On Two-User Gaussian Multiple Access Channels With Finite Input Constellations

• Published in: IEEE transactions on information theory Vol. 57; no. 3; pp. 1299 - 1327
• Main Authors: Harshan, J, Rajan, B S
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.03.2011; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Access methods and protocols, osi model; Applied sciences; Channels; Complexity theory; Computation; Constellation constrained capacity; Constellation diagram; Constellations; Convolutional codes; Decoding; Exact sciences and technology; Fading; Frequency division multiaccess; Gaussian; Information; Information theory; Information, signal and communications theory; Labeling; Mathematical analysis; Maximum likelihood method; MIMO; Modulation, demodulation; Multiple access; multiple access channels; Normal distribution; Signal and communications theory; space-time block codes; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Teleprocessing networks. Isdn; Transmission and modulation (techniques and equipments); trellis coded modulation; ungerboeck partitioning; Access control; Block code; Space-time codes; Partition method; Frequency division multiple access; Gaussian distribution; Time division multiple access; Algorithm complexity; Trellis coded modulation; Pulse amplitude modulation; MIMO; MISO system; Constellation constrained capacity; Fading; MIMO system; multiple access channels; Multiple access; Gaussian channel; Trellis code; Maximum likelihood decoding; Phase shift keying; ungerboeck partitioning; space-time block codes; Metric; SISO system; Multiple channel
• ISSN: 0018-9448; 1557-9654
• DOI: 10.1109/TIT.2011.2104491

Constellation Constrained (CC) capacity regions of two-user Single-Input Single-Output (SISO) Gaussian Multiple Access Channels (GMAC) are computed for several Non-Orthogonal Multiple Access schemes (NO-MA) and Orthogonal Multiple Access schemes (O-MA). For NO-MA schemes, a metric is proposed to compute the angle(s) of rotation between the input constellations such that the CC capacity regions are maximally enlarged. Further, code pairs based on Trellis Coded Modulation (TCM) are designed with PSK constellation pairs and PAM constellation pairs such that any rate pair within the CC capacity region can be approached. Such a NO-MA scheme which employs CC capacity approaching trellis codes is referred to as Trellis Coded Multiple Access (TCMA). Then, CC capacity regions of O-MA schemes such as Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) are also computed and it is shown that, unlike the Gaussian distributed continuous constellations case, the CC capacity regions with FDMA are strictly contained inside the CC capacity regions with TCMA. Hence, for finite constellations, a NO-MA scheme such as TCMA is better than FDMA and TDMA which makes NO-MA schemes worth pursuing in practice for two-user GMAC. Then, the idea of introducing rotations between the input constellations is used to construct Space-Time Block Code (STBC) pairs for two-user Multiple-Input Single-Output (MISO) fading MAC. The proposed STBCs are shown to have reduced Maximum Likelihood (ML) decoding complexity and information-losslessness property. Finally, STBC pairs with reduced sphere decoding complexity are proposed for two-user Multiple-Input Multiple-Output (MIMO) fading MAC.