X. L. WU ET AL.

Copyright © 2013 SciRes. CN

29

From Table 2, it is obvious that M is small when SNR

is low, while in high SNR, M is large. For each stage,

there will be substantial differences in the reliability of

constellation candidates after preprocessing with low

SNR, so the candidates with lower reliability can be re-

moved without anxiety. While in high SNR, the noise is

so weak that every constellation candidate has much the

same probability to become the ML solution, and the

removal of candidates will decrease the possibility of

finding ML solution, so the value of M should be large in

high SNR. Moreover, from the complexity figures of the

proposed detection algorithm, it can be found easily that

with the increase of M, the complexity increased accord-

ingly, which due to the reason that the larger M will in-

crease total lattices in the receiver end.

5. Conclusions

This paper proposed a sphere detection based adaptive

MIMO detection algorithm for LTE and LTE-A system.

In this algorithm, the receiver can adjust the number of

reserved constellation candidates of each stage according

to current value of SNR. Simulation results show that the

proposed algorithm almost achieves the same BER per-

formance as ML detection algorithm, and compared with

full constellation candidates sphere detection, in 2 × 2

MIMO and 4 × 4 MIMO LTE-A systems, the average

complexity of the proposed algorithm is reduced by

27.61% and 32.27% respectively.

6. Acknowledgements

This work is supported by the National Basic Research

Program of China (973 Program) under Grand No.2013

CB329003, Next Generation Wireless Mobile Commu-

nication Network of China under Grant No. 2012ZX

03001007-005, the Fundamental Research Funds for the

Central Universities under Grant No. HIT.NSRIF2012020,

Heilongjiang Postdoctoral Science-Research Foundation

under Grant No. LBH-Q12081, and China Scholarship

Council.

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