1,598 research outputs found
Interference Cancellation at the Relay for Multi-User Wireless Cooperative Networks
We study multi-user transmission and detection schemes for a multi-access
relay network (MARN) with linear constraints at all nodes. In a MARN, sources, each equipped with antennas, communicate to one
-antenna destination through one -antenna relay. A new protocol called
IC-Relay-TDMA is proposed which takes two phases. During the first phase,
symbols of different sources are transmitted concurrently to the relay. At the
relay, interference cancellation (IC) techniques, previously proposed for
systems with direct transmission, are applied to decouple the information of
different sources without decoding. During the second phase, symbols of
different sources are forwarded to the destination in a time division
multi-access (TDMA) fashion. At the destination, the maximum-likelihood (ML)
decoding is performed source-by-source. The protocol of IC-Relay-TDMA requires
the number of relay antennas no less than the number of sources, i.e., . Through outage analysis, the achievable diversity gain of the proposed
scheme is shown to be . When {\small}, the proposed scheme achieves the maximum
interference-free (int-free) diversity gain . Since concurrent
transmission is allowed during the first phase, compared to full TDMA
transmission, the proposed scheme achieves the same diversity, but with a
higher symbol rate.Comment: submitted to IEEE Transaction on Wireless Communicatio
Code diversity in multiple antenna wireless communication
The standard approach to the design of individual space-time codes is based
on optimizing diversity and coding gains. This geometric approach leads to
remarkable examples, such as perfect space-time block codes, for which the
complexity of Maximum Likelihood (ML) decoding is considerable. Code diversity
is an alternative and complementary approach where a small number of feedback
bits are used to select from a family of space-time codes. Different codes lead
to different induced channels at the receiver, where Channel State Information
(CSI) is used to instruct the transmitter how to choose the code. This method
of feedback provides gains associated with beamforming while minimizing the
number of feedback bits. It complements the standard approach to code design by
taking advantage of different (possibly equivalent) realizations of a
particular code design. Feedback can be combined with sub-optimal low
complexity decoding of the component codes to match ML decoding performance of
any individual code in the family. It can also be combined with ML decoding of
the component codes to improve performance beyond ML decoding performance of
any individual code. One method of implementing code diversity is the use of
feedback to adapt the phase of a transmitted signal as shown for 4 by 4
Quasi-Orthogonal Space-Time Block Code (QOSTBC) and multi-user detection using
the Alamouti code. Code diversity implemented by selecting from equivalent
variants is used to improve ML decoding performance of the Golden code. This
paper introduces a family of full rate circulant codes which can be linearly
decoded by fourier decomposition of circulant matrices within the code
diversity framework. A 3 by 3 circulant code is shown to outperform the
Alamouti code at the same transmission rate.Comment: 9 page
Maximum Rate of Unitary-Weight, Single-Symbol Decodable STBCs
It is well known that the Space-time Block Codes (STBCs) from Complex
orthogonal designs (CODs) are single-symbol decodable/symbol-by-symbol
decodable (SSD). The weight matrices of the square CODs are all unitary and
obtainable from the unitary matrix representations of Clifford Algebras when
the number of transmit antennas is a power of 2. The rate of the square
CODs for has been shown to be complex symbols per
channel use. However, SSD codes having unitary-weight matrices need not be
CODs, an example being the Minimum-Decoding-Complexity STBCs from
Quasi-Orthogonal Designs. In this paper, an achievable upper bound on the rate
of any unitary-weight SSD code is derived to be complex
symbols per channel use for antennas, and this upper bound is larger than
that of the CODs. By way of code construction, the interrelationship between
the weight matrices of unitary-weight SSD codes is studied. Also, the coding
gain of all unitary-weight SSD codes is proved to be the same for QAM
constellations and conditions that are necessary for unitary-weight SSD codes
to achieve full transmit diversity and optimum coding gain are presented.Comment: accepted for publication in the IEEE Transactions on Information
Theory, 9 pages, 1 figure, 1 Tabl
Application of Space-Time Diversity/Coding For Power Line Channels
The purpose of the present work is to evaluate the application of space-time block codes to the transmission of digital data over the power-line communication channel (PLC). Data transmitted over the power-line channel is usually corrupted by impulsive noise. In this work we analyse
the performance of space-time block codes in this type of environment and show that a significant performance gain can be achieved at almost no processing expense
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