Functional description

STLC2500A

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5.5.1

V1.2 detailed functionality - Extended SCO

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User Perspective - Extended SCO

This function gives improved voice quality since it enables the possibility to retransmit lost or

corrupted voice packets in both directions.

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Technical perspective - Extended SCO

eSCO incorporates CRC, negotiable data rate, negotiable retransmission window and multi-

slot packets. Retransmission of lost or corrupted packets during the retransmission window

guarantees on-time delivery.

Figure 3.

eSCO

5.5.2

V1.2 detailed functionality - Adaptive Frequency Hopping

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User Perspective - Adaptive Frequency Hopping

In the Bluetooth spec 1.1, the Bluetooth devices hop in the 2.4 GHz band over 79-channels.

As WLAN 802.11 has become popular, there are improvements in the Bluetooth spec 1.2

specifying how Bluetooth units can avoid jammed bands and provide an improved co-

existence with WLAN.

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Technical perspective - Adaptive Frequency Hopping

Figure 4.

AFH

First the Master and/or the Slaves identify the jammed channels. The Master decides on the

channel distribution and informs the involved slaves. The Master and the Slaves, at a

predefined instant, switch to the new channel distribution scheme.

No longer jammed channels are re-inserted into the channel distribution scheme. AFH uses

the same hop frequency for transmission as for reception.

SCO

SCO

SCO

SCO

ACL

ACL

SCO

SCO

eSCO retransmission window

t

t

WLAN used frequency

WLAN used frequency

t

f

f

AFH(79)

AFH(19<N<79)