Bulk SMS | SMS Gateway | MMSC | SMSC

What is bulk sms or bulk sms service?

Bulk sms is the process of sending many sms or text messages in short duration. A sms or text is a message encoded according to the gsm specifications in a fixed format. This enables and SMS to be displayed on any handset. There are following types of messaging is used.

A2P . Application to person, in this a software or application , sends the sms to a mobile device. Sending a sms from web portal is the example of A2P message.  May companies uses this message flow, e.g a bank sens the OTP , from its central system to authorize a transaction.

P2P, Person to Person , in this messaging , a message is sent from a mobile device to other mobile device. Sending a sms from your phone to a friend’s phone is the example of P2P messaging.

P2A, Person to Application, in this a sms ot text message is send from mobile device to a software or application. Sending sms for voting on short code (515151) is the example of P2A messaging.

What is sms:

SMS or short message is the service provide by mobile operators to send the text to/from a mobile device. SS7 protocol is used for sms. A sms text on wire is 160 bytes long. For sending a long message, the sms segments the long sms and  mobile phone reassembles the sms. This is the basic service which runs on all mobile phones. There are other applications for sending text, but requires internet connection.

Bulk SMS Service: 

There are vendors those provides platform for sending and receiving text. The service platform is reachable over internet.  Service providers exposes sms apis. APIs can be integrated by a sms user in a sms software application. This enables  user to send bulk text, without deploying a sms gateway software and connecting to complex telecom network.

Advantages of bulk SMS service:

  1. SMS service is the basic service on all mobile phones.  In many countries most of the population is living in rural area and don’t having internet.  This enable the advertisement on phones without a internet connection.
  2. People read sms more often than reading emails. SMS gives alert to user and then user checks sms in most of the cases.
  3. SMS can be targeted based on current location, while any other service do not have real time subscriber location.
  4. Alphanumeric sender id provides better brand awareness.  Sending a sms from mobile device displays the sender’s mobile number. With sms API, a service user gets an option to set sender id based on the brand he wants to promote.
  5. Huge coverage. These days almost every one carrying  a mobile. To advertise a business mobile phones are biggest platform.
  6. SMS gateway, hides complex structure of telecom network. The enables a service user to easily develop a bulk sms application.
  7. Almost every business model have use case for bul sms service. Banks, stores, schools etc. have need for bulk sms.

Bulk SMS software or SMS Gateway:

If a company or person wants to develop a software for bulk sms. There are different options.

Connecting Directly To Mobile Operators over SS7/Sigtran:

For direct mobile operator conenction, the SS7 or SIGTRANprotocol is used. The sms gateway or bulk sms application connects to all operators over ss7 or digtran link. For service user the application provides SMPP, of HTTP based bulk sms APIs. All protocol level difficulties are hidden by the sms gateway. Direct connection to ss7 or sigtran , enables the bulk sms service providers,  fast and accurate delivery of sms. Its a cheaper option , as this offloads the mobile operator’s SMSC.

Connecting To the SMSCs of mobile operators over SMPP.

With this option , bulk sms service application connects network operator SMSCs  over SMPP Protocol.  For sending and receiving text.

Using Agregators over SMPP or HTTP based APIs:

With this option sms gateway service provider connects to other agree-gators for sending sms to mobile phones.

Short code and long code:

Short code is a 5 or 6 digits number (e.g 344512) , which is easy to remember. A mobile device can send a sms to a short code , the short code routing is set in telecom network in such a way that a sms is sent to the sms gateway which is serving node for code. A content provider can rent out short code from sms service provider.  Content/service provider can get queries from market on short code and a web based panel connects to, shows the full inbox. SMS received have sending party, mobile number which is useful for business. No need to buy a database for target customers and get pool of interested customers for business.

A long code is a 10 digits number.

Shared long/short code:

A number can be shared between many content providers. Providers can differentiated based on KEYWORD. This option is low cost than have full dedicated short or long code.

MT-SMS Call flow: 

Mt sms call flow or A2P call flow, is for messages sending by a user or content provide from a software to a mobile device. Application submitted sms (text, mobile number, source number) over SMPP or HTTP , to the bulk sms gateway. Bulk sms gateway does a hlr lookup over  SS7/Sigtran to get IMSI and MSC number of the subscriber. In hlr lookup over ss7 , SRI-SM GSM MAP level message is sent over ss7 to the HLR of the subscriber.

If an error response is present in response of the hlr lookup, error is send to the sms application software from gateway in delivery report. If error is for temporary problem (e.g subscriber not reachable) , application may retries after some time. If error is permanent (e.g unknown subscriber), application may remover the phone number from list.

If IMSI and MSC number present in hlr lookup response. Gateway send MT Forward SM  to the MSC with IMSI, and delivery report is send back to the application upon receiving MT Forward SM response.

MO-SMS  Call flow for short or long code:

  1. P2A is type of MO-SMS.
  2. Mobile subscriber sends a sms to a long code or short code, roaming msc sends mo sms to SMSC of mobile operator.
  3. SMSC address is derived from smsc number stored in phone.
  4. The smsc sends text to  gateway serving the short/long code over SS7.
  5. Gateway sends the application which is serving the short/long code.

E-Mail to SMS service:

This services provides capability of sending email text to the mobile device in sms. A mobile subscriber may subscribe for this service from a sms gateway service provider. By using this facility a person can see email text even if there is no internet connectivity.

Excel To SMS service:

In this a service provider can get sms input in excel with a fix format. The excel have thousands of sms for a sms campaign marketing. To send bulk sms , a service user uploads the excel to the service provider portal for sending sms to all numbers mentioned in excel. After sending sms the, service provider provide a delivery reports.

SDK For bulk sms apis:

SDK is software software development kit. It is a like library of already developed functions to support interaction between user and gateway. Bulk sms providers , provides API to the service user. The sms service may required complex encodig/decoding of messages.  To hide the complexity sms service companies provides the SDK . By including SDK in an application, the user can easily develop sms applications. The sdk might be in java, php  etc.  For example, its difficult to parse the response for a message from hex stream. Sdk may provides a call back for a response , when user can get response code, text etc.

Bulk SMS Api selection:

Bulk sms provider provides the APIs for sending content in sms. APIs are accessible via internet from the sms gateway of service provider. One can choose any provide across the glob. The following factors helps in choosing bulk sms provide.

SMS Coverage:

Very important factor, if a provider don’t have coverage in area where sms needs to be send then no use of APIs. SMS Coverage might be for a country or for a city.

HLR Lookup:

Bulk sms senders uses HLR lookup service, to clean invalid numbers, get mobile number portability information and real time location information for a mobile user before sending a sms.  This saves cost and can target sms on basis of current location and serving mobile operator. If a mobile user of country A is roaming in country B , and sms is targeted to country A  offers, then no use of sending sms to the user. From mobile number portability, a sms can be targeted to the subscribers of a particular mobile operator. This is possible from information obtained by hlr lookup.

SMS Delivery Reports:

The accuracy and latency is important for sending sms. Before buying , get an test account and check the delivery repots and latency.

SMS Cost :

Choose the package which is most suitable for you.  Choose sms provider, giving more validity time for a package.


Bulk SMS Re seller: 

A bulk sms provider buys sms in large quantity from mobile operators. Now it can act as sms gateway for other bulk sms providers. For starting a business, a vendor can get connected to another bulk sms provider and can provided sms service to the end users. This provider is called re seller. This chain may grow further. Re seller always depends on original seller. If seller lost the coverage in an area, the re seller will also lost the coverage. Seller maintains multiple accounts for many re sellers. Each have own dashboard to check the statics of account. A re seller may get connections from multiple sellers, based on coverage and cost a seller gateway decided for sending sms.

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