User's Manual

CHAPTER 4. Message Flow
4-20
© SAMSUNG Electronics Co., Ltd.
Category Description
(1)~(3)
To request a handover, the MS sends the current S-RAS (Serving RAS) the
MOB_MSHO-REQ message containing the neighbor BS (RAS) ID and handover-
related parameters. The S-RAS sends the ACR the HO-Request message
containing the MOB_MSHO-REQ parameter received and the context information.
The ACR forwards the HO-Request message to the T-RAS (Target RAS).
(4)~(8)
The T-RAS sends the ACR the HO-Response message containing the capability
information for the T-RAS. The S-RAS sends the MS the MOB_BSHO-RSP
message containing the recommended neighbor BS-IDs, HO-ID, and parameter
result value.
(9)~(13)
The MS sends the S-RAS the MOB_HO-IND message containing the HO-IND type
and target BS-ID to provide notification that the handover will be performed.
The S-RAS sends the T-RAS the HO-Confirm message containing the context
information and data integrity information (e.g., buffered SDU SN) for the MS.
(14)~(15)
The T-RAS sends the ACR (authenticator) the Context-Request message to
request the AK Context information. The ACR responds with the Context-Report
message containing the AK context information.
(16)~(21)
The path pre-registration procedure is performed to set up a new data path
between the ACR and T-RAS. In addition, a forwarding path is set up so that the S-
RAS can send the T-RAS the traffic that it has not yet transmitted to the MS. The
traffic is transmitted to the T-RAS.
(22)
When the T-RAS accepts the handover request from the MS, it notifies the MS of
the UL_MAP IE so that the MS can send the HO Ranging Request message
through the uplink.
(23)
The MS sends the T-RAS the RNG-REQ message containing the MAC address,
serving BS-ID, HO indication, etc.
(24)~(26)
The path registration procedure is performed to exchange the SF information that will
be mapped to the data path between the ACR and T-RAS, which was created in steps
(16) to (18). (26) The procedure is performed if the Path PreReg procedure fails.
(27)
The T-RAS responds with the RNG-RSP message containing the HO Optimization
flag, CID_update, and SA-TEK_update.
(28)~(33)
After the S-RAS has sent all traffic to the T-RAS, the forwarding path is released.
(34)
When receiving the RNG-RSP message successfully, the MS sends the RAS the
Bandwidth Request (BR) MAC PDU as notification.
(35)~(36)
The T-RAS sends the S-RAS the HO-Complete message to provide notification
that the handover has finished.
(37)~(38)
The RAS notifies the ACR, which is the authenticator, of the new
CMAC_KEY_COUNT value updated by the MS.
(39)~(41)
When the handover procedure has finished, the old path between the S-RAS and
ACR is released.
Inter-ACR Handover (HO)
When performing a handover between ACRs in the same ASN, the path extension through
the R6 interface is considered. Therefore, the procedure for inter-ACR handover is the
same as inter-RAS handover.