User's Manual

CHAPTER 4. Message Flow

4-22

The HO signaling procedure is the same as in inter-RAS HO, but the HO signaling

message exchange steps through the R4 interface are added between the S-ACR and

T-ACR (Target ACR).

Category Description

(1)~(4) 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).

(5)~(11) 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.

(12)~(18) 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.

(19)~(22) The T-RAS sends the ACR (authenticator) the Context-Request message to request

the AK Context information. The ACR responds with the Context-Response message

containing the AK context information.

(23)~(28) 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.

(29) 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.

(30) The MS sends the T-RAS the RNG-REQ message containing the MAC address,

serving BS-ID, and HO indication.

(31)~(36) The path registration procedure is performed to exchange the SF (Service Flow)

information that will be mapped to the data path between the ACR and T-RAS, which

was created in steps (23) to (28). (35)~(36) The procedure is performed if the Path

PreReg procedure fails.

(37) The T-RAS responds by sending the RNG-RSP message containing the HO

Optimization flag, CID_update, and SA-TEK_update.

(38) When receiving the RNG-RSP message successfully, the MS sends the RAS the

Bandwidth Request (BR) MAC PDU as notification.

(39)~(41) The T-RAS sends the S-RAS the HO-Complete message to provide notification that

the handover has finished.

(42)~(45) The RAS notifies the ACR, which is the authenticator, of the new

CMAC_KEY_COUNT value updated by the MS.

(46)~(48) When the handover procedure has finished, the old path between the S-RAS and

ACR is released.