Phantom preamble is there, in your network

In this paper we investigate the inter-cell uplink RACH interference in a cellular network. The preamble transmission of a UE towards its serving cell can be received by the neighbouring cells. This is called a phantom preamble. The gNB that receives a phantom preamble transmits a random access response but no MSG3 is received in return, as the UE is not monitoring PDCCH of that gNB. Thus, the phantom preamble causes wasted PDCCH transmission, and we show with our simulations that this can happen up to 20% of all preamble transmissions, that can create a huge waste of downlink resources depending on the RACH load. In conclusion we indicate how the phantom preamble can be turned in to an advantage to obtain and maintain timing advance for the UEs on cell edge.