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ABSTRACT: In ultra-wideband (UWB) communication systems with impulse radio (IR)
modulation, the bandwidth is usually 1GHz or more. To process the received
signal digitally, high sampling rate analog-digital-converters (ADC) are
required. Due to the high complexity and large power consumption, monobit ADC
is appropriate. The optimal monobit receiver has been derived. But it is not
efficient to combat intersymbol interference (ISI). Decision feedback
equalization (DFE) is an effect way dealing with ISI. In this paper, we
proposed a algorithm that combines Viterbi decoding and DFE together for
monobit receivers. In this way, we suppress the impact of ISI effectively, thus
improving the bit error rate (BER) performance. By state expansion, we achieve
better performance. The simulation results show that the algorithm has about
1dB SNR gain compared to separate demodulation and decoding method and 1dB loss
compared to the BER performance in the channel without ISI. Compare to the full
resolution detection in fading channel without ISI, it has 3dB SNR loss after
state expansion.
10/2012;
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ABSTRACT: Interference alignment (IA) is a technique recently shown to achieve the
maximum degrees of freedom (DoF) of $K$-user interference channel. In this
paper, we focus on the precoder designs on manifolds for IA. By restricting the
optimization only at the transmitters' side, it will alleviate the overhead
induced by alternation between the forward and reverse links significantly.
Firstly a classical steepest descent (SD) algorithm in multi-dimensional
complex space is proposed to achieve feasible IA. Then we reform the
optimization problem on Stiefel manifold, and propose a novel SD algorithm
based on this manifold with lower dimensions. Moreover, aiming at further
reducing the complexity, Grassmann manifold is introduced to derive
corresponding algorithm for reaching the perfect IA. Numerical simulations show
that the proposed algorithms on manifolds have better convergence performance
and higher system capacity than previous methods, also achieve the maximum DoF.
09/2012;
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ABSTRACT: Future communication system requires large bandwidth to achieve high data
rate up to multigigabit/ sec, which makes analog-to-digital (ADC) become a key
bottleneck for the implementation of digital receivers due to its high
complexity and large power consumption. Therefore, monobit receivers for BPSK
have been proposed to address this problem. In this work, QPSK modulation is
considered for higher data rate. First, the optimal receiver based on monobit
ADC with Nyquist sampling is derived, and its corresponding performance in the
form of deflection ratio is calculated. Then a suboptimal but more practical
monobit receiver is obtained, along with iterative demodulation and small
sample removal. The effect of the imbalances between the In-phase (I) and
Quadrature-phase (Q) branches, including the amplitude and phase imbalances, is
carefully investigated too. To combat the performance loss caused by IQ
imbalances, monobit receivers based on double training sequences are proposed.
Numerical simulations show that the low-complexity suboptimal receiver suffers
only 3dB signal to noise ratio (SNR) loss in AWGN channels and 1dB SNR loss in
multipath static channels compared with the matched filter based monobit
receiver with full channel state information (CSI). The impact of the phase
difference between the transmitter and receiver is presented. It is observed
that the performance degradation caused by the amplitude imbalance is
negligible. Receivers based on double training sequences can efficiently
compensate the performance loss in AWGN channel. Thanks to the diversity
offered by the multipath, the effect of imbalances on monobit receivers in
fading channels is slight. I
02/2012;
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IEEE Communications Letters. 01/2012; 16:76-79.
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ABSTRACT: We investigate the Degrees of Freedom (DoF) Region of a cellular network,
where the cells can have overlapping areas. Within an overlapping area, the
mobile users can access multiple base stations. We consider a case where there
are two base stations both equipped with multiple antennas. The mobile stations
are all equipped with single antenna and each mobile station can belong to
either a single cell or both cells. We completely characterize the DoF region
for the uplink channel assuming that global channel state information is
available at the transmitters. The achievability scheme is based on
interference alignment at the base stations.
03/2011;
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ABSTRACT: We consider a single hop interference network with $K$ transmitters and $J$
receivers, all having $M$ antennas. Each transmitter emits an independent
message and each receiver requests an arbitrary subset of the messages. This
generalizes the well-known $K$-user $M$-antenna interference channel, where
each message is requested by a unique receiver. For our setup, we derive the
degrees of freedom (DoF) region. The achievability scheme generalizes the
interference alignment schemes proposed by Cadambe and Jafar. In particular, we
achieve general points in the DoF region by using multiple base vectors and
aligning all interferers at a given receiver to the interferer with the largest
DoF. As a byproduct, we obtain the DoF region for the original interference
channel. We also discuss extensions of our approach where the same region can
be achieved by considering a reduced set of interference alignment constraints,
thus reducing the time-expansion duration needed. The DoF region for the
considered system depends only on a subset of receivers whose demands meet
certain characteristics. The geometric shape of the DoF region is also
discussed.
01/2011;
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Proceedings of the 74th IEEE Vehicular Technology Conference, VTC Fall 2011, 5-8 September 2011, San Francisco, CA, USA; 01/2011
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Personal and Ubiquitous Computing. 01/2011; 15:75-84.
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Huarui Yin
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ABSTRACT: For a $K$-user interference channel with $M$ antenna at each transmitter and each receiver, the maximum total DoF of this channel has been previously determined to be $\max \sum_{k=1}^K d_k = MK/2$. However, the DoF region remains to be unknown. In this short note, through a simple time-sharing argument, we obtain the degrees of freedom (DoF) region of this channel. Comment: 2 pages
11/2010;
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ABSTRACT: Digital receivers for future high-rate high-bandwidth communication systems will require large sampling rate. This is especially true for ultra-wideband (UWB) communications with impulse radio (IR) modulation. Due to high complexity and large power consumption, multibit high-rate analog-to-digital converter (ADC) is difficult to implement. Monobit receiver has been previously proposed to relax the need for high-rate ADC. In this paper, we derive optimal digital processing architecture for receivers based on monobit ADC with a certain over-sampling rate and the corresponding theoretically achievable performance. A practically appealing suboptimal iterative receiver is also proposed. Iterative decision-directed weight estimation, and small sample removal are distinctive features of the proposed detector. Numerical simulations show that compared with full resolution matched filter based receiver, the proposed low complexity monobit receiver incurs only 2 dB signal to noise ratio (SNR) loss in additive white Gaussian noise (AWGN) and 3.5dB SNR loss in standard UWB fading channels.
IEEE Transactions on Communications 07/2010; · 1.68 Impact Factor
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IEEE Transactions on Communications. 01/2010; 58:1695-1704.
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01/2009
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43rd Annual Conference on Information Sciences and Systems, CISS 2009, The John Hopkins University, Baltimore, MD, USA, 18-20 March 2009; 01/2009
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Proceedings of the 69th IEEE Vehicular Technology Conference, VTC Spring 2009, 26-29 April 2009, Hilton Diagonal Mar, Barcelona, Spain; 01/2009
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ABSTRACT: Automatic repeat-request (ARQ) protocols for two-user cooperative diversity system employing Alamouti space-time coding are investigated in this paper. A whole cooperative transmit frame of the original cooperative system consists of three sub-frames. According to different feedback schedules in a transmit frame at the destination, two basic ARQ protocols, namely post-cooperating and pre-cooperating, are proposed and analyzed. We show that both proposed ARQ protocols can improve the throughput in two-user cooperative system. Pre-cooperating protocol yields 50% gains in users' throughput than post-cooperating protocol if both users have high user-destination average received signal-to-noise ratio (SNR) at the destination. Nevertheless, if both of user-destination average received SNRs are low, post-cooperating protocol is more effective than pre-cooperating protocol. Proposed protocols provide useful basic tools for designing more complicated ARQ protocols. Finally, simulation results verify our analysis.
Wireless Communications, Networking and Mobile Computing, 2008. WiCOM '08. 4th International Conference on; 11/2008
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ABSTRACT: In this paper, we propose a selective cooperative scheme based on overall power minimization in wireless networks. While cooperation can potentially improve communication quality, this improvement often comes at a price in terms of extra power consumption for protocol overhead and the relaying device running. As such, we contend that it is worthwhile to consider a scheme that satisfies an overall symbol error rate (SER) constraint such that cooperation is only invoked to save power when necessary. We study that issue by looking at the overall power consumptions of cooperative and non-cooperative schemes in a 3-node model. Optimal power allocation strategies under an overall SER constraint are derived for both non-cooperative scheme and DF cooperative scheme. Taking into account overhead power, the scheme with minimum overall consumed power is adopted for a source-destination pair. When cooperative scheme is used, the potential relay leading to minimum overall power is also selected as the best relay. To reduce the complexity of the selective scheme, three geographical parameters, which are used to make decisions in proposed selective scheme, are evaluated. Numerical results show that the selective cooperative scheme is more power-efficient than both non-cooperative scheme and conventional cooperative scheme.
Communications and Networking in China, 2008. ChinaCom 2008. Third International Conference on; 09/2008
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Proceedings of IEEE International Conference on Communications, ICC 2008, Beijing, China, 19-23 May 2008; 01/2008
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IEEE Transactions on Wireless Communications. 01/2008; 7:5108-5117.
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ABSTRACT: Burst communication is an important data transmission mode in wireless sensor network (WSN). Impulse radio ultra-wideband (IR UWB), which is a desired candidate of the physical layer of WSN, has been widely investigated. However, synchronization and timing recovery of coherent method requires a relative large system cost, which may constrain the widely use of impulse system. In this paper, we propose a coherent communication strategy while using non-coherent way to deal with the synchronization issue. This strategy can achieve a fast acquisition and precise timing with lower complexity, making the burst IR communication become promising in wireless sensor network.
Wireless Communications, Networking and Mobile Computing, 2007. WiCom 2007. International Conference on; 10/2007
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ABSTRACT: In this paper, the impulse radio (IR) system of pulse position amplitude modulation (PPAM) using an orthogonal sinusoidal correlation receiver (OSCR) is proposed. PPAM combines pulse position modulation (PPM) with pulse amplitude modulation (PAM) to provide higher data throughput with low computational complexity. But the performance of PPAM is considerably sensitive to timing jitter. OSCR has remarkable tolerance against timing jitter, and thus can process PPAM signals with little SNR degradation. Simulation results show that the proposed system can provide higher data throughput while maintain the BER performance even when timing jitter is relatively large
Wireless Networks, Communications and Mobile Computing, 2005 International Conference on; 07/2005
