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The Last decade saw significant growth in the digital terrestrial television (DTT) subscribers. The High peak-to-average power ratio (PAPR) of the transmitted signal is implied by the large fluctuations in its amplitude, which is a serious issue in the contemporary and next generation DTT broadcasting systems. These large fluctuations prevent feeding the high power amplifier (HPA) at an operating point near its non-linear (NL) saturation region, thereby lowering its power efficiency. For a better future, energy-efficient green communications is the need of hour. This paper focuses on digital predistortion (DPD), which is among the widely used techniques for HPA linearization in order to minimize the NL effects. DPD technique requires a feedback signal. This paper proposes a novel adding signal-based digital predistortion, where the output of the HPA is gradually linearized by adding a signal at the input in an iterative manner. By Taylor series approximation, the DPD problem can be posed as a convex one. We prove that a tighter upper bound exists for the convergence factor and instead of directly solving the convex problem, we pick a convergence factor value within its bounds that offers a good trade-off between convergence speed and residual error value. The simulation results show that the proposed technique can quickly linearize the HPA with good convergence. [ABSTRACT FROM AUTHOR]

This paper presents the research and implementation of a China Digital Radio (CDR) experimental network in Hubei, China with two FM-CDR transmitting stations and four FM-band channels. To study the coverage discontinuity problem in a large service area, the experimental network employs an intelligent networking solution that incorporates multiple service channels carrying Broadcast and Data Services (BADS) and a Common-Regional-Information Channel (CRIC) carrying both service data and system information. The electronic service guide (ESG) carried by CRIC can inform the receivers about the available contents from current and adjacent stations, which can significantly improve the service quality in the overlapping areas, especially under mobile reception environment. Two RF tuners are used in the receiving terminals to access the CRIC, and the BADS channel, respectively. This paper first presents the frequency analysis and coverage tests of the experimental network, and then summarizes the coverage performances with different transmission parameter combinations. The goal is to gain experience in frequency planning, coverage prediction, as well as supportable services of CDR digital audio broadcasting. [ABSTRACT FROM AUTHOR]

Terrestrial broadcast has traditionally targeted TV receivers in the home. But today’s most popular screens are those of SmartPhones and Tablet PCs. (Painful) Experience has shown that in order to reach those gadgets, IEEE- and 3GPP-specified solutions are required. Starting with TOoL+, the authors have proposed bridges between traditional broadcast and today’s wireless connectivity. Within the set of specifications of 3GPP such bridges named MBS, MBMS, and FeMBMS now exist – with limited acceptance by cellular network operators so far. The rapidly growing number of popular data services to SmartPhones, connected cars, etc., and 5G New Radio may change this in the future. Therefore, this paper presents a broadcast extension of today’s 5G New Radio supporting the implementation of High Tower High Power/Medium Power Medium Tower networks overlaying cellular networks. The extension was implemented using software defined radio and tested in a real-world field trial in Germany. [ABSTRACT FROM AUTHOR]

3GPP is now carrying forward the development of the point to multipoint transmission mode of 5G on the basis of the cellular infrastructure and standard. Since the dedicated proposal for multimedia broadcast multicast system (MBMS) was approved, the MBMS technologies are evolving with the update of the requirements from 3G to 5G. This paper reviews the latest progress during the evolved MBMS standardization, which focuses on the LTE-based 5G terrestrial broadcast mode. Some agreements in terms of two widely discussed topics during 3GPP meetings, cell acquisition subframe (CAS) enhancement and numerology refinement, are presented. The enhancement of CAS and the update of numerology aim to deal with the service outage issue in the case of covering large area and serving high-mobility users. To verify the improvement brought by the CAS enhancement and the new numerology, simulations from system level and link level are carried out by several organizations and the representative results are presented and analyzed in this paper. [ABSTRACT FROM AUTHOR]

In this paper, the ATSC 3.0 broadcast Radio Access Technology (RAT) is aligned with 3GPP 5G NR RAT in the context of 5G convergence starting in Release 16. The 5G system architecture release 16 includes a new 5G physical layer known as 5G NR “New Radio” and a “Cloud Native” 5G Core (5GC) using cloud computing. The 5GC is agnostic to the type of radio access technology used and is enabler of many types of convergence. A novel shared multi-tenant broadcast core network architecture designed to interwork with 5GC is discussed. With the 3GPP 5G NR unicast and Non-3GPP ATSC 3.0 broadcast synergistically aligned using methods of Release 16. This includes using 3GPP Access Traffic Steering, Switching, Splitting (ATSSS) and a multi-radio dual simultaneous connected User Equipment (UE). This aligns ATSC 3.0, the first forward looking (non-backward-compatible) native IP OFDM broadcast standard, with 3GPP LTE/5G unicast as a converged 5G vertical. The proposed method and architecture are orthogonal to LTE broadcast Release 16 and is synergistic to 5G NR mixed-mode multicast unicast in future. [ABSTRACT FROM AUTHOR]

High peak-to-average power ratio (PAPR) of the transmitted signal is a serious issue in multicarrier communication systems, such as second generation terrestrial digital video broadcasting (DVB-T2) systems. These large fluctuations prevent feeding the high power amplifier at an operating point near its non-linear saturation region thereby lowering its power efficiency. In recent years, tone reservation (TR) PAPR reduction techniques have been deeply studied and included in the DVB-T2 and the American digital video broadcasting (ATSC 3.0) specifications. It is based on a gradient iterative approach where, at each iteration, a predefined kernel is used to reduce one peak in time domain. In this paper, a novel TR PAPR reduction technique namely individual carrier allocation for multiple peaks (ICMPs) that is based on a new kernel signal is proposed. This algorithm, compatible with the DVB-T2 standard, offers better performance than the gradient-based DVB-T2 algorithm but suffers with increased complexity for higher modes of DVB-T2 and ATSC 3.0 as the number of required iterations is equal to the number of reserved tones. To overcome this issue, we propose an improved ICMP technique, called grouped ICMP defined with this new kernel. The main principle of this new algorithm consists in dividing the reserved tones into $G$ groups. This highly reduces the number of iterations, now equal to the number of groups, and thereby the latency. An in-depth performance analysis has been done by implementing our algorithm on a testbed platform with real power amplifiers. Both the simulation and experimental results demonstrated that the proposed PAPR reduction algorithm offers very good performance/complexity/latency tradeoff. [ABSTRACT FROM AUTHOR]

This paper addresses the challenge of broadcast and unicast convergence by proposing a PHY/MAC (Physical Layer/Medium Access Control) architecture for 5G New Radio (NR). The solution is based on Power domain Non Orthogonal Multiple Access (P-NOMA). The main PHY/MAC configuration parameters have been analyzed theoretically and their impact on the service configurations is presented in this manuscript. The system concept has been translated into a prototype model and different evaluation tests are presented. First, simulations show that the PHY layer performs better than Time Division Multiplexing/Frequency Division Multiplexing (TDM/FDM) choices of current broadband access systems. Second, performance tests using a network simulation tool are described. The results for capacity, latency and reliability demonstrate that the proposed solution offers an excellent broadcast/unicast convergence choice with significant gain values with respect to legacy PHY/MAC alternatives. [ABSTRACT FROM AUTHOR]

OFDM has been applied in a wide variety of wireless communications in recent years since it has the advantage over the conventional single-carrier modulation schemes when enduring the frequency-selective fading. However, intercarrier-interference (ICI) and interblock interference (IBI) due to the Doppler effect, carrier frequency drift of local oscillators and multipath fading limit the capability of OFDM systems. In this paper, a new generalized mathematical model for intercarrier and interblock interferences is derived for wireless mobile OFDM systems, in which Doppler frequency drift, local carrier frequency offset, multipath fading, and cyclic prefix coding are all present in reality. Such a new ICI/IBI model can be applied for OFDM performance evaluation in different environments. This new formulation of IBI and ICI provides a generalized framework which includes special ICI models appearing in the previous literature. Besides, the derived OFDM performance evaluation analysis in this paper can greatly benefit OFDM designers for wireless multimedia networks and digital video broadcasting technologies. [ABSTRACT FROM AUTHOR]

When adopting transmit diversity in the Chinese digital television terrestrial broadcasting (DTTB) system, there exists two kinds of interference: training sequences (TSs) from different transmit antennas are overlapped; and the TSs are interfered with OFDM data due to multipath fading. In order to distinguish different TSs, this paper proposes a method to design orthogonal TS set, which also have good correlation characteristic. Subsequently, an iterative algorithm to eliminate the interference between TSs and data is proposed and theoretically analyzed. Finally, simulations are performed and the results show that the system with the proposed scheme can achieve great diversity gain under acceptable computational complexity. [ABSTRACT FROM PUBLISHER]

The state-of-the-art time domain synchronous OFDM (TDS-OFDM) transmit diversity schemes are only suitable either for fast time-varying but weakly frequency-selective channels, or deeply frequency-selective but slowly time-varying channels. In this paper, a novel TDS-OFDM transmit diversity scheme based on the space-time shifted constant amplitude zero autocorrelation (CAZAC) sequence is proposed over doubly selective broadcasting channels. The space-shifted CAZAC sequence is used for the unbiased maximum likelihood (ML) channel estimation. The time-shifted sequence is utilized for the low-complexity cyclicity reconstruction of the received inverse discrete Fourier transform (IDFT) block. Compared with the existing solutions, the signal-to-noise ratio (SNR) gain of about 2.5 dB can be achieved by the proposed scheme at the uncoded bit error rate (BER) of 10^-2 over the deeply frequency-selective single frequency network (SFN) broadcasting channel when the receiver velocity is 140 km/h, at the cost of the spectral efficiency penalty of about 2.88%. [ABSTRACT FROM PUBLISHER]

After coarse synchronization in orthogonal frequency division multiplexing (OFDM) systems, there might still be a residual frequency offset (RFO) and a sampling clock frequency offset (SFO), which seriously degrade the performance of the systems. This paper suggests a simple way of estimating the SFO in OFDM-based digital radio mondiale (DRM) system. To demonstrate the efficiency of the proposed SFO estimator, comparisons are made with other existing estimators in terms of mean square error (MSE) performance, estimation range, and complexity. [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplexing (OFDM) systems are highly sensitive to carrier frequency offset and symbol timing error. This paper deals with estimation method of integer frequency offset (IFO) without the aid of pilot symbols. The proposed IFO estimator exploits two consecutive identical OFDM data symbols with only change of phase. In order to improve the accuracy of the IFO estimator, receive diversity is adopted. To demonstrate the efficiency of the proposed IFO estimators, comparisons are made with other existing estimators in terms of error performance, estimation range, and complexity. [ABSTRACT FROM AUTHOR]

In this paper, we propose a differential space-frequency block code—orthogonal frequency division multiplexing (DSFBC-OFDM) scheme as a multiple-input multiple-output (MIMO) transmission technique for next generation broadcasting system. A linear decoding method for DSFBC, which performs comparably to the ML decoding method, is derived for the cases of two or four transmit antennas. A simple table lookup method is proposed to improve the efficiency of the encoding/decoding process of DSFBC for the case of non-constant modulus constellations. This not only reduces the computational load, but also removes the necessity of channel estimation. Also, synchronization techniques with a DSFBC-encoded phase reference symbol (PRS) are discussed. Finally, an MIMO channel model for the next generation broadcasting system is developed by extending the 3GPP MIMO model to fit broadcasting environments. The MIMO channel model is then used to compare BER performances of differential space block code schemes for various channel environments. Simulation results show that the DSFBC-16QAM scheme using either four transmit antennas with one receive antenna or two transmit antennas with two receive antennas achieves a performance gain of 12 dB, with a data rate twice faster than that of the conventional DQPSK scheme. [ABSTRACT FROM AUTHOR]

The performance of the orthogonal frequency division multiplexing (OFDM) systems may be severely deteriorated when passing through wireless channels with the spectral nulls. Zero-Padding (ZP) for the OFDM signal guarantees the symbol recovery regardless of the channel spectral nulls if complicated ZP-OFDM-MMSE equalizer is used. In this paper we first establish a connection between ZP-OFDM and DFT codes and then two novel signal reconstruction schemes, signal projection and low-complexity signal reconstruction, are presented to deal with the spectral nulls based on the frames theory. The simulation results demonstrate that significant performance improvement can be achieved using our proposed methods over the so-called ZP-OFDM overlap and add (ZP-OFDM OLA) scheme. [ABSTRACT FROM AUTHOR]

It is well known that HPAs (High Power Amplifiers) are inherently nonlinear devices and many researches have focused on the predistortion for memoryless HPAs. However, memory effects of HPAs can no longer be ignored when communication systems have wider bandwidth. Memoryless predistortion techniques proposed previously seldom have satisfactory effectiveness for typical wideband applications such as OFDM (Orthogonal Frequency Division Multiplexing) systems. In this paper, an improved adaptive predistortion method called 2D LUT (2-dimension look-up table) with different accuracy levels is presented to linearize HPAs with memory effects. Simulation and experimental results show that 2D LUT implements excellent performance in mitigating the signal deterioration caused by memory effects, both rectifies the signal constellation distortion and suppresses the spectrum emission. Large scale matrix computation is also avoidable in these adaptive algorithms, which makes them feasible when a real-time system is necessary. [ABSTRACT FROM AUTHOR]

Transmit diversity can be applied to OFDM systems by adopting space time code. Since the received signal is the overlapped signals transmitted from different transmit antennas, channel estimation is a rather challenging task for space time coded OFDM (ST-OFDM) systems. Pilot structure can help the receiver to effectively separate the overlapped signals and perform accurate channel estimation. In this paper, we propose three different channel estimation algorithms based on specially designed comb type pilots inserted in frequency domain. One of our proposed algorithms is performed in frequency domain and the other two are performed in time domain. Such comb type pilot based algorithms can provide higher bandwidth efficiency than common significant-tap-catching algorithm using training block pilots. Numerical analyzes and computational simulation show that our proposed estimation schemes have the same good performance while the time domain methods have relatively simple structure. [ABSTRACT FROM AUTHOR]

This paper considers a problem of unwanted feedback interferences caused by coupling from the transmit antenna to the receive antenna in the digital video broadcasting-terrestrial (DVB-T) digital on-channel repeater (DOCR) system. We model the DVB-T DOCR system and propose a feedback interference cancellation method based on the linear minimum mean square error (LMMSE) estimation of the feedback interference channel. Since the accurate estimation of the feedback interference channel is an important factor that determines the performances of the feedback interference cancellation, the channel estimation by averaging the estimated channel and iterative decision feedback cancellation method are proposed. Simulation results of signal-to-noise ratio (SNR) relation between the reference SNR and the processed SNR are presented and the theoretical analysis is performed to verify the simulation results. The proposed methods are compared to the conventional method on the typical urban 6 channels with maximum Doppler frequencies of 0 Hz and 3 Hz in terms of SNR, bit error rate and various transmission modes in the DVB-T system. Simulation results and the theoretical results show that the proposed method outperforms the conventional method. [ABSTRACT FROM AUTHOR]

Digital on-channel repeater (DOCR) is regarded as a desirable solution to effectively build a wide-area network of mobile terrestrial-digital multimedia broadcasting (T-DMB) services. On the other hand, the DOCR mainly suffers from interference effects caused by a strong feedback signal and a time-varying channel dispersion. In this paper, we propose a novel DOCR for use in the T-DMB system in order to mitigate effectively both interference effects. First, we present an energy equalizer using the scarce pilot structure of T-DMB system to estimate a channel state information on every OFDM symbol. An optimum frequency domain channel estimation (FDCE) algorithm is then derived for the energy equalizer. In addition, a moving average filter (MAF) is employed to mitigate the phase distortion of truncated equalizer coefficients in deep null channel. Finally, in the performance evaluations, it is shown that the optimum FDCE outperforms a perfect FDCE. It is also shown that the DOCR equipped with the proposed interference cancellation can solve the problems caused by a limited channel information update, a phase distortion of the equalizer, and a residual feedback signal. [ABSTRACT FROM PUBLISHER]

In this paper, a super-imposed scheme for timing and frequency synchronization is proposed for orthogonal frequency division multiplexing (OFDM) systems. The proposed architecture includes a pre-defined pseudo-noise (PN) sequence, which is added to both the OFDM symbol and the cyclic prefix (CP) in time domain. In contrast to existing synchronization schemes, the proposed architecture has the advantage of better bandwidth utilization since it does not require extra pilot symbols. The peak-to-average power ratio (PAPR) is also significantly decreased. Both the timing and frequency offset estimators are derived using the maximum likelihood (ML) criterion. Efficiencies of the estimators are analyzed mathematically in AWGN channels. Simulation experiments are also conducted in frequency selective fading channels. Moreover, the optimal power allocation factor of the PN sequence is determined by minimizing the bit error rate using simulation experiments. [ABSTRACT FROM AUTHOR]

Intercarrier interference is deemed as one of the crucial problems in the wireless orthogonal frequency division multiplexing (OFDM) systems. The conventional ICI mitigation schemes involve the frequency-domain channel estimation or the additional coding, both of which require the spectral over- head and hence lead to the significant throughput reduction. Besides, the OFDM receivers using the ICI estimation rely on a large-dimensional matrix inverter with high computational complexity especially for many subcarriers such as digital video broadcasting (DVB) systems and wireless metropolitan-area net- works (WMAN). To the best of our knowledge, no semi-blind ICI equalization has been addressed in the existing literature. Thus, in this paper, we propose a novel semi-blind ICI equalization scheme using the joint multiple matrix diagonalization (JMMD) algorithm to greatly reduce the intercarrier interference in OFDM. However, the well-known phase and permutation indeterminacies emerge in all blind equalization schemes. Hence we also design a few OFDM pilot blocks and propose an iterative identification method to determine the corresponding phase and permutation variants in our semi-blind scheme. Our semi-blind ICI equalization algorithm integrating the, JMMD with the additional pilot-based iterative identification is very promising for the future high-throughput OFDM systems. Through Monte Carlo simulations, the QPSK-OFDM system with our proposed semi-blind ICI equalizer can achieve significantly better performance with symbol error rate reduction in several orders-of-magnitude. For the 16QAM-OFDM system, our scheme can also improve the performance over the plain OFDM system to some extent. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the performance of pilot-assisted least square (LS) and minimum mean squared error (MMSE) channel estimators for orthogonal frequency division multiplexing (OFDM) systems with transmit antenna diversity. We first provide a design of orthogonal pilot sequences to simplify the estimators. We then analyze the mean squared error (MSE) performance, and study the leakage effect. When a channel tap is not sample-spaced, our analysis shows that the power of the channel tap will leak to not only other taps of the same antenna, but also taps belonging to other antennas. The leakage across antennas is mainly determined by the phase separation between pilot sequences, which is further related to the ratio between the number of pilots and number of antennas. We demonstrate that the MSE performance can be improved if more pilots are used, or fewer channels are estimated simultaneously. [ABSTRACT FROM AUTHOR]

OFDM has been applied in the current wireless local-area networks and digital video broadcasting systems since it has the advantage over the conventional single-carrier modulation schemes when the frequency-selective fadings are present. Nevertheless, intercarrier-interference (ICI) due to Doppler frequency drift, phase offset, local oscillator frequency drift, and multipath fading will be a severe problem in OFDM systems. Previous ICI self-cancellation coding schemes can greatly reduce the ICI, but they are very sensitive to the phase ambiguity, which is due to the composite effect of the phase offset, the multipath fading and the local frequency drift. In this paper, the phase ambiguity and amplitude ambiguity problems in ICI self-cancellation coded OFDM receivers will be formulated and discussed. Then, a novel receiver which combines the current ICI self-cancellation coding techniques with a new expectation-maximizations-based joint phase/amplitude estimation and symbol detection scheme is proposed. The outstanding performance of this proposed scheme is shown and compared with other existing methods at different noise levels through OFDM simulations. [ABSTRACT FROM AUTHOR]

One of the major drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the transmitted OFDM signal. Partial transmit sequence (PTS) technique can improve the PAPR statistics of an OFDM signal. However optimum PTS (OPTS) technique requires an exhaustive search over all combinations of allowed phase factors, the search complexity increases exponentially with the number of sub-blocks. By combining sub-optimal PTS with a preset threshold, a novel reduced complexity PTS (RC-PTS) technique is presented to decrease the computational complexity. Numerical results show that the proposed approach can achieve better performance with lower computational complexity when compared to that of other PTS approaches. [ABSTRACT FROM AUTHOR]

A combination of orthogonal frequency division multiplexing (OFDM) with frequency-division multiple access (FDMA) called OFDMA is regarded as a promising solution for improving the performance of interactive wireless broadcasting systems. This work focuses on the performance of OFDM when used as a modulation and access technique for the uplink of an interactive wireless broadcasting system. In such an application, we present our investigations of the effects of symbol timing misalignments and peak-to-average power ratio (PAR). Under the condition of the same side information bits, the selective mapping (SLM) approach can be implemented by decimating OFDM samples, which is less complex compared to the ordinary SLM incurring a slight degradation of the PAR performance. Taking into account the effects of clipping operation and symbol timing misalignment, the bit error rate (BER) and throughput performances are investigated for a typical OFDMA uplink scenario. [ABSTRACT FROM AUTHOR]

We present the latest developments in the physical layer evolution for the transmission of Multimedia Broadcast Multicast Service (MBMS) over fifth generation (5G) cellular networks. We first provide an overview of how the MBMS physical layer has evolved during the initial releases of the Third Generation Partnership Project (3GPP) specifications and provide motivations and insights for key developments that have helped mature MBMS into a competitive broadcasting solution. We provide an overview of dedicated MBMS carriers for Multimedia Broadcast multicast service Single Frequency Network (MBSFN) transmission as well as Orthogonal Frequency Division Multiplexing (OFDM) numerologies with longer cyclic prefixes to support MBSFN transmission over large geographical areas with large distances between cooperating cell sites. Next, we describe the most recent enhancements to the MBMS physical layer, addressing advanced use cases in the recently completed release of the 3GPP specifications (Release 16). First, we describe the physical layer design for enabling MBSFN-based MBMS services for rooftop receivers with inter-site distances between cooperating cell sites as large as 125 km. In this realm, we demonstrate the need for an OFDM numerology with a 300-microsecond cyclic prefix to communicate effectively over channels with very large delay spreads. Next, we explain how support for high mobility up to 250 kmph was added to the standards by using an OFDM numerology that gracefully trades off inter-symbol interference due to large delay spreads and inter-carrier interference due to large doppler spreads to achieve better performance than existing numerologies at high speeds. Finally, we describe the enhancements that were made to the Cell Acquisition Subframe (CAS)—specifically, the introduction of larger aggregation levels for the Physical Downlink Control Channel (PDCCH) and the support of Physical Broadcast Channel (PBCH) repetitions—that significantly increase the coverage for the control and system information associated with MBMS that are carried by these subframes. [ABSTRACT FROM AUTHOR]

A novel Doppler frequency offset estimation method is proposed for the digital video broadcasting-terrestrial (DVB-T) system in the high-speed-train (HST) environment. Based on the analysis of the effect of the scattered components of the wireless channel on the accuracy of the Doppler frequency offset estimation, we separate the path with the Line-of-Sight(LOS) component from the multipath channel, and only use it to estimate the frequency offset caused by Doppler shift. Simulation results show that the mean square error (MSE) of the proposed scheme is far better than those of the available schemes. [ABSTRACT FROM AUTHOR]

Intercarrier interference (ICI) self-cancellation schemes were often employed in many OFDM systems as a simple and effective approach to suppress ICI caused by carrier frequency errors. The same procedure, however, can not perform very well at high frequency offsets. We propose a simple decision feedback scheme based on the general ICI self-cancellation scheme to perform estimation and tracking of the carrier frequency offsets. A system with the scheme does not consume additional bandwidth since it used the same data symbols employed for ICI cancellation for the estimation. After an initial estimation is completed, the scheme switches to the tracking mode to carry out the estimation of deviations in the frequency offsets. Finally this fine-tuned estimate is applied to the ICI self-cancellation scheme concurrently for frequency offset correction and hence improved the system performance greatly. Simulation results showed that our scheme allowed up to 9% of random variations in the frequency offset. The effectiveness of our scheme is further verified by calculating the bit error rate performance of various OFDM receivers. [ABSTRACT FROM AUTHOR]