1,720,964 research outputs found
Numerical Implementation of Multi-Packet Reception for the IEEE 802.11 MAC/PHY Layers
No full textThis paper presents a PHYsical (PHY) and Medium Access Control (MAC) layer design that enables Multi-Packet Reception (MPR) in an 802.11 network. The 802.11 stations are equipped with smart antenna systems and adopt efficient coding techniques to support multi-hop communications in a multipath-fading affected channel. The introduced MAC layer modifications are minimal and provide asynchronous access to the medium as long as the number of ongoing communications lies within a given threshold. The numerical investigations are performed by using an ad-hoc developed hybrid discrete-time discrete-event simulation platform, which is based on the integration between network simulator-2 (ns-2) and MATLAB
Deployment of a Reliable 802.11e Experimental Setup for Throughput Measurements
No full textThis paper describes an experimental setup for measuring the throughput of an 802.11 network that supports Quality of Service (QoS) mechanisms, addressing some issues concerning the comparison between experimental and theoretical results. The setup is an ad hoc network in which the nodes implement the Multiband Atheros Driver for Wireless Fidelity (MADWiFi). There are three main contributions of this study. The first one describes the adjustments to the MADWiFi source code that guarantee the control of the QoS parameters in ad hoc mode. The second contribution aims to provide a practical method for verifying if the backoff generated by a given wireless card is uniformly distributed, as dictated by the 802.11 standard. This represents a key point when theoretical and experimental results must be compared, since many vendors adopt nonuniform backoff distributions in their commercial cards. As a third contribution, this paper presents a theoretical nonsaturated analysis that provides the throughput and the successful packet delay of an 802.11 network supporting QoS in presence of nonuniform backoff. The throughput derived from this analysis using a uniform backoff, which is included in the proposed model as a particular case, is compared to the measurements provided by the deployed setup
A Practical Method for Verifying the Uniformity of the Backoff Distribution in 802.11 Network Cards
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On the Design of MAC Protocols for Multi-Packet Communication in IEEE 802.11 Heterogeneous Networks Using Adaptive Antenna Arrays
Full text linkThis paper discusses the design requirements for enabling multiple simultaneous peer-to-peer communications in IEEE 802.11 asynchronous networks in the presence of adaptive antenna arrays, and proposes two novel access schemes to realize multipacket communication (MPC). Both presented solutions, which rely on the information acquired by each node during the monitoring of the network activity, are suitable for distributed and heterogeneous scenarios, where nodes equipped with different antenna systems can coexist. The first designed scheme, called threshold access MPC (TAMPC), is based on a threshold on the load sustainable by the single-node, while the second protocol, called signal-to-interference ratio (SIR) access MPC (SAMPC), is based on an accurate estimation of the SIR and on the adoption of low density parity check codes. Both protocols, which are designed to be backward compatible with the 802.11 standard, are numerically tested in realistic scenarios. Furthermore, the performance of the two schemes is compared to the theoretical one and to that of the 802.11n extension in a mobile environment
A Software-Defined Radio implementation of an 802.11 OFDM Physical Layer transceiver
No full textThis work presents our effort in developing a complete, real-time, Software-Defined Radio implementation of an OFDM transceiver, compliant with the IEEE 802.11 Physical Layer specifications. All the baseband components in both the transmitter and the receiver are implemented with fast software functions, running on a General Purpose CPU. Real-time operation is achieved on a modern CPU by means of extensive code optimization, mostly using the SIMD instruction sets which are widely available on almost every modern CPU
Multi-Packet Communication in 802.11 Networks: A MAC/PHY Backward Compatible Solution
No full textThis paper presents a novel Medium Access Control (MAC) protocol for 802.11 networks in which the nodes can adopt smart antenna systems. The presented protocol is designed to satisfy two fundamental requirements: the exploitation of adaptive arrays to increase the network throughput and the backward compatibility of the novel scheme with the 802.11 MAC layer. The developed solution allows the simultaneous coexistence of multiple communications, while maintaining, for the legacy nodes, the same throughput levels achievable in the 802.11 standard. The performance and the backward compatibility of the proposed MAC protocol are tested in multipath-fading environment and considering heterogeneous scenarios, including 802.11 legacy stations together with nodes implementing the novel scheme and equipped with different antenna systems
Multi-Packet Communication in 802.11 Networks by Spatial Reuse: from Theory to Protocol
No full textThis paper analyzes the problem of modeling the collisions in a distributed and heterogeneous fixed wireless network supporting multi-packet communication (MPC) by spatial reuse. In an MPC scenario, where multiple node pairs can be simultaneously active, the result of a transmission attempt is typically established using two main approaches: one, more idealized but suitable for theoretical analyses, based on a threshold on the number of sustainable communications, and another one, more realistic, relying on the signal-to-interference ratio (SIR) experienced by the receiving node. The two approaches may lead to considerably different results, since the number of allowed communications is often estimated neglecting many physical aspects. This study investigates this issue by presenting a mathematical model, validated by independent simulations, which relates the capture probability to the statistic of the SIR. The developed framework, which accounts in detail for the network topology and the antenna system characteristics of each node, is applied to an 802.11-based multi-packet scenario to evaluate the saturation throughput of an MPC network
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