# Intro Dive into our comprehensive article discussing 2G - GSM technology, its history, impact and evolution. Explore how the 2G network revolutionized communication. GSM (Global System for Mobile Communications) is a standard developed to describe protocols for second-generation (2G) digital cellular networks used by mobile phones.
It became the default global standard for mobile communications, ensuring interoperability of mobile devices across different regions. {% @mailchimp/mailchimpSubscribe %} GSM technology operates in various frequency bands, primarily 900/1800 MHz, and utilizes time division multiple access (TDMA) to divide each frequency channel into time slots. This allows multiple users to share the same bandwidth efficiently. GSM supports voice calls, SMS, and limited data services, forming the backbone of modern mobile communication systems. {% embed url="" %} {% embed url="" %} {% embed url="" %} # Standards GSM Phase 1 - 1995 # Timeline ## 1988 ### GSM 900 Uplink - 890 Mhz to 915 Mhz Downlink - 935 Mhz to 960 Mhz ### GSM 1800 1710 Mhz to 1785 Mhz 1805 Mhz to 1880 Mhz ## 1995 ### GSM 1900 1850 Mhz to 1910 Mhz 1930 Mhz to 1990 Mhz ## 1996 120 GSM Networks ## 2000 150 million GSM users GSM (Global System for Mobile Communications) is a standard developed to describe protocols for second-generation (2G) digital cellular networks. By 1996, there were 120 GSM networks operating globally. By 2000, the number of GSM users had grown to 150 million, showcasing its rapid adoption and widespread usage. The frequency band 1930 MHz to 1990 MHz is commonly used for mobile communication services, including GSM, in various regions. # PCM30 #### GSM PCM30 GSM PCM30 is a telecommunications standard used to transmit multiple voice signals over a single medium. It employs the Pulse Code Modulation (PCM) technique to digitally encode analog voice signals. In PCM30, 30 voice channels are multiplexed into one transmission frame, with each channel allocated its own time slot. Additionally, 2 time slots are used for signaling and synchronization, resulting in a total of 32 time slots per frame. This setup allows efficient and high-quality voice communication in digital networks. # PCM24 # GSM Radio Stack ![Intro GSM Stack ](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FHU49fC0QhwyijyluvwC6%2Fslide_11.jpg?alt=media\&token=90cd1e4d-88e5-46b9-a765-0b44e235d99b) ## MS to BTS 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**](/gsm-interfaces/um-interface) − 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 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** − GSM signalling protocol’s third layer is divided into three sublayers − * Radio Resource Management (RR), * Mobility Management (MM), and * Connection Management (CM). {% embed url="" %} {% embed url="" %} # Layer 1 - Radio ## GSM Layer 1 - Radio GSM Layer 1, also known as the Physical Layer, handles the radio transmission and reception. It deals with modulation, demodulation, frequency hopping, and time-division multiple access (TDMA). This layer ensures the correct transmission of data between the mobile station and the network. In GSM, the Time Division Multiplexing (TDM) technique is used to allocate specific time slots to multiple users on the same frequency channel. Each user transmits in rapid succession, one after the other, each using their allocated time slot. This method enables multiple mobile stations to share the same frequency channel without interference, maximizing the efficiency of available bandwidth. # Layer 2 - LAP-Dm #### GSM Layer 2 - LAP-Dm GSM Layer 2, or the Link Access Protocol for the Dm channel (LAP-Dm), manages the data link control in GSM networks. LAP-Dm is responsible for: * Establishing a reliable communication link between Mobile Stations (MS) and the Base Transceiver Station (BTS). * Handling error correction, flow control, and frame synchronization. * Ensuring data integrity through frame acknowledgment and retransmission of corrupted frames. # Layer 3 − GSM signalling ### CM - Connection Management Layer 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 are treated as 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. Read More about it on `Paging Requests Messages` ### MM - Mobility Management Layer 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. ### RR - Radio Resource Management Layer 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 a mobile is in a dedicated mode, and the radio channels including the allocation of dedicated channels. # MS - Mobile Station **MS - Mobile Station** A Mobile Station (MS) refers to a wireless device used for communication in cellular networks. It comprises both the mobile equipment (ME), such as a smartphone, and the subscriber identity module (SIM), which stores user-related information and authentication data. The MS allows users to make calls, send texts, and access mobile data services. # ME - Mobile Equipment ### ME - Mobile Equipment Mobile Equipment (ME) refers to the physical hardware of a mobile device. This includes components like the phone casing, battery, screen, and internal electronics that facilitate communication and functionality of the device. The ME is identified by a unique IMEI number. ### IMEI - International Mobile Equipment Identity The International Mobile Equipment Identity (IMEI) is a unique 15-digit number used to identify mobile devices. It helps in differentiating each device on a mobile network and can be used for tracking or blocking a lost or stolen device. The IMEI is typically found printed inside the battery compartment of the device, and can also be displayed on the screen by dialing \*#06#. # Baseband # SIM Card - Subscriber Identity Module ## MSISDN Is stored on HLR from operator. ### Decoding MSISDN **00 351** 91 000 11 22 ### Prefixes National = 0 Internacional = +351 or 00351 (Portugal) ### MCC - Mobile Country Code 91 - Vodafone Portugal ### NDC - Network Destination Code 000 **Explanation**: The section above provides important codes and identifiers related to your mobile network and SIM card. * **Internacional**: The international dialing code for Portugal. * **MCC**: Mobile Country Code, specific to Vodafone Portugal. * **NDC**: Network Destination Code, often used in conjunction with MCC for routing. * **ICCID**: Identifies the SIM card uniquely. * **PIN**: Protects your SIM from unauthorized use. * **PUK**: Unblocks your SIM if the PIN is entered incorrectly multiple times. * **PIN2**: An additional security code for advanced features. **ICCID**: The Integrated Circuit Card Identifier is a unique number assigned to your SIM card. **PIN**: A Personal Identification Number is a security code that protects against unauthorized use of your SIM card. **PUK**: A PIN Unblocking Key is used to unblock your SIM card if the PIN is entered incorrectly multiple times. **PIN2**: Similar to the PIN, this is another security code used to access advanced SIM features. **PUK2**: This is the key used to unblock the PIN2 if it is entered incorrectly multiple times. # BSS - Base Station Subsystem # BTS - Base Transceiver Station ### Type of Channels 1. Common Control Channels 2. Dedicated Channels ### Base Transceiver Station A Base Transceiver Station (BTS) is a key component in the GSM architecture. It consists of: * **Transmitters and Receivers:** Handle communication with mobile phones via radio waves. * **Antennas:** Emit and receive signals within a specific coverage area. * **Signal Processing Units:** Manage the encoding, decoding, and encryption of signals. The BTS interfaces with the Mobile Station (MS) and the Base Station Controller (BSC). Responsible for managing radio resources, it facilitates user connectivity and communication services in a cellular network. ### Transmitters and Receivers Transmitters and Receivers are critical components of a BTS. The **transmitters** generate and send radio signals to the Mobile Station (MS), enabling communication. The **receivers**, on the other hand, capture incoming signals from the MS. Together, they facilitate two-way communication by converting data between radio waves and electrical signals within the GSM network. ### Antennas Antennas are integral parts of a BTS, responsible for transmitting and receiving radio waves to and from mobile stations within a designated coverage area. They convert electrical signals into radio waves for transmission and vice versa for reception. The design and placement of antennas determine the coverage and capacity of the network, ensuring that signals are effectively propagated and received. Different types of antennas, including omnidirectional and directional, are used based on the network requirements and geographical constraints. ### Signal Processing Units Signal Processing Units (SPUs) are vital components in a BTS that handle various tasks associated with digital signal processing. These units perform operations such as modulation, encoding, and error correction to ensure the integrity and clarity of communication signals. By converting analog signals to digital formats and vice versa, SPUs play a critical role in maintaining the quality and reliability of data transmission within the GSM network. # BSC - Base Station Controller ### BSC Functions 1. Manages BTSs 2. Manage Radio Resources 3. Monitor and Control Inter BTS handhovers 4. Connct to MSC to make calls ### Huawei BSC6900 ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FuK6AFQbtAuO8raDUARap%2FHuawei%20BSC6900.webp?alt=media\&token=c3012760-4738-4765-8af3-056491f9b7ff) {% file src="/files/cL1XydfJ2sqllqyCGGLA" %} ### BSC - Base Station Controller A Base Station Controller (BSC) is a critical component in a cellular network, responsible for managing multiple Base Transceiver Stations (BTS). It handles radio resource management, inter-BTS handovers, and connecting BTSs to the Mobile Switching Center (MSC) to facilitate call processing and mobility management. The BSC optimizes the network's performance and ensures seamless communication between mobile users. # NSS - Network Switching Subsystem #### Network Switching Subsystem (NSS) The Network Switching Subsystem (NSS) is a key component in a GSM network responsible for call processing and subscriber mobility management. It consists of several network elements, including: * **Mobile Switching Center (MSC):** Manages call setup, routing, and mobility. * **Home Location Register (HLR):** A database storing details of each subscriber. * **Visitor Location Register (VLR):** Temporarily holds data about subscribers currently in the MSC area. * **Authentication Center (AUC):** Provides data for verifying user identity. * **Equipment Identity Register (EIR):** Keeps records of mobile equipment to prevent fraud. The NSS facilitates communication between mobile users and connects them to other networks. # MSC - Mobile Switching Center #### Mobile Switching Center (MSC) The Mobile Switching Center (MSC) is a critical network element in a mobile telecommunications system responsible for performing call routing, call setup, and subscriber management. It interfaces with other networks such as public switched telephone networks (PSTN) and manages handovers between base stations to ensure seamless connectivity for mobile users. # HLR - Home Location Register #### HLR - Home Location Register The Home Location Register (HLR) is a central database in a mobile network that contains details of each mobile phone subscriber. It stores essential information such as: * Subscriber profiles * Current location * Service subscriptions * Authentication information The HLR ensures that calls, SMS, and other services are delivered to the correct subscriber, regardless of their current location within the network. # VLR - Visitor Location Register #### Visitor Location Register (VLR) The Visitor Location Register (VLR) is a database in mobile networks that temporarily stores information about subscribers who are currently within its coverage area. It supports the network in handling roaming and calls by storing data such as the subscriber's location, status, and service entitlements. # AuC - Authentication Center # EIR - Equipment Identity Register # VMS - Voice Mail Subsystem # IWF - Interworking Function # OSS - Operation Support Subsystem # OMC - Operation and Maintence Center # NMC - Network Managment Center # ABC - Administration & Billing Center ABC is responsible to provisioning SIM cards and insert the customer data inside HLR and equipment data inside AuC. Manage CDR - Call Records # Intro ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2Fb1xtoUyiHFHHYzNfNiyV%2F2.JPG?alt=media\&token=b0eb8343-327b-4bc5-9f5e-6ea78128ec87) [TS GSM 05.02](https://www.etsi.org/deliver/etsi_gts/05/0502/05.00.00_60/gsmts_0502v050000p.pdf) {% file src="/files/q1HQNS3mZSZq5vfuUmLM" %} {% embed url="" %} # Traffic Channels # TCH/F Full rate traffic channel (TCH/F). This channel carries information at a gross rate of 22,8 kbit/s. # TCH/H Half rate traffic channel (TCH/H). This channel carries information at a gross rate of 11,4 kbit/s. # Signalling Channels # Broadcast Channels # FCCH - Frequency Correction Channel FCCH is propagated by the BTS to syncronize the frequencies for downlink and Uplink. It negociate the ARFCN being used between BTS and Mobile Station. The Frequency Correction Channel (FCCH) is a special downlink channel used in GSM networks. It serves primarily to synchronize the frequency of the mobile station with that of the base transceiver station (BTS). When a mobile station is powered on, it initially listens for the FCCH to fine-tune its internal oscillator. This ensures that the mobile station's transmissions are aligned correctly to the network's frequencies, allowing for accurate signal reception and reducing interference. # SCH - Synchronization Channel Is used to synchronize the BTS and Mobile Station in timeslot Zero. Send data about TDMA Frame number that contains the Base Station Identity Code (BSIC) and compares with the information on SIM card to validate network operator if it fails it try again the FCCH channel. #### SCH - Synchronization Channel The Synchronization Channel (SCH) is a crucial component in the GSM network architecture. It is used to synchronize the Base Transceiver Station (BTS) with the mobile station during communication. Specifically, the SCH transmits time correction data and the TDMA (Time Division Multiple Access) frame number along with the Base Station Identity Code (BSIC). This information is essential for the mobile station to validate the network operator, ensuring a secure and accurate connection. The SCH operates in timeslot zero within the TDMA frame, playing a vital role in maintaining proper timing and network synchronization. # BCCH - Broadcast Control Channel The broadcast control channel broadcasts general information on a base transceiver station per base transceiver station basis. It negotiates the cipher to be used and other information about telco services. #### Broadcast Control Channel (BCCH) The Broadcast Control Channel (BCCH) is a crucial component in mobile communication systems. It operates within the GSM (Global System for Mobile Communications) framework and is responsible for broadcasting essential system information from a base transceiver station (BTS) to mobile stations (MS) within its cell. The BCCH carries data about the network's identity, available services, and operating frequencies, thus enabling mobile devices to initiate communication with the network effectively. Key functions of the BCCH include: * **Network Identification:** Provides the Mobile Station with the identity of the network it is connected to. * **Frequency Information:** Broadcasts the frequencies and hopping sequences utilized by the network. * **Service Information:** Details various services and capabilities available within the cell, such as SMS and call handling features. * **Neighbouring Cells Information:** Lists the neighbouring cells, aiding in efficient handover decisions as a mobile station moves between different cell coverage areas. The Broadcast Control Channel (BCCH) in GSM networks is essential for transmitting system information from a base transceiver station to mobile stations. It facilitates key functions such as providing network identification, broadcasting frequency and service information and listing neighboring cells to support effective communication and handover processes. # CBCH - Cell Broadcast Channel The CBCH, downlink only, is used to carry the short message service cell broadcast (SMSCB). The CBCH uses the same physical channel as the SDCCH. The Cell Broadcast Channel (CBCH) is a type of downlink channel used specifically for transmitting cell broadcast messages. It provides a mechanism for delivering short message service cell broadcast (SMSCB) messages to multiple users simultaneously within a specific geographic area. This channel operates using the same physical resources as the Stand-alone Dedicated Control Channel (SDCCH), optimizing the use of available frequency spectrums without disrupting other communication services. CBCH facilitates efficient real-time information dissemination, such as weather alerts or public announcements, to a broad audience. # Common Control Channels **GSM CCCHs(Common Control Channels)** are used for conveying information from network to the Mobile Subscribers(MSs) and provide access to the Mobile Subscribers. GSM CCCHs include PCH,RACH,AGCH and CBCH. Can be used on Uplink or Downlink but only one at time # Point-to-Multipoint Channels ## Downlink ### PCH - Paging Channel Used from BTS to MS when the subscriber is **called.** ### AGCH - Access Grant Channel It asign resources to a SDCCH channel. ## Uplink ### RACH - Random Access Channel Used from MS to BTS when subscriber makes a call. # PCH - Paging Channel Downlink - Used from BTS to MS when the subscriber is **called.** ### # RACH - Random Access Channel Uplink - Used from MS to BTS when subscriber makes a call. # AGCH - Access Grant Channel Downlink - It asign resources to a SDCCH channel. # Dedicated Channels Bi Directional Channels ### TCH/F - Traffic Channel Fullrate bit rate of 22.8 kbps ### TCH/H - Traffic Channel Halfrate bit rate of 11.4 kbps ### # Point-To-Point Signalling #### Point-To-Point Signalling Point-to-point signaling refers to a communication method where a direct and dedicated communication path is established between two endpoints. This type of signaling is often used in telecommunications and networking to facilitate reliable data transmission between specific nodes or devices without interference from others. Each connection in point-to-point signaling is unique, providing a secure and direct line for data exchange. # SDCCH - Stand-alone Dedicated Control Channel Signaling exchange with the network Authentication Cyphering Call setup Transmit SMS #### SDCCH - Stand-alone Dedicated Control Channel The Stand-alone Dedicated Control Channel (SDCCH) is a crucial component in GSM networks. It manages signaling and control operations between mobile stations and the network, facilitating tasks such as: * **Call Setup**: Handling the initial phase of establishing a voice call. * **Location Updating**: Allowing mobile devices to update their location in the network. * **SMS Transmission**: Assisting in sending and receiving SMS messages. * **Authentication and Encryption**: Ensuring secure communication through verification and privacy measures. SDCCH operates independently of traffic channels, enabling efficient management of network resources. # SACCH - Slow Associated Control Channel measurement reports to the network,power control and timing advance ### Slow Associated Control Channel (SACCH) The Slow Associated Control Channel (SACCH) is a dedicated channel used in mobile communications for the transmission of control and signaling information between the mobile station (MS) and the base station subsystem (BSS). It operates alongside voice or data channels to provide essential control functions. SACCH supports tasks such as: * **Measurement Reports:** The SACCH is responsible for transmitting measurement reports from the mobile station. These reports include information about the signal quality and strength of neighboring cells, which aids the network in making decisions about handovers and optimizing the connection quality. * **Power Control:** SACCH facilitates power control mechanisms by enabling the network to instruct the mobile station on the required power levels for transmission. This helps in maintaining optimal signal strength and reducing interference, thereby improving overall network efficiency. * **Timing Advance:** Additionally, SACCH manages timing advance adjustments, which are necessary to synchronize the timing of transmissions from the mobile station to the base station. This ensures that signals from different mobile stations do not interfere with each other, particularly in TDMA-based systems. By effectively handling these control activities, SACCH plays a crucial role in maintaining the quality and reliability of wireless communications. # FACCH - Fast Associated Control Channel #### Fast Associated Control Channel (FACCH) The Fast Associated Control Channel (FACCH) is a channel utilized in GSM networks to send urgent signaling information. It temporarily takes over voice traffic channels to ensure that critical control messages are transmitted with minimal delay. FACCH is particularly useful during call setup, handovers, and call release to ensure smooth operation and maintain connection quality without a noticeable impact on voice call continuity. # A interface A interface connects a MSC and BSC Transcoder. As data from User and Signaling 64 kbps per time slot 128 channels Adaptation from ISDN-S2M interface, the interface can handle up to 8192 kbps of data. This interface is crucial for ensuring efficient communication and data transfer between the MSC and BSC Transcoder, maintaining the integrity of both user data and signaling information. The adaptation from the ISDN-S2M interface ensures compatibility and streamlined operations within the cellular network infrastructure. #### Understanding the ISDN-S2M Interface in Cellular Networks The ISDN-S2M interface is essential for seamless integration within cellular networks, connecting the Mobile Switching Center (MSC) and the Base Station Controller (BSC) Transcoder. * **Data Handling:** The interface supports high-speed data transfer at rates up to 8192 kbps. * **Channel Capacity:** It utilizes 128 channels, with each time slot capable of transmitting at 64 kbps. * **Purpose:** This ensures that both user data and signaling information are transmitted effectively, maintaining data integrity across the network infrastructure. # A-ter interface Connection between BTS and BSC 16 kbps 32 channels #### A-ter Interface The A-ter interface is used to connect the BTS (Base Transceiver Station) to the BSC (Base Station Controller). It operates at a standard rate of 16 kbps per channel, with the capability of handling up to 32 channels. This interface facilitates the communication and control signals transmitted between BTS and BSC, ensuring efficient management and coordination of mobile network operations. # A-bis interface A-bis interface connects BSC to BTS by cable or microwave links. Type of Data: 1. User Information 2. Signalling Information 3. Synchronization data 4. O\&M alarms ### TRX Signalling between BSC and BTS (TRansceiver) is the device responsible for transmitting and receiving radio signals between the BTS and the mobile devices. Each TRX handles multiple channels and is crucial for maintaining communication in a mobile network. # Um interface Use TDM frame - 8 bits Mobile and BTS interface by Air ### ARFCN - Downlink & Uplink #### FDMA #### TDMA TDMA Frame has 8 time slots or physical channels - 4.62 ms 1. Hyperframe 2. Superframe 3. 51 multiframe 4. 26 multiframe ### Modulation GMSK TDMA (Time Division Multiple Access) is a channel access method for shared-medium networks. It allows multiple users to share the same frequency channel by dividing the signal into different time slots. Each user transmits in rapid succession, one after the other, each using their own time slot. This prevents interference from multiple transmissions over a single frequency. In TDMA, a frame consists of 8 time slots, or physical channels, each occupying 4.62 ms. This structure is organized as follows: 1. **Hyperframe**: The highest level in the GSM hierarchy, consisting of 2,048 Superframes. 2. **Superframe**: Comprises 51 Multiframes. 3. **51 Multiframe**: Contains 51 TDMA frames. 4. **26 Multiframe**: Contains 26 TDMA frames, typically used for control channels. Modulation in TDMA uses GMSK (Gaussian Minimum Shift Keying), a type of continuous-phase frequency shift keying that minimizes bandwidth and power requirements. # Cell Id **PLMN Cell ID** PLMN (Public Land Mobile Network) Cell ID is a unique identifier used in mobile telecommunication networks. It combines the PLMN code, which identifies the carrier's network, with the cell ID, which identifies a specific cell tower within that network. This identifier plays a crucial role in mobile communication, helping in tracking and managing connections across the network. # LAI - Location Area Identification are controller by VLH ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2Fne3gAOdnzc9wulA5R4MI%2FLAI_IMAGE.png?alt=media\&token=ff5f7f8e-590c-4cb3-a71d-f8e7f803812c) Location Area Identification (LAI) is a unique code used in mobile networks to identify a specific location area within a Public Land Mobile Network (PLMN). It consists of: * **Mobile Country Code (MCC)**: Identifies the country. * **Mobile Network Code (MNC)**: Identifies the network within the country. * **Location Area Code (LAC)**: Identifies the specific location area within the network. LAI is crucial for managing the location and registration of mobile subscribers when they move between different areas, ensuring seamless connectivity and effective resource allocation. # ARFCNs {% embed url="" %} An ARFCN (Absolute Radio Frequency Channel Number) is a unique identifier for a pair of physical radio carriers used in wireless communication. It helps in distinguishing different channels and aids in the effective allocation of frequency spectrum for mobile networks. # System information-1(SI1) Cell ARFCN, RACH parameters required to access the system by MS and hopping related information are sent in this SI message. System Information 1 (SI1) is a message broadcast by GSM base stations to provide critical information to mobile stations (MS). It includes the location area code (LAC), cell identity (CI), and information about neighboring cells. This data allows the MS to determine whether it can access the network and helps in the cell selection and reselection processes. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FO5EvAPoQcXFHYt6NYi2R%2Fimage.png?alt=media\&token=61d2223d-d056-441b-80a9-29f84ccfd28a) ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FQbnMa0bjtGPmInJlkzrt%2Fimage.png?alt=media\&token=cb01fc8e-e860-43d9-8a49-d6da51f30f32) {% embed url="" %} # System information-2(SI2) Neighbour BCCH frequencies and PLMN information are sent in this SI. MS uses these frequencies for signal strength measurements required for handover. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2F9ejow3Ee1Z7VbRlMmmqn%2Fimage.png?alt=media\&token=130605f2-4d55-4ba5-9d85-b5a4a3fbed78) #### System Information-2 (SI2) **System Information-2 (SI2)** is a critical broadcast message used in cellular networks. It contains essential configuration details, such as: * Access parameters for the Random Access Channel (RACH) * Information on the broadcast control channel (BCCH) * Timing Advance (TA) details This information helps devices establish and maintain communication with the network efficiently. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FDQQ2lhqZCnmt1Ezw3i0W%2Fimage.png?alt=media\&token=b2a086bc-c119-4877-aff7-0743c56395b1) # System information-2bis(SI-2bis) RACH control and BCCH extension on neighbor cells ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FUwxPAlbpzzCDty7KE3Jg%2Fimage.png?alt=media\&token=13d27510-1a69-4fb2-b08c-94ec1d8792bf) # System information-2ter(SI-2ter) Information of BCCH extended allocated on which neighbor cells are provided in this SI. Broadcasted optionally on BCCH by the network to all the MSs. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FWaFfRQS11q8jn8oyJrcd%2Fimage.png?alt=media\&token=6e9090e0-6f07-4fed-90c3-cfdb46d7000b) # System information-2 Quarter (SI-2Quater) 3G neighbor cell related information ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FGXKnFaWq95g9f8eJdJVw%2Fimage.png?alt=media\&token=609f15dc-22f5-4735-8683-d1693b9fc744) ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2Fy0zeT4HLYJXAIPnkIgzV%2Fimage.png?alt=media\&token=82cffd74-e757-4f45-a9ff-2cf0e43d7f2e) # System information-3 (SI3) Carry following : 1. LAI of the current location area, 2. Cell identity, 3. Control channel information required to calculate paging group, 4. Cell options to achieve good performance in the cell, 5. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FICyptpuEEjQp3U1FXkjf%2Fimage.png?alt=media\&token=96732c1d-1a14-4af0-a7cb-727ec1d33f6d) ![System information-3 (SI3)](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FkJM2FBWjE5jhaYTEW8Wb%2Fimage.png?alt=media\&token=982dd524-5a00-466b-9848-3d5376abf361) # System information-4 (SI4) CBCH and CBCH related frequency information, LAI, Cell selection parameters and RACH control information are carried by this SI4 message. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FjFtOuWiqnQfURQtogCS4%2Fimage.png?alt=media\&token=014ac1b6-6eda-44b7-94f5-be3f054c45c0) ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2F0rJJ34RHGGEgJG0PTvyk%2Fimage.png?alt=media\&token=add634c6-2b5d-41b6-9db2-78862391cea5) # System information-5 (SI5) It carries neighbor cell informations. In active mode, MS sends measurement reports in the uplink and output power/timing advance information in the downlink (on SACCH). Also gets BCCH carrier related ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FoNFQU33LtsEjYXGkxV3n%2Fimage.png?alt=media\&token=4dafa61e-784f-4473-a05b-60c45ec661be) ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FyhxZDcREEgW6X0C2omTl%2Fimage.png?alt=media\&token=b75c8762-c369-4d22-b28c-da8b9fca9506) ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FQvCKKoHNCh7QYheNboXG%2Fimage.png?alt=media\&token=2525f278-7b89-4509-9d04-dbf252ed13e7) # System information-6 (SI6) Information on LAI, cell options, Cell identity and PLMN permitted or not is transmitted on this SI. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2Fz9PHiHuVDt6n02IFSDz1%2Fimage.png?alt=media\&token=05b93f11-b3b6-4ec2-ae23-6c0cc51733d3) # System information-7 (SI7) Cell re-selection parameters needed by MS are sent on this SI.
# System information-8 (SI8) Cell re-selection parameters needed by MS are sent on this SI. # System information-9 (SI9) Scheduling related some of the informations are sent on this SI. # System information-13 (SI13) Carry GPRS related information needed for PS call. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FSjmwb8w1qwW4xKvdRQmD%2Fimage.png?alt=media\&token=024303ee-5a24-463b-8d87-3a85a0b8e889) # Page 2 {% file src="/files/y9vtKaKCTLPON1i0zGLS" %} # Paging request type 1 This message is sent on the CCCH by the network to up to two mobile stations to trigger channel access by these. The mobile stations are identified by their TMSI or IMSI. See Table 9.22/GSM 04.08. The L2 pseudo length of this message is the sum of lengths of all information elements present in the message except the P1 Rest Octets and L2 Pseudo Length information elements. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FieqrhCKeQVrgGavRJhwV%2Fimage.png?alt=media\&token=a7c1917b-fedd-4549-8202-2fa788db7d81) ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FXzFJ5oJEag4Qi8qdjKEn%2Fimage.png?alt=media\&token=d6b2db1d-c1f4-4cba-9a5d-acba5ceff610) This message is sent from the network on the Common Control Channel (CCCH) to prompt one or up to two mobile stations to initiate channel access. The targeted mobile stations are identified using their Temporary Mobile Subscriber Identity (TMSI) or International Mobile Subscriber Identity (IMSI). The L2 pseudo length, which is crucial for message integrity, is calculated by summing the lengths of all present information elements except for the P1 Rest Octets and L2 Pseudo Length information elements. For further details, refer to Table 9.22 in GSM 04.08. # Paging request type 2 This message is sent on the CCCH by the network to two or three mobile stations to trigger channel access by these. Two of the mobile stations are identified by their TMSI while the third is identified by its TMSI or IMSI. See Table 9.23/GSM 04.08. The L2 pseudo length of this message is the sum of lengths of all information elements present in the message except the P2 Rest Octets and L2 Pseudo Length information elements. ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FyxpPbcSMjWHI3tcK4NqW%2Fimage.png?alt=media\&token=32968904-d25d-44fb-902c-7d34e437d83a) ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FeW8Q1GAvX41EZQtVxZ3c%2Fimage.png?alt=media\&token=441420d6-9993-423c-b741-db60504d089a) # Intro Table 9.38/GSM 04.08 summarizes the messages for mobility management ![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2Fvte0zEofPaGBbIfFHGua%2Fimage.png?alt=media\&token=c30eeca0-e60a-474f-a670-43840a58ea87) To learn more about the GSM technical specifications, you can refer to the ETSI document linked [here](https://www.etsi.org/deliver/etsi_gts/04/0408/05.00.00_60/gsmts_0408v050000p.pdf). # Registration messages Registration messages: Reference IMSI DETACH INDICATION 9.2.12 LOCATION UPDATING ACCEPT 9.2.13 LOCATION UPDATING REJECT 9.2.14 LOCATION UPDATING REQUEST 9.2.15 {% embed url="" %} The document referenced appears to be about the GSM technical specifications, focusing on various signaling messages such as IMSI Detach Indication, Location Updating Accept/Reject, and Location Updating Request. For detailed explanations of these messages, please refer to the [ETSI GSM 04.08 document](https://www.etsi.org/deliver/etsi_gts/04/0408/05.00.00_60/gsmts_0408v050000p.pdf). IMSI DETACH INDICATION 9.2.12: This message is sent by a mobile station to notify the network that it is detaching, helping to manage resources effectively. LOCATION UPDATING ACCEPT 9.2.13: This message confirms that the location update request from a mobile station has been successfully processed. LOCATION UPDATING REJECT 9.2.14: This message is sent when a location update request cannot be processed by the network, including a reason code. LOCATION UPDATING REQUEST 9.2.15: This message is sent by a mobile station to update its location in the network. # IMSI DETACH INDICATION ### IMSI Detach Indication An IMSI Detach Indication is a signal sent by a mobile device to a network to indicate that the device is disconnecting and going offline. This helps the network update its records and manage resources efficiently. # LOCATION UPDATING ACCEPT # LOCATION UPDATING REJECT # LOCATION UPDATING REQUEST # Security messages # Connection management messages # Miscellaneous message