The two biggest influences on device selection are the solution's users (Who) and the functions or applications (What) the solution will provide. Other important factors are the environments (Where) where the devices will be used and business considerations (Why) such as cost and extensibility.
The characteristics of the application(s) will largely determine the device, since the device must have features to facilitate the operation of the application. If the application is highly specific or closely tied to a vertical process, then a special-purpose device may be needed. An inventory management application may call for a bar code scanning device, while a parts replenishment application may call for telemetry equipment. If the application is aimed at improving mobile worker productivity, then a more versatile, general-purpose device will likely suffice, and factors like user preferences, device portability, extensibility, and cost will greatly rule in or rule out certain device types.
Since devices are the most personal component of your wireless solution, your future end users are likely to have strong opinions about which devices they are willing to use. For example, executives may not have the patience or inclination to work with a multi-featured device. Repair technicians that will simultaneously operate other equipment may favor a device that can be used with a single hand. Salespeople may avoid stylus-oriented devices for fear of losing the stylus while traveling. In some cases, such as consumer applications or sales applications, your solution may have to support the devices already owned by your target audience. Try to develop a profile of your target audience so that a device can be selected that meets the group's rather than individual's needs.
When selecting requirements, remember that some device features are more important than others. For example, a color display may be a nice feature but add nothing to an order status application, and even be detrimental to battery life as compared to a monochrome unit. An application that relies primarily on voice processing may call for a device optimized for voice, such as a smart phone or communicator. In general, a laptop device will offer the richest functionality of all the mobile devices. When it comes to display size, data input mechanisms, processing power, memory, extensibility, wireless communications, and availability of third-party software, a laptop can't be beat. Laptops, however, may fail to satisfy user preferences. The large size and weight of a laptop, the long time to power on, and the complicated software and hardware environments lead many users to select a more portable, faster, and simpler device.
- Voice: Will the device need to support voice communication instead of, or in addition to, a data application? As described in Chapter 10, wireless device features are starting to merge, with PDAs supporting voice processing and telephones supporting data displays and Internet access. Additional capabilities are required if the solution calls for other voice processing such as recording or speech recognition.
- Size/Weight/Portability: These requirements - size, weight, and portability—are largely influenced by how the user expects to carry or wear the device. While some types of devices, like laptops, may be disfavored because of their size, other devices like PDAs may fit a wider variety of needs. In general, if a device is burdensome in terms of size, weight, or ability to be stowed, or limits the performance of other activities (I.E., requires two-handed use or cables), then a user will tend not to carry or wear the device.
- Display: Our natural inclination is to select the largest and most visually appealing display possible. Selecting the right device display, however, is likely to involve a compromise between display capabilities, portability, power requirements, and cost considerations. For example, a color display may be irrelevant to an order status application, and even be detrimental to battery life as compared to a monochrome unit. The best approach is to define the minimum requirements for the planned solution and to upgrade from those requirements when feasible during device selection. Three major criteria help to define device requirements: display size, display quality, and performance in variable lighting conditions. The volume of information that must be displayed at one time determines display size. At one extreme, a pager may display one line of text. At the other extreme, a laptop provides a full screen display. The quality of a display includes its resolution and color capabilities. Simple text can be displayed monochromatically in low resolution, while high resolution is necessary for graphics or video, or to display larger volumes of information on a small display. Variable lighting conditions require more flexible displays, such as a backlit display for dimly lit locations.
- Data input: How will the user interact with the device? How will information be entered into the device? How much data will be collected? Data collection may be automated through the use of scanners, readers, or sensors. In most cases, however, the user will interact with the device through a keyboard, touchscreen, or other data entry mechanism. The choice of mechanism depends on the volume of data being entered and the working style and personal preferences of the user. A full keyboard may be required to enter a large volume of text, but an inspector checking items on a form may work best with a stylus. A small, thumb-typing keyboard may be perfect for short e-mails, but difficult to use for someone wearing protective gloves. A user sitting at a desk can use a foldout keyboard, but a trader on the stock market floor needs a portable mechanism that can be used while standing.
- Processing power: Processing power is determined by the needs of the application(s) that will operate on the device. If the device merely displays data from other sources, processing requirements are low. Conversely, if the device has to support multiple concurrent applications or heavy calculations, it will need greater processing power. Limitations in processing power can sometimes be addressed through careful partitioning of functionality between device and server, a topic discussed in Chapter 12.
- Memory: Like processing power, memory is determined by the needs of the application(s) that will operate on the device. Running a single, simple application takes far less memory than supporting multiple concurrent applications. Multimedia applications, for example, will require more memory than a standard word processing application. The ability to add external memory to a device can help ease storage demands, but will not alleviate a persistent lack of memory.
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