Degrees of Freedom of MIMO-MAC with Random Access

• Published in: IEEE transactions on communications Vol. 61; no. 5; pp. 1956 - 1967
• Main Authors: Pourahmadi, V., Motahari, A. S., Khandani, A. K.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-05-2013; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Access methods and protocols, osi model; Access protocols; Antennas; Applied sciences; Data communication; Data transmission; Degrees of freedom; degrees of freedom (DoF); Exact sciences and technology; Interference; Mathematical analysis; MIMO; multiple access channel; multiple-input multiple-output (MIMO) system; Networks; Optimization; Radiocommunications; Random access; Random access network; Signal to noise ratio; Streams; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Teleprocessing networks. Isdn; Throughput; Transmission and modulation (techniques and equipments); Valuation and optimization of characteristics. Simulation; Access control; MIMO system; Multiple access; Data transmission; multiple-input multiple-output (MIMO) system; degrees of freedom (DoF); Upper bound; Transportation network; Multi-stream approach; Random access network; multiple access channel; Data transmission network; Random access; Access network; Multiple channel; Antenna
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/TCOMM.2013.021913.120299

A distributed random access network with K users and one Access Point (AP) is considered. It is assumed that users and the AP are equipped with M and N antennas, respectively. Each user independently decides whether to transmit in a time slot or not. We initially focus on two-user random access networks and characterize the network average Degrees of Freedom (DoF) 1 . For the K-user networks, an upper-bound on the network average DoF is first proposed. Then, it is shown that the proposed upper-bound can be achieved using single stream data transmission for many network configurations. Finally, we show through a few examples that there exist some network configurations where multi-stream data transmission in conjunction with interference alignment is necessary in order to achieve the upper-bound.