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/* Power Control, Rate Matching and QoS */
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
===Power Control, Rate Matching and QoSusing Code Hopping===According to one of the methods of dynamic power control (Code Hopping) used in W-CDMA technology, the Rate Information (RI) field in the uplink control channel in W-CDMA frame can be used to notify the base station about the variable bit rates (VBR) it wants to send, then the base station computes and assigns a new spreading factor for each data rate and hence the optimal powers power calculation is done according to the new spreading factor for each radio frameas follows. <br> Spreading factor(Gi) is defined as the ratio of bandwidth of the system to the data rate of the radio frame.
Mathematically,<br>
'''Gi = W / Ri''',where W=system bandwidth which is a constant for a system and Ri= data rate of radio frame.<br>
A power index (gi) is calculated from this Spreading Factor(Gi) using the following expression<br>
'''gi= (vi / (vi+Gi))''', where vi is minimum QoS for the ith session which is a constant.<br>
This power index will ascertain the optimal power to be alloted to each service channel(each data rate for different services).<br>
'''Pi = (gi*No*W )/ (Hi*(1-(Sgj)'''<br>
where No is AWGN(Additive White Guassian Noise)a constant,<br>
Hi is path loss which is dependent on the distance and is a costant constant for a path,<br>
and Sgj is sum of the power index of all the sessions which is constant for all sessions of the radio frame.
From the above analysis, we observe that the bit rate is inversely proportional to the spreading factor which will inversely effect the power index and hence the optimal power. Therefore, the Bit Rate and Optimal power go hand in hand, and have the same effect on Eb/I and QoS.
The method and algorithm to schedule optimal power is detailed in the IEEE paper 765366 [[Media:IEEEGurbuz.pdf|Dynamic Resource Scheduling for Variable QoS Traffic in W-CDMA - Ozgur Gurbuz, Henry Owen]].
Thus, we conclude that by adjusting the optimal power we are actually trying to implement a rate matching step.
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