CN105898875B - A kind of communication means and system of distribution multi channel networks - Google Patents

Abstract

The present invention relates to a kind of communication means of distributed multi channel networks, comprising: channel rate-determining steps: information source is successfully seized after channel by CSMA/CA, sends RTS control frame to the stay of two nights；Channel response step: the stay of two nights receives the RTS control frame that information source is sent, and sends CTS control frame；Cooperative node allocation step: alternative cooperative node listens to multiplex (MUX) RTS frame and CTS frame simultaneously, calculates the CSI value of different channels, and is added to the channel for obtaining maximum CSI；Optimal cooperative node selects step: according to the CSI value of each alternative cooperative node, it is grouped backoff contention three times and determines that optimal cooperative node, optimal cooperative node send RTH frame and seize channel, the communication cooperation point as the information source and the stay of two nights.Too relative to existing skill, the present invention greatly improves the actually active handling capacity of distributed multi channel networks, reduce the energy consumption of network, significant increase network performance.

Description

A communication method and system for a distributed multi-channel network

technical field

The invention belongs to the field of wireless communication, and in particular relates to a communication method and system of a distributed multi-channel network for cooperative communication through cooperative points.

Background technique

With the rapid development of communication technology, MIMO (Multiple Input Multiple Output) technology has become the focus due to its obvious advantages in wireless communication systems, but limited by the size and energy consumption of user terminal equipment, in distributed networks MIMO technology has not been widely used. However, virtual MIMO is realized through the cooperation of multiple terminals to form a virtual antenna array, which has become a feasible cooperative diversity technology under the current hardware conditions.

Although cooperative diversity technology has been widely studied in the physical layer, the research on cooperative communication in the upper MAC layer has not been fully explored. The MAC layer protocol itself is a technology that determines the right to use channel resources. How to design an effective cooperative MAC protocol to improve system performance has become one of the key technologies to promote the further development of wireless communication.

The MAC protocol used by the current user terminal is usually the IEEE 802.11 MAC protocol. The IEEE 802.11 series of standards are widely accepted industry standards in the industry, and the MAC protocol formulated by the IEEE 802.11 series has long been the de facto MAC standard in the communication field. In the IEEE802.11 standard, the method that the terminal equipment sets different transmission rates according to the channel conditions has become the cornerstone for many practical cooperative MAC protocols to gain considerable development.

In the traditional IEEE 802.11MAC protocol, when the distance between terminals is long and the channel transmission conditions are poor, the source can only use a lower transmission rate to transmit information, which not only affects the performance of the current transmission pair, but also leads to surrounding nodes. It takes a long time to have the opportunity to transmit, which reduces the performance of the system. By introducing a cooperative node that has better channel conditions with the source and sink to coordinate information transmission, a higher transmission rate is obtained and the entire network is improved. actual effective throughput.

In the current cooperative MAC protocol, the cooperative modes of cooperative nodes to the source are usually divided into two types, the cooperative mode based on relay and the cooperative mode based on virtual antenna array (VA). In the relay-based cooperative mode, the successfully selected cooperative nodes and the source and sink have good channel conditions. The source first sends data to the cooperative nodes, and the cooperative nodes then pass AF (amplification and forwarding), DF (decoding and forwarding) ) and other methods to send data to the sink to complete the cooperation, the essence of which is to use high-speed nodes to help low-speed nodes to send information, thereby increasing the data transmission rate. The difference between the VA-based operation method and the relay cooperation method is that the successfully selected cooperative nodes and signal sources jointly form a virtual antenna array, and jointly send information to the signal sink in a space-time coding manner. Compared with relay cooperation, the VA-based cooperation method can greatly improve the data transmission rate, fully realize the cooperative diversity, improve the robustness of the communication, and greatly improve the network performance. However, the VA-based cooperative MAC protocol often needs more The complex protocol process and more severe hardware conditions make the widespread implementation of the protocol still have some practical problems.

In the previous cooperative MAC protocols, the research focus is usually single-channel single-hop topology, especially taking wireless local area network, cellular system and so on as examples. However, with the popularization of user terminal equipment and the intelligentization of hardware equipment, the decentralized wireless distributed network will inevitably become one of the ways for wireless communication to gain greater application. However, for the actual situation of adjacent link multi-channel data transmission However, the problem of allocation and selection of cooperative nodes has not been well solved.

Therefore, under the current hardware conditions, the method based on single-node cooperation has a relatively clear application prospect, but in the case of multi-channel data transmission in a wireless distributed network, the problem of allocation and selection of cooperative nodes has not been implemented and has excellent performance so far. plan.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the shortcomings and deficiencies in the prior art, and to provide a communication method for a distributed multi-channel network.

The present invention is achieved through the following technical solutions:

A communication method for a distributed multi-channel network, comprising the following steps:

Channel control step: After the source successfully preempts the channel through CSMA/CA, it sends an RTS control frame to the sink;

Channel response step: the sink receives the RTS control frame sent by the source, and sends the CTS control frame;

Cooperative node allocation step: Nodes other than the source and sink serve as alternative cooperative nodes, listen to multi-channel RTS frames and CTS frames at the same time, calculate the CSI values of different channels, and assign the cooperative nodes to the one that obtains the maximum CSI. channel;

The optimal cooperative node selection step: for the candidate cooperative nodes that join the same channel, according to the CSI value of each candidate cooperative node, the optimal cooperative node is determined through three group backoff competitions, and the optimal cooperative node sends an RTH frame to preempt the channel, As the communication cooperation point of the information source and the information sink.

Compared with the prior art, the communication method of the distributed multi-channel network of the present invention determines the optimal cooperative node through the CSI value of the channel, and takes into account the overall gain of the cooperative node to the system during the allocation and selection of the cooperative node, which greatly improves the performance of the system. The actual effective throughput of the distributed multi-channel network reduces the energy consumption of the network and greatly improves the network performance.

Further, after the optimal cooperative node selection step, it further includes: a communication mode determination step: if the information source receives the RTH control frame, the information transmission is completed by the cooperative mode; if the RTH control frame is not received, the direct transmission mode is used. Complete the information transfer.

Further, the sink predicts the direct transmission CSI by monitoring the strength of the RTS signal, and places the direct transmission CSI in the CTS control frame, and the sink sends the CTS control frame to notify the source that the direct transmission can be performed in the current CSI state.

Further, the CSI value is calculated by the following formula:

Wherein U _H , U _Z are the actual throughput of the node participating in the cooperation under the current channel and the actual throughput of the direct transmission, respectively, W _H , W _Z are the energy consumption in the cooperative case and the energy consumption in the direct transmission case, respectively.

Further, the calculation formula of the throughput U is:

Among them, T _HCON is the control frame time in the case of cooperation, T _ZCON is the time of the control frame in the case of direct transmission, R _SH is the data transmission rate from the source to the alternative cooperation point, and R _HD is the data transmission from the cooperation point to the accommodation. rate, R _Z represents the data transmission rate from the source to the sink in the case of direct transmission.

Further, the energy consumption W calculation formula is as follows:

W _H =p _HX ×T _HCON +p _HF ×T _HT

W _Z =P _2X ×T _ZCON +P _ZF ×T _ZT

P _HX is the maximum transmit power of all nodes in the case of cooperation, P _HF is the actual data transmission power of the node in the case of cooperation, P _ZX is the maximum transmit power of the node in the case of direct transmission, and P _ZF is the actual data transmission power of the node in the case of direct transmission.

Further, the three-time group backoff competition algorithm is specifically:

First group backoff: by formula The grouping node that determines the minimum gi value participates in the second group backoff;

Second group backoff: by formula The grouping node that determines the minimum mi value participates in the third group backoff;

The third group backoff: through ki=random(min(2×K,K)), randomly assign values to the nodes in the group according to the parameter K, and select the node with the smallest ki value as the optimal cooperative node, where G, M , K is the grouping parameter, G is the number of groups in the first grouping backoff, M is the number of groups in the second grouping backoff, and K is the backoff window value.

Further, the minimum power control algorithm is used to control the transmission power of the nodes in the network, so that the transmission power of the nodes is the minimum while the receiving end just correctly receives the data information. The minimum power control algorithm formula is:

P _F =P _X /10 ^(SNR-θ)/10

Among them, PF is the actual data transmission power of the node, _{P X} is the maximum transmission power of the node, SNR is the instantaneous signal-to-interference noise ratio of the channel, and θ is the threshold value that data can be correctly received under different modulation modes.

In addition, the present invention also provides a communication system of a distributed multi-channel network, including: a source, a sink, an alternative cooperative node and an optimal cooperative node, wherein

After the source successfully preempts the channel through CSMA/CA, it sends an RTS control frame to the sink;

The sink receives the RTS control frame sent by the source, and sends the CTS control frame;

The alternative cooperative node is a node other than the source and the sink, which simultaneously listens to the multi-channel RTS frame and the CTS frame, calculates the CSI values of different channels, and joins the channel that obtains the maximum CSI;

The optimal cooperative node is a cooperative node that joins the same channel. According to the CSI value of each candidate cooperative node, the cooperative node is determined by three times of group backoff competition. The optimal cooperative node sends an RTH frame to preempt the channel as The communication cooperation point of the information source and the information sink.

Compared with the prior art, the communication system of the distributed multi-channel network of the present invention determines the optimal cooperative node through the CSI value of the channel, and considers the overall gain of the cooperative node to the system during the allocation and selection of the cooperative node, which greatly improves the performance of the system. The actual effective throughput of the distributed multi-channel network reduces the energy consumption of the network and greatly improves the network performance.

Further, if the information source receives the RTH control frame, the information transmission is completed in a cooperative manner; if the RTH control frame is not received, the information transmission is completed in a direct transmission manner.

Further, the sink predicts the direct transmission CSI by monitoring the strength of the RTS signal, and places the direct transmission CSI in the CTS control frame, and the sink sends the CTS control frame to notify the source that the direct transmission can be performed in the current CSI state.

Further, the CSI value is calculated by the following formula:

Wherein U _H , U _Z are the actual throughput of the node participating in the cooperation under the current channel and the actual throughput of the direct transmission, respectively, W _H , W _Z are the energy consumption in the cooperative case and the energy consumption in the direct transmission case, respectively.

Further, the calculation formula of the throughput U is:

Among them, T _HCON is the control frame time in the case of cooperation, T _ZCON is the time of the control frame in the case of direct transmission, R _SH is the data transmission rate from the source to the alternative cooperation point, and R _HD is the data transmission from the cooperation point to the accommodation. rate, R _Z represents the data transmission rate from the source to the sink in the case of direct transmission.

Further, the energy consumption W calculation formula is as follows:

W _H =p _HX ×T _HCON +p _HF ×T _HT

W _Z =P _ZX ×T _ZCON +P _ZF ×T _ZT

P _HX is the maximum transmit power of all nodes in the case of cooperation, P _HF is the actual data transmission power of the node in the case of cooperation, P _ZX is the maximum transmit power of the node in the case of direct transmission, and P _ZF is the actual data transmission power of the node in the case of direct transmission.

Further, the three-time group backoff competition algorithm is specifically:

First group backoff: by formula The grouping node that determines the minimum gi value participates in the second group backoff;

Second group backoff: by formula The grouping node that determines the minimum mi value participates in the third group backoff;

The third group backoff: through ki=random(min(2×K,K)), randomly assign values to the nodes in the group according to the parameter K, and select the node with the smallest ki value as the optimal cooperative node, where G, M , K is the grouping parameter, G is the number of groups in the first grouping backoff, M is the number of groups in the second grouping backoff, and K is the backoff window value.

Further, the minimum power control algorithm is used to control the transmission power of the nodes in the network, so that the transmission power of the nodes is the minimum while the receiving end just correctly receives the data information. The minimum power control algorithm formula is:

P _F =P _X /10 ^(SNR-θ)/10

Among them, PF is the actual data transmission power of the node, _{P X} is the maximum transmission power of the node, SNR is the instantaneous signal-to-interference noise ratio of the channel, and θ is the threshold value that data can be correctly received under different modulation modes.

In order to understand the present invention more clearly, the specific embodiments of the present invention will be described below with reference to the accompanying drawings.

Description of drawings

FIG. 1 is a system schematic diagram of the distributed multi-channel wireless network of the present invention.

FIG. 2 is a flow chart of steps of a communication method for a distributed multi-channel wireless network according to the present invention.

FIG. 3 is a schematic diagram of a CTS frame structure of the present invention.

FIG. 4 is a schematic diagram of selecting an optimal node by three-time group backoff competition according to the present invention.

FIG. 5 is a schematic diagram of the RTH frame structure of the present invention.

Fig. 6 is a flow chart of the steps of the cooperation node of the present invention working in the whole communication process.

Detailed ways

Aiming at the allocation and selection of cooperative nodes in the multi-channel transmission of the distributed wireless network, the invention proposes a communication method of the distributed multi-channel network considering the overall performance of the system. The method works in the MAC layer and is based on the IEEE 802.11 protocol. Improvements are made, and cooperative nodes are selected to join in assisting communication by calculating channel CSI (channel state information), which effectively improves the throughput and energy efficiency of the entire system.

The invention relates to the basic communication process and control frame of the IEEE 802.11 protocol. The IEEE 802.11 protocol uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection), that is, the carrier sense multiple access technology with collision detection, to perform channel competition.

In addition, the IEEE 802.11 protocol uses the RTS/CTS handshake method for data communication: first, terminal M sends an RTS signal to terminal N, indicating that M wants to send data to N, and after N receives RTS, it sends a CTS signal to all terminals, indicating that it is ready. , M can start sending data, while other terminals that want to send data to N will suspend sending; the two parties will start the real data transmission after the successful exchange of RTS/CTS signals (that is, the completion of the handshake), ensuring multiple invisible transmissions. When a station sends a signal to the same receiving station at the same time, actually only the station that receives the CTS response from the receiving station can send it, avoiding the occurrence of conflicts. Even if there is a conflict, it is only when the RTS is sent. In this case, since the CTS message from the receiving station cannot be received, the competition mechanism provided by the DCF (distributed coordination function) is used to assign a random backoff timing value and wait for After the next medium idle DIFS (distributed inter-frame gap), the RTS is sent competitively until it succeeds.

As shown in Figure 1, which is a system diagram of a distributed multi-channel wireless network of the present invention, in which node B sends data to D on channel 1, A sends data to C on channel 2, and nodes with good channel conditions around can serve as cooperative node, such as H. The distributed multi-channel wireless network described in the present invention is a completely distributed wireless network, all nodes are equal, and all nodes with good channel conditions can exist as cooperative nodes. That is to say, the more nodes there are, the easier it is for high-performance cooperative nodes to exist. The protocol itself does not have any limit on the number of nodes.

Based on the above inventive idea, the present application is described by the following specific embodiments.

Please refer to FIG. 2 , which is a flow chart of the steps of a communication method for a distributed multi-channel network according to the present invention. The communication method of the distributed multi-channel network of the present invention comprises the following steps:

S1: Channel control step: After the source successfully preempts the channel through CSMA/CA, it sends an RTS control frame to the sink.

The nodes in the distributed network compete for the channel through the CSMA/CD protocol, and use the mode based on the RTS/CTS handshake to reserve and control the channel.

The source node needs to send data. After CSMA/CA successfully preempts the channel, it sends an RTS control frame to the sink after a DIFS time interval. The duration field in the RTS contains the time reserved for the channel, which is used to record the network. Allocation vector (Network Allocation Vector, NAV for short), its calculation formula is as follows:

D _RTS =T _CTS +T _GI +T _MI +T _RE +T _RTH +5SIFS (I)

Among them, T _CTS is the transmission time of the control frame CTS, T _GI is the transmission time of the control frame GI, T _MI is the transmission time of the control frame MI, T _RE is the time consumed by the random backoff process, and T _RTH is the transmission time of the control frame RTH . Among them, the control frame GI is a broadcast control frame, the purpose is to tell the surrounding nodes that the channel is busy at the time, even if there is a better node, there is no need to select it, and the potential cooperative nodes around the place will give up the cooperation after hearing the GI control frame. The control frame MI is used to inform other nodes that the channel is busy and that a better node has appeared.

SIFS (Short interframe space) short interframe space, used for high-priority transmission occasions, such as RTS/CTS and affirmative acknowledgment frames. After a period of SIFS, high-priority transmission can be performed.

After the surrounding co-channel nodes hear the RTS, they will adjust their NAV according to the duration in the control frame. The D _RTS is set in this way to effectively combat the data transmission when the exposed terminal preempts the channel and causes the co-channel competition conflict, resulting in the failure of data transmission. , and also to reserve enough channel control time for cooperative existence to ensure successful cooperative transmission. In addition, the source needs to set a timer to wait for the arrival of the CTS. If the CTS is still not received after the timer is exceeded, the source abandons the transmission, and all source nodes re-enter the back-off process. The timer is set as in the following formula (2):

T _Sa = T _RTS + T _CTS + SIFS (2)

Wherein, T _RTS is the transmission time of the control frame RTS, and T _CTS is the transmission time of the control frame CTS.

S2: Channel response step: the sink receives the RTS control frame sent by the source, and sends the CTS control frame.

After the sink receives the RTS sent by the source, it predicts the direct CSI by listening to the RTS signal strength, and places the direct CSI in the CTS control frame. The sink sends the CTS control frame to notify the source that it can use the current CSI status Direct transmission, and adjust the corresponding receiving mode according to the different data transmission rates of the source. In addition, the surrounding candidate cooperative nodes obtain the direct transmission CSI by listening to the CTS, and further make a cooperative judgment. The channel reservation time and sink timer of CTS are set as follows:

D _CTS =L/R _SH +L/R _HD +T _GI +T _MI +T _RE +T _RTH +T _ACK +6SIFS (3)

T _D =T _CTS +T _GI +T _MI +T _RE +T _RTH +3sIFs(4)

Among them, R _SH is the data transmission rate from the source to the alternative cooperation point, and R _HD is the data transmission rate from the cooperation point to the accommodation.

Although the duration set in the CTS should be different in the direct transmission case and the cooperative case, in order to reserve enough time for the cooperative existence, to prevent the appearance of hidden terminals when the cooperation occurs, the sink cannot receive the RTH correctly, so the formula is as follows: (3) Set _DCTS .

As shown in Figure 3, it is the frame structure of the CTS frame, where Frame Contol is the frame type code, Source Address is the source node address, SNR(HD) is the channel signal-to-noise ratio between the source and the sink, and FCS is the frame calibration. code verification.

S3: step of cooperating node allocation: nodes other than the source and the sink serve as alternative cooperating nodes, listen to multi-channel RTS frames and CTS frames at the same time, calculate the CSI values of different channels, and allocate the cooperating nodes to obtain the maximum CSI value of the channel.

Nodes other than the source and the sink serve as the candidate cooperative nodes. These candidate cooperative nodes simultaneously listen to the candidate cooperative nodes of the multi-channel control frame, such as H in Figure 1, which can simultaneously listen to A-C and B-D. For the control frame information in two different channels, listen to the RTS control frame and the CTS control frame, predict the CSI from the cooperative node to the signal source and the signal sink respectively, and obtain the direct transmission CSI by receiving the CTS control frame.

Channel State Information (CSI) is channel state information. In the field of wireless communication, CSI is a channel attribute of a communication link. It describes the attenuation factor of the signal on each transmission path, that is, the value of each element in the channel gain matrix, such as signal scattering, environmental attenuation, distance attenuation and other information. CSI can make the communication system adapt to the current channel conditions, and provide a guarantee for high-reliability and high-rate communication in a multi-antenna system.

All candidate cooperating nodes can calculate CSI values under different channels through the following formulas 3 to 9. Find the largest CSI value and assign the node to the corresponding channel to participate in the cooperation:

W _H =p _HX ×T _HCON +p _HF ×T _HT (8)

W _Z =P _ZX XT _ZCON +P _XF XT _ZT (9)

Among them, U _H , U _Z are the actual throughput of the node participating in the cooperation under the current channel and the actual throughput of the direct transmission, W _H , W _Z are the energy consumption in the cooperative case and the energy consumption in the direct transmission case, respectively, T _HCON is The control frame time in the case of cooperation, T _ZCON is the time of the control frame in the case of direct transmission, R _SH is the data transmission rate from the source to the alternative cooperation point, R _HD is the data transmission rate from the cooperation point to the accommodation, R _Z represents In the case of direct transmission, the data transmission rate from the source to the sink directly, P _HX is the maximum transmission power of all nodes in the case of cooperation, P _HF is the actual data transmission power of the node in the case of cooperation, and P _ZX is the maximum transmission power of the node in the case of direct transmission. , P _ZF is the actual data transmission power of the node in the case of direct transmission.

S4: The optimal cooperative node selection step: for the candidate cooperative nodes joining the same channel, according to the CSI value of each candidate cooperative node, the optimal cooperative node is determined through three packet backoff competitions, and the optimal cooperative node sends an RTH frame to preempt The channel is used as the communication cooperation point between the information source and the information sink.

After the allocation of cooperative nodes is completed, the optimal cooperative node under the same channel is selected through a three-time grouping backoff competition algorithm, and the three-time grouping backoff competition algorithm is specifically:

First group backoff: by formula The grouping node that determines the minimum gi value participates in the second group backoff;

Second group backoff: by formula The grouping node that determines the minimum mi value participates in the third group backoff;

The third group backoff: through ki=random(min(2×K, K))(12), randomly assign values to the nodes in the group according to the parameter K, and select the node with the smallest ki value as the optimal cooperative node, where G, M, K are grouping parameters, G is the number of groups in the first grouping backoff, M is the number of groups in the second grouping backoff, and K is the backoff window value.

In the Helper node shown in Figure 4, the cooperative channel 1 is selected, and the optimal cooperative node is determined through three group backoff competitions, and finally the Helper node is selected. Then the Helper node cooperates with channel 1 and broadcasts the RTH control frame. The RTH control frame is shown in Figure 5, which includes the CSI from the selected cooperative node to the source and sink, where Frame Contol is the frame type code, and SourceAddress indicates the source node address. , Helper Address represents the address of the Helper node, SNR(SH) and SNR(HD) represent the channel signal-to-noise ratio between the source and the cooperating node, and the channel signal-to-noise ratio between the cooperating node and the sink, respectively. CSI is the channel state information. In this paper, the signal-to-noise ratio (SNR) of the channel is used as the indicator parameter. As shown in Figure 5, the fields of the control frame SNR (SH) and SNR (HD) are the CSI information, and FCS is the frame check code. . The duration is set to the following formula 13, and the cooperating node timer is set according to the formula 14.

D _RTH = L/R _SH + T _ACK + L/R _HD + 3SIFS (13)

T _H =L/R _SH +T _RTH +SIFS (14)

As shown in Figure 4, after receiving the data correctly, the cooperative node sends data information to the sink. The duration setting and cooperating node timer setting in the data frame are as follows:

D _SDDATA = T _ACK + SIFS (15)

T _HDATA = L/R _HD + T _ACK + SIFS (16)

S5: the communication mode determination step: if the source receives the RTH control frame, the information transmission is completed in the cooperative mode; if the RTH control frame is not received, the information transmission is completed in the direct transmission mode.

After the source receives the CTS from the sink, the source waits for a SIFS time interval. If it receives the RTH control frame sent by the cooperative node, the source will use the address of the cooperative node in the RTH and the instantaneous time between the source and the cooperative node. The CSI selects the corresponding modulation mode, and the data transmission rate and transmission power transmit data to the cooperative node address. The duration in the data frame is set as formula (17), and the surrounding nodes are notified to adjust the corresponding NAV. At the same time, the source sets the timer T _Sb again to wait for the ACK (acknowledgement control frame) of the sink, as shown in formula (18)

D _SHDATA = T _ACK + L/R _HD + 2SIFS (17)

T _Sb = L/R _SH + T _ACK + L/R _HD + 2SIFS (18)

If the source does not receive RTH, it adjusts the data transmission rate and transmit power according to the CSI contained in the CTS and sends data directly to the sink. The duration in the data frame is set as formula (19), and the source timer is set as formula ( 20).

D _SDDATA = T _ACK + SIFS (19)

T _sb =L/R _Z +T _ACK +SIFS (20)

If the source successfully receives the ACK, the transmission is successful. If the source does not receive the ACK beyond T _Sb , the system enters the retransmission mechanism or abandons the transmission.

As shown in Figure 5, it is a working flowchart of the cooperative nodes in the distributed multi-channel network in the whole communication process, including steps:

Sh1: The cooperative node is idle listening;

Sh2: judge whether there are channels RTS and CTS at the same time, if not, go to step Sh1 to continue idle listening, if yes, go to step Sh3;

Sh3: Determine whether there is a channel that can cooperate, if not, go to step Sh1 to continue idle listening, if yes, go to step Sh4;

Sh4: determine whether the cooperative node successfully competes for the channel, if not, go to step Sh1 to continue idle listening, if yes, go to step Sh5;

Sh5: Send RTH control frame;

Sh6: judge whether the information of the source is received, if not, go to step Sh1 to continue idle listening, if yes, go to step Sh7;

Sh7: Forward the information to the sink.

In addition, the communication method of the distributed multi-channel network of the present invention adopts the node power control mechanism: since in the distributed network, the energy of all nodes is limited, it is necessary to increase the energy as much as possible while considering the actual effective throughput of the system Utilize efficiency, reduce system energy consumption and prolong node service life. In the node power control mechanism, through the feedback of the channel information, the minimum power algorithm is used to control the power of the node when sending data, so that when the receiving end just receives the data information correctly, the sending power of the sending terminal is the smallest, thus improving the energy. Utilize efficiency and improve system performance. The minimum power control algorithm formula is as follows:

P _F = P _x /10 ^(SNR-θ)/10 (21)

Among them, PF is the actual data transmission power of the node, _{P X} is the maximum transmission power of the node, SNR is the instantaneous signal-to-interference noise ratio of the channel, and θ is the threshold value that data can be correctly received under different modulation modes.

According to the communication method of the distributed multi-channel network of the present invention, this paper also provides a communication system of the distributed multi-channel network, including: a source, a sink, an alternative cooperation node and an optimal cooperation node, wherein

The source and sink compete for the channel through the CSMA/CD protocol, and use the mode based on the RTS/CTS handshake to reserve and control the channel;

The candidate cooperative node is a node other than the source and the sink, which simultaneously listens to the multi-channel RTS frame and the CTS frame, calculates the CSI values of different channels, and joins the channel that obtains the maximum CSI;

The optimal cooperating node is a cooperating node that joins the same channel and is determined by three times of group backoff competition according to the CSI value of each candidate cooperating node. The optimal cooperating node sends an RTH frame to preempt the channel as the The communication cooperation point between the source and the sink.

Compared with the prior art, the communication method and system of the distributed multi-channel network of the present invention determines the optimal cooperative node through the CSI value of the channel, and considers the overall gain of the cooperative node to the system when the cooperative node is allocated and selected. It greatly improves the actual effective throughput of the distributed multi-channel network, reduces the energy consumption of the network, and greatly improves the network performance.

The present invention is not limited to the above-mentioned embodiments. If various changes or deformations of the present invention do not depart from the spirit and scope of the present invention, and if these changes and deformations belong to the claims of the present invention and the equivalent technical scope, then the present invention is also Intended to contain these alterations and variants.

Claims (8)

1. a kind of communication means of distribution multi channel networks, it is characterised in that: the following steps are included:

Channel rate-determining steps: information source is successfully seized after channel by CSMA/CA, sends RTS control frame to the stay of two nights；

Channel response step: the stay of two nights receives the RTS control frame that information source is sent, and sends CTS control frame；

Cooperative node allocation step: node other than information source and the stay of two nights alternately cooperative node, while listening to multichannel letter Road RTS frame and CTS frame calculate the CSI value of different channels, and the cooperative node are assigned to the channel for obtaining maximum CSI；Tool Body, it is calculated by the following formula the CSI value:Wherein, CSI is channel state information, U_H, U_ZRespectively The goodput of cooperation is participated in for present channel lower node and the goodput that direct transfers, W_H, W_ZRespectively energy under collaboration situation Energy consumption in the case of consuming and direct transferring；

Optimal cooperative node selects step: to the alternative cooperative node that same channel is added, according to each alternative cooperative node CSI value is grouped backoff contention three times and determines that optimal cooperative node, the optimal cooperative node send RTH frame and seize channel, make For the communication cooperation point of the information source and the stay of two nights.

2. the communication means of distribution multi channel networks according to claim 1, it is characterised in that: in optimal cooperative node After selecting step, further comprise: communication mode determines step: complete using cooperation mode if information source receives RTH control frame It is transmitted at information；If not receiving RTH control frame, information transmission is completed using the mode of direct transferring.

3. the communication means of distribution multi channel networks according to claim 2, it is characterised in that: the stay of two nights is by detecing RTS signal strength is listened to make prediction the CSI that direct transfers, and the CSI that will direct transfer is placed in CTS control frame, the stay of two nights sends CTS control frame Notify that information source can be to direct transfer under current CSI state.

4. the communication means of distribution multi channel networks according to claim 1, it is characterised in that: the handling capacity U meter Calculate formula are as follows:

Wherein, T_HCONIt is the control frame time under collaboration situation, T_ZCONIt is the time of control frame in the case of direct transferring, R_SHIt is that information source arrives The message transmission rate of alternative cooperation point, R_HDIt is message transmission rate of the cooperation point to lodging, R_ZInformation source in the case of expression direct transfers Directly arrive the message transmission rate of the stay of two nights.

5. the communication means of distribution multi channel networks according to claim 4, it is characterised in that: the energy consumption W Calculation formula is as follows:

W_H=P_HX×T_HCON+P_HF×T_HT

W_Z=P_ZX×T_ZCON+P_ZF×T_ZT

P_HXPower, P are sent for node maximums all under collaboration situation_HFPower, P are sent for collaboration situation lower node real data_ZX To direct transfer, situation lower node maximum sends power, P_ZFTo direct transfer, situation lower node real data sends power.

6. the communication means of distributed multi channel networks described in -5 any claims according to claim 1, it is characterised in that:

It is described to be grouped backoff contention algorithm three times, specifically:

Grouping is kept out of the way for the first time: passing through formulaDetermine that the packet node of minimum gi value participates in Second group is kept out of the way；

Second of grouping is kept out of the way: passing through formulaDetermine the grouping section of minimum mi value Point, which participates in third time group, to be kept out of the way；

Third time grouping is kept out of the way: by ki=random (min (2 × K, K)), being randomly assigned numerical value in grouping according to parameter K Node, and select the node of minimum k i value as optimal cooperative node, wherein G, M, K are packet parameters, and G is to be grouped for the first time Keep out of the way middle group of quantity, M is the quantity that second of grouping grouping keeps out of the way middle group, and K is to keep out of the way window value.

7. the communication means of distribution multi channel networks according to claim 6, it is characterised in that: by using least work Rate control algolithm controls the node transmission power in network, so that while meeting receiving end and being just properly received data information Node sends power minimum, the minimum power control algolithm formula are as follows:

P_F=P_X/10^(SNR-θ)/10

Wherein, P_FPower, P are sent for node real data_XPower is sent for node maximum, SNR is the instantaneous Signal to Interference plus Noise Ratio of channel, θ The threshold values that can be properly received for data under different modulating mode.

8. it is a kind of distribution multi channel networks communication system, it is characterised in that: include: information source, the stay of two nights, alternative cooperative node and Optimal cooperative node, wherein

The information source is successfully seized after channel by CSMA/CA, sends RTS control frame to the stay of two nights；

The stay of two nights receives the RTS control frame that information source is sent, and sends CTS control frame；

The alternative cooperative node is the node other than information source and the stay of two nights, listens to multiplex (MUX) RTS frame and CTS simultaneously Frame, calculates the CSI value of different channels, and is added to the channel for obtaining maximum CSI；Specifically, it is calculated by the following formula described CSI value:Wherein, CSI is channel state information, U_H, U_ZRespectively present channel lower node participates in cooperation Goodput and the goodput that direct transfers, W_H, W_ZEnergy consumption and energy consumption in the case of direct transferring respectively under collaboration situation；

The optimal cooperative node is to the alternative cooperative node that same channel is added, according to the CSI of each alternative cooperative node Value is grouped the cooperative node that backoff contention determines three times, and the optimal cooperative node sends RTH frame and seizes channel, as institute State the communication cooperation point of information source and the stay of two nights.