CDPD traffic performance for fading non-dedicated channels

The Cellular Digital Packet Data (CDPD) system is the first public wireless data ever deployed in the US. As its traffic continues to grow, potential new customers require to know the platform's quality-of-service (QoS) performance data prior to subscribing to the service. Consequently, network planners are searching for a simple model which can provide QoS analysis instantly, rather than conducting long (and costly) simulations. This paper provides such model. CDPD uses a random-access MAC layer protocol known as the DSMA/CD, to control the users packet transmission on the reverse link. In general, the success of the transmitted packets, as well as the delay incurred, depends heavily on both: the efficiency with which the DSMA/CD controls packet collisions, and the degree of error-free reception provided by the physical layer. Therefore, one must consider the joint operation of the two in order to produce quotable realistic traffic performance figures. This paper focuses on the joint operation of the two named layers.

A web-based camera (webcam) is expected to enhance construction site monitoring, which may result in better project control. However, in most cases, webcams are located on the outside of a building because their mobility is limited by cable wiring, thus occasionally the view of the camera is blocked as the project develops. If a webcam is integrated with emerging wireless network technologies such as IEEE 802 or Cellular Digital Packet Data (CDPD), construction professionals may be able to utilize the webcam to monitor interior construction operations without worrying about getting the network cables wired on the congested and dynamic construction job site. Especially, the CDPD technology should enable the webcam to transmit captured photos from any construction site as far as the cellular phone service is available. However, with the speed of CDPD (19.2 Kilobits per second), it would take as long as 6 minutes to send one Mega pixel digital image. One may ask if construction professionals could figure out operations implemented at the job site by observing a 6 minute interval time-lapsed photo set. How many mistakes should we anticipate when interpreting the time-lapsed photo set with this time interval? To what extent can the frame rate of the webcam be lowered for monitoring construction operations at the job site? To answer these questions, we then produced time-lapsed photos of brickwork at three different construction sites with various time intervals and investigated error rates in identifying construction crew’s productivity using these time-lapsed photos. This paper presents a preliminary result of our investigation.

Cellular Digital Packet Data (CDPD) is a technology that provides digital packet-switched data services through standard analog cellular channels. CDPD is implemented as an overlay to existing cellular networks allowing data to be sent in packets during idle times on the cellular voice channels. This overlay implementation makes use of existing cellular infrastructure, simultaneously transmitting voice and data from the same device. A cellular communication network has significant advantages over its wireline counterparts. Mobility and ease of use are two particularly attractive features to a large population of field employees. Based upon well known world standards, CDPD will provide connectivity anywhere anytime-a true realization of the well sought dream of having information at your fingertips. >

Early Cellular Digital Packet Data (CDPD) deployments have been a valuable learning experience for the cellular carriers that established them. The purpose of this paper, is to discuss the practical aspects of CDPD systems, based on such experience. Guidelines for the planning, deployment and management of cellular data networks are presented. This paper is intended for cellular service providers but may also benefit application developers who wish to understand the issues faced by carriers with respect to wireless data. The specific topics covered in this paper include deployment strategies, frequency planning and customer engineering. The conclusion emphasizes the importance of a well-developed strategy, coupled with the adaptability to meet the changing needs of an evolving customer base.

We present an end to end adaptive video coding and transmission system that is designed for the Cellular Digital Packet Data (CDPD) wireless networks. The proposed system consists of (1) an embedded wavelet bit-plane coding algorithm, which is capable of adapting the compression ratio to the available bandwidth; (2) an efficient and error resilient fixed-length packetization scheme based on randomization in the wavelet domain; and (3) a feedback rate control algorithm, which is capable of estimating the available network bandwidth based on the acknowledgement information received by the server. Experimental results show that our system achieves good perceptual quality while maintaining high bandwidth utilization.

The authors first discuss the basic cellular digital packet data (CDPD) architecture and its authentication protocols. They then present threats to the network. Next, they investigate the basic requirements of the security architecture and goals in light of attacks. Then they present the improved authentication protocol in operation, and how it deals with faults. Next, they add authenticated key exchange for confidentiality, followed by anonymity provisions. Then, they summarize the design and present the complete protocol, and identify which protocol transmissions goes on which CDPD message. Finally, they present further issues and concerns that are beyond the scope of this protocol.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

There is no doubt about it: Asynchronous Transfer Mode (ATM) traffic will soon connect to the wireless network. Its characteristics are very well adapted to provide a well-balanced mix of voice and data communications. The question here is where will adaptation layers be processed? Should the Wireless Carrier be burdened with converting ATM-based traffic in other interfaces such as Cellular Digital Packet Data, a solution leading to multiple and possibly unmanageable gateway functions? Or should an Air Interface be developed to carry ATM traffic? Pushing ATM adaptation layers closer to the point of consumption of voice, data or video holds many advantages. This paper attempts to shine some light on the subject.

At Carnegie Mellon University in Pittsburgh, staff and students are using mobile computers for various tasks such as transferring lecture notes, sending e-mails, or surfing the net. This possible due to the installation of a wireless network which will cover all 28 academic and administrative buildings on the 40-hectare campus, and provide service to 10000 people. As long as they are on campus, the university community will be able to take advantage of the network. The high speed wireless infrastructure installed at Carnegie Mellon is called Wireless Andrew. Started as a National Science Foundation-funded research network to support Carnegie Mellon's wireless research initiative, the network originally provided coverage in seven campus buildings. The challenges in building such a large network are far from trivial. They include designing the network so that coverage blankets the entire campus, providing enough capacity to handle the campus-wide traffic load. Further, the network must provide highly reliable service. It builds on the university's wired network infrastructure, which currently provides 10-Mb/s and 100-Mb/s Ethernet service. To supply high-speed wireless service to the campus, Lucent WaveLAN equipment has been installed, which uses direct sequence spread-spectrum radio to provide a raw data rate of 2 Mb/s. For wireless access off campus or otherwise out of the range of the WaveLAN network, cellular digital packet data is used.

Cellular digital packet data (CDPD) utilizes sleep mode mechanism to conserve the power of mobile end systems (M-ESs). A timer called T203 determines how quick an M-ES enters the sleep mode, and another timer called T204 determines how often the M-ES wakes up. A large T204 value and a small T203 value can effectively reduce the power consumption at the cost of degrading the frame transmission performance, i.e., more lost frames, longer frame waiting times, and larger waiting variance. When the power consumption budget is determined in a CDPD system design, our study provides guidelines to determine the timer values as well as the buffer size to optimize the frame transmission performance.

Mobile IP is a proposed standard protocol that builds on the Internet Protocol by making mobility transparent to applications and higher level protocols like TCP. Mobile IP (RFC 2002) is a standard proposed by a working group within the Internet Engineering Task Force; it allows the mobile node to use two IP addresses: a fixed home address and a care-of address that changes at each new point of attachment. The article presents the Mobile IP standard in moderate technical detail and points the reader toward a wealth of further information. Is also describes how Mobile IP will change with IP version 6, the product of a major effort within the IETF to engineer an eventual replacement for the current version of IP. Although IPv6 will support mobility to a greater degree than IPv4, it will still need Mobile IP to make mobility transparent to applications and higher level protocols such as TCP. There is a great deal of interest in mobile computing and apparently in Mobile IP as a way to provide for it. A quick Web search for items related to Mobile IP returned over 60,000 hits-impressive even given the notorious lack of selectivity for such procedures. Mobile IP forms the basis either directly or indirectly of many current research efforts and products. The Cellular Digital Packet Data (CDPD), for example, has created a widely deployed communications infrastructure based on a previous draft specification of the protocol. In addition, most major router vendors have developed implementations for Mobile IP.

Cellular packet data systems require medium access control (MAC) protocols that allow flexible resource allocation on both the uplink and the downlink. The overhead introduced for managing MAC functions should be minimized, and control fields should be well protected in order to provide robustness to channel errors. The IS-136 TDMA digital control channel specifies shared channel feedback (SCF) procedures and fields for managing uplink resources. However, the SCF mechanism is not well suited to long packet data transactions. We describe a simple and robust packet channel feedback (PCF) mechanism for an IS-136 based TDMA packet data channel by identifying the minimal set of functions and fields required to manage both contention access and reserved access. The proposed scheme has unambiguous state transitions and better performance under error conditions. The PCF scheme provides considerable flexibility in assigning bandwidth to multiple users, and allows the efficient scheduling of contention and reservation opportunities on each subchannel without wasted slots.

Modeling and analysis tools are essential for the design and evaluation of complex systems. This is particularly true for cellular systems, where, for instance, a variety of handoff, channel allocation, and data-transmission algorithms have been proposed. The capabilities of Petri nets (PNs) are used as a novel approach in the analysis of handoff, dynamic channel allocation (DCA), and cellular digital packet data resource management problems. The generalized stochastic PN (GSPN) models are obtained and analyzed as continuous-time Markov chains (MCs) derived from the reachability graphs. Solution of the MC results in performance indicators, which show the impacts of different algorithms on the system behavior.

The paper studies the value of data transmission over idle channels within cellular systems using frequency hopping techniques. In the beginning it seemed very logical that data transmission over cellular channels did not reduce voice capacity by hopping among idle channels. Actually, the analysis in the present paper indicates that although the hopping scheme creates additional capacity, it degrades system performance due to the additional interference contributed by data transmission. To implement a dedicated cellular digital packet data channel eventually would be the proper choice.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In this chapter, we consider a cellular downlink packet data system employing the space-time block coded (STBC) multiple- input-multiple-output (MIMO) scheme. Taking the CDMA high data rate (HDR) system for example, we evaluate the cross-layer performance of typical scheduling algorithms and a point-to-point power control scheme over a time division multiplexing (TDM)-based shared MIMO channel. Our evaluation focuses on the role of those schemes in multi-user diversity gain, and their impacts on medium access control (MAC) and physical layer performance metrics for delay-tolerant data services, such as throughput, fairness, and bit or frame error rate. The cross-layer evaluation shows that the multi-user diversity gain, which comes from opportunistic scheduling schemes exploiting independent channel oscillations among multiple users, can increase the aggregate throughput and reduce the transmission error rate. It also shows that STBC/MIMO and one-bit and multi-bit power control can indeed help the physical and MAC layer performance but only at a risk of limiting the multiuser diversity gain or the potential throughput of schedulers for delay-tolerant bursty data services.

A flow cytometer is made up of many different subsystems that work together to measure the optical properties of individual cells within a sample. The data acquisition system (also called the data system) is one of these subsystems, and it is responsible for converting the electrical signals from the optical detectors into list-mode data. This unit describes the inner workings of the data system, and provides insight into how the instrument functions as a whole. Some of the information provided in this unit is applicable to everyday use of these instruments, and, at minimum, should make it easier for the reader to assemble a specific data system. With the considerable advancement of electronics technology, it becomes possible to build an entirely functional data system using inexpensive hobbyist-level electronics. This unit covers both analog and digital data systems, but the primary focus is on the more prevalent digital data systems of modern flow cytometric instrumentation.