1. High-Speed Broadband Wireless LAN Solution
March 2007
doc.: IEEE /0402r0
March 2007
High-Speed Broadband Wireless LAN Solution
Date:
Authors:
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Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

2. High-Speed Broadband Wireless LAN Solution
March 2007
doc.: IEEE /0402r0
March 2007
Abstract
High-Speed Broadband Wireless LAN Solution
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

3. Contents Inadequacy in 802.11a/g Nufront solution
March 2007
doc.: IEEE /0402r0
March 2007
Contents
Inadequacy in a/g
Nufront solution
(1) Subchannel-modulation mode
(2) PHY superframe
(3) Advantages and benefits
Simulation and computation results
Conclusion
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

4. Inadequacy in 802.11a/g Low speed in data transmission
March 2007
doc.: IEEE /0402r0
Inadequacy in a/g
March 2007
Low speed in data transmission
Two factors that limit a/g data transmission speed:
(1) The ordinary OFDM is affected by the frequency-selective fading of channel
(2) Overhead in MAC access as well as in PHY frame
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

5. Frequency selective fading in 802.11a/g channel
March 2007
doc.: IEEE /0402r0
March 2007
Frequency selective fading in a/g channel
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

6. Nufront solution Subchannel-modulation mode:
March 2007
doc.: IEEE /0402r0
Nufront solution
March 2007
Subchannel-modulation mode:
Each chosen subchannel modulation mode is based on the gain of subchannel
PHY Superframe:
A PHY superframe is composed of several PHY frames
Advantages and benefits
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

7. Subchannel-modulation mode
March 2007
doc.: IEEE /0402r0
March 2007
Implementation steps:
1. Transmit station transmits a packet to receive station;
2. Receive station makes channel estimation with this packet, and then chooses modulation mode for each subchannel;
3. Receive station feeds back reference data of subchannel-modulation mode to transmit station;
4. Transmit station transmits data packets to receive station based on the chosen subchannel-modulation mode.
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

8. Subchannel-modulation mode
March 2007
doc.: IEEE /0402r0
Subchannel-modulation mode
March 2007
Innovations in the implementation:
1. Make use of MAC layer’s interaction (for example, RTS-CTS) to compute and feed back reference data of the subchannel-modulation mode
In the RTS-CTS interaction, the receive station uses RTS to estimate channel, and then uses CTS to feed back reference data of the subchannel-modulation mode.
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

9. Subchannel-modulation mode
March 2007
doc.: IEEE /0402r0
Subchannel-modulation mode
March 2007
2. “Reflexive” channel estimation
When a MAC frame is proved correct through FCS checking, it is transformed into a baseband signal sequence. This sequence is then taken as a new lengthened training sequence to get a much more accurate channel estimation.
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

10. Subchannel-modulation mode
March 2007
doc.: IEEE /0402r0
Subchannel-modulation mode
March 2007
3. Reconstruct the SIGNAL symbol of the PHY frame using subchannel-modulation mode
Swap Field “Duration” in MAC frame and Field “LENGTH” in PHY frame
Maximum PHY data rate: 72 Mbps
(256QAM)
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

11. Implementation steps:
March 2007
doc.: IEEE /0402r0
PHY Superframe
March 2007
Implementation steps:
1. Concatenating SIGNAL symbols and data symbols of different PHY frames to construct a superframe;
2. Adding a preamble to the superframe.
PREAMBLE
DATA 1 ……
SIGNAL 2 K
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

12. March 2007
doc.: IEEE /0402r0
PHY Superframe
March 2007
Group acknowledgement mechanism
Whenever a receive station gets a chance to respond, it responds to all the packets received since its last response.
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

13. Advantages and benefits
March 2007
doc.: IEEE /0402r0
Advantages and benefits
March 2007
(1) High data transmission speed
See “Simulation and computation results”
(2) Low complexity
It can be implemented by only replacing the a/g DSP unit with the DSP unit based on Nufront solution while keeping the existing RF unit unchanged
(3) Compatibility with a/g
The PHY and MAC frame structures of Nufront solution are almost as same as a/g
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

14. Simulation and computation results
March 2007
doc.: IEEE /0402r0
March 2007
Simulation and computation results
(1) PHY data rate achieved by the subchannel-modulation mode
(2) MAC throughput achieved by the PHY superframe
(3) Data transmission speed achieved
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

15. Achieved PHY data rate comparison among different modes
March 2007
doc.: IEEE /0402r0
March 2007
Achieved PHY data rate comparison among different modes
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

16. March 2007
doc.: IEEE /0402r0
March 2007
Comparison of achieved MAC throughput between superframe and a/g system
Achieved data rate in PHY layer
(Mbps)
Achieved MAC throughput (Mbps)
802.11a/g system
Superframe system(K=10)
Superframe system(K=20) 36
28.89
34.32
34.67 48
36.53
45.33
45.94 54
39.80
50.73
51.53 72
49.08
66.72
68.06
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

17. Data transmission speed achieved
March 2007
doc.: IEEE /0402r0
March 2007
Data transmission speed achieved
SNR
(dB)
Data transmission speed(Mbps) (802.11a/g)
Data transmission speed (Mbps)
(Nufront)
Number of HDTV and SDTV that can work 15
11.0
23.1
1 HDTV
or 5 SDTV 20
18.7
35.9
1 HDTV, 3 SDTV 25
20.7
49.8
2 HDTV, 2 SDTV
Or 1HDTV,7 SDTV
(K=10)
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

18. March 2007
doc.: IEEE /0402r0
March 2007
Conclusion
Nufront solution proposes the subchannel-modulation mode and the PHY superframe in a/g WLAN to improve the network’s PHY data rate and MAC throughput, respectively.
Simulation and computation results indicate that, based on Nufront solution, a much higher data transmission speed in comparison with the a/g system can be achieved. Thus HDTV can be transmitted through WLAN.
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

19. March 2007
doc.: IEEE /0402r0
March 2007
Conclusion
By only replacing the a/g baseband DSP unit with the DSP unit based on Nufront solution while keeping the existing RF unit unchanged, a high-speed WLAN system compatible with a/g can be achieved.
At the beginning of our R&D, we found an economic improvement and upgrade to is very important. We also found a chip with Nufront solution can be easily made through existing SoC technology.
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software

20. Thank You Very Much! March 2007 March 2007 doc.: IEEE 802.11-07/0402r0
Hamilton Young, Beijing Nufront Software
Hamilton Young, Beijing Nufront Software