CN102036389A - Multichannel diversity-based cognitive medium access control realizing method - Google Patents

Abstract

The invention discloses a multichannel diversity-based cognitive medium access control realizing method, which is designed on the basis of multichannel diversity. In the method, source nodes and target nodes compete for the right of use of a data channel through exchange control packets on a public control channel, node pairs wining the competition determine data channels and corresponding power allocation for the transmission according to power/channel combined allocation and are shifted to corresponding data channels to transmit a plurality of data packets continuously. The invention also provides a method for resolving power/channel combined allocation, which is to resolve the power/channel combined allocation by converting the power/channel combined allocation into a multi-choice knapsack problem and by dynamic planning. Simulation results show that the cognitive MAC protocol can effectively improve intra-node pair data transmission rate and network throughput under a condition that the total transmission power is limited compared with an opportunistic multiradio MAC (OMMAC) protocol.

Description

Implementation method based on the cognition MAC protocol of multichannel diversity

Technical field

The invention belongs to MAC (Medium Access Control) the layer protocol method for designing of the cognitive Ad Hoc network of wireless communication technology field, relate in particular to a kind of implementation method of the cognition MAC protocol based on the multichannel diversity.

Background technology

Along with the develop rapidly of wireless communication technology, frequency spectrum becomes rare day by day resource, and traditional fixed frequency spectrum method of salary distribution causes the wasting of resources and then the availability of frequency spectrum low, has become the key factor that the restriction cordless communication network further develops.Cognitive radio technology has the detection of primary user authorizes the situation that takies of frequency range and implements the ability that dynamic spectrum inserts it, can address the above problem effectively.Introducing cognitive radio technology in wireless Ad Hoc network is emerging in recent years research field, and design can realize that MAC agreement that the high-efficiency dynamic frequency spectrum inserts is one of the main challenge faced of cognitive Ad Hoc network and focus.

In cognitive Ad Hoc network, wireless channel is shared by multinode, the medium access control of coordinator node access channel (MAC) mechanism is one of key technology of cognitive Ad Hoc network, can it not only is related to make full use of radio channel resource, realize the fair competition of node to wireless channel, influencing the performance of network layer and transport layer protocol simultaneously, also is the key of cognitive Ad Hoc network support service quality (QoS).Yet, the characteristics of cognitive AdHoc network self (as distributed, have concealed terminal/exposed terminal problem, a network topology frequent variations etc.) make that research is efficient, fair, support the MAC mechanism of QoS to face very big challenge, become a research difficult point of cognitive Ad Hoc network.

Using diversity technique in Ad Hoc network is to improve the effective ways of network throughput.MOAR (Multi-channel Opportunistic Auto-rate MAC Protocol) agreement [3] is used the channel diversity technology, be node to the best channel of selective channel condition as data transmission channel, and source node regulation according to OAR (Opportunistic Auto-rate MAC Protocol) agreement on this channel send a plurality of packets continuously to destination node; Though this agreement can effectively improve network throughput, do not make full use of the available channel resources of network, still use a channel channel to communicate.OMAR (Opportunistic Medium Access and Auto Rate Protocol) agreement is used the link-diversity technology, be that source node selects the best node of channel condition as destination node in its neighbours' scope, and send packet to this node; Identical with the MOAR agreement, the OMAR agreement equally only allows a pair of node only to use a channel to carry out transmitted in packets, therefore, does not still make full use of the channel resource in the network.On the basis of channel diversity and link-diversity, OMMAC (Opportunistic Multiradio MAC Protocol) agreement is used many radio station diversity technique, allow source node to use different radio station on different channels, to carry out transmitted in packets with different destination nodes simultaneously, because this agreement has made full use of the channel resource in the network, therefore can obtain best network throughput; But, cause this agreement need consume too much resource (as power) and cost (more radio station) because the OMMAC protocol requirement is equipped with the multi-section radio station and does not have the gross power restriction for each node.

For cognitive Ad Hoc network, its MAC agreement can be divided three classes: insert class at random, time slot class and mixing class.SRAC-MAC (Single Radio Adaptive Channel-MAC) and HC-MAC (Hardware-Constrained Cog-nitive MAC) agreement belong to and insert quasi-protocol at random, and the transmission of controlling grouping and still be data all realizes by Random Access Channel.C-MAC (Cognitive MAC) agreement as the representative of time slot agreement is to add the CR function to obtain on the basis of revising the MMAC agreement, divide by being carried out strict time slot beacon period, for each neighbor node distributes unique signalling time slot, thereby realize the raising of network throughput, but this agreement is comparatively complicated, and extensibility is lower.In mixing quasi-protocol, the control grouping is transmitted by synchronization slot, transfer of data is subsequently then used the accidental channel access scheme, SYN-MAC (Synchronized MAC) agreement that proposes of people such as Y.R.Kondareddy for example, to be divided into the frame structure that repeats the time, the timeslot number that comprises in the frame is identical with the maximum available channel number and corresponding one by one, and the node that reservation is successful in the corresponding time slot of certain channel is to also competing this channel right to use according to IEEE 802.11 DCF modes in later time.

Summary of the invention

The object of the present invention is to provide a kind of implementation method of the cognition MAC protocol based on the multichannel diversity.This method can make better node between unite distribution by power/channel and use many data channels to finish transmitted in packets effectively, thereby effectively utilize the available channel resources in the network, improve node to message transmission rate, and then improve network throughput.

For achieving the above object, the technical solution used in the present invention is:

1) at first, to be divided into the identical a plurality of channel time slots of time span the time, each channel time slot was made up of " perception cycle " and " data transfer cycle ", in the perception cycle, all nodes are all data channels of perception successively, determine which data channel is not taken by naive user in this channel time slot, in data transfer cycle, node is to controlling the grouping competition data channel right to use by exchange and finishing power/channel and unite distribution on Common Control Channel, the successful node of competition is finished transmitted in packets to switching to respective data channels subsequently;

2) secondly, each node is all safeguarded a tabulation: data channel uses tabulation DCUL, writes down naive user and neighbor node channel and the power operating position in current channel time slot respectively;

3) once more, when node S has packet need be when destination node D sends, two nodes are finished transmitted in packets by following four-stage:

A.RTS divides into groups the transmission stage: source node S is at first intercepted Common Control Channel, and when back off time finish and in distributed coordination frame period DIFS subsequently Common Control Channel still idle, then send request and send grouping RTS, carry the DCUL of self in this RTS grouping to destination node D;

B.CTS divides into groups the transmission stage: if destination node D successfully receives the RTS grouping that source node S sends, then at first the DCUL of self DCUL and source node S is compared, if do not exist publicly available data channel promptly not have the identical data channel that is not taken among two DCUL by PU, then node D sends NCTS (Negative CTS) grouping to node S, expression competition failure; Otherwise node D carries out the distribution of uniting of power/channel according to the channel information that writes down among two DCUL, and determines transmission rate according to allocation result, and then determines the packet number of this transmission, and sends permission transmission grouping CTS to source node;

C.RES divides into groups the transmission stage: if source node S successfully receives the CTS grouping that destination node D sends, then behind short frame period SIFS, to destination node D loopback reservation packet RES, the information of record is identical in the CTS grouping that the information that this grouping is write down and node D send, if source node S successfully receives the NCTS grouping that destination node D sends, then cancel this transmission, because showing, the NCTS grouping do not have public available channel between source node and the destination node, therefore, in current channel time slot, node S will be no longer to node D transmission of data packets;

D. data transfer phase: after destination node D success reception sources node sent the RES grouping of S, two nodes switched to respective channel simultaneously, after SIFS, finish data packet transmission according to the power of determining;

4) last, the neighbor node that listens to CTS grouping or RES grouping is by the relevant information among following process renewal self DCUL;

A. intercept the CTS grouping: suppose that source node S and destination node D use K bar data channel to carry out transmitted in packets, its centre frequency is { f ₁..., f _K, power division is { P ₁..., P _K, if node I listens to the CTS grouping that node D sends, then node I at first calculates self and the channel gain of node D on Common Control Channel, and obtains self and the channel gain of node D on above-mentioned K bar channel thus; Secondly, node I computing node D is according to power division { P ₁..., P _KSend the interference of confirming that grouping ACK brings to self, and upgrade the total interference that self is subjected to; Once more, node I calculates from correctly receiving the maximum available transmit power of using under the prerequisite of packet on this K bar channel in not influencing node D; At last, upgrade network allocation vector NAV;

B. intercept the RES grouping: suppose that source node S and destination node D use K bar data channel to carry out transmitted in packets, its centre frequency is { f ₁..., f _K, power division is { P ₁..., P _K, if node I listens to the RES grouping that node S sends, then node I at first calculates self and the channel gain of node D on Common Control Channel, and obtains self and the channel gain of node D on above-mentioned K bar channel thus; Secondly, node I computing node D is according to power division { P ₁..., P _KSend the interference that packet brings to self, and upgrade the total interference that self is subjected to; Once more, node I calculates certainly in not influencing node D spendable maximum available transmit power under the prerequisite of the correct ACK of reception grouping on this K bar channel; At last, upgrade network allocation vector NAV.

But the calculating of said destination node D specified data grouping and ACK grouping transmitted power and transmission of data packets number is carried out according to the following steps:

Suppose to have the public available data channels of L bar between source node S and the destination node D, its centre frequency is { f ₁..., f _L; The centre frequency of Common Control Channel is f ₀Node can with set of data rates be R={R ₁, R ₂..., R _Q(R ₁＜...＜R _Q), corresponding Signal to Interference plus Noise Ratio thresholding set is SINR={SINR ₁, SINR ₂..., SINR _Q(SINR ₁＜...＜SINR _Q); Internodal mode is the ground return model;

Node D calculates self and the channel gain of node S on Common Control Channel according to (1) after receiving the RTS grouping that node S sends

$h_{\mathrm{SD}}^0=P_r^{\mathrm{RTS}}/P_{\max }---\left(1\right)$

Wherein,

And P _MaxBe respectively the received power and the transmitted power of RTS grouping;

Node D calculates self and the channel gain of node S on the public available data channels channel of this L bar according to (2)

$h_{\mathrm{SD}}^l=h_{\mathrm{SD}}^0\×{(f_0/f_l)}^2,l=1,...,L---\left(2\right)$

Wherein, f ₀And f _lBe respectively the centre frequency of Common Control Channel and the public available channel of l bar;

Make up node available transmission rate matrix R, shown in (3);

Wherein, R ^l=[R ^{L, 1}R ^{L, Q}] (l=1 ..., the L) set of data rates that node can be used on the expression l bar data channel, and R ^{L, q}=R _q(q=1 ..., Q);

Make up the set of node through-put power

Shown in (4);

Wherein, Indicate node on l bar data channel with speed R _qCarry out the required transmitted power of transmitted in packets, can calculate according to (5),

${\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}={\mathrm{SINR}}_q\·{[P}_n+P_{\inf }\left(l\right)]/h_{\mathrm{SD}}^l---\left(5\right)$

Wherein, P _nBe the power of additive white Gaussian noise, P _Inf(l) the total interference that on l bar data channel, is subjected to for node D, SINR _qFor data rate is R _qThe Signal to Interference plus Noise Ratio thresholding;

Make up optimization aim: source node S is from the transmitted power collection The middle transmitted power of selecting to one of more options, is no more than maximum power P at overall transmission power in each set _Max, the through-put power on every channel is no more than under the prerequisite of the maximum available power on this channel, makes overall data transmission rate R _SDMaximization is shown in (6);

$\max \mathrm{imise}{R}_{\mathrm{SD}}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{R}^{l,q}\·x^{l,q}$

$s.t.\left\{\begin{array}{c}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\·x^{l,q}\≤P_{\max }\\ {\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\≤P_{\max -s}\left(l\right),l=1,...,L;q=1,...,Q\\ \underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{x}^{l,q}\≤1,l=1,...,L\\ x^{l,q}\∈\left\{\mathrm{0,1}\right\},l=1,...,L;q=1,...,Q\end{array}\right.---\left(6\right)$

Wherein, R ^{L, q}Q the transmission rate of expression node on the public available channel of l bar, x ^{L, q}Whether the expression node uses R ^{L, q}Carry out transfer of data, P _MaxBe the spendable maximum power of node, P _Max-s(l) expression node spendable maximum power on the public available channel of l bar;

Use Dynamic Programming to find the solution, be about to the problems referred to above and be divided into the L step and find the solution, m (the step problem of 1≤m≤L) is shown in (7):

$\underset{l=1}{\overset{m}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{R}^{l,q}\·x^{l,q}$

$s.t.\left\{\begin{array}{c}\underset{l=1}{\overset{m}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\·x^{l,q}\≤P_{\max }\\ {\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\≤P_{\max -s}\left(l\right),l=1...m;q=1...Q\\ \underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{x}^{l,q}\≤1,l=1...m\\ x^{l,q}\∈\left\{\mathrm{0,1}\right\},l=1...m;q=1...Q\end{array}\right.---\left(7\right)$

When finding the solution m step problem, effectively separating that only need consideration (m-1) step problem draws gets final product, and by finding the solution L subproblem, can obtain optimum power/channel and unite distribution

Obtaining transmission rate R _SDAfter, node D determines the maximum data grouping number that this transmission can be transmitted; At first, determine maximum transmission time, shown in (8);

T _max≤L _DATA/R _basic (8)

Wherein, L _DATABe the length of a data grouping, R _BasicBe the data rate of node on Common Control Channel;

Because different channel gains will cause different power/channel associating allocation result, so the transmission time also must be satisfied the constraint of inequality (9);

T _SD≤min{CT(f ₁)，…，CT(f _L)}＝CT _min (9)

Wherein, CT (f _l) for centre frequency be f _lCoherence time of data channel;

Therefore, the data transmission period condition that finally should satisfy is shown in (10);

T _SD≤min{CT _min，T _max} (10)

Because the transmission time can be used (11) expression, wherein N _SDBe the packet number of transmission, L _DATAAnd L _ACKBe the length of packet and ACK grouping, T _SifsBe the time of short frame period;

T _SD＝(2N _SD-1)T _sifs+N _SD(L _DATA+L _ACK)/R _SD (11)

Therefore, by (11) and (10) but can obtain the constraints of transmission of data packets number, shown in (12);

The present invention uses Common Control Channel, node is to controlling the grouping competition data channel right to use by exchange on Common Control Channel, compete successful node and distribute employed data channel and corresponding transmitted power thereof in definite transmission course using power/channel to unite, subsequently, node uses corresponding power to finish the transmission of a plurality of packets to switching to respective data channels.

Description of drawings

Fig. 1 is channel time slot partition description figure;

Fig. 2 uses the structure key diagram of tabulation DCUL for data channel;

Fig. 3 is protocol transmission procedure declaration figure;

Fig. 4 is the simulation curve figure that throughput changes with euclidean distance between node pair between node;

Fig. 5 is the simulation curve figure that network throughput changes with Network.

Embodiment

Below in conjunction with accompanying drawing the present invention is described in further detail.

At first referring to Fig. 1 the channel time slot division is described, each channel time slot all is divided into " perception cycle " and " data transfer cycle " two parts.In the perception cycle, node is all data channels of perception successively, determine the untapped data channel of main user in the current time slots.In data transfer cycle, node uses the untapped data channel of main user to finish transmitted in packets.

Illustrate that referring to Fig. 2 data channel uses tabulation content and function that DCUL comprised, each list item comprises five partial contents.Which bar data channel what " channel number " represented this list item record information correspondence is.Whether " PU state " represents this channel by main CU, and " 0 " expression is unoccupied, and " 1 " expression is occupied." neighbor node state " represents whether this channel is used by neighbor node, and " 0 " expression is not used, and " 1 " expression is used." suffered interference " is illustrated in the suffered interference summation from other node of node on this channel." the maximum transmitted power that allows " is illustrated in the maximum of the transmitted power that node can be used on this channel.

Referring to Fig. 3 the transmission course of this agreement is described, supposes that source node is S, destination node is D.

1.RTS the grouping transmission stage: source node S is at first intercepted Common Control Channel, and when back off time finish and in DIFS subsequently Common Control Channel still idle, then send the RTS grouping to destination node D, carry the DCUL of self in this RTS grouping;

2.CTS the grouping transmission stage:, then at first the DCUL of self DCUL and source node S is compared if destination node D successfully receives the RTS grouping that source node S sends.If do not have publicly available data channel (promptly not having the identical data channel that is not taken by PU) among two DCUL, then node D sends NCTS (Negative CTS) grouping to node S, expression competition failure; Otherwise node D carries out the distribution of uniting of power/channel according to the channel information that writes down among two DCUL, and determines transmission rate according to allocation result, and then determines the packet number of this transmission, and sends the CTS grouping to source node;

Power/channel associating assigning process is as follows:

Suppose to have the public available data channels of L bar between source node S and the destination node D, its centre frequency is { f ₁..., f _L; The centre frequency of Common Control Channel is f ₀Node can with set of data rates be R={R ₁, R ₂..., R _Q(R ₁＜...＜R _Q), corresponding Signal to Interference plus Noise Ratio thresholding set is SINR={SINR ₁, SINR ₂..., SINR _Q(SINR ₁＜...＜SINR _Q); Internodal mode is the ground return model.

Node D calculates self and the channel gain of node S on Common Control Channel according to (1) after receiving the RTS grouping that node S sends

$h_{\mathrm{SD}}^0=P_r^{\mathrm{RTS}}/P_{\max }---\left(1\right)$

Wherein,

And P _MaxBe respectively the received power and the transmitted power of RTS grouping.

Node D calculates self and the channel gain of node S on the public available data channels channel of this L bar according to (2)

$h_{\mathrm{SD}}^l=h_{\mathrm{SD}}^0\×{(f_0/f_l)}^2,l=1,...,L---\left(2\right)$

Make up node available transmission rate matrix R, shown in (3).

Wherein, R ^l=[R ^{L, 1}R ^{L, Q}] (l=1 ..., the L) set of data rates that node can be used on the expression l bar data channel, and R ^{L, q}=R _q(q=1 ..., Q).

Make up the set of node through-put power

Shown in (4).

Wherein,

Indicate node on l bar data channel with speed R _qCarry out the required transmitted power of transmitted in packets, can calculate according to (5),

${\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}={\mathrm{SINR}}_q\·{[P}_n+P_{\inf }\left(l\right)]/h_{\mathrm{SD}}^l---\left(5\right)$

P in the formula _nBe additive white Gaussian noise, P _Inf(l) the total interference that on l bar data channel, is subjected to for node D.

Make up optimization aim: source node S is from the transmitted power collection

The middle transmitted power of selecting to one of more options, is no more than maximum power P at overall transmission power in each set _Max, the through-put power on every channel is no more than under the prerequisite of the maximum available power on this channel, makes overall data transmission rate R _SDMaximization is shown in (6).

$\max \mathrm{imise}{R}_{\mathrm{SD}}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{R}^{l,q}\·x^{l,q}$

$s.t.\left\{\begin{array}{c}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\·x^{l,q}\≤P_{\max }\\ {\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\≤P_{\max -s}\left(l\right),l=1,...,L;q=1,...,Q\\ \underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{x}^{l,q}\≤1,l=1,...,L\\ x^{l,q}\∈\left\{\mathrm{0,1}\right\},l=1,...,L;q=1,...,Q\end{array}\right.---\left(6\right)$

Use Dynamic Programming to find the solution, be about to the problems referred to above and be divided into the L step and find the solution, (the step problem of 1≤m≤L) is shown in (7) for m.

$\underset{l=1}{\overset{m}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{R}^{l,q}\·x^{l,q}$

$s.t.\left\{\begin{array}{c}\underset{l=1}{\overset{m}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\·x^{l,q}\≤P_{\max }\\ {\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\≤P_{\max -s}\left(l\right),l=1...m;q=1...Q\\ \underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{x}^{l,q}\≤1,l=1...m\\ x^{l,q}\∈\left\{\mathrm{0,1}\right\},l=1...m;q=1...Q\end{array}\right.---\left(7\right)$

When finding the solution m step problem, effectively separating that only need consideration (m-1) step problem draws gets final product.By finding the solution L subproblem, can obtain optimum power/channel and unite distribution

Obtaining transmission rate R _SDAfter, node D determines the maximum data grouping number that this transmission can be transmitted.At first, determine maximum transmission time, shown in (8).

T _max≤L _DATA/R _basic (8)

Because different channel gains will cause different power/channel associating allocation result, so the transmission time also must be satisfied the constraint of inequality (9).

T _SD≤min{CT(f ₁)，…，CT(f _L)}＝CT _min (9)

Wherein, CT (f _l) for centre frequency be f _lCoherence time of data channel.

Therefore, the data transmission period condition that finally should satisfy is shown in (10).

T _SD≤min{CT _min，T _max} (10)

Because the transmission time can be used (11) expression, wherein N _SDBe the packet number of transmission, L _DATAAnd L _ACKBe the length of packet and ACK grouping, T _SifsBe the time of short interFrameGap.

T _SD＝(2N _SD-1)T _sifs+N _SD(L _DATA+L _ACK)/R _SD (11)

Therefore, by (11) and (10) but can obtain the constraints of transmission of data packets number, shown in (12).

3.RES the grouping transmission stage: if source node S successfully receives the CTS grouping that destination node D sends, then behind SIFS, to destination node D loopback RES grouping, the information that this grouping is write down is identical with the information that writes down during the CTS that node D sends divides into groups.If source node S successfully receives the NCTS grouping that destination node D sends, then cancel this transmission.Do not have public available channel between source node and the destination node because the NCTS grouping shows, therefore, in current channel time slot, node S will be no longer to node D transmission of data packets;

4. data transfer phase: after destination node D success reception sources node sent the RES grouping of S, two nodes switched to respective channel simultaneously, after SIFS, finish data packet transmission according to the power of determining.

At last, listen to the neighbor node of CTS grouping or RES grouping by the relevant information among following process renewal self DCUL;

1. intercept the CTS grouping: suppose that source node S and destination node D use K bar data channel to carry out transmitted in packets, its centre frequency is { f ₁..., f _K, power division is { P ₁..., P _K.If node I listens to the CTS grouping that node D sends, then at first calculate itself and the channel gain of D on Common Control Channel according to (1)

And calculate self and the channel gain of D on this K bar data channel by (2)

Subsequently, node I presses power { P according to (13) computing node D ₁..., P _KOn this K bar channel, send the interference that the ACK grouping brings oneself, and upgrade the total interference that self is subjected to by (14).

$P_{\inf }^D\left(k\right)=P_k\·h_{\mathrm{ID}}^k,k=1,...,K---\left(13\right)$

$P_{\inf }\left(k\right)=P_{\inf }\left(k\right)+P_{\inf }^D\left(k\right),k=1,...,K---\left(14\right)$

Subsequently, node I calculates certainly in not influencing node D spendable maximum available transmit power under the prerequisite of correct reception packet on this K bar data channel by (15).

$P_{\max -s}\left(k\right)=P_{\min }^{\inf }/h_{\mathrm{ID}}^k,k=1,...,K---\left(15\right)$

Wherein,

Be that node D is guaranteeing correct following receptible maximum interference power of prerequisite that receives packet, even node I is with power P _Max-s(k) send, then can guarantee self to be in outside the interference range of node D.

Here it may be noted that suffered interference

With maximum available transmit power P _Max-s(k) T effective time _CTSShown in (16).

${\mathrm{NAV}}_{\mathrm{CTS}}=\frac{L_{\mathrm{RES}}}{R_{\mathrm{basic}}}+N_{\mathrm{trans}}\·\frac{L_{\mathrm{DATA}}+L_{\mathrm{ACK}}}{R_{\mathrm{SD}}}+(2N_{\mathrm{trans}}+1)T_{\mathrm{SIFS}}---\left(16\right)$

Wherein, R _SDFor uniting by power/channel, node S and D distribute the data rate that can reach, T _SIFSLength for SIFS.

2. intercept the RES grouping: suppose that source node S and destination node D use K bar data channel to carry out transmitted in packets, its centre frequency is { f ₁..., f _K, power division is { P ₁..., P _K.If node I listens to the RES grouping that node S sends, then the method computing node D that can provide according to (13)-(15) is according to { P ₁..., P _KSend interference that packet brings to self, upgrade total interference of self being subjected to, calculate from not influencing node D spendable maximum available transmit power under the prerequisite of the correct ACK of reception grouping on this K bar channel, and upgrade network allocation vector by (17).

$T_{\mathrm{RES}}=N_{\mathrm{trans}}\·\frac{L_{\mathrm{DATA}}+L_{\mathrm{ACK}}}{R_{\mathrm{SD}}}+2N_{\mathrm{trans}}\·T_{\mathrm{SIFS}}---\left(17\right)$

In order to verify the performance based on the cognition MAC protocol of multichannel diversity of proposition, we under NS-2 emulation this scheme.

1. uncontested scene: in uncontested scene, we only are provided with pair of source node and destination node, in this scene, source node is sustainable to send packet to destination node, and therefore the interference that brings when not existing neighbor node to send, can fully verify the advantage of multichannel diversity.Fig. 4 has provided under the uncontested scene based on the throughput of the cognition MAC protocol of multichannel diversity and the OMMAC agreement variation relation with euclidean distance between node pair.

2. the competition scene is arranged: in the competition scene was arranged, cognitive nodes was evenly distributed in the border circular areas that diameter is 250m, and each node all can carry out transmitted in packets with its neighbor node.Fig. 5 has provided to be had in the competition scene based on the throughput of the cognition MAC protocol of multichannel diversity and the OMMAC agreement variation relation with number of data streams.

Along with the increase of euclidean distance between node pair, no matter the MCD-CMAC agreement still is the OMMAC agreement, and its throughput all constantly reduces.But because node can only use three kinds of data rates, so the OMMAC agreement can only obtain three kinds of different total data rates.The MCD-CMAC agreement then can be united distribution by power/channel, obtains different power combination, thereby realizes multiple transmission rate, makes its performance be better than the OMMAC agreement far away.When euclidean distance between node pair was far away, because decay, the MCD-CMAC agreement can only be used a Channel Transmission grouping, and therefore, the throughput performance of MCD-CMAC agreement is identical with the OMMAC agreement.

Claims (2)

1. based on the implementation method of the cognition MAC protocol of multichannel diversity, it is characterized in that:

1) at first, to be divided into the identical a plurality of channel time slots of time span the time, each channel time slot was made up of " perception cycle " and " data transfer cycle ", in the perception cycle, all nodes are all data channels of perception successively, determine which data channel is not taken by naive user in this channel time slot, in data transfer cycle, node is to controlling the grouping competition data channel right to use by exchange and finishing power/channel and unite distribution on Common Control Channel, the successful node of competition is finished transmitted in packets to switching to respective data channels subsequently;

2) secondly, each node is all safeguarded a tabulation: data channel uses tabulation DCUL, writes down naive user and neighbor node channel and the power operating position in current channel time slot respectively;

3) once more, when node S has packet need be when destination node D sends, two nodes are finished transmitted in packets by following four-stage:

A.RTS divides into groups the transmission stage: source node S is at first intercepted Common Control Channel, and when back off time finish and in distributed coordination frame period DIFS subsequently Common Control Channel still idle, then send request and send grouping RTS, carry the DCUL of self in this RTS grouping to destination node D;

B.CTS divides into groups the transmission stage: if destination node D successfully receives the RTS grouping that source node S sends, then at first the DCUL of self DCUL and source node S is compared, if do not exist publicly available data channel promptly not have the identical data channel that is not taken among two DCUL by PU, then node D sends NCTS (Negative CTS) grouping to node S, expression competition failure; Otherwise node D carries out the distribution of uniting of power/channel according to the channel information that writes down among two DCUL, and determines transmission rate according to allocation result, and then determines the packet number of this transmission, and sends permission transmission grouping CTS to source node;

C.RES divides into groups the transmission stage: if source node S successfully receives the CTS grouping that destination node D sends, then behind short frame period SIFS, to destination node D loopback reservation packet RES, the information of record is identical in the CTS grouping that the information that this grouping is write down and node D send, if source node S successfully receives the NCTS grouping that destination node D sends, then cancel this transmission, because showing, the NCTS grouping do not have public available channel between source node and the destination node, therefore, in current channel time slot, node S will be no longer to node D transmission of data packets;

D. data transfer phase: after destination node D success reception sources node sent the RES grouping of S, two nodes switched to respective channel simultaneously, after SIFS, finish data packet transmission according to the power of determining;

4) last, the neighbor node that listens to CTS grouping or RES grouping is by the relevant information among following process renewal self DCUL;

A. intercept the CTS grouping: suppose that source node S and destination node D use K bar data channel to carry out transmitted in packets, its centre frequency is { f ₁..., f _K, power division is { P ₁..., P _K, if node I listens to the CTS grouping that node D sends, then node I at first calculates self and the channel gain of node D on Common Control Channel, and obtains self and the channel gain of node D on above-mentioned K bar channel thus; Secondly, node I computing node D is according to power division { P ₁..., P _KSend the interference of confirming that grouping ACK brings to self, and upgrade the total interference that self is subjected to; Once more, node I calculates from correctly receiving the maximum available transmit power of using under the prerequisite of packet on this K bar channel in not influencing node D; At last, upgrade network allocation vector NAV;

B. intercept the RES grouping: suppose that source node S and destination node D use K bar data channel to carry out transmitted in packets, its centre frequency is { f ₁..., f _K, power division is { P ₁..., P _K, if node I listens to the RES grouping that node S sends, then node I at first calculates self and the channel gain of node D on Common Control Channel, and obtains self and the channel gain of node D on above-mentioned K bar channel thus; Secondly, node I computing node D is according to power division { P ₁..., P _KSend the interference that packet brings to self, and upgrade the total interference that self is subjected to; Once more, node I calculates certainly in not influencing node D spendable maximum available transmit power under the prerequisite of the correct ACK of reception grouping on this K bar channel; At last, upgrade network allocation vector NAV.

2. the implementation method of the cognition MAC protocol based on the multichannel diversity according to claim 1 is characterized in that: the calculating of transmitted power and transmission of data packets number is carried out according to the following steps but grouping of said destination node D specified data and ACK divide into groups:

Suppose to have the public available data channels of L bar between source node S and the destination node D, its centre frequency is { f ₁..., f _L; The centre frequency of Common Control Channel is f ₀Node can with set of data rates be R={R ₁, R ₂..., R _Q(R ₁＜...＜R _Q), corresponding Signal to Interference plus Noise Ratio thresholding set is SINR={SINR ₁, SINR ₂..., SINR _Q(SINR ₁＜...＜SINR _Q); Internodal mode is the ground return model;

Node D calculates self and the channel gain of node S on Common Control Channel according to (1) after receiving the RTS grouping that node S sends

$h_{\mathrm{SD}}^0=P_r^{\mathrm{RTS}}/P_{\max }---\left(1\right)$

Wherein,

And P _MaxBe respectively the received power and the transmitted power of RTS grouping;

Node D calculates self and the channel gain of node S on the public available data channels channel of this L bar according to (2)

$h_{\mathrm{SD}}^l=h_{\mathrm{SD}}^0\×{(f_0/f_l)}^2,l=1,...,L---\left(2\right)$

Wherein, f ₀And f _lBe respectively the centre frequency of Common Control Channel and the public available channel of l bar;

Make up node available transmission rate matrix R, shown in (3);

Wherein, R ^l=[R ^{L, 1}R ^{L, Q}] (l=1 ..., the L) set of data rates that node can be used on the expression l bar data channel, and R ^{L, q}=R _q(q=1 ..., Q);

Make up the set of node through-put power

Shown in (4);

Wherein,

Indicate node on l bar data channel with speed R _qCarry out the required transmitted power of transmitted in packets, can calculate according to (5),

${\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}={\mathrm{SINR}}_q\·{[P}_n+P_{\inf }\left(l\right)]/h_{\mathrm{SD}}^l---\left(5\right)$

Wherein, P _nBe the power of additive white Gaussian noise, P _Inf(l) the total interference that on l bar data channel, is subjected to for node D, SINR _qFor data rate is R _qThe Signal to Interference plus Noise Ratio thresholding;

Make up optimization aim: source node S is from the transmitted power collection

The middle transmitted power of selecting to one of more options, is no more than maximum power P at overall transmission power in each set _Max, the through-put power on every channel is no more than under the prerequisite of the maximum available power on this channel, makes overall data transmission rate R _SDMaximization is shown in (6);

$\max \mathrm{imise}{R}_{\mathrm{SD}}=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{R}^{l,q}\·x^{l,q}$

$s.t.\left\{\begin{array}{c}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\·x^{l,q}\≤P_{\max }\\ {\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\≤P_{\max -s}\left(l\right),l=1,...,L;q=1,...,Q\\ \underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{x}^{l,q}\≤1,l=1,...,L\\ x^{l,q}\∈\left\{\mathrm{0,1}\right\},l=1,...,L;q=1,...,Q\end{array}\right.---\left(6\right)$

Wherein, R ^{L, q}Q the transmission rate of expression node on the public available channel of l bar, x ^{L, q}Whether the expression node uses R ^{L, q}Carry out transfer of data, P _MaxBe the spendable maximum power of node, P _Max-s(l) expression node spendable maximum power on the public available channel of l bar;

Use Dynamic Programming to find the solution, be about to the problems referred to above and be divided into the L step and find the solution, m (the step problem of 1≤m≤L) is shown in (7):

$\underset{l=1}{\overset{m}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{R}^{l,q}\·x^{l,q}$

$s.t.\left\{\begin{array}{c}\underset{l=1}{\overset{m}{\mathrm{\Σ}}}\underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\·x^{l,q}\≤P_{\max }\\ {\stackrel{\‾}{P}}_{\mathrm{SD}}^{l,q}\≤P_{\max -s}\left(l\right),l=1...m;q=1...Q\\ \underset{q=1}{\overset{Q}{\mathrm{\Σ}}}{x}^{l,q}\≤1,l=1...m\\ x^{l,q}\∈\left\{\mathrm{0,1}\right\},l=1...m;q=1...Q\end{array}\right.---\left(7\right)$

When finding the solution m step problem, effectively separating that only need consideration (m-1) step problem draws gets final product, and by finding the solution L subproblem, can obtain optimum power/channel and unite distribution

Obtaining transmission rate R _SDAfter, node D determines the maximum data grouping number that this transmission can be transmitted; At first, determine maximum transmission time, shown in (8);

T _max≤L _DATA/R _basic (8)

Wherein, L _DATABe the length of a data grouping, R _BasicBe the data rate of node on Common Control Channel;

Because different channel gains will cause different power/channel associating allocation result, so the transmission time also must be satisfied the constraint of inequality (9);

T _SD≤min{CT(f ₁)，…，CT(f _L)}＝CT _min (9)

Wherein, CT (f _l) for centre frequency be f _lCoherence time of data channel;

Therefore, the data transmission period condition that finally should satisfy is shown in (10);

T _SD≤min{CT _min，T _max} (10)

Because the transmission time can be used (11) expression, wherein N _SDBe the packet number of transmission, L _DATAAnd L _ACKBe the length of packet and ACK grouping, T _SifsBe the time of short frame period;

T _SD＝(2N _SD-1)T _sifs+N _SD(L _DATA+L _ACK)/R _SD (11)

Therefore, by (11) and (10) but can obtain the constraints of transmission of data packets number, shown in (12);

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