Equipment Considerations in Visual C#

Decode PDF-417 2d barcode in Visual C# Equipment Considerations

A common mistake is to use one brand of interface card and AP for the initial network design and then switch to a different brand in the final deployment This can lead to surprises stemming from different RF propagation characteristics, which leads to dead spots and lower bandwidth It is best to research available products before doing any RF measurements and base the purchase decision on such criteria as vendor stability, product quality, features, management capabilities, and upgrade potential That way, the IT department will not feel pressured to change its commitment with every new product announcement from alternative sources and possibly upset a carefully designed wireless infrastructure

For example, a company might like 80211a for its 54 Mbps throughput versus the stated throughput of 11 Mbps for 80211b Many companies that had plans to install 80211b equipment and start pilots for 80211a now have no reason for doing so This is because 54 Mbps will become available for 80211b using the 24 GHz RF band One popular configuration that is emerging consists of using 80211b to create blanket site coverage at a maximum usable bandwidth of 4 to 6 Mbps, with an eye to using 80211a products to create higher-bandwidth hot spots for power users or high-bandwidth applications Some vendors, including Agere, Cisco, and Intel, offer APs with two card slots so users can add 80211a when needed By using a dual-band AP, organizations can preserve investments in existing 11 Mbps WiFi equipment while supporting 54 Mbps WiFi5 hot spots for special purposes This is not to say that no good reasons exist for standardizing the entire organization on 80211a An 80211a WLAN should be considered when

The savings gained through higher system performance is more important than initial system cost An urgent need exists for bandwidth and speed to handle large graphics, audio, data, and video files A network capacity greater than what an 80211b WLAN can currently deliver is needed The WLAN must match the speed of wired networks There will be many users per AP The current wired network is to be replaced by a wireless one

A different set of circumstances may warrant consideration of an 80211b WLAN, despite its current bandwidth limitation An 80211b WLAN should be considered when

Initial system cost is the primary concern Data rates up to 11 Mbps are sufficient for current applications and the current number of users The goal is global implementation An existing 80211b WLAN needs to be expanded Handheld PCs need WLAN access A small number of users per AP exist A small number of users need to be added to the existing wired LAN

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Because data rates affect the range, selecting data rates during the network design stage is very important APs offer clients multiple data rates for the wireless link For 80211b links, the range is from 1 to 11 Mbps in four increments, while for 80211a links, the range is from 6 to 54 Mbps in seven increments The client cards automatically switch to the fastest possible rate supported by the AP Each data rate has a unique area of coverage or cell size: the higher the data rate, the smaller the coverage area or cell size The minimum data rate for any given cell must be determined early in the design stage Selecting only the highest data rate will require a greater number of APs to cover a given area This means care must be taken to develop a compromise between the required aggregate data rate and overall system cost Numerous vendors offer wireless APs and network adapters At the low end, vendors provide inexpensive 80211b devices aimed at home users who have little or no technical expertise Consequently, such APS and network adapters require minimal configuration and offer limited opportunity for customization At the high end, vendors offer premium-priced, enterpriseclass devices Enterprise APs, for example, may have metal covers, special seals for harsh environments, a choice of antenna, network management software, an advanced web-based user interface for administrators, a range of specialized software, and many proprietary features These vendor-exclusive features might include support for higher bandwidths using proprietary techniques that the IEEE standard does not sanction Although these vendor-exclusive features can frustrate interoperability, a number of other factors can also render systems incompatible One is software: Drivers available for one brand of network cards may not work with another brand of AP Another factor is that a given product may not come with the drivers needed to get it operating properly In some locations, a specialized antenna may be needed to shape and direct the radio transmission In that case, the AP must be able to accept an external antenna