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Transportation of MIMO Radio Signals over
RoF-Distributed Antenna System and its
Performance Analysis in the Presence of
I...
Outline
• Background
• Concept of RoF-DAS using optical TDM
• Configuration of RoF-DAS using optical
TDM
• Channel Model w...
Background


Requirements of Next Generation Network

Source2

Source1

High speed and
large capacity
wireless access

Ad...
RoF-DAS
RoF-DAS utilizes many antennas (RAU)
geographically located at different location.
CCS : Centralized Control Stati...
Concept of RoF-DAS using
optical TDM
• Radio on Fiber (RoF)
• Distributed Antenna
System (DAS)
• Optical TDM
• Merit
– Hig...
MIMO technique

x1

x2

Transmitter

h11

h12
h21
hM 1 h22

y1
y2

Receiver

H
xN

hM 2

hMN

yM

H air

 h1,1 h1, 2

 ...
Configuration of RoF-DAS using
optical TDM
a

b

c

d

e

a.Optical pulse source
emits periodic pulse
train
b.RF signal mo...
Configuration of RoF-DAS using
optical TDM
• Requirement of
SW
– Accuracy

• If Synchronization
mismatch happens,
(Problem...
Channel Model with
Synchronization Mismatch
• Ideal MIMO

𝒚 = H 𝒂𝒊𝒓 𝒙 + 𝒏

• Channel Model with synchronization mismatch,
...
Compensation of synchronization
mismatch (Proposed)
• ZF with compensation
We implemented the delay matrix estimator at
th...
Block Diagram

CCS (Centralized Control Station) RAUs (Remote Antenna Units)

Signal
Processor

E/O

TDM
Multiplexing

Fee...
Simulation
Modulation
Number of RAUs
Number of RAU’s Antennas
Number of MTs
Number of MT’s Antennas
Clock Delay
MIMO Detec...
Channel Capacity

• Shannon-Hartley theorem
𝛾0
𝐶 = log 2 det(𝑰 + (𝑯 𝑎𝑖𝑟 𝑻) 𝐻 (𝑯 𝑎𝑖𝑟 𝑻))
𝑛𝑡

( 𝑯 𝑒𝑠𝑡 = 𝑯 𝑎𝑖𝑟 𝑻)

𝛾0 : ratio...
Simulation (SNR=35dB &
16QAM)

14
Simulation (𝜏 = 0.4)

8.5dB

15
Summary & Future Work
• Summary
– To avoid critical degradation due to the
incomplete synchronization, a new
compensation ...
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Transportation of MIMO Radio Signals over RoF-Distributed Antenna System and its Performance Analysis in the Presence of Incomplete Synchronization in Optical TDM

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Radio on Fiber-Distributed Antenna System (RoF- DAS) is known to improve coverage and performance of wireless communications. Currently, various multiplexing schemes in RoF-DAS for transport Multiple Input Multiple Output (MIMO) signals in a fiber link are studied. The RoF-DAS over Wave- length Division Multiplexing - Passive Optical Network (WDM- PON) with optical Time Division Multiplexing (TDM) is actively researched. This system uses optical switcher to multiplex a set of MIMO radio signals in a fiber and transfer to the Remote Antenna Unit (RAU). Since a pair of switches multiplex and demultiplex MIMO radio signals, two switches are required to synchronize completely. Therefore, there is a problem that high performance switches are required to perform the clock extraction. This paper proposes asynchronous optical TDM. In this proposal, synchronization mismatch is compensated by estimating the amount of drifting and cancel it out at the RAU. The bit error ratio (BER) performance is evaluated by using computer simulation.

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Transportation of MIMO Radio Signals over RoF-Distributed Antenna System and its Performance Analysis in the Presence of Incomplete Synchronization in Optical TDM

  1. 1. Transportation of MIMO Radio Signals over RoF-Distributed Antenna System and its Performance Analysis in the Presence of Incomplete Synchronization in Optical TDM Nara Institute of Science and Technology , Japan Network System Lab Tatsuya Kidani, Takeshi Higashino, Minoru Okada 1
  2. 2. Outline • Background • Concept of RoF-DAS using optical TDM • Configuration of RoF-DAS using optical TDM • Channel Model with synchronization mismatch • Simulation • Summary & Future Work 2
  3. 3. Background  Requirements of Next Generation Network Source2 Source1 High speed and large capacity wireless access Adaptive control of base station Accommodations of various communication standards (Heterogeneous) Source1:Cisco VNI Mobile, 2011 Source2:ZTE ZTE technology N0.1, 2011  RoF-DAS using optical TDM (Time Division Multiplexing) [Radio on Fiber (RoF),Distributed Antenna System (DAS)] 3
  4. 4. RoF-DAS RoF-DAS utilizes many antennas (RAU) geographically located at different location. CCS : Centralized Control Station, RAU : Remote Antenna Unit This system can use multiple RAUs to coordinate as MIMO system RAU O/E Conversion E/O Modulation/ Demodulation ,scheduling (time,frequency), Signal processing (MIMO, etc.) CCS 4 Mobile Terminal RoF:Radio on Fiber RoF-link MIMO
  5. 5. Concept of RoF-DAS using optical TDM • Radio on Fiber (RoF) • Distributed Antenna System (DAS) • Optical TDM • Merit – High Coverage – Low Spatial Correlation – Reduction of transmission power CCS : Centralized Control Station, RAU : Remote Antenna Unit 5 MT : Mobile Terminal
  6. 6. MIMO technique x1 x2 Transmitter h11 h12 h21 hM 1 h22 y1 y2 Receiver H xN hM 2 hMN yM H air  h1,1 h1, 2   h2,1 h2, 2     h  M ,1 h M , 2  h1, N       hM , N 1    hM , N   y  H air x  n y MIMO technique can increase channel capacity proportional to the number of antennas. :Receive Vector 𝐇 𝑎𝑖𝑟 :Channel Matrix x :Transmit Vector n :Noise Vector 6
  7. 7. Configuration of RoF-DAS using optical TDM a b c d e a.Optical pulse source emits periodic pulse train b.RF signal modulates the optical pulse intensity c.Employ optical delay lines and the optical signals are combined d.O/E conversion is performed and signal is demultiplexed e.RF original signal are LN-MZM : lithium niobate - Mach-Zehnder modulator re-generated from TDM PD : Photo Diode demultiplexed signal with band pass filters 7 (BPFs)
  8. 8. Configuration of RoF-DAS using optical TDM • Requirement of SW – Accuracy • If Synchronization mismatch happens, (Problem) – Each signals is mixed (High Correlation) We estimate the amount of synchronization mismatch & compensate it. Prevent performance degradation 8
  9. 9. Channel Model with Synchronization Mismatch • Ideal MIMO 𝒚 = H 𝒂𝒊𝒓 𝒙 + 𝒏 • Channel Model with synchronization mismatch, 𝒙′ = = 𝑥1 1 − 𝜏 𝑥2 𝜏 𝑥2 1 − 𝜏 𝑥3 𝜏 𝑥3 1 − 𝜏 𝑥4 𝜏 𝑥1 𝜏 𝑥4 1 − 𝜏 1− 𝜏 𝜏 0 0 0 1− 𝜏 𝜏 0 0 0 1− 𝜏 𝜏 𝜏 0 0 1− 𝜏 𝒚′ = 𝑯 𝑻𝒙 + 𝒏 𝜏:Amount of mismatch (0 ≤ 𝜏 ≤ 1) 𝑥1 𝑥2 𝑥3 = 𝑻𝒙 𝑥4 Delay Matrix 9
  10. 10. Compensation of synchronization mismatch (Proposed) • ZF with compensation We implemented the delay matrix estimator at the RAU. In this proposal, we utilities pilot sequence 𝒑, 𝐓est = 𝐓𝐩𝐩T + 𝐧RoF 𝐩T 𝐧RoF : Noise in RoF Compensated transmission signal  𝒙′′ = 𝑻−1 𝒙 𝑒𝑠𝑡 𝒙 𝑐𝑜𝑚 = 𝑻𝑻−1 𝒙 𝑒𝑠𝑡 10
  11. 11. Block Diagram CCS (Centralized Control Station) RAUs (Remote Antenna Units) Signal Processor E/O TDM Multiplexing Feedback 𝑻−1 RoF O/E TDM Demultiplexing BPF Delay Matrix Estimator 11
  12. 12. Simulation Modulation Number of RAUs Number of RAU’s Antennas Number of MTs Number of MT’s Antennas Clock Delay MIMO Detection Pilot Sequence Noise Fading Channel (Air) QPSK, 16QAM, 64QAM 4 1 1 4 0.1~0.9 Zero-Forcing M-sequence AWGN i.i.d, Flat Rayleigh Fading 12
  13. 13. Channel Capacity • Shannon-Hartley theorem 𝛾0 𝐶 = log 2 det(𝑰 + (𝑯 𝑎𝑖𝑟 𝑻) 𝐻 (𝑯 𝑎𝑖𝑟 𝑻)) 𝑛𝑡 ( 𝑯 𝑒𝑠𝑡 = 𝑯 𝑎𝑖𝑟 𝑻) 𝛾0 : ratio between transmission power and noise power 𝑛 𝑡 : number of antenna at CCS 𝑰 : identity matrix 13
  14. 14. Simulation (SNR=35dB & 16QAM) 14
  15. 15. Simulation (𝜏 = 0.4) 8.5dB 15
  16. 16. Summary & Future Work • Summary – To avoid critical degradation due to the incomplete synchronization, a new compensation scheme is proposed. – This scheme can estimate amount of synchronization mismatch and also gives an improvement in BER performance. • Future Work – Application of Optical OFDM (Orthogonal Frequency Division Modulation). – The compensation of nonlinear distortion due to RoF characteristic. 16

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