Formulation and steady‐state analysis of diffusion mobile adaptive networks with noisy links

In partial diffusion-based least mean square (PDLMS) scheme, each node shares a part of its intermediate estimate vector with its neighbors at each iteration. In this paper, besides studying the general PDLMS scheme, we figure out how the noisy links deteriorate the network performance during the exchange of weight estimates. We investigate the steady state mean square deviation (MSD) and derive a theoretical expression for it. We also derive the mean and mean-square convergence conditions for the PDLMS algorithm in the presence of noisy links. Our analysis reveals that unlike the PDLMS with ideal links, the steady-state network MSD performance of the PDLMS algorithm is not improved as the number of entries communicated at each iteration increases. Strictly speaking, the noisy links condition imposes more complexity to the MSD derivation that has a noticeable effect on the overall performance. This term violates the trade-off between the communication cost and the estimation performance of the networks in comparison with the ideal links. Our simulation results substantiate the effect of noisy links on PDLMS algorithm and verify the theoretical findings. They match well with theory.

We demonstrate in the paper that the applied mobility model has great influences on the system performance of mobile cellular networks. We develop a novel mobility model with Abrupt Event Influence (AEI), as well as the system model, to study to what extent the influences will be, with focusing on the mobility model simulation. We concern the parameters that determine the system performance of mobile cellular networks. We show in this paper that these parameters vary while user mobility changes, but the effects are interactive. Since handoff calls are given a higher priority over new calls and GC mechanism is employed, our analysis shows that a mature mobile cellular network should make use of user mobility characteristics and dynamically adjust its reservation threshold of the handoff call requests. Extensive simulation results validate our analysis.

An overview is presented of compression and packet loss effects in speech biometrics. These new problems appear particularly in recent applications of biometrics over mobile or Internet networks. The influence of speech compression on speaker recognition performance in mobile networks is investigated. In a first experiment, it is found that the use of GSM coding degrades the performance. In a second experiment, the features for the speaker recognition system are calculated directly from the information available in the encoded bit stream. It is found that a low LPC order in GSM coding is responsible for most performance degradations. A speaker recognition system was obtained which is equivalent in performance to the original one which decodes and reanalyses speech before performing recognition. The joint packet loss and compression effects over IP networks are also studied. It is experimentally demonstrated that the adverse effects of packet loss alone are negligible, while the encoding of speech, particularly at a low bit rate, coupled with packet loss, can reduce the verification accuracy considerably.

Steady-state analysis of the deficient length incremental LMS adaptive networks with noisy links

The authors compare the performance of a mobile packet radio network with a hierarchical structure with one which is fully distributed. The network end-to-end throughput is used as the performance measure. The authors define the performance of network end-to-end throughput to be the number of network nodes times the inverse of the average end-to-end transmission delay for anode. It can be interpreted as the average number of packets successfully arriving at destinations per unit time in the network. To analyze the performance of the hierarchical network, first, a local-access algorithm is proposed. The local access scheme is designed for low cost nodes, which are required to provide the basic functions of receiving and transmitting packets with a fixed power radius. The authors show that the hierarchical network outperforms the fully distributed network for most scenarios due to the significant decrease in the average number of hops and increase in frequency reuse. >

Recently proposed distributed adaptive estimation algorithms for wireless sensor networks (WSNs) do not consider errors due to noisy links, which occur during the transmission of local estimates between sensors. In this paper, we study the effect of noisy links on the performance of distributed incremental least-mean-square (DILMS) algorithm for the case of Gaussian regressors. More specifically, we derive theoretical relations which explain how steady-state performance of DILMS algorithm (in terms of mean-square deviation (MSD), excess mean-square error (EMSE), and mean-square error (MSE)) is affected by noisy links. In our analysis, we use a spatial-temporal energy conservation argument to evaluate the steady-state performance of the individual nodes across the entire network. Our simulation results show that there is a good match between simulations and derived theoretical expressions. However, the important result is that unlike the ideal links case, the steady-state MSD, EMSE and MSE are not monotonically increasing functions of step size parameter when links are noisy. In addition, the optimal step size is found in a closed form for a special case which minimizes the steady-state values of MSD, EMSE, and MSE in each node.

Distortion performance of underwater acoustic mobile networks

Mobility modelling plays a pivotal role in evaluating the performance of Mobile Ad Hoc Networks (MANETs), as the movement patterns of nodes strongly influence routing efficiency, connectivity, and network stability. Existing mobility models, particularly entity and group-based frameworks, have proven useful in simulating various MANET applications but remain limited in capturing the complex movement behaviour characteristic of Search-and-Rescue (SAR) operations in disaster scenarios. This study proposes a realistic hybrid mobility model that integrates the essential features of both entity and group mobility paradigms to better represent the coordinated yet flexible dynamics of SAR teams. Three sets of simulations were performed using the Network Simulator 2 (NS2). The first and second simulations focused on generating and combining existing entity and group mobility patterns using the BonnMotion tool, resulting in two composite models (Real1 and Real2). The third simulation compared these models using AODV and DSDV routing protocols under varying node mobility levels and traffic conditions. Key performance metrics, including relative mobility, node degree, partition count, link duration, packet delivery ratio (PDR), throughput, and average end-to-end delay, were analysed. Results demonstrate that it is feasible to concatenate existing mobility models into a coherent hybrid framework. Among the developed models, Real2 exhibited superior performance in most test conditions, yielding higher PDR, lower delay, and more stable connectivity than its constituent models. These findings confirm that the performance of MANETs is highly dependent on mobility realism. Consequently, selecting a model that accurately reflects the behavioural characteristics of the target scenario is essential for credible MANET performance evaluation in emergency response contexts.

The performance of mobile ad-hoc networks (MANET) is related to the efficiency of the routing protocols in adapting to frequently changing network topology and link status. This paper addresses the issue by comparing the relative performance of three key ad-hoc routing protocols: destination-sequenced distance vector (DSDV), ad-hoc on-demand distance vector (AODV) and optimized link state routing (OLSR). The protocols are tested based on two scenarios, namely, tactical networks for ships and sensor-based network nodes. Four performance metrics were measured by varying the maximum speed of mobile hosts, network size and traffic load, to assess the routing capability and protocol efficiency. The simulation results indicate that AODV performs better than OSLR and DSDV in the first scenario. Although OLSR also performed relatively well, the associated high routing overhead is the dominant reason for not choosing it. On the other hand, OLSR emerged as the protocol of choice for sensor networks, where the high routing overhead is counteracted by consistently better performance in all other metrics. Due to the slow evolution of the sensor network topology, OLSR performed satisfactorily for best effort traffic but needed subtle adjustments to balance between latency and bandwidth to meet the requirements of delay-sensitive applications

Summary form only given. Simulation is an important tool in the development of mobile ad hoc networks. It has a number of important benefits in providing an environment to experiment and verify routing protocol correctness. However, there is no guarantee that the protocol works in practice because simulators contain assumptions and simplified models that may not reflect real network operation. For instance, while most widely used mobility models create a dynamic environment that can be used to stress a protocol in a mobile network, they do not generate realistic movement patterns. It has been shown that mobility model selection directly influences the performance of the routing protocol. Hence, the use of an unrealistic model results in predictions that do not reflect achievable performance in the real world. Other sources of predication inaccuracy stem from the omission of relevant, up-to-date protocol models. As a result of these simplifications, inaccuracies and omissions, mobile network performance can be incorrectly predicted. In particular, the performance of field networks can be orders of magnitude worse than the simulated performance of the same network. This poses a serious problem for mobile networking researchers, who have invested heavily in simulation as a tool for network development and evaluation. The talk describes some of the disparities between predicted and measured performance, and discuss mechanisms for bridging this gap.

Latency, an identified element of Internet protocol (IP) mobility protocol execution, can reduce handover performance in mobile networks. Although the performance can be improved by applying an effective network-based IP mobility scheme in place of the traditional host-based alternatives, the existing inter-domain extensions of network-based IP mobility continue to suffer from an extended handover latency. This paper proposes a new interdomain network-based IP mobility scheme based on node movement prediction. The proposed scheme accelerates the handover by preparing the future domain of the mobile node in a proactive manner. Analytical and simulation-based evaluations confirm improved performance of the proposed scheme in terms of handover latency and packet loss compared with existing schemes.

The new generations of cellular technologies and the current trend towards small cells or femtocells, will offer an improved spectral efficiency per area, but they also offer an opportunity to improve the energy efficiency, measured as the power consumption needed to provide a certain throughput in a given area. In this paper, two network performance indicators, aggregated throughput and energy efficiency, have been analyzed and compared in two network architectures; a traditional deployment based on outdoor macro base stations, for the provision of outdoor and indoor coverage, and a deployment where some of the indoor traffic is supported by femtocells. Performance simulations and energy calculations have shown that the introduction of a femtocell layer, complementing the macrocell layer is a great leap forward in system performance and energy efficiency, when compared with current indoor coverage based on outdoor macro and micro base stations. Additionally, this paper present a study on how much could be reduced the mobile network energy requirements of macrocell deployments in high density urban deployments, in low traffic conditions, based on the application of two Self Organizing Networks (SON) techniques for energy saving, selective disconnection and power reduction of eNodeBs and HeNBs.

In HTTP/1.1, it is necessary for the client to request an object (e.g. an image in a page) in order for the server to send it, even if the server knows in advance what the client will need. Server Push is a feature introduced in HTTP/2 that promises to improve page load times (PLT) by having the server push content to the browser in advance. In this paper, we investigate the benefits and challenges of using Server Push on mobile devices. We first examine whether pushing all content or just the CSS and Javascript files performs better, and find the former leads to much better web performance. Also, we find that sites making use of domain sharding or which otherwise have content divided across many servers do not benefit much from Server Push, a major challenge for Server Push going forward. Network performance characteristics also play a major role. Server Push is especially effective at improving performance at high loss rates (16% median PLT reduction with a 2% loss rate) and high latencies (14% PLT reduction with 100 ms latency), and has little benefit for high-speed Ethernet connections. This motivates its use on mobile devices, although we also find the limited processing power of these devices limits the benefits of Server Push. Server Push also offers modest energy benefits, with energy savings of 9% on LTE for one device. Overall, Server Push is a promising approach for improving web performance in mobile networks, but there are a number of challenges in achieving the full benefits of Server Push.

To save signaling overhead, Semi-Persistent Scheduling (SPS) is the standard for delivering Voice-over-IP (VoIP) in OFDM-based mobile networks. But uncompressed or variable-size compressed VoIP packets are problematic for SPS because they spill over the assigned semi-persistent resource whenever the ROHC (Robust Header Compression) mechanism is in an initialization or reset period, propagating system latency and accumulating unnecessary signaling overhead. In response, we propose a Self-Adaptive Scheduling (SAS) algorithm, where dynamic scheduling is used as an adaptive mechanism to assist in scheduling oversized packets, triggered by buffer information already known to the system, without requiring dedicated signaling. To analyze the performance of our proposal in theory, we created a novel theoretical model to describe VoIP traffic considering the uncompressed voice state. This is, to our best knowledge, the first effort to model the effect of uncompressed packets on VoIP performance in mobile networks from the system-level point of view. Theoretical analysis and simulation experiments validate our proposal, demonstrating its ability to enhance the VoIP user experience for a minor signaling overhead cost.

This paper presents an empirical study on the performance of mobile High Speed Packet Access (HSPA, a 3.5G cellular standard) networks in Hong Kong via extensive field tests. Our study, from the viewpoint of end users, covers virtually all possible mobile scenarios in urban areas, including subways, trains, off-shore ferries and city buses. We have confirmed that mobility has largely negative impacts on the performance of HSPA networks, as fast-changing wireless environment causes serious service deterioration or even interruption. Meanwhile our field experiment results have shown unexpected new findings and thereby exposed new features of the mobile HSPA networks, which contradict commonly held views. We surprisingly find out that mobility can improve fairness of bandwidth sharing among users and traffic flows. Also the triggering and final results of handoffs in mobile HSPA networks are unpredictable and often inappropriate, thus calling for fast reacting fallover mechanisms. We have conducted in-depth research to furnish detailed analysis and explanations to what we have observed. We conclude that mobility is a double-edged sword for HSPA networks. To the best of our knowledge, this is the first public report on a large scale empirical study on the performance of commercial mobile HSPA networks.