WO2013120265A1 - Régulation de puissance srs pour la planification coordonnée dans des réseaux hétérogènes tdd - Google Patents

Régulation de puissance srs pour la planification coordonnée dans des réseaux hétérogènes tdd Download PDF

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Publication number
WO2013120265A1
WO2013120265A1 PCT/CN2012/071226 CN2012071226W WO2013120265A1 WO 2013120265 A1 WO2013120265 A1 WO 2013120265A1 CN 2012071226 W CN2012071226 W CN 2012071226W WO 2013120265 A1 WO2013120265 A1 WO 2013120265A1
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WO
WIPO (PCT)
Prior art keywords
base station
srs
pico
macro base
pattern
Prior art date
Application number
PCT/CN2012/071226
Other languages
English (en)
Inventor
Minghai Feng
Jiming Guo
Neng Wang
Jilei Hou
Original Assignee
Qualcomm Incorporated
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Qualcomm Incorporated filed Critical Qualcomm Incorporated
Priority to PCT/CN2012/071226 priority Critical patent/WO2013120265A1/fr
Publication of WO2013120265A1 publication Critical patent/WO2013120265A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H04W52/243—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account interferences
    • H04W52/244—Interferences in heterogeneous networks, e.g. among macro and femto or pico cells or other sector / system interference [OSI]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0076—Distributed coding, e.g. network coding, involving channel coding
    • H04L1/0077—Cooperative coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/06—TPC algorithms
    • H04W52/14—Separate analysis of uplink or downlink
    • H04W52/146—Uplink power control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H04W52/242—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account path loss
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/26—TPC being performed according to specific parameters using transmission rate or quality of service QoS [Quality of Service]
    • H04W52/267—TPC being performed according to specific parameters using transmission rate or quality of service QoS [Quality of Service] taking into account the information rate
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/38—TPC being performed in particular situations
    • H04W52/50—TPC being performed in particular situations at the moment of starting communication in a multiple access environment

Definitions

  • aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to sounding reference signal (SRS) control for coordinated beamforming/scheduling in time division duplex (TDD) heterogeneous networks.
  • SRS sounding reference signal
  • Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, and the like. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources.
  • UTRAN Universal Terrestrial Radio Access Network
  • the UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3 GPP).
  • UMTS Universal Mobile Telecommunications System
  • 3 GPP 3rd Generation Partnership Project
  • multiple-access network formats include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.
  • CDMA Code Division Multiple Access
  • TDMA Time Division Multiple Access
  • FDMA Frequency Division Multiple Access
  • OFDMA Orthogonal FDMA
  • SC-FDMA Single-Carrier FDMA
  • a wireless communication network may include a number of base stations or NodeBs that can support communication for a number of user equipments (UEs).
  • a UE may communicate with a base station via downlink and uplink.
  • the downlink (or forward link) refers to the communication link from the base station to the UE
  • the uplink (or reverse link) refers to the communication link from the UE to the base station.
  • a base station may transmit data and control information on the downlink to a UE and/or may receive data and control information on the uplink from the UE.
  • a transmission from the base station may encounter interference due to transmissions from neighbor base stations or from other wireless radio frequency (RF) transmitters.
  • RF radio frequency
  • a transmission from the UE may encounter interference from uplink transmissions of other UEs communicating with the neighbor base stations or from other wireless RF transmitters. This interference may degrade performance on both the downlink and uplink.
  • Various aspects of the present disclosure are directed to sounding reference signal (SRS) power control for coordinated beamforming/scheduling in time division duplex (TDD) heterogeneous networks.
  • a macro eNB can implement interference cancelation by leveraging the channel reciprocity inherent in TDD systems.
  • the macro eNB estimates the channel to the pico UE by measuring the SRS transmitted from a UE coupled to the pico eNB.
  • the SRS signal from the pico UE may be low, due to a lower power selected in transmitting to the pico eNB and the path-loss experienced between the pico UE and the macro eNB.
  • the SRS power may even be too low for the macro eNB to decode the SRS.
  • the pico UE calculates the path-loss between the pico UE and the pico eNB and the path-loss between the pico UE and the macro eNB by measuring the reference signal receive power (RSRP) of both the pico eNB and the macro eNB and calculating an offset value.
  • the pico UE then transmits some of the scheduled SRS using a higher power level that includes the regular power and the offset value.
  • the macro eNB may then measure the enhanced SRS transmitted from the pico UE in order to calculate a more accurate channel estimate. Using the more accurate channel estimate, the macro eNB may then more accurately provide for interference cancelation.
  • Additional aspects of the present disclosure are directed to using coordinated scheduling to reduce the interference level at the macro eNB, such that the interference may be minimized when receiving the SRS transmitted from the pico UE.
  • the pico UE may transmit using the same power level targeting the uplink transmissions to the pico eNB.
  • a method of wireless communication that includes measuring, at a UE, a first receive power of a pico reference signal transmitted from a pico base station serving the UE and a second receive power of a macro reference signal transmitted from a macro base station, wherein the UE is located within the coverage area of the macro base station.
  • the method further includes determining, at the UE, a path-loss offset power using the first receive power and the second receive power, selecting an enhanced transmission power, comprising a pico uplink transmission power and the path-loss offset power, and transmitting, from the UE, at least one SRS in a pattern of SRS, wherein the SRS is transmitted at the enhanced transmission power.
  • a method for wireless communication includes measuring, at a macro base station, an enhanced SRS from a UE served by a pico base station located within a coverage area of the macro base station, wherein the enhanced SRS has a higher power than a pico SRS detected by the macro base station in a pattern of SRS from the UE.
  • the method also includes estimating a channel between the UE and the macro base station based, at least in part, on the measured enhanced SRS and scheduling a macro UE served by the macro base station in a null space of the UE, wherein the null space is determined, at least in part, by the estimated channel.
  • method for wireless communication includes scheduling, by a macro base station, at least one UE to reduce interference at the macro base station during transmission of SRS transmitted by a pico UE served by a pico base station within the coverage area of the macro base station.
  • the method further includes measuring, at the macro base station, at least one SRS transmitted by the pico UE during the reduced interference, estimating a channel between the pico UE and the macro base station based, at least in part, on the measured at least one SRS, and scheduling a macro UE served by the macro base station in a null space of the pico UE, wherein the null space is determined, at least in part, by the estimated channel.
  • an apparatus configured for wireless communication includes means for measuring, at a UE, a first receive power of a pico reference signal transmitted from a pico base station serving the UE and a second receive power of a macro reference signal transmitted from a macro base station, wherein the UE is located within the coverage area of the macro base station.
  • the apparatus further includes means for determining, at the UE, a path-loss offset power using the first receive power and the second receive power, means for selecting an enhanced transmission power, comprising a pico uplink transmission power and the path-loss offset power, and means for transmitting, from the UE, at least one SRS in a pattern of SRS, wherein the at least one SRS is transmitted at the enhanced transmission power.
  • an apparatus configured for wireless communication includes means for measuring, at a macro base station, an enhanced SRS from a UE served by a pico base station located within a coverage area of the macro base station, wherein the enhanced SRS has a higher power than a pico SRS detected by the macro base station in a pattern of SRS from the UE, means for estimating a channel between the UE and the macro base station based, at least in part, on the measured enhanced SRS, and means for scheduling, by the macro base station, a macro UE for transmission in a null space of the UE, wherein the null space is determined, at least in part, by the estimated channel.
  • an apparatus configured for wireless communication includes means for scheduling, by a macro base station, at least one UE to reduce interference at the macro base station during transmission of SRS transmitted by a pico UE served by a pico base station within the coverage area of the macro base station, means for measuring, at the macro base station, at least one SRS transmitted by the pico UE during the reduced interference, means for estimating a channel between the pico UE and the macro base station based, at least in part, on the measured at least one SRS, and means for scheduling a macro UE served by the macro base station in a null space of the pico UE, wherein the null space is determined, at least in part, by the estimated channel.
  • a computer program product has a computer-readable medium having program code recorded thereon.
  • This program code includes code to measure, at a UE, a first receive power of a pico reference signal transmitted from a pico base station serving the UE and a second receive power of a macro reference signal transmitted from a macro base station, wherein the UE is located within the coverage area of the macro base station.
  • the program code also includes code to determine, at the UE, a path-loss offset power using the first receive power and the second receive power, code to select an enhanced transmission power, comprising a pico uplink transmission power and the path-loss offset power, and code to transmit, from the UE, at least one SRS in a pattern of SRS, wherein the at least one SRS is transmitted at the enhanced transmission power.
  • a computer program product has a computer-readable medium having program code recorded thereon.
  • This program code includes code to measure, at a macro base station, an enhanced SRS from a UE served by a pico base station located within a coverage area of the macro base station, wherein the enhanced SRS has a higher power than a pico SRS detected by the macro base station in a pattern of SRS from the UE, code to estimate a channel between the UE and the macro base station based, at least in part, on the measured enhanced SRS, and code to schedule, by the macro base station, a macro UE for transmission in a null space of the UE, wherein the null space is determined, at least in part, by the estimated channel.
  • a computer program product has a computer-readable medium having program code recorded thereon.
  • This program code includes code to schedule, by a macro base station, at least one UE to reduce interference at the macro base station during transmission of SRS transmitted by a pico UE served by a pico base station within the coverage area of the macro base station, code to measure, at the macro base station, at least one SRS transmitted by the pico UE during the reduced interference, code to estimate a channel between the pico UE and the macro base station based, at least in part, on the measured at least one SRS, and code to schedule a macro UE served by the macro base station in a null space of the pico UE, wherein the null space is determined, at least in part, by the estimated channel.
  • an apparatus includes at least one processor and a memory coupled to the processor.
  • the processor is configured to measure, at a UE, a first receive power of a pico reference signal transmitted from a pico base station serving the UE and a second receive power of a macro reference signal transmitted from a macro base station, wherein the UE is located within the coverage area of the macro base station.
  • the processor is further configured to determine, at the UE, a path-loss offset power using the first receive power and the second receive power, to select an enhanced transmission power, comprising a pico uplink transmission power and the path-loss offset power, and to transmit, from the UE, at least one SRS in a pattern of SRS, wherein the at least one SRS is transmitted at the enhanced transmission power.
  • an apparatus includes at least one processor and a memory coupled to the processor.
  • the processor is configured to measure, at a macro base station, an enhanced SRS from a UE served by a pico base station located within a coverage area of the macro base station, wherein the enhanced SRS has a higher power than a pico SRS detected by the macro base station in a pattern of SRS from the UE, to estimate a channel between the UE and the macro base station based, at least in part, on the measured enhanced SRS, and to schedule, by the macro base station, a macro UE for transmission in a null space of the UE, wherein the null space is determined, at least in part, by the estimated channel.
  • an apparatus includes at least one processor and a memory coupled to the processor.
  • the processor is configured to schedule, by a macro base station, at least one UE to reduce interference at the macro base station during transmission of SRS transmitted by a pico UE served by a pico base station within the coverage area of the macro base station.
  • the processor is further configured to measure, at the macro base station, at least one SRS transmitted by the pico UE during the reduced interference, to estimate a channel between the pico UE and the macro base station based, at least in part, on the measured at least one SRS, and to schedule a macro UE served by the macro base station in a null space of the pico UE, wherein the null space is determined, at least in part, by the estimated channel.
  • FIG. 1 is a block diagram conceptually illustrating an example of a mobile communication system.
  • FIG. 2 is a block diagram conceptually illustrating an example of a downlink frame structure in a mobile communication system.
  • FIG. 3 is a block diagram conceptually illustrating time division multiplexed (TDM) partitioning in a heterogeneous network according to one aspect of the disclosure.
  • FIG. 4 is a block diagram conceptually illustrating a design of a base station/eNB and a UE configured according to one aspect of the present disclosure.
  • FIG. 5 is a block diagram illustrating a cell in a wireless network configured according to one aspect of the present disclosure.
  • FIG. 6 is a timing graph illustrating SRS transmission timing for an extended pico UE configured according to one aspect of the present disclosure.
  • FIG. 7 is a functional block diagram illustrating example blocks executed to implement one aspect of the present disclosure.
  • FIG. 8 is a functional block diagram illustrating example blocks executed to implement one aspect of the present disclosure.
  • FIG. 9 is a functional block diagram illustrating example blocks executed to implement one aspect of the present disclosure.
  • FIG. 10 is a block diagram illustrating a UE configured according to one aspect of the present disclosure.
  • FIG. 11 is a block diagram illustrating an eNB configured according to one aspect of the present disclosure.
  • a CDMA network may implement a radio technology, such as Universal Terrestrial Radio Access (UTRA), Telecommunications Industry Association's (TIA's) CDMA2000®, and the like.
  • UTRA Universal Terrestrial Radio Access
  • TIA's Telecommunications Industry Association's
  • the UTRA technology includes Wideband CDMA (WCDMA) and other variants of CDMA.
  • WCDMA Wideband CDMA
  • the CDMA2000® technology includes the IS-2000, IS-95 and IS-856 standards from the Electronics Industry Alliance (EIA) and TIA.
  • a TDMA network may implement a radio technology, such as Global System for Mobile Communications (GSM).
  • GSM Global System for Mobile Communications
  • An OFDMA network may implement a radio technology, such as Evolved UTRA (E- UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, and the like.
  • E- UTRA Evolved UTRA
  • UMB Ultra Mobile Broadband
  • Wi-Fi IEEE 802.11
  • WiMAX IEEE 802.16
  • Flash-OFDMA Flash-OFDMA
  • the UTRA and E-UTRA technologies are part of Universal Mobile Telecommunication System (UMTS).
  • 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are newer releases of the UMTS that use E-UTRA.
  • UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization called the "3rd Generation Partnership Project" (3 GPP).
  • CDMA2000® and UMB are described in documents from an organization called the “3rd Generation Partnership Project 2" (3GPP2).
  • 3GPP2 3rd Generation Partnership Project 2
  • the techniques described herein may be used for the wireless networks and radio access technologies mentioned above, as well as other wireless networks and radio access technologies.
  • LTE or LTE-A (together referred to in the alternative as "LTE/-A”) and use such LTE/-A terminology in much of the description below.
  • FIG. 1 shows a wireless network 100 for communication, which may be an LTE- A network.
  • the wireless network 100 includes a number of evolved NodeBs (eNBs) 110 and other network entities.
  • An eNB may be a station that communicates with the UEs and may also be referred to as a base station, a NodeB, an access point, and the like.
  • Each eNB 110 may provide communication coverage for a particular geographic area.
  • the term "cell" can refer to this particular geographic coverage area of an eNB and/or an eNB subsystem serving the coverage area, depending on the context in which the term is used.
  • An eNB may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell.
  • a macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider.
  • a pico cell would generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider.
  • a femto cell would also generally cover a relatively small geographic area (e.g., a home) and, in addition to unrestricted access, may also provide restricted access by UEs having an association with the femto cell (e.g., UEs in a closed subscriber group (CSG), UEs for users in the home, and the like).
  • An eNB for a macro cell may be referred to as a macro eNB.
  • An eNB for a pico cell may be referred to as a pico eNB.
  • an eNB for a femto cell may be referred to as a femto eNB or a home eNB.
  • a femto eNB or a home eNB.
  • the eNBs 110a, 110b and 110c are macro eNBs for the macro cells 102a, 102b and 102c, respectively.
  • the eNB 11 Ox is a pico eNB for a pico cell 102x.
  • the eNBs 1 lOy and 1 lOz are femto eNBs for the femto cells 102y and 102z, respectively.
  • An eNB may support one or multiple (e.g., two, three, four, and the like) cells.
  • the wireless network 100 may support synchronous or asynchronous operation.
  • the eNBs may have similar frame timing, and transmissions from different eNBs may be approximately aligned in time.
  • the eNBs may have different frame timing, and transmissions from different eNBs may not be aligned in time.
  • the techniques described herein may be used for either synchronous or asynchronous operations.
  • the UEs 120 are dispersed throughout the wireless network 100, and each UE may be stationary or mobile.
  • a UE may also be referred to as a terminal, a mobile station, a subscriber unit, a station, or the like.
  • a UE may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a wireless local loop (WLL) station, or the like.
  • PDA personal digital assistant
  • WLL wireless local loop
  • a UE may be able to communicate with macro eNBs, pico eNBs, femto eNBs, relays, and the like.
  • a solid line with double arrows indicates desired transmissions between a UE and a serving eNB, which is an eNB designated to serve the UE on the downlink and/or uplink.
  • a dashed line with double arrows indicates interfering transmissions between a UE and an eNB.
  • LTE/-A utilizes orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink.
  • OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, or the like.
  • K orthogonal subcarriers
  • Each subcarrier may be modulated with data.
  • modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM.
  • the spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth.
  • K may be equal to 128, 256, 512, 1024 or 2048 for a corresponding system bandwidth of 1.25, 2.5, 5, 10 or 20 megahertz (MHz), respectively.
  • the system bandwidth may also be partitioned into sub-bands.
  • a sub-band may cover 1.08 MHz, and there may be 1, 2, 4, 8 or 16 sub- bands for a corresponding system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.
  • FIG. 2 shows a downlink frame structure used in LTE/-A.
  • the transmission timeline for the downlink may be partitioned into units of radio frames.
  • Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms)) and may be partitioned into 10 sub frames with indices of 0 through 9.
  • Each sub frame may include two slots.
  • Each radio frame may thus include 20 slots with indices of 0 through 19.
  • Each slot may include L symbol periods, e.g., 7 symbol periods for a normal cyclic prefix (as shown in FIG. 2) or 6 symbol periods for an extended cyclic prefix.
  • the 2L symbol periods in each subframe may be assigned indices of 0 through 2L-1.
  • the available time frequency resources may be partitioned into resource blocks.
  • Each resource block may cover N subcarriers (e.g., 12 subcarriers) in one slot.
  • the eNB may send a Physical Control Format Indicator Channel (PCFICH) in the first symbol period of each subframe, as seen in FIG. 2.
  • the eNB may send a Physical HARQ Indicator Channel (PHICH) and a Physical Downlink Control Channel (PDCCH) in the first M symbol periods of each subframe.
  • PHICH Physical HARQ Indicator Channel
  • PDCH Physical Downlink Control Channel
  • the PDCCH and PHICH are also included in the first three symbol periods in the example shown in FIG. 2.
  • the PHICH may carry information to support hybrid automatic retransmission request (HARQ).
  • the PDCCH may carry information on resource allocation for UEs and control information for downlink channels.
  • the eNB may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each subframe.
  • the PDSCH may carry data for UEs scheduled for data transmission on the downlink.
  • the LTE-A may also transmit these control-oriented channels in the data portions of each subframe as well.
  • these new control designs utilizing the data region, e.g., the Relay-Physical Downlink Control Channel (R-PDCCH) and Relay-Physical HARQ Indicator Channel (R-PHICH) are included in the later symbol periods of each subframe.
  • the R-PDCCH is a new type of control channel utilizing the data region originally developed in the context of half-duplex relay operation.
  • R-PDCCH and R- PHICH are mapped to resource elements (REs) originally designated as the data region.
  • the new control channel may be in the form of Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), or a combination of FDM and TDM.
  • a UE may be within the coverage of multiple eNBs.
  • One of these eNBs may be selected to serve the UE.
  • the serving eNB may be selected based on various criteria such as received power, path loss, signal-to-noise ratio (SNR), etc.
  • the wireless network 100 uses the diverse set of eNBs 110 (i.e., macro eNBs, pico eNBs, femto eNBs, and relays) to improve the spectral efficiency of the system per unit area. Because the wireless network 100 uses such different eNBs for its spectral coverage, it may also be referred to as a heterogeneous network.
  • the macro eNBs HOa-c are usually carefully planned and placed by the provider of the wireless network 100.
  • the macro eNBs HOa-c generally transmit at high power levels (e.g., 5 W - 40 W).
  • the pico eNB 1 lOx which generally transmits at substantially lower power levels (e.g., 100 mW - 2 W), may be deployed in a relatively unplanned manner to eliminate coverage holes in the coverage area provided by the macro eNBs HOa-c and improve capacity in the hot spots.
  • the femto eNBs 110y-z which are typically deployed independently from the wireless network 100 may, nonetheless, be incorporated into the coverage area of the wireless network 100 either as a potential access point to the wireless network 100, if authorized by their administrator(s), or at least as an active and aware eNB that may communicate with the other eNBs 110 of the wireless network 100 to perform resource coordination and coordination of interference management.
  • the femto eNBs 110y-z typically also transmit at substantially lower power levels (e.g., 100 mW - 2 W) than the macro eNBs l lOa-c.
  • each UE In operation of a heterogeneous network, such as the wireless network 100, each UE is usually served by the eNB 110 with the better signal quality, while the unwanted signals received from the other eNBs 110 are treated as interference. While such operational principals can lead to significantly sub-optimal performance, gains in network performance are realized in the wireless network 100 by using intelligent resource coordination among the eNBs 110, better server selection strategies, and more advanced techniques for efficient interference management.
  • a pico eNB such as the pico eNB 1 lOx, is characterized by a substantially lower transmit power when compared with a macro eNB, such as the macro eNBs 1 lOa-c.
  • a pico eNB will also usually be placed around a network, such as the wireless network 100, in an ad hoc manner. Because of this unplanned deployment, wireless networks with pico eNB placements, such as the wireless network 100, can be expected to have large areas with low signal to interference conditions, which can make for a more challenging RF environment for control channel transmissions to UEs on the edge of a coverage area or cell (a "cell-edge" UE).
  • the potentially large disparity (e.g., approximately 20 dB) between the transmit power levels of the macro eNBs 1 lOa-c and the pico eNB 1 lOx implies that, in a mixed deployment, the downlink coverage area of the pico eNB 1 lOx will be much smaller than that of the macro eNBs 1 lOa-c.
  • the signal strength of the uplink signal is governed by the UE, and, thus, will be similar when received by any type of the eNBs 110.
  • uplink handoff boundaries will be determined based on channel gains. This can lead to a mismatch between downlink handover boundaries and uplink handover boundaries. Without additional network accommodations, the mismatch would make the server selection or the association of UE to eNB more difficult in the wireless network 100 than in a macro eNB-only homogeneous network, where the downlink and uplink handover boundaries are more closely matched.
  • the usefulness of mixed eNB deployment of heterogeneous networks will be greatly diminished.
  • the larger coverage area of the higher powered macro eNBs, such as the macro eNBs HOa-c limits the benefits of splitting the cell coverage with the pico eNBs, such as the pico eNB 11 Ox, because, the higher downlink received signal strength of the macro eNBs HOa-c will attract all of the available UEs, while the pico eNB 11 Ox may not be serving any UE because of its much weaker downlink transmission power.
  • the macro eNBs HOa-c will likely not have sufficient resources to efficiently serve those UEs. Therefore, the wireless network 100 will attempt to actively balance the load between the macro eNBs HOa-c and the pico eNB 11 Ox by expanding the coverage area of the pico eNB 1 lOx. This concept is referred to as range extension.
  • the wireless network 100 achieves this range extension by changing the manner in which server selection is determined. Instead of basing server selection on downlink received signal strength, selection is based more on the quality of the downlink signal. In one such quality-based determination, server selection may be based on determining the eNB that offers the minimum path loss to the UE. Additionally, the wireless network 100 provides a fixed partitioning of resources equally between the macro eNBs HOa-c and the pico eNB 11 Ox. However, even with this active balancing of load, downlink interference from the macro eNBs HOa-c should be mitigated for the UEs served by the pico eNBs, such as the pico eNB 11 Ox. This can be accomplished by various methods, including interference cancellation at the UE, resource coordination among the eNBs 110, or the like.
  • the pico eNB 11 Ox engages in control channel and data channel interference coordination with the dominant interfering ones of the macro eNBs HOa-c.
  • Many different techniques for interference coordination may be employed to manage interference. For example, inter-cell interference coordination (ICIC) may be used to reduce interference from cells in co-channel deployment.
  • ICIC inter-cell interference coordination
  • One ICIC mechanism is adaptive resource partitioning. Adaptive resource partitioning assigns subframes to certain eNBs. In subframes assigned to a first eNB, neighbor eNBs do not transmit. Thus, interference experienced by a UE served by the first eNB is reduced. Subframe assignment may be performed on both the uplink and downlink channels.
  • subframes may be allocated between three classes of subframes: protected subframes (U subframes), prohibited subframes (N subframes), and common subframes (C subframes).
  • Protected subframes are assigned to a first eNB for use exclusively by the first eNB.
  • Protected subframes may also be referred to as "clean" subframes based on the lack of interference from neighboring eNBs.
  • Prohibited subframes are subframes assigned to a neighbor eNB, and the first eNB is prohibited from transmitting data during the prohibited subframes.
  • a prohibited subframe of the first eNB may correspond to a protected subframe of a second interfering eNB.
  • the first eNB is the only eNB transmitting data during the first eNB's protected subframe.
  • Common subframes may be used for data transmission by multiple eNBs. Common subframes may also be referred to as "unclean" subframes because of the possibility of interference from other eNBs.
  • At least one protected subframe is statically assigned per period. In some cases only one protected subframe is statically assigned. For example, if a period is 8 milliseconds, one protected subframe may be statically assigned to an eNB during every 8 milliseconds. Other subframes may be dynamically allocated.
  • Adaptive resource partitioning information allows the non-statically assigned subframes to be dynamically allocated. Any of protected, prohibited, or common subframes may be dynamically allocated (AU, AN, AC subframes, respectively).
  • the dynamic assignments may change quickly, such as, for example, every one hundred milliseconds or less.
  • Heterogeneous networks may have eNBs of different power classes. For example, three power classes may be defined, in decreasing power class, as macro eNBs, pico eNBs, and femto eNBs.
  • macro eNBs, pico eNBs, and femto eNBs are in a co- channel deployment, the power spectral density (PSD) of the macro eNB (aggressor eNB) may be larger than the PSD of the pico eNB and the femto eNB (victim eNBs) creating large amounts of interference with the pico eNB and the femto eNB.
  • PSD power spectral density
  • Protected subframes may be used to reduce or minimize interference with the pico eNBs and femto eNBs. That is, a protected subframe may be scheduled for the victim eNB to correspond with a prohibited subframe on the aggressor eNB.
  • FIG. 3 is a block diagram illustrating time division multiplexed (TDM) partitioning in a heterogeneous network according to one aspect of the disclosure.
  • a first row of blocks illustrate subframe assignments for a femto eNB, and a second row of blocks illustrate subframe assignments for a macro eNB.
  • Each of the eNBs has a static protected subframe during which the other eNB has a static prohibited subframe.
  • the femto eNB has a protected subframe (U subframe) in subframe 0 corresponding to a prohibited subframe (N subframe) in subframe 0.
  • the macro eNB has a protected subframe (U subframe) in subframe 7 corresponding to a prohibited subframe (N subframe) in subframe 7.
  • Subframes 1-6 are dynamically assigned as either protected subframes (AU), prohibited subframes (AN), and common subframes (AC). During the dynamically assigned common subframes (AC) in subframes 5 and 6, both the femto eNB and the macro eNB may transmit data.
  • AU protected subframes
  • AN prohibited subframes
  • AC common subframes
  • Protected subframes have reduced interference and a high channel quality because aggressor eNBs are prohibited from transmitting.
  • Prohibited subframes (such as N/AN subframes) have no data transmission to allow victim eNBs to transmit data with low interference levels.
  • Common subframes (such as C/AC subframes) have a channel quality dependent on the number of neighbor eNBs transmitting data. For example, if neighbor eNBs are transmitting data on the common subframes, the channel quality of the common subframes may be lower than the protected subframes. Channel quality on common subframes may also be lower for UEs in the cell range extension (CRE) area as they may be strongly affected by aggressor eNBs.
  • CRE cell range extension
  • a UE in the CRE area may belong to a first eNB but also be located in the coverage area of a second eNB.
  • a UE communicating with a macro eNB that is near the range limit of a femto eNB coverage is a CRE UE.
  • a UE may operate in a dominant interference scenario in which the UE may observe high interference from one or more interfering eNBs.
  • a dominant interference scenario may occur due to restricted association.
  • the UE 120y may be close to the femto eNB 1 lOy and may have high received power for the eNB 1 lOy.
  • the UE 120y may not be able to access the femto eNB 1 lOy due to restricted association and may then connect to the macro eNB 110c (as shown in FIG. 1) or to the femto eNB HOz also with lower received power (not shown in FIG. 1).
  • the UE 120y may then observe high interference from the femto eNB HOy on the downlink and may also cause high interference to the eNB 1 lOy on the uplink.
  • the eNB 110c and the femto eNB HOy may communicate over the backhaul 134 to negotiate resources.
  • the femto eNB HOy agrees to cease transmission on one of its channel resources, such that the UE 120y will not experience as much interference from the femto eNB 1 lOy as it communicates with the eNB 110c over that same channel.
  • timing delays of downlink signals may also be observed by the UEs, even in synchronous systems, because of the differing distances between the UEs and the multiple eNBs.
  • the eNBs in a synchronous system are presumptively synchronized across the system. However, for example, considering a UE that is a distance of 5 km from the macro eNB, the propagation delay of any downlink signals received from that macro eNB would be delayed approximately 16.67 (5 km ⁇ 3 x 108, i.e., the speed of light, 'c'). Comparing that downlink signal from the macro eNB to the downlink signal from a much closer femto eNB, the timing difference could approach the level of a time-to-live (TTL) error.
  • TTL time-to-live
  • Interference cancellation often uses cross correlation properties between a combination of multiple versions of the same signal. By combining multiple copies of the same signal, interference may be more easily identified because, while there will likely be interference on each copy of the signal, it will likely not be in the same location. Using the cross correlation of the combined signals, the actual signal portion may be determined and distinguished from the interference, thus, allowing the interference to be canceled.
  • FIG. 4 shows a block diagram of a design of a base station/eNB 110 and a UE 120, which may be one of the base stations/eNBs and one of the UEs in FIG. 1.
  • the eNB 110 may be the macro eNB 110c in FIG. 1, and the UE 120 may be the UE 120y.
  • the eNB 110 may also be a base station of some other type.
  • the eNB 110 may be equipped with antennas 434a through 434t, and the UE 120 may be equipped with antennas 452a through 452r.
  • a transmit processor 420 may receive data from a data source 412 and control information from a controller/processor 440.
  • the control information may be for the PBCH, PCFICH, PHICH, PDCCH, etc.
  • the data may be for the PDSCH, etc.
  • the transmit processor 420 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively.
  • the transmit processor 420 may also generate reference symbols, e.g., for the PSS, SSS, and cell-specific reference signal.
  • a transmit (TX) multiple-input multiple-output (MIMO) processor 430 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 432a through 432t.
  • Each modulator 432 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream.
  • Each modulator 432 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal.
  • Downlink signals from modulators 432a through 432t may be transmitted via the antennas 434a through 434t, respectively.
  • the antennas 452a through 452r may receive the downlink signals from the eNB 110 and may provide received signals to the demodulators (DEMODs) 454a through 454r, respectively.
  • Each demodulator 454 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples.
  • Each demodulator 454 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols.
  • a MIMO detector 456 may obtain received symbols from all the demodulators 454a through 454r, perform MIMO detection on the received symbols if applicable, and provide detected symbols.
  • a receive processor 458 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120 to a data sink 460, and provide decoded control information to a controller/processor 480.
  • a transmit processor 464 may receive and process data (e.g., for the PUSCH) from a data source 462 and control information (e.g., for the PUCCH) from the controller/processor 480.
  • the transmit processor 464 may also generate reference symbols for a reference signal.
  • the symbols from the transmit processor 464 may be precoded by a TX MIMO processor 466 if applicable, further processed by the demodulators 454a through 454r (e.g., for SC-FDM, etc.), and transmitted to the eNB 110.
  • the uplink signals from the UE 120 may be received by the antennas 434, processed by the modulators 432, detected by a MIMO detector 436 if applicable, and further processed by a receive processor 438 to obtain decoded data and control information sent by the UE 120.
  • the processor 438 may provide the decoded data to a data sink 439 and the decoded control information to the controller/processor 440.
  • the controllers/processors 440 and 480 may direct the operation at the eNB 110 and the UE 120, respectively.
  • the controller/processor 440 and/or other processors and modules at the eNB 110 may perform or direct the execution of various processes for the techniques described herein.
  • the controllers/processor 480 and/or other processors and modules at the UE 120 may also perform or direct the execution of the functional blocks illustrated in FIGS. 7-9, and/or other processes for the techniques described herein.
  • the memories 442 and 482 may store data and program codes for the eNB 110 and the UE 120, respectively.
  • a scheduler 444 may schedule UEs for data transmission on the downlink and/or uplink.
  • FIG. 5 is a block diagram illustrating a cell 500 in a wireless network configured according to one aspect of the present disclosure.
  • Cell 500 is serviced by a macro eNB 501 and includes a pico cell deployment of a pico eNB 502 with a pico service area 503.
  • three UEs are served within cell 500, UEs 505-507.
  • UE 505 is served by pico eNB 502 within the pico service area 503.
  • UE 507 is located within cell 500 and is served by macro eNB 501.
  • UE 506 is located within the CRE area of pico eNB 502 between pico service area 503 and pico cell boundary 504. While located with this CRE area, the signal from pico eNB 502 may be weak and subject to higher levels of interference from neighboring cells. Thus, UE 506 may be served by either or both of macro eNB 501 and pico eNB 502. When served by both macro eNB 501 and pico eNB 502, the communication signals may be divided with one of the eNBs serving the data signals while the other eNB serves the control signals.
  • the macro eNB 501 may estimate a channel to the UE 506 served by the pico eNB 502 (a "pico UE") by measuring the sounding reference signal (SRS) from the pico UE and use channel reciprocity to estimate the downlink channel to the pico UE.
  • the macro eNB 501 may then schedule the UE 507 served by the macro eNB 501 (a "macro UE") in the null space of the pico UE on the same resource of the pico UE, depending on the inter-cell channel measured by the macro eNB 501 using the pico UE SRS.
  • macro eNB 501 measures the SRS from UE 506. Using channel reciprocity, macro eNB 501 estimates the downlink channel to UE 506, the pico UE, from the SRS measurement. Depending on the inter-cell channel measurements, macro eNB 501 schedules UE 507, the macro UE, for communication in the null space of UE 506, the pico UE, on the same resources used for UE 506. However, because it is within the null space, the chance that the UE 507 transmission will interfere with UE
  • UE 506 is restricted by the signal power used by the pico UE to transmit the SRS.
  • Pico UE SRS power is determined based on the targeting to the pico eNB 502.
  • UE 506 determines to transmit an SRS to pico eNB 502
  • it will set its power accordingly. Because the distance between UE 506 and eNB 502 is not great, the power would be lower than if UE 506 were transmitting SRS to a further eNB, such as macro eNB 501.
  • the received signal power at macro eNB 501 from the UE 506 SRS may be low due to the lower power selected by UE 506 and further because of the high path- loss that occurs between UE 506 and macro eNB 501. In fact, the received power may be so low that macro eNB 501 may not be able to decode the SRS.
  • the pico UE makes an adjustment to the SRS power to compensate for the path- loss between the pico UE and the macro eNB.
  • the power selected by the pico UE 506 in the CRE area is represented by Ppico.
  • the pico CRE UE 506 calculates the path- lost between the pico eNB 502 and macro eNB 501 by measuring the reference signal receive power (RSRP) of both the pico eNB 502 and macro eNB 501. From these measurements the extended pico UE, UE 506, calculates or determines a path-loss offset, Poffset.
  • RSRP reference signal receive power
  • the extended pico UE, UE 506, will transmit some SRS using a power of Ppico, to accommodate transmission to pico eNB 502, and will transmit other SRS using a modified power of Ppico + Poffset.
  • UE 506 measures the RSRP of pico eNB 502 and macro eNB 501 and calculates the path-loss offset, Poffset, using the measured RSRP values.
  • Poffset path-loss offset
  • UE 506 may alternate between transmitting the SRS using the power, Ppico, for a first scheduled SRS, and then transmitting the SRS using the power, Ppico + Poffset, for the next scheduled SRS, and continuing alternating SRS transmissions between to two power selections.
  • UE 506 may transmit the SRS using power, Ppico, on a different frequency than the UE 506 uses from transmitting the SRS with power, Ppico + Poffset.
  • the Ppico transmitted SRS may also be transmitted more often than the Ppico + Poffset transmitted SRS within a given SRS timing, and vice versa.
  • FIG. 6 is a timing graph 60 illustrating SRS transmission timing for an extended pico UE configured according to one aspect of the present disclosure. Instead of alternating transmission powers between Ppico and Ppico + Poffset, a pattern may be established that identifies when the extended pico UE will transmit its SRS according to Ppico and when it will transmit according to Ppico + Poffset. Timing graph 60 illustrates the SRS transmission timing of an extended pico UE. During the first three scheduled SRS transmissions, the extended pico UE transmits using Ppico 600. The fourth scheduled SRS transmission will be transmitted using Ppico + Poffset 601.
  • the SRS transmission pattern should be coordinated between the pico eNB and macro eNB.
  • pico eNB 502 indicates the SRS pattern information for UE 506 to macro eNB 501 via a backhaul interface, such as the X2 interface, SI interface, or the like, between pico eNB 502 and macro eNB 501.
  • the SRS pattern information includes information such as SRS period, sub-frame index, bandwidth, and the like. With this SRS pattern information, the macro eNB 501 may avoid SRS transmission from UE 507 when UE 506 is transmitting its SRS.
  • the macro eNB may establish or reserve the SRS transmission pattern and send information regarding that pattern to the pico eNB.
  • macro eNB 501 determines an SRS transmission pattern and communicates the pattern information to pico eNB 502 over the backhaul interface, as noted above.
  • the pico eNB 502 signals the SRS transmission pattern to the pico UE 506. Since the macro eNB 501 knows the SRS pattern for UE 506, macro eNB 501 may schedule UE 507 in such a way as to avoid interference during the times when UE 506 is transmitting its SRS.
  • interference is reduced around the pico SRS transmission so that macro eNB 501 may obtain a more accurate measurement of the SRS. This reduced interference results in a more accurate determination of the null space of UE 506, during which macro eNB 501 may schedule transmission for UE 507 to optimize interference coordination.
  • FIG. 7 is a functional block diagram illustrating example blocks executed to implement one aspect of the present disclosure.
  • a pico UE measures both a receive power of a pico reference signal transmitted from a pico base station serving the pico UE and a receive power of a macro reference signal transmitted from a macro base station.
  • the pico UE is located within the coverage area of the macro base station.
  • the UE determines a path- loss offset power using the measured received powers from the two reference signals.
  • the UE would compare and determine the difference between the RSRP of the pico base station and the RSRP of the macro base station in order to determine this path-loss offset power.
  • the UE selects an enhanced transmission power, in block 702, that is made up of the pico uplink transmission power and the path-loss offset power.
  • the enhanced transmission power includes the standard power that the pico UE would select for transmitting SRS to the pico base station.
  • an additional power amount is added to make up for the path-loss between the pico UE and the macro base station. This added power allows the macro base station a better opportunity to perform a more accurate measurement, which results in better interference cancelation.
  • the pico UE transmits at least one SRS at the enhanced transmission power within its pattern of SRS transmissions.
  • the pico UE may transmit various numbers the enhanced SRS at the higher power within its normal SRS transmission pattern.
  • the pico UE may alternate transmitting one enhanced SRS and then a regular SRS at the regular pico transmission power throughout its scheduled transmission pattern.
  • the UE may transmit one enhanced SRS in any given pattern. Referring back to FIG. 6, the pattern of SRS transmissions illustrated in timing graph 60 shows a single enhanced SRS transmission, at Ppico + Poffset 601, among five other regular SRS transmissions, at Ppico 600. In such a pattern, the regular SRS transmissions are transmitted more frequently than the enhanced SRS.
  • FIG. 8 is a functional block diagram illustrating example blocks executed to implement one aspect of the present disclosure.
  • a macro base station measures an enhanced SRS from a pico UE being served by a pico base station located within a coverage area of the macro base station.
  • the enhanced SRS as referenced in FIG. 7, has a higher power than a pico SRS detected by the macro base station in a pattern of SRS from the pico UE.
  • the pico UE transmits SRS routinely that are monitored by the macro base station.
  • the macro base station measures the one detected at the enhanced power level.
  • the macro base station estimates a channel between the pico UE and the macro base station based, at least in part, on the measured enhanced SRS.
  • the macro base station measures the enhanced SRS on the uplink of the pico UE and, through the inherent properties of channel reciprocity found in TDD heterogeneous network systems, estimates the downlink channel to the pico UE.
  • the macro base station may then schedule a macro UE, in block 802, for transmission during in a null space of the pico UE.
  • the macro base station is able to determine the null space, at least in part, by the estimated channel.
  • the macro UE may transmit while the pico UE is in its null space, which would minimize the risk of interference at the pico UE caused by the macro UE transmissions.
  • the SRS transmission may also be coordinated between the pico base station and macro base station.
  • the pico eNB 502 will have knowledge of the SRS transmission pattern information of the pico UE 506, located within its CRE area.
  • the SRS transmission pattern information may include information such as SRS period, sub-frame index, bandwidth, and the like.
  • the pico eNB 502 uses backhaul communication, such as X2, SI, and other such signaling interfaces, the pico eNB 502 sends the SRS transmission pattern information for UE 506 to the macro eNB 501.
  • macro eNB 501 may adjust the SRS transmission schedule of UE 507 to reduce any potential inference with the enhanced SRS transmission to be measured in block 800 (FIG. 8).
  • macro eNB 501 may determine an SRS transmission pattern to be applied to the pico UE, UE 506. Using the backhaul interface, macro eNB 501 may communicate the SRS transmission pattern information to pico eNB 502. The pico eNB 502 may then use that transmission pattern information to adjust the SRS transmission pattern of UE 506. Again, by knowing the SRS transmission pattern of UE 506, the macro eNB 501 may adjust the SRS transmission schedule of UE 507 to reduce potential interference, as noted above.
  • aspects of the present disclosure may improve the interference cancelation process without increasing transmission power at the pico UE.
  • FIG. 9 is a functional block diagram illustrating example blocks executed to implement one aspect of the present disclosure.
  • a macro base station schedules at least one macro UE to reduce interference at the macro base station during SRS transmissions by a pico UE.
  • the pico UE served by a pico base station located within the coverage area of the macro base station.
  • the macro base station schedules the macro UEs for limited or no transmissions during this time period.
  • the macro base station measures at least one SRS transmitted by the pico UE during the period of reduced interference. With the macro UEs scheduled for limited or no transmissions during this period, the macro base station should experience reduced interference when attempting to measure and decode the SRS transmission even considering the reduced power caused by the path loss between the pico UE and the macro base station.
  • the macro base station estimates a channel, in block 902, between the pico UE and the macro base station based, at least in part, on the measured SRS.
  • the channel estimate of the channel to the pico UE is based on the measurement of the SRS transmission over the uplink channel from the pico UE.
  • the nature of the TDD heterogeneous network allows the macro base station to use channel reciprocity to estimate the downlink channel based on the measurement characteristics of the uplink channel from the SRS transmission.
  • the macro base station may then schedule macro UEs for transmission during the null space of the pico UE.
  • the macro base station determines the null space using the estimated channel. This process allows for the coordination between the macro cell and the pico cell for interference cancelation. Because the macro base station is able to reduce the potential interference during the time when the pico UE is transmitting SRS, the channel estimate may be more accurate, which results in a better estimation of the null space and improved interference cancelation.
  • FIG. 10 is a block diagram illustrating a UE 120 configured according to one aspect of the present disclosure.
  • the UE 120 includes a controller/processor 480 which executes the program code and controls the operation of the features and functionality of UE 120.
  • UE 120 is located within a CRE area of a pico cell (not shown).
  • UE 120 transmits and receives communication signals using wireless wide area network (WW AN) radio 1000 under control of controller/processor 480.
  • WW AN radio 1000 may provide communications according to LTE, LTE-A, CDMA, and the like.
  • WWAN radio 1000 may include hardware and components, such as those illustrated in FIG. 4.
  • Controller/processor 480 accesses power measurement code 1003 stored in memory 482 and measures the receive power of reference signals from the pico base station and the macro base station received over WWAN radio 1000.
  • the combination of these components provides means for measuring a first receive power of a pico reference signal transmitted from a pico base station serving the UE and a second receive power of a macro reference signal transmitted from a macro base station, wherein the UE is located within the coverage area of the macro base station.
  • the controller/processor 480 uses an arithmetic component 1004 to determine a path-loss offset power by comparing and finding the difference between the RSRP of the pico cell and RSRP of the macro cell. The combination of these components provides means for determining a path-loss offset power using the first receive power and the second receive power.
  • UE 120 transmits SRS using WW AN radio 1000.
  • an SRS generator 1002, stored in memory 482, comprising logic for generating the SRS is executed by controller/processor 480 to generate an SRS for transmission over WW AN radio 1000.
  • Controller/processor 480 causes the SRS to be transmitted from UE 120 according to an SRS pattern 1001, stored in memory 482.
  • the SRS pattern 1001 may include information such as SRS period, sub-frame index, bandwidth, and the like.
  • controller/processor 480 selects an enhanced power level at which to transmit an SRS.
  • the enhanced power level comprises the regular UL pico transmission power plus the path-loss offset power.
  • controller/processor 480 selects the transmit power for an SRS at the enhanced power level.
  • the combination of these components provides means for selecting an enhanced transmission power, comprising a pico uplink transmission power and the path-loss offset power.
  • the controller/processor 480 executes SRS generator 1002 to generate the SRS and provides for the power control 1005 to supply power equal to the enhanced transmission power to WW AN radio 1000 for transmission of the SRS.
  • the combination of these components provides means for transmitting, from the UE, at least one sounding reference signal (SRS) in a pattern of SRS, wherein the at least one SRS is transmitted at the enhanced transmission power.
  • SRS sounding reference signal
  • FIG. 11 is a block diagram illustrating an eNB 110 configured according to one aspect of the present disclosure.
  • the eNB 110 may be a pico eNB, such as pico eNB 11 Ox (FIG. 1) and pico eNB 502 (FIG. 5), or may also be a macro eNB, such as eNB 110a (FIG. 1) and macro eNB 501 (FIG. 5), and may include various hardware components as illustrated in FIG. 4.
  • eNB 110 is a macro eNB.
  • Macro eNB 110 transmits and receives communication signals using transmitter 1100 and receiver 1 101, respectively, under control of controller/processor 480.
  • Transmitter 1100 and receiver 1101 may include a number of antennas and radios that allow for processing of multiple signals.
  • Controller/processor 440 accesses power measurement code 1104 stored in memory 442 and measures an enhanced SRS from a pico UE (not shown) being served in a pico cell (not shown) within the macro coverage area.
  • the enhanced SRS is received by eNB 110 through receiver 1101 and has a higher power level than a regular pico SRS.
  • the eNB 110 may also detect these regular pico SRS in an SRS pattern 1102 of SRS transmissions from the pico UE. However, the enhanced SRS will be received at the higher power level and may generally be more accurately detected and decoded.
  • the combination of these components provides means for measuring an enhanced from a pico UE served by a pico base station located within a coverage area of the macro base station.
  • the controller/processor 440 executes a channel estimator function 1103 stored in memory 442 to estimate a channel to the pico UE.
  • the controller/processor 440 measures the enhanced SRS and, through channel reciprocity, estimates the downlink channel to the pico UE.
  • the combination of these components provides means for estimating a channel between the UE and the macro base station based, at least in part, on the measured enhanced SRS.
  • the eNB 110 With the channel estimation of the downlink channel to the pico UE, the eNB 110, under control of controller/processor 440, controls scheduler 444 to schedule UEs served by eNB 110 for communication during the null space of the pico UE.
  • the controller/processor 440 determines the null space based on the channel estimate.
  • the controller/processor 440 then causes the scheduling signals to be transmitted to the appropriate macro UEs using transmitter 1100.
  • the combination of these components provides means for scheduling a macro UE served by the macro base station in a null space of the UE, wherein the null space is determined, at least in part, by the estimated channel.
  • the eNB 110 may receive the SRS pattern 1102 from the pico eNB (not shown) serving the pico UE.
  • controller/processor 440 may use the information in the SRS pattern 1102 to control scheduler 444 to send scheduling signals to the macro UEs through transmitter 1100. This scheduling prevents the macro UEs from transmitting their own SRS during the time when the pico UE will be transmitting SRS. Therefore, interference may be reduced when eNB 110 is measuring the enhanced SRS.
  • the eNB 110 may create the SRS pattern 1102, under control of controller/processor 440, and transmit the SRS pattern 1102 to the pico eNB serving the pico UE. The pico eNB would then schedule the SRS transmissions of the pico UE according to the SRS pattern information. As with the previous aspects, by knowing the SRS pattern 1102, eNB 110 may schedule macro eNBs to prevent interfering SRS transmission while it is measuring the enhanced SRS transmission from the pico UE.
  • the pico UEs transmit SRS only at the standard pico uplink transmission power.
  • the controller/processor 440 may improve the interference characteristics by controlling scheduler 444 to transmit scheduling signals to macro UEs to limit transmissions during the times that the pico UE are transmitting SRS. Controller/processor 440 would access SRS pattern 1102 in memory 442 to find out these times for the scheduling.
  • the combination of these components provides means for scheduling at least one macro UE to reduce interference at the macro base station during transmission of SRS from a pico UE served by a pico base station within the coverage area of the macro base station.
  • the controller/processor 440 executes power measurement code 1104 to measure the pico SRS received over receiver 1101.
  • the combination of these components provides means for measuring at least one SRS transmitted by the pico UE during the reduced interference.
  • the controller/processor 440 executes a channel estimator function 1103 stored in memory 442 to estimate a channel to the pico UE.
  • the controller/processor 440 measures the SRS, as noted above, and, through channel reciprocity, estimates the downlink channel to the pico UE.
  • the combination of these components provides means for estimating a channel between the pico UE and the macro base station based, at least in part, on the measured SRS.
  • the eNB 110 With the channel estimation of the downlink channel to the pico UE, the eNB 110, under control of controller/processor 440, controls scheduler 444 to schedule UEs served by eNB 110 for communication during the null space of the pico UE.
  • the controller/processor 440 determines the null space based on the channel estimate.
  • the controller/processor 440 then causes the scheduling signals to be transmitted to the appropriate macro UEs using transmitter 1100.
  • the combination of these components provides means for scheduling a macro UE served by the macro base station in a null space of the pico UE, wherein the null space is determined, at least in part, by the estimated channel.
  • information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.
  • the functional blocks and modules in FIGs. 7-9 may comprise processors, electronics devices, hardware devices, electronics components, logical circuits, memories, software codes, firmware codes, etc., or any combination thereof.
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • a general- purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine.
  • a processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
  • a software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
  • An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium.
  • the storage medium may be integral to the processor.
  • the processor and the storage medium may reside in an ASIC.
  • the ASIC may reside in a user terminal.
  • the processor and the storage medium may reside as discrete components in a user terminal.
  • the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium.
  • Computer-readable media includes both non- transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another.
  • a storage media may be any available media that can be accessed by a general purpose or special purpose computer.
  • non-transitory computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special- purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium.
  • Disk and disc includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

La présente invention concerne la régulation de puissance améliorée pour la planification dans un système de réseau hétérogène de duplexage par répartition temporelle (TDD) dans lequel des signaux de sondage de référence (SRS) transmis par un pico équipement utilisateur (UE) à sa pico station de base sont utilisés par la macro station de base pour évaluer le canal du pico UE. La macro station de base utilise le canal estimé pour planifier les macro UE desservis. Dans des aspects sélectionnés de l'invention, le pico UE détermine l'affaiblissement de puissance sur le trajet de transmission à la macro station de base et transmet au moins l'un de ses SRS à l'aide d'une puissance améliorée qui tient compte de l'affaiblissement de puissance sur le trajet. Dans des aspects supplémentaires, la macro station de base programme les macro UE afin de réduire les interférences pendant les périodes où le pico UE émet un SRS. La puissance plus forte du signal SRS ou l'interférence réduite permet à la macro station de base d'obtenir une estimation de canal plus précise, ce qui entraîne une meilleure annulation d'interférence.
PCT/CN2012/071226 2012-02-16 2012-02-16 Régulation de puissance srs pour la planification coordonnée dans des réseaux hétérogènes tdd WO2013120265A1 (fr)

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GB2506749A (en) * 2012-08-30 2014-04-09 Zte Wistron Telecom Ab Adjusting the power level of an initial preamble signal transmission using a calculated path loss difference in a heterogeneous network
CN103875219A (zh) * 2013-12-13 2014-06-18 华为技术有限公司 干扰协调方法、装置和系统
CN105722221A (zh) * 2014-12-05 2016-06-29 联想(北京)有限公司 时分双工系统中传输语音数据的方法和用户设备
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CN105722221A (zh) * 2014-12-05 2016-06-29 联想(北京)有限公司 时分双工系统中传输语音数据的方法和用户设备
CN105722221B (zh) * 2014-12-05 2019-03-08 联想(北京)有限公司 时分双工系统中传输语音数据的方法和用户设备

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