On the impact of link layer retransmission schemes on TCP over 4G satellite links

We study the impact of reliability mechanisms introduced at the link layer on the performance of transport protocols in the context of 4G satellite links. Specifically, we design a software module that performs realistic analysis of the network performance, by utilizing real physical layer traces of a 4G satellite service. Based on these traces, our software module produces equivalent link layer traces, as a function of the chosen link layer reliability mechanism. We further utilize the link layer traces within the ns-2 network simulator to evaluate the impact of link layer schemes on the performance of selected Transmission Control Protocol (TCP) variants. We consider erasure coding, selective-repeat automatic request (ARQ) and hybrid-ARQ link layer mechanisms, and TCP Cubic, Compound, Hybla, New Reno and Westwood. We show that, for all target TCP variants, when the throughput of the transport protocol is close to the channel capacity, using the ARQ mechanism is most beneficial for TCP performance improvement. In conditions where the physical channel error rate is high, hybrid-ARQ results in the best performance for all TCP variants considered, with up to 22% improvements compared to other schemes

An Agent-Based Modelling Simulation Approach to Calculate Processing Delay of GEO Satellite Payload

The global coverage of broadband multimedia and internet-based services in terrestrial-satellite networks demand particular interests for satellite providers in order to enhance services with low latencies and high signal quality to diverse users. In particular, the delay of on-board processing is an inherent source of latency in a satellite communication that sometimes is discarded for the end-to-end delay of the satellite link. The frame work for this paper includes modelling of an on-orbit satellite payload using an agent model that can reproduce the properties of processing delays. In essence, a comparison of different spatial interpolation methods is carried out to evaluate physical data obtained by an GEO satellite in order to define a discretization function for determining that delay. Furthermore, the performance of the proposed agent and the development of a delay discretization function are together validated by simulating an hybrid satellite and terrestrial network. Simulation results show high accuracy according to the characteristics of initial data points of processing delay for Ku bands

CLIFT: a Cross-Layer InFormation Tool for Latency Analysis Based on Real Satellite Physical Traces

New mobile technology generations succeed in achieving high goodput, which results in diverse applications profiles exploiting various resource providers (Wifi, 4G, 5G, . . . ). Badly set parameters on one of the network component may severely impact on the transmission delay and reduce the quality of experience. The cross layer impact should be investigated on to assess the origin of latency. To run cross-layer (from physical layer to application layers) simulations, two approaches are possible: (1) use physical layer models that may not be exhaustive enough to drive consistent analysis or (2) use real physical traces. Driving realistic measurements by using real physical (MAC/PHY) traces inside network simulations is a complex task. We propose to cope with this problem by introducing Cross Layer InFormation Tool (CLIFT), that translates real physical events from a given trace in order to be used inside a network simulator such as ns-2. Our proposal enables to accurately perform analysis of the impact of link layer reliability schemes (obtained by the use of real physical traces) on transport layer performance and on the latency. Such approach enables a better understanding of the interactions between the layers. The main objective of CLIFT is to let us study the protocols introduced at each layer of the OSI model and study their interaction. We detail the internal mechanisms and the benefits of this software with a running example on 4G satellite communications scenarios

A Model for Behavioral Tendency of TCP Congestion Control Variants in LTE Cellular and 802.11ac Networks

As a reliable protocol, TCP protocol configuration requires many parameters to be set before the actual packet transmissions happen. However, the TCP parameters need to be changed from the initial fixed default values to suit the network requirements since it is utilized on many dissimilar mobile networks, including the LTE cellular and the 802.11ac. On the other hand, LTE cellular and 802.11ac networks also have their own design parameters. In this case, utilizing the TCP in these networks will result in the TCP parameters to interact with LTE and 802.11ac parameters, which subsequently can optimize or degrade the network performance due to correct or poor parameters setting. Therefore, it is highly important to determine the correct values for both protocol parameters and network parameters to achieve optimal network performance. This work presents a model to determine the interaction between the TCP protocol parameters, including the congestion control variants and the size of packets and network parameters that include RLC modes in LTE and A-MPDU aggregation mechanism in 802.11ac. Drawn from an extensive set of scenarios and experiments, the results show significant performance improvements achieved by the verified matching parameters