AirMagnet Wireless LAN Design

Transcription

1 AirMagnet Wireless LAN Design Source: AirMagnet Survey Pro + Spectrum XT Tom Woodyer Senior Product Specialist APAC Q3, 2010

2 Todays agenda. Understand the media Wireless Network Basics Types of Wireless Networks Data, Voice, RFID or Mixed Purpose Why perform a survey and what to survey for? The importance of Spectrum Analysis Tools and Requirements for Surveying Survey Process

3 Understand the Media 2.4 and 5 GHz WLAN s utilize radio communication to transfer data at varying data speeds. Unlike wired networks the media is shared andnot not protected Many different devices can use the air both planned and un planned Have to take into account neighbors use of WiFi and also environmental interference

4 Understand the Media (cont) Shared air Only one device can talk at a time (half duplex) No collision detection (CSMA/CD versus CSMA/CA) Overhead on data exchange Unpredictable performance How many users. More users typically means less throughput Air quality issues Signal strength effects data rate Further away from AP means lower data rate

5 Understand the Media (cont) Standards b and g 2.4 GHz b up to 11 Mbps gup to 54 Mbps a 5 GHz a up to 54 Mbps n (Latest Standard) 5 GHz (Also ratified in 2.4 but this is typically just for home deployments) n up to 600 Mbps Signal strength (dbm) not the only indicator of success HIGHLY Complex compared to a/b & g

6 Wireless Network Basics Access Points ( AP + Antenna ) AP s areconfigured to operate on a single Channel within either the 2.4 or 5 GHz frequency bands Some AP s have two radios and can operate on one channel in 2.4 GHz and one channel in 5 GHz When configuring AP s we must chose a channel with minimal i linterference and also the power to transmit. Transmit power controls the area covered by an AP.

7 Wireless Network Basics (cont) Channels Both 2.4 and 5 GHz are split into multiple channels 2.4 has 14 channels of which only 3 do not overlap. Non overlapping channels are important as these do not cause interference and therefore do not degrade performance. 5 GHz has over 200 channels of which 8 channels do not overlap. More non overlapping channels means it is possible to install a higher density of AP s without causing channel interference.

8 Wireless Network Basics (cont) AP s are deployed to avoid AP s on non overlappingoverlapping channel overlap channels can co exist

9 Types of Wireless Networks Dt Data Laptop and Desktop access to WiFi network for normal office work. High throughput and streaming data applications will need higher density of AP s Voice High signal quality (Normally around 65dbm) Low number of users per AP Minimum data rate of 11Mbps High AP density and AP coverage areas must have overlap RFID High density with placements to provide good triangulation

10 Types of Wireless Networks (cont) Special consideration is needed for voice (VoIP) networks. It is important that AP coverage has a reasonable overlap to allow devices to roam

11 The Importance of Spectrum Analysis The 2.4 GHz frequency band is highly congested as it is unlicensed spectrum. Many devices use 2.4 not just WiFi You can perform the best survey possible, defining the correct AP placements, density and configuration BUT if you miss some significant RF interference the WLAN will perform badly Measure twice cut once!

12 Examples of Spectrum Interference Bluetooth Devices Microwave (Leaking) (non-leaking) Portable Phones 900 MHz 2.4 GHz 58GHz 5.8 Video Monitors Wide Band Jammers Wide Band Narrow Band

13 History Wireless Network Design Old Way Minimum # of Access Points Maximum Power 30+ Users per AP Bandwidth what Bandwidth New Way <10 Users per AP Minimum Power Lots of Access Points Bandwidth (& Signal Quality) is Paramount

14 Why Perform a Wireless Survey Without a proper p site survey it will difficult to determine costs to implement the wireless LAN. Money and time may be wasted on implementing inappropriate hardware incorrectly. Don t waste cap ex budget on unneeded equipment The wireless LAN may never work properly resulting in frustrated users. Ensure the network delivers the required level of coverage and performance to meet theusers needs.

15 Define the Goals of the Wireless Network Understand the business needs of the wireless LAN: What will the WLAN be used for? Bandwidth & Roaming requirements Determinesignal coverage and control: Where RF coverage should and should not be Understandand meet any security requirements Regulatory requirements Type and classification of data being transferred

16 Type of Wireless Surveys Live Site Survey Survey engineer uses a single AP Goes to site, positions and enables AP Walk the site to plot RF coverage of test AP Move the AP and then repeat the process until good AP placement are found and the whole site is covered Virtual Site Survey (Planned) Obtain floor plan and model in RF planning tool Easy to try out different AP configurations and placements Once planned go to customer site to test sample deployments

17 Prepare to Survey Obtain detailed floor plans of the survey site Understand number of users to be supported What arethe user bandwidth requirements Where are areas of high user density Meeting, TrainingandConference and rooms Canteen and Break areas What type of network is it? (Data, Voice, RFID) Are there security requirements such as no WiFi locations

18 Survey Process For live site survey you will need to obtain a scaled floor plan Engineer should mark areas where AP s should not be deployed Also good to mark cable closets to ensure viable cable runs

19 Survey Process (cont) Live Site Survey Engineer walks the site whilstrecording location. Survey application listens to the test AP and records signal and throughput results against location. Once good AP placement is found engineer move AP to next location and repeats Source: AirMagnet Survey Pro

20 Survey Process (cont) Live Site Survey After multiples AP placements have been testing the survey tool can be used to plot coverage for: Signal SNR Throughput Interference Create design reports for deployment and configuration teams Source: AirMagnet Survey Pro

21 Site Survey Process (cont) Virtual Site Survey A floor plan is loaded into survey toolandbuilding materials are drawn to create map of how RF is likely to propagate Source: AirMagnet Planner AP s are placed on the floor plan and then signal strengths and other factors can be calculated

22 Site Survey Process (cont) Virtual Site Survey Benefits of Virtual over Live Speed: Very quick to produce survey results Allows testing of many different AP configurations Placement Channel Tx Power Limited time on customer site reduces staff overhead and access problems Can plan for building even before construction Cautions for Virtual surveying Unlike a live site survey results are calculated and therefore are only as good as the operator of the planner software

23 Thank you For more information please see us on the Fluke Stand or contact: Tom Woodyer Eric Lie