Impact of variable transmission range in all-wireless networks

In this thesis, we propose three distributed algorithms for self-adjusting the transmission range of nodes in wireless network. The objective is to vary the transmission radii of selective sensor nodes to lower the energy spent in broadcasting or the diameter. The sensor nodes start arbitrarily with different transmission ranges. The nodes positions are fixed, and can adjust the transmission power. However, increasing the transmission power to reach more nodes may consume more energy. So, the goal is to reduce the transmission power (i.e., save energy) without reducing the reachability (in terms of the number of nodes); We propose two algorithms that increase the transmission range of nodes. Increasing the transmission range of selective nodes will lower the diameter but increase the total energy. The proposed algorithm computes the ratio of the increase in transmission range to the increase in number of nodes of every sensor node. The node with the smallest ratio will be selected to increase its transmission range; The third algorithm decreases the transmission range of the nodes. Decreasing the transmission range will lower the total energy but increase the diameter of the network. Ratio of decrease in the transmission range to the decrease in the number of nodes is calculated for every node, and the node with the highest ratio is selected to decrease its transmission range; A larger diameter implies a higher chance of interference between the neighboring nodes. When two nodes are in not in the communication range of each other, there is a probability that both the nodes send the packets to each other at the same time using the same channel. The nodes will not be able to decide by themselves, hence a collision will occur. This is known as hidden terminal problem. A lower diameter implies a higher chance of message duplication. Same message will be received twice; All three algorithms will be simulated and compared based on the experimental results

A stateless opportunistic routing protocol for underwater sensor networks

Routing packets in Underwater Sensor Networks (UWSNs) face different challenges, the most notable of which is perhaps how to deal with void communication areas. While this issue is not addressed in some underwater routing protocols, there exist some partially state-full protocols which can guarantee the delivery of packets using excessive communication overhead. However, there is no fully stateless underwater routing protocol, to the best of our knowledge, which can detect and bypass trapped nodes. A trapped node is a node which only leads packets to arrive finally at a void node. In this paper, we propose a Stateless Opportunistic Routing Protocol (SORP), in which the void and trapped nodes are locally detected in the different area of network topology to be excluded during the routing phase using a passive participation approach. SORP also uses a novel scheme to employ an adaptive forwarding area which can be resized and replaced according to the local density and placement of the candidate forwarding nodes to enhance the energy efficiency and reliability. We also make a theoretical analysis on the routing performance in case of considering the shadow zone and variable propagation delays. The results of our extensive simulation study indicate that SORP outperforms other protocols regarding the routing performance metrics

Energy-delay bounds analysis in wireless multi-hop networks with unreliable radio links

Energy efficiency and transmission delay are very important parameters for wireless multi-hop networks. Previous works that study energy efficiency and delay are based on the assumption of reliable links. However, the unreliability of the channel is inevitable in wireless multi-hop networks. This paper investigates the trade-off between the energy consumption and the end-to-end delay of multi-hop communications in a wireless network using an unreliable link model. It provides a closed form expression of the lower bound on the energy-delay trade-off for different channel models (AWGN, Raleigh flat fading and Nakagami block-fading) in a linear network. These analytical results are also verified in 2-dimensional Poisson networks using simulations. The main contribution of this work is the use of a probabilistic link model to define the energy efficiency of the system and capture the energy-delay trade-offs. Hence, it provides a more realistic lower bound on both the energy efficiency and the energy-delay trade-off since it does not restrict the study to the set of perfect links as proposed in earlier works

Modeling, Simulation and Analysis of Video Streaming Errors in Wireless Wideband Access Networks

Analysis of simulated models has become a veritable tool for investigating network behavioral patterns vis-à-vis transmitted content. The streaming video research domain employs modeling extensively due to availability of relevant tools. A vast majority of which are presented on the FOSS platform. The transmission of audio and video streaming services over different media is becoming ever more popular. This widespread increase is accompanied by the difficult task of maintaining the QoS of streaming video. The use of very accurate coding techniques for transmissions over wireless networks alone cannot guarantee a complete eradication of distortions characteristic of the video signal. A software- hardware composite system has been developed for investigating the effect of single bit error and bit packet errors in wideband wireless access systems on the quality of H.264/AVC standard video streams. Numerical results of the modeling and analysis of the effect of interference robustness on quality of video streaming are presented and discussed. Analytic results also suggest that the Markov model of packetization of error obtained from a real network for streaming video can be used in the simulations of transmission of video across networks in the hardware- software complex developed by the authors in a previous work

On the Interaction between TCP and the Wireless Channel in CDMA2000 Networks

In this work, we conducted extensive active measurements on a large nationwide CDMA2000 1xRTT network in order to characterize the impact of both the Radio Link Protocol and more importantly, the wireless scheduler, on TCP. Our measurements include standard TCP/UDP logs, as well as detailed RF layer statistics that allow observability into RF dynamics. With the help of a robust correlation measure, normalized mutual information, we were able to quantify the impact of these two RF factors on TCP performance metrics such as the round trip time, packet loss rate, instantaneous throughput etc. We show that the variable channel rate has the larger impact on TCP behavior when compared to the Radio Link Protocol. Furthermore, we expose and rank the factors that influence the assigned channel rate itself and in particular, demonstrate the sensitivity of the wireless scheduler to the data sending rate. Thus, TCP is adapting its rate to match the available network capacity, while the rate allocated by the wireless scheduler is influenced by the sender's behavior. Such a system is best described as a closed loop system with two feedback controllers, the TCP controller and the wireless scheduler, each one affecting the other's decisions. In this work, we take the first steps in characterizing such a system in a realistic environment

Effect of Wideband Wireless Access Systems Interference Robustness on the Quality of Video Streaming

The transmission of audio and video streaming services over different conduits (wireless access systems, Internet, etc.) is becoming ever more popular. This widespread increase is accompanied by the attendant new and difficult task of maintaining the quality of service of streaming video. The use of very accurate coding techniques for transmissions over wireless networks alone cannot guarantee a complete eradication of distortions characteristic of the video signal. A software-hardware composite system has been developed for investigating the effect of single bit error and bit packet errors in wideband wireless access systems on the quality of H.264/AVC standard bursty video streams. Numerical results of the modeling and analysis of the effect of interference robustness on quality of video streaming are presented and discussed