Volkan Rodoplu

Minimum energy mobile wireless networks

We describe a distributed position-based network protocol optimized for minimum energy consumption in mobile wireless networks that support peer-to-peer communications. Given any number of randomly deployed nodes over an area, we show that a simple local optimization scheme executed at each node guarantees strong connectivity of the entire network and attains the global minimum energy solution for the stationary case. Due to its localized nature, this protocol proves to be self-reconfiguring and stays close to the minimum energy solution when applied to the case of mobile nodes. Our simulations verify its performance.

UWAN-MAC: An Energy-Efficient MAC Protocol for Underwater Acoustic Wireless Sensor Networks

In this paper, we propose a distributed, scalable, energy-efficient media access control (MAC) protocol that works despite long, unknown propagation delays of the underwater acoustic medium. This protocol can be used for delay-tolerant applications such as underwater ecological sensor networks between energy-limited nodes. Our protocol differs significantly from ALOHA, multiple access with collision avoidance (MACA), and the media access protocol for wireless LANs (MACAW) in that energy is the main performance metric in our case rather than bandwidth utilization. We show that under a realistic underwater sensor network scenario, our MAC protocol wastes only 4% of the transmit energy and only 1.5% of the receive energy due to collisions, when the average number of neighbors is four, and the duty cycle is 0.004. This distributed, scalable MAC protocol has the potential to serve as a primer for the development of energy-efficient MAC protocols for future underwater sensor networks.

An energy-efficient MAC protocol for underwater wireless acoustic networks

We propose a distributed, scalable, energy-efficient MAC protocol that works despite long, unknown propagation delays of the underwater acoustic medium. This protocol can be used for delay-tolerant applications such as underwater ecological sensor networks between energy-limited nodes. Our protocol differs significantly from ALOHA, MACA, and MACAW protocols in that energy is the main performance metric in our case rather than bandwidth utilization. It is shown that under a realistic underwater sensor network scenario, our proposed MAC protocol wastes only 3 percent of the transmit energy due to collisions, when an average number of 1-hop neighbors is 5, and the duty cycle is 0.004. This distributed, scalable MAC protocol has the potential to serve as a primer for the development of energy-efficient MAC protocols for future underwater sensor networks

Distributed network protocols for wireless communication

This paper describes a network design strategy that focuses on energy conservation. This position-based network protocol is optimized for minimum energy consumption in wireless networks that support peer-to-peer communication. Given any number of randomly deployed communication nodes over an area, we show that a simple local optimization scheme executed at each node guarantees strong connectivity of the entire network and attains the global minimum energy solution for both stationary and mobile networks.

Position based CDMA with multiuser detection (P-CDMA/MUD) for wireless ad hoc networks

We propose a novel position-based MAC protocol based on multiuser detection for wireless ad hoc networks. We solve the duplex scheduling problem in ad hoc networks and allocate user signatures dynamically based on position. Our protocol leverages previous advances in low-power GPS receivers and low-complexity multiuser detectors. By using multiuser detection, we dispense with the notion of collisions at the MAC sublayer and give a throughput comparison between P-CDMA/MUD and 1-persistent CSMA. We show that P-CDMA/MUD can achieve a throughput one to two orders of magnitude over that of 1-persistent CSMA.

Algorithms for the MIMO Single Relay Channel

The MIMO single relay channel consists of a transmitter, a relay, and a receiver, all equipped with multiple antennas, located in an environment with distance-dependent path loss as well as scattering. We describe an optimal and a heuristic algorithm to solve the spatial energy allocation problem for the MIMO single relay channel when the scattering clusters on the direct and relay links are non-overlapping. These algorithms can be applied to existing wireless LAN systems that aim to increase their performance via relays. By simulations, we compare the performances of joint and uniform energy allocations across the spatial channels, and the performances of a direct transmission system and a system that utilizes the relay node

Challenges: automated design of networking protocols

This paper establishes a framework for the automated generation of networking protocols. The need for the rapid design of networking protocols in application-specific contexts has increased dramatically over the past five years. Each new application requires high performance in its own domain, as well as a rapid design cycle. Further, changes in physical layer technology quickly render previously high-performance protocols poor performance. Currently, there are no tools to automate the design of networking protocols. This paper addresses the challenge of building such tools. It proposes a methodology and a design chain for the automated generation of networking protocols, with the following novel ideas: (1) Formulation of the network protocol problem such that the exchange of protocol control information can be specified as part of the optimization program, (2) Optimal waveform generation, which specifies the optimal exchange of both control information and data, (3) Protocol Extraction: The extraction of the optimal protocol as a minimal description of the optimal waveforms. This methodology has the potential to dramatically change the future of networking protocol design by moving protocol design to a more abstract level, finding high-performance protocols not easily discovered by human intuition, and reducing the currently long protocol design cycles.

Computation of core capacity of wireless ad hoc networks

The core capacity region of energy-limited wireless ad hoc networks is defined as the set of achievable utility vectors that cannot be blocked by any coalition of the set of nodes. The core capacity region has been previously proved to be non-empty. In this paper, we present an algorithm to compute a utility vector in the core capacity region of wireless ad hoc networks. Our algorithm has a significantly smaller computational complexity than the application of Scarfs algorithm or the polyhedral Scarf algorithm to this problem and can be used to assess the capacity of ad hoc networks that can grow from small wireless islands such as Wi-Fi hotspots to a grand wireless network in the future.

RMR: Reliability based multi-hop routing in wireless tactical networks

We propose a novel routing protocol, RMR, for wireless tactical, high-mobility military networks that finds reliable routes through difficult terrains with possibly compromised regions. RMR uses an end-to-end reliability measure that includes both end-to-end connectivity as well as trustworthiness, and reactively discovers routes over spatial cells whose local reliability is proactively maintained by fast dissemination through the network. By using a space-centric approach where reliability is attributed to space rather than to nodes, RMR is able to find reliable routes through space that persist for longer durations than node-centric protocols. Via QualNet simulation studies, we compare the performance of our protocol with AODV in terms of end-to-end reliability as well as delay, and packet delivery ratio (PDR), and quantify the effects of node density, velocity, and traffic load on these performance metrics.

Core capacity region of portable wireless networks

We analyze the core capacity region of portable wireless networks under a concave utility model for a heterogeneous collection of asynchronous applications such as email and file transfers. We prove that the core capacity region is non-empty under the concave utility model. We show that there is no relaying among portable users in the core capacity region under the many-to-one traffic model for a single type of traffic. However, heterogeneous traffic induces cooperation when the channel conditions are matched to the type of traffic delivered. We demonstrate that each node can increase its utility by allocating its energy across different portable network configurations. The results motivate the use of energy-limited relays in next-generation wireless LAN systems.