The article introduces the mode and characteristics of machine communication. The most prominent feature is that the reverse small-flow service is the main body of machine communication. And the evolution trend of the communication network bearer machine communication is divided into three stages: namely, mixed bearer, differentiated bearer and independent bearer. The article believes that the initial stage of the machine communication business is to adapt the business to the network; and if the machine communication business is scaled to a certain extent, the network should adapt to the business.
Machine communication business will accelerate development in the direction of scale, ubiquity and industrialization
Machine communication has unique communication modes and characteristics, which put forward new requirements for communication networks
The evolution of communication network bearer machine communication can be divided into three stages: mixed bearer stage, differentiated bearer stage and long-term independent bearer stage
Since the birth of the communication network, it has always been the goal of meeting people's voice communication. After the rise of the Internet, in order to carry various new types of data communication services, corresponding evolutions have taken place at the access network, core network, and transmission network levels. Now, with the vigorous development of machine communication services and good expectations for its future, the evolution of communication networks has gained an important impetus.
1 Machine communication overview
Machine communication, also known as M2M communication, refers to a communication form in which one or both parties of a communication are machines, and the machine can automatically complete the entire communication process through program control. Machine communication includes machine-to-machine, man-to-machine and machine-to-man communication services. Through machine communication, not only can information be exchanged between machines, but machines can also respond to control commands from humans or back-end systems (also a type of machine), or transmit the collected information to humans or back-end systems. The machine communication business that this article focuses on mainly refers to the machine communication business of wide-area interconnection with the help of the telecommunications operator's communication network (hereinafter referred to as "communication network"). At the same time, the focus of the discussion is mainly on the machine communication service using mobile cellular network access.
Machine communication services already exist, but on the one hand, some machine communication services have nothing to do with public communication networks. For example, in some specific industries, data acquisition and monitoring system (SCADA) has long been used as a communication method for long-distance data collection and device control ; On the other hand, the business has not yet reached a certain scale, so the attention is relatively low.
As an important part of the Internet of Things system, the machine communication business started from the second half of 2009, and it seems that it has suddenly received the attention of the society, forming a new wave of industry. It is found that on the one hand, machine communication is currently used in many fields: environment-aware applications, in-vehicle information applications, wireless financial payment applications, telemetry applications, and asset monitoring applications; on the other hand, machine communications will be more extensive in the future Application: The connotation of existing applications will deepen, the scale will gradually expand, and there will be more energy-saving emission reduction, telemedicine, smart home and other fields that can be widely used.
For telecom operators, machine communication services have another important meaning: with the gradual saturation of the traditional communication market, machine communication services have become an important direction for operators to expand their space. This is because the number of machines connected to the network in the future is very considerable, even more than the number of people connected to the network. Telecommunication operators gradually began to attach importance to machine communication services and actively engaged in the promotion of machine communication services. For example, in the face of M2M business, Orange has launched channelized business, standard business platform business and industry customized business for customers with different needs. In China, both China Telecom and China Mobile have conducted a lot of exploration and practical work in the field of machine communications.
Facing the huge application demand, with the active promotion of all parties in the industry, the machine communication business will accelerate its development in the direction of scale, ubiquity and industrialization. So, what are the characteristics of machine communication compared to traditional data communication services? How do communication networks carry machine communication services? These problems have become the focus of attention in the current communication industry.
2 Machine communication features
We can observe and analyze the characteristics of machine communication from multiple angles. For example, the direction of data flow, the bandwidth required for data traffic, the mobility of machine terminals, the trigger mechanism and time characteristics of transmission operations, and so on.
(1) Reverse flow is the main flow of machine communication
Most of the current machine communication business is in the first stage of the development of machine communication, characterized by information collection. Such as meter reading applications in smart measurement, hydrological monitoring applications, environmental monitoring applications, etc. The flow of information is transmitted from the machine terminal of the collection point to the customer's back-end application system through the communication network. Borrowing the terminology of mobile cellular networks, the current machine communication business is dominated by reverse traffic. With the emergence of the second stage of the development of machine communications, the remote control function has been strengthened, and information release applications have appeared extensively. The forward traffic will gradually increase. In the third stage, the target of machine communication becomes other machines. In this scenario, the data flow characteristics may be basically symmetrical.
In general, the characteristics of integrated machine communication applications, especially the central intelligent features of back-end customer application systems, etc., reverse traffic will still be the main flow of machine communication for a long time. In contrast to this, the current data traffic of mobile phone terminals and the data traffic of Internet access cards are mainly forward traffic.
(2) Small traffic business is the main body of machine communication
From the perspective of the bandwidth required for data traffic, machine communication can be roughly divided into two categories: high-traffic services and low-traffic services. High-traffic services are mainly reflected in two types of applications: video acquisition applications and data aggregation transmission applications. Video capture applications collect video information from the surveillance area and upload it to the remote platform in the form of streaming media. It is actually used in environmental protection monitoring applications and bus monitoring applications. The main embodiment of data aggregation and transmission applications is the application scenario of using wireless routers.
In addition to high-traffic services, the broader machine communication needs are concentrated in low-traffic services. The typical characteristic of these small flow applications is that the data transmitted during a communication is extremely limited, which is between 1 ~ 10 kbit / s. This amount of data transmission can be completed within a few seconds in a 2.5 Gbit / s cellular network with better communication quality, such as a CDMA 1X network. Typical cases such as trajectory tracking of rental vehicles, a communication process mainly transmits positioning information to the back-end application system. The positioning information mainly includes longitude, latitude, altitude, speed and other information, and the data traffic is very small. Even in some digital applications, each time data transmission is only "on" or "off" information, the data flow is even smaller.
Judging from the current application situation, the small traffic service is the main body of machine communication.
(3) A large number of terminals have the characteristics of low mobility
From the point of view of the mobility of machine terminals, there are four cases of machine communication applications. The first type is a machine terminal with a large range of movement, such as a car terminal, especially a car terminal for a taxi vehicle; the second type is a nomadic machine terminal, such as a wireless POS; the third type is a mobile within a small range Machine terminals, such as remote health monitoring terminals in the home environment; the fourth type is basically not mobile, and can even be said to be a machine terminal that is accessed at a fixed location, such as many terminals used for environmental monitoring, basically fixed in the environmental protection Near the monitoring source.
Although there are 4 types of machine communication applications, it should be pointed out that there are not a few machine terminal applications that meet the fourth situation.
(4) The trigger mechanism and time characteristics of the machine terminal transmission operations are different
From the perspective of transmission operation trigger mechanism and time characteristics, it can be divided into three types.
The first type is the conditional trigger type of immediate transmission. Such machine terminals immediately transmit data containing relevant information to background applications when certain conditions are met. The so-called "certain conditions" will have different situations depending on the specific application. For example, in digital monitoring applications, the terminal should report the information as soon as the digital value changes; for indicator monitoring applications, the terminal should report the information once the threshold exceeds the threshold. Location triggered applications. Once the terminal reaches a certain area, the terminal should immediately report the information.
The second type is the time-triggered instant transmission type. For example, vehicle trajectory tracking applications. Under normal circumstances, the vehicle terminal will periodically report the vehicle's positioning information with a certain period of time. What triggers the data reporting operation is the internal trigger mechanism based on time.
The third type is the time-triggered non-immediate transmission type. Such applications are mainly used for data collection at specific moments, and back-end applications collect these data for post-analysis. Such applications do not emphasize the immediacy of data upload. The terminal can upload the data within a certain time after the data is generated.
(5) Other important features of machine communication
An important feature of machine communication is the "program automatic control" of the communication terminal. The program automatically controls communication operations, which is very different from man-made communication operations. Program automatic control mode allows the terminal to generate a large number of calls in a relatively short time. For example, mobile machine terminals may gather in a cell and all attempt to establish a data connection with the network. Due to the limited cell capacity, a connection failure occurs. The terminal that failed to connect was controlled by the program, and soon called the network again ... so back and forth, which aggravated the communication processing load of the cell and even caused cell congestion.
In addition, many industry terminals are scattered in places such as the field that cannot provide power. Although it can be powered by solar energy, for the sake of cost, most of these terminals can only be powered by batteries. In order to reduce maintenance costs, these battery-powered terminals can continue to work for at least six months, and the purpose can even reach more than 1 year. This requires that the entire terminal unit including the communication unit must have the characteristics of low power consumption or even ultra-low power consumption.
In addition, machine communication also has features such as "group-based features" and "bidirectional triggering". No more description here. In short, machine communication has unique communication modes and characteristics, and it puts forward new requirements for communication networks mainly based on traditional voice communication and Internet access services.
3 Evolution trend of communication network carrying machine communication
Current communication networks, especially cellular communication networks, are designed on the premise that the services they carry are mainly voice and Internet services. From the perspective of data channels, regardless of the multiple levels of bearer channel design, signaling interaction design, capacity and coverage planning, the main consideration is the business of the previous forward traffic, mainly mobile terminals and network cards. Under the prospect of large-scale development of machine communication services, the author believes that the evolution trend of machine communication carried by communication networks can be divided into three stages. As shown in Figure 1, the mixed bearer stage, the differentiated bearer stage, and the long-term independent bearer stage.
(1) At the initial stage of business development, the communication network adopts a mixed bearer method
In the mixed-bearing stage, the communication network starts from the access network and does not distinguish data services such as machine communications and network cards from all links to the core network. These different types of communication services are carried by the network in the same mode. The main reason for this situation is that the network side cannot currently differentiate services in a relatively simple manner. And although there is a certain demand, the business has begun to form a certain scale. But in the early days of machine communication, the business scale was still limited. From the point of view of input-output efficiency, there is not enough reason to start the transformation of the network.
In the mixed bearer stage, the basic processing strategy is that the network does not make major changes, and the network parameters remain basically unchanged. Some measures are mainly taken through the terminal side to deal with problems caused by program automation and other features, and indirectly enhance the network's carrying capacity for machine communication. At the same time, operators are also exploring the establishment of a business platform for machine communications, such as the M2M platform, by providing machine terminal monitoring and control, and business data routing and other functions, on the other hand to enhance the network's carrying capacity.
(2) The communication network should realize the differential bearer for machine communication
After all, machine communication has its characteristics that are different from traditional data communication in the past. With the continuous development of machine communication services and the increase of service scale, it gradually puts greater pressure on communication network resources including code number resources and transmission channel resources. In order to avoid this pressure from causing a large negative impact on the entire communication network, it is necessary to carry out corresponding transformations on the network side to achieve differentiated bearers.
Experts from the European Telecommunications Standardization Institute (ETSI) have explained this in the M2M functional architecture, as shown in Figure 2:
The experts of ETSI proposed that the access network, core network and transmission network may need to be modified to provide new network capabilities for carrying machine communications. In addition, some service capabilities need to be provided to support the bearing of machine communication services. The author believes that the latter will mainly rely on the evolution of the M2M platform, and the realization of the former requires corresponding improvement mechanisms based on the specific characteristics of machine communications. For example, for machine terminals with low mobility or even fixed installation, the signaling processing flow related to mobility management can be simplified. In this way, on the one hand, the signaling data traffic can be reduced, on the other hand, the signaling interaction of the terminal communication unit can be reduced, so as to achieve the purpose of reducing power consumption.
To realize the differentiated bearing of the machine communication service by the communication network, the communication network must have a targeted bearing mechanism. But first, the communication network needs to identify machine communication services from many data services before it can be treated differently. To achieve this recognition function, you can take a variety of measures, such as:
Machine terminal access network can use a separate network access identifier NAI;
The machine terminal can use an independent number segment to distinguish it from the terminal using the ordinary number segment;
In relevant equipment such as the home location register (HLR), a corresponding distinguishing mark is set for the machine terminal.
It should be noted that on the one hand, these measures have different implementation workloads; on the other hand, a variety of measures may be required to be used in combination to achieve better results. Moreover, not only network bearers, but also service bearers (service provisioning, billing, etc.) also need to be differentiated by these means.
(3) In the long run, the communication network may need to implement an independent bearer for machine communication
When the scale of machine communication services continues to expand, there will be greater mutual interference problems with other data services that share communication channels. It may be too complicated to solve them simply by technical means. In addition, a large number of machine communication services that require high communication service level agreements (SLAs) may appear. These factors lead to the need to use physically or logically isolated networks to carry (part of) machine communication services. This may include a physically or logically independent access network and a dedicated interconnection subnet in the core network.
4 Summary and outlook
In recent years, China and international communication standards organizations have begun to carry out related research on machine communication. The International Telecommunication Union Telecommunication Standardization Organization (ITU-T) focuses on the needs and architecture of ubiquitous networks from the perspective of next-generation networks (NGN). The 3rd Generation Partnership Project (3GPP) focuses on the needs of machine communications from the mobile network, as well as network improvement and optimization work for machine communications. In order to promote the research of M2M supporting technology, 3GPP2 also approved the M2M project at the Bangkok meeting in January 2010. It is clear that when an operator deploys M2M applications, it should bring lower operational complexity to the operator; optimize the network working mode to reduce the impact on the power consumption of M2M terminals and other research fields. The China Communications Standards Association (CCSA) established the ubiquitous network technical committee (TC10) in early February 2010 to uniformly deploy and carry out ubiquitous network application and technical research. But in general, the standards for machine communication are still in the stage of demand and architecture analysis, that is, in the initial stage.
From the perspective of several development directions of communication networks such as optical access, wireless broadband access, and intelligent service platforms, machine communication has put forward more requirements for wireless broadband access. Machine communication services have different communication modes and characteristics from the data communication services carried by mobile cellular networks in the past, and require adaptive changes in the network. If we say that the initial stage of the machine communication business, the business adapts to the network. Then we can say that the big development stage of the machine communication business should be the network adaptation business. Of course, this is a gradual process. However, it is currently in the process of transition from the mixed bearing stage to the different bearing stage.
In short, judging from the current status of the machine communication business and the vision of the future development of the Internet of Things, there are still many communication needs that cannot be met in the current communication network. The development of machine communication services will further promote the evolution of communication networks.
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