VIEW OF 4G MOBILE AND WIRELESS COMMUNICATION SYSTEMS

ABSTRACT

Due to the increase in demand for speed, multimedia support and other resources, the wireless world is looking forward for a new generation technology to replace the third generation. This is where the fourth generation wireless communication comes into play. 4G wireless communication is expected to provide better speed, high capacity, lower cost and IP based services. The main aim of 4G wireless is to replace the current core technology with a single universal technology based on IP. Yet there are several challenges that inhibit the progress of 4G and researchers throughout the world are contributing their ideas to solve these challenges. This project deals with understanding the features and challenges, the proposed architectural frameworks, multimedia support and multiple access schemes for 4G.

INTRODUCTION

Consumers demand more from their technology. Whether it is a television, cellular phone, or refrigerator, the latest technology purchase must have new features. With the advent of the Internet, the most-wanted feature is better, faster access to information. Cellular subscribers pay extra on top of their basic bills for such features as instant messaging, stock quotes, and even Internet access right on their phones. But that is far from the limit of features; manufacturers entice customers to buy new phones with photo and even video capability. It is no longer a quantum leap to envision a time when access to all necessary information the power of a personal computer , sits in the palm of one’s hand. To support such a powerful system, we need pervasive, high-speed wireless connectivity.
A number of technologies currently exist to provide users with high-speed digital wireless connectivity; Bluetooth and 802.11 are examples. These two standards provide very high speed network connections over short distances, typically in the tens of meters. Meanwhile, cellular providers seek to increase speed on their long-range wireless networks. The goal is the same: long-range, high-speed wireless, which for the purposes of this report will be called 4G, for fourth-generation wireless system. Such a system does not yet exist, nor will it exist in todayâ„¢s market without standardization. Fourth-generation wireless needs to be standardized throughout the world due to its enticing advantages to both users and providers.

VIEW OF 4G MOBILE AND WIRELESS COMMUNICATION SYSTEMS

4G Mobile and wireless communication systems should support following functions:

1. Higher transmission rate up to 100Mbps

2. Flexible to advanced Internet, QoS control

3. Enhanced security

4. Seamless operation across networks

5. Multiple broadband access options in combined public and private networks including wirelessLAN, wireless home link and ad-hoc network.

1G and 2G systems were voice communications, and digitized voice communications with some data communications, respectively, where a major difference was roaming between regions. 3G systems provide multimedia and wireless Internet at relatively high data rates, by utilizing packet switched services. However, significant paradigm shift should be taken into account for 4G systems, since wireless LAN, wireless MAN (WiMAX), wireless ad-hoc and sensor networks are becoming popular.

GOAL

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 (Internet Protocol) IP for video, packet data utilizing 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 (Internet Protocol).

The 4G providers of advanced cellular technology in FEC (Forward Error Correction) are adopting Concatenated Coding which has the capability of multiple QoS (Quality of Service) levels.  FEC coding adds redundancy to a transmitted coded signal through encoding prior to transmission.

The primary goal of the planned 4G cellular services will include the following:

•           Interactive Multimedia, Voice, Video Streaming

•           High Speed Global Internet Access – VPN Availability

•           Service Portability with Scalable Mobile Services

•           High Speed, High Capacity, Low Cost Services

•           Improved Information Security

•           QoS Enhancements

•           Multi-Hop Networking

•           Spectral Bandwidth Efficiencies (8bits/Second/Hz)

•           Seamless Network of Multiple Protocols - 4G must be all-IP*

NETWORKS AND SERVICES

The aim of 3G is ‘to provide multimedia multirate mobile communications anytime and anywhere’, though this aim can only be partially met. It will be uneconomic to meet this requirement with cellular mobile radio only. 4G will extend the scenario to an all-IP network (access + core) that integrates broadcast, cellular, cordless, WLAN (wireless local area network), short-range systems and fixed wire. The vision is of integration across these network—air interfaces and of a variety of radio environments on a common, flexible and expandable platform — a ‘network of networks’ with distinctive radio access connected to a seamless IP-based core network a (Fig. 3).

A vertical view of this 4G vision (Fig. 4) shows the layered structure of hierarchical cells that facilitates optimization for different applications and in different radio environments. In this depiction we need to provide global roaming across all layers.

Both vertical and horizontal handover between different access schemes will be available to provide seamless service and quality of service.

WIRELESS ACCESS

The radio part of the 4G system will be driven by the different radio environments, the spectrum constraints and the requirement to operate at varying and much higher bit rates and in a packet mode. Thus the drivers are:

·               Adaptive reconfigurability—algorithms

·               Spectral efficiency—air interface design and allocation of bandwidth

·               Environment coverage—all pervasive

·               Software—for the radio and the network access

·               Technology—embedded/wearable/low-power/high communication time/displays.

It has been decided within Mobile VCE not to become involved in technology issues or in the design of terminals. This is a large area, which is much closer to products and better suited to industry. The remaining drivers are all considered within the research programme.

It is possible, in principle, to increase significantly the effective bit rate capacity of a given bandwidth by using adaptive signal processing at both the base station and the mobile.

Arguably the most significant driver in the wireless access is the bandwidth availability and usage and whereabouts in the spectrum it will fall. Currently 3G technologies are based around bands at 2GHz, but limited spectrum is available, even with the addition of the expansion bands. The higher bit rates envisaged for 4G networks will require more bandwidth. Where is this to be found? The scope for a world-wide bandwidth allocation is severely constrained and, even if this were feasible, the bandwidth would be very limited. For CDMA, systems could use multicodes and adaptive interference cancellation, which again raise complexity issues. Alternatively one could move to OFDM-like systems (as in WLANs), which offer some reduction in complexity by operating in the frequency domain but raise other issues, such as synchronization. The choice of the air interface’s multiple access scheme and adaptive components will need to be based upon the ease of adaptation and reconfigurability and on the complexity.

A great deal of work on the characterization of radio environments has already been performed in the 2GHz and 5GHz bands within the first phase of Mobile VCE’s research, and spatial—temporal channel models have been produced. However, 4G systems will incorporate smart antennas at both ends of the radio link with the aim of using antenna diversity in the tasks of canceling out interference and assisting in signal extraction.

Coverage is likely to remain a problem throughout the lifetime of 3G systems. The network-of-networks structure of 4G systems, together with the addition of multimedia, multirate services, mean that coverage will continue to present challenges. We have already seen that the likely structure will be based upon a hierarchical arrangement of macro-, micro- and picocells. Superimposed on this will be the mega cell, which will provide the integration of broadcast services in a wider sense.

HAPS are not an alternative to satellite communications; rather they are a complementary element to terrestrial network architectures, mainly providing overlaid macro-/microcells for under laid picocells supported through ground-based terrestrial mobile systems. These platforms can be made quasi- stationary at an altitude around 21—25 km in the stratospheric layer and project hundreds of cells over metropolitan areas (Fig. 7).

Due to the large coverage provided by each platform, they are highly suitable for providing local broadcasting services. A communication payload supporting 3G/4G and terrestrial DAB/DVD air interfaces and spectrum could also support broadband and very asymmetric services more efficiently than 3G/4G or DAB/DVD air- interfaces could individually. ITU-R has already recognized the use of HAPS as high base stations as an option for part of the terrestrial delivery of IMT-2000 in the bands 1885—1980 MHz, 2010—2025 MHz and 2110—2170 MHz in Regions 1 and 3, and 1885—1980 MHz and 2110—2160 MHz in Region 2 (Recommendation ITU-R M (IMT-HAPS)).

The aim is to research new techniques which themselves will form the building blocks of 4G.

MAIN CHALLENGES

To achieve the desired features listed above researches have to solve some of the main challenges that 4G is facing. The main challenges are described below

Multimode user terminals: In order to access different kinds of services and technologies, the user terminals should be able to configure themselves in different modes. This eliminates the need of multiple terminals. Adaptive techniques like smart antennas and software radio have been proposed for achieving terminal mobility.

Wireless system discovery and selection: The main idea behind this is the user terminal should be able to select the desired wireless system. The system could be LAN, GPS, GSM etc. One proposed solution for this is to use software radio approach where the terminal scans for the best available network and then it downloads the required software and configure themselves o access the particular network.

Terminal Mobility: This is one of the biggest issues the researchers are facing. Terminal mobility allows the user to roam across different geographical areas that uses different technologies. There are two important issues related to terminal mobility.

One is location management where the system has to locate the position of the mobile for providing service. Another important issue is hand off management.

In the traditional mobile systems only horizontal hand off has to be performed where as in 4G systems both horizontal and vertical hand off should be performed. As shown in figure 1, horizontal hand off is performed when a mobile movies from on cell to another and vertical handoff is performed when a mobile moves between two wireless systems. Some solutions for achieving vertical hand off have been discussed in section IV.

 Hand off mechanisms [2]

Personal mobility: Personal mobility deals with the mobility of the user rather than the user terminals. The idea behind this is, no matter where the user is located and what device he is using, he should be able to access his messages.

Security and privacy: The existing security measures for wireless systems are inadequate for 4G systems. The existing security systems are designed for specific services. This does not provide flexibility for the users and as flexibility is one of the main concerns for 4G, new security systems has to be introduced.

Fault tolerance: As we all know, fault tolerant systems are becoming more popular throughout the world. The existing wireless system structure has a tree like topology and hence if one of the components suffers damage the whole system goes down. This is not desirable in case of 4G. Hence one of the main issues is to design a fault tolerant system for 4G.

Billing System: 3G mostly follows a flat rate billing system based where the user is charged just by a single operator for his usage according to call duration, transferred data etc. But in 4G wireless systems, the user might switch between different service providers and may use different services. In this case, it is hard for both the users and service providers to deal with separate bills. Hence the operators have to design a billing architecture that provides a single bill to the user for all the services he has used. Moreover the bill should be fair to all kinds of users.

APPLICATIONS OF 4G

Virtual Presence: This means that 4G provides user services at all times, even if the user is off-site.

Virtual navigation: 4G provides users with virtual navigation through which a user can access a database of the streets, buildings etc of large cities. This requires high speed data transmission.

Tele-Medicine: 4G will support remote health monitoring of patients. A user need not go to the hospital and can get videoconference assistance for a doctor at anytime and anywhere.

Tele-geoprocessing applications: This is a combination of GIS (Geographical Information System) and GPS (Global Positioning System) in which a user can get the location by querying.

Crisis management: Natural disasters can cause break down in communication systems. In today’s world it might take days or weeks to restore the system. But in 4G it is expected to restore such crisis issues in a few hours.

Education: For people who are interested in life long education, 4G provides a good opportunity. People anywhere in the world can continue their education online in a cost effective manner.

FEATURES OF 4G WIRELESS SYSTEMS

·                     Adaptive Modulation and Coding

·                     Speed, capacity and cost per bit

·                     Global mobility

·                     Service portability

·                     Scalable mobile networks

·                     Seamless switching

·                     Quality of Service (QoS) requirements

·                     Scheduling and call admission control techniques

·                     Ad hoc networks and multi-hop networks

Some main desired Features of 4G:

High usability and global roaming: The end user terminals should be compatible with any technology, at anytime, anywhere in the world. The basic idea is that the user should be able to take his mobile to any place, for example, from a place that uses CDMA to another place that employs GSM.

Multimedia support: The user should be able to receive high data rate multimedia services. This demands higher bandwidth and higher data rate.

Personalization: This means that any type of person should be able to access the service. The service providers should be able to provide customized services to different type of users.

CONCLUSION

4G seems to be a very promising generation of wireless communication that will change the people’s life in the wireless world. There are many striking attractive features proposed for 4G which ensures a very high data rate, global roaming etc. Table 1 shows the features and comparison between the different generations. New ideas are being introduced by researchers throughout the world, but new ideas introduce new challenges. There are several issues yet to be

solved like incorporating the mobile world to the IP based core network, efficient billing system, and smooth hand off mechanisms etc. 4G is expected to be launched by 2010 and the world is looking forward for the most intelligent technology that would connect the entire globe.

Posted in: Seminar,VIEW OF 4G MOBILE AND WIRELESS COMMUNICATION SYSTEMS