DocumentCode :
46924
Title :
Interference Channels With Coordinated Multipoint Transmission: Degrees of Freedom, Message Assignment, and Fractional Reuse
Author :
El Gamal, Abbas ; Annapureddy, Venkata Sreekanth ; Veeravalli, Venugopal V.
Author_Institution :
Dept. of Electr. & Comput. Eng., Univ. of Illinois at Urbana-Champaign, Urbana, IL, USA
Volume :
60
Issue :
6
fYear :
2014
fDate :
Jun-14
Firstpage :
3483
Lastpage :
3498
Abstract :
Coordinated multipoint (CoMP) transmission is an infrastructural enhancement under consideration for next generation wireless networks. In this paper, the capacity gain achieved through CoMP transmission is studied in various models of wireless networks that have practical significance. The capacity gain is analyzed through the degrees of freedom (DoF) criterion. The DoF available for communication provides an analytically tractable way to characterize the capacity of interference channels. The considered channel model has K transmitter/receiver pairs, and each receiver is interested in one unique message from a set of K independent messages. Each message can be available at more than one transmitter. The maximum number of transmitters at which each message can be available, is defined as the cooperation order M. For fully connected interference channels, it is shown that the asymptotic per user DoF, as K goes to infinity, remains at 1/2 as M is increased from 1 to 2. Furthermore, the same negative result is shown to hold for all M ≥ 2 for any message assignment that satisfies a local cooperation constraint. On the other hand, when the assumption of full connectivity is relaxed to local connectivity, and each transmitter is connected only to its own receiver as well as L neighboring receivers, it is shown that local cooperation is optimal. The asymptotic per user DoF is shown to be at least max {1/2, 2M/(2M + L)} for locally connected channels, and is shown to be 2M/(2M + 1) for the special case of Wyner´s asymmetric model where L = 1. An interesting feature of the proposed achievability scheme is that it relies on simple zero-forcing transmit beams and does not require symbol extensions. Also, to achieve the optimal per user DoF for Wyner´s model, messages are assigned to transmitters in an asymmetric fashion unlike traditional assignments where message i has to be available at transmitter i. It is also worth noting that some receivers have to be inactiv- , and fractional reuse is needed to achieve equal DoF for all users.
Keywords :
channel capacity; next generation networks; radio networks; radiofrequency interference; wireless channels; CoMP transmission; DoF criterion; K independent messages; K transmitter-receiver pairs; L neighboring receivers; Wyner asymmetric model; capacity gain; channel model; coordinated multipoint transmission; degrees of freedom; fractional reuse; interference channel capacity; local cooperation constraint; message assignment; next generation wireless networks; zero-forcing transmit beams; Channel models; Indexes; Interference channels; Radio transmitters; Receivers; CoMP Transmission; interference avoidance; interference-aware backhaul design; irreducible message assignments; locally connected channels; zero-forcing transmit beam-forming;
fLanguage :
English
Journal_Title :
Information Theory, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9448
Type :
jour
DOI :
10.1109/TIT.2014.2313083
Filename :
6777313
Link To Document :
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