Resource Allocation for the LTE Physical Downlink Control Channel

The next generation of wireless networks will simultaneously support many data and voice users. These users or UEs (User Equipment) will share the uplink and downlink radio resources and so, in each frame, the basestation must signal which UEs are being allocated resources and the location within the frame of the associated data. In the case of the Long Term Evolution (LTE) wireless standard, this signalling is performed over the Physical Downlink Control Channel (PDCCH). The amount of resources allocated to the PDCCH can be varied. However, if the allocated amount is too small then the uplink and downlink data schedulers will not be able to schedule all UEs that need to be served but if the allocated amount is too large then resources that could have been used for transmitting data are wasted. Two issues must therefore be addressed, the determination of the number of resources to be allocated to the PDCCH and, given this allocation, how should UEs be efficiently signalled over the PDCCH. Our focus in this paper is on the second issue but we also briefly address how one can approach the first issue. We propose a simple but near optimal algorithm for making PDCCH allocations within the subset of resources reserved for its use. We then illustrate, through simulations, the effectiveness of the approach.