Abstract
Two schemes - offline and online - for minimizing the total EMF emission in the uplink of OFDMA systems have been proposed in this chapter. The offline EMF emission reduction scheme is based on the assumption that the network can predict the long-term CSI of all the users for allocating them on subcarriers. Then an optimal rate -based water -filling is performed to obtain the rate and power allocations of each allocated user on each subcarrier allocated to the user. On the other hand, the online EMF emission reduction scheme, which is based on short-term CSI knowledge, allocates power to users by minimizing the transmit energy per bit of each user. Simulation results show that the proposed offline scheme performs close to the optimal solution and that it significantly outperforms existing SE- and EE -based schemes, by up to 3 and 2 orders of magnitude, respectively. Accordingly, the proposed online scheme outperforms the SE- and EE -based schemes by up to 2.5 and 2 orders of magnitude, respectively. It has also shown that EMF emission of the offline scheme is inversely related to the transmission window, which makes it suitable for delay tolerant transmissions. Additionally, the offline scheme proves to be very robust against the effects of imperfect channel prediction.