1. FEC on Sync Frame for the 802.22.1
Jan 2007
doc.: IEEE /0xxxr0
January 2007
FEC on Sync Frame for the
IEEE P Wireless RANs Date:
Authors:
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Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

2. Jan 2007
doc.: IEEE /0xxxr0
January 2007
Abstract
An enhanced Beacon Sync Frame scheme for IEEE Std is proposed. This new scheme will provide error correction and error detection capability for the Sync Frame. Compared to the previous proposal in [1], the number of parity bits was reduced and PSDU type information was added so that the WRAN can decide whether it should schedule Quiet Period to listen to the PSDU or not in advance.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

3. Content Enhanced Sync Frame Scheme Proposed Encoding and Decoding
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Content
Enhanced Sync Frame Scheme Proposed
Encoding and Decoding
Simulation Results
Conclusions
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

4. Enhanced Sync Frame Scheme Proposed (1/2)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Enhanced Sync Frame Scheme Proposed (1/2)
Sync Frame
With Index X
X-1
。。。
PSDU Frame
Sync Sequence
(15 bits)
PSDU Type
(1 bit)
Index
(6 bits)
Parity
(8 bits)
Sync Frame Structure
Super Frame Structure
DTX(2
bits)
Figure 1: The Enhanced Beacon Sync Frame structure
The Enhanced Beacon Sync Frame has now 32 bits in total, including 15-bit PN Sequence, 15-bit Information (consisting of 1-bit PSDU type information which tell the following PSDU is for WRAN or for beacon-to-beacon communication, 6-bit Index and 8-bit Parity) and 2-bit DTX (Discontinuous Transmission).
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

5. Enhanced Sync Frame Scheme Proposed (2/2)
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Enhanced Sync Frame Scheme Proposed (2/2)
Within the Sync Frame, the PSDU type and Index part need to be decoded successfully with high reliability. Otherwise, the receiver can’t decode the PSDU correctly. So we apply FEC (15, 7) to provide Error Correction and Error Detection capability on the PSDU type and Index part. Also, for the alignment reason, the Sync Frame should include integral number of bytes. So we add 2 DTX bits at the end of a Sync Frame to make it 32bits or 4 bytes in total.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

6. Encoding and Decoding (1/4)
January 2007
Encoding and Decoding (1/4)
The FEC code we select here is a code, which is a (n,k) = (15, 7) linear block code.
In the transmitter side, the encoding is just like adding a CRC. The generator polynomial we are using here is
The 1-bit PSDU Type and 6-bit Index are combined together as a message to be encoded and denoted in a polynomial form as
Wu Yu-Chun, Huawei Hisi

7. Encoding and Decoding (2/4)
January 2007
Encoding and Decoding (2/4)
Then The data will be transmitted in the order of where is transmitted first.
Wu Yu-Chun, Huawei Hisi

8. Encoding and Decoding (3/4) Figure 2: The Encoding Circuit of FEC
January 2007
Encoding and Decoding (3/4)
The Encoding procedure can be implemented as in the following diagram:
Figure 2: The Encoding Circuit of FEC
Wu Yu-Chun, Huawei Hisi

9. Encoding and Decoding (4/4) Figure 3: The Decoding Circuit of FEC
January 2007
Encoding and Decoding (4/4)
The decoder can be implemented as in the following circuit diagram: …
Figure 3: The Decoding Circuit of FEC
Wu Yu-Chun, Huawei Hisi

10. Simulation Results (1/2)
January 2007
Simulation Results (1/2)
The simulation results of 7-bit message without FEC and 15-bit with FEC(15,7) on the AWGN channel are plotted in the following figure.
Figure 4: Simulation Results of Sync Frame
Wu Yu-Chun, Huawei Hisi

11. Jan 2007
doc.: IEEE /0xxxr0
January 2007
Conclusions (1/2)
From the previous slides, we can see that the Enhanced Sync Frame Scheme has following advantages:
The Enhanced scheme provides error correction capability, which greatly improves the Sync performance (about 4.5dB in SNR sense and 1.5dB in Eb/N0 sense).
The FEC also provides error detection capability. This is very important to ensure that the WRAN does not waste a long Quiet Period to decode the PSDU when it did not get the correct start position of the PSDU.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

12. Jan 2007
doc.: IEEE /0xxxr0
January 2007
Conclusions (2/2)
The FEC used here has a very simple encoding algorithm as well as a very simple decoding algorithm. The encoding procedure is just like adding a CRC. Regarding decoding complexity, only three XOR operations, one addition operation, and one comparison operation are needed for each bit.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

13. Jan 2007
doc.: IEEE /0xxxr0
January 2007
References
《 _Huawei_Beacon_Sync_Frame_Proposal》.
《 _WRAN_Sensing_Window》
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

14. Any comments and questions will be highly appreciated!
Jan 2007
doc.: IEEE /0xxxr0
January 2007
Thank you!
Any comments and questions
will be highly appreciated!
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi