R. V. Prasad

Performance of Transport Control Protocol Over Dynamic Spectrum Access Links

Dynamic Spectrum Access (DSA) radio devices look for temporarily unoccupied frequency bands and attempt to communicate in them. It is envisioned that DSA can substantially increase the capacity of wireless networks by broadening the utilization of radio resources. Given the ubiquitous use of Internets Transport Control Protocol (TCP), it can be expected that TCP will be used in DSA networks in the future. Whether TCP can efficiently provide stable end-to-end transmissions over DSA links, given their dynamic and unpredictable nature, remained unclear. Therefore, we have studied by simulation the ability of various TCP flavors to efficiently utilize DSA links. We have performed simulations using the TCP stack from the Linux operating system. Our simulations show that modern TCPs can efficiently make use of the dynamic capacity of DSA links for bulk data transmission, under a wide range of conditions, but only if certain requirements are met. We also analytically determine the effect of Primary User (PU) detection errors on TCP performance and conclude that the dominating component responsible for TCP throughput reduction in a DSA environment is the observation time, not, as one might expect, PU detection errors.

An Analytical Energy Consumption Model for Packet Transfer over Wireless Links

We provide a detailed analytical model for estimating the total energy consumed to exchange a packet over a wireless link. Our model improves many of the current models by considering details such as consumed energy by processing elements of transceivers, packet retransmission, reliability of links, size of data packets and acknowledgments, and also the data rate of wireless links. To develop the model, we use experimental results based on IEEE 802.15.4 devices to show that consumed energy for receiving erroneous packets is comparable to the consumed energy for receiving error-free packets.

Toward a Seamless Communication Architecture for In-building Networks at the 60 GHz band

This paper addresses the issues of designing an infrastructure to support seamless in-building communication at the 60 GHz band. Recently, the 60 GHz band has received much attention due to its 5 GHz of available spectrum. However, the propagation of signals in this band is strongly hindered by attenuation and line-of-sight requirements. The situation gets worse in the in-building environment where signal propagation is obstructed by physical objects such as walls, furniture etc. In this paper, we present a novel radio over fiber (RoF) architecture that is cost-effective and is able to deliver high data-rate of the order of gigabits. To ensure a seamless communication environment at the 60 GHz band, we propose the concept of extended cells (EC) in order to create sufficient overlap areas. Finally, we illustrate the effectiveness of the proposed architecture by simulating an in-building network at the 60 GHz band employing the RoF and EC concepts

Address autoconfiguration in wireless ad hoc networks: protocols and techniques

With the advent of smaller devices having higher computational capacity and wireless communication capabilities, the world is becoming completely networked. Although, the mobile nature of these devices provides ubiquitous services, it also poses many challenges. In this article, we look in depth at the problem of addressing in wireless ad hoc networks and the currently available techniques and protocols for both IPv4 and IPv6. We present an exhaustive study of the literature and summarize the features of each technique. We believe that this analysis will be helpful for network and application designers, as well as for researchers.

Analyzing 60 GHz radio links for indoor communications

With the increase in the capacity of mobile communication devices, it is but natural to expect that these devices would work ubiquitously anywhere anytime to offer high data rate support. Recently 60 GHz frequency band has been identified as an obvious choice for the high data rate indoor communications. However, as the 60 GHz radio system relies on line-of-sight (LOS) transmission for achieving Gbps data rate, the communication can be easily interrupted by obstructions breaking the LOS link, which happens often due to the movement of people in a typical indoor environment. In this paper, we define and present an analytical model for assessing link stability of 60 GHz radio for indoor wireless networks. We have developed a ray-based model to calculate the shadowing loss caused by the presence of people around the communication link while taking into account the indoor channel characteristics of 60 GHz radio and the antenna configuration. We have further considered different types of mobility of people with the ray-based model of 60 GHz link to obtain a holistic link stability model in realistic scenarios. We have given examples to show the relevance of our model and its applicability using both simulation and numerical evaluations.

On the Stability of Ad Hoc Group Mobility Models

Group mobility has been modeled for simulators to evaluate protocols in wireless ad hoc networks. These mobility models have to be verified in terms of their instant and long-run behaviors. This paper discusses importance and challenges of the stability evaluation for ad hoc group mobility models; proposes analytical technique for the stability of group mobility model and evaluation of the same via simulation. As a case study, we evaluate the personal network group mobility model (PNMM). The evaluation method presented in this paper can be applied to all generic ad hoc group mobility models in terms of stability analysis and simulations.

A Self-organized Personal Network Architecture

This paper presents a self-organized architecture for personal networks. Personal Network (PN) is a user centric enabler for the next generation networks and services, which is dynamic in composition and involves heterogeneous networking technologies. One of the main research issues in the development of PNs is self-organization in order to be adaptive to the dynamics and heterogeneity of PNs. A PN architecture that consists of different self-organized functions is proposed in this paper. In addition, a personal network clustering protocol is proposed as one of the self-organized functions that forms a stable personal cluster and selects a master node of that personal cluster with a longer lifetime.

Architectures for intra-personal network communication

Personal Networks (PN) is a new concept related to pervasive computing with a strong user-focus view. The key to a successful PN realization is a general network architecture that is capable of bridging different current and future technologies and offers a homogeneous and clear view to the end-user. In this paper, we focus on forming a PN by connecting remote personal devices using infrastructure-based IP networks, including 3G networks and WLAN hotspots. One way is to upgrade the current access networks with new functionality to support PNs. Since many devices in PNs are mobile and battery powered, this may help them to achieve a faster service and to save energy. However, to deploy such functionality is not easy and may hamper the adoption of PNs altogether. Therefore, we propose an intra-PN communication architecture that will work over current IP networks. To discern the above proposal we also give a detailed picture of PN network architecture and infrastructure supported PNs. We believe that this will help the success of PNs.

DaRe: Data Recovery through Application Layer Coding for LoRaWAN

Internet of Things (IoT) solutions are increasingly being deployed for smart applications. To provide good communication for the increasing number of smart applications, there is a need for low cost and long range Low Power Wide Area Network (LPWAN) technologies. LoRaWAN is an energy efficient and inexpensive LPWAN solution that is rapidly being adopted all around the world. However, LoRaWAN does not guarantee reliable communication in its basic configuration. Transmitted frames can be lost due to the channel effects and mobility of the end-devices. In this study, we perform extensive measurements on a new LoRaWAN network to characterise spatial and temporal properties of the LoRaWAN channel. The empirical outage probability for the farthest measured distance from the closest gateway of 7.5km in our deployment is as low as 0.004, but the frame loss measured at this distance was up to 70%. Furthermore, we show that burstiness in frame loss can be expected for both mobile and stationary scenarios. Frame loss results in data loss, since in the basic configuration frames are only transmitted once. To reduce data loss in LoRaWAN, we design a novel coding scheme for data recovery called DaRe, which extends frames with redundant information that is calculated from the data from previous frames. DaRe combines techniques from convolutional codes and fountain codes. We develop an implementation for DaRe and show that 99% of the data can be recovered with a code rate of 1/2 for up to 40% frame loss. Compared to repetition coding DaRe provides 21% more data recovery, and can save up to 42% energy consumption on transmission for 10 byte data units. DaRe also provides better resilience to bursty frame loss. This study provides useful results to both LoRaWAN network operators as well as developers of LoRaWAN applications. Network operators can use the characterisation results to identify possible weaknesses in the network, and application developers are offered a tool to prevent possible data loss.

Exploring Multipath Capacity for Indoor 60 GHz Radio Networks

We study the application of multipath routing to enhance reliability of high quality video in 60 GHz radio indoor networks. We propose a cross-layer approach taking into account the possibility of layered-coding for video stream transportation and the characteristics of 60 GHz radio links based on our earlier studies on the stability of 60GHz radio links. Further three traffic allocation schemes have been investigated and compared for the best use of multipath capacity.