WiFi mesh network provides individual light

Radio network WiFi mesh network provides individual light

As part of measures to strengthen the quality of the location on Mönckebergstrasse through a Business Improvement District (BID), the simple street lamps have been replaced by smart mast lights for around 2.5 million euros. A WiFi mesh network provides atmospheric lighting scenarios.

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• The mesh network and thus the mast lamps are finally connected to the central control computer via a mesh node installed in a street distribution box.

• Advantage of the mesh network: If a connection fails due to a lack of visual contact or if the signal quality deteriorates, a different network route is automatically selected.

Mönckebergstraße, or Mö for short, is the main shopping street in Hamburg’s old town located between the main train station and the town hall. The name of the 800 m long promenade is well known beyond the Hanseatic city. Mönckebergstrasse was inaugurated on October 26, 1909, after the Senate, named after Johann Georg Mönckeberg, had decided to demolish the Gängeviertel and a generous redesign of the area at the end of the 19th century. Today the promenade shines in a new light at night, emitted by 54 smart designer lamps from the Italian company I Guzzini.

Automatic light control

To implement fully automated lighting control, the lamps had to be connected to each other or to the master computer. As it turned out during the project, this was quite a challenge. Since the existing lamps were only to be replaced initially, no communication lines could be laid to them. After the first attempts at a solution with Powerline, i.e. the transmission of Ethernet data via the power line, failed, the BID’s responsible party, Otto-Wulff-BID-Gesellschaft, entrusted Computer Mack with the implementation of the project. After extensive testing, managing director Michael Mack and his team then decided to use a wireless communication solution based on Mesh WiFi from Phoenix Contact.

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Expert on difficult projects

The company, based in Stadland-Rodenkirchen in the Wesermarsch district in Lower Saxony, founded by Michael Mack in 1996, currently offers more than the original IT services. Software development, especially for industrial building and lighting controls, represents a further focus of activity. Since 2017, electronics development that focuses on rapid prototyping has been supplementing the service portfolio. There, customer-specific products are implemented from the idea to the finished device in just a few weeks. The system house is characterized above all by the fact that difficult projects have been completed individually, solution-oriented and quickly to the satisfaction of the client for 25 years. The company vehicles therefore simply read “Runs” in large letters. Michael Mack and his employees make this promise to customers. Mack emphasizes: “We like to implement tasks that are at the limit of what is feasible.” The managing director proudly refers to the many complex challenges that he and his team have successfully mastered so far – including the fully automated lighting control on Mönckebergstrasse.

Communication with the master computer via Modbus TCP

The 9 m nine high lights were financed by BID Mönckebergstraße, an association of the landowners. In addition to the usual street lighting, which is still switched on by the city, the BID can now illuminate the promenade with individual lighting scenarios. The individual house facades can be illuminated using adjustable LEDs or the walkways can be illuminated in any imaginable color using colored light sources. For this purpose, twelve separately controllable LED lighting elements are installed in all mast lights.

In addition, every second mast luminaire has three additional interfaces for supplying and controlling decorative lighting, which is used, for example, at Christmas. The lighting elements are controlled via the Dali protocol from a PLC located in the mast luminaire. The Modbus-TCP protocol is used for communication between the individual light masts and the central control computer, which is housed in a street distribution box. The master computer, which can be maintained remotely via the Internet, is used to monitor the street lighting.

Cable laying not possible

Since the lighting project is about updating an existing system, there were neither communication lines nor empty conduits. The city administration had ruled out the subsequent laying of the cables in the street or under the sidewalks. The system house was therefore faced with the challenge of implementing the data transmission to the mast lamps.

Initially, Michael Mack and his team pursued the approach of exchanging the Ethernet data using the TCP / IP powerline over the existing power lines. The data is modulated onto the existing energy network. This concept was quickly rejected because in practice it turned out that both the reliability of the communication and the realizable data rate are clearly too low.

The use of radio technology offered itself as an alternative solution. Against this background, the Mack employees tested various methods for their suitability together with Elektro Schiebold, who is responsible for the electronics work. In the end, the lighting experts opted for the WLAN mesh approach from Phoenix Contact based on the modules of the WLAN product family 2100. WLAN mesh is the only solution examined that meets the functional criteria as well as the high demands on the reliability of data transmission.

Resilience through mesh routing

In addition to the usual access point and client mode, the industrial access point WLAN 2100 also includes the mesh operating mode. A WiFi mesh network is an autonomous, self-organizing ad hoc network. In contrast to the standard WLAN, it does not require a central infrastructure. It only includes WiFi mesh nodes with equal rights that automatically establish a connection (ad hoc) to all other mesh nodes in the same network, provided they are within their radio range. This means that a mesh node can be connected to many mesh participants at the same time. Because these participants in turn have further connections to other nodes, a mesh network is automatically created through which the mesh participants can communicate with each other.

If mesh participants cannot be reached directly, the connection is made via other mesh nodes via routing (hops). This results in path redundancy, so that if a mesh node is lost, the data is simply routed to its destination via an alternative path, which increases reliability.

As in a standard WLAN network, WPA-2 Security with AES encryption protects data transmission from manipulation and eavesdropping. Individual Ethernet devices and local Ethernet networks can be integrated into the WiFi mesh network via the local Ethernet port of the WiFi 2100 mesh nodes. From the point of view of the application or the end devices, the entire mesh network works logically like a distributed switch. The network traffic is encapsulated in the mesh network and sent to its destination.

Tree population not an obstacle

Michael Mack and his employees have now installed a WLAN 2100 mesh node in the upper area of ​​each of the mast lights set up along Mönckebergstrasse. The PLC for lamp control is then connected to the Ethernet connection of the mesh node. The mesh network and thus the mast lamps are finally coupled to the central control computer via a mesh node installed in a street distribution box. The distance between two lamps that are mounted on both sides of the street is usually around 30 m.

However, the sides of the street are overgrown with trees, which is why the radio range can be negatively affected. This is where one advantage of the mesh network becomes apparent: as it organizes itself, it dynamically adapts its connections to local conditions. If a connection fails due to a lack of visual contact or the signal quality deteriorates, a different route through the mesh network is automatically selected.

Optimization of the firmware

The project on Mönckebergstrasse in Hamburg is the largest network implemented to date with the WLAN mesh solution from Phoenix Contact. When it was implemented, some project-specific challenges arose which were successfully resolved thanks to the good cooperation between Computer Mack, Elektro Schiebold and Phoenix Contact. In addition to the experience gained, the radio specialists have further optimized the WiFi mesh firmware for such applications. Just in time for the darkening days, the smart lighting on Mönckebergstrasse went into operation at the end of 2020. Not only during the Christmas season it has already won over visitors to the promenade because of the beautiful lighting moods.

* Jürgen Weczerek, Product Manager Network Technology Wireless, Phoenix Contact Electronics, Bad Pyrmont

(ID: 47402378)