Browse Prior Art Database

GSM network sharing with multiple co-located BCCH

IP.com Disclosure Number: IPCOM000200505D
Original Publication Date: 2010-Oct-17
Included in the Prior Art Database: 2010-Oct-17
Document File: 3 page(s) / 187K

Publishing Venue

Motorola

Related People

Thomas, Howard: INVENTOR

Abstract

The idea I am disclosing is to broadcast 2 PLMN codes on the same physical resource, a first PLMN code being associated with one training sequence code (TSC) and a second PLMN code being associated with a second TSC. In one implementation the PLMN codes are broadcast simultaneously on timeslot zero (TS0). The mobiles per their PLMN preference will camp on to one PLMN code or the other. In one sub-case of this implementation, access grant resources on the TS0 are distinguished by TSC, while other resources in the cell are shared in a conventional manner with no set association between the used TSC and the PLMN. In a second implementation. The TS0 for the two networks are not broadcast simultaneously but with a fixed offset. In one sub-case, the other resources are shared in a conventional way, however, the timeslot numbering associated with the two BCCHs will not be aligned (need to check on guard period - is there one at the end of a frame? or just one per timeslot). This configuration allows the possibility of reducing the interference to the respective TS0 associated with a first PLMN code reducing the power transmitted in the overlapping slot associated with the second PLMN. The power can be set to zero or can be set to a lower limit. In any of the implementations, a preferred embodiment is to use a modified QPSK modulation when data transmissions are broadcast simultaneously on the same timeslot.

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          GSM network sharing with multiple co-located BCCH

By Howard Thomas

Motorola, Inc.

Motorola Solutions

 

ABSTRACT

The publication describes a method to broadcast 2 PLMN codes on the same physical resource, a first PLMN code being associated with one training sequence code (TSC) and a second PLMN code being associated with a second TSC. 

In one implementation the PLMN codes are broadcast simultaneously on timeslot zero (TS0).  The mobiles, per their PLMN preference, will camp on to one PLMN code or the other.  In one sub-case of this implementation, access grant resources on the TS0 are distinguished by TSC, while other resources in the cell are shared in a conventional manner with no set association between the used TSC and the PLMN.

In a second implementation.  The TS0 for the two networks are not broadcast simultaneously but with a fixed offset.  In one sub-case, the other resources are shared in a conventional way, however, the timeslot numbering associated with the two BCCHs will not be aligned.  This configuration allows the possibility of reducing the interference to the respective TS0 associated with a first PLMN code reducing the power transmitted in the overlapping slot associated with the second PLMN.  The power can be set to zero or can be set to a lower limit.

In any of the implementations, a preferred embodiment is to use a modified QPSK modulation when data transmissions are broadcast simultaneously on the same timeslot.

PROBLEM

There are an increasing number of scenarios where mobile network operators choose to share their radio access networks while maintaining separate core networks.  For example, operators may want to share base station sites to reduce operational costs but still manage the subscriptions of their subscribers in a separate way.

LTE and UMTS (from Rel-6 of the 3GPP standards) were designed to be able to transmit multiple PLMN codes thereby allowing the mobile to choose an appropriate PLMN before access the network.  However, this option could not be adopted in GSM as no room was available on the broadcast channel.  Consequently, only a single PLMN can be broadcast and mobiles may be directed to the wrong PLMN 50% of the time resulting in extra core network signalling and delays in access to the network.

The conventional solution to allow mobiles in GSm to directly access their preferred PLMN is to provide two entirely separate cells.  However, this is costly in terms of bandwidth and hardware required.

SOLUTION

A single physical cell can broadcast two separate BCCH codes associated with separate PLMNs.  This creates two separate GSM cells with a single set of radio resources.

In one embodiment, the network may be configured with the time slot zero (TS0) in the “two” cells offset in time.  Consequently, there will be no degradation of the coverage of the BCCH.  In this embodiment legacy mobiles may be used with no reduction in performance.

In a second embodiment, the TS0 of the...