Bluetooth Piconet Channel

Bluetooth Piconet Channel A piconet is formed, communication between the master slave and slave modes can started. A piconet channel is divided into 625 microseconds intervals, these called slots. Every slot has used different hop frequency. Every channel is shared between the master and the slave modes using a frequency hop / time division-duplex scheme. If two slaves need to communicate peer to peer, they can either form a separate at the piconet layer. At the 1 Mbps link speed, a 625 microseconds slot time is equivalent to the transition time of 625 bits. A single slot packet size in Bluetooth is only 366 bits. This requires enough good time to let the frequency synthesizers hop to the next channel frequency hop to the next channel frequency and stabilize. These are the following to link: Synchronous link: To transmit real-time voice, an application must require a slot in both directions at regular intervals. This is called a synchronous link. This link transfers the voice like telephone grade. Asynchronous link: Data communication between a master-slave pair involves a different set of considerations. Like the data payload must be protected by cyclic redundancy check (CRC), so that the receiver can determine whether the required bits are in error. A data path between master-slave pair meeting all of these requirements is called an asynchronous data link. These are following two advantages. 1. The master cell can ensure that the slave transmission do not collision. 2. The slots can be allocated to satisfy the quality of service (Qos) requirement of each asynchronous link. The base band specification does not mandate the use of any specific slot allocation scheme. Chip vendors can choose any policy that fits their target application. Lower part of stack, L2CAP can be viewed as the data plane of Bluetooth's link layer. Logical Link Control and Adaption Protocol L2CAP can be viewed as the data plane of the Bluetooth link layer. Because the base band packet size is too small for transporting higher layer packets, a thin layer is needed for exporting a bigger packet size to the higher layer. L2CAP layer which is highly optimized to work in conjuction with the base band layer. L2CAP does not support integrity checks because the base band packets are already CRC protected. The multiprocessing and de-multiprocessing of higher layer protocols is supported using channels. Multiple times of which can be created between any two L2CAP end points. L2CAP layer have established connection oriented in the string. The L2CAP specification also defines a connectionless channel for supporting broadcast and multicast group communication. Service Discovery Protocol (SDP) Both ends of a Bluetooth link must support compatible set of protocols and applications to successfully interchange data. Configuration settings cannot be chosen statically, since some parameters may require adjustment to match the features and services supported by the pair Bluetooth device. SDP based on the client server technology. The server maintains a list of services records, which describe the characteristics of services hosted at the server. A client can browse all available service records maintained at the server or retrieves specific attribute values from a service record. The Bluetooth SDP has two advantages. 1. The majority of complaint Bluetooth devices will be non IP devices. It’s to support IP only for the sake of supporting SLP would be costly. 2. SDP is optimized to run over L2CAP. Its limited search capabilities and non-text based attribute ID and attribute value descriptions land an efficient and small footprint implementation for small devices. Link Manager Protocol A device can establish the L2CAP channel, the link manager must carry out a number of baseband - specific actions. These function belong to the control plane of the Bluetooth link layer and require the link manager to exchange LMP messages over the air link. Example. The peer link controller can be instructed to switch to low-power mode, adjust its power level, increase the packet size, and change the requested QoS on an ACL.