Interference estimation in an aeronautical ad hoc network

Recent research have considered aeronautical ad hoc networks as a possible mean for future aeronautical communications. By introducing inter- aircraft links, they are supposed to become an alternative to existing solutions based on direct air- ground or satellite links. In this paper, we propose the use of asynchronous Code Division Multiple Access (CDMA) in aeronautical ad hoc networks. We then present a simulation model developed with OPNET Modeler that estimates the impact of Multiple Access Interference (MAI) on packets delivery. Finally, we give the results of some simulations made with an ATC/AOC traffic model, and with real aircraft positions over the French sky

UWB MAC Design Constraints and Considerations

In this paper, we consider the possibility of developing an optimal medium access control (MAC)layer for high data rate ultra-wideband (UWB) transmission systems that transmit minimal power. MAC in UWB wireless networks is required to coordinate channel access among competing devices. The unique UWB characteristics offer great challenges and opportunities in effective UWB MAC design. We first study the background of UWB and available MAC protocols that have been used in UWB. Secondly, we explore the constraints on UWB MAC design. Finally we present the considerations that need to be made in designing an optimal UWB MAC protocol

Media Access Control - уровень сверхширокополосных импульсных радиосетей

Описаны особенности и организация Media Access Control-уровня сетей на основе импульсных сверхширокополосных сигналов, приведена классификация соответствующих протоколов таких сетей и математическая модель для оценки пропускной способности наиболее простого протокола.The features and the organization of the Media Access Control-layer networks based on pulsed ultra-wideband signals are described, the classification of the corresponding protocols of such networks and the mathematical model for evaluating the throughput ability of the most simple protocol are given.Описано особливості і організація Media Access Control-рівня мереж на основі імпульсних надширокосмугових сигналів, подано класифікацію відповідних протоколів таких мереж та математичну модель для оцінки пропускної здатності найпростішого протоколу

A Joint PHY/MAC Architecture for Low-Radiated Power TH-UWB Wireless Ad-Hoc Networks

Due to environmental concerns and strict constraints on interference imposed on other networks, the radiated power of emerging pervasive wireless networks needs to be strictly limited, yet without sacrificing acceptable data rates. Pulsed Time-Hopping Ultra-Wide Band (TH-UWB) is a radio technology that has the potential to satisfy this requirement. Although TH-UWB is a multi-user radio technology, non-zero cross-correlation between time-hopping sequences, time-asynchronicity between sources and a multipath channel environment make it sensitive to strong interferers and near-far scenarios. While most protocols manage interference and multiple-access through power control or mutual exclusion (CSMA/CA or TDMA), we base our design on rate control, a relatively unexplored dimension for multiple-access and interference management. We further take advantage of the nature of pulsed TH-UWB to propose an interference mitigation scheme that reduces the impact of strong interferers. A source is always allowed to send and continuously adapts its channel code (hence its rate) to the interference experienced at the destination. In contrast to power control or exclusion, our MAC layer is local to sender and receiver and does not need coordination among neighbors not involved in the transmission. We show by simulation that we achieve a significant increase in network throughput

ZigZag Decoding: Combating Hidden Terminals in Wireless Networks

This paper presents ZigZag, an 802.11 receiver that combats hidden terminals. ZigZag exploits 802.11 retransmissions which, in the case of hidden terminals, cause successive collisions. Due to asynchrony, these collisions have different interference-free stretches at their start, which ZigZag uses to bootstrap its decoding. ZigZag makes no changes to the 802.11 MAC and introduces no overhead when there are no collisions. But, when senders collide, ZigZag attains the same throughput as if the colliding packets were a priori scheduled in separate time slots. We build a prototype of ZigZag in GNU Radio. In a testbed of 14 USRP nodes, ZigZag reduces the average packet loss rate at hidden terminals from 82.3% to about 0.7%

Zig Zag decoding : combating hidden terminals in wireless networks

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (leaves 59-62).This thesis presents ZigZag, an 802.11 receiver that combats hidden terminals. ZigZag exploits 802.11 retransmissions which, in the case of hidden terminals, cause successive collisions. Due to asynchrony, these collisions have different interference-free stretches at their start, which ZigZag uses to bootstrap its decoding. ZigZag makes no changes to the 802.11 MAC and introduces no overhead when there are no collisions. But, when senders collide, ZigZag attains the same throughput as if the colliding packets were a priori scheduled in separate time slots. We build a prototype of ZigZag in GNU Radio. In a testbed of 14 USRP nodes, ZigZag reduces the average packet loss rate at hidden terminals from 82.3% to about 0.7%.by Shyamnath GollakotaS.M