Achievable Net-Rates in Multi-User OFDMA with Partial CSI and Finite Channel Coherence

Rost, Peter

doi:10.1109/vtcfall.2012.6398885

Cited by 5 publications

(2 citation statements)

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“…The publications mentioned above inherently assume that CSI is precisely available at the scheduler. Scheduling with imperfect CSI has been studied in several works considering throughput maximization [16]- [18]. A PF scheduling scheme, which provides robustness against imperfect channel knowledge has been presented in our preliminary work [19].…”

Section: A Related Literaturementioning

confidence: 99%

Robust Rate Adaptation and Proportional Fair Scheduling With Imperfect CSI

Fritzsche

Rost²,

Fettweis

2015

IEEE Trans. Wireless Commun.

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In wireless fading channels, multi-user scheduling has the potential to boost the spectral efficiency by exploiting diversity gains. In this regard, proportional fair (PF) scheduling provides a solution for increasing the users' quality of experience by finding a balance between system throughput maximization and user fairness. For this purpose, precise instantaneous channel state information (CSI) needs to be available at the transmitter side to perform rate adaptation and scheduling. However, in practical setups, CSI is impaired by, e.g., channel estimation errors, quantization and feedback delays. Especially in centralized cloud based communication systems, where main parts of the lower layer processing is shifted to a central entity, high backhaul latency can cause substantial CSI imperfections, resulting in significant performance degradations. In this work robust rate adaptation as well as robust PF scheduling are presented, which account for CSI impairments. The proposed rate adaptation solution guarantees a fixed target outage probability, which is of interest for delay critical and data intensive applications, such as, video conference systems. In addition to CSI imperfections the proposed scheduler is able to account for delayed decoding acknowledgements from the receiver.

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Section: A Related Literaturementioning

confidence: 99%

Robust Rate Adaptation and Proportional Fair Scheduling With Imperfect CSI

Fritzsche

Rost²,

Fettweis

2015

IEEE Trans. Wireless Commun.

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“…There is a body of literature studying the associated signaling overhead. For instance in [22,23], the achievable sum rate with partial channel state information and with reduced signaling in the feedback link for OFDMA were studied. In [24][25][26], the authors proposed compression schemes for the channel state information that is transmitted in the feedback link.…”

Section: Research Related To Signaling Overheadmentioning

confidence: 99%

Improving the Efficiency of Control Signaling in Wireless Multiple Access Systems

Moosavi¹

2013

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To my lovely wife, my beloved parents, and my dear sisters; without them I would not be here."Even if you are on the right track, you'll get run over if you just sit there." Will Rogers AbstractPrior to the transmission of payload data in any multiple access system, there is generally a need to send control information such as scheduling assignments, transmission parameters and HARQ acknowledgments. This process is called control signaling and has a significant impact on the overall system performance. This dissertation considers different aspects of control signaling and proposes some novel schemes for improving it. The dissertation is split into two parts where in the first part the focus is on the transmission of scheduling assignments, and in the second part the focus is on improving the "blind decoding" process that is used to achieve adaptive coding and modulation in transmission of control information.More specifically, in the first part of the dissertation we first compare the two conventional schemes for control signaling using extensive system simulations. In doing so, we use practical assumptions on the scheduling algorithm as well as on the compression and transmission of the scheduling information. We then provide two schemes for reducing the amount of control signaling that concerns the transmission of scheduling assignments. The first scheme, which is reminiscent of source coding with side information, uses the knowledge that each user has about its own channel condition to compress the scheduling information more effectively. The second scheme uses the fact that in wireless multiple access systems, a user with a given channel condition can in principle decode the data intended to the users that have weaker channels. Therefore, the idea is to send the scheduling information of different terminals in a differential manner starting from the user with the weakest channel and letting all the terminals overhear the transmission of one another. Finally, in the last section of this part we use some of the recent results in information theory to form a general framework for the comparison of different control signaling schemes. We formulate an optimization problem that for a given desired error probability finds the minimum required number of channel uses for a given signaling scheme.In the second part of the thesis, we propose three schemes for reducing the complexity of the blind decoding process. The first one is a novel scheme for fast blind identification of channel codes. More precisely, we propose an efficient algorithm that for a given sequence of received symbols and a given linear channel code, finds the posterior probability that all the parity check relations of the code are satisfied. We then use this quantity to perform a sequential statistical hypotheses test that vii reduces the computational complexity of blind decoding. The idea in the second scheme is to broadcast a control message prior to the transmission of control information to instruct only a subset of the terminals (ideally only ...

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