Topic: MIMO TECHNOLOGY
Ramesh babu Vallabhaneni
Article Name: MULTIPLE I.P MULTIPLE O.P TECHNOLOGY.
In the present era of communication technology 3rd generation (3G) i.e. it is
optimally focused on using a single interface number and an advanced core network. The
main service component of 3G technology is quality and reliable internet data traffic.
The research & development (R &D) is already aiming at Fourth-Generation(4G).
This paper MULTIPLE INPUT MULTIPLE OUTPUT TECHNOLOGY. In
this paper covers the both advantage & disadvantage 3G, and also deals about fading
and what are promises and limitations of MIMO TECHNOLOGY.
Communication is one of the most fundamental and essential activity in every walk of
human life in the modern society, without which human kind cannot survive. Human
communication took a big leap when long distance electrical communication
technologies like Telephony and Telegraphy were invented in the 19th Century. This truly
lead to the communication revolution which Marjory contributed to the overall
development of human kind, by removing the traditional barriers of the language and the
The Basic Components of a electronic communication system are shown in fig.
Here in this content discus only for channel. The channel which can allows the
signal from TX to RX communication channels are of two type i.e. guided media &
If any physical connection is there b/w the transmitter and received thus type of media is
called guided media.
Ex:- Land to Land Telephone System.
If there is no physical connection b/w the transiting and received is called unguided
Ex:- Cellular, Wireless.
Here deals the advanced wireless system i.e. MULTIPLE INPUT MULTIPLE
The human acoustical communication has one important feature; For the purpose
of communication, the address of the user is unique and one. If my name is ramesh
anybody will call me by ramesh at any time, anywhere and for any communication.
This is not the case in todayâ„¢s telephony, mobile or computer network. Your telephone
number will be different from city to city, your mobile number will be different from
network to network, and your e- mail address in Ëœvsnlâ„¢ will be different from that in
Technological trends follow the natural paths. We invented aircrafts to fly like
birds. Computers are being at tempted to be as brainy as humans. In the same way, the
communication technology is going to be human- like but without limitation of coverage
area. So the future will see a single number for a person for communication World over.
The future communication aims at becoming all-wireless and mobile supporting
any communication (Voice, Video, Data, Images, Pictures, Graphics, etc) anywhere, any
time and for anybody with a single unique identification number(UTN, Universal
Telecommunication Number) of a person service(PCS) and may be supported by the
personal communication network (PCN)- a global wireless and mobile network.
Trends in Wireless and Mobile Technology:-
Last few years have seen rapid development of wireless-technologies. The stage is set for
third- generation (3G) technology and R & D is already aiming at fourth- generation (4G)
technology(see Figs 1 and 2).
2G technology for mobile communication organized during 1990â„¢s and it
revolved around GSM mainly for voice communication. It was focused on voice services
with circuit switching, whereas the current 2.5 G technology is focused on circuit
switched voice service and packet-switched data service.
Seamless Coverage &
Anytime and Any
TOWARDS WIRELESS COMMUNICATION SOCIETY
MULTIMEDIA CONTENT, HIGH BIT RATE AND IP TRANSPORT
Fig:1 PCN evolution/migration
The 3G technology is optimally focused on using a single interface number and an
advanced core network.
1. Anywhere and anytime mobile connection with low-cost and flexible handheld
2. Wireless data access, particularly with wireless Interest connection. This was
motivated by the exponential growth of Internet access.
3. High-speed multimedia or broadband services, causing shift from voice-oriented
services to Internet access(both data and voice, particularly with VoIP
technology), Video, Music, Graphics and other multimedia services.
4. Global roaming to support global communication.
5. Flexible network to support existing and future requirements.
The 2G technology offered quite satisfactory voice communication service, but
with growing data traffic, the 3G technology has mainly targeted data services,
particularly the Internet traffic. Thus the main service component of the 3G
technology is quality and reliable Internet data traffic.
Major Challenges before the implementation of 3G are:
1. Slow production of 3G mobile phones and devices.
2. Wireless Internet for exponentially growing users will be difficult to implement
until IPv6 is implemented.
3. Global roaming with a single number as proposed in the PCN is yet to be
4. Fixed- line access technologies like ADSL offering high data rates of 12 Mbps, as
well as IEEE 802.11b WLAN in Wireless local data interface, are giving a tough
5. The devices are still struggling with limited processing powers of
microprocessors, small display with limited resolution, limited battery life, limited
memory size, etc.
Comprehensive, broadband, integrated mobile communication will step forward into all-
mobile 4G services and communication. The 4G technologies will be a migration from
the other generations of mobile services to overcome the limitation of boundary and
achieve total integration.
The 4G systems will be developed to provide high-speed transmission, next- generation
Internet support (IPv6, VoIP aand IP), high-capacity, seamless integrated services and
coverage, utilization of higher frequency, lower system cost, seamless personal mobility,
mobile multimedia(standards), efficient s p e c t rum use, quality of service(QoS),
reconfigurable network and end-to-end IP systems.
Wireless technologies are not free from problems like limitation of the available
frequency spectrum, fading and multipath fading. Fading results in sudden drop of signal
power in the receiver. Multipath fading results when the transmitted signal bounces off
objects like buildings, office cabinets and hills, creating multiple paths for the signal to
reach the receiver. The same transmitted signal that follows the different paths reaches
the receiver at different times with different phases.
Added together, the several incidences of the same signal with different phases
and amplitudes may cancel each other, causing signal less or drop of signal power.
The expectations from future wireless mobile networks are high data rate, higher
network capacity, better quality of service and lower probability of call drop, With
increasing data rates, the problem of multipath fading becomes severe.
Multipath fading (Fig.3) may be delay spread, short-term fading, long-term fading
and Doppler effect. Delay spread results in spreading of the transmitted pulse on the time
axis and even in generation of multiple low-amplitude pulse trains. It occurs in fixed
The receiver may not adapt to the changes. This degrades the service quality.
Short-term fading occurs over short time duration.
Long-term fading results in decreased received power over long time/distance; as
time increase, the moving receiver usually goes farther away,
The Doppler effect occurs in fast moving mobiles. It results in shift of the
MIMO Technology :
Wireless channels input and output modulated signals. For the purpose of modulation ,
the two basic things considered are frequency and time. The frequency plan and the time
plan use bits per hertzâ„¢ and Ëœbits per secondâ„¢ as measures for data rate transportation. A
new dimensions to upgrade the data transport rate is spatial dimension. This is the basic
idea behind multiple-input multiple-output (MIMO) technology.
MIMO technology may be seen as an upgrade of single- input multiple-output
(SIMO) and multiple- input single-output (MISO) technologies (Fig. 4) All three
technologies, namely, SIMO, MISO and MIMO, are based on the philosophy of using
Ëœdisadvantages for achieving gainsâ„¢. These use multiple paths (the sources of fading)for
increasing the data rate, throughput and reliability. Multiple paths are used by multiple
transmit antennae and multiple receive antennae. This deviation form SISO brings all
gains for SIMO, MISO and finally MIMO.
Multiple antennae at one end, either at the transmitter or at the receiver, were in
use long ago. The then use of multiple antennae aimed at beam formatting and spatial
diversity, which are mainly used to increase the signal-to-noise ratio. The improved
signal-to-noise ratio decreases the bit error rate.
In fact, if SIMO and MISO achieve gains by multiple antennae at receivers and
transmitters, respectively, multiple antennae both at the transmitter and the receiver are
supposed to multiple the gain. In other words, we can say that MIMO=MISO+SIMO.
The use of multiple antennae adds a new dimension to the digital communication
technology-the basis of 3G and 4G. The natural dimension of digital technology is time.
Added with that, MIMO offers a new space-time axis to digital technology. MIMO is
thus often termed as Ëœspace-time wirelessâ„¢ or Ëœsmart antennaeâ„¢. Of course, it is the
improved extension of smart antennae. Digital MIMO is also called Ëœvolume-to-volume
wireless linksâ„¢ as it offers parallel bit pipes between the transmitter and the receiver.
MIMO technology promises higher data rate, higher quality of service and better
reliability by exploiting antenna arrays as both the transmitter and the receiver. Signals at
both the sides (transmitter and receiver) are mixed such that they either generate multiple
parallel, spatial bit-pipes and/or add diversity to decrease the bit-error rate.
Diversity helps in selecting the clearest signal out of many signals, resulting in
lower bit-error rate. Multiple bit-pipes effectively increase the data rate(quantitative
improvement), where as the reduced bit-error rate improves the quality of service,
through-put and reliability (qualitative improvement). MIMO creates benefits beyond the
diversity of multiple antennae at one end only. Thus while qualitative improvements,
SIMO and MISO each offer only the qualitative improvement.
By spreading the transmitted signal over multiple paths, the MIMO technology
increases the chances of signal reception at the receiver. It also increases the range of
In Fig.4, MIMO covers all the three base regions of conventional cellular
telephony. The transmitter can adjust power and phase of the signal fed to antennae,
which allows the best transmission quality.
Multipath fading causes distortion by scrambling different copies of signals
reaching the receiver via multipaths on bouncing off the objects. Then how do the
multipath signals work in MIMO? Proper algorithms are used at both the transmitter and
the receiver to analyze the signal received form different paths and different antennae of
the array. Proper spacing of the antennae and signal analysis via a matrix manipulation
technology that cross-correlates the signals are the requirements of the MIMO
Not Without Limitations:
Complex algorithm and design are required for operation of multiple antennae. This will
make the handset and the other mobile devices costlier.
For implementation of the MIMO technology, R & D is required in his model,
signal processing approaches, and information theory for coding and capacity. The
design of MIMO networks, both fixed and mobile wireless, needs to optimally consider
the CDMA,TDMA and FDMA techniques and medium-access control protocols. MIMO
chips, products and systems are expected to hit the market with three years.
Though hopes are running high, it has been found that for some environments the
capacity of MIMO system is low even for uncorrelated signals. The effect is known as
More recently, the new wireless applications have rapidly evolved to radically
transform the World into a true global village, providing new means interaction on the
basis of ANY WHERE, ANY ONE, ANY TIME and ANY SERIVCE. Today we
witness mobile telephony, mobile internet, mobile personal communication and
integrated multimedia information networks, rapidly deployed to reach every nook and
corner of the society so called information society serving the needs of modern
information hungry society.
It is difficult to image what happens if the entire telecom infrastructure fails for a
couple of minutes. Truly speaking, telecom networks are the basic pillars of the modern