Mobile WiMAX supports adaptive switching between these options to maximize the benefit of smart antenna technologies under different channel conditionsFor instance, SM improves peak throughput. However, when channel conditions are poor, the Packet Error Rate (PER) can be high and thus the coverage area where target PER is met may be limited. STC on the other hand provides large coverage regardless of the channel condition but does not improve the peak data rateData and pilot sub-carriers are grouped into subsets of sub-carriers called subchannels.