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Within buildings, a 100 Mbit Ethernet network is ideal.

It is fast and, due to its popularity, relatively cheap.

100 Mbit Ethernet is normally transmitted using

twisted-pair copper cables. The cables can be shielded

against noise. The maximum cable length should not

exceed 330 ft. (100 m), although most computer stores

can offer a variety of accessories for longer transmis-

sion distances, e.g. ﬁ ber optic transmitters, wireless

(radio) LANs, etc..

Transmission speeds are measured in bits per second,

8 bits making up one byte. To transmit one byte,

approximately two extra bits are needed for control.

This means that approximately 10 bits are required to

transmit one byte.

1 byte/s ~10 bit/s

1 kbit/s ~1,000 bit/s

1 Mbit/s ~1,000 kbit/s

Bandwidth (kbit/s) = File size (kB) x Frame rate (fps) x 10

The rest of this chapter is dedicated to describing the

many different kinds of transmission methods to connect

to networks.

PSTN and standard telephone modems

Modems are widely used for accessing the ‘outside

world’ over the Public Switched Telephone Network

(PSTN). They are cheap and practical, but have the

disadvantages of being slow and experiencing frequent

transmission errors.

The maximum speed for downloading ﬁ les via a

modem can be as fast as 56 kbit/s, the maximum speed

for uploading ﬁ les is signiﬁ cantly slower at 33.6 kbit/s.

You can connect directly from a PC to a remote

network camera via standard modems using the Point-

to-Point communications protocol. This protocol is sup-

ported in Windows Dial-up connections and is included

in most of today’s popular operating systems.

ISDN telephone modems

ISDN (Integrated Services Digital Network) is a popular

communications standard for sending voice, video, and

data over digital telephone lines or normal telephone

wires. ISDN telephone modems are popular in many

countries and are normally provided by the subscriber’s

telephone company. ISDN modems transmit data at a

maximum speed of 128 kbit/s over 2 (64 kbit) channels.

xDSL modems

With many different varieties of xDSL transmission

services now available from most telephone companies

and ISPs (Internet Service Providers), ADSL, HDSL,

IDSL, and VDSL modems are becoming more and more

popular. By paying a ﬁ xed monthly fee, you can spend

as much time on-line as you want. The speed will vary

from company to company and from standard to stan-

dard, so check this with your local companies.

NB. The speed differs for uploading and downloading.

Usually the download speed will be about 1 Mbit/s and

the upload speed will be about 250 kbit/s.

Cable TV modems

Cable TV modems transmit data over the very same

cabling used for sending their TV signals. The trans-

mission speed for these types of modems vary from

one location to another and depends on how many

people in the neighborhood are using the service simul-

taneously. A typical maximum speed is 1 Mbit/s.

Digital transmission

IP-based video can be transmitted almost anywhere. It is not limited

to any particular media and is currently in common use over switched

10 Mbit, 100 Mbit or 1 Gbit LAN, WLAN, ISDN, PSTN, PHS, CDCP and

GSM networks. The developer’s choice of transmission medium can be

completely steered by the type of application that is being developed.

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