Uplink scheduling in clustered 3G network with mobile relaying

Abstract

Hybrid wireless networks are characterized by simultaneously using several radio interfaces to boost system performances. A practical and promising architecture to achieve a better uplink throughput in the traditional CDMA cell is to locally aggregate mobile-generated traffic to some cluster heads through WLAN. Such an architecture opens up questions of the desired clustering structures as well as new uplink scheduling strategies. The scheduling of the aggregated traffic at the cluster heads (called relayed mobile terminals later) is investigated in this work.

The proposed uplink scheduling algorithm takes the aggregated traffic nature into account. The scheduling goal is to achieve good throughput under the traffic QoS requirements (e.g. BER, bit-error-rates) and limited power budget at the mobile station. The proposed scheduling algorithm consists of two levels: (1) we use a proportional scheduling algorithm to coordinate the transmission among relaying mobile terminals (RMTs), where the main objective is to achieve high spectrum efficiency and reasonable fairness; (2) within RMT, packets from different leave nodes, with different BER requirements are further scheduled via a link-adaptive CDMA (LA-CDMA) transmission scheme. By exploiting the QoS diversity of the queued packets, the LA-CDMA scheduler is able to generate better usage of power budget, which allows some BER-stringent packets to be transmitted at a higher data rate. The performance improvement of the LA-CDMA scheduler is demonstrated by our simulation results. The system goodput is increased by up to 17% for some traffic type. Our simulation also shows the dynamic of expected BERs, the allocation of transmission power and the modulation depth of the LA-CDMA scheduler.

Keywords:

• 3G network
• CDMA2000
• Uplink scheduling
• Relaying
• Out-cell-interference
• Power allocation

Notes

These mobiles are called RMTs in this paper and the non-RMT mobiles are referred to as leaf nodes.

In this paper, the throughput on the uplink is referred to as the cell (sector) throughput.

The pilot channel is transmitted in low power and uses only a small portion of a slot time to minimize the interference.

This should not be confused with the theoretical results from information theory, where the peak capacity is obtained under simultaneous transmission and path diversity.