Virtual Cell Layout Based Dynamic Source Routing (vb-dsr) For The Mobile Subsystem Of The Next Generation Tactical Communications Systems

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2002Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2002Telsiz ağlar, 1970’lerde ortaya çıkışlarından itibaren bilgisayar endüstrisinde çok yaygınlaşmıştır. Telsiz ağlar gezgin kullanıcılara nerede olduklarına bağlı olmadan heryerde iletişim kurma ve bilgiye erişim imkanı sağlar. Hiçbir sabit altyapıya gerek duymadan bu imkanı sağlayan ad hoc ağların zaman içinde gelişmesiyle ve askeri, ticari ve özel maksatlar için tercih edilir hale gelmesiyle, uygulamada bazı zorluklar başgöstermiştir. Çalışmamızda, bu zorlukları ve ad hoc ağlardan beklenenleri dikkate alarak Sanal Hücre Kalıbı (SHK) tabanlı Dinamik Kaynak Yol Atama (DKYA) yaklaşımını bir çözüm olarak sunuyoruz. SHK, etkili bir özkaynak yönetimi ve ağ ölçeklenebilirliği sağlayan çok-katmanlı öbek-yapılı bir yaklaşımdır. Biz SHK yapısının üzerine Dinamik Kaynak Yolatama protokolunu uyguladık. Sunduğumuz yaklaşım, SHK yapılı DKYA, iki düzeyli hiyerarşik öbek yapılı bir sistemdir. SHK yaklaşımında önerilen benzetim yaklaşımını geliştiriyoruz ve taktik iletişimlerin başarımlarının değerlendirmesinde bu benzetim yaklaşımını kullanıyoruz. Bu yöntemde, önceden gerçekleştirilen bilgisayar destekli askeri tatbikatlarda girilen emirleri, çok sayıdaki birliğe ait hareket, görev ve durum gibi verileri toplayan bir yapıcı (muharebe) model kullanarak tekrar işlemekteyiz. Daha sonra toplanan bu veriler daha da detaylandırılarak, başarı ölçütlerimize ait değerleri üreten benzetim kullanılmaktadır. Sistemi değerlendiren başarım ölçütleri, SHK-tabanlı DKYA’nın gezgin ad hoc ağlardan beklenenleri sağladığını göstermektedir.Wireless networks have become very popular in the computing industry after their emergence in the 1970’s. Wireless networks provide mobile user with ubiquitous communication capability and information access regardless of location. Mobile ad hoc networks, that manage it without a need to infrastructure networks, as evolved in time, exhibit some challenges to implement as they become more preferable for military, commercial and special purposes. By considering the challenges and expectations of mobile ad hoc networks, we propose an approach called VCL based DSR (VB-DSR), which uses Dynamic Source Routing (DSR) protocol over Virtual Cell Layout (VCL) structure. VCL is a multi-tier cluster-based approach that provides an efficient resource management and network scalability. We implemented Dynamic Source Routing protocol over VCL structure. Proposed approach, VB-DSR, is a cluster-based two level hierarchical scheme. We also enhance the simulation approach proposed by VCL structure, and use it for the evaluation of tactical communication systems. In this approach, the commands entered during the military computer aided exercises are replayed by running a constructive (combat) model which generates mobility, posture and status data for a number of units, then these data are enhanced and drive a simulation which produces the data related to the performance metrics. The evaluated performance of the system shows that VB-DSR approach satisfies the requirements of mobile ad hoc networks.Yüksek LisansM.Sc

The Spectrum Shortage Problem: Channel Assignment and Cognitive Networks

Recent studies have shown that the proliferation of wireless applications and services, experienced in the last decade, is leading to the challenging spectrum shortage problem. We provide a general overview regarding the spectrum shortage problem from the point of view of different technologies. First, we propose solutions based on multi-radio multi-channel wireless mesh networks in order to improve the usage of unlicensed wireless resources. Then, we move our focus on cognitive networks in order to analyze issues and solutions to opportunistically use licensed wireless resources. In wireless mesh networks, the spectrum shortage problem is addressed equipping each device with multiple radios which are turned on different orthogonal channels. We propose G-PaMeLA, which splits in local sub-problems the joint channel assignment and routing problem in multi-radio multi-channel wireless mesh networks. Results demonstrate that G-PaMeLA significantly improves network performance, in terms of packet loss and throughput fairness compared to algorithms in the literature. Unfortunately, even if orthogonal channels are used, wireless mesh networks result in what is called spectrum overcrowding. In order to address the spectrum overcrowding problem, careful analysis on spectrum frequencies has been conducted. These studies identified the possibility of transmitting on licensed channels, which are surprisingly underutilized. With the aim of addressing the resources problem using licensed channels, cognitive access and mesh networks have been developed. In cognitive access networks, we identify as the major problem the self-coexistence, which is the ability to access channels on a non-interfering basis with respect to licensed and unlicensed wireless devices. We propose two game theoretic frameworks which differentiate in having non-cooperative (NoRa) and cooperative (HeCtor) cognitive devices, respectively. Results show that HeCtor achieves higher throughput than NoRa but at the cost of higher computational complexity, which leads to a smaller throughput in cases where rapid changes occur in channels' occupancy. In contrast, NoRa attains the same throughput independent of the variability in channels' occupancy, hence cognitive devices adapt faster to such changes. In cognitive mesh networks, we analyze the coordination problem among cognitive devices because it is the major concern in implementing mesh networks in environments which change in time and space. We propose Connor, a clustering algorithm to address the coordination problem, which establishes common local control channels. Connor, in contrast with existing algorithms in the literature, does not require synchronization among cognitive mesh devices and allows a fast re-clustering when changes occur in channel's occupancy by licensed users. Results show that Connor performs better than existing algorithms in term of number of channels used for control purposes and time to reach and stay on stable configurations

Message Complexity Analysis of Mobile Ad Hoc Network (Manet) Address Autoconfiguration Protocols

This dissertation proposes a novel method to perform a quantitative analysis of message complexity and applies this method in comparing the message complexity among the mobile ad hoc network (MANET) address autoconfiguration protocols. The original publications on the address autoconfiguration protocols had many incomplete parts making them insufficient to use on practical MANETs. Therefore, the first objective of the executed research was to complete the address autoconfiguration protocols by filling in all the missing gaps to make them operational. The missing procedures that were filled in have been developed based on the most logical procedures being faithful to the original protocol publications. In this dissertation, to obtain the upper bound of the message complexity of the protocols, the O-notation of a MANET group of N nodes has been applied. To asymptotically calculate the total number of messages generated by a protocol's step or procedure, an investigation on the nodes broadcasting, unicasting, relaying, and receiving messages is conducted and used in obtaining the upper bound of the message complexity for each protocol.School of Electrical & Computer Engineerin