Modem Info -> Signal Strength

whyzeman · EVDO Heavy User Joined: 14 Dec 2007 Posts: 103

I've only seen this question asked in passing but I've never seen a clear answer. If there is one, my apologies.

Anyway, in the CTR350 router under "Modem Info", there's a "Signal Strength" line. Mine says "100". What I need to know is, does that mean "100 RSSI" or does that mean "100%"? I want to say 100% because I've never seen this number higher than 100, but I need to hear it from the professionals. *end flattery.

Here's a screenshot of it:

http://i65.photobucket.com/albums/h205/whyzeman/router.jpg

My problem now is, whenever I hook up an external antenna to it (including the Booster antenna I bought from here and a 13db antenna I ebay'd that claimed to be specifically for the Alltel KPC680), the connection drops every 15-20 seconds. I've used three different antenna adaptors (one from here, one from the ebay'd antenna, and one directly from Kyocera) with the same result.

So, if this 100 means "100%" (with no external antenna attached) and I'm lucky to get 500 kbps at 3 in the morning, then I need to make a call to Alltel because you really can't get any better signal than 100% regardless of what external antenna you hook to it, right?

I've already dropped almost 300 dollars on extra equipment and don't look forward to spending much more.

Thanks!

n6gn · Posted: Wed Jun 11, 2008 8:23 am Post subject:

My guess is that your guess as to what it means is about as good as anyone's.

Generally speaking, EVDO chipsets have a pretty good idea of signal strength and quality and maintain rapid real-time power control of both ends of the link. This is a fundamental part of CDMA.

Unfortunately, whoever provided the reference design for chipset software development may or may not have provided documentation to allow application developers to fully exploit this information.

Even more unfortunately, many applications designers (and developers) probably have a pretty poor understanding of the value, significance and use of signal level and signal quality information.

What ends up getting reported by an application such as this may be almost anything and "100%" could mean how full someone's coffee cup was when they coded. I can think of no internal, EVDO-related parameter that would accurately be expressed as 100% - unless it's something like frame error rate. Certainly signal levels have a range but no "100%" bounds unless you count "100% not there".

About the only way to be very sure of what it means is to perform a controlled experiment, with known signal levels and record the response of the software, that is, reverse engineer the functionality.

EVDO is a complex system, signal levels, signal quality and power control are an essential part of it but the user often has only a compromised glimpse into this. I think that it's really rather a shame.

n6gn

whyzeman · EVDO Heavy User Joined: 14 Dec 2007 Posts: 103

In other words...you don't know.

Alex · Posted: Wed Jun 11, 2008 8:54 am Post subject:

i know its NOT actual device's RSSI.

to get RSSI, operate your device with carrier's connection manager.

http://www.EVDOinfo.com/RSSI

n6gn · Posted: Wed Jun 11, 2008 8:56 am Post subject:

Jim_in_VA · Posted: Wed Jun 11, 2008 9:15 am Post subject:

sbi108 · EVDO Fledgling Joined: 10 Nov 2007 Posts: 14

Hi all,

I had an email exchange with the CradlePoint tech support folks about this issue. They told me that the signal strength reported is related to RSSI, but the calculation method varies with each modem. I asked about the Verizon USB727 and Pantech UM150. Here is what they told me:

Quoted from tech support email:
---------------------------------
This is the response our lead engineer gave me,

For the Novatel, we sample RSSI 10 times over 5 seconds. Then normalize the dbm reading from -65 (max) to -105 (min) dbm to a %. -65 = 100%, -105 = 0%, everything else is 2.5%/dbm.

For the Pantech, we return the value it provides for the RSSI query.

In future releases we will provide both % and raw RSSI values.
---------------------------------
end quote

best to all, sbi108

n6gn

sbi108 · EVDO Fledgling Joined: 10 Nov 2007 Posts: 14

Here's another version with the full range of signal strength numbers and their corresponding RSSI:

Signal Strength RSSI Signal Strength RSSI
100 65.00 50 85.00
99 65.40 49 85.40
98 65.80 48 85.80
97 66.20 47 86.20
96 66.60 46 86.60
95 67.00 45 87.00
94 67.40 44 87.40
93 67.80 43 87.80
92 68.20 42 88.20
91 68.60 41 88.60
90 69.00 40 89.00
89 69.40 39 89.40
88 69.80 38 89.80
87 70.20 37 90.20
86 70.60 36 90.60
85 71.00 35 91.00
84 71.40 34 91.40
83 71.80 33 91.80
82 72.20 32 92.20
81 72.60 31 92.60
80 73.00 30 93.00
79 73.40 29 93.40
78 73.80 28 93.80
77 74.20 27 94.20
76 74.60 26 94.60
75 75.00 25 95.00
74 75.40 24 95.40
73 75.80 23 95.80
72 76.20 22 96.20
71 76.60 21 96.60
70 77.00 20 97.00
69 77.40 19 97.40
68 77.80 18 97.80
67 78.20 17 98.20
66 78.60 16 98.60
65 79.00 15 99.00
64 79.40 14 99.40
63 79.80 13 99.80
62 80.20 12 100.20
61 80.60 11 100.60
60 81.00 10 101.00
59 81.40 9 101.40
58 81.80 8 101.80
57 82.20 7 102.20
56 82.60 6 102.60
55 83.00 5 103.00
54 83.40 4 103.40
53 83.80 3 103.80
52 84.20 2 104.20
51 84.60 1 104.60
0 105.00

If you cut & paste the columns into a text file with a monospace font, the columns should line up. Or you could paste the text into Excel and use the Data/Text to columns function to create the spreadsheet from which I copied this table.

best to all, sbi108

whyzeman · EVDO Heavy User Joined: 14 Dec 2007 Posts: 103

n6gn, my apologies. I didn't know the number was that complicated. Feels like a bunch of DirecTV guys sitting around a table trying to calculate why HBO is channel 501.

So, going by your (and sbi's) calculations, my 100 means my RSSI is at it's strongest strength possible which, in turn, means no boosters, antennas, enhancers, or amplifiers is going to help me get a stronger signal.

Looks like I need to call Alltel, but, since I can get 500, I already know what the canned answer is going to be: "We only guarantee 400-700 kbps". Man, I miss the 1.5-2.0 Mbps I was getting when I started this service!

Alex · Posted: Wed Jun 11, 2008 3:41 pm Post subject:

sbi108 · EVDO Fledgling Joined: 10 Nov 2007 Posts: 14

Hi whyzeman,

Please note that the calculation methods I gave apply only to the UM150 & USB727. I am not sure what modem you have. I suggest that you email the techs at CradlePoint, support@cradlepoint.com, and ask them specifically about your modem. Then you will have a better idea what your numbers mean.

best to all, sbi108

n6gn · Posted: Wed Jun 11, 2008 4:16 pm Post subject:

whyzeman · EVDO Heavy User Joined: 14 Dec 2007 Posts: 103

Alex, I can get a constant 300-500 kbps so I know it's EVDO and like I said at one point I was holding steady at 1.5 Mbps - even through the Cradlepoint without any boosters or antennas (they're collecting dust now). But, if your "just-out-of-range fast EVDO network" theory is true, then an amplifier would be the next step? It may not solve this particular problem, but I'm going to get the new CTR500 router in a few weeks.

Well, thanks to antenna search, I found the nearest Alltel tower (which is roughly 3 miles away) and was close enough to the tower to touch the fence surrounding it and still couldn't get +/- 500. According to QuickLink Mobile, the RSSI was EVDO at -54. When I went to a larger city (Jackson, MS), with that kind of RSSI, I was getting over 2 Mbps and it's Rev. 0. So, there's definitely a problem with the tower, right?

I'm skeptical of calling because of all the warstories I've read about people trying to get support.

Alex · Posted: Thu Jun 12, 2008 3:23 pm Post subject: