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Adaptive Resource Allocation in Multiuser OFDM Systems

Investigating key papers on adaptive multiuser OFDM systems to optimize power, data rate, and subcarrier allocation for improved system performance in 4G cellular environments.

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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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