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Deval

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Posts posted by Deval

  1. iDEN does not transceive a "pretty poor signal" as much as it does a more complex signal. Since iDEN uses only 25 kHz channels, it requires 16-QAM to achieve sufficient throughput within such narrowband channelization. The downside is that 16-QAM makes iDEN signals more susceptible to fading, noise, and interference.

     

    For a layman's analogy, imagine that someone a block or two away repeatedly holds up a sign with a single letter on it. In one scenario, the letter is one of only four: Q, R, S, or T. In a second scenario, the letter is one of 16: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, or P.

     

    In the first scenario, you can likely make out the letter each time the sign goes up because Q, R, S, and T are all quite orthogonal. In other words, even at a distance, their "signals" remain quite distinct.

     

    In the second scenario, however, you can likely make the letter sometimes but not other times, as B and E, C and O, F and P, I and L, for example, are not as easily distinguishable at a distance.

     

    Now, the first scenario represents QPSK, a four symbol RF modulation scheme that CDMA1X uses, while the second scenario represents 16-QAM, the 16 symbol RF modulation scheme that iDEN uses. Below, you can see how the layman's visual analogy applies, as these are the symbol constellations for QPSK and 16-QAM, respectively:

     

    200px-QPSK_Gray_Coded.svg.png

     

    200px-16QAM_Gray_Coded.svg.png

     

    In short, it is more difficult for a receiver to tell apart each of the 16 symbols in the 16-QAM constellation than it is the four symbols in the QPSK constellation. This is especially true as the signal is increasingly degraded by fading, noise, and interference. And that is basically why, despite a much lower frequency, iDEN 800/900 is generally similar to CDMA1X 1900 in site spacing and successful propagation distance.

     

    AJ

     

    AJ, I'd like to schedule some training with you lol

     

    Dude I've learned so much from your posts.

    • Like 2
  2. Its best not to think about it. Lets the ignorant stay ignorant I guess. iOS is suppose to have a "LTE" icon like it does on the iPad 3 in the screenshots above and the Google Nexus phones just say "4G" if they are connected to LTE. There is never going to be one uniform icon to let you know you are connected over LTE so its no point in thinking about it anymore.

     

    I agree, I normally don't worry, just bugs me as a phone guy :)

  3. The whole 4G nomenclature is annoying in my opinion on iOS devices. I was in Vegas last week, and a guy who works with my girl was on his AT&T iPhone showing off how it was a 4G iPhone :wall:

     

    I gave up trying to explain the difference, and sent back to the pool to drink.

  4. There are lots of reports of eHRPD going live well in advance of LTE in many markets. eHRPD needs to be completely deployed on all the sites around a live LTE site for it to work correctly. So they are typically bringing up eHRPD over a whole market before even the first LTE sites start going live.

     

    If Shentel is so close to going live with LTE around Harrisburg, their eHRPD either needs to be up now or very soon. It would also help serve as validation of the info.

     

    Robert

     

    Good to know!

  5.  

     

    I am just wondering if any of the regional carriers would have spectrum that matched up with sprints unused spectrum so that they would be able to offer extra LTE in the major metro areas? Especially if the spectrum is in the 800Mhz block as it has much better propagation characteristics (and we all know sprint could use better service in buildings &rural areas)

     

    I could be wrong, but I believe all the regional carriers have specturm holdings in 1900, 1700 (AWS), and some 700, none in the SMR (800mhz) that Sprint uses.

  6. Honestly, and this is strickly my opinion, but living in a dense area like mine, having just LTE on 1900 is good enough for me. Give me 800 1x for inbuilding coverage, where I most likely will have access to WIFI, and give me LTE on 1900 while I'm on my daily commute.

     

    I'm curious what the next iPhone (2013) will be, considering the speculation of this year's device.

    • Like 1
  7. Which brings me back to my question: Why is Sprint not doing the same for 1900PCS? In 95% of the nation they are not using but maybe 5Mhz+5MHz of their spectrum. Are they waiting for carrier aggregation? They could still have two 1900Mhz channels even without carrier aggregation. Does carrier aggregation require new hardware?

     

    Really? Now that's interesting, need to find out more.

  8.  

    As for "history of the other carriers and how they built out their networks," please elaborate. I am uncertain what type of information you are seeking.

     

    AJ

     

    That's what happens when I think faster than I type. :)

     

    What I was inquiring about was the deployment of the 4 major carriers of their networks, from the ground up. For example, Sprint purchased their PCS licences in a partnership with the cable companies (if I remember correctly), where as Verizon came about through the merger of Bell Atlantic Mobile, GTE, AirTouch.

     

    Since the majority of the our members are technical, and have a curiousity in Network, and development, I figured it would be a great conversation and learning excerise.

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