Mobile Communications/Characteristics of GSM - Revision history

Guenter at 16:41, 20 February 2023

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Guenter at 13:40, 20 February 2023

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Hwang at 15:18, 26 January 2023

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Hwang at 14:51, 26 January 2023

2023-01-26T14:51:11Z

@@ Line 55: / Line 55: @@
 The mapping of logical to physical channels is done using the GSM frame structure.&nbsp; Here we only look to traffic channels and to the mapping in time.&nbsp; In this case, each multi&ndash;frame of &nbsp; $120 \ \rm ms$&nbsp;  duration is divided into&nbsp; $26$&nbsp; TDMA frames (two of them for control channels) of&nbsp; $4.615\ \rm ms$&nbsp;  duration.&nbsp; Thus, the duration of a time slot is approximately&nbsp; $T_{\rm Z} = 576.9\ \rm &micro; s$.<br>
-[[File:EN_Mob_T_3_3_S3a.png||right|frame|Data and frame structure for GSM '''KORREKTUR: Daten'''|class=fit]]
+[[File:EN_Mob_T_3_3_S2_v3.png||right|frame|Data and frame structure for GSM|class=fit]]
 You can see from this graphic:

@@ Line 9: / Line 9: @@
 <br>
 $\rm GSM$&nbsp; $\rm (G$lobal&nbsp; $\rm S$ystem&nbsp; for&nbsp; $\rm M$obile Communication$)$&nbsp; is a strongly hierarchically structured system of different network components.&nbsp; You can see from the graphic:
-[[File:P ID2203 Mob T 3 3 S1 v1.png|right|frame|GSM system architecture '''KORREKTUR: Funkschnittstelle'''|class=fit]]
+[[File:EN_Mob_T_3_3_S1.png|right|frame|GSM system architecture|class=fit]]
 *The mobile station&nbsp; $\rm (MS)$&nbsp; communicates via the radio interface with the nearest&nbsp; base transceiver station&nbsp; $\rm (BTS$, transmit and receive base station).<br>
@@ Line 27: / Line 27: @@
 == Multiple access with GSM ==
 <br>
-[[File:EN_Mob_T_3_3_S2.png||right|frame|Realization of FDMA and TDMA with "GSM 900" '''KORREKTUR: Daten'''|class=fit]]
+[[File:EN_Mob_T_3_3_S2_v2.png|right|frame|Realization of FDMA and TDMA with "GSM 900"|class=fit]]
 GSM uses two multiple access methods in parallel:

@@ Line 96: / Line 96: @@
 Regarding the topic treated here&nbsp; (coherent or non-coherent demodulation of FSK)&nbsp; we refer to two exercises in the book "Digital Signal Transmission":
-*[[Aufgaben:Aufgabe_4.16:_Binary_Frequency_Shift_Keying|"Excercise 4.16: &nbsp; Binary Frequency Shift Keying"]],<br>
+*[[Aufgaben:Aufgabe_4.16:_Binary_Frequency_Shift_Keying|Excercise 4.16: &nbsp; Binary Frequency Shift Keying]],<br>
-*[[Aufgaben:Aufgabe_4.18Z:_BER_von_kohärenter_und_nichtkohärenter_FSK| "Excercise 4.18Z: &nbsp; BER of coherent and non-coherent FSK"]].<br><br>
 {{GraueBox|TEXT=
@@ Line 142: / Line 142: @@
 We should also mention the&nbsp; [[Mobile_Communications/General_Information_on_the_LTE_Mobile_Communications_Standard#Development_of_the_UMTS_mobile_phone_standards_towards_LTE|$\text{EDGE Evolution}$]]&nbsp; or "Evolved EDGE", i.e. the further development of the evolution of GSM in Release 7 (December 2007). For this, the developers specify data rates up to&nbsp; $1 \ \rm Mbit/s$&nbsp; and halved latency times&nbsp; $(10 \ \rm ms$ instead of $20 \ \rm ms)$&nbsp;. These values can be achieved among other things
 *by&nbsp; 32&ndash;QAM or &nbsp;16&ndash;QAM Modulation instead of 8&ndash;PSK,
-* an improved error correction through the use of&nbsp; [[Channel_Coding/Grundlegendes_zu_den_Turbocodes| $\text{Turbo&ndash;Codes}$]] '''KORREKTUR: Turbo codes?''', and
+* an improved error correction through the use of&nbsp; [[Channel_Coding/Grundlegendes_zu_den_Turbocodes| $\text{Turbo codes}$]], and
 * an increase of the symbol rate of&nbsp; $20\%$&nbsp; from&nbsp; $270.833 \ \rm ksymbol/s$&nbsp; to&nbsp; $325\ \rm ksymbol/s$.<br>

@@ Line 142: / Line 142: @@
 We should also mention the&nbsp; [[Mobile_Communications/General_Information_on_the_LTE_Mobile_Communications_Standard#Development_of_the_UMTS_mobile_phone_standards_towards_LTE|$\text{EDGE Evolution}$]]&nbsp; or "Evolved EDGE", i.e. the further development of the evolution of GSM in Release 7 (December 2007). For this, the developers specify data rates up to&nbsp; $1 \ \rm Mbit/s$&nbsp; and halved latency times&nbsp; $(10 \ \rm ms$ instead of $20 \ \rm ms)$&nbsp;. These values can be achieved among other things
 *by&nbsp; 32&ndash;QAM or &nbsp;16&ndash;QAM Modulation instead of 8&ndash;PSK,
-* an improved error correction through the use of&nbsp; [[Channel_Coding/Grundlegendes_zu_den_Turbocodes| $\text{Turbo&ndash;Codes}$]], and
+* an improved error correction through the use of&nbsp; [[Channel_Coding/Grundlegendes_zu_den_Turbocodes| $\text{Turbo&ndash;Codes}$]] '''KORREKTUR: Turbo codes?''', and
 * an increase of the symbol rate of&nbsp; $20\%$&nbsp; from&nbsp; $270.833 \ \rm ksymbol/s$&nbsp; to&nbsp; $325\ \rm ksymbol/s$.<br>

@@ Line 140: / Line 140: @@
 In practice, however, MCS&ndash;8&nbsp; $(54.4 \ \rm kbit/s)$&nbsp; and seven time slots are the maximum applicable.&nbsp; With this, one reaches&nbsp; $380.8 \ \rm kbit/s$&nbsp; and thus the order of magnitude of UMTS&nbsp; $(384 \ \rm kbit/s)$.<br>
-We should also mention the&nbsp; [[Mobile_Communications/General information on the LTE mobile communications standard#Entwicklung_der_UMTS-Mobilfunkstandards_hin_zu_LTE|$\text{EDGE Evolution}$]]&nbsp; or "Evolved EDGE", i.e. the further development of the evolution of GSM in Release 7 (December 2007). For this, the developers specify data rates up to&nbsp; $1 \ \rm Mbit/s$&nbsp; and halved latency times&nbsp; $(10 \ \rm ms$ instead of $20 \ \rm ms)$&nbsp;. These values can be achieved among other things
+We should also mention the&nbsp; [[Mobile_Communications/General_Information_on_the_LTE_Mobile_Communications_Standard#Development_of_the_UMTS_mobile_phone_standards_towards_LTE|$\text{EDGE Evolution}$]]&nbsp; or "Evolved EDGE", i.e. the further development of the evolution of GSM in Release 7 (December 2007). For this, the developers specify data rates up to&nbsp; $1 \ \rm Mbit/s$&nbsp; and halved latency times&nbsp; $(10 \ \rm ms$ instead of $20 \ \rm ms)$&nbsp;. These values can be achieved among other things
 *by&nbsp; 32&ndash;QAM or &nbsp;16&ndash;QAM Modulation instead of 8&ndash;PSK,
 * an improved error correction through the use of&nbsp; [[Channel_Coding/Grundlegendes_zu_den_Turbocodes| $\text{Turbo&ndash;Codes}$]], and

@@ Line 104: / Line 104: @@
 $\text{Example 1:}$&nbsp; The following graphic is to clarify the previous statements:
-[[File:EN_Mob_T_3_3_S4.png|right|frame|block diagram and signals with GMSK|class=fit]]
+[[File:EN_Mob_T_3_3_S4.png|right|frame|Block diagram and signals with GMSK|class=fit]]
 *Starting from a Dirac shaped source signal&nbsp; $q_\delta(t)$&nbsp; at point&nbsp; $(1)$&nbsp; you pass through a filter with the rectangular impulse response&nbsp; $g_{\rm R}(t)$&nbsp; to the rectangular signal&nbsp; $q_{\rm R}(t)$&nbsp; at point&nbsp; $(2)$.

@@ Line 99: / Line 99: @@
 *[[Aufgaben:Aufgabe_4.18Z:_BER_von_kohärenter_und_nichtkohärenter_FSK| "Excercise 4.18Z: &nbsp; BER of coherent and non-coherent FSK"]].<br><br>
-[[Diese beiden Aufgaben müssen später in DSÜ noch übersetzt werden]]
+[[Diese beiden Aufgaben müssen später in DSÜ noch übersetzt werden]] '''KORREKTUR'''
 {{GraueBox|TEXT=

@@ Line 86: / Line 86: @@
 GSM uses the very bandwidth-efficient modulation method&nbsp; [[Examples_of_Communication_Systems/Radio_Interface#Gaussian_Minimum_Shift_Keying_.28GMSK.29| $\text{Gaussian Minimum Shift Keying}$]]&nbsp; $\rm (GMSK)$.&nbsp; It should again be expressly mentioned that this modulation method, just like the FDMA/TDMA multiple access, is exclusively based on the air interface between the mobile station&nbsp; $\rm (MS)$&nbsp; and the base transceiver station &nbsp; $\rm (BTS)$, which is highlighted in yellow in the&nbsp; [[Mobile_Communications/Characteristics_of_GSM#System_architecture_and_basic_units_of_GSM|$\text{system architecture graphic}$]]&nbsp; at the beginning of the chapter. <br>
-GMSK has already been described in chapter&nbsp; [[Modulation_Methods/Nonlinear_Digital_Modulation#Properties_of_nonlinear_modulation_methods| "Properties of nonlinear modulation methods"]]&nbsp; of the book "Modulation Methods".&nbsp; The most important properties are briefly summarized here.
+GMSK has already been described in chapter&nbsp; [[Modulation_Methods/Non-Linear_Digital_Modulation#Properties_of_non-linear_modulation_methods| "Properties of nonlinear modulation methods"]]&nbsp; of the book "Modulation Methods".&nbsp; The most important properties are briefly summarized here.
-*GMSK is a special form of binary&nbsp; [[Modulation_Methods/Nichtlineare_digitale_Modulation#FSK_.E2.80.93_Frequency_Shift_Keying| $\text{Frequency Shift Keying}$]]&nbsp; $\rm (FSK)$.&nbsp; A prerequisite for the orthogonality between the two waveforms is that the modulation index&nbsp; $h$&nbsp; is a multiple of&nbsp; $0.5$&nbsp;. For integer values of&nbsp; $h$&nbsp; the demodulation can also be performed non-coherently.<br>
+*GMSK is a special form of binary&nbsp; [[Modulation_Methods/Non-Linear_Digital_Modulation#FSK_.E2.80.93_Frequency_Shift_Keying| $\text{Frequency Shift Keying}$]]&nbsp; $\rm (FSK)$.&nbsp; A prerequisite for the orthogonality between the two waveforms is that the modulation index&nbsp; $h$&nbsp; is a multiple of&nbsp; $0.5$&nbsp;. For integer values of&nbsp; $h$&nbsp; the demodulation can also be performed non-coherently.<br>
-*For GSM you use the smallest possible modulation index&nbsp; $h = 0.5$.&nbsp; A higher value would require a much larger bandwidth.&nbsp; Such an FSK with&nbsp; $h = 0.5$&nbsp; is also called [[Modulation_Methods/Nichtlineare_digitale_Modulation#MSK_.E2.80.93_Minimum_Shift_Keying|$\text{Minimum Shift Keying}$]]&nbsp;&nbsp; $\rm (MSK)$.&nbsp; However, a coherent demodulation is then required.<br>
+*For GSM you use the smallest possible modulation index&nbsp; $h = 0.5$.&nbsp; A higher value would require a much larger bandwidth.&nbsp; Such an FSK with&nbsp; $h = 0.5$&nbsp; is also called [[Modulation_Methods/Non-Linear_Digital_Modulation#MSK_.E2.80.93_Minimum_Shift_Keying|$\text{Minimum Shift Keying}$]]&nbsp;&nbsp; $\rm (MSK)$.&nbsp; However, a coherent demodulation is then required.<br>
 *A very narrow spectrum, however, is only obtained if the phase values at the symbol boundaries are matched to each other, thus avoiding phase jumps, which is given with MSK.&nbsp; Such methods are referred to as&nbsp; [[Modulation_Methods/Nonlinear_Digital_Modulation#General_Description_of_Continuous_Phase_Modulation|$\text{Continuous Phase Frequency Shift Keying}$]]&nbsp; $\rm (CP&ndash;FSK)$.&nbsp;<br>

@@ Line 75: / Line 75: @@
 ''Note:''
-*In GSM, besides the "Normal Burst" there are  some other&nbsp; [[Examples_of_Communication_Systems/Radio_Interface#The_different_burst_types_with_GSM|$\text{types of bursts}$]]:&nbsp; Frequency Correction Burst,&nbsp; Synchronization Burst,&nbsp; Dummy Burst,&nbsp; Access Burst, ... .
+*In GSM, besides the "Normal Burst" there are  some other&nbsp; [[Examples_of_Communication_Systems/Radio_Interface#The_different_burst_types_in_GSM|$\text{types of bursts}$]]:&nbsp; Frequency Correction Burst,&nbsp; Synchronization Burst,&nbsp; Dummy Burst,&nbsp; Access Burst, ... .
 *All these bursts have a uniform length of&nbsp; $156.25$&nbsp; bit durations.&nbsp; This is discussed in more detail in the&nbsp; [[Aufgaben:Exercise_3.2:_GSM Data Rates|"Excercise 3.2"]].