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3 votes
3 votes
Let N station share 60 kbps of slotted aloha channel. Frame size is 1024 bits which are send at every 40 seconds. The value of N is ?

3 Answers

Best answer
6 votes
6 votes

Given Bandwidth (B) = 60 Kbps = 60*103

Bitrate for each host (b) = 1024/40 = 25.6 b/s

 

In slotted ALOHA, Number of stations N = (0.368 * Bandwidth) / Bitrate of each station.

= (0.368 * 60*103) / 25.6

= 862.5 stations

 

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4 votes
4 votes

Efficiency Of Slotted Aloha = 36.8%

Throughput = Efficiency * Bandwidth

                    = 0.368 * 60Kbps

                    = 22.08Kbps

Now, this is the throughput of entire channel…

 

According To Question,

1024 bits are transferred every 40 secs. Also throughput of each station is bits transferred every second

Throughput of Each Station = 1024/40

                                                = 25.6 bits/sec

 

Let the channel have N stations, each having a throughput of 25.6 bits/sec, then

N * 25.6 bits/sec = 22.08Kbps

N = 22080 bps / 25.6 bps

N = 862.5

 

Taking the lower bound or floor value as we can’t have half station, Total Number of Stations 

 

                                                                          N = 862       

 

3 votes
3 votes
throughput of slotted aloha=(efficiency of slotted aloha)*(bandwidth of the channel)........(1)

throughput of slotted aloha=(number of stations in slotted aloha)*(throughput of each stations)...(2)

so from 1 and 2

(number of stations in slotted aloha)*(throughput of each stations)=(efficiency of slotted aloha)*(bandwidth of the channel)

where the efficiency of slotted aloha is 36.8% or 0.368......

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