A multiuser interference cancellation scheme for uplink OFDMA

Shamaiah, Manohar; Tikiya, V.; Sreedhar, D.; Chockalingam, A.

doi:10.1109/wcnc.2006.1683574

Cited by 3 publications

(2 citation statements)

References 12 publications

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“…Recent research has been witnessing increased focus on orthogonal frequency division multiple access (OFDMA) on the uplink [1]- [8]. Practical systems like IEEE 802.16e standard use OFDMA on the uplink [9].…”

Section: Introductionmentioning

confidence: 99%

“…An ability to handle large CFOs and TOs using IC techniques can allow low-cost transmit oscillators to be used at all user terminals in an open-loop mode, which can reduce cost and complexity. Receivers employing the IC approach to handle the effects of CFOs alone, assuming ideal time synchronization and sampling (in other words, assuming no orthogonality loss due to timing offsets) have been proposed in [6], [7], [8]. Several papers have reported the effect of TOs on OFDM/OFDMA performance [10]- [13].…”

Section: Introductionmentioning

confidence: 99%

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SIR Analysis and Interference Cancellation in Uplink OFDMA with Large Carrier Frequency and Timing Offsets

Raghunath

Chockalingam

2007

2007 IEEE Wireless Communications and Networking Conference

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Abstract-In uplink OFDMA, carrier frequency offsets (CFO) and/or timing offsets (TO) of other users with respect to a desired user can cause multiuser interference (MUI). In practical uplink OFDMA systems (e.g., IEEE 802.16e standard), effect of this MUI is made acceptably small by requiring that frequency/timing alignment be achieved at the receiver with high precision (e.g., CFO must be within 1% of the subcarrier spacing and TO must be within 1/8th of the cyclic prefix duration in IEEE 802.16e), which is realized using complex closed-loop frequency/timing correction between the transmitter and the receiver. An alternate open-loop approach to handle the MUI induced by large CFOs and TOs is to employ interference cancellation techniques at the receiver. In this paper, we first analytically characterize the degradation in the average output signalto-interference ratio (SIR) due to the combined effect of large CFOs and TOs in uplink OFDMA. We then propose a parallel interference canceller (PIC) for the mitigation of interference due to CFOs and TOs in this system. We show that the proposed PIC effectively mitigates the performance loss due to CFO/TO induced interference in uplink OFDMA.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

SIR Analysis and Interference Cancellation in Uplink OFDMA with Large Carrier Frequency and Timing Offsets

Raghunath

Chockalingam

2007

2007 IEEE Wireless Communications and Networking Conference

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Cancellation of Multiuser Interference due to Carrier Frequency Offsets in Uplink OFDMA

Shamaiah

Tikiya

Sreedhar

et al. 2006

2006 IEEE International Conference on Communications

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Abstract-In uplink orthogonal frequency division multiple access (OFDMA) systems, multiuser interference (MUI) occurs due to different carrier frequency offsets (CFO) of different users at the receiver. In this paper, we present a multistage linear parallel interference cancellation (LPIC) approach to mitigate the effect of this MUI in uplink OFDMA. The proposed scheme first performs CFO compensation (in time-domain) followed by K DFT operations (where K is the number of users) and multistage LPIC on these DFT outputs. We scale the MUI estimates by weights before cancellation and optimize these weights by maximizing the average signal-to-interference ratio (SIR) at the output of the different stages of the LPIC. We derive closed-form expressions for these optimum weights. The proposed LPIC scheme is shown to effectively cancel the MUI caused by the other user CFOs in uplink OFDMA. While our proposed approach performs CFO compensation in time-domain, an alternate approach proposed recently by Huang and Letaief performs CFO compensation and interference cancellation in frequency-domain. We show that our approach performs better than the Huang & Letaief's approach when the magnitude of the CFO differences (between desired user CFO and other user CFOs) are small, whereas their approach performs better when the magnitude of the individual CFOs (of other users) are small. Since the CFO values can be arbitrary at the receiver, in order to make the receiver robust under various CFO conditions, we propose simple metrics based on CFO knowledge, which the receiver can compute and use to choose between the time-domain (ours) and the frequency-domain (Huang & Letaief's) cancellers so that better performance among the two approaches is achieved under various CFO conditions. Index Terms-Carrier frequency offset, circular convolution, linear parallel interference cancellation, optimum weights, signalto-interference ratio, uplink OFDMA.

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A multiuser interference mitigation scheme in uplink MC-CDMA with CFO Estimation-MMSE FEQ technique

Mardhiyya

Astuti

Adriansyah

2017

2017 International Conference on Signals and Systems (ICSigSys)

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A multiuser interference cancellation scheme for uplink OFDMA

Cited by 3 publications

References 12 publications

SIR Analysis and Interference Cancellation in Uplink OFDMA with Large Carrier Frequency and Timing Offsets

SIR Analysis and Interference Cancellation in Uplink OFDMA with Large Carrier Frequency and Timing Offsets

Cancellation of Multiuser Interference due to Carrier Frequency Offsets in Uplink OFDMA

A multiuser interference mitigation scheme in uplink MC-CDMA with CFO Estimation-MMSE FEQ technique

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