Wireless technology has transformed our lives in many ways. Until very recently, we needed a computer wired to a port, to get online. Even wired telephones are becoming a thing of past. Nowadays, we use our mobile phones for banking, to check ticket availability at a Cinema Hall, and many more. Wireless communication is the transfer of information over a distance without the use of enhanced electrical conductors or "wires”. And, Wireless networking refers to any kind of networking that does not involve cables. It helps in saving the cost of cables for networking in addition to providing the mobility.
There are different types of wireless networks defined on the basis of their size, range and data transfer rate.· Wireless PAN - Personal area network Wireless Personal Area Networks
· Wireless LAN - Local Area Network
· Wireless MAN - Metropolitan Area Networks
· Wireless WAN- Wide Area Networks
· Mobile devices networks
Mobile networks have evolved tremendously in last 3 decades. Cellular concept was introduced with 1G (‘G’ stands for generation) networks. Today, 4G technology is getting ready to storm the markets. Not only that, research on 5G technology has already begun.
Evolution of Mobile Technologies
Zero Generation Technology (0G)
0G refers to pre-cell phone mobile telephony. Being the predecessors of the first generation of cellular telephones, these systems are called 0G (zero generation) systems. Usually vehicle mounted, they had the transceivers mounted in the vehicle trunk and dials & display mounted near the driver seat.
Technologies used in 0G systems included PTT (Push to Talk), MTS (Mobile Telephone System), IMTS (Improved Mobile Telephone Service), and AMTS (Advanced Mobile Telephone System).
First Generation Technology (1G)
1G refers to the first generation of wireless telecommunication technology, more popularly known as cell phones. In 1G, Narrow band analogue wireless network is used; with this we can have the voice calls. These services are provided with circuit switching. Through 1G, a voice call gets modulated to a higher frequency of about 150MHz and up as it is transmitted between radio towers using a technique called Frequency-Division Multiple Access (FDMA).
Different 1G standards prevalent were AMPS (Advanced Mobile Phone System) in the United States, TACS (Total Access Communications System) in the United Kingdom, NMT (Nordic Mobile Telephone), used in Nordic countries, Eastern Europe and Russia, etc.
Second Generation Technology
2G - 2G first appeared around late 1980’s; 2G system digitized the voice signal, as well as the control link. It provided the facility of short message service (SMS) unlike 1G that had its prime focus on verbal communication. Depending on the type of multiplexing used 2G technologies can be divided into Time Division Multiple Access (TDMA) based and Code Division Multiple Access (CDMA). 2G system offered better quality and much more capacity. 2G cellphone units were generally smaller than 1G units, since they emitted less radio power.
Based on TDMA, Global System for Mobile communications (GSM) is the first European standard & the first commercial network for use by the public for 2nd generation mobile (2G) telephony. A typical 2G G.S.M network service uses 800/900MHz or 1800/1900 frequency spectrum. Typical average data rate of GSM is 9.6 kbps. 2G CDMA (IS-95A) uses BPSK and offers data rate upto 14.4 kbps. The bandwidth of 2G is 30-200 KHz.
2.5G – GPRS (General Packet Radio Service) - 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. 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.
‘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).
GPRS (CS1 to CS4) uses GMSK modulation with symbol rate (& modulation rate) of 270 ksym/s. Typical data rate of GPRS is ~115 kbps. It can be used for services such as Wireless Application Protocol (WAP) access, Multimedia Messaging Service (MMS) and for accessing internet.
IS-95B or cdmaOne is the evolved version of IS-95A and is also designated as 2.5G with theoretical data rates of upto 115 kbps, with generally experienced rates of 64 kbps.
2.75 – EDGE (Enhanced Data rates for GSM Evolution) - EDGE (EGPRS) is an abbreviation for Enhanced Data rates for GSM Evolution, is a digital mobile phone technology, invented by AT&T. EDGE technology is an extended version of GSM & works in GSM networks. EDGE is add-on to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrades. It allows the clear and fast transmission of data. One need not install any additional hardware and software in order to make use of EDGE Technology. Also, there are no additional charges for utilizing this technology.
Uses 9 Modulation coding schemes (MCS1-9). MCS (1-4) uses GMSK, while MCS (5-9) uses 8PSK modulation. 8PSK Increases throughput by 3x (8-PSK – 3 bits/symbol vs GMSK 1 bit/symbol). Modulation bit rate is 810 kbps. It offers data rates of 384kbps, theoretically up to 473.6kbps.
Third Generation Technology (3G)
3G - G systems promise faster communications services, entailing voice, and fax and Internet data transfer capabilities. The aim of 3G is to provide these services anytime, anywhere throughout the globe, with seamless roaming between standards. ITU’s IMT-2000 is a, global standard for 3G.
3G networks are wide area cellular telephone networks which have evolved to incorporate high-speed internet access and video telephony. It offers large capacity and broadband capabilities. It has greater network capacity through improved spectrum efficiency. 3G technology supports around 144 Kbps, with high speed movement, i.e. in a vehicle, 384 Kbps locally, and up to 2Mbps for fixed stations, i.e. in a building. 3G technology uses CDMA, TDMA and FDMA. The data are sent through Packet Switching. Voice calls are interpreted through Circuit Switching. It is a highly sophisticated form of communication that has come up in the last decade.
3G has the following enhancements over 2.5G and previous networks:
· Enhanced audio and video streaming;
· Several Times higher data speed;
· Video-conferencing support;
· Web and WAP browsing at higher speeds;
· IPTV (TV through the Internet) support.
· Global Roaming
There are many 3G technologies as W-CDMA, CDMA2000. UMTS, DECT, WiMAX.
3.5G – HSDPA (High-Speed Downlink Packet Access)
High-Speed Downlink Packet Access (HSDPA) is a mobile telephony protocol, also called 3.5G. It is an enhanced version and the next intermediate generation of 3G UMTS allowing for higher data transfer speeds.
HSDPA is a packet-based data service in W-CDMA downlink with data transmission up to 8-10 Mbps (and 20 Mbps for MIMO systems) over a 5MHz bandwidth in WCDMA downlink. This high data rate is enabled by use of adaptive modulation can coding (AMC), hybrid automatic repeat-request (HARQ), and fast packet scheduling at the access point
3.75G – HSUPA (High-Speed Uplink Packet Access)
High Speed Uplink Packet Access (HSUPA) is a UMTS /WCDMA uplink evolution technology. The HSUPA mobile telecommunications technology is directly related to HSDPA and the two are complimentary to one another.
HSUPA will enhance advanced person-to-person data applications with higher and symmetric data rates, like mobile e-mail and real-time person- to person gaming.
4G Technology
Why 4G?
· 3G may not be sufficient to meet needs of future high-performance applications like multi-media, full-motion video, wireless teleconferencing.
· Multiple standards for 3G make it difficult to roam and interoperate across networks
· Requirement of a single broadband network with high data rates which integrates wireless LANs, Bluetooth, cellular networks, etc
4G - Also known as "Beyond 3G", 4G refers to the fourth generation of wireless communications. The deployment of 4G networks should be in the 2010-2015 timeframe and will enable another leap in wireless data-rate and spectral efficiency. ITU has specified IMT-A (IMT-Advanced) for 4G standards.
4G is all about convergence; convergence of wired and wireless networks, wireless technologies including GSM, wireless LAN, and Bluetooth as well as computers, consumer electronics, communication technology and several others. 4G is a Mobile multimedia, anytime anywhere, Global mobility support, integrated wireless solution, and customized personal service network system
4G wireless technology is also referred to by “MAGIC” which stands for Mobile multimedia, Any-where, Global mobility solutions over, integrated wireless and Customized services. 
4G is an all IP-based integrated system will be capable to provide 100 Mbps for high mobility and 1 Gbps for low mobility , with end-to-end QoS and high security, and will offering various services at any time as per user requirements, anywhere with seamless interoperability, at affordable cost. The user services include IP telephony, ultra-broadband Internet access, gaming services and High Definition Television (HDTV) streamed multimedia.
4G Requirements - As per ITU's IMT-A
· All-IP packet switched network.
· Data rates up to 100 Mbps for high mobility and up to 1 Gbps for low mobility.
· Seamless connectivity and global roaming
· Interoperability with existing wireless standards
· Smooth handovers.
· High QoS.
Key Components & Technologies in 4G
MIMO – OFDM
MIMO, in contrast to traditional communication systems, takes advantage of multipath propagation to increase throughput, range/coverage, and reliability. MIMO (Multiple Input Multiple Output) systems use spatial multiplexing, wherein multiple transmitting antennas and multiple receiving antennas are used. It permits pparallel streams to be transmitted simultaneously by those antennas. Because MIMO transmits multiple signals across the communications channel,
Data rate in MIMO systems gets multiplied by the number of antennas used.
2G and 3G systems used TDMA, FDMA and CDMA as channel access schemes. However, 4G uses OFDMA and other new technologies (Single Carrier FDMA, Interleaved FDMA, and Multi-carrier CDMA) instead of CDMA, which is used by all 3-G systems.
In OFDM, digital signal itself is split into different narrowband frequencies, modulated by data and then re-multiplexed to create the OFDM carrier. The main benefit of OFDM is high spectral efficiency, high immunity to RF interference, and lower multi-path distortion. Another key advantage of OFDM is that it dramatically reduces equalization complexity by enabling equalization in the frequency domain.
OFDM can be implemented efficiently by using Fast Fourier transforms (FFT) at the transmitter and receiver. FFT provides the channel response for each frequency. With MIMO, the channel response becomes a matrix and hence, MIMO-OFDM signals can be processed using relatively straightforward matrix algebra. Since complexity involved with space-time equalizers for MIMO-OFDM systems is less, they are preferred. Also, MIMO uses multipath propagation to its advantage.
IPv6 - IPv4 address exhaustion is likely to be in its final stages by the time of deployment of IPv6. Hence, for 4G technology, IPv6 has evolved to support a large number of devices. The packet structure for IPv6 is shown below.
IPv4 uses 32 bits and hence it is able to address 4294967269 possible addressable devices, whereas IPv4 uses 128 bits and is able to 3.4 X 1038 possible addressable devices
With IPv6, each device will have its own IP. Even if access point is changed, IP will remain same. IP based backbone or IP Core will allow everything to talk to each other, provided they follow the same protocol.
Smart Antennas
Smart or Intelligent antennas is also a multi-antenna concept which allows the radio beam to follow the user. This is done through beam forming which temporarily improve gain. They are also used to provide transmit and/or receive diversity.
Adhoc Networks
Adhoc networks refer to spontaneous self organisation of network of devices, not necessarily connected to internet. 4G will create hybrid wireless networks using adhoc networks. Intelligent routing to determine shortest path with least powers are used, i.e, data packets are sent through paths with minimal power requirements.
Adaptive Modulation And Coding (AMC)
Adaptive modulation and coding mechanism reacts to instantaneous variations in channel conditions and accordingly modify the modulation & coding formats. Based on feedback from the receiver, response of the channel is estimated and depending upon the channel conditions, AMC allows different data rates to be assigned to different users. Channel statistics aid the transmitter and receiver to optimize system parameters such as modulation, coding, bandwidth, channel estimation filters, and automatic gain control.
Adaptive Hybrid ARQ
Efficient and reliable Medium access control (MAC) layer performance is extremely important for reliable link performance over the lossy wireless channel. TO achieve this, an automatic retransmission and fragmentation mechanism called automatic Repeat Request (ARQ) is used, wherein the transmitter breaks up packets received from higher layers into smaller sub packets, which are transmitted sequentially. If a sub packet is received incorrectly, the transmitter is requested to retransmit it. This mechanism introduces time diversity into the system due to its capability to recover from noise, interference, and fades.
Improved Modulation
Previous standards used Phase-shift keying, more spectrally efficient modulation schemes such as 64-QAM (Quadrature Amplitude Modulation) is being used for 4G systems.
Software Defined Radio (SDR)
SDR is key to 4G systems. Software Defined Radio allows some of the functional modules of radio equipment like modulation/demodulation, signal generation, coding and link-layer protocols, that used to be traditionally implemented in special purpose hardware to be implemented in modifiable software or firmware operating on programmable processing technologies. Since 4G is all about convergence of diverse wireless standards, this can be efficiently realized using SDR technology
Comparison with 3G
| Parameters | 3G | 4G |
Network Architecture | cell-based | Integration of various wireless technologies |
Speeds | 384 Kbps to 2 Mbps | 100 Mbps to 1 Gbps |
Frequency Band | Dependent on country or continent (1800-2400 MHz) | Higher frequency bands (2-8 GHz) |
Bandwidth | 5-20 MHz | 100 MHz (or more) |
Switching Scheme | Circuit and Packet | Packet |
Access Technologies | W-CDMA, 1xRTT, Edge | OFDM and MC-CDMA |
IP | No. of air link protocols | All IP (IP6.0) |
4-G Systems
WirelessMAN-Advanced
o IMT-A compliant version of WiMAX or WiMAX 2 based on IEEE 802.16m
o WiMAX (Worldwide Interoperability for Microwave Access) is an IP based, wireless broadband access technology
o WirelessMAN is under development.
o Present implementation of WiMAX does not comply with 4G specifications
o Uses OFDM in uplink and downlink.
o Mobile WiMAX, IEEE 802.16e standard offers peak data rates of 128 Mbit/s downlink and 56 Mbit/s uplink over 20 MHz wide channel.
4G LTE (Long Term Evolution) Advanced
· IMT-A complaint version of LTE, also referred to as E-UTRA (Evolved UMTS Terrestrial Radio Access) or E-UTRAN(Evolved UMTS Terrestrial Radio Access Network).
· UMTS Long Term Evolution (LTE) was introduced in 3GPP Release 8 which supports data rates of up to 300 Mbps (4x4 MIMO) and up to 150 Mbps (2x2 MIMO) in the downlink and up to 75 Mbps in the uplink. Release 10 of LTE is likely to approach IMT-A, download upto 1 Gbps and upload upto 500 Mbps.
· Uses OFDMA for downlink & Uses Single Carrier Frequency Division Multiple Access (SC-FDMA) for uplink.
· Uses 64QAM modulation
· Uses MIMO and beam forming with up to 4 antennas
· All IP Network
Moving Beyond 4G
4G is not the end of all. "5G Technology" is already in research arena and is bound to up the data rate further.5G is going to alter the way of our usage of our cellphones; may replace our Desktop PCs/laptops. Coupled with innovations being done in the field of smart sensors, 5G mobile phones with extremely high data rates, IP core, and world-wide coverage will offer features which have not imagined so far.
Currently 5G is not a term officially used for any particular specification, however, it is being used in research papers and standardization bodies for the future wireless standards.
