A Wireless LAN technologies IEEE 802.11 Bluetooth A Wireless LAN technologies IEEE 802.11

Bluetooth technology discussed here aims at so-called ad-hoc piconets. Establishes a local area network with limited coverage and with no common infrastructure. The distance covered by Bluetooth will be about 10 meters. Swedish IT-company Ericsson initiated some studies in 1994 which was so-called multi-communicator link, and was later named as Bluetooth in the year 1998. These five companies Ericsson, Intel, IBM, Nokia and Toshiba were the first to use this technology. Introduction

Bridging of networks:

Architecture: Networking Bluetooth operates on 79 channels in the 2.4 GHz band with 1 MHz carrier spacing. Each device performs frequency hopping with 1,600 hops/s in a pseudo random fashion. A very important term in the context of Bluetooth is a piconet. Architecture:

Piconet

Piconet Master sends device ID and a clock to all the other devices. The hopping pattern is determined by the device ID, a 48- bit worldwide unique identifier. All active devices are assigned a 3-bit active member address (AMA). All parked devices use an 8-bit parked member address (PMA). As more users join the piconet, the throughput per user drops quickly This idea of forming groups of piconets called scatternet. Piconet

Piconet

Protocol stack

The core protocols of Bluetooth comprise the following elements Radio: Specification of the air interface, i.e., frequencies, modulation, and transmit power Baseband: Description of basic connection establishment, packet formats and timing. Link manager protocol: Link set-up and management between devices including security functions and parameter negotiation. Logical link control and adaptation protocol (L2CAP): Adaptation of higher layers to the baseband. Service discovery protocol: Device discovery in close proximity plus querying of service characteristics. The core protocols of Bluetooth comprise the following elements

Protocol stack (OBEX) RFCOMM is a cable replacement protocol. It replaces of serial line cables and enables many other applications and protocols to run over Bluetooth. Telephony control protocol specification – binary (TCS BIN) Voice and data calls between Bluetooth devices. The host controller interface (HCI). command interface to the baseband controller and link manager, and access to the hardware status and control registers. (OBEX) Calendar and business card objects (vCalendar/vCard) can be exchanged using the object exchange protocol as common with IrDA interfaces. Protocol stack

The radio specification deals with the carrier frequencies and output power. Bluetooth uses the license-free frequency band at 2.4 GHz allowing for worldwide operation with some minor adaptations to national restrictions. Frequency will be 1,600 hops per second. The time between two hops is called a slot, which is an interval of 625 μs. Radio layer

Bluetooth transceivers use Gaussian FSK for modulation and are available in three classes: Power class 1: Maximum power is 100 mW and minimum is 1 mW (typ. 100 m range without obstacles). Power control is mandatory. Power class 2: Maximum power is 2.5 mW, nominal power is 1 mW, and minimum power is 0.25 mW (typ. 10 m range without obstacles). Power control is optional. ● Power class 3: Maximum power is 1 mW. Radio layer

Performs frequency hopping for interference mitigation and medium access and also defines physical links and many packet formats. Baseband layer

Bluetooth packet at baseband layer

Bluetooth packet at baseband layer Access code: This first field of a packet is needed for timing synchronization and piconet identification. The access code consists of a 4bit preamble, a 64 bit synchronization field, and a 4 bit trailer. Bluetooth packet at baseband layer

The packet header decides the address, packet type, flow and error control, and checksum.

Physical links Synchronous connection-oriented link Bluetooth offers two different types of links. Synchronous connection-oriented link Asynchronous connectionless link: Physical links

Synchronous connection-oriented link (SCO): For this type of link, the master reserves two consecutive slots (forward and return slots) at fixed intervals. A master can support up to three simultaneous SCO links to the same slave or to different slaves. This link is used to carry voice. Forward error correction schema is used in these type of links. Synchronous connection-oriented link (SCO):

SCO packet diagram

Asynchronous connectionless link (ACL): For typical data application like symmetrical or asymmetrical data transfer, point-to-multipoint transfer we use ACL. Here the master uses poling schema for selecting the slaves. The packet pattern can be 1-slot, 3-slot or 5-slot. FEC will be used in noisy environment. There are 2 types of ACL packets DM(data medium) and DH(data high) Asynchronous connectionless link (ACL):

ACL packet format

It manages various aspects between radio link between master and a slave. The functions covered by this layer are Authentication, paring and encryption. Synchronization. Capability negotiation. Quality of service negotiation. Power control. Link supervision. State and transmission mode change. Link manager protocol

Logical link control adaptation protocol It installs logical links between the connected Bluetooth devices. The logical channels will be Connectionless Connection-oriented Signaling These logical channels will be identified by using Channel Identifier (CID). CID value 1 is signaling CID value 2 is connectionless CID unique value (>=64) is Connection-oriented. Logical link control adaptation protocol

Service directory protocol (SDP)

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