On April 14, Meng Fei and his partners boarded the ship again and headed east along the muddy yellow Yangtze River Estuary. The captain doesn't even need navigation. After all, he has run countless times for the "man" on the sea. From a distance, a floating bucket and a buoy are like a pair of conjoined people floating and sinking together.

After a series of operations, Meng Fei successfully completed the task and returned home.

In order to obtain buoy data, Meng Fei and his colleagues will repeat the above cumbersome steps every once in a while. But since the buoy has an antenna and can communicate wirelessly, why do you have to go so far to copy data?

original,Jiuduansha Nature Reserve (mostly like a piece of liver) is at least 8km away from the public network base station, with intermittent 2G signals and basically no 4G signals. The original design of the buoy only had cellular network communication, so the data sensed by various sensors on the buoy can only be downloaded during patrol inspection.

The traditional terrestrial IOT communication is mostly based on cellular network, Bluetooth, WiFi, etc., but the coverage radius of 2G base station is about 5-10km, that of 3G base station is about 2-5km, that of 4G base station is about 1-3km, and that of Bluetooth and WiFi is only a few hundred metersAs a result, the ground Internet of things cannot achieve global coverage。

howeverWith the advantage of wide coverage, satellite communication can achieve seamless global coverage, thus greatly expanding the business scope of the ground Internet of things. Compared with the ground Internet of things, LEO satellites have the advantages of wide coverage, large link capacity and strong persistence. Compared with traditional high orbit satellites, LEO satellites have the advantages of low loss, low delay, wide coverage and large order of magnitude. It is the best way to realize the global coverage of Satellite Internet of things.

LEO satellite

In the LEO Satellite Internet of things, the terminal is responsible for collecting data and uploading it to the satellite, the satellite is responsible for routing and forwarding, the satellite is forwarded to the ground network, and the gateway station and the main control station are responsible for data service processing, user access management, resource scheduling, etc. The satellite accesses massive data. According to the service type, some data needs the satellite to transmit the data back to the ground in real time. Inter satellite links are designed between satellites. The satellite is mainly responsible for routing and information transmission between the relay terminal and the ground section.

LEO satellite network architecture

The communication means of Satellite Internet of things are also as diverse as the ground Internet of things. For example, the well-known Beidou satellite can not only realize the positioning function, but also use short messages to realize communication; At the same time, Lora, nb-iot and other technologies also shine in the field of satellite communication. Let's understand how the above three technologies are applied in the field of Satellite Internet of things!

01. Beidou short message satellite communication

Beidou SystemRNSs and RDSS dual-mode structure system is adopted, which not only has the navigation, positioning and timing functions of GPS, but also provides RDSS two-way short message information service, that isFunctions of satellite communication，It is the first satellite navigation system in the world that integrates message communication in addition to positioning and time service, which is not possessed by the other three satellite navigation systems (GPS in the United States, Galileo in Europe and GLONASS in Russia), which is also the core advantage of Beidou system.

This is the original data of a section of Argo profile buoy:

internal ID number 0433

transmission ID number 404434

transmission type BEIDOU

positioning system BEIDOU

WMO ID number 2902758

start time [dd mm yyyy hh mm (Z)] 21 03 2021 02 17

launch time [dd mm yyyy hh mm (Z)] 21 03 2021 02 53

launch position [lat latm lon lonm] 16. 11.64 90. thirteen point nine eight

delay of first down time [hours] 0.5

down time [days] 4.583

up time [hours] 10

transmission repetition rate [sec] 75

clock drift [hours/hours] 0.

The data transmission mode adopts Beidou short message satellite communication, which transmits a message every five minutes, 628 bits and about 44 Chinese characters each time, which can solve the transmission problem of non real-time small data application scenarios.

02. Lora based satellite communication

In 2013, Semtech announced the development of Lora chip, which has high receiving sensitivity. Compared with the previous sub GHz chip with the highest process level, the chip can improve the receiving sensitivity by more than 20dB. A No. 5 battery can work for the terminal for more than 10 years and the power consumption is very low.

In order to promote the development of Lora technology, in 2015, Cisco, IBM, Semtech and other companies jointly established a non-profit organization Lora alliance, which standardized the lorawan protocol. Soon, Lora was widely used in scenarios such as the Internet of things, smart industry and smart city. At present, there are more than 100 countries deploying Lora in the world.In February 2018, at the TTN (the things network) conference, the receiver captured the Lora signal transmitted from the LEO satellite, which is a milestone to prove that Lora can be applied under the satellite Internet of things.

Lora signal acquisition from norsat2 satellite

In China, Lora is also widely used. In 2016, with the support of Lora alliance, China Lora application Alliance (Claa) initiated by ZTE was established. Claa hopes to cooperate with companies in the Internet of things with an open and shared attitude to jointly build Lora technology ecology and promote the better application and development of Lora industrial chain in China.

During the "Hangzhou & middot; cloud habitat conference" in 2018,Alibaba cloud has obtained the IP authorization of Lora chip, the diversified market form of domestic Lora chip suppliers has been gradually opened, which has promoted the development of Lora industry to a certain extent.

Due to the openness and flexibility of lorawan standard, China has become the largest market of Lora industry ecology. Thousands of domestic companies have businesses related to Lora. Among them,ZTE, Alibaba, Tencent, China Unicom, Guizhou Radio and television, iron tower companyIt is self-evident that the participation of heavyweight players is of great importance to the development and growth of China's Lora industry.

03. Satellite communication based on Nb IOT

A new expansion direction of Nb IOT is to develop to the space-based Internet of things, that is, to provide the global ubiquitous NB IOT network through satellites, so that the Internet of things can be connected whether in the ocean or in the mountains.

Nb-iot advantage analysis (data source: compiled by prospective industry research institute)

Skylo technologies of the United States provides ubiquitous connectivity services for users of the global Internet of things. One highlight is the launch of a satellite based global NB IOT network in the summer of 2020,thisAn NB IOT network is designed to provide services for mobile devices, mainly used in agriculture, transportation, navigation, emergency and other fields。 Skylo was founded in 2017 and obtained a round of financing of US $13 million from three institutions at the end of that year, one of which is the venture capital company of Eric Schmidt, former CEO of Google; Recently, the company obtained another round B investment of US $103 million led by Softbank.

Skylo's satellite based NB IOT network is a gateway deployed on earth by connecting skylo with geosynchronous communication satellites. The network operates in the frequency band defined by 3GPP in addition to the special geosynchronous satellite communication service frequency band. This is a two-way communication network. In addition to the gateway transmitting data back to the satellite, due to the proprietary antenna technology, the satellite can also feed back the data to the gateway without additional equipment. Among them, those gateways are 8 * 8 inch boxes, which are generally installed on fishing boats, train carriages and other scene equipment. The gateway box acts as a transceiver to collect local sensor data and transmit the data to the cloud platform through satellite network.

At present, there are a large number of satellite communication schemes, but the cost of satellite communication is generally very high, and the cost of Nb IOT network is not high. According to skylo, the cost of the network connection is 95% lower than that of the existing satellite communication scheme. Specifically, the network connection fee is about $1 per user per month, and the hardware cost is less than $100. Skylo's satellite NB IOT network first provides services in India. The first customer is Indian Railway Corporation. Indian Railway Corporation will install skylo's gateway in its carriage and use skylo's NB IOT network.

According to the data released by GSMA,By February 2021, there were 103 commercial NB IOT networks in the world。 While mainstream operators all over the world deploy NB IOT networks, satellite based NB IOT networks are practicing the mission of "connecting unconnected objects". On the one hand, they complement operators' cellular networks, on the other hand, they also compete with cellular networks to a certain extent.

In fact, skylo is not the exclusive manufacturer of satellite NB IOT. Ligado networks, another American Internet of things company, said that it is ready to build a satellite network using NB IOT standard in 1500mhz-1700mhz frequency band; A Luxembourg company called OQ technology has tested NB IOT wireless access of Software Defined Radio (SDR) on some commercial satellites.

In addition, we also see that in recent years, a large number of start-ups have launched low-cost LEO Satellite Internet of things solutions, and several domestic private satellite companies have promoted the progress of Satellite Internet of things. Of course, there is no satellite based NB IOT network in China.

04. Summary

In recent years, the Internet of things has penetrated into all aspects of people's work and life. It exists everywhere, such as smart home, smart gateway, smart driving and smart city. However, the "interconnected world" depicted by the Internet of things cannot be achieved only by relying on the ground communication network. In addition, 60% of today's global Internet of things are terminals requiring wide area low-power narrowband technology, which need to be connected with the Internet of things based on satellite communication architecture.

LEO satellite has the advantages of low orbit height, wide coverage and small signal attenuation. It is the best choice to realize the satellite Internet of things. LEO Satellite Internet of things is very suitable for the monitoring, tracking and sensor data acquisition of short data, remote or long-distance moving objects. It is an excellent path to solve the "interconnection of all things".

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