Abstract
We investigate receiver designs and CQI (channel quality indicator) measures for the jointly encoded (JE) and separately encoded (SE) types of MIMO transmission. For the JE transmission, we develop a per-Walsh code joint detection structure consisting of a front-end linear filter followed by joint symbol detection among all the streams. We derive a class of filters that maximize the so-called constrained mutual information, and show that the conventional LMMSE and MVDR equalizers belong to this class. This constrained mutual information also provides us with a CQI measure describing the MIMO limk quality, similar to the notion of generalized SNR. Such a measure is essential for both link adaptation and also to provide a means of link-to-system mapping. For the case of SE transmission, we extend the successive decoding algorithm of per-antenna rate control (PARC) to multipath Channels, and show that in this case successive decoding achieves the constrained mutual information. Meanwhile, similar to the case of JE schemes, we also derive proper CQI measures for the SE schemes.
Highlights
Information-theoretic studies in [4, 5] showed that multipletransmit, multiple-receive-antenna MIMO systems offer potential for realizing high spectral efficiency in a wireless communications system
We derive a class of filters that maximizes the so-called constrained mutual information, and show that the conventional linear minimum mean square error (LMMSE) and minimum variance distortionless response (MVDR) equalizers belong to this class
We derive a class of filters that maximize the so-called constrained mutual information and show that this mutual information can act as a single channel quality indicator (CQI) that characterizes the jointly encoded (JE) MIMO link
Summary
Information-theoretic studies in [4, 5] showed that multipletransmit, multiple-receive-antenna MIMO systems offer potential for realizing high spectral efficiency in a wireless communications system. Coded-VBLAST and its variants [8], as well as space-time codes [9], fall under the JE category, while schemes such as per-antenna rate control (PARC) and its variants belong to the SE category [2, 10, 11] For both JE and SE schemes, one key aspect of the MIMO-CDMA system study is to design receivers that can reliably decode the transmitted signals in a frequencyselective channel, where the signal is corrupted by both the interchip interference (ICI) and the cochannel interference (CCI). Similar to the notion of generalized SNR (GSNR) [1], this constrained mutual information provides us with a CQI measure describing the MIMO link quality. Such a CQI measure is essential in providing a simple one-dimensional mapping for both link adaption and generating short-term curves for the purpose of link-to-system mapping for JE schemes.
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