4G Mobile Technologies & Services

In telecommunications, 4G is the fourth generation of cellular wireless standards. It is a successor to the 3G and 2G families of standards. In 2009, the ITU-R organization specified the IMT-Advanced (International Mobile Telecommunications Advanced) requirements for 4G standards, setting 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).

A 4G system is expected to provide a comprehensive and secure all-IP based mobile broadband solution to laptop computer wireless modems, smartphones, and other mobile devices. Facilities such as ultra-broadband Internet access, IP telephony, gaming services, and streamed multimedia may be provided to users.

Pre-4G technologies such as mobile WiMAX and first-release Long term evolution (LTE) have been on the market since 2006 and 2009 respectively, and though often branded as 4G in marketing materials, the current versions of these technologies provide downstream peak bitrates of 144 Mbit/s and 100 Mbit/s respectively, and do consequently not fulfill the original ITU-R requirements of data rates approximately up to 1 Gbit/s for 4G systems.

IMT-Advanced compliant versions of the above two standards are under development and called “LTE Advanced” and “WirelessMAN-Advanced” respectively. ITU has decided that “LTE Advanced” and “WirelessMAN-Advanced” should be accorded the official designation of IMT-Advanced. On December 6, 2010, ITU announced that current versions of LTE, WiMax and other evolved 3G technologies that do not fulfill "IMT-Advanced" requirements could be considered "4G", provided they represent forerunners to IMT-Advanced and "a substantial level of improvement in performance and capabilities with respect to the initial third generation systems now deployed."

In all suggestions for 4G, the CDMA spread spectrum radio technology used in 3G systems and IS-95 is abandoned and replaced by OFDMA and other frequency-domain equalization schemes.[citation needed] This is combined with MIMO (Multiple In Multiple Out), e.g., multiple antennas, dynamic channel allocation and channel-dependent scheduling.

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History of 4G and pre-4G technologies

• In 2002, the strategic vision for 4G—which ITU designated as IMT-Advanced—was laid out.
• In 2005, OFDMA transmission technology is chosen as candidate for the HSOPA downlink, later renamed 3GPP Long Term Evolution (LTE) air interface E-UTRA.
• In November 2005, KT demonstrated mobile WiMAX service in Busan, South Korea.
• In June 2006, KT started the world's first commercial mobile WiMAX service in Seoul, South Korea.
• In mid-2006, Sprint Nextel announced that it would invest about US$5 billion in a WiMAX technology buildout over the next few years ($5.45 billion in real terms). Since that time Sprint has faced many setbacks, that have resulted in steep quarterly losses. On May 7, 2008, Sprint, Imagine, Google, Intel, Comcast, Bright House, and Time Warner announced a pooling of an average of 120 MHz of spectrum; Sprint merged its Xohm WiMAX division with Clearwire to form a company which will take the name "Clear".
• In February 2007, the Japanese company NTT DoCoMo tested a 4G communication system prototype with 4x4 MIMO called VSF-OFCDM at 100 Mbit/s while moving, and 1 Gbit/s while stationary. NTT DoCoMo completed a trial in which they reached a maximum packet transmission rate of approximately 5 Gbit/s in the downlink with 12x12 MIMO using a 100 MHz frequency bandwidth while moving at 10 km/h, and is planning on releasing the first commercial network in 2010.
• In September 2007, NTT Docomo demonstrated e-UTRA data rates of 200 Mbit/s with power consumption below 100 mW during the test.
• In January 2008, a U.S. Federal Communications Commission (FCC) spectrum auction for the 700 MHz former analog TV frequencies began. As a result, the biggest share of the spectrum went to Verizon Wireless and the next biggest to AT&T. Both of these companies have stated their intention of supporting LTE.
• In January 2008, EU commissioner Viviane Reding suggested re-allocation of 500–800 MHz spectrum for wireless communication, including WiMAX.
• On 15 February 2008 - Skyworks Solutions released a front-end module for e-UTRAN.
• In 2008, ITU-R established the detailed performance requirements of IMT-Advanced, by issuing a Circular Letter calling for candidate Radio Access Technologies (RATs) for IMT-Advanced.
• In April 2008, just after receiving the circular letter, the 3GPP organized a workshop on IMT-Advanced where it was decided that LTE Advanced, an evolution of current LTE standard, will meet or even exceed IMT-Advanced requirements following the ITU-R agenda.
• In April 2008, LG and Nortel demonstrated e-UTRA data rates of 50 Mbit/s while travelling at 110 km/h.
• On 12 November 2008, HTC announced the first WiMAX-enabled mobile phone, the Max 4G
• In December 2008, San Miguel Corporation, Asia's largest food and beverage conglomerate, has signed a memorandum of understanding with Qatar Telecom QSC (Qtel) to build wireless broadband and mobile communications projects in the Philippines. The joint-venture formed wi-tribe Philippines, which offers 4G in the country. Around the same time Globe Telecom rolled out the first WiMAX service in the Philippines.

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4G features assumed in early literature

The 4G system was originally envisioned by the Defense Advanced Research Projects Agency (DARPA). The DARPA selected the distributed architecture, end-to-end Internet protocol (IP), and believed at an early stage in peer-to-peer networking in which every mobile device would be both a transceiver and a router for other devices in the network eliminating the spoke-and-hub weakness of 2G and 3G cellular systems. Since the 2.5G GPRS system, cellular systems have provided dual infrastructures: packet switched nodes for data services, and circuit switched nodes for voice calls. In 4G systems, the circuit-switched infrastructure is abandoned, and only a packet-switched network is provided, while 2.5G and 3G systems require both packet-switched and circuit-switched network nodes, i.e. two infrastructures in parallel. This means that in 4G, traditional voice calls are replaced by IP telephony.

Cellular systems such as 4G allow seamless mobility; thus a file transfer is not interrupted in case a terminal moves from one cell (one base station coverage area) to another, but handover is carried out. The terminal also keeps the same IP address while moving, meaning that a mobile server is reachable as long as it is within the coverage area of any server. In 4G systems this mobility is provided by the mobile IP protocol, part of IP version 6, while in earlier cellular generations it was only provided by physical layer and datalink layer protocols. In addition to seamless mobility, 4G provides flexible interoperability of the various kinds of existing wireless networks, such as satellite, cellular wirelss, WLAN, PAN and systems for accessing fixed wireless networks.

While maintaining seamless mobility, 4G will offer very high data rates with expectations of 100 Mbit/s wireless service. The increased bandwidth and higher data transmission rates will allow 4G users the ability to utilize high definition video and the video conferencing features of mobile devices attached to a 4G network. The 4G wireless system is expected to provide a comprehensive IP solution where multimedia applications and services can be delivered to the user on an 'Anytime, Anywhere' basis with a satisfactory high data rate, premium quality and high security.

4G is described as MAGIC: mobile multimedia, any-time anywhere, global mobility support, integrated wireless solution, and customized personal service. Some key features (primarily from users' points of view) of 4G mobile networks are:

• High usability: anytime, anywhere, and with any technology
• Support for multimedia services at low transmission cost
• Personalization
• Integrated services

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Approaches – 4G

Principal technologies

• Physical layer transmission techniques are as follows:
• MIMO: To attain ultra high spectral efficiency by means of spatial processing including multi-antenna and multi-user MIMO
• Frequency-domain-equalization, for example Multi-carrier modulation (OFDM) in the downlink or single-carrier frequency-domain-equalization (SC-FDE) in the uplink: To exploit the frequency selective channel property without complex equalization.
• Frequency-domain statistical multiplexing, for example (OFDMA) or (Single-carrier FDMA) (SC-FDMA, a.k.a. Linearly precoded OFDMA, LP-OFDMA) in the uplink: Variable bit rate by assigning different sub-channels to different users based on the channel conditions
• Turbo principle error-correcting codes: To minimize the required SNR at the reception side

1. Channel-dependent scheduling: To utilize the time-varying channel.
2. Link adaptation: Adaptive modulation and error-correcting codes
3. Relaying, including fixed relay networks (FRNs), and the cooperative relaying concept, known as multi-mode protocol

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Objective and Approach of 4G

Objectives assumed in the literature

4G is being developed to accommodate the quality of service (QoS) and rate requirements set by further development of existing 3G applications like mobile broadband access, Multimedia Messaging Service (MMS), video chat, mobile TV, but also new services like HDTV. 4G may allow roaming with wireless local area networks, and may interact with digital video broadcasting systems.

In the literature, the assumed or expected 4G requirements have changed during the years before IMT-Advanced was specified by the ITU-R. These are examples of objectives stated in various sources:

• A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R
• A data rate of at least 100 Mbit/s between any two points in the world
• Smooth handoff across heterogeneous networks
• Seamless connectivity and global roaming across multiple networks
• High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, etc.)
• Interoperability with existing wireless standards
• An all IP, packet switched network
• IP-based femtocells (home nodes connected to fixed Internet broadband infrastructure

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4G and near-4G systems

The wireless telecommunications industry as a whole has early assumed the term 4G as a short hand way to describe those advanced cellular technologies that, among other things, are based on or employ wide channel OFDMA and SC-FDE technologies, MIMO transmission and an all-IP based architecture. Mobile-WiMAX, first release LTE, IEEE 802.20 as well as Flash-OFDM meets these early assumptions, and have been considered as 4G candidate systems, but do not yet meet the more recent ITU-R IMT-Advanced requirements.

TE Advanced (Long-term-evolution Advanced) is a candidate for IMT-Advanced standard, formally submitted by the 3GPP organization to ITU-T in the fall 2009, and expected to be released in 2012. The target of 3GPP LTE Advanced is to reach and surpass the ITU requirements. LTE Advanced is essentially an enhancement to LTE. It is not a new technology but rather an improvement on the existing LTE network. This upgrade path makes it more cost effective for vendors to offer LTE and then upgrade to LTE Advanced which is similar to the upgrade from WCDMA to HSPA. LTE and LTE Advanced will also make use of additional spectrum and multiplexing to allow it to achieve higher data speeds. Coordinated Multi-point Transmission will also allow more system capacity to help handle the enhanced data speeds. Release 10 of LTE is expected to achieve the LTE Advanced speeds. Release 8 currently supports up to 300 Mbit/s download speeds which is still short of the IMT-Advanced standards.

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ITU Requirements and 4G wireless Standards

This article uses 4G to refer to IMT-Advanced (International Mobile Telecommunications Advanced), as defined by ITU-R. An IMT-Advanced cellular system must fulfill the following requirements:

• Based on an all-IP packet switched network.
• Peak data rates of up to approximately 100 Mbit/s for high mobility such as mobile access and up to approximately 1 Gbit/s for low mobility such as nomadic/local wireless access, according to the ITU requirements.
• Dynamically share and use the network resources to support more simultaneous users per cell.
• Scalable channel bandwidth 5–20 MHz, optionally up to 40 MHz.
• Peak link spectral efficiency of 15 bit/s/Hz in the downlink, and 6.75 bit/s/Hz in the uplink (meaning that 1 Gbit/s in the downlink should be possible over less than 67 MHz bandwidth).
• System spectral efficiency of up to 3 bit/s/Hz/cell in the downlink and 2.25 bit/s/Hz/cell for indoor usage.
• Smooth handovers across heterogeneous networks.
• Ability to offer high quality of service for next generation multimedia support.
• In September 2009, the technology proposals were submitted to the International Telecommunication Union (ITU) as 4G candidates. Basically all proposals are based on two technologies:
• LTE Advanced standardized by the 3GPP
• 802.16m standardized by the IEEE (i.e. WiMAX)

Present implementations of WiMAX and LTE are largely considered a stopgap solution that will offer a considerable boost while WiMAX 2 (based on the 802.16m spec) and LTE Advanced are finalized. Both technologies aim to reach the objectives traced by the ITU, but are still far from being implemented.

The first set of 3GPP requirements on LTE Advanced was approved in June 2008. LTE Advanced will be standardized in 2010 as part of the Release 10 of the 3GPP specification. LTE Advanced will be fully built on the existing LTE specification Release 10 and not be defined as a new specification series. A summary of the technologies that have been studied as the basis for LTE Advanced is included in a technical report.

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History – Mobile Technology

The nomenclature of the generations generally refers to a change in the fundamental nature of the service, non-backwards compatible transmission technology, and new frequency bands. New generations have appeared about every ten years since the first move from 1981 analog (1G) to digital (2G) transmission in 1992. This was followed, in 2001, by 3G multi-media support, spread spectrum transmission and at least 200 kbit/s, in 2011 expected to be followed by 4G, which refers to all-IP packet-switched networks, mobile ultra-broadband (gigabit speed) access and multi-carrier transmission.

The fastest 3G based standard in the WCDMA family is the HSPA+ standard, which was commercially available in 2009 and offers 28 Mbit/s downstreams without MIMO, i.e. only with one antenna (it would offer 56 Mbit/s with 2x2 MIMO), and 22 Mbit/s upstreams. The fastest 3G based standard in the CDMA2000 family is the EV-DO Rev. B, which was available in 2010 and offers 15.67 Mbit/s downstreams.

In mid 1990s, the ITU-R organization specified the IMT-2000 specifications for what standards that should be considered 3G systems. However, the cell phone market only brands some of the IMT-2000 standards as 3G (e.g. WCDMA and CDMA2000), but not all (3GPP EDGE, DECT and mobile-WiMAX all fulfil the IMT-2000 requirements and are formally accepted as 3G standards, but are typically not branded as 3G). In 2008, ITU-R specified the IMT-Advanced (International Mobile Telecommunications Advanced) requirements for 4G systems.

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