M-Bus Vs Wireless M-Bus | Difference between M-Bus and Wireless M-Bus
This page on M-Bus Vs Wireless M-Bus describes difference between M-Bus and Wireless M-Bus. It also describes basics of M-Bus and Wireless M-Bus and provide links for further study.
Both are used as communication standard for reading utility metering devices. The two components in the utility system are reader devices and metering devices.
M Bus
Originally M-Bus was developed as two wire serial communication Bus standard. M-Bus standardization has been managed by CENELEC Technical Committee. The standards have been mentioned in the table below.
M-Bus protocol has 4 layer model consisting of physical layer, Link layer, network layer and application layer.
Wireless M-Bus
Unlike M-Bus, Wireless M-Bus works using radio frequency signals (868MHz and 169MHz). Hence it does not requires complex layout of wiring. It also referred as WM-Bus.
The Wireles M-Bus standard (EN13757-4) defines communication between metering device and other device(data concentrator or reader) Refer Wireless M-Bus Basics➤➤
Wireless M-Bus protocol layers consists of physical layer, Data link layer, Application layer and Security layer. There are different physical layer modes (R2, S1, S1m, S2, T1, T2) which supports different data rates.
| Specifications | M-Bus | Wireless M-Bus |
|---|---|---|
| Standard | EN13757-2 (Physical and Link Layer) EN13757-3 (Application Layer) |
EN13757-4 |
| Frequency of operation | Wired way of transmission, no RF frequency used | 868 to 870 MHz SRD band is used, N-mode works at 169MHz |
| Communication speed or data rate | 300 to 9600 bps | Different modes support different data rates, R2 (4.8 Kbps), S1/S1m (32768 Kbps), S2,T1,T2(support 100Kbps) |
| Distance coverage | 1000 meter using single twisted pair, upto 250 slaves can be connected | supports 1000 meter (in 868 to 870MHz) |
| Bit encoding (used at physical layer) | Bit 0 uses +36V(for master transmission), <1.5mA (for slave transmission) Bit 1 uses +24V(for master transmission), 11-20mA (for slave transmission) |
Different modes uses different encoding, All will have format consisting of preamble followed by sync word followed by encoding(either manchester or 3 out of 6 encoding) |
| Security layer | Not needed | Needed as the information travels wirelessly, Originally DES is used, Now AES 128 is employed |
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