It is well known that communication protocols such as Bluetooth and ZigBee have been widely used for close-range IoT communication with low power consumption, but in close-range scenarios such as smart cities and car networking, these close-range communication technologies are clearly Unable to meet the demand.
At present, the upstream and downstream of the Internet of Things industry chain are vigorously promoting low-power wide area networks (LPWAN), such as NB-IoT, LoRa, SigFox and RPMA, and even more types than near-field communication technologies. However, among these LPWAN technologies, there are only three types of licensed spectrums operating under the 3GPP (Third GeneraTIonPartnership Project), namely eMTC, NB-IoT and EC-GSM-IoT.
The biggest advantage of low-power WANs in these licensed bands is that they can be covered by existing sites. What are their characteristics?
eMTC
Coverage: 15dB higher than GPRS
Number of nodes: 100,000 single carriers
Power consumption life: at least 10 years under 5Wh
Rate: 1Mbps uplink and downlink
Frequency band: LTE
Bandwidth: 1.08MHz
The full name of eMTC is LTE enhancements for Machine Type CommunicaTIons. In order to adapt to the massive low-cost and low-bandwidth terminal access in the IoT environment, the 3GPP expert group retains the compatibility of the original LTE protocol on the hardware environment, and on the other hand, deletes the high-speed for the special application scenario of the Internet of Things. Unnecessary additional capabilities such as transmission, and finally cut and optimize the eMTC based on LTE.
The reference to "eMTC" was officially confirmed in Release 13 released by the 3GPP, and was previously referred to as Low-Cost MTC and LTE-M (ie, LTE-Machine-to-Machine). In the future, eMTC will evolve along with the LTE protocol family according to the development of technologies and application scenarios.
The eMTC defined in Release 13 supports 1.08MHz RF and baseband bandwidth, which is 15dB higher than GPRS coverage. Each carrier can support up to 100,000 device connections and can directly connect to existing LTE networks. FDD and TDD technical standards. More importantly, because it is compatible with LTE, eMTC can support VoLTE (Voice Over LTE) voice technology, and it may be applied to various intelligent hardware in the future.
In addition, eMTC also supports the peak rate of up to 1Mbps for uplink and downlink, far exceeding other technical standards such as GPRS, NB-IoT and LoRa. Moreover, in order to be applicable to the Internet of Things scene, the terminal module compatible with the eMTC protocol is also required to be able to stand by for more than 10 years under 5Wh of power, and the target cost requirement is controlled between 1 and 2 dollars, aiming at power consumption and cost. Networked applications have been fully considered.
In January of this year, South Korea's KT Telecom Group has teamed up with Nokia to complete the first trial run of the eMTC standard.
NB-IoT
Coverage: 20dB higher than GPRS
Number of nodes: 200,000 single carriers
Power consumption life: 5Wh power, 10 years
Rate: downlink peak 250Kbps; uplink single channel peak 20Kbps, multi-channel 250Kbps
Frequency band: LTE, LTE edge, independent frequency band (eg GSM)
Bandwidth: 180KHz
NB-IoT stands for Narrow Band Internet of Things. Compared with eMTC, its main feature is that it is further optimized according to the Internet of Things, which further reduces the network load while ensuring communication.
NB-IoT's deep optimization for the Internet of Things is mainly reflected in two aspects: one is to increase coverage, and the other is to increase system capacity. According to the introduction of 3GPP, NB-IoT greatly improves the demodulation efficiency of the system by reducing the coding rate, and reduces the signal transmission power of a single device (the protocol specifies a maximum of 200mW, and the standby power requires at least 10 years under 5Wh), which is reduced. The highest rate of uploading and downloading (upload and download rates can only reach 250Kbps), which is 20dB more than GPRS coverage, and can support up to 200,000 network connections per carrier. In addition, according to capacity requirements, NB-IoT can also expand the system bearer by adding more carriers, and has the ability to support millions of IoT connections at a time using a single base station.
In terms of deployment mode, NB-IoT is not based on LTE as eMTC, but supports three different deployment methods at the same time. The first is Standalone, which uses a separate frequency band with the advantage that it does not create interference and is straightforward. The second type is the Guard Band. The advantage of using the guard band at the edge of the LTE band is that it does not require an independent band. The disadvantage is that the signal strength is weak and it is easy to interfere with the LTE system. The third type is In Band, which is an idle band that directly uses a LTE band, and is fully compatible with LTE.
The reason why NB-IoT has such a complex deployment is due to its complex origin. The technology source of NB-IoT mainly includes two parts: one is NB-LTE (Narrowband-LTE) technology proposed by Nokia, Ericsson and Intel, and the other is NB-CIoT (Narrowband) proposed by Huawei and Vodafone. Cellular IoT) technology. The former is based on the simplification of LTE technology and can be compatible with the current LTE standard; the latter is almost a redesign and is completely customized based on the Internet of Things. At the September 2015 discussion meeting, NB-CIoT and NB-LTE technologies were unified, namely today's NB-IoT.
In China, Huawei is the main driver of the NB-IoT standard. At the end of 2015, Huawei's 21 industry giants, including mainstream operators, equipment manufacturers, chip manufacturers and related international organizations, established the GSMA NB-IoT Forum industry alliance in Hong Kong. Six of the operators also announced that they will jointly Huawei has established six NB-IoT open labs around the world, focusing on R&D and verification in the NB-IoT field. At present, China Unicom has built the world's first NB-IoT technology demonstration site in Shanghai.
EC-GSM-IoT
Coverage: 20dB higher than the normal GPRS at 33dBm power level
Number of nodes: 50,000 nodes in a single base station
Power consumption life: at least 10 years under 5Wh
Rate: up to and down peak of 70-350Kbps under GMSK modulation; up to and down peak of 240Kbps in 8PSK modulation mode
Frequency band: GSM
Bandwidth: single channel 200KHz, typical system total bandwidth 2.4MHz
The last one is EC-GSM-IoT, which is called Extended Coverage-GSM-IoT. As can be seen from the name, EC-GSM-IoT and GSM network standards have this close connection. It is an extension technology of GSM, which can directly use GSM base stations for communication.
According to the description of 3GPP, EC-GSM-IoT can achieve an uplink and downlink rate of 70-350 kbps in the modulation mode of GMSK, and a rate of 240 kbps under 8PSK modulation. 3GPP also requires that terminal modules that comply with the EC-GSM-IoT standard be able to stand for at least 10 years at 5Wh. EC-GSM-IoT's single base station capacity can reach up to 50,000 nodes. Compared with ordinary GPRS, the coverage at 33dBm power level is increased by 20dB, which is equivalent to NB-IoT.
In addition, in order to be more suitable for IoT applications, the 3GPP expert group has enhanced the EC-GSM-IoT standard's identity authentication, integrity check, security strength and device identification capabilities, compared to the original GSM technology. Security features.
EC-GSM-IoT is theoretically fully compatible with existing GSM. Existing GSM base stations can be applied to smart devices conforming to the EC-GSM-IoT standard with only a simple software upgrade, so it is relatively easy to deploy.
In February 2016, Ericsson and France's Orange Telecom and Intel jointly built the world's first EC-GSM-IoT technology demonstration site. At the subsequent MWC 2016, Ericsson also demonstrated its own EC-GSM-IoT technology paradigm.
to sum up
These three low-power wide-area networks have their own advantages and disadvantages: LTE-based eMTC, uplink and downlink rates can reach 1Mbps, the fastest; and NB-IoT, uplink and downlink rates can reach 250Kbps, suitable for a wide range, complex categories, communications Various underlying intelligent devices that are not demanding; GSM-based EC-GSM-IoT, the uplink and downlink rates are comparable to NB-IoT, and are most convenient for deployment and promotion. At the same time, however, the technical standards of some unlicensed frequency bands in the market are gradually rising, such as LoRa, SigFox and RPMA. Many companies are in charge of each other. Therefore, the construction of the WAN in the Internet of Things may be difficult to form a unified one in a short period of time. standard.
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