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This paper presents low-cost compressors for video display systems, which compress video data to reduce the size of the frame memory in a display panel in a television or a smartphone. The hardware solution exploits the discrete wavelet transform (DWT) and 1-D set partitioning in hierarchical trees (SPIHT) to support the raster-scan processing order in a display system and meet the fixed target compression ratio (CR). However, the compression efficiency and hardware cost often increase in proportion to the block size and thus, designing a compressor with low cost but high fidelity is challenging. This paper proposes a generic partitioned SPIHT algorithm, which achieves a low-cost design for mobile devices by allowing various sizes of partitioned sub-blocks. By taking advantage of DWT decomposition properties, the proposed algorithm partitions a coding block into sub-blocks, each of which can be processed independently. The independent coding operations among multiple sub-blocks allow the size of the hardware buffer to be decreased, by storing the temporary results only for an individual sub-block. However, the proposed sub-block coding slightly decreases the compression efficiency when each sub-block is compressed with the same target CR. To reduce the drop-off in the compression efficiency, the boundary-pixel handling in DWT is exploited and the proposed partitioned SPIHT method adjusts the target CR for each sub-block depending on the potential quality loss. When compared with the previous 1-D design, experimental results show that the hardware gate count and internal memory are reduced by 59.34% and 75%, respectively. Furthermore, the proposed boundary handling and bit-allocation schemes mitigate the PSNR degradation due to the sub-block coding by 1.11 dB. [ABSTRACT FROM PUBLISHER]

A new fast forward error correction (FEC) allocation algorithm for unequal error protection (UEP) of video transmission over wireless channels is proposed in this paper. First, an UEP scheme, which takes into consideration the non-uniformly distributed importance of frames in a group of pictures (GOP) and macroblocks in a video frame, is proposed. An enhanced video error propagation model, namely expected number of macroblocks error propagation (ENMEP) is also proposed in this paper to measure the amount of error propagation caused by transmission errors. Finally, by making use of our proposed ENMEP error propagation model, a fast FEC allocation algorithm for our proposed UEP scheme is also proposed. Simulation results demonstrate that our scheme outperforms the previous UEP scheme and the classical equal error protection (EEP) scheme. [ABSTRACT FROM AUTHOR]

This paper addresses a movement-aware vertical (MA V) handover algorithm between WLAN and Mobile WiMAX for seamless ubiquitous access. An MA V handover algorithm is proposed in this paper to exploit movement pattern for avoiding unnecessary handovers in the integrated WLAN and Mobile WiMAX networks. If a mobile station (MS) `s velocity is high and its movement pattern is irregular, unnecessary handovers likely occur more frequently. Therefore, the MS velocity and moving pattern are important factors for the handover decision procedure. To avoid unnecessary handovers, the MA V handover algorithm adjusts the dwell time adaptively and predicts the residual time in the cell of target base station (BS). Consequently, the adaptive dwell timer of MA V handover algorithm allows an MS a better connection as long as possible. Our simulation results show that the reduction of unnecessary handovers by leads to sign significant throughput improvements. [ABSTRACT FROM AUTHOR]

Recently, sensor network technologies are being applied to more places such as intelligent home, offices and universities. Localization algorithms are required for indoor wireless sensor network (WSN) applications because the identification of real positions can upgrade the importance of sensing information. In this paper, a sensor network, where small-sized, low-cost and low-rate sensors are uniformly deployed in an indoor WSN environment, is taken into account. We introduce efficient algorithms, termed multi- duolateration localization (MDL) and grouping multi- duolateration localization (GMDL), which can improve the accuracy of location identification by employing jumper setting. The MDL algorithm can estimate 2-dimensional coordinates with high accuracy by the acquisition of edge information from the setting. In addition, the GMDL algorithm can be applied to the estimation of 3-dimensional coordinates by the acquisition of edge and surface information from the setting. The proposed algorithms perform localization more accurately than trilateration and faster than multidimensional scaling (MDS). The results from a MATLAB simulation show the outperformance of the proposed algorithms and demonstrate the possibility of 3-dimensional localization. [ABSTRACT FROM AUTHOR]

When speech-based interfaces are used for small handheld devices such as cellular phones and personal digital assistants in mobile environments with unknown noises and surrounding talkers, all signals except the legitimate user's voice must be rejected as noise signals by the system. This paper proposes a new algorithm that detects the user's voice in spatial and temporal domains using directional and spectral information. It rejects undesirable signals that originate from noise sources or surrounding talkers. Experimental results indicate the proposed algorithm reduces the voice activity detection error rate by 34.3% relative to the conventional methods. [ABSTRACT FROM AUTHOR]

In this paper, a novel constellation extension algorithm, named as Peak-restricted Constellation Extension (PCE), is proposed for peak-to-average power ratio (PAPR) reduction in Orthogonal frequency division multiplexing (OFDM) system. This algorithm actively selects outer constellation points which contribute to the large peak magnitudes, and dynamically alter the amplitudes of these points to reduce PAPR. It does not require transmitting any side information to the receiver and there is no loss in data rate. As radio-over-fiber (ROF) network is proved to be one of the best solutions for the wireless-access technology, this algorithm is verified in an OFDM-ROF system. It is shown that this algorithm significantly reduces the PAPR of OFDM signals. The performances of the system with and without the algorithm are also compared. [ABSTRACT FROM AUTHOR]

A low complexity hierarchical quadrature amplitude modulation (QAM) symbol bits allocation algorithm for unequal error protection of video transmission over wireless channels is proposed in this paper. An unequal error protection (UEP) scheme using hierarchical QAM, which takes into consideration the non-uniformly distributed importance of intracoded frame (I-frame) and predictive coded frame (P-frame) in a group of pictures (GOP), is first proposed. In order to optimally allocate the hierarchical QAM's high priority (HP), medium priority (MP) and low priority (LP) symbol bits to the H.264/AVC video, a generic solution for optimal allocation of hierarchical QAM's high priority (HP), medium priority (MP) and low priority (LP) symbol bits to the H. 264/A VC video is then proposed. Finally, a low complexity symbol bits allocation algorithm, namely ranking search algorithm, which reduces the computational complexity of the proposed optimal symbol bits allocation algorithm, is proposed. Simulation results show that our proposed UEP scheme outperforms the classical equal error protection (EEP) scheme and also the previous UEP scheme. [ABSTRACT FROM AUTHOR]

In a GNSS software receiver, blocks of digitized intermediate-frequency (IF) data are prepared at the front end and sent to the processing unit for signal acquisition, tracking, demodulation, and position fix. A problem that is observed in practice when the GNSS software module is co-located with a mobile phone device is that the digitized IF data are subject to data intermittency. The intermittency results from the use of mobile phone when the GNSS signals are being received or the execution of higher priority routine in the host computer. An improper buffering scheme at the front end may also lead to such phenomena. Such data intermittency leads to bursttype errors (rather than bit-type errors) on the data to be processed, posing a challenge for the tracking of the GNSS signals. Indeed, if not properly handled, a typical tracking algorithm is not able to accommodate such a large data gap. In the paper, a decision-aided tracking algorithm is developed for a seamless tracking of codes and phases. The effects of data intermittency on code and phase tracking are analyzed. To accounting for the effect without going through the reacquisition process, a detector based on signal power and continuity is then implemented to facilitate decision making. It is shown, through the processing of field gathered data, that the proposed algorithm can indeed be able to continuously track codes and phases in the presence of data intermittency. [ABSTRACT FROM AUTHOR]

We present a new 3D mesh codec for mobile devices. Mobile devices have limited resources such as low memory, slow CPU speed, low power, and no floating-point processor. Considering these mobile characteristics, we suggest a new approach: a hybrid of a progressive geometry and a single-rate connectivity coding. By this approach, our algorithm achieves fast visual updates of progressive 3D point clouds on a small screen of a mobile device and later finalizes restoring faces of the mesh without intensive computing. For a progressive geometry coding, an octree is created and coded. For a single-rate connectivity coding, a new distance based algorithm is introduced. Our algorithm uses only fixed-point arithmetic with simple data structures. Our new 3D mesh codec has been tested on a real mobile phone and the statistical and visual results are also presented in this paper. [ABSTRACT FROM AUTHOR]

The issue of robustness in the presence of noise is regarded as a significant bottleneck in the commercialisation of speech recognition products, particularly in mobile environments. This paper examines the use of an auditory model combined with a speech enhancement algorithm as a robust front-end for a Distributed Speech Recognition (DSR) system, whereby front-end functionality is implemented on a limited-resource consumer device like a mobile phone, while back-end classifier functionality is carried out by a remote server. [ABSTRACT FROM AUTHOR]

The IEEE 802.15.3 standard aims at covering the gaps of current Wireless Personal Area Network (WPAN) technologies in supporting applications with very high-rate and/or quality of service requirements. To this end, the standard encompasses high-rate modulations and a flexible medium access mechanism that permits resource reservation. Whereas the standard defines the general resource management framework, the definition of practical scheduling algorithms is left open to proprietary solutions. In this paper we investigate the potentialities offered by the IEEE 802.15.3 framework for supporting multimedia services. More specifically, we analyze the performance of some classical scheduling policies in presence of intensive real-time and multimedia traffic, in order to identify the most effective strategy for the considered scenarios. The analysis has been performed by using a complete 802.15.3 c++ simulator, where we have realized the different scheduling strategies upon an entirely standard-compliant round robin polling procedure. Results show that the simple and well-known scheduling strategies considered in this study offer very good performance in a large set of realistic application scenarios. [ABSTRACT FROM AUTHOR]

This paper proposes a panoramic image mosaic system for mobile devices. The proposed panoramic mosaic system is optimized for mobile devices by integer- programmable algorithms, and is user-friendly designed by 4- directional auto-shot interface. The proposed system consists of image acquisition by auto-shot interface, image transform onto cylindrical mosaic surface, luminance and color compensation, local alignment, image stitching, and blending. The images are automatically captured by the auto-shot interface which senses the user ~ camera motion and takes a picture when the camera motion is matched to the predejIned motion model of images. The captured images are transformed and projected onto a cylindrical mosaic surface. Exposure difference is removed by color compensation, and the projected images are locally aligned by translational motion model. Then, the boundary of overlapped images are determined and synthesized by image stitching and blending. According to the experiments using real mobile devices, the proposed mosaic system shows good performance compared with other mosaic algorithms. Especially, since the proposed mosaic system operates on the usual mobile multimedia in real-time, the users can generate panoramic images easier than the personal computer based algorithms'. [ABSTRACT FROM AUTHOR]

In this paper, we propose an effective noise-robust modulation identification algorithm for adaptive receiver based on software defined radio. The proposed method can estimate the carrier frequency, symbol rate, and modulation scheme of the received signal without the use of the handshaking process requiring supplementary information such as the training sequence. Experimental results show that the proposed algorithm demodulates the signal with a low probability of error at the noisy channel conditions. [ABSTRACT FROM AUTHOR]

In wireless personal area networks (WPANs), the successful design of channel time allocation algorithm is a key factor in guaranteeing the various quality of service (QoS) requirements for the stringent real-time constraints of multimedia services. In this paper we propose a dynamic channel time allocation algorithm for providing delay guarantees to multimedia traffics such as MPEG streams in the IEEE 802.15.3 high-rate WPANs. The dynamic algorithm exploits the characteristics of MPEG stream, wherein devices (DEVs) send their channel time requests near at the end of superframe. The algorithm uses mini packets for feedback control in order to deliver dynamic parameters for channel time requests from DEVs to the piconet coordinator (PNC). In this scheme, the duration of channel time allocated to a DEV during a superframe is changed dynamically depending on the MPEG frame type, traffic load and delay bound of the frame, etc. Performance of the proposed scheme is investigated by simulation. Our results show that compared to conventional scheme, the proposed scheme is very effective and has high performance while guaranteeing the delay bound. [ABSTRACT FROM AUTHOR]

Until recently, consumer electronics devices, PCs, and peripherals in home have been primarily confined to the links that allow consumers to access them with wired connections. Furthermore, there are increasing demands for wireless home entertainment network In order to satisfy consumers' demands for wireless home entertainment network in order to support low cost, reliable and wireless connections, we propose DS-UWB system using STBC with Rake receiver capable of resolving multipath components. The significant improvement is achieved in the proposed system. This paper evaluates the performance of the proposed system and examines the algorithms for improving reliability and performance of the proposed system. [ABSTRACT FROM AUTHOR]

In this paper, an efficient decision feedback equalizer (DFE) is presented for sparse channels with large delay echoes, which are encountered in many high-speed wireless communication applications. Unlike the conventional DFE, this proposed equalizer considers that the channel is sparse and large number of DFE taps lead to noise accumulation problem. The new method can achieve efficient equalization by setting the active group for equalization taps and clearing the abandoned taps mechanism. As a result, it can both reduce hardware implementation complexity effectively and improve the performance compared to the conventional DFE. Brief analysis about noise accumulation effects in large-scale equalizer and working mechanism description of this effective algorithm exhibits us where the performance gain lies. Simulation results show that this modified DFE exhibits considerable computational savings, faster convergence, and better performance and improved tracking capabilities than the conventional ones. It is quite fit for applications in high-speed systems, such as high definition television (HDTV) and broadband mobile communication. [ABSTRACT FROM AUTHOR]

In this paper, we propose an efficient symbol detection algorithm for space-frequency OFDM (SF-OFDM) transmit diversity scheme and present the implementation results of the SF-OFDM wireless LAN (WLAN) baseband processor with the proposed algorithm. When the number of sub-carriers in SF-OFDM scheme is small, the interference between adjacent sub-carriers is generated. The proposed algorithm eliminates this interference in a parallel manner and obtains a considerable performance improvement over the conventional detection algorithm. The bit error rate (BER) performance of the proposed detection algorithm is evaluated by the simulation. In the case of 2 transmit and 2 receive antennas, at BER=10-4 the proposed algorithm obtains about 3 dB gain over the conventional detection algorithm. The packet error rate (PER), link throughput, and coverage performance of the SF-OFDM WLAN with the proposed detection algorithm are also estimated. For the target throughput at 80% of the peak data rate, the SF-OFDM WLAN achieves the average SNR gain of about 5.95 dB and the average coverage gain of 3.98 meter. The SF-OFDM WLAN baseband processor with the proposed algorithm was designed in a hardware description language and synthesized to gate-level circuits using 0.18μn 1.8V CMOS standard cell library. With the division-free architecture, the total logic gate count for the processor is 945K. The real-time operation is verified and evaluated using a FPGA test system. [ABSTRACT FROM AUTHOR]

Adaptive modulation is proposed by many researchers for future generation wireless networks based on multi-carrier transmission technologies. In this paper, we propose and investigate some blind mechanisms at the receiver of adaptive modulation based coded OFDM-CDMA systems in Rayleigh fading channels, for enhancement of the systems both in terms of practical implementation and data throughput capacity. In this respect, blind techniques to estimate the channel impulse response and modulation scheme are proposed and investigated and their effect on the BER performance of the systems are also analyzed A subspace based algorithm is proposed to estimate the channel impulse response blindly. This estimate is then used to coherently demodulate the OFDM-CDMA signals and adaptively switch the modulation schemes for varying channel conditions. Furthermore, an algorithm to estimate the modulation scheme at the receiver is also proposed Results show error free estimation of modulation scheme for a maximum 7 number of active users in the system at a channel condition of 20 dB. Simulation results show that in some situations, the systems based on blind channel estimation show little degradation in terms of the BER performance compared to the pilot based scheme. However, the advantages of blind estimation schemes far outweigh this degradation. [ABSTRACT FROM AUTHOR]

In this paper, we propose a power-efficient and QoS (Quality of Service) -aware MAC (Medium Access Control) scheduling algorithm for Bluetooth scatternet. If the inter-piconet scheduler in a bridge node between piconets operates simply by the Round Robin (RR) policy, a number of time slots may be wasted due to the guard time for piconet switching and the exchange of POLL-NULL packets. To overcome the link wastage problem in Bluetooth scatternet scheduling, several algorithms have recently been proposed. Although they can provide all of the links of a bridge node with fair service opportunities, they may cause waste of wireless resources since different Bluetooth devices may have various traffic characteristics. In addition, since Bluetooth devices are often required to operate under limited battery capacity, the number of unnecessary piconet switching has to be minimized for the power-efficient operation of a Bluetooth scatternet. Therefore, we propose a mechanism to support the power-efficient operation of a Bluetooth scatternet while guaranteeing various QoS requirements of Bluetooth devices. The proposed algorithm is compliant with the current Bluetooth specification, and we demonstrate its improved performance via simulations. [ABSTRACT FROM AUTHOR]

In order to enable the real-time image mosaic in mobile devices that have very limited computing power and memory, we propose an efficient image mosaic algorithm with integer arithmetic. The proposed algorithm is focused not only on the computational efficiency, but also on the performance improvement of image mosaic. For the efficient projection without transform estimation, we obtain successive images through the semitransparent viewfinder which shows the fixed amount of right part of previously captured image. We project each images onto cylindrical surface by the proposed projection equation and integer arithmetic. We align the projected images by hierarchical hexagon search and a matching measure that is robust to illumination changes caused by different exposures and vignette distortion. Finally, the images are naturally blended using color compensation and dynamic programming based stitching. The proposed mosaic algorithm is embedded and tested in mobile phone systems. According to various tests and experiments, the proposed algorithm shows good panorama composition in real-time compared with the other PC-based methods. [ABSTRACT FROM AUTHOR]

Secure wireless communications are fundamental in any interaction in order to avoid security and privacy breaches, especially from mobile devices. The use of this kind of communications is far more frequent and the number of users increases day after day. This paper shows and analyzes the support, performance and consumption of cryptographic algorithms and cipher suites in terms of time and energy when secure communications (i.e., using SSL) are established according to different security levels. This study has been performed in distinct operating systems, and using different browsers and libraries. [ABSTRACT FROM PUBLISHER]

New communication services among nearby passing people are growing rapidly thanks to the advance of short-range wireless communication technologies and the widespread use of mobile devices that use them. Time-offset communication capability will engender a new service paradigm and promote new service emergence. This paper presents a proposal of a new distributed mobile cache system to cache data temporarily in a designated local area. The system is realized through collaborative consumer electronics mobile devices which use no infrastructure network. The system overview and its middleware on the mobile devices are explained. Furthermore, new relay data algorithms are proposed to provide lower-overhead communication and a more robust caching capability. Finally, results of simulation experiments underscore the effectiveness of the proposed control algorithm in terms of the communication cost and the length of the cache time. [ABSTRACT FROM PUBLISHER]