Broadcast In Wireless Networks Research Articles

Scalable Network Coding for Heterogeneous Devices over Embedded Fields

In complex network environments, there always exist heterogeneous devices with different computational powers. In this work, we propose a novel scalable random linear network coding (RLNC) framework based on embedded fields, so as to endow heterogeneous receivers with different decoding capabilities. In this framework, the source linearly combines the original packets over embedded fields based on a precoding matrix and then encodes the precoded packets over GF(2) before transmission to the network. After justifying the arithmetic compatibility over different finite fields in the encoding process, we derive a sufficient and necessary condition for decodability over different fields. Moreover, we theoretically study the construction of an optimal precoding matrix in terms of decodability. The numerical analysis in classical wireless broadcast networks illustrates that the proposed scalable RLNC not only guarantees a better decoding compatibility over different fields compared with classical RLNC over a single field, but also outperforms Fulcrum RLNC in terms of a better decoding performance over GF(2). Moreover, we take the sparsity of the received binary coding vector into consideration, and demonstrate that for a large enough batch size, this sparsity does not affect the completion delay performance much in a wireless broadcast network.

Energy Efficient AoI Minimization in Opportunistic NOMA/OMA Broadcast Wireless Networks

The concept of Age of Information (AoI) minimization in wireless networks has garnered huge interest in recent times. While current literature focuses on scheduling for AoI minimization, there is also a need to efficiently utilize the underlying physical layer resources. In this paper, we consider the problem of energy-efficient scheduling for AoI minimization in an opportunistic NOMA/OMA downlink broadcast wireless network, where the user equipment operate with diverse QoS requirements. We first formulate a resource allocation problem to minimize the average AoI of the network, with energy-efficiency factored in by restricting the long term average transmit power to a predetermined threshold. A heuristic adaptation of the drift-plus-penalty approach from the Lyapunov framework is then utilized to solve the original long-term mixed-integer nonlinear problem on a per time-slot basis. The single time-slot problem is further decomposed into multiple sub-problems, solving for power allocation and user scheduling separately. However, the attained power allocation sub-problems being non-convex, we propose an efficient piece-wise linear approximation to obtain a tractable solution. The scheduling sub-problem is solved optimally by using the integrality property of the linear program. Finally, we provide extensive numerical simulations to show that our proposed approach outperforms the state of the art.

Constant-Length Labeling Schemes for Deterministic Radio Broadcast

Broadcast is one of the fundamental network communication primitives. One node of a network, called the s ource, has a message that has to be learned by all other nodes. We consider broadcast in radio networks, modeled as simple undirected connected graphs with a distinguished source. Nodes communicate in synchronous rounds. In each round, a node can either transmit a message to all its neighbours, or stay silent and listen. At the receiving end, a node v hears a message from a neighbour w in a given round if v listens in this round and if w is its only neighbour that transmits in this round. If more than one neighbour of a node v transmits in a given round, we say that a c ollision occurs at v . We do not assume collision detection: in case of a collision, node v does not hear anything (except the background noise that it also hears when no neighbour transmits). We are interested in the feasibility of deterministic broadcast in radio networks. If nodes of the network do not have any labels, deterministic broadcast is impossible even in the four-cycle. On the other hand, if all nodes have distinct labels, then broadcast can be carried out, e.g., in a round-robin fashion, and hence O (log n )-bit labels are sufficient for this task in n -node networks. In fact, O (log Δ)-bit labels, where Δ is the maximum degree, are enough to broadcast successfully. Hence, it is natural to ask if very short labels are sufficient for broadcast. Our main result is a positive answer to this question. We show that every radio network can be labeled using 2 bits in such a way that broadcast can be accomplished by some universal deterministic algorithm that does not know the network topology nor any bound on its size. Moreover, at the expense of an extra bit in the labels, we can get the following additional strong property of our algorithm: there exists a common round in which all nodes know that broadcast has been completed. Finally, we show that 3-bit labels are also sufficient to solve both versions of broadcast in the case where it is not known a priori which node is the source.

Throughput-Optimal Broadcast in Wireless Networks with Point-to-Multipoint Transmissions

We consider the problem of efficient packet dissemination in wireless networks with point-to-multipoint wireless broadcast channels. We propose a dynamic policy, which achieves the broadcast capacity of the network. This policy is obtained by first transforming the original multi-hop network into a precedence-relaxed virtual single-hop network and then finding an optimal broadcasting policy for the relaxed network. The resulting policy is shown to be throughput-optimal for the original wireless network using a sample-path argument. We also prove the NP-completeness of the finite-horizon broadcasting problem, which is in contrast with the polynomial-time solvability of the problem with point-to-point channels. Illustrative simulation results demonstrate the efficacy of the proposed broadcast policy in achieving the full broadcast capacity with low delay.

Scheduling Algorithms for Minimizing Age of Information in Wireless Broadcast Networks with Random Arrivals

Age of information is a new network performance metric that captures the freshness of information at end-users. This paper studies the age of information from a scheduling perspective. To that end, we consider a wireless broadcast network where a base-station (BS) is updating many users on random information arrivals under a transmission capacity constraint. For the offline case when the arrival statistics are known to the BS, we develop a structural MDP scheduling algorithm and an index scheduling algorithm, leveraging Markov decision process (MDP) techniques and the Whittle's methodology for restless bandits. By exploring optimal structural results, we not only reduce the computational complexity of the MDP-based algorithm, but also simplify deriving a closed form of the Whittle index. Moreover, for the online case, we develop an MDP-based online scheduling algorithm and an index-based online scheduling algorithm. Both the structural MDP scheduling algorithm and the MDP-based online scheduling algorithm asymptotically minimize the average age, while the index scheduling algorithm minimizes the average age when the information arrival rates for all users are the same. Finally, the algorithms are validated via extensive numerical studies.

Scheduling to Minimize Age of Synchronization in Wireless Broadcast Networks With Random Updates

In this work, a wireless broadcast network with a base station (BS) sending random time-sensitive information updates to multiple users under bandwidth constraint is considered. To measure the effect of data desynchronization when the updates appear randomly because of external environment, the metric Age of Synchronization (AoS) is adopted in this work. It shows the amount of the time elapsed since freshest information at the receiver becomes desynchronized. The AoS minimization scheduling problem is formulated into a discrete time Markov decision process and the optimal solution is approximated through structural finite state policy iteration. An index based heuristic scheduling policy based on restless multi-arm bandit (RMAB) is provided to further reduce the computational complexity. Simulation results show that the proposed index policy achieves compatible performance with the MDP and is close to the AoS lower bound. Our work indicates that, to obtain a small AoS over the entire network, users with larger transmission success probability and smaller random update probability are more likely to be scheduled at smaller AoS.

An analytical framework for reliability evaluation of d-dimensional IEEE 802.11 broadcast wireless networks

In this paper, we validate that the deterministic distance-based analytical model can be used to estimate the reliability of one-dimensional (1-D) 802.11 broadcast wireless networks compared with the interference-based analytical model. Therefore, we propose a deterministic distance-based reliability analytical framework for such networks in d-dimensional (d-D, $$d \ge 1$$ ) scenarios. This framework takes into account the fading channel and hidden terminal problem and makes three commonly used reliability metrics able to be resolved, including point-to-point packet reception probability (NRP), packet delivery ratio (PDR), and packet reception ratio (PRR). There are two key factors involved in deducing the effect of hidden terminals. One is to measure the hidden terminal transmission probability during the vulnerable period, which can be calculated based on the approximate solution of the semi-Markov process model capturing the channel contention and the back-off behavior. Another is the challenge to determine the size of the area to which the hidden terminals belong. First, we give a general mathematical expression on the size of the hidden terminal coverage affecting NRP which is an important part of the closed-form solution of NRP/PRR. Second, we adopt the Monte-Carlo method to solve the size of general hidden terminal coverage affecting PDR, making it possible to approximate PDR, as well as control the efficiency and accuracy by constraining the relative error. Finally, we adopt a multi-parameter optimization scheme to find the optimum settings for the network to ensure the quality of service and maximize channel utilization. A series of experimental results show that the framework can be used to access the reliability of 802.11 based d-D broadcast wireless network and pave the way for further optimization.

Cost Sharing Games for Energy-Efficient Multi-Hop Broadcast in Wireless Networks

We study multi-hop broadcast in wireless networks with one source node and multiple receiving nodes. The message flow from the source to the receivers can be modeled as a tree-graph, called broadcast-tree. The problem of finding the minimum-power broadcast-tree (MPBT) is NP-complete. Unlike most of the existing centralized approaches, we propose a decentralized algorithm, based on a non-cooperative cost-sharing game. In this game, every receiving node, as a player, chooses another node of the network as its respective transmitting node for receiving the message. Consequently, a cost is assigned to the receiving node based on the power imposed on its chosen transmitting node. In our model, the total required power at a transmitting node consists of (i) the transmit power and (ii) the circuitry power needed for communication hardware modules. We develop our algorithm using the marginal contribution (MC) cost-sharing scheme and show that the optimum broadcast-tree is always a Nash equilibrium (NE) of the game. Simulation results demonstrate that our proposed algorithm outperforms conventional algorithms for the MPBT problem. Besides, we show that the circuitry power, which is usually ignored by existing algorithms, significantly impacts the energy-efficiency of the network.

SoftHM: A Software-Based Hierarchical Modulation Design for Wireless System

Hierarchical Modulation (HM) is quite efficient for multimedia broadcast in wireless networks. It exploits the wireless broadcast advantage and allows a transmission to reach different users with various qualities. However, existing HM related schemes are based on specially designed hardware, leading to extra hardware and deployment cost in practice. As a remedy for this, we design and implement a software-based HM scheme, named as SoftHM. By carefully tuning the Physical Layer input of a packet (a sequence of “0” or “1” bits, known as PHY payload), a transmitter simply broadcasts the packet with a single rate (e.g., 54Mbps, the highest rate in 802.11g WLAN), while diverse receivers can decode and extract different amount of information (with different reception rate, e.g., 12Mbps or 54Mbps) from it based on their link qualities. Reverse engineering techniques are adopted so that SoftHM works in a plug-in mode, offering it high potentials for wireless systems without any changes in existing modulation and coding modules. We implement SoftHM based on Universal Software Radio Peripheral (USRP) B210 and Commercial of the Shelf (COTS) Wi-Fi devices. Both rigorous analysis on its performance and comprehensive implementation-based experiments show that compared with the traditional time-sharing approach, to support low-quality users with the same bandwidth, high-quality users in SoftHM achieve 111.1% to 616.7% higher throughput. Likewise, to serve high-quality users with the same bandwidth, low quality users in softHM achieve 176.9% to 390.9% higher throughput.

An efficient stream structure for broadcasting the encrypted XML data in mobile wireless broadcast channels

In mobile wireless broadcast networks, XML data is encrypted before it is sent over the broadcast channel in order to ensure the confidentiality of XML data. In these networks, mobile clients must not have access to all the XML data; rather they should have access to some parts of the XML data that are relevant to them and to which they are authorized to have access. In this paper, a new encrypted XML data stream structure is proposed which supports the confidentiality of XML data over the broadcast channel. In our proposed stream structure, the size of encrypted XML data stream is reduced by grouping the paths, XML nodes, texts, and attributes together. The proposed structure includes several indexes to skip from irrelevant data over the broadcast channel. The experimental results demonstrate that the use of our proposed stream structure efficiently disseminates XML data in mobile wireless broadcast networks in a secure manner and the indexes in our proposed stream structure improve the performance of XML query processing over the encrypted XML data stream.

Throughput-Optimal Broadcast in Wireless Networks with Dynamic Topology

We consider the problem of throughput-optimal broadcasting in a time-varying wireless network with an underlying Directed Acyclic (DAG) topology. Known broadcast algorithms route packets along pre-computed spanning trees. In large wireless networks with time-varying connectivities, the optimal trees are difficult to compute and maintain. In this paper, we propose a new online throughput-optimal broadcast algorithm, which takes packet-by-packet scheduling and routing decisions, obviating the need for any global topological structures, such as spanning trees. Our algorithm utilizes certain queue-like system-state information for making transmission decisions and hence, may be thought of as a generalization of the well-known back-pressure policy , which makes point-to-point unicast transmission decisions based on the local queue-length information. Technically, the back-pressure algorithm is derived by greedily stabilizing the queues. However, because of packet-duplications, the work-conservation principle is violated, and an analogous queueing process is non-trivial to define in the broadcast setting. To address this fundamental issue, we identify certain state variables whose dynamics behave like virtual queues . By stochastically stabilizing these virtual queues, we devise a throughput-optimal broadcast policy. We also derive new characterizations of the broadcast capacity of time-varying wireless DAGs and propose efficient algorithms to compute the capacity either exactly or approximately under various assumptions.

A Practical and Compatible Cryptographic Solution to ADS-B Security

As the heart of next-generation air transportation systems, the automatic dependent surveillance-broadcast (ADS-B) is becoming a substitute for the radar, because it can enhance flight safety by requiring aircraft to regularly broadcast their precise geographic positions. Despite its promise, the lack of security mechanisms, e.g., not providing data encryption and message authentication, is a significant barrier to realistically deploy this new technology. While many methods have been proposed for ADS-B security, they can deal with either privacy or integrity unilaterally, and also need to change current ADS-B standards. In this paper, we present a new cryptographic solution to ADS-B security by first carefully exploiting some cryptographic primitives, and then adapting them to the air traffic-monitoring scenario. In contrast to previous approaches, our proposed solution is not only of high compatibility with existing protocols of ADS-B, but also lightweight for congested data links and resource-constraint avionics. Furthermore, it can also tolerate package loss and disorder that frequently occur in ADS-B wireless broadcast networks, making the proposed solution easy-to-deploy and practical. Security analysis shows that our proposal simultaneously achieves the confidentiality and authenticity of ADS-B messages. In addition, performance evaluation also demonstrates the efficiency of communication and computation for the proposal by using flight data of OpenSky-a sensor network that covers Central Europe aiming at gathering ADS-B flight data. Finally, the deployment in a real airport environment also proves the effectiveness of our solution.

Profit Maximization for Sponsored Data in Wireless Video Transmission Systems

Recently, sponsored data started to gain wide-spread use in wireless networks. Existing approaches for regular data services when applying to video transmission in sponsored data faces tremendous challenges. In two-sided markets, internal and external competitions among service providers (SPs), content provider (CPs), and end-users (EUs) become more complex, because larger video-bandwidth significantly increases the cost. When the three parties benefit from sponsored data, pricing and transmission design become much more complicated and difficult in parameterized systems by profit decomposing models, because maximizing the total profits among the three parties is a NP-hard problem. In this paper, we address the problem of maximizing the total profits for sponsored video data. We propose a submodular-based optimization framework for wireless video transmission systems. First, we formulate the sponsored data models in wireless video transmission respective to SP, CPs and EUs sides. The proposed profit models are used in wireless broadcasting networks with a specific attention to sponsored video data. Second, we construct a layered video transmission model in two-sided market through incorporating submodularity. We approximate the NP-hard layered-video broadcasting problem by applying submodular theory. Third, we present a profit maximization framework that optimizes the number of sponsored users, pricing and bandwidth provision. The profit of SP is maximized as well as the profit of CPs is improved and the cost-effective QoE of EUs is guaranteed. To verify the efficiency, we perform the experiments for different pricing schemes. The simulation results demonstrate that the proposed method significantly outperforms existing approaches because the proposed method can achieve maximum profits of both SP and CPs in a wide range of transmission rates.

Scheduling Policies for Minimizing Age of Information in Broadcast Wireless Networks

We consider a wireless broadcast network with a base station sending time-sensitive information to a number of clients through unreliable channels. The Age of Information (AoI), namely the amount of time that elapsed since the most recently delivered packet was generated, captures the freshness of the information. We formulate a discrete-time decision problem to find a transmission scheduling policy that minimizes the expected weighted sum AoI of the clients in the network. We first show that in symmetric networks a Greedy policy, which transmits the packet with highest current age, is optimal. For general networks, we develop three low-complexity scheduling policies: a randomized policy, a Max-Weight policy and a Whittle's Index policy, and derive performance guarantees as a function of the network configuration. To the best of our knowledge, this is the first work to derive performance guarantees for scheduling policies that attempt to minimize AoI in wireless networks with unreliable channels. Numerical results show that both Max-Weight and Whittle's Index policies outperform the other scheduling policies in every configuration simulated, and achieve near optimal performance.

Adaptive modulation for completion time minimization in wireless broadcast networks

In this work we study the effect of hierarchical modulation on completion time minimization in wireless broadcast channels. Time needed to transmit all bits intended for a particular user is defined as its completion time. In this work we investigate minimizing the maximum completion time over all users in a broadcast channel using hierarchical modulation. We compare time division, opportunistic scheduling, and three different adaptive modulation schemes: rate adaptive hierarchical modulation assisted transmission (HA), modified HA (MHA) and optimal HA (OHA). While HA aims at maximizing total throughput, OHA minimizes the maximum completion time, and MHA provides an intermediate solution. It is observed that OHA always chooses the best superposition order and the constellation size to minimize the maximum completion time.

Energy-efficient broadcasting in ad hoc wireless networks

We study energy-efficient broadcasting in wireless networks of unknown topology (ad hoc). We measure energy efficiency by the maximum number of transmissions (‘shots’) allowed to any node in the network. In particular, we examine the case in which a bound k is given and a node may transmit at most k times during the broadcasting protocol. Initially, we focus on oblivious algorithms for k-shot broadcasting, that is, algorithms where at each step each node decides whether to transmit or not with no consideration of the transmission history. Our main contributions are (a) a lower bound of Ω(n2/k) on the broadcasting time of any oblivious k-shot broadcasting algorithm, and (b) an oblivious broadcasting protocol that achieves a matching upper bound, namely O(n2/k), for every k≤n and an upper bound of O(n3/2) for every k>n. We also study the general case of adaptive broadcasting protocols where nodes decide whether to transmit based on all the available information, namely the transmission history known to each. We prove a lower bound of Ω(n1+kk) on the broadcasting time of any protocol by introducing the transmission tree construction which generalizes previous approaches.

On the effect of the deployment setting on broadcasting in Euclidean radio networks

The paper studies broadcasting in radio networks whose stations are represented by points in the Euclidean plane (each station knows its own coordinates). In any given time step, a station can either receive or transmit. A message transmitted from station v is delivered to every station u at distance at most 1 from v, but u successfully hears the message if and only if v is the only station at distance at most 1 from u that transmitted in this time step. A designated source station has a message that should be disseminated throughout the network. All stations other than the source are initially idle and wake up upon the first time they hear the source message. It is shown in [17] that the time complexity of deterministic broadcasting algorithms depends on two parameters of the network, namely, its diameter (in hops) D and a lower bound d on the Euclidean distance between any two stations. The inverse of d is called the granularity of the network, denoted by g. Specifically, the authors of [17] present a deterministic broadcasting algorithm that works in time O (Dg) and prove that every broadcasting algorithm requires $$\varOmega \left( D \sqrt{g} \right) $$ΩDg time. In this paper, we distinguish between the arbitrary deployment setting, originally studied in [17], in which stations can be placed everywhere in the plane, and the new grid deployment setting, in which stations are only allowed to be placed on a d-spaced grid. Does the latter (more restricted) setting provide any speedup in broadcasting time complexity? Although the O (Dg) broadcasting algorithm of [17] works under the (original) arbitrary deployment setting, it turns out that the $$\varOmega \left( D \sqrt{g} \right) $$ΩDg lower bound remains valid under the grid deployment setting. Still, the above question is left unanswered. The current paper answers this question affirmatively by presenting a provable separation between the two deployment settings. We establish a tight lower bound on the time complexity of deterministic broadcasting algorithms under the arbitrary deployment setting proving that broadcasting cannot be completed in less than $$\varOmega (D g)$$Ω(Dg) time. For the grid deployment setting, we develop a deterministic broadcasting algorithm that runs in time $$O \left( D g^{5 / 6} \log g \right) $$ODg5/6logg, thus breaking the linear dependency on g.

Securing Multi Key Cryptography Policy based Session Authorized Access in Wireless Broad Cast Network

A wireless Broadcast communication system is the most significant and security needs in established communication model for authorization. Securing the broadcast network from the conflict is critical issue for broad cast environment. The cryptography standard provides randomize key assumption procedure to the systematic with the recent adoption of elliptic curve cryptography and diffusion of the broadcast network prototype in distributed systems such as wireless broadcast networks, there have been rapidly increasing demands and concerns for distributed data security. To propose a novel multi key policy scheme for a data allocation system by exploiting the attribute of the system construction. The projected scheme features achieve the security difficulty could be solved by multi attribute key issuing in wireless broadcast at the session that verifies using key policy algorithm which is constructed using the secure auditing computation between the key generation in session time and the data storing center and user revocation per each characteristic could be done by alternate encryption which takes advantage of the discriminating attribute group key distribution on crypto analysis. The security analysis of key performance indicates that the RBAC method is efficient to securely supervise the data distributed in the data allotment system.

Profit Optimization for Wireless Video Broadcasting Systems Based on Polymatroidal Analysis

This study addresses the problem of profit maximization between wireless service providers (WSPs) and content providers (CPs) in wireless broadcasting systems , while simultaneously providing high quality of experience for end-users (EUs). We first study the profit model in wireless broadcasting networks with a particular attention to the heterogeneous requirements of EUs, e.g., different display sizes and variable channel conditions. Then, we propose a profit formulation that describes the requirements of wireless service providers and content providers, as well as the satisfaction of EUs that essentially depends on video quality and service charges. We propose a new polymatroidal theoretic framework for maximizing the resulting three-side achievable profit through proper bandwidth allocation. Our framework exploits two particular structures, namely the underlying polymatroidal structure of the profit region and the contra- polymatroidal structure of the rate region. We then propose a profit maximization solution by finding a rate allocation vector on the sum-rate facet that satisfies the maximal achievable profit among the WSP, CPs, and EUs. Experiments on different broadcasting scenarios demonstrate the effectiveness of the proposed method. The WSP is capable of generating more revenues by applying the proposed approach to their marketing strategies while satisfying the demands from CPs and EUs.

Efficient [formula omitted]-shot broadcasting in radio networks

The paper concerns time-efficient k-shot broadcasting in undirected radio networks for n-node graphs of diameter D. In a k-shot broadcasting algorithm, each node in the network is allowed to transmit at most k times. Both known and unknown topology models are considered. For the known topology model, the problem has been studied before by Ga̧sieniec et al. (2008).We improve both the upper and the lower bound of that paper providing a randomized algorithm for constructing a k-shot broadcasting schedule of length D+O(kn1/2klog2+1/kn) on undirected graphs, and a lower bound of D+Ω(k⋅(n−D)1/2k), which almost closes the gap between these bounds. For the unknown topology model, we provide the first k-shot broadcasting algorithm.Assuming that each node knows only the network size n (or a linear upper bound on it), our randomized k-shot broadcasting algorithm completes broadcasting in O((D+min{D⋅k,logn})⋅n1/(k−1)logn) rounds with high probability for k≥2, and in O(D⋅n2logn) rounds with high probability for k=1. Moreover, we present an Θ(logn)-shot broadcasting algorithm that completes broadcasting in at most O(Dlogn+log2n) rounds with high probability. This algorithm matches the broadcasting time of the algorithm of Bar-Yehuda et al. (1992), which assumes no limitation on the maximum number of transmissions per node.