Browse Prior Art Database

FLOW CONTROL WITHOUT PRIOR KNOWLEDGE OF BANDWIDTH REQUIREMENTS

IP.com Disclosure Number: IPCOM000008863D
Original Publication Date: 1998-Sep-01
Included in the Prior Art Database: 2002-Jul-18
Document File: 3 page(s) / 156K

Publishing Venue

Motorola

Related People

Karen Brailean: AUTHOR [+3]

Abstract

In the iDEN system implementation of packet data (see Figure I), each site is connected to one or more Mobile Data Gateways (MD&). The MDGs provide, among other things, outbound packet data packets for subscriber units that are currently active on the site.

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MOTOROLA Technical Developments

FLOW CONTROL WITHOUT PRIOR KNOWLEDGE OF

BANDWIDTH REQUIREMENTS

by Karen Brailean, Bob Fredericks and Todd Leigh

BACKGROUND

  In the iDEN system implementation of packet data (see Figure I), each site is connected to one or more Mobile Data Gateways (MD&). The MDGs provide, among other things, outbound packet data packets for subscriber units that are currently active on the site.

  The MDGs are connected to the site via a fixed allocation of bandwidth on a Tl or El, using a frame relay protocol. The frame relay pipe is also shared with other services, such as dispatch call control and voice.

The site controls up to three cells, each of which may have a packet data channel (PCH) that SUs can

be camped on waiting to receive packet data packets from the MDG.

  It is desirable to maximize the use of the limited RF bandwidth available for the PCH, so the site tries to buffer sufficient packet data packets for each PCH such that it never runs out. It is also desirable, since SUs are mobile and can leave a cell's coverage at any time, to minimize the age of packet data packets in the site's buffer so that if a SU leaves, there aren't a lot of packets that have been provided to the site by the MDG that have to be discarded by the site and re-transmitted by the MDG to the site that the SU moves into.

  These requirements put a desired minimum and maximum queue depth on the sites packet data packet buffer.

  Another factor that complicates the issue is the dynamic nature of the packet channel. Packet data service is intended to use a cell's excess capacity (provided to allow for peak utilization during busy time periods) for transmission of packet data with- out the need to add additional bandwidth to the cell. Because of this requirement, the bandwidth allocat- ed to the PCH may change at any time, and thus buffer limits may also change dramatically from moment to moment (see Figure 2).

1 smax.

1 Site

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Controller ethemet l

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Fig. 1 iDEN Packet Data System Diagram

PCH WI voice PCH w/o voice Fig. 2 Packet Data Site Buffer Depths

19 Motorolr. 1°C. ,998

121 September 1998

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0 M MO-LA

Technical Deve1opment.s

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  In order to maintain the buffer within these lim- its, the site needs to control the flow of packet data packets from the MDGs. It does this using a chan- nel request/grant mechanism, similar to many simi- lar mechanisms as are well known in the art. When an MDG has data to send, it issues a channel request, and when the site determines that the request should be granted, taking into account the minimum and maximum buffer limits, it issues a channel grant, and the MDG begins sending data (see Figure 3).

Site Controller

to respond with the channel grant, more packets for the SU may arrive, and the MDG may bundle them together. This prevents the MDG from specifying the amount of data associated with the channel request in the channel re...