## 6 Other Technologies
### Bluetooth Low Energy Technology  
The developing process of this ultra-low-power Bluetooth technology is started within the FP6 funded project MIMOSA. The technology was released to public in October 2006 with the name \"Wibree\". Basically it is the simplified version of Bluetooth. It uses the same physical layer in 2.4 GHz ISM used by Bluetooth for interoperation with existing Bluetooth devices and allows 1 Mbit/s data rates in up to 10 meters range. Bluetooth low energy is designed to be very efficient at transmitting very small quantities of data at very low latencies to other devices. When compared to classic Bluetooth technology it is maximum 15 times more efficient. It achieves these efficiency gains by optimizing three basic areas of functionality: connectable and discoverable modes, the number of packets transmitted during connections, and the size of each individual packet.  
In classic Bluetooth technology, for a device to be connectable or discoverable it must enable its receiver. Therefore, the only way to be responsive is to have the radio active for a significant period of time. A basic requirement for two frequency hopping devices to communicate is that they need to use the same frequency or channel at the same time, i.e., they need to be synchronized. When the devices first start communicating, they are not synchronized, and they need to search different channels to find each other. In Bluetooth technology, 32 channels are used. Searching through that many channels takes time, and in Bluetooth technology it can take up to a couple of seconds for two devices to find each other, which consumes power. In Bluetooth low energy technology, instead, there are only three channels used for advertising. This brings Bluetooth low energy to be over 17 times more efficient than classic Bluetooth.  
There are two other major differences between the two version of the standard: Bluetooth low energy uses fewer channels, and the hop sequence used by the radios is different. There are two reasons why there are fewer channels: Bluetooth low energy uses a larger modulation index, meaning that its signal takes up more bandwidth, and has relaxed requirements for how steep the channel filters need to be. Because of this, Bluetooth low energy channels are spaced 2 MHz apart, rather than 1 MHz apart as in Bluetooth technology. Both of these design choices were made in order to provide a lower power consumption.  
Another important improvement of the low energy version, is that when a slave device does not have any data to transmit, it does not even have to bother listening to the master device's communication event packets. This enables the slave device to stay in the lowest possible power mode for as long as possible, further saving significant amounts of power. However, if it does have something important to transmit, then it can wake up at the next appropriate communication event and transmit its data very quickly. This enables an excellent compromise between ultra low power operation and low latency transmission of data.  
Regarding the network topology, instead, unlike Zigbee, 6 LowPAN, and Z-Wave, it does not support mesh networking.  
Development of the technology is currently under way. Texas Instruments and Nordic Semiconductor are developing compatible devices but transceivers are not on market yet.