This article introduce the GSM definded by 3GPP.

History

The following table shows some of the important events in the rollout of the GSM system.

Also refer to GSM History.

Standards

Refer to the table in section Specification Numbering for the GSM standards, and the table in section 3GPP Standards for the GSM features in each Release.

Network Structure

The following figure shows the GSM network structure, which is got from wikipedia:

Also refer to GSM Network Architecture for details in R4.

The following figure is UMTS domains and reference points from Rel-99_description_20160701:

R99 Network Structure

The following figure is UMTS and GSM Network Architecture from Rel-99_description_20160701:

Compare to R98, the entities in read blocks are new added.

R4 Network Structure

GSM Network Architecture

The following figure is Figure 1: GERAN reference architecture from TS 43.051-400 GSM/EDGE Radio Access Network (GERAN); Overall Description - Stage 2:

The following figure is Figure 4: User Plane protocols towards Packet Switched Core Network domain from TS 43.051-400 GSM/EDGE Radio Access Network (GERAN); Overall Description - Stage 2:

The following figure is Figure 5: Control Plane protocols towards Packet Switched Core Network domain from TS 43.051-400 GSM/EDGE Radio Access Network (GERAN); Overall Description - Stage 2:

The following figure is Figure 6: User Plane protocols towards Circuit-Switched Core Network domain from TS 43.051-400 GSM/EDGE Radio Access Network (GERAN); Overall Description - Stage 2:

The following figure is Figure 7: Control Plane Protocols towards Circuit-Switched Core Network Domain from TS 43.051-400 GSM/EDGE Radio Access Network (GERAN); Overall Description - Stage 2:

R5 Network Structure

The following figure is Figure 4: UTRAN Architecture from TS 25.401-5a0 UTRAN overall description:

The following figure is Figure 4b: UTRAN and GERAN Iu mode connection with Iur-g from TS 25.401-5a0 UTRAN overall description:

The following figure is Figure 1: Basic Configuration of a PLMN supporting CS and PS services and interfaces from TS 23.002-5c0 Network Architecture:

Compare to R4, the entities HLR and AuC are merged into entity HSS, and interfaces IuCS and IuPS are new added to BSC.

R6 Network Structure

The following figure is Figure 1: Basic Configuration of a PLMN supporting CS and PS services and interfaces from TS 23.002-6a0 Network Architecture:

Compare to R5, the entities CRF (Charging Rules Function), PDF (Policy Decision Function) and corresponding interfaces are new added.

R7 Network Structure

The following figure is Figure 1: Basic Configuration of a PLMN supporting CS and PS services and interfaces from TS 23.002-760 Network Architecture:

Compare to R6, the entities PDF (Policy Decision Function) and CRF (Charging Rules Function) are merged into PCRF (Policy and Charging Rules Function).

R8 Network Structure

The following figure is Figure 1: Basic Configuration of a PLMN supporting CS and PS services and interfaces from TS 23.002-870 Network Architecture:

The network structure in R8 is the same to that in R7.

R9 Network Structure

The following figure is Figure 1: Basic Configuration of a PLMN supporting CS and PS services and interfaces from TS 23.002-960 Network Architecture:

The network structure in R9 is the same to that in R7 and R8.

R10 Network Structure

The following figure is Figure 1: Basic Configuration of a PLMN supporting CS and PS services and interfaces from TS 23.002-a30 Network Architecture:

The network structure in R10 is the same to that in R7, R8 and R9.

R11 Network Structure

The following figure is Figure 1: Basic Configuration of a PLMN supporting CS and PS services and interfaces from TS 23.002-b00 Network Architecture:

The network structure in R11 is the same to that in R7, R8, R9 and R10.

R12 Network Structure

The following figure is Figure 1: Basic Configuration of a PLMN supporting CS and PS services and interfaces from TS 23.002-c70 Network Architecture:

The network structure in R12 is the same to that in R7, R8, R9, R10 and R11.

R13 Network Structure

The following figure is Figure 1: Basic Configuration of a PLMN supporting CS and PS services and interfaces from TS 23.002-d50 Network Architecture:

The network structure in R13 is the same to that in R7, R8, R9, R10, R11 and R12.

Interfaces

The following table shows the interfaces between difference nodes in GSM network:

The following table shows the interfaces in GSM/UMTS/LTE networks, refer to section 6 PLMN basic interfaces and reference points of TS 23.002-870 Network architecture:

Channels

R99 Channels

UMTS Channels

Logical Channel

According to section 4.3.2 Logical Channels of TS 25.321-3h0 Medium Access Control (MAC) protocol specification, the MAC layer defines the following logical channels:

Transport Channel

According to section 5.2 Layer 1 Services and Functions of TS 25.301-3b0 Radio Interface Protocol Architecture, the physical layer defines the following transport channels:

Physical Channel

According to section 6 Mapping and association of physical channels of TS 25.211-3c0 Physical channels and mapping of transport channels onto physical channels (FDD), the Physical layer defines the following physical channels:

Channel Mapping

The following figure shows the channel mapping of logical channels, transport channels and physical channels:

R4 Channels

UMTS Channels

Logical Channel

According to section 4.3.2 Logical Channels of TS 25.321-4a0 Medium Access Control (MAC) protocol specification, the MAC layer defines the following logical channels:

NOTE: The logical channels in R4 are the same with that in R99.

Transport Channel

According to section 5.2 Layer 1 Services and Functions of TS 25.301-440 Radio Interface Protocol Architecture, the Physical layer defines the following transport channels:

NOTE: The transport channels in R4 are the same with that in R99.

Physical Channel

According to section 6 Mapping and association of physical channels of TS 25.211-460 Physical channels and mapping of transport channels onto physical channels (FDD), the Physical layer defines the following physical channels:

NOTE: The physical channels in R4 are the same with that in R99.

Channel Mapping

The following figure shows the channel mapping of logical channels, transport channels and physical channels:

R5 Channels

UMTS Channels

Logical Channel

According to section 4.3.2 Logical Channels of TS 25.321-5e0 Medium Access Control (MAC) protocol specification, the MAC layer defines the following logical channels:

NOTE: The logical channels in R5 are the same with that in R4.

Transport Channel

According to section 5.2 Layer 1 Services and Functions of TS 25.301-560 Radio Interface Protocol Architecture, the Physical layer defines the following transport channels:

NOTE: The transport channel HS-DSCH is new added for HSDPA in R5.

Physical Channel

According to section 6 Mapping and association of physical channels of TS 25.211-580 Physical channels and mapping of transport channels onto physical channels (FDD), the Physical layer defines the following physical channels:

NOTE1: The physical channels PDSCH, AP-AICH, CSICH and CD/CA-ICH are deleted from R5. NOTE2: The physical channels HS-PDSCH, HS-SCCH and HS-DPCCH are new added for HSDPA in R5.

Channel Mapping

The following figure shows the channel mapping of logical channels, transport channels and physical channels:

R6 Channels

Logical Channel

According to section 4.3.2 Logical Channels of TS 25.321-6i0 Medium Access Control (MAC) protocol specification, the MAC layer defines the following logical channels:

NOTE: The logical channels MCCH, MSCH and MTCH are new added for MBMS in R6.

Transport Channel

According to section 5.2 Layer 1 Services and Functions of TS 25.301-660 Radio Interface Protocol Architecture, the Physical layer defines the following transport channels:

NOTE: The transport channel E-DCH is new added for HSUPA in R6.

Physical Channel

According to section 6 Mapping and association of physical channels of TS 25.211-6a0 Physical channels and mapping of transport channels onto physical channels (FDD), the Physical layer defines the following physical channels:

NOTE: The physical channels MICH, F-DPCH, E-DPDCH, E-DPCCH, E-AGCH, E-RGCH and E-HICH are new added for HSUPA and MBMS in R6.

Channel Mapping

The following figure shows the channel mapping of logical channels, transport channels and physical channels:

R7 Channels

UMTS Channels

Logical Channel

According to section 4.3.2 Logical Channels of TS 25.321-7j0 Medium Access Control (MAC) protocol specification, the MAC layer defines the following logical channels:

NOTE: The logical channels in R7 are the same with that in R6.

Transport Channel

According to section 5.2 Layer 1 Services and Functions of TS 25.301-750 Radio Interface Protocol Architecture, the Physical layer defines the following transport channels:

NOTE: The transport channels in R7 are the same with that in R6.

Physical Channel

According to section 6 Mapping and association of physical channels of TS 25.211-7a0 Physical channels and mapping of transport channels onto physical channels (FDD), the Physical layer defines the following physical channels:

NOTE: The physical channels in R7 are the same with that in R6.

Channel Mapping

The following figure shows the channel mapping of logical channels, transport channels and physical channels:

R8 Channels

UMTS Channels

Logical Channel

According to section 4.3.2 Logical Channels of TS 25.321-8g0 Medium Access Control (MAC) protocol specification, the MAC layer defines the following logical channels:

NOTE: The logical channels in R8 are the same with that in R7.

Transport Channel

According to section 5.2 Layer 1 Services and Functions of TS 25.301-750 Radio Interface Protocol Architecture, the Physical layer defines the following transport channels:

[NOTE1] RRC state: CELL_FACH state, IDLE mode [NOTE2] RRC state: CELL_DCH

NOTE: The transport channel E-DCH (Common type) is the new added in R8.

Physical Channel

According to section 6 Mapping and association of physical channels of TS 25.211-870 Physical channels and mapping of transport channels onto physical channels (FDD), the Physical layer defines the following physical channels:

NOTE: The physical channels in R8 are the same with that in R7.

Channel Mapping

The following figure shows the channel mapping of logical channels, transport channels and physical channels:

Mobile Station (MS)

The MT plus any TE constitutes the Mobile Station (MS). That’s: MS = MT + TE.

The following figure is Figure 1: PLMN Access Reference Configuration (in A/Gb mode and GERAN Iu mode) from TS 24.002-810 PLMN Access Reference Configuration:

There are two types of MT:

• MT0 includes functions belonging to the functional group MT, with support of no terminal interfaces.

• MT2 includes functions belonging to the functional group MT, and with an interface that complies with the 3GPP TS 27.00z series Terminal Adaptation Function specifications. Accordingly, the interchange circuit mapping at the MT2 to TE interface shall comply with the ITU-T V.24 recommendation; while the physical implementation shall conform either to the ITU-T V.28, or to the IrDA IrPHY Physical signalling standard specification, or to the PCMCIA 2.1, or to the PC-Card 3.0, electrical specification or to later revisions.

  • TS 27.001 - General on Terminal Adaptation Functions (TAF) for Mobile Stations (MS)
  • TS 27.002 - Terminal Adaptation Functions (TAF) for services using asynchronous bearer capabilities

  • TS 27.003 - Terminal Adaptation Functions (TAF) for services using synchronous bearer capabilities

  • ITU-T Recommendation V.24 (1996) - List of definitions for interchange circuits between data terminal equipment (DTE) and data circuit terminating equipment (DCE)”
  • ITU T Recommendation V.28 (1993) - Electrical characteristics for unbalanced double current interchange circuits
  • Infrared Data Association IrDA - IrPHY Physical layer signalling standard
  • Personal Computer Memory Card Association - PCMCIA 2.1 or PC Card 3.0 electrical specification or later revisions

The Mobile Station (MS) related standards include:

• TS 24.002 - PLMN Access Reference Configuration

GSM Radio Access Network (GERAN)

GERAN = BSC (Base Station Controller) + BTS (Base Transceiver Station)

Overview

• TS 43.051 - GSM/EDGE Radio Access Network (GERAN); Overall Description - Stage 2

Radio Interface (Um)

The following figure is Figure 3: Assumed GERAN Model from TS 43.051-400 GSM/EDGE Radio Access Network (GERAN); Overall Description - Stage 2:

The following figure is Figure 10: Radio Interface protocol architecture from TS 43.051-400 GSM/EDGE Radio Access Network (GERAN); Overall Description - Stage 2:

• TS 45.001 - GERAN Physical layer on the radio path - General description
• TS 45.002 - Multiplexing and multiple access on the radio path
• TS 45.003 - Channel coding
• TS 45.004 - Modulation

• TS 45.005 - Radio transmission and reception

• TS 45.008 - Radio subsystem link control
• TS 45.009 - Link adaptation
• TS 45.010 - Radio subsystem synchronization
• TS 45.015 - Downlink Advanced Receiver Performance (DARP); Implementation guidelines
• TS 45.022 - Radio link management in hierarchical networks
• TS 45.050 - Background for Radio Frequency (RF) requirements

• TS 45.056 - GSM Cordless Telephony System (CTS), Phase 1; CTS-FP Radio subsystem

• TR 45.902 - Flexible Layer One (FLO)
• TR 45.903 - Feasibility Study on Single Antenna Interference Cancellation (SAIC) for GSM networks
• TR 45.912 - Feasibility study for evolved GSM/EDGE Radio Access Network (GERAN)
• TR 45.913 - Optimized transmit pulse shape for downlink Enhanced General Packet Radio Service (EGPRS2-B)
• TR 45.914 - Circuit Switched Voice Capacity Evolution for GSM/EDGE Radio Access Network (GERAN)

Abis Interface

• TS 48.051 - BSC-BTS interface General aspects
• TS 48.052 - BSC-BTS Interface Principles
• TS 48.054 - BSC-BTS Layer 1 Specification
• TS 48.056 - BSC-BTS Layer 2 Specification
• TS 48.058 - BSC-BTS Layer 3 Specification
• TS 48.060 - Inband Control of Remote Transcoders and Rate Adaptors
• TS 48.061 - Inband Control of Remote Transcoders and Rate Adaptors for Half Rate Traffic Channels

A Interface

• TS 48.001 - BSS-MSC interface General aspects
• TS 48.002 - BSS-MSC interface Interface principles
• TS 48.004 - BSS-MSC interface Layer 1 specification
• TS 48.006 - Signalling transport mechanism specification for the BSS-MSC interface
• TS 48.008 - MSC-BSS interface Layer 3 specification

Gb Interface

• TS 48.016 - BSS-SGSN interface Network Service
• TS 48.018 - BSS-SGSN BSS GPRS Protocol (BSSGP)

GSM Core Network (MAP)

MAP for GSM (prior to Release 4) is specified by 3GPP TS 09.02 (MAP v1, MAP v2).

GSM Technical Details

The following GSM technical detail is from GSM Tutorial.

Modulation

Modulation is the process of transforming the input data into a suitable format for the transmission medium. The transmitted data is demodulated back to its original form at the receiving end. The GSM uses Gaussian Minimum Shift Keying (GMSK) modulation method. Refer to 3GPP TS 45.004 Modulation.

Access Methods

Radio spectrum being a limited resource that is consumed and divided among all the users, GSM devised a combination of TDMA/FDMA as the method to divide the bandwidth among the users. In this process, the FDMA part divides the frequency of the total 25 MHz bandwidth into 124 carrier frequencies of 200 kHz bandwidth.

Each BS is assigned with one or multiple frequencies, and each of this frequency is divided into eight timeslots using a TDMA scheme. Each of these slots are used for both transmission as well as reception of data. These slots are separated by time so that a mobile unit doesn’t transmit and receive data at the same time.

Refer to 3GPP TS 45.002 Multiplexing and multiple access on the radio path.

Transmission Rate

The total symbol rate for GSM at 1 bit per symbol in GMSK produces 270.833 K symbols/second. The gross transmission rate of a timeslot is 22.8 Kbps.

GSM is a digital system with an over-the-air bit rate of 270 kbps.

Frequency Band

The uplink frequency range specified for GSM is 933 - 960 MHz (basic 900 MHz band only). The downlink frequency band 890 - 915 MHz (basic 900 MHz band only). Refer to 3GPP TS 45.005 Radio transmission and reception.

Channel Spacing

Channel spacing indicates the spacing between adjacent carrier frequencies. For GSM, it is 200 kHz. Refer to 3GPP TS 45.005 Radio transmission and reception.

Duplex Distance

Duplex distance is the space between the uplink and downlink frequencies. The duplex distance for GSM is 80 MHz, where each channel has two frequencies that are 80 MHz apart. Refer to TS 45.005 Radio transmission and reception.

Speech Coding

For speech coding or processing, GSM uses Linear Predictive Coding (LPC). This tool compresses the bit rate and gives an estimate of the speech parameters. When the audio signal passes through a filter, it mimics the vocal tract. Here, the speech is encoded at 13 kbps.

GSM Services

GSM, LTE, UMTS and IMS Call Flows

GSM offers three basic types of services:

• Telephony services or teleservices
• Data services or bearer services
• Supplementary services

Procedures

• TS 43.022 - Functions related to Mobile Station in idle mode and group receive mode

GPRS (2.5G)

General Packet Radio Service (GPRS) is a packet oriented mobile data service on the 2G and 3G cellular communication system’s Global System for Mobile Communications (GSM). GPRS was originally standardized by European Telecommunications Standards Institute (ETSI) in response to the earlier Cellular Digital Packet Data (CDPD) and i-mode packet-switched cellular technologies. It is now maintained by the 3rd Generation Partnership Project (3GPP).

GPRS is a best-effort service, implying variable throughput and latency that depend on the number of other users sharing the service concurrently, as opposed to circuit switching, where a certain Quality of Service (QoS) is guaranteed during the connection. In 2G systems, GPRS provides data rates of 56–114 kbit/second. 2G cellular technology combined with GPRS is sometimes described as 2.5G, that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate-speed data transfer, by using unused Time Division Multiple Access (TDMA) channels in, for example, the GSM system. GPRS is integrated into GSM Release 97 and newer releases.

Based on specifications in Release 97, GPRS typically reached speeds of 40Kbps in the downlink and 14Kbps in the uplink by aggregating GSM time slots into one bearer. Enhancements in R98 and R99 meant that GPRS could theoretically reach downlink speeds of up to 171Kbps.

EDGE / EGPRS (2.75G)

Enhanced Data rates for GSM Evolution (EDGE), also known as Enhanced GPRS (EGPRS), is a digital mobile phone technology that allows improved data transmission rates as a backward-compatible extension of GSM. EDGE is considered a pre-3G radio technology and is part of ITU’s 3G definition. EDGE was deployed on GSM networks beginning in 2003 - initially by Cingular (now AT&T) in the United States.

EDGE is standardized also by 3GPP as part of the GSM family, which is introduced into Release 98. A variant, so called Compact-EDGE, was developed for use in a portion of Digital AMPS (D-AMPS) network spectrum.

Through the introduction of sophisticated methods of coding and transmitting data, EDGE delivers higher bit-rates per radio channel, resulting in a threefold increase in capacity and performance compared with an ordinary GSM/GPRS connection.

EDGE can be used for any packet switched application, such as an Internet connection.

Reading should start with the 44 series and 45 series of the 3GPP specifications.

Evolved EDGE

Evolved EDGE continues in Release 7 of the 3GPP standard providing reduced latency and more than doubled performance e.g. to complement High-Speed Packet Access (HSPA). Peak bit-rates of up to 1 Mbit/s and typical bit-rates of 400 kbit/s can be expected.

Evolved EDGE improves on EDGE in a number of ways. Latencies are reduced by lowering the Transmission Time Interval by half (from 20 ms to 10 ms). Bit rates are increased up to 1 Mbit/s peak bandwidth and latencies down to 80 ms using dual carrier, higher symbol rate and higher-order modulation (32QAM and 16QAM instead of 8PSK), and turbo codes to improve error correction. And finally signal quality is improved using dual antennas improving average bit-rates and spectrum efficiency. EDGE Evolution can be gradually introduced as software upgrades, taking advantage of the installed base. With EDGE Evolution, end-users will be able to experience mobile internet connections corresponding to a 500 kbit/s ADSL service.

EDGE Evolution has:

• Improved spectral efficiency with reduced latencies down to 100ms;
• Increased throughput speeds to 1.3Mbps in the downlink and 653Kbps in the uplink.

References

• GSM Quick Guide