Modeling and Analyzing Duty-Cycling, Pipelined-Scheduling MACs for Linear Sensor Networks

Linear sensor networks (LSNs) have recently attracted increasing attention due to the vast requirements on the monitoring and surveillance of a structure or area with a linear topology. However, there is little work on the network modeling and analysis based on a duty-cycling MAC protocol for LSNs. In this paper, we model a duty-cycling MAC with a pipelinedscheduling feature for an LSN, where each node is responsible for monitoring a certain area and can generate packets according to its sensed results. Based on the model, we analyze the network performance in terms of the system throughput, active time ratio per cycle of each node, and packet delivery latency.

Through the extensive OPNET-based simulations, we validate the model and reveal the dependency of the network performance on various system parameters. Besides enabling the effective estimation of the protocol performance by using our model, we believe that our model and analysis could provide an insightful understanding on the behavior of a duty-cycling MAC protocol and aid its design and optimization for a multi-hop LSN.

Opportunistic Routing With Congestion Diversity in Wireless Ad Hoc Networks

We consider the problem of routing packets across a multi-hop network consisting of multiple sources of traffic and wireless links while ensuring bounded expected delay. Each packet transmission can be overheard by a random subset of receiver nodes among which the next relay is selected opportunistically. The main challenge in the design of minimum-delay routing policies is balancing the trade-off between routing the packets along the shortest paths to the destination and distributing the traffic according to the maximum backpressure. Combining important aspects of shortest path and backpressure routing, this paper provides a systematic development of a distributed opportunistic routing policy with congestion diversity (D-ORCD).

D-ORCD uses a measure of draining time to opportunistically identify and route packets along the paths with an expected low overall congestion. D-ORCD with single destination is proved to ensure a bounded expected delay for all networks and under any admissible traffic, so long as the rate of computations is sufficiently fast relative to traffic statistics. Furthermore, this paper proposes a practical implementation of D-ORCD which empirically optimizes critical algorithm parameters and their effects on delay as well as protocol overhead. Realistic QualNet simulations for 802.11-based networks demonstrate a significant improvement in the average delay over comparable solutions in the literature.

An Agile and Efficient MAC for Wireless Access over TV Whitespaces

The FCC mandate of allowing TV Whitespaces for unlicensed access has the potential for dramatic improvements in wireless access data rates. We argue that an ideal MAC should account for diverse user-location and spectrum dependent channel rates to provide fair data rates and efficient utilization. Furthermore, due to limited tunable bandwidth of a radio and fragmented spectrum, the AP should support multiple radios. We make the following contributions by designing a MAC for wireless LAN access over TV Whitespace. (i) We propose an architecture and beaconing mechanism to enable such a MAC.

Our MAC is an evolution of 802.11 MAC. (ii) We propose an algorithm that chooses the Whitespaces for the different radios of the AP and assigns clients to the radios. Our algorithm has provable guarantee and is near-optimal in many scenarios. (iii) Extensive simulation over OMNET platform demonstrates the benefit of our design over a frequency and client-location agnostic Wi-Fi-like MAC. The typical throughput gain is 30-76 percent, whereas, the reduction in collisions is up to 80 percent. (iv) We implemented a proof-of-concept prototype (by modifying madWiFi drivers) that demonstrates feasibility of our design, robustness to temporal variation of available spectrum, and system throughput.

A comprehensive survey of TDD-based mobile communication systems from TD-SCDMA 3G to TD-LTE(A) 4G and 5G directions

TDD (Time Division Duplex) is one of the two duplex modes. TD-SCDMA (Time Division Synchronous CDMA) is the first TDD-based cellular mobile system which is commercialized in wide area and large scale and TD-SCDMA is also the first cellular mobile system which adopted smart antenna technology (also called as beamforming). As the long term evolution of TD-SCDMA, TD-LTE(A) (Time Division-Long Term Evolution, and TD-LTE Advanced) introduced OFDM (Orthogonal Frequency Division Multiplexing) and enhanced smart antenna technology together with MIMO (Multiple Input Multiple Output), which are adopted by LTE FDD (Frequency Division Duplex) either.

It is indicated that TD-SCDMA and TD-LTE(A) have opened a sustainable utilization era of TDD and smart antenna technologies in the wireless mobile communication. This paper aims to present a systematic introduction to TDD-based mobile communications from TD-SCDMA to TD-LTE and beyond, with particular focuses on TDD key technologies, principles of TDD cellular mobile systems, TDD evolution path, and future TDD 5G directions. The comparisons between TDD and FDD are also included. We hope that this paper will provide a comprehensive overview of TDD technology upgrade and its standard evolution, and serve as a valuable reference for research on 5G mobile communicationsystems. It is believed that TDD will play more important role in 5G.

An UHV Grid Security and Stability Defense System: Considering the Risk of Power System Communication

An ultra high voltage (UHV) ac and dc interconnection will become the foundation of China’s future smart grid. Due to the wide spread of interconnected regions, the distance between control stations will increase dramatically. Therefore, the communication {system’s} reliability and real-time performance will become increasingly crucial. However, failures of the communication {system}, such as interruptions, latency, and bit error, are inevitable. This paper uses the UHV grid security and stability defense system (SSDS) as an example to analyze its requirements for communication and the impact ofcommunication failure on the system’s performance.

The effect of communication latency on the power system’s stability is analyzed quantitatively and qualitatively. Based on this analysis, a framework of an UHV grid SSDS considering the risk of the communication system is proposed. A preliminary power system and communication system co-simulation tool is developed to perform a case study. The case study demonstrates that communication latency in the UHV grid changes the control strategy’s effectiveness due to a delay in executing the control strategy. Furthermore, communication latency will negatively affect the power grid’s stability.

Throughput and delay of single-hop and two-hop aeronautical communication networks

Aeronautical communication networks (ACN) is an emerging concept in which aeronautical stations (AS) are considered as a part of multi-tier network for the future wireless communication system. An AS could be a commercial plane, helicopter, or any other low orbit station, i.e., Unmanned air vehicle, high altitude platform. The goal of ACN is to provide high throughput and cost effective communicationnetwork for aeronautical applications (i.e., Air traffic control (ATC), air traffic management (ATM)communications, and commercial in-flight Internet activities), and terrestrial networks by using aeronautical platforms as a backbone. In this paper, we investigate the issues about connectivity, throughput, and delay in ACN. First, topology of ACN is presented as a simple mobile ad hoc network and connectivity analysis is provided. Then, by using information obtained from connectivity analysis, we investigate two communication models, i.e., single-hop and two-hop, in which each source AS is communicating with its destination AS with or without the help of intermediate relay AS, respectively.

In our throughput analysis, we use the method of finding the maximum number of concurrent successful transmissions to derive ACN throughput upper bounds for the two communication models. We conclude that the two-hop model achieves greater throughput scaling than the single-hop model for ACN and multi-hop models cannot achieve better throughput scaling than two-hop model. Furthermore, since delay issue is more salient in two-hop communication, we characterize the delay performance and derive the closed-form average end-to-end delay for the two-hop model. Finally, computer simulations are performed and it is shown that ACN is robust in terms of throughput and delay performances.

Selective DF Protocol for MIMO STBC Based Single/Multiple Relay Cooperative Communication: End-to-End Performance and Optimal Power Allocation

In this paper, we consider the performance of a selective decode-and-forward (DF) relaying based multiple-input multiple-output (MIMO) space-time block coded (STBC) cooperative communicationsystem with single and multiple relays. We begin with a single relay based MIMO STBC system and derive the closed form expression for the end-to-end PEP of coded block detection at the destination node. It is also demonstrated that the MIMO STBC cooperative communication system achieves the full diversity order of the system. We also derive the optimal source relay power allocation, which minimizes the end-to-end decoding error of the cooperative system for a given power budget. Subsequently, for the multiple relay scenario, we consider two different relaying protocols based on two-phase and multi-phase communication.

For each of these multi-relay protocols, we derive the closed form expressions for the end-to-end error rate, diversity order, and optimal power allocation. Simulation results are presented to validate the performance of the proposed single and multiple relay based cooperative communication schemes and the derived analytical results. Further, these schemes can also be seen to lead to a performance improvement compared to several other relaying schemes in existing literature.

Dual band microstrip patch antenna for MIMO system

This work targets design of microstrip patch antenna that will resonate at two different band of frequencies which can be used as elements of array for MIMO system. The proposed dual band antenna operates at ISM band (2.37Ghz-2.48Ghz) and Wimax band (3.46 GHz-3.56 GHz).Bandwidth of operation offered by the given microstrip antenna in ISM band is around 110 Mhz while in Wimax band is 110 Mhz.

The designed dual band antenna was optimized using simulation tool CAD-FEKO_v6.2 which works on Method of Moments. Antenna was manufactured on FR4 substrate having εr= 4.4.The results obtained from simulating antenna with the help of simulation software matches with results of manufactured antenna obtained from Antritsu vector network analyzer.

A Study on Energy Saving and co2 Emission Reduction on Signal Countdown Extension by Vehicular Ad Hoc Networks

Research on the broadcasting of signal countdown messages (SCMs) to vehicles via vehicular ad hocnetwork (VANET) technology has shown that it can reduce CO2 emissions and energy consumption; however, past studies have lacked consideration of car following and vehicle gliding mode. In this paper, two green driving suggestion models, namely, the Maximize Throughput Model (MaxTM) and the Minimize Acceleration and Deceleration Model (MinADM), are proposed to minimize the CO2 emissions by considering real-time traffic information nearby the intersection. The two proposed strategies are compared with an open traffic light control model (OTLCM).

The main facts this paper demonstrate are that traffic models lack consideration of car following, which would make the simulation result unrealistic, that the proposed MaxTM can reduce more CO2 emissions than the MinADM and the OTLCM, and the total travel time in the MaxTM is also better than the other two models so that the general traffic performance can be improved. Simulation results show that the performance of CO2emissions of the MaxTM is 5%-102% better than the MinADM and 13%-209% better than the OTLCM in the simulation cases, and the performance of CO2 emissions of the MaxTM is 8%-14% better than the MinADM and 15%-231% better than the OTLCM in the real traffic cases.

Throughput Analysis of Cooperative Communication in Wireless Ad HocNetworks With Frequency Reuse

In this paper, we investigate the network throughput achieved by both spatial diversity and spatial frequency reuse in a wireless ad hoc network with randomly positioned single-hop source-destination pairs and relays. Compared with conventional direct transmissions, cooperative communication can enhance single-link transmission reliability but reduce network-wide spatial frequency reuse due to relay transmissions. To study the tradeoff between these two competing effects, we construct a geographically constrained region for relay selection based on channel state information.

The networkthroughput, defined as the product of the success probability of each link and the expected number of concurrent transmissions, is derived as a function of the total number of links, relay density, size of relay selection region, and distance between the source and destination. The performance analysis is carried out for both selection combining and maximum ratio combining at the destination. Such analytical results can evaluate the effectiveness of cooperative communication and provide useful insights on the design of large-scale networks. Finally, extensive simulations are conducted to validate the performance analysis.