The Mesh network successfully overcomes the communication limitation, which is different from the architecture in which each network node is connected to a central node (also called a concentrator). Each node in the Mesh network can communicate with other nodes in the network whose communication distance is reachable. . If the message does not reach the addressed node directly, the other nodes will automatically relay this message until it reaches the destination.
Mesh networks provide a powerful solution for sensor networks such as Advanced Metering Infrastructure (AMI), which can efficiently connect hundreds or even thousands of sensors within coverage. Mesh architecture is commonly used in wireless communication networks such as ZigBee® and is currently used in the G3-PLC Power Carrier Communication, a new International Telecommunication Union® (ITU®) standard system. When used to build an AMI network, the PLC transceiver in the Mesh network can connect sensors (ie, meters) at a lower cost and is not limited by wall penetration and building obstruction. The Mesh network not only expands the transmission range of the PLC system, but also reduces the number of concentrators in the network.
Development and limitations of PLC technology
For decades, PLC has been widely used to periodically read the electricity consumption data of electric meters, eliminating the cost of manual meter reading. Based on single carrier frequency or dual carrier frequency shift keying (FSK) modulation technology, these PLC systems can usually connect 10-20 meters on one concentrator to achieve remote meter reading in the same cell. However, when the data transmission rate is increased to 2 kbps to 15 kbps, the FSK system cannot guarantee reliable communication, and its low transmission rate limits error correction. In other words, even if the meter only reads data once a month, it will take a lot of time to read the data repeatedly on the FSK system.
The PLC meter reading system has begun to reduce the operating costs of the power sector. There is no doubt that some similar public facilities construction has begun to follow suit. By expanding the network architecture of each concentrator to reduce costs, relying on "intelligent" communication management to build a smart grid. Finally, the purpose of saving electricity is achieved. However, there are some problems when using Mesh technology to extend the network and forward messages. If the forwarding is performed multiple times during transmission, the number of repeated transmissions increases dramatically, which will inevitably lead to a large transmission delay. The power department requires two-way communication between the meter and the concentrator in a matter of minutes to support the operation of the smart grid, including load response and peak pricing. Therefore, if the communication quality is not improved, the FSK PLC system must reduce the number of meters connected to each concentrator to improve response time and improve data transmission efficiency.
G3-PLC effectively increases data transfer rate and system reliability
In order to solve the challenge faced by PLC, Maxim cooperated with ERDF and Sagemcom to develop the G3-PLCTM communication protocol. In January 2012, the G3-PLC protocol was officially approved by the ITU as a new low-speed, narrowband power line communication standard (NB-PLC) based on Orthogonal Frequency Division Multiplexing (OFDM) technology. The G3-PLC system adopts OFDM technology, which greatly improves the data transmission rate on the power line, and improves the reliability of the system by interleaving data transmission in frequency and time. The protocol uses two layers of forward error correction (FEC) to improve noise immunity. Even if FEC takes up a certain amount of overhead, the G3-PLC's data transfer rate can reach 250kbps, which supports frequent two-way communication.
Although the distribution network is a single electrical network, building a PLC network on the power line is still limited by many factors such as signal attenuation and noise. The attenuation caused by power lines, transformers, capacitor banks and power monitors greatly reduces the PLC signal strength. It is difficult to deliver these attenuated signals to all meters, especially when the meter is placed close to a noisy environment such as home appliances or business machines.
In order to overcome the attenuation constraints, the Mesh network can be used to maintain sufficient signal levels in the G3-PLC standard. If each meter has Mesh networking capabilities, messages can be forwarded from one meter to another until they reach their destination, without the need for an additional concentrator to connect to the meter. The G3-PLC modem automatically forms the network and establishes a routing table connection concentrator and all meters. In this case, when the message cannot reach the responder directly from the sender, the G3-PLC modem can automatically receive the message and then forward it to the next modem or final destination.
For example, the concentrator sends a message to a meter that specifies that it delays the start of the water heater to reduce peak loads. The message is attenuated by an MV-LV transformer, and the noise on the high power inverter that is turned on at home also prevents the message reception of the specified meter. This meter is directly connected to the concentrator before receiving the message sent by the concentrator. After recognizing that the message has not been successfully received, the G3-PLC Mesh system will enable the nearby meter to forward the message, and after the signal relay is amplified, it will be delivered to the destination meter.
Forwarding information can reach meters on all distribution networks. The size of the network is limited only by smart grid communication specifications, including end-to-end delays and data transmission rates to each meter.
to sum up
By using G3-PLC technology and built-in Mesh network, PLC network scale can be extended to hundreds or even thousands of meters, significantly reducing the cost of basic design and construction. At the same time, the network is more reliable because it adapts to changing conditions, forwards messages as needed, and ultimately reaches all meters.
G3-PLC is a trademark of Maxim Integrated Products, Inc.
InternaTIonal Telecommunica TIon Union and ITU are registered trademarks of the International Telecommunication Union.
ZigBee is a registered trademark and registered service mark of the ZigBee Alliance.
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