NB-IoT technology: Internet of things in a smart city
NB-IoT (Narrow Band Internet of Things) is a cellular telemetry standard based on LTE for small data transfers.
The standard was developed by the 3GPP consortium as part of the work on next generation networks.
NB-IoT Network Architecture
NB-IoT refers to the LPWA (Low Power Wide Area) standard designed for M2M (Machine-to-Machine) applications that require low-speed data transmission and operation in automatic mode for a long period of time, including in remote or hard-to-reach places.
The most important thing is to remember an important feature:
NB-IoT is a separate existing “branch” based on the well-known LTE technology.
This is precisely part of the hierarchy of LTE networks, but with its own characteristics.
NB-IoT technology has inherited a lot from LTE, from the physical structure of the radio signal to the architecture of the network itself.
It was created with an eye on application in conditions of lower signal level and higher noise level, taking into account the saving of battery life.
The peculiarity of NB-IoT is that it is capable of transmitting small messages from various sensors and devices, i.e., the transmission of heavy content like video or audio does not apply in this case.
To understand the advantages and disadvantages of this technology in comparison with the same LTE, it is necessary to delve into the technical aspects of the radio access architecture.
LTE uses the principle of OFDM channel division, which means orthogonal frequency division multiplexing.
As we know, there are two directions of interaction:
Downlink - the direction from the base station and Uplink - the direction to the base station.
These channels are divided into 15 kHz subcarriers.
Downlink uses OFDMA and Uplink uses SC-FDMA.
The carrier itself in LTE is divided into resource blocks (Resource Block - RB), which in turn are divided into 12 subcarriers.
We get the total bandwidth of the occupied bandwidth: 12 × 15 kHz = 180 kHz.
Additionally, each resource block has 7 timeslots of 0.5 ms, for a total of 84 resource elements (Resource Element - RE).
Also, the division of the resource block into 48 resource elements of 3.75 kHz in the Uplink direction has already been standardized, this extends the timeslot to 2 ms.
To achieve higher throughput, additional technologies are used (QAM256, QAM64, MIMO2×2, MIMO4×4, etc.), because LTE is a high-speed standard.
Due to the limited power of NB-IoT subscriber devices (as well as LTE) up to 23 dBm (200 mW), signal transmission in a narrow band of 15 kHz can significantly increase the signal spectral density.
Accordingly, the signal-to-noise ratio will be most effective in NB-IoT compared to GSM/GPRS.
Additionally, it is possible to form a resource unit (Resource Unit - RU) from various variations of the use of resource elements (RE).
From RU, in turn, so-called transport blocks (Transport Block - TB) are formed, assigned to the user.
One TB can contain from one to ten RUs.
When the signal quality changes, NB may contain a different amount of useful information.
NB-IoT Capabilities
For NB-IoT technology, limited characteristics were determined in order to be able to use it on the basis of already existing cellular networks.
NB-IoT is limited to a total bandwidth of one RB 180kHz wide.
The radio part of a device using NB-IoT has only one antenna.
Transmission and reception are separated in time (half duplex).
It is possible to transmit data in the Uplink direction on one subcarrier.
Modulation types are limited, BPSK and QPSK are used.
Transmit repeats may be used.
Accordingly, the application of such restrictions was intended to reduce the overhead costs for energy consumption, size and, of course, the price of the device.
I would like to highlight one important feature of the NB-IoT technology, namely, repetitions of the transmitted signal (Coverage Enhancement).
This is not a retransmission of a packet in case of an error in its reception, this is the functionality of making a decision about the success of the received signal.
The decision occurs only after receiving all repeated messages.
The NB-IoT network standard defines three levels (coverage levels 0, 1 and 2).
The number of repetitions can be set individually within wide limits.
The standard provides three ways to allocate a frequency resource for NB-IoT:
Stand Alone - dedicated frequency channel;
In Band - resource allocation within the existing LTE range;
Guard Band - resource allocation in the guard interval of the existing LTE range.
Stand Alone is the most efficient, but at the same time the most costly way to allocate a resource.
A channel with a width of 200 kHz is allocated (10 + 10 kHz protection bands), plus it is necessary to additionally allocate a resource to exclude mutual signal interference.
In this regard, the overall frequency range can expand from 300 to 600 kHz, which is quite expensive, but this is the advantage of this method.
In Band. A carrier resource is selected within the existing LTE band. Has an impact on the main LTE band due to the increased transmission power of the NB-IoT signal by 6dB.
Good for saving frequency resource.
Guard band. The resource in the "guard interval" is selected. When allocating an LTE frequency resource, a guard interval is always allocated. For example, for a band of 10 MHz, 500 kHz of free spectrum are allocated, and it is this part that is used. It allows both saving the frequency resource and reducing the impact on the main LTE network. The transmission power of the NB-IoT signal is also increased by 6-9dB.
The negative point in this case is the deterioration of the parameters of out-of-band emissions of LTE.
NB-IoT speed
NB-IoT has inherited a lot from LTE, and LTE is considered a high-speed technology, so it would be immodest to ask about the speed of transmitted data.
IoT devices are positioned as compact, energy-efficient and autonomous, respectively, message transmission will occur infrequently and in small volumes.
The amount of data transmitted in these messages is also significantly small. Based on these data, the very concept of transfer rate for NB-IoT comes to naught.
But we can briefly describe the estimated speeds under good reception conditions.
Speed is a calculated value.
An NB-IoT device cannot occupy the entire available frequency resource.
The rest is distributed to other devices, and it will greatly depend on the settings of the mobile operator (coverage level, NPDCCH, NPDSCH, NPRACH and NPUSCH, etc.).
As a result, for Downlink the speed will be somewhere around 25.2 kbps, and for Uplink at the level of 22.2 kbps in single-tone and 58.8 kbps for multi-tone (Rel.13 3GPP)
In 3GPP Rel.14, according to the increased TB sizes, downlink and uplink speeds can exceed 100 kbps.
Application scenarios of NB-IoT technology ,
The birth of NB-IoT technology perfectly solves a number of problems:
NB-IoT can serve communication base station users, 10 times the bandwidth of GPRS, NB-IoT has ultra-low power consumption, normal communication and standby current is mA and uA level, module standby time can reach ten years from birth to slaughter Replace the battery and reduce the burden on workers.
NB-IoT has stronger and wider signal coverage, really realizing normal data transmission in remote areas.
NB-IoT technology really breaks the bottleneck of GPRS technology.
This technology has come into being and it has really realized what livestock farmers want and will definitely shine in the huge livestock industry.
NB-IoT application for remote meter reading:
Water and gas meters are closely related to our lives and are used in every home. The most primitive method is to manually visit the meter to read the statistics.
With the development of society, manual meter reading gives rise to various disadvantages:
low efficiency, high labor cost, error-prone data logging, owners who are afraid of strangers will not be able to enter the door, maintenance and management difficulties.
A remote GPRS meter reading method has emerged that solves a number of problems of manual meter reading, is more efficient and safer than manual meter reading technology. Along with this, new problems arise: GPRS remote meter reading also has disadvantages that do not allow it to be promoted on a large scale: communication base stations have a small user capacity, high power consumption and poor signal.
Remote meter reading of NB-IoT technology solves this problem;
The NB-IoT remote meter reading inherits the GPRS remote meter reading function, and also has a huge capacity.
The throughput of the same base station is 10 times that of the GPRS remote meter reading capabilities.
Low power consumption, NB-IoT terminal module standby time can reach more than ten years under the same environmental conditions.
The new technology provides stronger signal coverage (can cover rooms and basements) and lower module cost. It is expected that the cost of one connection module will not exceed 1 US dollar, and in the future it will be lower.
Thus, NB-IoT technology is the product of the development of a new era, which removes many of the previous limitations.
The future branch of the Internet of Things will certainly belong to nb-iot, which will realize the interconnection of everyone and everything.
NB-IoT Smart home application (smart lock)
With the growing popularity of the smart home industry in recent years, smart locks are appearing more and more often.
Currently, smart locks use non-mechanical keys as user identification technologies. Core technologies include contactless cards, fingerprint recognition and passwords.
Recognition, face recognition, etc. have greatly improved the security of access control, but the premise of the above security is that when the power is on, if the smart lock is in the off state, it is useless.
To improve security, the smart lock should have a built-in battery, collect various basic data, transmit data to the server, and automatically send an alarm to the user when collecting abnormal data.
Since the smart lock is not easy to disassemble after installation, the battery of the smart lock should have a long service life; the location of the door is in a closed corridor, and stronger signal coverage is required to ensure real-time transmission. network data; the number of smart home terminals should be sufficient; number of connections; most importantly, after adding the above features, it can also ensure that the equipment cost is controlled within an acceptable range.
The use of NB-IoT technology in the smart home system NB-IoT has the characteristics of low power consumption.
It can work for ten years with just two AA batteries, greatly reducing the subsequent maintenance costs, and super-strong signal coverage that can cover rooms and basements, ensuring signal stability.
Massive connections for simultaneous connection of multiple terminals in smart homes. Low cost, the price of one NB-IoT chip is less than $1.
NB-IoT is used to monitor street lights
At nightfall, the varied and colorful street lights of the city light up, putting on the magnificent attire of the city, under this magnificent appearance hides huge flaws.
Energy waste. People began to rest after a night in the city, and traffic on the streets began to decrease.
Some areas do not need much street lighting during special periods, resulting in wasted energy and increased unnecessary costs; maintenance Difficult due to manual inspection, which requires a lot of labor, and a large number of street lights, the real-time status of street lights cannot be obtained in time, resulting in extremely poor maintenance and troubleshooting efficiency of street lights. .
How to make street lamp control intelligent?
The monitoring center of the NB-IoT intelligent street light control system is the center of the entire operation, maintenance, processing, statistics, analysis and control of the entire street light monitoring system.
The monitoring center centralizes data management and monitoring, provides target lock, fast search and other operations, supports center monitoring and hierarchical control, can create multiple subordinate control centers, the network can be divided and divided to control, building a large street light control system; set up management strategies.
Street lights on both sides of the road are controlled by periods of time: all on, all off and on poles. The system can flexibly adjust the time to control street lighting according to local conditions, all-on, all-off and poles;
Using NB-IoT wireless network to realize remote distributed remote control; street lamp failure detection function, advance notification of the location of a defective street lamp; the communication bandwidth is large, and you don't have to worry about the situation where people can't communicate due to too many street lights.
Thank you.
