10-25-2008 Homework

Summarize 3GPP LTE in 200 words.


3GPP（3rd Generation Partnership Project）第三代合作夥伴計畫,由歐洲的ETSI,日本的ARIB和TTC,韓國的TTA以及美國的T1在1998年底發起成立,主要研究制定並推廣基於演進的GSM核心網路的3G標準,即有WCDMA, TD-SCDMA, EDGE...等.

LTE是Long Time Evolution的簡稱,也就是目前3G的主導單位所推展的行動網路標準,計劃設計出50倍於當前系統傳輸速率的新技術,同時該系統應亦具有高向下相容性,LTE的優點是可以採用既有的3G系統,讓營運商無須重頭開始建置,根據3GPP組織規劃,LTE將可達到最高下載速率100Mbps與上傳50Mbps以上為目標.

3GPP LTE提升資料速率,增進頻譜效率,增加涵蓋範圍與降低延遲.也定義了以 IP 為基礎的扁平化網絡架構,定義此一架構是「系統架構演進（SAE）」工作的一部分.LTE─SAE的架構與觀念設計始終如一：以有效率的方式,支持任何以IP為基礎之服務的大規模市場使用.其架構是以現有GSM/WCDMA核心網絡的演進為基礎,營運更簡單,部署順暢,具成本效益.

WiMAX當然是目前最流行的話題,不過對於歐洲人而言,LTE才是他們次代移動網路的主流,在技術的方面與WiMAX相當的接近,同樣使用OFDMA(Orthogonal Frequency Division Multiplexing)正交多頻分工,以及MIMO多輸入多輸出,其實OFDM技術問世已有段時間了,諸如ADSL,然而WiMAX與LTE兩者完全屬於不同體係,所以更是互不相容,這兩種都可能成為4G的標準技術,即將取代有線寬頻與無線連接,更高的數據吞吐量,更低的延遲,不再局限於電信行業,還可以應用於金融,醫療,教育,交通等行業.

Homework 10-4-2008

1. Why 2G is faster than 1G?


第一代行動電話(1G)是屬於類比式的蜂巢行動電話服務,僅能進行語音通話功能 ,主要是以AMPS(Advanced Mobile Phone System)系統,採用“細胞”的觀念,將一個通訊區域分成數個六角形彼此相接的蜂巢,以FDMA(Frequency Division Multiple Access)分頻多工接取的方式,在頻率上直接切割,將全數頻寬切成每個等寬頻帶的通道,每個通道可供一個用戶使用,所以一旦被佔用的話,其他人可能就不能通話.

第二代行動電話(2G)是屬於數位行動通信,目前世界上使用者最多的為歐洲推出的GSM(Global System for Mobil Communication)系統,採用多種語音編碼,將音頻壓縮,實現同步語音傳輸,TDMA 的技術,(Time Division Multiple Access)分時多工接取,利用相同頻率但不同時間來傳送訊息,比起FDMA,由於TDMA對於多使用者之時槽安排可隨時調整,以提供不同使用者不同之接取速率,因此TDMA之運用彈性較高,亦較容易整合數位語音與資料傳輸等服務.

與GSM同屬於第二代行動通訊系統的尚有QUALCOMM首先開發出來所發展的CDMA(Code Division Multiple Access),分碼多工接取,利用展頻的通訊技術,因而可以減少手機間的干擾,CDMA的傳送數據資料的速度要快上許多,因為CDMA利用直接序列展頻技術,將原本9.6 kbps的語音或數據資料,利用各種不同代碼彼此堆疊起來,用數位方式保密地大量傳送,並再依據對方機制還原成語音或數據資料,並且可以增加用戶的容量.

2. Why cellular is better than broadcast?

"廣播"是用無線電波的播音系統,一般常見的有調頻或調幅的方式,調頻（Freguency Modulation簡稱FM）指調變頻率,波幅不變,是依訊號變化調整頻率大小,以直線波傳送,只達視線所及之距離.調幅（Amplification Modulation簡稱AM）指調變波幅,頻率不變,是依訊號變化調整電壓大小,距離可傳達到遠方,不過容易受到干擾,雜音多.

蜂巢式,每個基地台電波的涵蓋範圍,稱為細胞(cell).當電信業者佈建了許多基地台,其涵蓋範圍連接在一起的形狀就像是蜂巢一樣,每個基地台發射的低功率電波只涵蓋自己所管轄的蜂巢內,因此同一個頻率可在兩個不相鄰接的基地台重複使用而不致於造成干擾,優點是利用最小的頻寬,服務大量用戶,而且訊號穩定,不易斷訊.

3. Describe a short history of development of cellular technology from 1G to 3G with a prediction of 4G and beyond.

1G:類比式蜂巢(Analoge Cellular),美國Bell Lab.貝爾實驗室於1940年代發展出所謂的蜂巢式無線電話系統,利用細胞分裂以及交替觀念,使得行動電話在基地台範圍內可以對外收發聲音.

2G:數位式蜂巢(Digital Cellular),有歐洲發展的GSM,美國所發展的CDMA, TDMA, 與日本發展的PDC,2G通訊的技術,像多個微細胞基地台構成狀似六邊形的細胞格,而且能夠進行國際漫遊,算是達到了真正的行動通訊.

3G:第三代行動通訊技術前主要有W-CDMA,CDMA2000,TD-SCDMA等三種,以CDMA的技術最為廣泛使用,CDMA推行初期並不順利,但由於南韓政府大力推動之下,與Qualcomm簽約開始引入CDMA行動通訊系統,因此CDMA開始嶄露頭角,成長速度不亞於GSM,成為3G之重要技術標準之一.

4G:目前對於第四代行動通訊技術還沒有正式的被正義,最近熱門的WiMAX (Worldwide Interoperability for Microwave Access) 全球互通微波存取,因為其寬頻的特性,被稱為第四代無線通訊,傳輸距離可達 50 公里,大幅改善前身 WLAN 的缺點,基地台數目將大為減少,我個人認為,手機看電視,上網漫遊,高速數位的傳輸,取代電腦...等,將推向更便利迅速的完美境界.

4. Read the article that discussed the future of mobile social networks.

Done.

Homework 9-27-2008

1. Install Google Browser Google Chrome and Firefox 3.0, try a few websites and compare their performance. For example, youtube, blogspot, msn, and yahoo.

Google's Chrome caused controversial discussions, both for its advantages and apparent lack of advanced features. But critics and fans agree that this thing is fast, really fast. You may be wondering why speed matters since your current browser already loads web pages in a snap. But here is the deal: Today’s web sites are not collections of individual pages anymore. You are probably using web applications on an everyday basis - on sites like Facebook or Google Docs. As more computing services move to the cloud, web applications are becoming more powerful and desktop-like. In this sense, a browser becomes an operating system for web applications and needs to do much more than take advantage of a broadband connection.
Mozilla Firefox Features:
- comprehensive popup controls to keep unwanted advertising off your desktop;
- a tab browsing mode that lets you open several pages in a single window, allowing you to load links in the background without leaving the page you're on;
- industry leading accessibility with Find As You Type - find links and page text by simply typing;
- a streamlined browser window that lets you see more of the page than any other browser while at the same time being more configurable; - a large variety of free downloadable extensions and themes that add specific functionality and visual changes to the browser.
I like Google Chrome,It's very cool,So Is Chrome the fastest browser? Who knows,No matter what youtube, blogspot, msn, and yahoo,A lot of users are still sitting on the sidelines, waiting to try it out.


2. Subscribe to our course website by Google reader, put the Google reader block on your iGoogle.




3. Comment on the article Serious potential in Google's Browser

Could the browser wars of the late 1990s web be upon us again? Then it was Netscape versus Internet Explorer, but now with the launch of Chrome it’s more than just two browsers pitted against each other. Google’s new entry in Chrome is certain to raise the temperature again. Internet Explorer has enjoyed dominance for around seven years. It has seen a small, but significant challenge from Firefox — which many users have been switching to simply because it is a faster, more efficient browser. So far, anecdotal reports point to Chrome being even faster than Firefox.

Google’s new browser is basic, with only core functionality, which focuses on what needs to be done best: Browsing. Some will find the lack of features an issue. Others will like the clean, minimalist look geared for fast browsing and a quick start-up.

It’s fast, minimalist and clean. Google’s browser is rightly about what’s in the viewing pane, and the viewing area is maximised, with ultra-thin browser borders and browser buttons taking up a small part of the viewing area.

Choose a new tab and you get option to select from your most visited sites. Saving me time already. Why didn’t the others think of that?

Google has kicked off Chrome with a strong product. Although the software feels polished and robust, the early stage of development is clearly revealed in its lack of support for advanced features like RSS integration and full bookmark management. If Google continues to invest in moving Chrome forward and manages to build up some community involvement, though, the new browser could quickly become a shiny new contender in the browser market.

4. Watch the video recording of Larry Page's "Broadband for the future."


done.

Homework 9-20-2008

1.Write a 200-word summary for today's discussion.

I am full of interest to the WiMAX, hence find again to look for mutually view information,WiMAX is a wireless digital communications system, also known as IEEE 802.16, that is intended for wireless "metropolitan area networks". WiMAX can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations. In contrast, the WiFi/802.11 wireless local area network standard is limited in most cases to only 100 - 300 feet (30 - 100m). With WiMAX, WiFi-like data rates are easily supported, but the issue of interference is lessened. WiMAX operates on both licensed and non-licensed frequencies, providing a regulated environment and viable economic model for wireless carriers.WiMAX can be used for wireless networking in much the same way as the more common WiFi protocol. WiMAX is a second-generation protocol that allows for more efficient bandwidth use, interference avoidance, and is intended to allow higher data rates over longer distances. The IEEE 802.16 standard defines the technical features of the communications protocol. The WiMAX Forum offers a means of testing manufacturer's equipment for compatibility, as well as an industry group dedicated to fostering the development and commercialization of the technology.

from:http://www.wimax.com/education

2.Watch the video recording of KF Lee's keynote speech on WWW 2008 Beijing on Cloud computing. Feel free to write what you think.

Cloud computing is a computing paradigm shift in which computing is moved away from personal computers or an individual application server to a "cloud" of computers. Users of the cloud only need to be concerned with the computing service being asked for, because the underlying details of how it is achieved are hidden. This method of distributed computing is done by pooling computer resources and managing them via software (rather than by a human).
There are four key attributes of cloud computing
(1)Data stored in the cloud
(2)Software services are increasingly moving to the cloud and accessed through the browser
(3)Based on standards and protocols
(4)Accessible from any device
Cloud computing liberates the user from having to remember where the data is, enables the user to access information anywhere once created, and makes services fast and powerful through essentially infinite information and computing. People are using cloud services to find, share, create, and organize information. People are also using cloud services to shop, bank, communicate, socialize. By using cloud computing, these capabilities will be accessible not only on PCs but also telephones, automobiles, televisions, and appliances...