Hana Khamfroush

We study the problem of minimizing the cost of packet transmission from a source to two receivers with the help of a relay and using network coding in wireless mesh networks consisting of many active neighbours sharing the same channel. Two simple heuristics are proposed to estimate the appropriate time for activating the relay to provide close-tooptimal performance. Our numerical results show that a judicious network coding enabled relay can bring up to 2.9x gains in the presence of active… Show more

We study the problem of minimizing the cost of packet transmission from a source to two receivers with the help of a relay and using network coding in wireless mesh networks consisting of many active neighbours sharing the same channel. Two simple heuristics are proposed to estimate the appropriate time for activating the relay to provide close-tooptimal performance. Our numerical results show that a judicious network coding enabled relay can bring up to 2.9x gains in the presence of active neighbours compared to multicasting directly from the source. We further show that in scenarios which the links between relay and destinations are not better than the links between source and destinations, a relay can still provide up to 1.7x gain.
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Network-coded cooperative communication (NC-CC) has been proposed and evaluated as a powerful technology that can provide a better quality of service in the next-generation wireless systems, e.g., D2D communications. Previous contributions have focused on performance evaluation of NC-CC scenarios rather than searching for optimal policies that can minimize the total cost of reliable packet transmission. We break from this trend by initially analyzing the optimal design of NC-CC for a wireless… Show more

Network-coded cooperative communication (NC-CC) has been proposed and evaluated as a powerful technology that can provide a better quality of service in the next-generation wireless systems, e.g., D2D communications. Previous contributions have focused on performance evaluation of NC-CC scenarios rather than searching for optimal policies that can minimize the total cost of reliable packet transmission. We break from this trend by initially analyzing the optimal design of NC-CC for a wireless network with one source, two receivers, and half-duplex erasure channels. The problem is modeled as a special case of Markov decision process (MDP), which is called stochastic shortest path (SSP), and is solved for any field size, arbitrary number of packets, and arbitrary erasure probabilities of the channels. The proposed MDP solution results in an optimal transmission policy per time slot, and we use it to design near-optimal heuristics for packet transmission in a network of one source and N ≥ 2 receivers. We also present numerical results that illustrate the performance of the proposed heuristics under a variety of scenarios. To complete our analysis, our heuristics are implemented in Aalborg University's Raspberry Pi testbed and compared with random linear network coding (RLNC) broadcast in terms of completion time, total number of required transmissions, and percentage of delivered generations. Our measurements show that enabling cooperation only among pairs of devices can decrease the completion time by up to 4.75 times, while delivering 100% of the 10000 generations transmitted, as compared to RLNC broadcast delivering only 88% of them in our tests.
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In this paper, we investigate the optimal design of cooperative network-coded strategies for a three-node wireless network with time-varying half-duplex erasure channels. To this end, first, we theoretically formulate the problem of minimizing the total cost of transmitting M packets from source to two receivers, and then a comprehensive analysis is carried out under different network conditions to extract optimal rules of packet transmission. Inspired by the extracted rules, we propose two… Show more

In this paper, we investigate the optimal design of cooperative network-coded strategies for a three-node wireless network with time-varying half-duplex erasure channels. To this end, first, we theoretically formulate the problem of minimizing the total cost of transmitting M packets from source to two receivers, and then a comprehensive analysis is carried out under different network conditions to extract optimal rules of packet transmission. Inspired by the extracted rules, we propose two near-optimal heuristics that are suitable for practical systems. We use two wireless channel models to analyze the performance of the proposed heuristics in practical wireless networks, namely; an infrastructure-to-vehicle communication in a highway scenario considering Rayleigh fading; and real packet loss measurements for WiFi using Aalborg University's Raspberry Pi test-bed. We compare our results with random linear network coding broadcasting schemes showing that our heuristics can provide up to 2 × gains in completion time and up to 4 × gains in terms of reliably serviced data packets.

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We consider the problem of finding an optimal packet transmission policy that minimizes the total cost of transmitting M data packets from a source S to two receivers R1, R2 over half-duplex, erasure channels. The source can either broadcast random linear network coding (RLNC) packets to the receivers or transmit using unicast sessions at each time slot. We assume that the receivers can share their knowledge with each other by sending RLNC packets using unicast transmissions.
We model this… Show more

We consider the problem of finding an optimal packet transmission policy that minimizes the total cost of transmitting M data packets from a source S to two receivers R1, R2 over half-duplex, erasure channels. The source can either broadcast random linear network coding (RLNC) packets to the receivers or transmit using unicast sessions at each time slot. We assume that the receivers can share their knowledge with each other by sending RLNC packets using unicast transmissions.
We model this problem as a Decision Making Process where the actions include the source of and type of transmission to be used in a given time slot given perfect knowledge of the system state. We study the distribution of actions selected by the optimal policy maker in terms of the knowledge at the receivers, the channel erasure probabilities, and the ratio between the cost of broadcast and unicast. This allowed us to learn from the optimal policy and devise two simple, yet powerful heuristics that are useful in practice. Our heuristics rely on different levels of feedback, namely, sending 1 or 2 feedback packets per receiver per M data packets by choosing the right moment to send this feedback. Our numerical results show that our heuristics are able to achieve the same performance of the optimal solution.
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This paper studies the problem of optimal use of a relay for reducing the transmission time of data packets from a source to a destination using network coding. More importantly, we address an effect that is typically overlooked in previous studies: the presence of active transmitting nodes in the neighborhood of such devices, which is typical in wireless mesh networks. We show that in systems with a fair medium access control mechanism (MAC), the use of a relay in a crowded medium brings forth… Show more

This paper studies the problem of optimal use of a relay for reducing the transmission time of data packets from a source to a destination using network coding. More importantly, we address an effect that is typically overlooked in previous studies: the presence of active transmitting nodes in the neighborhood of such devices, which is typical in wireless mesh networks. We show that in systems with a fair medium access control mechanism (MAC), the use of a relay in a crowded medium brings forth considerable and unforeseen improvements, including up to 3.5x gains in terms of throughput compared to using only the direct link in some of our examples, and a considerable extension of the operating region where using a relay is beneficial. Show less

We present a vehicular communication protocol, GeoCode, capable of containing broadcast transmissions within a confined region. The crux of the protocol is a modified directed diffusion policy, which is used to generate multiple paths within an ellipse, these paths may intersect each other at intermediate nodes which use network coding to maximize the throughput. A comparison with traditional multi-path routing algorithms, which deliver node-disjoint and non coding-aware solutions, reveals that… Show more

We present a vehicular communication protocol, GeoCode, capable of containing broadcast transmissions within a confined region. The crux of the protocol is a modified directed diffusion policy, which is used to generate multiple paths within an ellipse, these paths may intersect each other at intermediate nodes which use network coding to maximize the throughput. A comparison with traditional multi-path routing algorithms, which deliver node-disjoint and non coding-aware solutions, reveals that GeoCode is able to achieve the same throughput using only 1/3 of the transmission area, thus mitigating the interference and reducing the overall energy consumption. Show less