Browse Prior Art Database

Method to Reduce Latency in Data Traffic during High Speed Data Hand Off

IP.com Disclosure Number: IPCOM000126918D
Original Publication Date: 2005-Aug-10
Included in the Prior Art Database: 2005-Aug-10
Document File: 7 page(s) / 348K

Publishing Venue

Motorola

Related People

Roy Yang: INVENTOR [+2]

Abstract

Third Generation Data Networks poses unique issues as to how to handle bearer traffic flow between the Radio Network Controller (RNC) and the NodeB, as the determination of user data rate is handled by the NodeB according to RF condition of each user. The problem becomes acute in the situation of data hand over, in-effective buffer management can cause large amount of packet loss and long latency in handover performance. This article propose a new scheme to manage the bearer traffic between the RNC and NodeB, such that the size of the bearer buffer in the NodeB changes according to the user’s RF condition. This information is passed along to the RNC such that more effective flow control can be achieved, as a result, the latency of the bearer traffic during data hand off is greatly reduced, and the overall system performance improved.

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Method to Reduce Latency in Data Traffic during High Speed Data Hand Off

Roy Yang

and

Jason Chen

Network Advanced Technology Division

Motorola Networks, Motorola Inc.

1421 W.Shure Dr.

Arlington Heights

,

IL

60004

October 29, 2004

 

ABSTRACT

Third Generation Data Networks poses unique issues as to how to handle bearer traffic flow between the Radio Network Controller (RNC) and the NodeB, as the determination of user data rate is handled by the NodeB according to RF condition of each user. The problem becomes acute in the situation of data hand over, in-effective buffer management can cause large amount of packet loss and long latency in handover performance.

This article propose a new scheme to manage the bearer traffic between the RNC and NodeB,  such that the size of the bearer buffer in the NodeB changes according to the user’s RF condition. This information is passed along to the RNC such that more effective flow control can be achieved, as a result, the latency of the bearer traffic during data hand off is greatly reduced, and the overall system performance improved.    

1. INTRODUCTION

The problem of managing data flow between RNC and NodeB starts to take on more prominence as 3G (for example, HSDPA) data services develop. Unlike traditional NodeB, the 3G NodeB has the additional role of make resource allocation decisions by dynamically allocating data bandwidth to users according to their RF conditions. Since a user’s RF condition can change dramatically, NodeB needs to buffer bearer data traffic from RNC such that it does not under-run the bandwidth capacity that 3G scheduler offers.

In the case of data handoff, UE will stop receiving data traffic from one NodeB and start receiving the same traffic from another NodeB.

Figure 1. IOT Interfaces

In a typical UTRAN network, as shown in the above Figure, there is no direct connection interface between NodeBs [3]. For one NodeB to reach another NodeB, it needs to go through Iub interface, or in the case of a different RNC, additional Iur interface. As a result, RNC is responsible for directing the data traffic from the originating NodeB to the target NodeB. In the case when large amount of data are stored in the originating NodeB, RNC will not have the most immediate data for the target NodeB as it is already in the originating NodeB, instead, it rely solely on uppler layer ( RLC for example) to retransmit and re-construct the missing packet stuck in the originating NodeB. This could potentially create large latencies during hand off.

In the current HSDPA trial where the acknowledged mode (AM) RLC protocol is used, the approach [4] in high speed data handoff can be described as follows:

1.        Allocate large and fixed RLC retransmission window per traffic flow. The large window was aimed to increase the throughput for this flow. In fact, the larger the window size is, the potential higher throughput for this user;

2.        Use fixed high and low watermarks for the Node B flow control and ping-pon...