SPECTRUM SENSING PROCEDURE & SENSING TREE
- 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
- 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
- 8. SENSING TREE 7/10/2017 4:10 PM 8
- 9. SENSING TREE 7/10/2017 4:10 PM 9