International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 11 - May 2014
An Extensive Survey on Wi-Max SCOFDM System
Megha Raghuwansi1 Dr. Ashutosh Sharma2
1
M. Tech Research Scholar (Digital Communication), BIT Bhopal
2
Professer in Department of Electronics & Communication, BIT Bhopal
Abstract- The Wi-Max (Worldwide Interoperability for Microwaves
Access) is a widely used system which can offer rapid voice, feature
and information administration up to the client end. The
improvement of 802.16 norms for BWA (Broadband Wireless
Access) advances was spurred by the quickly developing
requirement for fast, pervasive and financially savvy access. The
Wi-Max can likewise be recognized to be the primary innovation in
the usage of different systems like remote sensor systems. Creating
an understanding of the Wi-Max framework could be best attained
by taking a gander at a model of the Wi-Max framework. Mobile
Wi-Max (general interoperability for microwave access) structure
has been starting late associated for the most part in distant
communication schemes. Wi-Max uses OFDM as a particular
stage because of high extraordinary benefit. This model is a
helpful device for BER (Bit Error Rate) execution assessment for
the continuous sound information correspondence by the Wi-Max
physical layer, under distinctive channel encoding rate, and
computerized tweak plans and channel conditions, other than
serving as a supportive asset for the people and the specialists who
need to base their studies and research in the field of Wi-Max.
Keywords- Worldwide Interoperability for Microwaves Access (WiMax), Orthogonal Frequency Division Multiplexing (OFDM),
Physical Layer (PHY). Additive White Gaussian Noise (AWGN),
Bit Error Rate (BER).
I.
INTRODUCTION
The WIMAX (Worldwide Interoperability for Microwave
Access) innovation speaks to a capable hopeful for the fourth
era of versatile correspondence frameworks. Around
distinctive renditions of the standard, the best business usage
was brought by IEEE 802.16e, some of the time alluded to as
versatile WIMAX. Some state of- the- craft sign handling and
systems administration calculations and strategies are
proposed by the specialized details of IEEE 802.16e for layers
1 and 2 (PHY and MAC separately). The MAC layer in
WIMAX is arranged on the Quality of Service (Qos). In this
manner, a few information conveyance administrations (UGS,
rtps, nrtps, ertps, BE) are characterized in the standard for the
radio interface, to oblige distinctive sorts of requisitions.
Moreover, the air interface in WIMAX depends on a clever
numerous access instrument. In uplink (UL), time and
recurrence assets are conceded by the Base Station (BS) upon
interest, inasmuch as in DL, the Mobile Stations (MS) are
booked to accept information basically focused around the
Qos parameters that must be satisfied for each specific
Service Flow.
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The Qos parameters are considered for asset allotment in UL
as well. Because of this insightful planning, there is no
controversy reporting in real time interface, with the
exception of a few parts of the physical casing included
specifically organize systems (system entrance, handover) [1].
Macintosh layer lives on the administrations gave by the PHY
layer. Its most critical characteristic is the utilization of
OFDMA (Orthogonal Frequency Division Multiple Access)
system. OFDMA is an expansion of OFDM that gives extra,
different access abilities. Different characteristics of the
physical layer are connection adjustment and the utilization of
a few Adaptive Antenna Systems (AAS) systems. For the
DL/UL partition, regardless of the fact that both Frequency
Division Duplex (FDD) and Time Division Duplex (TDD) are
permitted, the framework profiles given by WIMAX Forum
for portable WIMAX are focused around TDD. The
developments in the utilization of the data systems lead to the
requirement for new correspondence systems with higher
information rates.
The telecommunication business is additionally change, with
an interest for a more stupendous reach of administrations, for
example, feature gatherings, or requisitions with mixed media
substance, remote correspondence has pervaded about all
actualities of human life. Illustration home, work places, auto
and so forth. WIMAX (Worldwide Interoperability for
Microwaves Access) is a 4g innovation. Which is a based
upon IEEE 802.16 standard [1], that has been created by
working gathering number 16 of IEEE 802, gaining practical
experience in Broadband Wireless Access. It is upheld by a
wide number of industry organizations. The IEEE 802.16
standard for remote metropolitan zone system (WMAN) was
distributed for altered remote access (FWA) provision. This
standard is presently getting extensive modern consideration.
Later the standard augmented its operation through diverse
PHY determination to 2-11 Ghz recurrence band empowering
non observable pathway (NLOS) association.
III LITERATURE REVIEW
Xu Li, Zhan Xu[4], In the IEEE 802.16e OFDM (Orthogonal
Frequency Division Multiplexing) physical layer, the
discretionary LDPC (Low Density Parity Check) code
channel coding plan focused around the IEEE 802.16e
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 11 - May 2014
convention can be connected keeping in mind the end goal to
enhance the entire framework's BER (bit failure rate)
execution. Because of the incredible attributes and great lapse
remedying execution of LDPC code itself, it has turned into
the focal issue of current channel coding field with wide
requisition prospects. In this paper, we utilize the enhanced
BF (Bit Flipping) unraveling calculation, which is focused
around the structure of check framework and the convention's
procurements of LDPC coding plan, to supplant RS-CC
(Reed Solomon-Convolutional Codes) connected coding plan
on the thought of interpreting defer and further change of
BER execution. In the mean time, the capacity technique for
built weigh lattice said in this paper is additionally enhanced.
The enhanced BF interpreting calculation could be confirmed
by reproduction that change of BER execution is
acknowledged on premise of low unpredictability. Quang
Nguyen Duc, Lien Pham Hong, Tra Luu Thanh [5], in this
paper,the auther explained that the channel estimation
calculations are concentrated on for versatile WIMAX
standard. The brush sort pilot is utilized for channel
estimation framework. Kalman estimator had great execution
in moderate nature. Expanded Kalman Filter (EKF), an
improved adaptation of Kalman Filter, is dissected and sought
channel estimation. Recreation indicated that EKF would do
well to execution than Kalman estimator in moderate blurring
channel with low Doppler shift. Mean Squared Error (MSE)
and Bit Error Rate (BER) execution of the proposed
calculation are confirmed by workstation reproduction.
Zouggari, N. Hakem, G.y. Delisle [6], this paper shows the
configuration of a versatile channel which minimizes the
impact of impedance between two OFDM frameworks. The
proposed versatile channel can recuperate a true Wimedia
OFDM indicator from a Wimedia sign meddled by a WIMAX
OFDM motion keeping in mind the end goal to attain a great
concurrence and collaboration between these two.Jamal
Mountassir, Horia Balta, Marius Oltean, Maria Kovaci and
Alexandru Isar [7], Described WIMAX is a remote
engineering which offers high information rate transmission
in broadband. In this paper, the structural engineering of the
WIMAX physical layer test system is displayed. The
fundamental pieces are actualized with the help of the Matlab
programming dialect and the bit mistake rate (BER) bends are
displayed in Rayleigh blurring channel. Marius Oltean, Maria
Kovaci, Alexandru Isar, Jamal Mountassir, Petru Lazăr
[8],Explained a physical layer test system for the WIMAX
engineering is exhibited in this paper. The test system
incorporates the fundamental obstructs that manufacture the
physical layer from IEEE 802.16e. It permits to see a portion
of the physical layer instruments and systems utilized in
WIMAX and to reproduce different transmission situations.
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BER results are displayed for some appropriated stage plans,
with diverse advanced balances.Mukesh Patidar, Rupesh
Dubey, Nitin K.Jain,Sarita Kulpariya [9],Explained the
model building of the Wimax
physical layer using
simulink.This model is helpful for calculation of BER (bit
error rate) for the real time audio data communication by the
Wimax physical layer, under different channel encoding rate
and digital modulation schemes and channel conditions. In
this paper transmitter and receiver model are simulated to
evaluate the performance.Manal Al-bzoor, Khaled
Elleighy,[10] Proposed that
Wimax MAC layer and
PHYlayer that uses OFDM are discussed. The architecture is
explained in which Wimax uses PMP(point to
multipoint),mesh mode or the MMR(mobile multihop mode).
In this paper a discussion is made on Wimax technology PMP
and mesh deployments from main physical layer and MAC
layer features.Abdulrahman Yarali,Saifur Rahman,Bwanga
Mbula,[11],This paper explains Wimax and its applications in
higher generation wireless network. With the help of wireless
simulator tool a cellsite coverage simulation at different
frequencies is discussed. Also the marits and demerits of a
mobile Wimax network are presented.
III SYSTEM MODEL
PHY layer in Wi-Max:
The PHY layer in WIMAX depends on OFDMA, which
might be seen as an amplification of OFDM. The later is a
multi-transporter balance strategy that shows magnificent
power against the hindrances presented by the transmission
channel. An OFDM image is a whole of numerous orthogonal
transporters (the complex exponentials from connection 1),
regulated by the information images to be transmitted through
the channel (X[k]):
(1)
pT t is a sliding window of duration T which localizes the
signal on the time axis and gives the duration of an OFDM
symbol (T =1/Δf
in order to achieve subcarriers’
orthogonality). If the digital symbols to be transmitted (X[k])
came from different users, then OFDM transforms into
OFDMA. This requires perfect synchronization of the
framework, yet brings an extra measurement of numerous get
to as well. In this manner, separated from the time division
numerous access (all the transporters that make diverse
OFDM images may be committed to distinctive clients, on an
image by-image premise), a recurrence division various
access may be accomplished. This implies that, for the length
of time of a solitary OFDM image, the bearers may be
impacted by diverse clients, as indicated by the planning
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 11 - May 2014
made by the MAC layer. The vast majority of the
OFDM/OFDMA useful usages are focused around the
processing of the Inverse Fast Fourier Transform (IFFT) in
the modulator and of the immediate change in the
demodulator. This permits straightforward, indicator
preparing based usage of the multi-bearer regulation, taking
out the requirement for exorbitant oscillators required to
create the orthogonal transporters.
A bland structure of the PHY layer outline in TDD WIMAX
is demonstrated in fig. 1 [2]. The assets are allotted on a twodimensional,
time-recurrence
lattice:
sub-channels
(accumulations of subcarriers) are characterized on the y
pivot, while OFDM images are designated on the x hub. In
this manner, sub-channels speak to legitimate assets that may
be imparted around distinctive clients (fig. 2)[2]. Separated
from the zones that pass on information (blasts), some control
data areas (DLMAP, ULMAP, FCH and so on) are
characterized inside the edge. Moreover, a percentage of the
bearers don't transport any sort of framework data, being
utilized for unique purposes (pilot subcarriers- channel
estimation, watch subcarriers- at the edge of the band). The
subcarriers that form the sub-channels might be neighboring
in the physical range. This relies on upon the methodology
utilized to guide the physical assets (subcarriers) onto
coherent assets (sub-channel), handle that is alluded to as
stage [3]. A few stage sorts are characterized by the standard,
suited to distinctive purposes. FUSC (Fully Used Subchannelization) makes full use of the achievable recurrence
differing qualities: any accessible subcarrier inside the entire
range may be distributed to any sub-channel. PUSC (Partially
Used Sub-channelization) firstly parts the accessible
subcarriers in a few gatherings (fragments). The subcarriers
are then mapped to sub-channels inside every portion, freely.
This methodology is still arranged to recurrence differing
qualities, and permits a sort of "virtual sectorization": diverse
districts of the phone will compare to distinctive portions.
Fig.1 Wi-Max Radio Frame(TDD)
By facilitated arranging, the neighbor cells may utilize the
same recurrence band; the division permits decreasing the
obstruction. AMC (Adaptive Modulation and Coding) is the
name given to a contiguous stage: the subcarriers that form
the sub-directs are nearby in the range. This methodology
lessens the intricacy and is appropriate for the directs that
change gradually in time. Channel estimation is less
demanding (because of the way that the transporters are
neighboring), and thus the connection adjustment gets to be
easier too, which clarifies the name given to this change. The
base measure of assets that may be dispensed for a client is
called opening. The way that the opening is created fluctuates
for distinctive sorts of changes. Nonetheless, as a general
guideline, we may state that an opening is made out of one or
a few sub-channels (on the y hub, fig. 1) and one or a few
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OFDM images (on the x pivot, fig. 1). Besides, each of the
stage modes in WIMAX has its definition for a sub-channel.
There is likewise a distinction between allotment of the
information and pilot subcarriers in the sub-channel as for the
diverse conceivable stage modes. Subsequently, for DL
FUSC and PUSC, the pilot tones are apportioned first. The
remaining information subcarriers are partitioned into subchannel that is utilized solely for information. For UL PUSC,
the set of utilized subcarriers is initially apportioned into subchannel and afterward the pilot subcarriers are allotted from
inside each one sub-channel. Thus, in the FUSC mode, there
is one situated of regular pilot subcarriers, while in the uplink
PUSC mode; each one sub-channel holds its own particular
set of pilot subcarriers. For the downlink PUSC mode, there is
one situated of regular pilot subcarriers for each one
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 11 - May 2014
fragment. An illustration of physical layer consistent units
characterized in WIMAX for DL-PUSC is demonstrated in
fig.2[2].
[2] M. Nadeem khan, S. Ghauri. “The WIMAX 802.16e physical layer
model”, IET International conference on volume, 2008, pp 117-120, 2008.
[3] H. Balta, D. Bosneagu, M. Kovaci, M. Oltean "A Study of the
Permutation Schemes Used in the Mobile WIMAX", Acta Technical
Napocensis – Electronics and Telecommunications, pp.17-20, Volume 29,
Nr.3/2008.
[4] Xu Li, Zhan Xu, “A LDPC Encoding and Decoding Scheme of Low
Complexity Applied to Physical Layer 802.16e” International Conference on
Industrial Control and Electronics Engineering IEEE,2012.
[5] Quang Nguyen Duc, Lien Pham Hong, Tra Luu Thanh, “An Enhanced
Algorithm of Channel Estimation Based on Extended Kalman Filter for
Mobile WIMAX” International Conference on Control, Automation and
Information Sciences (ICCAIS) IEEE,2012.
Fig 2. Logical resources for DL-PUSC
A paramount venture of the PHY layer transforming is the
mistake insurance coding. This is connected to the idea of
AMC as well. Accordingly, clients with great radio conditions
may be booked to transmit with a large amount regulation
(e.g. 64 QAM) and with a high rate of coding. As channel
coding systems, a few alternatives are proposed by the
standard: convolutional coding, turbo-coding and LDPC
coding. Then again, the greater parts of the makers favor
convolutional Turbo codes (CTC) that attain a great exchange
off between intricacy and execution. The advanced balance
conspires that are proposed for WIMAX are QPSK, 16QAM
and 64QAM. In fusion with diverse coding rates, these
regulations create the tweak and coding profiles, utilized
within the AMC process.
IV CONCLUSION
In this paper a MATLAB based physical layer test system for
WIMAX is assessed. The test system permits a finer
understanding of the indicator transforming steps occurring at
the PHY layer relating to the IEEE 802.16e particulars.
Besides, it permits execution assessment in distinctive
situations, through BER reckoning. The viability of this
strategy was assessed utilizing machine reproduction. It has
been indicated through the enhanced BER execution that
mitigates the unfriendly time changing channel impedances
and diminishes the postponement impacts.
[6] Zouggari, N. Hakem, G.Y. Delisle, “Coexistence of OFDM systems for
underground communications” IEEE 2012.
[7] Jamal Mountassir, Horia Balta, Marius Oltean, Maria Kovaci and
Alexandru Isar, “A Physical Layer Simulator for WIMAX in Rayleigh
Fading Channel”
6th IEEE International Symposium on Applied
Computational Intelligence and Informatics Timisoara, Romania, May 19–
21, 2011.
[8] Marius Oltean, Maria Kovaci, Alexandru Isar, “A physical layer simulator
for WIMAX” IEEE 2010.
[9]
Mukesh
Patidar,
Rupesh
Dubey,
Nitin
K.Jain,Sarita
Kulpariya.“Performance Analysis of Wimax 802.16e Physical Layer
Model”.IEEE 2012.
[10] Manal Al-bzoor, Khaled Elleighy, “WIMAX Basics From PHY Layer
To Scheduling And Multicasting Approaches”IJCSES Feb 2011.
[11] Abdulrahman Yarali,Saifur Rahman,Bwanga Mbula, “Wimax: The
Innovative
Broad
Wireless
Access
Technology”.Journal
of
Communication,April 2008.
AUTHOR’S PROFILE
Megha Raghuwanshi is a research scholar and
pursuing M.-Tech with Digital communication
from Bhopal Institute of Technology, Bhopal,
affiliated to Rajiv Gandhi Technical University.
Her areas of research interest are WIMAX
SCOFDM.
REFERENCES
[1] IEEE 802.16-2004, “IEEE standard for local and Metropolitans Area
Network. Part-16; Air Interface for Fixes Broadband Wireless Access
Systems.” Rev. of IEEE 802.16-2001, pp 1-857, oct 2004.
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