Seven years on from its inception, Bluetooth has developed into the must have handset technology. Glenn Collinson looks at how it has moved forward

At the time of its initial inception in 1998, Bluetooth was intended, in its simplest form, as a wire replacement technology using short-range radio connections to transfer voice and data quickly. Isolated pundits scoffed at the technology, predicting that it would be forgotten in a few years. However, seven years later, Bluetooth is going from strength to strength and is recognised as being an essential feature for new mobile handset models.
This global recognition cannot simply be explained by commitment from the handset designers and silicon providers to the technology -- consumer demand for Bluetooth technology has proved insatiable. Indeed, in many equipment reviews, the lack of Bluetooth often has a significant negative impact on a product's final score. This trend has been further demonstrated by the recent adoption of Bluetooth by companies such as Samsung, who's first Bluetooth-enabled GSM handset was so popular that extra supplies had to be found from other parts of the globe in order to satisfy demand.
This article will explain why Bluetooth has enjoyed such popularity and why this popularity will continue to grow. It will examine the evolution of the Bluetooth standard and highlight the different enhancements brought by newer versions, along with details of new and existing applications for this technology.

The technology

A Bluetooth wireless link sends data to another Bluetooth radio in the form of data packets whichare sent at a rate of 1Mbit per second in the case of standard rate Bluetooth, and 3Mbits per second in the case of enhanced data rate Bluetooth. Voice packets (in synchronous connection oriented, or SCO channels) are given more bandwidth than data, thus maintaining a basic level of audio quality. However, more recent iterations of the Bluetooth standard, combined with new software providing an extra level of echo cancellation have contributed to the huge uptake of Bluetooth headsets, especially in countries where driving safety legislation has banned the use of a handset when at the wheel of a car.
Class 1 Bluetooth devices which offer the 100m range require more power and therefore tend to be featured in products with a ready and fixed power supply, such as a PC or printer. Smaller, battery-dependent devices like mobile phones, headsets or PDAs tend to be kept within a short distance of each other within the personal area network (PAN), and therefore often feature a Class 2 device with a range of approximately 10m.
Profiles included in the Bluetooth protocol stack determine the applications for which the device can be used. Common profiles include a handsfree profile for use with Bluetooth headsets of in-car handsfree systems, or dial up networking which allows a Bluetooth-enabled mobile phone to be used as a modem to connect a laptop or PDA to the Internet.
Bluetooth technology has moved on a lot in the past 18 months. In mid-2003, the Bluetooth Special Interest Group (SIG), which defines the Bluetooth standard, launched a major revision of the specification. The revision, named v1.2, brought with it an even more robust connection, as well as to enhance coexistence with other wireless standards, especially those in the 2.4GHz range -- such as Wi-Fi (802.11b/g).
In addition, in late 2004, v2.0+EDR was introduced bringing designers the chance to develop new Bluetooth-enabled products with faster data rates, even lower power consumption, and more robust voice and data connections. The evolution of the specification introduced many improvements to the technology. Some of the key improvements are detailed below with an explanation of the benefits they have brought in terms of additional applications that would otherwise have been unthinkable.

Adaptive Frequency Hopping

Adaptive Frequency Hopping (AFH) is one of these enhancements. AFH allows Bluetooth devices to monitor the link quality and then determine if there are poor channels (interference from other devices) present on specific frequencies. In such a case, the Bluetooth devices adjust their hopping sequence to avoid the bad channels, therefore improving data throughput.

Extended Synchronous Connection Oriented links

The addition of the extended Synchronous Connection Oriented (eSCO) link type is another valuable addition to the Bluetooth specification. These links allow the checking and retransmission of voice packets to enhance the quality of the audio link -- an extremely important feature for consumers who choose to invest in a Bluetooth headset.

Enhanced Data Rate

For any communications technology, faster is almost always better, and Bluetooth technology is no exception.  Enhanced Data Rate (EDR) was announced by the Bluetooth SIG in June 2004 and delivers raw data rates up to 3 times faster than basic rate Bluetooth spec. EDR is a subset of the latest v2.0 specification of Bluetooth, called v2.0+EDR.
However, EDR also brings benefits in multiple-connectivity. In isolation, standard Bluetooth-based applications do not generally demand more than the current 1 Mbps data rate. But as Bluetooth technology grows in popularity, users will increasingly run multiple Bluetooth links at the same time. This is particularly true for PCs, where it is easy to imagine a scenario where a user is operating a Bluetooth mouse and keyboard and at the same time listening to stereo audio over a pair ofBluetooth headphones. EDR gives Bluetooth the extra capacity it needs to handle links to multiple devices at data rates that users will find acceptable. In other words, users will not be tolerant of the need for the protocol to retransmit data packets if this means waiting for the mouse cursor to respond.

New areas for Bluetooth technology

he evolutionary changes to the Bluetooth specification detailed above give developers an expanded purview for application areas. The characteristics of AFH, eSCO, and EDR make Bluetooth technology appropriate for new and diverse tasks.
EDR and eSCO have made possible some interesting user scenarios. One of them has to do with the newly approved Audio Visual profiles. EDR enables stereo headsets to be used over a Bluetooth link at the same time as other Bluetooth connections. An example application would be a pair of Bluetooth stereo headphones that can be used for a phone call as well as for listening to music. The user listens via Bluetooth stereo headphones to an MP3 stream from a PC. When a phone call comes in the phone notifies the application in the PC via a Bluetooth link and this causes the phone to ask the user if they wish to answer the call. If the user chooses to take the call, the PC pauses the MP3 stream and tells the phone to proceed. Once the conversation is complete, the phone hangs up and tells the PC to resume the MP3 music.
Another related PC/phone/headset scenario is the "e-mail on the fly" situation. This scenario puts the user in, for instance, a busy airport. An e-mail is delivered to the PC via the Bluetooth link with a mobile handset. Software on the PC in the user's briefcase scans the e-mail and determines that it is important.  The application then performs a text-to-voice translation and "reads" the e-mail to the user via a Bluetooth headset. The user is then able to use the EDR link from the headset to the PC to send a high quality reply stream that is processed by a voice-to-text utility that composes an e-mail to be sent back to the original sender. The receipt, processing, and reply of e-mail can all happen 'on the fly' without the user having to stop and type e-mails.

Ultra-fast Bluetooth

The Bluetooth SIG recently announced that it intends to work towards developing a UWB Bluetooth standard which could potentially offer data transfer speeds of up to 480Mbits per second (compared to the top rate of 3Mbits per second for EDR Bluetooth). This proposal is still in the early stages of development but once the physical (PHY) layer is finalised from the competing standards currently fighting for dominance, the potential future applications for this new form of Bluetooth are vast. Its main attraction however will come from the ability to transfer huge media files such as high-definition TV programmes, films and music, instantly without the need for slower streaming data transfer.
Bluetooth has enjoyed global success in the consumer electronics market thanks to a number of different factors. The technology has evolved quickly to respond to potential coexistence or link quality issues. The rigorous testing and qualifications process demanded by the Bluetooth SIG also ensures optimum levels of compatibility between all Bluetooth products available to consumers. This evolution has also introduced applications that would otherwise have been unthinkable (for example, the highly advanced automotive telematics systems in high-end Japanese and European car models, using mobile phones connected over Bluetooth to update the car unit and utilise handsfree calling).  Further applications are already expected from the anticipated UWB-based ultra-fast Bluetooth, which may remove even more cabling from the home entertainment system.
In short, Bluetooth has proved itself a robust and secure technology which has delivered on past promises and offers more exciting future developments sure to capture consumer interest.       Glenn Collinson is co-founder of CSR

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