Finite Buffer Size Research Articles

Bayesian estimation of finite buffer size in single server Markovian queuing system

Bayesian estimation of finite buffer size in single server Markovian queuing system

Mitigating Jamming in FSO Cooperative Networks: A Buffer-Aided Relaying Approach

In this paper, we propose a buffer-aided relaying-based approach to counter the effects of jamming in free space optical (FSO) communication networks. An FSO cooperative system with a source node, a relay node, and a destination node is considered. The relay node consists of a finite-size buffer, and both relay and destination nodes are assumed to be affected by jamming. We use a Markov chain (MC) based approach to obtain the state transition matrix of the system, which is later used to evaluate the steady state probability of the proposed setup. A mixture of jamming and Gaussian noise is considered to evaluate the system’s performance. Novel expressions of the outage probability and average bit error rate of the considered FSO system are obtained. The system’s performance is then analyzed for different jamming powers and jamming probabilities. The proposed system is then compared with a non-buffer-aided (NBA) cooperative FSO system affected by a jammer; it is observed that the proposed buffer-aided FSO system significantly outperforms the NBA counterparts.

Joint Sensing and Communication-Rate Control for Energy Efficient Mobile Crowd Sensing

Driven by the rapid growth of Internet of Things applications, tremendous data need to be collected by sensors and uploaded to the servers for further process. As a promising solution, mobile crowd sensing (MCS) enables controllable sensing and transmission processes of multiple types of data in a single device. Despite the appealing advantages, existing works on MCS have mostly simplified two design issues, namely joint control of sensing and transmission processes and corresponding energy consumption. To address the above issues, a single-user MCS system is considered with a typical MCS device sensing and transmitting data to a server in a given time duration. In particular, there exists a busy time interval when the device is incapable of sensing. To minimize the sensing-and-transmission energy consumption of the device, an optimization problem is formulated, where the sensing and transmission rates are jointly optimized over time subjecting to the constraints on the sensing data sizes, transmission data sizes, data casualty, and busy time of sensing. This problem is highly challenging due to the coupling between the rates as well as the existence of the busy time. To deal with this problem, we first show that it can be equivalently decomposed into two subproblems, corresponding to a search for the amount of data size that needs to be sensed before the busy time (referred to as the height), as well as the control of sensing and transmission rates given the height. Next, we show that the latter problem can be efficiently solved by using the classical string-pulling method, while an efficient algorithm is proposed to progressively find the optimal height without the exhaustive search. Moreover, the solution approach is extended to a more complex scenario where there is a finite-size buffer at the server for receiving data. Last, simulations are conducted to evaluate the performance of the proposed designs.

Improved Buffer-Aided Selective Relaying for Free Space Optical Cooperative Communications

This paper tackles the performance analysis and relaying strategies for two-relays buffer-aided (BA) parallel relaying cooperative free space optical (FSO) networks. We first provide an asymptotic analysis of the existing selective relaying scheme that simultaneously activates the strongest source-relay (S-R) and relay-destination (R-D) optical links. We then propose an improvement of this scheme and highlight on its advantages by deriving closed-form accurate expressions for the asymptotic values of the outage probability (OP) and average packet delay (APD). The theoretical evaluation and numerical analysis demonstrate the capability of the improved scheme in enhancing the diversity order with finite buffer sizes unlike the selective relaying scheme that achieves diversity gains only with infinite-size buffers entailing infinite delays. The OP performance is significantly enhanced for all network topologies whether the relays are closer to S, closer to D or placed at the same distance from S and D. On the other hand, the reaped APD gains depend on the positions of the relays.

Performance analysis of PHY layer for RIS-assisted wireless communication systems with retransmission protocols

Reconfigurable intelligent surface (RIS) is one of the most promising technologies for constructing sixth-generation (6G) wireless networks. It has the capability of controlling the electromagnetic response, thereby improving the communication performance. Current studies about physical (PHY) layer analysis of RIS assisted WLC systems neglect the influence of retransmission protocols. Furthermore, the impacts of traffic rate and limited transit buffer on packet transmission and energy consumption are not considered for RIS assisted WLC systems. Focusing on the above problems, we put forward an insightful model to analyze the PHY layer performance of RIS assisted WLC systems using retransmission protocols. In the modeling process, we firstly provide an E2E (end to end) transmission model for the RIS assisted WLC system. The influence of typical retransmission protocols, containing ARQ (automatic repeat request) and hybrid ARQ (HARQ), channel fading types, frame duration on data transmission are comprehensively taken into consideration. Then, we establish an accurate energy consumption model through analyzing the queueing state of the transmitter with finite buffer size and traffic rate. Based on the above two models, we derive the closed-form expressions of PHY layer metrics for RIS assisted WLC systems considering the impact of retransmission protocols. In addition, we also analyze the bound performance of coverage range and expected power efficiency of RIS assisted WLC system with retransmission protocols. Finally, we evaluate the performance of RIS assisted WLC systems under different retransmission protocols and system parameters, and verify the proposed theoretical model.

Buffer State Based Relay Selection for Half-Duplex Buffer-Aided Serial Relaying Systems

This work investigates multi-hop serial relaying half-duplex (HD) networks comprising one source, one destination and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> decode-and-forward (DF) relays. Buffer-aided (BA) relays are considered where finite size buffers are added to relays. For this setup, we propose a novel BA relaying strategy that selects the node that must transmit over one epoch in a block fading environment. Selecting a node depends on the buffer state information of all relays and on the availability of the hops. Moreover, the proposed relaying scheme is controlled by an adjustable parameter that allows the system to achieve multiple levels of tradeoff between the average packet delay (APD) and the outage probability (OP). A Markov chain model is adopted to evaluate the system’s performance and simple closed-form expressions were derived for the APD and OP based on an asymptotic analysis. The performance analysis proves the ability of the suggested relaying scheme to achieve significant OP and APD gains with small buffer sizes. Two variants of the proposed relaying scheme are particularly appealing. The APD-prioritizing variant achieves the smallest APD of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2K$ </tex-math></inline-formula> without improving the diversity order. The second OP-prioritizing variant reaches the full diversity order of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K+1$ </tex-math></inline-formula> while increasing the asymptotic APD to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K(K+3)$ </tex-math></inline-formula> .

Multiclass Energy Packet Networks with finite capacity energy queues

Energy Packet Network (EPN) consists of a queueing network formed by N blocks, where each of them is formed by one data queue, that handles the workload, and one energy queue, that handles packets of energy.We study an EPN model where the energy packets start the transfer. In this model, energy packets are sent to the data queue of the same block. An energy packet routes one workload packet to the next block if the data queue is not empty, and it is lost otherwise.We assume that the energy queues have a finite buffer size and if an energy packet arrives to the system when the buffer is full, jump-over blocking (JOB) is performed, and therefore with some probability it is sent to the data queue and it is lost otherwise.We first provide a value of the jump-over blocking probability such that the steady-state probability distribution of packets in the queues admits a product form solution. The product form is established for multiserver and multiclass data packet queues under FCFS, preemptive LCFS and PS discipline. Moreover, in the case of a directed tree queueing network, we show that the number of data packets in each subtree decreases as the JOB probability increases for each block.

Age of Information of Jackson Networks With Finite Buffer Size

We investigate the Age of Information (AoI) of Jackson Networks with finite buffer size. We provide a closed form expression of an upper bound of the average AoI by using Stochastic Hybrid Systems (SHS) along with linear algebra tools. Since the computation of the bound requires inverting a N × N matrix, where N is the number of queues in the network, we provide a simple iterative algorithm and prove its convergence with geometric convergence rate. Numerical results allow us to assess the accuracy of our model in various settings.

On the Stochastic Analysis of a Quantum Entanglement Distribution Switch

We study a quantum entanglement switch that serves $k$ users in a star topology. We model variants of the system using Markov chains and standard queueing theory and obtain expressions for switch capacity and the expected number of qubits stored in memory at the switch. While it is more accurate to use a discrete-time Markov chain (DTMC) to model such systems, we quickly encounter practical constraints of using this technique and switch to using continuous-time Markov chains (CTMCs). Using CTMCs allows us to obtain a number of analytic results for systems in which the links are homogeneous or heterogeneous and for switches that have infinite or finite buffer sizes. In addition, we can model the effects of decoherence of quantum states fairly easily using CTMCs. We also compare the results we obtain from the DTMC against the CTMC in the case of homogeneous links and infinite buffer, and learn that the CTMC is a reasonable approximation of the DTMC. From numerical observations, we discover that decoherence has little effect on capacity and expected number of stored qubits for homogeneous systems. For heterogeneous systems, especially those operating close to stability constraints, buffer size and decoherence can have significant effects on performance metrics. We also learn that in general, increasing the buffer size from one to two qubits per link is advantageous to most systems, while increasing the buffer size further yields diminishing returns.

Secure Communication With Energy-Harvesting Buffer-Aided Jammer

Information security and self-sustainability are crucial to resource-limited wireless networks. In this paper, we assess the secrecy performance of the legitimate link without having eavesdropper's channel state information (CSI) while considering an energy harvesting (EH) jammer with finite and infinite energy buffer sizes. The EH jammer utilizes accumulated energy from its buffer and transmits artificial noise (AN) to ensure secure communication. To manage the uncertainty in harvested energy and consumption, we analyze on-off (OO) jamming and always-on (AO) jamming schemes. The analytical expressions are obtained for secrecy outage probability (SOP). This analysis models the energy arrival and departure process by a discrete-time continuous-state Markov chain to eliminate the computational complexity and inaccuracy of a discrete-state Markov chain. Both the schemes are compared using SOP and secure throughput. This analysis shows the adequacy of a finite buffer for an EH jammer and also the fact that the availability of jamming power has a more pronounced effect on SOP as compared to a larger number of antennas at the jammer.

MAC Performance Analysis for Reliable Power-Line Communication Networks with ARQ Scheme.

Power-line communication (PLC) networks have been increasingly used for constructing industrial IoT (internet of things) and home networking systems due to their low-cost installation and broad coverage feature. To guarantee the transmission reliability, ARQ (automatic repeat request) scheme is introduced into the link layer of reliable PLC networks, which allows the retransmission of a data frame several times so that it has a higher probability to be correctly received. However, current studies of performance analysis for PLC MAC (medium access control) protocol (i.e., IEEE 1901) do not take into account of the impact of ARQ scheme. To resolve this problem, we propose an analytical model to investigate the MAC performance of IEEE 1901 protocol for reliable PLC networks with ARQ scheme. In the modeling process, we first establish a PLC channel model to reflect the impacts of PLC channel types (containing Rayleigh fading and Log-normal fading), additive non-Gaussian noise feature and ARQ scheme on data transmission at link layer. Next, we employ Renewal theory and Queueing dynamics to capture the transmission attempt behavior of executing IEEE 1901 protocol in the unsaturated environment with finite transit buffer size. On the basis of combining these two models, we derive the closed-form expressions of 1901 MAC metrics considering the influence of the ARQ scheme. Furthermore, we prove that the proposed analytical model has the convergence property. Finally, we evaluate the MAC performance of 1901 protocol for reliable PLC networks with ARQ scheme and verify the proposed analytical model.

EVALUATION OF SIMULATION RESULTS OF DATA TRANSMISSION MODELING ON A CHANNEL WITH RANDOM ACCESS

The subject of the article is the evaluation of the results of a mathematical model consisting of systems of equations that describe the various states of the system and the laws of distribution of packet service time, which allows to investigate the main probability-time characteristics and analyze the operation of a single device. The purpose of the article is to evaluate the results of a mathematical model of the operation of a data network with competing access based on a switching device with a finite buffer size. To achieve the maximum probability, it is necessary to use switches with the optimal size of the buffer, so that the delay was small, and the buffer did not overflow too quickly at high load of the switch, which is the task of this article. A mathematical model consisting of systems of equations describing different states of the system and packet service time distribution laws is proposed, which allows to investigate the main probability-time characteristics and analyze the operation of a single system device and its interaction with other network devices based on the density of the probability distribution of packet service time. The final result is the obtained distribution densities of packet delivery time for different operating modes of the system that can be approximated by the corresponding analytical distribution law. The model allows to calculate the probability of data delivery, taking into account the final size of the buffers used by the data. The conclusion can be considered that, for achievement of the maximum probability it is necessary to use switches with the optimum size of the buffer that both delay was small, and the buffer is not overflowed too quickly at high loading of the switch. Thus, with the help of the developed model it is possible to solve the problem of choosing the optimal size of the switch buffer and estimating the data delivery time. Since buffer overflow leads to loss of information frames, which, in turn, leads to increased packet delivery time.

On the Stochastic Analysis of a Quantum Entanglement Switch

We study a quantum entanglement switch that serves k users in a star topology. We model variants of the system using continuous-time Markov chains (CTMCs) and obtain expressions for switch capacity and the expected number of qubits stored in memory at the switch. Using CTMCs allows us to obtain a number of analytic results for systems in which the links are homogeneous or heterogeneous and for switches that have infinite or finite buffer sizes. In addition, we can easily model the effects of decoherence of quantum states using this technique. From numerical observations, we discover that decoherence has little effect on capacity and expected number of stored qubits for homogeneous systems. For heterogeneous systems, especially those operating close to stability constraints, buffer size and decoherence can significantly affect performance. We also learn that, in general, increasing the buffer size from one to two qubits per link is advantageous to most systems, while increasing the buffer size further yields diminishing returns.

Hierarchical Capacity Provisioning for Fog Computing

The concept of fog computing is centered around providing computation resources at the edge of the network, thereby reducing the latency and improving the quality of service. However, it is still desirable to investigate how and where at the edge of the network the computation capacity should be provisioned. To this end, we propose a hierarchical capacity provisioning scheme. In particular, we consider a two-tier network architecture consisting of shallow and deep cloudlets and explore the benefits of hierarchical capacity provisioning based on queuing analysis. Moreover, we explore two different network scenarios in which the network delay between the two tiers is negligible and the case that the deep cloudlet is located somewhere deeper in the network and thus the delay is significant. More importantly, we model the first network delay scenario with bufferless shallow cloudlets and the second scenario with finite-size buffer shallow cloudlets, and formulate an optimization problem for each model. We also use stochastic ordering to solve the optimization problem formulated for the first model and an upper bound-based technique is proposed for the second model. The performance of the proposed scheme is evaluated via simulations in which we show the accuracy of the proposed upper bound technique and the queue length estimation approach for both randomly generated input and real trace data.

Performance of Random Access Markov Modelling for Two-Way Buffer-Aided Relaying Networks with Wireless Assisted Links

In this paper, we consider two-way relaying networks (TWRNs) in which information of two users randomly exchange via buffer-aided relay. We assume that all nodes work on half-duplex decode-and-forward for relaying of data packets. The relay is equipped with two finite-size buffers and both the users know the exact number of data packets. The data packets are scheduling with different channel access probabilities to avoid collision at relay. The protocols are developed on the basis of selective transmission scheme with states of Markov chain at relay for buffer state information (BSI) and Hybrid buffer state information/channel state information (BSI/CSI). On the basis of these protocols, we investigate closed-from expressions of maximum achievable sum throughput and end-to-end throughput for TWRNs. The numerical results are obtained with the help of CVX software package. Our proposed scheme significantly outperforms the existing two-way buffer-aided relaying scheme in literature.

Retrial Queuing System with Randomized Push-Out Mechanism and Non-Preemptive Priority

A single-server retrial queueing system with finite buffer size, Poisson arrivals, an exponentially distributed service time is considered. If an arriving customer finds the queue completely occupied, it joins a special retrial waiting group (named orbit) in order to seek service over again after some period of time which have exponential distribution. The primary customers take non-preemptive priority over secondary customers. We also introduce so-called randomized push-out buffer management mechanism. It allows you push secondary customers out of the system to free up space that could be taken by primary customers. It is shown that such a queueing system can be reduced to analogous model without retrials. Using generating function technique, the loss probabilities for both types of customers are obtained. Theoretical results allow to investigate the dependency of loss probabilities on the main model parameters (like push-out and retrial probabilities). Special areas of loads are found, where the model locks itself up for secondary customers or follows linear loss law as well. A detailed comparison is made with the case of preemptive priority, which was studied by the authors earlier.

Buffer-Aided Serial Relaying for FSO Communications: Asymptotic Analysis and Impact of Relay Placement

In this paper, we analyze multi-hop free-space optical (FSO) communications in the context of decode-and-forward serial relaying, where the relays are equipped with finite-size buffers. Based on a Markov chain analysis, we derive closed-form asymptotic expressions for the system outage probability (OP) and average packet delay (APD) for an arbitrary number of relays N, and an arbitrary buffer size L. The closed-form evaluation links the system performance to the various network parameters in a simple and intuitive manner, and it is useful for offering clear insight on the impact of the relay placement and the selection of the buffer size for practical FSO systems. We prove that buffer-aided multi-hop systems can reap a diversity gain that ranges from [(N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">τ</sub> /2)] + 1 to N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">τ</sub> + 1 compared with multi-hop buffer-free systems while the asymptotic APD values can range from N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">τ</sub> to (L - 1)N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">τ</sub> for L ≥ 2. Our analysis also highlights the optimal solutions capable of concurrently minimizing the OP and APD.

Queueing Analysis of Performance Measures Under a New Configurable Channel Allocation in Cognitive Radio

To help achieve optimal channel allocation for a cognitive radio network with multiple channels and multiple users, the authors propose a queueing analytical framework for implementing a configurable channel allocation method. Various allocation scenarios can be captured by the allocation method under different parameters. The influence of the parameters under different environmental parameters and system settings on the performance measures is investigated by the proposed framework. System settings such as imperfect spectrum sensing, adaptive modulation and coding scheme, automatic repeat and request, various primary user activity patterns, and finite secondary user buffer size are considered to make the proposed model practical. The procedures to derive performance measures, such as average queue length, packet loss rate, throughput, and average packet delay, are presented. Numerical results that reveal the relationship between various performance measures and the channel allocation method parameters under different channel conditions and secondary user system settings are shown. The allocation method and the analytical framework would be useful to help achieve optimal performance and evaluate different allocation methods.

Integrated Sized-Based Buffer Management Policy for Resource-Constrained Delay Tolerant Network

Delay tolerant network is a type of network where the end-to-end path is not available from source to destination due to the node mobility, dynamic topology and network partitioning or such a path is highly unstable and may split almost immediately after it has been explored. In this background, existing ad hoc routing protocols would be unsuccessful. Therefore, the concept of store-carry-forward mechanism is utilized by introducing a new layer on the top of transport layer called as bundle layer. The bundle layer store message(s) in a finite size buffer for the long duration of time. As a result, node buffer runs out of space and drop messages to overcome congestion. In this paper, we aim to schedule the node buffer by using local knowledge-based buffer management policies called as best message-size selections buffer management policy. We have utilized the local information available in message header such as message-size to control the drop of messages. The evaluation of proposed policy with the existing DOA, DLA, LIFO, MOFO, N-drop and SHLI have been analyzed in ONE simulator in terms of reducing message drop, overhead, latency and raising the delivery ratio.

Protocol Design and Performance Analysis of Multiuser Mixed RF and Hybrid FSO/RF Relaying With Buffers

In this paper, a multiuser mixed radio frequency (RF) and hybrid free-space optical (FSO)/RF system is considered, where multiple mobile users transmit their data to an intermediate decode-and-forward relay node through RF links using a virtual multiple-input multiple-output (MIMO) system, and the relay node forwards the multiplexed data of all users through a FSO link that is supported by a RF MIMO backup system to the destination. The relay node is equipped with a buffer in the physical layer for temporal storage of the users&#x2019; data until the best channel conditions at the relay-destination link are met. For this communication setup, we first propose a transmission protocol that achieves a multiplexing gain through a virtual MIMO system. After that, we derive closed-form expressions for the end-to-end outage probability, asymptotic outage probability, average symbol error rate, and the ergodic capacity when considering the delay-tolerant (finite buffer size) scenario. The results show that buffering in the physical layer provides a significant enhancement to the system performance (outage, error rate, and ergodic capacity). It is also found that pointing error and severe weather turbulence conditions become more tolerable with the existence of the relay&#x2019;s buffer and RF backup link (in the second hop). In addition, the proposed virtual MIMO scheme shows a significant performance enhancement at a high number of receiving antennas, which introduces potential low-complexity diversity gain-based massive MIMO schemes.