In this seminar, we learnt the interesting phenomenon that crowd is usually much smarter than the smartest individual. What I feel more persuasive is the advantage of diversity of a group. This is also the essential part of Web 2.0. We can have a lot of people from different divisions and provide broader images. For a same question, we can have answers from different perspectives. What's more, the minority's voice can also be heard.
Near the end of the seminar, Prof Gilbert talked about the working principle of mobile phone calling and sms. The network is extremely important.
I search for the mobile network operators (retrieved from wiki pedia): The China Mobile is the largest company in terms of the subscribers population. Second is Vadafone operated in United Kingdom. Interestingly, the third is still a Chinese company, China Unicom. For Singapore, SingTel, the ranking is 17 which is not bad. And the technology used in network in Singapore is GSM, UMTS.
There are various technologies used around the world: GSM, GPRS, EDGE, UMTS, HSDPA, CDMA, CDMA2000 1x, EV-DO,etc.
Here I want to introduce the GSM and UMTS since both of them are used in Singapore.
GSM
The Global System for Mobile Communications (GSM: originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world. GSM service is used by over 2 billion people across more than 212 countries and territories.
Network Structure:
The network behind the GSM system seen by the customer is large and complicated in order to provide all of the services which are required. It is divided into a number of sections and these are each covered in separate articles.
the Base Station Subsystem (the base stations and their controllers).
the Network and Switching Subsystem (the part of the network most similar to a fixed network). This is sometimes also just called the core network.
the GPRS Core Network (the optional part which allows packet based Internet connections).
all of the elements in the system combine to produce many GSM services such as voice calls and SMS.
the Base Station Subsystem (the base stations and their controllers).
the Network and Switching Subsystem (the part of the network most similar to a fixed network). This is sometimes also just called the core network.
the GPRS Core Network (the optional part which allows packet based Internet connections).
all of the elements in the system combine to produce many GSM services such as voice calls and SMS.
UMTS
Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile phone technologies. The currently most common form uses W-CDMA as the underlying air interface, is standardized by the 3GPP, and is the European answer to the ITU IMT-2000 requirements for 3G cellular radio systems.
To differentiate UMTS from competing network technologies, UMTS is sometimes marketed as 3GSM, emphasizing the combination of the 3G nature of the technology and the GSM standard which it was designed to succeed.
To differentiate UMTS from competing network technologies, UMTS is sometimes marketed as 3GSM, emphasizing the combination of the 3G nature of the technology and the GSM standard which it was designed to succeed.
Technology:
UMTS combines the W-CDMA, TD-CDMA, or TD-SCDMA air interfaces, GSM's Mobile Application Part (MAP) core, and the GSM family of speech codecs. In the most popular cellular mobile telephone variant of UMTS, W-CDMA is currently used. Note that other wireless standards use W-CDMA as their air interface, including FOMA.
UMTS over W-CDMA uses a pair of 5 MHz channels. In contrast, the competing CDMA2000 system uses one or more arbitrary 1.25 MHz channels for each direction of communication. UMTS and other W-CDMA systems are widely criticized for their large spectrum usage, which has delayed deployment in countries that acted relatively slowly in allocating new frequencies specifically for 3G services (such as the United States).
The specific frequency bands originally defined by the UMTS standard are 1885-2025 MHz for uplink and 2110-2200 MHz for downlink. In the US, the 1700MHz band will be used instead of 1900MHz - which is already in use - for the uplink by many UMTS operators. Additionally, UMTS is commonly run on 850MHz and 1900MHz (independently, for both the uplink and downlink) in some countries, notably in the US by Cingular Wireless.
For existing GSM operators, it is a simple but costly migration path to UMTS: much of the infrastructure is shared with GSM, but the cost of obtaining new spectrum licenses and overlaying UMTS at existing towers can be prohibitively expensive.
A major difference of UMTS compared to GSM is the air interface forming Generic Radio Access Network (GeRAN). It can be connected to various backbone networks like the Internet, ISDN, GSM or to a UMTS network. GeRAN includes the three lowest layers of OSI model. The network layer (OSI 3) protocols form the Radio Resource Management protocol (RRM). They manage the bearer channels between the mobile terminals and the fixed network including the handovers.
UMTS over W-CDMA uses a pair of 5 MHz channels. In contrast, the competing CDMA2000 system uses one or more arbitrary 1.25 MHz channels for each direction of communication. UMTS and other W-CDMA systems are widely criticized for their large spectrum usage, which has delayed deployment in countries that acted relatively slowly in allocating new frequencies specifically for 3G services (such as the United States).
The specific frequency bands originally defined by the UMTS standard are 1885-2025 MHz for uplink and 2110-2200 MHz for downlink. In the US, the 1700MHz band will be used instead of 1900MHz - which is already in use - for the uplink by many UMTS operators. Additionally, UMTS is commonly run on 850MHz and 1900MHz (independently, for both the uplink and downlink) in some countries, notably in the US by Cingular Wireless.
For existing GSM operators, it is a simple but costly migration path to UMTS: much of the infrastructure is shared with GSM, but the cost of obtaining new spectrum licenses and overlaying UMTS at existing towers can be prohibitively expensive.
A major difference of UMTS compared to GSM is the air interface forming Generic Radio Access Network (GeRAN). It can be connected to various backbone networks like the Internet, ISDN, GSM or to a UMTS network. GeRAN includes the three lowest layers of OSI model. The network layer (OSI 3) protocols form the Radio Resource Management protocol (RRM). They manage the bearer channels between the mobile terminals and the fixed network including the handovers.
