One of the lesser-known facts to emerge about the iPhone 4S yesterday is that it is the first phone to launch with Bluetooth 4.0, the latest version of Bluetooth. Not many products are available with Bluetooth 4.0 just yet–in fact, two of the most recent products to ship with Bluetooth 4.0 are also from Apple: the MacBook Air and the Mac Mini. Bluetooth 4.0 is backward-compatible with all other versions of Bluetooth, so you can pair existing Bluetooth headsets with the new iPhone without a problem.
The Apple iPhone 4S is the first phone to ship with Bluetooth 4.0.
So what’s so special about it?
According to Mike Foley, executive director of the Bluetooth SIG (Special Interest Group), the key new feature of Bluetooth 4.0 is its low-energy technology. This lets device manufacturers replace proprietary sensor technology with Bluetooth, which is a more widely adopted standard. An obvious example is in the health and fitness category. Most pedometers, heart rate straps, and blood glucose monitors are designed to only talk to a specific wristwatch or control unit. If these same devices had Bluetooth 4.0, they could speak to any Bluetooth 4.0 device, be it phone or computer, without requiring an intermediary.
“It’s an extremely optimized version of Bluetooth,” Foley said. “It enables an entirely new class of product into the Bluetooth world.”
This version of Bluetooth is thus targeted specifically for small battery-operated devices like Nike+ sensors, Fitbits, and similar products that require almost no power. Foley envisions that gyms and fitness centers would have Bluetooth-enabled computers so that you could automatically upload your fitness stats to the cloud after you finish your workout, for example. The first such device is a Dayton heart-rate chest strap using a Bluetooth 4.0 chip from Nordic Semiconductor.
Other potential uses of Bluetooth 4.0 include standardizing active 3D glasses so you don’t need line-of-sight for them to work, and possibly a wireless payment system similar to NFC.
Do I really need it?
It’s still early days for Bluetooth 4.0. As we mentioned, the iPhone 4S is currently the only phone to have this specification, and there aren’t that many Bluetooth 4.0 devices yet to make use of the technology. Still, we should see more Bluetooth 4.0-compatible products before the end of the year, with more phones adopting the standard as well. Hopefully developers will get on board to create custom apps to take advantage of Bluetooth 4.0 accessories. We wouldn’t rush out to get the phone just based on this one specification right now, but it might be a big deal in the future.
Bluetooth v1.0 and v1.0B
Versions 1.0 and 1.0B had many problems, and manufacturers had difficulty making their products interoperable. Versions 1.0 and 1.0B also included mandatory Bluetooth hardware device address (BD_ADDR) transmission in the Connecting process (rendering anonymity impossible at the protocol level), which was a major setback for certain services planned for use in Bluetooth environments.
- Ratified as IEEE Standard 802.15.1-2002
- Many errors found in the 1.0B specifications were fixed.
- Added possibility of non-encrypted channels.
- Received Signal Strength Indicator (RSSI).
This version is backward compatible with 1.1 and the major enhancements include the following:
- Faster Connection and Discovery
- Adaptive frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence.
- Higher transmission speeds in practice, up to 721 kbit/s, than in v1.1.
- Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets, and may optionally increase audio latency to provide better concurrent data transfer.
- Host Controller Interface (HCI) operation with three-wire UART.
- Ratified as IEEE Standard 802.15.1-2005
- Introduced Flow Control and Retransmission Modes for L2CAP.
Bluetooth v2.0 + EDR
This version of the Bluetooth Core Specification was released in 2004 and is backward compatible with the previous version 1.2. The main difference is the introduction of an Enhanced Data Rate (EDR) for faster data transfer. The nominal rate of EDR is about 3 Mbit/s, although the practical data transfer rate is 2.1 Mbit/s. EDR uses a combination of GFSK and Phase Shift Keyingmodulation (PSK) with two variants, π/4-DQPSK and 8DPSK. EDR can provide a lower power consumption through a reduced duty cycle.
The specification is published as “Bluetooth v2.0 + EDR” which implies that EDR is an optional feature. Aside from EDR, there are other minor improvements to the 2.0 specification, and products may claim compliance to “Bluetooth v2.0” without supporting the higher data rate. At least one commercial device states “Bluetooth v2.0 without EDR” on its data sheet.
Bluetooth v2.1 + EDR
Bluetooth Core Specification Version 2.1 + EDR is fully backward compatible with 1.2, and was adopted by the Bluetooth SIG on July 26, 2007.
The headline feature of 2.1 is secure simple pairing (SSP): this improves the pairing experience for Bluetooth devices, while increasing the use and strength of security.
2.1 allows various other improvements, including “Extended inquiry response” (EIR), which provides more information during the inquiry procedure to allow better filtering of devices before connection; and sniff subrating, which reduces the power consumption in low-power mode.
Bluetooth v3.0 + HS
Version 3.0 + HS of the Bluetooth Core Specification was adopted by the Bluetooth SIG on April 21, 2009. Bluetooth 3.0+HS provides theoretical data transfer speeds of up to 24 Mbit/s,though not over the Bluetooth link itself. Instead, the Bluetooth link is used for negotiation and establishment, and the high data rate traffic is carried over a collocated 802.11 link.
The main new feature is AMP (Alternate MAC/PHY), the addition of 802.11 as a high speed transport. The High-Speed part of the specification is not mandatory, and hence only devices sporting the “+HS” will actually support the Bluetooth over 802.11 high-speed data transfer. A Bluetooth 3.0 device without the “+HS” suffix will not support High Speed, and needs to only support a feature introduced in Core Specification Version 3.0 or earlier Core Specification Addendum 1.
- L2CAP Enhanced modes
- Enhanced Retransmission Mode (ERTM) implements reliable L2CAP channel, while Streaming Mode (SM) implements unreliable channel with no retransmission or flow control. Introduced in Core Specification Addendum 1.
- Alternate MAC/PHY
- Enables the use of alternative MAC and PHYs for transporting Bluetooth profile data. The Bluetooth radio is still used for device discovery, initial connection and profile configuration, however when large quantities of data need to be sent, the high speed alternate MAC PHY 802.11 (typically associated with Wi-Fi) will be used to transport the data. This means that the proven low power connection models of Bluetooth are used when the system is idle, and the faster radio is used when large quantities of data need to be sent. AMP links require enhanced L2CAP modes.
- Unicast Connectionless Data
- Permits service data to be sent without establishing an explicit L2CAP channel. It is intended for use by applications that require low latency between user action and reconnection/transmission of data. This is only appropriate for small amounts of data.
- Enhanced Power Control
- Updates the power control feature to remove the open loop power control, and also to clarify ambiguities in power control introduced by the new modulation schemes added for EDR. Enhanced power control removes the ambiguities by specifying the behaviour that is expected. The feature also adds closed loop power control, meaning RSSI filtering can start as the response is received. Additionally, a “go straight to maximum power” request has been introduced. This is expected to deal with the headset link loss issue typically observed when a user puts their phone into a pocket on the opposite side to the headset.
The high speed (AMP) feature of Bluetooth v3.0 was originally intended for UWB, but the WiMedia Alliance, the body responsible for the flavor of UWB intended for Bluetooth, announced in March 2009 that it was disbanding, and ultimately UWB was omitted from the Core v3.0 specification.
On March 16, 2009, the WiMedia Alliance announced it was entering into technology transfer agreements for the WiMedia Ultra-wideband (UWB) specifications. WiMedia has transferred all current and future specifications, including work on future high speed and power optimized implementations, to the Bluetooth Special Interest Group (SIG), Wireless USB Promoter Group and the USB Implementers Forum. After the successful completion of the technology transfer, marketing and related administrative items, the WiMedia Alliance will cease operations.
In October 2009 the Bluetooth Special Interest Group suspended development of UWB as part of the alternative MAC/PHY, Bluetooth v3.0 + HS solution. A small, but significant, number of former WiMedia members had not and would not sign up to the necessary agreements for the IP transfer. The Bluetooth SIG is now in the process of evaluating other options for its longer term roadmap.