Changes
/* Quality of Service(QoS) */
==Quality of Service(QoS)==
CDMA is being accepted as a third generation (3G) system and a specific feature of 3G systems is that they offer a radio interface adapted for all kinds of services and combination of services (such as data, voice, video etc). The big challenge is multiplexing these services which have do not have the same demands in terms of quality of service(QoS) which can be represented as BER(bit error rate), processing delay, frame error rate etc. Different QoS will require different channel encoding and interleaving strategies. The demand of BER can be satisfied when the coding bits have at least a code dependent ratio Eb/I(ratio of bit energy to interference). There are several influences that might change system performance(BER) and hence Eb/I ratio, of which the most effective is variation of Bit Rate by a step of '''Rate Matching'''. [[Image:cdma22.jpg|thumb|center|Rate matching and QoS]]
===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 following framework highlights the various steps involved in providing variable QoS. The received data from the transport block is classified into different processes based on their QoS. Data is split onto various transport channels to which a CRC code is attached for error correction. Further, all these transport channels are multiplexed on one line by concatenation, interleaved, segmented and then rate matched. The rate matching step is performed using the rate matching ratio and puncturing ratio which is received from the sending entity (an exchange of handshaking signals occurs).
[[Image:cdma20.jpg|thumb|600px|center|Rate matching and QoSManagement in CDMA - Pathway]]
The rate matching step in above figure is essentially implemented by repetition or puncturing, SEIMENS 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.
Anonymous user
