Chapter 25: 3rd Generation (3G) Wireless System

     3G or 3rd Generation Mobile Telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunication-2000 (IMT-2000) specifications by the International Telecommunication Union. Application services include wide-area wireless voice telephone , mobile Internet Access, Video Calls and Mobile TV, All in a mobile environment.

     Several Telecommunication companies market wireless mobile Internet as 3G, indicating that the advertised service is provided over a 3G wireless network. Services advertised as 3G are required to meet IMY-2000 technical standards, including standards for reliability and speed. To meet IMT-2000 standards , a system is required to provide peak data rates of at least 200 Kbit/s. However, many services advertised as 3G provide higher speed than the minimum technical requirements for a 3G service.

The following Standards are typically branded 3G:

• The UMTS system, first offered in 2001, standardized bu 3GPP, used widely and other regions by GSM 2G system infrastructure. The cell phones are typically UMTS and GSM hybrids. Several radio interfaces are offered, sharing the same infrastructure:

1. The Original and most widespread radio interface is called W-CDMA.
2. The TD-SCDMA radio interface was commercialized in 2009.
3. The latest UMTS release, HSPA+, can provide peak data rates up to 56MBit/s in the downlink and 22MBit/s in uplink.

• The CDMA2000 system, first offered in 2002, standardized by 3GPP2, sharing infrastructure with the IS-95 2G standard. The cell phones are typically CDMA2000 and IS-95 hybrids. 

     The above systems and radio interfaces are based on kindred spread spectrum radio transmission technology. while the GSM EDGE standard (2.9G), DECT cordless phones and mobile WiMAX standard formally also fulfill the IMT-2000 requirements and are approved as 3G standards by ITU.

  
Enhanced Data GSM Environment(EDGE)

     Beyond GPRS, EDGE takes the cellular community one step closer to UMTS. It provides higher data rates than GPRS and introduces a new modulation scheme called 8−Phase Shift Keying(PSK). The TDMA community also adopted EDGE for their migration to UMTS. The data rates allocated for EDGE are started at 384 Kbps and above as a second stage to GPRS. EDGE uses the same modulation techniques as many of our existing TDMA infrastructures using Gaussian Minimum Shift Keying (GMSK) 8−PSK. Moreover EDGE uses a combination of FDMA and TDMA as the multiple access control methods. If we look at this from an OSI stack model, EDGE uses FDMA and TDMA at the MAC layer (bottom half of layer 2 OSI).

Specialty of EDGE

     EDGE is a new modulation scheme that is more bandwidth efficient than the GMSK modulation scheme used in the GSM standard. It provides a promising migration strategy for HSCSD and GPRS. The technology defines a new physical layer: 8−PSK modulation, instead of GMSK. 8−PSK enables each pulse to carry 3 bits of information versus the GMSK 1−bit−per−pulse rate. Therefore, EDGE has the potential to increase the data rate of existing GSM systems by a factor of three. EDGE retains other existing GSM parameters, including a frame length, eight time slots per frame, and a 270.833 kHz symbol rate. The GSM 200 kHz channel spacing is also maintained in EDGE, enabling the use of existing spectrum bands. This fact is likely to encourage deployment of EDGE technology on a global scale.

Universal Mobile Telecommunication Service(UMTS)

     UMTS is a modular concept that takes full advantage of the trend of converging existing and future information networks, devices, and services, and the potential synergies that can be derived from such convergence. UMTS will move mobile communications forward from where we are today into the 3G services and will deliver speech, data, pictures, graphics, video communication, and other wideband information direct to people on the move. UMTS is one of the major new 3G mobile communications systems being developed within the framework, which has been defined by the ITU and is known as IMT−2000.

Wideband Code Division Multiple Access(WCDMA)


     WCDMA is an ITU standard derived from CDMA and is officially known as IMT−2000 direct spread. WCDMA is a 3G mobile wireless technology offering much higher data speeds to mobile and portable wireless devices than commonly offered in today's market. WCDMA can support mobile/portable voice, images, data, and video communications at up to 2 Mbps (local area access) or 384 Kbps (wide area access). The input signals are digitized and
transmitted in coded, spread−spectrum mode over a broad range of frequencies. A 5 MHz wide carrier is used, compared with a 200 kHz wide carrier for narrowband CDMA.