Adaptive loading for OFDM/SDMA-based wireless networks

Thoen, S.; Perre, Liesbet Van der; Engels, M.; Man, H. De

doi:10.1109/tcomm.2002.805260

Cited by 52 publications

(28 citation statements)

References 27 publications

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“…However, the use of these algorithms is rather limited for the following reasons: In [4], it is assumed that the average signal-to-noise ratios (SNRs) of all users are identical; [5] is based on a modification of the RA cost; and [6] considers the case where the total transmission power is equally distributed to all subcarriers. Adaptive loading techniques for OFDM systems with multiple antennas have been developed in [7] and [8]. This paper shows that the above nonlinear optimization problems [1] and [2] can be reformulated into integer programming (IP), thereby allowing the optimal subcarrier and bit allocation to be achieved.…”

mentioning

confidence: 99%

Use of Linear Programming for Dynamic Subcarrier and Bit Allocation in Multiuser OFDM

Kim

Park

Lee

2006

IEEE Trans. Veh. Technol.

185

153

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Abstract-An adaptive subcarrier allocation and an adaptive modulation for multiuser orthogonal frequency-division multiplexing (OFDM) are considered. The optimal subcarrier and bit allocation problems, which are previously formulated as nonlinear optimizations, are reformulated into and solved by integer programming (IP). A suboptimal approach that performs subcarrier allocation and bit loading separately is proposed. It is shown that the subcarrier allocation in this approach can be optimized by the linear-programming (LP) relaxation of IP, while the bit loading can be performed in a manner similar to a single-user OFDM. In addition, a heuristic method for solving the LP problem is presented. The LP-based suboptimal and heuristic algorithms are considerably simpler to implement than the optimal IP, plus their performances are close to those of the optimal approach. Index Terms-Integer programming (IP), linear programming (LP), multiuser orthogonal frequency-division multiplexing (OFDM), subcarrier and bit allocation.

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mentioning

confidence: 99%

Use of Linear Programming for Dynamic Subcarrier and Bit Allocation in Multiuser OFDM

Kim

Park

Lee

2006

IEEE Trans. Veh. Technol.

185

153

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“…such that the signal constellations across all subcarriers are identical 6 . The proposed non-uniform bit allocation algorithm does not employ Eq.…”

Section: If Bothpmentioning

confidence: 99%

“…Both Thoen et al [6] and Bartolome, Perez-Neira, & Ibars [7] examined the performance benefits of bit allocation employed in multicarrier systems employing multiple antennas. However, the bit allocation techniques employed in these implementations either used approximations of the closed form expressions for the bit error rate (BER), which may yield solutions far from the optimal allocation, or used an incremental approach, which is computationally expensive.…”

Section: Introductionmentioning

confidence: 99%

Loading Algorithm for Multicarrier Spatial Diversity Systems with Antenna Selection

Wyglinski

Labeau²,

Kabal³

2007

IEEE Trans. Wireless Commun.

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-This paper presents two novel loading algorithms for multicarrier systems performing spatial diversity. The algorithms use bit allocation techniques to increase throughput while ensuring the system remains below a specified error rate. One algorithm uses the same signal constellation across all subcarriers while the other varies the signal constellations. To reduce hardware costs, power consumption, and complexity, the proposed algorithms simultaneously perform antenna subset selection, choosing array configurations that yield further increases in the overall throughput. Our results show that the combination of multiple antennas and bit allocation by the proposed algorithms substantially increases throughput. Furthermore, hardware costs are reduced with a negligible penalty in throughput when antenna subset selection is employed.

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“…Fairness issues have been rarely evaluated in the literature, see e.g. [21], or the simplified approach in [14]. A theoretical study of fairness in multiantenna multi-user channels is conducted in [22].…”

Section: Reducing the Signaling Needsmentioning

confidence: 99%

“…As in other papers such as [5] or [13], we assume a ZF transmit beamforming, which is equivalent to the MMSE for a low number of users and also for high SNR [14]. Moreover, it provides a reasonable degradation with respect to the optimum sum capacity as shown in [15].…”

Section: Introductionmentioning

confidence: 99%

Practical bit loading schemes for multi-antenna multi-user wireless OFDM systems

Bartolome¹,

Pérez-Neira

Ibars³

Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers, 2004.

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Abstract-This paper deals with practical multi-antenna multiuser OFDM systems. With the additional degrees of freedom of multiple antennas and multiple subcarriers, the performance might be enhanced, but the scheduling complexity might increase exponentially. Since the scheduling with realistic integer signal mappings is an NP-complete combinatorial problem, suboptimum solutions based on the scalar product are good candidates to yield a fast and realizable practical implementation. We propose afterwards a power reuse strategy to lowerthe computational complexity, and show that the amount of signaling can be reduced by forcing an equal mapping for all the users at the same subcarrier.

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Adaptive loading for OFDM/SDMA-based wireless networks

Cited by 52 publications

References 27 publications

Use of Linear Programming for Dynamic Subcarrier and Bit Allocation in Multiuser OFDM

Use of Linear Programming for Dynamic Subcarrier and Bit Allocation in Multiuser OFDM

Loading Algorithm for Multicarrier Spatial Diversity Systems with Antenna Selection

Practical bit loading schemes for multi-antenna multi-user wireless OFDM systems

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