Misunderstandings about link adaptation for frequency selective fading channels

Lampe, M.; Rohling, Hermann; Zirwas, Wolfgang

doi:10.1109/pimrc.2002.1047314

Cited by 53 publications

(47 citation statements)

References 2 publications

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“…Results are based on Mode 4, but the PER distribution trend is consistent for all the PHY modes considered in Table 1. Further, these results show broadly similar trends to the results shown in [8] for different system and channel models. It can be observed that the average PER performance is highly dictated by the few, highly poor channel realisations.…”

Section: Conventional Phy Mode Selectionsupporting

confidence: 82%

“…OVER FADING CHANNELS As demonstrated in [8,13], the conventional MCS selection strategy based on the average PER performance (where the average is obtained across an ensemble of instances of the fading channel response) provides an unreliable estimation of the performance of the instantaneous channel, leading to considerably sub-optimal performance and failure to guarantee QoS for real-time traffic. This is due to the failure of this approach to accurately characterise the instantaneous channel performance, due to the large associated deviation of the average PER curve from the instantaneous samples from which it is comprised.…”

Section: Conventional Phy Mode Selectionmentioning

confidence: 99%

“…Under the assumption of some apriori knowledge of the propagation scenario, SNR mode switching thresholds can be established for either the throughput maximisation or the delay oriented LA algorithm. In [8,9] it was shown that this conventional approach fails to fully harness the benefits of LA as it fails to account for the non-deterministic nature of fading channels. Selecting the PHY mode based on an average PER curve in a channel affected by multipath can result in significant link 'missadaptations' returning a lower than expected throughput and/or higher than predicted packet retransmissions.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Multiuser, Multicarrier Link Adaptation Strategy for Fading Channels with PER Constraints

Nicolaou

Doufexi

Armour

et al. 2011

2011 IEEE 73rd Vehicular Technology Conference (VTC Spring)

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Link Adaptation (LA) adopted by many emerging standards, such as WCDMA, LTE and WiMAX is a key element for providing improved data rates and performance guarantees based on specified Quality of Service (QoS) requirements. Link Adaptation can dynamically adjust a number of transmission parameters, most often modulation and coding, to reflect the characteristics of the wireless link to improve throughput and maintain link reliability. Most LA algorithms require only an estimate of the signal-to-noise ratio (SNR) to select an appropriate PHY mode, relying on the assumption of an AWGN channel. For channels experiencing frequency selective fading however, the conventional approach fails to accurately represent the stochastic nature across independent channels. A new channel quality metric is proposed in this paper that attempts to estimate the likelihood of packet errors in a fading channel and adjust Modulation and Coding Scheme (MCS) selection across each fading realisation independently. Results show improved mode selection efficiency over the conventional LA approach with added flexibility, as this approach is independent of the channel environment, providing a universal solution to LA.

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Section: Conventional Phy Mode Selectionsupporting

confidence: 82%

Section: Conventional Phy Mode Selectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Multiuser, Multicarrier Link Adaptation Strategy for Fading Channels with PER Constraints

Nicolaou

Doufexi

Armour

et al. 2011

2011 IEEE 73rd Vehicular Technology Conference (VTC Spring)

View full text Add to dashboard Cite

show abstract

“…The LA approach considered in [7], whereby the non-deterministic nature of fading channels is accounted for, is extended to accurately represent multiuser channel statistics. This approach promises improved mode prediction accuracy over the conventional PHY mode selection approach based on the average SNR, achieving both increased throughput as well as QoS efficiency.…”

Section: Indroductionmentioning

confidence: 99%

“…Studies in [7,18] have shown that the conventional notion of performing LA based on the average PER performance fails, since the stochastic nature of individual fading channel realisations can vary considerably from the average, a result indicated in Figure 4 which shows that the instantaneous PER performance of a given fading realisation can vary by more than 10dB from the average. In [19] it has been argued that the causes of bit errors can be broadly attributed to the average received channel strength and the probability of resource allocation on fading instances.…”

Section: Qos Performance With Link Adaptation For Voipmentioning

confidence: 99%

Unitary beamforming techniques enhancing VoIP call admittance capacity

Nicolaou

Doufexi

Armour

et al. 2010

21st Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications

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Abstract:-Fourth Generation Networks will invariably adopt MIMO-OFDMA techniques, in order to cope with increased data rate demands and improved Quality of Service (QoS) requirements. OFDMA is a popular multiple access candidate, since it facilitates multi-user diversity by enabling two dimensional multiple access, in time and frequency domains. Random Beamforming enables exploitation of spatial multi-user diversity and spatial capacity multiplexing gain. Layered Random Beamforming is able to achieve further multiple access benefits by enabling different users to be scheduled on different spatial layers of the same time-frequency resource. This paper examines the QoS performance of SU-MIMO and MU-MIMO precoding schemes for a VoIP system under a realistic traffic and channel environment. A novel Link Adaptation algorithm operating under PER constraints for delay sensitive VoIP traffic that promises increased data rates, flexibility and improved QoS is proposed and examined in this paper.

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Radio resource management in cellular multihop networks

Zirwas

Lott

et al. 2004

Trans Emerging Tel Tech

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SUMMARYIn future mobile broadband radio systems, multihop for coverage extension is seen as a basic building block. Here, we investigate radio resource management (RRM) for multihop networks and assume that the central access point (AP) can control the whole multihop network based on channel state information (CSI) of all links. Specifically we investigate interference effects between neighboring multihop networks as well as within a single multihop network. Interference within a multihop network occurs only when the central scheduler allows simultaneous transmission at the same time and frequency, here called SIMU, on several radio links. It is shown, that SIMU can increase overall capacity of a multihop network compared to a fully orthogonal transmission, here called time division multiple access (TDMA), where only one single link is active at a time. For neighboring multihop networks it is shown that inter cell interference (ICI) may be treated as additive white Gaussian noise (AWGN) with typically only small performance degradation.

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Misunderstandings about link adaptation for frequency selective fading channels

Cited by 53 publications

References 2 publications

A Multiuser, Multicarrier Link Adaptation Strategy for Fading Channels with PER Constraints

A Multiuser, Multicarrier Link Adaptation Strategy for Fading Channels with PER Constraints

Unitary beamforming techniques enhancing VoIP call admittance capacity

Radio resource management in cellular multihop networks

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