Chapter 9 Flashcards
What did early cellular data use?
Circuit switching (CSD, HSCSD) CSD = circuit switched data HS = high speed
What technologies did 2G use
GSM, GPRS, EDGE ( Edge was fastest)
What technologies did 3G use?
UTMS, CDMA2000 and WiMax (WiMax is only for data no voice.)
By what has WiMax been standardised?
IEEE 802.16
What is the leading contender in 4G?
LTE
What was used before mobile technology?
Fixed line services
What technology is used for last-mile connectivity?
WiMax
How did PSTN/POTS work?
It uses electromachanical switches that replaced manual switches.
Why was DSL ( Digital Subscriber Loop) developed?
To build fast networks that can use the existing last kilometre copper cable
How does DSL work?
Uses existing copper phone lines
Carries data + voice simultaneously
Uses filters to separate voice and data
Different speeds (ASDL(most common), SDSL, RADSL)
How does ADSL work?
Prioritizes from internet to user
What replaced leased lines?
VPNs
Standard to exchange packets between telecom operators across borders?
X.25
What are the 2 types of ISDN channels?
B (bytes = used to carry data)
D = signaling + control
What channels does BRI use?
2B + D
What channels does PRI use?
30B + D
How many undersea cables connect to south africa?
3
Challenges of convergence?
interoperability, SLAs and troubleshooting
Performance measures
Bandwidth
Latency
Propagation delay
Jitter ( stability)
Reliability ( meant time between failures (MTBF) and mean time to repair (MTTR))
What is multiplexing?
Single physical channel into multiple logical channels
4 technologies used to “multiplex”
FDM(frequency division), TDM(time division), STDM (statistical tdm), CDM (code division)
What is the inverse of Multiplexing called?
bonding
How can we encode data?
Electric signals
Light
Radio
What is baud rate?
Number of states transmitted per second
