Need Help! - Brick/Concrete House

Remember those thick concrete walls are not solely concrete. Most likely they're chock full of steel rebar. Also, your thick reference makes me think of thermal storage. If active storage, there would be some plumbing to add and remove heat from the mass of concrete.

Part of the difference is likely cell site location. It could be that USC and I-Wireless share a third party's tower, but more likely that the cell sites are different.

The higher frequency, shorter wavelength PCS band can take better advantage of windows and doors by diffraction. It could be getting through the rebar spacing with its 158 mm wavelength, versus 353 mm for cellular.

It would useful to have a visitor with the other cellular carrier, Verizon Wireless(?), come by. If the results were similar to USC, I'd be more convinced it's frequency related.

Of course, you can change carriers easily if you're out of contact.

COtech

 

Hello Cubix, welcome to WA, glad you joined us.

What LG phone do you have, you can force an LG to be on PCS (1900) or Cellular(850), so you can judge for yourself if it is the frequency.

Typically 850 has better building penetration, so as Cotrch alluded to, in your case it could be the location of the IWireless tower vs the location of the USCC tower with respect to your house.

Hope this helps

 

Welcome Cellular operators don't always share the same antenna towers, so their coverage isn't always the same in all places. It seems i-Wireless has a tower closer to your house, and USC's is further away. So yes, your prolem can be solved as easy as switching carriers. You can probably infor USC that you moved and your house is in one of their dead-spots, and they may let you out of your contract early (they should know where their dead-spots are).

As for the frequencies (800/1900), lower frequencies will travel farther and have better building penetration, regardless of the technology, thats just physics. Think about when your neighbor cranks his stereo, you can hear the low freqs fine (ie: drum and bass) but the vocals and guitar is not always audiable (ie: the higher freqs). Same with cellular freqs. If you put a 800 and 1900 on the same tower, with all other things being equal, the 800 freq will travel about 30-40% farther than the 1900.

 

Thanks for the analogy - now maybe I won't have such a difficult time keeping this straight.

 

Yes, USCC only uses 850 Mhz in your area but typically they would have a roaming partner that is on 1900, and that is usually Verizon. Now if Verizon is also 850 in your area and only Sprint is 1900. It is highly unlikely that USCC would have Sprint as a roaming partner, so that may not work.

In an LG phone like the Rumor, you go in the menu and hit 0 and then all zeroes for the password. This brings up the menu where you can choose cell only or PCS only under "Force Mode*.

I am not sure if USCC changes the password when they activate the phones, I know Verizon does not.

One thing to keep in mind is that IWireless is a GSM provider and in my experience in IA, CDMA is much more prevalent than GSM, so if you do go with Iwireless make sure it works every place you need it to. Hopefully they have a trial period that you can use for this.

 

May i add my two cents here? Since I am a physicist, I pick up on these things. Sometimes a statement is generally true, but for the wrong reasons.

Lower frequencies do NOT travel further than, NOR penetrate better by nature of their frequency.

For example x-rays have higher frequencies than visible light; x-rays can penetrate skin, etc, but not light.

However, they can be less attenuated because of their shorter frequency.

But I can build you a material, either by nature of that material, or the wire structure's spacing in that material that will attenuate less for 1900 than 850. COtech picked up on this when he spoke about the rebar spacing or window apertures. There has been some very interesting papers published regarding this in the past on city building penetration and window spacing and size vs frequency penetration of that building.

This being the case, 1/2 the frequency does not mean 2x the travel distance. In space, outer space, in a vacuum, all frequencies travel the same distance. On earth, very low frequencies (ie waves from earthquakes) travel the furthest, because they are least absorbed by the earth (simplified somewhat).

But for a given material thickness, if the transmission power is larger for 1900 than 850, it will penetrate just as far. If I remember correctly, towers and handsets are sometimes designed to have higher power outputs for 1900 than 850. At least I remember that some years ago.

So yes 850, in general, does penetrate somewhat better than 1900, because of power loss in construction materials; but that can be corrected by a closer tower or higher power output from the tower...in which case the situation could be reversed.

But back to the original poster, you have a situation where 1900 works better than 850. It may be a quirk in your building construction, or that the other carrier has a tower closer to you (and therefore more power to overcome any loss at 850). Best to give the other carrier a try (with Charylee warnings), or buy that repeater for your home. That could help a lot!

 

That layer of wire mesh in the exterior walls is your major shielding, and the windows and doors are larger apertures (in wavelengths) for PCS than for cellular.

Do get your VZW using friend to come by, and a Sprint user also (PCS only, like I-Wireless) for comparison.

COtech

 

Hi ViewFly,
Thanks for your inputs from a physicisists point of view! You reminded me of a few things..

Speaking in pure physics terms you are right, but when applying physics to radio waves, free space loss does not attenuate all frequencies equally. Read into Friis equation.
Free-space path loss - Wikipedia, the free encyclopedia

or play around with any free-space-loss calc on the internet:
Support :: Calculations :: Free Space Loss :: Terabeam Wireless

I've made alot of GSM 900 and 1800 coverage simulations, and just off the top of my head from 10 years of using these tools, I'd say 900 travels about 30-40% farther than 1800, all things being equal. Also using point-to-point microwave prediction models, where it's all free-space loss, you can also see a big difference in the distance based on the frequency used.

That's true, you can build a thick mesh material that can attenuate 850 more than 1900, but in the real world, most materials like walls are made of solid material, and with solid materials lower frequencies pass thru easier. Yes, 1900 networks can compensate for this with a closer site-to-site distance, but then there another mathematical formula that involves a direct relation with $ and the number of sites an operator needs ...so given that, most operators prefer to take lower frequencies, given a choice. And me as well ...well, maybe except in really dense city enviornments...

 

Thanks RadioRaiders.

I think you understand what I am saying.

From the wiki article you mentioned above:

"The FSPL (free space loss) expression above often leads to the erroneous belief that free space attenuates an electromagnetic wave according to its frequency. This is not the case, as there is no physical mechanism that could cause this."

Lower frequencies do not travel 'further'. The FSPL frequency loss is at the receiving antenna and due to it's aperture difference for wavelengths (which is a physical size limit). So there is no freq. dependence of the radio wave getting to the antenna.

The bulk of FSPL is the freq. independent inverse square law, so for 5 miles of travel, 1900 vs 850Mhz, that is 116.2 vs 109.2 dB. The freq dependency is only 7 dB out of ~ 100 dB. That can be rectified by the antenna or amplifier gain. Given the dual band nature of the small mobile phones antenna, 1 or 2 dB is improved using 1900 vs 850 alone (perhaps more?). 6 dB is about 25%, as you know. It is not insignificant, I agree. You can pick up 6 dB just by moving outside of your car!

I only wish to shift the misconception of signal loss from propagation to absorption building material loss,etc. Yes, you are right that FSPL is important, but it is not correct to say certain freq. travel 'further'. The loss is at the receiving end, whether by antennal or building construction. Physics semantics.

Metal rebar in concrete is bad, as well as metal foils in insulation or metal structures in commercial buildings. The latter is quite common, from the steel girders, to the metal "2x4" 's that are used in today city construction.


Very valuable input BTW. Thanks. Is there a power output difference vs frequency for base stations (including antenna gain)? I seem to remember looking over this before. Or maybe my handset had a different power output. I do forget now. It seems there was some attempt to make a compensation for freq.

To the original poster Cubix, I think COtech hit upon the best answer. You say you have 1 bar inside...how many bars outside? If it is a big improvement outside, a Wilson type repeater for indoor use would really help you and allow you to keep your current provider.

 

Yea, I hate using wikipedia for technical references, and I saw that quote and figured you'd mention that ...I don't really agree with that statement (a physisist must have wrote that ). If you say that if you have a bigger receiving antenna for 1900 then the range can be just as good as 800, then all things are not being equal. Larger antenna means more gain.


I've made link budgets for GSM 900, 1800 and UMTS 2100, and there's alot of components in the link budget. Free-space loss is one of them. Fading margins are another big one. CDMA/WCDMA also has a soft-handover gain that GSM doesn't have. If you want to get deeper into radio wave propogation models, look into things like Walfish-Ikegami, Okumura-Hata and COST. I have some company internal documents, but I obviously can't post them on the internet. But here's something I found via Google. Skip to page 12 to see some differences in frequency losses:
http://culture.deis.unical.it/telelab/index.php?option=com_docman&task=doc_download&gid=13&Itemid=3

 

.
PS-

When it comes to emissions regulations, each technology and frequency is looked at differently, and hence affects the allowed output powers of base stations and phones. Here's the FCC's view of 850 vs 1900:

OET -- Human Exposure To Radiofrequency Fields From Cellular and PCS Radio Transmitters

...so, 1900 is more restricted in output power than 850, dealing yet another blow to it's allready inhibited range.

But anyway, to make a long and complicated story short, the main reasons 850 has better propogation than 1900 is mainly due to the free space loss difference, as well as building material attenuating higher freqs more. Here's a document I found showing the differences in attenuation of material on wifi signals at 2.4Ghz and 5Ghz:
http://www.google.ch/url?sa=t&sourc...z+5ghz&usg=AFQjCNG1DK3pqz9WIDk6lHnDH9n4qAf2gg

PPS- You can have a look at the specs of the Cisco router, sowing an outdoor range of 900ft on 2.4Ghz and only 650ft on 5Ghz
http://www.radioraiders.com/wlan-range.html

 

Heh heh, I love it when FSPL comes up in the 850 vs 1900 debate!

In practice 850 usually works better in concrete construction, but adding metal usually means 1900 has a chance because of diffraction, especially with windows. Of course cell site location is important, but most carriers (in well covered areas) co-locate or at least use similar locations.

Linn County shows USCC and VZW with the 850 licenses. Aside from Sprint and AT&T, its hard to tell who else has 1900 licenses (or leases) because of all the spectrum holding companies in your area.

I'd also like to see your signal comparisons from inside and right outside your home--that would help isolate your signal issues to your home construction or tower location. When you test though, you should attempt to see what band the phone is using--a VZW phone may be on 1900 even if they also have 850 in your area. Aside from USCC and VZW though, all the others should be 1900.

 

Cubix, sounds like you have a good solution. Keep in mind that Verizon I am pretty sure, has EVDO in your area & as as far I know IWireless has no 3G (at least they don't in WI). If that is the case you will be frustrated with the data speeds, a signal booster maybe a better choice rather than switch to IWireless.

I am guessing that you will be using data since you are getting a BB.

Just my 2 cents.
Palm850/v0100 Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 7.11)

 

I'd also keep in mind that while Verizon has a 30 day service cancellation guarantee, LetsTalk has a 15 day/60 minute return period for the equipment. Between 15 and 30 days you'd be returning the equipment to LetsTalk for an exchange.

 

Cubix, sorry about the distraction. I can be blamed for starting that. But you have good news in that your signal is strong outside your home. So an outside antenna that feeds an inside wireless repeater should give you good service with your current provider.

RadioRaider, I'm not disputing that in real world applications 850 will generally perform better than 1900 (we had a lively thread on that a number of years ago). But it is often incorrectly interpreted to mean that free space propagation is frequency dependent, and it is not. It is the use of the phase travels 'further' that bugs me, versus penetration and other effects. Many students today get that question wrong on the pop quiz The practical engineering losses are based on many things, that are frequency dependent, frequency selective, antenna design, multipath etc,etc (and I'm sure you have ample material to post on that ) Imagine the receiver being an entire sphere around the source, collecting all RF energy: all freq. can travel the same distance, since the wavelength dependent aperture is not considered. But all these things considered together mean that 850 is better than 1900; I think the difference is often overstated, however. For other electromagnetic spectrum, the propagation can be highly selective (think of water and microwaves).

In the case of building materials, the dominant absorption loss can be 20dB or more, while the frequency difference loss in that same material may only be 6dB. That 6db can be more easily compensated for locally, than moving the cell tower from 5km to 2.5 km, for example. Some research is going on today to model window size and spacing (and rebar in cement spacing) to optimize cell transmissions for new construction.

The OP situation is interesting in that it seems to flip the 1900 vs 850 situation on it's head.

Anyhow, sorry that I brought up my pet peeve and distracted the original posters question.

 

You mean "farther" right?

 

:O Whoops. Didn't have an app for that.

 

My apologies as well for derailing this thread :O
...but since it's an interesting topic...:browani:

1900 networks require about 30-40% more sites than 850 networks. When you consider a site costs roughly $50-100k and has reoccuring monthly costs of maybe $3-5k. If you were a network operator on a tight budget then you'll appreciate the difference a little more

You lost me a little there. If you're saying you can compensate for the higher freqs worse attenuation by building sites closer together, then see my answer above

...interesting, but what frequency would you optimize the construction for? 700, 850, 1700, 1800 or 2500Mhz are all used in the US today for cellular networks (WiMAX is on 2.5Ghz I beleive)

Back to the original poster: it's hard to say. If he has 4 signal bars of 850 outside and 1 or 0 inside, it could simply be the concrete attenuation. BArs don't say much about the dBm you are receiving. My Nokia N95 shows full bars on about -90dBm. A 10-15dBm drop in signal would bring me to about -105 which is about the threshold for making a voice call. And a thick concrete wall can easily have 20-30dB of attenuation. About the 1900 making it inside is curious tho. COuld just be the 1900 site is closer and "full bars" could mean a signal of -70 in which case a drop of 20-30dB would bring the signal down to the -90's which is still useable. Anyway, hard to guess.

...oh, and technically speaking, you're right, I won't say any more that "lower freqs travel farther", I'll be more correct and say "higher freqs are more easily attenuated"

 

So finally you said excatly what I said in my first post to Cubix. I am glad we agree, better late than never.

 

Yea, but a thread with only 2 posts is really dull Besides, I learned a few things in the ensuing 20 posts. Like, I've always been saying "travel farther" when I should really be saying "travel further"

 

LOL, so to sum it up may I say:

1. The Engineer & the Physicist went farther away from the topic of this thread than usual.
   
   
2. The Engineer & the Physicist could argue the 850 vs 1900 further, but they would not get any closer to agreeing.

Ok, that was pure and unadulterated fftopic: post

 

@cubix:
The best way to figure it out is to have phones where you can see the received signal strength in dbm. The range is usually between -60dbm (the strongest) and about -100dBm (the weakest). On your LG phone you can try to get it into "feild test" mode with the directions below (it may or may not work on your phone, but it's worth a try). I also attached a PDF file that explains how to get into feild test mode on other phones.

If you can get you phone to show the dbm value of the received signal (either "rx" value or RSSI), then stand outside your house and note down the average value (stand where the signal is strongest, and note the Cell ID as well). Then walk inside and compare the value to what you saw outside (make sure you're still on the same cell). If you could do this with both a USC and I-Wireless, then you would know for sure if one signal is getting attenuated more than the other. ex: if USC drops say 20db and Iwireless only drops maybe 10db

PS- Thanks for your posts. It stired up some interesting discussion, in addition to maybe even figuring out your reception problem

 

Nope, that is not what I was saying. It is much harder to move a tower km's than give your handset a better antenna arrangement beyond the poor performing internal ones in all handhelds. I use to attach my old Nokia to a 1/4 wave mag mount on top of my refrig to give a 10 db boost. I was only making the point that moving a tower to gain 6db is a big deal. There are other options.

Probably the higher 1900 ones for now, since the 850's do much better.

YAYYY!

 

I could not resist this timely example. Light frequencies are in the very high Terahertz (THz) range compared to 850MHz. It has all to do about attenuation. And in fact moving from 230 TeraHz (where light travels in fiber) to lower frequency 193 TeraHz (where light is very highly attenuated and unusable in fiber) is a world of difference. 20 km of high freq light in fiber is not uncommon without amplification or a boost.

Nobel Awarded for Advances in Harnessing Light

Today, Oct 6, 2009

"Fiber optic cables and lasers capable of sending pulses of light down them already existed when Dr. Kao started working on fiber optics. But at that time, the light pulses could travel only about 20 meters through the glass fibers before 99 percent of the light had dissipated. His goal was to extend the 20 meters to a kilometer.

In January 1966, Dr. Kao, then working at the Standard Telecommunication Laboratories in England, presented his findings. It was not the manufacturing of the fiber that was at fault, but rather that the ingredient for the fiber — the glass — was not pure enough. A purer glass made of fused quartz would be more transparent, allowing the light to pass more easily. In 1970, researchers at Corning Glass Works were able to produce a kilometer-long ultrapure optical fiber.

According to the academy in its prize announcement, the optical cables in use today, if unraveled, would equal a fiber more than a billion kilometers long."

 

C'mon, you can't compare bouncing light in a glass vacum to sending radiowaves thru the air, it's a totally different playing field ...but if you do, a speck of dirt in front of a 850Mhz antenna will have no effect, while a speck of dirt could completely block a fiber transmission in the 193Thz range Sigh, I'm afraid we'll never see the 500nm wavelength* at the end of this tunnel
*AKA: Light

I'll never get the further/farther thing correct :O ...yet another reason to say higher freqs are "more easily attenuated"

 

No, the comparison is right on the mark. We are talking about bulk attenuation in solid materials (I don’t know what you mean by ‘glass vacuum’??; that is a contradiction; light travel through a solid – glass). So regardless if it is construction material or solid glass, we are concerned with dB/distance. For an optical engineer, the unit is dB per km of solid glass to determine the signal loss. Meaning that light in a fiber transmits through 10’s of kilometers of solid glass fiber. The Noble prize was awarded for realizing that the material, not defects, was the problem with current fiber in the ‘60’s.
For bulk attenuation with radio waves, it is the same for construction materials; the dB loss per unit thickness of the material. The thicker the wall, the more attenuated the RF signal. The bulk attenuation changes if it is pure concrete or concrete with metal rebar inside.
The quirkiness of materials, and my point, is that the general rule that higher frequencies are more attenuated is not always true, since it depends on the absorption properties of the material.

A speck of the right matching dirt (metal foil) of the matching RF wavelength (35cm for 850Mhz), in front of that antenna will kill your signal too.

My german father also has me confused for life about further or farther.