HOW IS DOWNLINK POWER CONTROL USED IN LTE?

The simple answer is, there is no power control in the downlink for LTE.

However, power control or power boosting can be applied on both data and control channels of LTE in the downlink. The downlink data channel of LTE is PDSCH and the downlink control channels of LTE are:

• PBCH
• PDCCH
• PCFICH
• PHICH

Data Channels

By default, the data channel power is distributed uniformly over the scheduled resource blocks (i.e., no power control is used).

Total power is distributed over the bandwidth or Resource blocks. It is termed as Power Spectral Density (PSD)

More sophisticated strategies include:

1. Allocating relatively high power, but few resource blocks to power limited users and vice-versa for bandwidth-limited users
2. Allocating more power to resource blocks with good channel quality

Control Channels

Power control on the control channels may be used to improve coverage. For common control channels, which have to reach the cell border (e.g. PBCH and P/S -SCH), this can be done by borrowing power from user plane resource blocks transmitted simultaneously. In an extreme case, the full eNodeB power is allocated to the PBCH and Primary and Secondary Synchronization Channels. For control channels targeting individual UEs, (e.g., the PDCCH), a simple approach is to use similar strategy. Alternatively, dynamic power control based on the addressed UEs channel quality can be used. This will enable more PDCCHs to be multiplexed, and hence the ability to schedule more users in parallel.