14.4.1.1 Spreading, Modulation and Pulse Shaping

The AT86RF212B supports various physical layer (PHY) modes independent of the RF channel selection. Symbol mapping along with chip spreading, modulation and pulse shaping are a part of the digital base band processor.

Figure 14-37. Base Band Transmitter Architecture

The combination of spreading, modulation and pulse shaping are restricted to several combinations, as shown in the table below.

The AT86RF212B is fully compliant to the IEEE 802.15.4 low data rate modes of 20 kb/s or 40 kb/s, employing binary phase-shift keying (BPSK) and spreading with a fixed chip rate of 300 kchip/s or 600 kchip/s, respectively. The symbol rate is 20 ksymbol/s or 40 ksymbol/s, respectively. In both cases, pulse shaping is approximating a raised cosine filter with roll-off factor 1.0 (RC-1.0).

For optional data rates according to IEEE 802.15.4-2006, offset quadrature phase-shift keying (O-QPSK) is supported by the AT86RF212B with a fixed chip rate of either 400 kchip/s or 1000 kchip/s.

At a chip rate of 400 kchip/s, there is a choice between two different Pulse Shaping modes. One Pulse Shaping mode uses a combination of both half-sine shaping (SIN) and raised cosine filtering with roll-off factor 0.2 (RC-0.2) according to IEEE 802.15.4‑2006 [2] for the 868.3 MHz band. The other uses raised cosine filtering with roll-off factor 0.2 (RC‑0.2).

At a chip rate of 1000 kchip/s, pulse shaping is either half-sine filtering (SIN), as specified in IEEE 802.15.4-2006 [2], or, alternatively, raised cosine filtering with roll-off factor 0.8 (RC-0.8) as specified in IEEE 802.15.4c™‑2009 [3] and IEEE 802.15.4-2011 [4].

For O-QPSK, the AT86RF212B supports spreading according to IEEE 802.15.4-2006 with data rates of either 100 kb/s or 250 kb/s depending on the chip rate, leading to a symbol rate of either 25 ksymbol/s or 62.5 ksymbol/s, respectively.

Additionally, the AT86RF212B supports two more spreading codes for O-QPSK with shortened code lengths. This leads to higher but non-IEEE 802.15.4 compliant data rates for PSDU transmission at 200, 400, 500 and 1000 kb/s.

Table 14-30. Modulation and Pulse Shaping
Modulation	Chip Rate [kchip/s]	Supported Data Rate for PPDU Header [kb/s]	Supported Data Rates for PSDU [kb/s]	Pulse Shaping
BPSK	300	20	20	RC-1.0
BPSK	600	40	40⁽¹⁾	RC-1.0
O-QPSK	400	100	100, 200, 400	SIN and RC-0.2
	400	100	100, 200, 400	RC-0.2
	1000	250	250, 500⁽¹⁾, 1000	SIN
	1000	250	250, 500⁽¹⁾, 1000	RC-0.8

Support of two different spreading codes.