S.K.S. Yusof

Universiti Teknologi Malaysia, Bharu, Johor, Malaysia

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Publications (79)3.86 Total impact

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    ABSTRACT: In this paper, we present the end-to-end interference aware concept of Cognitive wireless mesh network (CWMN). CWMN is the leading upcoming technology with the advantage of cognitive radio (CR). We demonstrate that the end-to-end interference model has the ability to perform better from SINR base model. To enhance the utilization of the unused spectrum the channel selection strategy should have some awareness mechanism to avoid interference. In this paper, novel interference aware channel assignment (IACA) algorithm is proposed. The end-to-end delay, packet delivery ratio and the throughput is used to estimate the performance of the proposed algorithm. The numerical results demonstrate that the proposed algorithm is closer to the optimum resource utilization. Keywords— cognitive radio (CR), interference, channel assignment (CA), wireless mesh networks, primary user (PUs), secondary users (SUs).
    Malaysia International Conference on Communications, Malaysia; 11/2013
  • Jurnal Teknologi. 10/2013;
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    ABSTRACT: This article presents a novel method of optimizing sensor node location of wireless sensor network (WSN) in a circular arrangement. Appropriate selection of active collaborative beamforming (CB) nodes and cluster are needed each time to perform CB in WSNs. The nodes are modeled in circular array location in order to consider it as a circular antenna array (CAA). This newly proposed intelligent circular sensor node array (ICSA) is further presented to solve the problem. In particular, the selected collaborative nodes and the desired objective can vary significantly. Analyses obtained are compared to those from previous work. The findings demonstrate a better beamforming performance, and the difference is shown in normalized power gain.
    2013 Asia-Pacific Microwave Conference; 10/2013
  • Nuzli Mohamad Anas, Sharifah Kamilah Syed Yusof, Roslina Mohamad
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    ABSTRACT: This paper describes the performance of singular value decomposition (SVD) estimation techniques for multiband orthogonal frequency-division multiplexing (OFDM) of ultra-wideband (UWB) system in Saleh-Valenzuela channel modelling. The performance of SVD estimation is compared against LS and MMSE methods corresponding to zero-padded of a UWB system. The crucial limitation in UWB system is strictly low power transmission leads to many challenges in designing the system. However, most of the conventional channel estimation in frequency domain requires either pre-storing a large matrix or performing real-time matrix inversion, which should be avoided for UWB low complexity implementation. The intuition of this paper is to analyse further the complexity of SVD techniques against least squares (LS) and minimum mean square error (MMSE) estimation method. Consequently, this work implies that the SVD method gives an improvement of 3–5 dB if compared to the LS method while a significant complexity reduction of 57.8% as compared to MMSE methods.
    TENCON 2013 - 2013 IEEE Region 10 Conference (31194); 01/2013
  • Communications (MICC), 2013 IEEE Malaysia International Conference on; 01/2013
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    ABSTRACT: Multiple Description Coding (MDC) is a useful source coding method for concealing error in lossy networks. Network coding (NC) permits intermediate nodes within a network to apply algebraic mathematic process on independent streams in transmitter and receiver. This paper attempts to protect data and conceal errors happen in the network by joining MDC and p-cycle NC. First, input data (image) is zero padded and downsampled to four subimages. Then Wavelet and Lloyd-max quantization is applied to subimages. Later, four compressed and coded descriptions are transmitted through network and p-cycle network coding is applied to them in the network. Any lost description can be recovered exactly at the receiver part. In this method, no feedback system is needed. Results show that in the fixed bit rate, the PSNR (Peak Signal to Noise Ratio) of our reconstructed image and also subjective evaluation is better than previous work. Furthermore, proposed method has high throughput compared to another work.
    Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology (ECTI-CON), 2013 10th International Conference on; 01/2013
  • Salem Bindhaiq, Sharifah Kamilah Syed‐Yusof, Haleh Hosseini
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    ABSTRACT: SUMMARY 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 © 2013 John Wiley & Sons, Ltd.
    International Journal of Communication Systems 01/2013; · 1.11 Impact Factor
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    ABSTRACT: SUMMARY The IEEE 802.16j Mobile Multihop Relay (MMR) WiMAX network allows the number of hops between the end user and the base station to be more than two hops. It supports non-real-time Polling Service, which considers the minimum reserved rate and the maximum sustained rate as a QoS requirements. The reliability of sending the data over MMR WiMAX is achieved by using Transmission Control Protocol (TCP) in transport layer and automatic repeat request in the link layer. However, the use of automatic repeat request in the link layer makes the round trip time fluctuate rapidly, which increases the possibility of retransmission timeout (RTO) expiration. TCP performance degrades because of frequent timeout, and hence the QoS transmission rates cannot be satisfied. Therefore, this paper presents an RTO smoothing scheme and QoS aware transmission control to enhance the performance of data transmission over MMR WiMAX networks. The RTO smoothing scheme aims to reduce the frequent timeout occurrences. The slow start threshold and maximum congestion window are adjusted to satisfy the required QoS and it provides transmission rate fairness for the users at different hops. The results showed that, the proposed schemes reduce the timeout, and improve the utilization of the allocated resources and TCP throughput. Copyright © 2012 John Wiley & Sons, Ltd.
    International Journal of Communication Systems 11/2012; · 1.11 Impact Factor
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    ABSTRACT: Relaying is one of the technical specifications in LTE (Long Term Evolution)-Advanced. It is proposed to improve throughput at the cell edge and shadowing area. To enable relaying function in LTE-Advanced, current signaling should be modified because LTE does not support relaying technique. The enhancement work of LTE, proposed two architectures for RN (Relay Node) implementation which is called Architecture A and Architecture B. There are three alternatives in Architecture A and one alternative in Architecture B. This paper focused on the Architecture A. The control plane and user plane are discussed before the HO (Handover) signaling for each alternative in the Architecture A. L3 RN (Layer3 Relay Node) is considered in this architecture and work. The proposed signaling is based on HO scenario from a RN to a Target eNB (evolved NodeB) in a different cell.
    Jurnal Teknologi. 07/2012; 58:127-9696.
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    ABSTRACT: Coordinated Multipoint (CoMP) has been proposed as a promising way to enhance cell-edge performance in terms of throughput and coverage. Significant performance gain can be achieved in LTE-A through base station (eNB) coordination by exchanging information such as user data, channel state information (CSI) and scheduling decision. Multiple antennas technique (e.g., MIMO) on the other hand exploits antenna diversity which allows multiple simultaneous transmissions to a group of active users to enhance network performance. Therefore, user selection is important in maximizing system performance. Besides, system resources (e.g., power, bandwidth, transmission rate) in MIMO system must be managed efficiently. Optimal resource utilization should be used without performance compromise. In this paper we propose a joint approach of MIMO user selection strategy and optimal water filling (WF) power allocation in CoMP (JP) transmission. Simulation study shows that our proposed approach outperformed traditional CoMP with and without water filling power allocation.
    Wireless Technology and Applications (ISWTA), 2012 IEEE Symposium on; 01/2012
  • N. M. Anas, S. K. S. Yusof, R. Mohamad, S. Saaidin
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    ABSTRACT: Multiband Orthogonal Frequency Division Multiplexing (OFDM) has been deployed for practical implementation of low cost and low power UWB devices due to its ability to mitigate the narrowband interference and multipath fading effects. This paper review and investigates the performance of multiband OFDM techniques for UWB system under Saleh-Valenzuela channel modelling, proposed in IEEE wireless Personal Area Network (PAN) standard committee. The baseband systems described in this paper is based on ECMA-368 standard simulates under four different type of Saleh-Valenzuela channel model, namely CM 1 until CM 4.
    01/2012;
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    ABSTRACT: The unpredictable nature of the wireless network and exponential growth in traffics with different quality of service requirements has led hardware complexity to escalate. In order to effectively control and manage the network traffics, there is a need for intelligent call admission control (CAC) in admitting traffics into the wireless network that provides necessary quality of service. In this paper, we propose a fuzzy logic partition-based call admission control (FZ CAC). The scheme primarily partitions the total link bandwidth into three which corresponds to constant bit rate (CBR), variable bit rate (VBR) and handover (HO) services. The fuzzy logic admission control scheme was implemented in the HO portion to intelligently keep dropping probability as low as possible based on the available bandwidth. Simulation results showed that the proposed approach outperformed both partition-based CAC (PB CAC) and conventional bandwidth allocation CAC (CB CAC).
    ISRN Communications and Networking. 06/2011; 2011.
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    D.S. Shu'aibu, S.K.S. Yusof, N. Fisal
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    ABSTRACT: Packet scheduling in wireless network is one of the issues that requires attention to quality of service provision (QoS). In heterogeneous wireless network, whereby many packets of different QoS are involved, packet scheduling becomes more difficult. This paper presents packet scheduling algorithm that uses earliest deadline first for scheduling constant bit rate packets. We estimate the wireless link based on the total path loss and obtain SNR value of the packet for scheduling. The simulation shows that the proposed algorithm has achieved higher throughput.
    Modeling, Simulation and Applied Optimization (ICMSAO), 2011 4th International Conference on; 05/2011
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    ABSTRACT: Vehicular networks are highly mobile wireless networks that can provide wide variety of services and applications such as public safety communications, crash avoidance, multimedia and Internet access in highways. Designing routing algorithm in vehicular network is a challenging task due to rapidly changing topology and high speed mobility of vehicles. One of the critical issues of vehicular network is frequent path disruptions caused by high speed mobility that leads to broken links which results in low throughput. This poses complex challenge in ensuring quality of service (QoS). A lot of research around the world is being conducted to define the standards for vehicular communication. In this paper, we study the effect of different duration of transmitting packet and compare different packet size on sending and received packet rate in IEEE 802.16j MMR networks using NCTUns. Meanwhile, cross-layer routing approach is proposed to overcome the challenge. The routing approach is expected to significantly improve QoS in vehicular networks.
    Modeling, Simulation and Applied Optimization (ICMSAO), 2011 4th International Conference on; 05/2011
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    ABSTRACT: The issues of green technology nowadays give an inspiration to the researcher to make all the future design to be energy efficient. Medium Access Control (MAC) layer is the most effective layer to provide energy efficient due to its ability to control the physical radio directly. One of the important applications in the future is a video transmission that can be transmitted with low-cost and low power consumption. MPEG-4 is one of the international standards for moving video. MPEG-4 provide better compression and primarily design at low bit rate communication. In order to achieve good quality for video application, the design at MAC layer must be strong. Therefore, to increase the performance of the MPEG-4 in IEEE 802.15.4, in this paper we propose a cross layer design between MAC layer and Application layer. A priority queue will be implemented at MAC scheduling depends on the level of frame important in MPEG-4 format frame. A distributed Time division Multiple Access (TDMA) will be used for MAC protocol to provide reliable data transmission for high priority frame.
    Modeling, Simulation and Applied Optimization (ICMSAO), 2011 4th International Conference on; 05/2011
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    ABSTRACT: This paper presents the performance analysis of multiband OFDM technique for the UWB system under indoor environment using Zero padded prefix which has been suggested in ECMA-368 standard as to avoid power back off at the transmitter. A modified Saleh-Valenzuela channel modeling is considered as a realistic multipath indoor characteristic with four channel model: CM1, CM2, CM3 and CM4. These channel models are distinguished by cluster structure of the receiving path and its respective cluster and ray within cluster decay factors rate. Rayleigh fading is used as an upper bound limit of the analytical performance of UWB system.
    Computer Modelling and Simulation (UKSim), 2011 UkSim 13th International Conference on; 05/2011
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    Communication and Networking - International Conference, FGCN 2011, Held as Part of the Future Generation Information Technology Conference, FGIT 2011, in Conjunction with GDC 2011, Jeju Island, Korea, December 8-10, 2011. Proceedings, Part I; 01/2011
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    ABSTRACT: Traditional static spectrum allocation policy has resulted in current day spectrum scarcity and inefficient spectrum utilization. Dynamic Spectrum Access (DSA) technique allows cognitive (unlicensed) user (CU) to opportunistically transmit in a primary (licensed) user (PU) frequency band for a given time if it does not detect any ongoing operations. In this work, CU is implemented on Software Defined Radio (SDR) platform consisting of GNU Radio and USRP. This platform is then reconfigured for DSA based on Cognitive Radio (CR) technology which features include abilities to sense, learn, adapt and react according to the environment. The proposed design of the DSA based CR system consists of four main functional blocks: spectrum sensing, spectrum management, spectrum decision and data transmission. In this paper, we address the implementation of DSA based CR on IEEE802.15.4 standard. The result shows a significant improvement in term of Packet Reception Rate (PRR) for CU with DSA based CR system compared to the system without DSA capability.
    RF and Microwave Conference (RFM), 2011 IEEE International; 01/2011
  • A. Z. Anis Izzati, Norsheila Fisal, Sharifah K. Syed Yusof, Mazlan Abbas
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    ABSTRACT: Cooperative relay has been an interesting research area for the past years as it promotes higher data rates and robust to wireless environment. IEEE Work Group initiated the use of relay stations in the IEEE 802.16e standard and it is called IEEE 802.16j. This paper proposed a multi-hop cooperative relay system with space-time codes (STC), with the integration of relay selection. In changing environment, data transmission signals through wireless channels can be degraded by factors like shadowing, fading etc. Cooperative relay system is believed to offer robustness by multipath routes to destination. The cooperative relay system in this work adopted the virtual MIMO (multiple input multiple output) concept. Analysis of performances are made between topologies of space-time cooperative relay systems and compared with cooperative relay transmission.
    01/2011;
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    ABSTRACT: Self-organizing network/s (SON) was promoted by the Third Generation Partnership Project (3GPP) and Next Generation Mobile Networks (NGMN). SON has been introduced since in 3GPP Release-8, Release-9 and currently included in Release-10 framework as an excellent solution that promises improvements and market potential for future wireless networks. The purpose of this paper is to provide an overview on SON in advanced wireless networks such as Long Term Evolution (LTE) and LTE-Advanced systems. Although SON promises several advantages for both network operators and users, there are still challenges in implementing SON network in reality. Therefore, this paper addresses those possible challenges, discusses about SON implementation in inter-cell interference of cross-tier networks and provides future trends of the research area.
    01/2011;