JP2007251498A - Radio communication system, base station, and channel selection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To select an appropriate channel for transmitting an uplink signal, from a mobile station to a base station. <P>SOLUTION: The base station 102 receives a CQI value. The CQI value indicates the reception quality of a downlink signal received by a mobile station 101, and is transmitted from the mobile station 101. The interference power of the uplink signal, transmitted from the mobile station 101, is measured by an interference level measurement section 123 for each channel. An address is given to the channels sequentially from a channel having large measured interference power. A CQI extraction section 122 extracts the CQI value transmitted from the mobile station 101; a search start address, which starts search for the channel, according to the size of the extracted σQI value, is determined; and when a channel to which the search start address is given is vacant, the channel, to which the search start address is given, is assigned to a channel used for transmitting the uplink signal to the base station 102 from the mobile station 101 by an uplink channel determining section 124. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radio communication system, a base station, and a channel selection method for selecting a channel for transmitting a signal from a mobile station to a base station.

  In the conventional cellular radio communication system, the same TDMA (Time Division Multiple Access) / FDMA (Frequency Division Multiple Access) channel may be used in neighboring cells covered by adjacent base stations. In this case, the signal in the own cell becomes an interference signal in another cell. In order to prevent this, channel selection is a very important issue in increasing system capacity.

  As a channel selection method for selecting a channel in a cellular radio communication system, an Automatic Reuse Partitioning (hereinafter referred to as ARP) method, a channel segregation method, and the like have been studied.

  In the above-described ARP method and channel segregation method, a radio channel is selected based on reception SIR (Signal to Interference Ratio) in a base station or signal reception power. However, in recent wireless communication systems, a method of controlling transmission power for transmitting an uplink signal from a mobile station is generally used so that the reception SIR at the wireless base station becomes constant according to a change in propagation path. It is. Therefore, it becomes difficult to perform channel selection based on the reception SIR at the radio base station.

Therefore, a method of dynamically allocating channels on the uplink based on the magnitude of transmission path loss has been considered (see, for example, Patent Document 1).
JP 2001-238252 A

  However, in the method described in Patent Document 1, the channel to be used is uniformly selected from the empty channels with the highest priority according to a common priority for any mobile station. Depending on the magnitude of the loss, the procedure required for channel selection increases, and there is a problem that the processing time is increased.

  The present invention has been made in view of the problems of the conventional techniques as described above, and is a radio that can easily select an appropriate channel for transmitting an uplink signal from a mobile station to a base station. It is an object to provide a communication system, a base station, and a channel selection method.

In order to achieve the above object, the present invention provides:
In a wireless communication system comprising: a base station; and a mobile station that determines a CQI value indicating a reception state of a downlink signal transmitted from the base station and transmits the CQI value to the base station.
The base station measures the interference power of the uplink signal transmitted from the mobile station for each channel, assigns an address to the channel sequentially from the channel with the large interference power, and is transmitted from the mobile station. A search start address for starting the search of the channel is determined according to the size of the CQI value. When the channel to which the search start address is assigned is an empty channel, the channel to which the search start address is assigned is determined. And allocating to a channel used for transmission of an uplink signal from the mobile station to the base station.

  In addition, when the channel to which the search start address is assigned is not an empty channel, the base station sequentially increments the search start address one by one and determines whether the channel to which the incremented address is assigned is an empty channel. The channel is determined, and the channel determined to be an empty channel is allocated to a channel used for transmission of an uplink signal from the mobile station to the base station.

In addition, the CQI value indicating the reception quality of the downlink signal received by the mobile station is a base station that is transmitted and received from the mobile station,
Measure the interference power of the uplink signal transmitted from the mobile station for each channel, assign an address to the channel sequentially from the channel with the large interference power, and the magnitude of the CQI value transmitted from the mobile station If the channel to which the search start address is assigned is an empty channel, the channel to which the search start address is assigned is determined from the mobile station. Assign to a channel used for uplink signal transmission to the base station.

  When the channel to which the search start address is assigned is not an empty channel, the search start address is incremented one by one in order, and it is determined whether the channel to which the incremented address is assigned is an empty channel. The channel determined to be is assigned to a channel used for transmission of an uplink signal from the mobile station to the base station.

Further, channel selection in a radio communication system comprising a base station and a mobile station that determines a CQI value indicating a reception state of a downlink signal transmitted from the base station and transmits the CQI value to the base station A method,
The base station measures the interference power of the uplink signal transmitted from the mobile station for each channel, and
A process in which the base station sequentially assigns addresses to the channel from the channel with the large interference power;
A process of determining a search start address for starting the search of the channel according to the size of the CQI value transmitted from the mobile station;
When the channel to which the search start address is assigned is an empty channel, a process for assigning the channel to which the search start address is assigned to a channel used for transmission of an uplink signal from the mobile station to the base station. Have.

In addition, when the channel to which the search start address is assigned is not an empty channel, the base station sequentially increments the search start address one by one,
A process for determining whether the channel to which the incremented address is assigned is an empty channel;
And a process of allocating a channel determined to be an empty channel to a channel used for transmission of an uplink signal from the mobile station to the base station.

  In the present invention configured as described above, the CQI value indicating the reception quality of the downlink signal received by the mobile station is transmitted from the mobile station and received from the mobile station. The interference power of the transmitted uplink signal is measured for each channel, and addresses are sequentially given from the channels with the large interference power measured to the channels, and the size of the CQI value transmitted from the mobile station is set. Accordingly, when the search start address for starting the search for the channel is determined and the channel to which the search start address is assigned is an empty channel, the channel to which the search start address is assigned is transferred from the mobile station to the base station. Assigned to a channel used for uplink signal transmission.

  As a result, when searching for a channel used for uplink signal transmission from a mobile station that has transmitted a low CQI value, the search is started from a channel with low interference power, and the search time for the channel is shortened. Can be assigned.

  As described above, in the present invention, the CQI value indicating the reception quality of the downlink signal received by the mobile station is transmitted from the mobile station at the base station that is transmitted from the mobile station and received. The interference power of the uplink signal is measured for each channel, addresses are sequentially assigned to the channels with the large interference power measured for each channel, and the channel is determined according to the size of the CQI value transmitted from the mobile station. If the search start address for starting the search is determined and the channel to which the search start address is assigned is an empty channel, the channel to which the search start address is assigned is transmitted to the base station from the mobile station. Since it is configured to be assigned to a channel used for transmission, an appropriate channel for transmitting an uplink signal from the mobile station to the base station can be easily selected. Door can be.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of a wireless communication system of the present invention.

  As shown in FIG. 1, this embodiment includes a mobile station 101 and a base station 102. The mobile station 101 and the base station 102 are connected by radio, and the mobile station 101 receives a downlink signal transmitted from the base station 102. In addition, the base station 102 receives an uplink signal transmitted from the mobile station 101. In addition, although the mobile station 101 shown in FIG. 1 is one with respect to the base station 102, it cannot be overemphasized that a plurality may be sufficient.

  Further, the mobile station 101 is provided with a downlink signal reception unit 111, a reception level measurement unit 112, a CQI determination unit 113, and an uplink signal transmission unit 114.

  The downlink signal reception unit 111 receives a downlink signal transmitted from the base station 102. The reception level measurement unit 112 measures the reception level of the downlink signal received by the downlink signal reception unit 111. CQI determining section 113 determines a CQI value corresponding to the reception level measured by reception level measuring section 112. Uplink signal transmission section 114 maps the CQI value determined by CQI determination section 113 to a predetermined position of the uplink signal to be transmitted to base station 102 and transmits it to base station 102.

  Further, the base station 102 is provided with an uplink signal reception unit 121, a CQI extraction unit 122, an interference level measurement unit 123, an uplink channel determination unit 124, and a downlink signal transmission unit 125.

  The uplink signal receiving unit 121 receives an uplink signal transmitted from the mobile station 101. The CQI extraction unit 122 extracts a CQI value from the uplink signal received by the uplink signal reception unit 121. The interference level measurement unit 123 measures the interference power of the uplink signal received by the uplink signal reception unit 121, and replaces the measured interference power with several interference levels. Uplink channel determination section 124 determines a channel to be used by the uplink signal based on the CQI value extracted by CQI extraction section 122 and the interference level based on the interference power measured by interference level measurement section 123. To do. The downlink signal transmission unit 125 transmits the channel determined by the uplink channel determination unit 124 to the mobile station 101 together with the downlink signal.

  Below, the channel selection method in the radio | wireless communications system shown in FIG. 1 is demonstrated.

  First, as an initial setting, the interference level classified into several levels based on the interference power measured by the interference level measurement unit 123 of the base station 102 and the channel number used for transmitting the uplink signal are as follows. Stored in association. Here, using the measured interference power itself, the measured interference power may be associated with the channel number used for transmitting the uplink signal.

  FIG. 2 is a diagram illustrating an example of an association between the interference level based on the interference power measured by the interference level measurement unit 123 of the base station 102 and the channel number used for transmitting the uplink signal.

  As shown in FIG. 2, the channel number is associated with the interference level of the uplink signal using the channel number. Note that the interference level values shown in FIG. 2 are “1” to “5” for convenience of explanation, “5” is the largest interference level value, and “1” is the smallest interference level value. It is said. In the example illustrated in FIG. 2, for the uplink signal using the channel number “0”, the interference level based on the interference power measured by the interference level measurement unit 123 is “3”, and the channel number “1”. "Is an interference level based on the interference power measured by the interference level measurement unit 123, and an interference level measurement unit is configured for the uplink signal using the channel number" 2 ". The interference level based on the interference power measured in 123 is “2”, and the interference based on the interference power measured in the interference level measurement unit 123 is performed for the uplink signal using the channel number “3”. The level is “4”, and the interference level based on the interference power measured by the interference level measurement unit 123 for the uplink signal using the channel number “4” is “1”. A. This association is stored in storage means such as a memory by the interference level measurement unit 123.

  When the associations shown in FIG. 2 are stored, the associations are rearranged from those with the highest interference level, and addresses are sequentially assigned to the associations.

  FIG. 3 is a diagram illustrating an example of a first table in which the associations illustrated in FIG. 2 are rearranged from those having a high interference level, and addresses are sequentially assigned to the correspondences.

  As shown in FIG. 3, the association shown in FIG. 2 is rearranged in order from the largest to the smallest, such as the interference level “5” to “1”. Then, an address is sequentially assigned to each of the rearranged items. In the example illustrated in FIG. 3, the channel number “1” associated with the largest interference level “5” is assigned the address “0” and is associated with the next largest interference level “4”. The channel number “3” is assigned an address “1”, the channel number “0” associated with the next largest interference level “3” is assigned an address “2”, and The address “3” is assigned to the channel number “2” associated with the next largest interference level “2”, and the channel number “4” associated with the next largest interference level “1” is assigned. Is given the address “4”. The first table is stored in a storage unit such as a memory by the interference level measurement unit 123 or the uplink channel determination unit 124.

  When the first table shown in FIG. 3 is stored, the channel search start address for searching for a channel based on the CQI value extracted by the CQI extraction unit 122 is associated with the extracted CQI value. And stored as a second table.

  FIG. 4 shows an example of a second table that is a correspondence between the channel search start address for starting channel search based on the CQI value extracted by the CQI extraction unit 122 and the extracted CQI value. FIG. Note that the CQI value extracted by the CQI extraction unit 122 is encoded to a value of “0” to “30”, and “0” is the CQI value when the reception quality is the worst. 30 ”is the CQI value when the reception quality is the best.

  As shown in FIG. 4, the CQI values in the second table are classified into several levels having a predetermined width, and a channel search start address for starting a channel search corresponds to each level. Attached and stored. In the example of the second table shown in FIG. 4, the CQI values “26” to “30” are associated with the channel search start address “0”, and the CQI values are “21” to “25”. ”And the channel search start address“ 1 ”, the CQI values“ 16 ”to“ 20 ”are associated with the channel search start address“ 2 ”, and the CQI value is “11” to “15” are associated with channel search start address “3”, and CQI values “0” to “10” are associated with channel search start address “4” and stored. Has been. For example, when the CQI value extracted by the CQI extraction unit 122 is “23”, the channel search start address associated with the CQI value “23” is “1”. This second table is stored in storage means such as a memory by the uplink channel determination unit 124.

  FIG. 5 is a flowchart for explaining a channel selection method in the wireless communication system after the initial setting described above.

  After completion of the initial setting, a CPICH (Common Pilot Channel) is transmitted from the base station 102 to the mobile station 101. When the CPICH is transmitted from the base station 102 to the mobile station 101, the transmitted CPICH is received by the downlink signal receiving unit 111. Then, the reception power of CPICH received by downlink signal reception section 111 is measured by reception level measurement section 112.

  Then, based on the reception power measured by the reception level measurement unit 112, the CQI value that is reception quality is determined by the CQI determination unit 113. The CQI value determined by the CQI determination unit 113 is mapped to a predetermined position of the uplink signal and transmitted from the uplink signal transmission unit 114 to the base station 102.

  When the uplink signal mapped to the CQI value and transmitted from the uplink signal transmission unit 114 to the base station 102 is received by the uplink signal reception unit 121 of the base station 102, the uplink signal received by the uplink signal reception unit 121 is received. A CQI value is extracted from the signal (step S1).

  Based on the CQI value extracted by the CQI extraction unit 122, the uplink channel determination unit 124 determines an address for starting an uplink channel search (step S2). Here, the channel search start address is searched and determined from the second table shown in FIG. 4 using the CQI value extracted by CQI extraction section 122 as a search key.

  Thereafter, the uplink channel determination unit 124 determines whether the channel associated with the determined channel search start address is an empty channel (step S3). Here, it is determined whether or not the channel having the channel number associated with the determined search start address is being used by another user on the first table shown in FIG. The Rukoto.

  A channel used to transmit an uplink signal from the mobile station 101 to the base station 102 when it is determined that the channel having the channel number associated with the determined channel search start address is an empty channel. (Step S4).

  On the other hand, if it is determined that the channel with the channel number associated with the determined channel search start address is not free, the address is incremented by one (step S5). At this time, a counter may be provided in the uplink channel determination unit 124, and count-up may be performed using the provided counter.

  Thereafter, it is determined whether or not a channel is assigned to the incremented address (step S6). That is, it is determined whether there is a channel number associated with the address in the first table shown in FIG.

  If it is determined that a channel is assigned to the incremented address, the process returns to step S3 to determine whether the incremented address is an empty channel, and then the same process as described above is performed.

  On the other hand, if it is determined that no channel is assigned to the incremented address, it is determined that there is no usable channel, and the call is lost (step S7).

  Hereinafter, more specific processing from step S2 to step S7 will be described by taking as an example the case where the CQI value extracted by the CQI extraction unit 122 is “23”.

  Referring to the second table shown in FIG. 4, the channel search start address associated with the CQI value “23” is “1”. Then, referring to the first table shown in FIG. 3, the channel number associated with the address “1” is “3”. Therefore, when the CQI value extracted by the CQI extraction unit 122 is “23”, the channel number of the channel for which it is determined whether or not it is free is “3”. Here, when it is determined that the channel with the channel number “3” is free, the channel number “3” is assigned as a channel used for transmitting an uplink signal from the mobile station 101 to the base station 102. Become.

  On the other hand, if it is determined that the channel with channel number “3” is not free, the address is incremented by 1 to “2”. That is, the search for the channel with the next highest interference level is started.

  Then, it is determined whether or not there is a channel associated with the address “2” on the first table. This is a process that takes into account that the channel number corresponding to the address disappears by continuing to increment the address because the channel number is finite. Therefore, by continuing to increment the address, when there is no channel number corresponding to the address, it is determined that there is no channel that can be allocated, and the call is lost.

  In the first table shown in FIG. 3, since the channel number associated with the address “2” is “0”, it is determined whether or not the channel with the channel number “0” is free.

  In this way, it is sequentially determined whether or not the channel is vacant from a channel with a large interference level, and a channel determined to be vacant is assigned. Further, by using the second table shown in FIG. 4, the search is started from the channel having the interference level corresponding to the CQI value extracted by the CQI extraction unit 122, that is, the mobile station 101 having a low CQI value. Therefore, a search is started from a channel with a low interference level, and a channel approximately corresponding to a position where the mobile station 101 exists can be assigned with a search time of the channel reduced.

  Even when the state of the propagation path changes during communication between the mobile station 101 and the base station 102, the correspondence shown in FIG. 2 is shown in FIG. The channel may be reselected according to the state of the propagation path by rewriting the first table and the second table shown in FIG.

It is a figure which shows one Embodiment of the radio | wireless communications system of this invention. It is a figure which shows an example of matching with the channel number used for transmission of the uplink level and the interference level based on the interference power measured in the interference level measurement part of the base station. FIG. 3 is a diagram illustrating an example of a first table in which the associations illustrated in FIG. 2 are rearranged from those having a high interference level, and addresses are sequentially assigned to the correspondences. It is a figure which shows an example of the 2nd table which is matching with the channel search start address for starting the search of a channel based on the CQI value extracted in the CQI extraction part, and the extracted CQI value. It is a flowchart for demonstrating the channel selection method in the radio | wireless communications system after initialization.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Mobile station 102 Base station 111 Downlink signal receiving part 112 Reception level measurement part 113 CQI determination part 114 Uplink signal transmission part 121 Uplink signal reception part 122 CQI extraction part 123 Interference level measurement part 124 Uplink channel determination part 125 Downlink signal transmission part

Claims (6)

In a wireless communication system comprising: a base station; and a mobile station that determines a CQI value indicating a reception state of a downlink signal transmitted from the base station and transmits the CQI value to the base station.
The base station measures the interference power of the uplink signal transmitted from the mobile station for each channel, assigns an address to the channel sequentially from the channel with the large interference power, and is transmitted from the mobile station. A search start address for starting the search of the channel is determined according to the size of the CQI value. When the channel to which the search start address is assigned is an empty channel, the channel to which the search start address is assigned is determined. A radio communication system characterized by allocating to a channel used for transmission of an uplink signal from the mobile station to the base station. The wireless communication system according to claim 1, wherein
If the channel to which the search start address is assigned is not an empty channel, the base station sequentially increments the search start address by one to determine whether the channel to which the incremented address is assigned is an empty channel. A wireless communication system, wherein a channel determined to be an empty channel is assigned to a channel used for transmission of an uplink signal from the mobile station to the base station. A CQI value indicating a reception quality of a downlink signal received by the mobile station is transmitted from the mobile station and received;
Measure the interference power of the uplink signal transmitted from the mobile station for each channel, assign an address to the channel sequentially from the channel with the large interference power, and the magnitude of the CQI value transmitted from the mobile station If the channel to which the search start address is assigned is an empty channel, the channel to which the search start address is assigned is determined from the mobile station. A base station assigned to a channel used for transmission of an uplink signal to the base station. In the base station according to claim 3,
If the channel to which the search start address is assigned is not an empty channel, the search start address is incremented one by one in order, and it is determined whether or not the channel to which the incremented address is assigned is an empty channel. A base station characterized by allocating a channel determined to be a channel used for transmission of an uplink signal from the mobile station to the base station. A channel selection method in a wireless communication system comprising a base station and a mobile station that determines a CQI value indicating a reception state of a downlink signal transmitted from the base station and transmits the CQI value to the base station. There,
The base station measures the interference power of the uplink signal transmitted from the mobile station for each channel, and
A process in which the base station sequentially assigns addresses to the channel from the channel with the large interference power;
A process of determining a search start address for starting the search of the channel according to the size of the CQI value transmitted from the mobile station;
When the channel to which the search start address is assigned is an empty channel, a process for assigning the channel to which the search start address is assigned to a channel used for transmission of an uplink signal from the mobile station to the base station. Having a channel selection method. The channel selection method according to claim 5,
The base station, when the channel to which the search start address is given is not an empty channel, a process of sequentially incrementing the search start address one by one;
A process for determining whether the channel to which the incremented address is assigned is an empty channel;
A channel selection method comprising: allocating a channel determined to be an empty channel to a channel used for transmission of an uplink signal from the mobile station to the base station.

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