When Jaap Haartsen and Sven Mattisson developed the Bluetooth specification in1994, both were employees at Ericsson Mobile Platforms. They based the Bluetooth specification on a technology known as frequency-hopping spread spectrum (FHSS), which is a method of transmitting signals by quickly switching frequency channels during transmission. The advantages of using FHSS include:

• Resistance to narrowband interference
• Increased security by decreasing the probability of intercepting signals—intercepting FHSS signals is difficult
• Shared frequency bands with other transmission types results in little interference

In 1998, during the early stages of Bluetooth specification development, a Bluetooth Special Interest Group (SIG) was established by several large telecommunications and information technology vendors, formalizing the specifications developed by Haartsen and Mattisson. Today, more than 8,000 member companies and organizations around the world participate in the Bluetooth SIG.

Exploring Bluetooth versions

The early days of Bluetooth included versions 1.0 and 1.0B, which made Bluetooth communications possible but presented device incompatibility issues that delayed widespread use of the technology. The SIG resolved many of the problems with the release of version 1.1, which added support for non-encrypted channels as well as Received Signal Strength Indicator (RSSI), a measurement of power in received radio signals.

Bluetooth version 1.2 included a number of feature enhancements, including a faster transmission speed of up to 1 megabits per second (Mbps), improved resistance to radio frequency interference, the Host Controller Interface (HCI) and support for three-wire Universal Asynchronous Receiver/Transmitter (UART), among other features. In addition, version 1.2 was backward-compatible with version 1.1.

The next version of Bluetooth offered many improvements over the previous versions. Launched by the SIG in 2004, Bluetooth 2.0 + EDR incorporates an Enhanced Data Rate (EDR) of up to 3.0 Mbps, lower power consumption, more bandwidth and is also backward-compatible with version 1.1.

Bluetooth 2.0 + EDR caused confusion in the marketplace when released. Many vendors began promoting their equipment simply as "Bluetooth 2.0," which technically means the equipment is version 1.2 with bug fixes and doesn't necessarily include EDR's faster transfer rates. The only way to ensure a device is fully compliant with Bluetooth 2.0 + EDR is to carefully read the device's specification sheet.

This brings us to the current Bluetooth version as of this writing, 2.1 + EDR, which is also completely backward-compatible to version 1.1. In 2007, the Bluetooth SIG adopted version 2.1, which includes the following features:

• Sniff subrating: Reduces power consumption and/or battery life by three to 10 times when devices are set to sniff power mode, particularly on human interface devices such as keyboards, mice, joysticks, trackballs and so on
• Near Field Communication (NFC) cooperation: Automatically pairs two Bluetooth devices when they're brought within close proximity to one another, such as 1 inch, or tapped together
• Secure simple pairing (SSP): Improves the simplicity and security of the pairing process, using public key cryptography called Elliptic Curve Diffie-Hellman (ECDH) to avoid eavesdropping attacks
• Extended inquiry response: Provides more details early in the connection process, enabling better filtering; details include the list of services the device supports, the name of the device, time of day and pairing information
• Encryption pause resume: For purposes of stronger security, enables an encryption key to be refreshed while devices remain connected longer than 23.3 hours, which is equal to one Bluetooth day.

Now that you've explored Bluetooth from its inception, let's move on to how Bluetooth works.