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 is 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 of MT voice call routing is described in the picture. The step by step procedure is, 1. The GMSC receives the request from the MS with called party number. 2. The GMSC makes an interrogation with the HLR of the called number about thecurrent location details of the called number. The HLR is identified by the internal database of GSMC. 3. The HLR holding the current location of the mobile number initiates a transaction with the VMSC (Visiting MSC) to provide the location information for routing. 4. VMSC in turn allots a MSRN to the visited number and replies HLR with the allotted MSRN. 5. HLR conveys the MSRN info to GMSC. 6. Finally GMSC terminated the call to the visitor based on the received MSRNvalue. Need for MSRN: 1. It is not possible to define routing information in all exchanges for each and individual subscriber in the world. 2. As HLR is available to hold all the inherent information of the subscriber, it is sufficient to interrogate HLR for routing. 3. To hide the identity of the subscriber during the course of the call. 4. To optimize the routing of MT calls to subscriber. 5. The subscriber can be in any geographical location area and it is not possible to guess the visit. Wherever he is, the call has to be terminated. 6. An operator can have different series of MSISDN and each need not be defined by each and every operator 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 they 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 routings. Thus with MSRN allotted to standard MSC/VLR of the networks, it is possible to route any MT call to any subscriber in the world, irrespective of the number series. This applies to MT call scenario of both inbound 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 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 8 th 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 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 SP DATA 60 YES P01=1 R=0GRI2 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 analysis as 8. The HLR return the MSRN in this origin. R ROUTE PARAMETERS 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 ROUTE CHARGE L A 8-mcc99408 F=9 M=3 BNT=4 The final analysis ends with MTE. B-NUMBER MISCELL F/N ROUTE CHARGE L 9-9 9-99 9-994
9-9940 9-99408 9-994080 MTE CC=1 L=8 D=1-0 Facts about MSRN: 1. Even though the subscriber is in the serving area of the GMSC/MSC that initiates the interrogation, the analysis should compulsorily involve HLR. 2. The allocation of MSRN number series depends on the serving capability of the MSC/VLR. If the serving area is high with more subscribers, the numbers should be also high. 3. In case of congestion in the MSRN, it would result in Not reachable for the subscribers who were not allotted with MSRN. 4. The time supervision between the allocation of a MSRN and release of MSRN is very important and it should be kept optimum. 5. In Ericsson MSCs, block MRNR holds responsible for MSRN. 6. Normally the MSRN series will be similar to the mobile number series. 7. After MTE analysis, the MSC will page the mobile number with the location data available in VLR using the MSRN. 8. If MSRN is used for Inter-MSC handover, it is termed as HON (Handover Number series). 9. After the call is connected, the MSRN is released and used for terminating another call. 10. The exchange parameters for MSRN in Ericsson MSC are, MSRNHNDLIMIT-0 OPTIONAL MSRNHNDTIME-30 OPTIONAL MSRNHOMETHOD-0 OPTIONAL MSRNTCNTIME-30 OPTIONAL 11. Other command in Ericsson for MSRN are, MGRNP:MSRNS=ALL; ! To print the allotted series ! MGRSP:MSRN=ALL; ! To print the current status of individual MSRNs ! Update on 19-Apr09 with query from scribd 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. Upon the receipt of the 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 complete 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 optimum for good paging performance. I hope that 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=PA155&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 -
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