Subscriber Units

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• While the gap is smaller, many rural
  areas still have no ICT connection
                          WiMAX: key points
• LOS range: 50km
• NLOS range: 8km
• Cost: Goal of $100 CPE (customer premise
• NLOS allows indoor CPE installation
• Standardization
    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
• 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
           How 802.16 is different from
• MAC layer: scheduling vs contention
• Range: kilometers vs 100s of meters
• Spectrum Allocation/licensing

         Namibia, N$500 = $72

                    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
• 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
                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
                                      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
 ($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
                                The satellite dish

       • 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)[MYALIAS6]=Satellite%20vs%20fibre:%20different%20costs%20for%20different%20things&als[select]=4051
• Rural Satellite VSAT Market in
  Middle East and Africa
• 2002 : 7,000
• 2006 : 60,000

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