簡訊傳送模型之研究

Abstract

簡訊具備最基本的資料傳輸介面，最高的相容特性，無論是2G/3G或是4G手機，全部支援這個基礎服務，也因此廣泛的被運用為基本的傳輸界面，雖然行動通信進入了寬頻時代，簡訊至今仍是電信業者最重要的電信加值服務收入來源之一。 簡訊可以分為發送端及接收端：在發送端除了一般的使用者之外，有一大部份的簡訊來自於工商業的廣告及商用簡訊，例如：每日氣象通知、廣告促銷或是新聞消息的資訊發佈; 於本論文將討論發送端在送出簡訊時的時間分佈，依據時間及日期，將時間分佈圖區分為忙時、非忙時；並依日期的特性區分為特殊節日，特殊節日前一天、上班日以及假日等時間分佈圖進行分析，有了這個分佈函式，電信業者可以進行分析，提供更靈活的費率方案以疏解忙時的訊務量。 當簡訊送入簡訊中心後，簡訊中心會開始嘗試將簡訊發送到接收端，首先透過GSM MAP協定查詢接收端的受訊交換機位置，接著將簡訊實體內容發送到受訊交換機，受訊交換機再將簡訊轉發到接收端手機上；由於行動設置具備移動的特性，因此會有傳送失敗的狀況，當傳送失敗時，各電信業者的簡訊中心會在傳送期限前啟動簡訊重傳機制；而我們將會討論這個簡訊的重傳機制效能。 然而，由應用程式或是廣告(AP)發送的訊息長度，往往超過單一則的簡訊長度，因此，簡訊中心會將訊息予以切割；每則訊息長度約140 位元組，和單一段簡訊不同的在於被切割為多則的長簡訊，必需每一段都成功接收才可以視為成功傳送，任何一段的傳送失敗就視為失敗；因此，簡訊中心為提高企業的長簡訊發送成功率必需提供不同的長簡訊傳送機制，延伸單一段簡訊的研究，我們也討論長簡訊的重送機制。 最後，本論文以簡訊加值應用結合NGN MOD機上盒的功能，在家用MOD上提供另一個接收簡訊的應用。雖然，電信商的簡訊盈收因為OTT業者的聊天軟體應用普及，造成盈收下降的趨勢，但從資訊顯示這部份OTT造成的影響主要是對於一般使用者 ；在企業的簡訊量以及應用程式間的簡訊量依然持平，而對於M2M的設備間的訊息溝通，簡訊因為其普遍及方便性，日漸重要；因此，廣泛的將簡訊應用於不同的領域將是重要的議題，不同領域間的訊息處理也將會是我們日後重要的研究方向。

In the broadband era, narrowband short message service (SMS) is still the most popular wireless data service. Many studies have been conducted to investigate the performance of SMS based on the arrival rates of short messages. From Chunghwa Telecom’s commercial SMS call data records, we observed that even if the SMS arrival rates are the same, the distributions for the number of SMS arrivals per half hour are quite different for various observed days. We further identify that for the SMS traffic in a specific day, there are non-burst and burst periods. We investigate the SMS behaviors in weekdays, weekends, and holidays (specifically, new years’ days and eves). With the assistance of kernel-based fitting method, we derive the SMS arrival number distributions of various traffic types and observed days. Our approach fits each SMS arrival number distribution by three cubic polynomial functions that can accurately capture the SMS behaviors. Based on the SMS arrival number distributions derived from our model, the mobile operators have better understanding about the volumes of short messages in different times and days, which can be used to design more flexible short message charging rates. Based on the huge demand for SMS significantly increases network traffic, it is essential that mobile operators should provide efficient SMS delivery mechanism. We study the short message retransmission policies for single segments SMS and derive some facts about these policies. Then, we propose an analytic model to investigate the short message retransmission performance. The analytic model is validated against simulation experiments. We also collect SMS statistics from a commercial mobile telecommunications network. Our study indicates that the performance trends for the analytic/simulation models and the measured data are consistent. Performance of single-segment messages has been intensively investigated. On the other hand, multi-segment messages (with sizes larger than 140 octets) are seldom evaluated in the literature. We proposes analytic models to study two transmission policies for multi-segment short messages, which are validated by measured data. Then we use a commercial operation example to show how to select the transmission parameters (including the retransmission interval and the maximum number of transmissions) to improve the performance of the SMS delivery. By adjusting these parameters on the commercially operated SMS, the performance has been improved by over 20%. Therefore, our study provides useful guidelines for mobile operators to select appropriate parameters for multi-segment short message delivery. Finally, we show some value-added services in the Next Generation Network (NGN). IP Multimedia Subsystem (IMS) supports IP-based multimedia services through access networks of various wireless and wired access technologies. Through NGN/IMS, we shows how to integrate IPTV with mobile telecommunications networks to offer enhanced IPTV services for mobile subscribers. We use MOD (the IPTV service of Chunghwa Telecom) to illustrate that such integration can be efficiently achieved in the IMS/NGN. We specifically describe the implementations of two IMS/MOD convergence services: short message on TV screen and TV Shopping/Food ordering for mobile users.