Teletraffic performance evaluation of microcellular personalcommunication networks (PCN's) with prioritized handoff procedures

Evaluates four handoff priority-oriented channel allocation schemes. These give priority to handoff calls by reserving channels exclusively for handoff calls. The measurement-based handover channel adaptive reassignment scheme (MHAR-A) exclusively uses reserved handover channels for newly originated calls if a certain criterion is satisfied. All four schemes studied differ from the conventional guard channel-based handover priority-oriented channel allocation scheme. To study the schemes, a personal communication network (PCN) based on city street microcells is considered. A teletraffic simulation model accommodating a fast moving vehicle is developed, and the performance parameters are obtained. The performances of all four schemes are compared with the nonpriority scheme and the conventional guard channel-based handover priority-oriented channel allocation scheme. It was found that some of the channel allocation algorithms studied improved the teletraffic capacity over the nonpriority and the conventional guard case. Also, the probability of new call blocking and carried traffic was improved for three of the schemes when compared to the conventional guard scheme. The MHAR-A scheme did not perform up to expectation. Nevertheless, it can be used to finely control the communication service quality equivalent to the control obtained by varying the number of handoff channels in a fraction of one. Increasing the number of reserved handover channels in fraction of one can never be achieved in the conventional guard channel-based handover priority-oriented channel allocation scheme     

RSVP extensions for real-time services in wireless mobile networks

Currently, the RSVP model, which is efficient resource reservation in the fixed endpoints, becomes invalid under host mobility. We investigate the problems of standard RSVP in providing real-time services in wireless mobile networks. We also observe carefully how to interoperate IntServ services over DiffServ networks, and how to map IntServ QoS parameters into a wireless link. We then identify the advantages and drawbacks of the existing RSVP proposals to support QoS under both micromobility and macromobility. We finally propose a dynamic resource allocation scheme for reducing service disruption of real-time applications due to frequent mobility of a host     

Steady-state estimation of thermal contact conductance between sliding disk and stationary cylinder with similar/dissimilar materials under the isothermally heated boundary condition

An accurate understanding of the thermal contact conductance (TCC) is imperative for the enhancement of the performance and service life of metallic cylindrical joints. However, the evaluation of the TCC between conforming cylindrical solids is quite intricate, as it depends on the temperature, pressure, roughness, relative sliding speed, and thermophysical properties of solids. Instead of generating contacting surfaces stochastically, in this communication, an experimental setup in the lab-scale consisting of a stationary cylinder and a sliding hot disk has been fabricated in which temporal evolutions of the temperature on both solids are recorded by thermocouples. Effects of the disk temperature and relative sliding speed on the steady-state TCC have been investigated. There is a cylindrical interface between two conforming smooth solids of similar/dissimilar materials. As there is the differential expansion of cylindrical solids due to the temperature gradient, the diameter of sliding disks has been truncated to fix the radial gap (contact pressure). Inverse solution with the conjugate gradient method along with the adjoint problem has been applied to estimate the steady-state TCC. One-dimensional heat transfer analysis shows that frictional heating is negligible. The steady-state TCC is almost constant longitudinally along the axis of the steel cylinder. Under identical initial and isothermally heated boundary conditions, the TCC between the aluminum disk and cylinder is higher than that between steel disk and cylinder. Also, the TCC has been increased with a rising slope when the working temperature is enhanced. However, the augmentation of the relative sliding speed engenders a decreasing slope in the TCC graph.     

Addressing of software downloads to reconfigurable terminals in UMTS

Over-the-air software download is a key enabler for many aspects related to the reconfiguration of terminals based on software-defined radio (SDR). Different mechanisms for advertising the availability of software enhancements to a group of SDR terminals in universal mobile telecommunication system networks are evaluated. In order to exploit efficiencies in terms of transmission and processing, addressing strategies that allow the subsequent download to be performed in a multicast fashion are considered. A novel scheme for advertising software to only those terminals that are targeted by the download is introduced. On the basis of cost analysis, it is shown that the proposed scheme performs favourably compared with other viable schemes for performing software upgrade announcements     

Relay-based deployment concepts for wireless and mobile broadband radio

In recent years, there has been an upsurge of interest in multihop-augmented infrastructure-based networks in both the industry and academia, such as the seed concept in 3GPP, mesh networks in IEEE 802.16, and converge extension of HiperLAN/2 through relays or user-cooperative diversity mesh networks. This article, a synopsis of numerous contributions to the working group 4 of the wireless world research forum and other research work, presents an overview of important topics and applications in the context of relaying. It covers different approaches to exploiting the benefits of multihop communications via relays, such as solutions for radio range extension in mobile and wireless broadband cellular networks (trading range for capacity), and solutions to combat shadowing at high radio frequencies. Furthermore, relaying is presented as a means to reduce infrastructure deployment costs. It is also shown that through the exploitation of spatial diversity, multihop relaying can enhance capacity in cellular networks. We wish to emphasize that while this article focuses on fixed relays, many of the concepts presented can also be applied to systems with moving relays.     

Performance of a joint CDMA/PRMA protocol for mixed voice/datatransmission for third generation mobile communication

A joint code-division multiple-access/packet-reservation multiple-access (CDMA/PRMA) technique is proposed and investigated as a candidate for an uplink protocol for third generation mobile communication systems. Access to the radio channel is controlled such that compared to random access CDMA, interference variance is reduced and throughput increased. Mixed voice/data traffic is investigated for an isolated cell only, whereas voice-only traffic is also investigated in a cellular environment with a regular hexagonal cell structure. Intercell interference is assumed to be Gaussian, and only the average interference level is considered     

Power limitation and high-power amplifier nonlinearities inon-board satellite communications systems

The authors discuss the problem of power limitation in on-board satellite communications systems. They consider the nonlinear characteristics of on-board high-power amplifiers and corresponding linearisation techniques. It is shown that, with the recent development of solid-state high-power amplifier designs and linearisation techniques for travelling wave-tube amplifiers, it is now possible to operate on-board amplifiers near to saturation without increasing their nonlinear effects     

Calibration of smart antenna systems: measurements and results

Smart antennas (SAs) are viewed as a candidate enabling technology for modern wireless communication systems to increase network capacity and facilitate location-based services. By conducting measurements on an SA test-bed, the signal distortion introduced by the implementation of a practical system can be analysed. This distortion can have significant impact on the estimation of signal wavefronts. Measurements have been conducted at the system, sub-system and component levels, using an SA developed for this purpose and employing a uniform circular array. This has enabled the error introduced by an implemented system to be examined. Calibration procedures are developed to overcome these implementation limitations. The cause and effects of these errors are examined, and system manufacturing tolerances and temporal thermal effects on the analogue sub-systems are shown to be the major contributor to this error; these results are presented and analysed     

A multicast mechanism for UMTS

This article aims to investigate multicast deployment issues and requirements in the context of UMTS networks. We propose a multicast mechanism that supports resource-efficient multicast packet delivery. The proposed scheme allows multicast packets to be transferred in an optimal manner on shared links toward multiple destinations. We describe the mechanisms of the proposed scheme in establishing multicast tunnels within the network and performing group management. We explore the differences between the proposed scheme and the multimedia broadcast/multicast service of the 3GPP, and outline the advantages and disadvantages of both multicast schemes.     

Case analysis of a Cost-Optimal QoS aggregation policy for network mobility

The network mobility reservation protocol was proposed to increase the scalability of QoS provision in moving networks. However, its scalability is undermined when sessions are bursty and short-lived. QoS aggregation addresses this by holding requests at the mobile router for a time before sending a single aggregated reservation to the access network. This letter analyses a cost-optimal QoS aggregation policy under the case of bursty requests, and compares its expected cost efficiency and user waiting time with that of other previously proposed policies. It is shown that the C-policy reduces operator costs compared to other policies, whilst also reducing expected queueing times.