In one aspect, embodiments disclosed herein relate to a secondary cutting structure for use in a drilling assembly, the second cutting structure including a tubular body and a cutter block, extendable from the tubular body, the block including at least three rows of cutting elements. The base station 10 comprises a signal transmitter 11 configured to transmit the data signal a to the mobile station 30 within a predetermined period, and transmit each of retransmission signals a1 to a3 of the data signal a, in a form different from that of the data signal a, from the base station 10 to the mobile station 30 within the predetermined period A. No aggregates, joins, or sub-queries are required to retrieve a snapshot. A set of second processing elements generates, e.