Examples of Communication Systems/Radio Interface - Revision history

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2026-03-16T13:46:53Z

Join split $$ formula lines for correct rendering

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	*To allow easy demodulation,  the two signals with frequencies  $f_{\rm T} ± Δf$  should be orthogonal to each other within the symbol duration  $T$.  Consequently:		*To allow easy demodulation,  the two signals with frequencies  $f_{\rm T} ± Δf$  should be orthogonal to each other within the symbol duration  $T$.  Consequently:
	:$$\int^{T} _{0} \cos \big(2 \pi t \cdot (f_{\rm T}+ \Delta f_{\rm A} )\big)\cdot \cos \big(2 \pi t \cdot (f_{\rm T}- \Delta f_{\rm A} )\big)\,{\rm		:$$\int^{T} _{0} \cos \big(2 \pi t \cdot (f_{\rm T}+ \Delta f_{\rm A} )\big)\cdot \cos \big(2 \pi t \cdot (f_{\rm T}- \Delta f_{\rm A} )\big)\,{\rm d}t= 0\hspace{0.05cm}. $$
	d}t= 0\hspace{0.05cm}. $$
	*This results in the requirement for the  "frequency deviation":		*This results in the requirement for the  "frequency deviation":
	:$$\Delta f_{\rm A} = \frac{k}{4 \cdot T}\hspace{0.4cm}{\rm		:$$\Delta f_{\rm A} = \frac{k}{4 \cdot T}\hspace{0.4cm}{\rm with}\hspace{0.4cm}k = 1,\ 2,\ 3,\ \text{...}$$
	with}\hspace{0.4cm}k = 1,\ 2,\ 3,\ \text{...}$$
	*In FSK systems the  "modulation index"  is defined to  $h = 2 \cdot Δf_{\rm A} \cdot T$,  it follows  $h = k/2$.		*In FSK systems the  "modulation index"  is defined to  $h = 2 \cdot Δf_{\rm A} \cdot T$,  it follows  $h = k/2$.

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	*At point  <b>(1)</b>  the digital source signal consisting of a sequence of Dirac delta pulses at distance  $T$ weighted by the amplitude coefficients  $a_ν ∈ \{-1, +1\}$:		*At point  <b>(1)</b>  the digital source signal consisting of a sequence of Dirac delta pulses at distance  $T$ weighted by the amplitude coefficients  $a_ν ∈ \{-1, +1\}$:
	:$$q_\delta(t) = \sum_{\nu = - \infty}^{+\infty}a_{ \nu} \cdot \delta (t - \nu		:$$q_\delta(t) = \sum_{\nu = - \infty}^{+\infty}a_{ \nu} \cdot \delta (t - \nu\cdot T)\hspace{0.05cm}; $$
	\cdot T)\hspace{0.05cm}; $$
	*at point  <b>(2)</b>:  the rectangular source signal  $q_{\rm R}(t)$  after convolution with the rectangular pulse  $g(t)$  the duration  $T$  and the height  $1/T$  $($the amplitude was chosen this way for compatibility with later sections$)$:		*at point  <b>(2)</b>:  the rectangular source signal  $q_{\rm R}(t)$  after convolution with the rectangular pulse  $g(t)$  the duration  $T$  and the height  $1/T$  $($the amplitude was chosen this way for compatibility with later sections$)$:
	:$$q_{\rm R}(t) = \sum_{\nu = - \infty}^{+\infty}a_{ \nu} \cdot g (t - \nu		:$$q_{\rm R}(t) = \sum_{\nu = - \infty}^{+\infty}a_{ \nu} \cdot g (t - \nu\cdot T)\hspace{0.05cm}; $$
	\cdot T)\hspace{0.05cm}; $$
	*at point  <b>(3)</b>:  the frequency modulator,  which can be realized according to the description in chapter  [[Modulation_Methods/Frequency_Modulation_(FM)#Signal_characteristics_with_frequency_modulation\|"Signal characteristics in FM"]]  as an integrator followed by a phase modulator.  For the signal at point <b>(3)</b>  holds:		*at point  <b>(3)</b>:  the frequency modulator,  which can be realized according to the description in chapter  [[Modulation_Methods/Frequency_Modulation_(FM)#Signal_characteristics_with_frequency_modulation\|"Signal characteristics in FM"]]  as an integrator followed by a phase modulator.  For the signal at point <b>(3)</b>  holds:
	:$$\phi(t) = \frac{\pi}{2}\cdot \int_{0}^{t}		:$$\phi(t) = \frac{\pi}{2}\cdot \int_{0}^{t}q_{\rm R}(\tau)\hspace{0.1cm} {\rm d}\tau \hspace{0.05cm}.$$
	q_{\rm R}(\tau)\hspace{0.1cm} {\rm d}\tau \hspace{0.05cm}.$$

	:The phase values at  $\nu \cdot T$  are multiples of  $π/2 \ (90^\circ)$,  taking into account the modulation index  $h = 0.5$  valid for MSK.  The phase response is linear.		:The phase values at  $\nu \cdot T$  are multiples of  $π/2 \ (90^\circ)$,  taking into account the modulation index  $h = 0.5$  valid for MSK.  The phase response is linear.
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	*From this,  at the point  <b>(4)</b>  of the block diagram,  the MSK signal is given by		*From this,  at the point  <b>(4)</b>  of the block diagram,  the MSK signal is given by

	:$$s(t) = s_0 \cdot \cos \big(2 \pi f_{\rm T} \hspace{0.05cm}t +		:$$s(t) = s_0 \cdot \cos \big(2 \pi f_{\rm T} \hspace{0.05cm}t +\phi(t)\big) = s_0 \cdot \cos \big(2 \pi \cdot t \cdot (f_{\rm T}+a_{ \nu} \cdot {\rm \Delta}f_{\rm A} )\big) \hspace{0.05cm}.$$
	\phi(t)\big) = s_0 \cdot \cos \big(2 \pi \cdot t \cdot (f_{\rm T}+a_{ \nu} \cdot {\rm \Delta}f_{\rm A} )\big) \hspace{0.05cm}.$$

	<u>Note:</u>		<u>Note:</u>
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	*Without taking intersymbol interference into account,  the  »'''bit error probability'''«  is as follows:		*Without taking intersymbol interference into account,  the  »'''bit error probability'''«  is as follows:
	::$$p_{\rm B} = {\rm Q} \left(\sqrt{ {E_{\rm B} }/{N_0} }\hspace{0.09cm}\right) =		::$$p_{\rm B} = {\rm Q} \left(\sqrt{ {E_{\rm B} }/{N_0} }\hspace{0.09cm}\right) ={1}/{2}\cdot{\rm erfc} \left(\sqrt{ {E_{\rm B} }/{2N_0} }\hspace{0.09cm}\right)\hspace{0.05cm}.$$
	{1}/{2}\cdot{\rm erfc} \left(\sqrt{ {E_{\rm B} }/{2N_0} }\hspace{0.09cm}\right)
	\hspace{0.05cm}.$$
	:⇒   Compared to the QPSK,  there is a degradation of  $3\ \rm dB$.   <u>Note:</u>  The HTML5/JavaScript applet  [[Applets:Complementary_Gaussian_Error_Functions\|"Complementary Gaussian Error Functions"]]  provides the numerical values of the functions   ${\rm Q}(x)$  resp.  $1/2 \cdot {\rm erfc}(x)$  used here.		:⇒   Compared to the QPSK,  there is a degradation of  $3\ \rm dB$.   <u>Note:</u>  The HTML5/JavaScript applet  [[Applets:Complementary_Gaussian_Error_Functions\|"Complementary Gaussian Error Functions"]]  provides the numerical values of the functions   ${\rm Q}(x)$  resp.  $1/2 \cdot {\rm erfc}(x)$  used here.

Maintenance script: Add German interlanguage link

2026-03-16T12:26:09Z

Add German interlanguage link

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	{{Display}}		{{Display}}
			[[de:Beispiele_von_Nachrichtensystemen/Funkschnittstelle]]

Guenter at 16:48, 20 February 2023

2023-02-20T16:48:52Z

← Older revision		Revision as of 18:48, 20 February 2023
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	*Furthermore,  the radio interface is responsible for other functionalities such as the  "radio subsystem link control".		*Furthermore,  the radio interface is responsible for other functionalities such as the  "radio subsystem link control".

	[[File:~~EN_Bei_T_3_2_S1_v2~~.png\|right\|frame\|Compilation of the logical channels of GSM ~~'''KORREKTUR: full rate, half rate'''~~]]		[[File:EN_Bei_T_3_2_S1_v4.png\|right\|frame\|Compilation of the logical channels of GSM]]

	Let's start with the  »'''logical channels'''«.  These can occupy either an entire physical channel or only a portion of a physical channel and fall into two categories:		Let's start with the  »'''logical channels'''«.  These can occupy either an entire physical channel or only a portion of a physical channel and fall into two categories:
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	==The different burst types in GSM==		==The different burst types in GSM==
	<br>		<br>
	[[File:~~EN_Bei_T_3_2_S4_v3~~.png\|right\|frame\|The different burst types with GSM ~~'''KORREKTUR: logisch'''~~]]		[[File:EN_Bei_T_3_2_S4_v5.png\|right\|frame\|The different burst types with GSM]]
	As just shown,  a  »'''burst'''«  contains  $156.25$  bits each and has duration		As just shown,  a  »'''burst'''«  contains  $156.25$  bits each and has duration
	:$$T_{\rm burst} = T_{\rm Z} ≈ 577 \rm µ s.$$		:$$T_{\rm burst} = T_{\rm Z} ≈ 577 \rm µ s.$$

Guenter at 16:24, 11 February 2023

2023-02-11T16:24:49Z

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	#Access Burst  $\rm (AB)$.<br>		#Access Burst  $\rm (AB)$.<br>
	<br clear=all>		<br clear=all>
	'''(1)'''   The  »'''Normal Burst'''«  is used to transmit data from traffic and signaling channels.  The error protection encoded user data  $($blue,  two times  $57$  bits$)$  together with three tail bits each  $($red,  during this time the ~~transmit '''KORREKTUR:~~ transmitted~~?'''~~ power is regulated$)$,  two signaling bits  $($green) and  $26$  bits for the training sequence  $($yellow,  required for channel estimation and synchronization$)$  result in a total of  $148$  bits.  Added to this is the Guard Period of  $8.25$ bits  $($gray$)$.		'''(1)'''   The  »'''Normal Burst'''«  is used to transmit data from traffic and signaling channels.  The error protection encoded user data  $($blue,  two times  $57$  bits$)$  together with three tail bits each  $($red,  during this time the transmitted power is regulated$)$,  two signaling bits  $($green) and  $26$  bits for the training sequence  $($yellow,  required for channel estimation and synchronization$)$  result in a total of  $148$  bits.  Added to this is the Guard Period of  $8.25$ bits  $($gray$)$.

	The two  $($green$)$  signaling bits – also called  "stealing flags"  –  indicate whether the burst transports only user data or high-priority signaling information,  which is always to be transmitted without delay.  The  "training sequence"  is used to estimate the channel,  which is a prerequisite for applying an equalizer to reduce intersymbol interference.		The two  $($green$)$  signaling bits – also called  "stealing flags"  –  indicate whether the burst transports only user data or high-priority signaling information,  which is always to be transmitted without delay.  The  "training sequence"  is used to estimate the channel,  which is a prerequisite for applying an equalizer to reduce intersymbol interference.
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	Another function of the radio interface is the control of the radio link.  Thus,  the so-called  "Radio Subsystem Link Control"  performs the following tasks:		Another function of the radio interface is the control of the radio link.  Thus,  the so-called  "Radio Subsystem Link Control"  performs the following tasks:
	#It is responsible for the measurement of the reception quality. During an established traffic or signaling connection, the channel measurement of the mobile station is performed at regular intervals with regard to received field strength and bit error rate   ⇒   »'''Quality Monitoring'''«. These values are transmitted in a measurement report to the base station via the signaling channel SACCH and used by it for power control and handover.<br><br>		#It is responsible for the measurement of the reception quality. During an established traffic or signaling connection, the channel measurement of the mobile station is performed at regular intervals with regard to received field strength and bit error rate   ⇒   »'''Quality Monitoring'''«. These values are transmitted in a measurement report to the base station via the signaling channel SACCH and used by it for power control and handover.<br><br>
	#The  "Power Control"  is necessary to ensure that all mobile stations only radiate with the minimum required power.  The ~~transmit '''KORREKTUR:~~ transmitted~~'''~~ power can be adaptively controlled in steps of  $2 \ \rm dBm$  between  $43 \ \rm dBm$  $\text{(level 0:}$  $20\ \rm W)$  and  $13 \ \rm dBm$  $\text{(level 15:}$  $20\ \rm mW)$.<br><br>		#The  "Power Control"  is necessary to ensure that all mobile stations only radiate with the minimum required power.  The transmitted power can be adaptively controlled in steps of  $2 \ \rm dBm$  between  $43 \ \rm dBm$  $\text{(level 0:}$  $20\ \rm W)$  and  $13 \ \rm dBm$  $\text{(level 15:}$  $20\ \rm mW)$.<br><br>
	#Base station ~~transmit '''KORREKTUR:~~ transmitted~~'''~~ power is also adjusted in steps of  $2 \rm dBm$  to achieve optimum network capacity.  An exception is the BCCH carrier with constant ~~transmit '''KORREKTUR:~~ transmitted~~'''~~ power to allow mobile stations to make comparative measurements of neighboring BCCH carriers.<br><br>		#Base station transmitted power is also adjusted in steps of  $2 \rm dBm$  to achieve optimum network capacity.  An exception is the BCCH carrier with constant transmitted power to allow mobile stations to make comparative measurements of neighboring BCCH carriers.<br><br>
	#The  »'''Adaptive Frame Alignment'''«  – i.e. adaptive frame synchronization – is used to avoid collisions between uplink and downlink data to be transmitted or received by the mobile station offset by three time slots.<br>		#The  »'''Adaptive Frame Alignment'''«  – i.e. adaptive frame synchronization – is used to avoid collisions between uplink and downlink data to be transmitted or received by the mobile station offset by three time slots.<br>

Hwang at 18:43, 6 February 2023

2023-02-06T18:43:47Z

← Older revision		Revision as of 20:43, 6 February 2023
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	[[File:EN_Bei_T_3_2_S11.png\|right\|frame\|Adaptive Frame Alignment]]		[[File:EN_Bei_T_3_2_S11.png\|right\|frame\|Adaptive Frame Alignment]]
	<br>		<br>
	This is shown in the adjacent graph.  The downlink is represented in the middle area with a yellow background,  where the data arrives at the mobile station  $\rm (MS)$  by the time  $T_{\rm R}$  $($"Round Trip Delay Time",by the time  $T_{\rm R}$  $($"Round Trip Delay Time",  green marking$)$ later than it was sent by the  base transceiver station  $\rm (BTS)$.		This is shown in the adjacent graph.  The downlink is represented in the middle area with a yellow background,  where the data arrives at the mobile station  $\rm (MS)$  by the time  $T_{\rm R}$  $($"Round Trip Delay Time", by the time  $T_{\rm R}$  $($"Round Trip Delay Time",  green marking$)$ later than it was sent by the  base transceiver station  $\rm (BTS)$.

	In the upper area,  the uplink is shown without  "Timing Advance".		In the upper area,  the uplink is shown without  "Timing Advance".

Hwang at 18:43, 6 February 2023

2023-02-06T18:43:12Z

← Older revision		Revision as of 20:43, 6 February 2023
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	#It is responsible for the measurement of the reception quality. During an established traffic or signaling connection, the channel measurement of the mobile station is performed at regular intervals with regard to received field strength and bit error rate   ⇒   »'''Quality Monitoring'''«. These values are transmitted in a measurement report to the base station via the signaling channel SACCH and used by it for power control and handover.<br><br>		#It is responsible for the measurement of the reception quality. During an established traffic or signaling connection, the channel measurement of the mobile station is performed at regular intervals with regard to received field strength and bit error rate   ⇒   »'''Quality Monitoring'''«. These values are transmitted in a measurement report to the base station via the signaling channel SACCH and used by it for power control and handover.<br><br>
	#The  "Power Control"  is necessary to ensure that all mobile stations only radiate with the minimum required power.  The transmit '''KORREKTUR: transmitted''' power can be adaptively controlled in steps of  $2 \ \rm dBm$  between  $43 \ \rm dBm$  $\text{(level 0:}$  $20\ \rm W)$  and  $13 \ \rm dBm$  $\text{(level 15:}$  $20\ \rm mW)$.<br><br>		#The  "Power Control"  is necessary to ensure that all mobile stations only radiate with the minimum required power.  The transmit '''KORREKTUR: transmitted''' power can be adaptively controlled in steps of  $2 \ \rm dBm$  between  $43 \ \rm dBm$  $\text{(level 0:}$  $20\ \rm W)$  and  $13 \ \rm dBm$  $\text{(level 15:}$  $20\ \rm mW)$.<br><br>
	#Base station transmit power is also adjusted in steps of  $2 \rm dBm$  to achieve optimum network capacity.  An exception is the BCCH carrier with constant transmit power to allow mobile stations to make comparative measurements of neighboring BCCH carriers.<br><br>		#Base station transmit '''KORREKTUR: transmitted''' power is also adjusted in steps of  $2 \rm dBm$  to achieve optimum network capacity.  An exception is the BCCH carrier with constant transmit '''KORREKTUR: transmitted''' power to allow mobile stations to make comparative measurements of neighboring BCCH carriers.<br><br>
	#The  »'''Adaptive Frame Alignment'''«  – i.e. adaptive frame synchronization – is used to avoid collisions between uplink and downlink data to be transmitted or received by the mobile station offset by three time slots.<br>		#The  »'''Adaptive Frame Alignment'''«  – i.e. adaptive frame synchronization – is used to avoid collisions between uplink and downlink data to be transmitted or received by the mobile station offset by three time slots.<br>

Hwang at 18:42, 6 February 2023

2023-02-06T18:42:45Z

← Older revision		Revision as of 20:42, 6 February 2023
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	Another function of the radio interface is the control of the radio link.  Thus,  the so-called  "Radio Subsystem Link Control"  performs the following tasks:		Another function of the radio interface is the control of the radio link.  Thus,  the so-called  "Radio Subsystem Link Control"  performs the following tasks:
	#It is responsible for the measurement of the reception quality. During an established traffic or signaling connection, the channel measurement of the mobile station is performed at regular intervals with regard to received field strength and bit error rate   ⇒   »'''Quality Monitoring'''«. These values are transmitted in a measurement report to the base station via the signaling channel SACCH and used by it for power control and handover.<br><br>		#It is responsible for the measurement of the reception quality. During an established traffic or signaling connection, the channel measurement of the mobile station is performed at regular intervals with regard to received field strength and bit error rate   ⇒   »'''Quality Monitoring'''«. These values are transmitted in a measurement report to the base station via the signaling channel SACCH and used by it for power control and handover.<br><br>
	#The  "Power Control"  is necessary to ensure that all mobile stations only radiate with the minimum required power.  The transmit power can be adaptively controlled in steps of  $2 \ \rm dBm$  between  $43 \ \rm dBm$  $\text{(level 0:}$  $20\ \rm W)$  and  $13 \ \rm dBm$  $\text{(level 15:}$  $20\ \rm mW)$.<br><br>		#The  "Power Control"  is necessary to ensure that all mobile stations only radiate with the minimum required power.  The transmit '''KORREKTUR: transmitted''' power can be adaptively controlled in steps of  $2 \ \rm dBm$  between  $43 \ \rm dBm$  $\text{(level 0:}$  $20\ \rm W)$  and  $13 \ \rm dBm$  $\text{(level 15:}$  $20\ \rm mW)$.<br><br>
	#Base station transmit power is also adjusted in steps of  $2 \rm dBm$  to achieve optimum network capacity.  An exception is the BCCH carrier with constant transmit power to allow mobile stations to make comparative measurements of neighboring BCCH carriers.<br><br>		#Base station transmit power is also adjusted in steps of  $2 \rm dBm$  to achieve optimum network capacity.  An exception is the BCCH carrier with constant transmit power to allow mobile stations to make comparative measurements of neighboring BCCH carriers.<br><br>
	#The  »'''Adaptive Frame Alignment'''«  – i.e. adaptive frame synchronization – is used to avoid collisions between uplink and downlink data to be transmitted or received by the mobile station offset by three time slots.<br>		#The  »'''Adaptive Frame Alignment'''«  – i.e. adaptive frame synchronization – is used to avoid collisions between uplink and downlink data to be transmitted or received by the mobile station offset by three time slots.<br>

Hwang at 18:41, 6 February 2023

2023-02-06T18:41:31Z

← Older revision		Revision as of 20:41, 6 February 2023
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	Furthermore,  it should be noted:		Furthermore,  it should be noted:
	*Binary FSK – even with continuous phase matching – generally represents a nonlinear modulation process.&~~ndash~~; Therefore,&~~ndash~~; coherent demodulation is actually not possible.		*Binary FSK – even with continuous phase matching – generally represents a nonlinear modulation process.  Therefore,  coherent demodulation is actually not possible.

	*An exception is the MSK as a special case for the modulation index  $h = 0.5$,  which can be realized linearly as  "Offset-QPSK"  and thus can also be demodulated coherently.		*An exception is the MSK as a special case for the modulation index  $h = 0.5$,  which can be realized linearly as  "Offset-QPSK"  and thus can also be demodulated coherently.

Hwang at 18:36, 6 February 2023

2023-02-06T18:36:23Z

← Older revision		Revision as of 20:36, 6 February 2023
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	[[File:EN_Bei_T_3_2_S10.png\|right\|frame\|Power-spectral densities of QPSK and MSK]]		[[File:EN_Bei_T_3_2_S10.png\|right\|frame\|Power-spectral densities of QPSK and MSK]]

	⇒   The left graph shows the log power-spectral density  $10 \cdot \text{lg} \ {\it Φ}_s(f)/{\it Φ}_0$  of  "Minimum Shift Keying"  $\rm (MSK)$  compared to  "Quaternary Phase Shift Keying"  $\rm (QPSK)$,  where  ${\it Φ}_0$  was  "suitable"  ~~chosen.~~		⇒   The left graph shows the log power-spectral density  $10 \cdot \text{lg} \ {\it Φ}_s(f)/{\it Φ}_0$  of  "Minimum Shift Keying"  $\rm (MSK)$  compared to  "Quaternary Phase Shift Keying"  $\rm (QPSK)$,  where  ${\it Φ}_0$  was chosen  "suitable".

	On the abscissa is plotted the normalized frequency  $f \cdot T_{\rm B}$.  For MSK,  the bit duration  $T_{\rm B}$  is equal to the symbol duration  $T$,  while for QPSK holds:  $T_{\rm B} = T/2$.		On the abscissa is plotted the normalized frequency  $f \cdot T_{\rm B}$.  For MSK,  the bit duration  $T_{\rm B}$  is equal to the symbol duration  $T$,  while for QPSK holds:  $T_{\rm B} = T/2$.

Hwang at 18:23, 6 February 2023

2023-02-06T18:23:08Z

← Older revision		Revision as of 20:23, 6 February 2023
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	*Each cell is assigned some frequencies per  "cell allocation"  $\rm (CA)$.  In adjacent cells one uses different frequencies.		*Each cell is assigned some frequencies per  "cell allocation"  $\rm (CA)$.  In adjacent cells one uses different frequencies.

	*A subset of the CAs is reserved for logical channels.  The remaining channels are allocated to a mobile station as  "mobile allocation''  $\rm (MA)$.		*A subset of the CAs is reserved for logical channels.  The remaining channels are allocated to a mobile station as  "mobile allocation"  $\rm (MA)$.

	*This is used,  for example,  for  "frequency hopping",  where the data is sent over different frequency channels.  This makes the transmission more stable against channel fluctuations.  In most cases,  frequency hopping is performed in packets.		*This is used,  for example,  for  "frequency hopping",  where the data is sent over different frequency channels.  This makes the transmission more stable against channel fluctuations.  In most cases,  frequency hopping is performed in packets.