259 research outputs found
WIMAX 802.16 PHYSICAL LAYER IMPLEMENTATION AND WIMAX COVERAGE AND PLANNING.
Over the last decade, the impact of wireless communication on the way we live and carry out business has been surpassed only by impact of the internet. But wireless communications is still in its infancy and the next stage of its development will be supplementing or replacing network infrastructure that was traditionally wired. The advent and adoption of the computer and the myriad software packages available for it offered the ability to generate a new wave of communication combining art, pictures, music and words into a targeted multimedia presentation. These presentations are large so that is requires higher bandwidth transmission facilities. Coupling this with the need for mobility, the solution would be wireless data delivery putting in consideration the bandwidth request. WiMAX technology is based on the IEEE 802.16 standard, it was only recently when the first IEEE 802.16 based equipment broadband began to enter the market. The additional spectrum, bandwidth and throughout capabilities of 802.16 will remarkably improve wireless data delivery and should allows even more wireless data service areas to be deployed economically. In this Final Year Project, a study about the IEEE 802.16 standard and mainly concentrate on the 802.16 PHY Layer behaviors was performed. A Simulink based model for the 802.16 PHY Layer was built for simulation and performance evaluation of WiMAX. MATLA
A survey of digital television broadcast transmission techniques
This paper is a survey of the transmission techniques used in digital television (TV) standards worldwide. With the increase in the demand for High-Definition (HD) TV, video-on-demand and mobile TV services, there was a real need for more bandwidth-efficient, flawless and crisp video quality, which motivated the migration from analogue to digital broadcasting. In this paper we present a brief history of the development of TV and then we survey the transmission technology used in different digital terrestrial, satellite, cable and mobile TV standards in different parts of the world. First, we present the Digital Video Broadcasting standards developed in Europe for terrestrial (DVB-T/T2), for satellite (DVB-S/S2), for cable (DVB-C) and for hand-held transmission (DVB-H). We then describe the Advanced Television System Committee standards developed in the USA both for terrestrial (ATSC) and for hand-held transmission (ATSC-M/H). We continue by describing the Integrated Services Digital Broadcasting standards developed in Japan for Terrestrial (ISDB-T) and Satellite (ISDB-S) transmission and then present the International System for Digital Television (ISDTV), which was developed in Brazil by adopteding the ISDB-T physical layer architecture. Following the ISDTV, we describe the Digital Terrestrial television Multimedia Broadcast (DTMB) standard developed in China. Finally, as a design example, we highlight the physical layer implementation of the DVB-T2 standar
WIMAX TESTBED
WiMAX, the Worldwide Interoperability for Microwave Access, is a
telecommunications technology aimed at providing wireless data over long distances
in a variety of ways, from point-to-point links to full mobile cellular type access. It is
based on the IEEE 802.16 standard, which is also called Wire IessMAN. The name
WiMAX was created by the WiMAX Forum, which was formed in June 2001 to
promote conformance 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. This Final Year Project attempts
to simulate via Simulink, the working mechanism of a WiMAX testbed that includes
a transmitter, channel and receiver. This undertaking will involve the baseband
physical radio link. Rayleigh channel model together with frequency and timing
offsets are introduced to the system and a blind receiver will attempt to correct these
offsets and provide channel equalization. The testbed will use the Double Sliding
Window for timing offset synchronization and the Schmid! & Cox algorithm for
Fractional Frequency Offset estimation. The Integer Frequency Offset
synchronization is achieved via correlation of the incoming preamble with its local
copy whereas Residual Carrier Fr~quency Offset is estimated using the L th extension
method. A linear Channel Estimator is added and combined with all the other blocks
to form the testbed. From the results, this testbed matches the standard requirements
for the BER when SNR is 18dB or higher. At these SNRs, the receiver side of the
testbed is successful in performing the required synchronization and obtaining the
same data sent. Sending data with SNR lower than 18dB compromises its
performance as the channel equalizer is non-linear. This project also takes the first
few steps of hardware implementation by using Real Time Workshop to convert the
Simulink model into C codes which run outside MATLAB. In addition, the Double
Sliding Window and Schmid! & Cox blocks are converted to Xilinx blocks and
proven to be working like their Simulink counterparts
Design of a simulation platform to test next generation of terrestrial DVB
Digital Terrestrial Television Broadcasting (DTTB) is a member of our daily life
routine, and nonetheless, according to new users’ necessities in the fields of
communications and leisure, new challenges are coming up. Moreover, the current Standard is not able to satisfy all the potential requirements.
For that reason, first of all, a review of the current Standard has been performed
within this work. Then, it has been identified the needing of developing a new
version of the standard, ready to support enhanced services, as for example
broadcasting transmissions to moving terminals or High Definition Television
(HDTV) transmissions, among others.
The main objective of this project is the design and development of a physical
layer simulator of the whole DVB-T standard, including both the complete transmission and reception procedures. The simulator has been developed in Matlab. A detailed description of the simulator both from a functional and an architectural point of view is included. The simulator is the base for testing any
possible modifications that may be included into the DVB-T2 future standard. In fact, several proposed enhancements have already been carried out and their performance has been evaluated. Specifically, the use of higher order modulation schemes, and the corresponding modifications in all the system
blocks, have been included and evaluated. Furthermore, the simulator will allow
testing other enhancements as the use of more efficient encoders and
interleavers, MIMO technologies, and so on.
A complete set of numerical results showing the performance of the different parts of the system, are presented in order to validate the correctness of the implementation and to evaluate both the current standard performance and the
proposed enhancements.
This work has been performed within the context of a project called FURIA,
which is a strategic research project funded by the Spanish Ministry of Industry, Tourism and Commerce. A brief description of this project and its consortium
has been also included herein, together with an introduction to the current situation of the DTTB in Spain (called TDT in Spanish)
Evaluation of Channel Coding in OFDM Systems
Channel coding plays a very important role in OFDM systems performance.
The structure of OFDM systems makes channel coding more effective in confronting
fading channels. Sometimes Coded OFDM is known as COFDM. The role of channel
coding in conjunction with frequency and time interleaving is to provide a link between
bits transmitted on separated carriers of the signal spectrum, in such a way that the
information conveyed by faded carriers can be reconstructed in the receiver. Frequency
selectivity, currently known to be a disadvantage, is then turned into an advantage that
can be called frequency diversity. Using Channel State Information (CSI), channel
coding can yield some additional gain. Channel state information is frequency response
of the channel or signal to noise ratio in each carrier.
This thesis analyzes OFDM system and the effect of channel coding in reducing BER.
Along with this soft decoding and decoding with CSI is also studied. Besides,
performance of convolutional codes Turbo codes in OFDM systems is compared and
compared. Besides, we compare the performance of convolution and turbo codes in
OFDM systems. The results have been validated through simulations.
This thesis also presents Space-Frequency Coded OFDM system consisting of two
transmitters and a single receiver. Simple Alamouti space time code is used. An Mary
PSK modulation is used to modulate the symbols across an OFDM channel. We also
proposed a variation of the scheme which tries to spread additional symbols across timefrequency
attempting to increase the rate of transmission without changing the type of
modulation employed or increasing the bandwidth. A Rayleigh frequency selective slow
fading channel is assumed through out the analysis. SER performance of the above
systems is carried out with emphasis on the modulation scheme and number of carriers
Design of a simulation platform to test next generation of terrestrial DVB
Digital Terrestrial Television Broadcasting (DTTB) is a member of our daily life
routine, and nonetheless, according to new users’ necessities in the fields of
communications and leisure, new challenges are coming up. Moreover, the current Standard is not able to satisfy all the potential requirements.
For that reason, first of all, a review of the current Standard has been performed
within this work. Then, it has been identified the needing of developing a new
version of the standard, ready to support enhanced services, as for example
broadcasting transmissions to moving terminals or High Definition Television
(HDTV) transmissions, among others.
The main objective of this project is the design and development of a physical
layer simulator of the whole DVB-T standard, including both the complete transmission and reception procedures. The simulator has been developed in Matlab. A detailed description of the simulator both from a functional and an architectural point of view is included. The simulator is the base for testing any
possible modifications that may be included into the DVB-T2 future standard. In fact, several proposed enhancements have already been carried out and their performance has been evaluated. Specifically, the use of higher order modulation schemes, and the corresponding modifications in all the system
blocks, have been included and evaluated. Furthermore, the simulator will allow
testing other enhancements as the use of more efficient encoders and
interleavers, MIMO technologies, and so on.
A complete set of numerical results showing the performance of the different parts of the system, are presented in order to validate the correctness of the implementation and to evaluate both the current standard performance and the
proposed enhancements.
This work has been performed within the context of a project called FURIA,
which is a strategic research project funded by the Spanish Ministry of Industry, Tourism and Commerce. A brief description of this project and its consortium
has been also included herein, together with an introduction to the current situation of the DTTB in Spain (called TDT in Spanish)
Development And Implementation Of Improved Coded OFDM System Using SDR Platform
he increasing demand for high speed wireless connectivity at low cost poses new
challenges for communication system designers, to implement solutions that increase
the data rate by utilizing the limited radio resources more efficiently at a low
additional complexity. Adaptive Coding and Modulation (ACM) exploits the
flexibility of channel coding and constellation in Orthogonal Frequency Division
Multiplexing (OFDM) to obtain higher data rates. This technique employs multiple
modulation and coding schemes to instantaneously adapt to the variations in the
channel Signal to Noise Ratio (SNR), thus maximizing the system throughput and
improving Bit Error Rate (BER) performance. On the other hand, OFDM system
suffers from inter-symbol interference (ISI), especially in mobile communication
environments. This problem may be tackled by increasing the individual symbol
duration for each subcarrier together with the use of guard time. Nevertheless, this
does not solve the problem completely in multipath fading channel, because all
subcarriers will arrive at the receiver with different amplitudes. Unfortunately, some
subcarriers may be completely lost because of deep fades. Hence even though most
subcarriers may be detected without errors, the overall BER will be largely
dominated by a few subcarriers with bad SNR. To eliminate this problem, OFDM
based systems usually employ a special technique like error correction coding
(ECC). Various coding methods are adopted by many standards to mitigate the
effects of frequency selective channel which causes bit errors to occur in bur
Design and development of mobile channel simulators using digital signal processing techniques
A mobile channel simulator can be constructed either in the time domain using a tapped delay line filter or in the frequency domain using the time variant transfer function of the channel. Transfer function modelling has many advantages over impulse response modelling. Although the transfer function channel model has been envisaged by several researchers as an alternative to the commonly employed tapped delay line model, so far it has not been implemented. In this work, channel simulators for single carrier and multicarrier OFDM system based on time variant transfer function of the channel have been designed and implemented using DSP techniques in SIMULINK. For a single carrier system, the simulator was based on Bello's transfer function channel model. Bello speculated that about 10Βτ(_MAX) frequency domain branches might result in a very good approximation of the channel (where в is the signal bandwidth and τ(_MAX) is the maximum excess delay of the multi-path channel). The simulation results showed that 10Bτ(_MAX) branches gave close agreement with the tapped delay line model(where Be is the coherence bandwidth). This number is π times higher than the previously speculated 10Bτ(_MAX).For multicarrier OFDM system, the simulator was based on the physical (PHY) layer standard for IEEE 802.16-2004 Wireless Metropolitan Area Network (WirelessMAN) and employed measured channel transfer functions at the 2.5 GHz and 3.5 GHz bands in the simulations. The channel was implemented in the frequency domain by carrying out point wise multiplication of the spectrum of OFDM time The simulator was employed to study BER performance of rate 1/2 and rate 3/4 coded systems with QPSK and 16-QAM constellations under a variety of measured channel transfer functions. The performance over the frequency selective channel mainly depended upon the frequency domain fading and the channel coding rate
WIMAX 802.16 PHYSICAL LAYER IMPLEMENTATION AND WIMAX COVERAGE AND PLANNING.
Over the last decade, the impact of wireless communication on the way we live and carry out business has been surpassed only by impact of the internet. But wireless communications is still in its infancy and the next stage of its development will be supplementing or replacing network infrastructure that was traditionally wired. The advent and adoption of the computer and the myriad software packages available for it offered the ability to generate a new wave of communication combining art, pictures, music and words into a targeted multimedia presentation. These presentations are large so that is requires higher bandwidth transmission facilities. Coupling this with the need for mobility, the solution would be wireless data delivery putting in consideration the bandwidth request. WiMAX technology is based on the IEEE 802.16 standard, it was only recently when the first IEEE 802.16 based equipment broadband began to enter the market. The additional spectrum, bandwidth and throughout capabilities of 802.16 will remarkably improve wireless data delivery and should allows even more wireless data service areas to be deployed economically. In this Final Year Project, a study about the IEEE 802.16 standard and mainly concentrate on the 802.16 PHY Layer behaviors was performed. A Simulink based model for the 802.16 PHY Layer was built for simulation and performance evaluation of WiMAX. MATLA
Recommended from our members
Performance evaluation of fixed WiMax physical layer under high fading channels
This thesis was submitted for the degree of Master of Philosophy and awarded by Brunel University.A radio channel characteristic modelling is essential in every network planning. This project deals with the performance of WiMax networks in an outdoor environment while using fading channel models. The radio channels characteristics are analyzed by simulations have been done using Matlab programming. Stanford University Interim(SUI) Channels set was proposed to simulate the fixed broadband wireless access channel environments where IEEE 802.16d is to be deployed. It has six channel models that are grouped into three categories according to three typical different outdoor Terrains, in order to give a comprehensive study of fading channels on the overall performance of the system, WiMax system has been tested under SUI channels that modified into account for 30o directional antennas, with 90% cell coverage and with 99.9% reliability in its geographical covered area. Furthermore, in order to combat the fading which occurs in urban areas and improve the capacity and the throughput of the system, multiples antennas at both ends of communication link are used, the transmission gain obtained when using multiple antennas instead of only a single antenna. Space-time coding and maximum ratio combining for more than one transmit and receive antenna is implemented to allow performance investigations in various MIMO scenarios. It has been concluded that uses multiple antennas at the receiver offers a significant improvement of 3 dB of gain in the channel SNR. This thesis also contain implementation of all compulsory features of the WiMax OFDM physical layer specified in IEEE 802.16-2004 using Matlab coding. In order to combat the temporal variations in quality on a multipath fading channel, an adaptive modulation technique is used. This technique employs multiple modulation schemes to instantaneously adapt to the variations in the channel SNR, thus maximizing the system throughput and improving BER performance. WiMax transceiver has been tested with and without encoding and studied the effect of encoding on multipath channel. Testing the system with flexible channel bandwidth has been part of this thesis. Finally it has been explained in this thesis the affect of increasing the size of cyclic prefix on overall performance of WiMax system
- …