Comparison of NB-IoT and LoRa technology

There are many wireless communication technologies for the Internet of Things, which are mainly divided into two categories: one is Zigbee, WiFi, Bluetooth, Z-wave and other short-distance communication technologies; the other is LPWAN (low-powerWide-AreaNetwork, low-power wide area network), Namely WAN communication technology.

The rapid development of the Internet of Things puts forward higher requirements for wireless communication technology, and LPWAN, which is designed for low-bandwidth, low-power, long-distance, and massively connected IoT applications, is also rapidly emerging.

IoT applications need to consider many factors, such as node cost, network cost, battery life, data transmission rate (throughput rate), delay, mobility, network coverage, and deployment type. NB-IoT and LoRa have different technical and commercial characteristics, and they are also the two most promising low-power wide area network communication technologies. These two LPWAN technologies have the characteristics of wide coverage, multiple connections, low speed, low cost, and low power consumption. Both are suitable for low-power IoT applications and are actively expanding their ecosystems.

Introduction of NB-IoT and LoRa

1. NB-IOT

NB-IOT (NarrowBandInternetofThings, NB-IoT, also known as Narrowband Internet of Things) is a technical standard defined by the 3GPP standardization organization. It is a narrowband radio frequency technology designed specifically for the Internet of Things.

2. LoRa

LoRa (LongRange) is an ultra-long-distance wireless transmission scheme based on spread spectrum technology adopted and promoted by Semtech in the United States. The LoRa network is mainly composed of four parts: terminal (with built-in LoRa module), gateway (or base station), server and cloud, and application data can be transmitted in both directions.

Frequency band used by NB-IoT and LoRa

1. NB-IOT

NB-IoT uses licensed frequency bands and has three deployment methods: independent deployment, guardband deployment, and in-band deployment. The mainstream frequency bands in the world are 800MHz and 900MHz. China Telecom will deploy NB-IoT in the 800MHz frequency band, while China Unicom will choose 900MHz, and China Mobile may rebuild the existing 900MHz frequency band.

2. LoRa

LoRa uses the unlicensed ISM frequency band, but the usage of the ISM frequency band in different countries or regions is different. In the Chinese market, the China LoRa Application Alliance (CLAA) led by ZTE recommends 470-518MHz. The frequency band used by radio meters is 470-510MHz. Since LoRa works in an unlicensed frequency band, network construction can be carried out without application. The network architecture is simple and the operating cost is low. The LoRa Alliance is vigorously promoting the standardized Lo-RaWAN protocol around the world, so that devices that comply with the LoRaWAN specification can be interconnected.

Communication distance of NB-IoT and LORA

1. NB-IoT communication distance

The signal coverage of the mobile network depends on the base station density and link budget. NB-IoT has a link budget of 164dB, GPRS has a link budget of 144dB, and LTE has a link budget of 142.7dB. Compared with GPRS and LTE, the NB-IoT link budget has been increased by 20dB, and the signal coverage of the open environment can be increased by seven times. 20dB is equivalent to the loss of the signal penetrating the outer wall of the building, and the signal coverage of the NB-IoT indoor environment is relatively good. Generally, the communication distance of NB-IoT is 15km.

2. LoRa communication distance

LoRa provides a maximum link budget of 168dB with its unique patented technology. Generally speaking, the wireless distance range is 1-2 kilometers in the city, and the wireless distance can reach up to 20km in the suburbs.

NB-IoT and LoRa cost comparison

No matter how powerful the LPWAN protocol is, its low cost needs to be considered, otherwise they are not...

Using RSSI/TOF to judge distance?Let's talk about the RSSI/TOF range measurement.

RSSI(Received SignalStrength Indication) ranging is the strength indication of the received signal.A positioning technique that can be calculated by measuring the distance between the signal point and the receiver point by the signal strength and weakness received.

Distance-measurement

RSSI requires higher parameters for communication channels. The distance measurement theory is based on the principle that the signal power is attenuated by the distance transmitted by radio or sound waves.The distance between the nodes can be calculated by the attenuation model between the signal and distance based on the transmitting power of the beacon node and the signal power received by the node.However, due to distance and obstruction, the power intensity of the signal is attenuated, which indirectly affects the accuracy. It is important to understand that each distance measurement has its advantages and disadvantages.

1. Advantages of RSSI Distance Measurement Mode

• The power consumption of RSSI distance measurement was lower.
• The cost of RSSI distance measurement is low compared with TOF distance measurement. It is not affected by transmitting delay and antenna delay. The hardware cost, software cost and time cost are relatively low.

Easy to use.In general, it is a function of commercial wireless transceiver chips to calculate receiving wireless signal strength.

2. Restrictions on RSSI Distance Measurement

• Environmental factors. The accuracy of distance measurement is influenced by obstacles, weather and non-range signals.For example, the energy of electromagnetic waves is attenuated if there are obstacles on both sides, especially metal ones.
• Signal energy instability due to radio channel multidiameter decline
• The measurement accuracy is influenced by antenna orientation and antenna gain.

3. Completion 

In general, RSSI distance measurement is suitable for situations where the environment is empty and the environment is less disturbing. It is the only way to improve communication quality and reduce background noise.In practical environment, RSSI is mainly used in short distance measurement and indoor positioning.

TOF range measurement

TEF is called Time of Flight. TEF distance measurement is a method of flight time measurement. Traditional techniques include Two Way Ranging and one Way Ranging. The TOF distance measurement method is Two Way Rangin technology, which uses signal time between two transceivers to measure the distance between nodes.

Advantages of TOF Range

• The method of TOF distance measurement is two-way ranging, which reduces the error of distance measurement compared with one-way rang measurement.
• TOF distance measurement is dependent on flight time. Time measurement accuracy does not vary significantly with increasing test distance. The performance is more stable and the distance can be accurately measured is greater.

Error analysis of TOF distance measurement

1. The interval between wireless transceiver and wireless transmission is very short.In the TOF range measurement scheme, distance measurement depends on time measurement, but a small time error of up to 300,000 km/s can result in a larger distance error, so the exact distance required for the timing system of the transceiver and transceiver is also very high.

2. Time delay. Time delay includes sending delay, receiving delay, and antenna delay."When distance-measuring signals are processed and modulated by digital and analog signals, transmission and reception over the radio can result in some delay errors."Antenna transmitting/receiving signals may not be uniform because the delay in one radiation direction may be different from the other, and the delay time of different antennas may vary due to the quality of the antenna.

3. Multichannel refers to the phenomenon in which the transmitter is reflected and diffracted from the transmitter to the receiver.This effect becomes serious when there is an obstacle between the transmitter and the receiver....

What is the difference between LoRaWAN and NB-IoT？

1. Ecosystem

LoRaWAN is supported by the LoRa Alliance, an open non-profit association composed of more than 500 members. Its members work closely together and share experiences, promote and promote the success of the LoRaWAN protocol, and become the leading and open global standard for secure, carrier-grade Internet of Things LPWAN connections.

NB-IoT is supported by two telecommunications standards associations, 3GPP and GSMA, both of which have the same goal of promoting the interests of mobile networks and equipment.

2. Spectrum

LoRaWAN is optimized for ultra-low power consumption and remote applications. Therefore, network operators and equipment manufacturers can access the networks running on the license-free ISM Sub-1GHz spectrum for free.

NB-IoT uses a cellular spectrum network, which is optimized for spectrum efficiency. The licensing fee for frequency band usage is very high, and it is limited to a few operators.

3. Deployment status

According to the LoRa Alliance, 83 public network operators in 49 countries are currently using LoRaWAN, and more private companies are also using LoRaWAN networks.

GSMA is an organization representing the interests of NB-IoT, LTE and other mobile networks. According to it, 40 countries will launch NB-IoT networks in the future.

4. Deployment options

LoRaWAN network provides highly flexible deployment. It can be installed in a public, private, or mixed network, indoor or outdoor. LoRaWAN signals can penetrate into urban infrastructure, and each gateway can cover 30 miles (approximately 48.3 kilometers) in an open rural environment.

NB-IoT uses LTE cellular infrastructure, which is an outdoor public network and requires the deployment of 4G/LTE cellular towers. If the sensor exceeds the coverage area of the base station, the base station is not easy to move.

5. Protocol

The LoRaWAN protocol sends data asynchronously, and the data is sent only when needed. This can extend the battery life of the sensor device up to 10 years, and the battery replacement cost is low.

NB-IoT needs to maintain a synchronous connection to the cellular network, regardless of whether it needs to send data. For sensor devices, it consumes a long battery life, resulting in high battery replacement costs, which may be too costly in many applications.

6. Emission current

LoRaWAN provides 18 mA emission current at 10 dBm, and 84 mA emission current at 20 dBm. Modulation differences can enable LoRaWAN to support very low-cost batteries, including button batteries. 

The NB-IoT sensor consumes ~220 mA at 23 dBm and 100 mA at 13 dBm, which means that it needs more power to operate and requires more frequent battery replacement or a larger capacity battery.

7. Receive current

LoRaWAN provides lower sensor BOM cost and battery life for remote sensors. The receiving current is about 5 mA, and the overall power consumption is reduced by 3-5 times. 

The NB-IoT receiving current is about ~40 mA. The communication between the cellular network and the device consumes more than 110 mA on average, and a communication lasts for tens of seconds. The protocol overhead has a significant impact on the battery life of devices that need to work for 3, 5, or 10 years or more.

8. Data rate

LoRaWAN data rate is about 293 bps-50 kbps. The LoRaWAN protocol dynamically adjusts the data rate according to the distance between the sensor and the gateway, thereby optimizing the air time of the signal and reducing conflicts.

The peak data rate of NB-IoT is about 250 kbps, which is more suitable for use cases with higher power budget and higher data rate (above 50 kbps).

9. Link budget

LoRaWAN's MCL signal varies according to regional regulatory restrictions. The link budget is between 155 dB and 170 dB. 

NB-IoT needs to repeat remote sensors at a low bit rate in order to be able to support remote sensors. The link budget is up to 164 dB.

10. Mobility

LoRaWAN can support mobile sensors to track the...