# **蔡瀚興-讀書會-21/07/07**
## 推薦連結
- [LTE系統中的ID](https://www.twblogs.net/a/5b8ea9e42b7177188346cb83)
- [2-LTE Identification I](https://www.programmersought.com/article/23033832938/)
- [LTE中RNTI介紹](https://blog.csdn.net/jipengwang/article/details/72792463)
- [淺談IMEI及IMEUSV](https://blog.csdn.net/naresddin78/article/details/9428645)
## <font color="#FF0000">*PLMN*</font>
**Public Land Mobile Network(PLMN)**: indicating the network that user has subscribed to

     MMC           MNC
| ----------- | -------- |
      3          2 or 3     (digits)

- **MMC:** Mobile Country Code
- **MNC:** Mobile Network Code

## <font color="#FF0000">*IMSI*</font>
**International Mobile Subscriber Identity(IMSI)**: Permanent ID allocated to a mobile subscriber

     MMC           MNC           MSIN
| ----------- | -------- | ----------------- |
      3          2 or 3        up to 10        (digits)

- **MSIN:** Mobile Subscriber Identification Number
### Paths:
1. Identifying the home network of the subscriber based on the IMSI
2. Selecting an HSS holding the subscription information of the subscriber
3. Downloading the information from the HSS
### Notes:
- **Unique** number build in USIM which stored inside the phone
- IMSI installed in USIM,HSS and SPR is **permanent number**

## <font color="#FF0000">*GUTI*</font>
**Globally Unique Temporary Identifier(GUTI)**: Used instead of IMSI because of security problems


- **MMEGI:** MME Group Identifier
- **MMEC:** MME Code that represents an MME within the MME group
- **M-TMSI:** MME Temporary Mobile Subscriber Identity
- **MMEI:** MMEGI + MMEC
- **GUMMEI:** PLMN + MMEI
### Allocation:
#### *Attatches for the first time*
- UE attatches to a LTE Network **for the first time** ,it uses **IMSI** to request ,then MME sends back **GUTI**.
- **GUTI** set as **Temporary Identifier used in Next update(TIN)** by UE.
#### *Tracking Area Update(TAU)*
- UE **update the connection** to LTE Network ,it uses **IMSI** to request ,then MME sends back **GUTI**.
- **GUTI** set as **Temporary Identifier used in Next update(TIN)** by UE.
### Notes:
- It is a **temporary value** that is allocated by an MME

## <font color="#FF0000">*IP Address*</font>
### Static IP address allocation:
- At the time of subscription ,UE provisions the UE's IP address to an **HSS**
### Dynamic IP address allocation:
- **P-GW** dynamically assign an avaulable IP address from IP pools to UE
### Notes:
- UE can be connected to **more then one** PDN through LTE network
- LTE network allocates each UE a different IP address **per each PDN** the UE is connected to

## <font color="#FF0000">*C-RNTI*</font>
**Cell Radio Network Temporary Identifier(C-RNTI):** is the ID allocated to UE by an eNB
- UEs are **uniquely** identified by thier C-RNTI
- New C-RNTI is allocated when UE move from current cell to an other cell
- **eNB** notifies which UE can use resources in next **Transmission Time Interval(TTI)** by broadcasting a C-RNTI on the Physucal layer

## <font color="#FF0000">*S1AP*</font>
S1AP ID is used to distinguish UE in the paths between UE and MME
- **eNB UE SIAP ID:** In order to tell which S1AP message is for which UE between UE and MME
- **MME UE S1AP ID:** In order to tell which S1AP message is for the UE in which eNB between eNB and MME

## <font color="#FF0000">*X2AP*</font>
**Paired UE X2AP ID** are used to distinguish the UE between two eNB when UE is moving

1. A **source eNB** allocates an **Old eNB UE X2AP ID** to its Handover Request Message to a **target eNB**
2. Then ,a **target eNB** also allocates a **New eNB UE X2AP ID** to its Handover Request Acknowledge Message to the **source eNB**

## <font color="#FF0000">*ME IDs*</font>
Identifiers for Mobile Equipment
- **UE** = **ME** + **UMTS Subscriber Identity Module(USIM)**
- **ME** = **TE** + **MT**
- **Mobile Terminal(MT):** MT is where radio access protocols work
- **Terminal Equipment(TE):** TE is where the MT control funcions work

## <font color="#FF0000">*IMEI and IMEISV*</font>
**International Mobile Equipment Identity(IMEI)** is given when an ME is being manufactured
- **IMEI** = TAC + SNR　+ CD
- **IMEI/SV** = TAC + SNR　+ SVN
- **Type Allocation Code(TAC):** indicate a reporting body ID
- **Serial Number(SNR):** assign by the manufacturer
- **Check Digit(CD):** defined as a function of all other IMEI digits
- **Software Version Number(SVN)**

## <font color="#FF0000">*Closing*</font>