CN103501531B - A kind of Ad Hoc network MAC layer method for channel allocation controlled based on power - Google Patents

Abstract

The invention discloses a kind of wireless mac layer method for channel allocation controlled based on power, belong to Ad? Hoc network field.Multichannel Ad? in Hoc network, network node uses two transceivers, and one is fixed on control channel, another redirect between different pieces of information channel.Adopt maximum power at control channel transmission RTS frame and CTS frame, adopt minimum power at data channel transmission DATA frame and ACK frame.Minimum power can correctly receive according to receiving node and the minimal detectable power thresholding of decoding calculates.The transmitted power of nodes all in same collision domain is divided into different brackets, then according to the hierarchical selection respective data channels at minimum power place, thus link transmitted power differed greatly is allocated in different channels, the adverse effect of asymmetric link in same channel can be alleviated, improve network throughput and specific energy consumption throughput.Specific implementation CAPC agreement of the present invention, can be used as Ad? the mac-layer protocol of Hoc network node device selective channel uses.

Description

A kind of Ad Hoc network MAC layer method for channel allocation controlled based on power

Technical field

The invention belongs to AdHoc network field, relate to a kind of wireless network MAC layer method for channel allocation.

Background technology

AdHoc network is a kind of wireless self-organization network, has the features such as non-stop layer, topological dynamic change and resource, the energy is limited, is widely used in the fields such as personal communication, business application and military affairs.The mac-layer protocol of AdHoc network allows the network node transmitting data in parallel on the different channels in same interference territory, but, because AdHoc network node adopts the method allocated channel of Distributed Coordination, unavoidably bring more network data packet conflict, the shortcoming such as cause network throughput and specific energy consumption throughput is all lower, this can be alleviated by the mac-layer protocol improving network.Mac-layer protocol mainly solves how between the user vied each other, to distribute wireless channel problem, and namely radio node selects which wireless channel of access to carry out transmit data frames.The method for channel allocation controlled based on power is introduced in mac-layer protocol design, optimum transmitted power is selected according to the distance between sending node and receiving node and channel conditions, hidden terminal problem can be reduced, reduce the interference between different transmission, thus raising network throughput, and reduce network energy consumption.

The MAC layer method for channel allocation controlled based on power has good network performance, but the concrete mode that power controls needs well-designed.DCA-PC (DynamicChannelAllocation – PowerControl) agreement (Yu-CheeTseng, Shih-LinWu, Chih-YuLin, Jang-PingSheu.AMulti-ChannelMACProtocolwithPowerControlf orMulti-HopMobileAdHocNetworks.TheComputerJournal.2002, 45 (1): 101 ~ 110.) comparatively early power is controlled to introduce method for channel allocation, this agreement is with maximum power transfer RTS frame and CTS frame, then selective sequential idle data channel, calculate minimum power according to euclidean distance between node pair and send DATA frame and ACK frame.Power controls to combine with channel allocation by this agreement, and two kinds of independent execution of mechanism, be independent of each other, protocol architecture is simply effective.DPL (DistributedPowerlevel) agreement (KhaledHatemAlmotairi.DistributedPowerControlandMediumAcc essControlProtocolDesignforMulti-ChannelAdHocWirelessNet works.Waterloo, Ontario, Canada, 2012) adopt the dynamic channel assignment method of packet-oriented granularity, select different data channels according to the difference of Packet Generation power.Meanwhile, in order to reduce the impact of asymmetric link on network performance, when any node sends data on the same channel, onesize performance number is all adopted.

In above agreement, data channel is selected and is not relied on Packet Generation power, choosing of Packet Generation power does not rely on data channel selection yet, this causes asymmetric link problems in same channel comparatively serious, causes hidden terminal problem, affects network performance.In the method for channel allocation controlled based on power, if selected to combine with transmitted power by data channel, and select node transmitted power according to euclidean distance between node pair, and then determine the data channel that should select, then contribute to the hidden terminal problem reducing network, improve network performance.Introduce the relation between euclidean distance between node pair and node transmitted power below.

When in the transmission range that certain node is in sending node or receiving node, this node can correct receiving package, thus can keep out of the way corresponding duration according to the data transmission period in bag.When a node is only within the scope of the carrier sense of sending node or receiving node, and when correctly can not resolve bag, this node only keeps out of the way an EIFS duration.Transmission range and carrier sense scope are all relevant with transmitted power size.

In the method for channel allocation controlled based on power, when adopting smaller power to send data, need ensure that the received power of data is more than or equal to the threshold level of receiving node.Meanwhile, the received power of node also must meet formula (a), namely when node A adopts minimum power to send data to Node B, ensure that data correctly receive, data receiver power with interference signal received power P _intfwith noise power P _noisethe ratio of sum should be more than or equal to certain value, and this value is called Signal Interference and Noise Ratio thresholding, uses symbol T _sINRrepresent.Otherwise reception data will produce with interference signal collides, and causes communication failure.

$\frac{P_{recv}^{\left(B\right)}}{P_{noise}+P_{intf}}\≥T_{SINR}---\left(a\right)$

In formula (a), due to noise power P _noiserelative to the interference signal received power P that other node produces _intfless, can ignore.For ensureing effectively to receive data, in the worst cases, the ratio of received power and interference signal received power equals T _sINR, can formula (b) be obtained.

$\frac{P_{recv}^{\left(B\right)}}{P_{intf}}=T_{SINR}---\left(b\right)$

According to the free space fading model of wireless signal, the transmitted power of node A with the received power of Node B meet formula (c).

${\left(\frac{P_{trans}^{\left(A\right)}G}{P_{recv}^{\left(B\right)}}\right)}^{\frac{1}{\mathrm{\α}}}=d_{(A,B)}---\left(c\right)$

Wherein, α is path attenuation coefficient, and G is antenna gain.

Suppose only there is single interfering nodes in network, as this node adopts maximum power P _maxwhen sending data, cause certain receiving node correctly cannot receive data, then claim interfering nodes in the interference range of this receiving node.When the interference range border of interfering nodes at receiving node, according to formula (c), interference radius d _intfmeet formula (d)

$d_{\mathrm{int}f}={\left(\frac{P_{max}G}{P_{intf}}\right)}^{\frac{1}{\mathrm{\α}}}---\left(d\right)$

Formula (b), (c) are substituted into formula (d), can formula (e) be obtained

$d_{\mathrm{int}f}={\left(\frac{P_{trans}^{\left(A\right)}{\mathrm{GP}}_{\max }{T}_{SINR}}{P_{recv}^{\left(B\right)}{P}_{trans}^{\left(A\right)}}\right)}^{\frac{1}{\mathrm{\α}}}=d_{(A,B)}{\left(\frac{P_{max}{T}_{SINR}}{P_{trans}^{\left(A\right)}}\right)}^{\frac{1}{\mathrm{\α}}}---\left(e\right)$

From formula (e), when transmitting-receiving node spacing one timing, in the transmitted power of sending node and channel, the difference of maximum interference power is larger, and receiving node interference range is larger.When the data sending power of interfering nodes obtains maximum, the interference radius of node is greater than the transmission radius of CTS frame, thus produces the phenomenon of concealed terminal, causes data re-transmission, affects overall performance of network.

Summary of the invention

The technical problem to be solved in the present invention controls based on power, a kind of AdHoc network MAC layer method for channel allocation is proposed, the specific implementation of this method is called CAPC (ChannelAssignmentwithPowerControl) agreement, compared with the typical channel assignment protocol DCA-PC agreement controlled based on power, this agreement can improve network throughput and specific energy consumption throughput.

Network node uses two transceivers, and one is fixed on control channel, another redirect between different pieces of information channel.Adopt maximum power at control channel transmission RTS frame and CTS frame, adopt minimum power at data channel transmission DATA frame and ACK frame.Minimum power can correctly receive according to receiving node and the minimal detectable power thresholding of decoding calculates.The minimum power of nodes all in same collision domain is divided into different brackets, and the corresponding data channel of each grade, then according to the hierarchical selection respective data channels at minimum power place.The link differed greatly due to transmitted power is distributed in different channels, therefore can alleviate the adverse effect of asymmetric link in same channel, reduces possible collision, thus improves network throughput and specific energy consumption throughput.

Concrete technical scheme of the present invention is as follows:

Be a control channel and n data channel by multiple channel distribution of AdHoc network, data communication is initiated by sending node, and the selection of data channel is determined by receiving node.Each node has two wireless transceivers, and a transceiver is fixed on control channel, the redirect in multiple data channel of another one transceiver.Each node safeguards an information table, and node receives the control information that all neighbor nodes send, and by the neighbor node transmitted power comprised in control information, current reiving/transmitting state, and all data channel busy-idle conditions are saved in self information table.

Node adopts maximum power to send control information at control channel, adopts minimum power to send data message at data channel, minimum power P _mincan correctly to receive according to receiving node and the minimal detectable power thresholding of decoding calculates, as shown in formula (f):

$P_{\min }=\frac{P_{recv}{P}_{trans}^{RTS}}{P_{recv}^{RTS}}---\left(f\right)$

Wherein P _recvfor minimal detectable power thresholding, for the transmission power value of carrying in RTS frame, for the actual power of RTS frame received.

The minimum power of same collision domain interior joint is on average divided into n grade, and each grade is one section of power bracket.According to channel number, each grade is uniquely corresponded to a data channel.During node communication, the current transmit power range of each channel, self transmission power value are filled in RTS frame, and send to receiving node by sending node; Receiving node, according to information in RTS frame and the performance number calculating minimum power receiving RTS frame, is determined the power grade of minimum power subordinate, is then found the data channel that these level is corresponding; As this channel idle, namely select this channel to communicate, and power corresponding to channel number and this channel is sent back to sending node by CTS frame, thus complete channel allocation; As this channel busy, then this channel number is added 1, then judge that whether it is idle; As present channel has been No. n-th channel and busy, then node has been waited for; Node all recalculated minimum power before each transmission data, and the method is applicable to the network of node location dynamic change;

Beneficial effect of the present invention is, in each node communication of AdHoc network MAC layer, is assigned on different channels by different capacity value, communication node is calculated data bag transmitted power voluntarily, and then select the channel that this power is corresponding, effectively can reduce conflict, improve channel utilization.Compared with DCA-PC agreement, the CAPC agreement of this method is adopted to have advantage in network throughput and specific energy consumption throughput.

Accompanying drawing explanation

Fig. 1 is workflow diagram of the present invention.

Fig. 2 is the simulation curve figure of specific implementation CAPC agreement of the present invention and DCA-PC agreement, and contrast network throughput is with packet sending speed situation of change.

Fig. 3 is the simulation curve figure of specific implementation CAPC agreement of the present invention and DCA-PC agreement, and contrast network throughput is with bag size variation situation.

Fig. 4 is the simulation curve figure of specific implementation CAPC agreement of the present invention and DCA-PC agreement, and contrast network throughput is with mobile node number situation of change.

Fig. 5 is the simulation curve figure of specific implementation CAPC agreement of the present invention and DCA-PC agreement, and contrast network throughput is with channel number situation of change.

Fig. 6 is the simulation curve figure of specific implementation CAPC agreement of the present invention and DCA-PC agreement, and contrast specific energy consumption throughput is with packet sending speed situation of change.

Fig. 7 is the simulation curve figure of specific implementation CAPC agreement of the present invention and DCA-PC agreement, and contrast specific energy consumption throughput is with bag size variation situation.

Fig. 8 is the simulation curve figure of specific implementation CAPC agreement of the present invention and DCA-PC agreement, and contrast specific energy consumption throughput is with mobile node number situation of change.

Fig. 9 is the simulation curve figure of specific implementation CAPC agreement of the present invention and DCA-PC agreement, and contrast specific energy consumption throughput is with channel number situation of change.

In figure: 1CAPC agreement; 2DCA-PC agreement.

Embodiment

Specific embodiments of the invention are described in detail below in conjunction with summary of the invention and Figure of description.

Embodiment 1

Fig. 1 is workflow diagram of the present invention.In the ad hoc network, node A sends a packet to Node B, carries out according to following flow process.

Step one: according to information table, node A first judges whether following three transmission conditions meet before sending data to Node B:

(1) Node B is at T _dIFS+ T _rTS+ T _sIFS+ T _cTSbe idle after+2 τ times, if there is not the record of Node B in information table, then this condition meets automatically;

(2) at least there is a data channel at T _dIFS+ T _rTS+ T _sIFS+ T _cTSidle after+2 τ times;

(3) control channel is at T _dIFSidle after time.

When above three conditions all meet, node A sends RTS frame with maximum power; Otherwise node A needs to wait for, until three conditions are all satisfied, just send RTS frame.

Step 2: after Node B receives RTS frame, needs to calculate minimum power.During for ensureing data receiver, signal strength signal intensity reaches the minimal detectable power thresholding of receiving node, and Node B calculates the minimum power P of sending node needs according to formula (f) _min.Calculating completes P _minafterwards, Node B upgrades the minimum power in self information table.

Step 3: Node B is by P _mincompare with the transmission power value of preserving in self information table, according to P _minplace hierarchical selection data channel.If this channel is at T _sIFS+ T _cTSavailable after the+τ time, then reply CTS frame, and comprise selected channel number and minimal power values wherein; If this channel is unavailable, then channel number is added 1, continue to judge that whether this channel is idle; As present channel has been maximum numbering channel and busy, then calculates the stand-by period according to available channel the earliest, replied the CTS frame that refusal sends.

Step 4: after node A sends RTS frame, waits for T _sIFS+ T _cTS+ 2 τ times, if the CTS frame not receiving Node B reply at this moment, then get back to step one, if receive CTS frame, then judge its content.Allow to send if CTS frame indicates, then the channel adopting receiving node B selected and power transmit data, and at T _sIFSbroadcast RES frame after time, the performance number of channel number and the employing taken is described wherein.If do not allow to send, then read the stand-by period comprised in CTS frame, again attempt after waiting for the corresponding time sending RTS frame, forward step one to.

Step 5: after neighbor node receives the control frames such as RTS frame, CTS frame, RES frame at control channel, reads the neighbor node and data channel use information, then corresponding record in lastest imformation table that comprise in control frame.

Step 6: after node A sends data, waits for T _aCK+ T _sIFS+ 2 τ times, if the ACK frame not receiving Node B reply at this moment, then forward step one to, again reservation data channel.

Above each meaning of parameters is as shown in table 1:

Table 1 meaning of parameters

Embodiment 2

Utilize NS2 emulation platform, from network throughput and specific energy consumption throughput two aspects, the performance of contrast CAPC and DCA-PC agreement, simulation parameter is as shown in table 2.

Table 2 simulation parameter

First group is tested the mobile node number chosen is 60, and data package size is 1024 bytes, and channel number is 5, when comparing packet sending speed change, and the network throughput situation of change of CAPC agreement and DCA-PC agreement, as shown in Figure 2.When packet sending speed is in 0 ~ 1001 kilobit change per second, two kinds of agreement lower network total throughouts are all in rising trend, until close to saturated.CAPC agreement outperform DCA-PC agreement, this is because the existence of asymmetric link causes data receiver to collide in DCA-PC agreement, produce retransmit, throughput is impacted; And CAPC agreement effectively reduces the quantity of asymmetric link, reduce collision frequency, improve network throughput.

Second group is tested the mobile node number chosen is 60, and packet sending speed is that 100 kilobits are per second, and channel number is 4, when comparing bag size variation, and the network throughput situation of change of CAPC agreement and DCA-PC agreement, as shown in Figure 3.Can find out, when packet sending speed changes, the total throughout of CAPC agreement all the time higher than DCA-PC agreement, and packet more big-difference is more obvious.When continuing to increase data package size, due to data channel capacity restriction, the aggregate network throughput of two kinds of agreements is all close to saturated, and the saturation throughput of CAPC agreement is higher than DCA-PC by about 20%.

It is 512 bytes that data package size is chosen in 3rd group of experiment, and packet sending speed is that 1000 kilobits are per second, and channel number is 5, during the change of comparison node number, and the network throughput situation of change of CAPC agreement and DCA-PC agreement, as shown in Figure 4.When interstitial content changes within the scope of 30-70, the aggregate network throughput of two kinds of agreements is all in rising trend.This is because node number is more, network channel utilance is higher, and throughput is also larger.CAPC agreement performance significantly better than DCA-PC agreement because CAPC agreement according to transmitted power by allocation of packets in different pieces of information channel, decrease conflict, take full advantage of channel resource.

It is 512 bytes that data package size is chosen in 4th group of experiment, and packet sending speed is that 100 kilobits are per second, and mobile node number is 60, when comparing channel number change, and the network throughput situation of change of CAPC agreement and DCA-PC agreement, as shown in Figure 5.As can be seen from the figure, when channel number changes within the scope of 3-7, DCA-PC protocol network total throughout remains unchanged substantially, and in CAPC agreement, aggregate network throughput is then in obvious ascendant trend.Because DCA-PC protocol sequence selects data channel, in same channel, the data sending power of multiple sending node differs greatly, thus there is a large amount of hidden terminal problem, this causes more communication node to a part of channel of concentrated selection, therefore conflict comparatively large, and the castering action of the increase of channel number to throughput is little.And transmitted power is divided into different brackets according to channel number by CAPC agreement, select corresponding different channels, can maximum using channel resource, when channel number increases, aggregate network throughput also has obvious lifting, outperforms DCA-PC agreement.

It is 60 that mobile node number is chosen in 5th group of experiment, and data package size is 1024 bytes, and channel number is 5, when comparing packet sending speed change, and the specific energy consumption throughput situation of change of CAPC agreement and DCA-PC agreement, as shown in Figure 6.Along with packet sending speed increases, the specific energy consumption throughput of two kinds of agreements is all in rising trend, until close to saturated.CAPC agreement outperforms DCA-PC agreement, this is because in CAPC agreement, packet is distributed in different channels according to transmitted power, reduce the collision problem because asymmetric link causes, improve transmission success rate, therefore specific energy consumption throughput is larger all the time.

It is 60 that mobile node number is chosen in 6th group of experiment, and packet sending speed is that 100 kilobits are per second, and channel number is 5, when comparing bag size variation, and the specific energy consumption throughput situation of change of CAPC agreement and DCA-PC agreement, as shown in Figure 7.As can be seen from the figure, for two kinds of agreements, when data package size increases, specific energy consumption throughput slightly increases, and approaches to saturation gradually.This is because packet is larger, data channel utilance is higher, and the energy loss produced because of collision is less, so specific energy consumption throughput promotes gradually.Same because the connection of different capacity can be allocated in different channels by CAPC agreement, avoid the collision loss that asymmetric connection produces largely, save the energy retransmitting and need, therefore outperform DCA-PC agreement.

It is 512 bytes that data package size is chosen in 7th group of experiment, and packet sending speed is that 1000 kilobits are per second, and channel number is 5, during comparison node number of variations, and the specific energy consumption throughput situation of change of CAPC agreement and DCA-PC agreement, as shown in Figure 8.Because offered load is heavier, when node number increases, total throughout increases to some extent, but now network is more crowded, the retransmission energy consumption produced because of collision is larger, the speed that energy ezpenditure increases exceedes the speed that throughput increases, and therefore the specific energy consumption throughput of two kinds of agreements is all on a declining curve.But relative to DCA-PC agreement, CAPC agreement can avoid conflict as far as possible, reduce energy consumption, therefore its specific energy consumption throughput is still better than DCA-PC agreement all the time.

It is 512 bytes that data package size is chosen in 8th group of experiment, and packet sending speed is that 100 kilobits are per second, and mobile node number is 60, when comparing channel number change, and the specific energy consumption throughput situation of change of CAPC agreement and DCA-PC agreement, as shown in Figure 9.Can find out in figure that the specific energy consumption throughput of DCA-PC agreement is substantially unchanged along with channel number increases, CAPC agreement then continues to increase.This is because during DCA-PC agreement interior joint selection data channel, be selective sequential, and the concealed terminal existed in a large number causes the data channel of all sensor selection problem to concentrate in certain several channel, so the impact of the increase of channel number on experimental result is little.And in CAPC agreement, then according to channel number, transmitted power is carried out classification, thus maximum using channel resource, so unit energy utilance increases with the increase of channel number.

In sum, adopt the CAPC agreement of put forward the methods of the present invention, in network throughput and specific energy consumption throughput etc., be all better than DCA-PC agreement.

Claims (1)

1., based on the AdHoc network MAC layer method for channel allocation that power controls, it is characterized in that,

Be a control channel and n data channel by multiple channel distribution of AdHoc network, data communication is initiated by sending node, and the selection of data channel is determined by receiving node; Each node has two wireless transceivers, and a transceiver is fixed on control channel, the redirect in multiple data channel of another one transceiver; Each node safeguards an information table, and node receives the control information that all neighbor nodes send, and by the neighbor node transmitted power comprised in control information, current reiving/transmitting state, and all data channel busy-idle conditions are saved in self information table;

Node adopts maximum power to send control information at control channel, adopts minimum power to send data message at data channel, minimum power P _mincan correctly to receive according to receiving node and the minimal detectable power thresholding of decoding calculates, as shown in formula (1):

$P_{\min }=\frac{P_{recv}{P}_{trans}^{RTS}}{P_{recv}^{RTS}}---\left(1\right)$

Wherein P _recvfor minimal detectable power thresholding, for the transmission power value of carrying in RTS frame, for the actual power of RTS frame received;

The minimum power of same collision domain interior joint is on average divided into n grade, and each grade is one section of power bracket; According to channel number, each grade is uniquely corresponded to a data channel; During node communication, the current transmit power range of each channel, self transmitted power are filled in RTS frame, and send to receiving node by sending node; Receiving node, according to information in RTS frame and the performance number calculating minimum power receiving RTS frame, is determined the power grade of minimum power subordinate, is then found the data channel that these level is corresponding; As this channel idle, namely select this channel to communicate, and channel number and the corresponding power of this channel are sent back to sending node by CTS frame, thus complete channel allocation; As this channel busy, then this channel number is added 1, then judge that whether it is idle; As present channel has been No. n-th channel and busy, then node has been waited for; Node all recalculated minimum power before each transmission data, was applicable to the network of node location dynamic change.