Mohammad Kamrul Hasan

An investigation of femtocell network synchronization

Currently, Femtocell technology emerged for cellular wireless networks, which has rapidly engrossed cellular industry. The principle of femtocell to the mobile operators is to reduce cost and improve signal quality in indoor coverage which is also considered a possible path to the fixed-mobile convergence (FMC) goal. Femtocell extends network coverage and delivers high-quality mobile services inside residential and business buildings through broadband network, i.e. ADSL. Femtocell access point (FAP) or home base station (HBS) intends to serve small number of users, i.e. 4 users and covers about 30 meter square similar to existing WiFi access points. However, femtocell introduces new challenges to the telecom industries in terms of handoff between femto and macrocells, interference management, localization and synchronization. Among all of these challenges, synchronization is considered corner stone for proper working for femtocell. The problematic issue in femtocell synchronization is that all the data and control traffics travel through IP broadband network. The IP broadband network is usually owned and managed by third party and not by the mobile operator, which is complicated the synchronization. Unsynchronized FAPs may cause harm interferences and wrong handover dictions. In this study we investigate and overview the current femtocell synchronization techniques and compare between them. Possible improvements and recommendation for each method is identified. Proposed schemes and indicated future research areas are also discussed.

Cluster-Based Spectrum Sensing Scheme in Heterogeneous Network

In OFDM based Heterogeneous Networks (HetNet) deploying femtocells (HeNodeBs) causes’ inter-cell interference in uplink as well as downlink. Spectrum allocation is one of the technique as many researcher identified. However, using frequency reuse/cognitive system for dynamic spectrum reallocation is also a challenging issues. Therefore, this paper focuses on unused spectrum sensing (SS) through proposing cluster-based spectrum sensing for OFDM based two-tier HetNets. The proposed SS scheme adopted the basic model of energy detector and compared with cooperative spectrum sensing scheme. In the proposed scheme, the energy detection model is extended into multiple channel detection model. To detect spectrums from nearby macrocell (macro-eNodeB) HeNodeBs are grouped into cluster. A cluster formation algorithm is also proposed in where, cluster head (CH) and signaling node (SN) will detect implies the multi-channel SS technique. The simulation results demonstrate that the proposed scheme can improve the spectrum detection with minimum error. The performance of the proposed scheme is evaluated in Monte Carlo simulation validate the scheme performance.

Design and Implementation of a Multihoming-Based Scheme to Support Mobility Management in NEMO

With the worldwide deployment of different wireless access technologies and expanding requests for worldwide Internet accessibility, Network Mobility (NEMO) is turning out to be all the more requesting innovation. Therefore, NEMO Basic Support Protocol (NEMO BSP) has been anticipated by the NEMO Working Group for the continual worldwide connectivity of each node within the mobile network. Yet, NEMO BSP experiences from higher handoff delay and packet loss. Thus, fails to provide seamless handoff. This issue can be resolved by introducing multihoming concept in NEMO. The reason is to support concurrent use of multiple interfaces on a single Mobile Router. Therefore, the main objective of this paper is to propose an innovative Multihoming-based scheme to support Mobility management in Proxy NEMO (MM-PNEMO) environment. In addition, the performance is assessed utilizing simulation approach to certifying the applicability as well as the efficacy of the suggested scheme. The performance metrics used for evaluation are namely handoff delay, packet loss, packet delivery ratio, as well as throughput. The simulation is done using NS-3 network simulator. The simulation outcomes demonstrate that the proposed MM-PNEMO scheme outperforms the standard NEMO BSP and PNEMO in terms of packet loss (less than 1%) and handoff delay (average improvement by 76%).

Dynamic spectrum allocation scheme for heterogeneous network

Recently, femtocells (HeNBs) are deployed in heterogeneous network (HetNets) attributable to the addition of coverage, capacity and impeccable spectrum efficiency in private buildings/office complexes surroundings. This unplanned placement of HeNBs creates co-channel interference (CCI) in orthogonal frequency division multiple access (OFDMA). As a result service, disruption occurred at the macrocell user and femtocell user. Therefore, with always expanding interest for frequency spectrum, there is have to make available more resource allocation in order to permit more quantities of unlicensed clients to transmit their signals in the authorized groups. Cognitive-based approaches may increase the spectrum efficiency by sharing resources opportunistically from unlicensed/licensed network. However, spectrum management processes quite difficult, and a lot of chance to occur interference at the cell-edge users. Therefore, a dynamic spectrum allocation scheme is proposed for OFDMA based HetNets. The proposed scheme efficiently reduces the interferences through subchannel detection. To accomplish the CCI mitigation, the proposed scheme is functioning using the energy exposure with group creation algorithm for subchannel detection. Finally, the detected subchannel is allocated through applying power allocation algorithm. The simulation results represent that proposed scheme is able to maximize the spectrum detection and enhanced the spectral efficiency. The improved spectral efficiency recuperates the CCI situation at underlay HetNets.

Enhancements of the Dynamic TXOP Limit in EDCA Through a High-Speed Wireless Campus Network

IEEE802.11e is a concrete challenge to providing quality of service (QoS) aimed at interactive multimedia (IMM) applications due to the resource allocation parameter for heterogeneous traffic flows. This parameter is fixed for different specific IMM traffic flows in the IEEE802.11e standard. However, due to the variation in traffic load on wireless campus networks (WCNs), the fixed allocation of the channel resource parameter is not sufficient to guarantee QoS for IMM traffic flows. Thus, many researchers have investigated dynamic regulation of this resource allocation parameter to ensure QoS. However, there are still some unresolved problems with this parameter. This paper introduces an enhanced EDCA resource allocation parameter named dynamic transmission opportunity (TXOP) limit that regulates according to the variation in traffic load over WCN. This work also employs a mathematical modelling approach for the proposed parameter and numerical analysis of the existing and proposed parameters. The evaluation of the proposed model is simulated using Qualnet 5.1. The simulation results show that the proposed scheme allows improving the QoS performance of IMM traffic by reducing end-to-end delay. Additionally, the results show that the proposed scheme significantly improves global throughput.

Frequency Modulated Continuous Wave Radar Modeling for Landslide Detection in Malaysia

Landslide is one of natural hazards that is frequently happen after continuous heavy rainfall especially during monsoon season. It effects serious damages on property and also treat human being’s live. The objective of this paper is to design and evaluate the performance of a Frequency Modulated Continuous Wave (FMCW) radar for detecting of slow moving landslide movements in Malaysia. The performance of the proposed radar design is tested by using Agilent Advanced Design System (ADS) software. It operates at 2.4 GHz carrier frequency with a resolution range of 0.75 m. Its signal power increases around 38 dBm after de-ramping process. Hence, it increases the sensitivity of the radar to detect the landslide occurrences. The radar has capability to detect landslide movements of 20 m/s speed.

Design and Development of Hybrid Time Synchronization Scheme to Mitigate the Phase and Frequency error for Asynchronous Link in Heterogeneous Network

The arbitrary deployment of HeNodeBs high-lights the importance of interference minimization in order to capture the best. Timing as well as synchronization are equally essential for control of HeNodeBs in 4G LTE devices. So as to sustain HeNodeBs for management, IEEE1588 master slave strategies are being used in order to maintain HeNodeBs for the control purpose. Nonetheless, as a result of poor internet connectivity for a long period HeNodeBs undergoes synchronization problems that leads to clock offset problem. Asymmetric link delays, due to phase and frequency misalignment causes the effects on interference and system QoS. Moreover, to mitigate interference and for QoS synchronization is prerequisite for heterogeneous network. This paper inspects the pros and cons of the IEEE 1588 algorithm and IEEE Precision Timing Protocol (PTP). Therefore, this paper proposed a hybrid phase and frequency synchronization scheme. Comparing to IEEE1588 and PTP, hybrid scheme can improve the clock Phase (offset), and frequency error in two-tier Heterogeneous Network. The proposed scheme is evaluated by Monte Carlo system level simulation, and the results are benchmarked with the existing techniques. The simulation outcome ensures that the hybrid time synchronization strategy is much better in Heterogeneous network with regards to phase (offset) and frequency errors

A Self-organizing Approach: Time Synchronization for the HeNodeBs in Heterogeneous Network

In Heterogeneous Network (HetNet) for LTE/LTE-A system femtocells (HeNodeBs) are designed and implemented to extend coverage and capacity. The arbitrary usage of HeNodeBs supported for indoor coverage is linked through a third-party internet backhaul to the HeNodeB managing server, and this is a segment of the operators end. To sustain HeNodeBs to the control function IEEE1588, master slave strategy is put in effect. Nevertheless, caused by the absence of internet or unfortunate connectivity for a prolonged period HeNodeBs undergoes synchronization difficulties that leads to frequency mismatch With this paper, a kind of self-organizing method is suggested for time synchronization in Heterogeneous Network, and that is standardized using IEEE1588 master slave method along with Precision Timing Protocol (PTP). The proposed approach is two way message transmission system, adopting the Least-squares Linear Regression Algorithm (LSRA) to reduce offsets as well as frequency misalignments (drift).

Effects of Phase Offset Error for Asymmetric Communication Link in Heterogeneous Mobile Network

Due to augmentation of data traffic, imperfect coverage in indoor surroundings small base stations for instance femtocells (HeNodeBs) are deliberated and executed to extend coverage also capacity. The arbitrary placement of HeNodeBs are highlights the significance of interference mitigation to apprehend the ultimate. Timing and synchronization are identically imperative for control persistence for HeNodeBs in 4G LTE classifications. In order to conserve HeNodeBs for the control tenacity, IEEE 1588 be presented. Though, attributable to backhaul sufficiency for extensive time synchronization disputes to the neighbor HeNodeBs which leads to misalignment of the offsets. A tangible exploration has completed in order to substantiate the challenges of current systems. The model result indicates that the improved enhanced IEEE 1588 methodology is better in expressions of offsets error.

Cluster-based time synchronisation scheme for femtocell network

Femtocell is a recently developed technology in cellular wireless networks, which extends network coverage indoors, and is used to serve a small number of users. Synchronisation is one of the most significant technical challenges in femtocell networks and it guarantees an acceptable clock offset and frequency error skew. Clock offset and skew lead to severe interference between femtocell base stations fBSs or between fBSs and macrocell base stations mBSs. The ultimate objective of this paper is to develop cluster-based time synchronisation scheme to reduce clock offset and skew in terms of precise synchronisation in fBS neighbouring nodes. In consequence with the developed cluster-based time synchronisation scheme, the intra-cluster and inter-cluster time synchronisation is proposed. The proposed scheme is evaluated through analytical approach and benchmarked with mobile station-assisted synchronisation scheme. Results show that the proposed scheme is able to significantly reduce clock offsets to 53% and 60.32% for clock skew.