This paper considers a different approach from the conventional way of maximizing sum rate where the bandwidth is always assumed to be shared evenly among users in a power-constrained single-input single-output (SISO) channel or multiple-input multiple-output (MIMO) channel. Bandwidth is not used as a constraint for sum rate maximization. In these systems, it can be deduced that the sum rate can be increased beyond the value in the conventional method by maximizing the sum rate subject to both power and bandwidth constraints.