What is Dual Band GNSS?

Discussion in 'General GPS Discussion' started by Nuvi-Nebie, Feb 18, 2019.

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  1. Nuvi-Nebie

    Nuvi-Nebie Moderator

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    Dual Band (or Dual frequency) GNSS is an enhancement to the original 'GPS' system, it uses extra signals from satellites to provide much greater (sub-metre) accuracy.

    When satellite navigation was first made available for non-military use, it was a single set (or constellation) of 24 satellites operated by the USA, since then many more satellites have been added by various countries, some full constellations and some single or small groups of satellites intended to cover only part of the earth's surface, they include, Glonass (Russia), BeiDou (China), Galileo (European Union), ZQSS (Japan), NavIC (India) etc, the last two only cover their own countries, the term GNSS often refers to a system that utilizes more than one constellation

    In the first specifications for the GPS (USA) system, the transmitted signals from the satellites could be carried on up to 5 carrier frequencies ranging from L1 = 1.5GHz to L5 = 1.1GHz, although only L1 was available to non-military users


    GNSS_navigational_frequency_bands.png

    GNSS.jpg


    Some websites have described satellite navigation units that can utilise more than one constellation as 'Dual Band', however this is incorrect, a Dual Band unit is one that can utilise more than one transmitted frequency (or carrier) from a single satellite, e.g. L1 + L5 or E1 + E5a or B1 + B2a

    At present GPS (USA), Galileo (European Union) and BeiDou (China), have global systems of satellites that supply Dual Band frequencies, (ZQSS (Japan) does this but not globally)

    Until recently only very costly surveying units were 'Dual Band', while navigation chips in smart phones and even dedicated GNSS products used only the L1 band , however there are now low cost devices in smart phones and dedicated GNSS units etc. that are truly 'Dual Band'

    WHAT IS REQUIRED FOR SMARTPHONE DUAL BAND?

    Obviously the minimum requirement is a device fitted with a navigation chip that can handle 'Dual Band' (L1 + L5), there are presently a few manufactures that are supplying these devices for smart phones, tables etc. , devices that can do this include Broadcom BCM4775X family, Kirin 980, Snapdragon 855, Exynos9825 etc., however the presence of a 'Dual Band' chip on its own isn't enough, several levels of software also need to be in place, they include the correct level of operating system and enabled L1 + L5 software.

    At present, this article only covers smartphones / tablets that run on the Android operating system, as I have no knowledge of iOS devices, although Androids 7 and 8 had some enhancements for GNSS, all units should be running Andriod 9 or above, there is an Android App. that can help to show you what is happening with your device, it is called GPSTest, this name is not unique so here is a picture of the App. icon
    GPSTest.jpg

    Using this App. it is possible to see L/E1, L5/E5a and B1/B2a channels in the 'CF' column, the double ID entries are effectively the second 'Band', however the App. may not be able to get the info. it needs on all devices, even when the unit is working in 'Dual Band' mode

    both-L1-L5.jpg

    In the composite GPSTest screen above (from a Galaxy Tab A7 (2020) runing Android 11), the IDs with double entrys (L5, E5a and B2a) are indicating that a second frequency from a single satellite is being received, this is sometimes still visible even when the 'CF' column is not populated due to a lack of supporting software on the unit.

    Here is The GPS Test Database

    WHICH SMARTPHONES HAVE DUAL BAND?

    As there are now too many products on the market that are dual band to list, here is a list of chipsets to look out for :-

    GNSS-Chips.jpg

    Reference1
    Reference2
    GITHub FAQs

    Quite a lot of smartphones / Tablets are working with Dual Band or are Dual Band 'ready' manufactures include :-
    • Asus
    • Xiaomi
    • LG
    • OnePlus
    • OPPO
    • Samsung
    • Sony
    • ZTE

    Dedicated Dual band Products
    Garmin has started launching Dual-Band products (not before time), in the form of the GPSMap65/65s and GPSMap66rs, there is also talk of their sports watches being equipped with Dual-Band GNSS chips soon, details are a bit vague at the moment but the sports watches are rumoured to use Sony CXD5610 series of chips
     
    Last edited: Jun 16, 2021
    Nuvi-Nebie, Feb 18, 2019
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