A comparative study of bandwidth reservation and admission control schemes in QoS‐sensitive cellular networks

This paper compares five different schemes – called CHOI, NAG, AG, BHARG, and NCBF – for reserving bandwidths for handoffs and admission control for new connection requests in QoS‐sensitive cellular networks. CHOI and NAG are to keep the handoff dropping probability below a target value, AG is to guarantee no handoff drops through per‐connection bandwidth reservation, and BHARG and NCBF use another type of per‐connection bandwidth reservation. CHOI predicts the bandwidth required to handle handoffs by estimating possible handoffs from adjacent cells, then performs admission control for each newly‐requested connection. On the other hand, NAG predicts the total required bandwidth in the current cell by estimating both incoming and outgoing handoffs at each cell. AG requires the set of cells to be traversed by the mobile with a newly‐requested connection, and reserves bandwidth for each connection in each of these cells. The last two schemes reserve bandwidth for each connection in the predicted next cell of a mobile where the two schemes use different admission control policies. We adopt the history‐based mobility estimation for the first two schemes. Using extensive simulations, the five schemes are compared quantitatively in terms of (1) handoff dropping probability, connection‐blocking probability, and bandwidth utilization; (2) dependence on the design parameters; (3) dependence on the accuracy of mobility estimation; and (4) complexity. The simulation results indicate that CHOI is the most desirable in that it achieves good performance while requiring much less memory and computation than the other four schemes. This revised version was published online in July 2006 with corrections to the Cover Date.     

A cross-layer scheme for medium access control with QoS guaranteeing for Ad hoc networks

1 Introduction medium access control (MAC) protocols play a crucial role in determining the performance of Ad hoc networks. However, the design of MAC protocols for Ad hoc networks has traditionally been separated from that of the physical layer. In most …     

Novel optimal real‐time admission control and buffer management for the Video‐On‐Demand (VOD) service

In order to meet the Quality of Service (QoS) requirements of the VOD service, and, on the other hand, to maximize the system throughput (revenue), it is essential that the video call request admission control algorithm be carefully designed. In this paper, in addition to the Single Segment (SS) admission control first described in [7], we propose two new types of admission control schemes called Segmental Re‐tuned (SR) admission control and Multiple Segment (MS) admission control for variable‐bit‐rate video streams under various video server architectures. The basic approach to the algorithm development is first to formulate each problem as a mathematical problem and then to identify special structures and properties for such formulations so that optimal real‐time algorithms can be developed. In computational experiments, it is shown that the proposed algorithms for the considered video server architectures, compared with the traditional admission control scheme based upon the peak frame size, typically achieve over 175–200% improvement in the system throughput. In addition, the new proposed MS scheme performs 5–25% better than SS and SR schemes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Design and analysis of an algorithm for fair service in error‐prone wireless channels

In order to support diverse communication‐intensive real‐time and non‐real‐time data flows over a scarce, varying and shared wireless channel with location‐dependent and bursty errors, we define a service model that has the following characteristics: short‐term fairness among flows which perceive a clean channel, long‐term fairness for flows with bounded channel error, worst‐case delay bounds for packets, short‐term throughput bounds for flows with clean channels and long‐term throughput bounds for all flows with bounded channel error, expanded schedulable region, and support for both delay sensitive and error sensitive data flows. We present the wireless fair service algorithm, and show through both analysis and simulation that it achieves the requirements of the service model in typical wireless network environments. The key aspects of the algorithm are the following: (a) an enhanced fair queueing based service scheme that supports decoupling of delay and bandwidth, (b) graceful service compensation for lagging flows and graceful service degradation for leading flows, (c) support for real‐time delay sensitive flows as well as non‐real‐time error sensitive flows, and (d) an implementation within the framework of the simple and robust CSMA/CA wireless medium access protocol. This revised version was published online in July 2006 with corrections to the Cover Date.     

A center‐controlled dynamic rerouting scheme for fast and reliable handover in mobile ATM networks

This paper proposes a scheme for fast and reliable handover that uses dynamic rerouting controlled by a call setup control station (CCS) operating in mobile asynchronous transfer mode (ATM) networks. The CCS selects appropriate rerouted path and crossover switch (COS), and remotely controls the new path's setup. This omits crossover switch discovery process, and makes fast handover possible. The CCS can select the appropriate rerouted path because it directly and with little delay collects information about the state of links such as traffic loads, quality-of-service (QoS) parameters, and disconnection or restoration of links advertised from every ATM switch in its domain. This reduces blocking and congestion, and makes reliable handover possible. The CCS accepts a handover request message for either backward or forward handover, and can remotely control the new path's setup in the same manner for either handover. The scheme provides forward handover when the radio propagation conditions deteriorate unpredictably. This paper also shows sequences of call origination, connection pre-establishment, and route-change in our proposed scheme, and illustrates operation of the CCS and the ATM switches. This revised version was published online in June 2006 with corrections to the Cover Date.     

Design and analysis of low‐power access protocols for wireless and mobile ATM networks

This paper describes the design and analysis of a low‐power medium access control (MAC) protocol for wireless/mobile ATM networks. The protocol – denoted EC‐MAC (energy conserving medium access control) – is designed to support different traffic types with quality‐of‐service (QoS) provisions. The network is based on the infrastructure model where a base station (BS) serves all the mobiles currently in its cell. A reservation‐based approach is proposed, with appropriate scheduling of the requests from the mobiles. This strategy is utilized to accomplish the dual goals of reduced energy consumption and quality of service provision over wireless links. A priority round robin with dynamic reservation update and error compensation scheduling algorithm is used to schedule the transmission requests of the mobiles. Discrete‐event simulation has been used to study the performance of the protocol. A comparison of energy consumption of the EC‐MAC to a number of other protocols is provided. This comparison indicates the EC‐MAC has, in general, better energy consumption characteristics. Performance analysis of the proposed protocol with respect to different quality‐of‐service parameters using video, audio and data traffic models is provided. This revised version was published online in August 2006 with corrections to the Cover Date.     

Floor acquisition multiple access (FAMA) in single‐channel wireless networks

The FAMANCS protocol is introduced for wireless LANs and adhoc networks that are based on a single channel and asynchronous transmissions (i.e., no time slotting). FAMANCS (for floor acquisition multiple access with nonpersistent carrier sensing) guarantees that a single sender is able to send data packets free of collisions to a given receiver at any given time. FAMANCS is based on a threeway handshake between sender and receiver in which the sender uses nonpersistent carrier sensing to transmit a requesttosend (RTS) and the receiver sends a cleartosend (CTS) that lasts much longer than the RTS to serve as a busy tone that forces all hidden nodes to back off long enough to allow a collisionfree data packet to arrive at the receiver. It is shown that carrier sensing is needed to support collisionfree transmissions in the presence of hidden terminals when nodes transmit RTSs asynchronously. The throughput of FAMANCS is analyzed for singlechannel networks with and without hidden terminals; the analysis shows that FAMANCS performs better than ALOHA, CSMA, and all prior proposals based on collision avoidance dialogues (e.g., MACA, MACAW, and IEEE 802.11 DFWMAC) in the presence of hidden terminals. Simulation experiments are used to confirm the analytical results.     

Performance evaluation of path optimization schemes for inter‐switch handoff in wireless ATM networks

One of the major design issues in wireless ATM is the support of inter‐switch handoff. An inter‐switch handoff occurs when a mobile terminal moves to a new base station connecting to a different switch. Recently, a two‐phase handoff protocol has been proposed to support inter‐switch handoff in wireless ATM networks. With the aim of shortening handoff delay while using the network resources efficiently, the two‐phase handoff protocol employs path extension for each inter‐switch handoff, followed by path optimization if necessary. To implement the two‐phase handoff protocol efficiently, we need to determine when to trigger path optimization. In this paper, we propose and analyze three path optimization schemes, namely: periodic, exponential, and Bernoulli, for the two‐phase handoff protocol. The design objective is to determine the time to invoke path optimization such that the average cost per connection is minimized. We develop a discrete time analytical model and a discrete‐event simulation model for comparing the performance of the three path optimization schemes. Results indicate that the Bernoulli path optimization scheme outperforms the other two schemes by providing a lower average cost per connection. The proposed models can also be adapted to analyze other path optimization schemes in general. This revised version was published online in July 2006 with corrections to the Cover Date.     

A distributed congestion and power control algorithm to achieve bounded average queuing delay in wireless networks

Allocating limited resources such as bandwidth and power in a multi-hop wireless network can be formulated as a Network Utility Maximization (NUM) problem. In this approach, both transmitting source nodes and relaying link nodes exchange information allowing for the NUM problem to be solved in an iterative distributed manner. Some previous NUM formulations of wireless network problems have considered the parameters of data rate, reliability, and transmitter powers either in the source utility function which measures an application’s performance or as constraints. However, delay is also an important factor in the performance of many applications. In this paper, we consider an additional constraint based on the average queueing delay requirements of the sources. In particular, we examine an augmented NUM formulation in which rate and power control in a wireless network are balanced to achieve bounded average queueing delays for sources. With the additional delay constraints, the augmented NUM problem is non-convex. Therefore, we present a change of variable to transform the problem to a convex problem and we develop a solution which results in a distributed rate and power control algorithm tailored to achieving bounded average queueing delays. Simulation results demonstrate the efficacy of the distributed algorithm.     

Resource allocation of simultaneous wireless information and power transmission of multi-beam solar power satellites in space–terrestrial integrated networks for 6G wireless systems

Wireless Networks - The technique of simultaneous wireless information and power transmission (SWIPT) has been applied to wireless sensor networks, which employ static or mobile base stations (BSs)...     

Study on the performance of the A*Prune QoS routing algorithm for intelligent optical networks and its improvements

1 Introduction In the past few years, many routing algorithms for compu- ting constrained paths have been proposed in the networking community. In the earlier days, research study has been concentrated on a single additive constraint, especially the delay…     

A deadlock model for a multi‐service medium access protocol employing multi‐slot N‐ary stack algorithm (msSTART)

Many modern multi‐service medium access protocols (MACs) use a collision based capacity request signaling channel as part of a hybrid TDMA frame structure. Multi‐slot Stack Random Access Algorithm (msSTART) is proposed for use in IEEE 802.14 hybrid fiber/coaxial network and will be highly relevant for the S‐MAC development of evolving WATM MAC specifications. This paper studies the performance of msSTART as an example of a Q‐ary tree contention resolution algorithm (CRA) in the wireless environment using the novel Basic Deadlock model. We contrast approximate results for msSTART performance obtained by simulation under extreme inter‐station correlation with analytical results for the more popular p‐persistence CRA used in several testbed WATM implementations. Using three signaling channel schemes designed to provide support for increased system stability, to implement priority in the wireless MAC, and maximise efficiency, we provide comparative results for evaluation of msSTART and p‐persistence ALOHA under what the IEEE 802.14 working group has termed the “disaster scenario”. We find that of the three schemes evaluated the full Contention Mini‐Slot (CMS) sharing scheme employing multiple CMSs per data region extends the protocol's useable load region the furthest. We conclude that Q‐ary tree contention resolution algorithms (in particular msSTART) are best adapted to the wireless environment, providing less case sensitive performance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Performance evaluation of optimum combining and maximal ratio combining in the presence of co‐channel interference and channel correlation for wireless communication systems

Antenna diversity is an important technique to combat fading and reduce cochannel interference (CCI). In this paper, we present an analytical approach to derive bit error rate (BER) for Optimum Combining (OC) and Maximal Ratio Combining (MRC) in the presence of CCI. The paper has two parts. In the first part, the analysis of BER for OC with two cochannel interferers and MRC with an arbitrary number of interferers is presented for Marray antenna systems under the assumption that the channels of users are independent of each other. In the second part, the analysis of BER for OC and MRC in the presence of one dominant cochannel interferer is presented for dual antenna systems by assuming that the channels of the desired user or cochannel interferer are correlated. For DPSK signal, an exact BER expression is derived. The work presented here also yields an upper bound for BPSK or QAM signal based on the results of Foschini and Salz (1983).     

A routing algorithm for connection‐oriented Low Earth Orbit (LEO) satellite networks with dynamic connectivity

Low Earth Orbit (LEO) satellites move with respect to a fixed observer on the Earth surface. Satellites in the polar regions and the seam switch off their intersatellite links to the neighbor satellites. As a result, the connectivity pattern of the network changes. Ongoing calls passing through these links need to be rerouted. A large number of simultaneous rerouting attempts would cause excessive signaling load in the network. Moreover, the handover calls could be blocked because of the insufficient network resources in the newly established routes or large connection re‐establishment delay. In this paper, a routing protocol is introduced to reduce the number of routing attempts resulting from link connectivity change. The protocol does not use the links that will be switched off before the connection is over. Since the call durations are not known a priori, the proposed protocol utilizes a probabilistic approach. The performance of the protocol is evaluated through simulation experiments. The experimental results indicate that the routing protocol reduces the number of rerouting attempts resulting from connectivity changes of the network. This revised version was published online in July 2006 with corrections to the Cover Date.     

Design and realization of low profile dual-wideband monopole antenna incorporating a novel ohm (Ω) shaped DMS and semi-circular DGS for wireless applications

In this paper, a compact microstrip line fed dual-wideband printed monopole antenna (PMA) for wireless communication applications is presented. The proposed antenna consists of an asymmetric rectangular patch via a microstrip-fed line, an ohm (Ω) shaped DMS loaded at the rectangular patch, and dual semi-circular shaped DGS embedded in the partial rectangular ground plane. The combination of an ohm shaped DMS and two semi-circular DGS is used to broaden the bandwidth of the two bands and improve the return loss for the desired antenna. The measured 10 dB bandwidth for return loss are achieved to be 21.52% (3.40–4.22 GHz) and 47.32% (5–8.1 GHz) in the lower and upper band, respectively which covers the bandwidth requirements of 5.2/5.8 GHz WLAN and 3.5/5.5 GHz Wi-MAX application bands. Furthermore, the proposed antenna has a very simple planar structure and occupies a small area of only 621 mm² (23 mm × 27 mm). The proposed antenna has a desirable VSWR level, radiation pattern, radiation efficiency and gain characteristics which are suitable for wireless communication applications.     

A low-power,low-noise and high linearity 60 GHz wideband CMOS low-noise amplifier for wireless personal area network (WPAN) systems

A low power and low noise figure (NF) 60 GHz wideband low-noise amplifier (LNA) with excellent phase linearity for wireless personal local network (WPAN) systems using standard 90 nm CMOS technology is reported. To achieve sufficient power gain (S₂₁) and reverse isolation (S₁₂), the LNA comprises a common-source (CS) stage followed by a cascode stage and a CS stage. The LNA consumes 14.1 mW, achieving S₁₁ better than ?10 dB for frequencies 55.1–59.5 GHz, S₂₂ better than ?10 dB for frequencies 55.1–59.4 GHz, S₁₂ better than ?42.6 dB for frequencies 50–64 GHz, and group delay variation smaller than ±13.25 ps for frequencies 50.4–63 GHz. Additionally, high and flat S₂₁ of 9.9 ± 1.5 dB is achieved for frequencies 50.4–62.9 GHz, which means the corresponding 3-dB bandwidth is 12.5 GHz. Furthermore, the LNA achieves minimum NF of 3.88 dB at 55.5 GHz and NF of 4.73 ± 0.85 dB for frequencies 50–63.5 GHz, one of the best NF results ever reported for a 60 GHz CMOS LNA.     

Surface second harmonic generation in the characterization of anodic sulphide and oxide films on Hg1−xCdxTe (MCT)

Rotation anisotropy by second harmonic generation (SHG) is carried out on epitaxial Hg_1−xCd_xTe (MCT) and oxide- and sulphide-covered MCT surfaces and shows the fourfold symmetry pattern expected from the {100} surface (C_4v symmetry). The uneven nature of the four peaks confirm the vicinal surface obtained from the growth of the MCT on GaAs {100} substrate orientated 4° toward the 〈110〉 direction. The increase in the SH intensity observed for the oxide-covered MCT surface is associated with charge accumulation at the MCT/oxide interface since the oxide is centrosymmetric and cannot generate SH. The CdS layer on the other hand is strongly nonlinear active and generation here comes from a composite of one noncentrosymmetric layer on top of another. This leads to interactions in the observed SH arising from the coupling depths (∼40 nm) at the two interfaces and from the coherence length (∼1200 nm) in the CdS layer. The in-situ SHG measurements during the growth of the anodic oxide and sulphide layers would suggest that a species, most likely HgTe is embedded in the anodic layer during the initial stages and absorbs the SH radiation at 532 nm. The rotational anisotropy of the sulphide-covered MCT surface confirms that the CdS layer formed maintains the cubic closed pack symmetry of the underlying MCT.     

Adaptive control for enhancing tracking performances of flexible tendon–sheath mechanism in natural orifice transluminal endoscopic surgery (NOTES)

Tendon–sheath mechanism (TSM) has inherent advantages in the development of flexible robotic systems because of its simplicity, safety, flexibility, and ease of transmission. However, the control of TSM is challenging due to the presence of nonlinearities, namely friction, backlash-like hysteresis and the time-varying configuration of the TSM during its operations. Existing studies of TSM found in the literature only address tendon transmission under the assumption of fixed configuration and a complex inverse model of backlash is required. In order to flexibly use the system in a wider range of applications, the aforementioned nonlinear effects have to be characterized for the purpose of compensation. In this paper, we endeavor to address these issues by presenting a series of controller strategies, namely a feedforward control scheme under the assumption of known backlash-like hysteresis profile, and an adaptive control scheme to characterize the nonlinearities with unknown backlash hysteresis and uncertainties. The proposed control schemes do not require information of the tendon–sheath configurations, which is challenging to obtain in practice, in the compensation structures. In the absence of output position feedback, a simple direct inverse model-based feedforward has been used that efficiently reduce the tracking errors. The feedforward compensation does not require any complex algorithm for the inverse model. In the presence of output position feedback, a nonlinear adaptive controller has been developed to enhance the tracking performances of the TSM regardless of the random change in the tendon–sheath configurations during compensation. In addition, exact values of the model parameters are not required. They are estimated online during the operations. A dedicated experimental setup is introduced to validate the proposed control approaches. The results show that the proposed control schemes significantly improve the tracking performances for the TSM in the presence of uncertainties and time-varying configurations during the operations. There is a significant decrease of 0.0158 rad² (before compensation) to smaller value of 0.0012 rad² (use feedforward control) and 8.2815 × 10⁻⁵ rad² (use nonlinear controller) after compensation.     

Hall of fame for mobile commerce and its applications: A bibliometric evaluation of a decade and a half (2000–2015)

This study intends to evaluate the current development and trends of researches on mobile commerce and its applications through bibliometric analysis. Several publication characteristics were examined, on top of lists for most cited articles on this area and most studied mobile commerce applications. Through the data gathered from Web of Science database, this study employs several measures, namely impact factor, h-index, and citation counts to evaluate the productivity, impact, and research performance of countries, journals, authors, and research institutions. The number of publications are increasing yearly, with USA leading most of the times. Several international collaboration patterns were identified, and surprisingly some Asian countries have comparable performance to Western countries, in terms of the measures employed. Likewise, Asian authors and research institutions are found to have outstanding achievements too. Moreover, both the most studied mobile commerce applications and most cited lists offer some future directions. This study serves as a forerunner in using bibliometric analysis to evaluate researches on mobile commerce and its applications, and expected to benefit researchers in the area of mobile commerce, by identifying potential research directions. In addition, this study also serves as a useful guide to potential researchers and practitioners. However, improvements could be made, if extra analyses, such as content analysis, are added in.