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To: Rajala who wrote (16857)	10/21/1998 9:59:00 AM
From: engineer	Read Replies (1) \| Respond to of 152472

Rajala, Perhaps you would take some time and understand what a near far problem is. there is NO signalling involved. It is a well known system limitation of CDMA. It is also present in wideband CDMA. the problem is that when you are moving, you must estimate the power contol from recived signal strength. Moving around and mutipath fading cause this estimate to be slightly innaccurate. If how ever you stay fixed, you estiamte is very good. So your power control is very good. If you have your power control estimate veyr good, then your power request to the basestation is exactly your theorectical limit and thus you use the minimum amount of power needed to complete your link. This power control estimate is about 3dB, or a factor of two. GSM has no mechanism like this, as they must transmit full power all the time intot he chanel and when they use a time slot, they consume it fully. they have no way to back off the channel at all, thus have no savings for a fixed terminal over a mobile. the only saving they can attain is that when they are fixed, they can hang a large fixed antenna out the window and gain more cell radius, but in a fixed, dense populated area, this defeats the cell density argument. Since GSM has no real fixed frequency reuse advantage (i.e. they cannot do microcells well) then this is counterproductive to producing a large dense WLL community for them. I am still confused with your argument. Perhaps you could sit down and write out a clear technical explanation for us all one more time? best regards,

To: Rajala who wrote (16857)	10/21/1998 11:07:00 AM
From: Clarksterh	Respond to of 152472

Rajala - First of all, let's remember where the 3 x capacity advantage for WLL is supposed to come from: the reduced non-traffic signalling, such as power control etc. which is estimated to take 2/3 of CDMA1 capacity (!) when it takes only between 1/8 and 1/16 of GSM capacity. We are talking about the same basic functions, nicht wahr? Do we all accept that CDMA1 eats bandwidth like a lewinsky with 10 x more inefficient signalling than GSM? Engineer is right. You need to understand the basic limitations of each technology: 1) For TDMA the basic limitation is that you cannot be using the same frequencies in the neighboring cells. Therefore each cell only gets 1/7 (assuming a hexagonal layout) of the total frequency. In theory it is possible to reallocate these frequencies in real time as needed, but it is difficult especially when the users are continually moving around. 2) For CDMA the basic limitation is completely different. In an attempt to reuse the spectrum completely in each cell, each user interferes with every other user, but they are 'averaged out'. However they are much harder to average out when some of the users are getting louder then softer then louder, .... . As the users become fixed they vary their loudness much less. Viola! Secondly, the 30% (estimated) fewer basestations because of decreased mobility is not applicable. People expect much more availability from their fixed phone than their mobile, thus there's no need for that extra 30% in price comparison. It may be true that in the developed countries the users expect worse availability on a mobile than on a fixed, but if you had neither to begin with it isn't clear to me that that still holds. Thirdly, as I have stated before and someone even supported this (which does not happen too often to my opinions on this thread I might add), capacity is not a cost issue on WLL. If you get enough subscribers to exceed the max available channel potential (120 channels, that would be maybe 1000-3000 subscribers since people talk only every now and then) of a standard CDMA1 cell, you are talking about a freak case. If we assume a density of 1500 households per square mile (a low number for most of the places where customers live), and a distance of 6 miles (?? I'll look it up when I get to the office), you can soak up the entire capacity with a teledensity of less than 1 in 100. But, loathe as I am to help your case<g>, there are occasions where you are correct, but I suspect most of them are not driven by teledensity but by geographic limitations (hills, tall buidings, ...). Clark

To: Rajala who wrote (16857)	10/21/1998 12:59:00 PM
From: Clarksterh	Read Replies (1) \| Respond to of 152472

Rajala - Comparison of D-AMPS vs CDMAOne capacity I decided to go back through my Qualcomm documentation, and although I still could not find voice channels/carrier in the spec's, I did find a very interesting description in the Economic Report: Fixed Wireless Networks sent to me with the specs (teach me not to read all 200 pages of documentation): "In mobile networks, CDMA capacity is usually 3 or 4 times greater than D-AMPS for a single site. When the users are fixed in a network, the capacity of CDMA is typically 6 or 7 times greater than D-AMPS for a single cell site. The cell capacity increases because fixed subscribers create a lower level of interference and a more stable power control environment than mobile users, allowing a greater number of users to coexist within a single RF carrier for CDMA WLL. In a mobile CDMA network from Qualcomm, 24 calls per sector per carrier are possible. In a fixed network, the capacity increases to 45 users per sector per carrier." Note that this disagrees with QTelWatcher's documentation, but it is quite possible that things have been improved since I last did a survey (1 yr ago). Clark PS On the issue of range, 6 miles is probably a good conservative estimate. The Qualcomm documentation gives Urban=8.4 miles, Suburban = 23 miles and Rural = 34.5 miles. PPS On the matter of spec's. I find it mildly annoying that the specs sent out are more a glossy brochure than a true spec, but Qualcomm is not alone in this. In fact, once I got Qualcomm to send me documentation they sent me much more complete documentation than anyone else (it might be possible to read into this that the other technologies aren't as willing to make economic comparisons). They even sent me a bunch of documentation in Russian <g>.

To: Rajala who wrote (16857)	10/22/1998 2:04:00 AM
From: freak.monster1	Read Replies (1) \| Respond to of 152472

>>Well 4 or 5 times >>anyway (three times the number of users per base station plus >>30%(estimated) fewer basestations because the decreased mobility >>decreases the excess capacity needed in case users cluster). >Oh dear. >First of all, let's remember where the 3 x capacity advantage for >WLL is supposed to come from: the reduced non-traffic signalling, >such as power control etc. which is estimated to take 2/3 of CDMA1 >capacity (!) when it takes only between 1/8 and 1/16 of GSM >capacity. We are talking about the same basic functions, nicht wahr? >Do we all accept that CDMA1 eats bandwidth like a lewinsky with 10 x >more inefficient signalling than GSM? Rajala, I don't know what you do or don't know about GSM, you appear not to know much about CDMA. The capacity increase comes from: 1. reduced near-far problem 2. stationary/psuedo stationary channel as opposed to fast fading channel 3. no capacity loss due to mutliple sectors supporting mulitple mobiles in soft hand-off. 4. All the above leads to much better power control, leading to much less interference in an intereference limited system (CDMA), which in turn leads to higher capacity. Very little to do with signalling. In fact, WLL in CDMA will most likely have almost identical signalling overhead (IS-95A/B). I don't however know exactly what the capacity increase will be. Engineer has posted some numbers.