Lecture Topic: Network Edge & Internet Access Technologies

Bandwidth and Data Rate recap:
The data rate cannot exceed the capacity of the bandwidth of a given channel, this is where the formula $R \leq B_w log_2(1+\frac{S}{N}) \triangleq C$ comes from

Doubling the data rate means that you need a bandwidth that has at least as much capacity to handle the new data rate

Internet Access Technologies:
- DSL:
	- Using Frequency Division Multiplexing (FDM) it caries digital data through phone lines
	- Example: Voice 0-4 kHz, Upstream 4-50 kHz, Downstream 50 kHz-1 MHz
- Twisted Pair Cable Wire:
	- Constitute a fine antenna
	- Cancel out cross talk and produce less radiation
	- A number of pairs are bundled together in a cable
	- Used in telephone systems, unheralded twisted pair (UTP) for local area networks, computer networks within a building (Ethernet)
	- Data Rate: 10Mbps - 10Gbps
- Cable:
	- Use cable TV companies existing cable infrastructure
	- Hybrid fibre coaxial (HFC) access network
		- Coaxial cables are shared to reach individual homes
		- Fibre optics connect neighbourhood level junctions to CMTS
		- Asymmetric 40Mbps - 1.2Gbps downstream, 30Mbps - 100Mbps upstream
	- Data/TV are transmitted at different frequencies over shared cable
	- At the home, splits the signals into TV and Internet signals
- Coaxial Cable
	- More complex structure
	- Better performance
		- Excellent noise immunity because cable is very shielded
		- Can span longer distances
		- Bandwidth is close to 1 Ghz
		- Data rates are higher than other technologies, 100s Mbps per channel
- Fibre to the home (FTTH)
	- Optical network terminal in individual homes (ONT)
	- Optical line terminal in central office (OLT)
	- Fibre optic cables are similar to coax cables (lots of layers)
		- Class core with higher index of refraction than the outer glass
		- Light propagates through glass core
		- Thin plastic jacket to protect glass cladding
		- Fibres are typically grouped in bundles protected by an outer sheath
		- The outer layer keeps the light inside, not leaking any energy by reflecting the signal off an outer sheath
	- Has a few excellent features:
		- Very low signal attenuation up to 100km
		- Immune to electromagnetic interference
		- Larger bandwidth, support data rate up to 10s or 100s of Gbps
		- Hard to tap

Network Core:
- How is data moved through a network of links and packet switches?
- There are two fundamental approaches
	- Circuit switching
	- Packet switching
- 