# Patent

## Title
Systems and methods for facilitating intra-cell-peer-to-peer communication

## Abstract

Methods and systems for providing efficient communications between two mobile stations served by the same base station or relay station are provided. A base station maintains information identifying which mobile stations it is serving. When a connection is set up between two mobile stations, if they are both being served by the same base station, the base station forwards traffic directly between the two mobile stations without forwarding it on to higher level network entities.

## Background
PRIORITY CLAIM
This application is a continuation of U.S. patent application Ser. No. 14/918,690, entitled “Systems and Methods for Facilitating Intra-Cell-Peer-to-Peer Communication”, and filed on Oct. 21, 2015 (issued as U.S. Pat. No. 9,485,792 on Nov. 1, 2016), which is a continuation of U.S. patent application Ser. No. 13/944,264, of the same title and filed on Jul. 17, 2013 (issued as U.S. Pat. No. 9,191,978 on Nov. 17, 2015), which is a continuation of U.S. patent application Ser. No. 13/236,978, of the same title and filed on Sep. 20, 2011, which is a continuation of U.S. patent application Ser. No. 11/863,778, of the same title and filed on Sep. 28, 2007 (issued as U.S. Pat. No. 8,023,446 on Sep. 20, 2011), which claims the benefit of priority from U.S. Provisional Patent Application Ser. No. 60/827,334, entitled “Systems and Methods for MS-BS-MS and MS-RS-MS Operation” and filed on Sep. 28, 2006, all of which are fully incorporated herein by reference for all purposes.


BACKGROUND
Field of the Application
The invention relates to communications taking a path from a mobile station to a base station and back to a mobile station, or taking a path from a mobile station to a relay station and back to a mobile station.
Background of the Disclosure
If two mobile stations MS1 and MS2 are associated with the same base station (BS) (possibly via one or more relay stations (RS)) and MS1 wants to send data to MS2, the operation of the connections set up and data forwarding by the BS is defined herein as MS-BS-MS operation. The conventional approach to handling this is through a BSC (base station controller) or gateway server without regard to the fact that MS1 and MS2 are associated with the same BS.
SUMMARY
According to one broad aspect, the invention provides a method of facilitating intra-cell Peer-to-Peer Communication comprising: maintaining a CID mapping identifying each communication between two mobile stations served by a common network transceiver; upon receipt by the network transceiver of an uplink communication containing an uplink SDU, determining if there is a corresponding entry in the CID mapping table and if so, sending a downlink communication containing a corresponding downlink SDU.
In some embodiments, maintaining, determining and sending are performed in a network transceiver that is a base station.
In some embodiments, maintaining, determining and sending are performed in a network transceiver that is a relay station.
In some embodiments, the CID mapping comprises a CID mapping table, and each entry in the CID mapping table includes a source MS ID and a destination MS ID.
In some embodiments, each entry in the CID mapping table includes security information for the UL from the source MS, and security information for the DL to the destination MS.
In some embodiments, the method further comprises: upon receiving the uplink SDU, decrypting the SDU using the security information for the UL, and then re-encrypting using the security information for the DL to produce the corresponding downlink SDU.
In some embodiments, the method further comprises: maintaining a connection information table for the BS that includes all connections that are served by this BS; upon receipt of a packet from a source that is included in the connection information table for a destination that is included in the connection information table, adding an entry into the CID mapping.
In some embodiments, the method further comprises: upon receipt of first SDU for a destination that is being serviced by the same base station, establishing a downlink service flow to the destination.
In some embodiments, the downlink service flow is established using an existing security association.
In some embodiments, the downlink service flow is established using a dynamic security association.
According to another broad aspect, the invention provides a base station comprising: at least one antenna for receiving uplink communications and transmitting downlink communications; an uplink packet processor that processes uplink packets by: a) maintaining a CID mapping identifying each communication between two mobile stations served a common network transceiver; b) upon receipt by the network transceiver of an uplink communication containing an uplink SDU, determining if there is a corresponding entry in the CID mapping table; and a downlink packet processor that, upon there being a determination that there is a corresponding entry in the CID mapping table for an uplink SDU, sends a downlink communication containing a corresponding downlink SDU.
According to another broad aspect, the invention provides a relay station comprising: at least one antenna for receiving uplink communications and transmitting downlink communications; an uplink packet processor that processes uplink packets by: a) maintaining a CID mapping identifying each communication between two mobile stations served a common network transceiver; b) upon receipt by the network transceiver of an uplink communication containing an uplink SDU, determines if there is a corresponding entry in the CID mapping table; c) a downlink packet processor that, upon there being a determination that there is a corresponding entry in the CID mapping table for an uplink SDU, sends a downlink communication containing a corresponding downlink SDU.



BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the attached drawings in which:
FIG. 1 is a flowchart of an example method of table creation and update MS-BS-MS Operation Flow Chart of BS-1 for a case where source and destination addresses are in CS TLV compound of RSA-XXX message;
FIG. 2 is a flowchart of an example method of table creation and update MS-BS-MS Operation Flow Chart of BS-1 for a case where source and destination addresses are not in CS TLV compound of RSA-XXX message;
FIG. 3 is a flowchart of MS-BS-MS operation for Data forwarding; and
FIG. 4 is a block diagram of SDU processing.



DETAILED DESCRIPTION
The conventional approach to handling MS-BS-MS operation through a BSC (base station controller) or gateway server without regard to the fact that MS1 and MS2 are associated with the same BS causes unnecessary delay and resource wastage.
Embodiments of the invention provide systems and methods that provide more efficient traffic handling for the case where two MSs that are communicating are connected to the same base station or relay station.
An MS connection information Table is maintained that includes parameters for the connections of each mobile station served by the BS. In a particular example, the fields are SFID (service flow ID), UL CID (uplink connection ID), DL CID (downlink connection ID), SAID (security association ID), possibly including a (TEK) (traffic encryption key) and QoS (quality of service). The form that each of the parameters referred to might take is implementation specific. More generally, the information maintained in respect of each MS connection can be defined on an implementation specific basis. An example of a MS connection information table is provided below in Table 1.







TABLE 1





MS Connection Information Table





















MS1 (IP
SFID
UL CID
SAID (TEK)
QoS



address or
SFID
UL CID
SAID (TEK)
QoS



other
. . .
. . .
. . .
. . .



equivalent
SFID
DL CID
SAID (TEK)
QoS



address)
SFID
DL CID
SAID (TEK)
QoS



MS2 (IP
SFID
UL CID
SAID (TEK)
QoS



address or
SFID
UL CID
SAID (TEK)
QoS



other
. . .
. . .
. . .
. . .



equivalent
SFID
DL CID
SAID (TEK)
QoS



address)
SFID
DL CID
SAID (TEK)
QoS



. . .
. . .
. . .
. . .
. . .










An entry can be added to this table each time an UL or DL service flow is set up. In some embodiments, the SFID, SAID, CID and QoS are assigned by the network, for example by a base station and/or another network component.
MAC (medium access control) features are often organized into layers. One set of layers includes a convergence sub-layer (CS), common part sub-layer (CPS), and security sub-layer, although the security sub-layer is sometimes referred to as a component rather than a sub-layer. More generally, layer definitions are implementation specific.
In a specific example, the source address of a MS may be indicated in a CS source address TLV (type, length, value) in a DSA-REQ (dynamic service add request) or may be indicated in a CS destination address TLV of DL DSA-RSP (dynamic service add response).
A CID (connection identifier) mapping table is maintained that has entries that each represent a respective established communication between two MSs served by the BS. Table 2 below provides a specific example of the form such a table might take.















MS ID

SAID
MS ID




(or basic ID)
UL CID
(TEK)
(or basic ID)
DL CID
SAID (TEK)





















. . .
. . .
. . .
. . .
. . .










In the example illustrated, the first column contains the MS ID for the source, and the fourth column contains an MS ID entry (fourth column) for the destination. In some embodiments, the MS ID is a MAC ID, for example a 48 bit MAC ID. In other embodiments, the MS ID is a shorter basic ID (for example 16 bits) that is unique within the network. This is more efficient to use than the full MAC ID. Each entry in the CID mapping table indicates a UL CID and corresponding DL CID, as well as the SA parameters (SAID) for each of these connections. The UL CID is a CID for uplink traffic from a source MS to the base station for a given established communication between two MSs served by the BS. The DL CID is a CID for downlink traffic from the base station to the destination MS for the given established communication between two MSs served by the BS. In the event there is to be bi-directional communications, there would be two entries in the table, one for each direction, with the source and destination roles reversed.

The following are two examples of triggers for DL service flow set up that result in the creation of an entry in the CID mapping table.
First example: After an UL connection is setup from a MS served by a BS, if the destination address of the UL connection matches a MS's source address in the MS connection information table, then a DL service flow to the identified MS is established, and an entry is added to the CID mapping table.
Second Example: If the destination address in the very first SDU (Service data unit) on a UL connection matches a MS's source address in the MS connection info Table, then a DL service flow to the identified MS is established, and an entry is added to the CID mapping table.
In some embodiments, in order to establish the DL service flow, the BS may initiate a dynamic SA creation procedure per 7.3 (802.16d). The BS initiates DL service flow establishment procedure by sending DSx-XXX message, including the SAID, SFID, DL CID, QoS parameter set, etc. The use of dynamically assigned SA may solve a potential problem of multiple transmitters transmitting to the same receiver. In some embodiments, the PN synchronization between RS and BS is performed to avoid this potential problem.
In some embodiments, the new DL service flow is established using an existing SA. Multiple services can be mapped to a single SA (security association).
After the CID mapping table is established, L2 routing, instead of L3 routing, can be implemented to forward traffic. More specifically, the Connection ID (CID) is used to identify the destination connection, instead of using IP mapping.
Note that while the BS is described as creating the CID mapping table, more generally, any appropriate network entity may do this. Other examples include a BSC or a gateway. If an entity other than BS, creates the CID mapping table, that entity forwards the table to the BS for use in processing traffic.
For each received MAC PDU (payload data unit) on an UL connection that contains a CID listed in the CID mapping table the base station performs the following procedure:

    
    
        Decrypt the payload (privacy enabled service flow) using the corresponding UL connection TEK;
        Restore SDU;
        Create DL MAC PDU and encrypt using corresponding the DL connection TEK (for a privacy enabled connection); and
        Send the MAC PDU on the corresponding DL connection.

Extension of MS-BS-MS to MS-RS-MS

    
    


In some embodiments, if the source MS and destination MS of a data flow are both attached to a common RS (possibly via other RSs) the MS-BS-MS operation described above is applied to MS-RS-MS operation.
To achieve this, whenever a new entry in a CID mapping table is created (for example by a BS), the network (for example the BS) checks to determine whether both involved MSs are attached to a common RS (possibly via other RSs). If such an RS exists, BS forwards relevant information from the CID mapping table, for example a sub-table containing only the relevant entry, and corresponding SA materials to the RS.
At that point, the RS starts the same data forwarding operation as described above for the BS.
If a dynamic SA is established for the DL CID, there is no need for possible PN sequence number (used to identify the replay) synchronization between BS and RS. In some embodiments, the PN sequence number used by BS for other SF is identified to the RS and vice versa.
FIG. 1 is a flowchart of an example method of table creation and update MS-BS-MS Operation Flow Chart of BS-1 for a case where source and destination addresses are in CS TLV compound of RSA-XXX message. In step 102, BS-1 receives DSA REQ from MS1 including source and destination address. Then, in step 104, BS-1 sends DSA RVD to MS1. Next, in step 106, BS-1 assigns an SFID, UL CID, and SAID, and creates a new entry for the SF. In step 108, the BS-1 sends the DSA-RSP to MS1 and in step 110 receives the DSA ACK from MS1. Next, in step 112, the BS-1 checks if the destination address matches any MS source address in the MS connection information table. Assuming the destination address matches the source address of a MS2, in step 114 the BS-1 initiates dynamic security association (SA) creation by sending a SA Add message to MS2. It will be understood that step 114 is optional. Next, in step 116, the BS-1 assigns an SFID, DL CID, and SAID, and creates a new entry for this new DL SF. Then, in step 118, the BS-1 sends the DSA REQ to MS2 and in step 120 receives the DSA RSP from MS2. In step 122, the BS-1 sends a DSA ACK to MS2, and finally in step 124 creates a new entry in the CID mapping table.
FIG. 2 is a flowchart of an example method of table creation and update MS-BS-MS Operation Flow Chart of BS-1 for a case where source and destination addresses are not in CS TLV compound of RSA-XXX message. In step 202, BS-1 receives DSA REQ from MS1. Then, in step 204, BS-1 sends DSA RVD to MS1. Next, in step 206, BS-1 assigns an SFID, UL CID, and SAID, and creates a new entry for the SF. In step 208, the BS-1 sends the DSA-RSP to MS1 and in step 210 receives the DSA ACK from MS1. Then, in step 212, the BS-1 receives a first MAC SDU on the connection from MS1 and checks the source/destination addresses. Next, in step 214, the BS-1 checks if the destination address matches any MS source address in the MS connection information table. Assuming the destination address matches the source address of a MS2, in step 216 the BS-1 initiates dynamic security association (SA) creation by sending a SA Add message to MS2. It will be understood that step 216 is optional. Next, in step 218, the BS-1 assigns an SFID, DL CID, and SAID, and creates a new entry for this new DL SF. Then, in step 220, the BS-1 sends the DSA REQ to MS2 and in step 222 receives the DSA RSP from MS2. In step 224, the BS-1 sends a DSA ACK to MS2, and finally in step 226 creates a new entry in the CID mapping table.
FIG. 3 is a flowchart of MS-BS-MS operation for Data forwarding. In step 302, the UL MAC entity of the BS receives a MAC PDU from MS1 on the UL CID listed in the CID mapping table. Next, in step 304, the BS decrypts the received payload using the corresponding TEK for a privacy enabled service flow. In step 306, the SDU is restored and sent to the DL MAC entity. In step 308, the MAC PDU is created and the payload is encrypted for a privacy enabled service flow. Finally, in step 310, the created MAC PDU is sent to corresponding MS2's DL CID. The process repeats for each received MAC PDU from MS1.
MS-BS-MS Operation in Stand-Alone Mode
In some embodiments, a stand-alone mode of operation is provided that can be used in a BS when the BS has no connection with the network (e.g. no connection with other BS and any other control entities residing in network side).
In some embodiments, when this is to occur, the BS announces “enter stand-along mode” using a signaling message, which means communication can only happen among MSs/RSs associated with this BS.
MSs that have passed authorization before entering “stand alone mode”, are authorized to continue MS-BS-MS communication until reauthorization. At reauthorization, MS and BS may for example use RSA based procedure per 802.16e 7.8.2. Reauthorization might take place again for example after an AK (authorization timer) expires. Reauthorization may be possible without network involvement other than the BS.
A second option is again allow it to continue, but then to disable reauthorization. In some implementations, the MSs can no longer communicate. In other cases they are allowed to continue communicating.
The procedures that are followed have been described above, the only difference being that now MSs communicate with the BS while the BS is not in communication with the network. As such, only limited communication is possible.
MS-RS-MS Operation in Stand-Alone Mode
In some instances, a RS may lose its connection with the BS (no connection with network side) due to some unpredictable reasons. In some embodiments, a mode of operation in the RS is provided that is the same as that of MS-BS-MS operation in stand-alone mode.
In some embodiments, for this implementation, the RS is configured to implement a full set of MAC common part sub-layer (CPS) and may implement part of a convergence sub-layer (CS).
Referring to FIG. 4, shown is a block diagram of a BS with convergence sub-layer function to enable MS-BS-MS Operation. Note that if header suppression is not implemented, the SDU and corresponding CID transfer can be moved to MAC common part sub-layer (CPS).
A route function is provided that functions as follows:
upon receiving a SDU (service data unit) from the UL, the destination address is filtered. If the destination address is within the table, the SDU is routed to a DL convergence sub-layer; otherwise routed to upper layer through SAP (service access point).
Referring again to FIG. 4, in the left hand portion of the figure:
a packet is received from an MS or associated RS; this is reconstructed 402, and then subject to destination address filtering with the table that includes all addresses covered by the BS 404. If the address is not present, the packet is passed on to the SAP (service access point) 406, and then on to an upper layer entity. If the address is present, the packet is passed over to the DL convergence sub-layer 408, this being the functionality shown in the right hand side of the figure.
In the right hand side of the drawing:
a packet is received that is destined to another address that is served by that BS. DL classification and CID mapping is performed 410, and the packet goes out to another MS or associated RS.
In another embodiment, a similar design to that of FIG. 4 is employed in a RS.
The description of MS-BS-MS and MS-RS-MS are appropriate examples for where 802.16e is used to support this operation. Any other cellular system with or without relay stations can use a similar approach.
The CID mapping table described is an appropriate example table where 802.16e is used to support MS-BS-MS and MS-RS-MS. Any other type of tables which include any other MS identity could be possible for routing packets of MS or other relay stations by BS or relay station.
What has been described is merely illustrative of the application of the principles of the invention. Other arrangements and methods can be implemented by those skilled in the art without departing from the spirit and scope of the present invention.

## Claims

1. An apparatus, comprising:
at least one processor coupled to memory, wherein the at least one processor is configured to:
receive a message indicating that a common network transceiver has entered a stand-alone mode, wherein communication facilitated by the common network transceiver is enabled only between relay stations and/or mobile stations associated with the common network transceiver;
identify first security information associated with an uplink (UL) to at least one antenna of the common network transceiver;
transmit an UL communication to the at least one antenna of the common network transceiver, wherein the UL communication comprises an UL service data unit (SDU) using the first security information;

wherein the common network transceiver is configured to send, via the at least one antenna, a downlink (DL) communication to a second mobile station using second security information associated with the DL of the second mobile station of a plurality of mobile stations, wherein the DL communication comprises a DL SDU corresponding to the UL SDU.

2. The apparatus of claim 1,
wherein the common network transceiver is further configured to:
decrypt the UL SDU using the first security information for the UL of the apparatus; and
re-encrypt using the second security information to produce the DL SDU for the second mobile station.

3. The apparatus of claim 1,
wherein the common network transceiver is configured to enter the stand-alone mode in response to being disconnected from an infrastructure network.

4. The apparatus of claim 1,
wherein the common network transceiver is further configured to:
establish a DL service flow to the second mobile station, wherein the DL service flow is established using an existing security association.

5. The apparatus of claim 1,
wherein the common network transceiver is further configured to:
establish a new security association with the second mobile station to generate the second security information.

6. The apparatus of claim 1,
wherein the at least one processor is further configured to:
establish a new security association with the common network transceiver resulting in the first security information.

7. The apparatus of claim 6,
wherein the new security association is different from a security association that would be established with the common network transceiver when the common network transceiver is connected to an infrastructure network.

8. A mobile station, comprising:
at least one antenna; and
at least one processor coupled to a memory and associated with the at least one antenna, wherein the at least one processor is configured to:
receive a message indicating that a common network transceiver has entered a stand-alone mode, wherein communication facilitated by the common network transceiver is enabled only between relay stations and/or mobile stations associated with the common network transceiver;
identify first security information associated with an uplink (UL) to at least one antenna of the common network transceiver;
transmit an UL communication to the at least one antenna of the common network transceiver, wherein the UL communication comprises an UL service data unit (SDU) using the first security information;

wherein the common network transceiver is configured to send, via the at least one antenna, a downlink (DL) communication to a second mobile station using second security information associated with the DL of the second mobile station of a plurality of mobile stations, wherein the DL communication comprises a DL SDU corresponding to the UL SDU.

9. The mobile station of claim 8,
wherein the common network transceiver is further configured to:
decrypt the UL SDU using the first security information for the UL of the mobile station; and
re-encrypt using the second security information to produce the DL SDU for the second mobile station.

10. The mobile station of claim 8,
wherein the common network transceiver is configured to enter the stand-alone mode in response to being disconnected from an infrastructure network.

11. The mobile station of claim 8,
wherein the common network transceiver is further configured to:
establish a DL service flow to the second mobile station, wherein the DL service flow is established using an existing security association.

12. The mobile station of claim 8,
wherein the common network transceiver is further configured to:
establish a new security association with the second mobile station to generate the second security information.

13. The mobile station of claim 8,
wherein the at least one processor is further configured to:
establish a new security association with the common network transceiver resulting in the first security information.

14. The mobile station of claim 13,
wherein the new security association is different from a security association that would be established with the common network transceiver when the common network transceiver is connected to an infrastructure network.

15. A non-transitory computer readable memory medium storing program instructions executable by a processor of a mobile station to:
receive a message indicating that a common network transceiver has entered a stand-alone mode, wherein communication facilitated by the common network transceiver is enabled only between relay stations and/or mobile stations associated with the common network transceiver;
identify first security information associated with an uplink (UL) to at least one antenna of the common network transceiver;
transmit an UL communication to the at least one antenna of the common network transceiver, wherein the UL communication comprises an UL service data unit (SDU) using the first security information;
wherein the common network transceiver is configured to send, via the at least one antenna, a downlink (DL) communication to a second mobile station using second security information associated with the DL of the second mobile station of a plurality of mobile stations, wherein the DL communication comprises a DL SDU corresponding to the UL SDU.

16. The non-transitory computer readable memory medium of claim 15,
wherein the common network transceiver is further configured to:
decrypt the UL SDU using the first security information for the UL of mobile station; and
re-encrypt using the second security information to produce the DL SDU for the second mobile station.

17. The non-transitory computer readable memory medium of claim 15,
wherein the common network transceiver is configured to enter the stand-alone mode in response to being disconnected from an infrastructure network.

18. The non-transitory computer readable memory medium of claim 15,
wherein the common network transceiver is further configured to:
establish a DL service flow to the second mobile station, wherein the DL service flow is established using an existing security association.

19. The non-transitory computer readable memory medium of claim 15,
wherein the common network transceiver is further executable to:
establish a new security association with the second mobile station to generate the second security information.

20. The non-transitory computer readable memory medium of claim 15,
wherein the program instructions are further executable to:
establish a new security association with the common network transceiver resulting in the first security information, wherein the new security association is different from a security association that would be established with the common network transceiver when the common network transceiver is connected to the infrastructure network.