JP2004104434A - Radio network controller and method for controlling radio communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance an efficiency of a system service by increasing radio resources usable between a plurality of base station apparatuses. <P>SOLUTION: A DHO (diversity handover) elimination processing unit 153 in a call processing unit 151 of a radio network controller 150 retrieves and extracts a user terminal of a diversity handover state from data of each user terminal held by a user information managing unit 152, while communicating at a higher transmission rate than a predetermined reference rate. If a receiving quality level of the extracted user terminal is a predetermined reference value or more, a designation is given to radio resource managing units 110 of the base station apparatuses 100, 200, and the diversity handover state is eliminated. A rate change processing unit 154 retrieves the lower transmission rate of the user terminal than a desired rate, gives a designation to the units 110, and changes to a rate as the user terminal desires. <P>COPYRIGHT: (C)2004,JPO

Description

【００５０】
表１から次のことが分かる。例えば、＃１のユーザ端末の場合、現在１２８ｋｂｐｓで送信しており、１つの基地局当たりの消費無線リソース量は４０である。さらに、３つの基地局Ｂ１〜Ｂ３との受信品質は、それぞれ１０、８、７であり、基地局Ｂ１〜Ｂ３との間でダイバーシチハンドオーバ状態にあることを示している。なお、受信品質は、ＣＲＣ結果、ＢＥＲやＢＬＥＲ等を１０段階の数値に換算して評価し、値が大きいほど受信品質が良好であるとする。この受信品質は、受信品質測定部１５５からの結果によって定期的に更新される。
【００５１】
また、＃１のユーザ端末の希望下り送信レートは２５６ｋｂｐｓであり、現在の送信レート１２８ｋｂｐｓは希望値以下であることがわかる。この希望下り送信レートは、各ユーザ端末において測定した受信品質を基にして設定され、無線ネットワーク制御装置１５０に通知する。受信可能な下り送信レートは、ユーザ端末において受信した搬送波と妨害波の電力比を基準に設定する。搬送波と妨害波の比率が大きい場合は、高速レートに変更しても誤りなくデータを伝送できるので、高い伝送速度でデータを受信することができる。
【００５２】
＃１のユーザ端末の場合、１つの基地局当たりの消費無線リソース量は４０であり、これはダイバーシチハンドオーバを行っている基地局Ｂ１〜Ｂ３の間で等しく消費される。同様に、＃２〜＃ｎのユーザ端末について各基地局当たりの消費無線リソース量を換算すると、表２に示すように、基地局Ｂ１〜Ｂ３においてそれぞれ３４５、３３５、３２５となる。
【００５３】
【表２】

【００５４】
次に、呼処理部１５１のＤＨＯ解除処理部１５３におけるダイバーシチハンドオーバ解除の手順について、図２のフローチャートと表１のデータ例を参照しながら具体的に説明する。
【００５５】
まず、ユーザ情報管理部１５２に記憶されている情報から所定の基準レートより高い送信レートで通信しているユーザ端末を検索して抽出する（ステップＳ３１）。表１の例で基準レートが１２８ｋｂｐｓに設定されていたとすれば、抽出される対象のユーザ端末は＃１，＃３，＃６，＃ｎである。ここで、基準レートとは、ダイバーシチハンドオーバ状態を解除する分界点となるレートであり、基準レート以上で伝送しているユーザ端末がダイバーシチハンドオーバ状態の解除対象となる。従って、比較的低いレートを設定すると、システム内のほとんどのユーザ端末がダイバーシチハンドオーバ状態を解除され、ダイバーシチハンドオーバの効果を失ってしまって受信品質が著しく劣化するおそれがあるので、解除対象のユーザ端末数が限られるような比較的高いレートに設定するのが望ましい。
【００５６】
次に、抽出されたユーザ端末の中でダイバーシチハンドオーバ状態にあるユーザ端末を検索して抽出する（ステップＳ３２）。表１の例では、ステップＳ３１で抽出されたユーザ端末の全てがダイバーシチハンドオーバ状態をとっている。そして、ダイバーシチハンドオーバ状態にあるユーザ端末それぞれについて、通信を行っている各基地局装置毎の受信品質の最低値が所定の基準値以上であるか否かをチェックする（ステップＳ３３）。ここで、基準値以上である場合はステップＳ３１に戻ることにより、各基地局装置毎の受信品質の最低値が基準値以上であるユーザ端末のみを残す。表１の例で、例えば受信品質の基準値が７に設定されていたとすれば、該当するユーザ端末は＃１，＃３，＃６となる。
【００５７】
続いて、基地局装置１００、２００の無線リソース管理部１１０に指示を与え、当該ユーザ端末のダイバーシチハンドオーバ状態を解除する（ステップＳ３４）。このとき、解除するダイバーシチハンドオーバ状態の無線ブランチは、基地局装置からの受信品質が低いものから順に選び、最も受信品質が高いブランチを１つだけ残すようにする。なお、受信品質に基準値を用いているのは、ダイバーシチハンドオーバ状態であってもその時の受信品質が低ければ、無理にダイバーシチハンドオーバの解除を行うことにより、ユーザ端末自体の無線リンクが切れてしまうことを防止するためである。このように、ダイバーシチハンドオーバの解除は、受信品質が良好な無線ブランチを保持しながらダイバーシチハンドオーバを行っているユーザ端末のみを対象とする。
【００５８】
表１の例では、ユーザ端末＃１、＃３、＃６のダイバーシチハンドオーバ状態が解除され、最も受信品質の高い基地局装置との無線ブランチのみを残すと、ユーザ情報管理部１５２で管理するデータは、表３及び表４に示すようになる。
【００５９】
【表３】

【００６０】
【表４】

【００６１】
表４は、基地局装置毎の消費無線リソース量を表したもので、表２の場合に比較して基地局Ｂ１〜Ｂ３全ての消費無線リソース量が大幅に減少している。これは、使用可能となる無線リソースが新たに生成されたことを意味する。
【００６２】
次に、呼処理部１５１のレート更新処理処理部１５４におけるレート更新処理の手順について、図３のフローチャートと表３のデータ例を参照しながら具体的に説明する。このレート更新処理は、ＤＨＯ解除処理部１５３におけるダイバーシチハンドオーバ解除処理の後に行われる。
【００６３】
まず、現在送信しているレートが希望送信レートより低いユーザ端末を検索して抽出する（ステップＳ４１）。表３の例で、希望送信レートが現在の送信レートより高いユーザ端末は、＃１、＃５、＃６である。
【００６４】
次いで、基地局装置１００、２００の無線リソース管理部１１０に指示を与え、該当するユーザ端末の送信レートを希望通りに高くするように更新する（ステップＳ４２）。表３の例では、＃１、＃５、＃６全てのユーザ端末の送信レートを希望通りに高くする。これにより、ユーザ情報管理部１５２において、ダイバーシチハンドオーバ解除及びレート変更処理を行った後に記憶されるデータは、表５及び表６に示すようになる。
【００６５】
【表５】

【００６６】
【表６】

【００６７】
表１と表５、表２と表６をそれぞれ比較すると、次のことが明らかになる。
ダイバーシチハンドオーバ解除及びレート変更処理を行う前の状態を示す表１では、希望通りの送信レートで受信できていないユーザ端末が３つある。これに対し、図２及び図３に示した処理手順を実施した後の表５では、全ユーザ端末が希望通りの送信レートで受信できている。
【００６８】
また、各基地局装置の無線リソース量の合計は、ダイバーシチハンドオーバ解除及びレート変更処理を行う前は表２に示すように１００５だったのに対し、図２及び図３に示した処理手順を実行した後の表６では、８７５に減少させることができた。
【００６９】
このように、本実施形態の構成及び手順によれば、受信品質が十分に良好な高速レートでダイバーシチハンドオーバ状態にあるユーザ端末の無線リソースの一部を解放することにより、他のユーザ端末の平均的な伝送レートを向上させることができる。さらに、システム全体の無線リソース量を効率よく消費でき、システム容量を増加させることができる。
【００７０】
なお、ＤＨＯ解除処理部１５３は、基地局装置１００、２００の無線リソース管理部１１０に対して、ダイバーシチハンドオーバ状態にあり、かつ所定の受信品質を満たしているユーザ端末にダイバーシチハンドオーバ解除の指示を与える構成としたが、ダイバーシチハンドオーバ状態を維持しつつ無線ブランチの一部を解放するように指示してもよい。その際、解放する無線ブランチは、システムで保持する所定のしきい値を設け、このしきい値以上の良好な受信品質を有する無線ブランチを残すようにすればよい。これにより、無条件にダイバーシチハンドオーバ状態を解除したり、必要以上に無線ブランチの解放を行ったがために、受信品質の劣化を招くことがないようにすることができる。
【００７１】
また、ＤＨＯ解除処理部１５３による検索されたユーザ端末に対するダイバーシチハンドオーバ状態の解除指示は、基地局装置１００、２００において無線リソースの不足が原因で呼損が発生したときにのみ行うようにしてもよい。これにより、必要以上にダイバーシチハンドオーバ状態を解除することによって起こり得る受信品質の劣化や、別の呼損が発生することを回避することができる。
【００７２】
また、レート変更処理部１５４において、伝送レートを更新するユーザ端末を選択する場合、現在送信しているレートが希望送信レートを満たしていないユーザ端末の全てを対象にして検索したが、これまであまり高レートサービスを受けていないユーザ端末から優先的に選択するようにしてもよい。例えば、ユーザ情報管理部１５２において、ユーザ端末毎に所定時間内で所定のレート以上の送信を行うことができた時間を積算して記憶し、積算時間の少ないからユーザから順次選択するようにする。これにより、高速レートに変更することのできるユーザ端末を偏りなく選択することができ、伝送レートの平準化を図ることが可能となる。
【００７３】
また、レート変更処理部１５４において、伝送レートを更新するユーザ端末を選択して希望の送信レートに変更する際に、段階的に送信レートを高速にして希望の送信レートに近づけていくようにしてもよい。これにより、他のユーザ端末に対する干渉を小さくすることができる。
【００７４】
さらに、レート変更処理部１５４におけるレート更新処理は、ダイバーシチハンドオーバを解除することによって新たに発生した使用可能な無線リソース量を考慮し、この無線リソース量の範囲内でレート更新を行うようにしてもよい。例えば、ダイバーシチハンドオーバを解除することにより発生した無線リソース量をユーザ情報管理部１５２において記憶し、現在送信しているレートが希望送信レートを満たしていないユーザ端末を選択する際に、レート変更に伴って消費する無線リソースが記憶した無線リソースの範囲内であるユーザ端末についてのみレート変更処理を行う。これによって、新たに生成した無線リソースの制限を越えて高速レートに変更した場合に起こり得る、呼損の事態を回避することができる。
【００７５】
上述したように、本実施形態では、十分通信品質の良好なダイバーシチハンドオーバを行っているユーザ端末がシステム内に複数存在する場合、これらのユーザ端末のダイバーシチハンドオーバ状態を解除したり無線リソースの一部を解放することで、複数の基地局装置間で使用可能な無線リソースを増加させる。そして、増加させた無線リソースを高速にデータを受信することが可能な他のユーザ端末に割り当てて伝送レートを変更することにより、ユーザ端末が受信する平均的なデータ伝送レートを高くすることができ、システム全体の容量を増大させることができるため、システム運用の効率化を図ることが可能となる。
【００７６】
【発明の効果】
以上説明したように本発明によれば、複数の基地局装置間で使用可能な無線リソースを増加させ、システム運用の効率化を図ることができる無線ネットワーク制御装置を提供可能である。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る基地局装置及び無線ネットワーク制御装置の構成を示すブロック図
【図２】本発明の実施形態に係るダイバーシチハンドオーバ解除処理の手順を示すフローチャート
【図３】本発明の実施形態に係るレート更新処理の手順を示すフローチャート
【符号の説明】
１００、２００　基地局装置
１１０　無線リソース管理部
１５０　無線ネットワーク制御装置
１５１　呼処理部
１５２　ユーザ情報管理部
１５３　ダイバーシチハンドオーバ（ＤＨＯ）解除処理部
１５４　レート変更処理部
１５５　受信品質測定部
１５６　複製部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radio network controller for a mobile communication system, and more particularly, to a radio communication system such as a CDMA (Code Division Multiple Access) system, which is used between a user terminal such as a mobile phone as a mobile station and a base station device. The present invention relates to a wireless network control device and a wireless communication control method for performing a call control in the above.
[0002]
[Prior art]
In the CDMA mobile communication system, there are various services such as a packet communication service, a moving image communication service, and a multi-call service based on a combination thereof, in addition to a voice communication service mainly performed conventionally. These packet communication services, moving image communication services, and the like have a higher transmission rate than voice communication services, and accordingly, the amount of required radio resources also increases.
[0003]
In the CDMA scheme, a radio link is set between a terminal and a plurality of cells, and a reception signal over a plurality of radio links is combined, so that reception quality can be improved as compared with a reception signal over a single radio link. However, when performing diversity handover in which a plurality of wireless links are set over a plurality of base station devices, the plurality of base station devices consume the same amount of wireless resources.
[0004]
An example of a handover method in a mobile communication system is disclosed in Japanese Patent Application Laid-Open No. Hei 9-135377. In this conventional example, in a congested base station area, a radio channel of a certain user terminal is forcibly switched to an adjacent base station in order to allocate a communication channel to a request for calling a priority call such as police or fire. ing.
[0005]
[Patent Document 1]
JP-A-9-135377
[0006]
[Problems to be solved by the invention]
However, the conventional example described above has the following problems. For example, if a high-rate service that consumes a large amount of radio resources is performed under a situation where the number of call connections is increasing in a certain base station apparatus, the amount of radio resources held in the system is limited, so that a call loss Is more likely to occur. As described above, in the situation where the number of call connections increases and the amount of radio resources remains small, there is a high possibility that the amount of remaining radio resources also decreases in adjacent base station devices. For calls such as police and fire, which have a high priority but a small number of calls and require a relatively small amount of radio resources, there is a high possibility that they can be moved to an adjacent base station device. For a high-rate call that consumes a lot, there is a limit to generating free radio resources by a method of moving to an adjacent base station device.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radio network control apparatus and a radio network control apparatus capable of increasing the radio resources available between a plurality of base station apparatuses and improving the efficiency of system operation. An object of the present invention is to provide a communication control method.
[0008]
[Means for Solving the Problems]
A radio network control device according to the present invention is a radio network control device that performs radio communication control between a base station device and a user terminal that is a mobile station, and performs reception between the user terminal and the base station device. Receiving quality measuring means for measuring the quality, and, for each user terminal, storing user information including a transmission rate, a consumed radio resource amount, a receiving quality measured by the receiving quality measuring means, and a desired transmission rate of the user terminal. Searching for a user terminal in which the wireless communication with the base station apparatus is in a diversity handover state and satisfies a predetermined reception quality, from the user information managing means for managing the user information and the user information managed by the user information managing means. Gives an instruction to release the diversity handover state or partially release the wireless branch to the base station apparatus Rate change processing for searching a user terminal that does not satisfy the desired transmission rate from user information managed by the diversity handover processing means and the user information management means, and instructing the base station apparatus to change the transmission rate. Means.
[0009]
According to the above configuration, a part of the radio resources of the user terminal in the diversity handover state is released at a sufficiently high reception rate at a sufficiently high reception quality, and the transmission rate of the other user terminals is changed. It is possible to increase the amount of radio resources that can be used in the entire system without affecting the reception quality of existing user terminals that are communicating at a low rate. In addition, by limiting the radio branch of a user terminal that communicates at a high rate, it is possible to reduce the amount of interference with other user terminals.
[0010]
Further, the diversity handover processing means leaves only the radio branch with the highest reception quality when instructing the base station apparatus to cancel the diversity handover.
[0011]
According to the above configuration, by minimizing the number of remaining wireless branches, the amount of newly generated wireless resources can be maximized.
[0012]
Further, the diversity handover processing means, when instructing the base station apparatus to release a wireless branch, leaves a wireless branch having a reception quality equal to or higher than a predetermined threshold.
[0013]
According to the above configuration, it is possible to prevent the wireless branch from being unnecessarily released, and to prevent extreme degradation of the reception quality of the user terminal that may occur thereafter.
[0014]
Further, the user information management means accumulates the time during which transmission could be performed at a transmission rate equal to or higher than a predetermined value for each user terminal and stores the accumulated time as a high-speed communication accumulation time. An instruction to change the transmission rate for the user terminal is sequentially selected from the user terminals having a short high-speed communication integration time stored in the user information management means.
[0015]
According to the above configuration, the user terminals that can be changed to the high-speed rate can be selected without bias, and the transmission rates among the user terminals can be equalized.
[0016]
Further, the user information management means stores the amount of free wireless resources generated by releasing the diversity handover or partially releasing the wireless branch, and the rate change processing means determines that the currently transmitted transmission rate is the desired transmission rate. When selecting a user terminal that does not satisfy the condition, the rate change process is performed only for the user terminal whose consumed wireless resource amount consumed in accordance with the rate change is within the range of the free wireless resource amount stored in the user information management means. It is characterized by the following.
[0017]
According to the above configuration, a situation in which a call loss occurs can be avoided by changing to a high-speed rate beyond the limit of the newly generated wireless resource.
[0018]
Further, the rate change processing means is characterized in that when changing the transmission rate of a user terminal that does not satisfy the desired transmission rate, the transmission rate is gradually increased to approach the desired rate.
[0019]
According to the above configuration, since the transmission rate is changed stepwise, the influence of the amount of interference on other user terminals can be reduced.
[0020]
Also, the desired transmission rate stored and managed by the user information management means is determined based on the reception quality measured by the user terminal.
[0021]
According to the above configuration, the desired transmission rate is set at any time according to the call connection status, so that the influence of the amount of interference on other user terminals can be reduced.
[0022]
Also, the diversity handover processing means instructs the base station apparatus to cancel the diversity handover only when the base station apparatus confirms a call loss caused by a shortage of radio resources.
[0023]
According to the above configuration, it is possible to avoid deterioration of reception quality and occurrence of another call loss that can occur by canceling the diversity handover state more than necessary.
[0024]
A radio communication control method according to the present invention is a radio communication control method between a base station apparatus and a user terminal that is a mobile station, and includes a transmission rate, a consumed radio resource amount, and a reception quality stored for each user terminal. A high transmission rate terminal searching step of searching for user terminals communicating at a transmission rate higher than a predetermined reference rate from user information including a desired transmission rate, and a user terminal communicating at the searched high transmission rate Among them, a diversity handover terminal search step of searching for a user terminal that is in a diversity handover state and satisfies a predetermined reception quality, and whether to release the diversity handover state of the user terminal in the searched diversity handover state Or an instruction to release a part of the wireless branch to the base station apparatus. A diversity handover processing step to be provided; a low transmission rate terminal search step of searching for a user terminal having a transmission rate lower than a desired transmission rate from the user information; and a transmission of a user terminal lower than the searched desired transmission rate. A rate change processing step of giving an instruction to change the rate to the base station apparatus.
[0025]
According to the above procedure, a part of the radio resources of the user terminal in the diversity handover state is released at a sufficiently high reception rate at a sufficiently high reception quality, and the transmission rate of the other user terminals is changed. It is possible to increase the amount of radio resources that can be used in the entire system without affecting the reception quality of existing user terminals that are communicating at a low rate.
[0026]
Further, in the diversity handover processing step, when instructing the base station apparatus to cancel the diversity handover, only the radio branch having the highest reception quality is left.
[0027]
According to the above procedure, by minimizing the number of remaining wireless branches, the amount of newly generated wireless resources can be maximized.
[0028]
Further, in the diversity handover processing step, when instructing the base station apparatus to release a wireless branch, a wireless branch having reception quality equal to or higher than a predetermined threshold is left.
[0029]
According to the above-mentioned procedure, it is possible to prevent the release of the wireless branch more than necessary, and to prevent extreme degradation of the reception quality of the user terminal that may occur thereafter.
[0030]
Further, in the rate change processing step, the time during which transmission was possible at a transmission rate equal to or higher than a predetermined value for each user terminal is integrated and stored as a high-speed communication integration time. The transmission rate is changed by sequentially selecting the transmission rate.
[0031]
According to the above procedure, user terminals that can be changed to a high-speed rate can be selected without bias, and transmission rates between user terminals can be leveled.
[0032]
Further, in the rate change processing step, storing the amount of free radio resources generated by the release of the diversity handover or partial release of the radio branch, the user terminal whose current transmission rate does not satisfy the desired transmission rate At the time of selection, the transmission rate is changed only for a user terminal whose consumed wireless resource amount accompanying the rate change is within the free wireless resource amount range.
[0033]
According to the above procedure, a situation in which a call loss occurs can be avoided by changing to a high-speed rate beyond the limit of the newly generated radio resource.
[0034]
Further, in the rate change processing step, when changing the transmission rate of the user terminal that does not satisfy the desired transmission rate, the transmission rate is gradually increased to approach the desired rate.
[0035]
According to the above procedure, since the transmission rate is changed stepwise, the influence of the amount of interference on other user terminals can be reduced.
[0036]
Also, in the diversity handover processing step, the base station apparatus is instructed to cancel the diversity handover only when confirming a call loss caused by a shortage of radio resources in the base station apparatus.
[0037]
According to the above-described procedure, it is possible to avoid degradation of reception quality and occurrence of another call loss that may occur by canceling the diversity handover state more than necessary.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the present invention, in the mobile communication system, if there are a plurality of user terminals in the system performing diversity handover while sufficiently maintaining the reception quality, release the diversity handover state of some of these user terminals, a plurality of Radio resources that can be used in the base station apparatus. Then, by allocating the available radio resources to the user terminals that need to receive data at high speed, the average data transmission rate received by the user terminals is increased, the system capacity is increased, and the system operation is increased. To improve efficiency.
[0039]
FIG. 1 is a block diagram illustrating a configuration of a base station device and a radio network control device according to an embodiment of the present invention. A mobile communication system is formed together with the base station apparatus and the radio network control apparatus and a user terminal (for example, a mobile phone) which is a mobile station (not shown).
[0040]
The base station apparatus 100 includes an antenna 101, an antenna duplexer 102, a reception RF unit 103, a demodulation unit 104, a separation unit 105, a transmission control unit 106, a modulation unit 107, a code multiplexing unit 108, a transmission RF unit 109, and radio resource management. It is configured to include the unit 110.
[0041]
In this base station apparatus 100, the receiving operation is performed as follows. The signal from the user terminal received by antenna 101 is sent to reception RF section 103 via antenna duplexer 102. The reception signal is amplified by the reception RF section 103 and frequency-converted to an intermediate frequency or a baseband frequency. The frequency-converted received signal is demodulated by demodulation section 104 and sent to separation section 105, where it is separated into reception data and a signal for transmission power control.
[0042]
On the other hand, the transmission operation is performed as follows. Transmission power information and transmission data transmitted from separation section 105 are framed by transmission control section 106 and transmitted to modulation section 107. After the transmission data is modulated by modulation section 107, it is multiplexed with a modulation signal from another user terminal in code multiplexing section 108 and sent to transmission RF section 109. The transmission data that has been frequency-converted by the transmission RF section 109 and further amplified is transmitted from the antenna 101 via the antenna duplexer 102.
[0043]
In addition, the radio resource management unit 110 allocates and releases radio resources and changes the transmission rate for each user terminal according to an instruction from a call processing unit 151 of the radio network control device 150 described later.
[0044]
The wireless network control device 150 is connected to at least one or more base station devices, in the example of FIG. 1, the base station 100 and the base station device 200, and includes a call processing unit 151, a reception quality measurement unit (reception quality measurement unit) 155, It is configured to include the replication unit 156.
[0045]
The call processing unit 151 includes a user information management unit (user information management unit) 152, a diversity handover release processing unit (diversity handover processing unit) 153, and a rate change processing unit (rate change processing unit) 154. It instructs each radio resource management unit 110 of each of the station devices 100 and 200 to set and release a call, that is, to set and release a radio resource and change a transmission rate. In the following description and drawings, diversity handover may be abbreviated as DHO.
[0046]
The reception quality measurement unit 155 measures the quality of the received signal for each user terminal in each of the base station devices 100 and 200, and sends the measurement result to the user information management unit 152 of the call processing unit 151 for storage. The measured reception quality includes, for example, a bit error rate (BER) and a block error rate (BLER). Further, it has a function of synthesizing the received data and transmitting it to a higher-level device such as an exchange.
[0047]
Duplicating section 156 duplicates transmission data for base station apparatuses 100 and 200 and transmits the data to a plurality of base station apparatuses performing diversity handover.
[0048]
Next, the operation of the call processing unit 151 will be described. The user information management unit 152 of the call processing unit 151 stores information for each user terminal as shown in Table 1, for example, data such as a current transmission rate, a consumed radio resource, a reception quality of each base station device, and a desired transmission rate. Remember and manage. In the table below, a plurality of user terminals are represented by # 1 to #n, respectively, and communication partners of the user terminals corresponding to the base station apparatuses 100 and 200 are represented by base stations B1 to B3.
[0049]
[Table 1]

[0050]
The following can be seen from Table 1. For example, in the case of the user terminal # 1, transmission is currently performed at 128 kbps, and the amount of radio resources consumed per base station is 40. Furthermore, the reception qualities with the three base stations B1 to B3 are 10, 8, and 7, respectively, indicating that the base station B1 to B3 is in a diversity handover state. The reception quality is evaluated by converting the CRC result, BER, BLER, and the like into numerical values of 10 levels, and it is assumed that the higher the value, the better the reception quality. This reception quality is periodically updated based on the result from the reception quality measurement unit 155.
[0051]
In addition, the desired downlink transmission rate of the user terminal # 1 is 256 kbps, and the current transmission rate of 128 kbps is equal to or less than the desired value. The desired downlink transmission rate is set based on the reception quality measured at each user terminal, and is notified to the wireless network control device 150. The receivable downlink transmission rate is set based on the power ratio of the carrier wave and the interference wave received by the user terminal. When the ratio of the carrier wave and the interference wave is large, the data can be transmitted without error even if the rate is changed to a high rate, so that the data can be received at a high transmission rate.
[0052]
In the case of user terminal # 1, the amount of radio resources consumed per base station is 40, which is equally consumed among base stations B1 to B3 performing diversity handover. Similarly, when the radio resource consumption per base station for the user terminals # 2 to #n is converted, they become 345, 335, and 325 in the base stations B1 to B3, respectively, as shown in Table 2.
[0053]
[Table 2]

[0054]
Next, the procedure for releasing the diversity handover in the DHO release processing unit 153 of the call processing unit 151 will be specifically described with reference to the flowchart of FIG.
[0055]
First, a user terminal communicating at a transmission rate higher than a predetermined reference rate is searched and extracted from the information stored in the user information management unit 152 (step S31). Assuming that the reference rate is set to 128 kbps in the example of Table 1, the user terminals to be extracted are # 1, # 3, # 6, and #n. Here, the reference rate is a rate serving as a demarcation point for releasing the diversity handover state, and a user terminal transmitting at a reference rate or higher is a target for releasing the diversity handover state. Therefore, if a relatively low rate is set, most of the user terminals in the system are released from the diversity handover state, and the effect of the diversity handover may be lost and the reception quality may be significantly deteriorated. It is desirable to set a relatively high rate such that the number is limited.
[0056]
Next, among the extracted user terminals, a user terminal in a diversity handover state is searched for and extracted (step S32). In the example of Table 1, all of the user terminals extracted in step S31 are in the diversity handover state. Then, for each of the user terminals in the diversity handover state, it is checked whether or not the minimum value of the reception quality for each of the communicating base station apparatuses is equal to or higher than a predetermined reference value (step S33). If the value is equal to or more than the reference value, the process returns to step S31, and only the user terminals having the minimum value of the reception quality of each base station device equal to or more than the reference value are left. In the example of Table 1, if the reference value of the reception quality is set to 7, the corresponding user terminals are # 1, # 3, and # 6.
[0057]
Subsequently, an instruction is given to the radio resource management unit 110 of the base station apparatuses 100 and 200 to release the diversity handover state of the user terminal (step S34). At this time, the radio branches in the diversity handover state to be released are selected in descending order of the reception quality from the base station apparatus, and only one branch having the highest reception quality is left. The reason why the reference value is used for the reception quality is that, even in the diversity handover state, if the reception quality at that time is low, the wireless link of the user terminal itself is disconnected by forcibly canceling the diversity handover. This is to prevent that. As described above, the release of the diversity handover is performed only for the user terminal performing the diversity handover while holding the wireless branch having the good reception quality.
[0058]
In the example of Table 1, when the diversity handover state of the user terminals # 1, # 3, and # 6 is released and only the radio branch with the base station apparatus having the highest reception quality is left, the data managed by the user information management unit 152 Are as shown in Tables 3 and 4.
[0059]
[Table 3]

[0060]
[Table 4]

[0061]
Table 4 shows the amount of wireless resources consumed by each base station device. The amount of wireless resources consumed by all of the base stations B1 to B3 is significantly reduced as compared with the case of Table 2. This means that a usable radio resource is newly generated.
[0062]
Next, the procedure of the rate update process in the rate update processing unit 154 of the call processing unit 151 will be specifically described with reference to the flowchart of FIG. This rate update processing is performed after the diversity handover release processing in the DHO release processing unit 153.
[0063]
First, a user terminal whose current transmission rate is lower than the desired transmission rate is searched for and extracted (step S41). In the example of Table 3, user terminals whose desired transmission rate is higher than the current transmission rate are # 1, # 5, and # 6.
[0064]
Next, an instruction is given to the radio resource management unit 110 of the base station apparatuses 100 and 200, and the transmission rate of the corresponding user terminal is updated so as to be increased as desired (step S42). In the example of Table 3, the transmission rates of all user terminals # 1, # 5, and # 6 are increased as desired. As a result, the data stored after performing the diversity handover release and the rate change processing in the user information management unit 152 are as shown in Tables 5 and 6.
[0065]
[Table 5]

[0066]
[Table 6]

[0067]
Comparing Tables 1 and 5, and Tables 2 and 6, respectively, reveals the following.
In Table 1 showing the state before performing the diversity handover cancellation and the rate change processing, there are three user terminals that cannot receive the transmission rate as desired. On the other hand, in Table 5 after the processing procedure shown in FIGS. 2 and 3, all the user terminals can receive at the desired transmission rate.
[0068]
Also, while the sum of the radio resource amounts of the respective base station apparatuses was 1005 as shown in Table 2 before performing the diversity handover cancellation and the rate change processing, the processing procedure shown in FIGS. 2 and 3 is executed. In Table 6 after this, it could be reduced to 875.
[0069]
As described above, according to the configuration and the procedure of the present embodiment, by releasing a part of the radio resources of the user terminal in the diversity handover state at a sufficiently good high-speed reception quality, the average of the other user terminals Effective transmission rate can be improved. Further, the wireless resource amount of the entire system can be efficiently consumed, and the system capacity can be increased.
[0070]
The DHO release processing unit 153 gives the radio resource management unit 110 of the base station apparatuses 100 and 200 an instruction to release diversity handover to a user terminal that is in a diversity handover state and satisfies a predetermined reception quality. Although the configuration has been described, it may be instructed to release a part of the wireless branch while maintaining the diversity handover state. In this case, the radio branch to be released may be provided with a predetermined threshold held by the system, and the radio branch having good reception quality equal to or higher than this threshold may be left. As a result, it is possible to prevent the diversity handover state from being unconditionally released or the radio branch from being released more than necessary, so that the reception quality does not deteriorate.
[0071]
Further, the instruction to cancel the diversity handover state to the searched user terminal by the DHO cancellation processing unit 153 may be performed only when a call loss occurs due to a shortage of radio resources in the base station apparatuses 100 and 200. . By this means, it is possible to avoid degradation of reception quality and occurrence of another call loss, which can occur by releasing the diversity handover state more than necessary.
[0072]
When the user terminal whose transmission rate is to be updated is selected in the rate change processing unit 154, the search is performed for all the user terminals whose currently transmitted rates do not satisfy the desired transmission rate. The user terminal not receiving the high rate service may be preferentially selected. For example, the user information management unit 152 accumulates and stores the time during which transmission at a predetermined rate or more can be performed within a predetermined time for each user terminal, and sequentially selects the time from the user because the accumulation time is short. . As a result, user terminals capable of changing to the high-speed rate can be selected without bias, and transmission rates can be leveled.
[0073]
Further, when the rate change processing unit 154 selects a user terminal whose transmission rate is to be updated and changes the transmission rate to a desired transmission rate, the transmission rate is gradually increased to approach the desired transmission rate. Is also good. Thereby, interference with other user terminals can be reduced.
[0074]
Furthermore, in the rate update processing in the rate change processing unit 154, in consideration of the amount of available wireless resources newly generated by releasing the diversity handover, the rate update may be performed within the range of the amount of wireless resources. Good. For example, the radio resource amount generated by canceling the diversity handover is stored in the user information management unit 152, and when a user terminal whose current transmission rate does not satisfy the desired transmission rate is selected, the user terminal may receive the radio resource amount according to the rate change. The rate change process is performed only for user terminals that are within the range of the stored wireless resources. As a result, it is possible to avoid a call loss situation that may occur when the rate is changed to a high rate beyond the limit of the newly generated radio resource.
[0075]
As described above, in the present embodiment, when there are a plurality of user terminals performing diversity handover with sufficiently good communication quality in the system, the diversity handover state of these user terminals is released or some of the radio resources are released. Is released, the radio resources available between the plurality of base station apparatuses are increased. By allocating the increased radio resource to another user terminal capable of receiving data at high speed and changing the transmission rate, the average data transmission rate received by the user terminal can be increased. Since the capacity of the whole system can be increased, the efficiency of system operation can be improved.
[0076]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a radio network control device capable of increasing the radio resources usable between a plurality of base station devices and improving the efficiency of system operation.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a base station device and a radio network control device according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a procedure of a diversity handover release process according to the embodiment of the present invention.
FIG. 3 is a flowchart showing a procedure of a rate update process according to the embodiment of the present invention.
[Explanation of symbols]
100, 200 base station apparatus
110 Radio Resource Management Unit
150 Wireless network controller
151 call processing unit
152 User information management unit
153 Diversity handover (DHO) release processing unit
154 Rate change processing unit
155 Receive quality measurement unit
156 duplication unit

Claims (15)

A wireless network control device that performs wireless communication control between a base station device and a user terminal that is a mobile station,
Reception quality measurement means for measuring reception quality between the user terminal and the base station device,
For each of the user terminals, a transmission rate, a consumed radio resource amount, reception quality measured by the reception quality measurement unit, user information management means for storing and managing user information including a desired transmission rate of the user terminal,
From the user information managed by the user information management means, a user terminal in which wireless communication with the base station apparatus is in a diversity handover state and satisfies a predetermined reception quality is searched, and diversity is transmitted to the base station apparatus. Release of the handover state, or diversity handover processing means for giving an instruction to partially release the wireless branch,
From the user information managed by the user information management means, search for a user terminal that does not satisfy the desired transmission rate, rate change processing means for instructing the base station apparatus to change the transmission rate,
A wireless network control device comprising: 2. The wireless network control device according to claim 1, wherein the diversity handover processing unit leaves only the wireless branch having the highest reception quality when instructing the base station device to cancel the diversity handover. 2. The diversity handover processing unit according to claim 1, wherein when instructing the base station apparatus to release a wireless branch, the diversity handover processing unit leaves a wireless branch having reception quality equal to or higher than a predetermined threshold. Wireless network controller. The user information management means accumulates the time during which transmission was possible at a transmission rate equal to or higher than a predetermined value for each user terminal and stores the accumulated time as a high-speed communication integration time,
The method according to claim 1, wherein the rate changing means sequentially selects an instruction to change the transmission rate for the base station apparatus from user terminals having a short high-speed communication integration time stored in the user information managing means. The wireless network control device according to claim 1. The user information management means, the release of the diversity handover or storing the amount of free radio resources generated by the partial release of the radio branch,
The rate change processing means, when selecting a user terminal for which the currently transmitted transmission rate does not satisfy the desired transmission rate, the amount of radio resource consumed by the rate change is stored in the user information management means. The wireless network control device according to claim 1, wherein the rate change process is performed only for a user terminal that is within a range of an available wireless resource amount. 2. The method according to claim 1, wherein the rate change processing means increases the transmission rate stepwise to approach the desired rate when changing the transmission rate of a user terminal that does not satisfy the desired transmission rate. 3. The wireless network control device according to 1. The wireless network control device according to claim 1, wherein the desired transmission rate stored and managed by the user information management means is determined based on reception quality measured by a user terminal. The said diversity handover processing means instruct | indicates cancellation | release of the said diversity handover to the said base station apparatus, only when confirming the call loss caused by the shortage of radio resources in the said base station apparatus, The wireless network control device according to claim 1. A wireless communication control method between a base station device and a user terminal that is a mobile station,
A high transmission rate terminal that searches for user terminals communicating at a transmission rate higher than a predetermined reference rate from user information including a transmission rate, a consumed radio resource amount, a reception quality, and a desired transmission rate stored for each user terminal. A search step;
Among the user terminals communicating at the searched high transmission rate, a diversity handover terminal searching step of searching for a user terminal that is in a diversity handover state and satisfies a predetermined reception quality,
Diversity handover processing step of releasing the diversity handover state of the user terminal in the searched diversity handover state, or giving an instruction to release a part of the radio branch to the base station apparatus,
A low transmission rate terminal search step of searching for a user terminal whose transmission rate currently transmitting from the user information is lower than a desired transmission rate,
Rate change processing step of giving an instruction to change the transmission rate of the user terminal lower than the searched desired transmission rate to the base station apparatus,
A wireless communication control method, comprising: 10. The radio communication control method according to claim 9, wherein, in the diversity handover processing step, when instructing the base station apparatus to cancel the diversity handover, only a radio branch having the highest reception quality is left. 10. The diversity handover processing step, wherein when instructing the base station apparatus to release a wireless branch, a wireless branch having reception quality equal to or higher than a predetermined threshold is left. Wireless communication control method. In the rate change processing step, the time during which transmission could be performed at a transmission rate equal to or higher than a predetermined value for each user terminal is integrated and stored as a high-speed communication integration time, and the user terminals are sequentially selected from the user terminals with a small high-speed communication integration time. 10. The wireless communication control method according to claim 9, wherein the transmission rate is changed. In the rate change processing step, an available radio resource amount generated by releasing the diversity handover or partially releasing a radio branch is stored, and a user terminal whose transmission rate currently transmitting does not satisfy a desired transmission rate is selected. 10. The wireless communication control according to claim 9, wherein the transmission rate is changed only for a user terminal whose consumed wireless resource amount accompanying the rate change is within the range of the free wireless resource amount. Method. 10. The method according to claim 9, wherein, in the rate change processing step, when changing the transmission rate of the user terminal that does not satisfy the desired transmission rate, the transmission rate is gradually increased to approach the desired rate. 3. The wireless communication control method according to 1. In the diversity handover processing step, only when the base station device confirms a call loss caused by a shortage of radio resources, the base station device is instructed to release the diversity handover to the base station device. The wireless communication control method according to the above.

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