Simulcast

Synchronization to GPS Time

Posted by on Mar 28, 2013 in Blog, Simulcast, Tutorial | 0 comments

In the science side of my blog, I have frequently introduced concepts from special relativity that speak to limitations in synchronizing clocks that are separated by appreciable distances. In practice, the speed of light is about 1 foot per nanosecond. This seems rather odd then, in the context of metropolitan area paging networks that cover regions as large as San Diego to northern greater Los Angeles on a side and with distances between sites of tens to hundreds of miles. In what way can such systems be said to “simulcast” if simulcasting means “broadcasting...

Big fat paging bits

Posted by on Feb 15, 2013 in Blog, Simulcast, Tutorial | 0 comments

Back to our sponsor, paging, for a moment. In my very first post here, I took a comparative look at some distinctions between modern paging and digital cellular systems. I want to return to that idea, but with a slightly different point of view. This time, I want to consider the composition of the information-carrying components of these systems on a photon-by-photon basis. First, let’s go back to the basic aspects of a bit. A base station (BS) transmitter radiates electromagnetic power in sending a communications symbol for a certain amount of time. In the case of a paging system, say...

Simulcast signal behavior at the receiver

Posted by on Feb 16, 2012 in Blog, Simulcast | 0 comments

[latexpage] In my previous post on simulcast in paging, I mainly took a high level view of the system overall. In this post, I’m going to drill in a bit deeper at the receiver. To start simply, let’s assume we’re dealing with a relatively low data rate binary FSK scheme, like POCSAG at 512 or 1200 bit/s. In this case, the bit time is the symbol time, something like 1 to 2ms or so. Considering the speed of radio signals, at $300 \times 10^{6 }m\cdot s^{-1}$ the “length of a bit” will be around 150 to 300km. What this means is that radio signals will have every...

Simulcasting in paging

Posted by on Feb 13, 2012 in Blog, Simulcast | 2 comments

Simulcasting is perhaps the most arcane subject in all of land mobile radio communications. In William C. Jakes’ classic volume, Microwave Mobile Communications, simulcast receives no treatment at all. The first edition, dated 1974, certainly post-dated POCSAG, which goes back to 1982. The second IEEE edition, dated 1994, post-dated Golay and FLEX digital paging. There seems little reason to gloss over simulcast in this way. Finally, in 2010, Springer-Verlag published Wireless Personal Communications: Research Developments, edited by Woerner, Rappaport, and Reed; and this included in...

Why is paging resilient to disaster?

Posted by on May 3, 2011 in Blog, Simulcast, Tutorial | 0 comments

Paging/NPCS systems typically keep on running through disasters that bring down most other wireless or wireline telecommunications services. Examples include hurricanes (such as Andrew & Katrina), terrorist attacks (such as Ground Zero in NYC 9/11/01), and so on. There is an exceptional paper authored by Sag Harbor Consulting Group that reviews this information in detail. [Note that this will take a while to download.] Unfortunately, this work is now about 10 years old and showing signs of wear and tear. More updated material, although quite focussed at first responders using specialized...