An active search method in a wireless LAN system is disclosed. The active search method comprises the steps of: transmitting, through an arbitrary channel, a preceding probe request frame for confirming the existence of an access point; acquiring, from at least one access point, a probe ACK frame that is a response to the preceding probe request frame; setting a maximum waiting time on the basis of the number of probe ACK frames; and performing an active search for an access point in the arbitrary channel for the maximum waiting time. Therefore, the waiting time for receiving a probe response frame can be reduced.

The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and an apparatus for a terminal controlling uplink power in a carrier aggregation-based wireless communication system, comprising the steps of: configuring a first cell and a second cell; transmitting a first PUCCH signal from subframe #n in the first cell; and transmitting a second PUCCH signal from subframe #n in the second cell, wherein when the sum of transmit power of the first PUCCH signal and transmit power of the second PUCCHJ signal exceeds a predetermined maximum transmit power configured to the terminal, the transmit power of the PUCCH signal having a lower priority from among the first UCCH signal and the second PUCCH signal is reduced or the transmission is dropped.

A method and apparatus for uplink feedback for operating with a large number of carriers are disclosed herein. A method in a wireless transmit/receive unit (WTRU) includes receiving a plurality of transport blocks over a set of a plurality of configured carriers, generating hybrid automatic repeat request (HARQ)-acknowledgment (ACK) feedback for the transport blocks and determining a number of HARQ-ACK feedback bits to use for the HARQ-ACK feedback. Further, the WTRU may apply, to the HARQ-ACK feedback bits, Reed-Muller coding on a condition that the number of HARQ-ACK feedback bits is less than or equal to a threshold or convolutional coding on a condition that the number of HARQ-ACK feedback bits is greater than a threshold. The WTRU may then transmit the encoded HARQ-ACK feedback bits. In addition, the WTRU may conditionally append cyclic redundancy check (CRC) bits onto the HARQ-ACK feedback bits, and encode and transmit the CRC bits.

In one aspect, a wireless device receives a first data transmission from a base station in a first subframe interval and transmits HARQ feedback and/or CSI to the base station in a subsequent subframe interval, within a duration that is less than a maximum transmission duration that is possible within the subsequent subframe interval. In another aspect, a base station transmits a first data transmission to a wireless device in a first subframe interval and receives HARQ feedback and/or CSI from the wireless device in a subsequent subframe interval, within a duration that is less than a maximum transmission duration that is possible within the subsequent subframe interval.

Disclosed is an uplink (UL) multi-user (MU) transmission method of a station (STA) in a wireless LAN (WLAN) system. An UL MU transmission method of an STA in a WLAN system according to an embodiment of the present invention includes receiving a trigger frame including resource unit allocation information for orthogonal frequency division multiple access (OFDMA) transmission, sending an UL MU physical protocol data unit (PPDU) based on the resource unit allocation information, and receiving an ACK frame for the UL MU PPDU.

The present invention provides a method and device for transmitting/receiving an uplink signal. When a user equipment of the present invention is configured by multiple cell groups and multiple pieces of uplink control information (UCI) to be transmitted by the user equipment in a subframe are generated, the user equipment separately transmits, to the multiple cell groups, the UCI one by one from the piece of UCI having the highest priority, and drops the pieces of UCI having lower priorities among the multiple pieces of UCI.

A method for transmitting uplink control information and an apparatus therefor are disclosed. In a method for transmitting uplink control information using a physical uplink shared channel (PUSCH) in a wireless communication system, the method is performed by a terminal and includes receiving downlink control information including an accumulated number of physical downlink shared channels (PDSCH) transmissions associated with a cell group configured for the terminal, coding the uplink control information using the accumulated number of PDSCH transmissions, and transmitting the coded uplink control information using the PUSCH.

A system is proposed to provide handover in a mobile telecommunications environment, particularly applicable to 3GPP networks, which does not increase signalling overhead but minimises user data loss during handover. In the modified system, PDCP SDUs with Sequence numbers are buffered and retransmitted as necessary. At the time of handover, SDUs not received by the user device are forwarded to the target base station for forward transmission to the UE. The handover procedure is designed to minimise packet loss whilst keeping to a minimum the duplication of packet transmission over the air interface.

Methods, systems, and devices for wireless communications are described. A set of uplink control channel resources that are configured for acknowledgment transmissions may be shared among user equipments (UEs) that are enabled to receive multicast communications. Each of the shared set of uplink control channel resources may be associated with set(s) of channel state information. UEs may measure a multicast channel to determine channel state information for the multicast channel. After failing to receive a multicast transmission, UEs may transmit an acknowledgment feedback message over one of the shared uplink control channel resources that is associated with the set of channel state information determined by the UE. A base station that receives the acknowledgment feedback message may transmit a multicast retransmission for the UEs using transmission parameters that are adapted for the set(s) of channel state information associated with the occupied uplink control channel resource.

A method for requesting an uplink scheduling is provided. In the case that there is an SR PUCCH resource established on a secondary cell, not an SR PUCCH resource established on a primary cell, and a special secondary cell is in a state of de-activation at the time of sending an uplink scheduling request, the uplink scheduling request is stopped and a random access procedure is initiated. If the uplink scheduling request can be sent on a plurality of cells at the same point of time, that is, if there are a plurality of uplink resources available for the uplink scheduling request at the same point of time, the uplink scheduling request is sent only on one of the plurality of cells (and using only one uplink resource).