Multicast multigroup precoding for frame-based multi-gateway satellite communications

in Advanced Satellite Multimedia Systems Conference and the 14th Signal Processing for Space Communications Workshop (ASMS/SPSC), 2016 8th (2016, October 24)

The present work focuses on the forward link of fixed multibeam broadband satellite systems which employ aggressive frequency reuse patterns in the user-link. For such scenarios, the state-of-the art ... [more ▼]

The present work focuses on the forward link of fixed multibeam broadband satellite systems which employ aggressive frequency reuse patterns in the user-link. For such scenarios, the state-of-the art frame based precoding methods can improve the system performance, exploiting the super framing structure of the latest physical layer evolutions in satellite communications. Nevertheless, the limitations of feeder link need to be considered. Since the increase of the user link capacity leads to a proportional increase in the capacity requirements of the point-to-point feeder link, the deployment of multiple gateways to feed the satellite is examined. The main concept lies in each earth station being dedicated to serve a cluster of beams. In this context, the performance degradation due to inter-cluster interference is quantified. Since inter-cluster interference is expected to primarily affect cluster-edge users, the chosen performance metric is system fairness. Next, coordination between the multiple gateways is proposed as a means to mitigate interference between the different clusters and thus increase the minimum SINR over the coverage. Consequently, the gains in terms of system availability, a crucial metric in satellite communications, are exhibited via numerical system level simulations. The energy efficiency of the proposed system is also presented. [less ▲]

Total degradation analysis of precoded signals onto non-linear satellite channels

in 21st Ka Conference (2015, October)

Linear precoding exploits the spatial degrees of freedom offered by multi-antenna transmitters to manage interferences between multiple co-channel users. The adoption of precoding in practical systems ... [more ▼]

Linear precoding exploits the spatial degrees of freedom offered by multi-antenna transmitters to manage interferences between multiple co-channel users. The adoption of precoding in practical systems, however, entails a series of practical barriers. Amongst several issues, the focus herein is on the non-linear dependence of the input versus the output power of the efficient and reliable amplifiers that drive each transmit antenna, which limits the system performance. As a first step, the present work studies the impact of linear precoding on the peak-to-average power ratio (PAPR) of precoded waveforms in multibeam satellite systems using a finite alphabet. In this context, a sensitivity analysis of the PAPR at the input of each amplifier with respect to intrinsic system level parameters, such as the number of transmit feeds, is performed. Next, the performance of the whole non-linear satellite chain is analyzed with respect to the symbol-error-rate (SER) and the total degradation (TD) of the channel. Furthermore, two low-complexity solutions are considered for counteracting the effects of the non-linearities of the satellite channel on the precoded waveforms, namely an automatic gain control (AGC) operation and a non-linear equalization performed at the receiver side. [less ▲]

Cellular-Broadcast Service Convergence through Caching for CoMP Cloud RANs

in 22nd IEEE Symposium on Communications and Vehicular Technology in the Benelux (2015)

Cellular and Broadcast services have been traditionally treated independently due to the different market requirements, thus resulting in different business models and orthogonal frequency allocations ... [more ▼]

Cellular and Broadcast services have been traditionally treated independently due to the different market requirements, thus resulting in different business models and orthogonal frequency allocations. However, with the advent of cheap memory and smart caching, this traditional paradigm can converge into a single system which can provide both services in an efficient manner. This paper focuses on multimedia delivery through an integrated network, including both a cellular (also known as unicast or broadband) and a broadcast last mile operating over shared spectrum. The subscribers of the network are equipped with a cache which can effectively create zero perceived latency for multimedia delivery, assuming that the content has been proactively and intelligently cached. The main objective of this work is to establish analytically the optimal content popularity threshold, based on a intuitive cost function. In other words, the aim is to derive which content should be broadcasted and which content should be unicasted. To facilitate this, Cooperative Multi- Point (CoMP) joint processing algorithms are employed for the uni and broad-cast PHY transmissions. To practically implement this, the integrated network controller is assumed to have access to traffic statistics in terms of content popularity. Simulation results are provided to assess the gain in terms of total spectral efficiency. A conventional system, where the two networks operate independently, is used as benchmark [less ▲]

User Scheduling in Cooperative Satellite Systems

in Cooperative and Cognitive Satellite Systems (2015)

Sum Rate Maximizing Multigroup Multicast Beamforming under Per-antenna Power Constraints

in In Proc. of IEEE, Global Communications Conference, GLOBECOM (2014, December)

Frame Based Precoding in Satellite Communications: A Multicast Approach

in In Proc. of IEEE, Advanced Satellite Multimedia Systems Conference (2014, September)

Multibeam Joint Processing in Satellite Communications

Doctoral thesis (2014)

Cooperative Satellite Communications (SatComs) involve multi-antenna satellites enabled for the joint transmission and reception of signals. This joint processing of baseband signals is realized amongst ... [more ▼]

Cooperative Satellite Communications (SatComs) involve multi-antenna satellites enabled for the joint transmission and reception of signals. This joint processing of baseband signals is realized amongst the distinct but interconnected antennas. Advanced signal processing techniques –namely precoding and Multiuser Detection (MUD)– are herein examined in the multibeam satellite context. The aim of this thesis is to establish the prominence of such methods in the next generation of broadband satellite networks. To this end, two approaches are followed. On one hand, the performance of the well established and theoretically concrete MUD is analysed over the satellite environments. On the other, optimal signal processing designs are developed and evaluated for the forward link. In more detail, the present dissertation begins by introducing the topic of multibeam joint processing. Thus, the most significant practical constraints that hinder the application of advanced interference mitigation techniques in satellite networks are identified and discussed. Prior to presenting the contributions of this work, the multi-antenna joint processing problem is formulated using the generic Multiuser (MU) Multiple InputMultiple Output (MIMO) baseband signal model. This model is also extended to apply in the SatComs context. A detailed presentation of the related work, starting from a generic signal processing perspective and then focusing on the SatComs field, is then given. With this review, the main open research topics are identified. Following the comprehensive literature review, the first contribution of this work, is presented. This involves the performance evaluation of MUD in the Return Link (RL) of multiuser multibeam SatComs systems. Novel, analytical expressions are derived to describe the information theoretic channel capacity as well as the performance of practical receivers over realistic satellite channels. Based on the derived formulas, significant insights for the design of the RL of next generation cooperative satellite systems are provided. In the remaining of this thesis, the focus is set on the Forward Link (FL) of multibeam SatComs, where precoding, combined with aggressive frequency reuse configurations, are proposed to enhance the offered throughput. In this context, the alleviation of practical constraints imposed by the satellite channel is the main research challenge. Focusing on the rigid framing structure of the legacy SatCom standards, the fundamental frame-based precoding problem is examined. Based on the necessity to serve multiple users by a single transmission, the connection of the frame-based precoding and the fundamental signal processing problem of physical layer multigroup multicasting is established. In this framework and to account for the power limitations imposed by a dedicated High Power Amplifier (HPA) per transmit element, a novel solution for multigroup multicasting under Per Anntenna Constraints (PACs) is derived. Therefore, the gains offered by multigroup multicasting in frame-based systems are quantified over an accurate simulation setting. Finally, advanced multicast and interference aware scheduling algorithms are proposed to glean significant gains in the rich multiuser satellite environment. The thesis concludes with the main research findings and the identification of new research challenges, which will pave the way for the deployment of cooperative multibeam satellite systems. [less ▲]

Performance of the Multibeam Satellite Return Link With Correlated Rain Attenuation

in Wireless Communications, IEEE Transactions on (2014), 13(11), 6286-6299

Rain attenuation is among the major impairments for satellite systems operating in the K-band and above. In this paper, we investigate the impact of spatially correlated rain attenuation on the ... [more ▼]

Rain attenuation is among the major impairments for satellite systems operating in the K-band and above. In this paper, we investigate the impact of spatially correlated rain attenuation on the performance of a multibeam satellite return link. For a comprehensive assessment, an analytical model for the antenna pattern that generates the beams is also proposed. We focus on the outage capacity of the link and obtain analytical approximations at high and low signal-to-noise ratio. The derived approximations provide insights into the effect of key system parameters such as the interuser distance, the satellite beam radius, or the rain intensity, and simulation results show that it fits tightly with the Monte Carlo results. Additionally, the derived expressions can be easily particularized for the single-user case, providing some novel insights. [less ▲]

Linear Precoding in Multibeam SatComs: Practical Constraints

in ICSSC Conference (2013)

Multiuser precoding of the linear kind is one of the most promising candidate techniques required for managing inter-beam co-channel interference in aggressive frequency re-use multibeam High Throughput ... [more ▼]

Multiuser precoding of the linear kind is one of the most promising candidate techniques required for managing inter-beam co-channel interference in aggressive frequency re-use multibeam High Throughput Satellite (HTS) systems. Although academic research on precoding schemes for broadband interactive satellite communication (SatCom) systems is intensifying, there are a number of practical constraints in current DVB-S2-based HTS systems that may inhibit the application of precoding. These have not been dealt with hitherto in the literature. The present article attempts to list the relevant issues, propose some possible ways forward and present some preliminary simulation results [less ▲]

Multi-User Detection in Multibeam Mobile Satellite Systems: A Fair Performance Evaluation

in Proceedings of Vehicular Technology Conference, Spring 2013 (2013)

Multi-User Detection (MUD) techniques are currently being examined as promising technologies for the next generation of broadband, interactive, multibeam satellite communication (SatCom) systems. Results ... [more ▼]

Multi-User Detection (MUD) techniques are currently being examined as promising technologies for the next generation of broadband, interactive, multibeam satellite communication (SatCom) systems. Results in the existing literature have shown that when full frequency and polarization reuse is employed and user signals are jointly processed at the gateway, more than threefold gains in terms of spectral efficiency over conventional systems can be obtained. However, the information theoretic results for the capacity of the multibeam satellite channel are given under ideal assumptions, disregarding the implementation constraints of such an approach. Considering a real system implementation, the adoption of full resource reuse is bound to increase the payload complexity and power consumption. Since these novel techniques require extra payload resources, fairness issues in the comparison among the two approaches arise. The present contribution evaluates in a fair manner, the performance of the return link (RL) of a SatCom system serving mobile users that are jointly decoded at the receiver. In this context, the throughput performance of the assumed system is compared to that of a conventional one, under the constraint of equal physical layer resource utilization; thus the comparison can be regarded as fair. Results show, that even when systems operate under the same payload requirements as the conventional systems, a significant gain can be realized, especially in the high SNR region. Finally, existing analytical formulas are also employed to provide closed form descriptions of the performance of clustered systems, thus introducing insights on how the performance scales with respect to the system parameters. [less ▲]