z-wave physical layer | zwave PHY layer basics

This page on z-wave physical layer(PHY) covers basic features of zwave physical layer and mention z-wave PHY transmitter block diagram.

The following are the functions performed at z-wave physical layer(zwave PHY).

•  to assign RF profile to the zwave physical channel
•  to activate and deactivate RF transceiver
•  Transmission and reception of data frames i.e. payload
•  clear channel assessment
•  radio frequency selection
•  link quality check based on received frames

There are three different data rates supported in z-wave Physical layer. They are 9.6 kbps(designated as 'R1'), 40 Kbps(designated as 'R2') and 100 Kbps(designated as 'R3'). Based on this data rate different physical layer configuration is made.

z-wave physical layer,zwave PHY

As shown in the figure-1 z-wave physical layer consists of modulation and coding blocks. Based on the data rates R1, R2 or R3 different configurations of the z-wave PHY is made as mentioned in the table below.

Data Rate Designation Bit Rate Symbol Rate Accuracy
R1 9.6 Kbps 19.2 Kbaud +/- 27 ppm
R2 40 Kbps 40 Kbaud +/-27 ppm
R3 100 Kbps 100 Kbaud +/-27 ppm

Table-1: z-wave Data Rate and Accuracy

After the modulation and coding of the input MAC layer data, frame is formed as per format outlined in z-wave tutorial. In order to do this at physical layer preamble is inserted before 'SOF' field.

Data Rate Designation Modulation Coding separation Symbols
R1 FSK Manchester 40 KHz+/-10% Binary
R2 FSK NRZ 40 KHz+/-10% Binary
R3 GFSK (BT=0.6) NRZ 58 KHz+/-10% Binary

Table-2:Modulation and coding format in z-wave Physical Layer

As mentioned in the table-2 FSK modulation is employed for R1 and R2 rates while GFSK is used for R3 data rate. For R1 manchester coding is used while for R2/R3 NRZ coding types is used.

All the data is transmitted in little endian format. They are transmitted in blocks of 8 bit with MSB is sent first after manchester coding. Manchester coding will help in obtaining DC free signal.

At the z-wave physical layer receiver, preamble is used for synchronization before decoding and demodulation is carried out to retrieve the MAC layer data. After the decoding of the data, they will be passed to the upper layers for further processing.

Similar posts on z wave technology

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z-wave physical layer-PHY
z-wave MAC layer
z-wave protocol stack
z-wave security basics
z-wave device conformance testing

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