Adaptive Resource Allocation in Multiuser OFDM Systems

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 1Wong, 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 2Jang 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 3Shen, 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/proje
  cts/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