Frequency-Domain Link Adaptation for Wideband OFDMA Systems

Safjan, Krystian; Oszmianski, J.; Döttling, M.; Bohdanowicz, A.

doi:10.1109/wcnc.2008.304

Cited by 5 publications

(3 citation statements)

References 4 publications

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“…Because of the variation of the complex gain with frequency (due to the multipath propagation) and with time (due to mobility), the channel at payload positions will in general differ from that at the pilot positions. The coherence time and coherence bandwidth as defined in (11) and (12), respectively give an estimate of the order of the needed sampling interval in time and frequency for the mobile radio channel according to the sampling theorem [32]. However, the channel has to be estimated based on received noisy pilot symbols, and in a packet oriented system the channel resources needed per packet transmission are not very large.…”

Section: Block Size Effect On Channel Estimationmentioning

confidence: 99%

“…Adaptive Orthogonal Frequency Division Multiple Access (OFDMA) with a chunk-based Time Division Multiple Access (TDMA) component is such an FA multiple access scheme [9]. Adaptive TDMA/OFDMA can provide a large increase in the system capacity, also in presence of channel prediction errors due to gains in multiuser scheduling and chunk-wise link adaptation [10,11]. This is very important for high cell load situations.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Block Interleaved Frequency Division Multiple Access for Power Efficiency, Robustness, Flexibility, and Scalability

Svensson

Frank

Eriksson

et al. 2009

J Wireless Com Network

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The multiple access solution in an IMT-Advanced mobile radio system has to meet challenging requirements such as high throughput, low delays, high flexibility, good robustness, low computational complexity, and a high power efficiency, especially in the uplink. In this paper, a novel multiple access scheme for uplinks denoted as B-IFDMA is presented. We show that this scheme is able to provide equal or better error rate performance than the Single-Carrier Frequency Division Multiple Access (SCFDMA) schemes IFDMA and LFDMA, when considering realistic channel estimation performance at the receiver and no reliable channel state information at the transmitter. We also show that B-IFDMA provides better amplifier efficiency than OFDMA and can provide better end-to-end energy efficiency than IFDMA and LFDMA. Moreover, the scheme shows a promisingly high robustness to frequency-offsets and Doppler spread. Thus, this scheme can be regarded as a promising solution for the uplink of future mobile radio systems.

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Section: Block Size Effect On Channel Estimationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Block Interleaved Frequency Division Multiple Access for Power Efficiency, Robustness, Flexibility, and Scalability

Svensson

Frank

Eriksson

et al. 2009

J Wireless Com Network

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“…Efficient channel quality feedback schemes [9] support the design. It has recently been shown in a multicell system simulation context that the use of frequencyadaptive transmission significantly improves the spectral efficiency and the number of satisfied users, as compared to a case where each user can use only a single modulation and code rate within its allocated transmission resources [10].…”

Section: A Frequency Adaptive Transmissionmentioning

confidence: 99%

Resource Allocation and Control Signaling in the WINNER Flexible MAC Concept

Sternad

Svensson

Döttling

2008

2008 IEEE 68th Vehicular Technology Conference

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Abstract-The EU WINNER projects have studied OFDM-based packet data systems beyond 3G that use adaptivity on all timescales to obtain high flexibility and performance. The adaptive transmission in both downlink and uplink is scheduled and controlled at base stations and relay nodes and requires frequent transmission of control information over the downlink. The use of scheduling, adaptive modulation and coding, with fine granularity in both time and space, could potentially result in unrealistic bandwidth demands for such downlink control signaling. The present paper describes how this problem has been handled within WINNER in two cases: Frequency-adaptive transmission, which allows individual link adaptation within time-frequency resource units and non-frequency adaptive transmission, which averages over the channel variations in the frequency domain. An important tool for limiting the associated control information is to broadcast only a small essential set of control data to all user terminals, using a safe but therefore bandwidth-demanding code rate. The remaining control information is multicast to groups of users with different signal to interference and noise ratios (SINRs). The modulation and code rates of these transmissions are adjusted to the SINRs of these groups. The over-all coded data rate of the control transmission can thereby be reduced to acceptable levels.

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