Types and features of wireless Access Points

This article gives a small brief about the various types of Wireless Access Points available in the market – Single radio, dual radio, external antennas, internal antennas, a, b/g, b/g/n technologies, support for mesh networking, stand alone, controller based access points and support for multiple services.

Why are Wireless Access Points exciting?

¤ Access points are the basic elements of a wireless network – They scan for the wireless devices in its range and all the neighbouring Wi-Fi systems connect to the Access Point to communicate with the network.
¤ Access points offer a standard for connectivity – a, b/g, b/g/n which are all ratified by IEEE so that the Wi-Fi systems from various vendors can connect to the network.
¤ Access points connect to PC’s, laptops, PDA’s, mobiles, Wi-Fi phones, Wi-Fi Cameras, Wi-Fi display management systems and a host of other devices that work on the Wi-Fi standard.
¤ Access points can also scan the network for wireless threats and attacks.

Please note: Even thought Access Points provide wireless access to clients, they are themselves hooked to the network through Cables (Cat 5E/ Cat6) and hence the back bone of the wireless networks are most often wired. But there are exceptions.

Single Radio/ Dual Radio Access Points:

Some Access Points come with a single radio – They work in either IEEE 802.11a or b/g – This can be selected. Most of them work in the b/g standard as most of the network adaptors follow that standard. But some Access Points come with a dual radio option. One radio works in IEEE 802.11a and the other works simultaneously in IEEE 802.11b/g or even IEEE 802.11 b/g/n. Dual radio Access Points are useful for mesh networking, giving access to laptops containing only 802.11a network adaptors and also for wireless intrusion scanning/ prevention.

External Antennas/ In-built Antennas:

Most of the Access Points come with built-in antennas with a certain gain specified by the manufacturer. While they give a decent coverage, there may be certain applications where the no. of users may be small but the area to be covered may be large – like a lawn/ park. In these circumstances it is better to use Access Points with external antenna provisions as the external antennas come with a higher gain and can boost the signal strength to a higher distance. But in both the cases the bandwidth supported by an access point is standard.

IEEE Standard supported: 802.11a,b,g,n:

IEEE has standardised the wireless access protocols so that multi vendor systems can connect and talk to each other through Wi-Fi.

IEEE 802.11b supports upto 11 Mbps but IEEE 802.11a and g support upto 54 Mbps on a shared platform. IEEE 802.11n currently (in draft) supports upto 300 Mbps and in future would support 600 Mbps per Access Point (Please note: As the number of PC’s that connect to the AP’s increase, the bandwidth gets shared between them and the numbers are under ideal conditions, and practically achieved bandwidth may be half of what is specified per AP).

The standard Access Points should support upto 30 meters indoor and slightly more than double of that in outdoor (Although in practical applications there are many AP’s deployed within 30 meter distances based on the number of users and the bandwidth they require).

So, per radio, the Access Points can support either IEEE 802.11 a or IEEE 802.11b/g/n (As they operate at different frequencies) and based on the protocol supported by the Access Point, the bandwidth supported per AP would vary.

Practically, 15-20 users are recommended to simultaneously connect per AP in order to get a decent throughput.

Support for Mesh Networking:

Certain vendors support mesh networking in certain dual radio Access Points. While one radio of the AP connects to the clients, say in 802.11b/g, the other radio establishes a point to point back end connectivity to the neighbouring Access Point, say in 802.11a (Which is similar to this one) and hence eliminate the data cable connecting to the AP(but not the power cable). Though the AP’s can connect to each other in this fashion, with every hop the available bandwidth to the last Access Point(from the wired network) is halved. So, farther the AP to the wired network, lesser is the bandwidth.

Controller based Access Points and Stand-Alone Access Points:

Though this topic could be a post in itself, right now it is sufficient to mention that there are certain access point which operate independently and there are some more which operate only with a controller and there are some others which operate on a stand-alone basis and could be converted to a controller based one at a later stage.

If the wireless network is to be established over a small distance – single floor and 15 devices kind of an application, stand alone Access Points could suffice. But higher the distance and more the area to be covered, it makes more sense to go for the controller based Access Points as the management of the AP’s is easier through the controller and from a central point. Imagine having a huge campus and hundreds of Access Points. If a new user joins or a new upgrade is released for the AP, it is very difficult to update each AP individually. And controllers perform a lot more functions that are critical for maintaining a wireless network and enabling applications in it.

Support for Multiple Services:

Certain services like Wireless Intrusion Prevention (A method of scanning the whole area to locate for wireless threats and intrusions) can be performed simultaneously by the Access Point while giving network access (Dual Radio types). But certain vendors have a separate specialised Access Point to scan the network for identifying intrusions.

Most of the Enterprise Access Points support POE (Power over Ethernet – A feature where the electrical power required for the AP is sent along with the data via the Cat5E/ Cat6 network cable itself). Perhaps there could be some home AP’s that don’t support this feature.

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