A wireless access point (AP) is required for infrastructure mode wireless networking. To join the WLAN, the AP and all wireless clients must be configured to use the same SSID. The AP is then cabled to the wired network to allow wireless clients access to, for example, Internet connections or printers. Additional APs can be added to the WLAN to increase the reach of the infrastructure and support any number of wireless clients.
Compared to the alternative, ad-hoc wireless networks, infrastructure mode networks offer the advantage of scalability, centralized security management and improved reach. The disadvantage of infrastructure wireless networks is simply the additional cost to purchase AP hardware.
Note that home wireless routers all feature a built-in AP to support infrastructure mode.
To set up an ad-hoc wireless network, each wireless adapter must be configured for ad-hoc mode versus the alternative infrastructure mode. In addition, all wireless adapters on the ad-hoc network must use the same SSID and the same channel number.
An ad-hoc network tends to feature a small group of devices all in very close proximity to each other. Performance suffers as the number of devices grows, and a large ad-hoc network quickly becomes difficult to manage. Ad-hoc networks cannot bridge to wired LANs or to the Internet without installing a special-purpose gateway.
Ad hoc networks make sense when needing to build a small, all-wireless LAN quickly and spend the minimum amount of money on equipment. Ad hoc networks also work well as a temporary fallback mechanism if normally-available infrastructure mode gear (access points or routers) stop functioning.
Using ad hoc Wi-Fi mode eliminates the need for a network router or access point in a wireless home network. With ad hoc wireless, you can network computers together as needed without needing to be in reach of one central location. Most people use ad hoc Wi-Fi only in temporary situations to avoid potential security issues.
Optional Components -
Networking an ad hoc layout for Internet access, printers, or game consoles and other entertainment devices is not required for the rest of the home network to function. Simply omit any of these components shown that do not exist in your layout.
Limitations -
All devices connecting via ad hoc wireless must possess a working Wi-Fi network adapter. These adapters must be configured for "ad hoc" mode instead of the more typical "infrastructure" mode.
Because of their more flexible design, ad hoc Wi-Fi networks are also more difficult to keep secure than those using central wireless routers / access points.
Ad hoc Wi-Fi networks support a maximum of 11 Mbps bandwidth, while other Wi-Fi networks may support 54 Mbps or higher.
Many Wi-Fi bridging mode products exist with varying levels of functionality.
Some wireless bridges support only a single point-to-point connection to another AP. Others support point-to-multipoint connections to several other APs.
Each AP in bridging mode connects to a wired LAN. Some AP models simultaneously support wireless clients while operating in bridging mode, but others work as "bridge-only" and disallow any clients from connecting. Some APs only support bridging with other APs from the same manufacturer or product family.
AP bridging capability (when it is available) can be enabled or disabled through a configuration option. Normally, APs in bridging mode discover each other via Media Access Control (MAC) addresses that must be set as configuration parameters.
While operating in bridging mode, wireless APs utilize a substantial amount of bandwidth. Wireless clients on bridged Wi-Fi networks generally share the same bandwidth as the bridge devices. Therefore, clients tend to perform slower in bridging mode than otherwise.
In Wi-Fi, repeater mode is a variation on bridging. Rather than join multiple LANs, repeater mode is intended mainly to increase the range of a single wireless LAN by extending the same wireless signal.
A wireless access point
(sometimes called an "AP" or "WAP") serves to join or "bridge" wireless
clients to a wired Ethernet network. Access points centralize all WiFi
clients on a local network in so-called "infrastructure" mode. An access
point in turn may connect to another access point, or to a wired
Ethernet router.
Wireless access points are commonly used in large office buildings to create one wireless local area network (WLAN)
that spans a large area. Each access point typically supports up to 255
client computers. By connecting access points to each other, local
networks having thousands of access points can be created. Client
computers may move or "roam" between each of these access points as
needed.
In home networking, wireless access points can be used to
extend an existing home network based on a wired broadband router. The
access point connects to the broadband router, allowing wireless clients
to join the home network without needing to rewire or re-configure the
Ethernet connections.
shown above, wireless access points appear physically similar to
wireless routers. Wireless routers actually contain a wireless access
point as part of their overall package. Like wireless routers, access
points are available with support for 802.11a, 802.11b, 802.11g or
combinations.
REFERENCES
http://compnetworking.about.com/cs/wireless/f/infrawireless.htm
http://compnetworking.about.com/cs/wirelessfaqs/f/adhocwireless.htm
http://compnetworking.about.com/od/wireless/ss/wirelessgear_2.htm
