Joint beamforming and scheduling for a MIMO downlink with random arrivals (original) (raw)
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2009 IEEE Radio and Wireless Symposium, 2009
In this paper, the well known proportional fairness scheduling is investigated when we joint transmit beamforming and packet level scheduling taking into consideration the traffic arrival process with different packet lengths for the downlink of multiple-input multiple-output (MIMO) multiuser systems. The new scheduler called the proportional fairness zero-forcing beamforming (PF-ZB) can perform at the packet level and provide low average packet transmission delay as well as fairness to users. The scheduler is work conserving. We compare the performance of our scheduler with another well known MIMO scheduler when it is performing in the packet level with transmit beamforming. Simulations that consider the traffic characteristics show the low average packet transmission delay and demonstrate the fairness capabilities of PF-ZB.
Packet level scheduling schemes for multi-user MIMO systems with beamforming
Proceedings of the 6th International Wireless Communications and Mobile Computing Conference on ZZZ - IWCMC '10, 2010
We investigate the packet-level scheduling for the downlink of multiple-input multiple-output (MIMO) multiuser systems using beamforming. We consider the traffic arrival process and different packet lengths. We tackle low-complex practical implementation that provides low average packet transmission delay and bit error rates (BER) to users. We propose a work-conserving scheduling scheme that considers different users guarantees (heterogeneous users). We implement and compare different MIMO schedulers at the packet level. Simulations show the low average packet transmission delay and bit error rate of our proposed scheduler.
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2005
ABSTRACT We investigate the different usage of multiple transmit antennas in a SDMA/TDMA single-cell downlink system under random packet arrivals, correlated block-fading channels and non-perfect channel state information at the transmitter due to a feedback delay. We derive the arrival rate stability region and the adaptive scheduling policy that stabilizes any arrival rate point inside the region without knowing explicitly the fading and arrival statistics.
2007
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We consider random beamforming and user scheduling strategies in a multi-cell environment for downlink wireless communications. Our focus is on using combined scheduling and beamforming to mitigate performance losses due to inter-cell interference. Of interest are strategies requiring minimal intra-cell and inter-cell system information exchange. Indeed the acquisition and inter-cell exchange of such information can be significant overheads in a practical deployment. Random beamforming requires substantially less channel state information than linear zero forcing strategies to schedule transmissions. It is therefore of practical interest despite some limitations in controlling intra-cell interference. We consider how one can use a minimal exchange of information, in a multi-cell multistep pattern of exchanges, to improve the overall performance of random beamforming in a multi-cell environment.
Low complexity multiuser scheduling for maximizing throughput in the MIMO broadcast channel
Proc. Allerton Conf. …, 2004
We consider the general multiuser downlink scheduling problem with n receivers and m transmit antennas, where data from different users can be multiplexed. It is shown that there is a throughput-optimal policy which selects a subset of users to multiplex in each scheduling interval, according to their queue states and current rates achievable by dirty-paper coding. However, the computation of these rates and the selection of the best ordered subset has high complexity in n. It is observed that the simpler multiplexing method of zero-forcing can achieve close to optimal throughput especially when user rate demands are asymmetric. The strong dependence of the objective function with zeroforcing precoding on the queue sizes motivates an algorithm based on ordering users according to queues and making a selection out of a reduced set of users (typically a few multiples of m), which greatly reduces the computational complexity. It is shown that searching beyond this small set is unlikely to improve the objective function.
Proportional Fairness for MIMO Multi-user Schedulers with Traffic Arrival Process
2008 IEEE International Conference on Wireless and Mobile Computing, Networking and Communications, 2008
Packet scheduling at the data link layer may impact significantly the overall performance of a wireless system using multiple antennas. In this paper, we propose a novel packet scheduling scheme based on proportional fairness that considers the traffic arrival process with different packet lengths for the downlink of multiple-input multiple-output (MIMO) multiuser systems. We also provide analysis for the fairness of the new scheme in terms of time and service allocation. The scheduler, referred to as clock-time proportional fairness (C-T PF), performs at the packet level and can provide low average packet transmission delay as well as time and service fairness to users. It is work conserving and it can also take into consideration different users guarantees (heterogeneous users). We investigate an ideal service fair scheduler called C-T max-min for MIMO systems as well. We compare the performance of C-T PF with other MIMO schedulers. For the time and service fairness comparison of MIMO schedulers, we also propose time and service indexes. Simulations that consider the traffic characteristics and the mobility of users show the low average packet transmission delay and demonstrate the time and service fairness capabilities of C-T PF. I.
MIMO Downlink Scheduling with Non-Perfect Channel State Knowledge
IEEE Transactions on Communications, 2000
Downlink scheduling schemes are well-known and widely investigated under the assumption that the channel state is perfectly known to the scheduler. In the multiuser MIMO (broadcast) case, downlink scheduling in the presence of non-perfect channel state information (CSI) is only scantly treated. In this paper we provide a general framework that addresses the problem systematically. Also, we illuminate the key role played by the channel state prediction error: our scheme treats in a fundamentally different way users with small channel prediction error ("predictable" users) and users with large channel prediction error ("non-predictable" users), and can be interpreted as a near-optimal opportunistic time-sharing strategy between MIMO downlink beamforming to predictable users and space-time coding to nonpredictable users. Our results, based on a realistic MIMO channel model used in 3GPP standardization, show that the proposed algorithms can significantly outperform a conventional "mismatched" scheduling scheme that treats the available CSI as if it was perfect.
Coordinated user scheduling in the multi-cell MIMO downlink
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings, 2011
We propose a novel, coordinated user scheduling (CUS) algorithm for inter-cell interference (ICI) mitigation in the downlink of a multi-cell multi-user MIMO system. In the proposed algorithm, ICI mitigation is performed through the exchange of necessary channel state information (CSI) among the base stations, and the revision of the scheduling decisions and beamformer designs at each base station. Furthermore, ICI mitigation is performed only for the cell-edge users so that the amount of inter-base station signaling overhead is minimized. Our simulation results demonstrate that the proposed coordination scheduling algorithm significantly improves the cell-edge users' throughput compared to conventional systems with only a negligible amount of CSI sharing among the base stations and a relatively small throughput loss for the cell-interior users.
A Scheduling Algorithm Combined with Zero-forcing Beamforming for a Multiuser MIMO Wireless System
– In this paper, we introduce a scheduling algorithm over a MIMO broadcast channel. Given a set of users, the sched-uler selects more than one user and transmits independent data to them simultaneously by using zero-forcing beamforming. Taking computational complexity into account, a greedy method finding the best and most orthogonal channel vectors is proposed. Additionally , considering fairness among asymmetric users, we also propose an asymptotically fair scheduling algorithm.