6610-l7- - Wireless MAC 1 Puzzle Two great mathematicians S...

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1 Wireless MAC
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2 Puzzle Two great S knows the sum of two positive integers (> 1) x and y P knows the product of x and y S calls P and says “You cannot find the two numbers” P replies “I know the two numbers” S responds “I know the two numbers too” What are the two numbers?!! (Note: 2 <= x < 100, 2 <= y < 100
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3 Wireless MAC CSMA as wireless MAC? Hidden and exposed terminal problems make the use of CSMA an inefficient technique Several protocols proposed in related literature – MACA, MACAW, FAMA IEEE 802.11 standard for wireless MAC
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4 Hidden Terminal Problem A talks to B C senses the channel C does not hear A’s transmission (out of range) C talks to B Signals from A and B collide A B C Collision
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5 Exposed Terminal Problem B talks to A C wants to talk to D C senses channel and finds it to be busy C stays quiet (when it could have ideally transmitted) A B C D Not possible
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6 Hidden and Exposed Terminal Problems Hidden Terminal More collisions Wastage of resources Exposed Terminal Underutilization of channel Lower effective throughput
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7 IEEE 802.11 The 802.11 standard provides MAC and PHY functionality for wireless connectivity of fixed, portable and moving stations moving at pedestrian and vehicular speeds within a local area. Specific features of the 802.11 standard include the following: Support of asynchronous and time-bounded delivery service Continuity of service within extended areas via a Distribution System, such as Ethernet. Accommodation of transmission rates of 1, 2, 5.5, 11 Mbps (b), 6, 9, 12, 18, 24, 36, 48, 54 Mbps (a, g), upto 195 Mbps (n) Support of most market applications Multicast (including broadcast) services Network management services Registration and authentication services
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6610-l7- - Wireless MAC 1 Puzzle Two great mathematicians S...

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