Dual-Polarization Payloads for Higher Capacity Utilization

Status

Completed
Status date

2015-04-17
Activity Code

5A.024

Objectives

The objective of this activity is to investigate and design Ka-band multi-beam dual-polarization payloads for significantly higher capacity utilization with respect to conventional multi-beam payloads in the presence of unbalanced traffic demand.

In this respect, possible payload architectures and related technologies identifying key payload equipment for further development are to be defined, traded-off and assessed.

The activity covers the following aspects:

analysis of requirements and architectural trade-offs;
detailed design (including architectural and sub-systems design);
analysis, simulation and optimization of performance;
identification of required technology improvements and necessary developments;
compare results in terms of capacity utilization improvement.

Ideally, to cope with peaks of capacity demand on hot spots (see Fig. 1) the payload should be flexible to the extent that the overall available user-link bandwidth in both the orthogonal polarizations (i.e. Dual-Polarization, DP) should be assignable to a limited number of beams, while maintaining the Single Polarization (SP) at user level on the remaining less-demanding beams.

In contrast to past and on-going activities at ESA, the aim of the present study is to explore the possibility of using dual-polarization for the hot spots, with flexibility to adapt to the traffic demand evolution.

The activity indeed targets a capacity utilization improvement of 40% with respect to conventional multi-beam payloads.

The outcomes of the activity are the detailed design of the payload architectures, including payload block diagrams, mass/power/dissipation budgets, delta cost estimation and a hardware matrix, and high level specifications for the identified new payload equipment.

Challenges

The design of flexible dual polarization payloads is particularly challenging for the mass/power/accommodation aspects and efficient solutions must reduce hardware replication due to the use of two polarizations for the user beams.

It is also important to consider the additional complexity and costs associated with advanced payloads. For operators, delta-costs associated with flexibility must be offset by (at least) an equivalent economic return (e.g. traffic capacity increase, improvement of the satellite fill-factor, extension of the addressable market, reduction of in-orbit spares, etc.).

For these reasons, the additional payload mass, power consumption and thermal dissipation is expected to be kept within a limit of 20%-30% with respect to a conventional multi-beam payload.

Benefits

Multi-beam Ka-band satellites for Broad-Band Services (BBS) allow efficient use of orbit-spectrum and power resources reducing the cost of the space segment and making the service competitive.

One of the major challenges being faced by multi-beam BBS networks is how to maximize Operators’ revenues while coping with the highly uneven distribution of traffic over the coverage region.

The potential high variability of capacity demand throughout the satellite coverage has been confirmed by market studies performed in the past on the traffic distribution in the EU25 region, resulting in a few hot spot clusters and large low-demand regions.

The first generation of BSS systems has seen a widespread adoption, for the user-link, of dual-polarization frequency reuse schemes where each beam exploits a single polarization while adjacent beams make use either of the complementary polarization or of a different frequency band.

For this reason the first generation of payloads has limited allocated resources for flexibility as the dual-polarization is not allowed at user beam level, so that future solutions must rather aim at using the dual-polarization at user beam level for the hot spots with flexibility to maximize the capacity offer under variable and non-uniform capacity demand.

Solutions at system and payload level, aiming at matching the offered capacity to the required traffic demand, could therefore substantially increase operators’ revenues.

Features

An innovative Ka-band multi-beam satellite payload for BBS is proposed which is based on a conventional multi-beam payload architecture with an additional flexible payload section feeding a (Confocal) Steerable Antenna (see Fig. 2) system. Such enhanced payload architecture allows using the DP at user beam level on the hot spots in order to increase the capacity utilization on highly uneven traffic demand distribution throughout the satellite coverage. Moreover the use of an additional Steerable Antenna greatly increases the payload flexibility to adapt to predictable and unpredictable traffic demand evolution during the satellite mission lifetime.

The architectural design strategy is based on the assumption of a conventional payload section (in standard SP at user beam level) able to meet low-medium traffic demand all over the service area, which is enhanced by means of an additional flexible payload section in charge to meet the higher demand on the hot spots. The hot spots are served by the beams generated by a (Confocal) Steerable Antenna, where full band in DP can be potentially allocated.

In this respect the SP beams in the conventional payload section which correspond to the hot spots are accordingly turned-off and the frequency and power plans are simultaneously optimized in the two payload sections in order to maximize the overall capacity performance.

It is worth mentioning the advantage of concentrating the DP capability on the Steerable Antenna to serve the hot spots: if their position within the service area evolves during the mission, then the DP capability can be redirected accordingly, with correspondent turning on/off of the relevant SP beams of the conventional payload section.

Plan

The activity is organized in 4 tasks as follows:

Task 1 - System Requirements and Performance Evaluation Methodology
Task 2 - Payload Technology Investigation
Task 3 - Payload Trade-Offs and Preliminary Design
Task 4 - Design Consolidation

During Task 1, the mission requirements are to be consolidated, including a set of traffic distributions, against which system capacity is to be evaluated.

Moreover, some study cases are to be defined, including conventional and advanced systems, both for a high number of beams (~70) and for a very high number of beams (³150).

In Task 2, a survey of existing Intellectual Property Rights related to Ka-band multi-beam dual-polarization satellite systems and relevant payload technologies are to be performed. Preliminary payload architectures are to be identified for each system study case.

During Task 3, the Contractor shall the system and payload performances are to be analysed and traded-off and the baseline payload architecture is to be selected and consolidated.

Finally, in Task 4, a European roadmap for the identified payload technologies and building block developments is to be elaborated.