Thomas D. Lagkas

Priority-Oriented Adaptive Control With QoS Guarantee for Wireless LANs

In todays wireless networks, there is a great need for quality of service (QoS), because of the time-bounded voice, audio, and video traffic. A new QoS enhanced standard is being standardized by the IEEE 802.11e workgroup. It uses a contention free access mechanism called hybrid control channel access (HCCA) to guarantee QoS. However, HCCA is not efficient for all types of time-bounded traffic. This paper proposes an alternative protocol which could be adapted in hybrid coordination function (HCF). The priority-oriented adaptive control with QoS guarantee (POAC-QG) is a complete centralized channel access mechanism, it is able to guarantee QoS for all types of multimedia network applications, it enhances the parameterized traffic with priorities, and it supports time division access using slots. Furthermore, it instantly negotiates the quality levels of the traffic streams (TSs) according to their priorities, supporting multiple streams to the best quality it can achieve. POAC-QG, compared to HCCA, provides higher channel utilization, adapts better to the characteristics of the different traffic types, differentiates the TSs more efficiently using priorities, and, generally, exhibits superior performance.

QAP: A QoS supportive adaptive polling protocol for wireless LANs

A QoS supportive adaptive polling (QAP) protocol for wireless LANs is introduced. QAP operates under an infrastructure wireless LAN, where an access point (AP) polls the wireless nodes in order to grant them permission to transmit. The polled node sends data directly to the destination node. We consider bursty traffic conditions, under which the protocol operates efficiently. The polling scheme is based on an adaptive algorithm according to which it is most likely that an active node is polled. Also, QAP takes into account packet priorities, so it supports QoS by means of the Highest Priority First packet buffer discipline and the priority distinctive polling scheme. Lastly, the protocol combines efficiency and fairness, since it prohibits a single node to dominate the medium permanently. QAP is compared to the efficient learning automata-based polling (LEAP) protocol, and is shown to have superior performance.

HIPERSIM: A Sense Range Distinctive Simulation Environment for HiperLAN Systems

This paper presents the simulator “HIPERSIM” which was developed and used to examine the behavior of HIPERLAN (Type 1). HIPERSIM simulates the HIPERLAN network under various conditions, assuming that the communication range and the sense range (signal detection range) of a node are different. In a wireless LAN, like HIPERLAN, the medium access protocol, the hidden nodes, the packet forwarding and the power saving mechanism are important issues that significantly affect the overall performance. The intention is to provide a HIPERLAN specialized tool (HIPERSIM) which can simulate most of the features of this WLAN protocol, in order to examine the performance of HIPER-LAN. The main focus is to simulate the channel access mechanism accurately, so as to examine the effectiveness of the EY-NPMA protocol, and underline its advantages and the elements that need improvement. Also, in HIPERSIM, there is emphasis on the “hidden nodes” issue. More specifically, we distinguish between the communication range and the signal detection range of a node, since this is a characteristic of the wireless nature and it affects the network operation. The simulation results show that EY-NPMA is effective and suitable for WLANs. Probably there could be some improvement in order to avert the collisions close to the receiver.

A Novel Method of Serving Multimedia and Background Traffic in Wireless LANs

Wireless local area networks (LANs) require the efficient integration of multimedia and traditional data traffic. This paper proposes the priority-oriented adaptive polling (POAP) protocol that could be used in place of the enhanced distributed channel access (EDCA) part of the IEEE 802.11e access scheme. EDCA seems capable of differentiating traffic; however, it exhibits great overhead that limits the available bandwidth and degrades performance. POAP is collision free, prioritizes the different kinds of traffic, and is able to provide quality of service (QoS) for all types of multimedia network applications while efficiently supporting background data traffic. POAP, compared to EDCA, provides higher channel utilization, distributes resources to the stations adapting to their real needs, and generally exhibits superior performance.

A new approach to the design of MAC protocols for wireless LANs: combining QoS guarantee with power saving

An alternative WLAN protocol which could be adapted in the HCF access scheme defined by IEEE 802.11e, in place of the HCCA mechanism, is introduced. LEPOAC-QG (low energy priority oriented adaptive control with QoS guarantee) is a centralized access mechanism that supports low energy consumption, guarantees QoS for all types of multimedia network applications, enhances the parameterized traffic with priorities, and supports time division access. It instantly negotiates the quality levels of the traffic streams trying to support multiple streams with best possible quality. LEPOAC-QG, compared with HCCA, exhibits generally superior performance.

Modeling and performance analysis of an alternative to IEEE 802.11e Hybrid Control Function

Modern wireless networks are offering a wide range of applications that require the efficient integration of multimedia and traditional data traffic along with QoS provision. The IEEE 802.11e workgroup has standardized a new QoS enhanced access scheme for wireless LANs, namely Hybrid Control Function (HCF). HCF consists of the Enhanced Distributed Channel Access (EDCA) and the Hybrid Control Channel Access (HCCA) protocols which manage to ensure QoS support. However, they exhibit specific weaknesses that limit network performance. This work analyzes an alternative protocol, called Priority Oriented Adaptive Polling (POAP). POAP is an integrated channel access mechanism, is collision free, it employs priorities to differentiate traffic in a proportional way, it provides fairness, and generally supports QoS for all types of multimedia applications, while efficiently serving background data traffic. POAP is compared to HCF in order to examine the wireless network performance when serving integrated traffic.

Architecting the IoT paradigm: a middleware for autonomous distributed sensor networks

Actualizing Internet of Things undoubtedly constitutes a major challenge of modern computing and is a promising next step in realizing the unification of all seamlessly interacting entities, either human users or participating machines, under a shared, coherent architecture. While it has now become common belief that the related solutions should be based on compatible network infrastructure employing widely accepted communication schemes, the specifics of the intermediate system that would act as global interface for all involved “things” are yet to be determined. A rising trend to define such machine-based entities is through cyber-physical systems, in terms of collaborating elements with physical input and output. Certainly, sensor networks constitute the most representative realization of such systems. Taking these issues and opportunities under consideration, this work proposes a bioinspired distributed architecture for an Internet of Things that exhibits self-organization properties to enable efficient interaction between entities modeled as cyber-physical systems, mainly focusing on sensor networks. Furthermore, a middleware has been implemented according to the proposed architecture, which serves the role of the backbone of this network as a multiagent and autonomous distributed system. The evaluation results demonstrate the self-optimization properties of the introduced scheme and indicate global network convergence.

Hybrid 5G optical-wireless SDN-based networks, challenges and open issues

The fifth-generation (5G) mobile networks are expected to bring higher capacity, higher density of mobile devices, lower battery consumption and improved coverage. 5G entails the convergence of wireless and wired communications in a unified and efficient architecture. Mobile nodes, as defined in fourth-generation era, are transformed in heterogeneous networks to make the front-haul wireless domains flexible and intelligent. This work highlights a set of critical challenges in advancing 5G networks, fuelled by the utilisation of the network function virtualisation, the software defined radio and the software defined networks techniques. Furthermore, a novel conceptual model is presented in terms of control and management planes, where the inner architectural components are introduced in detail.

A high performance QoS supportive protocol for wireless LANs

A QoS supportive adaptive polling (QAP) protocol for wireless LANs is introduced. QAP operates under an infrastructure wireless LAN, where an access point (AP) polls the wireless nodes in order to grant them permission to transmit. The polled node sends data directly to the destination node. We consider bursty traffic conditions, under which the protocol operates efficiently. The polling scheme is based on an adaptive algorithm according to which it is most likely that an active node is polled. Also, QAP takes into account packet priorities, so it supports QoS by means of the highest priority first packet buffer discipline and the priority distinctive polling scheme. Lastly, the protocol combines efficiency and fairness, since it prohibits a single node to dominate the medium permanently. QAP is compared to the efficient learning automata-based polling (LEAP) protocol, and is shown to have superior performance.

Analysis of queue load effect on channel access prioritization in Wireless Sensor Networks

Resource allocation in Wireless Sensor Networks (WSNs) is certainly a challenging issue. WSNs are characterized by special features, like energy constraints and limited computing resources. Latest trends define that sensors should be able to provide Quality of Service (QoS) demanding data transmission. A modern approach in bandwidth sharing considers both the packet queue load as well as the traffic priority. A new QoS aware channel sharing approach is introduced, analyzing the effect of queue load in WSN Medium Access Control (MAC). The analysis reveals that the queue load factor has a great impact on QoS provision in bandwidth sharing, while packet priorities are also considered.