Tuesday, January 10, 2012

Gigabit WiFi For Video Streaming

WiFi hotspots, routers and access points have been deployed to such an extent that WiFi really is the default wireless connection. Bluetooth range is way too short. WiMax never deployed far enough, wide enough or fast enough. Cellular 3G and 4G are only valuable when you are away from WiFi access, since bandwidth is limited and overages are painful. Recent reports show that most tablets never use the built-in 3G wireless. WiFi is a replacement for cellular broadband, but it’s also becoming a replacement for wires.

WiFi speeds will increase dramatically with 802.11acThink about it. How much trouble and how expensive is it to string Ethernet cables through a home or office? Most people don’t have the skill or determination to snake wires through the walls of their two story home and don’t dare to try to wire an apartment. That means you are stuck with being in the same room as your DSL or Cable modem. Inexpensive WiFi routers got rid of that cable limitation. Now many PCs and printers come with WiFi access so that you can place them anywhere you want.

The other big tether is the television coax or HDMI cable. If you want to connect video, you have to string wires. The standard means for that has been RG-6 or RG-59 coax. But HD outputs are now HDMI, so your old coax is limited to SD video. That’s assuming you were able to get coax installed in every room you wanted.

Complicating matters now is that traditional video sources, such as satellite and DVD, are merging with the Internet. Many TVs, Blu-ray players and games now come with Ethernet jacks. You still need an Ethernet cable, but now it’s for video broadband not just web browsing. Or... do you?

Video is a need screaming for a wireless solution. The legacy WiFi 802.11b&g versions clearly are not up to the task. WiFi 802.11n does much better, but has trouble finding a clear path through the crowded 2.4 GHz ISM band. It's also pressed for enough bandwidth to support all things video. The solution? It’s an enhancement to WiFi-N called WiFi 802.11ac.

What’s better about WiFi-AC compared to WiFi-N? Most importantly, it pushes wireless bandwidth above the Gbps level. Total capacity of an 8 antenna system will reach almost 7 Gbps when this technology is fully developed. That should be enough to keep up with the rapid advancement of HD and 3D streaming video devices and become the way to eliminate Ethernet, HDMI and coaxial cabling in the home and office.

How does 802.11ac achieve this performance? First of all, it completely abandons the crowded 2.4 GHz band and uses the lesser populated 5 GHz band exclusively. That cuts out a lot of interference. Next, the transmission channels are widened to achieve more data carrying capacity. Channels are 40 MHz maximum in 802.11n. These are expanded to 80 MHz minimum and 160 MHz optional for the new standard.

WiFi-N introduced MIMO or Multiple Input Multiple Output antenna technology. MIMO is a way for transmitters and receivers to deal with scattering radio waves and interference by intelligently analyzing the received signals to determine which ones are valid. It’s a little like being able to tell which direction a sound originates by using two ears rather than one. Beamforming compensates for phase shift of multiple received signals to increase the total signal level. This allows higher bandwidth over a longer range.

A more complex modulation scheme is being introduced in 802.11ac called 256 QAM. The term QAM refers to Quadrature Amplitude Modulation. It uses both amplitude and phase shift to send data over two combined carriers differing by 90 degrees, called quadrature. Each combination of phase and amplitude represents one digital number. 802.11n used 64 QAM to send 6 bits per symbol. 256 QAM sends 8 bits per symbol, a third more efficient in use of the spectrum.

When will be see 802.11ac equipment on the market? Probably near the end of this year or the beginning of next. Broadcom recently announced the first chipset to support the protocol. They are dubbing it “5G WiFi” to emphasize the considerably higher performance from previous wireless standards, similar to how cellular carriers use 2G, 3G and 4G to describe their generations of technology.

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