Communications system and method
A mobile network comprises remote base transceiver station (BTS) nodes ( 3, 4 ) linked with a central base station controller (BSC) node ( 9 ). The latter is in turn linked with a mobile switching center (MSC, 10 ), a visitor location register (VLR, 11 ), and a home location register (HLR, 8 ). Mobile stations ( 2 , MS-A, MS-B, and MS-C) are located in the cells of the BTSs ( 3, 4 ). The remote nodes ( 3, 4, 3 ( a ), 4 ( a )) are connected to the central node BSC ( 9 ) over a remote backhaul satellite connection. Calls are routed locally while the central nodes continue to manage calls and services from central feature-rich and typically more reliable switches of a core network. This means that calls set up between subscribers on the same remote node get connected within the remote node but call supervision is still carried out by the central nodes. The features and services of the existing core network are preserved. For example, if the calling subscriber is a pre-paid GSM subscriber and their account runs out during the call a release signal will still be sent from the central node to the remote even though the voice traffic is being handled by the remote node.
1. A method of operation of a mobile network comprising a central node, an MSC and a HLR and at least one remote cell having remote nodes linked with the central node via a remote backhaul communication link, the method comprising steps of:
a mobile device registered with a remote cell making a voice or data call to a called device registered with the same or a different remote cell,
a central node intercepting a call setup message for said call,
the central node interrogating the HLR using the MSISDN contained in the intercepted call setup message to obtain the IMSI of the called subscriber,
the central network node caching said IMSI and maintaining and updating said cache, and replicating said cache in the remote node,
the central node or the remote node intercepting a paging message sent to alert the called subscriber,
the central node or the remote node looking up the cache, and
if an IMSI retrieved from the cache matches the IMSI received in the paging message:
the central node or the remote node making a decision to connect the call locally without it being routed through the MSC,
if the decision is made by the central node, the central node sending a signal to the remote node instructing it to directly connect the call, and
the remote node connecting the call locally.
2. The method as claimed in claim 1 , wherein a remote node routes a signalling channel for the call to a central node, but does not route a call channel.
3. The method as claimed in claim 1 , wherein a remote node routes a signaling channel for the call to a central node, but does not route a call channel; and wherein the decision is made by a central node and said central node transmits a switching instruction to a remote node.
4. The method as claimed in claim 1 , wherein the decision is made by a remote node, and the remote node transmits a data update to the central switching node to indicate status of the call which has been switched locally.
5. The method as claimed in claim 1 , wherein said central node replicates said cache in a remote node.
6. The method as claimed in claim 1 , wherein the remote nodes are in a plurality of remote network cells, and the call is connected locally between different remote mobile network cells.
7. The method as claimed in claim 1 , wherein the call is connected locally within the same remote mobile network cell.
8. The method as claimed in claim 1 , wherein the remote nodes are interconnected in a mesh.
9. The method as claimed in claim 1 , wherein the remote nodes are interconnected in a mesh; and wherein the mesh is a WiMax mesh.
10. The method as claimed in claim 1 , wherein, to update the cache, a call is made to a test mobile device or a message is sent to a test mobile device using the stable international subscriber identifier.
11. The method as claimed in claim 1 , wherein the call is routed locally by a remote cell transceiver proxy node.
12. The method as claimed in claim 1 , wherein the decision is made by a central base station controller proxy node.
13. The method as claimed in claim 1 , wherein the call is routed locally by a remote part of a physically split base station controller, the other part of the base station controller being centrally located.
14. The method as claimed in claim 1 , wherein the call is routed locally by a remote part of a physically split base station controller, the other part of the base station controller being centrally located; and wherein the base station controller part located centrally makes the decision.
15. A mobile network comprising remote cells with remote nodes linked via a remote backhaul communications link to central nodes including a switching node, wherein the network nodes are adapted to perform a method as claimed in claim 1 .
16. A method of operation of a mobile network comprising a central node, an MSC and a HLR and at least one remote cell having remote nodes linked with the central node via a remote backhaul communication link, the method comprising the steps of:
(i) a mobile device registered with a remote cell making a voice or data call to a called device registered with the same or a different remote cell,
(ii) a remote node or the central node inserting a special identifier into a setup message or a speech stream for said call,
(iii) the MSC including said special identifier in a setup message or speech stream sent to the called mobile device; and
(iv) said remote node or central node extracting the special identifier from said setup message or speech stream sent by the MSC and checking if it matches the identifier inserted in step (ii),
if the identifiers match:
the central node or the remote node making a decision to connect the call locally without it being routed through the MSC,
if the decision is made by the central node, the central node sending a signal to the remote node instructing it to directly connect the call, and
the remote node connecting the call locally.
17. The method as claimed in claim 16 , wherein the node which makes said decision is a central node.
18. The method as claimed in claim 16 , wherein the central node is a central proxy.
19. The method as claimed in claim 16 , wherein the node which makes said decision is a remote node.
20. The method as claimed in claim 16 , wherein, in step (b), the special identifier is inserted into a speech stream.