• Radio Bluetooth is the lowest level in the Bluetooth specification. Specifies the requirements of the Bluetooth receiver / transmitter running at 2.4 GHz.
• Bandwidth and connection control allows physical connection between Bluetooth units. Baseband deals with the processing and timing of the transmission channel, while the connection controller handles the control of channel access. There are two types of physical connections: SCO – Synchronous Connection Oriented and ACL (Asynchronous ConnectionLess). An ACL connection transfers data packets while SCO supports real-time audio traffic.
• Audio is not a true level of protocol stack but is shown here because it is treated specifically in Bluetooth communication. Audio data is usually routed directly to (or from) the baseband level via an SCO connection. Of course if a data channel is used then the audio data will be transmitted via ACL connection (such as VoIP applications).
• Link Manager Protocol (LMP) is responsible for creating and configuring connections between Bluetooth devices as well as managing and negotiating baseband packages. LMP also manages security aspects such as authentication and encryption by generating, exchanging and controlling encryption keys for connections.
• HCI provides an interface with radio commands, baseband controller, and connection manager. It is the only standard interface for accessing Bluetooth capabilities, hardware status, etc.
• Logical Link Control and Adaptation Protocol (L2CAP) hides upper-level protocols from low-level protocol details.
• SDP provides a good tool for applications that want to consult services and service features. Unlike a LAN connection where someone connects to the network and then finds the devices, in a Bluetooth environment you have to first find the device and then the service. In addition in an environment where devices move the valuable service group can change. Consequently SDP is different from the service of finding services in a traditional network environment. The SDP is located at the top of the L2CAP.
• Serial ports are one of the most common communication interfaces used in programming for communicating devices. The RFCOMM protocol creates serial port emulation over L2CAP. RFCOMM enables transport capabilities for top-level services that use serial interfaces as a transport mechanism. Allows multiple simultaneous connections for one device.
• For Bluetooth devices to be able to create networks and exchange information they need a common data packing format. The BNEP Protocol (Bluetooth Network Encapsulation Protocol) encapsulates packets from other network protocols and packets are transported directly over L2CAP. BNEP is an optional protocol developed after the 1.1 specification of Bluetooth.
• Telephony Control Protocol Specification, Binary (TCS binary) serves to control voice and data calls.
• Adapted protocols such as OBEX and Internet Protocol (IP) are all built on one of the protocols discussed above.
• Bluetooth SIG has also released newer protocols based on the above protocols but mostly they are built on L2CAP. Examples of the newest protocols are Hardcopy Control Channel, Hardcopy Notification Channel, Audio / Video Control Transport Protocol and Audio / Video Distribution Transport Protocol.
Figure 5.20 Bluetooth protocol stack
5.10.3 Bluetooth Profiles
In addition to Bluetooth SIG protocols, it also defines Bluetooth profiles. A Bluetooth profile shows the standard ways of using protocols and their features that enable specific usage models. In other words it determines how different parts of the Bluetooth specification can be used in a particular case of use. A profile can be described as a vertical cut of the protocol stack. It defines the options to be selected from the protocols so that the profile works. Dependence of profiles on levels
protocol varion. Two profiles can use different sets of protocol levels and different sets of features within the same level. A Bluetooth device can support one or more profiles.
802.15 is an IEEE-driven specification to develop a consensual standard for networks with short and personal range. It has Bluetooth-like purposes and rises above its foundations. This specification aims to standardize MAC (Media Access Control) and Physical (OGY) levels in order to create wider compatibility with as many wireless devices as possible.802.15 also deals with the problems of coexistence and interaction between networks. This standard is interesting for both customers and manufacturers and the main reasons are:
• Co-existence with other technologies such as Bluetooth and 802.11,
• higher transfer speeds and
• lower power consumption.
5.11 Satellite Networks
Satellite technology is still in development. It is downlink technology by which mobile computers can only receive broadcast information sent by satellite. Communication is started by the mobile computer via a DIAL-UP modem or any other wireless technology. Hughes Network Systems set up the DirecPC network which uses the Galaxy satellite which sends information at 400 kbps speed. DirecPC transmits continuous flow of multimedia information to CNN broadcasts, sports as well as news from the financial world. In addition to this system, today there are other satellite systems such as Iridium, GlobalStar, etc. Satellite systems began to appear in the early 1990s. Their goal was to create a wireless network for the entire planet without the need for mobile phones to roaming between networks. By the time satellite services became available for commercial purposes many of their services were already provided by mobile communication systems and moreover satellite tariffs were many times higher than existing ones. However the history of satellite systems is not a story with a bitter end. These systems provide exclusive long-distance and undetectable service for global positioning systems as well as on-the-go communication. Satellite network terminals vary from mobile devices to satellite receivers. Data transfer speeds range from 2