1. Read and then comment on the following papers.
1.1Yao-Jen Chang, Shan-Yao Wu, Ting-Liang Shih, Intersection Location Service and Performance Comparison of Three Location Service Algorithms for Vehicular Ad Hoc Networks in City Environments
ANS:
比較ILS (Intersection Location Service)與GLS (Grid Location Service) 及 HLS (Hierarchical Location Service)結果， ILS是將路口區域內所有的車輛當作位置伺服器，在網路裡移動的車輛會把位置更新與詢問的封包往區域內所有的車輛傳送。實驗發現，車輛移動方式、區域面積大小、車輛密度及車輛行駛速度，皆會影響此三種運算的結果，其中以車輛移動方式、區域面積大小、車輛密度影響HLS最嚴重，其次為ILS與GLS，但於車輛行駛速度來看的話，則GLS較嚴重其次才是ILS與HLS，透過測試證明ILS演算法比GLS及HLS在高速行駛狀況及大範圍車量更大的情形下有更佳的表現。
1.2Yao-Jen Chang, Tseng-Yun Wang, Shi-Kai Tsai, Yu-Chia Chuang, "Action Science Approach to Experimenting Nonprofit Web 2.0 Services for Employment of Individuals with Mental Impairments" 2007 International Workshop on Social Media Analysis in conjunction with ACM/IEEE Web Intelligence 2007. (EI)
ANS:
廣泛的運用Web2.0，將可擺脫以往Web1.0時，耗時費力製作開發網頁資訊，且Web2.0包含了更多的功能及優點，如人與人間互相溝通媒介、群體智慧、跨平台使用、使用者分享與參與、持續更新、內容與服務的整合、快速反應與功能新增等。利用Web2.0的這些優勢，建構一個對於學習或精神損傷者的學習歷程，在這些分享報告中，也可以迅速向同事傳遞工作資訊，也可以發佈一個靜態連結的通知訊息。透過靜態連結去檢查他人的部落格，可以立即了解學習進度，更進一步給予指導。亦有共同編輯平台，透過一定的審查過程及網友的評鑑，讓內容的可信度大為增加，也使用部落格作為社會學習的工具。
當然很重要的一點，對資源有限的非營利團體來說，使用低成本，甚至是免費開發平台相當重要，Web2.0便是其中的一項選擇。
2. Why is CSMA/CA instead of CSMA/CD used for 802.11?
Services for Employment of Individuals with Mental Impairments" 2007 International Workshop on Social Media Analysis in conjunction with ACM/IEEE Web Intelligence 2007. (EI)
ANS:
CSMA/CD的檢測方法是通過電纜中電壓的變化來檢測，當數據發生碰撞時，電纜中的電壓就會隨著發生變化。每個發送端都具備偵測網路是否空閒，若空閒則會進行傳送。但如果兩個發送端同時偵測網路空閒並傳送資料，因而造成衝突產生，這時傳送的資料是無效的，所以每個發送端都需要隨時檢測是否衝突，一但衝突發生，立即停止傳送，然後隨機延遲一段時間後，再重新檢測網路空閒，並重傳資料。
在WLAN中，對某個節點來說，其剛剛發出的信號強度要遠高於來自其他節點的信號強度，也就是說它自己的信號會把其他的信號給覆蓋掉，所以就會認為傳輸網路沒有處於衝突的狀態。通道利用率受傳輸距離和空曠程度的影響，當距離遠或者有障碍物影響時會存在隱藏終端機問題，降低通道利用率。
而CSMA/CA是採用三種檢測方法來檢測傳輸空間中的信號衝突，方法是能量檢測(ED)、載波檢測(CS )和能量載波混合檢測。 CSMA/CA利用ACK信號來避免衝突的發生，也就是說，只有當客戶端收到網路上返回的ACK信號後才確認送出的數據已經正確到達目的。以上這些方式可以盡量偵測到WLAN網路是否空閒。CSMA/CD協議就是盡可能保證網路上同時只有一個節點發送數據，減小數據“碰撞”概率。如果網路空閒，即沒有載波傳送，才將數據轉換成封包，經物理層發送出去。 如果網路繁忙時，則隨機的時間等待再監測網路是否空閒，再將數據轉換成封包傳送。
CSMA/CD 是具有偵測衝突的載波感測多重存取 的協定CSMA/CA 為 CSMA/CD 的改良協定，是具有避免衝突的載波感測多重存取 的協定。
故CSMA/CD一般是使用在乙太網路，CSMA/CA則是使用於無線網路。
2007年11月16日 星期五
2007年9月27日 星期四
Homework-9-22-2007
1. Read and then comment on the following papers.Yao-Jen Chang, Shih-Kai Tsai, Tsen-Yung Wang Wayfinding Systems Based on Passive RFID for Individuals with Cognitive Impairments
Answer:
RFID have been implementing in many fields today. In my company, we use it to audit and manage the inspection of power facilities. It is easy to deploy because of low cost and short time frame. The test results show the implementation is user friendly and promising with high reliability. The navigation server can records the positions, time, and user ID for the tracking purpose by using RFID. The wayfinding Systems based on passive RFID will be multi-functional and interactive.
Yao-Jen Chang, Tseng-Yun Wang, Yu-Chia Chuang, Shih-Kai Tsai, “Ontology-based Personalized Wayfinding System Using Deviation Detecting for Individuals with Cognitive Impairments”
Answer:
Ontology-based route personalization is proposed to adapt routes with respect to context and changing environment. A tracking function is integrated with a time constrained breadth-first search at the core of deviation detecting algorithm. The tracking system increases the sense of security and also lowers the entry threshold to accepting the assistive technology. It makes the wayfinding system can be suitable to the need of different people. The new traffic sign system will afford various routes to adopt route personalization.
2. Read Sec. 1-3-6 of Textbook.What is the disadvantage of Mobile IP and what's the solution?
Answer:
The disadvantage of Mobile IP is changeable IP. It means the position changing.
The proposed architecture uses mash-up of web services instead of the middleware platform such as CORBA or RMI. Therefore much fewer APIs are actually needed. This approach makes the architecture more modular and easier to leverage existing web services such as Google Maps. There is a location module at the client devices. The module handles the end-system device hardware and returns the requested user-location data to the application, regardless of the type of technology or method of implementation that actually calculates the user’s location. For example, Wi-Fi or GPS are commonly used to estimate the current location of the user. GPS requires a clear view of sky to function properly. Therefore, for the need of social services that take place indoors, Wi-Fi location technology is selected instead of GPS. An indoor positioning system using wireless LANs has been proposed and implemented.
3. According to lecture notes on Page 2, what is social network? Why is the positioning a major factor in mobile social network service?
Answer:
Social network are personal or professional sets of relationships between individuals.
This is because people are great sources of unique information, especially that which is location-specific, community-specific and time-specific. Often used as a measure of social “connectedness”,recognizing social networks assists in determining how information moves throughout groups, and how trust can be established and fostered. In the connected age, what happens and how it happens
depend on the network.” Mobile communication technology enables ubiquitous access which has the potential to create scenarios of increased human nteractions in forms of computer mediated communication.
Answer:
RFID have been implementing in many fields today. In my company, we use it to audit and manage the inspection of power facilities. It is easy to deploy because of low cost and short time frame. The test results show the implementation is user friendly and promising with high reliability. The navigation server can records the positions, time, and user ID for the tracking purpose by using RFID. The wayfinding Systems based on passive RFID will be multi-functional and interactive.
Yao-Jen Chang, Tseng-Yun Wang, Yu-Chia Chuang, Shih-Kai Tsai, “Ontology-based Personalized Wayfinding System Using Deviation Detecting for Individuals with Cognitive Impairments”
Answer:
Ontology-based route personalization is proposed to adapt routes with respect to context and changing environment. A tracking function is integrated with a time constrained breadth-first search at the core of deviation detecting algorithm. The tracking system increases the sense of security and also lowers the entry threshold to accepting the assistive technology. It makes the wayfinding system can be suitable to the need of different people. The new traffic sign system will afford various routes to adopt route personalization.
2. Read Sec. 1-3-6 of Textbook.What is the disadvantage of Mobile IP and what's the solution?
Answer:
The disadvantage of Mobile IP is changeable IP. It means the position changing.
The proposed architecture uses mash-up of web services instead of the middleware platform such as CORBA or RMI. Therefore much fewer APIs are actually needed. This approach makes the architecture more modular and easier to leverage existing web services such as Google Maps. There is a location module at the client devices. The module handles the end-system device hardware and returns the requested user-location data to the application, regardless of the type of technology or method of implementation that actually calculates the user’s location. For example, Wi-Fi or GPS are commonly used to estimate the current location of the user. GPS requires a clear view of sky to function properly. Therefore, for the need of social services that take place indoors, Wi-Fi location technology is selected instead of GPS. An indoor positioning system using wireless LANs has been proposed and implemented.
3. According to lecture notes on Page 2, what is social network? Why is the positioning a major factor in mobile social network service?
Answer:
Social network are personal or professional sets of relationships between individuals.
This is because people are great sources of unique information, especially that which is location-specific, community-specific and time-specific. Often used as a measure of social “connectedness”,recognizing social networks assists in determining how information moves throughout groups, and how trust can be established and fostered. In the connected age, what happens and how it happens
depend on the network.” Mobile communication technology enables ubiquitous access which has the potential to create scenarios of increased human nteractions in forms of computer mediated communication.
2007年9月18日 星期二
Homework 9/15/2007 -宏益g9378612
Q1. Translate or rewrite the abstract of the following papers. Wayfinding Systems Based on Geo-coded QR Codes and Social Computing for Individuals with Cognitive Impairment,
一種新穎的路徑搜尋系統被發明，是以促進認知障礙病人如腦部創傷患者、大腦性麻痺、精神遲緩、精神分裂及阿茲罕默等病人在工作場所及日常生活的獨立為目標。它將位置座標和社會關係計算嵌進地理編碼QR codes內為基礎，來幫助縮短使用者的學習歷程。根據空間導航的心理模式與重建慣性專業的需求，PDA在適當時間和位置提示空間圖像，幫助認知障礙者室內或道路導航。為了達到此目的，幾何編碼QR codes可以想像為一種新的交通號誌系統被傳送至路徑選擇位置。導航圖片的要求以提供使用者利用PDA內建照相機快照視界範圍內QR Codes。一種追蹤功能被整合能對參觀位置作時間郵戳並且在異常狀況時產生警告。追蹤系統增加了安全敏感度，並且降低接受輔助科技的入門阻礙，由路徑搜尋裝置、訓練部落格和追蹤系統組成的原型機已被設計並在校園中測試，相較於感知網路方法，QR Codes發展較容易且較快速，成本也較低。經驗結果證實，電腦人性化介面具親和力，且路徑搜尋能力是可信賴的。
A General Architecture of Mobile Social Network Services
手機的廣泛使用與使用者位置資訊的獲得正促進個人定位基礎應用。在今天的同意服務當中以目標能滿足娛樂、代為安排男女初次會面和找朋友或家人的需求。在這個研究，我們探索了在社會服務的脈络中行動人際關係網路服務的可行性。這個研究開始目標以利用行動社會網路服務來量測對於許多有其他方面才能而未被雇用、甚少獲得適當社區服務和被社會孤立的人社會連結的增進和生活品質的改善。一種互動、多重媒介和定位基本應用分法被提出來以滿足提供支援社會服務在此領域目前產生的需求。連結定位感知搜尋技術和個人檔案配對，建議模組和一般架構使社會工作者、他們的同事和其他參與專家能保持彼此連結、資訊通暢、團體組織如行動社區及成為一需求支援網。所提出架構的一個優點為沒有一個新的定位組件必須被建置在Wi-Fi分散網路或行動電話的核心網路。此外，利用混合式網路服務，這個方法使該架構更模組化和更容易去影響現有的網路。初始模型已應用建立並顯現出成果。
Q2. Read Sec. 1-1, 1-2 of Textbook and the presentation materials in class. What is the key factor which contributes to the integration of various media such as data, voice, and video on a single platform?
• All-IP
– Connecting data, Voice, Video
– Mobile & Fixed
– 3G, 3.5G
Q3. What are the major differences between wireless and wired communication?
• Multipath
• Fading
• Interference
• Hidden Terminal
一種新穎的路徑搜尋系統被發明，是以促進認知障礙病人如腦部創傷患者、大腦性麻痺、精神遲緩、精神分裂及阿茲罕默等病人在工作場所及日常生活的獨立為目標。它將位置座標和社會關係計算嵌進地理編碼QR codes內為基礎，來幫助縮短使用者的學習歷程。根據空間導航的心理模式與重建慣性專業的需求，PDA在適當時間和位置提示空間圖像，幫助認知障礙者室內或道路導航。為了達到此目的，幾何編碼QR codes可以想像為一種新的交通號誌系統被傳送至路徑選擇位置。導航圖片的要求以提供使用者利用PDA內建照相機快照視界範圍內QR Codes。一種追蹤功能被整合能對參觀位置作時間郵戳並且在異常狀況時產生警告。追蹤系統增加了安全敏感度，並且降低接受輔助科技的入門阻礙，由路徑搜尋裝置、訓練部落格和追蹤系統組成的原型機已被設計並在校園中測試，相較於感知網路方法，QR Codes發展較容易且較快速，成本也較低。經驗結果證實，電腦人性化介面具親和力，且路徑搜尋能力是可信賴的。
A General Architecture of Mobile Social Network Services
手機的廣泛使用與使用者位置資訊的獲得正促進個人定位基礎應用。在今天的同意服務當中以目標能滿足娛樂、代為安排男女初次會面和找朋友或家人的需求。在這個研究，我們探索了在社會服務的脈络中行動人際關係網路服務的可行性。這個研究開始目標以利用行動社會網路服務來量測對於許多有其他方面才能而未被雇用、甚少獲得適當社區服務和被社會孤立的人社會連結的增進和生活品質的改善。一種互動、多重媒介和定位基本應用分法被提出來以滿足提供支援社會服務在此領域目前產生的需求。連結定位感知搜尋技術和個人檔案配對，建議模組和一般架構使社會工作者、他們的同事和其他參與專家能保持彼此連結、資訊通暢、團體組織如行動社區及成為一需求支援網。所提出架構的一個優點為沒有一個新的定位組件必須被建置在Wi-Fi分散網路或行動電話的核心網路。此外，利用混合式網路服務，這個方法使該架構更模組化和更容易去影響現有的網路。初始模型已應用建立並顯現出成果。
Q2. Read Sec. 1-1, 1-2 of Textbook and the presentation materials in class. What is the key factor which contributes to the integration of various media such as data, voice, and video on a single platform?
• All-IP
– Connecting data, Voice, Video
– Mobile & Fixed
– 3G, 3.5G
Q3. What are the major differences between wireless and wired communication?
• Multipath
• Fading
• Interference
• Hidden Terminal
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