Terminal apparatus, base station apparatus, communication method, and integrated circuit

What is this patent about?

'955 is related to the field of wireless communication, specifically addressing uplink transmissions in cellular networks like LTE, particularly in scenarios involving Licensed Assisted Access (LAA) and carrier aggregation. The background involves the need for efficient uplink transmission in unlicensed bands, where Listen-Before-Talk (LBT) procedures are required to avoid interference with other devices.

The underlying idea behind '955 is to adjust the transmit power of the Physical Uplink Shared Channel (PUSCH) based on the number of Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols used for the initial transmission. The key inventive insight is recognizing that the number of available SC-FDMA symbols can be affected by the LBT procedure, and compensating for this by adjusting the transmit power calculation. This ensures efficient uplink transmission even when LBT reduces the number of symbols available for transmission.

The claims of '955 focus on a terminal apparatus and a base station apparatus, along with their respective communication methods. The core of the claims centers around calculating the transmit power of the PUSCH based on the number of SC-FDMA symbols used for the initial transmission, denoted as NPUSCH-initialsymb. This calculation takes into account both the total number of SC-FDMA symbols in an uplink slot (NULsymb) and a factor NLBT, which represents the impact of the LBT procedure.

In practice, the invention works by dynamically adjusting the PUSCH transmit power based on whether the terminal needs to perform LBT. If LBT is required and affects the first SC-FDMA symbol, the value of NLBT is set to 1. This indicates that one SC-FDMA symbol is effectively lost due to LBT. To compensate, the transmit power is adjusted accordingly, ensuring that the overall signal strength remains adequate for reliable communication. A key aspect is generating the time-continuous signal of the first SC-FDMA symbol based on the *content of the resource elements* of the *second SC-FDMA symbol*.

This approach differs from prior solutions by explicitly accounting for the impact of LBT on the number of available SC-FDMA symbols and adjusting the transmit power accordingly. Prior solutions might not have dynamically adjusted the transmit power based on the LBT outcome, potentially leading to inefficient use of resources or reduced signal quality. By considering NLBT in the transmit power calculation, '955 provides a more robust and efficient uplink transmission scheme, especially in unlicensed bands where LBT is mandatory. The use of an extended cyclic prefix is also a novel way to handle the LBT gap.