Changes

== Quality of Service(QoS) ==CDMA is being accepted as a third-generation system and a specific feature of 3G system is that it offers a radio interface adapted for all kinds of services and combination of services(data, voice, video, image etc.). The big issue is of multiplexing of 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 atleast 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'''. <br><br>

The patent '''EP 1385290 titled "Method for balancing Eb/I ratio in a service multiplexing CDMA system and a telecommunication system using this method"''' targets at this concept of Rate matching and introduces an algorithm of 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 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 is occuring).[[Media:Patent.pdf]][[Image:cdma20.jpg]]

'''gi= (gi vi / (givi+Gi))''', where gi vi is minimum QoS for the ith session which is a constant.<br>

[[Media:ieee1IEEE1.pdf]]

SPEECH transmission is the main service supported by the first two generations Transmission power of mobile communication systems. However, future systems should be able station is proportional to handle power control law, which is a wide variety function of different services with bit rate requirement ranging distance from a few kilobits/s to as much as 2 Mb/sthe base station, transmission rates, interference level (number of active users). There are many ways to design a In this method the Bit Error probability of the multi rate CDMA system to support multirate services . One way to do so mobile station is to spread all signals, independent calculated at the Base station using transmission rates of the bit rate, mobile.The Optimal power control functions are derived based on the Bit error probability at the base station and these power control functions are transmitted to the same bandwidth mobile. This is done by keeping The mobile calculates the chip rate constant. Users transmitting optimum power using DYNAMIC PROGRAMMING and transmits its data at low bit rate thus have a high processing gainthis power level. This allows those users It is of interest to transmit at a lower power. Therefore, note that the conventional constant received optimum power scheme level is not appropriate in such a multirate system. A more sophisticated related to power control scheme is needed to achieve diverse quality of service (QoS) and rate requirement. One such scheme index which explores will determine the relationship between spreading gain and hence the data overall bit rate, . Thus the QoS, and the transmit optimum power level is presented in acheived by transmitting the IEEE paper '''Power Control and Rate Management for Wireless Multimedia CDMA Systems Chi Wan Sung, Member, IEEE, and Wing Shing Wong, Senior Member, IEEEdata at the calculated bit rate.'''===Dynamic Resource Scheduling and QoS===Dynamic Resource Scheduling (DRS) has been proposed as an adaptive resource management and QoSprovisioning framework applicable to W-CDMA systems. Various spreading strategies like Fixed Spreading Gain (FSG), Variable Spreading Gain (VSG) and Multi Code (MC) strategies and their performance is compared in terms of power saving, resource allocation and QoS stability in the [[Media:IEEE paper '''DYNAMIC RESOURCE SCHEDULING STRATEGIES FOR QOS IN W-CDMA by Ozgur Gurbuz, Henry Owen.''' VSG-DRS and MC-DRS outperform the FSG-DRS for capacity as a result of the statistical multiplexing gain created by adaptive bandwidth usage2.pdf]]