200939800 - 九、發明說明： 【發明所屬之技術領域】 本發明是有關於一種多重網路下的換手方法’特別是 指一種針對多重網路介面行動裝置使用可適性遲滯區間之 換手方法。 【先前技術】 ' 隨著無線網路技術的發達’愈來愈多的行動設備都已 - 支援多個的無線通訊技術，例如：無線區域網路（Wireless ❹ Local Area Network，WLAN)，第三代（Third Generation， 3G)或微波存取全球互通（Worldwide Interoperability for Microwave Access，WIMAX)行動通訊網路…等。不同的無 線網路技術能提供不一樣的涵蓋範圍及傳輸頻寬，例如： WLAN在辦公室、校園等小範圍内，能提供較高的頻寬， 且WLAN的通訊費用也較為便宜。相反地，3G的涵蓋範圍 廣闊，但是所能提供的頻寬較小。因此，如何有效地整合 這些不同的無線通訊技術，使得當行動使用者持續移動的 ❹ 時候，所有的網路資訊服務可以連續不中斷，是一重要課 題。當換手（Handoff)發生在同網路之間時，例如：參閱圖1 ，從無線區域網路（Wireless Local Area Network，WLAN)存 取點（Access Point，AP) 102換手到另一個WLAN存取點 ' 104或從3G網路108到3G網路110，這種換手方式稱為水 平換手。如果是在異質網路間發生換手時，例如：在圖1 中，從WLAN存取點104換到3G網路108，這種換手方法 稱為垂直換手。水平換手或垂直換手都會導致資料中斷， 5 200939800 即當發生換手的期間，行動使用者無法接收資料。如果有 很多不需要的換手發生時，整體的效能會因而下降。大部 分已提出的換手解決方案是以接收到的訊號強度（Received Signal Strength，RSS)為導向，因為微弱的訊號只能提供低 傳輸速率。其中，以臨界值之接收訊號強度（RSS with Threshold，RSS-T)與遲滯區間和臨界值之接收訊號強度 (RSS with Hysteresis and Threshold，RSS-ΗΤ)的方法較為廣 泛使用® 在傳統的水平換手裡，RSS-T方法的換手發生在當原基 地台的訊號強度比預定的臨界值還低，且另一個基地台的 訊號比原基地台強時。而在垂直換手裡，這個RSS-T的換 手方法是：（1)當WLAN AP的訊號低於預定的臨界值時， 從WLAN垂直切換到蜂巢式（Cellular)網路；（2)當WLAN AP的訊號高於預定的臨界值時，從蜂巢式網路垂直換手到 WLAN網路。這種做法的缺點是，當行動使用者在WLAN 的邊緣移動時，因為訊號會在臨界值上下跳動而造成很多 不需要的換手動作。 為了避免這種不必要的乒乓效應，RSS-ΗΤ方法主要是 考量遲滯區間（Hysteresis Margin)。在水平換手裡，這種方 法的換手發生在當原基地台的訊號強度低於預定的臨界值 而且另一個基地台的訊號強度超過原基地台的訊號強度加 上遲滯區間時。然而在垂直換手中，這種RSS-ΗΤ的換手方 法通常都設有兩個固定的臨界值，一個臨界值比較高，另 一個臨界值比較低：（1)當WLAN AP的訊號低於預設較低 6 200939800BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of handing over multiple networks, and more particularly to a handoff method for using an adaptive hysteresis interval for a multi-network interface mobile device. [Prior Art] 'With the development of wireless network technology, more and more mobile devices have been available - supporting multiple wireless communication technologies, such as Wireless ❹ Local Area Network (WLAN), third Third Generation (3G) or Worldwide Interoperability for Microwave Access (WIMAX) mobile communication network...etc. Different wireless network technologies can provide different coverage and transmission bandwidth. For example: WLAN can provide high bandwidth in a small area such as office and campus, and WLAN communication cost is also cheaper. Conversely, 3G covers a wide range, but the bandwidth available is small. Therefore, how to effectively integrate these different wireless communication technologies, so that when the mobile users continue to move, all network information services can be continuously uninterrupted, which is an important topic. When Handoff occurs between the same network, for example, refer to Figure 1, changing from a Wireless Local Area Network (WLAN) Access Point (AP) 102 to another WLAN. The access point '104 or from the 3G network 108 to the 3G network 110, this handoff is called horizontal handoff. If a handoff occurs between heterogeneous networks, for example, in Figure 1, switching from WLAN access point 104 to 3G network 108, this handoff method is called vertical handoff. Horizontal or vertical hand changes will result in data interruption. 5 200939800 That is, during the change of hands, the mobile user cannot receive the data. If there are many unwanted hand changes, the overall performance will drop. Most of the proposed handoff solutions are based on received Received Signal Strength (RSS) because weak signals only provide low transmission rates. Among them, the method of RSS with Threshold (RSS-T) and the hysteresis interval and threshold value (RSS with Hysteresis and Threshold, RSS-ΗΤ) are widely used. In the hand, the exchange of the RSS-T method occurs when the signal strength of the original base station is lower than a predetermined threshold and the signal of the other base station is stronger than the original base station. In the vertical change, the RSS-T change method is: (1) when the WLAN AP signal is lower than the predetermined threshold, the WLAN is switched vertically from the WLAN to the Cellular network; (2) When the WLAN AP's signal is above a predetermined threshold, the cellular network is handed over vertically to the WLAN network. The disadvantage of this approach is that when the mobile user moves on the edge of the WLAN, the signal will jump up and down the threshold and cause many unwanted hand changes. In order to avoid this unnecessary ping-pong effect, the RSS-ΗΤ method mainly considers the hysteresis interval (Hysteresis Margin). In the horizontal change, the switching of this method occurs when the signal strength of the original base station is lower than a predetermined threshold and the signal strength of the other base station exceeds the signal strength of the original base station plus the hysteresis interval. However, in the vertical hand change, this RSS-ΗΤ handoff method usually has two fixed thresholds, one with a higher threshold and the other with a lower threshold: (1) when the WLAN AP signal is lower than the pre- Set lower 6 200939800
的臨界值時，從WLAN垂直切換到蜂巢式網路；⑺當 WLAN AP的訊號高於職的較高臨界值時，從蜂巢式網ς 垂直換手WLAN網路。當訊號是在遲滯區間時不會發生 任何的換手動作。然而，雖然這種方法能夠減少多餘㈣ 手動作’但因為訊號非常低時，才從WLAN換到其他的網 路’或者WLAN的訊號报高時，才會從蜂巢式換㈤机觸 ’所以會有需要換手的時候卻不會馬上換手之情況發生， 而導致延遲換手，以致會有傳輸效能下降之缺點。 鑒於習知RSS-T及RSS_HT方法具有如上所述之缺點 ’因此有必要尋求解決之道。 【發明内容】 因此，本發明之目的，即在提供-種多重網路下的換 手方法，僅需執行較少的換手次數、具有較低的封包遺失 率’並具較高的平均產量。 於是，本發明多重網路下的換手方法，包含下列步驟 .⑷若一第一高優先權網路中之-接收訊號強度小於一臨 界值與-可調變遲滯區間之差值時，谓測周圍是否有一第 ^優先權網路之訊號’·⑻當偵測到周圍有該第二高優先 •周路之Λ號時’水平換手到該第二高優先權網路；及⑷ :⑷步驟中_制圍無該第二高優先權網路之訊號時， 2換手到-低優先權網路，其中㈣—及第二高優先權 網路之優先權高於該低優先權網路。 因此，本發明之功效在於，僅需執行較少的換手次數 、具有較低的封包遺失率，並具較高㈣均產量。 7 200939800 • 【實施方式】 有關本發明之前述及其他技術内容、特點與功效，在 以下配合參考圖式之一個較佳實施例的詳細說明中，將可 清楚的呈現。 本發明多重網路下的換手方法是利用可適性遲滯區間 (AdaPtive Hysteresis Margin)的調變及一臨界值（Thresh〇id) 決定哪一個網路介面是最適當的。以下將詳細說明本發明 * 較佳實施例。 ❹ 遲滯區間最主要的用途在於避免過度頻繁的換手行為 。以往使用之遲滯區間皆為固定的，本發明的精髓在於提 出一個具動態改變之遲滯區間。根據本發明之分析，促使 遲滯區間值需要改變的變因為：（1)換手間隔；與（2)環境差 異。 首先，換手間隔是距離上一次換手行為之時間差。假 設距離上次換手之間隔很小，則應調大遲滞區間值，以減 〇 低換手行為的發生；另一方面，假設距離上次換手之間隔 很大’則可以縮小遲滞區間值，讓換手行為可以正常依據 當時訊號強度作判斷。 其次，由於地理環境的不同，相同規格的基地台於不 同地理環境中發送訊號，可能會因為地形、建築物或其他 遮蔽物的影響，使得每個區域内的訊號分佈不同，故各區 域内遲滯區間值勢必需要為不同程度的調變。 根據以上分析結論，本發明將遲滯區間值定義成方程 式（1)形式，其中△是代表預設的固定遲滞區間、△，是代表可 8 200939800 調變的可適性遲潘fS· ， ’遲咿“1 /代表則一次換手的時間到目前的 時間差2代表區間係數。區間係數決定可適性遲滞區間的 收斂時間，可由系統業者根據需求調整。由於透過此方程 式⑴可使遲滯區間根據需求動態改變，故稱為可適性遲滞 區間。 A，= A*/(U) ⑴ ❹ ❹ 本發明的精越在於定義出可適性遲滞區間應該根據換 手間隔與環境不同作調整，關於/(U)並沒有提出一個固定 的函數’只要符合要求的函數都屬於本發明精髓涵蓋的範 圍。需滿足的函數條件為：⑴和）=卜也就是當㈣時 ’可適性遲滞區間會恢復至預設的遲滯區間；（2)/(〇〇，#0 ’也t=c〇時’可適性遲滯區間會退化為零。方程式 ()為耗例函數’由於自然指數的性質，故方程式⑺滿足 上述兩個必要條件，可以作為本發明提出之可適性遲滯區 間調整函數使用。 △， '-t/λ (2) ，除了考慮遲滯區間之外’也需要考慮目前連結的網路 tit果目前的網路有較高的優先權時，代表行動使用 盡可能連到這種網路。相反地，如果目前網路的優 乂低時，表示當另一個較高優先權的網路存在時，行 用者會想要切換至較高優先權之網路。一般來說，高 權的網路能夠提供高傳輸速率且花費也較低，因為這 因素會直接影響到行動使用者想要連網路的欲望。在 這裡我們以3G(低優先權）和WLAN(高優先權）為例子來表示 200939800 - ，但本發明並不限用於3G和WLAN間的換手，例如，本 發明也可用於WIMAX行動通訊網路（低優先權）與WLAN 間的換手。 與3G比較起來，WLAN網路通常花費較低且能夠提供 較高的傳輸速率。因此，行動使用者會對WLAN網路有較 高的優先權。假設行動使用者目前用WLAN網路且定期偵 ' 測目前的WLAN AP訊號。參閱圖2，其描述在WLAN網路 • 下遲滞區間的調變。當RSS的值低於預設的臨界值 ❹ (Threshold，77z)減可調變遲滯區間（Δ〇時會觸發換手動作， 否則會繼續留在目前的WLAN ΑΡ。既然RSS的值不容易比 7Ά-Δ，表示行動使用者比較會留在WLAN網路。但是， 隨著可調變遲滯區間收斂為零，Ι7ί-Δ '的值也會越接近77z， 換言之，換手會比較容易觸發。因此，系統能換手到3G網 路或其他的WLAN AP。 既然3G通常需要花費較高且傳輸速率較低，比起 WLAN網路，3G的優先權較低。假設行動使用者目前連到The critical value is switched from the WLAN to the cellular network vertically; (7) when the WLAN AP's signal is higher than the higher threshold, the WLAN network is switched vertically from the cellular network. No hand-over action occurs when the signal is in the hysteresis zone. However, although this method can reduce the redundant (four) hand movements, but only when the signal is very low, only when the WLAN is switched to another network' or the WLAN signal is high, it will be switched from the cellular (five) machine. There is a need to change hands when there is a need to change hands, which leads to delays in hand-changing, resulting in a disadvantage of reduced transmission performance. Since the conventional RSS-T and RSS_HT methods have the disadvantages described above, it is therefore necessary to find a solution. SUMMARY OF THE INVENTION Therefore, the object of the present invention is to provide a handover method under a multiple network, which requires only a small number of hand changes, has a low packet loss rate, and has a high average yield. . Therefore, the handover method in the multiple network of the present invention includes the following steps. (4) If the received signal strength in a first high priority network is less than a difference between a threshold value and a tunable hysteresis interval, Measure whether there is a signal of the first priority network around the ''(8)' horizontally handing over to the second high priority network when detecting the nickname of the second highest priority • Zhou Road; and (4): (4) In the step _ when there is no signal of the second high priority network, 2 hands over to the low-priority network, wherein (4)- and the second high-priority network have higher priority than the low priority network. Therefore, the effect of the present invention is that only a small number of hand changes, a low packet loss rate, and a high (four) average yield are required. The above-mentioned and other technical contents, features and effects of the present invention will be apparent from the following detailed description of the preferred embodiments. The handoff method under the multiple network of the present invention is to use the modulation of the adaptive hysteresis interval (AdaPtive Hysteresis Margin) and a threshold (Thresh〇id) to determine which network interface is the most appropriate. DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below.最 The main purpose of the hysteresis interval is to avoid excessive frequent hand movements. The hysteresis intervals used in the past are fixed, and the essence of the present invention is to propose a hysteresis interval with dynamic changes. According to the analysis of the present invention, the variation of the hysteresis interval value needs to be changed because: (1) handoff interval; and (2) environmental difference. First, the handoff interval is the time difference from the last hand change. Assuming that the interval between the last hand changes is small, the hysteresis interval value should be increased to reduce the occurrence of low hand change behavior; on the other hand, it can be reduced by assuming a large interval from the last hand change. The interval value allows the change behavior to be judged according to the strength of the signal at that time. Secondly, due to different geographical environments, base stations of the same specification transmit signals in different geographical environments, which may cause the signal distribution in each area to be different due to the influence of terrain, buildings or other obstructions, so the delay in each area Interval values are bound to require varying degrees of modulation. According to the above analysis conclusion, the present invention defines the hysteresis interval value as the form of the equation (1), wherein Δ represents a preset fixed hysteresis interval, Δ, which is representative of the adaptability of the temperament of the 200939800 modulation.咿 “1 / delegates change the time of the hand to the current time difference 2 represents the interval coefficient. The interval coefficient determines the convergence time of the adaptive hysteresis interval, which can be adjusted by the system operator according to the demand. Since the equation (1) can make the hysteresis interval according to the demand Dynamic change, so called adaptive hysteresis interval. A, = A * / (U) (1) ❹ ❹ The essence of the invention lies in the definition of the adaptive hysteresis interval should be adjusted according to the change interval and the environment, about / (U) does not propose a fixed function 'as long as the function that meets the requirements belongs to the scope covered by the essence of the invention. The functional conditions to be satisfied are: (1) and) = b, that is, when (four), the adaptive delay interval will be restored. To the preset hysteresis interval; (2) / (〇〇, #0 'also t = c〇 'the adaptive hysteresis interval will degenerate to zero. The equation () is the consumption function ' due to the nature of the natural exponent Therefore, equation (7) satisfies the above two necessary conditions and can be used as the adaptive hysteresis interval adjustment function proposed by the present invention. △, '-t/λ (2), in addition to considering the hysteresis interval, it is also necessary to consider the currently connected network. If the current network has a higher priority, it means that the action is connected to the network as much as possible. Conversely, if the current network is low, it means another higher priority network. When present, users will want to switch to a higher priority network. In general, high-powered networks can provide high transmission rates and are less expensive, because this factor directly affects mobile users. The desire to connect to the Internet. Here we use 3G (low priority) and WLAN (high priority) as an example to represent 200939800 -, but the invention is not limited to the change between 3G and WLAN, for example, this The invention can also be used to change hands between WIMAX mobile communication networks (low priority) and WLANs. Compared with 3G, WLAN networks are usually cheaper and can provide higher transmission rates. Therefore, mobile users will be able to provide WLAN networks. Road has High priority. It is assumed that the mobile user currently uses the WLAN network and periodically detects the current WLAN AP signal. See Figure 2, which describes the modulation of the hysteresis interval in the WLAN network. When the RSS value is lower than The preset threshold ❹ (Threshold, 77z) minus the adjustable hysteresis interval (Δ〇 triggers the hand-over action, otherwise it will remain in the current WLAN. Since the value of RSS is not easy to compare with 7Ά-Δ, it means action The user will stay on the WLAN network. However, as the adjustable hysteresis interval converges to zero, the value of Ι7ί-Δ ' will be closer to 77z. In other words, the handoff will be easier to trigger. Therefore, the system can change hands. Go to a 3G network or other WLAN AP. Since 3G usually costs more and the transmission rate is lower, 3G has lower priority than WLAN networks. Assume that the mobile user is currently connected
Q 3G網路且定期在偵測WLAN AP的訊號。參閱圖3，其描 述在3G網路下遲滯區間的調變。當某一個WLAN AP的 RSS值高於預設的臨界值（77〇加可調變遲滯區間（Δ')時，會 觸發換手動作，否則會留在原來的3G網路。隨著可調變遲 — 滯區間收斂為零，：ΓΑ+Δ'的值也會越接近JTi，換言之，此時 會比較容易切換到可用的WLAN AP。 本發明在實施時可有兩種情況。第一種情況是行動使 用者原本在WLAN的網路；第二種情況是行動使用者原來 10 200939800 . 在3G網路。 參閱圖4,其描述本發明多重網路下的換手方法之較佳 實施例中假設行動使用者目前在WLAN網路時，相對應的 換手步驟。 如步驟402所示，行動使用者目前在WLAN網路，且 如步驟404所示，系統會定期從WLAN介面偵測原WLAN " AP的訊號變化。並且如步驟406所示，判斷目前連結的 - WLAN AP的RSS值是否低於77ί-Δ、如果RSS的值沒有低 Ο 於π-Δ W，則系統會保持在目前的WLAN網路，並且回到 步驟404持續監控訊號。 反之，當目前WLAN AP的RSS值一旦低於77ϊ-Δ'時， 則如步驟408所示，系統開始偵測周圍WLAN ΑΡ的訊號， 並如步驟410所示，判斷是否有其他的WLAN AP存在。在 步驟410中如果有偵測到其他WLAN AP的訊號時，則如步 驟412所示，系統會水平換手到RSS最大的另一個WLAN AP。反之，在步驟410中如果沒有偵測到其他的WLAN AP ^ 時，則如步驟414所示，系統會垂直換手至3G網路。 參閱圖5,其描述本發明多重網路下的換手方法之較佳 實施例中假設行動使用者目前在3G網路時，相對應的換手 步驟。 如步驟502所示，行動使用者目前在3G網路，並且如 步驟504所示，系統會定期監控WLAN AP的訊號。接著， 如步驟506所示，判斷周圍是否有WLAN AP。如果沒有偵 測到WLAN AP的訊號時，則回到步驟504，系統會保持在 11 200939800 - 3G網路並持續的監控WLAN AP的訊號。反之，如果有偵 測到WLAN AP的訊號時，則如步驟508所示，系統會垂直 換手到RSS最大的WLAN AP。 參閱圖6,其為本發明實施例中垂直換手及水平換手的 遲滯區間調變圖"圖6描述利用本發明連續的換手過程。 當行動使用者在3G網路時，換手的條件定為RSS要大於 77ί+Δ、如果從3G換手到WLAN網路時，換手條件會定為 RSS要小於ΓΑ-Δ'。因為77ι-Δ'的值較小，因此行動使用者 ® 會繼續保持在新的WLAN AP。如果從原WLAN AP換手到 另一個WLAN AP時，ΓΑ-Δ'會重新計算。因此可以避免馬 上又切換回來的問題。當從WLAN網路換手到3G網路時 ，換手條件會定為RSS要大於77ί+Δ'。因為ΓΑ+V的值較大 ，因此系統會保持在新的3G網路。因此，本發明能夠類似 RSS-ΗΤ的方法可以避免很常換手。但是經過一段時間後， 遲滯區間會收斂為0，就是遲滯區間沒有效應。因此當目前 的RSS低於或高於預設的臨界值ΓΑ時，必須立刻執行換手 ❹ 為了證明本發明的方法的效能，發明人已實際架設無 線網路漫遊環境。在此環境中包含2台IEEE 802.1 lb/g WLAN AP，且此兩台WLAN AP之涵蓋範圍有一半以上重 疊，3G網路是由台灣的電信業者提供且3G訊號涵蓋整個 環境。行動使用者以平均〇.7m/s速度在3G和兩個WLAN AP的範圍内移動。本發明的方法和習知RSS-T和RSS-HT 的方法比較之下，為了方便稱呼，本發明方法命名為可適 12 200939800 性遲滯區間及臨界值之接收訊號強度（RSS with Adaptive Hysteresis and Threshold，RSS-AHT)。以下分別在場景一以 及場景二中比較各個方法產生的效能，以及進一步分析各 個演算法的行為。 參閱如下表1，其即為場景一。如表1中所示，習知 RSS-T方法製造很多換手次數（19次），但習知RSS-ΗΤ方法 換手次數最少（6次）。與RSS-ΗΤ方法比較下，RSS-T方法 產生比較高的平均產量（Average Throughput卜至於，本發 明RSS-ΑΗΤ方法能彈性調整不同的區間係數A值。從表格 1中可以發現，當/1小於50的時候，平均產量有上升的趨 勢。相反地，當A大於50的時候，平均產量有下降的趨勢 。這是因為當A等於40的時候，換手次數已經收歛到最少 次（8次）。因此設定較高的A只會造成較高的延遲換手，也 就是說當需要換手時系統並不會馬上執行換手。如表1中 顯示，這種較高的延遲換手會降低平均產量且會造成較高 的封包遺失率（Packet Loss Rate)。不過比起習知RSS-T和 RSS-ΗΤ的方法，本發明RSS-ΑΗΤ能夠提供較高的平均產 量，但類似RSS-ΗΤ —樣，本發明RSS-ΑΗΤ只有執行少數 的換手次數。同時，本發明的封包遺失率比RSS-ΗΤ來的少 表1 換手演算 法 參數 平均產量 (Kbps) 換手 次數 封包 遺失率（％) 臨界值 遲滯區間 Λ RSS-T -130 - - 500 19 3.41(%) RSS-HT -120,-140 20 - 439 6 5.99(%) 13 200939800 RSS-AHT -130 10 10 508 11 3.32(%) RSS-AHT -130 10 20 526 10 3.55(%) RSS-AHT -130 10 30 529 9 3.63(%) RSS-AHT -130 10 40 533 8 3.65(%) RSS-AHT -130 10 50 535 8 3.69(%) RSS-AHT -130 10 60 534 8 3.69(%) RSS-AHT -130 10 70 527 8 3.88(%) RSS-AHT -130 10 80 525 8 3.85(%) RSS-AHT -130 10 90 524 8 3.91(%) RSS-AHT -130 10 100 522 8 4.02(%) RSS-AHT -130 10 110 507 8 4.66(%) RSS-AHT -130 10 120 505 8 4.72(%) RSS-AHT -130 10 130 506 8 4.74(%) RSS-AHT -130 10 140 506 8 4.94(%) RSS-AHT -130 10 150 506 8 4.96(%)The Q 3G network periodically detects the WLAN AP signal. Referring to Figure 3, the modulation of the hysteresis interval in the 3G network is described. When the RSS value of a WLAN AP is higher than the preset threshold (77〇 plus the adjustable hysteresis interval (Δ'), the handoff action will be triggered, otherwise it will remain in the original 3G network. The delay is delayed - the interval converges to zero, and the value of ΓΑ+Δ' is also closer to JTi. In other words, it is easier to switch to the available WLAN AP at this time. The present invention can be implemented in two cases. The situation is that the mobile user is originally in the WLAN network; the second case is the mobile user original 10 200939800. In the 3G network. Referring to Figure 4, a preferred embodiment of the handoff method under the multiple network of the present invention is described. Assume that the mobile user is currently in the WLAN network, and the corresponding handover step. As shown in step 402, the mobile user is currently on the WLAN network, and as shown in step 404, the system periodically detects the original from the WLAN interface. The signal of the WLAN " AP changes. And as shown in step 406, it is determined whether the RSS value of the currently connected-WLAN AP is lower than 77 ί-Δ, and if the value of the RSS is not lower than π-Δ W, the system will remain in the system. Current WLAN network, and return to step 404 to continuously monitor the signal On the other hand, when the RSS value of the current WLAN AP is lower than 77ϊ-Δ′, as shown in step 408, the system starts detecting the signal of the surrounding WLAN, and as shown in step 410, it is determined whether other WLAN APs exist. If the signal of the other WLAN AP is detected in step 410, the system will horizontally switch to the other WLAN AP with the largest RSS as shown in step 412. Otherwise, if no other is detected in step 410 For the WLAN AP ^, the system will manually switch to the 3G network as shown in step 414. Referring to Figure 5, a preferred embodiment of the handoff method under the multiple network of the present invention is assumed in the preferred embodiment of the mobile user. In the 3G network, the corresponding handoff step. As shown in step 502, the mobile user is currently on the 3G network, and the system periodically monitors the WLAN AP signal as shown in step 504. Then, as in step 506 If there is no WLAN AP detected, if it does not detect the WLAN AP signal, then return to step 504, the system will remain on the 11 200939800 - 3G network and continuously monitor the WLAN AP signal. When measuring the signal of the WLAN AP Then, as shown in step 508, the system will manually switch to the largest WLAN AP of the RSS. Referring to FIG. 6, which is a hysteresis interval modulation diagram of the vertical hand change and the horizontal hand change according to the embodiment of the present invention, FIG. 6 depicts the use. The continuous handoff process of the present invention. When the mobile user is in the 3G network, the condition for changing hands is set to be greater than 77 ί+Δ for RSS, and if the handoff is changed from 3G to WLAN, the handoff condition is determined to be RSS. Less than ΓΑ-Δ'. Because the value of 77ι-Δ' is small, Mobile User ® will continue to be on the new WLAN AP. If you switch from the original WLAN AP to another WLAN AP, ΓΑ-Δ' will be recalculated. Therefore, it is possible to avoid the problem of switching back on the horse. When switching from a WLAN network to a 3G network, the handoff condition is set to be greater than 77 ί + Δ' for RSS. Because the value of ΓΑ+V is large, the system will remain on the new 3G network. Therefore, the present invention can be similar to the RSS-ΗΤ method to avoid frequent handoffs. However, after a period of time, the hysteresis interval will converge to zero, that is, the hysteresis interval has no effect. Therefore, when the current RSS is lower or higher than the preset threshold ,, the handoff must be performed immediately. To prove the effectiveness of the method of the present invention, the inventor has actually set up a wireless network roaming environment. In this environment, there are two IEEE 802.1 lb/g WLAN APs, and the coverage of the two WLAN APs is more than half overlapping. The 3G network is provided by Taiwanese telecom operators and the 3G signal covers the entire environment. Mobile users move within 3G and two WLAN APs at an average speed of 77m/s. In comparison with the methods of the present invention and the conventional RSS-T and RSS-HT methods, the method of the present invention is named as suitable for the 2009 20090800 hysteresis interval and the threshold value of the received signal strength (RSS with Adaptive Hysteresis and Threshold). , RSS-AHT). The following compares the performance of each method in Scene 1 and Scene 2, and further analyzes the behavior of each algorithm. See Table 1 below, which is scenario 1. As shown in Table 1, the conventional RSS-T method creates a lot of turnovers (19 times), but the conventional RSS-ΗΤ method has the fewest turnovers (6 times). Compared with the RSS-ΗΤ method, the RSS-T method produces a relatively high average yield (Average Throughput). The RSS-ΑΗΤ method of the present invention can elastically adjust different interval coefficient A values. It can be found from Table 1 that when /1 When the temperature is less than 50, the average yield has an increasing trend. Conversely, when A is greater than 50, the average yield has a downward trend. This is because when A is equal to 40, the number of turnovers has converged to the least (8 times). Therefore, setting a higher A will only result in a higher delay to change hands, which means that the system will not perform the handoff immediately when it is necessary to change hands. As shown in Table 1, this higher delay is changed. Lowering the average yield and causing a higher Packet Loss Rate. However, compared to the conventional RSS-T and RSS-ΗΤ methods, the RSS-ΑΗΤ of the present invention can provide a higher average yield, but is similar to RSS- In the same way, the RSS-ΑΗΤ of the present invention performs only a small number of handoffs. At the same time, the packet loss rate of the present invention is less than that of the RSS-ΗΤ table. (%) Threshold hysteresis interval Λ RSS-T -130 - - 500 19 3.41(%) RSS-HT -120,-140 20 - 439 6 5.99(%) 13 200939800 RSS-AHT -130 10 10 508 11 3.32(%) RSS -AHT -130 10 20 526 10 3.55(%) RSS-AHT -130 10 30 529 9 3.63(%) RSS-AHT -130 10 40 533 8 3.65(%) RSS-AHT -130 10 50 535 8 3.69 (% RSS-AHT -130 10 60 534 8 3.69 (%) RSS-AHT -130 10 70 527 8 3.88 (%) RSS-AHT -130 10 80 525 8 3.85 (%) RSS-AHT -130 10 90 524 8 3.91 (%) RSS-AHT -130 10 100 522 8 4.02 (%) RSS-AHT -130 10 110 507 8 4.66 (%) RSS-AHT -130 10 120 505 8 4.72 (%) RSS-AHT -130 10 130 506 8 4.74 (%) RSS-AHT -130 10 140 506 8 4.94 (%) RSS-AHT -130 10 150 506 8 4.96 (%)
參閱圖7〜10之場景二，其中進一步分析每一個演算法 的換手行為。圖7〜9描述RSS-T、RSS-HT和本發明RSS-AHT的換手行為，圖10則顯示相對應當時的訊號RSS。如 圖10所示，在第110，220和500秒時，RSS在臨界值邊 〇 緣變動。因此，在圖7中可以看到在這些時間點時，RSS-T 的方法容易造成不必要的換手且會產生乒乓效應。至於， 在圖8和9中，RSS-ΗΤ和RSS-ΑΗΤ方法能夠避免多餘的 換手，故換手次數較少。但是，RSS-ΗΤ並沒有辦法達到最 佳的平均產量，因為它的遲滯區間是固定的。所以從圖8 可發現，RSS-ΗΤ方法留在3G的時間較久而只能接收較低 位元率（Bitrate)，例如：從第395秒到第533秒。相對的， 在圖9中，本發明RSS-ΑΗΤ方法在大部分時間保持在 14 200939800 WLAN的網路，例如：本發明只有從第4n秒到第4卯秒 時才換手到3G。因此，本發明RSS_AHT方法能夠比rss t 和RSS-HT的方法最佳化平均產量。 歸納上述，本發明多重網路下的換手方法利用可適性 遲滯區間的調變及臨界值決定哪一個網路介面是最好的， 藉以僅需執行較少的換手次數、具有較低的封包遺失率， 並具較高的平均產量，故確實能達成本發明之目的。…See scenario 2 of Figure 7-10 for further analysis of the handoff behavior of each algorithm. Figures 7 to 9 depict the handover behavior of RSS-T, RSS-HT and the RSS-AHT of the present invention, and Figure 10 shows the signal RSS corresponding to the time. As shown in Fig. 10, at the 110th, 220th and 500th seconds, the RSS edge changes at the critical value. Therefore, it can be seen in Fig. 7 that at these time points, the RSS-T method is liable to cause unnecessary handoffs and a ping-pong effect. As for, in Figures 8 and 9, the RSS-ΗΤ and RSS-ΑΗΤ methods can avoid redundant hand changes, so the number of hand changes is small. However, RSS-ΗΤ does not have the means to achieve the best average yield because its hysteresis range is fixed. So from Figure 8, we can see that the RSS-ΗΤ method stays in 3G for a long time and can only receive the lower bit rate (Bitrate), for example, from 395th to 533th. In contrast, in Fig. 9, the RSS-ΑΗΤ method of the present invention maintains the network of 14 200939800 WLAN for most of the time, for example, the present invention only switches to 3G from the 4th second to the 4th second. Therefore, the RSS_AHT method of the present invention is capable of optimizing the average yield over the methods of rss t and RSS-HT. In summary, the handoff method under the multiple network of the present invention utilizes the modulation and threshold of the adaptive hysteresis interval to determine which network interface is the best, so that only a small number of hand changes need to be performed, and the number is low. The packet loss rate, and a higher average yield, can indeed achieve the object of the present invention. ...
惟以上所述者，僅為本發明之較佳實施例而已，當不 能以此限定本發明實施之範圍，即大凡依本發明申請^利 範圍及發明說明内容所作之簡單的等效變化與修飾^仍 屬本發明專利涵蓋之範圍内。 【圖式簡單說明】 圖1是一示意圖，說明習知多重網路下之換手； 圖2是一圖表，說明本發明多重網路下之換手方法 WLAN網路下遲滯區間的調變； 'The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made in accordance with the scope of the invention and the description of the invention. ^ is still within the scope of the invention patent. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a conventional handover under multiple networks; FIG. 2 is a diagram illustrating a modulation of a hysteresis interval in a WLAN network of a handover method in accordance with the present invention; '
圖3是一圖表，說明本發明多重網 3G網路下遲滯區間的調變； 路下之換手方法在 明多重網路下的換手方法 之較佳實施例中假設行動使用者前 ,,^ 百曰刖在WLAN網路時，相 對應的換手步驟； 町祁 "札往圓 W I奶爹重網路下的換 之較佳實施例中假設行動使用者、/ 的換手步驟； …0網路時，相對應 圖6是一圖表，說明本發明多重網路下之垂直換手及 15 200939800 水平換手的遲滞區間調變圖； 圖7是一圖表，說明習知ASS-Τ方法的換手行為； 圖8是一圖表，說明習知ASS-ΗΤ方法的換手行為； 圖9是一圖表’說明本發明ASS-ΑΗΤ方法的換手行為 :及 圖10是-圖表，說明用以得出圖7〜9換手行為圖表之 兩個WLAN AP之訊號變化圖。 〇 16 200939800 . 【主要元件符號說明】 402〜414步驟 502〜508步驟3 is a diagram illustrating the modulation of the hysteresis interval in the multi-network 3G network of the present invention; the handover method under the road in the preferred embodiment of the handover method under the multi-network, assuming the action user, ^ The corresponding hand-over steps in the WLAN network; the 祁 祁 quot 札 圆 圆 WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI WI When the network is 0, the corresponding figure 6 is a diagram illustrating the vertical hand change under the multiple network of the present invention and the hysteresis interval modulation map of the 15 200939800 horizontal hand change; FIG. 7 is a diagram illustrating the conventional ASS- FIG. 8 is a diagram illustrating the hand-off behavior of the conventional ASS-ΗΤ method; FIG. 9 is a diagram illustrating the hand-off behavior of the ASS-ΑΗΤ method of the present invention: and FIG. 10 is a graph, The signal change diagrams of the two WLAN APs used to derive the handoff behavior chart of Figures 7-9 are illustrated. 〇 16 200939800 . [Main component symbol description] 402~414 steps 502~508 steps
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