Defining a Wireless Solution
5.5.1 Rethink Constraints
Is the perceived constraint truly a limitation or is it imposed arbitrarily? A given solution may require sending forms between the user and a corporate system. If the entire form is sent on each transmission, the bandwidth of a wireless wide area network may be insufficient. If the application is designed to transmit only the changed portions, however, current bandwidth may be more than adequate. Does a traveling salesperson really need instant access to account file updates or can files be updated once a day? System architects and designers used to working on unconstrained wired office systems may need to rethink their approach to solution design to work around, or even take advantage of, the differences in wireless capabilities.
5.5.2 Switch Paths
Ask yourself if you can accomplish the same goals with a different set of technology options. For example, if your main goal is to relay sales orders to your corporate office, you may enter the information through a wireless web page, use a custom designed form to transmit data across a digital cellular network, or use e-mail templates through an e-mail device. While the form of the data and the design of the application may be very different, the end result is the same—the sales order is relayed.
5.5.3 Reprioritize Features
5.5.4 Find Creative Workarounds
Look for creative workarounds if particular aspects or functions of your solution run into roadblocks. As an example, in an originally envisioned medical solution, emergency room doctors would have received an updated version of the emergency room's patient whiteboard on demand. Experience quickly showed, however, that the busy and highly mobile physicians could not tolerate having to initiate and wait for the updated whiteboard to load on their handheld devices. To overcome this issue, the project's design team switched to a "push" approach, automatically relaying updates once a minute to the doctors' devices. By restricting transmissions to only those items that had changed, transmissions were kept short and unobtrusive, enabling the doctors to simply look at their devices periodically to see up-to-date whiteboard contents.
5.5.5 Break the Problem into Smaller Parts
Sometimes a combination of approaches provides a more effective solution than a single approach. Penske Logistics uses wireless technology on its trucks and at its cross docks to keep customers informed about deliveries and manage driver routes and performance. An onboard computer manages and transmits data about arrival and departure times, delays, traffic conditions, and changes in schedules in near real time over a satellite network. More routine data about cargo pickups and drop-offs is captured via handheld devices used by delivery personnel. When a truck returns to a Penske terminal, the routine data on the handheld device is synchronized with the host system via a wired docking cradle. This hybrid approach provides immediate exchange of high-value information, with coverage across Penske's entire delivery range, with periodic bulk transfer of less time-dependent data at much lower network costs.
5.5.6 Phase Your Solution
If your solution is constrained by limitations in evolving areas, such as coverage or bandwidth, you can use a phased approach to implement a subset of features now and add new features as limitations disappear. For example, you can provide field service workers with a mobile solution for dispatch and work order invoicing with current technology and add capabilities, such as access to on-line repair manuals or videos of repairs in action, as network capacities increase.
5.6 Example Solutions
The best way to illustrate the principles of this chapter is to examine a few actual examples of wireless applications. This section describes four diverse types of applications: e-mail service (Figure 5.11), WLAN (Figure 5.12), data capture (Figure 5.13), and national tracking and location (Figure 5.14), and the considerations that influenced their designs.
E-mail Service Architecture
Wireless LAN Architecture
Data Capture Architecture
5.6.1 Example Architecture: E-mail Service
- Application Atlantic Envelope Company (AECO) wanted to give its salespeople wireless e-mail access and a custom application that would allow them to answer customer queries and submit changes to orders. AECO chose e-mail as the platform for person-to-person messaging, and as a method to exchange transactional data between client devices and a back-end server. To overcome expected device presentation and network bandwidth limitations, AECO designed its application to focus on customers' top ten queries and to use forms and templates to ease data entry and minimize data transfer.
- Information AECO isolated the data needed to support the application to order, customer account, and inventory information. Without a central source of this information, AECO created a program to draw the data from several back-end systems, store it on an application server, and refresh it twice daily, a timeframe sufficient to provide reasonably current information to the field.
- Device AECO had two important device requirements: the device had to be optimized for e-mail and give sales reps the ability to type freeform e-mail messages using a keyboard rather than a cryptic handwriting scheme. These two requirements led AECO to choose a RIM BlackBerry device equipped with a keyboard.
- Network Given the locations of its customers and the areas in which salespeople would roam, AECO had one viable network choice: a wireless WAN. Drawing a map of its customer locations, and superimposing this map on various carriers' coverage maps, led to the selection of Cingular Wireless as the carrier with the best overlap. Although maintaining the integrity of transmissions wasn't a key concern for AECO, the RIM devices and network allow for storing and forwarding of messages when a sales rep is out of the coverage area.
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