LTE: Inside Look
Good afternoon, Habr!
Today I would like to introduce the LTE community. Every self-respecting specialist already knows what LTE is, even on Habré there were articles - one , two , three , but in my opinion they all do not fully reveal the essence. I will try to stop in more detail on all aspects. For details, I ask under the cat.
In December 1998, an association of several organizations involved in standardization in the field of telecommunications was created, called 3GPP (3rd Generation Partnership Project) by signing the “ 3rd Generation Partnership Project Agreement” . This allowed us to combine efforts to create new technologies, as well as to ensure full compatibility of equipment in the world. Standardization organizations involved in the creation of 3GPP include ARIB (Japan), ETSI (Europe), TTA (Korea), TTS (Japan) and TIPI (USA). Among the developments 3GPP standards: W-CDMA (Wideband Code Division Multiple Access) , HSPA (High Speed Packet Access) , LTE (Long Term Evolution) .
The work of 3GPP on LTE began in November 2004 in an open discussion format accessible to any interested organizations (including non-members of 3GPP). Since December 2004, LTE has been studied for compliance with the basic requirements set forth in 3GPP TR 25.913.
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In November 2005, the main radio access technologies were chosen for use in the LTE standard. They are OFDMA on the downlink and SC-FDMA on the uplink. In July 2006, the study phase was completed and work began on creating a standard. In September 2007, the LTE specification was completed. Specs 8 versions were frozen in December 2008, and this was the basis for the first wave of LTE equipment. In September 2009, LTE 10 specifications were introduced, and from that time the technology became known as LTE-Advanced. At the end of November 2010, the International Telecommunication Union officially recognized LTE-Advanced as the fourth-generation 4G wireless standard. Formally, LTE version 7, 8, 9 (which is still used worldwide) is not 4G technology, since not recognized by the International Telecommunication Union. It was possible to reject all these formalities in the next version of the standard. It is this, the tenth, version and subsequent received the suffix "Advanced" and recognition. The new technology name comes from the term “IMT-Advanced”, which was introduced by the International Telecommunication Union in order to distinguish a new generation of mobile systems, the technical capabilities of which are beyond IMT-2000. The requirements for IMT-Advanced (International Mobile Telecommunications-Advanced) are as follows:
The structure of the LTE network is as follows:
From this scheme, it is clear that the network structure is very different from 2G and 3G networks. Significant changes have undergone both the base station subsystem and the switching subsystem. The data transfer technology between the user equipment and the base station has been changed. Data transfer protocols between network elements have also been changed. All information (voice, data) is transmitted in the form of packets. Thus, there is no longer a division into parts that process either voice information only or packet data only.
The following basic elements of the LTE network can be distinguished:
In order for the data to be transported through the LTE radio interface, various “channels” are used. They are used to distinguish different types of data and allow them to be transported through the access network more efficiently. The use of multiple channels provides a higher level interface within the LTE protocol and includes more clear and definite data segregation.
There are three categories into which various data transmission channels can be grouped:
The main manufacturers of LTE camera equipment today are Ericsson, Alcatel-Lucent, Nokia Siemens Networks, Fujitsu, Huawei Technologies, Motorola, Panasonic, Starent, ZTE. In Japan, LTE networks will be deployed in the 800 MHz, 1.5 and 2.1 GHz bands, in Europe (including Russia) - 2.5-2.7 GHz, in the USA - 700 MHz. It is assumed that by 2015, the total revenue of LTE standard network operators will be $ 150 billion (about 15% of global mobile services market revenues), and the number of subscribers worldwide will exceed 400 million.
LTE Scartel announced plans to build a LTE network in Russia in 2010, and already on December 20, 2011, the first (or the second, if you count Kazan, where the network worked for a day) was launched in Russia, the LTE network was in Novosibirsk. We are waiting, fingers crossed, launching LTE in 2012 in other cities.
Today I would like to introduce the LTE community. Every self-respecting specialist already knows what LTE is, even on Habré there were articles - one , two , three , but in my opinion they all do not fully reveal the essence. I will try to stop in more detail on all aspects. For details, I ask under the cat.
A bit of history
In December 1998, an association of several organizations involved in standardization in the field of telecommunications was created, called 3GPP (3rd Generation Partnership Project) by signing the “ 3rd Generation Partnership Project Agreement” . This allowed us to combine efforts to create new technologies, as well as to ensure full compatibility of equipment in the world. Standardization organizations involved in the creation of 3GPP include ARIB (Japan), ETSI (Europe), TTA (Korea), TTS (Japan) and TIPI (USA). Among the developments 3GPP standards: W-CDMA (Wideband Code Division Multiple Access) , HSPA (High Speed Packet Access) , LTE (Long Term Evolution) .
The work of 3GPP on LTE began in November 2004 in an open discussion format accessible to any interested organizations (including non-members of 3GPP). Since December 2004, LTE has been studied for compliance with the basic requirements set forth in 3GPP TR 25.913.
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In November 2005, the main radio access technologies were chosen for use in the LTE standard. They are OFDMA on the downlink and SC-FDMA on the uplink. In July 2006, the study phase was completed and work began on creating a standard. In September 2007, the LTE specification was completed. Specs 8 versions were frozen in December 2008, and this was the basis for the first wave of LTE equipment. In September 2009, LTE 10 specifications were introduced, and from that time the technology became known as LTE-Advanced. At the end of November 2010, the International Telecommunication Union officially recognized LTE-Advanced as the fourth-generation 4G wireless standard. Formally, LTE version 7, 8, 9 (which is still used worldwide) is not 4G technology, since not recognized by the International Telecommunication Union. It was possible to reject all these formalities in the next version of the standard. It is this, the tenth, version and subsequent received the suffix "Advanced" and recognition. The new technology name comes from the term “IMT-Advanced”, which was introduced by the International Telecommunication Union in order to distinguish a new generation of mobile systems, the technical capabilities of which are beyond IMT-2000. The requirements for IMT-Advanced (International Mobile Telecommunications-Advanced) are as follows:
- Global functionality and roaming;
- High energy efficiency;
- Interaction with other radio access systems (backward compatibility);
- Improved peak data rates to support advanced services and applications;
- High security system;
Network structure
The structure of the LTE network is as follows:
From this scheme, it is clear that the network structure is very different from 2G and 3G networks. Significant changes have undergone both the base station subsystem and the switching subsystem. The data transfer technology between the user equipment and the base station has been changed. Data transfer protocols between network elements have also been changed. All information (voice, data) is transmitted in the form of packets. Thus, there is no longer a division into parts that process either voice information only or packet data only.
The following basic elements of the LTE network can be distinguished:
- Serving SAE Gateway or simply Serving Gateway (SGW) is a serving LTE network gateway. Designed for processing and routing packet data coming from / to the base station subsystem. SGW has a direct connection to the networks of the second and third generations of the same operator, which simplifies the transfer of the connection to / from them for reasons of deterioration of the coverage area, overloads, etc. In SGW, there is no channel switching function for voice connections, since in LTE, all information, including voice, is switched and transmitted via packets.
- Public Data Network SAE Gateway or simply PDN Gateway (PGW) is the gateway to data networks of other operators for the LTE network. The main task of PGW is to route LTE network traffic to other data networks, such as the Internet, as well as GSM and UMTS networks.
- Mobility Management Entity (MME) is an LTE mobile network mobility management node. Designed for signaling processing, mainly related to the mobility management of subscribers in the network.
- Home Subscriber Server (HSS) - LTE standard subscriber data server. It is a large database and is designed to store subscriber data. In addition, the HSS generates the data necessary for encryption, authentication, and the like. An LTE network may include one or more HSSs. The number of HSS depends on the geographical structure of the network and the number of subscribers.
- The Policy and Charging Rules Function (PCRF) is an element of the cellular network of the LTE standard, which is responsible for managing the charging for communication services rendered, as well as for the quality of connections in accordance with the characteristics set for a particular subscriber.
Organization of information channels
In order for the data to be transported through the LTE radio interface, various “channels” are used. They are used to distinguish different types of data and allow them to be transported through the access network more efficiently. The use of multiple channels provides a higher level interface within the LTE protocol and includes more clear and definite data segregation.
There are three categories into which various data transmission channels can be grouped:
- Logical channels — Provides medium access control ( MAC ) services (Medium Access Control) within the LTE protocol structure. Logical channels according to the type of information transmitted are divided into logical control channels and logical traffic channels. Logical control channels are used to transmit various signaling and informational messages. Logical traffic channels transmit user data.
- Transport Channels - The physical layer transport channels offer information transfer to MAC and higher. The information of the logical channels after processing at the RLC / MAC levels is placed in the transport channels for further transmission over the radio interface in the physical channels. The transport channel determines how and with which characteristics information is transmitted over the radio interface. Informational messages at the transport level are divided into transport blocks. In each time interval of transmission (Transmission Time Interval, TTI) at least one transport block is transmitted over the air interface. With MIMO technology, it is possible to transfer up to four blocks in one TTI.
- Physical channels are transmission channels that carry user data and control messages. They vary between the ascending and descending flows, since each of them has different requirements and acts in its own way.
And finally
The main manufacturers of LTE camera equipment today are Ericsson, Alcatel-Lucent, Nokia Siemens Networks, Fujitsu, Huawei Technologies, Motorola, Panasonic, Starent, ZTE. In Japan, LTE networks will be deployed in the 800 MHz, 1.5 and 2.1 GHz bands, in Europe (including Russia) - 2.5-2.7 GHz, in the USA - 700 MHz. It is assumed that by 2015, the total revenue of LTE standard network operators will be $ 150 billion (about 15% of global mobile services market revenues), and the number of subscribers worldwide will exceed 400 million.
LTE Scartel announced plans to build a LTE network in Russia in 2010, and already on December 20, 2011, the first (or the second, if you count Kazan, where the network worked for a day) was launched in Russia, the LTE network was in Novosibirsk. We are waiting, fingers crossed, launching LTE in 2012 in other cities.
Source: https://habr.com/ru/post/136317/
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