The 802.11ad WiGig Standard
The first certified products for the new 802.11ad WiGig Wi-Fi standard were announced in October by the Wi-Fi Alliance, which provides compliance certification to ensure there is the widest possible interoperable vendor ecosystem.
802.11ad WiGig is somewhat different from the previous standards developed by IEEE and promoted by the Wi-Fi Alliance, the non-profit industry association representing Wi-Fi product and solution providers.
For a start, WiGig operates way up in the less-congested 60 GHz millimetre spectrum band (between 57 GHz and 66 GHz depending on region), rather than the usual 2.4 GHz and 5 GHz Wi-Fi bands. It is really designed to transmit very large amounts of data, very quickly, over short distances – typically between 1m and 10m.
Applications might include: wireless docking between devices such as smartphone, laptops, projectors and tablets; augmented reality; virtual reality; simultaneous multimedia streaming of HD videos and films; more immersive gaming; and networking applications, such as bandwidth-intensive applications in the enterprise.
Edgar Figueroa, president and CEO, Wi-Fi Alliance, tells Wireless: ‘Wi-Fi CERTIFIED WiGig products will deliver 8 Gbps performance, which is the fastest wireless broadband experience people have had, and it is very low latency too.
‘We’ve been working on 802.11ad for a number of years to standardise it and ensure interoperability between vendors. There’s likely to be a range of new applications that this technology will enable. A typical performance will provide a 5 Gb file in 12 seconds.’
Figueroa says he expects WiGig will reach laptops and other devices in 2017, but it is unlikely to be penetrating the mobile handset market until 2018.
WiGig uses wider channels (four 2.16 GHz wide channels) in 60 GHz to transmit data efficiently, allowing users to download an HD movie in just a few seconds. This level of performance is critical to delivering a wired-grade experience for a variety of in-room and outdoor line-of-sight scenarios, according to the Alliance.
OFDM and beamforming
The standard uses orthogonal frequency division multiplexing (OFDM) as one of its main forms of modulation. OFDM transmits signals by separating the channels into hundreds of smaller sub-channels, which are modulated with a low data rate.
The clever bit is that these signals would normally interfere with each other, being so close together. But by making them orthogonal – that is, turning each signal at a right-angle – they can be positioned much more closely together without interfering with each other. This greatly increases the spectral efficiency.
WiGig devices use beamforming to focus a directed signal between devices to eliminate interference from other nearby devices and to enable high performance even in dense 60GHz environments.
It can accomplish this kind of antenna beam management because the very high frequencies used mean the antennas are very small. The beamforming enables the equipment to shape the transmit and receive beams to get the best links. This also allows it to track and overcome any movement of the transmitter or receiver equipment or objects in between that might alter the characteristics of the transmission path.
WiGig uses the same MAC (media access control) layer standard as the existing 802.11 standards enabling multi-band Wi-Fi CERTIFIED products supporting 2.4, 5, and 60 GHz to handoff between frequency bands by selecting the most appropriate band and data rate for the application and surrounding environmental conditions.
Figueroa explains: ‘This ability to enable session transfer between 2.4 GHz, 5 GHz and 60 GHz allows users to maintain sessions. This capability is native to 802.11ad, but it is not something you will see immediately in products, but it is within the technology’s capability. We expect that multi-band devices will be popular straight away, however.’
ABI Research is forecasting that 180 million WiGig chipsets will ship to the smartphone market in 2017, with smartphone chipsets accounting for almost half of the 1.5 billion total market shipments in 2021. As part of the Wi-Fi ecosystem, WiGig delivers the highest level of security, and multi-band devices will interoperate with more than eight billion deployed Wi-Fi products.
The first Wi-Fi CERTIFIED WiGig products, which comprise the test bed for interoperability certification, are: Dell Latitude E7450/70; Intel Tri-Band Wireless; Peraso 60GHz USB Adapter Reference Design Kit; Qualcomm Technologies 802.11ad Wi-Fi client and router solution (based on the QCA9500 chipset); and the Socionext 802.11ad Reference Adapter.
The 802.11ax Standard
The latest widely available Wi-Fi standard is 802.11ac Wave 2, the first to use the 5 GHz band, which provides a big leap over the previous 802.11n generation of Wi-Fi systems. It brought: faster speeds of up to 7 Gbps; more spatial streams (four); wider channels (80 MHz and 160 MHz); 256 QAM (as opposed to 64 QAM for 11n); and beamforming.
802.11n uses single MIMO, but 11ac introduced multi user MIMO (MU-MIMO) enabling the system to set up multiple data streams on the same channel, thereby increasing the capacity of the channel and therefore its ability to support more simultaneous users.
802.11ax is being touted as the successor to 11ac. The IEEE’s High Efficiency WLAN Study Group began working on 11ax in May 2013, but the final specification is some way off yet as it is not expected to be ready until 2019. It will be even faster than 11ac. Huawei, which is leading the IEEE’s 11ax working group, has reached throughput speeds of 10 Gbps in the laboratory.
Detail is relatively sparse at the moment, but 11ax is expected to use MU-MIMO, and either OFDA (OFD Access) or OFDMA (OFD Multiple Access) to further improve spectral efficiency. Huawei has claimed OFDA could increase spectral efficiency by 10 times, but a 4 times increase is seen as more realistic. It will also use an even higher order 1024 QAM modulation for better throughputs. It is expected to work in 2.4 and 5 GHz bands.
‘People are very excited about 802.11ax,’ says Figueroa. ‘It will bring a new era of spectral efficiency planning for scheduling mechanisms for connections, which we have never had before. It will also coincide with 5G connectivity, so 11ax is aiming at many of the 5G use cases. It could be complementary to 5G, but I hope it will be integral to 5G, as I hope it will address a lot of those 5G use cases as well.’
The 802.11ah HaLow Standard
The proposed 802.11ah, also known as HaLow, is intended to support extended range, lower power Wi-Fi for Machine-to-Machine (M2M) and Internet of Things (IoT) applications in the sub-1 GHz unlicensed Industrial, Scientific and Medical (ISM) bands. The ISM bands differ around the world: Europe - 863-868 MHz; USA – 902-928 MHz; China – 755-787 MHz; and so on.
A new physical layer and MAC have been developed for 11ah to enable the above ISM frequencies to be used. It will have much greater range than other Wi-Fi standards, but a lower speed.
It will use an OFDM modulation scheme, although there are to be two versions; one for 1 MHz channel bandwidth operations for applications requiring an extended range, but which only send small amounts of data at low data rates; the second is for 2 MHz and above operations where higher data throughput rates are required.
The MAC layer requires some enhanced features to provide support for: large numbers of 11ah devices; power saving – a key pre-requisite for many M2M and IoT applications; and throughput enhancements to enable the
data to be transmitted as efficiently as possible.
Figueroa comments: ‘It is very early on for this, but there is a lot of interest in it. The sweet spot is the medium range, medium efficiency, so it is not aiming at super low or super long range, but the idea is it will be much more efficient than current Wi-Fi.’
The 802.11af White-Fi Standard
This standard proposes a solution for deploying Wi-Fi in unused TV spectrum, or TV White Space, as it is known. It is essentially a form of spectrum sharing, but it means there has to be a way to detect whether the primary TV operator is using the band.
One suggestion is to use cognitive radio technology to detect TV transmissions and move the Wi-Fi onto another channel to ensure there is no interference with the primary user of the band when using the same channels.
Another possibility being explored in some countries is to have a geographic database of where and when primary users transmit and on what channels. Secondary users would employ this ‘geographic sensing’ to ensure they only operate on unused channels at the right time.
Figueroa says: ‘802.11af is even further off than the others. Spectrum rules vary widely around the world, and many regulators have not opened up TV White Spaces yet, so it is a complicated environment and that is why there is not much progress on 11af as yet.’