, obtain Matrix C ^*and P ^*, for there being channel and the power resource of cognitive user optimal scheme of communication requirement.

In aforesaid cognitive radio, ensure, in the channel and power combined allocation method of continuity, in system, to set up a fixing control channel, carry out the mutual of frequency spectrum perception information and control information for cognitive user and cognitive base station.

In aforesaid cognitive radio, ensure in the channel and power combined allocation method of continuity, in the process of each stage cognitive user transmission data, if there is new cognitive user to propose communication request, cognitive base station is storage resource request information, and processes in next stage.

Compared with prior art, the present invention proposes the stage distribution method of the ascending resource (channel and power) in a kind of single cognitive radio community, cognitive base station, according to the channel condition information in each stage and cognitive user QoS requirement information, has been realized channel and the dynamic self-adapting in power resource stage and has been distributed.Simultaneously, before the resource in each stage is distributed, cognitive base station will judge whether all cognitive user have completed communication on last stage, in optimal assignment problem, add a restrictive condition, thereby the cognitive user that has made communication by hold over distribute on last stage and communicate at the subchannel that the current generation is not taken by primary user, emphasis has been considered the problem of cognitive user at different resource allocated phase continuity, avoid the process of cognitive user at the frequent switching channels of different allocated phases, reduce the energy consumption of system, ensure the continuity of cognitive user in different allocated phase communications.In the present invention, first judge at each allocated phase whether all cognitive user have completed communication in previous stage, then put cognitive user under two different set according to judged result and new communication request.For the user in two set, channel resource adopts the different methods of salary distribution, and power resource is still distributed unitedly.Take such distribution method, met the communication requirement of different user, realized the optimization of systematic function.

Existing channel and power associating Dynamic Assignment is all network configuration based on distributed or centralized.Although distributed strategy can improve user's autonomy, owing to lacking manager, make implemented strategy need a large amount of information interactions, increase the burden of network.Therefore, the present invention will adopt channel and the dynamic syndicated distribution method of power of centralized configuration, in cognition network, cognitive base station is set as Centroid, be responsible for receiving frequency spectrum perception information, the frequency spectrum resource application information etc. of cognitive user in network, according to dynamic allocation algorithm, realize the associating dynamic assignment of channel and power.

Suppose that having J sub-channels to be assigned to cognitive user n at i allocated phase uses, and cognitive user n do not complete communication in the i stage, now considers the continuity of i stage and i+1 stage cognitive user n.From the resource allocation methods of aforesaid guarantee continuity, only have when J sub-channels is in the time that the i+1 stage is all taken by primary user, cognitive user n just can be switched to new subchannel and communicate.Suppose that any one subchannel is all P at the probability of arbitrary allocated phase free time _s, to keep the probability of continuity in i stage and i+1 stage be P to cognitive user n _con=1-(1-P _s) ^j.Method of the present invention not only can ensure that cognitive user has very high continuity at different allocated phases, simultaneously owing to having avoided channel switching process frequently, the energy of system consumption is reduced.Suppose not adopt the method, cognitive user n must carry out the switching of D secondary channel just can complete the channel switching process in i+1 stage, and the energy that channel switching each time consumes is E _i(i=1, K D), adopts after the method, and the energy consumption that system can reduce is

The number N=2 that supposes cognitive user in network, is respectively SU ₁and SU ₂, system has completed channel and the power co-allocation process in i stage, and SU ₁do not complete the communication in i stage.Now consider i stage and i+1 stage SU ₁continuity.Fig. 5 has provided in 100 tests, SU ₁keep the number of times of continuity in i stage and i+1 stage, in each test, channel status is all random setting.As can be seen from Figure 5, along with the increase of system sub-channels number, SU ₁keep the number of times of continuity increasing gradually, the number of times that channel switches reduces relatively, by adopting combined distributing method of the present invention, cognitive user SU ₁keep the probability of continuity more than 70%.Owing to having reduced the number of times that channel switches, the energy of system consumption also will reduce.Suppose that it is 10mJ that cognitive user is carried out the energy of the handoff procedure consumption between adjacent channel, Fig. 6 has compared distribution method of the present invention and has not ensured that the method for continuity (not adding the restrictive condition that ensures continuity in channel and power division optimization problem) is in catabiotic size of i+1 stage.Mean consumption energy in Fig. 6 refers in 100 tests, SU ₁and SU ₂carry out the mean value of the energy of channel switching consumption.As can be seen from Figure 6, adopt method of the present invention can reduce system because channel switches the energy consuming.

In addition, the present invention has considered interference and the cognitive user service quality problem of cognitive user to primary user, in prior art, the QoS requirement of cognitive user is defined as to the rate requirement of cognitive user, and QoS requirement of the present invention is defined as lowest signal-to-noise requirement.When cognitive user communicates, if signal to noise ratio is too low, the information of transmission will be fallen into oblivion by noise, produces great distortion, therefore defines lowest signal-to-noise, can ensure the communication quality of cognitive user.

Brief description of the drawings

Fig. 1 is flow chart of the present invention;

Fig. 2 is system functional block diagram of the present invention;

Fig. 3 is the cognitive radio networks topological diagram based on centralized configuration in the present invention;

Fig. 4 is system protocol schematic diagram of the present invention;

Fig. 5 is the graph of a relation that system sub-channels number and cognitive user keep continuity number of times;

Fig. 6 is the graph of a relation that system sub-channels number and cognitive user are carried out channel switching consumption average energy.

Below in conjunction with the drawings and specific embodiments, the present invention is further illustrated.

Embodiment

Embodiments of the invention: the channel and the power combined allocation method that ensure continuity in a kind of cognitive radio, as shown in Figure 3, a random distribution N cognitive user (SU) in the cognitive radio networks of centralized configuration, a cognitive base station (BS) is set in the center of network, in network, usable spectrum is divided into the individual orthogonal subchannel of M (M > N), the bandwidth of every sub-channels is W, as shown in Figure 1 and Figure 2, comprises the following steps:

S1, cognitive user is cognitive radio electrical environment periodically, and cognitive base station adopts certain merging criterion, and the data message that N cognitive user collected merges, and obtains sub-channel information by the method for cooperative detection, uses vectorial I={I _m| I _m∈ { 0,1}} _{m × 1}represent, wherein, I _m=1 represents that subchannel m is taken by primary user (PU), I _m=0 represents the subchannel m free time;

S2, cognitive user sends communication request to cognitive base station, and informs the amount of information size (unit is bit) that need to transmit cognitive base station, uses vectorial R={R _n| R _n>=0} _{n × 1}represent R _n=0 represents that cognitive user n is without communication requirement, and meanwhile, cognitive base station gathers the QoS requirement information of each cognitive user, and QoS requirement information is weighed by signal to noise ratio, with vectorial γ={ γ _n} _{n × 1}represent;

S3, preferred channels and the power resource of starting stage, according to sub-channel information and QoS requirement information, distributed for cognitive user in cognitive base station by solving an optimization problem with Prescribed Properties, and cognitive user starts to communicate; This optimization problem comprises:

(a) target function

Taking maximum system throughput as target function, its expression formula is:

$\underset{C,P}{\max }\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{c}_{m,n}W{\log }_2(1+\frac{p_{m,n}{\left|h_{m,n}\right|}^2}{N_{0}W}),$

Wherein C and P represent respectively channel allocation matrix and power division matrix, c _{m, n}=1 represents that subchannel m distributes cognitive user n to use, p _m,nrepresent the transmitted power of cognitive user n on subchannel m, h _m,nrepresent the channel gain of cognitive user n on subchannel m, N ₀represent noise power spectral density;

(b) constraints

I. when cognitive user sends when communication request, cognitive base station is just its allocated channel, and only available free subchannel is just used to distribute to cognitive user use, and every sub-channels can only use by a cognitive user, therefore needs to meet c _{m, n}=0, n ∈ { n|R _n=0}, c _{m, n}=0, m ∈ { m|I _m=1}, with m ∈ { m|I _m=0};

II. for fear of the interference to primary user, must the transmitted power on each sub-channels limit cognitive user, need to meet wherein, P _mrepresent the interference power upper limit of primary user on subchannel m;

III. in order to reach the quality of service requirement of cognitive user, signal to noise ratio when each cognitive user is carried out transfer of data on subchannel need meet wherein, γ _nrepresent to ensure the lowest signal-to-noise requirement of cognitive user n telecommunication service quality;

Therefore, the optimization problem of channel and power co-allocation is described as:

$\underset{C,P}{\max }\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{c}_{m,n}W{\log }_2(1+\frac{p_{m,n}{\left|h_{m,n}\right|}^2}{N_{0}W})$

s.t.c _m，n∈{0,1}

c _m,n＝0, n∈{n|R _n＝0},

c _m，n＝0, m∈{m|I _m＝1},

$\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{c}_{m,n}=1,$ m∈{m|I _m＝0}

$\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{c}_{m,n}{p}_{m,n}{\left|h_{m,n}\right|}^2\&le;P_m,\&ForAll;m$

$\frac{\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{c}_{m,n}{p}_{m,n}{\left|h_{m,n}\right|}^2}{N_{0}W}\&GreaterEqual;{\mathrm{\&gamma;}}_n,\&ForAll;n$

By solving this optimization problem, obtain Matrix C ^*and P ^*, for there being channel and the power resource of cognitive user optimal scheme of communication requirement;

S4, in the time of the sign off of starting stage, upgrades sub-channel information and QoS requirement information, is carrying out next stage,, before the channel and power resource allocation in i (i > 1) stage, need complete following steps:

S41, before the channel in i stage and the distribution of power resource, need pass through be that formula (1) detects each cognitive user and whether completes i-1 phase communication; Wherein represent the amount of information that i-1 stage cognitive user n need to transmit; represent the rate of information throughput of i-1 stage cognitive user n, c _{m, n}=1 represents that subchannel m distributes cognitive user n to use, p _{m, n}represent the transmitted power of cognitive user n on subchannel m, h _m,nrepresent the channel gain of cognitive user n on subchannel m, N ₀represent noise power spectral density; T represents in each stage that cognitive user is for transmitting the time of data;

S42, if formula (1) is set up, represents that cognitive user n has completed the transmission of i-1 session information amount, otherwise represents that cognitive user n does not complete the transmission of i-1 session information amount;

S43, has judged whether the channel that the cognitive user of communication was assigned with in the i-1 stage is all taken by primary user in the i stage, if occupied, this cognitive user is put under to set Ψ ₂, otherwise put under set Ψ ₁;

S44, if having new cognitive user to send communication request to cognitive base station in the i stage, puts this cognitive user under set Ψ ₂;

S5, obtains gathering Ψ by step S4 ₁and Ψ ₂after, cognitive base station carries out the channel in i stage and the optimal joint of power distributes, wherein:

(1) for set Ψ ₁in the cognitive user that does not complete i-1 phase communication, cognitive base station allows them to hold over subchannel that the i-1 stage is assigned with and that do not taken by primary user in the current generation to communicate;

(2) suppose to distribute to set Ψ in the i-1 stage ₁in user and the set of the subchannel that do not taken by primary user in the current generation be ∏, in the optimization problem described in step S3, add a restrictive condition: m ∈ ∏, n ∈ Ψ ₁, wherein, c _{m, n}=1 represents that subchannel m distributes to cognitive user n and uses, and becomes channel and the optimization problem corresponding to power co-allocation in i stage, by solving the optimization problem adding after restrictive condition, is set Ψ ₂in user assignment preferred channels, and for set Ψ ₁and Ψ ₂in user assignment optimal power;

Suppose channel number M=4, cognitive user number N=2, a certain allocated phase obtains matrix by solving optimization problem $C^{*}=\left(\begin{array}{cc}0& 1\\ 1& 0\\ 0& 1\\ 0& 0\end{array}\right),$ $P^{*}=\left(\begin{array}{cc}0& P_{\mathrm{1,2}}\\ P_{\mathrm{2,1}}& 0\\ 0& P_{\mathrm{3,1}}\\ 0& 0\end{array}\right),$ Subchannel 1 and subchannel 3 will be distributed to cognitive user 2, and subchannel 2 is distributed to cognitive user 1 and used, and subchannel 4 is taken by primary user, is not assigned with.The transmitted power of cognitive user 1 on subchannel 2 is P _2,1, the transmitted power of cognitive user 2 on channel 1 and subchannel 3 is respectively P _1,2and P _3,1.

S6, complete after the channel in i stage and the distribution of the optimal joint of power, cognitive user continues periodically perception radio environment around, upgrades sub-channel information and QoS requirement information, realizes the optimum allocation of channel and the power resource of follow-up phase.

As shown in Figure 4, the cycle of cognitive user cognitive radio electrical environment determined by system protocol, and in one-period, cognitive user is τ for the time of cognitive radio electrical environment, is T for transmitting the time of data.

In step S1, cognitive base station takes the frequency spectrum sensing method of cooperation to detect the situation that takies of subchannel, obtains sub-channel information.

In system, set up a fixing control channel, carry out the mutual of frequency spectrum perception information and control information for cognitive user and cognitive base station.

In the process of each stage cognitive user transmission data, if there is new cognitive user to propose communication request, cognitive base station is storage resource request information, and processes in next stage.

Claims (5)

1. in a cognitive radio, ensure channel and the power combined allocation method of continuity, a random distribution N cognitive user in the cognitive radio networks of centralized configuration, a cognitive base station is set in the center of network, in network, usable spectrum is divided into M orthogonal subchannel, wherein M > N, the bandwidth of every sub-channels is W, it is characterized in that, comprises the following steps:

S1, cognitive user is cognitive radio electrical environment periodically, and the data message that collect N cognitive user cognitive base station merges, and obtains sub-channel information, uses vectorial I={I _m| I _m∈ { 0,1}} _{m × 1}represent, wherein, I _m=1 represents that subchannel m is taken by primary user, I _m=0 represents the subchannel m free time;

S2, cognitive user sends communication request to cognitive base station, and informs the amount of information size that need to transmit cognitive base station, uses vectorial R={R _n| R _n>=0} _{n × 1}represent R _n=0 represents that cognitive user n is without communication requirement, and meanwhile, cognitive base station gathers the QoS requirement information of each cognitive user, and QoS requirement information is weighed by signal to noise ratio, with vectorial γ={ γ _n} _{n × 1}represent;

S3, optimum channel and the power resource of starting stage, according to sub-channel information and QoS requirement information, distributed for cognitive user in cognitive base station by solving an optimization problem with Prescribed Properties, and cognitive user starts to communicate;

Optimization problem in described step S3 comprises:

(a) target function

Taking maximum system throughput as target function, its expression formula is:

$\underset{C,P}{\max }\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{c}_{m,n}W{\log }_2(1+\frac{p_{m,n}{\left|h_{m,n}\right|}^2}{N_{0}W}),$

Wherein, c _m,n=1 represents that subchannel m distributes to cognitive user n and uses, p _m,nrepresent the transmitted power of cognitive user n on subchannel m, h _m,nrepresent the channel gain of cognitive user n on subchannel m, N ₀represent noise power spectral density, C and P represent respectively channel allocation matrix and power division matrix;

(b) constraints

I. when cognitive user sends when communication request, cognitive base station is just its allocated channel, and only available free subchannel is just used to distribute to cognitive user use, and every sub-channels can only use by a cognitive user, therefore needs to meet $c_{m,n}=0,n\&Element;\left\{n\right|R_n=0\},\&ForAll;m,c_{m,n}=0,m\&Element;\{m|I_m=1\},\&ForAll;n$ With $\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{c}_{m,n}=1,m\&Element;\left\{m\right|I_m=0\};$

II. for fear of the interference to primary user, the transmitted power to cognitive user on each sub-channels limits, and needs to meet wherein, P _mrepresent the interference power upper limit of primary user on subchannel m;

III. in order to reach the quality of service requirement of cognitive user, signal to noise ratio when each cognitive user is carried out transfer of data on subchannel need meet wherein, γ _nrepresent to ensure the lowest signal-to-noise requirement of cognitive user n telecommunication service quality;

Therefore, the optimization problem of channel and power co-allocation is described as:

$\underset{C,P}{\max }\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{c}_{m,n}W{\log }_2(1+\frac{p_{m,n}{\left|h_{m,n}\right|}^2}{N_{0}W})$

$\begin{array}{ccc}s.t.& c_{m,n}\&Element;\left\{\mathrm{0,1}\right\}& \&ForAll;m,n\\ & c_{m,n=0,}& n\&Element;\left\{n\right|R_n=0\},\&ForAll;m\\ & c_{m,n}=0,& m\&Element;\left\{m\right|I_m=1\},\&ForAll;n\\ & \underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{c}_{m,n}=1,& m\&Element;\left\{m\right|I_m=0\}\\ & \underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{c}_{m,n}{p}_{m,n}{\left|h_{m,n}\right|}^2\&le;P_m,& \&ForAll;m\\ & \frac{\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{c}_{m,n}{p}_{m,n}{\left|h_{m,n}\right|}^2}{N_{0}W}\&GreaterEqual;{\mathrm{\&gamma;}}_n,& \&ForAll;n\end{array}$

By solving this optimization problem, obtain Matrix C ^*and P ^*, for there being channel and the power resource of cognitive user optimal scheme of communication requirement;

S4, in the time of the sign off of starting stage, upgrades sub-channel information and QoS requirement information, is carrying out next stage, and, before the channel and power resource allocation in i stage, wherein i > 1, need complete following steps:

S41, before the channel in i stage and the distribution of power resource, need pass through be that formula (1) detects each cognitive user and whether completes i-1 phase communication; Wherein represent the amount of information that i-1 stage cognitive user n need to transmit; represent the rate of information throughput of i-1 stage cognitive user n, c _m,n=1 represents that subchannel m distributes cognitive user n to use, p _m,nrepresent the transmitted power of cognitive user n on subchannel m, h _m,nrepresent the channel gain of cognitive user n on subchannel m, N ₀represent noise power spectral density; T represents in each stage that cognitive user is for transmitting the time of data;

S42, if formula (1) is set up, represents that cognitive user n has completed the transmission of i-1 session information amount, otherwise just represents that cognitive user n does not complete the transmission of i-1 session information amount;

S43, has judged whether the channel that the cognitive user of communication was assigned with in the i-1 stage is all taken by primary user in the i stage, if occupied, the cognitive user that this is not completed to communication puts set Ψ under ₂, otherwise put under set Ψ ₁;

S44, if having new cognitive user to send communication request to cognitive base station in the i stage, puts this new cognitive user under set Ψ ₂;

S5, obtains gathering Ψ by step S4 ₁and Ψ ₂after, cognitive base station carries out the channel in i stage and the optimal joint of power distributes, wherein:

(1) for set Ψ ₁in the cognitive user that does not complete i-1 phase communication, cognitive base station allows them to hold over subchannel that the i-1 stage is assigned with and that do not taken by primary user in the current generation to communicate;

(2) suppose to distribute to set Ψ in the i-1 stage ₁in user and the set of the subchannel that do not taken by primary user in the current generation be Π, in the optimization problem described in step S3, add a restrictive condition: m ∈ Π, n ∈ Ψ ₁, wherein, c _m,n=1 represents that subchannel m distributes to cognitive user n and uses, and becomes channel and the optimization problem corresponding to power co-allocation in i stage, by solving the optimization problem adding after restrictive condition, is set Ψ ₂in user assignment preferred channels, and for set Ψ ₁and Ψ ₂in user assignment optimal power;

S6, complete after the channel in i stage and the distribution of the optimal joint of power, cognitive user continues periodically perception radio environment around, upgrades sub-channel information and QoS requirement information, realizes the optimum allocation of channel and the power resource of follow-up phase.

2. in cognitive radio according to claim 1, ensure channel and the power combined allocation method of continuity, it is characterized in that: the cycle of cognitive user cognitive radio electrical environment is determined by system protocol, in one-period, cognitive user is τ for the time of cognitive radio electrical environment, is T for transmitting the time of data.

3. in cognitive radio according to claim 1 and 2, ensure channel and the power combined allocation method of continuity, it is characterized in that: in step S1, cognitive base station takes cooperative frequency spectrum sensing method to detect the situation that takies of subchannel, obtains sub-channel information.

4. in cognitive radio according to claim 1, ensure channel and the power combined allocation method of continuity, it is characterized in that: in cognitive radio system, set up a fixing control channel, carry out the mutual of frequency spectrum perception information and control information for cognitive user and cognitive base station.

5. according to the channel and the power combined allocation method that ensure continuity in the cognitive radio described in claim 1 or 4, it is characterized in that: in the process of each stage cognitive user transmission data, if there is new cognitive user to propose communication request, cognitive base station is storage resource request information, and processes in next stage.