Wireless Network

Gigabit Wi-Fi – 802.11ac : Advantages & Limitations

IEEE 802.11ac will be the next wireless (Wi-Fi) technology standard after 802.11n. A few consumer access points are already available with 802.11ac radios, but the currently available 802.11ac standard is only Draft 2.1. The final standard is expected to be released by late 2013. The first enterprise-grade Wi-Fi devices with 802.11ac radios are expected from early 2013.

While 802.11ac products will eventually support specifications like 8 spatial streams, 8 antennas and 160 MHz channel width, the early (enterprise) 802.11ac products may most probably support 4 spatial streams, 4 antennas and 80 MHz channel width.

The higher speeds/bandwidth supported by 802.11ac standard is expected to be useful for HD Video Streaming, Blue-Ray TV’s, HD Video Conferencing/Surveillance, Cloud Synchronization, Densely populated Wi-Fi networks and other such highly demanding Wi-Fi applications. Let us have a look at some advantages and disadvantages/limitations of 802.11ac/Gigabit Wi-Fi, in this article.

Advantages of 802.11ac/Gigabit Wi-Fi

  1. The amount of bandwidth/speeds supported by 802.11ac will depend mainly on factors like channel bandwidth, no. of spatial streams and guard intervals. The maximum speeds/bandwidth supported by 802.11ac will vary rom 433 Mbps to More than 7 Gbps (theoretical maximum). Hence, 802.11ac will support much more bandwidth when compared to 802.11n which supports a theoretical maximum of 600 Mbps.
  2. A single 802.11ac radio can accommodate more users/Wi-Fi devices than previous standards (for similar bandwidth requirements). Mostly they can even operate at a higher bandwidth.
  3. Since data rates decreases with increasing distances from the access point, it is important to note that 802.11ac will support higher data rate over longer distances. This is partly due to the more aggressive error correction codes supported by 802.11ac.
  4. 802.11ac products will use a concept called ‘beam-forming’, which strengthens the signal of the connection in one direction (where it is strong), instead of sending (weaker) signals in all directions. This results in better wireless throughput performance.
  5. 802.11ac will most probably use 256-QAM (Quadrature Amplitude Modulation) that provides almost 33% increase in throughput over 64-QAM used in 802.11n.
  6. While 802.11n uses MIMO technique, 802.11ac will use MU-MIMO (Multi User – MIMO) that will allow access points to transmit single/multiple streams to multiple clients at the same time. This enables better efficiencies for Wi-Fi networks where a large number of low-configuration Wi-Fi devices (like mobile phones) need to connect.
  7. Performance of wireless clients in dense Wi-Fi networks will be better with 802.11ac technology.
  8. While 802.11n supports a maximum configuration of 4×4:4; 802.11ac supports a maximum configuration of 8×8:8. This is of the format – TxR:S, where T – Transmit Antennas, R – Receive Antennas, S – Spatial Streams.
  9. The maximum speed/bandwidth supported by a 1×1:1 802.11n device is 150 Mbps. But the maximum speed supported by a 1×1:1 802.11ac device is 450 Mbps.
  10. Since 802.11ac operates in the 5 Ghz spectrum, there is lower interference from other wireless devices. There are more non-overlapping channels (23) in 5 Ghz and this provides a lot of design flexibility which results in improved operational efficiencies.
  11. 802.11ac technology can be used to create short, but high-speed/high-capacity wireless back-haul links for extending the network.

Disadvantages/Limitations of 802.11ac/Gigabit Wi-Fi

  1. Older 802.11n access points/client adapters cannot be upgraded to 802.11ac. That means, all the access points and client adapters in the organization needs to be changed (hardware replacement) to 802.11ac compliant products, if you want high-speed gigabit Wi-Fi in your premises. Hardware replacements might be required even if you want to upgrade from older version of 802.11ac to a newer version of 802.11ac, later on.
  2. Since the total bandwidth consumed by 802.11ac devices will be higher, the controller, edge switches, POE adapters, backbone network, etc. may need to be replaced, as well. The total cost of an 802.11ac upgrade project will most probably be much higher than an 802.11n-upgrade project.
  3. 802.11ac Wi-Fi adapters and access points will be more expensive (at least initially) as more antennas and better electronics/processors are required.
  4. 802.11ac can be implemented only in 5 GHz. All the older technologies (including 802.11n) that run predominantly in the 2.4 GHz band may need a separate radio/separate access points supporting 2.4 GHz, to connect to the network.
  5. In practical situations, 802.11ac network might be planned as an overlay to the existing 802.11n network. Exclusive 802.11ac network will remain a dream, in most cases.
  6. 802.11ac client adapters maybe released soon, but it will take a long time for users to get it in their laptops/tablets, etc.
  7. Like 802.11n, 802.11ac is the generic name of the technology. Individual 802.11ac products, however, will come in various flavors and configurations (No. of spatial streams, antennas supported, etc). The speed/performance of such devices varies according to these factors. There is a good chance that vendors will just advertise 802.11ac compliance and sell the lowest possible configuration. Buyers need to be aware of this and check what configuration they are going to get, before buying any products that are advertised as 802.11ac compliant.
  8. To obtain larger channel widths (80 MHz, 160 MHz), existing channels need to be combined. Hence, the total number of non-overlapping channels will be reduced when larger channel widths are employed. Avoiding interference from neighboring 802.11ac Wi-Fi devices in a dense network can create challenges in such cases.


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