Resource allocation for two source-destination pairs sharing a single relay with a buffer

In this paper, we obtain the optimal resource allocation scheme in order to maximize the achievable rate region in a dual-hop system that consists of two independent source-destination pairs sharing a single half-duplex relay. The relay decodes the received information and possesses buffers to enable storing the information temporarily before forwarding it to the respective destination. We consider both non-orthogonal transmission with successive interference cancellation at the receivers and orthogonal transmission. Also, we consider Gaussian block-fading channels and we assume that the channel state information is known and that no delay constraints are required. We show that, with the aid of buffering at the relay, joint user-and-hop scheduling is optimal and can enhance the achievable rate significantly. This is due to the joint exploitation of multiuser diversity and multihop diversity in the system. We provide closed-form expressions to characterize the average achievable rates in a generic form as functions of the statistical model of the channels. Furthermore, we consider sub-optimal schemes that exploit the diversity in the system partially and we provide numerical results to compare the different schemes and demonstrate the gains of the optimal one. © 2014 IEEE

Maximizing Expected Achievable Rates for Block-Fading Buffer-Aided Relay Channels

© 2002-2012 IEEE. In this paper, the long-term average achievable rate over block-fading buffer-aided relay channels is maximized using a hybrid scheme that combines three essential transmission strategies, which are decode-and-forward, compress-and-forward, and direct transmission. The proposed hybrid scheme is dynamically adapted based on the channel state information. The integration and optimization of these three strategies provide a more generic and fundamental solution and give better achievable rates than the known schemes in the literature. Despite the large number of optimization variables, the proposed hybrid scheme can be optimized using simple closed-form formulas that are easy to apply in practical relay systems. This includes adjusting the transmission rate and compression when compress-and-forward is the selected strategy based on the channel conditions. Furthermore, in this paper, the hybrid scheme is applied to three different models of the Gaussian block-fading buffer-aided relay channels, depending on whether the relay is half or full duplex and whether the source and the relay have orthogonal or non-orthogonal channel access. Several numerical examples are provided to demonstrate the achievable rate results and compare them to the upper bounds of the ergodic capacity for each one of the three channel models under consideration

OFDMA-Based Medium Access Control for Next-Generation WLANs

Existing medium access control (MAC) schemes for wireless local area networks (WLANs) have been shown to lack scalability in crowded networks and can suffer from widely varying delays rendering them unsuited to delay sensitive applications, such as voice and video communications. These deficiencies are mainly due to the use of random multiple access techniques in the MAC layer. The design of these techniques is highly linked to the choice of the underlying physical (PHY) layer technology. The advent of new PHY schemes that are based on orthogonal frequency division multiple access (OFDMA) provides new opportunities for devising more efficient MAC protocols. We propose a new adaptive MAC design based on OFDMA technology. The design uses OFDMA to reduce collision during transmission request phases and makes channel access more predictable. To improve throughput, we combine the OFDMA access with a carrier sense multiple access (CSMA) scheme. Data transmission opportunities are assigned through an access point that can schedule traffic streams in both time and frequency (subchannels) domains. We demonstrate the effectiveness of the proposed MAC and compare it to existing mechanisms through simulation and by deriving an analytical model for the operation of the MAC in saturation mode

Exploiting power-of-choices for load balancing in fog computing

Power-of-random choices is a well-known phenomenon exploited in load balancing algorithms to achieve an extraordinary improvement at low cost. These algorithms are particularly suitable for the Fog computing model, since they don't require coordination among different fog nodes when they decide to mutually share their resources. In this paper, we propose LL(F, T ) a power-of-random choices based distributed peer-to-peer load balancing algorithm running on a set of autonomous cooperating fog nodes, where F is the protocol fan-out and T a threshold. Nodes implement a random choice over F fog nodes when their current load is above T. Through a mathematical analysis and preliminary simulations we show that tuning T very close to the node saturation condition, this algorithm achieves practically the same performance of its classical implementation requiring a single global scheduler, without the need for each and every job execution to be preceded by a time costly probing phase, a clear benefit for the low delay requirement of fog applications

Distributed fair randomized (DFR): A resource sharing protocol for fog providers

Fog computing promises to support many emerging classes of applications that can't be rely on a cloud-only backend. Fog-to-Fog (F2F) cooperation is suggested in the openFog's Fog computing Reference Architecture, now adopted as an IEEE standard, as a way to improve the computation service provided by this computing delivery model.In this paper, we propose DFR-Distributed Fair Randomized, a distributed F2F cooperation algorithm that allows for sharing computation resources among fog providers that agree on a (reasonable) measure of fairness. We adopt an analytical approach to study the cooperation problem of providers subject to different load conditions. We initially put the cooperation problem in the light of a simple game-theory framework to capture the selfish behavior of providers without any fairness criteria and its consequence in limiting cooperation. Then, we cast the problem as an optimization problem that incorporates fairness. Preliminary simulations results show how DFR converges to the predicted optimal value. © 2019 IEEE

Sequential Randomization load balancing for Fog Computing

Fog Computing is considered a key enabler for meeting the computation requirements of the billions of objects or Things expected to be deployed in the near future. Fog nodes can be viewed as mini-clouds deployed close to the end users, that complement the current big but far cloud paradigm. Although load balancing among fog nodes is a poorly addressed topic, it may improve the capacity of fog nodes to deliver computation service. In this paper we study load balancing among fog nodes, addressing the specific problems arising from the fog model. In particular, we study how to exploit randomized based load balancing protocols leveraging the power-of-random choice property. We propose sequential probing in contrast to the classical randomization protocols based on parallel probing. We show by a mathematical analysis and simulations the superiority of the proposed solution

On the fairness of resource allocation in wireless mesh networks: A survey

This article presents a comprehensive survey of resource allocation techniques in Wireless Mesh Networks (WMNs). Wireless mesh networks have emerged as a key technology for next generation application specific multi-hop wireless networks. We analyze the state-of-the-art resource allocation schemes for WMNs, providing comprehensive taxonomy of the latest work and the future research trends in this field. In general, the resources that are available for WMNs include time, frequency, space, relays, and power. An efficient utilization of these resources can make the network more robust, reliable, and fair. We categorize the resource allocation into "radio" resource allocation, "physical" resource allocation, "utility" based resource optimization, and "cross layer" resource optimization. An ample review of resource allocation schemes within these categories is provided. 2013 Springer Science+Business Media New York.Qatar National Research FundScopu

Network-coding based event diffusion for wireless networks using semi-broadcasting

Publish/subscribe is a well known and powerful distributed programming paradigm with many potential applications. Publish/subscribe content dissemination techniques based on opportunistic networking and network coding-based epidemic routing are key techniques for optimizing network resources, simplifying network architecture, and providing a platform for realizing innovative networking applications and service. In this paper we consider the central problem of any pub/sub implementation, namely the problem of event dissemination, in the case of a wireless mesh network. We propose a new dissemination strategy based on the notion of semi-broadcast. In a semi-broadcast based protocol the actual content is disseminated in two phases. In the first phase only a fraction of the content is broadcasted (pushed) over the network and stored inside any node, whereas in the second phase the missed part is retried (pulled) on demand from other nodes. Thanks to network coding the partial content stored in each node at the end of the first phase is a set of random linear combinations over the whole content. This allows a very efficient recovery strategy as the missed part is found in nearby nodes with a high probability.The benefit of this approach is that only the interested subscribers, which can vary in number and position over time, can engage the pulling phase. We propose several protocols based on non-trivial forwarding mechanisms that employ network coding as a central tool for supporting adaptive event dissemination while exploiting the broadcast nature of wireless transmissions and guided to the semi-broadcast principle. We show a considerable enhancement in term of total flooding costs and full decoding rates by a self parameter control deployment during the dissemination procedure. (C) 2012 Elsevier B.V. All rights reserved

Chip-Level Modulated BPPM Fiber-Optic Code Division Multiple Access

Chip-Level Modulated Binary Pulse Position Modulation (CLM-BPPM) is proposed as a modulation scheme for Fiber-Optic Code Division Multiple Access (FO-CDMA) systems using Optical Orthogonal Code (OOC) for time domain signal spreading. The proposed scheme provides better synchronization and source activity detection at the receiver side as compared to On-Off Keying (OOK). A mathematical expression is derived for the BER of CLM-BPPM using a combinatorial interference pattern analysis approach. The mathematical model is verified using simulation. Numerical results demonstrate that CLM-BPPM has a BER that is very close to OOK. Moreover, increasing the average source activity causes the performance of the CLM-BPPM to approach that of the OOK system with an asymptotic BER equal to the BER of OOK at full user activity