Imran Baig

Review: A survey on routing techniques in underwater wireless sensor networks

Underwater Wireless Sensor Networks (UWSNs) are finding different applications for offshore exploration and ocean monitoring. In most of these applications, the network consists of significant number of sensor nodes deployed at different depths throughout the area of interest. The sensor nodes located at the sea bed cannot communicate directly with the nodes near the surface level; they require multi-hop communication assisted by appropriate routing scheme. However, this appropriateness depends not only on network resources and application requirements but also on environmental constraints. All these factors provide a platform where a resource-aware routing strategy plays a vital role to fulfill the different application requirements with dynamic environmental conditions. Realizing the fact, significant attention has been given to construct a reliable scheme, and many routing protocols have been proposed in order to provide an efficient route discovery between the sources and the sink. In this paper, we present a review and comparison of different algorithms, proposed recently in order to fulfill this requirement. The main purpose of this study is to address the issues like data forwarding, deployment and localization in UWSNs under different conditions. Later on, all of these are classified into different groups according to their characteristics and functionalities.

DCT precoded SLM technique for PAPR reduction in OFDM systems

High Peak to Average Power Ratio (PAPR) is still a most important challenge in Orthogonal Frequency Division Multiplexing (OFDM) system. In this paper, we propose a Discrete Cosine Transform (DCT) precoding based SLM technique for PAPR reduction in OFDM systems. This technique is based on precoding the constellation symbols with DCT precoder after the multiplication of phase rotation factor and before the Inverse Fast Fourier Transform (IFFT) in SLM-OFDM System. Simulation results show that our proposed technique can reduce the PAPR to about 5.5dB for N=64 and V=16 at clipping probability of 10−3.

PAPR analysis of DHT-precoded OFDM system for M-QAM

High Peak to Average Power Ratio (PAPR) is one of the major drawbacks in Orthogonal Frequency Division Multiplexing (OFDM). The High PAPR increases the complexity of Analogue to Digital (A/D) and Digital to Analogue (D/A) convertors and also reduces the efficiency of RF High Power Amplifier (HPA). In this paper we present an analysis of Discrete Hartley Transform (DHT) precoded OFDM system using M-QAM (where M=16, 32, 64, 256). We compare the computer simulation results of DHT precoded OFDM system with DFT precoded OFDM system, Walsh Hadamard Transform (WHT) precoded OFDM system, Selected Mapping (SLM) based OFDM system and OFDM conventional. Simulation results show that the PAPR of DHT precoded OFDM system is lower than WHT precoded OFDM system, SLM-OFDM system and OFDM conventional. We also concluded in this paper that DFT precoded OFDM system has zero PAPR.

A ZCMT Precoding Based Multicarrier OFDM System to Minimize the High PAPR

This paper presents a Zadoff-Chu matrix transform (ZCMT) precoding based multicarrier orthogonal-frequency-division-multiplexing (OFDM) system to minimize the high peak-to-average power ratio (PAPR). In the proposed system, ZCMT kernel is applied to the constellation symbols which not only reduces PAPR but also improves bit-error-rate (BER) performance. The ZCMT precoded OFDM signals allow the radio-frequency high-power-amplifier (HPA) to operate near its saturation level, thus maximize the power efficiency. Extensive computer simulations have been performed to analyze the PAPR, BER and power-spectral-density (PSD). Simulation results show that the proposed system has excellent PAPR gain and BER performance with no spectral distortion.

On the peak-to-average power ratio reduction in mobile WiMAX: A discrete cosine transform matrix precoding based random-interleaved orthogonal frequency division multiple access uplink system

Mobile worldwide interoperability for microwave access (Mobile WiMAX) is a broadband wireless solution that enables the convergence of mobile and fixed broadband networks through a common wide area radio-access (RA) technology and flexible network architecture. Since January 2007, the IEEE 802.16 working group (WG) has been developing a new amendment of the IEEE 802.16 standard i.e. IEEE 802.16m as an advanced air interface to meet the requirements of ITU-R/IMT-Advanced for 4G systems. The mobile WiMAX air interface adopts orthogonal frequency division multiple access (OFDMA) as multiple access technique for its uplink (UL) and downlink (DL) to improve the multipath performance. All OFDMA based networks, including mobile WiMAX experiences the problem of high peak-to-average power ratio (PAPR). This paper presents: Discrete-Cosine transform matrix (DCTM) precoding based random-interleaved OFDMA uplink system and selecting mapping (SLM) based DCTM precoded random-interleaved OFDMA uplink system respectively, for PAPR reduction in mobile WiMAX systems. PAPR of the proposed systems is analyzed with the root-raised-cosine (RRC) pulse shaping to keep out of band radiation low and to meet the transmission spectrum mask requirement. Simulation results show that, the proposed systems have low PAPR than the Walsh-Hadamard transform (WHT) precoded random-interleaved OFDMA uplink systems and the conventional random-interleaved OFDMA uplink systems. Symbol-error-rate (SER) performance of the proposed system is also better than the conventional random-interleaved OFDMA uplink systems and at par with WHT based random-interleaved OFDMA uplink systems. Good improvement in PAPR and SER offered by the proposed systems can notably reduce the cost and complexity of the transmitter.

A new ZCT precoded OFDM system with pulse shaping: PAPR analysis

This paper studies the Peak to Average Power Ratio (PAPR) improvements in various precoding based Orthogonal Frequency Division Multiplexing (OFDM) systems. In particular, the Zadoff-Chu matrix Transform (ZCT) precoder based PAPR reduction technique is analyzed. The ZCTs are obtained from Zadoff-Chu (ZC) sequences by filling ZCT kernel row-wise or alternatively column wise. Row wise filling gives rise to Constant Envelope OFDM (CE-OFDM) system with 0 dB PAPR, while column wise filling give rise 7.8 dB, at clip rate of 10−3 with system subcarriers N = 64 for QPSK modulation. However, since even CE-OFDM systems are required to operate with pulse shaping that helps in keeping out-of-band radiation low and meeting the transmission spectrum mask requirement, the PAPRs are no longer 0 dB. Therefore, in this paper, we present PAPR analysis of various precoding based OFDM systems with the popular Root Raised Cosine (RRC) pulse shaping. Simulation results show that, the ZCT Row-wise precoder based OFDM (ZCT-R-OFDM) system has lower PAPR than the ZCT Column-wise precoder based OFDM (ZCT-C-OFDM) system, the Hadamard Transform precoder based OFDM (WHT-OFDM) systems and the conventional OFDM systems.

A new DCT matrix precoding based RI-OFDMA uplink system for PAPR reduction

High peak-to-average power ratio (PAPR) is one of the major drawbacks in the transmitted random-interleaved orthogonal frequency division multiple access (RI-OFDMA) uplink signal. The PAPR increases the complexity of analogue-to-digital (A/D) and digital-to-analogue (D/A) convertors and also reduces the efficiency of RF high-power-amplifier (HPA). This paper presents a new Discrete-Cosine transform matrix (DCTM) precoding based RI-OFDMA uplink system for high PAPR reduction. Computer simulation results show that the proposed precoding based uplink system has low PAPR as compare to those of the Walsh-Hadamard transform (WHT) precoding based RI-OFDMA uplink systems and the conventional RI-OFDMA uplink systems respectively. Additionally, the biterror-rate (BER) performance of the proposed uplink system is much better than the conventional RI-OFDMA uplink systems and at par with the WHT precoded RI-OFDMA uplink systems. Therefore, such a good improvements in both PAPR and BER offered by the proposed precoding based uplink system can notably reduce the cost and complexity of the uplink transmitter.

On PAPR Reduction Techniques in Mobile WiMAX

The mobile Worldwide Interoperability for Microwave Access (Mobile WiMAX) air interface adopts orthogonal frequency division multiple access (OFDMA) as multiple access technique for its uplink (UL) and downlink (DL) to improve the multipath performance. All OFDMA based networks including mobile WiMAX experience the problem of high peak-toaverage power ratio (PAPR). The literature is replete with a large number of PAPR reduction techniques. Among them, schemes like constellation shaping, phase optimization, nonlinear companding transforms, tone reservation (TR) and tone injection (TI), clipping and filtering, partial transmit sequence (PTS), precoding based techniques, selective mapping (SLM), precoding based selective mapping (PSLM) and phase modulation transform are popular. The precoding based techniques, however, show great promise as they are simple linear techniques to implement without the need of any complex optimizations. This chapter reviews these PAPR reduction techniques and presents a Zadoff-Chu matrix transform (ZCMT) based precoding technique for PAPR reduction in mobile WiMAX systems. The mobile WiMAX systems employing random-interleaved OFDMA uplink system has been used for determining the improvement in PAPR performance of the technique. It has been further used in selective mapping (SLM) based ZCMT precoded random-interleaved OFDMA uplink system. PAPR of these systems are analyzed with the root-raised-cosine (RRC) pulse shaping to keep out-of-band radiation low and to meet the transmission spectrum mask requirement. Simulation results show that the proposed systems have low PAPR than the Walsh-Hadamard transform (WHT) precoded random-interleaved OFDMA uplink systems and the conventional random-interleaved OFDMA uplink systems. The symbol-error-rate (SER) performance of these uplink systems is also better than the conventional random-interleaved OFDMA uplink systems and at par with WHT based random-interleaved OFDMA uplink systems. The good improvement in PAPR offered by the presented systems significantly reduces the cost and the complexity of the transmitter.

A new ZCT precoding based SLM technique for PAPR reduction in OFDM systems

High Peak to Average Power Ratio (PAPR) in the transmitted signal is still a very important challenge in Orthogonal Frequency Division Multiplexing (OFDM) systems. In this paper, we present a new Zadoff-Chu matrix Transform (ZCT) precoded Selected Mapping (SLM) based OFDM (SLM-OFDM) system for PAPR reduction. The proposed system is based on precoding the constellation symbols with ZCT precoder after the multiplication of phase rotation factor and before the Inverse Fast Fourier Transform (IFFT) in SLM-OFDM Systems. At the clipping probability of 10−3, simulation results show that our proposed system can reduce the PAPR up to 5.0 dB with N=64 (System subcarriers) and V=16 (Dissimilar phase sequences) for QPSK modulation. Additionally, ZCT based SLM-OFDM systems also take advantage of frequency variations of the communication channel and can also offer substantial performance gain in fading multipath channels.

Wireless Sensor’s Civil Applications, Prototypes, and Future Integration Possibilities: A Review

Advances in wireless communication are forging new possibilities for sensors. New sensors are equipping major systems around us with unparalleled intelligence as in the case of smart grids, smart homes, and driverless vehicles. Considering the current developments in the field of sensor networks, one feels that it has reached an interesting stage, where the role of the sensors becoming crucial in numerous applications. This all speaks volumes of the fact that sensors are going to be at the front and center of most of future technologies, needless to say the Internet of Things. Considering their vital role from futuristic perspective this survey reports variety of sensors along with their characteristics and applications, which impact human life and well-being. In addition, this survey considers recent prototypes, leading sensor manufacturers as well as major projects that have made use of sensors since the last decade. Moreover, significance of this effort is that integration possibilities of sensors with other networks and major technologies are discussed, while possible challenges and key benefits are highlighted. This research effort focuses the latest developments in the area of sensors and sensor networks as research gears up to meet the challenges of the emerging technologies and their applications particularly those that emphasize smart sensors.