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EC SI (Extended Coverage System Information)

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Extended Coverage System Information (EC SI) is a type of signaling message in the Global System for Mobile Communications (GSM) standard that is used to provide additional network and service-related information to mobile devices. The EC SI messages are transmitted on a broadcast channel known as the BCCH (Broadcast Control Channel), which is continuously transmitted by the base station to all mobile devices within its coverage area.

The EC SI messages are designed to support the Extended Coverage (EC) feature, which is an optional feature that allows the network to extend its coverage area beyond its normal range. This feature is particularly useful in areas where the signal strength from the base station is weak or where there are natural obstacles that can interfere with the signal. The EC feature uses a technique called Frequency Hopping to improve the signal quality and reduce the effects of interference.

The EC SI messages contain information about the available network services, such as voice and data services, as well as information about the base station itself, such as its identity and location. This information is necessary for the mobile device to properly connect to the network and access its services. The EC SI messages are also used to provide information about the network's configuration and capabilities, such as the number of frequencies used for communication and the type of modulation used.

The EC SI messages are divided into different types, each containing specific information about the network and its services. The most common types of EC SI messages are:

  1. System Information Type 1 (SI1): SI1 contains general information about the network, such as the network's identity, the available services, and the type of modulation used. This message is broadcasted periodically, and it is one of the first messages that a mobile device receives when it enters the coverage area of a base station.
  2. System Information Type 2 (SI2): SI2 contains information about the available frequencies and their allocation. This information is used by the mobile device to determine which frequencies it can use to communicate with the network.
  3. System Information Type 3 (SI3): SI3 contains information about the neighboring base stations, their identity, and the frequencies they use. This information is used by the mobile device to perform a handover between base stations when it moves from one coverage area to another.
  4. System Information Type 4 (SI4): SI4 contains information about the broadcast channels used by the network, such as the BCCH, the Paging Control Channel (PCH), and the Common Control Channel (CCCH). This information is used by the mobile device to tune into the appropriate channels to receive the network's signaling messages.
  5. System Information Type 5 (SI5): SI5 contains information about the network's cell identity, the location area identity, and the routing area identity. This information is used by the mobile device to determine its location within the network and to properly route its communication.
  6. System Information Type 6 (SI6): SI6 contains information about the network's time and date, as well as information about the daylight saving time. This information is used by the mobile device to synchronize its clock with the network's clock.
  7. System Information Type 7 (SI7): SI7 contains information about the network's capabilities, such as the support for the Enhanced Data rates for GSM Evolution (EDGE) and High-Speed Packet Access (HSPA) standards.
  8. System Information Type 8 (SI8): SI8 contains information about the network's cell broadcast service, which is used to send broadcast messages to all mobile devices within a particular coverage area.

In addition to these types of messages, there are also extended versions of the SI messages, known as the Extended System Information (ESI) messages. The ESI messages contain additional information about the network's configuration and capabilities, such as the support for different types of handover procedures, the quality of service parameters, and the support for multimedia services. The ESI messages are broadcasted less frequently than the regular SI messages, as they contain more detailed and less frequently changing information.

The EC SI messages are transmitted using a specific format known as the System Information Message (SIM). The SIM format contains a fixed header and a variable number of information elements (IEs) that contain the actual information. The IEs are organized into different groups, each containing specific types of information. The mobile device decodes the SIM messages and extracts the relevant information from the IEs to perform different functions, such as registering with the network, selecting the appropriate frequency band, and initiating a handover procedure.

The EC SI messages play a crucial role in the operation of the GSM network, as they provide the necessary information for the mobile devices to connect to the network and access its services. The EC feature, enabled by the EC SI messages, allows the network to extend its coverage area and provide better quality of service to the users. The EC feature is particularly useful in rural areas, where the signal strength from the base station is weak or where there are natural obstacles that can interfere with the signal.

In summary, the Extended Coverage System Information (EC SI) messages are a type of signaling message in the GSM standard that provides additional network and service-related information to mobile devices. The EC SI messages support the Extended Coverage (EC) feature, which allows the network to extend its coverage area beyond its normal range using Frequency Hopping. The EC SI messages contain information about the available network services, the base station identity and location, the network's configuration and capabilities, and the neighboring base stations. The EC SI messages are transmitted periodically on the Broadcast Control Channel (BCCH) using the System Information Message (SIM) format. The EC SI messages are crucial for the mobile devices to connect to the network, access its services, and perform different functions, such as handover procedures and frequency selection.