Performance Improvement Of Mac Layer In Terms Of Reverse Direction Transmission Based On IEEE 802.11n

Medium access control (MAC) layer is one of the most prominent topics in the area of wireless networks. MAC protocols play a big role in improving the performance of wireless networks, and there are many challenges that have been addressed by the researchers to improve the performance of MAC layer in the family of IEEE 802.11. The physical data rate in IEEE 802.11n may reach 600 Mbps, this high data rate does not necessary transform into good performance efficiency, since the overhead at the MAC layer signifies that by augmenting PHY rates the effectiveness is automatically reduced. Therefore, the main objective of next generation wireless local area networks (WLANs) IEEE 802.11n is to achieve high throughput and able to support some applications such as TCP 100 Mbps and HDTV 20 Mbps and less delay. To mitigate the overhead and increase the MAC efficiency for IEEE 802.11n, one of the key enhancements at MAC layer in IEEE 802.11n is a reverse direction transmission. Reverse direction transmission mainly aims to accurately exchange the data between two devices, and does not support error recovery and correction; it drops the entire erroneous frame even though only a single bit error exists in the frame and then causes a retransmission overhead. Thus, two new schemes called (RD-SFF) Reverse Direction Single Frame Fragmentation and (RD-MFF) Reverse Direction Multi Frame Fragmentation are proposed in this study. The RD-SFF role is to aggregate the packets only into large frame, while RD-MFF aggregate both packets and frames into larger frame, then divided each data frame in both directions into subframes, Then it sends each subframe over reverse direction transmission. During the transmission, only the corrupted subframes need to be retransmited if an error occured, instead of the whole frame. Fragmentation method is also examined whereby the packets which are longer when compared to a threshold are split into fragments prior to being combined. The system is examined by simulation using NS-2. The simulation results show that the RD-SFF scheme significantly improves the performance over reverse direction transmission with single data frame up to 100%. In addition, the RD-MFF scheme improvers the performance over reverse direction transmission with multi data frames up to 44% based on network condition. These results show the benefits of fragmentation method in retransmission overhead and erroneous transmission. The results obtained by ON/OFF scheme takes into account the channel condition to show the benefits of our adaptive scheme in both ideal as well as erroneous networks. In conclusion, this research has achieved its stated objective of mitigation the overhead and increase the MAC efficiency for IEEE 802.11n. Additionally, the proposed schemes show a significant improvement over the reverse direction in changing network conditions to the current network state

Design a Novel Reverse Direction Transmission Using Piggyback and Piggyback With Block ACK to Improving the Performance of MAC Layer Based on Very High Speed Wireless LANs

A reverse direction transmission and block acknowledgement are the main features to improve the performance of MAC layer based on next generation wireless LANs. When the data send it in reverse direction from side A to B, side B does not need to send separate ACK, it may wait for a period of time is less than the sender’s time of period to avoid the retransmission at sender and send a piggyback frame (ACK+data) this called piggybacking. Piggyback with block ACK represented in multi data send from side A to B with block ACK request (BAR), side B send block ACK (BA) piggybacking with multi data to side A, this called piggybacking with block ACK. In our scheme here we want to propose a novel reverse direction transmission using piggyback and piggyback with block ACK which is divided each data frame send and receive into subframes and send each subframe separately, if there is an error happened during the transmission only retransmission the corrupted subframe instead of whole frame. We want to implement this work in NS2 simulator. The research contributions are summarized and the piggyback schemes that need to be investigated via high speed wireless LANs are also highlighted

Provisioning Quality of Service of Wireless Telemedicine for E-health Services

Telemedicine is not yet all worked out where it can be utilized constantly or flexibly. But, it has enormous potential to be a tremendous asset to the world and all its civilizations. Telemedicine has had a positive impact on some aspects of patient care. There is no arguing that the contributions it can make have endless possibilities however more time and effort will be needed to organize telemedicine for it to be confidently accepted. Asynchronous telemedicine does not require the simultaneous availability of the source and recipient of patient information. Telemedicine can be roughly characterized as either synchronous or asynchronous. Synchronous telemedicine involves caregivers acquiring and acting upon information about a remote patient in near real-time

Reverse Direction Transmission in Wireless Networks: Review

Reverse direction mechanism is a promising significant development that may lead to promoting the accuracy of TXOP. The transfer, in conventional TXOP operation, is one way direction out of the station which holds the TXOP and which is not applied to some network services using two lane traffic namely VoIP and on-line gaming. Therefore, the conventional TXOP operation enhances only the forward direction transfer, but not the reverse direction transfer. Moreover, reverse direction mechanism makes it possible for the holder of TXOP to reserve unused TXOP time for its receivers which may improve the channel utilization as well as the performance of reverse direction traffic flows. It is well-known that the reverse direction transfer scheme aims mainly to improve the effectiveness and that plays a key role in reducing the overhead and increasing the system throughput. Thus, this paper provides an overview of a research progress in reverse direction transmission scheme over high speed wireless LANs. Moreover, it addresses the reverse direction mechanism that has been proposed for the next generation wireless networks and the ones adopted by IEEE 802.11n standard. Furthermore, it stresses the reverse issues that require to be dealt with in order to bring further progress to the reverse direction transmission

A Review on Framework and Quality of Service Based Web Services Discovery

Selection of Web services (WSs) is one of the most important steps in the application of different types of WSs such as WS composition systems and the Universal Description, Discovery, and Integration (UDDI) registries. The more available these WSs on the Internet are, the wider the number of these services whose functions match the various service requests is. Selecting WSs with higher quality largely depends on the quality of service (QoS) since it plays a significant role in selecting such services. In achieving this selection of the best WSs, the potential WSs are ranked according to the user’s necessities on service quality. In many cases, the value of QoS ontology is realized by its support for nonfunctional features of WSs. This ontology is also capable of providing solutions to the interoperability of QoS description. Moreover, based on the QoS ontology, it becomes more possible to develop a framework of semantic WS discovery. The framework enhances the automatic discovery of WSs and can improve the users’ efficiency in finding the best web services. Thus, Web Services are software functionalities publish and accessible through the Internet. Different protocols and web mechanism have been defined to access these Services

Transmission Control Protocol Performance Comparison Using Piggyback Scheme In WLANS

The main problem at wireless networks is the overhead at MAC layer; when the data physical rate is increasing it causes increasing the overhead and decreasing at the MAC efficiency. In this study we study the performance comparison of TCP protocol in WLANs with and without using piggyback. The study of results concerning of implemented both mechanisms in NS2 simulator and find out the good performance from this comparison. Based on the results from our experiments show that the Piggyback scheme is one of the efficient ways to reduce the overhead at MAC wireless networks

An integral equation method for solving neumann problems on simply and multiply connected regions with smooth boundaries

This research presents several new boundary integral equations for the solution of Laplace’s equation with the Neumann boundary condition on both bounded and unbounded multiply connected regions. The integral equations are uniquely solvable Fredholm integral equations of the second kind with the generalized Neumann kernel. The complete discussion of the solvability of the integral equations is also presented. Numerical results obtained show the efficiency of the proposed method when the boundaries of the regions are sufficiently smooth

Provisioning Quality of Service of Wireless Telemedicine for E-Health Services: A Review

In general, on-line medical consultation reduces time required for medical consultation and induces improvement in the quality and efficiency of healthcare services. The scope of study includes several key features of present day e-health applications such as X-ray, ECG, video, diagnosis images and other common applications. Moreover, the provision of Quality of Service (QoS) in terms of specific medical care services in e-health, the priority set for e-health services and the support of QoS in wireless networks and techniques or methods aimed at IEEE 802.11 to secure the provision of QoS has been assessed as well. In e-health, medical services in remote places which include rustic healthcare centres, ships, ambulances and home healthcare services can be supported through the applications of e-health services such as medical databases, electronic health data and the transferring of text, video, sound and images. Given this, a proposal has been made for a multiple service wireless networking with multiple sets of priorities. In relation to the terms of an acceptable QoS level by the customers of e-health services, prioritization is an important criterion in a multi-traffic network. The requirement for QoS in medical networking of wireless broadband has paved the way for bandwidth prerequisites and the live transmission or real-time medical applications. The proposed wireless network is capable of handling medical applications for both normal and life-threatening conditions as characterized by the level of emergencies. In addition, the allocation of bandwidth and the system that controls admittance designed based on IEEE 802.16 especially for e-health services or wireless telemedicine will be discussed in this study. It has been concluded that under busy traffic conditions, the proposed architecture can used as a feasible and reliable infrastructure network for telemedicine

A Novel Equation of State: Determination and Validation for Dyes and Drugs Solubility Calculations in Supercritical Carbon Dioxide

Based on Pitzer correlations for the compressibility factor and virial equation of state, a new equation of state has been developed in this study, which is a function of total number of atoms present in the solute molecule, normal boiling point temperature and reduced temperature. Thirty dyes and sixty drugs solubility data, 2417 data points, have been collected from literature and compared with the Peng-Robinson EOS plus the two adjustable parameters van der Waals mixing rules, and the new proposed EOS. As the results show, the proposed EOS presents more accurate predictions for solubility data in Supercritical Carbon Dioxide

A Review on Provisioning Quality of Service of Wireless Telemedicine for E-Health Services

In general, on-line medical consultation reduces time required for medical consultation induces improvement in the quality and efficiency of healthcare services. All major types of current e-health applications such as ECG, X-ray, video, diagnosis images and other common applications have been included in the scope of the study. In addition, the provision of Quality of Service (QoS) for the application of specific healthcare services in e-health, the scheme of priority for e-health services and the support of QoS in wireless networks and techniques or methods for IEEE 802.11 to guarantee the provision of QoS has also been assessed. In e-health, medical services in remote locations such as rural healthcare centers, ambulances, ships as well as home healthcare services can be supported through the applications of e-health services such as medical databases, electronic health records and the routing of text, audio, video and images. Given this, an adaptive resource allocation for a wireless network with multiple service types and multiple priorities have been proposed. For the provision of an acceptable QoS level to users of e-health services, prioritization is an important criterion in a multi-traffic network. The requirement for QoS provisioning in wireless broadband medical networks have paved the pathway for bandwidth requirements and the real-time or live transmission of medical applications. From the study, good performance of the proposed scheme has been validated by the results obtained. The proposed wireless network is capable of handling medical applications for both normal and life-threatening conditions as characterized by the level of emergencies. In addition, the bandwidth allocation and admission control algorithm for IEEE 802.16- based design specifically for wireless telemedicine/e-health services have also been presented in the study. It has been concluded that under busy traffic conditions, the proposed architecture can used as a feasible and reliable infrastructure network for telemedicine