Broadband Technologies Part 2

1. Broadband TechnologiesPart 2

2. Overview

3. Broadband Overview

4. Why broadband? • Broadband is generally defined as any sustained speed of 128K or more. • Broadband can allow remote office staff and small office, home office (SOHOs) to connect to the central office (CO) LAN at high speeds. • The Internet is moving from dialup modems and slow connections to a world of high-speed broadband using a variety of technologies. • The most common problem with broadband access is lack of coverage area. • Broadband options include digital subscriber line (DSL), fast downstream data connections from direct broadcast satellite (DBS), fixed wireless providers, and high-speed cable modems. • Note: These are typically “residential” broadband options

5. What is broadband? From Whatis.com • In general, broadband refers to telecommunication in which a wide band of frequencies is available to transmit information. Because a wide band of frequencies is available, information can be multiplexed and sent on many different frequencies or channels within the band concurrently, allowing more information to be transmitted in a given amount of time (much as more lanes on a highway allow more cars to travel on it at the same time). Related terms are wideband (a synonym), baseband (a one-channel band), and narrowband (sometimes meaning just wide enough to carry voice, or simply "not broadband," and sometimes meaning specifically between 50 cps and 64 Kpbs). • Various definers of broadband have assigned a minimum data rate to the term. Here are a few: • Newton's Telecom Dictionary: "...greater than a voice grade line of 3 KHz...some say [it should be at least] 20 KHz." • Jupiter Communications: at least 256 Kbps. • IBM Dictionary of Computing: A broadband channel is "6 MHz wide." • It is generally agreed that Digital Subscriber Line (DSL) and cable TV are broadband services in the downstream direction.

6. Broadband • Broadband can be delivered to SOHOs via the following technologies: • Satellite • Wireless • Cable • DSL

7. Satellites

8. Satellite options • Older deployments from satellite data providers used asymmetric data paths a satellite downstream to the customer, and a dialup modem for the return path to the provider. • Today, a transmitter and a receiver are installed for communications. • Satellite services deliver data at downstream speeds up to 1,500 kbps, and upstream speeds as high as 125 kbps. • Due to the asymmetric nature of satellite communication, certain applications do not perform very well over satellite such as voice.

9. Satellite options • The typical satellite system requires: • small 1.2 m (3.9 ft) satellite dish • two standard coaxial cables to connect the satellite disk to a satellite modem • the satellite modem that connects to a PC through an Ethernet or USB port. • Satellite networks include: • geostationary orbit satellites (GSOs) (22,300 miles) • Disadvantage of ¼ second ground-satellite-ground delay • non-geostationaryorbit satellites (NGSOs). • NGSOs include low-earth-orbit satellites (LEOs).

10. Satellite Extras Satellite • big repeaters in the sky • transponders = repeater units carried by the satellite • 10 to 46 transponders per satellite • each transponder can carry up to 3,000 DS-0, (64 kbps) channels • uses radio waves to transmit data • bandwidth in the Mbps

11. Satellite Extras Geosynchronous / Geostationary satellites • orbits earth at an altitude of 22,300 miles above the equator • takes 24 hours to orbit earth • appears stationary to the human eye or to the satellite dish

12. Satellite Extras Advantages • large footprint broadcast, send once - receive many • cost effective for remote areas • 3 - 4 satellites can cover the earth

13. Satellite Extras Disadvantages • promulgation delay: long delay, .12 seconds for a “single hop” or .24 seconds (1/4 second) for “roundtrip” • limited “orbit space” or positions for these satellites • initially expensive to put in orbit • subject to noise and interference • two-way communications expensive (inexpensive: receive only)

15. Satellite Extras Low Earth Orbit Satellites (LEO) • non-stationary satellites of lower orbits which has a smaller promulgation delay • home satellite dishes act more like cellular phones, jumping from satellite to satellite as the satellites move in and out of range • Teledesic Network (A Microsoft Project): satellites at a low orbit about 435 miles

16. Satellite Extras • “An orbiting global constellation of 1,000 small, advanced, semi-autonomous, inter-connected satellites.” • prevents the signal delays inherent in the use of conventional geostationary communication satellites which operate at a higher altitude • Hughes Network Systems DirecPC: 400 kbps and in the future up to 92 Mbps • Iridium System - uses a central control station, 66 satellites, handheld phones and gateways to the PSTN.

17. Wireless Introduction

19. 802.11 Frames – This isn’t Ethernet! Distribution System (DS) IP Packet • 802.11 has some similarities with Ethernet but it is a different protocol. • Access Points are translation bridges. • From 802.11 to Ethernet, and from Ethernet to 802.11 • The “data/frame body” is re-encapsulated with the proper layer 2 frame. • Certain addresses are copied between the two types of frames. General 802.11 Frame IP Packet LLC

20. Station Connectivity

21. Authentication Process • On a wired network, authentication is implicitly provided by the physical cable from the PC to the switch. • Authentication is the process to ensure that stations attempting to associate with the network (AP) are allowed to do so. • 802.11 specifies two types of authentication: • Open-system • Shared-key (makes use of WEP)

22. Authentication Process – Open-System • Open-system authentication really “no authentication”. • Open-system authentication is the only method required by 802.11 • You could buy an AP that doesn’t support Shared-key • The client and the station exchange authentication frames.

23. Authentication Process – Shared-Key • Shared-key authenticationuses WEP (Wired Equivalent Privacy) and can only be used on products that support WEP. • WEP is a Layer 2 encryption algorithm based on the RC4 algorithm. • 802.11 requires any stations that support WEP to also support shared-key authentication. • Both the client and the AP must have a shared-key, password.

24. Authentication Process • We’ll look at the configuration of the client and AP later! • Example of open-system authentication. • Note: On “some” systems you can configure authentication (WEP) and WEP encryption separately. On the ACU you can have open-system authentication and also have WEP encryption. However, if you have Shared-key (WEP) authentication, you must use WEP encryption.

25. Authentication Process • Authentication • Open-System • Shared-Key (WEP) • Encryption • None • WEP only or If using Shared Key (WEP) authentication you are also using WEP encryption. Open System authentication can take place with or without WEP encryption.

26. Hey, I REALLY didn’t do anything and I am on the Internet! Station Connectivity • If not configured specifically to look for a network, some client utilities will automatically join the network that meets their vendor’s criteria (not specified in 802.11) such as signal strength and open-system authentication. • How a station chooses an AP is not specified in 802.11. • Or just find the open-system network and join. Beacon SSID = tsunami Authentication Request Authentication Response (Open-system)

27. Wireless Bridging

28. RBOC DS1 DS1 DS3 New remote office - No DS1 connection available Traditional WAN Connectivity Monthly Leased Line OpEx 2 DS1: $600 1 DS3: $5000 TOTAL: $5600 RBOC provides guaranteed level of service via a Service Level Agreement (SLA)

29. RBOC 2 Mbps 2 Mbps 22 Mbps 5 Mbps 802.11b Connectivity Monthly Line Cost 2 DS1: $600 1 Fractional DS3: $3000 TOTAL: $3600 Wireless Installation Cost 7 350 Series Bridges Installed: $12,500 USD Pay Back Period: 3 months New building connected Self managed

30. RBOC 14 Mbps 14 Mbps 50 Mbps 27 Mbps 802.11a/g Connectivity Monthly Line Cost 2 DS1: $600 1 DS3: $5000 TOTAL: $5600 Wireless Installation Cost 7 1400 Series Bridges Installed: $40,000 USD Pay Back Period: 8 months New building connected Self managed

31. Optional 2.4GHz Antennas for Long Range • 13.5 dBi Yagi • Distances over • 7.3 miles @ 2 Mbps • 11.7 Km @ 2 Mbps • 3.6 miles @ 11 Mbps • 5.8 Km @ 11 Mbps • 21 dBi Solid Dish • For distances up to • 25+ miles @ 2 Mbps • 40+ Km @ 2 Mbps • 20.5 miles @ 11 Mbps • 33 Km @ 11 Mbps

32. Richardson Elementary Yagi Weaver- Special Education Dish Roberts Middle School Dish High School 2 Bridges One 12 dBi omni One Dish Administration 2 Bridges One 12 dBi omni One Yagi Channel #1 Channel #6 Bolich Middle School Yagi Channel #11 Price Elementary Yagi Dewitt Elementary Yagi 802.11b Bridge Application: School District Bode Elementary Yagi Lincoln Elementary Yagi

33. Cable Technology

34. Cable options - Benefits • Cable usersaccess the Internet through a cable modem that connects to the service provider through a cable TV connection. • In this case, the Internet Service Provider (ISP) is the cable company. • Minimum of 27 Mbps downstream to customers and as much as9.4 Mbps in the return path. • Another key benefit of constant connectivity

35. Cable options - DOCSIS • Cable specifications are defined by Data Over Cable Service Interface Specification (DOCSIS). • Current specification: DOCSIS 2.0 • Defines the use of data over cable and other functional details. • Defines technical specifications for subscriber locations and cable operators’ headends (coming). • Allows for interoperability for multi-vendor solutions. • DOCSIS managed by non-profit CableLabs.

36. The original cable plant • Community Antenna Television (CATV), commonly called cable TV, was invented to solve a dire consumer problem, which was poor TV reception. • Cable service providers (CSPs)offer IP-based data and voice services to the business market as an opportunity to substantially expand their revenue potential and enhance their profit margins. Cisco UBR 7223 Cable Modem Router as used for high speed internet access over cable systems

37. Data over cable • Fiber is used to replace cable amplifiers throughout the plant. • Amplifiers are placed approximately every 610 m (2000 ft) to ensure all RF signals will be delivered to the home of the end-users with enough power and clarity to receive all channels within the spectrum, which is 50 to 860 MHz. • In a 20-mile plant, approximately 52 amplifiers would be used to reach the last house 27.3 km (20 miles) away. • Fiber allows the cable operator to run longer distances with a cleaner signal.  • Fiber also allows the cable operator to remove amplifiers from the link.

38. Data over cable • The downstream traffic emanates from the headend and is injected into a trunk cable. • A cable system consists of the headend and its connected coaxial cables and subscribers. • The operator of a cable system is referred to as a cable operator. • The headend is where the cable operator puts the different channels on the frequencies that are compatible with the cable network. • Larger cable systems are much more complex, and they may serve several communities in a geographical area. • Big companies that operate multiple systems are called multiple system operators (MSOs).

39. Data over cable • Headend at Dascom’s Minnesota Facility - a 45 channel system

40. Data over cable • The distribution network, which is made up of fiber and coaxial cabling, delivers television signals to the subscriber. • The last part and also one of the best known parts of the cable network is what is called the subscriber drop. • The subscriber drop includes the following: • All cable splitters, couplers, and amplifiers running from the nearest utility pole or pedestal to devices such as TV sets and cable modems. • Set-top box (STP) • Grounding and attachment hardware • Cable

41. Data over cable • Broadcast analog signal strength attenuates or weakens as it moves through conducting material (coax). • Outside noise, weather, and temperature all affect the impact signal strength through coaxial cable. • To combat these problems, cable operators came up with the idea to use fiber-optic cable in place of coaxial cable trunks. • The total system would have both fiber and coaxial cables, which created the term hybrid fiber-coaxial (HFC) networks. www.knology.com

42. Hybrid fiber-coaxial (HFC) architecture • To deliver data services over a cable network: • one 6 MHz television channel that is in the 50 MHz to 750 MHz range is typically allocated for downstream traffic to homes • one 6 MHz channel in the 5 MHz to 42 MHz band is used to carry upstream signals • A headend cable modem termination system (CMTS)communicates through these channels with cable modems located in subscriber homes to create a virtual LAN connection Scientific-Atlanta CMTS

43. Hybrid fiber-coaxial (HFC) architecture • The cable modem network only operates at Layers 1 and 2 www.twcarolina.com

44. Hybrid fiber-coaxial (HFC) architecture • An individual cable modem subscriber may experience access speeds from 500 kbps to 2.5 Mbps, depending on the network architecture and traffic load. • If congestion does begin to occur due to high usage, cable operators have the flexibility to add more bandwidth for data services. • A cable operator can simply allocate an additional 6 MHz video channel for high-speed data, which would double the downstream bandwidth available to users. Scientific-Atlanta CMTS

45. HFC • Another option for adding bandwidth is to subdivide the physical cable network by running fiber-optic lines deeper into neighborhoods. • This reduces the number of homes served by each network segment, and it increases the amount of bandwidth available to customers. www.synchronous.net

46. Digital signals over RF channels • When an FM radio is tuned to different radio stations across the spectrum, that radio is being tuned to different electromagnetic frequencies across the spectrum. • Cable works the same way.Cable carries TV channels or data carriers at different frequencies. • The equipment in the subscriber home can be tuned to those different frequencies. • This allows the customer to view the channel on the TV or through a cable modem and route that information to a computer. • The CATV industry uses the portion of the electromagnetic spectrum between approximately 5 MHz and 1 GHz

47. Identifying cable technology terms • Broadband refers to the ability to frequency-division multiplex (FDM) many signals in a wide RF bandwidth over an HFC network. • It also refers to the ability to handle vast amounts of information. • CATV is originally an acronym for community antenna television. • Today the term is generally accepted to mean cable TV. • Coaxial Cable is the principal physical media with which CATV systems are built. • Coaxial cable is used to transport RF signals. • Coaxial cable signal loss or attenuation is a function of the diameter of the cable, dielectric construction, ambient temperature, and operating frequency (f). • Headend is the location where the cable company aggregates, combines, mixes, and modulates all signals in order to send them downstream. • Upstream signals usually are received in the headend. • Downstream (DS) is the RF signal flow from headend toward subscribers. • It is also called forward path. • Upstream (US) is the RF signal flow from the subscribers to the headend. • It is also called the return or reverse path.

48. DSL Technology

49. What is DSL? • While considered an end-to-end solution, DSL only operates on the local loop between the customer premises equipment (CPE) and the DSL access multiplexer (DSLAM). • A DSLAM is a device in the central office (CO) (sometimes) used to terminate many Layer 1 DSL connections, such as dialup, cable, wireless, and T1.

50. What is DSL? • DSL uses the high frequency range of up to about 1 MHz. • For example, asymmetric digital subscriber line (ADSL) uses the frequency range of about 20 kHz to 1MHz. • ADSL does not overlap the plain old telephone service (POTS) voice frequency range. (300 – 3,400 Hz) • POTS and ADSL service can coexist over the same wire. • Other DSL variants like single-line digital subscriber line (SDSL) use a frequency range that overlaps the POTS voice frequency range. • POTS and SDSL service cannot coexist over the same wire.