Iridium Communications

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Iridium Communications Inc. (formerly Iridium Satellite LLC) is a publicly traded American company headquartered in McLean, Virginia. Iridium operates the Iridium satellite constellation, a system of 66 active satellites used for worldwide voice and data communication from hand-held satellite phones and other transceiver units. The Iridium network is unique in that it covers the whole Earth, including poles, oceans and airways, with 95 satellites launched so far. The satellites are frequently visible in the night sky as satellite flares, a phenomenon typically observed as short-lived bright flashes of light.

Iridium manages several operations centers, including Tempe, Arizona and Leesburg, Virginia, United States. The U.S. Department of Defense, through its own dedicated gateway, relies on Iridium for global communications capabilities.[4] The company derives its name from the chemical element iridium.

The Iridium communications service was launched on November 1, 1998 by what was then Iridium SSC. The first Iridium call was made by Vice President of the United States Al Gore to his wife Tipper Gore.[5] Motorolaprovided the technology and major financial backing.[6] The logo of the company was designed by Landor Associates, and represents the Big Dipper.[7]

The founding company went into Chapter 11 bankruptcy nine months later, on August 13, 1999.[8] The handsets could not operate as promoted until the entire constellation of satellites was in place, requiring a massive initial capital cost running into the billions of dollars.[9] The cost of service was prohibitive for many users, reception indoors was difficult and the bulkiness and expense of the hand held devices when compared to terrestrial cellular mobile phones discouraged adoption among potential users.[8]

Mismanagement is another major factor cited in the original program's failure. In 1999, CNN writer David Rohde detailed how he applied for Iridium service and was sent information kits, but was never contacted by a sales representative. He encountered programming problems on Iridium's website, and a "run-around" from the company's representatives.[10] After Iridium filed bankruptcy, it cited "difficulty gaining subscribers".[11]

The initial commercial failure of Iridium had a damping effect on other proposed commercial satellite constellation projects, including Teledesic. Other schemes (Orbcomm, ICO Global Communications, and Globalstar) followed Iridium into bankruptcy protection, while a number of other proposed schemes were never constructed.[8]

At one stage, there was a threat that the Iridium satellites would have to be de-orbited; however, they remained in orbit and operational.[12][13] Their service was restarted in 2001 by the newly founded Iridium Satellite LLC, which was owned by a group of private investors. Although the satellites and other assets and technology behind Iridium were estimated to have cost around US$6 billion, the investors bought the firm for about US$35 million.[9] In 2008, as part of a rebranding campaign by Media Graphics, Inc. the logo would be redesigned with updates to corporate color palette and font treatment.

On February 10, 2009, Iridium 33 collided with a defunct Russian satellite, Kosmos 2251, 800 kilometres (500 mi) over Siberia.[14] Two large debris clouds were created.

Present status
Iridium Satellite LLC merged with a special purpose acquisition company (GHQ) created by the investment bank Greenhill & Co. (NYSE: GHL) in September 2009 to create Iridium Communications, Inc. The public company trades on NASDAQ under the symbol "IRDM". The company had 850,000 subscribers as of the end of December 2016[16] (compared to 611,000 subscribers as of the end of December 2012). Revenue for the full year 2012 was US $383.5 million with operational EBITDA of US $250.7 million.[17] The system is being used extensively by the U.S. Department of Defense through the DoD gateway in Hawaii.[18] The service revenue to governments made up 23% of Iridium's revenues in 2012. An investigation was begun into the DoD contract after a protest by Globalstar, to the U.S. General Accounting Office that no tender was provided. A hold against the contract was lifted at the request of the Department of Defense, which cited national security reasons.[19] This allows the continued use of the network during the investigation.

The commercial gateway in Tempe, Arizona, provides voice, data, and paging services for commercial customers on a global basis. Typical customers include maritime, aviation, government, the petroleum industry, scientists, and frequent world travelers.

Iridium satellites are now an essential component of communications with remote science camps, especially the Amundsen–Scott South Pole Station. In December 2006, an array of twelve Iridium modems was put online, providing continuous data services to the station for the first time. Total bandwidth is 28.8 kbit/s.[20]

Matt Desch is the CEO of Iridium LLC.

Hosted Payload Alliance
Iridium is a founding member of the Hosted Payload Alliance (HPA), a satellite industry alliance formed to increase awareness of the benefits of hosted government payloads on commercial satellites. Membership in the HPA is open to satellite operators, satellite manufacturers, system integrators and other interested parties.[22]

Iridium satellite constellation
Main article: Iridium satellite constellation
The Iridium system requires 66 active satellites in orbit to complete its constellation and spare satellites are kept in-orbit to serve in case of failure. The satellites are in six polar low Earth orbital planes at a height of approximately 485 miles (780 km). Satellites communicate with neighboring satellites via Ka band intersatellite links to relay communications to and from ground stations. Most of these satellites were launched in the late 1990s before the company went through bankruptcy. Since the bankruptcy, until January 2017, only seven additional satellites were launched but an updated constellation of 66 satellites called Iridium NEXT is being rolled out, planned for launch between 2015 and 2017 on SpaceX Falcon 9 launch vehicles from Vandenberg AFB Space Launch Complex 4 in California.[23][24] On January 14th 2017, SpaceX successfully launched 10 of the new Iridium satellites into orbit.[25] The second launch of Iridium NEXT satellites took place on June 25th, 2017 on a SpaceX Falcon 9 rocket out of Vandenberg Air Force Base. This was the second of eight scheduled launches.[26] The third launch of NEXT satellites took place on October 9, 2017. A total of ten satellites were deployed after a successful launch on a SpaceX Falcon 9 rocket.

Subscriber equipment
The former Iridium provided phones from two vendors, Kyocera and Motorola. The Motorola 9500 phone is a design from the first commercial phase of Iridium, whereas the 9575 model is the current version of the handset and was released in 2011.[27] Until the release of the 9555 in 2008, the 9505A was the sole handset sold by the company - a functionally identical clone of the Motorola 9505 with some slightly different components.[28] In 2011, a highly durable Iridium Extreme (9575) phone was introduced with a built-in GPS emergency button and interface to advanced location-based services. An accessory was also introduced at the same time called Iridium Axcesspoint which, when connected to a 9555 or Extreme phone, creates a wi-fi hotspot for smartphone email, SMS and web connections.[29]

Kyocera phone models SS-66K and SD-66K are no longer in production but still available in the second-hand and surplus market. The KI-G100 phone is a small 900 MHz GSM phone that fitted in a cradle (model number SD-66K) that included a large antenna and facilitated connection to the Iridium network.[30] The SS-66K is a self-contained phone, but features a rather unusual ball antenna.

All handsets can receive SMS, but only the 9505, 9505A, 9555, Extreme and those based on the 9522 can send them.

Iridium Extreme (9575) — A jet-water, shock and dust resistant (IP65), as well as GPS enabled handset, operating temperature -15 - +35 °C, launched in September 2011.
Iridium 9555 — A satellite handset with integrated speakerphone and hands-free capability, launched in late 2008. USB data interface with a USB-to-RS-232 bridge chip.
Iridium 9505A — Large brick shaped satellite handset manufactured from 2002 to 2008 by the second corporate incarnation of Iridium. Externally almost identical to the original Motorola 9505. Native RS-232 data interface with proprietary pinout adapter.
Motorola 9505 — Large brick shaped handset manufactured from 1999 to 2002 by the first corporate incarnation of Iridium. Native RS-232 data interface with proprietary pinout adapter.
Kyocera SS-66K — Manufactured in very small numbers by Kyocera in 1998-1999 for the first Iridium corporation, very large handset. Can occasionally be found for sale on eBay.

The Motorola 9500 phone (with the antenna not extended)

The Kyocera KI-G100 GSM phone docked into the SD-66 Iridium adapter

Iridium 9505

The Iridium 9522A transceiver with an antenna and NAL Research DPL handset

Iridium 9555

US Air Force airmen inspecting an iridium phone in Antarctica.
Two pagers were made for the Iridium network — the Motorola 9501 and Kyocera SP-66K.[31] These are one-way devices that could receive messages sent in the form of SMS.

Other satellite phones[edit]
Several other Iridium-based telephones exist, such as payphones,[32] and equipment intended for installation on ships and aircraft. The DPL handset made by NAL Research combined with a 9522 transceiver is used for some of these products. This handset provides a user interface nearly identical to that of the 9505 series phones.[33]

Standalone transceiver units[edit]
These can be used for data-logging applications in remote areas, now a common practical use for Iridium's services. Some types of buoys, such as those used for the tsunami warning system, use Iridium satellites to communicate with their base. The remote device is programmed to call or send SBD (Short burst data, see below) messages to the base at specified intervals, or it can be set to accept calls in order for it to offload its collected data. Most of these units can be connected to a handset and used as a fixed telephone.

The following transceivers have been released over the years:

Iridium Core 9523 — Similar to the 9522B, a modular transceiver released in 2012, designed to be an embedded solution.
Iridium 9522B — A transceiver released in late 2008, is smaller than the 9522A and has similar features.
Iridium 9522A — Based on the 9522, some variants have built in GPS and autonomous reporting functions. Supports SBD.
Motorola 9522 — Last Motorola transceiver, supports outgoing SMS but no SBD.
Motorola 9520 — Original transceiver module, does not support outgoing SMS or SBD. Designed for use in vehicles with accompanying handset[34]
SBD Modems[edit]
These devices support only Short Burst Data for M2M services and do not use a SIM card.

Iridium 9601 — Supports only SBD, several tracking devices and other products have been built around this modem. It was an Iridium manufactured product designed as an OEM module for integration into applications that only use the Iridium Short Burst Data Service. Short Burst Data applications are supported through an RS-232 interface. Examples of these solutions include maritime vessel tracking or automatic vehicle tracking.[35]
Iridium 9602 — Smaller, cheaper version of 9601 (released in 2010).[36]
Iridium 9603 — One-fourth the volume and half the footprint of 9602 (32x30x8 mm)[37]
SIM card[edit]
Removable Subscriber Identity Modules (SIMs) are used in Iridium phones, much like those used for GSM. Prepaid SIM cards are usually green while post-paid cards are red. The 9601 and 9602 SBD modems don't use a SIM card, they are identified by the network solely through the IMEI of the device and the customer account associated with that IMEI.

OpenPort is a broadband satellite voice and data communications system for maritime vessels. The system is used for crew calling and e-mail services on sea vessels such as merchant fleets, government and navy vessels, fishing fleets and personal yachts. Iridium’s Global Service Program provides shipboard technical support to Iridium OpenPort customers.[38] OpenPort voice services are billed by the minute as with handheld phones, while data services are billed by the megabyte of data transferred (not by the connection time of the session).

Calls from Iridium phones can be made to any landline or wireless device in the world and typically cost between $0.75 to $1.50 per minute. Calls made to Iridium phones can be very expensive, costing several dollars per minute. For example, Google Voice charges $4.03USD per minute to directly call an Iridium phone.[39] It is possible to call with charges reversed by first dialing a number in Arizona; the call is charged to the receiver at the standard rate for satellite to landline calls, but the caller only pays for the call to Arizona.[40]

Since Iridium will not sell prepaid cards or even its subscription call service directly, it is hard to obtain the exact price of making a call. There are numerous distributors that will activate Iridium phones and sell pre-paid vouchers and SIM cards.

Voice and data calls
The Iridium system deals with "minutes", which are subdivided into several much smaller "units". These minutes are the "basic rate" to landlines and ordinary mobile phones around the world. For a 500-minute annual plan the cost of the "basic rates" fluctuates around US$1.25 per minute, depending on the distributor. There are also regional plans that offer slightly cheaper rates than the normal, but these minutes can only be used in a specified geographic location (such as Africa, North America, Canada or Alaska).

Calls to landlines worldwide: 1.00× basic rate
Calls to other Iridium phones or voice mail: 0.50×
Sending SMS messages: 0.33×
Calls to other operator's satellite phones: 5.00–13.50×
Data calls: 1.00×
Iridium and other satellite phones may be identifiable to the listener by the "clipping" effect of the data compression and the latency (time delay) due to the electronic equipment used and the distances the signal must travel. The voice codec used is called Advanced Multi-Band Excitation.

Iridium operates at only 2.2 to 3.8 kbit/s, which requires very aggressive voice compression[41] and decompression algorithms.[42] (By comparison, AMR used in 3G phones requires a minimum of 4.75 kbit/s, G.729 requires 6.4 kbit/s, and iLBC requires 13.33 kbit/s.) Latency for data connections averages 1800 ms round-trip, with a mode of 1300 to 1400 ms and a minimum around 980 ms.[43] Latency is highly variable depending on the path data takes through the satellite constellation as well the need for retransmissions due to errors, which may be around 2 to 3% for mobile originated packets under good conditions.

Despite the bandwidth limitations, transparent TCP/IP is supported. Iridium claims data rates up to 10 kilobits per second for their "direct Internet" service which utilizes v.42bis compression over a PPP dialup connection to Iridium's Arizona gateway. Actual data rates remain at 2300 to 2400 bit/s for any compressed data such as a JPG image or ZIP file, but plain text or HTML may transfer "up to" 10 kbit/s. Iridium 9500, 9505 and 9505A phones can be connected to computers using an RS-232 connection, as can the 9522A transceiver module. The 9555 and Extreme phones connect to computers with a standard USB cable, using an internal USB to serial bridge chip and Windows drivers to emulate a serial COM port for compatibility with standard PPP clients.

Once the next generation of satellites is in place, Iridium plans to provide higher-speed service that can reach up to 1.5 Mbit/s.

Prepaid service
Prepaid SIM cards are available from a variety of different outlets and sometimes appear on auction sites such as eBay. Their values range from 50 to 5,000 minutes; the 50 minute cards have no validity and the 75 minute vouchers are valid for only a month, but the 5,000 minute cards stay valid for two years. Since Iridium charges quite a bit for merely accessing their network without making calls it is possible to extend the validity of such an account by a month for around US$45. It is also possible to refill such an account without purchasing a new SIM card.

As of 2016 the 500 minute card is the most common one, which remains valid for one year and can usually be bought for US$600 to $750, while the 75 minute card can cost up to US$175 and the 5,000 minute card costs around US$4,000.

Post-paid service
Phone numbers
Iridium controls the virtual country codes +8816 and +8817, part of the 881 range designated by the ITU for the Global Mobile Satellite System. Each subscriber is given an 8-digit number prefixed by one of these country codes. However many regional telephone service operators have no interconnect agreement with Iridium or other satellite networks and users on these networks need to call reverse charge to a U.S.-based number.

It is also possible to call an Iridium phone by using a US-based gateway number at the Arizona gateway. In this arrangement, a person wishing to call an Iridium phone dials +1-480-768-2500, billed at the standard rates to call the United States from their location, waits for the prompt, enters the +8816 or +8817 number of the Iridium phone they are attempting to reach, and the network then attempts to complete the call. If the Iridium subscriber answers their phone, it will be billed at its standard usage rate, ranging from $0.95 to $1.50 USD per minute, or subtracting minutes from a pool of prepaid minutes assigned to the phone.[44]

Since spring 2007, postpaid Iridium subscribers have an option to associate their Iridium numbers with a direct U.S.-based number (the so-called +1 Access service).[40]

Paging service
The one-way paging service is still operational, despite the pagers not being in production for many years now[citation needed][when?]. Messages are delivered to pre-selected "MDAs" which cover a certain geographic area. Three of these MDAs may be selected on a web-based portal or updated automatically if the paging service is bound to an Iridium phone. Each country has its own MDA based on its country code; some of the larger countries are divided into several MDAs, while separate MDAs exist for sections of ocean and common aeronautic routes. This service costs around US$70 per month with a limited number of messages allowed, or US$140 for an unlimited number of inbound messages.

Pagers are assigned with telephone numbers in area code 480 and can also be contacted using email, SMS and the web-based interface used to send messages to Iridium phones.[45]

Short burst data
Special modems such as the 9522A, 9601, 9602 and Quake Q9612 can be used for sending and receiving short data bursts, less than 2 kilobytes at a time. This service is often used for asset tracking and remote monitoring. Messages are converted to be delivered in email format or over HTTP to a preconfigured address; the mobile unit does not include a destination address when sending a SBD message. A crude positioning report is also included in each message sent.[46] SBD messages take from 6 to 22 seconds to send or receive.[43] The latest generation of SBD transceiver, the Iridium 9602, can receive up to 270 bytes per SBD data message (defined by Iridium as "mobile terminated SBD") and can transmit a maximum of 340 bytes per SBD message (defined by Iridium as "mobile originated SBD"). A real-world example of the 9602 chipset in use are the YB Tracker[47] or the owa3x embedded Linux computer.[48]

Value added services
To check emails can be very expensive. To avoid this there is a service called SatNotify by Leaf Consulting which checks emails periodically and send a text message to the satellite phone, if there are new messages.[49][50]

Air safety communications
In July 2011, The Federal Aviation Administration (FAA) issued a ruling that approves the use of Iridium for Future Air Navigation System (FANS) data links, enabling satellite data links with air-traffic control (ATC) for aircraft flying in the FANS environment, including areas not served by Inmarsat (above or below 70 degrees latitude) which includes polar routes.[51]

Technical details
Air interface
Communication between satellites and handsets is done using a TDMA and FDMA based system using L-band spectrum between 1616 and 1626.5 MHz.[52] Iridium exclusively controls 7.775 MHz of this and shares a further 0.95 MHz. In 1999 Iridium agreed to timeshare a portion of spectrum, allowing radio astronomers to observe hydroxyl emissions; the amount of shared spectrum was recently reduced from 2.625 MHz.[53][54]

External "hockey puck" type antennas used with Iridium handheld phones, data modems and SBD terminals are usually defined as 3dBi gain, 50 ohm impedance with RHCP (right hand circular polarization) and 1.5:1 VSWR.[55] As Iridium antennas function in frequencies very close to that of GPS, a single antenna may be utilized through a pass-through for both Iridium and GPS reception.

The type of modulation used is normally DE-QPSK, although DE-BPSK is used on the uplink (mobile to satellite) for acquisition and synchronization.[56] Each time slot is 8.28 ms long and sits in a 90 ms frame. Within each FDMA channel there are four TDMA time slots in each direction.[57] The TDMA frame starts off with a 20.32 ms period used for simplex messaging to devices such as pagers and to alert Iridium phones of an incoming call, followed by the four upstream slots and four downstream slots. This technique is known as time-division multiplexing. Small guard periods are used between time slots. Regardless of the modulation method being used, communication between mobile units and satellites is performed at 25 kilobaud.

Channels are spaced at 41.666 kHz and each channel occupies a bandwidth of 31.5 kHz; this allows space for Doppler shifts.[52]

The Iridium system uses three different handoff types. As a satellite travels over the horizon, calls are handed to adjacent spot-beams; this occurs approximately every fifty seconds. A satellite only stays in view for seven minutes at the equator.[58] When the satellite disappears from view, an attempt is made to hand the call to another satellite. If no other satellite is in view, the connection is dropped. This may occur when the signal from either satellite is blocked by an obstacle. When successful, the inter-satellite handoff may be noticeable by a quarter-second interruption.[57]

The satellites are also able to transfer mobile units to different channels and time slots within the same spot beam.

Earth base-stations
Iridium routes phone calls through space. In addition to communicating with the satellite phones in its footprint, each satellite in the constellation also maintains contact with two to four adjacent satellites, and routes data between them, to effectively create a large mesh network. There are several earth stations which link to the network through the satellites visible to them. The space-based backhaul routes outgoing phone call packets through space to one of the earth station downlinks ("feeder links"). Station-to-station calls from one satellite phone to another can be routed directly through space without going through an earth station. As satellites leave the area of an earth station, the routing tables are updated and packets headed for the earth station are forwarded to the next satellite just coming into view of the earth station. Communication between satellites and earth stations is at 20 and 30 GHz.[59]

Gateways are located in

Tempe, Arizona (USA)
Wahiawa, Hawaii (USA) — owned by Defense Information Systems Agency (DISA) [18]
Izhevsk (Russia)[60]
The pre-bankruptcy corporate incarnation of Iridium built eleven gateways, most of which have since been closed.[61] Gateways were also built in Pune (India), Beijing (People's Republic of China), Moscow (Russia), Nagano (Japan), Seoul (South Korea), Taipei (Taiwan), Jeddah (Saudi Arabia) and Rio de Janeiro (Brazil). The company is seeking to reactivate gateways in several countries to comply with national laws in those countries.

Other technical information
Like other satellite networks, Iridium terminals need open line-of-sight to open sky in order to function. For instance, units will not work consistently indoors, or under forest cover. Iridium does have a very powerful paging channel that can ring the phone indoors, but the customer may have to walk outdoors to take the call.

There is a web/email to SMS gateway which enables messages to be sent from the internet or an e-mail account to Iridium handsets for free. There is also a voice mail service.

Iridium generally does not have roaming agreements with terrestrial/cellular operators. Telstra in Australia allows postpay GSM subscribers to use their SIM card. However, global roaming has to be activated and both incoming and outgoing calls are charged to this account, and the call rate is around US$4 per minute; the incoming calls are via the GSM phone number of the account, with country code, etc., prefixed. In order to use the network, it is necessary to have not only appropriate equipment, such as a handset or the optional cellular cassette for the Motorola 9505 phone, but also a pay-as-you-go or contract Iridium SIM card.

Tracking transceiver units
Without an extra global navigation satellite system, receiver tracking is difficult, but not impossible, as the position of a mobile unit can be determined using a Doppler shift calculation from the satellite. These readings however can be inaccurate with errors in the tens of kilometers.[46] Even without using Doppler shifts, a rough indication of a unit's position can be found by checking the location of the spot-beam being used and the mobile unit's timing advance.

The position readings can be extracted from some transceiver units and the 9505A handset using the -MSGEO AT command.[62] In the past, Iridium has used this method of tracking to block service to U.S. embargoed countries, such as North Korea and other politically unpopular regions, such as Northern Sri Lanka. It is also used to stop geographically bounded plans from being used outside the designated area.

The Iridium Extreme phone introduced in 2011 has a GPS location service embedded in the device, which the user can use to locate themselves or include in SMS messages. It can also be used to provide advanced services like Geo-fencing. A red emergency button on the top of the unit can be pressed to send the unit's position to emergency rescue agencies or other number pre-programmed by the user or distributor.

Credit: Wikipedia

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Typical latency across the Iridium network is 500-600ms

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