Everything you wanted to know about Wireless (Wi-Fi) networks


A Wireless network basically utilizes the wireless frequencies (2.4 Ghz or 5 Ghz spectrum) to transmit the data, voice and video from one point to another using the wireless signals as the medium – But it is very rare to have  a total stand-alone wireless network as the wireless transmission and reception is restricted from the client (PC/Laptop/Wi-Fi Phone etc) to the Wireless Access Point. Beyond that, the data is carried in the wired backbone network. A look at the below Wi-Fi architecture diagram would better clarify this point.

Wireless Network Architecture Diagram
Wireless Network Architecture Diagram

As shown in the above diagram, the various wireless devices like laptops, computers, tablets, wi-fi enabled cell phones, wi-fi phones, wireless cameras etc connect to the wireless access points present in their respective floors and from there, the data is transmitted over the copper UTP cables to the wired network switch in each department and then via the optical fiber network to the core switch/ router in the IT Department and then to the outside world (Internet). So, only the client access is on Wi-Fi technology, and in rare cases the backbone also could be on wireless technology (with some limitations) using a wireless mesh. We are talking only about the enterprise campus wide wireless networks and not about the city-wide or nation wide wireless connectivity.

So, why are wireless networks required at all?

Can’t we just have wired network to all the places? We can, but wireless networks have the following key advantages over wired networks:

  • Network Access from anywhere: It’s just much more convenient for us to access the network from any place in the campus and not just our seat alone. Think about it, you go to your project manager’s room for discussion, and you may want to show something from your laptop. You go to the conference room or cafeteria and might want to connect to the network. When laptop’s have become ultra portable, so must the network!
  • Cost Reduction: In certain places like hostels for example, it does not make sense to have wires running to each room for Internet connectivity. Its not only the cables but the additional switch ports, the passive components, I/O boxes, patch cords and so many components that come along with the wired network. So, having a wireless network in these high density browsing locations (hot-spots) reduces a lot of cost.
  • No cluttering of cables: A wireless network certainly eliminates clutter to a huge extant and makes the place look much more neat.
  • Good performance/ throughput: With the advent of IEEE 802.11n technology, wireless networks can now support higher throughput around the range of 300 Mbps. So, even if this bandwidth gets divided by the number of systems connecting to each access point, we are still left with a decent throughput. Let’s accept it – 1000 Mbps to the desktop offered by the wired networks are just not required!!

What do you need in order to set up a wireless network?

For Small Office/ Home Office (SOHO) (1-15 employees)

If your’s is a home office or a small office (with fewer than 15 users connecting to the network and within a compact area), then a small stand alone access point costing less than 100 USD would suffice your requirement. Just plug it to the wired network switch, and your network is ready! Some times, the broadband modem which terminates the broadband line comes with built in modem, and that might also suffice simple wi-fi requirements.

But always keep in mind that the laptops/ PC’s connecting to the wireless network should be having IEEE 802.11 a/b/g/n standards based wireless adapters. For laptops, this comes built-in mostly but for PC’s, you may need to add an USB based / PCMCIA slot based Wireless adaptor. So, if you are using only PC’s in your network, getting the wireless adaptors for all of them might increase the cost considerably! Also, some network devices like printers, servers etc require dedicated wired connectivity. So, keep these factors in mind while planning for a wireless network in a small office.

For medium sized organizations (20 – 100 employees):

This is where the confusion comes – should you go for a stand alone access points based wireless network or a controller based wireless network? Of course, the best option would be to go for a controller based wireless network (see next section for top reasons for the same) but this might increase the cost. If you go for a stand-alone access points based wireless network, you might not only lose a lot of centralized functionalities, but might also be prone to wireless interference between the neighboring access points. There are three options you could try in such cases (in case you decide to go for stand alone access points):

Set the frequency of operation for each access point manually so that the neighboring access points operate in different frequencies (But some access points do not allow to do this setting and the frequencies are reset every time the access points boot up – due to power failure for example – so such things need to be taken care of).

Go for stand alone access points that can be upgraded to controller based access points in the future – This means the access points still are stand alone types and can work individually without the controller, but when the network grows or there are excessive maintenance problems, you could buy a controller of the same make and manage all these access points through it, at a later date. There are a very few vendors who offer such access points, though.

Go for access points which support clustering within the stand-alone access points. Clustering is a technology that allows the access points to share certain information within themselves in order to provide some entry level centralized management for all these access points. But these access points can share information only when each of them are in range of at least one access point within the cluster group and there is also limitation in the maximum number of access points that can be part of a cluster group. If these access points can later on be upgraded to a controller based access points, it is even better!

For Large Organizations (More than 100 employees):

Its highly recommended that larger organizations go with a centralized controller based wireless solution where the wireless controller is used to provide centralized management functionalities to all the access points across the network. Below are a list of top five reasons for the same:

The Top 5 reasons to have a wireless controller:

Centralized Authentication and Encryption: If you have multiple stand alone access points at multiple locations, imagine having to update each access point with the list of MAC addresses that can connect to it. Consider maintaining such a set up as some employees are going to leave the organization and some will join. And what will happen to guests who want a temporary access to Internet? Wireless controllers integrate with centralized corporate directories like Active Directory/ LDAP etc to give user based authentication (User-name/password and(or) prior installed certificates). This would be applied to all the users irrespective of which access point they connect to. The guests can be given a temporary account with which they can access only certain resources and that too only for a certain time period with a wireless controller. All the communications between laptops and access points (and) access points and controller are encrypted for security.

Radio Management and Interference Mitigation: If two neighboring access points operate in the same frequency, there would be a lot of interference and would result in loss of data or loss of connections happening frequently. So, wireless controller can identify which access points are nearer to each other and assign them to operate in different frequencies. The controller can also do load balancing of users between access points and can push the users to another access points if the primary access point that they connect to, fails.

Network Access Control: Wireless Controller can organize users in to various groups and enforce certain policies on what network resources they can use and what they cannot. Some users may not be given Internet access but given ERP access and vice versa, for example.

Roaming: For voice clients like voice over wi-fi phones and dual mode cell phones, it is very critical that the connection does not terminate when the users are talking over them and moving across the campus simultaneously. So, controller supports roaming – fast hand-off of voice sessions to near by access points in order to keep a voice session from breaking abruptly when it goes beyond the range of one access point.

QoS and Network Visualization: For supporting real time applications like voice and video, the wireless network needs to support an end-to-end QoS setting for prioritization of the real time latency sensitive voice and video packets across the network. It would further help if the wired network is also configured with such QoS prioritization settings. Controller also allows administrators to see the signal strength levels across their network in a live heat map – this could be very helpful while maintaining huge wi-fi networks.

Which is better – 2.4 Ghz Spectrum or 5 Ghz Spectrum?

Wireless devices can connect to the wireless network in either 2.4 Ghz spectrum or 5 Ghz spectrum (depending on which spectrum the wireless adapter in the laptop and the access point, both support). While 5 Ghz spectrum is more cleaner and is rid of interference from sources like microwave etc, the commonly available laptops and access points mostly support only 2.4 Ghz. Actually, 2.4 Ghz spectrum allows only three non-overlapping channels for IEEE 802.11b/g! But with the advent of IEEE 802.11n technology, it is now possible to have wireless adaptors and dual radio access points supporting both the spectrum’s and the controller can decide (based on the load etc) as to which is better for individual clients.

What are the wireless standards for Wi-Fi ?

IEEE (Institute for Electrical and Electronic Engineers) have drafted certain standards for wireless equipments and each equipment needs to support one of them or multiples of them so that they can inter operate with wireless equipments made by other vendors. The different standards are:

IEEE 802.11 b – This was a very early standard and supports a maximum throughput of 11 Mbps and operates in the 2.4 Ghz spectrum

IEEE 802.11 a – This is a more recent standard supporting a maximum throughput of 54 Mbps and operates in the 5 Ghz spectrum

IEEE 802.11 g – This is the most common standard supporting a maximum throughput of 54 Mbps and operates in the 2.4 Ghz spectrum – Almost every laptop and access point should support this.

IEEE 802.11 n – This is the latest standard supporting a maximum throughput of 300 Mbps now and operates in both 2.4 Ghz as well as 5 Ghz spectrum’s.

Note: You cannot get the higher throughput offered by 802.11 n technology by just replacing the older access points with the newer access points – you need to replace the client adaptors to support 802.11n as well and you need to upgrade the backbone wired network to support 1000 Mbps throughput instead of the earlier 100 Mbps. The latest standards are backward compatible – IEEE 802.11n would support IEEE 802.11b/g or/and IEEE 802.11a.

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