CN105101448A - A method of data transmission - Google Patents

Abstract

The invention discloses a data transmission method. In a wireless communication network by adopting a CSMA access mechanism, a convergence transmission mechanism is introduced, and thus if data with the service priority is sent in competitive distribution acquired by low user priority service and idle resources still exist, the idle resources can be used for sending data with a higher user priority. By adopting the method of the invention, the transmission resource utilization rate can be improved, and a net channel estimation energy expenditure of a terminal node can be reduced.

Description

A method of data transmission

technical field

The invention relates to wireless communication technology, in particular to a data transmission method.

Background technique

With the intensification of my country's urbanization process and population aging, senile diseases and chronic diseases are becoming more and more common. In addition to bringing heavy economic burdens to patients and society, they also seriously affect the quality of life of patients and family happiness. The emergence of Wireless Body Area Network (WBAN) provides a simple and low-cost means of short-distance communication for home health monitoring of geriatric and chronic diseases. Based on WBAN technology, by arranging corresponding sensing devices on the human body surface or in the body, it automatically collects vital sign parameters such as human ECG, EEG, EMG, body temperature, blood pressure, blood sugar, blood oxygen, etc., to support real-time, convenient, and all-weather human life Sign monitoring. WBAN technology has become an important technical means to improve the efficiency of medical diagnosis, improve the quality of medical services, and carry out new telemedicine and home health monitoring.

Facing the important role of WBAN technology and the huge market demand, it is urgent to carry out standardization work for WBAN technology, realize the standardized management of human body signs and health information, and promote the large-scale application of WBAN technology. As a "human body" sensor network, WBAN has become a strategic research direction for the international medical care and communication industries. IEEE802.15 established the TG6 group in 2007 to carry out WBAN standardization research, and released the world's first WBAN standard - IEEE802.15.6 in March 2012, becoming the only WBAN international standard that has been released so far. The IEEE802.15.6 standard defines the physical (PHY) layer and medium access control (MAC) layer protocol of WBAN transmission, which basically meets the requirements of WBAN. In China, the China Communications Standards Association (CCSA) also passed the research project "Wireless Body Area Network Communication Technology Requirements for Medical and Health Applications" in November 2012. WBAN standard. Judging from domestic and foreign research, there is still a lot of research space and value for WBAN at present, and there is still a lot of work to be done in the research on the practicality and industrialization of WBAN standards in the future.

A typical WBAN network topology is shown in Figure 1. WBAN has a star network topology, in which there is only one central node, which is responsible for managing the access of multiple terminal nodes and coordinating the allocation of wireless resources. The number of terminal nodes in a WBAN can be one or more, and the IEEE802.15.6 standard stipulates that the maximum number of terminal nodes in a WBAN is 256. Frame transmission is directly performed on a 1-hop (1-Hop) link between the central node and the terminal node.

Terminal nodes are usually wearable or implanted in the body, and the equipment is small in size and limited in energy, which puts forward extremely high requirements on energy consumption, so ultra-low power consumption design is required. The terminal nodes are composed of various sensors, which are used to monitor various physical parameters, and the WBAN network mainly contains uplink data. IEEE802.15.6 uses carrier sense multipoint access/collision avoidance (CSMA/CA) random access technology to obtain uplink resources and send uplink data. The working principle of CSMA/CA is: the terminal node first performs Clear Channel Assessment (CCA) to detect whether the wireless channel is occupied, and only when it detects that the channel is idle can it send uplink data.

In the IEEE802.15.6 standard, the terminal nodes of the wireless body area network adopt the channel access method based on CSMA/CA to obtain uplink resources and send uplink data. As shown in Figure 2, a complete CSMA/CA process includes three stages.

(1) Phase 1: CSMA/CA parameter initialization

CSMA/CA parameters include contention window (ContentionWindow, CW), minimum contention window CWmin and maximum contention window CWmax. The values of CWmin and CWmax are determined by the service type. The terminal node sets CWmin and CWmax according to the user priority (UserPriority, UP) of the service to be sent. The mapping relationship between CSMA/CA parameters and UP is shown in Table 1.

user priority wxya CWmax Nmax business type 1 16 32 2 do your best 2 8 32 2 Excellent service 3 8 16 2 video 4 4 16 2 voice 5 4 8 2 general medical data 6 2 8 4 High Priority Medical Data 7 1 4 4 Reporting of medical emergencies

Table 1

The initial value of the CW value is not only related to the service type, but also related to the previous random access and data transmission status of the terminal node. The initial value setting method of CW value is as follows:

Set the CW value to CWmin[UP] if the terminal node has never received a competing allocation before. CWmin[UP] is the CWmin corresponding to the service whose user priority is UP.

If the terminal node successfully sent a MAC frame in the last contention allocation (ie received the acknowledgment ACK of the MAC frame), set the CW value to CWmin[UP].

If the MAC frame sent by the terminal node in the last competition allocation fails (that is, the ACK of the MAC frame is not received), the value of CW is set as follows:

If this is the mth transmission failure of the terminal node, then keep the value of CW unchanged. Among them, m is an odd number;

If this is the nth failure of the end node to send, then the value of CW is doubled. Wherein, n is an even number.

If the doubling of the CW value causes the value of CW to exceed CWmax[UP], the terminal node sets the value of CW to CWmax[UP]. CWmax[UP] is the CWmax corresponding to the service whose user priority is UP.

(2) Phase 2: Generate and maintain rollback counters.

a. Generate a rollback counter

The terminal node generates a uniformly distributed random integer in the range [1,CW] and assigns the value of this number to the backoff counter.

b. Maintenance rollback counter (lock, unlock, decrement)

Lock Backoff Counter: The endpoint locks backoff counter when any of the following conditions are met:

Condition 1. The channel is busy;

Condition 2. The current moment is outside the competitive access period;

Condition 3: The current moment is within the contention access period, but the interval between the end times of the current CSMA time slot and the end times of the contention access period is not enough to send a MAC frame.

Unlocking the backoff counter: The time interval between the end of the current CSMA slot and the end of the contention access period is enough to send a MAC frame, and the terminal node unlocks the backoff counter.

Decrementing the value of the backoff counter: If the backoff counter is unlocked, the terminal node will decrement the value of the backoff counter by 1 every time an idle CSMA time slot passes. The criterion for judging that the channel is idle is: if the channel is idle within pCCATime (63/symbol rate) after the start of the CSMA time slot, the terminal node determines that the CSMA time slot is idle.

(3) Phase 3: Obtain competitive allocation and send MAC frame

If the value of the backoff counter is reduced to 0 in the current CSMA slot, then the terminal node has obtained a contention allocation, which starts at the end of the current CSMA slot and ends at the end of the contention access period. At the start of the contention allocation, the terminal node starts sending MAC frames. After receiving an expected ACK, the terminal node can continue to send other MAC frames (retransmission or new transmission), as long as the UP value of the MAC frame is not lower than the UP value used to obtain this competition allocation.

It can be seen from the above CSMA/CA process that the UP value is inversely proportional to the contention access delay: the larger the UP value, the smaller the channel access delay; the smaller the UP value, the greater the channel access delay. The IEEE802.15.6 standard stipulates that the UP value of the MAC frame sent by the terminal node in the contention allocation cannot be lower than the UP value used when obtaining the contention allocation, that is, after the terminal node obtains the contention allocation, it can only send priority frames in the contention allocation. MAC frames greater than or equal to UP. The purpose of setting this regulation is to prevent malicious terminal nodes from occupying channel resources for a long time and affecting the normal data transmission of other devices. If not constrained by this criterion, each terminal will tend to use a high user priority value to seize channel resources, and use the channel resources to send data with low user priority after occupying the channel resources. According to this regulation, the smaller the UP value, the less chance of being sent; the larger the UP value, the greater the chance of being sent.

It can be seen that when there are multiple services with different UP values in the cache, it is necessary to adopt a reasonable channel access strategy: on the one hand, using a larger UP value can reduce the delay in accessing the channel; on the other hand, Using a smaller UP value can reduce the queuing delay of low-priority data. Therefore, when a variety of data with different user priorities are stored in the cache of the terminal node, how to improve the energy efficiency of data transmission and reduce the transmission delay by setting CSMA/CA parameters and adopting a reasonable channel access method is an important issue. A question that needs to be studied in depth.

Through the energy consumption analysis of CSMA/CA, it is found that for services with fixed user priority, no matter how much data is sent at a time, the same CCA energy will be consumed. In this way, the energy efficiency of data transmission can be maximized only when the MAC frame with the maximum transmittable data is transmitted in each transmission. The existing data transmission method adopts an independent transmission mechanism, that is, each service uses its own UP value to compete for access, and only sends its corresponding service data within the obtained competition allocation. In practical applications, a user needs to transmit The business data is not necessarily an integer multiple of the maximum number of MAC frames N _max that can be sent in each contention access. In this way, the actual amount of transmitted data is less than the amount of data that can be transmitted, resulting in transmission resource utilization. , which in turn leads to an increase in the total number of competing accesses in the system, which ultimately leads to an increase in system CCA energy overhead.

It can be seen that for a wireless communication network that introduces the CSMA access mechanism, due to the limitation of the maximum number of MAC frames N _max that can be sent in each contention access, the terminal node adopts the existing data transmission method, and there will be transmission resources The reduction of utilization rate and the large energy consumption of net channel assessment.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a data transmission method, which is applied to a wireless communication network using a CSMA access mechanism, can improve the utilization rate of transmission resources of uplink data, and reduce the energy of terminal net channel evaluation overhead.

In order to achieve the above object, the technical scheme proposed by the present invention is:

A data transmission method comprising:

a. For the data of each type of service i in the cache, the terminal node groups the data of the service i according to the maximum number N _{max_i} of MAC frames of the medium access control layer that the service can send in one competition allocation, and obtains the Ti group data ; wherein, the The N _i is the number of MAC frames contained in the data of the service i;

b. For all group data whose number of MAC frames does not reach the N _{max_i} of the service to which it belongs, according to the priority of the service to which the data belongs, reorganize according to the principle of combining high-priority service data with low-priority service data as much as possible, Wherein, each group of data after reorganization satisfies: the number of MAC frames in the group is less than N _{max_k} , and said N _{max_k} is the maximum number of MAC frames that can be sent in one competition allocation for the minimum priority service k corresponding to the data in the group;

c. For each current set of data, the maximum priority of the business corresponding to the set of data is used as the priority of the set of data; sort all sets of data according to the descending order of the priority of the data set;

d. For each set of sorted data, use the priority of the set of data to compete for access, and send the MAC frame of the set of data within the obtained contention allocation.

In summary, the data transmission method proposed by the present invention introduces a converged transmission mechanism. In a wireless communication network using a CSMA access mechanism, a converged transmission mechanism is introduced so that if the data transmission method is sent within the contention allocation obtained by a low user priority service If there are idle resources for service priority data, the idle resources can be used to send data with a higher service priority, thereby improving the utilization of transmission resources and reducing the net channel assessment energy overhead of terminal nodes.

Description of drawings

FIG. 1 is a schematic diagram of a WBAN star network topology;

Figure 2 is a schematic diagram of the CSMA/CA process;

FIG. 3 is a schematic flow chart of Embodiment 1 of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The core idea of the present invention is: in the wireless communication network adopting the CSMA access mechanism, introduce the convergence transmission mechanism, so that if there are idle resources when sending the data of this service priority in the contention allocation obtained by the low user priority service, Then, the idle resource can be used to send data with a higher service priority, so that the utilization rate of the transmission resource can be improved, and the net channel evaluation energy cost of the terminal node can be reduced.

Fig. 3 is a schematic flow chart of Embodiment 1 of the present invention, as shown in Fig. 3, this embodiment mainly includes:

Step 301. For the data of each type of service i in the buffer, the terminal node groups the data of the service i according to the maximum number N _{max_i} of MAC frames that can be sent by the service in one competition allocation, and obtains the T _i group data.

Among them, the The N _i is the number of MAC frames contained in the data of the service i, Represents the round-up function.

In this step, the maximum number N _{max_i} of MAC frames that can be sent by the service in one competition allocation is used as the number of standard MAC frames included in the unit group, and the data of various services in the current cache of the terminal node are grouped.

When the number of MAC frames contained in the data of a class of business does not reach the N _{max_i} of the business, only one set of data can be obtained after grouping. When it exceeds N _{max_i} , multiple sets of data will be obtained. In this case, if one When the number of MAC frames included in the number of business types is not an integer multiple of N _{max_i} , there will be a group of data whose number of MAC frames does not reach N _{max_i} . For this data group, data reorganization needs to be performed in subsequent steps to improve data Utilization of transmission resources.

Specifically, when T _i =1, the number of MAC frames contained in the T _i group of data is N _i ; when T _i >1, if N _i %N _{max_i} ≠0, % represents the remainder function, then the previous T _i The number of MAC frames contained in -1 group of data is N _{max_i} , the number of MAC frames contained in the Ti-th group of data is N _i %N _{max_i} , otherwise, the number of MAC frames contained in each group of data is N _{max_i} ; said N _i is the business The number of MAC frames contained in the data of i; the N _{max_i} is the maximum number of MAC frames that can be sent by the service i in one contention allocation.

Step 302: For all group data whose number of MAC frames does not reach the N _{max_i} of the service to which the data belongs, according to the priority of the service to which the data belongs, reorganize according to the principle of combining high-priority service data with low-priority service data as much as possible , wherein, each group of data after recombination satisfies: the number of MAC frames in the group is less than N _{max_k} , and N _{max_k} is the maximum number of MAC frames that can be sent by the minimum priority service k corresponding to the data in the group in one competition allocation.

In this step, according to the priority of the business to which the data belongs, according to the principle of combining high-priority business data with low-priority business data as much as possible, all group data containing MAC frames that do not reach the N _{max_i} of the business to which they belong Regroup. In this way, idle resources of low-priority services can be fully utilized to carry high-priority service data. In this way, transmission resources within contention allocation can be fully utilized to improve transmission efficiency and avoid resource waste under an independent transmission mechanism.

Preferably, step 302 can be implemented by the following steps:

Step 3021 : For all group data whose number of MAC frames does not reach the N _{max_i} of the service to which it belongs, sort them in descending order of the priority of the corresponding service to obtain a reassembly queue, and initialize the reassembly data set to be empty.

Step 3022, judging whether a set of data at the head of the reassembly queue is put into the current reassembly data set and whether the total number of MAC frames in the reassembly data set is not greater than N _{max_k} , and the N _{max_k} is that service k is in a competition The maximum number of MAC frames that can be sent within the allocation, the service k is the service corresponding to a group of data at the head of the team, if satisfied, go to step 3023; otherwise go to step 3024.

This step is used to judge whether a group of data at the head of the team can be reorganized with the data in the current reorganized data set, whether the judgment condition is satisfied: whether the total number of MAC frames in the set after it is added to the reorganized data set is not greater than the The group data corresponds to N _{max_k} of the service.

If it is not greater than N _{max_k} , it means that it meets one of the reassembly conditions in step 302 after being combined with the data in the current reassembly data set, that is, it can ensure that the number of MAC frames in the group is less than the minimum priority service corresponding to the data in the group. The maximum number of MAC frames that can be sent in a competition allocation. In addition, since it is based on sorting according to the business priority in step 3021, it is judged from the head of the team one by one. Compared with the data groups existing in the reorganized data set, the priority is low, so that the principle of combining high-priority service data with low-priority service data as much as possible can also be ensured. Therefore, here, when it is judged that it is not greater than N _{max_k} , execute 3023 to add the data group of the head of the team into the reorganized data set.

If it is greater than N _{max_k} , it means that the group of data cannot be reorganized with the data in the current reorganized data set. Therefore, step 3024 needs to be performed to recombine the data in the current reorganized data set to obtain a new data group.

Step 3023. Put a set of data at the head of the queue into the reorganized data set, and delete it from the reorganized queue, and execute step 3025.

Step 3024, reorganize the data in the reorganized data set into a set of data, cancel the corresponding original grouping, and make the reorganized data set empty.

In this step, the data in the current reorganized data set is reassembled to obtain a new set of data, and the data packets corresponding to these data before do not exist, and then these data will be transmitted based on the new data packets.

Step 3025 , judging whether the reassembly queue is currently empty, if yes, go to step 303 , otherwise, go to step 3022 .

This step is used to perform step 3022 to continue reorganizing a new set of data until all data groups in the queue are reorganized if there is unreorganized data in the current reorganization queue after obtaining a new data packet , that is, the queue is empty, then step 303 is executed, and data is sent based on all current data packets.

Step 303 , for each current group of data, use the highest priority of the service corresponding to the group of data as the priority of the group of data; sort all the group data according to the descending order of the priority of the data group.

Here, since some current data packets after step 302 are combined by data of multiple services, it is necessary to determine the service priorities corresponding to these packets. In this step, the maximum priority of the service corresponding to a group of data is taken as the priority of the group of data, so as to ensure that the transmission needs of high-priority services in the group are met.

Step 304 , for each group of sorted data, use the priority of the group of data to compete for access, and send the MAC frame of the group of data within the obtained contention allocation.

In the above technical solution, the aggregation transmission mechanism is introduced so that if there are idle resources when sending the data of this service priority within the contention allocation obtained by the low user priority service, the idle resource can be used to send data with a higher service priority. data, so that the utilization rate of transmission resources can be improved, and the energy cost of net channel estimation of the terminal can be reduced. It should be noted that the present invention is not only applicable to wireless body area networks, but in practical applications only using the CSMA access mechanism, there will be the above-mentioned problem of waste of resources. Therefore, the present invention is applicable to all wireless communications using the CSMA access mechanism in the network.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (3)

1. a data transmission method, is characterized in that, comprising:

A, data for class business i every in buffer memory, the media access control layer mac frame quantity N that terminal node can send at most in a competitory assignment according to business _{max_i}, the described data of this business i are divided into groups, obtain T _igroup data; Wherein, described in described N _ifor the mac frame number that the described packet of business i contains;

B, comprised mac frame number is not reached to the N of affiliated business _{max_i}all groups of data, the priority of business belonging to data, according to high-priority service data as far as possible with the principle of low priority traffice data assemblies, recombinate, wherein, each group of data after restructuring meet: the mac frame quantity in group is less than N _{max_k}, described N _{max_k}for organizing the mac frame quantity that minimum priority service k corresponding to interior data can send at most in a competitory assignment;

C, for current often group data, using the priority of the greatest priority of business corresponding for these group data as these group data; According to the descending of data group priority, all groups of data are sorted;

D, for the often group data after sequence, utilize the priority of these group data to be at war with access, and send the mac frame of these group data in the competitory assignment of acquisition.

2. method according to claim 1, is characterized in that, described step b comprises further:

B1, comprised mac frame number is not reached to the N of affiliated business _{max_i}all groups of data, sort according to the descending of the priority of corresponding business, obtain one restructuring queue, recombination data set is initialized as sky;

B2, judge whether one group of data of described restructuring queue Head-of-line meet after putting into current recombination data set: the mac frame sum of recombination data set is not more than N _{max_k}, described N _{max_k}for the mac frame quantity that business k can send at most in a competitory assignment, described business k is business corresponding to one group of data of described Head-of-line, if met, then performs step b3; Otherwise perform b4;

B3, one of described Head-of-line group of data is put into described recombination data set, and delete from described restructuring queue, perform step b5;

B4, the data in described recombination data set are reformulated one group of data, and cancel corresponding original grouping, sky is put in recombination data set;

B5, judge described restructuring queue current be whether empty, if so, then perform step c, otherwise, perform b2.

3. method according to claim 1, is characterized in that, works as T _iwhen=1, this T _ithe mac frame number that group packet contains is N _i; Work as T _iduring >1, if N _i%N _{max_i}≠ 0, then T before _ithe mac frame number that-1 group packet contains is N _{max_i}, the mac frame number that Ti group packet contains is N _i%N _{max_i}, otherwise the mac frame number that often group packet contains is N _{max_i}.