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Chapter 9
Fundamentals of Communication
Networks
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
1
Communication Network
Architecture
 Communication devices
 Network nodes
 Communication links
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Protocol Architecture
 Break communication task down into
subtasks
 Divide-and-conquer approach
 Hierarchical layers
 Protocols
 Define subtask operation within a layer
 TCP/IP protocols
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Switching Technologies
 Circuit switching
 Circuit establishment
 Data transfer
 Circuit termination
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Switching Technologies
 Packet switching
 Store-and-forward
 Network resources allocated on-demand
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Switching Technologies
 Virtual circuit switching
 Combining features of circuit switching
and packet switching
 Virtual circuit pre-established
 Link bandwidth shared efficiently
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Encapsulation and Multiplexing
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Naming and Addressing
 Domain name
 Domain Name System (DNS)
 Port number
 Well-known port numbers
 Ephemeral port numbers
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Naming and Addressing
 IP address
 Subnetting
 Socket: combination of an IP address
and a port number
 Medium Access Control (MAC)
address
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Multiple Access
 Media shared in a broadcast network
 Rules for hosts to access the media
 Media Access Control (MAC)
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Routing and Forwarding
 Network layer function
 Maintaining network topology
information
 Routing table
 Forwarding packets
 Packets forwarded hop-by-hop
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Congestion Control and Flow
Control
 Congestion control
 Router congestion
 Flow control
 Fast transmitter and slow receiver
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Error Control
 Checksum in TCP/IP
 Cyclic redundancy check (CRC) in
Ethernet
 Sequence numbers to detect lost
packets
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
New Challenges in Wireless
Networks
 Wireless transmissions
 Different concept of communication link
 Coupled channels
 Capacity limited by SINR
 Mobility
 Handoff in infrastructure-based wireless
networks
 Rerouting in infrastructureless wireless
networks
 Energy efficiency
 Significant impact in every layer
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Mobility Modeling
 The Random Waypoint Model
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Mobility Modeling
 Speed distribution
 Average speed
 Location distribution
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Perfect Simulation
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Power Control and Multiuser
Diversity
 Uplink of a infrastructure-based wireless
network
 Received signal at the base station is
 Frequency flat Reyleigh fading
 Objective
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Power Control and Multiuser
Diversity
 No power control
 Perfect power control
 Optimal power control
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Power Control and Multiuser
Diversity
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Multiple Access Schemes
 Classification of multi-access schemes
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Polling
 Queueing system with one server and m
stations
 Finite buffer and infinite buffer
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Polling
 Service policies
 Limited service
 Exhaustive service
 Gated service
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
ALOHA and Slotted ALOHA
 ALOHA
 A station transmits a packet whenever it
wants to
 Maximum throughput 0.184
 Slotted ALOHA
 Time is divided into slots
 Maximum throughput 0.368
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
CSMA
 User senses the medium before start
transmission
 Hold packets until the medium is free
 Strategies
 1-persistent CSMA
 Non-persistent CSMA
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
CSMA
 An example of collision in CSMA
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
CSMA
 A typical cycle of CSMA operation
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
CSMA/CA
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Hidden Terminal and Exposed
Terminal Problems
 Hidden terminal problem
 Exposed terminal problem
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Routing, Energy Efficiency and
Network Lifetime
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Maximizing Network Lifetime
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Congestion Control in Wireless
Networks
 TCP is not suitable for wireless networks
 Basic assumption: all loss are due to buffer
overflow
 Suffers from frequent route failures and MAC
layer contention
 TCP enhancements
 Link layer mechanisms
 Split TCP
 Explicit notification schemes
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Cross-layer Design and
Optimization
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)
Cross-layer Principles
 Interactions and the law of unintended
consequences
 Dependency graph
 Timescale separation and stability
 The chaos of unbridled cross-layer
design
“Cognitive Radio Communications and Networks: Principles and Practice”
By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)