KR101464701B1 - Apparatus and method for frame offset construction and transmission to reduce co-channel interference in mobile communication system - Google Patents

Abstract

The invention applies to the case in which the small base station control channel interference avoidance function on selected symbol in the same band interference mitigation method of the small base station in a mobile communication system that relates to interference mitigation in a corresponding subframe end C ₁ Number of When the process of booking a symbol and the small base station is applied to a control channel interference avoidance function to all of the symbols, N _S. Determining a number of sub-frames to limit the _PDCCH to the predetermined number and the sub-frame to the end of the limited N _{M. PDCCH} symbols and a common channel resource corresponding to a synchronization channel and a broadcast channel of another layer regardless of whether the control channel interference avoiding function is used or not is reserved in a corresponding subframe and reserved And transmitting the small base station frame to an offset determined in consideration of synchronization of the macro base station.

Interference mitigation, LTE, base stations, frames.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an offset frame configuration and transmission method for mitigating co-channel interference in a mobile communication system,

The present invention relates to a home base station (Home eNodeB: HeNB) or a small-sized base station that uses the same frequency band (Co-channel) in a LTE (Long Term Evolution) and LTE-Advanced system of a cellular based 3GPP When a base station (pico-cell eNodeB) is introduced, a physical synchronization channel (PSCH), a broadcast channel (PBCH) or a control channel having a low degree of scheduling freedom The present invention relates to an apparatus and method for configuring and transmitting a frame by setting a frame offset and reserving resources to mitigate interference of a physical downlink control channel (PDCCH).

When introducing a home base station or a small base station using the same frequency band (co-channel) in the LTE and LTE-Advanced systems, the downlink synchronization channel and the broadcast channel or the control channel having a low degree of scheduling freedom use the same frequency resource Interference occurs in defined relationships. Unlike the control channel or the common channel, the downlink synchronization channel and the broadcast channel are transmitted in a modulation and coding scheme in which the macro or the small base station is fixed to the same frequency resource, so it is difficult to avoid the interference through the scheduling.

FIG. 1 is a diagram illustrating a downlink frame structure based on an OFDM (Enhanced Universal Terrestrial Radio Access) based on an OFDM (Orthogonal Frequency Division Multiplex) and transmission positions of a sync channel, a physical layer broadcast channel, and a control channel in the frame structure.

Referring to FIG. 1, a radio frame having a total time length of 10 ms is composed of 10 subframes, and each subframe is composed of two slots. In one slot, 6 or 7 OFDM symbols are formed according to the length of a cyclic prefix (CP).

In FIG. 1, there are seven OFDM symbols for a general CP length. 1, a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) are located in subframes 0 and 5, and a PBCH is allocated to four OFDM symbols , And is transmitted on 72 subcarriers.

Since the 3GPP basically adopts the asynchronous network structure, the base station does not match the starting point of the radio frame using the GPS.

Of course, it is possible to operate LTE systems synchronously using network synchronization technology such as GPS, NTP (Network Time Protocol) and PTP (Precision Time Protocol) corresponding to IEEE 1588 Version 2, but the same interference problem Occurs.

However, when cell planning and sectorization are applied to a macro base station, the requirements for interference between adjacent cells, whether synchronous or asynchronous, can be satisfied. However, in the case of a small base station superimposed in a macro cell or in a case where a large number of small base stations are installed in a dense hierarchy in a lower hierarchy, interference control through a cell plan is not possible.

In order to reduce such interference, 3GPP standards have proposed a method of measuring interference between each other using a self configuration function and controlling transmission power between small base stations.

2 is a diagram illustrating a band allocation scheme of a macro base station and a small base station.

Referring to FIG. 2, when the capacity is smaller than that of a macro base station such as a Home eNB, a partial co-channel is used to use only a part of the macro base station as shown in FIG. 2- (2) And to reduce the interference by operating it.

When the small base station is operated as a partial band, the synchronization channel and the broadcast channel are naturally separated from the corresponding channel of the macro base station, and the other downlink and uplink channels can be scheduled to minimize mutual interference according to the UE Interference can be mitigated without changing the current LTE specification.

However, in the case of a small base station for a hot zone other than a home small base station, the bandwidth and the system capacity are similar to those of the macro base station except that the cell radius is small due to a small transmission power. -channel) is generated.

For a frequency resource having a low signal-to-interference and noise ratio (SINR) due to mutual interference in a common channel, the UE reports the measurement result to the serving BS, and the serving BS appropriately allocates the resource allocation The interference mitigation effect similar to that of the partial band allocation can be obtained.

However, for a downlink synchronization channel and a broadcast channel to be transmitted in a modulation and coding scheme fixed to the same frequency resource, and a downlink control channel (PDCCH) having a relatively low degree of scheduling freedom, The interference can not be controlled in the case of the same bandwidth allocation.

Therefore, in the hierarchical cell structure including the same-band small base station, in order to mitigate the interference to the synchronous and broadcast channels and the control channel, it is difficult to schedule the frequency resources regardless of whether the macro base station is synchronous or not. There is a need for techniques that can reduce the mutual interference to the channel.

It is an object of the present invention to provide an apparatus and method for transmitting and receiving an offset frame for mitigating the same band interference in a mobile communication system.

It is another object of the present invention to provide a mobile station and a mobile station in which when a small base station for a hot zone is operated in a co-channel in a macro cell in an LTE system, And an apparatus and method for transmitting and receiving a frame offset by setting a frame offset so as to control interference on a time axis with respect to a control channel.

It is still another object of the present invention to provide a method and apparatus for setting a frame offset for controlling interference on a time axis for a synchronous, a broadcast channel, and a control channel, in which frequency resource scheduling is difficult in an LTE system, A control unit for separating a downlink synchronization channel, a broadcast channel, and a control channel by intentionally adjusting a start position of a radio frame between a sub-base station and another sub-base station and allocating resources for a synchronization channel, a broadcast channel, And an apparatus and method for relieving mutual interference with respect to a corresponding channel by reservation.

According to a first aspect of the present invention, there is provided a method for mitigating the same band interference of a small base station in a mobile communication system, the method comprising: when the small base station applies the control channel interference avoiding function to only a part of symbols, At the end, C ₁ Number of When the process of booking a symbol and the small base station is applied to a control channel interference avoidance function for all N _{S symbols.} Determining a number of the sub-frame to limit the _PDCCH to the predetermined number and the sub-frame to the end of the limited N _{M. PDCCH} symbols and a common channel resource corresponding to a synchronization channel and a broadcast channel of another layer regardless of whether the control channel interference avoiding function is used or not is reserved in a corresponding subframe and reserved And transmitting the small base station frame to an offset determined in consideration of synchronization of the macro base station.

According to a second aspect of the present invention, there is provided a method of mitigating co- channel interference in a macro base station in a mobile communication system, wherein when the macro base station applies a control channel interference avoiding function to only a part of symbols , N _M. When the process of booking a _PDDCH following C ₂ OFDM symbols and the macro base station is applied to a control channel interference avoidance function for all N symbol _M in the corresponding _{subframe. PDDCH} the sound of the N _{S. The method} comprising the steps of reserving a _PDDCH OFDM symbol and reserving a common channel resource corresponding to a synchronization channel and a broadcast channel of another layer irrespective of whether the control channel interference avoiding function is used or not, And transmitting the macro base station frame to an offset determined in consideration of the synchronization of the macro base station, regardless of the reserved resource and the predetermined reserved resource, do.

According to a third aspect of the present invention, there is provided an apparatus for a small base station that mitigates the same band interference in a mobile communication system, comprising: a communication module for communicating with another node; and a control channel interference avoiding function Is applied to only a part of symbols , C ₁ Number of When scheduling the symbols and applying the control channel interference avoidance function the small base station to all of the symbols _{S N.} Determining a number of sub-frames to limit the _PDCCH to the predetermined number and the sub-frame to the end of the limited N _M. Reservation symbols in the _PDCCH number, schedule symbol including a common channel resources corresponding to the control channel interference avoidance feature the presence and the synchronization channel and the broadcast of the other layers, regardless of the channel in the corresponding subframe, the resources reserved And transmitting the small base station frame to an offset determined in preparation for synchronization of the macro base station.

According to a fourth aspect of the present invention for achieving the object of the present invention, the other nodes communicate with the communication module and the control channel interference avoidance function, which according to the macro base station device to relieve the same band interference in a mobile communication system, some symbols only If applicable, N _M in the corresponding subframe _. When _PDDCH following schedule a C ₂ OFDM symbols, and applying the control channel interference avoidance function for all N symbol _M in the corresponding _subframe. N _S after _{PDDCH . And allocates} common channel resources corresponding to a synchronization channel and a broadcast channel of another layer regardless of whether the control channel interference avoiding function is used or not and determines whether or not interference _cancellation function of the macro base station is performed And transmitting the macro base station frame to an offset determined in preparation for synchronization of the macro base station. The macro base station frame includes a macro base station frame and a macro base station frame.

In the present invention, when a small base station operates in a co-channel within a macrocell, a frame offset is set for a synchronization and broadcast channel and a control channel, in which scheduling of frequency resources is difficult, and a part of a common channel is reserved, There is an advantage in that it can be avoided.

The present invention can reduce the interference between the macro base station and the small base station by reserving only the 0.34% common channel based on the 20 MHz band when interference is avoided only for the synchronization and broadcast channels using the frame offset, It is advantageous to avoid interference by reserving resources from a minimum of 7.5% to 21.8% according to the maximum number of OFDM symbols of the control channel.

The present invention is advantageous in that the macro base station can adjust the resource loss caused by mutual interference by using interference control only in a small base station or by allowing interference in some control channels without reserving resources.

The present invention can control interferences with minimal resource loss in a hierarchical cell structure by changing the LTE standard, and can improve scheduler of macro base station and small base station without changing LTE standard according to the method of reserving resources, It is possible to control the downlink synchronization, the interference with the broadcast channel and the control channel only by adding the Over The Air Receiver (OTAR) or the network synchronization function of the base station.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, the present invention will be described with respect to an apparatus and method for transmitting and receiving an offset frame for mitigating the same band interference in a mobile communication system.

In the present invention, a small base station of a lower layer detects synchronization of a macro base station of an upper layer, and uses a frame offset set in a self configuration process with an OAM server, Alternatively, the resource to which the control channel is transmitted may be reserved by reserving a resource to mitigate the interference of the corresponding channel by not transmitting the signal.

The present invention relates to a method for mitigating interference by improving a scheduler and adding a modem of a small base station without changing the existing standard or changing the macro base station modem and by reducing the loss due to resource reservation by changing the standard in terms of standards .

3 is a diagram illustrating a hierarchical cell structure of a small base station superposed in a macro cell in a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 3, a hierarchical cell structure in which sub-small base stations are located in an upper macro base station is shown. In the present invention, small base stations can be superimposed on a lower layer according to a self-configuration scheme. The upper macro base station layer is capable of both synchronous and asynchronous network configurations, while the lower sub-base stations use a structure that synchronizes with the corresponding upper macro base station.

The method of synchronizing sub-small base stations to upper macro base stations is to always synchronize with macro base stations in GPS in synchronous network and synchronize by using network synchronization method such as NTP or PTP in asynchronous network.

In particular, when a small base station includes an Over The Air Receiver (OTAR) function, the synchronization of the macro base station can be directly detected regardless of the synchronous mode and the asynchronous mode.

Therefore, the small base station belonging to a certain layer always knows the start position of the frame of the upper macro base station, and the frame offset can be set between different layers based on this.

4 is a diagram illustrating a first offset structure for a sub-frame of a small base station for a synchronization channel and a broadcast channel according to an embodiment of the present invention.

Referring to FIG. 4, the small base station sets a frame offset in units of subframes and uses a structure for mitigating interference only for a synchronization channel and a broadcast channel. In this case, scheduling of frequency resources in the control channel is difficult but coding rate can be changed, so a low coding rate is applied so as to be robust against interference.

The sub-small base stations have frame offsets (N _offset = m, 0? M? 9) of different subframes for each group or layer based on the radio frame of the upper macro base station. Here, m is an integer and m = 0 is the frame offset of the macro base station.

The small base station delays or transmits the frame transmission by the corresponding subframe offset, and schedules the resource of the common channel having the synchronization channel and the broadcast channel of the different layers to reserve the resource virtually.

Therefore, it is possible to reduce the interference between the synchronous channel and the broadcast channel between the macro base station and the small base station or between the small base stations of other layers.

If the number of all-cell layer, the N _Layer, loss of frequency resources due to resource reservation for the mutual synchronization channel and the broadcast channel between the based on the LTE system having a normal cyclic prefix in 20MHz bandwidth _{6 / 100x8 / 140x (N Layer} - 1) x100 (%).

For example, if there is only one small base station layer in a macro cell, since N _layer = 2, reservation of only 0.34% of common channel resources in both macro base station and small base station can reduce the interference to the synchronization and broadcast channel have.

The accuracy of synchronization may be different according to the synchronization detection scheme of the upper macro base station applied to the small base station. Even if the start point of the frame is completely known, the difference between the distance between the macro base station and the small base station, There is an error in synchronization.

Accordingly, it is possible to reserve more resources than mutually interfering resources for a set frame offset. N _SCH = 2 is the number of transmission symbols for the synchronization channel, N _PBCH = 4 is the number of transmitted symbols for the broadcast channel, and N _RSV is defined as the number of reserved symbols for the synchronous and broadcast channels, then the number of reserved symbols for that channel satisfies the relationship:

N _Rsvv1 ≥ N _SCH + N _PBCH , N _Rsv2 ≥ N _SCH

This additional reservation of resources is necessary not only to alleviate the interference problem due to the synchronization error but also to minimize the change of the existing LTE base station and the terminal.

In the current LTE standard, resources are allocated over all symbols except for the PDCCH within one subframe. Existing LTE terminals use only the 0th and 5th subframes including the synchronization channel It is possible to detect a data packet allocated to some symbols.

Therefore, in order to minimize the loss due to the resource reservation, in addition to the 0th and 5th subframes in FIG. 4, an LTE standard is used to allow exceptional resource allocation and packet detection in a subframe reserved by a small- Should be changed.

5 is a diagram illustrating a second offset structure for a sub-frame of a small base station for a synchronization channel and a broadcast channel according to an embodiment of the present invention.

Referring to FIG. 5, in order to support the offset frame in the current LTE standard without changing the LTE standard, six resource blocks of all OFDM symbols are allocated to subframes included in the synchronization channels of base stations of different layers. RB) is reserved.

In this case, the macro base station transmits N _{M , R sv} = N _Subframe - N _{M , PDCCH} Reserve resources for the six resource blocks in the OFDM symbol and the small base station is N _{S, Rsv} = N _Subframe - N _{S , PDCCH} And reserves resources for six resource blocks of OFDM symbols.

Loss of frequency resources due to resource reservation for the synchronization channel and broadcast channel between each other is based on the LTE system having a 20MHz bandwidth _{6 / 100x (2xN x, RSV} ) / N Subframe x (N _Layer- 1) x100 (%).

Where N _{M , PDCCH} is the number of OFDM symbols used by the macro base station to transmit the PDCCH, N _{S , PDCCH} Is a small base station a number of OFDM symbols used for transmitting the PDCCH, _Subframe N is the number of OFDM symbols per subframe, x∈ (M, S} is a symbol indicating the macro base station and the small base station.

For example, only one small base station layer exists in a macro cell (N _Layer = 2), and N _{M, PDCCH} = N _{S , PDCCH} = 3, both the macro base station and the small base station can reduce the interference to the synchronization and broadcast channel without changing the current LTE standard only by the loss of the shared channel resource of about 0.94%.

6 is a diagram illustrating an OFDM symbol unit offset structure of a small base station including a downlink control channel according to an embodiment of the present invention.

Referring to FIG. 6, a frame offset is set for each OFDM symbol, and a proposed resource reservation scheme is applied to a control channel as well as a synchronization channel and a broadcast channel.

In the LTE physical layer standard, the control channel can transmit up to three OFDM symbols in every subframe. When the number of UEs allocated resources in a subframe increases, the number of OFDM symbols in the control channel increases.

Therefore, in general, the number of control channel OFDM symbols of the macro base station is smaller than or equal to the number of control channel OFDM symbols of the small base station, and the value that the OFDM symbol unit frame offset can have to avoid interference is expressed by the following equation.

N _offset = mx N _OFDM + N _{M , PDCCH} , 0? _M? 9, N _{M , PDCCH} ≤ 3

Here, N _OFDM Is the number of OFDM symbols per slot, 7 for normal cyclic prefix, and 6 for extended cyclic prefix. And N _{M and PDCCH} are the maximum values of the OFDM symbols for each subframe used for transmitting the control channel (PDCCH) by the macro base station in a given radio frame.

Therefore, the maximum number of OFDM symbols (N _{S , PDCCH} ) of the control channel that can be transmitted by the small base station is expressed by the following equation.

N _{S , PDCCH} = N _OFDM - N _SCH - N _{M , PDCCH}

Since the number of control channels may be changed for each subframe _{, if} N _{M and PDCCH} are fixed to 3 for convenience, there are five OFDM symbols before the synchronization channel transmission in case of the normal cyclic prefix. Therefore, The maximum number of OFDM symbols usable for control channel transmission is N _{S , PDCCH} = 2 < / RTI >

Of course, for subframes that do not need to reserve resources, N _{S , PDCCH} ≤ 3 can be applied, The above diagram  6 to the small base station (15- N _offset ) _{mod  10} = 3, 10-N _offset  = 8 subframes except for the 8th subframe N _{S , PDCCH} = 3 is assumed.

In this case, the macro base station reserves about 20.3% of the resources and the small base station reserves about 21.8% of the resources, thereby reducing the interference to the control channel as well as the synchronization and broadcast channels.

If the number of users per subframe is small and the maximum number of OFDM symbols of the control channel can be limited to one in both the macro base station and the small base station, the interference of the control channel can be reduced by a resource reservation of about 7.5% 2 >, some OFDM symbols used for the control channel may trade-off loss due to resource reservation by allowing interference, as in the following, without completely avoiding interference.

N _offset = mx N _OFDM + C ₁ , _1? C _1? N _{M , PDCCH?} 3, 0? C _2? C ₁ + N _{S , PDCCH} - N _{M , PDCCH}

Where C ₁ is the number of OFDM symbols that the small base station must reserve to avoid some of the interference to the macro base station's control channel and C ₂ is the macro base station's reservation to avoid some interference to the small base station's control channel ≪ / RTI >

FIGS. 7A and 7B are flowcharts illustrating a process of a small base station constructing a frame from frame offset information according to an embodiment of the present invention.

Referring to FIG. 7, a procedure for reserving a resource, constructing a frame, and transmitting a frame is performed so that a small base station avoids interference according to frame offset information.

In operation 710, the small base station receives a frame offset (N _offset ) of the cell from the Operations, Administration, and Maintenance (OAM) server through a self-configuration process.

If the current network is an asynchronous network (step 715), the synchronization of the macro base station of the upper layer is detected by the network synchronization or the OTAR function (step 720), and based on the detected frame base point, (Step 725)

If the current network is a synchronous network (step 715), frame offset is applied based on the frame start point of the macro cell in synchronization with the synchronization (step 725)

If the small base station applies the interference avoiding function for the control channel in step 730, the control channel is determined to be applied to the synchronization channel and the broadcast channel in step 735.

Thereafter, it is determined whether the control channel interference avoiding function is partially applied or not (step 745) . That is, the maximum possible OFDM Decide whether or not to apply to the number of symbols .

The maximum possible OFDM When applied to a number of symbols, N _S. Determining a number of sub-frames to limit the _PDDCH to 2 (step 750), at the end of the subframe N _{M. PDDCH} (Step 760).

Thereafter, common channel resources corresponding to the synchronization channel and the broadcast channel are reserved (step 765), and a small base station frame is configured excluding the reserved resources (step 770).

Thereafter, the small base station frame is transmitted at an offset (N _offset ) determined in preparation for synchronization of the macro base station (step 775).

The maximum possible OFDM If it does not apply to the number of symbols (step 745), that is, the control case to be only partially applied to the channel interference avoidance function, to make a reservation at the _first OFDM symbol C in the sub-frame ends (step 755).

Thereafter, a process after step 765 of reserving a common channel resource corresponding to the synchronization channel and the broadcast channel is performed.

If the small base station does not apply the interference avoiding function for the control channel in step 730, the interference avoiding function is determined to be applied only to the synchronous and broadcast channels in step 740, (Step 765) of performing the step of reserving the common channel resources.

Thereafter, the algorithm according to the present invention terminates.

8A and 8B are flowcharts illustrating a process in which a macro base station constructs a frame from frame offset information according to an embodiment of the present invention.

Referring to FIG. 8, a macro base station reserves resources for avoiding interference according to frame offset information, and constructs and transmits frames. The macro base station may not be able to apply the interference control through the resource reservation because the cell base station can perform the cell plan prior to the self setting and has a higher priority than the small base station.

In the case of applying the proposed interference avoidance to the macro base station, all of the sub-small base stations in the corresponding macro cell detect frame synchronization of the macro base station and operate based on the detected frame synchronization. Therefore, Use the starting point as is.

The macro base station receives the frame offset information for the sub-small base station layer similar to the small base station, reserves the common channel resources corresponding to the synchronization channel, the broadcast channel, or the control channel of the small base station layer, do.

In step 810, the macro base station receives a frame offset (N _offset ) of the corresponding cell from the OAM server through a self-configuration process.

If the macro base station performs the interference control function (step 815), the macro base station sets the start point of the macro base station frame as a reference (step 820).

Thereafter, if the macro base station applies the interference avoiding function for the control channel (step 825), the control channel is determined to be applied to the synchronization channel and the broadcast channel (step 830).

Thereafter, the control channel interference avoiding function is switched to the maximum possible OFDM It is determined whether or not to apply to the number of symbols (step 840). That is, it is determined whether only a part of the control channel is set as an interference avoiding target. If, in the case of setting a control channel, only a part of the interference avoidance target, _{M N.} The C ₂ OFDM symbols following the _PDDCH are reserved (step 850).

Thereafter, in step 855, a common channel resource corresponding to a synchronization channel and a broadcast channel of the sub-small base station is reserved (step 855), and a macro base station frame is configured excluding the reserved resource (step 860).

Thereafter, the macro base station frame is transmitted to the offset (N _offset = 0) determined for the synchronization of the macro base station (Step 865).

If the macro base station does not apply the interference avoiding function for the control channel (step 825), only the synchronization and broadcast channels are determined to be an object to which the interference avoiding function is applied (step 835) A step of reserving a common channel resource corresponding to a broadcast channel (step 855) is performed.

If the maximum possible OFDM If (step 840), that is, does not set up a control channel, only a part of the interference avoidance target when applying for a number of symbols, N _M. N _S after _{PDDCH . PDDCH} OFDM symbols are reserved (Step 845).

Thereafter, a process after the step 855 of reserving the common channel resources corresponding to the synchronization channel and the broadcast channel of the sub-small base station is performed.

If the macro base station does not perform the interference control function (step 815), the macro base station frame configuration step (step 860) is performed except for the reserved resources.

Thereafter, the algorithm according to the present invention terminates.

9 is a block diagram of a base station according to an embodiment of the present invention.

9, the base station includes a communication module 910, a control unit 920, a storage unit 930, and an offset frame management unit 940.

The communication module 910 is a module for communicating with other nodes, and includes a wireless processing unit and a wire processing unit, a wireless baseband processing unit, and a wired baseband processing unit. The radio processor converts the signal received through the antenna into a baseband signal and provides the baseband signal to the radio baseband processor. The baseband processor converts the baseband signal from the radio baseband processor into a radio signal, Lt; / RTI > The wired processing unit converts the signal received through the wired path into a baseband signal and provides the baseband signal to the wired baseband processing unit. The wired processing unit converts the signal received through the wired path into a baseband signal, And transmits through the wired path

The controller 920 controls the overall operation of the terminal. In particular, the control unit 940 controls the offset frame management unit 940 according to the present invention.

The storage unit 930 stores programs for controlling the overall operation of the apparatus and temporary data generated during program execution.

In the above-described block configuration, the controller 920 may perform the function of the offset frame manager 940. In the present invention, these are separately constructed and described in order to describe each function separately.

Therefore, when the product is actually implemented, the control unit 920 may process all the functions of the offset frame management unit 940, or may be configured to process only a part of the functions in the control unit 920 .

Now, the case where the base station is a small base station will be described as follows.

The offset frame management unit 940 of the small base station receives a frame offset (N _offset ) of the corresponding cell from the OAM server through a self-configuration process. If the current network is an asynchronous network, the synchronization of the macro base station of the upper layer is detected by the network synchronization or the OTAR function, and frame offset is applied based on the frame start point of the macro cell based on the detection.

If the current network is a synchronous network, the offset frame management unit 940 of the small base station applies a frame offset based on the frame start point of the macro cell in synchronization with the synchronization. When the interference avoiding function for the control channel is applied, in addition to the synchronization and broadcast channels, the control channel is also determined as an object to which the interference avoiding function is to be applied.

The offset frame management unit 940 of the small base station controls the control channel interference avoiding function to the maximum possible OFDM Determines whether to apply for the number of symbols , and determines whether the maximum possible OFDM When applied to a number of symbols, N _S. Determining a number of sub-frames to limit the _PDDCH to 2, and _M in the sub-frame N _{ends. PDDCH} ≪ / RTI > OFDM symbols. The offset frame management unit 940 of the small base station reserves the common channel resources corresponding to the synchronization channel and the broadcast channel, and configures a small base station frame excluding the reserved resources. Then, the small base station frame is transmitted to the offset (N _offset ) determined for the synchronization of the macro base station.

Offset-frame managing unit 940 of the small base station will schedule a _single OFDM symbol C in the sub-frame, if the end does not apply to the number of OFDM symbols as possible to the maximum. Then, a process after the step of reserving the common channel resources corresponding to the synchronization channel and the broadcast channel is performed.

If the small base station does not apply the interference avoiding function for the control channel, the offset frame managing unit 940 of the small base station determines that only the synchronization and broadcast channels are to be subjected to the interference avoiding function, And performs a process after the step of reserving the common channel resources.

Now, the case where the base station is a macro base station will be described as follows.

The offset frame management unit 940 of the macro base station receives a frame offset (N _offset ) of the corresponding cell from the OAM server through a self-configuration process. When the macro base station performs the interference control function, the macro base station sets the start point of the macro base station frame as a reference.

When the macro base station applies the interference avoiding function for the control channel, the offset frame managing unit 940 of the macro base station decides to additionally apply the control channel interference avoiding function to the synchronization and broadcast channels. Then, the control channel interference avoiding function is maximally enabled for OFDM Determines whether to apply for the number of symbols , and determines whether the maximum possible OFDM When applied to a number of symbols, N _{M. And reserves} C ₂ OFDM symbols following _PDDCH . A common channel resource corresponding to a synchronization channel and a broadcast channel of a sub-small base station is reserved, and a macro base station frame is configured excluding the reserved resources. Then, the macro base station frame is transmitted to the offset (N _offset = 0) determined for the synchronization of the macro base station.

When the macro base station does not apply the interference avoiding function for the control channel, the offset frame managing unit 940 of the macro base station determines that only the synchronization and broadcast channels are to be subjected to the interference avoiding function, And a step of reserving a common channel resource corresponding to the broadcast channel.

The offset frame management unit 940 of the macro base station determines whether the maximum possible or all OFDM If it does not apply to the number of symbols, N _M. N _S after _{PDDCH . PDDCH} < / RTI > OFDM symbols. And performs a process after a step of reserving a common channel resource corresponding to a synchronization channel and a broadcast channel of a sub-small base station.

If the macro base station does not perform the interference control function, the offset frame management unit 940 of the macro base station performs steps after the step of configuring the macro base station frame excluding the reserved resources.

In the above process, the reservation information is exchanged between the small base station and the macro base station so that the small base station and the macro base station know each other's reservation information.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

FIG. 1 is a diagram illustrating transmission positions of a synchronization channel, a physical layer broadcast channel, and a control channel in an OFDM (Orthogonal Frequency Division Multiplex) based downlink frame structure of Enhanced Universal Terrestrial Radio Access (EUTRA)

2 is a diagram illustrating a bandwidth allocation method of a macro base station and a small base station,

3 is a diagram illustrating a hierarchical cell structure of a small base station superposed in a macro cell in a mobile communication system according to an embodiment of the present invention;

4 is a diagram illustrating a first offset structure of a small base station in units of subframes for a synchronization channel and a broadcast channel according to an embodiment of the present invention;

5 is a diagram illustrating a second offset structure of a small base station in units of subframes for a synchronization channel and a broadcast channel according to an embodiment of the present invention;

6 is a diagram illustrating an OFDM symbol unit offset structure of a small base station including a downlink control channel according to an embodiment of the present invention;

FIGs. 7A and 7 are flowcharts illustrating a process of a small base station constructing a frame from frame offset information according to an embodiment of the present invention; FIG.

FIGS. 8A and 8B are flowcharts illustrating a process of forming a frame by a macro base station from frame offset information according to an embodiment of the present invention,

9 is a block diagram of a base station according to an embodiment of the present invention.

Claims (4)

A method for mitigating interference in a co-channel interference of a small base station in a mobile communication system, When the small base station applies the control channel interference avoiding function to only a part of symbols, the number of C ₁ Reserving a symbol, When the small base station applies the control channel interference avoiding function to all the symbols, it determines the number of subframes to be limited to a predetermined number of N _{S. PDCCHs} , and _allocates symbols of N _{M. PDCCHs} at the end of the subframe A reservation process, Comprising the steps of: reserving, in a corresponding subframe, a symbol including a sync channel of a different layer and a common channel resource corresponding to a broadcast channel regardless of whether the control channel interference avoiding function is used; Comprising the steps of: configuring a small base station frame excluding a symbol including the reserved common channel resource; And transmitting the small base station frame to an offset determined in preparation for synchronization of the macro base station, The _N.S. PDCCH indicates the number of OFDM symbols used by the small base station to transmit a Physical Downlink Control Channel (PDCCH) The N. _M PDCCH indicates the number of OFDM symbols used by the macro base station to transmit the PDCCH, Wherein C ₁ represents the number of OFDM symbols that the small base station should reserve to avoid some interference to the control channel of the macro base station. A method of mitigating co-channel interference in a macro base station in a mobile communication system, When the macro base station applies the control channel interference avoiding function to only a part of symbols, _reserving C ₂ OFDM symbols in an area excluding N _{M. PDDCH} OFDM symbols in the corresponding subframe, The process of the macro base station in this case to apply the control channel interference avoidance function in every symbol, schedule a _S.PDDCH N OFDM symbols to other than the N _M.PDDCH OFDM symbols in the subframe area; Reserving a shared channel resource corresponding to a synchronization channel and a broadcast channel of another layer regardless of whether the control channel interference avoiding function is used or not; Comprising the steps of: configuring a macro base station frame excluding the reserved common channel resource and the reserved resource regardless of whether the macro base station performs an interference mitigation function; And transmitting the macro base station frame to an offset determined in preparation for synchronization of the macro base station, The N _S. PDCCH indicates the number of OFDM symbols used by the small base station to transmit the PDCCH, The N. _M PDCCH indicates the number of OFDM symbols used by the macro base station to transmit the PDCCH, Wherein C ₂ represents the number of OFDM symbols that the macro base station must reserve in order to avoid some interference to the control channel of the small base station. A small base station apparatus for mitigating the same band interference in a mobile communication system, A communication module for communicating with another node, If the small base station applies the control channel interference avoiding function to only a part of symbols, the number of C ₁ And _allocates a control channel interference avoiding function to all symbols by determining a number of subframes to be limited to a predetermined number of N. _{S. PDCCHs} and _{allocating a} number of N _{M. PDCCHs} A symbol including a common channel resource corresponding to a synchronization channel and a broadcast channel of another layer is reserved in the corresponding subframe regardless of whether the control channel interference avoiding function is used or not, And a controller for transmitting the small base station frame to an offset determined in preparation for synchronization of the macro base station, The _N.S. PDCCH indicates the number of OFDM symbols used by the small base station to transmit the PDCCH, The N. _M PDCCH indicates the number of OFDM symbols used by the macro base station to transmit the PDCCH, Wherein C ₁ represents the number of OFDM symbols that the small base station should reserve in order to avoid some interference to the control channel of the macro base station. An apparatus of a macro base station for mitigating the same band interference in a mobile communication system, A communication module for communicating with another node, When the control channel interference avoiding function is applied to only a part of symbols , C ₂ OFDM symbols are reserved in an area excluding N _{M. PDDCH} OFDM symbols in the corresponding subframe, and when control channel interference avoiding function is applied to all symbols, shared channel to the other than the N _M.PDDCH OFDM symbols in the frame area reserved _S.PDDCH the N OFDM symbols, and corresponds to the control channel interference avoiding the presence and the synchronization channel and broadcast channel of the other layer, regardless of the function A macro base station frame excluding the reserved common channel resource and a predetermined reserved resource regardless of whether the macro base station performs the interference mitigation function or not, And a controller for transmitting the macro base station frame, The N _S. PDCCH indicates the number of OFDM symbols used by the small base station to transmit the PDCCH, The N. _M PDCCH indicates the number of OFDM symbols used by the macro base station to transmit the PDCCH, Wherein C ₂ represents the number of OFDM symbols that the macro base station should reserve in order to avoid some interference to the control channel of the small base station.

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