Aspects of the present disclosure provide various flexible search space designs that can handle UEs with various capabilities and limitations. In some aspects of the disclosure, the downlink bandwidth may be divided into several self-contained sub-bands. Each sub-band may include one or more OFDM subcarriers or tones, and each UE may be configured to monitor one or more of the sub-bands for its downlink control channel. The sub-band is self-contained in such a way that each sub-band includes CCEs that are mapped to resource elements contained in the same sub-band. In some aspects of the disclosure, different sub-bands can be configured with the different transmission modes and pilot densities. The transmission mode, pilot density, and layer-ID may be determined as a function of each UE's search space.