Chapter 3: Introduction of Wireless and Mobile Systems (Part II)

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Chapter 3Introduction of Wireless and Mobile
Systems (Part II)

• Associate Prof. Yuh-Shyan Chen
• Dept. of Computer Science and Information
  Engineering
• National Chung-Cheng University

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Outline

• PCS
• WLL (Wireless Local Loop)
• LMDS (Local Multipoint Distribution System)

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PCS

• Personal communication service
• Developed out of the need for more capacity and
  design flexibility than that provided by the
  initial cellular systems
• PCS
• Narrowband service
• Offers many enhanced data service
• The data throughput remained at 9.6 kbit/s

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The Challenge of wideband PCS

• Wideband PCS for offering high-speed data has not
  yet been deployed
• The obvious issue
• is coexistence with the current PCS system
• The need for more base station due to reduced
  sensitivity cased by increased bandwidth
• Is the offering of subscriber units that can act
  as dual band units

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PCS

• PCS band was broken into A, B, C, D, E, and F
  blocks
• A, B, C blocks involved a total of 30 MHz, while
  the D, E, and F blocks are allocated 10 MHz.
• PCS license boundaries are defined as
  metropolitan trading areas (MTAs) and basic
  trading areas (BTAs).
• The MTA has several BTAs within its geographic
  region

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PCS

• There are a total of 93 MTAs and 487 BTAs in USA
• All the frequency allocations are duplexed

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U.S. cellular spectrum chart
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PCS spectrum allocation
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WLL (Wireless Local Loop)

• The WLL system, is different from the cellular or
  PCS systems in its application, which is fixed.
• The fixed service is often referred to as a local
  multipoint distribution system (LMDS) or
• A fixed wireless point-to-multipoint (FWPMP)
  system
• In many case, WLL is the same as LMDS and FWPMP
  in its deployment and application

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WLL system

• WLL is most applicable in areas where local phone
  service is not available or cost effective
• WLL is a system that connects a subscriber to the
  PTSN or PTT (local telephone company) using a
  radio link as its transport medium instead of
  copper wires

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WLL Example
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More common types of WLL systems

• Cellular
• PCS
• Cordless telephone (CT-2)
• Digital European cordless telecommunication
  (DECT)

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WLL

• For a developed country
• WLL allows for use of a cordless phone as an
  extension of the house phone or private branch
  exchange (PBX), which is an added convenience
• For a emerging country
• Has areas without any access to a communication
  service
• The use of WLL can create profound changes
  because it is quicker, easier, and less expensive
  to install than a regular landline system

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LMDS (Local multipoint distribution system)

• The LMDS is a unique wireless access system whose
  purpose is to provide broadband access to
  multiple subscribers in the same geographic area.
• The LMDS utilizes microwave radio as the
  fundamental transport medium and is not really a
  new technology

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LMDS

• The LMDS system allows multiple users to access
  the same radio spectrum
• The LMDS is a wireless system that employs
  cellular-like design and reuse with the exception
  that there is no handoff
• Multiple subscribers (customers) surrounding an
  LMDS hub or base station

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Generic LMDS system
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LMDS

• The LMDS is a point-to-multipoint system where
  multiple subscribers can access the same radio
  platform utilizing both a multiplexing method as
  well as queuing
• Through overbooking
• There are QoS issues and specific service
  delivery requirements

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LMDS

• Provide vastly greater bandwidth requirements and
  service to a larger population than
  point-to-point system utilizing the same spectrum
  can

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The key differences between mobile systems and
LMDS

• The ubiquitous coverage is not required
• Operator only provide service where the customers
  are actually located thereby maximizing the
  capital infrastructure effectiveness and
  minimizing operating expenses

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Example Multiple Customer Location/Dwelling Unit