RFGSM vs. UMTS: A Comparison of Cellular Technologies
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This article delves into the differences between GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System), two prominent cellular wireless technologies used for mobile communications.
GSM operates based on Frequency and Time Division Multiple Access (FTDMA), while UMTS employs Code Division Multiple Access (CDMA). GSM was initially designed primarily for voice communication, but with the introduction of GPRS (General Packet Radio Service) and EDGE (Enhanced Data rates for GSM Evolution), data communication became a significant aspect of the standard.
In GSM, a specific frequency and time slot are allocated for communication in each direction for a mobile device. This explains the term FTDMA. It can also be referred to as an FDMA/TDD (Time Division Duplex) system. Conversely, CDMA uses pseudo-random codes, specifically Walsh codes, assigned for communication. These are known as spreading codes.
Key Differences Between GSM and UMTS
GSM, developed based on 3GPP standards, stands for Global System for Mobile Evolution. A GSM network comprises the Mobile Station, Base Station Subsystem (BTS, BSC), and the Network and Operation Subsystem (MSC). Data support in GSM is primarily provided through GPRS technology.
UMTS, also developed based on 3GPP standards, stands for Universal Mobile Telecommunications System. A UMTS network is composed of three main parts: User Equipment (UE), Radio Access Network (RAN), and Core Network. UMTS encompasses various technologies based on different releases from the 3GPP community and is often referred to as 3G.
WCDMA (Wideband Code Division Multiple Access) was introduced in Release 99. Subsequent releases from 3GPP brought HSDPA (High-Speed Downlink Packet Access), HSUPA (High-Speed Uplink Packet Access), HSPA (High-Speed Packet Access), LTE (Long-Term Evolution), and LTE-Advanced.
While UMTS supports both voice and data similarly to GSM, certain standards, such as HSPA, were specifically targeted at increasing the data rate capabilities of UMTS mobile terminals/dongles. In GSM, the Base Station is called BTS (Base Transceiver Station), while in UMTS, it’s referred to as NodeB. Similarly, in GSM, the Mobile Subscriber is referred to as ME (Mobile Equipment), and in UMTS, it is referred to as UE (User Equipment).
Frame structure, logical channels, and frequency bands differ between the two technologies, and these are explained in more detail in dedicated tutorials.
GSM vs. UMTS: Feature Comparison
The following table summarizes the key differences between GSM and UMTS.
| Features | GSM | UMTS |
|---|---|---|
| Frequency Band (MHz) | Various bands, mainly 850MHz, 900MHz, 1800MHz, and 1900MHz. Refer to GSM ARFCN to Frequency Conversion. | Various bands from Band-I to Band-VI. Each band specifies frequency and UARFCN. Refer to UMTS UARFCN to Frequency conversion. |
| Carrier Spacing (KHz) | 200 KHz | 1230 KHz (CDMA version) |
| Channel Types | Traffic channels and control channels, based on functionality within the system. Refer to GSM channels. | Logical, transport, and physical channels based on where they are used and their functions. Refer to UMTS channels. |
| Multiple Access technique | FDMA/TDMA | CDMA |
| Frame | Frame duration is about 4.615ms, GSM Frame. | Frame duration is about 10ms (consisting of 15 slots), UMTS Frame. |
| Network Architecture | Refer to GSM Architecture. | Refer to UMTS Architecture. |
| Channel rate (Kb/s) | 270.833 Kbps | 1228.8 kbps (in CDMA) |
| Modulation Efficiency | 1.35 b/s/Hz | 1.0 b/s/Hz (CDMA) |
| Standard versions | There are various documents specified by ETSI and 3GPP, 3GPP ™ TS 45-series | Various releases such as R99(WCDMA), R5 (HSDPA), R6(HSUPA) etc. Refer to UMTS releases. |
