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The best way to plan RF mesh networks

Posted by Espen Davidsen Jul 19, 2017 3:30:00 PM

Network illustration

What is the best way for distribution system operators (DSOs) to implement automated meter readings (AMR aka. AMS) in their infrastructure from all consumers in their net? Many DSOs have already seen the potential of building a dedicated network for meter readings, and the potential to extend into other utilities such as water, gas and central heating. RF mesh networks have proven itself to be a powerful and cost effective way of building up a distributed network over large areas with millions of meters. These five steps outline the process of planning a RF mesh network.

1. Identify and import all meter point data

In order to start planning, it's crucial to identify and import all meters you want to cover with your mesh network. Most important for planning is the unique ID of each meter and the position. The precision of the position may affect the end result, so it's a good idea to implement a process to wash and verify the data if you aren't fully confident in it. Data about the position of the meter, e.g. basement or outer wall, and building type is also useful to the coverage analysis process in step 5. The radio used with the meter is called a meter node in the mesh network. 

2. Identify available infrastructure

To collect data from the meters, it is common to use some kind of hub, often referred to as a concentrator, data hub, aggregator or master node. In the following, the term concentrator node is used in the mesh network. In many cases the most available sites for installing concentrator nodes are already property of the DSO. Such sites can be transformer stations, power cabinets or street light poles. The advantages are many. The infrastructure sites are already installed in areas close to the meters you would like to read, and the infrastructure is often owned/controlled by the DSO itself, so access should be easy. A good idea is to start with a top-down approach. Define all infrastructure sites as potential sites for a concentrator – we call it a concentrator-candidate-site

3. Tag preferred and restricted concentrator-candidate-sites

In most cases there are restrictions or good reasons to predefine some concentrator-candidate-sites. Some of the infrastructure sites might exist in restricted areas such as airports or near other critical infrastructure. Others might be installed in underground facilities. In both cases it's useful to tag the restricted sites. The restricted sites will not be considered as concentrator-candidate-sites.

On the other hand, you might have infrastructure sites that for good reasons should be tagged as predefined. This includes infrastructure where you want to read other site sensors or benefit from existing communication infrastructure – such as fiber optics, satellite or radio link – for the backhaul communication back to the central system (often called Head End System, or HES). The concentrator nodes are often built to aggregate the data and be able to compress and verify the data before forwarding it to the HES.

 

Concentrator node in RF mesh network

4. Configure radio and antenna properties

Based on the radio technology your organization or customer is using, you need to configure the radio properties in order to calculate coverage. The meter nodes and the concentrator nodes might use the same radio, but will often use different antennas and TX power (transmitter power).

The use of TX power and available frequencies are often strongly regulated when used for meter readings. It's therefore important to find the best antennas for the given frequencies and the TX power to be used, antenna type and antenna height being the most important properties to consider. There's a long range of available antennas with different properties and sizes.

In every case it's important to consider if omnidirectional or sector antennas are most suitable for the task. The omnidirectional antennas will send or receive the same radiation to or from all directions, while sector antennas are more directional and can be used to deliver most radiation in a certain direction or in a given directional pattern.

Example:

antenna characteristics

Omnidirectional vs Directional antenna caracteristics in a RF mesh network.

Directional antennas are very useful for fixed installations, from point A to point B. In RF mesh networks in general, the idea is that the network will be dynamic and in this sense not a fixed network. On the other side, directional antennas may be used to link clusters of RF mesh antennas or for routers and repeaters, as directional antennas typically will have a longer range in the defined direction.

5. Analyze and rate

Now the analysis and planning can start. Having configured the radio properties and antenna alternatives from all the meter point and infrastructure data, you can start to analyze the terrain and calculate the radio coverage from point to point in the mesh network.

The main task at this stage is to identify the best possible concentrator sites, primarily from the concentrator-candidate-sites list from step 2 in this blog post. The best possible concentrators will reach as many meter points as possible and at the same time not exceed its capacity. The geographical distribution of concentrators will have to take into account access to existing backhaul communication lines, e.g. fiber lines, or access to commercial mobile data such as 3G or 4G networks.

In large networks the number of calculations to all potential neighbors may be overwhelming.

In order to calculate radio coverage, the most important parameters are the terrain data and clutter data. The clutter information gives details about the vegetation and building density in an area. It's significant to know if the radio signal is traveling over water or through a dense industrial area.

In a dense urban area, the meters will typically be in close range, and the radio coverage might not be seen as an issue. More important might be the capacity of the concentrators. It's important that you make sure the maximum capacity is not exceeded, and that you have capacity left for failover scenarios, where one concentrator will have to handle data from other failing concentrators. On average, a concentrator should not exceed 66% of maximum capacity, saving the rest for a potential failover.      

Download E-book: Planning Radio Networks for SmartGrid    

Topics: CARMEN


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By: Espen Davidsen

Espen Davidsen is a computer systems professional with more than 15 years of experience with communication systems and distributed information systems. He is currently director of Telecom and Utilities at Teleplan Globe.

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