Conference Paper

Spectral Efficiency and Fairness for Opportunistic Round Robin Scheduling

Norwegian University of Science and Technology, Dept. of Electronics and Telecommunications, 7491 Trondheim, Norway, email:
DOI: 10.1109/ICC.2006.254803 Conference: Communications, 2006. ICC '06. IEEE International Conference on, Volume: 2
Source: IEEE Xplore

ABSTRACT In this paper we analyze the Opportunistic Round Robin (ORR) scheduling algorithm [1], [2]. This algorithm is able to exploit multiuser diversity (MUD) and at the same time provide short-term fairness between the users in a wireless cellular network. We analyze the spectral efficiency and the fairness for two scenarios. In the first scenario all the users have the same average carrier-to-noise ratios (CNR) and for the second scenario the users have different average CNRs. For the first scenario the absolute MUD is exploited while we exploit the so-called relative MUD between the users for the second scenario. The advantages and disadvantages of the different ORR implementations are highlighted by analyzing plots of our closed-form expressions.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Base station (BS) sleeping has emerged as a viable solution to enhance the overall network energy efficiency by inactivating the underutilized BSs. However, it affects the performance of users in sleeping cells depending on their BS association criteria, their channel conditions towards the active BSs, and scheduling criteria and traffic loads at the active BSs. This paper characterizes the performance of cellular systems with BS sleeping by developing a systematic framework to derive the spectral efficiency and outage probability of downlink transmission to the sleeping cell users taking into account the aforementioned factors. In this context, we develop a user association scheme in which a typical user in a sleeping cell selects a BS with \textbf{M}aximum best-case \textbf{M}ean channel \textbf{A}ccess \textbf{P}robability (MMAP) which is calculated by all active BSs based on their existing traffic loads. We consider both greedy and round-robin schemes at active BSs for scheduling users in a channel. Once the association is performed, the exact access probability for a typical sleeping cell user and the statistics of its received signal and interference powers are derived to evaluate the spectral and energy efficiencies of transmission. For the sleeping cell users, we also consider the conventional \textbf{M}aximum \textbf{R}eceived \textbf{S}ignal \textbf{P}ower (MRSP)-based user association scheme along with greedy and round-robin schemes at the BSs. The impact of cell-zooming is incorporated in the derivations to analyze its feasibility in reducing the coverage holes created by BS sleeping. Numerical results show the trade-offs between spectral efficiency and energy efficiency in various network scenarios. The accuracy of the analysis is verified through Monte-Carlo simulations.
    IEEE Transactions on Wireless Communications 01/2014; 13(10). · 2.76 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Opportunistic schedulers improve the network capacity by allocating the network resources to users with good link qualities. A drawback of these schedulers is that they deprive the remaining users from receiving a fair share of the network resources, or violate their quality-of-service (QoS) requirements. Fair schedulers on the other hand impose a degree of fairness by allocating the network resources to the users in a weighted manner. However, majority of the existing fair algorithms do not impose the same degree of fairness in heterogenous networks. Furthermore, majority of these algorithms require full feedback from all users in order to make a scheduling decision. In this paper, we propose a scheduling algorithm that reduces the feedback overhead, and thus the scheduling delay, while maintaining a degree of fairness in heterogeneous wireless networks. To impose a degree of fairness, the scheduler prioritizes a set of starved users and allocates the network resource to the user (starved) with the best link quality. To reduce the feedback overhead, the scheduler requests users to feedback their link qualities in a joint polling and contention manner. Numerical results show that the proposed algorithm attains the highest degree of fairness while reducing the overall feedback load when compared to other well known fair and greedy algorithms. Furthermore, we show that a trade-off exits between the attainable degree of fairness and the scheduling delay, and hence, the scheduler should strike a balance between fairness and delay depending on the network priority.
    Globecom Workshops (GC Wkshps), 2012 IEEE; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: Fractional frequency reuse (FFR) is an efficient way to mitigate inter-cell interference (ICI) in multi-cell orthogonal frequency division multiple access (OFDMA) networks. In this paper, we investigate the throughput and the optimal threshold for the FFR scheme. The average cell throughputs are derived for both round robin (RR) and maximum SINR (MSINR) scheduling strategies when users are uniformly distributed in the cell region. It is shown from the analysis and simulation results that the throughput increases and the optimal distance threshold decreases with the number of users for both scheduling strategies. The optimal distance threshold approaches the minimum distance that users can be away from the base station when the number of users goes to infinity. The optimal distance threshold increases with the frequency reuse factor of the cell-edge region when the MSINR scheduling is used. The impact of the RR scheduling strategy on the optimal threshold of the FFR scheme is negligible. Simulation also demonstrates that the FFR scheme with the optimal threshold significantly outperforms that with the existing fixed threshold.
    IEEE Transactions on Wireless Communications 01/2012; 11(8):2776-2785. · 2.76 Impact Factor

Full-text (2 Sources)

Available from
Nov 24, 2014