In a previous blog post, I described the ArcFM Fiber Manager™ 10.2.1a upgrade. This upgrade enables multiplexing functionality which necessitates the modeling of additional tables. In a recent deployment, these tables were also leveraged to model microwave towers which enable microwave frequency tracing (More Later).
Microwave Tower
Arguably the most famous and most photographed (if by accident) microwave tower is right behind the Hollywood Sign in Los Angeles. Figure 1 is a photograph that I took of that tower on top of the hill behind the sign. The tower and adjacent building is the City of Los Angeles Central Communications Facility which is used to support the city’s municipal agencies.
Microwave Transmission
Towers like the above are necessary because microwave transmission is direct line of sight. Unlike radio, microwave signals cannot go around hills or large buildings. Because of this limitation, relay stations must be established about every 35 miles. The high-frequency waves do have an increased information bandwidth of 30 times that of radio which helps justify this inconvenient limitation. Fiber optics have largely replaced the requirement for long distance microwave transmission, but microwave is still important for information transmission at short distances.
So…How can one leverage the multiplexing model for microwave transmission?
When I originally wrote my previous post on multiplexing, I had not conceived of utilizing the model for microwave transmission. I have modeled microwave towers in the past, but utilized a more traditional flexible data model and splitter means. While onsite recently, a client wanted to enable Fiber Manager™ functionality of their microwave instead of just showing it on a map. I started asking them questions:
- Do you transmit microwave in different frequencies? Yes.
- Does the same tower transmit to different locations? Yes.
- Do you want to be able to be able to trace a microwave signal based upon its frequency? Yes.
It became obvious to model the tower like a piece of multiplexing equipment.
Figure 2 is a graphic illustrating the multiplexing model with the parent MicrowaveDevice feature class. Assuming that the initial Schneider Electric instructions are followed carefully to establish the multiplexing object model (i.e. F_PassiveDevice, F_PassiveSplitPort, and F_PassiveCommonPort), all an administrator has to do is the following:
- Construct a MicrowaveDevice (i.e. Tower, Dish, etc.) feature class with the FIBERCONNECTIONCONTAINER, FIBEROBJECT, and MICROWAVEDEVICE model names.
- At a minimum, add and model the flexible data model fields (plenty of previous posts on this subject)
- Add MICROWAVEDEVICE and PASSIVEDEVICE (assuming no other connectable child objects of the Tower) as the field default value for the THISFIBERCLASSMODELNAME and FIBERCHILDCLASSMODELNAME fields respectively.
- Add the new MicrowaveDevice feature class as a junction to the telecommunications geometric network.
- Construct a Composite (1:M) relationship between the GLOBALID field of the parent MicrowaveDevice and FIBERPARENT field of the client F_PASSIVEDEVICE object.
- Assign the ArcFM™ Update Fiber Parent Field AutoUpdater to the relationship created.
Microwave Signal Path
Piece of cake! This is another use of the flexible data model. A microwave path linear feature class is modeled exactly like a fiber optic cable with no buffer tubes. Let’s build it.
- Create a line feature class (suggested name of MicrowavePath) with at least a NAME text field and the flexible data model fields.
- Assign the new feature class the following model names: FIBERDATATABLESOURCE, FIBEROBJECT, and WIRELESSPATH.
- Assign the following field model names to the NAME field: FIBERCIRCUITREPORTFIELD, FIBERTRACEREPORTFIELD, AND SHEATHID. Also, assign the flexible data model fields in the normal Fiber Manager™ documented way.
- Establish the MicrowavePath field default values for the THISFIBERCLASSMODELNAME and FIBERCHILDCLASSMODELNAME to WIRELESSPATH and WIRELESSPATHOBJECT respectfully.
- We now need to construct the F_WirelessPath table with at least a PATHNUMBER (Long Integer), FREQUENCY (Double), and the flexible data model fields.
- Create a Frequencies domain (if not already present) and populate it with the applicable frequencies. For 900 MHz, make the coded value 0.9. For 2.4 GHz, make the coded value 2.4.
- Assign the Frequencies domain to the FREQUENCY field of the F_WirelessPath table.
- Add WIRELESSPATHOBJECT as the field default value for the THISFIBERCLASSMODELNAME field.
- Add the following model names to the table: FIBERCIRCUITPARTICIPANT, FIBERCONNECTABLEOBJECT, FIBEROBJECT, and WIRELESSPATHOBJECT.
- To the PATHNUMBER field, assign FIBERCONNECTIONDISPLAYSORTFIELD and FIBERREPORTINGNAME field model names. To the FREQUENCY field, assign FIBERCONNECTIONDISPLAYFIELD. Also, assign the flexible data model fields.
- Add the new MicrowavePath feature class as a complex edge to the telecommunications geometric network.
- Construct a Composite (1:M) relationship between the GLOBALID field of the parent MicrowavePath and FIBERPARENT field of the client F_WirelessPath object.
- Lastly, assign the ArcFM™ Update Fiber Parent Field AutoUpdater to the relationship created.
Issues?
The only issue that has been observed utilizing this methodology is with units. A fiber optic cable’s frequency of light is measured in nanometers (nm). Microwave units of frequency are measured in megahertz (MHz) or gigahertz (GHz). Although the tracing tool is completely functional with microwave (Figure 4), it was designed with nanometers in mind.
As shown in Figure 5, if the user traces a microwave path at 2.4 GHz The default trace report also reports in nanometers. This could result in a bit of confusion.
But…Can one cook a hot dog with a microwave dish?
For fun and general knowledge, I did brief research on this subject. In short, if you want to cook a hot dog, you had better get a microwave oven. Telecommunications via microwave uses just too little power. Mythbusters tried to cook a turkey with mobile microwave transmission. Busted!
What do you think?