Radio apparatus, and method and program for controlling spatial path

Abstract

A PDMA terminal establishes communication by forming a plurality of spatial paths to another single radio apparatus. A plurality of antennas constituting an array antenna are divided into a plurality of subarrays corresponding to the plurality of spatial paths respectively. An adaptive array processing unit can perform an adaptive array processing for each of the plurality of subarrays. A memory stores in advance information on the number of antennas associated with the number of spatial paths that can be formed by the array antenna. A control unit controls a processing to transmit possible multiplicity information to another radio apparatus at a prescribed timing.

Description

RELATED APPLICATIONS

(interference power)=Σ|e(t)|/T
where T represents an observation time (or reference signal length).

With the above-described configuration as well, the communication quality for each path can be ascertained in terms of an amount of interference, and an effect as in the second embodiment can be obtained.

Operation in Second Embodiment or First Variation of Second Embodiment

FIG. 7 is a flowchart showing a flow in adaptive control of the number of paths set in PDMA terminal 2000 in the second embodiment described in connection with FIG. 5 or PDMA terminal 2200 in the first variation of the second embodiment described in connection with FIG. 6.

In the following, an operation of PDMA terminal 2000 in the second embodiment will basically be described, and subsequently, difference from the operation of PDMA terminal 2000 will be described with respect to an operation of PDMA terminal 2200 in the first variation of the second embodiment.

Referring to FIG. 7, first, terminal 2000 notifies base station CS1 of the number of antenna elements N in the terminal or the maximum number of paths P_MAX (step S100).

In terminal 2000, the total N antennas are used to form one subarray, and one path is set for communication (step S102).

In succession, in terminal 2000, communication quality is evaluated by the FER for each path. It is determined whether FERs of all paths are equal to or smaller than a prescribed threshold value, whether the number of paths that can be set has not yet been attained, and whether or not the communication speed is insufficient (step S104).

Here, the expression that “communication speed is insufficient” means that, when an amount of data to be transferred is compared with the current communication speed, transfer is not completed in a sufficiently short period of time in terminal 2000 with respect to a processing of an application during execution, for example.

When it is determined in step S104 that, with regard to the communication quality for each path and the number of paths that can be set, the number of paths can further be increased and the communication speed is insufficient, notification that an increase in the number of paths P by 1 is desired is transmitted from terminal 2000 to base station CS1 (step 106).

Then, when terminal 2000 receives permission for setting from base station CS1 (step S108), terminal 2000 increases the number of paths to be set by 1. In response, terminal 2000 selects P (P=P+1) subarrays for communication (step S110), and the processing returns to step S104.

On the other hand, when it is determined in step S104 that the communication status is poor or the communication speed is sufficient, or when permission for setting from the base station is not received in step S108, communication is performed with the current number of paths for a prescribed time period (step S112), and the processing returns to step S104.

With the above-described processing, while the number of paths to be set for multi-input multi-output communication is adaptively modified, communication between base station CS1 and terminal 2000 can be established. While maintaining excellent communication quality and excellent communication speed, communication in the MIMO scheme can be attained.

It is to be noted in FIG. 7 that the number of antennas is in principle divisible by the number of paths designated by the base station.

In other words, the number of antennas in the antenna set (subarray) transmitting/receiving an identical signal to be set is obtained by dividing the total number of antennas by the number of paths to be set.

For example, when a terminal has a total of 4 antennas and two paths are set, two pairs (subarrays) each formed with two antennas are prepared.

Then, each subarray performs transmission/reception in each path.

In an operation of terminal 2200 in the first variation of the second embodiment, in step S104, the communication quality of the path is evaluated not based on the FER value for each path but based on the amount of interference for each path.

Second Variation of Second Embodiment

In a second variation of the second embodiment described below, unlike FIG. 7, a method of adaptive control of the number of paths to be set, which is applicable even when the number of paths designated by the base station cannot divide the number of antennas, will be described.

Such an operation can also be processed in terminal 2000 and terminal 2200.

FIG. 8 is a flowchart showing a method of adaptive control of the number of paths to be set with regard to terminal 2000 in the second variation of the second embodiment.

Referring to FIG. 7, terminal 2000 notifies base station CS1 of the number of antenna elements N in the terminal. Alternatively, the maximum number of paths P_MAX may be notified (step S200).

In terminal 2000, one antenna is used to set one path (the number of paths P is set to 1) for communication (step S202).

In succession, in terminal 2000, it is determined whether FERs of all paths on terminal side are equal to or smaller than a prescribed threshold value, that is, the communication status is determined to be so excellent as to allow increase in the number of paths, whether the current number of paths has not yet reached the number of paths that can be set, whether or not the communication speed is insufficient, and whether or not an antenna element which is not yet allocated to the path is present (step S204).

When the conditions in step S204 are satisfied, notification that increase in the number of paths P by 1 is desired is transmitted from terminal 2000 to base station CS1 (step S206).

When terminal 2000 receives permission for setting from base station CS1 (step S208), terminal 2000 increases the number of paths to be set by 1 (P←P+1), and P antennas are selected to start communication (step S210), and the processing returns to step S204.

When the conditions in step S204 are not satisfied, or when permission for setting from base station CS1 is not received in step S208, whether or not an antenna which is not set for a path is present is determined (step S212). When an antenna which has not been set is remaining, one antenna element is further allocated to a path which is determined to have attained a quality lower than a prescribed level, so as to form a subarray (step S214).

In succession, communication is performed with the current number of paths P for a prescribed time period (step S216), and the processing returns to step S204.

On the other hand, when there is no remaining antenna which has not been set for a path in step S212, the processing moves to step S216.

In other words, in the second variation of the second embodiment, the number of antennas for each subarray is determined in the following manner. One antenna is first allocated to each set path. Then, among remaining antennas, an additional antenna is sequentially allocated to each path in accordance with the path identifier or the antenna identifier while determining necessity for the increase in the number of antennas. For example, when all subarrays are provided with two antennas each, remaining antennas are again allocated. With such a process, each subarray performs transmission/reception in each path.

With above-described allocation of antennas to each path, the optimal number of antennas can be arranged for each path even when the number of antennas is not necessarily divisible by the number of paths which perform transmission/reception between base station CS1 and terminal 2000. Communication in the MIMO scheme is thus enabled.

In an operation of terminal 2200 in the first variation of the second embodiment, in step S104, the communication quality of the path is evaluated not based on the FER value for each path but based on the amount of interference for each path.

Third Embodiment

In the first and second embodiments, an arrangement of antennas used in the MIMO scheme has not been limited in particular.

In a third embodiment, a configuration in which further improvement in the communication quality is attained by employing a specific arrangement of a plurality of antennas will be described.

FIG. 9 shows a configuration in which four antennas #1 to #4 are arranged for a notebook personal computer 3000.

Antennas #1 and #3 are arranged on opposing ends of a display 3010 of notebook personal computer 3000, and antennas #2 and #4 are arranged on opposing ends of a keyboard. Here, in such a spatial arrangement of the antennas, antennas #1 and #3 operate as antennas in an identical plane of polarization (vertical polarization), while antennas #2 and #4 operate as antennas in an identical plane of polarization (horizontal polarization).

FIG. 10 is a conceptual view illustrating an arrangement of four antennas attached to a mobile phone terminal 4000.

When a plurality of types of antenna elements are incorporated in mobile phone terminal 4000, as shown in FIG. 10, antennas #1 and #3 are arranged longitudinally and in parallel on opposing ends of a display 4010 so as to have an identical plane of polarization (vertical polarization), while antennas #2 and #4 are arranged so as to have an identical plane of polarization (horizontal polarization) with display 4010 and operation buttons 4020 interposed.

Though not specifically limited, antennas #1 and #3 arranged longitudinally may be whip antennas, while antennas #2 and #4 may be inverted-F shaped antennas.

In addition, antennas of the same type such as a chip antenna or a patch antenna may be arranged so as to form a set with respect to the identical plane of polarization.

In the above-described configuration, selection of antennas for forming a subarray may be made such that antennas with the identical plane of polarization form an identical subarray. Here, when a set of antennas constituting a subarray is selected in the second embodiment or the first variation of the second embodiment, or when a subarray is formed by sequentially allocating remaining antennas as described in the second variation of the second embodiment, antennas with the identical plane of polarization are allocated to an identical subarray.

By constituting one subarray with antennas having the identical plane of polarization in such a manner, the following effect can be obtained.

Under a condition of normal radio wave propagation, a path of an incoming radio wave tends to be spatially different if the plane of polarization is different. On the other hand, in order to obtain array gain with an adaptive array, sufficient array gain cannot be obtained if there is a great level difference between reception signals.

Therefore, in selecting a subarray when two subarrays are both available for communication, antennas which have the identical plane of polarization, that is, antennas which are expected to have approximately the same reception levels are selected, whereby sufficient array gain can be obtained.

In other words, constituting a subarray with antennas with the identical plane of polarization is particularly effective in an example in which variation in the reception levels of four antennas is observed due to different planes of polarization, though the reception levels thereof are all higher than the minimum reception level.

FIG. 11 is a flowchart illustrating an operation when antennas having an identical plane of polarization are selected for a subarray.

Referring to FIG. 11, terminal 3000 (or terminal 4000) notifies base station CS1 of the number of antenna elements N (step S300).

In succession, the number of paths M set by base station CS1 is sent back, which is received by mobile terminal 3000 (or terminal 4000) (step S302).

In mobile terminal 3000 (or terminal 4000), the number of antennas N is divided by the number of paths M, and the resultant value n is set as the number of antenna elements in a subarray. Here, antennas having the identical plane of polarization are selected as antenna elements constituting an identical subarray (step S504).

If the number of antennas with the identical plane of polarization is not an integer multiple of the number of antennas n in a subarray, remaining antennas may be allocated to other subarrays.

Then, a channel adapted to the multi-input multi-output scheme (MIMO channel) is set for each subarray between mobile terminal 3000 (or terminal 4000) and base station CS1 for communication (step S306).

With the above-described allocation process of the antennas, communication is achieved by a subarray constituted of a set of antennas implemented by preferentially selecting antennas with the identical plane of polarization for each spatial path.

FIG. 12 is a flowchart illustrating another method of allocating a plurality of antennas in a terminal to each path.

Referring to FIG. 12, first, terminal 3000 (or terminal 4000) notifies base station CS1 of the number of antenna elements N (step S400).

In succession, the number of paths M set by the base station is sent back, which is received by mobile terminal 3000 (or terminal 4000) (step S402).

Mobile terminal 3000 (or terminal 4000) includes an antenna group having x types (x≥M) of planes of polarization. Here, M antennas are selected and allocated to subarrays respectively such that corresponding planes of polarization are not overlapped with one another (step S404).

In succession, a value of a variable na is set to 1 (step S406).

In addition, whether an unallocated antenna is present or not is determined. When an unallocated antenna is present (step S408), the unallocated antenna is allocated to a subarray having na antennas. Here, the unallocated antenna is allocated such that the plane of polarization thereof is identical to that of the antenna already contained in the subarray (step S410).

Next, it is determined whether there is no longer an antenna that can be allocated on the basis of the identical plane of polarization. If an antenna to be allocated on that basis is still present (step S412), the value of variable na is incremented by 1 (step S414), and the processing returns to step S408.

On the other hand, when there is no antenna that can be allocated on the basis of the identical plane of polarization (step S412), an unallocated antenna is allocated to a subarray having na antennas (step S416). Then, the value of variable na is incremented by 1 (step S414), and the processing returns to step S408.

When there is no longer an unallocated antenna in step S408, an MIMO channel is set for each subarray for communication (step S420).

With the above-described allocation process of the antennas as well, communication is achieved by a subarray constituted of a set of antennas implemented by preferentially selecting antennas with the identical plane of polarization for each spatial path.

Fourth Embodiment

The third embodiment has described an example in which antennas having the identical plane of polarization constitute a subarray.

Depending on a communication status, however, enhanced transmission/reception performance can be obtained when the subarray is constituted of antennas having different planes of polarization.

Such an example will be described in the following.

In the third embodiment, in selecting antennas for forming a subarray, for example, a set of antennas can be selected so that antennas having reception levels or antenna gains proximate to one another are located in an identical subarray. Alternatively, the reception level is measured for each antenna in advance and antennas are ranked in terms of the reception level. The antennas can be allocated to a subarray so that antennas in a high rank in terms of the reception level are not unevenly distributed in a specific subarray.

Here, when a set of antennas constituting a subarray is selected in the second embodiment or the first variation of the second embodiment, or when a subarray is formed by sequentially allocating remaining antennas as described in the second variation of the second embodiment, antennas having reception levels or antenna gains proximate to one another are allocated to an identical subarray.

Under a condition of normal radio wave propagation, a path of an incoming radio wave will spatially be different if the plane of polarization is different. Accordingly, if something crosses the propagation path of the radio wave between the terminal and the base station, a phenomenon called “shadowing” in which reception power in a communication path abruptly falls may occur, when the communication path is formed solely by antennas with the identical plane of polarization.

If shadowing occurs, in some cases, the reception power in the path may abruptly fall as low as a level at which communication is difficult. In such a case, communication in that path may be disconnected. Therefore, in a communication environment in which shadowing often takes place, it is desirable to locate antennas with different planes of polarization in the identical subarray. With such a configuration of a subarray, even if the reception level of an antenna with a specific plane of polarization falls to a level disabling communication, an antenna with a different plane of polarization can maintain a level allowing reception. Accordingly, communication in all communication paths can be maintained.

As such, in control unit CNP, it is possible to selectively employ a method of constituting a subarray as described in the third embodiment and a method of constituting a subarray described below, in accordance with a degree of stability in path multiplicity and by comparing a current communication status and an allocation state of antennas to a subarray.

FIG. 13 is a schematic block diagram illustrating a configuration of a PDMA terminal 5000 capable of selecting antennas constituting a subarray based on information on the reception level or the plane of polarization as described above.

PDMA terminal 5000 is different from PDMA terminal 1000 in the first embodiment shown in FIG. 1 in that a reception level measurement device 30 capable of measuring a reception level for each antenna with respect to reception signals from respective antennas #1 to #4 is provided, a measurement result of the reception level measurement device is provided to control unit CNP, and control unit CNP causes memory MMU to store information on the reception level.

In addition, memory MMU stores not only the measurement result of the reception level, but also information on the plane of polarization of the antenna and information on occurrence of communication disruption seemingly caused by shadowing. In response, a subarray selector 32 notifies control circuit CNP of a set of antennas to be selected as a subarray, from the information on the plane of polarization of the antenna, the information on shadowing or the like stored in the memory.

In other words, reception level measurement device 30 measures the reception level for each antenna. Control circuit CNP measures reception level data for each antenna for a prescribed period of time, and measures “shadowing information” such as duration or frequency of a case in which reception is disabled for each antenna. Such results are stored in memory MMU. Subarray selector 32 selects a pair (or a set) of antennas to be selected as a subarray, from the shadowing information and the information on the plane of polarization in each antenna in memory MMU.

FIG. 14 is a flowchart illustrating an operation of control circuit CNP and subarray selector 32 among the operations described above.

First, control circuit CNP measures the reception level for each antenna in reception level measurement device 30, and measures duration or frequency of a case in which reception is disabled (shadowing information) for each antenna. Such results are stored in memory MMU (step S500).

Then, control unit CNP determines whether or not shadowing exceeds a prescribed reference (step S502).

Here, though not limited in particular, “a prescribed reference” refers to a determination reference such as whether or not shadowing lasting at least for a prescribed duration (0.5 second) occurs with a frequency more than a prescribed level (two times/60 seconds), for example.

When it is determined that shadowing exceeds the prescribed reference in step S302, subarray selector 32 selects antennas with different planes of polarization as an identical subarray (step S504).

On the other hand, when it is determined that shadowing does not exceed the prescribed reference in step S502, subarray selector 32 selects antennas with an identical plane of polarization as an identical subarray (step S506). Selection of a subarray in this case may follow the procedure described with reference to FIG. 11 or 12.

FIG. 15 is a flowchart illustrating a processing for allocating antennas in terminal 5000 to each path based on a reception level, when antennas having different planes of planarization are selected as an identical subarray in step S504 shown in FIG. 14.

First, terminal 5000 notifies base station CS1 of the number of antenna elements N (step S600).

In succession, terminal 5000 is notified of the number of paths M to be set from base station CS1 (step S602).

Terminal 5000 includes an antenna group having x types (x≥M) of planes of polarization. Terminal 5000 ranks the antennas in accordance with reception sensitivity (levels of signals from a base station to be connected). Then, antennas are allocated to each subarray so that antennas in a high rank in terms of the reception sensitivity are not unevenly distributed in a specific subarray, that is, an average of the reception levels is proximate to each other in each subarray, for example (step S604).

An MIMO channel is set for each subarray constituted in the above-described manner for communication (step S606).

With the method described above, stable communication adapted to the MIMO scheme can be achieved even in the communication environment where shadowing frequently takes place.

Here, antennas having the reception level or the reception sensitivity proximate to each other may preferentially be allocated to an identical subarray in step S604 so that the reception level or the reception sensitivity of antennas are balanced in forming a spatial path.

Fifth Embodiment

The third and fourth embodiments have described the arrangement of the antennas in a terminal and how antennas are allocated to each subarray in accordance with the communication status in initiating communication in the MIMO scheme.

Meanwhile, even after communication in the MIMO scheme is once started, it is also possible to control communication in the MIMO scheme adaptively in accordance with the communication status, by changing antennas allocated to a subarray in accordance with a change in the communication status in each spatial path.

Here, the communication status in each spatial path may refer to the FER for each spatial path described with reference to FIG. 5, or an amount of interference for each spatial path described in connection with FIG. 6, or alternatively, change with time in the reception level for each antenna described with reference to FIG. 13.

FIG. 16 is a flowchart illustrating another method of allocating each antenna to each path based on the reception level.

For example, when it is determined based on FER or the interference value that the communication quality in a path PA has deteriorated during communication (step S700), quality in a path other than path PA is checked, and whether or not the number of antenna elements in a subarray corresponding to that other path can be reduced is determined (step S702).

When a path capable of maintaining quality even if the number of antenna elements is reduced is present (step S704), one antenna in a subarray corresponding to the path capable of maintaining quality even if the number of antenna elements is reduced is selected.

A selection reference here is chosen from a plurality of references below by setting priority among them in advance. Alternatively, one of the plurality of references below may be chosen as a reference.

• • (1) An antenna having a plane of polarization identical to that of an antenna already contained in the target subarray is selected.
  • (2) An antenna having a reception level proximate to that of an antenna already contained in the target subarray is selected.
  • (3) An antenna having reception sensitivity proximate to that of an antenna already contained in the target subarray is selected.
  • (4) An antenna is selected randomly or in the order of antenna identifier.

An antenna selected in such a manner is incorporated in the subarray corresponding to the path in which quality has deteriorated (step S706).

Alternatively, when there is no path for which the number of antennas can be reduced in step S704, the processing in step S706 is not performed but communication is maintained in current state.

FIG. 17 is a conceptual view illustrating a configuration before and after a combination of antennas forming a path is changed in the above-described manner.

Before changing the combination, antennas #1 and #3 form one path, while antennas #2 and #4 form one path. Here, antennas #1 and #3 may have an identical plane of polarization, while antennas #2 and #4 may have an identical plane of polarization. Alternatively, a configuration in which a set of antennas #1 and #3 and a set of antennas #2 and #4 form subarrays respectively may minimize a difference in the reception levels between the two sets.

Here, it is assumed that deterioration in the communication quality in path PA formed by antennas #2 and #3 has been determined.

FIG. 18 is a conceptual view illustrating a state after a combination in a subarray is changed as a result of detection of deterioration in communication quality as shown in FIG. 3 17.

As shown in FIG. 18, for example, antenna #3 is incorporated in a path PB, antennas #2, #3 and #4 form one path, and antenna #1 alone performs transmission/reception in path PA.

In this manner, even if the communication quality is deteriorated, the number of antennas constituting the subarray is changed so as to maintain desired communication quality, thereby enabling transmission/reception in the MIMO scheme.

Here, a processing such as an adaptive array processing, a modulation processing, a demodulation processing, or a control processing performed by any PDMA terminal described above can be performed, individually or as an integrated processing, with software by means of a digital signal processor.

As described above, according to the present invention, in a terminal or a base station in a mobile communication system adapted to the MIMO scheme, communication in each spatial path is established by antennas divided into subarrays. As the antennas corresponding to each path or the number of paths are adaptively controlled in accordance with a communication status, stable communication in the MIMO scheme can be achieved.

INDUSTRIAL APPLICABILITY

The present invention is useful in a mobile communication system adapted to the MIMO scheme, because stable communication can be achieved by adaptively controlling the antennas corresponding to each path or the number of paths in accordance with a communication status, in a terminal or a base station in a mobile communication system adapted to the MIMO scheme.

Claims

1. A radio apparatus capable of communicating with another radio apparatus by forming a plurality of spatial paths therebetween, the radio apparatus comprising:

an adaptive array unit capable of performing adaptive array processing on signals corresponding to a plurality of antennas, respectively;

a storage unit which stores beforehand a value indicating possible multiplicity associated with the number of spatial paths formable by said adaptive array unit; and

a control unit which controls a processing of transmitting the value indicating possible multiplicity to the another radio apparatus at a predetermined timing.

2. A radio apparatus according to claim 1, wherein said control unit controls the processing of transmitting the value indicating possible multiplicity to the another radio apparatus in such a manner that the predetermined timing comes before a communication.

3. A radio apparatus according to claim 1, wherein said storage unit stores beforehand the number of spatial paths capable of attaining normal reception, as the value indicating possible multiplicity.

4. A radio apparatus capable of communicating with another radio apparatus by forming a plurality of spatial paths therebetween, the radio apparatus comprising:

a plurality of antennas constituting an array antenna;

an adaptive array unit capable of performing adaptive array processing on signals corresponding to the plurality of antennas, respectively;

a storage unit which stores beforehand a value indicating possible multiplicity associated with the number of spatial paths formable by said adaptive array unit; and

a control unit which controls a processing of transmitting the value indicating possible multiplicity to the another radio apparatus at a predetermined timing.

5. A radio apparatus according to claim 4, wherein said control unit controls the processing of transmitting the value indicating possible multiplicity to the another radio apparatus in such a manner that the predetermined timing comes before a communication.

6. A radio apparatus according to claim 4, wherein said storage unit stores beforehand the number of spatial paths capable of attaining normal reception, as the value indicating possible multiplicity.

7. A radio apparatus capable of multiplex communication with another radio apparatus by forming a plurality of spatial paths therebetween, the radio apparatus comprising:

an adaptive array unit capable of performing adaptive array processing on signals corresponding to a plurality of antennas, respectively, wherein said plurality of antennas comprise a plurality of antenna subarrays, and wherein the adaptive array unit is capable of changing a combination of the plurality of antennas allocated to each of the antenna subarrays;

a storage unit which stores prior to a request to establish a link channel with the another radio apparatus a value indicating a number of available spatial paths formable by said adaptive array unit for multiplex communication; and

a control unit which controls a process of transmitting the value to the another radio apparatus in the request to establish the link channel with said another radio apparatus, wherein the control unit is configured to allocate at least one antenna of the plurality of antennas to each of the antenna subarrays in a number corresponding to a number of spatial paths notified by the another radio apparatus.

8. The radio apparatus according to claim 7, wherein the value indicating the number of available spatial paths is less than a number of the plurality of antennas.

9. A radio apparatus capable of multiplex communication with another radio apparatus by forming a plurality of spatial paths therebetween, the radio apparatus comprising:

an adaptive array unit capable of performing adaptive array processing on signals corresponding to a plurality of antennas, respectively;

a storage unit which stores prior to a request to establish a link channel with the another radio apparatus a value indicating a number of available spatial paths formable by said adaptive array unit for multiplex communication; and

a control unit which controls a process of transmitting the value to the another radio apparatus in the request to establish the link channel with said another radio apparatus, wherein the control unit is configured to allocate at least one antenna of the plurality of antennas to each configuration of the plurality of antennas in a number corresponding to a number of spatial paths notified by the another radio apparatus.

10. The radio apparatus according to claim 9, wherein the value indicating the number of available spatial paths is based on one or more configurations of the plurality of antennas.

11. A radio apparatus capable of communicating with another radio apparatus by forming a plurality of spatial paths therebetween, the radio apparatus comprising:

a plurality of antennas constituting a plurality of antenna subarrays;

an adaptive array unit capable of performing adaptive array processing on signals corresponding to the plurality of antenna subarrays, respectively, and wherein the adaptive array unit is capable of changing a combination of the plurality of antennas allocated to each of the antenna subarrays;

a storage unit which stores prior to a request to establish a link channel being sent to the another radio apparatus a value indicating a number of available spatial paths formable by said adaptive array unit for multiplex communication; and

a control unit which controls a process of transmitting the value to the another radio apparatus in the request to establish the link channel with said another radio apparatus, wherein the control unit is configured to allocate at least one antenna of the plurality of antennas to each of the antenna subarrays in a number corresponding to a number of spatial paths notified by the another radio apparatus.

12. The radio apparatus according to claim 11, wherein the value indicating the number of available spatial paths is less than a number of the plurality of antennas.

13. A radio apparatus capable of multiplex communication with another radio apparatus by forming a plurality of spatial paths therebetween, the radio apparatus comprising:

a plurality of antennas constituting an array antenna;

an adaptive array unit capable of performing adaptive array processing on signals corresponding to the plurality of antennas, respectively;

a storage unit which stores prior to a request to establish a link channel being sent to the another radio apparatus a value indicating a number of available spatial paths formable by said adaptive array unit for multiplex communication; and

a control unit which controls a process of transmitting the value to the another radio apparatus in the request to establish the link channel with said another radio apparatus, wherein the control unit is configured to allocate at least one antenna of the plurality of antennas to each configuration of the plurality of antennas in a number corresponding to a number of spatial paths notified by the another radio apparatus.

14. The radio apparatus according to claim 13, wherein the value indicating the number of available spatial paths is based on one or more configurations of the plurality of antennas.

15. A radio apparatus capable of multiplex communication with another radio apparatus by forming a plurality of spatial paths therebetween, the radio apparatus comprising:

an adaptive array unit capable of performing adaptive array processing on signals corresponding to a plurality of antennas, wherein the plurality of antennas are divided into a plurality of antenna subarrays;

a storage unit which stores prior to a request to establish a link channel with the another radio apparatus a value indicating a number of available spatial paths formable by said adaptive array unit for multiplex communication; and

a control unit which controls a process of transmitting the value to the another radio apparatus in the request to establish the link channel with said another radio apparatus, wherein the control unit is configured to allocate at least one antenna of the plurality of antennas to each of the antenna subarrays in a number corresponding to a number of spatial paths notified by the another radio apparatus.

16. The radio apparatus according to claim 15, wherein the control unit is further configured, subsequent to allocating one antenna of the plurality of antennas to each of the antenna subarrays in a number corresponding to the number of available spatial paths notified by the another radio apparatus, to allocate remaining antennas of the plurality of antennas to each of the antenna subarrays in a prescribed order.

17. The radio apparatus according to claim 15, wherein each of the antenna sub-arrays correspond to one spatial path.

18. The radio apparatus according to claim 15, wherein the adaptive array unit is configured to change a combination of the plurality of antennas allocated to each of the antenna subarrays.

19. The radio apparatus according to claim 18, wherein the radio apparatus further comprises a monitor unit that monitors communication quality for each spatial path during communication, and the control unit is configured to change the number of the plurality of antennas allocated to each of the sub-arrays in accordance with a detection result of the monitor unit.

20. The radio apparatus according to claim 15, wherein the adaptive array unit can change a combination of the plurality of antennas allocated to each of the antenna subarrays to perform said adaptive array processing, said radio apparatus further comprising a monitor unit for monitoring communication quality for each available spatial path during communication, and said control unit changing the number of said plurality of antennas allocated to each said antenna subarray in accordance with a detection result of said monitor unit.

21. The radio apparatus according to claim 15, wherein the value indicating the number of available spatial paths is less than a number of the plurality of antennas.

22. A radio apparatus capable of multiplex communication with another radio apparatus by forming a plurality of spatial paths therebetween, the radio apparatus comprising:

a plurality of antennas constituting an array antenna, wherein said array antenna comprises a plurality of antenna subarrays;

an adaptive array unit capable of performing adaptive array processing on signals corresponding to the plurality of antennas, respectively;

a storage unit which stores prior to a request to establish a link channel being sent to the another radio apparatus a value indicating a number of available spatial paths formable by said adaptive array unit for multiplex communication; and

a control unit which controls a process of transmitting the value to the another radio apparatus in the request to establish the link channel from said radio apparatus to said another radio apparatus, wherein the control unit is configured to allocate at least one antenna of the plurality of antennas to each of the antenna subarrays in a number corresponding to a number of spatial paths notified by the another radio apparatus.

23. The radio apparatus according to claim 22, wherein the value indicating the number of available spatial paths is less than a number of the plurality of antennas.