Apparatus and method for data scheduling of base station using licensed assisted access in wireless communication system
The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. For licensed assisted access (LAA) technology used in a wireless communication system, an apparatus and a method for scheduling downlink data at a base station is provided. In the method, based on at least one part of parameters of a bearer to which the downlink data belongs, the base station determines a serving cell for scheduling the downlink data. Further, information about the identified serving cell is transmitted to a user equipment (UE).
1. A method for transmitting downlink data by a base station to a terminal, the method comprising:
determining, by at least one processor, whether a bearer associated with the downlink data is a radio link control-acknowledged mode (RLC-AM) bearer;
when the bearer is the RLC-AM bearer:
determining, by the at least one processor, whether the bearer is a signaling radio bearer (SRB);
when the bearer is the SRB:
determining, by the at least one processor, whether the bearer is included in a first SRB group or a second SRB group, wherein the first SRB group includes an SRB0 and an SRB1, and the second SRB group includes an SRB2;
when the bearer is included in the second SRB group, selecting, by the at least one processor, a first serving cell using a licensed band or a second serving cell using an unlicensed band for transmitting the downlink data; and
when the bearer is included in the first SRB group, selecting, by the at least one processor, the first serving cell using the licensed band for transmitting the downlink data;
when the bearer is not the SRB:
determining, by the at least one processor, whether transmission of the downlink data is an initial transmission;
when the transmission of the downlink data is the initial transmission, selecting, by the at least one processor, the first serving cell using the licensed band or the second serving cell using the unlicensed band for transmitting the downlink data;
when the transmission of the downlink data is a retransmission, determining, by the at least one processor, whether a number of transmission failures of the downlink data exceeds a first reference value;
when the number of transmission failures of the downlink data does not exceed the first reference value, selecting, by the at least one processor, the first serving cell using the licensed band or the second serving cell using the unlicensed band for transmitting the downlink data; and
when the number of transmission failures of the downlink data exceeds the first reference value, selecting, by the at least one processor, the first serving cell using the licensed band for transmitting the downlink data; and
transmitting, by a transceiver, the downlink data on the selected serving cell to the terminal.
2. The method of claim 1 , further comprising:
when the bearer is not the RLC-AM bearer, selecting, by the at least one processor, the first serving cell using the licensed band for transmitting the downlink data.
3. The method of claim 1 , further comprising:
when the bearer is the RLC-AM bearer:
determining, by the at least one processor, whether previous transmission of the downlink data is transmission on the first serving cell using the licensed band; and
when the previous transmission of the downlink data is not transmission on the first serving cell, selecting, by the at least one processor, the second serving cell using the unlicensed band for transmitting the downlink data.
4. The method of claim 1 , further comprising:
determining, by the at least one processor, whether a quality of service (QoS) class identifier (QCI) of the bearer has a specific value;
when the QCI of the bearer has the specific value, selecting, by the at least one processor, the first serving cell using the licensed band for transmitting the downlink data; and
when the QCI of the bearer fails to have the specific value, selecting, by the at least one processor, the first serving cell using the licensed band or the second serving cell using the unlicensed band for transmitting the downlink data.
5. The method of claim 1 , wherein the determining of the serving cell comprises:
determining, by the at least one processor, whether the bearer satisfies one of a first condition corresponding to a guaranteed bit rate, a second condition indicating that a packet delay budget of the bearer is smaller than a predetermined first reference value, a third condition indicating that a packet error loss rate of the bearer is smaller than a predetermined second reference value, and a fourth condition indicating that an allocation and retention priority of the bearer is smaller than a predetermined third reference value;
when at least one of the first, second, third and fourth conditions is satisfied, selecting, by the at least one processor, the first serving cell using the licensed band for transmitting the downlink data; and
when none of the first, second, third and fourth conditions is satisfied, selecting, by the at least one processor, the first serving cell using the licensed band or the second serving cell using the unlicensed band for transmitting the downlink data.
6. The method of claim 1 , further comprising:
determining, by the at least one processor, whether an allocation and retention priority (ARP) of the bearer is smaller than a predetermined fourth reference value;
when the ARP of the bearer is smaller than the fourth reference value, selecting, by the at least one processor, the first serving cell as the serving cell for scheduling the downlink data; and
when the ARP of the bearer is not smaller than the fourth reference value, selecting, by the at least one processor, the first serving cell using the licensed band or the second serving cell using the unlicensed band for transmitting the downlink data.
7. A base station for transmitting downlink data to a terminal, the base station comprising:
a transceiver configured to transmit or receive data to or from the UE; and
at least one processor coupled with the transceiver and configured to:
determine whether a bearer associated with the downlink data is a radio link control-acknowledged mode (RLC-AM) bearer;
when the bearer is the RLC-AM bearer:
determine whether the bearer is a signaling radio bearer (SRB);
when the bearer is the SRB:
determine whether the bearer is included in a first SRB group or a second SRB group, wherein the first SRB group includes an SRB0 and an SRB1, and the second SRB group includes an SRB2;
when the bearer is included in the second SRB group, select a first serving cell using a licensed band or a second serving cell using an unlicensed band for transmitting the downlink data; and
when the bearer is included in the first SRB group, select the first serving cell using the licensed band for transmitting the downlink data;
when the bearer is not the SRB:
determine whether transmission of the downlink data is an initial transmission;
when the transmission of the downlink data is the initial transmission, select the first serving cell using the licensed band or the second serving cell using the unlicensed band for transmitting the downlink data;
when the transmission of the downlink data is a retransmission, determine whether a number of transmission failures of the downlink data exceeds a first reference value;
when the number of transmission failures of the downlink data does not exceed the first reference value, select the first serving cell using the licensed band or the second serving cell using the unlicensed band for transmitting the downlink data; and
when the number of transmission failures of the downlink data exceeds the first reference value, select the first serving cell using the licensed band for transmitting the downlink data, and
control the transceiver to transmit, to the terminal, the downlink data on the selected serving cell.
8. The base station of claim 7 , wherein the at least one processor is further configured to:
when the bearer is not the RLC-AM bearer, select the first serving cell using the licensed band for transmitting the downlink data.
9. The base station of claim 7 , wherein the at least one processor is further configured to:
when the bearer is the RLC-AM bearer:
determine whether previous transmission of the downlink data is transmission on the first serving cell using the licensed band, and
when the previous transmission of the downlink data is not transmission on the first serving cell, select the second serving cell using the unlicensed band for transmitting the downlink data.
10. The base station of claim 7 , wherein the at least one processor is further configured to:
determine whether a quality of service (QoS) class identifier (QCI) of the bearer has a specific value,
when the QCI of the bearer has the specific value, select the first serving cell using the licensed band for transmitting the downlink data, and
when the QCI of the bearer fails to have the specific value, select the first serving cell using the licensed band or a second serving cell using the unlicensed band for transmitting the downlink data.
11. The base station of claim 7 , wherein the at least one processor is further configured to:
determine whether the bearer satisfies one of a first condition corresponding to a guaranteed bit rate, a second condition indicating that a packet delay budget of the bearer is smaller than a predetermined first reference value, a third condition indicating that a packet error loss rate of the bearer is smaller than a predetermined second reference value, and a fourth condition indicating that an allocation and retention priority of the bearer is smaller than a predetermined third reference value,
when at least one of the first, second, third and fourth conditions is satisfied, select the first serving cell using the licensed band for transmitting the downlink data, and
when none of the first, second, third and fourth conditions is satisfied, select the first serving cell using the licensed band or a second serving cell using the unlicensed band for transmitting the downlink data.
12. The base station of claim 7 , wherein the at least one processor is further configured to:
determine whether an allocation and retention priority (ARP) of the bearer is smaller than a predetermined fourth reference value,
when the ARP of the bearer is smaller than the fourth reference value, select a first serving cell using the licensed band for transmitting the downlink data, and
when the ARP of the bearer is not smaller than the fourth reference value, select the first serving cell using the licensed band or a second serving cell using the unlicensed band for transmitting the downlink data.