Enhanced uplink operation in soft handover

An apparatus comprising:

• a transmitter, wherein the transmitter transmits a data packet to a Node-B via a primary cell and at least one non-primary cell, the primary cell and the at least one non-primary cell being controlled by the Node-B, wherein the data packet is sent via the primary cell and the at least one non-primary cell over an enhanced uplink (EU) channel;
• and
• a receiver, wherein the receiver:
• receives an acknowledgement (ACK) from the Node-B on a condition that the transmitted data packet is successfully decoded;
• and
• receives a negative acknowledgement (NACK) from the Node-B on a condition that the transmitted data packet is not successfully decoded;
• wherein the NACK is received only via the primary cell.

A method for operating a Node-B, the method comprising:

• receiving a data packet from a wireless transmit/receive unit (WTRU) via a primary cell and at least one non-primary cell controlled by the Node-B, wherein the data packet is received from the WTRU over an enhanced uplink (EU) channel;
• combining the data packet received via the primary cell and the data packet received via the at least one non-primary cell into a combined data packet;
• transmitting an acknowledgement (ACK) to the WTRU on a condition that the combined data packet is successfully decoded;
• and
• transmitting a negative acknowledgement (NACK) to the WTRU on a condition that the combined data packet is not successfully decoded;
• wherein the NACK is transmitted only via the primary cell.

A Node-B comprising:

• a receiver and a transmitter;
• wherein the receiver:
• receives a data packet from a wireless transmit/receive unit (WTRU) via a primary cell and at least one non-primary cell controlled by the Node-B, wherein the data packet is received over an enhanced uplink (EU) channel;
• combines the data packet received via the primary cell and the data packet received via the at least one non-primary cell into a combined data packet;
• and
• decodes the combined data packet,
• and wherein the transmitter:
• transmits an acknowledgement (ACK) to the WTRU on a condition that the combined data packet is successfully decoded;
• and
• transmits, via only the primary cell, a negative acknowledgement (NACK) to the WTRU on a condition that the combined data packet is not successfully decoded.