MOBILE రేపు మా ఊరి పండుగ కాబట్టి అందరూ తప్పక రావాలి.ఇది నా అభ్యర్థన, నేను ఇక్కడే ఉన్నాను. ppt2.pptx

Good for students analysin రేపు మా ఊరి పండుగ కాబట్టి అందరూ తప్పక రావాలి.ఇది నా అభ్యర్థన, నేను ఇక్కడే ఉన్నాను.

1. MOBILE COMPUTING Chapter 2 Notes

2. FUNCTIONAL ARCHITECTURE OF GSM RSS – Radio Sub System NSS – Network Switching Sub System OSS – Operation Sub System MS – Mobile Station BSS – Base Station Subsystem BTS – Base Transceiver System BSC – Base Station Controller MSC – Mobile services Switching Center HLR – Home Location Register VLR – Visitor Location Register OMC – Operation and Maintenance Center AuC – Authentication Center EIR – Equipment Identity Register ISDN – Integrated Services Digital Network PSTN – Public Switched Telephone Network PDN – Public Data Networks GMSC – Gateway Mobile Switching Center

3. Radio Subsystem (RSS) : the radio subsystem (RSS) comprises all radio specific entities, i.e., The mobile stations (MS) and The base station subsystem (BSS) BSS (Base Station Subsystem) : A GSM network comprises many BSSs, each controlled by a base station controller (BSC). The BSS performs all functions necessary to maintain radio connections to an MS, coding/decoding of voice, and rate adaptation to/from the wireless network part. Besides a BSC, the BSS contains several BTSs BTS (Base Transceiver System) A BTS comprises all radio equipment, i.e., antennas, signal processing, amplifiers necessary for radio transmission. A BTS can form a radio cell or, using sectorized antennas, several cells, and is connected to MS via the Um interface (ISDN U interface for mobile use), and to the BSC via the Abis interface. - The Um interface contains all the mechanisms necessary for wireless transmission (TDMA, FDMA etc.) The Abis interface consists of 16 or 64 kbit/s connections. A GSM cell can measure between some 100m and 35km depending on the environment (buildings, open space, mountains etc.) but also expected traffic.

4. BSC (Base Station Controller) : The BSC basically manages the BTSs. It reserves radio frequencies, handles the handover from one BTS to another within the BSS, and performs paging of the MS. The BSC also multiplexes the radio channels onto the fixed network connections at the A interface MS(Mobile Station) : The MS comprises all user equipment and software needed for communication with a GSM network. An MS consists of user independent hard- and software and of the subscriber identity module (SIM), which stores all user-specific data that is relevant to GSM. Network and Switching Subsystem : The “heart” of the GSM system is formed by the network and switching subsystem (NSS). The NSS connects the wireless network with standard public networks, performs handovers between different BSSs, comprises functions for worldwide localization of users and supports charging, accounting, and roaming of users between different providers in different countries. The NSS consists of the following switches and databases:

5. MSC (Mobile Switching Service Centre) : The MSC is mostly associated with communications switching functions, such as call set-up, release, and routing. HLR (Home Location Register) : The Home Location Register (HLR) is the main database of permanent subscriber information for a mobile network. VLR (Visitor Location Register) : A visitor location register (VLR) is a database that contains information about the subscribers roaming within a mobile switching center’s (MSC) location area. MSC (Mobile Switching Center) MSCs are high-performance digital ISDN switches. They set up connections to other MSCs and to the BSCs via the A interface, and form the fixed backbone network of a GSM system. Typically, an MSC manages several BSCs in a geographical region. A gateway MSC (GMSC) has additional connections to other fixed networks, such as PSTN and ISDN. An MSC handles all signaling needed for connection setup, connection release and handover of connections to other MSCs.

6. The standard signaling system No. 7 (SS7) is used for this purpose.  SS7 covers all aspects of control signaling for digital networks (reliable routing and delivery of control messages, establishing and monitoring of calls). HLR (Home Location Register) The HLR is the most important database in a GSM system as it stores all user-relevant information. This comprises static information, such as the mobile subscriber ISDN number (MSISDN), subscribed services (e.g., call forwarding, roaming restrictions, GPRS), and the international mobile subscriber identity (IMSI). Dynamic information is also needed, e.g., the current location area (LA) of the MS, the mobile subscriber roaming number (MSRN), the current VLR and MSC. MS leaves its current LA, the information in the HLR is updated. This information is necessary to localize a user in the worldwide GSM network. HLRs can manage data for several million customers and contain highly specialized data bases which must fulfill certain real-time requirements to answer requests within certain time-bounds. VLR (Visitor Location Register) The VLR associated to each MSC is a dynamic database which stores all important information needed for the MS users currently in the LA that is associated to the MSC (e.g., IMSI, MSISDN, HLR address). If a new MS comes into an LA the VLR is responsible for, it copies all relevant information for this user from the HLR. This hierarchy of VLR and HLR avoids frequent HLR updates and long-distance signaling of user information. Some VLRs in existence, are capable of managing up to one million customers.

7. OSS (operation Subsystem) It contains the necessary functions for network operation and maintenance. The OSS possesses network entities of its own and accesses other entities via SS7 signaling. The following entities have been defined: OMC (Operation and Maintenance Centre) AuC (Authentication Center) EIR (Equipment Identity Register) AuC (Authentication Centre) As the radio interface and mobile stations are particularly vulnerable, a separate AuC has been defined to protect user identity and data transmission. The AuC contains the algorithms for authentication as well as the keys for encryption and generates the values needed for user authentication in the HLR. The AuC may, in fact, be situated in a special protected part of the HLR.

8. EIR (Equipment Identity Register) The EIR is a database for all IMEIs, i.e., it stores all device identifications registered for this network. As MSs are mobile, they can be easily stolen. With a valid SIM, anyone could use the stolen MS. --The EIR has a blacklist of stolen (or locked) devices. In theory an MS is useless as soon as the owner has reported a theft. Unfortunately, the blacklists of different providers are not usually synchronized and the illegal use of a device in another operator’s network is possible (the reader may speculate as to why this is the case). --The EIR also contains a list of valid IMEIs (white list), and a list of malfunctioning devices (gray list).

9. Call set up in gsm MOBILE ORIGINATED CALL MOBILE TERMINATED CALL

10. to initiate a call, the MS sends a request for radio resource allocation to the BSS, which mediates further connection to the Mobile Switching Center (MSC). The BSS assigns the MS a channel with a given frequency and time slot, which constitutes the communication route between the MS and the BSS. O nce the MS confirms the established channel, the BSS can initiate the connection to the MSC. O nce the MS has connected to the network, the subscriber needs to be authenticated. This can be done using the IMSI number stored in the SIM card, which allows the Authentication Center in the core network to verify the subscriber’s identity. After this step, the MS and the MSC can start communicating. To make sure the data sent over the radio network between the BSS and MS/MSC is secure, the MSC initiates a ciphering procedure which is transmitted to the BTS, which in turn forwards the message to the MS. The MS enables ciphering towards the BTS; as the BTS starts receiving ciphered data, it will start the ciphered transmission of information, finalizing the encryption procedure. 4. To initiate the call setup, the MSC verifies that the requested service is allowed for the subscriber. This information is available in the Virtual Location Register, which maintains temporary subscriber data (location, preferences, allowed services). Once the VLR confirms the service requested by the originating MS, the MSC starts the call setup. 5. for the call to take place, the MSC allocates a voice channel between the MSC and the BSS. The BSS notifies the MS about the change to voice mode, and the MS returns a confirmation message. The MSC routes the call to the dialed number. When the call is received in the PSTN, the MSC is notified that the called subscriber is being alerted, at which point the originating MS receives a ring notification. Mobile Originated Call

11. when a call is placed from the PSTN towards a given phone number, the PSTN uses the information in the phone number (country and if available, operator) to locate gateway MSC leading to the MSC where the subscriber is registered. the GMSC can request information about the subscriber’s core network and current location by interrogating the HLR (Home Location Register). the HLR constantly updates the locations of the MS stored in the VLRs of the networks the MS visits. In the HLR, the subscriber MSISDN (phone number) is associated with the IMSI number of the SIM card, which was used to authenticate the subscriber in the visited network as they registered. Since authentication is communicated to the MSC, the HLR is aware of the visited MSC/VLR of the MS at a given time. For the GMSC to pass the call to the MSC, the HLR asks for a temporary roaming phone number from the MSC (Mobile Station Roaming Number – MSRN). the MSRN is sent back from the HLR to the GMSC. the GMSC forwards the call to the MSC using the assigned MSRN. Having received the call, the MSC pages all the BSCs in the area that it serves. The BSC, in turn, page the BTSs assigned to them. the called MS responds to the paging from the BTS, asking to establish a radio channel to the BTS. the response is forwarded to the MSC, which, once notified, authenticates the MS and initiates the ciphering of the call using the same procedure as in MO calls. When the MSC sends back to the radio network the call confirmation message, the called MS starts to ring. At the other end, the MSC notifies the GMSC, which notifies the PSTN that the destination number is being alerted. Mobile Terminated Call

12. MOBILITY AND HANDOVER IN GSM Mobility -Orange Handover - Green TMSI -Temporary Mobile Subscriber Identity IMSI - International Mobile Subscriber Identity

13. to communicate to the network, the MS establishes the connection to the radio network, and sends a location update request to the current BSS. The BSS forwards the request to the MSC, which finds that the device was registered to a different MSC/VLR. the current MSC contacts the previous MSC to get information about the MS, by sending it the Temporary Mobile Subscriber Identity. in the old MSC, the IMSI is associated with the TMSI, so that the IMSI parameter is be sent to the new MSC. Once it reaches the MSC, the current location of the device is updated in the HLR; having the IMSI number, the HLR will be able to provide information about the subscriber (services allowed, preferences etc ) to the new MSC. the new VLR location is updated in the HLR. Information from the previous MSC/VLR is deleted. once the updates are communicated by the HLR to the new MSC, authentication is performed using the SIM card IMSI. After authentication, the MSC initiates ciphering and allocates a new temporary identity that will be used to update the subscriber’s next location. Mobility Management in GSM

14. I f the MS is engaged in a call session and changes location, the connection must continue uninterrupted and transfer to the new location must be done seamlessly to the subscriber. If the MS roams from one BSC to a new one, both managed by the same MSC, the MSC will be the one managing the handover. As the BSC is informed by the MS of the location change, the BSC sends a handover request to the MSC, including the code of the current location area (LAC) and the cell identifier, which uniquely identifies the cell in the network. Once the MSC receives the coordinates of the new BSC, it messages it requesting the assignation of a speech channel. The MSC then sends a request to the current BSC to perform the handover to the new cell. The BSC sends the MS the new time slot and frequency requirements for the new channel. A handover may also be requested between 2 different MSCs. This case scenario is illustrated in the diagram above in green color. when the BSC is informed of the location change and finds that the new location is not in its area, it forwards the handover request to the MSC, which acknowledges that the subscriber has roamed to a different MSC. The MSC has access to the LACs of neighboring MSCs, therefore it can determine the network in which the subscriber has roamed. the old MSC sends the request to the target MSC, which asks the corresponding BSC to establish the speech channel to the MS. the MS receives handover request via the initially established channel; communication is moved to the newly created channel of the second MSC. The MSC that initially assigned the MSRN for setting up the call is called an anchor MSC and is responsible for all the inter-MSC handover procedures that may occur during a call. in the case of a handover between different MSCs, a new authentication of the MS will also be performed in the new network. requests Handover in GSM

15. SMS MSRN - Mobile Station Roaming Number GMSC - Gateway Mobile Switching Center SMSC - Short Message Service Center MSISDN - Mobile Station International Subscriber Directory Number

16. T o send an SMS, the MS connects to the MSC, which performs the authentication of the subscriber and ciphers the communication in the same way as in the case of voice calls. after the MSC receives the message, it queries the VLR to check the allowed services for the subscriber. I f the service is allowed, the MSC forwards the message to the SMSC. Like in the case of voice calls, the HLR uses the IMSI to locate the current MSC/VLR in which the subscriber has registered. next, the HLR asks the MSC to assign a temporary MSRN number, which is passed to the GMSC. the GMSC then forwards the message to the MSC using this number. The MSC sends out a paging to all the BSCs in its area, which then page all the base stations serving them. the SMS is delivered to the MS after it responds to the BTS paging SMS

17. SECURITY Security Services offered by GSM are : ACCESS CONTROL AND AUTHENTICATION CONFIDENTIALITY ANONYMITY

18. The GSM network authenticates the identity of the subscriber through the use of a challenge-response mechanism. A 128-bit Random Number (RAND) is sent to the MS. The MS computes the 32-bit Signed Response (SRES) based on the encryption of the RAND with the authentication algorithm (A3) using the individual subscriber authentication key (Ki). Upon receiving the SRES from the subscriber, the GSM network repeats the calculation to verify the identity of the su bscriber . The individual subscriber authentication key (Ki) is never transmitted over the radio channel, as it is present in the subscriber's SIM, as well as the AUC, HLR, and VLR databases. If the received SRES agrees with the calculated value, the MS has been successfully authenticated and may continue. If the values do not match, the connection is terminated and an authentication failure is indicated to the MS. The calculation of the signed response is processed within the SIM. It provides enhanced security, as confidential subscriber information such as the IMSI or the individual subscriber authentication key (Ki) is never released from the SIM during the authentication process. Mobile Station Authentication

19. The SIM contains the ciphering key generating algorithm (A8) that is used to produce the 64-bit ciphering key (Kc). This key is computed by applying the same random number (RAND) used in the authentication process to ciphering key generating algorithm (A8) with the individual subscriber authentication key (Ki). GSM provides an additional level of security by having a way to change the ciphering key, making the system more resistant to eavesdropping. The ciphering key may be changed at regular intervals as required. As in case of the authentication process, the computation of the ciphering key (Kc) takes place internally within the SIM. Therefore, sensitive information such as the individual subscriber authentication key (Ki) is never revealed by the SIM. Encrypted voice and data communications between the MS and the network is accomplished by using the ciphering algorithm A5. Encrypted communication is initiated by a ciphering mode request command from the GSM network. Upon receipt of this command, the mobile station begins encryption and decryption of data using the ciphering algorithm (A5) and the ciphering key (Kc). Signalling and Data Confidentiality

20. S ubscriber I dentity C onfidentiality To ensure subscriber identity confidentiality, the Temporary Mobile Subscriber Identity (TMSI) is used. Once the authentication and encryption procedures are done, the TMSI is sent to the mobile station. After the receipt, the mobile station responds. The TMSI is valid in the location area in which it was issued. For communications outside the location area, the Location Area Identification (LAI) is necessary in addition to the TMSI.

21. GSM PROTOCOL STACK CM – Connection Management MM – Mobility Management RR – Radio Resource Management LAPD – Link Access Protocol, D Channel BTSM – BTS Management BSSAP – BSS Application Part PCM – Pulse Code Modulation SS7 - Signalling System No. 7

22. MS Protocols Based on the interface, the GSM signaling protocol is assembled into three general layers:   Layer 1 : The physical layer. It uses the channel structures over the air interface. Layer 2 : The data-link layer. Across the Um interface, the data-link layer is a modified version of the Link access protocol for the D channel (LAP-D) protocol used in ISDN, called the Link access protocol on the Dm channel (LAP-Dm). Across the A interface, the Message Transfer Part (MTP), Layer 2 of SS7 is used.   Layer 3 : The GSM signaling protocol’s third layer is divided into three sublayers: Radio Resource Management (RR), Mobility Management (MM), and Connection Management (CM). MS to BTS Protocols The RR layer is the lower layer that manages a link, both radio and fixed, between the MS and the MSC. For this formation, the main components involved are the MS, BSS, and MSC. The responsibility of the RR layer is to manage the RR session, the time when mobile is in a dedicated mode, and the radio channels including the allocation of dedicated channels. The MM layer is stacked above the RR layer. It handles the functions that arise from the mobility of the subscriber, as well as the authentication and security aspects. Location management is concerned with the procedures that enable the system to know the current location of a powered-on MS so that incoming call routing can be completed. The CM layer is the topmost layer of the GSM protocol stack. This layer is responsible for Call Control, Supplementary Service Management, and Short Message Service Management. Each of these services is treated as an individual layer within the CM layer. Other functions of the CC sublayer include call establishment, selection of the type of service (including alternating between services during a call), and call release.

23. BSC Protocols The BSC uses a different set of protocols after receiving the data from the BTS. The Abis interface is used between the BTS and BSC. At this level, the radio resources at the lower portion of Layer 3 are changed from the RR to the Base Transceiver Station Management (BTSM). The BTS management layer is a relay function at the BTS to the BSC. The RR protocols are responsible for the allocation and reallocation of traffic channels between the MS and the BTS. These services include controlling the initial access to the system, paging for MT calls, the handover of calls between cell sites, power control, and call termination. The BSC still has some radio resource management in place for the frequency coordination, frequency allocation, and the management of the overall network layer for the Layer 2 interfaces. To transit from the BSC to the MSC, the BSS mobile application part or the direct application part is used, and SS7 protocols is applied by the relay, so that the MTP 1-3 can be used as the prime architecture. MSC Protocols At the MSC, starting from the BSC, the information is mapped across the A interface to the MTP Layers 1 through 3. Here, Base Station System Management Application Part (BSS MAP) is said to be the equivalent set of radio resources. The relay process is finished by the layers that are stacked on top of Layer 3 protocols, they are BSS MAP/DTAP, MM, and CM. This completes the relay process. To find and connect to the users across the network, MSCs interact using the control- signalling network. Location registers are included in the MSC databases to assist in the role of determining how and whether connections are to be made to roaming users.

24. Each GSM MS user is given a HLR that in turn comprises of the user’s location and subscribed services. VLR is a separate register that is used to track the location of a user. When the users move out of the HLR covered area, the VLR is notified by the MS to find the location of the user. The VLR in turn, with the help of the control network, signals the HLR of the MS’s new location. With the help of location information contained in the user’s HLR, the MT calls can be routed to the user.

25. DECT – Digital Enhanced Cordless telecommunications Contains 2 components : Mobile station Base Station FT – Fixed Radio Terminal PT – Portable Radio Transmitter PA – Portable application

26. There are several uses of DECT systems and depending upon the usage there can be multiple physical techniques for the implementation of the system. But one thing which is to be kept in mind is that there is a single logical reference model of the system architecture which is the basis of all the implementations. There is a local communication structure that is connected to the outside world through a global network and the services are offered via interface D 1 . Public Switched Telephone Network (PSTN), Public Land Mobile Network (PLMN), Integrated Services Digital Network (ISDN), etc. are the  global networks . These networks allow the data transmission along with that the transfer of addresses and data routing between local networks also takes place. A  local network  of DECT can provide local telecommunication services such as simple switching to any call forwarding, any type of address translation, etc. Some of its major examples are private branch exchanges i.e., the ones belonging to the family of LANs. The overall implementation of the system is simple and therefore, the overall functions that the network possesses are to be integrated within the local or global network, containing databases such as home database (HDB) and visitor database (VDB). The database operations here are similar to that of GSM systems. In this case whenever there is a call in the local network then it gets automatically forwarded to the desired DECT user in the network and the necessary changes that occurred in the location are notified to the HDB by the VDB. It is clearly shown in the above figure that there is a Fixed Radio Terminal (FT) and Portable Radio Terminal (PT) which are responsible for multiplexing of the signals to take place whenever necessary. The fixed radio terminal is placed at the fixed network side while the portable radio terminal exists at the mobile network side of the network. Along with these here we have multiple portable applications abbreviated as  PA  that a device can implement.

27. Protocol architecture of dect

28. The C-plane contains the additional network layer used for forwarding the user data from one of the layers to the User-Plane. The lower layers of the DECT system belong to the management plane. Let us now understand the operation of each layer briefly. 1. Physical Layer : The physical layer of the network is responsible for functions like detection of the incoming signal, performing modulation and demodulation, maintaining synchronization between sender and receiver along with collecting the status information for the management plane. The physical channel structure is obtained by this layer with guaranteed throughput. When data is required to get transferred which is notified by the MAC layer then the physical layer allocates the channel for the transmission of data. In DECT, the standard TDMA frame structure used is shown here along with some data packets. The fundamental connection orientation over here is that there are 12 slots for uplink and downlink and the frame duration is  10 ms . While if we talk about an advanced connections scheme then in that case various allocation schemes can be implemented. 2. Medium Access Control (MAC) Layer : This layer is responsible for the activation and deactivation of physical channels in order to establish or release channels for higher layers. In the MAC layer, multiplexing of multiple logical channels onto physical channels is performed. While the logical channels that are present here are responsible for the transmission of user data, broadcasting or sending messages, paging, the network controlling, etc. Other than these some additional services provided by this layer are error controlling and correction along with division or reassembling of the packets. 3. Data Link Control Layer : It is abbreviated as DLC and is mainly responsible for forming connections between the mobile terminal and the base station. In this layer the Control Panel has assigned two services namely, one is paging which is assigned for connectionless broadcasting while the other is the point-to-point approach. Not only this, some other services include forward error correction, rate adaptation, and other services for enhancing the future system requirements. Suppose if ISDN data is to be transferred at  64 kbit/s  then the data transferred from DECT will also be  64 kbit/s . But in case, there is an error in the transmitted sequence then the rate of transfer is increased to  72 kbit/s  and forward error correction is implemented. Also, ARQ is performed where a buffer of up to eight blocks is maintained. Due to this buffer delay of around 80 ms is also introduced in the transmitted sequence.

29. 4. Network Layer : This layer works only for the control panel of the DECT structure and works in a similar manner as in ISDN and GSM. Mainly the services related to requesting, reserving checking, releasing, or controlling resources at fixed and mobile stations are offered by this layer. The necessary management relative to identity, authentication, or location is done by the Mobility Management (MM) present within the network layer. While there is Call Control (CC) which is responsible for handling the setting up, releasing, or managing the connection. The DECT system is connected with the outside world through this layer as it enables connection-oriented message service and connectionless message service so that data transfer can take place between the networking unit.

30. GPRS - General packet radio service MS – Mobile Station BSC –Base Station Controller PSTN – Public Switched Telephone Network HLR – Home Location Register MSC – Mobile Switching Center PCU – Packet Control Unit SGSN – Serving GPRS Support Node GGSN – Gateway GPRS Support Node PDN – Predefined Data Network

31. Umts – universal mobile telecommunication system ME – Mobile Equipment USIM – User Sim UMTS RAN – UMTS Radio Access Network RNC – Radio Network Controller UE – User Equipment SGSN – Serving GPRS Support Node GGSN – Gateway GPRS Support Node PDN – Predefined Data Network

32. Tetra - TErrestrial Trunked Radio systems IMT-2000 – International mobile Telecommunication 2000