3G Technology

What is 3G Technology?

3G is the next generation of technology which has revolutionized the telecommunication industry. Apart from increasing the speed of communication, the objective of this technology is to provide various value added services like video calling, live streaming, mobile internet access, IPTV, etc on the mobile phones. These services are possible because the 3G spectrum provides the necessary bandwidth.

Fig. 1: Representational Image of 3G Technology

Technically speaking 3G is a network protocol which refers to the generations of mobile phones and telecommunication equipments which are compatible with the International Mobile Telecommunications-2000 (IMT-2000) standards stated by International Telecommunication Union (ITU). The basic requirement for compiling to IMT-2000 standards is that the technology should provide peak data rates of atleast 200 kbit/s. It’s worth mentioning that speed isn’t the only criteria for deciding whether the network protocol is 3G or not. 3G isn’t just any high speed network but a protocol which has its own standards defined under IMT-2000 by ITU.

3G Technology is designed for multimedia communication. It provides services like higher data transfer rates. One of its key visions is to provide seamless global roaming, enabling users to move across borders while using the same number and handset. According to ITU it is expected that IMT-2000 will provide higher transmission rates: a minimum speed of 2Mbit/s for stationary or walking users, and 348kbit/s in a moving vehicle.

Birth of IMT-2000

The concept of IMT came into existence in the mid-1980s at ITU. It took more than ten years for the approval of standards for the next generation systems. These standards are branded as IMT-2000. Under the technical specifications the spectrum between 400 MHz and 3 GHz was dictated technically suitable for the third generation. IMT-2000 is the result of collaboration of many entities, inside the ITU (ITU-R and ITU-T), and outside the ITU (3GPP, 3GPP2, UWCC and so on). This approval has made possible the full interoperability and interworking of mobile systems.

It facilitates five radio interfaces based on three technologies namely FDMA, TDMA and CDMA. The accommodated radio interfaces are : IMT-DS, IMT-MC, IMT-SC, IMT-TC, IMT-FT

Contributor Technologies of 3G

The 3G technology is comprised of basically three technologies, but it is not the reason for its nomenclature as 3G. The technologies are:

· CDMA2000 – Code Division Multiple Access.

TD-SCDMA – Time-division Synchronous Code-division Multiple Access.

· W-CDMA (UMTS) – Wideband Code Division Multiple Access.

Let’s take a look on what these technologies are.

CDMA2000

Technically, it is the upgraded version of CDMA. CDMA 2000 specification was developed by the Third Generation Partnership Project 2 (3GPP2), a partnership consisting of ARIB and TTC in Japan, CWTS in China, TTA in Korea and TIA in North America. CDMA2000 is compatible with both 2G and 3G and has already been implemented to several networks as an evolutionary step from CDMA One. In other words CDMA2000 is not constrained to only the IMT-2000 band, but operators can also overlay a CDMA2000 1x system, which supports 144 kbps now and data rates up to 307 kbps in the future, on top of their existing CDMAOne network.

World Administrative Radio Conference (WARC) of the ITU (International Telecommunications Union), at its 1992 meeting, identified the frequencies around 2 GHz that were available for use by future third generation mobile systems, both terrestrial and satellite. At that time this spectrum was already auctioned in North America. Hence, third generation systems must be employed within the existing bandwidth. So, 3G networks are to be deployed using existing band. This is done via spectrum refarming approach. Hence, using the same frequency spectrum the former 2G operators can switch to 3G without having technical hindrances. This spectrum refarming was offered by CDMA2000 because of its compatability with IS-95 and IS-2000. Hence, this technology is broadly suitable for countries where there is no separate spectrum for 3G.

CDMA2000 Technical summary
Frequency band: Any existing band.
Minimum frequency band required: 1x: 2×1.25MHz, 3x: 2×3.75
Chip rate: 1x: 1.2288, 3x: 3.6864 Mcps
Maximum user data rate: 1x: 144 kbps now, 307 kbps in the future 1xEV-DO: max 384 kbps – 2.4 Mbps, 1xEV-DV: 4.8 Mbps.
Frame length: 5ms, 10ms or 20ms
Power control rate: 800 Hz
Spreading factors: 4 … 256 UL

TD-SCDMA
Time Division Synchronous CDMA (TD-SCDMA) was proposed by China Wireless Telecommunication Standards group (CWTS) and after approval by the ITU in 1999, this technology is being developed by the Chinese Academy of Telecommunications Technology and Siemens. TD-SCDMA uses the Time Division Duplex (TDD) mode, i.e., traffic from the mobile terminal to the base station (uplink) and vice versa (downlink) are transferred in the same frame in different time slots. The uplink and downlink spectrum is assigned flexibly, depending on the type of information to be transmitted. When services like telephony are used a symmetrical split in the uplink and downlink takes place whereas when asymmetrical data like e-mail and internet are transmitted from the base station, more time slots are used for downlink than for uplink.

TD-SCDMA Technical Summary
Frequency band: 2010 MHz – 2025 MHz in China (WLL 1900 MHz – 1920 MHz)
Minimum frequency band required: 1.6MHz
Frequency re-use: 1 (or 3)
Chip rate: 1.28 Mbps
Frame length: 10ms
Number of slots: 7
Modulation: QPSK or 8-PSK
Voice data rate: 8kbit/s
Circuit switched services: 12.2 kbits/s, 64 kbits/s, 144 kbits/s, 384 kbits/s, 2048 kbits/s
Packet data: 9.6kbits/s, 64kbits/s, 144kbits/s, 384kbits/s, 2048kbits/s
Receiver: Joint Detection, (mobile: Rake)
Power control period: 200 Hz
Number of slots / frame: 7
Frame length: 5ms
Multi carrier option
Handovers: Hard Smart antennas, Baton handover, Uplink synchronization
Physical layer spreading factors: 1, 2, 4, 8, 16

WCDMA (UMTS)

Wideband Code-Division Multiple-Access (W-CDMA) is one of the main technologies for the implementation of third-generation (3G) cellular systems. It is also known as IMT-2000 direct spread. It is developed by 3GPP (Third Generation Partnership Project). 3GPP is the joint standardization project of the standardization bodies from Europe, Korea, Japan, the USA and China. Within 3GPP, WCDMA is called UTRA (Universal Terrestrial Radio Access) FDD (Frequency Division Duplex) and TDD (Time Division Duplex), the name WCDMA being used to cover both FDD and TDD operation.

WCDMA is a wideband Direct-Sequence Code Division Multiple Access (DS-CDMA) System. WCDMA supports two basic modes of operation: Frequency Division Duplex (FDD) and Time Division Duplex (TDD). In the FDD mode, separate 5 MHz carrier frequencies are used for the uplink and downlink respectively, whereas in TDD only one 5 MHz is timeshared between the uplink and downlink. Uplink is the connection from the mobile to the base station, and downlink is that from the base station to the mobile.

The implementation of W-CDMA will be a technical challenge because of its complexity and versatility. The complexity of W-CDMA systems can be viewed from different angles: the complexity of each single algorithm, the complexity of the overall system and the computational complexity of a receiver. W-CDMA link-level simulations are over 10 times more compute-intensive than current second-generation simulations. In W-CDMA interface different users can simultaneously transmit at different data rates and data rates can even vary in time. UMTS networks need to support all current second generation services and numerous new applications and services.

FDD Technical summary

Frequency band:1920 MHz -1980 MHz and 2110 MHz – 2170 MHz (Frequency Division Duplex) UL and DL
Minimum frequency band required: ~ 2x5MHz
Frequency re-use: 1
Carrier Spacing: 4.4MHz – 5.2 MHz
Maximum number of (voice) channels on 2x5MHz: ~196 (spreading factor 256 UL, AMR 7.95kbps) / ~98 (spreading factor 128 UL, AMR 12.2kbps)
Voice coding: AMR codecs (4.75 kHz – 12.2 kHz, GSM EFR=12.2 kHz) and SID (1.8 kHz)
Channel coding: Convolutional coding, Turbo code for high rate data
Duplexer needed (190MHz separation), Asymmetric connection supported
Tx/Rx isolation: MS: 55dB, BS: 80dB
Receiver: Rake
Receiver sensitivity: Node B: -121dBm, Mobile -117dBm at BER of 10^-3
Data type: Packet and circuit switch
Modulation: QPSK
Pulse shaping: Root raised cosine, roll-off = 0.22
Chip rate: 3.84 Mcps
Channel raster: 200 kHz
Maximum user data rate (Physical channel): ~ 2.3Mbps (spreading factor 4, parallel codes (3 DL / 6 UL), 1/2 rate coding), but interference limited.
Maximum user data rate (Offered): 384 kbps (year 2002), higher rates ( ~ 2 Mbps) in the near future. HSPDA will offer data speeds up to 8-10 Mbps (and 20 Mbps for MIMO systems)
Channel bit rate: 5.76Mbps
Frame length: 10ms (38400 chips)
Number of slots / frame: 15
Number of chips / slot: 2560 chips
Handovers: Soft, Softer, (interfrequency: Hard)
Power control period: Time slot = 1500 Hz rate
Power control step size: 0.5, 1, 1.5 and 2 dB (Variable)
Power control range: UL 80dB, DL 30dB
Mobile peak power: Power class 1: +33 dBm (+1dB/-3dB) = 2W; class 2 +27 dBm, class 3 +24 dBm, class 4 +21 dBm
Number of unique base station identification codes: 512 / frequency
Physical layer spreading factors: 4 … 256 UL, 4 … 512 DL

IMT for 3G

Fig. 2:

History

History and evolution of 3G

The evolution of 3G technology was the result of high speed demands of smart phones. Smart phones, which is a combination of PDA and mobile supports different applications. Since, these smart phones require high speed data transfer therefore, high speed network become the demand which led to the evolution of 3G networks.

NTT DoCoMo launched the first 3G network in Japan, in the year 2001. It was branded as FOMA(Freedom of Mobile Multimedia Access) and was based on W-CDMA technology. SK Telecom, a South Korean telecom company launched the second 3G network based on CDMA 1xEV-DO technology. In Europe, 3G entered via UMTS technology introduced by Manx Telecom. Then, Telenor launched the first commercial 3G network in Europe. The first commercial United States 3G network was by Monet Mobile Networks, on CDMA2000 1x EV-DO technology.

There are still developments carried out in 3G. Long-Term (Radio) Evolution or LTE is an example of it. . It’s known as 3.9G or “Super 3G”. Its newer version LTE advanced is 4G. It is branded as 4G or pre-4Gin some parts of the world. It aims at peak data rates of 200 Mbps (DL) and 100 Mbps (UL). The first commercial LTE network was launched by TeliaSonera on 14 December 2009. They are offering pre-4G (or beyond 3G) services in Stockholm, Sweden and Oslo, Norway.

In December 2007, 190 3G networks were operating in 40 countries and 154 HSDPA networks were operating in 71 countries, according to the Global Mobile Suppliers Association (GSA). In Asia, Europe, Canada and the USA, telecommunication companies use W-CDMA technology with the support of around 100 terminal designs to operate 3G mobile networks.

4G

4G: Successor of 3G

4G is the successor technology of 3G with more bandwidth and services offered in the 3G. The technologies that fall in the 4G categories are UMTS, OFDM, SDR, TD-SCDMA, MIMO, LTE advanced and WiMAX to the some extent. As 3G is based on IMT-2000 standards likewise 4G is based on IMT-advanced standards stated by ITU. It envisages peak speed requirements for 4G service at 100 Mbit/s for high mobility communication (such as from trains and cars) and 1 Gbit/s for low mobility communication (such as pedestrians and stationary users). The bandwidth would be much wider (100 MHz) and data would be transferred at much higher rates.With 4G technology the dimensions of IT and telecommunication industry will witness a significant transformation. 4G technology is also referred as “MAGIC”, which stands for Mobile multimedia Anytime Anywhere Global mobility support, integrated wireless and personalized services.

UMB(Ultra Mobile Broadband) is also a 4G technology but it is discontinued by 3GPP2 to improve the CDMA2000 mobile phone standard for next generation applications and requirements. In November 2008, Qualcomm, the leading sponsor for UMB, announced it was ending development of the technology, for development of LTE instead.