SYSTEM AND METHOD FOR IMPLEMENTING USSD SERVICE IN A COMA NETWORK BACKGROUND [0001] The invention relates generally to a technique for data transmission over a telecommunication network, and in particularly to a technique for implementing unstructured supplementary service data (USSD) service in ·a code division multiple access (COMA) network. [0002] There are two significant telecommunication technologies - global system for mobile communication (GSM) and code division multiple access (COMA). Initially, short message service (SMS) was prevalent for sending and receiving information. SMS is an event based process but there is no session between mobile device and the service provider computer and the devices are not connected with each other. A session is basically an iterative process between the server and the device. A new standard has evolved which is called USSD (unstructured supplementary services data) for sending and receiving information (e.g., service messages). between service provider's computer and mobile device of service suhscriber over a session. The USSD service is an interactive data service ·based ,on a Global System for Mobile Communication ·(GSM) network. USSD is a session-based protocol used by GSM cellular telephones to communicate with the service provider's computers. USSD may be initiated by the Mobile Station (MS) user, or by the network (i.e., an application server). USSD messages travel over GSM signaling channels and are used to query information and trigger services. USSD may be used for W AP browsing, prepaid callback service (e.g., requesting another party to call you), mobile-money services (e.g., pre- · paid balance inquiry, inter-mobile balance transfer), location-based content services, menubased information services (e.g., voting or rating customer service: 1 =Good, 2=0K, 3=Bad after a call to a CSR), and as part of configuring the phone on the network. [0003] USSD messages are up to 182 alphanumeric characters in length. In the GSM network, both the USSD service and a Short Message Service (SMS) transmit data through a signaling channel of the network. The USSD service uses a Stand-alone Dedicated Control Channel (SDCCH) in a session state, and uses a Fast Associated Control Channel (F ACCH) in a non-session state. The difference between the USSD service and the SMS is that the SMS adopts a store and forward mode while the USSD service adopts a session-oriented 2 T_·p_ ..b n t= L 1-l ,... 2 - - - -- • ~ .!.. .o 5 - 1 Q. - ..... 0 1 5 16; 32. mode. Unlike Short Message Service (SMS) messages, USSD messages create a real-time connection during a USSD session between mobile handset and application handling the service. The connection remains open, allowing a two-way exchange of a sequence of data. This makes USSD more responsive than services that use SMS. USSD service has characteristics such as a fast response speed, strong interaction capacity, high reliability, etc., and is therefore suitable for providing services of payment type and transaction type for users, for example, account query, recharge, transfer accounts, report the loss, etc. [0004] However, there is no existing solution for employing the USSD service over a CDMA network. In the CDMA network, due to the limitation of the existing CDMA network protocol, the USSD service cannot be implemented, thereby it is impossible to provide users with the USSD services such as account query, recharge, etc. In the existing CDMA network, some mobile intelligent network services, such as Pre-Paid Charging (PPC) service, implements some USSD functions through a short number access management mode of USSD like; however, real-time message interaction cannot be performed between the user and the network, and thus, there is a limitation, and portability and scalability are poor. [0005] Current technique for routing ·a USSD message through a CDMA network includes providing a network component in the CDMA mobile switching center (MSC) whiCh shall handle the . forward path . messages originating from MS and MSC, and also reverse path delivery and conversion to the extent of Interoperability Specification (lOS) messages conversion and delivery to base station controller (BSC). However, in the current scenario, most of the CDMA network and MS does not comply with the above process. [0006] It is therefore desirable to provide a technique so as to send/receive session based messages on to the CDMA network. In other words, it is desirable to implement USSD service in a CDMA network. It is also desirable to provide such technique that is platform independent and without changing the legacy CDMA network system. BRIEF DESCRIPTION [0007] In accordance with some embodiments, the present invention provides a method, system and device for implementing a session based, real-time USSD service in a CDMA network such that session based communication can happen between the CDMA network in the server and device topology. The invention provides for complete end to end 3 IP.Q DELHI .0 s.- 1.0-2-01 S l .. G.: 3.2 : USSD solutions to CDMA cross network supporting the legacy CDMA network MSC and component without any change or update in the CDMA MSC. [0008] In accordance with some embodiments, the present invention further provides a USSD core to receive the message, to add a session to it, to add an identifier to it such that the MSC recognize it as USSD session, and to maintain the session. In some embodiments, the unified USSD core that handles the USSD data burst mode (DBM) originating from the mobile station (MS) and also serves the request originating from the non USSD compliant MS. [0009] In accordance with some embodiments, the present invention further facilitates the USSD service functionality in CDMA IX and 2X type of network. In some embodiments, the solution has the auto detection facility of to detect the incoming DBM and serve accordingly. Hence, the system is unique for porting and initiating CDMA based USSD sessions for IX and 2X compliant network. The present invention works seamlessly on IX and 2X network and does not require any change or upgrade either onto the network component or onto the device side. [00 I 0] In accordance with some embodiments, the present invention further provides a computer implemented method for implementing USSD service in a CDMA network. The method provides for receiving a message transacted via the CDMA network, determining if a USSD session is invoked by the message, and managing the USSD session via a USSD core upon a positive determination. The.USSD core manages the USSD session by initiating the USSD session with a CDMA mobile device, maintaining the USSD session by keeping the CDMA mobile device latched to the CDMA network during the USSD session, and releasing the CDMA mobile device at the end of the USSD session. Processor-based systems and computer programs that afford such functionality may be provided by the present technique. DRAWINGS [OOII] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 4 IPD DELHI 05~L8-20L5 !5;32 [0012] FIG. 1 is a schematic of.an exemplary telecommunication network wherein various embodiments of the present invention may be practiced; [0013] FIG. 2 is a flow chart of an exemplary process for implementing USSD service over a CDMA network in accordance with aspects of the presen~ invention; [0014] FIG. 3 is a flow chart of a detailed exemplary process for implementing USSD service over a CDMA network in accordance with aspects of the present invention; and [0015] FIG. 4 is a block diagram of an exemplary computer system for implementing embodiments of the present invention. DETAILED DESCRIPTION [0016] The present techniques are generally directed to implementing USSD service over a CDMA network. Before describing in detail various embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to method and system for implementing USSD service over a CDMA network. Accordingly, the apparatus components and. method steps have been represented where appropriate by conventional . symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. [0017] There is described herein preferred and exemplary embodiments for a system and method for implementing USSD service over a CDMA network. In one embodiment, the USSD messages are received, transmitted and routed over the CDMA network according to technique and protocol described in the present invention. [0018] Referring now to FIG. 1, aschematic of a telecommunication network 10 is illustrated. The network 10 is configured to implement the preferred and alternative embodiments for providing USSD service over a CDMA network in accordance with aspects of the present technique. The network 10 is a Code Division Multiple Access (CDMA) telecommunications wireless netweFk-and-includes one or more CDMA mobile stations (MS) 12 communicating wirelessly with CDMA radio access network (CDMA-RAN). The CDMA 5 XPO DELHI 05-10-2015 16;32 · mobile station (MS) 12 is typically a CDMA based user equipment or a CDMA based mobile device. Examples of the user equipment or the mobile device may include, but is not limited to, a cell phone, a smart phone, a tablet, a phablet, and a laptop. A CDMA base transceiver station (BTS) 14 and a CDMA base station controller (BSC) 16 form the CDMA-RAN. However, the depicted radio access networks are merely exemplary, and thus it will be understood that the teachings of the . disclosure contemplate other CDMA network architectures. [0019] The CDMA-RAN may be in communication with a CDMA core network which in turn may be in communication with external networks. The CDMA core network may be a circuit~switched core as well as a packet switched core for switching and routing calls and data to the external networks. The CDMA core network may include a CDMA mobile switching center (MSC) 18, a CDMA Home Location Register (HLR) 20, and a CDMA visitor location register (VLR) 22, a CDMA gateway MSC (GMSC) 24, a CDMA packet control function (PCF) 26, a CDMA packet data service node (PDSN) 28, and so forth in a typical CDMA network architecture. For example, in the illustrated embodiment, each of the CDMA base station controll~er (BSC) 16 is in communication with the CDMA mobile switching center (MSC) 18 for circuit-switched services and with the CDMA Packet Control Function (PCF) 26 for packet-switched services. The external networks may similarly · include circuit switched networks such as public switched telephone network (PSTN) 30 and packet switched networks such as the Internet 32. [0020] The telecommunication network 10 further includes a unified Unstructured Supplementary Service Data (USSD) core 34 · in accordance with aspects of the present technique. The unified USSD core 34 is configured to implement· USSD service over the CDMA network according to technique and protocol described in the present invention. In certain embodiments, the USSD core 34 resides within the core of the CDMA network but mutually exclusive to the core of CDMA network on to different set of machine and enables the entire subscriber base to send and receive the USSD messages on the CDMA network. However, it should be noted that, in certain embodiments, such USSD core 34 may reside in any of the one or more subsystem of the telecommunication network 10. Alternatively, it should be noted that, in certain embodiments, the USSD core 34 may exist separately on the telecommunication network 10 within a specialized subsystem. 6 IRQ DELHI Q.s·~!0-2015 16;32 . i .. [002I] The USSD core 34 makes the other network component passive and makes the network available for the USSD or session based message transaction. For example, in a session based messages, server may send a message "Hello do you want to know latest news, or breaking news or weather news; press I for breaking news, press 2 for latest news, press 3 for weather news." The user is prompted to enter dual-tone multi-frequency (DTMF) keys onto the .handset. Once the user enters I, 2, or 3 keys numbers, relevant messages may further prompt user for more options. The user may enter another option onto the DTMF key and further messages or options are presented to the user, thereby establishing the session. [0022] The USSD core 34 is a platform that synergizes or integrates with the legacy MSC of the operator and makes the system USSD compliant on 20 and 30 CDMA network. Without any change onto the MSCIHLRIVLR, one can implement the USSD across IX and 2X type of network environment. As will be appreciate by those skilled in the art, CDMA IX is a 20/2.50 network and typically used for voice and text related services while CDMA 2X is a 30 network used high speed data services over and above voice and text related services. As per 30PP2 and ITU standard for .CDMA 2X network, an option for USSD session is provided in the CDMA 2X network but network operators are unable identify the USSD session whenever. invoked and are therefore unable to provide the USSD service. The USSD core 34 solves this issue by identifying the USSD session and managing the USSD session, thereby enabling the network operators to provide the USSD service. Further, for CDMA IX network which do not have any option for USSD session at all, the USSD core enables implementation of USSD service by intelligently employing property of device to display flash texts or short message service. Thus, the USSD core 34 enables USSD session for both CDMA IX and CDMA 2X network and provides same user experience. [0023] In an exchange of messages, a switch (e.g., MSC) has to identify that what type of message it is receiving based on presence or absence of certain identifiers. Based on the identification, the switch typically does certain type of manipulation and transfer the message accordingly. So in the USSD kind of message, the identifiers are 77 & 78. If the switch determines code 77 or 78 in the header of the message being transacted, the switch should be capable of reading this code 77 & 78 and should treat this as USSD message and has make the session available till the session is aborted by the subscriber. . [0024] MSC I8 is basically a routing hub- a switch which does the routing ofthe call onto the different routing topologies which have been preconfigured which identifies the 7. originator and the called party, routes the call and connect it. These steps happens over a stack which is called signaling stack. The USSD core 34 communicates to the signaling stack for implementing USSD service in a CDMA netWork. Thus, there is no need to alter, change, or upgrade any of the legacy hardware in a typical CDMA network. The USSD core communicates to software which has global standard which is called signaling system 7 (SS7) topology. [0025] As will be appreciated by those skilled in the art, the USSD core 34 may be implemented in programmable hardware devices such as programmable gate arrays, programmable array logic, programmable logic devices, and so forth. Alternatively, the USSD core 34 may implemented in software for execution by various types of processors. An identified engine of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions which may, for instance, be organized as an object, procedure, function, module, or other construct. Nevertheless, the executables of an identified engine need not be physically located together, but may comprise disparate instructions stored. in different locations which, when joined logically together, comprise the engine and achi.eve the stated purpose of the engine. Indeed, an engine of executable code could be a single instruction, or many instructions, and may even be distributed over several different .code segments, among different applications, and across several memory devices. [0026] USSD core 34 manages 4 necessitates so as to transport the USSD messages onto the CDMA network. First, it manag~s the session - it is a session based activity where the request goes and it wait for the response. In other words, it triggers the session and keeps the session live by waiting for response. Second, it enables the Data Burst Mode (DBM) message type which needs to be identified at the application level. DBM is a topology which is present on the switch side of operator to narrate flow of messages. If message is coming to the USSD core, the USSD core needs to identify whether it is a SMS or USSD messages. Then the USSD core will translate the information on to the operator MSC or SS7. It is a SMS if DBM message type is "3" and a USSD ~essage if DBM message type is "9". Third, USSD core determines service option to identify whether it is a SMS or OTAF or USSD transaction. These identities are 77 & 78 in the message header for USSD message. So the USSD core has to identify the service option type as 77 & 78. Lastly, the USSD core initiates USSD session with device and keep the device latched with the system. Latching is important for keeping session live unless user intervenes. 8 TPD DELHI 05·-10~2015 1s.:32 [0027] The USSD core 34 is communicatively coupled· with the MSC 18. Thus, whenever the user dials a specific number to invoke the session, there should be an identifier push onto the MSC 18 which can routes the call onto the USSD core 34 so as to manage the USSD session. The MSC 18 in CDMA network 10 is not capable of managing the USSD session by itself. In one embodiment, the identifiers may be *-------#. The moment these special characters are received by the MSC 18, they identify it as USSD session and are handed over to USSD core 34. It should be noted that any other combination of general or special character may be employed as an identifier for USSD session. The USSD core may further be communicatively coupled to output of the legacy network system that is a global standard. As discussed above, in certain embodiment it is a SS7/Sigtran based communication which happens with the switch and the node ofUSSD core. [0028] There are two ways of initiating a USSD session - a user initiated USSD session and a network initiated USSD session. In a user initiated USSD session, the USSD core 34 makes the channel available with the subscriber base. The USSD core take and read the information like what the subscriber has requested and push a USSD portal to him. USSD portal is a bunch of text which guides user browsing like "Welcome to the USSD server of WPITS, press 1. for Astrology, 2 for news, 3 for breaking news etc." If the subscriber presses 1, it again back to USSD core, which in turn fetch the database and find out the news which is relevant . news and send this USSD message to the subscriber, subscriber reads the message and the session is killed by the subscriber only. If the subscriber does not kill the session, the session is killed out in every 3 - 4 seconds. [0029] In a network initiated USSD session, the USSD core 34 send a message to the subscribe.r by setting the DBM message type as "9", by setting the service option type as 77 & 78, and by blasting this message. The user receives those messages onto the handset and since the appropriate action has been taken care by the USSD core that they have sent the DBM type as 9, so the switch which is operator switch it identifies that it is an USSD message. The USSD core then makes the session available for the other transactions which may be initiated from the device side. Thus the USSD core intelligently determines and makes the connection available to the device tilL it gets the response from the device or the session gets expired. Thus, the software adds within the header and the footer the DBM value, the service option value in the string and gives it to the handset of the subscriber. 9 IP'O DELHI {:)r-1(:)-?f.'\1 C.: -J -- ---.....- 16".32 [0030] In short, the USSD core provides for intelligence in the legacy CDMA network system to receive the message, add a session to it, add an identifier to it such that the MSC recognize it as USSD session and maintains the session. [0031] As will be appreciated by one skilled in the art, a variety of techniques may be employed to implement USSD service in a CDMA network. For example, the exemplary network 10 and the associated USSD core 34 may implement USSD service in the CDMA network 10 by the-techniques discuSsed herein. In particular, as will be appreciated by those of ordinary skill in the art, control logic and/ot automated routines for performing the techniques and steps described herein may be implemented by the· network 10 and the associated USSD core 34, either by hardware, software, or combinations of hardware and software. For example, suitable code may be accessed and executed by the one or more processors on the network 10 and the associated USSD core 34 to perform some or all of the techniques described herein. Similarly application specific integrated circuits (ASICs) configured to perform some or all of the techniques described herein may be included in the one or more processors on the network 10 and the associated USSD core 34. [0032] For example, referring now to FIG. 2, exemplary control logic 36 for implementing USSD session via a CDMA network, such as netwo·rk 10, is depicted via a flowchart in accordance with aspect~ of the present technique. As illustrated in the flowchart, the control logic 36 includes the steps of receiving a message transacted via the CDMA network at step 38, determining if a USSD session is invoked by the message at step .40, and managing the USSD session via a USSD core upon a positive determination at step 42. Managing the USSD session via the USSD core at step 42 further includes the steps of initiating the USSD session with a CDMA mobile device at step 44, maintaining the USSD session by keeping the CDMA mobile device latched to the CDMA network during the USSD session at step 46,. and releasing the CDMA mobile device at the end of the USSD session at step 48. [0033] In some embodiments, determining at step 40 further comprises determining if the message comprises a pre-defined USSD identifier. It should be noted that the USSD session may be initiated by a user of the CDMA mobile device or by the CDMA network. In some embodiments, initiating the US~D session at step 44 further comprises enabling a data burst mode (DBM) message type at the application level in a network initiated USSD session, wherein the DBM message type corresponds to a USSD message type. Further, in some 10 IPO DELHI 05-10-2015- 16 32 . i I '. embodiments, initiating the USSD session at step 44 further comprises enabling a service option type for the message in a network initiated USSD session, wherein the service option type corresponds to a USSD message type. Moreover, in some embodiments, releasing the CDMA mobile device at step 48 is upon an indication by a user of the CDMA mobile device, upon a pre-defined time limit, or upon an expiry of the USSD session. [0034] Referring now to FIG. 3, exemplary control logic 50 for implementing USSD session via a CDMA network, such as network 10, is depicted in greater detail via a flowchart in accordance with aspects of the present technique. As illustrated in the flowchart, the control logic 50 includes the steps of receiving a message transacted via the CDMA network at step 52 and determining if the message comprises a pre-defined USSD identifier at step 54. If no identifier is present, the control logic 50 includes the step of routing the message normally· as per the standard procedure of the network at step 56. However, if the identifier is present, the control logic 50 includes the steps of enabling a data burst mode (DBM) message type corresponding to a USSD message type at the application level at step 58, enabling a · service option type for the message corresponding to the USSD message t)rpe at step 60, and ·keeping a CDMA mobile device latched to the CDMA network during the USSD session at step 62. In some embodiments, the DBM message type is enabled as "9" at the application level. Similarly, in some embodiments, the serviCe option types is enabled as·''77" and "78;' .. The control logic 50 further includes the step of determining if the USSD session has ended at step 64. If the session has not ended, the control logic 50 _flows back to step 62. However, ifthe session has ended, the control logic 50 includes the step ofreleasing the CDMA mobile device at step 66. [0035] As will be also appreciated, the above described techniques may take the form of computer or controller implemented processes and apparatuses for practicing those processes. The disclosure can also be embodied in the form of computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer or controller, the computer becomes an apparatus for practicing the invention. The