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Multimedia Communication and Networking Issues
Published in Sreeparna Banerjee, Elements of Multimedia, 2019
These considerations prompt the need for examining the QoS for multimedia data communication. The parameters which determine QoS are as follows: Data rate is the measure of the transmission speed in kilobits per sec, or megabits per sec.Latency is the maximum frame or packet delay. This indicates the maximum time needed from transmission to reception and is measured in milliseconds (ms). If the round-trip delay exceeds 50 ms in voice communication, then echo becomes perceptible; when the one-way delay is longer than 250 ms, talker overlap occurs.Packet loss or error gives the percentage error of the packet data transmission.Jitter or delay jitter is a measure of the smoothness of the audio/video playback. Jitter is related to the variance of frame/packet delays.Sync skew is a measure of the multimedia data synchronization, in ms. For accurate lip synchronization, the limit of sync skew is ±80 ms between audio and video. The general acceptable value is ±200 ms.
Wireless Networking Standards (WLAN, WPAN, WMAN, WWAN)
Published in K.R. Rao, Zoran S. Bojkovic, Dragorad A. Milovanovic, Wireless Multimedia Communications, 2018
K.R. Rao, Zoran S. Bojkovic, Dragorad A. Milovanovic
With regard to QoS, the IEEE 802.20 MAC and PHY layers are the primary components responsible for providing efficient QoS to users. The system should be intelligent enough to recognize that a user may be using several different applications with differing QoS requirements at the same time. For example, the user may be browsing the web and participating in a video conference that has separate audio and video streams associated with it. Clearly, the two services differ enough that they need separate QoS negotiations. The system should be able to recognize and categorize various kinds of IP traffic based on specific packet flows associated with each, such as delay, bit rate, error rate, and jitter. The bit rate, or data rate, should scale from the lowest allowable data rate to the maximum rate supported by the MAC/PHY. Delivery delay, also known as latency, should be in a range from 10 ms to 10 s. It should be noted, however, that 10 ms is the targeted objective for round-trip delay time, and that even 50 ms is considered by the IEEE 802.20 working group to be way too high. The error rate, after corrections have been made in the MAC and PHY, should be in the range from 10−8 to 10−1. Delay variation, also known as jitter, should fall in the range from 0 to 10 s.64
Land Mobile Radio and Professional Mobile Radio: Emergency First Responder Communications
Published in Jerry D. Gibson, Mobile Communications Handbook, 2017
The algorithmic delay of the TETRA voice codec is 30 ms plus an additional 5 ms look ahead. Such a delay is not prohibitive, but a more thorough calculation in the standard estimates an end-to-end delay of 207.2 ms, which is at the edge of what may be acceptable for high-quality voice communications. A round trip delay near 500 ms is known to cause talkers to talk over the user at the other end, thus causing difficulty in communications, especially in emergency environments [10,11].
An international value chain of China’s manufacturing industry based on big data technology
Published in Journal of Control and Decision, 2023
Liu Ning, Shen Zhifeng, Zang Jianglong, Li Xialing
Considering the queuing delay, we assume that the round-trip delay can be modelled as equation (6), where represents the fixed propagation delay, represents the link capacity, and represents the queue length of a single-congested router, which is a high-order polynomial function of time . Propagation delay is the time it takes for a signal to travel from one point to another over a communication channel, and it affects the performance of the TCP protocol. The round-trip delay (RTD) in TCP includes propagation delay and other communication path delays. Propagation delay is an important factor for long-distance communications and can limit overall throughput. It can be reduced by using faster communication channels or intermediate devices. A single-congested router is a networking equipment that is suffering congestion because to a traffic overload. This indicates that there is a backlog of packets that need to be forwarded because the router is receiving more data packets than it can process Po et al, 2020. As a result, in networking, the relationship between the queue length and duration of a single-congested router may be represented by a high-order polynomial function. Compared to simpler functions, this function enables more precise modelling of the queue length with time. Regression analysis may be used to collect information on the queue length at various periods in time and fit the data to generate such a function. Therefore, the queuing delay can be expressed as (Chen, 2019).