formulas and applications Flashcards
Familiarise variables, formulas and their applications (28 cards)
What is the formula for total transmission time for a frame of size L bits over a link of rate R and distance d?
Time= L/R + d/v
Where:
L: Frame length (bits)
R: Transmission rate (bps)
d: Distance between nodes
v: Propagation speed in medium
What does the variable L/R represent in a transmission delay formula?
Transmission delay — time to push all bits into the link
What does d/v represent in a transmission delay formula?
Propagation delay — time for a bit to travel from sender to receiver
Formula for channel efficiency in Stop-and-Wait ARQ?
η= L/L+2TpR
Where:
L: Frame size (bits)
Tp: Propagation time
R: Transmission rate
What is the efficiency of a Go-Back-N ARQ protocol?
𝜂=𝑊/1+2𝑎
Where:
W: Window size
𝑎=𝑇𝑝/𝑇𝑓 : Normalized propagation time
𝑇𝑓: Frame transmission time
In PPP, what are the byte stuffing escape sequences for 0x7E and 0x7D?
0x7E becomes 0x7D 0x5E
0x7D becomes 0x7D 0x5D
Formula to calculate link utilization?
𝑈=UsefulDataRate/ TotalTransmissionRate
What formula determines the number of crosspoints in a crossbar switch?
Ncrosspoints = 𝑛×𝑛,
where 𝑛 is number of inputs/outputs
What is the bit rate for a TDM system with
𝑁 channels each transmitting at 𝑅 bps?
Total rate = 𝑁×𝑅
What is the bandwidth requirement for a signal sampled at 𝑓𝑠 Hz with 𝑏 bits/sample?
Bitrate = 𝑓𝑠 × 𝑏
Q: What is the formula for transmission delay?
A: Transmission Delay = Packet Length (L) / Transmission Rate (R)
Q: What is the formula for propagation delay?
A: Propagation Delay = Distance (d) / Propagation Speed (s)
Q: What is the total nodal delay?
A: Total Delay = Processing + Queuing + Transmission + Propagation
Q: What is the formula for throughput?
A: Throughput = Total Data Sent / Total Time
Q: What is the formula for link utilization?
A: Utilization = Useful Time / Total Time
Q: How do you calculate round-trip time (RTT)?
A: RTT = 2 × Propagation Delay
Q: Formula for utilization in Stop-and-Wait ARQ?
A: Utilization = L / (L + 2RTT × R)
Q: How do you calculate Bit Error Rate (BER)?
A: BER = Number of Errors / Total Bits Sent
Q: What does the Shannon Capacity formula calculate?
A: C = B × log₂(1 + S/N), where B = bandwidth, S/N = signal-to-noise ratio
Q: How do you calculate the efficiency of Slotted ALOHA?
A: Efficiency = G × e^(-G), where G = average number of frames per slot
Q: How is window size related to bandwidth-delay product in sliding window protocols?
A: Window Size = Bandwidth × RTT
Q: What is the Go-Back-N ARQ retransmission condition?
A: Retransmit all frames starting from the one with error
Q: In Selective Repeat ARQ, what happens on error?
A: Only the erroneous frame is retransmitted
Q: What is the maximum utilization of Pure ALOHA?
A: Maximum Efficiency = 1 / (2e) ≈ 18.4%
