Bluetooth Technology

写在前面

大三上学期，2021年末，我们要做计算智能课程设计，但我所在的那个实验室没有校园网。虽说没有网络也能跑实验，但在出现bug要上网找解决方案的时候就很麻烦。我试着用手机热点给电脑提供网络，很可惜，我的电脑前段时间因为代理软件的原因，网络被重置，有的驱动和服务我还没调配，只能连校园网，却连不上手机热点。我看iPhone提示还能通过bluetooth上网，于是我尝试了这个方法，果然奏效了。在电脑连上网络的那一刻，我十分兴奋，同时也十分好奇。身为工科生，探索未知本身就是一件极具吸引力的事情，况且我还是大数据专业，与计算机和通信有着千丝万缕的联系，本着求知本能，我开始探索bluetooth的原理。

Bluetooth Introduction

Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances using UHF radio waves in the ISM bands, from 2.402 GHz to 2.48 GHz, and building personal area networks (PANs).[3] It was originally conceived as a wireless alternative to RS-232 data cables. It is mainly used as an alternative to wire connections, to exchange files between nearby portable devices and connect cell phones and music players with wireless headphones. In the most widely used mode, transmission power is limited to 2.5 milliwatts, giving it a very short range of up to 10 meters (30 feet).

History

The development of the “short-link” radio technology, later named Bluetooth, was initiated in 1989 by Nils Rydbeck, CTO at Ericsson Mobile in Lund, Sweden. The purpose was to develop wireless headsets, according to two inventions by Johan Ullman, SE 8902098-6, issued 1989-06-12 and SE 9202239, issued 1992-07-24. Nils Rydbeck tasked Tord Wingren with specifying and Dutchman Jaap Haartsen and Sven Mattisson with developing.[16] Both were working for Ericsson in Lund.[17] Principal design and development began in 1994 and by 1997 the team had a workable solution.[18] From 1997 Örjan Johansson became the project leader and propelled the technology and standardization.[19][20][21][22]

In 1997, Adalio Sanchez, then head of IBM ThinkPad product R&D, approached Nils Rydbeck about collaborating on integrating a mobile phone into a ThinkPad notebook. The two assigned engineers from Ericsson and IBM to study the idea. The conclusion was that power consumption on cellphone technology at that time was too high to allow viable integration into a notebook and still achieve adequate battery life. Instead, the two companies agreed to integrate Ericsson’s short-link technology on both a ThinkPad notebook and an Ericsson phone to accomplish the goal. Since neither IBM ThinkPad notebooks nor Ericsson phones were the market share leaders in their respective markets at that time, Adalio Sanchez and Nils Rydbeck agreed to make the short-link technology an open industry standard to permit each player maximum market access. Ericsson contributed the short-link radio technology, and IBM contributed patents around the logical layer. Adalio Sanchez of IBM then recruited Stephen Nachtsheim of Intel to join and then Intel also recruited Toshiba and Nokia. In May 1998, the Bluetooth SIG was launched with IBM and Ericsson as the founding signatories and a total of five members: Ericsson, Intel, Nokia, Toshiba and IBM.

The first consumer Bluetooth device was launched in 1999. It was a hands-free mobile headset that earned the “Best of show Technology Award” at COMDEX. The first Bluetooth mobile phone was the Ericsson T36 but it was the revised T39 model that actually made it to store shelves in 2001. In parallel, IBM introduced the IBM ThinkPad A30 in October 2001 which was the first notebook with integrated Bluetooth.

Bluetooth’s early incorporation into consumer electronics products continued at Vosi Technologies in Costa Mesa, California, USA, initially overseen by founding members Bejan Amini and Tom Davidson. Vosi Technologies had been created by real estate developer Ivano Stegmenga, with United States Patent 608507, for communication between a cellular phone and a vehicle’s audio system. At the time, Sony/Ericsson had only a minor market share in the cellular phone market, which was dominated in the US by Nokia and Motorola. Due to ongoing negotiations for an intended licensing agreement with Motorola beginning in the late 1990s, Vosi could not publicly disclose the intention, integration and initial development of other enabled devices which were to be the first “Smart Home” internet connected devices.

Vosi needed a means for the system to communicate without a wired connection from the vehicle to the other devices in the network. Bluetooth was chosen, since WiFi was not yet readily available or supported in the public market. Vosi had begun to develop the Vosi Cello integrated vehicular system and some other internet connected devices, one of which was intended to be a table-top device named the Vosi Symphony, networked with Bluetooth. Through the negotiations with Motorola, Vosi introduced and disclosed its intent to integrate Bluetooth in its devices. In the early 2000s a legal battle ensued between Vosi and Motorola, which indefinitely suspended release of the devices. Later, Motorola implemented it in their devices which initiated the significant propagation of Bluetooth in the public market due to its large market share at the time.

Communication and connection

A master BR/EDR Bluetooth device can communicate with a maximum of seven devices in a piconet (an ad hoc computer network using Bluetooth technology), though not all devices reach this maximum. The devices can switch roles, by agreement, and the slave can become the master (for example, a headset initiating a connection to a phone necessarily begins as master—as an initiator of the connection—but may subsequently operate as the slave).

The Bluetooth Core Specification provides for the connection of two or more piconets to form a scatternet, in which certain devices simultaneously play the master role in one piconet and the slave role in another.

At any given time, data can be transferred between the master and one other device (except for the little-used broadcast mode). The master chooses which slave device to address; typically, it switches rapidly from one device to another in a round-robin fashion. Since it is the master that chooses which slave to address, whereas a slave is (in theory) supposed to listen in each receive slot, being a master is a lighter burden than being a slave. Being a master of seven slaves is possible; being a slave of more than one master is possible. The specification is vague as to required behavior in scatternets.[25]