LTE Advanced: 3GPP Solution for IMT-Advanced

12.6 Enhanced Downlink Control Channel

The work on the enhanced downlink control channel is referring to the enhanced PDCCH (ePDCCH) to improve the capabilities and performance of the physical layer control signaling, with the actual work being started from the beginning of 2012, following earlier studies. The work focuses on the downlink and the related changes to the uplink operation are expected to be minor. The key targets for the work are to enable:

• Support for higher control channel capacity, which has linkage to the scenarios of the MTC with very large number of low data rate UEs accessing the network.
• Support for frequency domain scheduling and ICIC for downlink control channel.
• Support for beamforming. Due to transmit diversity operation, in Release 10 the downlink control channels are the only channels not benefitting from the increased number of eNodeB antennas in terms of beamforming gain (downlink) or RX diversity (uplink).

As introduced in Chapter 3, the Release 8 based PDCCH is scheduled over the full carrier bandwidth which prevents from performing frequency domain scheduling and interference avoidance for the physical layer downlink control signaling in a similar way as can be done for the actual user data. Furthermore, with more than two eNodeB transmit antennas the PDCCH is transmitted using transmit diversity, which while providing robust system operation on average, is clearly suboptimal especially when the number of eNodeB transmit antennas is great.

The ...