WO2012004663A2 - Method and enb for power saving in a heterogeneous network - Google Patents

Method and enb for power saving in a heterogeneous network Download PDF

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Publication number
WO2012004663A2
WO2012004663A2 PCT/IB2011/001608 IB2011001608W WO2012004663A2 WO 2012004663 A2 WO2012004663 A2 WO 2012004663A2 IB 2011001608 W IB2011001608 W IB 2011001608W WO 2012004663 A2 WO2012004663 A2 WO 2012004663A2
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WIPO (PCT)
Prior art keywords
enb
user equipment
overlay capacity
capacity boosting
boosting cell
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PCT/IB2011/001608
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French (fr)
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WO2012004663A8 (en
WO2012004663A3 (en
Inventor
Kaibin Zhang
Xiaobing Leng
Jimin Liu
Jiming Chen
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Alcatel Lucent SAS
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Alcatel Lucent SAS
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Publication of WO2012004663A2 publication Critical patent/WO2012004663A2/en
Publication of WO2012004663A3 publication Critical patent/WO2012004663A3/en
Publication of WO2012004663A8 publication Critical patent/WO2012004663A8/en
Anticipated expiration legal-status Critical
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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/02—Power saving arrangements
    • H04W52/0203—Power saving arrangements in the radio access network or backbone network of wireless communication networks
    • H04W52/0206—Power saving arrangements in the radio access network or backbone network of wireless communication networks in access points, e.g. base stations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the present invention relates to communication technology, more particularly, to the method and the Evolved Node-B (eNB) for power saving in a communication network.
  • eNB Evolved Node-B
  • a heterogeneous network (HTN) system is a wireless cellular mobile network that comprises two overlapped layers of networks, wherein the underlay network is used to provide the full coverage, generally consisted of the traditional cellular network and providing the basic access ability for a user equipment; the overlay network is consisted of a plurality of scattered smaller cells, typically used to increase the capacity of hot spots of hot zones.
  • the network entities used to serve the overlay network maybe a relay station, Femto station or pico station. They apply wired or wireless backhaul mode to connect to the mobile core network.
  • the heterogeneous network is considered as one of the key technologies for increasing and improving the capacity of the broadband wireless access network.
  • the related study and standardization activities have been carried out in major organization and standard bodies. In 3 GPP RAN, HTN technology has already been included into its LTE- Advanced study item. And it is also one of the key work items of Release 10.
  • the energy consumption of an eNB is mainly from the downlink transmission, because in the conventional cellular network, the eNB keeps transmitting downlink pilot and the related control signals so that the mobile terminals can be accessed anywhere and at anytime.
  • There are two sorts of cells in a wireless HTN one is the underlay basic coverage cell used to provide the full coverage, e.g. macro cell, and another is the overlay capacity boosting cell used to enhance the system capacity. These two sorts of cells construct a layered mobile wireless network.
  • a solution proposed for a power saving method in a wireless HTN mainly is that the small eNB serving the overlay capacity boosting cell is turned on only when it is necessary, for example, when the macro cell is nearly overloaded or for the reason of load balancing, etc. Its basic implementation is to let the eNBs of the underlay basic coverage cell monitor the traffic load of the cell. Once the monitored traffic satisfies the corresponding conditions (e.g. greater that a threshold), the overlay capacity boosting cell will be "waked up" or turned on, that is, the "turned on” of the overlay capacity boosting cell is triggered by the serving eNB of the underlay basic coverage cell, instead of autonomously by itself.
  • Such method brings the following drawbacks.
  • an underlay basic coverage cell generally has a plurality of hot spots of which the capacity needs to be enhanced; therefore there are a plurality of capacity boosting cells overlapped with the underlay basic coverage cell correspondingly.
  • the eNB serving the underlay basic coverage cell can detect or estimate the traffic of the whole cell. However, it is difficult for the eNB to estimate the traffic of a certain hot zone in the cell, and also difficult for the eNB to determine which eNB of the overlapped capacity boosting cell should be turned on in order to reduce the load of the cell.
  • the "wake up" indication must be transmitted from the eNB serving the underlay basic coverage cell to the eNB serving the overlay capacity boosting cell. Therefore, the definition of the existing X2 interface between the eNBs (interface between the eNBs) needs to be changed. And the backward compatibility cannot be ensured, which means the existing eNBs have to be upgraded.
  • a new power saving method and corresponding eNB in a HTC network are provided.
  • the eNB serving the overlay capacity boosting cell does not detect any user equipments accessing the overlay capacity boosting cell, turning off its downlink transmission; when the eNB serving the overlay capacity boosting cell detects that the user equipment is approaching its coverage area, turning on its downlink transmission.
  • the eNB serving the overlay capacity boosting cell has two working state, normal transmitting and receiving state, and receiving state, and the eNB serving the overlay capacity boosting cell autonomously turns on and turns off the downlink transmission according to the detecting results of itself, instead of relying on the intervening or indication from the eNB serving the underlay basic coverage cell, to achieve the aim of power saving.
  • a method of power saving in a heterogeneous network comprises an underlay basic coverage cell and an overlay capacity boosting cell, the heterogeneous network further comprises an eNB serving the underlay basic coverage cell and an eNB serving the overlay capacity boosting cell and a user equipment, the method comprises, in the transmitting and receiving state, when the eNB serving the overlay capacity boosting cell does not detect any user equipments accessing the overlay capacity boosting cell, the eNB serving the overlay capacity boosting cell turning off its downlink transmission and being in the receiving state; in the receiving state, when the eNB serving the overlay capacity boosting cell detects that the user equipment is approaching its coverage area, the eNB serving the overlay capacity boosting cell turning on its downlink transmission and being in the transmitting and receiving state.
  • the eNB serving the overlay capacity boosting cell detects that the number of the user equipments which are approaching its coverage area is greater than a predefined value, it turns on its downlink transmission and is in the transmitting and receiving state.
  • the eNB serving the overlay capacity boosting cell receives downlink information from the underlay basic coverage cell; and receives uplink data and control information transmitted by the user equipment; obtains a trigger condition value according to the received uplink data and the control information and compares the trigger condition value with a predefined threshold, if the trigger condition value is greater than the predefined threshold, determines that the user equipment approaching its coverage area has been detected; otherwise, determines that the user equipment approaching its coverage area has not been detected.
  • the downlink information comprises scheduling information and/or system information
  • the control information transmitted by the user equipment comprises an uplink sounding reference signal and/or a random access signal.
  • the trigger condition value is the signal strength of the preamble of the received random access signal.
  • the trigger condition value is the uplink signal SINR obtained according to the received uplink sounding reference signal.
  • the trigger condition value is the signal strength of the uplink data of the resource blocks used by the user equipment.
  • an eNB serves an overlay capacity boosting cell, the overlay capacity boosting cell works in a heterogeneous network, the heterogeneous network further comprises an underlay basic coverage cell, an eNB serving the underlay basic coverage cell and a user equipment, the eNB comprises,
  • a receiving means for receiving information and data
  • a downlink transmitting means for transmitting information and data via downlink in the transmitting and receiving state, and is being in the turned off state in the receiving state;
  • a first detecting means for detecting, in the transmitting and receiving state, if any user equipment accesses the overlay capacity boosting cell or not ;
  • a second detecting means for detecting, in the receiving state, if any user equipment is approaching the coverage area of the eNB serving the overlay capacity boosting cell or not ;
  • a switching means for turning on or turning off the downlink transmission of the eNB serving the overlay capacity boosting cell according to the results output by the first detecting means or the second detecting means, if the first detecting means does not detect any user equipments accessing the overlay capacity boosting cell, the eNB serving the overlay capacity boosting cell turns off its downlink transmission and the downlink transmission means is in the turning off state, the eNB works in the receiving state; if the second detecting means detects that the user equipment is approaching its coverage area, the eNB serving the overlay capacity boosting cell turns on its downlink transmission, the downlink transmission means is in the working state, the eNB is in the transmitting and receiving state.
  • the eNB further comprises a counting means, for calculating the number of the user equipment which is approaching the coverage area of the overlay capacity boosting cell according to the output result of the second detecting means; the switching means, for turning on the downlink transmission of the eNB serving the overlay capacity boosting cell according to the output result of the counting means, when the result output by the counting means is greater than a predefined value.
  • the receiving means in the receiving state, is used to receive downlink information from the underlay basic coverage cell; and is used to receive uplink data and control information transmitted by the user equipment; further, the second detecting means comprises an information processing means and a determining means, the information processing means is used to process the received data and the control information to obtain a trigger condition value, the determining means is for comparing the trigger condition value with a predefined threshold, if the trigger condition value is greater than the predefined threshold, determining that the user equipment approaching its coverage area has been detected; otherwise, determining that the user equipment approaching its coverage area has not been detected.
  • the downlink information comprises scheduling information and/or system information
  • the control information transmitted by the user equipment comprises an uplink sounding reference signal and/or a random access signal.
  • the trigger condition value is the signal strength of the received random access signal.
  • the trigger condition value is the uplink signal SINR obtained according to the received uplink sounding reference signal.
  • the trigger condition value is the signal strength of the uplink data of the resource blocks used by the user equipment.
  • the method provided in the present invention can enable the eNB serving a capacity boosting cell in a HTN to turn off the downlink transmission autonomously when no user equipments accesses the cell, and to turn on the downlink transmission autonomously when at least one user equipment is approaching its coverage area in order to achieve the aim of reduction in the energy consumption and the interference.
  • the new solution has the following advantages: the method needs not additional signaling or interface protocol introduced between the eNBs and has no additional signaling overhead and backward compatibility problems. Also the complexity of its implementation is low.
  • a overlay capacity boosting cell may be activated or turned on where there are many users or much traffic or only the overlay capacity boosting cell which can actually reduce the load of the underlay basic coverage cell is activated, so as to activate the overlay capacity boosting cells as little as possible based on the prerequisite that the load of the underlay cells is ensured to be reduced, and achieve the aim of the energy consumption reduction as much as possible.
  • FIG. l shows a flowchart of a power saving method in a HTN according to an embodiment of the present invention
  • FIG.2 shows a structure schema of an eNB according to an embodiment of the present invention
  • FIG.3 shows a structure schema of an eNB according to another embodiment of the present invention.
  • FIG. l shows a flowchart of a power saving method in a HTN according to an embodiment of the present invention.
  • the embodiment is applied for 3 GPP LTE- Advanced. It is assumed an underlay basic coverage cell is served by eNB2 (Evolved Node-B) and an overlay capacity boosting cell is served by eNB l .
  • eNB2 Evolved Node-B
  • eNB l When the network is initialized, eNB l is in the normal transmitting and receiving state. Then, when eNBl does not detect that user equipment (UE) accesses the overlay capacity boosting cell, it is in the state of turning off the downlink transmission.
  • UE user equipment
  • eNBl After turning off the downlink transmission, eNBl is in the receiving state and begins to receive the downlink control information from eNB2. Through the received downlink control information, eNBl can obtain the information of the underlay basic coverage cell, including the scheduling information in PDCCH (Physical Downlink Control Channel), uplink SRS (Sounding Reference Signal) configuration and/or PRACH (Physical Random Access Channel) configuration of the user equipment.. Meanwhile, eNBl receives the uplink data, uplink SRS and/or RACH transmitted by the user equipment. According to the information, eNB 1 determines if the user equipment is approaching its coverage area or not. If the user equipment is approaching its coverage area, eNB l will turn on its downlink transmission and work as a normal eNB; if no user equipment is approaching its coverage area, eNB l will still in the receiving state.
  • PDCCH Physical Downlink Control Channel
  • uplink SRS Sounding Reference Signal
  • PRACH Physical Random Access Channel
  • eNBl does not turn on its downlink transmission immediately after it determines that the user equipment is approaching its coverage area. However, eNB l will further calculate how many user equipments are approaching its coverage area. eNBl will turn on its downlink transmission only when a satisfied number of user equipments are approaching its coverage area, that is, the number of the user equipments which are approaching the coverage area is greater than a predefined value.
  • eNB 1 determines if a user equipment is approaching its coverage area.
  • eNBl calculates the signal strength of the preamble of PRACH according to the received PRACH, and sets the signal strength of the preamble as a trigger condition value. If the signal strength of the preamble is greater than a predefined threshold, eNBl determines the user equipment is approaching its coverage area; otherwise eNB l determines the user equipment is not approaching its coverage area.
  • eNBl estimates the uplink SRS SINR
  • SINR is greater than a predefined threshold, eNBl determines the user equipment is approaching its coverage area; otherwise eNBl determines the user equipment is not approaching its coverage area.
  • eNB 1 calculates the resource blocks used by the user equipment and calculates the signal strength of the uplink data of the resource blocks used by the user equipment according to the received uplink data from the user equipment, and sets the signal strength of the uplink data of the resource blocks used by the user equipment as a trigger condition value.
  • eNB l determines the user equipment is approaching its coverage area; otherwise eNB l determines the user equipment is not approaching its coverage area.
  • the network sets the trigger condition used to trigger the base station serving a overlay capacity boosting cell to autonomously turn on its downlink transmission by considering the following aspects: a overlay capacity boosting cell can turn on its downlink transmission only where there are many users or much traffic; or only the overlay capacity boosting cell which can actually reduce the load of the underlay basic coverage cell turns on its downlink transmission, so as to let the overlay capacity boosting cells turn on its downlink transmission as little as possible on the prerequisite that the load of the underlay cells is ensured to be reduced; therefore achieve the aim of the energy consumption reduction as much as possible.
  • the trigger condition used by eNB l to determine if a user equipment is approaching its coverage area is not limited, it may be a simple signal strength, or the size of the physical resource blocks used by the user equipment which is approaching the overlay capacity boosting cell, or may be the sum of the physical resources used by all the user equipments which are approaching the overlay capacity boosting cell, it may be an instantaneous measured value, or may be a statistical value measured in a time period.
  • the trigger condition can be set according to the detailed situation and the corresponding predefined threshold can be set according to the selected trigger condition.
  • the calculation of the trigger condition value can be implemented according to the common method used in the signal processing.
  • FIG.2 shows a structure schema of an eNB according to an embodiment of the present invention.
  • eNB 200 serves an overlay capacity boosting cell, the eNB 200 including a first detecting means 201 , a second detecting means 202, a receiving means 203, a downlink transmitting means 204 and a switching means 205.
  • eNB 200 When the network is initialized, eNB 200 is in the normal transmitting and receiving state, that is the switching means 205 is turned on, the downlink transmitting means 204 is turned on and in the work state.
  • the receiving means 203 is configured to receive data and information.
  • the receiving means 203 When eNB 200 is in the normal transmitting and receiving state, the receiving means 203 outputs the received data and information to the first detecting means 201 which is configured to detect whether there exists user equipment which accesses the overlay capacity boosting cell served by eNB 200 or not. Common technology methods are applied for the implementation of the first detecting means 201 and will not be described in detail here.
  • the receiving means 203 is configured to receive the downlink control information from the eNB serving the underlay basic coverage cell and the uplink signal from a user equipment and output the received data and information to the second detecting means 202 which is configured to detect whether there exists user equipment which is approaching the coverage area of eNB 200 or not according to the received data and information.
  • the switching means 205 is configured to turn on or turn off the downlink transmitting means 204 of the eNB according to the output result of the first detecting means 201 or the second detecting means 202.
  • the switching means 205 is configured to turn off the downlink transmitting means 204 of the eNB to enable the eNB 200 to work at receiving state; if the second detecting means 202 detects a user equipment is approaching to its coverage area, the switching means 205 is configured to turn on the downlink transmitting means 204 of the eNB to enable the eNB 200 to work in the normal transmitting and receiving state.
  • the second detecting means 202 comprises a signal processing means 206 and a determining means 207.
  • the signal processing means 206 processes the downlink control information output by the receiving means 203, it can obtain the information of the underlay basic coverage cell, including the scheduling information in PDCCH (Physical Downlink Control Channel), uplink SRS (Sounding Reference Signal) configuration and/or uplink PRACH (Physical Random Access Channel) configuration of the user equipment.
  • the signal processing means 206 processes the uplink data, uplink SRS and/or RACH from the user equipment output by the receiving means 203.
  • the signal processing means 206 carries out signal processing based on the information received by the receiving means 203, obtains a trigger condition value and outputs this value to the determining means 207.
  • the determining means 207 compares the received trigger condition value with a predefined threshold. If the trigger condition value is greater than the predefined threshold, it determines that the user equipment is approaching the coverage area of the eNB; otherwise it determines that the user equipment is not approaching the coverage area of the eNB.
  • the determining means 207 outputs the result to the switching means 205.
  • the switching means 205 turns on or turns off the downlink transmitting means 204 of the eNB according to the determining result.
  • the signal processing means 206 to carry out signal processing so as to obtain a trigger condition value and for the determining means 207 to determine whether a user equipment is approaching its coverage area or not.
  • the signal processing means 206 calculates the signal strength of the preamble of PRACH according to the received PRACH, and sets the signal strength of the preamble as a trigger condition value and outputs it to the determining means 207.
  • a corresponding predefined threshold is stored in the determining means 207. If the signal strength of the preamble is greater than the predefined threshold, the determining means 207 determines the user equipment is approaching its coverage area; otherwise the determining means 207 determines the user equipment is not approaching its coverage area.
  • the signal processing means 206 estimates the uplink SRS SINR (Signal-to-Interference plus Noise Ratio) according to the received SRS, and sets the uplink SRS SINR as a trigger condition value and outputs it to the determining means 207.
  • a corresponding predefined threshold is stored in the determining means 207. If the uplink SRS SINR is greater than the predefined threshold, the determining means 207 determines the user equipment is approaching its coverage area; otherwise the determining means 207 determines the user equipment is not approaching its coverage area.
  • the signal processing means 206 calculates the resource blocks used by the user equipment and calculates the signal strength of the uplink data of the resource blocks used by the user equipment according to the received uplink data from the user equipment, and sets the signal strength of the uplink data of the resource blocks used by the user equipment as a trigger condition value and outputs it to the determining means 207.
  • a corresponding predefined threshold is stored in the determining means 207. If the signal strength of the uplink data of the resource blocks used by the user equipment is greater than the predefined threshold, the determining means 207 determines the user equipment is approaching its coverage area; otherwise the determining means 207 determines the user equipment is not approaching its coverage area.
  • FIG.3 shows a structure schema of an eNB according to another embodiment of the present invention.
  • eNB 300 serves an overlay capacity boosting cell, the eNB 300 including a first detecting means 201 , a second detecting means 202, a receiving means 203, a downlink transmitting means 204 and a switching means 205 and a counting means 301.
  • the first detecting means 201 and the second detecting means 202 comprise a signal processing means 206, a determining means 207, a receiving means 203, a downlink transmitting means 204 and a switching means 205, which are all the same with the corresponding means given in the embodiments of FIG.2 and will not be introduced again here.
  • the counting means 301 is configured to calculate numbers. It further calculates how many user equipments are approaching its coverage area according to the determining result output by the second detecting means 202, and outputs the number to the switching means 205.
  • the switching means 205 will turn on its downlink transmission means 204 only when a satisfied number of user equipments are approaching the coverage area, that is, the number of the user equipment which is approaching the coverage area is greater than a predefined value; otherwise, the switching means 205 will not turn on its downlink transmission means 204.
  • the trigger condition used by eNBl to determine if a user equipment is approaching its coverage area is not limited, that is, the trigger condition value processed and output in the signal processing means 206 may be a simple signal strength, or the size of the physical resource blocks used by the user equipment which is approaching the overlay capacity boosting cell, or may be the sum of the physical resources used by all the user equipments which are approaching the overlay capacity boosting cell, it may be an instantaneous measured value, or may be a statistical value measured in a time period.
  • the trigger condition can be set according to the detailed situation and the corresponding predefined threshold can be set according to the selected trigger condition.
  • the calculation of the trigger condition value can be implemented according to the common method used in the signal processing.
  • the present invention may be implemented by hardware, software, firmware and their combination. It should be appreciated by those skilled in the art that the present invention may be embodied in computer program products set up in the signals carrying medium used by any suitable data processing systems. Such signals carrying medium may be transmission medium or recordable medium for machine-readable information, including magnetic medium, optical medium or other suitable medium.
  • the example of the recordable medium includes: floppy disks or hard disks in the hard disk drive, magnetic tapes, CD drivers used to the optical disk and other medium that could be bethought of by those skilled in the art. It should be appreciated by those skilled in the art that any communication equipments with suitable programming apparatuses can all execute the steps of the present invention method as embodied in the program products.

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Abstract

A method and an evolved Node-B (eNB) for power saving in a heterogeneous network are provided in the embodiments of the present invention. According to the present invention, when the eNB serving an overlay capacity boosting cell does not detect any user equipments accessing the overlay capacity boosting cell, it turns off its downlink transmission; when the eNB serving the overlay capacity boosting cell detects that the user equipment is approaching its coverage area, it turns on its downlink transmission. That is, the eNB serving the overlay capacity boosting cell has two working states, a normal transmitting and receiving state, and a receiving state. The eNB serving the overlay capacity boosting cell autonomously turns on and turns off the downlink transmission according to the detection results of itself, instead of relying on the intervening or indication from the eNB serving an underlay basic coverage cell, so as to achieve the aim of power saving.

Description

Network
Field Of The Invention
The present invention relates to communication technology, more particularly, to the method and the Evolved Node-B (eNB) for power saving in a communication network.
Background Of The Invention
A heterogeneous network (HTN) system is a wireless cellular mobile network that comprises two overlapped layers of networks, wherein the underlay network is used to provide the full coverage, generally consisted of the traditional cellular network and providing the basic access ability for a user equipment; the overlay network is consisted of a plurality of scattered smaller cells, typically used to increase the capacity of hot spots of hot zones. The network entities used to serve the overlay network maybe a relay station, Femto station or pico station. They apply wired or wireless backhaul mode to connect to the mobile core network. Nowadays the heterogeneous network is considered as one of the key technologies for increasing and improving the capacity of the broadband wireless access network. The related study and standardization activities have been carried out in major organization and standard bodies. In 3 GPP RAN, HTN technology has already been included into its LTE- Advanced study item. And it is also one of the key work items of Release 10.
Meanwhile, how to reduce the energy consumption is another research point in the communication area, because the energy consumption of the eNB is one of the major factors that increase operation expenditure for operators. In a HTN, the number of the cell or small eNBs in the overlay used to increase the capacity of the network is much greater than that of the underlay macro eNBs used to solve the basic coverage problem. Therefore, solving the power consumption problem of many small eNBs is not only required for the reduction of the operation expenditure of a wireless network, but also is the necessary requirement for the communication industry to improve the environment and reduce the carbon emission.
The energy consumption of an eNB is mainly from the downlink transmission, because in the conventional cellular network, the eNB keeps transmitting downlink pilot and the related control signals so that the mobile terminals can be accessed anywhere and at anytime. There are two sorts of cells in a wireless HTN, one is the underlay basic coverage cell used to provide the full coverage, e.g. macro cell, and another is the overlay capacity boosting cell used to enhance the system capacity. These two sorts of cells construct a layered mobile wireless network.
So far, a solution proposed for a power saving method in a wireless HTN mainly is that the small eNB serving the overlay capacity boosting cell is turned on only when it is necessary, for example, when the macro cell is nearly overloaded or for the reason of load balancing, etc. Its basic implementation is to let the eNBs of the underlay basic coverage cell monitor the traffic load of the cell. Once the monitored traffic satisfies the corresponding conditions (e.g. greater that a threshold), the overlay capacity boosting cell will be "waked up" or turned on, that is, the "turned on" of the overlay capacity boosting cell is triggered by the serving eNB of the underlay basic coverage cell, instead of autonomously by itself. Such method brings the following drawbacks. Firstly, an underlay basic coverage cell generally has a plurality of hot spots of which the capacity needs to be enhanced; therefore there are a plurality of capacity boosting cells overlapped with the underlay basic coverage cell correspondingly. The eNB serving the underlay basic coverage cell can detect or estimate the traffic of the whole cell. However, it is difficult for the eNB to estimate the traffic of a certain hot zone in the cell, and also difficult for the eNB to determine which eNB of the overlapped capacity boosting cell should be turned on in order to reduce the load of the cell. Secondly, the "wake up" indication must be transmitted from the eNB serving the underlay basic coverage cell to the eNB serving the overlay capacity boosting cell. Therefore, the definition of the existing X2 interface between the eNBs (interface between the eNBs) needs to be changed. And the backward compatibility cannot be ensured, which means the existing eNBs have to be upgraded.
Detailed Description Of The Invention
In order to solve the drawbacks mentioned above in the prior art, a new power saving method and corresponding eNB in a HTC network are provided. According to the present invention, when the eNB serving the overlay capacity boosting cell does not detect any user equipments accessing the overlay capacity boosting cell, turning off its downlink transmission; when the eNB serving the overlay capacity boosting cell detects that the user equipment is approaching its coverage area, turning on its downlink transmission. That is, the eNB serving the overlay capacity boosting cell has two working state, normal transmitting and receiving state, and receiving state, and the eNB serving the overlay capacity boosting cell autonomously turns on and turns off the downlink transmission according to the detecting results of itself, instead of relying on the intervening or indication from the eNB serving the underlay basic coverage cell, to achieve the aim of power saving.
More particularly, according to an embodiment of the present invention, A method of power saving in a heterogeneous network is provided, wherein the heterogeneous network comprises an underlay basic coverage cell and an overlay capacity boosting cell, the heterogeneous network further comprises an eNB serving the underlay basic coverage cell and an eNB serving the overlay capacity boosting cell and a user equipment, the method comprises, in the transmitting and receiving state, when the eNB serving the overlay capacity boosting cell does not detect any user equipments accessing the overlay capacity boosting cell, the eNB serving the overlay capacity boosting cell turning off its downlink transmission and being in the receiving state; in the receiving state, when the eNB serving the overlay capacity boosting cell detects that the user equipment is approaching its coverage area, the eNB serving the overlay capacity boosting cell turning on its downlink transmission and being in the transmitting and receiving state.
According to an alternative embodiment of the present invention, in the receiving state, when the eNB serving the overlay capacity boosting cell detects that the number of the user equipments which are approaching its coverage area is greater than a predefined value, it turns on its downlink transmission and is in the transmitting and receiving state.
According to an alternative embodiment of the present invention, in the receiving state, the eNB serving the overlay capacity boosting cell receives downlink information from the underlay basic coverage cell; and receives uplink data and control information transmitted by the user equipment; obtains a trigger condition value according to the received uplink data and the control information and compares the trigger condition value with a predefined threshold, if the trigger condition value is greater than the predefined threshold, determines that the user equipment approaching its coverage area has been detected; otherwise, determines that the user equipment approaching its coverage area has not been detected.
According to an alternative embodiment of the present invention, the downlink information comprises scheduling information and/or system information; the control information transmitted by the user equipment comprises an uplink sounding reference signal and/or a random access signal.
According to an alternative embodiment of the present invention, the trigger condition value is the signal strength of the preamble of the received random access signal.
According to an alternative embodiment of the present invention, the trigger condition value is the uplink signal SINR obtained according to the received uplink sounding reference signal.
According to an alternative embodiment of the present invention, the trigger condition value is the signal strength of the uplink data of the resource blocks used by the user equipment.
According to an another embodiment of the present invention, an eNB is provided, wherein the eNB serves an overlay capacity boosting cell, the overlay capacity boosting cell works in a heterogeneous network, the heterogeneous network further comprises an underlay basic coverage cell, an eNB serving the underlay basic coverage cell and a user equipment, the eNB comprises,
a receiving means, for receiving information and data;
a downlink transmitting means, for transmitting information and data via downlink in the transmitting and receiving state, and is being in the turned off state in the receiving state;
a first detecting means, for detecting, in the transmitting and receiving state, if any user equipment accesses the overlay capacity boosting cell or not ;
a second detecting means, for detecting, in the receiving state, if any user equipment is approaching the coverage area of the eNB serving the overlay capacity boosting cell or not ;
a switching means, for turning on or turning off the downlink transmission of the eNB serving the overlay capacity boosting cell according to the results output by the first detecting means or the second detecting means, if the first detecting means does not detect any user equipments accessing the overlay capacity boosting cell, the eNB serving the overlay capacity boosting cell turns off its downlink transmission and the downlink transmission means is in the turning off state, the eNB works in the receiving state; if the second detecting means detects that the user equipment is approaching its coverage area, the eNB serving the overlay capacity boosting cell turns on its downlink transmission, the downlink transmission means is in the working state, the eNB is in the transmitting and receiving state.
According to an alternative embodiment of the present invention, the eNB further comprises a counting means, for calculating the number of the user equipment which is approaching the coverage area of the overlay capacity boosting cell according to the output result of the second detecting means; the switching means, for turning on the downlink transmission of the eNB serving the overlay capacity boosting cell according to the output result of the counting means, when the result output by the counting means is greater than a predefined value.
According to an alternative embodiment of the present invention, in the receiving state, the receiving means is used to receive downlink information from the underlay basic coverage cell; and is used to receive uplink data and control information transmitted by the user equipment; further, the second detecting means comprises an information processing means and a determining means, the information processing means is used to process the received data and the control information to obtain a trigger condition value, the determining means is for comparing the trigger condition value with a predefined threshold, if the trigger condition value is greater than the predefined threshold, determining that the user equipment approaching its coverage area has been detected; otherwise, determining that the user equipment approaching its coverage area has not been detected.
According to an alternative embodiment of the present invention, the downlink information comprises scheduling information and/or system information; the control information transmitted by the user equipment comprises an uplink sounding reference signal and/or a random access signal.
According to an alternative embodiment of the present invention, the trigger condition value is the signal strength of the received random access signal.
According to an alternative embodiment of the present invention, the trigger condition value is the uplink signal SINR obtained according to the received uplink sounding reference signal.
According to an alternative embodiment of the present invention, the trigger condition value is the signal strength of the uplink data of the resource blocks used by the user equipment.
The method provided in the present invention can enable the eNB serving a capacity boosting cell in a HTN to turn off the downlink transmission autonomously when no user equipments accesses the cell, and to turn on the downlink transmission autonomously when at least one user equipment is approaching its coverage area in order to achieve the aim of reduction in the energy consumption and the interference. Compared with the existing solution, the new solution has the following advantages: the method needs not additional signaling or interface protocol introduced between the eNBs and has no additional signaling overhead and backward compatibility problems. Also the complexity of its implementation is low. And a overlay capacity boosting cell may be activated or turned on where there are many users or much traffic or only the overlay capacity boosting cell which can actually reduce the load of the underlay basic coverage cell is activated, so as to activate the overlay capacity boosting cells as little as possible based on the prerequisite that the load of the underlay cells is ensured to be reduced, and achieve the aim of the energy consumption reduction as much as possible.
Description of Drawings
With reference to the description according to the figures, and through the more comprehensive understanding of the present invention, other objects and effects of the present invention will be more apparent and easier to be understood, wherein,
FIG. l shows a flowchart of a power saving method in a HTN according to an embodiment of the present invention;
FIG.2 shows a structure schema of an eNB according to an embodiment of the present invention;
FIG.3 shows a structure schema of an eNB according to another embodiment of the present invention.
Wherein, through all figures above, same or similar reference numerals refer to corresponding same or similar features or functions.
Detailed description of embodiments
With reference to the figures, the embodiments of the present invention will be described in detail in the following.
FIG. l shows a flowchart of a power saving method in a HTN according to an embodiment of the present invention. The embodiment is applied for 3 GPP LTE- Advanced. It is assumed an underlay basic coverage cell is served by eNB2 (Evolved Node-B) and an overlay capacity boosting cell is served by eNB l . When the network is initialized, eNB l is in the normal transmitting and receiving state. Then, when eNBl does not detect that user equipment (UE) accesses the overlay capacity boosting cell, it is in the state of turning off the downlink transmission. The implementation of access procedure and access detection applies common technology methods and will not be described in detail here. After turning off the downlink transmission, eNBl is in the receiving state and begins to receive the downlink control information from eNB2. Through the received downlink control information, eNBl can obtain the information of the underlay basic coverage cell, including the scheduling information in PDCCH (Physical Downlink Control Channel), uplink SRS (Sounding Reference Signal) configuration and/or PRACH (Physical Random Access Channel) configuration of the user equipment.. Meanwhile, eNBl receives the uplink data, uplink SRS and/or RACH transmitted by the user equipment. According to the information, eNB 1 determines if the user equipment is approaching its coverage area or not. If the user equipment is approaching its coverage area, eNB l will turn on its downlink transmission and work as a normal eNB; if no user equipment is approaching its coverage area, eNB l will still in the receiving state.
Another embodiment is that, eNBl does not turn on its downlink transmission immediately after it determines that the user equipment is approaching its coverage area. However, eNB l will further calculate how many user equipments are approaching its coverage area. eNBl will turn on its downlink transmission only when a satisfied number of user equipments are approaching its coverage area, that is, the number of the user equipments which are approaching the coverage area is greater than a predefined value.
In the present invention, there are several implementation schemes for eNB 1 to determine if a user equipment is approaching its coverage area.
Several embodiments will be described in detail in the following.
In the first embodiment, eNBl calculates the signal strength of the preamble of PRACH according to the received PRACH, and sets the signal strength of the preamble as a trigger condition value. If the signal strength of the preamble is greater than a predefined threshold, eNBl determines the user equipment is approaching its coverage area; otherwise eNB l determines the user equipment is not approaching its coverage area.
In the second embodiment, eNBl estimates the uplink SRS SINR
(Signal-to-Interference plus Noise Ratio) according to the received SRS, and sets the uplink SRS SINR as a trigger condition value. If the uplink SRS
SINR is greater than a predefined threshold, eNBl determines the user equipment is approaching its coverage area; otherwise eNBl determines the user equipment is not approaching its coverage area.
In the third embodiment, eNB 1 calculates the resource blocks used by the user equipment and calculates the signal strength of the uplink data of the resource blocks used by the user equipment according to the received uplink data from the user equipment, and sets the signal strength of the uplink data of the resource blocks used by the user equipment as a trigger condition value.
If the signal strength of the uplink data of the resource blocks used by the user equipment is greater than a predefined threshold, eNB l determines the user equipment is approaching its coverage area; otherwise eNB l determines the user equipment is not approaching its coverage area.
In the present invention, the network sets the trigger condition used to trigger the base station serving a overlay capacity boosting cell to autonomously turn on its downlink transmission by considering the following aspects: a overlay capacity boosting cell can turn on its downlink transmission only where there are many users or much traffic; or only the overlay capacity boosting cell which can actually reduce the load of the underlay basic coverage cell turns on its downlink transmission, so as to let the overlay capacity boosting cells turn on its downlink transmission as little as possible on the prerequisite that the load of the underlay cells is ensured to be reduced; therefore achieve the aim of the energy consumption reduction as much as possible.
In the present invention, the trigger condition used by eNB l to determine if a user equipment is approaching its coverage area is not limited, it may be a simple signal strength, or the size of the physical resource blocks used by the user equipment which is approaching the overlay capacity boosting cell, or may be the sum of the physical resources used by all the user equipments which are approaching the overlay capacity boosting cell, it may be an instantaneous measured value, or may be a statistical value measured in a time period. The trigger condition can be set according to the detailed situation and the corresponding predefined threshold can be set according to the selected trigger condition. The calculation of the trigger condition value can be implemented according to the common method used in the signal processing.
FIG.2 shows a structure schema of an eNB according to an embodiment of the present invention. In the embodiment, eNB 200 serves an overlay capacity boosting cell, the eNB 200 including a first detecting means 201 , a second detecting means 202, a receiving means 203, a downlink transmitting means 204 and a switching means 205.
When the network is initialized, eNB 200 is in the normal transmitting and receiving state, that is the switching means 205 is turned on, the downlink transmitting means 204 is turned on and in the work state.
More particularly, the receiving means 203 is configured to receive data and information. When eNB 200 is in the normal transmitting and receiving state, the receiving means 203 outputs the received data and information to the first detecting means 201 which is configured to detect whether there exists user equipment which accesses the overlay capacity boosting cell served by eNB 200 or not. Common technology methods are applied for the implementation of the first detecting means 201 and will not be described in detail here. When eNB 200 works in the receiving state, the receiving means 203 is configured to receive the downlink control information from the eNB serving the underlay basic coverage cell and the uplink signal from a user equipment and output the received data and information to the second detecting means 202 which is configured to detect whether there exists user equipment which is approaching the coverage area of eNB 200 or not according to the received data and information. The switching means 205 is configured to turn on or turn off the downlink transmitting means 204 of the eNB according to the output result of the first detecting means 201 or the second detecting means 202. If the first detecting means 201 does not detect any user equipment accessing the overlay capacity boosting cell, the switching means 205 is configured to turn off the downlink transmitting means 204 of the eNB to enable the eNB 200 to work at receiving state; if the second detecting means 202 detects a user equipment is approaching to its coverage area, the switching means 205 is configured to turn on the downlink transmitting means 204 of the eNB to enable the eNB 200 to work in the normal transmitting and receiving state.
Further, the second detecting means 202 comprises a signal processing means 206 and a determining means 207. Wherein, the signal processing means 206 processes the downlink control information output by the receiving means 203, it can obtain the information of the underlay basic coverage cell, including the scheduling information in PDCCH (Physical Downlink Control Channel), uplink SRS (Sounding Reference Signal) configuration and/or uplink PRACH (Physical Random Access Channel) configuration of the user equipment. Further, the signal processing means 206 processes the uplink data, uplink SRS and/or RACH from the user equipment output by the receiving means 203. The signal processing means 206 carries out signal processing based on the information received by the receiving means 203, obtains a trigger condition value and outputs this value to the determining means 207. The determining means 207 compares the received trigger condition value with a predefined threshold. If the trigger condition value is greater than the predefined threshold, it determines that the user equipment is approaching the coverage area of the eNB; otherwise it determines that the user equipment is not approaching the coverage area of the eNB. The determining means 207 outputs the result to the switching means 205. The switching means 205 turns on or turns off the downlink transmitting means 204 of the eNB according to the determining result.
In the present invention, there are several implementation schemes for the signal processing means 206 to carry out signal processing so as to obtain a trigger condition value and for the determining means 207 to determine whether a user equipment is approaching its coverage area or not. Several embodiments will be described in detail in the following.
In the first embodiment, the signal processing means 206 calculates the signal strength of the preamble of PRACH according to the received PRACH, and sets the signal strength of the preamble as a trigger condition value and outputs it to the determining means 207. A corresponding predefined threshold is stored in the determining means 207. If the signal strength of the preamble is greater than the predefined threshold, the determining means 207 determines the user equipment is approaching its coverage area; otherwise the determining means 207 determines the user equipment is not approaching its coverage area.
In the second embodiment, the signal processing means 206 estimates the uplink SRS SINR (Signal-to-Interference plus Noise Ratio) according to the received SRS, and sets the uplink SRS SINR as a trigger condition value and outputs it to the determining means 207. A corresponding predefined threshold is stored in the determining means 207. If the uplink SRS SINR is greater than the predefined threshold, the determining means 207 determines the user equipment is approaching its coverage area; otherwise the determining means 207 determines the user equipment is not approaching its coverage area.
In the third embodiment, the signal processing means 206 calculates the resource blocks used by the user equipment and calculates the signal strength of the uplink data of the resource blocks used by the user equipment according to the received uplink data from the user equipment, and sets the signal strength of the uplink data of the resource blocks used by the user equipment as a trigger condition value and outputs it to the determining means 207. A corresponding predefined threshold is stored in the determining means 207. If the signal strength of the uplink data of the resource blocks used by the user equipment is greater than the predefined threshold, the determining means 207 determines the user equipment is approaching its coverage area; otherwise the determining means 207 determines the user equipment is not approaching its coverage area.
FIG.3 shows a structure schema of an eNB according to another embodiment of the present invention. In the embodiment, eNB 300 serves an overlay capacity boosting cell, the eNB 300 including a first detecting means 201 , a second detecting means 202, a receiving means 203, a downlink transmitting means 204 and a switching means 205 and a counting means 301.
More particularly, the first detecting means 201 and the second detecting means 202 comprise a signal processing means 206, a determining means 207, a receiving means 203, a downlink transmitting means 204 and a switching means 205, which are all the same with the corresponding means given in the embodiments of FIG.2 and will not be introduced again here.
The counting means 301 is configured to calculate numbers. It further calculates how many user equipments are approaching its coverage area according to the determining result output by the second detecting means 202, and outputs the number to the switching means 205. The switching means 205 will turn on its downlink transmission means 204 only when a satisfied number of user equipments are approaching the coverage area, that is, the number of the user equipment which is approaching the coverage area is greater than a predefined value; otherwise, the switching means 205 will not turn on its downlink transmission means 204.
In the present invention, the trigger condition used by eNBl to determine if a user equipment is approaching its coverage area is not limited, that is, the trigger condition value processed and output in the signal processing means 206 may be a simple signal strength, or the size of the physical resource blocks used by the user equipment which is approaching the overlay capacity boosting cell, or may be the sum of the physical resources used by all the user equipments which are approaching the overlay capacity boosting cell, it may be an instantaneous measured value, or may be a statistical value measured in a time period. The trigger condition can be set according to the detailed situation and the corresponding predefined threshold can be set according to the selected trigger condition. The calculation of the trigger condition value can be implemented according to the common method used in the signal processing.
The present invention may be implemented by hardware, software, firmware and their combination. It should be appreciated by those skilled in the art that the present invention may be embodied in computer program products set up in the signals carrying medium used by any suitable data processing systems. Such signals carrying medium may be transmission medium or recordable medium for machine-readable information, including magnetic medium, optical medium or other suitable medium. The example of the recordable medium includes: floppy disks or hard disks in the hard disk drive, magnetic tapes, CD drivers used to the optical disk and other medium that could be bethought of by those skilled in the art. It should be appreciated by those skilled in the art that any communication equipments with suitable programming apparatuses can all execute the steps of the present invention method as embodied in the program products.
From the description above, it could be understood that many modifications and variations may be made to the embodiments of the present invention without departing from the spirit of the present invention. The description in the present specification is only illustrative and should not be considered as limited. The scope of the present invention is only limited by the claims.

Claims

1. A method of power saving in a heterogeneous network, wherein the heterogeneous network comprises an underlay basic coverage cell and an overlay capacity boosting cell, the heterogeneous network further comprises an eNB serving the underlay basic coverage cell and an eNB serving the overlay capacity boosting cell and a user equipment, the method comprises, in the transmitting and receiving state, when the eNB serving the overlay capacity boosting cell does not detect any user equipments accessing the overlay capacity boosting cell, the eNB serving the overlay capacity boosting cell turning off its downlink transmission and being in the receiving state; in the receiving state, when the eNB serving the overlay capacity boosting cell detects that the user equipment is approaching its coverage area, the eNB serving the overlay capacity boosting cell turning on its downlink transmission and being in the transmitting and receiving state.
2. A method of power saving according to claim 1, characterized by, in the receiving state, when the eNB serving the overlay capacity boosting cell detects that the number of the user equipments which are approaching its coverage area is greater than a predefined value, the eNB serving the overlay capacity boosting cell turning on its downlink transmission and being in the transmitting and receiving state.
3. A method of power saving according to claim 1 or 2, characterized by, in the receiving state, the eNB serving the overlay capacity boosting cell receiving downlink information from the underlay basic coverage cell; and receiving uplink data and control information transmitted by the user equipment; obtaining a trigger condition value according to the received uplink data and the control information and comparing the trigger condition value with a predefined threshold, if the trigger condition value is greater than the predefined threshold, determining that the user equipment approaching its coverage area has been detected; otherwise, determining that the user equipment approaching its coverage area has not been detected.
4. A method of power saving according to claim 3, characterized in that the downlink information comprises scheduling information and/or system information; the control information transmitted by the user equipment comprises an uplink sounding reference signal and/or a random access signal.
5. A method of power saving according to claim 4, characterized in that the trigger condition value is the signal strength of the preamble of the received random access signal.
6. A method of power saving according to claim 4, characterized in that the trigger condition value is the uplink signal SINR obtained according to the received uplink sounding reference signal.
7. A method of power saving according to claim 4, characterized in that, the trigger condition value is the signal strength of the uplink data of the resource blocks used by the user equipment.
8. An eNB, wherein the eNB serves an overlay capacity boosting cell, the overlay capacity boosting cell works in a heterogeneous network, the heterogeneous network further comprises an underlay basic coverage cell, an eNB serving the underlay basic coverage cell and a user equipment, the eNB comprises,
a receiving means, for receiving information and data;
a downlink transmitting means, for transmitting information and data via downlink in the transmitting and receiving state, and being in the turned off state in the receiving state;
a first detecting means, for detecting, in the transmitting and receiving state, if any user equipment accesses the overlay capacity boosting cell or not ;
a second detecting means, for detecting, in the receiving state, if any user equipment is approaching the coverage area of the eNB serving the overlay capacity boosting cell or not ; a switching means, for turning on or turning off the downlink transmission of the eNB serving the overlay capacity boosting cell according to the results output by the first detecting means or the second detecting means, if the first detecting means does not detect any user equipments accessing the overlay capacity boosting cell, the eNB serving the overlay capacity boosting cell turns off its downlink transmission and the downlink transmission means is in the turning off state, the eNB works in the receiving state; if the second detecting means detects that the user equipment is approaching its coverage area, and the eNB serving the overlay capacity boosting cell turns on its downlink transmission, the downlink transmission means is in the working state, and the eNB is in the transmitting and receiving state.
9. An eNB according to claim 8, characterized in that, the eNB further comprises a counting means, for calculating the number of the user equipments which are approaching the coverage area of the overlay capacity boosting cell according to the output result of the second detecting means; the switching means is further used for turning on the downlink transmission of the eNB serving the overlay capacity boosting cell, according to the output result of the counting means, when the result output by the counting means is greater than a predefined value.
10. An eNB according to claim 8 or 9, characterized in that, in the receiving state, the receiving means is further used to receive downlink information from the underlay basic coverage cell; and is used to receive uplink data and control information transmitted by the user equipment; the second detecting means further comprises an information processing means and a determining means, the information processing means is used to process the received data and the control information to obtain a trigger condition value, the determining means is for comparing the trigger condition value with a predefined threshold, if the trigger condition value is greater than the predefined threshold, determining that the user equipment approaching its coverage area has been detected; otherwise, determining that the user equipment approaching its coverage area has not been detected.
11. An eNB according to claim 10, characterized in that, the downlink information comprises scheduling information and/or system information; the control information transmitted by the user equipment comprises an uplink sounding reference signal and/or a random access signal.
12. An eNB according to claim 11, characterized in that, the trigger condition value is the signal strength of the received random access signal.
13. An eNB according to claim 11, characterized in that, the trigger condition value is the uplink signal SINR obtained according to the received uplink sounding reference signal.
14. An eNB according to claim 11, characterized in that, the trigger condition value is the signal strength of the uplink data of the resource blocks used by the user equipment.
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