Control Protocol Design Research Articles

Performance evaluation of medium access control for multiple-beam antenna nodes in a wireless LAN

We consider the medium access control (MAC) protocol design for nodes in a wireless LAN that use a wide-azimuth switched beam smart antenna system comprised of a multiple beam antenna array. The one-hop performance of carrier sense multiple access (CSMA) as well as slotted aloha for such a system is presented analytically and through simulation. The problem of synchronization of multiple beams in CSMA is investigated in our analysis. Our results show that, under heavy offered load conditions, CSMA is a good choice with nodes that have multiple-beam smart antennas, despite the performance loss due to the beam synchronization, providing a stable throughput that approaches unity and is invariant to fluctuations in the offered load. Slotted Aloha, on the other hand, is capable of higher peak throughput in a narrow range of offered loads as more switched beams are employed, but performance drastically reduces beyond optimum offered loads. We also introduce a method, expanded receive rule (ERR), whereby the tight synchronization among different beams of a receiver node in CSMA is relaxed, which is observed to provide better throughput. Finally, we also present performance results for a 4-way-handshake-type carrier sense mechanism using multiple beam antennas.

A transport protocol for supporting multimedia streaming in mobile ad hoc networks

Transport protocol design for supporting multimedia streaming in mobile ad hoc networks is challenging because of unique issues, including mobility-induced disconnection, reconnection, and high out-of-order delivery ratios; channel errors and network congestion. In this paper, we describe the design and implementation of a transmission control protocol (TCP)-friendly transport protocol for ad hoc networks. Our key design novelty is to perform multimetric joint identification for packet and connection behaviors based on end-to-end measurements. Our NS-2 simulations show significant performance improvement over wired TCP friendly congestion control and TCP with explicit-link-failure-notification support in ad hoc networks.

Revisiting the fair queuing paradigm for end-to-end congestion control

Today, the dominant paradigm for congestion control in the Internet is based on the notion of TCP friendliness. To be TCP-friendly, a source must behave in such a way as to achieve a bandwidth that is similar to the bandwidth obtained by a TCP flow that would observe the same round-trip time (RTT) and the same loss rate. However, with the success of the Internet comes the deployment of an increasing number of applications that do not use TCP as a transport protocol. These applications can often improve their own performance by not being TCP-friendly, which severely penalizes TCP flows. To design new applications to be TCP-friendly is often a difficult task. The idea of the fair queuing (FQ) paradigm as a means to improve congestion control was first introduced by Keshav (1991). While Keshav made a fundamental step toward a new paradigm for the design of congestion control protocols, he did not formalize his results so that his findings could be extended for the design of new congestion control protocols. We make this step and formally define the FQ paradigm as a paradigm for the design of new end-to-end congestion control protocols. This paradigm relies on FQ scheduling with per-flow scheduling and longest queue drop buffer management in each router. We assume only selfish and noncollaborative end users. Our main contribution is the formal statement of the congestion control problem as a whole, which enables us to demonstrate the validity of the FQ paradigm. We also demonstrate that the FQ paradigm does not adversely impact the throughput of TCP flows and explain how to apply the FQ paradigm for the design of new congestion control protocols. As a pragmatic validation of the FQ paradigm, we discuss a new multicast congestion control protocol called packet pair receiver-driven layered multicast (PLM).

Design and Modeling of an Interval-based ABR Flow Control Protocol

A novel flow control protocol is presented for Availability Bit Rate (ABR) service in Asynchronous Transfer Mode (ATM) networks. This scheme features periodic explicit rate feedback that enables precise allocation of link bandwidth and buffer space on a hop-by-hop basis to guarantee maximum throughput, minimum cell loss, and high resource efficiency. With the inclusion of resource management cell synchronization and consolidation algorithms, this protocol is capable of controlling point-to-multipoint ABR services within a unified framework. The authors illustrate the modeling of single ABR connection, the interaction between multiple ABR connections, and the constraints applicable to flow control decisions. A loss-free flow control mechanism is presented for high-speed ABR connections using a fluid traffic model. Supporting algorithms and ATM signaling procedures are specified, in company with linear system modeling, numerical analysis, and simulation results, which demonstrate its performance and cost benefits in high-speed backbone networking scenarios.

Dynamic time slot scheduling schemes for uplink polling MAC TDD DS-CDMA protocol with adaptive antennas

The signal-to-interference-plus-noise ratio and the throughput in multicellular packet switching networks is improved by the joint design of an uplink polling medium access control protocol and a time division duplexing direct sequence code division multiple access physical layer with an adaptive antenna receiver implemented at the base station (BS).

Evaluation of concurrency control strategies for mixed soft real-time database systems

Previous research in real-time concurrency control mainly focuses on the schedulability guarantee of hard real-time transactions and the reduction of the miss rate of soft real-time transactions. Although many new database applications have significant response time requirements, not much work has been done in the joint scheduling of traditional non-real-time transactions and soft real-time transactions. In this paper, we study the concurrency control problems in mixed soft real-time database systems, in which both non-real-time and soft real-time transactions exist simultaneously. The objectives are to identify the cost and the performance tradeoff in the design of cost-effective and practical real-time concurrency control protocols, and to evaluate their performance under different real-time and non-real-time supports. In particular, we are interested in studying the impacts of different scheduling approaches for soft real-time transactions on the performance of non-real-time transactions. Instead of proposing yet another completely new real-time concurrency control protocol, our objective is to design an efficient integrated concurrency control method based on existing techniques. We propose several methods to integrate the well-known two phase locking and optimistic concurrency control with the aims to meet the deadline requirements of soft real-time transactions and, at the same time, to minimize the impact on the performance of non-real-time transactions. We have conducted a series of experiments based on a sanitized version of stock trading systems to evaluate the performance of both soft real-time and non-real-time transactions under different real-time supports in the system.

Design of a Link Control Protocol for Multimedia Services in Wireless Local Communication

The convergence of wireless systems with multimedia services is the challenge of future generation wireless networks. The large variety of QoS requirements of different media as well as the maintenance of synchronization of the different streams to be presented at receiver, demand from the Data link layer some extra functionalities. In this paper, we present an enhanced approach for the efficient management of multimedia applications in third-generation wireless networks. We advocate the use of multiple connections, one for each traffic component of the application, as the effective solution for the transport of multimedia applications in future-generation wireless networks. The effectiveness of this scheme is guaranteed by providing a new link control technique that works on top of a PRMA-type access protocol which jointly manages different streams of a multimedia application. For this purpose, we propose a two-level priority mechanism (static and dynamic priorities) specified by higher protocol layers for link activation, channel access, and admission control procedures specific to a multimedia application and for optimizing the sharing of radio channel resources and management of the reservation queue at the base station. We expect this priority-based mechanism to perform well, especially during periods in which system traffic load is high, and to react well to the deterioration of multimedia service quality, in terms of both QoS parameters and the synchronization of its traffic components.

The RTCP gateway: scaling real-time control bandwidth for wireless networks

In this paper, we identify the deficiencies of Real-Time Protocol (RTP) scaling when deployed in low-bandwidth or wireless networks. As RTP is used to support audio and video communication over the Internet, scalability over a wide bandwidth range is important to its continued acceptance. We describe the design and implementation of a real-time control protocol (RTCP) gateway which provides the scaling functions necessary to allow wireless participants to engage in high-bandwidth conferencing sessions. RTCP gateway functionality is compatible with the most commonly used data scaling strategies and does not affect RTP functions on the fixed network.

Wireless dynamic channel assignment performance under packet data traffic

With the increased subscription rate in Internet services and wireless communications services, a significant amount of traffic for the future wireless communications will be from Internet applications. Therefore, it is important to design a bandwidth-efficient channel allocation scheme to support Internet traffic, which are packet-switched in nature. Dynamic channel assignment (DCA) schemes are believed to achieve higher system capacity and spectrum efficiency in a frequency-reuse wireless system without frequency planning. This makes DCA a suitable candidate to provide high-speed wireless packet data services. This paper investigates the performance of two distributed measurement-based DCA schemes under Pareto-distributed packet data traffic, a well-known traffic model with heavy-tailed distribution and infinite variance. Performance comparisons of DCA schemes under different wireless packet data traffic conditions are also presented. The sensitivity of the channel setup delay on the SIR performance at access are discussed. These results can provide guidelines for the future design of DCA and medium access control (MAC) protocols for wireless Internet services.

Error and flow control in terabit intelligent optical backplanes

The design of a free-space optical backplane which supports error and flow control functions is described. Traditionally, these functions are implemented in custom high-speed electronic application specific integrated circuits, which are physically removed from the optical interconnect layer. In this paper, we consider migrating these functions directly into the optoelectronic layer, yielding an "intelligent optical backplane." Conventional error control protocols are infeasible with optical backplanes since they require excessive amounts of hardware. The design of an efficient error control protocol based upon a multidimensional parity check, along with the effective flow control protocol is proposed and analyzed. The key blocks of the protocol have been implemented in 0.8- and 0.5-/spl mu/m CMOS/SEED devices and are summarized. The protocols require significantly less hardware than alternative schemes, and smart pixel arrays supporting these protocols are scalable to higher bandwidths and lower latencies. A very large scale integration analysis indicates that using 2004 technology, a free-space backplane can potentially be clocked at 1 GHz and support 24 Tb/s of bandwidth. Finally, the proposed error control protocols should be useful in optical disks and holographic memory systems, which also perform error control on large two-dimensional arrays of optical bits.

ORMA: a high-performance MAC protocol for fiber-optic LANs/MANs

Emerging B-ISDN applications are accelerating the demand for high-speed and high-performance fiber optic local and metropolitan area networks (LANs and MANs). Most of the networks proposed for such an environment are based on either a folded bus or dual unidirectional bus technology, primarily due to the unidirectional nature of the fiber optic medium, their cost effectiveness, and their ability to carry asynchronous transfer mode (ATM) cells. Consequently, the design of the medium access control (MAC) protocols is the most crucial aspect for these networks since the decisions made at this level will determine the capabilities and the hardware cost of the network. The author proposes a novel MAC-layer protocol, called Optical Reservation Multiple Access (ORMA), which is suitable for data traffic on fiber optic folded bus MANs and LANs. Its main feature is an efficient optical reservation technique to allow stations to reserve transmission slots, which is attractive for use in fiber optic networks. Unlike conventional protocols. Where reservation is mostly done using software, ORMA performs its reservation using simple and effective optical circuits. Complete descriptions of the ORMA protocol and the associated nodes are given. Then the performance of ORMA is investigated as a function of the throughput, mean packet delay, and fairness among stations using analytical and simulation results. Our protocol is shown to achieve high throughput and small transmission delays while preserving the fairness of the whole network. Moreover, it compares favorably with related state-of-the-art networks. Thus, the ORMA protocol lends itself well to future-generation high-speed MANs and LANs.

Design of resource control protocols for Release [formula omitted] Broadband ISDN services

The addition of broadband technology to telecommunications networks will greatly enhance their capability to support multimedia, multipoint services, such as will be supported in the Release 2 3 timeframe for Broadband ISDN. In order to support these services, new features will need to be developed in network control signalling. This paper discusses the design of network resource control protocols in order to support multimedia and multipoint services. Some key design issues are discussed, such as call topology, distributed vs. centralized control, and handling of multiple call components. The paper describes the results of simulations comparing three protocol designs incorporating different design choices.

Concurrency Control for Time-constrained Transactions in Distributed Databases Systems

The design of concurrency control protocols for time-constrained transactions is complicated due to the requirements to maintain the database consistency and to satisfy the timing constraints of the transactions. In the past few years, various real-time locking protocols have been proposed for different real-time database systems (RTDBS). However, the use of these protocols for distributed real-time database systems (DRTDBS) has received much less attention, even though many RTDBS are distributed in nature. In this paper, two efficient real-time locking protocols are proposed for DRTDBS. The first one, based on dynamic locking, is called Distributed Hybrid Two Phase Locking (DHb2PL). Its performance has been compared in detail with three other distributed real-time locking protocols. The performance results indicate that DHb2PL is much better than the other protocols as a result of a better approach to resolving lock conflicts and its deadlock free property. The second one, called DRT-S2PL, is based on static locking where the locks required by a transaction are assumed to be known before its execution. Its relative performance as compared with DHb2PL is dependent on the proportion of remote locks required by a transaction. DRT-S2PL is more suitable for systems with transactions which have to set a large proportion of remote locks.

Design and performance evaluation of a new medium access control protocol for local wireless data communications

This paper proposes a new medium access control protocol for wireless data communications in local area, called the reservation-based multiple access with variable frame length (RMAV). We design RMAV under the consideration that the population of wireless terminals and the system load frequently change and are almost unpredictable in wireless data communications. RMAV is based on the slot reservation scheme and adopts a frame structure with variable length. The frame length increases as the number of active terminals and/or the system load increases. We evaluate the performance of RMAV by analysis and computer simulation. Due to its adaptability to traffic patterns, RMAV offers short delay in light load conditions and high throughput in heavy load conditions.

The Production of Quality Dietary Data: A Collaborative Effort of the Modification of Diet in Renal Disease Study

The production of research-quality dietary data for multicentered, long-duration, dietary intervention trials is complex and difficult. In the Modification of Diet in Renal Disease (MDRD) Study, quality control of dietary data has been accomplished through the cooperative efforts of MDRD clinical center dietitians, the MDRD Data Coordinating Center, and the MDRD Nutrition Coordinating Center. The rationale for and steps in the design of quality control protocols and the distribution of responsibilities among the MDRD collaborators are discussed. This model of shared responsibility may be a useful approach for future trials. The production of research-quality dietary data for multicentered, long-duration, dietary intervention trials is complex and difficult. In the Modification of Diet in Renal Disease (MDRD) Study, quality control of dietary data has been accomplished through the cooperative efforts of MDRD clinical center dietitians, the MDRD Data Coordinating Center, and the MDRD Nutrition Coordinating Center. The rationale for and steps in the design of quality control protocols and the distribution of responsibilities among the MDRD collaborators are discussed. This model of shared responsibility may be a useful approach for future trials.

A bound of deception capability in multiuser computer networks

An expression is developed to quantify the deception capability of an attacker in a multiuser computer network. A communication ends up with deception when any one or both of the communicating parties are deceived. The word deception is used to mean either the act of spoofing on an established association (i.e., a bidirectional data link), the process of setting up an unauthorized association, or both. In general, an attacker can use several different procedures to cheat a legitimate user of a data communication network. A subset of those procedures is examined to formulate an expression for the probability of a successful attack. This formulation is intended to be helpful for the design of robust message structures and fault-tolerant link control protocols for computer communication networks. The tradeoffs involved in achieving a desired level of authenticity of communicated messages are discussed. >

Flow control protocols for integrated networks with partially observed voice traffic

The design of flow control protocols for integrated networks with partially observed voice traffic on the data link level is investigated. A closed Markovian queueing network with two classes of users and a preemptive resume queueing discipline for modeling the integrated link is introduced. The class of admissible flow control policies analyzed maximizes the average data link throughput subject to an average system time delay constraint on a finite horizon. A separation principle between the flow control policy and an estimate of the state of the voice traffic is derived. In particular, it is shown that the optimum control law is bang-bang and the conditional mean estimate of the state of the voice traffic is a sufficient statistic for the optimal control strategy. Since the complexity of the analytical results prohibits finding the explicit flow control policy, a suboptimum and easily implementable adaptive window flow control mechanism is proposed. The window size changes dynamically according to the estimated state of the voice traffic at the destination node. The robustness of the estimator, the dynamics of the window size, and the effectiveness of the suboptimum scheme are verified by means of simulations.