Browse Prior Art Database

QOS AND FAIRNESS FOR CDMA PACKET DATA

IP.com Disclosure Number: IPCOM000009778D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-18
Document File: 7 page(s) / 407K

Publishing Venue

Motorola

Related People

Manish Airy: AUTHOR [+2]

Abstract

Motivated by higher bandwidths and a need to handle a range of packet data services, several enhancements over the IS 95AIB packet interface have been proposed for third generation (3G) CDMA systems: enhanced physical layer to provide data rates greater than 64 Kbps, enhanced MAC layer to support concurrent operation of any combination of voice, circuit and packet data, each with varying QoS and enhanced signaling to enable efficient resource management. The objective of this paper is to introduce concepts from queuing theory that address radio resource management issues for supporting packet data services over 3G CDMA systerns.

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MOTOROLA

Technical Developments

QOS AND FAIRNESS FOR CDMA PACKET DATA

by Manish Airy and Kamyar Rohani

ABSTRACT

Motivated by higher bandwidths and a need to handle a range of packet data services, several enhancements over the IS 95AIB packet interface have been proposed for third generation (3G) CDMA systems: enhanced physical layer to provide data rates greater than 64 Kbps, enhanced MAC layer to support concurrent operation of any combination of voice, circuit and packet data, each with varying QoS and enhanced signaling to enable efficient resource management. The objective of this paper is to introduce concepts from queuing theory that address radio resource management issues for supporting packet data services over 3G CDMA systerns.

INTRODUCTION

The average delay (queuing plus service times) for M/M/l queues is always less than M/Mlm for m > 1. Similarly, if the service times are no longer exponential, MIG/1 queues have lower average delays than M/G/m for m > 1. This is only valid if the second moment of the general service time distribution is fimte, [1]. For service time distributions with infinite variance, the average delays for M/Gll and M/G/m for m > I are infinite.

On the forward link, the probability of occurfence of a data rate depends upon the user SNR and number of shared power pipes or servers. In a user traffic model for web browsing sessions, [2], each web page (packet call) is composed of a varying number of packets. Packet lengths have a truncated Pareto distribution (truncated to 65536 bytes with a mean of 480 bytes ). The average size of a web page is 12 Kbytes. Thus, web page download time distribution-the ratio of packet call length to bit rate-is a function of bit rate, web page length and number of shared data pipes. If the variance of download or service times is large, an exhaustive service disci-

Motorola, Inc. 2000

pline may not be preferred. For example, it takes 55 secs for a 65536 byte packet to be exhaustively transmitted at 9.6 Kbps (cell edge or shadow faded location with poor SNR) and - 1.7 sec at 307.2 Kbps (high SNR user location). Because of this large variance, an exhaustive service discipline may cause periods of inordinately large short-terrn average delays. This can be mitigated by a combination of thresholding the maximum continuous service time per packet and a pre-emptive service discipline.

A pre-emptive service discipline imposes restrictions on implementation, specifically it requires a control channel for aborting and rescheduling the interrupted transmission.

The objective of a radio resource management policy is to maximize throughput. On the CDMA forward link, the shared resource is power. Efficient resource sharing dictates that the available power be split in a way that maximizes overall throughput.

For the same fraction of available power, a higher bit rate may be allocated to a user at higher SNR, typically identifying locations close to the cell site (ignoring shadow and Rayleigh fa...