# Telemedicine: A Survey of Telecommunication Technologies, Developments, and Challenges
## 4 Evolution of Communications Technologies for Telemedicine
### Long-Range Communications
#### 4.4.1 Satellite Communication in Telemedicine  
One of the most effective communication technologies in telemedicine is satellite communication. Satellite communication provides Broadcast Satellite Services (BSS), Fixed Satellite Services (FSS), and other telecommunication services, as well as Global Positioning System (GPS) services. It has the major advantage of world-wide reach. A useful benefit derived from satellite communication in telemedicine is access to broadband services in areas where other telecommunication services are inadequate or outright unavailable [87]. Satellite-based communication involves the transmission and reception of radio waves between a satellite launched into orbit and a base station on the ground. Geostationary Earth Orbit (GEO) satellites have near-global coverage, broadcast/multicast capability, and great capacity for use in telemedicine, especially in the rural areas where terrestrial communications are unavailable. However, this has a trade-off in terms of high end-to-endlatency, between 1700 ms to 3000 ms for GEO satellites [109]. Communication from the base station uses an uplink frequency; the radio waves are transmitted to the transponder of the satellite, and communication occurs via uplink/downlink frequencies. Table 3 shows the uplink and downlink frequency bands for satellite communication. Each satellite frequency band has several transponders used for different applications.  
Very Small Aperture Terminal (VSAT)  
VSAT is a form of an earth station often used to communicate with satellites. In [2], a wireless internet protocol was used to transmit data through a VSAT satellite system in a store-and-forward telemedicine system. C-band satellite communication was used for both audio and video data transmission. Other bands that can be used include the Ku-band and Ka-band satellite communication frequencies. The uplink/downlink frequencies of a number of satellite frequency bands are summarized in Table 3.  
In [29], the Chinese military used satellite channels to establish telemedicine communication between two hospitals in different locations. In a similar article [38], the authors highlighted satellite communication equipment housed in a van, with two-way online data transfer used to transmit scanned patient information to specialist doctors for telemedical services.  
The Thuraya satellite phone has been successfully utilised to break the communication barrier in certain unusual scenarios in which communication is otherwise impossible. The Thuraya phone is designed with the functionality of transmitting and receiving directly from a satellite. The phone has been made to integrate with terrestrial communication using a dual-SIM Thura phone. The first dual-SIM dual-mode Thuraya was the Thuraya XT-PRO DUAL, which used a satellite SIM card and a GSM SIM card to exploit communication services based on both technologies. Thuraya phones have been used in telemedicine systems, as reported in [109]; Figure 11 illustrates the use of the Thuraya phone for telemedicine.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Frequency Band** & **Uplink Frequency (GHz)** & **Downlink Frequency (GHz)** & **Services** & **Example** \\ \hline C-Band & 5.925–6.425 & 3.700–4.200 & FSS & Palapa-B Indonesia has 20 C-Band transponders \\ Ku-Band (Telecom) & 14.00–14.80 & 12.20–12.75 & FSS, BSS and Telecom & Superbird-6 satellite has 23 Ku-Band transponders \\ Ka-Band & 27.00–31.00 & 17.00–21.00 & FSS and BSS & Superbird-6 satellite has 6 Ka-Band transponders \\ \hline \hline \end{tabular}
\end{table}
Table 3: Satellite Band Uplink and Downlink Frequencies.