227 research outputs found
Analytical Modeling of Interference Aware Power Control for the Uplink of Heterogeneous Cellular Networks
Inter-cell interference is one of the main limiting factors in current
Heterogeneous Cellular Networks (HCNs). Uplink Fractional Power Control (FPC)
is a well known method that aims to cope with such limiting factor as well as
to save battery live. In order to do that, the path losses associated with
Mobile Terminal (MT) transmissions are partially compensated so that a lower
interference is leaked towards neighboring cells. Classical FPC techniques only
consider a set of parameters that depends on the own MT transmission, like
desired received power at the Base Station (BS) or the path loss between the MT
and its serving BS, among others. Contrary to classical FPC, in this paper we
use stochastic geometry to analyze a power control mechanism that keeps the
interference generated by each MT under a given threshold. We also consider a
maximum transmitted power and a partial compensation of the path loss.
Interestingly, our analysis reveals that such Interference Aware (IA) method
can reduce the average power consumption and increase the average spectral
efficiency. Additionally, the variance of the interference is reduced, thus
improving the performance of Adaptive Modulation and Coding (AMC) since the
interference can be better estimated at the MT.Comment: 13 pages, 1 table and 7 figures. This work has been submitted to the
IEEE for possible publication. Copyright may be transferred without notice,
after which this version may no longer be accessibl
Wireless Power Transfer in Massive MIMO Aided HetNets with User Association
This paper explores the potential of wireless power transfer (WPT) in massive
multiple input multiple output (MIMO) aided heterogeneous networks (HetNets),
where massive MIMO is applied in the macrocells, and users aim to harvest as
much energy as possible and reduce the uplink path loss for enhancing their
information transfer. By addressing the impact of massive MIMO on the user
association, we compare and analyze two user association schemes. We adopt the
linear maximal ratio transmission beam-forming for massive MIMO power transfer
to recharge users. By deriving new statistical properties, we obtain the exact
and asymptotic expressions for the average harvested energy. Then we derive the
average uplink achievable rate under the harvested energy constraint.Comment: 36 pages, 11 figures, to appear in IEEE Transactions on
Communication
A New Look at Physical Layer Security, Caching, and Wireless Energy Harvesting for Heterogeneous Ultra-dense Networks
Heterogeneous ultra-dense networks enable ultra-high data rates and ultra-low
latency through the use of dense sub-6 GHz and millimeter wave (mmWave) small
cells with different antenna configurations. Existing work has widely studied
spectral and energy efficiency in such networks and shown that high spectral
and energy efficiency can be achieved. This article investigates the benefits
of heterogeneous ultra-dense network architecture from the perspectives of
three promising technologies, i.e., physical layer security, caching, and
wireless energy harvesting, and provides enthusiastic outlook towards
application of these technologies in heterogeneous ultra-dense networks. Based
on the rationale of each technology, opportunities and challenges are
identified to advance the research in this emerging network.Comment: Accepted to appear in IEEE Communications Magazin
Decoupled Uplink and Downlink in a Wireless System with Buffer-Aided Relaying
The paper treats a multiuser relay scenario where multiple user equipments
(UEs) have a two-way communication with a common Base Station (BS) in the
presence of a buffer-equipped Relay Station (RS). Each of the uplink (UL) and
downlink (DL) transmission can take place over a direct or over a relayed path.
Traditionally, the UL and the DL path of a given two-way link are coupled, that
is, either both are direct links or both are relayed links. By removing the
restriction for coupling, one opens the design space for a decoupled two-way
links. Following this, we devise two protocols: orthogonal decoupled UL/DL
buffer-aided (ODBA) relaying protocol and non-orthogonal decoupled UL/DL
buffer-aided (NODBA) relaying protocol. In NODBA, the receiver can use
successive interference cancellation (SIC) to extract the desired signal from a
collision between UL and DL signals. For both protocols, we characterize the
transmission decision policies in terms of maximization of the average two-way
sum rate of the system. The numerical results show that decoupling association
and non-orthogonal radio access lead to significant throughput gains for
two-way traffic.Comment: 27 pages, 10 figures, submitted to IEEE Transactions on
Communication
Study of decoupled uplink and downlink access in 5G heterogeneus systems
El projecte analitzarà les funcionalitats i problemà tiques de l'Internet tà ctil.Uplink and downlink decoupling (DUDe) is a disruptive technique that has been proposed recently to reduce the uplink and downlink imbalance problem, which occurs in HetNets due to the strong transmit power disparities between macro and small cells. In this thesis, previous research done on DUDe, in particular the association probability derivation, is used to calculate how the capacity is affected when the association is made to any SCell in the scenario. This specific situation is highly realistic since one or several small cells might be unavailable due to overload reasons. Therefore, one of the main objectives of this thesis is to evaluate and compare the potential capacity gains of decoupling to any other small cell in the scenario with respect to the macro cell, association that follows classical downlink received power policies. Decoupling uplink from the macro cell can improve as well the uplink outage, metric also evaluated and compared in this study. Moreover, there is a strong trend in research to empower multi-connectivity solutions, where one user has more than one uplink connection. We refer to this case as a dual connectivity scenario, and the uplink is further studied by allowing decoupled associations in dual connectivity scenarios. Dual connectivity in the uplink is highly controversial, since the user has limited power to share between two different access points. Therefore, a part from comparing the decoupled association performance with the downlink received power policies, this study compares the performance of multi-connectivity against having one single serving cell. In this case, a comparison is done with respect to the best uplink serving cell. Results show that decoupling the access increases the capacity even if there are some SCells unreachable and presents great performance on DC scenario.El uplink and downlink decoupling (DUDe) es una novedosa técnica propuesta recientemente para reduir el problema del uplink and downlink imbalance. El uplink and downlink imbalance ocurre cuando las potencias de las antenas de una heterogeneus network (HetNet) son muy dispares. En este proyecto, teniendo en cuenta la investigación realitzada hasta la fecha sobre el DUDe (especialmente sobre la probabilidad de asociación), se calcula la capacidad asociándose a cualquier SCell. Esta situación es muy importante ya que puede ser que algunes celdas sean inalcanzables por el usuario debido a que puedn estar sobrecargadas. Por este motivo, uno de los principales objetivos del proyecto es aavaluar la mejora de capacidad al relaizar el DUDe con cualquier SCell y mantenir la asociaciÃn con la MCell tal y como se ha hecho hasta ahora. Esta técnica se llama downlink receive power (DRP). El DUDe también mejora la outage probability, indicador que también se evalua en el estudio. En los estudios mas recientes también se trabaja con dual connectivity para mejorar las prestacions de la conexión. Aunque dividir la transmisión en el enlace de subida puede disminuir la capacidad debido a la baja potencia del usuario, se compara la capacidad de desacoplar el acceso en dual connectivity con el escenario de single best association. Los resultados muestran que el DUDe aumenta la capacidad aun teniendo algunes SCells inalcanzables. También se ha demostrado que el DUDe funciona perfectamente con la dual connectivity.L’Uplink and downlink decoupling és una innovadora tècnica que ha sigut proposada recentment per reduir el problema de l’uplink and downlink imbalance. L’uplink and downlink imbalance es dona a les heterogeneus networks (HetNets) degut a la disparitat de potències entre les diferents antenes. Durant aquest projecte, tenint en compte la recent recerca sobre DUDe (sobretot sobre la probabilitat d’associació), s’utilitza per calcular la capacitat a qualsevol SCell. Aquesta situació és molt important d’analitzar ja que pot ser possible que algunes no estiguin accessibles per sobrecà rrega. Per aquest motiu, un dels principals objectius del projecte és avaluar la millora de capacitat entre realitzar el DUDe a qualsevol SCell i mantenir l’associació amb la MCell com s’havia fet fins ara, el que es coneix com downlink receive power (DRP). El DUDe també comporta moltes millores a la outage probability, indicador que també s’avalua a l’estudi. En els estudis més recents també treballen amb dual connectivity per millorar les prestacions. Tot i que dividir la transmissió a l’enllaç de pujada pot comportar perdre capacitat degut a la baixa potència de l’usuari, es compara la capacitat amb el DUDe en un escenari de dual connectivity amb el cas de single best association. Els resultats mostren que el fet de desacoblar l’accés augmenta la capacitat de la connexió tot i tenir algunes SCells inabastables. També s’ha demostrat que el DUDe funciona perfectament amb la dual connectivity
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