Modulacion Bluetootht

Chapter 3 BluetoothTM : Architecture and Functions

1.

Introduction

Bluetooth technology aims at allowing wireless short-range communications between several devices. Developed originally by Ericsson, Bluetooth undergoes an evolution of its specifications maintained and developed by the Special Lobby Special Interest Group (SIG) of Bluetooth and is accessorily standardized by the IEEEunder the reference IEEE 802.15.1. Today IEEE 802.15 subgroups and other forums such as the Wimedia Alliance are competing for the same field of operation. The governing idea behind Bluetooth consisted in specifying a wide scale integrated circuit to be deployed on a very large scale on various types of equipments with a very reduced energy consumption and thus announcing very low prices (Figure 3.1).1.1

SIG

In 1994, Ericsson Mobile Communications launched a feasibility study of lowcost low-consumption radio interface to be used between mobile telephones and their accessories. In February 1998, IBM, INTEL, Nokia and Toshiba joined the Swedish company and in May they created the SIG. It was widened by the arrival of 3Com, Agere (Lucent Technologies), Microsoft and Motorola during 2000and does not cease increasing thus gathering actors who cover several fields of expertise such as cellular telephony, portable computers, cars

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Wi-FiTM , BluetoothTM , ZigBeeTM and WiMAXTM

Fig. 3.1.

Bluetooth chip

and digital processing. Being an opened industrial specification, all the members of Bluetooth SIG can use it free in their products and services. Today, the SIGcounts more than 2500 manufacturers. It carries out a true fight to promote this world standard despite the large number of concurrent technologies essentially headed by Wi-Fi.

1.2

Bluetooth Does it Relate to Teeth by Any Sense?

Bluetooth comes from the name of a Viking: Harald Blätand (“Harald the blue tooth”) who succeeded the exploit of unifying within the same kingdom, Denmark andNorway, at the time where Europe was divided by religion quarrels and territories. The metaphor is beautiful: today Bluetooth carries out a true crusade of modern times to unify the whole of the manufacturers and their electronic instruments thanks to this new wireless standard. The icon is also based on the Bluetooth history because it is composed of two characters “H” and “B”: abbreviation for “HaraldBluetooth”. Bluetooth products have to go through a certification process to become the group products.

1.3

Applications

Mobile telephony is one of the first markets concerned by Bluetooth. Bluetooth chips are easily added in cellular equipments. Another type of application relates to the data-processing equipment such as mice, portable printers, PC, organizers, audio helmets, Hi-Fisystems, numerical cameras, remote banking payment and car applications. We call an application a profile. The profile gives details about protocols parameters and settings for device to be able to discover these applications and to communicate in a uniform way. Profiles are specified in the SIG.

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2. 2.1

Architecture and Throughputs ArchitectureBluetooth communication requires two preliminary things: first we have to know the devices in the neighbourhood (discovery) and second there must be a preestablished circuit. Communication is also based on a master–slave principle. A group of equipments forms a cell called piconet (see Figure 3.2). A piconet comprises a master and seven slaves at the maximum. Several piconets can overlap and form a“scatternet” (see Figure 3.3). In a piconet the communication is based on the master to harmonize the frequencies and channels. We know the neighbours through the discovery phase while in a scatternet there is a need to route data between masters and relay nodes. Scatternets in Bluetooth is not well developed. It has been improved by specific routing procedures in later standards such as ZigBee....