Throughput-Received Power Relationship for File Transfer Protocol (FTP) Service in Wireless Mesh Network (WMN)

In Wireless Mesh Network (WMN) the mesh nodes (APs) are configured with the same frequency channel creates a phenomenon called as co-channel interference. The purpose of selecting the same frequency channel is to make sure all the mesh nodes can talk each other within the frequency range. In order to study the effects of this phenomenon together with multipath fading for indoor environment, we have setup a wireless mesh network operating at 2.4GHz inside a 4-floors faculty building. Extensive measurement campaigns have been conducted at each floor. To observe the effects of these phenomena at the application layer perspective, we measure the network throughput of difference services such as the send and receive e-mail (SMTP and POP3) services, file transfer protocol (FTP) services and hyper text transfer protocol (HTTP) services, and mapped it to the physical layer performance parameter; received power. The relationship between the application and physical layers performance parameters is modelled numerically and the results are analyzed. One interesting finding is that the empirical relationship model for wireless mesh network does not follow the common exponential models as known in Wireless Local Area Network (WLAN). We can say that the throughput drop is too small and can be neglected and the average throughput is at 0.02Mbps, 1.0875Mbps, 0.885Mbps and 0.18Mbps for send and received or SMTP and POP3, FTP Get, FTP Put and HTTPtext services over all received powers. The result shows that the effects of both co-channel interference and multipath are very severe and need to be tackled properly in wireless mesh network design and deployment

Cooperative MIMO Communications in Wireless Sensor Networks: Energy Efficient Cooperative MAC Protocol

Multiple sensor nodes can be used to transmit and receive cooperatively and such a configuration is known as a cooperative Multiple-Input Multiple-Output (MIMO) system. Cooperative MIMO systems have been proven to reduce both transmission energy and latency in Wireless Sensor Networks (WSNs). However, most current work in WSNs considers only the energy cost for the data transmission component and neglects the energy component responsible for establishing a cooperative mechanism. In this work, both transmission and circuit energies for both components are included in the performance models. Furthermore, in previous work, all sensor nodes are assumed to be always on which could lead to a shorter lifetime due to energy wastage caused by idle listening and overhearing. Low duty cycle MAC protocols have been proposed to tackle this challenge for non-cooperative systems. Also in this work, we propose a new cooperative low duty cycle MAC protocol (CMAC) for two cooperative MIMO schemes: Beamforming (CMACBF) and Spatial Multiplexing (CMACSM). Performance of the proposed CMAC protocol is evaluated in terms of total energy consumption and packet latency for both synchronous and asynchronous scenarios. All the required energy components are taken into consideration in the system performance modeling and a periodic monitoring application model is used. The impact of the clock jitter, the check interval and the number of cooperative nodes on the total energy consumption and latency is investigated. The CMACBF protocol with two transmit nodes is suggested as the optimal scheme when operating at the 250 ms check interval with the clock jitter difference below 0.6Tb where Tb is the bit period corresponding to the system bit rate

Concept of night city: a new dimension to a city’s economy / Saniah Ahmad Zaki and Mohd Riduan Ngesan.

As an outcome of a comprehensive study on an area of 385.401 acres, a township in Alor Gajah, Malacca, was redesigned based on an innovative idea, ‘concept of night city’. The concept is believed to be economically viable. By using space syntax, an analysis of movement as well as the amount of activity likely to result from the movement is performed on the layout to determine if the redesign functions successfully. Results of the spatial analyses showed improvements in connectivity, integration, intelligibility and synergy levels. Based on the ßndings, the future town of Alor Gajah looks viable spatially

Narrow Bipolar Pulses and Associated Microwave Radiation

Narrow Bipolar Pulses (NBPs) is a special type of intra-cloud lightning discharge activities. It is known with other names also such as Narrow Bipolar Events (NBEs), energetic intracloud events, and Compact Intracloud Discharges (CIDs). NBP signatures have been measured by using various methods such as broadband antenna systems, HF-VHF direct measurement systems (filter-detector receiver), and satellite- based systems. To the best of our knowledge, there are no attempts have been made to measure NBP signatures at microwave region so far. In this paper, observations of microwave radiation from thunderstorms have been made during the northeast monsoon season of 2012 in Malaysia. Broadband fast antenna system and wideband microwave receiver captured simultaneous records of NBPs electric field change and microwave radiation, respectively. The wideband microwave receiver consisted a Low Noise Amplifier (LNA) connected to a Band Pass Filter (BPF) with operating frequencies between 1.5 and 3 GHz. Electrical signals induced by the incident electric fields on a whip antenna with omni directional pattern (E-plane half power beam width 19 degrees and 9 dBi gain) were directed towards the LNA by using a 5 meters 50Ω RG58 coaxial cable. The output electrical signals of the BPF were digitized directly by an oscilloscope at a rate of 2.5 Giga Samples/second. An oscilloscope at a rate of 25 Mega Samples/second digitized the output of electrical signals from the broadband fast antenna system. Strong noise-like burst of microwave radiation pulses associated with NBP events were detected. The total duration of the microwave bursts of the pulses is in the range between 5 and 8 μs meanwhile the total duration of the NBP pulses is in the range between 10 to 25 μs. We will provide detail time- frequency analysis of both NBP and its associated microwave radiation by using wavelet transform method

Adaptive Concurrent Medium Access Control for Wireless Mesh Network

This paper proposes an adaptive concurrent transmission protocol implemented in Wireless Mesh Network (WMN), which reduces the overhead due to signalling of the existing concurrent transmission protocols such as Medium Access Control (MAC) protocol with Acknowledgment and Parallel mechanism (MACA-P), Concurrent MAC with Short Signalling (CMAC-SS) and Distribution Coordination Function (DCF). DFC protocol is widely used and implemented in the existing IEEE 802.11b/g/n standard wireless networks. The use of DCF in WMN reduces the throughput per hop significantly due to exposed node avoidance mechanism such as Ready-to-Send and Clear-to-Send (RTS-CTS) signalling which allows only one transaction per node at one time; meaning that the waiting delay is higher in Wireless Mesh Network (WMN). MACA-P and CMAC-SS protocols introduce concurrent transmission mechanism that allows multiple transactions per hop at one time. The results from the simulation show that the performance of CMAC-SS is better than the MACA-P. However the design of both MACA-P and CMAC-SS considers fixed size of signalling which makes the protocol not scalable when the number of user within the network increases. In order to provide scalability, an adaptive size of signalling is introduced in this paper by manipulating the broadcast nature of the wireless network within the slotted framework. Such adaptive mechanism improves scalability and also the throughput per hop by 45% compared to CMAC-SS when the number of nodes is higher than 10

Wavelet Analysis of The First Pulse of Initial Breakdown Process in Lightning Discharges

The investigation is done using wavelet transformation in order to seek for differences in the initial breakdown process between negative cloud-to-ground flash (CG), positive CG, cloud flash (IC), and isolated breakdown (IB) process. A total of 66 waveforms were selected from the collection of 885 waveforms collected during summer thunderstorm between May and August 2010 at the premise of Uppsala University, Uppsala, Sweden. The recording unit consisted of a flat plate fast electric field broadband antenna measuring system with the sampling rate set to 20 Megasamples per second. The analysis was conducted only on the first pulse for each lightning events and the output from the wavelet transformation is shown as normalized power spectrum plotted in time-frequency domain as shown in Figure 1 below. The first pulses in negative CG are found to radiate intensely in average frequency range between 186 and 1637 kHz. The energy radiated by the first pulses of positive CG mainly concentrated in the average frequency range between 57 and 599 kHz. As for the cloud flash, the first pulses found to be spread out in the average frequency range between 398 and 3656 kHz and for isolated breakdown, the energy spread out between 44 and 279 kHz. The positive CG and IB flashes are tending to radiate at lower frequencies range within smaller range when compared to negative CG and IC. IB has the smallest average frequency range at 235 kHz while the average frequency range of IC and negative CG are more than 10 times and 6 times larger than IB, respectively. It can be speculated that the initial breakdown process of positive CG and IB flashes are most likely initiated from the same discharge process in the thundercloud. On the other hand, the initial breakdown process of negative CG and IC are most likely initiated from different discharge processes

Adaptive Concurrent Transmission Protocol for Wireless Mesh Network

This paper proposes an adaptive concurrent transmission protocol implemented in Wireless Mesh Network (WMN), which reduces the overhead due to signaling of the existing concurrent transmission protocols such as Medium Access Control (MAC) protocol with Acknowledgment and Parallel mechanism (MACA-P), Concurrent MAC with Short Signaling (CMAC-SS) and Distribution Coordination Function (DCF). DFC protocol is widely used and implemented in the existing IEEE 802.11b/g/n standard wireless networks. The use of DCF in WMN reduces the throughput per hop significantly due to exposed node avoidance mechanism such as Ready-to-Send and Clear-to-Send (RTS-CTS) signaling which allows only one transaction per node at one time; meaning that the waiting delay is higher in Wireless Mesh Network (WMN). MACA-P and CMAC-SS protocols introduce concurrent transmission mechanism that allows multiple transactions per hop at one time. The results from the simulation show that the performance of CMAC-SS is better than the MACA-P. However the design of both MACA-P and CMAC-SS considers fixed size of signaling which makes the protocol not scalable when the number of user within the network increases. In order to provide scalability, an adaptive size of signaling is introduced in this paper by manipulating the broadcast nature of the wireless network within the slotted framework. Such adaptive mechanism improves scalability and also the throughput per hop by 45% compared to CMAC-SS when the number of nodes is higher than 10

Electric Field Waveforms of Very Close Negative Cloud to Ground Flashes

Negative cloud-to-ground brings down negative charge from cloud to ground. In this paper, observations of the characteristics of fast and slow electric field within reversal distance (less than 7-8 km from lightning sensor) are reported. A total of four negative cloud to ground lashes detected very close to our measurement site in Universiti Teknikal Malaysia Melaka on 12th November 2019 were selected for analysis. The captured waveforms are compared with the location data provided by Tenaga Nasional Berhad Research (TNBR) for validation purposes. It can be observed that electric field changes of stepped leader and return stroke are always positive whether beyond or within reversal distance. Meanwhile, for cloud activities, the electric field change is always negative within reversal distance

MAC protocol for cooperative MIMO transmissions in asynchronous wireless sensor networks

Cooperative MIMO schemes can reduce both transmission energy and latency in distributed wireless sensor networks (WSNs). In this paper we develop a new Cooperative low power listening (LPL) Medium Access Control (MAC) protocol for two cooperative MIMO schemes: Optimal Beamforming (BF) and Spatial Multiplexing (SM). We develop analytical models for the total energy consumption and packet latency for both schemes and analyse the proposed MAC protocol in term of the total energy consumption and packet latency with imperfect synchronisation due to clock jitter. The impact of the clock jitter, the check interval and the number of cooperative nodes on the total energy consumption and latency are investigated. We observe that the Cooperative LPL MAC with Optimal BF is the most promising configuration and it is optimal when then number of co-operating nodes M=2 and jitter difference is below 0.6Tb