Mobile Device Feasibility

In the last five years we have seen an explosion of mobile devices within the general population so much that it is estimated that the typical British teenager owns six mobile devices, with 84% owning a smartphone, BBC (2013). Where as my generation grew up with vinyl, cassette and the ZX spectrum this generation is firmly plugged into connectivity and instant gratification.  Where the operation of technologies such as the touchscreen computer is as second nature to them as feeding their addiction of ‘looking charging points.’

As a business we can harness this almost inherent link to touchscreen devices to reduce the staff training and development cost through converting our systems to mirror the operating systems found on these devices (iSO and Android).  By taking this pathway we reduce or ICT hardware cost as these devices start at £50 unlike laptops and desktop computers. When combined with the development of online software such as MS Office 365 and Google Documents businesses and organisations no longer require local installation of software, only a platform to view and interact with the internet.

However, there are some key issues, well one key issue, that of power.  For using touchscreen tablets with a fix location such as in the office or other backrooms it is a matter of having the device plugged into the power socket. However, for roaming it is much more problematic especially when roaming is offsite.  The quickest and simplest solution for roaming on site is to provide a recharging bank which offers fully charged batteries or devices. However, offsite is somewhat more problematic where spare batteries offer a short-term solution, it is by no-means a true solution. Allow me to highlight this in the following examples.

The Salesman: The salesman has access to alternative power supplies such as in car charging and storage for spare batteries.  For this system, the biggest issue is accessibility to the company’s network via the internet.

The Street Recruiter: This is the next generation of “excuse me sir/ madam, I can I ask…” But instead of pen and paper they have a mobile device and they store the unsuspecting victims responses digitally. For this system the biggest issue is battery life as the data can be uploaded to the company’s network at the end of the day.

So we have two solutions first we increase the amount of power which a battery can hold and secondly we reduce the amount of power that the device uses. With reference to the battery the development of ‘nuclear batteries’ is yielding some interesting opportunities for public and commercial application (BBC (2009) and Phys.Org (2013)).  However, this technology is not within the reach of the commercial and public sectors.

So solution two is a much more realistic option, reduce the amount of power which the device uses.   However, how do we extend the battery life from a couple of hours to five or six hours.  I will use recent research by Carroll and Gernot (2010) and  Perrucci, Fitzek and Widmer (2011) to suggest how smart design and intelligent usage can extend the battery life. Please note that this is not a definitive explanation of all the influencing factors on battery life.

First, remove the video call functions as it consumes more than 2000 mW’s where 1400 mW’s is the 3G connection performing a one megabyte data burst. The 3G connection consumption rate indicates that the device should use this sparingly, which inturn infers that an Integrated App is the best approach when remote server connection is required. The number of data burst should be limited as the act of connecting to the 3G network consumes additional power.

Using the Wi-Fi connection on a mobile device can consume 1450 mW’s for a 4.5 megabyte burst or much higher depending on the Wi-Fi settings.  Using the Wi-Fi rather than the 3G connection provides a 3.5 megabyte advantage for the same power consumption. Where possible a hard-docking, synchronising and charging approach should be used to remove the need for all wireless connections.

The visual display is the next power gusler, consuming more power than the central processing unit (CPU) when activated. Of course the screen size will dictate the amount of power consumed but the screen size needs to allow the user to perform the task within the environment.  Consider, if the user has to wear gloves the screen size needs to big enough to allow a bigger finger to operate the software interface. It would be unreasonable to expect the user to remove their gloves every time they use the device.

The brightness and colours used on the display is also a key factor.  For example, a black background with a 100% intensity consumes about 260 mW’s compared to a white background with a 100% intensity which consumes about 527 mW’s.  Therefore, a software design feature would be to use black backgrounds with white contrasting fonts.  A black background with a 60% intensity will consume 99 mW’s.  During the test there was a significant difference in power consumption between 80% and 100% intensity.

Now, lets consider the power consumption of the CPU and reading and writing to the physical memory (harddrive and memory card). The CPU working at 100% capacity will use about 600 mW’s and at 50% capacity it 460 mW’s.  Indicating that a restricting the device operating speed to 50% capacity will save 140 mW’s.  However, if the device is slow it will reduce production efficiency and increase staff frustration.

The best place to save or write your data is to the flash memory which consumes 590 mW’s per megabyte compared to the memory card (microSD) 612 mW’s give a 22 mW difference. This does not seem much but when you consider how often the device is saving data with your permission (click on save button) or without your permission (temporary and auto save) this quickly adds up.

In conclusion, if you need to use a wireless connection use a Wi-Fi not 3G as you get an extra 3.5 megabytes of data for the 1400 mW’s of power. However, the frequency of remote connection needs to be reduce to a minimum and where possible a hard-docking, synchronising and charging approach should be used to remove the need for all wireless connections. The brightness of the screen needs to be lowered to about 60% intensity saving 273 mW’s for a white background and 161 mW’s for a black background. Suggesting that interface design needs to use darker colours to reduce power consumption. Finally, data should be written to the flash memory as this will save 22 mW’s for every megabyte stored.

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