Abstract
This paper presents the analysis of the throughput enhancement possible using threshold-based multiuser scheduling in WiMAX OFDMA. We consider a point-to-multipoint (PMP) WiMAX network where base station (BS) schedules downlink packets for simultaneous transmissions to multiple users using the WiMAX OFDMA system. WiMAX OFDMA standard specifies several subcarrier permutation options, such as the partial usage of subcarriers (PUSC), full usage of subcarrier (FUSC), and the band adaptive modulation and coding (band-AMC) among others, for mapping the physical subcarriers into logical subchannels assigned to users by the BS schedulers. In this paper, we propose the use of threshold testing prior to the process of subchannel assignment to users by the BS scheduler, as a means of throughput enhancement. In the proposed threshold-based multiuser scheduling scheme, the BS scheduler selects at any time instant users whose channel gains in the available subchannels equal or exceed a predetermined energy threshold. Thus, only users who can maximize BS throughput on the available subchannels are assigned data transmission opportunities which enhance the BS data rate, albeit at the expense of fairness to users. We quantify the throughput enhancement of the proposed system and illustrate its benefits by numerical simulations.
Highlights
The IEEE 802.16 standard-based WiMAX network specifies OFDMA as multiuser access method, where a base station (BS), in a point-to-multipoint (PMP) mode, communicates with multiple users simultaneously on different time-frequency resources [5, 6, 8, 10, 11]
In the randomly mapped system known as full usage of subcarriers (FUSC), the subcarriers in a subchannel are taken from different portions of the spectrum in a pseudo-random manner, while in the sequentially mapped system known as partial usage of subcarriers (PUSC), only subcarriers adjacent in the frequency spectrum are included in a subchannel
To optimize BS throughput in such case, we examine the use of threshold-based PUSC system, where users first undergo threshold test before the regular PUSC scheduling policy of the BS is applied
Summary
The IEEE 802.16 standard-based WiMAX network specifies OFDMA (orthogonal frequency division multiplexing access) as multiuser access method, where a base station (BS), in a point-to-multipoint (PMP) mode, communicates with multiple users simultaneously on different time-frequency resources [5, 6, 8, 10, 11]. In the context of multiuser scheduling in WiMAX network, we consider here the use of a threshold-based PUSC system, where a BS scheduler uses the energy threshold criterion to select the users to be scheduled for downlink transmission at any time instant. The advantage of this scheduling strategy is that at any time instant, only users whose channels are strong enough to sustain the network operator’s target data rate are scheduled. We show that the throughput gain in the threshold-based PUSC scheme is enhanced as the threshold level is increased
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