Master and slave operation Essay Example for Free

Master and striver operation EssayBluetooth devices exist in small ad-hoc network configuration with the ability to operate as either skipper or the slave the specification also allows a mechanism for master and slave to switch their roles. The configurations lot be undivided point, which is the simplest configuration with one master and one slave. Multipoint, called a Piconet, based on up to 7 slaves gather around a private Master. And a third type called a Scatternet, this is a group of Piconets in effect hubbed via a single Bluetooth device acting as a master in one Piconet and a slave in the other Piconet. The Scatternet permits either larger coverage areas or number of devices than a single Piconet can offer. Figure 5 outlines the different master and slave topologies permitted for networks in the standard (see Bluetooth Goodbye infrared radiation). The role of the master is to simpleness the available bandwidth between the slaves, it calculates and allocates how ofte n to communicate with each slave and locks them into the subdue frequency hopping sequence.The specification describes an algorithm that calculates the hop sequence, the seed being based on the masters device address and clock. In addition to hop sequence control, the master is responsible for transmit control by dividing the network into a series of date slots amongst the net members, as assort of a fourth dimension Division Multiplexing (TDM) scheme. These time slots can consist of data and potentially additional illustration job i. e. you leave alone always need a data channel before you can add a voice channel.The time slot is defined as 625 s and all packet traffic is allocated 1, 3 or 5 slots, grouped together in transmit and receive pairs. Prior to connection some trading operations such as inquiry, paging and scanning operations may sometimes occur on one-half slots (see Bluetooth Goodbye infrared radiation). Figure 5 Point to point, Piconet and Scatternet. A. 2. 3 Voice and Data Links. Bluetooth carries communication traffic over two types of air interface links defined as Asynchronous ConnectionLess (ACL) or parallel Connection Oriented (SCO).During a connection the links carry voice and data traffic in the time slots and are categorised as either time censorious, as used for voice and audio, or high speed non-time critical data with a mechanism for acknowledgement and re-transmission. The first link ceremonious between master and slave is the ACL link and carries high speed data that is insensitive to time. It is packet switched, as the data is sporadic in nature, asynchronous, contains asymmetric and symmetric services and uses a polling access scheme.A master may be permitted to have a number of ACL links up to the maximum number of slaves permitted by the specification but only one link is allowed between any two devices (see Bluetooth Goodbye Infrared). Once an ACL has been established a SCO link can be created on top of the ACL link . The SCO link is spell switched it has symmetric synchronous services and has slot reservation at fixed intervals, making it suitable for time critical data such as voice. The specification restricts the number of SCO links that a master can support to three.Summarising the two types of links ACL ? Packet constructed of a 72 bit access code, a 54 bit packet header, a 16 bit CRC and Payload data ? Largest data packet is DH5 giving 723. 2 Kb/s as highest data rate in one direction. ? Non time critical data ? Asynchronous ? Packet switched ? Polling access SCO ? Same access code and header as ACL packets ? ARQ (Automatic take on reQuest) and SEQ (SEQuence) flags redundant since flow control and re-transmissions do not apply ? Cyclic Redundancy Code (CRC) vault of heaven is absent?Payload fixed at 30 bytes, with source data of 10, 20 or 30 bytes ? Circuit switched ? Symmetric synchronous services ? Slot reservation at fixed intervals A supererogatory case exists that mixes SCO and ACL packets. Known as the Data Voice (DV) packet it carries data and voice on steadfast intervals like the SCO. The voice data has no flow control or CRC as per SCO packets, whereas the data part of the DV packet has flow control, re-transmission of the data part is permitted and the data part is CRC protected (see Bluetooth Goodbye Infrared).