Chapter 5 Hardware Implementation
5.3 Summary
Figure 5-4: Hardware design of timing synchronization
5.3 Summary
Table 5-1 Hardware specifications Hardware specifications
Application IEEE 802.11n MIMO-OFDM
Space-Time Coding 4×4 STBC
FFT/IFFT Size 64 point
Support Antenna Configuration 4 Tx, 1~4 Rx
Support Modulation Type BPSK, QPSK, 16-QAM, 64-QAM
Technology UMC 0.13 mμ
System Clock 20 MHz
The hardware specifications, area report and power report are listed in Table 5-1, Table 5-2, and Table 5-3, respectively.
Table 5-2 Area report Area Report
Combinational area 919236.062500 Noncombinational area 235669.484375 Total cell area 1155449.000000
Table 5-3 Power report Power Report
Global Operating Voltage 1.08(V)
Cell Internal Power 10.3144 mW (82%) Net Switching Power 2.2623 mW (18%) Total Dynamic Power 12.5767 mW (100%)
Cell Leakage Power 1.0648 mW
Chapter 6
Conclusion and Future Work
N this thesis, based on the share architecture and the preamble structure of IEEE 802.11n standard, a synchronization algorithm for IEEE 802.11n WLANs over TGN channels is proposed. A realistic channel model was employed, which includes the effects of physical channel, filtering, carrier offset, sampling clock offset, and impulsive inference. Loss in system performance due to synchronization error was used as a performance criterion.
6.1 Conclusion
In section 3.1.1, an autocorrelation based packet detection was introduced. The comparisons are shown in Table 6-1.
Table 6-1: Comparisons among state-of-the-art packet detection algorithm
[16] [17] [18] This work
Modulation CPM OFDM OFDM OFDM
Correlator N/A 1 3 1
Detection method One-shot One-shot One-shot FSM
Correlation window N/A 32 sample 32 sample 16 sample Redetection period 3 symbols N/A N/A 1 symbol
Required SNR 10 dB 10 dB 2.5 dB 0 dB
Packet loss rate 10% N/A 12% <1%
I
In section 3.1.2, cyclic extension of L-STS is used to synchronize the symbol boundary. Since the estimator uses the inherent information of the OFDM preamble form the buffer, no additional training sequence is needed. The correlation window size B is set as 13 sample. The comparisons are shown in Table 6-2.
Table 6-2: Comparisons among state-of-the-art packet symbol boundary detection algorithm
[22] [24] This work
System platform OFDM OFDM OFDM
Hardware Integration Autocorrelation
Moving-average Crosscorrelation Required Sample 16 sample 16/64 sample 13 sample
Required SNR N/A 10 dB 5 dB
In section 3.2, a timing synchronization algorithm using the boundary coefficient to made decision was proposed. In other words, the timing synchronization shared the hardware architecture with symbol detection. A multiphase generator with 22 phases was used. Each of coarse and fine timing synchronization used half a L-STS, equal to 8 samples, the overall timing synchronization used a L-STS. The comparisons were shown in Table 6-3.
Table 6-3: Comparisons among state-of-the-art timing synchronization algorithm
[25] [26] [27] [28] This work
Digital All-Digital All-Digital
Method DAC +
47
6.2 Future Work
A wireless communication system may experiment several kind of noise. In most of the cases, like thermal, atmospheric, or galactic noise, it can be represented by a Gaussian model. However, man-made noise that appears in urban environments cannot be assumed to be Gaussian. There are still some problems need to be solve. An exhaustive impulsive interference mode should be modified. Preamble and data compensations must be done.
As to the system, high QAM constellation likes 256-QAM for higher data rate is going to be deployed. Then, more antennas of transmitter and receiver like 8*8 are taken into consideration. Even huge FFT/IFFT (size bigger than 1000) is also a good research topic.
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