|
|
Iridium
|
Iridium is a mobile-satellite service (MSS) system that was first licensed by the FCC in 1995, and began commercial service in 1998.
Iridium utilizes an FDMA/TDMA Time Division Duplex (TDD) access technology, so that the same frequency band is used for both the user uplink and downlink transmissions, on a time-shared basis. It shares a portion of its spectrum (1617.775-1618.725 MHz) with Globalstar, which has mobile uplinks to its own MSS system in the 1610-1618.725 MHz band.
Each Iridium user uplink/downlink channel has a bandwidth of 31.5 kHz and is separated in frequency by 41.67 kHz to allow for Doppler shift. A single Iridium TDMA frame is 90 ms long, which begins with 22.48 ms guard time, followed by four user uplink and four user donwlink time slots (8.28 ms burst time each, separated by small guard times). A good discussion of the Iridium system architecture, constellation design, and multi-access scheme can be found in chapter 2 of the thesis by Abdul Jabbar (link below).
In February 2013, Iridium was granted authority by the FCC to provide aeronautical mobile-satellite (route) service (AMS(R)S) in the 1618.725-1626.5 MHz portion of its spectrum, limited to oceanic, polar, and remote regions. According to the FCC, "for purposes of this authorization, we consider oceanic regions to be those beyond 12 nautical miles from the baselines of the coastal states." Authorization for remote areas of other territories is contingent upon completing the agreement-seeking process under 5.367 of the ITU Radio Regulations.
At the end of 2012, Iridium reported approximately 368,000 subscribers. The company plans to launch a new generation of satellites, Iridium Next, beginning in 2015.
|
Frequency Bands |
Band | Use | Service | Table |
1617.775 - 1626.5 MHz | Iridium (user terminal uplinks and downlinks) | Mobile-satellite | N |
1618.725 - 1626.5 MHz | Iridium AMS(R)S | ARMR | N |
19.1 - 19.6 GHz | Iridium satellite gateway downlinks | Fixed-satellite | N |
22.55 - 23.55 GHz | Iridium inter-satellite links | Inter-satellite | N |
29.1 - 29.3 GHz | Iridium gateway uplinks | Fixed-satellite | N |
External Links:
Display this entry in a page by itself
Edit
|
|
|
|
ViaSat-1 Ka-band Satellite
|
ViaSat uses this spectrum for its Ka-band direct-to-consumer broadband Internet service, under the trade name "exede." The ViaSat-1 satellite was launched from Baikonur on October 19th, 2011, and entered commercial service on January 16th, 2012.
The satellite downlinks and uplinks use both right- and left-hand circular polarizations from a geostationary orbit at 115.1 deg west longitude.
ViaSat-1 has 72 user beams, of which 63 serve the U.S. Nine beams serve Canada.
User terminals utilize a dish of 0.695 m (about 27") maximum diameter, and will uplink using carriers between 625 kHz and 10 MHz wide using max EIRP between 47.2-50.3 dBW. The antennas have transmit gain of about 44 dBi, and receive gain of about 40 dBi. ViaSat is authorized for up to 250,000 such terminals in the continental U.S., operating under the callsign E120026.
The satellite downlink bandwidth is between 52-416 MHz.
As of March 2013, ViaSat claimed 512,000 customers. They have also announced plans for the ViaSat-2 satellite, to be launched in mid-2016, which will have 2.5 times the capacity of ViaSat-1, and will have a single beam that covers the continental U.S., Mexico, most of Canada, portions of Central America and the Caribbean, and the North Atlantic over to the western edge of Europe.
|
Frequency Bands |
Band | Use | Service | Table |
18.3 - 18.8 GHz | ViaSat-1 downlink | Fixed-satellite | N |
18.8 - 19.3 GHz | ViaSat-1 downlink | Fixed-satellite | N |
19.7 - 20.2 GHz | ViaSat-1 downlink | Fixed-satellite | N |
28.1 - 28.6 GHz | ViaSat-1 uplink | Fixed-satellite | N |
28.6 - 29.1 GHz | ViaSat-1 uplink | Fixed-satellite | N |
29.5 - 30 GHz | ViaSat-1 uplink | Fixed-satellite | N |
External Links:
Display this entry in a page by itself
Edit
|
|
|
|
|
|
|
|
|
Other 3 billion (03b) Networks
|
O3b is a planned satellite system that will help provide broadband service to the world's "other 3 billion" people, generally in the equatorial region, that do not otherwise have good access.
O3b consists of 12 satellites in equatorial medium Earth orbit (MEO) at 8,062 km altitude. The satellites will be able to provide optimal service to +/-45 deg latitude, with limited service to +/-45-62 deg. Therefore, O3b will be able to provide services outside the equatorial regions, including in developed countries, although its main target area is developing countries. MEO was chosen to reduce the latency (round trip travel time) of the data connection, compared to the much larger distance/travel time to geostationary orbit and back.
The satellites will provide broadband service to "Tier 1" customers such as Internet Service Providers (ISPs), and "Tier 2" customers including cellular backhaul and VSAT network services. Because the satellites are not in geostationary orbits, customers will have to use tracking antennas to communicate with the satellites.
Each satellite provides service using ten 216 MHz channels.
O3b will operate in the fixed-satellite service, although FSS allocations do not exist throughout the anticipated frequency range.
O3b is based in Jersey, Channel Islands, and is therefore governed by Ofcom, the U.K. telecommunications regulatory authority. Its network operations center is in Virginia (USA), and its satellite operations center will be in Luxembourg. Multiple ground stations will operate around the globe.
|
Frequency Bands |
Band | Use | Service | Table |
17.8 - 18.6 GHz | O3b Networks service and gateway downlinks | Fixed-satellite | N |
18.8 - 19.3 GHz | O3b Networks service, gateway, and TT&C downlinks | Fixed-satellite | N |
27.6 - 28.4 GHz | O3b Networks service and gateway uplinks | Fixed-satellite | N |
28.6 - 29.1 GHz | O3b Networks service, gateway, and TT&C uplinks | Fixed-satellite | N |
External Links:
Display this entry in a page by itself
Edit
|
|
|
|
|
|