Mobile Communications/Physical Layer for LTE - Revision history

Guenter at 13:52, 20 February 2023

2023-02-20T13:52:13Z

Guenter at 14:16, 10 February 2023

2023-02-10T14:16:08Z

Hwang at 15:01, 6 February 2023

2023-02-06T15:01:41Z

Hwang at 14:54, 6 February 2023

2023-02-06T14:54:22Z

Hwang at 14:53, 6 February 2023

2023-02-06T14:53:01Z

Hwang at 14:50, 6 February 2023

2023-02-06T14:50:59Z

Hwang at 14:46, 6 February 2023

2023-02-06T14:46:34Z

Hwang at 14:42, 6 February 2023

2023-02-06T14:42:27Z

Hwang at 14:39, 6 February 2023

2023-02-06T14:39:03Z

Hwang at 14:32, 6 February 2023

2023-02-06T14:32:23Z

@@ Line 223: / Line 223: @@
 == Scheduling for LTE ==
 <br>
-[[File:EN_LTE_T_4_4_S6.png|right|frame|Functionality of the scheduler in the LTE uplink '''KORREKTUR'''|class=fit]]
+[[File:LTE_T_4_4_S6_v2.png|right|frame|Functionality of the scheduler in the LTE uplink|class=fit]]
 All LTE base stations contain a scheduler that can be switched between
 *a total transfer rate as high as possible<br>

@@ Line 52: / Line 52: @@
 The third uplink channel&nbsp; $\rm PUCCH$&nbsp; is used exclusively for the transmission of control signals. By this one understands
-*positive and negative acknowledgements of receipt '''KORREKTUR: reception'''&nbsp; $\rm  (ACK/NACK)$,<br>
+*positive and negative acknowledgements of reception&nbsp; $\rm  (ACK/NACK)$,<br>
 *requests for repeated transmission&nbsp; $($in case of&nbsp;  $\rm  NACK)$, and<br>
 *the exchange of channel quality information between the terminal and the base station.<br><br>
@@ Line 152: / Line 152: @@
 With LTE,&nbsp; power control&nbsp; is only applied in the uplink, whereas it is more of an "slow" power control.&nbsp; This means that the procedure specified in LTE does not have to react as quickly as for example in UMTS ("W&ndash;CDMA"&nbsp;).&nbsp; The reason is that by using the orthogonal carrier system "SC&ndash;FMDA" the so-called&nbsp; [[Examples_of_Communication_Systems/Nachrichtentechnische_Aspekte_von_UMTS#Near.E2.80.93Far.E2.80.93Effekt| $\text{Near&ndash;Far problem}$]] does not exist.
-*To be precise, for LTE the power control does not control the absolute power, but the spectral power density '''KORREKTUR: power-spectral density''', i.e. the power per bandwidth.<br>
+*To be precise, for LTE the power control does not control the absolute power, but the  power-spectral density, i.e. the power per bandwidth.<br>
 *Instead of trying to smooth power peaks by temporarily reducing the transmission power, power peaks can also be used to increase the data rate for a short time.<br><br>

@@ Line 223: / Line 223: @@
 == Scheduling for LTE ==
 <br>
-[[File:EN_LTE_T_4_4_S6.png|right|frame|Functionality of the scheduler in the LTE uplink|class=fit]]
+[[File:EN_LTE_T_4_4_S6.png|right|frame|Functionality of the scheduler in the LTE uplink '''KORREKTUR'''|class=fit]]
 All LTE base stations contain a scheduler that can be switched between
 *a total transfer rate as high as possible<br>

@@ Line 183: / Line 183: @@
 == Modulation for LTE ==
 <br>
-LTE uses the modulation method&nbsp; [[Modulation_Methods/Quadratur%E2%80%93Amplitudenmodulation#Allgemeine_Beschreibung_und_Signalraumzuordnung|$\text{Quadrature Amplitude Modulation}$]]&nbsp; $\rm (QAM)$.&nbsp; Different variants are available in the uplink as well as in the downlink, namely
+LTE uses the modulation method&nbsp; [[Modulation_Methods/Quadrature_Amplitude_Modulation#General_description_and_signal_space_allocation|$\text{Quadrature Amplitude Modulation}$]]&nbsp; $\rm (QAM)$.&nbsp; Different variants are available in the uplink as well as in the downlink, namely
 [[File:P ID2290 LTE T 4 4 S5a v2.png|right|frame|Possible QAM signal space constellations in LTE|class=fit]]

@@ Line 161: / Line 161: @@
 == Hybrid Adaptive Repeat and Request ==
 <br>
-Every communication system needs a scheme for retransmission of lost data due to transmission errors to ensure sufficient transmission quality.&nbsp; In LTE&nbsp; "Hybrid Adaptive Repeat and Request"&nbsp; $\rm (HARQ)$&nbsp; was specified for this purpose.&nbsp; This procedure is also used in&nbsp; [[Examples_of_Communication_Systems/Weiterentwicklungen_von_UMTS#HARQ.E2.80.93Verfahren_und_Node_B_Scheduling| $\text{UMTS}$]]&nbsp; in a similar form.<br>
+Every communication system needs a scheme for retransmission of lost data due to transmission errors to ensure sufficient transmission quality.&nbsp; In LTE&nbsp; "Hybrid Adaptive Repeat and Request"&nbsp; $\rm (HARQ)$&nbsp; was specified for this purpose.&nbsp; This procedure is also used in&nbsp; [[Examples_of_Communication_Systems/Further_Developments_of_UMTS#HARQ_procedure_and_.22Node_B_Scheduling.22| $\text{UMTS}$]]&nbsp; in a similar form.<br>
 The procedure based on the&nbsp; "stop&ndash;and&ndash;wait"&nbsp; technique is as follows:

@@ Line 118: / Line 118: @@
 [[File:EN_LTE_T_4_4_S3b.png|left|frame|Distribution of reference symbols in the LTE downlink|class=fit]]
 <br><br><br><br><br><br><br><br>
-In addition to the&nbsp; $\rm PDCCH$,&nbsp; reference symbols are also required in the downlink to estimate the channel quality and calculate the&nbsp; "Channel Quality Indicator"&nbsp; (CQI).&nbsp;. These reference symbols are distributed over the subcarriers (different frequencies) or symbols (different times) as shown in the left graphic.
+In addition to the&nbsp; $\rm PDCCH$,&nbsp; reference symbols are also required in the downlink to estimate the channel quality and calculate the&nbsp; "Channel Quality Indicator"&nbsp; (CQI).&nbsp; These reference symbols are distributed over the subcarriers (different frequencies) or symbols (different times) as shown in the left graphic.
 <br clear=all>
 Regarding the other physical channels of the LTE downlink is to be noted:

@@ Line 86: / Line 86: @@
 == Physical channels in downlink==
 <br>
-In contrast to the uplink, LTE uses the multiple access method&nbsp; [[Mobile_Communications/The_Application_of_OFDMA_and_SC-FDMA_in_LTE#Differences_between_OFDMA_and_SC.E2.80.93FDMA|$\rm OFDMA$]]&nbsp; in the downlink, i.e. during transmission from the base station to the terminal.&nbsp; Accordingly, the 3GPP consortium specified the following physical channels for this purpose:
+In contrast to the uplink, LTE uses the multiple access method&nbsp; [[Mobile_Communications/The_Application_of_OFDMA_and_SC-FDMA_in_LTE#Differences_between_OFDMA_and_SC-FDMA|$\rm OFDMA$]]&nbsp; in the downlink, i.e. during transmission from the base station to the terminal.&nbsp; Accordingly, the 3GPP consortium specified the following physical channels for this purpose:
 *Physical Downlink Shared Channel</i>&nbsp; $\rm (PDSCH)$,<br>

@@ Line 41: / Line 41: @@
 == Physical channels in uplink==
 <br>
-LTE uses the multiple access method&nbsp; [[Mobile_Communications/The_Application_of_OFDMA_and_SC-FDMA_in_LTE#Functionality_of_SC.E2.80.93FDMA|$\rm SC&ndash;FDMA$]]&nbsp; in the uplink transmission from the terminal device to the base station.&nbsp; Accordingly, the following physical channels exist in the 3GPP specification:
+LTE uses the multiple access method&nbsp; [[Mobile_Communications/The_Application_of_OFDMA_and_SC-FDMA_in_LTE#Functionality_of_SC-FDMA|$\rm SC&ndash;FDMA$]]&nbsp; in the uplink transmission from the terminal device to the base station.&nbsp; Accordingly, the following physical channels exist in the 3GPP specification:
 *Physical Uplink Shared Channel&nbsp; $\rm (PUSCH)$,<br>
 *Physical Random Access Channel&nbsp; $\rm (PRACH)$,<br>
@@ Line 47: / Line 47: @@
-The user data are transmitted in the physical channel&nbsp; $\rm (PUSCH)$.&nbsp; The transmission speed depends on how much bandwidth is available to the user at that moment.&nbsp; The transmission is based on dynamically allocated resources in time and frequency range with a resolution of one millisecond or 180 kHz.&nbsp; This allocation is performed by the [[Mobile_Communications/Physical_Layer_for_LTE# Scheduling for LTE| $\text{Scheduler}$]]&nbsp; in the base station&nbsp; ("eNodeB").&nbsp;  A terminal device cannot transmit any data without instructions from the base station.<br>
+The user data are transmitted in the physical channel&nbsp; $\rm (PUSCH)$.&nbsp; The transmission speed depends on how much bandwidth is available to the user at that moment.&nbsp; The transmission is based on dynamically allocated resources in time and frequency range with a resolution of one millisecond or 180 kHz.&nbsp; This allocation is performed by the [[Mobile_Communications/Physical_Layer_for_LTE#Scheduling_for_LTE| $\text{Scheduler}$]]&nbsp; in the base station&nbsp; ("eNodeB").&nbsp;  A terminal device cannot transmit any data without instructions from the base station.<br>
 The exception is the use of the physical channel&nbsp; $\rm PRACH$, the only channel in the LTE uplink with non&ndash;synchronized transmission.&nbsp; The function of this channel is the request for permission to send data via one of the other two physical channels.&nbsp; By sending a&nbsp; "Cyclic Prefix"&nbsp; and a signature on the PRACH, the terminal and base station are synchronized and are thus ready for further transmissions.<br>