Telecom Overview

By

RGM TTC BSNL Chennai

Telecom Network

• Access

• Junction

• Long Distance

Access Network

• Subscriber to Switch

• Medium – Copper, Fiber, Wireless

Junction Network

• Switch to Switch

• Medium – Copper, Fiber, Wireless

Long Distance Network

• One Metro to Another

• Medium – (Copper), Fiber, Wireless

Telecom Traffic

• Measured in Erlangs

• 3 Parameters1) Number of Junctions2) GoS or Blocking Probability3) Traffic Handling Capacity of the switch

• Given any 2 parameters, the 3rd can be found from a table.

Telecom Traffic - Example

• Number of Trunks = 7

• GoS = 2%

• Traffic Capacity = 2.94 E

Telecom Traffic – Example…

• Rural Sub Average Call Holding Time = 1.5 min

• Traffic generated per Average Rural Sub = 1.5/60 E

• Number of Rural Subs supported = 2.94/(1.5/60) = (2.94 x 60)/1.5 = 117(app)

Telecom Traffic - Question

• Previous Example Data

• Traffic generated per Average Urban Sub = 40 mE

• Number of Urban Subs supported = ?

Signal Power

• Measured in dBm

• dBm – decibel with ref to 1 milli Watt

• P mW = 10 log10 P dBm

dBm - Example

• P = 1 mW

• 1 mW = 10 log10 1 dBm

• 1 mW = 10 x 0 dBm = 0 dBm

dBm – Example…

• 2 mW = 3 dBm

• 4 mW = 6 dBm

• When the Signal Power in mW doubles, Signal power in dBm is augmented by 3.

Gain/Loss of a Network

• Measured in dB

• Gain = 10 log10 (Pout / Pin) dB

• Loss = 10 log10 (Pin / Pout) dBwherePout – Network Output Signal powerPin – Network Input Signal power

Gain/Loss of a Network…

• Gain(in dB)

= Output(in dBm) – Input(in dBm)

• Loss(in dB)

= Input(in dBm) – Output(in dBm)

Gain/Loss of a Network - Ex

• Pout = 1 Watt

• Pin = 1 milli Watt

• Gain(in dB) = 30 dBm – 0 dBm = 30 dB