Chapter 2: Literature Review -

22 Pages·2010·0.59 MB·English

Chapter 2: Literature Review
2.1 Introduction
The main purpose of bandwidth utilization efficiency is to provide services so that users
can get higher data rates and wider coverage. However there is no single network that can
provide this kind of services [30]. 4G network is expected to integrate LAS-CDMA,
OFDM, MC-CDMA, UWB and Network-LMDS so that higher data rates and wider
coverage can be achieved [31]. In this integration, the users will be served by either one
of those networks. As a result, an important problem occurred in which in these
overlapping areas most of the network resources is not fully utilized since only one of
those networks serve the users.
The bandwidth utilization efficiency is so important for operators, because the
wireless communication cost and their profit are based on the network resources. Thus,
how to get the highest benefit from the available network resources is a key issue in the
wireless communication networks. In the research, we focus on the two bandwidth
integration of WLAN and CDMA2000 networks to efficiently utilize the two network
resources.
This chapter reviews the relevant literature to explain the existing researches. The
flow of the relevant literature is presented in the Figure 2-1 which focuses on the
evolution of wireless communication networks and bandwidth utilization efficiently for
4G. We have divided this chapter into eight sections. In the first section, we give a
general introduction. Section two discusses the developed evolution of wireless mobile
communication networks. Section three highlights the fourth generation wireless mobile
2-1
internet networks. WLAN protocol and frame will be presented in section four and the
PPPoE protocol in section five. In section six, we present the relevant literature on
bandwidth utilization. The related researches will then be presented in section seven
before we give the conclusions in section eight.

Figure 2-1: The Flow of the Literature
2.2 Evolution of Wireless Networks
The first generation (1G) wireless mobile communication system was an analog system
which was used for public voice service with the speed up to 2.4kbps [32]. The second
generation (2G) is based on digital technology and infrastructure network [33]. As
compared to the first generation, the second generation can support text messaging. The
success and the growth in demand for online information via the internet prompted the
2-2
development of cellular wireless system with improved data connectivity, which
ultimately lead to the third generation systems (3G) [34].
3G systems refer to the developing technology standards for the next generation of
mobile communications systems [35]. One of the main goals of the standardization
efforts of 3G is to create a universal infrastructure that is able to support existing and
future services. This requires that the infrastructure be designed so that it can evolve as
technology changes, without compromising the existing services on the existing networks.
Separation of access technology, transport technology, service technology and user
application from each other make this demanding requirement possible [36].
The goal of 3G wireless systems is to provide wireless data service with data rates of
144kbps to 384kbps in wide coverage areas, and 2Mbps in local coverage areas [37].
Possible applications included wireless web-based access, E-mail, as well as video
teleconferencing and multimedia services consisting of mixed voice and data streams.
Generally speaking, 3G means the third generation of wireless technology including
several features, which are enhanced roaming, broadband data services with video and
multimedia, superior voice quality, up to 2Mbps of always-on data services. Several
problems with current 3G are: the speed is still too slow for multimedia data, difficult to
roam globally and can not interoperate across networks. As a result, the 4th generation
(4G) wireless system has been proposed by academic researches and government projects.
The speeds of 4G can theoretically be promised up to 1Gbps. 4G is an evolution to move
beyond the limitations and problems of 3G [38].
2.3 The Forth Generation (4G) Wireless Networks
4G is a research item for next-generation wide-area cellular radio, which focuses on 4G
2-3
technologies, 4G networks and 4G systems [39]. 4G technologies shall include three
basic areas of connectivity which are personal area networking (such as Bluetooth), local
high-speed access points on the network such as wireless LAN technologies and cellular
connectivity. Under this umbrella, 4G can provide services for a wide range of mobile
devices that support global roaming and each device will be able to interact with
internet-based information.
At the moment, many countries have established projects for 4G systems
development [40, 41]. However, the organization that first started this project is the
Defense Advanced Research Projects Agency (DARPA), which is the same organization
that first developed the wired internet [42].

Figure 2-2: 4G Technologies [42]
Figure 2-2 shows that 4G technologies integrate with different current existing and
future wireless network technologies including fixed wireless broadband, wireless LAN,
2-4
3G-WCDMA and CDMA2000 to ensure that mobile node can have a freedom of
movement and seamless roaming from one technology to another. These will ensure that
mobile users can be supported by different technologies through a continuous and always
best connection as well.

Figure 2-3: 4G Networks [43]
Figure 2-3 shows that 4G networks can be supported by network connection like
Bluetooth, WiFi 802.11 family, WiMax 802.16 family, cellular and satellite networks [43
and 44]. Therefore, by integrating all of these networks, 4G can provide total coverage,
seamless roaming and best connected services. Each of these technologies will be briefly
explained in the following paragraph.
The Bluetooth is designed for personal area, which can cover theoretically 10 meters.
On a technical level, Bluetooth is an open specification for a cutting-edge technology that
enables short-range wireless connections between desktop and laptop computers and a
2-5
host of other peripheral devices- on a globally available frequency band (2.4GHz) for
worldwide compatibility.
802.11 802.11b 802.11a 802.11g
Raw Data Rate 6,9,12,1824,36,4 1,2,5.5,6,9,11,12,22,24,3
1,2 1,2,5.5,11
(Mbps) 8,54 3,36,54
Frequency(Hz) 2.4G 2.4G 5G 2.4G
Available
83.5MHz 83.5MHz 300MHz 83.5MHz
Spectrum
Modulation FHSS/DSSS/P
DSSS/CCK OFDM DSSS/OFDM
Encoding SK/PPM
Max MSDU 2304 2304 --- ---
Table 2-1: Comparison of IEEE 802.11 WLAN Standards [43]
The WiFi 802.11 family is designed for local area, which can cover up to 100 meters.
The IEEE 802.11 [45] has become wireless Ethernet networking technology standard,
and the products based on the standard have been made. To ensure interoperability
between these products, an organization named Wi-Fi was created. The original IEEE
802.11 standard and each of its supplemental standards are shown in Table 2-1, which
provides a basic overview of the current versions of the 802.11 technologies [46]. The
IEEE 802.11 family of WLANs has been widely utilized around the world.
The WiMax is designed for metropolitan area, which can cover few kilometers.
WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications
technology aimed at providing wireless data over long distances in a variety of ways,
from point-to-point links to full mobile cellular type access. It is based on the IEEE
802.16 standard, which is also called WirelessMAN. The name WiMAX was created by
the WiMAX Forum, which was formed in June 2001 to promote conformance and
interoperability of the standard [47]. The IEEE 802.16d stands for fixed WiMax which
cannot be handoffed from one base station to another, whereas the IEEE 802.16e stands
2-6
for mobile WiMax which can roam/handoff between different base stations.
The cellular networks are designed for wide area, which can cover any surface on
earth. It has experienced three generation in its life. 4G integrate three standards
(WCDMA, CDMA2000 and TD-SCDMA) of 3G into CDMA2000.
Figure 2-4 shows that the 4G system is an all IP-based wireless mobile network
system [48]. The features of 4G system may be summarized with one word—integration
[49]. The 4G systems are about seamlessly integrating terminals, networks, and
applications to satisfy increasing user demands. The issues related with the integration
will be presented as follows.
4G terminal interfaces are quite different from current existing interfaces [50]. The
current existing terminal interfaces are related with keyboard, display, and tablet such as
PC and mobile phone. 4G terminal interfaces however will be based on speech, touch,
vision, soft button, etc. In addition, the enhanced interfaces of 4G terminals will have
multiple user interfaces, adaptive techniques such as smart antennas, software radio, and
smart transceivers to further enhance interoperability through simultaneous support of
several radio interfaces in a single terminal. These enhanced new interfaces can support a
terminal to roam across different air interface standards and to connect with different
wireless access points, such as Bluetooth, WLAN and CDMA2000, by exchanging
configuration software. Therefore, 4G terminals can monitor and interact with the
physical world to report human or environmental factors, and it will be aware of location
and context.
The main function of 4G networks is as a platform, on which terminals and
applications can rapidly exchange information. Some new techniques have been
2-7
developed to achieve adaptability of 4G networks such as smart antennas, software radio,
and advanced base station. To make networks portable and adaptable, Ad hoc wireless
networks are deployed. It can dynamically share unlicensed radio spectrum. Network
reconfiguration is very important for seamless interconnection to mobile user. It can be
obtained by the reconfiguration of protocol stacks and programmability of network nodes.
Thus, when a channel condition change or a low or high data rate user appears, network
reconfiguration can adapt them dynamically. In addition, network resource is allocated
according to traffic load, channel condition, and service environment. Channel condition,
traffic load and service environment will be dynamically monitored and controlled via
techniques such as distributed control of network functionalities.

Figure 2-4: 4G Systems [50]
For applications, the most important thing is a user’s requirements, which can be
delivered in a way that the user preferred. Thus, adaptability will be one of the basic
requirements for mobile user applications, and because of the adaptability, the mobile
2-8
user can move in various locations and speeds. There are some techniques used for
adaptability such as adaptive multimedia and unified messaging [51 and 52]. These
techniques can ensure the request services can be received by the mobile user, and run on
the mobile node through a most suitable form. In this case, the most efficient channel can
be selected after the application negotiates with the network based on the mobile node
request, such as WLAN channel or CDMA2000 channel. In order to adapt the different
network requirements and the varying traffic conditions, the request services must be
tolerable. Therefore, services and applications can be smoothly delivered across
multiple domains of operators and service providers.
The core features of 4G are diversity and adaptability of targets, leading to seamless
integration in order to support the most efficient application by the user’s demands. Thus,
the final requirements of 4G should fulfill the situation that if a consumer can do his work
at home or in his office while wired to the internet, then he/she must be able to do it
wirelessly in a fully mobile environment.
2.4 WLAN Protocol and Frame Structure
2.4.1 WLAN Protocol Structure
WLAN protocol only covers the medium access (MAC) and physical (PHY) layers like
the other 802.x LAN standards. Figure 2-5 shows the basic reference of the protocol
model [53 and 54]. The physical layer is subdivided into a physical layer convergence
protocol (PLCP) and the physical medium dependent (PMD) sublayers. The basic tasks
of the MAC layer are medium access, fragmentation of user data, and encryption. The
PLCP sublayer provides a carrier sense signal, called clear channel assessment (CCA),
2-9
and provides a common PHY interface for the MAC that is independent of the
transmission technology. The PMD sublayer handles modulation and encoding/decoding
of signals. The function of data link layer is to fragment user data and encrypt them into
certain interfaces. In our research, the function of the proposed new protocol is to make a
choice of the two interfaces. The new protocol design is based on WLAN protocol frame
structure as in Figure 2-5.
Data Link Layer MAC SubLayer MAC Sublayer Management Entity
PLCP Sublayer Station Management Entity
Physical Layer PHY Sublayer Management Entity
PMD Sublayer

Figure 2-5: IEEE 802.11 Protocol Reference Modes [53]
2.4.2 WLAN Frame Structure
Figure 2-6 specifies the basic WLAN frame structure [53]. Each frame consists of the
following basic components:
(cid:1) A MAC header, which comprises frame control, duration, address, and sequence
control information;
(cid:1) A variable-length frame body, which contains information specific to the frame type;
(cid:1) A frame check sequence (FCS), which contains an IEEE 32-bit cyclic redundancy
code (CRC).
Octets: 2 2 6 6 6 2 6 0-2312 4
Frame Control Duration/ID Address 1 Address 2 Address 3 Sequence Control Address 4 Frame Body FCS
MAC Header
Figure 2-6: IEEE 802.11 Frame Structures [53]
The primary responsibility of the WLAN frame is to control medium access, but it
can also provide optional support for roaming, authentication, and power conservation.
The basic services provided by the frame are the mandatory asynchronous data service
2-10