How to improve Kannel SMS Gateway - sending SMS messages is slow

Question

I'm using kannel as an SMS Gateway to send SMS messages. I've downloaded kannel 1.4.3 and I use a Siemens TC35i as a GSM Modem. I can send messages by calling http://127.0.0.1:13013/cgi-bin/sendsms?username=username&password=password&to=recipient&text=message

However, if I atempt to send 100 messages to the same recipient, it is a bit slow (it takes about 10 minutes to send 100 messages to the same recipient), i.e. 1 sms / 6 seconds.

Is there any way to improve the rate?

Here is my smskannel.conf file

group = core
admin-port = 13000
smsbox-port = 13001
admin-password = bar
log-file = "/tmp/kannel.log"
log-level = 0
box-deny-ip = "*.*.*.*"
box-allow-ip = "127.0.0.1"
access-log = "/tmp/access.log"


group = smsc
smsc = at
modemtype = auto
device=/dev/ttyUSB0
my-number = 0040728467060
connect-allow-ip = 127.0.0.1
log-level = 0
speed = 115200


group = smsbox
bearerbox-host = 127.0.0.1
sendsms-port = 13013
global-sender = 0040728467060
log-file = "/tmp/smsbox.log"
log-level = 0
access-log = "/tmp/access.log"


group = sendsms-user
username = tester
password = foobar
concatenation = true
max-messages = 10000


group = sms-service
keyword = default
concatenation = true
catch-all = yes
max-messages = 10000
get-url = "http://localhost/sms?phone=%p&text=%a"

# There should be always a 'default' service. This service is used when no
# other 'sms-service' is applied.

group = sms-service
keyword = default
text = "No service specified"
max-messages = 1

include = "/etc/kannel/modems.conf"

Answer 1

GSM protocol takes 6 seconds to process one SMS sending (standard by protocol). You are using GSM modem, so you cannot gain more speed than this. If you need a faster connection, get an IP connection from the operator.

Answer 2

Considering your configuration, since you've not set any throughput limit, the only guess is that the mobile operator you're using is limiting message sending to about 1 sms per 6 second. There is nothing in your configuration that would limit you in such a way.