Preventive and Reactive Based TNL Congestion Control Impact on the HSDPA Performance

Abstract

High Speed Downlink Packet Access (HSDPA) is an extension of the Universal Mobile Telecommunications System (UMTS) technology of 3GPP Rel-99, with the objective to increase the data rate and reduce the latency in the downlink. The main focus of the work presented is to analyse the effect of congestion at the Iub interface on the HSDPA performance. The data flows should be adequately controlled in order to avoid congestion in the transport network. The 3GPP (3rd Generation Partnership Project) Rel. 5 specifications highlight two congestion detection mechanisms which are based on the frame sequence number (FSN) and the Delay Reference Time (DRT) fields of HSDPA data frame. In addition to these, a third congestion detection mechanism based of Checksum of HSDPA data frame is considered. This paper discusses a congestion control scheme deploying all three congestion detection methods. It is shown, that a congestion control algorithm can effectively work using these congestion detection triggers and can control the offered load to the transport network. The simulation results presented in this paper confirm that the congestion in the transport network can be avoided, and hence the performance of HSDPA network can be significantly improved in all aspects.

Window-based HSDPA Transport Network Congestion Control

“…For this purpose congestion detection specific fields were introduced to the Iub HS-DSCH Data frame [13]. This 3GPP architecture is used for congestion control purposes in [4] and [14]. In [4], a rate-based Congestion Control is proposed that operates in the Iub Framing Protocol layer.…”

Effect of the RLC and TNL congestion control on the HSUPA network performance

“…The congestion control is done in Node B upon the reception of the congestion indication which is sent by the corresponding congestion detection module. The congestion detection can be either reactive or preventive as discussed in [9]. The preventive congestion detection schemes identifies the congestion before it occurs but a very high probability it might occur in the near future; whereas the reactive congestion detection scheme detects the congestion at the starting of the congestion in the network.…”

“…The lub E-DCH congestion control is done in the Node B. The main difference from the HSDPA case [9] is that the E-DCH congestion control cannot rely on any rate control provided by the flow control, since E-DCH has no flow control by its standard. The congestion control algorithm (E-DCH_CC) has to monitor the UL E-DCH lub rate (per MAC-d Flow) in order to apply lub UL rate deduction properly.…”

“…At the congestion control state, HSUPA CC mechanism uses the AIMD (Additive-Increase-Multiplicative-Decrease) (a, b) algorithm [6,7,8,9]. The CC module decides the allowed capacity over the radio interface for each user flows and signals it back to the E-DCH scheduler in order to decide the uplink grants of the next TTl for the S-RLS users.…”

Adaptive QoS control in HSDPA systems

“…HSDPA congestion control (CC) was investigated in several papers [8,9], some of these addressed the need to harmonize the CC with the transport scheduling mechanisms [10]. The latter is an important aspect as proper QoS can be provided only by creating a harmonized end-to-end QoS architecture where the radio Figure 1.…”