What is the function of Bluetooth?

Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth products provide a way to connect and exchange information between devices such as mobile phones, laptop computers, PC’s, printers, PDA’s, over a secure, globally unlicensed short-range radio frequency. Bluetooth has even become a source to stream stereo music by using Bluetooth stereo headphones. Bluetooth headset in their ear, manufacturers offer Bluetooth speaker phones that can attach to car visors.
Bluetooth also simplifies the discovery and setup of services. Bluetooth devices advertise all services they provide. This makes the utility of the service that much more accessible, without the need to worry about network addresses, permissions and all the other considerations that go with typical networks.

The Bluetooth feature and profile

Most Bluetooth headsets have basic call features like the ability to answer and reject calls, last number redial, and so forth. Since sound quality is a priority with headsets, more advanced headsets like the Sound ID 510 and the BlueAnt Q2 also feature dual-microphone noise cancellation for better sound quality. Some headsets boast resistance to wind-noise, which is quite a difficult task, and the Plantronics Voyager Pro Plus is one headset that performs that job admirably. Perhaps most interesting is the Motorola Finiti, which actually uses bone conduction to transmit so as to eliminate background sound altogether.

Another advanced feature is multipoint technology, which lets you connect up to two different devices at the same time. This is useful if you use one headset with two phones, for example. Headsets with multipoint technology include the Plantronics Savor M1100 and the Jabra Extreme. And speaking of innovative features, the BlueAnt Q2 is one of the only Bluetooth headsets to offer full voice command control. This meant we could say things like "Call Home" and if you've programmed the headset to do so, it'll do just that. The voice command on the Q2 is independent from your phone, so you can use it even with phones that don't offer voice dialing.

There are multiple versions of Bluetooth, and not all Bluetooth specifications are the same, so you might want to make sure your two chosen devices will work with each other. All of the newer Bluetooth versions are backward-compatible, however, so as long as you're using the more basic Bluetooth features; you won't have much to worry about. Most products currently work on Bluetooth version 1.1, which offers such basic features as voice dialing, call mute, and last-number redial. In 2003, the Bluetooth Special Interest Group, a body that oversees the technology's development, released version 1.2 and rolled out version 2.0 a year later. Bluetooth 1.2 introduced new features to eliminate radio frequency interference through frequency hopping and added greater security to protect against snooping and tracking. Bluetooth 2.0 brought higher connection speeds (as much as three times faster, in some cases), improved performance, and less power consumption. The SIG recently introduced version 2.1, which aims to improve pairing without the need for a PIN, requires even lower power consumption, and offers more security. Check out the various profiles and their features in the chart below.

Headset Design

Most mono Bluetooth headsets can be grouped into two categories: models with a boom and models without. A boom is an extended microphone that arches toward the mouth and looks a bit like a telemarketer's headset. Though the mic's proximity to the mouth can result in better audio clarity, boom headsets have a tendency to be on the bulky side. Boom headsets are pretty rare these days, but there are still a few of them out there. There's the Motorola H17, which has a boom mic that flips open and close. In fact, when you do so, you actually power on and off the headset. Our favorite boom headset, however, is the Plantronics Voyager Pro, which has a rotating boom Mic that extends down the side of the face. It's not a very attractive headset, but it's actually quite comfortable due to the ear-hugging design.

How Bluetooth technology work?

 Unlike infra-red, Bluetooth does not require line-of-sight positioning of connected units. The technology uses modifications of existing wireless LAN techniques but is most notable for its small size and low cost. The current prototype circuits are contained on a circuit board 0.9cm square, with a much smaller single chip version in development. The cost of the device is expected to fall very fast, from $20 initially to $5 in a year or two. . They can establish a 1 megabit/s link (up to 2 Mbps in the second generation of the technology) with security and error correction, to use as required. The protocols will handle both voice and data, with very flexible network topography.

Bluetooth radio technology provides a universal bridge to existing data networks, a peripheral interface, and a mechanism to form small private ad hoc groupings of connected devices away from fixed network infrastructures. Designed to operate in a noisy radio frequency environment, the Bluetooth radio uses a fast acknowledgment and frequency hopping scheme to make the link robust. Bluetooth radio modules avoid interference from other signals by hopping to a new frequency after transmitting or receiving a packet.

Compared with other systems operating in the same frequency band, the Bluetooth radio typically hops faster and uses shorter packets. This makes the Bluetooth radio more robust than other systems. Short packages and fast hopping also limit the impact of domestic and professional microwave ovens. Use of Forward Error Correction (FEC) limits the impact of random noise on long-distance links. The encoding is optimized for an uncoordinated environment.

What Is a Bluetooth Stack?

A Bluetooth stack is an application installed on your computer that interacts with your Bluetooth devices. Two Bluetooth stacks are widely in use today:

•    The Microsoft Bluetooth stack, which comes with Windows XP Service Pack 2
•    The Widcomm Bluetooth stack

Most Bluetooth adapters use the Widcomm Bluetooth stack driver. Widcomm (acquired by Broadcom, http://www.broadcom.com) licenses its software to most Bluetooth manufacturers. Consequently, the installation, configuration, and use of different Bluetooth devices on Windows have a nearly identical look and feel.

The problem with the Bluetooth stack built into Windows XP SP 2 is that it has limited support for profiles. In particular, it does not support the Headset profile required to connect with Bluetooth headsets, and hence your Bluetooth headsets will not be able to work with your Windows XP PC.

To overcome the limitations in the Windows Bluetooth stack, you can install the Widcomm Bluetooth stack drivers from the manufacturer of your Bluetooth device. You can download the latest drivers and support software from the adapter vendor's web site. Because each vendor customizes the Widcomm software slightly, you should not use drivers from a vendor other than the one that manufactured your Bluetooth adapters.

How to buy a Bluetooth Headset?

A. Call Quality
Call quality is an issue in both directions; one headset might sound full and crisp in the earpiece, but then transmit a thin, computery-sounding version of your voice to the other person.
B . Noise Cancellation
Noise suppression performance is tough to measure from your end of the call, as it's what the other party hears that's important. Driving on a highway with the windows down, or standing on the floor of a noisy conference floor, can quickly separate the good performers from the bad. Headsets with two or three mics usually perform the best, as there's at least one mic dedicated to detecting ambient noise, which the headset can then cancel out using adaptive DSP algorithms. We test noise cancellation performance in every one of our Bluetooth headset reviews.
C  Battery Life
A guiding principle: If you don't want to charge, go large. Some of the bulkier, less fashionable headsets like the older Motorola HX1 can last for eight hours on a single charge; the Voyager Pro+ (no svelte elf itself) lasts about six-and-a-half hours. But watch out! There are some real turkeys out there, such as Jabra's Stone line, which can't even eke out two hours of talk time, so keep an eye on our test results.
D Comfort
This is a very personal choice. Some models, such as the Motorola CommandOne, feature a rubber earbud that sits partially inside your ear.
E Style
A certain portion of the population thinks that all Bluetooth headsets look silly—a view that's reinforced whenever they see people walking down the street wearing one, even when not in use.
F Range
There's not much variation in range of operation. Most headsets are limited to a theoretical range of 33 feet, which is a limitation of Bluetooth technology. Typically, you can go a good 10 to 15 feet before static starts to creep in, though a few headsets can make it to 20 feet and around a wall or two before this happens.
G Mono vs. Stereo Sound
Most Bluetooth headsets provide mono sound and fit in a single ear. But if you want to listen to stereo music wirelessly—say, for your workout—a few dual-ear models, like the Novero Tour and the quirky LG HBS-700, are worth considering.
H Bonus Features
Depending on the device you choose, you can get one (or more) nifty extras. The Jawbone Era leads the pack with its genuine app platform, which turns the headset into a fully programmable gadget.