[March 1, 2002]

Wi-Fi And Bluetooth As Complementary, Not Competing, Technologies

BY DR. LUNG YEH

Today's mobile professionals need to stay connected and have access to real-time information and business applications. The need to access information and exchange data without being tied to the desk has led to the development of two technologies: the IEEE 802.11b standard, also known as Wi-Fi, and the 802.15 WPAN standard, known as Bluetooth. Bluetooth and Wi-Fi both give mobile professionals the freedom to access the Internet and corporate networks at work, on the road, or at home through a broad range of devices such as PCs, notebooks, and personal digital assistants (PDAs).

As a result of the similarities between the two technologies, many have erroneously regarded Wi-Fi and Bluetooth as being in competition with one another. The development and deployment of Bluetooth and Wi-Fi has been depicted as a horse race, with only a single winner.

The reality is that Bluetooth and Wi-Fi will both flourish, based upon the specific benefits that each has to offer. Bluetooth is intended to connect all of the Bluetooth-enabled devices immediately surrounding a user, wherever that user may be located. The Bluetooth specification calls for a small form factor, low power consumption, and low cost, making it the ideal wireless technology for battery-powered devices. Wi-Fi, in contrast, was designed to be the best solution for a single specific application: connecting to the wireless local area network (WLAN). It offers benefits to users that wish to gain LAN or Internet access while moving about the enterprise or, in some cases, while traveling.

What some thought would be a horse race is, in fact, a stampede. Research firm Cahners In-Stat predicts there will be 780 million Bluetooth-enabled products in 2005, while Wi-Fi will see 10 million shipments in the same year. The explosion in Wi-Fi WLAN installations and the anticipated growth in the use of Bluetooth-enabled devices ensure that the two technologies will find themselves sharing space more and more often. So yes, the proverbial cats and dogs will be living together in the wireless world.

When comparing Bluetooth and Wi-Fi in the context of the enterprise, it is necessary to examine the actual capabilities of each technology, the corresponding requirements of the applications, and the real world considerations that affect performance. These elements are summarized in the table at the end of this article.

Power Consumption, Speed, And Portability
Bluetooth technology's low power characteristics are ideal for devices that spend most, if not all, of their operating hours on battery power. The Bluetooth specification incorporates a number of power-saving features in order to keep current draw to a minimum. These features include a standby mode as well as four connected modes: parked, hold, sniff, and active.

Devices such as PDAs are well-suited for Bluetooth-enabled wireless connectivity. A handheld with typical battery power can support a Bluetooth radio running in idle mode for more than 250 hours, on average, whereas Wi-Fi can only support 20-50 hours in sleep mode. If both technologies are in full transmit or receive mode, a PDA using Wi-Fi can expect little more than an hour of operation while a PDA using Bluetooth can operate for five to ten hours, based upon typical current consumption.

Conversely, Wi-Fi is better suited for devices in which speed is of the essence. Thus, a notebook computer user with a frequent need to transfer large data files to and from the network, especially while away from the desk, is an ideal Wi-Fi candidate. Required data rates are high, as is the need for mobility, and the notebook has the processing power to accommodate the 3 to 5 Mbps speeds characteristic of Wi-Fi.

Handhelds and PDAs, on the other hand, have little to gain from the addition of Wi-Fi, as either battery life or device size are compromised and speed is neither enhanced nor, typically, required. Adding Wi-Fi to a handheld usually requires the addition of a PC card; as we have learned, the impact on handheld battery life is substantial. The alternative is the addition of a second battery, often contained within a "sled" that attaches to the PDA. Although this approach succeeds in offering additional longevity to the PDA device, it transforms the PDA into a much bulkier piece of equipment.

As for speed, the data rate bottleneck for PDAs is not the wireless technology, but rather the PDA itself. Users expecting lightning speed from their Wi-Fi-equipped PDA will discover that the speed is typically less than 100 Kbps. Bluetooth technology has the ability to operate at speeds as high as 700 Kbps, far surpassing the capabilities of the current crop of handhelds, and even that speed cannot be used. Fortunately, the e-mail, Internet, and database lookup applications that account for most handheld use can be easily accommodated using the sub-100 Kbps data rates currently supported on handhelds. Bluetooth technology, therefore, enables handhelds to get the speed they need with major savings in battery life and device size, as compared to Wi-Fi.

Connectivity Ranges
The comparative range of the two technologies has been the subject of much misunderstanding. Most are familiar with Wi-Fi's range capability -- as much as 600 meters or more in outdoor environments and typically 100 meters or more indoors. Contrary to popular belief, Bluetooth technology supports multiple ranges, each suited to the application and device being used. In its cable replacement and ad hoc networking roles, Bluetooth technology is typically used at its lowest power setting and supports a range of approximately 10 meters between devices. This is an appropriate range for connecting devices that are within a user's personal area, such as printers and phones.

In its network access role, on the other hand, Bluetooth technology can support ranges of up to 100 meters between Bluetooth access points and low-power client devices. Thus, users that have PDAs equipped with Bluetooth can wander the workplace with little fear of being disconnected, if access points are deployed in densities comparable to Wi-Fi. Typical wireless deployments, whether Bluetooth or Wi-Fi, feature access points deployed with radii of approximately 20 meters. This distance between access points is governed not by range but by user density. Thus, the range afforded by Bluetooth access points can be more than adequate to support the networking needs of a typical office.

Security Issues
Wireless technologies have been wrestling with the challenge of ensuring that end users' transmissions are resistant to eavesdropping. In the case of Wi-Fi, the Institute of Electrical and Electronics Engineers (IEEE) is drafting a new standard, 802.1x, which will address the current shortcomings, maximize security, and centralize management functions. The proposed standard includes the integration of Remote Authentication Dial-In User Service (RADIUS) technology to assign wireless clients dynamic Wired Equivalent Privacy (WEP) keys on a per session basis. In fact, some vendors have already integrated dynamic session keys into their platforms, thus making for a substantially improved level of security.

Devices equipped with Bluetooth were designed to have security options flexible enough to allow for minimal demands on the user when security is not a priority, but also offer a high level of security when circumstances demand it. Bluetooth uses multiple levels of user authentication and data encryption as well as a data transmission protocol that provides an inherent degree of security. The frequency-hopping scheme that Bluetooth employs makes eavesdropping much more challenging by ensuring that only receivers synchronized with the transmitter can access information. Bluetooth's evolving standards will call for even more robust security measures in the future.

Conclusion
In the end, Wi-Fi and Bluetooth are complementary -- not competing -- technologies. Wi-Fi is intended to be a wireless replacement for Ethernet LANs. It is designed to enable portable devices such as notebook computers to easily move about an office or campus environment, while maintaining connectivity to the corporate LAN. Bluetooth, on the other hand, is a generic access technology meant for wirelessly connecting devices of all types, shapes, and sizes. It's intended to be ubiquitous, allowing the formation of ad hoc networks between devices -- wherever they may be located, with or without the user's intervention -- and the creation of connections between handhelds and their local networks and the Internet.

While Wi-Fi has become the high-speed network access technology of choice, Bluetooth will cement its position as the universal connectivity standard and as the network access technology of choice for small, battery-powered devices.

Dr. Lung Yeh is co-founder, president, and CEO of Pico Communications, Inc. Founded in December 1999, Pico Communications is a privately held technology company that provides simplified Bluetooth networking solutions. Pico delivers products and software to extend Personal Area Networking to the mobile professional at work and on the road to connect to the corporate LAN and the Internet. Pico Communications is an associate member of the Bluetooth Special Interest Group (SIG).

Table 1. A comparison of Bluetooth and Wi-Fi. [return to article]

	Bluetooth	Wi-Fi
Frequency	2.4 GHz	2.4 GHz
Specification	Bluetooth (802.15)	802.11b
Raw Data Rate	1 Mbps	11 Mbps
Data Throughput	Up to 723 Kbps	Up to 5.5 Mbps
Range for access points (Class I) in typical office environment	30m	35m
Transmission Scheme	Frequency Hopping Spread Spectrum (FHSS)	Direct Sequence Spread Spectrum (DSSS)
Power Requirements - Idle/Sleep	1.5 - 2 mA	10 - 32 mA
Power Requirements - Transmit	50 - 100 mA	340 - 450 mA
Power Requirements - Receive	50 - 80 mA	250 - 310 mA
Usage Scenarios	Cable replacement, peer-to-peer collaboration, Internet access via mobile phone, LAN and Internet access via Bluetooth access points.	Portable computing, high-speed, wireless local area network (LAN) and Internet access.