Wireless Communication Networks

1
Wireless Communication Networks

• Tzu-Chieh Tsai
• Department of Computer Science
• National Cheng-Chi University

2
Outline

• Background Introduction
• Cellular
• IEEE 802.11
• CDPD
• Recent work Mobile Police Information System

3
Introduction

• Layers
• physical layer
• data link layer
• MAC(Medium Access Control sublayer)
• Network layer (Routing, etc)
• Transport layer (Flow control, etc)
• Packet switching(store and forward) vs. circuit
  switching dynamic bandwidth

4
Introduction (Physical layer)

• Transmit power vs. connectivity
• multihop vs. single hop
• multiuser and near-far problem
• spatial reuse vs. transmit power
• A B C increase
  power A B C

5
Introduction (Data link layer)

• Two types of control are generally considered
• acknowledgement mechanisms (ARQ)
• forward error correction (FEC) coding
• Both ARQ and FEC are combined together to achieve
  an adequate level of link performance, usually.

6
Introduction(MAC layer)

• ALOHA
• random access, simple
• CSMA (Carrier Sense Multiple Access)
• CSMA/CD is not applicable
• TDMA (Time Division Multiple Access)
• CDMA (Code Division Multiple Access)

7
Introduction (Routing)

• A vast amount of literature Bellman-Ford,
  Dijkstra, distributed mobile routing(Corson and
  Ephremides 1995), and bandwidth routing (Gerla,
  1986)
• key issues
• how to choose an appropriate routing method, and
  how to spread minimum routing information to
  achieve efficient packet forwarding
• how much mobility such a routing scheme can
  support

8
Introduction (Flow control)

• dynamics of packet radio and channel sharing
  provides challenges
• admission control for a circuit assures that
  network resources will not be overtaxed and flow
  control when available resources are limited
• congestion control for connectionless traffic
  detection of congestion by measuring delay
• considerable research is still needed in this area

9
Traffic(Application Requirement)

• Traffic Type
• datagram (eg. email, file transfer) packet
  switching
• 100 correctness
• can suffer longer delay
• bursty
• time-bound traffic (eg. voice) circuit switching
• delay is very sensitive
• loss may be acceptance
• connection-oriented
• Different applications need different network
  protocol design

10
?????????--??????

• Goal Develop robust, but simple, implementable
  solutions
• Protocols include
• Location tracking and routing used for multihop
  routing and location management
• QoS routing and MAC used for time-bound
  traffic
• Mobile IP concept

11
Location Tracking and Routing

• ??
• (timestamp) A MG ?
  hello MGIP Seq hop
• x, y, z
  number
• 
  register
• 
  
• 
  ??
• C B
  A MGIP Seq (timestamp)
• 
  hop 1
• 
  register nodeMG
• 
  ???? x, y, z
• 
  
  (timestamp)
• a b x
  y z
• 
  hop 2
• 
  register node A

12
QoS routing and MAC

• QoS (delay, bandwidth) information collection
  --gt hard !
• scheduling
• dynamics
• MAC options
• IEEE 802.11 PCF (polling)
• TDMA
• QoS routing spread traffic as far as possible
  (spatial reuse)