Time Division Multiple Access Networks Research Articles

On the time complexity of achieving optimal throughput in time division multiple access communication networks

<abstract><p>The fundamental problem of finding transmission schedules for achieving optimal throughput in time division multiple access (TDMA) communication networks is known to be NP-hard. Let $ \mathcal{N} $ be a scheduled $ k $-time slot TDMA network with $ n $ stations and $ m $ links. We showed that an optimal link schedule for $ \mathcal{N} $ can be computed recursively with a recursion tree of logarithmic depth $ \mathcal{O}(\ln m) $ in expectation. Additionally, we showed that optimal link schedules for those TDMA networks, with recursion trees of depth meeting the expectation, can be found in time $ \mathcal{O}(m^{2+\ln k}) $. Likewise, we discuss analogous results for computing optimal station schedules of TDMA networks.</p></abstract>

A Just-in-Time Networking Framework for Minimizing Request-Response Latency of Wireless Time-Sensitive Applications

This article puts forth a networking paradigm, referred to as just-in-time (JIT) communication, to support client-server applications with stringent request-response latency requirement. Of interest is not just the round-trip delay of the network, but the actual request-response latency experienced by the application. The JIT framework contains two salient features. At the client side, the communication layer will “pull” a request from the client just when there is an upcoming transmission opportunity from the network. This ensures that the request contains information that is as fresh as possible (e.g., a sensor reading obtained just before the transmission opportunity). At the server side, the network ascertains that the server, after receiving and processing the request to generate a response (e.g., a control command to be sent to the client), will have a transmission opportunity at just this time. We realize the JIT system, including the protocol stack, over a time-division-multiple-access (TDMA) network implemented on a System-on-Chip (SoC) platform. We prove that a TDMA network with a power-of-2 time slots per superframe is optimal for realizing the server-side JIT function. Our experimental results validate that JIT networks can yield significantly lower request-response latency than networks without JIT support can.

Side-Channel Analysis for the Authentication Protocols of CDMA Cellular Networks

Time-division multiple access (TDMA) and code-division multiple access (CDMA) are two technologies used in digital cellular networks. The authentication protocols of TDMA networks have been proven to be vulnerable to side-channel analysis (SCA), giving rise to a series of powerful SCA-based attacks against unprotected subscriber identity module (SIM) cards. CDMA networks have two authentication protocols, cellular authentication and voice encryption (CAVE) based authentication protocol and authentication and key agreement (AKA) based authentication protocol, which are used in different phases of the networks. However, there has been no SCA attack for these two protocols so far. In this paper, in order to figure out if the authentication protocols of CDMA networks are sufficiently secure against SCA, we investigate the two existing protocols and their cryptographic algorithms. We find the side-channel weaknesses of the two protocols when they are implemented on embedded systems. Based on these weaknesses, we propose specific attack strategies to recover their authentication keys for the two protocols, respectively. We verify our strategies on an 8-bit microcontroller and a real-world SIM card, showing that the authentication keys can be fully recovered within a few minutes with a limited number of power measurements. The successful experiments demonstrate the correctness and the effectiveness of our proposed strategies and prove that the unprotected implementations of the authentication protocols of CDMA networks cannot resist SCA.

On the Delay/Throughput-Security Tradeoff in Wiretap TDMA Networks With Buffered Nodes

In this paper, we investigate the tradeoff between security and throughput and between security and queuing delay in wiretap time-division multiple access (TDMA) networks. We derive a simple relationship, characterized by a single key system parameter, between the stable-throughput region, where there are no perfect secrecy constraints on the data transmissions, and the secure stable-throughput region, where there are perfect secrecy constraints. We quantify the impact of the perfect secrecy constraints on the network’s average queuing delay and propose a novel cross-layer security scheme for delay-limited applications. We establish an insightful link between computational security (i.e., upper-layer security implemented through cryptographic schemes) and physical-layer (information-theoretically proved) security. For the two-user case, we derive a closed-form expression for the network’s minimum average queuing delay under the proposed security scheme and provide a relationship between the network’s minimum queuing delay under perfect secrecy constraints and computational-only secrecy constraints. Moreover, we investigate the impact of cooperative jamming on achieving perfect secrecy, minimum network’s queuing delay, and maximum throughput. We verify our theoretical findings through simulations.

Comparison Between TDMA and Random Multiple-Access Energy-Harvesting Networks Under Security Constraints

We study the maximum average energy transfer rate at a wireless charging energy-harvesting receiver when multiple transmitting nodes communicate their confidential information to a data receiver. We investigate both the time-division multiple-access (TDMA) and the random multiple-access (RMA) schemes and compare their performance. We address the question of which multiple-access scheme can maximize the average energy transfer rate under secrecy constraints. We also investigate the cases of the RMA scheme with equal access probabilities and the TDMA scheme with equal time-slot assignment probabilities.

Deep Learning-Based Spectrum Prediction Collision Avoidance for Hybrid Wireless Environments

With a growing number of connected devices relying on the Industrial, Scientific, and Medical radio bands for communication, spectrum scarcity is one of the most important challenges currently and in the future. The existing collision avoidance techniques either apply a random back-off when spectrum collision is detected or assume that the knowledge about other nodes’ spectrum occupation is known. While these solutions have shown to perform reasonably well in intra-Radio Access Technology environments, they can fail if they are deployed in dense multi-technology environments as they are unable to address the inter-Radio Access Technology interference. In this paper, we present Spectrum Prediction Collision Avoidance (SPCA): an algorithm that can predict the behavior of other surrounding networks, by using supervised deep learning; and adapt its behavior to increase the overall throughput of both its own Multiple Frequencies Time Division Multiple Access network as well as that of the other surrounding networks. We use Convolutional Neural Network (CNN) that predicts the spectrum usage of the other neighboring networks. Through extensive simulations, we show that the SPCA is able to reduce the number of collisions from 50% to 11%, which is 4.5 times lower than the regular Multiple Frequencies Time Division Multiple Access (MF-TDMA) approach. In comparison with an Exponentially Weighted Moving Average (EWMA) scheduler, SPCA reduces the number of collisions from 29% to 11%, which is a factor 2.5 lower.

Relay-Based Positioning in TDMA Networks

In this letter, we propose relay-based positioning in time division multiple access (TDMA) networks, called RPT. Although the concept of relay-based positioning is an improvement over the performance of relative navigation (RelNav), there are two problems to be solved when applying the relay concept to a TDMA network. First, measurement errors caused by mobility may degrade user accuracy because positioning references transmit navigation messages at their assigned times in TDMA, unlike conventional navigation systems, where all references continuously transmit. Second, a selection algorithm among airborne nodes is needed to relay messages to users. An RPT frame is designed to assign the slots for the broadcast and relay of navigation messages consecutively to minimize the effect of mobility. The selection algorithm determines the optimum set of airborne relays by selecting evenly distributed nodes depending on their distances to the master station. The simulation results indicate that RPT significantly improves user accuracy over RelNav.

Fair Resource Allocation with QoS Guarantee in Secure Multiuser TDMA Networks

We investigate a secure multiuser time division multiple access (TDMA) system with statistical delay quality of service (QoS) guarantee in terms of secure effective capacity. An optimal resource allocation policy is proposed to minimize the β‐fair cost function of the average user power under the individual QoS constraint, which also balances the energy efficiency and fairness among the users. First, convex optimization problems associated with the resource allocation policy are formulated. Then, a subgradient iteration algorithm based on the Lagrangian duality theory and the dual decomposition theory is employed to approach the global optimal solutions. Furthermore, considering the practical channel conditions, we develop a stochastic subgradient iteration algorithm which is capable of dynamically learning the intended wireless channels and acquiring the global optimal solution. It is shown that the proposed optimal resource allocation policy depends on the delay QoS requirement and the channel conditions. The optimal policy can save more power and achieve the balance of the energy efficiency and the fairness compared with the other resource allocation policies.

Estimating the number of users in TDMA networks based on redundancy of adaptive channel coding

Blind identification of protocols in wireless communication networks is a critical subject in non-cooperative context. In this paper, a novel method is proposed to estimate the number of active users (NoAU) in wireless time division multiple access (TDMA) networks based on the redundancy of adaptive channel coding. The proposed method, which is based on decision trees and machine learning, can also be used in adaptive coding systems to identify the number of distinct code rates employed by a single transmitter. Simulation results show that the proposed method can estimate the number of codes with accuracy around 99% in noiseless situation. Moreover, for noisy environments, reasonable accuracies compared to naïve methods are obtained.

산업플랜트 기계상태 동시신호 연속취득을 위한 무선센서 네트워크프로토콜 구현

Wireless sensors, installed on machinery, and Time Division Multiple Access (TDMA) transmission make an ideal system for monitoring machine conditions in industrial plants because there is no need for electronic wiring. However, there has not yet been a successful field application of such a system, capable of continuously transmitting data at sample rates greater than 100 Hz. In this research, a TDMA network protocol capable of acquiring data from multiple sensors at sample rates greater than 100 Hz was developed for field application. The protocol was implemented in a single cluster-star topology network, and the system was evaluated based on the node number and transmission distance. Network simulator 2 (ns-2) was used for a real field simulation. Non-TDMA and TDMA protocol cases were compared using four sensor nodes. In the cases of 20-s and 40-s transmission times, there was little difference between the reception rates of the non-TDMA and TDMA systems. However, the difference was much greater when using a 60-s transmission time.

Uplink scheduling for joint wireless orthogonal frequency and time division multiple access networks

In this paper, we present a deterministic resource allocation model for a hybrid uplink wireless orthogonal frequency and time division multiple access network. Since the input data of the model may be affected by uncertainty, we further consider a stochastic formulation of the problem which we transform into an equivalent deterministic binary second-order conic program (SOCP). Subsequently, we use this binary SOCP to derive an equivalent integer linear programming formulation. The proposed models are aimed at maximizing the total bandwidth channel capacity subject to user power and sub-carrier assignment constraints while simultaneously scheduling users in time. As such, the models are best suited for non-real-time applications where sub-channel multiuser diversity can be further exploited simultaneously in frequency and time domains. Finally, in view of the large execution times required by CPLEX to solve the proposed models, we propose a variable neighborhood search metaheuristic procedure. Our numerical results show tight bounds and near optimal solutions for most of the instances when compared to the optimal solution of the problem. Moreover, we obtain better feasible solutions than CPLEX in the stochastic case. Finally, these bounds are obtained at a very low computational cost.

A Distributed Sequential Link Schedule Combined with Routing in Wireless Mesh Networks

This letter proposes a new distributed scheduling scheme combined with routing to support the quality of service of real-time applications in wireless mesh networks. Next, this letter drives average end-to-end delay of the proposed scheduling scheme that sequentially schedules the slots on a path. Finally, this letter simulates the time division multiple access network for performance comparison. From the simulation results, when the average number of hops is 2.02, 2.66, 4.1, 4.75, and 6.3, the proposed sequential scheduling scheme reduces the average end-to-end delay by about 28%, 10%, 17%, 27%, and 30%, respectively, compared to the conventional random scheduling scheme.

Cognitive medium access control protocols for secondary users sharing a common channel with time division multiple access primary users

The unused time slots in a primary time division multiple access (TDMA) network are regarded as the potential channel access opportunities for secondary users (SUs) in cognitive radio (CR). In this paper, we investigate the medium access control protocols that enable SUs to access a common TDMA channel with primary users (PUs). The primary traffic is assumed to follow a Bernoulli random process. A two-state Markov chain is used to model the secondary traffic, and two different scenarios are considered. The first scenario assumes that the secondary packet arrivals are independent and follow a Bernoulli random process and a cognitive carrier sensing multiple access (Cog-CSMA) protocol is proposed. A Rayleigh fading channel is considered in evaluating Cog-CSMA, and its throughput expression is derived in this paper. The second scenario assumes that the packet arrivals follow a correlated packet arrival process and a cognitive packet reservation multiple access (Cog-PRMA) protocol is proposed. A Markov chain is used to model the different system states in Cog-PRMA and derive the throughput. Numerical results show that the Cog-CSMA and Cog-PRMA protocols achieve the objective of supporting secondary transmissions in a TDMA network without interfering the PUs' transmissions and improve the network bandwidth utilization. Copyright © 2012 John Wiley & Sons, Ltd.

On optimal spectrum-efficient routing in TDMA and FDMA multihop wireless networks

This paper addresses the problem of finding the route with maximum end-to-end spectral efficiency, under the constraint of equal bandwidth sharing, in multihop wireless networks that use time division multiple access (TDMA) or frequency division multiple access (FDMA). The conceptual difficulty of this problem arises from the fact that the associated routing metric is neither isotonic nor monotone, and, thus, it cannot be solved directly using shortest path algorithms. The author has recently presented the first polynomial-time algorithm that solves the problem to exact optimality for TDMA networks. The contribution of this paper is twofold. For TDMA networks, we present a new algorithm that achieves a significant improvement in the computational complexity as compared to the algorithms previously known. For FDMA networks, we introduce the first polynomial-time algorithm that provides provably optimal routes. The proposed algorithms rely on the divide-and-conquer principle and a modified Bellman–Ford algorithm for widest path computation. Our computational results further illustrate the efficiency of the proposed approach.

Modeling the reliability of a group membership protocol for dual-scheduled time division multiple access networks

We present reliability models for a group membership protocol designed for TDMA networks such as FlexRay, a protocol that is likely to become the de facto standard for next generation automotive networks. The models are based on discrete-time Markov chains and consider a comprehensive set of fault scenarios. Furthermore, they are parametric allowing for a sensitivity analysis. The results, obtained by a numeric solution of the models using the PRISM model-checker, show that they are computationally practical for realistic configurations and that the GMP can achieve reliability levels in the range required for safety critical applications.

Minimizing multiplayer interactive delay in multihop wireless networks

SUMMARYMinimizing the schedule frame length in spatial time division multiple access networks is essential in enhancing the performance of multiplayer interactive applications in multiple‐group multicasting environments. In this paper, the joint link scheduling and multiple‐group communication problem in such networks is referred to as a real‐time multiple‐group communication tree scheduling (RMGCTS) problem in which the objective is to minimize the total schedule frame length. It is shown that the RMGCTS problem can be represented as an integer linear programming problem. Two particular RMGCTS problems are considered, namely, back‐to‐back RMGCTS for applications with a receiving‐jitter constraint, and general RMGCTS for applications with a delay constraint. Two heuristic algorithms, designated as back‐to‐back scheduling and level‐by‐level scheduling, are proposed to provide efficient solutions of the back‐to‐back and general RMGCTS problems by maximizing the spatial reuse capability within each time slot, thereby minimizing the schedule frame length. The simulation results show that the proposed schemes yield an effective reduction in the length of the multicast schedule frame compared to that obtained from existing tree‐based or pure‐color scheduling algorithms. Copyright © 2011 John Wiley & Sons, Ltd.

A Fast Network Configuration Algorithm for TDMA Wireless Sensor Networks

The deployment of large-scale wireless sensor networks (WSNs) presents various challenges whose solution requires the design and development of power-and-time efficient protocols. In this context many proposals and various standards have suggested the use of time division multiple access (TDMA) in order to guarantee tight-time scheduling and high overall network throughput under high load conditions. However, in TDMA networks the time and overhead required during the setup phase are major drawbacks that are often overlooked. In this paper we introduce a simple and robust algorithm specially tailored to be used during the setup phase of a TDMA-based WSN. The proposed algorithm makes use of 2C, a conflict resolution protocol with some advantageous properties. As a case study, we consider the setup phase of the synchronous protocol SA-MAC. Our results show that the proposed algorithm is able to configure highly populated networks in significantly shorter times than traditional CSMA/CA. Furthermore, an experimental prototype has been developed allowing us to show the feasibility of deploying the proposal using off-the-shelf components.

Forward error correction in 10 Gbits/s Ethernet passive optical networks

The use of forward error correction (FEC) codes in future deployments of access networks is quite foreseeable and requires an analysis of the proper code for this purpose. Therefore, an overview of the most important classes of FEC codes is presented, assessing the most suitable to be used in time-division multiple access networks. Concerning the traffic characteristics and the properties of such networks, the Reed-Solomon codes were found to be the most appropriate, and an analysis of the performance improvement obtained with these codes is reported. The upstream performance of 10 Gbits/s Ethernet passive optical network systems employing the selected FEC code is evaluated and the benefits of introducing FEC are assessed, aiming for the minimization of characteristic impairments of such networks.

A combinatorial algorithm for the TDMA message scheduling problem

In this paper, we introduce a combinatorial algorithm for the message scheduling problem on Time Division Multiple Access (TDMA) networks. In TDMA networks, time is divided in to slots in which messages are scheduled. The frame length is defined as the total number of slots required for all stations to broadcast without message collisions. The objective is to provide a broadcast schedule of minimum frame length which also provides the maximum throughput. This problem is known to be \(\mathcal{NP}\) -hard, thus efficient heuristics are needed to provide solutions to real-world instances. We present a two-phase algorithm which exploits the combinatorial structure of the problem in order to provide high quality solutions. The first phase finds a feasible frame length in which the throughput is maximized in phase two. Computational results are provided and compared with other heuristics in the literature as well as to the optimal solutions found using a commercial integer programming solver. Experiments on 63 benchmark instances show that the proposed method is able to provide optimal frame lengths for all cases with near optimal throughput.

Single antenna interference cancellation (SAIC) for cellular TDMA networks by means of joint delayed-decision feedback sequence estimation

In this letter, single antenna co-channel interference cancellation for cellular time-division multiple access (TDMA) networks by means of joint delayed-decision feedback sequence estimation is studied. The performance is increased by a novel adaptive state allocation technique.