Contextual Bandit Based Rate Adaptation Mechanism for IEEE 802.11 Mobile Wireless LANs

<div>Rate adaptation (RA) is used in IEEE 802.11 WLANs to determine the optimal datarate for a particular channel condition. It becomes especially difficult to determine the optimal datarate for the new High-Throughput WLANs (802.11ac/ax) since the number of available datarates in these standards are very high. Moreover, a mobile environment poses additional challenge in RA as the channel conditions will keep on changing from time to time. In this paper, we propose a Contextual Bandits based Rate Adaptation (ContRA) algorithm for mobile users in IEEE 802.11ac/ax standards. Based on the Received Signal Strength Indicator (RSSI) range that the receiver is currently in, the RA algorithm tries to determine the optimal rate from the rate set suitable for packet transmission in that RSSI range. Performance studies show that the proposed RA algorithm is able to adapt to changing channel conditions and quickly choose a suitable datarate for those channel conditions.</div>

Contextual Bandit Based Rate Adaptation Mechanism for IEEE 802.11 Mobile Wireless LANs

<div>Rate adaptation (RA) is used in IEEE 802.11 WLANs to determine the optimal datarate for a particular channel condition. It becomes especially difficult to determine the optimal datarate for the new High-Throughput WLANs (802.11ac/ax) since the number of available datarates in these standards are very high. Moreover, a mobile environment poses additional challenge in RA as the channel conditions will keep on changing from time to time. In this paper, we propose a Contextual Bandits based Rate Adaptation (ContRA) algorithm for mobile users in IEEE 802.11ac/ax standards. Based on the Received Signal Strength Indicator (RSSI) range that the receiver is currently in, the RA algorithm tries to determine the optimal rate from the rate set suitable for packet transmission in that RSSI range. Performance studies show that the proposed RA algorithm is able to adapt to changing channel conditions and quickly choose a suitable datarate for those channel conditions.</div>

Experimental Study on the Performance of Rate Adaptation Algorithm in IEEE 802.11g Networks

<p>IEEE 802.11 technology provides a low-cost wireless networking solution. In the last few years, we have seen that the demand for high-bandwidth wireless local area networks increases rapidly, due to the proliferation of mobile devices such as laptops, smart phones and tablet PCs. This has driven the widespread deployment of IEEE 802.11 wireless networks to provide Internet access. However, wireless networks present their own unique problems. Wireless channel is extremely variable and can be affected by a number of different factors, such as collisions, multipath fading and signal attenuation. As such, rate adaptation algorithm is a key component of IEEE 802.11 standard which is used to vary the transmission data rate to match the wireless channel conditions, in order to achieve the best possible performance. Rate adaptation algorithm studies and evaluations are always hot research topics. However, despite its popularity, little work has been done on evaluating the performance of rate adaptation algorithms by comparing the throughput of the algorithm with the throughput of the fixed rates. This thesis presents an experimental study that compares the performance ofMikroTik rate adaptation algorithm andMinstrel rate adaptation algorithm against fixed rates in an IEEE 802.11g network. MikroTik and Minstrel rate adaptation algorithm are most commonly used algorithm around the world. All experiments are conducted in a real world environment in this thesis. In a real world environment, wireless channel conditions are not tightly being controlled, and it is extremely vulnerable to interference of surrounding environment. The dynamic changes of wireless channel conditions have a considerable effect on the performance of rate adaptation algorithms. The main challenge of evaluating a rate adaptation algorithm in a real world environment is getting different experiment behaviours from the same experiment. Experiment results may indicate many different behaviours which due to the leak of wireless environment controlling. Having a final conclusion from those experiment results can be a challenge task. In order to perform a comprehensive rate adaptation algorithm evaluation. All experiments run 20 times for 60 seconds. The average result and stand deviation is calculated. We also design and implement an automation experiment controlling program to help us maintain that each run of experiment is following exactly the same procedures. In MikroTik rate adaptation algorithm evaluation, the results show in many cases that fixed rate outperforms rate adaptation. Our findings raise questions regarding the suitability of the adopted rate adaptation algorithm in typical indoor environments. Furthermore, our study indicates that it is not wise to simply ignore fixed rate. A fine selection of a fixed rate could be made to achieve desired performance. The result ofMinstrel rate adaptation evaluation show that whilst Minstrel performs reasonably well in static wireless channel conditions, in some cases the algorithm has difficulty selecting the optimal data rate in the presence of dynamic channel conditions. In addition, Minstrel performs well when the channel condition improves frombad quality to good quality. However, Minstrel has trouble selecting the optimal rate when the channel condition deteriorates from good quality to bad quality. By comparing the experimental results between the performance of rate adaptation algorithms and the performance of fixed data rate against different factors, the experiment results directly pointed out the weakness of these two rate adaptation algorithms. Our findings from both experiments provide useful information on the design of rate adaptation algorithms.</p>

Experimental Study on the Performance of Rate Adaptation Algorithm in IEEE 802.11g Networks

<p>IEEE 802.11 technology provides a low-cost wireless networking solution. In the last few years, we have seen that the demand for high-bandwidth wireless local area networks increases rapidly, due to the proliferation of mobile devices such as laptops, smart phones and tablet PCs. This has driven the widespread deployment of IEEE 802.11 wireless networks to provide Internet access. However, wireless networks present their own unique problems. Wireless channel is extremely variable and can be affected by a number of different factors, such as collisions, multipath fading and signal attenuation. As such, rate adaptation algorithm is a key component of IEEE 802.11 standard which is used to vary the transmission data rate to match the wireless channel conditions, in order to achieve the best possible performance. Rate adaptation algorithm studies and evaluations are always hot research topics. However, despite its popularity, little work has been done on evaluating the performance of rate adaptation algorithms by comparing the throughput of the algorithm with the throughput of the fixed rates. This thesis presents an experimental study that compares the performance ofMikroTik rate adaptation algorithm andMinstrel rate adaptation algorithm against fixed rates in an IEEE 802.11g network. MikroTik and Minstrel rate adaptation algorithm are most commonly used algorithm around the world. All experiments are conducted in a real world environment in this thesis. In a real world environment, wireless channel conditions are not tightly being controlled, and it is extremely vulnerable to interference of surrounding environment. The dynamic changes of wireless channel conditions have a considerable effect on the performance of rate adaptation algorithms. The main challenge of evaluating a rate adaptation algorithm in a real world environment is getting different experiment behaviours from the same experiment. Experiment results may indicate many different behaviours which due to the leak of wireless environment controlling. Having a final conclusion from those experiment results can be a challenge task. In order to perform a comprehensive rate adaptation algorithm evaluation. All experiments run 20 times for 60 seconds. The average result and stand deviation is calculated. We also design and implement an automation experiment controlling program to help us maintain that each run of experiment is following exactly the same procedures. In MikroTik rate adaptation algorithm evaluation, the results show in many cases that fixed rate outperforms rate adaptation. Our findings raise questions regarding the suitability of the adopted rate adaptation algorithm in typical indoor environments. Furthermore, our study indicates that it is not wise to simply ignore fixed rate. A fine selection of a fixed rate could be made to achieve desired performance. The result ofMinstrel rate adaptation evaluation show that whilst Minstrel performs reasonably well in static wireless channel conditions, in some cases the algorithm has difficulty selecting the optimal data rate in the presence of dynamic channel conditions. In addition, Minstrel performs well when the channel condition improves frombad quality to good quality. However, Minstrel has trouble selecting the optimal rate when the channel condition deteriorates from good quality to bad quality. By comparing the experimental results between the performance of rate adaptation algorithms and the performance of fixed data rate against different factors, the experiment results directly pointed out the weakness of these two rate adaptation algorithms. Our findings from both experiments provide useful information on the design of rate adaptation algorithms.</p>

An Efficient Identification Algorithm to Identify Mobile RFID Tags

Tag identification in a fast-moving environment is an emerging challenge for future RFID systems. However, existing literatures on the tag reading protocol design primarily apply to stationary scenarios, which fail to cope with mobile environments with unreliable channel condition. In this paper, we first review various types of prior reading protocols and then discuss a new direction of mobile tag reading by proposing a novel partitioning strategy. This analysis and experimental results show its superiority in achieving reading performance for the UHF RFID system under a mobile environment.

BER of Various Modulation Techniques Under Atmospheric Turbulences

Noise in the communication channel is well established to be a threat to digital bit transmission, resulting in many mistakes at the bit level. Different modulation methods are studied in terms of BER, probability of error and SNR to better comprehend this. In the presence of specific levels of noise in the communication channel, this analysis yields an interesting conclusion that advises the employment of particular modulation methods. A comprehensive analysis of several modulation schemes has been considered. Those include On-Off Key modulation (OOK), Binary Phase Shift Key (BPSK), Quadrature Phase Shift Key (QPSK), Pulse Amplitude Modulation (PAM) and 8-Phase Shift Key (8-PSK). This analysis can aid in the selection of a modulation approach based on the channel condition.

Infants' Preference for Child-Directed Speech Over Time-Reversed Speech in On-Channel and Off-Channel Masking

Purpose This study aims to examine the development of auditory selective attention to speech in noise by examining the ability of infants to prefer child-directed speech (CDS) over time-reversed speech (TRS) presented in “on-channel” and “off-channel” noise. Method A total of 32 infants participated in the study. Sixteen typically developing infants were tested at 7 and 11 months of age using the central fixation procedure with CDS and TRS in two types of noise at +10 dB signal-to-noise ratio. One type of noise was an “on-channel” masker with a spectrum overlapping that of the CDS (energetic masking), and the second was an “off-channel” masker with frequencies that were outside the spectrum of the CDS (distractive masking). An additional group of sixteen 11-month-old infants were tested in quiet and served as controls for the “off-frequency” masker condition. Results Infants preferred CDS over TRS in both age groups, but this preference was more pronounced with “off-channel” masker regardless of age. Also, older infants demonstrated longer looking time for the target stimuli when presented with an “off-channel” masker compared to the “on-channel” masker. Looking time in quiet was similar to looking time in the “off-channel” condition, and looking time for CDS was longer in quiet compared to the “on-channel” condition. Conclusions These findings support the notion that (a) infants as young as 7 months of age are already showing preference for speech in noise, regardless of type of masker; (b) by 11 months of age, listening with the “off-channel” condition did not yield different results than in quiet. Thus, by 11 months of age, infants' cognitive–attentional abilities may be more developed.

Numerical Research of Fujiangsha Waterway Based on a Depth-integrated Hydro-sediment-morphodynamic Model

&lt;p&gt;Fujiangsha waterway is located in the tidal reach of Yangtze River, which is one of the key sections for channel regulation. The channel condition of the waterway is governed by the evolution of the channel bar and point bar. Groins are consequently set on both sides of the channel bar and the left edge of Fujiangsha island. To explore the impact of the regulation works on the evolution of bars and channels, a numerical research is carried out based on a depth-integrated hydro-sediment-morphodynamic model, using the method of nesting large-scale model with local model. The non-negligible impact on the quality and momentum of water flow caused by enormous sediment transport and drastic change of topography, as well as the complex flow condition in both tide and runoff working together, has been taken into account. The simulation successfully reproduces the hydrological process and changes of topography in Fujiangsha waterway. Results show that: 1) there is a silting trend at the head of the channel bar, and the effect of the regulation works in bar protection and sand stabilization is remarkable; 2) The erosion on both sides of the channel bar improves the channel condition, and the hydrodynamic performance of shallow area at the entrance of the south branch has been enhanced; 3) The control on the evolution of point bar is still weak, which will have an adverse effect on channel condition of north branch.&lt;/p&gt;

Greedy Based Radio Resource Allocation Algorithm with Water Filling Power Control Scheme in D2D Underlaying Communication

Device to Device (D2D) is communication between two devices directly without the intervention of eNodeB.This communication can improve sum-rate, spectral efficiency, and decrease the workload of eNodeBbecause using the same spectrum frequency with Cellular User Equipment (CUE). But this communicationshould use the same resource simultaneously with CUE which is called D2D underlaying. This sharingresources also causes interference and should be managed using the resource allocation algorithm. In thiswork, the resource allocation is allocated in a single cell and uplink communication using joint greedyalgorithm with water filling power control scheme. This algorithm is compared with greedy, joint greedy,and greedy algorithm with water filling power control scheme. Joint greedy algorithm works based on thecapacity of eNodeB and D2D pair. While in water filling power control, the power of the user is managedbased on the channel condition and impact to energy efficiency. After all the resource is allocated, theparameter performance of the system is calculated, such as spectral efficiency, energy efficiency, and D2Dfairness. From the simulation result, joint greedy algorithm with water filling power control scheme result29,34 bps/Hz in spectral efficiency, 0.939 x 107 bps/watt in energy efficiency, and 0,996 in D2D fairness.