说明：  注水算法是根据某种准则，并根据信道状况对发送功率进行自适应分配，通常是信道状况好的时刻，多分配功率，信道差的时候，少分配功率，从而最大化传输速率。实现功率的“注水”分配，发送端必须知道CSI。
(A water-filling algorithm is based on the criteria according to channel conditions and the transmission power allocation for adaptive usually good channel conditions in time, allocated more power when the channel is poor, less power distribution, thereby maximizing the transmission rate. Realize the power of the " water" distribution, the sender must know the CSI.)