1. Uplink Design Considerations for IEEE 802.16m
Document Number:
IEEE S802.16m-07_277,
Date Submitted:
Source:
Chandy Sankaran, Fan Wang, Amitava Ghosh {csankar1, fanw,
Motorola
Re:
TGm Call for comments on SDD, IEEE m-07/040
Abstract:
Discussed the functional of uplink design considerations and the relevant issues facing the working group
Purpose:
Discussion and adoption of functional area into SDD outline
Notice:
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2. Uplink: DFT Spread-OFDM
UL single carrier modulation options include IFDMA, DFT-SOFDMA etc.
DFT-SOFDMA is “functionally” equivalent to IFDMA but has differences in Numerology due to frequency-domain implementation
Easier to coexist with OFDMA
Adjacent sub-carrier mapping
Similar to narrowband single-carrier with cyclic-prefix (or IFDMA with repetition factor = 1)
Equally-spaced sub-carrier mapping
Similar to IFDMA with repetition factor > 1

3. Uplink Multiple Access Options
4.0 .
WCDMA vs XFDM COMPARISON ASSUMES SAME OCCUPIED BANDWIDTH
BPSK
* Tone reservation (TR) & clipping (C) ala R degrades EVM & needs 3-10MOPs/symbol
** RRC rolloff factor a
= 0.15 reduces PAPR/CM at expense of Spectral Efficiency (R )
QPSK
3.5
16QAM
64QAM
3.0
Release 6 PA
2.5
Aggressive TR+C*
(R , R )
(Relative to R99, Slope=1/1.85 for xFDM)
PA Backoff = CM (dB)
2.0
2.00 dB
1.5
Power
Reduction a **
=0.15 b
ed/ b c
> 2.7
1.0
0.5
0.61 dB
Slope = 1/1.85
0.0
WCDMA Rel-6
OFDMA
DFT-SOFDMA
IFDMA

4. Hybrid: UL OFDM & DFT-S-OFDM Slot Structure (Example)
Time (OFDM symbol)
Freq
1.25 msec
Data
Pilot
Data (or) Auxillary Pilot for MIMO
OFDM Slot
72 sub-carriers per slot:
12 OFDM symbols x 6 consecutive tones
1.25 msec duration
Primary pilot overhead = 12/72 ~ 17%
Auxillary pilots for MIMO/SDMA
Time (OFDM symbol)
Freq
1.25 msec
DFT-S-OFDM Slot
Can instead do CDD on symbols 3 & 9
In SLIDE8 we talk about frame dimensioning.
We see frames being of two lengths to better support different traffic requirements and possibly to account for different efficiencies driven by the various bandwidth modes
A short frame is constructed from a single sub-frame and supports small packets or packets with low latency requirements
Long frames are constructed from multiple sub-frames. One example is a long frame consisting of 4 – 0.5 ms sub-frames resulting in a long frame of length 2ms.
Frame size selection could be semi-static or signaled by a control channel in a frame or radio frame
45 seconds

5. UL Sub-Frame Illustration
One UL slot
Control (DFT & OFDM users)
User 1 (OFDM)
User 2 (DFT)
User 3 (OFDM)
User 1 (OFDM)
User 4 (DFT)
User 4 (DFT)
User 1 (OFDM)
Freq
Control (DFT & OFDM users)
1.25 msec
Time

6. UL Control Signaling
No data associated control signaling (Synchronous Non-Adaptive HARQ)
Control Transmission:
Control without Data:
Mapped to UL slots at carrier band edges (for both OFDM and DFT-S-OFDM SSs)
Control with Data:
For DFT-S-OFDM SSs: Multiplex Data and Control prior to DFT
Not an issue for OFDM SSs (can design to either multiplex with data or use band edge control region)

7. Summary
Several key issues must be agreed regarding uplink multiple access
DFT-SOFDMA has lower PAPR compared to OFDMA and warrants consideration for 16m
Beneficial for power limited users
For non power limited users OFDMA has link performance advantage
Performance of a pure DFT-S-OFDM system can be enhanced significantly with Turbo equalizer
Closes link performance gap with OFDM
Cost is higher complexity BS receiver
Hybrid of OFDMA and DFT-SOFDMA can also be considered for m
Provides enhanced cell-edge user throughput when compared to OFDMA
Lower PA backoff constraint when employing DFT-S-OFDMA
A major functional area of the SDD effort and outline should focus on uplink multiple access
Select OFDMA, DFT-S-OFDMA, or other as multiple access scheme for 16m
Identify methods for interoperating with legacy OFDMA

8. Proposal to m SDD
Include the following components in the SDD ToC
Uplink multiple access
[ The following options should be studied, and one of them should be included in SDD ToC
OFDMA
Pilot allocation
Resource block size and allocation
Single carrier FDMA
Hybrid single carrier and multicarrier FDMA ]
Uplink frame structure
Uplink control channel