vertical handover nawshad rehan rasha 1014052020
TRANSCRIPT
INTRODUCTION
What is handover?
Changing the point of connection while communicating
Why is handover needed?
Mobility
User preferences
What is the objective?
Handover procedure without a users notice
”break before make”
Hard Handover
Old connection is broken before a new connection is activated
Primarily used in FDMA and TDMA systems (e.g. GSM)
Different frequency ranges used in adjacent cells to minimize the interference
When to perform hard handover?
E.g. based on measurements of the signal quality
Different schemes to avoid unnecessary handovers
”make before break”
Soft Handover
New connection is activated before the old is broken
Used in UMTS to improve the signal quality
Uplink and downlink signals may be combined for better signal
A mobile may in UMTS spend a large part of the connection time in soft handover
Better connection reliability
Horizontal Handover
Horizontal handover is when a mobile terminal changes its point of connection within the same type of network
E.g. from a cell to another in GSM
E.g. from an access point to another in WiFi
Reasons for handover
Worse signal quality or loss of signal
Traffic load balancing
Cost
BSC
BS1 BS2 BS3
BSC
BS1 BS2 BS3
BSC
BS1 BS2 BS3
Vertical Handover
Vertical handover is when a mobile terminal changes its point of connection in a different type of network
E.g. from a wired Ethernet connection to an access point in WiFi
E.g. from an access point in WiFi to a cell in UMTS
Reasons for handover
Worse signal quality or loss of signal
Performance requirements (bandwidth)
Cost
Power consumption
Vertical Handover
Ethernet
WiFi
WiFi
UMTS
Ethernet
WiFi
UMTS
Ethernet
WiFi
UMTS
Ethernet
WiFi
WiFi
UMTS
Ethernet
WiFi
UMTS
Ethernet
WiFi
UMTS
Ethernet
WiFi
UMTS
Ethernet
WiFi
UMTS
Vertical Handover
In order to sustain connection and service in heterogeneous wireless environment, vertical handover is necessary. Now-a-days research focus is to optimize vertical handover so that optimized and application specific handover can be made possible.
Vertical handover refers to automatic switching the communication/data session from one technology to the other.
Vertical handover may be referred to a process of transferring call connected to a network/data session from one channel connected in a cell to the core network of another.
BSC
BS1 BS2 BS3
1. Connect to BS1 and start conversation2. Moving out of BS1’s coverage – connect to BS23. Moving out of BS2’s coverage – connect to BS34. Conversation ended – still within BS3’s coverage
Ethernet
WiFi
WiFi
UMTS
Ethernet
WiFi
UMTS
Ethernet
WiFi
UMTS
Ethernet
WiFi
UMTS
Ethernet
WiFi
UMTS
1. Wired connection at the working desk2. Moving indoor3. Moving outdoor4. Moving into a hot-spot
Difference between Vertical/Horizontal Handover
Vertical Handover
Horizontal Handover
Access Technology Changed Not
changed
QoS Parameters May be changed Not
changed
IP Address Changed Changed
Network Interface May be change Not
Changed
Network Connection More than on connections Single
connection
12
Handoff Metrics
Horizontal HO – mainly use received (RSS) to decide the handoff…
But Vertical HO? RSS?Offered bandwidth? Price?Power consumption?Speed? ….
14
Why Vertical Handover
Cost/Capacity/Coverage…..
If a laptop might be able to use both a high speed wireless LAN and a cellular technology for Internet access.
Wireless LAN connections generally provide higher speeds
benefit of utilizing the higher bandwidth and lower cost
Cellular technologies generally provide more ubiquitous coverage.
better mobility support and larger coverage
The laptop user might want to use a wireless LAN connection whenever one is available, and to 'fail over' to a cellular connection when the wireless LAN is unavailable.
Vertical Handover decision
As incorrect handoff decision may degrade the quality of service
even break off current communication
Decision depending upon multi-parameter handoff metrics.
Challenges in Vertical Handover
Multi-mode devices
Power consumption
QoS
Available capacity
Security
Timing
The business model
Session continuity
Input Parameters for VHD
Available Bandwidth (BAV)
Speed of mobile terminal (VMT )
Number of Users (UN)
Received Signal Strength (RSS)
Battery Level (BL)
Cost of operation (C)
Traffic Type ( TT )
Vertical Handoff Process
Three main phases:
Initiation: mobile terminal (or network controller) must know which wireless networks are reachable.
Decision: selection, through a VHO algorithm, of the access point, on the basis of proper performance metrics (RSSI, network connection time, available bw, power consumption, cost, security level, user preferences)
Execution: signaling operations to re-establish connection and carry out data transfer .
It handles all the connections in same manner. When all
TCP/IP connection automatically transfers from one interface
to another, in this situation only one wireless interface (the best
one) is used at that moment.
The second limitation of vertical handover is that vertical
handover need the same network interface. All the wireless
interfaces must be used as part of the same Mobile IP and DNS
infrastructure because mobile nodes and peers must be able to
reach the Mobile IP and DNS server.
20
LIMITATIONS OF VERTICAL HANDOVER