Handheld Terminals Research Articles

An Efficient OFDM Timing Synchronization for CMMB System

An accurate and rapid synchronization scheme is a prerequisite for achieving high-quality multimedia transmission for wireless handheld terminals, e.g. China multimedia mobile broadcasting (CMMB) system. In this paper, an efficient orthogonal frequency division multiplexing (OFDM) timing synchronization scheme, which is robust to the doubly selective fading channel, is proposed for CMMB system. TS timing is derived by performing an inverse sliding correlation (ISC) between the segmented Sync sequences in the Beacon, which possesses the inverse conjugate symmetry (ICS) characteristic. The ISC can provide sufficient correlative gain even in the ultra low signal noise ratio (SNR) scenarios. Moreover, a fast fine symbol timing method based on the auto-correlation property of Sync sequence is also presented. According to the detection strategy for the significant channel taps, the specific information about channel profile can be obtained. The advantages of the proposed timing scheme over the traditional ones have been demonstrated through both theoretical analysis and numerical simulations.

A Frame-Related Approach for Performance Improvement of MPE-FEC in DVB-H

Digital Video Broadcasting - Handheld (DVB-H) is a new digital terrestrial broadcasting standard customized for the multimedia service on the mobile devices and the handheld terminals. It introduces a technique known as multi-protocol encapsulation forward error correction (MPE-FEC) for the IP-datagrams in the data link layer to improve the mobile performance. Every MPE-FEC frame is constructed independently in the DVB-H standard. In this paper, a frame-related coding approach for MPE-FEC frames is proposed. When a MPE-FEC frame is built during the data link layer encoding process, the rightmost columns in the MPE part of the current MPE-FEC frame are filled with the data populated from the leftmost columns of its previous MPE-FEC frame. After the encoding process, a correlation is set up between the adjacent frames. This correlation can be utilized by the proposed decoding algorithm to enhance the error correction capability. The theoretical analysis and simulations results show that the proposed approach can provide better error correction capability than the DVB-H standard as well as the conventional zero-padding method in random noise channels. As a more efficient decoding strategy, the proposed approach is a good candidate for the decoding of MPE-FEC frame.

Effect of the User's Hands on the Operation of Lower UHF-Band Mobile Terminal Antennas: Focus on Digital Television Receiver

This paper deals with the effect of the user's hands on the performance of lower UHF-band antennas in handheld terminals. It is studied that how the input impedance, efficiency, and far-field directional pattern of the internal broadband digital television antenna are affected by the presence of the user's hands. The main part of the study has been carried out by applying finite-difference time-domain simulations. Measurements have been performed to support the results obtained by simulations. In the worst case, as much as 7-11 dB decrease of the antenna efficiency compared to free space case is shown. The results also indicate that the power absorption to the hand(s) is generally a more severe problem for the total efficiency than the change of the matching. On the other hand, it is also shown that in certain cases, the total efficiency of the antenna can even be improved due to the hands of the user. The results of this paper increase the understanding of the effect of the user's hands on the operation of the lower UHF-band antennas, whose operation is based on the radiation of a finite ground plane.

Broadband planar antenna with T-shaped strip and capacitively coupled shorted strip

This letter describes a broadband planar antenna embedded in LTE700/GSM handheld terminals. The antenna consists of a T-shaped strip fed by a 50-Ω coaxial cable and a shorted strip excited by capacitive coupling. The capacitively coupled shorted strip shows the resonance at the lower frequency band, and the T-shaped strip presents good matching at the higher frequency band, because the characteristics of input impedance are affected by the capacitive coupling. The proposed antenna was simulated and fabricated. The measured bandwidth based on 3:1 VSWR was 0.62–1.53 GHz, which covers the frequencies used for LTE700, GSM800/850/900 mobile communications as well as the military applications. This antenna would be also useful for broadband wireless communications using the technique such as software-defined radio or cognitive radio. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26211

Elevation Plane Beam Scanning of a Novel Parasitic Array Radiator Antenna for 1900 MHz Mobile Handheld Terminals

A novel internal antenna system is introduced for the GSM 1900 MHz frequency band which utilizes the electrically steerable parasitic array radiator (ESPAR) concept to steer the elevation plane beam in specific angular directions. The proposed antenna consists of a planar inverted-F antenna (PIFA) as the driven element and two inverted L antennas (ILAs) as parasitic elements. The ILAs are terminated with capacitive impedances at their bases. Full-wave analysis shows that the radiation beam can be scanned in space when the antenna is in free space as well as next to human head and hand phantoms. Measured results using varactor diodes controlling the base reactances show good return loss bandwidth.

Spatial spectrum sensing for wireless handheld terminals: design challenges and novel solutions based on tunable parasitic antennas [Dynamic Spectrum Management

This article addresses the major design challenges of antenna systems intended for cognitive transceivers under compactness constraints. The first part of the article provides an overview of the design challenges with regard to sensing over different frequencies and angular directions, referred to as spatial spectrum sensing. The second part describes a novel approach based on parasitic antenna theory aiming at making spatial spectrum sensing feasible for portable lightweight terminals. The idea is to replace the wideband antenna required for sensing over a large bandwidth by a tunable narrowband antenna for both sensing and communication purposes. The flexibility of the proposed antenna system lies in its capability to scan both the frequency and spatial resource dimensions simultaneously via a single RF chain within a miniaturized antenna system. This is done by properly tuning a set of reactive loads connected to a group of parasitic elements closely coupled to the driven (active) element. By doing so, the operational frequency subband leaps to another subband (frequency tuning). Moreover, at every subband, circular permutations of the reactive loads rotate the narrowband beam pattern to different angular positions, giving the cognitive transceiver the capability of sensing over various segments of the space.

Optimization of Multiservice Scheduling for Variable Bit Rate Video Transmission in DVB-H Systems

Digital Video Broadcasting for Handheld terminals (DVB-H) is assuming an ever growing importance for digital video transmission over wireless terminals. In such a context, Time Slicing has been implemented to achieve a better power saving and manage handover. Specifically, a generic user transmits bursts of data, interspaced by time periods in which no data are transmitted. In this paper, to improve time sliced multiservice transmission effectiveness, the Variable Burst Time (VBT) algorithm is presented and discussed. It dynamically varies the whole set of stream Burst Durations according to input stream data, available channel bandwidth, receiving buffer size and eventually stream priority. Burst Durations are derived by the minimization of a Total Loss Function (TLF) representing the amount of losses of the whole service set. Numerical results show the VBT effectiveness if compared with the time sliced transmission recommended in the DVB guidelines, for different numbers, types and quality degrees of VBR streams, receiving buffer sizes and stream priorities. This suggests that VBT could be efficiently exploited for transmission of VBR streams in DVB-H systems.

Low-power baseband filter for zero-intermediate frequency digital video broadcasting terrestrial/handheld receivers

Digital video broadcasting terrestrial (DVB-T) is being adopted by many countries all over the world. Recently, DVB-H, a new standard compatible with DVB-T, has been proposed for handheld terminals, which demands low power consumption. In this study, a continuous-time filter for DVB-T/H receivers is presented. High linearity and low noise are achieved by selecting a Gm-C filter topology implemented with a novel programmable transconductor based on MOS transistors in the triode region. The filter is tunable in a wide range, which makes it suitable for VLSI integration. The filter has been designed in a standard 0.5 m CMOS technology with a single 3.3 V supply voltage. Experimental results show an IM3 of 58 dB for a two tone experiment with 2 Vpp output signal centred at 2 MHz.

Avoiding Data Loss With Hard and Soft DVB-H Handovers

Digital Video Broadcasting-Handheld (DVB-H) allows the efficient transmission of rich multimedia services to small, handheld terminals. Such portable terminals pose specific requirements on the transmission technology, such as the need for seamless cell handover. This paper first presents mechanisms which allow loss-free hard handovers with DVB-H using only a single receiver front-end. It is then shown how even 3G-like soft handovers are possible with DVB-H, still using only a single receiver front-end. The proposed schemes are evaluated using simulations and field measurements.

Content and Service Protection for the Ubiquitous TV Based on Network Convergence

Today, the ubiquitous multimedia services are becoming more and more popular. However, the secure solutions that confirm the content and service security in these services are still open issues because of various network convergences and device interconnections. This paper investigates an ubiquitous multimedia service architecture and proposes a secure solution for it. In this service architecture, the multimedia content is encoded with scalable video coding and broadcasted via digital video broadcasting for handheld terminals (DVB-H) to mobile terminals, the access right is transmitted by global system for mobile (GSM/GPRS) channel, and the media content and access right can also be transferred from mobile terminals to home TV through WiFi based Wireless Local Area Network. The proposed secure solution supports three kinds of business models by using various content encryption modes and secure transmission protocols. The solution's security is evaluated and discussed. Since few work has been done to solve this problem, the work proposed in this paper is expected to attract more researchers. Additionally, the solution is also potential for other ubiquitous services.

Extensive Penetration Loss Measurements and Models for Different Building Types for DVB-H in the UHF Band

DVB-H networks allow high data rate broadcast access for hand-held terminals. Building penetration loss measurements of a DVB-H signal at 602 MHz are performed in 100 buildings in Belgium. Buildings are categorized in different types (office buildings, apartments, villas, mansions, row houses, stations) and the rooms are classified according to the number of outside radiated walls. The cumulative distribution function of the penetration loss is determined and lognormality is investigated. Models are developed to calculate the penetration loss as a function of the number of radiated walls. Also models for apartments as a function of the floor level are developed. This research enables the calculation of indoor coverage probability for wireless networks.

Linking satellite ICT application businesses with regional innovation centers and investors: The EC “INVESaT” project

In the sector of information and communication technologies (ICT), whether in the USA, Japan, or Europe, innovative services are already in use, based on large-scale space-based infrastructure investments. Such systems are e.g. earth observation, telecommunication, and navigation, timing and positioning satellites. In combination with the advent of powerful handheld terminals and the demand for ubiquitous services, it is expected that info-mobility applications will reveal new sources of business in the years ahead, using in particular the Earth observation and future GALILEO systems to position any feature or user anywhere in the world within a few meter accuracy. Hence, satellite-based capabilities provide new and unique opportunities for economic stimulation and development. Many incubators and innovation centers in Europe have already grasped this growth potential. Yet, for many European players business growth appears below expectations compared to developments in the USA following the launch of GPS (Global Positioning System). Europe still has to overcome intrinsic barriers to seize these new business opportunities faster and with more visible economic impact by leveraging on SMEs and regional innovation centers to expand the commercial utilization of satellite capabilities and mobilization of appropriate financial resources. The paper elaborates on the INVESat project (funded by the EuropeInnova—European Commission), which aims at bridging the gap between Innovative enterprises and financial In VEstors in the emerging markets of SaTellite applications. The critical success factors required to stimulate and support more efficiently investments in this bread of innovative services will also be highlighted.

New Method to Determine the Range of DVB-H Networks and the Influence of MPE-FEC Rate and Modulation Scheme

DVB-H networks allow high data rate broadcast access for hand-held terminals. A new method to determine the range of good reception quality of such a DVB-H network will be investigated in this paper. To this end, a new subjective criterion is proposed, based on the viewing experience of the users. This criterion is related to the percentage of valid reception. A comparison with existing criteria, based on measured signal strengths, is also made. The ranges are determined for mobile reception inside a car. The influence of the MPE-FEC rate and the modulation scheme on the range is also investigated, enabling wireless telecom operators to select optimal settings for future networks.

DVB-H Systems: Quality-Based Active Handoff Assisted by UMTS Return Channels

Digital Video Broadcasting for Handheld terminals (DVB-H) is a new standard developed by DVB Project consortium to enable the delivery of broadcast transmissions to mobile terminals (such as, cellular telephone, PDA, pocket PC, etc.). Being the DVB-H network characterized by a cellular structure, a key issue to avoid the service interruption in these systems is the design of effective handoff procedures. This paper introduces a novel seamless handoff approach for DVB-H networks, which is designed to reduce the user terminal power consumption and to make the handoff algorithm be driven by the quality of the user received signal. This implies the adoption of a method based on the constant monitoring of the Modulation Error Rate (MER), instead of standard RSSI-based procedures. Additional advantages in terms of power saving derive from the use of an Active Handoff procedure that exploits the UMTS return channel as an interaction channel. The proposed scheme has been successfully tested and obtained results make us confident that this can be an interesting research direction to investigate in the view of effective DVB-H handoff protocol design.

Robust video broadcasting over 802.11a/g in time-correlated fading channels

In order to deliver video streams efficiently over WiFi to many thousands of consumer handheld devices, broadcast protocols must be employed. In this mode of operation the received video quality can deteriorate rapidly as a result of high application layer packet loss which occurs because MAC frame retransmission cannot be used. In this paper we develop a robust video delivery solution for broadcast transmission over 802.11a/g. Using a cross-layer WiFi simulator in combination with an accurate time-correlated fading channel, the received video quality is evaluated for broadcast H.264 video sequences. Application layer cross-packet forward error correction is then used together with error concealment at the video client. Furthermore, the application of an external packet interleaver is considered. Combining a block size of two hundred packets (which introduces a 4.8 second delay) and an application layer FEC code rate of 0.75 our results demonstrate that video can be successfully broadcast over WiFi to many thousands of handheld terminals at large-scale spectator events.

Design and Performance Analysis of Compact Planar Inverted-L Diversity Antenna for Handheld Terminals

A compact planar inverted-L diversity antenna for handheld terminals is presented. Three diversity antennas operating at 2.15GHz are designed. The isolation is found to be higher than 13 dB and the usable bandwidth is about 13% in measurement. The measured radiation patterns of the proposed diversity antenna attain 2 dBi gain. Furthermore, the diversity performance with mean effective gain (MEG) is evaluated by taking both azimuth and elevation spectrum into account. A closed-form expression for MEG is presented. The effect of some parameters on MEG is analyzed numerically in indoor propagation environments.

Protecting Mobile TV Multimedia Content in DVB/GPRS Heterogeneous Wireless Networks

Normally, the multimedia content provider and network service providers are separated in mobile TV systems. The TV programs are broadcasted from the content provider to the mobile terminals through Digital Video Broadcasting Transmission System for Handheld Terminals (DVB-H), and the access information is unicasted from the service provider to the user via General Packet Radio Services (GPRS) networks. Due to the network architecture heterogeneity, protocols variation and algorithms difference, securing mobile TV content is becoming a significant challenge. In this paper, we present the architecture, protocol, user identification and digital right management (DRM) for protecting mobile TV multimedia content. The network architecture describes the integrated DVB-H and GPRS to provide secure mobile TV services. The efficient protocols and algorithms are proposed to encrypt the content and also decrypt the coded content. The user identification is able to identify the legal user by matching the username-password pair or the scanned fingerprint. The DRM is able to protect the data from both DVB-H and GPRS. Following this framework, the illegal usage of the mobile TV services can be efficiently prevented and the real-time multimedia Quality-of- Service (QoS) with respect to delay can be guaranteed. The real implementation has demonstrated the effectiveness of the multimedia content protection in the heterogeneous mobile networks. In addition, the delay is sufficiently low to provide live TV.

Implementing a DVB-T/H Receiver on a Software-Defined Radio Platform

Digital multimedia broadcasting is available in more and more countries with various forms. One of the most successful forms is Digital Video Broadcasting for Terrestrial (DVB-T), which has been deployed in most countries of the world for years. In order to bring the digital multimedia broadcasting services to battery-powered handheld receivers in a mobile environment, Digital Video Broadcasting for Handheld (DVB-H) has been formally adopted by ETSI. More advanced and complex digital multimedia broadcasting systems are under development, for example, the next generation of DVB-T, a.k.a. DVB-T2. Current commercial DVB-T/H receivers are usually built upon dedicated application-specific integrated circuits (ASICs). However, ASICs are not flexible for incoming evolved standards and less overall-area efficient since they cannot be efficiently reused and shared among different radio standards, when we integrate a DVB-T/H receiver into a mobile phone. This paper presents an example implementation of a DVB-T/H receiver on the prototype of Infineon Technologies' Software-Defined Radio (SDR) platform called MuSIC (Multiple SIMD Cores), which is a DSP-centered and accelerator-assisted architecture and aims at battery-powered mass-market handheld terminals.

Dual-wideband monopole antenna using a modified half-Sierpinski fractal gasket

A dual-wideband fractal monopole antenna for handheld terminals is proposed. A modified half-Sierpinski gasket patch is used to cover GPS, DCS1800, PCS1800, UMTS, IMT-2000, WiBro (Wireless Broadband Internet Service), Bluetooth, S-DMB (Satellite Digital Multimedia Broadcast) and WLAN bands. The proposed antenna exhibits two wideband frequency resonances. The measured −10 dB reflection bandwidths for two resonant frequencies are 55% (1517–2670 MHz) and 12.6% (5135–5828 MHz). The radiation characteristics and gain of the proposed antenna are also presented and discussed.

Influence of Reception Condition, MPE-FEC Rate and Modulation Scheme on Performance of DVB-H

DVB-H networks allow high data rate broadcast access for hand-held terminals. A method to analyze the performance is developed. The influence of different MPE-FEC rates and modulation schemes on the performance of a DVB-H network is analyzed in this paper for 9 different reception conditions. Portable (indoor and outdoor) and mobile reception (car, train, tram, bus) are investigated. This analysis enables better estimations of the performance of DVB-H systems and an optimized DVB-H performance model. The percentage of valid reception, MPE-FEC gains, carrier to interference-plus-noise ratios, and minimal signal strengths for the different reception conditions and modulation schemes are presented.