The current mobile cloud computing research uses a variety of connection protocols for communication including WiFi, Bluetooth, and 3G, though the majority has employed WiFi for many reasons.
WiFi. WiFi (wireless Ethernet 802.11b) and Bluetooth both operate in the unlicensed 2.4 GHz ISM band. WiFi was initially intended as replacement for cabling for resource and peripheral sharing (such as printers, shared storage devices) among PCs, terminals etc. for wireless local area networks (WLANs). WiFi has a longer range, with a radius within 100 m and supporting up to 11 Mbps data rates.
Bluetooth. Bluetooth on the other hand, was intended for nonresident equipment and applications such as wireless headsets etc wireless personal area network (WPAN), and is characterized by its low power requirements and low-cost transceiver chips [65]. The range for Bluetooth is typically in a radius of 10 m, depending on the device class, power, and physical obstacles in the environment. However, according to Bluetooth specifications, future versions will be faster up to 24 Mbps and consume less energy.12
3G. 3G (third generation mobile telecommunications) is a technology for mobile service providers and it shares the basic business model with that of the telecommunications services model. The infrastructure is owned and managed by the service provider and sold to customers typically on a monthly usage basis. Although the focus of cellular technology has been voice telephony, data services has also started to attract attention. Mobile broadband access of several Mbps is available via recent 3G releases such as 3.5G and 3.75G [66], although this is substantially lower than the data rate of WiFi.
Experimental results. Based on the experimental results presented in related research on mobile clouds, the energy consumption of 3G is shown to be higher than WiFi [24], though data for similar statistics for Bluetooth exists.
In MAUI [24], the mobile phone using 3G to offload work to a remote server consumed three times as much energy as WiFi with a 50 ms RTT, and five times the energy of WiFi with a 25 ms RTT, meaning that downloading a 100 kB file repeatedly over 3G will deplete the battery in less than two hours.
In CloneCloud [36], experiments conducted on three applications with WiFi displayed a latency of 69 ms and bandwidth of 6.6 Mbps, while offloading with 3G resulted in a latency of 680 ms, and bandwidth of 0.4 Mbps. Concerning speedups, WiFi gave speedups of 12×, 20×, and 10× while the energy consumption was 12×, 20×, and 9× less energy than the monolithic application. However, test results of 3G offloading gave lower gains; 7×, 16×, and 5× speed-up, and 6×, 14×, and 4× less energy for the same applications respectively. Greater latency and lower bandwidth of 3G is given as the cause of this.
An overview of connection protocols used, and their advantages and disadvantages regarding a mobile cloud is illustrated in Table 2.
- Table 2.Overview of connection protocols used in mobile clouds.
