WO2009051362A2

WO2009051362A2 - Method of controlling uplink power in multi-cell environment

Info

Publication number: WO2009051362A2
Application number: PCT/KR2008/005853
Authority: WO
Inventors: Dong Cheol Kim; Seung Hee Han; Min Seok Noh; Jin Sam Kwak; Yeong Hyeon Kwon; Hyun Woo Lee
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2007-10-19
Filing date: 2008-10-06
Publication date: 2009-04-23
Anticipated expiration: 2010-04-19
Also published as: WO2009051362A3; KR101386813B1; KR20090039919A

Abstract

A method of controlling uplink power in a multi-cell environment including a plurality of base stations includes receiving a power control message from a base station, wherein the power control message comprises an noise and interference (NI) level of at least one permutation zone of a neighbor base station, and controlling transmission power based on the power control message. The UE can be more accurately control its transmission power, so that the inter-cell interference can be reduced, the NI level can be lowered, and power consumption of the UE can be reduced.

Description

METHOD OF CONTROLLING UPLINK POWER IN MULTI- CELL ENVIRONMENT

Technical Field

[1] The present invention relates to wireless communications and, more particularly, to a method of controlling uplink transmission power by sharing power control information between cells in a multi-cell environment. Background Art

[2] A next-generation multimedia wireless communication system, which is being actively studied, is required to process various information such as images, wireless data, or the like, at a high data rate, beyond the voice-oriented services provided at an early stage.

[3] Thus, recently, orthogonal frequency division multiplexing (OFDM) exerting a high data rate receives much attention. The OFDM is a multi-carrier modulation scheme that divides a frequency band into a plurality of orthogonal subcarriers to transmit data. The OFDM can reduce an inter-symbol interference at a low complexity. The OFDM converts serially inputted data symbols into the N parallel data symbols, includes them in the N separated subcarriers, and transmits the same. The subcarriers maintain orthogonality in a frequency domain. The respective orthogonal channels experience mutually independent frequency selective fading, and the intervals of transmitted symbols is lengthened to minimize the inter-symbol interference. Orthogonal frequency division multiple access (OFDMA) refers to a multi-access scheme accomplishing multiple accesses by independently providing portions of available subcarriers to each user in a system using the OFDM as a modulation scheme. The OFDMA provides frequency resources called subcarriers to each user, and in general, the respective frequency resources are independently provided to multiple users so as not to overlap with each other. That is, frequency resources are mutually exclusively allocated to the users.

[4] The wireless communication system has a cell structure to effectively configure a system. A cell refers to a zone obtained by dividing a wide area into smaller zones to effectively use frequency of cell. In general, a base station (BS) is installed at the center of the cell to relay an user equipment (UE). The cell refers to a service region provided by a single BS.

[5] The wireless communication system uses a power control scheme to reduce a path loss according to the distance between a BS and a UE and an inter-cell interference by an adjacent cell. The power control scheme is adjusting transmission power to transmit data at the lowest power level while maintaining quality of service (QoS) of the wireless communication system. In particular, UEs located near a cell boundary in the multi-cell environment are much affected by the path loss and the inter-cell interference, so in transmitting data, the UEs should determine proper transmission power not to cause degradation of QoS by a path loss while not interfering with its adjacent cell.

[6] Thus, a method of controlling uplink power to minimize an inter-cell interference in the multi-cell environment is required.

[7]

Disclosure of Invention Technical Problem

[8] The present invention provides a method of controlling uplink power to minimize an inter-cell interference. Technical Solution

[9] In an aspect, a method of controlling uplink power in a multi-cell environment including a plurality of base stations includes receiving a power control message from a base station, wherein the power control message comprises an noise and interference (NI) level of at least one permutation zone of a neighbor base station, and controlling transmission power based on the power control message.

[10] In another aspect, a method of controlling uplink power in a multi-cell environment including a plurality of base stations, including: receiving power control information of a first base station from the first base station; receiving power control information of a second base station from the first base station; and controlling transmission power based on the power control information of the first base station and power control information of the second base station.

[H]

Advantageous Effects

[12] According to the present invention, an user equipment can more accurately control transmission power, so that an inter-cell interference can be reduced, an NI level can be reduced, and power consumption of the UE can be reduced. Brief Description of the Drawings

[13] FIG. 1 shows an example of a wireless communication system.

[14] FIG. 2 shows an example of a frame structure.

[15] FIG. 3 shows an example of a frame including a plurality of permutations.

[16] FIG. 4 shows another example of a wireless communication system.

[17] FIG. 5 shows an example of a network reference model.

[18] FIG. 6 shows functional entities of a network control and management system (NCMS).

[19] FIG. 7 shows a method of sharing information between base stations according to an embodiment of the present invention.

[20] FIG. 8 shows a flow chart illustrating the process of a method of controlling uplink power according to an embodiment of the present invention.

[21]

Mode for the Invention

[22] FIG. 1 shows an example of a wireless communication system. The wireless communication system can be widely deployed to provide a variety of communication services, such as voices, packet data, etc.

[23] Referring to FIG. 1, the wireless communication system includes base station (BS)

20 and user equipment (UE) 10. The UE 10 may be fixed or have mobility, and may be referred to as another terminology, such as a mobile station (MS), a user UE (UT), a subscriber station (SS), a wireless device, etc.

[24] The BS 20 is generally a fixed station that communicates with the UE 10 and may be called another terminology, such as a node-B, a base transceiver system (BTS), an access point, etc.

[25] There are one or more cells within the coverage of the BS 20. A cell is an area to which the BS 20 provides a communication service. A multi-cell may be formed as a plurality of BSs each having at least one cell are disposed. A cell of a BS providing a communication service to the UE 10 is called a serving cell, and a cell adjacent to the serving cell is called a non-serving cell. Here, it is shown that one serving cell and two adjacent cells, which is merely an example, and a plurality of BSs may be variously disposed as necessary and the configuration and coverage of the cells may variably change in the wireless communication system.

[26] Hereinafter, a downlink represents a communication link from the BS 20 to the UE

10, and an uplink represents a communication link from the UE 10 to the BS 20. In the downlink, a transmitter may be a part of the BS 20, and a receiver may be a part of the UE 10. In the uplink, the transmitter may be a part of the UE 10, and the receiver may be a part of the BS 20.

[27] The UE 10 included in the serving cell or the non-serving cell may transmit data through an uplink frame. The uplink frame may use various permutations. The permutation refers to map a logical subchannel to a physical subcarrier. Here, it is assumed that each UE 10 transmits uplink data by applying partial usage of subchannels (PUSCs), but it is merely an example and each UE 10 may use one or more different permutations. The structure and permutations of frames will be described hereafter. [28] There is no restriction on the multiple access scheme used in the wireless communication system. The multiple access scheme may be based on code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), single-carrier FDMA (SC-FDMA), orthogonal frequency division multiple access (OFDMA), or other well-known modulation schemes. To give a detailed explanation, the OFDMA-based wireless communication system will now be described.

[29] The orthogonal frequency division multiplexing (OFDM) uses a plurality of orthogonal subcarriers. The OFDM uses orthogonality between inverse fast Fourier transform (IFFT) and fast Fourier Transform (FFT). A transmitter performs IFFT on data and transmits the same. A receiver performs FFT on reception data to restore the original data. The transmitter uses IFFT to combine multiple subcarriers. The receiver uses the corresponding FFT in order to separate the multiple subcarriers. According to the OFDM, complexity of the receiver can be reduced in a frequency selective fading environment of a broadband channel and spectral efficiency can be increased through selective scheduling in a frequency domain by utilizing different channel characteristics of each subcarrier. OFDMA is a multi-access scheme based on the OFDM. According to the OFDMA, the efficiency of radio resources can be enhanced by allocating different subcarriers to multiple users.

[30] FIG. 2 shows an example of a frame structure. The frame refers to a data sequence during a fixed time period used by physical specifications. It may refer to 8.4.4.2 paragraph of "Part 16: Air Interface for Fixed Broadband Wireless Access Systems" of IEEE standards 802.16-2004.

[31] Referring to FIG. 2, the frame includes a downlink frame and an uplink frame. Time division duplex (TDD) refers to a method in which uplink and downlink transmissions share the same frequency but occur at each different time. The downlink frame temporally goes ahead of the uplink frame. The downlink frame includes a preamble, a frame control header (FCH), a DL (Downlink)-MAP, a UL (Uplink)-MAP, a burst region, starting in this order. A guard time for discriminating the uplink frame and the downlink frame is inserted into a middle portion of the frame (i.e., between the downlink frame and the uplink frame), and to a final portion (after the uplink frame). A transmit/receive transition gap (TTG) refers to a gap between the downlink burst and the subsequent uplink burst. A receive/transmit transition gap (RTG) refers to a gap between the uplink burst and a subsequent downlink burst.

[32] The preamble is used for initial synchronization, cell search, frequency offset, and channel estimation between a base station and a user equipment. The FCH includes the length of a DL-MAP message and coding information of the DL-MAP message.

[33] The DL-MAP is a region on which the DL-MAP message is transmitted. The DL- MAP message defines an access of a downlink channel. The DL-MAP message includes a configuration change count of a downlink channel descriptor (DCD) and a base station ID (Identifier). The DCD describes a downlink burst profile applied to a current map. The downlink burst profile refers to characteristics of a downlink physical channel, and the DCD is periodically transmitted by the base station via a DCD message.

[34] The UL-MAP is a region on which a UL-MAP message is transmitted. The UL-MAP message defines an access of an uplink channel. The UL-MAP message includes a configuration change count of a uplink channel descriptor (UCD) and a valid start time of uplink allocation defined by the UL-MAP. The UCD describes an uplink burst profile. The uplink burst profile refers to characteristics of an uplink physical channel, and the UCD is periodically transmitted by the base station via a UCD message.

[35] Hereinafter, a slot is a minimum available data allocation unit and defined as time and a subchannel. The number of subchannels depends upon the size of FFT and time- frequency mapping. Subchannels include a plurality of subcarriers. The number of sub- carriers per subchannel differs depending on permutations. Permutation refers to mapping of a logical subchannel to a physical subcarrier. In full usage of subchannels (FUSC), a subchannel includes 48 subcarriers, and in a partial usage of subchannels (PUSC), a subchannel includes 24 or 16 subcarriers. A segment refers to at least one subchannel set.

[36] Data of a physical layer is mapped to a physical subcarrier through two steps.

[37] In first step, data is mapped to at least one data slot in at least one logical subchannel.

In a second step, each logical subchannel is mapped to physical subcarriers. This is called permutation. Reference document 1 discloses FUSC, PUSC, O-FUSC (Optional-FUSC), adaptive modulation and coding (AMC), or the like. A set of OFDM symbols using the same permutation is called a permutation zone, and a single frame includes at least one permutation zone.

[38] The FUSC and the O-FUSC are used only for downlink transmission. The FUSC includes a single segment including every subchannel group. Each subchannel is mapped to a physical subcarrier distributed in the entire physical channels. This mapping changes for each OFDM symbol. A slot includes a single subchannel in a single OFDM symbol. The O-FUSC has a different pilot allocation method from that of the FUSC.

[39] The PUSC is used for both downlink transmission and uplink transmission. In downlink, respective physical channels are divided into clusters each having 14 contiguous subcarriers in two OFDM symbols. The physical channels are mapped to six groups. In each group, pilot is allocated to each cluster and is in a fixed position. In the uplink, each subcarrier may include a plurality of tiles including four contiguous physical subcarriers on three OFDM symbols. Each subchannel includes six tiles. Pilot is allocated to the corner of each tile. The O-PUSC is used only for uplink transmission, and each tile includes three continuous physical subcarriers on three OFDM symbols. Pilot is allocated to the center of each tile.

[40] FIG. 3 shows an example of a frame including a plurality of permutations. The frame may be a physical frame.

[41] Referring to FIG. 3, in a DL frame, a preamble, an FCH, and a DL-MAP necessarily appear in every frame. The PUSC permutation is applied to the FCH and the DL-MAP. In the DL frame, the PUSC, the FUSC, an optional FUSC, and an AMC permutation may appear. The permutations appearing in the downlink frame may be designated by the DL-MAP. In an UL frame, the PUSC, the optional PUSC, and the AMC permutation may appear. The permutations appearing in the UL frame may be designated by the UL-MAP.

[42] Data or control information of a frame can be accurately acquired through the preamble, the FCH, the DL-MAP, or the like, in each frame.

[43] FIG. 4 shows another example of a wireless communication system.

[44] Referring to FIG. 4, a BS 2OS of a serving cell provides a communication service to a

UE 1OS located in the serving cell. The UE 1OS in the serving cell transmits data to the BS 2OS of the serving cell through an uplink frame. A UE ION located in a non- serving cell transmits data to a BS 2ON that provides a communication service to the UE ION itself, through an uplink frame. At this time, the UE 1OS in the serving cell and the UE ION in the non- serving cell may transmit the uplink data by applying mutually different permutations. For example, the UE 1OS in the serving cell may transmit uplink data by applying the PUSC permutation, while the UE ION in the non- serving cell may transmit uplink data by applying the AMC and the O-PUSC permutations. The BS 2OS of the serving cell receives the signal of the UE 1OS in the serving cell as a valid data signal, and removes a signal of the UE ION in the non- serving cell from the entire received signals by regarding it as noise.

[45] If the same permutation is used in every cell, the BS would easily remove a signal received from a UE of an adjacent cell from valid data signals. If, however, permutations used by adjacent cells are different and each BS does not have information about permutations used by each BS, there is a difficulty in removing an inter-cell interference. Further, if transmission power of a UE in a cell is increased as each base station considers only its own noise and interference (NI) level, the amount of interference would be increased in the adjacent cells, and thus, in order to compensate the increased amount of interference, the UE would increase its transmission power. Through such vicious cycle, transmission power of every cell would be unnecessarily increased. [46] Thus, by sharing information about the permutations and NI levels used by each BS, the inter-cell interference can be reduced and proper transmission power can be maintained. The sharing of the information by BSs can be made via a backbone network. The backbone network can connect the BSs through a fixed line or wirelessly. In the wireless communication system, a networking system using the backbone network may be called a network control and management system (NCMS).

[47] FIG. 5 shows an example of a network reference model.

[48] Referring to FIG. 5, the network reference model may be defined as communication via an interface U between a BS and a UE. In this case, the BS and the UE include a network control and management system (NCMS) and a protocol entity. The protocol entity provides a communication method in conformity with a particular communication protocol. For example, the protocol entity may follow a communication protocol of IEEE standard 802.16. The NCMS and the protocol entity may exchange media access control (MAC) management information via a control service access point (C-SAP) or a management service access point (M-SAP). A physical layer (PHY) and a MAC layer are managed by exchanging a MAC message between the protocol entity of the BS and that of the UE.

[49] FIG. 6 shows functional entities of the network control and management system

(NCMS).

[50] Referring to FIG. 6, the NCMS provides various functions such as authorization, authentication, accounting (AAA) services, security services, mobility management services, radio resource management services, service flow management services, paging and idle mode services, multicast broadcast services (MBS) management, location based service (LBS) management, media independent handover (MIH) function services, subscriber station management (SSM), network management services, or the like. Entities providing the respective functions may gather in the NCMS or may be distributively provided in a network.

[51] BSs may share information via the NCMS. That is, BSs may share information about permutations and/or NI levels used by each base station via the NCMS in the multi-cell environment.

[52] FIG. 7 shows a method of sharing information between base stations according to an embodiment of the present invention, in which a radio resource management function of the NCMS is used.

[53] Referring to FIG. 7, the radio resource management function of the NCMS involves in communication between radio resource agents (RRA) and radio resource controllers (RRC) or between RRCs. The RRC is included in the NCMS and manages radio resources of the BS in relation to configuration, re-configuration and release of radio resources. The RRA is included in the protocol entity and responds to management of the radio resources from the RRC.

[54] The NCMS transmits neighbor BS information (ex. neighbor-BS PHY report) to the protocol entity by using a radio resource management message (ex. C-RRM-XXX). The radio resource management message indicating the neighbor BS information may be expressed by Table 1 shown below:

[55] Table 1 [Table 1]

[56] The radio resource management message includes ID of a neighbor BS (BSID) and information about an NI region of each BS. The BSID is a particular ID discriminating a BS. The NI region refers to a permutation zone using the same permutation or a control channel region for a transmission of particular control information. The BS may receive an NI level of each NI region of a neighbor BS through the radio resource management message. The BS may receive the NI level via the NCMS.

[57] Here, it has been described that the BSID and the NI level of the NI region are included in the radio resource management message, but it is a merely example, and the radio resource management message may include various information about the neighbor BS. For example, the radio resource management message may include various information such as a weight level with respect to the frequency in use of permutations used by the neighbor BS, an NI level with respect to a bandwidth, a comparison value with respect to a reference value of each permutation zone, or the like.

[58] FIG. 8 shows a flow chart illustrating the process of a method of controlling uplink power according to an embodiment of the present invention. [59] Referring to FIG. 8, the BS shares information with a neighbor BS (Sl 10). Ths BSs can hold information in common. The information shared with the neighbor BS may be transferred to the BS by the NCMS.

[60] The BS transmits a power control message including information about the neighbor BS to the UE (S 120). The power control message includes power control information required for the UE to control uplink transmission power. The power control information may be information about an NI level of the corresponding BS or the neighbor BS. If the information about the neighbor BS is cell common information, the power control message may be transmitted in a multicast or broadcast manner. If the power control message is a message regarding a particular UE, it may be transmitted through a unicast control channel.

[61] The power control message may be generated by using the information shared with the neighbor BS. The power control message may be generated according to one of the following methods and transmitted to the UE.

[62] 1. The BS may observe a permutation used by the neighbor BS for a predetermined time and inform the UE about a weight level according to the frequency in use of the permutation. Table 2 shows an example of weight levels of permutations used in an uplink frame.

[63] Table 2 [Table 2] [Table ]

[64] Discrimination of the permutation zones may be indicated in the form of a bitmap, and the size of the weight levels of each permutation zone may be expressed in a predefined form.

[65] 2. The BS may observe a permutation used by the neighbor BS for a predetermined time and inform the UE about an indicator according to the frequency in use of the permutation. Table 3 shows an example of the indicators in a binary form of the permutations used in the uplink frame.

[66] Table 3 [Table 3] [Table ]

[67] Permutation zones and used permutations may be expressed in the form of a predefined binary bitmap. For example, '100' may signify that the BS uses only the PUSC permutation or that the PUSC permutation has the highest frequency in use. [68] 3. The BS may inform the UE about only a single NI region with the highest frequency in use among the permutations used by the neighbor BS. The NI region with the highest frequency in use may be expressed in the form of a bitmap or an index of each NI region may be set and one index may be informed to the UE.

[69] 4. The BS may directly inform the UE about an NI level of each permutation zone of the neighbor BS. The permutation zones may be discriminated in the form of a bitmap, and the NI levels may be expressed in a predefined form.

[70] 5. The BS may inform the UE about an NI level of the overall bandwidth.

[71] 6. A particular reference value may be set for each permutation zone, and an indicator with respect to the difference between the reference value and a measured NI level may be received from the neighbor BS and then informed to the UE. The permutation zones may be discriminated in the form of a bitmap and the indicator may be expressed in a binary form.

[72] In case that the BS provides information about the frequency in use of permutations

(the methods 1 to 3) it may generate power control information by using only information of a particular neighbor BS or collect information of every neighbor BS to generate power control information.

[73] Table 4 shows an example of the power control message, in which a weight level or a binary indicator with respect to the frequency in use of each permutation is informed to the UE.

[74] Table 4

[Table 4] [Table ]

[75] When various permutations are applied in the uplink, the BS may inform the UE about the applied permutations in the form of a bitmap or inform the UE about a weight level or a binary indicator with respect to the frequency in use of each permutation. It may be transmitted together with a message informing about an NI level with respect to each permutation zone or may be periodically or non-periodically transmitted in the form of a message as shown in Table 4.

[76] Table 5 shows another example of the power control message, in which the NI level with respect to each permutation zone is informed together with a weight level or a binary indicator with respect to the frequency in use of each permutation to the UE (methods 1, 2, and 4)

[77] Table 5 [Table 5]

[78] Here, there are eight types of NIs, but without being limited thereto, the number of

NI regions may increase or decrease.

[79] If the power control message includes the NI level about every NI region, the weight level information according to the frequency in use of the neighbor BS, or the like, the overhead would be increased. However, if only a single NI region with the highest frequency in use among the permutations used by the neighbor BS is informed to the UE or if the NI level with respect to the overall bandwidth is informed to the UE (the methods 3 and 5), the overhead caused by the power control message can be reduced.

[80] In the case where a particular reference value is set for each permutation zone (the method 6), the neighbor BS previously sets a reference value of the NI level, compares it with a measured NI level, and then, informs the BS about a permutation zone in which the measured NI level exceeds or does not exceed the reference value through a binary indicator. In this case, the BS may transmit the binary indicator as informed by the neighbor BS to the UE as it is or may transmit it together with other power control information to the UE. Meanwhile, a binary indicator about the NI level of the neighbor BS may be directly received by the UE from the neighbor BS, not by way of the BS. When the UE directly receives the information about the NI level from the neighbor BS, the UE determines its transmission power by considering it together with a power control message transmitted from the BS.

[81] The UE controls its transmission power based on the power control message received from the BS (S 130). The UE may compare the NI level of the permutation zone with the high frequency in use of the neighbor BS and an NI level of a permutation zone to be used for a next transmission by the UE itself and control its transmission power. For example, with the UE having the information about an NI level of the permutation with a high frequency in use together with information (the methods 1, 2, and 3) about the frequency in use of the permutation used by the neighbor BS from the power control message, if the NI level of the permutation zone to be used by the UE is higher than the NI level of the permutation zone with the high frequency in use of the neighbor BS, the UE may lower its transmission power by a certain level, whereas if the NI level of the permutation zone to be used by the UE itself is lower, the UE may increase its transmission power by a certain level or may maintain its current transmission power as it is. If the UE knows only the frequency in use of the permutation used by the neighbor BS and an NI level value of its BS with respect to the permutation with the high frequency in use exceeds a target level, the UE would determine its transmission power increased as much with respect to the permutation. Thus, the UE may lower the MCS level by one stage or may increase the transmission power by a certain amount within an allowable range.

[82] Equation 1 shows an example of power controlling by the UE using the power control information transmitted by the BS.

[83] MathFigure 1

[Math.l] P(dBm) L+CJN+NI- 10log₁₀(R)+Oβset(SS_perSS)+Ofβet(BS_perSS)+F{NI_other£S)

[84] wherein 'P' is a transmission power level (dBm) of the UE, 'L' is an estimated average uplink loss, C/N is a carrier-to-noise ratio, 'R' is the number of repetitions with respect to a modulation method, NI is an estimated average noise and interference, Offset(SSperss) is a transmission power correction value determined by the UE, Offset(BSperss) is a transmission power correction value determined by the BS, and F(NIotherBs) is a transmission power correction value based on information about the neighbor BS.

[85] The UE transmits data with the transmission power controlled based on the power control message received from the BS (S 140).

[86] It has been described that the NI levels of each BS is shared by the BSs and applied to determining of the transmission power of the UE in the multi-cell environment. However, the factors that affect the communication in the multi-cell environment may be expressed in various manners, and there is no limitation in the method of sharing the environmental factors between the BSs and applying the same to the determining of the transmission power of the UE. For example, only an interference level of each BS may be taken into consideration or environmental factors of each BS may be expressed in the form of an interference over thermal noise.

[87] Meanwhile, when the BS knows the locations of every UE, it may generate a power control message suitable for situations of each UE in consideration of an interference level with a neighbor BS and transmits it. For example, if there is a room for a UE at a particular location to act as an interference source to a particular neighbor BS, the BS may configure a power control message to allow the UE to control transmission power in consideration of the particular neighbor base station, and transmit the same. By determining the transmission power level organically in consideration of the relationship between the UEs and the neighbor base station, the NI level among cells can be lowered overall compared with the case where the cell common power control information is applied. Namely, if the BS knows the location of the UE, the performance of the communication system can be improved by accurately considering the communication environment of the UE. Therefore, by considering the communication environment according to the locations of UEs, the system can be more effectively controlled, compared with the case where the characteristics according to user distribution in a cell are used.

[88] Every function as described above can be performed by a processor such as a microprocessor based on software coded to perform such function, a program code, etc., a controller, a micro-controller, an ASIC (Application Specific Integrated Circuit), or the like. Planning, developing and implementing such codes may be obvious for the skilled person in the art based on the description of the present invention.

[89] Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the invention. Accordingly, the embodiments of the present invention are not limited to the above-described embodiments but are defined by the claims which follow, along with their full scope of equivalents.

Claims

[1] A method of controlling uplink power in a multi-cell environment including a plurality of base stations, the method comprising: receiving a power control message from a base station, wherein the power control message comprises an noise and interference (NI) level of at least one permutation zone of a neighbor base station; and controlling transmission power based on the power control message.

[2] The method of claim 1, wherein the NI level is an NI level of each permutation zone used by the neighbor base station.

[3] The method of claim 1, wherein the NI level is an NI level of overall bandwidth.

[4] The method of claim 1, wherein the power control message further comprises a frequency in use of permutations used by the neighbor base station.

[5] The method of claim 4, wherein the frequency in use of permutations is represented as weight level according to the frequency.

[6] The method of claim 4, wherein the frequency in use of permutations is represented as indicator according to the frequency.

[7] The method of claim 1, wherein the power control message expresses one permutation zone with highest frequency in use of permutation used by the neighbor base station.

[8] The method of claim 1, wherein the transmission power is controlled according to equation shown below: P(dBm) L+C/N+NI- l0log₁₀(R)+O/βet(SS_perSS)+O/βet(BS_per&s)+F(NI_other£S) wherein 'P' is a transmission power level (dBm), 'L' is an estimated average uplink loss, C/N is a carrier-to-noise ratio, 'R' is the number of repetitions with respect to a modulation method, NI is an estimated average noise and interference, Offset(SSperss) is a transmission power correction value determined by a UE, Offset(BSperss) is a transmission power correction value determined by a base station, and F(NI_otherBs) is a transmission power correction value based on the NI level of the neighbor base station.

[9] A method of controlling uplink power in a multi-cell environment, the method comprising: receiving power control information of a first base station from the first base station; receiving power control information of a second base station from the first base station; and controlling transmission power based on the power control information of the first base station and power control information of the second base station. [10] The method of claim 9, wherein the power control information of the first base station is an offset determined by the first base station, and the power control information of the second base station is an NI level of the second base station.