KR20170072815A - Method and apparatus for cross-carrier scheduling according to delay of user traffic in multi-carrier environment - Google Patents

Abstract

A cross-carrier scheduling method and apparatus according to delay characteristics of user traffic in a multi-carrier environment are provided. The base station receives the user traffic from the terminal and determines the delay characteristics of the user traffic. And a radio resource is allocated in one of a frequency axis priority scheme and a time axis priority scheme according to a latency group determined according to the delay characteristics of user traffic.

Description

[0001] The present invention relates to a method and apparatus for scheduling a cross-carrier according to delay characteristics of user traffic in a multi-carrier environment,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cross-carrier scheduling, and more particularly, to a cross-carrier scheduling method and apparatus according to delay characteristics of user traffic in a multi-carrier environment.

The 5G (fifth generation) technology, which will be commercialized after 2020, aims to provide a service that supports a transmission rate of 1000 times compared to 4G at anytime and anywhere. However, the spectral efficiency reaches a near limit (for example, the Shannon limit), requiring a different technological alternative.

In IMT-Advanced (International Mobile Telecommunications-Advanced ) technology, a method of transmitting and receiving using a wide bandwidth is proposed as an alternative to meet a data transmission rate. The 3rd Generation Partnership Project (3GPP) sets the maximum supported bandwidth of LTE (Long Term Evolution) -Advanced to 100 MHz. However, because of the lack of frequency resources that can be allocated to a single 100 MHz bandwidth, CA (Carrier Aggregation) technology is introduced. CA technology is a communication technology that enables broadband transmission by integrating multiple small frequency bandwidths. CA technology, however, is technically difficult and increases product costs compared to technologies that use a single broadband.

On the other hand, LTE terminals using multi-carrier technology can transmit up to 75 Mbps in a single frequency bandwidth, while LTE-A terminals supporting CA technology can use up to 150 Mbps by combining two frequency bandwidths It is possible to transmit. In 3GPP, various CA combinations are defined for each release. Each carrier frequency band constituting the CA combination is defined as a component carrier (CC).

When a CA is used, a terminal can access a base station using one primary CC and a plurality of secondary CCs. Therefore, the terminal can simultaneously use up to five frequencies up to 20 MHz bandwidth including the primary CC to use up to 100 MHz. Currently, a total of 43 frequency bands and various combinations of CAs are defined in 3GPP TS 36.101. The CA combination may be classified into an intra-band CA combination that bundles the same frequency band and an inter-band CA combination that bundles different frequency bands. The intra-band CA combination can be classified into a contiguous CA and a non-contiguous CA. This is because the frequency bands allocated to and used by network operators are different.

In this conventional technology, although the maximum bandwidth of 100Mhz is supported by applying the CC technology, the 5G technology to be commercialized after 2020 can not satisfy the requirement of 1000 times the transmission rate of 4G. In addition, in the current band of 6 GHz or less, additional radio frequency resources are lacking to support this. In order to solve this problem, 5G technology is proposed as an alternative to use a millimeter wave band of 6 GHz or more for cellular communication.

Generally, the millimeter wave band has more propagation path loss than the cellular band, but has a strong interference tolerance. Therefore, it can be expected that a high-speed data transmission service of Gbps or higher per terminal can be provided on the basis of the signal characteristics of the millimeter-wave band, while it is expected to be installed in the form of a small support station having a small service coverage. In order to overcome the signal characteristics of the millimeter wave band, a beam forming technique can be applied. Using the beamforming technique, the base station can concentrate the transmission power into a beam of a narrow area, thereby increasing the transmission efficiency and expanding the transmission coverage.

On the other hand, in the base station using the beamforming technique, each beam uses the same frequency band in order to maximize the efficiency of frequency reuse. Since the available frequency resources are relatively abundant in the millimeter wave band, each beam can use a bandwidth of 1 GHz or more to increase the transmission amount. However, with current technology, broadband transmission of 1 GHz or more increases the complexity of wireless devices for both base stations and terminals. Therefore, a beam using a wide bandwidth needs to be composed of a plurality of beam CCs, that is, a beam FA by applying a CA technique. This means that each beam consists of a smaller unit beam CC (or FA) operating independently again. On the terminal side, it means that a specific beam CC (or FA) among the specific beams operated by the base station is connected to receive a service. Therefore, the BS must be capable of cross-carrier scheduling to transmit user traffic using a plurality of FAs that the UE can receive. That is, a user plane radio bearer data may be transmitted using different FAs or using two or more FAs simultaneously according to radio environments every TTI (Transmission time interval).

On the other hand, when a plurality of FAs are used, a base station can use a scheduling method of a time axis priority scheme or a scheduling method of a frequency axis priority scheme when a transmission rate is satisfied. For example, when allocating radio resources, radio resources may be allocated for a long time on a time axis using one FA, or radio resources may be allocated for a short period of time using multiple FAs. Although these two schemes are identical in terms of average transmission speed, they may differ in terms of latency. That is, by allocating radio resources on a time axis using 1 FA, the latency increases. Therefore, there is a need for a cross-scheduling method that can efficiently process radio resources according to delay characteristics of user traps when a plurality of FAs are used.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for performing cross-scheduling according to delay characteristics of user traffic in an environment using a multi-carrier.

It is another object of the present invention to provide a cross carrier scheduling method and apparatus capable of efficiently using radio resources in a multicarrier environment.

A cross carrier scheduling method according to aspects of the present invention is a cross carrier scheduling method in a multicarrier environment, the method comprising: receiving a user traffic from a terminal; Determining a delay characteristic of the user traffic; And allocating radio resources in one of a frequency axis priority scheme and a time axis priority scheme according to a latency group determined according to a delay characteristic of the user traffic.

According to an embodiment of the present invention, each base station operates a multi-beam in a millimeter wave band, and each beam is divided into a plurality of component carriers (CC), that is, It is possible to effectively perform cross-carrier scheduling according to the delay characteristics of user traffic in a base station operating in frequency allocation.

In addition, it is possible to efficiently use radio resources in a multi-carrier environment and to improve QoE (Quality of Experience) of users.

1 is a diagram illustrating a structure of a millimeter wave based beamforming base station.
2 is a diagram illustrating an example of a method of allocating and receiving a plurality of FAs per beam for a base station and a terminal according to an embodiment of the present invention.
3 is a diagram illustrating a structure of a base station and a terminal according to an embodiment of the present invention.
4 is a diagram illustrating multi-carrier scheduling according to delay characteristics of user traffic according to an embodiment of the present invention.
5 is a flowchart of a scheduling method according to an embodiment of the present invention.
6 is a structural diagram of a cross carrier scheduling apparatus according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification and claims, when a section is referred to as including an element, it is understood that it may include other elements as well, without departing from the other elements unless specifically stated otherwise.

Throughout the specification, a terminal may be referred to as a user equipment (UE), a mobile terminal (MT), a mobile station (MS), an advanced mobile station (AMS) a high reliability mobile station (HR-MS), a subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT) , AMS, HR-MS, SS, PSS, AT, and the like.

Also, a base station (BS) is an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B, eNodeB or eNB), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) a relay station (RS), a relay node (RN) serving as a base station, an advanced relay station (ARS) serving as a base station, a high reliability relay station A femto BS, a home Node B, a home eNodeB, a pico BS, a metro BS, a micro base station (BS) and a small base station (eNodeB), eNodeB, eNodeB, eNB, AP, RAS, BTS, MMR-BS, RS, RN, ARS, HR- And the like.

Hereinafter, a cross carrier scheduling method and apparatus according to an embodiment of the present invention will be described.

1 is a diagram illustrating a structure of a millimeter wave based beamforming base station.

1, the base station forms and manages a plurality of fixed beams (for example, 48 beams in FIG. 1). For example, multiple sectors in a base are grouped into a group (e.g., 16 beams in FIG. 1) to form a sector, and each beam in the sector has the same cell specific-reference signal (CRS). Thus, each of the base domestic beams has the same cell ID, while having different beam IDs. That is, a different BSI-RS (beam state information-reference signal) is allocated to each beam in the same sector. The BSI-RS has a function similar to the CSI-RS (Channel state information-reference signal).

On the other hand, in the millimeter wave band, since the available frequency resources are relatively abundant, a bandwidth of 1 GHz or more can be allocated to each beam. However, in the current technology, broadband transmission of 1 GHz or more increases the complexity of the radio equipment for both the base station and the terminal. For example, broadband transmission increases the sampling rate of transmitters and receivers, which directly affects the power consumption and complexity of the DAC / ADC (digital analog converter / analog digital converter) as well as the front-end digital signal processing give. Radio frequency (RF) components also generally suffer from the complexity of the design itself and the cost of manufacturing to increase in order to support a wide bandwidth. Therefore, it is necessary to use a CA (Carrier Aggregation) scheme for each beam using each optical bandwidth, and each beam should be composed of a plurality of beam CCs (i.e., beam FAs). This means that each beam is composed of a smaller unit beam CC, that is, FA, which operates independently again. On the terminal side, the service is received by connecting to a specific beam CC of a specific beam operated by the base station. Therefore, the BS must be capable of cross-carrier scheduling to transmit user traffic using a plurality of FAs that the UE can receive. That is, a user plane radio bearer data may be transmitted using different FAs or using two or more FAs simultaneously according to radio environments every TTI (Transmission time interval).

2 is a diagram illustrating an example of a method of allocating and receiving a plurality of FAs per beam for a base station and a terminal according to an embodiment of the present invention.

In FIG. 1, each beam supports high-speed mobile data service per terminal using a wide bandwidth in a millimeter wave band. In one example of the present invention, each beam in the millimeter wave band transmits data using a 1 GHz bandwidth. Then, each beam is divided into eight 125 MHz FAs. Therefore, a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH), a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH) , Physical Hybrid Automatic Repeat-ReQuest (HARQ) indicator channel (PHICH), physical uplink control channel (PUCCH), and physical random access channel (PRACH).

On the other hand, each FA operation is similar to CC operation in existing CA. However, due to the characteristics of the millimeter wave band, the bandwidth of each FA can be more than 20Mhz and the number of additional FAs can be more than five. In the example of FIG. 2, the frequency band per beam CC is 125 MHz and operates with 8 beams CC (beam FA) per beam. At this time, each beam is composed of one or more primary FAs and the remaining secondary FAs. The MS performs an initial connection procedure (RRC Connection Request / RRC Connection Re-establishment Request) using the primary FA designated by the BS. Then, the base station adds or removes the secondary FA by using the RRC Connection Reconfiguration message.

On the other hand, the primary FA always constitutes a pair with the uplink FA and is always active. On the other hand, the secondary FA is in a disabled state, and the base station activates or deactivates the secondary FA by using a MAC-CE (Control Element). Each beam in the cell broadcasts the same system information, that is, MIB (Master Information Block) and SIB (System Information Block) information.

Meanwhile, the UE can select a primary FA and a plurality of secondary FAs of eight 125 MHz FAs that the base station operates within the 1 GHz bandwidth, and can connect to the base station. The maximum number of FAs that can be received and processed by the terminal may be different for each implementation. The terminal accesses by using the primary FA when beam connection is made, and then adds the secondary FA according to the request of the terminal user. Therefore, the performance of the terminal depends on which beam is connected and which FA in the beam is used. If a plurality of FAs are used, the transmission rate of the UE and the latency of the user traffic may vary depending on which FA is scheduled for priority. Accordingly, the BS must be able to report CQI (channel quality indicator) information for each beam CC in a plurality of beams from the UE to the UE, and schedule the CQI according to the priority. The complexity of the scheduling of the beamforming base station (the base station of FIG. 1) increases in proportion to the number of peripheral base stations, the number of beams operated by the base station, and the number of beam CCs.

Meanwhile, the UE periodically performs CQI measurement on the currently-connected beam (Serving beam) and neighboring beam (Neighbor beam), and reports the result to the BS. According to the CQI report result, a handover (L3 handover) procedure is performed when the target neighbor beam is different from the current cell. On the other hand, if the target neighbor beam is the same as the current cell, a beam switching procedure is performed. The handover procedure in the embodiment of the present invention may follow a conventional procedure (e.g., an LTE handover procedure), but is not limited thereto.

3 is a diagram illustrating a structure of a base station and a terminal according to an embodiment of the present invention.

The base station 1 includes a base station transmitter 11 and a base station receiver 12 as shown in FIG. 3 for beam-based multi-FA processing. The base station transmitter 11 includes a PDCP / RLC (Packet Data Convergence Protocol / Radio Link Control) processor 111, a beam mapper 112, and a MAC (Media Access Control) processor 113. The base station receiver 12 includes a PDCP / RLC processor 121 and a MAC processor 122.

The PDCP / RLC processor 111 of the base station transmitter 11 processes a plurality of radio bearers for a plurality of terminals. For example, radio bearer # 1 and radio bearer #p transmit data to terminal #i.

The MAC processor 113 includes a plurality of beam processors 1131 and a scheduler 1132. Each beam processor 1131 includes a plurality of FA processors (FA # 1 processor, FA # 2 processor, FA # m processor).

The beam mover 112 maps the terminal #i to one of several beams in the MAC processor 113 and specifically maps it to one beam processor (e.g., Beam # k processor) of the MAC processor 113 Function.

Meanwhile, the terminal 2 includes a MAC reception processor 21 and a MAC transmission processor 22. The MAC reception processor 21 includes a beam processor 211 and the beam processor 211 includes a plurality of FA processors (FA # 1 processor, FA # 2 processor, FA # n processor). The MAC transmission processor 22 includes a beam processor 221.

In this structure, the UE # 2 is mapped to a specific beam in an RRC Connection Request / RRC Connection Re-establishment Request, and the primary FA processor in the specific beam (FA # 1 processor to FA # And is connected to the base station 1 by using one of them.

The base station 1 adds the secondary FA to the FA using the RRC reconfiguration message for the FAs other than the primary FA in the beam. That is, the base station 1 additionally activates the secondary FA to satisfy the QoS when setting the radio bearer # 1 and the radio bearer #p of the terminal #i (2).

In the embodiment of the present invention, the radio bearer #p is mapped to a specific beam, that is, beam #k, and the beam #k is transmitted to the terminal #i by using a plurality of FA processors. On the other hand, one FA processor of the beam processor 1131 of the base station 1 corresponds one-to-one with one FA processor included in the beam processor 211 of the MAC reception processor 21 of the terminal #i (2) And performs an HARQ (Automatic Repeat-reQuest) function. Therefore, in the embodiment of the present invention, the radio bearer of the PDCP / RLC processor 111 of the base station transmitter 11 is mapped to a plurality of FA processors in one beam of the MAC processor 113 and processed. The FA processor of the MAC processor 113 of the base station transmitter 11 performs a one-to-one transmission / reception function with the FA processor of the MAC reception processor 21 of the terminal 2.

4 is a diagram illustrating multi-carrier scheduling according to delay characteristics of user traffic according to an embodiment of the present invention.

When a plurality of FAs are used and a transmission rate is satisfied, a scheduling method of a time axis priority scheme or a scheduling method of a frequency axis priority scheme can be used. For example, in a high latency application, a radio resource may be allocated on a time axis using one FA (for example, an FA # 5 processor) when allocating radio resources. Alternatively, for low latency applications, radio resources may be allocated for a short period of time using multiple FAs (e.g., FA # 1 processor to FA # 4 processor). Even though these two schemes are the same in terms of average transmission rate, they may be different in terms of latency. That is, when radio resources are allocated on a time axis using a single FA, the latency increases. Therefore, in the embodiment of the present invention, when a plurality of FAs are used, cross scheduling is performed to efficiently process radio resources according to delay characteristics of user traps.

Conventionally, each radio bearer is assigned a QoS class identifier (QCI), and is subjected to QoS control according to the QCI value. For example, 13 QCI values may be defined. Based on this value, end-to-end packet forwarding can be performed from the UE to the P-GW (PDN gateway). Each QCI value can define different resource types, priority, packet delay budget, and packet error loss.

In the embodiment of the present invention, the traffic of the terminal can be classified into three groups according to QCI (including 13 previously defined QCIs and QCIs that can be added in the future) and packet delay budgets .

One) High latency group = {QCI | packet delay budget ≤100 ms}

2) Medium latency group = {QCI | 100ms <packet delay budget ≤200ms}

3) Low latency group = {200ms <packet delay budget>

In the embodiment of the present invention, the traffic of the terminals is classified into one group according to the user traffic delay characteristics based on the QCI, and the cross-scheduling is performed as follows.

Specifically, as shown in FIG. 4, the base station transmits a high-latency group (which may be referred to as a first group for the sake of convenience of explanation) wirelessly in a time axis priority manner so as to use an arbitrary number of FAs Allocate resources. The base station allocates radio resources in a frequency-axis priority manner so that at least half FAs that can be received by the terminal can be used for the intermediate latency group (which may be referred to as a second group for ease of description). The base station allocates radio resources in a frequency-axis priority manner so that the terminal can use all the FAs receivable for the low latency group (which may be referred to as the third group for ease of explanation).

5 is a flowchart of a scheduling method according to an embodiment of the present invention.

As shown in FIG. 5, a cross carrier scheduling procedure is performed according to the delay characteristics of user traffic in a multi-carrier environment.

The UE determines a beam for camp-on in the initial connection process and is connected to the base station through the primary FA of the beam. The base station adds another secondary FA in the beam through the RRC connection reconfiguration process, and the MAC Activate / deactivate secondary FA added using CE (Control element).

Specifically, the terminal #i is mapped to a specific beam (for example, beam # k) in the initial connection process, and the FA # 1 corresponding to the primary FA in the mapped beam (for example, one of the FA # (S100). In step S110, the BS adds the secondary FA to the FA using the RRC connection reconfiguration message for the FA excluding the primary FA in the beam. The base station can additionally set an arbitrary dedicated bearer for the terminal #i and further activate the secondary FA to satisfy the QoS (S120).

In this state, the base station receives user traffic from the EPC (Evolved Packet core) to the terminal #i in a state where the terminal is connected to the base station and is allocated a specific beam and can access the base station using the primary FA and the secondary FA S130).

The base station determines the delay characteristics of the user traffic. The base station classifies user traffic into one of a high latency group, a medium latency group, and a low latency group according to a QCI value.

If the received user traffic is a bearer of a low latency group, the base station allocates radio resources in a frequency-axis priority manner so that the UE can use all available FAs (S140, S150).

If the received user traffic is a medium latency group bearer, the base station allocates radio resources in a frequency-axis priority manner so that at least one or more FAs that can be received by the UE are available (S160, S170).

If the received user traffic is a high latency group bearer, the base station allocates radio resources in a time axis priority manner so as to use an arbitrary number of FAs according to a radio resource situation (S180, S190).

Thereafter, application traffic to the terminal #i is transmitted using the allocated radio resources (S200).

6 is a structural diagram of a cross carrier scheduling apparatus according to another embodiment of the present invention.

6, the cross-carrier scheduling apparatus 100 according to the embodiment of the present invention includes a processor 10, a memory 20, and a transceiver 30. As shown in FIG.

The processor 10 may be configured to implement the methods described above with respect to Figures 4 and 5 above.

The memory 20 is connected to the processor 10 and stores various information related to the operation of the processor 10. [ The memory 20 stores instructions to be executed by the processor 10 or temporarily stores the instructions loaded from a storage device (not shown).

The processor 10 may execute instructions that are stored or loaded into the memory 20. The processor 10 and the memory 20 are connected to each other via a bus (not shown), and an input / output interface (not shown) may be connected to the bus.

The embodiments of the present invention are not limited to the above-described apparatuses and / or methods, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention, a recording medium on which the program is recorded And such an embodiment can be easily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It belongs to the scope of right.

Claims (1)

A cross carrier scheduling method in a multi-carrier environment,
The base station receiving user traffic from the terminal;
Determining a delay characteristic of the user traffic; And
Allocating radio resources in one of a frequency axis priority scheme and a time axis priority scheme according to a latency group determined according to a delay characteristic of the user traffic
/ RTI &gt;

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