It is reported that the axial mode separation of a semiconductor
laser can be computed from the reflectance spectrum of a narrow
spectral range near the lasing frequency. The Kramers-Kronig dispersion
relation is used in this computation.
GaAs semiconductor laser is taken as an example. The computed
values of the...
Recent advances in computing, communication, and artificial intelligence (AI) technologies have made our world more interconnected and data-rich than ever with the proliferation of smart devices and sensors. As a result, we are increasingly dependent on electronic devices and sensors to automate away life’s mundane parts. For example, in business...
The recent increase in the number of wireless devices has been driven by the growing markets of smart homes and the Internet of Things (IoT). Consequently, current research has focused on efficient utilization of the radio frequency (RF) spectrum to accommodate such an increase in wireless bandwidth. Alternatively, latest free-space...
In this work, we study network coding technique, its relation to random matrices, and their applications to communication systems. The dissertation consists of three main contributions. First, we propose efficient algorithms for data synchronization via a broadcast channel using random network coding. Second, we study the resiliency of network coding...
Traditionally, networking protocol designs have placed much emphasis on point-to-point reliability and efficiency. With the recent rise of mobile and multimedia applications, other considerations such as power consumption and/or Quality of Service (QoS) are becoming increasingly important factors in designing network protocols. As such, we present a new flexible framework...
Coverage algorithms for deployment of WiFO - a hybrid femtocell architecture based on WiFi and Free Space Optical (FSO) technologies are studied to significantly increase wireless throughput of existing WiFi networks. In contrast with existing WiFi networks, WiFO incorporates small cell size, line of sight transmissions, and the Gaussian attenuation...
With explosive growth of Internet access from smart phones and tablets, increasing bandwidth for WIFI system is badly needed. Depending on two years’ research, we produced a novel communication system called WIFO system, which integrates both RF (Radio Frequency) and FSO (Free Space Optical) techniques. WIFO system can significantly increase...
As the price of broadband access service becomes more affordable, the number of homes with WiFi and public WiFi hotspots in the US are projected to increase significantly in the next few years. However, limited capacity of existing WiFi networks fail to provide adequate bandwidth for densely populated areas. Therefore,...
Peer-to-Peer (P2P) based distributed storage systems have gain much popularity in recent years. These systems rely greatly on the data redundancy to be robust under network dynamics, i.e., the dynamics of peer entering and departing the network. Hence, it is important to implement mechanisms for maintaining a certain level of...
Media application on the internet has become more and more popular as the bandwidth of the network links increase. The bottleneck of the existing media systems is no longer the link bandwidth at user’s end, but the server’s ability to handle streaming requests. These existing streaming systems do not scale...
We present a theoretical free-space optical (FSO) transmitter that utilizes a dynamically steered and shaped laser beam to communicate with a randomly moving receiver adorned with a retroreflector. The transmitter tracks the receiver's position by repeatedly scanning the field of view (FOV), measuring reflections from the retroreflector, and estimating the...
Forward Error Correction and retransmission are two approaches used to reliably broadcast data in a network with poor quality of service. Taking some assumptions, it has been suggested that a retransmission based reliable broadcasting scheme using network coding should in theory provide an increase in bandwidth efficiency by combining packets...
Gibbs sampling method is an important tool used in parameter estimation for many probabilistic models. Specifically, for many scenarios, it is difficult to generate high-dimensional data samples from its joint distribution. The Gibbs sampling provides a way to draw high-dimensional data via the conditional distributions which are typically easier to...
Since free riders in P2P network reduce the system's performance, how to maintain and encourage the nodes' cooperation is an important aspect of P2P related research. In this thesis, a P2P system is modeled based on two games: stag hunt game and snowdrift game. To relate the model to the...
Modern communication systems often have the ability to transmit signals on multiple communication mediums (e.g., RF, visible light) or interfaces (e.g., MAC layer protocols) at the same time. While each channel has different characteristics, a centralized controller with channel condition information will be able to schedule the resource allocated to...
As broadband Internet becomes widely available, Peer-to-Peer (P2P) applications over the Internet are becoming increasingly popular. Such an example is a video multicast application in which, one source streams a video to a large number of destination nodes through an overlay multicast tree consisting of peers.
These overlay multicast-based applications,...
In this thesis, convergence of time inhomogeneous Markov chains is studied using an adiabatic approach. The adiabatic framework considers slowly changing systems and the adiabatic time quantifies the time required for the change such that the final state of the system is close to some equilibrium state. This approach is...
Finding an efficient way of distributing content in Peer-to-Peer (P2P) networks has become important with the growing popularity of media streaming applications. Video multicast applications rely on the efficiency of content distribution from a single source to multiple receivers where one source streams a video to a large number of...
We consider the problem of wireless spectrum management in cognitive wireless networks that maximizes the revenue for a spectrum operator. Specifically, we study the problem on how a wireless spectrum operator can optimally allocate its limited spectrum to various classes users/devices who pay differently for their spectrum per unit time....
With the increase in demand for streaming media capabilities across the Internet, the focus has shifted from traditional client-server to peer-to-peer approaches. Content Distribution Networks (CDNs) have also recently moved from web acceleration to media streaming. P2P CDNs can be used both as a delivery mechanism and as an independent...