dslreports logo
site
 
    All Forums Hot Topics Gallery
spc

spacer




how-to block ads


Search Topic:
uniqs
1049
share rss forum feed

raytaylor

join:2009-07-28
kudos:1

1 edit

Do Satelites have routers in them?

This may sound like a stupid question but do satelites have routers in them, or are they just solar powered orbiting back-to-back amplifiers?

I was thinking just now
Wouldnt it be possible to put a bunch of hard drive SSD's (with a few hundred backups) and a few routers into one to lower the latancy when surfing by means of caching.

»arstechnica.com/business/2013/01···the-us/?

The article above says viasat has 140gbit of capacity through their new satelite - but when i read about how slow their service is, i keep thinking, alot of that bandwidth must be wasted due to latancy issues.


Inssomniak
The Glitch
Premium
join:2005-04-06
Cayuga, ON
kudos:2
I dont know anything about satellites, but Im gonna gather no, it would make it consume more power, heavier, have more points of failure. Im gonna fathom that they make them as complex as they need to be but thats it.

"shit, I gotta go up to the satellite, the raid 1 array failed :/"
--
OptionsDSL Wireless Internet
»www.optionsdsl.ca

LLigetfa

join:2006-05-15
Fort Frances, ON
kudos:1
Well... after February 15th, you might be needing to fix more than that when 2012 DA14 passes through the satellite belt.


TomS_
Git-r-done
Premium,MVM
join:2002-07-19
London, UK
kudos:5

4 edits

1 recommendation

reply to raytaylor
My understanding of Sat technology is: generally no

Satellites are really actually quite "dumb." Mostly they are a bunch of transponders, each of which receives on a frequency from the earth station, and re-transmits it back down to earth on another frequency (by a simple frequency conversion) to be received by a receiver.

As an example, the Optus D3 satellite has 32 Ku transponders in total, 24 are 125 watt and there are 8 backup transponders that can operate at 44 watts. (src Wikipedia)

In the case of an Internet service which is two way, Im not exactly sure how the return path is handled. It would likely be done with a second transponder, but Im not 100% sure.

The only smarts in a typical satellite will be the command and control electronics for telemetry, monitoring, positioning/maneuvering etc. Those are usually backed up with a spare in case it fails, and there are usually a couple of spare transponders that can be used for either occasional service, or to replace one if it fails.

Even in this configuration, with minimal electronics and "things that could go wrong", satellites are sometimes rendered useless, or partially useless when components fail.

I believe that future generations of satellites will contain more smarts like routers as component reliability has increased, or at least become so small and low on power consumption that it is possible to include a spare incase of a failure. This will allow satellites to route traffic between themselves without having to return to earth and make another trip back up**.

** Im not exactly a satellite freak, so this may have already been done

edit: Iridium satellites communicate amongst themselves in space


Inssomniak
The Glitch
Premium
join:2005-04-06
Cayuga, ON
kudos:2
reply to raytaylor
What is the free space loss in a vacuum? lol


Jerm

join:2000-04-10
Richland, WA
kudos:2
reply to raytaylor
Well it was sort of big news a couple years ago when Cisco got the first space-router:

»www.cisco.com/web/strategy/docs/···uter.pdf

»en.wikipedia.org/wiki/Internet_R···in_Space

Interesting how it now appears mainly to be targeted to the government. Very little commercial interest I suppose.

public

join:2002-01-19
Santa Clara, CA
reply to raytaylor
said by raytaylor:

The article above says viasat has 140gbit of capacity through their new satelite - but when i read about how slow their service is, i keep thinking, alot of that bandwidth must be wasted due to latancy issues.

Satellites contain lot more than just routers. All semicustom radhard modules, The system can be completely reconfigured to compensate for failures.
Slow speed us due to a heavy load. 10k users will easily use the bandwidth.
Latency and throughput are different concepts.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
said by public:

said by raytaylor:

article above says viasat has 140gbit of capacity ... lot of that bandwidth must be wasted due to latancy issues.

Satellites contain lot more than just routers ... Latency and throughput are different concepts.

I just wanted to clarify that geosynch orbit broadband satellites do not have any router/bridge/switch for data. Essentially they create a simple RF repeater from customer to gateway.

I used to write about the Google funded "Other 3 Billion" O3B low latency and high throughput medium orbit satellite network ... it is finally ready to launch in 2013.

Their blog has cool photos of the satellites and gateways as they are being built. »o3bnetworks.com/additional-pages/blog

Even in such a sophisticated system, all those radiation hardened electronics are mainly for RF and control/maintenance. Still no router on board.

There are some low orbit satellites with router and storage functions but they are low bit rate and aimed at tracking and emergency messaging.

some old threads:
»Truth or Consequences
»WISP backhaul using blimps
»Satellite Uplink for Remote WISP sites


WHT

join:2010-03-26
Rosston, TX
kudos:5
Welcome back Lutful...we missed ya.


TomS_
Git-r-done
Premium,MVM
join:2002-07-19
London, UK
kudos:5
reply to Jerm
Oh yeah, I forgot about that router Cisco put up there. I recall our Cisco sales rep at my previous employer telling me about it (though I dont really remember any of the details.)

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
»www.spacenewsfeed.co.uk/index.ph···business

"In November 2009 Cisco's 18400 Space Router was launched on the Intelsat 14 satellite to evaluate the benefits and viability of the Internet Routing In Space (IRIS) concept.
...
The really big question is whether the IRIS concept can be extended into mainstream satellite communications. If that happens, IRIS will be a game changer."


Unfortunately that has not happenned and dozens of new broadband satellites have been launched world wide since 2009 without on-board routing.

Although Exede marketing folks imply that the Viasat-1 has a "bridge" on board, detailed technical documents show it is still a bent-pipe architecture. Same for O3B satellites. They are just increasing number of beams and gateways to improve performance.


TomS_
Git-r-done
Premium,MVM
join:2002-07-19
London, UK
kudos:5
said by lutful:

They are just increasing number of beams and gateways to improve performance.

Dont fix what aint broke hey?

jim_p_price7

join:2005-10-28
Henryetta, OK
reply to TomS_
said by TomS_:

In the case of an Internet service which is two way, Im not exactly sure how the return path is handled. It would likely be done with a second transponder, but Im not 100% sure.

It's handled on a different plane. Customers recieve on one plane (I'll say vertical here, although it's really a 3 dimensional concept when you introduce skew) and transmit on the other. Plane isolation is critical to the two-way nature, at least it is with Hughes.


TomS_
Git-r-done
Premium,MVM
join:2002-07-19
London, UK
kudos:5
As in polarisation?

Or are we beyond that at this stage?

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
Yes, broadband satellites use polarity and frequency to provide enough isolation between TX and RX.

Someone asked about 140gbps spec for viasat-1 ... imagine there was a single large antenna receiving each beam at highest modulation ... then their hub transmitter would be pushing out that much raw data. This is higher than other broadband satellites because of more beams and some frequency tricks explained here:
»www.viasat.com/broadband-network···ess-pcma

Hahausuck
Premium
join:2003-12-14
kudos:2
reply to raytaylor
I've been to a few facilities. There is one here where I live. This particular sat ISP does their routing on earth. The space elements are just delivery devices.


54067323

join:2012-09-25
Tuscaloosa, AL

1 edit
reply to TomS_

said by TomS_:

In the case of an Internet service which is two way, Im not exactly sure how the return path is handled. It would likely be done with a second transponder, but Im not 100% sure.

For example with HughesNet on G3c where HughesNet has only a single horizontal transponder, subscribers will receive a download stream on 12.110 Ghz horizontal and will transmit an upload stream 14.410 Ghz horizontal.

Likewise the NOC will transmit up to the bird on 14.410 H and receive 12.110 H.

The transponder which is number 21 simply receives the signal and using an IF of 2.3Ghz block converts and amplifies and then downlinks what it receives.

Satellites on the uplink/downlink RF side are really dumb devices utilizing basic block convertors to do the frequency transconverting, they don’t do any error correction or frequency correction other than the IF reference on board.

It’s KISS at its best.



54067323

join:2012-09-25
Tuscaloosa, AL

1 edit
reply to lutful
said by lutful:

This is higher than other broadband satellites because of more beams and some frequency tricks explained here:

There are not more beams with PCMA as those are dependant upon the design of the bird, it PCMA is however for all intents and purposes predicative TDMA, that may and that is a big may, provide additional bandwidth per channel efficiency at the cost of higher transponder power demands and since on-board power is limited and metered out on a per channel/transponder basis users of PCMA may or may not realize the claimed benefit of higher bandwidth by deploying PCMA.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
said by 54067323:

said by lutful:

This is higher than other broadband satellites because of more beams and some frequency tricks explained here:

There are not more beams with PCMA ...

I wrote frequency "tricks" because I share your concerns about PCMA. Otherwise, I just implied that Viasat-1 has more beams than typical broadband satellites.


54067323

join:2012-09-25
Tuscaloosa, AL

3 edits
said by lutful:

I just implied that Viasat-1 has more beams than typical broadband satellites.

Beams or more precisely beam shaping is an old technology that allow the designers to aim power where it is desired versus just blanketing a continent and are nothing more than precise modifications of the downlink antenna reflector.

As for Viasat1 if you look into the company it becomes clear they are the remnants of WildBlue cobbled together hoping this one will make them profitable, but I wouldn’t hold my breath waiting for that to happen.

And as for PCMA it is really nothing more than carrier within carrier versus the standard single carrier per channel and is a technology that was developed back in 2010 so it's really not breaking news either.