Recently, I was reading about Apple’s new MacBook Air and its ultra-fast wireless capability, 802.11ac. After a little research, I thought wireless technologies would be a good topic to cover in this column.
One of the consistent trends we have seen in networking is the continuous increase in network speeds. In wired networks, more devices are appearing with 10 Gbps capability, while 40 Gbps and 100 Gbps is on the horizon.
Wireless, too, has seen a migration in its transmission capabilities. In cellular data, most current devices are either 3G or 4G, with 5G imminent (the “G” refers to the generation of wireless technology employed). Different vendors have various implementation solutions. It’s interesting to note that Samsung, in May 2013, announced a technical breakthrough in the use of millimeter-wave technology at 28 GHZ supporting their 5G approach, promising speeds in excess of 1 Gbps.
IEEE defines wireless standards in the 802.11 family. We should all be familiar with 802.11 a, b, and g (most home routers support these) and possibly 802.11n, which upped the maximum bandwidth ante over 802.11g from 54 Mbps to 600 Mbps. It did so by providing for the use of multiple antennas using MIMO (multiple input, multiple output) technology. 802.11n operates at either 2.4 GHz or 5 GHz and provides approximate ranges of 230 ft. (indoors) and 820 ft. (outdoors).
The first generation of 802.11n devices supported a maximum data rate of 300 Mbps by running two spatial streams. Each stream could carry 75 Mbps of data per 20 MHz of spectrum over a double-wide 40-MHz channel. Newer devices, supporting three spatial streams, offer 450 Mbps capability, and the maximum 600 Mbps can be achieved with four spatial streams.
So, what is a spatial stream? Spatial multiplexing (SM) splits up the data into pieces and sends each piece along parallel “spatial” channels (streams), providing greater speed and use of available spectrum. Space-division multiple access (SDMA) is a MIMO technique which concentrates power in the direction of the receiving unit for which the signal is directed and reducing it in the directions where other units are present.
The technique of “beamforming” is able to identify the rough location of the device it is talking to, relies on information about the wireless channel that is fed back to the transmitter by the receiver, and adjusts the appropriate antenna(s).
WiFi to Handle BYOD Issues
Fifth-generation Wi-Fi, 802.11ac, can be thought of as an enhanced 802.11n, but operates only at 5 GHz. It increases the number of parallel spatial streams to eight, with the effect of significantly improved wireless network speeds. It is expected to help accommodate the need for increased bandwidth to deal with increasing smart devices (BYOD) and the growing use of video streaming.
802.11ac devices are expected to be dual-band, meaning that they can operate on both the 2.4GHz and 5GHz frequency bands. If such a device can’t connect at 5GHz using the 802.11ac protocol, it will attempt to drop back to 2.4GHz using 802.11n. Dual-band routers are capable of operating networks on both frequencies simultaneously, providing the ability to use different bands for different applications, e.g., 5 GHz band for media streaming and other high-performance applications.
More Speed is Coming
The Wi-Fi Alliance has initiated a certification program for routers, adapters and other wireless networking gear based on the IEEE 802.11ac draft standard, although final ratification is not expected until Feb. 2014. Industry analysts expect initial products to offer from 433 to 1300 Mbps capability, followed by second-generation products with configurations operating at up to 3.47 Gbps. Indoor distance capability will approach 300 feet.
In Jan. 2013, IEEE announced the ratification if the 802.11ad “WiGig” standard. Operating as tri-band devices (2.4, 5, 60 GHz), the new standard can achieve a theoretical maximum throughput of up to 7 Gbps. While this is impressive throughput, the offset is that the higher 60 GHz frequency is line-of-sight, limited to very short distances and incapable of propagating through walls.