WO2012081063A1

WO2012081063A1 - Base station and configuration method of radio resources

Info

Publication number: WO2012081063A1
Application number: PCT/JP2010/007333
Authority: WO
Inventors: Boonsarn Pitakdumrongkija; Hiroaki Aminaka
Original assignee: Nec Corporation
Priority date: 2010-12-17
Filing date: 2010-12-17
Publication date: 2012-06-21
Also published as: JP2013546208A; JP5664944B2

Abstract

A base station located inside a first radio coverage of a first base station in a communications system, wherein the base station has smaller transmit power than the first base station, includes: a storage section for storing system resource assignment information on system radio resources divided into a first part and a second part, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and a controller for differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the base station according to the system resource assignment information.

Description

BASE STATION AND CONFIGURATION METHOD OF RADIO RESOURCES

The present invention relates to a radio communications system in a heterogeneous network, and more particularly to a technique of configuring radio resources in the radio communications system.

3GPP (3rd Generation Partnership Project) LTE-Advanced (Long Term Evolution Advanced) has been considering a heterogeneous cellular network for enhancing capacity and/or radio coverage of a macro-cellular network, which is constructed from only macro base stations (hereafter referred to as MeNB (Macro evolved Node B)). The heterogeneous cellular network is a network with deployment of different types of base stations such that low power nodes (LPNs) are embedded in the macro-cellular network. The LPN can provide an access to the core network for a user terminal (hereafter referred to as UE (User Equipment)) through a radio link similar to the MeNB, although it has a smaller transmit power than the MeNB. Examples of network nodes that are classified as LPNs are PeNB (Pico eNB), HeNB (Home eNB), and RN (Relay Node). The PeNB is a LPN with a wireline backhaul connection to the core network and it is open-access to all UEs. The HeNB is a LPN with a wireline backhaul connection to the core network and it only allows UEs belonging to a closed-subscriber group (CSG) to access. The RN is a LPN which connects to the core network through the MeNB via a wireless backhaul link and it is open-access to all UEs. As an example of major RN deployment scenario, the MeNB which manages the RN is configured to assign a part of time-domain resources denoted as backhaul subframes in system radio resources for communicating with the RN. On the other hand, at another part of time-domain resources, the MeNB and RN can simultaneously communicate with their respective UEs (see NPL1).

In this specification, the term LPN is used to refer to PeNB, HeNB, or RN commonly and the term LPN-UE is used to refer to the UE that establishes connection with the LPN. On the other hand, the terms PeNB-UE, HeNB-UE, and RN-UE are used to refer to the UEs that establish connections specifically with the PeNB, HeNB, and RN, respectively. Also, the term MeNB-UE is used to refer to the UE that establishes connection with the MeNB.

Currently, one of the issues about the heterogeneous network being considered in 3GPP RAN Working Groups (RAN WGs) is the interference between the MeNB and LPN when they communicate control channel, user data, and reference signal with their respective UEs on the same carrier frequency (see NPL2). The issue can be further divided into the case of the MeNB causing the interference to the LPN and the opposite case.

As one of major interference scenarios from LPN to MeNB-UE in a heterogeneous network, there is a problem of the LPN causing severe interference to the MeNB-UE especially that locates close to the LPN. This results in the degradation of throughput performance at the MeNB-UE. In order to address such interference problems, NPL3 discloses several techniques used to protect macro downlink control channels, such as time shifting for overlapped carriers, carrier offsetting and power control. For example, when LPN and MeNB are time-synchronized, the time shifting of LPN transmission relative to MeNB down link frame timing can be used. In the case of performing power control, LPN sets its own transmit power by measuring surrounding RF conditions of macro cells to mitigate interference to MeNB-UE and maintain good LPN coverage for LPN-UE.

{NPL 1} 3GPP TR 36.814 v9.0.0 (2010-03), "Further Advancements for E-UTRA physical layer aspects"
{NPL 2} 3GPP RP-100383, "New Work Item Proposal: Enhanced ICIC for non-CA based deployments of heterogeneous networks for LTE"
{NPL 3} 3GPP TR 36.921 v9.0.0 (2010-03), "HeNB RF requirements analysis"

Summary

When the heterogeneous network employs the techniques disclosed in NPL3, a transmit power or an amount of system radio resources assigned for transmitting to the LPN-UE of the LPN is statically or semi-statically controlled based on the assumption that the MeNB always transmits user data to the MeNB-UE and the LPN always generates interference to the MeNB-UE. However, since the MeNB does not always transmit user data to the MeNB-UE in reality, the method disclosed in NPL3 would more than necessarily control the transmit power or the amount of assigned resources at the LPN. Therefore, the problem of throughput performance degradation at the LPN still remains.

Accordingly, the present invention has been accomplished in consideration of the above mentioned problems, and an object thereof is to provide a base station in a communications system and a radio resource configuration method that can improve the throughput performance of a low power node without causing additional interference to the communication at a macro base station in a heterogeneous network.

According to the present invention, a base station located inside a first radio coverage of a first base station in a communications system, wherein the base station has smaller transmit power than the first base station, includes: a storage section for storing system resource assignment information on system radio resources divided into a first part and a second part, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and a controller for differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the base station according to the system resource assignment information.
According to the present invention, a base station having a radio coverage in which a low power node is located, wherein the low power node has smaller transmit power than the base station, includes: a storage section for storing system resource assignment information on system radio resources divided into a first part and a second part; and a scheduler for performing a user data communication function of transmitting user data to a terminal connecting to the base station when the first part is assigned and performing at least one function other than the user data communication when the second part is assigned, wherein the low power node changes at least one radio link parameter for data transmission of the low power node differentiates configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the low power node according to the system resource assignment information.

According to the present invention, a communications system includes: a first base station; at least one second base station inside a radio coverage of the first base station, wherein the second base station has smaller transmit power than the first base station; and at least one terminal connecting to each of the first and second base stations, wherein the first base station comprises: a first storage section for storing system resource assignment information on system radio resources divided into a first part and a second part; and a scheduler for performing a user data communication function of transmitting user data to a terminal connecting to the first base station when the first part is assigned and performing at least one function other than the user data communication when the second part is assigned, wherein the second base station comprises: a second storage section for storing the system resource assignment information, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and a controller for differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the second base station according to the system resource assignment information.

According to the present invention, a configuration method for radio resources in a base station located inside a first radio coverage of a first base station in a communications system, wherein the base station has smaller transmit power than the first base station, including the steps of: storing system resource assignment information on system radio resources divided into a first part and a second part, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the base station according to the system resource assignment information.
According to the present invention, a configuration method for radio resources in a base station having a radio coverage in which a low power node is located, wherein the low power node has smaller transmit power than the base station, including the steps of: storing system resource assignment information on system radio resources divided into a first part and a second part; performing a user data communication function of transmitting user data to a terminal connecting to the base station when the first part is assigned; and performing at least one function other than the user data communication when the second part is assigned, wherein the low power node differentiates configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the low power node according to the system resource assignment information.

As described above, according to the present invention, the throughput performance of a low power node can be improved without causing additional interference to the communication at a macro base station in a heterogeneous network.

{Fig. 1} Fig. 1 is a schematic diagram showing a radio communications system which is used in common for exemplary embodiments of the present invention.
{Fig. 2} Fig. 2 is a block diagram of an exemplary configuration of a first base station which is common for exemplary embodiments of the present invention.
{Fig. 3} Fig. 3 is a block diagram of an exemplary configuration of a second base station which is common for exemplary embodiments of the present invention.
{Fig. 4} Fig. 4 is a block diagram of an exemplary configuration of a user terminal which is common for exemplary embodiments of the present invention
{Fig. 5} Fig. 5 is a schematic diagram showing a configuration of system radio resources used by MeNB and LPN and a configuration of transmit power of the LPN according to a first exemplary embodiment of the present invention.
{Fig. 6} Fig. 6 is a sequence diagram showing a radio link parameter configuration method at a second base station according to the first exemplary embodiment.
{Fig. 7} Fig. 7 is a flow chart of an exemplary operation at the second base station according to the first exemplary embodiment.
{Fig. 8} Fig. 8 is a schematic diagram of another configuration of system radio resources according to the first exemplary embodiment.
{Fig. 9} Fig. 9 is a schematic diagram of the configuration of system radio resources used by MeNB and LPN and a configuration of a proportion of second resource portions with respect to the system radio resources according to the first exemplary embodiment.
{Fig. 10} Fig. 10 is a schematic diagram showing a configuration of system radio resources and a configuration of transmit power of the LPN according to a second exemplary embodiment of the present invention.
{Fig. 11} Fig. 11 is a sequence diagram showing a radio link parameter configuration method at a second base station according to the second exemplary embodiment.
{Fig. 12} Fig. 12 is a flow chart of an exemplary operation at a first base station according to the second exemplary embodiment.
{Fig. 13} Fig. 13 is a schematic diagram showing a radio communication system according to a third exemplary embodiment of the present invention.
{Fig. 14} Fig. 14 is a sequence diagram showing a radio link parameter configuration method at a second base station according to the third exemplary embodiment.
{Fig. 15} Fig. 15 is a flow chart of an exemplary operation at a first base station according to the third exemplary embodiment.
{Fig. 16} Fig. 16 is a flow chart of an exemplary operation at a third base station according to the third exemplary embodiment.
{Fig. 17} Fig. 17 is a schematic diagram showing a radio communication system according to a fourth exemplary embodiment of the present invention.
{Fig. 18} Fig. 18 is a sequence diagram showing a radio link parameter configuration method at a second base station according to the fourth exemplary embodiment.
{Fig. 19} Fig. 19 is a flow chart of an exemplary operation at a first base station according to the fourth exemplary embodiment.
{Fig. 20} Fig. 20 is a flow chart of an exemplary operation at a second base station according to the fourth exemplary embodiment.

Detailed Description of Preferred Embodiments

The preferred embodiments of the present invention will be explained by making references to the accompanied drawings.

1. System
In the following, the details disclosed in this section of the specification are assumed to be common for all embodiments to be described later unless explicitly stated otherwise.

As shown in Fig. 1, it is assumed for simplicity that a radio communication system includes a first base station 10, a second base station 20, a terminal 30A connecting to the first base station 10, and a terminal 30B connecting to the second base station 20. In this figure, the first base station 10, the second base station 20, the terminal 30A and the terminal 30B correspond to MeNB, LPN, MeNB-UE and LPN-UE as mentioned above, respectively. Hereafter, these abbreviations are used.

The MeNB 10 creates a radio coverage of MeNB-cell 51 and the LPN 20 creates a smaller radio coverage of LPN-cell 52 inside the MeNB-cell 51. The MeNB 10 and LPN 20 share the same system radio resources 40 (e.g. frequencies) for communicating user data with the MeNB-UE and LPN-UE, respectively. The details of the system radio resources will be described later. In the following explanation, it is assumed that the radio communication system is an OFDMA (Orthogonal Frequency Division Multiple Access) radio communication system such as LTE-Advanced.

1.1) Macro Base Station (MeNB)
As shown in Fig. 2, the MeNB 10 is provided with a radio communication section 101 which performs radio communications with the MeNB-UEs 30A and/or Relay Node (hereafter referred to as RN) through an antenna. The radio communication section 101 receives uplink signals from the MeNB-UEs 30A and/or RN and outputs the uplink received signals to a reception data processor 102. The reception data processor 102 performs procedures including signal combining, demodulation, and channel decoding to retrieve user data from the uplink received signals. The resulting received user data are forwarded to the core network through a communication section 103.

A transmission data processor 104 receives user data from the core network through the communication section 103 and performs channel encoding, rate matching, and interleaving on the user data in order to create transport channels. Then, the transmission data processor 104 adds control information to the transport channels and creates radio frames. The transmission data processor 104 also performs symbol mapping and creates transmission symbols. The radio communication section 101 modulates and amplifies transmission symbols to create downlink signals and then transmits the downlink signals to the MeNB-UEs 30A through the antenna.

A scheduler 105 controls radio resource allocation for transmitting and receiving user data to and from the MeNB-UEs 30A, respectively, by referring to assignment information of system radio resources at the MeNB 10 (hereinafter, referred to as system resource assignment information) stored in a memory 106. The assignments of system radio resources are determined in advance such that one part of system radio resources is assigned for the MeNB 10 to communicate user data with the MeNB-UEs 30A and another part for the MeNB 10 to perform at least one function other than the function of communicating user data with the MeNB-UEs 30A. The details of the assignments and method to determine the assignments will be described later.

The scheduler 105 can also send the system resource assignment information stored in the memory 106 to the LPN 20 over the radio link through the transmission data processor 104, the radio communication section 101, and the antenna, or send over the core network through the reception data processor 102 and the communication section 103. It should be noted that the scheduler 105 may be implemented by software programs running on a program-controlled processor such as a CPU (central processing unit).

1.2) Low Power Base Station (LPN)
As shown in Fig. 3, it is assumed that the LPN 20 has the same functionalities as the MeNB 10 with some exceptions that will be explained explicitly. A radio communication section 201, similar to the radio communication section 101 of the MeNB 10, receives uplink signals from the LPN-UEs 30B through an antenna. A reception data processor 202, similar to the reception data processor 102 of the MeNB 10, forwards the received user data to the core network or MeNB through a communication section 203. A transmission data processor 204, similar to the transmission data processor 104 of the MeNB 10, creates transmission symbols based on user data received from the core network or MeNB through the communication section 203. Then, the radio communication section 201 creates downlink signals from the transmission symbols and transmits them to the LPN-UEs 30B.

A scheduler 205 controls radio resource allocation for transmitting and receiving user data to and from the LPN-UEs 30B, respectively, by considering the configuration of system radio resources provided by a resource configuration controller 207. The resource configuration controller 207 configures radio link parameters of the system radio resources for communicating user data with the LPN-UEs 30B based on the system resource assignment information stored in a memory 206. The radio link parameters can be a transmit power and/or a proportion of resources to be assigned for communicating user data with the LPN-UEs 30B with respect to the system radio resources. The system resource assignment information can be received from the MeNB over the radio link through the radio communication section 201 and the reception data processor 202 or over the core network through the communication section 203 and the transmission data processor 204. The received system resource assignment information is stored in the memory 206 through the scheduler 205 and resource configuration controller 207. Alternatively, the system resource assignment information can be predefined and stored in the memory 206 by network operators. The resource configuration controller 207 can also send the configured transmit power information to the LPN-UE 30B through the scheduler 205, the transmission data processor 204, the radio communication section 201, and the antenna. It should be noted that the scheduler 205 and the resource configuration controller 207 may be implemented by software programs running on a program-controlled processor such as a CPU (central processing unit).

1.3) Terminal (UE)
Fig. 4 shows an exemplary configuration of the UE 30, which implies both the MeNB-UE 30A and LPN-UE 30B. A radio communication section 301 receives downlink signals from the MeNB 10 or the LPN 20 through an antenna. A reception data processor 302 performs a process for retrieving user data from the received downlink signals and forwards the user data to a processor 304 which controls the operations of the UE 30. The reception data processor 302 can also receive the configured transmit power information from the LPN 20 through the radio link communication section 301 and store it in a memory 303. Based on the configured transmit power information, the reception data processor 302 can configure a power offset value in calculating the RSRP (Reference Signal Received Power) or RSRQ (Reference Signal Received Quality), which indicates the quality of the radio link between the LPN 20 and the LPN-UE 30B. When user data to be transmitted are generated, the processor 304 outputs the user data under the control of a transmission data controller 305 to a transmission data processor 306. The radio communication section 301 create uplink signals from the user data received from the transmission data processor 306, and transmits them to the MeNB 10 or the LPN 20.

2. First exemplary embodiment
The first exemplary embodiment shows a case of the LPN 20 configuring a transmit power as the radio link parameter of system radio resources for transmitting user data to the LPN-UE 30B based on the assignment information of the system radio resources at the MeNB 10. Since this embodiment assumes a similar radio communication system as above-described in Figs. 1 to 4, their descriptions are omitted. The details specific to this embodiment will be described with references to Figs. 5-8.

2.1) Example of Resource configuration
As an example for explaining the present embodiment, Fig. 5 shows a configuration of the system radio resources 40 used by the MeNB 10 and LPN 20 and controlled transmit powers of the LPN 20 according to the configured system radio resources. In this resource configuration, the system radio resources 40 are divided in time domain into first resource portions 41 and second resource portions 42.

At the MeNB 10, the system radio resources are assumed to be configured in advance as shown in Fig. 5. The MeNB 10 is configured to assign the first resource portions 41 for transmitting user data to the MeNB-UE 30A and the second resource portions 42 for other functions than transmitting user data to the MeNB-UE 30A. At the LPN, the configuring radio link parameter of the system radio resources is assumed to be its own transmit power. As shown in Fig. 5, during a period of time corresponding to each first resource portion 41 for MeNB 10 to transmit user data to MeNB-UE, the transmit power of the LPN 20 is reduced to a power value P1 which is smaller than its maximum transmit power P2 (=Pmax) by a predetermined power reduction value, delta-P (denoted by uppercase Greek character in Figs. 5-7). The power reduction value, delta-P, is determined so as to obtain effective mitigation of interference from LPN to MeNB-UE. During a period of time corresponding to each second resource portion 42 when the MeNB 10 transmits no user data to the MeNB-UE 30A, the LPN 20 sets its transmit power to an increased power value or a normally preset power value for transmitting user data to the LPN-UE 30B. In this manner, the radio link parameter for the LPN 20 is controlled depending on which of the first resource portion 41 and the second resource portion 42 is scheduled according to the system resource assignment information.

2.2) Operation
As shown in Fig. 6, the system resource assignment information received from the MeNB 10 or preset by operators as described above is stored in the memory 206 of the LPN 20 (step S1101). Then, the resource configuration controller 207 of the LPN 20 configures the transmit power for transmitting user data to the LPN-UE 30B based on the system resource assignment information at the MeNB 10 stored in the memory 206 (step S1102).

At the time indexes each corresponding to the first resource portions 41, the resource configuration controller 207 configures the transmit power to be P1, which is obtained by the maximum transmit power (Pmax) of the LPN 20 minus a predefined power reduction value (delta-P) (step S1103). Then, the resource configuration controller 207 controls the scheduler 205 to assign the first resource portions 41 for transmitting user data to the LPN-UE 30B with the configured transmit power P1 (step S1104). After that, the LPN 20 transmits user data to the LPN-UE 30B (step S1105).

On the other hand, at the time indexes each corresponding to the second resource portions 42, the resource configuration controller 207 configures the transmit power to be P2, which is equal to Pmax (step S1106). Then, the resource configuration controller 207 controls the scheduler 205 to assign the second resource portions 42 for transmitting user data to the LPN-UE 30B with the configured transmit power P2 (step S1107). Then, the LPN 20 transmits the user data to the LPN-UE 30B (step S1108).

In Fig. 7, It is assumed that the memory 206 has already stored the system resource assignment information as described above. At step S1201, the scheduler 205 determines whether it is a starting of a new time index for user data transmission. If it is not yet the time (No of S1201), the scheduler 205 repeats the step S1201. If it is the time (Yes of S1201), the scheduler 205 instructs the resource configuration controller 207 to read the system resource assignment information from the memory 206 (step S1202). Then, the resource configuration controller 207 determines which portion of radio resources the current time index corresponds to (step S1203). If the current time index corresponds to the first resource portion (First resource portions of S1203), the resource configuration controller 207 configures the transmit power to be P1 = Pmax - delta-P (step S1204) and controls the scheduler 205 to assign the first resource portions 41 for transmitting user data to the LPN-UE 30B with the configured transmit power P1 (step S1205).

On the other hand, if the current time index corresponds to the second resource portions (Second resource portions of S1203), the resource configuration controller 207 configures the transmit power to be P2 = Pmax (step S1206) and controls the scheduler 205 to assign the second resource portions 42 for transmitting user data to the LPN-UE 30B with the configured transmit power P2 (step S1207). After the assignment is completed (step S1205 or S1207), the LPN 20 transmits user data to the LPN-UE 30B with the configured transmit power (step S1208). Then, the process returns to step S1201. Since an operation of the UE as shown in Fig. 4 is a general knowledge for those who have skills in the related art, its explanation is omitted.

2.3) Other examples
A resource configuration of the system radio resources 40 as disclosed in Fig. 5 is shown for the purpose of explanation and the present embodiment should not be limited to this example. As another example, the system radio resources can be divided into two separate sets of time-frequency coordinated resource: a first set of first resource portions 41 and a second set of second resource portions 42 as shown in Fig. 8. The MeNB 10 transmits user data to MeNB-UE using the first resource portions 41 and performs other functions than the transmission of user data using the second resource portions 42. In this case, the LPN configures the transmit power of itself such that the transmit power in second resource portions 42 is larger than that in the first resource portions 41.

Also, the configuration of the transmit powers P1 and P2 as described above is shown for the purpose of explanation and the present embodiment should not be limited to the example. As another example, the transmit power P1 can be a predefined transmit power (Pdef) less than Pmax and the transmit power P2 can be Pdef pluses a predefined power boosting value.

Referring to Fig. 9, as a configuring radio link parameter at the LPN 20, instead of the transmit power, a proportion of resources assigned for transmitting user data to the LPN-UE 30B with respect to the system radio resources may be used. In this case, under the assumption of system radio resources as disclosed in Fig. 8, the LPN 20 configures the proportion of second resource portion (R2) to be larger than that of first resource portions (R1) at each time index. Such proportion configuration is considered to be as effective as configuring the transmit power as described above. Also, it is also effective to configure both the transmit power and the assigned resources proportion.

2.4) Advantageous Effects
As described above, the resource configuration according to the present embodiment enables the LPN 20 to increase its transmit power for transmitting user data to the LPN-UE 30B when the MeNB 10 does not transmits user data to the MeNB-UE 30A. This improves a signal to interference plus noise ratio (SINR) in the radio link between the LPN 20 and the LPN-UE 30B. Therefore, the throughput performance of the LPN 20 can be improved due to the improved SINR without causing additional interference to MeNB-UE 30A.

3. Second exemplary embodiment
The second exemplary embodiment shows a case of the MeNB 10 assigning the second resource portions for limited usage of transmitting control channel and/or reference signal so as to obtain effective mitigation of interference from MeNB to LPN-UE. Since this embodiment assumes a similar radio communication system as above-described in Figs. 1-4, their descriptions are omitted. The details specific to this embodiment will be described with references to Figs. 10-12.

3.1) Example of Resource configuration
As an example for explaining the present embodiment, Fig. 10 shows a configuration of the system radio resources 40 used by the MeNB 10 and LPN 20 and controlled transmit powers of the LPN 20 according to the configured system radio resources. In this resource configuration, the system radio resources 40 are divided in time domain into first resource portions 41 and second resource portions 42. It should be noted that the present embodiment can be also applied to the system radio resources which are divided into two separate sets of time-frequency coordinated resource: a first set of first resource portions 41 and a second set of second resource portions 42, as shown in Fig. 8.

At the MeNB 10, the system radio resources are assumed to be configured in advance as shown in Fig. 10. The MeNB 10 is configured to assign the first resource portions 41 for transmitting user data to the MeNB-UE 30A and the second resource portions 42 for limited usage of transmitting control channel and/or reference signal. At the LPN, the configuring radio link parameter of the system radio resources is assumed to be its own transmit power. As shown in Fig. 10, during a period of time corresponding to each first resource portion 41 for MeNB 10 to transmit user data to MeNB-UE, the transmit power of the LPN 20 is reduced to a power value P1 which is smaller than its maximum transmit power P2 (=Pmax) by a predetermined power reduction value, delta-P (denoted by uppercase Greek character in Figs. 10 and 11). The power reduction value, delta-P, is determined so as to obtain effective mitigation of interference from LPN to MeNB-UE. During a period of time corresponding to each second resource portion 42, the LPN 20 sets its transmit power to an increased power value for transmitting user data to the LPN-UE 30B while the MeNB 10 limits transmission to control channel and/or reference signal.

3.2) Operation
Fig. 11 shows an exemplary sequence diagram of the second exemplary embodiment according to the above assumptions. Since steps of operation of the LPN 20 in this embodiment are the same as the steps S1101 to S1108 of the first exemplary embodiment in Fig. 6, the same reference numerals are used in Fig. 10 and their explanations are omitted.

Referring to Fig. 11, at step S1301, the predefined system resource assignment information at the MeNB 10 as described above are stored in the memory 106. At the time index corresponding to a first resource portion, the scheduler 105 assigns the first resource portion for transmitting user data to the MeNB-UE 30A based on the system resource assignment information stored in the memory 106 (step S1302). Then, the MeNB 10 transmits user data to the MeNB-UE 30A (step S1303). On the other hand, at the time index corresponding to a second resource portion, the scheduler 105 limits the resource assignment and transmission processes (step S1304). Since the operation of the LPN 20 in this embodiment is the same as that of the first embodiment, their explanations are omitted.

Referring to Fig. 12, it is assumed that the memory 106 has already stored the system resource assignment information at the MeNB 10 as described above. At step S1401, the scheduler 105 determines whether it is a starting of a new time index for user data transmission (step S1401). If it is not yet the time (No of S1401), the scheduler 105 repeats the step S1401. If it is the time (Yes of S1401), the scheduler 105 reads the system resource assignment information at the MeNB from the memory 106 (step S1402). Then, the scheduler 105 determines which portion of radio resources the current time index corresponds to (step S1403).

If the current time index corresponds to the first resource portion (First resource portion of S1403), the scheduler 105 assigns the first resource portion for transmitting user data to the MeNB-UE 30A (step S1404). Then, the user data are transmitted to the MeNB-UE 30A through the radio communication section 101 (step S1405). On the other hand, if the current time index corresponds to the second resource portions (Second resource portions of S1403), the scheduler 105 limits the assignment and transmission of the second resource portion (step S1406). After the transmission (step S1405) or the limited of assignment and transmission (step S1406), the process returns to step S1401. Since an operation of the UE as shown in Fig. 4 is a general knowledge for those who have skills in the related art, its explanation is omitted.

The assignment of the system radio resources at the MeNB as described above is shown for the purpose of explanation and the present embodiment should not be limited to the method. As another example, instead of or in addition to the transmit power, the LPN 20 can also configure the proportion of resources assigned for transmitting user data to the LPN-UE 30B with respect to the system radio resources as disclosed in the first exemplary embodiment.

3.3) Advantageous Effects
As described above, the resource configuration according to the present embodiment enables the mitigation of interference at the LPN-UE 30B from the MeNB 10 in addition to the LPN 20 increasing its transmit power for transmitting user data to the LPN-UE 30B when the MeNB 10 limits its transmission process. This further improves signal to interference plus noise ratio (SINR) in the radio link between the LPN 20 and the LPN-UE 30B as compared with the first exemplary embodiment. Therefore, the throughput performance of the LPN 20 can also be further improved without causing additional interferences of both the LPN 20 to the MeNB-UE 30A and the MeNB 10 to the LPN-UE 30B.

4. Third exemplary embodiment
While the second exemplary embodiment shows the case of the MeNB 10 assigning the second resource portions for limited transmission for mitigation of interference from MeNB to LPN-UE, the third exemplary embodiment shows a case of the MeNB 10 assigning the second resource portions for transmitting user data to a third base station, which is a relay node (RN). The details of this embodiment are described in the following.

4.1) System
As shown in Fig. 13, it is assumed for simplicity that a radio communication system includes a first base station (MeNB) 10, a second base station (LPN) 20, a third base station (RN) 20-1, a terminal connecting to the first base station (MeNB-UE) 30A, a terminal connecting to the second base station (LPN-UE) 30B, and a terminal connecting to the third base station (RN-UE) 30B-1. The MeNB 10, LPN 20, and RN 20-1 create radio coverages of MeNB-cell 51, LPN-cell 52, and RN-cell 52-1, respectively. The MeNB 10, LPN 20, and RN 20-1 use system radio resources 40 for communicating user data with the respective nodes.

Exemplary configurations of the MeNB 10, LPN 20, and UEs including the MeNB-UE 30A, LPN-UE 30B, and RN-UE 30B-1 are assumed to be the same as those disclosed above in Fig. 2, 3, and 4 respectively. Therefore, their explanations are omitted.

An exemplary configuration of the RN 20-1 is assumed to be similar to the configuration of the LPN 20 as disclosed above in Fig. 3 except for that the communication section 203 of the RN 20-1, which has the same function as the communication section 203 of the LPN 20 in Fig. 3, is connecting to the MeNB 10 instead of the core network. Accordingly, when referring to the configuration of the RN 20-1, a suffix "-1" is added to each reference numeral in Fig. 3, such as radio communication section 201-1, reception data processor 202-1, communication section 203-1, transmission data processor 204-1, scheduler 205-1, memory 206-1, and resource configuration controller 207-1.

Exemplary system radio resources 40 as shown in Fig. 5 is assumed. At the MeNB 10, the assignments of the system radio resources as shown in Fig. 5 are assumed to be configured in advance. The MeNB 10 is configured to assign the first resource portions 41 for transmitting user data to the MeNB-UE 30A and the second resource portions 42 for transmitting user data to the RN 20-1. At the LPN 20, the configuring radio link parameter of the system radio resources is assumed to be the transmit power.

4.2) Operation
Fig. 14 shows an exemplary sequence diagram of the second exemplary embodiment according to the above assumptions. Since steps of operation of the LPN 20 in this embodiment are the same as the steps S1101 to S1108 of the first exemplary embodiment in Fig. 6, the same reference numerals are used in Fig. 10 and their explanations are omitted.

Referring to Fig. 14, steps of operation of the MeNB 10 and RN 20-1 are explained in the following. At steps S1501 and S1502, the system resource assignment information at the MeNB 10 as described above is stored in the memory 106 of the MeNB 10 and in the memory 206-1 of the RN 20-1, respectively.

At the time index corresponding to the first resource portions, the scheduler 105 of the MeNB 10 assigns the first resource portions for transmitting user data to the MeNB-UE 30A based on the system resource assignment information stored in the memory 106 (step S1503). Also, the scheduler 205-1 of the RN 20-1, which has the same function as the scheduler 205 of the LPN 20 in Fig. 3, assigns the first resource portions for transmitting user data to the RN-UE 30B-1 based on the system resource assignment information stored in the memory 206-1 (step S1504). Then, the MeNB 10 and RN 20-1 transmit user data to the MeNB-UE 30A (step S1505) and RN-UE 30B-1 (step S1506), respectively.

On the other hand, at the time index corresponding to the second resource portions, the scheduler 105 of the MeNB 10 assigns the second resource portions for transmitting user data to the RN 20-1 (step S1507). Then, the MeNB 10 transmits user data to the RN 20-1 (step S1508).

In Fig. 15, it is assumed that the memory 106 has already stored the system resource assignment information at the MeNB 10 as described above. At step S1601, the scheduler 105 determines whether it is a starting of a new time index for user data transmission. If it is not yet the time (No of S1601), the scheduler 105 repeats the step S1601. If it is the time (Yes of S1601), the scheduler 105 reads the system resource assignment information at the MeNB from the memory 106 (step S1602). Then, the scheduler 105 determines which portion of radio resources the current time index corresponds to (step S1603). If the current time index corresponds to the first resource portions (First resource portion of S1603), the scheduler 105 assigns the first resource portion for transmitting user data to the MeNB-UE 30A (step S1604). Then, the user data are transmitted to the MeNB-UE 30A through the radio communication section 101 (step S1605). On the other hand, if the current time index corresponds to the second resource portion (Second resource portion of S1603), the scheduler 105 assigns the second resource portion for transmitting user data to RN 20-1 (step S1606). Then, the user data are transmitted to the RN 20-1 through the radio communication section 101 (step S1607). After the transmission to the MeNB-UE 30A (step S1605) or RN 20-1 (step S1607), the process returns to step S1601.

In Fig. 16, it is assumed that the memory 206-1 has already stored the system resource assignment information at the MeNB 10 as described above. At step S1701, the scheduler 205-1 determines whether it is a starting of a new time index for user data transmission. If it is not yet the time (No of S1701), the scheduler 205-1 repeats the step S1701. If it is the time (Yes of S1701), the scheduler 205-1 reads the system resource assignment information at the MeNB from the memory 206-1 (step S1702). Then, the scheduler 205-1 determines which portion of radio resources the current time index corresponds to (step S1703). If the current time index corresponds to the first resource portion (First resource portion of S1703), the scheduler 205-1 assigns the first resource portion for transmitting user data to the RN-UE 30B-1 (step S1704). Then, the user data are transmitted to the RN-UE 30B-1 through the radio communication section 201-1, which has the same function as the radio communication section 201 of the LPN 20 in Fig. 3 (step S1705). On the other hand, if the current time index corresponds to the second resource portion (Second resource portion of S1703), the scheduler 205-1 receives user data transmitted from the MeNB 10 (step S1706). After the transmission (step S1705) or reception (step S1706), the process returns to step S1701.

Since an operation of the UE as shown in Fig. 4 is a general knowledge for those who have skills in the related art, its explanation is omitted.

The assignment of the system radio resources at the MeNB as described above is shown for the purpose of explanation and the present embodiment should not be limited to the method. As another example, when the LPN 20 is also another RN different from the RN 20-1, the MeNB 10 can assign different parts of the second resource portions for transmitting user data to the LPN 20 and the RN 20-1. In this case, the LPN 20 can exclude the part for itself and include the part for the RN 20-1 to be assigned for transmitting user data to the LPN-UE 30B in addition to configuring the transmit power in order to be as effective as the example described above.

Moreover, instead of or in addition to the transmit power, the LPN 20 can also configure the proportion of resources assigned for transmitting user data to the LPN-UE 30B with respect to the system radio resources as disclosed in the first exemplary embodiment.

4.3) Advantageous Effects
As described above, the resource configuration according to the present embodiment enables the RN 20-1 to transmits user data to the RN-UE 30B-1 simultaneously with the MeNB 10 and the LPN 20 in addition to the LPN 20 increasing its transmit power for transmitting user data to the LPN-UE 30B when the MeNB 10 is transmitting user data to the RN 20-1. This further improves the throughput performance of the whole system, which includes the MeNB 10, LPN 20, and RN 20-1, as compared with the first exemplary embodiment, without causing additional interference to the MeNB-UE 30A.

5. Fourth exemplary embodiment
While the second exemplary embodiment shows the case of the LPN 20 controlling the transmit power based on the system resource assignment information at the MeNB 10, the fourth exemplary embodiment shows a case of the LPN 20 controlling the transmit power based on the system resource assignment information transmitted by the MeNB 10. The details of this embodiment are described in the following.

5.1) System
Referring to Fig. 17, the communication system includes a first base station (MeNB) 10, a second base station (LPN) 20, a terminal connecting to the first base station (MeNB-UE) 30A, and a terminal connecting to the second base station (LPN-UE) 30B. The MeNB 10 and LPN 20 create radio coverages of MeNB-cell 51 and LPN-cell 52, respectively. The MeNB 10 and LPN 20 use system radio resources 40 for communicating user data with the MeNB-UE 30A and LPN-UE 30B, respectively. A resource assignment information link RL is used to transmit system resource assignment information at the MeNB 10 to the LPN 20.

Exemplary configurations of the MeNB 10, LPN 20, and UEs including the MeNB-UE 30A and LPN-UE 30B are assumed to be the same as those disclosed above in Fig. 2, 3, and 4 respectively. Therefore, their explanations are omitted. An exemplary configuration of the system radio resources 40 as shown in Fig. 5 is assumed, therefore their explanations are omitted.

At the MeNB, the assignments of the system radio resources as disclosed in Fig. 5 are assumed to be configured by the network operators in advance. The MeNB 10 is configured to assign the first resource portions 41 for transmitting user data to the MeNB-UE 30A and the second resource portions 42 for limited usage of transmitting control channel and/or reference signal. It is also assumed that the system resource assignment information that was configured in advance by the network operators has already been stored in the memory 106 of the MeNB 10. At the LPN 20, the configuring radio link parameter of the system radio resources is assumed to be the transmit power.

5.2) Operation
Referring to Fig. 18, the MeNB 10 transmits the system resource assignment information to the LPN 20 through the resource assignment information link RL. Upon receiving the system resource assignment information from the MeNB 10, the LPN 20 stores the system resource assignment information in the memory 206 (step S1802). After that, steps of LPN operation are the same as the steps S1102 to S1108 of the first exemplary embodiment in Fig. 6. Also, steps of MeNB operation are the same as the steps S1302 to S1304 of the second exemplary embodiment in Fig. 11. Therefore, their explanations are omitted.

Fig. 19 shows an exemplary control flow at the MeNB 10 for transmitting user data to the MeNB-UE 30A. It is assumed that the memory 106 has already stored the system resource assignment information as described above. At step S1901, the MeNB 10 transmits the system resource assignment information to the LPN 20 through the resource assignment information link RL. After that, steps of MeNB operation are the same as the steps S1401 to S1406 of the second exemplary embodiment in Fig. 12. Therefore, their explanations are omitted.

Referring to Fig. 20, at step S2001, the scheduler 205 receives the system resource assignment information as described above from the MeNB 10. Then, the scheduler 205 forwards the received system resource assignment information to be stored in the memory 206 through the resource configuration controller 207 (step S2002). After that, steps of LPN operation are the same as the steps S1201 to S1208 of the first exemplary embodiment in Fig. 7. Therefore, their explanations are omitted. An exemplary data receiving operation of the UE is also omitted because it is a general knowledge for those who have skills in the related art.

Since the above-described method to transmit the system resource assignment information to the LPN 20 is shown for the purpose of explanation, the present embodiment should not be limited to be the method. As another example, the system resource assignment information can be transmitted to the LPN 20 through a higher layer network connecting to both the MeNB 10 and LPN 20 such as the core network.

Moreover, the method to transmit the system resource assignment information to the LPN 20 disclosed in this embodiment is also considered to be effective to all of the above preceding exemplary embodiments.

5.3) Advantageous Effects
As described above, the configuration according to the present embodiment enables the MeNB 10 to update the system resource assignment information stored at the LPN 20 when there is a change due to requirement. Therefore, the LPN 20 can adaptively control the transmit power with respect to the change in assignments at the MeNB 10 in addition to the LPN 20 increasing its transmit power for transmitting user data to the LPN-UE 30B when the MeNB 10 limits its transmission process. Therefore, the improvement of throughput performance of the LPN 20 without causing additional interference to the MeNB-UE 30A can achieve robustness against the change in the system resource assignment information at the MeNB 10.

6. Fifth exemplary embodiment
While the first exemplary embodiment shows the case of the LPN 20 configuring the transmit power based on the system resource assignment information at the MeNB 10, the fifth exemplary embodiment shows a case of the LPN 20 transmitting the configured transmit power information to the LPN-UE 30B in addition to the processes in the first exemplary embodiment. The details of this embodiment are described in the following. Since operations regarding configuration of transmit power of the LPN 20 in this embodiment is the same as the first exemplary embodiment disclosed in Fig. 1 to 7, their explanations are omitted.

After the transmit power of the LPN 20 is configured, the configured transmit power information is transmitted from the LPN 20 to the LPN-UE 30B through the radio communication section 201. Upon receiving this information, the reception data processor 302 in the LPN-UE 30B store it in the memory 303. Based on the configured transmit power information, the reception data processor 302 can configure a power offset value in calculating the RSRP or RSRQ, which indicates the quality of the radio link between the LPN 20 and the LPN-UE 30B.

Since the steps of operations at the LPN 20 and LPN-UE 30B as described above are general knowledge for those who have skills in the related art, their sequence diagrams and flow charts are omitted. Moreover, the method to transmit configured transmit power information from the LPN 20 to the LPN-UE 30B disclosed in this embodiment is also considered to be effective to all of the above preceding exemplary embodiments.

As described above, the configuration according to the present embodiment enables the LPN-UE 30B to have an accurate value of radio link quality indicator in addition to the LPN 20 increasing its transmit power for transmitting user data to the LPN-UE 30B when the MeNB 10 assigns the second resource portions for other functions than transmitting user data to the MeNB-UE 30A. Therefore, the accurate operation of the LPN-UE 30B such as the hand over decision can be achieved in addition to the improved throughput performance of the LPN 20 without causing additional interference to MeNB-UE 30A.

7. Supplementary Note
The whole or part of the exemplary embodiments disclosed above can be described as, but not limited to, the following supplementary notes.
(Supplementary note 1)
A base station located inside a first radio coverage of a first base station in a communications system, wherein the base station has smaller transmit power than the first base station, comprising:
a storage section for storing system resource assignment information on system radio resources divided into a first part and a second part, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and
a controller for differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the base station according to the system resource assignment information.
(Supplementary note 2)
The base station according to Supplementary note 1, wherein the controller configures as a radio link parameter a transmit power and/or a proportion of resources for the user data transmission of the base station, wherein the proportion of resources is a ratio of an amount of resources used for user data transmission of the base station with respect to an amount of the system radio resources.
(Supplementary note 3)
The base station according to Supplementary note 2, wherein the controller configures such that the transmit power and/or the proportion of resources when the second part is assigned is larger than when the first part is assigned.
(Supplementary note 4)
The base station Supplementary note 3, wherein the controller controls a transmission section so as to transmit information related to two transmit powers when the first and second parts are assigned, respectively, to the terminal connecting to the base station.
(Supplementary note 5)
The base station according to any one of Supplementary notes 1-4, wherein the system resource assignment information is received from the first base station or a higher-layer network entity connecting the base station and the first base station.
(Supplementary note 6)
A base station having a radio coverage in which a low power node is located, wherein the low power node has smaller transmit power than the base station, comprising:
a storage section for storing system resource assignment information on system radio resources divided into a first part and a second part; and
a scheduler for performing a user data communication function of transmitting user data to a terminal connecting to the base station when the first part is assigned and performing at least one function other than the user data communication when the second part is assigned,
wherein the low power node differentiates configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the low power node according to the system resource assignment information.
(Supplementary note 7)
The base station according to Supplementary note 6, wherein the scheduler transmits a control channel and/or a reference signal to the terminal connecting to the base station when the second part is assigned.
(Supplementary note 8)
The base station according to Supplementary note 6 or 7, wherein the low power node configures as a radio link parameter a transmit power and/or a proportion of resources for the user data transmission of the low power node, wherein the proportion of resources is a ratio of an amount of resources used for user data transmission of the low power node with respect to an amount of the system radio resources.
(Supplementary note 9)
The base station according to Supplementary note 8, wherein the low power node configures such that the transmit power and/or the proportion of resources when the second part is assigned is larger than when the first part is assigned.
(Supplementary note 10)
The base station Supplementary note 9, wherein the low power node controls a transmission section so as to transmit information related to two transmit powers when the first and second parts are assigned, respectively, to the terminal connecting to the low power node.
(Supplementary note 11)
The base station according to any one of Supplementary notes 6-10, wherein the scheduler transmits user data to a relay node connected to the base station using resources of the second part when the second part is assigned, wherein the relay node transmits user data to a terminal connecting to the relay node.
(Supplementary note 12)
A communications system comprising:
a first base station;
at least one second base station inside a radio coverage of the first base station, wherein the second base station has smaller transmit power than the first base station; and
at least one terminal connecting to each of the first and second base stations,
wherein the first base station comprises:
a first storage section for storing system resource assignment information on system radio resources divided into a first part and a second part; and
a scheduler for performing a user data communication function of transmitting user data to a terminal connecting to the first base station when the first part is assigned and performing at least one function other than the user data communication when the second part is assigned,
wherein the second base station comprises:
a second storage section for storing the system resource assignment information, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and
a controller for differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the second base station according to the system resource assignment information.
(Supplementary note 13)
A method for configuring radio resources in a base station located inside a first radio coverage of a first base station in a communications system, wherein the base station has smaller transmit power than the first base station, comprising:
storing system resource assignment information on system radio resources divided into a first part and a second part, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and
differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the base station according to the system resource assignment information.
(Supplementary note 14)
The method according to Supplementary note 13, wherein a transmit power and/or a proportion of resources for the user data transmission of the base station are configured as a radio link parameter, wherein the proportion of resources is a ratio of an amount of resources used for user data transmission of the base station with respect to an amount of the system radio resources.
(Supplementary note 15)
The method according to Supplementary note 14, wherein the transmit power and/or the proportion of resources when the second part is assigned is larger than when the first part is assigned.
(Supplementary note 16)
The method according to Supplementary note 15, wherein information related to two transmit powers when the first and second parts are assigned, respectively, is transmitted to the terminal connecting to the base station.
(Supplementary note 17)
The method according to any one of Supplementary notes 13-16, wherein the system resource assignment information is received from the first base station or a higher-layer network entity connecting the base station and the first base station.
(Supplementary note 18)
A method for configuring radio resources in a base station having a radio coverage in which a low power node is located, wherein the low power node has smaller transmit power than the base station, comprising:
storing system resource assignment information on system radio resources divided into a first part and a second part; and
performing a user data communication function of transmitting user data to a terminal connecting to the base station when the first part is assigned; and
performing at least one function other than the user data communication when the second part is assigned,
wherein the low power node differentiates configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the low power node according to the system resource assignment information.
(Supplementary note 19)
The method according to Supplementary note 18, wherein a control channel and/or a reference signal are transmitted to the terminal connecting to the base station when the second part is assigned.
(Supplementary note 20)
The method according to Supplementary note 18 or 19, wherein the low power node configures as a radio link parameter a transmit power and/or a proportion of resources for the user data transmission of the low power node, wherein the proportion of resources is a ratio of an amount of resources used for user data transmission of the low power node with respect to an amount of the system radio resources.
(Supplementary note 21)
The method according to Supplementary note 20, wherein the low power node configures such that the transmit power and/or the proportion of resources when the second part is assigned is larger than when the first part is assigned.
(Supplementary note 22)
The method according to Supplementary note 21, wherein the low power node controls a transmission section so as to transmit information related to two transmit powers when the first and second parts are assigned, respectively, to the terminal connecting to the low power node.
(Supplementary note 23)
The method according to any one of Supplementary notes 18-22, wherein the base station transmits user data to a relay node connected to the base station using resources of the second part when the second part is assigned, wherein the relay node transmits user data to a terminal connecting to the relay node.
(Supplementary note 24)
A storage device storing a program instructing a program-controlled processor to control radio resources in a base station located inside a first radio coverage of a first base station in a communications system, wherein the base station has smaller transmit power than the first base station, comprising:
storing system resource assignment information on system radio resources divided into a first part and a second part, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and
differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the base station according to the system resource assignment information.
(Supplementary note 25)
The storage device according to Supplementary note 24, wherein a transmit power and/or a proportion of resources for the user data transmission of the base station are configured as a radio link parameter, wherein the proportion of resources is a ratio of an amount of resources used for user data transmission of the base station with respect to an amount of the system radio resources.
(Supplementary note 26)
The storage device according to Supplementary note 25, wherein the transmit power and/or the proportion of resources when the second part is assigned is larger than when the first part is assigned.
(Supplementary note 27)
The storage device according to Supplementary note 26, wherein information related to two transmit powers when the first and second parts are assigned, respectively, is transmitted to the terminal connecting to the base station.
(Supplementary note 28)
The storage device according to any one of Supplementary notes 24-27, wherein the system resource assignment information is received from the first base station or a higher-layer network entity connecting the base station and the first base station.
(Supplementary note 29)
A storage device storing a program instructing a program-controlled processor to control radio resources in a base station having a radio coverage in which a low power node is located, wherein the low power node has smaller transmit power than the base station, comprising:
storing system resource assignment information on system radio resources divided into a first part and a second part; and
performing a user data communication function of transmitting user data to a terminal connecting to the base station when the first part is assigned; and
performing at least one function other than the user data communication when the second part is assigned,
wherein the low power node differentiates configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the low power node according to the system resource assignment information.
(Supplementary note 30)
The storage device according to Supplementary note 29, wherein a control channel and/or a reference signal are transmitted to the terminal connecting to the base station when the second part is assigned.
(Supplementary note 31)
The storage device according to Supplementary note 29 or 30, wherein the low power node configures as a radio link parameter a transmit power and/or a proportion of resources for the user data transmission of the low power node, wherein the proportion of resources is a ratio of an amount of resources used for user data transmission of the low power node with respect to an amount of the system radio resources.
(Supplementary note 32)
The storage device according to Supplementary note 31, wherein the low power node configures such that the transmit power and/or the proportion of resources when the second part is assigned is larger than when the first part is assigned.
(Supplementary note 33)
The storage device according to Supplementary note 32, wherein the low power node controls a transmission section so as to transmit information related to two transmit powers when the first and second parts are assigned, respectively, to the terminal connecting to the low power node.
(Supplementary note 34)
The storage device according to any one of Supplementary notes 29-33, wherein the base station transmits user data to a relay node connected to the base station using resources of the second part when the second part is assigned, wherein the relay node transmits user data to a terminal connecting to the relay node.

This invention can be applied to a heterogeneous cellular network with deployment of different types of base stations such that low power nodes are embedded in the macro-cellular cellular network, especially to a mobile communications system which is provided to the area including narrow aisles.

10 Base station (MeNB)
20 Base station (Low Power Node)
20-1 Base station (Relay Node)
30, 30-1, 30-2 User equipment (UE)
40 System radio resources
51 Radio coverage of MeNB
52 Radio coverage of LPN

Claims

A base station located inside a first radio coverage of a first base station in a communications system, wherein the base station has smaller transmit power than the first base station, comprising:
a storage section for storing system resource assignment information on system radio resources divided into a first part and a second part, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and
a controller for differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the base station according to the system resource assignment information.
The base station according to claim 1, wherein the controller configures as a radio link parameter a transmit power and/or a proportion of resources for user data transmission of the base station, wherein the proportion of resources is a ratio of an amount of resources used for user data transmission of the base station with respect to an amount of the system radio resources.
The base station according to claim 2, wherein the controller configures such that the transmit power and/or the proportion of resources when the second part is assigned is larger than when the first part is assigned.
The base station according to claim 3, wherein the controller controls a transmission section so as to transmit information related to two transmit powers when the first and second parts are assigned, respectively, to the terminal connecting to the base station.
A base station having a radio coverage in which a low power node is located, wherein the low power node has smaller transmit power than the base station, comprising:
a storage section for storing system resource assignment information on system radio resources divided into a first part and a second part; and
a scheduler for performing a user data communication function of transmitting user data to a terminal connecting to the base station when the first part is assigned and performing at least one function other than the user data communication when the second part is assigned,
wherein the low power node differentiates configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the low power node according to the system resource assignment information.
The base station according to claim 5, wherein the scheduler transmits a control channel and/or a reference signal to the terminal connecting to the base station when the second part is assigned.
The base station according to claim 5 or 6, wherein the scheduler transmits user data to a relay node connected to the base station using resources of the second part when the second part is assigned, wherein the relay node transmits user data to a terminal connecting to the relay node.
A communications system comprising:
a first base station;
at least one second base station inside a radio coverage of the first base station, wherein the second base station has smaller transmit power than the first base station; and
at least one terminal connecting to each of the first and second base stations,
wherein the first base station comprises:
a first storage section for storing system resource assignment information on system radio resources divided into a first part and a second part; and
a scheduler for performing a user data communication function of transmitting user data to a terminal connecting to the first base station when the first part is assigned and performing at least one function other than the user data communication when the second part is assigned,
wherein the second base station comprises:
a second storage section for storing the system resource assignment information, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and
a controller for differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the second base station according to the system resource assignment information.
A method for configuring radio resources in a base station located inside a first radio coverage of a first base station in a communications system, wherein the base station has smaller transmit power than the first base station, comprising:
storing system resource assignment information on system radio resources divided into a first part and a second part, wherein the first part is assigned to user data communication of the first base station with a terminal connecting to the first base station and the second part is assigned to at least one function of the first base station other than the user data communication; and
differentiating configurations of at least one radio link parameter of the first part and the second part assigned for user data transmission of the base station according to the system resource assignment information.
A method for configuring radio resources in a base station having a radio coverage in which a low power node is located, wherein the low power node has smaller transmit power than the base station, comprising:
storing system resource assignment information on system radio resources divided into a first part and a second part; and
performing a user data communication function of transmitting user data to a terminal connecting to the base station when the first part is assigned; and
performing at least one function other than the user data communication when the second part is assigned,
wherein the low power node differentiates configurations of at least one radio link parameter of the first part and second part assigned for user data transmission of the low power node according to the system resource assignment information.