Showing papers by "Borhanuddin Mohd Ali published in 2011"

A Low Complexity Partial Transmit Sequence for Peak to Average Power Ratio Reduction in OFDM Systems

Abstract: Partial transmit sequence (PTS) is one of the most important techniques for reducing the peak to average power ratio (PAPR) in OFDM systems. This paper presents a low complexity PTS scheme by applying a new phase sequence. Unlike the conventional PTS which needs several inverse fast Fourier transform (IFFT) operations, the proposed scheme requires half IFFT operations only at the expense of slight PAPR degradation. Simulation and results are examined with QPSK modulation and OFDM signal and power amplifier with memory effects.

Enhanced handover mechanism in long term evolution (LTE) networks

Abstract: Over the past decade, there have been great interests in cellular and fixed radio access technologies for providing mobile, nomadic and fixed telecommunication services. The fast pace development of this technology and the challenges it presents due to the increasing number of user equipments and the demand to have the service on-the-go, have presented new challenges on base stations capability and the handover (HO) techniques. To address these challenges intensive researches are being carried out to define algorithms that can handle the HO decisions based on user equipment (UE) requirements and quality of service (QoS) expectations. This paper investigates the improvement steps for HO mechanisms in long term evolution (LTE) system which is being formally submitted as a candidate 4G system. LTE network is expected to support mobility with speeds of up to 500 km/h, when the HO will then become more frequent and fast. The basis of the approach is to reduce the number of unnecessary HOs. The strengths and weaknesses for each algorithm are discussed, and conclusions are subsequently made. Key words: Long term evolution (LTE), handover/handoff (HO), user equipment (UE),ping-pong handover (HO), handover margin (HOM) time-to-trigger (TTT).

Gesture based automating household appliances

Abstract: Smart homes can be a potential application which provides unobtrusive support for the elderly or disabled that promote independent living. In providing ubiquitous service, specially designed controller is needed. In this paper, a simple gesture based automating controller for various household appliances that includes simple lightings to complex electronic devices is introduced. The system uses the gesture-based recognition system to read messages from the signer and sends command to respective appliances through the household appliances sensing system. A simple server has been constructed to perform simple deterministic algorithm on the received messages to execute matching exercise which in turn triggers specific events. The proposed system offers a new and novel approach in smart home controller system by utilizing gesture as a remote controller. The adapted method of this innovative approach, allows user to flexibly and conveniently control multiple household appliances with simple gestures.

Movement direction-based handover scanning for mobile WiMAX

Abstract: Mobile WiMAX is a broadband technology that is capable of delivering triple play services (voice, data, and video). However, mobility in WiMAX system is still an issue when the mobile station (MS) moves and be handovered between base stations (BSs). This issue can cause unnecessary neighboring BS scanning and association, handover delay, and MAC overhead which may affect real-time applications. In this paper, the MS movement direction prediction (MMDP) based MS scanning to overcome the mobile WiMAX handover issues is presented. In this scheme, only potential BS candidates will be chosen for scanning purpose. Hence, the MS scanning process reputation will be reduced with these shortlisted BS candidates instead of scanning all neighbors BSs. Simulation results show that the proposed scheme reduces total scanning delay and scanning interval duration by 25% and 50% respectively.

Quality-improved and secure multicast delivery method in mobile IPv6 networks

Abstract: With widespread deployment of multicast over Wireless Local Area Networks (WLANs), several issues including fixed data rate transmission, multicast key distribution security, and overlapped multicast address have to be addressed for accommodating an efficient multicast scheme for WLANs. The latter problem can be addressed by utilizing Internet Protocol version 6 (IPv6) which provides significantly more address space compare to existing IPv4. However, in multicast IPv6 over WLANs, when a mobile moves to the border of the multicast group, the data are transmitted at the lowest base rate to support more coverage area, leading to poor Quality of Service (QoS). In this paper, a novel multicast data delivery method over WLANs based on IPv6 protocol is proposed to overcome the problem of fixed base rate and security key distribution in WLANs. Specifically, the proposed method dictates a WLAN Access Point (AP) to encapsulate the multicast packets into unicast Medium Access Control (MAC) packets, and subsequently forward them to the mobile host. In addition, the AP is also responsible for updating and distributing security keys whenever a join or leave operation occurs. The results from our test-bed indicate that the proposed method significantly improve the QoS metrics (i.e., throughput and delay) compared to the existing multicast scenario, as well as able to reduce the amount of generated keys in the networks.

FPGA implementation of novel peak-to-average power ratio reduction in orthogonal frequency division multiplexing systems

Abstract: In this paper a new partial transmit sequence (PTS) scheme called enhanced PTS (EPTS) is introduced to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. This is followed with the implementation procedure in field programmable gate array (FPGA). The new phase sequence reduces complexity significantly due to a decrease in the number of searching to find the optimum phase sequence. Simulation results confirm comparable PAPR performance between simulation and implementation results.

WiFi/WiMAX Seamless Convergence with Adaptive Vertical Handover for Continuity of Internet Access

Abstract: The next generation of the wireless networks will consist of several overlapping tiers. Provision of undisrupted communication to mobile users is a challenging task. Handover delay is one of the problematic issues that users are faced in the heterogeneous networks. However, in the case of both the WiMAX and the WiFi technologies which are located at the same base station (BS), the vertical handover (VHO) delay will be less as compared with the two conventional WiMAX/WiFi heterogeneous networks with two different wireless Internet service providers (WISP). Nevertheless, protocol conversion is still adding delay and jitter for data exchange between the needed two technologies. In this paper, in order to reduce the delay in the protocol conversion, a new industrial design for WiWi (WiMAX and WiFi) adaptation layer is proposed. The realization of the interworking between these two standards is discussed and evaluated. The results show that the proposed scheme-with the scenario under study- has better performance than other related works.

Scalable Rekeying Algorithm in IEEE 802.16e

Abstract: IEEE 802.16e standard provides wide coverage and high bandwidth for subscribers in a metropolitan area network. It introduces Multicast and Broadcast Rekeying Algorithm (MBRA) which is a multicasting scheme to communicate with many users concurrently. Although ELAPSE (for Efficient sub-Linear rekeying Algorithm with Perfect SEcrecy) improves on the deficiencies of MBRA, the algorithm poorly responds to scalability issue. This paper proposes a Scalable Rekeying Algorithm (SRA) based on a complete binary tree structure. SRA is introduced with linear linked list structure in order to make the system more scalable. Evaluation analysis shows that SRA manages to improve the scalability issue in MBRA for Mobile WiMAX.

Energy efficient geographical and power based clustering algorithm for heterogeneous wireless sensor networks

Abstract: Wireless Sensor Network (WSN) has gained tremendous research attention recently due to their extensive applications. As sensor nodes being battery operated, many researchers have made attempts to prolong the lifespan of the WSN by reducing the-per node energy consumption and efficiently utilizing the sensor nodes. However, in the tradition WSNs, nodes were homogeneous and hence could not take full advantage of the presence of heterogeneity in the network. To solve this problem in this paper, we propose Geographical and power based clustering algorithm (GPCA): a heterogeneous-aware clustering protocol, which has significant impact on the entire energy dissipation of WSNs. In GPCA, a Virtual Header (VH) transfers data to the nearest VH, and the nearest VH forwards the data to sink node. In this way, the energy dissipation of the entire network is reduced because of the transmitting distance between VHs and the sink that is greatly shortened. Also, a large number of nodes are self-organized by a distributed cluster formation technique. Moreover, a randomized technique is used to rotate the local cluster-heads base on power label in order to evenly distribute the energy load among the sensors in the network. GPCA uses geographical position to enable scalability and robustness for dynamic networks. By using simulation, the proposed GPCA scheme shows superior performance over the current energy-efficient schemes in terms of network lifespan, Energy dissipation and number of alive nodes.

Study of BER in DVB-S2 satellite implemented in Matlab

Abstract: Satellite broadcasting has been considered lately as a promising media for IP streaming due to their wide coverage and high reliable bandwidth. Long propagation delay in GEO satellite system will affect the adaptive algorithms in DVBS-2/RCS systems. Long feedback delay will cause improper physical layer selection of modulation and coding (ModCod). This paper aims to provide an algorithm for physical layer selector in DVB-S2/RCS satellite systems. This algorithm will makeless ModCod switching of the adaptive coding and modulation (ACM) usingreduced number of ModCod combinations. We conclude that the number of ModCods in ACM algorithm can be relatively adjusted to maximize DVB-S2 system stability.

Review of interference avoidance schemes in femtocell networks

Abstract: Femtocell is a solution to increase the system capacity and coverage to meet the high demand of the next generation of services on broadband wireless access.However, the deployment of a new femtocell layer may have an undesired impact on the performance of the macrocell layer. The allocation of spectrum resources and the avoidance of electromagnetic interference are some of the more urgent challenges that operators face before femtocells become widely deployed. In this paper different interference avoidance schemes are described and compared. Special attention is paid to the use of uplink and downlink power control and self-configuration and self-optimization techniques for the avoidance of interference.From the review, we conclude that frequency planning is suitable for interference avoidance schemes for unplanned location of femtocells deployment. Key words: Femtocell, macrocell, cellular, orthogonal frequency division multiple access, interference avoidance.

Wireless Controller Area Network Using Token Frame Scheme

Abstract: The controller area network (CAN) has been long regarded as the pioneer in standardizing vehicle bus standard. Its influence has even been reached out to various applications in industrial automation; which includes military, aviation, electronics and many others. With wireless technology becoming more pervasive, there is a need for CAN too to migrate and evolve to its wireless counterpart. In this paper, a new wireless protocol named wireless controller area network (WCAN) is introduced. WCAN is an adaptation of its wired cousin, controller area network (CAN) protocol which has not being properly defined. The proposed WCAN uses the concept introduced in wireless token ring protocol (WTRP); a MAC protocol for wireless networks and efficient in a sense to reduce the number of retransmission due to collisions. Additionally, it follows most of its wired cousin attributes on message-based communication. Message with higher priority has the first priority in transmitting their message into the medium. In WCAN, stations or nodes take turns in transmitting upon receiving the token frame that are circulating around the network for a specified amount of time. WCAN was tested in a simulation environment and is found that it outperform IEEE 802.11 in a ring network environment.

Design considerations for efficient multicast wdm network scalable architecture

Abstract: In this paper, we present a method for designing a passive optical based single-hop wavelength division multiplexing multicast network architecture that can achieve a scalable structure and form the basis of a wavelength efficient single-hop WDM network. The proposed architecture minimizes the number of wavelengths required for efficient multicast service and also minimizes tunability requirement of the transceivers. The network size scalability is achieved by adding transmitters and receivers to the designated groups. We show that the proposed system can accommodate large tuning delays and keeps with suitable throughput when the number of wavelength is equal to the number of nodes. We also show that the design can lead to a scalable structure while minimizing the number of wavelengths and tunability of the transceivers required for an efficient multicast service resulting in an improved system throughput and delay performance

Weblog search engine based on quality criteria

Abstract: Nowadays, increasing amount of human knowledge is placed in computerized repositories such as the World Wide Web. This gives rise to the problem of how to locate specific pieces of information in these often quite unstructured repositories. Search engines is the best solved. Some studied show that, almost half of the traffic to the blog server comes from search engines. The more outgoing and informal social nature of the blogosphere opens the opportunity for exploiting more socially-oriented features. The nature of blogs, which are usually characterized by their personal and informal nature, dynamically and constructed on the new relational links required new quality measurement for blog search engine. Link analysis algorithms that exploit the Web graph may not work well in the blogosphere in general. (Goncalves et al 2010) indicated that most of the popular blogs in the dataset (70%) have a PageRank value equal -1, being thus almost invisible to the search engine. We expected that incorporated the special blogs quality criteria would be more desirably retrieved by search engines.

Self-Decision Route Selection for Energy Balancing in wireless sensor betworks.

Abstract: In many wireless sensor network (WSN) applications, data from the monitored environmental phenomenon only need to be sampled intermittently and transmitted to the base station. Hence, an intelligent protocol that balances the traffic load among the nodes and minimizes their energy usage, especially during routing and idle listening, which is necessary to extend the network lifetime. In this paper, a load balancing model that balances the rate of energy dissipation of the sensor nodes across the network is proposed. The proposed energy balancing scheme distributes the traffic load regularly and slowly over the sensor nodes during routing, such that the overall network life time is optimized, and the sensors die almost all at the same time. The proposed energy balancing protocol reduces the high energy consumption during the transmission and reception states, this is done by introducing multi-hop instead of single-hop communication of each node with the sink. Simulation results show that the proposed energy balancing protocol reduces the transmission energy usage by up to 64%, while the reception energy usage is reduced up to 67%. Moreover, the system throughput as well as the network lifetime increased up to 79% and 66%, respectively.

Fair bandwidth assignment in hierarchical scheduling for mobile WiMAX system

Abstract: The increasing demands for multimedia applications with various QoS requirements arouse the interest of researchers in the Fourth-generation wireless networks such as WiMAX. In order to ensure that the QoS requirements of these applications are met, effective scheduling algorithms must be designed. Even though it may be trivial to ensure that the minimum QoS of all service classes is attained, this often results in a marked degradation of the overall system throughput. In this paper, we propose a fair bandwidth assignment algorithm that allocates the bandwidth among different services classes based on a hierarchical scheduler. By taking the overall system throughput and the QoS requirements into consideration, our proposed algorithm dynamically assigns the available bandwidth to the various service classes in such a way that the network resource utilization is optimized. Simulations result showed that the proposed algorithm optimize the overall system throughput and assigns bandwidth effectively to the different service classes while ensuring that the QoS requirements are satisfied.

On fractional and semi-soft handover in long term evolution (LTE) networks

Abstract: The fast pace of development of telecommunications technology and the challenges presented with the increasing number of users for any service, anywhere, anytime, access creates new problems with on the base stations capability and the handover/handoff (HO) techniques. To face these challenges much research have been made to come out with algorithms that can handle handover of user equipment (UE) while maintaining their respective quality of service (QoS). In this paper a hybrid HO algorithms called semi-soft handover (SSHO) and fractional soft handover (FSHO) in long term evolution (LTE) system are studied. The outage probability, the main metric to evaluate handover, is compared for different handover techniques.

A Low Complexity Resource Allocation Algorithm for OFDMA Cooperative Relay Networks with Fairness and QoS Guaranteed

Abstract: This paper proposes a new resource allocation algorithm for uplink OFDMA-based cooperative relay networks, assuming multiple user nodes, multiple relay nodes and a single destination. The aim is to maximise the total sum of the users' data rates, while guaranteeing fairness among them with different QoS requirements. Assuming perfect channel state information (CSI) at the resource allocation controller, the optimisation problem is formulated such that each user is assigned a weight factor based on its QoS requirements. The ones with higher weights are given higher priorities to select their resources (relay stations and subcarriers) first. Once the required QoS is achieved for all users, the weight factor for all users is reduced to a small uniform value. The remaining resources are then allocated to the users with higher instantaneous rates in order of magnitude. The results show that the proposed algorithm outperforms the greedy and static algorithms in terms of outage probability and fairness, and at the same time outperforms Jeong's algorithm by 58% in terms of total sum rate, with an average 74% reduction in system complexity.

A lower complexity k best algorithm for multiple input multiple output detection

Abstract: This paper presents Multiple Input Multiple Output (MIMO) detection steps using tree search based method known as the ‘K’ best algorithm. This low complexity algorithm is based on probabilistic approach of sphere decoding with self adjustable capability depending on the levels (root, branch, leaf etc.) of a tree. While the tree was searched to estimate the transmitted symbols level by level, the algorithm took into account the effect of the undetected symbols in the search criteria. Simulation results showed that the proposed method reduced complexity (in terms of the average number of visited nodes) about 10% for higher (medium to high) signal to noise ratio (SNR) values without degrading the system BER performance. Key words: Multiple input multiple output, sphere decoding, K best algorithm.

A Novel Ternary CDMA Code for TPSK Modulation Scheme

Abstract: In code division multiple access (CDMA), two or more chips are grouped together to form symbols and each symbol is transmitted during the symbol period. The phase shift keying (PSK) modulation techniques map the digital baseband data into two or more possible signals by varying the phase of a radio frequency (RF) carrier. The recently proposed PSK scheme called ternary PSK (TPSK) scheme can convey three possible symbols. In this paper, a novel ternary based CDMA sequence so-called large area synchronous even ternary (LAS-ET) sequence is introduced to increase spectrum efficiency in TPSK scheme. Its sequence duty ratio and cross-correlation are analyzed. The performance analysis of this sequence is compared with the large area synchronous (LAS) sequence in term of symbol error rate and chip error rate (CER) over various channel models. It is shown that TPSK scheme in LAS-ET sequence outperforms LAS sequence in terms of CER evaluation. At the same time, the spectrum efficiency is doubled when a pair of chips in LAS-ET sequence is mapped into one symbol.

SP-AMC scheme for visual data transmisson over wireless fading channel

Abstract: In this paper, an efficient superposition coding with adaptive modulation and coding (SP-AMC) system, for the optimal system performance, is proposed. The proposed SP-AMC system switches its modulation and coding scheme (MCS) adaptively in order to select the suitable modulation order and coding rate that are best match with the instantaneous channel condition. Hence, better performances in both data rate and error probability can be attained. Moreover, the source data is divided into a number of different priority layers with different importance. The bit streams of these layers are then encoded and modulated individually with different unequal error protection (UEP) levels against channel corruption. The highest UEP level is assigned to the highest priority layer which has the highest effect on the reception quality, and vice versa. The modulated bit streams of all layers are then superimposed together and transmitted over Rayleigh fading channel. At the receiver side, a multi-stage decoding (MSD) receiver is used to reconstruct the source data by applying the ordered successive interference cancellation (O-SIC) technique, which demodulates the layers according to the order of their priorities.