The Bluetooth specification defines a communication channel of maximum 720 kb / s (1 Mbps of raw capacity) with optimal range of 10 meters (optionally 100 m with repeaters).
The radio frequency with which he works is in the range of 2.4 to 2.48 GHz with wide spectrum and frequency hopping with possibility of transmitting in full duplex with up to 1600 hops / s. Breaks frequently occur among a total of 79 frequencies at intervals of 1 Mhz, that allows for security and robustness.
The output power to transmit at a maximum distance of 10 meters is 0 dBm (1 mW), while long-range version passed between 20 and 30 dBm (100 mW and 1 W).
To achieve the goal of low power, low cost, they devised a solution that can be implemented on a single chip using CMOS circuits. Thus, it succeeded in creating a solution of 9x9 mm and consumes approximately 97% less energy than a regular cell phone.
The baseband protocol (single channel per line) combines circuit and packet switching. To ensure that the packets arrive out of order, the slots can be reserved for synchronous packets, a jump signal is used differently for each package. On the other hand, circuit switching can be asynchronous or synchronous. Three synchronous data channels (voice), or a data channel synchronous and one asynchronous, can be supported in a single channel. Each voice channel can support a transfer rate of 64 kb / s in each direction, which is adequate enough for voice transmission. An asynchronous channel can transmit at most 721 kb / s in one direction and 56 kb / s in the opposite direction, however, for an asynchronous connection can withstand 432.6 kb / s in both directions if the link is symmetric.
Hardware Architecture
The hardware that makes up the Bluetooth device is composed of two parts:
- A radio device, responsible for modulating and transmitting the signal
- A digital controller composed of a CPU, digital signal processor (DSP - Digital Signal Processor) called Link Controller (or Controller Link) and interfaces with the host device
The LC or Link Controller is responsible to the baseband processing and management of ARQ protocols and physical layer FEC. Furthermore, is responsible for the transfer functions (both asynchronous and synchronous), Audio coding and data encryption.
The CPU of the device is responsible for addressing the related instructions Bluetooth host device, to simplify their operation. For this, the CPU runs a software program called Link Manager that has the function to communicate with other devices through the PML protocol.
Among the tasks performed by the LC and the Link Manager include: - Sending and receiving data. - Empaginamiento and Petitions. - Identification of Connections. - Authentication. - Negotiating and determining types of bonds. - Determining the kind of body of each package1. - Location of the device in sniff mode or hold.
Bluetooth vs. Wi-Fi
Bluetooth and Wi-Fi cover different needs current home environments: from the creation of networks and print work to transfer files between PDAs and PCs. Both technologies operate in the unregulated frequency bands.
Bluetooth
Bluetooth is mainly used in many products such as telephones, printers, modems and headsets. Its use is appropriate when there may be two or more devices in a small area without large bandwidth needs. Its most common use is built into phones and PDA's, or through a Bluetooth headset or transferring files.
Bluetooth has the advantage of simplifying the discovery and configuration of devices, as these can indicate to other services offered, resulting in the accessibility of them without explicit control of network addresses, permissions and other typical aspects of traditional networks.
