IEEE 802.11ac : Next Generation Standard for Wireless Fidelity.


802.11 AC, the next step for Wi-Fi 802.11 will breach the barrier of gigabit capacity. Couple this with low latency and an improved power profile and you get the next must have feature of your gadget.

The IEEE 802.11ac standard has been developed to provide high throughput wireless local area network. It promises gigabit wireless speed to consumers.

The initial technical specification draft was confirmed by the IEEE 802.11 task group ac (Tag) last year while Wi-Fi Alliance ratification is expected by the end of this year. Though the 802.11ac standard is in draft form and yet to be ratified by the Wi-Fi alliance and IEEE, We have already begun to see products available in the market.

802.11ac Characteristics:

WLAN 802.11ac uses a variety of new methods to achieve the tremendous increase in performance to theoretically hit the gigabit capacity and provide high throughput, such as:

1. 6GHz band

2. High Density modulation up to 256 QAM.

3. Wider bandwidths through two 80MHz channels or one 160MHz channel

4. Up to eight multiple input multiple output spatial streams.

5. Multiuser MIMO the lower power consumption of 802.11ac present new challenges to design engineers working with the standard. Next, we discuss these challenges and solutions available that help the designing new products based on this standard.

Wider Bandwidths:

802.11ac features a wider bandwidth of 80 or even 160 MHz against the previous maximum of 40 MHz featured in the 802.11n standard. A wider bandwidth results in an improved maximum throughput for the digital communication system.

Amongst more complex challenges for design and development is the generation and analysis of wider bandwidth signals for 802.11ac. Testing equipment able to handle 80 MHz or 160 MHz will be required to test transmitters, receivers and components.

For generation 80 MHz signals, many RF signals generators do not have a high enough sampling rate to support the typical minimum 2X oversampling ratio, which can result in unnecessary images in the signal, Using proper filtering and oversampling of the Waveform file, it is possible to generate 80MHz signals with good spectral characteristics and EVM.

To Generate 160 MHz signals, a wide band arbitrary waveform generator (AWG), such as the Agilent 81180A, 8190A can be used to create the analogue I/Q signals. These signals can then be applied to the external I/Q. inputs in a vector signal generator for up conversion of RF frequencies. It is also possible to create a 160 MHz signal by using 80+80 MHz mode supported by the standard to create two 80 MHz segments in separate MCG or ESG signal generators and then combining the RF Signal.

MIMO:

MIMO is the use of multiple antenna to improve the performance of the communication system,. you might have seen certain Wi-Fi access points having more than one antenna sticking out of them these routers use MIMO technology.

Verifying MIMO designs is a change. Multi- channel signal generation and analysis can be user to provide insight into the performance of MIMO device and assist in troubleshooting and design verification.

Amplifier Linearity:

Amplifier Linearity is the characteristic of and amplifier by which the output signal of the amplifier remains faithful to the input signal as the signal drive increases. Real amplifiers are linear only to a limit after which the output saturates.

There are many techniques to improve amplifier linearity. Digital pre-distortion is one such technique. Design automation software like systemVue provides an application that simplifies and automates digital predistortion design for power amplifiers.

802.11ac Standard Devices:

Products featuring the new Wi-Fi standard are starting to hit the market. But their number is not enough to warrant a network upgrade. A Similar situation was observed with the 802.11n standard back in 2006. Several pre-standard devices were released by manufactures, but unfortunately these devices were not completely compatible with the ratified ones. Creating a frustration user experience for consumers. Quintana Communications has already launched an 802.11ac gigabit wireless solution for Wi-Fi routers and consumer’s electronics at consumers Electronics Show (CES) this year.

Broadcom also launched its first Gigabit speed 802.11ac chips at CES. Broadcom expects the first product to hit the market in the second half of 2012 starting with access points, followed by consumer electronics devices.

We can expect the huge handset industry to come up with 802.11ac technology on smartphones, tablets and everything in between. This is something to definitely look forward to as the power profile for the new standard is theoretically very promising. Repine signals have already announced an ultra-low power 802.11ac technology for smartphone application processors.

Should you upgrade your Network?

Since the standard is still in draft, it might take a while for 802.11ac ecosystem devices to gain popularity. Moreover the devices that first hit the market would be based on the draft version of the standard and thus carry a risk. Once the Wi-Fi alliance ratification is over, We can expect a greater influx of these devices into the market. At the same time, Radios featuring the new standard are backward compatible with the legacy 802.11 a/b/g/n devices. So any legacy devices you buy in the meantime will not go wasted.

Heard of 802.11ad?

Seemingly 802.11ac is not the only wireless technology about to hit the market. 802.11ad is another Wi-Fi technology which utilizes the 60GHz band to enable data transfer speed of up to 7 Gbps. On the downside, because this technology uses a very high frequency band of 60 GHz, it allows short range. A possible use case would be for transferring HD media wirelessly in a home entertainment system, where this technology could replace conventional HDMI cables.

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