Browse Prior Art Database

Reuse of a common time slot when 2 users are in the same cell

IP.com Disclosure Number: IPCOM000200504D
Original Publication Date: 2010-Oct-17
Included in the Prior Art Database: 2010-Oct-17
Document File: 3 page(s) / 181K

Publishing Venue

Motorola

Related People

Thomas, Howard: INVENTOR [+2]

Abstract

The invention detects when 2 users are engaged in the same conversation and are located in the same cell (or can be handed over to place them in the same cell). This also applies to conference calls. Such users can then be assigned to use a single uplink/downlink timeslot pair, the individual users are distinguished on the timeslot by use of separate training sequence codes. However, as both users are engaged in the same call, the users endeavour not to talk at the same time - or whilst talking at the same time do not listen to what the other party is saying. Consequently, the two users do not interfere with each other, or what interference there is is not intrusive as it occurs whilst the speaker is tending not to listen.

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Reuse of a common time slot when 2 users are in the same cell

By Howard Thomas, Author’s Luis Lopes

Motorola, Inc.

Motorola Solutions

 

ABSTRACT

The invention detects when 2 users are engaged in the same conversation and are located in the same cell (or can be handed over to place them in the same cell). This also applies to conference calls. Such users can then be assigned to use a single uplink/downlink timeslot pair, the individual users are distinguished on the timeslot by use of separate training sequence codes. However, as both users are engaged in the same call, the users endeavour not to talk at the same time - or whilst talking at the same time do not listen to what the other party is saying. Consequently, the two users do not interfere with each other, or what interference there is is not intrusive as it occurs whilst the speaker is tending not to listen.. 

PROBLEM

The multi user reuse of single slot (MUROS) / voice services over adaptive multi-usder orthogonal sub-channels (VAMOS) feature that was introduced into GSM standards and is documented in the technical report TR 45.914 increases the number of available radio channels by sharing a single timeslot between 2 users.  However, this also increases interference and creates a requirement for about 4dB extra carrier to interference ratio (CIR) to produce the same performance as without the feature.  Further, modified base station algorithms are required to decode the uplink transmissions and modified mobiles are required to make used of optimised training sequences designed for the feature.

The problem is to make use of the benefits of the feature while avoiding the drawbacks of extra CIR and requirement for updated base station decoding algorithms.

SOLUTION

The technique described in this publication addresses this problem for a sub set of mobile to mobile calls where both mobiles are connected to the same cell.

When the network has detected that such mobiles exist, and discontinuous transmission (DTX) is (or can be) utilised, the network instigates intra cell handover to switch the calls to share the same radio resource.

The mobiles are commanded to use separate raining sequences so that the network can distinguish them in the uplink.  However, as DTX is used, the occasions where both mobiles will be transmitting are very limited so legacy equipment may be used to support the feature.

OPERATION

First, mobile pairs that are engaged in a voice call where both call legs a...