Direct database connectivity and terminal emulation can work for both wired and
wireless networks. Most often, however, the optimum connectivity software for wireless
LANs is designed specifically for that medium. Wireless middleware software provides
intermediate communications between end-user devices and the application software
located on a server. The middleware, which generally runs on a dedicated platform
attached to the wired LAN, processes the packets that pass between the LAN and the
wireless access point. It provides efficient and reliable communications over the
wireless network, while maintaining appropriate connections to application software and
databases on the server via the more reliable wired LAN.
The following are features to look for in middleware products:
- Optimization techniques: Many middleware products include
data compression at the transport layer to help minimize the number of bits sent over
the wireless link. Some implementations of middleware use header compression, where
mechanisms replace traditional packet headers with a much shorter bit sequence before
- Intelligent restarts: With wireless networks, a transmission
may be unexpectedly cut at midstream. Intelligent restart is a recovery mechanism that
detects the premature end of a transmission. When the connection is reestablished, the
middleware resumes transmission from the break point instead of at the beginning.
- Data bundling: Some middleware is capable of combining smaller
data packets into a single large packet for transmission over the wireless network,
which can help lower transmission service costs of WANs. Since most wireless data
services charge users by the packet, data bundling results in a lower aggregate cost.
- Store-and-forward messaging: Middleware queues traffic to
ensure delivery to users who become disconnected from the network. Once the destination
station comes back online, the middleware sends the stored packets.
- Screen scraping and reshaping: The development environment of
some middleware products allows developers to use visual tools to "scrape"
and "reshape" portions of existing application screens to more effectively fit data on
the smaller display of some non-PC wireless devices.
- Support for
HREF="http://www.computer.org/internet/v2n1/perkins.htm">Mobile IP: Some
middleware products offer home and foreign agent functions to support the use of Mobile
IP protocols, which seamlessly handles changes in a client's point of attachment to the
Internet. This enables wireless users to roam across networks based on different