Microwave Engineering Europe - October 2007 - (Page 24)

24 WIRELESS HID Wireless HID – are you following the standard to another “average” product development? By Steve Kolokowsky, Cypress Semiconductor ustomization can save power, create data efﬁciency, and cut down on development cycle times. Standardization can lessen the learning curve, can reduce risk in a project, and can eliminate some design steps. The question is, what method is better when developing a Wireless USB system? When discussing Wireless USB standards, there are two options — follow a popular prevailing wireless standard, or develop using a proprietary solution optimized for your application. Are you bold enough to use a proprietary solution with the promise that it will give you a competitive advantage in the marketplace — or is “proprietary” too scary of a word to consider in your next design? As with any industry, the tech industry has two types of standards: • Open standards begin with organization of individuals or groups that develop consensus on speciﬁcations for implementing common requirements. Open standards permit access to anyone interested in using the “rules and regulations” when developing their product. • Proprietary standards generally evolve from a product line or speciﬁc vendor technological development. Proprietary standards are based on technology produced by a single entity as proprietary or exclusive. In today’s Wireless PAN (Personal Area Network) market, there are several different wireless standards available for wireless device communication to a PC, as seen in Table 1. Wi-Fi (802.11) provides a high-bandwidth connection and is mainly used for wireless networking, while WirelessUSB provides a lowbandwidth connection and Bluetooth, though driven largely by the cell-phone connectivity application, is also being used for wireless mice and keyboards. The ability to “plug and play” in any environment is a positive attribute of standardized devices. This interoperability is good for device producers and consumers. C Table 1: Wireless standards and PC interface type. Producers can focus on their design and manufacturing strengths, while consumers get more choices. One signiﬁcant disadvantage, however, of standards is that they can add a lot of functionality that your application may not need. If the standard is designed to be modular, it may be possible to remove all of the unnecessary functions but in many cases, the minimum set is just too big. For networking applications where products from different manufacturers need to communicate together, standards-based solutions are generally the right type of solution. But for products that are stand-alone connection points, complex network solutions are overkill and can be detrimental to a more simplistic design where the designer does not wish to bear the overhead of a complex network protocol. Bluetooth in Wireless HID (human interface device) applications is a good example of this issue of complexity. Let’s examine the Bluetooth implementation required compared to the customized implementation developed for WirelessUSB. Bluetooth implementations require anywhere from 15K to 64K of ROM space just to implement basic functionality. A full implementation of a WirelessUSB mouse takes 5.5K including code to handle the buttons and mouse sensor. To avoid confusion with Certiﬁed Wireless USB, WirelessUSB is Cypress Semiconductor’s line of low-power, USB interface products that operate in the 2.4-GHz ISM band with a range from 10 meters (at max 1 Mbit/s) to 50 meters (at max 62.5 kbit/s) and that use the existing USB driver infrastructure. WirelessUSB devices are much lower cost and lower power than Certiﬁed Wireless. Much of the issue with code space originates from the fact that Bluetooth was invented as a networking standard where devices can discover one another, device connectivity is ubiquitous across industries, and all worldwide vendors can design compatible products. To accomplish this, however, the Bluetooth protocol must be complex enough to manage different requirements — Figure 1 Unfortunately, use of a more complex protocol stack also means suffering from a more complex data transfer scheme. Figure 2 shows that despite using the Bluetooth stack in its most simple form, it still cannot compete with the simplicity of a carefully designed proprietary solution for the HID market. The nature of the Wireless HID market makes this a signiﬁcant difference in data length. With every moment data is being transferred, a device is consuming power and is susceptible to data corruption through interference. Poor battery life and missed data packets can have signiﬁcant negative impact on consumer experience. One signiﬁcant reason to create a custom protocol is differentiation. Though standards do allow a given level of certainty in design, they do not generally allow for much differentiation. In the world of HID design, standards limit innovation by limiting choices. Some areas ready for differentiation in the wireless HID space are interference immunity and power. Interference immunity is an important topic these days, especially in the 2.4-GHz unlicensed band. It seems like there are new WiFi hot-spots everywhere. More and more cell phones and other devices are Bluetooth-enabled. Cordless phones and microwave ovens are unpredictable sources of interference and Zigbee is just getting started. If you are following a standard, your interference immunity is ﬁxed. Microwave Engineering Europe ● October 2007 ● www.mwee.com 024-025_MWEE.indd 24 20/09/07 13:04:44 http://www.mwee.com

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Microwave Engineering Europe - October 2007 Contents Comment News CMOS RF: Si-On-Sapphire Goes Mainstream Cover Feature: New Data Protection Concept for UHF RFID Tags CMOS RF: RF Design Team Touts CMOS Spin for 3G PAs Wireless HID – Are You Following the Standard to Another “Average” Product Development? Phase Optimisation of the RF Front-End Direct Synthesis of UWB-WiMedia Signal Generation 4G Chips to Target 700 MHz Applications Femtocells Mobilize to Fight Wi-Fi in the Home Products Product Feature: AXIEM Pioneers the Future of EM Technology Calendar

Microwave Engineering Europe - October 2007

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