Wireless Systems Design

Chip Set Withstands WLAN's Future Blows

In This Solution, A Media-Access-Controller IC, PHY IC, And PA/Chireix Combiner Unite To Achieve A 50% Reduction In Power Consumption And A 2X Increase In Power Output.

The furious pace of WLAN announcements is almost drowning engineers. Because they're being inundated with so much information, it's hard for engineers to separate marketing hype from technical fact. Yet certain truths do exist. For example, the WLAN market will no longer be dominated by PC-based products. Increasingly, it's going to be driven by A/V and consumer-media devices. Examples of these devices include flat-panel-TV screens, PDAs, and Voice over IP (VoIP) phones. Of the 160 million WLAN devices that are expected to ship in 2006, 60% will be attributed to A/V and consumer-media devices. The 802.11a-based WLAN market also is expected to experience rapid growth. From 6.1 million units in 2003, it's estimated to reach 83.9 million units in 2007. One problem could unravel this prediction, however. High power consumption and limited performance continue to act as barriers to the adoption of 802.11a-based systems.

Fortunately, the Canadian-based IceFyre Semiconductor Corp. may have found a way to tame these issues. Its answer—the SureFyre chip set—is firmly rooted in sound engineering practices. It's characterized by more than 30 patents, which cover everything from the system architecture to the digital, mixed-signal, and analog-circuit designs. This full system solution delivers greater performance, power efficiency, and system flexibility than other currently available offerings. And it does so at a competitive cost.

According to the company, these claims translate into 50% better power consumption than traditional systems running at 1.5 W and higher. The chip set also boasts a 2X output-power improvement and much greater linearity. These strengths should empower SureFyre to meet the requirements of the next-generation, high-growth WLAN-equipment markets.

The SureFyre solution for IEEE 802.11a WLAN is comprised of three parts: the ICE5125 low-power, fully featured CMOS 802.11 media-access-controller (MAC) IC; the ICE5351 integrated CMOS baseband radio-frequency IC (RFIC); and the ICE5352 high-efficiency GaAs Class-F power amplifier/Chireix combiner (FIG. 1). The ICE5351 is a 5-GHz Orthogonal Frequency Division Multiplexing (OFDM) PHY. In creating this solution, IceFyre integrated full digital and analog circuitry onto a single chip. Its integration of a high-performance 5-GHz radio on the same die as full-featured baseband-processing logic is a first for the company. The future integration of MAC functionality is dependent only upon market demands.

In contrast, the ICE5352 5-GHz OFDM power amplifier (PA) was spawned out of partitioning. Specifically, it is derived from the partitioning that can be realized when an external GaAs PA—thanks to its higher carrier mobility—acts as a companion chip to the ICE5351 PHY. With this partitioning, the final stages of a PA can be realized as a separate GaAs die. The ICE5352 Class-F PAs and Chireix combiners achieve over 35% efficiency. They maintain a 300% efficiency advantage over class AB PAs from 40-to-200-mW RMS RF output levels.

Sophisticated hardware/software partitioning also gave way to the ICE5125 MAC. Partitioning enables this MAC to have low power and flexibility. The MAC provides flexible support for 802.11a/d(draft)/h(draft)/i(draft) and quality of service (QoS). Its scalable architecture can support data rates up to 174 Mbps.

From the MAC + PHY (baseband + RF) partitioning of the SureFyre solution, designers gain maximum design flexibility. Utilizing full chip sets, the partitioning supports the implementation of complete systems. It also supports PHY-only solutions, which interface with em-bedded host-based MAC technology or proprietary MAC ICs.

To detail its other features, the SureFyre solution delivers over 200-mW RMS RF output power. Its receive sensitivity is up to 10 dB better than the 802.11a specification. It boasts a transmit-signal linearity that's up to 2 dB better than the 802.11a specification. Reference designs based on the SureFyre solution promise to achieve greater range at all data rates. This claim even holds true for a range of more than 40 m at 54 Mbps. In addition, the solution features a 150-ns delay-spread multipath tolerance. Such tolerance provides fade-free support for demanding multimedia applications.

The peak chip-set power consumption is just under 720 mW. The sleep and idle power modes are 5 mW and 117 mW, respectively. With this combination of low peak power consumption and aggressive power management, high-data-rate WLAN operation can be enabled in power-constrained applications. Among these applications are ultra-portable handheld devices and Power-over-Ethernet infrastructure equipment.

At the heart of the SureFyre chip set lies a host of innovative engineering practices coupled with a unique chip architecture. The first innovation, dubbed FyrePower, is a series of computational engines. One of these engines—the Light Clipper—limits the peak-to-average power ratio (PAPR) of the OFDM signal to an acceptable level. The second engine, the Phasor Fragmentor, deconstructs the OFDM transmit signal into multiple, constant envelope signals with 0-dB PAPR. These two engines, working with the ICE5352 PA, solve the performance and power-efficiency deficiencies of traditional 802.11a modem designs.

Among the other engines is the Adaptive Predistortor, which im-proves transmit-signal linearity while reducing out-of-band emissions. All of these engines are included in the ICE5351 PHY. Thanks to them, the ICE5352 PA chip can be realized as Class-F amplifiers in a Chireix combining architecture.

Another ingredient in this solution's "secret sauce" is its equalization and processing technology. Known as TrueSygnal, it is a per-packet, per-carrier signal-equalization and decode-processing technology. In severe multipath environments, this technology enables substantial improvements in receive sensitivity. It also provides a dynamic channel-quality-assessment capability.

With this capability, devices can select the optimal channel of operation to avoid interference. The result is strong receive sensitivity and multipath performance. These benefits are delivered by a cost-effective, single-receiver-chain implementation of per-packet antenna diversity. An automatic gain controller (AGC) makes this possible by settling in after just a few short symbols. Another feature is Transmit per Packet Power Control (TPPC), which provides for dynamic interference avoidance. The transmitted power of each OFDM packet is adjusted for optimal AP-STA performance, but minimal RF network interference.

The SureFyre chip-set family is capable of 4.9-to-5.85-GHz operation. It features up to 23-dBm RMS RF output power and over 20 dB of power-control range. It boasts a −27-dB EVM at all data rates and power levels. With a −10-dBm maximum input signal strength, it supports close-proximity transmit and receive devices. It even supports 802.11h global access. Hardware-based Wi-Fi Protected Access and AES-CCM provide low-power, high-throughput security support.

In addition to the SureFyre 802.11a solution, IceFyre recently announced its TwinFyre 802.11a/b/g chip set. As the latest version of an existing product line, this chip set boasts strong 802.11b/g performance including −30-dB EVM, over 20-dB output power, and a 150-ns delay spread at 54 Mbps. In fact, the TwinFyre-based 802.11a/b/g reference designs deliver all of the performance, power consumption, and features of SureFyre. In addition, TwinFyre features up to 17-dBm and 22-dBm output power in 802.11b and 802.11g operation, respectively. Its 802.11g receive sensitivity is up to 10 dB better than specification.

The TwinFyre 802.11a/b/g solution is comprised of the following: SureFyre's ICE5125 MAC IC; the ICE5825 dual-band PHY; the ICE5352 5-GHz OFDM PA; and the ICE2501 802.11b/g radio. The PHY is actually an 802.11a BBP and RFIC with integrated complementary-code-keying (CCK) BBP.

As new classes of devices arrive, WLAN solutions will be burdened by diverse requirements. Such requirements may include dual-band operation and enhanced battery life. Among other possibilities are 54-Mbps performance in the presence of legacy 802.11b devices along with lower packet error rates. To enable portable devices, high tolerance to multipath and very low peak power consumption may be required. No matter what the requirements, it's clear that IceFyre's WLAN solutions are well positioned with their performance, power efficiency, and system flexibility.

The SureFyre ICE5351 and ICE5352 chips are now sampling. They are both available to customers in the ICE5301A-EVK evaluation kit (FIG. 2). The ICE5125 MAC is also sampling. It is available in the ICE5100A-EVK evaluation kit. Volume production of the SureFyre 802.11a chip-set family will begin in the first quarter of 2004. SureFyre-based Mini-PCI reference designs will be available this quarter. The TwinFyre 802.11a/b/g chip set will begin sampling in the second quarter of 2004. Volume production is scheduled to begin the following quarter.

IceFyre Semiconductor Corp.
300-411 Legget Dr., Kanata, ON, Canada K2K 3C9; (613) 599-3000, FAX: (613) 599-4965, www.IceFyre.com.

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