In 2009, 802.11n was ratified. It provides for up to 4x4 MIMO (Single user) along with wider bandwidths and a number of MAC layer improvements leading to a peak theoretical throughput in the order of 600 Mbps. Since the ratification of 802.11n, a new task group (TGac) has begun working on the next standard for even higher throughput within <6GHz spectrum. A closely coupled task group (TGad) is looking at very high throughput for spectrum >6Ghz (such as the 60 Ghz ISM band).
The IEEE 802.11ac Task Group (TG) has beendeveloping amendment to IEEE 802.11 having PHY (Physical layer) as well as MAC (Medium Access Control sub layer) enhancements. These are the following goals for designing the IEEE 802.11ac amendment.
• Backward compatibility with IEEE 802.11a and IEEE 802.11n operated in 5GHz.
• Single STA throughput: 802.11ac STA shall be capable of getting throughput up to 500Mbps.
• Multi-STA throughput: The aggregate throughput when 802.11ac system has multiple STAs connected should be greater than or equal to 1Gbps.
New features in this standard are the bandwidths of 80 MHz and 160 MHz (11n offered only 40 MHz), 256QAM, up to eight antennas and multi-user MIMO.Gross data rates of 293 Mbit/s are possible with only 80 MHz bandwidth, one antenna and 64QAM 5/6; all 802.11ac devices must support this mode. Optional modes using 256QAM and eight antennas under optimal conditions permit gross data rates of 3.5 Gbit/s. 802.11ac is designed only for license-free 5 GHz bands and will no longer include the 2.4 GHz industrial scientific medical (ISM) band previously used primarily for WLANs.
For details on the exact extensions in the PHY layer, see our whitepaper on 802.11ac PHY extensions.
SAI is developing 802.11ac PHY and MAC layer stacks, as well as system solutions with particular emphasis on MU-MIMO high performance implementation. This work is in collaboration with leading silicon and SoC vendors for 802.11ac.
04/01/13: SAI Eagle 4G LTE Cloud Wireless Broadband Router [Enterprise Class]
802.11ac Dual Band / Fiber / Cable
Concurrent with the802.11ac developments, a number of industry groups are looking at the ISM band at 60 Ghz (typically 57-66 Ghz) as the next frontier for WLANs. Clearly such a high center frequency (mm wave) comes with a number of challenges including
- Limited range, due to the proximity of the oxygen absorption band
- Implementation cost and high power consumption
MIMO techniques are helping overcome at least some of the range issue, and a 32x32 antenna array can be easily implemented on a CMOS process. Thus, as these hurdles are overcome the 60 Ghzband promises even higher data rates – up to 7 Gbps.
The IEEE 802.11ad standard adds a mm wave operating mode to the 802.11n with a mmSTA being a station that is capable of mm wave operations. Although the base protocol is an extension of 802.11n and 802.11ac, a number of mmWave mode specific packets and formats have been defined in this standard(for e.g., mmWave CTS). In addition, upto 5 bits are reserved for defining the number of beams, thus permitting as many as 32 beams.
Due to the strong dependence on beamforming, considerable effort is going into refining the beam forming procedures and transactions within the 802.11ad standard. Similarly the large number of receive and transmit chains required for such a system are pushing the standards committee to refine the power management techniques used in 802.11n/ac. MIMO for reducing power consumption and turning off some of these chains when not required without affecting network latency and performance.
This standard is in draft and still being developed, although initial silicon is available from a select set of companies.
Besides the 802.11ad standard, a few other standards are being pursued for the 60 Ghz ISM band.
SAI is working with leading 60 GHz chip vendors for 802.11ad implementation on CMOS platforms. This work clearly leverages SAI’s work on 802.11ac with a focus on high performance and low power solutions.
The WiGig specification was contributed to the IEEE 802.11ad standardization process, and was confirmed in May 2010 as the basis for the 802.11ad draft standard.