Need for MSRN

Need for MSRN

In mobile communication, the term MSRN is quite familiar to all types like GSM, CDMA or WCDMA. MSRN or Mobile Station Roaming Number is one of the important concepts used in terminating of a voice call to a subscriber. Basic concepts before getting in: The main objective of mobile communication co mmunication is mobility. mobility. It allows the user to roam freely without any boundary problem simultaneously sending and receiving all transactions. Thus the subscriber has to be confirmed with seamless connectivity wherever he roams. The basic concept concep t of MT voice call routing is described in the  picture.

GMSC

HLR 

VMSC

The step by step procedure is, 1. The GMSC GMSC receives receives the request request from from the the MS with with called called party number. number. 2. The GMSC GMSC makes an interrogat interrogation ion with with the HLR HLR of the the called called number about the the current location details of the called number. The HLR is identified by the internal database of GSMC. 3. The HLR holding holding the current current locatio location n of the mobile mobile number number initiates initiates a transac transaction tion with the VMSC (Visiting (Visiting MSC) to provide the location information for routing. 4. VMSC in turn allots allots a MSRN MSRN to the visit visited ed number and replies replies HLR HLR with the the allotted MSRN. 5. HLR conveys conveys the MSR MSRN N info info to to GMSC. GMSC. 6. Finally Finally GMSC GMSC terminated terminated the call call to the the visitor visitor based on on the received received MSRN MSRN value.

 Need for MSRN: 1. It is not possible possible to define define routing routing informat information ion in all exchange exchangess for each and and individual subscriber in the world. 2. As HLR is is available available to hold all all the inherent inherent inform information ation of the the subscriber subscriber,, it is sufficient to interrogate HLR for routing. 3. To hide the the identity identity of the subscri subscriber ber during during the cours coursee of the call. call. 4. To optimize optimize the routing routing of MT calls to subscribe subscriberr.

5. The subscriber subscriber can can be in any geographi geographical cal location location area area and it is not not possible possible to guess the visit. Wherever he is, the call has to be terminated. 6. An operator operator can can have different different series series of MSISD MSISDN N and each need not be defined defined  by each and every operator ope rator for routing MT calls to those subscribers. –update on 26/04/09

Concepts: Each serving MSC/VLR allots a dedicate range of number series complying with visiting network’s E.164 format for MSRN. The general format is VCC + VNDC + Subscriber Number where VCC is Visiting Country Code and VNDC is Visiting National Destination Code. As mentioned earlier, it complies E.164 (MSISDN) number format. This number series is not provided for subscribers and the y are also used as handover  number series for performing inter-MSC handovers. Thus when the HLR returns with the MSRN of the VMSC, the GMSC has no problem in routing the call towards VMSC  based on MSRN. When the called party is paged and terminated with the call, the MSRN is released for use of other numbers. Update on 26/04/09: As per point number six, each operator can have different number series for the network. This means, with the increase in subscriber base, new series can be allotted and thus the network base increases leading to complex c omplex routings. Thus with MSRN allotted to standard MSC/VLR of the networks, it is possible to route an y MT call to any subscriber  in the world, irrespective of the number series. This applies to MT call scenario of both inbound inbou nd and outbound subscribers. The difference is the HLR interrogated to get the MSRN values. Thus the complex routing process is eliminated.

Ericsson Perspective: In Ericsson GMSC/MSC, the concept is implemented as follows. The normal routing case directing to HLR is 60 or 61 with device dev ice type (DETY) as GRI. GRI is Gateway Roaming Interrogation. The interrogation should be performed with international format of the called number. The incoming origin for the reply from HLR is always 8 (BO=8) with the same international format.

Get the MSRN series from the roaming partner and make an analysis in the 8th origin. Perform the analysis in international format of the terminating network. If the MSRN  belongs to the same MSC/VLR then it will direct to origin 9 to change it to national

format. In the 9th origin, the analysis ends as MTE (Mobile Terminating Terminating Environment) that indicates, the MSC is terminating MSC.

In following example, the home number series starts with 9.Actual origin of analysis. It is directing to RC=60 30-98

RC=60

CC=1 L=8

M=0-968 D=13-0 TRD=193 BNT=1 RC 60 is a route that has device type as GRI. RC CCH BR ROUTING 60 YES P01=1 R=0GRI2

SP DAT DATA MM1 COT EST SI ESS ESR  0 0 1 0 BNT RN SPR OLI OLI2 00 0 ISC FCP D 0

The GRI route has incoming origin o rigin analysis as 8. The HLR return the MSRN in this origin. R ROUTE PARAMETERS ARAMETE RS 0GRI2 DETY=GRI RSV=48

MIS1=30

MIS2=2

MIS3=15 BO=8 CO=1

The analysis of the received MSRN will forward to origin 9 . Here mcc should be substituted by the actual country code. B-NUMBER MISCELL F/N 8-mcc99408 F=9 M=3 BNT=4

ROUTE

CHARGE L

ROUTE

CHARGE L

The final analysis ends with MTE.

B-NUMBER 9-9 9-99 9-994

MISCELL F/N

A

9-9940 9-99408 9-994080

MTE

CC=1 L=8

D=1-0

Facts about MSRN: 1. Even though though the subscrib subscriber er is in the the serving serving area of the the GMSC/MSC GMSC/MSC that that initiates initiates the interrogation, the analysis should compulsorily involve HLR. 2. The allocation allocation of MSRN number number series series depends depends on the serving serving capabili capability ty of the MSC/VLR. If the serving area is high with more subscribers, the nu mbers should  be also high. 3. In case case of congestion congestion in the MSRN, MSRN, it it would result result in Not reachable reachable for the the subscribers who were not allotted with MSRN. 4. The time supervi supervision sion between between the allocati allocation on of a MSRN MSRN and release release of MSRN MSRN is very important and it should be kept optimum. 5. In Ericsso Ericsson n MSCs, MSCs, block block MRNR MRNR holds holds responsib responsible le for MSRN. MSRN. 6. Normally Normally the MSRN MSRN series series will will be similar similar to the mobile mobile number number series. series. 7. After MTE MTE analysis, analysis, the MSC MSC will will page the mobile mobile number number with with the location location data available in VLR using the MSRN. 8. If MSRN MSRN is used for for Inter-M Inter-MSC SC handover handover,, it is termed termed as HON HON (Handover  (Handover   Number series). 9. After the the call is is connected, connected, the MSRN MSRN is released released and and used for termi terminating nating another call. 10. The exchange parameters for MSRN in Ericsson Ericsson MSC are, MSRNHNDLIMIT-0 OPTIONAL MSRNHNDTIME-30 OPTIONAL MSRNHOMETHOD-0 OPTIONAL MSRNTCNTIME-30 OPTIONAL 11. Other command command in Ericsson Ericsson for MSRN are, MGRNP:MSRNS=ALL; ! To To print the allotted series ! MGRSP:MSRN=ALL; ! To To print the current status of individual MSRNs !

Update on 19-Apr09 with query from scribd user JEROMENG user JEROMENG.. The query was “ Do you know exactly when the MSRN is released? Is it as soon as a page is performed, when a page response is received, or upon channel assignment? Thanks.. “

The reply from the VMSC towards the HLR for the “sendroutinginfo” is the MSRN. The MSC knows the IMSI of the number interrogated and allots a MSRN, an E.164 (MSISDN) number. HLR in turn, replies the GMSC with the MSRN along with the IMSI. The main use of MSRN is to make a normal routing and now the GMSC will initiate the routing towards the VMSC with MSRN as B-number. Due to this reason MSRN is in E.164 format. Till the arrival of the request in VMSC, the MSRN will be tied with the mobile number/IMSI. number/IMSI. Upon the receipt of the IAM, IAM, the MSC/VLR recognizes the MSRN and knows the IMSI for which it was allocated. At this point MSRN can be released to the pool for use of another call. Paging is purely based on TMSI, a 4 octet co mplete hex value or based on IMSI(rarely). The time between the allotment of MSRN and the release of MSRN is known as “MSRN holding time”. It should be b e optimum for good paging performance. p erformance. I hope that JEROMENG’s JEROMENG’s query was answered.

Ref: Wireless network performance handbook By Clint Smith, Curt Gervelis – Google Books. Or try this link  http://books.google.co.in/books?id=0HxC7pVrNTYC&pg=PA155&lpg=P http://books.google.co.in/books?id=0HxC7pVrNTYC&pg=P A155&lpg=PA155&dq=rele A155&dq=rele ase+of+%22MSRN%22+after+paging&source=bl&ots=KoNpo7pvGz&sig=qwCdhixqq0  pPSysvzUnyOhTKRNM&hl=en&ei=Qb3qScbWJ4mTsAa60byGBw&sa=X&oi=book_re sult&ct=result&resnum=1#PPA157,M1

-Ramanathan Sundaram For comments, questions and suggestions - [email protected]