Cross-layer Considerations Research Articles

Performance Analysis of Cognitive Radio Networks With Burst Dynamics

The impact of the traffic characteristics of secondary users (SUs) on the performance of cognitive radio networks (CRNs) should be understood for designing operation rules. This paper focuses on multi-type burst services and network congestion problem in CRNs and evaluates the QoS of SUs based on multiple cross-layer considerations. A two-state Markov-modulate Bernoulli process (MMBP-2) is adopted to model packet flows of SUs with different burst degrees in CRNs. We propose a two-dimensional discrete queuing model to consider spectrum access, burstiness of traffic, network congestion, channel environment, user activity and finite buffer. We construct an iterative algorithm to compute the steady-state distribution of the proposed queuing model and determine the performance metrics like the throughput, the average delay, the average queue length and the total packet loss probability. Numerical analysis evaluates the QoS of SUs under different burst environments.

The Importance of Cross-layer Considerations in a Standardized WSN Protocol Stack Aiming for IoT

The Internet of Things (IoT) envisages expanding the current Internet with a huge number of intelligent communicating devices. Wireless sensor networks (WSNs) integrating IoT will rely on a set of the open standards striving to offer scalability and reliability in a variety of operating scenarios and conditions. Standardized protocols will tackle some of the major WSN challenges like energy efficiency, intrinsic impairments of low-power wireless medium, and self-organization. After more then a decade of tremendous standardization efforts, we can finally witness an integral IP-based WSN standardized protocol stack for IoT. Nevertheless, the current state of standards has redundancy issues and can benefit from further improvements. We would like to highlight some of the cross-layer aspects that need to be considered to bring further improvements to the standardized WSN protocol stack for the IoT.

Analysis of Spectrum Access Strategy with Multiple Cross-Layer Considerations in Cognitive Radio Networks

In the multi-channel cognitive radio network, we build an M/M/1/K packet delay queueing model integrating multiple cross-layer considerations for secondary users. To minimize the total average packet delay, the optimal probability vector for spectrum access is determined by genetic algorithm. Furthermore, the total average packet loss rate is derived with another consideration that the limited tolerable retransmission attempt for ARQ. Numerical result proves that our proposed spectrum access strategy outperforms the strategies of random, equal probability and inverse proportion. Finally, under the proposed spectrum access strategy, the influences of related cross-layer parameters on average packet delay and packet loss rate are illustrated.

Assessing Routing Strategies for Cognitive Radio Sensor Networks

Interest in the cognitive radio sensor network (CRSN) paradigm has gradually grown among researchers. This concept seeks to fuse the benefits of dynamic spectrum access into the sensor network, making it a potential player in the next generation (NextGen) network, which is characterized by ubiquity. Notwithstanding its massive potential, little research activity has been dedicated to the network layer. By contrast, we find recent research trends focusing on the physical layer, the link layer and the transport layers. The fact that the cross-layer approach is imperative, due to the resource-constrained nature of CRSNs, can make the design of unique solutions non-trivial in this respect. This paper seeks to explore possible design opportunities with wireless sensor networks (WSNs), cognitive radio ad-hoc networks (CRAHNs) and cross-layer considerations for implementing viable CRSN routing solutions. Additionally, a detailed performance evaluation of WSN routing strategies in a cognitive radio environment is performed to expose research gaps. With this work, we intend to lay a foundation for developing CRSN routing solutions and to establish a basis for future work in this area.

System Design and Throughput Analysis for Multihop Relaying in Cellular Systems

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Wireless multihop relaying can provide a great improvement in systemwide throughput and coverage in a cellular system. However, since additional resources (time or frequency slots) and overhead are required to perform relaying, the addition of relays into a cellular system must be carefully designed for the system's specific geometry, topology, and propagation environment. Maximizing the benefit of multihop relaying requires that the medium access control (MAC) layer scheduler be aware of physical (PHY) layer conditions. Multihop relaying increases networkwide throughput by enabling spatial reuse within a cell and by significantly reducing the path loss on each hop. The most significant gain results from adding enough relays to create line-of-sight (LOS) paths on all relay hops. To assist with system design, we present a methodology of analyzing network throughput and area-averaged spectral efficiency for multihop relay-enhanced cellular systems, including cross-layer considerations. In addition, we describe a technique that may be used to determine spatial reuse schedules. In this paper, we use a realistic model and typical cellular scenarios to show how relaying can be used to improve coverage and throughput in a real-world system. </para>

A Statistical Approach to Contour Line Estimation in Wireless Sensor Networks With Practical Considerations

Contour line estimation in a monitored physical phenomenon using wireless sensor networks (WSNs) with cross-layer considerations is investigated in this paper. Herein, we present a statistical approach to locate contour points for contour line construction in the presence of irregular sensor deployment with the assistant of Delaunay triangular meshes. The proposed contour-estimation algorithm has certain error-correction capability, and it is robust to the data degradation coming from sensing and/or communication noise. To ensure the success of the proposed algorithm, we further analyze three sources of signal distortion: sensing noise, data quantization error, and data communication noise. We find that choosing a proper data quantization level can balance the communication cost and the desired signal quality. Meanwhile, the impact of channel impairment can be mitigated by the appropriate data-fusion mechanism. In this paper, an adaptive data-fusion mechanism is proposed to avoid excessive packet retransmissions. The correctness of the proposed approach is verified through simulation, and the effects of different system parameters on the overall system performance are also given to show the robustness of the proposed algorithm. This paper also offers some guidelines on the design of the WSN system.

Performance Optimization with Efficient Polling Mechanism in IEEE 802.16 Networks with Cross-Layer Consideration

IEEE 802.16 standard suite defines a reservation-based bandwidth allocation mechanism. A SS (Subscriber Station) has to be polled to request bandwidth reservation before transmits uplink data to a BS (Base Station). In this mechanism exist two main polling modes: the unicast polling mode and the contention-based polling mode. The different polling operations in MAC (Medium Access Control) result in different PHY (PHYsical layer) frame structure that deeply affect the performance. Therefore, there should be an optimal scheme to adopt these two polling modes in order to optimize the performance. Although the standard defines five service classes to adaptively use the polling modes to fit the QoS (Quality of Service) requirements of different applications, it does not specify exactly a scheme to adopt these two polling modes efficiently and fairly during the polling process. In~this paper, we investigate the polling mechanisms in IEEE 802.16 networks, and focus the attention on the performance caused by different adoption schemes. We also propose a simple but efficient polling mechanism to optimize the performance. The simulation results verify that the performance is conditioned to the fulfillment of the polling mechanisms and our proposed optimal polling scheme can allocate bandwidth more efficient and achieve better performance.

Routing optimization over network mobility with distributed home agents as the cross layer consideration

Routing optimization (RO) is an important support for Mobile IPv6 while performing handover. It can reduce the overhead of a home agent and make the traffic more fluent between MN and CN; however, Network Mobility (NEMO) in Mobile IPv6 lacks the capability of RO. In this paper, we propose an enhanced architecture by deploying Home Agents Location Registration Agents (HALRA) on cellular data switch (3G/B3G) network incorporating with Distributed Home Agents (NEMO-DHA) on NEMO for a Mobility Critical Area. Under this architecture, it can provide less handoff latency on the Mobility Critical Area and make a detour to avoid the perplexed NEMO routing optimization problem. Moreover, NEMO-DHA can also solve a sort of Nested-NEMO problems by setting authorized Mobile Routers to serve as a set of Distributed Home Agent, and we provides a Cross-Layer suggestion by utilizing R-bit to schedule fairly for NEMO connections. The wireless network can also benefit from Distributed Home Agents by cooperating cellular data switch network with sharing HALR resource. Most models in the paper are described through UML modeling language evaluated by a mathematical model and simulated by NS2-Mobiwan2 ( http://www.ti-wmc.nl/ , 2009).

Clear channel assessment in energyconstrained wideband wireless networks

This is intended as a tutorial review of the clear channel assessment (CCA) component of typical data link layers in wideband wireless networks that employ some form of channel sensing as part of their medium access mechanism. While channel sensing - the core component within CCA module - is implemented at the physical layer, its primary impact is on MAC throughput and energy efficiency, and this impact has not yet been adequately highlighted in the existing literature. We provide a description of CCA methods for wideband wireless networks like IEEE 802.11 and IEEE 802.15 followed by illustrations of their impact on the respective MAC protocols. We also demonstrate the need for a cross-layer consideration of MAC and CCA to optimize the performance of CSMA protocols.

Optimal routing for UWB-based sensor networks

This paper considers ultra-wideband (UWB)-based sensor networks and studies the following problem: given a set of source sensor nodes in the network each generating a certain data rate, is it possible to relay all these rates successfully to the base station? We will show that such problem is intrinsic cross-layer, and subsequently we formulate an optimization problem, with joint consideration of link-layer scheduling, power control, and network-layer routing. For large-sized networks, we propose an efficient heuristic algorithm by partitioning the given network into a core centered around the base station and a boundary edge. For the network core, we formulate a nonlinear programming problem, which can be solved by branch-and-bound approach. For data generated at network edge, we propose an algorithm to connect it to the network core. We use simulation results to demonstrate the efficacy of the proposed solution procedure, as well as the importance of cross-layer considerations.

Cross Layer Considerations for an Adaptive OFDM-Based Wireless Communication System

Future applications require high, but variable data rates and different quality of services (QoS) which is a real challenge for the communication system design. Additionally, the broadband radio channel can be assumed to be frequency selective and time variant, which means the transmission performance varies over time and frequency. The OFDM transmission technique is very flexible in adapting the transmission parameters to the current channel situation and to the application-specific requirements. This kind of flexibility will be applied to solve the technical tasks in the design procedures of future communication systems.