6,421 research outputs found
Full Diversity Space-Time Block Codes with Low-Complexity Partial Interference Cancellation Group Decoding
Partial interference cancellation (PIC) group decoding proposed by Guo and
Xia is an attractive low-complexity alternative to the optimal processing for
multiple-input multiple-output (MIMO) wireless communications. It can well deal
with the tradeoff among rate, diversity and complexity of space-time block
codes (STBC). In this paper, a systematic design of full-diversity STBC with
low-complexity PIC group decoding is proposed. The proposed code design is
featured as a group-orthogonal STBC by replacing every element of an Alamouti
code matrix with an elementary matrix composed of multiple diagonal layers of
coded symbols. With the PIC group decoding and a particular grouping scheme,
the proposed STBC can achieve full diversity, a rate of and a
low-complexity decoding for transmit antennas. Simulation results show that
the proposed codes can achieve the full diversity with PIC group decoding while
requiring half decoding complexity of the existing codes.Comment: 10 pages, 3 figures
Maximum-rate Transmission with Improved Diversity Gain for Interference Networks
Interference alignment (IA) was shown effective for interference management
to improve transmission rate in terms of the degree of freedom (DoF) gain. On
the other hand, orthogonal space-time block codes (STBCs) were widely used in
point-to-point multi-antenna channels to enhance transmission reliability in
terms of the diversity gain. In this paper, we connect these two ideas, i.e.,
IA and space-time block coding, to improve the designs of alignment precoders
for multi-user networks. Specifically, we consider the use of Alamouti codes
for IA because of its rate-one transmission and achievability of full diversity
in point-to-point systems. The Alamouti codes protect the desired link by
introducing orthogonality between the two symbols in one Alamouti codeword, and
create alignment at the interfering receiver. We show that the proposed
alignment methods can maintain the maximum DoF gain and improve the ergodic
mutual information in the long-term regime, while increasing the diversity gain
to 2 in the short-term regime. The presented examples of interference networks
have two antennas at each node and include the two-user X channel, the
interferring multi-access channel (IMAC), and the interferring broadcast
channel (IBC).Comment: submitted to IEEE Transactions on Information Theor
Full Diversity Unitary Precoded Integer-Forcing
We consider a point-to-point flat-fading MIMO channel with channel state
information known both at transmitter and receiver. At the transmitter side, a
lattice coding scheme is employed at each antenna to map information symbols to
independent lattice codewords drawn from the same codebook. Each lattice
codeword is then multiplied by a unitary precoding matrix and sent
through the channel. At the receiver side, an integer-forcing (IF) linear
receiver is employed. We denote this scheme as unitary precoded integer-forcing
(UPIF). We show that UPIF can achieve full-diversity under a constraint based
on the shortest vector of a lattice generated by the precoding matrix . This constraint and a simpler version of that provide design criteria for
two types of full-diversity UPIF. Type I uses a unitary precoder that adapts at
each channel realization. Type II uses a unitary precoder, which remains fixed
for all channel realizations. We then verify our results by computer
simulations in , and MIMO using different QAM
constellations. We finally show that the proposed Type II UPIF outperform the
MIMO precoding X-codes at high data rates.Comment: 12 pages, 8 figures, to appear in IEEE-TW
MMSE Optimal Algebraic Space-Time Codes
Design of Space-Time Block Codes (STBCs) for Maximum Likelihood (ML)
reception has been predominantly the main focus of researchers. However, the ML
decoding complexity of STBCs becomes prohibitive large as the number of
transmit and receive antennas increase. Hence it is natural to resort to a
suboptimal reception technique like linear Minimum Mean Squared Error (MMSE)
receiver. Barbarossa et al and Liu et al have independently derived necessary
and sufficient conditions for a full rate linear STBC to be MMSE optimal, i.e
achieve least Symbol Error Rate (SER). Motivated by this problem, certain
existing high rate STBC constructions from crossed product algebras are
identified to be MMSE optimal. Also, it is shown that a certain class of codes
from cyclic division algebras which are special cases of crossed product
algebras are MMSE optimal. Hence, these STBCs achieve least SER when MMSE
reception is employed and are fully diverse when ML reception is employed.Comment: 5 pages, 1 figure, journal version to appear in IEEE Transactions on
Wireless Communications. Conference version appeared in NCC 2007, IIT Kanpur,
Indi
Integer-Forcing Linear Receivers
Linear receivers are often used to reduce the implementation complexity of
multiple-antenna systems. In a traditional linear receiver architecture, the
receive antennas are used to separate out the codewords sent by each transmit
antenna, which can then be decoded individually. Although easy to implement,
this approach can be highly suboptimal when the channel matrix is near
singular. This paper develops a new linear receiver architecture that uses the
receive antennas to create an effective channel matrix with integer-valued
entries. Rather than attempting to recover transmitted codewords directly, the
decoder recovers integer combinations of the codewords according to the entries
of the effective channel matrix. The codewords are all generated using the same
linear code which guarantees that these integer combinations are themselves
codewords. Provided that the effective channel is full rank, these integer
combinations can then be digitally solved for the original codewords. This
paper focuses on the special case where there is no coding across transmit
antennas and no channel state information at the transmitter(s), which
corresponds either to a multi-user uplink scenario or to single-user V-BLAST
encoding. In this setting, the proposed integer-forcing linear receiver
significantly outperforms conventional linear architectures such as the
zero-forcing and linear MMSE receiver. In the high SNR regime, the proposed
receiver attains the optimal diversity-multiplexing tradeoff for the standard
MIMO channel with no coding across transmit antennas. It is further shown that
in an extended MIMO model with interference, the integer-forcing linear
receiver achieves the optimal generalized degrees-of-freedom.Comment: 40 pages, 16 figures, to appear in the IEEE Transactions on
Information Theor
- …