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In a cellular network with relays, the mobile station (MS) can benefit from both coverage extension and throughput enhancement. To improve the throughput of such cellular multi-hop networks, we propose an adaptive modulation (AM) combined with orthogonal frequency division multiplexing (OFDM). Using AM with OFDM enables the transmitter to change the order of the modulation on each subcarrier separately...
User scheduling and multiuser multi-antenna (MU-MIMO) transmission are at the core of high-rate data-oriented downlink schemes of the next-generation of cellular systems (e.g., LTE-Advanced). Scheduling selects groups of users according to their channels vector directions and channel quality indicator (CQI). However, when scheduling is applied independently in each cell, the inter-cell interference...
Coverage and capacity optimization is considered as one of the most important optimization items for cellular network. It is beneficial from energy consumption and interference deduction perspective if the downlink base station power can be regulated according to the UEs distribution and service requirements. A cellular base station downlink power regulation scheme is studied where the power regulation...
This paper presents a comparison between CDMA and SC-FDMA for reverse link (RL) cellular voice and data communications. The comparison is based on CDMA2000 1x (circuit-switched voice), CDMA2000 1xEV-DO (packet data) and 3GPP LTE Release 8 (SC-FDMA based packet voice and data). We illustrate various modes of LTE system operation and associated trade-offs. For the comparison of data communications we...
In this paper, a novel interference coordination scheme based on Dynamic Resource Allocation (DRA) for mitigating inter-cell interference in Long Term Evolution (LTE) cellular systems is presented. In both OFDMA and SC-FDMA systems, inter-cell interference is the most important interference source. Inter-cell interference coordination is considered to improve coverage and increase date rate at cell...
CoMP JP (Coordinated Multi-Point Joint Processing) is regarded as a promising technique to improve both cell edge user throughput and cell average user throughput in LTE-A downlink. CoMP JP can be categorized as CoMP JT (Joint Transmission) and COMP DCS (Dynamic Cell Selection). Compared with CoMP JT schemes, CoMP DCS provides a good trade-off between the transmission algorithm complexity, backhaul...
In the cooperative system with a large number of users, the base station may select a subset of users to serve in order to maximize the total throughput. The brute-force search for the optimal user set, however, is computationally prohibitive. We propose a clustering algorithm for cooperative communication systems, whose objective is to increase the cellular network throughput and further improve...
In this work, we develop mathematical and algorithmic tools for the self-optimization of mobile cellular networks. Scalable algorithms which are based on local measurements and do not require heavy coordination among the wireless devices are proposed. We focus on the optimization of transmit power and of user association. The method is applicable to both joint and separate optimizations. The global...
This paper considers multiple-input/multiple-output(MIMO) cooperative communication systems with a decode-and-forward (DF) relay. We propose novel rate maximization schemes which utilizes uniform channel decompositions (UCD)to decompose the MIMO channel between a base station (BS) and a relay station (RS). In the proposed scheme, the MIMO channel is decomposed into multiple independent subchannels...
User scheduling and multiuser multi-antenna (MU-MIMO) transmission are at the core of high-rate data-oriented downlink schemes foreseen in the next-generation cellular systems (e.g., LTE-Advanced). Scheduling exploits the knowledge of the users' instantaneous achievable coding rates. However, when it is applied independently in each cell, the level of inter-cell interference (ICI) experienced by each...
Data aggregation significantly reduces signaling overhead and delay by encapsulating multiple packets in queue into an aggregated packet in uplink two-hop relaying networks. In addition, hybrid automatic repeat request (HARQ) operation increases the system throughput by retransmitting the entire or part of the packet transmitted at the initial transmission. We combine data aggregation and HARQ schemes...
In next-generation cellular systems, Multi-User MIMO (MU-MIMO) schemes are expected to achieve very high downlink throughput, provided that issues such as Inter-Cell Interference (ICI), user scheduling, etc. are properly handled. In order to accomplish this goal, we consider a joint scheduling and cell clustering scheme where groups of adjacent cells (clusters) are jointly controlled and effectively...
Energy efficiency in information and communications technology, and in cellular mobile radio networks in particular, is gaining in importance not only with regard to the ecological assessment. Reducing the power consumption of mobile radio systems has recently attracted attention of network operators as energy costs make up a vast portion of today's operational expenditure. In this regard, it is often...
This paper studies the joint OFDMA resource allocation and QoS routing problem in a hybrid wireless network, which includes an OFDMA based cellular network and an ad-hoc network with many sensor nodes. In such application, each sensor node generates certain amount of data that need to be sent to cellular base station (BS). The cellular nodes act as gateway to forward all the uplink traffic. We formulate...
This paper studies the performance and coverage improvements introduced by relay deployment in LTE-Advanced systems. Different relay deployment strategies are investigated, namely, amplify-and-forward (AF) repeaters and decode-and-forward (DF) relays (orthogonal and non-orthogonal modes). First, the expressions of peak throughput (i.e., assuming allocate all resources in a cell to one user) for different...
The interference situation in the uplink of cellular networks, such as the 3GPP UTRAN Long Term Evolution (LTE), is usually highly volatile since from one transmission time interval to the other different users might be scheduled in nearby cells, thus often causing completely different levels of interference. This unstable behavior of the interference generally has a negative impact on the performance...
This paper studies the impact of HSPA equipments and devices evolution, from 3GPP R5 to R7 ones, on the capacity of a real macro-cell network. A simulation method has been developed. It combines drive test measurements, link-level simulations, and a statistical capacity model, which provides a reliable estimate of the network radio capacity. Different receiver schemes are simulated: linear receivers...
Various standardization activities leading to 4G and beyond networks have considered the synergy of OFDMA and multihop relaying thus giving way for the fixed relay station (FRS)-based radio access network. As such, the next-generation networks will comprise a plethora of performance enhancing devices among which is the plug-and-play nomadic relay station (NRS). It is essential for such dense and inevitably...
Performance of a decode-and-forward (DF) based two-hop multiuser cooperative transmission system is usually restricted by the link quality between a base station (BS) and a relay station (RS) as the number of users grows. Thus the BS-RS link quality should be improved to enhance the performance. In this paper, we propose two-hop cooperative communication systems with multiple receive antennas at the...
This paper presents a framework based on self-organization to jointly self-optimize the spectrum assignment and the transmission power in the context of downlink OFDMA femtocell deployments. It is a distributed framework where each femtocell acts as an autonomous entity. Femtocells perform spectrum and transmission power assignment based on users' reported measurements, which are employed to sense...
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