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MET TC670 B1 Computer Science Concepts in Telecommunication Systems

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Title: MET TC670 B1 Computer Science Concepts in Telecommunication Systems


1
MET TC670 B1Computer Science Concepts in
Telecommunication Systems
  • Fall 2003

2
Lecture 1, September 9, 2003
  • Course Syllabus and Policies
  • Introduction to Telecommunication Systems
  • Why Computer Science Concepts?
  • Introduction to Computer and Operating Systems
  • Preliminary Test on Computer Science Concepts

3
Instructor
  • Shudong Jin Office (617)-353-8924 Fax (617)
    353-6457 e-mail jins_at_cs.bu.edu
  • Make an appointment?
  • Course home page
  • http//cs-people.bu.edu/jins/tc670

4
Course Description
  • Learning basic computer science concepts in
    telecommunication systems. Operating system
    topics such as Processes and Threads,
    Inter-process communication, Concurrency Control,
    Multimedia Operating Systems and Communications
  • Touching emerging computer science topics related
    to telecommunication applications. Sensor Systems
    and Networks, multimedia communication protocols
  • Working on programming projects and
    algorithm/protocol designs related to
    telecommunication applications

5
Course Format
  • Lecture 3 hours / week
  • Homework assignments
  • Programming projects
  • Mid-term and final exams

6
Course Format - Lectures
  • Lectures will be given weekly.
  • Students are expected to attend all lectures.
    Attendance will often be recorded.
  • Each lecture has a recession of 15 minutes. Dont
    be late on the second leg!
  • Occasional tests during lectures, not graded.

7
Course Format - Homework
  • Homework assignments will be given during some
    lectures.
  • 4-5 homework assignments.
  • No collaboration! You should solve the problems
    independently.
  • Acceptable formats HTML, Word Document,
    PostScript, and PDF. Send an email to
    jins_at_cs.bu.edu. Written answers are acceptable,
    but not preferable.

8
Course Format - Projects
  • Two programming projects, one in each half of the
    semester. Due dates midterm exam and final exam.
    First project will be assigned very soon (in 2-3
    weeks).
  • Collaboration (a team of 2 students) is allowed.
    Independent work on programming projects is
    encouraged and may result in extra credit.
  • Acceptable formats Electronic format (including
    both commented source C/C/Java code as well as
    documents describing the implementation details).
  • Grading criteria correctness, completeness,
    neatness, and documentation.

9
Course Format Exams
  • Midterm exam will cover all topics discussed in
    the first half.
  • Final exam will emphasize the topics covered in
    the second half.

10
Grading Policies
  • Homework assignments 20 Project assignments
    20 Midterm exam 25 Final exam 35
  • Bonus on class attendance and active discussion
  • Expected medium grades B to B, may vary!
  • What I can do and can not do?

11
What I Can Do and Can Not Do
  • Be fair!
  • Make homework and project assignments clear.
  • If you attend class regularly
  • If you fare much better in final exam than you do
    in mid-term
  • Academic dishonesty

12
Lecture 1, September 9, 2003
  • Course Syllabus and Policies
  • Introduction to Telecommunication Systems
  • Why Computer Science Concepts?
  • Introduction to Computer and Operating Systems
  • Preliminary Test on Computer Science Concepts

13
Knowing Telecommunication
  • The basic components in telecommunications
  • Data versus voice network
  • What are telecommunication protocols?
  • Different types of telecommunication networks
  • Different network topologies
  • Example telecommunication applications

14
What Is Telecommunication?
  • The purpose of telecommunications is to convey
    information from one location to another.
  • The transmission of different forms of data (such
    as text, audio, video, images, graphics) from one
    set of electronic devices over media to another
    set of geographically separated electronic
    devices.

15
General Telecommunication Systems
16
Data versus Voice Networks
17
Data versus Voice Networks
  • Voice networks
  • Property More convenient to convey information,
    thats why voice communication has predominated
    for over a century.
  • Example the telephone network, until the last
    decade, was almost entirely analog.
  • Any data information had to be converted into a
    signal which emulated the analog speech signals.
  • Data networks
  • Precise communication. Digital information.
  • Example the Internet.
  • Recently we have a better proportion of data
    communications links and speech is being
    converted into digital forms as well as data
    will eventually be conveyed more naturally in
    these digital forms

18
Characteristics of Channels
  • Transmission rate
  • Bandwidth
  • Transmission mode
  • Transmission direction
  • Transmission signals

19
Characteristics of Channels
Characteristics
Description
Transmission rate
Rate at which channel carries data from one
computer to another. Volume or capacity of data
that a channel can carry. Ways by which data are
transmitted. Two ways include asynchronous (one
byte at a time) and synchronous (blocks of
bytes). Three directions for transmitting data
include simplex, half duplex, and full
duplex. Information travels as analog or digital
signals.
Bandwidth
Transmission mode
Transmission direction
Transmission signals
20
Telecommunication Protocols
  • Rules and formats that ensure efficient and
    error-free electronic communications between two
    or more computers.
  • Some agreements between the participants of
    communication process.

21
Components of A Protocol
  • A set of characters that mean the same thing to
    both the sender and the receiver
  • A set of rules for timing and sequencing messages
  • A set of methods for detecting and correcting
    errors

22
Types of Telecommunications
  • Classified based on the geographical distance
  • Private branch exchanges (PBX)
  • Integrated services digital network (ISDN)
  • Wide area networks (WAN)
  • Metropolitan area networks (MAN)
  • Value-added networks (VAN)

23
Private Branch Exchange (PBX)
  • An electronic switching device that connects the
    companys telephone lines to those of the local
    telephone company.

24
Integrated Services Digital Network(ISDN)
  • Integrated Services Digital Network (ISDN)
  • A digital network that uses commercial telephone
    systems to transmit voice and data.

ISDN
25
Local Area Network (LAN)
  • A network that links a number of independent
    electronic devices located within a relatively
    small area (usually within a radius of 1 to 10
    miles).
  • Examples Departmental network, small campus
    network.

26
Metropolitan Area Networks (MAN)
  • High-bandwidth WANs that link electronic devices
    distributed over a metropolitan area.

27
Wide Area Networks (WAN)
  • Networks that transmit data and voice
    communications to large geographical areas.
  • Example North-America.

28
Network Topology
  • Connectivity of various terminals and internal
    (intermediate) devices.
  • Four basic topologies

Bus topology
Ring topology
Star topology
Mesh topology
29
Network Topology Bus Topology
  • A network configuration in which all computers on
    the network are connected through a single
    circuit, such as twisted-pair cable. Messages
    are transmitted to all computers on the network,
    although only the targeted device responds to the
    message.

30
Network Topology Ring Topology
  • A network configuration in which computers are
    arranged in the form of a ring using
    twisted-wire, coaxial cable, or fiber optics.
    Messages are transmitted in one direction to all
    devices between the sending node and the
    receiving node.

31
Network Topology Star Topology
  • A topology in which a central host computer
    receives all messages and then forwards the
    message to the appropriate computer on the
    network.

32
Network Topology Mesh Topology
  • A topology which has no centralized authority but
    needs fully-distributed implementation.

33
Telecommunication Applications
  • Electronic Data Interchange (EDI)
  • Teleconferencing
  • Videoconferencing
  • Fax
  • Voice Mail

34
Lecture 1, September 9, 2003
  • Course Syllabus and Policies
  • Introduction to Telecommunication Systems
  • Why Computer Science Concepts?
  • Introduction to Computer and Operating Systems
  • Preliminary Test on Computer Science Concepts

35
Learning Systems
  • Computer systems are everywhere in
    telecommunication!
  • How can we manage the telecommunication resources
    using a computer system?
  • Issues
  • Managing telecommunication devices
  • Managing topologies
  • Managing switching

36
Learning Algorithms
  • Algorithms are important for correctness and
    performance of telecommunication systems!
  • Example 1 Job scheduling
  • Example 2 Efficient searching

37
Learning Protocols
  • Computer science concepts of the protocols.
  • Example 1 Synchronization of participants
  • Example 2 Avoidance of deadlocks

38
Learning Programming
  • Need often to write programs to drive the
    telecommunication devices!
  • Efficient implementation of algorithms and
    protocols.
  • Two programming projects.

39
Example Broadcasting Design
  • Naïve approach for video broadcasting
  • Broadcasting a video once in 60 minutes. The
    users simply subscribe the service.
  • Is it good?
  • Simple, and easy to implement
  • Users have to wait, not truly on-demand service
  • But if we want truly on-demand service

40
Periodic Broadcasting
A n algorithm where each channel repeatedly
broadcasts a portion and clients joins the
channels to receive data.
Video length
Cuts the video into
1 2 2 5 5 12
Time
5

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

Channel 6
41
Lecture 1, September 9, 2003
  • Course Syllabus and Policies
  • Introduction to Telecommunication Systems
  • Why Computer Science Concepts?
  • Introduction to Computer and Operating Systems
  • Preliminary Test on Computer Science Concepts

42
Computer Systems
  • Architecture the organization of a computer
    system (often a computer engineering topic)
  • Operating systems how to manage computer
    resources (classic computer science topic)
  • Database systems how to manage and process
    data/knowledge (a computerinfo science topic)

43
What is an Operating System?
  • An operating system (OS) is
  • a software layer to abstract away and manage
    details of hardware resources
  • a set of utilities to simplify application
    development

44
Operating Systems The Big Picture
  • The operating system (OS) is the interface
    between user applications and the hardware.
  • An OS implements a sort of virtual machine that
    is easier to program than the raw hardware.

User Applications
virtual machine interface
Operating System
physical machine interface
Architecture
45
The OS and Hardware
  • An OS mediates programs access to hardware
    resources
  • Computation (CPU)
  • Volatile storage (memory) and persistent storage
    (disk, etc.)
  • Network communications (TCP/IP stacks, Ethernet
    cards, etc.)
  • Input/output devices (keyboard, display, sound
    card, etc.)
  • The OS abstracts hardware into logical resources
    and well-defined interfaces to those resources
  • processes (CPU, memory)
  • files (disk)
  • programs (sequences of instructions)
  • sockets (network)

46
The OS and Hardware
interrupts
Processor
Cache
Memory Bus
I/O Bridge
I/O Bus
Main Memory
Disk Controller
Graphics Controller
Network Interface
Graphics
Disk
Disk
Network
47
Why Bother with An OS?
  • Application benefits
  • programming simplicity
  • see high-level abstractions (files) instead of
    low-level hardware details (device registers)
  • abstractions are reusable across many programs
  • portability (across machine configurations or
    architectures)
  • device independence 3Com card or Intel card?
  • User benefits
  • safety
  • program sees own virtual machine, thinks it
    owns computer
  • OS protects programs from each other
  • OS fairly multiplexes resources across programs
  • efficiency (cost and speed)
  • share one computer across many users
  • concurrent execution of multiple programs

48
Operating Systems The Classical View
The kernel sets up process execution contexts to
virtualize the machine.
processes in private virtual address spaces
data
data
...and upcalls (e.g., signals)
system call traps
Threads or processes enter the kernel for
services.
shared kernel code and data in shared address
space
CPU and devices force entry to the kernel to
handle exceptional events.
49
The Major OS Issues
  • Structure how is the OS organized?
  • Sharing how are resources shared across users?
  • Naming how are resources named (by users or
    programs)?
  • Security how is the integrity of the OS and its
    resources ensured?
  • protection how is one user/program protected
    from another?
  • Performance how do we make it all go fast?
  • Reliability what happens if something goes wrong
    (either with hardware or with a program)?
  • Extensibility can we add new features?
  • Communication how do programs exchange
    information, including across a network?

50
More OS Issues
  • Concurrency how are parallel activities
    (computation and I/O) created and controlled?
  • Scale what happens as demands or resources
    increase?
  • Persistence how do you make data last longer
    than program executions?
  • Distribution how do multiple computers interact
    with each other?
  • Accounting how do we keep track of resource
    usage, and perhaps charge for it?

51
OS History
  • In the very beginning
  • OS was just a library of code that you linked
    into your program programs were loaded in their
    entirety into memory, and executed
  • interfaces were literally switches and blinking
    lights
  • And then came batch systems
  • OS was stored in a portion of primary memory
  • OS loaded the next job into memory from the card
    reader
  • job gets executed
  • output is printed, including a dump of memory
    (why?)
  • repeat
  • card readers and line printers were very slow
  • so CPU was idle much of the time (wastes )

52
Multiprogramming
  • To increase system utilization, multiprogramming
    OSs were invented
  • keeps multiple runnable jobs loaded in memory at
    once
  • overlaps I/O of a job with computing of another
  • while one job waits for I/O completion, OS runs
    instructions from another job
  • to benefit, need asynchronous I/O devices
  • need some way to know when devices are done
  • interrupts
  • polling
  • goal optimize system throughput
  • perhaps at the cost of response time

53
Timesharing
  • To support interactive use, create a timesharing
    OS
  • multiple terminals into one machine
  • each user has illusion of entire machine to
    him/herself
  • optimize response time, perhaps at the cost of
    throughput
  • Time-slicing
  • divide CPU equally among the users
  • if job is truly interactive (e.g. editor), then
    can jump between programs and users faster than
    users can generate load
  • permits users to interactively view, edit, debug
    running programs (why does this matter?)
  • MIT Multics system (mid-1960s) was the first
    large timeshared system
  • nearly all OS concepts can be traced back to
    Multics

54
Distributed OS
  • Distributed systems to facilitate use of
    geographically distributed resources
  • workstations on a LAN
  • servers across the Internet
  • Supports communications between jobs
  • interprocess communication
  • message passing, shared memory
  • networking stacks
  • Sharing of distributed resources (hardware,
    software)
  • load balancing, authentication and access
    control,
  • Speedup isnt the issue
  • access to diversity of resources is goal

55
Embedded OS
  • Ubiquitous computing
  • cheap processors embedded everywhere
  • how many are on your body now? in your car?
  • cell phones, PDAs, network computers,
  • Typically very constrained hardware resources
  • slow processors
  • very small amount of memory (e.g. 8 MB)
  • no disk
  • typically only one dedicated application

56
TC 670 OS Concepts
  • We will learn
  • Process and thread scheduling
  • Inter-process communication and concurrency
    control
  • Memory management
  • I/O systems
  • File systems
  • Multimedia OS
  • .

57
Process Management
  • An OS executes many kinds of activities
  • users programs
  • batch jobs or scripts
  • system programs
  • print spoolers, name servers, file servers,
    network daemons,
  • Each of these activities is encapsulated in a
    process
  • a process includes the execution context
  • PC, registers, VM, OS resources (e.g. open
    files), etc
  • plus the program itself (code and data)
  • the OSs process module manages these processes
  • creation, destruction, scheduling,

58
Processes
  • Note that a program is totally passive
  • just bytes on a disk that contain instructions to
    be run
  • A process is an instance of a program being
    executed
  • at any instance, there may be many processes
    running copies of the same program (e.g. an
    editor) each process is separate and (usually)
    independent

process B
process A
code stack PC registers
code stack PC registers
page tables resources
page tables resources
59
Process Operations
  • The OS provides the following kinds operations on
    processes (I.e. the process abstraction
    interface)
  • create a process
  • delete a process
  • suspend a process
  • resume a process
  • clone a process
  • inter-process communication
  • inter-process synchronization
  • create/delete a child process (subprocess)

60
Lecture 1, September 9, 2003
  • Course Syllabus and Policies
  • Introduction to Telecommunication Systems
  • Why Computer Science Concepts?
  • Introduction to Computer and Operating Systems
  • Preliminary Test on Computer Science Concepts
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