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UNB/Year 4/Semester 2/CS3873/2024-01-17.md

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+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
+-