In this paper we develop models that incorporate general mobility patterns that are induced by th... more In this paper we develop models that incorporate general mobility patterns that are induced by the cell topography (e.g., road layout, street orientation, density of intersections). In particular, we study the effect of the different mobility patterns on the handoff probability. The mobility patterns are induced by common terrains such as random, Manhattan, circular and highway. We study the circular mobility pattern in detail and examine the impact of the base station placement on the handoff probability. The results in this paper suggest that we may be able to estimate the handoff probabilities from a knowledge of the cell terrain, the mobile trajectory, and the vehicular movements in a cellular network, and this may serve as a useful guide for cellular network engineering
Motivated by the emerging standards for indoor pico-cellular wireless systems, such as the Blueto... more Motivated by the emerging standards for indoor pico-cellular wireless systems, such as the Bluetooth, we propose and study the scheduling policies for master driven time division duplex (TDD) wireless networks. In these networks, the frequency band is divided into time slots, and each end (i.e., master or slave) takes turns in using the time slots. In Bluetooth, a slave transmits packets in the reverse slot only after the master polls the slave in a forward slot (by sending data to it). The conventional scheduling policies such as round robin do not perform well in these systems as they are not suited to the tight coupling of the uplink-downlink. We propose new scheduling policies, (i) the priority scheme, and, (ii) the K-fairness scheme that utilize the state at the master and slaves to schedule the TDD slots effectively. Active slaves are differentiated based upon the binary information (i.e., the presence or absence of packets in a slave queue) about the master-slave queue pairs. The priority scheme achieves high throughput as compared to the packet-by-packet generalized processor sharing (PGPS) based policies while guaranteeing a minimal service to each active slave while the K-fairness policy is characterized by a tight fairness bound as well as high system throughput. We then extend these policies for scheduling variable size data in the presence of voice. Further, since Bluetooth supports variable size data packets (1, 3 or 5 slots) on the same connections, the segmentation and reassembly (SAR) can significantly impact scheduling of data packets by varying packet size distribution. We propose an intelligent SAR policy (ISAR) and compare it with the naive random-SAR in which the data packet sizes (i.e., 1, 3 or 5) are assigned probabilistically. ISAR adapts MAC packet size at the master and slave queues depending on the data arrival rates at both the queues
Teletraffic modelling of users is crucial for cellular system layout and planning, and to evaluat... more Teletraffic modelling of users is crucial for cellular system layout and planning, and to evaluate tradeoffs in system design issues. In order to be useful, the model should capture mobility under the most generalized conditions. We develop models that incorporate general mobility patterns that are induced by the cell topography (e.g., road layout, street orientation, density of intersections). In particular, we study the effect of the different mobility patterns on the handoff probability. The mobility patterns are induced by common terrains such as random, Manhattan, circular and highway. The results suggest that we may be able to estimate the handoff probabilities from a knowledge of the cell terrain, the mobile trajectory, and the vehicular movements in a cellular network, and thus may serve as a useful guide for cellular network engineering
Reliable transport protocols such as the Transmission Con-trol Protocol (TCP) are tuned to perfor... more Reliable transport protocols such as the Transmission Con-trol Protocol (TCP) are tuned to perform well in traditional wireline networks where packet losses occur mostly because of congestion. However, networks with wireless and lossy links also suffer from significant ...
This paper introduces and analyzes a class of nonlinear con-gestion control algorithms called bin... more This paper introduces and analyzes a class of nonlinear con-gestion control algorithms called binomial algorithms, moti-vated in part by the needs of streaming audio and video ap-plications for which a drastic reduction in transmission rate upon congestion is problematic. ...
This paper describes the implementation and evaluation of an operating system module, the Congest... more This paper describes the implementation and evaluation of an operating system module, the Congestion Manager (CM), which provides integrated network flow management and exports a convenient programming interface that allows applications to be notified of, and adapt to, changing network conditions. We describe the API by which applications interface with the CM, and the architectural considerations that factored into the design. To evaluate the architecture and API, we describe our implementations of TCP; a streaming layered audio/video application; and an interactive audio application using the CM, and show that they achieve adaptive behavior without incurring much end-system overhead. All flows including TCP benefit from the sharing of congestion information, and applications are able to incorporate new functionality such as congestion control and adaptive behavior.
In this paper we develop models that incorporate general mobility patterns that are induced by th... more In this paper we develop models that incorporate general mobility patterns that are induced by the cell topography (e.g., road layout, street orientation, density of intersections). In particular, we study the effect of the different mobility patterns on the handoff probability. The mobility patterns are induced by common terrains such as random, Manhattan, circular and highway. We study the circular mobility pattern in detail and examine the impact of the base station placement on the handoff probability. The results in this paper suggest that we may be able to estimate the handoff probabilities from a knowledge of the cell terrain, the mobile trajectory, and the vehicular movements in a cellular network, and this may serve as a useful guide for cellular network engineering
Motivated by the emerging standards for indoor pico-cellular wireless systems, such as the Blueto... more Motivated by the emerging standards for indoor pico-cellular wireless systems, such as the Bluetooth, we propose and study the scheduling policies for master driven time division duplex (TDD) wireless networks. In these networks, the frequency band is divided into time slots, and each end (i.e., master or slave) takes turns in using the time slots. In Bluetooth, a slave transmits packets in the reverse slot only after the master polls the slave in a forward slot (by sending data to it). The conventional scheduling policies such as round robin do not perform well in these systems as they are not suited to the tight coupling of the uplink-downlink. We propose new scheduling policies, (i) the priority scheme, and, (ii) the K-fairness scheme that utilize the state at the master and slaves to schedule the TDD slots effectively. Active slaves are differentiated based upon the binary information (i.e., the presence or absence of packets in a slave queue) about the master-slave queue pairs. The priority scheme achieves high throughput as compared to the packet-by-packet generalized processor sharing (PGPS) based policies while guaranteeing a minimal service to each active slave while the K-fairness policy is characterized by a tight fairness bound as well as high system throughput. We then extend these policies for scheduling variable size data in the presence of voice. Further, since Bluetooth supports variable size data packets (1, 3 or 5 slots) on the same connections, the segmentation and reassembly (SAR) can significantly impact scheduling of data packets by varying packet size distribution. We propose an intelligent SAR policy (ISAR) and compare it with the naive random-SAR in which the data packet sizes (i.e., 1, 3 or 5) are assigned probabilistically. ISAR adapts MAC packet size at the master and slave queues depending on the data arrival rates at both the queues
Teletraffic modelling of users is crucial for cellular system layout and planning, and to evaluat... more Teletraffic modelling of users is crucial for cellular system layout and planning, and to evaluate tradeoffs in system design issues. In order to be useful, the model should capture mobility under the most generalized conditions. We develop models that incorporate general mobility patterns that are induced by the cell topography (e.g., road layout, street orientation, density of intersections). In particular, we study the effect of the different mobility patterns on the handoff probability. The mobility patterns are induced by common terrains such as random, Manhattan, circular and highway. The results suggest that we may be able to estimate the handoff probabilities from a knowledge of the cell terrain, the mobile trajectory, and the vehicular movements in a cellular network, and thus may serve as a useful guide for cellular network engineering
Reliable transport protocols such as the Transmission Con-trol Protocol (TCP) are tuned to perfor... more Reliable transport protocols such as the Transmission Con-trol Protocol (TCP) are tuned to perform well in traditional wireline networks where packet losses occur mostly because of congestion. However, networks with wireless and lossy links also suffer from significant ...
This paper introduces and analyzes a class of nonlinear con-gestion control algorithms called bin... more This paper introduces and analyzes a class of nonlinear con-gestion control algorithms called binomial algorithms, moti-vated in part by the needs of streaming audio and video ap-plications for which a drastic reduction in transmission rate upon congestion is problematic. ...
This paper describes the implementation and evaluation of an operating system module, the Congest... more This paper describes the implementation and evaluation of an operating system module, the Congestion Manager (CM), which provides integrated network flow management and exports a convenient programming interface that allows applications to be notified of, and adapt to, changing network conditions. We describe the API by which applications interface with the CM, and the architectural considerations that factored into the design. To evaluate the architecture and API, we describe our implementations of TCP; a streaming layered audio/video application; and an interactive audio application using the CM, and show that they achieve adaptive behavior without incurring much end-system overhead. All flows including TCP benefit from the sharing of congestion information, and applications are able to incorporate new functionality such as congestion control and adaptive behavior.
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