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Adaptive Resource Allocation in Multiuser OFDM Systems

Adaptive Resource Allocation in Multiuser OFDM Systems. Malik Meherali Saleh EE 381-14 March 08, 2005. Introduction/Background. 4G cellular system proposes hybrid of Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM)

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Adaptive Resource Allocation in Multiuser OFDM Systems

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  1. Adaptive Resource Allocation in Multiuser OFDM Systems Malik Meherali Saleh EE 381-14 March 08, 2005

  2. Introduction/Background • 4G cellular system proposes hybrid of • Multiple Input Multiple Output (MIMO) • Orthogonal Frequency Division Multiplexing (OFDM) • OFDM eliminates Intersymbol Interference • TDMA/FDMA solutions for Multiuser OFDM • Fixed allocation of subcarriers • Multiuser Environment • Creates channel diversity • Assign users high gain subcarriers • Motivation : Adaptive Multiuser OFDM systems

  3. Key Paper #1[Wong, Cheng, Letaief and Murch, 1999] • Optimal: Minimize total transmit power • Perfect Channel knowledge assumed • Assumes fixed data rate for users • Adaptive assignment of subcarriers, bits and power level to each user. • Suboptimal solution • Subcarrier allocation • Single user bit allocation is applied to the assigned subcarrier for each user

  4. Key Paper #2[Jang and Lee, 2003] • Fixes total transmit power and maximizes sum capacity • Applies Subcarrier allocation first • Follows it up by transmit power allocation • Provides 2 methods for power allocation • Water filling policy • Equal distribution • Results show total data rate increases with increase in users

  5. Key Paper #3[Shen, Andrews and Evans, (Draft) 2004] • Focus on Quality of Service parameter • Power constraint with adaptive rate • Maintains proportional rates between users • Predetermined ratios, variable fairness index • Reduce computation complexity by suboptimal algorithm • Subcarrier allocation • Maximizing sum capacity with Power allocation • Both blocks include proportional values

  6. What I propose to do • I propose to study Paper 2 and 3 in detail and simulate them with controlled parameters and compare them on BER/signal quality, sum capacity, the number of users, average channel power per user. • Simulation files • I plan to use the simulation files provided for Paper 3 at http://www.ece.utexas.edu/~bevans/projects/ofdm • For Paper 1, I hope to get in touch with the authors for the simulation code • I will also compare sum capacity of Paper 2 & 3 to TDMA/FDMA approach in Multiuser OFDM

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