Defining a Wireless Solution, Page 4
5.3 From Business Requirements to Technical Requirements
This section describes how to implement the Solution Requirements layer of the Wireless Decision Process. It offers guidance for translating the business requirements captured through the 5 W's approach from Chapter 4 into a set of technical requirements to facilitate component selection and architecture design. This process is primarily an exercise of mapping solution needs, described in business terms, into technical parameters by wireless component category. For example, evaluating the physical environment where a building inspector performs his or her job identifies the ability to operate under poor lighting conditions as an important business requirement. Within the wireless architecture, lighting conditions are addressed by the characteristics of client device's display. The building inspector's lighting needs translate into a requirement for a backlit display within the Device Requirements section.
The table in Figure 5.4 shows the mapping of the 5 W's questions into the major selection criteria for the four wireless architecture categories.
Five W's Table
The subsections below help you to identify quickly the major technical requirements for each wireless architecture category. Each subsection has a short "cheat sheet" questionnaire to assist you in setting high-level selection parameters. Use these parameters to hone in on the component options that best fit your needs. While more thorough and detailed research is needed to create formal technical requirements documentation, use the "cheat sheet" approach as a shortcut for moving from requirements to design in Section 5.4.
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 relative importance of these business requirements to device selection is shown in Figure 5.5.
Device Requirements Table
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.
The major criteria for defining device requirements are shown in Figure 5.6, the Device Selection Cheat Sheet. Refer to Chapter 10 for more detailed descriptions of each criteria.
The Device Selection Cheat Sheet
The Device Selection Cheat Sheet
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 (e.g., 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.
- Durability Mobile devices are often subject to adverse conditions and abuse. A stationary device within a controlled office environment faces the fewest durability issues, while a device used outdoors on a construction site must be rugged to survive. A device used in dusty or damp conditions better have good sealing. If the device is apt to be dropped, and most will be, can it withstand the impact? Will it be dropped on carpet (in an office), or on concrete (outside or in a warehouse)?
- Battery Life Battery life is not an issue for devices installed in offices or on vehicles with easy access to power, but becomes an important issue for mobile devices used away from convenient power sources. Factors that affect battery life are expected level of use (occasional versus constant use), power draw by the device and application, availability of recharge power sources, length of downtime needed to recharge, and the convenience of carrying and inserting spare batteries. Figuring out power needs before a device and application are used in real versus simulated conditions is guesswork. If loss of battery power could cause significant damage or problems, however, it pays to consider battery options and mitigation strategies upfront.
- Built-In Capabilities An important tradeoff when selecting a wireless device is whether to have as many of the necessary capabilities already integrated in the chosen device or opt for an extensible device amenable to add-ons. Fully integrated devices tend to be bulkier, heavier, and more power-hungry than extensible general-purpose devices, affecting portability to a degree, but eliminating the inconvenience of carrying a device with separate attachments. When carrying and accounting for multiple pieces of equipment is problematic, simpler is better. For example, a package delivery person collecting signatures at each drop-off location, or a lineman climbing a telephone pole, won't want to carry any more components than necessary. Conversely, an executive user may prefer a smaller device, and be willing to keep extra components in a briefcase until needed. Consider whether the additional capabilities will be used constantly, such as a network connection, or only occasionally such as a foldout keyboard for an executive's PDA. If a wireless application requires a highly specialized set of features, the best approach may be a custom-built device that integrates all of the features. In addition to network support, special features that could be incorporated in an integrated unit include bar code scanning, credit card processing, and voice recording. One disadvantage of a highly integrated device is the need to scrap and replace it when capability requirements change over time.
- Extensibility Extensibility is the flip side of built-in capabilities. It assesses the ability and desire to add and attach new features to the selected device. Extensibility is a means of getting around constraints, such as adding a foldout keyboard to enable higher volume data entry into a PDA. Add-on features include flash memory for back-ups and data transfer, plug-ins for voice and games, modems and cards for network communications, and other data entry mechanisms such as scanners and credit card readers. Special-purpose devices such as e-mail appliances tend to be less extensible, whereas PDAs and laptops are more extensible. Extensibility adds to the lifespan of the device and solution by allowing it to evolve to meet new requirements. On the other hand, users may resist carrying separate add-ons for commonly used capabilities.
- Bundled Software Devices, such as PDAs, are provided with a set of bundled software. This software includes the operating system and applications such as a spreadsheet and word processor. In single-purpose solutions, such as e-mail on an e-mail appliance, the particulars of the bundled software are unimportant to the solution. In other cases, the availability of a particular bundled application, such as word processing, may be an attractive feature that can differentiate between two otherwise close options. For other applications, the characteristics of bundled software are critical. For instance, the choice of application or middleware may necessitate the use of a particular operating system. If you plan on developing custom applications, your developers may come up with their own specific requirements for the device.
- Availability of Third-Party Software Depending on the business problem being addressed, availability of third-party software for a given device may be the number one factor driving selection or may be totally unimportant. Third-party software can provide base application functionality, add-on applications, and/or development and support tools tailored to the specific platform. Some ERP, CRM, and SFA software vendors offer mobile extensions to their solutions for certain wireless devices. The availability of third-party software for a given platform can be an important proof point of its level of adoption within the marketplace. If the business requirements are sufficiently unique or leading edge to require a custom programmed solution, availability of third-party software may be unimportant.
- Personal Information Management (PIM) PIM tools such as contacts, calendars, task lists, and alarms were the original applications provided on PDAs. These tools are increasingly offered on a variety of wireless devices. They may be important and attractive to sales and executive solutions, but less important or unnecessary for many special-purpose applications. If PIM features are desirable, it is important to ensure that the wireless versions and office versions are compatible.
- Internet Access The ability to access and surf the Internet through a mobile device is not a requirement for many applications. In other cases, such as for executives and salespeople, it can be a "nice to have" feature that is used occasionally. Given their smaller display size and slow data transfer rates, devices such as WAP telephones offer access only to specially enabled web sites. For the mobile professional, Internet access may still be useful for information such as weather reports and stock quotes. If full Internet access is a necessity, a laptop and access to a high-speed network become requirements.
- E-mail Access E-mail is the killer application for many wireless solutions. Devices vary widely in the quality and ease-of-use of their e-mail support. If e-mail is an essential application, it is important to evaluate how well the device can send/receive, display, and manage e-mail messages and attachments. If limited access to short text messages is sufficient, a wider range of devices can be considered. While e-mail access may be essential to an executive solution, it may be entirely unnecessary for a device used on a manufacturing shop floor.
- Cost If you are providing a wireless service to end users who already own devices, device costs are irrelevant. Similarly, the cost of supplying an executive with a PDA is insignificant compared to the value of fast response to business issues. Price sensitivity may be an issue, however, for users, such as students, that must purchase their own devices. Also, although wireless devices can be relatively cheap compared to desktop workstations, total device costs will mount quickly if there are thousands of expected users.