324 research outputs found
Interference-Aware Downlink Resource Management for OFDMA Femtocell Networks
Femtocell is an economical solution to provide high speed indoor communication instead of the conventional macro-cellular networks. Especially, OFDMA femtocell is considered in the next generation cellular network such as 3GPP LTE and mobile WiMAX system. Although the femtocell has great advantages to accommodate indoor users, interference management problem is a critical issue to operate femtocell network. Existing OFDMA resource management algorithms only consider optimizing system-centric metric, and cannot manage the co-channel interference. Moreover, it is hard to cooperate with other femtocells to control the interference, since the self-configurable characteristics of femtocell. This paper proposes a novel interference-aware resource allocation algorithm for OFDMA femtocell networks. The proposed algorithm allocates resources according to a new objective function which reflects the effect of interference, and the heuristic algorithm is also introduced to reduce the complexity of the original problem. The Monte-Carlo simulation is performed to evaluate the performance of the proposed algorithm compared to the existing solutions
Open vs Closed Access Femtocells in the Uplink
Femtocells are assuming an increasingly important role in the coverage and
capacity of cellular networks. In contrast to existing cellular systems,
femtocells are end-user deployed and controlled, randomly located, and rely on
third party backhaul (e.g. DSL or cable modem). Femtocells can be configured to
be either open access or closed access. Open access allows an arbitrary nearby
cellular user to use the femtocell, whereas closed access restricts the use of
the femtocell to users explicitly approved by the owner. Seemingly, the network
operator would prefer an open access deployment since this provides an
inexpensive way to expand their network capabilities, whereas the femtocell
owner would prefer closed access, in order to keep the femtocell's capacity and
backhaul to himself. We show mathematically and through simulations that the
reality is more complicated for both parties, and that the best approach
depends heavily on whether the multiple access scheme is orthogonal (TDMA or
OFDMA, per subband) or non-orthogonal (CDMA). In a TDMA/OFDMA network,
closed-access is typically preferable at high user densities, whereas in CDMA,
open access can provide gains of more than 200% for the home user by reducing
the near-far problem experienced by the femtocell. The results of this paper
suggest that the interests of the femtocell owner and the network operator are
more compatible than typically believed, and that CDMA femtocells should be
configured for open access whereas OFDMA or TDMA femtocells should adapt to the
cellular user density.Comment: 21 pages, 8 figures, 2 tables, submitted to IEEE Trans. on Wireless
Communication
Opportunistic Third-Party Backhaul for Cellular Wireless Networks
With high capacity air interfaces and large numbers of small cells, backhaul
-- the wired connectivity to base stations -- is increasingly becoming the cost
driver in cellular wireless networks. One reason for the high cost of backhaul
is that capacity is often purchased on leased lines with guaranteed rates
provisioned to peak loads. In this paper, we present an alternate
\emph{opportunistic backhaul} model where third parties provide base stations
and backhaul connections and lease out excess capacity in their networks to the
cellular provider when available, presumably at significantly lower costs than
guaranteed connections. We describe a scalable architecture for such
deployments using open access femtocells, which are small plug-and-play base
stations that operate in the carrier's spectrum but can connect directly into
the third party provider's wired network. Within the proposed architecture, we
present a general user association optimization algorithm that enables the
cellular provider to dynamically determine which mobiles should be assigned to
the third-party femtocells based on the traffic demands, interference and
channel conditions and third-party access pricing. Although the optimization is
non-convex, the algorithm uses a computationally efficient method for finding
approximate solutions via dual decomposition. Simulations of the deployment
model based on actual base station locations are presented that show that large
capacity gains are achievable if adoption of third-party, open access
femtocells can reach even a small fraction of the current market penetration of
WiFi access points.Comment: 9 pages, 6 figure
Enhanced Inter-Cell Interference Coordination Challenges in Heterogeneous Networks
3GPP LTE-Advanced has started a new study item to investigate Heterogeneous
Network (HetNet) deployments as a cost effective way to deal with the
unrelenting traffic demand. HetNets consist of a mix of macrocells, remote
radio heads, and low-power nodes such as picocells, femtocells, and relays.
Leveraging network topology, increasing the proximity between the access
network and the end-users, has the potential to provide the next significant
performance leap in wireless networks, improving spatial spectrum reuse and
enhancing indoor coverage. Nevertheless, deployment of a large number of small
cells overlaying the macrocells is not without new technical challenges. In
this article, we present the concept of heterogeneous networks and also
describe the major technical challenges associated with such network
architecture. We focus in particular on the standardization activities within
the 3GPP related to enhanced inter-cell interference coordination.Comment: 12 pages, 4 figures, 2 table
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