170 research outputs found
Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks
Soaring capacity and coverage demands dictate that future cellular networks
need to soon migrate towards ultra-dense networks. However, network
densification comes with a host of challenges that include compromised energy
efficiency, complex interference management, cumbersome mobility management,
burdensome signaling overheads and higher backhaul costs. Interestingly, most
of the problems, that beleaguer network densification, stem from legacy
networks' one common feature i.e., tight coupling between the control and data
planes regardless of their degree of heterogeneity and cell density.
Consequently, in wake of 5G, control and data planes separation architecture
(SARC) has recently been conceived as a promising paradigm that has potential
to address most of aforementioned challenges. In this article, we review
various proposals that have been presented in literature so far to enable SARC.
More specifically, we analyze how and to what degree various SARC proposals
address the four main challenges in network densification namely: energy
efficiency, system level capacity maximization, interference management and
mobility management. We then focus on two salient features of future cellular
networks that have not yet been adapted in legacy networks at wide scale and
thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and
device-to-device (D2D) communications. After providing necessary background on
CoMP and D2D, we analyze how SARC can particularly act as a major enabler for
CoMP and D2D in context of 5G. This article thus serves as both a tutorial as
well as an up to date survey on SARC, CoMP and D2D. Most importantly, the
article provides an extensive outlook of challenges and opportunities that lie
at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201
Coalitional Games with Overlapping Coalitions for Interference Management in Small Cell Networks
In this paper, we study the problem of cooperative interference management in
an OFDMA two-tier small cell network. In particular, we propose a novel
approach for allowing the small cells to cooperate, so as to optimize their
sum-rate, while cooperatively satisfying their maximum transmit power
constraints. Unlike existing work which assumes that only disjoint groups of
cooperative small cells can emerge, we formulate the small cells' cooperation
problem as a coalition formation game with overlapping coalitions. In this
game, each small cell base station can choose to participate in one or more
cooperative groups (or coalitions) simultaneously, so as to optimize the
tradeoff between the benefits and costs associated with cooperation. We study
the properties of the proposed overlapping coalition formation game and we show
that it exhibits negative externalities due to interference. Then, we propose a
novel decentralized algorithm that allows the small cell base stations to
interact and self-organize into a stable overlapping coalitional structure.
Simulation results show that the proposed algorithm results in a notable
performance advantage in terms of the total system sum-rate, relative to the
noncooperative case and the classical algorithms for coalitional games with
non-overlapping coalitions
Dynamic Uplink/Downlink Resource Management in Flexible Duplex-Enabled Wireless Networks
Flexible duplex is proposed to adapt to the channel and traffic asymmetry for
future wireless networks. In this paper, we propose two novel algorithms within
the flexible duplex framework for joint uplink and downlink resource allocation
in multi-cell scenario, named SAFP and RMDI, based on the awareness of
interference coupling among wireless links. Numerical results show significant
performance gain over the baseline system with fixed uplink/downlink resource
configuration, and over the dynamic TDD scheme that independently adapts the
configuration to time-varying traffic volume in each cell. The proposed
algorithms achieve two-fold increase when compared with the baseline scheme,
measured by the worst-case quality of service satisfaction level, under a low
level of traffic asymmetry. The gain is more significant when the traffic is
highly asymmetric, as it achieves three-fold increase.Comment: 7 pages, 7 figures, ICC 2017 Worksho
Overview of interference management techniques in Femtocell networks : challenges and approach.
The most important use of techniques for the new technology network called femtocell, is to improve coverage and enhance capacity in mobile network. However, the deployment of femtocell over macrocell network has a new technology has attracted benefits in telecommunication industry. Several technical challenges toward the mass deployment of these new technology called femtocell have been addressed in industry. Interference mitigation between femtocell and macrocell, and among the neighboring femtocell user, is considered to be one of the major issues in femtocell networks due to sharing the same licensed frequency spectrum with macrocell. In this paper, we provide different techniques schemes for interference mitigation and general view for the efficiency of interference management techniques in femtocell network
Busy burst technology applied to OFDMA–TDD systems
The most significant bottleneck in wireless communication systems is an ever-increasing disproportion
between the bandwidth demand and the available spectrum. A major challenge in
the field of wireless communications is to maximise the spatial reuse of resources whilst avoiding
detrimental co-channel interference (CCI). To this end, frequency planning and centralised
coordination approaches are widely used in wireless networks. However, the networks for the
next generation of wireless communications are often envisioned to be decentralised, randomly
distributed in space, hierarchical and support heterogeneous traffic and service types. Fixed
frequency allocation would not cater for the heterogeneous demands and centralised resource
allocation would be cumbersome and require a lot of signalling. Decentralised radio resource
allocation based on locally available information is considered the key.
In this context, the busy burst (BB) signalling concept is identified as a potential mechanism
for decentralised interference management in future generation networks. Interference aware
allocation of time-frequency slots (chunks) is accomplished by letting receivers transmit a BB
in a time-multiplexed mini-slot, upon successful reception of data. Exploiting channel reciprocity
of the time division duplex (TDD) mode, the transmitters avoid reusing the chunks
where the received BB power is above a pre-determined threshold so as to limit the CCI caused
towards the reserved chunks to a threshold value. In this thesis, the performance of BB signalling
mechanism in orthogonal frequency division multiple access - time division duplexing
(OFDMA-TDD) systems is evaluated by means of system level simulations in networks operating
in ad hoc and cellular scenarios. Comparisons are made against the state-of-the-art centralised
CCI avoidance and mitigation methods, viz. frequency planning, fractional frequency
reuse, and antenna array with switched grid of beams, as well as decentralised methods such as
the carrier sense multiple access method that attempt to avoid CCI by avoiding transmission on
chunks deemed busy. The results demonstrate that with an appropriate choice of threshold parameter,
BB-based techniques outperform all of the above state-of-the-art methods. Moreover,
it is demonstrated that by adjusting the BB-specific threshold parameter, the system throughput
can be traded off for improving throughput for links with worse channel condition, both
in the ad hoc and cellular scenario. Moreover, by utilising a variable BB power that allows a
receiver to signal the maximum CCI it can tolerate, it is shown that a more favourable trade-off
between total system throughput and link throughput can be made. Furthermore, by performing
link adaptation, it is demonstrated that the spatial reuse and the energy efficiency can be traded
off by adjusting the threshold parameter. Although the BB signalling mechanism is shown to
be effective in avoiding detrimental CCI, it cannot mitigate CCI by itself. On the other hand,
multiple antenna techniques such as adaptive beamforming or switched beam approaches allow
CCI to be mitigated but suffer from hidden node problems. The final contribution of this thesis
is that by combining the BB signalling mechanism with multiple antenna techniques, it is
demonstrated that the hybrid approach enhances spatial reusability of resources whilst avoiding
detrimental CCI.
In summary, this thesis has demonstrated that BB provides a flexible radio resource mechanism
that is suitable for future generation networks
Improving Macrocell - Small Cell Coexistence through Adaptive Interference Draining
The deployment of underlay small base stations (SBSs) is expected to
significantly boost the spectrum efficiency and the coverage of next-generation
cellular networks. However, the coexistence of SBSs underlaid to an existing
macro-cellular network faces important challenges, notably in terms of spectrum
sharing and interference management. In this paper, we propose a novel
game-theoretic model that enables the SBSs to optimize their transmission rates
by making decisions on the resource occupation jointly in the frequency and
spatial domains. This procedure, known as interference draining, is performed
among cooperative SBSs and allows to drastically reduce the interference
experienced by both macro- and small cell users. At the macrocell side, we
consider a modified water-filling policy for the power allocation that allows
each macrocell user (MUE) to focus the transmissions on the degrees of freedom
over which the MUE experiences the best channel and interference conditions.
This approach not only represents an effective way to decrease the received
interference at the MUEs but also grants the SBSs tier additional transmission
opportunities and allows for a more agile interference management. Simulation
results show that the proposed approach yields significant gains at both
macrocell and small cell tiers, in terms of average achievable rate per user,
reaching up to 37%, relative to the non-cooperative case, for a network with
150 MUEs and 200 SBSs
- …