WiFi Architecture
Contents
1. Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 3 m Event Site WiFi Testing 1 e Planning days before the event will minimize surprises on the day of the event Discuss requirements with the site s network administrator Test with multiple tablets and laptop Test from many locations corridors cafeteria rest rooms Perform Stress Test to see network behavior under load e Sometimes routing will be blocked between WiFi clients for security reasons thereby preventing tablets access to the GMS laptop This does not affect Cloud Mode e Sometimes a WiFi system will be configured to support multiple 255 255 255 0 24 segments and routing may be blocked between segments Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 4 Typical site layout Radio blocking cinderblock wall Rooms Pit Area 230 x 230 110 x 200 Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Many events are in high school gyms Arena and pit areas are in the same line of sight area Judge s room amp cafeteria may be adjacent One WiFi AP will typically cover all areas quite well Page 5 More complex site layout eal Radio blocking cinderblock walls gt a L 110 x 200 Pit Area 130 x 130 400 ft end to end Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Sometimes there are walls between important areas We need to have WiFi coverage in2. all areas Judge s rooms may be ona different floor Cafeterias need to be covered Staff expect GMS to work there Page 6 rs WiFi Access Point locations Vee Sept 21 2013 2013 Rajaram Pejaver MyFon Inc e Three access points will provide sufficient coverage at most events e Walls amp floors can block or reflect signals Page 7 rN Transmission range lee e Typical Wifi range indoors is about 80 150 e A mobile device has to transmit only 80 to the nearest AP e Try to place APs to optimize coverage e Place AP as high up as possible 80 ft Mm 400 ft end to end Yt Or Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 8 Wired backbone network Sept 21 2013 2013 Rajaram Pejaver MyFon Inc 802 11 LAN cables connect access points Use 200 CAT 5 cables run along corridors Connect laptops to APs using a Ethernet cable in Judge s room and at LRI station Wired laptops reduce WiFi traffic by 50 A More is better lee e Can easily extend to more than 3 Access Points if needed e Multiple hops on the wired network are OK e A star configuration is simple but not necessary Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 10 WiFi G Channels 4234 5 67 8 9 10 4412 13 14 2 412 2 437 2 462 2 484 82400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2 500 GHz GHz GHz GHz GHz GHz GHz GHz GHz GHz
3. GHz 22 MHz e WiFi G 2 4 GHz has 3 good non interfering channels Shown in blue above Channels 1 6 and 11 Avoid other channels shown in red Configure APs to use these channels for FRC events 5 GHz channels work fine too use them for FTC FLL events They are not yet approved by FIRST for FRC Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 11 Channel assignment Vee e Assign channels to APs so that channels do not interfere Scan for signals from other WiFi APs and avoid using the same channels Or simply use Auto Channel scan 5GHz WIFI N Supports 24 non overlapping channels Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 12 AP configuration concepts lege e One AP will act as the Router t allocates DHCP IP addresses for all devices It connects to the Internet if available e All other APs function as Bridges They extend the WiFi range e All APs will have the same SSID and Password Allows mobile devices to roam between APs e Automatically connect to closest AP SSID should not be broadcast e But they are not a big secret e They can be seen by anyone who has a GMS tablet Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 13 AP Routing Example I WAN WiFi Router 10 10 111 2 WiFi Bridge e 10 10 111 3 WiFi Bridge 10 10 111 11 Judge s lt eerie Station 10 10 111 12 ee f ae In Judge s Pit
4. the same channel e We do not reveal the WiFi shared key password All tablets are pre configured with the key and given to users WiFi key cannot be extracted from configured tablets e Using MAC Address filtering can help sometimes e Security details http gms pejaver com Security htm Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 20
5. Administrator a room in Pit Area E E E e DD WRT is really nice but DAP 1522 can be used too e Configured as AP Router and as AP Bridges e All devices wired and wireless are on 10 10 111 0 24 e Results in a flat LAN e Allows UDP broadcasts to devices e Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 14 Configuring a DAP 1522 e Either Hardware Version A old or Version B current can be used e Configure one AP as the Router and rest as Bridges e Common Settings for both Router and Bridges Set sliding switch on back to AP Mode not Bridge not Auto Reset the DAP 1522 if necessary by poking a pin into Reset hole e A DAP 1522 User Manual is available at http s3 amazonaws com szmanuals a316344a9c846a9 75925 794f04 1ccOc Use an Ethernet cable to connect a PC to a DAP 1522 port e Set PC s IP address to static 192 168 0 10 use SetStaticIP bat in GMS directory Login to the DAP 1522 using a browser e URL 192 168 0 50 User Name Admin Password lt blank gt Set new password e Maintenance gt Admin gt Password lt yourPassword gt lt press Save gt Configure DAP 1522 to get its WAN IP address via DHCP e Setup gt Network Settings gt LAN Connection Type DHCP Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 15 Configuring a DAP 1522 e Common WiFi settings for both Router and Bridge continued Setup gt Wireless Settings gt Manual Wireless Setup gt Wire
6. WiFi networking for GMS Rajaram Pejaver Sept 21 2013 For more info see http gms pejaver com Overview htm WiFi configuration guide http qms pejaver com WiFiConfig htm FIRST the FIRST logo FRC and Gracious Professionalism are registered trademarks of the United States Foundation for Inspiration and Recognition of Science and Sept 21 2013 Technology FIRST Everything else is mine unless it is already someone else s lin which case it is theirs whosoever they are Role of WIFI lege e GMS uses WiFi for communications Tablets communicate only with laptops Tablets do not talk to each other 2 4 Gig 802 119 is used 5 GHz is also OK e FRC FTC amp FLL robots are not affected Different bands and channels are used FRC FMS uses 5 GHz FITC FLL use 2 4 GHz e Communications are secure amp protected Traffic volume is low and load resistant Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Preexisting Event Site WiFi e Schools often have WiFis installed Open access may be available for guests Separate private SSIDs for staff e Advantages no WiFi set up is necessary major win the coverage is usually good major win Internet access Is usually available major win e Disadvantages Testing will be required to determine its suitability see next page SSL encryption must be used minor hassle wired access may not be available for the laptop no big deal
7. checked Press Save Settings Connect a Bridge Ethernet port to Router Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 17 Connecting Devices to AP e Windows PC stations If possible connect via wired Ethernet to a AP e Set PC to Obtain an IP address automatically DHCP e Disable WiFi on PC Don t allow multiple routes to tablets Otherwise connect PC to WiFi network e Android Settings gt WiFi set to ON Settings gt WiFi gt Click SSID if it is visible in the list Otherwise touch the icon to add a network e Type in the SSID e Select security WRA WPA2 e Click Save Enter WiFi Password and click Connect lt Need to test WiFi Protected Setup on DAP 1522 before recommending it gt Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 18 rN AP Device Selection lege Low end routers lack some useful features e DNS or DNSMasq Allows names to be used for LRI Station SSL security certificates can use name not IP e Disabling NAT router mode vs gateway Allows UDP notifications to be sent to clients e Predictable routing e Suggest re flashing an inexpensive router to DD WRT Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 19 Capacity amp Security KEJI e GMS bandwidth usage is low and bursty e There are only about 50 users on the GMS WiFi net e f a transmission fails GMS queues and re transmits it e Contention is mainly from other APs on
8. less Network Settings e Enable Wireless Checked e Wireless Network Name SSID Staff1 e 802 11 Band 2 4GHz Use 5GHz for FTC FLL events e 802 11 Mode Mixed 802 11n 802 119 e Enable Auto Channel Scan Checked Uncheck to manually select Wireless Channel if you know what you are doing e Channel Width Auto 20 40 MHz e Visibility Status Invisible Setup gt Wireless Settings gt Manual Wireless Setup gt Wireless Security Mode e Security Mode WPA Personal e WPA Mode WPA2 Only e Cipher Type TKIP e Passphrase lt xxxxxxxx gt at least 8 chars lt Press Save Settings gt Sept 21 2013 2013 Rajaram Pejaver MyFon Inc Page 16 Configuring a DAP 1522 e Configure one DAP as a Router Advanced gt DHCP Server gt DHCP Server Settings e Enable DHCP Server Checked e IP Assigned From 10 10 111 15 for mobile devices e Default Subnet Mask 255 255 255 0 e Default Gateway 10 10 111 1 Press Save Settings e Reset PC s IP address to DHCP use RestoreDHCP bat in GMS directory Optionally assign static IP addresses for laptops as follows Advanced gt DHCP Server gt DHCP Reservation e Enter MAC address as 12 23 34 45 56 67 your PC MAC address e Enter IP address as 10 10 111 11 or 12 13 Press Save Settings Connect WAN Ethernet port to the Internet if available e Configure other DAPs as Bridges Advanced gt DHCP Server gt DHCP Server Settings e Enable DHCP Server Un
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