GNSS: Subtle Improvements

Section by Brian Klug

Like the iPhone 4S and the iPhone 4 CDMA before it, Apple has gone with the GNSS (Global Navigation Satellite System) leveraging both GPS and Russian GLONASS which lives entirely on the Qualcomm baseband. In the case of the iPhone 4S and 4 CDMA, that was onboard MDM6610 and MDM6600 respectively, both of which implemented Qualcomm’s gpsOneGen 8 with GLONASS tier. Going to on-baseband GNSS is really the way of the future, and partially the reason why so many of the WLAN, BT, and FM combos don’t include any GNSS themselves (those partners know it as well). In this scheme GNSS simply uses a dedicated port on the transceiver for downconversion, additional filtering (on RTR8600), and then processing on the baseband. The advantage of doing it all here is that often it eliminates the need for another dedicated antenna for GNSS, and also all of the assist and seed information traditionally needed to speed up getting a GPS fix already exists basically for free on the baseband. We’re talking about both a basic location seed, precision clock data, in addition to ephemeris. In effect with all this already existing on the baseband, every GPS start is like a hot start.

There was a considerable bump in both tracking accuracy and time to an assisted GPS fix from the iPhone 4 which used a monolithic GPS receiver to the 4 CDMA and 4S MDM66x0 solution. I made a video last time showing just how dramatic that difference is even in filtered applications like Maps.app. GLONASS isn’t used all the time, but rather when GPS SNR is either low or the accuracy of the resulting fix is poor, or during initial lock.

With MDM9615 now being the baseband inside iPhone 5, not a whole lot changes when it comes to GNSS. MDM9615 implements gpsOneGen 8A instead of just 8, and I dug around to figure out what all has changed in this version. In version 8A Qualcomm has lowered power consumption and increased LTE coexistence with GPS and GLONASS, but otherwise functionality remains the same. MDM9x25 will bring about gpsOneGen 8B with GLONASS, but there aren’t any details about what changes in that particular bump.

I spent a lot of time playing with the iPhone 5 GNSS to make sure there aren’t any issues, and although iOS doesn’t expose direct NMEA data, things look to be implemented perfectly. Getting good location data is now even more important given Apple’s first party turn by turn maps solution. Thankfully fix times are fast, and getting a good fix even indoors with just a roof between you and clear sky is still totally possible.

Cellular Connectivity: LTE with MDM9615 WiFi: 2.4 and 5 GHz with BCM4334
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  • medi01 - Wednesday, October 17, 2012 - link

    1) Compare ipad2's gamut, cough
    2) Check values on toms
    http://media.bestofmicro.com/3/4/331888/original/g...
    http://www.tomshardware.com/reviews/ipad-3-benchma...

    Unlike anand, toms was beyond primitive contrast/brightness benchmarking for quite a while.
    Reply
  • thunng8 - Thursday, October 18, 2012 - link

    Not sure if I should trust Tom's figures compared to Anands's.

    In any case, both show the ipad3 has higher gamut, especially in sRGB.
    Reply
  • steven75 - Wednesday, October 17, 2012 - link

    I think what you meant to say is that AMOLEDs win on black levels and that's about it. LCDs still win in accuracy and most importantly ability to see them in outdoor settings. Reply
  • KoolAidMan1 - Tuesday, October 16, 2012 - link

    Not even close. Even the better Android displays like the Galaxy S3 has a PenTile display. Despite having more "pixels" it actually has fewer subpixels than the iPhone does. Unless you have bad eyesight the S3 display looks really bad in comparison, and this is before we get to even worse smartphone displays out there by HTC, etc. Reply
  • Sufo - Tuesday, October 16, 2012 - link

    Old pentile displays were visibly jaggy on vertical lines - even my old lumia 800 exhibited this to some extent. On the GS3 tho, it is not noticeable and it has nothing to do with eyesight.

    Your comment makes it sound (to someone who has seen many different smartphone displays in person) as though you haven't spent much time with the GS3 (read: many smartphones) at all. Simply mentioning that is uses pentile subpix config, from you, sounds like regurgitated information. Not only that, but you seem to gloss over the many benefits that amoled panels bring. It's arguable that these benefits are more important than an accurate colourspace on (specifically) a mobile phone - although it is ofc entirely subjective.

    This brings me to the last tell of ignorance I noted; your mention of HTC. Have you used a One X? For those who do not like amoled panels, the display on the one x is perhaps nicer than both the gs3 and the ip5. Ofc you may say Android is not your cup of tea, and that's a perfectly justifiable stance, however it has nothing to do with display tech.

    tl;dr You sound like you don't know what you're talking about
    Reply
  • KoolAidMan1 - Tuesday, October 16, 2012 - link

    I do know what I'm talking about given that I've seen many smartphones, and I've calibrated my share of desktop displays to sRGB.

    Differences in display tech aside, Android phones have never gotten color profiles right, EVER. They're almost always oversaturated, have too much contrast, and are inaccurate. Anand even posted a difference in color accuracy between several devices, and the profile for the S3 is totally what I expected.

    The S3 really doesn't look good, period, but then again there are people who argue that TN panels are just fine against IPS. I'm used to hearing nonsense on forums when it comes to display from people who don't know what to look for.
    Reply
  • KoolAidMan1 - Tuesday, October 16, 2012 - link

    BTW, apologies if that came out harsh, but the difference in color and contrast accuracy between something like the S3 and a properly calibrated device is a night and day difference to me. I'm pretty sensitive to display quality though; my main desktop display at home is still an NEC and my plasma is a Pioneer Elite (RIP) Reply
  • rocketbuddha - Tuesday, October 16, 2012 - link

    For Android you have the following 720p HD Displays

    SLCD - HTC Rezound (2011 tech)
    SLCD 2 - HTC One X, Sony HD
    HD SAMOLED Pentile - GS3, Galaxy Nexus, Moto Razr HD
    HD SAMOLED RGB - Galaxy Note II
    True IPS LCD - LG Optimus 4X, Optimus G
    Super IPS LCD -Asus Padphone, Sharp phones etc

    So you have big set of choices. If dark contrasts are important then SAMOLED is the way to go. SAMOLED RGB over SAMOLED Pentile.
    If overall color and whites are important go with SLCD2.
    IPS LCDs are the closest to the Retina Display and u have a choices there too. You can pick and choose what is good for you and have alternatives.
    Reply
  • Spunjji - Thursday, October 18, 2012 - link

    The HTC One X has what is hailed to be one of the best LCD smartphone displays out there. Your claim is invalid.

    Similarly, the Galaxy Note 2 has an AMOLED display without PenTile. Sure, it's lower density, but one does not hold a 5.5" screen so close to one's face.
    Reply
  • medi01 - Wednesday, October 17, 2012 - link

    ""The iPhone 5 display is better than any current Android display.""
    Why don't you go hit your dumb head with something heavy, ipad would do?
    Reply

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