Kevin Fall Intel Labs, Berkeley Microsoft Connecting the Next
Billion Workshop 28/29-Aug-2010 Agra, India [email protected] 1
Developing Long Distance WiFi for Rural and Developing World
applications
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A Parallel Effort at Intel / UCB 2 Timeframe: 2005-2009 [mostly
05-08] UC Berkeley: students doing WiLD research Intel:
collaborators building product in parallel Quick Summary: UCB:
Algorithms and s/w prototype on x86 platform NSDI WiLDNet Paper
UCB: Algorithms and hw/sw prototype on ARM Rural Connectivity
Platform (RCP) Product (Zcom) Some other work as well
Slide 3
Why WiFi 3 Widely understood / deployed system Inexpensive,
high-power hardware Compatible directional antennas Unlicensed
operation Some alternative spectrum options (depends on vendor)
Ability to be coupled with embedded PC Opportunity for innovation
and research Of interest to Intel and TIER project Used in p2p and
p2p-multihop setups
Slide 4
Why Not WiFi 4 Designed for office environment Stop-and-wait
(ACKs): degrades tput w/dist Unnecessary beacon/join protocol
Resists interference poorly CSMA/CA with CCA is conservative [low
tput] Interference from nearby devices Driver guts are proprietary
Limits innovation opportunities / research Setup/maintenance can be
challenging
Slide 5
Recommended Solutions 5 Switch from Stop-and-Wait to selective
ACK / repeat (bulk ACKs) improve channel utilization Switch from
CSMA/CA (DCF) to slotted TDMA Also disable CCA no interference (but
not so friendly) Can use SW (OS) timer or HW (based on beacon)
Modify mgmt frames to disable random association, select master and
timing info Use simultaneous xmit across devices at multi-hop nodes
(idea from 2P protocol) FEC or other error control sometimes
useful
Slide 6
What is the RCP? 6 IP Router and Application Server Intel IXP
425 network processor Atheros-based 802.11 a/b/g mini-PCI cards 512
MB compact flash storage customized Linux OS (later, FreeBSD)
outdoor enclosure Antennas Power supply using PoE
Slide 7
The Base Hardware 7 Gateworks Avila GW2348-4 Intel IXP 425/533
Mhz 64MB SDRAM/16MB Intel Strataflash 4x Type III mini-PCI [4.5 W
avail to each] 2x 10/100 Wired Ethernet compact flash socket 1KB
serial EEPROM, GPIO battery backed-up RTC voltage/temp monitor
available to software watchdog timer thermally-activated fan
controller 9-48VC via PoE or connector ; 5W typical -40C to +85C
operating temp range
Slide 8
Hardware Additions/Mods 8 Senao/Engenius NMP8602+ (later
Ubiquiti cards) mini-PCI 802.11 a/b/g up to 400mW xmit power -98dB
recv sensitivity 2x U.FL antenna connectors Atheros AR5006 (AR5414)
chipset 0C-+55C operating range -20C +70C storage range Base
hardware mod PoE on both Ethernet
Slide 9
The Box 9 Outdoor enclosure based on WRAP box www.mini-box.com
modified by Gateworks paint 4x N holes, connector/pigtails mounting
plate fan weatherized connector housings
Slide 10
Box on Pole 10
Slide 11
The Software 11 Development platform started with uCLinux
Extensive modifications special hw-based TDMA WiFi driver
autoconfiguration and set-up web gui remote firmware
upgrade/install Provides p2p link, AP capability, time
synchronization, DHCP, DNS, NAT Experimental multicast version of
dnsmasq find which RCP device has this address please
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12
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HW Prices [retail, low qty] 13 Boards: $284, WiFi: 2x$86 Cases:
$160, Power Injector: $29 Total:$645 Does not include antennas,
which vary: rubber duck: $15 directional: $50-$100 omni:
$30-$80
Slide 14
And Finally to Product 14 Zcom ZC-3625-5-23 and ZC-3625-55-23
Overview Designed for outdoor environment application, Value series
ZC-3625-5-23 wireless professional equipment adopts Intel RCP
concept to provide an affordable and reliable rural connectivity
solution. With rigorous design: IP67 watertight enclosure, Level 17
Beaufort Scale and high reliability surge protection, it provides
high reliable, stable transmission and outstanding performance in
almost any harsh outdoor environment.
Slide 15
Splashpage 15
Slide 16
Some Learnings 16 Research experimentation and prototype
difficult to share as target for product development
Auto-configuration and GUI challenges not to be underestimated
Remote update / recovery is crucial Power, poles, antennas and
deployment can be tricky Many people are conditioned to know WiFi
is office only
Slide 17
Future Possibilities (we didnt pursue) 17 Ad-Hoc/Mesh Operation
IPv6 beyond 802.11 a/b/g Security beyond WPA2 Antenna / aiming
wizard & guide Other languages Audio (e.g., for help &
alignment) Services: cache, sip
Slide 18
Thanks / Credits 18 Eric Brewer and TIER group (UC Berkeley)
Sam Leffler (contractor, now at Google) Matt Podolsky (contractor,
now at UC Berkeley ) Willy Agatstein, Jeff Galinovsky, Tony
Salvador, Larry Carr, David Sidhu, Albert Teng (some formerly
Intel/EMPG) Alan Mainwaring (Intel Labs Berkeley) Ron Eisworth
(Gateworks) Thanks for listening