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Summer Practical Training At Reliance Communications, Navi Mumbai
INTRODUCTION: MINS is an IP based solution that shall be designed to cater to a subscriber base of around 1000 subscribers. It shall support all the features and functionalities provided by the legacy switching systems. MINS was required as the rate of the “Qualcomm chipset “for the BSC (base station controller) was rising day by day. Qualcomm company is extracting 5$ per subscriber from any Indian company for using their chipset that why in MINS, BSC is constructed not using any hardware but by binding the system by some algorithms. It means that in MINS, software is prepared which can do the work of the hardware chip for BSC instead of using that Qualcomm chipset. The basic aim of designing of the MINS project is the removal of the Qualcomm chipset for BSC. MINS is not the whole network; it is the part of a network which contains following networks identities. They are:- 1. BTS CONTROLLER-Base transceiver system controller 2. BSC-Base station controller 3. MSC-Mobile switching centre 4. HLR-Home location register 5. VLR-Visitor location register MINS also contains some essential parts other than which are specified above. They may be either the parts of the four of them specified above or other ones. They should be considered in following lines as they come into the act. Some assumptions are made preparing the MINS project. They are:- Ø SSD (Shared secret data) is shared with the VLR, in case of Authentication. MINS system shall work with the Soft switch MGC (Media Gateway Controller) for all the calls originating from/terminating to the PSTN or GSM networks.
SCOPE OF TRAINING The basic scope or we can say the aim of the training was putting our theories to practice. What we have learned in two years of the B.E. degree, were put to practice. Any which we just learn as a theory subject we will forget that thing very quickly, but if we have put that thing to practice we will not forget that thing in our whole life. It is not possible for a single college to provide the practical training for all the 350 students because it is too costly to provide such machines or systems that a multinational company can provide to the trainees. I have done my summer practical training at Reliance Communication at Dhirubhai Ambani Knowledge City(DAKC), Navi Mumbai. It was a great experience to work with such great and intelligent colleagues. The whole DAKC so well designed and architect any beauty lover can’t move away from that. I think for me it was an educational tour. My training was based on MINS (Mobile integrated network system). It was a newly prepared project for wireless communication by the Reliance infocomm. MINS was a under launch product whose testing was on the way. According to the project manager of MINS it will take 2-3 yrs to launch this product. So it was not possible for us to the get the whole knowledge about the MINS so we divided our training to following phases: · Theoretical knowledge about the networks and layers. · Theoretical knowledge about the MINS from the document SRS_MINS which was provided by the company to us on our personal computer at Reliance Communications. · Testing of the project –It includes the checking of the message flow between the network subsystem when a call is initiated or released. · Preparing of the training report. I learned a one more thing that preparing a project is just not preparing it but it includes it’s testing also which is tedious work to do. It was very difficult for me to stay 45 days away from my family and parents. For me it was also one of the aims to recover from family fever. It is compulsory for every student to complete training of 90 days till we complete our B.E. degree. It is done in two phases – · 45 days after 2nd year. · 45 days after 3rd year.
LEARNING OBJECTIVE It was a long term training in which were thought theory about the MINS project and we worked on the testing of MINS project. In testing we worked on the UNIX operating system. MINS project team had prepared the testing environment on the operating system UNIX. They have chosen the UNIX environment as on UNIX multithreading is possible. Multithreading is process in which multiple system can work at a time. What do we mean with a thread? Technically, a thread is defined as an independent stream of instructions that can be scheduled to run as such by the operating system. But what does this mean? In the UNIX environment a thread: · Exists within a process and uses the process resources · Has its own independent flow of control as long as its parent process exists and the OS supports it · May share the process resources with other threads that act equally independently (and dependently) · Dies if the parent process dies – or something similar METHODOLGY The project manager Mr. Praveen singhal had allotted me a computer on which we study or understand the theoretical knowledge of the MINS project using the SRS_MINS document (Software requirement document_ MINS) in our half time. After having my lunch when I came back to office then they allot me a laptop which connected to one of the subsystem of the network like BSC, BTS etc. I have to submit a report at 6:00 p.m. every evening what we have concluded while we are testing the project. After we put the project (MINS system) we put to a tester which they named as load test. What we do whole day manually, is known as manual test and then when we put it to a tester is known as load test. The flow of messages which we get in the load test can be seen in the logs of the BTS and BSC subsystem. That was work of the employees or I can say the work of my seniors or my teachers there. When we left from there a viva voce was conducted by the project manager and we submitted the project report to them.
CONTENTS OF TRAINING 1. Initialization of the Project-(Phases) 2. Requirement of these Phases 3. Some Definitions 4. MS-Mobile system 5. Complete description of MINS 6. Call scenario of voice call flow 7. Call initiated by the MS of MINS 8. General call flow for MINS 9. Advantages of MINS
INITIALIZATION OF THE PROJECT:
MINS is a very huge and lengthy project to design and launch for single man and to work on it respectively. So phases are divided and some teams are set up to make this project a grand success. The MINS project is divided into 2 Phases listed below Phase 1A: The Scope of Phase 1A is to demonstrate a successful Intra MINS and Inter MINS call along with CDR generation. Handoff functionality will not be supported in this phase of MINS. Phase 1: Phase 1 will be focused on interfaces towards Billing and Mediation, NMS, Legal Interception System, and PSTN World. This phase will also have capability to interact with the prepaid system. Along with this all the bugs observed in Phase 1A will be fixed in Phase 1. At the end of Phase 1, it will be possible to make inter MINS calls, Intra MINS Calls, Calls to PSTN world, Call to Existing Reliance Wireless Network and Send SMS on the MINS network. Also the Handoff and announcement functionality shall be supported in this Phase. The Load test as per the Specifications will be carried out after successful demonstration of all the services and integration with the network elements present in the Reliance network. It will include PCF functionality and integration with data network (R world), OTAF (Over The Air Functionality) and VMS (Voice Mail System). Also all the supplementary services development will be taken up in this phase.
REQUIREMENT OF THESE PHASES · Phase 1A Requirement— Feature or function that shall be supported by the system to be delivered in in the phase 1A.These are mandatory for the Intra MINS and Inter MINS call establishment. All Phase 1A requirements are flagged by the letter “PH 1A.” · Phase 1 Requirement— Feature or function that shall be supported by the system to be delivered in the phase 1.These are mandatory for supporting Prepaid functionality, SMS functionality and calls terminating on /from PSTN or GSM network as well as to offer Supplementary services. All Phase 1 requirements are flagged by the letter “PH 1.” · Phase 2 Requirement— Feature or function that shall be supported by the system to be delivered in the phase 2.All Phase 2 requirement are flagged by the letter “PH 2.”
SOME DEFINITIONS: Some definitions should be useful for upcoming information. · Assured Mode. Mode of delivery that guarantees that a PDU will be delivered to the peer. A PDU sent in assured mode is retransmitted by the LAC Sublayer, up to a maximum number of retransmissions, until the LAC entity at the sender receives an acknowledgement for the PDU. See also Confirmation of Delivery · Authentication: A procedure used to validate mobile stations or subscriber’s identity. · Base Station. A fixed station used for communicating with mobile stations. Depending upon the context, the term base station may refer to a cell, a sector within a cell, an MSC, or other part of the cellular system. See also MSC · Common Location Register (CLR): A proprietary node that contains the MDN and MIN ranges and the corresponding HLR addresses. · ESN: The unique serial number of a cellular phone that identifies it to the cellular system for the purpose of placing and receiving calls. · Home Location Register (HLR): The HLR is the location register to which a user identity is assigned for record purposes such as subscriber information (e.g. ESN, MDN, Profile Information, Current Location, and Authorization Period). · IS-41: The network standard that allows all switches to exchange information about subscribers. · Layer 1 (L1). Layer 1 (Physical Layer) provides for the transmission and reception of radio signals between the base station and the mobile station · Layer 2 (L2). Layer 2 provides for delivery of signaling messages generated by Layer 3 (see below). Layer 2 consists of two sub layers: the LAC Sublayer and the MAC Sublayer (see below). Layer 2 makes use of the services provided by Layer 1 · Layer 3 (L3). Layer 3 originates and terminates signaling messages according to the semantics and timing of the communication protocol between the base station and the mobile station. Layer 3 makes use of the services provided by Layer 2 · Logical channel. A communication path between stations, described in terms of the intended use of, and access to, the transferred data, and direction of transfer. A logical channel can be “mapped” to and from one or more physical channels · Lower Layers. In this document, layers below the LAC Sublayer (e.g., Layer 1 and the MAC Sub layer) · MAC Sub layer. See Medium Access Control Sublayer · Mapping. In this context, the technique for forming associations between logical and physical channels · Message. Signaling data unit transferred between the base station and the mobile station. In this document, it should be interpreted as the Layer 3 PDU or the LAC SDU · Medium Access Control (MAC) Sublayer. The MAC Sublayer is the lower sub layer of Layer 2. It implements the medium access protocol and is responsible for transport of LAC protocol data units using the services provided by Layer 1 · Message Control and Status Block (MCSB). In this document, a parameter block representing the interface control information transferred between Layer 3 and the LAC Sublayer. The MCSB is also used to carry relevant information within the LAC Sublayer.
· MDN (Mobile Directory Number): It is a 10 digit unique number, which identify a mobile subscriber · MIN: It is a unique 10-digit decimal number programmed into the MS. This MIN is transmitted over the air interface during registration to inform the network of the identity of the mobile station accessing the network. It is also used as a key field to access the subscriber profile record stored in the HLR
· Mobile Switching Center (MSC): A configuration of equipment that provides cellular or PCS service
· MS (Mobile Station): The Mobile Station (MS) is the equipment that subscribers use to originate and receive information and calls via the wireless network. The MS provides the user with access to the radio network and performs other functions for the user · Visitor location registers (VLR). The VLR database contains temporary information about subscribers that is needed by the mobile services switching center (MSC) in order to service visiting subscribers. When a mobile station roams into a new mobile services switching center (MSC) area, the visitor location register (VLR) connected to that MSC will request data about the mobile station from the HLR, reducing the need for interrogation of the home location register (HLR).
MS (MOBILE STATION) The mobile station (MS) consists of the mobile equipment (the terminal) and a smart card called the Subscriber Identity Module (SIM). The SIM provides personal mobility, so that the user can have access to subscribed services irrespective of a specific terminal. By inserting the SIM card into another GSM terminal, the user is able to receive calls at that terminal, make calls from that terminal, and receive other subscribed services. The mobile equipment is uniquely identified by the International Mobile Equipment identity (IMEI). The SIM card contains the International Mobile Subscriber Identity (IMSI) used to identify the subscriber to the system, a secret key for authentication, and other information. The IMEI and the IMSI are independent, thereby allowing personal mobility. The SIM card may be protected against unauthorized use by a password or personal identity number.
COMPLTETE DESCRIPTION OF “MINS” MINS is composed of the following parts which were stated in on of the above section. They are as below: - 1. BTS Controller 2. Base station controller 3. Mobile switching centre 4. Home location register 5. Visitor location register OVERVIEW OF MINS (MOBILE INTEGRATED NETWORK SYSTEM)
Description of the above parts is as follows: 1. BTS Controller- BTS controller shall be a PowerPC based General Purpose Microcontroller residing in the BTS hardware. For the Phase 1A the BTS hardware shall be the BTS development platform made up of Commercial Off-the-Shelf (COTS) cards and associated software. The PowerPC 8245 shall have a Real Time Operating System (RTOS) called OSE delta running on it. The BTS controller shall perform following functions: CDMA2000 Physical Layer Control: This function will interact closely with the Base band processing algorithms running on the Tigers ARC 201 (TS-201) DSPs. Abis functions on the BTS side: This function involves packet sing physical layer frames into IP PDUs, open sockets and send IP PDUs to the BSC entity of MINS as per the Abis protocol. Similar functions are executed for the receipt of IP packets from BSC entity. OA&M functions for the BTS: This will broadly include the Configuration, Fault and Performance management functions. In Phase 1 A only a small subset of these functions shall be implemented. The definition of the entire set of function and this small subset is in progress. The Base Transceiver Station houses the radio transceivers that define a cell and handles the radio-link protocols with the Mobile Station. In a large urban area, there will potentially be a large number of BTSs organize, thus the requirements for a BTS are ruggedness, reliability, portability, and minimum cost.
2. BSC-The Base Station Controller manages the radio resources for one or more BTSs. It handles radio-channel setup, frequency hopping, and handovers, as described below. The BSC is the connection between the mobile station and the Mobile service Switching Center (MSC).
In the construction of the BSC, there are following parts. They are as follows: 1. CP-Call processing 2. Layer 3 3. LAC 4. MAC 5. ABIS 6. Transport layer Description of all the above stated parts is as follows: 1. Call processing (CP) – Call processing is, just like a heart to the human being, for BSC. It creates the messages which are used to be exchanged in between the BSC and BTS, BSC and MSC etc. As a example we take a ORM i.e. Origination message. Origination message contain three things mainly. They are: · IMSI-international mobile station identity · ESN-electronic serial number · MDN-mobile directory number · Other matter also Call processing prepares the message as follows below:-
1. Layer 3 (L3) - Following L3 signaling messages will be supported in MINS BSC Subsystem, which will be sent or received on logical channels f-csch & r-csch. Same way the user traffic messages will be carried on logical channels f-dsch & r-dsch. When message is passed to the L3 from the call processing then L3 will add a header to the message. Now message will be seen like as below:
2. LAC Sub layer- LAC Sub layer shall implement a data link protocol that provides for the correct transport and delivery of signaling messages generated by Layer 3. LAC Sub layer will also add a header to the above message.
3. MAC Sub layer- The MAC Sub layer shall implement the medium access protocol and is responsible for transport of LAC protocol data units using the services provided by Layer 1. The MAC Sub layer shall also control the access to and from upper layer signaling, Data Services (not in phase 1A) and voice services to physical layer resources. MAC sub layer will also add a header to the above message.
4. ABIS - The Abis Interface is defined as the interface that provides signaling and traffic between Base Transceiver System (BTS) and Base Station Controller (BSC) for MINS Network. The signaling procedures on Abis are divided as follows: · Abis Application Control Signaling those associated with O & M signaling and Abis Signaling. · Abis Traffic Signaling are those that directly associated with a call. They include transmit and receive message to/from Mobile Station. · Abis Transport Signaling Procedures to set up and manage the stable link between BTS and BSC. Abis interface also add a similar header to the above message.
5. Transport layer (TL) – Transport layer is used to take the message from Abis of the BSC to the Abis of the BTS controller.
3. MSC –The MSC subsystem of the MINS will be responsible for the call routing functionalities. It will be responsible for Call processing and the Mobility management functions. In order to install, initialize and configure the Subsystem there will be an EMS function and to ensure the availability of the subsystem there will be maintenance functionality built in the system. The central component of the Network Subsystem is the Mobile Switching Center (MSC). It acts like a normal switching node of the PSTN or ISDN, and additionally provides all the functionality needed to handle a mobile subscriber, such as registration, authentication, location updating, handovers, and call routing to a roaming subscriber. These services are provided in conjunction with several functional entities, which together form the Network Subsystem. The MSC provides the connection to the fixed networks (such as the PSTN or ISDN). Signaling between functional entities in the Network Subsystem uses Signaling System Number 7 (SS7), used for trunk signaling in ISDN and widely used in current public networks.
4. HLR (Home location register) The HLR is a database used for storage and management of subscriptions. The home location register stores permanent data of the subscribers; including subscriber’s service profile, location information, and activity status. HLR tracks and manages individual subscriber information that is needed by the network to confirm that callers are valid customers, to route calls, and to provision services. HLR is a centralized database application that provides call completion data for cellular subscribers. The HLR database contains the administrative information for each subscriber registered in the network, along with the subscriber’s current location. The HLR database is “dipped” whenever the switch in the mobile network requires subscriber information to complete a call. The HLR is the location register to which a user identity is assigned for record purposes such as subscriber information (e.g. ESN, MIN, MDN, Profile Information, Current Location, and Authorization Period). The HLR shall provide these two basic functions:
· It shall be responsible for providing instructions/data to MSCs for MS registration, call origination and call delivery.
5. VLR (Visitor location register) The Visitor Location Register (VLR) contains selected administrative information from the HLR, necessary for call control and provision of the subscribed services, for each mobile currently located in the geographical area controlled by the VLR. Although each functional entity can be implemented as an independent unit, all manufacturers of switching equipment to date implement the VLR together with the MSC, so that the geographical area controlled by the MSC corresponds to that controlled by the VLR, thus simplifying the signaling required. Note that the MSC contains no information about particular mobile stations --- this information is stored in the location registers. CALLS SCENARIO OF VOICE CALL FLOW The call scenarios that shall be supported in MINS Phase 1A can be broadly classified into the following types based on the voice path: 1) Intra-Network: These are the calls between subscribers located within the MINS network (home & roamed subscribers). These calls can further be classified into two sub-categories: I. Intra MINS: Intra MINS calls are the calls in which the voice path shall be established between A-party and B-party both belonging to the same MINS. The scenarios of this category shall be a. A11-B11 b. A11-B21 c. A12-B22 d. A12-B12 e. A21-B21 f. A11-BL1 g. A21-BL1 h. AL1-BL1 i. AL1- B11 j. AL1-B21 II. Inter MINS: Inter MINS calls are the calls in which the voice path shall be established between A-party and B-party belong to different MINS. The scenarios of this category shall be: a. A11-B22 b. A11-B23 c. A11-B12 d. A12-B11 e. A12-B21 f. AL1-B22 g. A11-BL2 h. AL1-BL2 2) Inter-Network: These are calls between MINS and other networks. The scenarios of this category shall be: A. Normal Cases: · RIM-MINS(ALL- B11) · MINS-RIM(A11-BLL) · MINS-PSTN · PSTN-MINS B. Roaming Cases : · A11-B1L · ALL-BL1 · A1L-BL1 · AL1-B2L CALL INITIATED BY THE MS OF MINS
1. Starting of BSC and BTS 2. Successful Link establishment Between BTS and BSC 3. BTS Registration 4. Successful Mobile Originated call (for the A-party) |
