Feasibility analysis report of LoRaWAN technology applied to electricity/water consumption information collection
With the development of the Internet of Things, many IoT applications have small data packets, greater tolerance for delays, and need to be deployed in a wide range, or are located in remote, underground and other heavily shielded places, with existing wireless communication or the signal of mobile communication technology is not easy to reach. For the above-mentioned problem, long-distance and low-power communication technologies have been developed, collectively referred to as Low Power Wide Area Network (LPWAN). LPWAN has the advantages of low power consumption, long distance, and large connection, so it is suitable for applications that require a wide range of deployment and small amount of data transmission. It is very suitable for the application requirements of data collection of smart energy meters. LPWAN can be divided into two camps: authorized frequency band and unauthorized frequency band according to the frequency band used. The unlicensed frequency band LPWAN technology developed earlier, and the main technology is LoRaWAN.
1. Introduction to LoRaWAN
LoRaWAN is a set of communication protocol and system architecture designed for LoRa long-distance communication network. It defines how data is transmitted in the LoRaWAN network (the network here refers to nodes, gateways and servers), defines the message type, data frame structure and security encryption method; and introduces the specific operations of the network, and explains the difference between master and slave devices.
In the design of the protocol and network architecture, LoRaWAN fully considers several factors such as node power consumption, network capacity, security and network application diversity.
2. LoRaWAN network architecture
LoRaWAN network architecture diagram
A LoRaWAN network architecture includes four parts: terminal, base station, NS (network server), and application server. Star and cellular network topologies are used between base stations and terminals. Due to the long-distance characteristics of LoRa, single-hop transmission can be used between them. The terminal node can send to multiple base stations at the same time. The base station forwards the LoRaWAN protocol data between the NS and the terminal, and carries the LoRaWAN data on the LoRa radio frequency transmission and TCP/IP respectively.
3. Overview of LoRaWAN Protocol
3.1 Classification of terminal nodes
In terms of technical specifications, the transmission rate of LoRaWAN is about 30bit/s-50kbit/s, the transmission distance is about 2-5 kilometers in the urban area, and the longest can reach 15 kilometers in the suburbs. It supports two-way transmission, and the transmission method depends on the delay requirements and functions of power consumption can be divided into three levels: Baseline (Class A), Beacon (Class B) and Continuous (Class C). The Class A method will only transmit when the terminal device sends a request, the power consumption is the lowest. It is used in water meters and gas meters. Class C means continuous data transmission, with the shortest transmission delay time. Class C is generally used in electric meters.
3.2 Uplink and downlink transmission of terminal nodes
This is the sequence diagram of Class A uplink and downlink. Currently, the receiving window RX1 generally starts 1 second after the uplink, and the receiving window RX2 starts 2 seconds after the uplink.
Class C and A are basically the same, except that when Class A is sleeping, it opens the receiving window RX2.
3.3 Method of the terminal node join the network
There are two ways to join the network: Over-the-Air Activation (OTAA) and Activation by Personalization (ABP).
Commercial LoRaWAN networks generally follow the OTAA activation process, so that security can be guaranteed. This method needs to prepare the three parameters, including: DevEUI, AppEUI, and AppKey.
DevEUI is a globally unique ID similar to IEEE EUI64, which identifies a unique terminal device. It is equivalent to the MAC address of the device.
AppEUI is a globally unique ID similar to IEEE EUI64, which identifies a unique application provider.
AppKey is assigned to the terminal by the owner of the application.
Terminal initiates the “Join” command, and the NS (network server) confirms that it is correct, it will reply to the terminal and assign the network address DevAddr (32-bit ID). Both parties use the relevant information in the network response and AppKey, generate session keys NwkSKey and AppSKey, which are used to encrypt and verify data.
If the second screening method(ABP activation) is used, directly configure the final communication parameters of DevAddr, NwkSKey, and AppSKey, and the join process is no longer required. In this case, the device can send application data directly.
3.4 Data transmission and reception
After join the network, the application data is encrypted.
There are two types of LoRaWAN data frame: Confirmed or Unconfirmed, that is, the type that requires response and other one that does not require response. Manufacturers can choose the appropriate type according to application needs.
In addition, it can be seen from the introduction that LoRaWAN is to support application diversity. In addition to using AppEUI to divide applications, the FPort application port can also be used to process data separately during transmission. The value range of FPort is (1~223), which is specified by the application layer.
3.5 ADR mechanism
There is a spreading factor in LoRa modulation, and different spreading factors have different transmission distances and transmission rates, and have no influence on data transmission.
In order to expand the LoRaWAN network capacity, a LoRa rate adaptation (Adaptive data rate-ADR) mechanism is designed in the protocol. Devices with different transmission distances will use the fastest data rate possible according to the transmission conditions. This also makes the overall data transmission more efficient.
4. LoRaWAN features
LoRaWAN has the characteristics of wireless transmission, strong anti-interference ability, encrypted communication, wide coverage, low power consumption, large connection, and low cost.
Long distance: LoRa achieves approximately twice the communication distance of cellular technology.
Large capacity: Many nodes of IoT, and a LoRaWAN network can easily connect tens of thousands of nodes.
Easy capacity expansion: When a LoRaWAN network needs to increase its capacity, just add a gateway.
Security: LoRaWAN is a double-encrypted Internet of Things. It is suitable for the information application of electric meter.
5. Specification of LoRaWAN gateway
5.1 Gateway
5.2 LoRaWAN module
Low power consumption: Lowest standby current is 1.5uA
High sensitivity: It can reach -139dBm@SF12/125KHz
Anti-interference: High-performance extension frequency communication, and efficient cycle interleaving error correction
Strong penetrating ability, its coverage range can reach more than 2km.
6. Testing report
6.1 Distance testing
At a linear distance of 3.7KM from Wuhan Radarking Electronics Corp., the signal strength is -94, the SNR is -6.0, and the built-in antenna and external antenna data packets are normal.
6.2 Penetration testing in the building: The gateway is installed in the meter’s well on the 15th floor of the 4th building of the first phase of the Huangjinkou Binjiang Garden.
| Test building | ||||
| External Antenna | Built-in Antenna | |||
| Signal strength | SNR | Signal strength | SNR | |
| F32 | -83 | 3 | -90 | -8 |
| -85 | 4 | -90 | -8 | |
| -85 | 1 | -91 | -7 | |
| -85 | 2 | -88 | -8 | |
| -84 | 4 | -91 | -8 | |
| F25 | -85 | 2 | -91 | -5 |
| -87 | 2 | -87 | -6 | |
| -85 | 1 | -90 | -7 | |
| -84 | 1 | -90 | -6 | |
| -85 | 1 | -91 | -5 | |
| F20 | -66 | 9 | -76 | 9 |
| -64 | 9 | -81 | 8 | |
| -66 | 9 | -78 | 9 | |
| -63 | 9 | -77 | 9 | |
| -88 | 9 | -77 | 9 | |
| F10 | -64 | 10 | -73 | 11 |
| -63 | 10 | -72 | 9 | |
| -61 | 9 | -75 | 9 | |
| -62 | 9 | -72 | 9 | |
| -63 | 9 | -72 | 9 | |
| F5 | -84 | 1 | -90 | -7 |
| -88 | 1 | -90 | -5 | |
| -86 | 1 | -90 | -8 | |
| -85 | 1 | -89 | -9 | |
| -88 | 1 | -89 | -10 | |
| F2/F1 | -78 | 9 | -91 | -9 |
| -88 | -5 | -90 | -8 | |
| -83 | 3 | -89 | -4 | |
| -88 | 1 | -91 | -9 | |
| -89 | -10 | -90 | -7 | |
In the above table, the signal strength is above -100dbm (far greater than the module's receiving sensitivity limit -139dbm), and the SNR is above -10 to achieve two-way reliable communication. Therefore, when we installing the gateway on the 15th floor, the signal can coverage whole 32 floors.
6.3 The success rate test of data upload
Test conditions: 120 electric meters, one gateway (8-channel half-duplex)
| Communication mode: Without confirmation, resend once time. | |||
| Testing No. | The number of the meters which data upload successfully | Success rate(%) | Time to upload(Second) |
| 1 | 119 | 99.2 | 154 |
| 2 | 118 | 98.3 | 155 |
| 3 | 120 | 100 | 155 |
| 4 | 120 | 100 | 155 |
| 5 | 118 | 98.3 | 155 |
| 6 | 119 | 99.2 | 155 |
| 7 | 119 | 99.2 | 155 |
| 8 | 120 | 100 | 155 |
| 9 | 120 | 100 | 155 |
| 10 | 120 | 100 | 155 |
| Communication mode: Without confirmation, resend twice times. | |||
| Testing No. | The number of the meters which data upload successfully | Success rate(%) | Time to upload(Second) |
| 1 | 120 | 100 | 155 |
| 2 | 120 | 100 | 154 |
| 3 | 120 | 100 | 155 |
| 4 | 119 | 99.2 | 154 |
| 5 | 118 | 98.3 | 159 |
| 6 | 119 | 99.2 | 154 |
| 7 | 118 | 98.3 | 158 |
| 8 | 119 | 99.2 | 158 |
| 9 | 120 | 100 | 154 |
| 10 | 118 | 98.3 | 154 |
It can be seen from the above test data that 120 meters can upload data within 3 minutes, and the average success rate is over 99%.
In conclusion:
1. The use of built-in antennas in the city can ensure normal communication within 2-3km, and the use of external antennas can reach longer distances.
2. It can penetrate 10-15 floors
3. Using an 8-channel half-duplex gateway with 120 meters, reliable data transmission can be completed within 3 minutes, and a 16-channel half-duplex gateway can achieve reliable data transmission of more than 200 meters.
LoRaWAN technology can effectively realize the collection and control of water and electric meter information.
Contact Person: Mrs. Ada Yang
Tel: 86 15623095278
Fax: 86-27-84967521
