![]() A slave can have three sco links with the master and can send data at 64 Kbps.Damaged packet are not retransmitted over sco links.In an sco link, a physical link is created between the master and slave by reserving specific slots at regular intervals.It is used where fast delivery is preferred over accurate delivery. sco is used for real time data such as sound.The ACL can achieve a maximum data rate of 721 kbps by using one, three or more slots.Thus ACL link is used where correct delivery is preferred over fast delivery.A slave can have only one ACL link to its master.Frames can be lost & may have to be retransmitted. ACL delivers traffic on a best effort basis.It is used for packet switched data that is available at irregular intervals.In Baseband layer, two types of links can be created between a master and slave.The slave sends in the next odd-numbered slot if the packet in the previous slot was addressed to it. If piconet has more than one slave, the master uses even numbered slots.In slot 0, master sends & secondary receives in slot 1, secondary sends and primary receives. Both master and slave communicate in half duplex mode. If the piconet has only no slave the master uses even numbered slots (0, 2, 4, …) and the slave uses odd-numbered slots (1, 3, 5, ….In TDD- TDMA, communication is half duplex in which receiver can send and receive data but not at the same time.The master in each piconet defines the time slot of 625 µsec.Master and slave stations communicate with each other using time slots.Bluetooth uses a form of TDMA called TDD-TDMA (time division duplex TDMA).Baseband layer is equivalent to the MAC sublayer in LANs.In order to change bits into a signal, it uses a version of FSK called GFSK i.e. FSK with Gaussian bandwidth filtering.Bluetooth hops 1600 times per second, i.e. each device changes its modulation frequency 1600 times per second.Bluetooth uses the Frequency Hopping Spread Spectrum (FHSS) method in the physical layer to avoid interference from other devices or networks. This band is divided into 79 channels of 1MHz each.It is a low power system that uses 2.4 GHz ISM band in a range of 10 meters.The radio layer moves data from master to slave or vice versa.It deals with ratio transmission and modulation.The Bluetooth radio layer corresponds to the physical layer of OSI model.The different layers and Bluetooth Protocol architecture. ![]() The layer structure of Bluetooth does not follow OSI model, TCP/IP model or any other known model.Bluetooth standard has many protocols that are organized into different layers. ![]()
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