CN103501531A - Power control-based Ad Hoc network MAC (Media Access Control) layer channel allocation method - Google Patents

Abstract

The invention discloses a power control-based wireless MAC (Media Access Control) layer channel allocation method, which belongs to the field of Ad Hoc networks. In a multi-channel Ad Hoc network, two transceivers are used by a network node, of which one is fixedly arranged in a control channel, and the other one jumps between different data channels. An RTS (Request To Send) frame and a CTS (Clear To Send) frame are transmitted at the control channel by using the maximum power; a DATA frame and an ACK (Acknowledgement) frame are transmitted at the data channels by using the minimum power. The minimum power is calculated according to the minimum receiving power threshold which can be correctly received and decoded by a receiving node. The transmitting powers of all nodes in a same collision domain are divided into different grades, and then a corresponding data channel is selected according to the grade of the minimum power, so that links with larger transmitting power difference are allocated to different channels, the adverse effect of asymmetric links in the same channel can be relieved, and the network throughput and the unit energy consumption throughput are improved. The concrete implementation CAPC (Channel Assignment with Power Control) protocol can be used as an MAC layer protocol of the channel selected by Ad Hoc network node equipment.

Description

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

Technical field

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

Background technology

Ad Hoc network is a kind of wireless self-organization network, has without characteristics such as center, topological dynamic change and resource, the energy are limited, is widely used in personal communication, business application and the field such as military.The mac-layer protocol of Ad Hoc network allows the network node parallel transmission data on different channels in same interference territory, but, method allocated channel due to Ad Hoc network node employing Distributed Coordination, unavoidably bring more network data packet conflict, cause all shortcomings such as lower of network throughput and specific energy consumption throughput, this can alleviate by the mac-layer protocol that improves network.Mac-layer protocol mainly solves how between the user who vies each other, to distribute the wireless channel problem, and radio node selects which wireless channel of access to carry out transmit data frames.Introduce the method for channel allocation of controlling based on power in the mac-layer protocol design, select optimum transmitted power according to distance and channel conditions between sending node and receiving node, can reduce hidden terminal problem, reduce the interference between different transmission, thereby the raising network throughput, and reduce network energy consumption.

The MAC layer method for channel allocation of controlling based on power has network performance preferably, but the concrete mode that power is controlled needs well-designed.DCA-PC(Dynamic Channel Allocation – Power Control) agreement (Yu-Chee Tseng, Shih-Lin Wu, Chih-Yu Lin, Jang-Ping Sheu.A Multi-Channel MAC Protocol with Power Control for Multi-Hop Mobile Ad Hoc Networks.The Computer Journal.2002, 45 (1): 101～110.) early power is controlled and introduced 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.This agreement is controlled power to combine with channel allocation, and two kinds of independent execution of mechanism, be independent of each other, and protocol architecture is simply effective.DPL(Distributed Power level) agreement (Khaled Hatem Almotairi.Distributed Power Control and Medium Access Control Protocol Design for Multi-Channel Ad Hoc Wireless Networks.Waterloo, Ontario, Canada, 2012) adopt the dynamic channel assignment method of packet-oriented granularity, according to the difference of Packet Generation power, select different data channels.Simultaneously, in order to reduce the impact of asymmetric link on network performance, any node all adopts onesize performance number while on same channel, sending data.

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

In the time of in the transmission range of certain node in sending node or receiving node, this node can correctly receive bag, thereby can keep out of the way corresponding duration according to the data transmission period in bag.When a node only in the carrier sense scope in sending node or receiving node, and can not correctly resolve bag the time, this node is only kept out of the way an EIFS duration.Transmission range and carrier sense scope are all relevant with the transmitted power size.

In the method for channel allocation of controlling based on power, when adopting smaller power to send data, need to guarantee that the received power of data is more than or equal to the threshold level of receiving node.Simultaneously, the received power of node also must meet formula (a),, when node A adopts minimum power to send data to Node B, guarantee 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 the Signal Interference and Noise Ratio thresholding, uses symbol T _sINRmean.Otherwise receive data and will produce collision with interference signal, cause communication failure.

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

In formula (a), due to noise power P _noisethe interference signal received power P produced with respect to other node _intfless, can ignore.For guaranteeing effectively to receive data, under worst case, the ratio of received power and interference signal received power equals T _sINR, can obtain formula (b).

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

According to the free space decline model of wireless signal, the transmitted power of node A

received power with Node B

meet formula (c).

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

Wherein, a is the path attenuation coefficient, and G is antenna gain.

Suppose in network only to exist single interfering nodes, as this node adopts maximum power P _maxwhile sending data, cause certain receiving node can't correctly receive data, claim interfering nodes in the interference range of this receiving node.During interference range border when interfering nodes at receiving node, according to formula (c), disturb radius d _intfmeet formula (d)

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

By formula (b), (c) substitution formula (d), can obtain formula (e)

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

From formula (e), when one timing of transmitting-receiving node spacing, in the transmitted power of sending node and channel, the difference of maximum interference power is larger, and the 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, thereby 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 is based on power and controls, a kind of Ad Hoc network MAC layer method for channel allocation is proposed, the specific implementation of this method is called CAPC(Channel Assignment with Power Control) agreement, with the channel allocation agreement DCA-PC agreement of typically controlling based on power, compare, this agreement can improve network throughput and specific energy consumption throughput.

Network node is used two transceivers, and one is fixed in control channel, and another is in the redirect of different pieces of information interchannel.Adopt maximum power at control channel transmission RTS frame and CTS frame, adopt minimum power at data channel transmission DATA frame and ACK frame.The minimal detectable power thresholding that minimum power can correctly receive and decode according to receiving node calculates.The minimum power of all nodes in same collision domain is divided into to different brackets, and the corresponding data channel of each grade, then select respective data channels according to the grade 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, thereby improves network throughput and specific energy consumption throughput.

Concrete technical scheme of the present invention is as follows:

By a plurality of channel distribution of Ad Hoc network, be a control channel and n data channel, 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 in control channel, the redirect in a plurality of data channels of another one transceiver.Each node is safeguarded 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 the 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 _minthe minimal detectable power thresholding that according to receiving node, can correctly receive and decode calculates, as shown in formula (f):

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

P wherein _recvfor the minimal detectable power thresholding,

for the transmission power value of carrying in the RTS frame,

actual power for the RTS frame received.

The minimum power of node in same collision domain on average is divided into to n grade, and each grade is one section power bracket.According to channel number, that each grade is unique corresponding to a data channel.During node communication, sending node is filled into the current transmit power range of each channel, self transmission power value in the RTS frame, and sends to receiving node; Receiving node calculates minimum power according to information in the RTS frame and the performance number that receives the RTS frame, determines the power grade of minimum power subordinate, then finds data channel corresponding to these level; As this channel idle, select this channel to communicate, and channel number and power corresponding to this channel are sent back to sending node by the CTS frame, thereby complete channel allocation; As this channel busy, this channel number is added to 1, then judge that whether it is idle; As current channel has been n channel and busy, node is waited for; Node all again calculated 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 Ad Hoc network MAC layer, the different capacity value is assigned on different channels, communication node is calculated data bag transmitted power voluntarily, and then select the channel that this power is corresponding, and can effectively reduce conflict, improve channel utilization.Compare with the DCA-PC agreement, adopt the CAPC agreement of this method thering is advantage aspect network throughput and specific energy consumption throughput.

The 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 the contrast network throughput is with the 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 the 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 the 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 the contrast network throughput is with channel number of variations situation.

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 the 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 of variations situation.

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

Embodiment

Describe specific embodiments of the invention in detail below in conjunction with summary of the invention and Figure of description.

Embodiment

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

Step 1: before node A sends data to Node B, first according to information table, judge whether following three transmission conditions meet:

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

(2) at least exist a data channel at T _dIFS+ T _rTS+ T _sIFS+ T _cTSafter+2 τ times, be idle;

(3) control channel is at T _dIFSafter time, be idle.

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

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

Step 3: Node B is by P _minwith the transmission power value of preserving in the self information table, compare, according to P _minthe place grade is selected a data channel.If this channel is at T _sIFS+ T _cTSavailable after the+τ time, reply the CTS frame, and comprise therein selected channel number and minimal power values; If this channel is unavailable, channel number is added to 1, continue to judge that whether this channel is idle; As current channel has been maximum numbering channel and busy, according to available channel the earliest, calculate the stand-by period, reply the CTS frame that refusal sends.

Step 4: after node A sends the RTS frame, wait for T _sIFS+ T _cTS+ 2 τ times, if do not receive the CTS frame that Node B is replied at this moment, get back to step 1, if receive the CTS frame, judge its content.Allow to send if the CTS frame indicates, adopt the selected channel of receiving node B and power to transmit data, and at T _sIFSbroadcast the RES frame after time, the channel number that explanation takies therein and the performance number of employing.If do not allow to send, read the stand-by period comprised in the CTS frame, again attempt sending the RTS frame after waiting for the corresponding time, forward step 1 to.

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

Step 6: after node A sends data, wait for T _aCK+ T _sIFS+ 2 τ times, if do not receive the ACK frame that Node B is replied at this moment, forward step 1 to, again the reservation data channel.

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

Table 1 meaning of parameters

Comparative Examples

Utilize the NS2 emulation platform, from network throughput and two aspects of specific energy consumption throughput, 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 of choosing is 60, and data package size is 1024 bytes, and the channel number is 5, when relatively packet sending speed changes, and the network throughput situation of change of CAPC agreement and DCA-PC agreement, as shown in Figure 2.When packet sending speed, when 0～1001 kilobit per second changes, two kinds of agreement lower network total throughouts are all in rising trend, until approach saturated.The CAPC agreement outperform the DCA-PC agreement, this is because in the DCA-PC agreement, the existence of asymmetric link causes the data receiver collision, produces and retransmits, and throughput is impacted; And the CAPC agreement has effectively reduced the quantity of asymmetric link, reduced the collision frequency, improved network throughput.

Second group is tested the mobile node number of choosing is 60, and packet sending speed is 100 kilobit per seconds, and the channel number is 4, while relatively wrapping 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 is all the time higher than the DCA-PC agreement, and packet more big-difference is more obvious.When continuing to increase data package size, due to the data channel capacity limit, the aggregate network throughput of two kinds of agreements all approaches saturated, and the saturation throughput of CAPC agreement is higher by about 20% than DCA-PC.

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

It is 512 bytes that data package size is chosen in the 4th group of experiment, and packet sending speed is 100 kilobit per seconds, and the mobile node number is 60, when relatively channel number changes, 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 the channel number changes in the 3-7 scope, DCA-PC protocol network total throughout remains unchanged substantially, and in the CAPC agreement, aggregate network throughput is obvious ascendant trend.Because the DCA-PC protocol sequence is selected data channel, in same channel, the data sending power of a plurality of sending nodes differs greatly, thereby there are a large amount of hidden terminal problems, this causes more communication node to select a part of channel to concentrating, therefore conflict is larger, and the increase of channel number is little to the castering action of throughput.And the CAPC agreement is divided into different brackets according to the channel number by transmitted power, select corresponding different channels, can the maximum using channel resource, when the channel number increases, aggregate network throughput also has obvious lifting, outperforms the DCA-PC agreement.

It is 60 that the mobile node number is chosen in the 5th group of experiment, and data package size is 1024 bytes, and the channel number is 5, when relatively packet sending speed changes, 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 approach saturated.The CAPC agreement outperforms the DCA-PC agreement, and this is because, in the CAPC agreement, packet is distributed in different channels according to transmitted power, has reduced the collision problem caused because of asymmetric link, improved the transmission success rate, so the specific energy consumption throughput is larger all the time.

It is 60 that the mobile node number is chosen in the 6th group of experiment, and packet sending speed is 100 kilobit per seconds, and the channel number is 5, while relatively wrapping 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, the specific energy consumption throughput slightly increases, and approaches to saturation gradually.This is that the data channel utilance is higher because packet is larger, and the energy loss produced because of collision is less, so the specific energy consumption throughput promotes gradually.Same because the CAPC agreement can be allocated in different channels by the connection of different capacity, as to have avoided largely asymmetric connection to produce collision loss, saved and retransmitted the energy needed, and therefore outperforms the DCA-PC agreement.

It is 512 bytes that data package size is chosen in the 7th group of experiment, and packet sending speed is 1000 kilobit per seconds, and the channel number is 5, during the 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 the 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 consumption increases surpasses the speed that throughput increases, and therefore the specific energy consumption throughput of two kinds of agreements is all on a declining curve.But, with respect to the DCA-PC agreement, the CAPC agreement can avoid conflict as far as possible, reduce energy consumption, so its specific energy consumption throughput still is better than the DCA-PC agreement all the time.

It is 512 bytes that data package size is chosen in the 8th group of experiment, and packet sending speed is 100 kilobit per seconds, and the mobile node number is 60, when relatively channel number changes, 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 the channel number increases, the CAPC agreement continues to increase.This is, while because of node in the DCA-PC agreement, selecting data channel, be selective sequential, and the data channel that a large amount of concealed terminal existed causes all nodes to be selected to be concentrated in certain several channel, so the increase of channel number is little on the impact of experimental result.And, in the CAPC agreement, according to the channel number, transmitted power is carried out to classification, thus the maximum using channel resource, so the 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, at aspects such as network throughput and specific energy consumption throughputs, all be better than the DCA-PC agreement.

Claims (1)

1. an Ad Hoc network MAC layer method for channel allocation of controlling based on power, is characterized in that,

By a plurality of channel distribution of Ad Hoc network, be a control channel and n data channel, 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 in control channel, the redirect in a plurality of data channels of another one transceiver; Each node is safeguarded 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 the 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 _minthe minimal detectable power thresholding that according to receiving node, can correctly receive and decode calculates, as shown in Equation (1):

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

P wherein _recvfor the minimal detectable power thresholding,

for the transmission power value of carrying in the RTS frame,

actual power for the RTS frame received.

The minimum power of node in same collision domain on average is divided into to n grade, and each grade is one section power bracket; According to channel number, that each grade is unique corresponding to a data channel; During node communication, sending node is filled into the current transmit power range of each channel, self transmitted power in the RTS frame, and sends to receiving node; Receiving node calculates minimum power according to information in the RTS frame and the performance number that receives the RTS frame, determines the power grade of minimum power subordinate, then finds data channel corresponding to these level; As this channel idle, select this channel to communicate, and channel number and the corresponding power of this channel are sent back to sending node by the CTS frame, thereby complete channel allocation; As this channel busy, this channel number is added to 1, then judge that whether it is idle; As current channel has been n channel and busy, node is waited for; Node all again calculated minimum power before each transmission data, was applicable to the network of node location dynamic change.

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