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Base station coordination has received much attention as a means to reduce the inter-cell interference in cellular networks. However, this interference reducing ability comes at the expense of increased feedback, backhaul load and computational complexity. The degree of coordination is therefore limited in practice. In this paper we explore the trade-off between capacity and feedback load in a cellular...
Opportunistic beamforming is investigated in the context of multicell LTE uplink resource allocation. A scheduling algorithm based on beam and resource block (RB) allocation with opportunistic beamforming is presented. Beams are formed in a pseudorandom fashion thus allowing users to opportunistically benefit from the antenna gain and interference rejection capabilities. Results show that enhanced...
Channel reciprocity is regarded as one of the most important advantages of TDD systems. However, the RF front-ends contribute to the channel experienced, and their TX/RX mismatches might cause reciprocity error, and thus degrade system throughput. Therefore, channel reciprocity calibration is a crucial issue. Among the existing calibration methods, Over-the-air (OTA) calibration is a promising approach...
This paper focuses on the problem of queue-aware resource allocation for OFDMA cellular systems supporting both real-time and non-real-time services. A set of practical algorithms is proposed to solve the problem of maximizing the system utility under the constraints of both system resources and the actual amounts of data to be transmitted in buffers. Moreover, an upper bound is devised to quantify...
It is demonstrated that the suitable relay selection or power control method is very important to network performance. However, there is little work concerning the combination of them in the multi-cell scenario. In this paper, we propose a cross-layer design to associate relay selection with power control scheme to increase the average network capacity, as well as to mitigate interference, where the...
Multicell joint processing has been proven to be very efficient in overcoming the interference-limited nature of the cellular paradigm. However, for reasons of practical implementation global multicell joint decoding is not feasible and thus clusters of cooperating Base Stations have to be considered. In this context, intercluster interference has to be mitigated in order to harvest the full potential...
An interference management method for coordinating downlink transmission in a Multiple-Input Multiple-Output (MIMO) cellular network is proposed. The problem is to efficiently manage inter-cell interference in a multi-cell environment, by so-called transmitter cooperation, in order to reduce the diminishing effects of interference on the networks performance. To allow for application in deployable...
Different-complexity Multi-Cell Processing (MCP) schemes employing Distributed Signal-to-Interference-Leakage-plus-Noise-Ratio (SILNR) precoding techniques are proposed, which require reduced back-haul data exchange in comparison to the conventional MCP structure. Our results demonstrate that the proposed structures are capable of increasing the achievable cell-edge throughput and offering different...
We consider the problem of fair resource allocation in interference channels, for the case of one-dimensional cells. We propose simple interference channel models based upon the deterministic channel model, assuming zero queuing delay. This enables study of how the interference induces coupling among the rates available in the channels and evaluation of resource allocation. A sequence of models of...
We consider the use of Blind Interference Alignment (BIA) in a cellular environment as a means for supporting downlink Multi-User MIMO (MU-MIMO) transmission without the need for channel state information at the transmitter (CSIT). This “CSIT-blind” characteristic of BIA is of particular interest for Frequency Division Duplex (FDD) systems, since it allows one to eliminate overheads and impairments...
We consider smart “cognitive” femtocells, that can decode the base station control channel and make decision on their transmission opportunities based on the scheduling and resource allocation of the overlaying macrocell. The operation of such femtocells is somehow reminiscent of “Type II” relays, as specified in the IEEE 802.16j standard. Under certain system assumptions, we consider the tradeoff...
Cooperative techniques for cellular networks promise very high data rates, but require additional and precise knowledge of the serving and interference channels. We show, how the pilot symbols required for achieving this information affect the possible data rates. The measurements of the channels are suffering from pilot contamination, due to the measurements in adjacent cells. On the one hand, with...
We develop a tractable, flexible, and accurate model for downlink heterogeneous cellular networks. It consists of K tiers of randomly-located base stations (BSs), where each tier may differ in terms of the average transmit power, the supported data rate and the BS density. This allows elements spanning traditional, micro, pico, and femtocell BSs to be simultaneously considered. Assuming a mobile user...
The degrees of freedom of a cellular system in a fading environment are determined. An arbitrary number of base stations with multiple antennas and an arbitrary, but similar per cell, number of users with multiple antennas is considered. Two distributed algorithms which possibly achieve interference alignment are presented. Simulations show that the proposed algorithms achieve the optimal degrees...
We consider a reuse-1 cellular system and study the improvement in SINR possible for a fixed/nomadic receiver, from the use of an optimally oriented directional patch antenna or a Uniform Linear Array (ULA) with 2 or 4 antenna elements along with Minimum Mean Square Error (MMSE) combining. We perform the studies with a ray-tracing propagation model as well as an empirical statistical model that is...
In this paper, we present a novel approach to evaluate the downlink Erlang capacity of a cellular Orthogonal Frequency Division Multiple Access (OFDMA) system with 1:1 frequency reuse. Erlang capacity analysis of traditional cellular systems like Global System for Mobile communications (GSM) cannot be applied to cellular OFDMA because in the latter, each incoming call requires a random number of subcarriers...
In this paper, we address the problem of optimal relay placement in cellular networks for maximum extension of coverage area. We present a novel definition of the coverage radius after the introduction of relays. Using this, we determine the optimal relay positions to maximize the coverage radius and estimate the number of relays required per cell. We also analyze relay placement in the multi-cell...
In this paper, discrete event simulation by batch-means of a M/M/∞ queuing system is utilised to simulate a cellular CDMA system. The details of the simulation model, warm-up period, and simulation run time are discussed. The warm-up period is studied because it affects the accuracy of the results in simulation of communication systems. During the warm-up period-when the simulation system has not...
In this work a strategy for triggering an interradio access technology cell reselection in UMTS user equipment is proposed. All mobile devices within the effective range of a transmitter radiating a noise-like RF signal on the UMTS downlink frequency bands are forced to leave the UMTS cells and camp on non-UMTS cells, such as e.g., GSM. This allows to use a GSM based localization technique even in...
Cellular base stations typically orthogonalize downlink transmissions, although this approach is not always throughput-optimal. Indeed, it can be shown that removing the orthogonality constraint (as in Superposition Coding) can provide significant benefits in some scenarios. Based on this principle, we propose a scheduling algorithm for a two-user downlink that leverages the disparity in their respective...
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