A brief comparison of 11n vs 11ac vs 11ad. And what services will we see in the future

    Earlier, at the dawn of the commercial development of the 802.11 group of standards, wireless networks were slow compared to wired networks when considering bandwidth. With the introduction of the 802.11n standard, we already got pretty similar speeds with conventional mass wired connections. Now the main development of the standards is moving towards 802.11ac and 802.11ad, which will allow you to get speeds at the level of several gigabits per second over a wireless network.

    A brief comparison of these standards is presented in the table.

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    802.11n

    This technology is widely known, so in this article we will not dwell on the technical details.

    The possible services here often seem clear and well-known, but in fact there are many options for very interesting services based on 802.11n technology in the world. The practical implementation of unusual services on 11n networks can be found in the next article , especially in its second half.

    802.11ac

    The 802.11ac standard works only in the 5GHz spectrum. Backward compatibility with 802.11n (at 5GHz) and 802.11a devices will be provided. At the same time, a significant increase is expected not only in bandwidth, but also in coverage.

    Broadcom, which was the first to release a chip for 802.11ac, believes that the maximum speed will be up to 3.47Gbps at short distances. For cases of basic implementation of 802.11ac, for example, on smartphones and other basic user devices in terms of Wi-Fi (one antenna and radio module, 80MHz channel, one spatial stream), speeds of up to 433Mbps at distances up to 10m can be expected. This is several times more compared to 802.11n in the same conditions. Broadcom also claims that the released 802.11ac SoC chip is three times faster and six times more energy efficient than 11n solutions. The chip supports both 2.4GHz and 5GHz, so it is backward compatible with current platforms (only 11n is supported in 2.4GHz).

    Netgear concludes that devices with an 802.11ac chip and one radio module (one antenna) will achieve similar speeds with identical power consumption with the current fastest solutions for 802.11n (3 radio modules / 3 antennas, etc.). This means that a typical tablet computer with one 11n radio module and supporting up to 150Mbps, with an 11ac module in a similar design will be able to reach maximum speeds of 450Mbps.

    802.11ac supports up to 8 antennas and radio modules (11n to 4), therefore, an 8x8 MIMO level is theoretically achievable here. At the same time, you can work with modulation up to 256QAM and transmit data through 8 spatial streams. An important innovation is the MU-MIMO (Multiple User) technology. This is actually a spatial radio switch that allows you to simultaneously transmit and receive data from multiple users on the same frequency channel.

    Broadcom released in mid-February 2012 the first version of the 802.11ac chip (SoC / System on Chip). The closest competitor Atheros (owned by Qualcomm since 2011) should release its version in the second quarter of 2012.

    According to forecasts, ABI Research 802.11ac will become the dominant standard by 2014. In-Stat also predicts rapid 11ac growth with shipments of around 1 billion devices with 11ac chips until 2015. Moreover, by 2015, already 100% of Access Points will be delivered with 802.11ac chips.

    In terms of 802.11ac services, on the one hand, it is focused on a much more complete replacement for wired access at high speeds than 802.11n. On the other hand, of course, there is a goal in the effective support of multimedia services around high-resolution streaming video.

    The other side of the coin is the availability of frequency channels in the 5GHz spectrum, which varies significantly from country to country, and in the Russian Federation is, for example, only 100MHz (5150-5250MHz), details here. Therefore, until our regulator thinks deeply about the need to release part of the 5GHz spectrum for Wi-Fi tasks, as has been done in many countries, such an attractive technology will remain a beautiful fairy tale in our realities.

    802.11ad

    The standard will operate in the 60GHz spectrum, which is not licensed in most countries. Significantly more free bandwidth is available here than in the overloaded 2.4GHz and already loaded 5GHz spectrum.

    In terms of services, this standard focuses on supporting high-definition video (HD). Also here, the emergence of services such as "wireless docking" is expected, when all devices are a computer, monitor, projector, etc. have wireless data exchange. Thus, this is a great option for how you can assemble nearby various devices that require a wide band connection, and completely remove data cables and video cables from the solution, including removing HDMI cables for HD video. Used ultra-high frequency leads to the fact that the signals are quite narrowly targeted. Also, many problems arise due to the intense absorption of signals when passing through obstacles, so the main expected use case is the interaction of devices within a room.

    Also, 802.11ad should become the basis for technology in Wi-Fi Display, which is being developed by the Wi-Fi Alliance. Intel’s Wi-Di is now its predecessor, although Wi-Di is far from the 11ad specifications and requires specialized Intel chips in the hardware.

    802.11ad is expected to be compatible with the WiGig standard.

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