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.
