Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [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. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [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
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/30—Transmission power control [TPC] using constraints in the total amount of available transmission power
  • H04W52/34—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
  • H04W52/343—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading taking into account loading or congestion level
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/06—TPC algorithms
  • H04W52/14—Separate analysis of uplink or downlink
  • H04W52/146—Uplink power control

Definitions

• the embodiments of the present invention generally relate to wireless communication, particularly to a method and device for uplink power control.
• a small radio base station having a low power level and covering a small scale communication area is adopted to enable efficient reuse of spectrum with an existing macro cell base station in a heterogeneous network (HetNet) .
• HetNet heterogeneous network
• a femto cell base station such as a Home evolved Node B (HeNB) specified in the Third Generation Partnership Project ⁇ 3GPP) Release 9, is a short-range low-cost low-power base station installed by consumers, which communicates with a cellular network over a broadband connection such as digital subscriber line (DSL) , cable modem or a separate radio frequency (RF) backhaul channel .
• DSL digital subscriber line
• RF radio frequency
• Fig. 1 illustrates a general structure of a HetNet 100 comprising at least one macro cell and at least one femto cell according to related art.
• a plurality of HeNBs may exist within the coverage of a macro base station, evolved Node B (eNB) , 110.
• eNB evolved Node B
• eNB evolved Node B
• a plurality of Macro User Equipments (MUEs) can be served by the Macro eNB 110 and a plurality of Femto User Equipment ⁇ FUE) can be served by the HeNB 120.
• MUEs Macro User Equipments
• FUE Femto User Equipment
• an uplink signal from the FUE is a source of interference for uplink of the MUE. Meanwhile, uplink of the FUE also suffers interference from uplink transmission of the MUE.
• the interference for uplink both the macro cell and the femto cell would decrease the throughput of the HetNet 100 evidently.
• BSR buffer status reporting
• European patent publication No. EP2063587 Al discloses a solution for controlling transmission rate based on buffer occupancy of radio mobile stations in a WCDMA/HSUPA system. It does not relate to a solution for uplink power control either .
• an embodiment of the present invention provides a method for uplink power control.
• the method comprises: receiving information indicative of uplink traffic load for at least one user terminal; determining target uplink signal strength for the at least one user terminal according to the information indicative of uplink traffic load; and executing uplink power control based on the determined target uplink signal strength.
• an embodiment of the present invention provides a base station.
• the base station comprises: receiving unit configured to receive information indicative of uplink traffic load for at least one user terminal; determining unit configured to determine target uplink signal strength for the at least one user terminal according to the information indicative of uplink traffic load; power control unit configured to execute uplink power control based on the determined target uplink signal strength.
• an embodiment of the present invention provides a computer program product.
• the computer program product comprises instructions which, when loaded into a processor, enable the processor to perform a method for uplink power control according to an embodiment of the present invention.
• the uplink power of user terminals served by one base station such as a femto base station in a heterogeneous network can be adjusted according to uplink traffic demand of those user 12 076199 terminals, so that uplink interference between user terminals served by one base station and user terminals served by another base station can be reduced.
• Fig. 1 schematically illustrates a general structure of a HetNet according to related art
• Fig. 2 schematically illustrates a flow chart of a method for uplink power control according to an embodiment of the present invention
• Figs. 3A and 3B schematically illustrate exemplary structures of a buffer status report information element according to an embodiment of the present invention.
• Fig. 4 schematically illustrates a block diagram of a base station according to an embodiment of the present invention.
• any cell served by a low power base station such as a pico cell, a femto cell and wireless relays can be collectively called a femto cell, in which the embodiments of the present invention can be implemented to improve the uplink throughput of the HetNet by reducing co-channel interference between different kinds of cells that re-use the same frequency resource in the HetNet. Therefore, for the purpose of non-limitation, embodiments of the present invention will be described in conjunction with a HetNet environment where macro cells and femto cells are mixed.
• the embodiments of the present invention provide a mechanism for uplink power control so that uplink power of user terminals served by a femto base station in a HetNet can be set adaptively.
• target uplink signal strength for at least one user terminal served by a femto base station is adjusted according to information indicative of uplink traffic load of the at least one user terminal.
• uplink of a femto cell is used to bear control signaling and thus the traffic load on uplink is moderate. Only in some period the uplink traffic bursts to a high level, such as a period when a user(s) in the femto cell wants to share video or transfer big files to his/her friend (s) , uplink will have heavy load.
• target uplink signal strength is determined and adjusted based on traffic demand so as to achieve the goal of enhancing uplink throughput of the HetNet including at least a femto cell and a macro cell. Specifically speaking, referring to the HetNet of Fig.
• the target uplink signal strength of the FUE ⁇ s can be set as a relative low level so as to meet the requirement of lower SINR.
• the target uplink signal strength of the FUE(s) can be set as a relative high level so as to resist the interference from the MUE(s) of the macro cell and ensure good enough SINR for high throughput requirement.
• uplink SINR and throughput in the macro cell served by the Macro eNB 110 in the HetNet 100 is improved due to less interference from the femto cell serving by the HeNB 120.
• uplink capacity of the femto cell is enhanced by increasing uplink power in this certain period.
• a higher SINR in the femto cell results in a shorter time window of transmission with high power. That means the macro cell served by the Macro eNB 110 can enjoy a longer period with low interference from the femto cell served by the HeNB 120 as much as possible.
• Fig. 2 schematically illustrates a flow chart of a method for uplink power control according to an embodiment of the present invention.
• step S210 information indicative of uplink traffic load for at least one user terminal is received at a femto base station, such as the HeNB 120.
• the information indicative of uplink traffic load can be reported periodically by the user terminals.
• existing BSR procedure specified in current Long Term Evolution (LTE) standards can be used to provide the information indicative of uplink traffic load.
• LTE Long Term Evolution
• 3GPP TS 36.331 V9.5.0 and 3GPP TS 36.321 V10.4.0 as examples of relevant LTE standards are incorporated by reference herein in their entirety .
• the period for adjusting target uplink signal strength of the femto cell can be configured as the basis of one or more BSR periods.
• RRC radio resource control
• the parameter periodicBSR-Timer in the information element MAC-MAINConfig stands for the BSR period and can be configured as a basic unit of the period for adjusting target uplink signal strength Period_Powe TargetAd ust.
• the HeNB needs to configure the parameter Period_PowerTarge Adjtis in advance so as to perform the processing flow of Fig.l.
• the information indicative of uplink traffic load reported from each user terminal can be its buffer status (es) in respective periods of adjusting target uplink signal strength of the femto cell.
• the buffer status information can be carried in a BSR MAC control element, which has been specified in 3GPP TS 36.321 V10.4.0.
• BSR MAC control elements consist of either:
• Short BSR and Truncated BSR format one logical channel group (LCG) ID field and one corresponding Buffer Size field, as shown in Fig. 3A or
• Long BSR format four Buffer Size fields, corresponding to LCG IDs #0 through #3, as shown in Fig. 3B.
• the Logical Channel Group ID field identifies the group of logical channel (s) whose buffer status is being reported.
• the length of the field is 2 bits;
• the Buffer Size field identifies the total amount of data available across all logical channels of a logical channel group after all MAC Protocol Data Units (PDUs) for the Transmission Time Interval (TTI) have been built. The amount of data is indicated by the number of bytes. It shall include all data that is available for transmission in the RLC layer and in the PDCP (Packet Data Convergence Protocol) layer. The length of this field is 6 bits. If extended BSR size levels are not configured, the values taken by the Buffer Size field are shown in Table 1. If extended BSR size levels are configured, the values taken by the Buffer Size field are shown in Table 2.
• target uplink signal strength for said at least one user terminal is determined according to the information indicative of uplink traffic load from the user terminal (s). In one example, same target uplink signal strength is determined for two or more user terminals, particularly for a cell with small amount of users. In another example, target uplink signal strength is determined specifically for each user terminal.
• uplink of all user terminals is ensured to have a same target uplink signal strength, for example denoted as a parameter P_UplinkNominal at an antenna of the femto base station, such as the HeNB 120. Furthermore, P_UplinkNominal is always fixed in the conventional solution.
• the embodiments of the present invention provide a mechanism to adjust target uplink signal strength based on the information indicative of uplink traffic load from the user terminal (s).
• target uplink signal strength can be determined for respective logical channel groups of the user terminals served by the femto base station, such as the HeNB 120.
• the target uplink signal strength for the user terminals can be determined according to a function of the information indicative of uplink traffic load reported from respective user terminals. For example, it would be advantageous that the target uplink signal strength for the user terminals can be determined according to a maximum of the information indicative of uplink traffic load. That means the target uplink signal strength can be adjusted according to the maximum uplink load of respective user terminals or even of respective logical channel groups of respective user terminals. Alternatively, the target uplink signal strength for the user terminals can be determined according to an average of the information indicative of uplink traffic load.
• the HeNB 120 can get a BSR MAC control element in a short or long BSR format from all user terminals. From this information element, the HeNB 120 could know the buffer sizes of the respective logical channel group (s) that are available for transmission.
• a BSR MAC control element uses 6 bits to express index of buffer sizes for each logical channel group of a user terminal (referring to Figs. 3A and 3B as well as Tables 1 and 2) .
• the adjustment of the target uplink signal strength at this period k P_UplinkAdjust_k can be determined based on specific Index_UplinkBuffer_Function_k .
• the adjustment value of the target uplink signal strength can be determined based on a predefined mapping between the buffer statuses and adjustment values of the target uplink signal strength.
• Table 3 shows an example of mapping between the parameters Index_UplinkBuffer_max_k and P_UplinkAdjus _k with respect to the embodiment where the maximum of the information indicative of uplink traffic load is adopted to determine the target uplink signal strength.
• P UplinkAd ust k Index UplinkBuffer P_UplinkAdjust k Index UplinkBuffer max k max k
• mapping table can be predefined in the embodiments where any other function of the information indicative of uplink traffic load, such as average, weighted average, etc., is adopted to determine the target uplink signal strength.
• ⁇ Index_UplinkBuffer_n_m_k ⁇ should be considered as a modification or variant of the embodiments of the present invention.
• an abstract function F() can be defined to show the mapping relationship between ⁇ Index_UplinkBuffer_n_m_k ⁇ and P_UplinkAdjust_k :
• P_UplinkAdjust_k FUNCTION ( ⁇ Index_UplinkBuffer_n_m_k ⁇ ) .
• the target uplink signal strength at the HeNB 120 for k+1 period can be set as:
• P_UplinkTarger_k+l P_UplinkNominal + P_UplinkAdjust_k .
• uplink power control is executed based on the determined target uplink signal strength.
• the HeNB 120 can execute existing procedure for uplink power control . And when executing uplink power control in k+1 uplink power adjustment period, the HeNB 120 updates the parameter of target uplink signal strength at the antenna as P UplinkTarger_k+l, which is determined in k uplink power adjustment period.
• the HeNB 120 can use an existing RRC protocol to command user terminals to adjust uplink power, as specified in 3GPP TS 36.331 V9.5.0. According to 3GPP TS 36.331 V9.5.0, by means of the information elements UplinkPowerControlDedicated and
• the HeNB 120 can adjust nominal uplink power of user terminals for PUSCH and PUCCH. Furthermore, by means of the information elements TPC-PDCCH-Config and TPC-PDSCH-Config in message RRCConnectionReconfiguration, the HeNB 120 performs inner loop uplink power control.
• Fig.4 schematically illustrates a block diagram of a base station according to an embodiment of the present invention.
• a base station 400 comprises a receiving unit 410, a determining unit 420, and a power control unit 430.
• the base station 400 can operate as a femto base station, such as the HeNB 120 serving at least one user terminal in a femto cell.
• the receiving unit 410 is configured to receive information indicative of uplink traffic load for the at least one user terminal. According to an embodiment of the present invention, the receiving unit 410 receives buffer status information of the BSR procedure in every period for adjusting target uplink signal strength of the femto cell. In an implementation of the embodiment of the present invention, the buffer status information can be carried in a BSR MAC control element, which is received by the receiving unit 410 and has been specified in 3GPP TS 36.321 V10.4.0.
• the determining unit 420 is configured to determine target uplink signal strength for the at least one user terminal according to the information indicative of uplink traffic load received by the receiving unit 410. According to an embodiment of the present invention, the determining unit 420 determines the target uplink signal strength for respective logical channel groups of the user terminals served by the base station 400.
• the determining unit 420 can be configured to determine the target uplink signal strength for the user terminals according to a function of the information indicative of uplink traffic load reported from respective user terminals. For example, it would be advantageous that the determining unit 420 can be configured to determine the target uplink signal strength for the user terminals according to a maximum of the information indicative of uplink traffic load. In another example, the determining unit 420 can be configured to determine the target uplink signal strength according to an average of the information indicative of uplink traffic load.
• the determining unit 420 can be configured to determine an adjustment value of the target uplink signal strength based on a predefined mapping between the buffer statuses and adjustment values of the target uplink signal strength. As such, the determining unit 420 can determine the target uplink signal strength in k+1 uplink power adjustment period as the sum of the target uplink signal strength in k uplink power adjustment period and the determined adjustment value.
• the power control unit 430 can be configured to execute uplink power control based on the target uplink signal strength determined by the determining unit 420. According to an embodiment of the present invention, based on the target uplink signal strength determined by the determining unit 430, the power control unit 430 can execute an existing procedure for uplink control.
• the power control unit 430 updates the parameter of target uplink signal strength at an antenna (not shown in Fig. 4 ⁇ of the base station 400 as the target uplink signal strength that is determined by the determining unit 420 in k uplink power adjustment period.
• the base station 400 as illustrated in Fig. 4 is described with the modules or components which are most relevant to the embodiments of the present invention.
• the base station 400 also comprises other modules and components for performing the functionality of cellular communication, including antennas; transceiver (having a transmitter (TX) and a receiver (RX) ) ; processors such as one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architecture; memory module of any type suitable to the local technical environment and implemented using any suitable data storage technology; etc.
• Those modules or components are well known in the art and the description thereof is omitted for the purpose of conciseness .
• the interference between user terminals served by different base stations can be reduced by adjusting uplink power through adjusting target uplink signal strength based on the uplink traffic load.
• the uplink power can be increased to enhance uplink capacity when the traffic load is relatively low, and be decreased uplink power when the traffic load is relatively high, thus the uplink throughput of macro cells in proximity of the femto base station or HeNB in the heterogeneous network can be increased to a great extent by reducing co-channel interference.
• Embodiments of the present invention as described in details above could be implemented into a LTE cellular network with little impact to the whole system.
• a femto base station such as the HeNB 120 can know the current uplink demand from the BSR information reported from user terminals. Based on this information, the HeNB 120 only needs to adjust target uplink signal strength at its antenna, and then execute an existing power control procedure. That is, based on the updated target signal strength at the antenna, the HeNB 120 is able to calculate the required uplink power for a next uplink power adjustment period and notify the respective user terminals of the calculated uplink power.
• one or more embodiments of the present invention are capable of increasing the overall uplink throughput of a heterogeneous network by adaptively adjusting uplink power of user terminals served by a femto base station, and are capable of decreasing the interference to macro user terminal as much as possible, with no or little impact to the existing requirement of uplink throughput and meanwhile.
• the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logical or any combination thereof.
• some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.
• firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.
• various aspects of the exemplary embodiments of this invention may be illustrated and described as block and signaling diagrams, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logical, general purpose hardware or controller or other computing devices, or some combination thereof.
• the present invention may also be embodied in the computer program product which comprises all features capable of implementing the method as depicted herein and may implement the method when loaded to the computer system.

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Citations (4)

• 2012
  • 2012-05-29 WO PCT/CN2012/076199 patent/WO2013177750A1/fr not_active Ceased

Patent Citations (4)

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