S=2: each bit is encoded as 2 symbols, giving 500 kbps data rate and approximately 5 dB coding gain. S=8: each bit encoded as 8 symbols, giving 125 kbps and approximately 12 dB coding gain. S=8 provides maximum range but 8x longer on-air time, increasing power consumption per packet.

How much range increase?

S=8 provides approximately 12 dB additional link budget vs 1M PHY. In free space, this translates to approximately 4x range. In practice (obstructed indoor), 2-3x improvement is typical. Combined with +20 dBm TX power (BLE 5.0 max), links exceeding 1 km LOS have been demonstrated.

Power consumption impact?

S=8 takes 8x longer per packet than 1M PHY. A 20-byte payload takes approximately 16 ms at S=8 vs 2 ms at 1M. The radio draws current for the full duration. However, for infrequent sensor reports (once per minute), the absolute energy difference is small and the extended range eliminates the need for range extenders or mesh networking.

Wireless Protocols

BLE Coded PHY

BLE Coded PHY is a physical layer option in Bluetooth 5.0 that applies forward error correction (FEC) to extend range by trading data rate for coding gain. S=2 mode encodes each bit as 2 symbols (500 kbps, +5 dB), and S=8 encodes each bit as 8 symbols (125 kbps, +12 dB). At S=8, the receiver sensitivity improves to approximately −103 dBm (vs −97 dBm for 1M PHY), enabling 4× range extension in line-of-sight conditions.

Category: Wireless Protocols

Modes: S=2 (500k), S=8 (125k)

Understanding BLE Coded PHY

The Coded PHY still transmits at 1 Msymbol/s GFSK (same as 1M PHY), but each data bit is represented by multiple symbols using convolutional coding and pattern mapping. The FEC decoder at the receiver can correct bit errors that would cause packet loss on uncoded PHY, effectively improving sensitivity without hardware changes.

The access address and coding indicator (CI) are always sent at 1M rate, so the receiver first decodes the preamble at 1M, then switches to the coded rate for the payload. This allows mixed-mode operation within a single packet.

Coded PHY Link Budget

Coding gain:
S=2: +5 dB (√2× range)
S=8: +12 dB (~4× range)

Link budget at +0 dBm TX:
1M: 0 − (−97) = 97 dB
Coded S=8: 0 − (−103) = 103 dB

Coded PHY Mode Comparison

Mode	Symbols/Bit	Data Rate	Sensitivity	Range vs 1M
1M (uncoded)	1	1 Mbps	−97 dBm	1×
Coded S=2	2	500 kbps	−100 dBm	~1.4×
Coded S=8	8	125 kbps	−103 dBm	~4×

Common Questions

Frequently Asked Questions

S=2 vs S=8?

S=2: 500 kbps, +5 dB gain. S=8: 125 kbps, +12 dB gain. S=8 gives maximum range but 8× longer packets.

Range increase?

S=8: ~4× in LOS, 2-3× practical indoor. With +20 dBm TX, links exceeding 1 km demonstrated.

Power impact?

S=8 packets take 8× longer. For infrequent sensors (1/min), the energy difference is small and eliminates mesh/repeater needs.

Related Terms

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