Classical Slotted ALOHA Research Articles

Raptor-IRSA Grant-free Random Access protocol for smart grids applications

This paper deals with the reliability of random access (RA) protocols for massive wireless smart grid communication (m-SGC). We propose and analyze an improved grant-free RA (GF-RA) protocol for critical SG applications under strict QoS m-SGC requirements. At first, we discuss the main features of the SG neighborhood area network (NAN) architecture. We explore the main features of low-rate machine-type wireless networks, and also we describe a technology characterization of wireless neighborhood area networks (WNAN) in medium-range coverage applications. We propose a new-improved irregular repetition slotted ALOHA, combining Raptor codes and irregular ALOHA, namely RapIRSA random access protocol, to better respond to critical high-reliability QoS requirements under a 5G network perspective. Then, we compare and comprehensively analyze the proposed RapIRSA protocol with two existing RA protocols, the IRSA protocol, and the classical Slotted Aloha. Finally, We summarize the potential challenges in implementing the proposed RA protocol for SG critical applications considering a massive number of smart sensors (SS).

Rate Selection for Wireless Random Access Networks Over Block Fading Channels

We study uncoordinated random access over fading channels where each user independently decides whether to send a packet or not to a common receiver at any given time slot. Specifically, we develop an information theoretic formulation to characterize the overall system throughput. We consider two scenarios: classical slotted ALOHA, where no multiuser detection (MUD) capability is available and slotted ALOHA with MUD. In each case, in order to maximize the system throughput, we provide methods to obtain the optimal rates and channel activity probabilities using the user distances to the receiver (or, equivalently, their average signal to noise ratios) assuming a Rayleigh block fading channel. The results demonstrate that the newly proposed optimal rate selection solutions offer significant increase in the expected system throughputs compared to the “same rate to all users” approach commonly used in the literature. In addition to the overall throughput optimization, we also address the issue of fairness among users and propose approaches guaranteeing a minimum amount of individual throughput to each user, and design systems with limited individual outage probabilities for increased energy efficiency and reduced delay.

Delay and Stability Analysis of Connection-Based Slotted-Aloha

In recent years, connection-based slotted-Aloha (CS-Aloha) has been proposed to improve the performance of random access networks. In this protocol, each node attempts to send a request to the access point (AP) before packet transmission. Once this attempt is successful, the node can transmit up to M packets to the AP. Previous works indicated that the CS-Aloha can achieve a higher throughput than the classical slotted Aloha (S-Aloha), if M is large enough. However, the impact of M on the delay performance and stability is still unknown. To solve this problem, we model each node of the CS-Aloha as a vacation queueing system with limited service discipline, where we consider each batch of packet transmissions as a busy period, and the attempt process between two successive busy periods as a vacation period. We derive the delay distribution, which is turned out to be a geometric distribution. From this result, we further obtain the mean delay, the delay jitter, and the bounded delay region. Our analysis shows that increasing M can accelerate the clean-up of the buffer in each node and thus decrease the attempt rate, which can reduce the average time needed by a node to make a successful attempt. As a result, a large M can decrease the mean delay and the delay jitter, and enlarge the bounded delay region. Also, we obtain the condition to achieve the minimum mean delay under different values of M .

On the Resource Consumption of M2M Random Access: Efficiency and Pareto Optimality

The advent of Machine-to-Machine communication has sparked a new wave of interest to random access protocols, especially in application to LTE Random Access (RA). By analogy with classical slotted ALOHA, state-of-the-art models LTE RA as a multi-channel slotted ALOHA. In this letter, we direct the attention to the resource consumption of RA. We show that the consumption is a random variable dependent on the contention parameters. We consider two approaches to include the consumption into RA optimization: by defining resource efficiency and by the means of a bi-objective optimization, where resource consumption and throughput are the competing objectives. We then develop the algorithm to obtain Pareto-optimal RA configuration under resource constraint. We show that the algorithm achieves lower burst resolution delay and higher throughput than the state-of-the-art.

Throughput Region of Random-Access Networks of General Topology

A random-access model is introduced and studied, which is a generalization of the classical slotted Aloha model. Unlike in the slotted Aloha, where two or more simultaneous transmissions on any subset of links collide and “erase” each other, a quite general interference structure is considered, where transmission on link <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> erases a simultaneous transmission on link <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</i> with some fixed probability φ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ij</i> . In particular, it is allowed that φ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ij</i> ≠ φ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ji</i> , which captures possible asymmetric interference in real-most notably wireless-communication networks. Results characterizing the maximum achievable link throughput region and its Pareto boundary are derived. In some cases, the Pareto boundary characterization is almost as simple and explicit as that derived in prior work for the classical slotted Aloha system.

A Channel Aware MAC Protocol in an ALOHA Network with Selfish Users

We consider a game theoretic model incorporating channel state information into slotted ALOHA in a fading environment. Each user sets a threshold for her channel gain and sends a packet only when the channel gain is higher than the threshold at a given slot. This threshold is decided to maximize the net benefit of a user, utility minus power consumption. The asymptotic behaviors of the total throughput at a symmetric Nash equilibrium point are studied for fading and non-fading environments in a homogeneous system. It is shown that the total throughput in a fading environment increases as the number of users increases, while the total throughput in the simple classical slotted ALOHA decreases when users are sensitive enough to power consumption. Convergence to the symmetric Nash equilibrium is also studied.

A Game-Theoretic Approach for Exploiting Multiuser Diversity in Cooperative Slotted Aloha

Multiuser diversity gains can be achieved by assigning channels to users with better channel quality in multiuser systems. To avoid the extensive information exchange required for centralized approaches, we propose a distributed fair pricing strategy for a slotted Aloha system in which users act selfishly to improve their own utilities for both the collision model and the multipacket reception (MPR) model. Based on a game theoretic framework, we show that multiuser diversity gains can be achieved by appropriately designing the Nash equilibrium thresholds for the selfish users to preserve the throughput and revenue achieved in the classical slotted Aloha systems. The network enforces fairness among different users by employing a pricing policy that favors equal access probabilities. Our simulation results show that significant multiuser diversity gains are achieved in terms of energy consumption and/or spectral efficiency.

Increasing Deadline-Constrained Throughput in Multi-Channel ALOHA Networks via Non-Stationary Multiple-Power-Level Transmission Policies.

Multi-channel Slotted ALOHA is currently used primarily in satellite-based networks for transaction processing (e.g., credit card payments at cash registers). For these applications, maximization of attainable throughput while adhering to a maximum-delay constraint with a required probability reflects both the user's requirements, the network owner's desires, and the non-deterministic nature of ALOHA. This paper explores the judicious use of multiple power levels as a priority mechanism; e.g., the last transmission attempt uses higher power. It focuses on the practical and relevant range of three transmission attempts, up to three power levels, and maximum values of the permissible probability of missing the deadline (Pe) in the range 10-5 < Pe < 102. Our scheme increases the attainable delay-constrained throughput by 84-355% (two power levels) and 140-762% (three levels) over classical slotted ALOHA. An optimized combination of multiple copies and two power levels outperforms classical slotted ALOHA by 144-1240%. The smaller Pe, the greater the improvement. The benefit of our schemes is thus dramatic, and far exceeds the contribution of power capture to (unconstrained) capacity of ALOHA.

A unified framework for the study of wireless packet access in the presence of slow propagation impairments

The paper introduces a unified analytical framework which allows accurate study of multiple access performance in wireless packet systems. The method is based on the analysis of the interference statistics and takes into account slowly varying shadowing and best base station assignment, as well as the effect of the nonuniform traffic distribution induced transmission failures. As an example of application of the technique, two protocols are considered: (1) the classic slotted ALOHA, for which a comprehensive study in a realistic wireless environment has not yet been presented, despite the many analyses published in the past; and (2) the capture division packet access (CDPA). An important conclusion of our study is that if power control and best cell site assignment are jointly used, the performance loss due to slow shadowing is almost negligible.

Steady-state behavior of interacting queues-a numerical approach

The M queues that interact according to a model of multiple-access transmissions over a collision channel are considered. Each queue receives messages that it attempts to transmit in a classical slotted ALOHA fashion. The steady-state behavior of such systems is unknown except in certain simple cases. A numerical approach is proposed that permits the calculation, within any desired accuracy, of the joint queue size distribution as well as of the moments. The approach uses a technique that involves auxiliary systems of queues that dominate, in a well-defined sense, the given ones. Consideration of such dominating systems in some cases permits the study of the ergodic region of the original systems. The methodology developed here is applicable to contexts more general than that of multiple-access transmissions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Multi-station packet-radio network

A new structure for packet-radio networks, called the multi-station network, is suggested and analyzed. We describe the salient features of this structure that consists of a large number of nodes and several stations. We then focus on one of the main problems within the suggested structure, the problem of forwarding packets from the nodes to the stations through a shared radio channel. Two basic forwarding schemes are investigated and compared. The classical slotted ALOHA is considered as an access scheme to the shared channel.