On the Interaction between TCP and the Wireless Channel in CDMA2000 Networks

In this work, we conducted extensive active measurements on a large nationwide CDMA2000 1xRTT network in order to characterize the impact of both the Radio Link Protocol and more importantly, the wireless scheduler, on TCP. Our measurements include standard TCP/UDP logs, as well as detailed RF layer statistics that allow observability into RF dynamics. With the help of a robust correlation measure, normalized mutual information, we were able to quantify the impact of these two RF factors on TCP performance metrics such as the round trip time, packet loss rate, instantaneous throughput etc. We show that the variable channel rate has the larger impact on TCP behavior when compared to the Radio Link Protocol. Furthermore, we expose and rank the factors that influence the assigned channel rate itself and in particular, demonstrate the sensitivity of the wireless scheduler to the data sending rate. Thus, TCP is adapting its rate to match the available network capacity, while the rate allocated by the wireless scheduler is influenced by the sender's behavior. Such a system is best described as a closed loop system with two feedback controllers, the TCP controller and the wireless scheduler, each one affecting the other's decisions. In this work, we take the first steps in characterizing such a system in a realistic environment

TCP over CDMA2000 Networks: A Cross-Layer Measurement Study

Modern cellular channels in 3G networks incorporate sophisticated power control and dynamic rate adaptation which can have significant impact on adaptive transport layer protocols, such as TCP. Though there exists studies that have evaluated the performance of TCP over such networks, they are based solely on observations at the transport layer and hence have no visibility into the impact of lower layer dynamics, which are a key characteristic of these networks. In this work, we present a detailed characterization of TCP behavior based on cross-layer measurement of transport layer, as well as RF and MAC layer parameters. In particular, through a series of active TCP/UDP experiments and measurement of the relevant variables at all three layers, we characterize both, the wireless scheduler and the radio link protocol in a commercial CDMA2000 network and assess their impact on TCP dynamics. Somewhat surprisingly, our findings indicate that the wireless scheduler is mostly insensitive to channel quality and sector load over short timescales and is mainly affected by the transport layer data rate. Furthermore, with the help of a robust correlation measure, Normalized Mutual Information, we were able to quantify the impact of the wireless scheduler and the radio link protocol on various TCP parameters such as the round trip time, throughput and packet loss rate

TCP over CDMA2000 Networks: A Cross-Layer Measurement Study

Modern cellular channels in 3G networks incorporate sophisticated power control and dynamic rate adaptation which can have a significant impact on adaptive transport layer protocols, such as TCP. Though there exists studies that have evaluated the performance of TCP over such networks, they are based solely on observations at the transport layer and hence have no visibility into the impact of lower layer dynamics, which are a key characteristic of these networks. In this work, we present a detailed characterization of TCP behavior based on cross-layer measurement of transport, as well as RF and MAC layer parameters. In particular, through a series of active TCP/UDP experiments and measurement of the relevant variables at all three layers, we characterize both, the wireless scheduler in a commercial CDMA2000 network and its impact on TCP dynamics. Somewhat surprisingly, our findings indicate that the wireless scheduler is mostly insensitive to channel quality and sector load over short timescales and is mainly affected by the transport layer data rate. Furthermore, we empirically demonstrate the impact of the wireless scheduler on various TCP parameters such as the round trip time, throughput and packet loss rate

Dimming cellular networks

We propose a novel technique called dimming to improve the energy efficiency of cellular networks by reducing the capacity, services, and energy consumption of cells without turning off the cells. We define three basic methods to dim the network: coverage, frequency, and service dimming. We construct a multi-time period optimization problem to implement frequency dimming and extend it to implement both frequency and service dimming together. We illustrate the ability of dimming techniques to adapt the capacity and network services in proportion to the dynamic spatial and temporal load resulting in significant energy savings through numerical results for a sample network. ©2010 IEEE

Flexible application driven network striping over Wireless Wide Area Networks

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 157-161).Inverse multiplexing, or network striping, allows the construction of a high-bandwidth virtual channel from a collection of multiple low-bandwidth network channels. Striping systems usually employ a packet scheduling policy that allows applications to be oblivious of the way in which packets are routed to specific network channels. Though this is appropriate for many applications, many other applications can benefit from an approach that explicitly involves the application in the determination of the striping policy. Horde is middleware that facilitates flexible striping over Wireless Wide Area Network (WWAN) channels. Horde is unusual in that it separates the striping policy from the striping mechanism. It allows applications to describe network Quality-of-Service (QoS) objectives that the striping mechanism attempts to satisfy. Horde can be used by a set of data streams, each with its own QoS policy, to stripe data over a set of WWAN channels. The WWAN QoS variations observed across different channels and in time, provide opportunities to modulate stream QoS through scheduling. The key technical challenge in Horde is giving applications control over certain aspects of the data striping operation while at the same time shielding the application from low-level details. Horde exports a set of flexible abstractions replacing the application's network stack. Horde allows applications to express their policy goals as succinct network-QoS objectives. Each objective says something, relatively simple, about the sort of network QoS an application would like for some data stream(s). We present the Horde architecture, describe an early implementation, and examine how different policies can be used to modulate the quality-of-service observed across different independent data streams. Through experiments conducted on real and simulated network channels, we confirm our belief that the kind of QoS modulation Horde aims to achieve is realistic for actual applications.by Asfandyar Qureshi.M.Eng

Power control for WCDMA

This project tries to introduce itself in the physical implementations that make possible the denominated third generation mobile technology. As well as to know the technology kind that makes possible, for example, a video-call in real time. During this project, the different phases passed from the election of WCDMA like the access method for UMTS will appear. Its coexistence with previous network GSM will be analyzed, where the compatibility between systems has been one of the most important aspects in the development of WCDMA, the involved standardization organisms in the process, as well as the different protocols that make the mobile communications within a network UTRAN possible. Special emphasis during the study of the great contribution that has offered WCDMA with respect to the control of power of the existing signals will be made. The future lines that are considered in the present, and other comment that already are in their last phase of development in the field of the mobile technology. UMTS through WCDMA can be summarized like a revolution of the air interface accompanied by a revolution in the network of their architecture

Quality of service analysis for audio over cellular voice networks and cellular wireless wide area networks

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 51-[55]).Cellular Wireless Wide Area Networks (WWANs) are most prevalent and offer high-bandwidth data transfer. We believe WWANs can be availed for voice communications employing Voice Over IP technologies. Such a communication will be of better quality and offer higher resilience compared to voice communication over a cellular phone (using cellular voice networks). We present a Quality of Service analysis of one-way voice communication over cellular voice networks and cellular WWANs. By studying different quality metrics we test if WWANs offer a better solution for voice communications compared to traditional cellular voice networks. We also study if employing more than one WWANs or cellular voice networks leads to a higher resilience in voice communication.by Omair S. Malik.M.Eng