WO2015019179A2

WO2015019179A2 - Method and device for mitigating interference

Info

Publication number: WO2015019179A2
Application number: PCT/IB2014/002007
Authority: WO
Inventors: Chongxian Zhong; Tao Yang
Original assignee: Alcatel Lucent
Priority date: 2013-08-09
Filing date: 2014-08-08
Publication date: 2015-02-12
Also published as: TW201521370A; WO2015019179A3; CN104349437A; CN104349437B

Abstract

Embodiments of the present invention provide a method of mitigating interference in user equipment at a transmitting end and corresponding user equipment. The method comprises: obtaining a maximum available transmit power; determining a first path loss power of at least one desired D2D link to user equipment at a receiving end, and determining a second path loss power of at least one interference link; determining an estimated transmit power according to the first path loss power and the second path loss power; and selecting a smaller power from the maximum available transmit power and the estimated transmit power, as a transmit power. By employing the method according to embodiments of the present invention, the transmit power of the user equipment at the transmitting end is controlled, which not only ensures communication quality of the desired D2D link but also effectively mitigates the interference caused by the transmitting end of the desired D2D link to the receiving ends of other links multiplexing the same resource blocks as it since interference of an interference link is considered, thereby improving the capability of interference mitigation in D2D communication.

Description

METHOD AND DEVICE FOR MITIGATING INTERFERENCE

FIELD OF TECHNOLOGY

[0001] The present invention relates to the field of communication, and more specifically, to a method and device for mitigating interference in D2D (Device-to-Device) communication.

BACKGROUND OF THE INVENTION

[0002] The researches in the field of communication are currently focused on introducing D2D communication into a cellar communication system. The D2D communication refers to direct communication between user equipment (User Equipment) by multiplexing cell resource of a cellular network. The use cases of D2D communication are as shown in Fig. l. Use Case 1 is unicast where two user equipment communicate with each other; Use Case 2 is group-cast where one user equipment sends information simultaneously to multiple user equipment in a same group of membership; Use Case 3 is broadcast where one user equipment simultaneously broadcasts information to all user equipment in a certain range; Use Case 4 is relay wherein one user equipment serves as a relay and relays messages sent by a base station or other user equipment for one or more other user equipment.

[0003] The D2D communication is introduced with many advantages such as efficient radio resource usage, high spectrum efficiency, low power consumption, performance improvement for cell-edge users, etc.. However, since D2D communication multiplexes cell resource of the cellular network and the same cell resource may be multiplexed between different D2D links according to a resource configuration policy, there may be interference between a D2D link and a cellular link of the cellular network and between different D2D links. In order to improve overall communication quality of the system, interference needs to be mitigated in the D2D communication.

[0004] In current solutions, a method of mitigating interference in the cellular network communication is used and then a method of interference mitigation is presented by controlling a transmit power of user equipment at a transmitting end in the unicast D2D communication. The method specifically comprises: obtaining a maximum available transmit power; determining a path loss power of one desired D2D link to user equipment at a receiving end; determining an estimated transmit power according to the determined path loss power; selecting a smaller power from the maximum available transmit power and the estimated transmit power, as the transmit power.

[0005] However, the current solutions have the following problems:

[0006] Since the path loss power of only one desired D2D link is determined, the interference can only be mitigated in the unicast D2D communication, rather than in group-cast, broadcast and relay D2D communication in which there are a plurality of D2D links, so that the current technical solutions have certain limitations in use. Besides, the current technical solutions only consider the path loss power of the desired D2D link to control the transmit power of the user equipment at the transmitting end so as to ensure communication quality of the desired D2D link. However, when the user equipment at the transmitting end applies the finally-selected transmit power to transmit information, there still is larger interference to a further D2D link and cellular links that are multiplexing the same resource blocks. It has less capability to mitigate the interference.

SUMMARY OF THE INVENTION

[0007] In view of the technical problems existing in the prior art, embodiments of the present invention provide a method and user equipment for mitigating interference.

[0008] According to an embodiment of the present invention, there is provided a method of mitigating interference in user equipment at a transmitting end. The method comprises: obtaining a maximum available transmit power; determining a first path loss power of at least one desired D2D link to user equipment at a receiving end, and determining a second path loss power of at least one interference link; determining an estimated transmit power according to the first path loss power and the second path loss power; and selecting a smaller power from the maximum available transmit power and the estimated transmit power, as a transmit power.

[0009] According to another embodiment of the present invention, there is provided an apparatus. The apparatus comprises: an obtaining means configured to obtain the maximum available transmit power; a first determining means configured to determine a first path loss power of at least one desired D2D link to user equipment at a receiving end, and determine a second path loss power of at least one interference link; a second determining means configured to determine an estimated transmit power according to the first path loss power and the second path loss power; and a selecting means configured to select a smaller power from the maximum available transmit power and the estimated transmit power, as a transmit power.

[0010] The technical solution of mitigating interference provided by the embodiments of the present invention are adapted to mitigate the interference in many kinds of D2D communication such as unicast, group-cast, broadcast and relay D2D communication.

[0011] According to embodiments of the present invention, the estimated transmit power is determined according to the first path loss power of the desired D2D link and the second path loss power of the interference link, so that a smaller power may be selected as a transmit power from the maximum available transmit power and the estimated transmit power. As a result, transmitting the information by the user equipment at the transmitting end applying the selected transmit power not only ensures communication quality of the desired D2D link but also effectively mitigates the interference caused by the transmitting end of the desired D2D link to the receiving ends of other links multiplexing the same resource blocks as it since interference of an interference link is considered, which thereby improves the capability of interference mitigation in D2D communication.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Other features, objects and advantages of the present invention will be more apparent by reading the following detailed description of non-limitation embodiments with reference to figures. In the figures, identical and similar reference numbers denote identical or similar means or steps of a method, wherein:

[0013] Fig.l illustrates schematically use cases in D2D communication;

[0014] Fig.2 illustrates schematically various links in D2D communication;

[0015] Fig.3 illustrates schematically a flow chart of a method of mitigating interference in user equipment at a transmitting end according to one embodiment of the present invention;

[0016] Fig.4 illustrates schematically a block diagram of user equipment in which the method of mitigating interference is implemented according to one embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0017] Exemplary embodiments of the present invention provide a method and device of mitigating interference. In some embodiments of the present invention, interference is mitigated based on power control of user equipment at a transmitting end of a desired D2D link. In some other embodiments of the present invention, interference is mitigated based on communication mode selection for the user equipment at the transmitting end of the desired D2D link and resource block configuration for the desired D2D link.

[0018] An application of an exemplary embodiment of the present invention lies in the following: in D2D communication, when a desired D2D link uses the same resource block as a cellular link and a further D2D link, user equipment at a transmitting end of the desired D2D link, upon using the resource block to transmit information, will cause interference to the cellular link and the further D2D link which are also using the resource block to transmit information. Interference mitigation is required to guarantee communication quality of the whole network. Furthermore, although the D2D communication may multiplex both uplink resource and downlink resource of the cellular network, multiplexing the uplink resource is more advantageous than multiplexing the downlink resource. For example, receiving ends in downlink of the cellular network are user equipment whose positions change constantly, so it is difficult to estimate the interference thereto caused by the user equipment at the transmitting end of the desired D2D link and therefore it is difficult to perform interference mitigation. For another example, uplink throughput of the cellular network is generally smaller than downlink throughput, so compared with downlink multiplexing, D2D communication multiplexing the uplink resource causes less influence to communication of the cellular network. Considering various factors, the uplink resource of the cellular network is usually allocated when establishing D2D communication. Therefore, exemplary embodiments of the present invention take into account the issue about interference mitigation when the desired D2D link multiplexes the uplink resource of the cellular network. In Fig.2, it illustrates the desired D2D link, an interference link, other D2D links and cellular links.

[0019] Various embodiments of the present invention will be described in detail with reference to the figures.

[0020] Fig.3 illustrates schematically a flow chart of a method 300 of mitigating interference in user equipment at a transmitting end according to one embodiment of the present invention. The method may be implemented in any user equipment serving as a transmitting end and performing D2D communication so to mitigate interference.

[0021] At step S301 of the method 300, a maximum available transmit power is obtained. The maximum available transmit power may be varied as the user equipment at the transmitting end is affected by its communication condition, so it is necessary to obtain the current maximum available transmit power. At step S302 of the method 300, a first path loss power of at least one desired D2D link to user equipment at a receiving end is determined, and a second path loss power of at least one interference link is determined. Then at step S303 of the method 300, an estimated transmit power is determined according to the first path loss power and the second path loss power, and at step S304, a smaller power is selected from the maximum available transmit power and the estimated transmit power, as a transmit power. It may be appreciated that step S301 may be performed before step S302, or after step S302 or S303, so long as the maximum available transmit power and the estimated transmit power are obtained before step S304 of the method 300.

[0022] According to an embodiment of the present invention, in the method 300, the desired D2D link may include one or more desired D2D links, depending on the D2D communication use case employed by the user equipment at the transmitting end. For example, in Figure 2, the user equipment at the transmitting end is Al and it employs the group-cast D2D communication use case to perform D2D communication with user equipment A3, A2 and A4 at the receiving end. Therefore, there are three desired D2D links.

[0023] According to an embodiment of the present invention, determining the first path loss power of at least one desired D2D link to the user equipment at the receiving end in the method 300 comprises: determining a first estimated path loss power of each desired D2D link to the user equipment at the receiving end; and determining the first path loss power according to the determined first estimated path loss power.

[0024] When determining the first estimated path loss power of each desired D2D link to the user equipment at the receiving end, since positions of the user equipment at the receiving end and the user equipment at the transmitting end in each desired D2D link change constantly and the transmit power of the user equipment at the transmitting end also changes constantly, the path loss power on each desired D2D link may be difficult to be accurately determined.

[0025] According to an embodiment of the present invention, determining the first estimated path loss power of each desired D2D link comprises a processing approach (al) determining the first estimated path loss power of each desired D2D link to the user equipment at the receiving end comprises: obtaining a first RSRP (Reference Signal Received power) of each desired D2D link to the user equipment at the receiving end, and determining the first estimated path loss power of each desired D2D link according to the first RSRR

[0026] The first RSRP refers to a received power upon receiving a reference signal after the reference signal is transmitted on each desired D2D link. The reference signal may be transmitted by the user equipment at the receiving end of each desired D2D link using a predetermined transmit power (e.g., the maximum available transmit power) and then may be received by the user equipment at the transmitting end; the reference signal may also be transmitted by the user equipment at the transmitting end using a predetermined transmit power (e.g., the maximum available transmit power) and then may be received by the user equipment at the receiving end of each desired D2D link. The user equipment at the receiving end of each desired D2D link may regard the received power of the received reference signal as the first RSRP, and send the first RSRP to the user equipment at the transmitting end, so that the user equipment at the transmitting end obtains the first RSRP. In an embodiment, the first RSRP may be directly regarded as the first estimated path loss power of each desired D2D link. In another embodiment, a function relationship stratified between the first RSRP and the first estimated path loss power may be determined by modeling, so that the first estimated path loss power is obtained by performing function operation according to the first RSRP.

[0027] According to another embodiment of the present invention, determining the first estimated path loss power of each desired D2D link comprises a processing approach (a2): determining a first distance to the user equipment at the receiving end of each desired D2D link, and determining the first estimated path loss power of each desired D2D link according to the first distance.

[0028] The first distance between the user equipment at the transmitting end and the user equipment at the receiving end of each desired D2D link may be determined by using existing positioning techniques, such as positioning via GPS (Global Positioning System), Bluetooth, or Wi-Fi network, etc.. The path loss on a desired D2D link is related to the distance between the transmitting end and the receiving end of this desired D2D link, so the first distance may reflect the path loss power of the desired D2D link. In an embodiment, the first distance may be directly used to represent the first estimated path loss power of each desired D2D link. In another embodiment, a function relationship stratified between the distance and the path loss is determined by modeling, and the first estimated path loss power may be obtained by performing function operation according to the first distance.

[0029] To more accurately determine the first estimated path loss power of each desired D2D link, according to an embodiment of the present invention, determining the first estimated path loss power of each desired D2D link comprises a processing approach (a3): receiving a first reference signal transmitted by user equipment in a first geographic range applying a first predetermined transmit power, and a received power of the first reference signal determining, wherein the user equipment at the transmitting end acknowledges the first predetermined transmit power in advance; determining a D2D actual path loss power of the link between the user equipment within the first geographic range and the user equipment at the transmitting end, according to the first predetermined transmit power and the received power of each first reference signal. The D2D actual path loss power between each user equipment included in the at least one desired D2D link among the user equipment within the first geographic range and the user equipment at the transmitting end is regarded as the first estimated path loss power of each desired D2D link.

[0030] In order to enable the user equipment within the first geographic range to apply the first predetermined transmit power to transmit the first reference signal, according to an embodiment of the present invention, the user equipment at the transmitting end applies a preconfigured transmit power to broadcast a measurement request, and defines user equipment receiving the measurement request as the user equipment within the first geographic range; and receives the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power. The preconfigured transmit power may be the maximum available transmit power of the user equipment at the transmitting end so as to broadcast the measurement request to user equipment at the receiving ends of all desired D2D links.

[0031] Likewise, in order to enable the user equipment within the first geographic range to apply the first predetermined transmit power to transmit the first reference signal, according to another embodiment of the present invention, the user equipment at the transmitting end receives the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power upon receiving the measurement request transmitted a base station in a cell where the user equipment at the transmitting end lies; wherein the base station in the cell where the user equipment at the transmitting end lies acknowledges a geographic position of the user equipment within the first geographic range in advance. The base station in the cell where the user equipment at the transmitting end lies, upon transmitting the measurement request, may determine its transmit power according to a size of the pre-known geographic range so as to accurately transmit the measurement request to a user equipment in a preset geographic range.

[0032] In such embodiment, due to different positions of the user equipment within the first geographic range, the base station in the cell where the user equipment at the transmitting end lies transmits the measurement request in different manners. Therefore, according to an embodiment of the present invention, receiving the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power upon receiving the measurement request transmitted by the base station in the cell where the user equipment at the transmitting end lies comprises: if the user equipment within the first geographic range are all located in the cell where the user equipment at the transmitting end lies, receiving the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power upon receiving the measurement request directly transmitted by the base station in the cell where the user equipment at the transmitting end lies; if the user equipment within the first geographic range are not all located in the cell where the user equipment at the transmitting end lies, receiving the first reference signal transmitted by the user equipment among the user equipment within the first geographic range located in the cell where the transmitting end lies by applying the first predetermined transmit power upon receiving the measurement request directly transmitted by the base station in the cell where the user equipment at the transmitting end lies, and receiving the first reference signal transmitted by other user equipment among the user equipment within the first geographic range other than those located in the cell where the transmitting end lies by applying the first predetermined transmit power upon receiving the measurement request first transmitted by the base station in the cell where the user equipment at the transmitting end lies to a base station of a predetermined neighboring cell and then forwarded by the base station of the predetermined neighboring cell. The predetermined neighboring cell refers to a cell(s) where other user equipment among the user equipment within the first geographic range other than those located in the cell where the transmitting end lies are located.

[0033] According to an embodiment of the present invention, in the above processing approach (a3), the D2D actual path loss power(s) of the link between the user equipment within the first geographic range and the user equipment at the transmitting end is determined according to the first predetermined transmit power and the received power of each first reference signal. In an embodiment, a difference value between the first predetermined transmit power and the received power of each first reference signal is considered as the D2D actual path loss power of the link between the user equipment within the first geographic range and the user equipment at the transmitting end. The first predetermined transmit power used by each user equipment within the first geographic range may not be completely the same, and the user equipment at the transmitting end may distinguish in advance the first predetermined transmit power used by each user equipment within the first geographic range.

[0034] It may be appreciated that, in the above processing approach (a3), the user equipment within the first geographic range comprise the user equipment at the receiving end of the desired D2D link, and the user equipment at the transmitting end acknowledges the user equipment at the receiving end of the desired D2D link in advance. Therefore, the D2D actual path loss power between each of user equipment included in at least one desired D2D link among the user equipment within the first geographic range and the user equipment at the transmitting end may be regarded as the first estimated path loss power of each desired D2D link. Here, since the D2D actual path loss power is determined according to the transmit power and received power of the reference signal on the desired D2D link, it may represent the path loss on the desired D2D link more accurately. The first estimated path loss power of each desired D2D link will be made more accurate by regarding the D2D actual path loss power as the first estimated path loss power.

[0035] According to an embodiment of the present invention, determining the first estimated path loss power of each desired D2D link comprises a processing approach (a4): applying a second predetermined transmit power to transmit a second reference signal, and determining a received power of user equipment receiving the second reference signal; determining a D2D actual path loss power of a link between each user equipment receiving the second reference signal and the user equipment at the transmitting end, according to the second predetermined transmit power and the received power of each user equipment receiving the second reference signal; and regarding the D2D actual path loss power between each user equipment included in the at least one desired D2D link among user equipment receiving the second reference signal and the user equipment at the transmitting end, as the first estimated path loss power of each desired D2D link.

[0036] In the processing approach (a4), as the user equipment at the transmitting end transmits the reference signal, the user equipment at the transmitting end may control a magnitude of the second predetermined transmit power and thereby control the user equipment in a certain geographic range to receive the second reference signal. In an alternative embodiment, the user equipment at the transmitting end may use its maximum available power to transmit the second reference signal.

[0037] After the user equipment at the transmitting end transmits the second reference signal, the user equipment receiving the second reference signal may determine the received power of the second reference signal. According to an embodiment of the present invention, the user equipment receiving the second reference signal directly transmits the received power of the second reference signal to the user equipment at the transmitting end, or to the base station in the cell where it lies, and the base station in the cell where it lies may then transmit the received power to the user equipment at the transmitting end. The user equipment at the transmitting end, after receiving the received power of the second reference signal, calculates the D2D actual path loss power based on the received power. According to another embodiment of the present invention, the user equipment receiving the second reference signal acknowledges the second predetermined transmit power in advance so as to determine the D2D actual path loss power according to the second predetermined transmit power and the received power of the second reference signal, and then directly transmit the determined actual D2D path loss to the user equipment at the transmitting end, or transmit to the base station in the cell where it lies, and the base station in the cell where it lies may then transmit the determined actual D2D path loss to the user equipment at the transmitting end. If the base station in the cell where the user equipment receiving the second reference signal lies is different from the base station in the cell where the user equipment at the transmitting end lies, the base station in the cell where the user equipment receiving the second reference signal lies may transmit the information to be transmitted to the user equipment at the transmitting end to the base station in the cell where the user equipment at the transmitting end lies, and the base station in the cell where the user equipment at the transmitting end lies then forwards the information to the user equipment at the transmitting end.

[0038] It may be appreciated that, in the above processing approach (a4), the user equipment receiving the second reference signal includes the user equipment at the receiving end of the desired D2D link, and the user equipment at the transmitting end acknowledges the user equipment at the receiving end of the desired D2D link in advance. Therefore, the D2D actual path loss power between each of user equipment included in at least one desired D2D link among the user equipment receiving the second reference signal and the user equipment at the transmitting end may be regarded as the first estimated path loss power of each desired D2D link. In the above processing approach (a4), since the D2D actual path loss power is determined according to the transmit power and received power of the reference signal on the desired D2D link, it may represent the path loss on the desired D2D link more accurately. The first estimated path loss power of each desired D2D link will be made more accurate by regarding the D2D actual path loss power as the first estimated path loss power.

[0039] According to the above embodiments, the first estimated path loss power of each desired D2D link may be determined, and the first estimated path loss power reflects a communication condition of each desired D2D link. In the method 300, upon determining the transmit power of the user equipment at the transmitting end, there is tradeoff between communication quality of the desired D2D link and interference mitigation of the interference link. Hence, it is feasible to determine the first path loss power according to the determined first estimated path loss power(s) and use the first path loss power to reflect the communication condition of each desired D2D link.

[0040] According to an embodiment of the present invention, determining the first path loss power according to the determined first estimated path loss powers comprises a processing approach (bl): determining a maximum first estimated path loss power in the determined first estimated path loss powers as the first path loss power.

[0041] For example, a maximum value in the determined first estimated path loss powers may be determined by using the following formula: ^Desired effective ^mdA [^Desired link, '-' ^Desired link_K J

^{1 1 K J} , (1)

[0042] Where ξβ^_ά effective represents a linear value of the first path loss power; K represents the number of the desired D2D links; f°^2D

¹ 'Desired .. Im. k . _j ,...,£ 'D?e²s^Dired , , lm. k , _K re ^rpresents linear values of the first estimated path loss powers of the 1th to ^th desired D2D links.

[0043] In another embodiment of the present invention, determining the first path loss power according to the determined first estimated path loss powers comprises a processing approach

(b2): calculating a harmonic average value of the determined first estimated path loss powers, and regarding the calculated harmonic average value as the first path loss power.

[0044] For example, the harmonic average value may be calculated by using the following formula: eD2D

bDesired effective ^' (2)

[0045] Where ξ§^_κα effective represents a linear value of the first path loss power; ^ represents the number of the desired D2D links; ¹ £ 'D°e²s^Dired .. Im. k . _j ,...,£ 'D?e²s^Dired , , lm. k , _K re ^rpresents linear values of the first estimated path loss powers of the 1th to ^th desired D2D links.

[0046] According to yet another embodiment of the present invention, determining the first path loss power according to the determined first estimated path loss powers comprises a processing approach (b3): calculating a linear combination average value of the determined first estimated path loss powers, and regarding the calculated linear combination average value as the first path loss power.

[0047] For example, the linear combination average value may be calculated by using the following formula:

eD2D v^^D2D 4- A,-) v^^D2D

ί Desired effective "A ^x ¾esired link, ⁺ - - ^{+ ω}Κ ^x ¾esired link_K ' ^J )

[0048] Where ^D²s°ed effective represents a linear value of the first path loss power; ^ represents the number of the desired D2D links; ¹ £ 'D°e²s^Dired .. li.nk . , ,...,£ 'D?e²s^Dired , , Im. k , ^ re ^rpresents linear values of the first estimated path loss powers of the 1th to Kt desired D2D links; fi¾,■■■, <%- is weights of corresponding desired D2D links, and ° + ···+ <¾ = 1 .

[0049] Wherein the first path loss power determined in (bl) guarantees communication of the link with worst communication quality among the desired D2D links; the first path loss power determined in (b2) harmonizes communication qualities of all desired D2D links; (b3) guarantees communication qualities of different desired D2D links based on the weights of different desired D2D links. For example, a higher weight may be allocated to a desired D2D link having a higher priority, and so on and so forth.

[0050] Those skilled in the art may appreciate that for the sake of accuracy of calculating the harmonic average value and the linear average value, in an embodiment, the linear value of the first estimated path loss power of each desired D2D link may be used and then the obtained first interference path loss power is also linear. When the estimated transmit power is determined at the subsequent step S303, a log value may be obtained for the linear value of the first interference path loss power to obtain a log expression of a commonly-used power (e.g., with dB as a unit). However, in some embodiments, upon selecting the maximum first estimated path loss power in the processing approach (bl), the selection is not limited to use of the linear value or log value of the first estimated path loss power.

[0051] It may be appreciated that determining the processing of the first path loss power according to the determined first estimated path loss powers stated above is only exemplary and illustrative. Embodiments of the present invention are not limited to the specific processing approaches disclosed herein. Those skilled in the art, according to the teaching of the description, may employ other suitable (existing or to-be-developed) methods to determine the first path loss power.

[0052] Besides determining the first path loss power of at least one desired D2D link to the user equipment at the receiving end , a second path loss power of at least one interference link is needed to be determined at the step S302 of the method 300. It may be appreciated that at step S302, determining the first path loss power of at least one desired D2D link to the user equipment at the receiving end and determining the second path loss power of at least one interference link may be executed simultaneously or in any sequential order. [0053] When the second path loss power of at least one interference link is determined, the interference link refers to a link causing interference to other user equipment or base stations when the user equipment at the transmitting end of the desired D2D link transmits information to the receiving end of the desired D2D link. The interference link comprises a D2D interference link consisting of user equipment at a receiving end and a transmitting end of a further D2D link using the same resource block as the desired D2D link, and/or a cellular interference link consisting of user equipment at a receiving end and a transmitting end of a cellular link using the same resource block as the desired D2D link. In the exemplary embodiment of the present invention, since the desired D2D link multiplexes the uplink resource of the cellular network, an interfered object on the D2D interference link is the user equipment at the receiving end that is receiving the information in the D2D interference link; an interference object on the cellular interference link is a base station that is receiving the uplink information in the cellular link. The number of the D2D interference links and cellular interference links included by the interference link depends on the allocation situations of the actual uplink resource. For example, in Fig.2, the user equipment Al at the transmitting end uses the same resource block as other D2D links and cellular links to transmit information, and thereby interference links are formed. There are two D2D interference links: Al to Bl, and Al to CI; there are three cellular interference links: Al to S I, Al to S3, and Al to S5.

[0054] Since the path loss of the D2D interference link and cellular interference link vary with the interfered objects, the path loss power on different types of interference links may be determined respectively. According to an embodiment of the present invention, the determining the second path loss power of at least one interference path comprises: determining a first interference path loss power of the D2D interference link, and/or determining a second interference path loss power of the cellular interference link; determining the second path loss power according to the first interference path loss power and/or the second interference path loss power.

[0055] The determining the first interference path loss power of the D2D interference link and determining the second interference path loss power of the cellular interference link may be executed simultaneously or in any sequential order.

[0056] According to an embodiment of the present invention, the determining the first interference path loss power of the D2D interference link comprises: determining a second estimated path loss power of each D2D interference link; and determining the first interference path loss power according to the determined second estimated path loss power.

[0057] Like the desired D2D link, the D2D interference link is a link formed between two user equipment, so the determining the second estimated path loss power of each D2D interference link is similar to the determining the first estimated path loss power of each desired D2D link.

[0058] According to an embodiment of the present invention, the determining the second estimated path loss power of each D2D interference link comprises a processing approach (cl): obtaining a second RSRP of each D2D interference link, and determining the second estimated path loss power of each D2D interference link according to the second RSRP.

[0059] According to another embodiment of the present invention, the determining the second estimated path loss power of each D2D interference link comprises a processing approach (c2): determining a second distance to the user equipment at the receiving end of each D2D interference link, and determining the second estimated path loss power of each D2D interference link according to the second distance.

[0060] As can be seen from the above, the processing approaches (cl) and (c2) are respectively similar to the processing approaches (al) and (a2) of determining the first estimated path loss power of each desired D2D link, and will not be detailed here. Furthermore, to accurately determining the second estimated path loss power of each D2D interference link, like the processing approaches of determining the first estimated path loss power of each desired D2D link, the following embodiments are provided in the present invention further.

[0061] According to another embodiment of the present invention, the determining the second estimated path loss power of each D2D interference link comprises a processing approach (c3): receiving a first reference signal transmitted by the user equipment within a first geographic range applying a first predetermined transmit power, and determining a received power of the first reference signal, wherein the user equipment at the transmitting end acknowledges the first predetermined transmit power in advance; and determining a D2D actual path loss power of a link between the user equipment within the first geographic range and the user equipment at the transmitting end, according to the first predetermined transmit power and the received power of the respective first reference signal. User equipment among the user equipment within the first geographic range other than the user equipment included in the at least one desired D2D link constitute the D2D interference link with the user equipment at the transmitting end. The D2D actual path loss power of each D2D interference link is determined as the second estimated path loss power of the D2D interference link.

[0062] The above processing approach (c3) is similar to the processing approach (a3) of determining the first estimated path loss of each desired D2D link, and reference may be made to the above processing (a3) for a specific implementation. However, in the above processing approach (c3), user equipment among the user equipment within the first geographic range other than the user equipment included in the desired D2D link are user equipment subjected to interference of the user equipment at the transmitting end of the desired D2D link. Therefore, the above mentioned user equipment constitute the D2D interference link with the user equipment at the transmitting end, and the previously-determined actual D2D path loss power is regarded as the second estimated path loss of the D2D interference link.

[0063] According to a further embodiment of the present invention, the determining the second estimated path loss power of each D2D interference link comprises a processing approach (c4): applying a second predetermined transmit power to transmit a second reference signal, and determining a received power of user equipment receiving the second reference signal; determining a D2D actual path loss power of a link between each user equipment receiving the second reference signal and the user equipment at the transmitting end, according to the second predetermined transmit power and the received power of each user equipment receiving the second reference signal; wherein user equipment among the user equipment receiving the second reference signal other than the user equipment included in the at least one desired D2D link constitute the D2D interference link with the user equipment at the transmitting end; and the D2D actual path loss power of each D2D interference link is determined as the second estimated path loss power of the D2D interference link.

[0064] The above processing approach (c4) is similar to the processing approach (a4) of determining the first estimated path loss of each desired D2D link, and reference may be made to the above processing (a4) for a specific implementation. However, in the above processing approach (c4), user equipment among the user equipment receiving the second reference signal other than the user equipment included in the desired D2D link are user equipment subjected to interference of the user equipment at the transmitting end of the desired D2D link. Therefore, the above mentioned user equipment constitute the D2D interference link with the user equipment at the transmitting end, and the previously-determined actual D2D path loss power is regarded as the second estimated path loss of the D2D interference link.

[0065] In the above processing approaches (c3) and (c4), the second estimated path loss power is obtained according to a difference value of the transmit power and the received power of the reference signal when being transmitted on the D2D interference link. The second estimated path loss power determined according to the above processing approaches (c3) and (c4) is more accurate than the second estimated path loss power obtained according to the above processing approaches (cl) and (c2).

[0066] According to the above embodiments, the second estimated path loss power of each D2D interference link may be determined, and the second estimated path loss power reflects an interference condition of each D2D interference link. In the method 300, upon determining the transmit power of the user equipment at the transmitting end, there is tradeoff between communication quality of the desired D2D link and interference mitigation of the interference link. Hence, it is feasible to determine the first interference path loss power according to the determined second estimated path loss power and use the first interference path loss power to reflect an interference condition of all D2D interference links.

[0067] According to an embodiment of the present invention, determining the first interference path loss power according to the determined second estimated path loss powers comprises a processing approach (dl): determining a minimum second estimated path loss power in the determined second estimated path loss powers as the first interference path loss power.

[0068] For example, the minimum value within the first interference path loss powers may be determined by using the following formula: eD2D - min l^⁰²⁰ ί^Ό2Ό

¾Interf. effective [^Interf. lin^ ' -' ^Interf. link _M J

[0069] Where ¾¾¾ _effective represents a linear value of the first interference path loss power; M represents the number of the D2D interference links; °_t ²°_{f link} ,-,ξ^_{{ link} represents linear values of the second estimated path loss powers of the 1th to th D2D interference links.

[0070] According to an embodiment of the present invention, determining the first interference path loss power according to the determined second estimated path loss power comprises a processing approach (d2): calculating a harmonic average value of the determined second estimated path loss powers, and regarding the calculated harmonic average value as the first interference path loss power.

[0071] For example, the harmonic average value may be calculated by using the following formula:

£D2D

rlnterf. effective

- + ... + - sO2O ··· £D2D

'Interf. link, 'Inferf. link .

(5)

[0072] Where ¾¾¾ _effective represents a linear value of the first interference path loss power; M represents the number of the D2D interference links; °²°_{f link} ,-, ξ^_{{ link} represents linear values of the second estimated path loss powers of the 1th to Mth D2D interference links.

[0073] According to another embodiment of the present invention, determining the first interference path loss power according to the determined second estimated path loss power comprises a processing approach (d3): calculating a linear combination average value of the determined second estimated path loss power; and regarding the calculated linear combination average value as the first interference path loss power.

[0074] For example, the linear combination average value may be determined by using the following formula: ftnterf. effective - ^ X f. link, ^{+ "}- ^{+ x} £_Interf. link_M ' (°)

[0075] Wherein ^g_t¾ _effective represents a linear value of the first interference path loss power; M represents the number of the D2D interference links; °²°_{f link} ,-, ξ^_{{ link} represents linear values of the second estimated path loss powers of the 1th to Mth D2D interference links; <¾¾,..., i¾ are weights of corresponding D2D interference links, and <¾ + ···+ <¾/ ⁼ 1 ·

[0076] The first interference path loss power determined in (dl) is intended to mitigate the interference on a link among the D2D interference links subjected to the maximum interference; the first interference path loss power determined in (d2) is intended to harmonize and mitigate the interference on all D2D interference links; (d3) mitigates the interference of all D2D interference links based on the weights of different D2D interference links. For example, a higher weight may be allocated to an interference link having a smaller interference standing capability, and so on and so forth.

[0077] Those skilled in the art may appreciate that for the sake of accuracy of calculating the harmonic average value and the linear average value, in an embodiment, the linear value of the second estimated path loss power of each D2D interference link may be used for calculation and the obtained first interference path loss power is also linear. When the second path loss power is determined subsequently, a log value may be obtained for the linear value of the first interference path loss power to obtain a log expression of a commonly-used power (e.g., with dB as a unit). However, in some embodiments, upon selecting the maximum second estimated path loss power in the processing approach (dl), the selection is not limited to use of the linear value or log value of the second estimated path loss power.

[0078] It may be appreciated that determining the processing of the first interference path loss power according to the determined second estimated path loss power stated above is only exemplary and illustrative. Embodiments of the present invention are not limited to the specific processing approaches disclosed herein. Those skilled in the art, according to the teaching of the description, may employ other suitable (existing or to-be-developed) methods to determine the first interference path loss power.

[0079] The above introduces the processing approach of determining the first interference path loss of the D2D interference link, and then the processing approach of determining the second interference path loss of the cellular interference link is introduced below. According to an embodiment of the present invention, the determining the second interference path loss of the cellular interference link comprises: determining a cellular actual path loss power of each cellular interference link; and determining the second interference path loss power according to the determined cellular actual path loss powers.

[0080] As previously mentioned, upon considering that the user equipment at the transmitting end of the desired D2D link causes interference to the cellular link, the interference object is a base station in the cellular link, and the base station may be a macro base station or a micro base station, which depends on an actual configuration of the cellular network. Since a position of the base station is usually fixed and the transmit power is also usually fixed, it is possible to relatively accurately determine the actual cellular path loss power of each cellular interference link consisting of the base station and the user equipment at the transmitting end.

[0081] According to an embodiment of the present invention, the determining the cellular actual path loss power of each cellular interference link comprises a processing approach (e): receiving a third reference signal transmitted by the receiving end of each cellular interference link applying a third predetermined transmit power, wherein the user equipment at the transmitting end acknowledges the third predetermined transmit power in advance; determining a received power of the received third reference signal; and determining the actual cellular path loss power of each cellular interference link according to the received power of the received third reference signal and the third predetermined transmit power.

[0082] Since the user equipment at the transmitting end may obtain the transmit power and the received power of the third reference signal, the actual cellular path loss power may be determined according to a difference value of the third predetermined transmit power and the received power of the third reference signal. The third predetermined transmit power used by the receiving end of each cellular interference link may be different, and the user equipment at the transmitting end of the desired D2D link may distinguish in advance the third predetermined transmit powers of different cellular interference links so as to determine the actual cellular path loss power of each cellular interference link.

[0083] According to the above embodiment, the actual cellular path loss power of each interference link may be determined, and actual cellular path loss power reflects an interference condition of each cellular interference link. In the method 300, upon determining the transmit power of the user equipment at the transmitting end, there is tradeoff between communication quality of the desired D2D link and interference mitigation of the interference link. Hence, it is feasible to determine the second interference path loss power according to the determined actual cellular path loss power and use the second interference path loss power to reflect an interference condition of all cellular interference links. It is appreciated that the second interference path loss power reflects the interference condition of the cellular interference links. [0084] As the cellular interference link and the D2D interference link are both interference links, the basis for determining the second interference path loss power according to the determined actual cellular path loss power is similar to the basis for determining the first interference path according to the determined second estimated path loss power of the D2D interference path.

[0085] According to an embodiment of the present invention, determining the second interference path loss power according to the determined actual cellular path loss power comprises a processing approach (fl): determining a minimum actual cellular path loss power in the determined actual cellular path loss powers as the second interference path loss power.

[0086] For example, the minimum value in the second interference path loss powers may be determined by using the following formula:

_Pf cellular _ · { _p/-cellular p^cellular 1

^nterf. effective ^{~ lmo} [^nterf. lin ^'' ^terf. link_w J , ( ' )

[0087] Where ¾!^_effective represents a linear value of the first interference path loss power; N represents the number of the D2D interference links;

--■^pz _¾lr_f ^r _iink represents linear values of the actual cellular path loss powers of the 1th to Nth cellular interference links.

[0088] According to an embodiment of the present invention, determining the second interference path loss power according to the determined actual cellular path loss power comprises a processing approach (f2): calculating a harmonic average value of the determined actual cellular path loss power, and regarding the calculated harmonic average value as the second interference path loss power.

[0089] For example, the harmonic average value may be calculated by using the following formula:

pTcellular 1

r^LTnted. effective j 1 , (8)

p_rcellular + · · · + _cellular

uiterf. link_j uiferf. link^

[0090] Where ¾ _e ^u^_effective represents a linear value of the first interference path loss power; N represents the number of the D2D interference links;

[0091] According to a further embodiment of the present invention, determining the second interference path loss power according to the determined actual cellular path loss power comprises a processing approach (f3): calculating a linear combination average value of the determined actual cellular path loss power; and regarding the calculated linear combination average value as the second interference path loss power.

[0092] For example, the linear combination average value may be determined by using the following formula:

pxcellular _ pxcellular pxcellular

^Tnterf. effective ^" ° ^X ^lnterf. link_j + - ^{+ ω}Ν ^χ ^nterf. link^ > W

[0093] Where ^in_effective represents a linear value of the first interference path loss power; N represents the number of the D2D interference links;

--■^pz _¾lr_f ^r _iink represents linear values of the actual cellular path loss powers of the 1th to Nth cellular interference links; fi¾ , ..., fi¾V is weights of corresponding cellular interference links, and ° +^■■■ + <¾ ^{= 1} .

[0094] The second interference path loss power determined in (fl) is intended to mitigate the interference on a link among the cellular interference links subjected to the maximum interference; the second interference path loss power determined in (f2) is intended to harmonize and mitigate the interference on all cellular interference links; (d3) mitigates the interference of all cellular interference links based on the weights of different cellular interference links. For example, a higher weight may be allocated to an interference link having a smaller interference standing capability, and so on and so forth.

[0095] Those skilled in the art may appreciate that for the sake of accuracy of calculating the harmonic average value and the linear average value, in an embodiment, the linear value of the actual cellular path loss power of each cellular interference link may be used for calculation and the obtained second interference path loss power is also linear. When the second path loss power is determined subsequently, a log value may be obtained for the linear value of the second interference path loss power to obtain a log expression of a commonly-used power (e.g., with dB as a unit). However, in some embodiments, upon selecting the maximum actual cellular path loss power in the processing approach (f 1), the selection is not limited to use of the linear value or log value of the actual cellular path loss power.

[0096] It may be appreciated that determining the processing of the second interference path loss power according to the determined cellular path loss power stated above is only exemplary and illustrative. Embodiments of the present invention are not limited to the specific processing approaches disclosed here. Those skilled in the art, according to the teaching of the description, may employ other suitable (existing or to-be-developed) methods to determine the second interference path loss power.

[0097] After the first interference path loss of the D2D interference link and the second interference path loss of the cellular interference link are determined, the second path loss power of the interference link may be determined on this basis. According to an embodiment of the present invention, the second path loss power may be obtained by directly summating the first interference path loss and the second interference path loss. According to another embodiment of the present invention, different weights may be allocated for the first interference path loss and the second interference path loss, and the linear combination average value of the two may be calculated as the second path loss power.

[0098] After step S302, the method 300 proceeds to step S303. At step S303, an estimated transmit power is determined according to the first path loss power and the second path loss power. According to an embodiment of the present invention, the estimated transmit power may be obtained by directly summating the first path loss power and the second path loss power. Alternatively, according to another embodiment of the present invention, different weights may be allocated for the first path loss power and the second path loss power, and the linear combination average value of the two may be calculated as the estimated transmit power.

[0099] Alternatively, in some other embodiments of the present invention, a system parameter may be considered. The determining the estimated transmit power according to the first path loss power and the second path loss power comprises: determining the estimated transmit power according to the first path loss power, the second path loss power and a system parameter, wherein the system parameter includes one or more of: a predetermined open loop power control parameter, the number of allocated resource blocks on the desired D2D link, compensation of a transmission format and a predetermined closed loop power control parameter. These system parameters are preconfigured in the system or may be obtained. In an embodiment, the estimated transmit power may be determined by using the following formula: ^~τΤΥ?Γ) n \ ι ΎΥ?Γ) cellular , ^, .

^PEstimated = ^Ρ0 + ^Desired link + β ^lnterf. link + /^Interf. link + 101og₁₀ R + A_TF + f (A) _f (9)

[00100] Where PEstimated represents the estimated transmit power, Po represents the predetermined open loop power control parameter; fr?e²sired link represents the first path loss power; ¾nterf. link represents the first interference path loss power, PLtaterf unk represents the second interference path loss power,

link wholly represents the second path loss power; R represents the number of allocated resource blocks on the desired D2D link; A_TF represents the compensation of the transmission format; represents the predetermined closed loop power control parameter; oc , β , λ , represents predetermined parameters.

[00101] In an embodiment, fr?e²sired link may be a dB value of the linear value ^Desired effective in the above formulas (1) to (3),

link may be a dB value of the linear value ¾nierf. effective in the above formulas (4) to (6), and PLmterUink may be a dB value of the linear value ^^^f effective ^m the above formulas (7) to (9).

[00102] It may be appreciated that the above formula are exemplary and non-limitation manners of calculating the estimated transmit power. Embodiments of the present invention are not limited to the specific formulas disclosed here. Those skilled in the art, according to the teaching of the description, may employ other suitable (existing or to-be-developed) methods to determine the estimated transmit power according to the first path loss power and the second path loss power.

[00103] Then the method 300 proceeds to step S304. At step S304, a smaller power is selected as the transmit power from the maximum available transmit power and the estimated transmit power. Since the estimated transmit power balances the communication quality of the desired D2D link and the interference situation of the interference link, when the estimated transmit power is smaller than the maximum available transmit power, selecting the estimated transmit power as the transmit power can effectively mitigate interference generated by the D2D communication, and meanwhile can guarantee the communication quality of the desired D2D link. Certainly, if the estimated transmit power is greater than the maximum available transmit power, the maximum available transmit power should be selected as the transmit power to achieve the purpose of balancing the communication quality of the desired D2D link and the interference mitigation of the interference link.

[00104] The above method 300 of mitigating interference by controlling the transmit power of the user equipment at the transmitting end is a real-time interference-mitigating method in the D2D communication. It may be appreciated that the above method 300 may be used as the user equipment at the transmitting end upon any D2D communication.

[00105] However, when the method 300 is used to mitigate interference, this indicates that interference has already existed in the system. If the interference on the interference link is too large, it may be possible that the interference cannot be effectively mitigated by using the method 300. Therefore, furthermore, embodiments of the present invention further provide some proactive methods of mitigating the interference before generation of the interference.

[00106] According to an embodiment of the present invention, before the method 300, the desired D2D link is established with the user equipment at the receiving end upon each of the user equipment at the transmitting end and the user equipment at the receiving end satisfies a D2D communication condition. In this embodiment, before establishment of the desired D2D link, thoughts are first given to whether the user equipment at the transmitting end and the receiving end of the desired D2D link satisfy a certain D2D communication condition, and these D2D communication conditions can well restrain generation of excessive interference after establishment of the desired D2D link, i.e., this may be used as a proactive method of mitigating the interference.

[00107] When use cases such as group-cast, broadcast or relay having multiple desired D2D links, it is difficult to present a suitable judgment criterion to determine that the multiple desired D2D links may be established. Therefore, in exemplary embodiments of the present invention, thoughts are given to the situation that there is one desired D2D link, namely, one-to-one unicast D2D communication. Each of the user equipment at the transmitting end and the user equipment at the receiving end needs to satisfy one or a combination of more of the following D2D communication conditions (gl) to (g6):

[00108] (gl) A third RSRP of the desired D2D link is greater than or equal to a fourth RSRP of a link between each user equipment and a base station in a cell where it lies. [00109] The condition (gl) considers the communication quality of the desired D2D link. When the third RSRP is greater than or equal to the fourth RSRP of the link between each user equipment and the base station in the cell where it lies, it indicates that the communication quality of each user equipment on the desired D2D link is better than the communication quality of each user equipment and the base station in the cell where it lies, so the desired D2D link may be established.

[00110] (g2) A first predetermined proportion of the RSRP is greater than or equal to a fifth RSRP of a link between each user equipment and a receiving end of a cellular link using the same resource block as the desired D2D link.

[00111] The condition (g2) considers a situation in which each user equipment is subjected to the interference of the interference link. Here the interference link is considered as a link between each user equipment and the transmitting end of the cellular link using the same resource block as the desired D2D link. If the first predetermined proportion of the RSRP is greater than or equal to a fifth RSRP of each user equipment on the interference link, this indicates that the interference on the interference link is within a permissible range, and the desired D2D link may be established.

[00112] (g3) A second predetermined proportion of sixth RSRP is greater than or equal to the fourth RSRP, wherein the sixth RSRP is a RSRP of the cellular link using the same resource block as the desired D2D link.

[00113] The condition (g3) considers the communication quality of the cellular link in the cellular network. The interference of each user equipment in the established desired D2D link to the receiving end of the cellar link should not cause excessive interference to the communication quality of the cellular link. The sixth RSRP indicates the communication quality of the cellular link. If the second predetermined proportion of the sixth RSRP is greater than the fourth RSRP, it indicates that the interference of the established desired D2D link to the cellular link is within a permissible range, and the desired D2D link may be established.

[00114] (g4) A CQI (Channel Quality Indicator) of the link between each user equipment and a base station in a cell where it lies in a predetermined time duration is smaller than a first preset threshold.

[00115] The condition (g4) considers the CQI of the link between each user equipment and the base station in the cell where it lies in the predetermined time duration, it indicate that the communication quality of the link between each user equipment and the base station in the cell where it lies is better and the desired D2D link needn't be established because establishment of the desired D2D link needs to perform the power control as in the method 300 and resource allocation as provided below to mitigate the interference.

[00116] (g5) The number of allocated resource blocks on the desired D2D link is smaller than a second preset threshold.

[00117] The condition (g5) considers the number of resource blocks to be allocated on the desired D2D link. If the number of resource blocks to be allocated on the desired D2D link is greater than or equal to the second preset threshold, the desired D2D link needn't be established. If the number of resource blocks to be allocated on the desired D2D link is smaller than the second preset threshold, the desired D2D link may be established.

[00118] (6g) A total spectrum use rate after establishment of the desired D2D link is greater than or equal to a total spectrum use rate before establishment of the desired D2D link.

[00119] The condition (g6) considers the total spectrum use rate before and after establishment of the desired D2D link. If the total spectrum use rate after establishment of the desired D2D link increases, the desired D2D link may be established. In an embodiment, a manner of determining the total spectrum use rate may be selected from formula (10) or (11) discussed in detail below.

[00120] In some embodiments, when each of the user equipment at the transmitting end and the user equipment at the receiving end satisfies any one of the D2D communication conditions (gl) to (g6), the desired D2D link is established. In some other embodiments, when each user equipment in the user equipment at the transmitting end and the user equipment at the receiving end satisfies any combination of more of the D2D communication conditions (gl) to (g6), the desired D2D link is established.

[00121] According to an embodiment of the present invention, before the method 300 and after establishment of desired D2D link, a resource block needs to be allocated to the established desired D2D link. It may be appreciated that if the resource block allocated on the desired D2D link is shared by more other D2D links or cellular links, the interference in the system is greater. Therefore, in order to effectively mitigate the interference and meanwhile in consideration of the use rate of the resource block, according to an embodiment of the present invention, there is provided the following method of allocating resource blocks: before determining the maximum available transmit power, for any resource block, if a second sum data rate is greater than or equal to a first sum data rate, the resource blocks are allocated to the desired D2D link.

[00122] The first sum data rate is a sum data rate of a further D2D link and cellular links when the resource blocks are allocated to the further D2D link and cellular link rather than to the desired D2D link; the second sum data rate is a sum data rate of the further D2D link, the cellular links and the desired D2D link in the case of the resource block is allocated to the further D2D link and the cellular link and then allocated to the desired D2D link.

[00123] The sum data rate may be calculated based on a signal to interference plus noise power ratio on the D2D and cellar links. Since the second sum data rate is an estimate of sum data rate in this case before the resource block is allocated to the desired D2D link, an actual signal to interference plus noise power ratio cannot be obtained because at this time the resource block is not yet really allocated to the desired D2D link. Therefore, according to an embodiment of the present invention, the first sum data rate is determined according to the RSRP of each link in the further D2D link and the cellular link and the RSRP on the interference links thereof; the second sum data rate is a sum data rate determined according to the RSRP of each link in the further D2D link, the cellular link and the desired D2D link and the RSRP on the interference links thereof. The RSRP of each link may be taken as a signal received power, and a sum of the RSRP on the interference links thereof may be taken as a noise received power so as to estimate the second sum data rate. In another embodiment, the noise receiving rate may further include a Gaussian white noise received power.

[00124] In an exemplary embodiment of the present invention, it is difficult to determine the sum data rate in the case of multiple desired D2D links, so thoughts are given here to the situation that there is one desired D2D link. In one embodiment, the first sum data rate and the second sum data rate may be calculated by using the following formula:

P

R ",before 1 ∑log₂ , (10)

P+l RSRP_k

¾_er2 =∑^lo ₂ , (11)

∑ RSRF _k + N₍

[00125] Where the formula (10) is used to calculate the first sum data rate, and the formula (11) is used to calculate the second sum data rate, ^beforei represents the first sum data rate; ^_after2 represents the second sum data rate; P represents the number of other D2D links and cellular links to which the resource block is allocated before the resource block is allocated to the desired D2D link; P+l represents the number of other D2D links, cellular links and the desired D2D link to which the resource blocks is allocated after the resource block is allocated to the desired D2D

RSRP

link; RSRP_k represents the RSRP of the kth receiving end on its own desired D2D link;

represents the RSRP on the link between the kth receiving end and the z^'th transmitting end of the interference link, i being not equal to k; N₀ represents the Gaussian white noise.

[00126] It may be appreciated that the above formulas are only exemplary and non-limitation manners of calculating the first and second sum data rate. Embodiments of the present invention are not limited to the specific formulas disclosed herein. Those skilled in the art, according to the teaching of the description, may employ other suitable (existing or to-be-developed) methods to calculate the first sum data rate and second sum data rate.

[00127] After the first sum data rate and the second sum data rate are determined, the magnitude of the first sum data rate and second sum data rate may be judged. If the second sum data rate is greater than the first sum data rate, this indicate that the sum data rate of the system can be improved after the resource block is allocated to the desired D2D link, and then the resource block may be allocated to the desired D2D link.

[00128] Fig.4 illustrates schematically a block diagram of user equipment 400 in which the method of mitigating interference is implemented according to one embodiment of the present invention. In some embodiments, the user equipment 400 may be a mobile phone, flat panel computer, portable notebook computer, laptop notebook computer, or the like. As shown in Fig.4, an obtaining means 401 is configured to obtain the maximum available transmit power; a first determining means 402 is configured to determine a first path loss power of at least one desired D2D link to user equipment at a receiving end, and determine a second path loss power of at least one interference link; a second determining means 403 is configured to determine an estimated transmit power according to the first path loss power and the second path loss power; and a selecting means 404 is configured to select a smaller power as a transmit power from the maximum available transmit power and the estimated transmit power.

[00129] It can be seen that the user equipment 400 in Fig.4 may implement the method shown in Fig.3, and even not further shown though, the user equipment 400 may comprise more means or functional units to implement various units for performing steps of the method in the multiple embodiments as described in connection with the method 300 of Fig.3.

[00130] The flow chart and block diagram illustrated with reference to figures describe exemplary embodiments of the present invention. It should be noted that, the method disclosed in the embodiments of the present invention can be implemented in software, hardware or the combination thereof. The hardware part can be implemented by a special logic; the software part can be stored in a memory and executed by a proper instruction execution system such as a microprocessor or a personal computer (PC). In some embodiments, the present invention is implemented as software, which includes, but is not limited to firmware, residence software and microcode.

[00131] Moreover, the present invention may be implemented as a computer program product usable from computers or accessible by computer-readable media that provide program codes for use by or in connection with a computer or any instruction executing system. For the purpose of description, a computer-usable or computer-readable medium may be any tangible means that can contain, store, communicate, propagate, or transport the program for use by or in connection with an instruction execution system, apparatus, or device.

[00132] The medium may be an electric, magnetic, optical, electromagnetic, infrared, or semiconductor system (apparatus or device), or propagation medium. Examples of the computer-readable medium would include the following: a semiconductor or solid storage device, a magnetic tape, a portable computer diskette, a random access memory (RAM), a read-only memory (ROM), a hard disk, and an optical disk. Examples of the current optical disk include a compact disk read-only memory (CD-ROM), compact disk-read/write (CR-ROM), and DVD.

[00133] The purpose for providing the description of the present invention is to explain and describe, but not to exhaust or limit the present invention within the disclosed form. To an ordinary skilled in the art, various modifications and alternations are feasible. Thus, selecting and describing the preferred embodiments is to better illustrate principles and a practical application of the present invention and to enable an ordinary skilled in the art to appreciate that all the modifications and alterations fall within the protection scope of the present invention as limited by the appending claims, without departing the spirit of the present invention.

Claims

WHAT IS CLAIMED IS:

1. A method of mitigating interference in user equipment at a transmitting end, comprising: obtaining a maximum available transmit power;

determining a first path loss power of at least one desired D2D link to user equipment at a receiving end, and determining a second path loss power of at least one interference link;

determining an estimated transmit power according to the first path loss power and the second path loss power; and

selecting a smaller power from the maximum available transmit power and the estimated transmit power, as a transmit power.

2. The method according to claim 1, wherein the determining the first path loss power of at least one desired D2D link to the user equipment at the receiving end comprises:

determining a first estimated path loss power of each desired D2D link to the user equipment at the receiving end; and

determining the first path loss power according to the determined first estimated path loss powers.

3. The method according to claim 2, wherein the determining the first estimated path loss power of each desired D2D link to the user equipment at the receiving end comprises:

obtaining a first reference signal received power RSRP of each desired D2D link to the user equipment at the receiving end, and determining the first estimated path loss power of each desired D2D link according to the first RSRP; or

determining a first distance to the user equipment at the receiving end of each desired D2D link, and determining the first estimated path loss power of each desired D2D link according to the first distance.

4. The method according to claim 2, wherein the determining the first estimated path loss power of each desired D2D link to the user equipment at the receiving end comprises:

receiving a first reference signal transmitted by user equipment within a first geographic range applying a first predetermined transmit power, and determining a received power of the first reference signal, wherein the user equipment at the transmitting end acknowledges the first predetermined transmit power in advance;

determining a D2D actual path loss power of a link between the user equipment within the first geographic range and the user equipment at the transmitting end, according to the first predetermined transmit power and the received power of the respective first reference signal; and regarding the D2D actual path loss power between each user equipment included in the at least one desired D2D link among the user equipment within the first geographic range and the user equipment at the transmitting end, as the first estimated path loss power of each desired D2D link.

5. The method according to claim 2, wherein the determining the first estimated path loss power of each desired D2D link to the user equipment at the receiving end comprises:

applying a second predetermined transmit power to transmit a second reference signal, and determining a received power of user equipment receiving the second reference signal;

determining a D2D actual path loss power of a link between each user equipment receiving the second reference signal and the user equipment at the transmitting end, according to the second predetermined transmit power and the received power of each user equipment receiving the second reference signal; and

regarding the D2D actual path loss power of the link between each user equipment included in the at least one desired D2D link among user equipment receiving the second reference signal and the user equipment at the transmitting end, as the first estimated path loss power of each desired D2D link.

6. The method according to any one of claims 2-5, wherein the determining the first path loss power according to the determined first estimated path loss powers comprises:

determining a maximum first estimated path loss power in the determined first estimated path loss powers as the first path loss power;

calculating a harmonic average value of the determined first estimated path loss powers, and regarding the calculated harmonic average value as the first path loss power; or

calculating a linear combination average value of the determined first estimated path loss powers, and regarding the calculated linear combination average value as the first path loss power.

7. The method according to claim 1, wherein the interference link includes a D2D interference link consisting of user equipment at a receiving end and a transmitting end of a further D2D link using the same resource block as the desired D2D link, and/or a cellular interference link consisting of user equipment at a receiving end and a transmitting end of a cellular link using the same resource block as the desired D2D link,

wherein the determining the second path loss power of the at least one interference path comprises:

determining a first interference path loss power of the D2D interference link, and/or determining a second interference path loss power of the cellular interference link;

determining the second path loss power according to the first interference path loss power and/or the second interference path loss power.

8. The method according to claim 7, wherein the determining the first interference path loss power of the D2D interference link comprises:

determining a second estimated path loss power of each D2D interference link; and determining the first interference path loss power according to the determined second estimated path loss powers.

9. The method according to claim 8, wherein the determining the second estimated path loss power of each D2D interference link comprises:

obtaining a second RSRP of each D2D interference link, and determining the second estimated path loss power of each D2D interference link according to the second RSRP; or

determining a second distance to the user equipment at the receiving end of each D2D interference link, and determining the second estimated path loss power of each D2D interference link according to the second distance.

10. The method according to claim 8, wherein the determining the second estimated path loss power of each D2D interference link comprises: receiving a first reference signal transmitted by user equipment within a first geographic range applying a first predetermined transmit power, and determining a received power of the first reference signal, wherein the user equipment at the transmitting end acknowledges the first predetermined transmit power in advance;

determining a D2D actual path loss power of a link between the user equipment within the first geographic range and the user equipment at the transmitting end, according to the first predetermined transmit power and the received power of the respective first reference signal; wherein user equipment among the user equipment within the first geographic range other than the user equipment included in the at least one desired D2D link constitute the D2D interference link with the user equipment at the transmitting end; and

the D2D actual path loss power of each D2D interference link is determined as the second estimated path loss power of the D2D interference link.

11. The method according to claim 8, wherein the determining the second estimated path loss power of each D2D interference link comprises:

determining a D2D actual path loss power of a link between each user equipment receiving the second reference signal and the user equipment at the transmitting end, according to the second predetermined transmit power and the received power of each user equipment receiving the second reference signal;

wherein user equipment among the user equipment receiving the second reference signal other than the user equipment included in the at least one desired D2D link constitute the D2D interference link with the user equipment at the transmitting end; and

12. The method according to any one of claims 8-11, wherein the determining the first interference path loss power according to the determined second estimated path loss powers comprises: determining a minimum second estimated path loss power in the determined second estimated path loss powers as the first interference path loss power;

calculating a harmonic average value of the determined second estimated path loss powers, and regarding the calculated harmonic average value as the first interference path loss power; or calculating a linear combination average value of the determined second estimated path loss powers, and regarding the calculated linear combination average value as the first interference path loss power.

13. The method according to claim 7, wherein the determining the second interference path loss of the cellular interference link comprises:

determining a cellular actual path loss power of each cellular interference link; and determining the second interference path loss power according to the determined cellular actual path loss powers.

14. The method according to claim 13, wherein the determining the cellular actual path loss power of each cellular interference link comprises:

receiving a third reference signal transmitted by a receiving end of each cellular interference link applying a third predetermined transmit power, wherein the user equipment at the transmitting end acknowledges the third predetermined transmit power in advance;

determining a received power of the received third reference signal; and

determining an actual cellular path loss power of each cellular interference link according to the received power of the received third reference signal and the third predetermined transmit power.

15. The method according to claim 13 or 14, wherein determining the second interference path loss power according to the determined actual cellular path loss powers comprises:

determining a minimum actual cellular path loss power in the determined actual cellular path loss powers as the second interference path loss power;

calculating a harmonic average value of the determined actual cellular path loss powers, and regarding the calculated harmonic average value as the second interference path loss power; or calculating a linear combination average value of the determined actual cellular path loss powers, and regarding the calculated linear combination average value as the second interference path loss power.

16. The method according to claim 4 or 10, wherein the receiving the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power comprises:

applying a preconfigured transmit power to broadcast a measurement request, and defining user equipment receiving the measurement request as the user equipment within the first geographic range; and

receiving the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power.

17. The method according to claim 4 or 10, wherein the receiving the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power comprises:

receiving the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power upon receiving a measurement request transmitted by a base station in a cell where the user equipment at the transmitting end lies;

wherein the base station in the cell where the user equipment at the transmitting end lies acknowledges a geographic position of the user equipment within the first geographic range in advance.

18. The method according to claim 17, wherein the receiving the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power upon receiving the measurement request transmitted by the base station in the cell where the user equipment at the transmitting end lies comprises:

if the user equipment within the first geographic range are all located in the cell where the user equipment at the transmitting end lies, receiving the first reference signal transmitted by the user equipment within the first geographic range applying the first predetermined transmit power upon receiving the measurement request directly transmitted by the base station in the cell where the user equipment at the transmitting end lies;

if the user equipment within the first geographic range are not all located in the cell where the user equipment at the transmitting end lies, receiving the first reference signal transmitted by the user equipment located in the cell where the transmitting end lies among the user equipment within the first geographic range by applying the first predetermined transmit power upon receiving the measurement request directly transmitted by the base station in the cell where the user equipment at the transmitting end lies, and receiving the first reference signal transmitted by other user equipment among the user equipment within the first geographic range other than those located in the cell where the transmitting end lies by applying the first predetermined transmit power upon receiving the measurement request first transmitted by the base station in the cell where the user equipment at the transmitting end lies to a base station of a predetermined neighboring cell and then forwarded by the base station of the predetermined neighboring cell.

19. The method according to claim 1, wherein the determining the estimated transmit power according to the first path loss power and the second path loss power comprises:

determining the estimated transmit power according to the first path loss power, the second path loss power and a system parameter;

wherein the system parameter include one or more of: a predetermined open loop power control parameter, the number of allocated resource blocks on the desired D2D link, compensation of a transmission format and a predetermined closed loop power control parameter.

20. The method according to claim 1, wherein before determining the maximum available transmit power, the desired D2D link is established with the user equipment at the receiving end upon each of the user equipment at the transmitting end and the user equipment at the receiving end satisfies a D2D communication condition.

21. The method according to claim 20, wherein there is one desired D2D link, and each of the user equipment at the transmitting end and the user equipment at the receiving end satisfies one or a combination of more of the following D2D communication conditions:

a third RSRP of the desired D2D link is greater than or equal to a fourth RSRP of a link between each user equipment and a base station in a cell where it lies;

a first predetermined proportion of the third RSRP is greater than or equal to a fifth RSRP of a link between each user equipment and a receiving end of a cellular link using the same resource block as the desired D2D link;

a second predetermined proportion of a sixth RSRP is greater than or equal to the fourth RSRP, wherein the sixth RSRP is a RSRP of the cellular link using the same resource block as the desired D2D link;

a channel quality indicator CQI of the link between each user equipment and a base station in a cell where it lies in a predetermined time duration is smaller than a first preset threshold;

the number of allocated resource blocks on the desired D2D link is smaller than a second preset threshold;

a total spectrum use rate after establishment of the desired D2D link is greater than or equal to a total spectrum use rate before establishment of the desired D2D link.

22. The method according to claim 1, wherein before determining the maximum available transmit power, for any resource block, if a second sum data rate is greater than or equal to a first sum data rate, the resource block are allocated to the desired D2D link;

wherein the first sum data rate is a sum data rate of a further D2D link and a cellular link when the resource block is allocated to the further D2D link and the cellular link rather than to the desired D2D link; the second sum data rate is a sum data rate of the further D2D link, the cellular link and the desired D2D link in the case of the resource block is allocated to the further D2D link and the cellular link and then allocated to the desired D2D link.

23. The method according to claim 22, wherein there is one desired D2D link, the first sum data rate is a sum data rate determined according to a RSRP on each of the further D2D link and the cellular link and the RSRP on the interference links thereof; the second sum data rate is a sum data rate determined according to a RSRP on each of the further D2D link, the cellular link and the desired D2D link and a RSRP on the interference links thereof.

24. User equipment, comprising:

an obtaining means configured to obtain the maximum available transmit power;

a first determining means configured to determine a first path loss power of at least one desired D2D link to user equipment at a receiving end, and determine a second path loss power of at least one interference link;

a second determining means configured to determine an estimated transmit power according to the first path loss power and the second path loss power; and

a selecting means configured to select a smaller power from the maximum available transmit power and the estimated transmit power, as a transmit power.