On Qos performance of different voice codecs over ad hoc networks in underground mines

Abstract

Ad hoc networks have been paid more attention recently in underground mines. Due to its flexibility and quick deployment, ad hoc networks are widely used in emergency occasions such as mine collapses when communication infrastructure is destroyed. However, underground mines are harsh environment where corrosive water, dust and toxic and explosive gases are commonly present. And the characteristic of confined space in underground mines will lead to diffraction, attenuation, multipath, scattering and fading phenomena that could interfere with radio signals. In this paper, we will focus on studying performance of underground mines' ad hoc network in a VoIP context by means of simulating VoIP over ad hoc network. We compare the performance of three different codecs, G.711, G.723, and G.729. The results demonstrate that G.723 will obtain highest Mean Opinion Score and is suitable for encoding voice and transmitting through the ad hoc networks.

Study on the Mechanical Properties of ABS Enhanced by Magnesium Hydroxide Whiskers

“…Magnesium hydroxide whiskers(MH) is a new kind of inorganic flame retardant and reinforced material. It with diameter less than 1µm is on the growth of single and extremely subtle crystal fibers in the special control of the synthesis condition [2][3][4][5][6][7][8]. Magnesium hydroxide whiskers can be used in PE, PVC, PP, and unsaturated polyester as reinforcing materials.…”

Study on the Flame Retardant Property of Magnesium Hydroxide Whiskers/PE Composites

“…Magnesium hydroxide whiskers (MH), is a new kind of inorganic flame retardant and reinforced material. The product with diameter less than 1µm is on the growth of single and extremely subtle crystal fibers in the special control of the synthesis condition [3][4][5][6][7][8][9]. Magnesium hydroxide whisker is used as inorganic flame retardants [10][11][12], with the advantages below： non-toxic, inhibiting the smoke, decomposition at 340℃, which is higher 100℃ than aluminum hydroxide，not producing bubbles in the processing.…”

Qos Constrained Communication using Voice Codecs over Multicast Ad Hoc Networks

“…end to end delay and jitter etc. which are quite important for measuring QoS constraints[8].Yi Deng et al[14] did analysis of voice transmission over ad hoc networks established in underground mines using different voice codecs i.e. G.711, G.723, and G.729 etc.…”