Cross Layer Design to Reduce the Latency for Effective Scheduling Technique for Mobile Ad hoc Networks

Wireless Mesh Networking (WMN) technology provides a key revolutionary to the future backbone network access. WMN adopt a multihop based transmission to improve end to end data delivery. The 802.11s MAC (Medium Access Control) is designed using CSMA (Carrier Sense Medium Access) protocol which result in collision of slot due to failure in detecting hidden node in WMN. Various methodologies have been developed to optimize the MAC and hidden node and exposed node detection algorithm in recent time to utilize slot efficiently and reduce latency. Slot reutilization is an effective way in reducing latency but due to improper detection of hidden node of existing algorithm the latency is increased. To overcome this, our work propose an efficient device classification based MAC scheduler by adopting a cross layer design to reduce the latency. The experiment are conducted by varying network size and density and the outcome shows that the proposed approach perform better than existing CSMA/OCA in term of latency

PRACB: A Novel Channel Bonding Algorithm for Cognitive Radio Sensor Networks

Wireless sensor networks (WSNs) can utilize the unlicensed industrial, scientific and medical (ISM) band to communicate the sensed data. The ISM band has been already saturated due to overlaid deployment of WSNs. To solve this problem, WSNs have been powered up by cognitive radio (CR) capability. By using CR technique, WSNs can utilize the spectrum holes opportunistically. Channel bonding (CB) is a technique through which multiple contiguous channels can be combined to form a single wide band channel. By using channel bonding (CB) technique, CR based WSN nodes attempt to find and combine contiguous channels to avail larger bandwidth. In this paper, we show that probability of finding contiguous channels decreases with the increase in number of channels. Moreover, we propose two algorithms of primary radio (PR) activity based channel bonding schemes and compare with sample width algorithm (SWA). The simulation results show that our algorithm significantly avoids PR-CR harmful interference and CB in cognitive radio sensor networks (CRSNs) provides greater bandwidth to CR nodes

Estudi bibliomètric any 2014. Campus del Baix Llobregat: EETAC i ESAB

En el present informe s’analitza la producció científica de les dues escoles del Campus del Baix Llobregat, l’Escola d’Enginyeria de Telecomunicació i Aerospacial de Castelldefels (EETAC) i l’Escola Superior d’Agricultura de Barcelona (ESAB) durant el 2014.Postprint (author’s final draft

On the Performance of Channel Assembling and Fragmentation in Cognitive Radio Networks

[EN] Flexible channel allocation may be applied to multi-channel cognitive radio networks (CRNs) through either channel assembling (CA) or channel fragmentation (CF). While CA allows one secondary user (SU) occupy multiple channels when primary users (PUs) are absent, CF provides finer granularity for channel occupancy by allocating a portion of one channel to an SU flow. In this paper, we investigate the impact of CF together with CA for SU flows by proposing a channel access strategy which activates both CF and CA and correspondingly evaluating its performance. In addition, we also consider a novel scenario where CA is enabled for PU flows. The performance evaluation is conducted based on continuous time Markov chain (CTMC) modeling and simulations. Through mathematical analyses and simulation results, we demonstrate that higher system capacity can be achieved indeed by jointly employing both CA and CF, in comparison with the CA-only strategies. However, this benefit is obtained only under certain conditions which are pointed out in this paper. Furthermore, the theoretical capacity upper bound for SU flows with both CF and CA enabled is derived when PU activities are relatively static compared with SU flows.This work was supported by the EU Seventh Framework Programme FP7-PEOPLE-IRSES under Grant agreement 247083, project acronym S2EuNet. The work of L. Jiao was supported by the Research Council of Norway through the ECO-boat MOL project under Grant 210426. The work of V. Pla was supported in part by the Ministry of Economy and Competitiveness of Spain under Grant TIN2010-21378-C02-02. The associate editor coordinating the review of this paper and approving it for publication was H. Wymeersch.Jiao, L.; Balapuwaduge, IAM.; Li, FY.; Pla, V. (2014). On the Performance of Channel Assembling and Fragmentation in Cognitive Radio Networks. IEEE Transactions on Wireless Communications. 13(10):5661-5675. https://doi.org/10.1109/TWC.2014.2322057S56615675131

Next-Generation Indoor Wireless Systems: Compatibility and Migration Case Study

The indoor connected environment has witnessed significant research and development attention from industries and academia due to the growing number of smaller smart indoor devices around us. Developing an effective and efficient wireless access standard is one of the challenging tasks to enable the next generation indoor connected environment. The technical characteristics of existing wireless access standards, including IEEE 802.11a, 802.11n, and 802.11ac, are considerably limited for realizing indoor connected environments, particularly with a growing number of smaller intelligent devices. Moreover, their backward compatibility and migration strategies are significant for developing the next-generation wireless access standard for the indoor Internet of Things environment. In this context, this paper presents an indoor environmental experimental study focusing on the backward compatibility and migration-centric performance analysis of existing wireless access standards. Three wireless access standards that operate in the 5 GHz frequency spectrum are evaluated considering the metrics, including throughput, range, efficiency, and backward compatibility in an indoor environment. The experimental results are also compared with the analytical path loss model to observe the attributes for next-generation wireless access between the observed and analytical models. The evaluation can attest to the suitable migration strategy for stable next-generation wireless access development and deployment for an indoor smart Internet of Things environment

Channel Allocation and post-CCA based Bandwidth Adaptation in Wireless Local Area Networks with Heterogeneous Bandwidths

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 박세웅.The new prominent 802.11ac standard aims at achieving Gbps data throughput for individual users while at the same time guaranteeing backward compatibility. The approaches to achieving this goal use enhanced physical-layer features, such as higher modulation levels, MIMO (Multiple Input Multiple Output), and wider bandwidth. As for the bandwidth, the channel bonding technique that makes use of multiple 20MHz channels in 5GHz band is adopted. However, the heterogeneity of bandwidth in a network can cause asymmetric interferences in which some transmissions are not sensed by some nodes. As a result, the conventional CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) may not work well in 802.11ac networks and the Gbps throughput, which is attainable for a single link, is not achievable network-widely, which we call the Hidden Channel (HC) problem. In this dissertation, we illustrate the HC problem with a 802.11ac network as a reference system. Then we analyze the problem using Markov chain technique and show how the contention parameters and transmission time affect collision probability and fairness in some deployment scenarios. The validity of the analysis is verified through simulation in the same chapter. As a solution to the HC problem, a centralized and heuristic channel allocation algorithm, PCA (Primary Channel Allocation), in an enterprise local area network is proposed in the next part of this dissertation. The PCA algorithm, an extended version of well known ``University Timetabling'' algorithm for incorporating multi-channel purpose, is designed to avoid HC problem effectively. Through simulations, we demonstrate that our proposed channel allocation algorithm lowers the packet error rate (PER) compared to uncoordinated and RSSI (Received Signal Strength Indicator) based allocation schemes and increases the network-wide throughput as well as the throughput of a station that experiences poor performance. This implies improved fairness performance among transmission pairs with various channel bandwidths. Then, simple experiments are conducted with USRP and WARP boards to show that the problem is real and to prove that the validity of our next solution. Based on that, we argue for the need of bandwidth adaptation based on post-CCA, which is another clear channel assessment (CCA) procedure after finishing a transmission. The post-CCA helps mimic the CSMA/CD (CSMA with Collision Detection) mechanism in the wired Ethernet, thus enhancing channel assessment capability. Then, we propose PoBA (Post-CCA based Bandwidth Adaptation) that alters bandwidth and channel configuration dynamically. Using simulation, we confirm that the PoBA increases network-wide throughput, channel utilization and fairness, and decreases packet error probability.1 Introduction 1 1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Contributions and Outline . . . . . . . . . . . . . . . . 6 2 The HC (Hidden Channel) Problem 11 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 11 2.2 Problem Description . . . . . . . . . . . . . . . . . . . 15 2.3 Numerical Analysis . . . . . . . . . . . . . . . . . . . . 20 2.4 Simulation Results . . . . . . . . . . . . . . . . . . . . 27 2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . 31 3 PCA (Primary Channel Allocation) 33 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 33 3.2 Channel Allocation for Alleviating HC . . . . . . . . . 39 3.2.1 Problem Formulation . . . . . . . . . . . . . . 43 3.2.2 A Heuristic Primary Channel Assignment Algo- rithm . . . . . . . . . . . . . . . . . . . . . . . 51 iv 3.3 Simulation Results . . . . . . . . . . . . . . . . . . . . 57 3.3.1 Case for a Network with Two APs . . . . . . . 58 3.3.2 Case for a Chain Topology with Six APs . . . . 60 3.3.3 Case for Various Sized Random Networks . . . 62 3.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . 68 4 PoBA (Post-CCA based Bandwidth Adaptation) 69 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 69 4.2 Experimental Results . . . . . . . . . . . . . . . . . . . 72 4.3 Post-CCA & PoBA . . . . . . . . . . . . . . . . . . . . 78 4.3.1 Post-CCA Operation . . . . . . . . . . . . . . . 78 4.3.2 PoBA Algorithm . . . . . . . . . . . . . . . . . 81 4.4 Simulation Results . . . . . . . . . . . . . . . . . . . . 89 4.4.1 Case for a Chain Topology with Six APs . . . . 90 4.4.2 Case for Various Sized Random Networks . . . 92 4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . 96 5 Conclusion 97 5.1 Research Contributions . . . . . . . . . . . . . . . . . 97 5.2 Future Research Directions . . . . . . . . . . . . . . . 99Docto

Channel assembling and resource allocation in multichannel spectrum sharing wireless networks

Submitted in fulfilment of the academic requirements for the degree of Doctor of Philosophy (Ph.D.) in Engineering, in the School of Electrical and Information Engineering, Faculty of Engineering and the Built Environment, at the University of the Witwatersrand, Johannesburg, South Africa, 2017The continuous evolution of wireless communications technologies has increasingly imposed a burden on the use of radio spectrum. Due to the proliferation of new wireless networks applications and services, the radio spectrum is getting saturated and becoming a limited resource. To a large extent, spectrum scarcity may be a result of deficient spectrum allocation and management policies, rather than of the physical shortage of radio frequencies. The conventional static spectrum allocation has been found to be ineffective, leading to overcrowding and inefficient use. Cognitive radio (CR) has therefore emerged as an enabling technology that facilitates dynamic spectrum access (DSA), with a great potential to address the issue of spectrum scarcity and inefficient use. However, provisioning of reliable and robust communication with seamless operation in cognitive radio networks (CRNs) is a challenging task. The underlying challenges include development of non-intrusive dynamic resource allocation (DRA) and optimization techniques. The main focus of this thesis is development of adaptive channel assembling (ChA) and DRA schemes, with the aim to maximize performance of secondary user (SU) nodes in CRNs, without degrading performance of primary user (PU) nodes in a primary network (PN). The key objectives are therefore four-fold. Firstly, to optimize ChA and DRA schemes in overlay CRNs. Secondly, to develop analytical models for quantifying performance of ChA schemes over fading channels in overlay CRNs. Thirdly, to extend the overlay ChA schemes into hybrid overlay and underlay architectures, subject to power control and interference mitigation; and finally, to extend the adaptive ChA and DRA schemes for multiuser multichannel access CRNs. Performance analysis and evaluation of the developed ChA and DRA is presented, mainly through extensive simulations and analytical models. Further, the cross validation has been performed between simulations and analytical results to confirm the accuracy and preciseness of the novel analytical models developed in this thesis. In general, the presented results demonstrate improved performance of SU nodes in terms of capacity, collision probability, outage probability and forced termination probability when employing the adaptive ChA and DRA in CRNs.CK201