Outage probability analysis of Co-Tier interference in heterogeneous network

In Heterogeneous Network (HetNet), the femtocell (HeNB) has been deployed by the telecommunication industries to provide extensive coverage as well as capacity in an indoor. These HeNBs are Customer Premise Equipment (CPE) which is randomly used in co-channel with macrocell (MeNB) and causes the Co-Tier Interference (CTI) in OFDMA. The effect of CTI in OFDMA systems can lead the system throughput degradation and service disruption. Because of quick direct changing features in Rayleigh channel, it is compulsory to succeed the satisfactory performance. The signal-to-interference noise ratio (SINR) is arbitrary which drives the highest capacity to be an irregular variable. However, this paper derives the expressions of outage probabilities based on the hybrid Genetic Algorithm (GA) with biogeography based dynamic subcarrier allocation (HGBBDSA) algorithm is implemented in reducing the outage probability. The outage probability countenance is expressed for the moment-generating function of the total SINR at the receivers end. The simulation results demonstrate that the HGBBDSA can lessen the outage to 45 % than existing methods

Femto Cells: Current Status and Future Directions

This is a survey paper on the recently developed and rapidly evolving field of femtocells. Quite often, it is noticed that cell-phone signals are strongly attenuated, when indoors, leading to call dropping or poor call quality. Femtocells are mini base stations that are deployed in users’ homes so that the user can directly connect to the cellular network through the femtocell instead of the outdoor macrocell, thereby increasing call quality. In the later stages of the paper, we also discuss the integration of the femtocell into the 3G architecture, as well as the various interference issues that the femtocell faces

Self Organising Network Techniques to Maximise Traffic Offload onto a 3G/WCDMA Small Cell Network using MDT UE Measurement Reports

This paper presents a number of Self-Organising Network (SON) based methods using a 3GPP Minimisation of Drive Testing (MDT) approach or similar and the analysis of these geo-located UE measurements to maximise traffic offload onto lamppost mounted 3G/WCDMA microcells. Simulations have been performed for a real 3G/WCDMA microcell deployment in a busy area of central London and the results suggest that for the network studied a traffic increase on the microcell layer of up to 175% is achievable through the novel SON methods presented

A review of femtocell

The popularity of wireless networks has attracted the attention of researchers to improve the network system and this motivated the operators to find a new technology called femtocells with the aim of meeting the increased coverage and data demand in the indoor environment. The application of femtocells in both indoors and office environment has provided good quality service and high performance network gains. However, femtocells face challenges of interference management which deteriorate the capacity and quality of network. But to cope with these challenges, many researchers have come up with solutions to solve the problems, some of which include interference cancellation and interference avoidance

On placement and dynamic power control of femtocells in LTE HetNets

Femto cells a.k.a. Low Power Nodes (LPNs) are used to improve indoor data rates as well as to reduce traffic load on macro Base Stations (BSs) in LTE cellular networks. These LPNs are deployed inside office buildings and residential apartment complexes to provide high data rates to indoor Users. With high SINR (Signal-to-Interference plus Noise Ratio) the users experience good throughput, but the SINR decreases significantly because of interference and obstacles such as building walls, present in the communication path. So, efficient placement of Femtos in buildings while considering Macro-Femto interference is very crucial for attaining desirable SINR. At the same time, minimizing the power leakage in order to improve the signal strength of outdoor users in a high interference (HIZone) around the building area is important. In our work, we have considered obstacles (walls, floors) and interference between Macro and Femto BSs. To be fair to both indoor and outdoor users, we designed an efficient placement and power control SON (Self organizing Network) algorithm which optimally places Femtos and dynamically adjusts the transmission power of Femtos based on the occupancy of Macro users in the HIZone. To do this, we solve two Mixed Integer Programming (MIP) methods namely: Minimize number of Femtos (MinNF) method which guarantees threshold SINR (SINRTh) -2dB for all indoor users and optimal Femto power (OptFP) allocation method which guarantees SINRTh (- 4 dB) for indoor users with the Macro users SINR degradation as lesser than 2dB

Optimizing Signal Behavior of Femtocells for Improved Network

The high demand for network coverage in an indoor setting brought about the acceptance of femtocell technology as a solution using the backhaul connectivity in the existing network. The quality of signal, voice calling, Internet, security and data are improved through the use femtocell at the indoor environment. Here the service provider attempts to reduce their operation cost by presenting self-organizing mechanisms for optimization of the network. The remarkable part is that, femtocells improves coverage, enhances the data rate at the indoor environment. Therefore, the challenges of the femtocell also known as interference deteriorates the capacity and quality performance of the whole cellular network. In this paper we simulate the bit error rate against signal behaviour at the indoor environment and we also simulate the transmitting power over signal for both macrocells and femtocells. We focus on the transmitting power that might cause interference within the cellular network

Improving Macrocell - Small Cell Coexistence through Adaptive Interference Draining

The deployment of underlay small base stations (SBSs) is expected to significantly boost the spectrum efficiency and the coverage of next-generation cellular networks. However, the coexistence of SBSs underlaid to an existing macro-cellular network faces important challenges, notably in terms of spectrum sharing and interference management. In this paper, we propose a novel game-theoretic model that enables the SBSs to optimize their transmission rates by making decisions on the resource occupation jointly in the frequency and spatial domains. This procedure, known as interference draining, is performed among cooperative SBSs and allows to drastically reduce the interference experienced by both macro- and small cell users. At the macrocell side, we consider a modified water-filling policy for the power allocation that allows each macrocell user (MUE) to focus the transmissions on the degrees of freedom over which the MUE experiences the best channel and interference conditions. This approach not only represents an effective way to decrease the received interference at the MUEs but also grants the SBSs tier additional transmission opportunities and allows for a more agile interference management. Simulation results show that the proposed approach yields significant gains at both macrocell and small cell tiers, in terms of average achievable rate per user, reaching up to 37%, relative to the non-cooperative case, for a network with 150 MUEs and 200 SBSs

On placement and efficient resource allocation of LAA/LTE-U base stations in HetNet

LTE operation in unlicensed spectrum is considered as a promising solution to meet the increase in user data demand. Licensed Assisted Access (LAA), and duty cycled LTE-U are two options for LTE to operate in the unlicensed band for fair sharing of unlicensed spectrum with IEEE 802.11 (Wi-Fi). Due to restriction on the transmission power in the unlicensed band, LAA/LTE-U Base Stations (BSs) will get deployed mostly inside residential and office buildings to provide high data rates for indoor User Equipments (UEs). In an indoor scenario, walls and other obstacles in the communication path along with co-tier and cross-tier interferences decrease the Signal-to-Interference plus Noise Ratio (SINR) significantly which results in throughput decrease. Hence, an optimal placement of LAA BSs is essential. As the available bandwidth in the unlicensed spectrum is more compared to the licensed spectrum, an efficient resource allocation is also necessary for ensuring minimum throughput for the indoor UEs. In this paper, our goal is to find the optimal number of LAA/LTE-U BSs with minimum throughput guarantee inside the building using licensed and unlicensed bands. To do this, we formulate an optimization model (MinLAA) for LAA BSs placement which is Mixed Integer Non-Linear Programming (MINLP) problem. So, we propose a heuristic algorithm to find the minimum number of LAA/LTE-U BSs such that all the users inside the building get minimum guaranteed throughput