Title :
Increase in capacity of multiuser OFDM system using dynamic subchannel allocation
Author :
Rhee, Wonjong ; Cioffi, John M.
Author_Institution :
STAR Lab., Stanford Univ., CA, USA
Abstract :
This paper investigates the problem of dynamic multiuser subchannel allocation in the downlink of OFDM systems. The assumptions are that the channel model is quasi-static and that the base station has perfect channel information. In traditional TDMA or FDMA systems, resource allocation for each user is non-adaptively fixed, and the water-filling power spectrum is known to be optimal. Since the subchannel allocations among the users are not optimized, a group of users is likely to suffer from poor channel gains resulting from large path loss and random fading. To resolve this problem, we derive a multiuser convex optimization problem to find the optimal allocation of subchannels, and propose a low-complexity adaptive subchannel allocation algorithm. Simulation results show that the proposed algorithm performs almost as well as the optimal solution. Also, a higher spectral efficiency is achieved for a larger number of users in a cell due to the multiuser diversity
Keywords :
OFDM modulation; Rayleigh channels; adaptive systems; cellular radio; channel allocation; channel capacity; computational complexity; frequency division multiple access; multiuser channels; optimisation; radio links; time division multiple access; FDMA; TDMA; base station; cellular radio; channel gain; downlink; dynamic multiuser subchannel allocation; frequency selective Rayleigh fading; large path loss; low-complexity adaptive subchannel allocation algorithm; multiuser OFDM system; multiuser convex optimization problem; multiuser diversity; optimal solution; perfect channel information; quasi-static channel model; random fading; resource allocation; simulation results; spectral efficiency; water-filling power spectrum; Channel capacity; Fading; Frequency conversion; Frequency division multiaccess; Maximum likelihood decoding; OFDM; Radio spectrum management; Resource management; Throughput; Time division multiple access;
Conference_Titel :
Vehicular Technology Conference Proceedings, 2000. VTC 2000-Spring Tokyo. 2000 IEEE 51st
Conference_Location :
Tokyo
Print_ISBN :
0-7803-5718-3
DOI :
10.1109/VETECS.2000.851292