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—The design and simulation of coding schemes, Medium Access Control (MAC), and link-layer protocols for future industrial wireless local area networks can be supported by some understanding of the statistical properties of the bit error patterns delivered by a wireless link (which is an ensemble of transmitter, channel, receiver, modems). We present results(More)
This technical report explores the degree of accuracy to which the propagation delay of WLAN packets can be measured using today's commercial, inexpensive equipment. The aim is to determine the distance between two wireless nodes for location sensing applications. We conducted experiments and measured the time difference between sending a data packet and(More)
SUMMARY Quality models predict the perceptual quality of services as they calculate subjective ratings from measured parameters. In this article, we present a new quality model that evaluates VoIP telephone calls. In addition to packet loss rate, coding mode and delay, it takes into account the impairments due to changes in the transmission configuration(More)
—In this paper we present an algorithm that measures the round trip times of IEEE 802.11 MAC packets in order to trilaterate WLAN nodes. We show that if we use packet sequences (e.g., RTS, CTS, DATA and ACK) instead of packet pairs (e.g., DATA and ACK), the TOA measurements can be implemented more easily and a higher observation rate can be achieved. In(More)
IEEE 802.11b compliant WLAN technology is increasingly used for cordless telephone services. Often, a WLAN phone is moved during a call. In the present paper we explore to what extent slow user motion influences the wireless link quality. We conducted extensive measurements with speech over commercial WLAN equipment using an experimental environment(More)
Quality models predict the perceptual quality of services as they calculate subjective ratings from measured parameters. In this paper we present a new quality model that evaluates VoIP telephone calls in order to control their transmission at run-time. In addition to packet loss rate, coding mode and delay it takes into account the impairments due to(More)
If low-rate VoIP is transmitted over congested links, both the coding and the packet rate need to be adapted to achieve the best conversational quality: On an Ethernet network it is better to jointly change packet rate and speech coding rate; in WLAN networks it is sufficient to change the packet rate. We also study whether TCP-friendly rate control(More)
— Depending on the content of speech frames, the quality impairment after their loss differs widely. In previous publications we described an off-line measurement procedure to determine the loss impairment – the importance – of single speech frames. We showed that knowing the importance of frames can enhance the transmission performance of VoIP telephones(More)