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WLAN Definition and Basic Architectures - Section 1 [From Beginner to Expert - WLAN Fundamentals]

Latest reply: Dec 30, 2020 21:27:29 6214 20 14 0 6

Hello, everyone!


This post brings you more information on WLAN definition and basic architectures, as part of the 'From Beginner to Expert - WLAN Fundamentals' section of the Community. Please see more as you read further down.

WLAN Definition and Basic Architectures

Throughout our daily lives, we frequently enjoy the convenience brought to us by WLANs. In our homes, wireless routers free us from being stuck in chairs in front of desktop computers. We can check our emails while watching our favorite films online, from the comfort of our sofas and beds (or even our toilets!). In train or bus station waiting rooms, more and more people now use laptops and tablets instead of reading newspapers and magazines. In coffee shops, it's not the menu people look for first, but the Wi-Fi password.

With WLANs, we are no longer bound by cables.


 57611c6de641a.png

As the use of WLANs increasingly becomes a part of everyday life, many people want to understand how WLAN technologies work. WLAN has become a hot topic and I am pleased to discuss WLAN technologies, and address some WLAN problems, with you today, and help you to understand this most familiar stranger.

WLAN is short for wireless local area network. Quite simply, WLANs are local area networks that provide network communication using radio frequencies such as lasers and infrared signals, instead of physical connections. They provide wireless network communication using high-frequency radio frequencies (such as 2.4 GHz and 5 GHz bands) and comply with the IEEE 802.11 series standards. The 802.11 series standards define wireless communication specifications and are the mainstream standards for WLANs.

During the evolution and development of WLANs, many technical standards, for example, Bluetooth, 802.11 series standards, and HyperLAN2, are introduced to build WLANs. 802.11 series standards define relatively simple technologies, provide reliable communications, and require lower costs. These features make the 802.11 standards the mainstream for WLANs and also a synonym for technical standards for WLANs.

The 802.11 standards will be introduced in detail later.

As mentioned before, we use WLANs in both our homes and larger venues, such as train station waiting rooms. A waiting room is much larger than a household and so a home router cannot provide blanket coverage in a waiting room. In our homes, only a few tens of users access the WLAN while hundreds or even thousands of users may access the WLANs in waiting rooms. The question is, how can WLANs accommodate so many users in a waiting room? The answer lies in different WLAN architectures.


 57611cd2b1bbf.png

There are two basic WLAN architectures, Fat AP architecture (also referred to as autonomous architecture) and AC+Fit AP architecture (also referred to as centralized architecture), with AC being short for access controller and AP for access point.

Home wireless routers adopt the Fat AP architecture. Not only does a fat AP provide wireless channels for STAs to access the WLAN, but they also implement encryption, user authentication, and user management. On a home wireless router, we can set WLAN passwords, configure blacklists or whitelists to control user access, and manage users accessed to the WLAN, for example, by setting user rates. These features make the home wireless router a fat AP.

The following figure shows a simple network based on the fat AP architecture.


57611d07df116.png 

Due to the powerful functions, independence, and autonomous capability of fat APs, the fat AP architecture is also known as autonomous architecture. Fat APs can independently control user access, encrypt and forward service packets without the need of management devices. Since fat APs can work independently, the deployment of fat APs is easy and cost-effective. They are often the best choice for home WLANs or small business WLANs.

The autonomous capabilities of Fat APs are, however, also their shortcoming.

In a large area, for example, a waiting room, a large number of users need access to the WLAN, which requires many Fat APs running simultaneously. Because each fat AP works independently and there is no management device to centrally manage them, managing the entire network can be difficult and requires a lot of resources. Furthermore, autonomous fat APs cannot overcome roaming issues. For these reasons, in medium- to large-sized venues, we usually do not choose the fat AP architecture, but use the AC+Fit AP architecture instead.

(If you are not sure what roaming is, think about how we use mobile phones. When we are traveling on a train, our mobile phones repeatedly disconnect from serving networks and connect to new networks throughout our journey. This is called roaming. Or, when we move from our home to our neighbor's home with tablets or other wireless devices and connect our devices to our neighbor's WLAN, this process is also called roaming. Roaming will be discussed in detail later.)

So how do Fit APs differ to Fat APs?

Fit APs provide radio signals but do not offer management functions. To construct a WLAN, Fit APs have to work with separate management devices, namely, ACs. This architecture is known as AC+Fit AP architecture. AC+Fit AP architecture is more cost-effective and efficient than fat AP architecture in large venues and so is more commonly used in these scenarios.

The following figure shows a WLAN based on the AC+Fit AP architecture for a large-scale enterprise.


 57612c468e72b.png

In the preceding figure, ACs are deployed on the aggregation layer or core layer depending on the managed areas and throughput. Fit APs are deployed on the access layer in different branches of the enterprise. This hierarchical AC+Fit AP architecture features centralized management. Therefore, this architecture is also referred to as centralized architecture.

In the AC+Fit AP architecture, the AC delivers configurations to Fit APs and upgrades Fit APs in batches. Moreover, the number of working Fit APs can be controlled for different time periods. As a result, WLAN management and maintenance costs are reduced significantly. ACs centrally control user access so that user roaming becomes easier.

A home wireless router adopts the fat AP architecture.

57611d645e8e0.png 


 

The AC+Fit AP architecture is often used in large venues.


57611d91a4b4f.png 

So far we have discussed the WLAN definition and its basic architectures. If you have any question, feel free to post queries to be answered.

Question:

1.         Can you describe the architectures of WLANs that are used in our daily lives?

The post is synchronized to: From Beginner to Expert-WLAN Fundamentals

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user_2790689
Created Jun 16, 2016 04:02:46

Good!
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fantasio
Created Mar 13, 2017 15:46:13

good
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wissal
MVE Created Apr 30, 2018 05:23:53

clear and useful document, thanks
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gurunge
Created Nov 20, 2018 09:36:55

useful one
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faysalji
Created Nov 27, 2018 04:48:50

helpful
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faysalji
Created Nov 27, 2018 04:49:47

explained well
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faysalji
Created Nov 27, 2018 04:49:57

Thank you!
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Pogo
Created Jul 5, 2019 07:30:55

Nice document! Great help.
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Fernando_Ag
Created Aug 22, 2019 21:29:37

Thanks for sharing
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