This paper studies the problem of broadcasting layered video streams over heterogeneous single-hop wireless networks using feedback-free random linear network coding (RLNC). We combine RLNC with unequal error protection (UEP) and our main purpose is twofold: to systematically investigate the benefits of UEP+ RLNC layered approach in servicing users with different reception capabilities and to study the effect of not using feedback, by comparing feedback-free schemes with idealistic full-feedback schemes. To these ends, we study “expected percentage of decoded frames” as a key content-independent performance metric and propose a general framework for calculation of this metric, which can highlight the effect of key system, video, and channel parameters. We study the effect of number of layers and propose a scheme that selects the optimum number of layers adaptively to achieve the highest performance. Assessing the proposed schemes with real H.264 test streams, the trade-offs among the users' performances are discussed and the gain of adaptive selection of number of layers to improve the trade-offs is shown. Furthermore, it is observed that the performance gap between the proposed feedback-free scheme and the idealistic scheme is very small and the adaptive selection of number of video layers further closes the gap.

This paper studies the problem of transmitting multiple independent layered video streams over single-hop wireless networks using network coding (NC). We combine feedback-free random linear NC (RLNC) with unequal error protection (UEP) and our goal is to investigate the benefits of coding across streams, i.e. inter session NC. To this end, we present a transmission scheme that in addition to mixing packets of different layers of each stream (intra-session NC), mixes packets of different streams as well. Then, we propose the analytical formulation of the layer decoding probabilities for each user and utilize it to define a theoretical performance metric. Assessing this performance metric under various scenarios, it is observed that inter-session NC improves the trade-off among the performances of users. Furthermore, the analytical results show that the throughput gain of inter-session NC over intra-session NC increases with the number of independent streams and also by increasing packet error rate, but degrades as network becomes more heterogeneous.

In this paper, we consider the issue of throughput and packet drop rate (PDR) optimization as two performance metrics for delay sensitive applications in network coded time division duplex (TDD) satellite systems with large round trip times (RTTs). We adopt random linear network coding (RLNC) and our purpose is to obtain the optimum RLNC-based transmission strategy. We start with a single-user case and propose a systematic framework to investigate the advantage of using feedback by comparing feedback-free and feedback schemes. Showing analytically that the feedback-free scheme gives better performance for our system of interest, we extend it to multi-user broadcast case. To this end, we consider a number of different broadcast scenarios and optimize the system parameters such that the best overall performance is achieved. Furthermore, the complicated interplay of the mean throughputs and PDRs of different users with different packet erasure conditions is discussed. Finally, it is shown that the optimized feedback-free RLNC broadcast scheme works close enough to an idealistic RLNC scheme, where the complete and immediate knowledge about the reception status of all users is assumed to be available at the sender.

In this paper, we consider the problem of guaranteeing the quality of service (QoS) in delay sensitive network coded broadcast systems over time division duplex (TDD) satellite channels. We adopt feedback-less systematic random linear network coding (RLNC) and our goal is to design the system such that the required QoS is guaranteed. We focus on two classes of QoS requirements that necessitate the minimum/mean throughput of the users be higher than a threshold with a predefined probability and at the same time the packet drop rates (PDR) of the users be minimized within the delivery deadline requirements of the system. To this end, we start with formulating the probability and cumulative density functions (PDF and CDF) of users' throughputs. Then by utilizing the calculated functions, the optimum system design parameters that meet the QoS requirements can be obtained. The achieved results on the PDF and CDF of users' throughputs offer good insights about the performances of different users with different packet erasure conditions, and more importantly provide design guidelines for TDD satellite broadcast systems. Furthermore, the results show that the proposed feedback-less scheme performs nearly as well as an idealistic scheme using immediate and perfect feedbacks.