It2402 Essay

4212 WordsFeb 4, 201317 Pages
Adhiparasakthi college of Engineering IT2402 VII Sem/ IT Mobile Communication UNIT-I TWO MARKS Q&A 1.. Define SAMA. Spread Aloha Multiple Access is a combination of CDMA and TDMA. The CDMA better suits for connection oriented services only and not for connection less bursty data traffic because it requires to program both sender and receiver to access different users with different codes. 2.Define CDMA. Code Division Multiple Access systems use codes with certain characteristics to separate different users. To enable access to the shared medium without interference. The users use the same frequency and time to transmit data. The main problem is to find good codes and to separate this signal from noise. The good code can be found the following 2 characteristic 1.Orthogonal. 2.AutoCorrelation. 3.What are the several versions in CSMA? There are several versions in CSMA, they are as follows a) non-persistent CSMA b) p-persistent CSMA c) 1-persistent CSMA 4. What is meant by non-persistent CSMA? In, non-persistent CSMA, stations sense the carrier and start sending immediately if the medium is idle., if the medium is busy, the station pauses a random amount of time before sensing the medium again and repeating this pattern. 5.What is meant by p-persistent CSMA? In p-persistent CSMA system nodes also sense the medium, but only transmit with a probability of p. With the station deferring to the next slot with the probability 1-p, i.e. access is slotted in addition. 6. What is SDMA? Space Division Multiple Access (SDMA) is used for allocating separated spaces to users in wireless networks. The basis for the SDMA algorithm is formed by cells and sectorized antennas which constitute the infrastructure implementing space division multiplexing (SDM) 7. What is FDD? In FDMA, the base station and the mobile station establish a duplex channel.

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