Green deployment for cellular eNodeBs has been proposed recently to save power and reduce the huge amount of carbon dioxide CO 2 emitted by traditional power-hungry base stations. Green eNodeBs should also be subjected to restrictions on high data rate and quality of service QoS, which both entail a high level of power consumption. In this regard, this paper addresses the trade-off between energy efficiency EE and spectral efficiency SE in both traditional and green long-term evolution eNodeBs without sacrificing the QoS. EE is proved to monotonically increase with SE in traditional macrocells and quasi-concave in green macrocells. Accordingly, a new mapping between channel quality indicator and modulation and coding scheme is proposed to address EE-SE trade-off with the use of a multi-criteria decision-making technique. Then, a self-configured link adaptation SCLA algorithm is developed to ensure that the priority weights related to EE and SE are adapted according to network load with the use of real-time cross-layer optimization. Simulation results show that the proposed SCLA provides a significant gain in EE and 52% reduction of CO 2 while maintaining SE close to the optimal value. Current and next-generation cellular networks require such interactive techniques in order to be self-optimised without complex modifications. Copyright © 2014 John Wiley & Sons, Ltd.

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A self-configured link adaptation for green LTE downlink transmission

We consider a multiuser downlink transmission from a base station with multiple antennas (MIMO) to mobile terminals (users) with a single antenna, using orthogonal frequency division multiplexing (OFDM). Channel conditions are reported by a feedback from users with limited rate, and the base station schedules transmissions and beamforms signals to users. We show that an important set of schedulers using a general utility function can be reduced to a scheduler maximizing the weighted sum rate of the system. For this case we then focus on scheduling methods with many users and OFDM subcarriers. Various scheduling strategies are compared in terms of achieved throughput and computational complexity and a good tradeoff is identified in greedy and semiorthogonal user selection algorithms. In the greedy selection algorithm, users are selected one by one as long as the throughput increases, while in the semiorthogonal approach users are selected based on the channel correlation. An extension of these approaches from a flat-fading channel to OFDM is considered and simplifications that may be useful for a large number of subcarriers are presented. Results are reported for a typical cellular transmission of the long-term evolution (LTE) of 3GPP.

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A comparison of scheduling strategies for MIMO broadcast channel with limited feedback on OFDM systems

Future generation cellular networks are expected to deliver an omnipresent broadband access network for an endlessly increasing number of subscribers. Long term Evolution (LTE) represents a significant milestone towards wireless networks known as 4G cellular networks. A key feature of LTE is the implementation of enhanced Radio Resource Management (RRM) mechanism to improve the system performance. The structure of LTE networks was simplified by diminishing the number of the nodes of the core network. Also, the design of the radio protocol architecture is quite unique. In order to achieve high data rate in LTE, 3rd Generation Partnership Project (3GPP) has selected Orthogonal Frequency Division Multiplexing (OFDM) as an appropriate scheme in terms of downlinks. However, the proper scheme for an uplink is the Single-Carrier Frequency Domain Multiple Access due to the peak-to-average-power-ratio (PAPR) constraint. LTE packet scheduling plays a primary role as part of RRM to improve the system’s data rate as well as supporting various QoS requirements of mobile services. The major function of the LTE packet scheduler is to assign Physical Resource Blocks (PRBs) to mobile User Equipment (UE). In our work, we formed a proposed packet scheduler algorithm. The proposed scheduler algorithm acts based on the number of UEs attached to the eNodeB. To evaluate the proposed scheduler algorithm, we assumed two different scenarios based on a number of UEs. When the number of UE is lower than the number of PRBs, the UEs with highest Channel Quality Indicator (CQI) will be assigned PRBs. Otherwise, the scheduler will assign PRBs based on a given proportional fairness metric. The eNodeB’s throughput is increased when the proposed algorithm was implemented.

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3GPP Long Term Evolution LTE Scheduling

Institut for Elektroniske Systemer Radio Access Technology by Author: Victor Alvarez Roig The requirements of the International Telecommunication Union (ITU) for the 4th generation of mobile devices raised up to 100 Mbps for high and 1Gbps for low mobility conditions. Reaching such challenging targets requires the deployment of picocells and femtocells. These techniques permit to achieve large cell capacity but also lead to difficulties in terms of interference. The GRACE algorithm, based on Cognitive Radio and Game Theory, has shown a fair balance between cell capacity and outage as well as short convergence time, low complexity and easy scalability. The aim of this work is to find an efficient power control algorithm that fits GRACE these goals. Therefore, a study of Cognitive Radio, Game Theory and Power Control algorithms is developed and a new power control algorithm is proposed. The simulation results show that the Fractional Power Control can increase notably the outage performance and the energy saving to the mobile devices.

/pdf/study-and-development-of-power-control-schemes-within-a-28c2ltzyni.pdf

Study and Development of Power Control Schemes within a Cognitive Radio-based Game Theoretic Framework

The long term evolution(LTE) program of 3GPP is the biggest research program launched in recent years.It has achieved many great progresses since it has been initiated in 2004.3GPP LTE has fulfilled the high data rate,low latency and all-packet basis.This paper introduced its design objectives for E3G system service capabilities and the advanced technologies and novel concepts related to the physical layer in LTE program.

Liu Lian-fu

Papers

Long term evolution of 3GPP and its physical layer technologies