SMS can be used by the network operators to provide services like balance enquiry in case of prepaid cards using SMS.SMS is particularly suited for these kinds of short messages because SMS is much cheaper than calling some one and giving the same message. Calling some one to give the same message would invariably take more time and hence more cost.Many of these limitations are the driving force behind the developments and initiatives being taken in the field of short messaging.Using SIM-Toolkit, now a part of GSM specifications, SMS can be used to have on the air activation of features.SMS can be used as a bearer service for WAP and until 2.5G services like GPRS become common, SMS would be increasingly used as a bearer for WAP. By sending codes embedded in short messages from the server network operators can remotely provision the user's wireless terminal Some of the limitations of SMS are:
- Messages are plain vanilla in nature. You can only send simple text messages. There is no scope for any graphics or audio.
- The messages are limited by size. An SMS message can’t exceed 160 characters.The need to break the messages into several smaller segments could make SMS comparatively costlier in comparison to GPRS.
- The limitation of easy input mechanisms in mobile devices makes it very uncomfortable sending messages larger than even 5-6 words.
- Many proprietary protocols are used by SMS operators and application developers need to implement different interfaces for making their applications work with different SMS centers. X.25 is used as a popular protocol for connecting with SMS centers.
- SMS protocol data units as defined in GSM 03.40 are also not very efficient. The various header fields in the PDU are fixed which puts a constraint on the scenarios that can be indicated. 3G specifications are being looked up to look and address these constraints.
- Data rate and latency. GPRS and USSD provide better data rates and lower latency compared to SMS. This is because SMS uses the slow signaling channel, which is used for many other things also in GSM.
- The store and forward nature of SMS, though useful in many applications makes SMS not very suitable for WAP.
- You have greater network latency (delay in message delivery) when sending SMS alerts. This happens because the e-mail hub, serving as a proxy, processes e-mail messages for all mobile devices on the network. At times, the e-mail hub queues messages for later distribution over the SMS network.
SMS is an old service with a long history, and it shows. In the end, these limitations have not impeded its success. Its network reach – a property that has taken decades of carrier federation to achieve – are an incredibly valuable asset and a difficult one for a competitor to achieve. The SMS alternatives need to address the gaps – which are many – but also overcome the network effects challenge of competing with SMS.SMS uses a channel designed to send small packets of information between cell phones and cell towers. The 160-character SMS limit is simply a consequence of the originally modest use to which this channel was put. The channel was chosen as the basis for SMS because the system could be implemented easily, with minimal need for new infrastructure.The limit on the number of SMS that could be send on one day for one sim was set by the authority to keep a check on the menace of pesky SMS messages. Though there is no restriction on commercial messages sent through telemarketing companies registered with the TRAI, it has kept certain service providers and organisations constrained with the 100 SMS limit.