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Bhabani P. Sinha Advanced Computing and Microelectronics Unit Indian Statistical Institute, Calcutta Mobile and Sensor Networks.

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Presentation on theme: "Bhabani P. Sinha Advanced Computing and Microelectronics Unit Indian Statistical Institute, Calcutta Mobile and Sensor Networks."— Presentation transcript:

1 Bhabani P. Sinha Advanced Computing and Microelectronics Unit Indian Statistical Institute, Calcutta email : bhabani@isical.ac.in Mobile and Sensor Networks : Prospects, Challenges and Social Implications

2 Organization Introduction Present Scenario Cellular Mobile Networks Ad hoc Mobile Networks Sensor Networks Future Challenges Social Implications

3 Introduction Wireless communication services –Cordless Telephones –High-Speed Wireless Local-Area Networks –Wide-Area Wireless Data Systems –Cellular Mobile Radio systems –Satellite-Based Mobile Systems

4 Introduction (Contd.) Characterization of Mobile Networks –Mobile elements are resource-poor relative to static elements – Mobility is inherently hazardous – Mobile connectivity is highly variable in performance and reliability –Mobile elements rely on a finite energy source Sensor Networks -Both Mobile and Static depending on application -Energy constraint is more important

5 Types of Mobile Networks Two different types of mobile networks Cellular Ad Hoc

6 Introduction (Cont.) Overview of a Cellular System Cells : overlapping regions of circular, hexagonal, or any arbitrary shape Base stations : transceivers in each cell for communication among mobiles using wireless links Base station controllers (BSC) : concentrating points to which base stations are connected Mobile switching centre (MSC) : to switch calls to mobiles of the networks MSC BSC cell base station X Y

7 Introduction (Contd.) –Ad hoc Network No existing Robust Communication Infrastructure No Wired Communication Links Only Wireless Communication between Mobile Terminals Distributed System with no Central Arbiter Mostly Single Channel Networks –Communication over Unique Common Radio Frequency – usually TDMA

8 Bandwidth management Mobility management –Location management –Handoff management –Exact location identification –Internetworking Security Cellular Networks : Major Research Areas

9 Ad hoc Networks : Major Research Areas Initialization Assign distinct IDs (1 to n) to Mobile Terminals 1 2 3 4 5 6 7

10 –Leader Election Identify a Mobile Terminal as Leader Inform all others Nodes in the Network Ad hoc Networks : Major Research Areas

11 Clustering Clustering Reduce Information Update Overhead (e.g. Routing Tables) Reduce Information Update Overhead (e.g. Routing Tables)

12 Ad hoc Networks : Major Research Areas –Time Slot assignment Avoiding collision Detecting and resolving collision –Communication Protocols Broadcasting Multicasting Gossiping

13 Present Scenario

14 Bandwidth Management

15 Wireless Communication constitutes the fastest growing segment of communication industry 200 million subscribers of cellular communication systems listed in 1997 (Akilydiz et al., Proc. IEEE, Aug. 1999) 1,50,000 new subscribers joining every day more than 1000 million subscribers all over the world Increasing demand for mobile multimedia services - voice - data - image - video conferencing

16 Bandwidth Management Fourth Generation Wireless Systems Characteristics : Support interactive multimedia services - teleconferencing, wireless Internet, etc. Wider bandwidths, higher bit rates Global mobility and service portability Scalability of mobile networks.

17 Bandwidth Management New Features in 4G Entirely packet-switched networks All network elements are digital Higher bandwidths to provide multimedia services at lower cost (up to 100Mbps) Tight network security

18 Comparisons between 3G and 4G 3G Back compatible to 2G Circuit and packet switched networks Combination of existing & evolved equipment Data rate up to 2 Mbps 4G Extend 3G capacity by one order of magnitude Entirely packet switched networks All network elements are digital Higher bandwidth (up to 100 Mbps)

19 Bandwidth Management (Contd.) Frequency Allocation (1992 World Administrative Radio Conference) Total spectrum : 1885 - 2025 MHz, 2110 - 2200 MHz frequency gaps between 2025-2110 MHz and beyond 2200 MHz used for remote sensing, cable TV, space research Available bandwidth : 230 MHz 170 MHz bandwidth reserved for terrestrial use 60 MHz for satellite satellite band : 1980 - 2010 MHz, 2170 - 2200 MHz Revised Frequency Allocation (1995 ITU World Radio Conference) Satellite allocation for America and Carribean : 1990-2025 MHz and 2160-2200 MHz (total 75 MHz) Difficult for US service providers to support Mobile Terminals Bandwidth management is a crucial issue

20 Bandwidth Management (Contd.) The Channel Assignment Problem (CAP) : Assigning frequency channels to the cells :- Satisfying : – Channel requirement for each cell – Frequency separation constraints Avoiding : – Channel interference Using : – As small bandwidth as possible. In its most general form the problem is NP-Complete [Hale, 1980].

21 Bandwidth Management (Contd.) Essential to develop : Heuristic Algorithms / Approximation Algorithms Lower Bounds on Bandwidth Simulation of algorithms on benchmark problems Engineering Approach : Exploit the hexagonal symmetry of cellular networks Static / Long-term assignments : maximum execution time is of the order of 10 to 20 seconds Short-term assignments : maximum execution time is ~ 0.5 sec

22 Design a hierarchy of algorithms (with low overhead ~ 1%) to be used in a practical situation long term assignment (say, every hour) optimal, execution time ~ 10 seconds intermediate term assignment (say, every 10 minutes) near-optimal, possibly with some blocked calls execution time ~ 1 second short term assignment (say, every minute or on demand for handoff) execution time ~ few tens of milliseconds Bandwidth Management (Contd.)

23 Mobility Management

24 Location Management Location Management : a two-stage process Location update : time, movement and distance based ­ MT periodically notifies the network of its new access point - mobile user is authenticated by the network - user location profile is revised Call delivery - network is queried for the user location profile - current position of the mobile host is found

25 Location Management Two commonly used standards for location management in PLMN IS - 41 (Interim Standard - 41) (Electronic and Telephone Industry Association EIA/ TIA) used in North America, Personal Access Communication Services (PACS) GSM MAP (Global System for Mobile Telecommunications - Mobile Application Part) used in Europe, Digital Cellular System - 1800 (DCS - 1800) & pcs - 1900 networks Both are similar, but GSM MAP facilitates personal mobility and user selection of network providers

26 Every mobile has an entry in a database in the MSC to keep track of its last known location which is periodically updated: HLR : Home Location Register - keeps information about each user VLR : Visitor Location Register- stores information about users visiting its associated area Location Management

27 Location Management (contd.) Two possible situations An MT can be far away from its HLR a large number of message communication may be involved An MT can be called from a nearby MT no need to refer to the HLR of the called MT Research Objectives - Minimization of overall signaling traffic (particularly because of the rapid increase in the number of mobile subscribers) - Minimization of registration and call setup time Strategy - design of a suitable database architecture - design of efficient update algorithms

28 Location Management (contd.) Design of database architecture - Centralized Database (extension of IS - 41 strategy) - Distributed Database Centralized Database Architectures Dynamic hierarchical database architecture Directory register (DR) each covers a number of MSCs DR periodically computes and stores the location pointer configuration for MT Three types of pointers in a DR - local pointer (indicating the current serving MSC of MT) - direct remote pointer to the currently serving DR - indirect remote pointer pointing to the currently serving DR

29 Location Management (contd.) Distributed Database Architectures - Distributed Hierarchical Tree-based Database - Partitioning - Database Hierarchy

30 Location Management for Mobile IP Mobile IP Architecture Mobile NodeHome AgentCorrespondent (before move) Node Subnet A Subnet C Internet Subnet B Mobile Node (after move) Foreign Agent

31 Location Management for Mobile IP Two IP addresses assigned to a mobile node while it visits a foreign link Its own identification Care of Address (CoA) Association between CoA and Mobile Nodes home address done by a Mobility binding table with an associated life time

32 Location Management for LEO Satellite Networks LEO satellite altitudes:500 -1500 Km MEO satellite altitudes:5,000 - 13,000 Km Geostationary satellite:35,823 Km LEO satellites are used for covering regions where terrestrial wireless systems are economically infeasible (rough terrain or insufficient population) Iridium provided service for voice and low bit-rate data transfer Teledesic : proposed for broad-band access

33 Location Management for LEO Satellites (contd.) High mobility of LEO Satellites needs ISL (intersatellite links) for routing messages - Handoff is very frequent - Coverage area of a single satellite consists of small-sized cells : Spotbeams - Different spotbeams use different frequencies Handoffs in LEO satellites : Intersatellite handoff Spotbeam (intrasatellite) handoff Link handoff

34 Location Management (contd.) Research Issues on Location Management Security (user authentication) Dynamic updates (delay constraints) Centralized vs. Distributed database architecture Paging delay minimization All these issues are network independent (independent of protocols used in PLMN, PSTN, ISDN, IP, X.25 or ATM networks)

35 Handoff Management

36 Initiation Handoff Management Resource Allocation New Connection Generation Data Flow Control User Movement Buffering/ Sequencing Network Conditions Connection Routing Multicast

37 Handoff Management (contd.) Handoff management may be of two types intracell handoff transfer of the on-going call to a new radio channel at the same BS intercell handoff handoff to a new BS Two phases of handoff : Soft handoff mobile terminal may be connected to multiple BSs simultaneously during handoff Some form of signaling diversity is used to combine multiple signals Hard Handoff Only one BS is connected at a time Before handoff - the old BS After handoff - the new BS

38 Location Identification Wide Range of Applications Wide Range of Applications Military Maneuvers Military Maneuvers Emergency Search & Rescue Operations Emergency Search & Rescue Operations Tracking Targets and Users Tracking Targets and Users Location Sensitive Commercial & Residential Services Location Sensitive Commercial & Residential Services

39 Location Identification (contd.) Global Positioning System (GPS) Provide accurate location Provide accurate location High infrastructure cost High infrastructure cost Constellation of satellites Constellation of satellites Suitable only for outdoor rural environments Suitable only for outdoor rural environments Suffers from NLOS errors Suffers from NLOS errors Signal Reflection and Obstruction in Indoor Environments Signal Reflection and Obstruction in Indoor Environments

40 Location Identification (contd.) Modeling of indoor environments difficult Modeling of indoor environments difficult Environments vary widely Environments vary widely NLOS Error time and location dependent NLOS Error time and location dependent Requires Non-parametric Approaches Requires Non-parametric Approaches Prohibitive Time and Cost Factors Prohibitive Time and Cost Factors

41 Location Identification (contd.) Existing Approaches attempt Location Estimation Existing Approaches attempt Location Estimation Least Squares Method Least Squares Method Residual Weighing Algorithm (RWGH) Residual Weighing Algorithm (RWGH) Computationally Intensive Computationally Intensive Probabilistic Measure Probabilistic Measure No Error Bound Guaranteed No Error Bound Guaranteed

42 Location Identification (contd.) Computational Geometric Approach Computational Geometric Approach (IWDC 2005, Sinha and DattaChowdhury) Returns Region, instead of Point Estimate Returns Region, instead of Point Estimate Node Guaranteed to be found in Region Node Guaranteed to be found in Region Objective: Minimize Region of Residence of All Nodes in Network Objective: Minimize Region of Residence of All Nodes in Network

43 Location Identification (contd.) Location Sensing Techniques Triangulation or Trilateration Triangulation or Trilateration Multi-lateration for better Accuracy Multi-lateration for better Accuracy Angulation Angulation Measure Angle or Bearing Relative to Points with known Separation Measure Angle or Bearing Relative to Points with known Separation Proximity: Measure Nearness to known Set of Points Proximity: Measure Nearness to known Set of Points Scene Analysis: Examine View from Particular Vantage Point Scene Analysis: Examine View from Particular Vantage Point

44 Location Identification (contd.) Survey of Location Systems Survey of Location Systems Global Positioning System (GPS) Global Positioning System (GPS) Technique: Radio time-of-flight Lateration Technique: Radio time-of-flight Lateration Accuracy: 1-5 meters 95% to 99% Accuracy: 1-5 meters 95% to 99% Scale: 24 Satellites Worldwide Scale: 24 Satellites Worldwide Cost: Expensive Infrastructure, $100 per Receiver Cost: Expensive Infrastructure, $100 per Receiver Limitations: Not Suitable for Indoors Limitations: Not Suitable for Indoors Research on Improving Indoor GPS Systems and Accuracy Research on Improving Indoor GPS Systems and Accuracy

45 Location Identification (contd.) VHF Omni-directional Ranging VHF Omni-directional Ranging Technique: Angulation Technique: Angulation Accuracy: 1 degree radial (100 %) Accuracy: 1 degree radial (100 %) Scale Scale Several Transmitters per Metropolitan Area Several Transmitters per Metropolitan Area Cost Cost Expensive Infrastructure, Inexpensive Aircraft Receivers Expensive Infrastructure, Inexpensive Aircraft Receivers Comments: Range of 30 to 140 Nautical Miles, Line-of- sight Required Comments: Range of 30 to 140 Nautical Miles, Line-of- sight Required

46 Location Identification (contd.) Emergency 911 Service (E911) Emergency 911 Service (E911) Technique: Triangulation Technique: Triangulation Accuracy: 150 to 300 m Accuracy: 150 to 300 m Scale: Density of Cellular Infrastructure Scale: Density of Cellular Infrastructure Cost Cost Upgrading Phone Hardware, Cell Infrastructure Upgrading Phone Hardware, Cell Infrastructure

47 Location Identification (contd.) Active Badge System Active Badge System Technique: Infra-red, Cellular Proximity Technique: Infra-red, Cellular Proximity Accuracy: Room Size Accuracy: Room Size Scale Scale 1 Base per Room 1 Base per Room 10 sec to Process Badge per Base 10 sec to Process Badge per Base Cost Cost Administration, Setup Cost Administration, Setup Cost Cheap Tags and Bases Cheap Tags and Bases Limitations: Sunlight and Fluorescent Light Limitations: Sunlight and Fluorescent Light

48 Location Identification (contd.) Active Bats System Active Bats System Technique: Ultrasound and RF, Time-of-flight, Lateration, Statistical Pruning to Eliminate NLOS Errors Technique: Ultrasound and RF, Time-of-flight, Lateration, Statistical Pruning to Eliminate NLOS Errors Accuracy: 9cm (95%) Accuracy: 9cm (95%) Scale Scale 1 Base per 10 sq. meter 1 Base per 10 sq. meter 25 Computations per Room per Sec 25 Computations per Room per Sec Cost Cost Administration, Setup Cost Administration, Setup Cost Cheap Tags and Sensors Cheap Tags and Sensors Limitations: Required Ceiling Sensor Grid, Sensitive to Precise Placement of Sensors Limitations: Required Ceiling Sensor Grid, Sensitive to Precise Placement of Sensors

49 Location Identification (contd.) Microsoft RADAR Microsoft RADAR Technique: 802.11 RF Scene Analysis and Triangulation Technique: 802.11 RF Scene Analysis and Triangulation Accuracy: 3m (Scene Analysis) to 4.3m Accuracy: 3m (Scene Analysis) to 4.3m Scale: 3 Base Stations per Floor Scale: 3 Base Stations per Floor Cost Cost 802.11 Installation 802.11 Installation

50 Location Identification (contd.) Summary Summary Most Existing Commercial Products use Signal Strength Attenuation Based Solutions Most Existing Commercial Products use Signal Strength Attenuation Based Solutions Cheaper Hardware Cheaper Hardware Not Very Accurate, Especially for Indoors Not Very Accurate, Especially for Indoors Signal Strength Database Systems for Office, Hospitals & Warehouse Environments – Relatively Static Parameters Signal Strength Database Systems for Office, Hospitals & Warehouse Environments – Relatively Static Parameters Ongoing Research in TOA, TDOA, AOA Techniques – More Promising than Signal Strength Based Solution Ongoing Research in TOA, TDOA, AOA Techniques – More Promising than Signal Strength Based Solution Bottomline : Still No Ubiquitous, Scalable High Precision Location System Bottomline : Still No Ubiquitous, Scalable High Precision Location System

51 Sensor Networks What are Sensor Networks ?

52 Sensor Networks (contd.)

53

54

55 Major Applications Environmental Monitoring –Monitoring air, soil and water, condition based maintenance Habitat Monitoring –Determining the plant and animal species population and behavior Seismic detection Military surveillance Inventory tracking

56 Sensor Networks (contd.) Major Issues and Features Size of Node: Size of Node: Sensor node is small in size. It is difficult to accommodate sophisticate hardware. Sensor node is small in size. It is difficult to accommodate sophisticate hardware. Limited energy resources : Limited energy resources : It requires power control in software level e.g., It requires power control in software level e.g., Power aware routing protocol. Low Computational Efficiency: Low Computational Efficiency: Requires robustness in calculations Requires robustness in calculations

57 Sensor Networks (contd.) Major Issues and Features Low Bandwidth: Low Bandwidth: Reduction of traffic overhead in the network. Reduction of traffic overhead in the network. Limited Memory: Limited Memory: An operating system suitable for sensor nodes. An operating system suitable for sensor nodes. Fault tolerance: Fault tolerance: Due to short lifetime Due to short lifetime limited power supply limited power supply environmental change environmental change Security: Security: Nodes are very vulnerable in nature. Intruder (possibly nature) can inject malicious information Nodes are very vulnerable in nature. Intruder (possibly nature) can inject malicious information

58 Sensor Networks (contd.) Major Issues and Features Ad-Hoc Network: Ad-Hoc Network: Probably the sensor nodes dropped from air Probably the sensor nodes dropped from air Sensor network has no pre-defined structure. Sensor network has no pre-defined structure. Localization of Nodes: Localization of Nodes: No unique ID as Internet. The position with respect to some reference can identify a sensor node. No unique ID as Internet. The position with respect to some reference can identify a sensor node. To react to the target, it is necessary to know the location of the target. To react to the target, it is necessary to know the location of the target. Calibration: Calibration: Needs high accuracy in estimation of location of objects. Needs high accuracy in estimation of location of objects.

59 Future Challenges

60 Topics for Exploration Interoperability of Mobile Devices Different technologies : CDMA, GSM Different backbone Networks – PLMN, WATM, MIP, Satellite Different Communication Protocols – Deterministic / Randomized Algorithms

61 Topics for Exploration Efficient Global Roaming Capability Fast and Low Cost Location Management Technology Fast and Low Cost Handoff Technology More Accurate Location Identification Methodology – Outdoor and Indoor locations

62 Topics for Exploration Effective Utilization of Sensors Fast and Efficient Routing Strategy Improvement of Life Time

63 Social Implications

64 Benefits – Connectivity to remote rural areas land line telephone links are either infeasible (difficult – to – access terrain) or uneconomical –Ubiquitous connectivity even when people are on the move –Business promotion and economic growth through continuous awareness of the market condition –Continuous remote medical facilities through on-line connectivity to the doctors / hospitals

65 Social Implications Benefits –Agricultural promotion through information broadcast among the farmers –Disaster relief (Earthquakes, Flood, Cyclones) –Defense Applications in remote inaccessible places –Exact location identification - useful for tourists, emergency medical service on highways, request for police protection when attacked by terrorists/ robbers –Aids in criminal investigation

66 Social Implications Hazards –Health hazards due to continuous exposure to harmful radio signals *** –Noise pollution Roads, public vehicles, meeting rooms, theater halls –Security threat (if the mobile device is stolen or lost)

67 Conclusion Most popular and widely used technology during the last decade –Great impact on the society as a whole –But not without any associated hazards Scientists need to work not only for the technological advances for the next generation mobile communication and computing, but also to find ways to eliminate health hazards, in particular

68 THANK YOU !


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