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Universal Mobile Telecommunications System (UMTS) is a third-generation cellular network that enables high-speed mobile Internet access. This paper evaluates and compares the performance of two well-known versions of Transmission Control Protocol (TCP), namely, Vegas and Reno, in a UMTS environment. Bulk data transfer was considered in the simulation with varying radio channel conditions. We assume that data losses are only due to the radio channel. Simulation results show that the performance of Vegas is worse than Reno even though data losses incurred by the radio channel are completely recovered by the UMTS radio link control layer. This has led us to conduct a thorough investigation on the behavior of Vegas in order to identify the cause of performance degradation in Vegas. The poor performance of Vegas is attributed to the UMTS radio interface characteristics which resulted in large and highly variable TCP round-trip times. Vegas would interpret the round-trip time variation as a sign of congestion, and consequently, shrink its window size which reduces the transmission rate. Furthermore, a sudden increase in the instantaneous round-trip time can trigger spurious timeouts at the TCP sender using Vegas which performs unnecessary retransmissions. Spurious timeouts can lead to significant throughput reduction. Reno, on the other hand, does not show any abnormality and delivers the expected performance.

Fiber to the Rooms paradigm is gaining a lot of attention recently. In this paradigm, the last mile wireless (viz., IEEE 802.11×) connectivity, backed by optical fiber infrastructure, supports uncompressed high data rate while rendering seamless mobility and higher frequency reuse. To provide cost effective solution, Access Points (AP) in each room are replaced by distributed antennas. A centralized home communication controller provides AP functionality. WiFi inherently suffers from the problem of hidden nodes (HN). This problem persists even in the Fiber-Wireless (Fi-Wi) hybrid world causing degradation of throughput. In this paper we propose a Multi-User Multiple Input Multiple Output (MU-MIMO) uplink technique using both spatial and optical wavelength multiplexing. This scheme can increase the data rate significantly through diversity gain or spatial multiplexing. The proposed scheme is compared against an eminent joint decoding technique called Successive Interference Cancellation (SIC) adapted for operability in Fi-Wi indoor environment. The main contribution is that we propose an unique MU-MIMO uplink technique for Fi-Wi Hybrid indoor environment which address the problem of HN. We evaluate the performance of our proposed MU-MIMO technique based on ergodic capacity and probability of bit error.

Energy, especially Electricity has become a critical concern of society. The generation and distribution are, to a large extent, not matched with each other. There are many initiatives to balance the load on the Grid vis-à-vis production and consumption. Recently, technology has made it possible to generate small amounts of energy in each household with solar, thermal, wind and other sources. With storage devices, it is possible to use the generated energy at the sources i.e., localized generation and consumption of energy. The system can be made efficient and possibly design a zero or positive-energy home with the use ICT infrastructure, wireless sensor networks, in particular. This paper proposes a three-layered architecture for this system and also lists several associated issues and challenges.

The current service- and device discovery protocols are not platform- and network independent Therefore, proxy servers will be needed to extend the range of IP-based discovery protocols to non-IP domains. We developed an architecture of a proxy that enables UPnP devices and services to be discovered on the Bluetooth network and vice versa, and allows Bluetooth devices and UPnP control points to access and utilize services located on devices in the other network. We managed to keep all functionality needed for effective proxying running on a single device, e.g. the mobile phone or the Residential Gateway. © 2007 IEEE.

Personal Networks (PN) are future communication systems that combine wireless and infracuture based networks to provide users a variety of services anywhere and anytime. PNs introduce new design challenges due to the heterogeneity of the involved technologies, the need for self-organization, the dynamics of the system composition, the application-driven nature, the co-operation with infrastructure-based networks, and the security hazards. This paper discusses the challenges of security and QoS provisioning in designing self-organized personal networks and combines them all into an integrated architectural framework.

Universal Mobile Telecommunications System (UMTS) is a third-generation mobile communications system that supports wireless wideband multimedia applications. This paper investigates the video quality attained in streaming MPEG-4 video over UMTS networks using an integrated tool environment, which comprises an MPEG-4 encoder/decoder, a network simulator and video quality evaluation tools. The benefit of such an integrated tool environment is that it allows the evaluation of real video sources compressed using an MPEG-4 encoder. Simulation results show that UMTS Radio Link Control (RLC) outperforms the unacknowledged mode. The latter mode provides timely delivery but no error recovery. The acknowledged mode can deliver excellent perceived video quality for RLC block error rates up to 30% utilizing a playback buffer at the streaming client. Based on the analysis of the performance results, a self-adaptive RLC acknowledged mode protocol is proposed.

This paper discusses the research issues that need to be addressed in order to create a personal distributed environment where people interact with various companion, embedded, or invisible computers not only in their close vicinity but potentially anywhere. These systems are called personal networks (PNs). They constitute a category of distributed systems with very specific characteristics. They are configured in an ad hoc fashion, as the opportunity and the demand arise, to support personal applications. PNs consist of communicating clusters of personal digital devices, devices shared with other people and even infrastructure-based systems. At the heart of a PN is a core Personal Area Network (PAN), which is physically associated with the owner of the PN. Unlike the present PANs that have a geographically limited coverage, the Personal Operating Space, PNs have an unrestricted geographical span, and incorporate devices into the personal environment regardless of their geographic location. In order to do this they need the services of infrastructure-based networks and ad-hoc networks to extend their reach. A PN extends and complements the concept of pervasive computing. We show that PNs introduce new design challenges due to the heterogeneity of the involved technologies, the need for self-organization, the dynamics of the system composition, the application-driven nature, the co-operation with infrastructure-based networks, and the security hazards. We discuss the impact of these problems on network design, assess present and proposed solutions, and identify the research issues.

We describe a source-rooted WDM multicast tree construction protocol to support IP dense mode multicast routing protocols in all-optical lambda-switched networks. Using a receiver-initiated approach, the protocol relies on a mechanism that collects information on the capabilities of WDM nodes. This mechanism provides receivers with sufficient information to setup WDM multicast trees in networks consisting of nodes with heterogeneous WDM capabilities. Knowledge of the network topology, group-wide membership information and capability of every WDM network node is not required.

This report gives an overview of some of the protocol and networking design issues that have been addressed in Flamingo, a major ongoing project which investigates the use of WDM optical technology in local access networks. Quality of service delivery and wavelength assignment are focused on in this report. A brief introduction to optical networks and WDM as well as a brief description of Flamingo are also included in this report.

The Orwell and ATMR basic access mechanisms are modelled in this paper. The full slots are either released or reused by the destination station. The traffic matrix is fully symmetric, and a station may send to itself, as well. The new approximate analytic model is based on a random polling model with the Markovian server routing. Its accuracy is proved by comparing to the simulations results.

The main theme of this paper is the presentation of some critical issues such as transcoding, transport interworking, handover, congestion control and network scalability, that influence the integration of the UMTS and B-ISDN. Solutions to these issues will also be discussed. Furthermore, we will address a number of quantitative (i.e. performance) aspects of an integrated UMTS/B-ISDN system.