FIELD

The present invention relates to a base station and a user equipment. More specifically, the present invention relates to a base station and a user equipment with prioritized transmission considerations.

BACKGROUND

According to the current specification of the fifth generation of mobile communication technology (5G), the core network establishes at least one Packet Data Unit (PDU) session for each user equipment and the Next Generation Radio Access Network (NG-RAN) establishes at least one Data Radio Bearer (DRB) together with each PDU session. Within one PDU session, each Quality of Service (QoS) flow is identified by a QoS Flow ID (QFI). Due to the fact that the applications provided by 5G are quite diverse but the radio resources are limited, the maximum number of DRBs that can exist within one PDU session is 32 and the maximum number of QoS flows that can exist within one PDU session is 256. Therefore, it is often the case that several QoS flows are mapped to one DRB. The Service Data Adaptation Protocol (SDAP) layer of the base station (the base station may be referred to as a gNodeB or gNB according to the current specification of 5G) is in charge of the mapping between the QoS flows and the DRBs.

Packet Data Convergence Protocol (PDCP) duplication (also known as packet duplication) is the key to low latency and high reliability. To meet the Ultra-Reliable and Low Latency Communication (URLLC) and Time Sensitive Network (TSN) requirements, the Radio Resource Control (RRC) layer of the base station can configure up to 4 Radio Link Control (RLC) entities per DRB (i.e. up to 4 legs per DRB) for PDCP duplication according to the current specification of 5G. In other words, a packet of a service flow that requires URLLC and TSN can be duplicated to 4 copies at most. Nevertheless, the duplication efficiency will be impaired in two aspects based on the current specification of 5G.

The first aspect of the impairment of the duplication efficiency is described herein. The Medium Access Control (MAC) layer provides a plurality of logical channels for data transmission services, and each logical channel corresponds to a transmission restriction. The transmission restriction of each logical channel may comprise one or more parameters, such as a parameter indicating the allowed serving cell, a parameter indicating the maximum Physical Uplink Shared Channel (PUSCH) duration allowed for transmission, a parameter indicating whether a configured grant (Type1) can be used for transmission, a parameter indicating the allowed subcarrier spacing for transmission (but not limited thereto). The MAC layer is in charge of scheduling the packets of the logical channels according to their transmission restrictions when there is a granted resource, and this procedure is known as Logical Channel Prioritization (LCP). However, the MAC layer has no specific information regarding whether a packet in a logical channel is related to a service requiring high reliability or not (e.g. whether a packet is a duplicated packet of a service flow requiring URLLC and TSN). As a consequence, the MAC layer may not handle a packet related to a service requiring high reliability at the first place when scheduling and, hence, the duplication efficiency is impaired.

The second aspect of the impairment of the duplication efficiency is described herein. According to the current specification of 5G, downlink pre-emption is specified for New Radio (NR) allowing the latest downlink assignment (i.e. dynamic grant) to override the previous downlink assignment (i.e. configured grant). When pre-emption occurs, the MAC layer sends an indication to the Physical (PHY) layer. The previous MAC PDU will be discarded and cannot be recovered through Hybrid Automatic Repeat request (HARQ). In some cases, the higher layer (e.g. PDCP layer) may not be aware of a transmission on the pre-empted grant if the transmission of the configured grant is completely pre-empted at the PHY layer. Due to transmission mismatch, the duplication efficiency is impaired.

Therefore, to achieve the URLLC and TSN requirements thoroughly, 5G needs a scheduling and transmission technique that has prioritized transmission considerations of the higher layer (e.g. PDCP layer) and has no impairment to the duplication efficiency.

SUMMARY

Provided is a base station. The base station may comprise a transceiving interface and a processor, wherein the processor is electrically connected to the transceiving interface. The processor is configured to generates a Radio Resource Control (RRC) configuration message for a user equipment. The RRC configuration message comprises a first information element regarding a Physical (PHY) layer, wherein the first information element is associated with a Downlink Control Information (DCI) format for a specific indication, and the specific indication is related to a prioritized transmission mode. The RRC configuration message further comprises a second information element regarding a Medium Access Control (MAC) layer, wherein the second information element defines a transmission restriction of each of a plurality of logical channels, and at least one of the transmission restrictions corresponds to the prioritized transmission mode. The transceiving interface further transmits the RRC configuration message to the user equipment.

Also provided is a user equipment. The user equipment may comprise a transceiving interface and a processor, wherein the processor is electrically connected to the transceiving interface. The transceiving interface receives an RRC configuration message from the base station. The processor reads a first information element regarding a PHY layer from the RRC configuration message, wherein the first information element is associated with a DCI format for a specific indication, and the specific indication is related to a prioritized transmission mode. The processor further reads a second information element regarding a MAC layer from the RRC configuration message, wherein the second information element defines a transmission restriction of each of a plurality of logical channels, and at least one of the transmission restrictions corresponds to the first prioritized transmission mode.

The base station and the user equipment provided by the present invention are with prioritized transmission considerations, and the prioritized transmission considerations are achieved by embedding a first information element regarding a PHY layer and a second information element regarding a MAC layer in an RRC configuration message. The first information element defines a DCI format for a specific indication, wherein the specific indication is related to a prioritized transmission mode (e.g. high reliability, preemption prohibition). The second information element defines a transmission restriction of each of a plurality of logical channels, wherein at least one of the transmission restrictions corresponds to the prioritized transmission mode. The base station transmits the RRC configuration message to the user equipment so that the user equipment learns the first information element and the second information element from the RRC configuration message.

Thereafter, the base station and the user equipment can utilize the DCI format in various ways to schedule the packets in the logical channels. As the DCI format is designated for a specific indication related to a prioritized transmission mode, the packets in the logical channels will be scheduled with prioritized transmission considerations. Therefore, the URLLC and TSN requirements can be thoroughly achieved, and duplication efficiency will not be impaired.

The detailed technology and exemplary embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for a person having ordinary skill in the art to well appreciate the features of the claimed invention.

