Wednesday, 10 August 2016

Planning And Surveying For Good Wireless LAN

Life Cycle of Wireless:


Bad WiFi designs:

--The attenuation and propagation of RF signal is important and use case again depends on the deployment requirements.
--Its important where APs are placed.
--Bad WIFI design results in "coverage hole" "sticky client behavior""throughput issue"client disconnection""application drop" and more.

Pic courtesy "Bad-fi"

Steps for Deploying a Good Wireless LAN:

Step 1: Information Gathering("THE INTERVIEW")
--Type of Environments
--Client device type to be used                                                
--Application to be used
--Expected growth vs Current growth 

#Access point to be used:
--Mounting concerns
--Coverage Vs Capacity planning
--Device Density
--Security Enterprise and Guest use

#Its all about the client:
--What clinet type & capabilities
--How many devices
--Application Requirements
--Determine Capacity Requirements
--Proper Floor plan and Scales

I would recommend try using capacity planner from Andrew Von Nagy

Step2: Predictive Survey

--Once you are on target with your data gathering  for designing the WI-FI, you should be good to go.
--You have Tool from Airmagnet and Ekahua planners  for predictive designing a WLAN.

Step3: Pre-Deployment Survey:

--A site visit comes handy before implementing the output design from the Predictive site survey tool based from our requirement.

--Here an example from Aaron Scott where he was told its an dry wall and what he found behind the dry wall during the onsite visit.

#Understand the Environment:

--Noise Floor
--Existing interference
--Structural attenuation

Step4: Validation survey

--After the deployment its important to run validate a post deployment survey to see if the network meets the client requirement in coverage Capacity and Application capacity for the business.
--Check the noise floor  not the RSSI. Having a good signal strength will not help the client to get good MCS rate. 
--It needs a better SNR for good MCS rate

Step5: Spectrum Analysis/Protocol Anlaysis

--The WiFi spectrum has to be analysed periodically to avoid the WiFi Network getting  choked by wifi and any other non wifi interference.
--These non wifi interference just uses all the airtime and makes the wifi devices life miserableness.
--You can use the spectrum analyzer from the Airmagnet and Ekahua to identify the source of interference.
--The interference from a microwave has the following signature patter which is compared with a no interference view.

--Protocol Analysis to be done, so you can find if an Rouge AP or Rouge Devices which is causing security threat can be figured out.
--You could use "Savvius Omnipeek" for packet captures and protocol analysis.

Basic RF Fundamentals

RF Basics:

Frequencies(Specific location in RF space):How often an RF wave cycles per sec
Waves(Actual medium we manipulate to send Data) components includes: Wavelength, Amplitude, Phase(in/out).

Radios(The radio do the job of transmitting and receiving data).

--Wavelength=360* movment of an RF wave
--Amplitude=powerleve of an RF frame
--Phase=The relationship between two signal based on when their alternate current raising and falling.
--Frequency=Number of wavelength in Sec.

Five RF Fundamental


2.4-->Lower Frequency (2.4 billion cycle/sec)

         Channel:5 Ghz

                            --5Ghz for wlan is divided into UNII band 1,2,3 
                            --ISM band is now added in UNII band 3
                            --Channel 169 is a 20mhz only channel.
                            --Channel 144 is just got added, no not much devices are using that.
      RF Behaviour:

                                --Behavior of RF defers based on the surface it impacts with.
                                --Reflection ,Absorption,Scattering,Refraction,Diffraction.
                                --Reflection and Absorption converts the RF into heat.
                                --These RF behavioral changes are taken advantage in N and AC networks                                          because of MIMO technologies. 

   RF Measurements:

                          --Inorder to connect at higher MCS rate the device needs to operate in higher QAM
                          --Device to operate at 64 and 254 QAM, it needs to get connected at high SNR

  RF Interference:

                            --When an external modulated or Un-modulated RF influences affect the ability of the                                RF receiver is called RF interference
                            --Interference happens at the receiver
                            --Low duty cycle interference can be tolerated.
                            --High duty cycle interference can wreak havoc on the channel

  RF Analysis :

                       --We have different type of interference and the non wifi interference are the ones which                          stays unknown mostly in our network.
                       --We have Tools which should be able to help you in finding out the wifi and non wifi                                 interference in you network.
                                   Tools for spectrum analysis and  site survey:
                                           AirMagnet Wi-Fi spectrum XT
                                           Ekahau Site Survey pro with planner
                                           metageek wispy DBX with channalyzer pro
                                           Metageek inSSIDer
                                           Xirrus WI-FI Inspector

Introduction to Wireless Local Area Network

Wireless Network:

        A  wireless local-area network (LAN) uses radio waves to connect devices such as laptops to the Internet and to your business network and its applications. When you connect a laptop to a WiFi hotspot at a cafe, hotel, airport lounge, or other public place, you're connecting to that business's wireless network.

Increases working efficiency and productivity.
Roaming support: extended on-line times 
-> universal access & seamless services

No new wiring and installation on difficult-to-wire areas
Offices, public places, and homes
Factories, vehicles, roads, and railroads

Reduced installation time
No cabling time
Easy setup

How are Wireless LANs (WLANs) Similar to (wired) LANs?

5 Essentials for High Density Wireless LAN

Its all about how well you design your wifi in the initial stage of Wlan life cycle. How much time spent on the wifi design.

1.High Signal Strength
2.High client Data Rate.
3.Disable legacy client(802.11b/g) /disable low data rate.
4.Maximum Spectrum usage and min overhead
*(Use 5ghz)
*Reduce channel overlap by strategic AP placement :Room based AP placement(mim CCI)
*Reduce extra ssids                                                   
5.You need to calculate the capacity(Atleast 2-3 years frm tr)
*No of clients.
*Distribution of clients(wr located)
*client types
*clients pipe i.e, special stream:mimo
*Application need