802.11ac - What is it and what will it mean to us all?
There is a new standard that is currently being developed ( 802.11ac ) which is focusing on delivering much higher throughput than the recently ratified 802.11n standard. This standard is very much in its early stage of development with a draft of the Technical Specification being confirmed earlier this year. It could be anyone’s guesses as to when the final 802.11ac standard will be confirmed, but most within the industry are predicting approval in 2013. Although if 802.11n was anything to go by it could be years after that we actually see a final, standard.
So what are the new features and technologies that we might see in 802.11ac and what is it promising to deliver?
VHT (Very high Throughput)
The VHT PHY provides support for 20 MHz, 40 MHz, 80 MHz, and 160 MHz channel widths as well as 80+80 MHz non-contiguous channel width
A VHT station shall support:
- 80 and 160 MHz channel widths - (160 optional)
- MCSs 0 through 7 in all supported channel widths
Optional features for a VHT Station are:
- 2 or more streams (transmit and receive)
- 400ns short guard interval (transmit and receive)
- Respond to transmit beamforming sounding (provide compressed V feedback)
- STBC (transmit and receive)
- LDPC (transmit and receive)
- MU-MIMO PPDUs (transmit and receive)
- Support for 160 MHz channel width
- Support for 80+80 MHz channel width
- MCSs 8 and 9 (transmit and receive)
256 QAM rates 3/4 and 5/6 (compared to 64 QAM in 802.11n)
VHT MCSs for optional 160 MHz and 8 spatial streams
MU-MIMO - Multi-user MIMO
A technique where multiple STAs, each with potentially multiple antennas, transmit and/or receive independent data streams simultaneously.
SU-MIMO and MU-MIMO beamforming are techniques used by an STA (the beamformer) to steer signals using knowledge of the channel to improve packet reception at another STA. With SU-MIMO beamforming, all spatial streams in the transmitted signal are intended for reception at a single STA. With MU-MIMO beamforming, subsets of the spatial streams are intended for reception at two or more STAs.
SDMA – Space Division Multiple Access – Spatial streams not separated by frequency but are instead resolved spatially, analogous to 802.11n MIMO
MU-MIMO Downlink MIMO -transmitted by an AP to multiple receiving non-AP stations.
MIMO spatial streams
Support for up to 8 spatial streams (compared with 4 in 802.11n)
Larger channel Widths
80 MHz and 160 MHz channel bandwidths (compared 20/40 in 802.11n) Stations will use 80 MHz and mandatory and 160 MHz as optional
Backward compatibility for 802.11n
Feedback format for beamforming
So what could this potentially bring to the WLAN industry? Obviously providing higher throughput will enable a much larger range of applications and services to be delivered, with video and media streaming being an obvious choice to benefit from 802.11ac. The extra throughput will untether devices that at current 802.11a/g/n speeds were constraint to being cabled. 802.11ac will also help deliver higher throughput for PTP (Point to Point) and PtMP (Point to multi Point) outdoor networks enabling a new level of products for vendors. Currently most PTP vendors are using 802.11n chipsets allowing them to achieve an average of about 200mbps throughput.
Am guessing that top vendors like Ruckus and Cisco are already looking towards these standards and will be developing their portfolio as soon as a final release of the standard has been confirmed.