The embodiments discussed herein are related to a wireless communication system, a base station, a relay station, and a wireless communication method.
A relay station is conventionally used in wireless communication systems. Relay stations include non-regenerating types that amplify and transmit received signals, and regenerating types that amplify and transmit received signals after first decoding the signal and regenerating the original data. Among mobile communication systems, a system is known that can determine communication paths capable of realizing high speed communication by multi-hop. For example, a mobile communication system includes a communication path determining unit that based on the interference level of the signals respectively received by a relay station and a base station, which form a communication path between communicating stations, determines a communication path that offers the fastest communication speed or that satisfies a specified line quality (see, for example, International Publication Pamphlet No. 2003/101132).
With conventional regenerating type relay stations, since signals subject to amplification can be controlled according to user, the source of interference can be controlled. However, the decoding process takes time and consequently regenerating type relay stations have a problem in that a greater delay occurs than with non-regenerating type relay stations. Meanwhile, with conventional non-regenerating type relay stations a problem arises in that since amplification is performed at a constant gain factor for all bands, the relay station may become a source of interference.
According to an aspect of an embodiment, a wireless communication system includes a calculator that calculates the number of mobile stations for which amplification is to be performed or the rate of mobile stations for which amplification is to be performed among all mobile stations; an allocator that based on a calculation result obtained by the calculator, allocates from among a plurality of bands, one or more bands for performing amplification; and an amplifier that performs amplification with respect to the one or more bands allocated by the allocator. The calculator is included at a base station and the allocator and the amplifier are included at a relay station, or the calculator and the allocator are included at the base station and the amplifier is included at the relay station.
The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.
Preferred embodiments of the present invention will be explained with reference to the accompanying drawings. The invention is not limited by the embodiments below.
In a first embodiment, a base station calculates the number of mobile stations whose signals require amplification at a relay station or the rate of mobile stations whose signals require amplification among all of the mobile station within the cell. Hereinafter, “the number of mobile stations whose signals require amplification at a relay station, or the rate of mobile stations whose signals require amplification among all of the mobile station within the cell” is simplified as “the number of or the rate of mobile stations requiring amplification”. The relay station, based on the number of or the rate of mobile stations requiring amplification, performs amplification with respect to one or more bands among multiple bands.
For example, when the reception state of the wireless signals respectively transmitted from mobile station A6a and mobile station C6c is good, the base station 1 determines that amplification of wireless signals to and from mobile station A6a and mobile station C6c do not require amplification. When the reception state of the wireless signal transmitted from mobile station B6b is poor, the base station 1 determines that wireless signals to and from mobile station B6b require amplification. Therefore, in the depicted example, the number of mobile stations for which amplification is required is one and the rate of mobile stations requiring amplification is ⅓.
As depicted in
According to the first embodiment, since the relay station performs amplification with respect to one or more of the bands, based on the number of or the rate of mobile stations requiring amplification, necessary and sufficient amplification can be performed according to the number of or the rate of mobile stations requiring amplification. In other words, configuration can be such that the relay station does not perform amplification with respect to more bands than is necessary. Therefore, compared to a case where amplification is performed at a constant gain with respect to all of the bands, the relay station can be prevented from becoming a source of interference.
In a second embodiment, the entire active band of the wireless communication system is, for example, divided into sub-bands. In a Long Term Evolution (LTE) system, the active band is, for example, 20 MHz. For an LTE-Advanced system, which is an expansion of LTE, active band on the order of 100 MHz is under investigation. To maintain compatibility between LTE systems and LTE-Advanced systems, for example, making the active band of LTE-Advanced systems a multiple (e.g., 5) of the active band of LTE systems is under investigation. In other words, in an LTE-Advanced, for example, active band on the order of 100 MHz would be divided among five 20 MHz-sub-bands. The second embodiment is applicable to such an LTE-Advanced system. Here, as the second embodiment, an example of application to an LTE-Advanced system will be described.
The base station calculates the number of or the rate of mobile stations requiring amplification. Based on the number of or the rate of mobile stations requiring amplification as calculated by the base station, the relay station, from among the sub-bands, allocates one or more sub-bands for performing amplification. The relay station amplifies input signals of the sub-bands allocated for performing amplification.
The determiner 14 compares mobile station reception quality and a threshold. The determiner 14, for example, determines that amplification is not necessary for a mobile station whose reception quality is equal to or exceeds the threshold. The determiner 14 determines that amplification is necessary for a mobile station whose reception quality does not exceed the threshold. The calculator 15, based on the determination results obtained by the determiner 14, calculates the number of or the rate of mobile stations requiring amplification. The base station 11, via the switch 17 and the antenna 16, gives notification of (broadcasts) the number of or the rate of mobile stations requiring amplification as calculated by the calculator 15. The antenna 16, the switch 17, the measurer 12, table 13, the determiner 14, and the calculator 15, for example, operate as the calculator 3 in the first embodiment.
Table 23 stores correspondence relationships between the number of or the rate of mobile stations requiring amplification and the number of amplifying sub-bands (see
The calculator 24, based on the number of or the rate of mobile stations requiring amplification received by the first receiver 22 and the correspondence relationships indicated in table 23, calculates the number of amplifying sub-bands. The second receiver 25 receives and stores information provided by other non-depicted relay stations. The information provided by the other relay stations, for example, includes information indicating the sub-bands of signals subject to amplification by the respective relay stations. The allocator 26, based on the number of amplifying sub-bands calculated by the calculator 24, allocates from among the sub-bands, sub-bands of the number calculated by the calculator 24. A dynamic allocation method and a random allocation method may be given as examples of the sub-band allocation method.
The dynamic allocation method is an allocation method of allocating, as sub-bands for performing amplification, sub-bands that are not in-use. The sub-bands are allocated based on, for example, information that is received by the second receiver 25 and that indicates the sub-bands of signals subject to amplification by other relay stations. The dynamic allocation method can prevent the relay stations in the cell of the base station and the relay stations in a neighboring cell from amplifying signals of the same sub-bands, thereby preventing interference from occurring. The random allocation method is a method of allocating, as sub-bands for performing amplification, an arbitrary sub-band, without referring to information indicating the sub-bands of signals subject to amplification by other relay stations. The random allocation method facilitates processing at the relay device since the sharing of information indicating the sub-bands of signals subject to amplification does not need to be shared among the relay stations.
Configuration may be such that during operation, the relay station 21 switches between the two allocation methods depending on whether a preliminarily set condition is satisfied. The allocation method of the relay station 21 may be fixed as either one of the allocation methods according to the environment where the relay station 21 is installed. If the allocation method of the relay station 21 is fixed as the random allocation method, the second receiver 25 and the notifier 27 described hereinafter do not operate. Therefore, if the allocation method of the relay station 21 is fixed as the random allocation method, the second receiver 25 and the notifier 27 may be omitted.
The notifier 27 provides to other relay stations and via an antenna 30, information indicating the sub-bands allocated by the allocator 26, i.e., information indicating the sub-bands of the signals subject to amplification at the relay station 21. The amplifier 28 amplifies analog input signals of the sub-bands allocated by the allocator 26. The amplified signal is transmitted via the antenna 30. The antenna 29, the first receiver 22, table 23, the calculator 24, the second receiver 25, and the allocator 26, for example, operate as the allocator 4 in the first embodiment. The amplifier 28, for example, operates as the amplifier 5 in the first embodiment.
The relay station receives the number of or the rate of mobile stations requiring amplification broadcasted by the base station; and based on the number of or the rate of mobile stations requiring amplification and the correspondence relationship of the number of or the rate of mobile stations requiring amplification and the number of amplifying sub-bands, the relay station determines the number of amplifying sub-bands (step S13). The relay station further receives information that is provided by other relay stations and that indicates the sub-bands of signals subject to amplification by the other relay stations (step S14). The relay station, based on the number of amplifying sub-bands determined at step S13 and the information received at step S14 and indicating the sub-bands of signals subject to amplification by the other relay stations, allocates as sub-bands for performing amplification, sub-bands of the number determined at step S13. In other words, the relay station dynamically allocates the amplifying sub-bands (step S15). The relay station provides to the other relay stations, information indicating the amplifying sub-bands allocated at step S15 (step S16). The relay station further amplifies analog input signals of the sub-bands allocated at step S15. In this series of operations, the execution timing of step S14 may be before or after step S13.
According to the second embodiment, effects similar to those of the first embodiment can be obtained. Further, a scheduler provided at the base station, allocates wireless resources of a mobile station, whose reception quality is poor, to sub-bands for which the reception quality has been improved by amplification at a relay station, whereby the reception quality of the mobile station having poor reception quality can be improved. Furthermore, a regenerating type relay station may be used.
In a third embodiment, similar to the second embodiment, the entire active band of the wireless communication system is, for example, divided into sub-bands. As the third embodiment, an example of application to an LTE-Advanced system will be described. The base station calculates the number of or the rate of mobile stations requiring amplification and based on the calculation results, allocates from among the sub-bands, one or more sub-bands for performing amplification. The relay station amplifies input signals of the sub-bands allocated by the base station.
The transceiver 36 transmits to other base stations, information indicating the sub-bands of signals that are subject to amplification by relay stations within the cell of the base station 31. The transceiver 36 receives and stores information that is from other base stations and that indicates the sub-bands of signals that are subject to amplification by the relay stations in the cells of the other base stations. The base stations exchange information through a line for communicating control information. An X2 Control Plane Interface may be given as an example of the line for communicating control information.
The allocator 37, from among the sub-bands, randomly allocates sub-bands of the number calculated by the second calculator 35. Further, the allocator 37, based on the information received by the transceiver 36 and indicating the sub-bands of signals that are subject to amplification by other relay stations, dynamically allocates from among the sub-bands, sub-bands of the number calculated by the second calculator 35. In the case of dynamic allocation, the allocator 37 may allocate from among the sub-bands and in a given order such as descending order of frequency, the sub-bands of signals that are not subject to amplification by the relay station (available sub-bands).
The base station 31, via the switch 17 and the antenna 16, broadcasts information indicating the sub-bands allocated by the allocator 37. Other aspects of the configuration of the base station 31 are similar to those of the second embodiment. The antenna 16, the switch 17, the measurer 12, the first table 32, the determiner 14, and the first calculator 33, for example, operate as the calculator 3 in the first embodiment. The second table 34, the second calculator 35, the transceiver 36, and the allocator 37, for example, operate as the allocator 4 in the first embodiment.
The base station, based on the sub-bands extracted at step S34, determines whether there is a sub-band for which amplification can be performed, i.e., a sub-band of signals that are not being amplified by another relay station (an available sub-band) (step S35). If there is a sub-band for which amplification can be performed (step S35: YES), the base station allocates the sub-band for performing amplification (step S36). Here, the base station may allocate available sub-bands according to a given order, such as in descending order of frequency. If there is no sub-band for which amplification can be performed (step S35: NO), the base station randomly allocates a sub-band for performing amplification (step S37). Random allocation of a sub-band for performing amplification lowers the possibility of the same sub-band being allocated by relay stations within a range of interacting with one another, whereby interference can be prevented from occurring.
When allocation of the sub-band ends, the base station provides to other base stations, information indicating the sub-bands allocated for performing amplification (step S38). The base station further broadcasts the information indicating the sub-bands allocated for performing amplification (step S39). The relay station receives the information that is provided by base station and that indicates the sub-bands allocated for performing amplification, and amplifies analog input signals of the allocated sub-bands (step S40). In this series of operations, the execution timing of step S34 may be before or after step S33, before step S32, or before step S31. Further, the execution timing of step S38 may be before or after step S39, or after step S40.
According to the third embodiment, effects similar to those of the first embodiment can be obtained. Further, similar to the second embodiment, the reception quality of a mobile station having poor reception quality can be improved. Furthermore, a regenerating type relay station may be used. The allocation method of the base station may be fixed to the random method of allocating sub-bands. When the allocation method of the base station 31 is fixed to the random method, the transceiver 36, which performs communication, may be omitted. Further, when the allocation method of the base station 31 is fixed to the random method, steps S34 to S36 and step S38 in the flowchart depicted in
In a fourth embodiment, the relay station of the third embodiment has information related to the mobile stations for which the relay station is to perform amplification. The relay station allocates sub-bands of a number corresponding to the number of mobile stations included in both information related to the mobile stations for which amplification is to be performed by the relay station and information related to mobile stations selected by the base station, as mobile station for which amplification is to be performed.
The first determiner 64 compares mobile station reception quality and a threshold. In general, the closer the mobile station is to the relay station, the better the reception quality is for the mobile station. The first determiner 64, for example, with respect to a mobile station whose reception quality exceeds the threshold, determines that the mobile station is nearby. A mobile station that has been determined to be nearby is a mobile station candidate for which amplification is to be performed by the relay station. The first determiner 64, for example, with respect to a mobile station whose reception quality does not exceed the threshold, determines that the mobile station is not nearby. A mobile station that has been determined to not be nearby is not a mobile station candidate for which amplification is to be performed by the relay station. The generator 65, based on the determination result obtained by the first determiner 64, generates a list of mobile station candidates for which amplification is to be performed by the relay station.
The first receiver 66 is similar to the receiver 42 in the third embodiment. The second receiver 67 receives and stores information that is from the base station and related to mobile stations for which amplification has been determined to be necessary by the base station. The second determiner 68, based on the mobile station candidate list and the information related to the mobile stations for which amplification has been determined to be necessary by the base station, determines whether to perform amplification operations at the relay station. When amplification operations are to be performed at the relay station, the second determiner 68, based on information indicating the sub-bands allocated by the base station, determines the sub-bands for actually performing amplification at the relay station.
For example, when all of the mobile stations for which amplification has been determined necessary by the base station are included in the mobile station candidate list of the relay station, the second determiner 68 determines all of the sub-bands allocated by the base station to be sub-bands for actually performing amplification at the relay station. When a portion of the mobile stations for which amplification has been determined necessary by the base station are included in the mobile station candidate list of the relay station, the second determiner 68 determines sub-bands of a number corresponding to the number of the mobile stations (for which amplification has been determined necessary by the base station) included in the mobile station candidate list of the relay station, to be sub-bands for actually performing amplification. In other words, among the mobile stations for which the base station has determined amplification necessary, the relay station 61 need not perform amplification with respect to the portion that is not included in the mobile station candidate list of the relay station. Therefore, when determining the sub-bands for performing amplification at the relay station, the second determiner 68 may, for example, randomly eliminate from among all of the sub-bands allocated by the base station, sub-bands of a number corresponding to the number of mobile stations for which amplification is not to be performed at the relay station. Correspondence relationships between the number of mobile stations for which amplification is to be performed at the relay station and the number of sub-bands to be eliminated may be preliminarily obtained, for example, by simulation using a computing device.
When none of the mobile stations for which amplification has been determined necessary by the base station are included in the mobile station candidate list of the relay station, the second determiner 68 determines none of the sub-bands allocated by the base station to be sub-bands for actually performing amplification. In other words, when none of the mobile stations for which amplification has been determined necessary by the base station are included in the mobile station candidate list of the relay station, the relay station 61 need not perform amplification. The second determiner 68 notifies the amplifier 28 of the sub-bands allocated for performing amplification. The amplifier 28 amplifies analog input signals of the allocated sub-bands determined by the second determiner 68. Other aspects of the configuration of the relay station 61 are similar to those of the third embodiment. The antenna 29, the measurer 62, the table 63, the first determiner 64, the generator 65, the first receiver 66, the second receiver 67, the second determiner 68, and the amplifier 28, for example, operate as the amplifier 5 in the first embodiment.
On the other hand, the relay station measures the reception quality between the relay station and mobile stations, such as the SIR of the mobile stations. The relay station compares the reception quality of each mobile station with a predetermined threshold; and for example, for a mobile station whose reception quality exceeds the threshold, determines that the mobile station is nearby. The relay station creates a list of mobile stations that have been determined to be nearby (step S45). The relay station determines whether all of the mobile stations for which amplification has been determined to be necessary by the base station are included in the mobile station candidate list of the relay station (step S46). If all of the mobile stations are included in the mobile station candidate list of the relay station (step S46: YES), the relay station performs amplification with respect to all of the sub-bands allocated by the base station, for performing amplification (step S47).
If a portion of the mobile stations for which amplification has been determined necessary by the base station are included in the mobile station candidate list of the relay station (step S46: NO, step S48: YES), the relay station performs amplification with respect to sub-bands of a number that corresponds to the number of the mobile stations for which amplification has been determined to be necessary by the base station, included in the mobile station candidate list of the relay station (step S49). When none of the mobile stations for which amplification has been determined to be necessary by the base station are included in the mobile station candidate list of the relay station (step S48: NO), the relay station does not perform amplification with respect to any of the sub-bands allocated by the base station (step S50). In this series of operations, the execution timing of step S45 may be before or after step S44, before step S43, before step S42, or before step S41.
According to the fourth embodiment, effects similar to those of the first embodiment can be obtained. Further, since the relay station performs amplification with respect to sub-bands of a number corresponding to the number of mobile stations for which amplification has been determined necessary by the base station, included in the mobile station candidate list of the relay station, configuration can be such that the relay station does not perform amplification with respect to sub-bands of a number corresponding to the mobile stations not included in the mobile station candidate list of the relay station. Therefore, the relay station can be prevented from becoming a source of interference. Further, similar to the second embodiment, the reception quality of a mobile station whose reception quality is poor can be improved. Furthermore, a regenerating type relay station may be used.
In a fifth embodiment, the base station of the third embodiment allocates, based on the inner-cell interference power of each sub-band, one or more sub-bands for performing amplification. The configuration of the base station in the fifth embodiment is, for example, as depicted in
The third calculator 75, based on sub-band inner-cell interference power and a threshold in the third table 74, determines the sub-bands for which amplification can be performed at the relay station. The third calculator 75, for example, determines sub-bands having an interference power that is less than or equal to the threshold to be sub-bands for which amplification can be performed at the relay station. The third calculator 75, for example, determines sub-bands having an interference power that exceeds the threshold to be sub-bands for which amplification cannot be performed at the relay station.
The allocator 37, based on information received by the transceiver 36 and indicating the sub-bands for which amplification is being performed at the relay station, obtains the sub-bands for which the relay station is not performing amplification (available sub-bands). The allocator 37, from among the available sub-bands, extracts the sub-bands for which amplification can be performed at the relay station as determined by the third calculator 75. The allocator 37, from among the extracted sub-bands, in a given order (e.g., in descending order of interference power), allocates for performing amplification, sub-bands corresponding in number to that calculated by the second calculator 35. Alternatively, the allocator 37, from among the extracted sub-bands, allocates arbitrary sub-bands corresponding in number of that calculated by the second calculator 35. When the number of amplifying sub-bands calculated at the second calculator 35 is greater than the number of sub-bands for which amplification can be performed as determined at the third calculator 75, the allocator 37 allocates all of the sub-bands for which amplification can be performed at the relay station. Other aspects of the configuration of the base station 71 are similar to those of the third embodiment. The antenna 16, the switch 17, the first measurer 72, the first table 32, the determiner 14, and the first calculator 33, for example, operate as the calculator 3 in the first embodiment. The second table 34, the second calculator 35, the transceiver 36, the allocator 37, the second measurer 73, the third table 74, and the third calculator 75, for example, operate as the allocator 4 in the first embodiment.
The base station decrements k and m by 1, respectively (step S56). The base station determines whether the resulting value of k is 0 (step S57). If the value of k is 0 (step S57: YES), there are no more amplifying sub-bands and consequently, the base station ends the allocation process. If the value of k is not 0 (step S57: NO), the base station determines whether the value of m is 0 (step S58). If the value of m is 0 (step S58: YES), there are no more sub-bands having an inner-cell interference power that is less than or equal to the threshold and consequently, the base station ends the allocation process. If the value of m is not 0 (step S58: NO), the base station returns to step S55, at which time, for example, the base station allocates the sub-band having the lowest interference power (step S55).
Steps S55 to S58 are repeated until there are no more amplifying sub-bands or until there are no more sub-bands having an inner-cell interference power that is less than or equal to the threshold. In this series of operations, the execution timing of step S53 may be before or after step S52, or before step S51. Further, the execution timing of step S54 may be before or after step S53, before step S52, or before step S51. The processes performed at the base station and the relay station, respectively, after sub-bands have been allocated by the base station are similar to those of the third embodiment.
According to the fifth embodiment, effects similar to those of the first embodiment can be obtained. Further, the base station allocates sub-bands having an inner-cell interference power that is less than or equal to a threshold and consequently, the amplification of signals of sub-bands having an inner-cell interference power that exceeds the threshold can be prevented. Therefore, the relay station can be prevented from becoming a source of interference. Further, similar to the second embodiment, the reception quality of a mobile station whose reception quality is poor can be improved. Furthermore, a regenerating type relay station may be used.
In a sixth embodiment, the base station of the third embodiment calculates gain for each sub-band, based on the inner-cell interference power of each sub-band. Configuration of the base station according to the sixth embodiment is, for example, as depicted in
The third calculator 85 calculates gain for each sub-band, based on sub-band inner-cell interference power and a threshold in the third table 84. The third calculator 85, based on the gain for each sub-band, determines the sub-bands for which amplification can be performed at the relay station. The third calculator 85, for example, determines a sub-band for which the gain is greater than or equal to the threshold, to be a sub-band for which amplification can be performed. The third calculator 85, for example, determines a sub-band for which the gain is less than the threshold to be a sub-band for which amplification cannot be performed at the relay station. The threshold used for determining, at the third calculator 85, whether amplification can be performed at the relay station may be, for example, preliminarily obtained by simulation using a computing device. The threshold used for determining, at the third calculator 85, whether to perform amplification at the relay station may be, for example, 0 dB.
From among the sub-bands determined by the third calculator 85 as sub-bands for which amplification can be performed at the relay station, the allocator 37 allocates as sub-bands for performing amplification, sub-bands of the number calculated by the second calculator 35. The allocator 37 allocates the sub-bands in a given order, such as in ascending order of gain, i.e., in descending order of interference power. Further, the allocator 37, from among the sub-bands determined by the third calculator 85 as sub-bands for which amplification can be performed at the relay station, allocates as sub-bands for performing amplification, sub-bands of the number calculated by the second calculator 35. When the number of amplifying sub-bands calculates at the second calculator 35 is greater than the number of sub-bands determined at the third calculator 85, the allocator 37 allocates all of the sub-bands determined at the third calculator 85 as sub-bands for which amplification can be performed at the relay station, to be sub-bands for performing amplification. The base station 81 broadcasts, via the switch 17 and the antenna 16, the gain of each of the sub-bands that have been allocated by the allocator 37. Other aspects of the configuration of the base station 81 are similar to those of the third embodiment. The antenna 16, the switch 17, the first measurer 82, the first table 32, the determiner 14, and the first calculator 33, for example, operate as the calculator 3 in the first embodiment. The second table 34, the second calculator 35, the allocator 37, the second measurer 83, the third table, 84, and the third calculator 85, for example, operate as the allocator 4 in the first embodiment.
The configuration of the relay station in the sixth embodiment is similar to that in the third embodiment. However, in the relay station 41 of the third embodiment depicted in
Similar to steps S56 to S58 in the fifth embodiment, the base station reduces k and m by 1 (step S65), determines whether resulting value of k is 0 (step S66), and determines whether the resulting value of m is 0 (step S67). If the value of k is 0 (step S66: YES), there are no more amplifying sub-bands and consequently, the base station ends the allocation process. If the value of m is (step S67: YES), there are no more sub-bands for which gain is greater than or equal to the threshold and consequently, the base station ends the allocation process. In this series of operations, the execution timing of step S63 may be before or after step S62, or before step S61. The processes performed at the base station and relay station, respectively, after sub-bands have been allocated by the base station are similar to those of the third embodiment. However, the base station need not notify other base stations of information indicating the sub-bands that have been allocated for performing amplification.
According to the sixth embodiment, effects similar to those of the first embodiment can be obtained. Further, the base station allocates sub-bands for which gain is greater than or equal to a threshold and consequently, the amplification of signals of sub-bands for which gain is less than the threshold, i.e., sub-bands having an inner-cell interference power that is greater than a given value, can be prevented. Therefore, the relay station can be prevented from becoming a source of interference. Further, similar to the second embodiment, the reception quality of a mobile station whose reception quality is poor can be improved. Furthermore, a regenerating type relay station may be used.
In a seventh embodiment, the base station of the third embodiment allocates for performing amplification, the frequency band used by mobile stations for which amplification is to be performed. The configuration of the base station in the seventh embodiment is, for example, as depicted in
The allocator 37, based on the information that is from the scheduler 94 and that indicates the wireless resources of the mobile stations for which amplification has been determined to be necessary, allocates for performing amplification, the frequency bands of the mobile stations. The base station 91 broadcasts, via the switch 17 and the antenna 16, information indicating the frequency bands allocated by the allocator 37, for performing amplification. The base station 91 may broadcast information concerning other wireless resources in addition to the information indicating the frequency bands allocated for performing amplification. Other aspects of the configuration of the base station 91 are similar to those in the third embodiment. The antenna 16, the switch 17, the measurer 12, the table 92, the determiner 14, and the extractor 93, for example, operate as the calculator 3 in the first embodiment. However, in the seventh embodiment, the number of or the rate of mobile stations requiring amplification is not calculated. The scheduler 94 and the allocator 37, for example, operate as the allocator 4 in the first embodiment.
The configuration of the relay station in the seventh embodiment is similar to that in the third embodiment. However, in the relay station 41 of third embodiment depicted in
According to the seventh embodiment, effects similar to those of the first embodiment can be obtained. Further, the base station allocates for performing amplification, the frequency bands of the mobile stations for which amplification is necessary and the relay station performs amplification with respect to the frequency bands used by the mobile stations for which amplification is necessary, consequently, the reception quality of a mobile station whose reception quality is poor can be improved. Furthermore, a regenerating type relay station may be used.
According to the disclosed communication system, base station, relay station, and wireless communication method, a relay station can prevented from becoming a source of interference.
All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
This application is a continuation application of International Application PCT/JP2009/062916, filed Jul. 16, 2009, and designating the U.S., the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/JP2009/062916 | Jul 2009 | US |
Child | 13344754 | US |