Performance analysis of the IEEE 802.11e block ACK scheme in a noisy channel

A block ACK (BTA) scheme has been proposed in IEEE 802.11e to improve medium access control (MAC) layer performance. It is also a promising technique for next-generation high-speed wireless LANs (WLANs) such as IEEE 802.11n. We present a theoretical model to evaluate MAC saturation throughput of this scheme. This model takes into account the effects of both collisions and transmission errors in a noisy channel. The accuracy of this model is validated by NS-2 simulations

Performance Evaluation of Varying Contention Window Size for Bandwidth Constrained Routing in Adhoc Networks

Providing bandwidth efficient routing in ad hoc networks is a challenging task. Available bandwidth of nodes is accurately evaluated before finding route from source to destination. Accuracy of available bandwidth is mainly affected by collision and overhead due to the execution of backoff scheme. Existing bandwidth constrained routing uses binary exponential backoff which follows serial transmission and causes unfair channel access. To overcome these, implicit pipelined backoff procedure is proposed to improve the available bandwidth and reduce the overhead associated with the backoff scheme employed in medium access control layer. In this, when two nodes are sharing the channel, the remaining nodes start the channel contention procedure in parallel to transmit next packet. Thus the channel waiting time is reduced. Each node maintains separate contention window for each phase in pipelined backoff. Proper choice of contention window size has great effect on performance of the network. This proposed algorithm is combined with a reactive link disjoint multipath routing protocol called AOMDV (Adhoc Ondemand Multipath Distance Vector) to find the best path based on bandwidth. Experimental results show that this algorithm outperforms existing approach in terms of QoS metrics such as delay, throughput, packet delivery ratio and energy consumption for different contention window sizes

Analyzing Split Channel Medium Access Control Schemes

In this work, we analyze and evaluate the maximum achievable throughput of split-channel MAC schemes that are based on the RTS/CTS (Ready-To-Send/Clear-To-Send) dialogue and that rely on pure ALOHA or on p-persistent Carrier Sensing Multiple Access (CSMA) contention resolution techniques. Our results show that, when radio propagation delays are negligible and when the pure ALOHA mechanism is used, then for a network with relatively large number of nodes, the maximum achievable throughput of the split-channel MAC schemes is lower than that of the corresponding single-channel MAC schemes. When the split-channel MAC schemes employ the p-persistent CSMA mechanism, then they out-perform the corresponding single-channel schemes when the maximum end-to-end propagation delays are at least 25% of the transmission time of the control packets on the single shared channel

Modular Software-Defined Radio

<p>In view of the technical and commercial boundary conditions for software-defined radio (SDR), it is suggestive to reconsider the concept anew from an unconventional point of view. The organizational principles of signal processing (rather than the signal processing algorithms themselves) are the main focus of this work on modular software-defined radio. Modularity and flexibility are just two key characteristics of the SDR environment which extend smoothly into the modeling of hardware and software. In particular, the proposed model of signal processing software includes irregular, connected, directed, acyclic graphs with random node weights and random edges. Several approaches for mapping such software to a given hardware are discussed. Taking into account previous findings as well as new results from system simulations presented here, the paper finally concludes with the utility of pipelining as a general design guideline for modular software-defined radio.</p

IEEE TRANS. ON WIRELESS COMMUNICATIONS, TO APPEAR 1 Analyzing Split Channel Medium Access Control Schemes

Abstract — In this work, we analyze and evaluate the maximum achievable throughput of split-channel MAC schemes that are based on the RTS/CTS (Ready-To-Send/Clear-To-Send) dialogue and that rely on pure ALOHA or on p-persistent Carrier Sensing Multiple Access (CSMA) contention resolution techniques. Our results show that, when radio propagation delays are negligible and when the pure ALOHA mechanism is used, then for a network with relatively large number of nodes, the maximum achievable throughput of the split-channel MAC schemes is lower than that of the corresponding single-channel MAC schemes. When the split-channel MAC schemes employ the p-persistent CSMA mechanism, then they out-perform the corresponding single-channel schemes when the maximum end-to-end propagation delays are at least 25 % of the transmission time of the control packets on the single shared channel

Implementing Efficient and Multi-Hop Image Acquisition In Remote Monitoring IoT systems using LoRa Technology

Remote sensing or monitoring through the deployment of wireless sensor networks (WSNs) is considered an economical and convenient manner in which to collect information without cumbersome human intervention. Unfortunately, due to challenging deployment conditions, such as large geographic area, and lack of electricity and network infrastructure, designing such wireless sensor networks for large-scale farms or forests is difficult and expensive. Many WSN-appropriate wireless technologies, such as Wi-Fi, Bluetooth, Zigbee and 6LoWPAN, have been widely adopted in remote sensing. The performance of these technologies, however, is not sufficient for use across large areas. Generally, as the geographical scope expands, more devices need to be employed to expand network coverage, so the number and cost of devices in wireless sensor networks will increase dramatically. Besides, this type of deployment usually not only has a high probability of failure and high transmission costs, but also imposes additional overhead on system management and maintenance. LoRa is an emerging physical layer standard for long range wireless communication. By utilizing chirp spread spectrum modulation, LoRa features a long communication range and broad signal coverage. At the same time, LoRa also has low power consumption. Thus, LoRa outperforms similar technologies in terms of hardware cost, power consumption and radio coverage. It is also considered to be one of the promising solutions for the future of the Internet of Things (IoT). As the research and development of LoRa are still in its early stages, it lacks sufficient support for multi-packet transport and complex deployment topologies. Therefore, LoRa is not able to further expand its network coverage and efficiently support big data transfers like other conventional technologies. Besides, due to the smaller payload and data rate in LoRa physical design, it is more challenging to implement these features in LoRa. These shortcomings limit the potential for LoRa to be used in more productive application scenarios. This thesis addresses the problem of multi-packet and multi-hop transmission using LoRa by proposing two novel protocols, namely Multi-Packet LoRa (MPLR) and Multi-Hop LoRa (MHLR). LoRa's ability to transmit large messages is first evaluated in this thesis, and then the protocols are well designed and implemented to enrich LoRa's possibilities in image transmission applications and multi-hop topologies. MPLR introduces a reliable transport mechanism for multi-packet sensory data, making its network not limited to the transmission of small sensor data only. In collaboration with a data channel reservation technique, MPLR is able to greatly mitigate data collisions caused by the increased transmission time in laboratory experiments. MHLR realizes efficient routing in LoRa multi-hop transmission by utilizing the power of machine learning. The results of both indoor and outdoor experiments show that the machine learning based routing is effective in wireless sensor networks

Fair power-controlled multiple access in mobile ad hoc networks

Previous power-controlled media access control (MAC) protocols for mobile ad hoc networks (MANET) suffer from the unfair channel access problem, i.e., it is difficult for a node to communicate with a distant node because of nearby ongoing communications. In this paper, we propose a fair power-controlled MAC protocol (FPCMA) by integrating senderinitiated busy tone with traditional power-controlled protocol. The sender-initiated busy tone is used to assist in channel access, and will be set up when a node finds it difficult to access the channel. Nearby nodes overhearing the tone will yield their transmission rights to the attempting node, thus solving the unfairness problem. Through analysis and simulation, we demonstrate that our protocol is able to balance the tradeoff between fair channel access and throughput, and is therefore more flexible than both the traditional dual busy tone and power-controlled MAC protocols.published_or_final_versio

The abstract MAC layer

A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an Abstract MAC Layer. This service provides reliable local broadcast communication, with timing guarantees stated in terms of a collection of abstract delay functions applied to the relevant contention. Algorithm designers can analyze their algorithms in terms of these functions, independently of specific channel behavior. Concrete implementations of the Abstract MAC Layer over basic radio network models generate concrete definitions for these delay functions, automatically adapting bounds proven for the abstract service to bounds for the specific radio network under consideration. To illustrate this approach, we use the Abstract MAC Layer to study the new problem of Multi-Message Broadcast, a generalization of standard single-message broadcast, in which any number of messages arrive at any processes at any times. We present and analyze two algorithms for Multi-Message Broadcast in static networks: a simple greedy algorithm and one that uses regional leaders. We then indicate how these results can be extended to mobile networks.Cisco Systems, Inc.Lehman Brothers (1993-2008)CUNY (A New MAC-Layer Paradigm for Mobile Ad-Hoc Networks)National Science Foundation (U.S.) (NSF Award Number CCF-0726514)National Science Foundation (U.S.) (NSF Award Number CNS-0715397

Energy-efficient, On-demand Reprogramming of Large-scale Sensor Networks

As sensor networks operate over long periods of deployment in difficult to reach places, their requirements may change or new code may need to be uploaded to them. The current state of the art protocols (Deluge and MNP) for network reprogramming perform the code dissemination in a multi-hop manner using a three way handshake whereby meta-data is exchanged prior to code exchange to suppress redundant transmissions. The code image is also pipelined through the network at the granularity of pages. In this paper we propose a protocol called Freshet for optimizing the energy for code upload and speeding up the dissemination if multiple sources of code are available. The energy optimization is achieved by equipping each node with limited non-local topology information, which it uses to determine the time when it can go to sleep since code is not being distributed in its vicinity. The protocol to handle multiple sources provides a loose coupling of nodes to a source and disseminates code in waves each originating at a source, with mechanism to handle collisions when the waves meet. The protocol’s performance with respect to reliability, delay, and energy consumed, is demonstrated through analysis, simulation, and implementation on the Berkeley mote platform