The UWB-RF channel has recently become available in the USA (e.g., in the frequency range 3.1 GHz-10.6 GHz allocated for indoor as well as outdoor use). European and Japanese authorities are preparing similar rules to enable commercial marketing and use of UWB-RF devices.
Short-range wireless technologies in the wireless local area network (WLAN) space as well as the wireless personal and body area network spaces (WPAN/WBAN) continue to proliferate rapidly. In particular, wireless links based on infrared (IR or Ir) light emission have experienced an enormous growth in the recent past owing to ease of use and low cost. The Infrared Data Association (IrDA) has projected a total shipment of 1.3 Billion units by the year 2003, with over 250 Million IrDA devices installed in mobile phones and personal digital assistants (PDAs). This high adoption rate reflects the presence of a large number of IrDA applications in the marketplace and a sizable investment by the industry and users alike. On the other hand, radio-based short-range wireless devices such as Bluetooth™ (Bluetooth is a trademark owned by Bluetooth SIG, Inc.) are also deployed at a rapid pace, thereby reducing the relative size of the IrDA-based market segment rather quickly. This will influence the IR-based industry which is looking for alternate ways to leverage their investments and continue their business.
Two dominant technologies in the short-range wireless space—Bluetooth and IrDA —were specifically designed for replacing short-range wired communication links. Bluetooth is based on an RF technology offering less than 1 Mb/s of user data rate and IrDA offers a number of data rates, e.g., SIR (115 Kb/s), FIR (4 Mb/s), and VFIR (16 Mb/s). IrDA uses optical-IR transmission which requires line of sight (LOS) between transmitter and receiver. IrDA and Bluetooth technologies are also used for consumer-based applications within the single office/home office (SOHO) environment. Each has its own strengths and weaknesses with respect to link range, data rates, required regulation and costs.
While some of these technologies' intended uses and applications overlap, each of the two systems offer all of the hardware and software layers that constitute a set of communication protocols. IrDA is an established and well proven point-to-point, narrow-angle, data-transmission standard that operates at bit rates between 9600 b/s and 16 Mb/s over distances of 0-1 m (mostly 20 cm). It has a wide range of supported hardware and software platforms and is well introduced in the market place. Though IrDA's benefits seem to abound, the technology has its disadvantages. For many applications, its limited range and pointing angle is rather inconvenient and its optical signals fail to penetrate walls or propagate around obstructions (IrDA was not designed to rely on diffused optical signal propagation). Additionally, IrDA devices must be nearly stationary to achieve synchronization with other IrDA devices (narrow optical beam). Where IrDA fails to be user friendly, radio-based systems offer advantages, such as non-line-of-sight (NLOS) transmission through walls and other obstructions. However, many RF-based systems, such as Bluetooth, are regulated differently in various countries worldwide and thus suffer non-trivial insertion into the markets.
The two main markets for short-range wireless devices are the portable and desktop computing and handheld markets. Due to architectural and range constraints, the level of adoption of IrDA in the desktop space has been relatively low. Current desktop designs in the marketplace are more appropriate for placing the desktop in a cabinet or on the floor. However, such a usage scenario is not favorable for point-and-shoot optical link applications as offered by IrDA.
The disadvantages of optical-IR communication links and the investments from the manufacturers and the user community in IrDA-based technology and applications could both be leveraged and maintained into the future by replacing or enhancing the optical transceiver of the IrDA system (i.e., part of the PHY layer) with a suitable radio-based transceiver.
Given the recent introduction of a license-free spectrum band between 3.1 GHz and 10.6 GHz (USA/FCC) for UWB radio devices, a new and inherently compatible radio technology has become available to design and implement such radio-based systems. As a result, the many applications and protocol stacks, including medium access control protocols, originally conceived for wireless optical links should be useable on the UWB radio channel.
It would be advantageous if the two types of communication systems could be brought together to make use of the wireless optical system and the radio channel. Owing to the different transmission media used (optical and radio frequency, respectively) as well as because of legacy considerations, these different wireless communication systems have traditionally also been designed with different medium access control (MAC) mechanisms; in addition, their positioning in the market place have been different in general, although their applications do overlap in certain areas (e.g., PDA data base synchronization with PC data base).