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In this paper, we study how the downlink received signal quality and throughput will be affected by deploying the Open Subscriber Group (OSG) Femtocell [1] using Location-Dependent Power Setting (LDPS) scheme with spectrum allocation (1, 3, 3) in the next generation mobile network. The LDPS scheme aims to use a suitable power for femtocell base station to maintains its indoor user coverage. The design...
In OFDMA systems adopting fractional frequency reuse, we can allocate orthogonal bandwidth to femtocells, which mitigates throughput degradation of macrocell users. In this paper, we discuss the optimal power allocation for femtocells with different orthogonal subbands, based on analysis of macrocell interferences.
In this letter, we focus on intercell fairness in OFDM femtocell networks. Serious degradation of any cell cannot ensure fairness for entire network, thus, intercell fairness is important for the satisfaction of all users. In order to improve intercell fairness, we devise a cooperative resource-allocation algorithm, which is an enhanced modified iterative water-filling (EMIWF). The proposed algorithm...
In this paper we consider the downlink of an OFDM cellular system. The objective is to maximise the system utility by means of fractional frequency reuse and interference planning. The problem is a joint scheduling and power allocation problem. Using gradient scheduling scheme, the above problem is transformed to a problem of maximising weighted sum-rate at each time slot. At each slot, an iterative...
The cyclic prefix comb spectrum code division multiple access (CP-CS-CDMA) has comb spectrum in frequency domain. Its different code groups can be separated with a simple hopping accumulator. In the paper, we combine OFDMA and CP-CS-CDMA, and propose a new multiple access scheme, hybrid multiple access (HMA). Then we propose a new reuse partitioning system with HMA. The cell of the system has two...
We consider the downlink of a cellular wireless network where the base stations are equipped with multiple transmit antennas and operate in the same frequency band. Each base station serves one user per orthogonal frequency-division multiplexing (OFDM) sub-carrier by means of spatial precoding. Due to temporal scheduling, the active users change rapidly in time and consequently, intercell interference...
Fractional frequency reuse (FFR) is an interference coordination technique well-suited to OFDMA based wireless networks wherein cells are partitioned into spatial regions with different frequency reuse factors. This work focuses on evaluating the two main types of FFR deployments: Strict FFR and Soft Frequency Reuse (SFR). Relevant metrics are discussed, including outage probability, network throughput,...
The low-power and low-cost femtocells can improve indoor coverage and capacity. However, when femtocells are deployed extensively, the serious two-tier interference problem occurs. The method to access the femtocell is the key to manage the interference in the femtocell systems. In this paper, we investigate the impacts of access methods and directional antenna on link reliability and capacity for...
We study in the present paper the spectral efficiency of OFDMA cellular networks which is a classical indicator of their performance usually calculated by simulations. On the other hand, due to an increasing interest on the environmental impact of these networks, we study also their energy efficiency which may be defined as the ratio of the spectral efficiency and the consumed energy. We give an explicit...
In this paper, a novel cell architecture in relay-enhanced Orthogonal Frequency-Division Multiple Access (OFDMA) cellular networks is proposed. By spatially reusing the spectrum in the same cell, the frequency efficiency is enhanced, while the co-channel interference is reduced by dividing the coverage of both the base stations (BSs) and the relays into sectors, thus the MSs at the cell edge can attain...
This paper exploits the use of location information of wireless terminals to improve the performance of a beamforming system and support multiple access. Based on a system providing real-time 3D coordinate information of all terminals in the environment, a novel feedback-free multi-user scheduler is proposed. It chooses a set of angularly separated wireless terminals for simultaneous transmission...
In this paper, we present a pilot design for an OFDM cellular system based on Costas arrays. The design provides pilot symbols for both common and dedicated pilots for MIMO transmission. The pilot symbols are designed so that pilots from different cells intersect minimally. The design results in a large number of available distinct pilot symbol patterns with minimally overlapping resource elements...
Inter-cell interference is a major problem in multi-cell OFDMA systems and can severely degrade the system throughput, particularly for cell-edge users. An efficient technique to mitigate inter-cell interference (ICI), is interference coordination that allocates certain resources among users in different cells. In this paper, we propose a novel and distributed algorithm in order to mitigate the inter-cell...
Orthogonal Frequency Division Multiplexing (OFDM) is very sensitive to carrier frequency offsets (CFO). The CFO results in intercarrier interference (ICI). This drawback of OFDM is inherited to Orthogonal Frequency Division Multiple Access (OFDMA). In this paper, we propose a new ICI model for an uplink OFDMA system that takes into account the presence of the cyclic prefix which is usually ignored...
This paper addresses the effect of timing synchronization errors for two different multicarrier techniques CPOFDM and FBMC. Such errors degrade the performance of the reference receiver by causing multi user interference. This interference occurs when the signals from different transmitters arrive at a given receiver with arbitrary timing misalignments, leading to the destruction of orthogonality...
We consider a cellular network MIMO OFDM system where cooperating base stations apply joint signal processing to the receive signals of several users. In this situation, due to geometry, the problem of unavoidable differences in time of arrival between the users' signals occurs. As a result, symbol timing offsets can be larger than the cyclic prefix, which leads to OFDM inter-symbol interference....
We consider wireless telecommunications systems with orthogonal frequency bands, where each band is referred to as a channel, e.g., orthogonal frequency-division multiple access (OFDMA). For a given snap-shot in time, two joint channel assignment and power allocation optimization problems are presented, one in downlink and one in uplink. The objective is to maximize the minimum total Shannon capacity...
It is well known that symbol timing offsets larger than the cyclic prefix as well as carrier frequency offsets between transmitter and receiver stations destroy the orthogonality among OFDM subcarriers and induce additional interference. In conjunction with MIMO transmission on frequency selective fading channels where different users interfere with each other, these effects strongly degrades the...
The LTE-Advanced (LTE-A) system is currently under development to allow for significantly higher spectral efficiency and data throughput than LTE systems. In a wireless system based on orthogonal frequency division multiplexing (OFDM) with frequency reuse factor one such as LTE, the achievable cell spectral efficiency is often limited by the inter-cell interference or coverage shortage of base stations...
It is well known that symbol timing offsets larger than the cyclic prefix between transmitter and receiver stations destroy the orthogonality among OFDM subcarriers inducing interblock interference by coupling subsequent OFDM symbols. In conjunction with MIMO transmission over frequency selective channels, this effect on top of multi-user interference strongly degrades performance. In this paper we...
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