1. Telecommunications systems (Part 2) School of Business Eastern Illinois University © Abdou Illia, Spring 2007 (Week 12, Thursday 3/29/2007) T-1 Digital Subscriber Line (DSL) Cellular Telephone System Integrated Services Digital Network (ISDN)

2. 2 Learning Objectives n Describe and compare types of connections offered by telephone companies n Explain Cellular Telephone System

3. T-1 Leased lines

4. 4 Trunk lines n Trunk lines = Type of transmission lines that connect nodes. n Trunk lines operate at speed from 56 kbps to 40+ Gbps Trunk lines T-11.544 Mbps T-3 45 Mbps SONET768 40+ Gbps Synchronous Optical Network

5. 5 T-1 Lines Computer Telephone Switch Telephone Switch Telephone Switch Server Access Line T-1 Trunk Line (1.544 Mbps) T-1 Leased Line (1.544 Mbps) End-to-End Circuit with Trunk Line Speed Trunk Line

6. 6 T-1 Leased lines n T-1 Leased lines: – Extend T-1 trunk line speeds to end-to-end circuits between two locations (e.g. 2 customer offices) – Require fiber optic or at least a special data-grade twisted Pair (Note: fiber optic is used for T-3 and SONET) Data-Grade Twisted Pair Q: What is the difference between T-1 Trunk line and T-1 Leased line? Q: In T-1 Leased lines, what kind of TP is used to connect a customer to the 1 st telephone switch?

7. 7 T-1 Lines n The customer can request Fractional T-1 lines that offer low-speed choices, typically: n 128 bps n 256 kbps n 384 kbps n 512 kbps n 768 kbps n T-1 Costs depend on distance: – ~$350-400/mo for local connection (non long-distance) – ~$1200/mo plus 2.50/mile for long-distance connection

8. Digital Subscriber Line - DSL

9. 9 Digital Subscriber Line (DSL) n Standard telephone line (Cat 1 UTP) – Capable of handling more than 3.1 Khz bandwidth n DSL exploits Standard telephone line’s “extra capacity” to transmit data without disturbing the line’s ability to transmit voice n Bandwidth usage for some Asymmetric DSL (ADSL) services: – 0 - 4 Khz band for Voice conversation – Upstream data transmission in 25 – 160 Khz band – Downstream data transmission in 240 – 1500 Khz band n DSL uses filters (splitters) to separate voice and data signals – Typically a filter is needed for each analog device (telephone, fax, etc.)

10. 10 Digital Subscriber Line (DSL) Data WAN PSTN DSLAM* DSL Modem Splitter Telephone Telephone Company End Office Switch Standard telephone line PC * DSL Access Multiplexer: (1) mixes data from many customers and (2) forwards mixed packets User End

11. 11 Digital Subscriber Line (DSL) Data WAN PSTN DSLAM DSL Modem Splitter Telephone User End Telephone Company End Office Switch PC Q: On the user end, what elements are needed to establish a DSL connection?

12. 12 Digital Subscriber Line (DSL) n DSL speed: 256 kbps – 24000 kbps n Digital Subscriber Lines (DSLs) – Asymmetric DSL (ADSL) n Standard ADSL – Downstream (to customer): 256 kbps to over 1.5 Mbps – Upstream (from customer): 64 kbps or higher n ADSL2 – Downstream (to customer): 5 Mbps to aver 12 Mbps – Upstream (from customer): 1 Mbps to 3.5 Mbps Q: How can a 3.5 Mbps upstream speed be achieved with Cat 1 UTP ?

13. 13 Digital Subscriber Line (DSL) n Digital Subscriber Lines (DSLs) – HDSL (High-rate DSL) n Needed in business. (ADSL primarily for home and small business access.) n Maximum range: 3 kilometers n Symmetric speed over voice-grade twisted pair – HDSL: symmetric 768 kbps – HDSL2: symmetric 1.544 Mbps or symmetric 2.3 Mbps

14. 14 Summary Questions 1.What is the difference between a T-1 Trunk line and T-1 Leased line? Answer: A T-1 trunk line only runs between two switches within the telephone network. T-1 Leased lines extend T-1 trunk line speeds to end-to-end circuits between 2 locations. 2.In T-1 Leased lines, what kind of twisted pair wire is used to connect a customer to the 1st telephone switch? Answer: Data-grade TP which is a category 2 TP.

15. 15 Summary Questions 3) On the user end, what elements are needed to establish a DSL connection? A DSL modem and splitter(s) to separate regular analog channel from the DSL data channels. 4) ADSL provides for higher downstream speeds than upstream speeds. (a) Is this good for web service? (b) Is it good for videoconferencing? n a) Asymmetric speeds are good for web service because http requests tend to be small but downloaded material are large. n (b) It is not good for videoconferencing, which needs high speed in both directions.

16. 16 Twisted Pair wires

17. Cellular Telephone System

18. 18 Cells, Cellsites, MTSO B E H D I G L K F C M A J N P O PSTN Mobile Telephone Switching Office Cellsite Metropolitan service area is divided into cells. Cellsite in each cell communicates with cellphones. MTSO controls all cellsites, links cellular system to PSTN.

19. 19 Cellular Telephone: The big picture B E H D I G L K C M A J N P O PSTN Mobile Telephone Switching Office Cellsite Cellsite main components: - Transceiver - Devices for supervising cellphones’ operation (initiating calls, terminating calls, etc.) F

20. 20 Why cells? B E H D I G L K F C M A J N P O PSTN Mobile Telephone Switching Office Cellsite Why cells? So channels can be reused in different cells. Channel reuse allows more customers to be supported. Channel 47

21. 21 Mobility n Handoff – Switching service from one cellsite to another when users move from cells to cell in a system (city) n Roaming – Switching service from one MTSO to another when users move from one system (city) to another. L N P O Handoff

22. 22 Generations of Cellular Technology Generation1G2nd3G Year198019902002 SignalingAnalogDigital Data Transfer Rate Data transfer is difficult; ~5 kbps 10 kbps 30 kbps to 500 kbps Technology Frequency Division Multiplexing FDM Code Division Multiplexing CDM

23. 23 Summary Questions 1)In cellular technology, what is: a)A cell? b)A cellsite? 2)What is the benefit of using cells instead of a large geographical area? 3)What are the main functions of a Mobile Telephone Switching Office (MTSO)? 4)Distinguish between handoff and roaming.

24. Integrated Services Digital Network- ISDN

25. 25 Integrated Services Digital Network Personal Computer Desktop Telephone 2. 64 kbps B Channel Analog Voice Signal On Telephone Wires 1. 64 kbps B Channel Digital Signal On Serial Cable (1010) ISDN Wall Jack (RJ-45) Original idea: one voice channel, one data channel

26. 26 Integrated Services Digital Network Personal Computer Desktop Telephone “ISDN Modem” 64 kbps B Channel Digital Signal On Serial Cable (1010) Internal DSU Converts Serial Port Signal to Digital B Channel Signal at 64 kbps (1010) All-digital Service (1101001..) ISDN Wall Jack (RJ-45) The Data Channel Uses 232 Serial Cable

27. 27 Integrated Services Digital Network Personal Computer Desktop Telephone 64 kbps B Channel Analog Voice Signal On Telephone Wires “ISDN Modem” Internal Codec Converts Analog Voice Signal to Digital B Channel Signal at 64 kbps (000010000)) All-digital Service (1101001..) ISDN Wall Jack (RJ-45) The Voice Channel Uses Home Telephone Cord

28. 28 Integrated Services Digital Network Personal Computer Desktop Telephone “ISDN Modem” 64 kbps B Channel Digital Signal On Serial Cable (1010) Internal DSU Converts Serial Port Signal to Digital B Channel Signal at 64 kbps (1010) All-digital Service (1101001..) ISDN Wall Jack (RJ-45) Bonding Use Both B Channels for Data Send and Receive at 128 kbps

29. 29 Integrated Services Digital Network n Dial Up: Not always connected – Do not have to pay for full-time use – Good if usage is small per day, say to upload sales data from retail once per night

30. 30 ISDN Costs n Must install an ISDN line – Will cost more than telephone line n Actually, could use your existing phone line – But then would need one B channel for telephony

31. 31 ISDN Costs n Need “ISDN modem” (expensive) n Costs for standard ISDN service – $40/mo plus $1.00/minute for usage ISDN tend to be used as a backup service. Example: Most banks communicate with headquarters using T-1, SONET, etc. If these services fails, they activate the ISDN connection.

32. 32 Summary Questions 5.(a) What is the highest speed you can have to and from an ISP using ISDN? (b) Is ISDN an always- active service? (c) How is it likely to be used in corporations? Why? (a) With bonding, ISDN can provide 128 kbps Internet access. (b) ISDN is NOT an always-on service. It is a dial- up service like ordinary telephone service. (c) It is likely to be a backup service because ISDN payments are modest except when the service is being actively used