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ABSTRACT: The feature of 6LoWPAN is the capability of the dynamic assignment of 16-bit short addresses. Hierarchical routing (HiLow) algorithm that uses dynamically assigned 16-bit unique short address as its interface identifier has an advantage of memory saving. The 16-bit unique short address is assigned to a 6LoWPAN device during an association operation with a neighbor node which is also called parent node in HiLow. Besides reducing the overhead of maintaining routing table, HiLow also supports for larger scalability. However, previous research did not deal with the path recovery when sensor nodes in HiLow are failed. The node failure may be due to the battery lifetime of the 6LoWPAN device. This kind of failure will cause the expiration of the association event and make the previously assigned 16-bit short address of the child node from the failure parent node become invalid within PAN. In this paper, a new path recovery mechanism so-called step parent node (SPN) algorithm is proposed to conventional HiLow to reassign the valid 16-bit short addresses for the child nodes of the failure parent node and provide the path robustness. The child nodes of the failure parent node will broadcast a step parent node request message (spn_request) to the neighbor nodes. The neighbor node whose child nodes do not exceed the maximum child value will act as a step parent node of the new child nodes. It enhances the reliability of conventional hierarchical routing mechanism.
Computer and Communication Engineering (ICCCE), 2010 International Conference on; 06/2010
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ABSTRACT: This paper proposes a cross-layer optimized strategy that reduces the effect of interferences from neighboring nodes within
a mesh networks. This cross-layer design relies on the routing information in network layer and the scheduling table in medium
access control (MAC) layer. A proposed routing algorithm in network layer is exploited to find the best route for all subscriber
stations (SS). Also, a proposed centralized scheduling algorithm in MAC layer is exploited to assign a time slot for each
possible node transmission. The cross-layer optimized strategy is using multi-channel single transceiver and single channel
single transceiver systems for WiMAX mesh networks (WMNs). Each node in WMN has a transceiver that can be tuned to any available
channel for eliminating the secondary interference. Among the considered parameters in the performance analysis are interference
from the neighboring nodes, hop count to the base station (BS), number of children per node, slot reuse, load balancing, quality
of services (QoS), and node identifier (ID). Results show that the proposed algorithms significantly improve the system performance
in terms of length of scheduling, channel utilization ratio (CUR), system throughput, and average end to end transmission
delay.
KeywordsWMN-Routing-Scheduling-Multi-Channel Single Transceiver
12/2009: pages 316-332;
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ABSTRACT: Outcomes-based education (OBE) system is a motivated and reformed education system. OBE has been implemented in Bachelor of Engineering (B. Eng) programme offered by the Faculty of Engineering, Universiti Putra Malaysia since 2006. The learning process focuses on measuring the students' outcomes empirically. To contrast to OBE, the conventional learning system is primarily focuses on the resources available to students and to lecturers. In this paper, we present the relationship between the workload and the current implemented OBE learning system. Suggestions to improve the current OBE learning systems are also presented in order to enhance the learning method to benefit every entity involve in this system A survey was conducted to the student in the Department of Computer and Communication Systems Engineering. Most of the respondents do understand and aware about the concept of OBE since it was implemented. From the survey, more than 80 % of the respondents aware the implementation of OBE in the department and 75% of them agree that OBE system has increased their workload.
Research and Development (SCOReD), 2009 IEEE Student Conference on; 12/2009
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ABSTRACT: Mobility of sensor nodes posed new challenges particularly in energy consumption and demands researchers' attention. Some real applications impose combined environments of fixed and mobile sensor nodes in the same network, while others demand a complete mobile sensors environment. Packet loss that occurs due to mobility of the sensor nodes is one of main challenges in Wireless Sensor Network (WSN) and it comes in parallel with energy consumption. In this paper, we propose adaptive Time Division Multiple Access (TDMA) scheduling and round free cluster head protocol called Cluster Based Routing (CBR) protocol for Mobile Nodes in Wireless Sensor Network (CBR Mobile-WSN). In this protocol the cluster head receive data from not only its member during the TDMA allocated time slot but also other sensor nodes that just enter the cluster when it has free time slots, each cluster head takes turn to be the free cluster head in the network. CBR Mobile-WSN change TDMA scheduling adaptively according to traffic and mobility characteristics. The proposed protocol sends data to cluster heads in an efficient manner based on received signal strength. The performance of proposed CBR Mobile-WSN protocol is evaluated using MATLAB and it has been observed that the proposed protocol reduces the packet loss by 25% compared to LEACH-Mobile protocol.
Collaborative Technologies and Systems, 2009. CTS '09. International Symposium on; 06/2009
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ABSTRACT: High quality of data transmission services is an important task for wireless broadband communication systems. This paper is concerned with the design problem of real-time wireless data transmission which provides unequal error protection (UEP). Using superposition coding, the rea-time data stream is divided into two streams, high priority (HP) and low priority LP streams depending on their interest. These two bit streams are encoded separately, and then superimposed together with two different level of power to achieve the UEP for them in the receiver end. Feedback of channel state information (CSI) is used in adaptive physical layer channel for efficient use of the current available bandwidth. In this proposed scheme, same recourses; time, bandwidth and power are used to increase the transmission efficiency compared with other schemes which are use transmission of one data stream with one power level but in different techniques to exploit the available bandwidth.
Innovations in Information Technology, 2008. IIT 2008. International Conference on; 01/2009
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ABSTRACT: This paper presents a developed RFID based theft prevention system such that luxurious belongings, such as laptops which are monitored from being stolen. Global systems mobile (GSM) module is added to provide a complementary system to feedback to the users. The laptop tag ID and its timer sensed from RFID reader are registered in the system server. When the connectivity is broken when the laptop is taken away by more than its allowable distance, an alarm system will be alerted from server. A short message alerting the owner will be sent via the GSM module within a short period of time. This integrated system of RFID and GSM modules form a robust wireless security system. This system can be improved by using Bluetooth pervasive technology such that it can be exploited easily since it is been embedded in most of the mobile devices.
RF and Microwave Conference, 2008. RFM 2008. IEEE International; 01/2009
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ABSTRACT: The WiMAX mesh networks based on IEEE 802.16 standard was developed with the base station (BS) as a coordinator for centralized scheduling. However, interferences from transmission of the neighbouring nodes within the mesh networks are inevitable. This paper proposes a centralized scheduling algorithm that can reduce interferences by constructing routing tree with multi-channel single transceiver system in WiMAX mesh networks. In this algorithm, each node has one transceiver that can be tuned to any of the channels, intending to eliminate the secondary interference. The parameters of interference, hop-count, no. of children per node, spatial reuse, fairness, load balancing, quality of services (QoS) and node identifier (ID) are considered. The results of analysis show that this proposed algorithm greatly improves the length of scheduling and the channel utilization ratio (CUR).
RF and Microwave Conference, 2008. RFM 2008. IEEE International; 01/2009
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M. A. M. Azau,
A. F. Abas,
M. I. Saripan,
W. A. Wan Adnan, N. K. Noordin,
Ismail A,
Mokhtar M,
Samsudin K,
Mashohor S,
M.F.A. Rasid,
R. S. A. Raja Abdullah,
Arif F
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ABSTRACT: This paper presents a new method in engineering education called a continuous-grouped-self-learning (CGSL) system. In general, based on feedbacks acquired from the student at the end of the implementation, students better understanding and appreciation to the courses been taught. Out of 60 students 71.7% admitted that this learning system has improved their study style and knowledge acquisition, which then agreed to be implemented in future. The observation shows that this system increases the appreciation to the knowledge better than conventional method. Apart from that the system also produced better students in term of responsibility, self-confidence, competitiveness, group work, and knowledge sharing. This is realized with the implementation of mock teaching assessment.
International Education Studies. 01/2009;
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ABSTRACT: The WiMAX mesh networks based on IEEE 802.16 standard is a key topology for the next generation wireless networking. However, interferences from transmission of the neighboring nodes within the mesh networks are inevitable. Cross-layer design for tree-type routing and level-based centralized scheduling is proposed as the optimization strategy. The cross-layer design here is relying on the routing information in network layer and centralized scheduling in the medium access control (MAC) layer. This paper proposes a centralized scheduling algorithm that can reduce interferences by constructing routing tree with multi-channel single transceiver system in WiMAX mesh networks. In this algorithm, each node has one transceiver that can be tuned to any of the channels, intending to eliminate the secondary interference. The results of analysis show that this proposed algorithm greatly improves the length of scheduling, channel utilization ratio (CUR) and throughput.
TENCON 2008 - 2008 IEEE Region 10 Conference; 12/2008
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ABSTRACT: In this paper, we consider a V-BLAST/STBC wireless communication architecture, which integrates Alamouti space-time block codes (STBC) layer with vertical Bell-labs layered space-time (V-BLAST) layer, in MIMO wireless communication system with four transmitter and three receiver antennas over Rayleigh flat-fading channel. We propose an algorithm, which combines the algorithm of successive interference cancellation zero-forcing (SIC ZF) and successive interference cancellation zero-forcing with maximum a posteriori probability (SIC ZF MAP). The proposed algorithm (SIC ZF / ZF MAP) reduces the complexity if compared with the algorithm of SIC ZF MAP alone. Simulation results show the symbol error rate performance degradation of the proposed algorithm is small compared to SIC ZF MAP detection.
Advances in Electronics and Micro-electronics, 2008. ENICS '08. International Conference on; 11/2008
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ABSTRACT: Nowadays, a lot of efforts have been given to reduce hardware and software development cost. Many of today's military and commercial communication systems use Software Defined Radio (SDR) technology to create various different hardware combinations in term of software control. In this paper, we present an approach to design a SDR based traffic management system by tuning between two different digital modulation schemes: ASK and FSK. The wavelet transform technique has been used for modulation identification. The performance of the identification scheme is investigated through simulations, for different signal to noise ratio (SNR). The system identification performance is improved more than 95% when SNR is more than 9dB.
Telecommunication Technologies 2008 and 2008 2nd Malaysia Conference on Photonics. NCTT-MCP 2008. 6th National Conference on; 09/2008
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ABSTRACT: This document gives some definitions about PHY and MAC layer displaying its internal architecture and major functions to both layers. And as the same time states some information about cross-layer design, discussing the architecture of the cross-layer, and focusing on major methods of interfacing with giving one example of data transmission and interfacing which is meant to be very useful in this stage. Each researcher may walk through some problems during time of enhancement and optimization for the cross-layer, so here we stated some challenges to solve some problems with concentrating on number of points of classifications for cross-layer solutions.
Telecommunication Technologies 2008 and 2008 2nd Malaysia Conference on Photonics. NCTT-MCP 2008. 6th National Conference on; 09/2008
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ABSTRACT: This paper investigates the problem of peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) system. It presents a new PAPR reduction method based on addition of power of random signals in a complex Gaussian distribution form to the data constellation points in frequency domain. The added signals alter the constellation shape by shifting the constellation points from their original positions into new positions. This change in shape is accompanied by changes in the statistical properties and reduction in the PAPR value. There is no need to send side information to the receiver for signal recovery. This scheme significantly reduces the PAPR value without decrease in the bit rate or BER performance. Moreover, there is no out-of-band distortion resulted. For 64-PSK OFDM system using 128 data sub-carriers, >4 dB reduction in the PAPR value is achieved by using the proposed PAPR reduction method.
Computer and Communication Engineering, 2008. ICCCE 2008. International Conference on; 06/2008
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ABSTRACT: In this paper, an adaptive time-domain (TD) channel estimation scheme, based on recursive least squares (RLS) algorithm, is proposed for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) based wireless local area networks (WLANs). The estimator is then extended to perform decision-directed (DD) channel tracking during data transmission. The channel is assumed to be constant during one OFDM symbol but evolves in time according to the first-order Markov process. Different training rates at different Doppler frequencies were investigated. Simulation results show that the proposed estimation scheme has excellent performance measured in terms of the mean squares error (MSE) and the bit error rate (BER), provided that the forgetting factor of the RLS algorithm is optimally selected.
Computer and Communication Engineering, 2008. ICCCE 2008. International Conference on; 06/2008
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ABSTRACT: Wireless sensor network (WSN) is made up of large numbers of sensor nodes. Each sensor node possesses the ability to monitor some aspect of its environment. Since data diffusion is vital in WSN, optimized protocols need to be used to guarantee an energy efficient operation of the network by extending the lifetime of individual sensors. To achieve this goal, the transmission range of sensors is first decomposes into certain ranges based on a minimal distance between consecutive forwarding sensors and then classifies these ranges due to Degree of Interest. The work also focuses on the selection of sensors as forwarders which lie on or closely to the shortest path between a source sensor and the sink to yield minimum energy consumption and delay. The energy-aware challenge is presented through the computation of lower and upper bounds on energy consumption and source-to-sink delay.
Communications, 2007. APCC 2007. Asia-Pacific Conference on; 11/2007
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ABSTRACT: In this paper, exponentially-weighted recursive least squared (EW-RLS) channel estimation for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is investigated. Channel estimation in time-domain (TD) as well as frequency-domain (FD) is investigated through exploiting preambles and pilot symbols inserted in TD and FD, respectively. The channel is assumed to be slowly time-varying frequency-selective, constant during one OFDM symbol but changing from symbol to symbol. Simulation results show that the TD EW-RLS estimator has better estimation performance in terms of the mean-squares error (MSE) and bit-error rate (BER), compared to FD EW-RLS estimation approach. The computational complexity is significantly reduced by recursively updating the channel estimates and by applying the matrix inversion lemma.
Communications, 2007. APCC 2007. Asia-Pacific Conference on; 11/2007
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ABSTRACT: In this paper, an adaptive channel estimation scheme for MIMO OFDM systems based on time-domain training and recursive least squared (RLS) algorithm is proposed. Time orthogonal as well as simultaneously transmitted training sequences are considered. The channel is assumed to be slowly varying time-dispersive, i.e., constant during one OFDM symbol but changing from symbol to symbol. Channel estimation is performed in time-domain followed by zero-forcing equalization in the frequency-domain. The computational complexity is significantly reduced by applying the matrix inversion lemma. Simulation results show that the proposed estimator with time orthogonal training sequences has better estimation performance over a range of Doppler spreads compared to the case when the training sequences are simultaneously transmitted from the different transmit antennas.
Telecommunications and Malaysia International Conference on Communications, 2007. ICT-MICC 2007. IEEE International Conference on; 06/2007
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ABSTRACT: This paper describes a multiple-input single-output (MISO) orthogonal frequency division multiplexing employing space-time-frequency coding with antenna selection at the receiver. The system in tested in a severe IEEE 802.16 broadband wireless access channels. Adaptive multiple antenna selection (AdMAS) was performed based on the second-order moment of the channel impulse response and only good channels were use for data transmission. Results show that our second-moment-based AdMAS scheme with 2 most faded transmitters turned off outperforms similar schemes based on the mean of the CIR, and conventional coded STF-OFDM. Second-moment-based scheme shows significant gain in terms of Signal to Noise Ratio (SNR) requirement especially at higher level constellations which makes it a potential scheme to be employed for realization of high data rates system.
International Journal of Engineering and Technology. 01/2007; 4:166-174.
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ABSTRACT: In this paper we present an adaptive multiple antenna selection (AdMAS) employing a maximum of 4 transmit (4 Tx) and 1 receive (1 Rx) antenna in conjunction with coded space-time-frequency (STF) orthogonal frequency division multiplexing (OFDM) over wireless local area network (WLAN) IEEE 802.11 channels. Our coded STF-OFDM is a product of 4-QAM STF block code which has been concatenated with convolutional codes of rate 1/2 with length of 5. In transmitting data we adaptively select channel with least fade and turn off the most faded channel at the transmitter side. We determine levels of fading of each transmitter channel based on the statistical average of the channel impulse response (CIR). We also compare results when level of fading is based on the variance of the CIR. Results show that, the employment of AdMAS does not significantly contribute to performance improvement (less than a dB gain), either adapting to mean or variance-based scheme, at shorter delay spreads (e.g. 100 ns). However at longer delay spreads (e.g. 1.3 μm) our proposed AdMAS scheme outperforms coded STF-OFDM scheme by as much as 4 dB to achieve a BER of 10<sup>-3</sup>.
Applied Electromagnetics, 2005. APACE 2005. Asia-Pacific Conference on; 01/2006
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ABSTRACT: In this paper we present an adaptive multiple antenna selection (AdMAS) employing a maximum of 4 transmit (4 Tx) and 1 receive (1 Rx) antenna in conjunction with coded space-time-frequency (STF) orthogonal frequency division multiplexing (OFDM) over broadband wireless access IEEE 802.16 Stanford Interim University (SUI) channels. Our coded STF-OFDM is a product of phase-shift-keying (PSK) modulated STF block code which has been concatenated with convolutional codes of rate 1/3, constant length of 8, and code generator of [225 331 367]. In transmitting data we adaptively select channel(s) with least fade and turn off the most faded channel(s) at the transmitter side. We determine levels of fading of the channel from each transmitter based on the calculated second moment of the channel impulse response (CIR). We also compare results when level of fading is based on the mean of the CIR. We tested our scheme in the most severe case of SUI channel, i.e SUI6. Results show that the employment of AdMAS does not give significant gain at low-level constellations. However significant gain is observed at higher constellations which makes our proposed scheme a potential scheme to be employed for the high data rate system.
Networks, 2005. Jointly held with the 2005 IEEE 7th Malaysia International Conference on Communication., 2005 13th IEEE International Conference on; 12/2005
