SMS Bandwidth requirements
High-performance SMS system designers often ask what is the minimum bandwidth requested regarding the SMS Gateway for IP SMS connections? This question is hard to answer because the bandwidth requirement depends on many circumstances. In this text, you can find information about what affects the requirement and an example calculation to give you an idea.
Why bandwidth is important in SMS sending systems
Low bandwidth allows for slow message sending, which can cause significant delays when sending millions of SMS (high-performing SMS systems). Therefore, it is important to know at what speed the SMS system sends and receives messages.
The bandwidth requirement depends on the following:
- SMS message size: A standard 160-character SMS occupies 140 bytes
(1 120 bits) when encoded with the 7-bit GSM-7 alphabet. Even concatenated
messages or messages containing Unicode characters only marginally increase
the per-segment size, so the payload remains well below 2 KB. Because the
per-message data volume is trivial, overall bandwidth demand is determined by
message volume and speed rather than by the payload itself.
- Message volume: The total bandwidth needed depends on how many messages are being sent per second (MPM/MPS). For example, sending 10 messages per second (MPM) would require roughly 27.68 Kbit/s.
- SMS Protocol Utilisation: The SMS protocol is a highly efficient
mechanism designed to minimise network-resource consumption. Its original
objective was to enable short text messages to be transmitted over mobile
networks-either alongside or independently of voice calls-by exploiting
low-bandwidth channels such as the signalling channel traditionally
reserved for call-setup procedures.
To satisfy contemporary throughput, security, and integration requirements, the protocol is now routinely conveyed over SMPP, UCP, HTTP/HTTPS, REST, or other IP-based SMS transports. Regardless of bearer, each transport introduces a modest protocol-specific overhead-on the order of a few tens of bytes per message-which slightly increases the aggregate data volume but remains negligible in relation to overall traffic volume. - The mobile service provider's SMSC capacity, response, processing,
and receiving capabilities.
- The message handling speed of the sms sending hardware infrastructure is also an influencing factor when sending large amounts of SMS (in the case of sending thousands or millions of SMS).
- Concurrent connections to the SMS provider's SMSC: In the case of high-capacity SMS sending, companies send messages from a self-hosted SMS gateway (Ozeki NG SMS Gateway) directly to the mobile service provider's SMS center via the Internet, which makes sending significantly faster. This is IP-based SMS sending (IP SMS), which is typically done via one of the SMS protocols: SMPP, UCP, HTTP(S), etc.
SMS bandwidth capacity example
Let's suppose we send 120-160 character long SMS messages over the SMPP protocol. An average SMS takes about 2 Kbytes. Meaning that on a 1 Mbps network connection you can transfer 64 messages per second. (1 Mbps/8 bit = 128 Kbyte/sec)
Conclusion
Bandwidth use in SMS messaging depends on the following few key factors:
- Bandwidth calculation: One 160-character SMS is ~140 bytes; multiply by messages-per-second to find Kbit/s requirement.
- Message volume dominance: Total throughput is driven by MPS rate, not individual payload size.
- Protocol overhead: SMPP, UCP, HTTP(S) add small headers; VPN can further inflate traffic slightly.
- Concurrent connections: Each parallel link to the SMSC multiplies the needed Mbps, so plan capacity accordingly.
- Hardware & SMSC limits: Gateway throughput and provider SMSC processing speed often cap real-world MPS before bandwidth does.
- IP SMS efficiency: Internet-based delivery via SMPP on a 1 Mbps line supports ~64 SMS/sec, proving SMS remains a low-bandwidth protocol.
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