1. Inter-BS Synchronization and Fast Detection of WRAN Systems
2006 March
Inter-BS Synchronization and Fast Detection of WRAN Systems
IEEE P Wireless RANs Date:
Authors:
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2. Inter-BS Synchronization
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3. TWO INTER-BS SYNCHRONIZATIONS
Problems to be solved
For the requirement of co-existence among WRAN systems in an overlapped coverage area, synchronization among these base stations (BSs) should be performed within an overlapped coverage area.
Only a complementary method for synchronization slide scheduling by using time offsets extracted from received beacon signals is suggested.
Two inter-BS synchronizations
Synchronization between two base stations
Synchronization among multiple base stations
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4. 2006 March
Part 1:
Synchronization between Two Base Stations
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5. 2006 March
BACKGROUND
The same operations are applied to CBPs received directly by BS itself and through a bridge CPE.
Different synchronization results can be obtained for both cases.
For the case that a BS performs synchronization according to CBPs received directly by itself :
at the BS, signals from different BSs arrive at the BS simultaneously.
at the CPEs, signals from different BSs do not arrive simultaneously.
 Compensation should be made according to the size of coverage of a BS
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6. 2006 March
HUAWEI’S PROPOSAL
Add compensation according to the size of coverage of a BS
Modify equations of Slide Amount and Directionin Section :
where GuardSymbol is the number of symbols corresponding to the compensation range ( ).
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7. 2006 March
CONCLUSIONS
The different operations are applied to CBPs received by BSs and CPEs
Compensation is made according to the radius of coverage area of own BS to CBPs received by BS itself.
Downstream subframes at each BS and upstream subframes at each neighboring BS are transmitted at different times after Synchronization.
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8. 2006 March
Part 2:
Synchronization among Multiple Base Stations
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9. AN EXAMPLE OF OVERLAPPING BSs
2006 March
AN EXAMPLE OF OVERLAPPING BSs
A different priority to each BS is assigned. BS A B C D E
priority 3 1 4 2 5
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10. SYNCHRONIZATION RULES
2006 March
SYNCHRONIZATION RULES
Synchronization procedure :
Step 1
BSA and BSC are synchronized with BSB because BSB has the highest priority.
BSE is synchronized with BSD because BSD has the higher priority.
Step 2
BSD is synchronized with BSC
BSE is synchronized with BSA
Synchronization priority can be set according to parameters of the BS such as MAC address or IP address
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11. SYNCHRONIZATION INITIALIZATION
Syn_Pri
synchronization priority of a BS, given by the manufacturer or other.
High_Syn_Pri:
highest synchronization priority of a BS, used for storing the highest priority which the BS is being synchronized to.
High_Syn_Pri and Syn_Pri will be set to an equal value when they are initializing.
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12. SYNCHRONIZATION NEGOTIATION
When there are active CPEs in an overlapped area between BSs and these CPEs have received SCHs or CBPs from the other BS in quiet periods (QPs) scheduled by their BS, the BS can perform synchronization operations using these active CPEs as bridges.
That is, CBP packets can be relayed to a neighboring BS through CPEs.
When a BS is close enough to the neighboring BS, the messages in the previous slide can also be received by the neighboring BS directly.
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13. CBP MAC PDU Syntax Size Notes CBP MAC PDU () {
2006 March
CBP MAC PDU
Syntax
Size
Notes
CBP MAC PDU () {
1 OFDM symbol, using known modulation method
Syn Pri
n bits
Synchronization priority, can be set with MAC address, IP address etc. of BS.
Reception Offset
Indicates the offset (in units of slot duration) relative to the start of the first slot of the PHY PDU (including preamble) frame where the beacon was received. The time instants indicated by the Reception Offset values are the reception times of the first slot of the beacon including preamble (if present).
HCS
8 bits
Header Check Sequence }
Here only necessary fields about synchronization priority are listed here.
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14. FLOW CHART Syn_Pri: synchronization priority of own BS
2006 March
FLOW CHART
Syn_Pri: synchronization priority of own BS
High_Syn_Pri: highest priority synchronized so far
High_Syn_Pri and Syn_Pri will be set to an equal value when they are initializing.
Details of confirmation and tracking of synchronization can be seen in Section of Reference [1]. In this reference, for tracking of synchronization, only a CBP packet with a synchronization priority equals to High_Syn_Pri should be tracked.
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15. 2006 March
CONCLUSIONS
Establishment and confirmation and tracking of synchronization can be achieved with the same procedures described in the current draft of the standard.
Frequent sliding can be avoided for synchronization
Synchronization can be assured in all BS.
Rapid synchronization can be achieved among multiple BSs.
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16. Fast Detection of WRAN Systems under Lower SINR Conditions
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17. 2006 March
BACKGROUND
CPEs in the overlapping area may not detect WRAN signals and can not notify WRAN system that there is interference as in hidden incumbent cases.
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18. OUR PROPOSAL Detect long training sequences in frame preambles
2006 March
OUR PROPOSAL
Detect long training sequences in frame preambles
Detect short training sequences in frame preambles (optional)
Detect long training sequences in superframe preambles
The main reason for the above proposal is that the repeated period of superframe preambles is much larger than that of frame preambles.
Frame preamble detection can be performed with preamble training sequence, which includes long training sequence and short training sequence. However we propose to detect frame preamble long training sequence to increase detection rate. During slide detection, we can use 1/2 FFT block as a unit to slide. It is feasible that 1/2 FFT block is slid as a unit because LT in the second OFDM symbol of preamble is repeated twice. So wherever slide initial position is, 1/2 FFT block selected always inside FFT time occupied preamble LT. In addition, to reduce probability of miss detection, after preamble LT is detected, ST need be detected to confirm WRAN existence.
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19. represents no. of preamble FFT samples
2006 March
DETECTION PROCEDURE
represents no. of preamble FFT samples
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20. SIMULATION RESULT 1 Determine detection threshold for SIR of -12 dB
2006 March
SIMULATION RESULT 1
Determine detection threshold for SIR of -12 dB
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21. 2006 March
SIMULATION RESULT 2
Detection probability VS SIR , relative threshold=0.9
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22. CONCLUSIONS Can capture WRAN system signals in low SNR situations.
2006 March
CONCLUSIONS
Can capture WRAN system signals in low SNR situations.
Combine frame preambles with superfame preambles to achieve rapid detection.
Low probabilities of false detection can be achieved.
Huawei