Radio communication apparatus, radio communication method, and non-transitory computer readable medium storing radio communication control program

A combination of antennas to be used is selected based on a distance between a plurality of antennas or the polarization direction of a radio signal to be transmitted/received.

INCORPORATION BY REFERENCE

This application is based on Japanese Patent Application No. 2009-253257 filed on Nov. 4, 2009 and including specification, claims, drawings and summary. The disclosure of the above Japanese Patent Application is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a radio communication apparatus and a radio communication method, which can change the antenna configuration at the time of carrying out spatial-multiplexing based communication, and a recording medium recording a radio communication control program which can change the antenna configuration at the time of carrying out spatial-multiplexing based communication.

BACKGROUND ART

In the 3GPP (3rd Generation Partnership Project) which is the international standardization body for the third generation mobile communication systems, standardization of E-UTRA (Evolved-UMTS Transmitter Radio Access) is fostered. The E-UTRA aims at speeding up the 15 generation, UTRA, and is positioned as the 3.9 generation called LTE (Long Term Evolution).

In the LTE, communication is carried out based on spatial multiplexing such as MIMO (Multi-Input Multi-Output) to achieve fast and mass information transfer and improve the frequency use efficiency. Further, the fourth generation, IMT-Advanced, which involves a greater number of spatial multiplexing channels and a wider band has been studied. The MIMO is the communication system that uses a plurality of antennas to increase paths based on spatial multiplexing and improve the throughput. This communication system also uses the same frequency to provide a satisfactory frequency use efficiency. MIMO whose number of inputs is a and whose number of outputs is b is called a×bMIMO. In the LTE, for example, the quantity of antennas at a base station (maximum spatial multiplexing channels) and the quantity of antennas of a terminal (maximum of four), which is 2×2MIMO (4×4MIMO at a maximum).

A terminal in the LTE acquires the quantity of antennas at a base station from information included in a PBCH (Physical Broadcast CHannel) which is a common control channel to globally inform control information unique to systems and cells. This terminal uses an RS (Reference Signal) to calculate a spatial matrix from the RS received at each antenna, uses a PUCCH (Physical Uplink Control CHannel) to inform the base station of a PMI (Precoding Matrix Indicator), RI (Rank Indicator), and CQI (Channel Quality Indicator). The base station decides the precoding and transmission mode based on the PMI, RI and CQI, and uses a PDCCH (Physical Downlink Control CHannel) to inform the terminal of the result of the decision.

When there are a large number of low-correlation spatial multiplexing channels available, for example, communication at a maximum of about 300 Mbps is possible in DL (Down Link). When the radio wave environment is poor, however, a base station carries out communication with transmission diversity in transmission mode. In the latter case, transmission of same data from two antenna ports may not improve the throughput, but can enhance the redundancy to achieve stable communication.

Unexamined Japanese Patent Application KOKAI Publication No. 2008-166855 discloses the configuration that carries out communication using a plurality of antennas.

With the speed of mobile communication improved, the use of spatial multiplexing typified by MIMO further improves the throughput and the frequency use efficiency. However, increasing the number of spatial multiplexing channels brings about various problems such that the quantity of antennas is increased, and dissipation power is increased by an increase in the amount of signal processing. Therefore, there is a limit to the quantity of antennas mountable to a portable terminal which is used in mobile communication.

It is therefore desirable to increase the quantity of antennas in carrying out communication. However, the technique described in Unexamined Japanese Patent Application KOKAI Publication No. 2008-166855 is about where antennas are mounted, such as an external antennaslement is provided at the battery pack of a cellular phone. It is therefore difficult to keep a satisfactory communication state by flexibly changing the antenna configuration according to various situations.

SUMMARY

Accordingly, it is an exemplary object of the present invention to provide a satisfactory communication state by flexibly changing the antenna configuration to be used in spatial-multiplexing based communication according to various situations.

To achieve the object, according to a first exemplary aspect of the invention, there is provided a radio communication apparatus including an antenna set including a plurality of antennas and executing spatial-multiplexing based communication, including:

an antenna selection unit that selects from the antennas a combination of antennas whose quantity is equal to or less than a quantity of counterpart antennas to be communicated, as a combination of antennas to be used in spatial-multiplexing based communication;

a signal processing unit that executes signal processing for communication using the combination of antennas selected by the antenna selection unit; and

an antenna configuration specifying unit that specifies a physical configuration of the plurality of antennas,

the antenna selection unit selecting the combination of antennas to be used based on the configuration selected by the antenna configuration specifying unit.

The antenna configuration specifying unit may specify a physical inter-antenna distance as the physical configuration of the plurality of antennas, and

the antenna selection unit may select a combination of antennas which maximizes the physical inter-antenna distance specified by the antenna configuration specifying unit.

the antenna selection unit may select a combination of antennas with different polarization directions specified by the antenna configuration specifying unit.

To achieve the object, according to a second exemplary aspect of the invention, there is provided a radio communication apparatus including an antenna set including a plurality of antennas and executing spatial-multiplexing based communication, including:

an antenna selection unit that selects from the antennas a combination of antennas whose quantity is equal to or less than a quantity of counterpart antennas to be communicated, as a combination of antennas to be used in spatial-multiplexing based communication;

a signal processing unit that executes signal processing for communication using the combination of antennas selected by the antenna selection unit; and

a reception quality detecting unit that detects a reception quality for each combination of a plurality of antennas,

the antenna selection unit selecting the combination of antennas to be used according to a result of comparison of reception qualities detected by the reception quality detecting unit.

The radio communication apparatus may further include a communication environment detecting unit that detects a predetermined amount of variation in communication environment of the radio communication apparatus,

wherein the antenna selection unit may vary a period of changing a combination of antennas to be selected, depending on whether the amount of variation detected by the communication environment detecting unit is equal to or less than a predetermined reference value.

The radio communication apparatus may further include a communication environment change detecting unit that detects a time-dependent change in a predetermined amount of variation in communication environment of the radio communication apparatus,

wherein the antenna selection unit may vary a period of changing a combination of antennas to be selected, depending on whether the time-dependent change in the amount of variation detected by the communication environment change detecting unit is equal to or less than a predetermined reference value.

The signal processing unit may include a plurality of signal processing circuits that process signals to be transmitted/received in association with the a plurality of antennas included in the antenna set, and

power supply to that one of the plurality of signal processing circuits which is not used may be stopped based on the combination of antennas selected by the antenna selection unit.

The signal processing unit may include a plurality of signal processing circuits that process signals to be transmitted/received in association with the a plurality of antennas included in the antenna set, and

a setting value for carrying out communication with the antennas to be communicated or another antenna to be communicated may be acquired by using an antenna which is not selected by the antenna selection unit and that signal processing circuit which is associated with the antenna.

The antenna set may include:

a first antenna set including a plurality of first antennas in which polarization directions of adjacent antennas are orthogonal to each other; and

a second antenna set including a plurality of second antennas in which polarization directions of adjacent antennas are orthogonal to each other.

The antenna set may include:

a first antenna set including a plurality of first antennas which cause polarization directions of signals to be transmitted/received are identical to each other; and

a second antenna set including a plurality of second antennas which cause polarization directions of signals to be transmitted/received are identical to each other, and

the polarization direction of the signals to be transmitted/received by the plurality of first antennas may be orthogonal to the polarization direction of the signals to be transmitted/received by the plurality of second antennas.

The first antenna set or the second antenna set may be configured to be dismountable from the radio communication apparatus, and

the radio communication apparatus may further include a mount detection unit that detects if the first antenna set or the second antenna set is mounted to the radio communication apparatus.

The antenna selection unit may select a combination of antennas in such a way as to always transmit/receive a signal having a certain polarization direction.

To achieve the object, according to a third exemplary aspect of the invention, there is provided a radio communication apparatus including an antenna set including a plurality of antennas and executing spatial-multiplexing based communication, including:

antenna selection means that selects from the antennas a combination of antennas whose quantity is equal to or less than a quantity of counterpart antennas to be communicated, as a combination of antennas to be used in spatial-multiplexing based communication;

signal processing means that executes signal processing for communication using the combination of antennas selected by the antenna selection means; and

antenna configuration specifying means that specifies a physical configuration of the plurality of antennas,

the antenna selection means selecting the combination of antennas to be used based on the configuration selected by the antenna configuration specifying means.

To achieve the object, according to a fourth exemplary aspect of the invention, there is provided a radio communication apparatus including an antenna set including a plurality of antennas and executing spatial-multiplexing based communication, including:

antenna selection means that selects from the antennas a combination of antennas whose quantity is equal to or less than a quantity of counterpart antennas to be communicated, as a combination of antennas to be used in spatial-multiplexing based communication;

signal processing means that executes signal processing for communication using the combination of antennas selected by the antenna selection means; and

reception quality detecting means that detects a reception quality for each combination of a plurality of antennas,

the antenna selection means selecting the combination of antennas to be used according to a result of comparison of reception qualities detected by the reception quality detecting means.

To achieve the object, according to a fifth exemplary aspect of the invention, there is provided a radio communication method of executing spatial-multiplexing based communication using an antenna set including a plurality of antennas, including:

an antenna selection step of selecting from the antennas a combination of antennas whose quantity is equal to or less than a quantity of counterpart antennas to be communicated, as a combination of antennas to be used in spatial-multiplexing based communication;

a signal processing step of executing signal processing for communication using the combination of antennas selected by the antenna selection unit; and

an antenna configuration specifying step of specifying a physical configuration of the plurality of antennas,

the antenna selection step selecting the combination of antennas to be used based on the configuration selected in the antenna configuration specifying step.

To achieve the object, according to a sixth exemplary aspect of the invention, there is provided a radio communication method of executing spatial-multiplexing based communication using an antenna set including a plurality of antennas, including:

an antenna selection step of selecting from the antennas a combination of antennas whose quantity is equal to or less than a quantity of counterpart antennas to be communicated, as a combination of antennas to be used in spatial-multiplexing based communication;

a signal processing step of executing signal processing for communication using the combination of antennas selected by the antenna selection unit; and

a reception quality detecting step of detecting a reception quality for each combination of a plurality of antennas,

the antenna selection step selecting the combination of antennas to be used according to a result of comparison of reception qualities detected in the reception quality detecting step.

To achieve the object, according to a seventh exemplary aspect of the invention, there is provided a recording medium recording a program allowing a computer that controls a radio communication apparatus which executes spatial-multiplexing based communication using an antenna set including a plurality of antennas, to function as:

an antenna configuration specifying unit that specifies a physical configuration of the plurality of antennas;

an antenna selection unit that selects from the antennas a combination of antennas whose quantity is equal to or less than a quantity of counterpart antennas to be communicated, as a combination of antennas to be used in spatial-multiplexing based communication, based on the configuration specified by the antenna configuration specifying unit; and

a signal processing unit that executes signal processing for communication using the combination of antennas selected by the antenna selection unit.

To achieve the object, according to a eighth exemplary aspect of the invention, there is provided a recording medium recording a program allowing a computer that controls a radio communication apparatus which executes spatial-multiplexing based communication using an antenna set including a plurality of antennas, to function as:

a reception quality detecting unit that detects a reception quality for each combination of a plurality of antennas;

an antenna selection unit that selects from the antennas a combination of antennas whose quantity is equal to or less than a quantity of counterpart antennas to be communicated, as a combination of antennas to be used in spatial-multiplexing based communication, according to a result of comparison of reception qualities detected by the reception quality detecting unit; and

a signal processing unit that executes signal processing for communication using the combination of antennas selected by the antenna selection unit.

The present invention can provide a satisfactory spatial-multiplexing based communication by changing the antenna configuration flexibly.

EXEMPLARY EMBODIMENT

An exemplary embodiment of the present invention will now be described with reference to the accompanying drawings.FIG. 1shows one configuration example of a portable terminal device using the MIMO system in the E-UTRA as an application to a radio communication apparatus.

A terminal0shown inFIG. 1is a radio communication apparatus as a portable terminal device, and includes an antenna selection unit2, an RF switch4, a signal processing unit5, a control unit6, a connector unit7, an antenna11, an antenna12, an RF unit31, and an RF unit32. In the configuration example shown inFIG. 1, the antenna11and antenna12are incorporated in the terminal0, and are mounted in such a way that each antenna can receive radio signals.

The antenna selection unit2is a switch which connects or disconnects the antenna11, the antenna12and the connector unit7, which are incorporated in the terminal0, to and from the RF unit31and the RF unit32. Each of the RF units31and32has a capability of frequency-converting high-frequency signals each of two lines (maximum of four lines) received at the respective antennas including the antenna11and the antenna12. Each of the RF units31and32has two inputs x and y. Hereinafter, the input x of the RF unit31is also denoted as “RF unit31x”, and the input y of the RF unit31as “RF unit31y”. Likewise, the input x of the RF unit32is also denoted as “RF unit32x”, and the input y of the RF unit32as “RF unit32y” hereinafter.

Each of the RF units31and32may include an amplifier, such as LNA (Low Noise Amplifier), so as to be able to amplify a received signal. In addition, each of the RF units31and32may include a weighable attenuator so as to be able to adjust the amplitude of a received signal. Further, each of the RF units31and32may include a phase shifter using, for example, a delay circuit, so that the phase of a received signal can be adjusted. As apparent from the above, the RF units31and32should be able to perform various kinds of signal processing on received signals as a pre-stage of demodulation or the like of the signal processing unit5. It is to be noted that the RF units31and32may be configured to be able to perform various kinds of signal processing on transmission signals as a post-stage of modulation or the like of the signal processing unit5.

The RF switch4can connect an input52of the signal processing unit5to the ground. The signal processing unit5processes output signals of the RF units31and32. For example, the signal processing unit5should perform signal processing, such as orthogonal detection, analog-to-digital (A/D) conversion or fast Fourier transform, using the output signals of the RF units31and32, so that data transmitted in a plurality of sub carriers can be demodulated and decoded. The control unit6performs various kinds of control, such as setting the individual sections and ON/OFF actions. The connector unit7serves to connect the terminal0to an external device.

FIG. 2is a diagram shows a configuration example when an external antenna is connected to the terminal0. An external antenna13and an external antenna14has a configuration (e.g., a plug) to be connectable to (detachable from) the connector unit7, and has frequency characteristics similar to those of the antennas11and12. The control unit6should detect the connection (mounting) of the external antenna13and the external antenna14by means of a change in the electrical characteristic of the connector unit7, a switch or the like. The connection (mounting) of the external antenna13and the external antenna14can permit signals of not only two lines but signals of up to four lines to be transmitted and received, so that the combination of antennas to be used in spatial-multiplexing based communication can be changed flexibly. When the combination of the antennas11and12is selected, the space of the terminal0can be saved (reduced) by removing the external antenna13and the external antenna14.

FIGS. 3A and 3Bshow examples of the configuration of the antenna selection unit2. In the configuration example shown inFIG. 3A, the antenna selection unit2always transfers (outputs) a signal received at the antenna11to the input x of the RF unit31(RF unit31x). The antenna selection unit2shown inFIG. 3Aincludes three antenna switches22to24. The antenna switch22can be switched to transfer (output) a signal received at any one of the antenna12, the antenna12, and the external antenna14to the input y of the RF unit31(RF unit31y). Therefore, it is possible to select an antenna which has a low correlation to the antenna11as an antenna to be used with the antenna11. The antenna switch23can be switched whether or not to transfer (output) a signal received at the external antenna13to the input x of the RF unit32(RF unit32x), making it possible to select whether the external antenna13is connected to the input x of the RF unit32or to a terminal d to be the ground. The antenna switch24can be switched whether or not to transfer (output) a signal received at the external antenna14to the input y of the RF unit32(RF unit32y), making it possible to select whether the external antenna14is connected to the input y of the RF unit32or to the terminal d to be the ground.

In this manner, the antenna switch23and the antenna switch24can connect the inputs of the RF unit32(RF unit32x, RF unit32y) to the ground. This can prevent signals received at the external antenna13or the external antenna14from being input to the circuit board or the RF unit32, thereby inhibiting occurrence of interference signals.

An antenna selection unit201with a configuration exemplified inFIG. 3Bmay be used as the antenna selection unit2. In the configuration example shown inFIG. 3B, the antenna selection unit201can freely select connection of each antenna to each RF unit. That is, the antenna selection unit201differs in configuration from the antenna selection unit2shown inFIG. 3Ain that, for example, the antenna11is not directly connected to the input x of the RF unit31(RF unit31x). The antenna selection unit201shown inFIG. 3Bincludes four antenna switches211,221,231and241. Each antenna switch211,221,231,241can be switched to select one of the four antennas (antenna11, antenna12, external antenna13and external antenna14) and the terminal d to be the ground, and connect the selected element to the input of the corresponding RF unit. The configuration of the antenna selection unit201provides various selectable combinations of antennas, so that the combination of antennas to be used can be selected flexibly to ensure satisfactory communication based on spatial multiplexing.

In the terminal0, a satisfactory spatial multiplexing based communication is established by flexibly changing the combination of antennas to be used to carry out spatial-multiplexing based communication according to various situations. To achieve the purpose, the control unit6reads and executes an operational program stored in a storage unit (e.g., flash memory, ROM, RAM, HDD, optical disc storage device, or magneto-optical disk storage device) incorporated in the terminal0or externally connected thereto to realize functions as shown inFIG. 4. As shown inFIG. 4, the control unit6should function as an antenna configuration specifying unit61, a communication state detecting unit62, a using-antenna selection setting unit63, a signal processing setting unit64, etc.

The antenna configuration specifying unit61specifies the antenna configuration, such as the layout of antennas. The antenna configuration is specified by setting data or the like indicative of the physical distance between a plurality of antennas (antenna11, antenna12, external antenna13, external antenna14, etc.) which can be used by the terminal0, and the directions of the individual antennas (directions of reception polarizations).

The antenna configuration specifying unit61may read out setting data from the storage unit incorporated in the terminal0to specify the structures or the like of antennas. Alternatively, the structures or the like of antennas may be specified by reading setting data externally input to the terminal0. As another option, the terminal0may include an input unit through which the manufacturer or user of the terminal0can input data indicative of the structures of antennas, so that the antenna configuration specifying unit61may read the data input through the input unit to specify the structures or the like of antennas.

Further, the antenna configuration specifying unit61should specify the structures or the like of antennas by detecting the connection state of the external antenna13or the external antenna14in the connector unit7. In addition, the antenna configuration specifying unit61may specify the structures or the like of antennas based on the results of reception at other antennas.

The communication state detecting unit62detects various states relating to the communication operation of the terminal0. For example, the communication state detecting unit62should detect the communication state based on the connection states of the external antenna13and the external antenna14in the connector unit7, the selected setting of antennas in the antenna selection unit2, the results of processing received signals in the RF units31and32, and the signal processing unit5, etc.

The communication state detecting unit62may detect the charged amount (remaining amount) of the battery of the terminal0, the amount of data to be communicated, the inclination of the terminal0, the moving speed thereof, the moving direction thereof, the result of transmitting/receiving a reference signal for measurement, and the like, as a state relating to the communication operation.

The using-antenna selection setting unit63performs setting to select a combination of antennas to be used to carry out spatial-multiplexing based communication from a plurality of antennas including the antenna11, the antenna12, the external antenna13and the external antenna14. For example, the using-antenna selection setting unit63should select a combination of antennas by sending a select control signal corresponding to the combination of antennas to be used to the antenna selection unit2based on the antenna configuration (structures or the like) specified by the antenna configuration specifying unit61. The using-antenna selection setting unit63should select a combination of antennas by sending a select control signal based on the state of the communication operation of the terminal0which is detected by the communication state detecting unit62.

The signal processing setting unit64performs process setting of communication signals in various circuits included in the terminal0in association with the combination of antennas selected by the using-antenna selection setting unit63. For example, the signal processing setting unit64should change over and control the operations of various circuits or the like by sending a changeover control signal corresponding to the combination of antennas set by the using-antenna selection setting unit63to the RF switch4, the RF unit31, the RF unit32and the signal processing unit5.

The operation of the terminal0which has the foregoing configuration and functions will be described below. First, the process of the terminal0in normal standby mode will be described. Various processes to be described below may be realized, for example, as the control unit6in the terminal0reads and executes the program stored in the storage unit (e.g., flash memory, ROM, RAM, HDD, optical disc storage device, or magneto-optical disk storage device) incorporated in the terminal0or externally connected thereto to control the individual configurations of the terminal0and achieve the individual functions of the control unit6.

In normal standby mode, signal received at the antenna11and the antenna12incorporated in the terminal0travel through the antenna selection unit2to be input to the RF unit31. At this time, processing is carried out in two lines in the terminal0. Accordingly, the RF unit31is enabled, and the RF unit32is disabled by the signal processing setting unit64or the like in the control unit6. Disabling the RF unit32which will not be used stops power supply to the RF unit32, reducing dissipation power. Further, the control unit6sets open the terminal of the antenna selection unit2which is connected to the connector unit7for external antenna by means of the using-antenna selection setting unit63or the like, thereby connecting the RF unit32xand RF unit32yor the inputs of the RF unit32to the ground.

The RF switch4sets the output of the disabled RF unit32open, and connects the input to the signal processing unit5to the ground. The output of the RF unit31is input to the signal processing unit5, which calculates a usable RI and PMI from the RS transmitted from the base station, and informs the base station of the RI and PMI using the PUCCH as CQI. The base station maps the DCI with the RI and PMI included in the PDCCH, and informs the terminal0subframe by subframe. The signal processing unit5performs decoding through the process informed by the base station. 2×2MIMO based communication using two lines can be carried out this way.

When the external antenna13and the external antenna14are connected to the connector unit7as shown inFIG. 2, by way of contrast, the terminal0may be configured to have four antennas. In this case, the terminal0can perform 4×4MIMO based communication using four lines, and ensure communication twice as fast as the 2×2MIMO based communication.

A description will now be given of a case where the base station has four antennas.FIG. 5Aexemplifies a case where a base station104has four antennas114. In this example, the maximum number of spatial multiplexing is four. In the terminal0, the signal processing setting unit64or the like in the control unit6performs ON control on the RF switch4, and enables the RF unit32. At this time, the set values of the RF unit31and the signal processing unit5which have already been operating before the setting may be reflected on the setting of the RF unit32and the signal processing unit5. This can make the activation process faster.

For example, the signal processing setting unit64in the control unit6may read various settings, such as the frequency band, system bandwidth, frame structure, CP length, cell ID and gain setting, from the operational contents of the RF unit31and the signal processing unit5. Alternatively, those settings may be detected by the communication state detecting unit62, and the signal processing setting unit64may be informed of the detection result.

With the RF unit32enabled, the terminal0has a 4-antennas configuration and can process signals of four lines. The terminal0receives the RS from the base station after performing predetermined setting, and informs the base station of the PMI and CQI. The base station informs the terminal0of the setting, and initiates 4×4MIMO based communication when the radio wave environment is satisfactory. A portable terminal device which can achieve 4×4MIMO can be provided this way, thus ensuring communication with the maximum throughput in the DL of LTE. Of course, enabling the RF unit32and increasing paths (channels) increase the load on the signal processing unit5, increasing dissipation power. To cope with it, the RF unit32may be disabled properly.

FIG. 6is a flowchart illustrating an example of a process of changing the antenna configuration. In the process illustrated inFIG. 6, the control unit6of the terminal0checks the amount of data to be communicated and the remaining amount of the battery when setting is started (S1001). At this time, it is determined whether the amount of data to be communicated and the remaining amount of the battery are large or small (S1002). For example, reference values for determining whether the amount of data to be communicated and the remaining amount of the battery are large or small are prestored in the control unit6, and the communication state detecting unit62determines whether the amount of data to be communicated and the remaining amount of the battery are equal to or less than the reference values. When the amount of data to be communicated and the remaining amount of the battery are equal to or less than the reference values, it is determined that the amount of data to be communicated and the remaining amount of the battery are small.

When it is determined that the amount of data to be communicated and the remaining amount of the battery are small (S1002; Yes), the control unit6changes over the antenna selection unit2, the RF switch4, etc. to set two antennas to be selected by using the using-antenna selection setting unit63, the signal processing setting unit64, etc. (S1003). Accordingly, the control unit6sets the antenna configuration to connect the antenna11and the antenna12to the RF unit31. The signal processing setting unit64in the control unit6disables the RF unit32which is not connected to the selected antennas (S1005), and initiates the communication process (S1006).

When at least one of the amount of data to be communicated and the remaining amount of the battery is larger than the reference value, i.e., when the amount of data is large or the remaining amount of the battery is large (S1002; No), on the other hand, the control unit6changes over the antenna selection unit2and the RF switch4to set four antennas to be selected (S1004). In this case, the signal processing setting unit64in the control unit6initiates the communication process without disabling the RF unit31and the RF unit32(S1006).

As apparent from the above, when the amount of data to be communicated is small or the remaining amount of the battery is small, power can be saved by disabling the RF unit32or reducing the load on the signal processing unit5. The antenna configuration may be changed according to whether the terminal0is connected to an AC power supply or not. When the terminal0is connected to an AC power supply, for example, the quantity of antennas to be selected through the process of S1004may be set to four, whereas when the terminal0is not connected to an AC power supply, the quantity of antennas to be selected through the process of S1003may be set to two.

When the remaining amount of the battery is small although the amount of data to be communicated is large, the base station or a counterpart terminal or the like may be notified that communication is not possible, so that the communication process will not be initiated. When the remaining amount of the battery is large although the amount of data to be communicated is small, the quantity of antennas to be used and whether the RF units are usable or not may be set based on designation made by the user of the terminal0.

Subsequently, a description will be given of a case where the base station has two antennas.FIG. 5Bexemplifies a case where a base station102has two antennas112. In this example, the maximum number of spatial multiplexing is two. The E-UTRA standards do not support a case where the quantity of antennas in the terminal is larger than the quantity of antennas in the base station, as in the case of 2×4 MIMO where the quantity of antennas in the base station is two and the quantity of antennas in the terminal0is four. From the viewpoint of power saving, therefore, it is desirable that the terminal0should avoid taking a 4-line configuration provided by the antennas31, the RF unit32and the signal processing unit5when the quantity of antennas in the base station is two. For example, the using-antenna selection setting unit63in the control unit6sets only two antennas to be used, namely, the antenna11and the antenna12, and disables the RF unit32by means of the signal processing setting unit64or the like to stop feeding power to the RF unit32which is not used. In addition, the setting to allow the signal processing unit5to perform 2-line signal processing can reduce the load on the signal processing unit5, thereby reducing dissipation power. As apparent from the above, antennas whose quantity is equal to or less than the quantity of antennas in the counterpart base station to be communicated should be selected in the terminal0under control of the control unit6to determine the antenna configuration for spatial-multiplexing based communication.

In the above example, the antenna11and the antenna12are selected when the quantity of antennas to be used in the terminal0is two. In the case of the MIMO that uses a plurality of antennas, the lower the correlation between antennas is, the greater the effect of spatial multiplexing can be expected. Accordingly, the description will be given of configuration examples and operational examples of the embodiment for selecting a combination of antennas with low correlation in case of selectively using some of the four antennas, namely, the antenna11, the antenna12, the external antenna13and the external antenna14, which can be used by the terminal0. It is generally known that as the distance between antennas becomes longer, the correlation therebetween gets lower. Therefore, if antennas which maximizes the physical inter-antenna distance, such as the antenna11and the external antenna14shown inFIG. 2, are selected, the correlation between the antennas becomes lower, which provides a satisfactory configuration for carrying out spatial-multiplexing based communication.

In addition to the antenna11and the external antenna14, for example, one of the antenna12and the external antenna13may be selectively used. In this case, the distances among each of the antenna12and the external antenna13and the antenna11and the external antenna14which have already been selected should be specified, and the one which provides a larger sum of the specified inter-antenna distances should be selected. That is, a combination of antennas to be used should be selected in such a way that the sum of the physical inter-antenna distances becomes maximum. The selection of antennas which maximize the sum of the inter-antenna distances increases the isolation between antennas and reduces the coupling between antenna's elements, thereby improving the precision of calculating the correlation coefficient that indicates the degree of correlation. In this manner, antennas to be used should be selected based on the physical distances among a plurality of antennas to determine the antenna configuration for carrying out spatial-multiplexing based communication.

It is known that the correlation between antennas whose polarizations are orthogonal to (different from) each other is low. As another example of selecting a combination of antennas with low correlation, configuration examples and selection operations which take polarization into account will be described.

In a configuration example shown inFIG. 7A, the antenna11and the antenna12are antennas for vertical polarization, which are vertical to the ground. On the other hand, the external antenna13and the external antenna14are antennas for horizontal polarization, which are horizontal to the ground. In this case, the antenna11and the antenna12whose transmitted/received signals have the identical polarization direction constitute one antenna set (first antenna set). The external antenna13and the external antenna14whose transmitted/received signals have the identical polarization direction constitute another antenna set (second antenna set). The first antenna set and the second antenna set are arranged in such a way that the polarization direction of a signal transmitted/received by the antenna11or the antenna12included in the first antenna set is orthogonal to the polarization direction of a signal transmitted/received by the external antenna13or the external antenna14included in the second antenna set. The second antenna set including the external antenna13and the external antenna14is configured to be attachable to and detachable from the terminal0. In such a configuration example, the combination of the antenna11or the antenna12and the external antenna13or the external antenna14can make the correlation between two antennas lower. That is, arbitrary selection of one antenna included in the first antenna set and one antenna included in the second antenna set provides a combination of antennas with low correlation, so that a satisfactory spatial-multiplexing based communication can be provided. The first antenna set and the second antenna set may be replaced with each other.

In a configuration example shown inFIG. 7B, the antenna11and the external antenna13are antennas for vertical polarization, which are vertical to the ground. On the other hand, the antenna12and the external antenna14are antennas for horizontal polarization, which are horizontal to the ground. In this case, the antenna11and the antenna12whose polarization directions are orthogonal to each other are located adjacent to each other to constitute one antenna set (first antenna set). The external antenna13and the external antenna14whose polarization directions are orthogonal to each other are located adjacent to each other to constitute another antenna set (second antenna set). The second antenna set including the external antenna13and the external antenna14is configured to be attachable/detachable to/from the terminal0. In such a configuration example, the combination of the antenna11or the external antenna13and the antenna12or the external antenna14can reduce the correlation between two antennas. That is, proper selection of one antenna included in the first antenna set or the second antenna set, and one antenna included in the first antenna set or the second antenna set provides a combination of antennas with low correlation, thus providing a satisfactory spatial-multiplexing based communication. In addition, even when the external antenna13and the external antenna14are not connected to the terminal0, the antenna11and the antenna12if selected can be a combination of antennas with low correlation. The first antenna set and the second antenna set may be replaced with each other.

FIGS. 8A to 8Cshow configuration examples of antennas laid out three-dimensionally. Antennas311to314shown inFIGS. 8A to 8Care linear polarization antennas. Arrows in the diagrams represent the directions of polarizations corresponding to the respective antennas.

FIG. 8Ashows the configuration of three antennas with an antenna312in the x direction, an antenna313in the y direction and an antenna311in the z direction laid out so as to be orthogonal (90°) to one another to make the correlation between antennas lower.FIG. 8Bshows the configuration of four antennas laid out three-dimensionally. When the four antennas are arranged two-dimensionally and four antennas are selected (all antennas are selected) as shown inFIGS. 7A and 7B, there are two pairs of antennas which are not orthogonal. In the antenna configuration shown inFIG. 8B, an antenna314in the −y direction is disposed in addition to the antenna configuration shown inFIG. 8A. Therefore, antennas which do not orthogonal to each other are a pair of the antenna313and antenna314whose polarization directions are the same, making it possible to reduce a pair of antennas whose polarization directions are not orthogonal to each other as compared with the two-dimensional layout.FIG. 8Cshows a configuration example where four antennas are laid out so as to cross one another at angles of 120°. In this configuration example, while the antennas are not exactly orthogonal to one another, the polarization directions do not become identical, so that the correlation between the antennas can be set lower.

The combination of some or all of the antenna11, the antenna12, the external antenna13and the external antenna14or the combination of the antennas311to314allows antennas with orthogonal (different) polarizations to be selectively used. This can provide the antenna configuration which reduces the correlation between a plurality of antennas and is satisfactory for carrying out spatial-multiplexing based communication.

For example, in case of reading setting data indicative of the physical distances among the individual antennas or setting data indicative of the directions of polarizations corresponding to the respective antennas to select some (a plurality of antennas) of all the antennas, the antenna configuration specifying unit61in the control unit6should select antennas to be used according to the physical configurations of the individual antennas in such a way as to reduce the correlation among a plurality of antennas.

The method of specifying the physical configurations of a plurality of antennas is not limited to reading setting data prepared in advance, and a predetermined measurement may be performed.FIG. 9is a flowchart illustrating an example of a process of selecting antennas to be used according to the physical configurations of individual antennas specified based on the result of the predetermined measurement. In this example, the antenna11is preset (fixed) as an antenna to be used.

When the process shown inFIG. 9starts, the control unit6, e.g., the communication state detecting unit62, in the terminal0determines whether it is a standby state or not, i.e., whether it is in standby mode, before measurement of RS, before initiation of communication, or no communication state, by detecting the operational state of the signal processing unit5or the like (S2001). When having determined that it is not in standby mode (S2001; No), the control unit6repeatedly executes the process of S2001. When having determined that it is in standby mode (S2001; Yes), on the other hand, the control unit6transmits a reference signal for measurement from the antenna11by causing, for example, the antenna configuration specifying unit61or the communication state detecting unit62to output a predetermined command signal to the signal processing unit5and the RF unit31(S2002).

The reference signal transmitted from the antenna11in S2002is received by another antenna12, external antenna13, or external antenna14. At this time, the physical configuration of each antenna, such as the positional relation and the degree of correlation, from the reception level, the phase, the measured reception quality, the correlation coefficient, etc. (some or all of them) (S2003). Then, the control unit6selects an antenna to be used with the antenna11from the antenna12, the external antenna13and the external antenna14based on the result of measurement in S2003(S2004to S2006). When such an antenna is selected based on the result of measuring the reception level, for example, an antenna whose reception level for the reference signal is the lowest is selected from the antenna12, the external antenna13and the external antenna14. This is the antenna farthest from the antenna11that has transmitted the reference signal, or the antenna whose polarization direction provides the largest difference from the polarization direction of a radio signal to be transmitted/received from/at the antenna11, and it can be assumed that the antenna has low correlation to the antenna11. After antenna selection is finished this way, the control unit6, e.g., the sisal processing setting unit64, performs operational setting of the RF switch4, the signal processing unit5, the RF unit31and the RF unit32according to the selected antenna. As a result, signal processing for carrying out communication with the combination of the selected antennas is started (S2007).

Selecting a combination of antennas with low correlation according to the physical configuration of each antenna specified based on the result of such a predetermined measurement can provide a satisfactory antenna configuration for spatial-multiplexing based communication. When one of the antenna12, the external antenna13and the external antenna14is preset (fixed) as an antenna to be used, the reference signal for measurement is transmitted from the antenna to be used in S2002. The antenna with low correlation should be selected based on the result of the measurement performed then in S2003. The phase difference when the reference signal transmitted from the antenna11is received at other antennas (antenna12, external antenna13and external antenna14) may be measured, and the antenna with the largest phase difference may be selected. In this manner, a combination of antennas with low correlation can be selected based on the result of a predetermined measurement performed when the reference signal transmitted from one of the antenna11and antenna12incorporated in the terminal0, and the external antenna13and external antenna14connected to the terminal0is received at the other antennas.

Further, a description will be given of a case where a reception quality report showing CQI, RI, etc., for example, as another example of selecting a combination of antennas to be used in spatial-multiplexing based communication.FIG. 10is a flowchart illustrating an example of a process of selecting antennas to be used based on a predetermined reception quality report. It is assumed in this example too that the antenna11is preset (fixed) as an antenna to be used as in the process example illustrated inFIG. 9.

In the process illustrated inFIG. 10, first, the antenna12is selected (S3001). Then, a reception quality report when the antenna11and the antenna12are used is held (S3002). For example, the communication state detecting unit62in the control unit6should predict the DL channel characteristic from the result or the like of executing signal processing in the signal processing unit5, and prepare a reception quality report showing the predicted DL channel characteristic. After the reception quality report is held in S3002, selection of the antenna12is stopped, and the external antenna13is selected (S3003). Subsequently, a reception quality report when the antenna11and the external antenna13are used is held (S3004). After the reception quality report is held in S3004, selection of the external antenna13is stopped, and the external antenna14is selected (S3005). At this time, a reception quality report when the antenna11and the external antenna14are used is held (S3006). In this manner, all reception qualities corresponding to cases where any one of the antenna12, the external antenna13and the external antenna14is used with the antenna11are detected, and a reception quality report showing those detection results is held. Thereafter, the reception quality reports are compared with one another. Then, an antenna with the best reception quality is determined in the antenna combinations with the antenna11based on the result of the comparison (S3007). Thereafter, an antenna to be used with the antenna11is selected (S3008to S3010). After antenna selection is finished this way, the signal processing setting unit64, for example, performs operational setting of the RF switch4, the signal processing unit5, the RF unit31and the RF unit32according to the selected antenna. As a result, signal processing for carrying out communication with the combination of the selected antennas is started (S3011).

Selecting a combination of antennas with low correlation based on the result of comparison of such reception quality reports can provide a satisfactory antenna configuration for spatial-multiplexing based communication. The reception quality report should show arbitrary measurements which can specify the DL channel characteristic, and may show, for example, signal to interference and noise ratio (SINR), the bit error ratio (BER), the energy per bit to noise power spectral density ratio (Eb/No) or the like.

Next, configuration examples and operational examples when a portable terminal device includes a sensor will be described. In the configuration examples shown inFIGS. 1A and 1B, the terminal0includes a sensor8. The sensor8is, for example, an azimuth sensor using an acceleration sensor or the like, which can detect the inclination of the terminal0. The sensor8may be provided as separate from the control unit6in the terminal0, or may be provided inside the control unit6as part of the communication state detecting unit62, for example. Further, the sensor8is not limited to the type which is incorporated in the terminal0, and may be externally connected to the terminal0to transfer data indicative of the detection result to the control unit6.

In this configuration example, the terminal0incorporates an antenna15and an antenna16in addition to the antenna11and the antenna12. The antenna15and the antenna16are not limited to the type which is incorporated in the terminal0, and, like the external antennas13and14, may be configured as detachable external antennas. In addition, terminals0shown inFIGS. 11A and 11Beach include a processing unit50which has all the functions of the foregoing RF units31and32and the signal processing unit5. That is, the processing unit50can process signals of four lines (four high-frequency signals).

When the terminal0is placed in the direction as shown inFIG. 11A, the antenna11and the antenna12become antennas for vertical polarization, and the antenna15and the antenna16become antennas for horizontal polarization. As one example of the operation in this case, the combination of the antennas11and12provides an antenna configuration which maximizes the inter-antenna distance, has low correlation and is satisfactory for receiving vertical polarized signals.

When the terminal0is tilted and placed in the direction as shown inFIG. 11Bthereafter, the antenna15and the antenna16which have been horizontal become vertical to be able to receive vertical polarized signals. At the time the use of the terminal0views a streaming video, for example, the layout of the terminal0may be changed to change the screen direction from the vertical screen for selecting a program to the horizontal screen for viewing a video. At this time, the inclination of the terminal0is detected by the sensor8, and when a certain or greater inclination is detected, the control unit6changes the antennas to be used. As one example, upon detection of a change of 45° or greater from the initial value (inclination angle) when the antenna configuration has been determined first, the antennas to be used should be changed to the antennas15and16from the antennas11and12. Alternatively, the combination of antennas to be used may be changed according to whether the state of the terminal0in use is the vertical screen or the horizontal screen.

As apparent from the above, the antenna configuration can be changed so that the inclination of the terminal0is detected by the sensor8to always ensure reception of. The antenna configuration can be changed flexibly based on the result of detecting that the layout of the terminal0(position and direction, the state or the like) has been changed, thereby achieving satisfactory spatial-multiplexing based communication. The polarization direction of signals to be transmitted/received normally is not limited to the vertical direction, and may be a predetermined arbitrary direction such as the horizontal direction.

In the above example, the initial setting of the antenna configuration which has low correlation and can carry out satisfactory communication is set to the state where the antennas11and12for vertical polarization are selected for signal reception based on the inter-antenna distance. Alternatively, a combination of antennas which provides a satisfactory antenna configuration may be predicted and set so that, for example, the initial setting state is set to the state where the antenna11for vertical polarization and the antenna15for horizontal polarization are selected for signal reception based on the polarization directions of signals to be transmitted/received. Setting the combination of antennas to the initial setting state can shorten the set time at the time of activation or can ensure previous setting in consideration of the characteristic unique to the device.

The sensor8is not limited to the type which detects the inclination of the terminal0, and may be of a type which can detect an arbitrary amount of variation in the communication environment of the terminal0. As one specific example, a speed sensor for a vehicle, a range sensor therefor, or the like may be configured as an external sensor8and data indicative of the detection result may be transferred to the control unit6when the terminal0is mounted to the vehicle. The control unit6may execute a process of determining whether a predetermined amount of variation in the communication environment of the terminal0is equal to or less than a predetermined reference value, or is greater than the reference value. In addition, the setting of the cycle of changing the combination of antennas to be used may be varied according to whether the predetermined amount of variation in the communication environment of the terminal0has exceeded the reference value or not. For example, the control unit6should vary the setting of the cycle of executing the process as shown in, for example,FIG. 6,FIG. 9orFIG. 10according to whether the predetermined amount of variation in the communication environment of the terminal0has exceeded the reference value or not. That is, regardless of the case where the combination of antennas to be used is changed based on the physical configurations of the individual antennas, or the case where the combination of antennas to be used is changed based on the result of detecting the reception quality, the changing cycle should be varied according to a predetermined amount of variation in communication environment.

The following operation may take place as one example of such an operation of varying the cycle of changing the antenna configuration based on a predetermined amount of variation in communication environment. When the amount of variation detected is equal to or less than the reference value and there is a little change in communication environment, for example, the cycle of changing the antenna configuration is set to a predetermined first cycle. When the amount of variation detected exceeds the reference value to show a large change in communication environment, on the other hand, the cycle of changing the antenna configuration is set to a second cycle shorten than the first cycle. Accordingly, when there is a little change in the communication environment of the terminal0(e.g., when the moving speed of the terminal0is slow), the frequency of executing the process of changing the antenna configuration can be reduced to prevent the dissipation power from increasing. When there is a large change in the communication environment of the terminal0(e.g., when the moving speed of the terminal0is fast), the frequency of executing the process of changing the antenna configuration can be increased to quickly cope with the varying communication environment and change the antenna configuration, so that a satisfactory communication state can be maintained.

As one example of the operation of varying the cycle of changing the antenna configuration based on a predetermined amount of variation in communication environment, the amount of variation which has been detected regularly, for example, may be recorded, and the setting of the cycle of changing the antenna configuration may be varied according to the characteristic of the time-dependent change. When a time-dependent change in the amount of variation detected is equal to or less than the reference value and the communication environment is changing by substantially a constant change, for example, the cycle of changing the antenna configuration is set to a predetermined third cycle. When the time-dependent change in the amount of variation detected exceeds the reference value so that the communication environment is changing by a random change, on the other hand, the cycle of changing the antenna configuration is set to a fourth cycle longer than the third cycle. That is, when the time-dependent change in the amount of variation in the communication environment of the terminal0is large and the amount of variation in the moving distance, the moving direction or the like is changing at random, the frequency of executing the process of changing the antenna configuration is reduced. This can prevent frequent changes between specific (e.g., two or three) antenna configurations, such as the antenna configuration returning to the original antenna configuration after being changed to another antenna configuration, thus preventing an increase in dissipation power. When there is a little change in the amount of variation in the communication environment of the terminal0and the amount of variation in the moving distance, the moving direction or the like is changing substantially constantly, the frequency of executing the process of changing the antenna configuration is increased. This makes it possible to quickly cope with the varying communication environment and change the antenna configuration, thereby maintaining a satisfactory communication state.

According to the invention, as described above, when antennas whose quantity is equal to or less than the quantity of antennas of a base station to be communicated are selected to carry out spatial-multiplexing based communication, the setting is made to select a combination of antennas with low correlation, and stop power supply to the RF units which corresponds to the antennas which are not selected, thereby reducing the load on the signal processing unit. This makes it possible to change the antenna configuration to the one which can provide a satisfactory spatial-multiplexing based communication state while reducing the dissipation power, thereby improving the convenience (user-friendliness) and stability of the radio communication apparatus.

To select antennas with low correlation, a combination of antennas to be used should be selected based on the physical configurations of the individual antennas, as in the case of selecting a combination of antennas whose inter-antenna distance becomes maximum or the case of selecting a combination of antennas which transmit/receive radio signals whose polarization directions differ from one another. This can permit the antenna configuration to be changed flexibly and provide a satisfactory spatial-multiplexing based communication state. To specify a combination of antennas with low correlation according to the physical configurations of the individual antennas, the reference signal for measurement which has been transmitted from one antenna may be received at other antennas, and the level of receiving the reference signal, the phase thereof, the reception quality and the like may be measured.

A combination of antennas to be used may be changed based on the operational state of the radio communication apparatus, such as whether the amount of data to be communicated is large or small, or the remaining amount of the battery is large or small. This makes it possible to reduce the quantity of antennas to be used and the loads on the RF unit and the signal processing unit, thereby preventing the dissipation power from increasing, when the amount of data to be communicated is small, or when the remaining amount of the battery is small.

The invention is not limited to the foregoing embodiment, and various modifications and applications can be made thereto. For example, the foregoing description of the embodiment has been given of the case the RF unit31is enabled while the RF unit32is disabled when the quantity of antennas in a base station is two. However, the invention is not limited to this case, and even when the quantity of antennas in a base station is two, both of the RF units31and32may be enabled so that the RF unit32and the signal processing unit5ensure simultaneous use with another network system (e.g., UMTS, CDMA, HRPD, EvDO, GPS, or Bluetooth), monitoring, handover, or the like. To realize such an operation, the RF unit31, the RF unit32and the signal processing unit5should be configured by a multi-mode IC capable of coping with plural types of network systems.

The following will describe connection to another network system. In this example, the terminal0uses the antenna11, and selectively uses one of the antenna12, the external antenna13and the external antenna14. It is assumed that the combination of the antenna11and the antenna12is selected and data communication is carried out using the RF unit31and the signal processing unit5. At this time, signal processing for executing communication in another network system is performed by the RF unit32or the like using the external antenna13and the external antenna14which are not unused.

As a specific example, the RF unit32may execute signal processing for malting a voice call using the CDMA. This can permit simultaneous execution of data communication using the LTE and a voice call using the CDMA, thus improving the convenience of the terminal0. The RF unit32has two processing circuits which are capable of frequency-converting two high-frequency signals. When communication is feasible in another network system different from the LTE using only one processing circuit, an antenna (e.g., external antenna14) whose inter-antenna distance becomes physically maximum as viewed from the antenna that is using the LTE should be selected as an antenna to be used Apparently, even when communication is carried out in a plurality of network systems, antennas with low correlation among the individual network systems are selected to minimize the influence on the communication in the network systems, thereby ensuring satisfactory communication.

Other network systems which are used with the LTE may be given priority levels, so that a network system to be used can be set properly according to various situations. Given that network systems to be used are set with different priority levels according to the time, place, moving speed, etc. beforehand, for example, it is possible to shorten the connection delay and stabilize communication. When using another network system significantly degrades the existing communication performance provided by the LTE, the procedure to connect to another network system may be interrupted.

When LTE-based communication is carried out with the combination of the antennas11and12selected, the external antenna13and the external antenna14which are not used, and the RF unit32may be used to acquire cell information needed to select a cell again. When the current cell registered in the terminal0is not optimal, it is necessary to select a cell again. In this case, various measurements and decisions on the states of peripheral cells are made so that a certain interruption time (delay time) is generated by re-establishment of a link, random access and the like. According to the LTE, when reselection of a cell is performed without the current cell's fulfilling a predetermined decision criterion, a maximum time of 100 ms is needed.

To cope with it, cell information needed for re-selection of a cell is acquired prior to the re-selection process, and the priority levels of cells are determined so as to shorten the time (interruption time) needed to resume communication through re-establishment of a link or the like. As one example, the priority levels of cells should be applied to re-selection of a cell using the RF unit31or the like while LTE-based communication is taking place. As another example, the communication operation may be changed over in such a way that communication is started using the RF unit32or the like according to the priority levels of cells based on the cell information acquired using the RF unit32or the like, and the operation of the RF unit31is stopped (disabled).

The external antenna13and the external antenna14according to the foregoing embodiment need not be configured as dedicated external antennas, but may be mounted to, for example, a cradle9as shown inFIG. 12. The connection of the external antenna13or the external antenna14with the terminal0may be established when the terminal0is held into the cradle9which may be is used to charge and set the terminal0and perform communication therewith, e.g., when a connector91is fitted into the connector unit7.

According to the embodiment, the terminal0has a 4-line configuration to be able to use four antennas at a maximum and have two 2-line RF units (RF unit31and RF unit32). However, the invention is not limited to this configuration, and the maximum quantity of antennas and the number of lines of the transmission/reception circuits, the quantity thereof, and so forth can be optionally set according to the specifications for executing spatial-multiplexing based communication. For example, the terminal0may have an 8-line configuration including eight 1-line RF units, or an 8-line configuration including a single 8-line RF unit.

The invention can be worked out using a computer that controls not only a dedicated radio communication apparatus, but also an ordinary radio communication apparatus which performs spatial-multiplexing based communication. That is, a program for allowing the computer that controls a radio communication apparatus to function as the foregoing components to execute the foregoing processes may be recorded on a predetermined recording medium so that a microprocessor such as a CPU reads out and executes the program to allow the computer to function as the radio communication apparatus according to the embodiment. Such a program may be recorded in a computer readable recording medium, such as a FD, CD, DVD, MO or IC memory, for distribution. Further, the program may be stored in a file system included in an FTP (File Transfer Protocol) server or the like provided on an electric communication network such as the Internet, and may be downloaded into a computer in the form of a signal superimposed on a carrier wave.