STANDARDIZATION MOVES

Before elaborating on standardization, let us study some of the existing wireless standards which are summarized in table 1.

Table 1: The existing wireless standards 

1G	NMT, AMPS, Hicap, CDPD, Mobitex, DataTAC
2G	GSM, iDEN, D-AMPS, IS-95/cdmaOne. PDC, CSD, PHS, 2.5G - GPRS, HSCSD, WiDEN, 2.75G - CDMA2000, IxRTT/IS-2000, EDGE (EGPRS)
3G	W-CDMA, UMTS (3GSM). FOMA, lxEV-DO/IS-856, TD-SCDMA, GAN/UMA, 3.5G - HSDPA, 3.75G - HSUPA
4G	WiMax, WiBro

The two groups within the International Telecommunication Union (ITU) are specifically engaged to define the next generation of mobile wireless. These two groups are:

• Working Party 8F (WP8F) in section ITU-R.
• Special Study Group (SSG) "IMT 2000 and Beyond" in section ITU-T.

WP8F is focused on the overall radio-system aspects of 4G, such as radio interfaces, Radio-Access Networks (RANs) spectrum issues, service and traffic characteristics, and market estimations as shown in figure 7. The SSG "IMT - 2000 and Beyond" is primarily responsible for the network or wireless aspects of future wireless systems including wireless Internet, convergence of mobile and fixed networks, mobility management, internetworking and interoperability.

 

Figure 1: Structure of WP 8F

The main deliverable of WP8F is Recommendation ITU-R M 1645. This recommendation contains the overall goals for the future development of wireless communications. The list of the suggestions that are contained in the recommendation are:(i) the framework for 4G systems should fuse elements of current cellular systems with nomadic wireless-access systems and personal-area networks in a seamless layered architecture that is transparent to the user; (ii) data rates of 100 Mbps for mobile applications and 1 Gbps for nomadic applications should be achievable by the year 2010; (iii) Worldwide common spectrum and open, global standardization should be pursued.

Not only above, but the process of developing a standard is a long one, carried out by other several groups, which include Standards Development Organizations (SDOs),industry forums, and companies, such as OEMs, that have a stake in the end product. Some of the major SDOs are nonprofit regional or governmental bodies, such as ETSI (European Telecommunications Standards Institute) in Europe, CCSA (China Communications Standards Association) in China, and the TTA (Telecommunications Technology Association) in Korea. 3GPP and 3GPP2 are examples of industry SDOs (Service Data Objects) that develop and maintain standards for current 2G and 3G technologies. In April 2007, the ITU convened a global congress to set a course for the 4G standards development process. China has expressed interest to submit the standard in 2010. Presently it is doubtful that standard will emerge 2012. Nor are standards necessarily the final word on the subject. In the meantime, there is nothing to stop the various SDOs and wireless operators from deploying so-called 4G systems without waiting for the completion of the formal standards process.

The World Radio Communication Conference (WRC) in October/November 2007 at Switzerland discussed on the spectrum assignment for 4G. The road map of the ITU-R (International Telecommunication Union Radio communication Sector) targets the availability of 4G standard proposals for the year 2012. As soon as frequency bands for 4G are defined, 4G standardization activities are expected to start.

Various Technologies

Though several technologies available today play a role in achieving roadmap for 4G as it materializes; highlights few of them:

1. Orthogonal Frequency Division Multiplexing (OFDM) and OFD Multiple Access (OFDMA) transmits data by splitting radio signals that are broadcast simultaneously over different frequencies. OFDMA, used in mobile WiMax, also provides signals that are immune to interference and can support high data rates. It utilizes power more efficiently than 3G systems while using smaller amplifiers and antennas. This all translates to expected lower equipment costs for wireless carriers. In OFDM and related modulations technology, multiple coherent sub-carriers are modulated and codes are used to insure that encoded bits can be decoded even if some of the sub-carriers arrive at very low SNR. OFDM is more resistant to inter-symbol interference. OFDM could be used both as multiple access technology and modulation scheme in 4G, but has many challenges. The OFDM has many uses for 4G:
   1. Most efficient transmission technique for digital audio and video broadcasting system. Processing data at rates of 10 Mbps or higher results in a small computer inside the phone but requires higher power in the amplifier
   2. Provide robust, reliable broadband service to the most people at the greatest distance with the least amount of infrastructure,
   3. OFDM is easier to implement then CDMA by small companies, as CDMA networks need more experienced engineers.
2. Mobile WiMAX is an IEEE specification also known as 802.16e and designed to support as high as 12Mbps data-transmission speeds. It uses OFDMA and is the next-generation technology of choice for many Service provider.
3. Ultra Mobile Broadband (UMB), also known as CDMA2000 EV-DO, is an expected path to 4G for legacy CDMA network providers. It's an IP-based technology that is said to support 100Mbps through Gbps data-transmission speeds.
4. Multiple-input multiple-output (MIMO) wireless LAN technology supports two or more radio signals in a single radio channel, increasing bandwidth. MIMO does this by using multiplexing. MIMO is expected to support data rates as high as 15Mbps in 36MHz of spectrum.
5. Long Term Evolution (LTE) is a modulation technique designed for GSM/UMTS -based technology that uses OFDM and MIMO. It's being developed by the Third Generation Partnership Project (3GPP) and is said to support 45M to 144Mbps in test networks today.
6. Software Defined Radio (SDR), sometimes shortened to software radio (SR). refers to wireless communication in which the transmitter modulation is generated or defined by a computer, and the receiver uses a computer to recover the signal intelligence. To select the desired modulation type, the proper programs must be run by microcomputers that control the transmitter and receiver (Bedell, 2005). Moreover, SDR is one form of Open Wireless Architecture (OWA). Since 4G is the collection of wireless standards, the final form of the 4G device will constitute all standards. This can be realized using SDR technology. Software-Defined Radio (SDR) is a radio communication technology that is based on software defined wireless communication protocols instead of hardwired implementations: frequency band, air interface protocol and functionality can be upgraded with software download instead of a complete hardware replacement. An SDR is capable of being re-programmed or reconfigured to operate with different waveform & protocols through dynamic loading of new waveforms and protocols. These waveforms and protocols can contain a number of different parts, including modulation techniques, security and performance characteristics defined in software as part of the waveform itself. Public safety radios, as well as commercial wireless applications, can use SDR for flexibility, and field upgradeability of their products. The ultimate goal of SDR technology is to provide a single radio transceiver capable of playing the roles of cordless telephone, cell phone, wireless fax, wireless e-mail system, pager, wireless videoconferencing unit, wireless Web browser, Global Positioning System (GPS) unit, and other functions still in the realm of science fiction, operable from any location on the surface of the earth, and perhaps in space as well. It is now possible that the future commercial viability of 3G and 4G wireless networks will depend upon capacity enhancing algorithms such as smart antennas and multi-user detection, and that these are prime candidates for implementation by SDR.
7. All IP-based core networks: 4G will resemble a convergence of existing technologies rather than an entirely new standard. An all IP based 4G wireless network has many advantages as it will be compatible as well as independent of actual radio access technology. IP radio protocols can be designed a core-network that give complete flexibility in the access network type, like 802.11, WCDMA, Bluetooth, hyper LAN and new CDMA protocols. Considering the cost of the equipments for 4G, IP based wireless networks is one-fourth to one-tenth of the equipments for 2G and 3G wireless infrastructure. There will be reduction in the cost by using interoperability in equipment for service provider.
   An IP Wireless network would completely replace the old SS7 signaling system because access signal transmission consumes a large part of network bandwidth even when there is no signaling traffic. IP networks use less bandwidth expensive mechanisms to achieve reliability (Sharma, 2002).
8. Full adopted multi-layer protocol architecture: The four major factors in achieving the high degree of integration, flexibility and efficiency envisioned in 4G are seamless integration, a high performance physical layer, flexible and adaptive multiple access, and high service and application adaptation.
9. Mesh Network is a local area network (LAN) that employs one of two connection arrangements, full mesh topology or partial mesh topology. In the full mesh topology, each node (workstation or other device) is connected directly to each of the others (Govil, 2008). In the partial mesh topology, some nodes are connected to all the others, but some of the nodes are connected only to those other nodes with which they exchange the most data. But above definition mention no dependency on any time parameter -- nothing is necessarily dynamic in a mesh. However, in recent years, and in connection with wireless networks, the term "mesh" is often used as a synonym for "ad hoc" or "mobile" network. Obviously, combining the two characteristics of a mesh topology and ad hoc capabilities is a very attractive proposition.
   
   

 Figure 1: Roadmap to 4G communication system

The figure 2 shows a full mesh network with five nodes. Each node is shown as a sphere, and connections are shown as straight lines. The connections can be wired or wireless.

Figure 2: Mesh network

MIGRATION TO 4G

Due to success of the second generation (2G) mobile system, the third generation (3G) system was developed. 3G systems were designed to provide higher data rate services. A range of wireless systems including GPRS, IMT - 2000, Bluetooth, WLAN and Hyper-LAN have been developed, each with their own merits and short comings. No single system exists for integration of all these technologies; thus a 4G system that integrates existing and newly developed wireless systems is a more feasible option. 4G technology is still in the research & development stage and international standards do not exist. 3G technology has proper standards and many big companies have invested huge sums to acquire the needed spectrum space. The predicament is whether or not companies should bypass 3G and adopt 4G straight away. It is being argued that 3G and 4G technologies are not mutually exclusive but are complementary to each other (Sharma, 2002). Those countries that have made huge investments in 3G require a evolutionary path for migration to 4G, but developing countries which have not made investments for 3G need not follow the 3G-migration route, as they can easily by-pass 3G technology and adopt directly 4G networks. 4G networks are being designed to accommodate WLANs and PANs based on Bluetooth technologies. 3G has bandwidth limitations. 4G core networks are all IP networks which have been extended to radio access nodes, so the disadvantages of circuit switching are totally absent. These networks will be incorporating advanced IPv6; even the signaling will be done through IP. The setting up cost will be lower as they can be built on top of existing network and won't require operators to completely retool. Hence, 4G technology will be suitable to esp. those countries which have not yet adopted 3G.

Figure 1 gives an understanding of driving forces behind the adoption of 4G and impeding forces that forces the corporate house to use it commercially in future in adopting 4G Wireless networks.

 
Figure 1: Driving and impeding forces for adoption of 4G wireless network

Roadmap for Achieving 4G

Recently there have been major advances in wireless access technologies for planning roadmap to 4G. Among the new schemes of technology being proposed for 4G, 802.16e and 802.20 standards are OFDMA, Single Carrier FDMA, and MC-CDMA. The new technologies, while offering the efficiencies of the older technologies such as CDMA, also offer advantages in scalability. Current working assumptions for physical layer multiple access schemes is OFDMA for downlink and Single Carrier FDMA (SC-FDMA) for uplink.

One way to increase system capacity is to implement a Multiple-Input Multiple-Output (MIMO) antenna scheme. A wireless system with single antennas obeys Shannon's classical limit for capacity, which can be expressed as C = log₂(1+SNR). Ideal capacity therefore increases as the log of the signal-to-noise ratio. MIMO systems, on the other hand, are modeled to increase capacity linearly with respect to the number of transmit and receive pairs that are used.

Advantages of 4G

Though 4G has many benefits like high usability, anytime, anywhere through a range of technologies, increased data transfer speed, and improved quality of service etc., other indirect advantages in alignment with ideal world are:

1. Unregulated: Presently 4G is unregulated, it requires no license.
2. Wireless: It can by-pass low capacity wired connection from the street to the home.
3. Market: Due to cheap bandwidth the market for PCs, consumer electronics, microprocessors and software will rise.
4. Cheap: Simple and cheap technology.
5. Multi Media: Users will experience multi media service at any place, at any time, at any acceptable cost.
6. Reduce Network Load: Conversion of public and 4G networks will reduce network cost by allowing capacity to be shared among Carriers and private users.
7. Upgradability: 4G is cheap and allow carriers to upgrade inexpensively and the success will depend on better packaging than DSL and better pricing.
8. No Digging: As 4G will be completely wireless no ditch digging requirements.
9. Easy Buying: 4G is so cheap that much of the network infrastructure will be bought by the consumers with their visa cards, saving carriers' balance sheet.
10. Fast Data Exchange: New type input/output devices for fast data exchange (glasses, displaying 3D virtual world, collapsible screens, e-paper, and voice and handwriting recognition).
11. Easy Availability of Terminals: New type semiconductor industry will rise (by means of plastic based chip technology, electronic tools will be common, 4G terminals will be available to everyone).
12. Easy Access: Access to the fourth generation mobile systems will be low-priced (advertisements will be displayed on the screen of 4G terminals).
13. Good Number of Users: Amount of users will reach a high level.
14. Internet Access: Quality of Internet access by wire or wireless will be equal or almost the same (quality of content providing will be excellent using a mobile terminal).
15. Availability of Multimedia: Multimedia will be required to the trivial work (means a kind of extra information).
16. VPN (Virtual Private Network): Some economic, social or state groups could maintain own part-networks (virtual private networks will be used well at administration, personal data-managing - for example mobile ID- and voting a president).
17. More Opportunities: New business opportunities will arise due to high data rates. There will be a heavy competition between applications and service-providers for users.
18. 24-Hour Availability: It follows that the mobile networks should be stable and dependable, should be available for 24 hour per day.
19. Inter Connection: Easy interconnection of different system (e.g. GPS, Internet, other communication networks).

Potential Applications of 4G

Some key potential applications of 4G are:

1. Virtual Presence: 4G system gives mobile users a "virtual presence"; for example, always-on connections that keep people involved in business activities regardless of whether they are on-site or off.
2. Virtual Navigation: A remote database contains the graphical representation of streets, buildings, and physical characteristics of a large metropolis. Blocks of this database are transmitted in rapid sequence to a vehicle, where a rendering program permits the occupants to visualize the environment ahead .
3. Tele-medicine: 4G will support remote health monitoring of patients; for example, the paramedic assisting the victim of traffic accident in a remote location must access medical records and may need videoconference assistance from a surgeon for an emergency intervention. The paramedic may need to relay back to the hospital the victim's x-rays taken locally.
4. Tele-Geoprocessing Applications: The combination of Geographical Information Systems (GIS). Global Positioning Systems (GPS). and high-capacity wireless mobile systems will enable a new type of application referred to as tele-geoprocessing. Queries dependent on location information of several users, in addition to temporal aspects have many applications.
5. Crisis-Management Applications: Natural disasters can affect the entire communications infrastructure is in disarray. Restoring communications quickly is essential. With wideband wireless mobile communications Internet and video services, could be set up in hours instead of days or even weeks required for restoration of wireline communications.
6. Education: Educational opportunities available on the internet for individuals interested in life-long education high speeds are unavailable to client in remote areas because of the economic unfeasibility of providing wideband wireline internet access. 4G wireless communications provides a cost-effective alternative in these situations

4G Transition Components

Some of the 4G transition components in brief are:

• Multi-Antenna Systems: To foster the growing data rate needs of 4G, deploying multiple antennas at the transmitter and receiver.
• Software Defined Radio (SDR): SDR is one form of Open Wireless Architecture (OWA). Since 4G is the collection of wireless standards, the final form of the 4G device will constitute all standards. SDR Technology offers one possible realization.
• Smart antennas and beam forming: These offer a significantly improved solution to reduce interference levels and improve the system capacity. With this technology, each user's signal is transmitted and received by the base station only in the direction of that particular user. This drastically reduces the overall interference in the system.
• Adaptive Modulation and Coding Techniques: The modulation and coding techniques change according to the network resource, user requirement and physical channel conditions.
• Access Schemes: The scarce resource frequency and network infrastructure is accessed using the channel accessing schemes. The existing wireless standards use TDMA (Time Division Multiple Access). FDMA (Frequency Division Multiple Access). CDMA (Code Division Multiple Access) and combinations of these. Recently, new access schemes like OFDMA (Orthogonal Frequency-Division Multiple Access) and MC-CDMA (Multi Carrier CDMA System) gained more importance in 802.16e and 802.20 standards.
• IPv6: It is generally believed that 4th generation wireless networks would support great number of wireless devices that are addressable and routable. Therefore in the context of 4G, IPv6 is an important network layer technology and standard that can support great number of wireless enabled devices. In addition to increasing the number of IP addresses, IPv6 also removes the need for Network Address Translation (NAT)—atechnique used in 3G and other networks to make private IP addresses work with Internet applications. In the context of 4G, IPv6 also enables a number of applications with better multi-cast, security and route optimization capabilities. With the available address space and number of addressing bits in IPv6, many innovative coding schemes can be developed for 4G devices and applications that could aid deployment of 4G networks and services.
• Mesh Networks: A mesh network is reliable and offers redundancy. If one node can no longer operate, all the rest can still communicate with each other, directly or through one or more intermediate nodes. Mesh networks work well when the nodes are located at scattered points that do not lie near a common line 

4G Objective

Before studying the objectives of 4G, let us understand some of the characteristics of 4G, which are summarized here in table 1.

Table 1: Characteristics of 4G 

Achievable Data Rates	10 Mbps (wide coverage) to 1 Gbps (local area). These are design targets and represent cell overall throughput.
Networking	All-IP network (access and core networks). Plug & Access network architecture. An equal opportunity network of networks.
Ubiquitous	Mobile, seamless communications.
Cost Reduction	Cost per bit: 1/10-1/100 lower than 3G Infrastructure cost-1/10 lower than 3G.
Connected Abilities	Person to person communication Person to Machine communication/Machine to machine communication.

The objective of 4G is to cater the quality of service and rate requirements set by the forthcoming applications like wireless broadband access, Multimedia Messaging Service, video chat, mobile TV, High definition TV content, DVB and minimal service like voice and data at anytime and anywhere 4G is being developed, the 4G working groups have defined the following as the objectives of the 4G wireless communication standard.

• Spectrally efficient system (in bits/s/Hz and bit/s/Hz/site)
• High network capacity, 10 times higher than 3G
• Nominal data rate of 100 Mbps at high speeds and 1 Gbps at stationary conditions as defined by the ITU-R
• Data rate of at least 100 Mbps between any two points in the world
• Smooth handoff across heterogeneous network
• Seamless connectivity and global roaming across multiple networks i.e. seamless services with fixed NW (Net Work) and private
• High quality of service for next generation multimedia support (real time audio, high speed data, High-Definition Television (HDTV) video content, mobile TV, etc)
• Higher frequencies: Microwave: 3-10 GHz
• Interoperable with the existing wireless standards
• All IP system, packet switched network
• Next-generation Internet support: IPV6, QoS, MoIP (Mobile over IP)
• Lower system costs: 1/10 of IMT-2000

In summary, the 4G system should dynamically share and utilize the network resource to meet the minimal requirements of all the 4G enabled users. Figure 1 illustrates here a prospective view of physical layer of 4G.

Figure 1: Prospective physical layer of 4G

 

Key Parameters

The move to 4G is complicated by attempts to standardize on a single 3G protocol. Without a single standard on which to built, designers face significant additional challenges.

Table 2 compares some of the key parameters of 3G and 4G. Though 4G does not have any solid specification as of yet, it is clear that some standardization is in order.

Table 2: Comparison of key parameters of 3G and 4G 

Key Parameters	3G	4G
Frequency Band	1.8-2.5 GHz	2-8 Ghz
Bandwidth	5-20 MHz	5-20 MHz
Data Rate	Upto 2 Mbps	Upto 20 Mbps
Access	W-CDMA	MC-CDMA or OFDM (TDMA)
Forward Error Correction	Convolutional Rate	Concatenated coding scheme
Switching	Circuit/Packet	Packet
Mobile Top Speeds	200 km/h	200 km/h
Component Design	Optimized antenna design, multi-band adapters	Smarter Antennas, software multiband and wideband radios
IP	A number of air link protocols, including IP 5.0	All IP (IP6.0)

4G Network Requirement

From above it is clear that 4G is immensely complicated and hence there will be special requirement for future networks. Some of these tentative requirements are hereby summarized in table 3.

Table 3: Requirement for future networks (tentative) 

Media	Transmission speed	Delay	Connection Latency	Terminal capabilities
Speech/3D Audio	< 1 Mbps	< 50ms	< 1 sec	3D sound field control High efficiency loud speakers
Video/3D video	10 Mbps (2D video) - 30 Gbps (3D video)	< 50ms	< 1 sec	Real time hologram
Enhanced Reality	< 1 Mbps	≪ 50 ms Should be predictable	N/A	Eyeglass display 3D and multimodal UI
Five senses communications	< 1 Mbps	< 50ms	N/A	Five sense sensors
Tele-existence	< 10Mbps (Robotic I/F) < 1 Gbps (Virtual avatar) < 100 Mbps (Alter-ego existence)	< 10 ms < 30ms < 5 ms (Small and known jitter)	1 Sec	Alter-ego robot

Development of 4G

There are many phases of developing 4G mobile communication systems. Let us study here two phases, i.e. development period and maturity period, which are described in table 4.

Table 4: Stepwise development of 4G mobile communications 

4G Mobile Communications
	Phase 1 (2009-2010): Developmental Period	Phase 2 (2011): Maturity Period
Core cellular systems	3.5G 3.5G mobile-communications system enhancing IMT-2000 (HSDPA/1xEV-DV)	4G 4G Mobile-communications systems
Transmission speed	30 Mbps	50 Mbps-100 Mbps
Service level	High-level application service	Service with higher-level authentication and security
Main users	Advanced users	General users
Functions	Basic functions	Fully-fledged system
Seam-lessness with other systems	Flexible realization of seamlessness with other systems	Seamlessness with no awareness thereof
Social impact	Positioning with social functions	Positioning as a factor inducing changes in social structure.

The Goal of 4G

4G must be clearly more than 3G in terms of services, applications, and technology. As a comparison, 4G is not a combination of High Speed Uplink/Downlink Packet Access (HSUPA/HSDPA) or Wireless LAN (WLAN).

3G networks are inadequate to accommodate WLANs as access networks, which offer data rates of 11 Mbps. The goal of 4G will be to replace the entire core of cellular networks with a single worldwide cellular network completely standardized based on the IP for video, Voice over IP (VoIP) and multimedia services. The newly standardized networks would provide uniform video, voice, and data services to the cellular handset or handheld Internet appliance, based entirely on IP. As 4G standards are not defined so there is plenty of room for other applications to overlap into the 4G space.

The 4G providers of advanced cellular technology are adopting Concatenated Coding which has the capability of providing multiple Quality of Service (QoS) levels. forward error correction (FEC) coding adds redundancy to a transmitted coded signal through encoding prior to transmission. A major advantage of Concatenated Coding over the Convolution Coding method will be an improved network performance by the combining of two or more coding techniques, such as a Reed-Solomon and a Convolution Code into one Concatenated Code. The combination improves error correction combining with error detection. FEC using Concatenated Coding allows a wireless network to send much larger blocks of data while reducing bit-error rate, thereby increasing the overall through-put.

The primary goal of the planned 4G cellular services will include: Interactive Multimedia, Voice, Video Streaming, High Speed Global Internet Access. Virtual Private Network (VPN) Availability, Service Portability with Scalable Mobile Services, High Speed, High Capacity, Low Cost Services, Improved Information Security, QoS Enhancements, Multi-Hop Networking.

Table 1 compares here various Wireless Communication Technologies.

Table 1: Comparison of wireless communication technologies 

	1G	2G	2.5G	3G	4G
Transmission	Analog	Digital	Digital	Digital	Digital
Architecture		Circuit Switch	Packed-Switch	Circuit and Packet Switch	Packet Switch
Speeds		9.6 to 14.4 Kbits/s	64 to 144 Kbits/s	384 Kbits/s to 2 Mbits/s	100 Mbits/s to 1000 Mbits/s
Standards	AMPS	TDMA, CDMA, GSM	GPRS, EDGE, 1×RTT	WCDMA, CDMA-2000	Single unified standard
Service	Mobile telephony (voice)	Digital voice, short messaging	Higher capacity, packetized data	Integrated high quality audio, video and data	Dynamic information access, wearable devices
Multiplexing	FDMA	TDMA, CDMA	TDMA, CDMA	CDMA	CDMA
Core Network	PSTN	PSTN	PSTN and Packet network	Packet network	Internet
Handoff	Horizontal	Horizontal	Horizontal	Horizontal	Horizontal and Vertical