CN101489304A - Media access control method based on differentiate service of wireless multimedia sensor network - Google Patents

Abstract

The media access control method based on the differentiated service of the wireless multimedia sensor network relates to the design of the MAC layer protocol of the wireless multimedia sensor network, and is mainly used for providing differentiated services for different services. When there are audio and video information in the multimedia sensor network, and there may be text information at the same time, different applications require different QoS. At this time, it is required to design a MAC protocol that can provide differentiated services for different services, and at the same time realize the effective use of resources in the entire network. use. The method of the present invention proposes a MAC protocol based on a differentiated service of a wireless multimedia sensor network, adopts a dynamic time slot allocation scheme according to a service level, thereby achieving a differentiated service MAC protocol based on TDMA, and adjusts according to a service by dividing multi-layer time slots Time slot allocation, while dynamically adjusting the service level, and increasing the dormancy of inactive nodes, thus prolonging the life of the wireless multimedia sensor network and improving the coordination and quality of service of the sensor network.

Description

Media Access Control Method Based on Differentiated Services in Wireless Multimedia Sensor Networks

technical field

The invention relates to the design of the MAC layer protocol of the wireless multimedia sensor network, and is mainly used for providing differentiated services for different services.

Background technique

Wireless multimedia sensor network is a distributed sensor network composed of a group of multimedia sensor nodes with perception, computing and communication capabilities. It collects various media information (audio, video, image, etc.) of the surrounding environment through the multimedia sensor on the node, and collects the data to the aggregation node through multi-hop mode to realize comprehensive and effective environmental monitoring.

In wireless multimedia sensor networks, the transmitted data is mainly audio and video data. The amount of video data information is huge. If the video data is continuously transmitted on the wireless link, the wireless channel bandwidth will become the bottleneck of the system. The network will quickly run out of energy, and the life cycle of the network will be greatly shortened. The medium access control (MAC, medium access control) protocol is used to establish a reliable point-to-point, point-to-multipoint or multi-point shared communication link technology. It is the direct controller who sends and receives control messages on the wireless channel, solves the problem of how the nodes in the wireless sensor network share the media to ensure satisfactory network performance, and whether the MAC protocol can efficiently use the wireless channel is the guarantee for wireless multimedia sensors. One of the most critical factors of network communication.

When there are audio and video information in the multimedia sensor network, and there may be text information at the same time, different applications require different QoS. At this time, it is required to design a MAC protocol that can provide differentiated services for different services, and at the same time realize the effective use of resources in the entire network. use.

Most of the existing wireless sensor network MAC protocol research assumes that it is based on a single "best effort" (best effort) data transmission service model, and all kinds of services compete equally for network resources. Service transmission with high quality of service requirements.

Competition-based MAC protocols, such as S-MAC, T-MAC, Sift, etc., can greatly reduce the chance of collisions and achieve the purpose of reducing energy consumption by solving problems such as collision retransmission, idle listening, and excessive control information. They are usually difficult to guarantee real-time requirements, and are suitable for some networks that do not require high predictability, and are not suitable for multimedia sensor networks.

The contention-free single-channel MAC protocol is mainly based on the TDMA mechanism. There is no collision and retransmission problem in the contention mechanism, and there is no need for too much control information during data transmission. The node can go to sleep in time when the slot is idle to save energy. It can be applied through improvement to multimedia sensor networks. Clustered TDMA, DEANA, TRAMA, etc. are based on TDMA, but statically and fixedly allocate time slots, so it is difficult to meet the requirements of service differentiation.

Contents of the invention

Technical problem: The purpose of the present invention is to provide a media access control method based on differentiated services in wireless multimedia sensor networks, which is used to solve the unbalanced transmission of MAC protocol services in existing wireless sensor networks and poor adjustability. The invention provides differentiated services for different applications of the multimedia sensor network, and significantly improves resource utilization and transmission efficiency of the multimedia sensor network.

Technical solution: Time division multiplexing is a simple and mature mechanism for realizing channel allocation. The TDMA mechanism is adopted in the sensor network, which is to allocate an independent time slot for data transmission or reception for each node, and the nodes switch to other idle time slots. to sleep. The TDMA mechanism does not have the collision retransmission problem of the competition mechanism, but requires strict time synchronization of nodes. Most sensor networks use the energy wake-up mechanism of listening/sleeping, and use time synchronization to realize automatic conversion of node states. The TDMA mechanism has shortcomings in network scalability: it is difficult to adjust the length of the time frame and the allocation of time slots.

Aiming at the lack of network expansion of TDMA, the present invention designs a dynamic time slot control method on the basis of TDMA, so that the multimedia sensor network can provide different services according to business types.

Method flow:

The steps included in the MAC protocol design process of differentiated service based on wireless multimedia sensor network are as follows:

1. a kind of medium access control method based on wireless multimedia sensor network differentiated service, it is characterized in that the method comprises the following steps:

Step 1) Define the service priority: according to the requirements of the service quality of the audio, video and text information of the current application, the data is delayed and the data packet loss rate is set to the corresponding service level, that is, the service priority;

Step 2) Define the frame structure: time division multiplexing assigns fixed time slots to each node for sending and receiving data, and on this basis, a frame structure is designed, which includes 3 subframes: State (state) subframe, Allocate (allocation) subframe, Action (behavior) subframe;

Step 3) Design State subframe: include SNodeID (source node number), SendFlag (send data flag bit), DataSize (data packet size), PRI (data priority flag) successively, and this priority is based on the service designed in step 1) Priority acquisition, time slot occupancy flag TimeUsed (time slot occupancy flag);

Step 4) design Allocate subframe: comprise SNodeID (source node number), DNodeID (target node number), DataNum (data grouping number) successively;

Step 5) Designing the Action subframe: including sending data Data (sent data);

Step 6) time slot initialization: assuming that there are N nodes in this wireless multimedia sensor network, the three types of subframes mentioned in step 2) are each divided into N sub-slots, that is, there are 3*N sub-slots; Arranged in the order of State->Allocate->Action, microscopically, each subframe is arranged in the order of each node time slot, and sub-slot i is the main time slot of node i;

Step 7) State frame initialization: complete the current node state confirmation behavior of the State subframe, if this node has a request to send data, fill in the source node number, send data flag, data packet size, data priority flag; if there is no data transmission request, Fill in the sending data flag, the data packet size, and the data priority flag are 0, during which other nodes are in a dormant state, and automatically wake up in sequence according to the time processing and repeat step 7);

Step 8) complete the dynamic time slot allocation process: finally obtain the State subframe according to step 7, set an Action time slot to send K data packets; first locate the node with the highest SendFlag=1 and PRI, check its data packet size, if less than K, then confirm that this slot is occupied, and set TimeUsed=1; if it is greater than K, it means that this sub-slot is not enough to send the entire data packet at one time, and other time slots need to be occupied for sending. Query the node with SendFlag=0 and TimeUsed=0 in the frame, if it exists, use this slot to send the remaining data, and set the SNodeID of this slot to the SNodeID of the current node and TimeUsed to 1 to indicate that it is already occupied; if it does not exist , query the node with the smallest PRI, the smallest DataSize and TimeUsed=0, occupy the time slot of this node, set TimeUsed=1, and set SNodeID to the SNodeID of the current node; if the remaining data size still exceeds K, execute this step in a loop , until all the data is assigned to the low priority time slot; when the slot occupancy is completed, there must be some data with low priority that cannot be sent, and will still be stored in the data sending buffer. In order to avoid such data from dying Locks can never be sent, and the priority will be raised by one level in the next State state to improve competitiveness;

Step 9) Allocate phase: all time slot allocation information is reflected in the State frame; the Allocate phase fills the Allocate frame structure according to the information in the State frame, and visits sequentially according to the order of nodes, and the node of SendFlag=0 in the State frame is It is still in a dormant state when accessing; if the current node number is the same as the SNodeID in the State subframe, assuming that the number of SNodeIDs in the State subframe is n, divide the data packet to be sent into n parts, and fill them in the Allocate subframe according to the order of node access In the corresponding time slot in the frame, specifically fill in the source node number SNodeID, the destination node number DNodeID, and the data transmission number DataNum, and visit each node in turn according to the above operation to complete the allocation of the Allocate subframe;

Step 10) Action stage: visit each current node in turn, when this node corresponds to SendFlag=0 in the State subframe, calculate according to the sleep time designed so as to sleep in this period of time; otherwise, according to the SNodeID and DNodeID of the Allocate corresponding frame Fill data packet items with DataNum, and wake up the target node to receive data according to DNodeID;

Follow the above operations to visit each node to complete the data sending and data receiving of all nodes.

Beneficial effects: the method of the present invention proposes a MAC protocol based on differentiated services in wireless multimedia sensor networks, and adopts a dynamic time slot allocation scheme according to service levels to achieve a differentiated services MAC protocol based on TDMA, which has the following beneficial effects.

(1) A single time slot is subdivided into multiple time slots, and some fine control time slots are divided to complete the preliminary preparation and dynamic time slot allocation process of time slot allocation, which increases the flexibility of time slot allocation and facilitates custom services The grades are adapted to differentiated service applications and guarantee the quality of service.

(2) The subdivision of time slots increases the sleep time of inactive nodes, reduces the waste of node resources, and prolongs the life cycle of wireless multimedia sensors.

(3) The setting of dynamic service priority effectively ensures that all sensory data can be sent out safely without sending deadlock.

Description of drawings

Figure 1 MAC layer macro frame structure diagram.

Figure 2 MAC layer micro frame structure diagram.

Fig. 3 is based on the MAC protocol design flowchart of the differentiated service of the wireless multimedia sensor network.

Detailed ways

The specific process of the MAC protocol based on the differentiated services of the wireless multimedia sensor network is as follows:

Step 1) Define service priority.

According to the current application (audio, video, text information, etc.) service quality requirements, such as data delay, data packet loss rate, etc., set the corresponding service level, that is, the service priority. According to the general application of multimedia sensor networks, to avoid the high delay of audio and video information and affect the reception effect, here we define the video data as the highest priority 3, the audio data as 2, and the text information as 1. Of course, these settings can be modified according to different applications.

Step 2) Define the frame structure.

Time-division multiplexing assigns each node a fixed time slot for sending and receiving data. On this basis, a frame structure is designed. This frame structure includes 3 subframes: State subframe, Allocate subframe, and Action subframe.

a) Design the State subframe: the State subframe mainly records whether each node needs to send data and some specific information required when sending data. It includes the source node number SNodeID, the sending data flag SendFlag, the data packet size DataSize, the data priority flag PRI, and the time slot occupancy flag TimeUsed.

Frame structure details:

SendFlag: = 1 indicates that there is data to be sent;

= 0 means no data is sent.

PRI: Acquired according to the service priority designed in step 1.

TimeUsed: = 1 indicates that this slot has been occupied;

= 0 means that the slot is not occupied yet.

b) Design the Allocate subframe: the Allocate subframe mainly determines the occupancy of each time slot according to the designed time slot allocation algorithm based on the information of each time slot recorded in the State subframe. Contains the source node number SNodeID, the target node number DNodeID, and the data packet number DataNum in turn.

c) Design Action subframe: Action subframe contains sending data Data

Step 3) Timeslot initialization.

Assuming that there are N nodes in the wireless multimedia sensor network, each of the three types of subframes mentioned in step 2 is divided into N subslots, that is, there are 3*N subslots. Macroscopically, it is arranged in the order of State->Allocate->Action, and microscopically, each subframe is arranged in the order of each node number, and sub-slot i is the main time slot of node i.

Step 4) State frame initialization

Complete the state confirmation behavior of the current node in the State subframe, visit a single node in sequence according to the node number, this node will automatically wake up according to time division multiplexing, and other nodes will remain in a dormant state. Monitor whether the wake-up node has a request to send data, and fill in the State frame structure.

There is a data sending request: SendFlag=1;

DataSize is filled according to the actual data packet size;

PRI is filled according to the currently sent data type;

TimeUsed = 0.

No data sending request: SendFlag=0;

DataSize=0;

PRI = 0;

TimeUsed = 0.

After monitoring, the awakened node enters the dormant state, continues to wake up automatically in sequence and processes other nodes according to this process, until all nodes complete the State frame status confirmation.

Step 5) Complete the dynamic slot allocation process

The State subframe is finally obtained according to step 4, and K data packets can be sent in one Action time slot. First locate the node with SendFlag=1 and the highest PRI, check the size of its data packet, if it is less than K, then confirm that this slot is occupied, and set TimeUsed=1; if it is greater than K, it means that this sub-slot is not enough to send a complete packet at one time Data packets need to occupy other time slots for sending. Firstly, query the node with SendFlag=0 and TimeUsed=0 in the State subframe of other nodes. SNodeID is set to the SNodeID of the current node and TimeUsed is set to 1, indicating that it is already occupied; if it does not exist, query the node with the smallest PRI, the smallest DataSize and TimeUsed=0, occupy the time slot of this node, set TimeUsed=1, and set SNodeID It is the SNodeID of the current node. If the size of the remaining data still exceeds K, execute this step in a loop until all data are allocated to low-priority time slots. When the slot occupation is completed, there will inevitably be some data with low priority that cannot be sent and will still be stored in the data sending buffer. In order to avoid deadlock of this kind of data, it will never be sent. In the next State state, the priority will be set automatically Move up a level to increase your competitiveness.

Step 6) Allocate stage

After completing the dynamic slot allocation process, all slot allocation information is reflected in the State frame. In the Allocate stage, the Allocate frame structure is filled according to the information in the State frame. The nodes are visited sequentially, and the nodes with SendFlag=0 in the State frame are still in the dormant state when they are visited. If the current node number is the same as the SNodeID in the State subframe, assuming that the number of SNodeIDs in the State subframe is n, divide the data packet to be sent into n parts, and fill them in the corresponding time slots in the Allocate subframe according to the order of node access. Fill in the source node ID SNodeID, destination node ID DNodeID, and data sending ID DataNum. Follow the above operations to visit each node in turn to complete the Allocate subframe allocation.

Step 7) Action stage

This stage is the data sending stage, and each current node is visited in turn. When SendFlag=0 in the corresponding State subframe of this node, it is calculated according to the designed sleep time to sleep during this time. On the contrary, according to the SNodeID, DNodeID and DataNum of the frame corresponding to Allocate, the data packet item is filled, and at the same time, the target node is awakened to receive data according to the DNodeID. Follow the above operations to visit each node to complete the data sending and data receiving of all nodes.

Claims (1)

1. media access control (MAC) method applicable based on the wireless multimedia sensor network Differentiated Services is characterized in that this method may further comprise the steps:

Step 1) definition service priority: according to the audio frequency of current application, video, the requirement of the service quality of text message, with data delay, the data packet loss is set the corresponding grade of service, i.e. service priority;

Step 2) definition frame structure: time division multiplexing distributes fixing time slot to be used for transceive data for each node, designs a kind of frame structure on this basis, and this frame structure comprises 3 subframes: the state subframe, distribute subframe, the behavior subframe;

Step 3) design point subframe: comprise source node SNodeID successively, send Data Labels position SendFlag, data packet size DataSize, data priority mark P RI, this priority is obtained Time Slot Occupancy sign TimeUsed according to the service priority of step 1) design;

The step 4) design distributes subframe: comprise source node SNodeID successively, destination node DNodeID, packet numbering DataNum;

Step 5) design behavior subframe: comprise transmission data Data;

The initialization of step 6) time slot: supposing has N node in this wireless multimedia sensor network, with step 2) in the 3 class subframes mentioned respectively be divided into and be N sub-slots, 3*N sub-slots promptly arranged; On the macroscopic view according to state State-distribute Allocate-the sequence arrangement of behavior Action, each subframe is arranged by each node time-slot sequence on the microcosmic, sub-slots i is the main time slot of node i;

The initialization of step 7) state subframe: the behavior of completion status subframe present node state confirmation, if this node has the transmission data demand, fill source node number, send the Data Labels position, data packet size, data priority sign; If free of data sends requirement, fill and send the Data Labels position, data packet size, data priority is masked as 0, other nodes are in resting state during this period, wake repeated execution of steps 7 successively automatically up according to the processing of time);

Step 8) is finished the dynamic slot assigning process: finally obtain the state subframe according to step 7, establish an Action time slot and can send K data grouping; At first locate SendFlag=1 and the highest node of PRI, check its data packet size,, confirm that then this time slot is occupied, TimeUsed=1 is set if less than K; If greater than K, representing then that this sub-slots is disposable sends whole packet inadequately, need take other time slots sends, at first in the State of other nodes subframe, inquire about the node of SendFlag=0 and TimeUsed=0, if exist, then take this time slot and send remaining data, and the SNodeID of this time slot is set to the SNodeID of present node and TimeUsed and is set to 1 expression and takies; If do not exist, inquiry PRI minimum, the node of DataSize minimum and TimeUsed=0 takies the time slot of this node, and TimeUsed=1 is set, and SNodeID is set to the SNodeID of present node; If the remaining data size still surpasses K, then this step is carried out in circulation, all is assigned in the time slot of low priority up to all data; When time slot take finish after, will inevitably the low data of some priority can not send, still be kept at data and send in the buffering area, for fear of this type of data generation deadlock, can not be sent out forever, when State state next time with priority from promoting one-level to improve the competitiveness;

The step 9) allocated phase: all time slot allocation information all embody in the State frame to some extent; The Allocate stage is promptly filled the Allocate subframe structure according to the information in the State subframe, visits successively according to node sequence, still is in resting state when the node of SendFlag=0 is accessed in the State subframe; If present node number is identical with SNodeID in the State subframe, the quantity of supposing SNodeID in the State subframe is n, packet to be sent is divided into n part, be filled into time slot corresponding in the Allocate subframe successively according to the node visit order, the concrete source node SNodeID that fills, destination node DNodeID, data send numbering DataNum, finish the Allocate sub-frame allocation thereby visit each node successively according to as above operation;

Step 10) behavioral phase: visit each successively and work as node,, thereby calculate dormancy in during this period of time according to the dormancy time of design when in this node corresponding states subframe SendFlag=0 the time; Otherwise according to the SNodeID of the corresponding frame of Allocate, DNodeID and DataNum padding data bag item receive data according to DNodeID wake up target node simultaneously;

Thereby the data of finishing all nodes according to as above each node of operational access send and Data Receiving.

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