Shayla Islam

Macro mobility scheme in NEMO to support seamless handoff

In order for the mobile networks to stay connected to the Internet, Network Mobility (NEMO) is involved with the management of the different types of movements by mobile routers during rapid changes of the Point of Attachment (PoA). Accordingly to achieve seamless handoff with lower delay and packet loss in NEMO environment, it is very important to get better performance of mobility management protocol. As the main idea of Network Mobility Basic Support Protocol (NEMO BSP) is to create bi-directional tunnel between the Serving Mobile Routers (SMR) with its Home Agent (HA) and perform the handoff after complete layer 2 switching. Therefore, it should limit frequent registrations of Mobile Network Nodes (MNNs) with their HAs. Furthermore, creating bi-directional tunnel between MR and its HA for all communications makes sub-optimal problem, in which all the packets are tunneled and encapsulated via HA of the Serving MR. This increases handoff delay, packet loss and disconnections probability. To overcome handoff related problems, the Fast Hierarchical Mobile IPv6 (FHMIPv6) works as a solution for host mobility. However, in nested NEMO environment applying improved FHMIPv6 mechanism is a challenging task since consideration has to be given to both MR and its MNNs as well. This paper proposed macro mobility scheme in order to achieve seamless handoff through modification of signaling messages. Additionally, location update cost is calculated and compared with NEMO BSP via analytical approach. The analytical result shows that the location update cost for the proposed scheme is about 69 % less than that of NEMO-BSP.

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.

The challenges of wireless internet access in vehicular environments

The economics of currently available broadband access technologies motivate for innovate and deploy new system designs and applications in vehicular communication. The widely available and flexible Wi-Fi technique meets the cost and suitability targets for vehicular applications. To cope with the special requirements of vehicular, amendments of 802.11 standards at the MAC and PHY protocol level has been introduced in IEEE802.11p. IEEE 802.11p is the proposed standard for physical and MAC layer of wireless access in vehicular environment (WAVE) devices. The main objective of the new standard is to amend 802.to support vehicle mobility up to 150km/hr and distance 1000km by changing the frame format and increase delay spread tolerance introduced, in which the channel bandwidth is scaled from 20 MHz in 802.11a to 10 MHz in 802.11p. This paper reviews the challenges of wireless internet connectivity in vehicular communication. Transmission range, data handover and security are also covered in the paper. Other related works is reviewed and analyzed as well.

Inter-cell interference coordination in Heterogeneous Network: A qualitative and quantitative analysis

Heterogeneous Networks (HetNet) comprise networks with specially designed architecture. To cover large areas, established base stations (macro sites) are used; for coating buildings, microcells are employed; for covering individual levels or floors in a building, Pico-cells are utilized; and finally for providing wireless coverage to individual apartments, small offices, and home based businesses, femtocells (HeNodeBs) are exploited. The goal behind the implementation of HetNets involves incrementing the capacity, modifying spectrum use, lowering the capital and operating costs, as well as offering steady user-based experience of network architecture. Furthermore, HeNodeBs have been developed for voice, data, video services in home and offices and a certain outdoor scenario with a very limited geographical coverage. However, these random HeNodeB deployments raises co-tier and cross-tier inter-cell interference which results system performance degradation. The existing approaches have tried to solve Inter-cell Interference (ICI) issues. Yet, these techniques are become unsatisfactory for recent communications as aggressive frequency reuse is desired to maintain high data-rates. In this paper, we investigated and identified recent issues of inter-cell interference coordination problems. The related schemes and techniques are also analyzed in order to highlight the pros and cons of each of the schemes.

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.

Performance Analysis of Spectrum Sensing Methods: A Numerical Approach

Recent enhancement of Long Term Evolution / Advanced (LTE/LTE-A) is aimed to increase the throughput of the Orthogonal Frequency Division Multiplexing (OFDM) system. This is quite obvious where both frequency and time division are employed in order to augment the system capacity. In LTE/LTE-A heterogeneous Networks (Het Nets), femto cells (He Node Bs) are the optimal choice to extend the coverage within indoor environment. Nonetheless, the deployment of such base stations, somewhat to certain extent, does create cross-tier and co-tier interferences with the macro cell users (UEmacro-eNB) that ostensibly can become a critical challenge. It is implied that the unutilized / idle spectrums reallocation might be one of the solutions to mitigate such challenge. However, the errorless spectrum sensing does pose another issue. This paper outlines the investigation findings where spectrum sensing techniques is deployed to maximize the spectrum detection capacity with minimum error in OFDM based Het Nets. In addition, in the attempt to increase the efficiency of spectrum resources, this paper proposes a sensing technique which is imposed over advanced energy detection technique to detect the idle spectrums. The result of the proposed scheme is evaluated using Monte Carlo simulation.

Inter-cluster synchronization scheme for femtocell network

Femtocell is for indoor coverage, and cannot use a GPS antenna for time synchronization. High-precision crystal oscillators can solve the timing problem, but they are often too expensive for consumer grade devices. Since fBS and macrocell Base Station (mBS) network operate on the same frequency under a licensed spectrum fBS network can interfere with the macrocell network. In addition, fBSs can also interfere with each other if multiple units are in close proximity. In some cases, conflicting base stations may simultaneously raise transmit power in order to improve signal quality, thereby creating some interference. Furthermore, in a flat fBS structured network using IEEE 1588 synchronization algorithm and fBS-fBS synchronization scheme creates offset and frequency error which results inaccurate synchronization. However, in this paper an inter-cluster synchronization scheme is proposed in order to reduce offset and frequency error (skew) to achieve precise synchronization in fBS neighbor nodes. The analytical result shows that the proposed scheme is able to reduce the offset and skew significantly through inter-cluster synchronization ultimately increases synchronization accuracy. Therefore, achieved synchronization accuracy is 90% higher than the existing MS-assisted schemes.

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.

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