# Telemedicine: A Survey of Telecommunication Technologies, Developments, and Challenges
## 4 Evolution of Communications Technologies for Telemedicine
### Short Range Communication Technologies
#### 4.3.1 Bluetooth Low-Energy (BLE) Communication  
Bluetooth is one of the most popular wireless technologies, enabling connectivity with other compactible devices for effective communication. It operates at the 2.4 GHz frequency in the ISM Frequency band. It is a low-cost and low-power device that supports wireless voice and data transmission to devices at different data rates, reaching up to 2 Mbps (BLE 5.0) depending on the version (whether fixed or mobile within a 10 m range for Bluetooth and over 240 m for Bluetooth 5.0 [89; 90]). The communicating BLE devices are  
Figure 10: Classification of Communications Technologies used in Telemedicine.  
automatically set up in a network known as a piconet [65; 82; 89; 91; 92; 93; 94; 95; 96], where the maximum number of connected devices is eight; alternatively, a scatternet [65; 82; 94; 96] can be used for more than eight connected devices. Bluetooth 4.x and Bluetooth 5.0 use star-bus and mesh network topologies, and can support an unlimited number of nodes [97]. Different versions of Bluetooth are currently available for use based on application requirements. Table 2 shows basic technical information on different Bluetooth versions and other related wireless communication technologies. BLE has been applied in telemedicine and reported in several studies. For instance, in [98] it was used in an ECG monitoring system. BLE 4.0 was used along with Wi-Fi and an IOS mobile application to display the results on a mobile phone in a telemedicine application. The ECG signal collection module of the biosensor acquired the ECG signal from the patient, the BLE 4.0 transmits the data to the mobile app in the mobile phone, and the Wi-Fi embedded in the mobile phone transmitted the data to the provider database for use by an authorized physician. In [89; 99], the authors demonstrated the use of BLE in data transmission in a BAN. The work of [89] showed that BLE has a better energy consumption for data traffic in a BAN sensor compared to ZigBee.  
BLE continues to gain more acceptance in telemedicine applications. Among the reasons for this increasing acceptance are:  
Merits:  
1. Frequency hopping: BLE uses adaptive frequency hopping (AFH) as a technique for media access. This means that BLE devices are sensitive to other nearby wireless networks and continuously change their channels to mitigate or reduce interference. Data transmission is hardly ever interrupted, as Bluetooth devices can determine which channels are occupied and use the available channels in the hop sequence.
2. Number of nodes: Bluetooth devices can have unlimited active slave connections. Older versions of Bluetooth have a maximum of seven slave nodes, making for a maximum number of eight connections when the master is counted. As can be seen in Table 2, Bluetooth 4 and Bluetooth 5 can support unlimited nodes.
3. Cost efficiency [100]: BLE is optimised for devices that use small batteries due to the reduction of the number of channels from 79 channels ay 1 MHz to 40 at 2 MHz.
4. Low power consumption: BLE has been developed taking into consideration the minimisation of power requirements, especially when comparing newer Bluetooth versions to older ones.
5. BLE is easy to integrate into networks.
6. It has a relatively more secure connectivity than Wi-Fi connections.  
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Demerits:  
The major downsides of Bluetooth technology lies in older versions, and have been appreciably addressed in BLE and Bluetooth 5.0. Issues with past versions include:  
1. High power consumption;
2. Frequent connection or pairing loss;
3. Non-automatic support of network formation.  
Fortunately, these have been taken care of with the introduction of BLE.