Beam alignment method for antenna array, multi beam transmission system, and multi-beam transmission apparatus

A multi-beam transmission system, comprising:

• a base station using a plurality of multi-modal beam patterns as beam patterns for transmitting several synchronization signals, wherein each of the multi-modal beam patterns comprises a plurality of main lobes that can distinguish directions, and directions of the main lobes between the different multi-modal beam patterns do not overlap each other;
• and
• a user equipment scanning the synchronization signals, determining a synchronization signal with the strongest received power and a receive beam direction corresponding to the synchronization signal with the strongest received power, and transmitting, through a random access channel, an initial access message including index information indicating the synchronization signal with the strongest received power, wherein
• the base station receives the initial access message on the random access channel by using a plurality of single-modal beam patterns, wherein coverage of a main lobe of each of the single-modal beam patterns comprises only at most one of the main lobes of each of the multi-modal beam patterns;
• and
• the base station determines a single-modal beam pattern with the strongest access power for the initial access message, and compares the determined single-modal beam pattern having the strongest access power with a main lobe of the multi-modal beam pattern corresponding to the index information, indicating the synchronization signal having the strongest received power, in the initial access message, to determine an optimal beam direction for the transmission to the user equipment.

A multi-beam transmission apparatus, comprising:

• an array antenna;
• a transceiver coupled to the array antenna, and generating, by using the array antenna, beams of a plurality of multi-modal beam patterns and a plurality of single-modal beam patterns, wherein each of the multi-modal beam patterns comprises a plurality of main lobes that can distinguish directions, and directions of the main lobes between the different multi-model beam patterns do not overlap each other;
• and
• a processor coupled to the transceiver and controlling the transceiver to:
• use the multi-model beam patterns as beam patterns for transmitting several synchronization signals to a user equipment, wherein the user equipment scans the synchronization signals, determines a synchronization signal with the strongest received power and a receive beam direction corresponding to the synchronization signal with the strongest received power, and transmits, through a random access channel, an initial access message including index information indicating the synchronization signal with the strongest received power;
• receive, by using the plurality of single-modal beam patterns on the random access channel, an initial access message transmitted by the user equipment, wherein coverage of a main lobe of each of the single-modal beam patterns comprises only at most one of the main lobes of each of the multi-modal beam patterns;
• and
• determine a single-modal beam pattern with the strongest access power for the initial access message, and compare the determined single-modal beam pattern having the strongest access power with a main lobe of the multi-modal beam pattern corresponding to the index information, indicating the synchronization signal having the strongest received power, in the initial access message, to determine an optimal beam direction for the transmission to the user equipment.