Intercell interference mitigation in long term evolution (LTE) and LTE-advanced

University of Technology Sydney. Faculty of Engineering and Information Technology.Bandwidth is one of the limited resources in Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks. Therefore, new resource allocation techniques such as the frequency reuse are needed to increase the capacity in LTE and LTE-A. However, the system performance is severely degraded using the same frequency in adjacent cells due to increase of intercell interference. Therefore, the intercell interference management is a critical point to improve the performance of the cellular mobile networks. This thesis aims to mitigate intercell interference in the downlink LTE and LTE-A networks. The first part of this thesis introduces a new intercell interference coordination scheme to mitigate downlink intercell interference in macrocell-macrocell scenario based on user priority and using fuzzy logic system (FLS). A FLS is an expert system which maps the inputs to outputs using “IF...THEN” rules and an aggregation method. Then, the final output is obtained through a deffuzifaction approach. Since this thesis aims to mitigate interference in downlink LTE networks, the inputs of FLS are selected from important metrics such as throughput, signal to interference plus noise ratio and so on. Simulation results demonstrate the efficacy of the proposed scheme to improve the system performance in terms of cell throughput, cell edge throughput and delay when compared with reuse factor one. Thereafter, heterogeneous networks (HetNets) are studied which are used to increase the coverage and capacity of system. The focus of the next part of this thesis is picocell because it is one of the important low power nodes in HetNets which can efficiently improve the overall system capacity and coverage. However, new challenges arise to intercell interference management in macrocell-picocell scenario. Three enhanced intercell interference coordination (eICIC) schemes are proposed in this thesis to mitigate the interference problem. In the first scheme, a dynamic cell range expansion (CRE) approach is combined with a dynamic almost blank subframe (ABS) using fuzzy logic system. In the second scheme, a fuzzy q-learning (FQL) approach is used to find the optimum ABS and CRE offset values for both full buffer traffic and video streaming traffic. In FQL, FLS is combined by q-learning approach to optimally select the best consequent part of each FLS rule. In the third proposed eICIC scheme, the best location of ABSs in each frame is determined using Genetic Algorithm such that the requirements of video streaming traffic can be met. Simulation results show that the system performance can be improved through the proposed schemes. Finally, the optimum CRE offset value and the required number of ABSs will be mathematically formulated based on the outage probability, ergodic rate and minimum required throughput of users using stochastic geometry tool. The results are an analytical formula that leads to a good initial estimate through a simple approach to analyse the impact of system parameters on CRE offset value and number of ABSs

A fuzzy Q-learning approach for enhanced intercell interference coordination in LTE-Advanced heterogeneous networks

© 2014 IEEE. Since the transmission power of macro eNodeB (eNB) is higher than pico eNB in long term evolution-advanced heterogeneous network, the coverage area of picocell is small. In order to address the coverage problem, cell range expansion (CRE) technique has been recently proposed. However, CRE can lead to the downlink interference problem on both data and control channels when users are connected to pico eNB. In order to mitigate the downlink interference problem, a new dynamic almost blank subframe (ABS) scheme is proposed in this paper. In this scheme, a fuzzy q-learning approach is used to find the optimum ABS value. Simulation results show that the system performance can be improved through the proposed scheme

Dynamic Almost Blank Subframe Scheme for Enhanced Intercell Interference Coordination in LTE-A Heterogeneous Networks

In LTE-A heterogeneous network, traffic load may be distributed unequally because the transmission power of macro eNodeB (eNB) is higher than pico eNB. To address the coverage problems resulting from nodes with different transmission powers, cell range expansion (CRE) technique has been proposed as a cell selection technique. However, in this case, the intercell interference (ICI) problem can occur on both data and control channels when users connect to pico eNB. To mitigate ICI problem, a new dynamic almost blank subframe (ABS) scheme is proposed in this paper. In this scheme, a fuzzy logic system is deployed to monitor the system performance and then obtain the required number of ABSs. Simulation results show that the cell throughput and user throughput can be improved using the proposed dynamic ABS scheme

A dynamic almost blank subframe scheme for video streaming traffic model in heterogeneous networks

© 2015 IEEE. In heterogeneous network (HetNet), the coverage area of picocell is small due to transmission power difference between macro eNodeB (eNB) and pico eNB. As a result, the traffic load is distributed unequally which yields to macrocell overloading. In order to overcome this issue, cell range expansion (CRE) technique has been proposed. However, the CRE approach can affect the downlink signal quality of the offloaded users and then these users experience high downlink interference from macro eNB on their control and data channels. Therefore, such inter-cell interference coordination (ICIC) techniques are needed to realize the promised capacity and coverage. Enhanced ICIC (eICIC) is a time domain technique to mitigate interference in HetNets using almost blank subframes (ABSs). However, the static ABS value cannot support the dynamic changing of network conditions. In this paper, a dynamic ABS scheme is proposed based on Genetic Algorithm to find the best ABS value and ABS locations in a frame to mitigate interference problem between macrocell and picocells for video streaming traffic model. Exhaustive simulation results show that the proposed scheme can improve the system performance in terms of throughput, outage probability and delay

System level simulation for femtocellular networks

© 2014 IEEE. LTE is an emerging wireless data communication technology to provide broadband ubiquitous Internet access. Femtocells are included in 3GPP since Release 8 to enhance the indoor network coverage and capacity. System level simulation is used for performance evaluation of LTE-Femtocellular networks. Research works on performance optimization could not be justified since there was no common reference simulator to do so until the inception of LTE-Sim. The simulation scenarios for Femtocells in LTE-Sim encompasses two-tier macro-femto scenario but to the best of our knowledge there is no published work on coding and scripting of femtocell scenario in LTE-Sim. In this paper, the development of a femtocell scenario is discussed with simulation outcomes

An enhanced intercell interference coordination scheme using fuzzy logic controller in LTE-advanced heterogeneous networks

© 2014 National Institute of Information and Communicatio. In heterogeneous network, the coverage area of a picocell is small due to transmission power difference between a macro eNodeB (eNB) and a pico eNB. As a result, the traffic load is distributed unequally which leads to macrocells overloading. In order to address the coverage problem, cell range expansion (CRE) technique has been recently proposed. However, the interference can occur on both data and control channels for users located in range expanded area as they experience the low signal to interference plus noise ratio. To mitigate the interference problem, an enhanced intercell interference coordination (eICIC) scheme is proposed in this paper. In this scheme, a dynamic CRE approach is combined with a dynamic almost blank subframe (ABS) using fuzzy logic controller. Simulation results show that the system performance can be improved using the proposed eICIC scheme

Survey of intercell interference mitigation techniques in LTE downlink networks

This paper presents a survey of intercell interference mitigation techniques in long term evolution (LTE) networks and focuses on algorithms which are more relevance with LTE downlink networks. A total of 20 different algorithms are reviewed and a qualitative comparison is done in terms of cell throughput and cell edge throughput. The comparison provided in this paper can be used to select the most appreciate technique for each particular goal. © 2012 IEEE

An intercell interference coordination scheme in LTE downlink networks based on user priority and fuzzy logic system

The Intercell Interference (ICI) problem is one of the main challenges in Long Term Evolution (LTE) downlink system. In order to deal with the ICI problem, this paper proposes a joint resource block and transmit power allocation scheme in LTE downlink networks. The proposed scheme is implemented in three phases: (1) the priority of users is calculated based on interference level, Quality of Service (QoS) and Head of Line (HoL) delay; (2) users in each cell are scheduled on the specified subbands based on their priority; and (3) eNodeBs dynamically control the transmit power using a fuzzy logic system and exchanging messages to each other. Simulation results demonstrate that the proposed priority scheme outperforms the existing Reuse Factor one (RF1) and Soft Frequency Reuse (SFR) schemes in terms of cell throughput, cell edge user throughput, delay and interference level

Performance evaluation of cell selection techniques for picocells in LTE-advanced networks

This survey paper provides a performance evaluation of some cell selection techniques proposed for picocells in the Long Term Evolution-Advanced (LTE-A) networks. Picocell is the focus of this study because it can be deployed in areas with high volume of traffic (such as hotspots) so as to improve the overall system capacity. A number of techniques are evaluated such as maximum Reference Signal Received Power (RSRP), Cell Range Expansion (CRE) with static offset value and adaptive offset value as well as using Almost Blank Subframes (ABS) ratio. Then a comparison is provided in terms of cell throughput, cell edge throughput and Physical Downlink Control Channel (PDCCH) outage rate. The comparison described in this paper can be useful for readers interested to select the most appreciate cell selection technique for their particular goal. © 2013 IEEE

A dynamic cell range expansion scheme based on fuzzy logic system in LTE-advanced heterogeneous networks

© 2014 IEEE. In heterogeneous network, the coverage area of picocell is usually small due to transmission power difference between macro eNodeB (eNB) and pico eNB. As a result, the traffic load is distributed unequally which yields to macrocell overloading. In order to overcome this issue, cell range expansion (CRE) technique has been recently proposed. However, the fixed CRE scheme cannot follow the UE distribution and then satisfy the system requirements. Therefore, fixed CRE scheme is unable to proportionally offload the traffic between the macrocells and picocells. In order to deal with the mentioned problem, this paper proposes a dynamic CRE scheme based on fuzzy logic system. Simulation results demonstrate that the proposed scheme can improve the system performance in terms of throughput and outage probability