Voice Quality on MB Bluetooth - review of RAZR V3 cradle

[Skylaw]

After reviewing a number of reports of poor voice quality with the Mercedes Bluetooth implementation, especially the report by Carlsbad at Bluetooth - Poor sound quality - MBWorld.org Forums. I discussed the matter with AWS. In particular, Carlsbad had purchased the new RAZR V3 cradle with Bluetooth. I was interested in the same unit; purchased it, and have just finished testing it in normal use in my local driving area. See Connectivity Options at Welcome to AWS for Mercedes-Benz I apologize for the length, but there is no other way to cover it in depth. For you bottom line only types, the V3 cradle for MHI provides good to very good voice quality with approved equipment and firmware, and is worth having. There, you can stop reading. For those who want to know what’s going on, not only with the V3 cradle but with MB Bluetooth compatbility generally, please continue.

The RAZR V3 cradle is available for MHI equipped vehicles (’05 and on). It is fundamentally a Bluetooth device, but adds a connection to the car’s external antenna and also permits charging the RAZR. Both of these are desirable because the RAZR has weak signal reception and notorious battery problems. The V3 cradle slips into the same MHI mount that the Bluetooth puck or a plug-in phone cradle would. Up to four phones may be paired with it (but not used simultaneously; the cradle first searches for the last phone paired). While its instructions specify RAZR phones may be paired, AWS indicated that any approved Bluetooth phone could be paired to the Bluetooth component (of course, only a RAZR can be docked). According to the instructions, the RAZR V3c and V3m (CDMA RAZRs) do not allow viewing incoming SMS; that is supported for GSM RAZRs. Of course, phone books, etc. are downloaded. 3-way calling, download of stored SMS, and call waiting are not supported for any, although an audible beep identifies an incoming call. Not all ring tones are supported.

When I discussed the problems experienced by Carlsbad at the link above, AWS was emphatic concerning two points. The representative stated that 1) signal strength has to do with connectivity (the ability to stay connected to the network), claiming that signal strength had no bearing on voice quality; and 2) voice quality was related only to firmware and the phone used.

While both of those statements may be true to a degree, they slightly overstated, and are dependent on what is meant by “voice quality.” Plainly, while a weak signal between the cell phone and the network (tower) may result in dropped calls (lost connectivity), it may also result in greater background static, brief dropouts in the transmission without dropping the call, and greater vulnerability to interference from other radio signals (RF interference). All can result in more difficulty understanding what is said, and may be viewed by the user as poor voice quality. These factors are influenced by coverage (unobstructed distance from the nearest cell tower), signal strength (affected by coverage and also the phone or car’s antenna), and presence of high levels of other radio signals near the cell frequency band that may interfere with the cell signal.

As to equipment and firmware, AWS said that the principal factor in success in communicating between the phone and the Bluetooth equipment in the car is the compatibility of the cell provider’s firmware. AWS stated that it tests both phones and firmware for 3 months before approving it; and the firmware is tested for consistency of result and noninterference with the firmware of COMAND and MHI. Approved firmware will connect to the car, provide good voice transmission and reception, download what it is designed to download, and not fail to download those items over time; and will not freeze or otherwise interfere with the MHI system or COMAND. AWS was emphatic that a) approved phones using approved firmware will perform as they are supposed to, absent an equipment malfunction; b) some persons who are using unapproved firmware and equipment may have success because their firmware is in fact compatible, but has not been tested yet; and c) some persons using unapproved equipment or firmware may have brief success with downloads but downloads that worked initially may cease over time as firmware corruption occurs; and in the worst case, the MHI or COMAND may freeze altogether. AWS was emphatic that most voice quality problems occur with use of unapproved and incompatible firmware or equipment, with the principal variable being the firmware compatibility. With respect to equipment, the better its quality, the better the results would be.

I observe that in addition to transmissions between the phone and the cell tower, Bluetooth transmissions between the phone and the MHI are RF transmissions, and are subject to attenuation and to signal interference from other radio signals as well. Such interference could affect voice quality without interfering with connectivity to the cellular network. AWS’s assurances did not address this directly.

That said, on to the testing. Prior to installing the V3 cradle I had used a V710 in its cradle with my system. The microphones, phone, MHI system, and antennas all worked, and provided cell voice quality that was clear and intelligible, but it was not the equivalent of the best land line communication (cell communication rarely is).

I installed the V3 cradle, simply replacing the V710 cradle. Pairing was simple. Phone book download started when pairing was complete.

My phone is a Verizon V3c CDMA RAZR using firmware version GATW_01.15.04. Both are AWS approved (and by the way, AWS does approve phones it does not sell for use with its BT systems; however, they have begun insisting on verification of the customer’s use of approved firmware and equipment before they will fill an order, and especially, accept a return). AWS also cautions that newer firmware cannot automatically be assumed to function as well as older approved software with the BT equipment. In some cases it has not, leaving the user to try to get the older firmware reinstalled.

The RAZR V3c suffers from poor signal strength in the first place, because of its antenna design. Then, when placing any cell phone behind the original equipment IR (metallic) tinted glass inside the car, you have decreased signal strength. That can result in connectivity problems, static, dropout, etc. In the Tampa, FL area, which generally has very good coverage, my undocked V3c will get only one to four bars of strength, and usually only 2. In my home, which sits in a relatively small spot of poor coverage, I get "no service" to one bar with the undocked phone. In the car (’05 S-Class), undocked, the phone never indicated more than 2 bars of strength even in the strongest areas (the signal strength when paired, but undocked, is indicated on COMAND). When docked with the RAZR cradle, thereby connecting the phone to the car’s external antenna, signal strength was 4 to 5 bars in most areas (and 2 bars at my house, decreasing immediately to “no service” when undocked). The advantage of using the car’s external antenna is immediately apparent.

To test the setup, I called from the car in the undocked and docked modes; and I called land lines, cell phones that were themselves using Bluetooth connections, and cell phones used alone. I made long distance and local calls to each. I initiated calls in the weak signal areas near my house, from strong signal areas in town, and calls from near the runway at the International Airport (a source of much RF activity that could cause interference with either the phone’s Bluetooth or its cellular signals). I felt like a well-known commercial - “Can you hear me now?” – actually, I did long test counts.

All calls were intelligible, and I would characterize them as “good” in voice quality. The calls made from weak signal areas had somewhat more background static (hiss), and were ever so slightly more muffled, but not enough to interfere with intelligibility. There was occasional brief dropout (less than a half a second) when calling from the weakest signal areas. Some of the calls made to land lines were characterized as being as good as that on the 5.8 Ghz wireless phone we use over fiber optics at home. Essentially, I found the V3 BT cradle to provide good to very good (not excellent) voice quality, and to be worth keeping.

Unfortunately, I did not come across a likely source of the problem reported by Carlsbad, who also reports that AWS has told him of four other cars having problems similar to his. I can say, however, that a system that is functioning normally seems to be adequate; and I can only surmise that despite extensive replacement of equipment in his car, something is still malfunctioning – whether the phone’s own Bluetooth circuitry, the V3 cradle he was provided, or some other component. My experience has been nothing like his.

I also note that in the past I have reported poor voice quality on my wife’s Peiker-manufactured BT unit in her Lincoln Town Car. Discussing this at length, we determined that she had made most of the calls near locations with very high levels of intense RF activity. Under those circumstances, the voice quality on the end outside the car was bad, with static, high levels of hiss, and frequent dropouts. Since she has begun initiating calls several miles further away from these sources, the voice quality is much improved. I surmise that the high level of RF (including microwave) activity interfered with either the cellular band, or with the Bluetooth transmissions within the car, or both. I would anticipate that very high levels of RF energy would interfere with any cell system.

[Diesel Benz]

Although I'm not using the BT HF puck, I did read the post with interest. Should be even more useful for US members of the forum.

A couple of notes I think I did not see mentioned. On important fact with the BT HF approach is that you easily use the phone in your pocket during conversations (otherwise one would lose a lot of the interest for BT in the first place). The antenna performance of the phone when kept in a pocket or a bag or similar is a lot worse than the antenna performance when the phone is held up next to your ear. This combined with the Razr basic performance can easily result to radio link problems for the reverse link (mobile to base). Usually this is the weak link in a cell phone connection (not always, depends on the site installation details) which is bad because your phone end quality may be perfect while the other end is struggling. The beauty of the Euro BT puck is in the fact that it is not using the phone antenna, only the BT connection for audio (and some control) from the phone to the car.

Skylaw, I did not see you describing how did you place the phone when you were testing BT, can you clarify that?

As you describe, signal strength on digital systems only affects the voice quality when the C/I gets poor but still there is an area where speech quality is affected before the call completely drops.

It is true when AWS says that a later phone SW may perform worse with the BT puck than an older one. This would be from a new, not identified bug in the new SW. This however should be quite unlikely (even if possible) and the new SW should fix other issues. Considering going back in the SW versions, not all phone brands allow this. The point is that in some cases certain security issues have been improved (I mean like SIM lock protection etc.) and the phone is built not to accept a later SW.

AWS also explains it a bit oversimplified when problems later appear on SW that initially seems to work. The phone SW itself would not get corrupted (all devices lie the cell phone would always check the SW integrity at power on) but the user data that changes, may later on reveal an existing SW bug that did not appear initially.

[Skylaw]

Thank you for the thoughtful elaboration. You are correct in each point. I did not continue further because I wrote this for both BenzWorld and MBWorld for widest dissemination, and I ran up against a character limit on one forum. Even had to shorten it.

You are entirely correct that it is pointed toward U.S. spec cars, since it dealt with MHI only. One of my long-standing irritations is that MB did not implement the U.S. specification MHI to include onboard cell equipment that would function as UHI does, and eliminate many of the concerns. That also gets me into the lack of RDS, lack of an aux input for iPod in the '05 COMAND in the U.S., and many other shortfalls in the U.S. versions that are present in Europe and elsewhere.

But back to the topic - you are entirely correct that the location of the phone when in an undocked mode is important. One section I deleted from the original draft dealt with cell phones in metal briefcases, or having a metal container (a makeup kit in a purse, for example) blocking it and attenuating the Bluetooth voice channels. In the undocked mode in my trial, I had the phone in my left trouser pocket (where I normally carry it, containing some change but no key cases).

You are correct that most new software should attempt to correct bugs or add capability to older software; however, our experience with Verizon in the U.S. clearly shows that sometimes it is meant to cripple an existing feature so that a desired capability must be purchased from a business partner. The main point AWS wanted to make is that one should call AWS before upgrading from approved software, to see that the new software is also approved. If it isn't there is risk that the BT will not function satisfactorily, and you may not be able to go back to the older software!! AWS will confirm software versions simply on a call - you don't have to be buying a new phone or BT equipment at the time. I could wish they'd post a listing, by brand and provider, of approved software - it would simplify things and lessen the workload of their reps.

I did not go into detail with AWS on the firmware corruption; however, their concern was with corruption of firmware on COMAND (and the car's phone system), not the cell phone - especially where such corruption has led to freezes of the COMAND system. I have never seen this happen, but have read of it several times with users requesting how to escape the problem. I don't have that answer, if the problem lingers after shutdown and restart of the car to re-boot the COMAND, short of re-flashing the COMAND unit.

Thanks again for your comment.

[Diesel Benz]

Thanks for the further clarifications Skylaw. I could not think of this option that operators sort of downgrade phones in some cases. We do have branded phones in Europe too, I consider those quite crippled but am not aware of operators making that worse (from the user's perspective) on a new SW but I understand even that could happen. I also see it positive that AWS can be consulted about the potential issues on the MB setup, after a SW update.

I misunderstood the SW corruption issue. Again, the Command SW should equally not get modified from a SW bug but in the worst case even a data change could freeze it. Comand should not get frozen from messaging with an incorrectly built phone but this still is always possible with complex software. Always good if AWS or others have tried to make sure that MB owners can enjoy Comand without any unnecessary hassle. I remember a friend's case where a car kit that connected to the CAN bus of an Audi, made the car fail to start. A bug on both sides probably and should not happen, but it did.

[Skylaw]

Following up on the correspondence with Diesel Benz, I placed my RAZR V3 into a metal (Zero Halliburton) briefcase, and put the briefcase in the trunk of the car. The Zero Halliburton is aluminum; greater RF attenuation could be anticipated with ferrous metal or copper containers. In the Zero Halliburton briefcase, the phone paired successfully with the MB BT cradle/puck combo, and I had connection to the cell tower (at differing signal strengths based on my location) as set out below.

I made three calls at differing signal strengths from the cell tower, all to my answering machine. I used the answering machine because I could easily compare the results within a short time for comparison purposes (including the results of earlier tests with the phone undocked and in my pocket). Voice quality on the phone with the answering machine is usually better received "live" with the handset than when recorded with the answering machine.

--At five bars of signal strength from the cell tower, the call was intelligible but somewhat more muffled than when the phone was undocked and in my pocket. There was also a slightly perceptible increase in noise (pops and hiss) in the car when the phone was in the metal briefcase, vice having it in my pocket. The hiss was not noticeable on the end outside the car, likely because my answering machine does not record higher frequencies very well. However, the message was intelligible (less so when I turned up the volume on playback of the answering machine), though it suffered from a "roughness" not present when the phone is docked, or undocked but in my pocket. Conclusion: The metal briefcase attenuated the connection to the Bluetooth electronics somewhat, but not enough to make voice quality unuseable.

--At two bars the outgoing voice was less intelligible and more muffled, with more static noticeable on my answering machine. The voice message received in the car suffered from more hiss and pops (static). Conclusion: The attenuation because of the briefcase would be the same as in the first test; however, with attenuation of the Bluetooh signal there was some data loss that was then compounded by a weak signal between the phone and the cell tower.

--At one bar of signal strength, the noise and static heard in the car was high, although the message could be made out. On my answering machine, the message was intelligible only at low volume levels, and sounded very 'rough." At high volume levels on the answering machine, the message received was unintelligible. Conclusion: The attenuation of the Bluetooth signal was severely compounded by the weak signal strength between the phone and the cell tower, and the gaps and missing data were even more noticeable when the voice message was amplified by turning up the volume of the answering machine.

I believe the results indicate that having the phone in a metal briefcase degrades the signals between the phone and the Bluetooth unit somewhat. This resulted in some signal loss, resulting in hiss and some audio breakup. This did not render the voice message unintelligible when the signal between the cell tower and the car was strong ; however, the hiss and audio loss (breakup, static, pops) was compounded by a weaker signal beteween the phone and the cell tower, and voice quality (intelligibility, clarity) degraded more as the signal between the cell tower and the car became weaker.

This is a result that could be expected, and verifies what I had speculated upon in (but edited from) the original writeup. Good quality in the Bluetooth connection plus a strong cell tower signal yields good voice quality both ways, when using an approved phone and approved firmware. A lesser quality of Bluetooth connection can still result in intelligible voice quality where the cell signal is strong, but degrading to unintelligible (especially outside the car) where the cell signal is weak.

Metal objects placed between the phone and the BT module can degrade the Bluetooth signal, even if not enough to prevent pairing. I would anticipate that the greater the degradation of the Bluetooth signal between the phone and car, the worse the results would be.

[nevadajack]

Thanks Skylaw for an excellent post. I noted also that when I installed the V3 BT Cradle with my Cingular RAZR that the signal strength and "voice quality" improved. Several people on long distance calls thought I was using a land line and said they didn't think I was using a cell.

On another thread I tried pairing my V557 at the request of a poster who wanted to know if the cradle would pair with a phone other than the RAZR. I did not have any success in trying but I also am not a master at cell phone usage. It is of no consequence to me since I now have two cradles..one for the V557 and the BT RAZR model...:-)

Nice to talk with you again...

[Skylaw]

Hi, Jack - good to hear from you.

My RAZR cradle instructions from AWS say specifically that up to four RAZRs may be paired (though not simultaneously - the BT unit searches first for the last phone paired). However, I doubt thet the BT component of the cradle is unique to the RAZR; my bet is that any phone with approved (compatible) firmware would pair successfully - but of course, the cradle will only allow docking of the RAZR.

[nevadajack]

Originally Posted by Skylaw

Hi, Jack - good to hear from you.

My RAZR cradle instructions from AWS say specifically that up to four RAZRs may be paired (though not simultaneously - the BT unit searches first for the last phone paired). However, I doubt thet the BT component of the cradle is unique to the RAZR; my bet is that any phone with approved (compatible) firmware would pair successfully - but of course, the cradle will only allow docking of the RAZR.

I tried again to pair the V557 and the phone would not find the cradle so I had no chance to enter the passkey. I am really not interested in pairing the V557 but just trying to help out a poster. I am really pleased with the peformance of the RAZR now with the cradle...I still use the two phone concept but have an extra cradle...:-)

[benltc]

I just purchased the MB PUCK for my 2001 S430. I also purchase a RAZAR 3m phone from Verizon. will this phone work with the PUCK or do I need to purchase a MB phone?

Thanks,
Ben

[Skylaw]

You do not need an MB branded phone. As stated (somewhat at length, I'm afraid) in the first post, you need to be sure you have compatible firmware. Some newer Verizon firmware is not compatible. Check with AWS, as was advised. You may have a length of time under which you may return the RAZR if its firmware is not compatible and compatible firmware cannot be loaded.