“A Study of Next Generation Cellular Technology”
Overview of Cellular Network
A cellular network is a radio network made up of a number of radio cells (or just cells) each served by at least one fixed-location transceiver known as a cell site or base station. These cells cover different land areas to provide radio coverage over a wider area than the area of one cell, so that a variable number of portable transceivers can be used in any one cell and moved through more than one cell during transmission.
Cellular networks offer a number of advantages over alternative solutions:
- increased capacity
- reduced power usage
- larger coverage area
- reduced interference from other signals
1.2 General characteristics
With FDMA, the transmitting and receiving frequencies used in each cell are different than the frequencies used in each neighboring cell. In a simple taxi system, the taxi driver manually tuned to a frequency of a chosen cell to obtain a strong signal and to avoid interference from signals from other cells. The principle of CDMA is more complex, but achieves the same result; the distributed transceivers can select one cell and listen to it. Other available methods of multiplexing such as polarization division multiple access (PDMA) and time division multiple access (TDMA) cannot be used to separate signals from one cell to the next since the effects of both vary with position and this would make signal separation practically impossible. Time division multiple access, however, is used in combination with either FDMA or CDMA in a number of systems to give multiple channels within the coverage area of a single cell.
1.3 Mobile phone networks
The most common example of a cellular network is a mobile phone (cell phone) network. A mobile phone is a portable telephone which receives or makes calls through a cell site (base station), or transmitting tower. Radio waves are used to transfer signals to and from the cell phone. Large geographic areas (representing the coverage range of a service provider) may be split into smaller cells to avoid line-of-sight signal loss and the large number of active phones in an area. In cities, each cell site has a range of up to approximately ½ mile, while in rural areas, the range is approximately 5 miles. Many times in clear open areas, a user may receive signals from a cell site 25 miles away. All of the cell sites are connected to cellular telephone exchanges “switches”, which connect to a public telephone network or to another switch of the cellular company.
As the phone user moves from one cell area to another cell, the switch automatically commands the handset and a cell site with a stronger signal (reported by each handset) to switch to a new radio channel (frequency). When the handset responds through the new cell site, the exchange switches the connection to the new cell site.
With CDMA, multiple CDMA handsets share a specific radio channel. The signals are separated by using a pseudonoise code (PN code) specific to each phone. As the user moves from one cell to another, the handset sets up radio links with multiple cell sites (or sectors of the same site) simultaneously. This is known as “soft handoff” because, unlike with traditional cellular technology, there is no one defined point where the phone switches to the new cell.
Modern mobile phone networks use cells because radio frequencies are a limited, shared resource. Cell-sites and handsets change frequency under computer control and use low power transmitters so that a limited number of radio frequencies can be simultaneously used by many callers with less interference.
Since almost all mobile phones use cellular technology, including GSM, CDMA, and AMPS (analog), the term “cell phone” is used interchangeably with “mobile phone”. However, satellite phones are mobile phones that do not communicate directly with a ground-based cellular tower, but may do so indirectly by way of a satellite.
There are a number of different digital cellular technologies, including: Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), Code Division Multiple Access (CDMA), Evolution-Data Optimized (EV-DO), Enhanced Data Rates for GSM Evolution (EDGE), 3GSM, Digital Enhanced Cordless Telecommunications (DECT), Digital AMPS (IS-136/TDMA), and Integrated Digital Enhanced Network (iDEN).
1.4 Evolution Of Cellular Technology
0G Mobile Phone TECHNOLOGY
0G refers to pre-cellphone mobile telephony technology, such as radio telephones that some had in cars before the advent of cellphones.
One such technology is the Auto Radio Puhelin (ARP) launched in 1971 in Finland as the country’s first public commercial mobile phone network.
1G Mobile Phone TECHNOLOGY
1G (or 1-G) is short for first-generation wireless telephone technology, cellphones. These are the analog cellphone standards that were introduced in the 80’s and continued until being replaced by 2G digital cellphones.
One such standard is NMT (Nordic Mobile Telephone), used in Nordic countries, Eastern Europe and Russia. Another is AMPS (Advanced Mobile Phone System) used in the United States.
Anticedant to 1G technology is the mobile radio telephone, or 0G.
2G Mobile Phone TECHNOLOGY
2G (or 2-G) is short for second-generation wireless telephone technology. It cannot normally transfer data, such as email or software, other than the digital voice call itself, and other basic ancillary data such as time and date. Nevertheless, SMS messaging is also available as a form of data transmission for some standards.
2G services are frequently referred as Personal Communications Service or PCS in the US.
2G technologies can be divided into TDMA-based and CDMA-based standards depending on the type of multiplexing used. The main 2G standards are:
GSM (TDMA-based), originally from Europe but used worldwide
IDEN (TDMA-based), proprietary network used by Nextel in the United States and Telus Mobility in Canada
IS-136 aka D-AMPS, (TDMA-based, commonly referred as simply TDMA in the US), used in the Americas
IS-95 aka cdmaOne, (CDMA-based, commonly referred as simply CDMA in the US), used in the Americas and parts of Asia
PDC (TDMA-based), used exclusively in Japan
The GSM operates in the 850Mhz. and 1900Mhz. bands in the US, & 900Mhz. and 1.8Mhz. bands in the rest of the world.
2.5G services are already available in many countries and 3G will be widely available in many countries during 2004. Work on 4G has already started although its scope is not clear yet.
2.5G Mobile Phone TECHNOLOGY2.5G is a stepping stone between 2G and 3G cellular wireless technologies. The term “second and a half generation” is used to describe 2G-systems that have implemented a packet switched domain in addition to the circuit switched domain. It does not necessarily provide faster services because bundling of timeslots is used for circuit switched data services (HSCSD) as well.
2.5G provides some of the benefits of 3G (e.g. it is packet-switched) and can use some of the existing 2G infrastructure in GSM and CDMA networks. GPRS is a 2.5G technology used by GSM operators. Some protocols, such as EDGE for GSM and CDMA2000 1x-RTT for CDMA, can qualify as “3G” services (because they have a data rate of above 144 kbit/s), but are considered by most to be 2.5G services (or 2.75G which sounds even more sophisticated) because they are several times slower than “true” 3G services.
While the terms “2G” and “3G” are officially defined, “2.5G” is not. It was invented for marketing purposes only.
2G is the current generation of full digital mobile phone systems. It transmits primarily voice but is used for circuit-switched data service and SMS as well.
3G is now the third generation of mobile phone systems. They provide both a packet-switched and a circuit-switched domain from the beginning. It requires a new access network, different from that already available in 2G systems. Due to cost and complexity, rollout of 3G has been somewhat slower than anticipated.
2.5G, which stands for “second and a half generation,” is a cellular wireless technology developed in between its predecessor, 2G, and its successor, 3G.
“2.5G” is an informal term, invented solely for marketing purposes, unlike “2G” or “3G” which are officially defined standards based on those defined by the International Telecommunication (ITU). The term “2.5G” usually describes a 2G cellular system combined with General Packet Radio Services (GPRS), or other services not generally found in 2G or 1G networks.
GPRS is a service commonly associated with 2.5G technology. It has data transmission rates of 28 kbps or higher. GPRS came after the development of the Global System for Mobile (GSM) service, which is classified as 2G technology, and it was succeeded by the development of the Universal Mobile Telecommunication Service (UMTS), which is classified as 3G technology.
A 2.5G system may make use of 2G system infrastructure, but it implements a packet-switched network domain in addition to a circuit-switched domain. This does not necessarily give 2.5G an advantage over 2G in terms of network speed, because bundling of timeslots is also used for circuit-switched data services (HSCSD).
2.75G Mobile Phone TECHNOLOGY
A 2G mobile phone is a circuit switched digital mobile phone. A 3G mobile is a digital phone with rapid data according to one of the standards being a member of the IMT-2000 family of standards. After those terms were defined, slow packet switched data was added to 2G standards and called 2.5G. 2.75G is the term which has been decided on for systems which don’t meet the 3G requirements but are marketed as if they do (e.g. CDMA-2000 without multi-carrier) or which do, just, meet the requirements but aren’t strongly marketed as such. (e.g. EDGE systems).
The term 2.75G has not been officially defined anywhere, but as of 2004 is beginning to be used quite often in media reports.
2.75G is a pretty recent standard, allows for downloading faster. Since mobile devices have become both a TV and a ‘walkman’ or music player, people needed to be able to watch streaming video and download mp3 files faster – that’s precisely what EDGE allows for and that’s for the good news. The bad news is that if EDGE rocks at downloading, it’s protocol is asymmetrical hence making EDGE suck at uploading i.e. broadcasting videos of yours for instance. Still an interesting achievement thanks to which data packets can effectively reach 180kbytes/sec. EDGE is now widely being used.
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3G Mobile Phone TECHNOLOGY
A short perusal of the major tech blogs on the internet, like Mobile Magazine, will inevitably result in at least a small handful of entries drooling over 3G mobile phone technology, with everyone drooling over the latest 3G offering coming out of cell phone manufacturers in Korea, Japan, and the rest of the world. But what exactly does 3G mean?3G technologies are an answer to the International Telecommunications Union’s IMT-2000 specification.
In a nutshell, 3G simply refers to the third generation of cellular phone technology.
3G (or 3-G) is short for third-generation mobile telephone technology. The services associated with 3G provide the ability to transfer both voice data (a telephone call) and non-voice data (such as downloading information, exchanging email, and instant messaging.
By and large, most of the mobile phones on the market today are a part of the second generation, or “2G”. This includes such standards as GSM (Global System for Mobile Communications: like the services offered by T-Mobile), and iDEN (Integrated Digital Enhanced Network: as developed by Motorola and deployed by Sprint/Nextel).
Several handsets and networks are also capable of higher speed data than standard 2G technology. These are often referred to as part of the 2.5G or 2.75G. The most common 2.5G technology is GPRS, or General Packet Radio Service, which works in tandem with GSM networks. Further along the spectrum are such technologies as CDMA2000 1xRTT (1 times Radio Transmission Technology) and EDGE (Enhanced Data rates for GSM Evolution). Each successive generation has provided faster and faster data transfer rates, in order to keep up with high demand services like picture messaging, ringtone downloading, and mobile web.
So What’s the Big Deal with 3G?
3G Mobile Phone Technology is said to be a substantial leap forward in data transfer rates for cellular phones, and as people demand more and fuller content, mobile networks need to keep up and send the data faster than ever.
Video conferencing was said to be the “killer app” for 3G. As such, many 3G handsets feature not one, but two cameras. The “primary” camera is typically on the back of the phone and is a megapixel (or better) picture taker. Finding phones with 2-megapixel cameras or better is no longer out of the ordinary, with some units offering as high as 8 megapixels. The “secondary” camera, however, is usually next to the display and a simple VGA unit. This is meant to be used for video telephony. However, in areas where 3G is more prevalent, like urban regions of Japan, video telephony has not been as popular as previously predicted.
Mobile TV and Web
For more on mobile TV, check out the official Mobile TV article here on LoveToKnow Cell Phones. While mobile television is technically a separate issue from 3G mobile phone technology, the two are often discussed in the same breath. Oftentimes, users download short video clips and even streaming movies using 3G technology, especially where “conventional” mobile television — like T-DMB — is not available.
Ringtones, Music, and More
Where 3G has really begun to shine, even before it has reached widespread deployment in the United States and Canada, is its use in downloading mobile content. Cell Phone Ringtones are incredibly popular, with several services being offering allowing users to customize their mobile phones with unique ringtones, especially since so many handsets are capable of MP3 ringtones these days. Instead of a standard ring, imagine hearing your phone blast out the latest Lil Jon hit, or a classic Frank Sinatra song.
Musicphones, like the Walkman line from Sony Ericsson, are also growing in prevalence. In fact, some have said that by 2010, over-the-air mobile music services — that is, downloading music onto your cell phone directly on a purely wireless basis, rather than using your home computer as an intermediary — will have more users than online music stores (read: iTunes). 3G technology (and successive generations) have had, and will continue to have a lot to do with this trend.
There are three main 3G standards that have already been deployed in selected regions around the globe.
W-CDMA: Not to be confused with standard CDMA (which is the direct competitor for GSM), W-CDMA is “Wideband” Code Division Multiple Access, and is allied with 2G GSM.
Originally, 3G was supposed to be a single, unified, worldwide standard, but in practice, the 3G world has been split into three camps.
UMTS (Universal Mobile Telephone System), based on W-CDMA technology, is the solution generally preferred by countries that used GSM, centered in Europe. UMTS is managed by the 3GPP organization also responsible for GSM, GPRS and EDGE.
FOMA, launched by Japan’s NTT DoCoMo in 2001, is generally regarded as the world’s first commercial 3G service. However, while based on W-CDMA, it is not generally compatible with UMTS (although there are steps currently under way to remedy the situation).
The other significant 3G standard is CDMA2000, which is an outgrowth of the earlier 2G CDMA standard IS-95. CDMA2000’s primary proponents are outside the GSM zone in the Americas, Japan and Korea. CDMA2000 is managed by 3GPP2, which is separate and independent from UMTS’s 3GPP.
A less well known standard is TD-SCDMA which is being developed in the People’s Republic of China by the companies Datang and Siemens. They are predicting an operational system for 2005.
There are two main forms: UMTS stands for Universal Mobile Telecommunications System, and is sometimes referred to as 3GSM. UMTS is said to be capable of data transfer rates of up to 1920 kbit/sec.
FOMA stands for Freedom of Mobile Multimedia Access and is the brand name for 3G services offered through NTT DoCoMo of Japan. A pioneer in 3G, FOMA was officially launched way back in 2001. 1xEV-DO, initially designed by Qualcomm, is CDMA’s answer to W-CDMA, if that makes any sense. EV-DO stands for Evolution Data Optimized, and is a broadband data standard that has already been adopted by such wireless service providers as Telus Mobility of Canada and Verizon Wireless, the latter of which marketing its EV-DO services as “V CAST”. EV-DO’s data transfer rate is right in line with W-CDMA, offering approximately 2Mbit/sec downlinks.
TD-SCDMA is being developed by and for the People’s Republic of China. Standing for Time Division-Synchronous Code Division Multiple Access, TD-SCDMA was meant to provide the Chinese people with high speed data that wasn’t “dependent on Western technology“. TD-SCDMA testing is currently underway, with full deployment expected before the end of the year.
What the Future Holds
HSDPA: Even before 3G has been fully adopted, cellular phone technology companies have already started working on and testing the next sub-generation of wireless data. As part of the 3.5G, HSDPA (high-speed downlink packet access) is a new mobile telephony protocol, and it is said to be an extension of WCDMA in much the same way that CDMA2000 was improved upon to become EV-DO.
HSUPA: Whereas HSDPA allowed for “downlinks” (cell phones receiving data), HSUPA allows for “uplinks” (cell phones sending data). In this way, it naturally accompanies HSDPA, and is said to be 3.75G.
List of countries that have deployed 3G:
Argentina (CDMA2000 1x) Australia (W-CDMA) (CDMA2000 1x)
Austria (W-CDMA) Azerbaijan (CDMA2000 1x)
Belarus (CDMA2000 1x) Bermuda (CDMA2000 1x)
Brazil (CDMA2000 1x) Canada (CDMA2000 1x)
Chile (CDMA2000 1x) China (CDMA2000 1x)
Colombia (CDMA2000 1x) Cyprus (W-CDMA)
Denmark (W-CDMA) Dominican Republic (CDMA2000 1x)
Ecuador (CDMA2000 1x) Finland (W-CDMA)
Georgia (CDMA2000 1x) Germany (W-CDMA)
Greece (W-CDMA) Guatemala (CDMA2000 1x)
Hong Kong (W-CDMA) India (CDMA2000 1x)
Indonesia (CDMA2000 1x) Israel (W-CDMA)
Italy (W-CDMA) Jamaica (CDMA2000 1x)
Japan (W-CDMA, CDMA2000 1x) Kazakhstan (CDMA2000 1x)
Kyrgyzstan (CDMA2000 1x) Mexico (CDMA2000 1x)
Moldova (CDMA2000 1x) Netherlands (W-CDMA)
New Zealand (CDMA2000 1x) Nicaragua (CDMA2000 1x)
Nigeria (CDMA2000 1x) Norway (W-CDMA)
Pakistan (CDMA2000 1x) Panama (CDMA2000 1x)
Peru (CDMA2000 1x) Poland (CDMA2000 1x)
Portugal (W-CDMA) Romania (CDMA2000 1x)
Russia (CDMA2000 1x) Singapore (W-CDMA)
Slovenia (W-CDMA) South Korea (CDMA2000 1x)
South Africa (W-CDMA in testing) Spain (W-CDMA),
Sweden (W-CDMA) Taiwan (CDMA2000 1x)
Thailand (CDMA2000 1x) United Arab Emirates (W-CDMA)
United Kingdom (W-CDMA), US (CDMA2000 1x) (W-CDMA in testing)
Uzbekistan (CDMA2000 1x) Venezuela (CDMA2000 1x)
Vietnam (CDMA2000 1x)
3.5G Mobile Phone TECHNOLOGY
High-Speed Downlink Packet Access or HSDPA is a mobile telephony protocol which is theoretically 6 times faster than UMTS (up to 3.6 Mbytes/sec)!. Also called 3.5G (or “3½G”) High Speed Downlink Packet Access (HSDPA) is a packet-based data service in W-CDMA downlink with data transmission up to 8-10 Mbit/s (and 20 Mbit/s for MIMO systems) over a 5MHz bandwidth in WCDMA downlink. HSDPA implementations includes Adaptive Modulation and Coding (AMC), Multiple-Input Multiple-Output (MIMO), Hybrid Automatic Request (HARQ), fast cell search, and advanced receiver design.
HSDPA is beginning to reach deployment status in North America. Cingular has announced that they will begin to deploy UMTS with expansion to HSDPA in 2005.
In 3rd generation partnership project (3GPP) standards, Release 4 specifications provide efficient IP support enabling provision of services through an all-IP core network and Release 5 specifications focus on HSDPA to provide data rates up to approximately 10 Mbit/s to support packet-based multimedia services. MIMO systems are the work item in Release 6 specifications, which will support even higher data transmission rates up to 20 Mbit/s. HSDPA is evolved from and backward compatible with Release 99 WCDMA systems.
4G Mobile Phone TECHNOLOGY
4G (also known as Beyond 3G), an abbreviation for Fourth-Generation, is a term used to describe the next complete evolution in wireless communications. A 4G system will be a complete replacement for current networks and be able to provide a comprehensive and secure IP solution where voice, data, and streamed multimedia can be given to users on an “Anytime, Anywhere” basis, and at much higher data rates than previous generations
4G (or 4-G) is short for fourth-generation the successor of 3G and is a wireless access technology. It describes two different but overlapping ideas.
High-speed mobile wireless access with a very high data transmission speed, of the same order of magnitude as a local area network connection (10 Mbits/s and up). It has been used to describe wireless LAN technologies like Wi-Fi, as well as other potential successors of the current 3G mobile telephone standards.
4G is being developed to accommodate the quality of service (QoS) and rate requirements set by forthcoming applications like wireless broadband access, Multimedia Messaging Service (MMS), video chat, mobile TV, HDTV content, Digital Video Broadcasting (DVB), minimal service like voice and data, and other streaming services for “anytime-anywhere”. The 4G working group has defined the following as objectives of the 4G wireless communication standard:
- A spectrally efficient system (in bits/s/Hz and bits/s/Hz/site),<href=”#cite_note-spectral_efficient-1 title=””>
- High network capacity: more simultaneous users per cell,<href=”#cite_note-4gfeatures-2 title=””>
- A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R,<href=”#cite_note-4groadmap-0 title=””>
- A data rate of at least 100 Mbit/s between any two points in the world,<href=”#cite_note-4groadmap-0 title=””>
- Smooth handoff across heterogeneous networks,<href=”#cite_note-mobilitymanagement-3 title=””>
- Seamless connectivity and global roaming across multiple networks,<href=”#cite_note-beyond3garticle-4 title=””>
- High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, etc)<href=”#cite_note-beyond3garticle-4 title=””>
- Interoperability with existing wireless standards,<href=”#cite_note-pathto4g-5 title=””> and
- An all IP, packet switched network.<href=”#cite_note-beyond3garticle-4 title=””>
In summary, the 4G system should dynamically share and utilize network resources to meet the minimal requirements of all the 4G enabled users.
1.5 Key Technology of Each Generations
We briefly listed all the key technologies and protocols used in each generation of the mobile wireless communications in th following table:
|0G||0G refers to pre-cellular mobile telephony technology in 1970s. These mobile telephones were usually mounted in cars or trucks, though briefcase models were also made.|
|PTT||Push to talk|
|MTS||Mobile Telephone System|
|IMTS||Improved Mobile Telephone Service|
|AMTS||Advanced Mobile Telephone System|
|0.5G||0.5G is a group of technologies with improved feature than the basic 0G technologies.|
|Autotel/PALM||Autotel, or PALM (Public Automated Land Mobile)|
|ARP||Autoradiopuhelin, Car Radio Phone|
|HCMTS||High Capacity Mobile Telephone System|
|1G||1G (or 1-G) is the first-generation wireless telephone technology, cellphones. These are the analog cellphone standards that were introduced in the 1980s.|
|NMT||Nordic Mobile Telephone|
|AMPS||Advanced Mobile Phone System|
|TAGS||Total Access Communication System (TACS) is the European version of AMPS.|
|JTAGS||Japan Total Access Communication System|
|2G||2G (or 2-G) is the second-generation wireless telephone, which is based on digital technologies. 2G networks is basically for voice communications only, except SMS messaging is also available as a form of data transmission for some standards.|
|GSM||Global System for Mobile Communications|
|iDEN||Integrated Digital Enhanced Network|
|D-AMPS||Digital Advanced Mobile Phone System based on TDMA|
|cdmaOne||Code Division Multiple Access technology defined by IS-95|
|PDC||Personal Digital Cellular|
|TDMA||Time Division Multiple Access|
|2.5G||2.5G is a group of bridging technologies between 2G and 3G wireless communication. It is a digital communication allowing e-mail and simple Web browsing, in addition to voice.|
|GPRS||General Packet Radio Service|
|WiDEN||Wideband Integrated Dispatch Enhanced Network|
|2.75G||2.75G refer to the technologies which don’t meet the 3G requirements but are marketed as if they do.|
|CDMA2000 1xRTT||CDMA-2000 is a TIA standard (IS-2000) that is an evolutionary outgrowth of cdmaOne. CDMA2000 with 1xRTT is slight weaker than 3G requirements.|
|EDGE||Enhanced Data rates for GSM Evolution|
|3G||3G stand for the third generation of wireless communication technologies, which support broadband voice, data and multi-media communications over wireless networks.|
|W-CDMA||Wideband Code Division Multiple Access|
|UMTS||Universal Mobile Telecommunications System|
|FOMA||Freedom of Mobile Multimedia Access|
|CDMA2000 1xEV||More advanced CDMA2000 with 1xEV technology satisfy 3G requirements.|
|TD-SCDMA||Time Division Synchronous Code Division Multiple Access|
|3.5G||The 3.5G generally refer to the technologies beyond the well defined 3G wireless/mobile technologies.|
|HSDPA||High-Speed Downlink Packet Access|
|3.75G||The 3.75G refer to the technologies beyond the well defined 3G wireless/mobile technologies.|
|HSUPA||High-Speed Uplink Packet Access|
|4G||4G is the name of technologies for high-speed mobile wireless communications designed for new data services and interactive TV through mobile network.|
2.1 Overview of WiMAX
WiMAX, meaning Worldwide Interoperability for Microwave Access, is a telecommunications technology that provides wireless transmission of data using a variety of transmission modes, from point-to-multipoint links to portable and fully mobile internet access. The technology provides up to 3 Mbit/s broadband speed without the need for cables. The technology is based on the IEEE 802.16 standard (also called Broadband Wireless Access). The name “WiMAX” was created by the <href=”#wimax_forum title=””>WiMAX Forum, which was formed in June 2001 to promote conformity and interoperability of the standard. The forum describes WiMAX as “a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL”.
WiMAX base station equipment with a A pre-WiMAX CPE of a 26 km
ground (2004, Lithuania).
2.2 Wireless Introduction
Before we begin a real thoery of WiMax, let’s spend few minutes to understand background concepts on which WiMax has evolved.
Wireless means transmitting signals using radio waves as the medium instead of wires. Wireless technologies are used for tasks as simple as switching off the television or as complex as supplying the sales force with information from an automated enterprise application while in the field. Now cordless keyboards and mice, PDAs, pagers and digital and cellular phones have become part of our daily life.
Some of the inherent characteristics of wireless communications systems which make it attractive for users, are given below:
Mobility: A wireless communications system allows users to access information beyond their desk and conduct business from anywhere without having a wire connectivity.
Reachability: Wireless communications systems enable people to be better connected and reachable without any limitation of any location.
Simplicity: Wireless communication system are easy and fast to deploy in comparision of cabled network. Initial setup cost could be a bit high but other advantages overcome that high cost.
Maintainability: Being a wireless system, you do no need to spend too much to maintain a wireless network setup.
Roaming Services: Using a wireless network system you can provide service any where any time including train, busses, airoplans etc.
New Services: Wireless communications systems provide new smart services like SMS and MMS.
2.3 Wireless Network Topologies:
There are basically three ways to setup a wireless network.
Point-to-point bridge: As you know a bridge is used to connect two networks. A point-to-point bridge interconnects two buildings having different networks. For example, a wireless LAN bridge can interface with an Ethernet network directly to a particular access point.
Point-to-multipoint bridge: This topology is used to connect three or more LANs that may be located on different floors in a building or across buildings.
Mesh or ad hoc network: This network is an independent local area network that is not connected to a wired infrastructure and in which all stations are connected directly to one another.
2.4 Wireless Technologies:
Wireless technologies can be classified in different ways depending on their range. Each wireless technology is designed to serve a specific usage segment. The requirements for each usage segment are based on a variety of variables, including Bandwidth needs, Distance needs and Power.
Wireless Wide Area Network (WWAN):
This network enables you to access the Internet via a wireless wide area network (WWAN) access card and a PDA or laptop.
These networks provide a very fast data speed compared with the data rates of mobile telecommunications technology, and their range is also extensive. Cellular and mobile networks based on CDMA and GSM are good examples of WWAN.
Wireless Personal Area Network (WPAN):
These networks are very similar to WWAN except thier range is very limited.
2.5 Wireless Local Area Network (WLAN):
This network enables you to access the Internet in localized hotspots via a wireless local area network (WLAN) access card and a PDA or laptop.
It is a type of local area network that uses high-frequency radio waves rather than wires to communicate between nodes.
These networks provide a very fast data speed compared with the data rates of mobile telecommunications technology, and their range is very limited. Wi-Fi is the most widespread and popular example of WLAN technology.
2.6 Wireless Metropolitan Area Network (WMAN):
This network enables you to access the Internet and multimedia streaming services via a wireless region area network (WRAN).
These networks provide a very fast data speed compared with the data rates of mobile telecommunication technology as well as other wireless network, and their range is also extensive.
2.7 Issues with Wireless Networks:
There are following three major issues with Wireless Networks.
Quality of Service (QoS): One of the primary concerns about wireless data delivery is that, like the Internet over wired services, QoS is inadequate. Lost packets, and atmospheric interference are recurring problems wireless protocols.
Security Risk: This has been another major issue with a data transfer over a wireless network. Basic network security mechanisms like the service set identifier (SSID) and Wireless Equivalency Privacy (WEP). These measures may be adequate for residences and small businesses but they are inadequate for entities that require stronger security.
Reachable Range: Normally wireless network offers a range of about 100 meters or less. Range is a function of antenna design and power. Now a days the range of wireless is extended to tens of miles so this should not be an issue any more.
2.8 Wireless Broadband Access (WBA):
Broadband wireless is a technology that promises high-speed connection over the air. It uses radio waves to transmit and receive data directly to and from the potential users whenever they want it. Technologies such as 3G, Wi-Fi, WiMAX and UWB work together to meet unique customer needs.
BWA is a point-to-multipoint system which is made up of base station and subscriber equipment. Instead of using the physical connection between the base station and the subscriber, the base station uses an outdoor antenna to send and receive high-speed data and voice-to-subscriber equipment.
BWA offers an effective, complementary solution to wireline broadband, which has become globally recognized by a high percentage of the population.
2.9 What is Wi-Fi ?
Wi-Fi stands for Wireless Fidelity. Wi-Fi is based on the IEEE 802.11 family of standards and is primarily a local area networking (LAN) technology designed to provide in-building broadband coverage.
For more detail on Wi-Fi, please look into our Wi-Fi Tutorial.
2.10 What is WiMAX ?
WiMAX is one of the hottest broadband wireless technologies around today. WiMAX systems are expected to deliver broadband access services to residential and enterprise customers in an economical way.
Loosely, WiMax is a standardized wireless version of Ethernet intended primarily as an alternative to wire technologies ( such as Cable Modems, DSL and T1/E1 links ) to provide broadband access to customer premises.
More strictly, WiMAX is an industry trade organization formed by leading communications component and equipment companies to promote and certify compatibility and interoperability of broadband wireless access equipment that conforms to the IEEE 802.16 and ETSI HIPERMAN standards.
WiMAX would operate similar to WiFi but at higher speeds, over greater distances and for a greater number of users. WiMAX has the ability to provide service even in areas that are difficult for wired infrastructure to reach and the ability to overcome the physical limitations of traditional wired infrastructure.
WiMAX was formed in April 2001, in anticipation of the publication of the original 10-66 GHz IEEE 802.16 specifications. WiMAX is to 802.16 as the Wi-Fi Alliance is to 802.11.
Acronym for Worldwide Interoperability for Microwave Access.
Based on Wireless MAN technology.
A wireless technology optimized for the delivery of IP centric services over a wide area.
A scaleable wireless platform for constructing alternative and complementary broadband networks.
A certification that denotes interoperability of equipment built to the IEEE 802.16 or compatible standard. The IEEE 802.16 Working Group develops standards that address two types of usage models:
A fixed usage model (IEEE 802.16-2004).
A portable usage model (IEEE 802.16e).
2.11 What is 802.16a ?
WiMAX is such an easy term that people tend to use it for the 802.16 standards and technology themselves, although strictly it applies only to systems that meet specific conformance criteria laid down by the WiMAX Forum.
The 802.16a standard for 2-11 GHz is a wireless metropolitan area network (MAN) technology that will provide broadband wireless connectivity to Fixed, Portable and Nomadic devices.
It can be used to connect 802.11 hot spots to the Internet, provide campus connectivity, and provide a wireless alternative to cable and DSL for last mile broadband access.
2.12 WiMax Speed and Range:
WiMAX is expected to offer initially up to about 40 Mbps capacity per wireless channel for both fixed and portable applications, depending on the particular technical configuration chosen, enough to support hundreds of businesses with T-1 speed connectivity and thousands of residences with DSL speed connectivity. WiMAX can support voice and video as well as Internet data.
WiMax will be to provide wireless broadband access to buildings, either in competition to existing wired networks or alone in currently unserved rural or thinly populated areas. It can also be used to connect WLAN hotspots to the Internet. WiMAX is also intended to provide broadband connectivity to mobile devices. It would not be as fast as in these fixed applications, but expectations are for about 15 Mbps capacity in a 3 km cell coverage area.
With WiMAX users could really cut free from today.s Internet access arrangements and be able to go online at broadband speeds, almost wherever they like from within a MetroZone.
WiMAX could potentially be deployed in a variety of spectrum bands: 2.3GHz, 2.5GHz, 3.5GHz, and 5.8GHz
2.13 Why WiMax ?
WiMAX can satisfy a variety of access needs. Potential applications include extending broadband capabilities to bring them closer to subscribers, filling gaps in cable, DSL and T1 services, Wi-Fi and cellular backhaul, providing last-100 meter access from fibre to the curb and giving service providers another cost-effective option for supporting broadband services.
WiMAX can support very high bandwidth solutions where large spectrum deployments (i.e. >10 MHz) are desired using existing infrastructure keeping costs down while delivering the bandwidth needed to support a full range of high-value, multimedia services.
WiMAX can help service providers meet many of the challenges they face due to increasing customer demands without discarding their existing infrastructure investments because it has the ability to seamlessly interoperate across various network types.
WiMAX can provide wide area coverage and quality of service capabilities for applications ranging from real-time delay-sensitive voice-over-IP (VoIP) to real-time streaming video and non-real-time downloads, ensuring that subscribers obtain the performance they expect for all types of communications.
WiMAX, which is an IP-based wireless broadband technology, can be integrated into both wide-area third-generation (3G) mobile and wireless and wireline networks, allowing it to become part of a seamless anytime, anywhere broadband access solution.
Ultimately, WiMAX is intended to serve as the next step in the evolution of 3G mobile phones, via a potential combination of WiMAX and CDMA standards called 4G.
2.14 WiMAX Goals:
A standard by itself is not enough to enable mass adoption. WiMAX has stepped forward to help solve barriers to adoption, such as interoperability and cost of deployment. WiMAX will help ignite the wireless MAN industry, by defining and conducting interoperability testing and labeling vendor systems with a “WiMAX Certified™” label once testing has been completed successfully.
2.15 WiMAX Major Benefits
Benefits to Component Makers:
Creates a volume opportunity for silicon suppliers.
Benefits to Equipment Makers:
Innovate more rapidly because there exists a standards-based, stable platform upon which to rapidly add new capabilities.
No longer need to develop every piece of the end-to-end solution.
Benefits to Operators:
A common platform which drives down the cost of equipment and accelerates price/performance improvements unachievable with proprietary approaches.
Generate revenue by filling broadband access gaps.
Quickly provision T1 / E1 level and “on demand” high margin broadband services.
Reduce the dollar risk associated with deployment as equipment will be less expensive due to economies of scale.
No longer be locked into a single vendor since base stations will interoperate with multiple vendors’ CPEs.
Benefits to Consumers:
More broadband access choices, especially in areas where there are gaps: worldwide urban centers where building access is difficult; in suburban areas where the subscriber is too far from the central office; and in rural and low population density areas where infrastructure is poor.
More choices for broadband access will create competition which will result in lower monthly subscription prices.
2.16 WiMAX and Wi-Fi Comparison
WiMAX is similar to the wireless standard known as Wi-Fi, but on a much larger scale and at faster speeds. A nomadic version would keep WiMAX-enabled devices connected over large areas, much like today.s cell phones. We can compare it with Wi-Fi based on the following factors.
Wi-Fi is based on IEEE 802.11 standard where as WiMAX is based on IEEE 802.16. However both are IEEE standards.
Wi-Fi typically provides local network access for around a few hundred feet with speeds of up to 54 Mbps, a single WiMAX antenna is expected to have a range of up to 40 miles with speeds of 70 Mbps or more. As such, WiMAX can bring the underlying Internet connection needed to service localWi-Fi networks.
Wi-Fi is intended for LAN applications, users scale from one to tens with one subscriber for each CPE device. Fixed channel sizes (20MHz).
WiMAX is designed to efficiently support from one to hundreds of Consumer premises equipments (CPE)s, with unlimited subscribers behind each CPE. Flexible channel sizes from 1.5MHz to 20MHz.
Wi-Fi works at 2.7 bps/Hz and can peak up to 54 Mbps in 20 MHz channel.
WiMAX works at 5 bps/Hz and can peak up to 100 Mbps in a 20 MHz channel.
Quality of Service:
Wi-Fi does not guarantee any QoS but WiMax will provide your several level of QoS.
As such, WiMAX can bring the underlying Internet connection needed to service local Wi-Fi networks. Wi-Fi does not provide ubiquitous broadband while WiMAX does.
2.17 Comparsion Table:
|Wireless LAN||Wireless LAN|
2 G to 11 GHz
|2.4 GHz ISM||2.4 GHz ISM (g)
5 GHz U-NII (a)
1.25 M to 20 MHz
|25 MHz||20 MHz|
|<=5 bps/Hz||<=0.44 bps/Hz||<=2.7 bps/Hz|
16-, 64-, 256-QAM
(AES in 802.11i)
(AES in 802.11i)
|In development||In development|
2.18 WiMAX – Salient Features
WiMAX is a wireless broadband solution that offers a rich set of features with a lot of flexibility in terms of deployment options and potential service offerings. Some of the more salient features that deserve highlighting are as follows:
Two Type of Services:
2.19 WiMAX can provide two forms of wireless service:
Non-line-of-sight: service is a WiFi sort of service. Here a small antenna on your computer connects to the WiMAX tower. In this mode, WiMAX uses a lower frequency range — 2 GHz to 11 GHz (similar to WiFi).
Line-of-sight: service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. The line-of-sight connection is stronger and more stable, so it’s able to send a lot of data with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz.
2.20 OFDM-based physical layer:
The WiMAX physical layer (PHY) is based on orthogonal frequency division multiplexing, a scheme that offers good resistance to multipath, and allows WiMAX to operate in NLOS conditions.
2.21 Very high peak data rates:
WiMAX is capable of supporting very high peak data rates. In fact, the peak PHY data rate can be as high as 74Mbps when operating using a 20MHz wide spectrum.
More typically, using a 10MHz spectrum operating using TDD scheme with a 3:1 downlink-to-uplink ratio, the peak PHY data rate is about 25Mbps and 6.7Mbps for the downlink and the uplink, respectively.
2.22 Scalable bandwidth and data rate support:
WiMAX has a scalable physical-layer architecture that allows for the data rate to scale easily with available channel bandwidth.
For example, a WiMAX system may use 128, 512, or 1,048-bit FFTs (fast fourier transforms) based on whether the channel bandwidth is 1.25MHz, 5MHz, or 10MHz, respectively. This scaling may be done dynamically to support user roaming across different networks that may have different bandwidth allocations.
2.23 Adaptive modulation and coding (AMC):WiMAX supports a number of modulation and forward error correction (FEC) coding schemes and allows the scheme to be changed on a per user and per frame basis, based on channel conditions.AMC is an effective mechanism to maximize throughput in a time-varying channel.
2.24 Link-layer retransmissions:WiMAX supports automatic retransmission requests (ARQ) at the link layer for connections that require enhanced reliability. ARQ-enabled connections require each transmitted packet to be acknowledged by the receiver; unacknowledged packets are assumed to be lost and are retransmitted.
2.25 Support for TDD and FDD:IEEE 802.16-2004 and IEEE 802.16e-2005 supports both time division duplexing and frequency division duplexing, as well as a half-duplex FDD, which allows for a low-cost system implementation.
2.26 WiMAX uses OFDM:
Mobile WiMAX uses Orthogonal frequency division multiple access (OFDM) as a multiple-access technique, whereby different users can be allocated different subsets of the OFDM tones.
2.27 Flexible and dynamic per user resource allocation:
Both uplink and downlink resource allocation are controlled by a scheduler in the base station. Capacity is shared among multiple users on a demand basis, using a burst TDM scheme.
2.28 Support for advanced antenna techniques:
The WiMAX solution has a number of hooks built into the physical-layer design, which allows for the use of multiple-antenna techniques, such as beamforming, space-time coding, and spatial multiplexing.
2.29 Quality-of-service s