Digital Terrestrial Television Broadcasting Research Articles

On the Interaction Between Joint Tx/Rx IQI and Channel Estimation Errors in DVB-T Systems

Digital video broadcasting terrestrial (DVB-T) systems use hierarchical modulation, which involve a “high-priority” and a “low-priority” (LP) bit stream. An inherent weakness of this scheme is the severe performance degradation of the less protected LP stream. In addition, the presence of inphase quadrature imbalance (IQI) at both transmitter/receiver front end may significantly reduce the detection accuracy. Here, we propose an improved receiver design for OFDM-based DVB-T systems confronting the effects of both imperfect channel estimation and IQI. First , we propose a specific pilot-symbol arrangement inside the OFDM symbol that facilitates derivation of the posterior distribution of the perfect channel conditioned on its maximum-likelihood (ML) estimate. The latter posterior distribution plays an important role toward an improved receiver design for taking into account channel estimation errors in the presence of IQI at the receiver side. Second , we derive the formulation of an improved and efficient detector under channel estimation errors when IQI is also present only at the receiver side. Third , we generalize our proposed improved detector for the case where IQI is present at both transmitter and receiver sides. The proposed approach is able to reduce the impact of channel uncertainty on the receiver's performance in the presence of IQI. Our results are compared to those achieved by the conventional mismatched ML detector, which uses the imperfect channel as perfect channel and to those obtained by the detector based on the expectation-maximization algorithm. Numerical results over a realistic COST 207 channel model show that significant performance improvement is achieved for bit error rate of the LP stream in the considered DVB-T system.

New technique combining the Tone Reservation method with Clipping technique to reduce the Peak-to-Average Power Ratio

Nonlinear distortions and impairments appear in multicarrier signal with high fluctuations when amplified by a Radio Frequency Power Amplifier (RF PA). Clipping (CL) technique offers a simple way to reduce these fluctuations in Orthogonal Frequency Division Multiplexing (OFDM) Technique, but may degrade seriously the transmission quality. This is why the new mobile standards propose other methods, like the Tone Reservation (TR) technique in the Digital Video Broadcasting-Terrestrial (DVB-T), that reduce the Peak-to-Average Power Ratio (PAPR) without reaching optimal performances. This paper deals with how we can use the TR technique, which exploits null sub-carriers for generating corrective signal, in combining to CL technique in order to improve PAPR reduction without data loss. Also, we show some comparison results on the PAPR reduction obtained with proposed scheme and other techniques. Experiments using a simulated example on a complete WiMax 802.16e transmitter have been made in order to investigate the PAPR reduction performances on presence of the non-linear Power Amplifier model based on gain compression response and phase distortion.

A Critical Review of Digital Terrestrial Television Broadcasting in Nigeria

The digitization of analog broadcasting signal has brought a significant change in the broadcasting environment today. This means introducing a new way to transmit content, a new and improved mechanism that will provide better reception and increase user satisfaction. This work has taken into account the technical aspect of concerned with digital terrestrial broadcasting, it's evolution, prospects and challenges in Nigeria. Findings show that the future is bright if the challenges such as power, government policies are addressed. Government participation and proper policy management are also key to sustaining the digitization process.

Improved Detection Performance for Passive Radars Exploiting Known Communication Signal Form

In this paper, we address the problem of target detection in passive multiple-input-multiple-output (MIMO) radar networks. A generalized likelihood ratio test is derived, assuming prior knowledge of the signal format used in the non-cooperative transmit stations. We consider scenarios in which the unknown transmitted signal uses either a linear digital modulation scheme or the Orthogonal Frequency-Division Multiplexing (OFDM) modulation scheme. These digital modulation schemes are used in popular standards including Code-Division Multiple Access (CDMA), Digital Video Broadcasting-Terrestrial (DVB-T) and Long Term Evaluation (LTE). The performance of the generalized likelihood ratio test in the known signal format case is often significantly more favorable when compared to the case that does not exploit this information. Further, the performance improves with increasing number of samples per symbol and, for a sufficiently large number of samples per symbol, the performance closely approximates that of an active radar with a known transmitted signal.

Passive bistatic radar using digital video broadcasting-terrestrial receivers as general-purpose software-defined radio receivers.

We investigate the use of low-cost digital video broadcasting-terrestrial (DVB-T) receivers as general-purpose software-defined radio (SDR) receivers for passive bistatic radar (PBR) applications. Two DVB-T receivers are synchronized using a common clock to perform coherent measurements. By exploiting the direct-path signal in the surveillance channel, we use the cross-correlation process to estimate the time offset between the data streams of reference and surveillance channels caused by the universal serial bus communication. We demonstrate the detection of static and moving targets as well as short-range targets, including a landing airplane at 8 km, multiple ships with different velocities, and vehicles within 20 m from the receiver acquiring at a 2 MHz bandwidth, by using Japan's Integrated Services Digital Broadcasting Terrestrial digital TeleVision (TV) signal broadcast. We also propose to improve the range resolution of the designed PBR system by combining multiple SDR receivers tuned to different carrier frequencies. The designed system and proposed method can be used for various applications, such as airplane navigation, harbor protection, and traffic density monitoring.

Quasi-Optimal Tone Reservation PAPR Reduction Algorithm for Next Generation Broadcasting Systems: A Performance/Complexity/Latency Tradeoff With Testbed Implementation

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.

Optimal LTE-Protected LPDA Design for DVB-T Reception Using Particle Swarm Optimization With Velocity Mutation

A near-optimal design of a log-periodic dipole array (LPDA), suitable for digital video broadcasting-terrestrial (DVB-T) reception (470–790 MHz), is presented. The LPDA is required to provide low standing wave ratio as well as high-gain radiation pattern with sufficient gain flatness over the entire passband, and concurrently achieve low gain for frequencies above 800 MHz to reject LTE800 signals and thus improve the reception quality in the DVB-T band. All the above requirements are better satisfied by applying a novel particle swarm optimization (PSO) variant, called PSO with velocity mutation (PSOvm). PSOvm induces mutation on the velocities of those particles, which are unable to improve their fitness. As shown in this paper, PSOvm comes closer to the above requirements compared to four well-known optimization methods and outperforms the traditional LPDA design method proposed by Carrel. The LPDA geometry chosen for optimization is not the conventional one, and therefore the dipoles are not considered to be included inside a specified angle as proposed by Carrel. Thus, the dipole lengths and distances as well as the boom dimensions are independently optimized. The PSOvm-based LPDA sufficiently meets all the above requirements and thus is suitable for DVB-T reception without the use of an external LTE-band rejection filter.

Range-Doppler Fast Block LMS algorithm for a DVB-T-based Passive Bistatic Radar

In this paper, we propose a novel algorithm based on fast block LMS (least mean square) adaptive filter, called RD-FBLMS (range-Doppler fast block LMS) for direct path and multipath interferences cancellation in DVB-T (digital video broadcasting—terrestrial) passive bistatic radars (PBRs). These interferences represent some of the major problems in PBR systems, generated by signals received from the illuminator of opportunity and their multiple reflections through the surveillance channel, which is only dedicated to receive targets echoes. It is known that classical adaptive filtering can only be used for cancellation of zero Doppler interferences. Based on successive reference signal modulations and suppressions of nonzero Doppler multipath interferences, the RD-FBLMS algorithm exhibits a faster convergence rate, a shorter processing time and a better cross-ambiguity function than well-known existing algorithms.

Generalized Spatial Modulation-Based Multi-User and Signal Detection Scheme for Terrestrial Return Channel With NOMA

The terrestrial return channel provides interactive services in digital television terrestrial broadcasting systems to meet various consumers’ demands around the world. The extension of non-orthogonal multiple access and generalized spatial modulation multiple-input multiple-output to the terrestrial return channel improves both the spectral and energy efficiencies of the system, but it puts forward detection challenges. In this paper, a joint user activity and signal detection scheme based on the block-sparse compressive sensing (BS-CS) method in the terrestrial return channel is proposed, in which the generalized spatial modulation technology is used. By exploiting the structure and sparsity of the multi-user generalized spatial modulation signal, we formulate the detection problem into a block-sparse recovery problem. Then a BS-CS-based detection algorithm, enhanced structured block-sparse compressive sampling matching pursuit (ESB-CoSaMP), is proposed to detect the active users and transmitted data efficiently. Moreover, the information of active antennas at each user is exploited in ESB-CoSaMP to further improve the accuracy. Simulations show that the proposed detection scheme outperforms the conventional CS and BS-CS-based schemes.

Power optimization of LTE-800 and coexistence with DVB-T services

The emergence of cognitive radio technologies and the reallocation of the upper Ultra High Frequency (UHF) band (790−862 MHz) for broadband services has led to interference concerns for the DVB-T (Digital Video Broadcasting-Terrestrial) services. The DVB-T receivers need to be protected from aggregate interference coming from in-band and out-of-band transmissions, especially from the LTE-800 (Long-Term Evolution at 800 MHz) networks due to the operation in near spectral and location proximity. Although operating in different, but neighboring bands, the LTE-800 networks can be a serious threat to the DVB-T services due to excessive aggregate out-of-band interference caused to the DVB-T receivers. The regulators have assessed and defined the protection criteria for these cases. The power optimization of the LTE cellular networks, operating in near one spectral reuse factor, also remains an open issue due to the non-convex optimization problems. This paper proposes a novel algorithm for LTE-800 power allocation algorithm for capacity maximization of an LTE-800 network under DVB-T protection criteria. The algorithm uses k-means clustering to find the most critical geographical areas based on the DVB-T receivers protection ratios. It also adapts a local D.C. (Difference of two Convex functions/sets) programming approach to make the power optimization problem convex and perform the LTE-800 coverage and capacity optimization. The simulation analysis of the algorithm include realistic data for DVB-T modeling and Poisson Point Process for LTE-800 base stations (BS) spatial modeling. The proposed algorithm is compared to two extreme approaches, i.e. the max LTE BS power approach totally ignoring the DVB-T protection and the uniform power scaling approach that certainly protects the DVB-T service. The results prove the performance increase introduced by the proposed algorithm in terms of spatial capacity and coverage and DVB-T service protection.

Spectral Overlap Optimization for DVB-T2 and LTE Coexistence

In this paper, we analyze the spectral coexistence between the second generation terrestrial digital video broadcasting (DVB) and the long term evolution (LTE) networks. In particular, the global spectral efficiency (SE) of both systems is investigated when a partial spectral overlap between DVB and LTE signals occurs. Our contribution lies in twofold: 1) the interfering signal variance in each network is derived analytically according to the frequency overlap while taking into account the difference between the characteristics of LTE and DVB networks, especially the OFDM subcarrier spacing and then the OFDM symbol duration and 2) SE is derived with uniform and non uniform power allocation between overlapped and non overlapped subcarriers of the two networks. This derivation offers an analytical evaluation of the effect of the spectral overlap ratio variation and different power allocation scenarios and provides insightful results on the cooperation between the two networks.

Spatial Interpolation of Cyclostationary Test Statistics in Cognitive Radio Networks: Methods and Field Measurements

The focus of this paper is on evaluating different spatial interpolation methods for the construction of radio environment map using field measurements obtained by cyclostationary-based mobile sensors. Mobile sensing devices employing cyclostationary detectors provide lot of advantages compared to the widely used energy detectors, such as robustness to noise uncertainty and ability to distinguish among different primary user signals. However, mobile sensing results are not available at locations between the sensors making it difficult for a secondary user (possibly without a spectrum sensor) to decide whether to use primary user resources at that location. To overcome this, spatial interpolation of test statistics measured at limited number of locations can be carried out to create a channel occupancy map at unmeasured locations between the sensors. For this purpose, different spatial interpolation techniques for the cyclostationary test statistic have been employed in this paper such as inverse distance weighting, ordinary kriging, and universal kriging. The effectiveness of these methods is demonstrated by applying them on extensive real-world field measurement data obtained by mobile-phone-compliant spectrum sensors. The field measurements were carried out using four mobile spectrum sensors measuring eight digital video broadcasting-terrestrial (DVB-T) channels at more than hundred locations encompassing roughly one-third of the area of the city of Espoo in Finland. The accuracy of the spatial interpolation results based on the field measurements is determined using the cross-validation approach with the widely used root mean square error as the metric. Field measurement results indicate that reliable results with spatial coverage can be achieved using kriging for cyclostationary based test statistics. Comparison of spatial interpolation results of cyclostationary test statistics is also carried out with those of energy values obtained during the measurement campaign in the form of received signal strength indicator. Comparison results clearly show the performance improvement and robustness obtained using cyclostationary based detectors instead of energy detectors.

地上デジタル放送波を利用した高精度かつ高安定な発振器の製作

地上デジタル放送波を利用した高精度かつ高安定な発振器の製作

An Improvement of the Error Correction Capability of the Digital Terrestrial Television Broadcasting Receiver

An Improvement of the Error Correction Capability of the Digital Terrestrial Television Broadcasting Receiver

Elevation Pattern Analysis of Common Passive Bistatic Radar Illuminators of Opportunity

In this paper, the elevation coverage of common passive radar illuminators of opportunity is evaluated. In constructing radar performance metrics, it is imperative to include the radiation characteristics of the source, both in azimuth and elevation. Many passive radar performance studies have considered only one plane, the azimuth, neglecting to incorporate the elevation plane in models. The noninclusion of elevation patterns has primarily been due to lack of precise detail of their specification and nature. The authors have consulted the broadcast antenna manufacturing industry and present here transmitter elevation patterns for the three prevalent passive radar illuminators of opportunity: frequency modulation radio, digital audio broadcast, and digital video broadcast terrestrial. The patterns presented are typical of broadcast patterns in use throughout the world. The patterns have already been used by a number of national research institutes for more accurate passive radar system modeling. Simulations will show that airborne targets frequently reside outside of the elevation main lobe, which has direct consequences for target detection performance.

Parasitic effects of the metallic towers on the characteristics of the broadcast antennas

In this article, we use a tool NEC (Numerical Electromagnetic Code) to model antenna on top of a tower structure. Simulation results for the parasitic effect of the tower on characteristics of broadcast DVB-T (Digital Video Broadcasting Terrestrial) antenna such as input impedance, return loss, gain, front-to-back ratio and radiation patterns are reported. In addition, the effect of a nearby tower on antenna characteristics is studied. A 3D tower and broadband antenna in the UHF (470-862) MHz band are constructed. The antenna works for both digital and analog TV with return loss (RL) ≥ 10 dB, fractional bandwidth of 87% and gain of 12.3 dBi at center frequency. The effective radiated power is calculated by mounting the antenna at each face of the tower to give a satisfactory coverage to a region around the antenna.

PAPR effect remedy in OFDM-based wireless systems

An enhancement proposition for a Terrestrial Digital Video Broadcasting (DVB-T) systems is discussed in this work. DVB-T physical layer uses a powerful technique namely Orthogonal Frequency Division Multiplexing (OFDM) technique, which has been used to combat the channel’s effect. However, it has a major drawback that degrades its efficiency; namely Peak-to-Average Power Ratio (PAPR). Two criteria have been used for this purpose; BER curves and CCDF curves in order to distinguish the powerfulness of those propositions in reducing the PAPR effect. In fact, a powerful special averaging technique results are compared to previously published propositions, namely based on wavelet transformations and the one that is based on the pulse width modulation. A mathematical model has been drawn in order to check both of the CCDF and the BER curves, and simulated at same channel limitations and specifications. The proposition gives extra 35% noise immunity over our previously published work that is based on entropy wavelet, and an enhancement of over 25% from the CCDF point of view in combatting the PAPR. Furthermore, a complexity reduction has been attained by decreasing the side information transmission in compared with the work in the literature.

Wireless Technology Recognition Based on RSSI Distribution at Sub-Nyquist Sampling Rate for Constrained Devices.

Driven by the fast growth of wireless communication, the trend of sharing spectrum among heterogeneous technologies becomes increasingly dominant. Identifying concurrent technologies is an important step towards efficient spectrum sharing. However, due to the complexity of recognition algorithms and the strict condition of sampling speed, communication systems capable of recognizing signals other than their own type are extremely rare. This work proves that multi-model distribution of the received signal strength indicator (RSSI) is related to the signals’ modulation schemes and medium access mechanisms, and RSSI from different technologies may exhibit highly distinctive features. A distinction is made between technologies with a streaming or a non-streaming property, and appropriate feature spaces can be established either by deriving parameters such as packet duration from RSSI or directly using RSSI’s probability distribution. An experimental study shows that even RSSI acquired at a sub-Nyquist sampling rate is able to provide sufficient features to differentiate technologies such as Wi-Fi, Long Term Evolution (LTE), Digital Video Broadcasting-Terrestrial (DVB-T) and Bluetooth. The usage of the RSSI distribution-based feature space is illustrated via a sample algorithm. Experimental evaluation indicates that more than 92% accuracy is achieved with the appropriate configuration. As the analysis of RSSI distribution is straightforward and less demanding in terms of system requirements, we believe it is highly valuable for recognition of wideband technologies on constrained devices in the context of dynamic spectrum access.

Joint Wireless Positioning and Emitter Identification in DVB-T Single Frequency Networks

Digital television (DTV) signal has been recognized as a promising signal for navigation and positioning. However, due to the single frequency network (SFN) transmission within the European standard digital video broadcasting terrestrial (DVB-T) system, emitter confusion problem occurs in navigation and positioning, resulting in that a receiver is unable to know from which emitter a received signal comes. In this paper, we consider the wireless positioning with emitter confusion problem in DVB-T SFN networks. A joint wireless positioning and emitter identification algorithm is proposed, which is based on the expectation maximization (EM) method. The proposed algorithm is tested in a scenario, where signals are received from three to five emitters. Simulation results show that, relying on more than three emitters used in the tests for 2-D positioning, the EM-assisted positioning algorithm is feasible to achieve accurate positioning results in the existence of the emitter confusion problem. Our studies show that the performance achieved by the proposed algorithm approaches the Cramer-Rao bound. Furthermore, the proposed algorithm is effective to identify the DTV emitters, and the positioning performance is robust to the emitter identification error. Additionally, our methodology is general, and can be employed for time of arrival-based positioning in any SFNs.

Dynamic Clutter Suppression and Multitarget Detection in a DVB-T-Based Passive Radar

This paper examines the problem of suppressing the dynamic clutter and multitarget detection in a digital video broadcasting-terrestrial (DVB-T)-based passive bistatic radar (PBR). A two-step low-complexity clutter suppression method is presented to attenuate the nonstationary multipath/clutter in a multiple-frequency network. In the first step, we estimate the multipath signals, as orthogonal frequency-division multiplexing channel coefficients, in a symbolwise approach. The variation of the clutter signal is tracked, using the complex exponential basis expansion model, in the second step. Then, the estimated multipath/clutter signals are subtracted from the received signals. An iterative algorithm is also proposed for detecting targets sequentially in a multitarget scenario. The performance of the proposed method is derived analytically, and a criterion is suggested for comparing different clutter cancellation schemes. The resulting solution is shown to be more efficient than other methods in terms of time and memory complexities.