Bluetooth Core Specification V4.0

Bluetooth Core System

官方文档

The Bluetooth Core system consists of a Host, a Primary Controller and zero or more Secondary Controllers.

1. A Host is a logical entity defined as all of the layers below the non-core profiles and above the Host Controller Interface (HCI).
   L2CAP,SDP and GAP blocks comprise a BR/EDR Host. L2CAP,GAP ,SMP,Ad ATT,GATT blocks comprise an LE Host.
   
2. A Controller is a logical entity defined as all of the layers below HCI.
   Two types of Controllers are defined in this version of the Core Specification: Primary Controllers and Secondary Controllers.
   Primary Controller:
   • BR/EDR Controller including the Radio, Baseband, Link Manager and optionally HCI.
   • an LE Controller including the LE PHY, Link Layer and optionally HCI.
   • a combined BR/EDR Controller portion and LE controller portion into a single Controller. 
   Secondary Controller:
   Alternate MAC/PHYs (AMP) are secondary Controllers in the Bluetooth core system. 

   AMP 是Bluetooth 3.0的核心。这是一种全新的交替射频技术，允许蓝牙协议栈针对任一任务动态地选择正确射频。蓝牙3.0的传输速度更高，而秘密就在802.11无线协议上。通过集成"802.11 PAL"(协议适应层)，蓝牙3.0的数据传输率提高到了大约24Mbps.AMP修改了标准蓝牙核心架构以便在L2CAP层下使用多重交替广播，同时使用标准蓝牙射频(标注基本码率(BR)和扩展码率(EDR)分别为1 Mbps和3 Mbps)实现复原和连接以及匹配。

   其通俗一点的原理是允许消费类设备使用已有的蓝牙技术，同时通过使用第二种无线技术来实现更快的吞吐量。蓝牙模块仅仅是用来创建两台设备之间配对，数据传输本身是通过Wi-Fi射频来完成.
   The BR/EDR radio, the primary radio, is used to perform discovery, association, connection establishment, and connection maintenance. Once an L2CAP connection has been established between two devices over the BR/EDR radio, the AMP Managers can discover the AMPs that are available on the other device. When an AMP is common between the two devices, the Core system provides mechanisms for moving data traffic from BR/EDR Controller to an AMP Controller.
   

   L2CAP channels may be created on, or moved to, an AMP. L2CAP channels may also be moved back to the BR/EDR radio when those capabilities are not necessary or when the AMP physical link has a link supervision timeout. 

Bluetooth Core System Architecture

• Channel Manager
  The channel manager is responsible for creating, managing and closing L2CAP channels for the transport of service protocols and application data streams.
  The channel manager interacts with its local link manager or an AMP PAL to create new logical links (if necessary) and to configure these links
  
• L2CAP Resource Manager
  The L2CAP resource manager block is responsible for managing the ordering of submission of PDU fragments to the baseband and some relative scheduling between channels to ensure that L2CAP channels with QoS commitments are not denied access to the physical channel due to Controller resource exhaustion. 
  
• Security Manager Protocol
  This block is only used in LE systems. Similar functionality in the BR/EDR system is contained in the Link Manager block in the Controller.
  
• Attribute Protocol
  The ATT client communicates with an ATT server on a remote device over a dedicated fixed L2CAP channel. 
  
• Generic Attribute Profile(GATT)
  
• Generic Access Profile
  The Generic Access Profile (GAP) block represents the base functionality common to all Bluetooth devices such as modes and access procedures used by the transports, protocols and application profiles. GAP services include device discovery, connection modes, security, authentication, association models and service discovery.
  
• Device Manager
  The device manager is the functional block in the baseband that controls the general behavior of the Bluetooth device. It is responsible for all operations of the Bluetooth system that are not directly related to data transport, such as inquiring for the presence of nearby Bluetooth devices, connecting to Bluetooth devices, or making the local Bluetooth device discoverable or connectable by other devices.
  
• Link Manager
  The link manager is responsible for the creation, modification and release of logical links (and, if required, their associated logical transports), as well as the update of parameters related to physical links between devices. 
  The link manager achieves this by communicating with the link manager in remote Bluetooth devices using the Link Management Protocol (LMP) in BR/EDR and the Link Layer Protocol (LL) in LE.
  
• Link Controller
  The link controller is responsible for the encoding and decoding of Bluetooth packets from the data payload and parameters related to the physical channel, logical transport and logical link.

Data Transport Architecture:

• Physical Channel:The physical channel is sub-divided into time units known as slots. Data is transmitted between Bluetooth devices in packets that are positioned in these slots. 
• Physical Link:Within a physical channel, a physical link is formed between a master device and slave devices. The physical link provides bidirectional packet transport between the master and slave devices. Since a physical channel could include multiple slave devices, there are restrictions on which devices may form a physical link. There is a physical link between each slave and the master.
• Logcail Link:The physical link is used as a transport for one or more logical links. Traffic on logical links is multiplexed onto the physical link by occupying slots assigned by a scheduling function in the resource manager.
• Logical Transport:
A control protocol for the baseband and physical layers is carried over logical links in addition to user data. This is the link manager protocol (LMP).
Devices that are active in a piconet have a default asynchronous connection-oriented logical transport that is used to transport the LMP protocol signaling. 
The Link Manager function uses LMP to control the operation of devices in the piconet and provide services to manage the lower architectural layers (radio layer and baseband layer). 
• L2CAP: L2CAP layer provides a channel-based abstraction to applications and services. It carries out segmentation and reassembly of application data and multiplexing and de-multiplexing of multiple channels over a shared logical link.

Bluetooth transport architecture entities