51 research outputs found
Adaptive beamforming in mobile, massively multiuser satellite communications: A system perspective
No full textNetwork Coding Channel Virtualization Schemes for Satellite Multicast Communications
No full textIn this paper, we propose two novel schemes to solve the problem of finding a quasi-optimal number of coded packets to multicast to a set of independent wireless receivers suffering different channel conditions. In particular, we propose two network channel virtualization schemes that allow for representing the set of intended receivers in a multicast group to be virtualized as one receiver. Such approach allows for a transmission scheme not only adapted to per-receiver channel variation over time, but to the network-virtualized channel representing all receivers in the multicast group. The first scheme capitalizes on a maximum erasure criterion introduced via the creation of a virtual worst per receiver per slot reference channel of the network. The second scheme capitalizes on a maximum completion time criterion by the use of the worst performing receiver channel as a virtual reference to the network. We apply such schemes to a GEO satellite scenario. We demonstrate the benefits of the proposed schemes comparing them to a per-receiver point-to-point adaptive strategy
Physical layer aware adaptive network coding schemes for satellite communications
No full textNetwork coding is a technology that provides core benefits to communication services, in terms of reliability, latency, and data rate, by leveraging on a coding structure that reduces the necessity for retransmissions of packets. Satellite communications are one of the potential applications that can leverage on the benefits of network coding due to their challenging fading environments and high round trip times. By introducing physical layer awareness, network coding offers further gains to such communications systems. In this paper, we propose different rate and energy efficient adaptive network coding schemes for time-variant channels. We compare our proposed physical layer aware adaptive schemes to physical layer nonadaptive network coding schemes for time-variant channels. The proposed schemes demonstrate that adaptation of packet transmissions based on the channel variations over time, and their corresponding time-dependent erasures, allows for significant gains in terms of throughput, delay, and energy efficiency. We shed light on the trade-off between energy efficiency and delay-throughput gains, demonstrating that conservative adaptive approaches that favor less transmission under high erasures might cause higher delay and less-throughput gains in comparison to nonconservative approaches that favor more transmissions to account for high erasures. We show that such schemes are robust with regimes of large or small packet sizes; albeit the energy per bit is affected, similar rate and energy gains can be obtained. In turn, we show that the performance gains are driven by the duty cycle of the packets silent transmission and not by the packet size
Adaptive network coding schemes for satellite communications
No full textIn this paper, we propose two novel physical layer aware adaptive network coding schemes for time variant channels, one aiming to maximize the energy efficiency, the other exploiting also the variable modulation order, in an adaptive way. The proposed schemes have been applied to different satellite communications scenarios with different Round Trip Times (RTT). Compared to adaptive network coding, and classical non-adaptive network coding schemes for time variant channels, used as benchmarks, the proposed schemes demonstrate that adaptation of packet transmission based on the channel variation and corresponding erasures allows for significant gains in terms of throughput, delay and energy efficiency. We shed light on the trade-off between energy efficiency and delay-throughput gains, demonstrating that conservative adaptive approaches that favor less transmission under high erasures, might cause higher delay and less throughput gains in comparison to non-conservative approaches that favor more transmission to account for high erasures
Energy efficient Adaptive Network Coding Schemes for Satellite Communications
No full textIn this paper, we propose novel energy efficient adaptive network coding and modulation schemes for time variant channels. We evaluate such schemes under a realistic channel model for open area environments and Geostationary Earth Orbit (GEO) satellites. Compared to non-adaptive network coding and adaptive rate efficient network-coded schemes for time variant channels, we show that our proposed schemes, through physical layer awareness can be designed to transmit only if a target quality of service (QoS) is achieved. As a result, such schemes can provide remarkable energy savings
Network Coding Power Control Mechanisms for Time Varying Channels
Get PDFIn this paper, we propose a model for large scale fading channels via markov
process. We exploit the channel delay profile and the dependency between
channel states via a first order autoregressive model that cast insight to the
channel variations under fading and the closed form delay induced. We propose a
network-coding structure that can be employed to compensate for the channel
variations under fixed power and to the period of zero packet transmissions
under adaptive power control. Satellite communications is an application to the
model proposed
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