a software that capture the packets and analyze their protocols. Free to download from
http://www.ethereal.com
星期六, 5月 27, 2006
Google Maps Mania
Take a look at what others mash up Google maps.
http://googlemapsmania.blogspot.com/
http://googlemapsmania.blogspot.com/
星期五, 5月 26, 2006
Spread Spectrum, Technology behind 3G
On May 27, we will talk about spread spectrum, the technology used in GPS, 3G, and 802.11b.
星期日, 5月 21, 2006
星期六, 5月 20, 2006
4G
4G communication at 100 Mbit/s while moving, and 1 Gbit/s while stationary.
Pervasive networks
See Wikipedia 4G
Pervasive networks
- simultaneously connected to several wireless access technologies (Wi-Fi, UMTS for example) and can seamlessly move between them (handover)
- smart-radio aka cognitive radio technology to efficiently manage spectrum use and transmission power
- mesh routing protocols
- 4G may use OFDM , and also OFDMA.
- packet switching only
See Wikipedia 4G
星期五, 5月 19, 2006
2G, 2.5G, 3G
cellular: 2G/3G
channel bandwidth: 200 kbps (8 time slots) / 5 MHZ
multiple access: TDMA / CDMA
SMS, Short Message Service, up to 160 bytes
SMS, EMS use control channels while MMS use regular channels shared by data and voice.
Data Services
Worldwide deployment of HSDPA
WAP, content bearer protocol, certificate, cookies
WML, wireless markup language (or HTML-C as in i-Mode, XHTML)
MMS, Multimedia Messaging Service
Tariff
3G, GPRS vs. GSM
flat rate, data volume or air time
Security features
WIM: A Wireless Identity Module (WIM) can contain
both trusted and client certificates, private keys
and algorithms needed for WTLS handshaking,
encryption/decryption and signature generation.
The WIM module can be placed on a SIM card
and is then referred to as a SWIM card.
authentication and billing of wlan with SIM card
channel bandwidth: 200 kbps (8 time slots) / 5 MHZ
multiple access: TDMA / CDMA
SMS, Short Message Service, up to 160 bytes
SMS, EMS use control channels while MMS use regular channels shared by data and voice.
Data Services
- GSM, Circuit Switching, 9.6 (*2), 12.4(*2, HSCSD)
- GPRS, General Packet Radio Services, Packet Switching, 9.05 kbps/13.4 kbps (*1,2,3,4), speed denoted as *u*d
- EDGE, 3 times of speed of GPRS by using 8-PSK instead of binary GMSK
- 3G, 384kbps, up to 2 Mbps, uplink is 128 kbps
- 3.5G HSDPA (High Speed Downlink Packet Access) 8-10 Mbps (R5), and 20 Mbps (R6) by MIMO, uplink is 384 kbps
Worldwide deployment of HSDPA
WAP, content bearer protocol, certificate, cookies
WML, wireless markup language (or HTML-C as in i-Mode, XHTML)
MMS, Multimedia Messaging Service
Tariff
3G, GPRS vs. GSM
flat rate, data volume or air time
Security features
WIM: A Wireless Identity Module (WIM) can contain
both trusted and client certificates, private keys
and algorithms needed for WTLS handshaking,
encryption/decryption and signature generation.
The WIM module can be placed on a SIM card
and is then referred to as a SWIM card.
authentication and billing of wlan with SIM card
- authentication
- billing
- coverage of both 802.11 & GPRS/3G
- roaming across APs and WISPs
- user base
知識經濟時代的農產變革: 生產履歷介紹
台灣第一條有身分證的健康魚
- 歐盟2005年1月1日起實施食品訊息可追蹤系統（食品追蹤紀錄管理辦法），未來若食品無法提供生產履歷，將無法進入歐盟市場
- 日本於e-Japan戰略中也已明確指出「在2010年前實現所有食品生產履歷」的目標，並於2004年12月1日起開始實施牛隻生產履歷紀錄制度。
- 產銷履歷源自Food Traceability，也就是食品可追蹤性，「追蹤農產品的生產至末端銷售完成的履歷過程」。
- 資訊不對稱以及觀望心態是最需要克服的難題之一。
星期六, 5月 06, 2006
Multiradio Wireless Mesh
- Architecture and Algorithms for an IEEE 802.11-based Multi-channel Wireless Mesh Network (A Raniwala, Prof Chiueh) in proc of IEEE Infocom '05 [pdf] [slides]
未來研究的方向是考慮 802.11 n,
以及 VoIP 所需要的 QoS
這篇paper 裡面的演算法不適用於802.11n
因此需要新的演算法
在mesh 架構下使用 802.11n 效能應該會大有提升.
- Centralized Channel Assignment and Routing Algorithms for Multi-channel Wireless Mesh Networks (A Raniwala, K Gopalan Prof Chiueh) - in ACM SIGMOBILE Mobile Computing and Communications Review (MC2R) April '04 issue [pdf]
- Joint Channel Assignment and Routing for Throughput Optimization in Multiradio Wireless Mesh …M Alicherry, R Bhatia, LE Li
Antenna Diversity for 802.11 b/g
Refer to PC Card and Mini PCI Antenna Integration Notes - group of 2 »
AD Considerations, D Tips, P Testing, OIPC Cards - 2600hz.net
... for integration into portable ICT devices (for example, notebook computers, handheld ...
one or two antennas, and possibly an antenna diversity switch. ...
AD Considerations, D Tips, P Testing, OIPC Cards - 2600hz.net
... for integration into portable ICT devices (for example, notebook computers, handheld ...
one or two antennas, and possibly an antenna diversity switch. ...