Evaluating the influence of multiplexing schemes and buffer implementation on perceived VoIP conversation quality |
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| Authors: | Jose Saldana Julián Fernández-Navajas José Ruiz-Mas Jenifer Murillo Eduardo Viruete Navarro José I Aznar |
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| Affiliation: | 1. Roxelyn and Richard Pepper School of Communication Sciences & Disorders, Northwestern University, Evanston, IL, USA;2. Department of Psychology, Brain & Mind Institute, University of Western Ontario, London, Canada;3. School of Communication Sciences & Disorders, University of Western Ontario, London, Canada;4. Department of Clinical Neurological Sciences, University of Western Ontario, London, Canada;1. Research Division, Institute of Mental Health/Woodbridge Hospital, Singapore;2. Department of General Psychiatry 1, Institute of Mental Health/Woodbridge Hospital, Singapore;3. Saw Swee Hock School of Public Health, National University of Singapore, Singapore;1. Department of Linguistics, University of Pécs, Hungary;2. Department of General and Evolutionary Psychology, University of Pécs, Hungary;3. Department of Psychiatry and Psychotherapy, Medical Faculty, University of Pécs, Hungary;1. Movement Physiology Research Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Parktown, South Africa;2. Division of Orthopaedics, Charlotte Maxeke Johannesburg Academic Hospital, Faculty of Health Sciences, University of the Witwatersrand, Parktown, South Africa;3. School of Physiotherapy and Exercise Science, Curtin University, Bentley Campus, Perth, Australia;4. Occupational Therapy, Speech Therapy and Social Work, Curtin University, Bentley Campus, Perth, Australia;5. Department of Exercise Sciences, Faculty of Science, University of Auckland, Newmarket, Auckland, New Zealand |
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| Abstract: | This work presents a study of RTP multiplexing schemes, which are compared with the normal use of RTP, in terms of experienced quality. Bandwidth saving, latency and packet loss for different options are studied, and some tests of Voice over IP (VoIP) traffic are carried out in order to compare the quality obtained using different implementations of the router buffer. Voice quality is calculated using ITU R-factor, which is a widely accepted quality estimator. The tests show the bandwidth savings of multiplexing, and also the importance of packet size for certain buffers, as latency and packet loss may be affected. The customer’s experience improvement is measured, showing that the use of multiplexing can be interesting in some scenarios, like an enterprise with different offices connected via the Internet. The system is also tested using different numbers of samples per packet, and the distribution of the flows into different tunnels is found to be an important factor in order to achieve an optimal perceived quality for each kind of buffer. Grouping all the flows into a single tunnel will not always be the best solution, as the increase of the number of flows does not improve bandwidth efficiency indefinitely. If the buffer penalizes big packets, it will be better to group the flows into a number of tunnels. The router processing capacity has to be taken into account too, as the limit of packets per second it can manage must not be exceeded. The obtained results show that multiplexing is a good way to improve customer’s experience of VoIP in scenarios where many RTP flows share the same path. |
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