CN101938792B - DCF protocol rate self-adapting method capable of supporting congestion identification - Google Patents

Abstract

The invention discloses a DCF protocol rate self-adapting method capable of supporting congestion identification, which comprises the following steps: (1) monitoring congestion by selecting the speed of a receiving party and avoiding congestion and selecting a transmission speed; (2) introducing an appointed broadcast frame to update the interception information of neighbor nodes in the transmission ranges of an RTS frame and a CTS frame; and (3) introducing a two-dimensional network distribution component to support virtual carrier detection under a multi-speed conduction. In the method, through the monitoring of the congestion by selecting the speed of the receiving party and avoiding congestion and through the introduction of the appointed broadcast frame and the two-dimensional network distribution component, the multi-speed self-adaptive transmission of a physical layer is realized, and the problem that high-speed transmission data packets are likely to encounter congestion undera heavy load condition can be solved effectively.

Description

A kind of DCF agreement speed self-adaption method of supporting congested identification

Technical field

What the present invention relates to is a kind of radio network technique field, in particular a kind of DCF agreement speed self-adaption method of supporting congested identification.

Background technology

Ad hoc network (wireless ad hoc networks) is a kind of novel wireless network.It is comprised of the mobile node of the complete equality in a series of status, need not any fixing or default network facilities.Each node in the network be terminal be again router, they under the control of channel access control (Medium Access Control, MAC) agreement, the mode access wireless channel of sharing with multi-hop.Because have networking fast and flexible, reliability height, ad hoc network is widely used in providing in the environment of fixed communication infrastructure, such as field communication, rescue and relief work, open-air scientific investigation, temporary meeting etc.

The MAC agreement is the key content of ad hoc network protocol stack research, and it determines the occupation mode of sharing wireless channel, is responsible for node and distributes wireless communication resources and control the node physical layer, thereby directly determining the overall performance of network.Development along with the communication technology, the communications speed that the node physical layer can be supported is more and more higher, yet in order to guarantee that signal can be received the node reliable decoding, by the relation of the error rate and signal to noise ratio under the modulation system of different transmission rates as can be known, transmission rate and the effective propagation path relation of being inversely proportional to, the node transmission rate is higher, and the effective propagation path of signal is then shorter.Therefore, the rate adaptation system of selection in the MAC agreement arouses widespread concern.

IEEE 802.11 agreements be the WLAN (wireless local area network) field first by the standard of international endorsement, it has comprised the standard of physical layer and MAC layer, the distributed coordination function that this agreement provides (Distributed CoordinationFunction, DCF) avoid conflict between the sending node by Physical carrier-sense mechanism and virtual carrier testing mechanism, and employing RTS/CTS (Request To Send/Clear To Send, i.e. request sends/allows and sends) solution of control frame handshake mechanism part the hidden terminal problem under the multihop network environment, thereby be widely used in various emulation and the test envelope of ad hoc network, become actual ad hoc Medium Access Control Protocols standard.In recent years, continuous Evolution Development along with 802.11 protocol architectures, the standard of its physical layer is progressively developed into by initial support single transmission speed supports multiple transmission rate, for example the transmission rate that allows of 802.11b agreement has 1Mbps, 2Mbps, 5.5Mbps and 11Mbps, and 802.11a and 802.11g agreement are supported from 6Mbps to 54Mbps eight kinds of transmission rates etc.Yet, although above-mentioned agreement is supported multiple transmission rate in physical layer, only the transmission rate of dissimilar frames has been carried out simple agreement at the MAC layer, and has not allowed node to select and switch the transmission rate of optimum according to channel status.

Carrier detect mechanism in the IEEE 802.11DCF agreement comprises that physical carrier detects and the virtual carrier of MAC layer detects.The method that physical carrier detects is called clear channel and estimates (Clear Channel Assessment, CCA), and when the signal power that detects when node was higher than given CCA thresholding with the noise power sum, physical layer notice MAC layer channel become by the free time and hurry.Network allocation vector of each node maintenance of virtual carrier testing requirement (Network Allocation Vector, NAV), the inside has comprised channel booking time span field (Duration).When node receives RTS, CTS that other nodes send or Data frame (Frame), can know from these frames that this secondary data sends the temporal information that will continue, and come the more NAV value of new node with this information.Yet, support that in physical layer but there is certain limitation in the virtual carrier testing mechanism that the DCF agreement provides in the situation of the many speed rates of mac frame:

(1) many speed rates may cause node can't know actual channel subscription time length.

Consider interception node 0, sending node 1, recipient node 2, interception node 3 is arranged in order 4 chain-shaped network topologys, and sending node 1 sends packet to recipient node 2.Because interception node 0 is within the transmission range of sending node 1, outside the transmission range of receiving node 2, so interception node 0 can know the channel booking time according to the Duration field in the RTS frame that listens to and the Data frame, thereby the value of NAV is set; And interception node 3 is outside the transmission range of sending node 1, and within the transmission range of receiving node 2, thereby interception node 3 can only arrange according to the Duration field in the CTS frame that listens to the value of NAV.Adopt at all types of mac frames in the situation of single-rate transmission, it is identical that interception node 0 and 3 detects the channel booking time that arranges by virtual carrier.

Yet under the condition of many speed rates, the effective propagation path that adopts different rates to send mac frame is different, thereby the effective range of virtual carrier testing mechanism is not identical yet.If basic rate sends the RTS/CTS frame, receiving node is selected the transmission rate of Data frame, and notifies sending node with this speed by replying the CTS frame.In the situation that receiving node is selected to adopt two-forty to send the Data frame, interception node 3 can be known accurately channel booking time span by intercepting the CTS frame, and after interception node 0 listens to subscription information in the RTS frame, but might can't know because receiving the Data frame of high-speed transfer the actual channel subscription time length after transmission rate changes.In this case, the erroneous cognition of 0 pair of channel booking time generation of interception node can cause the collision avoidance mechanism decrease in efficiency of MAC layer, thereby the network in general performance is had a negative impact.

(2) virtual carrier of one dimension NAV variable under can't many speed rates of effective support condition detects.

The NAV variable that the DCF agreement is used to indicate the channel booking time is an one dimension variable, after node listens to a mac frame, soon the current value of the channel booking time of Duration field indication and NAV variable compares in the frame, if the channel booking time of Duration field indication greater than the value of NAV variable, then is the value of Duration field indication with the NAV variable update; And if the channel booking time of Duration field indication is less than or equal to the current value of NAV variable, then the NAV variable remains unchanged.Therefore, in the situation that adopts the single-rate transmission, the value of the NAV variable of the current subscription time of indicating channel only may increase and can not reduce.

Different from the situation of single-rate transmission, adopt at node in the situation of many speed rates, suppose that the Data frame transmission rate that receiving node is selected is higher than the speed that sending node transmits the RTS frame, then the interception node in the sending node neighbours scope is by after intercepting the RTS frame and knowing the channel booking time and the NAV variable is set, if this node continues to listen to new mac frame, and know the channel booking time less than the value of the current NAV variable of node by the Duration field, then exist following two kinds may:

(1) if being sending node, the mac frame that continues to listen to successfully preengages behind the channel Data frame with high rate data transmission, then since this moment the Data frame indicated be the actual channel subscription time, thereby node should be reduced to the value of NAV variable the indicated channel booking time of Data frame;

(2) if node is received/sent out to the mac frame that continues to listen to sending by other, then identical with processing method in the single-rate transmission situation, node should remain unchanged the currency of NAV variable.

Yet, because it is an one dimension variable that the DCF agreement is used to indicate the NAV variable of channel booking time, therefore when exist around the interception node many to receive/when a node is preengage channel simultaneously, if node knows that by the Duration field of intercepting mac frame the channel booking time shortens, then node can't be distinguished above-mentioned two kinds of possible situations according to this one dimension NAV variable is correct, thereby causes the virtual carrier of finishing that node can't be correct to detect.

By above-mentioned two point analysis as can be known, the virtual carrier testing mechanism in the DCF agreement is supporting there is certain limitation aspect many speed rates.Therefore, rational many speed rates scheme must detect the virtual carrier of DCF agreement and adjust, thereby the interception node in the receipts of the assurance/node neighbours scope can be known the accurately channel booking time.

Simultaneously, ad hoc network is a kind of wireless network that the via node multi-hop is transmitted transmission of data packets that relies on, thereby selects in the node physical layer under the heavy duty condition of high rate data transmission packet, and the network hot spot region is easy to occur local congestion.If it is congested that the MAC agreement can't correctly be identified and control, then the congested channel resource waste that causes will affect the network in general performance greatly.

Summary of the invention

Goal of the invention: the object of the invention is to overcome the deficiencies in the prior art, a kind of DCF agreement speed self-adaption method of supporting congested identification is provided, when having realized the transmission of physical layer multi-velocity self-adapting, can also effectively avoid the congestion problems that may occur under the heavy duty condition of high rate data transmission packet.

Technical scheme: the present invention is achieved by the following technical solutions, the present invention includes following steps:

(1) monitors congested by choosing with the method for Congestion Avoidance of debit's speed, select transmission rate;

(2) introduce the subscription time broadcast frame, the interception information of neighbor node in the transmission range of RTS frame and CTS frame is upgraded;

(3) introduce the two-dimensional network allocation vector, support that the virtual carrier under many rate conditions detects.

Described step (1) may further comprise the steps again:

(1a) form of RTS frame and CTS frame is revised, the Duration field that is used for the expression channel booking time in the frame is revised as the Rate Adaptive field of 6 byte lengths, in the RTS frame, the RateAdaptive field comprises the IsFinal territory of 4 bits and the Length territory of 12 bits, in the CTS frame, Rate Adaptive field comprises the Rate territory of 4 bits and the Length territory of 12 bits;

(1b) there is packet to send to the MAC layer in the meshed network layer queue, node is before transmission RTS frame, judge the whether final address of this forwarding of packets, address that this secondary data sends, if final address, then the IsFinal territory of node RTS frame Rate Adaptive field is set to True, if not the final address, but the down hop forwarding address of this packet, then this territory of node is set to False, simultaneously, node with the length write of current data grouping in the Length territory of Rate Adaptive field;

After (1c) receiving node is received the RTS frame of sending node, if the value in IsFinal territory is False, then RTS frame receiving node is the relay forwarding node of current data grouping, if the meshed network layer queue is full, can't continue the forwarding data grouping, then node carries out this data retransmission with refusal, avoids the congested invalid transmission that causes of formation, if the meshed network layer queue less than, then node can carry out this data retransmission;

If (1d) value in IsFinal territory is True, then RTS frame receiving node is the final purpose node of current data grouping, and receiving node is received after this packet not to be needed this packet is added the network layer transmit queue directly to upper layer transfers;

(1e) receiving node writes the data packet length of RTS frame indication in the Length territory of CTS frame Rate Adaptive field, simultaneously, carry out at refusal in the situation of this Frame forwarding, the Rate territory of receiving node CTS frame Rate Adaptive field is set to 0, thereby by replying the CTS frame congestion information is informed sending node, if and can transmit or receive this Frame, receiving node then will be selected rational transmission rate according to the current signal to noise ratio condition of channel, and this value write the Rate territory of CTS frame Rate Adaptive field, thereby by replying the CTS frame Data frame transmission rate that the debit determines is informed sending node.

The subscription time broadcast frame of introducing in the described step (2) comprises the channel booking time field of 2 bytes, the Data frame transmission rate of selecting the debit is greater than basic transmission rate, perhaps refuse in the situation of data retransmission because formation is congested, sending node adopts basic transmission rate broadcasting RTB frame, can be informed the neighbor node in its RTS frame transmission range the new channel booking time.

In the described step (2) the channel booking time obtain and renewal may further comprise the steps:

After (2a) neighbor node of sending node listens to the RTS frame, because the actual speed rate of unknown sending node transmission Data frame, thereby suppose that the Data frame sends with basic transmission rate, the RTS interception node is obtained the channel booking time T _RTSReserveFor:

T _RTSReserve＝Length/R _Basic+T _CTS+T _ACK+3×SIFS

R _BasicBe basic transmission rate, T _CTSAnd T _ACKBe the transmission time of CTS frame and ACK frame, SIFS is the interFrameGap time;

After (2b) receiving node is received the RTS frame, can reply the CTS frame to sending node according to stipulations, after the neighbor node of receiving node listened to the CTS frame, the CTS interception node was obtained the channel booking time T _CTSReserveFor:

$T_{\mathrm{CTSReserve}}=\left\{\begin{array}{cc}0,& \mathrm{Rate}=0\\ \mathrm{Length}/\mathrm{Rate}+T_{\mathrm{ACK}}+2\×\mathrm{SIFS},& \mathrm{Rate}=R_{\mathrm{Basic}}\\ \mathrm{Length}/\mathrm{Rate}+T_{\mathrm{RTB}}+T_{\mathrm{ACK}}+3\×\mathrm{SIFS},& \mathrm{Rate}>R_{\mathrm{Basic}}\end{array}\right.$

T _RTBBe the transmission time of RTB frame, if the value in Rate territory is 0, receiving node refusal forwarding data frame, then the CTS interception node is 0 with the channel booking set of time, if the value in Rate territory is R _Basic, the Data frame transmission rate that receiving node is selected is basic transmission rate, then the CTS interception node draws the channel booking time according to the stipulations of DCF agreement, if the value in Rate territory is greater than R _Basic, the Data frame transmission rate that receiving node is selected is greater than basic transmission rate, and then the CTS interception node should count the transmission time of RTB frame the channel booking time;

After (2c) sending node is received the CTS frame that receiving node replys, if the Data frame transmission rate of knowing in the territory by Rate Adaptive field Rate in the frame is greater than basic transmission rate, perhaps the transmission of Data frame is refused by the debit, then sending node upgrades the channel booking time that the RTS interception node is obtained by broadcasting RTB frame, and the RTB interception node is upgraded the channel booking time T _RTBReserveFor:

T _RTBReserve＝Length/Rate+T _ACK+2×SIFS。

Two-dimensional network allocation vector in the described step (3) is a data structure of storing with the linear linked list form in node memory, each node in the described linear linked list is comprised of the pointer field of storage successor node positional information and the data field of store data element information, wherein: the pointer in the tail node pointer field be " sky " (NULL), pointer in all the other node pointer fields then points to the storage address of next node in the linear linked list, and the data field of each node comprises the time (T by neighbor node address (ScrID) field and this neighbor node reservation channel _Reserve) two-dimensional signal that forms of field.

Beneficial effect: the present invention monitors congested by choosing with the method for Congestion Avoidance of debit's speed, introduce subscription time broadcast frame and two-dimensional network allocation vector, when having realized the transmission of physical layer multi-velocity self-adapting, can also effectively avoid the congestion problems that may occur under the heavy duty condition of high rate data transmission packet.

Description of drawings

Fig. 1 is the form schematic diagram of frame of the present invention;

Wherein: a is the RST frame, and b is the CTS frame;

Fig. 2 is mac frame transmitting-receiving sequential chart of the present invention;

Fig. 3 is simulation result figure of the present invention;

Wherein: a is the end to end network overall average throughput under the different loads condition, and b is the transmitted in packets success rate under the different loads condition.

Embodiment

The below elaborates to embodiments of the invention, and present embodiment is implemented under take technical solution of the present invention as prerequisite, provided detailed execution mode and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

Present embodiment has proposed to support the DCF agreement rate adaptation mechanism (CongestionAware Rate Adaptive, CARA) of congested identification, may further comprise the steps:

(1) monitors congested by choosing with the method for Congestion Avoidance of debit's speed, select transmission rate;

(2) introduce the subscription time broadcast frame, the interception information of neighbor node in the transmission range of RTS frame and CTS frame is upgraded;

(3) introduce the two-dimensional network allocation vector, support that the virtual carrier under many rate conditions detects.

Described step (1) may further comprise the steps again:

(1a) as shown in Figure 1, form to RTS frame and CTS frame is revised, the Duration field that is used for the expression channel booking time in the frame is revised as Rate Adaptive (adaptation rate) field of 6 byte lengths, in the RTS frame, Rate Adaptive field comprises the IsFinal territory of 4 bits and the Length territory of 12 bits, in the CTS frame, Rate Adaptive field comprises the Rate territory of 4 bits and the Length territory of 12 bits;

(1b) because the Length Ratio Data frame of the frames such as RTS, CTS is short a lot, thereby the transmission time of adopting the two-forty transmission control frame to save is very limited, in order to simplify stipulations, the CARA mechanism that present embodiment proposes adopts basic transmission rate to send all types of control frames.There is packet to send to the MAC layer in the meshed network layer queue, node is before transmission RTS frame, judge the whether final address of this forwarding of packets, address that this secondary data sends, if final address, then the IsFinal territory of node RTS frame Rate Adaptive field is set to True, if not the final address, but the down hop forwarding address of this packet, then this territory of node is set to False, simultaneously, node with the length write of current data grouping in the Length territory of Rate Adaptive field;

After (1c) receiving node is received the RTS frame of sending node, if the value in IsFinal territory is False, then RTS frame receiving node is the relay forwarding node of current data grouping, if the meshed network layer queue is full, can't continue the forwarding data grouping, then node carries out this data retransmission with refusal, avoids the congested invalid transmission that causes of formation, if the meshed network layer queue less than, then node can carry out this data retransmission;

If (1d) value in IsFinal territory is True, then RTS frame receiving node is the final purpose node of current data grouping, and receiving node is received after this packet not to be needed this packet is added the network layer transmit queue directly to upper layer transfers;

(1e) receiving node writes the data packet length of RTS frame indication in the Length territory of CTS frame Rate Adaptive field, simultaneously, carry out at refusal in the situation of this Frame forwarding, the Rate territory of receiving node CTS frame Rate Adaptive field is set to 0, thereby by replying the CTS frame congestion information is informed sending node, if and can transmit or receive this Frame, receiving node then will be selected rational transmission rate according to the current signal to noise ratio condition of channel, and this value write the Rate territory of CTS frame Rate Adaptive field, thereby by replying the CTS frame Data frame transmission rate that the debit determines is informed sending node.

The neighbor node of sending node and receiving node is known the channel booking time by intercepting mac frame in the described step (2).Because what present embodiment adopted is the method that the debit selects the Data frame transmission rate, thereby selects the debit in the situation of high rate data transmission Data frame, the transmission range of Data frame will be less than the RTS frame transmission range that sends with basic rate.Part neighbor node in the sending node RTS frame transmission range then may be by intercepting the actual channel subscription time after the Data frame is known the transmission rate change.Simultaneously, refuse because formation is congested in the situation of data forwarding of packets at receiving node, the neighbor node in the sending node RTS frame transmission range then should be updated to 0 with the channel booking time.

In order to upgrade the channel booking temporal information of the neighbor node in the sending node RTS frame transmission range, present embodiment has been introduced a kind of new short control frame, be subscription time broadcast frame (RTB), this frame comprises the channel booking time field of 2 bytes, the Data frame transmission rate of selecting the debit is greater than basic transmission rate, perhaps thus formation congested and the refusal data retransmission situation under, sending node adopts basic transmission rate broadcasting RTB frame, can be informed the neighbor node in its RTS frame transmission range the new channel booking time.Simultaneously, because broadcasting RTB frame has been realized the announcement of channel booking time, thereby has removed the Duration field of Data frame header for the expression sending duration, thereby save the expense of Data frame transmission.

As shown in Figure 2, in the described step (2) the channel booking time obtain and renewal may further comprise the steps:

After (2a) neighbor node of sending node listens to the RTS frame, because the actual speed rate of unknown sending node transmission Data frame, thereby supposition Data frame sends with basic transmission rate, according to the value in RTS frame Rate Adaptive field Length territory, and mac frame is received/is sent out sequential and can draw the RTS interception node and obtain the channel booking time T _RTSReserveFor:

T _RTSReserve＝Length/R _Basic+T _CTS+T _ACK+3×SIFS

R _BasicBe basic transmission rate, T _CTSAnd T _ACKBe the transmission time of CTS frame and ACK frame, SIFS is the interFrameGap time;

After (2b) receiving node is received the RTS frame, can reply the CTS frame to sending node according to stipulations.After the neighbor node of receiving node listens to the CTS frame, can be according to the value in Rate Adaptive field Length territory and Rate territory in the frame, and different mac frames is received/is sent out sequential and draws the CTS interception node and obtain the channel booking time T _CTSReserveFor:

$T_{\mathrm{CTSReserve}}=\left\{\begin{array}{cc}0,& \mathrm{Rate}=0\\ \mathrm{Length}/\mathrm{Rate}+T_{\mathrm{ACK}}+2\×\mathrm{SIFS},& \mathrm{Rate}=R_{\mathrm{Basic}}\\ \mathrm{Length}/\mathrm{Rate}+T_{\mathrm{RTB}}+T_{\mathrm{ACK}}+3\×\mathrm{SIFS},& \mathrm{Rate}>R_{\mathrm{Basic}}\end{array}\right.$

T _RTBBe the transmission time of RTB frame, if the value in Rate territory is 0, receiving node refusal forwarding data frame, then the CTS interception node is 0 with the channel booking set of time, if the value in Rate territory is R _Basic, the Data frame transmission rate that receiving node is selected is basic transmission rate, then the CTS interception node draws the channel booking time according to the stipulations of DCF agreement, if the value in Rate territory is greater than R _Basic, the Data frame transmission rate that receiving node is selected is greater than basic transmission rate, and then the CTS interception node should count the transmission time of RTB frame the channel booking time;

After (2c) sending node is received the CTS frame that receiving node replys, if the Data frame transmission rate of knowing in the territory by Rate Adaptive field Rate in the frame is greater than basic transmission rate, perhaps the transmission of Data frame is refused by the debit, then sending node upgrades the channel booking time that the RTS interception node is obtained by broadcasting RTB frame, and the RTB interception node is upgraded the channel booking time T _RTBReserveFor:

T _RTBReserve＝Length/Rate+T _ACK+2×SIFS。

Two-dimensional network allocation vector in the described step (3) is a data structure of storing with the linear linked list form in node memory, each node in the described linear linked list is comprised of the pointer field of storage successor node positional information and the data field of store data element information, wherein: the pointer in the tail node pointer field be " sky " (NULL), pointer in all the other node pointer fields then points to the storage address of next node in the linear linked list, and the data field of each node comprises the time (T by neighbor node address (ScrID) field and this neighbor node reservation channel _Reserve) two-dimensional signal that forms of field.

When node listens to a mac frame of neighbor node transmission, node is namely searched this neighbor node in the node data field ScrID of TDNAV field address:

(1) if the address of this neighbor node has been recorded in the ScrID field of a certain node data field of TDNAV, then node is with the T of this data field _ReserveThe value of field is updated to be intercepted the channel booking time that current mac frame is known;

(2) if the address of this neighbor node is not recorded in the ScrID field of arbitrary node data field of TDNAV, then node inserts a new node at the afterbody of TDNAV, and with the address of this neighbor node and intercept ScrID and the T that channel booking time that current mac frame knows is recorded in new node data field _ReserveField.

Sending node is by searching all node data field T of TDNAV _ReserveThe maximum of field can know that channel will continue the time that becomes busy, thereby back-off wait avoids conflict, and realizes that virtual carrier detects.

As shown in Figure 3, consider in the length of side to be in the square area of 1000m, 50 nodes of random distribution adopt Random Waypoint motion model, and the maximal rate of node motion is 5m/s, and minimum speed is 1m/s, and the Stop-wait time is 0s.Simulation time is 50s, from emulation zero hour, sets up at random 5 and make a start and the equal not identical CBR stream of receiving end in 50 nodes.Accompanying drawing 3 has provided RBAR agreement that the people such as DCF agreement, HOLLAND G propose and present embodiment Performance Ratio.Simulation results show the validity of present embodiment.

Claims (1)

1. a DCF agreement speed self-adaption method of supporting congested identification is characterized in that, may further comprise the steps:

(1) monitors congested by choosing with the method for Congestion Avoidance of debit's speed, select transmission rate;

(2) introduce the subscription time broadcast frame, the interception information of neighbor node in the transmission range of RTS frame and CTS frame is upgraded;

(3) introduce the two-dimensional network allocation vector, support that the virtual carrier under many rate conditions detects;

Described step (1) may further comprise the steps:

(1a) form of RTS frame and CTS frame is revised, the Duration field that is used for the expression channel booking time in the frame is revised as the Rate Adaptive field of 6 byte lengths, in the RTS frame, Rate Adaptive field comprises the IsFinal territory of 4 bits and the Length territory of 12 bits, in the CTS frame, Rate Adaptive field comprises the Rate territory of 4 bits and the Length territory of 12 bits;

(1b) there is packet to send to the MAC layer in the meshed network layer queue, node is before transmission RTS frame, judge the whether final address of this forwarding of packets, address that this secondary data sends, if final address, then the IsFinal territory of node RTS frame Rate Adaptive field is set to True, if not the final address, but the down hop forwarding address of this packet, then this territory of node is set to False, simultaneously, node with the length write of current data grouping in the Length territory of Rate Adaptive field;

After (1c) receiving node is received the RTS frame of sending node, if the value in IsFinal territory is False, then RTS frame receiving node is the relay forwarding node of current data grouping, if the meshed network layer queue is full, can't continue the forwarding data grouping, then node carries out this data retransmission with refusal, avoids the congested invalid transmission that causes of formation, if the meshed network layer queue less than, then node can carry out this data retransmission;

If (1d) value in IsFinal territory is True, then RTS frame receiving node is the final purpose node of current data grouping, and receiving node is received after this packet not to be needed this packet is added the network layer transmit queue directly to upper layer transfers;

(1e) receiving node writes the data packet length of RTS frame indication in the Length territory of CTS frame Rate Adaptive field, simultaneously, carry out at refusal in the situation of this Frame forwarding, the Rate territory of receiving node CTS frame Rate Adaptive field is set to 0, thereby by replying the CTS frame congestion information is informed sending node, if and can transmit or receive this Frame, receiving node then will be selected rational transmission rate according to the current signal to noise ratio condition of channel, and this value write the Rate territory of CTS frame Rate Adaptive field, thereby by replying the CTS frame Data frame transmission rate that the debit determines is informed sending node;

The subscription time broadcast frame of introducing in the described step (2) comprises the channel booking time field of 2 bytes, the Data frame transmission rate of selecting the debit is greater than basic transmission rate, perhaps refuse in the situation of data retransmission because formation is congested, sending node adopts basic transmission rate broadcasting subscription time broadcast frame RTB, can be informed the neighbor node in its RTS frame transmission range the new channel booking time;

The described channel booking time obtain and renewal may further comprise the steps:

After (2a) neighbor node of sending node listens to the RTS frame, because the actual speed rate of unknown sending node transmission Data frame, thereby suppose that the Data frame sends with basic transmission rate, the RTS interception node is obtained the channel booking time T _RTSReserveFor:

T _RTSReserve＝Length/R _Basic+T _CTS+T _ACK+3×SIFS

R _BasicBe basic transmission rate, T _CTSAnd T _ACKBe the transmission time of CTS frame and ACK frame, SIFS is the interFrameGap time;

After (2b) receiving node is received the RTS frame, can reply the CTS frame to sending node according to stipulations, after the neighbor node of receiving node listened to the CTS frame, the CTS interception node was obtained the channel booking time T _CTSReserveFor:

$T_{\mathrm{CTSReserve}}=\left\{\begin{array}{cc}0,& \mathrm{Rate}=0\\ \mathrm{Length}/\mathrm{Rate}+T_{\mathrm{ACK}}+2\×\mathrm{SIFS},& \mathrm{Rate}=R_{\mathrm{Basic}}\\ \mathrm{Length}/\mathrm{Rate}+T_{\mathrm{RTB}}+T_{\mathrm{ACK}}+3\×\mathrm{SIFS},& \mathrm{Rate}>R_{\mathrm{Basic}}\end{array}\right.$

T _RTBBe the transmission time of RTB frame, if the value in Rate territory is 0, receiving node refusal forwarding data frame, then the CTS interception node is 0 with the channel booking set of time, if the value in Rate territory is R _Basic, the Data frame transmission rate that receiving node is selected is basic transmission rate, then the CTS interception node draws the channel booking time according to the stipulations of DCF agreement, if the value in Rate territory is greater than R _Basic, the Data frame transmission rate that receiving node is selected is greater than basic transmission rate, and then the CTS interception node should count the transmission time of RTB frame the channel booking time;

After (2c) sending node is received the CTS frame that receiving node replys, if the Data frame transmission rate of knowing in the territory by Rate Adaptive field Rate in the frame is greater than basic transmission rate, perhaps the transmission of Data frame is refused by the debit, then sending node upgrades the channel booking time that the RTS interception node is obtained by broadcasting RTB frame, and the RTB interception node is upgraded the channel booking time T _RTBReserveFor:

T _RTBReserve＝Length/Rate+T _ACK+2×SIFS；

Two-dimensional network allocation vector in the described step (3) is a data structure of storing with the linear linked list form in node memory, each node in the described linear linked list is comprised of the pointer field of storage successor node positional information and the data field of store data element information, wherein: the pointer in the tail node pointer field be " sky " (NULL), pointer in all the other node pointer fields then points to the storage address of next node in the linear linked list, and the data field of each node comprises the time (T by neighbor node address (ScrID) field and this neighbor node reservation channel _Reserve) two-dimensional signal that forms of field.

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