KR101888267B1 - Scheduling method and apparatus considering hardware noise - Google Patents

Abstract

A scheduling apparatus and method are provided. A scheduling apparatus according to an embodiment of the present invention includes a first scheduling group classifier for classifying the MTC terminals into a plurality of first scheduling groups using class information of MTC terminals located in a serving cell of the base station; A second scheduling grouping unit classifying MTC terminals belonging to the same first scheduling group into a plurality of second scheduling groups using fading information, available energy information, and hardware noise figure of each MTC terminal for each of the first scheduling groups; And a transmission power setting unit for setting a transmission power of the MTC terminals for each of the classified second scheduling groups, wherein the class information of the MTC terminals is based on a traffic request index required for each MTC terminal and the hardware noise index And independent scheduling is performed for each of the first scheduling groups. The traffic request index is determined using at least one of a required data rate, a packet size, a reliability, and a latency.

Description

[0001] SCHEDULING METHOD AND APPARATUS CONSIDERING HARDWARE NOISE [0002]

The present invention relates to a scheduling method and apparatus, and more particularly, to a scheduling technique for MTC terminals in a mobile communication system in a massive MIMO environment.

In the conventional mobile communication system, user scheduling is preceded by obtaining accurate channel information in order to guarantee quality of service. Due to the characteristics of the channel changing over a short period of time, inevitably, a short period of reference signal transmission for scheduling in need.

On the other hand, a random access method may be used to intermittently access the control signal while reducing the control signal overhead. However, due to the nature of the method, collision can occur and transmission without channel information makes it difficult to guarantee quality of service.

In the next generation mobile communication, 5G, it is expected that communication between objects such as MTC (Machine-Type Communication) and IoT (Internet of Things) will increase sharply. In addition, the use of massive MIMO (Multi Input Multi Output) is expected to increase the degree of freedom.

In such a mobile communication environment, the conventional scheduling method has a problem in that it can not fully utilize a new communication environment.

In particular, existing mobile communication operates in a way that guarantees service quality above a predetermined threshold performance. However, if service quality is guaranteed in the same 5G environment as in the conventional mobile communication system, , And there is a considerable delay in terms of scheduling.

Devices such as MTC, which are used for inter-object communication, are likely to use relatively low-cost RF chips, and these devices are expected to have a higher noise level because they are expected to have poor RF performance in existing mobile communication terminals.

Although there are various studies on inter-object communication in the 5G environment, there is little research on the communication method in case of using the low-performance RF chip in inter-object communication.

One aspect of the present invention is to propose a scheduling method and apparatus suitable for inter-object communication with a small control signal overhead.

Another aspect of the present invention is to propose a scheduling method and apparatus considering noise of a communication device.

Another aspect of the present invention is to propose a scheduling method and apparatus capable of ensuring low latency and high reliability.

In order to achieve the above object, according to an aspect of the present invention, there is provided a method for allocating a first scheduling group, which classifies MTC terminals into a plurality of first scheduling groups, using class information of MTC terminals located in a serving cell of a base station, A classification section; A second scheduling grouping unit classifying MTC terminals belonging to the same first scheduling group into a plurality of second scheduling groups using fading information, available energy information, and hardware noise figure of each MTC terminal for each of the first scheduling groups; And a transmission power setting unit for setting a transmission power of the MTC terminals for each of the classified second scheduling groups, wherein the class information of the MTC terminals is based on a traffic request index required for each MTC terminal and the hardware noise index Wherein the independent scheduling is performed for each of the first scheduling groups and the traffic requirement index is determined using at least one of a required data rate, a packet size, a reliability, and a latency, Device is provided.

Wherein the scheduling apparatus comprises: a scheduling period determining unit for determining a scheduling period of each of the second scheduling groups; And a resource element allocator allocating a number of resource elements to be used for each of the second scheduling groups according to the determined scheduling period.

The second scheduling group classifier calculates a quality parameter by dividing the value obtained by multiplying the fading information by the available energy information by a value based on the hardware noise index, and classifies the second scheduling group based on the quality parameter.

The second scheduling group classifier compares the quality parameters of the MTC terminals and classifies the case where the difference is equal to or less than a predetermined threshold value into the same scheduling group.

The transmission power setting unit sets the transmission power so that the MTC terminals belonging to the same second scheduling group use the same transmission power.

The scheduling period is set so as to satisfy a QoS requirement including a packet size, a data rate, and a reliability, and is set to maximize the number of MTC terminals to be accommodated, or to minimize a bandwidth when the number of MTC terminals is preset Direction.

When the delay time is additionally considered to the QoS requirement, the scheduling period is determined so as not to exceed the delay time.

The scheduling apparatus includes scheduling information including at least one of a second scheduling group, a power difference indicator for the second scheduling group, and information on the allocated resource elements in the determined scheduling period Scheduling Grant Information).

According to another aspect of the present invention, there is provided a method for allocating MTC terminals, comprising the steps of: (a) classifying the MTC terminals into a plurality of first scheduling groups using class information of MTC terminals located in a serving cell; (b) classifying MTC terminals belonging to the same first scheduling group into a plurality of second scheduling groups using fading information, available energy information, and hardware noise figure of each MTC terminal for each of the first scheduling groups; (c) setting a transmission power of the MTC terminals for each of the classified second scheduling groups, wherein the class information of the MTC terminals is based on a traffic request index required for each MTC terminal and the hardware noise index Wherein the independent scheduling is performed for each of the first scheduling groups and the traffic requirement index is determined using at least one of a required data rate, a packet size, a reliability, and a latency, Method is provided.

According to another aspect of the present invention, there is provided a MTC terminal for communicating with a base station according to scheduling of a base station, the MTC terminal comprising: a processor; A hardware noise figure calculating unit for calculating a hardware noise figure by the RF chip; A memory coupled to the processor; And a communication unit connected to the processor, wherein the memory transmits a Physical Uplink Shared CHannel signal to the base station via the communication unit, receives a traffic request for the MTC terminal from the base station through the communication unit, First scheduling group information and fading information based on MTC class information set based on the index and the hardware noise figure, second scheduling group information set based on available energy information and the hardware noise index, And receiving scheduling information including information on a resource element and transmission power allocated to the second scheduling group based on the received scheduling information and using the allocated resource element together with other MTC terminals belonging to the second scheduling group, With reference to the assigned transmit power, And storing the program instructions executable by the processor to transmit a data signal to the base station, wherein the traffic requirement index uses at least one of a required data rate, a packet size, a reliability, and a latency The MTC terminal is determined.

According to the present invention, it is possible to perform scheduling suitable for inter-object communication and taking noise of a communication device into consideration.

Further, according to the present invention, scheduling that can ensure low latency and high reliability can be achieved.

1 is a diagram showing the structure of a downlink sub-frame;
2 is a diagram illustrating an uplink subframe structure;
3 is a diagram illustrating a structure of a mobile communication system to which a scheduling method according to an embodiment of the present invention is applied.
4 is a diagram showing an example for classifying a class of the MTC terminal;
5 is a diagram illustrating a structure of a frame used in uplink scheduling according to an embodiment of the present invention;
FIG. 6 is a block diagram illustrating a configuration of an uplink scheduling apparatus according to an embodiment of the present invention; FIG.
7 is a flowchart illustrating an uplink scheduling process according to an embodiment of the present invention.
8 is a block diagram showing a configuration of an MTC terminal according to an embodiment of the present invention.
9 is a diagram illustrating a configuration of second scheduling information according to an embodiment of the present invention;
FIG. 10 is a flowchart illustrating a procedure when a new MTC terminal enters according to an embodiment of the present invention; FIG.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

Before describing the scheduling method and apparatus according to an embodiment of the present invention, the structures of the downlink subframe and the uplink subframe will be described first. The scheduling scheme of the present invention relates to a scheduling scheme in the uplink.

1 is a diagram illustrating a structure of a downlink sub-frame.

In a subframe, a maximum of three OFDM symbols in the first part of the first slot corresponds to a control area to which a control channel is allocated.

The remaining OFDM symbols correspond to a data area to which a Physical Downlink Shared Chanel (PDSCH) is allocated.

The basic unit of transmission is one subframe. That is, PDCCH and PDSCH are allocated over two slots.

The downlink control channels used in the 3GPP LTE system include, for example, a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical HARQ indicator channel (Physical Hybrid Automatic Repeat Request Indicator Channel (PHICH)).

The PCFICH includes information on the number of OFDM symbols transmitted in the first OFDM symbol of the subframe and used for control channel transmission in the subframe.

The PHICH includes an HARQ ACK / NACK signal as a response to the uplink transmission.

The control information transmitted through the PDCCH is referred to as downlink control information (DCI).

The DCI includes uplink or downlink scheduling information or includes an uplink transmission power control command for an arbitrary terminal group.

The PDCCH includes a resource allocation and transmission format of a downlink shared channel (DL-SCH), resource allocation information of an uplink shared channel (UL-SCH), paging information of a paging channel (PCH), system information on a DL- A set of transmission power control commands for individual terminals in an arbitrary terminal group, transmission power control information, activation of VoIP (Voice over IP), resource allocation of upper layer control messages such as random access response And the like.

A plurality of PDCCHs can be transmitted in the control domain, and the UE can monitor a plurality of PDCCHs.

The PDCCH is transmitted in a combination of one or more contiguous Control Channel Elements (CCEs).

Here, CCE is a logical allocation unit used to provide the PDCCH with a coding rate based on the state of the radio channel.

The CCE corresponds to a plurality of resource element groups, and the format of the PDCCH and the number of available bits are determined according to the correlation between the number of CCEs and the coding rate provided by the CCE.

The base station determines the PDCCH format according to the DCI transmitted to the user terminal and adds a cyclic redundancy check (CRC) to the control information.

Here, the CRC is masked with an identifier called a Radio Network Temporary Identifier (RNTI) according to the owner or use of the PDCCH.

If the PDCCH is for a particular UE, the cell-RNTI (C-RNTI) identifier of the UE may be masked in the CRC.

Alternatively, if the PDCCH is for a paging message, a Paging Indicator Identifier (P-RNTI) may be masked in the CRC.

If the PDCCH is for system information (more specifically, the System Information Block (SIB)), the system information identifier and the system information RNTI (SI-RNTI) may be masked to the CRC.

A random access-RNTI (RA-RNTI) may be masked to the CRC to indicate a random access response that is a response to the transmission of a random access preamble of the user terminal.

2 is a diagram illustrating an uplink subframe structure.

The UL subframe may be divided into a control region and a data region in the frequency domain.

A physical uplink control channel (PUCCH) including uplink control information is allocated to the control region, and a physical uplink shared channel (PUSCH) including user data is allocated to the data region. do.

In order to maintain the single carrier characteristic, one user terminal can selectively transmit the PUCCH and the PUSCH.

The PUCCH for one user terminal is allocated to a resource block pair (RB pair) in a subframe.

The resource blocks belonging to the resource block pair occupy different subcarriers for two slots, and the resource block pair allocated to the PUCCH is frequency-hopped at the slot boundary.

It should be apparent to those skilled in the art that the subframe structure shown in FIGS. 1 and 2 is for a subframe of LTE for convenience of explanation, and that the subframe structure may vary depending on the communication environment to which the present invention is applied.

3 is a diagram illustrating a structure of a mobile communication system to which a scheduling method according to an embodiment of the present invention is applied.

A mobile communication system according to an embodiment of the present invention is based on a massive MIMO environment, and may include a plurality of base stations, terminals, and a network entity.

For reference, the network entity may be implemented as a base station or an arbitrary node of the core network, and may perform uplink / downlink scheduling using information collected from base stations.

In addition, each base station may have at least one serving cell. If Carrier Aggregation is used to group different frequency bands and use them as one frequency, multiple serving cells can be set up in one base station. For example, one primary cell and one or more secondary cells are set in one base station.

3, there is a plurality of MTC terminals 200 that desire to be scheduled with one base station 100 and the base station 100, and a plurality of MTC terminals 200 are connected to the base station 100 at the same time, The case where communication is performed will be described.

The base station 100 uses the Physical Uplink Shared CHannel (PUSCH) received from the MTC terminals 200 in the serving cell to transmit the long- Long-term or large-scale fading information (hereinafter, referred to as 'fading information') can be obtained.

Here, each MTC terminal 200 may use a unique non-orthogonal reference signal through a PUSCH channel, or may use an orthogonal reference signal.

And 'fading information' may mean average channel information in the long-term.

For reference, as the number of antennas of the base station 100 increases, the fluctuation of an instantaneous channel between the MTC terminal 200 and the base station 100 can be ignored. That is, the performance of the corresponding channel can be estimated using the fading information of the channel between the MTC terminal 200 and the base station 100.

This can be confirmed by the formula of Favorable Propagation used for sending and receiving in the massive mimo environment.

Where M is the number of antennas of the base station 100, K is the channel between the MTC number of terminals 200, G _l is K × antenna and MTC terminal 200 in the l-th base station 100 by M matrix, D _l Is the diagonal matrix (k, k) th element is beta _lk .

Also, β _lk is the large-scale fading or average channel power between the l-th base station 100 and the k-th MTC terminal 200.

For reference, G _l includes both small-scale fading and large-scale fading between the antenna of the base station 100 and the MTC terminal 200.

Equation (1) above means that as the number of antennas of the base station 100 increases, the channel variation between the MTC terminal 200 and the base station 100 antenna can be ignored.

In other words, the performance of the corresponding channel can be estimated with the large-scale fading information of the channel between the base station 100 and the MTC terminal 200.

For reference, the base station 100 does not need to receive additional reference signals or feedback from the MTC terminals 200 to acquire fading information by using the PUSCH signal.

In addition, the base station 100 can acquire available energy information of the MTC terminals 200.

Here, 'available energy' represents energy that can be used per resource element (RE) for the MTC terminal 200 to access the base station 100.

For reference, the available energy may vary according to the battery state of the MTC terminal 200, the charging process or the power consumption policy of the MTC terminal 200, but such a change is extremely small or negligible when considering the long-term .

In addition, the base station 100 determines MTC class information using the hardware noise figure and the traffic requirement index of each MTC terminal 200. [ Here, the hardware noise figure represents information obtained by quantifying noise generated due to the use of a relatively low-performance RF chip. The traffic requirement index indicates the required data rate, packet size, reliability, and latency It means numerical information summed by quantifying information. Of course, it will be apparent to those skilled in the art that other traffic related information other than the above-mentioned data rate, packet size, reliability and delay time may be considered in the traffic requirement index.

The hardware noise figure may be calculated by the MTC terminal 200 and may be calculated in the base station 100 by receiving basic information for calculating the hardware noise figure from the MTC terminal.

For example, when the noise of the MTC terminal is n, the transmission signal for the reference signal may be expressed as x _j = s + n _j , where s is a known reference signal, n is noise, . The hardware noise can be modeled as a Gaussian random process and defined as n - CN (0, δ ² ), and the hardware noise figure of the terminal can be expressed as δ ² .

On the other hand, when the BS calculates the hardware noise figure, the reception signal r of the base station is defined as r _j = h (s + n _j ) + v _j . Where n is the channel noise and v is the hardware noise and can be defined as v ~ CN (0, δ ² ). y _j = hn _j + v _j , the noise figure δ ² can be defined as the following equation (2).

4 is a diagram showing an example for classifying the class of the MTC terminal.

Referring to FIG. 4, an MTC class A is set according to a traffic requirement index required for a terminal, and an MTC class B is set according to a hardware noise figure (? ² ) of the terminal. The final MTC class is determined by the combination of A and B, and the combination of A and B may be determined in various ways. For example, the final MTC class can be determined by the product of A and B or the sum of A and B.

The base station 100 performs scheduling using an MTC class, a hardware noise figure of the MTC terminal, fading information, and available energy. The scheduling according to an embodiment of the present invention includes first scheduling for classifying a scheduling group to be independently scheduled and second scheduling for allocating resources to each MTC terminal 200 for each first scheduling group.

The first scheduling classifies UEs having the same or similar MTC class into the same first scheduling group. If the first scheduling group is classified by the first scheduling, second scheduling independent of each first scheduling group is performed. Setting the terminals having the same or similar MTC class to the same first scheduling group enables effective scheduling when the terminals of similar characteristics are simultaneously scheduled.

The second scheduling is performed using hardware noise figure, fading information, and available energy of the MTC terminal. In the second scheduling, a time resource and a frequency resource to be communicated with the base station are allocated to each of the first scheduling groups. At this time, a second scheduling group is set, which is a MTC terminal group that uses the same resource (hereinafter, referred to as a "resource element"). When the second scheduling group is set, the uplink transmission power to be used for each second scheduling group is set.

For example, the MTC terminals 200 belonging to the same second scheduling group can use the same uplink transmission power.

At this time, the base station 100 can determine the allocation ratio of the uplink transmission power to the reference signal and the data signal (Data Signal) for each MTC terminal 200 belonging to the same scheduling group.

In addition, the base station 100 may determine a resource element usage rate for each second scheduling group based on a data rate of MTC terminals belonging to each second scheduling group.

Here, the data rate and the usage ratio of the resource element are inversely proportional to each other. That is, a scheduling group having a relatively higher data rate among the plurality of second scheduling groups uses a smaller ratio of resource elements than a scheduling group having a lower data rate.

Then, the base station 100 sets an uplink scheduling period for each second scheduling group, and allocates resource elements (number) for each scheduling group according to a set uplink scheduling period.

Then, the base station 100 transmits to the MTC terminals 200 existing in the same first scheduling group the second scheduling group information to which the MTC terminal 200 belongs, the resource element information allocated to the second scheduling group, MTC terminals 200 may transmit reference signals and data signals in accordance with the scheduling information received from the base station 100. The MTC terminals 200 may transmit the reference signals and the data signals.

At this time, the MTC terminals 200 can determine whether to use the resource element allocated to the scheduling group to which the MTC terminal 200 belongs according to the scheduling information received from the base station 100.

In the conventional scheduling scheme, the MTC terminal 200 has to use the resource allocated to itself according to the scheduling received from the base station 100. [

However, the scheduling method according to an embodiment of the present invention can directly determine whether the resource element allocated to the second scheduling group to which the MTC terminal 200 belongs is used (this is 'grant free' do). That is, the MTC terminal 200 does not need to use resource elements that are resources scheduled by the base station 100.

Also, in a conventional mobile communication system including LTE (Long-Term Evolution), it is difficult to predict the performance of the corresponding channel due to the channel fluctuation between the MTC terminal 200 and the base station 100, There was no.

Therefore, in the conventional scheduling method in the mobile communication system, it is necessary to precede the process of acquiring accurate channel information in order to guarantee the quality of service, and in the mobile communication environment, Inevitably, there is a need for a short period reference signal transmission process for scheduling.

However, in the conventional scheduling scheme, since the MTC terminals 200 transmit the uplink reference signal prior to the scheduling, a plurality of uplink reference signals are required, so that the spectral efficiency of the entire mobile communication system is lowered. The channel information of the unscheduled MTC terminal 200 is not discarded or utilized, and the energy efficiency of the MTC terminal 200 is lowered.

The uplink / downlink transmission is performed in the order of uplink-> downlink-> uplink, and this conversion causes considerable delay in the time division duplex (TDD) or frequency division duplex (FDD) situations .

Therefore, in order to solve the above-mentioned conventional problems, it is necessary to transmit a short reference signal for scheduling using the fading information of the channel between the MTC terminal 200 and the base station 100, So that the data rate of all the MTC terminals 200 located in the serving cell is maintained at a constant value so that the MTC terminal 200 which is not scheduled is not present, and the time delay due to the repetition of the uplink and the downlink And the frequency efficiency of the system and the energy efficiency of the terminal can be improved.

In addition, the scheduling for existing MTC terminals has been performed on the assumption that all MTC terminals have excellent RF performance. However, since a variety of MTC terminals are used in the future 5G environment, and a large number of MTC terminals do not require voice communication and high-speed data transmission, it is highly likely that a relatively low-performance RF chip is used. However, We did not consider MTC terminals using RF chips of performance. The present invention can perform efficient resource allocation and management for MTC terminals having low RF performance by performing the first scheduling and the second scheduling using the hardware noise figure.

5 is a diagram illustrating a structure of a frame used in uplink scheduling according to an embodiment of the present invention.

The uplink frame according to an exemplary embodiment of the present invention includes a Scheduling Information Broadcast (SIB) portion for the base station 100 to inform the MTC terminals 200 in the serving cell of scheduling information, And a plurality of frames composed of a reference signal and a data signal transmitted to the base station 100.

In one embodiment, a frame of a system using OFDMA may be composed of a plurality of resource elements occupying a unit time-frequency.

Here, one frame may be composed of a plurality of sub-frames, and one sub-frame may be composed of a plurality of resource elements.

The resource elements included in one subframe may be allocated to one or more scheduled MTC terminals 200. One MTC terminal 200 may allocate one or more subframes, Can receive.

In FIG. 5, one frame is composed of a total of NW / F resource elements, and one subframe consists of N total resource elements.

For reference, resource elements constituting one subframe can be assigned to a reference signal and a data signal.

And adjacent resource elements can be used to transmit the reference signal and its position can be changed flexibly without being fixed.

The resource element allocated to the reference signal can transmit the reference signal that the base station 100 and the MTC terminal 200 have previously agreed to at a predetermined position.

6 is a block diagram illustrating a configuration of an uplink scheduling apparatus according to an embodiment of the present invention.

The uplink scheduling apparatus according to an embodiment of the present invention may be included in the base station 100 or may exist separately from the base station 100 and be connected to the base station 100.

Hereinafter, the case where the uplink scheduling apparatus is included in the base station 100, the uplink scheduling apparatus is represented by the base station 100.

The base station 100 according to an embodiment of the present invention includes a channel information feedback unit 110, a first scheduling group classifying unit 115, a second scheduling group classifying unit 120, a transmission power setting unit 130, A period setting unit 140, a resource element assigning unit 150, a communication unit 160, and a control unit 170.

The channel information feedback unit 110 obtains the fading information of the MTC terminals 200, that is, the average channel information in the long-term using the PUSCH signal received from the MTC terminals 200 .

At this time, the large-scale fading information can be calculated using the following equation (3).

Where P is the uplink transmission power and the index t represents the index of the resource element.

The first scheduling group classifying unit 115 classifies the first scheduling group using the class of the MTC terminal set using the information about each MTC terminal 200 based on the information provided from each MTC terminal 200 do. As described above, the MTC class is classified based on the traffic request index for the MTC terminal and the hardware noise index of each MTC terminal. As described above, the traffic requirement index can be determined based on packet size, data rate, delay time, and reliability. When the first MTC terminal and the second MTC terminal are classified into different first scheduling groups, the scheduling for the first MTC terminal and the second MTC terminal is performed independently.

The second scheduling group classifier 120 classifies a plurality of MTC terminals 200 classified into the same first scheduling group into a plurality of second scheduling groups.

The second scheduling group classifier 120 uses the fading information (hereinafter referred to as ? ) Of each MTC terminal 200, the available energy (hereinafter referred to as 'E'), and the hardware noise figure of the MTC terminal Classify the scheduling group. The second scheduling group classifier 120 calculates quality parameters using fading information β , available energy E and hardware noise figure δ ² and classifies the second scheduling group based on the quality parameter .

According to an embodiment of the present invention, the quality parameter may be defined as Equation (4).

According to an aspect of the present invention, the threshold values for the quality parameter are preset and the MTC terminals 200 having a preset threshold value or less can be classified into the same second scheduling group.

In one embodiment, the second scheduling grouping unit 120 orders the MTC terminals 200 in the order of a larger quality parameter value, and transmits the order of the first MTC terminal, the second MTC terminal, the first MTC terminal, The third MTC terminal, and the first MTC terminal, the fourth MTC terminal, and the like, sequentially comparing the values of the quality parameters of the MTC terminal having the highest quality parameter value and the other MTC terminals, And may classify the terminals 200 into one same second scheduling group.

That is, in the same second scheduling group, the difference between the MTC terminal having the largest quality parameter value and the smallest MTC terminal is equal to or less than a preset threshold value.

It will be obvious to those skilled in the art that scheduling group classification based on quality parameters can be performed using various optimization conditions and the like in addition to the above-described methods.

Meanwhile, the second scheduling group classifier 120 may reflect the transmission probabilities of the MTC terminals 200 in the second scheduling group classification when the MTC terminals 200 are classified into the second scheduling group. Here, the 'transmission probability' may mean the possibility that the MTC terminal 200 determines to use the resource element among the results of determining whether to use the resource element that is the resource allocated to the corresponding scheduling according to the scheduling of the base station 100 . Considering such a transmission probability, it is possible to schedule more MTC terminals to be included in one second scheduling group.

The transmission power setting unit 130 sets the uplink transmission power for each second scheduling group. It is preferable that the MTC terminals belonging to the same second scheduling group transmit uplink signals with the same power. For this purpose, the transmission power setting unit 130 determines an uplink transmission power to be used for each MTC terminal 200, and determines a transmission power of the corresponding scheduling group 200 based on the MTC terminal 200 having the lowest uplink transmission power for each scheduling group The uplink transmission power can be set.

In addition, the transmission power setting unit 130 may determine the allocation ratio of the reference signal and the uplink transmission power to the data signal for each MTC terminal 200 belonging to the same scheduling group.

At this time, the transmission power setting unit 130 may determine the allocation ratio of the reference signal and the data signal so that the Signal to Interference plus Noise Ratio (SINR) is maximized.

Meanwhile, the scheduling period setting unit 140 may determine a scheduling period for each second scheduling group to determine a usage ratio of the resource elements for each second scheduling group.

According to the first embodiment of the present invention, the scheduling period setting unit 140 may determine a period for each second scheduling group based on a data rate expected from all the scheduled UEs.

According to the second embodiment of the present invention, the scheduling period may be determined in such a manner as to maximize the number of MTC terminals servicing while satisfying the required QoS or to minimize the bandwidth.

The scheduling period determination method in the first embodiment will be described as follows.

In the first embodiment, the resource element usage rate per scheduling group is determined, wherein the usage ratio of resource elements for each second scheduling group can be set based on the expected data rate from each scheduling group, It can be proportional to the quality parameter described above.

For reference, assuming that the size of the transmitted packet is the same, the expected data rate and the usage ratio of the resource element are inversely proportional to each other. That is, the second scheduling group having a relatively higher data rate among the plurality of second scheduling groups uses a smaller ratio of resource elements than the second scheduling group having a lower data rate.

For example, if the ratio of the data rates for the second and third scheduling groups A and B is 3: 1, the ratio of the resource elements allocated to the scheduling groups A and B becomes 1: 3.

As a result, the scheduling period setting unit 140 adjusts the different data rates of the MTC terminals 200 by adjusting the usage ratio of the resource elements according to the ratio of the data rates.

Thereafter, the scheduling period setting unit 140 can determine the 'expected data rate for all the MTC terminals 200' belonging to the same first scheduling group.

The 'expected data rate for all MTC terminals' is the data of all the MTC terminals 200 so that there is no MTC terminal 200 that can not be scheduled among the MTC terminals 200 of the first scheduling group located in the serving cell Quot; means a data rate at which a rate maintains a constant value.

Hereinafter, the 'expected data rate for all the MTC terminals' will be referred to as 'SE (common spectral efficiency)', and the scheduling period setting unit 140 can calculate the SE using the following Equation (5) have.

Here, Ω _i is the data rate value of the MTC terminal 200 included in the i-th scheduled group, η is a value that indicates the inefficiency of bandwidth η _s = WT / F≥1, W is a bandwidth of the resource elements, T _s denotes a time interval, N denotes a symbol at T _s , and F denotes a subframe in the frame.

The scheduling period setting unit 140 may set a scheduling period D for each second scheduling group using the calculated SE.

Here, the 'scheduling period' means a SIB (Scheduling Information Broadcast) interval for informing scheduling information to the MTC terminals 200 in the serving cell of the base station 100, that is, the number of element resources to be scheduled at one time do.

At this time, the scheduling period setting unit 140 may calculate a scheduling period for each scheduling group using Equation (6) below.

Where W is the bandwidth of the resource element and T _th is the volume size of the desired data (voice communication or data communication, etc.) per service category as a parameter of quality of service (QoS).

According to the second embodiment, the scheduling period is set so as to satisfy the quality including at least one of the packet size, the data rate, the delay time, and the reliability, but is set to accommodate as many MTC terminals as possible while satisfying the quality.

If the number of MTC terminals is fixed, the scheduling period may be determined in a direction to minimize the bandwidth while satisfying the required quality.

As a result, according to the second embodiment, the scheduling period is determined so as to minimize the number or bandwidth of the MTC terminals to be accommodated while satisfying the required quality.

If the delay time is considered when determining the scheduling period according to the second embodiment, the scheduling period should be set shorter than the delay time required in preference to the number of MTC terminals and the bandwidth.

If there are a large number of MTC terminals to be served and the scheduling period must exceed the delay time, the second scheduling group may be further divided.

The resource element allocation unit 150 allocates resource elements (number) to each second scheduling group according to a scheduling period for each second scheduling group set by the scheduling period setting unit 140. [

The communication unit 150 may receive a PUSCH signal for acquiring fading information from the MTC terminals 200, and may include scheduling group information set from the above-described components, information on resource elements used for each group, To the MTC terminals 200 through the broadcast channel. The MTC terminals 200 transmit the scheduling information to the MTC terminals 200 through the broadcast channel.

Meanwhile, the controller 170 may control the components 110 to 150 to perform the operations described above.

7 is a flowchart illustrating an uplink scheduling process according to an embodiment of the present invention.

The base station 100 acquires fading information, available energy information, hardware noise index, and traffic requirement index of the MTC terminals 200 using the PUSCH signal received from the MTC terminals 200 (step 600).

The base station 100 sets the class of each MTC terminal existing in the serving cell using the hardware noise figure and the required traffic requirement index (step 602). As described above, the class of the MTC terminal is set by appropriately combining the hardware noise figure and the traffic requirement index.

When the class of the MTC terminals is set, the base station 100 performs the first scheduling for classifying the first scheduling group based on the class of the MTC terminals (step 604). UEs having similar MTC classes belong to the same first scheduling group, and second scheduling independent for each first scheduling group is performed.

The base station 100 classifies MTC terminals belonging to the same first scheduling group into a plurality of second scheduling groups using fading information, available energy, and hardware noise figure (step 606).

When the second scheduling grouping is completed, the base station 100 sets the power of the uplink transmission signal for each scheduling group (step 608). At this time, the base station 100 may separately set the ratio of the transmission power to the reference signal and the data signal. As described above, the MTC terminals belonging to the same second scheduling group preferably have the same uplink signal power.

When the uplink transmission power is determined, the base station 100 determines a scheduling period of each second scheduling group (step 610).

When the scheduling period is determined, resource elements (number) are allocated to each second scheduling group according to the determined uplink scheduling period (step 612).

The base station 100 broadcasts the set scheduling information to the MTC terminals 200 (step 614). Here, the scheduling information may include the second scheduling group information to which the MTC terminal 200 belongs, the resource element information allocated to the corresponding scheduling group, and the uplink power information.

8 is a block diagram illustrating the configuration of an MTC terminal according to an embodiment of the present invention.

The MTC terminal 200 according to an embodiment of the present invention may include a controller 210 which is a processor, a memory 220 connected to the controller 210, a communication unit 230 and a hardware noise figure calculating unit 240 have.

The hardware noise figure calculating unit 240 calculates the hardware noise figure of the MTC terminal. The calculation of the hardware noise figure can be done in various ways. For example, a hardware noise figure can be calculated by measuring the original signal and the signal output by the RF chip. Alternatively, the hardware noise figure may be set in advance according to the RF chip used.

The control unit 210 controls the communication unit 230 to transmit fading information, available energy information, required data rate information, and hardware noise figure information to the base station 100.

Also, when the scheduling information is received from the base station 100 through the communication unit 230, the control unit 210 can determine whether to use the resource element allocated to the second scheduling group to which the scheduling information belongs.

Here, the scheduling information received from the base station 100 may include information on a second scheduling group to which the MTC terminal 200 belongs, resource elements allocated to the second scheduling group, and uplink transmission power.

The control unit 210 transmits the reference signal and the data signal to the communication unit (not shown) with the allocated uplink transmission power by using the allocated resource element together with other MTC terminals of the second scheduling group to which it belongs according to the received scheduling information 230 to the base station 100.

Meanwhile, the memory 220 may be connected to the control unit 210 and may store program instructions that enable the control unit 210 to execute the operations described above.

The communication unit 230 may receive the scheduling information from the base station 100 or may transmit the reference signal and the data signal to the base station 100 under the control of the control unit 210. [

9 is a diagram illustrating a configuration of second scheduling information according to an embodiment of the present invention.

The second scheduling information according to an embodiment of the present invention includes information on a second scheduling group, information on resource elements allocated on a scheduling group basis (RE allocation indicator), and uplink transmission power set on a scheduling group basis (Power Difference Indicator).

Here, the 'information on the second scheduling group' is information indicating which scheduling group the MTC terminal belongs to, and can indicate the number of groups and the number of MTC terminals belonging to each group.

In FIG. 9, 11 MTC terminals existing in the first scheduling group are classified into three scheduling groups, and the MTC terminals belonging to each group are shown.

For reference, the information on the scheduling group indicates the size of the aggregate, that is, the index of the MTC terminal. For example, the index of the MTC terminal can be sorted according to RSS (Recived Signal Strength).

That is, the index 1 can be given to the MTC terminal a having the largest RSS.

Accordingly, the following procedure may be performed between the base station 100 and the MTC terminals 200 in the cell access procedure.

When the new MTC terminal accesses the base station 100, the MTC terminal 200 broadcasts the RSS of the corresponding MTC terminal in the downlink, and the MTC terminals 200 existing in the cell compares the received RSS with the RSS of its own, If it is bigger, the index is incremented by 1, and if it is smaller, the current index can be maintained.

If the MTC terminal existing in the cell leaves the cell, the base station 100 broadcasts the index of the corresponding MTC terminal on the downlink, and the MTC terminals 200 existing in the cell transmit the index If index is less than 1, the index is decremented by 1, and if it is larger, the current index can be maintained.

The above-described change in the index performed in the MTC terminal 200 is transmitted to the base station 100 so that the base station 100 can grasp the index of each MTC terminal 200.

In addition, 'information on resource elements allocated per scheduling group' may indicate the number of resource elements used by the corresponding scheduling group.

FIG. 10 is a flowchart illustrating a procedure when a new MTC terminal enters according to an embodiment of the present invention.

Referring to FIG. 10, when a new MTC terminal enters a serving cell, the new MTC terminal transmits MTC class information and available energy information through the RACH (step 1000).

Upon receiving the information from the new MTC terminal, the base station determines whether the new MTC terminal can be supported (step 1002).

The base station performs scheduling for a new MTC terminal according to the above-described method, transmits scheduling information (resource element information to be used and allocation for transmission power information) to the new MTC terminal, and transmits the scheduling information to the existing MTC terminal (Step 1004).

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (16)

A first scheduling grouping unit classifying the MTC terminals into a plurality of first scheduling groups using class information of MTC terminals located in a serving cell of the base station;
A second scheduling grouping unit classifying MTC terminals belonging to the same first scheduling group into a plurality of second scheduling groups using fading information, available energy information, and hardware noise figure of each MTC terminal for each of the first scheduling groups; And
And a transmission power setting unit for setting a transmission power of the MTC terminals for each of the classified second scheduling groups,
Wherein the class information of the MTC terminals is determined based on a traffic request index required for each MTC terminal and the hardware noise index and independent scheduling is performed for each first scheduling group, , A packet size, a reliability and a latency,
Wherein the second scheduling group classifier calculates a quality parameter that is set to increase as the size of the fading information and the available energy information increases and is set to decrease as the size of the hardware noise figure increases, To classify the second scheduling group.

The method according to claim 1,
A scheduling period determining unit for determining a scheduling period of each of the second scheduling groups; And
And a resource element allocating unit allocating a number of resource elements to be used for each of the second scheduling groups according to the determined scheduling period.
The method according to claim 1,
Wherein the second scheduling group classifier divides the value obtained by multiplying the fading information by the available energy information by a value based on the hardware noise figure to calculate the quality parameter and classifies the second scheduling group based on the quality parameter The scheduling device comprising:
The method of claim 3,
The second scheduling group classification unit
And compares the quality parameters of the MTC terminals and classifies the case where the difference is equal to or less than a predetermined threshold value into the same scheduling group.
The method according to claim 1,
The transmission power setting unit
And the MTC terminals belonging to the same second scheduling group set transmission power to use the same transmission power.
3. The method of claim 2,
The scheduling period
Packet size, data rate, and reliability, but is set in a direction for maximizing the number of MTC terminals to be accommodated, or in a direction for minimizing the bandwidth when the number of MTC terminals is preset Wherein the scheduling apparatus comprises:
The method according to claim 6,
Wherein the scheduling period is determined so as not to exceed the delay time when the delay time is additionally considered to the QoS requirement.
8. The method of claim 7,
In the determined scheduling period
Scheduling Grant Information including at least one of a Group Indicator for the second scheduling group, a Power Difference Indicator for the second scheduling group, and information on the allocated resource elements is broadcast Wherein the scheduling unit further comprises:
A scheduling method of a scheduling apparatus,
(a) classifying the MTC terminals into a plurality of first scheduling groups using class information of MTC terminals located in a serving cell;
(b) classifying MTC terminals belonging to the same first scheduling group into a plurality of second scheduling groups using fading information, available energy information, and hardware noise figure of each MTC terminal for each of the first scheduling groups;
(c) setting a transmission power of the MTC terminals for each of the classified second scheduling groups,
Wherein the class information of the MTC terminals is determined based on a traffic request index required for each MTC terminal and the hardware noise index and independent scheduling is performed for each first scheduling group, , A packet size, a reliability and a latency,
Wherein the step (b) comprises: calculating a quality parameter that is set to increase as the size of the fading information and the available energy information increases, and to decrease as the size of the hardware noise figure increases; and based on the quality parameter And classifying the second scheduling group.
10. The method of claim 9,
(d) determining a scheduling period of each of the second scheduling groups; And
(e) allocating a number of resource elements to be used for each of the second scheduling groups according to the determined each scheduling period
The scheduling method comprising the steps of:
11. The method of claim 10,
(f) scheduling information including at least one of a group indicator for the second scheduling group, a power difference indicator for the second scheduling group, and information on the allocated resource elements in the set scheduling period, Further comprising the step of broadcasting scheduling grant information.
10. The method of claim 9,
Wherein the step (b) calculates the quality parameter by dividing the value obtained by multiplying the fading information by the available energy information by a value based on the hardware noise figure, and classifies the second scheduling group based on the quality parameter / RTI >
13. The method of claim 12,
Wherein the step (b) compares the quality parameters of the MTC terminals and classifies the case where the difference is equal to or smaller than a predetermined threshold value into the same second scheduling group.
10. The method of claim 9,
And the MTC terminals belonging to the same second scheduling group use the same transmission power in step (c).
11. The method of claim 10,
The step (d)
Packet size, data rate, and reliability, but is set in a direction for maximizing the number of MTC terminals to be accommodated, or in a direction for minimizing the bandwidth when the number of MTC terminals is preset .
A MTC terminal communicating with the base station according to a scheduling of a base station,
A processor;
A hardware noise figure calculating unit for calculating a hardware noise figure by the RF chip;
A memory coupled to the processor; And
A communication unit
, ≪ / RTI &
The memory
A Physical Uplink Shared CHannel (CHS) signal is transmitted to the BS through the communication unit,
Based on the traffic request index for the MTC terminal and the first scheduling group information and the fading information based on the MTC class information set based on the hardware noise index from the base station through the communication unit and the available energy information and the hardware noise index Receiving scheduling information including information on second scheduling group information to be set, resource elements allocated to the second scheduling group, and transmission power,
In accordance with the received scheduling information, to transmit the reference signal and the data signal to the base station with the allocated transmission power using the allocated resource element together with other MTC terminals belonging to the second scheduling group Store executable program instructions,
The traffic requirement index is determined using at least one of a required data rate, a packet size, a reliability and a latency,
Wherein the second scheduling group is classified based on a quality parameter set to increase as the size of the fading information and the usable energy information increases and to be set to decrease as the size of the hardware noise figure increases. Terminal.

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