Signaling Load Research Articles

Presence Network Agent: A Simple Way to Improve the Presence Service

The article examines a possible way of improving the performance of the presence service within IMS networks without modifying the presence and group management enabler. This can be achieved by means of a presence network agent (PNA). The PNA has been defined by 3GPP; it is a new logic entity within the IMS core network that is able to publish the presence information on behalf of the presentity user agent. The PNA improves performance because it reduces the presence signaling load within the radio access network without downgrading the freshness and richness of the presence information. The article's goal is to provide the reader with useful information about the PNA and our experience with PNA implementation and deployment. We first describe the PNA concept as defined by 3GPP, highlighting the open issues still present in the standardization and the possible optimizations, subsequently we present an actual implementation of a PNA handling busy/idle states for IMS calls.

A stochastic vehicle mobility model with environmental condition adaptation capability

AbstractIn mobile communication systems, mobility modeling is involved in several aspects such as signaling and traffic load analysis. In particular, accurate mobility models are essential for the evaluation of the system design alternatives and network implementation cost issues. In this paper, we propose a mobility model that is appropriate for practical analysis of the mobile systems' design issues. Our model provides different levels of details for the user mobility behavior and can be adapted to any environmental topology. This model considers direction and velocity of the user mobility. The motion direction is modeled based on real street patterns and is described by discrete state Gauss–Markov technique whose parameters are calculated by combining the information derived by the topological map and wireless network performance report (WNPR) of the simulation area. In the proposed method, the user velocity is assumed to be the average velocity that is found based on traffic condition and type of the street. The computational complexity of our model is to the extent that can be used not only in mobility management test procedures but also in order to calculate some useful parameters of these procedures. In this paper, we apply real data to validate the proposed model by simulation which is used to confirm the accuracy of the proposed model and its analytical analysis. Copyright © 2008 John Wiley & Sons, Ltd.

Performance comparison of vertical handover strategies for psdr heterogeneous networks

In this article we suggest a vertical handover (VHO) solution able to optimize mobility management over heterogeneous networks in terms of handoff delay and signaling load. The presented strategy discriminates the best mobility protocol to be used based on a scheduling policy. It is specifically designed for an integrated network architecture to provide PSDR organizations using TETRA and TETRA2 systems with the capability to exploit WiFi and WiMAX broadband access technologies in order to enjoy advanced services. The article presents the operational scenarios where integration between TETRA and WiFi/WiMAX is needed and the main resulting benefits. Performances of the suggested VHO management scheme are described and evaluated against other protocol solutions.

An MDP-Based Vertical Handoff Decision Algorithm for Heterogeneous Wireless Networks

The architecture for the Beyond 3rd Generation (B3G) or 4th Generation (4G) wireless networks aims at integrating various heterogeneous wireless access networks. One of the major design issues is the support of vertical handoff. Vertical handoff occurs when a mobile terminal switches from one network to another (e.g., from wireless local area network to code-division multiple-access 1x radio transmission technology). The objective of this paper is to determine the conditions under which vertical handoff should be performed. The problem is formulated as a Markov decision process with the objective of maximizing the total expected reward per connection. The network resources that are utilized by the connection are captured by a link reward function. A signaling cost is used to model the signaling and processing load incurred on the network when vertical handoff is performed. The value iteration algorithm is used to compute a stationary deterministic policy. For performance evaluation, voice and data applications are considered. The numerical results show that our proposed scheme performs better than other vertical handoff decision algorithms, namely, simple additive weighting, the technique for order preference by similarity to ideal solution, and Grey relational analysis.

Design and evaluation of flow handoff signalling for multihomed mobile nodes in wireless overlay networks

With the increasing deployment of wireless overlay networks, a mobile node with a range of network interfaces can be connected to multiple heterogeneous or homogeneous access networks simultaneously. Such host multihoming technology can be exploited to distribute (or hand off) application flows among the most appropriate interfaces and access networks dynamically to achieve end-to-end seamless, robust and even quality-of-service-aware communications for mobile users. It is essential that an efficient and effective flow handoff signalling scheme be in place. Nevertheless, little prior work has addressed this problem sufficiently in a systematic way and little performance evaluation is readily available. We propose a set of signalling procedures for a comprehensive, flexible yet standard-oriented flow handoff solution. Two candidate schemes are designed by extending and optimising related IETF work based on Mobile IPv6 or Network Mobility (NEMO). Theoretical analyses are performed and numerical results are then presented with a focus on signalling loads to compare the two proposals and to demonstrate that the designs can largely meet the requirements on desired signalling performance. Preliminary implementations and experimental results are also reported to validate the concepts of the designs, investigate the flow handoff signalling delays and verify the effectiveness of the policy-based flow handoff support for typical real-time and non-real-time applications.

Optimization of Handover Parameters for Traffic Sharing in GERAN

Cellular network traffic is unevenly distributed both in time and space, which greatly complicates network dimensioning. As a result, some cells in the network are permanently congested, while others are underutilized. In a previous paper, the authors showed that this problem can be effectively solved in GSM/EDGE Radio Access Networks (GERAN) by modifying handover boundaries. However, several drawbacks prevent operators from fully exploiting the potential of this technique. This paper investigates the limitations of current traffic-sharing approaches with tight frequency reuses in GERAN. To deal with such limitations, an algorithm is proposed to jointly optimize handover margins and signal-level constraints based on network statistics for traffic sharing in GERAN. A complementary algorithm is proposed to adjust cell (re)selection offsets to minimize the number of handovers. Simulation results show that the proposed method achieves a significant reduction in call blocking without excessive call quality impairment or increase of network signaling load when compared to the current approaches. More traffic can thus be handled without the need for any hardware upgrades, providing a cost-effective means to increase network capacity.

Evaluation of signaling loads in 3GPP networks

3GPP Release 5 is the first step toward an all-IP cellular network. While Release 99 is still heavily based on a core network inherited from 2G networks, Release 5 introduces a new core network architecture based on IETF protocols. In particular, SIP is used for initiating, managing, and terminating media sessions. However, the use of SIP can result in a significant increase of the signaling and computational loads inside the core network, due to its larger message size and increased requirements on network nodes. This article compares the core network signaling loads of 3GPP Release 99 and Release 5, and elaborates on possible enhancements to improve the bandwidth efficiency of the signaling in Release 5.

PROPOSED METHOD FOR HANDOVER IN MOBILE NETWORK USING FUZZY LOGIC

Processing handoffs is an important task in any cellular radio system. Handoffs must be performed successfully and as infrequently as possible, and be imperceptible to the users. In order to meet these requirements, system designers must specify an optimum signal level at which initiate a handoff. Once a particular signal level is specified as the minimum usable signal for acceptable voice quality at the base station receiver, a slightly stronger signal level is used as a threshold at which a handoff is made. This margin, given by Δ= P r handoff – P r minimum usable, cannot be too large or too small [1]. Therefore, Δ is chosen carefully to meet these conflicting requirements. Handover Controls an essential component of radio resource management that imposes considerable signaling load on the network. The amount of undesirable signaling load depends directly on the speed of the hand set. In this paper, we propose that an handoff can be initiated by measuring parameters like link quality, location of the mobile and signal power w.r.t neighboring base station using Fuzzy Logic. This method will prevent the unnecessary handoff between the base station in turn reducing the burden of the base station & preventing traffic conjunction.

Alternative approach to dynamic I/V characterisation of microwave FETs

A new and simple approach for the measurement of active device dynamic output I/V characteristics is presented. Device characterisation is performed making use of multi-harmonic exciting signal and variable loads at the output port. The measurement bench has been used to characterise a GaAs 1 mm gate periphery PHEMT as a test vehicle. The results, obtained making use of the proposed setup, successfully compare with those obtained via traditional pulsed measurement systems.

On capacity planning for the GMPLS network control plane

This article presents capacity planning rules for the control plane of all-optical networks featuring GMPLS and RSVP-TE as a connection setup protocol. As per RSVP standard, a refresh message mechanism is incorporated to RSVP such that the state is periodically refreshed on a link per link basis. We provide analytical expressions for the bandwidth and buffer sizes to be provided such that no flows are torn down due to lack of refresh messages. Our findings show that small buffers (several KBytes) suffice to sustain the signaling load for as much as 400 RSVP flows per link, with the simplest RSVP refresh mechanism (neither using link bundling nor acknowledgments). On the other hand, we also find the packet drop probability per link for a given network topology for the case that the flow survival probability is larger than a given threshold. We provide numerical examples based on the COST 239 european network topology and real RSVP traffic traces from early-commercial switching equipment.

Trial Results of Intelligent Paging in GERAN

In cellular networks, location managements has a strong impact on signaling load. To minimise mobility-based signaling traffic. Location Areas (LAs) have to be defined correctly. Large LAs increase paging traffic, while small LAs increase location updates. Thus, operators have to trade-off these two constraints to maximize network performance. Several authors have proposed selective paging to reduce paging load. This paper describes an intelligent paging algorithm based on most-recent interaction data. Trial results in a live GSM-EDGE Radio Access Network (GERAN) show that the algorithm can reduce paging traffic significantly, while keeping paging success rates almost unaltered.

A New Digital Control Algorithm to Achieve Optimal Dynamic Performance in DC-to-DC Converters

In this paper, a new control algorithm is proposed to achieve optimal dynamic performance for dc-to-dc converters under a load current change and for a given set of circuit parameters, such as the output inductor, output capacitor, switching frequency, input voltage, and output voltage. Using the concept of capacitor charge balance, the proposed algorithm predicts the optimal transient response for a dc-to-dc converter during a large signal load current change. During steady state operation, conventional current mode proportional-integral-derivative (PID) is used. During large signal transient conditions, the new control algorithm takes over. The equations needed to calculate the transient time and the required duty cycle series are presented. By using the proposed algorithm, the optimal transient performances, including the smallest output voltage overshoot/undershoot and the shortest recovery time, is achieved. In addition, since the large signal dynamic response of the power converter is successfully predicted, the large signal stability is guaranteed. Experimental results show that the proposed method produces superior dynamic performance over a conventional current mode PID controller.

Signaling Channel for Coordinated Multicast Service Delivery in Next Generation Wireless Networks

Multicast delivery in heterogeneous wireless networks requires careful coordination, in order to take full advantage of the resources such an interworking network environment can offer. Effective coordination, however, may require interworking signaling from coordinating network entities to receivers of a multicast service. Scalable delivery of such signaling is of great importance, since a large number of receivers may be interested in a multicast service. This paper therefore investigates the use of a multicast signaling channel (MSCH) to carry such interworking signaling in a scalable manner. Applications of interworking signaling for multicast service delivery in heterogeneous wireless networks are presented, motivating the need for an MSCH. Then a comparative study is performed analysing potential benefits of employing an MSCH for signaling message delivery compared to conventional unicast signaling. The analysis reveals that the benefits of the MSCH depend mainly on the selection of an appropriate signaling network to carry the MSCH and also on efficient addressing of a subset of receivers within the MSCH. Based on the findings, guidelines for the selection of a suitable signaling network are provided. Furthermore a novel approach is proposed that allows efficient addressing of a subset of receivers within a multicast group. The approach minimizes the required signaling load on the MSCH by reducing the size of the required addressing information. This is achieved by an aggregation of receivers with common context information. To demonstrate the concept, a prototype of the MSCH has been developed and is presented in the paper.

A Two-Layered Mobility Architecture Using Fast Mobile IPv6 and Session Initiation Protocol

This paper proposes an integrated mobility scheme that combines the procedures of fast handover for Mobile IPv6 (FMIPv6) and session initiation protocol (SIP) mobility for realtime communications. This integrated approach is based on the context of the applications utilized. Furthermore, to reduce system redundancies and signaling loads, several functionalities of FMIPv6 and SIP have been integrated to optimize the integrated mobility scheme. The proposed scheme aims at reducing the handover latency and packet loss for an ongoing realtime traffic. Using ns-2 simulation, we analyze the performance of the proposed integrated scheme and compare it with the existing protocols for a VoIP and for a video stream traffic. This mobility architecture achieves lower handover delay and less packet loss than using either FMIPv6 or SIP and hence presents a powerful handover mobility scheme for next generation IP-based wireless systems.

Impedance/admittance model of ultrasonic transducer system in thermosonic bonding

An impedance and admittance model of transducer system,which includes system features such as material,size, loss factor,resonance frequency,exciting electrical signal and different loads,is established by equivalent circuit method.For two different loads with/without bonding tool,the impedance and admittance of transducer system are calculated based on above model.The numerical computations show that,there are four axial vibration modes of transducer system in 100 kHz. Comparing to no-tool condition,each resonance frequency and its impedance increase when with bonding tool.The result of sweeping measurement by impedance analyzer and FEM model are used to verify the impedance/admittance model.

Mobility model used for QoS management for wireless multimedia networks

A radio service and more particularly for multimedia services, the availability of the resources often fluctuates, according to the load, mobility of users and variation of the transmission quality. The fluctuation is a major problem for radio network operators to adapt the use of the resources considering the mobility of the users. The allocation of the bandwidth of various types of traffic is done only at fresh call arrival or for a handover. The mobility of the users has an important influence on the configuration of the network. Such intercellular handover modifies the distribution of the traffic in the system and generates additional signalling load. In this study, we consider the mobility of the users in the dimensioning network and four traffic models (voice, video, www and ftp). This mobility model allows us to determine at the cell level as well as at the entire system level, for QoS parameters, threshold values beyond which a call can be blocked.

DIP-MIP: Distributed individual paging extension for mobile IP in IP-based cellular networks

The mobility-enabling protocol Mobile IP supports location registration but not paging. However, current cellular networks use registration as well as paging procedures to minimize signaling cost. Accordingly, an extension to Mobile IP using distributed individual paging, the so-called DIP-MIP, is proposed. In DIP-MIP, each mobile host derives its own paging area size by optimizing a signaling cost function based on its individual mobility pattern. The cost function itself may use either of two mobility models – fluid flow and random walk – and the performance of DIP-MIP is analyzed for both. The impact of various parameters on the DIP-MIP signaling cost is studied as well. The performance of DIP-MIP is shown to be superior to that of Mobile IP (MIP) in reducing signaling load, managing mobility and supporting a large number of mobile users in IP-based cellular networks.

Handoff latency analysis of mobile IPv6 protocol variations

Mobile Ipv6 (MIPv6) is a protocol proposed for the future all-IP mobile Internet access. The goal of MIPv6 is to provide uninterrupted network connectivity while moving between different domains or access points. To date, there are various technologies under development for enhancing and optimizing the existing MIPv6 protocol. Using three simulated scenarios, this paper compares the effects of these variations on the handoff latency. The first simulation scenario studies the latency of linear movement of mobile nodes; and the second scenario studies the latency of ping-pong (continuous changing of domains) movement of mobile nodes; the third scenario studies latency, handoff success and effect of signaling load on handoffs by gradually increasing from 5 nodes to 50 nodes. The experimental scenarios were simulated in an open source Network Simulator 2 (ns-2). This paper also discusses the deployment challenges and proposes the most suitable variation of the Mobile IPv6 protocol for reducing handoff latency.

A performance comparison of mobility anchor point selection schemes in Hierarchical Mobile IPv6 networks

Hierarchical Mobile IPv6 (HMIPv6) introduces a mobility anchor point (MAP) that localizes the signaling traffic and hence reduces the handoff latency. In addition to processing binding update messages from mobile nodes (MNs) on behalf of MNs' home agents (HAs), the MAP performs data traffic tunneling destined to or originated from MNs, both of which will burden the MAP substantially as the network size grows. To provide scalable and robust mobile Internet services to a large number of visiting MNs, multiple MAPs will be deployed. In such an environment, how to select an appropriate MAP has a vital effect on the overall network performance. In this paper, we choose four MAP selection schemes: the furthest MAP selection scheme, the nearest MAP selection scheme, the mobility-based MAP selection scheme, and the adaptive MAP selection scheme. Then, we compare their performances quantitatively in terms of signaling overhead and load balancing. It can be shown that the dynamic schemes (i.e., the mobility-based and the adaptive MAP selection schemes) are better than the static schemes (i.e., the furthest and the nearest MAP selection schemes), since the dynamic schemes can select the serving MAP depending on the MN's characteristics, e.g., mobility and session activity. In addition, the adaptive MAP selection scheme achieves low implementation overhead and better load balancing compared with the mobility-based MAP selection scheme.

Reactive Handover Optimization in IPv6-Based Mobile Networks

In recent years, there has been a rapid growth in the need to support moving hosts and moving networks in IPv6-based mobile networks. As the number of such hosts and networks grows, so will the demand for delay sensitive real-time applications, such as voice over IP (VoIP), that require seamless handover. Two well-known approaches to reduce the handover latency have been proposed in the literature: proactive and reactive approaches. While proactive handover is known to generally outperform reactive handover, its reliability and practicality are still questionable since it basically depends on predictive information which may be unreliable in some cases. In this paper, based on the standard specification for IPv6 mobility support, we analyze the existing movement detection and address configuration procedures which are the main components of reactive handover approach. We also propose a novel reactive handover procedure which employs our optimized movement detection and address configuration schemes. The proposal is simple and robust because it does not need any predictive information and it requires a minimum number of signaling messages. The performance evaluation shows that the proposal substantially reduces the signaling load on wireless/wired networks and its handover latency is reduced enough to support seamless services