Everyone wants wireless access to large amounts of stored information these days. With demands on wireless networks increasing and more IoT devices emerging every day, the previous wireless standards are not efficient enough. As a result, IEEE 802.11 standards need to steadily evolve.
Wi-Fi: The Background
Wi-Fi, a term coined at least as early as 1999, refers to any wireless local area network (WLAN) product which is based on the IEEE 802.11 standards. However, nowadays, the word Wi-Fi is generally used as a synonym for WLAN because most modern WLANs are based on the 802.11 standards.
Wi-Fi allows wireless communication between various devices such as laptops, tablets, and smartphones via a wireless network. Although very useful, wireless communication is less secure than that passed through wired means, mainly due to the possibility of being eavesdropped.
The IEEE standard was originally designed to provide simple web browsing and e-mail connectivity in airports, hotels, etc. However, now everyday Internet users want constant connectivity to multiple apps as well as access to large amounts of stored information such as pictures and movies.
In order to satisfy the rapidly changing lifestyles of consumers, we need to improve coverage range, throughput, security, and also find a way for connections to be less prone to interference. That is why so many amendments have been presented to the 802.11 standard since its creation.
The developers of the standard know very well that a one-size-fits-all model is no longer applicable and that they should use a combination of different standards. As an example, while many Wi-Fi networks utilize the frequency bands around 2.4GHz and 5GHz, communication at 60GHz has been investigated and standardized, especially during the last decade.
As briefly discussed below, the choice between frequencies presents many trade-offs that directly affects the range, throughput, and even security.
Each standard of the 802.11 family offers a different coverage range. Image courtesy of Electronic Design.
A very important feature of the developed standard amendments is that they are highly backward-compatible.
Here we will review the most important standards of 802.11.
802.11ac, approved in January 2014 by the IEEE Standards Association, is trying to provide high-throughput WLAN on the 5GHz band. It is mainly about achieving faster rates. To this end, the standard provides wider channels (up to 160MHz) with more antennas and spatial streams (up to 8). This standard is an extension of 802.11n which used 40MHz channels with four spatial streams.
Moreover, 802.11ac considers some techniques such as beam forming to further improve the communication efficiency. Simply put, beam forming is utilizing more than one antenna to transmit a signal in such a way that a receiver in a particular position gets the signal with the maximum possible power. In other words, with more than one antenna, we shape the overall radiation beams.
With beam forming, there are places in space that the overall radiation is very small, whereas some other places will receive much stronger signals than could be provided by a single antenna. Explicit beam forming uses feedback from the receiver to modify the signal transmitted by the antennas to give specific receivers the maximum amount of power.
A Wi-Fi LAN with/without beam forming. Image courtesy of PC World.
The result is that real-world speeds of the 802.11ac are almost 2.5 times faster than that of its predecessor, 802.11n.
Another important feature of 802.11ac and 802.11n is that the communication is done over a much quieter band, 5GHz. Many previous Wi-Fi standards employed the ISM 2.4GHz band which was shared with other technologies such as Bluetooth, ZigBee, and even microwave ovens.
Theoretically, we expect a 2.4GHz transmission to have higher coverage range in comparison with that of the 5GHz transmission; however, in practice, this is not the case mainly due to the high amount of interference at the 2.4GHz. Also note that 802.11ac relies on beam forming to further increase its coverage range.
802.11ax, which is the successor that will supersede 802.11ac, is expected to have a top speed of about 10Gbit/s. The standard, which is in the early stages of development, will be released in 2019. It will use several techniques such as orthogonal frequency-division multiple access (OFDMA) to improve spectral efficiency.
WiGig, which is the first specific-use Wi-Fi standard developed, attempts to extend the throughput of the conventional wireless LAN devices.
WiGig utilizes the license-free band around 60GHz to transfer data at very high speed; however, it does so over relatively short ranges. We have around 5-9 GHz of unlicensed bandwidth at 60GHz in most countries. The following figure visualizes how big the bandwidth offered by WiGig is in comparison with the frequency bands of the conventional standards.
Comparison of the available bandwidth at 2.4, 5, and 60GHz. Image courtesy of Intel (PDF).
While the bandwidth at 2.4GHz and 5GHz are 90MHz and 500MHz respectively, WiGig provides about 7GHz of bandwidth. Such a high bandwidth makes it possible to download HD movies from a movie kiosk to a tablet in under a minute.
WiGig can cut many cords while maintaining the high-speed communication. With a WiGig-enabled device, it is possible to have streaming HD video from a tablet or a server to a television. Another application of WiGig is the formation of strong wireless infrastructure for high-bandwidth data transmission. This would allow for more publically-accessible wireless access and also better connectivity between core networks and subnetworks.
Blu Wireless Lightning modules used in the first experimental 60GHz mesh network of Europe. Image courtesy of Electronic Design.
Although still maturing, WiGig is the most established of the mmWave technologies. Early this year, Panasonic built a WiGig experimental network in Narita Airport which allows visitors to download a 120-minute movie in approximately 10 seconds.
Unfortunately, the 60GHz signals cannot pass through walls so the transmitter and the receiver need to be in the line of sight of each other. In addition, the path loss is high and the coverage range is typically about 10 meters. However, in many applications, such as streaming HD/UHD video from a tablet to a television or enabling high-speed sync or data transfer, the short range or the necessity to be in the line of sight is not an issue.
Considering these challenges, the 60GHz WiGig needs beam forming even more than the previous lower-frequency standards. With beam forming, it would be possible to achieve higher ranges and/or increase the signal to noise ratio in a WiGig device.
With so many advantages of communication in 60GHz, various chipset vendors are increasingly becoming interested in developing WiGig-based devices. Since testing of these products faces many challenges, National Instrument, which possesses a comprehensive product portfolio for wireless testing, has recently announced a technology to test WiGig products. The technology is based on the company’s wideband mmWave transceiver, which has been used to prototype advanced radar and 5G systems.
The Wireless Gigabit Alliance (originally called "WiGig"), founded by Ali Sadri, started to develop a faster and more efficient communication technology in 2007. In 2010, WiGig and the Wi-Fi Alliance announced cooperation in combining the 60GHz communication with the traditional Wi-Fi networking. WiGig contributed significantly to the IEEE 802.11ad standardization process which was published in 2012. Although the WiGig merged with the Wi-Fi alliance in 2013, the WiGig technology kept its name.
While WiGig is developed to transfer large amounts of data over short ranges, HaLow (pronounced HAY-low) targets low-power transmission of small amounts of data over long distances. The low-power standard, which utilizes the 900MHz band, is suitable for IoT uses.
Presenting low power consumption and wide coverage range, HaLow is expected to be highly competitive with Bluetooth. HaLow has been under development over the last few years and its chipsets are expected to be available very soon.
The main applications of the low-power standard are isolated systems which need to work for more than 10 years with a single battery. HaLow is not the only standard aiming at such applications. LTE-M, which is based on the well-established 3GPP standard, is already becoming popular. Considering the popularity of LTE-M (it's been pegged as AT&T's choice for cellular IoT devices) some people believe that HaLow may not arrive in time to take over the market.
White-Fi, or 802.11af, relies on the unused white space in the television spectrum to transmit large amounts of data over long distances. The TV white space spectrum includes unused TV channels between 54 to 790MHz. These frequencies can offer a several-mile coverage range which is more than that of the HaLow standard. The channel width will be 6 to 8MHz wide.
The standard, which was approved in January 2014, is quite new. So far, no White-Fi-based chipset has been announced.
The technology will utilize the concept of cognitive radio to avoid interference. This will limit interference to the primary users such as analog TV, digital TV, and the wireless microphones.