We propose an enhanced version of trellis coded multiple access (TCMA), an overloaded multiple access scheme that outperforms the original TCMA in terms of achieved spectral efficiency. Enhanced TCMA (ETCMA) performs simultaneous transmission of multiple data streams intended for users experiencing similar signal-to-noise ratios and can be employed both in the uplink and in the downlink of wireless systems, thus overcoming one of the main limitations of TCMA. Thanks to a new receiver algorithm, ETCMA is capable of delivering a significantly higher spectral efficiency. We show that ETCMA approaches the capacity of the Additive White Gaussian Noise channel for a wide range of signal-to-noise ratios.
Compress-forward (CF) relays can improve communication rates even when the relay cannot decode the source signal. Efficient implementation of CF is a topic of contemporary interest, in part because of its potential impact on wireless technologies such as cloud-RAN. There exists a gap between the performance of CF implementations in the high spectral efficiency regime and the corresponding information theoretic achievable rates. We begin by re-framing a dilemma causing this gap, and propose an approach for its mitigation. We utilize trellis coded quantization (TCQ) at the relay together with mu…
Orthogonal vs Non-Orthogonal Multiple Access with Finite Input Alphabet and Finite Bandwidth
对于两用户高斯多址接入信道(GMAC)、频分多址接入(FDMA),众所周知的正交多址接入(O-MA)方案比非正交多址接入(NO-MA)方案更优选,因为FDMA可以仅用单用户解码复杂度[ \emph{Chapter 14, Elements of Information Theory by Cover and Thomas} ]实现信道的总容量。然而,在有限的字母表,在本文中,我们表明,NO-MA是优于O-MA的两个用户的GMAC。我们绘制的星座约束(CC)容量区域的两个用户的GMAC与FDMA和时分多址(TDMA),并将它们与CC容量区域与网格编码多址(TCMA),最近推出的NO-MA计划。与高斯字母表的情况不同,示出了具有FDMA的CC容量区域严格地包含在具有TCMA的CC容量区域内。特别地,对于给定的带宽,具有TCMA和FDMA的CC容量区域之间的间隙被示出为随着平均功率约束的增加而增加。此外,对于给定的功率约束,具有TCMA和FDMA的CC容量区域之间的间隙被示出为随着带宽的增加而减小。因此,对于有限字母表,诸如TCMA的NO-MA方案优于公知的O-MAC方案、FDMA和TDMA,这使得NO-MA方案值得在实践中用于两用户GMAC。