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A highly stable intermediate hydrated MnHPO4 is used to synthesize a well-crystallized LiMn0.8Fe0.2PO4@C cathode, which exhibits a high electrical conductivity of 6.823 × 10−2 S cm−1 and excellent cycling stability with a capacity retention of 98.62%.

The high degree of crystallinity of discharging intermediates of Li-S batteries (Li2S2/Li2S) causes a severe capacity attenuation at low temperatures. Herein, a sulfur-rich polymer is fabricated, which enables all the discharging intermediates to exist in an amorphous state without long-range order, promoting the substantial conversion of discharging intermediates and enhancing Li-S batteries' performance at low temperatures greatly. This cathode material exhibits excellent performance both at room and low temperatures. Even under an extremely low temperature (–40 ℃), the discharge capacity can remain 67% of that at room temperature. Besides, in-situ UV/Vis spectroscopy and density functional theory calculations reveal that this organosulfur cathode undergoes a new mechanism during discharge. Li2S6 and Li2S3 are the primary discharging intermediates that are quite different from conventional Li-S batteries. These results provide a new direction for a broader range of applications of Li-S batteries.

Single-atom catalysts (SACs) pave new possibilities to improve the utilization efficiency of sulfur electrodes arising from polysulfide shuttle effects and sluggish kinetics due to their excellent applicability in atomic-scale reaction mechanisms and structure-activity relationships. Herein, nitrogen (N)-anchored SACs on the highly ordered N-doped carbon nanotube arrays are reported as the sulfur host for fast redox conversion in lithium-sulfur (Li-S) batteries. The cube structure of the aligned carbon nanotubes can promote the rapid mass transfer under high sulfur loadings, and abundant single-atom active sites further accelerate the conversion of lithium polysulfides (LiPSs). The synergistic enhancement effect induced by adjacent single atoms with interatomic distances1 nm further accelerates the rapid multi-step reaction of sulfur at high sulfur loadings. As a result, the obtained Li-S batteries exhibit outstanding cycle stability with a high areal capacity of 5.6 mAh cm

Lithium (Li) metal anodes have been considered as the ultimate anode materials for the next-generation rechargeable batteries. However, uneven dendrite formation and anode volume expansion still can put a brake on the development of Li metal anode. Here, freestanding three-dimensional Li metal foam accompanied by inherent solid electrolyte interphase (SEI) capsulation formed by template-free chemical etching is constructed to promote the uniform lithium deposition and suppress dendritic Li growth. Contrary to planar Li metal foil, the 3D porous Li matrix can buffer the volume change and guide Li deposition inside its porous structure. Moreover, the encapsulated artificial SEI layer, which efficiently uniform the diffusion of Li ions on the interface, enables deeply deposited Li metal. Benefiting from the unique deposition kinetics, the Li plating/stripping process based on our strategy can be deeply cycled at various current densities with low overpotential between 1.0 and 20.0 mA cm−2 and achieve long lifetime up to 350 h. Moreover, Li metal batteries with LiNiCoMnO2 (Ni:Co:Mn=1:1:1) cathode exhibit excellent electrochemical performance at high current density and active material loading for more than 20.4 mg cm−2. In terms of both porous Li matrix and inherent dense SEI layer, our cell greatly suppresses the gassing process and reduces heat generation, further demonstrating the reliability and security of the batteries.

The sluggish solid-solid conversion kinetics from Li2S4 to Li2S during discharge is considered the main problem for cryogenic Li-S batteries. Herein, an all-liquid-phase reaction mechanism, where all the discharging intermediates are dissolved in the functional thioether-based electrolyte, is proposed to significantly enhance the kinetics of Li-S battery chemistry at low temperatures. A fast liquid-phase reaction pathway thus replaces the conventional slow solid-solid conversion route. Spectral investigations and molecular dynamics simulations jointly elucidate the greatly enhanced kinetics due to the highly decentralized state of solvated intermediates in the electrolyte. Overall, the battery brings an ultrahigh specific capacity of 1563 mAh g-1sulfur in the cathode at -60 °C. This work provides a strategy for developing cryogenic Li-S batteries.

The electroreduction of nitrogen to ammonia offers a promising alternative to the energy-intensive Haber–Bosch process. Unfortunately, the reaction suffers from low activity and selectivity, owing to competing hydrogen evolution and the poor accessibility of nitrogen to the electrocatalyst. Here, we report that deliberately triggering a salting-out effect in a highly concentrated electrolyte can simultaneously tackle the above challenges and achieve highly efficient ammonia synthesis. The solute ions exhibit strong affinity for the surrounding H2O molecules, forming a hydration shell and limiting their efficacy as both proton sources and solvents. This not only effectively suppresses hydrogen evolution but also ensures considerable nitrogen flux at the reaction interface via heterogeneous nucleation of the precipitate, thus facilitating the subsequent reduction process in terms of both selectivity and activity. As expected, even when assembled with a metal-free electrocatalyst, a high Faradaic efficiency of 71 ± 1.9% is achieved with this proof-of-concept system., The electroreduction of nitrogen to ammonia offers a promising alternative to the Haber–Bosch process but suffers from low activity and selectivity. Here, authors demonstrate that triggering a salting-out effect in a highly concentrated electrolyte can achieve highly efficient ammonia synthesis.

Low utilization of active metallic sodium (Na) and uncontrollable growth of Na dendrites remain significant challenges for high-performance Na metal batteries, which are limited to inefficient Na utilization (1%) and shallow cycling conditions (0.25-1.0 mAh cm

Lithium-sulfur (Li-S) batteries have been explored extensively for high-capacity electric-power storage, but their practical application has been prevented by severe issues stemming from the use of a lithium anode and an organic-liquid electrolyte in which Li2Sx intermediates of the cell discharge reaction are soluble and shuttle to the anode. Both problems are addressed using bis(4-nitrophenyl) carbonate as an additive in the organic-liquid electrolyte. The soluble Li2Sx polysulfides react with the additive to create insoluble polysulfides with a lithium byproduct; this byproduct reacts with the Li-metal anode to create an anode passivation layer that is a good Li+ conductor, which allows for safe and rapid plating/stripping of lithium metal with a low impedance.

The practical application of lithium (Li) metal anodes is limited by various issues, especially the uncontrolled growth of dendrites. Herein, we report single-cluster Au uniformly dispersed on activated carbon cloth as a model to control directed Li deposition and suppress Li dendrite growth. Single-cluster Au can induce Li plating with zero nucleation overpotential, due to an optimized electron field distribution, as validated by DFT calculations. Stable and reversible Li metal anodes were achieved by virtue of single-cluster Au, exhibiting excellent cycling stability for more than 900 cycles with almost 100% coulombic efficiency and deeply cyclable behavior at a high areal capacity of up to 20 mA h cm−2. Benefiting from guided Li deposition and maximum Li-utilization, we found that Li metal batteries with high-loading cathodes also deliver an outstanding electrochemical performance, showing promise for future rechargeable Li metal battery technologies.

The reduction of elemental sulfur to lithium sulfides is a complicated process and it involves a series of redox reactions; this leads to a variety of dominating obstructions for the commercial applications of lithium–sulfur (Li–S) batteries. Herein, we improved the performance of lithium–sulfur batteries by covalently immobilizing the discharge products on carbon nanofibers by using cysteamine as a medium, which enabled us to achieve unprecedented capacity retention of ∼87.6% after 500 cycles at a current rate of 1C (1C = 1675 mA g−1) with high sulfur loading of 4.5 mg cm−2. Significantly, in situ UV/vis spectroscopy and X-ray absorption spectroscopy (XAS) of the electrolyte offered direct evidence for the proposed mechanism. No detectable signals of dissoluble polysulfides in the electrolyte were observed at any intermediate states, indicating the effect of covalent bonds on the reduction of long-chain polysulfide Li2Sx (4 < x ≤ 8) production. Theoretically, DFT calculations indicated the presence of different S–S bond lengths in linear polysulfanes and verified the presence of short-chain polysulfide Li2Sx (1 ≤ x ≤ 4) intermediates during discharge. This strategy provides an important way to solve one of the essential issues limiting the commercial applications of Li–S batteries.

The persistent reduction reactions between the hyperactive lithium metal (Li) and dissolved polysulfides would passivate the Li metal and rapidly decrease the cathodic active materials, thus leading to low Coulombic efficiency and a short cycle life of lithium-sulfur (Li-S) batteries. Herein, we construct artificial lithium isopropyl-sulfide macromolecules as an ion-selective interface on the Li metal (IS-Li) by a facile electrochemical polymerization method, in which the polymer network improves the elasticity and toughness to accommodate the volume change of the Li anode and the formed lithium-organosulfides provide great mechanical strength to resist the destruction of Li dendrites. Importantly, this interfacial layer is proved to be sufficient in damping polysulfide anion diffusion and stopping irreversible reduction between polysulfides and metallic Li, which greatly contribute to the performance improvement of Li-S batteries. The resulting Li-S batteries exhibit long-term stability with high capacity retention and Coulombic efficiency. This effective strategy sets a new approach for regulating the interfacial chemistry of Li metal anodes, which is significant for highly stable Li-S batteries.

Latent heat storage using organic phase change materials (PCMs) have the potential to alleviate the contradiction between supply and demand in energy. However, the usage of PCMs is compromised by deficiencies including liquid leakage during liquidation and solidification, poor thermal conductivity and inferior thermal stability. Herein, we successfully fabricated a series of novel form-stable phase change materials (FSPCMs), using the polyolefin elastomer (POE) along with the octadecylamine-functionalized graphene (C18-rGO) acted as the supporting networks and paraffin as the thermal energy storage material. The octadecyl chain incorporated on the surface of graphene not only prevented from the graphene aggregation, but also endowed excellent structural stability to the composite FSPCMs. Meanwhile, the toughness of the composites was further improved with the addition of POE. Paraffin was tightly imprisoned in the frameworks formed by POE and the C18-rGO, resulting in no leakage even above their phase change temperature. As expected, the composite FSPCMs demonstrated reliable thermal stability and high thermal energy storage capacity. In particular, the composite FSPCMs was capable of absorbing or releasing stored thermal energy at a high rate, illustrating a great potential to be used as the effective thermal energy storage and thermal management systems.

Water pollution caused by domestic and industrial sewage exacerbates the shortage of freshwater, with major negative consequences for society and the environment. Solar-to-steam energy conversion systems, namely the extraction of steam using solar energy, are a promising eco-friendly and cost-effective approach for water purification. However, current technologies still exhibit low efficiency and high energy consumption. Here we report a polymer wastewater collector with a cross-scale hierarchical structure based on Defective polypyrrole-modified activated carbon paper substrate (DPAC), and its use for sporadic wastewater collection and efficient solar-driven sewage purification. Strong absorption of the solar spectrum at an arbitrary incident angle was achieved, which continuously provides heat for evaporation. Water molecules are prone to aggregate around the defective polypyrrole networks, where the generated heat is directly transferred to the water molecules, resulting in a low heat loss and high conversion efficiency for purifying seawater. In addition, DPAC exhibits superior domestic and industrial sewage evaporation rates of 1.37 and 1.28 kg m−2h−1 under one sun irradiation with corresponding solar-to-steam conversion efficiencies of 91.8% and 85.8%, respectively. The principle of this solar steam generator may provide useful insights towards the efficient and energy-saving treatment of domestic and industrial sewage.

Sodium-ion battery (SIB) is especially attractive in cost-effective energy storage device as an alternative to lithium-ion battery. Particularly, metal phosphides as potential anodes for SIBs have recently been demonstrated owing to their higher specific capacities compared with those of carbonaceous materials. Unfortunately, most reported metal phosphides consist of irregular particles ranged from several hundreds nanometers to tens of micrometers, thus delivering limited cyclic stability. This paper reports the sodium storage properties of additive-free Cu3P nanowire (CPNW) anode directly grown on copper current collector via an in situ growth followed by phosphidation method. Therefore, as a result of its structure features, CPNW anode demonstrates highly stable cycling ability with an ≈70% retention in capacity at the 260th cycle, whereas most reported metal phosphides have limited cycle numbers ranged between 30 and 150. Besides, the reaction mechanism between Cu3P and Na is investigated by examining the intermediate products at different charge/discharge stages using ex situ X-ray diffraction measurements. Furthermore, to explore the practical application of CPNW anode, a pouch-type Na+ full cell consisting of CPNW anode and Na3V2(PO4)3 cathode is assembled and characterized. As a demonstration, a 10 cm × 10 cm light-emmiting diode (LED) screen is successfully powered by the Na+ full cell.

A sustainable route from the biomass byproduct okara as a natural nitrogen fertilizer to high-content N-doped carbon sheets is demonstrated. The as-prepared unique structure exhibits high specific capacity (292 mAh g(-1) ) and extremely long cycle life (exceeding 2000 cycles). A full battery is devised for the practical use of materials with a flexible/wearable LED screen.

Supercapacitor electrodes composed of a 3D V2O5 network with polypyrrole (PPy) uniformly decorated onto each nanowire were fabricated to enhance their pseudocapacitive performance. The continuous 3D network creates channels for better ion transport, and the high degree of pore connectivity in the network enhances the mass transport. The PPy shell could enhance the electric conductivity and prevent the dissolution of vanadium. These merits together with the ideal synergy between V2O5 and PPy lead to a high specific capacitance of 448 F g−1, which is three times higher than that of the stacked V2O5. The all-solid-state symmetric supercapacitor device assembled by the V2O5/PPy core/shell 3D network exhibits a high energy density (14.2 W h kg−1) at a power density of 250 W kg−1 and good cyclic stability (capacitance retention of 81% after 1000 cycles). Furthermore, the prepared device could power a red light-emitting diode indicator efficiently after charging for only 10 s.

A new approach using polypyrrole as the nitrogen source has been demonstrated for the fabrication of nitrogen-doped graphene, which subsequently served as nucleation centers for the growth of metal oxides. The thin layers of the nitrogen-doped graphene are not only used as conductive pathways accelerating the electrical conductivity of metal oxides but also serve as buffer layers to improve the electrical contact with metal oxide nanostructures during the delithiation/lithiation of lithium ions. As anodes for lithium ion batteries, the nitrogen-doped graphene and their hybrids with MnO2 nanorods exhibit exceptionally excellent capacity retention for 3000 cycles at 2500 mA g−1, and ultrafast rate capability, which pave the way for developing electrode materials for long cycle-life energy storage devices.

A new type of amino polar binder with 3D network flexibility structure for high energy Li-S batteries is synthesized and successfully used with commercial sulfur powder cathodes. The binder shows significant performance improvement in capacity retention and high potential for practical application, which arouse the battery community's interest in the commercial application of high energy Li-S battery.

Sodium-ion batteries are especially attractive in the field of sustainable and cost-effective energy storage devices as promising alternatives to lithium-ion batteries. In this work, a lamellar carbon anode derived from biomass byproduct maize husks (LCMH) and a suitable NASICON structured Na3V2(PO4)3 cathode are utilized to assemble a full sodium-ion battery, which exhibits an extremely long cycle life of ∼1000 cycles and a high voltage of 4.1 V. More importantly, a stable reversible capacity of 239.6 mA h g(-1) for the LCMH anode is obtained, along with an ultra-long cycling performance of ∼5000 cycles and a high mass loading density of 8.31 mg cm(-2). Significantly, in-situ X-ray diffraction measurements are introduced to reveal the Na-storage mechanism and structure evolution upon battery cycling. This strategy provides a brand-new direction for building advanced electrode materials for full sodium-ion batteries.

Flexible/bendable electronic equipment has attracted great interest recently, while the development is hindered by fabricating flexible/bendable power sources due to the lack of reliable materials that combine both electronically superior conductivity and mechanical flexibility. Here, a novel structure of manganese oxide, like fabric foam, was constructed, which was then cocooned with a carbon shell via chemical vapor deposition. Serving as a binder-free anode, the self-knitted MnO2@Carbon Foam (MCF) exhibits high specific capacitance (850-950 mAh/g), excellent cycling stability (1000 cycles), and good rate capability (60 C, 1 C = 1 A/g). Moreover, a flexible full lithium battery was designed based on an MCF anode and a LiCoO2/Al cathode, and the outstanding performance (energy density of 2451 Wh/kg at a power density of 4085 W/kg) demonstrates its promising potential of the practical applications.

It is highly challenging to explore high-performance bi-functional oxygen electrode catalysts for their practical application in next-generation energy storage and conversion devices. In this work, we synthesize hierarchical N-doped carbon microspheres with porous yolk-shell structure (NCYS) as a metal-free electrocatalyst toward efficient oxygen reduction through a template-free route. The enhanced oxygen reduction performances in both alkaline and acid media profit well from the porous yolk-shell structure as well as abundant nitrogen functional groups. Furthermore, such yolk-shell microspheres can be used as precursor materials to motivate the oxygen reduction activity of oxygen evolution oriented materials to obtain a desirable bi-functional electrocatalyst. To verify its practical utility, Zn-air battery tests are conducted and exhibit satisfactory performance, indicating that this constructed concept for preparation of bi-functional catalyst will afford a promising strategy for exploring novel metal-air battery electrocatalysts.

We introduce a new method for fabricating unique on-chip supercapacitors based on CuO/polypyrrole core/shell nanosheet arrays by means of direct electrochemical co-deposition on interdigital-like electrodes. The prepared all-solid-state device demonstrates exceptionally high specific capacitance of 1275.5 F cm(-3) (∼40 times larger than that of CuO-only supercapacitors) and high-energy-density of 28.35 mWh cm(-3), which are both significantly greater than other solid-state supercapacitors. More importantly, the device maintains approximately 100% capacity retention at 2.5 A cm(-3) after 3000 cycles. The in situ co-deposition of CuO/polypyrrole nanosheets on interdigital substrate enables effective charge transport, electrode fabrication integrity, and device integration. Because of their high energy, power density, and stable cycling stability, these newly developed on-chip supercapacitors permit fast, reliable applications in portable and miniaturized electronic devices.

The dramatic growth of the Internet traffic and corresponding specific IP service requirements motivate the Internet service providers, network equipment manufacturers, and researchers not only to focus on scalability and cost effectiveness of the next generation optical network architecture design, but also on the need to provide assured quality of service (QoS) for Internet applications. We address the issues of supporting the QoS in one alternative optical network called PetaWeb network, proposed by Nortel Networks. PetaWeb is based on the use of adaptive core and edge switches, which can accommodate traffic fluctuations through reconfiguration of channels periodically. In order to achieve end-to-end QoS over PetaWeb network, a QoS-aware edge node and QoS-aware channel allocation algorithm come in consideration. This increases the effective capacity of the network, reduces packet loss and packet delay, so satisfying the desired services. Simulations are also implemented to evaluate and verify the network QoS performance.

Due to the dynamic network topology and bandwidth constraints of Mobile Ad hoc NETworks (MANETs), existing quality of service (QoS) models for wired networks, i.e. Integrated Service (InteServ) and Differentiated Service (DiffServ) are not applicable on MANETs. In this paper, we propose the SRL-Enabled QoS Model (SEQM) for MANETs by extending a QoS routing protocol: Supernode-based Reverse Labeling (SRL) algorithm, which considers QoS provisioning, specifically bandwidth and delay together. SRL utilizes a hierarchical structure to improve performance and enhance QoS routing. Besides extending SRL with on-demand service proxy, SEQM also includes dynamic traffic negotiation and resource provisioning. Preliminary simulation results show that SEQM performs effectively in terms of throughput and end-to-end delay.

The rapid growth of wireless networks and services, integrated with the next-generation mobile communication systems, has led to the era of the pervasive computing. The popularity of the lightweight portable computers with the growing demands of transmitting real-time multimedia applications over the wireless Internet provides strong motivations to the service providers to support not only seamless user mobility, but also continuous and seamless service provisions to the customers. We propose a mobile differentiated services architecture for next generation wireless networks based on the hierarchical mobile MPLS (H-MPLS). We also propose an extension to the current H-MPLS protocol and make it applicable to our architecture. This mobile differentiated services mechanism is applied to satisfy the QoS requirements of mobile users who subscribe services in their home domain and move into some other foreign domains. Hence, the mobile users could enjoy the continuous services without worrying about where they are. A series of simulations, with multimedia applications like video and voice, were performed to evaluate the proposed system.

Mobile MPLS is a new scheme that integrates mobile IP and MPLS protocols, in order to enable the MPLS protocol to support mobility. In mobile MPLS, when a correspondent node (CN) wants to communicate with a mobile user, the CN will first send its packets to the mobile user's home domain. Then, the home agent (HA) of the mobile user will forward the packets to the mobile user through the label switched path (LSP) from the HA to the current location of the mobile user. This forwarding process leads to a "triangle routing" problem. Even if route optimization is applied, several of the packets transmitted at the beginning of the connection will still be forwarded through the remote HA of the mobile user, since there is no address binding for the mobile user in the cache of the CN at the very beginning of the transmission. However, if the mobile user's behavior, e.g. the user's mobility pattern, travel schedule, are predictable or well-known before the transmission of the packets, this kind of "triangle routing" problem can be avoided. We propose a profile-based mobile MPLS protocol. The profiles maintain the regular behaviors of the mobile users. If the CN is able to obtain the profile of the mobile user, it will know (to some extend of accuracy) the current location of the mobile user and forward its traffic to the area the user is expected to be, thus eliminating the "triangle routing". Two schemes are proposed to maintain the profiles of the mobile users. One is based on a distributed, the second on a centralized approach. In the distributed scheme, the profiles are obtained directly from the mobile users, while in the centralized scheme a profile server is applied to maintain the profiles of all the mobile users in a domain. With the profile-based mobile MPLS approach, the delay for the traffic to the mobile user is reduced and the network performance is enhanced.

In this paper, the supernode-based reverse labeling (SRL), a quality of service (QoS) routing algorithm for mobile ad hoc networks (MANET), is extended to provide adaptive multicast service. The algorithm, termed AM-SRL (Adaptive Multicast operation of Supernode-based Reverse Labeling), adaptively builds an on-demand multicast mesh by exploiting the hierarchical structure of SRL. The virtual route discovery process of SRL functions as multicast member distribution awareness agent in AM-SRL and the reverse route establishment algorithm enables the adaptive generation of the multicast mesh. AM-SRL guides the redundant level of the multicast mesh by introducing a partial mesh factor. The adaptivity of virtual route selection, reverse route establishment and mesh formation make the algorithm efficient, robust and reliable.

We present a supernode-based reverse labeling (SRL) algorithm for quality-of-service (QoS) provisioning, specifically bandwidth and delay, in mobile ad hoc networks (MANETs). SRL utilizes a hierarchical structure, which is formed by dynamically electing supernodes through simple algorithms, to perform effective route discovery and local route information management. The SRL QoS routing computation has three key components: virtual route discovery, reverse link labeling and dynamic route repairing. SRL not only considers bandwidth and delay provisioning together on MANETs, it also reacts quickly and effectively to the dynamics of MANETs as well. Simulation results show that SRL is efficient in terms of the packet delivery ratio and average end-to-end delay. The robust end user connection reduces the packet loss ratio and route request overhead that are invoked by node mobility.

In this paper, we present simulation results assessing the performance of DiffServ-capable networks supporting real time multimedia traffic. We evaluate the performance of voice traffic, H263 video traffic and distributed interactive virtual environments (DIVE) applications with Web background traffic in a DiffServ-capable network. Particularly, the performance of weighted fair queuing (WFQ) algorithm is studied, and a realistic Web workload model generating aggregation of self-similar bursty traffic flows is developed and used to evaluate the performance of all above multimedia applications. Our analysis demonstrates that these multimedia applications can be well supported by DiffServ-capable networks even under the bursty Web style traffic, given that the subscribed bandwidth of the application is no less than its source generating data rate. According to our results, even for the most demanding DIVE application, bandwidth reservation at twice the source-generating rate is enough.

With the dramatic increase of the capacity of the Internet core, it has become an inherently challenging task to provide strict delay bound guarantees to applications such as multimedia, voice over IP, interactive distance learning, and interactive distribution simulations such as those based on distributed interactive virtual environments. The provision of a seamless integration of these applications into the broadband networks has been a subject of intensive research for the last few years. In addition, with the globalization of the telecommunications markets, service providers are deemed to inter-operate, cooperate, and possibly compete to ensure that over all performance metrics are met. We propose an intelligent traffic engineering approach in a differentiated services model for end-to-end packet delay assurance in an interdomain environment assuming an underlying multiprotocol label switching (MPLS) network infrastructure.

Mobile MPLS is a new scheme that integrates Mobile IP and MPLS protocols to support mobility to MPLS. However, some wireless networks have been implemented based on small-size cells (micro-cells) to allow higher system capacity. Micro-cell implementation will increase the handoff rate of the mobile hosts dramatically. So in such an environment, MPLS based on normal Mobile IP is no longer an optimal solution. To overcome the limitations of the Mobile IP protocol, in this paper we propose hierarchical mobile MPLS that is a practical approach to support local mobility for MPLS. We also propose a fast signaling process to support a "make-before-break" mechanism in mobile MPLS. An LSP is established before the mobile host moves into a new foreign network. We demonstrate through simulations, that with hierarchical mobile MPLS, the delay the mobile hosts experience during handoff periods is considerably decreased. Taking into consideration the growing popularity of wireless networks and wireless Internet, the sensitivity of several core applications-such as voice and video-to delays and delay jitter, the move towards pervasive computing and the use of smart intelligent appliances (e.g. sensors, monitors etc.), which might be supporting applications sensitive to delays and jitter (e.g. security, health, tele-control etc.) it is important that our wireless networks become capable of providing low delay guarantees. Our work is a positive step towards this direction.

This paper evaluates the differentiated services (DiffServ) mechanism proposed by IETF to provide QoS and resource reservation under bursty Web traffic. Particularly, the performance of the weighted fair queuing (WFQ) algorithm is studied, using a two-node network configuration. A realistic Web workload model generating the aggregation of Web-accessing traffic flows is developed and used to evaluate the performance. Our analysis demonstrates that due to the burstiness of Web traffic, DiffServ cannot achieve all the desired QoS guarantees, especially packet delay and jitter.

In the past few years, new types of Internet applications that require performance guarantees beyond the best effort service have emerged. These applications have spread to include voice, video teleconferencing, and a new set of pervasive computing devices that demand hard delay bound guarantees. The Differentiated services model when combined with traffic engineering can provide a suitable architecture for ensuring QoS guarantees to such applications, especially when multiple parallel paths to the same destination exist in a provider's network. Multiprotocol label switching (MPLS) is a new technology that facilitates significantly the process of traffic engineering in IP networks. With MPLS and differentiated services traffic engineering (DS-TE), it is possible to define explicit routes with different performance guarantees on each route to ensure QoS constraints are met. We introduce a probe packet approach to measure the delay on established label switched paths (LSPs) between ingress/egress edge routers pair. These measurements are then used in a delay estimation algorithm to provide the measure of the expected delay within the path. We demonstrate, through simulations, that our proposed model provides a better service to higher priority traffic classes.

The tremendous increase in customer bandwidth demands has led to the necessity of better utilization of available bandwidth resources. We present an artificial intelligence based pricing mechanism for control of user demand in the obtainable forwarding (OF) service in DiffServ networks. By deploying a fuzzy logic controller at the DiffServ boundary node, we are able to adjust dynamically the price per unit bandwidth, depending on customer bandwidth demands and bandwidth availability. In the case of elastic traffic, a small change in price leads to a small change in customer demand. As the decision to buy bandwidth or not lies in the hands of the customer (his grade of utility), it is difficult to estimate the parameters for the customer bandwidth utility function. The suggested fuzzy controller implements rules, easily obtainable at the boundary node, using terms such as "small change", "big increase". We present an evaluation of the utilization of dynamically changing bandwidth demand.