It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

Praise for the Third Edition: "This is one of the best books available. Its excellent organizational structure allows quick reference to specific models and its clear presentation . . . solidifies the understanding of the concepts being presented."IIE Transactions on Operations EngineeringThoroughly revised and expanded to reflect the latest developments in the field, Fundamentals of Queueing Theory, Fourth Edition continues to present the basic statistical principles that are necessary to analyze the probabilistic nature of queues. Rather than presenting a narrow focus on the subject, this update illustrates the wide-reaching, fundamental concepts in queueing theory and its applications to diverse areas such as computer science, engineering, business, and operations research.This update takes a numerical approach to understanding and making probable estimations relating to queues, with a comprehensive outline of simple and more advanced queueing models. Newly featured topics of the Fourth Edition include:Retrial queuesApproximations for queueing networksNumerical inversion of transformsDetermining the appropriate number of servers to balance quality and cost of serviceEach chapter provides a self-contained presentation of key concepts and formulae, allowing readers to work with each section independently, while a summary table at the end of the book outlines the types of queues that have been discussed and their results. In addition, two new appendices have been added, discussing transforms and generating functions as well as the fundamentals of differential and difference equations. New examples are now included along with problems that incorporate QtsPlus software, which is freely available via the book's related Web site.With its accessible style and wealth of real-world examples, Fundamentals of Queueing Theory, Fourth Edition is an ideal book for courses on queueing theory at the upper-undergraduate and graduate levels. It is also a valuable resource for researchers and practitioners who analyze congestion in the fields of telecommunications, transportation, aviation, and management science.

Fundamentals of Queueing Theory

This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

Summary form only given. The layered architecture is one of the key reasons behind the explosive and continuing growth of the Internet. There are, however, special networks in which cross-layer design is appropriate and may even be necessary. Two such cases are small wireless LAN and large-scale sensor networks. We consider first the design of medium access control (MAC) for a small wireless LAN based on a multiuser physical layer. We present a complete characterization of the throughput region and present conditions under which ALOHA is optimal. Next we consider the estimation of signal field using data collected from a large scale sensor network. The impact of medium access control on estimation is examined. We show that there exists a threshold on sensor outage probability above which a distributed random access protocol (such as ALOHA) outperforms the centralized deterministic schedulers.

On cross-layer design of wireless networks

Hypertension and aging

Mild cognitive impairment (MCI) is a common condition in the elderly. It is characterized by deterioration of memory, attention, and cognitive function that is beyond what is expected based on age and educational level. MCI does not interfere significantly with individuals' daily activities. It can act as a transitional level of evolving dementia with a range of conversion of 10%-15% per year. Thus, it is crucial to protect older people against MCI and developing dementia. The preventive interventions and appropriate treatments should improve cognitive performance, and retard or prevent progressive deficits. The avoidance of toxins, reduction of stress, prevention of somatic diseases, implementation of mental and physical exercises, as well as the use of dietary compounds like antioxidants and supplements can be protective against MCI. The modification of risk factors such as stopping smoking, as well as the treatment of deficiency in vitamins and hormones by correcting behaviors and lifestyle, can prevent cognitive decline in the elderly. The progressive increase in the growth rate of the elderly population can enhance the rate of MCI all over the world. There is no exact cure for MCI and dementia; therefore, further studies are needed in the future to determine causes of MCI and risk factors of progression from MCI to dementia. This will help to find better ways for prevention and treatment of cognitive impairment worldwide.

/pdf/mild-cognitive-impairment-and-its-management-in-older-people-3vb0y9l6hk.pdf

Mild cognitive impairment and its management in older people.

Mobility of sensor nodes posed new challenges particularly in energy consumption and demands researchers' attention. Some real applications impose combined environments of fixed and mobile sensor nodes in the same network, while others demand a complete mobile sensors environment. Packet loss that occurs due to mobility of the sensor nodes is one of main challenges in Wireless Sensor Network (WSN) and it comes in parallel with energy consumption. In this paper, we propose adaptive Time Division Multiple Access (TDMA) scheduling and round free cluster head protocol called Cluster Based Routing (CBR) protocol for Mobile Nodes in Wireless Sensor Network (CBR Mobile-WSN). In this protocol the cluster head receive data from not only its member during the TDMA allocated time slot but also other sensor nodes that just enter the cluster when it has free time slots, each cluster head takes turn to be the free cluster head in the network. CBR Mobile-WSN change TDMA scheduling adaptively according to traffic and mobility characteristics. The proposed protocol sends data to cluster heads in an efficient manner based on received signal strength. The performance of proposed CBR Mobile-WSN protocol is evaluated using MATLAB and it has been observed that the proposed protocol reduces the packet loss by 25% compared to LEACH-Mobile protocol.

/pdf/cluster-based-routing-protocol-for-mobile-nodes-in-wireless-3ej4ms8tev.pdf

Cluster Based Routing protocol for Mobile Nodes in Wireless Sensor Network

Mobility of sensor nodes in wireless sensor network (WSN) has posed new challenges particularly in packet delivery ratio and energy consumption. Some real applications impose combined environments of fixed and mobile sensor nodes in the same network, while others demand a complete mobile sensors environment. Packet loss that occurs due to mobility of the sensor nodes is one of the main challenges which comes in parallel with energy consumption. In this paper, we use cross layer design between medium access control (MAC) and network layers to overcome these challenges. Thus, a cluster based routing protocol for mobile sensor nodes (CBR-Mobile) is proposed. The CBR-Mobile is mobility and traffic adaptive protocol. The timeslots assigned to the mobile sensor nodes that had moved out of the cluster or have not data to send will be reassigned to incoming sensor nodes within the cluster region. The protocol introduces two simple databases to achieve the mobility and traffic adaptively. The proposed protocol sends data to cluster heads in an efficient manner based on received signal strength. In CBR-Mobile protocol, cluster based routing collaborates with hybrid MAC protocol to support mobility of sensor nodes. Schedule timeslots are used to send the data message while the contention timeslots are used to send join registration messages. The performance of proposed CBR-Mobile protocol is evaluated using MATLAB and was observed that the proposed protocol improves the packet delivery ratio, energy consumption, delay and fairness in mobility environment compared to LEACH-Mobile and AODV protocols.

/pdf/cluster-based-routing-protocol-for-mobile-nodes-in-wireless-ce23n5fy43.pdf

Cluster Based Routing Protocol for Mobile Nodes in Wireless Sensor Network

The routing protocol for Wireless Sensor Networks (WSNs) is defined as the manner of data dissemination from the network field (source) to the base station (destination). Based on the network topology, there are two types of routing protocols in WSNs, they are namely flat routing protocols and hierarchical routing protocols. Hierarchical routing protocols (HRPs) are more energy efficient and scalable compared to flat routing protocols. This paper discusses how topology management and network application influence the performance of cluster-based and chain-based hierarchical networks. It reviews the basic features of sensor connectivity issues such as power control in topology set-up, sleep/idle pairing and data transmission control that are used in five common HRPs, and it also examines their impact on the protocol performance. A good picture of their respective performances give an indication how network applications, i.e whether reactive or proactive, and topology management i.e. whether centralized or distributed would determine the network performance. Finally, from the ensuring discussion, it is shown that the chain-based HRPs guarantee a longer network lifetime compared to cluster-based HRPs by three to five times.

/pdf/a-review-on-hierarchical-routing-protocols-for-wireless-3qks8tvt1n.pdf

A Review on Hierarchical Routing Protocols for Wireless Sensor Networks

Internet Engineering Task Force (IETF) working group has standardized the transmission of internet protocol version 6 (IPv6) packets over IEEE 802.15.4 low power wireless personal area network (LoWPAN) as 6LoWPAN protocol. It provides the wireless sensor network (WSN) node with IP communication capabilities by putting an adaptation layer above the 802.15.4 link layer. Different mechanisms performed by adaptation layer require the 6LoWPAN header encapsulation in the packet. Although routing is among the key issues of 6LoWPAN research, the way to encapsulate a new routing header in the 6LoWPAN packet has yet been investigated thoroughly. In this paper, different ways of routing header encapsulation in 6LoWPAN protocol stack is discussed. The simplified version Ad-Hoc On-Demand Distance Vector (AODV) such as On-Demand Distance Vector (LOAD) and Dynamic MANET On-demand for 6LoWPAN (DYMO-low) have currently been proposed in 6LoWPAN routing. Hierarchical routing (HiLow) is another routing protocol that is used in 6LoWPAN to increase the network scalability. Some comparisons of these routing protocols have been made in terms of their routing metric such as number of hops count. The used control messages for the route discovery in different routing protocols have also been investigated. These comparisons show that each routing protocol has its own advantage depends on the involved applications. There are some tradeoffs of respective routing protocols. The routing protocol that uses hello message may provide more reliable but results a higher delay in the packet routing.

http://archive.apan.net/meetings/Hanoi2010/Session/Slides/NetworkResearch/paper/Wireless_Reviewof6LoWPANRoutingProtocols.pdf

Chee Kyun Ng

Papers

Mild cognitive impairment and its management in older people.

Cluster Based Routing protocol for Mobile Nodes in Wireless Sensor Network

Cluster Based Routing Protocol for Mobile Nodes in Wireless Sensor Network

A Review on Hierarchical Routing Protocols for Wireless Sensor Networks

A Review of 6LoWPAN Routing Protocols