Browse Prior Art Database

RANDOM ACCESS SCHEDULING SCHEME FOR PACKET DATA SYSTEMS

IP.com Disclosure Number: IPCOM000008618D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-27
Document File: 4 page(s) / 239K

Publishing Venue

Motorola

Related People

Loren J. Rittle: AUTHOR [+2]

Abstract

Consider a multi-user, multi-frequency, digital, * a population of half- and full-duplex mobile TDMA, cellular RF packet data system (Figure 1) subscriber units with attached mobile computers. composed of: * full-duplex, stationary base radios operating in conjunction with support infrastructure; and Fig. 1 Cellular RF packet data system Each base station radio controls one or more pairs of RF communication channels. One channel of each pair is designated the inbound channel and the other the outbound channel. To simplify the remaining discussion, we assume each base station radio has only one pair of communication channels. The base station simultaneously transmits on the outbound channel and receives on the inbound channel. Each half-duplex subscriber unit of the population may transmit or may receive on any one communication channel within its range in the sys- tem at any given time. Each full-duplex subscriber unit may do both operations concurrently.

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MOTOROLA Technical Developments

RANDOM ACCESS SCHEDULING SCHEME FOR PACKET DATA SYSTEMS

by Loren J. Rittle and Guy G. Roman0

1 BACKGROUND

  Consider a multi-user, multi-frequency, digital, * a population of half- and full-duplex mobile TDMA, cellular RF packet data system (Figure 1) subscriber units with attached mobile computers. composed of:

* full-duplex, stationary base radios operating in conjunction with support infrastructure; and

Fig. 1 Cellular RF packet data system

  Each base station radio controls one or more pairs of RF communication channels. One channel of each pair is designated the inbound channel and the other the outbound channel. To simplify the remaining discussion, we assume each base station radio has only one pair of communication channels. The base station simultaneously transmits on the outbound channel and receives on the inbound channel. Each half-duplex subscriber unit of the population may transmit or may receive on any one communication channel within its range in the sys- tem at any given time. Each full-duplex subscriber unit may do both operations concurrently.

Consider that each communication channel is broken into fixed-sized slots. Further consider that:

* Each slot of the outbound channel is broken into a control and payload portion.

* Each slot on the inbound channel will be one of the following types as dictated by a control field of a related slot on the outbound channel:
- random access (any subscriber unit may transmit a reservation request given that certain rules are observed) or
- reserved access (channel is allocated for exactly one subscriber unit to transmit payload).

* A slotted reservation-aloha protocol is used to allow subscriber units to signal to the base station their desire to transmit payload on the inbound channel.

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MOTOROLA Technical Developments

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* An arbitration mechanism is followed within the base station to allocate slots for all known pending payloads destined to be transmitted on either com- munication channel. This mechanism schedules channel use so that no half-duplex subscriber unit is forced to try to transmit and receive concurrently.

* Through a static database or some dynamic means, each base station knows the duplex status of each subscriber unit in the population.

. Some payloads are special. Once a half-duplex subscriber unit sees a key payload, it knows to stay in a receive mode for some time in the future. During this lock period, the unit may not attempt random access.

* In this context, each slot payload is a higher layer packet or some portion of a packet. A higher layer protocol determines the exact meaning of these payloads.

  Only a minor portion of the background context given above is actually required for the problem, which is described next, to occur. The additional context approximates the media access and control layer of the iDEN (TM)...