Christopher W. Rice

Design and Characterization of a Full-Duplex Multiantenna System for WiFi Networks

In this paper, we present an experiment- and simulation-based study to evaluate the use of full duplex (FD) as a potential mode in practical IEEE 802.11 networks. To enable the study, we designed a 20-MHz multiantenna orthogonal frequency-division-multiplexing (OFDM) FD physical layer and an FD media access control (MAC) protocol, which is backward compatible with current 802.11. Our extensive over-the-air experiments, simulations, and analysis demonstrate the following two results. First, the use of multiple antennas at the physical layer leads to a higher ergodic throughput than its hardware-equivalent multiantenna half-duplex (HD) counterparts for SNRs above the median SNR encountered in practical WiFi deployments. Second, the proposed MAC translates the physical layer rate gain into near doubling of throughput for multinode single-AP networks. The two results allow us to conclude that there are potentially significant benefits gained from including an FD mode in future WiFi standards.

Measurement and modeling of an ultra-wide bandwidth indoor channel

This paper describes the results of frequency-domain channel sounding in residential environments. It consists of detailed characterization of complex frequency responses of ultra-wideband (UWB) signals having a nominal center frequency of 5 GHz. A path loss model as well as a second-order autoregressive model is proposed for frequency response generation of the UWB indoor channel. Probability distributions of the model parameters for different locations are presented. Also, time-domain results such as root mean square delay spread and percent of captured power are presented.

A statistical path loss model for in-home UWB channels

This paper describes a simple statistical model for evaluating the path loss in residential environments. It consists of detailed characterization of path loss model parameters of ultra-wideband band (UWB) signals having a nominal center frequency of 5 GHz. The proposed statistical path loss model is for the in-home channel and it is based on over 300,000 frequency response measurements. Probability distributions of the model parameters for different locations are presented. Also, time domain results such as RMS delay spread and percent of captured power are presented.

Autoregressive modeling of an indoor UWB channel

Based on frequency domain measurements in the 4.375-5.625 GHz band a channel model for the frequency response of the indoor radio channel is introduced. In particular. a second-order Autoregressive (AR) model is proposed for frequency response generation of the ultra wide band indoor channel. A complete characterization of the model parameters is described along with probability distributions and dependencies between parameters.

IPTV session mobility

This article describes a novel architecture for delivering personalized IPTV experiences to the end users. The framework leverages the IP Multimedia Subsystem (IMS) to quickly enable new innovative, multi-media services. We describe the session flows for a single IPTV session switch between multiple set top boxes (STBs) and between a STB and a PC/mobile device SIP user agent. We also demonstrate how supplementary services like caller ID and advanced telephony features can also be migrated across multiple devices.

IMS-TV: An IMS-based architecture for interactive, personalized IPTV

This article describes a novel architecture for delivering personalized IPTV experiences to end users. The framework leverages the IP Multimedia Subsystem to quickly enable new innovative, multi-media services. We describe the session flows for important use cases, such as accessing the electronic service guide, VoD, fast channel changing, and enhanced parental control services. Important parameters are quantified for the session experience in each of these use cases.

A network-based architecture for seamless mobility services

Given the tremendous growth in mobile voice and data usage and the emergence of new multifunction, multiradio handheld devices, there is an emerging interest in seamless mobility - applications and services that provide service portability and application persistence across multiple network connections. Seamless mobility ultimately allows users to transparently access all of their data and services in a consistent method. This article describes an implementation of a network-based architecture for seamless mobility services that supports the full range of applications voice, data, video, and messaging - using bimode devices that interface to both Global System for Mobile Communications (GSM) and wireless fidelity (Wi-Fi) networks. This solution provides advanced functionality to existing cellular devices, while providing a solid migration path to full IP-based multimedia services. The solution relies on network-based interfaces and systems, providing a multinetwork-capable, scalable solution with a unified service experience for the user from a single device

In-building software radio architecture, design and analysis

An architecture, design, and analysis of a prototype TIA/EIA-136 TDMA in-building software radio base station is presented. The classical radio and software radio related noise and dynamic range components that affect performance are identified and quantified. IF bandwidth and sampling rate requirements are explained. Static receiver sensitivity and two-tone intermodulation test requirements are analyzed. The noise figure, ENOB, and sampling rate also determine the receiver static sensitivity. The analog sections of the radio are designed such that the dynamic range of the A/D converter is optimally designed for acceptable quantization noise at low levels and sufficient headroom for strong levels. The phase noise of the local oscillators (LOs) from both the desired and interfering channels degrades the sensitivity of the receiver; these effects have also been characterized.

mPub: A mobile presence aggregation framework

Presence systems are widely used today to get information of user availability and their willingness to communicate. As presence and Unified Communications (UC) services are viewed as productivity enhancements within enterprises, the need to connect these services across enterprise WANs and MANs becomes more important. Adding to the availability to communicate is the growing use of mobile devices in the workforce. This paper investigates a protocol that can be efficiently supported across mobile networks and between domains of enterprises. Specifically, we propose a compact presence vocabulary that uses HTTP and SMS protocols to publish to a presence server in the network. The proposed architecture extends the current standardization efforts in OMA PAL working group for non-SIP enabled mobiles. We present a reference implementation of the middleware server and the mobile publisher and show by experiments that our compact protocol is bandwidth (38% to 89%) and energy efficient.

Blending of external applications with advanced telephony services in the IP Multimedia Subsystem (IMS)

Advanced feature servers are at the core of enterprise IP telephony, offering traditional services, such as call hold, voicemail and find-me-follow-me. These feature servers have begun to be deployed as IMS Application Servers to support both in-house (premises based) or hosted service (IP Centrex) offerings. At the same time, there exist applications that are external to IMS that can provide a richer communications experience, when integrated. The application layer in IMS allows these external applications to be blended with the advanced telephony features. An example of this is the use of Microsoft Office Communicator for call control. Several current implementations integrate this feature through a back-end proprietary interface to specific feature servers. We present an architecture for generalizing this integration with a CSTA/IMS gateway that can interact with any IMS feature server.