Digital media sets the stage

main content:
1. What is 802.11ac?
2. Power amplifier solution suitable for 802.11ac standard
3. TriQuint's WLAN solution
4. Summary of this article

Since its introduction in 1997, the 802.11 wireless area network standard has achieved great success over the past decade. From the beginning, it was regarded as a technology mainly used for vertical industry productivity improvement. Now, the standard is not only the most mature and popular wireless network technology in the information industry; but with the continuous development of technology, the 802.11 standard has also evolved into Ubiquitous, an important technology widely used by the public.

As consumer demand for download speeds continues to increase to support more high-bandwidth applications, the 802.11 standard is also evolving, and each new technology generation provides an increasingly high-quality user experience. From 802.11b with a transmission rate of 11 Mbps in 1999, to 802.11g / a with 54 Mbps in 2002, and 802.11n with 600 Mbps in 2007, this year, the industry is ready to transition to the fifth-generation Gigabit 802.11ac.

Based on a strong installation foundation, the new 802.11ac standard will further promote new applications and market opportunities. ABI Research predicts that following the realization of small-scale shipments in 2012, shipments in 2013 will increase significantly. By 2014, IEEE 802.11ac will become the dominant WiFi protocol. In-Stat also predicts that by 2015, shipments of equipment using the new 802.11ac technology will reach 1 billion units.

This article will introduce the advantages of the 802.11ac standard and the new applications it will promote. At the same time, from the perspective of the power amplifier, we will also analyze the challenges that the new standard will bring, as well as the RF front-end solutions of RF solution manufacturer TriQuint Semiconductor.

What is 802.11ac?

The formulation of the 802.11ac standard is mainly intended to provide high throughput in the 5GHz band. In addition to bringing fast and high-quality video streams, it can also provide data synchronization and backup for laptops, tablets and mobile phones almost instantly.

In theory, this specification will achieve a multi-site WLAN throughput of at least 1 Gbit / s and a maximum single link throughput of at least 500 Mbit / s. This is achieved by extending the air interface concept adopted by 802.11n: wider RF bandwidth (up to 160MHz channels), more heavy input / output (MIMO), spatial streaming (up to 8), multi-user MIMO, and high Density modulation and demodulation (up to 256 QAM).

Since 802.11ac only works in the less crowded and "cleaner" 5GHz spectrum, the competition for airwaves from other devices will be much less, which will greatly increase the transmission rate. The width of the communication channel is nearly four times wider than the channel in 802.11n, which can provide higher speed. At the same time, 802.11ac incorporates beamforming technology, which is the ability of a WiFi transmitter to "learn" to avoid invalid paths between it and the target device being transmitted.

With these enhancements, the reliability and coverage of 802.11ac technology will be greatly improved. The entry-level 1 & TImes; 1 802.11ac product rate will reach 450Mbit / s. If the current 802.11n standard is adopted, the 3 & TImes; 3 system configuration is required to achieve such speed. Because the new standard gives manufacturers the flexibility to develop products with different levels of performance, some high-speed IEEE 802.11ac devices will provide wireless transmission rates in excess of 1 Gbit / s-such an excellent rate will allow IEEE 802.11ac wireless networks to surpass the large Most limited networks. Faster file transfer also helps extend the battery life of the phone. Of course, devices using the new IEEE 802.11ac standard should also be backward compatible, allowing seamless interaction with old WiFi products.

With higher throughput and data transmission rate, and enhanced support for single link and multi-site, the 802.11ac standard will help to achieve some new WLAN usage scenarios, such as simultaneous transmission of HD video to multiple users in the home , Fast synchronization and backup of large data files, wireless display, large campus / hall deployment, and manufacturing workshop automation.

In addition to the above, for the fast-growing smartphone market, the 802.11ac standard will operate with NFC and 4G / LTE to provide fast synchronization applications and help reduce the burden of mobile video traffic on 4G cellular networks.

Power amplifier solution suitable for 802.11ac standard

Since the 802.11ac standard can target a variety of applications, the choice of a suitable WiFi solution depends largely on whether the needs of the end market are met. For example, its application in access points (A / P), routers, and WiFi-only solutions will be more common. Since these products are powered from higher voltage wall outlets, power consumption and PAE (Additional Power Efficiency) conditions are not as severe as battery-powered devices.

For A / P and routers, coverage is critical. Therefore, in terms of the system-level requirements of such devices, the front-end power amplifier needs to have a higher output power (Pout). For mobile applications such as smartphones and tablets, size and power consumption are more important because of smaller form factors and limited battery life.

As the 802.11 standard continues to evolve, output power and EVM requirements have become increasingly challenging for power amplifier design. EVM (error vector level) is a means to quantify the performance of digital radio transmitters or receivers. The lower the EVM, the better the linearity. For the 802.11ac standard, the original EVM limit of 2.8% to 3% in 802.11n has now dropped to below 2%, and the output power demand is also increasing.

The main reason is that, compared with the 64QAM signal of 802.11n, 802.11ac uses 256QAM high-density modulation and demodulation. Therefore, the receiver input needs a higher signal-to-noise ratio to successfully receive the signal to support the higher data transmission rate of 802.11ac.

This is why in the 802.11ac standard, the EVM of the PA must be reduced below 2%, because a higher signal-to-noise ratio means that the 802.11ac transmitter must be more linear than the 802.11n transmitter. Therefore, a power amplifier with better linearity than 802.11n must be used, or it can operate at a lower output power.

On the other hand, increasing the power consumption of the power amplifier or providing a pre-correction mechanism can help improve linearity. Although these design methods require higher DC power, the high data rate of 802.11ac can complete the transmission operation in a shorter time, so as a whole, the power consumption caused by the transmission data can still be reduced.

TriQuint's gallium arsenide (GaAs) -based power amplifier, whether it uses E / D pHEMT, HBT, or BiHEMT process technology, has lower power consumption and better PAE than other competitor solutions on the market. Can provide excellent performance for the new generation of 802.11 standards.

TriQuint's WLAN solution

TriQuint has been providing solutions for high-performance WLAN applications, including recent single-band 2.4G, single-band 5G and dedicated dual-band applications for smartphones and tablets. Since 2009, TriQuint ’s WiFi module shipments have reached nearly 300 million units, and driven by consumer demand for network connectivity whenever and wherever possible, its sales revenue is still steadily increasing.

TriQuint uses E / D pHEMT, BiHEMT and HBT technologies to integrate active and passive devices into a complete and compact front-end package, enabling better wireless connectivity. These integrated WLAN solutions simplify RF design, reduce PCB board footprints, shorten design cycles, and enable faster development of next-generation wireless products.

Among them, E / D pHEMT technology allows multiple components, such as power amplifiers, switches, LNAs and bias network controllers, to be integrated into a smaller footprint, which is significantly better than multi-die and stacked solutions. TriQuint also developed the first high-volume GaAs enhancement and consumption mode (enhancement and depleTIon-mode) pHEMT foundry process.

In addition, TriQuint devices based on BiHEMT and HBT technology can achieve better PAE, which helps reduce battery consumption and significantly extend the use time, which are key factors in the mobile market. Using these two technologies can produce smaller die, providing a more compact overall solution.

Based on these technologies, TriQuint integrated single-band WLAN module can replace up to 4 discrete devices; dual-band WiFi front-end module can replace up to 7 discrete devices. TriQuint's GaAs-based solutions provide faster data transfer rates, longer battery life, and better weak signal amplification to achieve a wider operating range than competitor technologies.

In the future, TriQuint will build on its past success, while utilizing autonomous technologies such as bulk acoustic wave (BAW) for WiFi-LTE coexistence filters, and continue to develop higher-performance front-ends for mobility and connectivity applications solution.

As the industry is ready to transition to 802.11ac, TriQuint will work closely with its chipset partners and end customers to provide the most competitive WLAN solutions that meet the end user's size, performance, and cost requirements.

Summary of this article

The growing number of digital media and wireless connection devices require faster and more reliable wireless protocols, which sets the stage for the rapid adoption of the 802.11ac standard. Although the standard is still in draft form, chip manufacturers are already showing 802.11ac chipset products. This year, the 802.11ac system for home network applications is expected to come out, and smartphones and tablets using the 802.11ac standard are expected to be launched in 2013. 802.11ac is expected to drive more innovative applications. In order to seize this huge market opportunity and be fully prepared, equipment manufacturers must choose the most suitable solution for their products according to different applications and function combinations.


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