If you own a mobile phone, computer, laptop or smart home device, then it’s almost certain that you’ve come across and recognise the following symbol:
So how has one of the most recognised logos in today’s modern world become so important to the audio industry when it was originally designed as a short-range connection for mobile phones in order to limit the use of short cables for basic tasks in close proximity?
We’ve put together this short guide to give you an overview and history of Bluetooth and how it has become so ubiquitous in the technology world and used in everyday products and tasks from wireless headphones, pairing and communication of keyboards, mice and gaming equipment and in some cases the transfer of data.
We pay particular focus to key milestones and advancements in technology that continue to evolve this wireless standard, further enhancing its capabilities and features.
Back in 1993 when mobile phones were starting to build traction and become more common and mainstream, an electrical engineer named Jaap Haartsen who worked for Ericsson (one of the world’s largest networking and telecommunications companies) was tasked with developing a short range wireless protocol in order to better enhance the functionalities of close proximity communication between mobile handsets.
Prior to the introduction of Bluetooth, wires and cables were the only way to transfer information or communicate with neighbouring devices, as you can imagine this would have been incredibly irritating, especially to complete simple tasks over very short distances.
For the next 5 years, Haartsen and a wider team continued researching and developing new ways of trying to solve this problem. At the same time many other tech giants including Intel, IBM, Nokia and Toshiba all had grand plans to introduce their own type of short-range wireless communication technology.
Fortunately, they all realised that in order to bring to market a true cross platform and device protocol, it had to be standardised for universal use. In 1998 this resulted in the establishment of the Bluetooth Special Interest Group, otherwise known as SIG. It was via this group of companies the protocol was named “Bluetooth” (after a 10th century Danish King, known for unifying groups of people). SIG grew from its early modest number of 5 or so members to having more than 35 thousand members today.
In its simplest form, Bluetooth is a short-link radio technology that operates at the 2.45Ghz band and uses micro radios in order to make a connection between two devices. Bluetooth is a packet-based protocol with a master and slave formation. It splits the transmitted data into packets and transmits each packet on one of the 79 designated channels.
One of the main reasons Bluetooth continues to evolve and become so powerful is because the network that supports it can handle any sort of data from music to data files. In the early days Bluetooth took a long time to become a mainstream consumer wireless technology. It wasn’t until the early 2000s when an influx of Bluetooth devices hit the market from mobile phones, headsets, mice and keyboards for computers and also printers. Another reason for it’s long standing position in the marketplace is its ability to be future proof. Although the principles and fundamentals of the technology remain the same, it has evolved to support all the latest features one would come to accept from a modern-day wireless protocol, some 20 years after its initial introduction.
Bluetooth standards and major milestones
When it all began back in 2001 the 1.0 standard was the first commercial incarnation of the Bluetooth protocol. Being a relatively new technology, it came with some problems and also limitations. Some of these included connection problems, anonymity, peak data speeds of only 721 kbps and a transmission distance of no further than 10 meters. The original standard was capable of wireless voice transmission for headsets, dial-up networking, fax and small file transfers. This limited bandwidth is of huge disparity to the current standards which can transfer CD quality audio and, in some cases, High-Res audio.
Fast forward to 2003 and a major update to Bluetooth came with revision 1.2 that increased the data speed to 1Mbs. It also addressed some bugs making it easier to discover and connect to devices faster and more efficiently. One of the biggest progressions of 1.2 was the increase in latency allowing for higher quality audio playback.
Bluetooth 2.0 and 2.1
The next significant update came between 2005 and 2007, with version 2.0 and subsequently 2.1. This update introduced Enhanced Data Rate (EDR) which offered data transfer speeds 3 times that of the previous version. This increased bandwidth whilst also allowing for a more economical battery life. NFC (Near-field communication) was also incorporated into version 2.1 which allowed a close contact communication (4cm) for pairing devices.
The next major milestone with Bluetooth came in 2009 with the 3.0 standard, introducing a new high-speed channel. Although this offered theoretical data transfer speeds of up to 24 Mbit/s, the transfer of data wasn’t happening over the Bluetooth. Instead, the Bluetooth link was used for connection establishment only, and the high data rate traffic was carried over Wi-Fi.
This significant increase in bandwidth allowed for Bluetooth to now transfer video data as well as audio. This increase in bandwidth and speed was the largest between any Bluetooth standard revision.
Bluetooth 4.0, 4.1 and 4.2
The next 3 revisions of Bluetooth were released between 2010 and 2014. These brought about many exciting new changes with the most noteworthy being the addition of a Low Energy technology (BLE). This was introduced so Bluetooth could be used within smaller products that required much less power consumption like smartwatches and fitness trackers etc.
Along with adding 128-bit encryption for improved security, 4.1 also allowed Bluetooth devices to perform as both a hub and point at the same time, this meant devices could seamlessly communicate information to smartphones and vice versa.
Bluetooth 5.0, 51 and 5.2
Bluetooth 5.0 to 5.2 were announced and released from 2016 through to present day. These releases yet again saw considerable improvements in the areas of bandwidth, range and multi device compatibility. Bluetooth 5.0 saw the protocol's wireless range increase to 240 meters and max data speeds of up to 50 Mbs. a big step up from previous versions. A new feature which really advanced Bluetooth and its usability in real world environments was its capability of transmitting audio between two devices at the same time, this allowed for simultaneous audio playback on two headphones at once, and also multi room functionality for smart speakers in the home.
Bluetooth for audio
Whilst it’s clear to see from the previous section that Bluetooth has progressed substantially over the last 20 years, these improvements to the core technology have allowed for it to be used more extensively for audio streaming applications. Increases in bandwidth and speed have given rise to various codecs being developed allowing for higher quality audio to be streamed over Bluetooth to headphones and other receiving devices.
The quality of Bluetooth audio was appalling when it first came out, mainly because it was never initially developed for transferring audio but instead pairing input devices. By contrast, one of the most recent developments by Sony called LDAC allows for streaming of high-resolution audio over Bluetooth connections at up to 990 kbps at 24 bit/96 kHz.
With over 4 billion devices being manufactured annually that have Bluetooth, the demand for high quality Bluetooth audio continues to grow. The next section will review and compare two of the main codecs which have become synonymous and widely used by audio fanatics as a means to get the highest possible audio quality over Bluetooth.
In 2016, Qualcomm (one of the world’s largest mobile chipset manufacturers based in America) launched aptX HD. Although the aptX codec has been around since the 80s the newly developed HD version is capable of wirelessly transmitting 24-bit hi-res audio. What makes aptX and aptX HD so unique and effective are their abilities to transmit audio over Bluetooth using a complex compression algorithm. AptX can transmit CD-like 16-Bit/44.1kHZ music at a rate of 352kbps. Due to its use of compression, it can’t be classed as full CD quality streaming.
The increase in popularity of Hi-Res audio led to the release of aptX HD which supports the transmission of audio at 24-bit/48kHz with a bitrate of 576kbps. The compression ratio is the same as aptX at 4:1, due to this, there is constant debate as to whether its quality can really compare to a direct feed of equivalent audio quality from a wired source.
Although aptX HD is a codec, a new type of hardware chipset is required for one to use the new standard. Therefore, both the sending and receiving component must utilise the CSR8675 Bluetooth audio SOC. The good news is that the newer types of chipset that have this SOC are backward compatible therefore you’ll have no problems using the standard aptX codec.
As of 2016 the list of hardware manufacturers that support aptX HD continues to grow, so most modern smartphones using android will offer support for this right out of the box. The same applies for other manufacturers of headphones, AV receivers, portable audio players and other consumer electronics products.
Unfortunately for users of Apple devices aptX HD is not a supported codec on their smartphones, they have chosen instead to adopt the AAC codec.
LDAC was announced in 2015 by tech giant Sony along with a plethora of high-resolution personal audio products. Pitched as being able to transmit 24-bit/96kHz Hi-Res audio at a top speed of 990kbps, it trumps the competition. Sony also claims that the codec can transmit CD quality 16-bit/44.1kHz completely untouched.
Being a Sony product, it took some time to see LDAC being used by other 3rd party mobile phone and consumer electronics manufacturers. Nowadays most modern-day android smartphones have LDAC built in.
LDAC has a neat feature which allows for altering connection types depending on conditions and setup. These are, quality priority, normal and connection priority. Bitrates will fluctuate from 990 kbps all the way down to 330 kbps in order to maximise performance and sound quality depending on connection quality.
One main difference between Sony’s LDAC and Qualcomm’s aptX HD technology is that LDAC works by variation of bitrates, depending on the available hardware, connection speed, and connection strength, whilst aptX is a constant bandwidth codec. So as the LDAC bit depth decreases, the amount of compression and noise also increases, by contrast aptX is set to continuously work at the same bitrate. Even though Sony’s option offers more flexibility, it is more resource intensive with regards to encoding and decoding, also making it harder to know exactly what audio quality you are receiving.
Bluetooth audio and consumer demand for this technology means it is clearly here to stay. For close range wireless audio on the go it is currently the most widely used and convenient technology. Unfortunately, no Bluetooth codecs offer a true lossless solution to date, however over the past 20 years we’ve seen the technology vastly improve with significant advancements made in the last 2-3 years with regards to better overall audio quality.
LDAC and aptX HD are not a direct path to superior audio quality, final sound quality will depend also on your source material and quality of headphones, earphones or speakers being used. They are however the most advanced and best sounding solutions for Bluetooth currently available. Fortunately, most modern-day devices support both codecs so trying them out and seeing which one sounds best to you is easily capable.