Overload Control for Signaling Congestion of Machine Type Communications in 3GPP Networks

<div><p>Because of the limited resources on radio access channels of third generation partnership projection (3GPP) network, one of the most challenging tasks posted by 3GPP cellular-based machine type communications (MTC) is congestion due to massive requests for connection to radio access network (RAN). In this paper, an overload control algorithm in 3GPP RAN is proposed, which proactively disperses the simultaneous access attempts in evenly distributed time window. Through periodic reservation strategy, massive access requests of MTC devices are dispersed in time, which reduces the probability of confliction of signaling. By the compensation and prediction mechanism, each device can communicate with MTC server with dynamic load of air interface. Numerical results prove that proposed method makes MTC applications friendly to 3GPP cellular network.</p></div

Access delay with different number of MTC device.

<p>Access delay with different number of MTC device.</p

Parameters for evaluations.

<p>Parameters for evaluations.</p

Probability of confliction comparison with the traditional access dispersion mechanism (M = 1000).

<p>Probability of confliction comparison with the traditional access dispersion mechanism (M = 1000).</p

Scenario for machine type communication.

<p>Scenario for machine type communication.</p

Probability of confliction with different number of devices.

<p>Probability of confliction with different number of devices.</p

Exogenous PABA improves thermotolerance of strain <i>8213</i>.

<p>(A) Strains <i>02</i> and <i>8213</i> mycelium culture were supplied with or without 5 mg/L PABA, followed by high temperature treatment at 33°C for 48 hours, the images were taken at the indicated time post-heat stress. The control groups were cultured under regular temperature of 23°C. (B) Dose-dependent protection by PABA of mycelium intactness under heat stress at 33°C for 48 hours. Strain <i>02</i> and strain <i>8213</i> were treated with different concentrations of PABA followed by high-temperature treatment at 33°C for 48 h, and the percentage of intact mycelia was counted. The intact mycelia percentage was calculated as compared to the control group (23°C). Three independent biological replicates were performed. Data are expressed as average ± SEM. Unpaired t-tests were performed between samples with and without PABA addition within each strain, respectively, ns: P>0.05, *: P<0.05, **: P<0.01.</p

Transgenic overexpression of PABA synthase improves thermotolerance of strain <i>8213</i>.

<p>(A) Relative mRNA level of <i>Pabs</i> gene of strains <i>02</i>, <i>8213</i> and two <i>Pabs</i>-overexpressing transgenic strains <i>TB-2</i> and <i>TB-3</i> (derived from <i>8213</i>) under normal temperature (23°C) and heat stress (33°C). The mRNA of corresponding samples was extracted and analyzed after 24 hours of treatment. (B) The PABA content of strains <i>02</i>, <i>8213</i> and <i>TB-2</i> and <i>TB-3</i> under normal temperature (23°C) and heat stress (33°C) for 3 days. The PABA content of corresponding samples was extracted and measured after 3 days of treatment. (C) The mycelia growth of Strains <i>02</i>, <i>8213</i> and <i>TB-2</i> and <i>TB-3</i> under normal temperature (23°C) and heat stress (33°C). Mycelia cultures were photographed after 2 weeks of treatment. (D) The mycelia elongation of strains <i>02</i>, <i>8213</i> and <i>TB-2</i> and <i>TB-3</i> under normal temperature (23°C) and heat stress (33°C). The mycelia length is measured after 14 and 21 days of treatment. Three independent biological replicates were performed for each analysis. Data are expressed as average ± SEM. Unpaired t-tests were performed between strain <i>8213</i> and all other strains as indicated within each treatment condition, ns: P>0.05, *: P<0.05, **: P<0.01.</p

PABA mediates the accumulation of defense-related proteins in <i>02</i>, <i>8213</i> and <i>TB-2</i> under heat stress.

<p>(A) Defense-related proteins HSPs and Chitinase accumulated more in thermotolerant strain <i>02</i> than in thermo-sensitive strain <i>8213</i> under heat stress (33°C). (B) Exogenous PABA (1 mM) application increases accumulation of HSPs and Chitinase in <i>8213</i> under heat stress (33°C). (C) PABA synthase inhibitor Sulfanilamide (0.1 mM) decreases accumulation of HSPs and Chitinase in <i>02</i> under heat stress (33°C). D) <i>Pabs</i>-overexpressing transgenic line <i>TB-2</i> accumulates more HSPs and Chitinase than the parent strain <i>8213</i> under heat stress (33°C). Three independent biological replicates were performed for each sample.</p

Schematic model for the role of PABA in enhancing thermotolerance of mushroom.

<p>See Discussion for details.</p