Mobile Communications/Technical Innovations of LTE - Revision history

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 $\text{Example 2:}$&nbsp; The term&nbsp; "MIMO"&nbsp; summarizes multi-antenna techniques with different properties, each of which can be useful in certain situations.&nbsp; The following description is based on the four diagrams shown here.<br>
-[[File:EN_Mob_T_4_2_S5b.png|right|frame|Four multi-antenna procedures with different properties '''KORREKTUR: multiple simultaneous'''|class=fit]]
+[[File:EN_Mob_T_4_2_S5b_v2.png|right|frame|Four multi-antenna procedures with different properties|class=fit]]
 *If the mostly independent channels of a MIMO system are assigned to a single user (top left diagram), one speaks of&nbsp; "Single&ndash;User MIMO".&nbsp; With 2&times;2 MIMO, the data rate is doubled compared to SISO operation and with four transmitting and receiving antennas each, the data rate can be doubled again under good channel conditions.<br>

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 In the course of the introduction of LTE, the backhaul had to be redesigned.&nbsp; It was important to keep an eye on future security, since the next generation&nbsp; "LTE Advanced"&nbsp; was already in place before the introduction.&nbsp; If one believes the experts' propaganda&nbsp; "Moore's Law" for mobile phone bandwidths, the most important factor for future security is the expensive new installation of better cables.<br>
-Due to the purely packet-oriented transmission technology, the Ethernet standard, which is also IP based, is suitable for the LTE backhaul, which is realized with the help of optical fibers.&nbsp; In 2009, the company Fujitsu presented in the study&nbsp; [Fuj09]<ref name='Fuj09'>Fujitsu Network Communications Inc.:&nbsp; 4G Impacts to Mobile Backhaul.&nbsp; [http://www.fujitsu.com/downloads/TEL/fnc/whitepapers/4Gimpacts.pdf $\text{PDF Internet document}$].</ref>,&nbsp; also the thesis that the current infrastructure will continue to play an important role for LTE backhaul for the next ten to fifteen years.<br>
+Due to the purely packet-oriented transmission technology, the Ethernet standard, which is also IP based, is suitable for the LTE backhaul, which is realized with the help of optical fibers.&nbsp; In 2009, the company Fujitsu presented in the study&nbsp; [Fuj09]<ref name='Fuj09'>Fujitsu Network Communications Inc.:&nbsp; 4G Impacts to Mobile Backhaul.&nbsp; [http://www.fujitsu.com/downloads/TEL/fnc/whitepapers/4Gimpacts.pdf "PDF Internet document"].</ref>,&nbsp; also the thesis that the current infrastructure will continue to play an important role for LTE backhaul for the next ten to fifteen years.<br>
 There are two approaches for the generation change to an Ethernet based&nbsp; backhaul</i>&nbsp;:

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 Unlike previous mobile phone standards, LTE only supports&nbsp; &raquo;'''packet-oriented transmission'''&laquo;.&nbsp; However, for speech transmission (sometimes the term "voice transmission" is used for this), a connection-oriented transmission with fixed reservation of resources would be better, since a "fragmented transmission", as is the case with the packet-oriented method, is relatively complicated.<br>
-The problem of integrating speech transmission methods was one of the major challenges in the development of LTE, as speech transmission remains the largest source of revenue for network operators.&nbsp;  There were a number of approaches, as it can be seen in the internet article &nbsp; [Gut10]<ref name='Gut10'>Gutt, E.:&nbsp; LTE - a new dimension of mobile broadband use.&nbsp; [http://www.ltemobile.de/uploads/media/LTE_Einfuehrung_V1.pdf $\text{PDF Internet document}$], 2010.</ref>.
+The problem of integrating speech transmission methods was one of the major challenges in the development of LTE, as speech transmission remains the largest source of revenue for network operators.&nbsp;  There were a number of approaches, as it can be seen in the internet article &nbsp; [Gut10]<ref name='Gut10'>Gutt, E.:&nbsp; LTE - a new dimension of mobile broadband use.&nbsp; [http://www.ltemobile.de/uploads/media/LTE_Einfuehrung_V1.pdf "PDF Internet document"], 2010.</ref>.
 '''(1)''' &nbsp; A very simple and obvious method is&nbsp; "Circuit Switched Fallback"&nbsp; $\rm (CSFB)$.&nbsp; Here a wireline transmission is used for the speech transmission.&nbsp; The principle is:

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 *The new thing about LTE is not the actual use of&nbsp; "Multiple Input Multiple Output", but the particularly intensive one, namely&nbsp; 2&times;2 MIMO&nbsp; in the uplink and maximum&nbsp; 4&times;4 MIMO&nbsp; in the downlink.
-*In the successor&nbsp; [[Mobile_Communications/LTE-Advanced - a Further Development of LTE|"LTE Advanced"&nbsp; the use of MIMO is even more pronounced, namely "4&times;4" in the uplink and "8&times;8" in the opposite direction.}}
+*In the successor&nbsp; [[Mobile_Communications/LTE-Advanced - a Further Development of LTE|"LTE Advanced"]]&nbsp; the use of MIMO is even more pronounced, namely "4&times;4" in the uplink and "8&times;8" in the opposite direction.}}
 A MIMO system has advantages compared to&nbsp; "Single Input Single Output"&nbsp; (SISO, only one transmitting and one receiving antenna).&nbsp; A distinction is made between several gains depending on the channel:
-*&raquo;<b>Power gain</b>&laquo;&nbsp; according to the number of receiving antennas: &nbsp; <br>If the radio signals arriving via several antennas are combined in a suitable way &nbsp; &rArr; &nbsp; [https://en.wikipedia.org/wiki/Maximal-ratio_combining $\text{Maximal-ratio combining}$], the   received power is increased and the radio connection is improved.&nbsp; By doubling the antennas, a power gain of maximum 3 dB is achieved.<br>
+*&raquo;<b>Power gain</b>&laquo;&nbsp; according to the number of receiving antennas: &nbsp; <br>If the radio signals arriving via several antennas are combined in a suitable way &nbsp; &rArr; &nbsp; [https://en.wikipedia.org/wiki/Maximal-ratio_combining "Maximal-ratio combining"], the   received power is increased and the radio connection is improved.&nbsp; By doubling the antennas, a power gain of maximum 3 dB is achieved.<br>
-*&raquo;<b>Diversity gain</b>&laquo; through&nbsp; [https://en.wikipedia.org/wiki/Antenna_diversity $\text{Spatial Diversity}$]:&nbsp; <br>If several spatially separated receiving antennas are used in an environment with strong multipath propagation, the fading at the individual antennas is mostly independent from each other and the probability that all antennas are affected by fading at the same time is very low.<br>
+*&raquo;<b>Diversity gain</b>&laquo; through&nbsp; [https://en.wikipedia.org/wiki/Antenna_diversity "Spatial Diversity"]:&nbsp; <br>If several spatially separated receiving antennas are used in an environment with strong multipath propagation, the fading at the individual antennas is mostly independent from each other and the probability that all antennas are affected by fading at the same time is very low.<br>
 *&raquo;<b>Data rate gain</b>&laquo;: &nbsp; <br> This increases the efficiency of MIMO, especially in an environment with increased multipath propagation, especially when transmitter and receiver do not have a direct line of sight and the transmission is done via reflections.&nbsp; Tripling the number of antennas for the transmitter and receiver results in approximately twice the data rate.<br><br>
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 *The redesign of the base stations&nbsp; ("eNodeB"&nbsp; instead of&nbsp; "NodeB")&nbsp; and the interface&nbsp; "X2"&nbsp; are the decisive further developments from UMTS towards LTE.&nbsp;
 *The graphic on the right illustrates in particular the reduction in complexity compared to UMTS that goes hand in hand with the new technology (left graphic).
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 The&nbsp; $\text{LTE system architecture}$&nbsp; can be divided into two major areas, too:
 *the LTE core network&nbsp; "Evolved Packet Core"&nbsp; $\rm (EPC)$,<br>
-*the air interface&nbsp; "Evolved UMTS Terrestrial Radio Access Network"&nbsp; $\rm (EUTRAN)$, a further development of&nbsp; [[Examples_of_Communication_Systems/UMTS_Network_Architecture#Access_level_architecture|$\text{UMTS Terrestrial Radio Access Network}$]]&nbsp; $\rm (UTRAN)$.<br><br>
 EUTRAN transmits the data between the terminal and the LTE base station&nbsp; ("eNodeB")&nbsp; via the so-called&nbsp; "S1"&nbsp; interface with two connections, one for the transmission of user data and a second for the transmission of signalling data.&nbsp;  You can see from the above graphic:
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 *The services previously transported through the slow "E1" standard lines would have to be switched immediately to a packet-based procedure.
 *Ethernet does not offer&nbsp; (unlike the current standard)&nbsp; any&nbsp; end&ndash;to&ndash;end&nbsp; synchronization, which can lead to severe delays or even service interruptions when changing radio cells, thus a huge loss of service quality.
-* However, in the concept&nbsp; [https://en.wikipedia.org/wiki/Synchronous_Ethernet $\text{Synchronous Ethernet}$]&nbsp; $\rm (SyncE)$, the Cisco company has already made suggestions as to how synchronization could be realized.<br>
 For conurbations, a direct conversion of the backhaul would certainly be worthwhile, as relatively few new cables would have to be laid for a comparatively high number of new users.
-In rural areas, however, major excavation work would quickly result in high costs.&nbsp; However, this is exactly the area which must be covered first, according to the&nbsp; [[Mobile_Communications/General Information on the LTE Mobile Communications Standard#LTE frequency band splitting|$\text{agreement reached}$]]&nbsp; between the federal government and the (German) mobile phone operators.&nbsp; Here, the mostly existing microwave radio link would have to be (and probably will be) extended to high data rates.<br>
+In rural areas, however, major excavation work would quickly result in high costs.&nbsp; However, this is exactly the area which must be covered first, according to the&nbsp; [[Mobile_Communications/General Information on the LTE Mobile Communications Standard#LTE frequency band splitting|"agreement reached"]]&nbsp; between the federal government and the (German) mobile phone operators.&nbsp; Here, the mostly existing microwave radio link would have to be (and probably will be) extended to high data rates.<br>
 ==Exercises for the chapter==

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 == Multiple Antenna Systems==
 <br>
-If a radio system uses several transmitting and receiving antennas, one speaks of&nbsp; $\text{Multiple Input Multiple Output}$&nbsp; $\rm (MIMO)$.&nbsp; This is not an LTE specific development.&nbsp; WLAN, for example, also uses this technology.
+If a radio system uses several transmitting and receiving antennas, one speaks of&nbsp; &raquo;'''Multiple Input Multiple Output'''&raquo;&nbsp; $\rm (MIMO)$.&nbsp; This is not an LTE specific development.&nbsp; WLAN, for example, also uses this technology.
 {{GraueBox|TEXT=
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 *The new thing about LTE is not the actual use of&nbsp; "Multiple Input Multiple Output", but the particularly intensive one, namely&nbsp; 2&times;2 MIMO&nbsp; in the uplink and maximum&nbsp; 4&times;4 MIMO&nbsp; in the downlink.
-*In the successor&nbsp; [[Mobile_Communications/LTE-Advanced - a Further Development of LTE|$\text{LTE Advanced}$]]&nbsp; the use of MIMO is even more pronounced, namely "4&times;4" in the uplink and "8&times;8" in the opposite direction.}}
+*In the successor&nbsp; [[Mobile_Communications/LTE-Advanced - a Further Development of LTE|"LTE Advanced"&nbsp; the use of MIMO is even more pronounced, namely "4&times;4" in the uplink and "8&times;8" in the opposite direction.}}

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 '''(1)''' &nbsp; A very simple and obvious method is&nbsp; "Circuit Switched Fallback"&nbsp; $\rm (CSFB)$.&nbsp; Here a wireline transmission is used for the speech transmission.&nbsp; The principle is:
-*The terminal device logs on to the LTE network and in parallel also to a GSM  or UMTS network.&nbsp; When an incoming call is received, the terminal device receives a message from the&nbsp; "Mobile Management Entity"&nbsp; $\text{(MME}$,&nbsp; control node in the LTE network for user authentication$)$, whereupon a wireline transmission via the GSM  or the UMTS network is established.
+#The terminal device logs on to the LTE network and in parallel also to a GSM  or UMTS network.&nbsp; When an incoming call is received, the terminal device receives a message from the&nbsp; "Mobile Management Entity"&nbsp; $\text{(MME}$,&nbsp; control node in the LTE network for user authentication$)$, whereupon a wireline transmission via the GSM  or the UMTS network is established.
-*A disadvantage of this solution&nbsp; (actually it is a "problem concealment")&nbsp; is the greatly delayed connection establishment.&nbsp; In addition,&nbsp; CSFB prevents the complete conversion of the network to LTE.
+#A disadvantage of this solution&nbsp; (actually it is a "problem concealment")&nbsp; is the greatly delayed connection establishment.&nbsp; In addition,&nbsp; CSFB prevents the complete conversion of the network to LTE.
-'''(2)''' &nbsp; Another possibility for the integration of speech/voice in a packet-oriented transmission system is offered by&nbsp; "Voice over LTE via GAN"&nbsp; $\rm (VoLGA)$, which is based on the &nbsp; [https://en.wikipedia.org/wiki/Generic_Access_Network $\text{Generic Access Network}$]&nbsp; developed by&nbsp; [[Mobile_Communications/General_Information_on_the_LTE_Mobile_Communications_Standard#3GPP_-_Third_Generation_Partnership_Project| $\text{3GPP}$]].&nbsp; In brief, the principle can be described as follows:
+'''(2)''' &nbsp; Another possibility for the integration of speech/voice in a packet-oriented transmission system is offered by&nbsp; "Voice over LTE via GAN"&nbsp; $\rm (VoLGA)$, which is based on the &nbsp; [https://en.wikipedia.org/wiki/Generic_Access_Network "Generic Access Network"]&nbsp; developed by&nbsp; [[Mobile_Communications/General_Information_on_the_LTE_Mobile_Communications_Standard#3GPP_-_Third_Generation_Partnership_Project| $\text{3GPP}$]].&nbsp; In brief, the principle can be described as follows:
-* GAN enables line-based services via a packet-oriented network (IP network), for example $\rm WLAN$&nbsp; ("Wireless Local Area Network").&nbsp; With compatible end devices one can register oneself in the GSM network over a WLAN connection and use line-based services.&nbsp; VoLGA uses this functionality by replacing WLAN with LTE.
+# GAN enables line-based services via a packet-oriented network (IP network), for example $\rm WLAN$&nbsp; ("Wireless Local Area Network").&nbsp; With compatible end devices one can register oneself in the GSM network over a WLAN connection and use line-based services.&nbsp; VoLGA uses this functionality by replacing WLAN with LTE.
-* The fast implementation of VoLGA is advantageous, as no lengthy new development or changes to the core network are necessary.&nbsp; However, a so-called&nbsp; "VoLGA Access Network Controller"&nbsp; $\rm (VANC)$&nbsp; must be added to the network as hardware.&nbsp; This takes care of the communication between the end device and the&nbsp; "Mobile Management Entity"&nbsp; or the core network.<br><br>
+# The fast implementation of VoLGA is advantageous, as no lengthy new development or changes to the core network are necessary.&nbsp; However, a so-called&nbsp; "VoLGA Access Network Controller"&nbsp; $\rm (VANC)$&nbsp; must be added to the network as hardware.&nbsp; This takes care of the communication between the end device and the&nbsp; "Mobile Management Entity"&nbsp; or the core network.<br><br>
 Even though VoLGA does not need to use a GSM  or UMTS network for voice connections like CSFB, it was considered by the majority of the mobile community as an (unsatisfactory) bridge technology due to its user-friendliness.&nbsp; T&ndash;Mobile has long been a proponent of the VoLGA technology, but they also stopped further development in February 2011.<br>
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 The technical facts about IMS are:
-*The IMS basic protocol is the one from&nbsp; "Voice over IP"&nbsp; known&nbsp; [https://de.wikipedia.org/wiki/Session_Initiation_Protocol $\text{Session Initiation Protocol}$]&nbsp; $\rm (SIP)$.&nbsp;  This is a network protocol that can be used to establish and control connections between two users.
+*The IMS basic protocol is the one from&nbsp; "Voice over IP"&nbsp; known&nbsp; [https://de.wikipedia.org/wiki/Session_Initiation_Protocol "Session Initiation Protocol"]&nbsp; $\rm (SIP)$.&nbsp;  This is a network protocol that can be used to establish and control connections between two users.
 * This protocol enables the development of a completely&nbsp; (for data <u>and</u> voice)&nbsp; IP based network and is therefore future-proof.<br>
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 According to all the experts, VoLTE will have a positive impact on mobile telephony in the same way that LTE has driven the mobile Internet forward since 2011.&nbsp; Key benefits for users are:
-*A higher voice quality, as VoLTE uses&nbsp; [[Examples_of_Communication_Systems/Telecommunications_Aspects_of_UMTS#Improvements_regarding_speech_coding| $\text{AMR Wideband Codecs}$]]&nbsp; with 12.65 or 23.85 kbit/s.&nbsp; Furthermore, the VoLTE data packets are prioritized for lowest possible latencies.<br>
+*A higher voice quality, as VoLTE uses&nbsp; [[Examples_of_Communication_Systems/Telecommunications_Aspects_of_UMTS#Improvements_regarding_speech_coding| "AMR wideband codecs"]]&nbsp; with 12.65 or 23.85 kbit/s.&nbsp; Furthermore, the VoLTE data packets are prioritized for lowest possible latencies.<br>
 *An enormously accelerated connection setup  within one or two seconds, whereas with&nbsp; "Circuit Switched Fallback" (CSFB) it takes an unpleasantly long time to establish a connection.<br>
@@ Line 56: / Line 57: @@
 *A better spectral efficiency: &nbsp; Twice as many calls are possible in the same frequency band than with "3G".&nbsp; In other words: &nbsp; More capacity is available for data services for the same number of calls.<br>
-*An easy implementation of&nbsp; [https://en.ryte.com/wiki/Rich_Media $\text{Rich Media Services}$]&nbsp; $\rm (RCS)$, e.g. for video telephony or future applications that can be used to attract new customers.<br>
+*An easy implementation of&nbsp; [https://en.ryte.com/wiki/Rich_Media "Rich Media Services"]&nbsp; $\rm (RCS)$, e.g. for video telephony or future applications that can be used to attract new customers.<br>
 *A better acceptance of the higher provisioning costs by LTE customers if you don't need to outsource to a "low-value" network like "2G" or "3G" for telephony.
@@ Line 69: / Line 70: @@
 *Often LTE is operated in the "frequency neighborhood" of established radio transmission systems, which are expected to be switched off soon.&nbsp; If the demand increases, LTE can be gradually expanded to the frequency range that is becoming available.<br>
-*For example, the migration of television channels after digitalization: &nbsp; A part of the LTE network will be located in the VHF frequency range around 800 MHz, which has now been freed up, see&nbsp; [[Mobile_Communications/General_Information_on_the_LTE_Mobile_Communications_Standard#LTE_frequency_band_splitting|$\text{Frequency Band Splitting graphic}$]].<br>
+*For example, the migration of television channels after digitalization: &nbsp; A part of the LTE network will be located in the VHF frequency range around 800 MHz, which has now been freed up, see&nbsp; [[Mobile_Communications/General_Information_on_the_LTE_Mobile_Communications_Standard#LTE_frequency_band_splitting|"frequency band splitting graphic"]].<br>
 *Actually the bandwidths could be selected with a degree of fineness of up to 15 kHz&nbsp; (corresponding to an OFDMA subcarrier).&nbsp; However, since this would unnecessarily produce overhead, a duration of&nbsp; &raquo;'''one millisecond'''&laquo;&nbsp; and a bandwidth of&nbsp; &raquo;'''180 kHz'''&laquo;&nbsp; has been specified as the smallest addressable LTE resource.&nbsp; Such a block corresponds to twelve subcarriers (180 kHz divided by 15 kHz).<br><br>
@@ Line 87: / Line 88: @@
 Since otherwise some LTE specific functions would not work, at least six blocks must be provided.
 *The relative overhead is comparatively high at small channel bandwidth (1.4 MHz): &nbsp; (1.4 &ndash; 6 &middot; 0.18)/1.4 &asymp; 22.8%.
 *From a bandwidth of 3 MHz the relative overhead is constant 10%.
 *It also applies that all end devices must also support the maximum bandwidth of 20 MHz &nbsp; [Ges08]<ref name='Ges08'></ref>
 == FDD, TDD and half-duplex method==
 <br>
-[[File:EN_Mob_T_4_2_S3a.png|right|frame|Transmission scheme for FDD (top) or TDD (bottom)|class=fit]]
+Another important innovation of LTE is the half&ndash;duplex procedure, which is a mixture of the two from UMTS already known  [[Examples_of_Communication_Systems/General_Description_of_UMTS#Full_duplex|"duplex procedures"]]:
-Another important innovation of LTE is the half&ndash;duplex procedure, which is a mixture of the two from UMTS already known  [[Examples_of_Communication_Systems/General_Description_of_UMTS#Full_duplex|$\text{duplex procedures}$]]:
-*$\text{Frequency Division Duplex}$&nbsp; $\rm (FDD)$, and<br>
+*&raquo;'''Time Division Duplex'''&laquo;&nbsp; $\rm (TDD)$ .<br><br>
 Such duplexing is necessary to ensure that uplink and downlink are clearly separated from each other and that transmission runs smoothly.&nbsp; The diagram illustrates the difference between FDD based and TDD based transmission.<br>
 Using the FDD and TDD methods, LTE can be operated in paired and unpaired frequency ranges.
-<br clear=all>
 The two methods are present opposing requirements:
 *$\rm FDD$&nbsp; requires a paired spectrum, i.e. one frequency band for transmission from the base station to the terminal ("downlink") and one for transmission in the opposite direction ("uplink").&nbsp; Downlink and uplink can be used at the same time.<br>
@@ Line 108: / Line 113: @@
 *$\rm TDD$&nbsp; was designed for unpaired spectra.&nbsp; Now only one band is needed for uplink and downlink.&nbsp; However, transmitter and receiver must now alternate during transmission.&nbsp; The main problem of TDD is the required synchronicity of the networks.<br><br>
-In the graphic above the differences between FDD and TDD can be seen. In TDD a&nbsp; "Guard Period"&nbsp; has to be inserted when changing from downlink to uplink (or vice versa) to avoid an overlapping of the signals.<br>
+In the graph the differences between FDD and TDD can be seen: &nbsp;
 Although FDD is likely to be used more in practice&nbsp; (and FDD frequencies were much more expensive for the providers), there are several reasons for TDD:
@@ Line 124: / Line 131: @@
 The fact that this aspect was of great importance in the standardization can also be seen in the use of&nbsp; "OFDMA"&nbsp; in the downlink and of&nbsp; "SC&ndash;FDMA"&nbsp; in the uplink:
 *This results in a longer battery life of the end devices and allows the use of cheaper components.
 *More about this can be found in chapter&nbsp; [[Mobile_Communications/The_Application_of_OFDMA_and_SC-FDMA_in_LTE | "The Application of OFDMA and SC-FDMA in LTE"]].

@@ Line 160: / Line 160: @@
 [[File:EN_Mob_T_4_2_S5b.png|right|frame|Four multi-antenna procedures with different properties '''KORREKTUR: multiple simultaneous'''|class=fit]]
-*If the mostly independent channels of a MIMO system are assigned to a single user (top left diagram), one speaks of&nbsp; "Single&ndash;User MIMO".&nbsp; With 2&times;2 MIMO, the data rate is doubled compared to SISO operation and with four transmit '''KORREKTUR: transmitting''' and receiving antennas each, the data rate can be doubled again under good channel conditions.<br>
+*If the mostly independent channels of a MIMO system are assigned to a single user (top left diagram), one speaks of&nbsp; "Single&ndash;User MIMO".&nbsp; With 2&times;2 MIMO, the data rate is doubled compared to SISO operation and with four transmitting and receiving antennas each, the data rate can be doubled again under good channel conditions.<br>
 ::LTE allows maximum 4&times;4 MIMO but only in the downlink.&nbsp; Due to the complexity of multi-antenna systems, only laptops with LTE modems can be used as receivers (end devices) for 4&times;4 MIMO.&nbsp; For a mobile phone, the use is generally limited to 2&times;2 MIMO.