Overlap-add methods for time-scaling of speech
Speech Communication
On the scalability of IEEE 802.11 ad hoc networks
Proceedings of the 3rd ACM international symposium on Mobile ad hoc networking & computing
Computer Networks: The International Journal of Computer and Telecommunications Networking
Re-routing Instability in IEEE 802.11 Multi-hop Ad-hoc Networks
LCN '04 Proceedings of the 29th Annual IEEE International Conference on Local Computer Networks
Security issues in IEEE 802.11 wireless local area networks: a survey: Research Articles
Wireless Communications & Mobile Computing - Special Issue: Emerging WLAN Apllications and Technologies
Transmission of VoIP Traffic in Multihop Ad Hoc IEEE 802.11b Networks: Experimental Results
WICON '05 Proceedings of the First International Conference on Wireless Internet
Lessons gained from test beds of ad hoc networks and perspectives
REALMAN '06 Proceedings of the 2nd international workshop on Multi-hop ad hoc networks: from theory to reality
Adaptive playout scheduling and loss concealment for voice communication over IP networks
IEEE Transactions on Multimedia
Design and implementation of a WLAN/cdma2000 interworking architecture
IEEE Communications Magazine
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The IEEE 802.11 WLAN technology has become the de facto standard for wireless Internet access. The spotty coverage of WLAN access points, however, confines the applicability of many real-time services such as VoIP within the boundary of the WLAN service area. In this paper, we investigate the problem of enhancing VoIP service for ubiquitous communication in a WLAN with spotty service area. We consider a university campus that has an established infrastructure for supporting SIP-based VoIP service through either wired or wireless data networks. The campus WLAN service does not have 100% full coverage, and hence users cannot make untethered VoIP calls anywhere on campus. The goal of this paper is to overcome the limitations of such ''dead spots'' for motivating the use of campus IP telephony service. To proceed, we start with two approaches called one-hop extension and dual-mode communication. The first approach uses multi-hop relay to extend the WLAN coverage, while the second approach leverages the availability of dual-mode handsets for ubiquitous voice communication. We implement the two approaches, and evaluate their performance in the campus testbed environment. We find that while the two approaches can effectively allow voice communication in WLAN dead spots, they have one common problem as the potential lack of support for voice call continuity that can cause degradation of the speech quality to an active call. We adopt a cross-layer solution based on signal processing algorithms to address the problem, thus achieving seamless voice call continuity while enabling ubiquitous voice communication on campus. Testbed evaluation shows promising results for future research along the proposed direction.