DVB-T2

With the spectrum liberation obtained by the deployment of Digital Terrestrial Television (DTT) and the analog TV switch-off, new bands are being assigned to IMT Long Term Evolution (LTE). In the first cellular deployments in the digital dividend at the 800 MHz band, problems emerged due to the interference that cellular networks can cause to DTT signals. Possible solutions imply either an inefficient use of the spectrum (increasing the guard band and reducing the number of DTT channels) or a high cost (using anti-LTE filters for DTT receivers). The new spectrum allocated to mobile communications is the 700 MHz band, also known as second digital dividend. In this new IMT band, the LTE Uplink is placed in the lower part of the band. Hence, the ITU-R invited to perform several studies and reported the results to WRC-15. In this paper, we analyze the coexistence problem in the 700 MHz band and evaluate the interference of LTE signals into DTT services. Several coexistence scenarios have been considered and laboratory tests have been performed to measure interference protection ratios.

The DVB-S2 standard is the second generation of DVB-S European standard for satellite wave's digital broadcasting that introduced in 1995 and generated latest edition in 2008.DVB-T is the European standard for digital TV broadcasting. This system was used in British in 1997 for the first time. The next DVB-T standard has a higher flexibility for pictures broadcasting with HD resolution that it introduced whit DVB-T2 title. The advantage of these standards to former versions is having higher thirty percentage performance. In this project DVB-S2 and DVB-T2 standards are analyzed. For mentioned standards only sending part has standard protocol and design of the receiving parts respected to related individuals and designers. In this article the receiving parts of above standards are designed according to sending parts and the various parts of receiving section are analyzed. For this reason that one of the purposes of this project is building common platform for these two standards, the various parts of these two digital receivers divided to two common block and uncommon block according to their performance. The parts of common block have unique performance for two digital receivers. The parts of uncommon block have various performances for two digital receivers. According as flexibility is one of the other purposes of this project, the common block with ASIC chip and the uncommon block with DSP chip are designed. The respected system can perform the mentioned standards with above chips and SDR techniques. The new capability of this system is smart to perform the other standards. This technique with switching between ASIC/DSP and full DSP architecture will achieve. This system performs the updating capability for various standards. The other new technique in this architecture designing is respecting system control operations to general processor replace to other chips. For analyzing the designed architectures in this article,

TV digital semakin berkembang di Indonesia, Pemerintah juga telah memperluas area Uji Coba penyiaran TV digital terestrial penerimaan tetap tidak berbayar (free to air). Perkembangan dimulai sejak tahun 2009 hingga sekarang 2017. Era Uji Coba TV digital dengan standar DVB-T2 dimulai sejak 9 Juni 2016. Telah banyak perundangan yang ditetapkan berkaitan dengan peralihan TV analog ke TV digital, namun tidak semua peraturan berpihak adil kepada semua pihak, sehingga perlua adanya pengkajian ulang (judicial review) mengenai peraturan tersebut. Belum ditetapkannya Undang-Undang pengganti UU No. 32 Tahun 2002 menjadi sebuah kendala yang berarti dalam proses migrasi karena Undang-Undang Penyiaran merupakan dasar pelaksanaan Penyiaran. Selain kendala dalam landasan hukum, kendala lain yang berarti terdapat dalam proses sosialisasi dan distribusi set top box-nya.

Kata kunci – TV Digital; Roadmap; DVB-T2; Peraturan;

Perkembangan industri penyiaran di Indonesia telah memasuki era digitalisasi .  Dalam memasuki era digitalisasi, para penyedia jasa penyiaran mulai mengembangkan teknologi digital baik dari format konten program maupun dari teknologi penyiarannya. Dari segi konten program format HD(High Definition) menjadi pilihan untuk menyajikan kualitas gambar dan suara yang lebih baik dari format SD(Standar Definition). Sedangkan dari segi teknologi penyiaran , teknologi DVBT2 menjadi teknologi yang terus dikembangkan hingga saat ini.
Dari hasil kajian literatur beberapa jurnal, didapatkan sebuah fakta bahwa kombinasi setting parameter DVBT2 sangat berpengaruh dengan karakteristik penerimaan dan menentukan besar kecilnya datarate maksimal sebuah multiplexer yang dapat tergabung dalam system pemancar DVBT2. Penyedia jasa pelayanan penyiaran harus menentukan target pemirsa yang ingin diraih sehingga dapat menentukan setting kombinasi parameter yang tepat.
Metode yang diambil pada penelitian ini untuk memanajemen bandwidth sehingga mendapatkan nilai estimasi maksimal program atau channel yang tergabung pada multiplexer adalah metode Stat Mux open loop dan metode Stat Mux closed loop. Perbedaan Stat Mux open loop dengan metode closed loop adalah adanya parameter QM(Quality Metering) pada metode Stat Mux closed loop  yang menjadi standar kualitas video. Standar QM didapat dari hasil depth interview.
Dari hasil pengujian metode Stat Mux closed loop memiliki tingkat efisiensi bandwidth yang cukup tinggi, karena dapat mengalokasikan jumlah program sebanyak 2 kali lipat lebih banyak dibanding saat menggunakan metode Stat Mux open loop maupun saat tidak menggunakan manajemen bandwidth.

Kata Kunci: DVBT2, Video HD,  Stat Mux open loop, Stat Mux closed loop

Abstrak Siaran televisi digital pada saat ini tengah berkembang di Indonesia. Salah satu model transmisi yang digunakan dalam siaran televisi digital yaitu siaran terrestrial yang menggunakan antenna pada bagian penerima dan berfungsi sebagai penerima sinyal dari siaran televisi local. Pemerintah sudah menetapkan bahwa standart siaran di televisi Indonesia sudah wajib menggunakan DVB-T2. Menyambut implementasi standar tersebut diperlukan perangkat yang memenuhi standar tersebut. Salah satu permasalahan ang dihadapi adalah sulitnya memilih antenna yang baik untuk menerima siaran televisi digital ini. Pada tugas akhir ini akan membandingkan penggunaan antena monopole yang dipasang pada dalam ruangan (indoor) serta antena biquad yagi yang dipasang pada luar ruangan (outdoor) sebagai antena penerima sinyal siaran televisi digital. Hasil dari pengukuran pada skripsi ini menunjukkan pola radiasi dari antena monopole dan antena biquad yagi memiliki pola radiasi omnidireksional dan bidireksional dengan nilai VSWR pada antena monopole sebesar 1,53 sedangkan nilai VSWR pada antena biquad yagi sebesar 1,02. Kemudian dari segi pengukuran parameter DVB-T2 yaitu C/N dan sensitifitas input didapatkan hasil. Dari hasil tersebut, maka antena monopole dan antena biquad yagi yang lebih cocok untuk digunakan pada sisi penerima teknologi DVB-T2.

With the exception of some households that have been able to recycle their Yagi-Uda antennas (VHF, UHF or Dualband types) for reception of ATSC most North American households will continue to have television reception quality far below what the 8VSB signal transmission system is capable of achieving.

Historically : NTSC, PAL or SECAM fadeout events generally are "long duration" events due to the continuous wave nature of the traditional TV transmission signal.

These fadeout events were tolerable (or at least interesting) to the traditional analogue television viewer.

ATSC 8VSB fadeout events in the digital television era are generally catastrophic and random.

These fadeout events alienate less technically inclined television viewers, as the cause of reception failure is often not obvious.

Viewers in general expect digital television (regardless of how it is transmitted) to be more reliable than analogue television. This reliability has not yet been achieved.

Most 8VSB set top box decoders (as of the mid to late 2010s) only possess "2nd generation" adaptive reception chipsets.

These chipsets [and their associated receiver subsystems] have on average only adequate sensitivity to weak signals.

These receivers possess only a limited ability to cope with
instantaneous fade out events.

Longer duration fade out events are at best "coped with" generally with variable degrees of success.

The most up to date 3rd and 4th generation 8VSB adaptive reception chipsets often do not perform as optimally as their designers originally hoped.

There are a myriad of subtle (and gross) design and transmission issues that these receivers must cope with that are beyond the ability of a laboratory to simulate adequately.

Currently the ATSC HDTV viewer is left only with ongoing frustration.

Most 8VSB decoders uniformly fail to tell the viewer that the received signal is unhealthy before a link loss event.

Long duration fade events (as with analogue television) don't really happen with 8VSB as the digital television transmitters use 2/3rds to 1/3rd less power than their previous analogue relative.

Essentially, fractal antennas are the only way to make 8VSB HDTV reception reliable again, at the lowest possible cost to all parties involved.

Transisi televisi digital, juga disebut switchover digital (DSO), switch-off analog (ASO), migrasi digital, atau shutdown analog, adalah proses di mana teknologi penyiaran televisi analog yang lebih tua dikonversi ke dan digantikan oleh televisi digital. Dilakukan oleh masing-masing negara pada jadwal yang berbeda, ini terutama melibatkan konversi infrastruktur penyiaran televisi terestrial analog ke terestrial digital (DTT), manfaat utama adalah frekuensi ekstra pada spektrum radio dan biaya penyiaran yang lebih rendah, serta peningkatan kualitas menonton bagi konsumen.

Rotated constellation with Q-delay (RQD) is a new modulation scheme adopted by some wireless standards including the second generation of the digital video broadcasting for terrestrial (DVB-T2) system. This scheme offers significant improvement over unrotated modulation in terms of bit error rate (BER) performance due to its signal space diversity. In this paper, we present four novel computationally efficient demodulation schemes with hybrid soft-hard outputs used in hard demapping of data. The main idea is to take advantage of the unique projections the rotated cells have in the RQD system. The proposed schemes reduce the number of log likelihood ratio (LLR) computations. One proposed scheme gives the same BER performance as traditional LLR while reducing the computational complexity by 34% at SNR = 20 dB. Another scheme reduces the computations by 25% independent of the SNR level. The other two schemes offer a tradeoff between computational complexity and power efficiency.

Digital terrestrial television is a modern broadcasting technology that has permitted broadcasters to offer television service with excellent image and sound quality. Many countries have been assigned a new digital television standardization process and many studies are underway regarding digital multimedia broadcasting technology. This paper investigates the utilization of a coded cooperative multiple-input and multiple-output (MIMO) transmission scheme in modern digital broadcasting systems to achieve additional transmit diversity and coding gains. The main idea of this work is the implementation of a coded cooperative MIMO scheme based on a low-density parity check code. A coded cooperative transmission can obtain a robust forward error correction. In this way, it is possible to achieve more stable system performance and improved mobility for next generation handheld systems. In order to show the potential for practical implementation, the performance of the proposed method is evaluated on the basis of the Digital Video Broadcasting-Second Generation Terrestrial (DVB-T2) system. The simulation results show that the proposed scheme can be utilized for the development of future DVB broadcasting systems that should support high mobility handheld devices, such as the Digital Video Broadcasting–Next Generation Handheld (DVB–NGH) system.

Rotated constellation with Q-Delay (RQD) is an innovative scheme that appeared to give better performance compared to the traditional unrotated modulation. The bit error rate (BER) decreases due to the RQD scheme signal space diversity. The authors presented four novel computationally efficient demodulation schemes with hybrid soft-hard outputs in [1] that took advantage of the unique projections the rotated cells have in the RQD system. The Coded Modulation (CM) system can utilize the hybrid computationally efficient demodulation schemes for obtaining better results in terms of BER and computation complexity. One of the hybrid schemes was tested with Low Density Parity Check (LDPC) coder/decoder through two proposed hard to soft assigning algorithms (HSA). These algorithms assign estimated Log-Likelihood Ratio (LLR) values to the hard mapped bits, so that the LDPC decoder receives an all-soft stream. Numerical results show that HSA algorithms give better performance than the original all-soft stream at a moderate SNR range.

Universitas 17 Agustus 1945 Jakarta 1 syah.alam@uta45jakarta.ac.id, 2 ikhwanul.kholis@uta45jakarta.ac.id Abstrak Dalam paper ini dibahas tentang antena mikrostrip yang dirancang untuk aplikasi TV Digital (DVB T2) pada frekuensi kerja 586 MHz dengan menggunakan metode peripheral slits. Metode peripheral slits digunakan untuk membuat ukuran antena menjadi lebih kecil dan compact sehingga dapat digunakan untuk aplikasi TV Digital DVB T2 untuk kondisi dalam gedung (indoor). Antena yang didesain memiliki bentuk patch segiempat yang diberi beban beberapa slit untuk dapat membuat antena menjadi kecil. Bahan substrat yang digunakan pada perancangan antena ini adalah FR 4 Epoxy yang memiliki nilai konstanta dielektrik (єr) = 4,3 dengan ketebalan bahan (h) 1,53 mm. Dari hasil simulasi dengan bantuan perangkat lunak diperoleh nilai return loss-18,56 dB dengan nilai VSWR 1,269. Abstract This paper discussed about the microstrip antenna designed for the Digital TV (DVB T2) application at the working frequency of 586 MHz using peripheral slits. The peripheral slits method was used to make the antenna size smaller and compact so it could be used for the DVB T2 Digital TV applications in the building (indoor). The antenna design was a rectangular patch which was loaded with the multiple slit to make the antenna small. The substrate materials used in the design of this antenna was Epoxy FR 4 that had a dielectric constant values (єr) = 4.3 with the material thickness (h) of 1.53 mm. The result obtained from the simulation with the help of software was the return loss value of-18.56 dB and the VSWR value of 1.269. Penyiaran televisi digital merupakan suatu teknologi yang tidak dapat dihindari oleh negara-negara manapun di dunia. Perkembangan teknologi penyiaran televisi digital menjadi suatu tuntutan global dimana setiap negara telah dan sedang dalam proses menuju peralihan dari sistem penyiaran analog ke digital. Keuntungan implementasi penyiaran televisi digital, antara lain penerimaan gambar dan suara yang lebih tajam dan

Regulasi TV Digital sangat sulit untuk diterima pada penyiaran pertelevisian Indonesia, sehingga masyarakat sebagai konsumen masih sangat sedikit untuk dapat merasakan siaran TV Digital Free to Air. ITU-T menegaskan  siaran televisi analog di Indonesia untuk dapat beralih kedalam TV Digital karena keterbatasan bandwidth frekuensi. Kondisi lain adanya kurang kesiapan industri televisi dengan keterbatasan pada perangkat infrastruktur terrestrial sampai pembuat konten, sehingga perkembangan TV Digital diindonesia menjadi terhambat. Beberapa fitur yang telah ditawarkan dalam penyiaran TV Digital yang diantaranya yaitu EWS (Early Warning System) dirancang oleh BPPT untuk informasi bencana, juga EPG (Electronic Program Guide) sebagai informasi jadwal penayangan tidak begitu membuat masyarakat menjadi tertarik kepada aplikasi TV Digital..
MHEG (Multimedia Hybrid Expert Group) adalah salah satu fitur yang terus dikembangkan dengan pesat di Australia dan Europa. Platform ini dapat memberikan banyak informasi text secara gratis dari media interaksi antara penonton dengan remote TV pada aplikasi multitext. Selain itu Aplikasi MHEG ini dapat diimplementasikan pada platform smart phone android. Platform MHEG memiliki fleksibilitas yang sangat tinggi, dimana platform ini dapat terintegrasi dengan internet. Aplikasi data MHEG yang telah dikombinasikan dengan video audio akan membangun multimedia yang menarik. Multimedia pada gadget memiliki nilai pasar yang sangat cepat, oleh karena itu penelitian ini akan fokus kepada strategi untuk membangun platform MHEG standar DVB-T2 free to air dengan penerima mobile
Platform MHEG dapat menjadi sebuah startegi baru untuk dapat memberikan ketertarikan kepada konsumen. Selain akan memberikan nilai informasi yang sangat terupdate, selanjutnya akan memberikan banyak multimedia yang dapat digunakan secara interaktif. Strategi bisnis yang akan digunakan untuk mendukung adanya TV Digital ini menggunakan strategi blue ocean, dimana platform ini belum diimplementasikan sama sekali diindonesia. Sehingga platform ini menjadi sebuah strategi terbaru untuk dapat mempercepat perkembangan implementasi TV Digital standar DVB-T2. Selanjutnya  teknologi SFN yang harus diimplementasikan agar penerimaan siaran TV Digital secara free to air dapat digunakan juga untuk penerima mobile.
Kata kunci : MHEG, Aplikasi Mobile, DVB-T2

Background. Currently digital microwave radio relay links operating in centimeter bands and in the lower part of millimeter bands (3.4-40.5 GHz) are widely used in the leading countries to construct their telecommunication infrastructure. Taking into account the lack of spectrum in these frequency bands and growing necessity to transmit high-rate applications with the help of brand-new radio relay equipment of the world leading manufacturers of such equipment, tendency to operate in higher parts of millimeter bands is becoming more real and practicable. At the same time, the terahertz band (100-3000 GHz) which is not used at the present time (because of complexity of construction of radio relay equipment that could operate in this band) is also very perspective for introduction of the future radio relay equipment (for the reason of high information capacity of 100-3000 GHz band). The Research Telecommunication Institute of the National Technical University of Ukraine and the Institute of Electronics and Communications of the Ukrainian Academy of Science developed the prototype of the transceiver for operation in the lower part of the terahertz band (130-132 GHz band). For this reason there was a necessity to conduct research concerning operation of the prototype in 130-132 GHz band (that is to test quality of operation of separate blocks of transceiver by changing parameters of transmitting signals passing through it). Objective. The purpose of the research is the parameters variation of multichannel digital broadcasting TV signals based on DVB-C standard when TV signal is transmitted through the 130 GHz transceiver prototype. DVB-C standard has been chosen for this research to have opportunity to analyze signals with different modulation schemes (from QAM-64 to QAM-256), which allowed investigating the influence of certain prototype node parameters on the signal parameters that were transmitted through it Methods. To conduct the research the experimental installation has been constructed with several parts in it (transceiver, subsystem for generation of DVB-C television signals, subsystem for measurement of DVB-C television signal parameters). The research has been conducted in three stages using a step-by-step approach with application of one-channel, two-channel and three-channel signals of DVB-C standard. Results. Results of the research showed that the use of the transceiver (that has common heterodyne for transmitting and receiving parts) in the lower part of terahertz band (130 GHz) permits to transmit three TV broadcasting channels of DVB-C standard in 24 MHz bandwidth with transmission rate of 125 Mbit/s with high subjective quality of all TV programs. Conclusions. The results of the research demonstrated high quality of digital TV signals transmission by means of transceiver constructed for application in terahertz band (130-132 GHz). The reason for such conclusion is that harmonic distortions have not been observed and phase noise of heterodyne has not led to significant channel symbols distortion on signal constellation. The next step in future research will include the research of the quality of DVB-C signal transmission for cases when terahertz radio link is used and specific heterodynes are applied in transmitting and receiving parts of the transceiver prototype. In the future the transceiver can be used for construction of digital microwave radio relay links in terahertz band for transmission and reception of digital TV signals with high rate both for broadcasting and other applications such as Internet.

Orthogonal Frequency Division Multiplexing (OFDM) with pilot assisted channel estimation is widely applied in wireless communication systems due to its high rate transmission capability and its robustness to multi-path fading and delay. In this paper an improved channel estimation method for OFDM in second generation Digital Video Broadcasting for Terrestrial (DVB-T2) is presented based on a pilot arrangement in time-varying frequency-selective fading channels. A new method which is based on an improved Domain Transform Least Square Estimation method (DTLSE) and a Two Dimensional Interpolation method (2-DI) have been proposed. The proposed methods give a good BER performance compared to other considered methods .The estimation matrix size for obtaining Channel Impulse Response (CIR) depends only on the length of the channel not on the number of pilot subcarriers nor the size of OFDM symbol, it does not require knowledge of channel statistics and works for any pilot pattern. The Minimum Mean Squared Error (MMSE) channel estimation was considered as the reference method that gives the best BER performance but suffers from a high computational load. The proposed method is compared with the two other methods: the improved DTLSE and MMSE. The proposed method proves to give a reduction in complexity compared to the MMSE technique with a comparable performance but better than the DTLSE one.

Perkembangan industri penyiaran di Indonesia telah memasuki era digitalisasi. Dalam memasuki era digitalisasi, para penyedia jasa penyiaran mulai mengembangkan teknologi digital baik dari format konten program maupun dari teknologi penyiarannya. Dari segi konten program format HD(High Definition) menjadi pilihan untuk menyajikan kualitas gambar dan suara yang lebih baik dari format SD(Standar Definition). Sedangkan dari segi teknologi penyiaran , teknologi DVBT2 menjadi teknologi yang terus dikembangkan hingga saat ini. Metode yang diambil pada penelitian ini untuk memanajemen bandwidth sehingga mendapatkan nilai estimasi maksimal program atau channel yang tergabung pada multiplexer adalah metode Stat Mux open loop dan metode Stat Mux closed loop. Perbedaan Stat Mux open loop dengan metode closed loop adalah adanya parameter QM(Quality Metering) pada metode Stat Mux closed loop yang menjadi standar kualitas video. Standar QM didapat dari hasil depth interview. Dari hasil pengujian metode Stat Mux closed loop memiliki tingkat efisiensi bandwidth yang cukup tinggi, karena dapat mengalokasikan jumlah program sebanyak 2 kali lipat lebih banyak dibanding saat menggunakan metode Stat Mux open loop maupun saat tidak menggunakan manajemen bandwidth. Kata Kunci: DVBT2, Video HD, Stat Mux open loop, Stat Mux closed loop.

Kata Kunci: DVBT2, Video HD,  Stat Mux open loop, Stat Mux closed loop

In this paper, we present a flexible architecture for an LDPC decoder that fully exploits the structure of the codes defined in the DVB-T2 standard (Digital Video Broadcasting - Second Generation Terrestrial). We propose a processor and memory architecture which uses the flooding schedule and has no memory access conflicts, which are encountered in serial schedule decoders proposed in the literature. Thus, unlike previous works, we do not require any extra logic or ad hoc designs to resolve memory conflicts. Despite the typically slower convergence of flooding schedule compared to serial schedule decoders, our ar- chitecture meets the throughput and BER requirements specified in the DVB-T2 standard.
Our design allows a trade-off between memory size and performance by the selection of the number of bits per message without affecting the general memory arrangement. Besides, our architecture is not algorithm specific: any check-node message processing algorithm can be used (Sum-Product, Min-Sum, etc.) without modifying the basic architecture. Furthermore, by simply adding relevant small ROM tables, we get a decoder that is fully compatible with all three second generation DVB standards (DVB-T2, DVB-S2 and DVB-C2). We present simulation results to demonstrate the viability of our solution both functionally and in terms of the bit-error rate performance. We also discuss the memory requirements and the throughput of the architecture, and present preliminary synthesis results in CMOS 130nm technology.

DVB-T2 (Digital Video Broadcasting Terrestrial Second Generation) reception requires a sufficient quality of the received signal. CNR (carrier-to-noise ratio) and BER (bit-error-rate) are two of quantities describing the quality. This paper presents the range of each quantity providing a successful reception based on real data obtained by field-measurements. This data was collected from MO (mobile-outdoor) and SI (stationary-indoor) receiving-systems capturing signal sent by some on-air trial transmitters broadcasting services focused on the fixed-receivers. The result indicated that the successful and failed receptions were split into two quite separated (concentrated) ranges of post-decoded BER and therefore a boundary distinguishing them could be prominently defined. In contrast, they were spread in a wide common range of CNR and pre-decoded BER. Furthermore, the boundary that corresponded to this last quantity was ambiguous. In the case of MO reception as numerical examples, the two split ranges of post-decoded BER were less than about 10 5 and more than about 2.7 × 10 4 for the successful and failed receptions, respectively, whereas CNR as high as about 14 dB could be viewed as a soft boundary distinguishing these both reception-success conditions. 1. INTRODUCTION The performance of a communication system can be evaluated from the quality of the received signal. Two quantities commonly used to describe the quality are CNR and SNR (signal-to-noise ratio). In digital communication systems, some of other describing quantities are BER [1],[2], SER (symbol-error rate) [2], and MER (modulation-error-ratio). Therefore, these quantities are also used to describe the digital television (DTV) received signal quality [3]-[5]. As one of DTV standards [6], DVB-T2 [7],[8] has adopted in many countries. Improving the reception-quality can be carried-out by several schemes, such as by implementing a MISO (multiple-input single-output) technique [9] at the transmitting-side, deploying a SFN (single-frequency-network) [10],[11] or OCR (on-channel repeater) [12],[13] in the network segment, or employing a multiple-antenna (MA) method [14],[15] at the receiving-end. Several field-measurements and field-trials of DVB-T2 have also been carried-out [16]-[21]. Based on the obtained data, the required SNR threshold [19] and minimum CNR [16] are estimated, by referring to the FBER (frame block error rate) and QEF (quasi error-free) criteria, respectively. By defining the successful reception as a condition when the receiver produces a moving picture, then the relationship of either CNR or BER and reception-success is probabilistic, not deterministic [20],[21]. However, the range of either CNR or BER providing a successful

Orthogonal Frequency Division Multiplexing (OFDM) with pilot symbol assisted channel estimation is a well-known multicarrier technique for high rate transmission over wireless frequency selective fading channels. In this paper a comparative study of channel estimation techniques is presented based on a pilot arrangement used in the second generation for Digital Video Broadcasting Terrestrial (DVB-T2) system in time-varying frequency-selective fading channels. A modified method based on Domain Transform Least Square Estimation (DTLSE) has been proposed which reduces the computational complexity by avoiding the use of the matrix inversion .The estimation matrix size for obtaining Channel Impulse Response (CIR) depends only on the length of the channel not on the number of pilot subcarriers nor the size of OFDM symbol. Two Dimensional Linear Interpolation (2-DLI) is discussed which performs better than one Dimensional Linear Interpolation (1-DLI)but suffers from long processing delay and higher sensitivity to Doppler frequency shifts. The Minimum Mean Squared Error (MMSE) channel estimation is also considered as a reference method because it has a good performance close to the perfect estimation at the cost ofhigh computational complexity and the necessity of prior knowledge ofchannel statistics. The proposed method is compared with three other methods DTLSE, 2-DLI and MMSE.The proposed method provesto give a better performance compared to the other methods which suffer from either a much higher computational load or less robustness to Doppler shifts.

Среды распространения радиосигналов систем радиосвязи содержат в себе неоднородные локальные области малых размеров, которые приводят к поглощению энергии радиоволн во времени. Такие физические процессы изменяется в зависимости от частоты, поляризационных характеристик и пространственных координат радиоволн. На радиоволны в их средах распространения кроме мультипликативных помех действуют также аддитивные помехи, создаваемые различными источниками электромагнитного излучения.

In this paper we present effective means of digital image transmission by means of Forward Error Correcting (FEC) schemes and Orthogonal Frequency Division Multiplexing (OFDM). The transmission was simulated over the AWGN and a Rayleigh fading channel whose power delay profile was adopted from the ITU channel model. The FEC and OFDM parameters were adopted from the DVB-T, WiMAX, and DVB-T2 standards. The results presented herein are in terms of BER, PSNR and visual performances. It is evident from the presented results that effective FEC schemes are necessary for reliable transmission of digital media in a mobile wireless scenario.