Digital Signal Processing Reference
In-Depth Information
blocker power
0dBm
0dBm
-
5dBm
-
23dBm
-
23dBm
-
33dBm
-
33dBm
-
43dBm
-
43dBm
76dB
out-of-ba
n
d
56dB
out-of-band
sensitivity loss due to blockers
3dB
-
102dBm
sensitivity level w/o blockers
minimal CNR
9dB
-
111dBm
rms noise level
maximal implementation loss
9.8dB
frequen
c
y
-
120.8dBm
channel background noise (bw=200kHz)
f
c
Figure 1.9.
Blocking profile and link budget for a gsm-900 mobile station. Data
was taken from the pan-European gsm 05
.
05 technical specifications
[Eur05].
Unlike for the unlicensed 2
.
4 GHz band used by the 802
.
11g devices, the loca-
tion of interferers in the gsm-900 frequency band is more or less predictable.
The bandwidth of a gsm receiver is 180 kHz. The gsm system employs a
very strict frequency allocation protocol and the interference from the first
adjacent channel is separated by 600 kHz from the center frequency of the
receiver. Specifications of the gsm systems require that the sensitivity of a
gsm-compliant mobile station (ms) is better than
102 dBm. Furthermore,
the blocking specifications state that this performance requirement is met for a
useful signal that is 3 dB higher than the reference sensitivity level in combina-
tion with a blocker signal of
−
43 dBm at 600 kHz offset. The implementation
loss (il) is thus better than 3 dB, for a blocker signal that is up to 56 dB -
more than five orders of magnitude! - higher than the signal-of-interest. In
the imaginary case that the same in-band blocking specifications should be re-
quested for an ofdm receiver, more than 10 extra bits would be required in
the ad-converter to provide sufficient headroom. It is clear that the dream of a
software-only radio receiver is not achievable in the foreseeable future.
15
−
1.5
Organizational overview of this text
The work that is presented hereafter introduces a new wideband transceiver
architecture, which is optimized for use in short-range high-speed data transfer
applications. It is our purpose to armour the core of the system so that it is able
