Product Info

DS-2472-01 <Rev.0.0> page 15/ 63
The key features of the DKL 1908_V.1 PHY are:
 RF frequency ranges from 2400 to 2483.5 MHz with 1MHz programmable resolution.
 Offset QPSK (O-QPSK) modulation with DSSS : 125kbps and 250kbps.
 Minimum-Shift Keying (MSK) : 1Mbps, and 2 Mbps
 Innovative and patented on-fly multi-rate detection
For all MSK modes, 4:32 spreading codes of DSSS are used for PHY header including preamble, SFD and Frame
Length (FL) but no spreading codes are used for the PHY payload data. The transmission rate of the
un-spreading PHY payload data bits is 8 times of PHY header. Thus the data rate of MSK modes is 8 times than
OQPSK-DSSS modes.
The 125Kbps OQPSK-DSSS mode and the 1Mbps MSK mode have the same chip rate 1Mcps and occupy an RF
channel bandwidth of 1MHz.The 250kbps OQPSK-DSSS mode and t
he 2Mbps MSK mode have the same chip
rate 2Mcps and occupy an RF channel bandwidth of 2MHz.
The DKL 1908_V.1 PHY provides on-fly multi-rate detection function. The DKL 1908_V.1 PHY provides on-
fly multi-rate detection function to permit multi-rate transmission and on fly detection of transmission rate.
The DKL 1908_V.1 PHY comprises the transmitter configured to set a predetermined bit in the PHY header of
the transmission frame to indicate whether the transmission frame is encoded by OQPSK-DSSS encoding
mode or by MSK encoding mode and the receiver configured to decode the received transmission
frame according to whether the predetermined bit in the PHR of the received transmission frame
indicates the received transmission frame is encoded by OQPSK-DSSS encoding mode or by MSK encoding
mode. The 8th digit bit of the frame length is used to identify which modulation is used in PHY payload
data. By detecting whether the 8th digit bit of the frame length is a 0 or a 1 on the fly, the receiver
distinguishes between the OQPSK-DSSS mode and the MSK mode and determines whether 4:32 spreading
codes of DSSS is being used without predefining which mode is used.
The packet includes a 6-byte PHY header and a 8-39-byte PHY payload. The 6-byte PHY header includes 4
bytes of preamble, 1 byte of SFD, and 1 byte of frame length. Preamble and SFD are used for receiver packet
detection and synchronization. The FL field specifies the length of the PHY payload. The length is valid from 6
to 31 bytes. The 8th bit of FL field is used for indicating OQPSK-DSSS mode when the 8th bit is a 0, and MSK
mode when the 8th bit is a 1. The frame format is as below:
Figure 4. PHY Layer Frame Format
4 bytes 1 byte 1 byte 8~39 bytes
Preamble
Start of Frame
Delimiter
Frame
Length
PHY Payload
PHY header