Broadcast Scheduling Algorithms Research Articles

Optimal Broadcast Scheduling Algorithm for a Multi-AUV Acoustic Communication Network

In systems of multiple autonomous underwater vehicles (AUVs), to achieve cooperative operation and cluster intelligence, information is often disseminated via broadcasting. However, due to the long propagation delay and slow transmission rate of underwater acoustic communication, traditional broadcast scheduling algorithms require a long broadcast period to avoid signal collision. To improve the channel utilization rate as much as possible and improve the update rate for broadcast information, we propose an optimal broadcast scheduling algorithm. This algorithm uses the location information of AUVs to adjust the broadcast sequence and broadcast schedule, to achieve the shortest possible collision-free broadcast period in the broadcast network for the current node distribution. Simulation experiments show that this algorithm can achieve a broadcast period much shorter than that of traditional TDMA and higher channel utilization without signal collision. In addition, the simulations prove the feasibility of applying the algorithm in an actual MAC protocol.

A computationally efficient genetic algorithm for MIMO broadcast scheduling

In conventional single-input single-output (SISO) systems, the capacity is limited as base station can provide service to only one user at any instant. However, multiuser (MU) multiple-input multiple-output (MIMO) systems deliver optimum system capacity by providing service to multiple users (as many as transmit antennas) simultaneously according to dirty paper coding (DPC) scheme. However, DPC is an exhaustive search algorithm (ESA) where the user encoding sequence is important to transmit data to multiple users. Exhaustive search becomes imperative as the search space grows with number of users and number of transmit antennas in the MU MIMO system. This can be treated as an optimization problem of maximizing the achievable system sum-rate. In this paper, it has been demonstrated that combined user and antenna scheduling (CUAS) with binary genetic algorithm (BGA) adopting elitism and adaptive mutation (AM) achieves about 97–99% of system sum-rate obtained by ESA (DPC) with significantly reduced computational and time complexity. It has been shown that BGA is able to find the globally optimum solution for MU MIMO systems well within the time interval of modern wireless packet data communications. However, it is interesting to observe that BGA is able to find a solution to CUAS close to the optimum value quite rapidly. In this paper, it is also shown that BGA with elitism and AM achieves higher throughput than limited feedback scheduling schemes as well.

Performance Improvement of Topology-Transparent Broadcast Scheduling in Mobile Ad Hoc Networks

Broadcasting is a key function in mobile ad hoc networks. Topology-dependent scheduling algorithms depend on the detailed network connectivity information and cannot adapt to dynamic topological changes in mobile networks. To overcome this limitation, topology-transparent broadcast scheduling algorithms have been proposed. Due to the large overhead of implement- ing the acknowledgement mechanism in broadcast communica- tions and to guarantee that there is at least one collision-free transmission in each frame, most existing topology-transparent broadcast scheduling algorithms require a node to transmit the same packet repeatedly at multiple slots during one frame. This is very inefficient. In this paper, we propose an efficient topology- transparent broadcast scheduling algorithm. First, instead of transmitting the same packet repeatedly during one frame, each node collects transmission codes of its two-hop neighbors and transmits several different packets during one frame. Second, noting that many unassigned slots are not utilized, we propose several methods to utilize the unassigned slots efficiently in a collision-free and traffic-adaptive manner. Thus, our algorithm provides a guaranteed throughput and achieves a much better average throughput. The analytical and simulation results show that our proposed algorithm outperforms other existing topology- transparent broadcast algorithms dramatically.

Better Scalable Algorithms for Broadcast Scheduling

In the classical broadcast scheduling problem , there are n pages stored at a server, and requests for these pages arrive over time. Whenever a page is broadcast, it satisfies all outstanding requests for that page. The objective is to minimize average flow time of the requests. For any ϵ > 0, we give a (1+ϵ)-speed O (1/ϵ 3 )-competitive online algorithm for broadcast scheduling. This improves over the recent breakthrough result of Im and Moseley [2010], where they obtained a (1+ϵ)-speed O (1/ϵ 11 )-competitive algorithm. Our algorithm and analysis are considerably simpler than Im and Moseley [2010]. More importantly, our techniques also extend to the general setting of nonuniform page sizes and dependent requests . This is the first scalable algorithm for broadcast scheduling with varying size pages and resolves the main open question from Im and Moseley [2010].

Broadcast Scheduling with Latency and Redundancy Analysis for Cognitive Radio Networks

Cognitive radio networks (CRNs) introduce a new communication paradigm that enables unlicensed users to opportunistically access spectrum bands assigned to licensed users. Interestingly, the broadcast problem, which is one of the most fundamental operations in CRNs, has not been well studied. Existing works for the broadcast issue in CRNs are heuristic solutions either without a performance guarantee or with performance far from the optimal solution. In this paper, we study the minimum-latency broadcast scheduling (MLBS) issue for CRNs. Our contributions are threefold. First, we propose a mixed broadcast scheduling (MBS) algorithm under the unit disk graph (UDG) model, denoted by MBS-UDG. MBS-UDG finishes a broadcast task by employing mixed unicast and broadcast communication modes in two phases. We show that the latency performance of MBS-UDG is $O(\hbar+\Delta_{T})$ when $\Delta_{T}\leq \hbox{1}/p$ or $O(\hbar+\log_{1-p}(\hbox{1}/p\Delta_{T}))$ when $\Delta_{T}>\hbox{1}/p$ , where $\hbar$ and $\Delta_{T}$ are the height and the maximum number of leaf nodes connected by a second user (SU)of the broadcasting tree, respectively, and $p$ is the spectrum opportunity for a secondary communication. Furthermore, the redundancy performance of MBS-UDG is analyzed. Second, we extend MBS-UDG to a more general MBS algorithm under the protocol interference model and analyze its latency and redundancy performance. Finally, simulations are conducted to validate MBS, which indicate that MBS significantly improves existing algorithms with respect to both latency and redundancy.

Robust Spatial Reuse Scheduling in Underwater Acoustic Communication Networks

Resource assignment in underwater acoustic communication (UWAC) networks has recently drawn much attention in the research community. Although in most applications the number of nodes in the UWAC network is relatively small, the long propagation delay of acoustic signals underwater motivates the application of spatial reuse in channel access protocols for throughput enhancement. In this paper, we address the problem of spatial-reuse scheduling in UWAC networks that support frequent transmission of broadcast packets and require robustness to inaccurate topology information. Taking the possibility of outdated network topology information into account is of great importance for UWAC applications due to time-varying topologies in the underwater environment. Our main contribution is the derivation of a broadcast scheduling algorithm that combines topology-transparent and topology-dependent spatial-reuse scheduling methodologies to achieve high throughput in static and dynamic topology scenarios. Simulation results demonstrate that our protocol provides a favorable tradeoff between network throughput and robustness to outdated topology information due to topology changes, and that it also achieves fairness in terms of per-node throughput.

Energy‐ and latency‐efficient broadcasting mechanism supporting long‐term evolution e‐multimedia broadcast/multicast service transmission

To provide increasing multimedia broadcast/multicast services (MBMSs), the third generation partnership project modified long-term evolution release nine documents to further support evolved MBMSs (e-MBMS). This study designed a data-broadcasting method called evolved broadcast scheduling algorithm (eBSA). This eBSA provides new scheduling technology for e-MBMS and a new information searching method for user equipments (UEs) that simultaneously conserves UE energy and maintains favourable access latency of broadcast messages. The eBSA constructs index and message channels based on the message popularities, using the index channel to guide UEs to rapidly locate the position of the desired message in the message channel. If searching for unpopular messages, the index channel guides UEs directly to conduct a linear search. Consequently, a short mean access time and mean turning time can be attained. The results of numerical analysis verify that when access messages possess skewed-access characteristics, the proposed eBSA method performs exceptionally. Additionally, by adequately adjusting the parameter provided by the eBSA method, the optimal tradeoff between energy conservation and access latency performance can be attained.

A segmentation approach for file broadcast scheduling

We study the broadcast scheduling problem in which clients send their requests to a server in order to receive some files available on the server. The server may be scheduled in a way that several requests are satisfied in one broadcast. When files are transmitted over computer networks, broadcasting the files by fragmenting them provides flexibility in broadcast scheduling that allows the optimization of per user response time. The broadcast scheduling algorithm, then, is in charge of determining the number of segments of each file and their order of transmission in each round of transmission. In this paper, we obtain a closed form approximation formula which approximates the optimal number of segments for each file, aiming at minimizing the total response time of requests. The obtained formula is a function of different parameters including those of underlying network as well as those of requests arrived at the server. Based on the obtained approximation formula we propose an algorithm for file broadcast scheduling which leads to total response time which closely conforms to the optimum one. We use extensive simulation and numerical study in order to evaluate the proposed algorithm which reveals high accuracy of obtained analytical approximation. We also investigate the impact of various headers that different network protocols add to each file segment. Our segmentation approach is examined for scenarios with different file sizes at the range of 100 KB to 1 GB. Our results show that for this range of file sizes the segmentation approach shows on average 13% tolerance from that of optimum in terms of total response time and the accuracy of the proposed approach is growing by increasing file size. Besides, using proposed segmentation in this work leads to a high Goodput of the scheduling algorithm.

Evolved broadcast scheduling mechanism supporting energy conserving e-MBMS transmission

This study designed a data broadcasting method called evolved broadcast scheduling algorithm (eBSA) to further support LTE evolved multimedia broadcast/multicast services (e-MBMS). This eBSA provides new scheduling technology for e-MBMS and a new information searching method for user equipments that simultaneously conserves user equipment energy and maintains favorable access latency of broadcast messages. The eBSA constructs index and message channels based on the message popularities, using the index channel to guide user equipments to rapidly locate the position of the desired message in the message channel. Consequently, a short mean access time and mean turning time can be attained. The results of numerical analysis verify that when access messages possess skewed access characteristics, the proposed eBSA method performs exceptionally. Additionally, by adequately adjusting the parameter provided by the eBSA method, the optimal tradeoff between energy conservation and access latency performance can be attained.

Broadcast Scheduling for Wireless Mesh Networks Based on Transmission Demand

The performance of a time division multiple access (TDMA) based wireless mesh network (WMN) depends highly on the broadcast scheduling algorithm (BSA) applied. In this paper, it is demonstrated that the required throughput of a node is based on the amount of packets generated at that node and also the packets that need to be relayed through the node. Therefore, depending on the node's position within the WMN, nodes will have different throughput requirements. In order to quantify the required throughput of a node, the metric transmission demand (TD) is defined and a TD based BSA is proposed. Second, a TD based channel utilization metric named transmission efficiency is introduced and a modified way to use the Pollaczek-Khintchine (P-K) formula is also proposed to include the influence of TD in average delay computations. Results demonstrate that the proposed BSA is scalable and provides higher throughput and less average delay compared to other BSAs.

An evolutionary algorithm for broadcast scheduling in wireless multihop networks

A technical challenge in successful deployment and utilization of wireless multihop networks (WMN) are to make effective use of the limited channel bandwidth. One method to solve this challenge is broadcast scheduling of channel usage by the way of time division multiple access (TDMA). Three evolutionary algorithms, namely genetic algorithm (GA), immune genetic algorithm (IGA) and memetic algorithm (MA) are used in this study to solve broadcast scheduling for TDMA in WMN. The aim is to minimize the TDMA cycle length and maximize the node transmissions with reduced computation time. In comparison to GA and IGA, MA actively aim on improving the solutions and is explicitly concerned in exploiting all available knowledge about the problem. The simulation results on numerous problem instances confirm that MA significantly outperforms several heuristic and evolutionary algorithms by solving well-known benchmark problem in terms of solution quality, which also demonstrates the effectiveness of MA in efficient use of channel bandwidth.

Transmission scheduling for wireless mesh network systems equipped with multiple directional antennas

All existing broadcast scheduling algorithms (BSAs) were designed for omnidirectional antenna (OA) packet radio (PR) nodes of a wireless mesh network (WMN). However, when WMN nodes are equipped with multiple directional antennas (DAs), a signal sent from a neighboring node may be received by more than one DA of the receiving node, and some nodes may receive signals from multiple DAs sent from the same node. When existing OA BSAs are used for scheduling transmission time-slots in time division multiple access (TDMA), due to the multiple DA signal detection phenomenon a weak performance in average time delay and channel utilization is obtained. Therefore, a novel transmission scheduling algorithm (TSA) for WMN nodes equipped with multiple DAs is proposed. Simulation results demonstrate that a significant performance gain can be obtained from using the proposed DA-TSA scheme.

One-Hop Neighbor Based Broadcast Scheduling in Wireless Sensor Networks

SUMMARY For wireless sensor networks in which resources are limited and network topology dynamically changes, we propose the one-hop neighbor based broadcast scheduling (ONBS) algorithm to provide reliable delivery service of broadcast packets. The proposed algorithm reduces the scheduling overhead by allowing each joining node to decide its broadcast schedule based on only its one-hop neighbor information in an on-line and distributed manner. Also, once the broadcast schedule is decided, it is not changed to accommodate a newly joining node in order to prevent the consecutive changes of existing schedules. The network simulation results show that the proposed algorithm provides low latency and high reachability despite low overhead and on-line algorithm design.

Improved algorithm for broadcast scheduling of minimal latency in wireless ad hoc networks

A wide range of applications for wireless ad hoc networks are time-critical and impose stringent requirement on the communication latency. One of the key communication operations is to broadcast a message from a source node. This paper studies the minimum latency broadcast scheduling problem in wireless ad hoc networks under collision-free transmission model. The previously best known algorithm for this NP-hard problem produces a broadcast schedule whose latency is at least 648(rmax/rmin)2 times that of the optimal schedule, where rmax and rmin are the maximum and minimum transmission ranges of nodes in a network, respectively. We significantly improve this result by proposing a new scheduling algorithm whose approximation performance ratio is at most (1 + 2rmax/rmin)2 + 32. Moreover, under the proposed scheduling each node just needs to forward a message at most once.

Broadcast Scheduling in Interference Environment

Broadcast is a fundamental operation in wireless networks and naive flooding is not practical because it cannot deal with interference. Scheduling is a good way to avoid interference, but previous studies on broadcast scheduling algorithms all assume highly theoretical models such as the unit disk graph model. In this work, we re-investigate this problem using the 2-disk and the signal-to-interference-plus-noise-ratio (SINR) model to realize it. We first design a constant approximation algorithm for the 2-disk model and then extend it to the SINR model. This result is the first result on broadcast scheduling algorithms in SINR model, to the best of our knowledge.

Broadcast scheduling with MIMO links in multi-hop ad hoc networks

As the current medium access control protocols with Multiple Input Multiple Output (MIMO) links only bear point to point service, broadcast scheduling algorithm in ad hoc networks with MIMO links is proposed. The key to the proposed broadcast scheduling algorithm is the time slot scheduling algorithm which guarantees collision-free transmissions for every node and the minimum frame length. The proposed algorithm increases the simultaneous transmissions of MIMO links efficiently. Due to the interference null capacity of MIMO links, the interference node set of each node can decrease from two-hop neighbors to one-hop neighbors possibly. Simulation results show that our algorithm can greatly improve network capacity and decrease average packet delay.

High performance data broadcasting systems

Data broadcasting as a means of efficient data dissemination is a key technology facilitating ubiquitous computing. For this reason, broadcast scheduling algorithms have received a lot of attention. However, all existing algorithms make the core assumption that the data items to be broadcast are immediately available in the transmitter's queue, ignoring the key role that the disk subsystem and the cache management play in the overall broadcast system performance. With this paper we contribute a comprehensive system's perspective towards the development of high performance broadcast systems, taking into account how broadcast scheduling, disk scheduling, and cache management algorithms affect the overall performance. We contribute novel techniques that ensure an efficient interplay between broadcast scheduling, cache management, and disk scheduling. We study comprehensively the performance of the broadcast server, as it consists of the broadcast scheduling, the disk scheduling, the cache management algorithms, and the transmitter. Our results show that the contributed algorithms yield considerably higher performance. Furthermore, one of our algorithms is shown to enjoy considerably higher performance, under all values of the problem and system parameters. A key contribution is the result that broadcast scheduling algorithms have only a small effect on the overall system performance, which necessitates the definition of different focal points for efforts towards high performance data broadcasting.

Randomized Broadcast Channel Access Algorithms for Ad Hoc Networks.

The problem of broadcast channel access in single-hop and multihop ad hoc networks is considered. Two novel randomized and distributed channel access algorithms are developed and analyzed for single-hop and multihop networks, respectively. These algorithms are designed based on maximizing the worst-case channel efficiency, by optimizing some key parameters, including the backoff probability distribution and the slot length. The proposed algorithm for single-hop networks offers significantly higher throughput than the CSMA methods when the traffic load is heavy, while still achieving good performance when the load is light or medium. The proposed algorithm for multihop networks can flexibly adapt to the traffic load, and offers much better throughput performance than the existing broadcast scheduling algorithms in light or medium load.

Efficient algorithms for scheduling data broadcast

With the increasing acceptance of wireless technology, mechanisms to efficiently transmit information to wireless clients are of interest. The environment under consideration is asymmetric in that the information server has much more bandwidth available, as compared to the clients. It has been proposed that in such systems the server should broadcast the information periodically. A broadcast schedule determines what is broadcast by the server and when. This paper makes the simple, yet useful, observation that the problem of broadcast scheduling is related to the problem of fair queueing. Based on this observation, we present a log-time algorithm for scheduling broadcast, derived from an existing fair queueing algorithm. This algorithm significantly improves the time-complexity over previously proposed broadcast scheduling algorithms. Modification of this algorithm for transmissions that are subject to errors is considered. Also, for environments where different users may be listening to different number of broadcast channels, we present an algorithm to coordinate broadcasts over different channels. Simulation results are presented for proposed algorithms.