CN105721082A - Multiuser channel sensing method applied to cognitive radio - Google Patents

Abstract

The invention discloses a multiuser channel sensing method applied to cognitive radio. The multiuser channel sensing method disclosed by the invention can be used for realizing the channel sensing of a plurality of secondary users, and the secondary users have low collision probability, high average system throughput and low system complexity. The multiuser channel sensing method comprises the following steps: firstly, sequencing and numbering all available channels; then, obtaining all channel sensing sequences of previous m channels of the secondary users by adopting an exhaustive method; randomly combining the channel sensing sequences of m secondary users, and calculating the average system throughputs under all combinations, wherein the maximum average system throughput corresponds to an optimal sensing sequence combination of the previous m channels of the m secondary users; then sensing the (m+1)th channel, adding a channel Sm+1 while keeping the relative sensing sequence positions of the original m channels unchanged, and obtaining the optimal sensing sequence combination of the previous m+1 channels of the m secondary users; and so on, finally obtaining the optimal sensing sequence of N channels of the m secondary users.

Description

A kind of multiuser channel cognitive method being applied to cognitive radio

Technical field

The present invention relates to cognitive radio technology field, be specifically related to a kind of multiuser channel cognitive method being applied to cognitive radio.

Background technology

In different regions, the world, wireless frequency spectrum is mostly allocated to panoramic mechanism.Along with the development of science and technology, the shortage of frequency spectrum will become one of bottleneck of wireless communication technology development.In recent years, cognitive radio technology enters the popular visual field, it is intended to makes full use of and idle authorizes the frequency spectrum problem to alleviate spectrum shortage.

In cognitive radio networks, secondary user's (unauthorized user) can carry out receiving and transmitting signal when primary user (authorized user) does not use relevant frequency range.This means that the priority of secondary user's will lower than primary user.So when frequency spectrum accesses, secondary user's must before being transmitted, and perception is currently in use this frequency spectrum with or without primary user.Owing to substantial amounts of potential channel exists, secondary user's can select multi-channel transmission.This technology is called multichannel cognition Access Control.

First secondary user's selects a channel to carry out perception, if channel idle, starts to transmit signal, if channel is occupied, keeps mourning in silence, be not transmitted and perception within a period of time.On the other hand, secondary user's can continuous channel perception in order, till perceiving idle channel.In this context, channel-aware order and relevant stopping rule (namely when stop perception and when start to transmit signal) are very necessary.

When multiuser distributed perception, can there is multiple secondary user's and detect the situation that this channel is not used by primary user and determines to be concurrently accessed this channel simultaneously, cause conflict, so needing to formulate different perception according to different user and stop strategy.

At present, the main perception order in single secondary user's of research of the relevant cognitive radio perceptual strategy of major part and relevant stop tactful, and the aspect such as the centralized perception of pure strategy.And for the distributed perceptual strategy research of multi-user carry out less, the method being generally adopted exhaustive search at present carries out the formulation of perceptual strategy, and when the more and potentially useful channel of secondary user's is more, algorithm complex is high, poor practicability.

Summary of the invention

In view of this, the invention provides a kind of multiuser channel cognitive method being applied to cognitive radio, it is possible to realize the channel-aware of multiple secondary user's, and secondary user's collision probability is low, system average throughput high, system complexity is low, and performance comparable intends Brute-force search algorithm.

The multiuser channel cognitive method being applied to cognitive radio networks of the present invention, described network includes m secondary user's, N number of potentially useful channel, N > > m, m >=2, channel-aware method comprises the steps:

Step 1, by all potentially useful channels by its probability not used by primary user in a time slot, is ranked up from big to small and numbers；

Step 2, m channel before perception, including following sub-step:

Step 2.1, for front m channel S₁,S₂,...S_m, each secondary user's is respectively adopted the method for exhaustion and obtains all possible channel-aware order, and each secondary user's all has m！Plant channel-aware order；Calculate the secondary user's handling capacity under each channel-aware order；

Step 2.2, respectively from the m of each secondary user's！Kind channel-aware order arbitrarily selects one be combined, total (m！)^mPlanting combination, calculate the system average throughput under each combination, described system average throughput is the secondary user's handling capacity summation of m secondary user's under this combination；

Step 2.3, finds the combination that maximum system average throughput is corresponding, the channel-aware sequential combination A of each secondary user's that this combination is corresponding_mB_mC_mD_m... it is the optimum perception sequential combination of front m the channel of m secondary user's；Wherein, A_mFor the optimum perception order of front m the channel of user 1, B_mFor user 2 front m channel optimum perception order, the like；

Step 3, the m+1 channel of perception, including following sub-step:

Step 3.1, each secondary user's is respectively by channel S_m+1Add to the optimum perception order of this secondary user's of step 2 acquisition, and keep original m channel S₁,S₂,...S_mRelative perceptual ordinal position constant, each secondary user's all have m+1 kind channel-aware order；Calculate the secondary user's handling capacity under each channel-aware order；

Step 3.2, arbitrarily selects one from the m+1 kind channel-aware order of each secondary user's respectively and is combined, total (m+1)^mPlant combination；Calculate the system average throughput under each combination；

Step 3.3, finds the combination that maximum system average throughput is corresponding, the channel-aware sequential combination A of each secondary user's that this combination is corresponding_m+1B_m+1C_m+1D_m+1... it is the optimum perception sequential combination of front m+1 the channel of m secondary user's；Wherein, A_m+1For the optimum perception order of front m+1 the channel of user 1, B_m+1For user 2 front m+1 channel optimum perception order, the like；

Step 4, according to the mode of step 3, successively perception m+2, m+3 ..., N number of channel, the optimum perception sequential combination of N number of channel of final m the secondary user's obtained is the channel-aware sequentially A of N number of channel of m final secondary user's_NB_NC_ND_N...；Wherein, A_NFor the optimum perception order of N number of channel of user 1, B_NFor user 2 N number of channel optimum perception order, the like.

Beneficial effect:

(1) present invention concentrates the perceptual strategy formulating repeatedly level user by coordinator, reduces the probability that multiple secondary user's clashes, adds system average throughput.

(2) compared with tradition exhaustive search algorithm, under the cost only losing fraction performance, the complexity of many secondary user distribution formula perceptual strategies is reduced.The computation complexity of tradition exhaustive search algorithm is O ((N！)^m), and the complexity of the delta algorithm that the present invention proposes is only

Accompanying drawing explanation

Fig. 1 is the inventive method flow chart.

Fig. 2 is the structure of time slot of perceptive mode of the present invention.

Detailed description of the invention

Develop simultaneously embodiment below in conjunction with accompanying drawing, describe the present invention.

The invention provides a kind of multiuser channel cognitive method being applied to cognitive radio, under the premise that secondary user's collision probability, lifting system average throughput are greatly reduced, performance comparable intends Brute-force search algorithm, and complexity is low, can be used for many secondary user distribution formula perception.

Energy and feature detection are two kinds of main flow cognitive methods.In energy measuring method, one channel of perception normally only needs the time less than 1ms, and feature detection then requires more than 20ms.Owing to each user needs the multiple channel of continuous perception at each time slot, so the present invention is only applicable to use the sensing network of energy detection method.

Consider a kind of cognition network containing a coordinator and m secondary user's.Assume that the potentially useful channel set of network is S (S={s₁,s₂,...,s_N, N > > m, m >=2), each user once can one channel of perception, and have the perception order of oneself.Such as: the perception order of user 1 is by (a₁,a₂,...,a_k,...,a_N) represent, the perception order of user 2 is by (b₁,b₂,...,b_k,...,b_N) expression etc..Wherein subscript k represents the perceived position of channel, i.e. a_kRepresent that user 1 kth needs the channel of perception, b_kRepresent that user 2 kth needs the channel of perception, by that analogy.

Whole sensing network assumes stringent synchronization, and perceptive mode adopts structure of time slot simultaneously, is divided into, with transmission, multiple time slots that duration is t by signal sensing total time.Perception structure of time slot is as shown in Figure 2.In FIG. 2, it is assumed that user finds the free time when perceiving kth channel, then utilize the remaining time of this time slot at kth channel transmission data.In time slot, the time for each channel of perception represents with τ.Each time slot comprises perception part (maximum N × τ) and hop (minimum t-N × τ).If a user completes perception at kth channel, then sense part is divided into k τ, and hop is t-k τ.The percentage ratio that time slot efficiency is accounted for whole time slot by hop represents.When a user completes perception at kth channel, then time slot efficiency c_kFor

c_k=(t-k τ)/t (1)

In each time slot, each channel only exists and whole is taken by primary user, taken or unoccupied three kinds of situations by secondary user's is whole.By in advance to the characteristic of channel and primary user to prior informations such as the use habits of this channel, can in a time slot channel s_iThe probability not used by primary userFor each channel, primary user in the state of certain time slot independent of other time slots, also independent of other channels.

In channel set S, channel according toSize is ranked up numbering, it may be assumed that

Channel, when each time slot starts, is carried out perception according to respective perception order, until finding idle channel by each secondary user's.If certain secondary user's determines to access certain channel, claim this user in this channel " stopping ".Each secondary user's all needs channel perception at each time slot and selects certain idle channel transmission signal.If certain secondary user's determines to stop at certain channel, this secondary user's will select corresponding speed R to transmit signal.

The present invention is perceived as starting point with many secondary user collaboratives, consider the computational complexity of coordinator, making, under the premise of not large losses performance, to reduce the computation complexity of cognitive method as far as possible, the channel-aware method of multiple secondary user's realizes especially by following steps:

Step one: for all m secondary user's, front m channel-aware takes tradition Brute-force search algorithm.Due to channel 1 to channel m primary user's free time probability (respectively) maximum, so potentially useful channel set is { s₁,s₂,...,s_m}.If a user completes perception, the data throughout U of one secondary user's of definition at kth channel_kIt is the information bit that can transmit of a time slot, it may be assumed that

U_k=R c_k(2)

For each secondary user's, exhaustive method is adopted to obtain the perception order of its all possible front m channel.For secondary user's 1, all possible perception order respectively (s of its front m channel₁,s₂,s₃...,s_m), (s₂,s₁,s₃...,s_m), (s₁,s₃,s₂...,s_m),…,(s_m,s_m-1,s_m-2...,s₁), (m altogether！) kind order.Then corresponding to the first perception order (s of secondary user's 1₁,s₂,s₃...,s_m), the now handling capacity U of secondary user's 1_{1_1}For:

$\begin{array}{c}{U}_{1\_1}={\mathrm{\θ}}_{s_1}\·R\·c_1+(1-{\mathrm{\θ}}_{s_1})\·{\mathrm{\θ}}_{s_2}\·R\·c_2+(1-{\mathrm{\θ}}_{s_1})\·(1-{\mathrm{\θ}}_{s_2})\·{\mathrm{\θ}}_{s_3}\·R\·c_3+\mathrm{...}\\ +(1-{\mathrm{\θ}}_{s_1})\·(1-{\mathrm{\θ}}_{s_2})\·\mathrm{...}\·(1-{\mathrm{\θ}}_{s_{m-1}})\·{\mathrm{\θ}}_{s_m}\·R\·c_m\end{array}---\left(3\right)$

The second perception order (s corresponding to secondary user's 1₂,s₁,s₃,s₄,...,s_m), the now handling capacity U of secondary user's 1_{1_2}For:

$\begin{array}{c}{U}_{1\_2}={\mathrm{\θ}}_{s_2}\·R\·c_1+(1-{\mathrm{\θ}}_{s_2})\·{\mathrm{\θ}}_{s_1}\·R\·c_2+(1-{\mathrm{\θ}}_{s_2})\·(1-{\mathrm{\θ}}_{s_1})\·{\mathrm{\θ}}_{s_3}\·R\·c_3\\ (1-{\mathrm{\θ}}_{s_2})\·(1-{\mathrm{\θ}}_{s_1})\·(1-{\mathrm{\θ}}_{s_3}){\mathrm{\θ}}_{s_4}\·R\·c_4+\mathrm{...}\\ +(1-{\mathrm{\θ}}_{s_2})\·(1-{\mathrm{\θ}}_{s_1})\·\mathrm{...}\·(1-{\mathrm{\θ}}_{s_{m-1}})\·{\mathrm{\θ}}_{s_m}\·R\·c_m\end{array}---\left(4\right)$

The third perception order (s corresponding to secondary user's 1₁,s₃,s₂,s₄,s₅...,s_m), the now handling capacity U of secondary user's 1_{1_3}For:

$\begin{array}{c}{U}_{1\_3}={\mathrm{\θ}}_{s_1}\·R\·c_1+(1-{\mathrm{\θ}}_{s_1})\·{\mathrm{\θ}}_{s_3}\·R\·c_2+(1-{\mathrm{\θ}}_{s_1})\·(1-{\mathrm{\θ}}_{s_3})\·{\mathrm{\θ}}_{s_2}\·R\·c_3\\ +(1-{\mathrm{\θ}}_{s_1})\·(1-{\mathrm{\θ}}_{s_3})\·(1-{\mathrm{\θ}}_{s_2}){\mathrm{\θ}}_{s_4}\·R\·c_4+(1-{\mathrm{\θ}}_{s_1})\·(1-{\mathrm{\θ}}_{s_3})\·(1-{\mathrm{\θ}}_{s_2})(1-{\mathrm{\θ}}_{s_4})\·{\mathrm{\θ}}_{s_5}\·R\·c_5\mathrm{...}\\ +(1-{\mathrm{\θ}}_{s_1})\·(1-{\mathrm{\θ}}_{s_3})\·(1-{\mathrm{\θ}}_{s_2})\·\mathrm{...}\·(1-{\mathrm{\θ}}_{s_{m-1}})\·{\mathrm{\θ}}_{s_m}\·R\·c_m\end{array}---\left(5\right)$

The like, obtain the secondary user's 1 handling capacity U that all possible perception order of secondary user's 1 is corresponding_{1_1},U_{1_2},...,U_{1_ (m！)}。

Similarly, it is thus achieved that the secondary user's handling capacity of all of perception order correspondence of each secondary user's.

System average throughput is the summation of m secondary user's handling capacity, total (m！)^mThe situation of kind, the secondary user's handling capacity combination that corresponding each secondary user's difference perception order is corresponding, namely

U_{tol_1}=U_{1_1}+U_{2_1}+...+U_{m_1}

U_{tol_2}=U_{1_1}+U_{2_1}+...+U_{m_2}

.

.

.

$U_{tol-{(m!)}^m}=U_{1-(m!)}+U_{2-(m!)}+...+U_{m-(m!)}$

Through to, after the calculating of system average throughput and comparing, maximum system average throughput U being obtained_{tol_x}, each secondary user's handling capacity U corresponding to maximum system average throughput can be obtained_{1_i},U_{2_j},...U_{m_w}, and then find the perception sequential combination of each secondary user's of correspondence, it is designated as: It is the optimum perception sequential combination of front m the channel of m secondary user's.

Owing to adopting tradition Brute-force search algorithm, in epicycle perception, computation complexity is O ((m！)^m)。

Step 2: the m+1 channel of perception.Can being obtained by step one, the optimum perception sequential combination of front m channel isRemembering under this optimum combination, front m the channel-aware order of user 1 is A_m=(a₁,a₂,a₃,...a_m), front m the channel-aware order of user 2 is B_m=(b₁,b₂,b₃,...,b_m), by that analogy.Next need to increase channel S_m+1To A_mIn, it is maintained with original m channel S₁,S₂,...S_mRelative perceptual ordinal position constant.Then adding channel S_m+1Afterwards, new perception order isWherein, A' has m+1 kind situation, i.e. (s_m+1,a₁,a₂,...,a_m),(a₁,s_m+1,a₂,...,a_m),...,(a₁,a₂,...,a_m,s_m+1).Equally, B' also has m+1 kind situation (s_m+1,b₁,b₂,...,b_m),(b₁,s_m+1,b₂,...,b_m),...,(b₁,b₂,...,b_m,s_m+1), the like.

Calculate each secondary user's and add channel S_m+1Afterwards, the secondary user's handling capacity that all possible perception order is corresponding.It is example for 1, the first perception order (s of A'_m+1,a₁,a₂,...,a_m) corresponding secondary user's handling capacity is

$\begin{array}{c}{U}_{A^{\′}\_1}={\mathrm{\θ}}_{s_{m+1}}\·R\·c_1+(1-{\mathrm{\θ}}_{s_{m+1}})\·{\mathrm{\θ}}_{a_1}\·R\·c_2+(1-{\mathrm{\θ}}_{s_{m+1}})\·(1-{\mathrm{\θ}}_{a_1})\·{\mathrm{\θ}}_{a_2}\·R\·c_3\mathrm{...}\\ +(1-{\mathrm{\θ}}_{s_{m+1}})\·(1-{\mathrm{\θ}}_{a_1})\·\mathrm{...}\·(1-{\mathrm{\θ}}_{a_{m-1}})\·{\mathrm{\θ}}_{a_m}\·R\·c_{m+1}\end{array}$

The second perception order (a of A'₁,s_m+1,a₂,...,a_m) corresponding handling capacity is

$\begin{array}{c}{U}_{A^{\′}\_2}={\mathrm{\θ}}_{a_1}\·R\·c_1+(1-{\mathrm{\θ}}_{a_1})\·{\mathrm{\θ}}_{s_{m+1}}\·R\·c_2+(1-{\mathrm{\θ}}_{a_1})\·(1-{\mathrm{\θ}}_{s_{m+1}})\·{\mathrm{\θ}}_{a_2}\·R\·c_3\mathrm{...}\\ +(1-{\mathrm{\θ}}_{a_1})\·(1-{\mathrm{\θ}}_{s_{m+1}})\·\mathrm{...}\·(1-{\mathrm{\θ}}_{a_{m-1}})\·{\mathrm{\θ}}_{a_m}\·R\·c_{m+1}\end{array}$

The like, obtain user 1 and add channel S_m+1Afterwards, corresponding for all possible perception order A' secondary user's handling capacity U_{A'_1},U_{A'_2},...,U_{A'_m+1}, (m+1) plants altogether.

Similarly, obtain all secondary user's and add channel S_m+1Afterwards, the secondary user's handling capacity that all possible perception order is corresponding.

With m secondary user's, therefore there is (m+1)^mKind possible perception combination (A', B' ... .).

Calculate all of perception combination (A', B' ... .) under system average throughput, it may be assumed that

U_{tol_1}=U_{A'_1}+U_{B'_1}+U_{C'_1}+U_{D'_1}+...

U_{tol_2}=U_{A'_2}+U_{B'_1}+U_{C'_1}+U_{D'_1}+...

U_{tol_3}=U_{A'_3}+U_{B'_1}+U_{C'_1}+U_{D'_1}+...

.

.

.

$U_{tol-{(m+1)}^m}=U_{A^{\′}\_(m+1)}+U_{B^{\′}\_(m+1)}+U_{C^{\′}\_(m+1)}+U_{D^{\′}\_(m+1)}...$

Through to, after the calculating of system average throughput and comparing, maximum system average throughput U being obtained_{tol_y}, can obtain each secondary user's handling capacity corresponding to maximum system average throughput, and then find the perception sequential combination of each secondary user's of correspondence, be designated as:Optimum perception sequential combination for front m+1 the channel of m secondary user's.

Then the computation complexity of epicycle perception is O ((m+1)^m)。

Step 3: according to the mode of step 2, successively perception m+2, m+3 ..., N number of channel.

Wherein, during perception jth channel, this computation complexity taking turns perception is O (j^m), j=m+2, m+3 ..., N.

Finally, the perception order that can obtain whole N number of potentially useful channel is:

Then the computation complexity of inventive algorithm is

Step 4: the perception order of the N number of potentially useful channel that each secondary user's obtains according to step 3Carry out distributed perception, and carry out data transmission.

If multiple secondary user's detect this channel and do not used by primary user and determine to be concurrently accessed this channel simultaneously, three kinds of situations will produce below:

Situation 1: new perception of unsuccessfully laying equal stress on: each user utilizes same compensation mechanism, to avoid possible conflict.1 secondary user's has won competition and has utilized time slot to transmit signal remaining time.All the other secondary user's continue according to original perception order other channels of perception.

Situation 2: failure is also exited: similar to situation 1, multiple secondary user's adopt certain compensation mechanism to avoid conflict.Wherein 1 secondary user's wins competition and utilizes time slot to transmit signal remaining time.And other secondary user's no longer carry out perception and transmission signal in this timeslot, " exit " this time slot.This situation does not have practical significance, compares as just a kind of extreme case.

Situation 3: conflict.There is no compensation mechanism.When multiple secondary user's at the same time it is wished that stop same channel (multiple secondary user's detect this channel simultaneously and are not used by primary user and determine to access this channel) time, multiple secondary user's all utilize this channel transmission data, lead to a conflict generation, does not finally have user can utilize this channel.

Simulating scenes supposes that number of users is 2, there is 7 potentially useful channels (N=7), time slot duration t=1, each channel-aware time τ=0.1.Primary user's free time probability of channel i is θ_i=0.05 × κ_i, wherein κ_iIt it is a regulation coefficient.For this scene, implement as follows.

Embodiment 1, κ_iFor even number and 2≤κ₁≤ 18,2≤κ₂≤κ₁, 2≤κ₃≤κ₂And 0≤κ_i≤κ_i-1, i=4,5,6,7, then wherein θ_i∈[0,0.9]。

Embodiment 2,10≤κ₇≤κ₆≤κ₅...≤κ₁≤ 18, then wherein θ_i∈[0.5,0.9]。

Embodiment 3,1≤κ₇≤κ₆≤κ₅...≤κ₁≤ 10, then wherein θ_i∈[0.05,0.5]。

In each case, the maximum system average throughput obtained by exhaustive search method is by T_optRepresent, and the system average throughput of the delta algorithm gained proposed by the present invention is T_incremental, the relative mistake of the two performance is from being defined as (T_opt-T_incremental)/T_opt。

Coordinator adopts abovementioned steps and Fig. 1 algorithm flow chart to carry out the formulation of perception order, and each secondary user's carries out distributed perception according to the optimum perception order finally given, and carries out data transmission.

Table 1 is the result of implementation in various situation.It can be seen that the relative performance gap of inventive algorithm is very nearly the same with exhaustive search method, complexity is thenO ((N much smaller than exhaustive search method！)^m)。

Table 1

In sum, these are only presently preferred embodiments of the present invention, be not intended to limit protection scope of the present invention.All within the spirit and principles in the present invention, any amendment of making, equivalent replacement, improvement etc., should be included within protection scope of the present invention.

Claims (1)

1. being applied to a multiuser channel cognitive method for cognitive radio networks, described network includes m secondary user's, N number of potentially useful channel, and N > > m, m >=2, it is characterised in that comprise the steps:

Step 1, by all potentially useful channels by its probability not used by primary user in a time slot, is ranked up from big to small and numbers；

Step 2, m channel before perception, including following sub-step:

Step 2.1, for front m channel S₁,S₂,...S_m, each secondary user's is respectively adopted the method for exhaustion and obtains all possible channel-aware order, and each secondary user's all has m！Plant channel-aware order；Calculate the secondary user's handling capacity under each channel-aware order；

Step 2.2, respectively from the m of each secondary user's！Kind channel-aware order arbitrarily selects one be combined, total (m！)^mPlanting combination, calculate the system average throughput under each combination, described system average throughput is the secondary user's handling capacity summation of m secondary user's under this combination；

Step 2.3, finds the combination that maximum system average throughput is corresponding, the channel-aware sequential combination A of each secondary user's that this combination is corresponding_mB_mC_mD_m... it is the optimum perception sequential combination of front m the channel of m secondary user's；Wherein, A_mFor the optimum perception order of front m the channel of user 1, B_mFor user 2 front m channel optimum perception order, the like；

Step 3, the m+1 channel of perception, including following sub-step:

Step 3.1, each secondary user's is respectively by channel S_m+1Add to the optimum perception order of this secondary user's of step 2 acquisition, and keep original m channel S₁,S₂,...S_mRelative perceptual ordinal position constant, each secondary user's all have m+1 kind channel-aware order；Calculate the secondary user's handling capacity under each channel-aware order；

Step 3.2, arbitrarily selects one from the m+1 kind channel-aware order of each secondary user's respectively and is combined, total (m+1)^mPlant combination；Calculate the system average throughput under each combination；

Step 3.3, finds the combination that maximum system average throughput is corresponding, the channel-aware sequential combination A of each secondary user's that this combination is corresponding_m+1B_m+1C_m+1D_m+1... it is the optimum perception sequential combination of front m+1 the channel of m secondary user's；Wherein, A_m+1For the optimum perception order of front m+1 the channel of user 1, B_m+1For user 2 front m+1 channel optimum perception order, the like；

Step 4, according to the mode of step 3, successively perception m+2, m+3 ..., N number of channel, the optimum perception sequential combination of N number of channel of final m the secondary user's obtained is the channel-aware sequentially A of N number of channel of m final secondary user's_NB_NC_ND_N...；Wherein, A_NFor the optimum perception order of N number of channel of user 1, B_NFor user 2 N number of channel optimum perception order, the like.