Abstract:Abstract-In adaptive time division duplex (TDD) broadcast multi-antenna orthogonal frequency division multiplexing (OFDM) systems, non-reciprocal transceiver chains at the base station (BS) cause multi-user interference. This is due to the inappropriate spatial filter design at the BS based on the reverse link estimate. Hence, BS transceiver calibration is required. Provided that an estimate of the forward link channel is available at the BS, e.g., in a calibration phase, the transceiver parameters can be esti… Show more
“…It is modeled by a MMSE error model with constant estimation error variance σ 2 e [9]. Accordingly, this results in…”
Section: A Single-carrier System With Pre-equalization In Frequencydmentioning
confidence: 99%
“…To ensure a sufficient length of the solution vector, L c ≥ L f should be guaranteed, thus, for equal physical channel lengths, zero padding can be applied in (9) for the UL channel vectors. As a consequence, the length of the impulse responses must be chosen carefully to ensure a solution to (9). The existing block-diagonal structure of G C can be exploited by simply decomposing (9) into N M single-filter equations due to the joint linear correspondence.…”
Section: A Derivation Of the Stls Problemmentioning
confidence: 99%
“…As a consequence, the length of the impulse responses must be chosen carefully to ensure a solution to (9). The existing block-diagonal structure of G C can be exploited by simply decomposing (9) into N M single-filter equations due to the joint linear correspondence. It is worth to mention that a multiple application of the proposed algorithm can be parallelized, but may lead to different solutions of the individual filter vectors for different channel realizations as compared to the stacked formulation (9).…”
Section: A Derivation Of the Stls Problemmentioning
confidence: 99%
“…An even closer approximation to this solution can be achieved by overparameterization of (9). Therefore, simply multiple measurements of UL and DL channels can be used and the calibration time τ p is increased such that …”
Section: A Derivation Of the Stls Problemmentioning
confidence: 99%
“…By establishing a calibration phase during regular transmission with the help of additional feedback, almost equivalent effective UL and DL channels can be recovered. The authors demonstrated the superior performance of the application of such a scheme in comparison with robust pre-equalizer strategies for multicarrier systems [8], [9], where the transceiver influences are assumed to be frequencyindependent. There, total least squares (TLS) problems must be solved to acquire estimates of the RF front-end parameters.…”
Abstract-In general, the unequal RF circuitry in the transmit and receive chains at the base station (BS) prevents the exploitation of the uplink (UL) channel estimate for proper preequalization in time division duplex (TDD) systems. To avoid additional transceiver hardware costs for matching networks, the idea of relative calibration was introduced to cope with the different effective channel impulse responses of UL and downlink (DL) by means of signal processing. However, multiple-input multipleoutput (MIMO) transmission in frequency-selective channels does not allow for classical frequency-domain calibration principles based on total least squares (TLS) approaches. Consequently, more complex structured total least squares (STLS) problems must be solved.In this paper the application of the signal property mapping principle is introduced to iteratively solve the STLS calibration problem. Exemplified by simulation results for single-carrier frequency-domain pre-equalization (SC-preFDE) systems the algorithm indicates good and fast convergence behavior and effectively exploits noisy UL and DL channel measurements for system calibration.
“…It is modeled by a MMSE error model with constant estimation error variance σ 2 e [9]. Accordingly, this results in…”
Section: A Single-carrier System With Pre-equalization In Frequencydmentioning
confidence: 99%
“…To ensure a sufficient length of the solution vector, L c ≥ L f should be guaranteed, thus, for equal physical channel lengths, zero padding can be applied in (9) for the UL channel vectors. As a consequence, the length of the impulse responses must be chosen carefully to ensure a solution to (9). The existing block-diagonal structure of G C can be exploited by simply decomposing (9) into N M single-filter equations due to the joint linear correspondence.…”
Section: A Derivation Of the Stls Problemmentioning
confidence: 99%
“…As a consequence, the length of the impulse responses must be chosen carefully to ensure a solution to (9). The existing block-diagonal structure of G C can be exploited by simply decomposing (9) into N M single-filter equations due to the joint linear correspondence. It is worth to mention that a multiple application of the proposed algorithm can be parallelized, but may lead to different solutions of the individual filter vectors for different channel realizations as compared to the stacked formulation (9).…”
Section: A Derivation Of the Stls Problemmentioning
confidence: 99%
“…An even closer approximation to this solution can be achieved by overparameterization of (9). Therefore, simply multiple measurements of UL and DL channels can be used and the calibration time τ p is increased such that …”
Section: A Derivation Of the Stls Problemmentioning
confidence: 99%
“…By establishing a calibration phase during regular transmission with the help of additional feedback, almost equivalent effective UL and DL channels can be recovered. The authors demonstrated the superior performance of the application of such a scheme in comparison with robust pre-equalizer strategies for multicarrier systems [8], [9], where the transceiver influences are assumed to be frequencyindependent. There, total least squares (TLS) problems must be solved to acquire estimates of the RF front-end parameters.…”
Abstract-In general, the unequal RF circuitry in the transmit and receive chains at the base station (BS) prevents the exploitation of the uplink (UL) channel estimate for proper preequalization in time division duplex (TDD) systems. To avoid additional transceiver hardware costs for matching networks, the idea of relative calibration was introduced to cope with the different effective channel impulse responses of UL and downlink (DL) by means of signal processing. However, multiple-input multipleoutput (MIMO) transmission in frequency-selective channels does not allow for classical frequency-domain calibration principles based on total least squares (TLS) approaches. Consequently, more complex structured total least squares (STLS) problems must be solved.In this paper the application of the signal property mapping principle is introduced to iteratively solve the STLS calibration problem. Exemplified by simulation results for single-carrier frequency-domain pre-equalization (SC-preFDE) systems the algorithm indicates good and fast convergence behavior and effectively exploits noisy UL and DL channel measurements for system calibration.
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