Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

SELF-SYNCHRONIZING NETWORK PROTOCOL FOR SPATIALLY DISJOINT NETWORKS

IP.com Disclosure Number: IPCOM000009694D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2002-Sep-11
Document File: 5 page(s) / 260K

Publishing Venue

Motorola

Related People

Mike Durkin: AUTHOR

Abstract

Many communications networks are, either by design or by the nature of the medium, disjoint. By this we mean that the members of the network are not able to connect to all other members. In fact a member need only connect to one other to affect all members in the network (e.g. by his use of the net- work's medium resource).

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 25% of the total text.

Page 1 of 5

0 M MO-LA Technical Developments

SELF-SYNCHRONIZING NETWORK PROTOCOL FOR SPATIALLY DISJOINT NETWORKS

by Mike Durkin

  Many communications networks are, either by design or by the nature of the medium, disjoint. By this we mean that the members of the network are not able to connect to all other members. In fact a member need only connect to one other to affect all members in the network (e.g. by his use of the net- work's medium resource).

   The multi-path, blockage and reflection charac- teristics of the RF links between RF devices result in a wide variation in the distances spanned by a link. Figure 1 shows a typical office situation where a group of devices are physically distributed so that some are able to connect to many and some to only a few. The purpose of this memo is to describe a frame-based, time-division, multiple-access (TDMA) protocol which hopefully solves the pmb- lem of members interfering with each other and pm- vides for automatic synchronization of network members. A central concept here is the dissemina- tion of network status among members by relay.

GENERAL DESCRIPTION OF THE PROTOCOL

  The solution presented here to combat interfer- ence, relies on the fact that the RF links in a network are reciprocal. (This assumes that all members employ equal EIRPs and have comparable receiver sensitivity.) The protocol gives a network member a view of all members he is capable of impacting by forcing any member involved in communication with another to transmit at least a short burst during the frame, even if he is simply receiving from anoth- er member.

  This is effected by the ACK/NAK slots shown in Figure 2. According to Figure 2, the protocol defines a sequence of M+l frames where M is the number of active network members. This sequence will be termed an epoch. The last frame of the epoch is used for a new member to enter the network. Each TDMA frame is partitioned into a sync slot, N com-

munications slots and N corresponding ACIUNAK (acknowledge/negative-acknowledge) slots. Each member takes a turn transmitting the sync slot and has one turn during each epoch.

  The success of the protocol relies on informa- tion about the network population being disseminat- ed among all members via relay from user to user. This information is needed so a member may deter- mine when he should transmit a sync slot as indicat- ed by the following reasoning:

  A member may hear only one other network member. Since the network has no central timing control, members must measure time from the reception of other members sync slots. It is therefore necessary that each sync slot carry the sender's posi- tion in the epoch (between 1 and M) and the net- work member count (population). With this infor- mation, each member can calculate the time offset between sync slots he receives and his position in the epoch and thereby determine when he should transmit a sync slot relative to receptions thereof.

FRAME DEFINITION

  If a member is capable of disrupt...