Sharifah K. Syed-Yusof

Proposed transport protocol for reliable data transfer in wireless sensor network (WSN)

Reliable data transport is one of the most important requirements in wireless sensor network where different applications have different reliability requirements. Additionally, the characteristic of wireless sensor network, especially dense deployment, limited processing ability, memory and power supply, provide unique design challenges at transport protocol. Therefore, assuring reliable data delivery between sensor nodes and the sink in Wireless Sensor Networks (WSN) is a challenging task. A reliable protocol in wireless sensor network is a protocol that allows data transfer reliably from source to destination with reasonable packet loss. The current issues of transport protocol are how to implement reliable data transport, congestion control and energy efficient. Most of the existing transport protocols only provide reliable data transport or congestion control. However, there are several protocols that provide both functions of the transport protocol. To overcome these issues, the transport layer protocols that provide both reliable data delivery and congestion control should be taken under consideration. Besides that, transport layer algorithm also allow maximum network lifetime due to limited operating lifetime of sensor node. Thus, to prolong the lifetime of wireless sensor network, an efficient transport protocol need to support reliable message delivery and provide congestion control in most energy efficient. This paper focuses on the existing transport protocols and the future protocol that provide the entire requirement of transport protocol.

Proactive integrated handoff management in cognitive radio mobile ad hoc networks

In cognitive radio networks, the secondary users (SUs) switch the data transmission to another empty spectrum band to give priority to primary users (PUs). In this paper, channel switching in cognitive radio mobile ad hoc networks (CR-MANETs) through an established route is modeled. The probability of channel availability in this route is calculated based on the PUs activity, SUs mobility, and channel heterogeneity. Based on the proposed model, the channel and link availability time are predicted. These predictions are used for channel assignment in the proposed channel allocation scheme. A handoff threshold as well as a life time threshold is used in order to reduce the handoff delay and the number of channel handoffs originating from the short channel usage time. When the channel handoff cannot be done due to the SUs mobility, the local flow handoff is performed to find an appropriate node in the vicinity of a potential link breakage and transfer the current data flow to it. The local flow handoff is performed to avoid possible flow disruption and also to reduce the delay caused by the link breakage. The study reveals that the channel heterogeneity and SUs mobility must be considered as important factors, which affect the performance of the handoff management in the CR-MANETs. The results emphasize on the improvement of the route maintenance probability after using the local flow handoff. It is also stated that the amounts of handoff requirement and handoff delay are decreased after using the predicted channel usage life time and handoff threshold time.

Proactive integrated handoff management in CR-MANETs: A conceptual model

In cognitive radio (CR), CR users or also known as secondary users (SUs) are considered as “visitors” to the licensed spectrum. During the case when the primary user (PU) claims the band of the spectrum that is occupied by the SU, the SUs ongoing call must be transferred to another unused spectrum band. The variation in spectrum band is called spectrum mobility. Spectrum mobility leads to a new handoff in cognitive radio networks, namely spectrum handoff, in which the SUs handover their spectrum band and continue their ongoing calls on an unused spectrum band with different frequency upon the appearance of the PU. In this paper, we investigate a new concept of integrated handoff management in mobile cognitive radio Ad hoc networks (CR-MANET), along with a conceptual framework, its connections and related handoff algorithm.

Multicasting Multiple Description Coding Using p-cycle Network Coding

This paper deliberates for a multimedia transmission scheme combining multiple description coding (MDC) and network coding (NC). Our goal is to take advantage from the property of MDC to provide quantized and compressed independent and identically distributed (iid) descriptions and also from the benefit of network coding, which uses network resources efficiently to recover lost data in the network. Recently, p-cycle NC has been introduced to recover and protect any lost or distorted descriptions at the receiver part exactly without need of retransmission. So far, MDC have not been explored using this type of NC. Compressed and coded descriptions are transmitted through the network where p-cycle NC is applied. P-cycle based algorithm is proposed for single and multiple descriptions lost. Results show that in the fixed bit rate, the PSNR (Peak Signal to Noise Ratio) of our reconstructed image and also subjective evaluation is improved significantly compared to previous work which is averaging method joint with MDC in order to conceal lost descriptions.

Performance Study of the Coexistence of Wireless Sensor Networks (WSN) and Wireless Local Area Networks (WLAN)

This paper presents a special state machine of interference temperature multiple access (ITMA) that characterizes both interference and noise with single parameter in wireless sensor networks (WSN) application. By measuring current interference temperature before data transmission, cognitive node is able to determine transmit power and data rate that should be used to achieve desired capacity without violating interference temperature limit at other co-channel transceiver. Simulations of NS-2 are shown to simultaneously satisfy the three main objectives of extending battery life of cognitive node through optimum transmit power provision, maximizing the traffic carrying of networks capacity and limit interference to other coexist node. Hence, cognitive node is feasible to support QoS provisioning, and fairness among WSN and WLAN users.

Efficient In-Band Spectrum Sensing Using Swarm Intelligence for Cognitive Radio Network

Spectrum sensing mechanisms enable cognitive radio networks to detect primary users (Upsi) and utilize spectrum holes for secondary user (SU) transmission. However, precise PU detection leads to longer sensing time and lower achievable throughput. In this paper, we propose a particle swarm optimization (PSO)-based scheme for an in-band local spectrum sensing to address the tradeoff between sensing time and throughput. Using methodological analysis, a fast convergence PSO (FC-PSO) scheme is derived by implementing a distribution-based stopping criterion subject to detection performance, optimization time, and SU gain. At the target probability of detection of at least 90%, the results show significant improvements of ~45% for sensing time, 70% for the probability of false alarm, and 12% for achievable throughput compared with nonoptimal sensing scheme at signal-to-noise ratio of 0 dB. FC-PSO also outperforms other optimization schemes in terms of convergence speed. The proposed scheme is proved to be an energy-efficient solution for practical implementation as it outperforms the other algorithms in terms of lower computational complexity as well as providing the best tradeoff values in meeting the objective function of sufficient opportunistic access for an SU under optimized sensing time for maximized throughput, while providing high protection to the PU.

Performance analysis of Doppler shift effects on OFDM-based and MC-CDMA-based cognitive radios

The present development of high data rate wireless applications has led to extra bandwidth demands. However, finding a new spectrum bandwidth to accommodate these applications and services is a challenging task because of the scarcity of spectrum resources. In fact, the spectrum is utilized inefficiently for conventional spectrum allocation, so Federal Communications Commission has proposed dynamic spectrum access mechanism in cognitive radio, where unlicensed users can opportunistically borrow unused licensed spectrum, which is a challenge to obtain contiguous frequency spectrum block. This also has a significant impact on multicarrier transmission systems such as orthogonal frequency division multiplexing OFDM and multicarrier code division multiple access MC-CDMA. As a solution, this paper develops non-contiguous OFDM NC-OFDM and non-contiguous MC-CDMA NC-MC-CDMA cognitive system. The implementation of NC-OFDM and NC-MC-CDMA systems provides high data rate via a large number of non-contiguous subcarriers without interfering with the existing transmissions. The system performance evaluates NC-OFDM and NC-MC-CDMA for mobile scenario where each propagation path will experience Doppler frequency shift because of the relative motion between the transmitter and receiver. The simulation results of this paper proved that NC-OFDM system is a superior candidate than NC-MC-CDMA system considering the mobility for cognitive users. Copyright

TDMA-based cooperative sensing using SDR platform for cognitive radio

The current trend and demand of wireless services requires more efficient spectrum usage. With Cognitive Radio (CR) technology, spectrum efficiency will be increased by exploiting unused licensed or primary users spectrum. Spectrum sensing mechanism is one of the main cores in CR system. To combat the problems of shadowing, multipath fading, and hidden nodes, cooperative spectrum sensing has been proposed. Testbed prototyping for sensing is a challenging task. The demand for cooperative sensing to solve the above mentioned problems leads to proposals of PHY and MAC layer solutions. Therefore, in this paper, we demonstrate an experimental platform using USRP board that can facilitate the development of PHY and MAC layers functionality for cooperative spectrum sensing. In this paper, TDMA-based MAC protocol for cooperative sensing mechanism is proposed. The observation of the preliminary experimental measurement shows significant performance in term of feasibility of cooperative decision mechanism in wireless condition.

Compressed Wavelet Packet-Based Spectrum Sensing With Adaptive Thresholding for Cognitive Radio

Cognitive radio is a system to utilize spectrum holes efficiently as a solution of spectrum scarcity. The availability of channels for secondary users is determined in the spectrum sensing phase by energy detection. Energy levels of sampled primary users (PUs) signal can be measured by wavelet transform with more accuracy compared with Fourier-based methods. Wavelet packet-based spectrum sensing measures the energy level at each subcarrier and sets the decision threshold. However, at the first step of energy detection for wideband spectrum sensing, high-rate analog-to-digital converter (ADC) sampling requires a large dynamic range and high-speed signal processors. In this paper, compressed sampling for PUs signal acquisition is proposed to reduce the rate of sampling and solve the implementation complexity of ADC. The simulation results verify that this mechanism is promising to estimate the power spectrum density (PSD) of PUs signals. The graphs prove low side-lobes of the detected PSD and acceptable probability of detection and false alarm due to the target values and certain compression ratio.

Space Time Frequency Block Codes for MIMO-OFDM system using intercarrier interference self-cancellation schemes

This paper highlights the space time frequency block codes (STFBC) that exploit spatial, time and frequency diversity can be designed using orthogonal frequency division multiplexing (OFDM). However, OFDM suffers from ICI. Hence, a new OFDM-MIMO using STFBC method combining ICI-SC scheme is investigated to reduce ICI and error correction effectively. The technique of reducing ICI using Space Time Frequency diversity is recognized to be an ultimate means to achieve the objective of this work and providing diversity at the same time. The system developed is analyzed with CFO and compared in terms of BER performance. It can be seen from the simulation results that the system developed improved the BER performance with high diversity order and successfully reduce ICI effect.