Beamforming for random access channel (RACH)

A network node comprising:

• a radio interface comprising a beamforming antenna;
• a processor;
• and
• memory,
• wherein the memory stores instructions which, when executed by the processor, cause the network node to:
• obtain information relating to a plurality of signals received or transmitted using a set of receiving beams or a set of transmitting beams of the network node, wherein the information relates to one or more of:
• path loss between a receiving device and the network node;
• signal strength of a signal of the plurality of signals transmitted by the network node;
• and
• a random access success ratio for a beam of the set of beams used by the network node to transmit the plurality of signals;
• and the information is derived from multiple measurements performed over a period of time and each individual beam of the set of transmitting beams having a unique beam direction;
• determine a set of candidate beams for use by the network node for synchronisation signal, SS, transmission or random access channel, RACH, detection;
• based on the obtained information, select one or more of the determined candidate beams, wherein selecting the one or more of the candidate beams comprises:
• selecting a first subset of the set of candidate beams and selecting a second subset of the set of candidate beams, and further cause the network node to use the selected first subset for individual narrow-beam SS transmission or RACH detection and to use the selected second subset for broad-beam SS transmission or RACH detection;
• and
• use the one or more determined candidate beams for SS transmission or RACH detection by the network node.

A system comprising:

• a network node;
• and
• one or more wireless devices,
• wherein the network node is configured to:
• transmit a plurality of signals into a coverage area of the network node using a set of transmitting beams of the network node, each individual beam of the set having a unique beam direction;
• receive one or more signals from the one or more wireless devices using a set of receiving beams of the network node, each individual beam of the set having a unique beam direction,
• wherein the system is configured to:
• obtain information relating to the signals received or transmitted using the set of receiving beams or the set of transmitting beams of the network node wherein the information relates to one or more of:
• path loss between a receiving device and the network node;
• signal strength of a signal of the plurality of signals transmitted by the network node;
• and
• a random access success ratio for a beam of the set of beams used by the network node to transmit the plurality of signals;
• and
• the information is derived from multiple measurements performed over a period of time and;
• determine a set of candidate beams for use by the network node for synchronization signal, SS, transmission or random access channel, RACH, detection;
• based on the obtained information, select one or more of the determined candidate beams,
• and wherein the network node is further configured to:
• use the selected one or more of the determined candidate beams for SS transmission or RACH detection by the network node, wherein selecting the one or more of the candidate beams comprises:
• selecting a first subset of the set of candidate beams and selecting a second subset of the set of candidate beams, and further cause the network node to use the selected first subset for individual narrow-beam SS transmission or RACH detection and to use the selected second subset for broad-beam SS transmission or RACH detection.