synchronous ranging structure (awd-15.3.9.1.4.2) document number: ieee c80216m-09/1493r1 date...
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Synchronous Ranging Structure (AWD-15.3.9.1.4.2)
Document Number: IEEE C80216m-09/1493r1
Date Submitted: 2009-07-06
Source:Yih-Shen Chen, Pei-Kai Liao and Paul Cheng E-mail: [email protected], [email protected] Inc.Yan-Xiu Zheng E-mail: [email protected]
Venue: IEEE Session #62, San Francisco, USA
Response to IEEE 802.16m-09/0028r1, “Call for Comments and Contributions on Project 802.16 Amendment Content” Category: AWD comments / Area: Chapter 15.3.9 (UL-CTRL) “Comments on AWD 15.3.9.1.4.2 Ranging channel for synchronized AMSs”
Base Contribution: This is base contribution
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Design Considerations for Synchronized Ranging Channel
• Design considerations:– RCP length: Same CP size as data channel’s CP– Time accuracy criterion
• EX: <± (Tb/32)/4 (about 0.7143 us) for IEEE 802.16 system– Large cell coverage– Low overhead and high spectral efficiency
• Synchronized ranging channel can be applied for– Macrocell:
• Periodic ranging– Femtocell:
• Initial ranging (IR), handover ranging (HOR)– Purposes of initial ranging
» UL synchronization: Time/power/frequency adjustment» Contention-based access request for network entry
– Due to limited coverage, UL synchronization can be skipped after DL synchronization is done
• Periodic ranging (PR)
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Proposed Structure for Synchronized Ranging Structure (1/3)
• Basic structure: 1-subband x 1 OFDMA symbol– Time-domain repetition can be applied for larger
coverage• 2 or 3• There are three PR opportunities in one subframe if 2
repetitions are applied• There are two PR opportunities in one subframe if 3
repetitions are applied for larger coverage
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Proposed Structure for Synchronized Ranging Structure (2/3)
• In macrocell, three ranging opportunities are allocated in a subframe if repetition number is 2
• Allocation of “1-subband x 1-subframe” every M superframes in a 10 MHz BW– No entry delay constraint in PR
• For a smaller macrocell,
time-domain repetition won’t
be necessary and the rest of
subcarriers can be formed as
data resource blocks, just like
that in a femtocell
. . .
. . .
. . .
72 subcarriers
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Proposed Structure for Synchronized Ranging Structure (3/3)
• In femtocell, synchronized ranging channel is TDM with data channel– The ranging channel occupies 72 subcarriers x 1 OFDM symbol– The rest of subcarriers can be formed as five-symbol CRUs
• The allocation of synchronous IR channel appears every N superframes
– N must meet the idle-> active delay requirement (i.e., 100ms)
• Advantages:– Enough time accuracy– No extra entry delay– Higher spectral efficiency
• Disadvantage:– There exists two kinds of data PRUs in one subframe
. . .
. . .72
subcarriers
IR channeldata channel
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Proposed Code Sequence~ Circularly-Shifted Padded ZC (PZC) Code
• Code sequence
– Number of ZC =71– m denotes circular shift value for each cell
• 0, 10, 20, 30, 40, 50, 60
• 70 sequences with u=1,…,70 are allocated per cell– 70*7=490 sequences– PAPR=6.1089
ZC
N
mkmkju
umk
Nk
mkcs ZC
,,0 where
exp)()1)((
,1
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Simulations Results~ configuration
• Single user to six users performance is evaluated
• Only the best quality user is estimated based on non-coherent detection
• Padded ZC code provides enhanced performance when the number of user increases– Padded Zadoff-Chu code
rejects interference from other users
Channel Bandwidth 10MHz
Over-sampling Factor 28/25
FFT Size 1024
Cyclic prefix (CP) ratio 1/8
Channel Condition PB3, VA30 VA120, VA350
The Number of Antennas
Tx:1, Rx:2
Modulation MPSK
Number of Users 1, 2, 3, 4, 5, 6
Receiver Detection: non-coherent MLD
Estimation: differential detection
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Simulations Results~ Single-user case
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Simulations Results~ Two-user case
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Simulations Results~ Three-user case
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Simulations Results~ Four-user case
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Simulations Results~ Five-user case
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Simulations Results~ Six-user case
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Mis-Detection Issues for Overlaying Macrocell/Femtocell Deployment
• Since the ranging code/structure is reused in both macrocell and femtocell, there might be a signal mis-detection problem
• Solution:– The allocations of ranging opportunities are separated in time domain
Superframe20 ms
For macrocell PR For femtocell IR/PR For femtocell IR/PR For macrocell PR
200 ms
For femtocell IR/PR For femtocell IR/PR
For femtocell IR/PRFor femtocell IR/PR
5-Symbol CRUsRanging Channels
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Conclusion
• The proposed synchronous ranging structure can fulfill the requirement of timing accuracy – Better spectral efficiency
• The synchronous ranging structure can also be applied in femtocells as IR, HOR and PR
• Compared with ZC code, Padded ZC code can provide better timing estimation performance
Text Proposal (1/4)
[Modify section 15.3.9.1.4.2 of AWD with the following text]
15.3.9.1.4.2 Ranging channel for synchronized AMSs
The ranging channel for synchronized AMSs is used for periodic ranging. Only the AMSs that are already synchronized to the target ABS are
allowed to transmit the periodic ranging signal. For femtocells, the synchronous ranging channel can be applied for initial ranging, handover
ranging and periodic ranging as well. The basic structure of the synchronous ranging structure is shown in Fig. YYY, which consists of
contiguous 72 subcarriers by M OFDMA symbol time. For macrocells, M=2 or 3, which means time domain repetition is applied. For femtocells,
M=1. For the case of M=1, the rest of radio resource forms five-symbol CRUs for data transmission.
Power control operation described in subclause [TBD] applies to ranging signal transmission.
Text Proposal (2/4)
copy samples copy samples
M OFDM Symbols
TbTg Tg Tb
72 Sub-carriers
Fig. YYY: The allocation of code symbol on time and frequency domain
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Text Proposal (3/4)
[Add the following text into a new section (15.3.9.2.4.2) of AWD]
15.3.9.2.4.2 Ranging channel for synchronized AMSs
Ranging preamble codes
Padded Zadoff-Chu code is applied for ranging preamble code, which is expressed by eqn. XXX. The first code symbol is the same as the last
code symbol. NZC is 71. u ranges from 1 to 70 and m=0, 10, 20, 30, 40, 50, 60. It generates 490 padded ZC codes.
ZC
N
mkmkju
umk
Nk
mkcs ZC
,,0 where
exp)()1)((
,1
(Eq. XXX)
Fig. ZZZ shows an allocation example, which consists of 72 subcarriers by 2 OFDMA symbols. The code is allocated from the first subcarrier to
the 72th subcarrier, in which s72,m=s1,m. The second OFDM symbol duplicates the symbols from the first OFDM symbol. If M is 3, the third
OFDM symbol duplicates the symbols from the first OFDM symbol.
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Text Proposal (4/4)
Fig. ZZZ: The allocation of code symbol on time and frequency domain