Networking & Cellular
E05A Data Transmission & Signaling — Study Guide
This guide covers Data Transmission & Signaling as part of Networking & Cellular. Start with the vocabulary, then try to answer each question before revealing the answer. Connect these facts to a real network or cellular connection and practice the subject in the arcade when you are ready.
Acronyms first
| Term | Meaning |
|---|---|
| MODEM | MOdulator/DEModulator |
| PSTN | Public Switched Telephone Network |
| ATM | Asynchronous Transfer Mode |
| SONET | Synchronous Optical Network |
| VSAT | Very Small Aperture Terminal |
| OTAR | Over-The-Air Rekeying |
Key facts
Which method uses a single fixed digital frequency occupying the cable's entire bandwidth — only one device transmits at a time?
Baseband
Which method carries multiple analog channels on one cable so multiple devices transmit simultaneously?
Broadband
Which signal type uses on/off (binary) values of voltage, current, or light?
Digital
Which signal type uses a continuously varying waveform (RF, sound, music)?
Analog
A modem converts…
digital signals to analog and vice versa
The combination, integration and evolution of voice, data, video, pictures, music is called…
Digital Telecommunications Convergence
The original fixed-line analog telephone system was called…
POTS (Plain Old Telephone Service)
The internet shares the same infrastructure as the PSTN for intercontinental communication.
True
Early PSTN modem data rates topped out around…
56 kbps
The global target for PSTN switch-off is by…
2030
Some countries aim to cease PSTN services as early as…
2025
How many voice channels does a DS-0 carry?
1 (64 Kbps)
DS and T standards describe digital circuits over ____; OC standards use ____.
copper; fiber-optic
Which standards are widely used for WAN lines (per slides)?
E1 and E3
T1 (DS-1): how many channels and what aggregate rate?
24 channels; 1.544 Mbps
T3 (DS-3): channels and aggregate?
672; 44.736 Mbps
E1: channels and aggregate?
32; 2.048 Mbps
E3: channels and aggregate?
512; 34.368 Mbps
OC1: aggregate rate?
51.84 Mbps
OC3 (STM1): aggregate rate?
155.52 Mbps
OC768 (STM256): aggregate rate?
39.813 Gbps
How many Kbps is a single DS-0 channel?
64
DSL is a modulation scheme that packs data onto…
copper lines / existing PSTN infrastructure
Which DSL is the residential version with faster download than upload (8 Mbps / 800 Kbps)?
ADSL
Which DSL is business-oriented with equal up/down rates (10/10 Mbps)?
SDSL
Which DSL is today's replacement, running fiber to neighborhoods — 100 Mbps symmetric to 300 Mbps asymmetric?
VDSL
ATM is a primary choice as a WAN ____ for long-haul, high-bandwidth needs over the PSTN.
backbone
ATM bandwidth is measured in terms of…
OC levels
ATM connected networks together while ____ handled each network's individual voice/data connections.
DSL
ATM is connection-oriented; its circuits are either…
Permanent or Switched
Which ATM circuit is dedicated and pre-configured by your ISP?
Permanent
Which ATM circuit is per-call and disconnects when the call ends?
Switched
SONET uses which kind of signal, providing synchronous communications?
Baseband
Order the steps of SONET communication.
Multiplexer combines signals into one optical signal → Re-generator boosts the signal → Demultiplexer splits back into individual signals
In the ATM + SONET partnership, which is the UNDERLYING signaling technology?
ATM
The area on Earth a satellite signal strikes is its…
footprint
A satellite's footprint is determined by orbital pattern, altitude, and…
velocity
How many basic satellite orbits are listed?
5
Which orbit is MOST common with the SMALLEST footprint?
LEO (Low Earth Orbit)
Which orbit is used for GPS with a moderate footprint?
MEO (Medium Earth Orbit)
Which orbit is the SECOND most common — a 24-hour orbit for communication and broadcasting?
GSO (Geosynchronous Orbit)
GSO altitude?
22,236 miles
Which orbit is a specific type of GSO fixed above the equator?
GEO (Geostationary)
Which orbit is elongated for high dwell time and needs 2+ satellites for consistent coverage?
HEO (Highly Elliptical Orbit)
VSAT services are delivered using which satellites?
Geostationary
Which VSAT topology requires ONE satellite hop?
Mesh
Which VSAT topology routes through a hub and requires TWO satellite hops?
Star
Which VSAT configuration is used for TV and radio broadcasts?
Point-to-multipoint
Which VSAT configuration (star, hub receiver) do TACTICAL satellite architectures use?
Multipoint-to-point
VSAT point-to-point uses which topology?
Mesh
Which access method divides frequency bands into channels — used in SATCOM and PTT radio, and by analog cellular?
FDMA
In FDMA, a call occupies its channel, which cannot be reused until the call is finished.
True
TDMA divides each digital channel into how many time slots?
3
TDMA supports about how many times as many users as FDMA in the same spectrum?
3 or more
TDMA uses two identical frames called…
Forward link and Reverse link
What ensures TDMA transmissions do NOT overlap?
Guard times
In a mobile environment TDMA yields lower co-channel interference and more efficient hand-off because transmission isn't continuous.
True
TDMA data rate range listed?
64 kbps to 120 Mbps
Which is a TDMA DISADVANTAGE?
Call dropped if all slots in the gaining cell are full
Multipath distortion in TDMA affects…
timing synchronization
Which access method lets numerous signals share one channel using ADC plus spread spectrum and a code?
CDMA
CDMA signals can only be intercepted by a receiver programmed with…
the same code
CDMA spreading creates what kind of signal?
Wide-band, noise-like
SSMA's two main spread spectrum techniques are…
FHSS and DSSS
Which technique varies carrier frequencies in a pseudo-random fashion?
FHSS (Frequency Hopped)
Which is the MOST commonly used technology for CDMA — multiplying the signal by a Pseudo Random Noise code?
DSSS
In DSSS, each user's code word is ____ to other users' codes.
orthogonal
Which military encryption encrypts entire blocks of bits at once (e.g., 64- or 256-bit)?
Bulk encryption
Which encryption applies an algorithm per bit as transmitted?
Stream encryption
OTAR is used when…
the distant end lacks cryptographic equipment
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