3. • The spectrum sensing algorithm senses the whole spectrum of
interests serially, sub-band by sub-band.
• To acquire spectrum utilization within a sub-band quickly, we
discriminate traffic signal of the primary system from noise and
interference caused by the received energy and extracting signal
feature, including the fundamental symbol rate and CP, and then
ensure the existence of the active primary (OFDMA) system.
• We then consider the existence of the inactive primary system by
means of the control signal under three conditions: background
noise (C0), interfering traffic signal (C3 and C4) and interfering
control signal (C5).
• When an active primary system exists, we acquire the utilization
status of each channel along the time axis to further increase
spectrum efficiency by decoding the frame header, and then
determine the radio resource to secondary system(s).
INTRODUCTION
7/10/2017 4:10 PM
3
4.
5. • This general sensing algorithm is summarized as follows:
1. Initially, set channel state table as S0 and reset radio resource table.
2. For n=1 to NF (sub-band), do the following sub-steps. Then, go to Step 3.
2.1 Measure RSSI and distinguish the hypothesis test
a. H0: traffic signals do not exist
b. H1: traffic signals exist
c. If H0 is true, go to Step 2.6, else go to Step 2.2.
2.2 Track fundamental symbol rate of the primary system
a. H0: traffic signals with fundamental symbol rate of the primary
system do not exist
b. H1: traffic signals with fundamental symbol rate of the primary
system exist
c. If H0 is true, go to Step 2.7, else go to Step 2.3.
2.3 By CP of OFDMA signal, separate non-collaborative interference and
traffic signal from the primary system
i. H0: traffic signals with CP property of the primary system do not
exist
ii. H1: traffic signals with CP property of the primary system exist
iii. If H0 is true, go to Step 2.7, else go to Step 2.4.
2.4 Synchronise with the primary base station, including carrier and
timing synchronization, and channel estimation by preamble. Then, go
to Step 2.5.
SENSING PROCEDURE
7/10/2017 4:10 PM
5
6. 2.5 Decode frame header (DL_MAP and UL_MAP in this case) and obtain
transmission parameters of the primary system, including FEC rate, modulation
scheme and resource allocation. These parameters are used to set nth row of
channel state table from S2 to S4. Then, go to Step 2.9.
2.6 Measure energy of the control signal and detect the hypothesis test
a. H0: control signals do not exist
b. H1: control signals exist
c. If H0 is true, go to Step 2.9, else go to Step 2.8.
2.7 Extract control signal of the primary system from non-collaborative
interference
a. H0: control signals of the primary system do not exist
b. H1: control signals of the primary system exist
c. If H1 is true, set the nth row of channel state table as S1. Then, go to Step 2.9.
2.8 Track period of the control signal and discriminate between control signals
from the primary system and other systems
a. H0: control signals of the primary system do not exist
b. H1: control signals of the primary system exist
c. If H1 is true, set the nth row of channel state table as S1. Then, go to Step 2.9.
2.9 (optional) Identify system by fundamental symbol rate, cyclic properties of
OFDMA systems and control signal. This is critical information in cognitive
and cooperative networking. Then, go to Step 2.
3. According to channel state table, set radio resource table. Then, end of
sensing.
7/10/2017 4:10 PM
6
