S.K.S. Yusof

Universiti Teknologi Malaysia, Bharu, Johor, Malaysia

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Publications (90)9.04 Total impact

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    Mathematical Problems in Engineering 11/2014; · 1.08 Impact Factor
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    ABSTRACT: Wireless mesh networks (WMNs) have gain attention from researchers in telecommunication engineering field due to its potential to provide low cost internet broadband access, wireless local area network coverage and network connectivity for stationary or mobile host. This network consists of multiple wireless routers that are used to relay each other's packet in multi-hop fashion. Hence, routing protocol plays an important part in maintaining the connectivity of WMNs. In this paper, two routing protocols, Ad hoc On-demand Distance Vector (AODV) and Hybrid Wireless Mesh Routing Protocol (HWMP) are compared in terms of their performance in WMNs. A random wireless mesh topology with router nodes is modelled in Network Simulator 3 by assuming that the router nodes are connected to its client nodes. The simulations are performed in two different topologies with varied number of nodes. Three merits are taken into account when making the comparisons which are packet delivery fraction, throughput, and end-to-end delay. The simulation results demonstrate that HWMP is more suitable to be applied in WMNs compared to AODV.
    2013 IEEE International RF and Microwave Conference (RFM); 12/2013
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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
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    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
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    ABSTRACT: This paper presents a novel collaborative beamforming (CB) method of wireless sensor network (WSN) by organizing sensor node location in a circular arrangement. Appropriate selection of active CB nodes and cluster is needed each time to perform CB. The nodes are modeled in circular array location in order to consider it as a circular antenna array (CAA). This newly proposed circular collaborative beamforming (CCB) is further presented to solve two different objectives, that is, sidelobe level (SLL) suppression and first null beamwidth (FNBW). Analyses obtained are compared to those from previous work. The findings demonstrate a better CB performance of intelligent capability, and the difference is shown in normalized power characteristic.
    International Journal of Distributed Sensor Networks 07/2013; 2013. · 0.92 Impact Factor
  • 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
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    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: Computer and wireless communication require Internet accessibility at anytime and anywhere; this includes in a high-speed mobile station such as in speedy trains, fast moving cars as vehicle-to-infrastructure communication. However, wireless Quality of Service (QoS) provisioning in such an environment is more challenging. This increased the development of numerous schemes concerning the need of smooth handover of the mobile nodes. Conversely, transport layer (L4 in ISO layers) protocols such as stream control transmission protocol can support such a seamless handover in high-speed mobility users. This article highlights on the issues of moving users in mobile WiMAX networks. An adaptation of transport layer protocol of the high mobility vehicle that supports seamless handover can guarantee and maintain QoS for rapid handover rates. The results show an improvement of L4 protocol in terms of delay time and throughput in order to enable efficient and robust mobility aware protocols.
    EURASIP Journal on Wireless Communications and Networking 01/2012; 2012(1). · 0.81 Impact Factor
  • International Journal of Computer Applications 08/2011; 27(2):48-53. · 0.82 Impact Factor
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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