All types of 802.11 wireless networks have two basic components:
- Wireless access point (usually built-in to a router)
- Wireless network cards
An access point is a bookend-size device that uses one or more 8P8C (RJ45) ports to attach to a 10BASE-T or 10/100/1000 Ethernet network (if desired) and contains a radio transceiver, encryption, and communications software. It translates conventional Ethernet signals into wireless Ethernet signals that it broadcasts to wireless NICs on the network and then performs the same role in reverse to transfer signals from wireless NICs to the conventional Ethernet network.
Most people don’t buy an access point as a separate stand-alone item, instead they would purchase a router that has an access point built-in. Wireless routers normally include a router, switch, and a wireless access point, but may also include a cable/DSL modem, file/print server, and other features.
Note: In SOHO networks that provide Internet access, the access point is usually incorporated into a wireless router that also includes an Ethernet switch.
For coverage of a large area, you can use two or more access points and connect them to an Ethernet switch. This enables users to roam inside a building without losing contact with the network. Some access points can communicate directly with each other via radio waves, enabling you to create a wireless backbone that can cover a wide area (such as a warehouse) without the need to run network cabling. You can also purchase a wireless Ethernet range extender that can receive and boost weak Wi-Fi signals. Some access points are designed to be used as either access points or range extenders. Some range extenders are designed only to work with the same brand of access point or router.
Access points are not necessary for direct peer-to-peer networking (also called ad hoc mode), but they are required for a shared Internet connection or a connection with another network. When access points are used, the network is operating in infrastructure mode.
Note: Wireless clients running in ad hoc mode cannot connect to the Internet unless one of the stations on the network is connected to a bridge or uses another network adapter as a bridge.
NICs equipped for wireless Ethernet communications have a fixed or detachable radio antenna. Wireless NICs come in four forms:
- CardBus (32-bit PC Card) or ExpressCard (PCIe) cards for use in laptop computers that do not include “integrated” wireless support
- Mini PCI or PCIe Mini cards that provide wireless and wired Ethernet and dial-up modem support for laptop computers
- PCI cards for use in desktop computers with PCI slots
- USB adapters for use in both desktop and laptop computers
Most laptop computers with Wi-Fi hardware onboard use the Mini PCI or PCIe Mini interface for the wireless adapter and place the antenna inside the display housing.
Note: Mini PCI or PCIe Mini cards are installed inside laptop computers. (They can be removed or replaced by opening the system.) Because Mini PCI and PCIe Mini cards are installed inside laptops, they are not usually sold as retail components. However, some vendors sell them as OEM components, or you can buy them from the laptop vendor’s parts department.
Because you can mix and match Wi-Fi-certified products that use the same frequency band, you can incorporate any mix of desktop and laptop computers into your wireless network. The following image illustrates typical wireless network hardware.
Although most recent laptop computers include 802.11b/g/n wireless Ethernet or dual-mode 802.11a/b/g/n support through an integrated Mini PCI or PCIe Mini card, you can add support for other 802.11 wireless networks by either upgrading the internal card or by attaching an additional card via a CardBus slot, ExpressCard slot, or USB port.
When a Wi-Fi-enabled system receives multiple Wi-Fi signals, client systems lock onto the strongest signal from access points and automatically roam (switch) to another access point when the signal strength is stronger and the error level is lower than the current connection. Of course, if you want the system to lock onto a specific signal, that can be done via the OS or manufacturer-provided software.
Most people use a wireless router as the basis of a wireless network. A wireless router normally contains a router (which is connected to a cable/DSL modem), switch, and access point. When looking for a wireless router, I recommend only those that include gigabit Ethernet switches as well as a gigabit Ethernet WAN port for connecting the router to a cable/DSL modem.
Additional hardware you might need to add to your network includes the following:
- Wireless bridges—These devices enable you to connect a wired Ethernet device, including noncomputer items such as video games or set-top boxes, to a wireless network. These are sometimes called wireless gaming adapters.
- Wireless repeaters/range extenders—A repeater can stretch the range of an existing wireless network. Some can also serve as access points or wireless bridges.
- Specialized antennas—The “rabbit ears” antennas used by most access points and routers are adequate for short distances, but longer distances or problems with line-of-sight reception can be solved by attaching high-gain replacements for the originals, or by attaching more specialized directional antennas, possibly on extension cables to mount them higher for greater range.
- Signal boosters—In addition to or as an alternative to replacement antennas, some vendors also sell signal boosters that piggyback onto an existing access point or router. Note that, in most cases, these signal boosters are vendor specific.