Melbourne Barton

Statistical characterization of multiple-input multiple-output (MIMO) channel capacity

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.

Unequal error protection for wireless ATM applications

Variable rate error protection will be required to support the broad range of quality of service (QoS) requirements for multimedia services and other applications that are likely to be encountered in future asynchronous transfer mode (ATM)-based wireless networking systems. Performance results are presented for several forward error correction (FEC) coding schemes that can provide unequal error protection (UEP) for messages on the wireless access segment of an ATM-based wireless networking system. UEP is based on punctured (or shortened) convolution, Bose-Chaudhuri-Hocquenghem (BCH), and Reed-Solomon (RS) coding. A rate-compatibility restriction is imposed on the encoder to allow for the use of a single encoder for each type of code, even when the code rates are changed. The example air interface packet (AIP) formats used in this study are the types that are envisaged for various flavors of wireless ATM. It is shown that UEP at the wireless physical layer is a feasible strategy to provide variable rate error protection for the types of services and applications that are likely to be encountered in future ATM-based wireless networking systems.

On the performance of an asymmetrical digital subscriber lines QAM transceiver

The author presents an analysis of an asymmetrical digital subscriber line (ADSL) transceiver that uses the quadrature amplitude modulation (QAM) passband transmission system. Output signal-to-noise ratio curves versus carrier and guardband frequencies are presented for the 16-, 64-, and 256-point rectangular constellations, assuming ADSL impairments consisting of self-far-end crosstalk, thermal noise generated by the loop, and receiver noise that is generated primarily by amplifiers in the front-end of the receiver. The simulation results show that an ADSL system with these impairments is viable even on loops that are at the extreme range of the loop plant. In addition, 16-QAM signaling generally performs better than any of the other constellations. The study assumed perfect timing and carrier recovery.<<ETX>>

Performance analysis of Packet Loss Concealment in mobile environments with a two-state loss model

This paper presents and exercises a model to estimate the performance of Packet Loss Concealment (PLC) in wireless field environments. In particular, we estimate the probability of successfully receiving a random packet transmitted over an unreliable wireless link where a packet loss concealment algorithm such as the IETFs RFC 2198 standard schemes 1 and 2 are used. The model assumes a channel with a two-state loss system. Results generated are useful in understanding how packet loss concealment schemes can be designed to support high quality for real-time wireless applications such as VoIP on ad hoc networks.

Performance analysis of a multicarrier PACS system

The personal access communications system (PACS) is a 2 GHz band personal communications services (PCS) standard that supports 32 kbps wireless access services for fixed and mobile subscribers. This paper presents a physical layer architecture, and evaluates the performance, of a multicarrier PACS (MPACS) system based on a combination of orthogonal frequency division multiplexing (OFDM) and time division multiple access (TDMA) technologies. It supports nominal user data rates of 32-256 kbps at distances beyond the current range of PACS. For shorter ranges, higher-speed extensions up to 768 kbps are incorporated in the design.

Impulse noise performance of an asymmetrical digital subscriber lines passband transmission system

An analytical method for estimating the bit error probability performance of a quadrature amplitude modulation (QAM) transmission system in the presence of impulse noise is presented. Numerical results are demonstrated, using parameters that are typical of the recently proposed asymmetrical digital subscriber lines (ADSLs) for digital transmission over the local copper telephone loop plant. It is shown that impulse noise can significantly affect the performance of QAM systems, such as the QAM-based ADSL, when they operate on local telephone loops.<<ETX>>