OFDMA_Part16 - the design of the OFDMA system more complex...

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16 Figure 4. Definitions of OFDM-TDMA, OFDMA and OFDM-CDMA In OFDMA, the entire bandwidth is divided into a number of subcarriers for parallel transmission of symbols from different users. Assignment of subcarriers to users is a very important issue and greatly influences the performance of the OFDMA system. The ability to allocate power resources and change modulation techniques for each subcarrier also adds to the performance of OFDMA. The performance of an OFDMA system can be increased even further if channel state information is periodically computed and subcarriers, power and other resources are adaptively allocated [19] [20]. However, adaptive resource allocation understandably makes
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Unformatted text preview: the design of the OFDMA system more complex and engineers consider this tradeoff between performance and cost when designing OFDMA systems. Currently, cellular data services are becoming increasingly popular. The multiple-access version of OFDM, i.e. OFDMA, is being considered for upcoming 3G and 4G mobile standards because of its flexibility in allocating subcarriers and other resources to users. OFDMA hit the jackpot by being considered for the downlink of the upcoming 3GPP LTE standard. Unfortunately, the high...
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  • Spring '09
  • Prof
  • WiMAX, 3GPP Long Term Evolution, Universal Mobile Telecommunications System, CDMA2000, change modulation techniques

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