Simulcast signal behavior at the receiver

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

Simulcast signal behavior at the receiver

[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...

Read More

Modulation in modern paging, Part II

Posted by on May 7, 2011 in Blog, Tutorial | 0 comments

Modulation in modern paging, Part II

Phase Trellis Before going further, it might be worth to show the phase trellis for binary MSK and GMSK. We’ll come back to these diagrams in what follows. When looking at these diagrams, there are a couple of things worth noting. First, they show exact phase accumulations at the optimum sampling times. Second, if they were differentiated to show, instead, instantaneous frequency, the result would be a classic “eye diagram”. A quick consideration of the instantaneous changes in line-slopes on the MSK trellis suggests that, assuming filtering or bandwidth issues over the...

Read More

Modulation in modern digital paging

Posted by on May 4, 2011 in Blog, Tutorial | 0 comments

Modulation in modern digital paging

Apology First, this post is going to get technical. Sorry. If you’re not into that sort of thing, you might just want to skip all the way down to the conclusions or skip this whole post altogether. OTOH, if you’re into things wireless, this might be refreshing in the sense that you may walk away with a better appreciation for the level of technical detail that went into the design of modern digital paging systems. Abstract-It is commonly known that the RF modulation in the GSM is Gaussian Minimum Shift Keying (GMSK). It is not so commonly known that the modulations in ReFLEX and...

Read More