reverse engineering How we made Bluetooth Bluetooth allows electronic devices to communicate over short distances and is used by billions of devices worldwide. Jaap Haartsen recalls the developments that led to the establishment of the Bluetooth wireless technology standard. Jaap Haartsen

n 1990, after completing my PhD at Delft uncertainty by not using all 79 carriers University of Technology, I was hired by during connection establishment, but INils Rydbeck who had just started the only 32 carriers. Since this did not satisfy Ericsson–GE mobile phone division in the FCC Part 15 requirements for FH, Research Triangle Park, North Carolina, spreading codes were used at connection USA. Rydbeck also headed the Ericsson establishment to satisfy the FCC’s hybrid mobile phone division in Lund, Sweden, and FH/DS spreading requirements. had created an ideal environment for young Early in 1995, Sven Mattisson joined engineers to play around with different ideas the Ericsson division in Lund. An expert and technologies without being restricted by on radio implementations, he started to commercial barriers. My first manager was work on the hardware development of the Paul Dent, a great inventor who taught me radio. The intent was to make a low-power how to map ideas into patent applications. radio in complementary metal–oxide– I initially worked on digital cellular semiconductor (CMOS) technology without telephony, but after a while I moved to Credit: Ibrandify / Alamy Stock Vector any external components. With the hardware indoor communications. team, I worked on system solutions to create In the summer of 1994, I moved to Lund, a full CMOS implementation. In Lund, where Rydbeck asked me to work on a new spreading would be required. Spreading the project was called MC Link. MC came concept: a short-range radio link between distributes the signal power over a larger from a multi-communicator Ericsson was a cellular phone and nearby electronic part of the frequency spectrum, which can developing: a small personal assistant that devices, supporting both voice and data. be accomplished either by jumping back and could be connected to the cellular phone via At the time, there was an ongoing project forth with a narrowband, low-rate signal a wireless link. called Cornelius that investigated a wireless (FH) or by using a wide bandwidth with a In 1997, after nearly four years as a link between a phone and a voice headset. high-rate signal (DS). Furthermore, since research project, Ericsson hired Örjan However, this was based on an analogue this was a licence-free band, a radio system Johansson to create a business around the technology and did not support data. And operating in it had to deal with interference short-range radio concept. An ecosystem because of the choice of spectrum, it could from other users, ranging from garage door was needed, involving other industries. not be used worldwide. I started to look openers to baby monitors. To deal with this Intel was the first interested party. Together at other technologies, like the cordless interference, I selected frequency hopping with key people from Intel, including Jim phone standard Digital Enhanced Cordless because, instantaneously, the radio occupies Kardach and Simon Ellis, other companies Telecommunications (DECT) or wireless only a small part of the spectrum and nearby were approached: Nokia, Toshiba and IBM. local area network (WLAN) 802.11, but interferers can be suppressed by channel The codename Bluetooth was used for this none fulfilled the requirements of peer filtering. And at the same time, the radio, on international project. Together, the five connectivity, support for voice and data, and average, hops through the entire ISM band, companies created the Bluetooth Special low-power consumption. providing robustness against fading and Interest Group in 1998. The rest is history. Later in 1994, I attended an IEEE static interferers. The technology was publicly announced in conference in The Hague, the Netherlands, One of the challenges in the radio system May 1999 and the first specifications were that hosted symposia on both personal, was establishing a connection quickly. released in July 1999. In 2000, Ericsson indoor and mobile radio communications, For optimal robustness, the 80 MHz of launched its first Bluetooth product: and wireless computer networks, the first the 2.4 GHz band was divided into 79 a wireless voice headset. Interestingly, with focus on voice and the second on frequencies (matching the carrier plan of it came with an adaptor for the phone data. At the conference, I learned more the WLAN 802.11 FH variant). When not since the phones did not yet have about the use of the 2.4 GHz industrial, connected, the device is hopping around in Bluetooth embedded. ❐ scientific and medical (ISM) radio band the spectrum, scanning at a low duty cycle as a global spectrum for communications, for other devices that may want to connect. Jaap Haartsen and knew that this would be the way The other device does not know when the Jaap Haartsen Consultancy Company, Rolde, forward. Regulations, such as the US Federal first device will scan and at what frequency. the Netherlands. Communications Commission (FCC) Part 15, There is both an uncertainty in time and e-mail: [email protected] however, put restrictions on the use of the in frequency. How to solve this problem at ISM band, and, therefore, frequency hop low power consumption and low latency? Published online: 13 December 2018 (FH) spreading or direct-sequence (DS) The solution was to reduce the frequency https://doi.org/10.1038/s41928-018-0186-x

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