A scheme of linear dispersive space-time codes was presented for downlink multiuser MIMO systems under the condition only limited rates could be employed by basestation for transmitting downlink data. The combination optimization problem with respect to the design was deduced

and a suboptimal algorithm with low computational complexity was given. The designed scheme does not require the condition of continuous downlink rates

which was assumed in previous work. Simulations show that the designed scheme has better performance than previous schemes.