arXiv subjects

Sanjit K. Kaul

Publications and source records attributed to Sanjit K. Kaul.

26 records · Page 2Linked to original sources

arXiv2018

QAware: A Cross-Layer Approach to MPTCP Scheduling

Multipath TCP (MPTCP) allows applications to transparently use all available network interfaces by creating a TCP subflow per interface. One critical component of MPTCP is the scheduler that decides which subflow to use for each packet. Existing schedulers typically use estimates of end-to-end path properties, such as delay and bandwidth, for making the scheduling decisions. In this paper, we show that these scheduling decisions can be significantly improved by incorporating readily available local information from the device driver queues in the decision-making process. We propose QAware, a novel cross-layer approach for MPTCP scheduling. QAware combines end-to-end delay estimates with local queue buffer occupancy information and allows for a better and faster adaptation to the network conditions. This results in more efficient use of the available resources and considerable gains in aggregate throughput. We present the design of QAware and evaluate its performance through simulations, and also through real experiments, comparing it to existing schedulers. Our results show that QAware performs significantly better than other available approaches for various use-cases and applications.

cs.NI↗

arXiv2018

Improving the Performance of WLANs by Reducing Unnecessary Active Scans

We consider the problem of excessive and unnecessary active scans in heavily utilized WLANs during which low rate probe requests and responses are broadcast. These management frames severely impact the goodput. Our analysis of two production WLANs reveals that lesser number of non-overlapping channels in $2.4$ GHz makes it more prone to the effects of increased probe frames than $5$ GHz. We find that not only up to $90$% of probe responses carry redundant information but the probe traffic can be as high as $60$\% of the management traffic. Furthermore, active scanning severely impacts real-time applications at a client as it increases the latency by $91$ times. We present a detailed analysis of the impact of active scans on an individual client and the whole network. We discuss three ways to control the probe traffic in production WLANs -- access point configurations, network planning, and client modification. Our proposals for access point configuration are in line with current WLAN deployments, better network planning is device agnostic in nature, and client modification reduces the average number of probe requests per client by up to $50$% without hampering the ongoing WiFi connection.

cs.NI↗

arXiv2018

A Reinforcement Learning Approach to Jointly Adapt Vehicular Communications and Planning for Optimized Driving

Our premise is that autonomous vehicles must optimize communications and motion planning jointly. Specifically, a vehicle must adapt its motion plan staying cognizant of communications rate related constraints and adapt the use of communications while being cognizant of motion planning related restrictions that may be imposed by the on-road environment. To this end, we formulate a reinforcement learning problem wherein an autonomous vehicle jointly chooses (a) a motion planning action that executes on-road and (b) a communications action of querying sensed information from the infrastructure. The goal is to optimize the driving utility of the autonomous vehicle. We apply the Q-learning algorithm to make the vehicle learn the optimal policy, which makes the optimal choice of planning and communications actions at any given time. We demonstrate the ability of the optimal policy to smartly adapt communications and planning actions, while achieving large driving utilities, using simulations.

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arXiv2018

A Game Theoretic Approach to DSRC and WiFi Coexistence

We model the coexistence of DSRC and WiFi networks as a strategic form game with the networks as the players. Nodes in a DSRC network must support messaging of status updates that are time sensitive. Such nodes would like to achieve a small age of information of status updates. In contrast, nodes in a WiFi network would like to achieve large throughputs. Each network chooses a medium access probability to be used by all its nodes. We investigate Nash and Stackelberg equilibrium strategies.

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arXiv2017

The Age of Information: Real-Time Status Updating by Multiple Sources

We examine multiple independent sources providing status updates to a monitor through simple queues. We formulate an Age of Information (AoI) timeliness metric and derive a general result for the AoI that is applicable to a wide variety of multiple source service systems. For first-come first-served and two types of last-come first-served systems with Poisson arrivals and exponential service times, we find the region of feasible average status ages for multiple updating sources. We then use these results to characterize how a service facility can be shared among multiple updating sources. A new simplified technique for evaluating the AoI in finite-state continuous-time queueing systems is also derived. Based on stochastic hybrid systems, this method makes AoI evaluation to be comparable in complexity to finding the stationary distribution of a finite-state Markov chain.

cs.IT↗

arXiv2017

More Than The Sum Of Its Parts: Exploiting Cross-Layer and Joint-Flow Information in MPTCP

Multipath TCP (MPTCP) is an extension to TCP which aggregates multiple parallel connections over available network interfaces. MPTCP bases its scheduling decisions on the individual RTT values observed at the subflows, but does not attempt to perform any kind of joint optimization over the subflows. Using the MPTCP scheduler as an example, in this paper we demonstrate that exploiting cross-layer information and optimizing scheduling decisions jointly over the multiple flows, can lead to significant performance gains. While our results only represent a single data point, they illustrate the need to look at MPTCP from a more holistic point of view and not treat the connections separately, as is currently being done. We call for new approaches and research into how multiple parallel connections offered by MPTCP should be used in an efficient and fair manner.

cs.NI↗

arXiv2017

Optimizing Networks for Internet Access Using Tethering

We investigate scenarios where Internet access to a user device (node) is available only via the cellular network. However, not every node may connect directly to it. Instead, some may use tethering to connect over WiFi to a node sharing its Internet connection. In effect, nodes split into hotspots and clients. Hotspots are nodes that connect directly to the cellular network and can provide Internet connectivity to other nodes to whom they are connected over WiFi. Clients connect to the cellular network only via hotspots. In this work, we consider the problem of determining the split of hotspots and clients, and the association between them, which maximizes the sum of the rates of all nodes, subject to the constraint that any node gets at least the rate it gets when all nodes are directly connected to the cellular network. Via tractable networks, we provide insights into the interplay between WiFi connectivity amongst nodes and rates of their links to the cellular tower, the splits that maximize sum rate, with provably optimal splits for a few cases. We propose a novel heuristic approach to split any network and provide a detailed exposition of gains available from tethering, via simulations.

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arXiv2017

Status Updates Over Unreliable Multiaccess Channels

Applications like environmental sensing, and health and activity sensing, are supported by networks of devices (nodes) that send periodic packet transmissions over the wireless channel to a sink node. We look at simple abstractions that capture the following commonalities of such networks (a) the nodes send periodically sensed information that is temporal and must be delivered in a timely manner, (b) they share a multiple access channel and (c) channels between the nodes and the sink are unreliable (packets may be received in error) and differ in quality. We consider scheduled access and slotted ALOHA-like random access. Under scheduled access, nodes take turns and get feedback on whether a transmitted packet was received successfully by the sink. During its turn, a node may transmit more than once to counter channel uncertainty. For slotted ALOHA-like access, each node attempts transmission in every slot with a certain probability. For these access mechanisms we derive the age of information (AoI), which is a timeliness metric, and arrive at conditions that optimize AoI at the sink. We also analyze the case of symmetric updating, in which updates from different nodes must have the same AoI. We show that ALOHA-like access, while simple, leads to AoI that is worse by a factor of about 2e, in comparison to scheduled access.

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