1. Adaptive Resource Allocation in Multiuser OFDM Systems
Malik Meherali Saleh EE
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
Maintain proportional rates among users for EACH channel realization.
Explicitly control the capacity ratios among users, each user meets his target data rate
Ratios are predetermined and fairness measures the fraction of capacity, 1 meaning all users have same ratios/capacity
Like 1 and 2 the system is broken up into two blocks, the only difference is that the subcarrier allocation takes into account the proportional fairness, different from the first two
The second block consists of power allocation over the predetermined subcarriers with proportional fairness

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
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