| 1. |
- Kim, Thanh Tung, et al.
(författare)
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Decode-and-forward relaying with quantized channel state feedback : An outage exponent analysis
- 2008
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Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 54:10, s. 4548-4564
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Tidskriftsartikel (refereegranskat)abstract
- The problem of resource allocation to maximize the outage exponent over a fading relay channel using the decode-and-forward protocol with quantized channel state feedback (CSF) is studied. Three different scenarios are considered: relay-to-source, destination-to-relay, and destination-to-source-and-relay CSF. In the relay-to-source CSF scenario, it is found that using merely one bit of CSF to control the source transmit power is sufficient to achieve the multiantenna upper bound in a range of multiplexing gains. In the destination-to-relay CSF scenario, the systems slightly outperform dynamic decode-and-forward (DDF) at high multiplexing gains, even with only one bit of feedback. Finally, in the destination-to-source-and-relay CSF scenario, if the source-relay channel gain is unknown to the feedback quantizer at the destination, the diversity gain only grows linearly in the number of feedback levels, in sharp contrast to an exponential growth for multiantenna channels. In this last scenario, a simple scheme is shown to perform close to the corresponding upper bound.
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| 2. |
- Kim, Thanh Tung, et al.
(författare)
-
Diversity Gains of Power Control With Noisy CSIT in MIMO Channels
- 2009
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Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 55:4, s. 1618-1626
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Tidskriftsartikel (refereegranskat)abstract
- A multiantenna channel with partial channel state information at the transmitter (CSIT) is studied. The partial CSIT takes the form of the channel matrix corrupted by additive white Gaussian noise (AWGN) with a variance that is assumed to decay as a power of the signal-to-noise ratio (SNR). It is shown that under a long-term power constraint and in the regime of asymptotically high SNR, a large diversity gain over the channel can be achieved by using rarely a high power at the transmitter that compensates for bad channel realizations. Examples relating the diversity gain of the systems with the channel Doppler bandwidth are discussed.
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| 3. |
- Kim, Tung Thanh, et al.
(författare)
-
Diversity-multiplexing tradeoff in MIMO channels with partial CSIT
- 2007
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Ingår i: IEEE Transactions on Information Theory. - : IEEE Information Theory Society. - 0018-9448 .- 1557-9654. ; 53:8, s. 2743-2759
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Tidskriftsartikel (refereegranskat)abstract
- The diversity-multiplexing (D-M) tradeoff in a multiantenna channel with optimized resolution-constrained channel state feedback is characterized. The concept of minimum guaranteed multiplexing gain in the forward link is introduced and shown to significantly influence the optimal D-M tradeoff. It is demonstrated that power control based on the feedback is instrumental in achieving the D-M tradeoff, and that rate adaptation is important in obtaining a high diversity gain even at high rates. A criterion to determine finite-length codes to be tradeoff optimal is presented, leading to a useful geometric characterization of the class of extended approximately universal codes. With codes from this class, the optimal D-M tradeoff is achievable by the combination of a feedback-dependent power controller and a single codebook for single-rate or two codebooks; for adaptive-rate transmission. Finally, lower bounds to the optimal D-M tradeoffs based on Gaussian coding arguments are also studied. In contrast to the no-feedback case, these random coding bounds are only asymptotically tight, but can quickly approach the optimal tradeoff even with moderate codeword lengths.
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| 4. |
- Kim, Thanh Tung, et al.
(författare)
-
On the DMT-Optimality of Nondynamic DF Relaying in Asymmetric Nakagami Fading Channels
- 2010
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Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 56:7, s. 3304-3309
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Tidskriftsartikel (refereegranskat)abstract
- The optimality of nondynamic DF relaying over a general three-node Nakagami fading channel in terms of the diversity-multiplexing tradeoff (DMT) is established. In particular, when the fading of the relay-source link is less severe than that of the relay-destination link, both orthogonal and nonorthogonal DF protocols are shown to be DMT-optimal over certain ranges of the multiplexing gains. It is also shown that when the multiplexing gains are sufficiently high, the DMT of the DF protocols is completely independent of the statistical properties of the relay-destination link.
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| 5. |
- Kim, Thanh Tung, et al.
(författare)
-
Quantifying the Loss of Compress-Forward Relaying Without Wyner-Ziv Coding
- 2009
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Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448 .- 1557-9654. ; 55:4, s. 1529-1533
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Tidskriftsartikel (refereegranskat)abstract
- The compress-and-forward (CF) strategy achieves the optimal diversity-multiplexing tradeoff (DMT) of a three-node half-duplex relay network in slow fading, under the assumption that the relay has perfect knowledge of all three channel coefficients and that the relay makes use of Wyner-Ziv (WZ) source coding with side information. This paper studies the achievable DMT of the same network when the relay is constrained to make use of standard (non-WZ) source coding. Under a short-term power constraint at the relay, using source coding without side information results in a significant loss in terms of the DMT. For multiplexing gains r <= 2/3 this loss can be fully compensated for by using power control at the relay. On the contrary, for r is an element of (2/3, 1), the loss with respect to WZ coding remains significant.
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