The demand for faster data transmission and higher security has led to significant changes in the popular wireless standard GSM. The introduction of 3G networks brought with it various terminological complications such as USIM, USAT…
Technology experts tend to name new applications as extensions of the original terms. This is the root cause of much confusion, as on the surface, many people equate GSM with UMTS, SIM with USIM, SAT with USAT, and ICC with UICC.
The letter ‘U’ in the new terminology stands for Universal. However, in these cases, U is understood as “the ability to control more than one system” rather than necessarily referring to applications that are globally comprehensive.
UMTS – Universal Mobile Telecommunications System
The 3G technology that has been most frequently mentioned recently is UMTS (Universal Mobile Telecommunications System), which has developed directly from GSM but fiercely competes with its predecessor. The term “Universal” in UMTS signifies going beyond the borders of Europe. This technology has a transmission speed of about 1,920 Kb/s, supporting customers in downloading music, videos, and participating in group conferences. However, recent surveys in Japan have shown that the demand for video calls is not as high as expected.
As is known, CDMA (Code Division Multiple Access) is a technology that is in fierce competition with TDMA (Time Division Multiple Access) within GSM networks. However, UMTS, the “successor” to GSM, has separated from TDMA and utilizes technologies such as W-CDMA, TD-SCDMA, or TD-CDMA.
USIM and UICC
USIM (Universal Subscriber Identity Module) is an application of UMTS technology that operates on the UICC smart card in 3G phones. It contains user data, authentication information, and provides storage capacity for messages.
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| The UICC card measuring 25 x 15 mm from Vodafone New Zealand. |
UICC (Universal Integrated Circuit Card) contains the SIM in GSM phones and houses the USIM in UMTS networks. This smart card, typically with a capacity of several hundred KB, ensures the integration and security of personal information. Each UICC can include multiple applications, allowing access to both networks, storing contacts, and running additional applications.
The UICC card consists of a CPU, ROM, RAM, EEPROM (Electrically Erasable Programmable Read-Only Memory), and I/O circuits (Input/Output). The first versions measured 85 x 54 mm but have since been reduced to just 25 x 15 mm.
USAT and USAT-I
USAT (USIM Application Toolkit) can be understood in two different ways. In the first sense, it is a natural evolution from SAT in the GSM network entering the “U world”. USIM facilitates interaction between the phone and the network, while USAT fundamentally uses the phone to transmit commands or information between the user and the network system.
However, this technology takes on a completely different meaning when referred to as USAT-I (USAT Interpreter). It is also an application of UICC, similar to USIM and USAT. The difference here is that USIM in the smart card memory is a single, fixed application, with all its operations predetermined by the 3G standards. In contrast, USAT, also located in this memory, allows the network operator to implement new services without adhering to the predetermined standards.
Conversely, USAT-I does not shape the operational method of an application but acts as a byte decoder. It processes any encoded program that passes through it, similar to Java. Java cards allow for the loading and management of applets (small application programs that perform specific tasks), while USAT-I supports loading and executing “USATlets”. However, applets are a fixed part of the smart card, whereas “USATlets” are temporarily transmitted through the smart card and will be deleted upon completion of their tasks.
The predecessor of 3G is the 2G phone systems such as GSM, CDMA, PDC, and PHS. GSM was later upgraded to GPRS, also known as 2.5G. GPRS supports speeds of 140.8 Kb/s, although the common rate is only 56 Kb/s. E-GPRS, or EDGE, is a significant advancement from GPRS with a data transmission capability of 180 Kb/s, classified as a 2.75G system.
In 2006, the UMTS network in Japan will upgrade to HSDPA (High Speed Downlink Packet Access), considered a 3.5G network, with speeds of 14.4 Mb/s. The process of improving speeds with HSUPA (High-Speed Uplink Packet Access) is also currently underway.
Hai Nguyen
