As 6G networks evolve, offloading extended reality (XR) applications emerges as a key use case, leveraging reduced latency and edge processing to migrate computationally intensive tasks, such as rendering, from user devices to the network. This enables lower battery consumption and smaller device form factors in cellular environments.

Discontinuous reception (DRX) has been included in 4G-LTE as the main power saving mechanism for user equipment (UE). However, the existing 3-state DRX model is not sufficient for new use cases introduced by 4G and 5G. For example, the device discovery process in device to device (D2D) communication has a significant impact on delay and power consumption, but the existing conventional 3-state DRX model is unable to capture this impact. In this article, we propose a novel 5-state DRX model for D2D communications using a semi-Markov process, with separate arrival processes for data and discovery messages. The proposed model includes separate states for the discovery process, and is general and easy to extend for possible future changes. Our model allows us to investigate the behavior of the system under various DRX and discovery parameters. Numerical results show significant influence of the discovery phase on the performance of the DRX mechanism and provide new insights into how it affects power saving and delay.

It is well known that load balancing in data centres can lead to unnecessary energy usage if all servers are kept active. Using dynamic server provisioning, the number of servers that serve requests can be reduced by turning off idle servers and thereby saving energy. However, such a scheme, usually increases the risk of instability of server queues. In this work, we analyze the trade-off between energy usage and stability of servers in a data center when we balance the load by dispatching arriving jobs. We propose algorithms to solve a stability and energy objective stochastic optimization problem with a high degree of flexibility to handle the trade-off between these two objectives. We consider variable size jobs to apply load balancing on selected active servers and find that the optimal solution is an NP-hard problem. We therefore develop two computationally efficient greedy and randomized approximation schemes to achieve the trade-off between these objectives. We investigate the performance of our proposed algorithms in minimizing the risk of queue length growth as well as the number of active servers needed to serve jobs, and compare it with several metrics in heterogeneous load scenarios.

We study a scenario where a monitor is interested in the freshest possible update from a remote sensor. The monitor also seeks to minimize the number of updates that exceed a certain freshness threshold, beyond which, the information is deemed to be too old. Previous work has presented results for First Come First Served (FCFS) systems. However, it has been shown that Last Come First Served (LCFS) with preemption is more effective in terms of average Age of Information (AoI); we therefore study an M/G/1 LCFS system with preemption. The generality of the busy time distribution gives the advantage of applicability on any distribution inside the model. For example, one can use a deterministic distribution to study a TDMA system, a gamma distribution to model a routing network, or a more complicated distribution to study a CSMA access scheme. We find a general procedure to derive the exact expression of the outage update probability — i.e. the portion of time updates have information older than a certain threshold. We compare different busy time distributions to the ones already present in literature for equivalent FCFS systems, showing the benefit of using the former discipline. We further study how the variance of the busy time distribution affects the update outage probability. We find two instances of the busy time distribution, where at low thresholds and low loads, higher variance gives an advantage in terms of update outage probability. First, we compare the M/D/1 LCFS with preemption against the M/Γ/1 LCFS with preemption and let the variance of the busy time of the latter vary, while maintaining the same average busy time for both systems. We further compare various M/H2/1 LCFS with preemption with different coefficient of variation and same expected value, thus covering a wider spectrum of variation of the busy time.

User generated content (UGC) makes up a significant portion of Internet traffic. As opposed to other content, UGC has so far been left outside over-the-top providing network operators content distribution networks (telco-CDN) due to the difficulty in determining optimised placement of such content. The side effect of this is that UGC content is not placed close to end users and therefore occupy unnecessary network resources. The difficulty in determining optimal placement of UGC stems from the different geographical and dynamic behaviour of the content generators, and a further complication is that with UGC, it is necessary to place content in real-time which this has an impact on performance optimality. Even though CDNs have been widely studied in the literature, little attention has been given to the challenging case of UGC placement. In this paper, we propose an on-line placement algorithm and compare its performance with the off-line counterpart based on integer programming, both under the assumption that the popularity of content is known to the algorithms. In order to determine the popularity, we present an on-line learning model to predict spatial patterns in content requests. Furthermore, we couple the model with an algorithm for learning the early popularity of content, i.e., shortly after the content becomes known. We show that together, these approaches enable service providers to effectively place UGC and minimise the cost of serving UGC in their networks.

In this paper we study reliability, timeliness and load reduction in an hybrid Mobile Edge Computing (MEC)/Cloud game streaming infrastructure. In our scenario, a user plays a game streamed by the producer to their handheld device - or User Equipment (UE). The UE communicates user actions to the edge/cloud via the mobile communication infrastructure; the object is to retrieve the latest game status, of which the most important information is the rendered frame. Particularly, we study reliability through replication in a number of MEC-servers, timeliness through Age of Information (AoI) and load reduction by leveraging the X2 interface at the edge, in order to abort useless frame rendering computations. We translate it as a scenario where a sink - representing the UE - is interested in the freshest possible update from distributed nodes. Each node sends updates following a Last Come First Served (LCFS) policy with preemption. We consider two scenarios; the first is n parallel LCFS systems sending updates, and the second adds a feedback loop aimed at decreasing the number of jobs sent per second by the nodes, thus decreasing the load per node. We analyze the number of jobs sent per second and average peak Age of Information at the sink, showing that the second scheme achieves a significantly lower rate of jobs compared with the first, while maintaining constant AoI, thus reducing the load at the edge. We also find that using the feedback loop, we achieve the maximum saving in transmitted jobs per second when the average arrival rate per system is equal to the inverse of the average busy time in every node.

We study a scenario where a monitor is interested in the freshest possible update from a remote sensor. The monitor also seeks to minimize the number of updates that exceed a certain freshness threshold, beyond which, the information is deemed to be too old. Previous work has presented results for First Come First Served (FCFS) systems. However, it has been shown that Last Come First Served (LCFS) with preemption is more effective in terms of average Age of Information (AoI); we therefore study an M/G/1 LCFS system with preemption. The generality of the busy time distribution gives the advantage of applicability on any distribution inside the model. For example, one can use a deterministic distribution to study a TDMA system, a gamma distribution to model a routing network, or a more complicated distribution to study a CSMA access scheme. We find a general procedure to derive the exact expression of the outage update probability -- i.e. the portion of time updates have information older than a certain threshold. We compare different busy time distributions to the ones already present in literature for equivalent FCFS systems, showing the benefit of using the former discipline. We further study how the variance of the busy time distribution affects the update outage probability. We compare the M/D/1 LCFS with preemption against the M/Γ/1 LCFS with preemption and let the variance of the busy time of the latter vary, while maintaining the same average busy time for both systems. We find that at low thresholds and low loads, higher variance gives an advantage in terms of update outage probability.

We jointly optimize Discontinuous Reception (DRX) cycle length and LTE scheduling to minimize mobile devices' energy usage for video delivery, utilising the now well-established potential to predict future channel conditions in cellular networks. Employing in-network caching, we set a strict buffer constraint which provides zero buffer underflow to improve Quality of Experience. Our study provides insight into the energy saving potential sophisticated DRX schemes hold, compared with the currently used static method. To this end, two novel DRX approaches are proposed and studied. The results show that more sophisticated DRX schemes (with variable DRX cycle length) can potentially save 69 percent energy for mobile devices, encouraging further research in the field.

Cooperative content replication and request routing (C2R3) has emerged as a promising technique to enhance the efficiency of content delivery networks (CDN). Most existing approaches to C2R3focus on efficient bandwidth usage and assume a hierarchical CDN architecture targeted towards the delivery of specific content types (e.g., video). Therefore, C2R3problem of covering the broad range of content types with minimum content access delay in a general CDN architecture has attracted little attention. As a potential solution to C2R3, cooperative web caching techniques have become mature. However, these techniques were designed to improve performance indicators tailored to web contents only (i.e., hit rate and byte hit rate). Arguably, improving such indicators does not necessarily lead to optimal access delay especially when the current trend of user-generated contents with diverse popularities and sizes are taken into account. In this paper, we formulate C2R3as an optimization problem with the objective of minimizing content access delay in a general CDN architecture. A new performance indicator is introduced, and two popularity-based cooperative algorithms are proposed to approach the NP-hard C2R3problem. Under broad ranges of cache size and popularity distribution parameters, we compare the proposed methods with a cooperative recency-based web caching method. Our simulation results show that the popularity-based methods outperform the recency-based method, and demonstrate close to optimal performance in representative scenarios of real-world situations.

As average packet sizes in wireless networks shrink and data rates increase, the fundamental CSMA mechanism in the 802.11 protocol family is put under stress. With the emerging 802.11ax standard, the carrier sensing mechanism is lowering the efficiency of the protocol to the level of random access (ALOHA), and as future-generation 802.11 standards emerge, CSMA-based protocols will fall below this level. In this paper we make two main contributions to the literature. First, we will extend previous analysis to examine more closely the quality of the information obtained from channel sensing, in particular the probability of this information being incorrect and the correlation between true and sensed channel state. Second, we examine how to use this analysis to improve existing CSMA-based protocols, in particular the 802.11 protocol family.

For some time, directional antennas have been considered to solve connectivity and interference issues in wireless networks. Several scenarios have been presented and often the conclusions drawn are positive, showing increase in capacity. However, to date there has been no effort to assess a holistic picture of the benefit/cost tradeoff and previous work mainly concerns either link scheduling or antenna placement but not the two combined. Such consideration will become increasingly important in the near future with the advent of heterogeneous networks and other possible combinations of mesh and public access networks.

In the emerging Delay Tolerant Networks (DTNs) content dissemination platform, mobile nodes opportunistically exchange content as they meet, with the intent of sharing content among nodes with common interests. During a meeting, nodes can exchange both content of direct interest to themselves as well as content that is of interest to a larger set of nodes that may be encountered in the future. The utility of a DTN is governed by the content exchange opportunity (the amount of content that can be exchanged during a meeting) as well as the selection of content to be exchanged in order to maximise the interest nodes will have in information they are exposed to. Considering that there is a cost associated with the content exchange (e.g. battery usage, buffer occupancy or consumed transmission opportunity) the aim for nodes participating in content dissemination should be to maximise their payoff. In this paper, we contribute a generic framework for describing the characteristics of content exchange among participating nodes in a network. We incorporate a distributed information popularity measurement and the pairwise interaction of nodes modelled as a bargaining problem. The outcome of this process is the fair split up of transmission opportunity as a network resource and the selection of content objects to exchange in order to maximise the nodes' payoff. The framework is generally intended as a capstone for investigation of content dissemination properties and various content exchange strategies in a DTN. The paper further presents experiments conducted to validate the function and correctness of the proposed framework.

Welcome to the first workshop on Vehicular Networks from Theory to Practice, VTP 2012. Vehicular networks have emerged as a very active area of research with large scale efforts and investments on both sides of the Atlantic. The services these networks promise to enable will lead to leap changes in road traffic safety and management and potentially revolutionize modern traffic systems. However, these network constructs are also largely untested and many unknowns exist before they can be realized in live systems. This workshop provides a forum for researchers and practitioners to meet and discuss all aspects of bringing theoretical results to practical implementations.

With the introduction of standards such as DSRC and WAVE, vehicular ad hoc networks (VANET) are being considered as candidates to improve road safety. Safety applications developed on top of VANET enable vehicle and driver improved awareness of the road situation through vehicles sharing their status and knowledge of the road conditions. In order for these systems to operate, they depend on reliable communication. To overcome fading, shadowing and other effects that cause packet loss, such applications commonly use retransmission schemes to improve packet delivery. However, the wireless channels used for these applications are bandwidth constrained, and retransmission can cause interference which in turn will degrade the reliability of the communication channel. Therefore, it is necessary to find a strategy that balances retransmission with channel occupancy for optimal reliability. In this paper, we present a cooperative retransmission algorithm that overcomes shadowing caused by blocking objects such as heavy vehicles in order to combat the resulting unreliability, whilst controlling the interference caused by retransmissions. The proposed algorithm weighs up the additional area a node can cover, with the amount of interference a retransmission by the same node would cause. We evaluate the performance of the algorithm in urban scenarios using the NS-3 simulator, and find that the proposed algorithm is effective in overcoming the negative effects of shadows caused by blocking objects.

Vehicular traffic density is a key factor in determining the behaviour of radio overlapping and thus impacts performance of data and safety message communication in Vehicular Ad hoc Networks (VANETs). In this paper, we propose a novel density model for urban traffic systems and employ this model for the purpose of spatial-temporal analysis of radio overlapping. To model traffic density, we consider a signalized junction and road segments linked to that junction as basic building blocks of urban traffic systems. The density model enables us to derive a framework to explain trends and critical regions of radio overlapping corresponding to VANET scenarios targeted for urban transportation systems, which cannot be derived from uniform density models widely used in existing literature. We apply the derived radio overlapping model to study channel load associated with periodic beaconing, a fundamental mechanism for safety message communication in VANETs. This study also provides a generic analytical framework to investigate other performance aspects of data and safety message communication in VANETs. Our experimental results using the proposed realistic density model demonstrate the need for an adaptive mechanism to adjust transmission power and data rate to reduce channel loads associated with dense traffic conditions.

Road safety is one of the most important emerging applications envisioned for Vehicular Ad hoc Networks (VANETs). Generally, such applications involve the broadcast of safety messages, consisting of beacons transmitting vehicles' state (e.g. position and velocity) with a regular period, as well as emergency messages warning about unexpected critical events. From the perspective of safety, the application performance depends foremost on two metrics: for the event-driven warning messages, the probability of message reception; and for periodic messages, the variability of the inter-reception time (IRT), which ultimately determines the freshness of the information received by the driver. In this paper, we develop an analytical model to compute the above metrics in an urban traffic scenario. Focusing on a road segment linked to a signalized junction as a basic building block of urban traffic systems, we apply a novel road traffic density model to investigate the dynamics of the reliability metrics and characterize the region(s) on the road segment according to the achieved safety level. Our numerical study shows that in broadcast mode, the hidden terminal effect is the driving factor determining the reliability of transmissions. Furthermore, the impact of hidden terminals has the greatest effect in road sections where vehicles have high velocity, leading to the poorest performance in regions where reliable reception is needed the most in order to minimize the risk of accidents.

Wireless access using contributed access points is fast becoming a reality. Technological means are now available for realizing this “anywhere anytime” low-cost wireless access whereby un-utilized wireless resources can be harnessed to form a collaborative network for public access. The success of such access facilities depend largely on the provisioning of fast authentication among the access points. This is crucial for supporting real-time applications such as Voice Over IP (VoIP). In our earlier work, we had developed an inter-domain fast authentication scheme based on the concept of “trust-clouds”. A trust-cloud is formed among neighbouring access points based on a relationship among the owners of the access points. Fast authentication among these inter-domain sites is achieved through cooperation among the trust-cloud members. In previous work, we theoretically formulated the concept of trust-clouds. In this paper we report on the implementation and experimental results of the “trust-clouds” fast authentication concept on legacy hardware. The experimental results verify that the trust-cloud framework can yield significant delay gains for the authentication process when handing off between administrative domains. It is also shown that no special computing platform is needed to achieve these benefits, indeed our testbed was implemented on low end hardware.

In recent years, Worldwide Interoperability for Microwave Access (WiMAX) has become an important technology providing wireless connections for mobile terminals in a wireless Metropolitan Area Network (MAN), due to its large radio range. In a MAN environment, wireless clients always have high mobility; therefore, it is possible that the mobile clients will move away from the service coverage of serving base stations and change their associating base stations. The process of switching between different base stations is known as the handoff process. During the handoff process, the connection between the mobile terminal and the serving base station ceases. The quality of mobile wireless networks is significantly affected by handoff latency and packet loss ratio. In this paper, we propose a fast handoff scheme using mobility patterns for WiMAX networks. Mobility patterns are adopted to predict the next base station and therefore waive unnecessary scans, and the serving base station forwards the data packets received during the handoff process to the target base station for the minimizing of the packet loss ratio. Extensive simulation experiments are conducted to evaluate the performance of the proposed scheme. The results demonstrate that our scheme can shorten the handoff latency.

Hundreds of technical, special interest Internet weblogs are already generating thousands of niche articles worldwide, and many institutions are starting to create internal blogs for team collaboration. As this style of communication becomes more pervasive in the lives of employees and researchers, the difficulty of finding relevant information only grows with the number of authors and articles. To reduce the load, we propose using implicit group messaging (IGM) to automatically deliver relevant content to readers grouped by shared characteristics or interests. In this paper, we outline a context-aware application suited to special interest messaging and describe three alternative delivery models including our peer-to-peer (P2P) design called SPICE and a broker-based design. We investigate the advantages and disadvantages of each approach through detailed simulations driven by realistic data and actual national/global network topologies. We find that although a broker-based design is generally the most network efficient and lowest latency, a structured P2P system can offer exceptionally low and fair loading across peers and network links without relying on specialized broker nodes.

It is well known that WLAN based on the IEEE 802.11 standard suffers from interference and scalability problems due to a limited number of non-overlapping channels. In order to mitigate the interference problem, channel assignment algorithms have been a popular research topic in recent years. It has been shown that such algorithms can greatly reduce the interference among wireless access points. However, in this paper we show that previously proposed channel assignment algorithms may lead to an increased number of hidden nodes in dense network deployments. We also show that this can significantly decrease the performance of the network. Furthermore, we present results from experiments showing that the RTS/CTS mechanism is unable to solve the hidden node problem in infrastructure WLANs and therefore, careful consideration needs to be taken when choosing channel assignment strategies in densely deployed wireless networks. To this end, we propose two novel channel assignment algorithms. Using a simulation study, we show that the proposed algorithms can outperform traditional channel assignment in densely deployed scenarios, in terms of QoS sensitive VoIP support without compromising the aggregate throughput and are therefore a better performing alternative in such settings.

A grid differs from traditional high performance computing systems in the heterogeneity of the computing nodes as well as the communication links that connect the different nodes together. In grids there exist users and service providers. The service providers provide the service for jobs that the users generate. Typically the amount of jobs generated by all the users are more than any single provider can handle alone with any acceptable quality of service (QoS). As such, the service providers need to cooperate and allocate jobs among them so that each is providing an acceptable QoS to their customers. QoS is of particular concerns to service providers as it directly affects customers' satisfaction and loyalty. In this paper, we propose a game theoretic solution to the QoS sensitive, grid job allocation problem. We model the QoS based, grid job allocation problem as a cooperative game and present the structure of the Nash Bargaining Solution. The proposed algorithm is fair to all users and represents a Pareto optimal solution to the QoS objective. One advantage of our scheme is the relatively low overhead and robust performance against inaccuracies in performance prediction information.

In multiowner wireless networks, access points (APs) are owned and operated by different administrations, leading to significant authentication delays during handoff between APs. We propose to exploit the trust between the owners of neighboring APs for reducing the authentication delay. In the proposed authentication scheme, neighboring APs that trust each other share the security key for the visiting node to avoid lengthy authentication routines each time the visiting node switches APs. The performance of the proposed trust-based authentication scheme is evaluated using a Markov model. Using numerical experiments, we first study a basic scenario where mobile nodes are not aware of the trust networks that exist in a given neighborhood. Subsequently, we consider an advanced scenario where a mobile node functionality is augmented to discover the trust network so as to minimize roaming beyond the trusted APs. We find that, even with the basic implementation, the average number of full authentications needed for a roaming mobile reduces linearly as the likelihood of two neighboring APs trusting each other increases. With the advanced implementation, our experiments show that quadratic reduction is achieved. The Markov model is validated using discrete event simulation.

Wireless mesh networks (WMN) have attracted considerable interest in years as a convenient, flexible and low-cost alternative to wired communication infrastructures in many contexts. However, the great majority of research on metropolitan-scale WMN has been centered around maximization of available bandwidth, suitable for non-real-time applications such as Internet access for the general public. On the other hand, the suitability of WMN for mission-critical infrastructure applications remains by and large unknown, as protocols typically employed in WMN are, for the most part, not designed for real-time communications. In this paper, we describe the smart transport and roads communications (STaRComm) project at National ICT Australia (NICTA), which sets a goal of designing a wireless mesh network architecture to solve the communication needs of the traffic control system in Sydney, Australia. This system, known as SCATS (Sydney coordinated adaptive traffic system) and used in over 100 cities around the world, connects a hierarchy of several thousand devices - from individual traffic light controllers to regional computers and the central traffic management centre (TMC) - and places stringent requirements on the reliability and latency of the data exchanges. We discuss our experience in the deployment of an initial testbed consisting of 7 mesh nodes placed at intersections with traffic lights, and share the results and insights learned from our measurements and initial trials in the process.

In this paper, we present a monitoring assisted routing scheme for wireless mesh networks which exploits the broadcast nature of wireless transmissions at special routers with added monitoring functionalities. These routers listen to the transmissions in neighborhood and compare the routing behavior against the routing state collectively maintained by them. If any inconsistency is found, as a result of software/hardware malfunction, these routers try to determine the node causing it and recover from it in a timely fashion. The scheme is developed for wireless mesh networks where the communication overhead is a critical issue. The performance evaluation of our scheme shows considerable improvement in reliability (i.e., delivery ratio) with minimal overhead under situations of malfunctions.

In this paper, we propose a novel inter-domain fast-authentication scheme based on a concept of "trust clouds". A trust cloud is formed among neighbouring access points based on a relationship among the owners of the access points. Fast-authentication for inter-domain sites is achieved through cooperation among the trust cloud members. The approach is distributed without a central authentication server being involved in distributing the security master key to the access points belonging to the trust cloud. We propose two algorithms for mobile visiting nodes to perform authentication at handoff and show through a simulation study that the approach significantly reduces authentication delay compared with traditional server based schemes.

This paper introduces project TITAN, which investigates an alternative construct of residential broadband access. The aim of the project is to increase the utilisation of deployed broadband capacity such as xDSL and cable modem connections. In order to achieve this, we propose a Collaborative Community Network (CCN) where residential broadband users contribute their spare broadband capacity to other users over a wireless medium, to form a collaborative community wireless Internet access network. Our novel design has the strength that it can provide high data-rate wireless Internet access by utilising existing infrastructure, while utilising the community pool of network resources to provide a distributed network management. We build an autonomous high capacity wireless access network using a combination of cognitive wireless access mechanisms and a distributed processing platform to continuously optimise the configuration and utilisation of the network. A novel and interesting consequence of our architecture is a paradigm shift in terms of the boundary between service providers and consumers. In our model, consumers collaborate with the service providers to achieve the goals of high availability, high capacity wireless network access. This paper introduces the TITAN model and functional components and discuss the main research challenges associated with the model.

WLANs based on IEEE 802.11 are becoming more and more popular both in commercial and residential settings. However, the very success of 802.11 may become a threat to the technology itself. Since there are only a limited number of non-overlapping channels available in the IEEE 802.11 WLAN standards, this can lead to interference among WLANs in dense areas. In this paper, we investigate the effects of interference on WLANs when they operate in DCF, PCF, and EDCA modes in order to support QoS sensitive traffic, such as Voice over IP (VoIP). The results show that DCF, PCF, and EDCA will suffer considerably under these conditions and will not be able to provide good support for real-time applications. From our results, we can infer that the polling mechanism with centralized control on which the 802.11e standard is based will not be a suitable access control mechanism under spectrum competition. Thus, there is a need to change the current technical direction of QoS support in WLANs for future dense deployments.

We propose a decoupled distribution paradigm for connecting large numbers of content publishers and consumers called implicit group messaging (IGM). Unlike traditional multicast or publish/subscribe messaging, IGM delivers content to "implicit groups" of consumers matching combinations of attributes specified by the publisher at the time of publication. The contributions of this paper include a characterisation of IGM encompassing the types of groups that must be supported, and an innovative distributed P2P implementation that we compare via simulation to a functionally equivalent client/server approach. Our results show the P2P model to efficiently support a range of implicit groups with acceptable delivery times and vastly less maximum peer and link stress than a client/server approach

The limited IPv4 address space has driven the cellular industry to start using IPv6 addresses for mobile users in 3G-networks. However, there is a potential threat to the success of 3G-network deployment, as the success will depend on the services offering to the end users. Currently, the overwhelming proportion of services resides in the IPv4 address space, which makes them inaccessible to users in the IPv6 address space. Thus, users cannot directly communicate with and access services without an intermediate translation mechanism. Previous studies on network address translation methods have shown that REBEKAH-IP with Port Extension, RPX is promising in that it provides excellent theoretical maximum scalability while supporting all types of services without limitations for the users in the network. However, the initial RPX proposal does not support host mobility to different networks, despite the fact that mobility is the most important feature of a wireless communication system. In this paper, we propose to extend the RPX scheme with a mobility support scheme based on mobile IP. RPX allows more than one host to use a single IPv4 address and therefore we have augmented Mobile IP with a new tunneling mechanism called IP-in-FQDN tunneling. The mechanism allows for unique mapping despite the sharing of IP addresses while maintaining the scalability of RPX. In addition, we present simulation results that indicate that the proposed scheme performs well in terms of scalability, connection request delay and packet transmission delay compared to mobile IP

In this paper we present a novel concept and methodology for generating tailored communication protocols specific to an application's requirements and the operating environment for a mobile node roaming among different access networks within the global Internet. Since the scheme that we present employs a universal technique, it can be also deployed in small-scale independent networks such as sensor networks to generate application-specific lightweight transport protocols as is appropriate to its energy-constrained operating environments. We present preliminary experimental and analytical results that confirm and justify the feasibility of our method based on a practical example applicable to the sensor network environment.

Since the point coordination function (PCF) in the IEEE 802.11 is based on a centralized polling protocol, some bandwidth is wasted due to the polling overheads and also due to null packets that are issued in case a polled station does not have any data to transmit. In order to reduce this waste and increase the channel utilization, we have proposed a modified version of the standard PCF. The modified PCF uses a distributed polling protocol (DPP) as the access mechanism for the uplink transmission of real-time traffic. The transmission period in the modified PCF consists of a distributed polling protocol period (DPPP) which is controlled by the DPP and the real-time traffic downlink period (KTDP). Our proposal further includes a technique for dealing with the hidden station problem for use together with the proposed modification. In this paper, an analysis is done to compare the performance of the modified PCF with the standard PCF in terms of number of supportable stations in a contention-free period (CFP) and the channel efficiency. The analytical results show that the modified PCF can support a much higher number of stations than the standard PCF. In addition, the channel efficiency of the modified PCF is better under the assumption that there is no hidden station in the system. The results imply that the channel utilization of the modified PCF is better than the standard PCF.

This paper describes a novel framework for managing connections to mobile hosts in the Internet. The framework, SLM, integrates the notions of quality of service management and mobility management and forms a base for overall session management. We compare SLM with the currently most widely adopted mobility management framework, Mobile IP, and show how some of Mobile IP's deficiencies are overcome. The paper further presents some initial experimental results and future research.