Frequency-Domain Channel Estimation for Single- Carrier Transmission in Fast Fading Channels Tetsuya Yamamoto Department of Communications Engineering, Graduate School of Engineering, Tohoku University Wireless Signal Processing & Networking Workshop Advanced Wireless Technologies II @Tohoku University 18 February, 2013
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Frequency-Domain Channel Estimation for Single- Carrier … · 2013-02-19 · TS-Based Frequency-Domain Channel Estimation Channel estimation accuracy is poor due to the interference
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Frequency-Domain Channel Estimation for Single-Carrier Transmission in Fast Fading Channels
Tetsuya Yamamoto
Department of Communications Engineering,
Graduate School of Engineering, Tohoku University
Wireless Signal Processing & Networking Workshop
Advanced Wireless Technologies II @Tohoku University 18 February, 2013
Outline
Introduction
Transmission System Model
Frequency-Domain Channel Estimation Schemes
Simulation Results
Conclusion
2
Introduction
Broadband single-carrier (SC) transmissions
– must deal with inter-symbol interference (ISI) arising from the severe
frequency-selectivity of the channel.
Frequency-domain equalization (FDE) [A, B]
– is simple, but effective to combat frequency-selective fading channel.
3
Frequency Channel gain
f
Received signal spectrum
FDE
[A] D. Falconer, et. al., “Frequency domain equalization for single-carrier broadband wireless systems,” IEEE Commun. Mag., Apr. 2002.
[B] F. Adachi, et. al., “Introduction of frequency-domain signal processing to broadband single-carrier transmissions in a wireless channel,”
IEICE Trans. Commun., Sept. 2009.
f
Transmitted signal spectrum FDE weight
f
Equalized signal spectrum
Introduction
SC-FDE is a block transmission and DFT is used at the receiver.
– Cyclic prefix (CP) is often inserted in front of each data block.
» to avoid the inter-block interference (IBI)
» to make the received signal to be a circular convolution of the
transmit signal block and the channel impulse response
4
Time
CP Data CP Data
CP Data CP Data
… …
… …
Direct path
CP-SC
Delayed path
FDE
DFT
Introduction
Instead of CP insertion, a known training sequence (TS) insertion
[C, D] can be used.
– Identical TS is used for all blocks.
– The TS in the previous block acts as the CP in the present block.
– The TS can be utilized for channel estimation.
» No pilot block is needed unlike CP-SC transmission.
5
Time
TS Data TS Data
TS Data TS Data
… …
… …
TS-SC
FDE
DFT
CP Pilot CP Data … … CP-SC CP Pilot CP Data …
TS Data TS Data … … TS-SC TS Data TS Data … TS
[C] L. Deneire, et. al., “Training sequence versus cyclic prefix - a new look on single carrier communication,” IEEE Commun. Lett., July, 2001.
[D] F. Adachi, et. al., “Capacity and BER performance considerations on single-carrier frequency-domain equalization,” Proc. ICICS 2011, Dec. 2011.
Introduction
Conventional channel estimation for TS-SC transmission [E, F]
– TS of 2L-symbol length, which is constructed from a TS of L-symbol
length, is used.
» Interference from the data block can be avoided.
» The channel can be estimated in frequency-domain by exploiting
the circular property of the TS.
We introduce frequency-domain channel estimation schemes
which require a TS of L-symbol length.
6
•L: Channel length
Transmission efficiency reduces.
[E] J. Coon, et. al., “Channel and noise variance estimation and tracking algorithms for unique-word based single-carrier systems,”
IEEE Trans. Wireless Commun., June 2006.
[F] Y. Hou et. al., “Improvement on the channel estimation of pilot cyclic prefixed single carrier (PCP-SC) system,” IEEE Signal Processing Lett., Aug. 2009.
Time
TS Data TS Data
TS Data TS
… …
…
Channel estimation
TS TS
TS TS Data …
Conv. CE
Time
Data TS Data … …
Prop. CE
Channel estimation
TS
Data TS Data … … TS
L symbols L symbols
Transmission System Model
Transmitter and receiver structure
Block structure
– TS can be viewed as a CP of an Nc+Ng-symbol block.
» The received signal is decomposed into Nc+Ng orthogonal
frequency components by applying (Nc+Ng)-point DFT.
» Simple one-tap FDE can be applied as in CP-SC. 7