Real-time Packet Research Articles

STORM: A Framework for Integrated Routing, Scheduling, and Traffic Management in Ad Hoc Networks

A cross-layer framework is introduced for the effective dissemination of real-time and elastic traffic in multihop wireless networks called Scheduling and Traffic Management in Ordered Routing Meshes (STORM). Unicast and multicast routes are established in coordination with the scheduling of transmissions and bandwidth reservations in a way that bandwidth and delay guarantees can be enforced on a per-hop and end-to-end basis. The routes established in STORM are shown to be loop-free and real-time packets forwarded along these routes are shown to have bounded end-to-end delays. Results from detailed simulation experiments show that, compared to a protocol stack consisting of 802.11 DCF for channel access, AODV or OLSR for unicast routing, and ODMRP for multicast routing, STORM attains similar or better performance for elastic traffic, and up to two orders of magnitude improvement in end-to-end delays, with twice the amount of data delivery for real-time traffic while inducing considerably less communication overhead.

Packet Scheduling for Downlink OFDMA Wireless Systems with Heterogeneous Traffic

In this paper, we propose a packet scheduling algorithm for downlink OFDMA wireless systems in which users have heterogeneous traffic. The proposed scheduling algorithm not only focuses on channel state and fairness but also takes the users’ queue length into consideration. With the idea of beta deadline parameter, we convert the delay bound of real-time traffic to date rate domain QoS parameter, and extend the idea for non real-time traffic with the minimum average throughput requirement. According to the subscribers’ QoS parameter, we divide the whole band into chunks with different size flexibly. Chunks are allocated to users in accordance with the scheduling rule. Simulation results demonstrate that the proposed scheduling algorithm can acclimatize itself to active user number in the system and the users’ requirements for radio resource. Its performance in terms of spectral efficiency, packet loss ratio, and the real-time traffic packets’ delay, is better than algorithms with fixed chunk size dividing.

FPGA 기반 네트워크 침입탐지 시스템 하드웨어 설계 및 구현

Deep packet inspection which perform pattern matching to search for malicious patterns in the packet is most computationally intensive task. Hardware-based pattern matching is required for real-time packet inspection in high-speed network. In this paper, we have designed and implemented network intrusion detection hardware as a Microblaze-based SoC using Virtex-6 FPGA, which capture the network input packet, perform hardware-based pattern matching for patterns in the Snort rule, and provide the matching result to the software. We verify the operation of the implemented system using traffic generator and real network traffic. The implemented hardware can be used in network intrusion detection system operated in wire-speed.

Constant Bit Rate Packets Transmission in IEEE 802.15.4 LR-WPANs

In IEEE 802.15.4 LR-WPANs, quality-of-service (QoS) is supported by using the guaranteed time slots (GTS) to transmit real-time packets, where a LR-WPAN device does not need to contend for channel. Requests of GTS are allocated based on the first-come-first-service policy in the PAN coordinator. However, with the increasing of multimedia applications, this original design has suffered from a lack of priority mechanism to support transmission of real-time packets. In this paper, we propose a nonpreemptive priority-based polling scheme for the GTS allocation in IEEE 802.15.4 LR-WPANs. The proposedscheme can ensure the connections with higher priority cantransmit real-time packets faster. The simulations show that the proposed scheme can achieve more GTS allocations, higher throughput, better bandwidth utilization and lower packets access delay time.

Tail distribution of the delay in a general batch-service queueing model

Batch servers are capable of processing batches of packets instead of individual packets. Although batch-service queueing models have been studied extensively during the past decades, the focus was mainly put on calculating performance measures related to the buffer content, whereas less attention has been paid to the packet delay. In this paper, we focus on the tail probabilities of the delay that a random packet experiences in a general batch-service queueing model. More specifically, we establish approximations for these probabilities, which are highly accurate and easy to calculate. These results, for instance, allow to accurately assess the probability that real-time packets experience an excessive delay in practical telecommunication systems.

Combined Queue Management and Scheduling Mechanism to Improve Intra-User Multi-Flow QoS in a Beyond 3,5G Network

Packet scheduling and buffer management are the two important functions adopted in networks design to ensure the Quality of Service (QoS) when different types of packets with different needs of quality share the same network resources. The Packet scheduling policy determines packet service priorities at the output link, it can reduce packet delay and delay jitter for high-priority traffic. The buffer management involves packet dropping and buffer allocation. The overall goal of such schemes proposed in High Speed Downlink Packet Access (HSDPA) is to take advantage of the channel variations between users and preferably schedule transmissions to a user when the channel conditions are advantageous; it does not take in consideration the characteristics of the flows composing the transmitted traffic to the user. This paper compares two queue management mechanisms with thresholds applied for packets transmitted to an end user in HSDPA network. Those mechanisms are used to manage access packets in the queue giving priority to the Real Time (RT) packets and avoiding the Non Real Time (NRT) packets loss. The authors show that the performance parameters of RT packets are similar in the two mechanisms, where as the second mechanism improves the performance parameters of the NRT packets.

End-to-End Flow Control for Visual-Haptic Communication under Bandwidth Change

This paper proposes an end-to-end flow controller for visual-haptic communication. A visual-haptic communication system transmits non-real-time packets, which contain large-size visual data, and real-time packets, which contain small-size haptic data. When the transmission rate of visual data exceeds the communication bandwidth, the visual-haptic communication system becomes unstable owing to buffer overflow. To solve this problem, an end-to-end flow controller is proposed. This controller determines the optimal transmission rate of visual data on the basis of the traffic conditions, which are estimated by the packets for haptic communication. Experimental results confirm that in the proposed method, a short packet-sending interval and a short delay are achieved under bandwidth change, and thus, high-precision visual-haptic communication is realized.

Packet-Hiding Methods for Preventing Selective Jamming Attacks

The open nature of the wireless medium leaves it vulnerable to intentional interference attacks, typically referred to as jamming. This intentional interference with wireless transmissions can be used as a launchpad for mounting Denial-of-Service attacks on wireless networks. Typically, jamming has been addressed under an external threat model. However, adversaries with internal knowledge of protocol specifications and network secrets can launch low-effort jamming attacks that are difficult to detect and counter. In this work, we address the problem of selective jamming attacks in wireless networks. In these attacks, the adversary is active only for a short period of time, selectively targeting messages of high importance. We illustrate the advantages of selective jamming in terms of network performance degradation and adversary effort by presenting two case studies; a selective attack on TCP and one on routing. We show that selective jamming attacks can be launched by performing real-time packet classification at the physical layer. To mitigate these attacks, we develop three schemes that prevent real-time packet classification by combining cryptographic primitives with physical-layer attributes. We analyze the security of our methods and evaluate their computational and communication overhead.

Software Design of Packet Analyzer based on Byte-Filtered Packet Inspection Mechanism for UW-ASN

The rapid growth of UnderWater Acoustic Sensor Networks (UW-ASNs) has led researchers to enhance underwater MAC protocols against limitations existing in underwater environment. We propose the customized robust real-time packet inspection mechanism with addressing the problem of the search for the data packet loss and network performance quality analysis in UW-ASNs, and describe ow- experiences using this approach. The goal of this work is to provide a framework to assess the network real-time performance quality. We propose a customized and adaptive mechanism to detect, monitor and analyze the data packets according to the MAC protocol standards in UW-ASNs. The packet analyzing method and software we propose is easy to implement, maintain, update and enhance. We take input stream as real data packets from sniffer node in capture mode and perform fully analysis. We were interested in developing software and hardware designed tool with the same capabilities which almost all terrestrial network packet sniffers have. Experimental results confirm that the best way to achieve maximum performance requires the most adaptive algorithm. In this paper, we present and offer the proposed packet analyzer, which can be effectively used for implementing underwater MAC protocols.

Time-domain simulation of electron diffraction in crystals

Transmission electron microscopy (TEM) and low-energy electron diffraction (LEED) simulations are performed by propagating electron wave packets in real space and real time. The method accurately describes electron scattering in solids for high ($>$200 keV) and low (20--200 eV) energies. The applicability of the method is demonstrated by calculating TEM images and LEED intensities of silicon and graphene.

An improved security-aware packet scheduling algorithm in real-time wireless networks

Developing security-aware packet scheduling algorithms can efficiently enhance the security while delivering packets through wireless links. Existing scheduling algorithms developed for real-time wireless networks provide security at the cost of other important performance, e.g., schedulability. The performance problem becomes especially apparent when wireless networks are heavily loaded. To address this issue, we propose in this paper an improved security-aware packet scheduling algorithm (or ISAPS in short) in wireless networks. ISAPS first gives high priority to deal with schedulability when the real-time system is heavily loaded. When the system is under light workload, ISAPS strives to improve the security levels while achieving high schedulability for real-time packets. Compared with the existing packet scheduling algorithm SPSS, ISAPS shows excellent scheduling quality under a wide range of workload characteristics.

Network-on-Multi-Chip (NoMC) with Monitoring and Debugging Support

This paper summarizes recent research on network-on-multi-chip (NoMC) at Poznań University of Technology. The proposed network architecture supports hierarchical addressing and multicast transition mode. Such an approach provides new debugging functionality hardly attainable in classical hardware testing methodology. A multicasttransmission also enables real-time packet monitoring. The introduced features of NoC network allow to elaborate a model of hardware video codec that utilizes distributed processing on many FPGAs. Final performance of the designed network was assessed using a model of AVC coder and multi-FPGA platforms. In such a system, the introduced multicast transmission mode yields overall gain of bandwidth up to 30%. Moreover, synthesis results show that the basic network components designed in Verilog language are suitable and easily synthesizable for FPGA devices.

MCRT

As many radio chips used in today’s sensor mote hardware can work at different frequencies, several multichannel communication protocols have recently been proposed to improve network throughput and reduce packet loss for wireless sensor networks. However, existing work cannot utilize multiple channels to provide explicit guarantees for application-specified end-to-end communication delays, which are critical to many real-time applications such as surveillance and disaster response. In this article, we propose MCRT, a multichannel real-time communication protocol that features a flow-based channel allocation strategy. Because of the small number of orthogonal channels available in current mote hardware, MCRT allocates channels to network partitions formed based on many-to-one data flows. To achieve bounded end-to-end communication delay for every data flow, the channel allocation problem has been formulated as a constrained optimization problem and proven to be NP-complete. We then present the design of MCRT, which includes a channel allocation algorithm and a real-time packet forwarding strategy. Extensive simulation results based on a realistic radio model and empirical results on a real hardware testbed of Tmote nodes both demonstrate that MCRT can effectively utilize multiple channels to reduce the number of deadlines missed in end-to-end communications. Our results also show that MCRT outperforms a state-of-the-art real-time protocol and two baseline multichannel communication schemes.

A potential evolution of the policy and charging control/QoS architecture for the 3GPP IETF-based evolved packet core

The 3rd Generation Partnership Project (3GPP) Release 8 defines the specifications of a low latency, high-data rate all-IP Core Network (CN) capable of supporting real-time packet services over multiple access technologies, including the new Long-Term Evolution (LTE) access network. The mobile communications industry is maturing. In order to remain competitive many operators now focus on reducing their capital and operational expenditures (CAPEX and OPEX), by outsourcing some of their business activities and/or by sharing some network infrastructures. This article presents a possible evolution of the 3GPP Policy and Charging Control (PCC) and Quality of Service (QoS) architecture to better support Fixed-Mobile Convergence (FMC) and more flexible CN sharing solutions. This goal is achieved with a clearer separation of the business roles (e.g. access and network providers) and the introduction of a Network Policy Function (NPF) for the management of the CN.

Performance Evaluation of Real-Time QoS Guarantee Based on Schedulability of Packets

In this paper,the authors describe stochastically change of arrival and serving of real-time packets by a statistical traffic envelope and statistical service curve.To characterize the requirement of some elastically real-time applications for delay,a novel concept named probabilistic schedulability is proposed.The probabilistic schedulability is related to time t at packets arrival,so instantaneous characteristic can be analyzed and cumulative packets would be scheduled at any given real-time interval by the method.The paper investigates the probabilistic schedulability of real-time packets under exponential distribution and general distribution service time in a FIFO network.The numerical analysis based on the theoretic results is consistent with the simulation analysis.The results show that the method has more flexibility to characterize the schedulability of real-time packets.

QoS and Channel-Aware Packet Bundling for Capacity Improvement in Cellular Networks

We study the problem of multiple-packet bundling to improve spectral efficiency in cellular networks. The packet size of real-time data, such as voice over Internet Protocol (VoIP), is often very small. However, the common use of time-division multiplexing (TDM) limits the number of VoIP users supported because a packet has to wait until it receives a time slot, and if only one small VoIP packet is placed in a time slot, capacity is wasted. Packet bundling can alleviate such a problem by sharing a time slot among multiple users. A recent revision of cdma2000 1xEV-DO has introduced the concept of the multiuser packet (MUP) in the downlink to overcome limitations on the number of time slots. However, the efficacy of packet bundling is not well understood, particularly in the presence of time-varying channels. We propose a novel quality-of-service (QoS) and channel-aware packet bundling algorithm that takes advantage of adaptive modulation and coding. We show that optimal algorithms are nondeterministic polynomial time (NP)-complete, recommend heuristic approaches, and use analytical performance modeling to show the gains in capacity that can be achieved from our packet bundling algorithms. We show that channel utilization can be significantly increased by slightly delaying some real-time packets within their QoS requirements while bundling those packets with like channel conditions. We validate this paper through extensive OPNET simulations with a complete evolution-data optimized (EV-DO) implementation.

Buffer Management in Cellular IP Networks using Evolutionary Algorithms

Real-time traffic in Cellular IP network is considered to be important and therefore given priority over non-real-time. Buffer is an important but scarce resource and to optimize Quality of Service by managing buffers of the network is an important and complex problem. Evolutionary Algorithms are quite useful in solving such complex optimization problems, and in this regard, a two-tier model for buffer, Gateway and Base Station, management in Cellular IP network has been propsed. The first tier applies a prioritization algorithm for prioritizing real-time packets in the buffer of the gateway with a specified threshold. Packets which couldn’t be served, after the threshold, is given to the nearest cells of the network to be dealt with in the second tier, while Evolutionary Algorithm (EA) based procedures are applied in order to optimally store these packets in the buffer of the base stations. Experiments have been conducted to observe the performance of the proposed models and a comparative study of the models, GA based and PSO based, has been carried out to depict the advantage and disadvantage of the proposed models.

무선 센서 네트워크를 위한 임계치 기반 효율적인 혼잡 탐지 및 제어 알고리즘

This paper reports a new mechanism for congestion controls. The proposed congestion detection algorithm can be provided with delay and unnecessary energy consumption. Conventional congestion control methods decide congestion by queue occupancy or mean packet arrival rate of MAC layer only, however, our method can perform precise detection by considering queue occupancy and mean packet arrival rate. In addition, the congestion avoiding method according to congestion degree and scheduling method using priority for real time packets are proposed. Finally, simulation results show that proposed congestion detection and control methods outperforms conventional scheduling schemes for wireless sensor network.

Broadcast Authentication for Wireless Sensor Networks Using Nested Hashing and the Chinese Remainder Theorem

Secure broadcasting is an essential feature for critical operations in wireless sensor network (WSNs). However, due to the limited resources of sensor networks, verifying the authenticity for broadcasted messages is a very difficult issue. μTESLA is a broadcast authentication protocol, which uses network-wide loose time synchronization with one-way hashed keys to provide the authenticity verification. However, it suffers from several flaws considering the delay tolerance, and the chain length restriction. In this paper, we propose a protocol which provides broadcast authentication for wireless sensor networks. This protocol uses a nested hash chain of two different hash functions and the Chinese Remainder Theorem (CRT). The two different nested hash functions are employed for the seed updating and the key generation. Each sensor node is challenged independently with a common broadcasting message using the CRT. Our algorithm provides forward and non-restricted key generation, and in addition, no time synchronization is required. Furthermore, receivers can instantly authenticate packets in real time. Moreover, the comprehensive analysis shows that this scheme is efficient and practical, and can achieve better performance than the μTESLA system.

Exploiting slack time for just-in-time scheduling in wireless sensor networks

We consider the problem of real-time data collection in wireless sensor networks, in which data need to be delivered to one or more sinks within end-to-end deadlines. To enhance performance with respect to end-to-end deadline miss ratio, existing approaches schedule packets by prioritizing them based on per-packet deadlines and other factors such as the distance to the sink. However, important factors affecting the end-to-end performance such as queuing delays and buffer overruns have largely been ignored in the existing real-time schemes. Packet prioritization by itself cannot assist with these issues, and may in fact, exacerbate them for real-time data collection, since many high priority packets may simultaneously contend for the constrained network resources. In sensor networks, where the channel bandwidth and buffer space are often quite limited, these issues can dramatically impact real-time performance. Based on this observation, we propose Just-in-Time Scheduling (JiTS) strategies where packets are judiciously delayed within their slack time to reduce contention and load balance the use of the network buffers. We explore several policies for delaying data packets at different intermediate nodes considering potential contention. In addition, we also show that the routing protocol has a significant impact on real-time performance. In particular, shortest path routing leads to considerably better performance than geographic forwarding, which is often used for real-time data transmission in wireless sensor networks. Using an extensive simulation study, we demonstrate that JiTS can significantly improve the deadline miss ratio and packet drop ratio compared to two state-of-the-art approaches for real-time packet delivery for sensor networks (RAP and SPEED) under various scenarios. Notably, JiTS requires neither lower layer (e.g., MAC layer) support nor synchronization among the sensor nodes.