This document discusses satellite-based high altitude platforms (HAPs) that can provide wireless connectivity and services from stratospheric altitudes of 17-22km. It compares HAPs to terrestrial broadband and satellite systems, and describes two main architectures for HAPs - bent-pipe architectures where HAPs act as repeaters, and regenerative architectures where HAPs function as base stations. Applications of HAPs include military communications, emergency response, and providing coverage to remote areas not served by terrestrial networks. Challenges include dealing with winds at high altitudes.

1. SATELLITE BASED HIGH
ALTITUTE PLATFORM (HAP)
By
Satya Prakash Rout
Roll No: 2181091

2. AGENDA
 Introduction to High Altitude Platform (HAP)
 Comparison between Broadband terrestrial, HAPS and Satellite Services
 Architectures of HAPs
 Bent-Pipe HAPS Architecture
 Regenerative HAPS Architecture
 Applications of HAPS
 Conclusion
 References

3. HIGH ALTITUDE PLATFORM
 It is also known as High Altitude Platform Stations or High Altitude Pseudo
Satellites.
 HAPs are aircrafts basically unmanned airships or airplanes positioned above
17km-22km in the stratosphere.
 They could be high-altitude free floating balloons, airships or powered fixed-wing
aircraft that uses either the solar power or an on-board energy sources.
 It has the capability of providing global wireless connectivity and data services such
as high speed wireless backhaul, Industrial Internet of Things (IIoT) and public
safety for large scale areas not serviced by terrestrial networks.
 There are many HAPS projects are going on across the world such as Google Loon,
HAPSMobile and Airbus Zypher for 4G-LTE and 5G services across the populated
area [1][5][6].

4. HAPS PROJECTS
The Zeppelin NT airship, launched in June 2000
(Courtesy of Zeppelin Luftschifftechnik GmbH) [4]
Artist’s impression of Cargolifter (Courtesy of
Cargolifter GmbH) [5]
Lindstrand HAP concept (Courtesy of Milk Design
and Lindstrand Balloons Ltd.) [6]

5. COMPARISON BETWEEN BROADBAND
TERRESTRIAL, HAPS AND SATELLITE SERVICES
Broadband Terrestrials HAPS LEO Satellites GEO Satellites
Station Coverage (in diameter) < 1km Upto 200km > 500km Upto global
Cell Diameter 0.1-1km 1-10km 50Km 400km minimum
Total Service Spot service National/Regional Global Quasi-global
Maximum transmission rate
per user
155Mbit/s 25–155Mbit/s < 2Mbit/s up
64Mbit/s down
155Mbit/s
System deployment Several base stations before
use
Flexible Many satellite before use Flexible, but long lead time
Estimated cost of varies Varies $50million upwards? $9billion >$200million
In-service date 2000 2003-2008 2005 1998
Table 1: Comparison between Broadband Terrestrial, HAPS & Satellite Services [2][3]

6. ARCHITECTURES OF HAPS
 There are two types of architectures in HAPS
1. Transparent or Bent-Pipe HAPS Architecture: HAPS as Repeater
2. Regenerative HAPS Architecture: HAPS as Base Station

7. TRANSPARENT/BENT-PIPE HAPS
ARCHITECTURE
 In this HAPS architecture, the HAPS station worked as a
repeater or relay
 The repeaters can be a simple RF repeater, an advanced
repeater with beam control, or a relay station (integrated
access and backhaul, IAB), each with different payload
and power consumption requirements.
 In the design of a BP (Bent-Pipe) architecture system, a
repeater is equipped on the HAPS to provide consistent
connectivity and data service from the ground gateway
station to a large area.
 The repeater on the BP HAPS is working as a bi-
directional amplifier of RF signals in both downlink (2.1
GHz) and uplink (1.8 GHz). The repeater model
specified in 3GPP TR 25.956 [13] is used for the BP
architecture HAPS system, with 105 dB repeater gain, 7
dB repeater noise figure, and the maximum average
output power of 30 dBm.
 The Bent Pipe architecture requires low weight and
power consumption on HAPS.
Fig 1: Bent Pipe Architecture of HAPS [1]

8. REGENERATIVE HAPS ARCHITECTURE
 The second type is regenerative (RG)
architecture where the HAPS is
working as a base station (e.g., radio
unit (RU), distributed unit (DU) + RU,
or full baseband unit (BBU)) shown in
the Fig 2
 The RG architecture HAPS can utilize
independently optimized designs for
AL and FL but it has higher power and
weight requirements on HAPS.
Fig 2: Regenerative Architecture of HAPS [1]

9. ADVANTAGES OF HAPS
 Large Area of Coverage and Less Interference
 Flexibility to respond to traffic demands
 Low cost
 Incremental deployment
 Rapid deployment
 Platform and payload upgrading
 Environmentally friendly
 No use of any Launch Vehicle

10. DISADVANTAGE OF HAPS
 The presence of wind in the stratosphere creates a major challenge for HAPS
system.
 Sudden wind or gust beyond the velocity of 30-40 m/s with an altitude of 65000
and 75000 ft causes temporal loss or total loss of communication

11. APPLICATIONS OF HAPS
 Military communications
 Emergency or Disaster applications
 3G/2G applications
 Developing world applications
 Two way hybrid communication
 Intelligent Communication & Networks
 Environmental Monitoring
 Earth Observation

12. CONCLUSION
In this presentation the satellite based HAPS has been discussed along with the basic
architecture of HAPS. The different types of HAPS Architecture i.e. Bent-Pipe and
Regenerative architecture has been studied. The HAPS promotes a lots of advantages
as compared to broadband terrestrial in terms of lack of launch vehicles requirement,
low cost deployment and extreme coverage to the dense populated area.

13. REFERENCES
1. Y. Xing, F. Hsieh, A. Ghosh, and T. S. Rappaport, “High Altitude Platform Stations
(HAPS): Architecture and System Performance,” 2021 IEEE 93rd Vehicular Technology
Conference (VTC-Spring), April 2021, pp. 1-6.
2. Grace, D., Daly, N. E., Tozer, T. C., and Burr, A. G.: ‘LMDS from high altitude
aeronautical platforms’. Proc. IEEE GLOBECOM’99, Rio de Janeiro, Brazil, 5th–9th
December 1999, 5, pp.2625–2629.
3. S. Karapantazis and F. Pavlidou, “Broadband communications via high altitude platforms:
A survey,” IEEE Communications Surveys Tutorials, vol. 7, no. 1, , May 2005, pp. 2–31
4. Zeppelin, see http://www.zeppelin-nt.com
5. SkyStation, see http://www.skystation.com
6. Advanced Technologies Group, see http://www.airship.com