telecommunication

1. Contemporary Telecommunication
Technologies

2. Contemporary Telecommunication Technologies
•5.1. WCDMA
•5.2. GSM
•5.3. ISDN
•5.4. VPN
Rick Graziani graziani@cabrillo.edu 2

3. GSM
Global System for Mobile communication

4. It all started like this
• First telephone (photophone) – Alexander Bell,
1880
• The first car mounted radio
telephone – 1921

5. Going further
• 1946 – First commercial mobile radio-telephone
service by Bell and AT&T in Saint Louis, USA. Half
duplex(PTT)
• 1973 – First handheld cellular phone – Motorola.
• First cellular net
Bahrein 1978

6. What’s cellular Phone Network?
HLR,
VLR, AC,
MSC
PSTN
BS

7. Cellular principles
• Frequency reuse – same frequency in
many cell sites
• Cellular expansion – easy to add new cells
• Handover – moving between cells
• Roaming between networks

8. GSM Overview

9. Into the architecture
• Mobile phone is identified by SIM card.
• Key feature of the GSM
• Has the “secret” for authentication

10. Into the architecture(2)
• BTS – houses the radiotransceivers of the
cell and handles the radio-link protocols with
the mobile
• BSC – manages radio resources (channel
setup, handover) for one or more BTSs

11. Into the architecture(3)
• MSC – Mobile Switching Center
• The central component of the network
• Like a telephony switch plus everything for a
mobile subscriber: registration,
authentication, handovers, call routing,
connection to fixed networks.
• Each switch handles dozens of cells

12. Channels
• The physical channel in GSM is the timeslot.
• The logical channel is the information which
goes through the physical ch.
• Both user data and signaling are logical
channels.

13. TDMA
• Time Division Multiple Access
• Each channel is divided into timeslots, each
conversation uses one timeslot.
• Many conversations are multiplexed into a
single channel.
• Used in GSM

14. CDMA
• Code Division Multiple Access
• All users share the same frequency all the time!
• To pick out the signal of specific user, this signal is
modulated with a unique code sequence.

15. ISDN
Digital Telephone Network

16. Rick Graziani graziani@cabrillo.edu 16
Introducing ISDN
• Telephone companies developed ISDN (Integrated Services Digital
Network) as part of an effort to standardize subscriber services.
• This included the User-Network Interface (UNI), better known as the
local loop.
• The ISDN standards define the hardware and call setup schemes for
end-to-end digital connectivity.
• These standards help achieve the goal of worldwide connectivity by
ensuring that ISDN networks easily communicate with one another.
• In an ISDN network, the digitizing function is done at the user site
rather than the telephone company.

17. Rick Graziani graziani@cabrillo.edu 17
Cisco Interfaces
• In the United States, the
customer is required to
provide the NT1.
• In Europe and various
other countries, the
telephone company
provides the NT1 function
and presents an S/T
interface to the customer.
S/T interface requires an
NT1 connection.

18. Rick Graziani graziani@cabrillo.edu 18
BRI S/T Interface – Cisco 2503

19. VIRTUAL PRIVATE NETWORKS
(VPN)

20. Traditional Connectivity

21. What is VPN?
Virtual Private Network is a type of private network
that uses public telecommunication, such as the
Internet, instead of leased lines to communicate.
Became popular as more employees worked in
remote locations.
Terminologies to understand how VPNs work.

22. Private Networks vs. Virtual Private Networks
Employees can access the network (Intranet)
from remote locations.
Secured networks.
The Internet is used as the backbone for VPNs
Saves cost tremendously from reduction of
equipment and maintenance costs.
Scalability

23. Remote Access Virtual Private Network

24. Brief Overview of How it Works
Two connections – one is made to the Internet and the
second is made to the VPN.
Datagrams – contains data, destination and source
information.
Firewalls – VPNs allow authorized users to pass through
the firewalls.
Protocols – protocols create the VPN tunnels.

25. Four Critical Functions
Authentication – validates that the data was sent
from the sender.
Access control – limiting unauthorized users from
accessing the network.
Confidentiality – preventing the data to be read or
copied as the data is being transported.
Data Integrity – ensuring that the data has not been
altered

26. Encryption
Encryption -- is a method of “scrambling”
data before transmitting it onto the Internet.
Public Key Encryption Technique
Digital signature – for authentication

27. Advantages
VS.
Disadvantages

28. • Eliminating the need for expensive long-distance
leased lines
• Reducing the long-distance telephone charges for
remote access.
• Transferring the support burden to the service
providers
• Operational costs
Advantages: Cost Savings

29. Flexibility of growth
Efficiency with broadband technology
Advantages: Scalability

30. VPNs require an in-depth understanding of public
network security issues and proper deployment of
precautions
Availability and performance depends on factors
largely outside of their control
Immature standards
VPNs need to accommodate protocols other than IP
and existing internal network technology
Disadvantages

31. Industries That May Use a VPN
Healthcare: enables the transferring of confidential patient
information within the medical facilities & health care provider
Manufacturing: allow suppliers to view inventory & allow
clients to purchase online safely
Retail: able to securely transfer sales data or customer info
between stores & the headquarters
Banking/Financial: enables account information to be
transferred safely within departments & branches
General Business: communication between remote
employees can be securely exchanged

32. Statistics From Gartner-Consulting*
50%
63%
79%
90%
0% 20% 40% 60% 80% 100%
Access to network for
business
partners/customers
Site-to-site connectivity
between offices
Remote access for
employees while
traveling
Remote access for
employees working out
of homes
% of Respondents
Percentages
*Source: www.cisco.com