JP2004349811A - Wireless communication system, gateway, node, and access node - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system or the like wherein a mobile terminal needs no position registration every time the mobile terminal moves between cells under a prescribed condition. <P>SOLUTION: The wireless communication system transfers packets to the mobile terminal via any of a plurality of access nodes. The wireless communication system includes: a mobile prediction information storage section 11 for storing a plurality of mobile prediction information items for correlating time information and identification information of the access node; a first transfer time storage section 14 for managing the first transfer time of the packets up to each access node AR; and a destination access node determining section 16 for determining the access node AR being a packet destination on the basis of a plurality of the mobile prediction information items, the first transfer time, and the present time. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

また、宛先アクセスノード決定部１６は、統計的に電波状況の悪い領域を移動端末ＭＮ１が通過する通過時刻を考慮して、パケットの宛先アクセスノードを決定するように構成されていてもよい。
【００６０】
具体的には、図４に示すように、宛先アクセスノード決定部１６は、上述の方法で「ＡＲｎ」を宛先アクセスノードとして決定した場合であっても、パケットが「ＡＲｎ」に到着する時刻が「Ｔ_ｎ＋１」と「Ｔ_ｎ＋１＋γ_ｎ＋１」との間であると判断される場合には、「ＡＲｎ＋１」を宛先アクセスノードとして決定する。
【００６１】
ヘッダ付与部１７は、宛先アクセスノード決定部１６によって決定された宛先アクセスノードＡＲｎのアドレスを「終点アドレス（宛先アドレス）」とするヘッダを、受信したパケットに付与すると共に、当該宛先アクセスノードＡＲｎに対応する第１の移動予測情報を、受信したパケットに付与するものである。
【００６２】
図５の例では、ヘッダ付与部１７は、ＩＰ ｉｎ ＩＰカプセル化によって、「始点アドレス＝ゲートウェイＧＷのアドレス」及び「終点アドレス＝アクセスノードＡＲ１」とするカプセル化ヘッダを、受信したパケット（オリジナルのパケット）に対して付与する。
【００６３】
また、ヘッダ付与部１７は、ＩＰヘッダの中継点オプションヘッダを拡張することによって、受信したパケット（オリジナルのパケット）に対して、時刻情報（到着時刻）とアクセスノードの識別情報（到着時刻に到着するアクセスノードのアドレス）とを関連付ける移動予測情報を付与する。
【００６４】
図５の例では、ヘッダ付与部１７は、アクセスノードＡＲ１に対応する第１の移動予測情報と、アクセスノードＡＲ２に対応する第２の移動予測情報と、アクセスノードＡＲ３に対応する第３の移動予測情報とを含む中継点オプションヘッダを、オリジナルのパケットに対して付与している。
【００６５】
ここで、パケットのオーバヘッドを考慮すると、付与される移動予測情報の数は少ない方が望ましい。
【００６６】
また、ヘッダ付与部１７は、無線リンク上のＭＴＵ（Ｍａｘｉｍｕｍ Ｔｒａｎｓｆｅｒ Ｕｎｉｔ）を超えないように、移動予測情報を付与するように構成されている。
【００６７】
さらに、ヘッダ付与部１７は、付与されている移動予測情報の数を容易に判断することを可能とするために、中継点オプションヘッダを固定長にすることもできる。
【００６８】
ルーティング部１８は、第１の移動予測情報が付与されたパケットをルーティングするものである。図５の例では、ルーティング部１８は、カプセル化ヘッダに基づいて、受信したパケットをノード＃１又は＃２に対してルーティングして転送する。
【００６９】
本実施形態では、移動予測情報データベース１１、移動予測情報管理部１２、所要時間測定部１３、所要時間データベース１４は、ゲートウェイＧＷ内の機能として設けられているが、これらの機能の全部又は一部が、ゲートウェイＧＷと別個の装置として設けられていてもよい。
【００７０】
ノード＃１及び＃２は、ゲートウェイＧＷから転送されたパケットを受信して、他のノードやアクセスノードに転送するものである。ノード＃１の機能とノード＃２の機能は、基本的に同一であるので、以下、ノード＃１の機能について説明する。
【００７１】
ノード＃１は、図６に示すように、所要時間測定部３３と、所要時間データベース３４と、受信部３５と、宛先アクセスノード決定部３６と、ヘッダ変更部３７と、ルーティング部３８とを具備するものである。
【００７２】
所要時間測定部３３は、ゲートウェイＧＷの所要時間測定部１３と同様の機能を具備するものであり、各アクセスノードＡＲ１乃至ＡＲ３までのパケットの第２の転送時間、すなわち、ノード＃１から送信されたパケットが各アクセスノードＡＲ１乃至ＡＲ３に到着するのに要する時間を測定するものである。所要時間測定部３３は、周期的に、Ｐｉｎｇコマンド等を用いて、当該第２の転送時間を測定することができる。
【００７３】
所要時間データベース３４は、上述の第２の転送時間を管理する第２の転送時間記憶部である。図６の例では、所要時間データベース３４は、所定区間を示す「区間」と、当該所定区間をパケットが転送される際に要する時間を示す「所要時間」とを関連付けて記憶している。
【００７４】
なお、図６の例では、所要時間データベース３４は、ノード＃１と各アクセスノードＡＲ１乃至ＡＲ３と間の区間における所要時間（第２の転送時間）Ａだけでなく、アクセスノードＡＲ１乃至ＡＲ３とエリア＃１乃至＃３に存在する移動端末ＭＮ１との間の区間のそれぞれにおける所要時間Ｂを記憶している。
【００７５】
ここで、所要時間Ａは、所要時間測定部３３によって測定されたものであり、所要時間Ｂは、統計情報に基づいて生成されたものである。また、所要時間Ｂは、ゲートウェイＧＷの所要時間データベース１３が管理する所要時間βと同じ値を取るものであってもよい。したがって、所要時間Ａと所要時間Ｂを加算することによって、ノード＃１と各エリア＃１乃至＃３に存在する移動端末ＭＮ１との間の区間における所要時間を算出することができる。
【００７６】
図６に示す所要時間によれば、例えば、ノード＃１とアクセスノードＡＲ２との間の区間をパケットが転送される時間は「Ａ_２」であり、アクセスノードＡＲ２とエリア＃２に存在する移動端末ＭＮ１との間の区間をパケットが転送される時間は「Ｂ_２」である。
【００７７】
受信部３５は、ゲートウェイＧＷや他のノード等からパケットを受信するものである。
【００７８】
宛先アクセスノード決定部３６は、受信にしたパケットに付与されている移動予測情報と第２の転送時間と現在時刻とに基づいて、受信部３５を介して受信したパケットの宛先アクセスノードを決定するものである。
【００７９】
具体的には、宛先アクセスノード決定部３６は、以下のように、宛先アクセスノードを決定する。ここで、現在時刻は、「Ｔ’」であり、受信したパケットに付与されている移動予測情報（時刻情報，アクセスノードの識別情報）は、（Ｔ_１，ＡＲ１）、（Ｔ_２，ＡＲ２）、…（Ｔ_ａ，ＡＲａ）であるものとする。また、Ｔ’＜Ｔ_１とし、Ｔ_１＜Ｔ_２＜…＜Ｔ_ａとする。
【００８０】
さらに、ノード＃１から各アクセスノードＡＲ１乃至ＡＲａまでパケットが転送されるのに要する第２の転送時間は、それぞれＡ_１、Ａ_２、…Ａ_ａである。
【００８１】
また、各アクセスノードＡＲ１乃至ＡＲａから移動端末ＭＮ１までパケットが転送されるのに要する時間は、それぞれＢ_１、Ｂ_２、…Ｂ_ａである。ここで、各アクセスノードＡＲ１乃至ＡＲａまでパケットが転送されるのに要する時間は、リアルタイムに取得できない場合には、Ｂ_１、Ｂ_２、…Ｂ_ａの統計値を用いるように構成されていてもよい。
【００８２】
宛先アクセスノード決定部３６は、受信したパケットに付与されている移動予測情報の中から、「Ｔ’＋（Ａ_ａ＋Ｂ_ａ）（ａ＝１，２，…ａ）」より大きく、かつ、最も「Ｔ’＋（Ａ_ａ＋Ｂ_ａ）」に近い「Ｔ_ａ」を決定し、決定した「Ｔ_ａ」に対応するアクセスノードＡＲａを、宛先アクセスノードとして決定する。
【００８３】
また、宛先アクセスノード決定部３６は、上述のゲートウェイＧＷの宛先アクセスノード決定部１６と同様に、統計的に電波状況の悪い領域を移動端末ＭＮ１が通過する通過時刻を考慮して、パケットの宛先アクセスノードを決定するように構成されていてもよい。
【００８４】
ヘッダ変更部３７は、受信部３５を介して受信したパケットのヘッダを、宛先アクセスノード決定部３６による決定に応じて変更するものである。
【００８５】
具体的には、ヘッダ変更部３７は、カプセル化ヘッダの「終点アドレス（宛先アドレス）」を、宛先アクセスノード決定部３６によって決定された宛先アクセスノードＡＲａのアドレスに変更すると共に、中継オプションヘッダを、当該宛先アクセスノードに対応する移動予測情報を「第１の移動予測情報」とするように変更する。
【００８６】
この際、ヘッダ変更部３７は、一旦、ＩＰ ｉｎ ＩＰカプセル化を解き、「始点アドレス＝ノード＃１のアドレス」及び「終点アドレス＝アクセスノードＡＲａ」とするカプセル化ヘッダを、受信したパケット（オリジナルのパケット）に対して付与する。
【００８７】
ここで、ヘッダ変更部３７は、宛先アクセスノード決定部３６によって決定された宛先アクセスノードのアドレスが、受信したパケットのカプセル化ヘッダに設定されている場合、当該カプセル化ヘッダの「終点アドレス（宛先アドレス）」を変更しない。
【００８８】
また、ヘッダ変更部３７は、設定されている到着時刻が、現在時刻よりも古い時刻である移動予測情報を削除するように構成されていてもよい。
【００８９】
ルーティング部３８は、カプセル化ヘッダに基づいて、受信したパケットをルーティングするものである。
【００９０】
アクセスノードＡＲ１乃至ＡＲ６は、それぞれエリア＃１乃至＃６に存在する移動端末ＭＮとの間で、無線リンクを確立して無線通信を行うものである。例えば、基地局やアクセルルータ等が、アクセスノードＡＲ１乃至ＡＲ６に該当する。アクセスノードＡＲ１乃至ＡＲ６の機能は、基本的に同一であるため、以下、アクセスノードＡＲ１の機能について説明する。
【００９１】
アクセスノードＡＲ１は、図７に示すように、受信部５１と、無線リンク情報管理部５２と、バッファ５３と、送信部５４と、移動予測情報修正要求部５５と、到着予定時刻受信部５６と、ヘッダ変換部５７とを具備する。
【００９２】
受信部５１は、ノード＃１からのパケットを受信し、受信したパケットを送信部５４に転送する。
【００９３】
無線リンク情報管理部５２は、移動端末ＭＮとの間の無線リンク情報を記憶するものである。具体的には、無線リンク情報管理部５２は、図８に示すように、「移動端末ＩＤ」と「接続状況」と「確立時刻」とを関連付けて記憶する。
【００９４】
「接続状況」は、「移動端末ＩＤ」により識別される移動端末ＭＮとの間の無線リンクが未だ確立されていないことを示す「未到着（第１の状況）」、「移動端末ＩＤ」により識別される移動端末ＭＮとの間の無線リンクが接続中であることを示す「接続中（第２の状況）」、移動端末ＩＤ」により識別される移動端末ＭＮとの間の無線リンクの接続が既に完了したことを示す「通過（第３の状況）」のいずれかである。
【００９５】
ずなわち、「接続状況」が「未到着（第１の状況）」である場合には、移動端末ＭＮ１は、アクセスノードＡＲ１が管理するエリア＃１に未だ到着していない。また、「接続状況」が「接続中（第２の状況）」である場合には、移動端末ＭＮ１は、エリア＃１内に存在している。さらに、「接続状況」が「通過（第３の状況）」である場合には、移動端末ＭＮ１は、エリア＃１を既に通過している。
【００９６】
また、「確立時刻」は、「接続状況」が「接続中（第２の状況）」である場合、当該無線リンクが確立された時刻を示すものである。
【００９７】
バッファ５３は、送信部５４からの指示に応じて、受信部５１から転送されたパケットをバッファリングするものである。また、バッファ５３は、各パケットのバッファリング時間及びバッファリングしているパケットのデータ量を管理している。
【００９８】
送信部５４は、無線リンク情報管理部５２を参照して、受信部５１から受信したパケットの宛先移動端末ＭＮに係る無線リンク情報に応じて、当該パケットをバッファリングするか、又は、当該パケットを転送するかについて決定するものである。
【００９９】
具体的には、送信部５４は、受信部５１から受信したパケットの宛先移動端末ＭＮに係る無線リンク情報が「未到着（第１の状況）」又は「通過（第３の状況）」である場合、当該パケットをバッファ５３においてバッファリングする。一方、送信部５４は、上述の無線リンク情報が「接続中（第２の状況）」である場合、当該パケットを当該宛先移動端末ＭＮに対して転送する。
【０１００】
また、送信部５４は、無線リンク情報管理部５２を監視しており、バッファ５３内でバッファリングされているパケットの宛先移動端末に係る無線リンク情報が「接続中（第２の状況）」に変更された場合、当該パケットを当該宛先移動端末ＭＮに転送する。
【０１０１】
ここで、送信部５４は、当該パケットを当該宛先移動端末ＭＮに転送するにあたって、当該パケットに付与されているカプセル化ヘッダ（図５参照）を削除する。
【０１０２】
また、送信部５４は、統計的に電波状況の悪い領域を移動端末ＭＮが通過する通過時刻を管理しており、上述の無線リンク情報が「接続中（第２の状況）」である場合であっても、当該通過時刻の間、当該パケットをバッファ５３にバッファリングするように構成されていてもよい。
【０１０３】
また、送信部５４は、到着予定時刻受信部５６から通知された移動端末ＭＮの到着時刻に、バッファ５３内にバッファリングされている当該移動端末ＭＮ宛てのパケットを送信できるように準備する。すなわち、送信部５４は、上述の到着時間以降は、当該移動端末ＭＮ宛てのパケットをバッファリングしている領域を、他のパケットのバッファリング用領域として割り当てることができる。
【０１０４】
また、送信部５４は、ヘッダ変換部５７から送信されたパケットを、当該パケットのヘッダに基づいてルーティングして転送する。
【０１０５】
さらに、送信部５４は、ゲートウェイＧＷから一斉呼び出し（ページング）を受信した場合、無線リンク情報管理部５２を参照して、当該一斉呼び出しで指定されている移動端末ＭＮとの間で無線リンクを確立しているか否かを検索し、無線リンクが確立されている場合、その旨及び無線リンクの確立時刻をゲートウェイＧＷに通知するように構成されている。
【０１０６】
移動予測情報修正要求部５５は、バッファ５３を監視しており、「無線リンク情報」が「未到着（第１の状況）」である特定のパケットのバッファリング時間が所定時間を経過した場合、当該パケットに付与されている移動予測情報の修正要求をゲートウェイＧＷに送信する。
【０１０７】
また、移動予測情報修正要求部５５は、バッファ５３を監視しており、バッファ５３内にバッファリングされているパケット（「無線リンク情報」が「未到着（第１の状況）」であるパケット）のデータ量が所定の閾値を超えた場合、移動予測情報の修正要求をゲートウェイＧＷに送信する。
【０１０８】
また、移動予測情報修正要求部５５は、無線リンク情報が「通過（第３の状況）」であるために、バッファリングされているパケットに付与されている移動予測情報の修正要求を送信する。
【０１０９】
さらに、移動予測情報修正要求部５５は、上述の移動予測情報の修正要求に応じてゲートウェイＧＷから送信された移動予測情報（修正された移動予測情報）を受信してヘッダ変換部５７に通知する。
【０１１０】
到着予定時刻受信部５６は、ゲートウェイＧＷから、バッファ５３内でバッファリングされているパケットの宛先移動端末ＭＮとの間で無線リンクが確立される予定確立時刻を受信するものである。
【０１１１】
ヘッダ変換部５７は、移動予測情報修正要求部５５から通知された移動予測情報（修正された移動予測情報）に応じて、バッファ５３内にバッファされているパケットのヘッダを変換するものである。
【０１１２】
例えば、ヘッダ変換部５７は、修正された移動予測情報を、該当するパケットの中継オプションヘッダに挿入する。そして、ヘッダ変換部５７は、修正された移動予測情報を付与したパケットを送信部５４に転送する。
【０１１３】
（本実施形態に係る無線通信システムの動作）
図９乃至図１２を参照して、本実施形態に係る無線通信システムの動作を説明する。第１に、図９を参照して、本実施形態に係るゲートウェイＧＷの動作を説明する。
【０１１４】
図９に示すように、ステップ１００１において、ゲートウェイＧＷの所要時間測定部１３が、所定周期で、所要時間データベース１４の内容を更新する。
【０１１５】
ステップ１００２において、ゲートウェイＧＷの受信部１５が、ＩＰネットワーク２を介して、通信相手ＣＮから移動端末ＭＮ１宛てのパケットを受信した場合、本動作は、ステップ１００３に進む。
【０１１６】
宛先アクセスノード決定部１６は、ステップ１００３乃至１００６に示す方法で、受信したパケットの宛先アクセスノードを決定する。ここで、「Ｔ」は、現在時刻を示し、「ＡＲｎ」は、移動予測情報データベース１１内の「Ｔｎ」に対応するアクセスノードである。また、「α_ｎ」は、ゲートウェイＧＷとアクセスノードＡＲｎとの間の区間においてパケットの転送に要する所要時間（第１の転送時間）を示し、「β_ｎ」は、アクセスノードＡＲｎとエリア＃ｎ内の移動端末ＭＮ１との間の区間においてパケットの転送に要する所要時間を示す。「α_ｎ」及び「β_ｎ」は、所要時間データベース１４内に記憶されているものである。
【０１１７】
ステップ１００３乃至１００６に示す方法で、宛先アクセスノード決定部１６は、「Ｔ＋（α_ｎ＋β_ｎ）（ｎ＝１，２，…ｎ）」より大きく、かつ、最も「Ｔ＋（α_ｎ＋β_ｎ）」に近い「Ｔ_ｎ」を決定し、決定した「Ｔ_ｎ」に対応するアクセスノードＡＲｎを、宛先アクセスノードとして決定する。
【０１１８】
ステップ１００７において、ヘッダ付与部１７は、アクセスノードＡＲｎに対応する第１の移動予測情報と、アクセスノードＡＲｎ＋１に対応する第２の移動予測情報と、アクセスノードＡＲｎ＋２に対応する第３の移動予測情報とを、受信したパケットに付与する。
【０１１９】
具体的には、ヘッダ付与部１７は、アクセスノードＡＲｎを宛先アドレスとするカプセル化ヘッダで、受信したパケットをカプセル化すると共に、第１乃至第３の移動予測情報を含む中継オプションヘッダを当該パケットに挿入する。
【０１２０】
ステップ１００８において、ルーティング部１８は、カプセル化ヘッダに基づいて当該パケットをルーティングする。
【０１２１】
第２に、図１０を参照して、本実施形態に係るノード＃１の動作を説明する。
【０１２２】
図１０に示すように、ステップ２００１において、ノード＃１の所要時間測定部３３が、所定周期で、所要時間データベース３４の内容を更新する。
【０１２３】
ステップ２００２において、ノード＃１の受信部３５が、ゲートウェイＧＷから移動端末ＭＮ１宛てのパケットを受信した場合、本動作は、ステップ２００３に進む。ここで、受信したパケットのカプセル化ヘッダの宛先アドレスは、アクセスノードＡＲ１のアドレスとなっている。
【０１２４】
宛先アクセスノード決定部３６は、ステップ２００３乃至２００７に示す方法で、受信したパケットの宛先アクセスノードを決定する。ここで、「Ｔ’」は、現在時刻を示し、「Ｔ_ａ」は、受信したパケットに挿入されているａ番目の移動予測情報内の到着時刻を示す。また、「Ａ_ａ」は、ノード＃１とａ番目の移動予測情報内のアクセスノードＡＲａとの間の区間においてパケットの転送に要する所要時間（第２の転送時間）を示し、「Ｂ_ａ」は、アクセスノードＡＲａとエリア＃ｎ内の移動端末ＭＮ１との間の区間においてパケットの転送に要する所要時間を示す。「Ａ_ａ」及び「Ｂ_ａ」は、所要時間データベース３４内に記憶されているものである。
【０１２５】
ステップ２００３乃至２００７に示す方法で、宛先アクセスノード決定部３６は、受信したパケットに付与されている複数の移動予測情報の中から、「Ｔ’＋（Ａ_ａ＋Ｂ_ａ）（ａ＝１，２，…ａ）」より大きく、かつ、最も「Ｔ’＋（Ａ_ａ＋Ｂ_ａ）」に近い「Ｔ_ａ」を決定し、決定した「Ｔ_ａ」に対応するアクセスノードＡＲａを、宛先アクセスノードとして決定する。
【０１２６】
ステップ２００７において、宛先アクセスノード決定部３６によって決定された宛先アクセスノードＡＲａが、第１の移動予測情報に対応するものである場合、当該パケットのヘッダは変更されることなく、本動作は、ステップ２０１０に進む。
【０１２７】
また、宛先アクセスノード決定部３６によって宛先アクセスノードＡＲａを決定することができなかった場合も、当該パケットのヘッダは変更されることなく、本動作は、ステップ２０１０に進む。
【０１２８】
一方、宛先アクセスノード決定部３６によって決定された宛先アクセスノードＡＲａが、第２（又は第３）の移動予測情報に対応するものである場合、本動作は、ステップ２００８に進む。
【０１２９】
ステップ２００８において、ヘッダ変更部３７は、当該宛先アクセスノードＡＲａを宛先アドレスとするカプセル化ヘッダで、受信したパケットをカプセル化すると共に、中継オプションヘッダから第１（及び第２）の移動予測情報を削除する。
【０１３０】
ステップ２０１０において、ルーティング部３８は、カプセル化ヘッダに基づいて当該パケットをルーティングする。
【０１３１】
第３に、図１１を参照して、本実施形態に係るアクセスノードＡＲ１の動作を説明する。
【０１３２】
図１１に示すように、ステップ３００１において、アクセスノードＡＲ１の受信部５１が、ノード＃１から送信されたパケットを受信して送信部５４に転送する。
【０１３３】
ステップ３００２において、送信部５４は、無線リンク情報管理部５２を参照して、当該パケットの宛先移動端末ＭＮ１に係る無線リンク情報を確認する。
【０１３４】
当該無線リンク情報が「接続中（第２の状況）」である場合、ステップ３００３において、送信部５４が、当該パケットに付与されているカプセル化ヘッダ（図５参照）を削除して、接続中である無線リンクを介して当該パケットを移動端末ＭＮ１に対して送信する。
【０１３５】
一方、当該無線リンク情報が「通過（第３の状況）」である場合、ステップ３００４において、送信部５４が、当該パケットをバッファ５３内にバッファリングする。
【０１３６】
ステップ３００５において、移動予測情報修正要求部５５が、移動予測情報の修正要求をゲートウェイＧＷに送信する。
【０１３７】
ステップ３００６において、移動予測情報修正要求部５５が、ゲートウェイＧＷから修正された移動予測情報を受信し、ステップ３００７において、ヘッダ変換部５７が、修正された移動予測情報に基づいて、バッファリングされているパケットのヘッダを変換し、ステップ３００８において、送信部５４が、変換したヘッダに基づいて、当該パケットをルーティングして転送する。ここで、当該パケットは、例えば、アクセスノード＃２等の他のアクセスノードに転送される。
【０１３８】
また、当該無線リンク情報が「未到着（第１の状況）」である場合、ステップ３００９において、送信部５４が、当該パケットをバッファ５３内にバッファリングする。
【０１３９】
送信部５４は、ステップ３０１０において、当該無線リンク情報が「接続中（第２の状況）」に変更されたことを検知すると、ステップ３００３において、当該パケットを移動端末ＭＮ１に対して送信する。
【０１４０】
一方、ステップ３０１１において、当該無線リンク情報が「接続中（第２の状況）」に変更されることなく、当該パケットのバッファリング時間が所定時間を経過した場合（又は、当該無線リンク情報が「未到着（第１の状況）」である移動端末宛てのパケットのデータ量が所定の閾値を超えた場合）、送信部５４は、ステップ３０１２において、ゲートウェイＧＷに対して、当該パケットの宛先移動端末ＭＮ１に係る移動予測情報の修正を要求する。
【０１４１】
ステップ３０１３において、到着予定時刻受信部５６は、ゲートウェイＧＷから当該宛先移動端末ＭＮ１の到着予定時刻を受信する。送信部５４は、到着予定時刻に、当該パケットを移動端末ＭＮ１に対して送信するように準備する（ステップ３００３）。
【０１４２】
次に、図１２を参照して、本実施形態に係る無線通信システムにおいて、移動予測情報を修正する動作を示す。
【０１４３】
ステップ４００１において、アクセスノードＡＲ１の送信部５４は、ノード＃１から受信したパケットの宛先移動端末ＭＮ１に係る無線リンク情報が「通過（第３の状況）」である場合、当該パケットをバッファリングすると共に、ゲートウェイＧＷに対して、当該パケットの宛先移動端末ＭＮ１に対応する移動予測情報を修正するように要求する。
【０１４４】
ステップ４００２において、ゲートウェイＧＷの宛先アクセスノード決定部１６は、受信した移動予測情報修正要求に応じて、当該宛先移動端末ＭＮ１宛てのパケットに挿入すべき移動予測情報を再度算出する。図１２の例では、アクセスノードＡＲ３に対応する移動予測情報を、第１の移動予測情報をして当該パケットに挿入すべきであると算出されたものとする。
【０１４５】
ステップ４００３において、ゲートウェイＧＷの移動予測情報管理部１２は、修正した第１の移動予測情報として、アクセスノードＡＲ３に対応する移動予測情報を、アクセスノードＡＲ１に対して送信する。
【０１４６】
ステップ４００４において、アクセスノードＡＲ１のヘッダ変換部５７は、バッファリングされているパケットに対して、アクセスノードＡＲ３のアドレスを宛先アドレス（アクセスノードＡＲ１のアドレスを発信元アドレス）とするカプセル化ヘッダを付与すると共に、アクセスノードＡＲ２に対応する移動予測情報を第１の移動予測情報として付与する。
【０１４７】
ステップ４００５において、アクセスノードＡＲ１の送信部５４は、上述のカプセル化ヘッダに基づいて、当該パケットをアクセルノードＡＲ３にルーティングして転送する。
【０１４８】
ステップ４００６において、アクセスノードＡＲ３の送信部５４は、アクセスノードＡＲ１から受信したパケットの宛先移動端末ＭＮ１に係る無線リンク情報が「接続中（第２の状況）」であることを確認して、当該パケットを宛先移動端末ＭＮ１に送信する。
【０１４９】
（本実施形態に係る無線通信システムの作用・効果）
本実施形態に係る無線通信システムによれば、宛先アクセスノード決定部１６が、複数の移動予測情報と第１の転送時間と現在時刻とに基づいて、パケットの宛先アクセスノードＡＲを決定するため、移動端末ＭＮ１がセル（エリア）間移動を行った場合であっても、当該移動端末ＭＮ１が再度位置登録を行うことなく、当該パケットを当該移動端末ＭＮ１に転送することが可能となる。
【０１５０】
また、本実施形態に係るゲートウェイＧＷによれば、移動端末ＭＮ１が、統計的に電波状況の悪い領域である二つのセル（エリア＃ｎ及び＃ｎ＋１）が重なり合っている領域に存在する場合（すなわち、セル間移動中の場合）、宛先アクセスノード決定部１６は、移動元のアクセスノードＡＲｎではなく移動先のアクセスノードＡＲｎ＋１に対してパケットを転送することによって、パケットロスを防ぐことが可能となる。
【０１５１】
また、本実施形態に係るゲートウェイＧＷによれば、移動端末ＭＮ１が既に通過してしまったセル（エリア＃１）を管理するアクセスノードＡＲ１が、当該移動端末ＭＮ１宛てのパケットを受信した場合、修正した移動予測情報に基づいて、当該移動端末ＭＮ１が存在するセル（エリア＃３）を管理するアクセスノードＡＲ３に対して、当該パケットを再転送することが可能となる。
【０１５２】
また、本実施形態に係るゲートウェイＧＷによれば、移動端末ＭＮ１が未だ到着していないため、当該移動端末ＭＮ１宛てのパケットをバッファリングしているアクセスノードＡＲ１に対して、当該移動端末ＭＮ１の到着時刻を通知することができる。
【０１５３】
また、本実施形態に係るノード＃１によれば、宛先アクセスノード決定部３６は、受信したパケットに付与されている第１の移動予測情報によって指示されているアクセスノードＡＲ１と異なるアクセスノードＡＲ２に当該パケットをルーティングすることによって、当該パケットの転送が遅延している場合等にも柔軟に対応することができる。
【０１５４】
また、本実施形態に係るアクセスノードＡＲ１によれば、移動端末ＭＮ１が、未だ到着していない場合や既に通過してしまった場合、すなわち、当該移動端末ＭＮ１との間で無線リンクが確立していない状態では、当該移動端末宛てのパケットをバッファリングすることによって、パケットロスを防ぐことができる。
【０１５５】
また、本実施形態に係るアクセスノードＡＲ１によれば、統計的に電波状況の悪い領域を移動端末ＭＮ１が通過する通過時刻の間、当該移動端末ＭＮ１宛てのパケットをバッファリングすることによって、パケットロスを防ぐことができる。
【０１５６】
また、本実施形態に係るアクセスノードＡＲ１によれば、受信した予定確立時刻まで、パケットのバッファリングを継続することによって、バッファ容量を無駄に使用することなく、パケットロスを防ぐことができる。
【０１５７】
また、本実施形態に係るアクセスノードＡＲ１によれば、移動端末ＭＮ１が既に通過してしまったセル（エリア＃１）を管理するアクセスノードＡＲ１に当該移動端末ＭＮ１宛てのパケットが転送された場合であっても、送信部５４が、修正された移動予測情報に基づいて、バッファリングしているパケットをルーティングすることによって、当該パケットを廃棄することなく当該移動端末ＭＮ１に転送することが可能となる。
【０１５８】
【発明の効果】
以上説明したように、本発明によれば、ある一定の条件の下、移動端末ＭＮ１によるセル（エリア）間移動の度に位置登録を必要としない無線通信システム、ゲートウェイ、ノード及びアクセスノードを提供することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る無線通信システムの全体構成図である。
【図２】本発明の第１の実施形態に係る無線通信システムのゲートウェイの機能ブロック図である。
【図３】本発明の第１の実施形態に係る無線通信システムのゲートウェイの移動予測情報データベース及び所要時間データベースの一例を示す図である。
【図４】本発明の第１の実施形態に係る無線通信システムにおいて、統計的に電波状況の悪い領域を移動端末が通過する通過時刻を説明するための図である。
【図５】本発明の第１の実施形態に係る無線通信システムで用いられるパケットフォーマットの一例を示す図である。
【図６】本発明の第１の実施形態に係る無線通信システムのノードの機能ブロック図である。
【図７】本発明の第１の実施形態に係る無線通信システムのアクセスノードの機能ブロック図である。
【図８】本発明の第１の実施形態に係る無線通信システムのアクセスノードの無線リンク情報管理部の内容の一例を示す図である。
【図９】本発明の第１の実施形態に係る無線通信システムのゲートウェイの動作を示すフローチャートである。
【図１０】本発明の第１の実施形態に係る無線通信システムのノードの動作を示すフローチャートである。
【図１１】本発明の第１の実施形態に係る無線通信システムのアクセスノードの動作を示すフローチャートである。
【図１２】本発明の第１の実施形態に係る無線通信システムにおいて、移動予測情報が修正される場合のシーケンス図である。
【符号の説明】
ＡＲ…アクセスノード
ＧＷ…ゲートウェイ
ＭＮ…移動端末
１…電車
２…ＩＰネットワーク
１１…移動予測情報データベース
１２…移動予測情報管理部
１３、３３…所要時間測定部
１４、３４…所要時間データベース
１５、３５、５１…受信部
１６、３６…宛先アクセスノード決定部
１７…ヘッダ付与部
１８、３８…ルーティング部
３７、５７…ヘッダ変更部
５２…無線リンク情報管理部
５３…バッファ
５４…送信部
５５…移動予測情報修正要求部
５６…到着予定時刻受信部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless communication system, a gateway, a node, and an access node for transferring a packet to a mobile terminal via any one of a plurality of access nodes.
[0002]
[Prior art]
In a conventional wireless communication system, each time a mobile terminal performs inter-cell movement, it is necessary to perform location registration with the wireless communication system via a base station (access node) managing a destination cell. Was. The reason is that the conventional wireless communication system is configured to manage the identification information of the mobile terminal and the current position of the mobile terminal as position information, and to transfer a packet to the mobile terminal based on the position information. Because it is.
[0003]
Further, in a conventional wireless communication system, a technique of giving one scheduled arrival time to one packet for priority control of the packet is known (for example, Patent Document 1).
[0004]
In the future, wireless communication systems are expected to handle large-capacity traffic (for example, gigabit class) such as future communication such as biological information communication. Along with this, minimizing the size of the cell managed by the base station is supposed for the purpose of increasing the density of wireless channels with the aim of increasing the wireless transmission capacity. Also, with the diversification of mobile terminals, it becomes necessary to consider providing services to mobile terminals that move at a very high speed.
[0005]
[Patent Document 1]
JP-A-2000-78188
[0006]
[Problems to be solved by the invention]
However, in the conventional wireless communication system, when the cell size is minimized or when a service is provided to a mobile terminal that moves at high speed, the frequency of the inter-cell movement by the mobile terminal increases. As a result, there has been a problem that the frequency of location registration also increases, and there is a concern that the processing load on the network and the communication quality may deteriorate.
[0007]
Also, the technique disclosed in Patent Document 1 does not consider the routing (route control) when the mobile terminal moves.
[0008]
The present invention has been made in view of the above points, and provides a wireless communication system, a gateway, a node, and an access node that do not require location registration every time a mobile terminal moves between cells under certain conditions. The purpose is to:
[0009]
[Means for Solving the Problems]
A first feature of the present invention is a wireless communication system for transferring a packet to a mobile terminal via any one of a plurality of access nodes, wherein a plurality of pieces of movement prediction information that associate time information with identification information of the access node are provided. A movement prediction information storage unit for storing, a first transfer time storage unit for managing a first transfer time of a packet to each access node, the plurality of movement prediction information, the first transfer time, and a current time; And a destination access node determining unit that determines a destination access node of the packet based on the above.
[0010]
A second feature of the present invention is a gateway used in a wireless communication system for transferring a packet to a mobile terminal via any of a plurality of access nodes, wherein the gateway associates time information with identification information of the access node. A destination access node determining unit that determines a destination access node of the received packet based on the movement prediction information, a first transfer time of the packet to the access node, and a current time, corresponding to the destination access node; The gist of the present invention is to include an assigning unit that assigns first movement prediction information to the packet, and a routing unit that routes the packet to which the first movement prediction information is assigned.
[0011]
According to the invention, the destination access node determination unit determines the destination access node of the packet based on the plurality of pieces of movement prediction information, the first transfer time, and the current time. Even in such a case, the packet can be transferred to the mobile terminal without the mobile terminal performing location registration again.
[0012]
In the second aspect of the present invention, the destination access node determination unit may determine a destination access node of the packet in consideration of a passing time when the mobile terminal passes through a region where the radio wave condition is statistically poor. it can.
[0013]
According to this invention, when the mobile terminal exists in an area where two cells, which are areas where the radio wave condition is statistically poor, overlap with each other (that is, when moving between cells), the destination access node determination unit includes: By transferring the packet to the destination access node instead of the source access node, packet loss can be prevented.
[0014]
In the second aspect of the present invention, when a request for correcting the movement prediction information is received from the destination access node, identification information of an access node that has established a wireless link with the mobile terminal, and identification information of the wireless link. A detection unit that detects the establishment time, a movement prediction information correction unit that corrects the movement prediction information based on the detection result, and a notification unit that notifies the destination access node of the corrected movement prediction information. can do.
[0015]
According to this invention, when the access node that manages the cell to which the mobile terminal has already passed receives a packet addressed to the mobile terminal, based on the corrected movement prediction information, the cell in which the mobile terminal exists Can be retransmitted to the access node that manages the packet.
[0016]
In the second aspect of the present invention, based on the detection result, further comprising a calculating unit that calculates a scheduled establishment time at which a wireless link is established between the destination access node and the mobile terminal, wherein the notifying unit is Instead of the movement prediction information, the schedule establishment time can be notified to the destination access node.
[0017]
According to this invention, since the mobile terminal has not yet arrived, the arrival time of the mobile terminal can be notified to the access node that is buffering the packet addressed to the mobile terminal.
[0018]
A third feature of the present invention is a node used in a wireless communication system for transferring a packet to a mobile terminal via any of a plurality of access nodes, and stores a second transfer time of the packet to the access node. A second transfer time storage unit that associates time information with identification information of an access node, a plurality of pieces of movement prediction information added to the received packet, the second transfer time, and a current time. And a destination access node determining unit for determining a destination access node of the packet based on the destination, and routing the packet to the determined destination access node.
[0019]
According to this invention, the destination access node determination unit delays the transfer of the packet by routing the packet to an access node different from the access node indicated by the movement prediction information given to the received packet. It is possible to flexibly cope with such cases.
[0020]
A fourth feature of the present invention is an access node that forwards a packet to a mobile terminal, a wireless link information storage unit that stores wireless link information between the mobile terminal, and when the packet is received, In the case where the radio link information is a first situation indicating that the connection has not been established yet or a third situation indicating that the connection has already been completed, the buffer for buffering the packet and the radio link information may be connected. In the case of the second situation indicating that the mobile terminal is in the middle, a gist of the invention is to include a transfer unit that transfers the packet to the mobile terminal.
[0021]
According to this invention, if the mobile terminal has not yet arrived or has already passed, that is, if the wireless link has not been established with the mobile terminal, the packet addressed to the mobile terminal is not sent. Buffering can prevent packet loss.
[0022]
In the fourth aspect of the present invention, the passing time at which the mobile terminal passes through an area where the radio wave condition is statistically poor is managed, and the packet can be buffered during the passing time.
[0023]
According to this invention, packet loss can be prevented by buffering packets addressed to the mobile terminal during the passage time when the mobile terminal passes through an area where the radio wave condition is statistically poor.
[0024]
In the fourth aspect of the present invention, when the packet is buffered because the radio link information is the first situation, a buffering time of the packet, or a buffering time of the buffered packet. A monitoring unit that monitors the amount of data, and when the buffering time exceeds a predetermined time, or when the amount of data exceeds a predetermined threshold, the movement prediction information that associates the time information with the identification information of the access node. The mobile terminal may include a correction request transmitting unit that transmits a correction request, and a scheduled establishment time receiving unit that receives a scheduled establishment time at which a wireless link is established with the mobile terminal.
[0025]
According to this invention, the access node can prevent the packet loss without wasting the buffer capacity by continuing the buffering of the packet until the received scheduled establishment time.
[0026]
In the fourth aspect of the present invention, when the packet is buffered because the radio link information is in the third situation, correction of movement prediction information that associates time information with identification information of an access node. A correction request transmitting unit for transmitting a request, a movement prediction information receiving unit for receiving the corrected movement prediction information, and adding the corrected movement prediction information to the packet, based on the corrected movement prediction information. A routing unit for routing the packet.
[0027]
According to this invention, even when a packet addressed to the mobile terminal is transferred to an access node that manages a cell that has already passed by the mobile terminal, the routing unit performs the processing based on the corrected movement prediction information. By routing the buffered packet, it is possible to transfer the packet to the mobile terminal without discarding the packet.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
(Configuration of the wireless communication system according to the first embodiment of the present invention)
The configuration of the wireless communication system according to the first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the wireless communication system according to the present embodiment forms a hierarchical structure including a gateway GW, a plurality of nodes # 1 to # 2, and a plurality of access nodes # 1 to # 6. .
[0029]
In the present embodiment, the wireless communication system transfers a packet transmitted by a communication partner CN connected to the IP network 2 to the mobile terminal MN1 via any one of the plurality of access nodes # 1 to # 6. And
[0030]
Further, in the present embodiment, it is assumed that the mobile terminal MN1 is moving on the train 1 that is almost accurate in time and moves in a fixed direction. In the present embodiment, it is assumed that one area (cell) # 1 to # 6 is formed between stations. In the present embodiment, it is assumed that the packet is transferred by the Internet protocol. In addition, it is assumed that all pieces of time information held by all devices included in the wireless communication system according to the present embodiment match exactly.
[0031]
The gateway GW is connected to the IP network 2 and transmits and receives packets to and from the IP network. As shown in FIG. 2, the gateway GW includes a movement prediction information database 11, a movement prediction information management unit 12, a required time measurement unit 13, a required time database 14, a reception unit 15, a destination access node determination unit 16 , A header providing unit 17 and a routing unit 18.
[0032]
The movement prediction information database 11 is a movement prediction information storage unit that stores, for each mobile terminal MN, a plurality of pieces of movement prediction information that associates “time information” and “access node identification information”.
[0033]
FIG. 3A shows an example of the movement prediction information managed by the movement prediction information database 11 (for the mobile terminal MN1). In the example of FIG. 3A, the movement prediction information includes “time information” indicating a predetermined time and “access node identification” indicating an access node scheduled to establish a radio link with the mobile terminal MN1 at the predetermined time. "Information" and "CoA address" indicating a network address used when the mobile terminal MN1 is connected to the access node.
[0034]
According to the movement prediction information shown in FIG. 3A, for example, the mobile terminal MN1 ₁ Is to be connected to the access node AR1, that is, to exist in the area # 1 managed by the access node AR1, and "CoA1" is to be used as the CoA address at this time.
[0035]
The movement prediction information management unit 12 performs a management process on the movement prediction information stored in the movement prediction information database 11.
[0036]
Specifically, the movement prediction information management unit 12 acquires from the mobile terminal MN1 information indicating that the mobile terminal MN1 is moving on the train 1 that is almost accurate in time and moves in a fixed direction. Next, with the above acquisition as a trigger, the movement prediction information management unit 12 creates a movement schedule table of the train 1 from an operation table of the train 1 or the like.
[0037]
Then, the movement prediction information management unit 12 calculates the time at which the train 1 passes through each of the areas # 1 to # 6 managed by the access nodes AR1 to AR6 based on the above-described movement schedule table of the train 1. Then, the movement prediction information in the movement prediction information database 11 described above is created.
[0038]
In addition, the movement prediction information management unit 12 creates a network address (CoA address) used by the mobile terminal MN1 under the control of each of the areas # 1 to # 6 in advance, as needed, and generates the mobile terminal MN1 and the access nodes AR1 to AR1. The network address may be configured to be distributed to the AR 6 in advance.
[0039]
In addition, the movement prediction information management unit 12 acquires additional information such as the disorder of the timetable of the train 1 and, based on the acquired additional information, the movement schedule table of the train 1 and the movement prediction information in the movement prediction information database 11. Is changed (corrected). Here, the movement prediction information management unit 12 may be configured to acquire the above-described additional information from the management company of the train 1, the mobile terminal MN1, or the like.
[0040]
In addition, when receiving a request to modify movement prediction information from the access node AR, the movement prediction information management unit 12 establishes a wireless link with the mobile terminal MN1 specified by the received modification request. And the establishment time of the wireless link.
[0041]
At this time, the movement prediction information management unit 12 performs a simultaneous call (paging) to the access nodes AR1 to AR6 connected under the control of the gateway GW, to thereby establish a wireless link with the above-described mobile terminal MN1. May be configured to acquire the identification information of the access node and the establishment time of the wireless link from the access node that establishes the wireless link.
[0042]
In addition, when acquiring the identification information of the access node and the establishment time of the radio link, the movement prediction information management unit 12 may be configured to acquire the additional information from the access node. .
[0043]
Further, the movement prediction information management unit 12 modifies the movement prediction information of the mobile terminal MN1 in the movement prediction information database based on the above detection result, and notifies the access node AR of the corrected movement prediction information. May be configured.
[0044]
In addition, when receiving a request to modify the movement prediction information from the access node AR, the movement prediction information management unit 12 establishes a wireless link between the access node AR and the mobile terminal MN1 based on the corrected movement prediction information. The schedule establishment time to be calculated may be calculated, and the calculated schedule establishment time may be notified to the access node AR. Here, the movement prediction information management unit 12 may use the scheduled arrival time at which the mobile terminal MN1 arrives in the area managed by the access node AR as the scheduled establishment time.
[0045]
Further, the movement prediction information management unit 12 may be configured to statistically manage in advance the quality of a radio link in an area managed by each access node AR.
[0046]
The movement prediction information management unit 12 can manage the passing time at which the mobile terminal MN1 passes through an area where the radio wave condition is statistically poor, based on the quality of the radio link. For example, as shown in FIG. 4, the movement prediction information management unit 12 sets a region (hatched portion in FIG. 4) where a radio wave intensity may be significantly deteriorated statistically, such as a region where cells overlap. As a passing time when MN1 passes, T _n Or (T _n + Γ _n ) During the period γ _n And T _{n + 1} Or (T _{n + 1} + Γ _{n + 1} ) During the period γ _{n + 1} Etc. can be managed.
[0047]
The required time measuring unit 13 measures a first transfer time of a packet to each of the access nodes AR1 to AR6, that is, a time required for a packet transmitted from the gateway GW to reach each of the access nodes AR1 to AR6. It is. The required time measuring unit 13 can periodically measure the first transfer time using a Ping command or the like.
[0048]
The required time database 14 is a first transfer time storage unit that manages the above-described first transfer time. FIG. 3B shows an example of the first transfer time managed by the required time database 14. In the example of FIG. 3B, the required time database 14 stores a “section” indicating a predetermined section and a “required time” indicating a time required when a packet is transferred in the predetermined section in association with each other. I have.
[0049]
In the example of FIG. 3B, the required time database 14 includes not only the required time (first transfer time) α in the section between the gateway GW and each of the access nodes AR1 to AR6, but also the access nodes AR1 to AR6. And the required time β in each section between the mobile terminal MN1 in the areas # 1 to # 6.
[0050]
Here, the required time α is measured by the required time measuring unit 13, and the required time β is generated based on statistical information. Therefore, by adding the required time α and the required time β, it is possible to calculate the required time in the section between the gateway GW and the mobile terminals MN1 existing in the areas # 1 to # 6.
[0051]
According to the required time shown in FIG. 3B, for example, the time during which a packet is transferred in the section between the gateway GW and the access node AR2 is “α”. ₂ , And the time during which a packet is transferred in the section between the access node AR2 and the mobile terminal MN1 existing in the area # 2 is “β ₂ ".
[0052]
The receiving unit 15 receives a packet from the communication partner CN via the IP network 2 and receives a correction request for movement prediction information transmitted from the access nodes AR1 to AR6.
[0053]
The destination access node determining unit 16 determines a destination access node of a packet received via the receiving unit 15 based on a plurality of pieces of movement prediction information, a first transfer time, and a current time.
[0054]
Specifically, the destination access node determination unit 16 determines a destination access node as follows. Here, the current time is “T”, and the movement prediction information (time information, access node identification information) is (T ₁ , AR1), (T ₂ , AR2), ... (T _n , ARn). Also, T <T ₁ And T ₁ <T ₂ <… <T _n And
[0055]
Further, the first transfer time required for a packet to be transferred from the gateway GW to each of the access nodes AR1 to ARn is α ₁ , Α ₂ , ... α _n It is.
[0056]
The time required for a packet to be transferred from each of the access nodes AR1 to ARn to the mobile terminal MN1 is β ₁ , Β ₂ , ... β _n It is. Here, the time required for the packet to be transferred to each of the access nodes AR1 to ARn is β if the packet cannot be obtained in real time. ₁ , Β ₂ , ... β _n May be configured to use the statistical value of.
[0057]
The destination access node determination unit 16 determines “T + (α _n + Β _n ) (N = 1, 2,... N) and the most “T + (α) _n + Β _n )) _n Is determined, and the determined “T _n Is determined as the destination access node.
[0058]
Also, the destination access node determination unit 16 calculates the average value of “+” indicating the approximate packet transfer time from the gateway GW to the mobile terminal (α + β) by (Equation 1). _Av Is calculated in advance, and in the above-described method of determining the destination access node, (α _n + Β _n ) Instead of average (α + β) _Av May be used.
[0059]
(Equation 1)

Further, the destination access node determination unit 16 may be configured to determine the destination access node of the packet in consideration of the passage time when the mobile terminal MN1 passes through a region where the radio wave condition is statistically poor.
[0060]
Specifically, as shown in FIG. 4, the destination access node determining unit 16 determines that the time when the packet arrives at “ARn” is determined even when “ARn” is determined as the destination access node by the above-described method. "T _{n + 1} "And" T _{n + 1} + Γ _{n + 1} ”, It is determined that“ ARn + 1 ”is the destination access node.
[0061]
The header adding unit 17 adds, to the received packet, a header that sets the address of the destination access node ARn determined by the destination access node determining unit 16 as the “end address (destination address)”, and provides the destination access node ARn with the header. The corresponding first movement prediction information is added to the received packet.
[0062]
In the example of FIG. 5, the header providing unit 17 converts the encapsulated headers “start address = gateway GW address” and “end address = access node AR1” into the received packet (the original address) by IP in IP encapsulation. Packet).
[0063]
In addition, the header adding unit 17 extends the relay point option header of the IP header to provide the received packet (original packet) with time information (arrival time) and access node identification information (arriving at the arrival time). Movement prediction information for associating the movement prediction information with the address of the access node to be accessed.
[0064]
In the example of FIG. 5, the header adding unit 17 performs the first movement prediction information corresponding to the access node AR1, the second movement prediction information corresponding to the access node AR2, and the third movement corresponding to the access node AR3. A relay point option header including prediction information is added to the original packet.
[0065]
Here, in consideration of the packet overhead, it is desirable that the number of pieces of movement prediction information to be added is small.
[0066]
In addition, the header adding unit 17 is configured to add the movement prediction information so as not to exceed the MTU (Maximum Transfer Unit) on the wireless link.
[0067]
Furthermore, the header adding unit 17 can also set the relay point option header to a fixed length in order to easily determine the number of the added pieces of movement prediction information.
[0068]
The routing unit 18 routes the packet to which the first movement prediction information has been added. In the example of FIG. 5, the routing unit 18 routes and forwards the received packet to the node # 1 or # 2 based on the encapsulation header.
[0069]
In the present embodiment, the movement prediction information database 11, the movement prediction information management unit 12, the required time measurement unit 13, and the required time database 14 are provided as functions in the gateway GW, but all or some of these functions are provided. May be provided as a separate device from the gateway GW.
[0070]
The nodes # 1 and # 2 receive the packet transferred from the gateway GW and transfer the packet to another node or an access node. Since the function of node # 1 and the function of node # 2 are basically the same, the function of node # 1 will be described below.
[0071]
As shown in FIG. 6, the node # 1 includes a required time measuring unit 33, a required time database 34, a receiving unit 35, a destination access node determining unit 36, a header changing unit 37, and a routing unit 38. Is what you do.
[0072]
The required time measuring unit 33 has the same function as the required time measuring unit 13 of the gateway GW, and transmits the second transfer time of the packet to each of the access nodes AR1 to AR3, that is, the packet is transmitted from the node # 1. It measures the time required for the received packet to arrive at each of the access nodes AR1 to AR3. The required time measuring unit 33 can periodically measure the second transfer time using a Ping command or the like.
[0073]
The required time database 34 is a second transfer time storage unit that manages the above-described second transfer time. In the example of FIG. 6, the required time database 34 stores the “section” indicating a predetermined section and the “required time” indicating the time required to transfer a packet in the predetermined section in association with each other.
[0074]
In the example of FIG. 6, the required time database 34 includes not only the required time (second transfer time) A in the section between the node # 1 and each of the access nodes AR1 to AR3, but also the access nodes AR1 to AR3 and the area. The required time B in each section between the mobile terminals MN1 existing in # 1 to # 3 is stored.
[0075]
Here, the required time A is measured by the required time measuring unit 33, and the required time B is generated based on statistical information. Further, the required time B may take the same value as the required time β managed by the required time database 13 of the gateway GW. Therefore, by adding the required time A and the required time B, the required time in the section between the node # 1 and the mobile terminals MN1 existing in the areas # 1 to # 3 can be calculated.
[0076]
According to the required time shown in FIG. 6, for example, the time during which a packet is transferred in the section between the node # 1 and the access node AR2 is “A ₂ , And the time during which the packet is transferred in the section between the access node AR2 and the mobile terminal MN1 existing in the area # 2 is "B ₂ ".
[0077]
The receiving unit 35 receives a packet from the gateway GW, another node, or the like.
[0078]
The destination access node determining unit 36 determines a destination access node of the packet received via the receiving unit 35 based on the movement prediction information, the second transfer time, and the current time provided to the received packet. Things.
[0079]
Specifically, the destination access node determination unit 36 determines a destination access node as follows. Here, the current time is “T ′”, and the movement prediction information (time information, access node identification information) given to the received packet is (T ₁ , AR1), (T ₂ , AR2), ... (T _a , ARa). Also, T '<T ₁ And T ₁ <T ₂ <… <T _a And
[0080]
Further, the second transfer time required for a packet to be transferred from the node # 1 to each of the access nodes AR1 to ARa is A ₁ , A ₂ , ... A _a It is.
[0081]
The time required for a packet to be transferred from each of the access nodes AR1 to ARa to the mobile terminal MN1 is B ₁ , B ₂ … B _a It is. Here, the time required for the packet to be transferred to each access node AR1 to ARa is B ₁ , B ₂ … B _a May be configured to use the statistical value of.
[0082]
The destination access node determining unit 36 selects “T ′ + (A)” from the movement prediction information given to the received packet. _a + B _a ) (A = 1, 2,... A) ”and the most“ T ′ + (A _a + B _a )) _a Is determined, and the determined “T _a Is determined as the destination access node.
[0083]
Further, the destination access node determining unit 36, similarly to the destination access node determining unit 16 of the gateway GW described above, considers the passage time when the mobile terminal MN1 passes through a region where the radio wave condition is statistically poor, and considers the destination of the packet. It may be configured to determine an access node.
[0084]
The header changing unit 37 changes the header of the packet received via the receiving unit 35 according to the determination by the destination access node determining unit 36.
[0085]
Specifically, the header changing unit 37 changes the “end address (destination address)” of the encapsulation header to the address of the destination access node ARa determined by the destination access node determination unit 36, and changes the relay option header. Then, the movement prediction information corresponding to the destination access node is changed to be “first movement prediction information”.
[0086]
At this time, the header changing unit 37 temporarily removes the IP-in-IP encapsulation, and sets the received packet (original packet) to the encapsulation header in which “start address = address of node # 1” and “end address = access node ARa” Packet).
[0087]
Here, when the address of the destination access node determined by the destination access node determining unit 36 is set in the encapsulation header of the received packet, the header changing unit 37 determines that the “end address (destination address) Address)].
[0088]
The header changing unit 37 may be configured to delete the movement prediction information in which the set arrival time is earlier than the current time.
[0089]
The routing unit 38 routes the received packet based on the encapsulation header.
[0090]
The access nodes AR1 to AR6 establish wireless links and perform wireless communication with the mobile terminals MN existing in the areas # 1 to # 6, respectively. For example, base stations and accelerator routers correspond to the access nodes AR1 to AR6. Since the functions of the access nodes AR1 to AR6 are basically the same, the function of the access node AR1 will be described below.
[0091]
As shown in FIG. 7, the access node AR1 includes a receiving unit 51, a radio link information managing unit 52, a buffer 53, a transmitting unit 54, a movement prediction information correction requesting unit 55, and an estimated arrival time receiving unit 56. , A header conversion unit 57.
[0092]
The receiving unit 51 receives the packet from the node # 1 and transfers the received packet to the transmitting unit 54.
[0093]
The wireless link information management unit 52 stores wireless link information with the mobile terminal MN. Specifically, as shown in FIG. 8, the wireless link information management unit 52 stores “mobile terminal ID”, “connection status”, and “establishment time” in association with each other.
[0094]
The “connection status” is represented by “not arrived (first status)” indicating that a wireless link with the mobile terminal MN identified by the “mobile terminal ID” has not yet been established, and “mobile terminal ID”. Connection of the wireless link with the mobile terminal MN identified by “connected (second situation), mobile terminal ID” indicating that the wireless link with the identified mobile terminal MN is being connected Is "passing (third situation)" indicating that has already been completed.
[0095]
That is, when the “connection status” is “not arrived (first status)”, the mobile terminal MN1 has not yet arrived in the area # 1 managed by the access node AR1. When the “connection status” is “connected (second status)”, the mobile terminal MN1 exists in the area # 1. Further, when the “connection status” is “pass (third status)”, the mobile terminal MN1 has already passed through the area # 1.
[0096]
The “establishment time” indicates the time at which the wireless link was established when the “connection status” is “connecting (second status)”.
[0097]
The buffer 53 buffers packets transferred from the receiving unit 51 in accordance with an instruction from the transmitting unit 54. The buffer 53 manages the buffering time of each packet and the data amount of the buffered packet.
[0098]
The transmission unit 54 refers to the radio link information management unit 52 and buffers the packet according to the radio link information on the destination mobile terminal MN of the packet received from the reception unit 51, or It is determined whether to transfer.
[0099]
Specifically, the transmitting unit 54 indicates that the radio link information of the destination mobile terminal MN of the packet received from the receiving unit 51 is “not arrived (first situation)” or “passed (third situation)”. In this case, the packet is buffered in the buffer 53. On the other hand, when the above-mentioned wireless link information is “connected (second situation)”, the transmitting unit 54 transfers the packet to the destination mobile terminal MN.
[0100]
Further, the transmission unit 54 monitors the wireless link information management unit 52, and the wireless link information relating to the destination mobile terminal of the packet buffered in the buffer 53 becomes “connected (second situation)”. If changed, the packet is forwarded to the destination mobile terminal MN.
[0101]
Here, when transmitting the packet to the destination mobile terminal MN, the transmitting unit 54 deletes the encapsulation header (see FIG. 5) attached to the packet.
[0102]
Further, the transmitting unit 54 manages the passing time at which the mobile terminal MN passes through a region where the radio wave condition is statistically poor, and the transmitting unit 54 performs the process when the above-mentioned wireless link information is “connecting (second situation)”. Even so, the packet may be buffered in the buffer 53 during the passing time.
[0103]
Also, the transmitting unit 54 prepares to transmit the packet addressed to the mobile terminal MN buffered in the buffer 53 at the arrival time of the mobile terminal MN notified from the estimated arrival time receiving unit 56. That is, after the above-described arrival time, the transmitting unit 54 can allocate an area where a packet addressed to the mobile terminal MN is buffered as an area for buffering another packet.
[0104]
In addition, the transmitting unit 54 routes and transfers the packet transmitted from the header converting unit 57 based on the header of the packet.
[0105]
Further, when the transmitting unit 54 receives the paging from the gateway GW, the transmitting unit 54 refers to the radio link information management unit 52 and establishes a radio link with the mobile terminal MN designated by the paging. It is configured to search whether or not the wireless link has been established, and if the wireless link has been established, notify the gateway GW of the fact and the establishment time of the wireless link.
[0106]
The movement prediction information correction requesting unit 55 monitors the buffer 53, and when the buffering time of a specific packet whose “wireless link information” is “not arrived (first situation)” has passed a predetermined time, A request for correcting the movement prediction information attached to the packet is transmitted to the gateway GW.
[0107]
Further, the movement prediction information correction requesting unit 55 monitors the buffer 53, and packets buffered in the buffer 53 (packets in which the “radio link information” is “not arrived (first situation)”). When the data amount exceeds a predetermined threshold value, a request for correcting movement prediction information is transmitted to the gateway GW.
[0108]
In addition, the movement prediction information correction request unit 55 transmits a correction request for the movement prediction information added to the buffered packet because the wireless link information is “pass (third situation)”.
[0109]
Further, the movement prediction information correction requesting unit 55 receives the movement prediction information (corrected movement prediction information) transmitted from the gateway GW in response to the above-described movement prediction information correction request, and notifies the header conversion unit 57 of the movement prediction information. .
[0110]
The scheduled arrival time receiving unit 56 receives, from the gateway GW, a scheduled establishment time at which a wireless link is established with the destination mobile terminal MN of the packet buffered in the buffer 53.
[0111]
The header conversion unit 57 converts the header of the packet buffered in the buffer 53 according to the movement prediction information (corrected movement prediction information) notified from the movement prediction information correction request unit 55.
[0112]
For example, the header conversion unit 57 inserts the corrected movement prediction information into the relay option header of the corresponding packet. Then, the header conversion unit 57 transfers the packet to which the corrected movement prediction information is added to the transmission unit 54.
[0113]
(Operation of the Wireless Communication System According to the Present Embodiment)
The operation of the wireless communication system according to the present embodiment will be described with reference to FIGS. First, the operation of the gateway GW according to the present embodiment will be described with reference to FIG.
[0114]
As shown in FIG. 9, in step 1001, the required time measuring unit 13 of the gateway GW updates the content of the required time database 14 at a predetermined cycle.
[0115]
In step 1002, when the receiving unit 15 of the gateway GW receives a packet addressed to the mobile terminal MN1 from the communication partner CN via the IP network 2, the operation proceeds to step 1003.
[0116]
The destination access node determining unit 16 determines the destination access node of the received packet by the method shown in steps 1003 to 1006. Here, “T” indicates the current time, and “ARn” is an access node corresponding to “Tn” in the movement prediction information database 11. Also, "α _n Indicates the time required for packet transfer in the section between the gateway GW and the access node ARn (first transfer time), and “β” _n Indicates the time required for packet transfer in a section between the access node ARn and the mobile terminal MN1 in the area #n. "Α _n ”And“ β _n Is stored in the required time database 14.
[0117]
In the method shown in steps 1003 to 1006, the destination access node determining unit 16 determines that “T + (α _n + Β _n ) (N = 1, 2,... N) and the most “T + (α) _n + Β _n )) _n Is determined, and the determined “T _n Is determined as the destination access node.
[0118]
In step 1007, the header adding unit 17 generates the first movement prediction information corresponding to the access node ARn, the second movement prediction information corresponding to the access node ARn + 1, and the third movement prediction information corresponding to the access node ARn + 2. Are added to the received packet.
[0119]
Specifically, the header adding unit 17 encapsulates the received packet with an encapsulation header having the access node ARn as the destination address, and also adds the relay option header including the first to third movement prediction information to the packet. Insert
[0120]
In step 1008, the routing unit 18 routes the packet based on the encapsulation header.
[0121]
Second, the operation of the node # 1 according to the present embodiment will be described with reference to FIG.
[0122]
As shown in FIG. 10, in step 2001, the required time measuring unit 33 of the node # 1 updates the content of the required time database 34 at a predetermined cycle.
[0123]
In step 2002, when the receiving unit 35 of the node # 1 receives a packet addressed to the mobile terminal MN1 from the gateway GW, the operation proceeds to step 2003. Here, the destination address of the encapsulation header of the received packet is the address of the access node AR1.
[0124]
The destination access node determination unit 36 determines the destination access node of the received packet by the method shown in steps 2003 to 2007. Here, “T ′” indicates the current time and “T” _a Indicates the arrival time in the a-th movement prediction information inserted in the received packet. Also, "A _a Indicates the time required for packet transfer in the section between the node # 1 and the access node ARa in the a-th movement prediction information (second transfer time), and "B" _a Indicates the time required for packet transfer in a section between the access node ARa and the mobile terminal MN1 in the area #n. "A _a "And" B _a Is stored in the required time database 34.
[0125]
In the method shown in steps 2003 to 2007, the destination access node determining unit 36 selects “T ′ + (A _a + B _a ) (A = 1, 2,... A) ”and the most“ T ′ + (A _a + B _a )) _a Is determined, and the determined “T _a Is determined as the destination access node.
[0126]
In step 2007, if the destination access node ARa determined by the destination access node determining unit 36 corresponds to the first movement prediction information, the header of the packet is not changed and this operation is performed in step Proceed to 2010.
[0127]
Also, when the destination access node determination unit 36 cannot determine the destination access node ARa, the operation proceeds to step 2010 without changing the header of the packet.
[0128]
On the other hand, when the destination access node ARa determined by the destination access node determining unit 36 corresponds to the second (or third) movement prediction information, the operation proceeds to step 2008.
[0129]
In step 2008, the header changing unit 37 encapsulates the received packet with an encapsulation header having the destination access node ARa as a destination address, and also converts the first (and second) movement prediction information from the relay option header. delete.
[0130]
In step 2010, the routing unit 38 routes the packet based on the encapsulation header.
[0131]
Third, the operation of the access node AR1 according to the present embodiment will be described with reference to FIG.
[0132]
As shown in FIG. 11, in step 3001, the receiving unit 51 of the access node AR1 receives the packet transmitted from the node # 1 and transfers the packet to the transmitting unit.
[0133]
In step 3002, the transmitting unit 54 refers to the wireless link information management unit 52 to check the wireless link information on the destination mobile terminal MN1 of the packet.
[0134]
If the wireless link information is “connecting (second situation)”, in step 3003, the transmitting unit 54 deletes the encapsulation header (see FIG. 5) attached to the packet and connects the packet. Is transmitted to the mobile terminal MN1 via the wireless link.
[0135]
On the other hand, when the wireless link information is “pass (third situation)”, the transmitting unit 54 buffers the packet in the buffer 53 in step 3004.
[0136]
In step 3005, the movement prediction information correction requesting unit 55 transmits a request for correcting the movement prediction information to the gateway GW.
[0137]
In step 3006, the movement prediction information correction requesting unit 55 receives the corrected movement prediction information from the gateway GW, and in step 3007, the header conversion unit 57 performs buffering based on the corrected movement prediction information. In step 3008, the transmitting unit 54 routes and transfers the packet based on the converted header. Here, the packet is transferred to another access node such as access node # 2.
[0138]
If the wireless link information is “not arrived (first situation)”, the transmission unit 54 buffers the packet in the buffer 53 in step 3009.
[0139]
Upon detecting that the wireless link information has been changed to “connected (second situation)” in Step 3010, the transmitting unit 54 transmits the packet to the mobile terminal MN1 in Step 3003.
[0140]
On the other hand, in step 3011, if the buffering time of the packet has passed the predetermined time without changing the wireless link information to “connected (second situation)” (or if the wireless link information is “ When the data amount of the packet addressed to the mobile terminal that has not arrived (the first situation) exceeds a predetermined threshold), in step 3012, the transmitting unit 54 sends the destination mobile terminal of the packet to the gateway GW. A request is made to correct the movement prediction information relating to MN1.
[0141]
In Step 3013, the estimated arrival time receiving unit 56 receives the estimated arrival time of the destination mobile terminal MN1 from the gateway GW. The transmitting unit 54 prepares to transmit the packet to the mobile terminal MN1 at the estimated arrival time (step 3003).
[0142]
Next, with reference to FIG. 12, an operation of correcting the movement prediction information in the wireless communication system according to the present embodiment will be described.
[0143]
In step 4001, the transmission unit 54 of the access node AR1 buffers the packet received from the node # 1 when the wireless link information of the destination mobile terminal MN1 is “passed (third situation)”. At the same time, it requests the gateway GW to correct the movement prediction information corresponding to the destination mobile terminal MN1 of the packet.
[0144]
In step 4002, the destination access node determination unit 16 of the gateway GW calculates again the movement prediction information to be inserted into the packet addressed to the destination mobile terminal MN1, in response to the received movement prediction information correction request. In the example of FIG. 12, it is assumed that it is calculated that the movement prediction information corresponding to the access node AR3 should be inserted into the packet as the first movement prediction information.
[0145]
In step 4003, the movement prediction information management unit 12 of the gateway GW transmits the movement prediction information corresponding to the access node AR3 to the access node AR1 as the corrected first movement prediction information.
[0146]
In step 4004, the header conversion unit 57 of the access node AR1 attaches an encapsulated header having the address of the access node AR3 as the destination address (the address of the access node AR1 as the source address) to the buffered packet. At the same time, the movement prediction information corresponding to the access node AR2 is given as the first movement prediction information.
[0147]
In step 4005, the transmission unit 54 of the access node AR1 routes and transfers the packet to the accelerator node AR3 based on the above-described encapsulation header.
[0148]
In step 4006, the transmitting unit 54 of the access node AR3 confirms that the radio link information on the destination mobile terminal MN1 of the packet received from the access node AR1 is “connecting (second situation)”, The packet is transmitted to the destination mobile terminal MN1.
[0149]
(Operations and effects of the wireless communication system according to the present embodiment)
According to the wireless communication system according to the present embodiment, the destination access node determination unit 16 determines the destination access node AR of the packet based on the plurality of pieces of movement prediction information, the first transfer time, and the current time. Even when the mobile terminal MN1 moves between cells (areas), the packet can be transferred to the mobile terminal MN1 without the mobile terminal MN1 performing location registration again.
[0150]
Further, according to the gateway GW according to the present embodiment, the mobile terminal MN1 exists in an area where two cells (areas #n and # n + 1), which are areas where the radio wave condition is statistically poor, overlap with each other (namely, , During inter-cell movement), the destination access node determining unit 16 can prevent packet loss by transferring the packet to the destination access node ARn + 1 instead of the source access node ARn. .
[0151]
Further, according to the gateway GW according to the present embodiment, when the access node AR1 managing the cell (area # 1) through which the mobile terminal MN1 has already passed receives a packet addressed to the mobile terminal MN1, the correction is made. Based on the predicted movement information, the packet can be retransmitted to the access node AR3 that manages the cell (area # 3) in which the mobile terminal MN1 exists.
[0152]
Further, according to the gateway GW according to the present embodiment, since the mobile terminal MN1 has not yet arrived, the arrival of the mobile terminal MN1 reaches the access node AR1 buffering the packet addressed to the mobile terminal MN1. The time can be notified.
[0153]
Further, according to the node # 1 according to the present embodiment, the destination access node determination unit 36 determines whether the access node AR2 is different from the access node AR1 specified by the first movement prediction information attached to the received packet. By routing the packet, it is possible to flexibly cope with a case where the transfer of the packet is delayed.
[0154]
Further, according to the access node AR1 according to the present embodiment, when the mobile terminal MN1 has not yet arrived or has already passed, that is, a wireless link has been established with the mobile terminal MN1. In the absence state, packet loss can be prevented by buffering the packet addressed to the mobile terminal.
[0155]
In addition, according to the access node AR1 according to the present embodiment, during the transit time when the mobile terminal MN1 passes through an area where the radio wave condition is statistically poor, the packet addressed to the mobile terminal MN1 is buffered, so that the packet loss is reduced. Can be prevented.
[0156]
Further, according to the access node AR1 according to the present embodiment, by continuing packet buffering until the received scheduled establishment time, it is possible to prevent packet loss without wasting the buffer capacity.
[0157]
Further, according to the access node AR1 according to the present embodiment, when a packet addressed to the mobile terminal MN1 is transferred to the access node AR1 managing the cell (area # 1) that the mobile terminal MN1 has already passed. Even so, the transmission unit 54 routes the buffered packet based on the corrected movement prediction information, so that the packet can be transferred to the mobile terminal MN1 without discarding the packet. .
[0158]
【The invention's effect】
As described above, according to the present invention, a radio communication system, a gateway, a node, and an access node that do not require location registration every time a mobile terminal MN1 moves between cells (areas) under certain conditions are provided. can do.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a wireless communication system according to a first embodiment of the present invention.
FIG. 2 is a functional block diagram of a gateway of the wireless communication system according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a movement prediction information database and a required time database of a gateway of the wireless communication system according to the first embodiment of the present invention.
FIG. 4 is a diagram for explaining a passing time when a mobile terminal passes through a region where the radio wave condition is statistically poor in the wireless communication system according to the first embodiment of the present invention.
FIG. 5 is a diagram illustrating an example of a packet format used in the wireless communication system according to the first embodiment of the present invention.
FIG. 6 is a functional block diagram of a node of the wireless communication system according to the first embodiment of the present invention.
FIG. 7 is a functional block diagram of an access node of the wireless communication system according to the first embodiment of the present invention.
FIG. 8 is a diagram showing an example of the content of a radio link information management unit of the access node of the radio communication system according to the first embodiment of the present invention.
FIG. 9 is a flowchart illustrating an operation of the gateway of the wireless communication system according to the first embodiment of the present invention.
FIG. 10 is a flowchart illustrating an operation of a node in the wireless communication system according to the first embodiment of the present invention.
FIG. 11 is a flowchart illustrating an operation of an access node in the wireless communication system according to the first embodiment of the present invention.
FIG. 12 is a sequence diagram when the movement prediction information is modified in the wireless communication system according to the first embodiment of the present invention.
[Explanation of symbols]
AR: access node
GW… Gateway
MN: Mobile terminal
1 ... Train
2. IP network
11 ... movement prediction information database
12: Movement prediction information management unit
13, 33 ... required time measuring unit
14, 34: Time required database
15, 35, 51 ... receiving unit
16, 36... Destination access node determination unit
17: Header addition unit
18, 38 ... routing unit
37, 57: Header change unit
52 ... Wireless link information management unit
53 ... buffer
54 ... Transmission unit
55: Movement prediction information correction request unit
56 ... arrival time reception section

Claims (10)

A wireless communication system for transferring a packet to a mobile terminal via any of a plurality of access nodes,
A movement prediction information storage unit that stores a plurality of movement prediction information that associates the time information and the identification information of the access node;
A first transfer time storage unit that manages a first transfer time of a packet to each access node;
A wireless communication system comprising: a destination access node determining unit that determines a destination access node of the packet based on the plurality of pieces of movement prediction information, the first transfer time, and a current time. A gateway used in a wireless communication system for transferring a packet to a mobile terminal via any of a plurality of access nodes,
A destination for determining a destination access node of the received packet based on a plurality of pieces of movement prediction information for associating time information with identification information of the access node, a first transfer time of the packet to the access node, and a current time; An access node determining unit;
An assigning unit that assigns first movement prediction information corresponding to the destination access node to the packet;
A routing unit for routing the packet to which the first movement prediction information has been added. 3. The destination access node determining unit according to claim 2, wherein the destination access node determination unit determines a destination access node of the packet in consideration of a passing time at which the mobile terminal passes through a region where the radio wave condition is statistically poor. gateway. A detecting unit that detects, when receiving a correction request for the movement prediction information from the destination access node, identification information of an access node that has established a wireless link with the mobile terminal and establishment time of the wireless link; ,
A movement prediction information correction unit that corrects the movement prediction information based on the detection result;
3. The gateway according to claim 2, further comprising: a notifying unit that notifies the corrected movement prediction information to the destination access node. Based on the detection result, comprising a calculating unit that calculates a scheduled establishment time when a wireless link is established between the destination access node and the mobile terminal,
The gateway according to claim 4, wherein the notifying unit notifies the destination access node of the scheduled establishment time instead of the movement prediction information. A node used in a wireless communication system for transferring a packet to a mobile terminal via any of a plurality of access nodes,
A second transfer time storage unit that stores a second transfer time of a packet to the access node;
A destination access node of the packet, based on a plurality of pieces of movement prediction information associated with the received packet, which is associated with time information and identification information of an access node, the second transfer time, and a current time. A destination access node determining unit for determining
Routing the packet to the determined destination access node. An access node for forwarding a packet to a mobile terminal,
A wireless link information storage unit that stores wireless link information between the mobile terminal;
When the packet is received, the radio link information is in a first state indicating that the connection has not been established yet or in a third state indicating that the connection has already been completed, and a buffer for buffering the packet. ,
An access node comprising: a transfer unit configured to transfer the packet to the mobile terminal when the wireless link information is in a second state indicating that connection is being established. The access node according to claim 7, wherein the access node manages a passing time at which the mobile terminal passes through an area where the radio wave condition is statistically bad, and buffers the packet during the passing time. For the radio link information is the first situation, if the packet is buffered, the buffering time of the packet, or a monitoring unit that monitors the data amount of the buffered packet,
A modification request transmitting unit that transmits a modification request of movement prediction information that associates time information with identification information of an access node when the buffering time has elapsed a predetermined time or when the data amount exceeds a predetermined threshold. When,
The access node according to claim 7, further comprising: a scheduled establishment time receiving unit configured to receive a scheduled establishment time at which a wireless link is established with the mobile terminal. A correction request transmission unit that transmits a correction request for movement prediction information that associates time information with identification information of an access node when the packet is buffered because the radio link information is the third situation; ,
A movement prediction information receiving unit that receives the corrected movement prediction information,
The access node according to claim 7, further comprising: a routing unit configured to add the corrected movement prediction information to the packet, and route the packet based on the corrected movement prediction information.

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