http://www.wimaxforum.org/technology/downloads/WiMAX_to_Bridge_the_Digitaldivide.pdf
• While the gap is smaller, many rural
areas still have no ICT connection
http://www.wimaxforum.org/technology/downloads/WiMAX_to_Bridge_the_Digitaldivide.pdf
WiMAX: key points
• LOS range: 50km
• NLOS range: 8km
• Cost: Goal of $100 CPE (customer premise
equipment)
• NLOS allows indoor CPE installation
• Standardization
http://www.wimaxforum.org/technology/downloads/WiMAXNLOSgeneral-versionaug04.pdf
Combining several techniques
•
•
•
•
Subchannelization
Directional antennas
Diversity schemes
Adaptive modulation
– Flex to actual fading conditions, so don’t have to
budget for worst-case
• Error correction
• Power control
– Base station tells CPE how much transmit power is
needed, so don’t need to budget for worst-case
•
http://www.wimaxforum.org/technology/downloads/WiMAXNLOSgeneral-versionaug04.pdf
• Subscriber Units
• WiMAX subscriber units are available in both indoor and outdoor
versions from several manufacturers. Self-install indoor units are
convenient, but radio losses mean that the subscriber must be
significantly closer to the WiMAX base station than with professionally
installed external units. As such, indoor installed units require a much
higher infrastructure investment as well as operational cost (site lease,
backhaul, maintenance) due to the high number of base stations
required to cover a given area. Indoor units are comparable in size to a
cable modem or DSL modem. Outdoor units are roughly the size of a
textbook, and their installation is comparable to a residential satellite
dish. (from wikipedia.com)
How 802.16 is different from 802.11
• MAC layer: scheduling vs contention
• Range: kilometers vs 100s of meters
• Spectrum Allocation/licensing
•
Wikipedia.com
Namibia, N$500 = $72
•
http://www.mweb.com.na/index.php?fArticleId=1483811
VSAT Advantages
• Availability: VSAT services can be deployed anywhere having a
clear view of the Clarke Belt
• Diversity: VSAT provides a wireless link completely independent of
the local terrestrial/wireline infrastructure - especially important for
backup or disaster recovery services
• Deployability: VSAT services can be deployed in hours or even
minutes (with auto-acquisition antennas)
• Homogenity: VSAT enables customers to get the same speeds and
SLAs at all locations across their entire network regardless of
location
• Acceleration: Most modern VSAT systems use onboard
acceleration of protocols such as TCP ("spoofing" of
acknowledgement packets) and HTTP (pre-fetching of recognized
HTTP objects); this delivers high-quality Internet performance
regardless of latency (see below)
• Multicast: Most current VSAT systems use a broadcast download
scheme (such as DVB-S) which enables them to deliver the same
content to tens or thousands of locations simultaneously at no
additional cost
• Security: Corporate-grade VSAT networks are private layer-2
networks over the air
Wikipedia.com
VSAT disadvantages
• Latency: Since they relay signals off a satellite in geosynchronous
orbit 22,300 miles above the Earth, VSAT links are subject to a
minimum latency of approximately 500 milliseconds round-trip. This
makes them a poor choice for "chatty" protocols or applications such
as online gaming
• Encryption: The acceleration schemes used by most VSAT systems
rely upon the ability to see a packet's source/destination and
contents; packets encrypted via VPN defeat this acceleration and
perform slower than other network traffic
• Environmental concerns: VSATs are subject to signal attenuation due
to weather ("rain fade"); the effect is typically far less than that
experienced by one-way TV systems (such as DirecTV or DISH
Network) that use smaller dishes, but is still a function of antenna
size and transmitter power and frequency band
• Installation: VSAT services require an outdoor antenna installation
with a clear view of the southern sky; this makes installation in
skyscraper urban environments or locations where a customer does
not have "roof rights" problematic
Wikipedia.com
VSAT training
• Fees for participants based in Nigeria:
• NGN 50 000 per person.
NGN 48 000 per person for two per company.
NGN 45 000 per person for three to nine people per
company.
($1 = NGN 132, NGN50000 = $410)
• Fees for International Participants (participants
attending from outside Nigeria):
US$ 550 per person.
US$ 530 per person for two per company.
US$ 520 per person for three to nine people per
company.
•
http://www.jidaw.com/vsattrain/index.html
The satellite dish
•
http://www.jidaw.com/vsattrain/index.html
• minimum US$1800-2000 per mbps per
month for satellite
• SAT3: US$7,000 – US$15,000
(SAT3/WASC/SAFE Consortium is an international fibre that goes from
Portugal to South Africa and out across the Indian Ocean to Asia)
http://fibreforafrica.net/main.shtml?x=4051583&als[MYALIAS6]=Satellite%20vs%20fibre:%20different%20costs%20for%20different%20things&als[select]=4051
582
• Rural Satellite VSAT Market in
Middle East and Africa
• 2002 : 7,000
• 2006 : 60,000
http://www.tmcnet.com/usubmit/2007/04/25/2553510.htm