CN102111897A - Method for realizing polarization-diversity-based directional cognitive medium access control (MAC) protocol - Google Patents

Abstract

The invention provides a method for realizing a polarization-diversity-based directional cognitive medium access control (MAC) protocol. The method is designed based on polarization diversity and a directional antenna. A source node and a destination node compete for a data channel usage right by exchanging a control packet on a public control channel. The node successful in the competition uses the directional antenna to complete data packet transmission on a switched selected data channel according to the agreed polarization direction and power. The simulation result shows that: compared with the traditional dynamic spectrum access DSA-MAC protocol, the protocol has the advantages of effectively improving network throughput and reducing end-to-end transmission delay.

Description

Implementation method based on the directivity cognition MAC protocol of polarization diversity

Technical field

The invention belongs to MAC (MediumAccess 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 directivity cognition MAC protocol based on polarization 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.

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 802.11DCF mode in later time.

In above-mentioned achievement in research, node only uses omnidirectional antenna, and does not consider the polarization problem of antenna.But along with the development of antenna technology, user tropism and poliarizing antenna can significantly improve network performance.At present, this research only limits to traditional Ad Hoc network.

Summary of the invention

The object of the present invention is to provide a kind of implementation method of the directivity cognition MAC protocol based on polarization diversity.This method makes node can make full use of frequency and space resources by user tropism's antenna and polarization diversity technique, thereby improves network throughput, reduces end-to-end time delay.

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 the data channel that in this channel time slot, taken and corresponding plan mode thereof by naive user, in data transfer cycle, node is to controlling the grouping competition data channel right to use by exchange on Common Control Channel, the node that competition is successful is finished transmitted in packets to switching to respective data channels according to polarization mode and the transmitted power determined subsequently;

2) secondly, each node is all safeguarded tabulation: an available channel list ACL, writes down naive user and neighbor node channel, polarization 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.DRTS divides into groups the transmission stage: source node S at first directivity is intercepted Common Control Channel, and when back off time finish and in distributed frame interval D IFS subsequently Common Control Channel still idle, then ask to send grouping grouping DRTS, carry the ACL of self in this DRTS grouping to destination node D transmit leg tropism;

B.DCTS divides into groups the transmission stage: if destination node D successfully receives the DRTS grouping that source node S sends, then at first the ACL of self ACL and source node S is compared; If do not have publicly available data channel among two ACL, then node D sends negative DCTS grouping NDCTS, expression competition failure to node S; Otherwise node D determines that according to the channel information that writes down among two ACL this transmits employed data channel, polarization mode and transmitted power, and allows to send grouping DCTS to source node transmit leg tropism;

C.DDTS divides into groups the transmission stage: if source node S successfully receives the DCTS grouping that destination node D sends, then behind short frame period SIFS, determine to send grouping DDTS to destination node D loopback directivity, the information that this grouping is write down is identical with the information that writes down during the DCTS that node D sends divides into groups; If source node S successfully receives the NDCTS 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 NDCTS grouping shows, 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 DDTS grouping of S, two nodes switched to respective channel simultaneously, after short frame period SIFS, finish data packet transmission according to polarization mode and the transmitted power determined;

4) last, the neighbor node that listens to DCTS grouping or DDTS grouping is by the relevant information among following process renewal self ACL;

A. intercept DCTS grouping: suppose that the channel that source node S and destination node D are used for transmission of data packets is D (SD), centre frequency is f _{D (SD)}If node I listens to the DCTS 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 channel D (SD) thus; Secondly, node I determines oneself whether to be in the transmission range of node D on this channel; Once more, node I calculates from not influencing spendable maximum available transmit power under the prerequisite that node D correctly receives packet; At last, upgrade directivity network allocation vector DNAV;

B. intercept DDTS grouping: suppose that it is A (SD) that source node S and destination node D are used for the divide into groups channel of ACK of acknowledge, centre frequency is f _{A (SD)}If node I listens to the DDTS grouping that node S sends, then node I at first calculates self and the channel gain of node S on Common Control Channel, and obtains self and the channel gain of node D on channel A (SD) thus; Secondly, node I determines oneself whether to be in the transmission range of node S on this channel; Once more, node I calculates from not influencing spendable maximum available transmit power under the prerequisite that node S correctly receives the ACK grouping; At last, upgrade directivity network allocation vector DNAV.

Said destination node D specified data grouping and ACK packet transmission channel, polarization mode and transmitted power are calculated and are carried out according to the following steps:

Suppose to have the public available data channels of M bar between source node S and the destination node D, its centre frequency is { f ₁..., f _M; The centre frequency of Common Control Channel is f ₀The signal-noise ratio threshold that node can correctly receive packet is SNR _ThInternodal mode is the ground return model; The antenna gain of node under omni-directional mode is G ^o, the antenna gain under directional mode is G ^D

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

${\mathrm{<figure-callout\; id="0"\; label="h\; SD"\; filenames="HDA0000038470210000013.png"\; state="\{\{state\}\}">h</figure-callout>}}_{\mathrm{SD}}^{}=P_r^{\mathrm{DRTS}}/P_{\max }---\left(1\right)$

Wherein,

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

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

$h_{\mathrm{SD}}^m={\mathrm{<figure-callout\; id="0"\; label="h\; SD"\; filenames="HDA0000038470210000013.png"\; state="\{\{state\}\}">h</figure-callout>}}_{\mathrm{SD}}^{}\&times;{({\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="HDA0000038470210000013.png"\; state="\{\{state\}\}">f</figure-callout>}}_0/f_m)}^4,m=1,...,M---\left(2\right)$

Wherein, f ₀And f _mBe respectively the centre frequency of Common Control Channel and the public available channel of m bar.

To public available channel m, if this channel is taken (supposing the polarization of naive user usage level) by naive user, then node D need determine whether to use perpendicular polarization to transmit on this channel; The signal power that arrives node D place shown in (3),

$P_r^{\left(T\right)}\left(f_m\right)=P_r^{\left(v\right)}\left(f_m\right)+P_r^{\left(h\right)}\left(f_m\right)=h_{\mathrm{SD}}^m{P}_t^S\left(f_m\right)---\left(3\right)$

Wherein,

Be the received signal gross power at node D place,

With Be respectively the signal power of node D place received signal on vertical and horizontal direction,

Be the transmitted power of node S on perpendicular polarization; In addition,

With Between relation also available (4) expression,

$P_r^{\left(v\right)}\left(f_m\right)=d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}\&CenterDot;P_r^{\left(h\right)}\left(f_m\right)---\left(4\right)$

Wherein, d _SDBe the distance between node S and the D, χ is that average is μ _c, standard deviation is σ _cLognormal variable, a is constant (a ∈ [0,1]);

Can get by (3) and (4)

With

Shown in (5),

$\left\{\begin{array}{c}{P}_r^{\left(v\right)}\left(f_m\right)=\frac{d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}\&CenterDot;h_{\mathrm{SD}}^m\&CenterDot;P_t^S\left(f_m\right)}{1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}}\\ P_r^{\left(h\right)}\left(f_m\right)=\frac{h_{\mathrm{SD}}^m\&CenterDot;P_t^S\left(f_m\right)}{1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}}\end{array}\right.---\left(5\right)$

Because the cross polarization signal power can not surpass power threshold P _Mask(f _m), so the maximum available transmit power on this channel shown in (6),

$P_{\max }^m=(1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;})P_{\mathrm{mask}}\left(f_m\right)/h_{\mathrm{SD}}^m---\left(6\right)$

On this channel, use the required minimum transmit power of perpendicular polarization to be,

$P_t^S\left(f_m\right)=\frac{(1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;})\&CenterDot;\mathrm{SN}{R}_{\mathrm{th}}\&CenterDot;P_n}{d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}\&CenterDot;h_{\mathrm{SD}}^m}---\left(7\right)$

Wherein, P _nBe noise power; If

Then this channel can be added packet candidate channel set CDCS;

If public available channel m is not used by naive user, but used by neighbor node, then node S can use another kind of polarization mode to transmit, and transmitted power can be calculated by (7); If transmitted power satisfies

Then this channel can be added CDCS;

If public available channel m is not promptly taken by naive user, do not taken again by neighbor node, then node S can calculate transmitted power by (7)

If Then this channel can be added CDCS;

After whole public available channels were all checked as stated above, the channel D (SD) that is used for transmission of data packets can select by (8), and corresponding packet transmitted power is

$D\left(\mathrm{SD}\right)=\arg \min \left\{m\right|P_t^S\left(f_m\right),m\&Element;\mathrm{CDCS}\}---\left(8\right)$

Use identical method can be identified for the channel A (SD) and the corresponding transmitted power of transferring ACK grouping

In addition, the node that listens to DCTS or DDTS grouping also needs to upgrade relevant information among its ACL; Suppose that node I listens to the then at first calculating oneself and the channel gain of node D on channel D (SD) of DCTS grouping that node D sends

Secondly, whether node I calculates by (9) if node D upward sends the DCTS grouping at channel D (SD) and oneself can correctly receive;

$P_r^{\mathrm{DCTS}}\left(f_{D\left(\mathrm{SD}\right)}\right)=h_{\mathrm{ID}}^{D\left(\mathrm{SD}\right)}\&CenterDot;P_{\max }---\left(9\right)$

If Then node I is in the transmission range of node D on channel D (SD); At this moment, node I can use another kind of polarization mode to use this channel; Suppose node D usage level polarization, then node D on this letter horizontal polarization directions endurable maximum power shown in (10),

$P_{\max }^{\left(h\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=P_{\max }^{\inf }\&CenterDot;d_{\mathrm{ID}}^{-a}\&CenterDot;\mathrm{\&chi;}---\left(10\right)$

Wherein,

Be the endurable maximum interference power of node, d _IDBe the distance between node I and the D;

Therefore, node D endurable maximum power on two polarised directions is,

$P_{\max }^{\left(T\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=(1+d_{\mathrm{ID}}^{-a}\&CenterDot;\mathrm{\&chi;})P_{\max }^{\inf }---\left(11\right)$

Thereby, the maximum transmit power that node I allows on horizontal polarization directions shown in (12),

$P_{\max }^{D\left(\mathrm{SD}\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=\frac{d_{\mathrm{ID}}^4\&CenterDot;L}{G^D\left(f_{D\left(\mathrm{SD}\right)}\right)G^O\left(f_{D\left(\mathrm{SD}\right)}\right)h_t^2{h}_r^2}{P}_{\max }^{\left(T\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)---\left(12\right)$

Wherein, L is the path loss factor, h _tAnd h _rBe respectively the antenna height of transmitting antenna and reception antenna, G ^D(f _{D (SD)}) and G ^O(f _{D (SD)}) be respectively the antenna gain of transmitting antenna and reception antenna;

If node I listens to the DDTS grouping that node S sends, can upgrade relevant information among its ACL by identical mode.

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 to switching to respective data channels, finish packet and ACK transmission packets according to polarization mode and the transmitted power determined.

Description of drawings

Fig. 1 is channel time slot partition description figure;

Fig. 2 is the structure key diagram of available channel list ACL;

Fig. 3 is the performance simulation curve chart of static scene lower network;

Fig. 4 is the performance simulation curve chart of dynamic scene lower network.

Embodiment

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

At first the channel time slot division is described referring to Fig. 1, 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 the data channel that in this channel time slot, taken and corresponding plan mode thereof by naive user, in data transfer cycle, node is to controlling the grouping competition data channel right to use by exchange on Common Control Channel, the node that competition is successful is finished transmitted in packets to switching to respective data channels according to polarization mode and the transmitted power determined subsequently;

Referring to Fig. 2 content and the function that available channel list ACL is comprised is described, each list item comprises four partial contents.Which bar data channel what " channel number " represented this list item record information correspondence is." channel status " represents whether this channel is taken by main user or neighbor node.The polarization mode that this channel allowed is used in " available polarization mode " expression." the maximum transmitted power that allows " is illustrated in the maximum of the transmitted power that node can be used on this channel.

The transmission course of this agreement is as follows, supposes that source node is S, and destination node is D.

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

2.DCTS the grouping transmission stage:, then at first the ACL of self ACL and source node S is compared if destination node D successfully receives the DRTS grouping that source node S sends.If do not have publicly available data channel among two ACL, then node D sends NDCTS (NegativeDCTS) grouping to node S, expression competition failure; Otherwise node D determines that according to the channel information that writes down among two ACL this transmits employed data channel, polarization mode and transmitted power, and sends the DCTS grouping to source node;

The process that is used for transmission of data packets and ACK grouped channels is as follows:

Suppose to have the public available data channels of M bar between source node S and the destination node D, its centre frequency is { f ₁..., f _M; The centre frequency of Common Control Channel is f ₀The signal-noise ratio threshold that node can correctly receive packet is SNR _ThInternodal mode is the ground return model; The antenna gain of node under omni-directional mode is G ^o, the antenna gain under directional mode is G ^D

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

${\mathrm{<figure-callout\; id="0"\; label="h\; SD"\; filenames="HDA0000038470210000013.png"\; state="\{\{state\}\}">h</figure-callout>}}_{\mathrm{SD}}^{}=P_r^{\mathrm{DRTS}}/P_{\max }--\left(1\right)$

Wherein,

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

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

$h_{\mathrm{SD}}^m={\mathrm{<figure-callout\; id="0"\; label="h\; SD"\; filenames="HDA0000038470210000013.png"\; state="\{\{state\}\}">h</figure-callout>}}_{\mathrm{SD}}^{}\&times;{({\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="HDA0000038470210000013.png"\; state="\{\{state\}\}">f</figure-callout>}}_0/f_m)}^4,m=1,...,M---\left(2\right)$

To public available channel m, if this channel is taken (supposing the polarization of naive user usage level) by naive user, then node D need determine whether to use perpendicular polarization to transmit on this channel.The signal power that arrives node D place shown in (3),

$P_r^{\left(T\right)}\left(f_m\right)=P_r^{\left(v\right)}\left(f_m\right)+P_r^{\left(h\right)}\left(f_m\right)=h_{\mathrm{SD}}^m{P}_t^S\left(f_m\right)---\left(3\right)$

Wherein,

Be the received signal gross power at node D place,

With Be respectively the signal power of node D place received signal on vertical and horizontal direction,

Be the transmitted power of node S on perpendicular polarization.In addition,

With

Between relation also available (4) expression,

$P_r^{\left(v\right)}\left(f_m\right)=d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}\&CenterDot;P_r^{\left(h\right)}\left(f_m\right)---\left(4\right)$

Secondly, d _SDBe the distance between node S and the D, χ is that average is μ _c, standard deviation is σ _cLognormal variable, a is constant (a ∈ [0,1]).

Can get by (3) and (4)

With

Shown in (5),

$\left\{\begin{array}{c}{P}_r^{\left(v\right)}\left(f_m\right)=\frac{d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}\&CenterDot;h_{\mathrm{SD}}^m\&CenterDot;P_t^S\left(f_m\right)}{1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}}\\ P_r^{\left(h\right)}\left(f_m\right)=\frac{h_{\mathrm{SD}}^m\&CenterDot;P_t^S\left(f_m\right)}{1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}}\end{array}\right.---\left(5\right)$

Because the cross polarization signal power can not surpass P _Mask(f _m), so the maximum available transmit power on this channel shown in (6),

$P_{\max }^m=(1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;})P_{\mathrm{mask}}\left(f_m\right)/h_{\mathrm{SD}}^m---\left(6\right)$

On this channel, use the required minimum transmit power of perpendicular polarization to be,

$P_t^S\left(f_m\right)=\frac{(1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;})\&CenterDot;\mathrm{SN}{R}_{\mathrm{th}}\&CenterDot;P_n}{d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}\&CenterDot;h_{\mathrm{SD}}^m}---\left(7\right)$

Wherein, P _nBe noise power.If

Then this channel can be added packet candidate channel set CDCS.

If public available channel m is not used by naive user, but used by neighbor node, then node S can use another kind of polarization mode to transmit, and transmitted power can be calculated by (7).If transmitted power satisfies

Then this channel can be added CDCS.

If public available channel m is not promptly taken by naive user, do not taken again by neighbor node, then node S can calculate transmitted power by (7)

If

Then this channel can be added CDCS.

After whole public available channels were all checked as stated above, the channel D (SD) that is used for transmission of data packets can select by (8), and corresponding packet transmitted power is

$D\left(\mathrm{SD}\right)=\arg \min \left\{m\right|P_t^S\left(f_m\right),m\&Element;\mathrm{CDCS}\}---\left(8\right)$

Use identical method can be identified for the channel A (SD) and the corresponding transmitted power of transferring ACK grouping

3.DDTS the grouping transmission stage: if source node S successfully receives the DCTS grouping that destination node D sends, then behind SIFS, to destination node D loopback DDTS grouping, the information that this grouping is write down is identical with the information that writes down during the DCTS that node D sends divides into groups.If source node S successfully receives the NDCTS 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 NDCTS 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 DDTS grouping of S, two nodes switched to respective channel simultaneously, after SIFS, finish data packet transmission according to polarization mode and the transmitted power determined.

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

1. intercept the DCTS grouping: suppose that source node S and destination node D use data channel D (SD) transmission of data packets, its centre frequency is f _{D (SD)}If node I listens to the then at first calculating oneself and the channel gain of node D on channel D (SD) of DCTS grouping that node D sends Secondly, whether node I calculates by (9) if node D upward sends the DCTS grouping at channel D (SD) and oneself can correctly receive.

$P_r^{\mathrm{DCTS}}\left(f_{D\left(\mathrm{SD}\right)}\right)=h_{\mathrm{ID}}^{D\left(\mathrm{SD}\right)}\&CenterDot;P_{\max }---\left(9\right)$

If

Then node I is in the transmission range of node D on channel D (SD).At this moment, node I can use another kind of polarization mode to use this channel.Suppose node D usage level polarization, then node D on this letter horizontal polarization directions endurable maximum power shown in (10),

$P_{\max }^{\left(h\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=P_{\max }^{\inf }\&CenterDot;d_{\mathrm{ID}}^{-a}\&CenterDot;\mathrm{\&chi;}---\left(10\right)$

Wherein,

Be the endurable maximum interference power of node, d _IDBe the distance between node I and the D.

Therefore, node D endurable maximum power on two polarised directions is,

$P_{\max }^{\left(T\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=(1+d_{\mathrm{ID}}^{-a}\&CenterDot;\mathrm{\&chi;})P_{\max }^{\inf }---\left(11\right)$

Thereby, the maximum transmit power that node I allows on horizontal polarization directions shown in (12),

$P_{\max }^{D\left(\mathrm{SD}\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=\frac{d_{\mathrm{ID}}^4\&CenterDot;L}{G^D\left(f_{D\left(\mathrm{SD}\right)}\right)G^O\left(f_{D\left(\mathrm{SD}\right)}\right)h_t^2{h}_r^2}{P}_{\max }^{\left(T\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)---\left(12\right)$

Wherein, L is the path loss factor, h _tAnd h _rBe respectively the antenna gain of transmitting antenna and reception antenna.

2. intercept the DDTS grouping: suppose that source node S and destination node D use data channel A (SD) transmission of data packets, its centre frequency is f _{A (SD)}If node I listens to the DDTS grouping that node S sends, then can calculate spendable maximum available transmit power on this channel according to the method that (9)-(12) provide.

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

1 static scene: referring to Fig. 3, in static scene, 10 nodes are randomly dispersed in 500 * 500m ²The zone in, use the transmission range of omnidirectional antenna to be 250m, the transmission range of user tropism's antenna is 500m, the beamwidth of directive antenna is 30 °, network internal storage is at 3 data channels, every channel is 0.5 by the probability of main CU, and the node application layer is used the CBR business, and network layer is used the AODV Routing Protocol.

2. dynamic scene: referring to Fig. 4, in dynamic scene, 10 nodes are randomly dispersed in 500 * 500m ²The zone in, use the transmission range of omnidirectional antenna to be 250m, the transmission range of user tropism's antenna is 500m, the beamwidth of directive antenna is 30 °, network internal storage is at 3 data channels, every channel is 0.5 by the probability of main CU, and the node application layer is used the CBR business, and network layer is used the AODV Routing Protocol.In addition, the movement velocity of node is 15m/s.

We can find, no matter at static scene still in dynamic scene, compare with DSA-MAC, the PD-CMAC agreement can significantly improve network throughput and see Fig. 3 a, Fig. 4 a, and grant an interview with Fig. 3 b, Fig. 4 b when effectively reducing network end-to-end.This mainly is because of PD-CMAC agreement while user tropism's antenna and Polarization technique, thereby can fully develop the frequency and the space resources of network, for the node access network provides more opportunity.

Claims (2)

1. based on the implementation method of the directivity cognition MAC protocol of polarization 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 the data channel that in this channel time slot, taken and corresponding plan mode thereof by naive user, in data transfer cycle, node is to controlling the grouping competition data channel right to use by exchange on Common Control Channel, the node that competition is successful is finished transmitted in packets to switching to respective data channels according to polarization mode and the transmitted power determined subsequently;

2) secondly, each node is all safeguarded tabulation: an available channel list ACL, writes down naive user and neighbor node channel, polarization 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.DRTS divides into groups the transmission stage: source node S at first directivity is intercepted Common Control Channel, and when back off time finish and in distributed frame interval D IFS subsequently Common Control Channel still idle, then ask to send grouping grouping DRTS, carry the ACL of self in this DRTS grouping to destination node D transmit leg tropism;

B.DCTS divides into groups the transmission stage: if destination node D successfully receives the DRTS grouping that source node S sends, then at first the ACL of self ACL and source node S is compared; If do not have publicly available data channel among two ACL, then node D sends negative DCTS grouping NDCTS, expression competition failure to node S; Otherwise node D determines that according to the channel information that writes down among two ACL this transmits employed data channel, polarization mode and transmitted power, and allows to send grouping DCTS to source node transmit leg tropism;

C.DDTS divides into groups the transmission stage: if source node S successfully receives the DCTS grouping that destination node D sends, then behind short frame period SIFS, determine to send grouping DDTS to destination node D loopback directivity, the information that this grouping is write down is identical with the information that writes down during the DCTS that node D sends divides into groups; If source node S successfully receives the NDCTS 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 NDCTS grouping shows, 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 DDTS grouping of S, two nodes switched to respective channel simultaneously, after short frame period SIFS, finish data packet transmission according to polarization mode and the transmitted power determined;

4) last, the neighbor node that listens to DCTS grouping or DDTS grouping is by the relevant information among following process renewal self ACL;

A. intercept DCTS grouping: suppose that the channel that source node S and destination node D are used for transmission of data packets is D (SD), centre frequency is f _{D (SD)}If node I listens to the DCTS 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 channel D (SD) thus; Secondly, node I determines oneself whether to be in the transmission range of node D on this channel; Once more, node I calculates from not influencing spendable maximum available transmit power under the prerequisite that node D correctly receives packet; At last, upgrade directivity network allocation vector DNAV;

B. intercept DDTS grouping: suppose that it is A (SD) that source node S and destination node D are used for the divide into groups channel of ACK of acknowledge, centre frequency is f _{A (SD)}If node I listens to the DDTS grouping that node S sends, then node I at first calculates self and the channel gain of node S on Common Control Channel, and obtains self and the channel gain of node D on channel A (SD) thus; Secondly, node I determines oneself whether to be in the transmission range of node S on this channel; Once more, node I calculates from not influencing spendable maximum available transmit power under the prerequisite that node S correctly receives the ACK grouping; At last, upgrade directivity network allocation vector DNAV.

2. the implementation method of the directivity cognition MAC protocol based on polarization diversity according to claim 1 is characterized in that: said destination node D specified data grouping and ACK packet transmission channel, polarization mode and transmitted power calculating are carried out according to the following steps:

Suppose to have the public available data channels of M bar between source node S and the destination node D, its centre frequency is { f ₁..., f _M; The centre frequency of Common Control Channel is f ₀The signal-noise ratio threshold that node can correctly receive packet is SNR _ThInternodal mode is the ground return model; The antenna gain of node under omni-directional mode is G ^o, the antenna gain under directional mode is G ^D

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

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

Wherein, And P _MaxBe respectively the received power and the transmitted power of DRTS grouping;

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

$h_{\mathrm{SD}}^m=h_{\mathrm{SD}}^0\&times;{(f_0/f_m)}^4,m=1,...,M---\left(2\right)$

Wherein, f ₀And f _mBe respectively the centre frequency of Common Control Channel and the public available channel of m bar.

To public available channel m, if this channel is taken (supposing the polarization of naive user usage level) by naive user, then node D need determine whether to use perpendicular polarization to transmit on this channel; The signal power that arrives node D place shown in (3),

$P_r^{\left(T\right)}\left(f_m\right)=P_r^{\left(v\right)}\left(f_m\right)+P_r^{\left(h\right)}\left(f_m\right)=h_{\mathrm{SD}}^m{P}_t^S\left(f_m\right)---\left(3\right)$

Wherein,

Be the received signal gross power at node D place,

With Be respectively the signal power of node D place received signal on vertical and horizontal direction,

Be the transmitted power of node S on perpendicular polarization; In addition,

With Between relation also available (4) expression,

$P_r^{\left(v\right)}\left(f_m\right)=d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}\&CenterDot;P_r^{\left(h\right)}\left(f_m\right)---\left(4\right)$

Wherein, d _SDBe the distance between node S and the D, χ is that average is μ _c, standard deviation is σ _cLognormal variable, a is constant (a ∈ [0,1]);

Can get by (3) and (4)

With Shown in (5),

$\left\{\begin{array}{c}{P}_r^{\left(v\right)}\left(f_m\right)=\frac{d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}\&CenterDot;h_{\mathrm{SD}}^m\&CenterDot;P_t^S\left(f_m\right)}{1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}}\\ P_r^{\left(h\right)}\left(f_m\right)=\frac{h_{\mathrm{SD}}^m\&CenterDot;P_t^S\left(f_m\right)}{1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}}\end{array}\right.---\left(5\right)$

Because the cross polarization signal power can not surpass power threshold P _Mask(f _m), so the maximum available transmit power on this channel shown in (6),

$P_{\max }^m=(1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;})P_{\mathrm{mask}}\left(f_m\right)/h_{\mathrm{SD}}^m---\left(6\right)$

On this channel, use the required minimum transmit power of perpendicular polarization to be,

$P_t^S\left(f_m\right)=\frac{(1+d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;})\&CenterDot;\mathrm{SN}{R}_{\mathrm{th}}\&CenterDot;P_n}{d_{\mathrm{SD}}^{-a}\&CenterDot;\mathrm{\&chi;}\&CenterDot;h_{\mathrm{SD}}^m}---\left(7\right)$

Wherein, P _nBe noise power; If

Then this channel can be added packet candidate channel set CDCS;

If public available channel m is not used by naive user, but used by neighbor node, then node S can use another kind of polarization mode to transmit, and transmitted power can be calculated by (7); If transmitted power satisfies

Then this channel can be added CDCS;

If public available channel m is not promptly taken by naive user, do not taken again by neighbor node, then node S can calculate transmitted power by (7) If

Then this channel can be added CDCS;

After whole public available channels were all checked as stated above, the channel D (SD) that is used for transmission of data packets can select by (8), and corresponding packet transmitted power is

$D\left(\mathrm{SD}\right)=\arg \min \left\{m\right|P_t^S\left(f_m\right),m\&Element;\mathrm{CDCS}\}---\left(8\right)$

Use identical method can be identified for the channel A (SD) and the corresponding transmitted power of transferring ACK grouping

In addition, the node that listens to DCTS or DDTS grouping also needs to upgrade relevant information among its ACL; Suppose that node I listens to the then at first calculating oneself and the channel gain of node D on channel D (SD) of DCTS grouping that node D sends Secondly, whether node I calculates by (9) if node D upward sends the DCTS grouping at channel D (SD) and oneself can correctly receive;

$P_r^{\mathrm{DCTS}}\left(f_{D\left(\mathrm{SD}\right)}\right)=h_{\mathrm{ID}}^{D\left(\mathrm{SD}\right)}\&CenterDot;P_{\max }---\left(9\right)$

If

Then node I is in the transmission range of node D on channel D (SD); At this moment, node I can use another kind of polarization mode to use this channel; Suppose node D usage level polarization, then node D on this letter horizontal polarization directions endurable maximum power shown in (10),

$P_{\max }^{\left(h\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=P_{\max }^{\inf }\&CenterDot;d_{\mathrm{ID}}^{-a}\&CenterDot;\mathrm{\&chi;}---\left(10\right)$

Wherein,

Be the endurable maximum interference power of node, d _IDBe the distance between node I and the D;

Therefore, node D endurable maximum power on two polarised directions is,

$P_{\max }^{\left(T\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=(1+d_{\mathrm{ID}}^{-a}\&CenterDot;\mathrm{\&chi;})P_{\max }^{\inf }---\left(11\right)$

Thereby, the maximum transmit power that node I allows on horizontal polarization directions shown in (12),

$P_{\max }^{D\left(\mathrm{SD}\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=\frac{d_{\mathrm{ID}}^4\&CenterDot;L}{G^D\left(f_{D\left(\mathrm{SD}\right)}\right)G^O\left(f_{D\left(\mathrm{SD}\right)}\right)h_t^2{h}_r^2}{P}_{\max }^{\left(T\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)---\left(12\right)$

Wherein, L is the path loss factor, h _tAnd h _rBe respectively the antenna height of transmitting antenna and reception antenna, G ^D(f _{D (SD)}) and G ^O(f _{D (SD)}) be respectively the antenna gain of transmitting antenna and reception antenna;

If node I listens to the DDTS grouping that node S sends, can upgrade relevant information among its ACL by identical mode.

Images