I-HSPA throughput troubleshooting (FTP, TCP)
The setup of live or trial I-HSPA network should follow the guidelines of HSPA radio and I-HSPA transport network
planning guides. Official planning guides can be found in IMS:
https://sharenetims.inside.nokiasiemensnetworks.com/livelink/livelink?func=ll&objId=364981390&objAction=Browse
RTT and TCP throughput
RTT is an important factor and easy to measure in order to troubleshoot the TCP throughput. If you are using default
TCP window size in client PC (64KB) and server PC, RTT is the only factor to determine max. TCP throughput. So, when
you start TCP throughput troubleshooting, make sure what is the RTT between source (your PC) and destination PC, the
destination PC should be as close to GGSN as possible. You can use ping command from DOS prompt. Use average
number, but not higher or lower numbers.
Ping has to be executed when the UE is in RRC Cell_DCH state
TCP Throughput = Window size (Default 64Kbytes) / RTT
Reference RTT values
Customer Trial Test Results
RTT
Size
64
kbps/ 384
kbps/ HSUPA
16QAM
16QAM
2Mbps/16QA
M
NSN Target
32B ping
80ms
65ms
60ms
Customer “A” Austria (Sept. 2008)
32B ping
83ms
NA
62ms
Customer “B” China (Dec. 2008)
32B ping
NA
NA
48ms
Example with 32 byte ping and HSUPA/16QAM: (65536 * 8) Kbps / 0.048 = 10.9 Mbps
In case RTT is close to the above values, but TCP troughput is poor, the most likely problem source is the ftp server or
the client PC.
Also, the max. packet size in the network should be verified as described below.
In case RTT values differ more than 20 ms of these values, here is a checklist

UE signal strength
o
Signal readings





HSDPA CQI value
o

Strength in dBm = in negative number - closer to zero the better (-70 or stronger)
Noise in dBm = in negative number - closer to -100 the better (-85 or higher)
Signal to Noise Ratio - higher number the better: signal/noise strength (15 or higher)
Ec/No in dB - closer to zero the better (-7 or stronger)
CQI value should be over 22
Verify the default window size in client and server
o

Verify the hops on the path to the ftp server with traceroute, example: tracert –d x.x.x.x
o

is APN for Direct Tunnel mode or for two tunnel mode (user plane goes via SGSN). If
possible verify the hops by both APN’s, direct tunnelling APN and two tunnel APN.
The most common throughput related parameters in I-ADA and their recommended values
o
o
o
o
o
o
o
o
o

fragmentation problems if ping is not successful. The problematic NE can be found by
pinging the routers (hops) on the way towards the ftp server with 1500 bytes ping found by
traceroute.
Verify the APN in use
o

Optimum ftp server and ping target are directly connected to GGSN. Optimal hop count is
below five. The amount of router hops is directly linked to the RTT and thus to the available
throughput.
Verify the max. packet size with ping to the ftp server, example: ping x.x.x.x –l 1500
o

64KB
<p name="PDUSize656WithHSDSCH">2</p>
<p name="PDUSizeCodeThreshold">15</p>
<p name="MaxBitRateNRTMACDFlow">9600</p> or in Rel2
<p name="MaxBitRateNRTMACDFlow">13440</p>
<p name="HSPDSCHCodeSet">32768</p>
<p name="MaxTotalUplinkSymbolRate">1</p>
<p name="FlexUpgrUsage">1</p>
<p name="DynUsageHSDPAReturnChannel">1</p>
<p name="PSOpThroUsage">15</p>
Verify the HSDPA and HSUPA categories of the used UE
HSDSCH
category
Cat 1
Cat 2
Cat 3
Cat 4
Cat 5
Cat 6
Cat 7
Cat 8
Cat 9
Cat 10
Cat 11
Cat 12
Maximum number of
HS-DSCH
codes
received
5
5
5
5
5
5
10
10
15
15
5
5
Minimum
inter-TTI
interval
3
3
2
2
1
1
1
1
1
1
2
1
Modulation
Data rate
at L1 in Mbits
QPSK/QAM
QPSK/QAM
QPSK/QAM
QPSK/QAM
QPSK/QAM
QPSK/QAM
QPSK/QAM
QPSK/QAM
QPSK/QAM
QPSK/QAM
QPSK
QPSK
1.2
1.2
1.8
1.8
3.6
3.6
7.2
7.2
10.1
14.4
0.9
1.8
E-DCH
category
Maximum
number of
E-DCH
codes
transmitted
Minimum
spreading factor
Support for 10 and
2 ms TTI E-DCH
Data rate at L1 in Mbps
Cat 1
Cat 2
1
2
SF4
SF4
10 ms TTI only
10 ms and
2 ms TTI
0.71
1.45
1.4
E-DCH
category
Maximum
number of
E-DCH
codes
transmitted
Minimum
spreading factor
Support for 10 and
2 ms TTI E-DCH
Data rate at L1 in Mbps
Cat 3
Cat 4
2
2
SF4
SF2
Cat 5
Cat 6
2
4
SF2
SF2
10 ms TTI only
10 ms and
2 ms TTI
10 ms TTI only
10 ms and
2 ms TTI
1.45
2
2.89
2
2
5.76
If the above steps are acceptable, then:
1. Reset Client PC
o
verify RTT
2. Reset SGSN PAPU where I-ADA is connected – if two tunnel mode APN in use
o
verify RTT
3. Reset I-ADA
o
verify RTT
4. Reset Flexi BTS
o
verify RTT