732 research outputs found
Joint Multi-Cell Resource Allocation Using Pure Binary-Integer Programming for LTE Uplink
Due to high system capacity requirement, 3GPP Long Term Evolution (LTE) is
likely to adopt frequency reuse factor 1 at the cost of suffering severe
inter-cell interference (ICI). One of combating ICI strategies is network
cooperation of resource allocation (RA). For LTE uplink RA, requiring all the
subcarriers to be allocated adjacently complicates the RA problem greatly. This
paper investigates the joint multi-cell RA problem for LTE uplink. We model the
uplink RA and ICI mitigation problem using pure binary-integer programming
(BIP), with integrative consideration of all users' channel state information
(CSI). The advantage of the pure BIP model is that it can be solved by
branch-and-bound search (BBS) algorithm or other BIP solving algorithms, rather
than resorting to exhaustive search. The system-level simulation results show
that it yields 14.83% and 22.13% gains over single-cell optimal RA in average
spectrum efficiency and 5th percentile of user throughput, respectively.Comment: Accepted to IEEE Vehicular Technology Conference (VTC Spring), Seoul,
Korea, May, 201
Passive Eavesdropping Can Significantly Slow Down RIS-Assisted Secret Key Generation
Reconfigurable Intelligent Surface (RIS) assisted physical layer key
generation has shown great potential to secure wireless communications by
smartly controlling signals such as phase and amplitude. However, previous
studies mainly focus on RIS adjustment under ideal conditions, while the
correlation between the eavesdropping channel and the legitimate channel, a
more practical setting in the real world, is still largely under-explored for
the key generation. To fill this gap, this paper aims to maximize the
RIS-assisted physical-layer secret key generation by optimizing the RIS units
switching under the eavesdropping channel. Firstly, we theoretically show that
passive eavesdropping significantly reduces RIS-assisted secret key generation.
Keeping this in mind, we then introduce a mathematical formulation to maximize
the key generation rate and provide a step-by-step analysis. Extensive
experiments show the effectiveness of our method in benefiting the secret key
capacity under the eavesdropping channel. We also observe that the key
randomness, and unmatched key rate, two metrics that measure the secret key
quality, are also significantly improved, potentially paving the way to
RIS-assisted key generation in real-world scenarios.Comment: Accepted by Globecom 202
On Providing Downlink Services in Collocated Spectrum-Sharing Macro and Femto Networks
Femtocells have been considered by the wireless industry as a cost-effective
solution not only to improve indoor service providing, but also to unload
traffic from already overburdened macro networks. Due to spectrum availability
and network infrastructure considerations, a macro network may have to share
spectrum with overlaid femtocells. In spectrum-sharing macro and femto
networks, inter-cell interference caused by different transmission powers of
macrocell base stations (MBS) and femtocell access points (FAP), in conjunction
with potentially densely deployed femtocells, may create dead spots where
reliable services cannot be guaranteed to either macro or femto users. In this
paper, based on a thorough analysis of downlink (DL) outage probabilities (OP)
of collocated spectrum-sharing orthogonal frequency division multiple access
(OFDMA) based macro and femto networks, we devise a decentralized strategy for
an FAP to self-regulate its transmission power level and usage of radio
resources depending on its distance from the closest MBS. Simulation results
show that the derived closed-form lower bounds of DL OPs are tight, and the
proposed decentralized femtocell self-regulation strategy is able to guarantee
reliable DL services in targeted macro and femto service areas while providing
superior spatial reuse, for even a large number of spectrum-sharing femtocells
deployed per cell site
Capacity Enhancement in 60 GHz Based D2D Networks by Relay Selection and Scheduling
Millimeter-wave or 60 GHz communication is a promising technology that enables data rates in multigigabits. However, its tremendous propagation loss and signal blockage may severely affect the network throughput. In current data-centric device-to-device (D2D) communication networks, the devices with intended data communications usually lay in close proximity, unlike the case in voice-centric networks. So the network can be visualized as a naturally formed groups of devices. In this paper, we jointly consider resource scheduling and relay selection to improve network capacity in 60 GHz based D2D networks. Two types of transmission scenarios are considered in wireless personal area networks (WPANs), intra and intergroup. A distributed receiver based relay selection scheme is proposed for intragroup transmission, while a distance based relay selection scheme is proposed for intergroup transmission. The outage analysis of our proposed relay selection scheme is provided along with the numerical results. We then propose a concurrent transmission scheduling algorithm based on vertex coloring technique. The proposed scheduling algorithm employs time and space division in mmWave WPANs. Using vertex multicoloring, we allow transmitter-receiver (Tx-Rx) communication pairs to span over more colors, enabling better time slot utilization. We evaluate our scheduling algorithm in single-hop and multihop scenarios and discover that it outperforms other schemes by significantly improving network throughput
Exact distributions of finite random matrices and their applications to spectrum sensing
The exact and simple distributions of finite random matrix theory (FRMT) are critically important for cognitive radio networks (CRNs). In this paper, we unify some existing distributions of the FRMT with the proposed coefficient matrices (vectors) and represent the distributions with the coefficient-based formulations. A coefficient reuse mechanism is studied, i.e., the same coefficient matrices (vectors) can be exploited to formulate different distributions. For instance, the same coefficient matrices can be used by the largest eigenvalue (LE) and the scaled largest eigenvalue (SLE); the same coefficient vectors can be used by the smallest eigenvalue (SE) and the Demmel condition number (DCN). A new and simple cumulative distribution function (CDF) of the DCN is also deduced. In particular, the dimension boundary between the infinite random matrix theory (IRMT) and the FRMT is initially defined. The dimension boundary provides a theoretical way to divide random matrices into infinite random matrices and finite random matrices. The FRMT-based spectrum sensing (SS) schemes are studied for CRNs. The SLE-based scheme can be considered as an asymptotically-optimal SS scheme when the dimension K is larger than two. Moreover, the standard condition number (SCN)-based scheme achieves the same sensing performance as the SLE-based scheme for dual covariance matrix [Formula: see text]. The simulation results verify that the coefficient-based distributions can fit the empirical results very well, and the FRMT-based schemes outperform the IRMT-based schemes and the conventional SS schemes
Comparison of a unified analysis approach for family and unrelated samples with the transmission-disequilibrium test to study associations of hypertension in the Framingham Heart Study
Population stratification is one of the major causes of spurious associations in association studies. A unified association approach based on principal-component analysis can overcome the effect of population stratification, as well as make use of both family and unrelated samples combined to increase power (family-case-control, or FamCC). In this study, we compared FamCC and the transmission-disequilibrium test (TDT) using data on hypertension, systolic blood pressure, and diastolic blood pressure in the Framingham Heart Study. Our study indicated FamCC has reasonable type I error for both the unrelated sample and the family sample for all three traits. For these three traits, we found results from FamCC were inconsistent with those from the TDT. We discuss the reasons for this inconsistency. After correcting for multiple tests, we did not detect any significant single-nucleotide polymorphisms by either FamCC or the TDT
- …