One of the biggest advantages of IrDA from the point of view of manufacturers is its low cost. Infrared ports can be incorporated into a device at a cost of only $ 1, a very low cost compared to other WPAN standards.
Bluetooth is a wireless LAN technology designed to connect devices with various functions such as phones, notebooks, computers (desktop and laptop), cameras, printers, coffee machines and so on. A Bluetooth LAN is an ad-hoc network, which means that the network is formed spontaneously, devices often called Gadgets, find each other and form a network called piconets. A Bluetooth LAN can even be connected to the Internet if one of the Gadgets has this feature. A Bluetooth LAN, by nature, can’t be too big for you. If there are too many Gadgets trying to connect, there is chaos.
Bluetooth technology has several applications.
– Peripherals such as mouse or wireless keyboard can communicate with the computer through this technology.
– Monitoring devices can communicate with sensor devices in a small healthcare center.
– Home security devices can use this technology to connect various sensors to the central security controller.
Bluetooth was originally launched as a project by Sony Ericsson. She is named after Harald Blaatand, King of Denmark (940-981), who united Denmark and Norway. Blaatand translates to English Bluetooth. Today, Bluetooth technology is the implementation of a protocol set by the IEEE 802.15 standard. The standard defines a wireless network (Personal Area (PAN)), which operates in an area the size of a room or a hall.
When two or more devices connect to bluetooth they form a small ad hoc network (piconet) which consists of a maximum of eight devices. Any device in a piconet can communicate directly with other devices. It is also possible to create networks with more than eight devices. In this case, some pic components can be combined into a larger network (scatternet). In a scatternet configuration not all devices can see each other. Figure 5.16 helps to illustrate how this works. This figure shows a scatternet consisting of five picons. The mobile phone is part of one of the three piconettes and is capable of communicating directly with headphones, Bluetooth pencil and access point, but cannot communicate directly with portable computers, the printer or the fax machine.
Figure 5.16 Example of a five-picon scatternet
In a picon that can have up to eight stations, only one is called primary, while the rest are called secondary. All secondary stations synchronize their hours and dance sequence with the primary. So a piconet can only have one main station. Communication between primary and secondary can be one-to-one or one-to-many. Figure 5.17 shows a piconet.
Figure 5.17 Piconet
A secondary station in one piconet may be primary in another piconet. This Station can receive messages from the primary to the first piconet (as a secondary) and, acting as a primary, sends them to the secondary to the second piconet. A Station can be a member of two piconets.
Figure 5.18 shows a scatternet.
Figure 5.18 Scatternet
5.10.1 Stack / Stack Architecture Architecture for Bluetooth Communication
Bluetooth communication as well as many other communication technologies is based on receiving and sending packets. Consequently there is a protocol stack (Bluetooth protocol stack) which is divided into two basic components: Bluetooth host and Bluetooth controller. HCI (Host Controller Interface) creates a standardized interface between Host and Controller.
Figure 5.20 illustrates the Bluetooth host and the classification of Bluetooth devices.
The Bluetooth host is known as the top of the stack and is usually implemented in software. It is generally integrated into the system software or the host utilization system. Bluetooth profiles rise to the top of protocols. They are generally software and run on the host hardware device. While the Bluetooth radio module or controller is usually a hardware module in the form of a PC card which is placed on the postal device. Bluetooth controllers are placed embedded ready in the device. The top of the stack is represented by the Bluetooth radio module via HCI. The Bluetooth radio module is integrated with the postal system via the standard I / O, USB or UART mechanism. Although we classified devices into Bluetooth hosts and Bluetooth controllers, some devices integrate both and do not use HCI such as headphones. The other blocks shown in Figure 5.19 are part of the Bluetooth protocol stack that will be further addressed.
Figure 5.19 Bluetooth protocol stack architecture
5.10.2 Bluetooth Protocol
Figure 5.20 shows a diagram of the Bluetooth protocol stack. In the Bluetooth specification some protocols are defined but the Figure shows the most common. Gray rectangles show protocols that are addressed to Java APIs for Bluetooth wireless technologies (JABWT API). Protocol Stiva / Stack consists of specific protocols for Bluetooth wireless technology (such as Service Discovery Protocol (SDP)) and other adaptive protocols (such as Object Exchange protocol OBEXTM).