Estudio, modelamiento y simulación de alocación adaptiva de bits en sistemas multiuser ofdm

Abstract

This paper studies the problem of the adaptive bit allocation for Multiuser OFDM. A key issue in OFDM is the subcarrier and power allocation among users sharing the channel. Two solutions have been analyzed and proposed: the first one is based on an equal power distribution, whereas the second one proposes a proportional distribution of capacity and then tries to optimize the power allocation, once the subcarrier allocation has been achieved. Subcarrier and power allocation are carried out separately, in order to reduce the complexity of the solution. The algorithm proposed as solution was applied over a VDSL2 system, where Additive White Gausian Noise and FEXT were considered as the only disturbers. For resources allocation simulation, a total of 15 and 25 users were considered, and distances of 500, 1000 and 1500 m. Finally, a mathematical model is proposed in order to find the capacity variation as the number of users gets increased. For such variation, a total of up to 50 users were considered in the simulation.