On the OFDMA FDD mode in 3G-LTE (original) (raw)
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2007
New generations of cellular radio systems are currently being developed based on OFDM transmission with OFDMA as the multiple access scheme. The demand for high data rates in reasonably large areas is omnipresent, but the conventional cellular architecture offers does not only a maximum rate depending on the distance. Close to the base station, the higher received SINR valueallows the highest Modulation&Coding scheme (PhyMode), which offers the highest data rate. In this paper we user the mutual information approach to calculate the maximum data rate based on the SINR at all positions in an interference-limited radio cell. Near the cell border the offered data rate is one order of magnitude lower. Relaying or Multihop operation is an option to massively improve the coverage as well as the capacity issue at low cost, without the need of a cable or fibre access. In this method, the base station coordinates the partitioning of radio resources within the relay enhanced cell (REC). Frequ...
2015
Abstract—New generations of cellular radio systems are currently being developed based on OFDM transmission with OFDMA as the multiple access scheme. The demand for high data rates in reasonably large areas is omnipresent, but the conven-tional cellular architecture offers does not only a maximum rate depending on the distance. Close to the base station, the higher received SINR valueallows the highest Modulation&Coding scheme (PhyMode), which offers the highest data rate. In this paper we user the mutual information approach to calculate the maximum data rate based on the SINR at all positions in an interference-limited radio cell. Near the cell border the offered data rate is one order of magnitude lower. Relaying or Multihop operation is an option to massively improve the coverage as well as the capacity issue at low cost, without the need of a cable or fibre access. In this method, the base station coordinates the partitioning of radio resources within the relay enhanced cell (R...
An FDD Multihop Cellular Network for 3GPP-LTE
VTC Spring 2008 - IEEE Vehicular Technology Conference, 2008
The future cellular radio networks like 3G-LTE [1] are based on an OFDMA physical layer. The duplex scheme is preferably frequency division (FDD) because of its advantages in long range. Huge area coverage in a cost-efficient way is important problem for the early deployment. Time after time the demand in densely populated areas will grow, so a higher cell capacity over the area is needed. The requirements are expensive to solve with a traditional cellular architecture, because a fibre line access will be needed at any base station location, which are sometimes only a few 100 meters apart. This paper deals with Multihop operation as an option to improve the coverage as well as the capacity issue at low cost. Homogeneous Relays act like Base Stations, but without the need of a cable or fibre access. They are simply fed by the same radio technology in their first hop.
This paper addresses the Co-Channel Interference (CCI) mitigation in Relay-Assisted (R-A) cellular systems to improve Cell Edge User's (CEU's) performance. Analytical treatments are conducted. The network performance improvement through reducing CCI effects are evaluated using two proposed interference mitigation models. These models denote the R-A sectored Fractional Frequency Reuse (FFR) and R-A Soft Frequency Reuse (SFR). Each model contains two different scenarios for further network performance improvement. The first scenario considers three Relay Stations (RSs) per cell while the other one proposes six RSs in each cell. The best RS placement is proposed. Moreover, closed form expressions for worst cases CEU's SIR, Cell Centre User's (CCU's) SIR and inner radius are implemented. These expressions are used to compare between the considered models using different performance evaluation metrics. The work outcomes enable the system designer to characterize and optimize the multi-cell network performance without a need to execute complex calculations. Also the obtained results contributes to achieve much higher network performance improvement with a lower cost.
Analytical Model of Intercell Interference in Relay Based Cellular OFDMA Networks
Ijca Special Issue on Wireless Communication and Mobile Networks, 2012
In order to improve the coverage and capacity of next generation cellular networks, low cost relays are deployed in the area, where users do not get required Signal to Noise Ratio (SNR) from the base station (BS), especially at the cell edge. The deployment of relays not only reduces the infrastructure cost of setting up new BSs but also supports the rapidly growing number of subscribers. However introduction of Relays introduces additional interferences, which affects the system capacity. In this paper, we analyze this interference in Relay based Orthogonal Frequency Division Multiplexing Access (OFDMA) system. We present an analytical model to characterize the interference experienced by a particular user in a reference cell from all interfering cells irrespective of the position of user. We consider the effect of path loss, shadowing and fading on interference powers from various cells. Then, we determine the Cumulative Distribution Function (CDF) of interference.
1 An FDD Multihop Cellular Network for 3GPP-LTE
2013
— The future cellular radio networks like 3G-LTE [1] are based on an OFDMA physical layer. The duplex scheme is preferably frequency division (FDD) because of its advantages in long range. Huge area coverage in a cost-efficient way is important problem for the early deployment. Time after time the demand in densely populated areas will grow, so a higher cell capacity over the area is needed. The requirements are expensive to solve with a traditional cellular architecture, because a fibre line access will be needed at any base station location, which are sometimes only a few 100 meters apart. This paper deals with Multihop operation as an option to improve the coverage as well as the capacity issue at low cost. Homogeneous Relays act like Base Stations, but without the need of a cable or fibre access. They are simply fed by the same radio technology in their first hop. The contribution of this paper is especially the multihop operation in the FDD mode and performance results for the ...
Frequency Reuse Scheme With Three Regions in Cooperative Relaying For Multi-cell OFDMA Systems
Cooperative relaying has shown as promissing approach to improve transmission reliability in cellular network. In this paper cooperative relaying and frequency reuse partitioning are exploited to avoid the co-channel cell interference (CCI) in the downlink multi-cell OFDMA systems. In our system layout, each cell is divided into three regions: the central region, the middle region and the edge region. The frequency reuse factor (FRF) is set to 1 in the central region. Depending on the number of sectors in the middle and the edge region, the FRFs of 3, 7/3, 7/4, 4 and 6 have been applied. A fixed relay station (RS) by sector, which amplifies and forwards the received signal to the mobile, is placed at the limit of the middle region and the edge region. Numerical results are presented to demonstrate the effectiveness of the proposed cooperative scheme for CCI mitigation in the edge of the cell.
Dynamic resource allocation in relay-assisted OFDMA cellular system
Transactions on Emerging Telecommunications Technologies, 2011
This study investigates a relay-assisted orthogonal frequency division multiple access cellular system with joint consideration of direct and relaying paths. In this system, a novel implementation adopting full-duplex relaying is proposed for joint relay-destination selection, subcarrier and power allocation. This new implementation can be shown to significantly improve spectrum efficiency as compared with the conventional half-duplex relaying orthogonal frequency division multiple access. In addition, the proposed scheme enables flexible controllability on the tradeoff between system capacity and user fairness.
Analysis of Blocking Probability in a Relay-Based Cellular OFDMA Network
Wireless Personal Communications, 2015
Relay deployment in Orthogonal Frequency Division Multiple Access (OFDMA) based cellular networks helps in coverage extension and/or capacity improvement. To quantify capacity improvement, blocking probability of voice traffic is typically calculated using Erlang B formula. This calculation is based on the assumption that all users require same amount of resources to satisfy their rate requirement. However, in an OFDMA system, each user requires different number of subcarriers to meet its rate requirement. This resource requirement depends on the Signal to Interference Ratio (SIR) experienced by a user. Therefore, the Erlang B formula can not be employed to compute blocking probability in an OFDMA network. In this paper, we determine an analytical expression to compute the blocking probability of relay based cellular OFDMA network. We determine an expression of the probability distribution of the user's resource requirement based on its experienced SIR. Then, we classify the users into various classes depending upon their subcarrier requirement. We consider the system to be a multi-dimensional system with different classes and evaluate the blocking probability of system using the multi-dimensional Erlang loss formulas. This model is useful in the performance evaluation, design, planning of resources and call admission control of relay based cellular OFDMA networks like LTE.
Performance optimization of amplify-and-forward relaying schemes for uplink OFDMA communications
Cooperative communication is a promising technique to enhance the system performance by exploiting the spatial diversity provided by the relay use. Incremental relaying techniques are proposed to limit the resources use to only bad channel conditions. In this paper, we deal with AF and IAF performance optimization for uplink Orthogonal Frequency Division Multiple Access (OFDMA) communications, carried on a packet-per-packet basis. For OFDMA cellular system, we define a cost that reliably quantifies the additional multipleaccess interference (MAI) inherent to the relaying use. This MAI cost expression depends highly on the adopted frequency reuse pattern. The optimization, in terms of Packet-Error-Rate (PER), is carried out while keeping this MAI cost constant, for regular and fractional frequency reuse patterns. For FFR, different frequency reuse factors are applied to cell-center and cell-edge areas. Simulation results are showing that IAF relaying outperforms the direct transmission scheme by more than 15 dB gain, in terms of the reduction of the MAI. Additionally, IAF seems to be usually more powerful than AF.