4,191 research outputs found
Diversity Order Gain with Noisy Feedback in Multiple Access Channels
In this paper, we study the effect of feedback channel noise on the
diversity-multiplexing tradeoff in multiuser MIMO systems using quantized
feedback, where each user has m transmit antennas and the base-station receiver
has n antennas. We derive an achievable tradeoff and use it to show that in
SNR-symmetric channels, a single bit of imperfect feedback is sufficient to
double the maximum diversity order to 2mn compared to when there is no feedback
(maximum is mn at multiplexing gain of zero). Further, additional feedback bits
do not increase this maximum diversity order beyond 2mn. Finally, the above
diversity order gain of mn over non-feedback systems can also be achieved for
higher multiplexing gains, albeit requiring more than one bit of feedback.Comment: Proceedings of the 2008 IEEE International Symposium on Information
Theory, Toronto, ON, Canada, July 6 - 11, 200
Modulation Diversity for Spatial Modulation Using Complex Interleaved Orthogonal Design
In this paper, we propose modulation diversity techniques for Spatial
Modulation (SM) system using Complex Interleaved Orthogonal Design (CIOD) meant
for two transmit antennas. Specifically, we show that by using the CIOD for two
transmit antenna system, the standard SM scheme, where only one transmit
antenna is activated in any symbol duration, can achieve a transmit diversity
order of two. We show with our simulation results that the proposed schemes
offer transmit diversity order of two, and hence, give a better Symbol Error
Rate performance than the SM scheme with transmit diversity order of one.Comment: 7 page
On the Maximal Diversity Order of Spatial Multiplexing with Transmit Antenna Selection
Zhang et. al. recently derived upper and lower bounds on the achievable
diversity of an N_R x N_T i.i.d. Rayleigh fading multiple antenna system using
transmit antenna selection, spatial multiplexing and a linear receiver
structure. For the case of L = 2 transmitting (out of N_T available) antennas
the bounds are tight and therefore specify the maximal diversity order. For the
general case with L <= min(N_R,N_T) transmitting antennas it was conjectured
that the maximal diversity is (N_T-L+1)(N_R-L+1) which coincides with the lower
bound. Herein, we prove this conjecture for the zero forcing and zero forcing
decision feedback (with optimal detection ordering) receiver structures.Comment: 10 pages. Submitted to the IEEE Transactions on Information Theor
Cooperative Relaying in a Poisson Field of Interferers: A Diversity Order Analysis
This work analyzes the gains of cooperative relaying in interference-limited
networks, in which outages can be due to interference and fading. A stochastic
model based on point process theory is used to capture the spatial randomness
present in contemporary wireless networks. Using a modification of the
diversity order metric, the reliability gain of selection decode-and-forward is
studied for several cases. The main results are as follows: the achievable
\emph{spatial-contention} diversity order (SC-DO) is equal to one irrespective
of the type of channel which is due to the ineffectiveness of the relay in the
MAC-phase (transmit diversity). In the BC-phase (receive diversity), the SC-DO
depends on the amount of fading and spatial interference correlation. In the
absence of fading, there is a hard transition between SC-DO of either one or
two, depending on the system parameters.Comment: 5 pages, 2 figures. To be presented at ISIT 201
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