Browse Prior Art Database

CONTROL CHANNEL INTERFERENCE DETECTION INS TDMA SYSTEMS WITH FREQUENCY RE-USE

IP.com Disclosure Number: IPCOM000007495D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2002-Apr-01
Document File: 2 page(s) / 133K

Publishing Venue

Motorola

Related People

Alex Rozenstrauch: AUTHOR [+2]

Abstract

In a wireless communication system (analog or digital), interference on a control channel can completely or partially destroy the systems' capabil- ity to provide communication among Mobile Subscribers. A digital communication system based upon a Time Division Multiple Access (TDMA) pro- tocol has the same susceptibility.

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MO7VROLA Technical Developments

CONTROL CHANNEL INTERFERENCE DETECTION INS TDMA SYSTEMS WITH FREQUENCY RE-USE

by Alex Rozenstrauch and Mark Poulin

  In a wireless communication system (analog or digital), interference on a control channel can completely or partially destroy the systems' capabil- ity to provide communication among Mobile Subscribers. A digital communication system based upon a Time Division Multiple Access (TDMA) pro- tocol has the same susceptibility.

  A method is given to detect interference on an inbound control channel (Mobile Subscriber to Base) in a TDMA system. This type of interference will effect all types of communication (i.e. calls) since a call setup protocol typically requires one or more messages to be exchanged between a Mobile Subscriber and a Base regardless of the call's direc- tions (e.g. Mobile subscriber validation or a Traffic Channel assignment). Therefore, the procedure to detect inbound interference land potential elimina- tion of consequences by switching control hmctions to another Radio Frequency (RF) carrier} can significantly increase robustness of a TDMA based communication system.

  For a non-allocated 'traffic channel, any RSSI measurement above that ilevel indicates presence of another signal on the given frequency (i.e. inbound interference). Thus, the control channel utilizing one of the TDMA slots on the same frequency may have interference present as well and a recovery action is required usually in the form of a control channel frequency reassignment?

  Naturally, some sampling over a period of time is required to eliminate instantaneous "spikes" and noise bursts.

  Further complications exist in the systems with multiple sites with geographic hequency reuse which may have some overlapping coverage (see Figure

INTRODUCTION

2).

DESCRIPTION

  The method for detecting inbound control chan- nel interference in a TDMA system consists of peri- odically measuring the Received Signal Strength Indi- cation (RSSI) on each of the slots of a control channel bearing RF carrier. As shown in the Figure 1, the inbound RF frequency is subdivided into 6 time slots' (6:l TDMA). One of the slots is allocated to per- form control hmctions (i.e. control channel) and the other slots form 5 traffic channels. Each...