WO2015174892A1

WO2015174892A1 - Lte-a control apparatus, user equipment, method of controlling the same, and communication system for coordination of resources across adjacent cells

Info

Publication number: WO2015174892A1
Application number: PCT/SE2014/050575
Authority: WO
Inventors: Varun Joshi; Karupaiah RAJENDRAN
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2014-05-12
Filing date: 2014-05-12
Publication date: 2015-11-19
Anticipated expiration: 2016-11-12

Abstract

A control apparatus acquires information indicating a reserved subset of the wireless resources for allocation to cell-edge UEs and information indicating a first cell-edge-UEreserved subset allocation order different from a second order first cell-edge-UE reserved subset allocation order of the neighboring cell. The apparatus receivesa measurement report message indicating whether or not a value of a signal measurement for the neighboring cell is within a predetermined threshold from avalue of thesignal measurement forthe serving cell, and uses it to determine whether the first UEis a cell-edge-UE. If the first UE it is a cell-edge-UE, the apparatus allocates awireless resource from the reserved subset to the first UE.

Description

DESCRIPTION

LTE-A CONTROL APPARATUS, USER EQUIPMENT, METHOD OF CONTROLLING THE SAME, AND COMMUNICATION SYSTEM FOR COORDINATION OF RESOURCES ACROSS ADJACENT

CELLS

TECHNICAL FIELD

[0001] The present invention generally relates to a control apparatus, a user equipment, a method of controlling the same, and a communication system.

BACKGROUND

[0002] In recent years, orthogonal frequency- division multiple access (OFDMA) based cellular

networks, such as Long Term Evolution (LTE) networks, have been deployed with a frequency reuse factor (FRF) of 1. In other words, every sector of every cell in such a network may use all available wireless resources for transmission. In such communication systems, interference tends to be dominated by user equipments (UE) of neighboring cells using the same wireless resources. A neighboring cell of a UE is a cell that is adjacent to a serving cell of the UE, and a serving cell of a UE is a cell served by a control apparatus (an eNodeB, for example) with which the UE performs communication. Interference with a UE of a neighboring cell using the same wireless resource is known as inter-cell co-channel interference.

[0003] Cell-edge user equipments ( cell-edge-UEs ) , are UEs which are determined to be located in a region of a cell that corresponds to a cell edge. Cell-edge- UEs which are located relatively far from center of the cell are more susceptible to, and more likely to cause, inter-cell co-channel interference. When a UE

experiences high interference, this may necessitate the use of a more robust, lower throughput, modulation scheme to ensure communication quality. Therefore, a reduction in such interference may result in an

improvement in throughput, especially for cell-edge-UEs .

[ 0004 ] In order to avoid inter-cell co-channel interference, interference mitigation techniques may be employed. Such techniques can be broadly categorized into those in which cells coordinate to reduce

interference, and those without coordination. Non- coordinated interference avoidance techniques generally involve partitioning of wireless resources. Examples of systems that use such a technique are networks that do not use the same wireless resources in neighboring cells, for example. However, the greater the

partitioning of the wireless resources, the greater the capacity that will be lost due to the restrictions imposed upon the resources. In LTE networks,

coordinated interference avoidance techniques known as inter-cell interference coordination (ICIC) are

currently employed (See "Feasibility study for evolved Universal Terrestrial Radio Access (UTRA) and Universal Terrestrial Radio Access Network (UTRAN) ", 3GPP TS 25.912, version 11.0.0, and "Evolved Universal

Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN) ;

Overall description; Stage 2", 3GPP TS 36.300, version 12.1.0.) . In ICIC techniques, information, such as resource usage status, or traffic load, is continuously communicated between eNodeBs over an X2 interface.

Based on such information, the eNodeBs coordinate the scheduling of wireless resources in the frequency domain so as not to simultaneously allocate wireless resources of the same frequencies, or in the time domain, so that resource scheduling is coordinated in time .

SUMMARY

[0005] In light of the above circumstances, the inventors of the present application conceived that it is advantageous if it is possible to identify cell- edge-UEs in an efficient manner and suppress the occurrence of inter-cell co-channel interference while suppressing the communication load on the X2 interface.

[0006] According to a first aspect of the present invention, there is provided a control apparatus. The control apparatus is for use in an OFDMA-based

communication system including the control apparatus serving a serving cell and a neighboring control apparatus serving a neighboring cell, and is operable to allocate wireless resources from a plurality of wireless resources to user equipments of the serving cell. The neighboring control apparatus is also operable to allocate wireless resources from the plurality of wireless resources to user equipments of the neighboring cell. The control apparatus comprises an acquisition unit configured to acquire reserved resource information and order information, the

reserved resource information indicating a first reserved subset of the plurality of wireless resources reserved for allocation to cell-edge user equipments, the order information indicating a first order

according to which wireless resources of the first reserved subset are allocated to cell-edge user

equipments of the serving cell, and the first order being different from a second order according to which wireless resources of the first reserved subset are allocated to cell-edge user equipments of the

neighboring cell. The control apparatus also comprises a communication unit configured to receive a

measurement report message from a first user equipment of the serving cell, the measurement report message including information indicating whether or not a value of a signal measurement for the neighboring cell is within a predetermined threshold from a value of the signal measurement for the serving cell. The control apparatus also comprises a determination unit

configured to determine whether or not the first user equipment is a cell-edge user equipment based on the measurement report message received by the

communication unit. The control apparatus also

comprises an allocation unit configured to, if the first user equipment is determined to be the cell-edge user equipment, select a wireless resource, which has not been allocated by the control apparatus, from the first reserved subset in accordance with the first order, and allocate the selected wireless resource to the first user equipment.

[ 0007 ] According to a second aspect of the present invention, there is provided a user equipment. The user equipment is for use in an OFDMA-based

communication system including a control apparatus serving a serving cell and a neighboring control apparatus serving a neighboring cell. The user

equipment comprises a measurement unit configured to perform a signal measurement for the neighboring cell and to perform the signal measurement for the serving cell in accordance with a measurement control message from the control apparatus. The user equipment also comprises an analysis unit configured to determine whether or not a value of the signal measurement for the neighboring cell is within a predetermined

threshold from a value of the signal measurement for the serving cell. The user equipment also comprises a generation unit configured to generate a measurement report message indicating whether or not the value of the signal measurement for the neighboring cell is within the predetermined threshold from the value of the signal measurement for the serving cell in

accordance with the determination of the analysis unit. The user equipment also comprises a communication unit configured to transmit the measurement report message to the control apparatus, which determines whether or not the user equipment is a cell-edge user equipment based on the measurement report message.

[ 0008 ] According to a third aspect of the present invention, there is provided a method of controlling a control apparatus, for use in an OFDMA-based

communication system including the control apparatus serving a serving cell and a neighboring control apparatus serving a neighboring cell. The control apparatus is operable to allocate wireless resources from a plurality of wireless resources to user

equipments of the serving cell. The neighboring control apparatus is also operable to allocate wireless resources from the plurality of wireless resources to user equipments of the neighboring cell. The method comprises an acquisition step of acquiring reserved resource information and order information, the

neighboring cell. The method also comprises a

communication step of receiving a measurement report message from a first user equipment of the serving cell, the measurement report message including information indicating whether or not a value of a signal

measurement for the neighboring cell is within a

predetermined threshold from a value of the signal measurement for the serving cell. The method also comprises a determination step of determining whether or not the first user equipment is a cell-edge user equipment based on the measurement report message received in the communication step. The method also comprises an allocation step of, if the first user equipment is determined to be the cell-edge user

equipment, selecting a wireless resource, which has not been allocated by the control apparatus, from the first reserved subset in accordance with the first order, and allocating the selected wireless resource to the first user equipment.

[ 0009 ] According to a fourth aspect of the present invention, there is provided a method of controlling a user equipment for use in an OFDMA-based communication system including a control apparatus serving a serving cell and a neighboring control apparatus serving a neighboring cell. The method comprises a measurement step of performing a signal measurement for the

neighboring cell and performing the signal measurement for the serving cell in accordance with a measurement control message from the control apparatus. The method also comprises an analysis step of determining whether or not a value of the signal measurement for the neighboring cell is within a predetermined threshold from a value of the signal measurement for the serving cell. The method also comprises a generation step of generating a measurement report message indicating whether or not the value of the signal measurement for the neighboring cell is within the predetermined threshold from the value of the signal measurement for the serving cell in accordance with the determination of the analysis step. The method also comprises a communication step of transmitting the measurement report message to the control apparatus, which

determines whether or not the user equipment is a cell- edge user equipment based on the measurement report message . [ 0010 ] According to a fifth aspect of the present invention, there is provided an OFDMA-based

communication system. The system comprises a control apparatus serving a serving cell and operable to allocate wireless resources from a plurality of wireless resources to user equipments of the serving cell, a neighboring control apparatus serving a

neighboring cell and also operable to allocate wireless resources from the plurality of wireless resources to user equipments of the neighboring cell, and a user equipment served by the control apparatus. The control apparatus comprises an acquisition unit configured to acquire reserved resource information and order

information, the reserved resource information

indicating a first reserved subset of the plurality of wireless resources reserved for allocation to cell-edge user equipments, the order information indicating a first order according to which wireless resources of the first reserved subset are allocated to cell-edge user equipments of the serving cell, and the first order being different from a second order according to which wireless resources of the first reserved subset are allocated to cell-edge user equipments of the neighboring cell. The control apparatus also comprises a communication unit configured to receive a

measurement report message from the user equipment of the serving cell, the measurement report message including information indicating whether or not a value of a signal measurement for the neighboring cell is within a predetermined threshold from a value of the signal measurement for the serving cell. The control apparatus also comprises a determination unit

configured to determine whether or not the user

equipment is a cell-edge user equipment based on the measurement report message received by the

communication unit. The control apparatus also

comprises an allocation unit configured to, if the user equipment is determined to be the cell-edge user equipment, select a wireless resource, which has not been allocated by the control apparatus, from the first reserved subset in accordance with the first order, and allocate the selected wireless resource to first user equipment. The user equipment comprises a measurement unit configured to perform a signal measurement for the neighboring cell and to perform the signal measurement for the serving cell in accordance with a measurement control message from the control apparatus. The user equipment also comprises an analysis unit configured to determine whether or not a value of the signal

measurement for the neighboring cell is within a predetermined threshold from a value of the signal measurement for the serving cell. The user equipment also comprises a generation unit configured to generate the measurement report message in accordance with the determination of the analysis unit. The user equipment also comprises a communication unit configured to transmit the measurement report message to the control apparatus .

[0011] By virtue of the above features, it is possible to identify cell-edge-UEs in an efficient manner and suppress the occurrence of inter-cell co- channel interference while suppressing the

communication load on the X2 interface.

[0012] Further features and advantages of the present invention will be apparent from the following description with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF DRAWINGS

[0013] Fig. 1 is a view illustrating wireless resources allocated in an OFDMA-based communication system according to some embodiments.

[0014] Fig. 2 is an overall view for explaining the OFDMA-based communication system according to some embodiments .

[0015] Fig. 3 is a functional block diagram of an eNodeB according to some embodiments.

[0016] Fig. 4 is a functional block diagram of a user equipment (UE) according to some embodiments.

[0017] Fig. 5 is a graph for explaining a condition for triggering a measurement report message according to some embodiments.

[0018] Fig. 6 is a sequence diagram for

illustrating operation of eNodeBs and the UE according to some embodiments.

[0019] Fig. 7 is a flowchart for illustrating processing of the eNodeB for acquiring information identifying cell-edge-UEs according to some embodiments.

[0020] Fig. 8 is a flowchart for illustrating processing of the UE for reporting information

indicating whether the UE is a cell-edge-UE according to some embodiments.

[0021] Fig. 9 is a view for illustrating orders for allocation of wireless resources to cell-edge-UEs according to some embodiments.

[0022] Fig. 10 is a flowchart for illustrating processing of the eNodeB for allocating a wireless resource to a UE according to some embodiments.

[0023] Fig. 11 is a view for illustrating an organization of wireless resources according to some embodiments .

[0024] Fig. 12 is a flowchart for illustrating processing of the eNodeB for allocating a wireless resource to a UE according to some embodiments.

DETAILED DESCRIPTION [0025] Fig. 1 is a view illustrating wireless resources allocated in an OFDMA-based communication system according to some embodiments. Here, the OFDMA- based communication system will be explained as an LTE system.

[0026] As can be seen in Fig. 1, in the LTE system, wireless resources are shared between a plurality of users (user A, user B) . These wireless resources have a time component and a frequency component. The wireless resources are allocated in units of resource blocks (RBs) as are indicated by the blocks of Fig. 1. The RBs may be 180kHz wide, and have a time component of 0.5 ms, for example. A control apparatus known as an eNodeB may allocate RBs to user equipments (UEs) in a serving cell for each time instance.

[0027] Fig. 2 is an overall view for explaining the LTE system according to some embodiments. Note that for ease of explanation, Fig. 2 is simplified. It should be understood that in an actual implementation, the LTE system may include more eNodeBs and UEs, and that each eNodeB may serve a number of sectors.

[0028] A mobility management entity (MME) 104 is a control node for the LTE access network that performs such tasks as idle mode user equipment (UE) paging, user authentication, and the like. The MME 104 is connected communicably with eNodeBs 101, 102 and 103 by an SI interface. Each of the eNodeBs 101, 102 and 103 may serve UEs in respective cells. For example eNodeBs

101 and 102 serve UEs 105 and 107 respectively. UEs 105 and 107 are determined to be cell-edge-UEs, and so they are both more susceptible to, and more likely to cause, inter-cell co-channel interference. For example, if eNodeB 101 allocates the same RB to UE 105 (same in the frequency and time domains) as eNodeB 102 allocates to UE 107, the respective signals of UE 105 and UE 107 will interfere with each other.

[ 0029 ] According to embodiments, eNodeBs 101 and

102 respectively identify that UEs 105 and 107 are cell-edge-UEs by instructing, with measurement control messages, that the UEs 105 and 107 perform event-based reporting, and receiving corresponding measurement report messages. Event-based reporting is a term for describing an approach to reporting, by a UE to an eNodeB, of information of signal measurements taken by the UE . In event-based reporting, an eNodeB sends a measurement control message which instructs a UE to perform signal measurements, and which indicates a

"trigger event" condition. The UE performs the

corresponding signal measurements and uses them to determine if the trigger event condition is satisfied. When the trigger event condition is satisfied, i.e. the event occurs, the UE sends a measurement report message to the eNodeB. In some embodiments, a trigger

condition of this event-based reporting includes that a value of a signal measurement (reference signal

received power (RSRP) , for example) for a neighboring cell is within a predetermined threshold from the value of the signal measurement for the serving cell. This will be explained in more detail with reference to Fig. 5.

[0030] The neighboring eNodeBs 101, 102 and 103 can communicate with each other over an X2 interface. Note that a neighboring eNodeB is an eNodeB that serves a neighboring cell. For example, the neighboring eNodeBs may communicate information to coordinate allocation of wireless resources. Minimizing such information has the effect of reducing X2 interface load, which may reduce delays in X2 interface data forwarding, for example. In some embodiments, the eNodeBs 101, 102, and 103 limit information transmitted to coordinate RB allocation to a subset of RBs reserved for cell-edge-UEs , and different allocation orders for each neighboring cell for RBs of this reserved subset. By generating these allocation orders so that they correlate in such a way as to avoid simultaneous RB allocation in neighboring cells, inter-cell co-channel interference can be avoided, as is explained in detail with reference to Fig.s 9 and 10.

[0031] UE 106, which is served by eNodeB 101 is a central-UE. A central-UE is a UE that is not a cell- edge-UE, i.e. a central-UE is a UE located away from the edge of the cell. UE 106 is located relatively close to eNodeB 101, and does not fall within the coverage of the neighboring eNodeBs 102 and 103.

Therefore, even if the same RB is allocated to a cell- edge-UE of the eNodeB 102 or the eNodeB 103, the UE 106 may not experience significant interference. In

addition, because of its proximity to the eNodeB 101, in some embodiments the transmission power for the UE 106 is reduced. In such a case, even if the same RB is allocated to a cell-edge-UE of the eNodeB 102 or the eNodeB 103, the signals of the UE 106 will not cause significant interference on such cell-edge-UEs. For this reason, in some embodiments, in addition to the subset of RBs reserved for cell-edge-UEs, disjoint subsets of RBs are reserved for allocation to power- reduced-UEs ( Power-reduced-UEs are UEs for which a transmission power is less than a predetermined amount) . These RBs may be allocated to cell-edge-UEs without significantly increasing interference, for example.

This is discussed in detail with reference to Fig.s 11 and 12.

[0032] Fig. 3 is a functional block diagram of the eNodeBs 101, 102 and 103 according to some embodiments. For simplicity, explanation will be given using the eNodeB 101.

[0033] The eNodeB 101 comprises a central

processing unit (CPU) 301, a random access memory (RAM) 302, a read-only memory (ROM) 303, a communication unit 304, an allocation unit 305, an acquisition unit 306, a determination unit 307, and a generation unit 308.

Note that there may be multiple instances of a

component. The components may be connected by a bus, and capable of communication with each other thereupon.

[0034] In embodiments, the communication unit 304 includes wireless links, via sending/receiving antennas for example. It is capable of communication with external devices such as the UE 105 over one or more networks .

[0035] In some embodiments, the functionality of the units 305 through 308 is implemented by the CPU 301 executing a software program stored in the ROM 303 using the RAM 302 as a work area. In some embodiments, the units 304 through 308 are implemented using

dedicated hardware. In other embodiments, the units 304 through 308 are implemented using a combination of software and hardware. The detailed operation of the units 304 through 308 will be described with reference to Fig.s 6, 7, 10 and 12.

[0036] Fig. 4 is a functional block diagram of the

UE 105 according to some embodiments.

[0037] The UE 105 comprises a central processing unit (CPU) 401, a random access memory (RAM) 402, a read-only memory (ROM) 403, a communication unit 404, a measurement unit 405, an analysis unit 406, and a generation unit 407. Note that there may be multiple instances of a component. The components may be

connected by a bus, and capable of communication with each other thereupon.

[0038] In embodiments, the communication unit 404 includes wireless links, via sending/receiving antennas for example. It is capable of communication with external devices such as the eNodeBs 101, 102 and 103 over one or more networks .

[0039] In some embodiments, the functionality of the units 405 through 407 is implemented by the CPU 401 executing a software program stored in the ROM 403 using the RAM 402 as a work area. In some embodiments, the units 404 through 407 are implemented using

dedicated hardware. In other embodiments, the units 404 through 407 are implemented using a combination of software and hardware. The detailed operation of the units 404 through 407 will be described with reference to Fig.s 6 and 8.

[0040] Fig. 5 is a graph for explaining a

condition for triggering a measurement report message according to some embodiments.

[0041] The eNodeBs 101, 102 and 103, according to embodiments, identify cell-edge-UEs , as discussed above, using event-based reporting. For example, the eNodeB 101 transmits a measurement control message to the UE 105. This measurement control message may contain information such as what kind of signal measurement that the UE 105 should perform, information about the cells in the system, and information of a condition for triggering the measurement report message. Note that in some embodiments, such a measurement control message may include other information, or may be broken up into a number of separate messages from the eNodeB 101 to the UE 105.

[0042] In accordance with the measurement control message, the UE 105 may perform signal measurements for cells in its proximity. The UE 105 analyzes these signal measurements in accordance with the trigger condition indicated by the message. When the trigger condition is determined to be satisfied based on these signal measurements, the UE 105 generates, and

transmits to the eNodeB 101, a measurement report message. The trigger condition may include both an entering condition, and a leaving condition in some embodiments. In such a case, when the eNodeB 101 receives the measurement report message from the UE 105 indicating the entering condition, it may determine that the UE 105 has become a cell-edge-UE . Conversely, the eNodeB 101 may determine that the UE 105 ceases to be a cell-edge-UE upon receiving the measurement report message from the UE 105 indicating the leaving

condition .

[0043] The entering condition, according to embodiments, corresponds to a value of a signal measurement for a neighboring cell becoming within a predetermined threshold from the value of the signal measurement for a serving cell. The leaving condition may correspond to the value of the signal measurement for the neighboring cell ceasing to be within the predetermined threshold from the value of the signal measurement for the serving cell, for example. Note that according to embodiments, in a case of carrier aggregation, the serving cell corresponds to the primary cell. Specifically, the primary cell of a UE refers to the serving cell of the UE that provides Non- Access-Stratum (NAS) mobility information, and security input at radio resource control (RRC) connection re- establishment/handover .

[0044] In some embodiments the signal measurement values of these conditions correspond to RSRP

measurement values. As the UE 105 approaches an edge of the cell served by the eNodeB 102, the serving and neighboring RSRP values may approach each other. The value of an RSRP measurement for a particular cell becomes higher as a UE becomes closer to the eNodeB corresponding to that cell (from an antenna of that eNodeB to be exact) . Therefore, as the UE 105

approaches the neighboring eNodeB 102, the RSRP value for eNodeB 102 will increase.

[0045] As the UE 105 approaches the neighboring eNodeB 102, it simultaneously becomes farther from eNodeB 101, and so the RSRP value for the serving cell will decrease. The closer the RSRP value of the serving cell is to that of the neighboring cell, the higher the interference the UE will potentially

experience or cause with respect to the neighboring cell. Therefore, the predetermined threshold of the above condition can be chosen such that when the absolute difference of the neighboring cell RSRP and the serving cell RSRP is within this threshold,

significant interference may occur. In other words, in such a case the UE corresponds to a cell-edge-UE . Note that RSRP is used as an example, and another kind of signal measurement having similar characteristics may be used.

[0046] Equation 1 illustrates an example of an equation, indicated by the measurement control message, that the UE 105 uses to evaluate whether the entering condition or the leaving condition is satisfied. Note that in other embodiments, the equation may be

different, and may include hysteresis values, cell index offsets, or the like. Furthermore, a time-to- trigger parameter, which indicates a duration over which the condition must be satisfied for the event to be triggered, may also be indicated by the measurement control message.

[0047] |Ms - Mn| < Th Equation 1

Here, Ms corresponds to a measured value for a serving cell. For example, this may be an RSRP

measurement made by the UE 105 for the serving cell (eNodeB 101) . Mn corresponds to the measured value for a neighboring cell. For example, this may be an RSRP measurement made by the UE 105 for the neighboring cell corresponding to eNodeB 102. The inequality of

Equation 1 is satisfied when the absolute difference of Ms and Mn is less than or equal to a threshold Th. In other words, the inequality is satisfied when a signal measurement for the neighboring cell (Mn) is within a predetermined threshold (Th) from the value of the signal measurement for the serving cell (Ms) . Fig. 5 illustrates an example of event-based reporting by the UE 105 to the eNodeB 101. In Fig. 5, the vertical axis corresponds to signal measurement value (in this case an RSRP measurement) , and the horizontal axis

corresponds to time. A solid line and a dashed line indicate the RSRP measurement values for the primary cell (eNodeB 101) which corresponds to Ms in Equation 1, and the neighboring cell (eNodeB 102) which corresponds to Mn in Equation 1 respectively. Time 501 is a point in time at which the entering condition is first

satisfied. Because at time 501, the absolute

difference of the RSRP value of the serving cell (Ms) and that of the neighboring cell (Mn) equals the threshold Th, the entering condition is satisfied.

This causes the event to be triggered, and the UE 105 transmits a corresponding measurement report message to the eNodeB 101 indicating that it is now a cell-edge-UE .

[0048] On the other hand, at time 502, the

absolute difference of the RSRP value of the serving cell and that of the neighboring cell becomes greater than the threshold Th, and so the leaving condition is satisfied. This causes an event to be triggered and so the UE 105 transmits a corresponding measurement report message to the eNodeB 101 indicating that it ceases to be a cell-edge-UE.

[0049] In this way, the eNodeB 101 can identify whether or not the UEs that it serves (UE 105, for example) are cell-edge-UEs. This approach to

identifying users is advantageous in that it can more exactly identify cell-edge-UEs than approaches that use mathematical models to do so. Also, because the event- based reporting is performed directly between the eNodeB 101 and the UE 105, it does not suffer from communication delays that may occur in communication with an entity other than the eNodeB 101 and the UE 105. When, by the event-based reporting, the eNodeB 101 determines (identifies) that the UE 105 is a cell-edge- UE, the eNodeB 101 allocates wireless resources to the UE 105 from the cell-edge-UE reserved subset, in

accordance with the cell-edge-UE allocation order for eNodeB 101 to avoid inter-cell co-channel interference, as will be described in detail with reference to Fig. 10.

[0050] Fig. 6 is a sequence diagram for

illustrating operation of the eNodeBs 101, 102 and 103, and the UE 105 according to some embodiments.

[0051] In step S601, the communication unit 304 of the eNodeB 101 transmits cell condition information to the eNodeB 102 over the X2 interface. This information may include a ratio of cell-edge-UEs to central-UEs, priority of neighbor relation information, number of handovers over a certain period of time, or the like. Similarly, the eNodeB 103 transmits cell condition information, corresponding to the cell of the eNodeB 103, to the eNodeB 102 over the X2 interface in step S602.

[0052] In step S603, the eNodeB 102 analyzes the cell condition information received from the eNodeB 101 in step S601 and the eNodeB 103 in step S602. The eNodeB 102 analyzes this information, and also similar cell condition information of its own cell, and

determines the previously-mentioned subset of RBs reserved for cell-edge-UEs, and information indicating different allocation orders for each of eNodeB 101, 102 and 103 to allocate RBs to cell-edge-UEs from this reserved subset. In some embodiments, the eNodeB 102 further determines the previously-mentioned disjoint subsets of RBs reserved for power-reduced-UEs for each of eNodeBs 101, 102 and 103 based on the cell condition information. In step S604, the eNodeB 102 generates corresponding reserved subset information and cell- edge-UE allocation order information.

[0053] Next, in step S605, the eNodeB 102

transmits, to the eNodeB 101, the reserved subset information and the cell-edge-UE allocation order information for eNodeB 101. Note that similar

information is also transmitted to eNodeB 103, but the processing related to eNodeB 103 is omitted from here on because it is similar to that of eNodeB 101. The eNodeB 101 receives this information and stores it in a storage medium such as the RAM 302. Note that this information need not be continuously transmitted from the eNodeB 102, and may be reused by the eNodeB 101 for allocation over multiple scheduling operations. Thus, the load on the X2 interface for interference avoidance is kept to a minimum. This may be advantageous because delays resulting from high X2 interface load due to continuously transmitting coordination information over the X2 interface may be avoided.

[0054] It should be noted that the processing of the eNodeB 102 in steps S601-S605 may alternatively be performed by an entity (control apparatus) other than an eNodeB in some embodiments. For example, a central entity may exist that is communicable with each of the eNodeBs 101, 102 and 103. In some embodiments, this central entity may be a centralized self-organizing- network (SON) server, for example. Such an entity may receive the cell condition information, from each of the eNodeBs 101, 102, and 103, and reply to each eNodeB with the reserved subset information and the allocation information generated based on analysis of the cell condition information.

[0055] In step S606, the eNodeB 101 transmits a measurement control message to the UE 105, as described with reference to Fig. 5. It should be noted that the eNodeB 101 may transmit such a message to each of the UEs that the eNodeB 101 serves.

[0056] In step S607, the UE 105 performs signal measurements in accordance with the measurement control message, as described with reference to Fig. 5. When the trigger condition indicated by the measurement control message is satisfied, the UE 105, in step S608, transmits a measurement report message. In other words, when the UE 105 becomes a cell-edge-UE, or when the UE 105 ceases to be a cell-edge-UE, the UE 105 transmits the measurement report message to the eNodeB 101. As described earlier, in some embodiments, the measurement report indicates that the UE 105 has become a cell- edge-UE in the case of the entering condition, and indicates that the UE 105 ceases to be a cell-edge-UE in the case of the leaving condition. [0057] In step S609, the eNodeB 101 identifies whether the UE 105 is a cell-edge-UE based on the measurement report received in step S608. As described above, in some embodiments it stores information in a storage medium such as the RAM 302 indicating whether the UE 105 is currently a cell-edge-UE based upon the measurement report messages. Next, in step S610, the eNodeB 101 allocates, in accordance with the allocation order received in step S605, one or more RBs of the subset of RBs reserved for cell-edge-UEs , information of which is received in step S605, to the UE 105 when the UE 105 is identified to be a cell-edge-UE in step S609. Note that step S610 may be performed many times using the same order and cell-edge-UE reserved set received in step S605, reducing X2 interface load.

Because the allocation order correlates with the

allocation orders that neighboring cells use for cell- edge-UEs so that collisions are avoided, inter-cell co- channel interference can be mitigated.

[0058] Fig. 7 is a flowchart for illustrating processing of the eNodeB 101 for acquiring information identifying cell-edge-UEs according to some embodiments.

[0059] In step S701, the generation unit 308 generates the measurement control message, as in step S606 of Fig. 6. This measurement control message instructs the UE 105 to perform event-based reporting. The measurement control message indicates an event trigger condition corresponding to whether or not a value of a signal measurement for the neighboring cell is within a predetermined threshold from the value of the signal measurement for the serving cell. As

described in detail with reference to Fig. 5, in some embodiments the signal measurements are for RSRP, where eNodeB 101 serves as the primary cell of the UE 105, and the event trigger condition includes both entering and leaving triggers.

[0060] In step S702, the communication unit 304 transmits the measurement control message to the UE 105. In some embodiments, this step is performed when the UE 105 first enters a cell that the eNodeB 101 serves.

[0061] In step S703, the determination unit 307 determines whether the communication unit 304 received, from the UE 105, a measurement report message triggered by the measurement control message. When such a

measurement report message is determined to be received, the processing proceeds to step S704, otherwise the determination of step S703 is repeated.

[0062] In step S704, the determination unit 307 analyzes the received measurement report message and determines, based on the measurement report message, whether or not the UE 105 is a cell-edge-UE .

Specifically, the determination unit 307 determines that the UE 105 is a cell-edge-UE when the measurement report message indicates that it was triggered by an entering event, as described with reference to Fig. 5. The determination unit 307 determines that the UE 105 is not a cell-edge-UE when the measurement report message indicates that it was triggered by a leaving event, as described with reference to Fig. 5.

[0063] When the UE 105 is determined to be a cell- edge-UE, the processing proceeds to step S705, and the UE 105 is added to a list of cell-edge-UEs stored in a storage medium such as the RAM 302. On the other hand, when the UE 105 is determined to not be a cell-edge-UE, the processing proceeds to step S706, and the UE 105 is removed from this list of cell-edge-UEs.

[0064] In this way, it is possible for the eNodeB

101 to maintain information (the list of cell-edge-UEs) that can be used to determine whether or not a UE (UE 105, for example) that the eNodeB 101 serves is

currently a cell-edge-UE precisely, and without

significant delay. This information can then be used when allocating RBs reserved for cell-edge-UEs in accordance with the cell-edge-UE allocation order determined, in step S604, so as to avoid inter-cell co- channel interference. This will be described in more detail with reference to Fig.s 10 and 12.

[0065] Fig. 8 is a flowchart for illustrating processing of the UE 105 for reporting information indicating whether the UE 105 is a cell-edge-UE

according to some embodiments. [0066] In step S801, the communication unit 404 receives the measurement control message transmitted from the eNodeB 101 in step S702.

[0067] Next, the measurement unit 405, in

accordance with the information indicated by the measurement control message, performs signal

measurements. In some embodiments, these signal measurements are for RSRP, and are performed for the serving cell of eNodeB 101 and for the neighboring cells of eNodeB 102 and 103 periodically.

[0068] In step S803, the analysis unit 406

analyzes the results of signal measurements taken in step S802 and determines whether or not a trigger- condition indicated by the measurement control message is satisfied. Note that in some embodiments the UE 105 maintains information in a storage medium such as the RAM 402 indicating whether the measurement report message previously sent to the eNodeB 101 corresponded to the entering condition or the leaving condition. In other words, this information indicates whether the UE 105 is currently a cell-edge-UE or not (an

initialization value may be set for this information as appropriate) . In such cases, the analysis unit 406 may determine whether the leaving condition is satisfied, in a case where the stored information indicates that the UE 105 is currently a cell-edge-UE. Conversely, the analysis unit 406 may determine whether the entering condition is satisfied, in a case where the stored information indicates that the UE 105 is

currently not a cell-edge-UE . Fig. 8, for simplicity, shows the example of a case where the UE 105 up until this point was not a cell-edge-UE.

[0069] When the trigger-condition is determined to not be satisfied, the processing returns to step S802. On the other hand, when the trigger-condition is determined to be satisfied, the processing proceeds to step S804 and the generation unit 407 generates a corresponding measurement report message. This

measurement report message indicates that the UE 105 became a cell-edge-UE in this case. The measurement report message may include information of the RSRP signal measurement values taken for not only the neighboring cell for which the condition was satisfied, but also for other neighboring cells for which signal measurements were taken. The eNodeB 101 may then use this information for scheduling, for example. In addition, the measurement report message may indicate whether the triggered condition corresponds to the entering condition or the leaving condition. The communication unit 404 then transmits the generated measurement report message to the eNodeB 101 in step S805.

[0070] Fig. 9 is a view for illustrating

allocation orders for allocation of wireless resources to cell-edge-UEs according to some embodiments.

[0071] RBs are divided into non-reserved RBs and reserved RBs. The reserved RBs are reserved for

allocation to cell-edge-UEs. Note that the use of the term "reserved" does not mean that the effective

frequency reuse factor (FRF) does not equal 1. Here the reserved RBs are allocated to cell-edge-UEs

preferentially, but in a case where the non-reserved RBs are exhausted, an RB may be allocated from the cell-edge-UE reserved subset to a central-UE, for example .

[0072] In this example, for simplicity, the RBs all correspond to the same scheduling time. Note, however, that in other embodiments, the allocation orders may cover RBs that differ in the time domain.

As can be seen, the cell-edge-UE allocation orders differ for each of the eNodeBs 101, 102 and 103, and are mutually correlated so as to avoid allocation collisions between eNodeBs. Specifically, in this example, each of eNodeB 101, 102 and 103 can allocate, in accordance with their respective orders, 20 RBs before reaching the starting RB of a neighboring eNodeB. Note that in this example, the order for eNodeB 103 wraps around to the starting RB in the order for eNodeB 101 after reaching the bottom-right RB in Fig. 9.

[0073] In other embodiments, the starting RBs for each of the eNodeBs 101, 102 and 103 are not equally separated from each other. For example, in step S603 of Fig. 6, the eNodeB 102 may determine weightings for each of the eNodeBs 101, 102 and 103 based on cell condition information for each cell, or the like. For example, in some embodiments the eNodeB 102 may

determine in step S603 that the eNodeB 101 is likely to have a larger number of cell-edge-UEs than the eNodeBs 102 and 103. In such a case the eNodeB 102 may

determine that the weighting for eNodeB 101 should be higher than that of the eNodeBs 102 and 103. Based on the weightings determined for each cell, the eNodeB 102 may determine the cell-edge-UE allocation orders for each eNodeB. So, in the case where eNodeB 101 has a higher weighting, the closest starting RB of the order for a neighboring eNodeB may be determined so that the eNodeB 101 will be able to allocate more RBs from the cell-edge-UE reserved subset before allocating an RB that will collide with a neighboring eNodeB.

[ 0074 ] Note that the allocation orders need not be sequential orders and may be more complicated. An order may be chosen to start at a central RB and alternatively work its way outwards from that central RB, for example. In some embodiments the orders may be sequential in direction but may skip a certain number of RBs each time. More complicated orders may have an advantage in terms of diversifying the frequencies of the RBs allocated to a single UE when a number of RBs are allocated to the single UE in a single scheduling. On the other hand, using a simple sequential order may be advantageous in terms of minimizing complexity and X2 interface load.

[0075] Fig. 10 is a flowchart for illustrating processing of the eNodeB 101 (control apparatus) for allocating an RB to the UE 105, according to some embodiments .

[0076] In step S1001, the acquisition unit 306 acquires information of the subset of RBs reserved for cell-edge-UEs , and a cell-edge-UE allocation order for the eNodeB 101. Note that in some embodiments, this information is included in the information transmitted from eNodeB 102 in step S605 of Fig. 6, for example. In such a case the acquisition unit 306 may acquire the information from the RAM 302, where it was stored.

[0077] In step S1002, the acquisition unit 306 acquires information indicating whether the UE 105 in the serving cell is a cell-edge-UE. For example, this information may be the cell-edge-UE list described with reference to Fig. 7. Note that this information is based on a measurement report message received by the communication unit 304. In some embodiments, step S1002 is performed before step S1001.

[0078] In step S1003, the determination unit 307 determines whether or not the UE 105 is a cell-edge-UE using the information acquired in step S1002. For example, in a case where the UE 105 is currently included in the cell-edge-UE list, the determination unit 307 determines that the UE 105 is a cell-edge-UE, and the processing proceeds to step S1004. On the other hand, when the UE 105 is not in the cell-edge-UE list, the determination unit 307 determines that it is not a cell-edge-UE, and the processing proceeds to step S1005.

[0079] In step 1004, the allocation unit 305 selects one or more RBs, which have not been allocated by the eNodeB 101 in the current scheduling operation, from the subset reserved for cell-edge-UEs in

accordance with the order corresponding to eNodeB 101, and allocates the selected RBs to the UE 105. Note that when there are no available RBs in the cell-edge- UE reserved subset, non-reserved RBs may be allocated to the UE 105 even though the UE 105 is a cell-edge-UE.

[0080] On the other hand, in step S1005, the eNodeB 101 allocates one of the non-reserved RBs to the UE 105 because the UE 105 is not currently a cell-edge- UE. Note that when there are no available non-reserved RBs, cell-edge-UE reserved RBs may be allocated to the UE 105 even though it is a central-UE.

[0081] By virtue of the processing explained above, it is possible to precisely identify cell-edge-UEs and allocate RBs to them in such as way as to avoid inter- cell co-channel interference. Moreover, this can be accomplished with a minimal load on the X2 interface between eNodeBs. The processing achieves these goals while maintaining an effective frequency reuse factor of 1.

[0082] Fig. 11 is a view for illustrating an organization of wireless resources according to some embodiments .

[0083] As described with reference to Fig.s 2 and

6, in some embodiments, in addition to the subset of RBs reserved for cell-edge-UEs, disjoint subsets of RBs are reserved for allocation to power-reduced-UEs . Note again that the use of the term "reserved" here does not mean that these RBs are allocated exclusively to power- reduced-UEs. Rather they are allocated preferentially to power-reduced-UEs, and may be allocated to non- power-reduced-UEs when all other RBs are exhausted, for example .

[0084] The subsets of RBs reserved for power- reduced-UEs for eNodeBs 101, 102, and 103 are disjoint, that is they do not overlap each other. Because transmission power of the power-reduced-UEs is reduced, the transmission power of power-reduced-UEs does not cause substantial inter-cell co-channel interference for cell-edge-UEs of neighboring cells. Therefore, the eNodeBs 101, 102 and 103 are able to allocate RBs from the power-reduced subsets for their respective

neighboring eNodeBs to cell-edge-UEs without causing substantial interference.

[0085] In some embodiments, information indicating which RBs correspond to the subset of RBs reserved for power-reduced-UEs for each of the eNodeBs 101, 102 and 103 is transmitted from the eNodeB 102 in step S605 of Fig. 6. In some embodiments, this information is stored in a storage medium such as the RAM 302.

[0086] In some embodiments, the allocation unit

305 first allocates the RBs of the power-reduced subsets of the neighboring cells to cell-edge-UEs.

When the power-reduced subset is exhausted, the allocation unit 305 then moves on to the cell-edge-UE reserved subset. This may be advantageous as it may make RB allocation collisions in the cell-edge-UE reserved RB subset less likely.

[0087] Fig. 12 is a flowchart for illustrating processing of the eNodeB 101 (control apparatus) for allocating an RB (wireless resource) to the UE 105 according to some embodiments. In the example shown in Fig. 12, it is assumed that the RB organization explained with reference to Fig. 11 is taken. Note that steps S1002, S1003, S1004 and S1005 are the same as in Fig. 10, and so explanation of these is omitted.

[0088] In step S1201, the acquisition unit 306 acquires information of the subset of RBs reserved for cell-edge-UEs, and a cell-edge-UE allocation order for the eNodeB 101. In addition, the acquisition unit 306 acquires the information of the subset of RBs reserved for power-reduced-UEs , as described with reference to Fig. 11. Note that in some embodiments, this

information is included in the information transmitted from the eNodeB 102 in step S605 of Fig.6, for example. In such a case the acquisition unit 306 may acquire the information from the RAM 302, where it was stored.

[0089] In step S1204, the determination unit 307 determines whether or not there is an RB available in the subsets of RBs reserved for power-reduced RBs for eNodeB 102 and 103. Specifically, it determines whether there exist any RBs in the subsets of RBs reserved for power-reduced-UEs for eNodeB 102 or 103 that have not yet been allocated by the allocation unit 305 in the current scheduling operation. In a case where there does not exist an available RB reserved for power-reduced-UEs for eNodeB 102 or 103, the processing proceeds to step S1004. In a case where there does exist an available RB reserved for power-reduced-UEs for eNodeB 102 or 103, the processing proceeds to step S1207.

[0090] In step S1207, the allocation unit 305 selects the RB of the subset reserved for power- reduced-UEs for the neighboring cell determined to be available in step S1204, and allocates the RB to the UE 105.

[0091] By virtue of the processing explained above, it is possible to further avoid inter-cell co-channel interference by putting off allocation of RBs to cell- edge-UEs that have the potential to cause inter-cell co-channel interference.

[ 0092 ] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.

Claims

1. A control apparatus (101), for use in an OFDMA- based communication system including the control apparatus serving a serving cell and a neighboring control apparatus (102) serving a neighboring cell, operable to allocate wireless resources from a

plurality of wireless resources to user equipments of the serving cell, the neighboring control apparatus also being operable to allocate wireless resources from the plurality of wireless resources to user equipments of the neighboring cell, the control apparatus

comprising :

an acquisition unit (306) configured to acquire reserved resource information and order information, the reserved resource information indicating a first reserved subset of the plurality of wireless resources reserved for allocation to cell-edge user equipments, the order information indicating a first order

according to which wireless resources of the first reserved subset are allocated to cell-edge user equipments of the serving cell, and the first order being different from a second order according to which wireless resources of the first reserved subset are allocated to cell-edge user equipments of the

neighboring cell;

a communication unit (304) configured to receive a measurement report message from a first user equipment of the serving cell, the measurement report message including information indicating whether or not a value of a signal measurement for the neighboring cell is within a predetermined threshold from a value of the signal measurement for the serving cell;

a determination unit (307) configured to

determine whether or not the first user equipment is a cell-edge user equipment based on the measurement report message received by the communication unit; and an allocation unit (305) configured to, if the first user equipment is determined to be the cell-edge user equipment, select a wireless resource, which has not been allocated by the control apparatus, from the first reserved subset in accordance with the first order, and allocate the selected wireless resource to the first user equipment.

2. The control apparatus according to claim 1, wherein :

the determination unit determines that the first user equipment is the cell-edge user equipment when the measurement report message indicates that the value of the signal measurement for the neighboring cell is within the predetermined threshold from the value of the signal measurement for the serving cell, and determines that the first user equipment is not the cell-edge user equipment when the measurement report message indicates that the value of the signal

measurement for the neighboring cell is not within the predetermined threshold from the value of the signal measurement for the serving cell.

3. The control apparatus according to claim 1 or 2, wherein

the first order and the second order are

determined based on a first weighting for the control apparatus and a second weighting for the neighboring control apparatus.

4. The control apparatus according to claim 3, wherein

the first weighting and the second weighting are determined based on cell condition information of the control apparatus and the neighboring control apparatus.

5. The control apparatus according to claim 4, wherein

the cell condition information of the control apparatus and the neighboring control apparatus

includes ratios of user equipments that are cell-edge user equipments to the total number of user equipments in the respective cell.

6. The control apparatus according to claim 4, wherein

includes a number of handovers that occurred for the serving cell over a predetermined period of time and a number of handovers that occurred for the neighboring cell over the predetermined period of time .

7. The control apparatus according to claim 4, wherein

includes priority of neighbor relation information.

8. The control apparatus according to any one of claims 1-7, wherein

the acquisition unit further acquires information indicating a second reserved subset of the plurality of wireless resources for allocation to power-reduced users by the neighboring control apparatus, the power- reduced users being user equipments served by the neighboring control apparatus for which a transmission power is less than a predetermined amount, and

the allocation unit, if the first user equipment is determined to be the cell-edge user equipment,

when there exists a wireless resource of the second reserved subset that has not been allocated by the control apparatus, allocates the wireless resource to the first user equipment, and

when there does not exist a wireless resource of the second reserved subset has not been allocated by the control apparatus, selects a wireless resource from the first reserved subset in accordance with the first order, and allocates the selected wireless resource to the first user equipment.

9. The control apparatus according to any of claims 1-8, wherein:

the serving cell is a primary cell of the first user equipment.

10. A user equipment (105) for use in an OFDMA-based communication system including a control apparatus (101) serving a serving cell and a neighboring control apparatus (102) serving a neighboring cell, the user equipment comprising:

a measurement unit (405) configured to perform a signal measurement for the neighboring cell and to perform the signal measurement for the serving cell in accordance with a measurement control message from the control apparatus;

an analysis unit (406) configured to determine whether or not a value of the signal measurement for the neighboring cell is within a predetermined threshold from a value of the signal measurement for the serving cell;

a generation unit (407) configured to generate a measurement report message indicating whether or not the value of the signal measurement for the neighboring cell is within the predetermined threshold from the value of the signal measurement for the serving cell in accordance with the determination of the analysis unit; and

a communication unit (404) configured to transmit the measurement report message to the control apparatus, which determines whether or not the user equipment is a cell-edge user equipment based on the measurement report message.

11. The user equipment according to claim 10,

wherein :

the user equipment is determined to be the cell- edge user equipment when the measurement report message indicates that the value of the signal measurement for the neighboring cell is within the predetermined

threshold from the value of the signal measurement for the serving cell, and the user equipment is determined not to be the cell-edge user equipment when the

measurement report message indicates that the value of the signal measurement for the neighboring cell is not within the predetermined threshold from the value of the signal measurement for the serving cell.

12. The user equipment according to claim 10 or 11, wherein :

the serving cell is a primary cell of the user equipment .

13. A method of controlling a control apparatus (101), for use in an OFDMA-based communication system

including the control apparatus serving a serving cell and a neighboring control apparatus (102) serving a neighboring cell, the control apparatus operable to allocate wireless resources from a plurality of

wireless resources to user equipments of the serving cell, the neighboring control apparatus also being operable to allocate wireless resources from the plurality of wireless resources to user equipments of the neighboring cell, the method comprising:

an acquisition step of acquiring (S1001, S1002) reserved resource information and order information, the reserved resource information indicating a first reserved subset of the plurality of wireless resources reserved for allocation to cell-edge user equipments, the order information indicating a first order

neighboring cell;

a communication step of receiving (S702) a measurement report message from a first user equipment of the serving cell, the measurement report message including information indicating whether or not a value of a signal measurement for the neighboring cell is within a predetermined threshold from a value of the signal measurement for the serving cell;

a determination step of determining (S1003) whether or not the first user equipment is a cell-edge user equipment based on the measurement report message received in the communication step; and

an allocation step of, if the first user

equipment is determined to be the cell-edge user equipment, selecting (S1005) a wireless resource, which has not been allocated by the control apparatus, from the first reserved subset in accordance with the first order, and allocating the selected wireless resource to the first user equipment.

14. A method of controlling a user equipment (105) for use in an OFDMA-based communication system

including a control apparatus (101) serving a serving cell and a neighboring control apparatus (102) serving a neighboring cell, the method comprising:

a measurement step (S607, S802) of performing a signal measurement for the neighboring cell and

performing the signal measurement for the serving cell in accordance with a measurement control message from the control apparatus;

an analysis step (S803) of determining whether or not a value of the signal measurement for the

neighboring cell is within a predetermined threshold from a value of the signal measurement for the serving cell ;

a generation step (S804) of generating a

measurement report message indicating whether or not the value of the signal measurement for the neighboring cell is within the predetermined threshold from the value of the signal measurement for the serving cell in accordance with the determination of the analysis step; and

a communication step (S805) of transmitting the measurement report message to the control apparatus, which determines whether or not the user equipment is a cell-edge user equipment based on the measurement report message.

15. An OFDMA-based communication system comprising a control apparatus (101) serving a serving cell and operable to allocate wireless resources from a

plurality of wireless resources to user equipments of the serving cell, a neighboring control apparatus (102) serving a neighboring cell and also operable to

allocate wireless resources from the plurality of wireless resources to user equipments of the

neighboring cell, and a user equipment (105) served by the control apparatus, wherein

the control apparatus comprises:

neighboring cell;

a communication unit (304) configured to receive a measurement report message from the user equipment of the serving cell, the measurement report message including information indicating whether or not a value of a signal measurement for the neighboring cell is within a predetermined threshold from a value of the signal measurement for the serving cell;

a determination unit (307) configured to

determine whether or not the user equipment is a cell- edge user equipment based on the measurement report message received by the communication unit; and

an allocation unit (305) configured to, if the user equipment is determined to be the cell-edge user equipment, select a wireless resource, which has not been allocated by the control apparatus, from the first reserved subset in accordance with the first order, and allocate the selected wireless resource to first user equipment,

and the user equipment comprises:

an analysis unit (406) configured to determine whether or not a value of the signal measurement for the neighboring cell is within a predetermined

threshold from a value of the signal measurement for the serving cell;

a generation unit (407) configured to generate the measurement report message in accordance with the determination of the analysis unit; and a communication unit (404) configured to transmit the measurement report message to the control apparatus.