BACKGROUND

Emerging applications for cellular technology such as alarm reporting, automotive safety, factory process control, and machine type communications (MTC) may benefit from the utilization of low latency cellular communications. Low latency applications may find a 1 ms transmission time interval (TTI) and associated latencies that may, for example, be used in an LTE Advanced (LTE-A) system, insufficient. Existing applications such as gaming and real-time applications such as Voice Over LTE (VoLTE) and video telephony/conferencing, may also benefit from reduced latency in terms of, for example, increased perceived quality of experience. Some applications may use a short TTI (sTTI) in order to reduce latency; however, use of a sTTI reduces the available processing time.

SUMMARY

A method and apparatus are described herein for handling reduced available processing time in systems configured to reduce latency such as systems using configurable transmission time intervals (TTIs) or short TTIs (sTTIs).

A wireless transmit/receive unit (WTRU) may be configured to determine one or more processing capabilities, send a processing capability (PC) indication to an eNodeB (eNB) based on the determined processing capabilities, receive a PC configuration from the eNB, determine a maximum timing advance or maximum Rx-Tx time difference based on the PC configuration or the determined processing capabilities, and limit an applied timing advance or Rx-Tx time difference to the maximum timing advance or maximum Rx-Tx time difference for a specific TTI length. The WTRU may also be configured to measure a processing value (PV) of a processing parameter, determine the amount of headroom, which is the difference between the PV and the PC, and report the headroom based on a condition. The WTRU may also perform an action based on the condition.

In one example, the WTRU may be configured to use a PC. The WTRU may receive a TTI configuration. The WTRU may determine the PC of the WTRU. The PC may be determined based on at least one of the TTI configuration and a processing criteria. The WTRU may then transmit a report of the determined PC. The report may be transmitted to and eNB. The PC may be a timeline, and the timeline may be reported as a number of time units, wherein a time unit is at least one of a symbol, a TTI, a time sample, and a set of time samples.

In another example, a WTRU may be configured to use a configurable TTI. The WTRU may receive a TTI configuration. The WTRU may determine a PC of the WTRU for the TTI configuration based on a processing criteria. The WTRU may then transmit a report of the determined PC, and the determined PC may be based on a number of symbols in the TTI or TTI length that is used and/or configured. The WTRU may also determine a current processing value (PV). The report may be based on the satisfaction of a proximity condition, suspending one or more UL transmissions, or dropping a UL transmission. The processing criteria may include for example, a number of symbols in the TTI or TTI length that is used and/or configured.

In another example, a WTRU may be configured to use an sTTI. The WTRU may receive an sTTI configuration and determine a PC of the WTRU for the sTTI configuration based on a processing criteria. The WTRU may determine a current PV. The WTRU, based on the determined PC and the determined PV, may report a PC proximity based on the satisfaction of a proximity condition, suspending one or more UL transmissions, or dropping a UL transmission. In this example, processing criteria may include but are not limited to the following: sTTI length, timeline, transport block (TB) size, uplink (UL) channel type, time between an sTTI of the short physical downlink control channel (sPDCCH) and an sTTI of the UL.

