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Abstract
The Boomerang is one of the newest power quality measurement offerings by PMI. Capable of measuring voltage, current and real power, the Boomerang comes in multiple different measurement configurations and form-factors to meet a diverse array of requirements (Figure 1).
Figure 1. Boomerang lineup
The Boomerang is an “always-there” device – or, in other words, it is more or less a “permanent fixture.” While other PMI recorders are typically used for spot measurements (though some can be used for more long-term analysis), the Boomerang is almost exclusively used for long-term analysis. Traditionally, this would have presented its own series of challenges as, at least for many years, users were required to periodically connect to the recorders to download the information from them – either by physically removing the device and taking it back to the office, or by sending someone to the device with a laptop and perhaps using a Bluetooth connection (which required the user to be in close proximity).
This paradigm has been replaced with the Boomerang which uses a cellular modem to periodically stream its measured voltage, current and/or real power readings into a remote Canvass server. Alternatively, it can be polled through a SCADA system over the cellular network either through the wireless carrier’s public network or through a private tunnel back to the utility’s local area network (LAN). (That is not to say that Canvass and SCADA configurations are mutually exclusive – a Boomerang is capable of reporting to both systems simultaneously.)
This white paper is going to discuss the different cellular configuration options (and some of the terminology that surrounds them) that are available when provisioning a Boomerang for service directly from a wireless carrier (versus using one of the available PMI provisioning offerings).
Available Offerings
The PMI Engineering department has previously published a whitepaper detailing the plans that PMI offers to customers who do not wish to procure cellular service directly from the wireless provider. That whitepaper, “Choosing a Cell Plan for Boomerangs” can be found here.
Briefly, PMI offers three different “tiers” of wireless choices:
Tier 1 – 2MB per month
Tier 2 – 25MB per month
Tier 3 – 250MB per month
The tier selected is directly proportional to the type of Boomerang being activated and the Boomerang’s use case (Canvass vs SCADA or enabling both). For instance, if the user is provisioning a single phase, voltage-only Boomerang for Canvass, then a 2MB per month plan is recommended. The relatively slow data streaming rate for just a single phase of voltage (even at 1-second averages) is still small enough after compression to fit within this 2MB per month plan.
On the other hand, a user provisioning a three phase voltage, current and power Boomerang that will be polled by SCADA in addition to reporting regularly into Canvass will likely be better suited with a 250MB per month plan, as the bandwidth necessary to stream the increase in data is significant.
For customers that are interested in using a PMI plan with private networking (for more information on private vs public network, see below: Boomerang Networking for SCADA and Canvass), PMI can work with a utility’s IT department to facilitate this configuration.
Boomerang Networking for SCADA and Canvass
From a high level perspective, there are really only two ways to network a cellular Boomerang: through a wireless carrier’s private network, or over the “public” internet (also by way of the wireless carrier).
These options are essentially exactly what they sound like. In the “private network” scenario, the Boomerangs are firewalled off from the public internet and operate on one of the private, reserved IPv4 address ranges (10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16). Use of the private network option requires the customer to go through a bit of extra legwork: they must set up peering points, typically using IPSec and GRE (Generic Routing Encapsulation) tunneling and will likely be using BGP (Border Gateway Protocol) to broadcast and receive private network routes. In short, there is a bit more complexity involved when joining a utility’s private network with that of the wireless carrier. The payoff, of course, is that the device is not “reachable” through the public internet and that all traffic is both tunneled and encrypted end-to-end. The Boomerangs in a private network cannot be reached by any node that is not directly connected to the utility’s private network.
The “public network” scenario is pretty much as it sounds as well. When a Boomerang is provisioned using this method, a public IPv4 address (which may either be statically or dynamically assigned – options will be discussed below) is assigned to the device and is then addressable (“reachable”) from anywhere on the public Internet.
Note: Configuration with a Boomerang can be password protected with configuration from the user. Without the correct password, device settings cannot be changed and the device cannot be controlled. Regardless of the networking options selected by the user (public or private networking), PMI highly recommends setting a password to protect the Boomerang from intrusion.
Note: If a user elects to directly provision a Boomerang through the wireless carrier and a private networking option is selected, this can potentially prohibit a Boomerang from reporting to Canvass, unless specific routing options are provided when the tunnel between the utility and the carrier is established. In these cases, the Canvass functionality will be somewhat limited as Canvass does not reside inside of the private network and cannot, therefore, address (“reach”) the Boomerang for user-initiated polling (such as settings, realtime readings, etc.).
Selecting a Data Plan
As mentioned above, PMI offers a condensed set of options (see: Available Offerings) that cover the blanket use cases of a Boomerang. Many utilities, however, already have established relationships with different wireless carriers and prefer to continue working directly with the carrier. Others prefer the direct control of the data plans and billing – or for myriad other reasons.
When discussing a new data plan with a carrier – whether for the first time or for the hundredth time – there are some terms and options that will be offered up by the carrier. The more significant of those terms and options will be briefly discussed below.
Machine to Machine (M2M) Telemetry Plan – This is the type of plan that the Boomerangs are built to use. When discussing the type of plan to use with a carrier, this is what should be selected.
Mobile Terminated Connections – This is an option wherein a remote node (i.e. a machine that is not the Boomerang) can connect to the Boomerang. This is a necessary option that must be selected. (This option allows the users to use software such as the NMS or Canvass to control and configure a Boomerang.)
Mobile Originated Connections – This is an option where the Boomerang can create a connection to a remote node. This option is necessary to allow Boomerangs to connect to Canvass, or send Unsolicited Response By Exception SCADA messages.
Connection Pooling – This is an option that allows the “sharing” of data limits among all devices in the same connection pool. For instance, if a user were to procure three Boomerangs, each with a 25MB data limit, the “pooled” limit would be 75MB. In this scenario, if Boomerang A were to use only 2 MB of data, that would leave an additional 23MB of data that could be consumed by Boomerang B and Boomerang C without incurring any overage charges. This is a very useful option when purchasing many Boomerangs where the amount of bandwidth produced by them can vary from month to month.
Mobile to Mobile Connections – This option would allow the mobile unit (in our case a Boomerang) to communicate directly with another Boomerang. This is an unnecessary option as the Boomerang will only communicate with a SCADA system or with Canvass and never with another “mobile unit” (Boomerang).
To summarize, a Boomerang cell plan should be a machine-to-machine telemetry data plan allowing mobile originated and mobile terminal connections with connection pooling. Voice and SMS should be disabled.
Other Considerations
Many M2M plans come with the same three basic elements that a user would typically see in a private cellular phone plan: voice, data and SMS (“text messaging”). In the case of the Boomerang, the user is going to want a data-only plan (no voice and no SMS as the Boomerang is incapable of using those additional-cost features).
The network type – public or private (see above: Boomerang Networking for SCADA and Canvass) – is also determined at this point. PMI typically recommends using a public networking option (which is, for the utility, the easiest to configure) and, when using this option, to use public, unrestricted static IP addresses. A static IP address is assigned once when the Boomerang is activated and does not change. This can be beneficial for IT departments who wish to be able to track the asset in their network by IP address. It also is immensely helpful when trying to configure the Boomerang (no need to discover the device’s IP address before communicating with it). The other IP addressing option is “dynamic”, wherein the IP address of a device can change as frequently as several times an hour or as infrequently as once every few weeks. The frequency at which the IP address changes is controlled by the IP networking configurations of the wireless carrier.
The final consideration in selecting a data plan is the data rate. The data rate should be selected based on the type of Boomerang being used and the use case of the Boomerang (Canvass, SCADA or both). Following is a series of tables that provide typical monthly bandwidth consumption for different device types and applications as well as the typical packet sizes (in bytes) for different traffic types. These tables can be used in conjunction with a knowledge of the user’s anticipated use case to help calculate the minimum monthly bandwidth in order to not incur overage charges (Table 1).
Table 1. Minimum monthly bandwidth
The following table (Table 2) shows the typical sizes of different IP headers and packets used for TCP / UDP and for some more specific SCADA traffic.
Table 2. Typical sizes of IP headers and packets
Activating the Boomerangs
Once the Boomerangs have been purchased and a data plan has been selected and initiated with a wireless carrier, it is now time to activate the Boomerang.
When the user receives a Boomerang from PMI they will receive all of the information that the wireless provider will require for activation – in this particular case the ESN (Electronic Serial Number). The wireless provider will request the ESN for each Boomerang to be activated and once activated will supply the user with the Boomerang’s new IP address and phone number.
Once the ESN has been given service, the Boomerang can be powered up. Upon power up the Boomerang’s LED will flash red for potentially several minutes during the OTAP (Over The Air Provisioning) cycle. Once the provisioning is complete, the Boomerang – if configured for Canvass use – will automatically connect to Canvass and will start reporting data.
Conclusion
The provisioning of cellular service for a Boomerang can be approached in a number of ways. This white paper has shown how if a user so desires, they may acquire that service directly from a wireless carrier and, with careful planning and consideration, a data plan that fits the user’s requirements can be properly selected.
Caleb Payne
Software Manager
cpayne@powermonitors.com
http://www.powermonitors.com
(800) 296-4120
