MWC2014: MIMO 2x2: 2 in phones, routers in SFP-modules ...

    Among the many announcements MWC2014 I want to highlight two. Alone, louder, from Broadcom, he himself will still make a lot of noise. The second, be quiet, from Huawei - everything is there "without noise and dust", but it is very interesting.

    Broadcom announced a WLAN chipset for mobile devices with support for 802.11ac 2x2: 2 MIMO (867Mbps), causing considerable excitement in the press. Let's get it right.

    So, 867Mbps, say?
    • Does anyone have gigabit internet at home?
    • Has anyone seen how fast the hotspot is?
    • Does anyone have a NAS for movies with really fast RAID? Even a single SSD cannot always deliver data so fast. [UPD] Here I got a little excited, having mixed up Mb and MB. [/ UPD]
    • Who has the confidence that the phone will be able to write this so quickly to the built-in flash memory (not to mention the card)? My data shows speeds of the order of 35-65Mbps for an average phone.
    • Two antennas = at least twice the power consumption. How will this affect battery life?

    What then is the use of him, speak?

    Well, for starters, if you transmit something twice as fast - it will take half as much time. Since the airtime is the key resource of the Wi-Fi network, the total cell capacity (the number of clients or average speed per client with the same number) will increase. At the same time, because antennas are less busy with transmission, you can save a little energy. But this is all only with a small amount of transfers (browsing) that will go directly to the phone RAM (if the manufacturer has implemented such a feature). Yes, and then, you still need to, nevertheless, give the data at such a speed - which means buffering on the point, and decent, otherwise there will be no difference with the “usual” 802.11ac@433Mbps.

    But what really can help is technology.MRC and STBC , combined with 2x2: 1 or, generally, 1x2: 1.
    • With two receiving antennas, MRC allows you to mathematically recombine the original data stream from copies of the received signal, improving the sensitivity of the receiver (“medium temperature hospital” by 3 dB) and significantly increasing noise immunity as a whole (reducing the number of errors and, accordingly, relaying packets).
    • With two transmitting antennas, STBC allows mathematics to transmit one data stream so that the MRC receives the signal in its best form, adding “mathematical” gain to the transmission.
    • As a result, we obtain a significant improvement in the Rate-over-Range parameter due to a better signal-to-noise ratio and a reduction in the number of errors. Which, you see, is important for a small-sized device, most of the antennas of which are closed by the user's palm.

    In total, as well as with 802.11ac itself, the main improvement here is not the speed (which marketers will sell us), but the range and purity of the signal. Again, purely for battery reasons, I am interested in comparing this 2x2: 2 and 1x2x1 (it takes less energy to receive) and see if the game is worth the candle. Time will tell - it seems that such a chipset is in the Galaxy S5.

    But what was really missed by most MWC observers under the noise of smartphone announcements is this thing :


    This is a full-fledged router in SFP format. With support for IPv6 and even SDN. The level of all these supports, of course, should be checked - but the idea itself! Imagine what you can potentially do with such a thing, especially by adding a WWAN modem to it?

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