CN102111897B - 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

The implementation method of the directivity cognition MAC protocol based on 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 day by day rare resource, traditional fixed frequency spectrum method of salary distribution cause the wasting of resources so that the availability of frequency spectrum low, become the key factor that further develops of restriction cordless communication network.Cognitive radio technology has the ability that detection of primary user authorizes the situation that takies of frequency range and implements dynamic spectrum access it, can effectively address the above problem.In Wireless Ad Hoc network, introducing cognitive radio technology is emerging in recent years research field, and the MAC agreement that design can realize high-efficiency dynamic frequency spectrum access 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: access at random class, time slot class and mixing class.SRAC-MAC (Single Radio Adaptive Channel-MAC) and HC-MAC (Hardware-Constrained Cog-nitive MAC) agreement belong to random access quasi-protocol, control packet or the transmission of data all realizes by Random Access Channel.As C-MAC (Cognitive MAC) agreement of time slot agreement representative, be to add CR merit getable on the basis of revising MMAC agreement, by being carried out to strict time slot beacon period, divide, 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, control packet transmits by synchronization slot, transfer of data subsequently is used accidental channel access scheme, SYN-MAC (Synchronized MAC) agreement that the people such as such as Y.R.Kondareddy propose, be divided into the frame structure repeating the time, the timeslot number comprising in frame is identical with maximum available channel number and corresponding one by one, in the corresponding time slot of certain channel, preengages successful node to also must compete this channel right to use according to IEEE 802.11DCF mode within the time subsequently.

In above-mentioned achievement in research, node is only used 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.The method is by using directive antenna and polarization diversity technique to make node can make full use of frequency and space resources, thereby raising network throughput reduces end-to-end time delay.

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

1) first, time is divided into multiple channel time slots that time span is identical, each channel time slot was comprised of " perception cycle " and " data transfer cycle ", within the perception cycle, all nodes are all data channels of perception successively, determine the data channel and the corresponding plan mode thereof that in this channel time slot, by naive user, are taken, in data transfer cycle, node to competing the data channel right to use by exchange control packet in Common Control Channel, compete subsequently successful node and according to definite polarization mode and transmitted power, complete transmitted in packets to switching to respective data channels,

2) secondly, each node is all safeguarded list: an available channel list ACL, records respectively naive user and neighbor node channel, polarization and the power service condition in current channel time slot;

3) again,, when node S has packet to send to destination node D, two nodes, by following four-stage, complete transmitted in packets:

The a.DRTS transmission phase of dividing into groups: source node S first directivity is intercepted Common Control Channel, and when back off time finishes and the still free time of Common Control Channel in distributed frame interval D IFS subsequently, to destination node D transmit leg tropism, ask to send grouping grouping DRTS, in this DRTS grouping, carry the ACL of self;

The b.DCTS transmission phase of dividing into groups: if destination node D successfully receives the DRTS grouping that source node S sends, first the ACL of self ACL and source node S is contrasted; If there is not publicly available data channel in two ACL, node D sends negative DCTS grouping NDCTS to node S, represents to compete unsuccessfully; Otherwise node D determines according to the channel information recording in two ACL data channel, polarization mode and the transmitted power that this transmission is used, and allow to send grouping DCTS to source node transmit leg tropism;

The c.DDTS transmission phase of dividing into groups: if source node S successfully receives the DCTS grouping that destination node D sends, after short frame period SIFS, to destination node D loopback directivity, determine and send grouping DDTS, in the DCTS grouping that the information that this grouping is recorded sends with node D, the information of record is identical; If source node S successfully receives the NDCTS grouping that destination node D sends, cancel this transmission; Because NDCTS grouping shows not have public available channel between source node and 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: when destination node D success reception sources node sends after the DDTS grouping of S, two nodes switch to respective channel simultaneously, after short frame period SIFS, complete data packet transfer according to definite polarization mode and transmitted power;

4) last, listen to the neighbor node of DCTS grouping or DDTS grouping by the relevant information in following process renewal self ACL;

A. intercept DCTS grouping: suppose that source node S and destination node D are D (SD) for the channel of transmission of data packets, centre frequency is f _{d (SD)}; If node I listens to the DCTS grouping that node D sends, first node I calculates self and the channel gain of node D in Common Control Channel, and obtains thus self and the channel gain of node D on channel D (SD); Secondly, whether node I determines own on this channel in the transmission range in node D; Again, node I calculates spendable maximum available transmit power under the prerequisite in not affecting node D and correctly receive packet; Finally, upgrade directivity network allocation vector DNAV;

B. intercept DDTS grouping: suppose that source node S and destination node D are A (SD) for the channel of acknowledge grouping ACK, centre frequency is f _{a (SD)}; If node I listens to the DDTS grouping that node S sends, first node I calculates self and the channel gain of node S in Common Control Channel, and obtains thus self and the channel gain of node D on channel A (SD); Secondly, whether node I determines own on this channel in the transmission range in node S; Again, node I calculates spendable maximum available transmit power under the prerequisite in not affecting node S and correctly receive ACK grouping; Finally, 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 destination node D, its centre frequency is { f ₁..., f _m; The centre frequency of Common Control Channel is f ₀; The signal-noise ratio threshold that node can correctly receive packet is SNR _th; Internodal mode is 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 is receiving after the DRTS grouping that node S sends, and according to (1), calculates self and the channel gain of node S in Common Control Channel

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

Wherein,

and P _maxbe respectively 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)

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

Wherein, f ₀and f _mbe respectively the centre frequency of Common Control Channel and m article of public available channel.

To public available channel m, if this channel is taken (supposing the polarization of naive user usage level) by naive user, node D need to determine whether to use perpendicular polarization to transmit on this channel; Arrive the signal power at node D place as 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, for the reception total power signal at node D place,

with

be respectively node D place and receive the signal power of signal in vertical and horizontal direction,

for the transmitted power of node S in perpendicular polarization; In addition,

with

between relation also available (4) represent,

$P_r^{\left(v\right)}\left(f_m\right)=d_{\mathrm{SD}}^{-a}\·\mathrm{\χ}\·P_r^{\left(h\right)}\left(f_m\right)---\left(4\right)$

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

By (3) and (4), can be obtained

with

as shown in (5),

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

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

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

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

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

Wherein, P _nfor noise power; If this channel can be added to packet candidate channel set CDCS;

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

this channel can be added to CDCS;

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

if

this channel can be added to CDCS;

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

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

Use identical method can be identified for 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 the relevant information in its ACL; Suppose that node I listens to the 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 oneself can correctly receive in the upper DCTS of the transmission grouping of channel D (SD) if calculate node D by (9);

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

If

node I in node D the transmission range on channel D (SD); Now, node I can be used another kind of polarization mode to use this channel; Suppose node D usage level polarization, node D in this letter horizontal polarization directions endurable maximum power as shown in (10),

$P_{\max }^{\left(h\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=P_{\max }^{\inf }\·d_{\mathrm{ID}}^{-a}\·\mathrm{\χ}---\left(10\right)$

Wherein,

for the endurable maximum interference power of node, d _iDfor the distance between node I and D;

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

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

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

$P_{\max }^{D\left(\mathrm{SD}\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=\frac{{\mathrm{<figure-callout\; id="4"\; label="d\; ID"\; filenames="HDA0000038470210000014.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{ID}}^{}\&CenterDot;L}{G^D\left(f_{D\left(\mathrm{SD}\right)}\right)G^O\left(f_{D\left(\mathrm{SD}\right)}\right)h_t^2{h}_r^2}{P}_{\max }^{\left(T\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)---\left(12\right)$

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 the relevant information in its ACL by identical mode.

The present invention uses Common Control Channel, node is to competing the data channel right to use by exchange control packet in Common Control Channel, compete successful node to switching to respective data channels, according to definite polarization mode and transmitted power, complete the transmission of packet and ACK grouping.

Accompanying drawing explanation

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.

First referring to Fig. 1, channel time slot division is described, time is divided into multiple channel time slots that time span is identical, each channel time slot was comprised of " perception cycle " and " data transfer cycle ", within the perception cycle, all nodes are all data channels of perception successively, determine the data channel and the corresponding plan mode thereof that in this channel time slot, by naive user, are taken, in data transfer cycle, node to competing the data channel right to use by exchange control packet in Common Control Channel, compete subsequently successful node and according to definite polarization mode and transmitted power, complete transmitted in packets to switching to respective data channels,

Referring to Fig. 2, content and the function that available channel list ACL comprises is described, each list item comprises four partial contents." channel number " represent this list item record information corresponding be any bar data channel." channel status " represents whether this channel is taken by primary user or neighbor node." available polarization mode " represents the polarization mode of using this channel to allow." the maximum transmitted power that allows " is illustrated in the maximum of the transmitted power that on this channel, node can be used.

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

The 1.DRTS transmission phase of dividing into groups: source node S first directivity is intercepted Common Control Channel, and when back off time finishes and the still free time of Common Control Channel in DIFS subsequently, to destination node D, send DRTS grouping, in this DRTS grouping, carry the ACL of self;

The 2.DCTS transmission phase of dividing into groups: if destination node D successfully receives the DRTS grouping that source node S sends, first the ACL of self ACL and source node S is contrasted.If there is not publicly available data channel in two ACL, node D sends NDCTS (NegativeDCTS) grouping to node S, represents to compete unsuccessfully; Otherwise node D determines according to the channel information recording in two ACL data channel, polarization mode and the transmitted power that this transmission is used, and send DCTS grouping to source node;

Process 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 destination node D, its centre frequency is { f ₁..., f _m; The centre frequency of Common Control Channel is f ₀; The signal-noise ratio threshold that node can correctly receive packet is SNR _th; Internodal mode is 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 is receiving after the DRTS grouping that node S sends, and according to (1), calculates self and the channel gain of node S in Common Control Channel

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

Wherein, and P _maxbe respectively 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)

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

To public available channel m, if this channel is taken (supposing the polarization of naive user usage level) by naive user, node D need to determine whether to use perpendicular polarization to transmit on this channel.Arrive the signal power at node D place as 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,

for the reception total power signal at node D place,

with

be respectively node D place and receive the signal power of signal in vertical and horizontal direction, for the transmitted power of node S in perpendicular polarization.In addition,

with

between relation also available (4) represent,

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

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

By (3) and (4), can be obtained

with

as 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 cross polarization signal power can not exceed P _mask(f _m), so the maximum available transmit power on this channel as 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 _nfor noise power.If this channel can be added to packet candidate channel set CDCS.

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

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

if

this channel can be added to CDCS.

After whole public available channels all check as stated above, for the channel D (SD) of transmission of data packets, can select by (8), 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 channel A (SD) and the corresponding transmitted power of transferring ACK grouping

The 3.DDTS transmission phase of dividing into groups: if source node S successfully receives the DCTS grouping that destination node D sends,, after SIFS, to destination node D loopback DDTS grouping, the information recording in the DCTS grouping that the information that this grouping is recorded sends with node D is identical.If source node S successfully receives the NDCTS grouping that destination node D sends, cancel this transmission.Because NDCTS grouping shows not have public available channel between source node and destination node, therefore, in current channel time slot, node S will be no longer to node D transmission of data packets;

4. data transfer phase: when destination node D success reception sources node sends after the DDTS grouping of S, two nodes switch to respective channel simultaneously, after SIFS, complete data packet transfer according to definite polarization mode and transmitted power.

Finally, the neighbor node that listens to DCTS grouping or DDTS grouping is by the relevant information in following process renewal self DCUL;

1. intercept DCTS grouping: suppose source node S and destination node D usage data channel D (SD) transmission of data packets, its centre frequency is f _{d (SD)}.If node I listens to the 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 oneself can correctly receive in the upper DCTS of the transmission grouping of channel D (SD) if calculate node D by (9).

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

If

node I in node D the transmission range on channel D (SD).Now, node I can be used another kind of polarization mode to use this channel.Suppose node D usage level polarization, node D in this letter horizontal polarization directions endurable maximum power as 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,

for the endurable maximum interference power of node, d _iDfor the distance between node I and D.

Therefore, node D endurable maximum power in 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 in horizontal polarization directions as shown in (12),

$P_{\max }^{D\left(\mathrm{SD}\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)=\frac{{\mathrm{<figure-callout\; id="4"\; label="d\; ID"\; filenames="HDA0000038470210000014.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{ID}}^{}\&CenterDot;L}{G^D\left(f_{D\left(\mathrm{SD}\right)}\right)G^O\left(f_{D\left(\mathrm{SD}\right)}\right)h_t^2{h}_r^2}{P}_{\max }^{\left(T\right)}\left(f_{D\left(\mathrm{SD}\right)}\right)---\left(12\right)$

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

2. intercept DDTS grouping: suppose source node S and destination node D usage 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, can calculate spendable maximum available transmit power on this channel according to the method that (9)-(12) provide.

In order to verify the performance of the directivity cognition MAC protocol based on 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 ²region in, using the transmission range of omnidirectional antenna is 250m, using the transmission range of directive antenna is 500m, the beamwidth of directive antenna is 30 °, network internal storage is at 3 data channels, the probability that every channel is taken by primary user is 0.5, and node application layer is used CBR business, and network layer is used AODV Routing Protocol.

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

We can find, no matter at static scene or in dynamic scene, compared with DSA-MAC, 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 while effectively reducing network end-to-end.This is mainly because PD-CMAC agreement is used directive antenna and Polarization technique simultaneously, thus the fully frequency of developing network and space resources, for node access network provides more chance.

Claims (2)

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

1) first, time is divided into multiple channel time slots that time span is identical, each channel time slot was comprised of " perception cycle " and " data transfer cycle ", within the perception cycle, all nodes are all data channels of perception successively, determine the data channel and the corresponding plan mode thereof that in this channel time slot, by naive user, are taken, in data transfer cycle, node to competing the data channel right to use by exchange control packet in Common Control Channel, compete subsequently successful node and according to definite polarization mode and transmitted power, complete transmitted in packets to switching to respective data channels,

2) secondly, each node is all safeguarded list: an available channel list ACL, records respectively naive user and neighbor node channel, polarization and the power service condition in current channel time slot;

3) again,, when node S has packet to send to destination node D, two nodes, by following four-stage, complete transmitted in packets:

The a.DRTS transmission phase of dividing into groups: source node S first directivity is intercepted Common Control Channel, and when back off time finishes and the still free time of Common Control Channel in distributed frame interval D IFS subsequently, to destination node D transmit leg tropism, ask to send grouping grouping DRTS, in this DRTS grouping, carry the ACL of self;

The b.DCTS transmission phase of dividing into groups: if destination node D successfully receives the DRTS grouping that source node S sends, first the ACL of self ACL and source node S is contrasted; If there is not publicly available data channel in two ACL, node D sends negative DCTS grouping NDCTS to node S, represents to compete unsuccessfully; Otherwise node D determines according to the channel information recording in two ACL data channel, polarization mode and the transmitted power that this transmission is used, and allow to send grouping DCTS to source node transmit leg tropism;

The c.DDTS transmission phase of dividing into groups: if source node S successfully receives the DCTS grouping that destination node D sends, after short frame period SIFS, to destination node D loopback directivity, determine and send grouping DDTS, in the DCTS grouping that the information that this grouping is recorded sends with node D, the information of record is identical; If source node S successfully receives the NDCTS grouping that destination node D sends, cancel this transmission; Because NDCTS grouping shows not have public available channel between source node and 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: when destination node D success reception sources node sends after the DDTS grouping of S, two nodes switch to respective channel simultaneously, after short frame period SIFS, complete data packet transfer according to definite polarization mode and transmitted power;

4) last, listen to the neighbor node of DCTS grouping or DDTS grouping by the relevant information in following process renewal self ACL;

A. intercept DCTS grouping: suppose that source node S and destination node D are DSD for the channel of transmission of data packets, centre frequency is f _dSD; If node I listens to the DCTS grouping that node D sends, first node I calculates self and the channel gain of node D in Common Control Channel, and obtains thus self and the channel gain of node D on channel DSD; Secondly, whether node I determines own on this channel in the transmission range in node D; Again, node I calculates spendable maximum available transmit power under the prerequisite in not affecting node D and correctly receive packet; Finally, upgrade directivity network allocation vector DNAV;

B. intercept DDTS grouping: suppose that source node S and destination node D are ASD for the channel of acknowledge grouping ACK, centre frequency is f _aSD; If node I listens to the DDTS grouping that node S sends, first node I calculates self and the channel gain of node S in Common Control Channel, and obtains thus self and the channel gain of node D on channel ASD; Secondly, whether node I determines own on this channel in the transmission range in node S; Again, node I calculates spendable maximum available transmit power under the prerequisite in not affecting node S and correctly receive ACK grouping; Finally, 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: the grouping of destination node D specified data and ACK packet transmission channel, polarization mode and transmitted power are calculated and carried out according to the following steps:

Suppose to have the public available data channels of M bar between source node S and destination node D, its centre frequency is { f ₁..., f _m; The centre frequency of Common Control Channel is f ₀; The signal-noise ratio threshold that node can correctly receive packet is SNR _th; Internodal mode is 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 is receiving after the DRTS grouping that node S sends, the channel gain in Common Control Channel according to 1 calculating self and node S

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

Wherein,

and P _maxbe respectively received power and the transmitted power of DRTS grouping;

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

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

Wherein, f ₀and f _mbe respectively the centre frequency of Common Control Channel and m article of public available channel;

To public available channel m, suppose the polarization of naive user usage level, if this channel is taken by naive user, node D need to determine whether to use perpendicular polarization to transmit on this channel; Arrive the signal power at node D place as shown in 3,

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

Wherein,

for the reception total power signal at node D place, with

be respectively node D place and receive the signal power of signal in vertical and horizontal direction,

for the transmitted power of node S in perpendicular polarization; In addition,

with between relation also available 4 represent,

$P_r^{\left(v\right)}\left(f_m\right)=d_{\mathrm{SD}}^{-a}\&CenterDot;x\&CenterDot;P_r^{\left(h\right)}\left(f_m\right)---4$ Wherein, d _sDfor the distance between node S and D, χ is that average is μ _c, standard deviation is σ _clognormal variable, a is constant, a ∈ [0,1];

By (3) and (4), can be obtained

with

as shown in 5,

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

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

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

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

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

Wherein, P _nfor noise power; If

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

If public available channel m is not used by naive user, but by neighbor node, used, node S can be used another kind of polarization mode to transmit, and transmitted power can be by 7 calculating; If transmitted power meets this channel can be added to CDCS;

If public available channel m is not taken by naive user, by neighbor node, do not taken again, node S can be by 7 calculating transmitted powers if

this channel can be added to CDCS;

After whole public available channels all check as stated above, for the channel DSD of transmission of data packets, can select by 8, corresponding packet transmitted power is

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

Use identical method can be identified for channel ASD and the corresponding transmitted power of transferring ACK grouping

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

secondly, if sending DCTS grouping by 9 calculating node D on channel DSD, node I oneself whether can correctly receive;

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

If

node I in node D the transmission range on channel DSD; Now, node I can be used another kind of polarization mode to use this channel; Suppose node D usage level polarization, node D in this channel horizontal polarization directions endurable maximum power as shown in 10,

$P_{\max }^{\left(h\right)}\left(f_{\mathrm{DSD}}\right)=P_{\max }^{\inf }\&CenterDot;d_{\mathrm{ID}}^{-a}\&CenterDot;x---10$ Wherein,

for the endurable maximum interference power of node, d _iDfor the distance between node I and D;

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

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

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

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

Wherein, L is the path loss factor, h _tand h _rbe respectively the antenna height of transmitting antenna and reception antenna, G ^d(f _dSD) and G ^o(f _dSD) 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 the relevant information in its ACL by identical mode.

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