WO2011105407A1 - 無線基地局およびその適応変調制御方法 - Google Patents
無線基地局およびその適応変調制御方法 Download PDFInfo
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- WO2011105407A1 WO2011105407A1 PCT/JP2011/053933 JP2011053933W WO2011105407A1 WO 2011105407 A1 WO2011105407 A1 WO 2011105407A1 JP 2011053933 W JP2011053933 W JP 2011053933W WO 2011105407 A1 WO2011105407 A1 WO 2011105407A1
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- 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]
- H04W52/262—TPC being performed according to specific parameters using transmission rate or quality of service QoS [Quality of Service] taking into account adaptive modulation and coding [AMC] scheme
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- 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
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
- H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0044—Arrangements for allocating sub-channels of the transmission path allocation of payload
- H04L5/0046—Determination of how many bits are transmitted on different sub-channels
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- 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
Definitions
- the present invention relates to a radio base station that adaptively controls a modulation scheme and a coding scheme used for connection with a radio terminal, and more particularly to power saving of such a radio base station.
- Non-Patent Document 1 In a wireless communication system in which channel quality between a transmitter and a receiver varies depending on time and place, a method of adaptively changing a modulation scheme according to channel quality is known. This is a technique called adaptive modulation, and is widely used in mobile communication systems and wireless local area networks. The principle of adaptive modulation is known, and is described in Non-Patent Document 1, for example.
- adaptive coding is also known as a method for adaptively changing the coding scheme according to channel quality.
- the principle of adaptive encoding is also described in Non-Patent Document 1.
- adaptive modulation coding combining adaptive modulation and adaptive coding is also known.
- a method is selected according to channel quality, and adaptive coding and adaptive modulation coding can be basically considered in the same manner as adaptive modulation in that transmission power changes according to the selected method.
- adaptive modulation will be mainly described here, adaptive coding and adaptive modulation coding are also included in the term adaptive modulation when it is not necessary to distinguish between them.
- the term “modulation method” includes a coding method and a combination of the modulation method and the coding method.
- FIG. 1 is a model diagram of a communication system for explaining adaptive modulation.
- the transmitter 2000 selects an appropriate modulation scheme and coding rate, and modulates and encodes the transmission signal.
- transmitter 2000 selects a modulation scheme and a coding rate based on the channel quality estimation result obtained from receiver 2020 via feedback channel 2030. This channel quality is called CQI (Channel Quality Indicator).
- CQI Channel Quality Indicator
- the transmitter 2000 selects a modulation scheme and a coding rate so that a required signal-to-interference noise power ratio (SINR) or signal-to-noise power ratio (SNR) is satisfied.
- SINR signal-to-interference noise power ratio
- SNR signal-to-noise power ratio
- the signal transmitted from the transmitter 2000 is added with time-varying power gain, noise, and interference wave in the channel 2010 and reaches the receiver 2020.
- the receiver 2020 extracts the received signal by performing demodulation and decoding on the signal from the transmitter 2000.
- the receiver 2020 performs channel estimation and transmits the obtained channel quality information to the transmitter 2000 via the feedback channel 2030.
- adaptive modulation often used in wireless communication is to select a modulation method so as to maximize the line capacity. That is, the modulation scheme having the largest amount of transmission information per symbol (multilevel) is selected for the channel quality estimation result obtained from the feedback channel.
- the SNR required for QPSK modulation in which the information amount per symbol is 2 [bits] is Z1 [dB]
- the SNR required for 16 QAM modulation in which the information amount per symbol is 4 [bits].
- the SNR required for 64QAM modulation in which the amount of information per symbol is 6 [bits] is Z3 [dB]
- any of QPSK modulation, 16QAM modulation, and 64QAM modulation can be applied.
- 16QAM modulation it is possible to obtain a line capacity that is twice that of QPSK modulation
- 64QAM modulation it is possible to obtain a line capacity that is three times that of QPSK, so that 64QAM modulation is generally selected.
- the average throughput can be improved by increasing the multi-level determined by the modulation scheme and coding rate.
- the transmission power can be reduced by Z3-Z2 [dB] or Z3-Z1 [dB], respectively. As a result, power saving in wireless communication can be achieved. it can.
- Patent Document 1 is a technique for reducing the power consumption of a radio base station by adaptive modulation.
- Patent Document 1 when the amount of data to be transferred is less than a predetermined threshold, or when the amount of radio resources that can be used for data transfer is greater than or equal to a predetermined value, power saving is achieved by lowering the multivalue level. A method of aiming is disclosed.
- Patent Document 1 describes that power saving is achieved by partially stopping the transmission unit and / or the reception unit during a time period other than the busy time period. Further, in Patent Document 1, when the amount of data to be transferred is equal to or greater than a predetermined threshold, the line capacity is increased by increasing the multivalue level.
- Non-Patent Document 2 power is saved by adaptively switching the level (MCS level) of the adaptive modulation and coding scheme (Modulation and Coding Scheme, MCS) in the uplink of a wireless communication system in accordance with the IEEE 802.16 standard. It shows how to do the control.
- MCS level corresponds to a modulation scheme or a coding scheme.
- Non-Patent Document 2 when there is a vacancy in the line capacity, that is, the utilization rate of the uplink subframe, power saving control is performed in two stages: Expand Scheme and Replacement Scheme.
- a mobile terminal having the most room for reducing transmission power is selected in order from a plurality of mobile terminals, and the MCS level of the mobile terminal is changed, so that the transmission power of the mobile terminal is lowest. Apply degree of value. If this is repeated until there is no available line capacity or the change of the MCS level of all the mobile terminals is completed, the process moves to Replacement Scheme.
- the line used as the whole cell is within the line capacity range and transmission power can be reduced. , So change the MCS level.
- wireless terminals of various channel qualities are mixed in a wireless cell such as a mobile communication system.
- the applicable multivalue level differs depending on the wireless terminal. Further, the capacity for accommodating the wireless terminal in the wireless cell changes with time. For this reason, in order to minimize power consumption while avoiding congestion, it is required to appropriately set the multivalue level for each wireless terminal.
- Patent Literature 1 does not describe which wireless terminal is selected from a group of wireless terminals having various channel qualities to change the modulation scheme. For this reason, depending on the selection of the wireless terminal whose modulation method is to be changed, the most effective reduction of the transmission power may not always be achieved as a whole.
- the required transmission power and SNR tend to increase exponentially. For this reason, if the channel gain and interference are constant, it is preferable in terms of transmission power reduction to reduce the number of wireless terminals using a multi-level modulation scheme that maximizes the transmission power.
- Non-Patent Document 2 if there is an available line capacity, the multivalue level is changed from the wireless terminal having the largest room for reducing transmission power.
- the room for reducing the transmission power is the largest, it does not necessarily mean that the transmission power can be reduced. Therefore, effective transmission power may not be reduced.
- An object of the present invention is to reduce transmission power in a radio base station connected to a plurality of radio terminals using adaptive modulation.
- a radio base station of the present invention is a radio base station connected to a radio terminal using adaptive modulation, First processing means for determining a target value of the total number of bits to be mapped to radio resources of traffic to the radio terminal; First, a modulation scheme for the radio terminal is determined by adaptive modulation so that the total number of bits to be transmitted is limited in association with the target value, while free resources of the radio resource are reduced and transmission power density is constant and small. 2 processing means.
- the control method of the present invention is an adaptive modulation control method in a radio base station connected to a radio terminal using adaptive modulation, Determining a target value of the total number of bits to be mapped to radio resources of traffic to the radio terminal; A modulation scheme for the radio terminal is determined by adaptive modulation so that the total number of bits to be transmitted is limited in association with the target value, while free resources of the radio resource are reduced and the transmission power density is constant and small. It is.
- FIG. 2 is a block diagram showing a basic system configuration of the present embodiment.
- the mobile communication system according to the present embodiment includes a radio base station 11 and a radio terminal 12.
- FIG. 3 is a block diagram showing a basic configuration of the radio base station of the present embodiment.
- the radio base station 11 includes a primary processing unit 21 and a secondary processing unit 22.
- a mobile communication system in which the radio base station 11 communicates with the radio terminal 12 using radio resources is assumed.
- the wireless base station 11 performs transmission while limiting the total number of bits to be transmitted by the secondary processing unit 22 when free resources are generated in the wireless resources after the primary adaptive modulation is performed by the primary processing unit 21.
- Secondary adaptive modulation is performed using additional free resources so as to keep the power density constant and small. Thereby, the transmission power of the radio base station can be effectively reduced.
- the primary processing part 21 showed the example which performs adaptive modulation here, this invention is not limited to this.
- the primary processing unit 21 refers directly to a predetermined table without performing adaptive modulation and mapping by the adaptive modulation and mapping based on the total amount of traffic to the wireless terminal 12 or the queue length of the buffer.
- the number of bits (that is, the total number of bits targeted in the secondary processing unit 22) may be determined.
- the primary processing unit 21 performs primary adaptive modulation based on the channel quality information
- the secondary processing unit 22 uses a free resource to make the transmission power density constant and small, based on the channel quality.
- the secondary adaptive modulation may be performed such that the total number of bits obtained from the secondary adaptive modulation approaches the total number of bits in the primary adaptive modulation.
- the multi-value level for each wireless terminal 12 can be lowered to an appropriate multi-value level according to the channel quality (CQI).
- the secondary processing unit 22 matches the total number of bits obtained from the secondary adaptive modulation with the total number of transmission bits obtained by the primary adaptive modulation, and a plurality of radio terminals having different channel qualities.
- the adaptive modulation control may be sequentially tried. Accordingly, power saving can be realized by using the total number of bits of mapping by primary adaptive modulation by a general method or the like and adding secondary adaptive modulation.
- the secondary processing unit 22 sequentially attempts adaptive modulation control for a plurality of wireless terminals 12, the secondary processing unit 22 maintains the modulation scheme determined by the primary processing unit 21 for wireless terminals whose priority is higher than a predetermined threshold. You may decide to do it.
- the radio base station 11 increases the scheduling metric and the priority is increased for the terminal that is waiting for data until the state is improved, the transmission power is increased when performing resource allocation for the standby terminal having a high priority. Data can be transmitted without reducing the density.
- the radio base station 11 further includes a control signal communication unit 23.
- the control signal communication unit 23 is a downlink indicating a difference between the power density of the transmission pilot signal and the transmission power density obtained by the secondary processing unit 22.
- the control signal may be transmitted to the wireless terminal 12.
- the radio terminal 12 is notified of the power difference between the pilot signal and the channel carrying the data as a result of controlling the adaptive modulation so that the transmission power density is constant and small. Processing becomes possible.
- the primary processing unit 21 determines the ratio of available radio resources to free resources or the entire radio resources according to the traffic amount to be transmitted to the radio terminal 12, and performs mapping using the available radio resources.
- the total number of bits to be transmitted may be determined.
- an appropriate total number of bits can be set as a constraint condition according to the traffic volume, so that appropriate secondary adaptive modulation can be performed.
- the primary processing unit 21 determines the ratio of available radio resources to available resources or the entire radio resources according to the queue length of the transmission buffer in which data to be transmitted is temporarily stored, and can be used.
- the total number of bits to be transmitted may be determined by mapping using various radio resources. As a result, the traffic volume can be easily obtained from the queue length of the transmission buffer and used as a constraint condition.
- the secondary processing unit 22 may control the adaptive modulation so that the transmission power density is within a predetermined range from a certain value. As a result, even if the values that the transmission power density can take are discrete, it is possible to control such that the transmission power is effectively reduced by controlling the values within a certain range.
- the radio resources are defined in the frequency direction and the time direction as shown in FIG.
- the radio resource is divided into coherent bands in the frequency direction and into coherent time in the time direction.
- this division is described as dividing radio resources into resource blocks.
- a modulation scheme (MCS or the like) corresponding to the radio terminal determined by adaptive modulation is mapped to the resource block.
- Each resource block includes one or more subcarriers, and includes one or more symbols in the time direction.
- the channel gain and the interference component are considered to be almost constant in the resource block.
- This resource block is the basic unit for scheduling and mapping.
- the power consumption of the radio base station can be effectively reduced.
- a continuous system is shown here. Strictly speaking, a discrete system is used in an actual system, but a difference between a continuous system and a discrete system is treated as an error generated in quantization from a continuous system to a discrete system.
- x of the resource block x is an expanded direction in which the radio resources are expanded and rearranged in a one-dimensional manner including all the radio terminals in the frequency direction and the time direction, and are ordinal numbers of the resource blocks that are discretely expanded.
- the wireless base station Since the total amount of information sent from the wireless cell, that is, the wireless base station is b,
- the power consumption amount J is defined as follows by the bit correspondence consumption function G (f) indicating the power consumed by the bit correspondence transmission power amplifier according to the number of bits to be transmitted.
- P h (x) is a power-converted channel gain, and if P h (x) is large, the transmission power can be reduced accordingly.
- the power consumed by the transmission power amplifier by the resource block x is actually
- I a comparison function, and a stationary function that becomes an extreme value function
- equation (14) becomes equation (16).
- the above-described functional is an extreme value function that minimizes the total power consumption J.
- the total power consumption J is minimized when the power consumed by the transmission power amplifiers of each resource block is all equal, in other words, when the transmission power is all equal by the resource block x, that is, the transmission power density is constant. It's time.
- P h (x) is included in the above G.
- the power consumption corresponding to the transmission power is also constant in the actual transmission power amplifier. Obviously, the total power consumption J is minimized when the transmission power density is constant.
- the case where the channel gain is constant over the resource block x is shown.
- the total power consumption when the channel gain and the interference of the resource block x corresponding to each of the resource blocks x are expanded in one dimension in the x direction including all frequency bands, time, wireless terminals, etc. Can be minimized.
- P h (x) is first fixed and omitted is illustrated. Similar to the above analysis, the power consumption J in this case is
- G (f) is a bit-corresponding consumption function G (f) indicating the power consumed by the transmission power amplifier according to the number of bits to be transmitted f.
- G (f) can take an arbitrary shape corresponding to an actual transmission power amplifier.
- Equation (30) is obtained.
- the above-described functional is an extreme value function that minimizes the total power consumption J. That is, the condition for minimizing the total power consumption J is that G (f (x)) is constant.
- G (f (x)) is the power consumed by the transmission power amplifier by the resource block x.
- the total power consumption J is minimized when the power consumed by the transmission power amplifier of each resource block is all equal, in other words, when the transmission power of the resource block x is all equal, that is, the transmission power density is constant. It's time. More specifically, G (f (x)) is a function of the number of transmission bits f (x). Therefore, the total power consumption J is minimized when the number of transmission bits f (x) by each resource block x is equal.
- modulation schemes are mapped to radio resources by primary adaptive modulation as shown in FIG.
- the method used for primary adaptive modulation is not particularly limited, but some existing adaptive modulation method is used.
- the existing adaptive modulation used here is called general adaptive modulation.
- the first maps QPSK modulation.
- QPSK can transmit 2 bits per symbol.
- the power for sending this QPSK is 1.
- the resource block used here includes one subcarrier in the frequency direction and one symbol in the time axis direction.
- 64QAM modulation is mapped to the second to fourth resource blocks.
- 64QAM can transmit 6 bits per symbol. In order to maintain the same quality in these multilevel modulations, it is necessary to increase the transmission power almost four times every 2 bits.
- the power (power density) corresponding to the resource block is described above the bar indicating the modulation scheme mapped to each resource block.
- a mapping that saves power using the above principle with the same total number of bits as the above mapping is shown on the right side of FIG. Based on the above principle, when each resource block x has the same number of transmission bits f (x), the total power consumption J is minimized. Therefore, as shown on the right side of FIG. 7, the multi-value level is lowered so that the same modulation method can be obtained as much as possible using empty resources. In this example, there are some bits, so there are some differences in the multi-level. Note that lowering the multi-value level so as to achieve the same modulation scheme is the same as reducing the transmission power density to be constant.
- the first and sixth resource blocks map QPSK.
- QPSK can transmit 2 bits per symbol, and its power is 1.
- the second to fifth resource blocks are mapped to 16QAM.
- 16QAM can transmit 4 bits per symbol, and its power is 4.
- the total number of transmission bits is the same, it can be seen that the total transmission power is drastically reduced from 49 [W] to 18 [W]. That is, it is understood that the total power consumption J is minimized when mapping is performed so that each resource block x has the same number of transmission bits f (x), in other words, the transmission power density is constant and small.
- the calculation of the transmission power described above uses an approximation from Shannon's capacity formula in the information theory that the transmission power is quadrupled for every 2 bits transmitted.
- this is referred to as exponential approximation
- the transmission power obtained by exponential approximation corresponds to the power consumption when an ideal transmission power amplifier is used.
- G (f) used in the analysis process of the above-described principle is a bit-corresponding consumption function G (f) indicating the power consumed by the transmission power amplifier according to the number of bits f to be transmitted. Any shape corresponding to can be taken. Since the solution obtained by the above-described principle is an optimal solution that minimizes the total power consumption J obtained under the condition that an arbitrary condition can be taken, it goes without saying that the above-described principle can be applied to an actual transmission power amplifier. Yes.
- the example described above is an example in which the channel gain is constant over the resource block x.
- the state (channel quality) of the transmission path composed of channel gain and interference components differs depending on the resource block.
- the above principle that the total power consumption J is minimized when the number of transmission bits f (x) by each resource block x is equal is no longer true.
- the transmission power density is constant and the formula (23) that the total power consumption J is minimized is the optimal solution in a state where channel gain and interference are different. This is compared with an example when the channel quality of each resource block is equal to or different from each other. In order to avoid complication, the interference component is considered to be included in the channel gain Ph (x) here.
- FIG. 8A and 8B are diagrams for explaining an example in which the above-described principle is applied.
- FIG. 8A shows an example in which the channel quality varies depending on the resource block
- FIG. 8B shows an example in which the channel quality is uniform across the resource blocks.
- FIG. 8A First, looking at the upper table when the channel quality varies depending on the resource block, in the mapping using general adaptive modulation, the total number of transmission bits is 38 [bit], and the total transmission power is 70 [W]. It has become. In the mapping to which the adaptive modulation based on the principle described above is applied, the total number of transmission bits is 38 [bit] and the total transmission power is 22.5 [W] as shown in the middle part of FIG. 8A. In this case, free resources are also used, and the power of each resource block is constant. That is, mapping to radio resources is performed with the multivalue level lowered so that the power density is constant and small.
- the modulation scheme used is not shown in the figure, if the number of transmission bits f (x) is 2, the modulation scheme is QPSK, and if f (x) is 4, the modulation scheme is 16QAM. , F (x) is 6, the modulation scheme is 64QAM.
- the multi-value level is lowered so that the total number of transmitted bits is 38 [bits], which is the same as when general adaptive modulation is used.
- the total transmission power is 70 [W]
- the total transmission power is drastically reduced to 22.5 [W]. .
- the number of transmission bits f (x) 2 in order to adjust the total number of bits, and the modulation method is QPSK.
- f (x) 4 and the modulation method is 16QAM.
- the total number of transmission bits at this time is 38 [bits], which is the same as in the case of using general adaptive modulation, and the total transmission power is 41.88 [W].
- general adaptive modulation since the total transmission power is 70 [W] as shown in the upper part, it can be seen that the transmission power is further reduced.
- the degree of reduction is low compared to the case where the total transmission power is 22.5 [W]. That is, even when the channel quality varies depending on the resource block, it can be said that the arrangement of the modulation scheme so that the transmission power density is constant and small is more effective for power saving than the equal bit arrangement.
- FIG. 8B the case where the channel quality is uniform across the resource blocks, that is, the case of an AWGN (Additive White Gaussian Noise) channel is seen.
- AWGN Additional White Gaussian Noise
- channel gain Ph (x) is 1 in all columns, it is omitted.
- the total number of bits is 38 [bit] and the total transmission power is 169 [W].
- the total number of bits is 38 [bit] and the total transmission power is 37 [W]. . That is, the total transmission power is drastically reduced.
- the power in each resource block is constant, that is, the power density is constant, and the modulation level for radio resources is reduced by reducing the multilevel so that the power density is small. If mapping is performed, an equal bit arrangement is obtained in which the number of transmission bits f (x) by each resource block x is equal. For this reason, the power saving effect is equal between the adaptive modulation of the present invention and the adaptive modulation of equal bit arrangement.
- FIGS. 9A and 9B are diagrams for explaining a second example to which the above-described principle is applied.
- the channel gain Ph (x) is different from the example of FIGS. 8A and 8B, but since the method applied is the same as that described with reference to FIGS. 8A and 8B, the details are omitted.
- the total number of transmission bits is 40 [bit] and the total transmission power is 70 [W] as shown in the upper part.
- the adaptive modulation of the present invention is applied to this, the total number of transmission bits is 40 [bit] and the total transmission power is 27.5 [W] as shown in the middle stage.
- the modulation method is assigned to the radio resource by using a low resource and reducing the multi-value level so that the power in each resource block is constant, that is, the power density is constant and the power density is small.
- the total transmission power was 70 [W] in the general adaptive modulation by reducing the multi-level of the modulation scheme while keeping the total number of transmission bits at 40 [bit], which is the same as in the case of using the general adaptive modulation.
- the adaptive modulation of the present invention drastically decreases to 27.5 [W].
- channel gain Ph (x) is 1 in all columns, it is omitted.
- the total number of bits is 40 [bit] and the total transmission power is 181 [W].
- the total number of bits is 40 [bit] and the total transmission power is 40 [W]. . That is, the total transmission power is drastically reduced.
- the power in each resource block is constant, that is, the power density is constant, and the modulation level for radio resources is reduced by reducing the multilevel so that the power density is small. If mapping is performed, an equal bit arrangement is obtained in which the number of transmission bits f (x) by each resource block x is equal. For this reason, the power saving effect is equal between the adaptive modulation of the present invention and the adaptive modulation of equal bit arrangement.
- FIG. 10 is a schematic diagram showing a configuration of a mobile communication system.
- the mobile communication system has a radio base station 810 and radio terminals 811 to 81n (USER1 to n).
- the radio base station 810 accommodates the radio cells 801 to 803, performs scheduling for each radio terminal 811 to 81n for each cell, determines the communication order, modulation scheme, transmission power, etc., and determines the radio terminals 811 to 81n. Map traffic to radio resources.
- the wireless terminals 811 to 81n are located in the wireless cell 801, and transmit channel quality including channel gain and interference components to the wireless base station 810 as CQI information. Based on the obtained CQI information, the radio base station 810 maps the traffic of the radio terminals 811 to 81n by adaptive modulation to radio resources in the radio cell 801.
- FIG. 11 is a schematic diagram showing a schematic configuration of the radio base station 810.
- the radio base station 810 includes a transmission buffer 101, a scheduler 102, a mapping unit 103, and a transmission power amplifier 104.
- the transmission buffer 101 temporarily stores data to be transmitted to each wireless terminal, and manages the data by a queue for each wireless terminal.
- the scheduler 102 calculates a scheduling metric which is a transmission priority based on the CQI information sent from the wireless terminal, and acts to preferentially send data having a large metric. Specifically, data with a large metric is preferentially read from the transmission buffer 101 and delivered to the mapping unit 103.
- the mapping unit 103 functionally has an internal configuration as shown in FIG. 12, and maps data sent from the scheduler 102 to radio resources by this configuration.
- the mapping unit 103 includes a primary mapping unit 201 and a secondary mapping unit 202.
- the primary mapping unit 201 first performs mapping by a general method. In this mapping, the primary mapping unit 201 determines a modulation scheme to be applied to each data by general adaptive modulation, and determines the arrangement of data to which the modulation scheme is applied to radio resources.
- the secondary mapping unit 202 performs mapping again using the free resource if there is a free radio resource in the mapping by the primary mapping unit 201.
- the secondary mapping unit 202 also uses the free resources, and uses the free transmission resources in the frequency direction, the time direction, or both the frequency and time directions, and the total transmission bits under the constraint condition associated with the total number of transmission bits determined by general adaptive modulation. While limiting the number, adaptive modulation is performed such that the transmission power density is constant and small. Since the control is in the direction of lowering the relatively high transmission power density, the multi-level of the modulation scheme is in the direction of lowering. Then, the mapping unit 103 determines the arrangement of the data to which the modulation scheme subjected to adaptive modulation is applied to the radio resource.
- the secondary mapping unit 202 notifies the transmission power amplifier 104 of the transmission power level obtained as a result of the secondary mapping.
- the transmission power amplifier 104 amplifies the data mapped to the radio resource by the secondary mapping of the mapping unit 103 to the transmission power level notified from the mapping unit 103 and transmits the data.
- FIG. 13 is a schematic diagram for explaining an example of the mapping operation.
- primary mapping section 201 performs general adaptive modulation on the data from scheduler 102 based on CQI information obtained from wireless terminals 811 to 81n, and uses the determined modulation scheme as a radio resource. Deploy. Primary mapping section 201 inputs the resulting total number of transmission bits to comparator 1003.
- the other input of the comparator 1003 is the total number of transmission bits generated as a result of the adaptive mapping performed by the secondary mapping unit 202 using free resources.
- the comparator 1003 compares the two inputs and inputs a comparison result indicating which input has the larger total number of transmission bits to the converter 1004.
- the output of the converter 1004 is input to the CQI converter 1005.
- the converter 1004 and the CQI converter 1005 convert the CQI information from the wireless terminals 811 to 81n.
- the CQI information is converted in a direction to lower the CQI.
- the CQI information is converted in a direction to increase the CQI.
- the converted CQI information is input to the secondary mapping unit 202.
- the feedback loop acts in a direction to lower the CQI for the resource block including the free resource.
- the adaptive modulation of the secondary mapping unit 202 is controlled so that the transmission power density is constant and small in the resource block with the number of transmission bits as a constraint. As a result, the multivalue level is lowered, so that the transmission power level notified to the transmission power amplifier 1006 is lowered, and power saving is realized.
- the following shows a process in which the primary mapping unit 201 applies adaptive modulation based on CQI information to radio resources, and a secondary mapping unit 202 performs adaptive modulation so that the transmission power density is constant and small including free resources. It is an operation example in which processing to be applied to radio resources is sequentially tried under a constraint on the total number of transmission bits.
- FIG. 14 is a flowchart illustrating an operation example of the mapping unit 103 in which the primary mapping unit 201 and the secondary mapping unit 202 sequentially try the processing.
- the primary mapping unit 201 performs primary mapping by applying adaptive modulation based on CQI information obtained from the radio terminals 811 to 81n to radio resources (step 1101).
- the mapping unit 103 lowers the transmission power of the entire signal for each of the wireless terminals 811 to 81n, that is, the transmission power density by ⁇ dB (step 1102).
- Adaptive modulation here is controlled as MCS, which is a set of modulation methods and coding methods, including adaptive coding, including adaptive coding. The higher the MCS, the more the multilevel modulation level and coding rate become. Go up.
- the mapping unit 103 determines whether there are wireless terminals (resource blocks) 811 to 81n that cannot maintain the current MCS as a result of lowering the transmission power density (step 1103). If there is no such wireless terminal, mapping section 103 repeats further lowering the transmission power density and the accompanying CQI level by ⁇ until a wireless terminal (resource block) that cannot maintain MCS appears.
- the mapping unit 103 lowers the MCS of the wireless terminal (resource block) and frees the wireless terminal so that the same number of transmission bits can be secured. Resources are allocated (step 1104).
- the mapping unit 103 determines whether there is a free resource (step 1105). If there are still free resources, the mapping unit 103 returns to step 1102 to further lower the transmission power density and the CQI level associated therewith by ⁇ , and repeats the same processing until there is no free resource block as determined in step 1105.
- the mapping unit 103 When there are no more free resource blocks, the mapping unit 103 notifies the transmission power amplifier 104 of the transmission power level corresponding to the transmission power density that has been lowered so far, and ends the processing (step 1106).
- the transmission power density of the resource block allocated in the primary mapping may be maintained and the mapping change by the secondary mapping may be excluded.
- the processing of the secondary mapping unit 202 that has stopped sending data to a wireless terminal having a large scheduling metric, and to send data to the wireless terminal.
- each of the wireless terminals 811 to 81n demodulates received data based on the power level of a reference signal called a pilot signal from the wireless base station 810.
- a reference signal called a pilot signal from the wireless base station 810.
- the radio base station 810 decreases the transmission power density of signals to the radio terminals 811 to 81n
- the radio terminals 811 to 81n cannot receive signals at a power level that should be based on the power level of the pilot signal.
- the wireless terminals 811 to 81n may not be able to correctly demodulate data. Therefore, the radio base station 810 sends the difference between the transmission power density of the pilot signal and the transmission power density of the data in advance as a control signal as the control signal, and the radio terminals 811 to 81n receive the assumed reception according to the control signal. The level may be adjusted. As a result, the radio terminals 811 to 81n can correctly demodulate the received data from the signal whose radio power is lowered by the radio base station 810 to save power
- the resource block x in the explanation of the principle described above can be replaced with time t.
- the condition for minimizing the power consumption J is:
- the two transmission methods (1) and (2) shown in FIG. 15 are compared.
- data of b [bit] is first transmitted using a high multi-level modulation level, and then the transmission power amplifier 104 is turned off. Assume that 64QAM is used as high-order modulation.
- data of b [bit] is transmitted on average within T time with a low multilevel modulation level. Assume that QPSK is used as low-order modulation.
- the modulation method is 64QAM, 6 bits can be sent at a time. Therefore, the transmission time t can be a time for one transmission. After that time, no power is consumed because the transmission power amplifier is OFF.
- equations (38) and (39) is established. That is, it is understood that power saving can be realized by averaging traffic as much as possible and using a low-order modulation method corresponding to the average.
- the primary mapping unit 201 may estimate the traffic volume of the transmission data, limit the data volume mapped to the radio resource according to the traffic volume, and average it over time. Since the amount of data mapped to the radio resource by the secondary mapping unit 202 is limited to the total number of transmission bits obtained by the primary mapping unit 201, the data transmitted from the mapping unit 103 is temporally averaged. It will be a thing.
- the primary mapping unit 201 may use a radio resource utilization rate to estimate the traffic volume. Alternatively, the primary mapping unit 201 may estimate the traffic amount based on the queue length of the transmission data accumulated in the transmission buffer 101. The primary mapping unit 201 may map the data amount corresponding to the queue length to the radio resource.
- FIG. 17 is a graph of a simulation result showing the effect of power saving.
- the number of wireless terminals is 8, and the number of subcarriers is 256.
- One resource block includes 16 subcarriers in the frequency direction.
- the channel quality is different for each resource block.
- MCS QPSK, 16QAM, and 64QAM are used, including combinations with a plurality of coding schemes (coding rates), and seven stages of MCS from 0 to 6 are used.
- FIG. 18 is a list of MCS used for the simulation.
- CQI is notified using subband CQI for each resource block. Scheduling is performed for each subband, and data to a radio terminal having a high scheduling metric is preferentially mapped to radio resources.
- the exponential approximation model is an approximation from Shannon's capacity formula in information theory, and was used as an ideal model.
- the Doherty amplifier and the class B amplifier were used as models of actual transmission amplifiers.
- the same general adaptive modulation coding by MCS as the adaptive modulation coding to which the present invention is applied is used.
- the transmission power amplifier is turned off so as not to consume power.
- the power consumption of the application example of the present invention is drastically reduced as compared with the power consumption of the comparison target as the traffic volume decreases.
- the application example of the present invention has a power consumption amount of about 1/4 compared to the comparison target.
- the ideal exponential approximation model but also the Doherty amplifier and the class B amplifier, which are actual transmission power amplifier models, show the same tendency.
- a wireless base station connected to a wireless terminal using adaptive modulation First processing means for determining a target value of the total number of bits to be mapped to radio resources of traffic to the radio terminal; First, a modulation scheme for the radio terminal is determined by adaptive modulation so that the total number of bits to be transmitted is limited in association with the target value, while free resources of the radio resource are reduced and transmission power density is constant and small.
- Two processing means A wireless base station.
- the first processing means determines the total number of bits when the modulation scheme for the wireless terminal is determined by primary adaptive modulation as the target value
- the second processing means when mapping is performed by the modulation method determined by the primary adaptive modulation and a free resource is generated in a radio resource, the transmission power density is made constant and small while limiting the total number of bits.
- the radio base station according to attachment 1.
- the first processing means performs the primary adaptive modulation based on channel quality information;
- the second processing means uses the free resources so that the transmission power density is constant and small, and the total number of bits obtained from the secondary adaptive modulation based on the channel quality is the primary bit number. Performing the secondary adaptive modulation so as to approach the total number of bits in the adaptive modulation.
- the radio base station according to appendix 2.
- the second processing means is configured to match the total number of bits obtained from the secondary adaptive modulation with the total number of transmitted bits obtained from the primary adaptive modulation, Sequentially trying to control adaptive modulation for wireless terminals, The radio base station according to attachment 3.
- the second processing means controls adaptive modulation so as to maintain the transmission power density determined by the first processing means for wireless terminals having a priority higher than a predetermined threshold.
- the radio base station according to appendix 3 or 4.
- Appendix 6 Any one of appendices 1 to 5, further comprising control signal communication means for transmitting a downlink control signal indicating a difference between the power density of the transmission pilot signal and the transmission power density obtained by the second processing means.
- the radio base station according to item.
- the first processing means determines a ratio of usable radio resources to the free resources or the whole of the radio resources according to the traffic amount, and performs the target by mapping using the usable radio resources.
- the radio base station according to appendix 7, which determines a value.
- the first processing means determines a ratio of usable radio resources to the free resources or the whole of the radio resources in accordance with the queue length, and performs mapping using the available radio resources to perform the target
- the second processing means controls the adaptive modulation so that the transmission power density falls within a predetermined range from a constant value;
- the radio base station according to any one of appendices 1 to 10.
- the radio resource is a region defined in the frequency direction, or the time direction, or both the frequency and time directions, The radio base station according to any one of appendices 1 to 11.
- An adaptive modulation control method in a radio base station connected to a radio terminal using adaptive modulation Determining a target value of the total number of bits to be mapped to radio resources of traffic to the radio terminal; While limiting the total number of bits to be transmitted in association with the target value, the modulation method for the wireless terminal is determined by adaptive modulation so that the available resources of the wireless resource are reduced and the transmission power density is constant and reduced.
- Adaptive modulation control method Determining a target value of the total number of bits to be mapped to radio resources of traffic to the radio terminal; While limiting the total number of bits to be transmitted in association with the target value.
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Abstract
Description
チャネル品質に応じて方式を選択し、選択した方式に応じて送信電力が変化する点において適応符号化も適応変調符号化も基本的に適応変調と同様に考えることができる。ここでは主に適応変調について説明するが、特に区別する必要が無い場合には適応変調という語に適応符号化および適応変調符号化も含まれるものとする。また、その場合には変調方式という語に、符号化方式、および変調方式と符号化方式の組み合わせも含まれるものとする。
前記無線端末へのトラフィックの、無線リソースにマッピングする総ビット数の目標値を決定する第1の処理手段と、
送信すべき総ビット数を前記目標値に関連付けて制限しつつ、前記無線リソースの空きリソースを少なくし、送信電力密度を一定かつ小さくするように、適応変調により前記無線端末に対する変調方式を定める第2の処理手段と、を有している。
前記無線端末へのトラフィックの、無線リソースにマッピングする総ビット数の目標値を決定し、
送信すべき総ビット数を前記目標値に関連付けて制限しつつ、前記無線リソースの空きリソースを少なくし、送信電力密度を一定かつ小さくするように、適応変調により前記無線端末に対する変調方式を定めるものである。
極値関数となる停留点では、
(1)では、最初に高い多値変調レベルを用いてb[bit]のデータを送信し、その後に送信電力増幅器104をOFFする。高次変調として64QAMを用いるものとする。
(2)では、低い多値変調レベルでT時間内にb[bit]のデータを平均的に送信する。低次変調としてQPSKを用いるものとする。
適応変調を用いて無線端末と接続する無線基地局であって、
前記無線端末へのトラフィックの、無線リソースにマッピングする総ビット数の目標値を決定する第1の処理手段と、
送信すべき総ビット数を前記目標値に関連付けて制限しつつ、前記無線リソースの空きリソースを少なくし、送信電力密度を一定かつ小さくするように、適応変調により前記無線端末に対する変調方式を定める第2の処理手段と、
を有する無線基地局。
前記第1の処理手段は、一次的な適応変調により前記無線端末に対する変調方式を定めた場合の総ビット数を前記目標値と定め、
前記第2の処理手段は、前記一次的な適応変調により定まる前記変調方式によりマッピングを行うと無線リソースに空きリソースができる場合、前記総ビット数を制限しつつ、前記送信電力密度を一定かつ小さくするように、前記空きリソースを含めた二次的な適応変調により前記無線端末に対する変調方式を定める、
付記1に記載の無線基地局。
前記第1の処理手段は、チャネル品質情報に基づいて前記一次的な適応変調を行い、
前記第2の処理手段は、前記空きリソースも使って前記送信電力密度が一定かつ小さくなるようにした、前記チャネル品質に基づく前記二次的な適応変調から得られる総ビット数が、前記一次的な適応変調における総ビット数に近づくように、前記二次的な適応変調を行う、
付記2に記載の無線基地局。
前記第2の処理手段は、前記二次的な適応変調から得られる前記総ビット数を、前記一次的な適応変調で得られた総送信ビット数と一致させつつ、チャネル品質がそれぞれ異なる複数の無線端末に対する適応変調の制御を逐次的に試行する、
付記3に記載の無線基地局。
前記第2の処理手段は、優先度が所定の閾値より高い無線端末については前記第1の処理手段が定めた送信電力密度を維持するように適応変調を制御する、
付記3または4に記載の無線基地局。
送信パイロット信号の電力密度と、前記第2の処理手段によって得られた前記送信電力密度との差を示す下りの制御信号を送信する制御信号通信手段を更に有する、付記1~5のいずれか1項に記載の無線基地局。
前記第1の処理手段は、前記無線端末へのトラフィック量に応じて前記目標値を決定する、付記1~6のいずれか1項に記載の無線基地局。
前記第1の処理手段は、前記トラフィック量に応じて、前記空きリソース、あるいは前記無線リソースの全体に対する使用可能な無線リソースの割合を決定し、使用可能な無線リソースを用いたマッピングにより、前記目標値を決定する、付記7に記載の無線基地局。
前記第1の処理手段は、送信すべきデータが一時的に格納される送信バッファのキュー長に応じて前記目標値を決定する、付記1~6のいずれか1項に記載の無線基地局。
前記第1の処理手段は、前記キュー長に応じて、前記空きリソース、あるいは前記無線リソースの全体に対する使用可能な無線リソースの割合を決定し、使用可能な無線リソースを用いたマッピングにより、前記目標値を決定する、付記9に記載の無線基地局。
前記第2の処理手段は、前記送信電力密度を一定値から所定の範囲内となるように前記適応変調を制御する、
付記1~10のいずれか1項に記載の無線基地局。
前記無線リソースは、周波数方向、または時間方向、または周波数および時間の両方向にて規定される領域である、
付記1~11のいずれか1項に記載の無線基地局。
適応変調を用いて無線端末と接続する無線基地局における適応変調制御方法であって、
前記無線端末へのトラフィックの、無線リソースにマッピングする総ビット数の目標値を決定し、
送信すべき総ビット数を前記目標値に関連付けて制限しつつ、前記無線リソースの空きリソースを少なくし、送信電力密度を一定かつ小さくするように、適応変調により前記無線端末に対する変調方式を定める、
適応変調制御方法。
Claims (10)
- 適応変調を用いて無線端末と接続する無線基地局であって、
前記無線端末へのトラフィックの、無線リソースにマッピングする総ビット数の目標値を決定する第1の処理手段と、
送信すべき総ビット数を前記目標値に関連付けて制限しつつ、前記無線リソースの空きリソースを少なくし、送信電力密度を一定かつ小さくするように、適応変調により前記無線端末に対する変調方式を定める第2の処理手段と、
を有する無線基地局。 - 前記第1の処理手段は、一次的な適応変調により前記無線端末に対する変調方式を定めた場合の総ビット数を前記目標値と定め、
前記第2の処理手段は、前記一次的な適応変調により定まる前記変調方式によりマッピングを行うと無線リソースに空きリソースができる場合、前記総ビット数を制限しつつ、前記送信電力密度を一定かつ小さくするように、前記空きリソースを含めた二次的な適応変調により前記無線端末に対する変調方式を定める、
請求項1に記載の無線基地局。 - 前記第1の処理手段は、チャネル品質情報に基づいて前記一次的な適応変調を行い、
前記第2の処理手段は、前記空きリソースも使って前記送信電力密度が一定かつ小さくなるようにした、前記チャネル品質に基づく前記二次的な適応変調から得られる総ビット数が、前記一次的な適応変調における総ビット数に近づくように、前記二次的な適応変調を行う、
請求項2に記載の無線基地局。 - 前記第2の処理手段は、前記二次的な適応変調から得られる前記総ビット数を、前記一次的な適応変調で得られた総送信ビット数と一致させつつ、チャネル品質がそれぞれ異なる複数の無線端末に対する適応変調の制御を逐次的に試行する、
請求項3に記載の無線基地局。 - 前記第2の処理手段は、優先度が所定の閾値より高い無線端末については前記第1の処理手段が定めた送信電力密度を維持するように適応変調を制御する、請求項3または4に記載の無線基地局。
- 送信パイロット信号の電力密度と、前記第2の処理手段によって得られた前記送信電力密度との差を示す下りの制御信号を送信する制御信号通信手段を更に有する、請求項1~5のいずれか1項に記載の無線基地局。
- 前記第1の処理手段は、前記無線端末へのトラフィック量に応じて前記目標値を決定する、請求項1~6のいずれか1項に記載の無線基地局。
- 前記第1の処理手段は、前記トラフィック量に応じて、前記空きリソース、あるいは前記無線リソースの全体に対する使用可能な無線リソースの割合を決定し、使用可能な無線リソースを用いたマッピングにより、前記目標値を決定する、請求項7に記載の無線基地局。
- 前記第1の処理手段は、送信すべきデータが一時的に格納される送信バッファのキュー長に応じて前記目標値を決定する、請求項1~6のいずれか1項に記載の無線基地局。
- 前記第2の処理手段は、前記送信電力密度を一定値から所定の範囲内となるように前記適応変調を制御する、
付記1~9のいずれか1項に記載の無線基地局。
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JP2019518354A (ja) * | 2016-04-12 | 2019-06-27 | グァンドン オッポ モバイル テレコミュニケーションズ コーポレーション リミテッドGuangdong Oppo Mobile Telecommunications Corp., Ltd. | サービス通信のコーデックモードセットを確定するための方法及び装置 |
US11102266B2 (en) | 2016-04-12 | 2021-08-24 | Guangdong Oppo Mobile Telecommunications Corp., Ltd. | Method and device for determining codec mode set for service communication |
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Also Published As
Publication number | Publication date |
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JP5704160B2 (ja) | 2015-04-22 |
JPWO2011105407A1 (ja) | 2013-06-20 |
CN102783210A (zh) | 2012-11-14 |
EP2541984A1 (en) | 2013-01-02 |
CN102783210B (zh) | 2015-07-22 |
US20120320858A1 (en) | 2012-12-20 |
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