Tag Archives: 802.11ah

Comparing Wireless Standards 802.11ad & 802.11ah

Wireless LAN standards were first set up for serving the needs of laptops and PCs in homes and offices. These were IEEE 802.11a and b, and these later served to allow connectivity in different places such as in shopping malls, Internet cafes, hotels and airports. The main functionality of the standards was providing a wireless link to a wired broadband connection for email and Web browsing.

Initially, speed of the broadband being a limited factor, a relatively slow wireless connection was enough. Therefore, 802.11a offered up to 54Mb/s at 5GHz and 802.11b up to 11Mb/s at 2.4GHz, with both frequencies being in the unlicensed spectrum bands. To reduce interference from other equipment, both standards were heavily encoded using forms of spread-spectrum transmission. In 2003, a new standard 802.11g used the 2.4GHz band maintaining the maximum data rate of 54MB/s.

However, by this time, people started realizing the need for higher throughput, especially with increased data sharing amongst connected devices in the home or small office. By 2009, a new standard, 802.11n came up, which improved the single channel data rate to over 100Mb/s. The new standard also introduced spatial streaming or MIMO, multiple inputs, multiple outputs. The new modems had up to four separate transmit and receive antennas, carrying independent data that was aggregated in the modulation/demodulation process.

However, new WLAN usage models were continually raising the demand on throughput, such as projection to TV or projectors, streaming from camcorders to displays, video streaming around the house, airplane docking, public safety mesh and more. Catering to these VHT or very high throughput demands made it necessary to generate two new standards 802.11ac (an extension of 802.11n) and 802.11ad.

Standard 802.11ac runs in the 5GHz band, providing a minimum of 500Mb/s on a single link and 1Gb/s overall throughput. On the other hand, 802.11ad provides up to 6.7Gb/s using a spectrum of about 2GHz at 60GHz, but at short range. Operation at high frequencies limits the transmission range and obstacle penetrating capacity of the signals.

With the proliferation of local sensor networks working on low power, billions of IoT or Internet of Things and M2M or machine-to-machine device connections, a new standard is now deemed necessary. This new standard is the 802.11ah, working in the license-exempt 1GHz band and its final version is expected in 2016.

Standard 802.11ah is a down-clocked version of the 802.11ac standard. While adding some enhancements in the MAC and PHY layers, the new standard offers advantages such as power savings, multiple station support, better coverage and mobile reception.

For the standard 802.11ah, three main use-case categories are under consideration. These are Wi-Fi extended range networks, backhaul networks for sensors and meter data and sensor networks. The standard 802.11ah extends the transmission range with 1 and 2MHz mandatory modes, allows ultra-low power consumption, thereby offering multi-year battery life for large scale sensor networks and is optimized for long sleep times while handling small packet sizes.

Therefore, with 802.11ah, you can have several devices such as light sensors, temperature sensors and smart meters set up throughout the home, enabling your home devices and appliances to be considered smart.