Cellular - Wifi Handoff

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Cellular - Wifi Handoff

• Robert Thompson

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What is Cellular to Wifi Handoff?

• It is the seamless handoff of a connection
  between cellular and wireless networks.

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Example

• A cellular phone user in the midst of a call
  should be able to enter an 802.11 network hotspot
  and be seamlessly handed off from a cellular
  network to the 802.11 network and back again when
  leaving the hotspot.

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Standards

• IEEE 802.21
• UMA(Unlicensed Mobile Access)/GAN(Generic Access
  Network)

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802.21

• Emerging IEEE standard
• Support algorithms to enable seamless handover
  between networks of the same type as well as
  different network types

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802.21 Supports

• GSM
• WiFi/802.11 networks
• Bluetooth
• GPRS (2.5G GSM)

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802.21
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802.21
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UMA/GAN

• Adapted by 3GPP in April 2005
• System to allow seamless handover between local
  networks and wide area networks

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UMA/GAN

• Local Network/Unlicensed spectrum
• Bluetooth
• 802.11
• Wide Networks
• GSM/GPRS
• UMTS

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UMA/GAN

• Cellular network stays the same.
• Once a LAN is detected a secure IP connection
  thru a gateway is made to a server called a GAN
  Controller(GANC).
• The GANC translates the signals to make it appear
  to be coming from another BSC.

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UMA/GAN

• When the handset moves from GSM to WiFi, the core
  network treats it as though it was a handoff
  between BSCs.

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UMA/GAN
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UMA/GAN Terms

• UNC - UMA Network Controller
• SGSN - Serving GPRS Support Node
• PLMN - Public land mobile network
• UMAN Unlicensed Mobile Access Network

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UMA/GAN
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UMA
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UMA/GAN

• Mobile identity on cellular network and wireless
  networks are the same.
• This means current core mobile network will
  remain the same. Lowers the cost to offer the new
  service.
• Independent of current Wifi technology.

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UMA/GAN Modes

• GERAN-only only cellular networks used.
• GERAN-preferred Cellular if available.
  Otherwise, Wifi is used.
• GAN-preferred Use a Wifi if in range. Otherwise,
  use the cellular network.
• GAN-only Use only the Wifi connection.

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UMA/GAN

• Nokia 6136 
• Samsung P200 
• Motorola A910 

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Advantages

• Better coverage
• Relieves congestion
• Combine Services

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Advantages

• For Subscribers
• Cheaper prices
• Convenient
• Fix coverage issues yourself

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Problems

• Two standards
• Industries are split
• Battery Life
• 2 hours

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Questions

• What is Cellular-Wifi handoff?
• Answer Seamless handoff between a cellular and
  another wireless network.
• What are the standards?
• Answer IEEE 802.21 and UMA/GAN
• How does a handoff work?
• Answer Much the same way as current BS to BS
  handoffs. See slide 16

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