Base Station Location and

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Base Station Location and Service Assignment
in W-CDMA Networks
Joakim Kalvenes1 Jeffery Kennington2 Eli
Olinick2 Southern Methodist University 1Edwin
L. Cox School of Business 2School of Engineering
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Wireless Network Design Inputs

• Potential locations for radio towers (cells)
• Hot spots concentration points of
  users/subscribers (demand)
• Potential locations for mobile telephone
  switching offices (MTSO)
• Locations of access point(s) to Public Switched
  Telephone Network (PSTN)
• Costs for linking towers to MTSOs, and MTSOs to
  PSTN

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Wireless Network Design Problem

• Determine which radio towers to build (base
  station location)
• Determine how to assign subscribers to towers
  (service assignment)
• Determine which MTSOs to use
• Maximize profit revenue per subscriber served
  minus infrastructure costs

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Wireless Network Design Tool
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Code Division Multiple Access (CDMA)Technology

• The basis for 3G cellular systems
• Channel (frequency) allocation is not an explicit
  issue since the full spectrum is available in
  each cell
• New calls cause incremental noise (interference)
• New calls admitted as long as the signal-to-noise
  ratio stays with in system limit
• Power transmitted by handset depends on distance
  to assigned radio tower
• Tower location and assignment of customer
  locations to towers must be determined
  simultaneously

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Power Control Example
Received signal strength must be at least the
target value Ptar
Signal is attenuated by a factor of g13
Subscriber at Location 1 Assigned to Tower 3
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Signal-to-Interference Ratio (SIR)
Tower 3
Tower 4
Subscriber at Location 1 assigned to Tower 3
Two subscribers at Location 2 assigned to Tower 4
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Constants and Sets Used in the Model

• L is the set of candidate tower locations.
• M is the set of subscriber locations.
• gml is the attenuation factor from location m to
  tower l.
• is the set
  of tower locations that can service customers in
  location .
• is the set of customer locations that
  can be serviced by tower l.

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More Constants and Sets Used in the Model

• dm is the demand (channel equivalents) in
  location
• r is the annual revenue generated per channel.
• is the FCC mandated minimum service
  requirement.
• is the cost of building and operating a
  tower at location .
• SIRmin is the minimum allowable
  signal-to-interference ratio.
• s 1 1/SIRmin.

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Decision Variables Used in the Model

• yl 1 if a tower is constructed at location l
  and zero, otherwise.
• The integer variable xml denotes the number of
  customers (channel equivalents) at
  that are served by the tower at location
• The indicator variable qm 1 if and only if
  location m can be served by at least one of the
  selected towers.

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Integer Programming Model

• The objective of the model is to maximize profit
• subject to the following constraints

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Integer Programming Model
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Quality of Service (QoS) Constraints

• For known attenuation factors, gml, the total
  received power at tower location l, PlTOT , is
  given by
• For a session assigned to tower l
• the signal strength is Ptarget
• the interference is given by PlTOT Ptarget
• QoS constraint on minimum signal-to-interference
  ratio for each session (channel) assigned to
  tower l

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Quality of Service (QoS) Constraints