Changes
[[Image:cdma18.jpg]]
'''Effect of Power Control''': Power control is capable of compensating the fading fluctuation. Received power from all MS are controlled to be equal.　NearNear-Far problem is mitigated by the power control.
[[Image:cdma19.jpg]]
[[Image:cdma25.jpg|thumb|600px|center|QoS Management in CDMA - Pathway]]
The process of Implementation of rate Matching is done using Puncturing or Repetition. If the number of bits are more than the calculated rate of transmission then the bits of transmission block are punctured otherwise they are repeated till the calculated size is reached. SEIMENS Siemens has proposed an algorithm to ETSI, to obtain a non-integer punture/repetition ratio referenced SM/G2/UMTS-L1/Tdoc428/98 and it is given as follows. This algorithm is used as a standard approach for Rate Matching. [[Image:cdma21.jpg|thumb|700px|center|Rate matching algorithm by SEIMENSSiemens]]
===Rate Matching and QoS===
The patent [http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=EP1385290&F=0 EP1385290] titled "Method for balancing Eb/I ratio in a service multiplexing CDMA system and a telecommunication system using this method" targets this concept of Rate matching and introduces an algorithm for calculating effective data output bits by a process of repetition or puncturing of the input bits governed by a '''rate matching ratio''' and '''puncturing ratio''' received from the sending entity (can be a BS or MS). The Parameters Ei(Energy per bit),Pi(Max puncture Rate) and Xi(Input data rate) are the characteristic constants of a transport channel both at the Mobile Station(MS) and the Base Station(BS). Initially Ei,Pi and Xi are determined at the Base Station and a maximum possible payload is calculated. This is known as the intermediate size and and a vector of expected is transmitted to the Mobile Station(MS) along with the parameters Ei and Pi. Using the values of Pi,Ei and Xi the mobile will also calculate its output frame size Yi. Then final step is matching this value of Yi with the received vector of Intermediate values Yi and decide the final frame size. The bits are repeated or punctured according to the required Final Frame Size.<br>
The rate matching step in above figure is essentially implemented by repetition or puncturing, SEIMENS Siemens has proposed an algorithm to ETSI, to obtain a non-integer punture/repetition ratio referenced SM/G2/UMTS-L1/Tdoc428/98 and it is given as follows. This algorithm is used as a standard approach for Rate Matching. [[Image:cdma21.jpg|thumb|700px|center|Rate matching algorithm by SEIMENSSiemens]]
The above algorithm avoids puncturing consecutive bits when operating in the puncturing mode. In the repetition mode, the repetition bits follow the bits which they repeat. [[Interleaving]] is an essential step in a communication systems. In the current scenario of repetition,when interleaving is executed after rate matching it would space the repeated bits apart. While Puncturing, if the interleaver precedes the rate matching it may puncture consecutive bits of the channel encoder which were dispersed by interleaving. Hence it is always preffered to have the rate matching step as close as possible to the Channel Encoder
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