Link technologies”Reaching the Network of

networks”

Alberto Escudero-Pascual aep@it.kth.sehttp://www.it.kth.se/~aep

Royal Institute of TechnologySweden

1st International Workshop on Open Access4-7 June 2003, Stockholm, Sweden

Link level technologies… or how to get connected to the Internet

Goal:Brief technical overview of some of the most common technologies to connect to Internet in developing countries…

How: What is the Internet? What is to be connected? Review five (radio) link level technologies.

What is the Internet?

Federal Networking Council (DoD, NASA et al), Internet Monthly Reports, October 1995 agrees that the following language reflects our definition of the term "Internet".

"Internet" refers to the global information system that:

is logically linked together by a globally unique address space based on the Internet Protocol (IP) or its subsequent extensions/follow-ons;

is able to support communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite or its subsequent extensions/follow-ons, and/or other IP-compatible protocols; and

provides, uses or makes accessible, either publicly or privately, high level services layered on the communications and related infrastructure described herein.

What is the Internet?

The Internet is a group of interconnected networks which has evolved more-or-less independently of any social, political, or governmental control.

The Internet is a network of networks - billions of computers, all connected together.

The Internet is the internet of networks

What is the Internet?

Humanities and Arts: Sharing Center Stage on the Internet, IETF RFC2150, 1997

People, computers and information electronically linked around the world by a common Protocol for communicating with each other.

We, the ”linked”…

Connected to the Internet?

Reach a computer that can exchange “IP” packets with other computers around the world at anytime.

Reach the ”linked”, reach those ”connected”.

or reach a concrete service gateway.

Connect to the Internet is to make sure that the information that we send (receive) can reach a place where can be routed (forwarded) inside of IP

packet to others.

Connect to the Internet is being able to reach a ”IP-based Post office”

Reaching the linked world…

• VSAT

• DVB (MPE)

• Wi-Fi (IEEE 802.11)

• Packet Radio (AX.25)

• HF-Mail

VSAT

VSAT, very small aperture terminal

VSAT, very small aperture terminal

VSAT, very small aperture terminal

VSAT, very small aperture terminal

VSAT, very small aperture terminal

VSAT, very small aperture terminal

The frequency bands can be any of C band 4/6 GHz, Ku band 10-12/14 GHz Bi-directional Central Hub is ”connected” 270 ms delay 1 Mbps 500–700 USD

DVB-IP

DVB (Digital Video Broadcast)• Users access Web sites through their low-speed Internet connection • Receive multimegabit data streams back through a “TV” dish antenna on the roof.

• The DVB cards convert incoming RF satellite signals and place them back in the TCP/IP stack.

• DVB uses IP encapsulation technology to make Internet traffic look like MPEG-2 data.

• Cheap receivers (200 USD)

DVB (Digital Video Broadcast)

• Sending Wi-Fi (LaoTel) • Receiving (DVB-IP)

• Sending VSAT (SCPC) • Receiving (DVB-IP)

Wi-Fi (IEEE 802.11)

IEEE 802.11 (Wi-Fi) Used for terrestrial

outdoor link Connecting to the

”connected” (range of 1-30 Kms)

Low power (100 mW – 1W)

Requires line-of-sight Mass-produced

equipment, ”open” standard

Wi-Fi: The radio technology

2.4 Ghz radio band Following the ETSI regulations Unlicenced spectrum Running IEEE 802.11b (WiFi). Using Open Source code (GNU/Linux) PtP links ~ 2000 USD

Wi-Fi: PtP Radio link with repeater

Wi-Fi: Hardware

Antennas Low loss cable Connectors Radio transcivers Radio Bridges (Linux) Routers

Wi-Fi: Radio Equipment

Wi-Fi: Radio Kits

Wi-Fi: Radio Kits (Supermarket technology)

Wi-Fi : Nora-Digerberget-Ås

Ås Nora

4.5 Km5.3 Km

Wi-Fi: Ås - Digerberget

Wi-Fi: Ås school

Wi-Fi: Line-of-sight

Packet Radio (AX.25)

Packet Radio (AX.25)

AX.25 is considered the defacto standard protocol for amateur radio since early 70’s

3-30 Mhz (HF), 140 Mhz (VHF) and 435 Mhz (UHF)

Connected & connectionless modes of operation, and is used either by itself for point-point links, or to carry other protocols such as TCP/IP and NetRom.

For HF packet, 300 BPS data is used over single side band (SSB) modulation.

For 1200/2400 bps UHF/VHF packet, commonly available narrow band FM voice radios are used.

For high speed packet (starting at 9600 bps), special radios or modified FM radios must be used.

Packet Radio (AX.25)

Packet Radio (AX.25)

More info

http://www.ehas.org

HF mail gateway

HF-mail gateway

Connect to a “connected” service as a mail server via a HF (100 – > 1000 Kms) Using two HF radio modems talking:

Codan 9002 SCS PTC-II Clover-2000 Clover-500 Pactor-1 Pactor-2 SITOR

HF-mail gateway

HF radio modes

SITOR ARQ  100 bits/second Open standardupper case only, no error correction

CCIR-476 Same as SITOR AMTOR       Same as SITOR PACTOR-1  200 bits/sec G-TOR            300 bits/sec PACTOR 2  508 bits/sec  Clover-400 600 bits/sec Clover-500 750 bits/sec Clover-2000     3000 bits/sec

(minus overhead: 1936 bits/second uncompressed) Codan 9002      2400 bits/sec + built-in compression = 6000 bits/sec 

or 1475 bits/sec uncompressed

Codan 9002, SCS PTC-II, Clover-2000, Clover-500, Pactor-1, Pactor-2 and SITOR

How is the Internet World?

How is the Internet World?

How is the Internet World?