Afaz Uddin Ahmed

A Review on Femtocell and its Diverse Interference Mitigation Techniques in Heterogeneous Network

In third generation wireless network, the demand of wireless multimedia service is responsible for the enormous growth of data traffic. Cellular operators throughout the world are facing challenges in increasing system capacity, coverage and residential connectivity in sub-urban and urban environments due to the huge investment that follows. Femtocell offers an economically appealing way to improve quality, coverage and service in the existing network. Currently the use of femtocell is being supported primarily by the argument of improved indoor coverage for consumers and substantial cost savings for operators due to capacity offload. The Quality of Service is mainly effected by the limited bandwidth in wireless links. Femtocell can be an effective alternative to divert and carry out a big portion of the traffic from the Macro Base Station. The only issue in its vast implementation is lack of effective schemes to mitigate interference that creates challenge in maintaining customers’ satisfaction. This paper presents the role of femtocell in heterogeneous network and discusses diverse interference mitigation techniques.

Estimating DoA From Radio Frequency RSSI Measurements Using Multi-Element Femtocell Configuration

In this paper, a method to estimate the direction of arrival (DoA) of a radio signal using a multi-element antenna based femtocell device is presented. The femtocell estimates the DoA by identifying the peak of received signal strength indicator (RSSI) measurement using multi-element microstrip antenna. This paper is a modified version of a previously reported work titled as estimation of DoA from radio frequency RSSI measurements using an actuator reflector. In long term evaluation, ultradense deployment of the femtocell device is mainly supported by the intelligent beam forming that translates directly to the constraint of DoA estimation. Use of multi-element antenna over omnidirectional antenna in femtocell is mandated by coverage optimization and reduction of cell overshooting. DoA estimation using microstrip antenna alone is a challenging problem, but it is easier with a multiple number of directive antennas covering the whole plane. Other DoA estimation methods, such as phase arrays, are unsuitable for a small device like femtocell due to the complexity and cost limitations. The proposed method to estimate the DoA is simple enough to be applicable for femtocell indoor applications. Both simulation and experimental results are analyzed to evaluate the performance of the method. Results show that the error in estimated DoA has a mean <;7° and standard deviation <;4°.

Microstrip Antenna Design for Femtocell Coverage Optimization

A mircostrip antenna is designed for multielement antenna coverage optimization in femtocell network. Interference is the foremost concern for the cellular operator in vast commercial deployments of femtocell. Many techniques in physical, data link and network-layer are analysed and developed to settle down the interference issues. A multielement technique with self-configuration features is analyzed here for coverage optimization of femtocell. It also focuses on the execution of microstrip antenna for multielement configuration. The antenna is designed for LTE Band 7 by using standard FR4 dielectric substrate. The performance of the proposed antenna in the femtocell application is discussed along with results.

A fractional path-loss compensation based power control technique for interference mitigation in LTE-A femtocell networks

Introduction of Femtocells in heterogeneous network enhances the capacity, indoor coverage of the existing macrocell based network. It also allows high-speed data services for the multi-media application and software. However, in dense co-channel deployment scenarios femtocells cause severe interference to the neighbouring cells users. In this paper, a downlink-power-control scheme is presented for femtocell with no overhead signalling exchange with the macrocell. The femtocell adjusts the transmit power subject to home user equipment (HUE) measurements. The minimum level of transmit power is determined by the target Signal to Interference and Noise Ratio (SINR) of femtocell user that is set according to the required Quality of Service (QoS) of the femtocell users. The system level simulations confirm that, the proposed scheme reduces the outage probability of the nearby macrocell user equipment (MUE) up to 16.7% compared to fixed power setting, while maintaining the spectral efficiency of femtocell users. Furthermore, the transmit power can be reduced by 52.6% which leads to power effective solution of the interference scenario.

A Novel User Classification Method for Femtocell Network by Using Affinity Propagation Algorithm and Artificial Neural Network

An artificial neural network (ANN) and affinity propagation (AP) algorithm based user categorization technique is presented. The proposed algorithm is designed for closed access femtocell network. ANN is used for user classification process and AP algorithm is used to optimize the ANN training process. AP selects the best possible training samples for faster ANN training cycle. The users are distinguished by using the difference of received signal strength in a multielement femtocell device. A previously developed directive microstrip antenna is used to configure the femtocell device. Simulation results show that, for a particular house pattern, the categorization technique without AP algorithm takes 5 indoor users and 10 outdoor users to attain an error-free operation. While integrating AP algorithm with ANN, the system takes 60% less training samples reducing the training time up to 50%. This procedure makes the femtocell more effective for closed access operation.

Design of a compact dual-band band-pass filter for Global Positioning System and Fixed Satellite applications

In this article, a dual-band band-pass filter is developed for Global Positioning System (GPS) and Fixed Satellite (FS) applications. The filter is a planar structure composed of parallel coupled lines with reduced length. The dual band filter is developed using the cascaded coupled lines. High isolation between two pass-bands is achieved. Compared to the previous works, the proposed filter has lower insertion loss at 1.5 GHz and 7.5 GHz. A compact size of 15.7 mm × 33.4 mm is achieved for the proposed filter using Arlon DiClad 880 substrate with a thickness of 0.508 mm.

A compact 5G antenna printed on manganese zinc ferrite substrate material

In this article, a compact antenna is proposed using new microwave dielectric ceramic (MDC) substrate for 5G millimetre wave application. The distinctive novelties exhibited in this article are used of MDCs substrate material for antenna designing and performances analysis for wireless communication. The proposed antenna achieves impedance bandwidth of 2.66 GHz (from 27.235 GHz to 29.895 GHz), which covers the top interest (28 GHz) for 5G mm-wave in some countries and trials have been reported. The proposed antenna attains average gain of 5.44 dB and 93% of radiation efficiency with antenna size of 1.32λ × 1.32λ × 0.094λ.

SINR performance for steerable beamforming techniques in LTE-Advanced system

In 5G wireless communication systems, steerable beamforming techniques will become one of the techniques that will draw high attention in telecommunication industries. The steerable beamforming technique not only provides high throughput, but also increases the capacity of the system. Furthermore, steerable beamforming techniques hold the potential to overcome the interference problem in dense deployment of the serving cell in heterogeneous networks. Since the LTE Advanced system has been proposed by the 3rd Generation Partnership Project (3GPP), which is based on OFDMA, it will eliminate the intra-cell interference. However, the cell edge users suffer from inter-cell interference (ICI) coming from adjacent cells in the same frequency channel. This effects the system performance and degrades the Quality of Service (QoS). In this paper, the main focus is on the performance of the steerable beamforming techniques in terms of signal-to-interference-plus-noise ratio (SINR) result and its based on the user density. At first, this study will discusses brief overview about the beamforming. Then, the detail overview of the techniques is covered.

Multiband Patch Antenna for Femtocell Application

A microstrip patch antenna for multiple LTE (long term evaluation) frequency bands for femtocell application is proposed in this paper. Distributed antenna solution (DAS) has been introduced in cellular network to achieve homogenous indoor coverage. Femtocell is the latest extension to these solutions. It is a smart solution to both coverage and capacity scales. Femtocell operation in LTE band is occupied by higher frequency bands. For multiband femtocell application, miniature antenna design is quite essential. The antenna proposed here is composed of basic monopole structure with two parasitic elements at both sides of the active element. A rectangular slot is introduced at the ground plane of the proposed antenna. The antenna is designed using ElnoS HK light CCL substrate material of relative permittivity of 9.4, dielectric loss-tangent of 0.003 and thickness of 3 mm. The S11 response of the antenna is shown to have a bandwidth of 1.01 GHz starting from 1.79 GHz to 2.8 GHz. The characteristics of the antenna are analysed using Ansoft HFSS software.