Optimization of orbital assignment and specification of service areas in satellite communications

The mathematical nature of the orbital and frequency assignment problem for communications satellites is explored, and it is shown that choosing the correct permutations of the orbit locations and frequency assignments is an important step in arriving at values which satisfy the signal-quality requirements. Two methods are proposed to achieve better spectrum/orbit utilization. The first, called the delta S concept, leads to orbital assignment solutions via either mixed-integer or restricted basis entry linear programming techniques; the method guarantees good single-entry carrier-to-interference ratio results. In the second, a basis for specifying service areas is proposed for the Fixed Satellite Service. It is suggested that service areas should be specified according to the communications-demand density in conjunction with the delta S concept in order to enable the system planner to specify more satellites and provide more communications supply

Resource allocation and optimization techniques in wireless relay networks

Relay techniques have the potential to enhance capacity and coverage of a wireless network. Due to rapidly increasing number of smart phone subscribers and high demand for data intensive multimedia applications, the useful radio spectrum is becoming a scarce resource. For this reason, two way relay network and cognitive radio technologies are required for better utilization of radio spectrum. Compared to the conventional one way relay network, both the uplink and the downlink can be served simultaneously using a two way relay network. Hence the effective bandwidth efficiency is considered to be one time slot per transmission. Cognitive networks are wireless networks that consist of different types of users, a primary user (PU, the primary license holder of a spectrum band) and secondary users (SU, cognitive radios that opportunistically access the PU spectrum). The secondary users can access the spectrum of the licensed user provided they do not harmfully affect to the primary user. In this thesis, various resource allocation and optimization techniques have been investigated for wireless relay and cognitive radio networks

An application of queueing theory to the design of channel requirements for special purpose communications satellites

Special purpose satellites are very cost sensitive to the number of broadcast channels, usually will have Poisson arrivals, fairly low utilization (less than 35%), and a very high availability requirement. To solve the problem of determining the effects of limiting C the number of channels, the Poisson arrival, infinite server queueing model will be modified to describe the many server case. The model is predicated on the reproductive property of the Poisson distribution

Models and Solution Techniques for Frequency Assignment Problems

Wireless communication is used in many different situations such as mobile telephony, radio and TV broadcasting, satellite communication, and military operations. In each of these situations a frequency assignment problem arises with application specific characteristics. Researchers have developed different modeling ideas for each of the features of the problem, such as the handling of interference among radio signals, the availability of frequencies, and the optimization criterion. This survey gives an overview of the models and methods that the literature provides on the topic. We present a broad description of the practical settings in which frequency assignment is applied. We also present a classification of the different models and formulations described in the literature, such that the common features of the models are emphasized. The solution methods are divided in two parts. Optimization and lower bounding techniques on the one hand, and heuristic search techniques on the other hand. The literature is classified according to the used methods. Again, we emphasize the common features, used in the different papers. The quality of the solution methods is compared, whenever possible, on publicly available benchmark instances

Models and Solution Techniques for Frequency Assignment Problems

Wireless communication is used in many different situations such as mobile telephony, radio and TV broadcasting, satellite communication, and military operations. In each of these situations a frequency assignment problem arises with application specific characteristics. Researchers have developed different modeling ideas for each of the features of the problem, such as the handling of interference among radio signals, the availability of frequencies, and the optimization criterion. This survey gives an overview of the models and methods that the literature provides on the topic. We present a broad description of the practical settings in which frequency assignment is applied. We also present a classification of the different models and formulations described in the literature, such that the common features of the models are emphasized. The solution methods are divided in two parts. Optimization and lower bounding techniques on the one hand, and heuristic search techniques on the other hand. The literature is classified according to the used methods. Again, we emphasize the common features, used in the different papers. The quality of the solution methods is compared, whenever possible, on publicly available benchmark instances

펨토셀 네트워크에서 자원 관리에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2014. 8. 전화숙.모바일 트래픽 수요가 폭발적으로 증가함에 따라 실내 사용자들에게 낮은 비용으로 고품질의 데이터 서비스를 제공할 수 있는 펨토셀이 주목을 받고 있다. 본 논문에서는 펨토셀이 기존의 매크로셀 위에 구축된 two-tier 펨토셀 네트워크에서 주파수 효율과 에너지 효율 향상을 위한 두 가지 자원 관리 기법을 제안하였다. 먼저, 주파수 효율을 향상시키기 위한 펨토셀들과 중첩 매크로셀 사이의 하향 링크 무선 자원 분할(radio resource partitioning) 기법을 설계하였다. 제안하는 무선 자원 분할 기법에서는 모바일 데이터 폭증 문제에 대한 또 다른 해결 방안인 분할 주파수 재사용(fractional frequency reuse, FFR) 기술이 적용된 매크로셀 네트워크를 고려하였다. FFR 구조에서 매크로셀의 주파수 대역은 다수의 주파수 분할들(frequency partitions, FPs)로 나누어지고, FP마다 다른 전송 전력이 할당된다. 제안한 기법에서 각 FP는 다시 매크로 전용 부분(macro-dedicated portion), 공용 부분(shared portion), 그리고 펨토 전용 부분(femto-dedicated portion)으로 구성되고, 이 세 부분의 비율은 FP마다 다르게 설정된다. 제안하는 기법은 최적화 방식을 이용하여 주파수 효율을 최대화하도록 각 FP 내 자원 분할 비율을 결정한다. 다음으로, 공항 및 쇼핑몰과 같이 사용자들이 밀집된 공공장소에 많은 수의 펨토 기지국들이 설치된 개방형 펨토셀 네트워크에서 에너지 효율을 향상시키기 위한 자원 관리 기법을 제안하였다. 고려하는 펨토셀 네트워크에서는 펨토 기지국들이 최대 트래픽 부하를 지원하기 위해 높은 밀도로 설치되기 때문에 대부분의 동작 시간 동안 펨토셀들은 무선 자원을 충분히 활용하지 않는다. 따라서 사용자들의 셀 접속을 적절히 조정하여 가능한 적은 펨토 기지국들을 활성화시키고 그 이외의 펨토 기지국들을 수면 모드(sleep mode)로 동작시킨다면 해당 펨토셀 설치 지역에서의 네트워크 에너지 효율을 크게 향상시킬 수 있을 것이다. 따라서 본 논문에서는 에너지 효율을 향상시키기 위해 펨토 기지국의 동작 모드(active 또는 sleep)와 사용자들의 셀 접속을 동시에 결정하는 펨토 기지국 동작 모드 결정 및 사용자 접속 (femto BS sleep decision and user association, SDUA) 기법을 설계하였다. 제안하는 기법에서 SDUA 문제는 사용자들에게 만족할 만한 서비스를 제공하면서 전체 에너지 소모를 최소로 하는 것을 목표로 하는 최적화 문제로 정식화되었다. SDUA 문제는 기지국의 동작 모드와 사용자의 셀 접속이 상호 영향을 주어서 계산 복잡도가 높으므로 본 논문에서는 먼저 활성화 펨토 기지국들의 집합이 주어진 상태에서 최적의 사용자 접속(user association, UA) 문제를 풀고, 각기 다른 집합들에 대해서 최적화 UA를 반복적으로 수행함으로써 최선의 활성화 펨토 기지국 집합을 찾는 휴리스틱 알고리즘을 설계하였다. 제안하는 두 자원 관리 기법들이 각각 주파수 효율과 에너지 효율에 대해서 기존의 기법들보다 우수한 성능을 보임을 시뮬레이션을 통해 확인하였다.Femtocell has received wide attention as a promising solution to meet explosively increasing traffic demand in cellular networks, since it can provide high quality data services to indoor users at low cost. In this thesis, we study resource management in two-tier femtocell networks where the femtocells are underlaid by macrocells, from two different aspects: spectral effciency and energy eciency. First, we design a downlink radio resource partitioning scheme between femtocells and their overlaid macrocell to enhance the spectral eciency. We consider that the overlaid macrocell network adopts the fractional frequency reuse (FFR) techniques, which is also one of solutions to the mobile data surge problem. With FFR, the frequency band of a macrocell is divided into several frequency partitions (FPs) and the transmission power levels assigned to FPs differ from each other. With the proposed scheme, every FP is divided into the macro-dedicated, the shared, and the femto-dedicated portions. The ratio of these three portions is different for each FP. We suggest a method to determine a proper ratio of portions in each FP, by using optimization approach. Next, we propose a scheme to enhance the energy efficiency in open access femtocell networks where many femto base stations (BSs) are deployed in a large public area such as office building, shopping mall, etc. In those areas, the femtocells are overlapped and underutilized during most of the operation time because femto BSs are densely deployed to support the peak traffic load. So, if we properly coordinate the user association with cells and put the femto BSs having no associated users to sleep, the network energy efficiency in the femtocell deployment area can be greatly enhanced. Therefore, we propose a femto BS sleep decision and user association (SDUA) scheme that jointly determines the operation modes (i.e., active or sleep) of femto BSs and the association between users and the active BSs. The SDUA problem is formulated as an optimization problem that aims at minimizing the total energy consumption while providing the satisfied service to users. Since the SDUA problem is too complicated to be solved, we first solve the optimal user association (UA) problem for given set of active femto BSs and then design a heuristic algorithm that finds the best set of active femto BSs by iteratively performing the optimal UA with each different set. By simulation, it is shown that the proposed schemes achieve their design goals properly and outperform existing schemes.1 Introduction 1.1 Background and Motivation 1.2 Proposed Resource Management Schemes 1.2.1 Radio Resource Partitioning Scheme for Spectral Efficiency Enhancement 1.2.2 Base Station Sleep Management Scheme for Energy Efficiency Enhancement 1.3 Organization 2 Radio Resource Partitioning Scheme for Spectral Efficiency Enhancement 2.1 System Model 2.1.1 Heterogeneous Network 2.1.2 Capacity Model 2.2 Proposed Downlink Radio Resource Partitioning Scheme 2.2.1 Macrocell Protection Mechanism 2.2.2 Determination of Dedicated Portion for Macrocell/Femtocell Users 2.3 Capacity Estimation 2.3.1 Achievable Macrosector Capacity 2.3.2 Achievable Femtocell Capacities 2.3.3 SHG Availability of Femtocell 3 Base Station Sleep Management Scheme for Energy Efficiency Enhancement 3.1 System Model 3.1.1 Open Access Femtocell Network 3.1.2 Operation Modes and Power Consumption of a BS 3.1.3 Energy Efficiency 3.2 Analysis on Energy Efficiency 3.2.1 Mathematical Model 3.2.2 Derivation of Energy Efficiency 3.2.3 Numerical Results and Discussion 3.3 Proposed Femto BS Sleep Decision and User Association (SDUA)Scheme 3.3.1 Problem Formulation 3.3.2 Solution Approach 3.3.3 Implementation Example of SIR Estimation 4 Performance Evaluation 4.1 Radio Resource Partitioning Scheme 4.1.1 Simulation Model 4.1.2 Simulation Results 4.2 Base Station Sleep Management Scheme 4.2.1 Simulation Model 4.2.2 Simulation Results 5 Conclusion Bibliography AbstractDocto