BC41B143A-DS-001PE Datasheet, PDF (48/102 Pages) List of Unclassifed Manufacturers – BlueCpre 4-ROM Single Chip Bluetooth v2.0 System with EDR

Enhanced Data Rate
9 Enhanced Data Rate
Enhanced Data Rate (EDR) has been introduced to provide 2x and 3x⁽¹⁾ data rates with minimal disruption to
higher layers of the Bluetooth stack. BlueCore4-ROM supports both of the new data rates and is compliant with
the Bluetooth v2.0 + EDR specification.
Note:
(1) _{The inclusion of 3x data rates is optional.}
9.1 Enhanced Data Rate Baseband
At the baseband level EDR utilises the same 1.6kHz slot rate and 1MHz symbol rate as the basic data rate.
Where EDR differs is that each symbol in the payload portion of a packet represents 2 or 3-bits. This is achieved
using two new distinct modulation schemes. These are summarised in Table 9.1 and in Figure 9.1.
Link establishment and management are unchanged and still use GFSK for both the header and payload portions
of these packets.
Data Rate Scheme
Basic Data Rate
EDR
EDR
Bits Per Symbol
1
2
3
Table 9.1: Data Rate Schemes
Modulation
GFSK
π/4 DQPSK
8DPSK (optional)
Figure 9.1: Basic Data Rate and Enhanced Data Rate Packet Structure
9.2 Enhanced Data Rate π/4 DQPSK
The 2x rate for EDR uses a π/4 DQPSK. Each symbol represents two bits of information. The constellation is
shown in Figure 9.2 . It is described as having two places, each with four points. Although there appear to be
eight possible phase states, the encoding ensures that the trajectory of the modulation between symbols is
restricted to the four states in the other plane.
For a given starting point, each phase change between symbols is restricted to +3π/4, +π/4, -π/4 or -3π/4 radians
(+135°C, +45°C, -135°C or -45°C). For example, the arrows shown in Figure 9.2 represents trajectory to the four
possible states in the other plane. The phase shift encoding of symbols is shown in Table 9.2.
There are two primary advantages in using π/4-DQPSK modulation:
! The scheme avoids crossing the origin (a +π or –π phase shift) and therefore minimises amplitude
variations in the envelope of the transmitted signal. This is in turn allows the RF power amplifiers of
the transmitter to be operated closer to their compression point without introducing spectral
distortions. Consequently, the DC to RF efficiency is maximised.
! The differential encoding also allows for demodulation without the knowledge of an absolute value
for the phase of the RF carrier.
BC41B143A-ds-001Pe
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