TY - JOUR
T1 - Impact of channel estimation errors and power allocation on analog network coding and routing in two-way relaying
AU - Tabataba, Foroogh S.
AU - Sadeghi, Parastoo
AU - Hucher, Charlotte
AU - Pakravan, Mohammad Reza
PY - 2012
Y1 - 2012
N2 - In this paper, we study two important transmission strategies in full-duplex two-way relaying in the presence of channel estimation errors. In analog network coding (ANC), the relay transmits the combined signals that were received from both sources, with the aim of achieving better spectral efficiency. However, due to imperfect channel-state information (CSI), sources cannot perfectly cancel their own data in the relayed signal. We derive an achievable information rate for ANC in imperfect-CSI conditions and show how the ANC performance can significantly be degraded as a result. Moreover, we derive cut-set bounds with channel estimation errors for traditional routing (TR), in which time sharing is used at the relay. Although it has been previously shown that ANC outperforms TR when the CSI is perfect, we find that it may not maintain its superiority in imperfect-CSI case at low signal-to-noise ratio (SNR) conditions. Next, we propose practical power allocation techniques that can be used in the sources and relay for both ANC and TR. The proposed power allocation schemes are relatively simple to compute and rely only on long-term channel statistics. Nevertheless, they are shown to be effective and close to optimal solutions for a wide range of SNRs, to different positions of the relay, and for both perfect- and imperfect-CSI conditions. By using the proposed power allocation techniques, it is possible to bring back advantages of ANC over TR for a wide range of SNRs in imperfect-CSI conditions.
AB - In this paper, we study two important transmission strategies in full-duplex two-way relaying in the presence of channel estimation errors. In analog network coding (ANC), the relay transmits the combined signals that were received from both sources, with the aim of achieving better spectral efficiency. However, due to imperfect channel-state information (CSI), sources cannot perfectly cancel their own data in the relayed signal. We derive an achievable information rate for ANC in imperfect-CSI conditions and show how the ANC performance can significantly be degraded as a result. Moreover, we derive cut-set bounds with channel estimation errors for traditional routing (TR), in which time sharing is used at the relay. Although it has been previously shown that ANC outperforms TR when the CSI is perfect, we find that it may not maintain its superiority in imperfect-CSI case at low signal-to-noise ratio (SNR) conditions. Next, we propose practical power allocation techniques that can be used in the sources and relay for both ANC and TR. The proposed power allocation schemes are relatively simple to compute and rely only on long-term channel statistics. Nevertheless, they are shown to be effective and close to optimal solutions for a wide range of SNRs, to different positions of the relay, and for both perfect- and imperfect-CSI conditions. By using the proposed power allocation techniques, it is possible to bring back advantages of ANC over TR for a wide range of SNRs in imperfect-CSI conditions.
KW - Analog network coding (ANC)
KW - Rayleigh fading channels
KW - capacity
KW - channel estimation
KW - channel-state information (CSI)
KW - power optimization
KW - routing
UR - http://www.scopus.com/inward/record.url?scp=84866498559&partnerID=8YFLogxK
U2 - 10.1109/TVT.2012.2201969
DO - 10.1109/TVT.2012.2201969
M3 - Article
SN - 0018-9545
VL - 61
SP - 3223
EP - 3239
JO - IEEE Transactions on Vehicular Technology
JF - IEEE Transactions on Vehicular Technology
IS - 7
M1 - 6209447
ER -