M/D/C queue with priority: application to trunked mobile radiosystems

A procedure is presented for estimating the mean waiting time in an M/D/C queue with two levels of nonpre-emptive priority. The approximation gives a maximum relative error of 10% for heavy load and is greater than the simulated results. This makes the procedure useful for evaluating trunked radio systems     

Design and Modelling of Internode: A Mobile Provider Provisioned VPN

This paper presents the design and architecture of a mobile Provider Provisioned VPN (PPVPN) together with a performance evaluation oriented model that allows first estimates of the VPN set-up delay to be computed. At the same time, some consequences of the discussion can be applied to the design of the VPN configuration parameters. Many different technologies and protocols are used: access is supplied through GPRS or WaveLANs, IP mobility is supported by Mobile IP, and the VPN is based on the IPSec protocol from IPv4. Also, PKI security is used to protect some registration processes. The proposed model is useful for planning the necessary capacity and resources of future mobile PPVPNs.     

Power control at the combiner output to maximize the uplinkcapacity on a cellular spread spectrum system

The benefits of applying maximal ratio combining instead of selection combining when using macrodiversity in a cellular code-division multiple access (CDMA) system were studied. In particular, using maximal ratio combining with power control made at the combiner output, and assuming equal interference at every base station, we provide a simple proof to show that we can achieve on the uplink the same capacity per cell as with an isolated cell. On extending the study to a practical case with a limited number of cells in macrodiversity in comparison with the unrestricted theoretical case, we found that the results on cell capacity with maximal ratio combining were quite close to the results with an isolated cell     

Frequency assignments in IEEE 802.11 WLANs with efficient spectrum sharing

As the number of WLAN users grows, the need to perform efficient radio resource management strategies becomes essential due to the fact that most popular technologies, those based on IEEE 802.11 standards, use unlicensed frequency bands. A good channel assignment improves the network performance, producing benefits that are perceived by the users and also by the network administrators. In this paper, we present a new frequency management scheme for IEEE 802.11 WLANs in the 2.4 GHz ISM band that minimizes interference to increase the throughput available to client stations by adapting a weighted DSATUR algorithm for graph coloring. The algorithm takes both co‐channel and adjacent channel interference into account, and makes use of all available channels instead of the traditional non‐overlapping three. In this way, collisions as well as transmission errors are minimized, thus improving the network capacity and the user experience. Different architectures are discussed for the implementation of our approach, including the possibility to incorporate client stations into the management system. Copyright © 2008 John Wiley & Sons, Ltd.     

Deploying Large-Scale IEEE802.11 Networks Using IP Paging with Link-Specific Capabilities: A Standard Compliant Approach and its Performance Analysis

IEEE802.11 is a layer two technology that offers limited mobility support. It suffers from scalability problems caused by the performance of the mechanisms related to the address resolution and the discovery and maintenance of the path information. In this paper, we propose using IP paging with link-specific capabilities to solve this problem. The need of these capabilities is justified showing the limitations of pure-IP solutions when they interact with IEEE802.11 specific functions, mainly the power save mode (PSM). Then, a comprehensive proposal for an IP paging solution that is an extension of the Mobile IPv4 Regional Registration (MIPv4-RR) protocol is presented. Its strengths lie in the fact that there are no interaction problems with PSM, and it is fully compliant with existing IEEE802.11 devices. Finally, in order to show the excellent scalability of our link-specific solution, we carry out an analytical study of its mobility signaling and compare it with the standard MIPv4-RR protocol and IIPP (Integrated IP Paging Protocol), another IP paging solution that does not implement link-specific functions.     

Web browsing optimization over 2.5G and 3G: end‐to‐end mechanisms vs. usage of performance enhancing proxies

2.5 Generation (2.5G) and Third Generation (3G) cellular wireless networks allow mobile Internet access with bearers specifically designed for data communications. However, Internet protocols under‐utilize wireless wide area network (WWAN) link resources, mainly due to large round trip times (RTTs) and request‐‐reply protocol patterns. Web browsing is a popular service that suffers significant performance degradation over 2.5G and 3G. In this paper, we review and compare the two main approaches for improving web browsing performance over wireless links: (i) using adequate end‐to‐end parameters and mechanisms and (ii) interposing a performance enhancing proxy (PEP) between the wireless and wired parts. We conclude that PEPs are currently the only feasible way for significantly optimizing web browsing behavior over 2.5G and 3G. In addition, we evaluate the two main current commercial PEPs over live general packet radio service (GPRS) and universal mobile telecommunications system (UMTS) networks. The results show that PEPs can lead to near‐ideal web browsing performance in certain scenarios. Copyright © 2006 John Wiley & Sons, Ltd.