Reduced Complexity Subcarrier Allocation Schemes for DFT-Precoded OFDMA Uplink Systems

Abstract

A resource allocation problem of maximizing total achievable rates for multi-user DFT-precoded orthogonal frequency division multiplexing (OFDM) uplink systems is investigated in this paper. A suboptimal subcarrier allocation scheme is proposed, which uses a proposed spectral efficiency enhancement parameter as an index to assign subcarriers to users. The proposed scheme has a lower computational complexity than that of the existing scheme which is shown to be close to the multiuser waterfilling solution. The simulation results show the proposed suboptimal scheme outperforms the existing scheme. Besides, an iterative subcarrier allocation scheme is proposed to improve the performance.Index Terms-Orthogonal frequency division multiplexing (OFDM), orthogonal frequency division multiple access (OFDMA), resource allocation, subcarrier allocation.

A Combined User-order and Chunk-order Algorithm to Minimize The Average BER for Chunk Allocation in SC-FDMA Systems

“…To reduce the complexity, the subcarrier allocation using equal power allocation is proposed in [9], [14][15][16][17][18][19][20][21][22]. In [9,17], subcarrier allocations are developed on subcarrier by subcarrier based while in [14][15][16], [18][19][20][21][22] are developed on chunk by chunk based which could impact the decrease of complexity. In [9,14], [16][17], [19][20][21], the spectral efficiency are maximized while in [15,18], data rate fairness are maximized.…”

“…In [9,17], subcarrier allocations are developed on subcarrier by subcarrier based while in [14][15][16], [18][19][20][21][22] are developed on chunk by chunk based which could impact the decrease of complexity. In [9,14], [16][17], [19][20][21], the spectral efficiency are maximized while in [15,18], data rate fairness are maximized. In [20], chunk by chunk based using waterfilling power allocation are developed while fractional power control is implemented for limiting the user's transmit power.…”

“…Chunkbased allocation in [22] can balances among spectral efficiency and fairness by introducing the weighting factor between them. For solving chunk allocation problem, the allocation in [9][10][11][12][13][14][15][16][17], [20][21] are performed using greedy-based while in [18][19], [22] are deployed based on meangreedy algorithms. Considering the time complexity, solving the chunk allocation problem based on mean greedy algorithm is preferable than conventional greedy-based algorithm due to the lower of its time complexity.…”

Improved Performance of Mean Greedy Algorithm for Chunk Allocation in SC-FDMA Uplink Systems using Joint-User and Chunk-Based Allocation

“…Using equal power allocation, the problem of resource allocation becomes a problem of subcarrier allocation. The subcarrier allocations described in [16] and [18] are performed on a subcarrier-bysubcarrier basis and in [2], [8]- [9], [17], [19] on a chunk-by-chunk basis so that the time complexity is reduced. In [20][21], chunk-by-chunk allocation algorithms using power allocation based on waterfilling are investigated.…”

“…The velocity was varied between 0 and 240 km/h. The channel state information of all users was perfectly known by the base station and the coherence time of channel when a user moved at a speed of 240 km/h was 2.16 ms, based on (18) of [28]. This means that a user moved a distance of 0.035 meters per TTI.…”