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Network Issues for Hybrid Ad Hoc Mobile Computer Networks

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Title: Network Issues and Implementation for a Mobile Information System Author: ttsai Last modified by: ttsai Created Date: 7/22/1999 6:52:46 AM Document ... – PowerPoint PPT presentation

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Title: Network Issues for Hybrid Ad Hoc Mobile Computer Networks


1
Network Issues for Hybrid Ad Hoc Mobile Computer
Networks
  • Tzu-Chieh Tsai, Associate Professor
    (ttsai_at_cs.nccu.edu.tw)
  • Department of Computer Science
  • National Chengchi University
  • Taipei, Taiwan

2
Outline
  • Hybrid Ad Hoc Mobile Computer Networks
  • Disaster recovery or battle field
  • Mobile Police Information System (MPIS)
  • Network Issues
  • MAC (Medium Access Control)
  • QoS (Quality of Service)
  • internet access
  • Our work other works can be applied to MPIS
  • Implementation

3
Introduction
  • Wireless/Mobile communication world is coming
  • information retrieval and two-way communication
    at any time, at any place
  • wireless network system
  • voice cellular phones, GSM
  • mobile data CDPD(Cellular Digit Packet Data),
    GSM GPRS (General Packet Radio Service)
  • wireless LAN IEEE 802.11, HIPERLAN
  • b/w ? data rate ? error rate ?

4
Introduction
  • Mobile computing
  • multimedia big challenge
  • QoS (Quality of Service) next-G telecom packet
    switching
  • security EM wave can penetrate buildings
  • mobility car speeds, network topology changing,
    control is dynamic

5
A Real Mobile Information System
  • Goal design and implement a mobile information
    system
  • Support real-time, multimedia traffic
  • with capability
  • instant deployed infrastructure
  • internet access

6
Network Components
  • Wireless LAN
  • free, no license (FCC regulations, spread
    spectrum)
  • 2 Mbps (will be upgraded to 10Mbps soon)
  • Mobile Data Network
  • CDPD (Cellular Digital Packet Data) technique
    ?????
  • expensive
  • 19.2 Kbps
  • coverage area (in the future, GSM GPRS or
    IMT-2000)

7
MPIS Examples
  • Mobile Police Information System (MPIS)
  • integration of the above 2 network components
  • Examples
  • 110, 119 needs suspects pictures information
    on the scene
  • Search needs maps keeps tracks of position
    (e.g. kidnapping)
  • Fire fighting needs to know how dangerous (e.g.
    chemical factory)
  • On-line real-time query, consultation

8
MPIS Architecture
9
MPIS Attributes
  • Every policeman equipped with a PDA that has
    multimedia capability (e.g. image, voice)
  • 2-level network architecture
  • Reason
  • air-time is expensive
  • real-time vs. non-real-time
  • Advantages of Mobile Gateway (MG)
  • more mobility support
  • rapid deployment, mobile infrastructure
  • easy to management (compared to pure ad-hoc)
  • internet access

10
Network Issues
  • Multihop Architecture Control
  • Channel Access
  • QoS, Multimedia Support
  • Routing
  • Roaming and Mobile IP

11
Other MPIS Issues
  • Query and reply while an unstable, low-speed
    wireless connection is concerned
  • data replicate
  • security and authentication
  • mobile agent management

12
Network Issues (Multihop Architecture Control)
  • MG which mobile hosts are under its control
  • Mobile Hosts which MG is nearest to it
  • Record
  • (timestamp) A MG send hello? MGIPSeq
    hop number
  • x, y, z
  • register Record
  • C B A MGIP Seq
    (timestamp)
  • Hop 1
  • Register node
    MG
  • Relay nodes
    for x, y, z
  • (timestamp)
  • a b x y z hop 2
  • register
    node A

13
Network Issues (Location Tracking Algorithm)
  • MG periodically sends out hello message (own
    IP, Sequence , hop number distance to MG)
  • Node A,B,C receive hello increase hop number
    by 1, update routing table and timestamp, then
    send out register message to MG
  • Node x, y, z receive register update routing
    table, and repeat send register

14
MPIS Issues (Channel Access)
  • Mobile Data Network for WAN
  • CDPD (Cellular Digital Packet Data)
  • Satellite
  • GSM GPRS (General Packet Radio Service)
  • IMT-2000
  • Multihop Wireless LAN
  • IEEE 802.11 Standards
  • time-bounded service vs. datagram service

15
Cellular Concept
  • Frequency Reuse
  • Channel Assignment Strategies
  • Handoff
  • Interference (SIR Signal to Interference Ratio)
  • Power Control
  • QoS (Quality to Service)
  • uplink vs. downlink
  • control channel

16
Cellular Frequency Reuse
17
CDPD (Cellular Digital Packet Data)
  • Based on traffic engineering fact
  • 19.2 Kbps
  • connectionless service

18
Why we choose CDPD as our mobile data network?
  • Currently, only CDPD is available in Taiwan
  • Support IP internet access
  • packet switching

19
GSM GPRS
  • Provide packet data service over GSM
    infrastructure
  • 2 alternative approaches
  • allocate specific GSM channels for packet
    transmission shared by all active packet
    subscribers
  • fast establishment of a GSM traffic channel on
    any radio resource available
  • Interworking with Public Switched Packet Data
    Networks and Internet

20
IMT-2000
  • Universal Mobile Telecommunications System
    (UMTS)/International Mobile Telecommunications
    (IMT-2000)
  • support 144kbps, preferably 384kbps for wide-area
    coverage(full mobility) and 2Mbps for local
    coverage(limited mobility)
  • 3rd Generation W-CDMA, and/or TDMA
  • research is still going

21
IEEE 802.11 infrastructure network
22
IEEE 802.11 MAC
  • Contention Mode
  • All stations require to contend for access to the
    channel for each packet transmitted
  • Contention-free mode
  • During the contention-free period (CFP)
  • medium usage is controlled by the Access Point
    (AP)

23
IEEE 802.11 MAC Architecture
24
IEEE 802.11 DCF w/o RTS/CTS
25
Hidden Terminal Problem
  • data
    hidden to A
  • A B
    C

26
IEEE 802.11DCF w/ RTS/CTS CSMA/CA (Collision
Avoidance)
27
IEEE 802.11 PCF
  • Connection-oriented
  • provide contention-free frame transfer

28
IEEE 802.11 PCF
29
Network Issues (QoS Multimedia Support)
  • Traffic Type
  • datagram (e.g. email, file transfer) packet
    switching
  • 100 correctness
  • can suffer longer delay
  • bursty
  • time-bound traffic (e.g. voice) circuit
    switching
  • delay is very sensitive
  • loss may be acceptance
  • connection-oriented

30
Multimedia Support
  • Different applications need different QoSgt
    different protocol design
  • Difficulty
  • control
  • dynamic traffic, network resource, mobility
  • negotiate QoS, admission control

31
Network Issues (Routing)
  • With help of location tracking algorithm
  • Minimum hop routing
  • Spatial reuse (QoS) routing (load balance)
  • Internet traffic choose the nearest MG
  • Traffic inside an MG coverage area
  • distributed Bellman-Ford minimum hop routing
  • MG source routing traffic up to MG, then down to
    destination or by request, get routing path from
    MG
  • complexity vs. delay tradeoff

32
Network Issues (Routing)
  • Record
  • (timestamp) A MG send hello? MGIPSeq
    hop number
  • x, y, z
  • register Record
  • C B A MGIP Seq
    (timestamp)
  • Hop 1
  • Register node
    MG
  • Relay nodes
    for x, y, z
  • (timestamp)
  • a b x y z hop 2
  • register
    node A

33
QoS Routing Example
  • Bandwidth calculation is difficult and dynamic

34
MPIS MG bandwidth management
  • 2 MAC mechanisms to support QoS (bandwidth) for
    real time traffic
  • reservation-TDMA (or PRMA)
  • polling as in IEEE 802.11 PCF (with Access Point
    case)
  • MG (synchronization)
  • collection bandwidth information (done along with
    location tracking algorithm)
  • slot scheduling, or polling frequency assignment

35
Network Issues (Roaming and Mobile IP)
  • IEEE 802.11 compliant wireless network adapters
    support roaming inside the same subnet
  • IP availability can use psuedo IP
  • MG has 2 IPs
  • legal IP on WAN mobile data card
  • psuedo IP on WLAN card
  • MG encapsulate its mobile nodes psuedo IP with
    its legal IP
  • Mobile IP
  • MGs can work as foreign agents

36
Mobile IP Concept
  • Goal mechanism to deliver datagrams to the
    mobile node when it is away from home network
    without changing its original IP (gain a new IP
    address)
  • Home Agent a router on a mobile nodes home
    network
  • Foreign Agent a router on a mobile nodes
    visited network, cooperates with home agent

37
Mobile IP Concept
  • Home address vs. Care-of-address
  • Protocol Overview
  • Agent Discovery mobile agents periodically
    broadcast
  • Registration mobile node registers its
    care-of-address with its home agent
  • tunneling encapsulate home address with
    care-of-address

38
Mobile IP Concept
39
Mobile IP Concept
  • Triangular routing problem
  • Route optimization
  • mobile node may send binding warning control
    message to home agent indicating a correspondent
    node unaware of care-of-address
  • Correspondent node may send a binding request
  • Home Agent sends an authenticated binding update
    containing mobile nodes care-of-address
  • smooth handoff mobile node sends a binding
    update

40
Smooth Handoff
41
MPIS Implementation
  • Issues
  • Multihop (WLAN cards have no such functions)
  • TCP/IP socket transparent (all TCP/IP
    applications transparent)
  • MG (handles 2 cards, internet access)
  • roaming
  • 2 platforms
  • Windows
  • Linux

42
Windows NDIS
internet
MG
TCP/IP app.
Multi- hop
43
Windows VxD approach
  • VxD (Virtual Device Driver) rawether
  • interface to NDIS
  • capture all TCP/IP packets passing NDIS
  • works closely with device driver
  • provide limited functions unless obtaining device
    driver source code

44
Windows Sygate approach
  • Sygate Proxy concept
  • remote client relay client MG
  • telnet, http, ftp
    internet
  • Disadvantage not dynamic!

45
Windows winsock approach
  • Provide a special winsock function along with
    multihop relay daemon
  • make a winsock connection to relay client first
    then relay client makes another winsock to MG
  • with help of routing path
  • disadvantage for our own applications only, not
    for all TCP/IP applications
  • Other approach is still being searched

46
Linux
  • Use bridge to support multihop
  • provide an interface program
  • on-line change routing path, i.e. decide if needs
    to relay or not
  • use IP Masquerade
  • support IP transparency through MG (between WLAN
    and internet)
  • Details http//sparc1.cs.nccu.edu.tw/s8427

47
Current Status
  • Location tracking program
  • implemented on socket level (due to Windows NDIS
    difficulty)
  • will tightly work with multihop platforms for
    both Windows and Linux
  • Routing algorithm
  • currently, minimum hop routing
  • QoS regarding bandwidth allocation (scheduling)
    will be developed

48
Current Status
  • Roaming will be tested
  • Query application programs will be integrated

49
Conclusions
  • MPIS architecture is presented
  • Mobile data systems introduced
  • CDPD, GPRS, IMT-2000
  • WLAN MAC protocols introduced
  • IEEE 802.11
  • Multihop Architecture
  • QoS Routing
  • Mobile IP

50
Conclusions
  • Implementation
  • location tracking algorithms
  • Windows
  • NDIS, VxD
  • Proxy
  • Winsock
  • Linux
  • bridge relay
  • MG IP encapsulation, Mobile IP

51
Questions?
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