Putting EDR To The Test

Steve Flooks looks at the product testing and compliance issues raised by Bluetooth 2.0 plus Enhanced Data Rate.

The success of Bluetooth will be enhanced by the introduction of Bluetooth 2.0 plus Enhanced Data Rate (EDR). Offering faster data throughput, reduced power consumption, and the potential for multiple devices working simultaneously, it is a compelling proposition for potential users. Even so, it raises a number of important new issues for manufacturers, not least of which is the complex process of product testing and regulatory compliance. This process remains critical to the acceptance and successful uptake of any Bluetooth device.

Reliable wireless connectivity is becoming the Holy Grail of communication. It's not that the basic capability doesn't exist, it's just hard to convert that basic tool into reliable, usable products that routinely possess attributes such as interoperability, speed, consistency, and robustness.

The Bluetooth connectivity protocol is about providing short-range wireless links between mobile computers, mobile phones and other portable handheld devices.

Importantly, Bluetooth doesn't compete with long-range wireless network technologies, such as WiFi, but fills a complementary niche as an enabler of wireless Personal Area Networks (PANs).

As an industry standard, Bluetooth is not owned by any one organisation, but falls within the auspices of the Bluetooth Special Interest Group (SIG). Founding members include IBM, Intel, Nokia, Sony Ericsson, and Toshiba, although the number of Associate and Adopter members is growing rapidly. A central function of the SIG is to maintain and update the core specification whilst maintaining backwards compatibility. Since November 2004, the officially adopted specification is version 2.0. This version is now commonly referred to as Version 2.0 + EDR (Enhanced Data Rate), because, although the addition of EDR is a relatively minor technical addendum, it is of enormous significance for manufacturers and users.

EDR: MORE DATA FOR LESS POWER
The most noticeable feature of Version 2.0 + EDR is the improved data-transmission speed. Earlier rates of around 700Kb/s in version 1.2 did a modest but adequate job of transmitting text-based information, yrt struggled with anything much more complex than that. As Wi-Fi confidently took on the transmission of large files, graphical data, and images, the pressure has been on Bluetooth to retain its niche. Its answer is EDR, which now offers speeds at least three times faster than before—comfortably achieving data rates of 2.1Mb/s as standard, and up to a maximum of 3Mb more for bandwidth-critical applications.

EDR works by sending several data packets at once, instead of just one, via new modulation schemes. A standard Bluetooth data packet comprises an Access Code (to connect with the receiving device); a Header (which describes the packet type); the Payload (the actual data); and an Inter-packet Guard Band (which retunes between frequencies). Version 1.2 uses only one modulation technique, GFSK (Gaussian frequency shift keying) is used. In version 2.0, EDR uses up to three modulation schemes: GFSK plus a mandatory 4-phase DQPSK (differential quaternary phase-shift keying) to reach transmission rates of 2.1Mb/s; and an optional 8-phase DPSK (which further boosts the data rate to 3Mb/s). The main benefit is that a far greater volume of data can be transmitted at the same time.

This doesn't make Bluetooth a direct competitor to WiFi (which is primarily concerned with PCs and networked handhelds), but it does make it a far better connectivity fit for a highly mobile volume business, such as mobile phones. In that respect, it also offers reduced power consumption. Since more data is sent at one time, the sending device is on for correspondingly less time, dramatically reducing its power needs. This in turn makes it easier to employ Bluetooth technology in more and smaller devices, and enables these devices to do far more. Once this happens, multiple Bluetooth devices can be used at one time—you might send email over a Bluetooth PDA using a Bluetooth mouse and keyboard, whilst listening to music over a Bluetooth headset. This, combined with lower manufacturing costs for Bluetooth compared to Wi-Fi, makes Bluetooth 2.0 + EDR a highly appealing and cost-effective solution for mobile device users.

IT CAN'T BE THAT EASY
The readily identifiable benefits of Bluetooth + EDR have sent manufacturers scurrying to their product development labs. In many instances, the benefits are enhanced even further by the relatively straightforward process of transition—new chipsets simply replace old ones, enabling users to gain at least some benefits before new hardware capable of exploiting Bluetooth's audio and video capabilities reaches the market.

And it is here that the manufacturers might be caught out. Prior to release, all products with Bluetooth technology must be qualified by passing rigorous conformance and interoperability testing in a series of procedures defined by the Bluetooth SIG. This can be a demanding stage of product development, absolutely unavoidable but sometimes underestimated or even omitted from time-to-market schedules. Specialist cellular test provider and SIG-accredited Bluetooth Qualification Test Facility, RFI Global, estimates that the testing requirement for enhanced Bluetooth devices could almost double, in terms of time and cost, compared to the standard version 1.2 tests.

The testing procedure begins at the physical layer of the device with radio-frequency (RF) conformance testing, where the standard 30 hours required for a RF test will increase to a potential 25 hours per data rate for 2Mb and 3Mb devices. Although substantial, this impact will not, at least, be carried through to subsequent tests. Protocol and Profile conformance testing (which covers, for example, the operation of the Baseband, Link Manager, L2CAP, Service Discovery, RFCOMM, GAP, and SPP), remains of comparable duration at another 30 hours in total as only some protocol layers are affected by the EDR update. Profile Interoperability testing, which deals with around 25 "applications" such as Dial Up Networking and File Transfer—defined as Interoperability testing (product versus product tests)—require about half a day's testing per profile.

A test facility such as RFI-Cellular can run all of these tests in parallel. While there are no shortcuts around for each of the required tests, multiple parallel testing cuts the total time and total cost, getting products certified and out to market promptly and reliably.

Accurately gauging the time and cost of vital product testing is a key element in getting new products to market before the competition. As an Adopter member of the Bluetooth SIG, a member of the Bluetooth Technical Advisory Board (BTAB) and Bluetooth Test and Interoperability (BTI) groups, RFI-Cellular can offer pre-test consultancy. This begins by advising manufacturers when to schedule testing, particularly when new requirements are forthcoming. By scheduling testing to coincide with the release of new requirements, it becomes possible to be the first to market with a standards-compliant product whilst minimising or eliminating costly re-testing if a new test becomes mandatory.

More routinely, RFI-Cellular enables manufacturers to define the optimum sequence and combination of tests to meet their test obligations in the most timely and cost-effective manner. Bluetooth 2.0 + EDR is an exciting new development in an exciting marketplace, and could well shift Bluetooth out of its Personal Area Network niche into something more akin to the wireless networks driven by Wi-Fi. But to ensure their success, Bluetooth 2.0 products must be reliable, robust, safe and secure—and that requires comprehensive, rigorous testing.

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TAGS: Mobile Intel
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