1 00:00:00,840 --> 00:00:07,350 Because it is impossible for wireless stations to detect collisions, contention batteries required 2 00:00:07,350 --> 00:00:09,270 to arbitrate access to the network. 3 00:00:09,960 --> 00:00:17,880 This method is the CSI may see a method that is collision avoidance method which is used now. 4 00:00:17,880 --> 00:00:25,410 It requires a more involved process of checking for existing wireless traffic before Afrim can be transmitted 5 00:00:25,410 --> 00:00:26,070 wirelessly. 6 00:00:26,790 --> 00:00:32,700 The stations must also acknowledge the frames upon receiving the frame or sending the frame. 7 00:00:33,420 --> 00:00:37,380 Now let us have a look at the process of TSMC. 8 00:00:38,280 --> 00:00:42,830 Now consider two pieces laptop and laptop and laptop. 9 00:00:42,840 --> 00:00:50,640 It has to wirelessly send a frame to laptop B, so before sending laptop it must check for traffic in 10 00:00:50,640 --> 00:00:51,670 two ways, right? 11 00:00:52,140 --> 00:00:58,740 First, it performs a carrier sense, which means it listens to see whether any radio waves are being 12 00:00:58,740 --> 00:01:00,340 received on its transmitter. 13 00:01:01,140 --> 00:01:09,180 So next, if the channel is not clear the traffic is being transmitted, laptop E will decrement an 14 00:01:09,180 --> 00:01:15,030 internal countdown mechanism called Random Backoff Algorithm, which we have just discussed. 15 00:01:15,840 --> 00:01:21,660 This counter will have started counting after the last time the station was allowed to transmit and 16 00:01:21,660 --> 00:01:25,000 all the stations will be counting down that individual times. 17 00:01:26,570 --> 00:01:33,650 Now, if laptop checks for the careers ends and then there is no traffic and it's timer hits zero, 18 00:01:34,070 --> 00:01:37,730 it will send the frame and the frame is restricted access point. 19 00:01:39,610 --> 00:01:45,760 Now, the access point sent an acknowledgement back to the laptop e saying that it has received Afrim 20 00:01:45,760 --> 00:01:53,710 from laptop E until that acknowledgement is received by laptop E, all of those stations must remain 21 00:01:53,710 --> 00:01:54,310 silent. 22 00:01:54,760 --> 00:02:00,610 This is very important unless and until the laptop receives acknowledgement from the access point that 23 00:02:00,970 --> 00:02:02,850 had you to have received your frame. 24 00:02:04,090 --> 00:02:05,980 So I'll do my work now. 25 00:02:06,180 --> 00:02:11,080 Until this conversation, all other stations on the network must remain silent. 26 00:02:12,100 --> 00:02:18,580 The access point will cache the frame where it already may have other cached frames that need to be 27 00:02:18,580 --> 00:02:20,140 related to other stations. 28 00:02:21,250 --> 00:02:25,150 Each frame that the access point needs to relay must wait. 29 00:02:25,160 --> 00:02:33,030 It's done to send the frame using the same mechanism that we have seen now in the frames, stone comes 30 00:02:33,040 --> 00:02:33,930 up in the cache. 31 00:02:33,940 --> 00:02:38,410 Q The frame from laptop E it'll be relayed to laptop B. 32 00:02:39,920 --> 00:02:46,040 And Laptop B, send an acknowledgement back to the access point thing that, hey, dude, I have received 33 00:02:46,250 --> 00:02:49,210 an acknowledgement, I received a frame from you. 34 00:02:49,430 --> 00:02:55,020 So this is the acknowledgement and all of the stations must again remain silent. 35 00:02:55,850 --> 00:03:01,890 So this was the walking of C as MFC, a matter contention method for wireless networks. 36 00:03:02,360 --> 00:03:09,050 Now, if we haven't understood the walking, I recommend you to go back and see the video again so that 37 00:03:09,050 --> 00:03:12,110 we have a clear shot at CSM committed. 38 00:03:12,620 --> 00:03:18,470 Again, if you have any doubt, please feel free to ask us in the Q&A section where we'll try to answer 39 00:03:18,470 --> 00:03:20,280 your questions within 48 hours. 40 00:03:20,840 --> 00:03:26,480 And again, if you're enjoying this course, I really request you to please leave a rating for our course. 41 00:03:26,780 --> 00:03:31,610 You can see the rating tap on the right hand top corner of your laptop or website. 42 00:03:31,970 --> 00:03:38,390 If you're using a laptop machine in the next lecture, we will see a different contingent method which 43 00:03:38,390 --> 00:03:40,070 is used for a wired network. 44 00:03:40,400 --> 00:03:44,690 And I hope you understand the difference between these two mechanisms.