CN101778436A - General methods for accessing two groups of cognitive users to authorized frequency bands - Google Patents

Abstract

The invention discloses a method for accessing cognitive users with two technical standards to a plurality of authorized frequency bands in a cognitive wireless network, which belongs to the technical field of cognitive radio communication. The method mainly comprises three contents of: firstly, establishing general methods for accessing two groups of the cognitive users to the authorized frequency bands under three conditions without spectrum switching, with spectrum switching and with channel reservation respectively by using a Markov theory; secondly, deducing two important parameters namely the forced outage probability and the blocking probability of a system under the three conditions respectively by using a model; and thirdly, putting forward a channel reservation method to balance the forced outage probability and the blocking probability so as to meet performance requirements of the system.

Description

The conventional method of accessing two groups of cognitive users to authorized frequency bands

Technical field

The present invention is a kind of method that is used for cognition wireless network cognitive user insertion authority frequency band, belongs to the cognition wireless technical field of telecommunications.

Background technology

Cognitive radio can change the transmission of self automatically and receive parameter by the mutual perception of wireless communications environment that it is worked, thereby dynamically reuses usable spectrum.It is crowded day by day wireless communication system and the equipment fine prospect that realized high efficiency of spectrum utilization, coexistence, compatibility and interaction display.

In the cognition wireless network that constitutes by authorized user (main user) and unauthorized user (cognitive user), because main user is not the authorized frequency bands that uses it when the somewhere, so cognitive radio users can use the temporary transient untapped frequency band of main user to communicate always.But when main user wants to reuse these frequency bands, cognitive user these frequency bands that just should withdraw on one's own initiative.For keeping normal communication, and seek suitable idle frequency band once more.Therefore cognitive user dynamically perception and location those not have the frequency band of use, and can utilize those untapped frequency bands to communicate and the main user who uses this frequency is not formed harmful interference.When this kind situation took place, the affected communication link of cognitive user can be interrupted, if but have this moment the free sub-band of adaptation to exist, they just can utilize these sub-bands to rebuild communication link continuation communication, and Here it is, and frequency spectrum switches.

Cognitive user dynamically inserts frequency spectrum, and untapped frequency band (" white cavity ") is reached minimize, thus the service efficiency of raising frequency spectrum.Now, universal model based on one group of cognitive user insertion authority frequency band of constructed standard has been proposed, but, the communication technology had obtained fast development in the last few years, the wireless communication system that emerges in an endless stream will comprise various Radio Access Networks with different transmission rates, coverage, power system capacity and service level for the network environment that the user provides isomery.Therefore, it is particularly necessary to set up the conventional method that a cognitive user based on the multiple technologies standard inserts a plurality of authorized frequency bands.

Summary of the invention

Technical problem: the purpose of this invention is to provide the conventional method and the channel reservation scheme of an accessing two groups of cognitive users to authorized frequency bands,, can provide important parameters for the design of system by this model.

Technical scheme: the conventional method of accessing two groups of cognitive users to authorized frequency bands of the present invention, utilize the markov theory that the situation of main user and cognitive user busy channel is carried out modeling, represent the seizure condition and the situation of change of channel with its state and the rate of transform respectively; Based on the markov theory, the conventional method of accessing two groups of cognitive users to authorized frequency bands and have the conventional method of frequency spectrum accessing two groups of cognitive users to authorized frequency bands when switching when foundation does not have frequency spectrum to switch, and the conventional method of accessing two groups of cognitive users to authorized frequency bands when having channel reservation;

A. set up the conventional method of accessing two groups of cognitive users to authorized frequency bands when not having frequency spectrum to switch: as long as there is idle channel to exist, new cognitive user just can insert; When main user occurs, cognitive user will be vacated the sub-band that it is taking, and cognitive user will be interrupted in this case, not allow to switch; Based on the markov theory, draw corresponding state transition model, i.e. access model;

B. set up the conventional method of accessing two groups of cognitive users to authorized frequency bands when having the frequency spectrum switching: as long as there is idle channel to exist, new cognitive user just can insert; When main user occurred, cognitive user utilized the frequency spectrum switched and transferred to continue communication to those idle subchannels, was forced to interrupt taking place as long as there is idle sub-channels not exist with regard to not having in such cases, did not just interrupt when having idle sub-channels to exist; Based on the markov theory, draw corresponding state transition model, i.e. access model;

C. set up the conventional method of accessing two groups of cognitive users to authorized frequency bands when having channel reservation: when the number of remaining idle sub-channels during greater than the number of the subchannel of reserving, allow new cognitive user and insert this moment; When the number of remaining idle sub-channels is less than or equal to the number of subchannel of reservation, does not then allow new cognitive user and insert; When the number of all remaining idle sub-channels during less than main user's bandwidth requirement, then this moment, then the part cognitive user will be interrupted if there is new main user to occur, and another part cognitive user switches on the subchannel of those reservations and continues communication; Based on the markov theory, draw corresponding state transition model, i.e. access model.

The described conventional method of accessing two groups of cognitive users to authorized frequency bands when not having frequency spectrum to switch, its method for building up is as follows:

1. use an integer to (i, j, k) the occupied state of expression frequency band, wherein i and j represent respectively by the total number of the sub-band of two groups of cognitive CU, k represents by the number of the dominant frequency band of main CU, the communication mode that cognitive user adopts FDMA utilizes a plurality of different sub-bands to carry out transfer of data

2. under the situation that does not have frequency spectrum to switch: when main user occurs, cognitive user will be vacated its sub-band, and the service of cognitive user will occur from state (i like this, j k) has no progeny in being forced to and transfers to one of following state: (i-1, j, k), (i-2, j, k) ..., (i-1, j-m, k+1) ..., (i, j k+1), uses γ _{(i-l, j-m, k+1)} ^{(i, j, k)}Expression from state (i, j, k) to (i-1, j-m, transition probability k+1), then state transition rate is:

3. according to the effective status in 2. (i, j k) and the state transition rate of each state, list equilibrium equation, calculate state probability P (i, j, k), P (i-1, j, k) ..., P (i, j, k+1).

The described conventional method of accessing two groups of cognitive users to authorized frequency bands when not having frequency spectrum to switch, the blocking probability of system and to be forced to the method for building up of outage probability as follows:

1. blocking probability: expression when all available channels are all occupied, the unaccepted probability of the call request of cognitive user.

2. be forced to outage probability: expression is because main user's appearance causes some subchannel of cognitive user to be forced to interrupt probability, and its expression formula is the ratio that cognitive user is forced to interrupt the rate of transform and cognitive user access rate.

Described conventional method with frequency spectrum accessing two groups of cognitive users to authorized frequency bands when switching, its method for building up is as follows:

1. with integer to (i, j, k) expression frequency band occupied state, wherein i and j represent the total number of the sub-band of two groups of cognitive CU respectively, k represents the number of the dominant frequency band of main CU, and the communication mode that cognitive user adopts FDMA utilizes a plurality of different sub-bands to carry out transfer of data;

2. have under the situation that frequency spectrum switches when main user occurs, cognitive user will be vacated its sub-band and transfer to immediately and continue communication on other idle subchannels, in this case, as long as there is idle frequency band to exist, just do not have and will not be forced to interrupt generation; (i, j k), if i+j+Nk≤(M-1) is N, even then there is main user to arrive, are forced to interrupt also can not taking place for state.This moment, state transition rate was zero;

If 3. (i, j k) do not satisfy the N of i+j+Nk≤(M-1), and its state transition rate is:

${\mathrm{\γ}}_{(i-l,l-m,k+1)}^{(i,j,k)}=\frac{\left(\begin{array}{c}i\\ l\end{array}\right)\left(\begin{array}{c}j\\ m\end{array}\right)}{\left(\begin{array}{c}i+j\\ l+m\end{array}\right)}{\mathrm{\λ}}_p---\left(2\right)$

4. list equilibrium equation, obtain state probability.

The described conventional method of accessing two groups of cognitive users to authorized frequency bands when having channel reservation utilizes channel reservation method to be forced to the performance requirement that outage probability and blocking probability satisfy system with balance, wherein channel reservation method set up as follows:

1. according to the traffic carrying capacity of input and the Markov model of foundation, calculate the probability of each state;

2. according to state probability, by the numerical value enumeration method, even r=1,2 ..., the blocking probability when calculating r respectively and getting different value and be forced to outage probability, select the best number r that reserves subchannel, make blocking probability and be forced to the performance requirement that outage probability satisfies system.

The described conventional method of accessing two groups of cognitive users to authorized frequency bands when having channel reservation, its method for building up is as follows:

1. when the number of all remaining idle sub-channels during, promptly when i+j+Nk≤NK-r, then then will interrupt if there is new main user to occur this moment less than main user's bandwidth requirement N;

2. when the number of remaining idle sub-channels during greater than the number r of the subchannel of reserving, promptly when (K-1) N＜i+j+Nk≤NK-r, can allow new cognitive user and insert this moment;

3. when the number of remaining idle sub-channels is less than or equal to the number r of subchannel of reservation, promptly when i+j+Nk=NK-r or i+j+Nk≤NK, does not then allow new cognitive user and insert;

4. when if channel reservation is arranged, promptly when i+j+Nk≤NK-r, then the cognitive user of these interruptions can switch on the subchannel of those reservations and continue communication;

5. list equilibrium equation, obtain state probability.

The conventional method of accessing two groups of cognitive users to authorized frequency bands when having channel reservation utilizes channel reservation method to be forced to the performance requirement that outage probability and blocking probability satisfy system with balance, wherein blocking probability and to be forced to the method for building up of outage probability as follows:

1. equilibrium equation can be listed according to the state transition diagram of the number (i+j+Nk) of the occupied subchannel of representing with Markov model, the number of subchannels r that reserves and total bandwidth NK, the state probability that system is in each state can be obtained according to equilibrium equation;

Each state probability sum when 2. the blocking probability of system is expressed as number (i+j+Nk) and the subchannel number r sum of reserving when occupied subchannel greater than total bandwidth NK;

3. the outage probability that is forced to of system is expressed as the ratio that being forced to when having channel reservation interrupted the rate of transform and service access rate.

Beneficial effect: the present invention has the following advantages:

1. this model provides the conventional method that the two groups of cognitive user inserts a plurality of authorized frequency bands, can easily expand to the conventional method that many group cognitive user insert a plurality of authorized frequency bands;

2. utilize channel reservation method to come balance to be forced to outage probability and blocking probability to satisfy the performance requirement of system;

3. cognitive user can dynamically insert frequency spectrum, thereby improves the service efficiency of frequency spectrum;

4. realize high efficiency of spectrum utilization, solve the shortage problem of wireless communication resources.

Description of drawings

Fig. 1 is a schematic network structure.

Fig. 2 is the common frequency band schematic diagram that uses of main system and cognitive radio system.

Fig. 3 is the Markov model schematic diagram that the cognitive user of two kinds of technical standards inserts a plurality of authorized frequency bands.

Fig. 4 is state (i, j, transition diagram k) when having frequency spectrum switching and channel reservation.

Embodiment

The present invention mainly comprises three contents: the one, utilize the theoretical cut-in method of setting up when not having frequency spectrum to switch and having frequency spectrum two groups of cognitive user when switching of markov; The 2nd, utilize this method, derive when not having frequency spectrum to switch respectively and have frequency spectrum two important system parameterss when switching, promptly be forced to outage probability and blocking probability; The 3rd, propose to utilize channel reservation method to be forced to the performance requirement that outage probability and blocking probability satisfy system with balance.

The foundation of two groups of cognitive user access method and the derivation of system parameters when (1) not having frequency spectrum to switch

The foundation of two groups of cognitive user access method when a. not having frequency spectrum to switch

Main user and cognitive user are shared same frequency spectrum, and it takies process and carries out modeling with the Markov chain of continuous time, and Markov chain is represented with its state and the rate of transform.Utilize the theoretical universal model of setting up accessing two groups of cognitive users to authorized frequency bands when not having frequency spectrum to switch of markov, its method for building up is as follows:

1. with integer to (i, j, k) expression frequency band occupied state, wherein i and j represent the number of the sub-band of two groups of cognitive CU respectively, the communication mode that cognitive user adopts FDMA utilizes a plurality of different sub-bands to carry out transfer of data; K represents the number of the dominant frequency band of main CU.

2. when main user occurs, because main user has the priority of using frequency spectrum, cognitive user will be vacated its sub-band, and the service of cognitive user will occur from state (i like this, j k) has no progeny in being forced to and transfers to one of following state: (i-1, j, k), (i-2, j, k) ..., (i-1, j-m, k+1) ..., (i, j k+1), uses γ _{(i-l, j-m, k+1)} ^{(i, j, k)}Expression from state (i, j, k) to (i-l, j-m, rate of transform k+1), then state transition rate is:

3. represent the set of all effective statuses of Markov chain with φ,

Be the indicator function of φ, promptly

With P (i, j, k) the expression state (i, j, state probability k), list equilibrium equation:

$\underset{i=0}{\overset{\mathrm{NK}}{\mathrm{\Σ}}}\underset{j=0}{\overset{\mathrm{NK}}{\mathrm{\Σ}}}\underset{k=0}{\overset{\mathrm{NK}}{\mathrm{\Σ}}}{P}_{\mathrm{\φ}}(i,j,k)=1---\left(4\right)$

Wherein: i, j=0,1 ..., NK, j=0,1 ..., K

4. according to equation (1), (2), (3), (4) can obtain state (i, j, k), (i-1, j, k) ..., (i, j, state probability P k+1) (i, j, k), P (i-1, j, k) ..., P (i, j, k+1).

B. the derivation of system parameters

The blocking probability of system is not expressed as when all available channels are all occupied when having frequency spectrum to switch, the unaccepted probability of the call request of cognitive user, and it is set up expression formula and is:

Wherein

When not having frequency spectrum to switch system be forced to outage probability, its method for building up is:

Being forced to outage probability represents to cause some subchannel of cognitive user to be forced to interrupt probability owing to main user's appearance, when state from (i, j, k) transfer to (i-l, j-m, k+1) time, m cognitive user among cognitive user of the l among the i and the j will be forced to interrupt communication, and it is forced to interrupt the rate of transform and is expressed as:

(k), the state transition rate when the two groups of cognitive user has l respectively and m is connected is γ for i, j for state _{(i-l, j-m, k+1)} ^{(i, j, k)}P _φ(i, j, k).Therefore, (whole rates of transform k) can obtain by summation state for i, j

And whole connection rates is (1-P _B) (λ _A+ λ _B), can obtain being forced to outage probability to (8) substitution (7) and be

The outage probability that is forced to that also can obtain the two groups of cognitive user thus is respectively

The foundation of two groups of cognitive user access method when (2) having the frequency spectrum switching

The method for building up of two groups of cognitive user access model is as follows when having the frequency spectrum switching:

1. with integer to (i, j, k) the occupied state of expression frequency band, wherein i and j represent respectively by the total number of the sub-band of two groups of cognitive CU, k represents by the number of the dominant frequency band of main CU, the communication mode that cognitive user adopts FDMA utilizes a plurality of different sub-bands to carry out transfer of data

2. have under the situation that frequency spectrum switches when main user occurs, because main user has the priority of using frequency spectrum, cognitive user will be vacated its sub-band and transfer to immediately and continue communication on other idle subchannels, in this case, as long as there is idle frequency band to exist, just do not have and be forced to interrupt taking place; (i, j k), if i+j+Nk≤(M-1) is N, even then there is main user to arrive, are forced to interrupt also can not taking place for state.This moment, state transition rate was zero.

If 3. (i, j k) do not satisfy the N of i+j+Nk≤(M-1), and its state transition rate is:

${\mathrm{\γ}}_{(i-l,l-m,k+1)}^{(i,j,k)}=\frac{\left(\begin{array}{c}i\\ l\end{array}\right)\left(\begin{array}{c}j\\ m\end{array}\right)}{\left(\begin{array}{c}i+j\\ l+m\end{array}\right)}{\mathrm{\λ}}_p---\left(12\right)$

4. list equilibrium equation, obtain state probability.

(3) utilize channel reservation method to be forced to outage probability and blocking probability with balance

The method for building up of cognitive user access model is as follows when having channel reservation:

1. when the number of all remaining idle sub-channels during, promptly when i+j+Nk≤NK-r, then then will interrupt if there is new main user to occur this moment less than main user's bandwidth requirement (N subchannel).

2. when the number of remaining idle sub-channels during greater than the number (r) of the subchannel of reserving, promptly when (K-1) N＜i+j+Nk≤NK-r, can allow new cognitive user and insert this moment.

3. when the number of remaining idle sub-channels is less than or equal to the number of subchannel of reservation, promptly when i+j+Nk=NK-r or i+j+Nk≤NK, does not then allow new cognitive user and insert.

4. when if channel reservation is arranged, promptly when i+j+Nk≤NK-r, then the cognitive user of these interruptions can switch on the subchannel of those reservations and continue communication.

5. list equilibrium equation, obtain state probability.

Channel reservation method is set up as follows:

1. according to the traffic carrying capacity of input and the Markov model of foundation, calculate the probability of each state;

2. according to state probability, by the numerical value enumeration method, even r=1,2 ..., the blocking probability when calculating r respectively and getting different value and be forced to outage probability, select the best number r that reserves subchannel, make blocking probability and be forced to the performance requirement that outage probability satisfies system.

Have that frequency spectrum switches and during channel reservation the blocking probability of system with to be forced to the outage probability method for building up as follows:

State transition diagram according to the number (i+j+Nk) of the occupied subchannel of representing with Markov model, the number of channel r that reserves and total bandwidth NK can be listed equilibrium equation, uses P _{φ r}(state probability when k) expression has r channel reservation can obtain the blocking probability of system and be forced to outage probability being expressed as respectively for i, j

Wherein, δ _FrBe the state indicator function, it has represented the state of system under the different situations shown in the right 5, is defined as δ _Fr((it is made up of 0＜l+m≤N) (16) three conditions the N δ of i+j+Nk＞(K-1)=δ ((i-l)+(j-m)-(K-k-1) N) δ: the scope indicated condition of the number of filling condition (as long as promptly having idle channel just can not interrupt), communication end condition (not having idle channel) and cognitive user interrupt communication.

Conventional method and channel reservation scheme thereof that the cognitive radio users of two kinds of technical standards of the present invention inserts a plurality of authorized frequency bands comprise following content:

1. system model

System model as shown in Figure 1, cognition wireless network and master network (authorisation network) are present in the same area jointly, by cognition technology, cognitive user can be used the temporary transient untapped authorized frequency bands of those main users.

Suppose that in this wireless system, main system and cognitive system are operated in the same frequency spectrum.The frequency spectrum of system is made up of K primary band, and each dominant frequency band is divided into the N sub-frequency bands again, and the bandwidth of each main channel is W _P, then the bandwidth of each subchannel is W _S=W _P/ N, as shown in Figure 2.Main user has the right of preferential these frequency bands of use, can regain the sub-band that those are temporarily used by cognitive user at any time, and main user does not know which sub-band is taken by cognitive user, looking those sub-bands that taken by cognitive user is idle frequency band, and promptly cognitive user is transparent fully concerning main user.But when cognitive user perceives main user when bringing into use those temporary transient unappropriated frequency bands, they can initiatively abdicate the right to use of frequency band.

Cognitive user access model when 2. not having frequency spectrum to switch

The process that takies of frequency spectrum can be carried out modeling with the Markov chain of continuous time, and Markov chain is represented with its state and the rate of transform.Because the NK sub-frequency bands of system is shared by main user and two groups of cognitive user, in this case, available integer is to (i, j, k) represent the occupied state of frequency band, wherein i and j represent respectively by the total number of the sub-band of two groups of cognitive CU, and k represents by the number of the dominant frequency band of main CU.Suppose the voice of main user and cognitive user or the arrival process obedience Poisson distribution of data service, its arrival rate and service rate are respectively λ _p(μ _p), λ _S ^A(μ _S ^A) and λ _S ^B(μ _S ^B).S wherein _AAnd S _BBe used to identify two groups of cognitive user group, the arrival rate of main user and two groups of cognitive user group is respectively λ _P, λ _s ^AAnd λ _s ^B, service rate is respectively μ _P, μ _s ^AAnd μ _s ^B, terminal use's number of two groups of cognitive user group is respectively l and m.In this system, the communication mode that cognitive user adopts FDMA can utilize a plurality of different sub-bands to carry out transfer of data as required.Because main user has the priority of using frequency spectrum, cognitive user can be by main user's preemption, the phenomenon of being forced to interrupt will appear in the service of cognitive user like this, so cognitive user need obtain a suitable sub-band immediately by certain intelligent algorithm and keeps the desired bandwidth of proper communication.Fig. 3 has represented the schematic diagram of the general Markov model of accessing two groups of cognitive users to authorized frequency bands, and wherein dotted line is represented an example of the transfer between the state of being forced to, from state (i-1, j-m, k+1) be forced to transfer to state (i, j, k).From Markov chain shown in Figure 3 as can be seen, be forced to interrupt occurring in a main user and will use a certain dominant frequency to bring row communication into, but its one or several sub-frequency bands are being taken by cognitive user.

When main user occurs, cognitive user will be vacated its sub-band.The number of this main user's who takies according to cognitive user sub-band, state (i, j k) will transfer to one of following state through having no progeny in being forced to: (and i-1, j, k), (i-2, j, k) ..., (i-1, j-m, k+1) ..., (i, j, k+1), as Fig. 3.The transition probability that is forced to interrupt depends on the number of this main user's that cognitive user takies sub-band.In order to calculate the transition probability that is forced to interrupt, suppose that cognitive user has just taken this main user's k sub-frequency bands.Therefore, system from state (i, j, k) through having no progeny in being forced to, will transfer to state (i-1, j-m, k+1), 1≤l wherein, m≤N.Use γ _{(i-l, j-m, k+1)} ^{(i, j, k)}Expression from state (i, j, k) to (transition probability k+1) then can obtain through calculating for i-1, j-m:

Represent the set of all effective statuses of Markov chain shown in Figure 3 with φ,

Be the indicator function of φ, promptly

With P (i, j, k) the expression state (state probability k) according to Fig. 3, can obtain following equilibrium equation for i, j:

$\underset{i=0}{\overset{\mathrm{NK}}{\mathrm{\Σ}}}\underset{j=0}{\overset{\mathrm{NK}}{\mathrm{\Σ}}}\underset{k=0}{\overset{\mathrm{NK}}{\mathrm{\Σ}}}{P}_{\mathrm{\φ}}(i,j,k)=1---\left(4\right)$

Wherein: i, j=0,1 ..., NK, j=0,1 ..., K

According to these equations, can draw each state probability P _φ(i, j, k).

3. system parameters

Blocking probability is an important characteristic value of cognition wireless network, and it is represented when all available channels are all occupied, the unaccepted probability of the call request of cognitive user.If do not consider the priority of handoff request, then call request has identical blocking probability to handoff request with new business.When all channels are all occupied, when new customer call request, then will block, promptly (i, j when k) satisfying i+j+Nk=NK, then block state.Use P _BThe expression blocking probability, its expression formula is

Wherein δ (x) is the indication function, promptly

Being forced to outage probability is particularly another important characteristic value of real-time system of cognition wireless network, and its expression is because main user's appearance causes some subchannel of cognitive user to be forced to interrupt probability.For real-time system, it is more important than blocking probability to be forced to outage probability, because it is more frustrating to be forced in the communication process to interrupt getting clogged than at the very start, so is forced to outage probability and should remains in a certain scope of allowing.(i, j is k) to (in the time of k+1), m cognitive user among cognitive user of the l among the i and the j will be forced to interrupt communication for i-l, j-m, and therefore, being forced to outage probability according to definition can be expressed as from state when expression

(k), the state transition rate when the two groups of cognitive user has l respectively and m is connected is γ for i, j for state _{(i-l, j-m, k+1)} ^{(i, j, k)}P _φ(i, j, k).Therefore, (whole rates of transform k) can obtain by summation state for i, j

And whole connection rates is (1-P _B) (λ _A+ λ _B), can obtain being forced to outage probability to (8) substitution (7) and be

The outage probability that is forced to that also can obtain the two groups of cognitive user thus is respectively

The cut-in method and the channel reservation scheme of cognitive user when 4. having the frequency spectrum switching

If allow frequency spectrum to switch, then preoccupied cognitive radio is called out and will be transferred to immediately on other idle subchannels, continues communication.This channel heavily distributes and can be carried out by the base station, also can be undertaken by suitable distributed algorithm by the cognition wireless electric terminals.This method is divided into following five kinds of situations:

(i) utilize frequency spectrum to switch,, just do not have and be forced to interrupt taking place as long as when new main user occurs, there is idle sub-channels to exist.This situation can Fig. 4 (a) expression.

(ii) when the number of all remaining idle sub-channels during less than main user's bandwidth requirement (N subchannel), then then will interrupt if there is new main user to occur this moment, this process can use Fig. 4 (b)-(e) to represent.

(iii) when the number of remaining idle sub-channels during greater than the number (r) of the subchannel of reserving, can allow new cognitive user and insert this moment, and this process is with Fig. 4 (b) expression;

(iv) when the number of remaining idle sub-channels is less than or equal to the number of subchannel of reservation, does not then allow new cognitive user and insert, this process is with Fig. 4 (c)-(e) expression.

(v) if channel reservation arranged, then the cognitive user of these interruptions can switch on the subchannel of those reservations and continue communication, and this process can use Fig. 4 (d)-(e) to represent.

By analysis as can be known, (i, j k), if i+j+Nk≤(M-1) is N, even then there is main user to arrive, are forced to interrupt also can not taking place for state.Otherwise, if (i, j k) do not satisfy the N of i+j+Nk≤(M-1), and its rate of transform is

${\mathrm{\γ}}_{(i-l,l-m,k+1)}^{(i,j,k)}=\frac{\left(\begin{array}{c}i\\ l\end{array}\right)\left(\begin{array}{c}j\\ m\end{array}\right)}{\left(\begin{array}{c}i+j\\ l+m\end{array}\right)}{\mathrm{\λ}}_p---\left(12\right)$

Utilize the channel reservation scheme to reduce to be forced to outage probability in this proposition.The number of representing the subchannel reserved with r switches and uses (r=0 represents there is not channel reservation) to carry out frequency spectrum.State (i, j, transition diagram k) when r subchannel reserved in Fig. 4 (d)-(e) expression.In the case, the condition of cognitive user generation obstruction is: the number of current occupied subchannel (i+j+Nk) adds that the number of channel r of reservation equals total bandwidth NK.

According to this model, selecting best a kind of very natural method of reserving the number r of subchannel is to make user's throughput maximum, and optimum r can pass through the numerical value enumeration method (even r=1,2 ...) obtain.

List equilibrium equation according to the Markov model shown in Fig. 4 (a)-(e), use P _{φ r}(state probability when k) expression has r channel reservation can obtain the blocking probability of system and be forced to outage probability being expressed as respectively for i, j

Wherein, δ _FrBe the state indicator function, it has represented the state of system under the different situations shown in the right 5, is defined as δ _Fr=δ ((i-l)+(j-m)-(K-k-1) N) δ (N δ (0＜l+m≤N) (16) of i+j+Nk＞(K-1)

It is made up of three conditions: the scope indicated condition of the number of filling condition (as long as promptly having idle channel just can not interrupt), communication end condition (not having idle channel) and cognitive user interrupt communication.

Claims (7)

1. the conventional method of an accessing two groups of cognitive users to authorized frequency bands, it is characterized in that: utilize the markov theory that the situation of main user and cognitive user busy channel is carried out modeling, represent the seizure condition and the situation of change of channel with its state and the rate of transform respectively; Based on the markov theory, the conventional method of accessing two groups of cognitive users to authorized frequency bands and have the conventional method of frequency spectrum accessing two groups of cognitive users to authorized frequency bands when switching when foundation does not have frequency spectrum to switch, and the conventional method of accessing two groups of cognitive users to authorized frequency bands when having channel reservation;

A. set up the conventional method of accessing two groups of cognitive users to authorized frequency bands when not having frequency spectrum to switch: as long as there is idle channel to exist, new cognitive user just can insert; When main user occurs, cognitive user will be vacated the sub-band that it is taking, and cognitive user will be interrupted in this case, not allow to switch; Based on the markov theory, draw corresponding state transition model, i.e. access model;

B. set up the conventional method of accessing two groups of cognitive users to authorized frequency bands when having the frequency spectrum switching: as long as there is idle channel to exist, new cognitive user just can insert; When main user occurred, cognitive user utilized the frequency spectrum switched and transferred to continue communication to those idle subchannels, was forced to interrupt taking place as long as there is idle sub-channels not exist with regard to not having in such cases, did not just interrupt when having idle sub-channels to exist; Based on the markov theory, draw corresponding state transition model, i.e. access model;

C. set up the conventional method of accessing two groups of cognitive users to authorized frequency bands when having channel reservation: when the number of remaining idle sub-channels during greater than the number of the subchannel of reserving, allow new cognitive user and insert this moment; When the number of remaining idle sub-channels is less than or equal to the number of subchannel of reservation, does not then allow new cognitive user and insert; When the number of all remaining idle sub-channels during less than main user's bandwidth requirement, then this moment, then the part cognitive user will be interrupted if there is new main user to occur, and another part cognitive user switches on the subchannel of those reservations and continues communication; With the markov theory is that the basis draws corresponding state transition model, i.e. access model.

2. the conventional method of accessing two groups of cognitive users to authorized frequency bands according to claim 1 is characterized in that the described conventional method of accessing two groups of cognitive users to authorized frequency bands when not having frequency spectrum to switch, and its method for building up is as follows:

1. use an integer to (i, j, k) the occupied state of expression frequency band, wherein i and j represent respectively by the total number of the sub-band of two groups of cognitive CU, k represents by the number of the dominant frequency band of main CU, the communication mode that cognitive user adopts FDMA utilizes a plurality of different sub-bands to carry out transfer of data

2. under the situation that does not have frequency spectrum to switch: when main user occurs, cognitive user will be vacated its sub-band, and the service of cognitive user will occur that (i, j k) have no progeny and transfer to one of following state: (i-1 from state in being forced to like this, j, k), (i-2, j, k),, (i-l, j-m, k+1) ..., (i, j, k+1), with γ (i-l, j-m, k+1) (k) expression is from state (i, j for i, j, k) arrive (i-l, j-m, transition probability k+1), then state transition rate is:

3. according to the effective status in 2. (i, j k) and the state transition rate of each state, list equilibrium equation, calculate state probability P (i, j, k), P (i-1, j, k) ..., P (i, j, k+1).

3. the universal model of accessing two groups of cognitive users to authorized frequency bands according to claim 1, it is characterized in that the described conventional method of accessing two groups of cognitive users to authorized frequency bands when not having frequency spectrum to switch, the blocking probability of system and to be forced to the method for building up of outage probability as follows:

1. blocking probability: expression when all available channels are all occupied, the unaccepted probability of the call request of cognitive user.

2. be forced to outage probability: expression is because main user's appearance causes some subchannel of cognitive user to be forced to interrupt probability, and its expression formula is the ratio that cognitive user is forced to interrupt the rate of transform and cognitive user access rate.

4. the conventional method of accessing two groups of cognitive users to authorized frequency bands according to claim 1 is characterized in that described conventional method with frequency spectrum accessing two groups of cognitive users to authorized frequency bands when switching, and its method for building up is as follows:

1. with integer to (i, j, k) expression frequency band occupied state, wherein i and j represent the total number of the sub-band of two groups of cognitive CU respectively, k represents the number of the dominant frequency band of main CU, and the communication mode that cognitive user adopts FDMA utilizes a plurality of different sub-bands to carry out transfer of data;

2. have under the situation that frequency spectrum switches when main user occurs, cognitive user will be vacated its sub-band and transfer to immediately and continue communication on other idle subchannels, in this case, as long as there is idle frequency band to exist, just do not have and will not be forced to interrupt generation; (i, j k), if i+j+Nk≤(M-1) is N, even then there is main user to arrive, are forced to interrupt also can not taking place for state.This moment, state transition rate was zero;

If 3. (i, j k) do not satisfy the N of i+j+Nk≤(M-1), and its state transition rate is:

4. list equilibrium equation, obtain state probability.

5. the conventional method of accessing two groups of cognitive users to authorized frequency bands according to claim 1, it is characterized in that the described conventional method of accessing two groups of cognitive users to authorized frequency bands when having channel reservation, utilize channel reservation method to be forced to the performance requirement that outage probability and blocking probability satisfy system with balance, wherein channel reservation method set up as follows:

1. according to the traffic carrying capacity of input and the Markov model of foundation, calculate the probability of each state;

2. according to state probability, by the numerical value enumeration method, even r=1,2 ..., the blocking probability when calculating r respectively and getting different value and be forced to outage probability, select the best number r that reserves subchannel, make blocking probability and be forced to the performance requirement that outage probability satisfies system.

6. the conventional method of accessing two groups of cognitive users to authorized frequency bands according to claim 1 is characterized in that the described conventional method of accessing two groups of cognitive users to authorized frequency bands when having channel reservation, and its method for building up is as follows:

1. when the number of all remaining idle sub-channels during, promptly when i+j+Nk≤NK-r, then then will interrupt if there is new main user to occur this moment less than main user's bandwidth requirement N;

2. when the number of remaining idle sub-channels during greater than the number r of the subchannel of reserving, promptly when (K-1) N＜i+j+Nk≤NK-r, can allow new cognitive user and insert this moment;

3. when the number of remaining idle sub-channels is less than or equal to the number r of subchannel of reservation, promptly when i+j+Nk=NK-r or i+j+Nk≤NK, does not then allow new cognitive user and insert;

4. when if channel reservation is arranged, promptly when i+j+Nk≤NK-r, then the cognitive user of these interruptions can switch on the subchannel of those reservations and continue communication;

5. list equilibrium equation, obtain state probability.

7. the conventional method of accessing two groups of cognitive users to authorized frequency bands according to claim 5, the conventional method of accessing two groups of cognitive users to authorized frequency bands when it is characterized in that having channel reservation, utilize channel reservation method to be forced to the performance requirement that outage probability and blocking probability satisfy system, wherein blocking probability and to be forced to the method for building up of outage probability as follows with balance:

1. equilibrium equation can be listed according to the state transition diagram of the number (i+j+Nk) of the occupied subchannel of representing with Markov model, the number of subchannels r that reserves and total bandwidth NK, the state probability that system is in each state can be obtained according to equilibrium equation;

Each state probability sum when 2. the blocking probability of system is expressed as number (i+j+Nk) and the subchannel number r sum of reserving when occupied subchannel greater than total bandwidth NK;

3. the outage probability that is forced to of system is expressed as the ratio that being forced to when having channel reservation interrupted the rate of transform and service access rate.

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