KR101726371B1 - Method and apparatus for setting barring factor for controlling access of user equipments in consideration of slope of variation in the number of access attempting terminals - Google Patents

Abstract

Provided are a method and an apparatus for setting a barring factor in an access control technique of an access class barring scheme in a wireless communication network. According to one embodiment of the present invention, the method for setting the barring factor for controlling access of a terminal includes: a barring factor setting step of setting the blocking factor based on access attempt information of terminals; and a barring factor transmission step of transmitting the set barring factor to the terminal. In the barring factor setting step, one of beta distribution curves having a plurality of intervals is selected based on the access attempt information of the terminals, and the barring factor is adjusted by a difference value corresponding to the selected interval. According to the present invention, one of the beta distribution curves having the intervals is selected based on the access attempt information of the terminals, and the barring factor is adjusted by the difference value corresponding to the selected interval, so that an access success rate is increased and communication efficiency is increased as compared with an existing method when access attempts are rapidly increased.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for setting a blocking factor for a terminal access control considering a slope of a change in the number of access attempting terminals, and a method and apparatus for setting a blocking factor for controlling accessing of user equipments.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for setting a blocking factor for terminal connection control, and more particularly, to a method and apparatus for setting a blocking factor in an access class blocking .

1 is a block diagram illustrating a mobile communication system. The mobile communication system includes a core network (CN) 106, a base station 102, and terminals 104a to 104n. A base station 102 is a fixed station that communicates with terminals 104a-104n and may be referred to in other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, have. One base station 102 may have more than one cell. One cell is set to one of the bandwidths of 1.25, 2.5, 5, 10, and 20 MHz, and provides a downlink or uplink transmission service to a plurality of UEs. At this time, different cells may be set to provide different bandwidths. Terminals 104a-104n may be fixed or mobile and may be referred to by other terminology such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT) .

Machine-type communication (hereinafter referred to as 'MTC') refers to communication between small devices without human intervention, and can be performed using existing mobile communication networks. Hereinafter, the terminal will be referred to as an MTC device and the base station will be referred to as an eNB.

MTC devices transmit and receive a small amount of data by using LTE-A communication network. However, since a large number of devices attempt to access the same channel (RACH: Random Access Channel) at the same time, overload and congestion congestion phenomenon. A random access procedure will be described with reference to FIG. FIG. 2 is a data flow chart showing a simplified random access procedure. FIG.

64 preambles are used for communication in the RACH in which the MTC apparatus UE tries to access. Each MTC device selects an arbitrary preamble out of 64 and notifies the eNB (Evolved NodeB) of its transmission intention by attempting to access the RACH channel (S21). The eNB checks whether there are different devices using the same preamble. Devices using the same preamble will fail to access the RACH due to a collision, and only those devices that do not collide will be given the right to access the network and transmit desired data to the eNB. If there is no collision, the eNB transmits a random access response to the corresponding MTC device using the same preamble (S22). Then, the MTC device sends its ID and requests a RRC (Radio Resource Control) connection (S23). Then, the eNB performs contention resolution (S24).

However, if more devices are attempted to connect, the frequency of collision increases and the data transmission efficiency becomes lower. There are Access Class Barring (ACB) among the methods for preventing collision at the time of random access. In the ACB, the eNB periodically transmits ACB-related parameters in a SIB (System Information Block), and this parameter includes a barring factor (a value between 0 and 1) and a barring duration . The ACB scheme is activated when the congestion degree of the network (congestion = 1 - (number of successful connection terminals in a predetermined period / number of connection request terminals in a predetermined period) increases and the communication network is overloaded.

When the ACB method is activated, the devices to be connected to the network generate random numbers from 0 to 1, and if the value is smaller than the blocking factor, the random access continues. If the value is large, the random access is restored during the blocking period, The random access is attempted again. Therefore, how to set the blocking factor value has a great effect on reducing the overload and congestion of the communication network.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for efficiently setting a blocking factor in a connection control scheme of an access class barring scheme in a wireless communication network.

The method for setting a blocking factor for terminal access control according to an embodiment of the present invention includes a blocking factor setting step of setting a blocking factor based on connection attempt information of terminals, Blocking factor transmission step. In the blocking factor setting step, one of the beta distribution curves having a plurality of intervals is selected based on the connection attempt information of the terminals, and the blocking factor is adjusted by the difference value corresponding to the selected interval.

A blocking factor setting apparatus for controlling access to a terminal according to an embodiment of the present invention includes a processor, a memory, and a wireless communication unit for wireless communication with the terminals, And sets a barring factor to transmit the set blocking factor to the terminal. The blocking factor may be determined by selecting one of the beta distribution curves having a plurality of intervals based on the connection attempt information of the terminals and adjusting the blocking factor by a preset blocking factor increase / .

The plurality of intervals may be set so that the number of intervals of the increasing interval is smaller than the number of intervals of the decreasing interval.

The interval selection calculates the slope of the change in the number of connection attempt terminals during the latest continuous moving window and performs based on the calculated slope.

The blocking factor adjustment is performed by increasing the blocking factor by the blocking factor increasing factor δ _{j in} the increasing period when the interval is selected and by decreasing the blocking factor by the blocking factor increasing factor δ _{j in the} decreasing interval.

P _max is the maximum value of the blocking factor, P _min is the minimum value of the blocking factor, M _inc is the number of intervals of the increasing interval, and M _dec is the number of intervals of the decreasing interval,

The blocking factor increase / decrease factor δ _j of the interval r _j ,

Respectively,

The decrease factor δ _j of the interval r _j ,

.

When the beta distribution function is Beta (?,?), The number of increasing sections is?, The number of decreasing sections is?, And the total time is T,

Lt; / RTI >

When the total number of MTC devices is N, the Access Intensity is

, ≪ / RTI >

R _size of the interval for the slope s _j r _j when as divided by the time elapsed before the disabled from the time the overload control is enabled by the total number of intervals is

.

According to the present invention, one interval of the beta distribution curve having a plurality of intervals is selected based on the connection attempt information of the terminals, and the blocking factor is adjusted by the difference value corresponding to the selected interval, In case of a sudden increase, the connection success rate is increased and the communication efficiency is increased as compared with the existing method.

1 is a block diagram showing a configuration of a mobile communication system to which a machine type communication is applied.
FIG. 2 is a data flow chart showing a simplified random access procedure. FIG.
3 is a flowchart showing an operation flow of a blocking factor setting method for terminal connection control according to the present invention.
4 is a graph showing a beta distribution curve.
5 is a graph showing a data set when applied to a smart electric meter.
6 is a graph showing the access intensity in a state in which the overload control is operated.
7 is a performance evaluation graph using the access success probability.
8 is a performance evaluation graph using collision probability.
9 is a performance evaluation graph using an approach delay.

In the present invention, the beta distribution curve is divided into a plurality of intervals, and the blocking factor is adjusted to match the characteristics of each interval. For this purpose, the slope and the cutoff factor are set in advance for each section of the beta distribution curve. That is, the most suitable beta distribution curve interval is selected from the connection attempt information of the terminals, and the blocking factor is adjusted using the increase / decrease factor of the blocking factor set for the interval. The method of the present invention can be performed in a base station apparatus including a processor, a memory, and a wireless communication unit for wireless communication with terminals.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

This will be described with reference to FIG. 3 is a flowchart showing an operation flow of a blocking factor setting method for terminal connection control according to the present invention.

In the present invention, the eNB sets a barring factor based on the connection attempt information of the UEs. The setting of the blocking factor is performed by selecting a section of the beta distribution curve having a plurality of intervals based on the connection attempt information of the terminals, And a blocking factor adjusting step (S32) for adjusting the parameter. The thus set blocking factor is transmitted to the UEs (S33). Then, the UEs perform random access to the RACH according to the ACB scheme using the received blocking factor.

Next, the section selection step S31 will be described. In the present invention, the blocking factor is adjusted using a bata distribution curve. To this end, the eNB selects one of the beta distribution curves having a plurality of intervals based on the connection attempt information of the terminals. First, a slope of a change in the number of connection attempt terminals during a recent continuous moving window is calculated, and a section is selected based on the slope. This will be described in detail.

The bata distribution used as the MTC traffic model in the 3GPP LTE-A standard is as shown in Equation (1) and has the form shown in FIG. Equation (1) is a beta distribution in the case where there are three increasing periods and four decreasing periods, where T represents the total time and Beta represents the beta function. The beta function is defined in the 3GPP standard document. (3rd Generation Partnership Project, Technical Specification group radio access network, study on RAN improvements for machine-type communications, 3GPP TR 37.868 V11.0.0, 2011.)

In the present invention, the beta distribution curve is divided into a plurality of intervals, and the blocking factor is adjusted to match the characteristics of each interval. In the beta distribution curve of FIG. 3, the number of devices attempting random access in the interval between the i-th period, that is, the interval between t _i and t _{i +1} , can be calculated as shown in Equation (2). Where N represents the total number of MTC instruments.

As shown in FIG. 3, in the portion where the number of devices attempting random access increases, it increases steeply for a short time, and in the portion where the number of devices decreases, it decreases slowly for a relatively long time . In the present invention, using this characteristic of the beta distribution, the entire section is divided into M regions from r ₁ to r _M as shown in FIG. In addition, overload control is deactivated in both end sections where overload control is not required, and overload control is activated only in the remaining sections (r ₁ to r _M ).

The slope s _j of the interval j is obtained as shown in Equation (3). In this equation, Rsize is the time from the moment when the overload control is activated to the moment when it is inactivated divided by M.

Also, by taking advantage of the asymmetric characteristic of the beta distribution curve, the number of intervals of the increasing interval can be set to be smaller than the number of intervals of the decreasing interval. Next, based on the connection attempt information of the devices in the actual environment, i.e., the change slope s' of the number of connection attempt devices during the recent continuous moving window is calculated as shown in Equation (4). In this equation, Msize represents the size of the moving window.

In the present invention, the interval of the beta distribution curve is selected using s' thus calculated. If the slope s' is increased and the interval (s'≥0), s'≤s _j s is _j, r _j selects the interval. If there is more than one s _j satisfying the condition, the smallest s _j is selected. If the slope s' is the decreasing interval (s' ≤ ₀ ) and there is s _j with s' ≥ s _j , then the interval r _j is selected. If there is more than one s _j satisfying the condition, the largest s _j is selected.

Next, the blocking factor adjustment step (S32) will be described in detail. In the present invention, the blocking factor increase / decrease coefficient is set in advance for each section. The increase / decrease factor of the blocking factor can be obtained statistically by experiments. If the interval is determined, the eNB increases or decreases the existing blocking factor by the blocking factor increase / decrease factor of the corresponding interval based on this.

Asymmetric characteristics of the beta distribution curve are used to determine the number of intervals of the increment interval (M _inc ) and the number of intervals of the decrement interval (M _dec ) to be different from each other, as described above. And may be set to be the same in some cases.

The method of determining the increase / decrease factor of the blocking factor in the increasing and decreasing sections is explained. The blocking factor increasing / decreasing coefficient? _J of the section r _j , which is an increasing section, is set as shown in Equation (5). In this equation, P _max represents the maximum value of the blocking factor and P _min represents the minimum value.

The blocking factor increasing / decreasing coefficient δ _j of the section r _j , which is the decreasing section, is set as shown in Equation (6).

When the blocking factor increasing factor δ _j is determined, the blocking factor is increased by the blocking factor increasing factor δ _j in the increasing period, and the blocking factor is decreased by the blocking factor increasing factor δ _j in the reducing period.

Next, an experimental example experimented by applying the method of the present invention will be described.

In this experiment, we use three performance evaluations: access success probability, collision probability, and access delay. The connection success probability is defined as the probability of successfully completing a random access procedure before transmitting the maximum number of preambles. The collision probability is defined as the ratio of the total number of opportunities in the same period to the number of random access attempt transmissions from two or more devices in the same preamble. The original ACB was used for performance comparison. In the original ACB, the blocking factor is set to 0.1 when overload control is activated. IEEE Communications Magazine, vol. 51, no. 6, pp. 86-90 (1986), "Random Access for Machine-to-Machine Communication in LTE-Advanced Networks: Issues and Approaches," M. Hasan, E. Hossain, 93, Jun. 2013.)

In the experiment, MTC traffic model for smart electric meter was used as experimental scenario. Here, a large number of devices are connected to the network in a highly synchronized fashion (Intel Corporation, Further performance evaluation of EAB information update mechanisms, 3GPP R2-120270, RAN WG2 Meeting # 77, 2012. Reference). This model considers the density of dwellings in central London, ie 35670 homes per cell. The frequency at which the meter should transmit measurements affects the random access strength generated by the smart meter within the cell. Smart meters are used in various fields such as automatic electricity metering, energy demand management, and micro power generation management. The cycle of reporting the metric ranges from 5 minutes to 24 hours. In this experiment, this period was set to 5 minutes. Other parameters of the random access channel of the LTE-A communication network are shown in Table 1.

In this experiment, the distribution of the traffic model in the cell follows the MTC traffic model 2. (See 3GPP TR 37.868 V11.0.0, 2011.), the " 3rd Generation Partnership Project, " Technical specification group radio access network,

The curve of the traffic model is divided into five sections, two of which are positive slopes (increasing) and three of which are negative (negative). The blocking factor increase / decrease factor δ _j is set to [0.5, 0.1, 0.1, 0.4, 0.7] for each of these sections. For the performance evaluation according to the size of the moving window, the size of the moving window was set to 500 ms, 1000 ms, and 2000 ms. In the following drawings, the x-axis represents the time from 0 to 300 seconds, and the y-axis represents the access intensity.

5 is a graph showing the data set applied to the smart electric meter for 5 minutes (300,000 ms) compared with the beta distribution traffic model. In Figure 5, the red line represents the beta distribution traffic model and the blue point represents the dataset. From the graph of FIG. 5, it can be seen that a highly synchronized dataset of this field is following the beta distribution traffic model.

Figure 6 shows an overload control method, i.e. a change of the access intensity when the original ACB and the method of the present invention are applied. 6, when the method of the present invention is applied when the size of the moving window is set to 2000 ms and the size of the moving window is set to 1000 ms in the red diamond shape, When the method of the present invention is applied, the blue circle shows a case where the method of the present invention is applied when the size of the moving window is set to 500 ms.

The inner red curve in this graph represents the connection strength when the method of the present invention is activated and the blue curve outside represents the connection strength when the original ACB is activated. As can be seen from this graph, the top of the outer curve is flatter than the top of the inner curve. The length of the time interval in which the approach intensity was rapidly increased was shorter than that of the original ACB of the present invention. This means that the method of the present invention effectively reduces the intensity of the approach intensity.

FIG. 7 is a graph of performance evaluation using the approach success probability and shows a comparison between the case where the method of the present invention is applied and the case where the original ACB is applied. 7, when the method of the present invention is applied when the size of the moving window is set to 2000 ms, and the size of the moving window is set to 1000 ms in the case of the red diamond, When the method of the present invention is applied, the blue circle shows a case where the method of the present invention is applied when the size of the moving window is set to 500 ms.

As can be seen from this graph, the method of the present invention shows an average performance improvement of about 20% as compared with the case where the original ACB is applied. That is, the method of the present invention shows a performance improvement of about 20%, 13.5%, and 25.2%, respectively, compared with the original ACB for the sizes of the different moving windows (500 ms, 1000 ms, and 2000 ms). Since the size of the moving window is small, the weight of the recent change in the approaching strength is weighted.

8 is a performance evaluation graph using collision probability. In FIG. 8, when the method of the present invention is applied when the size of the moving window is set to 2000 ms, and the size of the moving window is set to 1000 ms, the red diamond shape is used when the size of the moving window is set to 1000 ms When the method of the present invention is applied, the blue circle shows a case where the method of the present invention is applied when the size of the moving window is set to 500 ms.

As can be seen from this graph, the method of the present invention shows an average collision probability reduction of about 47% as compared with the case where the original ACB is applied. That is, the method of the present invention shows a performance improvement of about 52%, 40%, and 59%, respectively, compared to the original ACB for the sizes of the different moving windows (500 ms, 1000 ms, and 2000 ms). In conclusion, the method of the present invention adaptively adjusts the blocking factor by analyzing recent traffic load changes and estimating future load changes through slope comparison.

9 shows the average access delay time of the MTC apparatus as a performance evaluation graph using the approach delay. 9, when the method of the present invention is applied when the size of the moving window is set to 2000 ms and the size of the moving window is set to 1000 ms in the case of the red diamond, When the method of the present invention is applied, the blue circle shows a case where the method of the present invention is applied when the size of the moving window is set to 500 ms.

The connection delay time when the method of the present invention was applied was improved by about 53% as compared with the case where the original ACB was applied. That is, the method of the present invention shows a performance improvement of about 51%, 46%, and 64%, respectively, compared with the original ACB for the sizes of the different moving windows (500 ms, 1000 ms, and 2000 ms). Thus, it can be seen that the method of the present invention provides a satisfactory service when the connection delay of the device is reduced and applied to a smart electric meter.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. That is, within the scope of the present invention, all of the components may be selectively coupled to one or more of them. Also, some or all of the components may be implemented as a computer program having a program module that selectively combines to perform some or all of the functions combined in one or a plurality of hardware. The codes and code segments constituting the computer program may be easily deduced by those skilled in the art. Such a computer program can be stored in a computer-readable storage medium, readable and executed by a computer, thereby realizing an embodiment of the present invention.

Furthermore, the terms "comprises", "comprising", or "having" described above mean that a component can be implanted unless otherwise specifically stated, But should be construed as including other elements.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (13)

delete A blocking factor setting step of setting a blocking factor based on connection attempt information of terminals,
A blocking factor transmission step of transmitting a set blocking factor to the terminal
And,
The blocking factor setting step includes:
Selecting one of the beta distribution curves having a plurality of intervals based on the connection attempt information of the terminals;
A blocking factor adjustment step of adjusting the blocking factor by a predetermined increase / decrease factor of the blocking factor for the selected section
/ RTI >
In the selecting step,
Calculating a slope of a change in the number of connection attempt terminals during a recent continuous moving window,
Selecting a section based on the calculated slope
And setting a blocking factor for terminal connection control.
3. The method of claim 2,
For each section of the beta distribution curve, the slope and cutoff factor is set in advance,
Wherein the step of selecting an interval based on the calculated slope comprises:
If the slope set for the section r _j is s _j and the slope of the change in the number of connection attempting terminals during a recent continuous moving window is s'
Slope s 'is increased and the interval (s'≥0) select interval r _j corresponding to a smallest among the s _j s _{j j} s'≤s and slope s' is reduced and the interval (s'≤0), blocking factor setting method for a control terminal connected, characterized in that for selecting the interval r _j corresponding to the largest among the s _j s _{j j} s'≥s.
4. The method according to claim 3,
If the interval is selected in the increasing section increases the blocking factor decrease coefficient δ _j as blocking factor and reduce the blocking interval factor decrease coefficient block parameter setting method for a control terminal connected, comprising the step of reducing the blocking factor by δ _j.
5. The method of claim 4,
P _max is the maximum value of the blocking factor, P _min is the minimum value of the blocking factor, M _inc is the number of intervals of the increasing interval, and M _dec is the number of intervals of the decreasing interval,
The blocking factor increase / decrease factor δ _j of the interval r _j ,

Respectively,
The decrease factor δ _j of the interval r _j ,

And setting a blocking factor for terminal connection control.
6. The method according to any one of claims 3 to 5,
When the beta function is defined as Beta (?,?), The number of increasing sections is?, The number of decreasing sections is?, And the total time is T,

Lt; / RTI >
When the total number of MTC devices is N, the Access Intensity is

, ≪ / RTI >
R _size of the interval for the slope s _j r _j when as divided by the time elapsed before the disabled from the time the overload control is enabled by the total number of intervals is

And setting a cutoff factor for terminal connection control.
6. The method according to any one of claims 2 to 5,
Wherein the plurality of intervals are set so that the number of intervals of the increase interval is smaller than the number of intervals of the decrease interval.
delete A processor,
A memory,
And a wireless communication unit for wireless communication with the terminals,
The processor sets a barring factor based on the connection attempt information of the terminals and transmits a set blocking factor to the terminal,
The blocking factor may be determined by selecting one of the beta distribution curves having a plurality of intervals based on the connection attempt information of the terminals and adjusting the blocking factor by a preset blocking factor increase / Respectively,
For each section of the beta distribution curve, the slope and cutoff factor is set in advance,
The interval selection is performed by calculating a slope of a change in the number of connection attempt terminals during a recent continuous moving window and selecting an interval based on the calculated slope,
Blocking factor adjustment interval is selected, growth period, blocking factors decrease coefficient increasing the δ _j as blocking factor and reduces period, blocking factors decrease coefficient which is performed by decreasing the cut-off factor as δ _j, for a terminal connected to the control Blocking factor setting device.
10. The method of claim 9,
Selecting a section based on the calculated slope may be accomplished by:
If the slope set for the section r _j is s _j and the slope of the change in the number of connection attempting terminals during a recent continuous moving window is s'
Slope s 'is increased and the interval (s'≥0) select interval r _j corresponding to a smallest among the s _j s _{j j} s'≤s and slope s' is reduced and the interval (s'≤0), blocking factor setting unit for the terminal connection control, characterized in that for selecting the interval r _j corresponding to the largest among the s _j s _{j j} s'≥s.
11. The method of claim 10,
P _max is the maximum value of the blocking factor, P _min is the minimum value of the blocking factor, M _inc is the number of intervals of the increasing interval, and M _dec is the number of intervals of the decreasing interval,
The blocking factor increase / decrease factor δ _j of the interval r _j ,

Respectively,
The decrease factor δ _j of the interval r _j ,

Is set to < RTI ID = 0.0 > 1, < / RTI > 12. The method according to any one of claims 9 to 11,
When the beta distribution function is Beta (?,?), The number of increasing sections is?, The number of decreasing sections is?, And the total time is T,

Lt; / RTI >
When the total number of MTC devices is N, the Access Intensity is

, ≪ / RTI >
R _size of the interval for the slope s _j r _j when as divided by the time elapsed before the disabled from the time the overload control is enabled by the total number of intervals is

Is set to a predetermined value. 12. The method according to any one of claims 9 to 11,
Wherein the plurality of intervals are set so that the number of intervals of the increasing interval is smaller than the number of intervals of the decreasing interval.

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