JP2008288690A - Radio communication device and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a terminal and a radio communication method, for improving frequency utilization efficiency by properly determining whether to permit a change in the number of carriers of the terminal and improving data overall throughput of a base station. <P>SOLUTION: This terminal 100 is provided with: a transmission power change amount acquiring section 150b for acquiring a transmission power change amount in using the changed number of carriers when an allocation change determination section 150a determines a change in the number of carriers; a signal quality estimating section 150c for estimating the quality of an uplink signal when the changed number of carriers is used, on the basis of the transmission power change amount; a total throughput increase determination section 150e for determining whether or not an estimated total throughput calculated by the estimated total throughput calculating section 150d increases for a total throughput of present uplink communication on the basis of the estimated signal quality; and an allocation control section 150f for controlling so as to perform uplink communication using allocated frequencies the newly when determined that the total throughput increases. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless communication device capable of performing wireless communication with a base station using a plurality of frequencies simultaneously, and a wireless communication device wirelessly communicating with a base station using a plurality of frequencies simultaneously. The present invention relates to a wireless communication method capable of performing communication.

2. Description of the Related Art In recent years, a multi-carrier wireless communication system in which one terminal performs data communication using a plurality of frequencies (carrier frequencies) in accordance with an increasing trend in the amount of information processed by wireless communication apparatuses (hereinafter also referred to as terminals). Has been developed. In such a wireless communication system, as long as there are vacant channels and slots available to the terminal, the terminal can communicate with the base station using a plurality of carrier frequencies.
And in the said radio | wireless communications system, the communication using an adaptive modulation system technique (link adaptation) is also considered. The above-mentioned adaptive modulation scheme technology is a technology for selecting an optimal encoding modulation scheme according to the quality (communication quality) of radio waves transmitted and received by the base station and the terminal. When good, a high-speed modulation scheme can be applied to maintain a high data rate, and when communication quality is poor, a low-speed modulation scheme can be applied to avoid disconnection of the communication line.
As a conventional example of a wireless communication system using an adaptive modulation scheme technique, there is one disclosed in Patent Document 1, for example.

  As a conventional frequency channel allocation method in the wireless communication system, there is an allocation method in which a base station allocates resources of empty channels and empty slots in accordance with the MAC protocol (Fairness Mac). However, since this allocation method does not consider multi-carrier support, the terminal performs transmission / reception with the base station within the maximum transmission power in one time slot, and the maximum modulation class that can be used at that time Will be adopted.

JP 2000-324081 A

  As described above, since the multi-carrier frequency allocation method has not been considered at all, the terminal cannot handle a plurality of carrier frequencies in one time slot, handles only one carrier frequency, and limits the maximum transmission power limit. Only the maximum data rate per carrier within the range is considered. Therefore, even if a plurality of carrier frequencies are used simultaneously, even if the total throughput increases, wireless communication cannot be performed with the base station using the plurality of carrier frequencies simultaneously.

The present invention provides wireless communication capable of improving the data throughput of the entire base station by improving the use efficiency of frequency resources by accurately determining whether or not to change the number of assigned frequencies to the wireless communication apparatus. It is a first object to provide an apparatus.
The present invention provides wireless communication capable of improving the data throughput of the entire base station by improving the use efficiency of frequency resources by accurately determining whether or not to change the number of assigned frequencies to the wireless communication apparatus. A second object is to provide a method.

  In order to achieve the first object, a wireless communication device according to claim 1 is a wireless communication device capable of performing wireless communication with a base station using a plurality of frequencies simultaneously, An allocation number change determination means for determining whether or not to change the allocation number, and a transmission power change for determining a transmission power change amount when the frequency of the allocation number after the change is used when it is determined to change the frequency allocation number Based on the obtained amount of change in transmission power, signal quality estimation means for estimating the signal quality of uplink communication when the frequency of the allocated number after the change is used, and estimation based on the estimated signal quality Estimated total throughput calculating means for calculating the total throughput, and determining whether the calculated estimated total throughput increases with respect to the total throughput based on the signal quality of the current uplink communication. And total throughput increase determination means, when it is determined that the total throughput increases, characterized in that it comprises a control means for controlling to perform uplink communication using the allocated number of frequency after the change.

  When the wireless communication is adaptive modulation wireless communication, the total throughput increase determining means compares the total throughput in the modulation class set for each frequency before and after the change of the frequency allocation number. Therefore, it is preferable to determine whether or not the total throughput is increased in order to accurately determine whether or not to change the frequency allocation number for the wireless communication apparatus.

  It is preferable to use the amount of change in signal quality on the base station side as the amount of change in transmission power in order to accurately determine whether or not to change the frequency allocation number for the wireless communication apparatus.

  In order to achieve the second object, a wireless communication method according to claim 4 is a wireless communication method in which a wireless communication device can perform wireless communication with a base station using a plurality of frequencies simultaneously. Thus, when changing the number of assigned frequencies, the signal quality of uplink communication when using the changed number of assigned frequencies based on the amount of change in transmission power when using the changed number of assigned frequencies. A signal quality estimation step to be estimated, an estimated total throughput calculation step to calculate an estimated total throughput based on the estimated signal quality, and it is determined that the calculated estimated total throughput increases with respect to the total throughput based on the signal quality of the current uplink communication In this case, a control step of performing control so as to perform uplink communication using the frequency of the allocated number after the change is performed.

  According to the present invention, the frequency allocation number is changed only when it is determined that the estimated total throughput increases with respect to the total throughput based on the signal quality of the current uplink communication. Therefore, the frequency allocation to the radio communication apparatus (terminal) is performed. It becomes possible to accurately determine whether or not to change the number. Therefore, since the utilization efficiency of frequency resources is improved, it is possible to provide a wireless communication apparatus and a wireless communication method that can improve the data throughput of the entire base station.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a wireless communication apparatus of a wireless communication system to which a wireless communication method according to a first embodiment of the present invention is applied. A wireless communication device (wireless communication terminal; also referred to as a terminal) 100 illustrated in FIG. 1 is a wireless communication device capable of performing wireless communication with a base station using a plurality of frequencies (carrier frequencies) simultaneously. The antenna 110, the RF unit 130, the RF control unit 140, the system control unit 150, the input unit 160, the display unit 170, the system storage unit 180, and the like are included. 140a and transmission unit 140b, the system control unit 150 includes an allocation number change determination unit 150a, a transmission power change amount acquisition unit 150b, a signal quality estimation unit 150c, an estimated total throughput calculation unit 150d, A throughput increase determination unit 150e and an allocation number control unit 150f are included.

The RF unit 130 converts data to be transmitted in a wireless communication system into a high frequency signal and transmits it from the antenna 110, or converts data input from the antenna 110 into a high frequency signal.
The RF control unit 140 controls communication (transmission / reception) of a wireless communication system and measures the strength of an electric field (RSSI or the like) from a base station (not shown) received by an antenna. Corresponding to the high-frequency signal input from the unit 130 and the high-frequency signal output to the RF unit 130, it functions as the receiving unit 140a and the transmitting unit 140b.

The system control unit 150 is a control unit that performs overall control of each unit of the wireless communication apparatus 100.
The allocation number change determination unit 150a determines whether or not to change the allocation number of the carrier frequency. Usually, a request for increasing the allocation number of the carrier frequency (for example, increasing from 1 to 2) is requested by the base station. Judgment is made based on whether or not it is transmitted from the station.
When the transmission power change amount acquisition unit 150b determines to change the allocation number of carrier frequencies, the transmission power change amount acquisition unit 150b obtains a transmission power change amount (transmission power attenuation amount in this embodiment) when the frequency of the allocation number after the change is used. Is.
The signal quality estimation unit 150c, based on the obtained transmission power change amount, uses signal frequency (SINR; Signal-to-Interference.) Of uplink (up-link) communication when the frequency of the changed number of carrier allocations is used. and Noise power Ratio: Estimate the signal-to-noise ratio.
The estimated total throughput calculation unit 150d calculates an estimated total throughput when the frequency of the changed number of carrier allocations is used based on the estimated signal quality.
The total throughput increase determination unit 150e determines whether or not the calculated estimated total throughput increases with respect to the total throughput based on the current uplink communication signal quality.
When it is determined that the total throughput increases, the allocation number control unit 150f performs control so that uplink communication is performed using the frequency of the allocation number after the change.

The input unit 160 is used when inputting information or selecting one of the options displayed on the display screen of the display unit 170, and has various keys and various buttons. Note that the input unit 160 and the display unit 170 may be omitted as necessary.
The system storage unit 180 includes a memory such as a RAM, and stores application programs and temporary data.

  As a wireless communication system to which the wireless communication method of the present embodiment is applied, a wireless broadband system is preferable. In particular, a wireless communication system called “iBurst (registered trademark) system” proposed by the applicants of the present application is proposed. It is preferably applied to a broadband system. The “iBurst (registered trademark) system” is a TDMA / TDD system adopting multi-carrier, and the number of uplink (uplink) and downlink (downlink) time slots is 6 times in total of 3 time slots. It is composed of slots, and has an asymmetrical configuration with different upstream and downstream time slot lengths, with a particular emphasis on downstream data transfer rates. The symbol rate of the iBurst (registered trademark) system is 500 k symbols / sec. In the case of one carrier, the maximum data transfer rate at which one user uses all three time slots is 1061 kbps for downlink and 346 kbps for uplink. Become. The frequency band used in the iBurst (registered trademark) system is 5 MHz, the band per carrier is 625 kHz, and one frame of the iBurst (registered trademark) system is 5 msec. When applied to an iBurst (registered trademark) system, the wireless communication apparatus 100 is an iBurst (registered trademark) compatible wireless communication terminal, and the base station is an iBurst (registered trademark) compatible base station.

  Next, in a wireless communication system to which the wireless communication method of the present embodiment is applied, the relationship between the number of carrier frequencies allocated to terminals (hereinafter also referred to as the number of carriers) and the amount of transmission power change (hereinafter also referred to as power attenuation), The relationship among the modulation class, target signal quality (terget SINR) and throughput when the terminal performs communication will be described with reference to FIGS.

  As shown in FIG. 2, the power attenuation when the number of carriers is increased from 1 to 2 is −3 (dB), and the power attenuation when the number of carriers is increased from 2 to 3 is −1.77. (DB), and the power attenuation when the number of carriers is increased from 3 to 4 is -1.23 (dB). When the number of carriers is reduced, the reverse is true.

  As shown in FIG. 3, the target signal quality (terget SINR) in modulation class 0 is −0.8 (dB), the uplink communication throughput (up-link throughput) is 19.2 (kbps), The target signal quality (terget SINR) in the modulation class 1 is 0.8 (dB), the uplink communication throughput (up-link throughput) is 38.4 (kbps), and the target signal quality in the modulation class 2 ( terget SINR) is 2.5 (dB), the uplink communication throughput (up-link throughput) is 76.8 (kbps), and the target signal quality (terget SINR) in modulation class 3 is 5.4 ( dB), the uplink communication throughput (up-link throughput) is 129.6 (kbps), the target signal quality (terget SINR) in modulation class 4 is 7.5 (dB), and the uplink communication Throughput is Up-link throughput) is 216.0 (kbps), target signal quality (terget SINR) in modulation class 5 is 9.8 (dB), and uplink communication throughput (up-link throughput) is 292. 2 (kbps), target signal quality (terget SINR) in modulation class 6 is 11.9 (dB), uplink communication throughput (up-link throughput) is 345.6 (kbps), and modulation The target signal quality (terget SINR) in class 7 is 13.2 (dB), and the uplink communication throughput (up-link throughput) is 427.2 (kbps).

2 and 3, it is possible to numerically determine the target signal quality (terget SINR) on the base station side determined for each modulation class and the amount of power attenuation due to the change (increase) in the number of assigned carrier frequencies. become.
Here, simply assuming that “power attenuation amount = SINR attenuation amount on the base station side”, for example, the number of allocations of carrier frequencies to terminals in communication of modulation class 2 at one carrier frequency 2 is increased from 1 to 2, the uplink received SINR per carrier frequency is attenuated by 3 (dB) from FIG. 2, so that the target signal quality (terget SINR) of modulation class 0 shown in FIG. 3 can be satisfied. Disappear. In such a case, by not changing the number of carrier frequency allocations, useless radio resources are eliminated and the data throughput of the entire base station is increased. “Determining whether or not the carrier frequency allocation number can be changed” means that the amount of decrease in received SINR due to transmission power attenuation after the change in the carrier frequency allocation number is the target signal quality (terget SINR) defined for each modulation class. ) Is the basic criterion.

Next, communication control including a change in the number of assigned carrier frequencies for terminals in the wireless communication system of this embodiment will be described. In the following, the case where the change in the number of allocations of carrier frequencies is an increase in the number of allocations of carrier frequencies is described. It can be controlled.
The transmission power in a multi-carrier terminal does not exceed the maximum transmission power limit value regardless of the number of assigned carrier frequencies during transmission at the same time (same time slot). It is necessary to do so. Therefore, in the present embodiment, the number of carrier frequencies allocated in a multicarrier terminal is optimized by executing a control program shown in FIG. 4 described below.

  FIG. 4 is a flowchart showing a control program for communication control including a change in the number of assigned carrier frequencies for the wireless communication apparatus (terminal) in the wireless communication system of the first embodiment. First, in step S11, it is determined whether or not the allocation number of carrier frequencies is to be changed. If it is determined to be changed (YES), the process proceeds to step S12, and if it is determined not to be changed (NO). It ends as it is. The determination in step S11 is, for example, whether or not a request for changing the number of allocations of carrier frequencies to the terminal has been sent from the base station that has predicted data retention, or the terminal itself has issued a request for changing the number of allocations of carrier frequencies Depending on whether or not. In step S12, an uplink received SINR (received SINR at the base station) corresponding to the signal quality of the uplink communication is estimated (acquired) from the transmission power and the modulation class. In the next step S13, a power attenuation amount that is a transmission power change amount when using the changed number of carrier frequencies is acquired. For example, when the number of assigned carrier frequencies before the change is 1 and the number of assigned carrier frequencies is 2, the power attenuation is obtained by referring to FIG. For example, the terminal may acquire the power attenuation amount by sending it from the base station.

  In the next step S14, the presence / absence of a modulation class is determined when the changed number of assigned carrier frequencies are used. If there is a modulation class (YES), the process proceeds to step S15, and if there is no modulation class (NO). It ends as it is. The determination of the presence / absence of the modulation class reduces the modulation class because the modulation class before the change cannot be maintained with the transmission power attenuated as the number of allocations of the carrier frequency increases, but the modulation class before the change is 0. In this case, since the modulation class cannot be lowered any further, “no modulation class (NO)” is indicated, and in other cases, “modulation class exists (YES)”. In step S15, an estimated total throughput is obtained (calculated) when the changed number of assigned carrier frequencies are used. This acquisition (calculation) of the estimated total throughput is, for example, that a terminal in communication with modulation class 2 at one carrier frequency performs communication with modulation class 0 at two carrier frequencies by increasing and changing the allocation number of carrier frequencies. In this case, by referring to FIG. 3, the estimated total throughput = 19.2 × 2 = 38.4 (kbps).

  In the next step S16, it is determined whether or not the estimated total throughput increases with respect to the total throughput based on the signal quality of the current uplink communication. If it increases (YES), the process proceeds to step S17, and if it does not increase (NO) ) Ends as it is. In step S17, communication control is performed so that uplink communication is performed using the changed number of carrier frequencies.

Next, communication control operation including change of the number of assigned carrier frequencies for the wireless communication apparatus (terminal) will be described.
First, in step S11 of the control program of FIG. 4, it is determined whether or not the carrier frequency allocation number is to be changed. When the carrier frequency allocation number is to be changed, in step S12, the current transmission power and The uplink received SINR is acquired from the modulation class. At this time, if communication is established with the number of allocations of a certain carrier frequency and a certain modulation class, it is assumed that the target signal quality (terget SINR) in the modulation class is satisfied as shown in FIG. In addition, the numerical value shown in FIG. 3 is an example, and the uplink reception SINR is periodically notified from the base station in addition to the method of acquiring the uplink reception SINR with reference to FIG. 3 as in the present embodiment. Various methods such as a method can be used.

Next, in step S13, the power attenuation when the changed number of assigned carrier frequencies is used is acquired. The transmission power in a multi-carrier terminal needs to be such that the total transmission power at each carrier frequency does not exceed the maximum transmission power limit value. That is, as the number of assigned carrier frequencies increases, the transmission power per carrier frequency must be attenuated so as to follow the relationship shown in FIG.
Next, in step S14, it is determined whether or not there is a modulation class when using the changed number of carrier frequencies. Specifically, the uplink reception SINR when using the changed number of carrier frequencies after the change is obtained from the current uplink reception SINR and power attenuation, and compared with the target signal quality (terget SINR), after the change The modulation class that can be communicated when the carrier frequency of the assigned number is used is obtained. At that time, if the uplink reception SINR is impossible even in the modulation class 0 (in the case of −0.8 dB or less), the carrier frequency allocation number cannot be changed.

  Next, after obtaining (calculating) the estimated total throughput of the uplink when using the changed number of assigned carrier frequencies in step S15, in step S16, the present uplink total throughput is compared with the estimated uplink total throughput. Thus, it is determined whether or not the estimated total throughput increases with respect to the total throughput based on the current signal quality of uplink communication. For example, when a terminal in communication of modulation class 2 at one carrier frequency changes (increases) the number of allocation of carrier frequencies from 1 to 2, communication of modulation class 0 at two carrier frequencies is performed. 3, by referring to FIG. 3, the total uplink throughput before change = 76.8 (kbps)> the estimated uplink total throughput after change = 19.2 × 2 = 38.4 (kbps). Since the previous total uplink throughput is higher, the carrier frequency allocation number is not changed. When determining in step S16, by referring to the data amount of uplink communication, it is possible to determine whether the cause of the carrier frequency allocation number change request is in uplink communication or in downlink communication. It is possible to avoid the disadvantages caused by the implementation of “changing the number of assigned carrier frequencies”.

  According to the radio communication apparatus of the present embodiment and the radio communication method of the present embodiment implemented in the radio communication system including the radio communication apparatus and the base station, the carrier is considered in consideration of the conditions for improving the total throughput of the base station. Since it is determined whether or not the frequency allocation number can be changed, in other words, only when it is determined that the estimated total throughput increases with respect to the total throughput based on the signal quality (SINR) of the current uplink communication, Since the change is performed, it is possible to accurately determine whether or not the change in the number of allocations of carrier frequencies to the wireless communication apparatus should be performed, and the number of allocations of carrier frequencies and the modulation class applied on the terminal side are optimized. Will be. Therefore, since the utilization efficiency of the frequency resource of the base station is improved, the wireless communication apparatus and the wireless communication method can improve the data throughput of the entire base station.

It is a block diagram which shows schematic structure of the radio | wireless communication apparatus of the radio | wireless communications system to which the radio | wireless communication method of 1st Embodiment of this invention is applied. It is a figure which illustrates the relationship between the allocation number (carrier number) of the carrier frequency with respect to a radio | wireless communication apparatus (terminal) and the transmission power variation | change_quantity (power attenuation amount) in the radio | wireless communications system of 1st Embodiment. It is a figure which illustrates the relationship between the modulation class, target signal quality (terget SINR), and throughput when a wireless communication apparatus (terminal) performs communication in the wireless communication system of the first embodiment. It is a flowchart which shows the control program of communication control including the change of the allocation number of the carrier frequency with respect to the radio | wireless communication apparatus (terminal) in the radio | wireless communications system of 1st Embodiment.

Explanation of symbols

100 wireless communication device (wireless communication terminal; terminal)
110 antenna 130 RF unit 140 RF control unit 140a reception unit 140b transmission unit 150 system control unit 150a allocation number change determination unit 150b transmission power change amount acquisition unit 150c signal quality estimation unit 150d estimated total throughput calculation unit 150e total throughput increase determination unit 150f Allocation number control unit 160 Input unit 170 Display unit 180 System storage unit

Claims (4)

A wireless communication device capable of performing wireless communication with a base station using a plurality of frequencies simultaneously,
An allocation number change determining means for determining whether or not to change the frequency allocation number;
When it is determined that the frequency allocation number is to be changed, transmission power change amount obtaining means for obtaining a transmission power change amount when the frequency of the allocation number after the change is used;
Based on the obtained transmission power change amount, signal quality estimation means for estimating the signal quality of uplink communication when using the frequency of the allocated number after the change,
An estimated total throughput calculating means for calculating an estimated total throughput based on the estimated signal quality;
A total throughput increase determination means for determining whether or not the calculated estimated total throughput increases with respect to the total throughput based on the signal quality of the current uplink communication;
And a control unit configured to control to perform uplink communication using the frequency of the allocated number after the change when it is determined that the total throughput is increased.   When the wireless communication is adaptive modulation wireless communication, the total throughput increase determining means compares the total throughput in the modulation class set for each frequency before and after the change of the frequency allocation number. The wireless communication apparatus according to claim 1, wherein it is determined whether or not the total throughput has increased.   The radio communication apparatus according to claim 1, wherein an amount of change in signal quality on the base station side is used as the amount of change in transmission power. A wireless communication method in which a wireless communication device can perform wireless communication with a base station using a plurality of frequencies simultaneously,
When changing the frequency allocation number, based on the transmission power change amount when using the frequency of the allocation number after the change, the signal quality of uplink communication when using the frequency of the allocation number after the change is estimated A signal quality estimation step;
An estimated total throughput calculating step for calculating an estimated total throughput based on the estimated signal quality;
When it is determined that the calculated estimated total throughput increases with respect to the total throughput based on the signal quality of the current uplink communication, a control step is performed to perform control so that uplink communication is performed using the frequency of the allocated number after the change. A wireless communication method.

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