JP2012120180A - Communication control method, base station and wireless communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for improving throughput of an entire communication system by allocating a frequency band number to a terminal in consideration of an upper limit of power consumption.SOLUTION: A base station which performs OFDMA system wireless communication with wireless communication terminals determines a wireless resource to be allocated to each wireless communication terminal based on information indicating an upper limit value grounded on current consumption of the wireless communication terminal.

Description

  The present invention relates to a communication control method, a base station, and a radio communication terminal that allocate a frequency band number considering the power consumption upper limit of the terminal to the terminal and improve the throughput of the entire communication system.

  In recent years, an orthogonal frequency division multiple access (OFDMA) system is a wireless communication system that has been developed and researched for the purpose of improving throughput. In an orthogonal frequency division multiple access (OFDMA) wireless communication system, propagation path estimation information is calculated from a CN value (Carrier to noise Ratio) or received power from a terminal, and a transmission path is used within the entire frequency band of the received multicarrier signal. Specify a frequency region in good condition. The radio terminal identifies a frequency region with a good propagation path state by selecting a subchannel with a good propagation path state, and notifies the base station of this subchannel information. As a result, only a region having a good propagation path state in the used frequency band is notified from the wireless terminal to the base station side, so that communication quality can be improved and throughput of the communication system can be improved. The power consumption of the terminal can be suppressed (see Patent Document 1).

  Further, there is a conventional technique in which a receiving station in a wireless communication system reserves a plurality of frequency bands in preparation for transmission error occurrence. For example, a technique in which a receiving station reserves a necessary wireless transmission band by reporting a transmission error occurrence state based on a measurement result of the transmission error occurrence state to a wireless transmission device of a communication partner (see Patent Document 2) .) Has been proposed.

JP-A-2005-244598 JP 2002-051050 A

  In the technique of Patent Document 1, the base station calculates propagation path estimation information based on a CN value (Carrier to noise Ratio) or received power given from a terminal, and thus in the entire used frequency band of the received multicarrier signal. Since the configuration is such that a good frequency region is specified and the specified good frequency band is notified to the terminal, there is a problem that band requests from the terminal are concentrated in the good frequency region. In the technique of Patent Document 2, when a terminal reserves a plurality of bands and occupies the radio resource, other terminals cannot use the resource, and the communication system as a whole There is a problem that the throughput cannot be improved.

  In addition, the base station estimates the propagation path state from the CN value given from the terminal and identifies a good frequency region, but the terminal transmits transmission power that cannot be realized in that band. In this case, the terminal cannot achieve the expected performance. That is, only a part of the frequency band reserved for one terminal is used due to the limit of transmission power, and the occupied unused band is used as another terminal even though there is an unused band. However, the bandwidth of other terminals is limited. Therefore, there is a problem that the performance of the entire system is degraded.

  An object of the present invention is to provide a technique (method, apparatus) that improves the throughput of the entire communication system by allocating the number of frequency bands in consideration of the upper limit of current consumption and the upper limit of power consumption of the terminal to the terminal.

  In order to solve the above-described problems, the communication control method according to the first aspect of the present invention provides a base station that performs OFDMA wireless communication with a wireless communication terminal, and sets an upper limit of a value based on current consumption of the wireless communication terminal. A radio resource to be allocated to the radio communication terminal is determined based on the indicated information.

  A base station according to the second aspect of the present invention is a base station that performs OFDMA wireless communication with a wireless communication terminal, and is based on information indicating an upper limit of a value based on current consumption of the wireless communication terminal, A control unit that determines radio resources to be allocated to the radio communication terminal is provided.

  In addition, the communication control method according to the third aspect of the present invention provides an upper limit of a value based on a current consumption of a radio communication terminal for a base station to which the radio communication terminal allocates an OFDMA radio resource to the radio communication terminal. Is transmitted to the base station.

  A wireless communication terminal according to a fourth aspect of the present invention is a wireless communication terminal, and is a value based on a current consumption of the wireless communication terminal for a base station that allocates an OFDMA wireless resource to the wireless communication terminal. A transmission unit that transmits information indicating the upper limit to the base station.

  As described above, the solution of the present invention has been described as a communication control method, a base station, and a wireless communication terminal, but the present invention records devices (systems, etc.), methods, programs, and programs substantially corresponding to these. It can be realized as a storage medium, and it should be understood that these are also included in the scope of the present invention.

  According to the present invention, it is possible to improve the throughput of the entire communication system by performing band (number of frequency bands) allocation in consideration of the current consumption of the terminal and the power consumption upper limit.

1 is a block diagram of a wireless communication terminal using an OFDMA communication scheme according to an embodiment of the present invention. 1 is a block diagram of a base station (apparatus) using an OFDMA communication system according to an embodiment of the present invention. FIG. It is explanatory drawing of the BandAMC system which is the band allocation system of OFDMA used by this invention. It is explanatory drawing of the PUSC system which is a band allocation system of OFDMA. It is a flowchart of the process performed with the radio | wireless communication terminal by one embodiment of this invention. It is a flowchart of the process performed in the base station by one embodiment of this invention. It is a flowchart of the process which determines the number of operable bands. 6 is a flowchart of a process for determining an operable band position according to an embodiment of the present invention. It is the table which linked | related terminal type and maximum current consumption. It is a figure which shows the message format transmitted to a base station. It is a figure explaining the band allocation by the technique of this invention. It is a figure which shows the application band and band position which the data which a terminal (SS) transmits to a base station (BS), and a base station (BS) set by the process of this invention. It is a figure which shows the determined applicable band and band position.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a block diagram of a wireless communication terminal using an OFDMA communication system according to an embodiment of the present invention.

  As shown in the figure, the radio communication terminal 100 includes an antenna ANT, an RF unit 110, an A / D conversion unit 120, a modem unit 130, a power supply unit 140, a control unit 150, a storage unit 160, an operation unit (interface unit) 170, A reception state measurement unit 180 is provided.

  The control unit 150 includes a band number determination unit 151. The RF unit 110 processes a radio signal received from the antenna ANT at the time of reception, and processes a signal digital / analog converted by the A / D conversion unit 120 at the time of transmission and transmits the signal from the ANT. That is, the RF unit 110, the A / D conversion unit 120, and the modem unit 130 perform transmission / reception, encoding, and decoding of radio waves with the base station. Since the OFDMA system is multi-carrier communication, the modem unit 130 performs processing such as FFT (First Fourier Transform) and IFFT (Inverse FFT).

  The control unit 150 performs control so that information is manipulated and displayed based on the received data and the like, and the information is stored in the storage unit 160. Some terminals have a function to interface with other devices such as notebook PCs, and can also send and receive information. Further, the control unit 150 has a function of controlling the maximum current consumption of the own terminal to be stored in the storage unit 160 and a function of calculating the remaining battery level of the own terminal from the power supply unit 140. The reception state measurement unit 180 measures and calculates the CN value from the received signal in the RF unit 110, the A / conversion unit 120, and the modem unit 130, and stores the CN value in the storage unit 160. The band number determination unit 151 determines the number of frequency bands (number of bands = number of subcarriers) to be requested from the base station that is the communication partner based on the measured and calculated CN value.

  FIG. 2 is a block diagram of a base station (apparatus) that uses the OFDMA communication scheme according to an embodiment of the present invention. As illustrated, the base station 200 includes a power supply unit 210, a control unit 220, a storage unit 230, a network unit 240, a modem unit 250, an A / D conversion unit 260, an RF unit 270, and an adaptive array antenna AAA.

  The control unit 220 includes a band number determination unit 221, a band number setting unit 222, a band position setting unit 223, and an information acquisition unit (terminal information acquisition unit) 224. The adaptive array antenna AAA is composed of six antennas ANT1-6. In order to process signals for the six antennas, the RF unit 270 includes the RF circuit RF1-6, and the A / D conversion unit 260 includes the A / D converter A / D1-6. . As described above, the base station 200 includes a plurality of antennas in order to realize beam forming using the adaptive array antenna technology and MIMO (Multi Input Multi Output) technology. The received data is controlled by the control unit 220. Since the base station 200 is connected to other base stations and servers (not shown) via a network, the base station 200 holds a network unit 240.

  The information acquisition unit 224 acquires information indicating the upper limit of the value based on the current consumption of the communication partner wireless communication terminal. The information indicating the upper limit of the value based on the current consumption includes the maximum current consumption (capacity) in the wireless communication terminal and the maximum power consumption (value) based on the power supply of the wireless communication terminal. Further, the information acquisition unit 224 acquires the number of frequency bands requested from the wireless communication terminal. For example, the information acquisition unit 224 receives a consumption current ID from the wireless communication terminal as information indicating the upper limit of the value based on the consumption current, and associates the maximum consumption current with the consumption current ID stored in the storage unit 230 ( Referring to FIG. 9), the upper limit of the value based on the current consumption of the wireless communication terminal can be acquired. In addition to acquiring the current consumption ID from the wireless communication terminal, the information acquisition unit 224 can change the type of the wireless communication terminal from another base station or a higher-level device (base station control device), for example, at the time of handover. It is also possible to acquire information to be specified and acquire the maximum current consumption and the power consumption upper limit with reference to the table of FIG. 9 associated with the terminal type based on such information.

  The band number determination unit 221 determines (calculates) the number of frequency bands to be allocated to the wireless communication terminal based on information indicating the upper limit of the value based on the current consumption acquired by the information acquisition unit 224. When the number of frequency bands requested from the wireless communication terminal is equal to or less than the number of frequency bands determined by the band number determination unit 221, the band number setting unit 222 sets the number of the first frequency bands to the wireless communication terminal. Set to the number of frequency bands to be assigned to. Based on the information indicating the reception state of the wireless communication terminal acquired from the wireless communication terminal and the “number of frequency bands to be allocated” determined by the band number setting unit 222, the band position setting unit 223 Set each position.

  FIG. 3 is an explanatory diagram of the BandAMC scheme, which is an OFDMA band allocation scheme used in the present invention. The BandAMC (band Adaptive Modulation and Coding) scheme is a method in which subcarriers arranged on the frequency axis of physical subcarriers are arranged at the same position on the frequency axis of logical subcarriers. For example, in the BandAMC system, physical subcarriers C1, C2, C3, C4, and C5 that are continuously arranged are arranged in the order of C1, C2, C3, C4, and C5 in the logical subcarrier arrangement. The In addition to the BandAMC method, there is an allocation method called a PUSC (Partial Usage of Sub-channels) method.

  FIG. 4 is an explanatory diagram of a PUSC scheme that is an OFDMA band allocation scheme. As shown in the figure, the subcarriers arranged on the frequency axis of the physical subcarrier are changed to a completely random arrangement on the frequency axis of the logical subcarrier. For example, in the PUSC system, physical subcarriers C1, C2, C3, C4, and C5 that are continuously arranged are not normally continuous in the logical subcarrier arrangement, such as C2, C1, C5, and C4. Arranged in random order. In the BandAMC scheme, since the physical subcarrier and the logical subcarrier are at the same position, it is used when beamforming is performed, and a large beamforming effect can be obtained when the terminal speed is not high. In the PUSC system, physical subcarriers and logical subcarriers are arranged completely different from each other, and it is known that they are not easily affected by Fading when moving.

  FIG. 5 is a flowchart of processing executed by the wireless communication terminal according to an embodiment of the present invention. As shown in the figure, in step S1, the terminal receives a DL-MAP (Downlink-MAP). The terminal that has received the DL-MAP notifies the source base station of its own CINR and transmission power. Therefore, CINR of each band (subcarrier) at the used frequency is measured (step S2). Based on the CINR, which is information indicating such a reception state and serves as an index of propagation path information, the number of requested bands is determined using arithmetic means (a processor such as a CPU or MPU) (step S3).

  The terminal can know in advance what kind of terminal it is, such as a mobile phone type or a PCMCIA card type. In the case of a mobile phone, the power source used is a lithium ion battery, and the current consumption is constant to some extent in any mobile phone. With reference to the consumption current table shown as an example in FIG. 9, the own terminal can read the consumption current ID = 1 of the corresponding mobile phone. The table in FIG. 9 is also held on the base station side, and is used to determine the number of bands based on the current consumption ID transmitted from the terminal.

  In step S4, the terminal that has read the current consumption ID of its own terminal in the table of FIG. 9 measures the transmission power of the terminal in step S5. Thereafter, in step S6, the terminal transmits CINR, transmission power, number of requested bands, and current consumption ID to the base station.

  FIG. 10 is a diagram illustrating a message format to be transmitted to the base station. FIG. 10 (a) shows a conventional message format, and FIG. 10 (b) shows a message format that has been partially changed to correspond to the present invention. As shown in FIG. 10 (a), it is composed of a MAC header (bandwidth request header) for storing MAC information, a payload for storing data, and a CRC for error checking.

  The conventional MAC header includes a bandwidth increase request (BWIR) at the field position ff1, but in the present invention, a current threshold (CTH) is used instead of the bandwidth increase request (BWIR) as shown in FIG. That is, the current consumption ID is transmitted. The above is the operation of the terminal.

  FIG. 6 is a flowchart of processing executed in a base station according to an embodiment of the present invention. As shown in the figure, in step S11, the CINR, the number of requested bands, and the current consumption ID notified from the terminal are received. Next, in step S12, the number of operable bands is calculated from the received content, and details thereof will be described later with reference to FIG. Thereafter, in step S13, the operable band position is calculated from the terminal CINR and the number of operable bands. Details of this will be described later with reference to FIG. Next, in step S14, the used band (number of bands, band position) of the terminal is determined based on the number of operable bands and the band position. Finally, in step S15, the content of the band used (number of bands, band position, etc.) is notified to the terminal, and the process is terminated.

<Band number determination processing>
FIG. 7 is a flowchart of processing for determining the number of operable bands. As shown in the figure, since the maximum number of bands (subcarriers) in the BandAMC scheme is 24 in step S21, it is set. In step S22, the band number determination loop LP1 is started. In step S23, the number of Tmp_Bands matching the current consumption ID is read from a table (FIG. 9) held in advance by the base station. After that, in step S24, it is determined whether or not the Tmp_Band number is equal to or less than the requested band number transmitted from the terminal. If it is equal to or less, the process proceeds to step S25, and the requested band number is set to the Tmp operable band number. To do. If the Tmp_Band number is not less than or equal to the requested band number transmitted from the terminal, that is, if the Tmp_Band number is larger than the requested band number, the process proceeds to step S27, and the Tmp_Band number is set to the Tmp operable band number. By so doing, it is possible to limit the number of requested bands so as not to exceed the maximum number of bands that can be realized by the terminal.

  Step S26 repeats the loop LP1 until the loop end condition indicating that the process has been performed on all the terminals is satisfied, and if the end condition is satisfied (that is, if all the terminals have been processed), the loop process is performed. Exit through to the following steps.

  It is necessary to limit the number of bands used by each terminal so as not to exceed “24” which is the maximum band number of the BandAMC method. Therefore, in step 28, it is determined whether or not the total value “Sum (number of Tmp operable bands)” of each terminal is equal to or greater than Total Band Num. If “Sum (number of Tmp operable bands)” is equal to or greater than Total Band Num, the number of operable bands is determined in preference to the largest number of Tmp operable bands.

  Next, in step S30, adjustment is performed so as to satisfy the number of guaranteed bands in the table of FIG. 9 so that all terminals can transmit to the base station. For example, it may be possible to extract from the one having the maximum operable band number, or to give priority to the one having the maximum operable band number and assign the band number from the second or third one. . If the number of Tmp operable bands of each terminal is less than the Total Band Num, the maximum number of bands of the BandAMC method will not be exceeded, and the operable band number determination process is terminated.

<Band position determination process>
FIG. 8 is a flowchart of a process for determining an operable band position according to an embodiment of the present invention. As shown in the figure, in step S31, the band position determination loop LP2 of each terminal is started. In step S32, each terminal determines a predetermined rank, here, up to the fifth highest CINR and its band. Thereafter, in step S33, the band is determined from the number of operable bands with the maximum band position that is the maximum CINR as the center.

  Here, if the number of operable bands is an even number, the center position is temporarily set to the higher frequency. There may occur a case where the determined bandwidths collide with each other. Therefore, in step S34, it is determined whether or not the determined bandwidth overlaps (collises) between terminals. When it is determined that the bands (bands) determined between the terminals overlap, in step S35, in order to give priority to the one with a good propagation path condition, the band allocation process is performed with priority on the one having the largest maximum CINR. Further, in order to comply with the restriction that the total bandwidth of each terminal should not exceed the maximum number of 24 bands, it is determined whether or not the obtained bandwidth (band) exceeds 24 bands in step S36. To do. If it exceeds, the process proceeds to step S37, and the center position of the obtained band group is shifted and adjusted so as not to exceed 24 bands. Step S38 repeats the loop LP2 until the loop end condition that the process has been performed for all the terminals is satisfied, and if the end condition is satisfied (that is, the process of all terminals is completed), the loop process Exit the process.

  Specific examples when frequency allocation is performed by the wireless communication method according to the present invention are shown in FIGS. FIG. 12 is a diagram showing data transmitted from the terminal (SS) to the base station (BS), an applicable band and a band position set by the base station (BS) according to the processing of the present invention. FIG. 13 is a diagram showing the determined applied band and band position. In FIG. 12, assuming that there are three users as an example, the base station side is notified of the current consumption, propagation path status (CINR), and required bandwidth of the terminals used by the users, The station determines the number of bands and their location for each terminal.

  Although CINR is written here, it is assumed that there are actually CINRs for 24 bands and that the maximum CINR is extracted this time. User A has a very good CINR, so the bandwidth request also requires a high bandwidth of 12 bands, but since it is a USB terminal, the current consumption is as low as 300 mA and transmission power cannot be transmitted for the number of bands. .

  Therefore, the applicable band is 3 bands by the allocation technique of the present invention. Similarly, in the case of user B, CINR is as good as 15 dB, and since the terminal is also a modem type and power is stably supplied from an AC power source, a sufficient band can be secured.

  For user B, the bandwidth request is also 10 bands, which is smaller than the bandwidth of the modem type terminal in the table of FIG. 9, so the request is used as it is. In the case of user C, CINR is not so high, and the required bandwidth is set slightly low. Since it is a mobile phone terminal type, the current consumption is 700 mA, which is sufficient for transmitting 8 bands, so it can be used as it is in the applicable band.

  The band positions are arranged as shown in FIG. The best position of CINR is prioritized and the optimal position is set so as not to go out of band.

  Here, there is a band where nothing is transmitted between the user B and the user A. In order to increase the overall throughput, at the end of the flowchart in the figure, if the total applicable bandwidth is lower than 24 bands, as a remedy, increase the number of bands for user B so that the number of operable bands is not exceeded. May be performed. In this case, 2 bands can be increased.

  Although an extremely simple example is given as an example, even when a user uses the same terminal and requests the same required bandwidth, it is possible to make a determination by CINR, so that priority can be given. Even if there are many terminals having a large required bandwidth, the number of operable bands is set so as not to exceed “24” which is the Total Band Num, and SDMA (Spatial Division Multiple Access) is implemented. If the spatial multiplexing number is 2, 48 bands can be used, and if the spatial multiplexing number is 3, the number of usable bands is 72 bands. Therefore, since the number of bands increases in SDMA, versatility increases.

  The above is an embodiment of the present invention. When one user can use 24 bands in the present invention, the terminal is not moving or less than 10 km due to GPS (Global Positioning System) information or the like. If the terminal is moving at low speed, the BandAMC method is used, and if the terminal is moving at a medium to high speed of 10 km or more, the PUSC method that is strong in speed dependency is used. By doing so, the system throughput can be further improved.

  The effects and advantages of the present invention will be described again. According to the present invention, when the base station obtains power information that can be transmitted on the terminal side, a region with a good propagation path state based on propagation path estimation, a band of power that the terminal can transmit at the maximum transmission power, The base station compares the transmission power request by the power control between the station and the terminal and issues a request that can achieve the maximum performance to the terminal, thereby reducing the current consumption and power consumption of the terminal and reducing the throughput on the system. It can be improved to the maximum. In addition, when the entire band can be used, a PUSC (Partially Used Subchannelization) method that randomly extracts partially necessary subcarriers from the determined band is realized, thereby achieving a medium speed from the frequency diversity effect. It is possible to eliminate performance degradation due to speed dependence during high-speed movement.

  FIG. 11 is a diagram illustrating band allocation according to the technique of the present invention. FIG. 11 (a) shows band allocation by a normal BandAMC method for comparison. In the normal BandAMC method, the bands B1, B3, B5, B6, and B8 used by each terminal are arranged in a different manner in the band used, and therefore transmission must be performed with all frequency bands B1 to B8. That is, since the apparent band becomes large, the current consumption increases accordingly. In this way, when the bandwidth is expanded with the same transmission power, the current consumption of the terminal increases, and there is a possibility that the operation time of the terminal and the operation time of the PC etc. on which the terminal is installed may be reduced. There may be a case where the terminal or the attached PC is reset. In that case, it is possible to cope with the problem by lowering the transmission power, but communication quality may be deteriorated due to a decrease in the transmission power.

  Therefore, if the technique of the present invention is used, as shown in FIG. 11 (b), when the terminal uses 5 bands, instead of transmitting in a band of disjoint positions, as shown in bands B3 to B7, By arranging the bands continuously without a gap, the apparent band can be made narrower (smaller), and thus the current consumption of the terminal can be kept low.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each unit, each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of means, steps, etc. can be combined or divided into one. It is.

  DESCRIPTION OF SYMBOLS 100: Wireless communication terminal, 110: RF part, 120: A / D conversion part, 130: Modem part, 140: Power supply part, 150: Control part, 151: Band number determination part, 160: Storage part, 170: Operation part 180: reception state measurement unit, ANT: antenna, 200: base station, 210: power supply unit, 220: control unit, 221: band number determination unit, 222: band number setting unit, 223: band position setting unit, 224: Information acquisition unit, 230: storage unit, 240: network unit, 250: modem unit, 260: A / D conversion unit, 270: RF unit, RF1-6: RF circuit, A / D1-6: A / D converter AAA: adaptive array antenna, ANT1-6: antenna, ff1: field position.

Claims (4)

  A base station that performs OFDMA wireless communication with a wireless communication terminal determines a wireless resource to be allocated to the wireless communication terminal based on information indicating an upper limit of a value based on current consumption of the wireless communication terminal; A communication control method characterized by the above. A base station that performs OFDMA wireless communication with a wireless communication terminal;
A base station comprising: a control unit that determines a radio resource to be allocated to the radio communication terminal based on information indicating an upper limit of a value based on current consumption of the radio communication terminal.   A wireless communication terminal transmits, to the base station, information indicating an upper limit of a value based on current consumption of the wireless communication terminal for a base station that allocates an OFDMA wireless resource to the wireless communication terminal; A communication control method characterized by the above. A wireless communication terminal,
For a base station that allocates OFDMA radio resources to the radio communication terminal,
A wireless communication terminal comprising: a transmission unit that transmits information indicating an upper limit of a value based on current consumption of the wireless communication terminal to the base station.

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