Nokia :: E52 Choppy VoIP Due To WLAN Interruptions And Defect Of Power-Management System

I love my Nokia E52, but one of the main reasons I bought it (the combination of WiFi Wireless Lan support and fully integrated Voice over IP client) is not usable due to very laggy, unsteady WLAN connection (while having perfect signal strength - E52 shows 100% (same room)).Because of this I get choppy VoIP (cracks and interruptions up to several words in my VoIP conversations).

My E52:
Software version: 031.012
Modell: E52-1
Type: RM-469

This is not a problem of the VoIP Client, audio-codec, or SIP provider/internet connection.It is the Wireless Lan connection between my E52 and my Router. I tried 3 different access points, with and without wireless encryption, 802.11b (1M...11M data-rate) and 802.11g - problem always the same.
I can track it down by pinging my E52 (idle without any programs running) from my Linux box:

192.168.0.100 is the IP of my E52 assigned by DHCP.
1.) 64byte pings, once per second:

PING 192.168.0.100 (192.168.0.100) 56(84) bytes of data.
64 bytes from 192.168.0.100: icmp_seq=1 ttl=69 time=6.36 ms
64 bytes from 192.168.0.100: icmp_seq=2 ttl=69 time=57.9 ms
64 bytes from 192.168.0.100: icmp_seq=3 ttl=69 time=80.9 ms
64 bytes from 192.168.0.100: icmp_seq=4 ttl=69 time=203 ms
64 bytes from 192.168.0.100: icmp_seq=5 ttl=69 time=128 ms
64 bytes from 192.168.0.100: icmp_seq=6 ttl=69 time=50.0 ms
64 bytes from 192.168.0.100: icmp_seq=8 ttl=69 time=324 ms
64 bytes from 192.168.0.100: icmp_seq=9 ttl=69 time=79.7 ms
64 bytes from 192.168.0.100: icmp_seq=10 ttl=69 time=37.5 ms
64 bytes from 192.168.0.100: icmp_seq=11 ttl=69 time=60.0 ms

64byte pings using a good wireless 802.11g connection should be around 1ms and constant!!It's not because of bandwith limit of E52 wlan/cpu, because the higher ping times stay the same, even if I increase ping-packet-size 150x:
2.)10000byte pings (150x times bigger packages!), once per second [still ping times look quite similar]:

PING 192.168.0.100 (192.168.0.100) 10000(10028) bytes of data.
10008 bytes from 192.168.0.100: icmp_seq=1 ttl=69 time=175 ms
10008 bytes from 192.168.0.100: icmp_seq=2 ttl=69 time=89.8 ms
10008 bytes from 192.168.0.100: icmp_seq=3 ttl=69 time=115 ms
10008 bytes from 192.168.0.100: icmp_seq=4 ttl=69 time=234 ms
10008 bytes from 192.168.0.100: icmp_seq=5 ttl=69 time=153 ms
10008 bytes from 192.168.0.100: icmp_seq=6 ttl=69 time=83.7 ms

3.) Small 64byte pings, but now ten pings per second:
Now it gets even more strange:
# ping 192.168.0.100 -i 0.1
PING 192.168.0.100 (192.168.0.100) 56(84) bytes of data.
64 bytes from 192.168.0.100: icmp_seq=1 ttl=69 time=200 ms
64 bytes from 192.168.0.100: icmp_seq=2 ttl=69 time=95.0 ms
64 bytes from 192.168.0.100: icmp_seq=3 ttl=69 time=2.25 ms
64 bytes from 192.168.0.100: icmp_seq=4 ttl=69 time=5.93 ms
64 bytes from 192.168.0.100: icmp_seq=5 ttl=69 time=4.34 ms
64 bytes from 192.168.0.100: icmp_seq=6 ttl=69 time=8.45 ms
64 bytes from 192.168.0.100: icmp_seq=7 ttl=69 time=5.91 ms
64 bytes from 192.168.0.100: icmp_seq=8 ttl=69 time=2.69 ms
64 bytes from 192.168.0.100: icmp_seq=9 ttl=69 time=2.31 ms
64 bytes from 192.168.0.100: icmp_seq=10 ttl=69 time=5.90 ms
64 bytes from 192.168.0.100: icmp_seq=72 ttl=69 time=8.42 ms
64 bytes from 192.168.0.100: icmp_seq=73 ttl=69 time=7.25 ms
64 bytes from 192.168.0.100: icmp_seq=74 ttl=69 time=7.28 ms
64 bytes from 192.168.0.100: icmp_seq=75 ttl=69 time=7.25 ms
64 bytes from 192.168.0.100: icmp_seq=76 ttl=69 time=7.24 ms
64 bytes from 192.168.0.100: icmp_seq=77 ttl=69 time=7.92 ms
64 bytes from 192.168.0.100: icmp_seq=78 ttl=69 time=7.24 ms
64 bytes from 192.168.0.100: icmp_seq=79 ttl=69 time=8.69 ms
64 bytes from 192.168.0.100: icmp_seq=80 ttl=69 time=10.9 ms
64 bytes from 192.168.0.100: icmp_seq=81 ttl=69 time=10.6 ms
64 bytes from 192.168.0.100: icmp_seq=150 ttl=69 time=213 ms
64 bytes from 192.168.0.100: icmp_seq=151 ttl=69 time=105 ms
64 bytes from 192.168.0.100: icmp_seq=152 ttl=69 time=3.09 ms
64 bytes from 192.168.0.100: icmp_seq=153 ttl=69 time=2.23 ms
64 bytes from 192.168.0.100: icmp_seq=154 ttl=69 time=2.14 ms
64 bytes from 192.168.0.100: icmp_seq=155 ttl=69 time=3.78 ms
64 bytes from 192.168.0.100: icmp_seq=156 ttl=69 time=3.02 ms
64 bytes from 192.168.0.100: icmp_seq=157 ttl=69 time=5.48 ms
64 bytes from 192.168.0.100: icmp_seq=158 ttl=69 time=2.15 ms
64 bytes from 192.168.0.100: icmp_seq=159 ttl=69 time=2.13 ms
^C
--- 192.168.0.100 ping statistics ---
159 packets transmitted, 30 received, 81% packet loss, time 16866ms
rtt min/avg/max/mdev = 2.130/25.327/213.218/54.102 ms, pipe 2

Note: My Linux Ping Command doesn't say something like "Request timed out." for lost packets (like Windows Ping does). So if there is a jump from icmp_seq=81 to icmp_seq=150 it is because everything in between got lost.

You see, in 3.) it has the slow pings once in a while and in between almost normally fast pings, but suddenly a long lag of 6-7sec (this is deadly for voip) and then the circle repeats.Is my E52 wlan chip defect, or is this some kind of Power-Management system? How can I turn it off?I don't need a fast wlan connection on my E52. 1MBit/s is more than enough. But it has to be steady, without lags.