5. Bad Connection

Once I got the phone programmed, it successfully registered with my VoIP provider and I made my first call. The call completed just fine, but was basically unintelligible on both ends. I double checked settings and tried again (and again...) but could not make an intelligible call. When I told ZyXEL of my problem, they provided me with a different SIP account so that I could eliminate that variable, but trying the new account didn't resolve the problem.

To make a long story short and condense days of troubleshooting into a bottom line, the problem was caused by a bad phone. The second phone ZyXEL sent was able to successfully associate and work with the Westell 327W wireless router (firmware version: 03.00.63a) that provides my DSL connection and a Linksys WRT54G (original hardware version and firmware version: v2.04.4, Aug. 3, 2004), which didn't work with the first phone. It also worked fine with a ZyXEL G-2000 Plus, which was the only thing I could get to work with the first phone.

I started out with a few test calls, first to an answering machine on my normal VoIP line. I could hear my outgoing message fine, but when I checked the test message I left, it sounded somewhat muffled. I then called a colleague, who also complained of static and "lousy" voice quality, although I could hear him just fine.

In order to get a more objective measure of voice quality, I tried some calls to TestYourVoip.com's Golden Phone, which generally confirmed the results of my subjective tests. The best I got was a MOS score of 4.4 (best possible) when the phone was connected to a ZyXEL G-2000 Plus 802.11g router.

But MOS scores of 4.3 and 4.2 were achieved when I connected via the Linksys WRT54G where packet loss and discards accounted for about 25% of the degradation. My runs with the WEP-enabled Westell 327W were the worst (Figure 10), coming in at 3.7 (with about 50% of the degradation due to packet loss). Thinking the poor result might be due to WEP, I disabled it and tried again, but the results were essentially the same. Note that the largest source of degradation - Codec - is expected and accounts for the difference between the 4.4 "best possible" and 5.0 "perfect" scores.

Figure 10: Golden Phone results - Westell 327W
(click image to enlarge)

I was able to test the phone's range by calling my local telco and slowly working my way through its robo-operator menus and walking around my home. I also ran a continuous ping from a desktop to the phone as a double check for connection drops. I found coverage throughout my two level home to be comparable to what I get with my 900 MHz cordless phones - some spots that require standing in particular positions, but generally ok.

At least all the testing and debugging gave me good information about battery life. I found that a couple of hours of making and receiving short test calls drained the battery to the point where I had to put it on the charger. The good news is that with a few hours of recharge time, the phone was ready to go again.