Transmission Priority Research Articles

Dynamic Routing Control based on Informed Priority, and its Application to Monitoring Sensor Network

Routing method with dynamic channel selection in wireless sensor networks is an effective to specify a route, is different from communication between nodes in a common channel, and is able to transmit the data included the attribute information. In this case, a node to be located in the middle of a course uses a different channel, a normal communication between nodes is stayed temporarily and throughput decreases as a result. Instead, for applications to be built by another wireless network originally, it could be expected as an effective communication traffic control method that we are able to avail ourselves to this route, such as emergency information need to send data immediately for example. In this study, we propose a time division communication system that can give right of priority for data transmission involved attribute information by adding element of priority information to transmission data packet. This method has the rule that each router comes up relay node in the middle of priority path temporarily occupies as these nodes of the string, and in contrast, lays other relay nodes not on the course stay all the time, while priority path goes on.

Performance Analysis of VoIP Traffic in WiMAX using Various Service Classes

Worldwide Interoperability for Microwave Access (WiMAX) is currently one of the hottest technologies in wireless, it is a standard-based on the IEEE 802.16 wireless technology that provides high throughput broadband connections over long distance, which supports Point to MultiPoint (PMP) broadband wireless access. In parallel, Voice over Internet Protocol is a promising new technology which provides access to voice communication over internet protocol based network, it becomes an alternative to public switched telephone networks due to its capability of transmission of voice as packets over IP networks. Therefore VoIP is largely intolerant of delay and hence it needs a high priority transmission. In this paper we investigate the performances of the most common VoIP codecs, which are G711, G7231 and G729 over a WiMAX network using various service classes and NOAH as a transport protocol. To analyze the QoS parameters, the popular network simulator ns2 was used. Various parameters that determine QoS of real life usage scenarios and traffic flows of applications is analyzed. The objective is to compare different types of service classes with respect to the QoS parameters, such as, throughput, average jitter and average delay.

Transforming healthcare and medical telemetry through cognitive radio networks

The Wireless Medical Telemetry Services (WMTS) band has been established by the FCC in the United States for transmission of data related to a patient's health, and similar reserved channels exist for life-critical communications throughout the world. However, transmissions in the WMTS band are severely hampered by interferences from adjacent digital television channels, and due to non-uniform access priority, as this band is also shared by utility telemetry and government installations. In this article, we propose the use of cognitive radio technology to dynamically utilize the WMTS frequencies based on the activity patterns of the high priority users, and the quality of service constraints of the patients' data, while ensuring protection to existing higher priority transmissions and the safe operation of sensitive medical equipment. The priority users here are utility telemetry transmissions in certain portions of the WMTS band, government run radar sites, and legacy medical telemetry equipment without cognitive radio capability. We provide the first measurements on the complete WMTS spectrum activity at two major hospital locations in the Boston area, and outline an optimization framework that assigns frequency and transmission power jointly in this setting. The article also discusses the current state of the art and the major challenges in the implementation of this new cognitive radio assisted medical telemetry paradigm.

An Adaptive Hierarchical QAM Scheme for Enhanced Bandwidth and Power Utilization

Hierarchical quadrature amplitude modulation (HQAM) enables unequal priority transmission through the use of non-uniformly spaced constellations. In this paper, we propose an adaptive HQAM (A-HQAM) scheme where the ratios between the constellation distances are regularly adjusted based on the channel condition with the objective of maximizing the transmission efficiency. The source bit stream is divided into multiple sub-streams which are simultaneously transmitted, each on a different priority level. When using A-HQAM, the high priority sub-stream maintains an acceptable bit error rate performance over all channel conditions. As the channel condition improves, the required protection for the high priority sub-stream is reduced allowing for increasing the protection level of lower priority sub-streams. Hence, the number of sub-streams with acceptable BER performances is incrementally increased as the channel condition improves. Analysis and simulation results show that the proposed A-HQAM not only enhances the transmission efficiency but also provides reduced peak to average power ratio (PAPR). The proposed scheme offers reduced complexity by using one constellation size, unlike conventional adaptive schemes which require the use of several constellation sizes. Moreover, a practical A-HQAM implementation is presented which enables the receiver to successfully demodulate the received signal without knowing the varying transmission parameters.

Scheduling and channel assignment algorithm for IEEE 802.16 mesh networks using clique partitioning technique

The IEEE 802.16 standard for wireless metropolitan area networks, also known as WiMAX, is defined to meet the need of widespread broadband wireless access and provide a cost efficient alternative to cabled access networks. This paper proposes a channel assignment and a centralized scheduling algorithm for multi-channel IEEE 802.16 mesh networks. In channel assignment, clique partitioning technique is used to find out the set of links that should be assigned the same channel, so that the number of channels required to eliminate secondary interference is minimized. In scheduling, a priority scheme has been proposed, which avoids accumulation of packets in any node of the network. Clique partitioning technique is used to select the optimal set of links having maximum priority for transmission in each time slot. Simulation results show that our channel assignment algorithm minimizes the number of channels required to eliminate secondary interference, and our scheduling algorithm minimizes the length of the scheduling cycle as well as the size of the relay buffer required for the nodes. In addition, in case sufficient number of channels is available, our scheduling algorithm requires relay buffer of unit size for all nodes in the network, independent of the network traffic.

Structural Solutions for Dynamic Scheduling in Wireless Multimedia Transmission

In this paper, we propose a systematic solution to the problem of scheduling delay-sensitive media data for transmission over time-varying wireless channels. We first formulate the dynamic scheduling problem as a Markov decision process that explicitly considers the users' heterogeneous multimedia data characteristics (e.g., delay deadlines, distortion impacts and dependences, and so on) and time-varying channel conditions, which are not simultaneously considered in state-of-the-art packet scheduling algorithms. This formulation allows us to perform foresighted decisions to schedule multiple data units for transmission at each time in order to optimize the long-term utilities of the multimedia applications. The heterogeneity of the media data enables us to express the transmission priorities between the different data units as a priority graph, which is a directed acyclic graph. This priority graph provides us with an elegant structure to decompose the multidata unit foresighted decision at each time into multiple single-data unit foresighted decisions which can be performed sequentially, from the high priority data units to the low priority data units, thereby significantly reducing the computation complexity. When the statistical knowledge of the multimedia data characteristics and channel conditions is unknown a priori, we develop a low-complexity online learning algorithm to update the value functions, which capture the impact of the current decision on the future utility. The simulation results show that the proposed solution significantly outperforms existing state-of-the-art scheduling solutions.

Improving MANET performance by a hop‐aware and energy‐based buffer management scheme

ABSTRACTA hop‐aware and energy‐based buffer management scheme (HEB) is proposed in this paper. HEB can provide better quality of service to packets with real‐time requirements and improve MANET power efficiency. In our algorithm, the buffer is divided into real‐time and non‐real‐time partitions. We consider the number of hops passed, the power levels of the transmitting node, the predicted number of remaining hops, and waiting time in the buffer to determine packet transmission priority. In addition, specialized queue management and a probabilistic scheduling algorithm are proposed to decrease retransmissions caused by packet losses. Mathematical derivations of loss rates and end‐to‐end delays are also proposed. Coincidence between mathematical and simulation results is also shown. Finally, the HEB is compared with first in first out, random early detection, and hop‐aware buffering scheme. Simulation results show that the proposed algorithm reduces loss rates, power consumption, and end‐to‐end delays for real‐time traffic, considerably improving the efficiency of queue management in MANET. Copyright © 2012 John Wiley & Sons, Ltd.

Deploying Circuit Emulation Services (CES) Over EPON Using Preemptive Priority Medium Access Controller

Circuit Emulation Services (CES) technology has emerged as an option to mitigate traditional Time Division Multiplexing (TDM) circuits supporting legacy applications across managed packet networks and the Ethernet Passive Optical Network (EPON) is becoming a major technology for pervasive access. The primary benefits of CES over EPON (CESoEPON) are the low cost and simplicity of deployment to support all types of legacy TDM applications across EPONs. Thus, the QoS-guarantee for highly delay-sensitive services on EPONs could be enhanced. This paper investigates a preemptive priority transmission technique that works on MAC and PHY layer of downstream EPONs. The proposed novel scheme effectively reduces the frame queuing delay as well as jitter, so as to enhance precise time synchronization in EPONs. Through simulation experiments, we show that the proposed scheme achieves superior and precise QoS control compared to existing non-preemptive priority methods. A feasible implementation of the proposed solution is also addressed. Finally, we present a general conclusion of the paper as well as address the pros and cons for practical deployment in future works.

Data Compression by Temporal and Spatial Correlations in a Body-Area Sensor Network: A Case Study in Pilates Motion Recognition

We consider a body-area sensor network (BSN) consisting of multiple small, wearable sensor nodes deployed on a human body to track body motions. Concerning that human bodies are relatively small and wireless packets are subject to more serious contention and collision, this paper addresses the data compression problem in a BSN. We observe that, when body parts move, although sensor nodes in vicinity may compete strongly with each other, the transmitted data usually exist some levels of redundancy and even strong temporal and spatial correlations. Unlike traditional data compression approaches for large-scale and multihop sensor networks, our scheme is specifically designed for BSNs, where nodes are likely fully connected and overhearing among sensor nodes is possible. In our scheme, an offline phase is conducted in advance to learn the temporal and spatial correlations of sensing data. Then, a partial ordering of sensor nodes is determined to represent their transmission priorities so as to facilitate data compression during the online phase. We present algorithms to determine such partial ordering and discuss the design of the underlying MAC protocol to support our compression model. An experimental case study in Pilates exercises for patient rehabilitation is reported. The results show that our schemes reduce more than 70 percent of overall transmitted data compared with previous approaches.

Hybrid RFID - OWC with an Adaptive Priority Transmission Scheme

This paper presents hybrid RFID – OWC with an adaptive priority transmission scheme. In this model, we apply optical wireless communication (OWC) for transmitting confidential information to a radio frequency identification (RFID) reader. Since OWC provides high security, this improves the security of our system. The priority of information is assigned according to the level of confidentiality and significance of the information. The more confidential information is transmitted by OWC with adaptive data rate, and the rest of the information (if there is any) is transmitted by RFID. The energy harvesting of RFID is used to modulate the reflected optical signal by Corner Cube Retroreflector (CCR). Bit error rate (BER) is analyzed regarding the half-power angle of the transmitter, optical transmit power, data rate, and the angle between tag and reader. The analytical results indicate that by employing the adaptive priority transmission scheme, the required BER of OWC transmission is achieved.

Improving transmission quality of MPEG video stream by SCTP multi-streaming and differential RED mechanisms

SCTP is an emerging transmission protocol with the advanced advantage of supports multi-homing and multi-streaming, which can provide high availability and increase reliability. To improve the performance of MPEG video over Internet, the present study modifies the multi-streaming mechanisms of SCTP, which enable SCTP to use network resources efficiently and provide a differential transmission priority for the encoding frame types of MPEG video stream. Furthermore, to further enhance the decodable frame ratio, the present study also modifies the queue management mechanism of RED which enable the modified RED to provide differential stream protection for MPEG video stream. The simulation results presented in this study confirmed that the proposed scheme can improve the performance of MPEG video stream.

Adaptive Bandwidth Reservation and Scheduling for Efficient Wireless Telemedicine Traffic Transmission

Telemedicine traffic carries critical information with regard to a patients' condition; hence, it requires the highest transmission priority compared with all other types of traffic in the cellular network. The need for expedited errorless transmission of multimedia telemedicine traffic calls for a guaranteed bandwidth to telemedicine users. This condition, however, creates a tradeoff between the satisfaction of the very strict quality-of-service (QoS) requirements of telemedicine traffic and the loss of this guaranteed bandwidth in the numerous cases when it is left unused due to the infrequent nature of telemedicine traffic. To resolve this complex problem, in this paper, we propose and combine the following two techniques: 1) an adaptive bandwidth reservation scheme based on road map information and on user mobility and 2) a fair scheduling scheme for telemedicine traffic transmission over wireless cellular networks.

QoS Based Adaptive Admission Controller for Next Generation Wireless Networks

In 4G networks admission control will need to deal with many heterogeneous networks and admit new sessions to a network that is most appropriate to supply the requested QoS. In order to avoid the degradation of the QoS of low priority sessions, in this paper we propose a QoS Based Adaptive Admission Controller (QAAC). The service request is classified into two types new or handoff and the traffic is classified as real-time and non real-time. Then depending on the traffic class and type of service, the request is finally classified into four categories and priorities are assigned for each category. The admission control algorithm manages the various service requests in their queues and adaptively schedules them as per their assigned priorities. The basic concept of the algorithm is to simultaneously provide transmission priority and space priority for the data flows of the same end-user. The algorithm tries to minimize the number of the sessions that are blocked due to insufficient resources in the target network. By simulation results, we show that our proposed technique yields better throughput with reduced delay.

On Improving Fairness and Providing Proportional Loss Differentiation in OBS Networks

Unfairness is a known undesirable characteristic of OBS networks whereby data flows which traverse longer routes and/or bottleneck links suffer higher data loss. The solutions to this problem presented in the literature, which are mostly based on giving preference to the data flows with longer routes, have not achieved fully satisfactory results. We face the unfairness problem from a different perspective, and propose the Reactive Unfairness Reduction technique, or RUR, which reactively gives transmission priority to those flows which are currently undergoing higher data loss rates. We also present Proportional differentiation RUR (P-RUR), which extends the operation of RUR for not only providing fairness, but also edge-to-edge proportional loss differentiation. Both mechanisms are evaluated through simulation.

Opportunistic and Cooperative Spatial Multiplexing in MIMO Ad Hoc Networks

With the fast progress of multiple-input-multiple-output (MIMO) technology and its growing applications in networks, it is important to develop techniques to enable more efficient MIMO network communications. However, it is very challenging to coordinate node transmissions in a MIMO-based ad hoc network. In this work, we propose schemes that take advantage of the meshed topology of ad hoc networks to fully exploit the multiuser diversity and spatial diversity in order to maximize the data rate of the network while supporting different transmission priorities, reducing transmission delay, and ensuring fair transmissions among nodes. We formulate a concrete physical model and present cross-layer centralized and distributed scheduling algorithms that exploit physical-layer channel information to opportunistically schedule cooperative spatial multiplexed transmissions between nodes. We also propose a new MAC scheme to support our distributed algorithm. The performance of our algorithms are studied through extensive simulations, and the results demonstrate that our algorithms are very effective and can significantly increase the network throughput while reducing the transmission delay.

Study on bandwidth control for multiple transmission rates in IEEE 802.11e EDCAF

AbstractIEEE 802.11e supports the guaranteed quality of service (QoS) by providing different transmission priorities. IEEE 802.11e improves the media access control layer of IEEE 802.11 to satisfy the different QoS requirements by introducing two channel access functions: the enhanced distributed channel access (EDCA) and the hybrid coordination function (HCF) controlled channel access (HCCA). Signal quality may affect the available bandwidth and transmission rate, because the characteristic of communication channel in wireless environment is in random time‐variation manner. Generally a station using a lower transmission rate will occupy communication channel for a longer time and degrade system performance, which causes unfairness and cannot provide the guaranteed QoS for the stations with higher transmission rates. We propose a bandwidth control scheme (BCS) by combining the IEEE 802.11e enhanced distributed channel access function (EDCAF) protocol to overcome the guaranteed bandwidth issue in multirate environments. A multirate discrete Markov chain model is analyzed for the multirate transmission system in this paper. According to the obtained results, BCS improves performance especially in throughput and makes the different QoS requirements be processed efficiently and flexibly. Copyright © 2009 John Wiley & Sons, Ltd.

On the Throughput, Delay, and Energy Efficiency of Distributed Source Coding in Random Access Sensor Networks

In this work, we analyze the throughput, delay, and energy efficiency of random access sensor networks that employ Slepian-Wolf distributed source coding (DSC) and study the impact of MAC protocol design on these performances. Suppose that N sensors observe correlated information from the environment and that their local data are sent to a sink node through direct transmission links. To eliminate data redundancy, we allow sensors to encode their local messages using the Slepian-Wolf DSC method. We assume that sensors are ordered sequentially and that each sensor's message is compressed by exploiting the joint data statistics between itself and the sensors earlier in the sequence. Due to properties of DSC, a message can be decoded only if all messages transmitted by sensors earlier in the sequence are successfully decoded. The loss of one message may cause failure in decoding many other messages. Hence, the sensors' messages are not of equal importance and should be given different transmission priorities by the MAC. Based on the properties of DSC, we provide analytical tools to study the throughput, delay, and energy efficiency of slotted ALOHA random access protocols. Utilizing these tools, we compare between the performance of different transmission probability assignments and study the impact of MAC protocol design on the performance of these systems. Furthermore, an adaptive MAC protocol is also proposed to improve upon the throughput and delay of the original system.

On the Throughput, Delay, and Energy Efficiency of Distributed Source Coding in Random Access Sensor Networks

In this work, we analyze the throughput, delay, and energy efficiency of random access sensor networks that employ Slepian-Wolf distributed source coding (DSC) and study the impact of MAC protocol design on these performances. Suppose that N sensors observe correlated information from the environment and that their local data are sent to a sink node through direct transmission links. To eliminate data redundancy, we allow sensors to encode their local messages using the Slepian-Wolf DSC method. We assume that sensors are ordered sequentially and that each sensor's message is compressed by exploiting the joint data statistics between itself and the sensors earlier in the sequence. Due to properties of DSC, a message can be decoded only if all messages transmitted by sensors earlier in the sequence are successfully decoded. The loss of one message may cause failure in decoding many other messages. Hence, the sensors' messages are not of equal importance and should be given different transmission priorities by the MAC. Based on the properties of DSC, we provide analytical tools to study the throughput, delay, and energy efficiency of slotted ALOHA random access protocols. Utilizing these tools, we compare between the performance of different transmission probability assignments and study the impact of MAC protocol design on the performance of these systems. Furthermore, an adaptive MAC protocol is also proposed to improve upon the throughput and delay of the original system.

Novel Radio Link Buffer Management Schemes for End-User Multi-class Traffic in High Speed Packet Access Networks

The requirement to provide multimedia services with QoS support in mobile networks has led to standardization and deployment of high speed data access technologies such as the High Speed Downlink Packet Access (HSDPA) system. HSDPA improves downlink packet data and multimedia services support in WCDMA-based cellular networks. As is the trend in emerging wireless access technologies, HSDPA supports end-user multi-class sessions comprising parallel flows with diverse Quality of Service (QoS) requirements, such as real-time (RT) voice or video streaming concurrent with non real-time (NRT) data service being transmitted to the same user, with differentiated queuing at the radio link interface. Hence, in this paper we present and evaluate novel radio link buffer management schemes for QoS control of multimedia traffic comprising concurrent RT and NRT flows in the same HSDPA end-user session. The new buffer management schemes—Enhanced Time Space Priority (E-TSP) and Dynamic Time Space Priority (D-TSP)—are designed to improve radio link and network resource utilization as well as optimize end-to-end QoS performance of both RT and NRT flows in the end-user session. Both schemes are based on a Time-Space Priority (TSP) queuing system, which provides joint delay and loss differentiation between the flows by queuing (partially) loss tolerant RT flow packets for higher transmission priority but with restricted access to the buffer space, whilst allowing unlimited access to the buffer space for delay-tolerant NRT flow but with queuing for lower transmission priority. Experiments by means of extensive system-level HSDPA simulations demonstrates that with the proposed TSP-based radio link buffer management schemes, significant end-to-end QoS performance gains accrue to end-user traffic with simultaneous RT and NRT flows, in addition to improved resource utilization in the radio access network.

Scheduling for long term proportional fairness in a cognitive wireless network with spectrum underlay

In this paper we study fair rate scheduling in an ad hoc cognitive wireless network with spectrum underlay. Transmissions in the network are allowed provided their interference to the primary network is below a predefined threshold. An optimal scheduling problem is formulated with an objective to achieve proportional fairness (PF) of the long-term average transmission rates among different links. Implementing the optimum scheduling requires high complexity. Two practical scheduling schemes are then proposed. In the first scheme, transmission priorities of the links are determined by their potential contributions to an objective utility function, assuming there is no co-channel interference within the network. In the second scheme, transmission priorities are derived from both the objective function and interference to the primary network. We also consider using exclusive regions to limit interference among simultaneous transmissions in order to improve the system throughput. The scheduling schemes can be implemented distributively in the ad hoc cognitive wireless network with limited assistance from the primary network. Our results show that the proposed PF scheduling schemes can achieve high overall throughput and close-to-optimum fairness, and using exclusive regions can improve the system utility without compromising the fairness performance.