IP Transmission over TETRA Packet Data Service: Simulation and Measurement Results

This paper evaluates the packet data performance of Internet Protocol (IP) over TErrestrial Trunked RAdio (TETRA), focusing on the effects of packet size and message transmission rate. We performed a range of simulations to evaluate the average packet delay and packet failure probability corresponding to IP datagram transmission on the Packet Data CHannel (PDCH) in a TETRA cell. We employed IP packets of different sizes and we considered a number of different scenarios with respect to the number of users in a cell and datagram transmission rate. The simulation results offer TETRA operators the means for facilitating network planning and optimization of datagram-based services. Apart from the simulation, we also conducted an extensive measurement survey on the performance of IP over the TETRA PDCH. In particular, we carried out measurements in a client–server communication scenario with different datagram sizes and typical user mobility and radio propagation conditions. Measurement results include throughput, delay jitter, percentage of lost datagrams and out-of-order datagrams. The results obtained through our measurement survey can extent and enhance the simulation results because they are more realistic and consider user mobility as well as channel impairments.

mWSN for Large Scale Mobile Sensing

This paper reviews the state-of-the-art features introduced by sink mobility into wireless sensor networks (WSN), and introduces the architecture of mobile enabled Wireless Sensor Network (mWSN) to realize large-scale information gathering via networked wireless sensors and mobile sinks. After introducing the mobile sensing scenarios, some fundamental design parameters in mWSN have been investigated, such as cluster size, sink velocity, transmission range, and packet length. Our contributions include: (1) A cluster formation method has been proposed via multihop forwarding to form a cluster around the expected position of a mobile sink, in order to guarantee packet delay and minimize energy consumption. (2) Analysis of the performance influence by sink mobility leads to the conclusion that the optimal sink velocity must make a compromise between sink-sensor meeting delay and message delivery delay. (3) Finding that large transmission range and short packet length are both of benefit to lower the outage probability of packet transmission. Extensive simulations have been designed to evaluate the performance of mWSN in terms of packet delay, energy consumption and outage probability of packet transmission.

A New Buffer Algorithm for Speech Quality Improvement in VoIP Systems

Jitter buffer plays an important role in Voice over IP (VoIP) applications because it provides a key mechanism for achieving good speech quality to meet technical and commercial requirements. The main objective of this paper is to propose a new, simple-to-use jitter buffer algorithm as a front-end to conventional static or adaptive jitter buffer algorithms to provide improved performance, in terms of enhanced user-perceived speech quality and reduced end-to-end delay. Supported by signal processing features, the new algorithm, the so-called Play Late Algorithm, alters the playout delay inside a speech talkspurt without introducing unnecessary extra end-to-end delay. The results show that the new algorithm achieves the best performance under different network conditions when compared to conventional static and adaptive jitter buffer algorithms. The results reported here are based on live tests and emulated network conditions on real mobile phone prototypes. The mobile phone prototypes use AMR codec and support full IP/UDP/RTP stack with IPSec function in some of the tests. The method for perceived speech quality measurement is based on the ITU-T standard for speech quality evaluation (PESQ).

A Study on Ultra Low-Latency Mobile Networks

Traffic demand for real-time services as well as non real-time services has recently been increasing, due to the rapid improvement in transmission bit-rate within communication networks. In the future ubiquitous network society, in addition to traffic demand for user-to-user real-time communications services, traffic of real-time applications is set to explode due to new communications traffic for machine-to-machine communications. This paper proposes “ultra low-latency mobile networks,” where the target value for unidirectional end-to-end latency per IP packet is 10 ms, in order to establish a new communications infrastructure capable of providing next-generation real-time services. This paper introduces a model of such ultra low-latency mobile networks and the results of a feasibility study are also presented. The simulation study shows the potential to realize a mobile network with ultra low-latency of less than 10 ms for IP packets and a low IP packet error rate of  < 0.1% through simulations. A test-bed developed to measure actual latency is also introduced in this paper as well as measurement results using this test-bed. The measurement results also confirm the possibility indicated by the simulation studies.

Analysis of Fast Handover Mechanisms for Hierarchical Mobile IPv6 Network Mobility

When a mobile network dynamically changes its point of attachment to the Internet, the various types of movements by a mobile router require handovers, and network mobility (NEMO) is concerned with the management of this movement of mobile networks. Accordingly, this paper investigates the mobile router movement patterns in NEMO network environments, and defines fast hierarchical NEMO handover scenarios based on classified movement patterns. Due to unexpected link breakdowns during the handover procedure, the NEMO handover requires additional latency and packet delivery costs depending on when the breaks occur. For the various handover failure cases, it is also essential to analyze these overhead costs to evaluate and compare the performance of a fast handover. In this paper, the overheads associated with a NEMO fast handover include the latency, buffering cost, and packet loss cost, all of which are formulated based on a timing diagram.

An effective buffering architecture for optical packet switching networks

A novel optical buffering architecture for Optical Packet Switching (OPS) networks is proposed in this article. The architecture which adopts a fiber-sharing mechanism aims at solving the problem of using a large number of fiber delay lines that are used to solve resource contention in the core node in OPS networks. The new architecture employs fewer fiber delay lines compared to other simple architectures, but can achieve the same performance. Simulation results and analysis show that the new architecture can decrease packet loss probability effectively and achieve reasonable performance in average packet delay.

All-optical cross-connect using feed-forward optical buffers with and without QoS: an analysis

An analytical model is derived to evaluate the performance of an optical switch using a feed-forward fiber delay line (FDL) per output for contention resolution. Two different forwarding algorithms for the switch are presented and evaluated: a simple forwarding algorithm (SFA) that is easier to implement, and an enhanced algorithm that provides better performance in terms of both packet loss probability and packet delay. The analytical model can be utilized with both packet and burst switching schemes to characterize the performance of the proposed architecture. Results show that the proposed architecture reduces the packet loss probability compared to that without FDLs. Finally, the same architecture is shown to be capable of supporting Quality of Service (QOS).

EPON bandwidth allocation algorithm based on automatic weight adaptation to provide client and service differentiation

In this article, a new dynamic bandwidth allocation algorithm for the upstream channel of Ethernet Passive Optical Networks, called DySLa, is proposed not only to provide service differentiation but also to offer subscriber differentiation. In contrast to previous methods in which the performance of each class of service is not insured, DySLa is continuously evaluating the mean packet delay and guarantees that the highest priority services fulfil the packet delay requirements in the access network for every type of client. Simulation results show that DySLa can maintain both the mean packet delay and packet loss ratio below the maximum upper bounds permitted for the most sensitive services of every class of customer. Moreover, DySLa outperforms other dynamic bandwidth allocation algorithms which provide service and client differentiation and it makes a fairer bandwidth distribution than those methods.

Modeling Channel Access Delay and Jitter of IEEE 802.11 DCF

With the ever-increasing requirement of WLAN to support real-time services, it is becoming important to study the delay properties of WLAN protocols. This paper constructs a new model to analyze the channel access delay and delay jitter of IEEE 802.11 DCF in saturation traffic condition. Based on this analytical model, average channel access delay and delay jitter are derived for both basic access and RTS/CTS-based access scheme. The accuracy of the analytical model is validated by simulations and furthermore we discuss the impact of initial contention window, maximal backoff stage, and packet size on channel access delay and delay jitter of 802.11 DCF using the proposed model.

GMZRP: Geography-aided Multicast Zone Routing Protocol in Mobile Ad Hoc Networks

This paper presents the design and evaluation of a highly efficient on-demand multicast routing protocol for mobile ad hoc networks (MANETs). The protocol, called Geography-aided Multicast Zone Routing Protocol (GMZRP), eliminates as much as possible duplicate route queries by using a simple yet effective strategy for propagating the multicast route request (MRREQ) packets. GMZRP is the first hybrid multicast protocol taking the advantages of both topological routing and geographical routing. It partitions the network coverage area into small zones and guarantees that each geographic zone is queried only once. GMZRP maintains a multicast forwarding tree at two levels of granularities, i.e., the zone granularity and the node granularity. By doing this, it can easily handle route breakage since the zone level information can help recover the link failure at the node level. The results of the performance evaluation of GMZRP using simulation show that, comparing with the well-known multicast protocol ODMRP (On-Demand Multicast Routing Protocol), GMZRP has much lower protocol overhead in terms of query packets and, meanwhile, achieves competing packet delivery ratio and shorter delivery latency.

Queueing Delay Analysis for the Joint Scheduling Exploiting Multiuser Diversity over a Fading Channel

In this paper, we consider a joint packet scheduling algorithm for wireless networks and investigate its characteristics. The joint scheduling algorithm is a combination of the Knopp and Humblet (KH) scheduling, which fully exploits multiuser diversity, and the probabilistic weighted round-robin (WRR) scheduling, which does not use multiuser diversity at all. Under the assumption that the wireless channel process for each user is described by the Nakagami-m model, we develop a formula to estimate the tail distribution of the packet delay for an arbitrary user under the joint scheduling. Numerical results exhibit that under the joint scheduling, the ratio of the number of slots assigned for the WRR scheduling to that for the KH scheduling dominates the characteristics of the delay performance.

Cluster-Based Autoconfiguration for Mobile Ad hoc Networks

IP address autoconfiguration of mobile nodes is highly desirable in the practical usage of most mobile ad hoc networks (MANETs). This paper proposes cluster-based autoconfiguration, a novel approach for the efficient address autoconfiguration of MANETs. The cluster structure derived from clustering techniques is used to manage address assignment and conflict resolution. By introducing the concept of virtual address agents (AAs), the proposed approach can be applicable to many existing clustering protocols. Finally, analysis and simulation demonstrate that the proposed scheme outperforms the previous autoconfiguration approaches.

Deflection-based transmission protocol for LAN operation in a PON system

In this paper, we propose and evaluate a new deflection transmission scheme for communication between local customers in a passive optical network (PON). In particular, we provide an analytical model to approximate the average packet delay of the proposed scheme in a local area network (LAN) operating within the PON (referred to as LAN-PON system). The accuracy of our model is validated by simulation. Furthermore, our simulation results show that a LAN-PON with a deflection scheme can achieve > 80% bandwidth gain using < 125 μs switching time compared to that of the traditional PON system for the cases studied.

Robust Packet Video Transport Over Wireless Fading Channels Using a Joint Source-channel Coding Approach

In this paper, we address the problem of robust video transmission over wireless networks. Specifically, we consider packet video transmission over wireless IP networks based on the RTP/UDP/IP protocol stack. Digital video delivered over wireless networks is expected to suffer quality degradation from both packet loss and bit errors in the payload. In this paper, both packet loss and bit errors in the payload are considered and the performance of a joint source-channel coding (JSCC) approach employing forward error-correction (FEC) coding schemes for H.263 +  video transmission is studied. Results indicate that with an appropriate JSCC approach, FEC-based error-control techniques can significantly improve the packetization efficiency for a given end-to-end quality requirement and lead to more acceptable video delivery quality over time-varying wireless networks. Another important observation is that with a JSCC approach the fading effects of wireless links upon end-to-end video quality are substantially decreased compared to a system without using channel coding, resulting in attractive robust performance characteristics.

A route maintaining algorithm using neighbor table for mobile sinks

In the wireless microsensor networks, both source and sink nodes can be changed or mobile. The movement of source and sink may lead to the breakage of existing routes. In most routing protocols, query packets are broadcasted to correct a broken route between source and sink, which causes significant communication overhead in terms of both energy and delay. In order to support the sink mobility of conventional routing protocols, we propose a simple route maintaining algorithm which does not use the flooding method. Since the proposed algorithm does not require the information on the geometric location of sensor nodes, it can be easily adopted in most existing routing protocols including Ad Hoc On Demand Distance Vector (AODV) and Direct Diffusion (DD). Experimental results show that the proposed algorithm drastically improves the conventional routing protocols in terms of both energy and delay in case of mobile sinks.

A Novel GPS-free Method for Mobile Unit Global Positioning in Outdoor Wireless Environments

This paper investigates a Global Positioning system (GPS)-free positioning method for mobile units (MUs) in outdoor wireless environments by using the Bayesian filtering formulation. The procedure utilizes simulated inertial measurements, cell-ID of the serving base station, and pre-determined locations grouped according to cell antennas radio coverage in the experimentation area. The developed algorithm makes no assumptions on the initial position of the MU. However, the algorithm takes some time to converge. Experiments show the range of inertial measurement errors that would maintain reliable location information with accuracy comparable to GPS positioning.

A Location Aware Mobility based Routing Protocol for the Bluetooth Scatternet

Bluetooth is a most promising technology designed for the wireless personal area networks for the cable replacement. In this paper, a location aware mobility based routing scheme for the Bluetooth scatternet is proposed that constructs the links dynamically. Our proposed routing protocol requires location information of the nodes and constructs the route between any source and destination and reduces the number of hops. Besides, the network routing problems are analyzed and role switch operations are proposed to mitigate the problems. Moreover, the roles switch and route optimization operations are also proposed to improve route performance. Rigorous simulation works are done to evaluate the performance of our protocol in terms of mobility speed and number of mobile nodes and to compare our results with similar Bluetooth routing protocols. It is observed that our protocol outperforms in terms of energy consumption and transmission packet overheads as compared to similar Bluetooth routing protocols.

Improving performance of TCP over mobile wireless networks

Mobile IP is a network layer protocol for handling mobility of hosts in the Internet. However, mobile IP handoff causes degradation of TCP performance. Hence, there is a need for improving performance of TCP over mobile IP in wireless mobile networks. We propose an approach which handles losses due to both wireless link errors and host mobility. To handle losses due to host mobility, a method for seamless handoff is proposed. Empirical results show that the scheme provides substantial improvement of performance.

Partial CRC Checksum of SCTP for Error Control over Wireless Networks

In the Stream Control Transmission Protocol (SCTP), when a portion of a packet is corrupted, the entire packet will be discarded at the receiver side. This may result in degradation of the throughput of SCTP over wireless networks with a high bit error rate. This paper proposes a new error control scheme of SCTP using a partial Cyclic Redundancy Check (CRC) checksum to enhance the throughput performance, in which a new ‘checksum chunk’ is introduced to effectively identify any corruptions of data chunks contained in the SCTP packet. In the proposed scheme, an SCTP data packet can carry one or more data chunks depending on the channel condition, and the newly defined ‘checksum’ chunk will contain the partial CRC checksums of the individual data chunks and/or the base header of the packet. By referring to these partial checksums, the receiver can discard only the corrupted data chunks, whereas the other available data chunks can be recovered. Simulation results show that the proposed scheme significantly provides better performance than the standard SCTP in the wireless networks.

On the Performance of Broadband Mobile Internet Access System

In this paper, we evaluate the performance of OFDMA/TDD-based broadband mobile internet access system with the features of adaptive modulation & coding (AMC) and hybrid ARQ. We present a framework of system-level simulation and furthermore, intend to derive the insightful results towards understanding the performance of broadband mobile internet access system. The average system throughput as well as delay performance is evaluated for the different channel characteristics and system parameters, which allows for predicting the system capacity in the varying cellular network environment.