pharding

Which is better technology for audio quality: CDMA or GSM or some other technology?

Which Cell Phone Network has the best audio quality?

Why is European GSM better than US GSM?

Currently I have Cingular becasue of the broad US coverage. Is there a better network? Is there a better network for the Bluetooth Technology of my car?

I look forward to seeing what board members have to say on this one. Thanks.

BangleBox_530d

The whole world uses GSM, except for the US and a few places that the US "made" them to choose non-GSM.

If you only ever need to use you phone in the US, then why go for a poor setup of GSM (not good coverage in the US). But there are some phones which do CDMA and GSM, so if you want the best, choose one of those.

I presume that the US GSM network is poor only because there's not enough cells installed.

Maybe one day the whole world will have the same phone network technology, the same power voltage, etc.

BTW do you guys know that some US officials tried to force CDMA onto Iraq, instead of GSM. Common sense prevailed, somehow, and GSM is now being installed. The same as every other country in the region.

hinckley

GSM is superior, but in the US, we're stuck with the first generation technology. The GSM networks here just don't have the coverage that the "traditional" networks do.

I beleive that Verison is considered to have the best US network. But the only Verizon BT phone that BMW has certified for the E60 is old and has actually been discontinued by Verizon!!

As a current Verizon customer, I'm about to jump to cingular, which I believe is considered to have the 2nd best network here.

pharding

GSM in Europe has amazing audio quality. My cell phone calls from Germany to the US were as good if not better than land line, wired, conventional phone calls in the US.

BangleBox_530d

Yes, a good mobile call should be impossible to tell if it's landline or mobile.

I remember when GSM was first introduced. The audio quality wasn't great. Maybe you guys have the old stuff over there now.

alohalc

agree . i used to be a verizon customer and i was so happy with the reception and customer service . i even talked inside the elevator and people stared at me like i'm crazy . people always asked me what kind of phone i have. but after i switched to t-mobile, i'm having hard time to get clear reception...even at home ! and their customer service is not much better than my dealer . so bottom line is if you don't travel to foreign countries a lot, stick with the better reception verizon .

gdavis

Pharding,

GSM is the same technology worldwide. There is GSM in the US through Cingular/ATT and also with lesser covered T-Mobile. The only small difference in the US is that GSM uses a slightly different frequency than Europe, but that has no bearing on the quality.

The best technology is NOT GSM or CDMA, but 3G and it is being phased in in Europe and shortly to come to the US. It has huge bandwiths, better audio quality, potential for video feed and more. But it will not be here for a year +.

Don't bother switching from what you have. It is great, and nothing else is any better.

Just hold on and wait for 3G and go for that in a year.

(PS, GSM I am almost certain was invented in the US by Motorola. The only reason everyone doesn't use one technology in the US is that it was set up 1st with analog, then became a 'free-market' environment, and newer technologies were brought along by competing companies all in the same cells).

wnrussell

Many people wonder what carrier to go with, and you'll see arguements over coverage and features from one carrier to the next. Most don't even realize what CDMA, TDMA, or GSM stand for, let alone the advantages of each.

CDMA- Code Division Multiple Access! What does that mean. In Analog, there is one voice call (one user) per channel. So in each sector, you can only fit the number of users as there are different channels. In TDMA (Time Division Multiple Access, as used by AT&T, and Cingular) they take each channel and divide the channel into three time slots. So now you can have three users per channel by sharing the time on that channel. This is done in the micro-seconds, so the users will never detect the breaks in the audio. In CDMA, we assign perfectly orthagonal codes to each channel. Its like adding a long sequence of codes onto the channel so that all the users have a unique code. Now each code is spread in such a way that they do not interfere with each other. In short, this allows you to have 64 users on the same channel, compared to 1 in AMPS and 3 in TDMA. HIGHER CAPACITY PER CHANNEL. Problem in AMPS and TDMA is if User A is transmitting on channel "1" in to one tower, User B cannot use the same channel on the next tower over, or they will interfere with each other. So you are limited in the number of channels per sector you can use. In CDMA, because of the Code Divisions be so unique, you can multiple users on the same frequency in the same sector; let alone repeating that in adjacent cells. (This is limited by Soft Handoffs)

TDMA- Time-Division Multiple Access, is a basic method of transmitting digital signals over radio waves, is the basis for several major wireless standards, including GSM, iDEN, and IS-136. IS-136 is commonly referred to as simply "TDMA".

In AMPS, power is screaming. The power output from an AMPS system is enormous in comparison to CDMA. (This is EXTREMELY difficult to explain without graphs). Each user is combined and spread throughout the entire useable spectrum, and the network is constantly sending out either a power up bit, or a power down bit. The goal is to keep each user at just enough power to be able to "see" the base station and vice versa. This not only prolongs battery life significantly, but also reduces the amount of radiation to the user and the system. This helps overcome what is known as the near/far problem. A user close to the base station is going to be screaming at the tower, (which raises the total noise floor), prohibiting the user at the far fringe of the cell from getting a clear signal. So the base station tells the near mobile to reduce its power output to a whisper so as not to interfere with the user at the fringe. This is done through both open loop (the base station tells the mobile to set its transmit power to 10 d, and closed loop (the base station asks the mobile to report its receive power, and then subsequently tells the mobile to power down a little or power up a little)

Handoffs occur when you move from one cell tower to the next. In AMPS and TDMA, your connection is broken at the first tower and thrown over to the next tower without any confirmation that the new signal is useable. Think of a quarterback throwing a pass. Once he releases the ball, it's not his concern whether or not you have dropped the pass. In CDMA, we use Soft Handoffs. The call is effectively, during a Handoff, being transmitted to both cell towers at the same time, until the mobile reports back that the new signal is strong enough and stable enough to maintain the call without dropping it. Then the call is released on the older fading tower. This is what has statistically given Verizon Wireless customers the lowest Drop Call rate of any other US carrier.

Multi-path. RF signals bounce off walls, trees, and buildings. In AMPS and TDMA, the mobile locks onto the strongest signal it sees. If another signal (perhaps one that's bouncing off the billboard) becomes stronger (say, because you walked behind the building), then the handset effectively handsoff to that stronger signal. In CDMA, we use rake receivers which effectively slow the call down a little bit in order to allow all the signals to combine. This gives the mobile a total signal power that is the sum of all that it sees, instead of just the best. This delay is done in the milli seconds and cannot be heard by the human ear.

These are just a couple VERY BASIC advantages CDMS has over the other technologies. Some people say GSM is the future because everybody in Europe and the rest of the world is using it. Does that make it the best choice? In fact, there are more GSM carriers adopting some derrivative of CDMA than there are CDMA carriers entertaining the thought of switching to GSM.

GSM - Global System for Mobile Communication. GSM is currently the dominant 2G digital mobile phone standard for most of the world. It determines the way in which mobile phones communicate with the land-based network of towers. GSM has not been the most popular standard in the United States in the past. CDMA and TDMA, competing standards, together shared most of the market. In the case of GSM, it was probably a less expensive technology to deploy, and was one that made it a lot easier to connect the entire European Union together. I'm sure there was a reason, but it wasn't because it was superior to CDMA. But one thing's for sure, as someone who travels to Europe every now and then, it sure would be great to be able to 'swap out' cards and use my phone over there like GSM users can. Well, the biggest reason why GSM took off is because CDMA wasn't on the market when they were making GSM.

The future of wireless is data. Not just internet, but wireless Video phones. In order to accomplish Video Phones, you need the fastest data rates you can get, and GSM does not have a viable option for fast throughput speeds anywhere even close to what CDMA has now, and what is coming down the pike for 4G. So the TDMA carriers, if they are to hope to compete for your business when 4G CDMA Wireless Video Phones come out, they have to change their entire infrastructure now. Carriers like Verizon Wireless and Sprint are already in the CDMA market and poised and ready to tansition their networks to 4G VoIP and Video Phones.

So, this was a real quick down and dirty tutorial of only a few benefits that CDMA has to offer.

Thanks for reading!

pharding

gdavis and wnrussell:

What a great explanation of current and future cell phone technologies. Now I can make an informed decision. Thank you very much.

wnrussell

Paul:

Many phones (Verizon as one example) are advertised as being "tri-mode" or "dual-band", etc. These refer to the combination of technologies and frequncy bands the phone supports.

AMPS is the analog technology, which has inferior features and quality, but often superior coverage. Digital technologies include CDMA, TDMA, and GSM.

The two frequency bands in the US are 800 MHz (Cellular) and 1900 MHz (PCS). Europe and many other parts of the world use 900 MHz and 1800 MHz. The 800 MHz band is also sometimes referred to as 850, specfically when referring to the new "GSM 850" mode.

As an example, a CDMA tri-mode phone would support AMPS 800, CDMA 800, and CDMA 1900. That means it would work in both frequency bands in digital, and also work in analog (which is only 800 MHz.) The same is true for TDMA.

A dual-mode CDMA phone could be either AMPS 800 / CDMA 1900, or AMPS 800 / CDMA 800. Same for TDMA.