1. HNS Proposal for 802.11n Physical Layer
doc.: IEEE n
Sept 2004
HNS Proposal for n Physical Layer
Mustafa Eroz, Feng-Wen Sun, & Lin-Nan Lee
Hughes Network Systems
11717 Exploration Lane
Germantown, MD 20876
Mustafa Eroz, Hughes Network Systems
Mustafa Eroz, Hughes Network Systems

2. Proposal Topics PHY and Air Interface Description
doc.: IEEE n
Sept 2004
Proposal Topics
PHY and Air Interface Description
Supported Rate Set (mandatory/optional)
Preamble Design Approach
Block Diagram used for Simulation
Spectral Mask with non-linear model
Short Block Length LDPC Performance Curves
Mustafa Eroz, Hughes Network Systems
Mustafa Eroz, Hughes Network Systems

3. Sept 2004
PHY and Air Interface
The air interface is built upon IEEE a (1999) PHY specifications and associated overhead
OFDM Modulation with PSK and QAM
(20/64) MHz channel spacing, 52 Sub-carrier set
48 data carriers and 4 pilots (center location not used)
Preamble modified for MIMO
Compatible with a air-interface
2, 3 and 4 TX antenna HT modes support
One TX Antenna mode for legacy STA support
PHY-MAC maximum efficiency of 60% assumed
In AP-STA test, 100Mbps at MSDU  167 Mbps at PHY
Mustafa Eroz, Hughes Network Systems

4. 802.11n Rate Set Supported Sept 2004
No. of TX Antennas
Modulation Type
Transmit bits per channel use
Code Rate
Info. Bytes per channel. use
PHY Info Rate (Mbps)
MAC Info Rate of PHY Rate 4
BPSK
192
1/2 12 30 18
2/3 45 27
QPSK
384 24 60 36
8-PSK
576 90 54
16-QAM
768 48
120 72
32-QAM
960
150
64-QAM
1152
180
108 96
240
144 3
288
864 56
140 84 2 6 15 9
480 75
Mustafa Eroz, Hughes Network Systems

5. Preamble/ Pilot Approach to HNS PHY Proposal
Sept 2004
Preamble/ Pilot Approach to HNS PHY Proposal
We base our approach on the a OFDM Specifications
There are 53 frequency bins in a OFDM
Indexed -26, -25, …-1, 0, 1 … 25 and 26.
The zero index (frequency location) is not used.
-21, -7, 7 and 21 are used as Pilots during data transmission
Modulated by127 bit long PN code (x7 + x4 + 1) on the ‘1st’ Antenna
Use the same frequency set on each of the TX Antennas
Use different phase of the 127 bit PN (quasi-orthogonal) on each of the other Antennas
48 remaining bins are used for data transmission
Each TX antenna uses the same 48 sub-carrier set but with different data stream
The transmission commences with an a specified preamble called the PLCP preamble
8 usec ‘short’ preamble with only 12 sub-carriers active
8 usec ‘long’ preamble all sub-carriers active per a specified 52 bit sequence
Short preamble empty bins are used by secondary antennas  4 TX supported
52 bits of the Long preamble are transmitted sequentially over the TX antenna set
Mustafa Eroz, Hughes Network Systems

6. Preamble Approach for Multiple TX Antennas
Sept 2004
(-26)
(26) Δf
MHz
Proposed: Long Preamble Sequence Spread Sequentially over the Four TX Antennas
Proposed: Short Training Preamble (First 8 usec) over one ‘First’ and Three ‘Other’ Antennas
1+ j
-1- j
Preamble Duration = 8 usec
Preamble duration = 8 usec
1.0
IEEE a Standard Short Training Preamble (i.e. first 8 usec) from one TX Antenna
- 26
+ 26
First Antena (s0)
Other Antennas (s1, s2 and s3)
L-26,26 per section Std a -1999
Preamble Approach for Multiple TX Antennas
Mustafa Eroz, Hughes Network Systems

7. Simulation Block Diagram: 3 TX by 2 RX Example
Sept 2004
Simulation Block Diagram: 3 TX by 2 RX Example
IFFT
Prefix
Digital-RF-PA
FFT
Remove P/fix
OFDM
Symbol
Generator
(frequency domain)
Preamble
Attachment
&
1:3 OFDM
Demux
Insert
Pilots
PSK/QAM
Modulator
LDPC
Encoder
MIMO LDPC
Block Formatter
Information bits
MIMO Preambles
RF-Digital
PA = Rapp’s model, p=3
LNA NF = 10dB
Prefix Timing/Channel Estimation/Symbol Timing/ Frequency/Phase Acquisition/Tracking
DETECTION
MAP
(LLR)
Iterative
Detector
DECODER y1 y2
y = [y1 y2]T
y = Ax + n,
‘A’ per n
Channel Model
Reconstruct
PSDU In
out
x = [x1 x2 x3]T x1 x2 x3
iteration
Channel Estimates
Mustafa Eroz, Hughes Network Systems

8. Simulation Conditions
Sept 2004
Simulation Conditions
2,3 and 4 TX antenna cases simulated
NLOS Model for B, D and E used in simulation
Used Florescent light effects for Model D&E
Antenna Spacing of half-wavelength used
Mustafa Eroz, Hughes Network Systems

9. Transmit Spectrum of the OFDM Signal Through PA Model
Sept 2004
Transmit Spectrum of the OFDM Signal Through PA Model
OFDM Signal 16-QAM after Non-linear Amplifier IBO = 8 dB
OFDM Signal 16-QAM after Non-linear Amplifier IBO = 3 dB
Fully compliant with spectral mask
Essentially the same spectral density for 64-QAM
Mustafa Eroz, Hughes Network Systems

10. Simulation Methodology
Sept 2004
Simulation Methodology
Coding and BB TX module
Applies appropriate padding to info bits at encoder input as needed
192 Transmission (coded) bit blocks into a LDPC encoder
Perform row-column interleaving
generate PSK/QAM modulation symbols
OFDM and Channel Model
Arranges into transmission vector for 2, 3 or 4 TX antennas
Converts modulation symbol stream into OFDM symbols with cyclic prefix, 4 usec/OFDM Symbol
Runs through channel model
Detects OFDM signals on each of the RX antenna
Delivers demodulated samples from each RX antenna to MAP detector
Mustafa Eroz, Hughes Network Systems

11. Performance for Channel Model B
doc.: IEEE n
Sept 2004
Performance for Channel Model B
Mustafa Eroz, Hughes Network Systems
Mustafa Eroz, Hughes Network Systems

12. Performance for Channel Model D
Sept 2004
Performance for Channel Model D
Mustafa Eroz, Hughes Network Systems

13. Performance for Channel Model E
Sept 2004
Performance for Channel Model E
Mustafa Eroz, Hughes Network Systems

14. AWGN Channel Performance
Sept 2004
AWGN Channel Performance
Mustafa Eroz, Hughes Network Systems