Preamble Start subframedelimiter P_sdu = data Pause PHY - Frame 2 bytes 2 bytes 38 bytes 3 bytes Figure 3 – Time slot and physical frame structure The bytes are sent from the most signif
Domaine d'application et objet
This section of IEC 61334 outlines the requirements for S-FSK (spread frequency shift keying) modulation in relation to the services provided by the physical layer and the MAC sublayer It is assumed that the distribution network at the medium voltage (MV) and low voltage (LV) levels serves as the transmission medium.
MAC décrite dans cette norme sert d’interface avec la couche LLC (logical link control) décrite dans la CEI 61334-4-32.
The three components—modulation, the physical layer, and the MAC sublayer—are interconnected to achieve optimal performance levels in terms of cost.
The profile outlined in this standard is part of a series of profiles (described in IEC 61334-5) designed for data transmission over distribution networks Due to advancements in technology, these profiles are initially released as technical specifications, aiming to incorporate functional profiles into established standards.
Définitions
Pour les besoins de la présente partie de la CEI 61334 les définitions contenues dans les normes ISO/IEC 7498-1 et EN 50065-1 s'appliquent.
Objectif
S-FSK is a modulation and demodulation technique that merges the benefits of traditional spread spectrum systems, such as resistance to narrowband jammers, with the advantages of classic Frequency Shift Keying (FSK) systems, which are known for their simplicity and well-researched implementations.
2.2 Le principe S-FSK (spread frequency shift keying)
L'ộmetteur affecte la frộquence espace f S à ôdonnộe 0ằ et la frộquence marque f M à ôdonnộe 1ằ.
The difference between the S-FSK system and the classic FSK system lies in the increased separation between the frequencies \( f_S \) and \( f_M \) By positioning the signal further away from the mark, the quality of their respective transmissions becomes independent, meaning that the effects of minor band disturbances and signal attenuations are not influenced by one frequency affecting the other.
The receiver performs classic FSK demodulation on two possible frequencies (the half-channels), resulting in two demodulated signals, \(d_S\) and \(d_M\) If the average reception quality of both half-channels is similar, the decision unit selects the demodulated channel with the higher signal (outputting 0 if \(d_S > d_M\) and 1 if \(d_S < d_M\)) However, if the average reception quality of one half-channel is significantly better than the other, the decision unit compares the demodulated signal of the superior channel to a threshold \(T\), disregarding the other channel.
Les mesures de qualité et le calcul du seuil peuvent être fondés sur un préambule prédéfini précédant la transmission de la trame de données réelles.
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IEC 61334-4-511:2000, Distribution automation using distribution line carrier systems – Part 4-511:
Data communication protocols – Systems management – CIASE protocol
IEC 61334-4-512, Distribution automation using distribution line carrier systems – Part 4-512:
Data communication protocols – Systems management using profile 61334-5-1 MIB 1)
ISO/IEC 7498-1:1994, Information technology – Open Systems Interconnection – Basic
Reference Model – The Basic Model
ISO/IEC 7498-3:1997, Information technology – Open Systems Interconnection – Basic
Reference Model – Naming and addressing
EN 50065-1:1991, Signalling on low-voltage electrical installations in the frequency range
3 kHz to 148,5 kHz – Part 1: General requirements, frequency bands and electromagnetic disturbances
For the purpose of this part of IEC 61334, the definitions of ISO/IEC 7498-1 and EN 50065-1 apply.
S-FSK is a modulation and demodulation technique that merges the benefits of traditional spread spectrum systems, such as resistance to narrowband interference, with the advantages of classical Frequency Shift Keying (FSK) systems, including low complexity and established implementations.
2.2 Spread frequency shift keying (S-FSK) principle
The transmitter assigns the space frequency f S to "data 0" and the mark frequency f M to "data 1".
The key distinction between S-FSK and classical FSK is the significant separation between the frequencies \( f_S \) and \( f_M \) This spreading of the signals for "space" and "mark" enhances transmission quality, making it independent of small-band interferences and signal attenuations at both frequencies.
The receiver conducts conventional FSK demodulation on two half-channels, producing demodulated signals d S and d M When the average reception quality of both channels is comparable, the decision unit selects the higher signal, determining "data 0" if d S > d M and "data 1" if d S < d M Conversely, if one half-channel exhibits significantly better reception quality, the decision unit focuses on the superior channel's demodulated signal, comparing it to a threshold T and disregarding the inferior channel.
The quality measurements and the threshold computation may be based on a predefined preamble which precedes the transmission of the actual data frame.
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Niveau de bruit pour ôespaceằ similaire à celui pour ômarqueằ
Figure 1 – Qualitộ ôespaceằ similaire à qualitộ ômarqueằ
Niveau de bruit pour ôespaceằ nettement supérieur à celui pour ômarqueằ
Figure 2 – Qualitộ ômarqueằ nettement meilleure que qualitộ ôespaceằ
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Noise level for "space" similar to noise level for "mark"
Figure 1 – Quality "space" similar to quality "mark"
Noise level for "space" much higher than for "mark" f S
Figure 2 – Quality "mark" much better than quality "space"
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The absolute value of the frequency deviation \(|f_M - f_S|\) ensures that the transmission qualities of signals at frequencies \(f_M\) and \(f_S\) are independent of each other Based on the measurements outlined in IEC 61334-1-4, it is advisable to use a specific value for optimal performance.
fM–f S > 10 kHz. f M et f S doivent être situées dans la bande de fréquence définie dans la norme EN 50065-1.
Plusieurs essais sur les performances garantissent la qualité de l'implémentation Les essais peuvent être effectués dans les mêmes conditions qu'en laboratoire et doivent être reproductibles.
TEB (Bit Error Rate) measurements are conducted through the transmission of a preamble, a frame delimiter, and a 38-byte data block It is essential that no frame synchronization errors occur during this process The TEB is determined by counting the errors within the data block.
Les essais décrits dans les paragraphes suivants doivent être effectués pour les signaux d'entrée du récepteur dans la plage comprise entre 2 mV eff et 2 V eff
Plusieurs types de brouilleurs sont ajoutés au signal transmis.
2.4.2 Essais sur le TEB du bruit blanc
Le bruit blanc gaussien est ajouté au signal transmis.
The noise power spectral density, denoted as N 0 [W/Hz], is measured at the receiver's input across the frequencies f c –f d, f c, and f c +f d It is essential to ensure that the noise spectrum remains flat between the frequencies f c –f d and f c +f d.
The term \$E_b[Ws]\$ represents the energy of the signal received per bit, where \$E_b = V_{signal}^2 (eff.)\$, and \$V_{signal} (eff.)\$ denotes the effective value of the signal transmitted to the receiver's input The bandwidth of the effective voltmeter must accommodate the entire frequency range of the signal.
The channel can behave differently at each transmitted frequency, resulting in varying noise levels and attenuation To assess additive white noise, tests are conducted using different signal levels Here, \(E_{b1}\) represents the energy of the received signal when logical '1' is transmitted, while \(E_{b0}\) denotes the energy of the received signal for logical '0' Consequently, the average energy per bit is calculated as \(E_b = \frac{(E_{b1} + E_{b0})}{2}\).
Le rapport entre les deux niveaux d'énergie de signal est indiqué en tant que rapport d'énergie x, ó x = E b1 /E b0
Les valeurs E b /N 0 suivantes ne doivent pas être dépassées lorsque les TEB donnés sont atteints.
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To ensure independent signal transmission qualities at frequencies \$f_M\$ and \$f_S\$, the absolute frequency deviation \$|f_M - f_S|\$ should exceed 10 kHz, as recommended by IEC 61334-1-4 Additionally, both frequencies must fall within the frequency band specified in EN 50065-1.
The quality of the implementation is guaranteed by different performance tests The tests can be performed under laboratory conditions and shall be reproducible.
The bit error rate (BER) is determined by sending a preamble and a frame delimiter, followed by a 38-byte data block, under the assumption of no frame synchronization errors BER is calculated by counting the number of errors within this data block.
The tests which will be described in the following subclauses shall be accomplished for receiver input signals in the range of 2 mV rms to 2 V rms
Different kinds of interferences are added to the transmitted signal.
White Gaussian noise is added to the transmitted signal.
N 0 [W/Hz] denotes the noise power spectral density measured at the input of the receiver at frequencies f c –f d , f c and f c +f d It shall be ensured that the noise spectrum is flat between f c –f d and f c +f d
The term \$E_b[Ws]\$ represents the energy of the received signal per bit, calculated as \$E_b = V_{signal (r.m.s.)}^2\$, where \$V_{signal (r.m.s.)\$ is the actual root mean square value of the transmitted signal at the receiver's input It is essential that the bandwidth of the r.m.s voltmeter encompasses the complete frequency range of the signal.
The behavior of the channel can vary for different transmitted frequencies due to factors like noise levels and attenuation To assess this, AWGN (additive white Gaussian noise) tests are conducted at various signal levels The energy of the received signal when a "logical 1" is transmitted is denoted as \(E_{b1}\), while the energy for a "logical 0" is represented as \(E_{b0}\) Consequently, the average energy per bit is calculated as \(E_b = \frac{(E_{b1} + E_{b0})}{2}\).
The ratio between the two signal energy levels is denoted as energy ratio x, where x = E b1 /E b0
The following E b /N 0 values shall not be exceeded while achieving the given BERs.
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Tableau 1 – Valeurs E b /N 0 maximales permises pour atteindre un TEB donné
TEB –5 dB < x < 5 dB x = ±10 dB x = ±20 dB
NOTE Il convient que les limites E b /N 0 servent de directives Elles dépassent d'au moins 3 dB les valeurs pouvant être théoriquement atteintes.
2.4.3 Essais sur le TEB du brouilleur de bande étroite