The complementary characteristics of universal mobile telecommunication system (UMTS) and 802.11 wireless local area network (WLAN) networks make them attractive for integration to offer the best of both technologies. However to make their integration effective, seamless mobility between the two networks is necessary. In this paper we address mobility management procedures within and between UMTS and 802.11 WLAN for various integration scenarios. For each integration option we consider, we give the interaction between various networks elements and new procedures required to ensure seamless mobility.

High capacity real-time data communications in sensor networks usually require multihop routing and ad hoc routing protocols. Unfortunately, ad hoc routing protocols usually do not scale well and cannot handle dense situations efficiently. These two issues-scalability and density-are the major limitations when we apply ad hoc routing schemes to sensor networks. Passive clustering (PC) classifies ad hoc/sensor nodes into critical and noncritical nodes without any extra transmission. By 2-b piggybacking and monitoring user traffic (e.g., data polling requests from a sink), PC deploys the clustering structure "for free". Moreover, PC makes even the first flooding as efficient as all subsequent floodings (i.e., no initialization overhead). PC introduces many benefits, including efficient flooding and density adaptation. As a result, PC reduces control overhead of ad hoc routing protocols significantly and, as a consequence, enables ad hoc routing in large, dense sensor networks. The resulting structure can be utilized in cluster-based ad hoc network/sensor networking as well as for active node selection.

We present alternatives for the integration of Mobile Internet Protocol (Mobile IP) versions with IP Security (IPSec) to secure IP communications over the wireless link. We focus on network layer security and provisioning of security services while roaming to a foreign network, without having to trust the foreign network. Additionally, such a scheme does not require the correspondent host (CH) to participate in protecting the wireless link. We note, however, that end-to-end security can still be provisioned, should the end user and CH have the capability to do so. Finally, our implementation allows seamless mobility at the network layer, while supporting higher layer services and security features.

We derive precise as well as good approximate statistical characterizations, such as probability density functions and statistical moments of capacity, for different MIMO wireless channels. The characterizations help us to understand and predict the capacity gain expected from the MIMO technique, in terms of system parameters and channel dimension. It also helps us to design space-time modulation schemes that can take full advantage of the MIMO link for various wireless channels.

A personal communications services (PCS) system that provides access to, and interworks with, the ATM network will have the capability to support future multimedia services. PCS access to fixed ATM networks is one of the wireless access scenarios being considered by the ATM Forum for standardization. This paper provides a system level description of a PCS-to-ATM interworking scenario. It proposes a variable-rate forward error correction (FEC) coding scheme for the wireless physical (PHY) layer that is based on rate-compatible punctured convolutional (RCPC) coding. Through numerical analysis, using a two-ray Rayleigh fading channel model, it is shown that RCPC coding at the wireless PHY layer can be effective in providing reliable PCS access to the ATM infrastructure network. RCPC coding at the wireless PHY can be augmented with ARQ at the data link control layer (DLC) to form a hybrid ARQ/FEC protocol.

Computer simulation results are presented for the loop range coverage of an asymmetric digital subscriber lines (ADSL) system that uses the quadrature amplitude modulation (QAM) signaling scheme, ADSL performance is evaluated in the presence of background additive white Gaussian noise (AWGN), and crosstalk noise from existing services in the local telephone loop plant. It is shown that coverage of the extreme carrier serving area (CSA) is possible at transmission rates that are well above the existing T1 rate.

This paper presents design considerations for future-generation personal communication networks (PCN) that integrate wireless access with the broadband wireline asynchronous transfer mode (ATM) network. Apart from the wireless ATM network architecture, some of the other issues that we report on include the design of the wireless-to-wireline network interfaces, and the specification of a wireless protocol reference model. Two examples are given of ways to accomplish diversity and related handoffs in the wireless ATM network.

The growing demand to transmit high-speed digital data in many local area networks (LANs) and digital subscriber lines (DSLs) has resulted in a wide variety of transmission systems that have to co-exist on twisted wire copper pairs. In this paper, we address the problem of maintaining spectrum compatibility between various services that may use different transmission technologies, by shaping in an optimal manner, the power spectral density (PSD) of the transmit signal. A multitone modulation scheme such as discrete multitone (DMT) has the flexibility of optimizing the power spectrum over more than one (disjoint) frequency band, and is suitable for twisted pair subscriber loops, and other transmission media, where the optimized transmit spectrum is likely to occupy more than one frequency band. DMT has been selected by the American National Standards Institute (ANSI) T1E1.4 Standards Committee as the standard modulation scheme for asymmetric DSL (ADSL). The results presented in this paper are for the specific application of DMT to transport ADSL payloads of over 6 Mb/s from the network to the customer. We consider spectral compatibility between ADSL, the T1 repeater system, high bit-rate DSL (HDSL), and integrated services digital networks (ISDN) basic rate access (BRA) systems. The simulation results show that: 1) one can customize the transmit PSD to achieve optimum ADSL performance in a specified noise environment; 2) this optimum performance can result in as much as approximately 6 dB improvement in signal-to-noise ratio (SNR) when compared to the nonoptimized PSD chosen by the T1E1.4 committee; 3) in achieving the above improvements, the total maximum transmit power is still consistent with the limit set by the T1E1.4 committee. Further work is required to support the simulation results with measured data. The mathematical analysis is based on the use of Lagrange multipliers to solve the constrained optimization problem, and is easily extended to other asymmetric and full-duplex wireline transmission systems operating at much higher data rates. The practicality of implementing the proposed optimization routine requires further investigation

This letter presents an analytical method to numerically evaluate the bit error Probability (BEP) performance of a quadrature amplitude modulation (QAM) transmission system in the presence of impulse noise. This work facilitates characterization of the two-wire twisted-pair loop plant for high-speed digital communications. Simulation results are presented to demonstrate the effectiveness of this approach using parameters that are typical of the recently proposed Asymmetric Digital Subscriber Lines (ADSL) for high-speed digital transmission over local copper telephone loops.>

A suboptimum, linear, minimum mean-squared error (MMSE) data communication receiver that is based on a parametric model for a linear, time-invariant, or slowly time-varying channel is shown to perform well at reasonable input signal-to-noise ratios (SNRs) and for short training periods. The receiver makes use of a fractionally spaced equalizer (FSE) design whose time span is a single symbol period. It is assumed that a parametric model, with parameter estimates that are obtainable from a training sequence prior to data acquisition, is adequate for representing the impulse response of the equivalent baseband channel.>

Two improvements are presented for adaptive equalization of communication channels for data transmission. One of them is designed to mitigate the effects of impulsive noise on the channel through data-adaptive nonlinear filtering. The other improvement uses low-rank approximation techniques to adaptively prefilter the received training waveform which is to be used for adaptive equalization. This permits successful equalization to be carried out with less received data and at lower values of signal-to-noise ratio (SNR).