HSP3824
TABLE 7. BIT RATE TABLE EXAMPLES
DATA RATE
FOR 11
CHIPS/BIT
(MBPS)
DATA RATE
FOR 13
CHIPS/BIT
(MBPS)
DATA RATE
FOR 15
CHIPS/BIT
(MBPS)
DATA RATE
FOR 16
CHIPS/BIT
(MBPS)
SAMPLE
CLOCK MCLK TX SETUP CR 3
DATA
MODULATION
RX SET UP
CR 2 BITS 4, 3
(MHz)
BITS 4, 3
00 (N = 2)
01 (N = 4)
10 (N = 8)
11 (N = 16)
00 (N = 2)
01 (N = 4)
10 (N = 8)
11 (N = 16)
DQPSK
DQPSK
DQPSK
DQPSK
DBPSK
DBPSK
DBPSK
DBPSK
44
00
01
10
11
00
01
10
11
4
2
3.385
1.692
0.846
0.423
1.692
0.846
0.423
0.212
2.933
1.467
0.733
0.367
1.467
0.733
0.367
0.183
2.75
22
1.375
0.688
0.344
1.375
0.688
0.344
0.171
11
1
5.5
44
0. 5
2
22
1
11
0.5
0.25
5.5
into consideration the noise and interference requirements in
conjunction with the desired probability of detection vs prob-
ability of false alarm for signal acquisition.
Header/Packet Description
The HSP3824 is designed to handle continuous or pack-
etized Direct Sequence Spread Spectrum (DSSS) data
transmissions. The HSP3824 can generate its own preamble
and header information or it can accept them from an exter-
nal source.
The five available fields for the header are:
SFD Field (16 Bits) - This field carries the ID to establish
the link. This is a mandatory field for the HSP3824 to estab-
lish communications. The HSP3824 will not declare a valid
data packet, even if it PN acquires, unless it detects the spe-
cific SFD. The SFD field is required for both Internal pream-
ble/header generation and External preamble/header
generation. The HSP3824 receiver can be programmed to
time out searching for the SFD. The timer starts counting the
moment that initial PN synchronization has been established
from the preamble.
When preamble and header are internally generated the
device supports a synchronization preamble up to 256 sym-
bols, and a header that can include up to five fields. The pre-
amble size and all of the fields are programmable. When
internally generated the preamble is all 1's (before entering
the scrambler). The actual transmitted pattern of the pream-
ble will be randomized by the scrambler if the user chooses
to utilize the data scrambling option.
Signal Field (8 Bits) - This field indicates whether the data
packet that follows the header is modulated as DBPSK or
DQPSK. In mode 3 the HSP3824 receiver looks at the signal
field to determine whether it needs to switch from DBPSK
demodulation into DQPSK demodulation at the end of the
always DBPSK preamble and header fields.
When the preamble is externally generated the user can
choose any desirable bit pattern. Note though, that if the pre-
amble bits will be processed by the scrambler which will alter
the original pattern unless it is disabled.
The preamble is always transmitted as a DBPSK waveform
with a programmable length of up to 256 symbols long. The
HSP3824 requires at least 126 preamble symbols to acquire
in a dual antenna configuration (diversity), or a minimum of
78 preamble symbols to acquire under a single antenna con-
figuration. The exact number of necessary preamble sym-
bols should be determined by the system designer, taking
Service Field (8 Bits) - This field can be utilized as required
by the user.
Length Field (16 Bits) - This field indicates the number of
data symbols contained in the data packet. The receiver can
be programmed to check the length field in determining
CR #0 BITS
HEADER
COUNT
BIT 4 BIT 3
N (Preamble) +
16 (Header) Bits
0
0
1
1
0
1
0
1
Preamble (SYNC) SFD
N Bits Up to 256) 16 Bits
N (Preamble) +
32 (Header) Bits
Preamble (SYNC) SFD
N Bits Up to 256) 16 Bits
CRC16
16 Bits
N (Preamble) +
48 (Header) Bits
Preamble (SYNC) SFD
N Bits Up to 256) 16 Bits
Length Field CRC16
16 Bits
16 Bits
N (Preamble) +
64 (Header) Bits
Preamble (SYNC) SFD
N Bits Up to 256) 16 Bits
Signal Field
8 Bits
Service Field Length Field CRC16
8 Bits
16 Bits
16 Bits
HEADER
PREAMBLE
FIGURE 10. PREAMBLE/HEADEAR MODES
15
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