WiMAX Handover

The WiMAX architecture extends the 802.16 standard and that also includes the mech-
anisms for handovers. While the 802.16 standard provides support for handover between
base stations WiMAX offer protocols for handover higher up in the network structure.
The WiMAX architecture shall support mechanisms such as intra/inter ASN handover,
roaming between NSPs, seamless handover at vehicular speed and micro/macro mobility.
This section will study the architecture and its handover procedures more thoroughly
with the focus on intra/inter ASN handovers.

Access Service Network
Inside an ASN network entity there are at least one ASN Gateway (ASN GW) and a
base station. The BS handles the connection to the MS while the ASN GW takes care
of the contact with the CSN. An ASN GW can be associated with one or more BSs and
a BS can have relations to one or more ASN GWs. This segmentation
of the ASN enables multi vendor systems where different vendors can produce different
parts of the ASN and they still function together.
Depending on which role a BS or ASN GW take on in a handover they get different
names. The BS in charge of the MS before the handover
is called the serving BS and the ASN GW the serving BS forwards the data to is the
serving ASN GW. The BS and ASN GW associated with the MS after the handover are
the target BS and target ASN GW respectively. The term anchoring ASN GW is used
when an ASN GW relays MS data to the serving ASN GW.

Anchoring
The anchoring ASN GW is the network’s or CSN’s attachment to the MS. Incoming
data will be sent to the anchoring ASN GW and the CSN does not need to know at
which ASN GW the MS’s current BS is located. The forwarding of data to the serving
ASN GW is performed by the anchoring ASN GW. This makes the mobility of the MS
transparent to the CSN and the need to change IP-address becomes less frequent. In
the case where the serving ASN GW is receiving the data directly from the network the
serving ASN GW is also the anchor. The anchoring ASN GW does not need to be any
of the serving or target ASN GWs.

ASN Reference Points
To identify the different interfaces used to communicate within an ASN, with the MS and
the rest of the network a number of reference points are introduced [19], see figure 5.1
on the facing page. These reference points define the set of protocols and procedures
needed in the communication. Most of the reference points are logical mappings but
when, as in the case of R1, the functional entities are in different physical devices the
reference point refers to a physical interface.
R1 and R3 are the reference points used in communication with entities outside of
the ASN while R6 and R8 are used inside an ASN. The R4 interface is used both inside
and outside of the ASN since it is the logical link between ASN GWs regardless of
whether they are within the same ASN or in different ASNs. R1 is the physical interface
between the MS and the serving BS and R3 is the logical link between ASN GW and
CSN. The communication among BSs is handled through R8 while the BS-ASN GW
interaction goes via R6.

Inter ASN Handover
An inter ASN handover is a handover between BSs not part of the same ASN, see
figure 5.4 on the next page. During an inter ASN handover ASN GWs in separate ASNs
need to coordinate their actions to make the handover smooth to the MS. There are two
possible ways of dealing with the data flow during an inter ASN handover, anchoring
and re-anchoring. The purpose of anchoring is to avoid an path update and hence a
redirection of the data path, where in the re-anchoring case an update will be performed.
The decision to anchor or re-anchor the data path is made by the target or an-
chor ASN GW and there are three different decision procedures with two possible out-
comes 5.3.4. Either both parties can decide that a re-anchoring is not needed or one
of the ASN GW decides that it wants a re-anchoring. If the target ASN GW wants a
re-anchoring the anchor ASN GW will follow that decision and vice versa. It is always
the target ASN GW who will make its decision first. What this decision is based upon is
implementation dependent and not included in the scope of the WiMAX documen.

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WiMax over other technology

Over the last few years many types of broadband access technologies such as DSL (Digital subscriber loop) technology, HFC (Hybrid fiber coaxial) network, FBWAN (Fixed broadband wireless access network) have been implemented.
DSL is based on the wired technology, it is quite impossible to provide service to many locations such as rural areas, home users. Besides, an xDSL local loop provides services over long distance decreasing data rate that is a great problem for communication. Moreover, The DSL uses amplifiers, repeaters which are costly and risky and hard to maintain.
Some service providers are using WLL (Wireless Local Loop) for providing services in remote areas. WLL provides bandwidth from 35kbps to 70kbps for voice and data, which is inadequate for broadband services.
WiMAX has the following advantages over other technologies.
• Flexible Architecture: WiMax supports several system architectures, including Point- to-Point, Point-to-Multipoint, and ubiquitous coverage
• High Security: WiMax supports AES (Advanced Encryption Standard) and 3DES (Triple DES, where DES is the Data Encryption Standard). By encrypting the links between the BS and the SS, WiMax provides subscribers with privacy and security across the broadband wireless interface. Security also provides operators with strong protection against theft of service.
• Quick Deployment: Compared with the deployment of wired solutions, WiMax requires little or no external plant construction.
• Interoperability: WiMax makes it easier for end-users to transport and use their SS at different locations, or with different service providers. Interoperability protects the early Investment of an operator since it can select equipment from different equipment vendors.
• Portability: WiMax SS is powered up, it identifies itself, determines the characteristics of the link with the BS, as long as the SS is registered in the system database, and then negotiates its transmission characteristics accordingly.
• Mobility: The IEEE 802.16e amendment has added key features in support of mobility. Improvements have been made to the OFDM and OFDMA physical layers to support devices and services in a mobile environment. These improvements, which include Scaleable OFDMA, MIMO, and support for idle/sleep mode and hand-off, will allow full mobility at speeds up to 160 km/hr.
• Cost-effective: WiMax will drive costs down dramatically, and the resultant competitive pricing will provide considerable cost savings for service providers and end-users.
• Wider Coverage: WiMax dynamically supports multiple modulation levels, Including BPSK, QPSK, 16-QAM, and 64-QAM. WiMax systems are able to cover a large geographic area when the path between the BS and the SS is unobstructed.
• High Capacity: WiMax uses higher modulation (64-QAM) and channel bandwidth of currently 7 MHz. WiMax systems can provide significant bandwidth to end-users [27-29]

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WiMAX Applications

WiMAX attribute opens the technology to a wide variety of applications because of its high transmission rate and large range. It serves as a backbone for Wi-Fi for connectivity to the Internet. It can provide broadband connec-tivity over large coverage area as compared to 802.11 standard. WiMAX is a broadband wireless communication system, which enables convergence of mobile and fixed broadband networks through a common wide-area and
flexible network architecture. The mobile WiMAX air interfaces use OFDMA for improvement in multiple path interference in nonline-of-sight environ-ment. Its ability to support both line-of-sight and nonline-of-sight connections makes it suitable for ubiquitous services offered in rural and urban areas alike. High speed and symmetrical bandwidth satisfy the needs of individual customers, public administration, and enterprises of all sizes . The technology also provides fast and cheap broadband access to markets that lack infrastructure (fiber optics or copper wire), such as rural and unwired countries. Currently, several companies offer proprietary solutions for wireless broadband access, many of which are expensive because they use chipsets from adjacent technologies, such as 802.11. Early field experiments in various countries confirm that expectations in terms of coverage, performance, and usage scenarios are indeed justified. WiMAX has changed the scenario of wireless broadband from proprietary solutions to a standards-based industry. It supports fast Internet access, high-quality audio and video communications, education, entertainment, telemedicine, telemetering, and telesurveillance. WiMAX supports personal broadband services on both fixed and mobile settings because of its high spectral efficiency and wide channelization as well as the advanced antenna technologies. This flexibility in providing both fixed and mobile access within the same infrastructure is unprecedented among wireless technologies, which are typically optimized for either mobile or fixed access.

Figure 1: WiMAX Applications.

1 Cellular Application

The main merit of WiMAX is in the area of mobile service. For a large number
of cell phone operators the major monthly operating expense on T1 backhaul
that supports their base stations as shown in Figure 2. A WiMAX substitute
for the cell phone infrastructure could be operated with as little as 10% of T1
backhaul. While replacing a cell phone infrastructure with WiMAX one can
send a large amount of data because the bandwidth of WiMAX is far greater.
The data can include voice, mobile data, TV, videoconferencing, video on
demand, etc.

Figure 2: Cellular architecture using T1 as back haul.

2 WiMAX Military Applications

As WiMAX uses higher frequencies than current military and commercial communications, existing antenna towers share a WiMAX cell tower without compromising the current communication services. WiMAX can be used to support training and war game simulations. An initial deployment of WiMAX has already been constructed by the U.S. Army Fortdix. The U.S. army is testing prestandard WiMAX gear and Xacta secure wireless system from Telos Corporation in Fort Carson in Colorado for point-to-point and point-to-multipoint communications.

The forces at different locations can be connected through WiMAX as shown in Figure 3. They can exchange their information from multiple sources, rapidly and flexibly. This is ideally suited to meet the demands of the tactical defense operations model. The mobile antennas can be attached to a vehicle and the latest data can be provided to the soldiers. A communication from command centers can be made to the different centers, regardless of the distance, and directions can be delivered to the army people. The best part of WiMAX is the handover strategy. It uses “make-before-break’’ sequence rather than “break-before-make’’ sequence.

Figure 3: WiMAX architecture for Military Applications.

3 Medical Applications

In an emergency situation where patients require immediate medical support,
WiMAX can serve as the foundation of a mobile hospital. It can be a platform
for e-health. In e-health services a doctor can diagnose his patient at some

far location with the help of e-media. The doctor ’s computer equipped with the medical instruments can be connected to the patient’s computer through WiMAX.

A patient at location 2 can send his reports, for example, blood pressure, through his computer to the doctor ’s computer as shown in Figure 4. The doctor can diagnose the patient’s disease and give him necessary treatment. The connection between the doctor and the patient is through the Internet. The two computers are connected through WiMAX.

Figure 4: Medical Applications.

Also in some emergency situations, a video consultation with a doctor can be set up and the doctor can instruct the paramedic to mobilize the victim without inflicting further damage. With WiMAX, mobile hospital vans can communicate data and other instructions within a disaster zone. The information through WiMAX can be encrypted and made secure. So in diverse conditions WiMAX can provide to the patient valuable information recommended by doctors over large distances.

4 Security Systems

WiMAX offers a simple and convenient system for security on the borders and within the country to save the nation from some terrorist attacks.
A video camera can be mounted on WiMAX antenna or some separate pole, which can be controlled at the headquarters as shown in Figure 5. This camera will keep an eye over the different activities of the enemies thereby assisting in security planning. It can also be used to provide video surveillance of smuggling and illegal entries along the borders.

WiMAX is a medium for the security of not only army but also navy.
Through the use of WiMAX one can monitor the activities on the sea. A video
camera that is mounted on the antenna of a shipyard can monitor the nearby
activities and report to the headquarter as shown in Figure 5. So WiMAX
can effectively monitor shipyards, nuclear facilities, and key transport routes.

Figure 5: WiMAX architecture for security applications.

5 Disaster Applications

WiMAX can be used in recovery from disasters, such as earthquakes and floods, when the wired networks break down. It helps in connecting the disaster location to telephone services, hospitals, and other important services. In recent hurrican disasters, WiMAX networks were installed to help recovery missions. WiMAX can enable efficient communications with emergency operation centers regardless of the distance. Similarly, WiMAX is used as backup links for broken wired links.

6 Connectivity of Banking Networks

The banking system where security is the major concern can be connected
through the WiMAX networks. Owing to the broad coverage and large con-
nectivity, WiMAX can connect a large number of diversely located banks and

ATM locations. WiMAX networks provide not only
security but also a high degree of scalability. Through WiMAX, telephone
voice, financial transactions, email, Internet, intranet, surveillance, and close
circuit television (CCTV) type of data can be communicated easily.

7 Public Safety

Through WiMAX, public safety agencies can be connected with each other. During any mishap, such as accident, fire, etc., the control office can send its command to the police station, hospital, or fire brigade office. The corresponding agencies immediately can connect to the accidental location by using WiMAX-enabled vehicles.

The video images and data from the site of accidental location can be sent to corresponding agencies. These data can be examined by the experts of the emergency staff and accordingly prescription can be communicated. A video camera in the ambulance can send the latest images of the patient before the ambulance reaches the hospital so that the doctors can get ready for further action quickly. Through WiMAX, a fireman can download the data about the best route to a fire scene.

8 Campus Connectivity

Campus system requires high data capacity, a large coverage, and high
security. WiMAX can connect various blocks within the campus.
Through this connectivity voice, data, and video information can be sent to
various interconnecting blocks as shown in Figure 6. It is very difficult to
connect various blocks through cables because the lead time to deploy a wired
solution is much longer than the lead time to deploy a WiMAX solution.

Figure 6: WiMAX campus connectivity.

9 Educational Building Connectivity

WiMAX can connect boards, colleges, schools, and the main head offices as shown in Figure 7. Through this, telephone voice, data, email, Internet, question papers, intranet, video lectures, presentations, and students’ results can be communicated at a very high rate.

By video conferencing the students can interact with the teachers of another institution (i.e., engineering college, medical colleges, etc.) like as Figure 7. A camera at college 1 delivers real-time classroom instruction to college 2, allowing the colleges to simultaneously deliver instruction from a recognized subject matter expert to a large

Figure 7: WiMAX educational building connectivity.

number of students. Colleges and schools in rural areas can be connected through WiMAX with other institutions having better facilities through WiMAX so that remotely located students can also be benefitted.

Hence it can be concluded that this broadband wireless standard supports
both the computer and telecom industries worldwide, making this technology
highly cost effective. It helps enterprises, consumers, public services, and peo-
ple in urban and rural areas over a large range with high data throughput.

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WiMAX Forum

IEEE 802 standards provide only the technology. It is then needed to have other organisms for the certification of conformity and the verification of interoperability. In the case of IEEE 802.11 WLAN, the Wireless Fidelity Alliance (WiFi or Wi-Fi) Consortium had a major role in the success of the WiFi technology, as it is now known. Indeed, the fact that two WiFi certified IEEE 802.11 WLAN devices are guaranteed to work together paved the way for the huge spread of WiFi products.

The certification problem was even more important for WiMAX as many product manufacturers claimed they had verified the 802.16 standard. The WiMAX (Worldwide Interoperability for Microwave Access) Forum (http://www.wimaxforum.org) was created in June 2001 with the objective that the WiMAX Forum plays exactly the same role for IEEE 802.16 as WiFi for 802.11. The WiMAX Forum provides certification of conformity, compatibility and interoperability of IEEE 802.16 products. After a period of low-down, the WiMAX Forum was reactivated in April 2003. Some sources indicate this latter date as the date of the creation of the WiMAX Forum. Intel and Nokia, along with others, played a leading role in the creation of the Forum. Then Nokia became less active, claiming that it wished to concentrate on 3G. However, Nokia is again an active player of WiMAX.

WiMAX Forum members are system and semiconductors manufacturers, other equipment vendors, network operators, academics and other telecommunication actors. A complete list of the WiMAX Forum members can be found on the Forum Member Roster web page. A nonexhaustive list of WiMAX members is proposed in Table 1.

Table 1: Some WiMAX Forum members
Open table as spreadsheet

Manufacturers	Airspan, Alcatel, Alvarion, Broadcom, Cisco, Ericsson. Fujitsu, Huawei, Intel, LG, Lucent, Motorola, Navini, Nokia, Nortel, NEC Proxim, Sagem, Samsung, Sequans, Siemens, ZTE, etc.
Service providers	British Telecom, France Telecom, KT (Korea Telecom), PCCW, Sprint Nextel, Telmex, etc.

The site of the WiMAX Forum indicates that its objective is to facilitate the deployment of broadband wireless networks based on the IEEE 802.16 standard by ensuring the compatibility and interoperability of broadband wireless equipment.

1 WiMAX Forum Working Groups

The WiMAX Forum is organised into Working Groups (WGs).The scope of these WGs is given in Table 2, as indicated on the WiMAX Forum website.

Table 2: WiMAX Forum working groups. As of July 2006, the Forum website also indicates the Global Roaming Working Group (GRWG)
Open table as spreadsheet

Working group name	Scope
Application Working Group (AWG)	Defines applications over WiMAX that are necessary to meet core competitive offerings and are uniquely enhanced by WiMAX
Certification Working Group (CWG)	Handles the operational aspects of the WiMAX Forum certification program; interfaces with the certification lab(s); selects new certification lab(s).
Marketing Working Group (MWG)	Promotes the WiMAX Forum, its brands and the standards that form the basis for worldwide interoperability of BWA systems
Network Working Group (NWG)	Creates higher-level networking specifications for fixed, nomadic, portable and mobile WiMAX systems, beyond what is defined in the scope of 802.16; specifically, the NWG defines the architecture of a WiMAX network
Regulatory Working Group (RWG)	Influences worldwide regulatory agencies to promote WiMAX-friendly, globally harmonised spectrum allocations
Service Provider Working Group (SPWG)	Gives service providers a platform for influencing BWA product and spectrum requirements to ensure that their individual market needs are fulfilled
Technical Working Group (TWG)	Develops conformance test specifications and certification services and profiles based on globally accepted practices to achieve worldwide interoperability of BWA systems

2 WiMAX Forum White Papers

The WiMAX Forum regularly publishes White Papers. These are a very useful information source about WiMAX, freely available on the Forum website. In Table 3, a nonexhaustive list of White Papers is proposed (until July 2006).

Table 3: WiMAX Forum (http://www.wimaxforum.org) White Papers, last update: July 2006. Table was drawn with the help of Ziad Noun
Open table as spreadsheet

Title	Date of latest version	Number of pages	Brief description
IEEE 802.16a standard and WiMAX -Igniting BWA	Date not mentioned	7	An overview of IEEE 802.16a standard, its PHY and MAC layers; talks also about the WiFi versus WiMAX scalability
Regulatory position and goals of the WiMAX Forum	August 2004	6	Describes the goals of WiMAX Forum (interoperability of broadband wireless products); describes also the initial frequency bands (license and license exempt)
Business case for fixed wireless access in emerging markets	June 2005	22	Describes the characteristics of emerging markets and discusses the service and revenue assumptions for business case analysis (urban, suburban, rural)
WiMAX deployment considerations for fixed wireless access in the 2.5 GHz and 3.5 GHz licensed bands	June 2005	21	About the licensed spectrum for WMAN, the radio characteristics, the range and the capacity of the system in different sccnarios (urban, suburban. etc.)
Business case models for fixed broadband wireless access based on WiMAX technology and the 802.16 standard	October 2004	24	Describes the WiMAX architecture and applications, the business case considerations and assumptions and the services oftered by WiMAX
Initial certification profiles and the European regulatory framework	September 2004	4	Describes the profiles currently identified for the initial certification process and the tentative profiles under consideration for the next round of the certification process
WiMAX's technology for LOS and NLOS environments.	August 2004	10	About the characteristics of OFDM and the other solutions used by WiMAX to solve the problems resulting from NLOS (subchannelisation, directional antennas, adaptive modulation, error correction techniques, power control, etc.)
Telephony's ‘Complete Guide to WiMAX’	May 2004	10	About WiMAX marketing and policy considerations
What WiMAX Forum certified products will bring to Wi-Fi	June 2004	10	Why WiFi is used in WiMAX, the OFDM basics, the 802.16/HiperMAN PHY and MAC layers, the operator requirements for BWA systems and the products certification
What WiMAX Forum certified products will bring to 802.16	June 2004	6	The certified products: where do WiMAX Forum certified products fit and why select them?
Fixed, nomadic, portable and mobile applications for 802.16-2004 and 802.16e WiMAX networks	November 2005	16	Compares the two possibilities of deployment for an operator: fixed WiMAX (802.16-2004) or mobile WiMAX (802.16e)
The WiMAX Forum certified program for fixed WiMAX	March 2006	15	Describes the general WiMAX certification process and specifically the fixed WiMAX system profiles certifications
Third WiMAX Forum plugfest - test methodology and key learnings	March 2006	18	Describes WiMAX March 2006 plugfest
Mobile WiMAX - Part I: a technical overview and performance evaluation	March 2006	53	Technical overview of 802.16e system (mobile WiMAX) and the corresponding WiMAX architecture
Mobile WiMAX - Part II: a comparative analysis	May 2006	47	Compares elements between mobile WiMAX and presently used 3G systems (1xEVDO and HSPA)
Mobile WiMAX: the best personal broadband experience!	June 2006	19	Provides mobile WiMAX advantages in the framework of mobile broadband access market
Executive summary: mobile WiMAX performance and comparative summary	July 2006	10	Brief overview of mobile WiMAX and summary of previous White Papcr performance data

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WiMAX Advantages

The IEEE 802.16 standard is designed for WMAN networks. It provides inter-
operable broadband wireless connectivity to fixed and nomadic users. It
provides up to 50 km of service area and allows the users to get broadband
connectivity without the need of direct line of sight to the base station. It pro-
vides a total data rate of up to 75 Mbps, which is enough to simultaneously
support a lot of business and home requirements. The advantages of WiMAX
are given as follows.

1. High Capacity
A single WiMAX main station can serve hundreds of users. It targets a range
of up to 31 miles with target transmission rate exceeding 100 Mbps. By using
higher modulation, bandwidth can further be increased. Through WiMAX
one can transfer data, voice, Internet, video images, pictures, video conferencing, etc., at a very high data rate. So WiMAX can provide sufficient bandwidth to the end users

2. Quality of Service
The MAC layer of the WiMAX architecture is responsible for Qos. Subchannelization and different coding schemes enable end-to-end QoS. High data rate and flexible scheduling can enhance the QoS.

3. Flexible Architecture
The architecture of WiMAX is highly flexible. Depending upon the require-
ment it can connect different stations on point-to-point or point-to-multipoint
basis. Further the range can be increased with the help of directional antennas.

4. Mobility
In WiMAX, the user device can maintain an operating network data service session for real-time application as it moves at vehicular speeds within the network coverage area. It supports optimized handover schemes with latencies less than 50 ms to ensure real-time application such as voice over Internet protocol (VoIP) without service degradation. Flexible key management assures that security is maintained during handover.

5. Improved User Connectivity
The IEEE 802.16 standard keeps more users connected by virtue of its flexible channel bandwidths and adaptive modulation. WiMAX uses channels narrower than the fixed 20 MHz channels used in Wi-Fi. It can serve lower data rate users without wasting bandwidth. Adaptive modulation helps to connect them in the noisy or low-signal strength conditions.

6 Robust Carrier Class Operation
As the number of users accessing the data increases, the aggregate bandwidth is shared because of which the individual throughput starts decreasing linearly. The decrease is lesser than what is experienced under Wi-Fi. So this standard is designed for carrier class operation.

7. Scalability
WiMAX system offers scalability in network architecture as well as in radio access technology. It provides a great deal of flexibility in network deployment options and service offerings. It is designed to work in different forms of channelization from 1.25 to 20 MHz to comply with varied worldwide requirements. It can also fulfill the needs such as providing affordable Internet access in rural areas versus enhancing the capacity of broadband access in metro and suburban areas only.

8. Nonline-of-Sight Connectivity
WiMAX is based on OFDM technology and can handle nonline-of-sight connectivity. This capability helps WiMAX to communicate in a nonline-of-sight environment, which other wireless products cannot. The nonline-of-sight coverage can further be increased by using directional antennas or adaptive modulation .

9. Cost Effectiveness
Mass adoption of the standard and the use of low-cost, mass-produced chipsets can reduce costs dramatically, and the resultant competitive pric-
ing will provide considerable cost saving for service providers and end users.
Further, base stations and base station equipments need not be installed in
totality at the outlet, but can be deployed over a period of time to address
specific market segments or geographical areas of Internet to the operator.

10. Fixed and Nomadic Access
WiMAX can provide both fixed and nomadic access to its users. In fixed
access, the user device is assumed to be fixed in a single geographical area
for the duration of the network subscription. Here the user can connect and
disconnect from the network. It can select the best base station while entering
the network. The user is associated only with the same base station sector or
cell, and any reassociation with other cell is controlled by the network.
In nomadic access, the user device is assumed to be fixed in a geographical
location at least as long as the network data service session is in operation
if the user shifts to a new location in the same wireless network. The user
subscription is recognized, and a new data service session is established. The
user device is associated with the same base station during a data service
session. So WiMAX complements third-generation mobile networks by pro-
viding “nomadic’’ broadband access. Vendors can now compete to sell their
equipment, which benefits the customer base by providing lower costs and
enabling broadband access in emerging markets.

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What do you mean by WiMAX Standard

WiMAX technology is specified by IEEE as IEEE 802.16 standard. The technology extends as IEEE 802.16 a, b, d, and e and they operate in different frequencies band and different data rate. TheIEEE802.16-2004 includes P2P, P2MP and mesh access networks while the IEEE 802.16e-2005 includes mobility. Table 1.1 shows WiMAX Standards.

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History of Mobile Cellular System

First Generation(1G)

The 1G period began in the late 1970s and lasted through the 1980s. These systems featured the first true mobile phone systems, known at first as "cellular mobile radio telephone." These networks used analog voice signaling, and were little more sophisticated than the repeater networks used by amateur radio operators.
Second Generation (2G)
The 2G phase began in the 1990s and much of this technology is still in use. The 2G cell phone features digital voice encoding. Examples include CDMA and GSM. Since its inception, 2G technology has steadily improved, with increased bandwidth, packet routing, and the introduction of multimedia.

Third Generation (3G)
3G refers to the third generation of developments in wireless technology, especially mobile communications. The third generation, as its name suggests, follows the first generation (1G) and second generation (2G) in wireless communications.
3G includes capabilities and features such as:
• Enhanced multimedia (voice, data, video, and remote control).
• Usability on all popular modes (cellular telephone, e-mail, paging, fax, videoconferencing, and Web browsing).
• Broad bandwidth and high speed (upwards of 2 Mbps).
• Roaming capability throughout Europe, Japan, and North America.

3G offers the potential to keep people connected at all times and in all places. Researchers, engineers, and marketers are faced with the challenge of accurately predicting how much technology consumers will actually be willing to pay for. Another challenge faced by 3G services is competition from other high-speed wireless technologies, especially mobile WiMAX, and ability to roam between different kinds of wireless networks.
The current status of mobile wireless communications, as of July 2007, is a mix of 2nd and 3rd generation technologies.

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WiMAX, How do WiMAX Works?

Worldwide interoperability for microwave access (WiMAX), based on the
Institution of Electrical & Electronics Engineering (IEEE) 802.16 standards,
enables wireless broadband access anywhere, anytime, and on virtually
any device. When users want broadband service today, they are generally
restricted to a T1, digital subscriber loop (DSL), or cable modem-based con-
nection. However, these wireline infrastructures can be considerably more
expensive and time-consuming to deploy than a wireless system. In addi-
tion, rural areas and developing countries lack optical fiber or copper wire
infrastructure for broadband services, and service providers are unwilling
to install the necessary equipments in these areas because of little profit and
potential. WiMAX is an ideal technology for backhaul applications because
it eliminates expansive leased line or fiber alternative. WiMAX promises to
deliver high data rates over large areas to a large number of users (Shows Fig w).
It can provide broadband access to locations in the world’s rural and developing areas
where broadband is currently unavailable.

Fig w: WiMAX network

WiMAX has numerous advantages, such as improved performance and
robustness, end-to-end internet protocol (IP)-based network, secure mobility,
and broadband speeds for voice, data, and video. It is a wireless metropolitan
area network (WMAN) technology that provides interoperable broadband
wireless connectivity to fixed, portable, and nomadic users within 50 km of
service area. It allows the users to get broadband connectivity without the
need of direct line-of-sight communication to the base station and provides
total data rates up to 75 Mbps with sufficient bandwidth to simultaneously
support hundreds of residential and business areas with a single base station.
In fact WiMAX is not a technology, but rather a configuration mark, or
“stamp of approval’’ given to equipments that meet certain conformity and
interoperability tests for the IEEE 802.16 family of standards. A similar con-
fusion surrounds the term Wi-Fi (wireless fidelity), which like WiMAX, is
a certification mark for equipments based on a different set of IEEE stan-
dard from the 802.11 working group for wireless local area network (WLAN).
Neither WiMAX nor Wi-Fi is a technology but their names have been adopted
in popular usage to denote the technologies behind them. This is due to the
difficulty of using terms like IEEE 802.11 in common speech and writing.
WiMAX is a term coined to describe standard, interoperable implementation
of IEEE 802.16 wireless networks in a way similar to Wi-Fi being interopera-
ble of the 802.11 WLAN standards. However, the working of WiMAX is very
different from Wi-Fi.

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