Category Archives: FDMA

A Tale of Three “Cities”

I am not sure why, but my brain always likes to analyze things in columns and rows. Hence, I find myself doing lots of “spreadsheet analysis.”

Recently, I came across Icom‘s Spencer County Case Study. I was very impressed by the cost. In light of even Senators writing about government spending, I thought that it might be fun to do a bit of cost comparison via “spreadsheet analysis” of Indiana’s Spencer County vs. what we are seeing in Virginia. So, here it is:

Yes, you are reading this right! The taxpayers in Indiana are paying up to 18+ times less for a radio system than the taxpayers in Virginia! I argue that these savings are because Indiana is willing to accept competitive bids for standards-based radio communication solutions.

If you would like to figure out how standards-based radio communication solutions can save you 18.3 X, feel free to contact us at (804) 625-4233 or sales AT richmondrf DOT com.

Why aren’t we TDMA fanboys

A fanboy is defined as “A person who loves something without question.”

Accepting things without question is counter to part of our mission to provide radio communication solutions that provide choice, performance, and best-value.

Here are some of the reasons that we don’t just accept TDMA without question:

Interference with other devices. This is documented MANY places, including here and here.
New accessories are required because of this interference.
FDMA should have better coverage.
Two-slot TDMA radio must transmit twice the transmit power to have the same energy per bit as the FDMA radio. Would you like to guess about the transmit power requirements for four-slot TDMA? Six-slot TDMA?
Amplifiers are expensive.
Increased potential for time delay interference exists.
Access Control is an afterthought.
Nextel failed. Would you like to guess what technology their network was based on?

Many of the comparisons above are between TDMA and FDMA. I don’t want you to get the wrong impression; I don’t think FDMA is perfect. (As a matter of fact, recently a really smart friend predicted that CDMA will ultimately win this battle.) On the other hand, I do want to encourage you to think about things like interference, coverage, and cost before purchasing a new radio communication solution.

(some of) the power of Radio over IP

Lately, in the lab, we have been tinkering with Radio Over IP Gateways. Since we love standards, we spent a significant amount of time with Icom America’s VE-PG3, because it “speaks” the Session Initiation Protocol (SIP).

Just like most other Radio Over IP Gateways in the marketplace, the VE-PG3 can connect two or more radio sites over an IP network. In this configuration, received radio audio is bridged to opposing radio sites of the network. This bridge mode can connect dispersed radio sites over the network and can provide cross band, cross category communication.

This technology is already in use by the Virginia State Police. They call it COMLINC (Commonwealth’s Link to Interoperable Communications). It enables adjoining jurisdictions totally different radio systems (such as Hanover County’s 800 MHz system and Powhatan County’s VHF system) to be connected. This is how they are going to catch you if you go speeding from Hanover into Powhatan!

I believe that we will see this technology being used even more in the near future. One example I can think of is Virginia’s electric cooperatives. If Northern Neck Electric Cooperative (IDAS on 153MHz) needs to talk to Rappahanock Electric Cooperative (TaitNet MPT 1327 on 217MHz), this is a great way to make it happen.

But, going beyond connecting two or more radio sites is where the VE-PG3 really starts to shine, because it can convert radio audio into SIP.

These were some of the immediate benefits that we were able to see in the lab:

Eliminate EXPENSIVE virtual radio/dispatcher software on PCs by using any SIP softphone/hard phone. (Hint, here are 20 FREE SIP Softphones.)
Use a SIP softphone on any device (think Android, iPhone, etc.) to talk to your radios.
Use a SIP Trunk to talk to your radios. Anyone with any phone can call a telephone number and talk to your radios.
Use all of the features of Asterisk on your radio system. Imagine the literally endless possibilities:

Get Call Detail Records for all of your radio traffic
Record all of your radio traffic
(Conference Bridging.) Bridge any mix of any number of PCs, Androids, iPhones, analog phones, radio systems, paging systems, etc.

If you couldn’t tell, we are excited to see standards coming to the Radio over IP marketplace.

If you are looking to take advantage of Radio over IP, please contact us at (804) 625-4233 or sales AT richmondrf DOT com.

Are we creating a modern Tower of Babel?

You need only look at our Twitter Bio to recognize the fact that we are advocates of standards-based radio communication solutions. However, in reading a recent forum post (and reflecting on some of our blog posts), we realized that the wireless industry may not share the same affinity for standards-based radio communication solutions.

As the wireless industry moves to digital, different digital technologies are being chosen by different customers. For example:

Most public safety organizations seem to be implementing the P25 Phase 1 digital technology
However, some public safety organizations are implementing NXDN/other digital technologies
Some think that P25 Phase 2 is the only way to go
Metropolitan Transportation Authority (MTA) is implementing the NXDN digital technology
Electrical cooperative is implementing the TETRA digital technology
Yet others are implementing the DMR digital technology

So, what happens when there is an emergency and it is critical that the local public safety organization communicates with the local MTA, the local electrical cooperative, a neighboring public safety organization, etc.??? Nothing!!! None of these radio communication solutions can communicate with the other; we have created a modern day Tower of Babel! Add encryption into this mess and even fewer organizations can communicate.

In our next post, we hope to address possible solutions to this problem.

Thanks for reading! And, if you see any typos/mistakes, please contact us at (804) 625-4233 or sales AT richmondrf DOT com.

The digital standards and the manufacturers

In a previous blog post, we referenced the fact that digital standards are maturing. So, while we were at IWCE, we started a spreadsheet to:

compare the digital standards
list which manufacturers are involved with which standards

Below is this spreadsheet. You can learn a lot from it. For example, there appear to be as many manufacturers focused on DMR (if you add in the Chinese manufacturers) as there are manufacturers focused on P25. (This is pretty significant when you consider the marketshare of P25 in public safety agencies or the fact that EF Johnson and Midland only have P25 offerings.)

Enjoy! And, if you see any typos/mistakes, please contact us at (804) 625-4233 or sales AT richmondrf DOT com.

	NXDN	DMR	P25 Phase 1	TETRA
kHz	12.5 or 6.25	12.5	12.5	25
	FDMA	TDMA	FDMA	TDMA
		2-slot		4-slot
EF Johnson			Yes
Harris		Yes	Yes	Yes
Hytera		Yes		Yes
Icom	Yes		Yes
Kenwood	Yes		Yes
Midland			Yes
Motorola		Yes	Yes	Yes
Tait		Yes	Yes
Vertex Standard		Yes

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