WO2014117366A1

WO2014117366A1 - Method and apparatus for interference coordination in heterogeneous network

Info

Publication number: WO2014117366A1
Application number: PCT/CN2013/071211
Authority: WO
Inventors: Lei Jiang; Ming Lei; Yongming Huang; Shiwen HE; Shi Jin; Lvxi Yang
Original assignee: Nec(China) Co., Ltd.
Priority date: 2013-01-31
Filing date: 2013-01-31
Publication date: 2014-08-07
Also published as: CN104956708A; CN104956708B

Abstract

Embodiments of the disclosure provide a method and apparatus for interference coordination in a heterogeneous network. The method may comprise: obtaining types of a plurality of UE in the heterogeneous network, wherein the heterogeneous network comprises at least one macro BS and at least one LPN, and wherein each of the types is macro central area type, macro non-central area type, LPN central area type, or LPN non-central area type; and determining one or more user pairs from the plurality of UEs based on the obtained types, such that the plurality of UEs are scheduled based on the one or more user pairs to reduce inter-cell interference.

Description

METHOD AND APPARATUS FOR INTERFERENCE COORDINATION IN HETEROGENEOUS NETWORK

FIELD OF THE INVENTION

[0001] Embodiments of the present invention generally relate to communication techniques. More particularly, embodiments of the present invention relate to a method and apparatus for interference coordination in a heterogeneous network. BACKGROUND OF THE INVENTION

[0002] With the development of user equipment (UE) and the proliferation of bandwidth intensive applications, traffic load in cellular networks increases in an unexpected manner. Recently, a new framework of heterogeneous networks (HetNets) has attracted much attention, which has emerged as a flexible and cost-effective way of handling the exploding and uneven wireless data traffic demands. The heterogeneous network is deployed by including low power nodes (LPNs), such as pico base station (BS), femto BS, relay node and remote radio head (RRH), overlaid in coverage of a macro cell.

[0003] In order to fully exploit the role of low power node and balance the user loading of macro cell, a concept of range expansion for lower power node cell was introduced in the HetNet. Specifically, a positive range expansion bias (REB) is added to the downlink (DL) reference signal strengths (RSSs) of a lower-power node pilot signal when a UE is making decision of association. As a result, the UE possibly gets associated to the lower power node even though the DL link quality of the Macro BS (MBS) is in favorable condition. This would be useful for load balancing and the exploitation of spatial reuse, and also helps to mitigate uplink (UL) inter-cell interference through reducing UL transmit power. However, in downlink phase the UEs in the range expansion area will suffer serious DL inter-cell interference from the MBS. Therefore, it is important to develop inter-cell interference coordinated technology for the HetNet.

[0004] 3GPP long term evolution (LTE) Release 10 standard specification adopted the almost blank subframe (ABS) technology to partially address this problem, which is defined a new subframe where no transmission on the physical DL shared channel (PDSCH) is allowed from MBS. In order to efficiently use the ABS, the lower power node must have perfect knowledge of the ABS patterns to make proper user scheduling. Besides this strategy, interference control (IC) based on limited feedback, such as the best companion cluster (BCC), was also intensively studied and extended to HetNets. However, these schemes involve too much undesired overhead and would result in a loss of the degrees of freedom for user pairing.

[0005] In view of the foregoing problems, there is a need to develop an interference coordination scheme in the heterogeneous network, so as to effectively and efficiently improve performance of the heterogeneous network.

SUMMARY OF THE INVENTION

[0006] The present invention proposes a solution which develops an interference coordination scheme in the heterogeneous network. Specifically, embodiments of the present invention provide methods and apparatuses for interference coordination in a heterogeneous network, which can effectively improve performance of the heterogeneous network, as well as reduce undesired overhead and increase the degree of freedom for user pairing.

[0007] According to a first aspect of the present invention, embodiments of the invention provide a method for interference coordination in a heterogeneous network. The method may comprise: obtaining types of a plurality of UE in the heterogeneous network, wherein the heterogeneous network comprises at least one macro BS and at least one LPN, and wherein each of the types is macro central area type, macro non-central area type, LPN central area type, or LPN non-central area type; and determining one or more user pairs from the plurality of UEs based on the obtained types, such that the plurality of UEs are scheduled based on the one or more user pairs to reduce inter-cell interference.

[0008] According to a second aspect of the present invention, embodiments of the invention provide an apparatus for interference coordination in a heterogeneous network. The apparatus may comprise: an obtainer configured to obtain types of a plurality of UEs in the heterogeneous network, wherein the heterogeneous network comprises at least one macro BS and at least one LPN, and wherein each of the types is macro central area type, macro non-central area type, LPN central area type, or LPN non-central area type; and a determiner configured to determine one or more user pairs from the plurality of UEs based on the obtained types, such that the plurality of UEs are scheduled based on the one or more user pairs to reduce inter-cell interference.

[0009] Other features and advantages of the embodiments of the present invention will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Embodiments of the invention are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings, where

[0011] FIG. 1 illustrates a schematic diagram of a heterogeneous network 100 according to embodiments of the invention;

[0012] FIG. 2 illustrates a flow chart of a method 200 for interference coordination in the heterogeneous network according to embodiments of the invention;

[0013] FIG. 3 illustrates a flow chart of a method 300 for obtaining types of UEs in the heterogeneous network according to further embodiments of the invention;

[0014] FIG. 4 illustrates a flow chart of a method 400 for determining user pairs from the UEs according to still further embodiments of the invention;

[0015] FIG. 5 illustrates a block diagram of an apparatus 500 for interference coordination in the heterogeneous network according to embodiments of the invention;

[0016] FIG. 6 A and FIG. 6B illustrate schematic diagrams of the average relative rate loss and the LPN user coordination bias according to some embodiments of the invention, respectively;

[0017] FIG. 7A and FIG. 7B illustrate schematic diagrams of the average relative rate loss and the LPN user coordination bias according to some other embodiments of the invention, respectively;

[0018] FIG. 8 A and FIG. 8B illustrate schematic diagrams of the average relative rate loss and the macro user coordination bias according to some embodiments of the invention, respectively; and [0019] FIG. 9 A and FIG. 9B illustrate schematic diagrams of the average relative rate loss and the macro user coordination bias according to some other embodiments of the invention, respectively.

[0020] Throughout the figures, same or similar reference numbers indicate same or similar elements.

DETAILED DESCRIPTION OF EMBODIMENTS

[0021] Embodiments of the invention will be described thoroughly hereinafter with reference to the accompanying drawings. It will be apparent to those skilled in the art that the invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments and specific details set forth herein. Like numbers refer to like elements throughout the specification.

[0022] Various embodiments of the present invention are described in detail with reference to the drawings. The flowcharts and block diagrams in the figures illustrate the apparatus, method, as well as architecture, functions and operations executable by a computer program product according to the embodiments of the present invention. In this regard, each block in the flowcharts or block may represent a module, a program, or a part of code, which contains one or more executable instructions for performing specified logic functions. It should be noted that in some alternatives, functions indicated in blocks may occur in an order differing from the order as illustrated in the figures. For example, two blocks illustrated consecutively may be actually performed in parallel substantially or in an inverse order, which depends on related functions. It should also be noted that block diagrams and/or each block in the flowcharts and a combination of thereof may be implemented by a dedicated hardware-based system for performing specified functions/operations or by a combination of dedicated hardware and computer instructions.

[0023] The features, structures, or characteristics of the invention described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the usage of the phrases "some embodiments," "in some other embodiments," or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. [0024] Embodiments of the present invention may be applied in the heterogeneous networks, including but not limited to the LTE system. Given the rapid development in communications, there will of course also be future type wireless communication technologies and systems with which the present invention may be embodied. It should not be seen as limiting the scope of the invention to only the aforementioned system.

[0025] In the disclosure, a base station (BS) may refer to a node B (NodeB or NB) or an evolved NodeB (eNodeB or eNB). A base station may be a macrol BS or a LPN (i.e., small cell BS). According to the present invention, a macro BS may be a base station which manages a macrocell, for example, a macro eNB, and a small cell BS may be a base station which manages a small cell, for example, a pico eNB, a femto eNB, a relay node, a RRH BS and some other suitable low power nodes.

[0026] In the disclosure, a user equipment (UE) may refer to a terminal, a Mobile Terminal (MT), a Subscriber Station (SS), a Portable Subscriber Station (PSS), Mobile Station (MS), or an Access Terminal (AT), and some or all of the functions of the UE, the terminal, the MT, the SS, the PSS, the MS, or the AT may be included.

[0027] Embodiments of the present invention provide a method and apparatus for random access in a wireless network. According to embodiments of the present invention, types of UEs in the heterogeneous network are first obtained, and then user pair(s) may be determined from the UEs based on their types. By scheduling the user pair(s) determined according to embodiments of the present invention, cross-layer interference between the macro cell and small cells may be effectively reduced. In this way, a good tradeoff between coordination gain and overhead can be exploited. Now some exemplary embodiments of the present invention will be described below with reference to the figures.

[0028] Reference is first made to FIG. 1, which illustrates a schematic diagram of a heterogeneous network 100 according to embodiments of the invention.

[0029] In FIG. 1, a heterogeneous network 100 is exemplarily illustrated as comprising a macro BS 110 and three LPNs, 120, 130 and 140. The coverage of each LPN is in the coverage of the macro cell, or at least partially overlapped with the coverage of the macro cell. Five UEs 101-105 are exemplarily shown in the heterogeneous network 100 and each has a different type. These UEs 101-105 may receive signals from one or more BSs in the heterogeneous network 100. For example, one or more of UEs 101-105 may receive signals from the macro BS 110, LPN 120, LPN 130 and/or LPN 140.

[0030] It is to be noted that although one macro BS and three LPNs are shown in the heterogeneous network 100, there may be more than one macro BS in the heterogeneous network 100 in practice and more or less LPNs may be deployed. It is also to be noted that although five UEs 101-105 have been shown in the heterogeneous network 100, they are examples, rather than limitations. Those skilled in the art will appreciate that more or less UEs are applicable to the interference coordination scheme according to embodiments of the present invention.

[0031] For better understanding, the following embodiments of the present disclosure are described based on the heterogeneous network shown in FIG. 1. As can be appreciated by those skilled in the art, the present disclosure can be applicable to any other suitable heterogeneous network, but not limited to the specific arrangement shown in FIG.1.

[0032] Reference is now made to FIG. 2, which illustrates a flow chart of a method 200 for interference coordination in the heterogeneous network according to embodiments of the invention. The heterogeneous network may comprise at least one macro BS and at least one LPN, e.g., the heterogeneous network 100 shown in FIG. 1. In accordance with embodiments of the present invention, the method 200 may be carried out by a macro BS, a LPN, a controller, a central unit, a server, a UE, or any other applicable device.

[0033] At step S201, types of a plurality of UEs in the heterogeneous network are obtained.

[0034] The type of a UE may be defined in several ways. According to embodiments of the present invention, the type of a UE may be macro central area type, macro non-central area type, LPN central area type, or LPN non-central area type. For example, with respect to a UE in macro central area, the type of the UE may be macro central area type. Likewise, with respect to a UE in macro non-central area, LPN central area or LPN non-central area, the type of the UE may be macro non-central area type, LPN central area type, or LPN non-central area type.

[0035] As shown in FIG. 1, in the heterogeneous network 100, UE 101 is located in the macro central area, thus the type of UE 101 is the macro central area type. Accordingly, since UE 102 is located in the LPN non-central area, UE 103 is located in the macro non-central area, UE 104 is located in the LPN non-central area, and 105 is located in the LPN central area, it may be determined that the type of UE 102 is the LPN non-central area type, the type of UE 103 is the macro non-central area type, the type of UE 104 is the LPN non-central area type, and the type of UE 105 is the LPN central area type.

[0036] In accordance with embodiments of the present invention, the types of a plurality of UEs in the heterogeneous network may be obtained in multiple ways. In some embodiments, the types of UEs may be determined by a macro BS, a LPN, a controller, a central unit, a server, a UE, and so on. As such, the obtaining of the types of UEs may comprises the following steps: obtaining a LPN user coordination bias; obtaining a macro user coordination bias; obtaining first signal strength and second signal strength of each UE of the plurality of UEs, wherein the first signal strength indicates strength of signals received at the each UE from the LPN and the second signal strength indicates strength of signals received at the each UE from the macro BS; and determining a type of the each UE based on the LPN user coordination bias, the macro user coordination bias, the first signal strength and the second signal strength. Further details for determination of the types of UEs may be found in embodiments illustrated with FIG. 3.

[0037] In some other embodiments, the obtaining of the types of UEs may be implemented by receiving information on the type of a UE from the UE; and/or receiving information on the type of a UE from a macro BS or a LPN serving the UE. For example, when the type of a UE is determined by the UE itself, the apparatus (e.g., a macro BS, a LPN, a controller, a central unit, a server, etc.) performing method 200 may receive information on the type of a UE from the UE, without unnecessarily determination of the UE's type. For another example, when the type of a UE is determined by the macro BS, the apparatus (e.g., a LPN, a controller, a central unit, a server, a UE, etc.) performing method 200 may receive information on the type of a UE from the macro BS.

[0038] At step S202, one or more user pairs from the plurality of UEs are determined based on the obtained types, such that the plurality of UEs are scheduled based on the one or more user pairs to reduce inter-cell interference

[0039] Referring to FIG. 1 again, with the knowledge of the types of the UEs

101-105, one or more user pairs may be determined from the UEs 101-105 according to embodiments of the present invention. By employing the determined user pairs in scheduling, inter-cell interference in the heterogeneous network 100 may be effectively reduced. Further details may be found in descriptions in connection to embodiments illustrated with FIG. 4.

[0040] Reference is now made to FIG. 3, which illustrates a flow chart of a method 300 for obtaining types of UEs in the heterogeneous network according to further embodiments of the invention. Method 300 may be considered as an embodiment of step S201 of method 200 described above with reference to FIG. 2. In the following description of method 300, the types of the UEs are determined by comparing the second signal strength with a sum of the first signal strength and the LPN user coordination bias, a sum of the first signal strength and the macro user coordination bias and a sum of the first signal strength and a range expansion bias. However, it is noted that this is only for the purpose of illustrating the principles of the present invention, rather than limiting the scope thereof.

[0041] After method 300 starts, at step S301, a LPN user coordination bias is obtained.

[0042] In accordance with embodiments of the present invention, the LPN user coordination bias may be obtained in several ways.

[0043] In some embodiments, the LPN user coordination bias may be predefined or preset. For example, the LPN user coordination bias may be preset according to experience of an operator or a skilled in the art; the LPN user coordination bias may also be predefined according to concrete communication conditions of the heterogeneous network. It is to be noted that the above examples are described for illustration, and the LPN user coordination bias may be obtained in other ways besides the above examples.

[0044] In some other embodiments, the LPN user coordination bias may be determined by: obtaining a first rate achieved by a UE which is of the LPN non-central area type and performs inter-cell interference coordination, and a second rate achieved by a UE which is of the LPN non-central area type and does not perform inter-cell interference coordination; and determining the LPN user coordination bias based on the first rate and the second rate. According to embodiments of the present invention, the LPN user coordination bias may be determined based on the first rate and the second rate as follows. First, a average relative rate loss may be first calculated based on the first rate and the second rate; then, one or more saturated points with respect to the average relative rate loss may be determined; and then, based on the one or more saturated points, a candidate from the candidates may be selected as the LPN user coordination bias. According to embodiments of the present invention, a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the LPN user coordination bias. With respect to multiple candidates of the LPN user coordination bias, there may be one or more saturated points.

[0045] In accordance with embodiments of the present invention, the first rate indicates a rate achieved by a UE which is of the LPN non-central area type and performs inter-cell interference coordination. In some embodiments of the present invention, for a UE (also referred to as "LPN UE") served by a LPN and of the LPN non-central area type, the first rate (denoted as R _c ) indicates the rate achieved by the

UE performing inter-cell interference coordination. It is to be noted that during the determination of the LPN user coordination bias, there may be a plurality of candidates for the LPN user coordination bias. With respect to one candidate, the type of a UE may be determined. As such, it may be determined whether a UE has the LPN non-central area type or not. In some embodiments of the present invention, for a UE (also referred to as "LPN UE") served by a LPN, especially, having the LPN non-central area type, and performing inter-cell interference coordination, the first rate (denoted as R_jC ) achieved by the UE may be calculated as

where denotes the beamformer for the LPN UE;

WY denotes the interference coordinated beamformer of the LPN UEfor the macro BS;

P_m and P_r denote the transmit power of the macro BS and the LPN, respectively; a™_T denotes the large scale fading coefficient from the macro BS to the LPN

UE;

a _T denotes the large scale fading coefficient from the LPN to the LPN UE; h™_r denotes the small scale fading coefficient from the macro BS to the i^th LPN

UE;

h_i ^r _r denotes the small scale fading coefficient from the LPN to the LPN UE; and

σ denotes the variance of additive Gaussian white noise with zero mean.

[0046] In accordance with embodiments of the present invention, the second rate indicates a rate achieved by a UE which is of the LPN non-central area type and does not perform inter-cell interference coordination. According to embodiments of the present invention, the second rate R^_IC may be calculated by

[0047] By using the first rate and the second rate, e.g., calculated by equations (1) and (2), an average relative rate loss may be calculated as

w re

[0048] According to embodiments of the present invention, the LPN user coordination bias (denoted as Θ ) may be calculated based on the average relative rate loss as follows:

where θ₀ is an optimal value obtained according to equation (3) for the LPN user coordination bias Θ ; and ξ is defined as a LPN collaboration relative gain factor, which indicates the average relative rate loss corresponding to the optimal value θ₀ for the LPN user coordination bias Θ .

[0049] According to embodiments of the present invention, one or more saturated points with respect to the average relative rate loss may be determined, wherein a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the LPN user coordination bias; and then, a candidate from the candidates may be selected as the LPN user coordination bias based on the one or more saturated points.

[0050] Reference is made to FIG. 6A and FIG. 6B, which respectively illustrate schematic diagrams of the average relative rate loss and the LPN user coordination bias according to some embodiments of the invention.

[0051] FIGs. 6A and 6B show the average relative rate loss varying with different candidates of the LPN user coordination bias Θ. Generally, the average relative rate loss decreases with Θ decreasing. However, the relative coordination gain gradually becomes smaller and a floor is observed, where the interference avoidance become less important for the system improvement. This is due to the fact that with Θ decreasing, the users in the cooperation region will have enlarging difference between the RSRPs from the macro BS and the RRH node, resulting in the decreasing of the interference coordination efficiency. This behavior of the average relative loss indicates that expanding the cooperation area would not always bring much gain. There may be some saturated points which could achieve reasonable tradeoff between the gain and the cost.

[0052] According to embodiments of the present invention, key factors that influence the behavior of the relative rate loss may include the capability of the interference coordination strategy, the LPN (e.g., RRH) location (assuming the transmit power of the macro BS and the RRH node is fixed), and so on. The employment of different codebook size, i.e., 32 or 64 (as shown in FIGs. 6A and 6B), or the employment of different distance between the macro BS and the LPN (as shown in FIGs. 7A and 7B), produces different ranges for the value of the average relative rate loss. However, it should be noted that, a common observation in these figures is that the slope of the average rate loss with Θ changing is only sharp in a small range. This means that only in this range the interference coordination would bring much gain and be very efficient. Based on this observation, the LPN user coordination bias and the LPN collaboration relative gain factor ξ may be determined based on the points that end this sharp-slope range, so as to achieve a good tradeoff between the coordination gain and the cost. In embodiments of the present invention, such points are referred to as saturated points, each of which indicates a sharp change of the average relative rate loss in view of candidates of the LPN user coordination bias. As shown in FIG. 6A, the cross points SI and S2 are both the saturated points. According to embodiments of the present invention, the value of the LPN user coordination bias Θ may be determined based on the saturated points SI and S2. In some embodiments, a target saturated point may be selected from the saturated points and the LPN user coordination bias Θ may be determined according to the target saturated point. For example, the saturated point indicating the sharpest change of the average relative rate loss in view of candidates of the LPN user coordination bias may be selected as the target saturated point. As shown in FIG. 6A, the cross point between the second slope line h and the third slope line I3, i.e., the saturated point S2, may be determined as the target saturated point, because it indicates a sharper change than the cross point between the first slope line /; and the second slope line I2, i.e., the saturated point SI . Based on the target saturated point S2, it may be determined that the LPN user coordination bias Θ is -6 (i.e., θ₀ = -6 ) and the corresponding average relative loss ratio (i.e., the LPN collaboration relative gain factor ξ ) is 0.375.

[0053] As discussed above, factors that may influence the behavior of the average relative rate loss include, e.g., the capability of the interference coordination strategy, LPN location (assuming the transmit power of the macro BS and the LPN is fixed), and so on. In some embodiments, the behavior of the average relative rate loss may be affected by the employed codebook size. As shown, the codebook size used in embodiments in connection with FIG. 6A is 32 and the codebook size used in embodiments in connection with FIG. 6B is 64. As can be seen from FIG. 6B, there are two saturated points S3 and S4, which may indicate different ranges for the value of the average relative rate loss.

[0054] In some other embodiments, the behavior of the average relative rate loss may be affected by distance between the LPN and the macro BS. FIG. 7A and FIG. 7B respectively illustrate schematic diagrams of the average relative rate loss and the LPN user coordination bias according to some other embodiments of the invention. The distance (denoted as D_{m r}) between the LPN and the macro BS are different in embodiments of FIG. 7 A and FIG. 7B. Specifically, the distance used in embodiments in connection with FIG. 7 A is 150m and the distance used in embodiments in connection with FIG. 7B is 200m.

[0055] At step S302, a macro user coordination bias is obtained.

[0056] In accordance with embodiments of the present invention, the macro user coordination bias may be obtained in several ways.

[0057] In some embodiments, the macro user coordination bias may be predefined or preset. For example, the macro user coordination bias may be preset according to experience of an operator or a skilled in the art; the macro user coordination bias may also be predefined according to concrete communication conditions of the heterogeneous network. It is to be noted that the above examples are described for illustration, and the macro user coordination bias may be obtained in other ways besides the above examples.

[0058] In some other embodiments, the macro user coordination bias may be determined by: obtaining a third rate achieved by a UE which is of the macro non-central area type and performs inter-cell interference coordination, and a fourth rate achieved by a UE which is of the macro non-central area type and does not perform inter-cell interference coordination; and determining the macro user coordination bias based on the third rate and the fourth rate. According to embodiments of the present invention, the macro user coordination bias may be determined based on the third rate and the fourth rate as follows. First, a average relative rate loss may be calculated based on the first rate and the second rate; then, one or more saturated points may be determined with respect to the average relative rate loss, wherein a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the macro user coordination bias; and then, a candidate may be selected from the candidates as the macro user coordination bias based on the one or more saturated points.

[0059] In accordance with embodiments of the present invention, the third rate indicates a rate achieved by a UE which is of the macro non-central area type and performs inter-cell interference coordination. In some embodiments of the present invention, for a UE (also referred to as "macro UE") served by a macro BS, especially, having the macro non-central area type, and performing inter-cell interference coordination, the third rate (denoted as R"_c ) achieved by the UE may be calculated as

where ^li i denotes the beamformer for the i^th macro UE (i.e, a UE served by the macro BS);

^U'- m denotes the interference coordinated beamformer of the i^th macro UE for the LPN;

P_m and P_r denote the transmit power of the macro BS and the LPN, respectively; a i^r,m denotes the larg oe scale fading o coefficient from the LPN to the i^th macro

UE;

a i^m,m denotes the larg oe scale fading o coefficient from the macro BS to the i^th macro UE;

h_i ^r _m denotes the small scale fading coefficient from the LPN to the i^th macro

UE;

h™_m denotes the small scale fading coefficient from the macro BS to the i •th macro UE; and

σ² denotes the variance of additive Gaussian white noise with zero mean.

[0060] In accordance with embodiments of the present invention, the fourth rate indicates a rate achieved by a UE which is of the macro non-central area type and does not perform inter-cell interference coordination. According to embodiments of the present invention, the fourth rate R^_IC may be calculated by

[0061] By using the third rate and the fourth rate, e.g., calculated by equations (4) and (5), an average relative rate loss may be calculated as

[0062] According to embodiments of the present invention, the macro user coordination bias (denoted as a ) may be calculated based on the average relative rate loss as follows:

where a₀ is an optimal value obtained according to equation (6) for the macro user coordination bias ; and ς is defined as a macro collaboration relative gain factor, which indicates the average relative rate loss corresponding to the optimal value a₀ for the macro user coordination bias .

[0063] According to embodiments of the present invention, one or more saturated points with respect to the average relative rate loss may be determined, wherein a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the macro user coordination bias; and then, a candidate from the candidates may be selected as the macro user coordination bias based on the one or more saturated points.

[0064] Reference is made to FIG. 8 A and FIG. 8B, which respectively illustrate schematic diagrams of the average relative rate loss and the macro user coordination bias according to some embodiments of the invention.

[0065] FIGs. 8 A and 8B show the average relative rate loss varying with different candidates of the macro user coordination bias . Generally, the average relative rate loss decreases with increasing. However, the relative coordination gain gradually becomes smaller and a floor is observed, where the interference avoidance become less important for the system improvement. This is due to the fact that with increasing, the users in the cooperation region will have enlarging difference between the RSRPs from the macro BS and the RRH node, resulting in the decreasing of the interference coordination efficiency. This behavior of the average relative loss indicates that expanding the cooperation area would not always bring much gain. There may be some saturated points which could achieve reasonable tradeoff between the gain and the cost.

[0066] The employment of different codebook size, i.e., 32 or 64 (as shown in FIGs. 6A and 6B), or the employment of different distance between the macro BS and the LPN (as shown in FIGs. 7A and 7B), may produce different ranges for the value of the average relative rate loss. However, it should be noted that, a common observation in these figures is that the slope of the average rate loss with a changing is only sharp in a small range. This means that only in this range the interference coordination would bring much gain and be very efficient. Based on this observation, the macro user coordination bias and the macro collaboration relative gain factor ξ may be determined based on the points that end this sharp- slope range, so as to achieve a good tradeoff between the coordination gain and the cost. In embodiments of the present invention, such points are referred to as saturated points, each of which indicates a sharp change of the average relative rate loss in view of candidates of the macro user coordination bias. As shown in FIG. 8A, the cross point S5 is a saturated point. According to embodiments of the present invention, the value of the macro user coordination bias a may be determined based on the saturated point S5, which indicates the sharpest change of the average relative rate loss in view of candidates of the macro user coordination bias. As shown in FIG. 8A, based on the target saturated point S5, it may be determined that the macro user coordination bias a is 28 (i.e., a₀ = 28 ) and the corresponding average relative loss ratio (i.e., the macro collaboration relative gain factor ς ) is 0.18.

[0067] According to embodiments of the present invention, factors that may influence the behavior of the average relative rate loss include, e.g., the capability of the interference coordination strategy, LPN location (assuming the transmit power of the macro BS and the LPN is fixed), and so on. In some embodiments, the behavior of the average relative rate loss may be affected by the employed codebook size. As shown, the codebook size used in embodiments in connection with FIG. 8A is 32 and the codebook size used in embodiments in connection with FIG. 8B is 64. As can be seen from FIG. 8B, there is a saturated point S6, which may indicate a different range for the value of the average relative rate loss.

[0068] In some other embodiments, the behavior of the average relative rate loss may be affected by distance between the LPN and the macro BS. FIG. 9A and FIG. 9B respectively illustrate schematic diagrams of the average relative rate loss and the macro user coordination bias according to some other embodiments of the invention. The distance (denoted as D_m__r) between the LPN and the macro BS are different in embodiments of FIG. 9 A and FIG. 9B. Specifically, the distance used in embodiments in connection with FIG. 9A is 150m and the distance used in embodiments in connection with FIG. 9B is 200m.

[0069] At step S303, first signal strength and second signal strength of each UE of the plurality of UEs are obtained.

[0070] The first signal strength may indicate strength of signals received at the each UE from the LPN, and the second signal strength may indicate strength of signals received at the each UE from the macro BS. According to embodiments of the present invention, the first signal strength may be reference signal receiving power (RSPR) from the LPN, and/or the second signal strength may be RSPR from the macro BS.

[0071] In accordance with embodiments of the present invention, the type of the each UE may be determined based on the LPN user coordination bias (e.g., obtained at step S301), the macro user coordination bias (e.g., obtained at step S302), the first signal strength and the second signal strength (e.g., obtained at step S303). The determination of the type may be implemented in several ways. The following steps S304-S307 are provided for example. It is to be noted that steps S304-S307 are given for illustration, rather than limitation.

[0072] At step S304, if the second signal strength is larger than or equal to a sum of the first signal strength and the LPN user coordination bias, and the second signal strength is less than a sum of the first signal strength and a range expansion bias, the type is determined to be the LPN non-central area type.

[0073] According to embodiments of the present invention, the first signal strength, i.e., the strength of signals received at a UE from the LPN, is denoted as RSRP^ , and the second signal strength, i.e., the strength of signals received at the UE i from the macro BS, is denoted as RSRP™ . The UE may be determined as having the LPN non-central area type if the following condition is satisfied:

RSRP + θ < RSRP < RSRP + β (7) where Θ denotes the LPN user coordination bias; and β denotes the range expansion bias, which may be predetermined in several ways, where θ < β . For example, β may be preset as a predetermined value, e.g., 8dB. For another example, β may be predetermined according to existing solutions, which are not detailed here.

[0074] According to embodiments of the present invention, the minimum value ( 0_min ) of the LPN user coordination bias Θ may be calculated according to the large scale fading estimation as follows:

#mm i ^'% (128.1 + 37.6 * log₁₀( /?,„)) - (¾ - ( 140.7 + 36.7 * iog₁₀( ,. ))) where M_r denotes the minimum distance between the LPN user and the LPN, e.g., in km; R_m denotes the macrocell service radius, e.g., in km; P_d ^r _B and P™_B denote the transmit power of the LPN and macro BS, e.g., in dB, respectively. In some embodiments, Θ = 0 denotes the equal RSRP point.

[0075] At step S305, if the second signal strength is less than a sum of the first signal strength and the LPN user coordination bias, the type is determined to be the LPN central area type.

[0076] According to embodiments of the present invention, the UE may be determined as having the LPN central area type if the following condition is satisfied:

RSRP™≤ RSRP; + Θ . (9)

[0077] At step S306, if the second signal strength is larger than or equal to a sum of the first signal strength and the range expansion bias, and the second signal strength is less than a sum of the first signal strength and the macro user coordination bias, the type is determined to be the macro non-central area type.

[0078] According to embodiments of the present invention, the UE may be determined as having the macro non-central area type if the following condition is satisfied:

RSRP' + β < RSRP^™ < RSRP + a (10) where a indicates the macro user coordination bias, and a > β .

[0079] In some embodiments, the estimated maximum value ( a_max ) of the macro user coordination bias a may be calculated according to the large scale fading estimation as follows:

- = P - (128.1 + 37.6 * bg _{! (J} i M₍₁J ) - (F_dB - ( 1 40.7 + 36.7 * log_!0 (!>„._,· + β„>.) ^'}) _{( 1 1 )} where M_m denotes the minimum distance between the macro user and the macro BS, e.g., in km; and D_{m r} denotes the distance between the LPN and the macro BS, e.g., in km.

[0080] At step S307, if the second signal strength is larger than a sum of the first signal strength and the macro user coordination bias, the type is determined to be the macro central area type.

[0081] According to embodiments of the present invention, the UE may be determined as having the macro central area type if the following condition is satisfied:

RSRP + a≤ RSRP™ . (12)

[0082] Reference is now made to FIG. 4, which illustrates a flow chart of a method 400 for determining user pairs from the UEs according to still further embodiments of the invention. Method 400 may be considered as an embodiment of step S202 of method 200 described above with reference to FIG. 2. In the following description of method 400, user pairs are determined based on codeword information comprising information about a preferable codeword or information about a preferable codeword and recommended codeword cluster. However, it is noted that this is only for the purpose of illustrating the principles of the present invention, rather than limiting the scope thereof.

[0083] After method 400 starts, at step S401, whether the type of a UE of the plurality of UEs belongs to a set of UE types comprising the LPN non-central area type and the macro non-central area type is determined.

[0084] According to embodiments of the present invention, the method 400 is performed after the types of a plurality of UEs in the heterogeneous network are obtained. With the knowledge of the types of the plurality of UEs, at step S401, it may be determined whether one UE of the plurality of UEs has the LPN non-central area type/ the macro non-central area type. In other words, whether the UE has a non-central area type (either the LPN non-central area type or the macro non-central area type) may be determined, such that codeword information may be obtained according to the determined UE type.

[0085] At step S402, in response to determining that the type of the UE belongs to the set of UE types, information on a preferable codeword preferred by the UE and information on a recommended codeword cluster as codeword information are obtained.

[0086] If the UE has a non-central area type (either the LPN non-central area type or the macro non-central area type), the codeword information may at least comprise information on a preferable codeword preferred by the UE and information on a recommended codeword cluster. In accordance with embodiments of the present invention, the recommended codeword cluster may indicate a codeword cluster which is recommended to a BS by a UE.

[0087] In embodiments of the present invention, denoting the codebook of the Macro BS as B^m and the codebook of the LPN as B ^r as follows respectively

B'^» = · · · !¾} ₍₁₃₎ and

B¹ = { ■ ^■■ . H ^. } _ (₁₄) where M and N denote the number of codeword cluster; B™ and B denote the codeword clusters in the macro BS and LPN codebook, respectively. 7™ and l denote the sizes of the codeword clusters B™ and B , respectively.

[0088] According to embodiments of the present invention, if the UE has the LPN non-central area type, the preferable codeword denoted as ^'^¹¹^· and the recommended codeword cluster denoted as ^¾'^ΤΑΜ;,. may be calculated as follows: tt'P i, ,. = m x

7 = 1 ,^■·· ,/"

[0089] In some other embodiments, if the UE has the macro non-central area type, the preferable codeword and the recommended codeword cluster may be calculated likewise.

[0090] Optionally, the channel quality may be obtained for scheduling procedures. According to embodiments of the present invention, the channel quality may comprise information which reflects the quality of the channel. For example, the channel quality may comprise signal to interference plus noise ratio (SINR), Signal to Noise Ratio (SNR), Signal to Interference Ratio (SIR), Carrier to Interference plus Noise Ratio (CINR), Carrier to Noise Ratio (CNR), Channel Quality Indication (CQI) and so on.

[0091] In some embodiments, the channel quality may be denoted as SIN _; ,. and calculated by (if the UE has the LPN non-central area type): , H

SIN ; .,. = rnin

\ H

(14) where R,^r denotes the codeword cluster index, i.e., the 5™ include the LPN non-central area UE recommend codeword.

[0092] In some other embodiments, if the UE has the macro non-central area type, the channel quality may be calculated likewise.

[0093] At step S403, in response to determining that the type of the UE does not belong to the set of UE types, information on a preferable codeword preferred by the UE as codeword information is obtained.

[0094] If it is determined that that the type of the UE does not belong to the set of UE types, in other words, if the UE has a central area type (either the LPN central area type or the macro central area type), the codeword information may comprise information on a preferable codeword preferred by the UE. According to embodiments of the present invention, if the UE has the LPN central area type, the preferable codeword (denoted as ^U'^PMI> may be calculated by

[0095] In some other embodiments, if the UE has the macro central area type, the preferable codeword may be calculated likewise.

[0096] According to embodiments of the present invention, optionally, the channel quality may be obtained for scheduling procedures. For example, the channel quality may be denoted as and calculated by (if the UE has the LPN central area type):

F'MI.;,,.

[0097] In some other embodiments, if the UE has the macro central area type, the channel quality may be calculated likewise.

[0098] At step S404, one or more user pairs are determined based on the codeword information. [0099] According to embodiments of the present invention, the user pairs may be determined based on the codeword information in multiple ways. In some embodiments, a UE of the LPN central area type and a UE of the macro central area type may be determined as a user pair.

[00100] In some other embodiments, a UE of the LPN central area type and a

UE of the macro non-central area type may be determine as a user pair, if the preferable codeword of the UE of the LPN central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type.

[00101] In some other embodiments, a UE of the LPN non-central area type and a UE of the macro central area type may be determine as a user pair, if the preferable codeword of the UE of the macro central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type.

[00102] In some other embodiments, a UE of the LPN non-central area type and a UE of the non-macro central area type may be determine as a user pair, if the preferable codeword of the UE of the macro non-central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type, and the preferable codeword of the UE of the LPN non-central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type.

[00103] It is to be noted that, for the purpose of illustrating spirit and principle of the present invention, some specific embodiments thereof have been exemplarily described above. The embodiments are illustrated for example, rather than limitation. It will be appreciated by a person skilled in the art that embodiments of the present invention may be varied or modified without departing from the scope of the present invention.

[00104] According to embodiments of the present invention, based on the user pairs (e.g., those determined at step S404), the plurality of UEs in the HetNet may be scheduled. The scheduling may be performed in several ways known in the art. For example, the user pairs may be scheduled based on the Proportional Fair (PF) scheduler. In this way the intercell interference may be effectively reduced.

[00105] Reference is now made to FIG. 5, which illustrates a block diagram of an apparatus 500 for interference coordination in the heterogeneous network according to embodiments of the invention. As shown, the apparatus 500 comprises: an obtainer 510 configured to obtain types of a plurality of UEs in the heterogeneous network, wherein the heterogeneous network comprises at least one macro BS and at least one LPN, and wherein each of the types is macro central area type, macro non-central area type, LPN central area type, or LPN non-central area type; and a determiner 520 configured to determine one or more user pairs from the plurality of UEs based on the obtained types, such that the plurality of UEs are scheduled based on the one or more user pairs to reduce inter-cell interference.

[00106] In accordance with embodiments of the present invention, the obtainer 510 may comprise: a first obtaining unit configured to obtain a LPN user coordination bias; a second obtaining unit configured to obtain a macro user coordination bias; a third obtaining unit configured to obtain first signal strength and second signal strength of each UE of the plurality of UEs, wherein the first signal strength indicates strength of signals received at the each UE from the LPN and the second signal strength indicates strength of signals received at the each UE from the macro BS; and a first determining unit configured to determine a type of the each UE based on the LPN user coordination bias, the macro user coordination bias, the first signal strength and the second signal strength.

[00107] According to embodiments of the present invention, the first obtaining unit of the obtainer 510 may comprise: a fourth obtaining unit configured to obtain a first rate achieved by a UE which is of the LPN non-central area type and performs inter-cell interference coordination, and a second rate achieved by a UE which is of the LPN non-central area type and does not perform inter-cell interference coordination; and a second determining unit configured to determine the LPN user coordination bias based on the first rate and the second rate.

[00108] According to embodiments of the present invention, the second determining unit may comprise: a first calculating unit configured to calculate a average relative rate loss based on the first rate and the second rate; a first saturated point determining unit configured to determine one or more saturated points with respect to the average relative rate loss, wherein a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the LPN user coordination bias; and a first selecting unit configured to select a candidate from the candidates as the LPN user coordination bias based on the one or more saturated points. [00109] According to embodiments of the present invention, the second obtaining unit may comprise: a fifth obtaining unit configured to obtain a third rate achieved by a UE which is of the macro non-central area type and performs inter-cell interference coordination, and a fourth rate achieved by a UE which is of the macro non-central area type and does not perform inter-cell interference coordination; and a fourth determining unit configured to determine the macro user coordination bias based on the third rate and the fourth rate.

[00110] According to embodiments of the present invention, the fourth determining unit may comprise: a second calculating unit configured to calculate a average relative rate loss based on the first rate and the second rate; a second saturated point determining unit configured to determine one or more saturated points with respect to the average relative rate loss, wherein a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the macro user coordination bias; and a second selecting unit configured to select a candidate from the candidates as the macro user coordination bias based on the one or more saturated points.

[00111] According to embodiments of the present invention, the first determining unit may be further configured to: if the second signal strength is larger than or equal to a sum of the first signal strength and the LPN user coordination bias, and the second signal strength is less than a sum of the first signal strength and a range expansion bias, determine the type to be the LPN non-central area type; if the second signal strength is less than a sum of the first signal strength and the LPN user coordination bias, determine the type to be the LPN central area type; if the second signal strength is larger than or equal to a sum of the first signal strength and the range expansion bias, and the second signal strength is less than a sum of the first signal strength and the macro user coordination bias, determine the type to be the macro non-central area type; and if the second signal strength is larger than a sum of the first signal strength and the macro user coordination bias, determine the type to be the macro central area type.

[00112] According to embodiments of the present invention, the first determining unit may comprise: a first type determining unit configured to, if the second signal strength is larger than or equal to a sum of the first signal strength and the LPN user coordination bias, and the second signal strength is less than a sum of the first signal strength and a range expansion bias, determine the type to be the LPN non-central area type; a second type determining unit configured to, if the second signal strength is less than a sum of the first signal strength and the LPN user coordination bias, determine the type to be the LPN central area type; a third type determining unit configured to,, if the second signal strength is larger than or equal to a sum of the first signal strength and the range expansion bias, and the second signal strength is less than a sum of the first signal strength and the macro user coordination bias, determine the type to be the macro non-central area type; and a fourth type determining unit configured to, if the second signal strength is larger than a sum of the first signal strength and the macro user coordination bias, determine the type to be the macro central area type.

[00113] According to embodiments of the present invention, with respect to each UE of the plurality of UEs, the first signal strength is RSPR from the LPN and/or the second signal strength is RSPR from the macro BS.

[00114] In accordance with embodiments of the present invention, the obtainer 510 may comprise: a first receiving unit configured to receive information on the type of a UE from the UE; and/or a second receiving unit configured to receive information on the type of a UE from a macro BS or a LPN serving the UE.

[00115] In accordance with embodiments of the present invention, the determiner 520 may comprise: a sixth obtaining unit configured to obtain codeword information associated with each UE of the plurality of UEs based on the types of the plurality of UEs; and a fifth determining unit configured to determine the one or more user pairs based on the codeword information.

[00116] According to embodiments of the present invention, the sixth obtaining unit may comprise: a sixth determining unit configured to determine whether the type of a UE of the plurality of UEs belongs to a set of UE types, wherein the set of UE types comprise the LPN non-central area type and the macro non-central area type; a seventh obtaining unit configured to, in response to determining that the type of the UE belongs to the set of UE types, obtain information on a preferable codeword preferred by the UE and information on a recommended codeword cluster; and an eighth obtaining unit configured to, in response to determining that the type of the UE does not belong to the set of UE types, obtain information on a preferable codeword preferred by the UE.

[00117] According to embodiments of the present invention, the fifth determining unit may be further configured to: determine a UE of the LPN central area type and a UE of the macro central area type as a user pair; determine a UE of the LPN central area type and a UE of the macro non-central area type as a user pair, if the preferable codeword of the UE of the LPN central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type; determine a UE of the LPN non-central area type and a UE of the macro central area type as a user pair, if the preferable codeword of the UE of the macro central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type; and determine a UE of the LPN non-central area type and a UE of the non-macro central area type as a user pair, if the preferable codeword of the UE of the macro non-central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type, and the preferable codeword of the UE of the LPN non-central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type.

[00118] According to embodiments of the present invention, the fifth determining unit may comprise: a first user pair determining unit configured to determine a UE of the LPN central area type and a UE of the macro central area type as a user pair; a second user pair determining unit configured to determine a UE of the LPN central area type and a UE of the macro non-central area type as a user pair, if the preferable codeword of the UE of the LPN central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type; a third user pair determining unit configured to determine a UE of the LPN non-central area type and a UE of the macro central area type as a user pair, if the preferable codeword of the UE of the macro central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type; and a fourth user pair determining unit configured to determine a UE of the LPN non-central area type and a UE of the non-macro central area type as a user pair, if the preferable codeword of the UE of the macro non-central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type, and the preferable codeword of the UE of the LPN non-central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type.

[00119] It is to be noted that the apparatus 500 may be implemented in a macro BS, a LPN, a controller, a central unit, a server, a UE, or any other applicable device, and the apparatus 500 may be applied in several heterogamous networks, such as a LTE network. It is also to be noted that the obtainer 510 and determiner 520 may be implemented by any suitable technique either known at present or developed in the future. Further, a single device shown in FIG. 5 may be alternatively implemented in multiple devices separately, and multiple separated devices may be implemented in a single device. The scope of the present invention is not limited in these regards.

[00120] It is noted that, in some embodiment of the present disclosure, the apparatus 500 may be configured to implement functionalities as described with reference to FIGs. 2-4. Therefore, the features discussed with respect to any of methods 200 to 400 may apply to the corresponding components of the apparatus 500. It is further noted that the components of the apparatus 500 may be embodied in hardware, software, firmware, and/or any combination thereof. For example, the components of the apparatus 500 may be respectively implemented by a circuit, a processor or any other appropriate selection device. Those skilled in the art will appreciate that the aforesaid examples are only for illustration not limitation.

[00121] In some embodiment of the present disclosure, the apparatus 500 comprises at least one processor. The at least one processor suitable for use with embodiments of the present disclosure may include, by way of example, both general and special purpose processors already known or developed in the future. The apparatus 500 further comprises at least one memory. The at least one memory may include, for example, semiconductor memory devices, e.g., RAM, ROM, EPROM, EEPROM, and flash memory devices. The at least one memory may be used to store program of computer executable instructions. The program can be written in any high-level and/or low-level compilable or interpretable programming languages. In accordance with embodiments, the computer executable instructions may be configured, with the at least one processor, to cause the apparatus 500 to at least perform according to any of methods 200, 300 and 400 as discussed above.

[00122] In some embodiment of the present disclosure, the apparatus 500 comprises at least one processor. The at least one processor suitable for use with embodiments of the present disclosure may include, by way of example, both general and special purpose processors already known or developed in the future. The apparatus 500 further comprises at least one memory. The at least one memory may include, for example, semiconductor memory devices, e.g., RAM, ROM, EPROM, EEPROM, and flash memory devices. The at least one memory may be used to store program of computer executable instructions. The program can be written in any high-level and/or low-level compilable or interpretable programming languages. In accordance with embodiments, the computer executable instructions may be configured, with the at least one processor, to cause the apparatus 500 to at least perform according to method 200, 300 or 400 as discussed above.

[00123] Based on the above description, the skilled in the art would appreciate that the present disclosure may be embodied in an apparatus, a method, or a computer program product. In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[00124] The various blocks shown in FIGs. 2 to 4 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). At least some aspects of the exemplary embodiments of the disclosures may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, FPGA or ASIC that is configurable to operate in accordance with the exemplary embodiments of the present disclosure. [00125] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any disclosure or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular disclosures. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[00126] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[00127] Various modifications, adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. Any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure. Furthermore, other embodiments of the disclosures set forth herein will come to mind to one skilled in the art to which these embodiments of the disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings.

[00128] Therefore, it is to be understood that the embodiments of the disclosure are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:

1. A method for interference coordination in a heterogeneous network, comprising: obtaining types of a plurality of user equipments (UEs) in the heterogeneous network, wherein the heterogeneous network comprises at least one macro base station (BS) and at least one low power node (LPN), and wherein each of the types is macro central area type, macro non-central area type, LPN central area type, or LPN non-central area type; and

determining one or more user pairs from the plurality of UEs based on the obtained types, such that the plurality of UEs are scheduled based on the one or more user pairs to reduce inter-cell interference.

2. The method of Claim 1, wherein obtaining types of a plurality of UEs in the heterogeneous network comprises:

obtaining a LPN user coordination bias;

obtaining a macro user coordination bias;

obtaining first signal strength and second signal strength of each UE of the plurality of UEs, wherein the first signal strength indicates strength of signals received at the each UE from the LPN and the second signal strength indicates strength of signals received at the each UE from the macro BS; and

determining a type of the each UE based on the LPN user coordination bias, the macro user coordination bias, the first signal strength and the second signal strength.

3. The method of Claim 2, wherein obtaining a LPN user coordination bias comprises:

obtaining a first rate achieved by a UE which is of the LPN non-central area type and performs inter-cell interference coordination, and a second rate achieved by a UE which is of the LPN non-central area type and does not perform inter-cell interference coordination; and

determining the LPN user coordination bias based on the first rate and the second rate.

4. The method of Claim 3, wherein determining the LPN user coordination bias based on the first rate and the second rate comprises:

calculating a average relative rate loss based on the first rate and the second rate; determining one or more saturated points with respect to the average relative rate loss, wherein a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the LPN user coordination bias; and

selecting a candidate from the candidates as the LPN user coordination bias based on the one or more saturated points.

5. The method of Claim 2, wherein obtaining a macro user coordination bias comprises:

obtaining a third rate achieved by a UE which is of the macro non-central area type and performs inter-cell interference coordination, and a fourth rate achieved by a UE which is of the macro non-central area type and does not perform inter-cell interference coordination; and

determining the macro user coordination bias based on the third rate and the fourth rate.

6. The method of Claim 5, wherein determining the macro user coordination bias based on the first rate and the second rate comprises:

calculating a average relative rate loss based on the first rate and the second rate; determining one or more saturated points with respect to the average relative rate loss, wherein a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the macro user coordination bias; and

selecting a candidate from the candidates as the macro user coordination bias based on the one or more saturated points.

7. The method of Claim 2, wherein determining the type of the each UE based on the LPN user coordination bias, macro user coordination bias, the first signal strength and the second signal strength comprises:

if the second signal strength is larger than or equal to a sum of the first signal strength and the LPN user coordination bias, and the second signal strength is less than a sum of the first signal strength and a range expansion bias, determining the type to be the LPN non-central area type;

if the second signal strength is less than a sum of the first signal strength and the LPN user coordination bias, determining the type to be the LPN central area type;

if the second signal strength is larger than or equal to a sum of the first signal strength and the range expansion bias, and the second signal strength is less than a sum of the first signal strength and the macro user coordination bias, determining the type to be the macro non-central area type; and

if the second signal strength is larger than a sum of the first signal strength and the macro user coordination bias, determining the type to be the macro central area type.

8. The method of Claim 2, wherein with respect to each UE of the plurality of UEs, the first signal strength is reference signal receiving power (RSPR) from the LPN and/or the second signal strength is RSPR from the macro BS.

9. The method of Claim 1, wherein obtaining a type of each of UEs in the heterogeneous network comprises:

receiving information on the type of a UE from the UE; and/or

receiving information on the type of a UE from a macro BS or a LPN serving the UE.

10. The method of Claim 1, wherein determining one or more user pairs from the plurality of UEs based on the obtained types comprises:

obtaining codeword information associated with each UE of the plurality of UEs based on the types of the plurality of UEs; and

determining the one or more user pairs based on the codeword information.

11. The method of Claim 10, wherein obtaining codeword information associated with each UE of the plurality of UEs based on the types of the plurality of UEs comprises:

determining whether the type of a UE of the plurality of UEs belongs to a set of UE types, wherein the set of UE types comprise the LPN non-central area type and the macro non-central area type;

in response to determining that the type of the UE belongs to the set of UE types, obtaining information on a preferable codeword preferred by the UE and information on a recommended codeword cluster; and

in response to determining that the type of the UE does not belong to the set of UE types, obtaining information on a preferable codeword preferred by the UE.

12. The method of Claim 11, wherein determining the one or more user pairs based on the codeword information comprises:

determining a UE of the LPN central area type and a UE of the macro central area type as a user pair;

determining a UE of the LPN central area type and a UE of the macro non-central area type as a user pair, if the preferable codeword of the UE of the LPN central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type;

determining a UE of the LPN non-central area type and a UE of the macro central area type as a user pair, if the preferable codeword of the UE of the macro central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type; and

determining a UE of the LPN non-central area type and a UE of the non-macro central area type as a user pair, if the preferable codeword of the UE of the macro non-central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type, and the preferable codeword of the UE of the LPN non-central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type.

13. An apparatus for interference coordination in a heterogeneous network, comprising:

an obtainer configured to obtain types of a plurality of user equipments (UEs) in the heterogeneous network, wherein the heterogeneous network comprises at least one macro base station (BS) and at least one low power node (LPN), and wherein each of the types is macro central area type, macro non-central area type, LPN central area type, or LPN non-central area type; and

a determiner configured to determine one or more user pairs from the plurality of UEs based on the obtained types, such that the plurality of UEs are scheduled based on the one or more user pairs to reduce inter-cell interference.

14. The apparatus of Claim 13, wherein the obtainer comprises:

a first obtaining unit configured to obtain a LPN user coordination bias;

a second obtaining unit configured to obtain a macro user coordination bias;

a third obtaining unit configured to obtain first signal strength and second signal strength of each UE of the plurality of UEs, wherein the first signal strength indicates strength of signals received at the each UE from the LPN and the second signal strength indicates strength of signals received at the each UE from the macro BS; and

a first determining unit configured to determine a type of the each UE based on the LPN user coordination bias, the macro user coordination bias, the first signal strength and the second signal strength.

15. The apparatus of Claim 14, wherein the first obtaining unit comprises:

a fourth obtaining unit configured to obtain a first rate achieved by a UE which is of the LPN non-central area type and performs inter-cell interference coordination, and a second rate achieved by a UE which is of the LPN non-central area type and does not perform inter-cell interference coordination; and

a second determining unit configured to determine the LPN user coordination bias based on the first rate and the second rate.

16. The apparatus of Claim 15, wherein the second determining unit comprises: a first calculating unit configured to calculate a average relative rate loss based on the first rate and the second rate;

a first saturated point determining unit configured to determine one or more saturated points with respect to the average relative rate loss, wherein a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the LPN user coordination bias; and

a first selecting unit configured to select a candidate from the candidates as the LPN user coordination bias based on the one or more saturated points.

17. The apparatus of Claim 14, wherein the second obtaining unit comprises:

a fifth obtaining unit configured to obtain a third rate achieved by a UE which is of the macro non-central area type and performs inter-cell interference coordination, and a fourth rate achieved by a UE which is of the macro non-central area type and does not perform inter-cell interference coordination; and

a fourth determining unit configured to determine the macro user coordination bias based on the third rate and the fourth rate.

18. The apparatus of Claim 17, wherein the fourth determining unit comprises: a second calculating unit configured to calculate a average relative rate loss based on the first rate and the second rate;

a second saturated point determining unit configured to determine one or more saturated points with respect to the average relative rate loss, wherein a saturated point indicates a sharp change of the average relative rate loss in view of candidates of the macro user coordination bias; and

a second selecting unit configured to select a candidate from the candidates as the macro user coordination bias based on the one or more saturated points.

19. The apparatus of Claim 14, wherein the first determining unit comprises:

a first type determining unit configured to, if the second signal strength is larger than or equal to a sum of the first signal strength and the LPN user coordination bias, and the second signal strength is less than a sum of the first signal strength and a range expansion bias, determine the type to be the LPN non-central area type;

a second type determining unit configured to, if the second signal strength is less than a sum of the first signal strength and the LPN user coordination bias, determine the type to be the LPN central area type;

a third type determining unit configured to, if the second signal strength is larger than or equal to a sum of the first signal strength and the range expansion bias, and the second signal strength is less than a sum of the first signal strength and the macro user coordination bias, determine the type to be the macro non-central area type; and a fourth type determining unit configured to, if the second signal strength is larger than a sum of the first signal strength and the macro user coordination bias, determine the type to be the macro central area type.

20. The apparatus of Claim 14, wherein with respect to each UE of the plurality of UEs, the first signal strength is reference signal receiving power (RSPR) from the LPN and/or the second signal strength is RSPR from the macro BS.

21. The apparatus of Claim 13, wherein the obtainer comprises:

a first receiving unit configured to receive information on the type of a UE from the UE; and/or

a second receiving unit configured to receive information on the type of a UE from a macro BS or a LPN serving the UE.

22. The apparatus of Claim 13, wherein the determiner comprises:

a sixth obtaining unit configured to obtain codeword information associated with each UE of the plurality of UEs based on the types of the plurality of UEs; and

a fifth determining unit configured to determine the one or more user pairs based on the codeword information.

23. The apparatus of Claim 22, wherein the sixth obtaining unit comprises:

a sixth determining unit configured to determine whether the type of a UE of the plurality of UEs belongs to a set of UE types, wherein the set of UE types comprise the LPN non-central area type and the macro non-central area type;

a seventh obtaining unit configured to, in response to determining that the type of the UE belongs to the set of UE types, obtain information on a preferable codeword preferred by the UE and information on a recommended codeword cluster; and

an eighth obtaining unit configured to, in response to determining that the type of the UE does not belong to the set of UE types, obtain information on a preferable codeword preferred by the UE.

24. The apparatus of Claim 23, wherein the fifth determining unit comprises: a first user pair determining unit configured to determine a UE of the LPN central area type and a UE of the macro central area type as a user pair;

a second user pair determining unit configured to determine a UE of the LPN central area type and a UE of the macro non-central area type as a user pair, if the preferable codeword of the UE of the LPN central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type;

a third user pair determining unit configured to determine a UE of the LPN non-central area type and a UE of the macro central area type as a user pair, if the preferable codeword of the UE of the macro central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type; and

a fourth user pair determining unit configured to determine a UE of the LPN non-central area type and a UE of the non-macro central area type as a user pair, if the preferable codeword of the UE of the macro non-central area type belongs to the recommended codeword cluster of the UE of the LPN non-central area type, and the preferable codeword of the UE of the LPN non-central area type belongs to the recommended codeword cluster of the UE of the macro non-central area type.