Scheduling and resource allocation (original) (raw)
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Downlink Multi-Cell Radio Resource Management for Coordinated Base Stations
VTC Spring 2009 - IEEE 69th Vehicular Technology Conference, 2009
This paper addresses the design of joint multi-cell resource allocation and scheduling with coordination among neighboring base stations (BS). Considering N s neighboring sectors, the solution that maximizes the sum-rate in the covered area is found for TDMA and TDMA/OFDMA access. The optimum solution exhibits low complexity as it presents the useful property that its computation admits a decomposition such that each BS is responsible for the selection of the users to be scheduled in its own sector. This result is proved analytically.
Radio resource management for OFDMA uplinks
2007
The next generation of wireless networks (4G) will use OFDMA (Orthogonal Frequency Division Multiple Access) in the reverse link. In OFDMA, the reverse link resources assigned to a user are called tiles each of which consists of a subset of consecutive subcarriers. Since at most one user is assigned to each of these tiles then reverse link transmissions within a sector are orthogonal. However, the transmission is affected by intercell interference since users in adjacent sectors may also have been assigned to the same tile. If those users in the adjacent sectors transmitted with high power then the intercell interference may severely limit the SINR achieved by the user. Therefore user transmission powers must be carefully managed to avoid excessive intercell interference. In this paper we propose a distributed algorithm for the problem and use numerical results to illustrate its performance.
Radio Resource Management in Multi-Tier Cellular Wireless Networks
Radio Resource Management in Multi-Tier Cellular Wireless Networks, 2013
X2 interface, defined as a direct eNB-to-eNB interface, allows for inter-cell interference coordination (ICIC) S1 interface supports transfer of user and data traffic between the corresponding nodes. Un interface refers to an air interface between DeNB and RN. Un is based on a modified interface between the eNB and UE in order to allow half duplex operation for the RN. 12/80 One RB consists of 12 subcarriers in the frequency domain (180 kHz) and one subframe in the time domain (1 ms) Subframes are further grouped in 10 ms radio frames. A reference or pilot signal, referred to as a common reference signal (CRS), is used for mobility measurements as well as for demodulation of the DL control and data channels CRS transmission is distributed in time and frequency
On the Rate Gap Between Multi- and Single-Cell Processing Under Opportunistic Scheduling
IEEE Transactions on Signal Processing, 2012
Base station (BS) coordination is a key technique to handle intercell interference (ICI) in cellular networks. Nevertheless, recent work on scheduling indicates that the value of coordination is less prominent when the number of users grows large. More specifically, the loss in sum rate due to ICI in uncoordinated networks can be made arbitrarily small as the number of users goes to infinity. However, the gap in performance for a finite number of users has remained unknown so far. From this perspective we study the gains of multicell zero-forcing beamforming (ZFBF) on the downlink of a Wyner-type network. We first identify the beamforming weights and the optimal scheduling policy under a per-base power constraint. To compare ZFBF with single-cell processing (SCP) we focus on the extra number of users that is needed per cell to compensate for ICI. Specifically, we find the number of users n1 with ZFBF and n2 with SCP that gives the same mean postscheduling signal-to-interference-plus-noise ratio (SINR) as an interference free network with n users. The results show that the ratio n n grows logarithmically with n. Finally, we demonstrate that the difference in sum-rate between SCP and multicell ZFBF goes to zero as O ln ln n ln n. As a consequence of the slow convergence there is a significant gain with multicell ZFBF for all practical numbers of users. Index Terms-Base station (BS) coordination, multiuser scheduling, zero-forcing beamforming (ZFBF).
Wireless Communications and Mobile Computing, 2012
In this paper, we propose several frequency reuse coordination schemes for interference management in orthogonal frequency division multiple access. The aim of these schemes, working together with time and frequency domain packet scheduling, is to achieve reuse of 1 at sector level in a tri-sectorized base station scenario. Inter-sector interference is strong at the frontier between sectors, and a tight coordination scheme needs be applied. To support this coordination scheme, the users' location information is then essential to determine if a user is prone to suffer strong inter-sector interference. The performance of these resource allocation algorithms is compared with schemes based on fractional frequency reuse, where reuse of 1 at cell level is assumed.
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 Maximum best-case Mean channel Access Probability (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 Maximum Received Signal Power (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.
From intra-cell resource allocation to inter-cell multi-operator spectrum sharing
2011 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks, 2011
This research work deals with efficient resource utilization in the downlink of cellular networks which use Orthogonal Frequency Division Multiple Access, as the Long Term Evolution of 3GPP technology. Efficiency is considered first of all in an intra-cell context, where Base Stations exploit the multiuser diversity by adaptive resource allocation. Then, the focus is extended to a scenario with several adjacent Base Stations belonging to different network operators, and a new paradigm is explored. Instead of the classical static orthogonal division of the spectrum, a spectrum sharing approach is introduced where operators share part of their frequencies. Game Theory is the mathematical tool used to model the systems in both steps. Simulative approach is employed for the quantitative evaluation.
Resource Allocation for Cellular Radio Systems
1997
High terminal tra c densities are expected in urban multiuser radio systems. An e cient allocation of resources is the key to high system capacity. In this paper a distributed dynamic resource allocation(DDRA) scheme based on local signal and interference measurements is proposed for multi-user radio networks. It o ers "soft capacity", for time division multiple access (TDMA) and frequency division multiple access (FDMA) systems, bounded above by N per base station, where N is the total number of channels in the system.
Information Technology: Transmission, Processing and Storage, 2007
Objectives -The cellular wireless communications emerged as an answer to a need for a fully mobile telephone service. The service objectives are mobility, full duplex voice, ubiquity -service everywhere and all the time, and capacity -multiple independent sessions within the same area. Grade of service (GoS) is measured by the availability of call access and uninterrupted session continuation, and quality of service (QoS) -by the quality of the voice, where comparison is made to the voice quality of the line telephone.
Uplink resource allocation algorithms for Single-Carrier FDMA systems
2010 European Wireless Conference (EW), 2010
We have focused on SC-FDMA based resource allocation in uplink cellular systems. Subchannel and power allocation constraints specific to SC-FDMA are considered. We considered a binary integer programming-based solution recently proposed for weighted sum rate maximization and extended it to different problems. We considered problems such as rate constraint satisfaction with minimum number subchannels and sum-power minimization subject to rate constraints. Besides stating the binary integer programming formulations for these problems, we propose simpler greedy algorithms for the three problems. Numerical evaluations show that the greedy algorithms perform very close to the optimal solution, with much less computation time.