Mobile Oriented Future Internet (MOFI):Architectural Design and Implementations

With the recent growth in smartphone services, the “mobile” environment has become a key factor to consider in the design of the future Internet. In this paper, we propose Mobile‐Oriented Future Internet (MOFI), which is a new architecture for the future Internet for mobile‐oriented environments. The MOFI architecture is designed with three functional features: global identifier and local locator in the identifier‐locator separation, query‐first data delivery for route optimization, and distributed control of identifier‐locator mapping. The proposed architecture and functional operations are implemented and tested using the Linux platform. From the experiment results, we see that the MOFI architecture performs better than the existing identifier‐locator separation schemes, such as Proxy Mobile IP and Host Identity Protocol, in terms of data throughout, mapping control overhead, and handover delay.     

A mapping forwarding approach for supporting mobility in networks with identifier/locator separation

The identifier/locator separation has been widely recognized as a feasible solution for addressing the current Internet's routing scaling problem. Moreover, such a separation solution in terms of mobility can keep connection survivability and support global seamless roaming. A critical challenge in supporting efficient mobility is how to update the identifier‐to‐locator mappings of mobile nodes (MNs). In this paper, we propose a mapping forwarding (MF) scheme for location management in the identifier/locator separation architecture. In the MF scheme, a tunnel router (xTR) is selected as an agent of an MN and keeps the MN's identifier‐to‐locator mapping invariable by setting up an MF chain. As long as the MN is managed by the same xTR, the MN's mapping stored in the xTR of each correspondent node of the MN does not need to be updated, thus reducing the location update signaling cost. Meanwhile, the unchanged mapping assures the correct forwarding of packets, which reduces mobility‐related disruption and enhances the location management's reliability. In addition, for the handoff in two MF chains, we propose a data‐triggered update scheme that can achieve route optimization. To evaluate the proposed MF scheme, we establish two analytical models and formulate the blocking probability and the total protocol cost. The performance results show how the blocking probability changes under various parameters and how the MF scheme can effectively reduce the blocking probability compared with the location management scheme without the MF strategy. Meanwhile, our analysis demonstrates that the MF scheme has a lower overhead when the mobility rate is high. Copyright © 2011 John Wiley & Sons, Ltd.     

A unifying co‐operative web caching architecture

Network caching of objects has become a standard way of reducing network traffic and latency in the web. However, web caches exhibit poor performance with a hit rate of about 30%. A solution to improve this hit rate is to have a group of proxies form co‐operation where objects can be cached for later retrieval. A co‐operative cache system includes protocols for hierarchical and transversal caching. The drawback of such a system lies in the resulting network load due to the number of messages that need to be exchanged to locate an object. This paper proposes a new co‐operative web caching architecture, which unifies previous methods of web caching. Performance results shows that the architecture achieve up to 70% co‐operative hit rate and accesses the cached object in at most two hops. Moreover, the architecture is scalable with low traffic and database overhead. Copyright © 2002 John Wiley & Sons, Ltd.     

Distributed mapping management of identifiers and locators in mobile‐oriented Internet environment

Many schemes have recently been proposed for the separation of identifier (ID) and locator (LOC), which include the Host Identity Protocol, the Identifier‐Locator Network Protocol, and the Locator Identifier Separation Protocol. However, all of these schemes were originally designed in fixed network environment, rather than mobile network environment. In particular, these schemes are based on a centralized map server that is used as an anchor point for mobile nodes, and thus intrinsically subject to some limitations in a mobile environment. In this paper, we propose a distributed ID‐LOC mapping management scheme in a mobile‐oriented Internet environment. In the proposed scheme, we assume that a host has a globally unique and hierarchical Host ID (HID) that contains the information of its home network domain. Each network domain has a distributed map server for distributed management of ID‐LOC mappings. For roaming support, each distributed map server maintains its own home HID register and visiting HID register, which are used to keep the mappings of HID and LOCs for mobile nodes in the distributed manner. By performance analysis, it is shown that the proposed distributed scheme can give better performance than the existing centralized schemes in terms of ID‐LOC binding update and data delivery costs. Copyright © 2012 John Wiley & Sons, Ltd.     

A distributed mobility management scheme in networks with the locator/identifier separation

In traditional Internet architectures, current centralized mobility management schemes face scalability issues because of the creation of network bottlenecks and a single mobility agent of failures. To address these issues, we propose a distributed mobility management scheme in locator/identifier separation networks (DMMLIS). We divide the network into many domains according to the area of autonomous systems. Each domain consists of a mapping server and several tunnel routers (xTRs). The mapping server stores global mappings between endpoint identifier (EID) prefixes and autonomous system numbers (ASNs) to lookup the mobile nodes' (MNs') home domain. Meanwhile, the mapping server also contains ASN‐to‐xTR mappings so that it can forward Map‐Register and Map‐Request messages to any xTR of the MN's home domain, thus enhancing reliability. In addition, the xTRs in each domain constitute one‐hop distributed hash table ring. Moreover, any xTR in the MN's home domain may be the home agent of MNs, and the MNs' EID‐to‐RLOC (routing locator) mapping is stored in two xTRs using two hash functions. In this way, it not only supports quick lookup but also improves scalability and survivability. To evaluate the survivability and the efficiency of DMMLIS, we analyze the service blocking probability, the system response time, and the total protocol cost. We also present numerical results to demonstrate the performance of the proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

Dynamic Probabilistic Caching Algorithm with Content Priorities for Content‐Centric Networks

This paper presents a caching algorithm that offers better reconstructed data quality to the requesters than a probabilistic caching scheme while maintaining comparable network performance. It decides whether an incoming data packet must be cached based on the dynamic caching probability, which is adjusted according to the priorities of content carried by the data packet, the uncertainty of content popularities, and the records of cache events in the router. The adaptation of caching probability depends on the priorities of content, the multiplication factor adaptation, and the addition factor adaptation. The multiplication factor adaptation is computed from an instantaneous cache‐hit ratio, whereas the addition factor adaptation relies on a multiplication factor, popularities of requested contents, a cache‐hit ratio, and a cache‐miss ratio. We evaluate the performance of the caching algorithm by comparing it with previous caching schemes in network simulation. The simulation results indicate that our proposed caching algorithm surpasses previous schemes in terms of data quality and is comparable in terms of network performance.     

A zone co‐operation approach for efficient caching in mobile ad hoc networks

Mobile Ad hoc NETwork (MANET) presents a constrained communication environment due to fundamental limitations of client resources, insufficient wireless bandwidth and users' frequent mobility. Caching of frequently accessed data in such environment is a potential technique that can improve the data access performance and availability. Co‐operative caching, which allows the sharing and co‐ordination of cached data among clients, can further explore the potential of the caching techniques. In this paper, we propose a novel scheme, called zone co‐operative (ZC) for caching in MANETs. In ZC scheme, one‐hop neighbours of a mobile client form a co‐operative cache zone. For a data miss in the local cache, each client first searches the data in its zone before forwarding the request to the next client that lies along routing path towards server. As a part of cache management, cache admission control and value‐based replacement policy are developed to improve the data accessibility and reduce the local cache miss ratio. An analytical study of ZC based on data popularity, node density and transmission range is also performed. Simulation experiments show that the ZC caching mechanism achieves significant improvements in cache hit ratio and average query latency in comparison with other caching strategies. Copyright © 2006 John Wiley & Sons, Ltd.     

Analysis of multi‐user detection of multi‐rate transmissions in multi‐cellular CDMA

In this paper, we address the issue of multi‐user receiver design in realistic multi‐cellular and multi‐rate CDMA systems based on performance analysis. We consider the multi‐user detection (MUD) technique, denoted interference subspace rejection (ISR), because it offers a wide range of canonic suppression modes that range in performance and complexity between interference cancellers and linear receivers. To further broaden our study, we propose a modified ISR scheme called hybrid ISR to cope better with multi‐rate transmissions. The performance analysis, which is based on the Gaussian assumption (GA) and validated by simulations, takes into account data estimation errors, carrier frequency mismatch, imperfect power control, identification errors of time‐varying multipath Rayleigh channels and intercell interference. This analysis enables us to optimize the selection of the MUD mode for multi‐rate transmissions in different operating conditions. The effectiveness of interference cancellation is indeed investigated under different mobile speeds, numbers of receiving antennas, near‐far situations, channel estimation errors, and out‐cell to in‐cell interference ratios. This investigation suggests that the out‐of‐cell interference, the residual in‐cell interference, the noise enhancement as well as low mobility favor the simplest MUD modes as they offer the best performance/complexity tradeoffs. Copyright © 2008 John Wiley & Sons, Ltd.     

Performance of Two‐User Two‐Way Amplify‐and‐Forward Relaying Systems with Scheduling

In this paper, we study scheduling schemes for two‐user two‐way wireless relaying systems. Two transmission modes are considered: point‐to‐point direct transmission and two‐way amplify‐and‐forward relaying. An optimal scheduling scheme that opportunistically selects the best transmission mode for each user is proposed to minimize the sum bit error rate (BER). The performance lower bound of the optimal scheduling scheme is analyzed, and closed‐form expression of the lower‐bound BER is derived. However, for optimal scheduling, the scheduler requires the knowledge of channel state information (CSI) of all links. To reduce the feedback information of CSI, we also propose a suboptimal scheduling scheme that selects the transmission mode using only the CSI of two direct links. Simulation results show that there are 4 dB to 8 dB gains for the proposed optimal and suboptimal schemes over the fixed direct transmission and fixed two‐way relayed transmission scheme. The performance gap between the optimal and suboptimal scheduling schemes is small, which implies a good trade‐off between implementation complexity and system performance.     

Coreless Fiber‐Based Whispering‐Gallery‐Mode Assisted Lasing from Colloidal Quantum Well Solids

Whispering gallery mode (WGM) resonators are shown to hold great promise to achieve high‐performance lasing using colloidal semiconductor nanocrystals (NCs) in solution phase. However, the low packing density of such colloidal gain media in the solution phase results in increased lasing thresholds and poor lasing stability in these WGM lasers. To address these issues, here optical gain in colloidal quantum wells (CQWs) is proposed and shown in the form of high‐density close‐packed solid films constructed around a coreless fiber incorporating the resulting whispering gallery modes to induce gain and waveguiding modes of the fiber to funnel and collect light. In this work, a practical method is presented to produce the first CQW‐WGM laser using an optical fiber as the WGM cavity platform operating at low thresholds of ≈188 µJ cm^?2 and ≈1.39 mJ cm^?2 under one‐ and two‐photon absorption pumped, respectively, accompanied with a record low waveguide loss coefficient of ≈7 cm^?1 and a high net modal gain coefficient of ≈485 cm^?1. The spectral characteristics of the proposed CQW‐WGM resonator are supported with a numerical model of full electromagnetic solution. This unique CQW‐WGM cavity architecture offers new opportunities to achieve simple high‐performance optical resonators for colloidal lasers.     

A Lease Algorithm to Maintain Strong Mapping Cache Consistency

In the Locator/ID separation protocol (LISP) network, mapping caches are usually used in Ingress tunnel routers to cache recently used identifier-to-locator mappings of remote hosts. When the original mapping in the Egress tunnel router changes, it introduces the problem of cache consistency. In general, the mapping cache supports weak cache consistency by using the time-to-live (TTL) mechanism. However, a stale mapping could lead the packets to a wrong destination. In this paper, we first evaluate the performance of TTL by trace-driven simulation and the results indicate that maintaining strong mapping cache consistency has become an indispensable mechanism in the LISP network. Then we design the lease algorithm to realize the strong consistency and propose analytical models to decide the lease duration based on the state space overhead and the control message overhead, respectively. We present numerical results to estimate the mapping change frequency, to show the impact of different parameters on the lease duration and to explore the relationship between the state space and control message overhead. Finally, we do the trace-driven simulation to compare the lease algorithm to polling-every-time and invalidation in terms of the state space and control messages. The lease algorithm with an appropriate lease duration can balance the state space and the control message overhead while providing strong mapping cache consistency.     

Multi‐Stimuli‐Responsive Microcapsules for Adjustable Controlled‐Release

Novel multi‐stimuli‐responsive microcapsules with adjustable controlled‐release characteristics are prepared by a microfluidic technique. The proposed microcapsules are composed of crosslinked chitosan acting as pH‐responsive capsule membrane, embedded magnetic nanoparticles to realize “site‐specific targeting”, and embedded temperature‐responsive sub‐microspheres serving as “micro‐valves”. By applying an external magnetic field, the prepared smart microcapsules can achieve targeting aggregation at specific sites. Due to acid‐induced swelling of the capsule membranes, the microcapsules exhibit higher release rate at specific acidic sites compared to that at normal sites with physiological pH. More importantly, through controlling the hydrodynamic size of sub‐microsphere “micro‐valves” by regulating the environment temperature, the release rate of drug molecules from the microcapsules can be flexibly adjusted. This kind of multi‐stimuli‐responsive microcapsules with site‐specific targeting and adjustable controlled‐release characteristics provides a new mode for designing “intelligent” controlled‐release systems and is expected to realize more rational drug administration.     

An efficient in‐network caching decision algorithm for Internet of things

Recently, content‐centric networking (CCN) has become one of the important technologies for enabling the future networks. Along with its recognized potentialities as a content retrieval and dissemination solution, CCN has been also recently considered as a promising architecture for the Internet of things (IoT), because of 2 main features such as named‐based routing and in‐network caching. However, IoT is characterized by challenging features: small storage capacity of resource‐constrained devices due to cost and limitation of energy and especially transient data that impose stringent requirements on the information freshness. As a consequence, the intrinsic caching mechanisms existing in CCN approach do not well suit IoT domains; hence, providing a specific caching policy at intermediate nodes is a very challenging task. This paper proposes an effective multiattribute in‐network caching decision algorithm that performs a caching strategy in CCN‐IoT network by considering a set of crucial attributes including the content store size, hop count, particularly key temporal properties like data freshness, and the node energy level. Simulation results proved that our proposed approach outperforms 2 cache management schemes (probabilistic least recently used and AlwaysCache–first in first out in terms of improving total hit rate, reducing data retrieval delay, and enhancing content reusability in IoT environment).     

Tri‐band Microstrip Bandpass Filter Using Dual‐Mode Stepped‐Impedance Resonator

This letter presents a compact dual‐mode tri‐band bandpass filter by using a short‐circuited stub‐loaded stepped‐impedance resonator (SIR) and a short‐circuited stub‐loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short‐circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even‐odd mode theory. For demonstration purposes, a tri‐band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured.     

Pre-judgment and Incomplete Allocation Approach for Query Result Cache

Query result caching is a crucial technique employed in search engines,reducing the response time and load of the search engines.As search engines continuously update their indexes,the query results in long-lived cache entries may become stale.It is important to provide the refresh mechanism to enhance the degree of freshness of cached results.We present a prejudgment approach to improve the freshness of the result cache and design an incomplete allocation algorithm.We introduce the queryTime-to-live (TTL) and term-TTL structure to prejudge the result cache.The query-TTL is used to pre-check the likelihood of a cache hit and term-TTL is applied to maintain all terms of the latest posting list.For the cache structure,we design a Queue-Hash structure and develop the corresponding incomplete allocation algorithm.The preliminary results demonstrate that our approaches can improve the freshness of cached results and decrease processing overhead compared with no prejudgment approaches.     

Low peak‐to‐average power ratio and efficient multicarrier spread spectrum transceivers using hybrid and quadrature cyclic shift orthogonal keying

This paper proposes two bandwidth and power efficient multicode multicarrier spread spectrum (MCSS) system modes based on a new cyclic shift orthogonal keying (CSOK) scheme that leads to low peak‐to‐average power ratio (PAPR) signals. Both system modes can improve the bandwidth efficiency by loading more data bits per symbol block. The first system mode is the hybrid CSOK (HCSOK) mode, which combines phase shift keying (PSK) or quadrature amplitude modulation (QAM) modulation symbol with the CSOK symbol, for example, the important hybrid quadrature PSK (QPSK)–CSOK case. The second is the quadrature CSOK (QCSOK) mode that transmits two parallel binary phase shift keying (BPSK)–CSOK branches at the same time. For both modes, maximum likelihood receivers are derived and simplified, leading to efficient fast Fourier transform‐based structures for maximum ratio combining and cyclic‐code correlation. Theoretical bit error rate (BER) analysis is conducted for the hybrid QPSK–CSOK case. Simulation results demonstrate that both the two system modes considerably outperforms the traditional Walsh‐coded MCSS system in terms of bandwidth efficiency, PAPR, BER, and antijamming capability. Furthermore, in indoor channel, QCSOK performs slightly worse than QPSK–CSOK, but it has almost twice the data rate when the code length is large. Copyright © 2011 John Wiley & Sons, Ltd.     

Low‐complexity de‐mapping algorithms for 64‐APSK signals

Due to its high spectrum efficiency, 64‐amplitude phase‐shift keying (64‐APSK) is one of the primary technologies used in deep space communications and digital video broadcasting through satellite‐second generation. However, 64‐APSK suffers from considerable computational complexity because of the de‐mapping method that it employs. In this study, a low‐complexity de‐mapping method for (4 + 12 + 20 + 28) 64‐APSK is proposed in which we take full advantage of the symmetric characteristics of each symbol mapping. Moreover, we map the detected symbol to the first quadrant and then divide the region in this first quadrant into several partitions to simplify the formula. Theoretical analysis shows that the proposed method requires no operation of exponents and logarithms and involves only multiplication, addition, subtraction, and judgment. Simulation results validate that the time consumption is dramatically decreased with limited degradation of bit error rate performance.     

1.5 V Sub‐mW CMOS Interface Circuit for Capacitive Sensor Applications in Ubiquitous Sensor Networks

In this paper, a low‐power CMOS interface circuit is designed and demonstrated for capacitive sensor applications, which is implemented using a standard 0.35‐μm CMOS logic technology. To achieve low‐power performance, the low‐voltage capacitance‐to‐pulse‐width converter based on a self‐reset operation at a supply voltage of 1.5 V is designed and incorporated into a new interface circuit. Moreover, the external pulse signal for the reset operation is made unnecessary by the employment of the self‐reset operation. At a low supply voltage of 1.5 V, the new circuit requires a total power consumption of 0.47 mW with ultra‐low power dissipation of 157 μW of the interface‐circuit core. These results demonstrate that the new interface circuit with self‐reset operation successfully reduces power consumption. In addition, a prototype wireless sensor‐module with the proposed circuit is successfully implemented for practical applications. Consequently, the new CMOS interface circuit can be used for the sensor applications in ubiquitous sensor networks, where low‐power performance is essential.     

Packet‐level‐based traffic aggregation to optimize NDN content delivery

In recent years, named data networking (NDN) has been accepted as the most popular future paradigm and attracted much attention, of which the routing model contains interest forwarding and content delivery. However, interest forwarding is far from the bottleneck of routing optimization; instead, the study on content delivery can greatly promote routing performance. Although many proposals on content delivery have been investigated, they have not considered packet‐level caching and deep traffic aggregation, which goes against the performance optimization of content delivery. In this paper, we propose a packet‐level‐based traffic aggregation (PLTA) scheme to optimize NDN content delivery. At first, the packet format is devised, and data plane development kit (DPDK) is used to ensure same size for each packet. Then, the whole delivery scheme with traffic aggregation consideration is presented. The simulation is driven by the real YouTube dataset over Deltacom, NSFNET, and CERNET topologies, and the experimental results demonstrate that the proposed PLTA has better delivery performance than three baselines in terms of cache hit ratio, delivery delay, network load, and energy efficiency.     

40 GHz Vertical Transition with a Dual‐Mode Cavity for a Low‐Temperature Co‐fired Ceramic Transceiver Module

A new vertical transition between a substrate integrated waveguide in a low‐temperature co‐fired ceramic substrate and an air‐filled standard waveguide is proposed in this paper. A rectangular cavity resonator with closely spaced metallic vias is designed to connect the substrate integrated waveguide to the standard air‐filled waveguide. Physical characteristics of an air‐filled WR‐22 to WR‐22 transition are compared with those of the proposed transition. Simulation and experiment demonstrate that the proposed transition shows a ?1.3 dB insertion loss and 6.2 GHz bandwidth with a 10 dB return loss for the back‐to‐back module. A 40 GHz low‐temperature co‐fired ceramic module with the proposed vertical transition is also implemented. The implemented module is very compact, measuring 57 mm × 28 mm × 3.3 mm.