ABSTRACT
Call admission control (CAC) is one of the radio resource management (RRM) techniques that regulates and provide resources for new call requests or active call requests in the network. The existing call admission control schemes waste bandwidth due to its failure to check whether the degraded bandwidth will be enough to admit the new call requests. It also increases the call dropping probability (CDP) and calling blocking probability (CBP) of real time calls as a result of the delay incurred when bandwidth is degraded from the admitted real time (RT) calls. In this study, an Enhanced Adaptive Call Admission Control (EA-CAC) scheme with bandwidth reservation was proposed. The scheme proposed a prior-check mechanism which ensures bandwidth to be degraded will be enough to admit the new call request. It further incorporates an adaptive degradation mechanism which will degrade non-real time (NRT) calls first before degrading the RT calls, this also ensure that all admitted calls are not degraded below their minimum bandwidth requirement. The performance of the proposed scheme was evaluated against the benchmark scheme using different performance metrics. The EA-CAC increases the throughput of RT calls by 25% and also reduces the CBP and CDP by 12.2% and 15.2% respectively. The scheme performed better than the benchmark scheme in terms of throughput, CBP and CDP of RT calls without sacrificing the performance of the NRT calls.
TABLE OF CONTENTS
TITLE PAGE i
DEDICATION ii
CERTIFICATION iii
ACKNOWLEDGEMENTS iv
TABLE OF CONTENTS v
LIST OF FIGURES vii
LIST OF TABLES viii
ABSTRACT ix
CHAPTER ONE:
GENERAL INTRODUCTION
1.1 Introduction 1
1.2 Problem Statement 3
1.3 Aim and Objectives of the Study 3
1.4 Motivation 4
1.5 Scope of the Study 4
1.6 Significant of the Study 5
1.7 Organization of the Dissertation 5
CHAPTER TWO:
LITERATURE REVIEW
2.1 Introduction 7
2.2 Long Term Evolution (LTE) Network 7
2.3 Radio Resource Management (RRM) in LTE 9
2.4 Call Admission Control (CAC) in LTE 11
2.5 Review of Related Works 13
2.6 Summary of Reviewed Literatures 19
CHAPTER THREE: METHODOLOGY
3.1 Introduction 24
3.2 Performance Evaluation Techniques 24
3.3 Vienna LTE System Level Simulator 25
3.4 Research Framework 28
3.5. Enhanced Adaptive Call Admission Control (EA-CAC) Scheme with 29
Bandwidth Reservation for LTE networks.
3.6. Performance Metrics 36
CHAPTER FOUR:
RESULTS AND DISCUSSIONS
4.1 Introduction 37
4.2 Simulation Topology 37
4.3 Results and Discussions 38
4.3.1 Results of Throughput Achieved by the Schemes 39
4.3.2 Results of CBP Achieved by the Schemes 40
4.3.3 Results of CDP Achieved by the Schemes. 42
4.4 Summary of Discussions 44
CHAPTER FIVE:
SUMMARY, CONCLUSION AND RECOMMENDATIONS
5.1 Introduction 46
5.2 Summary 46
5.3 Conclusion 47
5.4 Recommendations 48
5.5 Future Works 49
5.6 Publications from the work 49
References 51
Appendices 54
LIST OF FIGURES
Figure 2.1: LTE System Architecture (3GPP, 2013) 8
Figure 2.2: Description of Basic CAC scheme 13
Figure 3.1: Overview of Vienna LTE System Level Simulator 26
Figure 3.2: Research Framework 29
Figure 3.3: Diagrammatic Description of the Benchmark Scheme 30
Figure 3.4: Diagrammatic Description of the Proposed EA-CAC Scheme 33
Figure 4.1 Simulation Topology 38
Figure 4.2 Throughput Achieve by the two Schemes for RT calls 39
Figure 4.3 Throughput Achieve by the two Schemes for NRT calls 40
Figure 4.4 CBP Achieve by the two Schemes for RT calls 41
Figure 4.5 CBP Achieve by the two Schemes for NRT calls 42
Figure 4.6 CDP Achieve by the two Schemes for RT calls 43
Figure 4.4 CDP Achieve by the two Schemes for NRT calls 44
LIST OF TABLES
Table 2.1: Summary of Reviewed Related Literatures 22
Table 4.1: Simulation Parameters 37
CHAPTER ONE
GENERAL INTRODUCTION
1.1 Introduction
Today, wireless broadband (WiBB) technologies are fast evolving to satisfy the present and future demand of users for efficient transmission of multimedia applications. Long Term Evolution (LTE) is one of such WiBB technologies designed by the Third Generation Partnership Project (3GPP) for efficient transmission of multimedia applications. The LTE standard is focused on delivering high data rates for bandwidth-demanding applications, improving flexibility and spectral efficiency. These features make LTE an attractive solution for both users and mobile operators (Angelos, Elli, Luis and Christos, 2011).
The fundamental objective of LTE is to guarantee quality of service (QoS) requirements and minimize network congestion for different users (Mamman, Zurina, Azizol and Abdullah, 2018). This can be achieved through the radio resource management (RRM) techniques. Radio resource management techniques are employed by wireless networks to improve the utilization of radio resources. Radio resources are utilized using various schemes that can are categorized into three major groups (Mohamed, 2005). The first group represents frequency or time resource allocation schemes which include channel allocation, scheduling, transmission rate control and, bandwidth reservation schemes. The second group represents power allocation and control schemes which include transmitter power of the terminals and base stations. The third group represents access port connection schemes which include call admission control, base station assignment and handoff control algorithms. An efficient RRM technique that handles the network resources efficiently is required, this is because in most cases the network resources are scarce and therefore need to be efficiently handled (Daniel, Edem and Enoch, 2014). Specifically, an efficient Call admission control (CAC) scheme which regulates and provides resources for new call requests or active calls is needed.
Several CAC schemes have been proposed for LTE with the aim of reducing call blocking probability (CBP), call dropping probability (CDP), guaranteeing QoS requirements and utilization of network resources (Lei, Yu, Zhao, Chang and Yang, 2008; Ali, Fauzi and Lotfi, 2010; Chadchan and Akki, 2011; Senkapa and Franklin, 2012; Khabazian, Kubbar and Hassanein, 2012; Ramraj, Habibi and Ahmad, 2014; Belghith, Turki, Cousin and Obaidat, 2016a; Belghith, Turki, Cousin and Obaidat, 2016b; AlQahtani, 2017). An adaptive call admission control scheme with bandwidth reservation was proposed by Maharazu, Zurina, Azizol, and Abdullah (2017) to provide efficient resource utilization and prevent BE traffic starvation. The scheme deals with Real-Time (RT) and Non-Real Time (NRT) services. The scheme degrades bandwidth from admitted RT calls when a call arrives and there is no sufficient bandwidth to admit the call. It ensures that all the admitted calls at least retain their minimum bandwidth requirement to avoid call drop. The scheme increases the throughput of BE traffic and reduces both CBP and CDP for BE traffic. However, the scheme causes bandwidth wastage because it fails to check if the bandwidth to be degraded will be enough to admit the new requested call. The scheme also increases the delay of already admitted RT calls which consequently leads to an increase in CBP and CDP of RT calls.
To address the aforementioned problems, this study proposed an Enhanced Adaptive Call Admission Control (EA-CAC) scheme with Bandwidth Reservation which reduced the wastage of bandwidth by ensuring that the bandwidth to be degraded will be enough to admit the new call request. The EA-CAC scheme also reduced the CBP and CDP of RT calls without sacrificing the performance of NRT calls.
1.2 Problem Statement
CAC schemes in LTE generally focus on either reducing the call blocking and call dropping probabilities of calls or guaranteeing the QoS requirements of users or increasing resource utilization.
The schemes proposed by Ali et al. (2010); Senkapa and Franklin (2012); and Ramraj et al. (2014) which focused on reducing call blocking and call dropping probabilities for both new and handoff calls but suffers from starvation of lower priority call requests and poor network resource utilization. While the schemes by Chadchan and Akki (2011); Khabazian et al. (2012); Belghith et al. (2016a); AlQahtani (2017) were concerned with guaranteeing QoS of different users also relatively increases the CBP and CDP of the lower priority call request.
Recently, Maharazu et al. (2017) proposed an adaptive call admission control scheme with bandwidth reservation to provide efficient resource utilization and prevent BE traffic starvation. The scheme increases the throughput of BE traffic and also reduces both CBP and CDP of BE traffic. However, the scheme wastes bandwidth due to its failure to check whether the resources to be degraded from the already admitted RT calls will be enough to admit the new call request. In most cases where network resources are scarce, utilization of the limited available resources is very important. Also, the scheme increases the CBP and CDP of RT calls as a result of the delay incurred when bandwidth is degraded from all admitted RT calls.
1.3 Aim and Objectives of the Study
This work aimed to propose a Call Admission Control scheme that will improve the performance of LTE networks. This was achieved through the following objectives:
1. To propose a prior-check mechanism that will make sure that the bandwidth to be degraded will be enough to admit the new request.
2. To incorporate an adaptive degradation mechanism into the CAC procedure which will reduce the delay incurred by ongoing RT calls, thus decreasing CBP and CDP of RT and NRT calls.
3. To evaluate the performance of the benchmark scheme against the proposed EA-CAC scheme in terms of throughput, CBP and CDP of RT and NRT calls.
1.4 Motivation
LTE is a wireless standard developed by the 3GPP which focused on delivering high data rates for bandwidth-demanding applications and improving flexibility and spectral efficiency (Angelos et al, 2011). The 3GPP standard for LTE does not define any standard for Call Admission Control schemes, therefore it is left open for vendors and network operators to decide on how CAC schemes are developed. Users are always demanding for a better service, therefore there is always the need for an effective radio resources management technique such as call admission control.
1.5 Scope of the Study
This research work mainly concentrates on the radio resource management (RRM) technique that ensures effective resource utilization and guarantees QoS for users with diverse applications in LTE. It focuses on call admission control (CAC) which controls the numbers of connections or requests admitted in a network and also maintains the QoS of admitted/active connections or users.
1.6 Significance of the Study
The attraction of wireless technologies is increasing almost daily because of its flexibility and simplicity. Users on the network are always demanding a better service i.e. they need their QoS requirements to be satisfied. LTE is one of the latest fourth-generation (4G) wireless technology which has high speed and it’s quicker than the third-generation (3G) wireless technology. LTE is compatible with previous mobile technologies such as GSM, EDGE, HSPA, etc. It also has better technology for the power consumption of mobile terminals. Satisfying the QoS requirements for different users requires efficient RRM strategies/techniques such as a CAC scheme. An efficient CAC scheme will control the number of users or request to be admitted in a network as well as improve the utilization of network resources. It will also improve the overall system throughput. An efficient CAC scheme will as well improve the revenue generated by service providers i.e. (in the case of revenue-based CAC).
1.7 Organization of the Dissertation
The rest of this dissertation is organized as follows: Chapter two presents an overview of the LTE network by explaining some of the core components of its architecture. Radio resource management (RRM) in the LTE network was also highlighted as well as call admission control (CAC) procedure in LTE were also discussed in the chapter. The chapter further discusses some of the related existing CAC schemes in LTE by highlighting the operations, strengths, and weaknesses of each scheme. Finally, the chapter concludes by summarizing the schemes reviewed in the literature.
In chapter 3, the performance evaluation technique used for this research work was presented. It also presented the description of the Vienna LTE system Level Simulator which was used to evaluate the performance of the proposed scheme against the benchmark scheme. The chapter also presented the research framework for this research work. It further described the proposed EA-CAC scheme by showing its diagrammatic representation and the pseudo- code. Performance evaluation metrics used to evaluate the performance of the proposed EA- CAC scheme against the benchmark scheme were also presented in the chapter.
Chapter 4 presented the simulation topology that was used for the simulation experiment. The chapter further presents the simulation parameters used for the simulation experiment. The simulation experiment results obtained were presented using graphs. The results were presented and discussed for all the performance metrics which are throughput, CBP and CDP of both RT and NRT calls. The chapter concludes by summarizing the discussion of the simulation experiment results that were obtained.
Finally, Chapter 5 presents the summary of this research work by highlighting the problems of the benchmark scheme which the proposed EA-CAC scheme addressed. It also presents how the proposed scheme was implemented and the results that were achieved after the simulation experiments. The chapter also presented a conclusion by highlighting what was achieved by the research and recommends some future work that can help to improve the research. It also presented the articles/papers that were published in the course of this research work.
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