Geeta Jayanti


Dear all,

Once again I wish to invite you all for Geeta Jayanti celebration. Please join at Raghevndra Swami Math. It is off CMH read. Near KFC signal. Opposite to A2B. We will have a wonderful evening together. The even it organized by Ulsoor division of Samskrit Bharati - an NGO working to promote Sanskrit/Samskrit. 

This time Dr. B.Mahadevan Professor from IIM-Bangalore is the president. Dr. Vishwas is a key speaker. He is chief mentor at Samskrit Bharati. 

So see you all there on 15th December, 3:30 PM. 


First of all, let me introduce myself. I am the youngest blogger of the world. Do you know who am I? I got my name on 2nd December. Ojaswee.  Today I want to share that story with you all - the readers - of my father’s blog “Express YourSelf !

Just two and half month back I arrived on this beautiful planet earth. A team of doctors and nurses cleaned me, weighed me. I found this is a complete different environment. So far I was managing in very little space, at a warm and dark place, surrounded by water. Now suddenly no water, full of space, light, cold and air. I was scared and started crying. It made others smile. All people seemed happy because of me. Wow, now, I could move my little limbs as there was enough space! Nurses kept me at warmer, for a while. I liked the warm heat coming from top. I enjoyed. I stopped crying. I was smiling, playing, and moving my little limbs. Then I met my mother, so far I had heard her voice only. We both were eager to see each other. Finally she picked me up with great care and affection. Later on they shifted us to a different room. 

I stayed there for few days. Here also, daily, I got warm heat of the rising sun from windows. Most of the time I was sleeping. Whenever I wake up, I take attendance of people. I found my mother was always with me in that room. Few people I found often present. Many people, just came to see me. That includes men, women and kids also. The elder people gifted me cloths, toys and some of them kept some papers and coins in my hand. It is called money. Later on my parents collected them all from me.  I do not want all such gifts. I enjoyed more with kids. I met few fairies with white dresses and purple dresses (nurses). They always smiled at me, played with me. I liked them, even though they harassed me by needles (injections), water, soap foams and what not.

One day, my mother introduced me that guy. That guy is really horrible. Daily he shouts something “Agadam Bagadam”, in my ears. One aunty told, he is chanting Sanskrit Slokas. No, they were not slokas. I regularly heard Gayatri mantra before my birth. So I know, about slokas. I always confuse what he wants to convey me? Probably he also does not know. Many times I noticed, he speaks, similar to my mother, with other people. However whenever he looked at me he speaks entirely different language. What is it called? Yes Sanskrit.  My mother introduced him. He is my father. Daily morning, he goes somewhere. He comes back evening, sometime night, after my third dinner.

And what’s this? Where are those big windows for sun heat? I think, now again I am at some different room. Yes, I can recall that, I was going down and then up in a small cabin. It is called lift or elevator. I remember, we all sat in a car. It had small windows. Everything was moving, outside the windows. Lights were moving. Other vehicles were moving. People were also moving. And I felt the car was also like the cradle. May be, it was also moving. Oh, and now some other room. My mother introduced me, “this is our home”. She also introduce me different rooms in our home. What is home? Then  they made me slept on a small table. My grandmother was reciting something and suggesting me to dance. 

“Maare Aangan Beto Naache, Beti Naache. Naach Beti Naach”. 

I do not know; even, how to stand up, then how can I dance?  My parents kept some paper, pen and lamp below table. I was wondering and smiling. I know, whenever I smile, all people like and whenever I cry all are doing all kinds of JUGAADs to make me smile. On that night, all people wanted me to cry !! That was surprising. Then all prayed to “Vidhata Mata” to write good luck for me on the eve of 6th night. Oh! Then I understood the reason for keeping paper and pen there. By the way, who is Vidhata Mata? Will she also put some money in my hands or give me some big gift? How Vidhata Mata will know, paper and pen are here. I will inform her. Let her come.
My major activities are sleeping and eating only. Yet I am busy. As, I am doing so many other extra activities also. I smile at all people. Daily I take bath. One lady daily rubs my whole body. I do not like her. She does not understand, how painful it is. She pulls my lags, hands. I always wonder, about reason for it. While doing that he is smiling and talking with me, some other “Agdam Bagdam” language. My mother informed me, it is Kannada. I like my mother’s language only.  Gujarati. My parents are planning to teach me 5 languages. Gujarati, Sanskrit, Kannada, Hindi and English. I may learn more than 5 languages. But you know? From the day one itself, I use the best language of the world. Smile. It is the language of heart and love.
The regular physical exercises are a vital part of my busy schedule. I exercise while lying down itself. I perform few Yogasanas like Sarvangason, Dhanurasan, Gorakhasan etc. In spite of Yoga and exercises, my stomach is upset. People are saying there is gas in my stomach. I cry aloud due to this gas. Then my mother put some bitter drops in my mouth. I tried to stop her, but my father holds my hands. They hold my cheeks also, so I cannot close my mouth!! Then I cry further louder. Overall my mother is good. She loves me. She feeds me. I do not like her, only when she puts those bitter taste drops in my mouth. 

Now let me come back to main topic about my name. One day I was tired due to whole day sleeping, eating, smiling, bath, exercise and bitter drops etc. You know, generally, day time I am very busy and at night, I kept my parents busy. On that night, after dinner, I was sleeping. My parents were talking, so I woke up, but did not open my eyes. They were talking about my name. I like ‘Ojaswee’ as my name very much. I told them many times. It seems, like, my parents asked opinion of many people, about my name. My father referred a dictionary also! One friend suggested, some mathematics on name, called numerology. Mathematics is really good subject. It is all about numbers. How can one apply mathematics on text? My mother also believes such thing.

They found more than 100 names. My father wrote all names in some open black box, called laptop. My grandfather once said him, that, “now this little one is your laptop”. Am I a laptop? No, not me, the black thin box is laptop. On that night, my parents had long discussion about my name. Their friends suggested many good names by e-mail, SMS, telephone call and face-to-face. I thought my parents will call me Aasthha only. All these voting, opinion, list of names etc. are just formalities. No. I was wrong. My parents were serious. They sort listed top 10 names, based on voting. Then they removed some names that they do not like at all. They also added few name. One name, my father did not like, but my mother liked. So unwillingly my father kept it. What was that name? Yes, I remember, but I will not tell you. I opened my eyes and I was just kept saying them, “I like Ojaswee.” They did not understand. They finalized five good names for me. Aashtha, Anuvruti, Ira, Isha, and thank God, Ojaswai was one of them. 

My parents were planning for my naming ceremony. What is naming ceremony? I did not know, at that time. I came to know about it next day only. My mother wanted to have some fun, some excitement in naming ceremony. My father was feeling sleepy. Yet, he started his black box laptop. Look below, he prepared something like this. 

Next day, morning, when I was sleeping, I heard some sweet mantras. Two persons were chanting Gurupuja mantras. I felt some divine presence. I woke up after sometime, when there was so much of singing voices at our home. I noticed many people at our home. They all were singing. They were singing hymns, glory and name of God. Someone was playing musical instrument Tabala. My grandfather was also singing. Then I opened my eyes. At that time, I was in my mother’s hands. One person was holding something and showing to all people. It was handicam. Other person was holding similar other thing, that was flashing. It was camera. They wished me Happy birthday by song.

“Saagar Main Ek Laher Uthi Tere Naam Ki…
Tuje Mubarak Khusiya Aatmagyan ki…
Tujako hai anantame jaakar mil jana…
Tu hai sundai fool is samsara ki”

My birthday gone 2 months back. It was my 0th birthday. My mother commented, “Tere Naam Ki? Her name… !!??!! But she does not have any name, that is why we all are gathered here.”

I shouted “please give me the name Ojaswee”. Then I saw Khusu – a small kid. Yes, he will understand my name. I saw, a plate of rice and a bowl with 5 papers were kept in front of God. I noticed, yesterday what my father prepared in laptop, it is now in our TV along with my photographs. The guests still wanted to suggest few more names for me. I want only one name: Ojaswee. Khusu’s mother requested Khusu to pick up a chit from the bowl. No reaction. All were eager to know my official final name. Last time Khusu told, my name is doll. Doll is a toy. Am I a toy? That day, he did not pick up any paper at all, for a while. I heard my mother was saying, “We took 2 months to decide her name, so let Khusu also take 5 minutes to pick up the paper chit.” My mother and her mother showed him chocolate. I wondered about chocolate. What is it? When they will offer it to me? All people, including me, prayed the God to assign a good name to me. 

Finally he picked up a paper. My father opened it and with great excitement he read my name. Ojaswee. Thank God! I got a nice name. My mother is also happy that this name is perfect as per numerology as well. It is a meaningful name, that indicates brightness, that is my characteristics.

Umaji guided my father about next rituals. He wrote it in a plate of rice with his finger and thumb. First he wrote the lord Ganesh’s name, then my name. He wrote first latter of my name, very wide. So at the end, there was little space to accommodate all characters. Somehow he managed. All were happy and clapping. Then Shivaji guided him, to inform me my name. So he pronounced my name in my right ear, with so much love, two times. First time, he separated all characters and spoke at slow pace. “O…JA…S…Wee. Ojaswee” All clapped.

Few more rituals. Now my mother kept me in a cradle. Four girls moved my cradles and sang

Oli Joli Pipal Pan, Fai E Paadyu Ojaswee Naam.

I was just thinking “PAN? The Green leave?” Meanwhile my mother corrected, Naming is not done by Fai, it is done by Maasi. What is difference between Fai and Maasi? Whatever !

That day also many people came to see me, meet me, play with me. They all are happy people. Few of them gave me money, some big boxes of gifts. They all went down for lunch. They like that day’s lunch. My father informed them that lunch came from a temple and prepared by saints. It was authenticate south Indian cuisine. Few people came very late. Few people even came at time of dinner. They were asking about my name. If they would have come early, then they could have also sing hymns and see my naming ceremony. All were happy with me, my name and many people blessed me that day.

Thus I got a name, Ojaswee as per my choice, our choice.

I will write again on my father’s blog. Till that time, bye and Keep Smiling. Even you have gas trouble then also keep smiling. My parents expect this from me. :) 

- Ojaswee 

P.S. After consulting Sanskrit experts, my father changed my name from Ojaswee to Ojasvini. 


Sanskrit is an excellent methodological language. There are many online resources available to learn Sanskrit. Here, I have listed out some of them

Online Dictionary  

Knowledge Representation in Sanskrit and AI


  • All India Radio news in all languages including Sanskrit

If one read the news daily then it helps to build vocabulary for words useful in day to day life

  • News Archive

Text Archive

MP3 archive

Video archive

Google group


  • Online grammar reference:

  • Panini Grammer
  • Verbs


Here I searched sanskrit or sanskrith
I found about 70 articles. I like the following

Other Interesting articles
about Bhagvad Gita
about OM
3.;year=2007;volume=40;issue=2;spage=121;epage=121;aulast=Watson  about "Sanskrit for speech problem"

Sanskrit documents:

Book: India: What it can teach us? By Max Muller


YouTube Videos
  • Sanskrit Stories on page 8 and 9 on bookboxinc channel

  • Session on (1) verbs DHATU  (2) SAMAAS (3) VIBHAKTI

  1. Sanskrit Upanyasam - Swami Omkarananda
  2. Sanskrit speech by Sringeri Sankaracharya Sri Bharathi Theertha Mahaswamiji on Sanskrit
  3. Adi Shankara -Sanskrit Movie
  4. Scientific verification of Vedas
Felicitation program of Dr Vanitha Ramaswamy  on 7 Sep 2013 at Jayarama Mandali, Jayanagar, Bengalruru.  Part 1 --- Part 2  --
Android Games



I wish it will be useful to all. Please share if you have any link to add to this list. You can find one more such article, that is also collection of Sanskrit online resource:

Circuit Switched Data Call

Innovation Name: Circuit Switched Data Call

Intent : To establish connection between two PCs without Internet at just rate of local call.

Context:  GSM provides Fax and data call service since long time. Generally people use GPRS, 3G and now LTE etc PS service only for data connectivity and Internet. This idea describes how to exploit basic CS Data call service. Nowadays Internet is omnipresent and wireless data rate is also decreasing. The local call rate for CS voice call is even cheaper in India.

  • This application can provide IP connectivity using GSM network, across the globe between a pair of computer.
  • No need of Internet.
  • Provide minimum 9.6kbps dedicated link.
  • With HSCSD one can get upto 38.4 kbps speed. 
  • In case of wireless Internet by GPRS and 3G, the radio resources are shared among all the active user cover by a single cell. So the Internet bandwidth will be low, if more users are accessing the network. The CSD call provides dedicated link, so the Internet bandwidth does not depend upon presence of other active users in the same cell.  

Two PCs and two mobiles


Each mobile can be connected to one PC over USB interface. Here mobile acts as modem. So mobile handsets obeys the AT commands. The application can be built using AT commands to initiate CSD call at one PC and to receive CSD call at another PC. Once the call is establish, the both PCs are connected over serial interface. One can use any application like chat, file transfer, etc over serial interface.

The more sophisticated application can be built using IP connectivity. The CSD call originator can be client and CSD call receiver can be server. The server will run PPP demon over Linux. It will also acts as DHCP server. Over windows RAS (Remote Access Server) can be configured. The server waits for incoming CSD call. The client will establish CSD call. The Linux client will run PPP client script and acquire IP address. The Windows client can run any dialer application and acquire IP address. The PPP protocol will use IPCP protocol to exchange the initial IP addresses. After successful CSD call and PPP negotiation, both PCs are connected to ad-hoc LAN network with IP address. So any kind of networking applications can be run.

The simple serial interface, without PPP will be simpler and more efficient. There will be no overhead for PPP framing and IP, TCP, UDP headers.

Known Uses:

The possible usage can be as follows. 
  • In the Machine to Machine (M2M) communication, CSD (Circuit Switch Data) call can be more economical in some countries.
  • It can be useful by media to report image/video etc in case of Internet backbone is destroyed.
  • It is useful for individual also to share photos, videos etc.
  •  CSD call can be useful to transfer periodic images surveillance purpose.
  • CSD can be used for telemedicine and remote health care.
  • This can be also used to share network resources like printer, fax etc across the geographical boundary. 
  • One can also his Internet connection over this CSD call, then wireless Internet can be much chipper. 
  • The data rate is very slow. Just 9.6 kbps
  • The GSM coverage is required.  
Future Scope

With proper usage, marketing and killing applications, GSM CSD can be popular in developing countries like India

Related Solution 

CDMA technology may also provide such CSD facility. I am not sure. 
If any two PCs are connected over Internet, then they can use many applications for screen sharing, video chat, etc etc. However, CSD call can be done without Internet. 


·         3GPP standard TS 27.007



With Google Analytics I noticed that LTE related articles are the most popular ones at our blog Express YourSelf ! These articles are written in colloquial language and they are more informal. So let me write a single article with more formal language. Here I have tried to make this white paper concise with lucid language. 

Comments, suggestions are always welcome. 

Direct Link to the white paper "LTE NAS Procedures"

By chance, if you do not have access to Scribd, then read this article below. 

LTE NAS Procedures


Non-Access Stratum is a functional layer protocol stack between core network and UE in LTE. For LTE, It is the highest stratum in the control plane between UE and MME. NAS layer runs over Uu interface between UE and eNB, and over S1-MME interface between eNB and MME. The main functions for NAS protocols are (1)mobility management, (2)session management, (3)connection management and (4)security. Security has two aspects: integrity and ciphering. This article describes all the NAS procedures and relevant concepts.

1.     Introduction

UTRAN is access network for LTE. Whenever UE does any signaling message exchanges related to radio resources and accessing the UTRAN, those are Access Stratum procedures. After acquiring radio resources, UE needs to communicate to core network nodes. All signaling message exchanges related to accessing the core network are Non-Access Stratum procedures. The subsequent chapters of this article describe EMM, ECM and ESM NAS procedures, their sub-categories and other related concepts.

2.     EMM

EMM protocol provides elementary procedures for UE’s mobility, when UE uses E-UTRAN. Such procedures include determining UE's location, user's authentication, confidentiality, and connection management. The procedure is a group of NAS messages exchange, like request and response, with specific purpose. There are two kinds of EMM elementary procedures: common procedures and specific procedures.

a.     Relationship among EMM procedures

The EMM common procedures are invoked optionally by some of the EMM specific procedures. If one look at this, from object oriented design point of view, this is like aggregation relationship, where specific procedures are “whole” and common procedure(s) are “part”. The below diagrams depicts this relationship with UML notations.

The class diagram looks like Composite design pattern. This diagram does not indicate any specific NAS module design neither at UE nor at MME. The italic fonts indicates abstract class. All the procedures in the diagrams are just categories. The subsequent sections describe all procedures, which belong to these categories.

EMM specific procedure has specific purpose of (1) mobility management and (2) connection management.

b.     EMM Mobility Management

The mobility management specific procedures are (1)Attach, (2)Detach and (3) TAU. The attach procedures and detach procedures are similar to such procedures in GPRS and UMTS. When UE is powered ON, or, enters to LTE coverage area, it performs attach procedure. At the time of power OFF, UE performs detach procedure. UMTS coverage area is subdivided in multiple Routing Areas (RAs), same way, LTE coverage area is subdivided in multiple Trekking Areas (TAs). Any TA is formed by coverage are of a group of cell sites (eNBs). The eNB broadcasts TAI. Whenever the any UE detects the TAI change, due to UE’s mobility, UE informs the network about its new TA or TA list. UE invokes the “normal TAU procedure”. Even the stationary UE periodically reports its TA with “periodic TAU procedure”.

·         Combined procedures

The LTE network also supports combined attach, combined detach and combined TAU procedure. The combined procedures differ from the normal procedures by presence of few optional IEs. The combined procedures save radio resources, as the LTE networks, intimate the legacy GPRS / UMTS network about UE attach, detach and periodic update over wireline interface. So UE does not need to perform similar procedures over legacy network. Thus, the combined procedures also save UE’s battery. However such supports are optional for LTE network deployment.

GPRS MS have three categories: class A, class B and class C. The similar way LTE UE belongs to three categories. The “PS only mode” UE works only with LTE networks. These UEs are not mobile handsets but they are USB dongle or PC card. They never perform combined procedure. The “PS only mode” UE is similar to class C GPRS MS. The other two LTE UE categories are “CS/PS mode 1 UE” and “CS/PS mode 2 UE”. They are dual mode UEs. If UE is under coverage of both LTE and legacy GPRS/UMTS, then “CS/PS mode 1 UE” prefers non-EPS (GPRS/UMTS) service and mode 2 UE prefers EPS(LTE) service. However, they can attach to both networks, (1) EPS(LTE) network and (2) non-EPS (legacy GPRS/UMTS) network.

·         EMM FSM

EMM FSM has seven states. (1) EMM Null, (2) EMM DeRegistered, (3) EMM DeRegistered initiated, (4) EMM Registered, (5) EMM Registered initiated, (6) EMM TAU initiated, (7) EMM Service Request initiated. Out of these seven states, most of them are transient states. EMM FSM has major two states only. EMM DeRegistered and EMM Registered. They are correspond to UE is detached from LTE network and UE is attached to LTE network respectively.

c.      EMM Connection Management (ECM)

The connection is established between UE and MME for session management and for SMS transfer. The connection management specific procedures are: paging, CS service notification, service request, extended service request and transport of NAS.

·         Paging

The LTE networks supports only PS data call. The UE can receive paging signal for incoming PS data call. The legacy networks (GSM and UMTS) support both CS voice call and PS data call. The network can send paging signal to UE for incoming CS voice call using LTE E-UTRAN. Thus, paging procedure is used for incoming CS voice call and PS data call both.

The Paging ECM specific procedure is used by network to establish NAS context for incoming CS or PS call. The NAS context consists of security parameters between UE and MME for NAS message exchanges. In the absence of NAS context, the first message will not be encrypted. The EMM procedures may invoke other common EMM procedure for security purpose. Over the air interface Uu RRC protocol carries NAS messages and provides ciphering and data integrity both. In addition to that the NAS security module provides data integrity and optionally ciphering of the NAS messages.

Generally LTE network address the UE with its S-TMSI in “Paging” procedure. However if MME restart or somehow, MME lost S-TMSI of UE, then it uses IMSI. The usage of IMSI over air interface is rare case and is used to only recover from the error, in abnormal conditions.

·         CS Service Notification

The paging procedure is used to establish NAS context. If MME already has valid NAS context for a UE, then MME does not invoke paging procedure for incoming CS call. Instead of paging procedure, MME invokes ‘CS Service Notification’ procedure for incoming CS call from legacy GSM and UMTS networks.

·         Service Request

UE initiates “Service Request” ECM specific procedure, in response to paging. After successful “Service Request” procedure for connection management, the ECM FSM transits to ECM connected (EMM connected) state.

·         Extended Service Request

The “Extended Service Request” procedure is a variant of “Service Request” procedure. It is used for CS fallback for voice call and handoff with non-3GPP networks. The examples of non-3GPP networks are CDMA network, EVDO (HRPD) network, WiMAX network, etc.

·         Transport of NAS

The “Transport of NAS” ECM specific procedure is used for sending or receiving SMS over LTE network.

·         ECM FSM

ECM can have its FSM. For EMM Registered state, ECM FSM has two states. (1) ECM idle and (2) ECM connected. They are also known as EMM Idle and EMM Connected respectively.

d.     Common Procedure

The EMM common procedures are invoked optionally by EMM specific procedures. They are related to security aspects like authentication and ciphering. For example, EMM mobility management specific procedure named Attach may invoke other EMM common procedure(s) like (1)GUTI relocation, (2)Authentication, (3)Security Mode control, (4)Identification, (5)EMM Information and (6)ESM Information. Another example, EMM connection management specific procedure, “Service Request” may initiate optional common procedure(s):  (1) Authentication and/or (2) Security Mode Control. All the common procedures are optional. These common procedures set security parameters at NAS context.

e.     EMM Summary

Most of the EMM specific procedures for mobility management and connection management are initiated by UE. “Paging” and “CS service notification” procedures are always initiated by network. “Detach” and “Transport of NAS” procedures can be invoked by either network or UE.

Here, the quick recap of all EMM specific procedures.

EMM Elementary procedures:

  1. Mobility management specific procedure
    1. Attach
                                                              i.      Attach
                                                             ii.      Combined Attach
    1. Detach
                                                              i.      Detach
                                                             ii.      Combined Detach
    1. TAU
                                                              i.      Normal TAU
                                                             ii.      Periodic TAU

  1. Connection Management specific procedure
    1. Service Request
                                                              i.      Service Request
                                                             ii.      Extended Service Request
    1. Paging
                                                              i.      With S-TMSI
                                                             ii.      With IMSI
    1. CS Service Notification
    2. Transport of NAS (for SMS)

  1. Common procedure
    1. GUTI reallocation
    2. Authentication
    3. Security Mode control
    4. Identification
    5. EMM information
    6. ESM information

3.     ESM: Useful concepts

a.     Multiple ESM

The NAS procedures for EMM and ECM apply per UE, so UE software can have single instance of ECM module and single instance of EMM module. However the NAS procedures for ESM are for session management. A UE can have multiple active sessions (EPS bearers). Each bearer has its own ESM FSM. So UE software can have multiple instances of ESM module.

b.     PDN and APN

LTE infrastructure includes eUTRAN and EPC. PDN is some network external to operator’s LTE infrastructure. The Internet is the most common example of PDN. Other possible PDN examples can be IMS network, corporate VPN, MMS etc. If one look at the big picture, LTE or any other wireless network just provides layer-2 connectivity between UE and PDN. So the UE can transfer its layer-3 user packets (most likely IP packets) to external network PDN (most likely Internet). The ‘name of PDN’ is ‘APN value’. The P-GW node is at boundary between LTE network and PDN. So generally APN value is FQDN, which map to IP address of P-GW by DNS server. This DNS server is private one, and accessible only within PLMN.

c.      EPS bearer

An EPS bearer connects UE and exit gateway (P-GW) of LTE network. Unlike, UMTS, in LTE one default bearer is established during attach procedure itself. LTE NAS procedure standard also recommends bundling of LTE EMM NAS procedure and ESM NAS procedure in a single packet. The default bearer has neither QoS treatment nor TFT filters for user data. The default bearer just provides a basic connectivity between UE and P-GW for a single PDN.

Some mobile applications need QoS treatment for user data. E.g. VoIP call. The dedicated bearer provides QoS treatment and TFT for user data.

UE has single IP address per PDN, regardless of multiple bearers (default bearer and dedicated bearer). However, if UE and PDN both support IPv4 and IPv6 dual stack, then only, UE can have two default bearers and two IP addresses (IPv4 address and IPv6 address) per PDN.

If UE and network both capable to provide connectivity to multiple PDNs, then UE can have multiple default bearers and multiple IP addresses. It is analogous to having multiple Ethernet card to a desktop PC, so one can connect the PC to multiple networks and configure it with multiple IP address. Ethernet cards are layer-2 entities. Here, LTE network appears a single layer-2 interface consisting of E-UTRAN and EPC. However still LTE network can emulate like multiple different layer-2 entities. So, a UE can have multiple layer-3 network layers (IP layers) at user plane. Each layer-3 entity can be connected to different P-GWs and so to different PDNs. Within a single layer-3, UE can have default bearer for best effort treatment and optional dedicated bearer(s) for QoS treatment and TFT

d.     EPS Bearer ID

All EPS bearers (i.e. default and dedicated) have EPS Bearer ID (EBI), assigned by the network. The legacy GPRS and UMTS networks were assigning NSAPI value for each PDP context.  EBI is analogous to NSAPI. UE can have one default bearer and zero or more dedicated bearer(s) per PDN. So at UE side few EBI values are used for default bearer(s) and rest are for dedicated bearer(s). It is not possible to discriminate between default bearer and dedicated bearer just by EBI values. LBI plays important role to link EBI values and bundle them together. All dedicated bearer related messages contain LBI IE. The value of LBI IE is EBI value of default bearer for that PDN.

e.     IP address

UE may have static IP address configured APN/PDN. Generally, P-GW acts as DHCP server and assigns dynamic IP address to UE. P-GW consults external DHCP server or radius server or diameter server to allocate dynamic IP address for UE. Dynamic IP address is allocated during default bearer creation. This IP address does not change for all other subsequent new dedicated bearer(s) for that PDN.

PCO IE is used to carry UE address. It also carries Primary and Secondary DNS addresses for that particular PDN. So the application can query and resolve any domain name to IP address by contacting the DNS server, within that PDN. All these three IP addresses can be IPv4 address or IPv6 address or both. If UE already knows their values, it mentions them in PCO, to confirm. Else, UE mention value as (for IPv4 case) and/or ::0 (for IPv6 case) to request network for new assignment. PCO IE contains PPP. The PPP contains IPCP for all these IP addresses. PPP can also contain PAP and/or CHAP protocol(s) for user authentication. The PCO and TFT are important IEs, that are exchanged between P-GW and UE. They are transparently carried by eNB, MME and S-GW.

f.       Summary
The following tree makes this concept clearer.

  1. LTE layer-2 connectivity using eUTRAN+EPC
    1. Layer-3 IP (IPv4 or IPv6)connectivity to PDN1, UE IP = ip1 (ip1 is IPv4 address or IPv6 address)
                                                              i.      Default bearer. No QoS and no TFT. EBI = ebi1
                                                             ii.      Dedicated bearer 1 with QoS1, EBI = ebi2, LBI = ebi1
                                                           iii.      Dedicated bearer 2 with QoS2, EBI = ebi3, LBI = ebi1
    1. Layer-3 IP (IPv4 or IPv6)connectivity to PDN2, UE IP = ip2 (ip2 is IPv4 address or IPv6 address)
                                                              i.      Only single default bearer. No QoS and no TFT, EBI = ebi4
    1. Layer-3 IP (IPv4)connectivity to PDN3, UE IP = ip3 (ip3 is IPv4 address)
                                                              i.      Default bearer. No QoS, EBI = ebi5
                                                             ii.      Dedicated bearer 1 with QoS3, EBI = ebi6, LBI = ebi5
    1. Layer-3 IP (IPv6)connectivity to PDN3, UE IP = ip4 (ip4 is IPv6 address)
                                                              i.      Default bearer. No QoS EBI = ebi7
                                                             ii.      Dedicated bearer 1 with QoS4, EBI = ebi8, LBI = ebi7

Here PDN1, PDN2 and PDN3 all are different, having different APN values. The values for ip1, ip2, ip3 and ip4 may or may not be different. QoS1, QoS2, QoS3 and QoS4 may or may not different. EBI1 to EBI8 all are different values, not necessary they are in sequence.

The minimum implementation without QoS can be as below:

  1. LTE layer-2 connectivity using eUTRAN+EPC
    1. Layer-3 IP (IPv4)connectivity to only single PDN 1, UE IP = ip1
                                                              i.      Only single Default bearer. No QoS, EBI = ebi1

4.     ESM procedures

ESM procedures also have two categories. (1) “Procedures related to EPS Bearer Context”. As the name suggest, these ESM procedures are used for EPS bearer. (2) “Procedures related to transaction”. However these ESM procedure categories are quite different from EMM procedures category. In case of EMM, the specific procedures are optionally made up of common procedure. So first, an EMM specific procedure starts. Then it optionally invokes one more EMM common procedure(s). Then EMM common procedure(s) get completed and finally the EMM specific procedure also gets completed.

If a UE wants to manipulate EPS bearer context, then first UE invokes ESM specific “Procedure relate to transaction”. UE includes PTI IE in the first message. In the response to that network invokes ESM specific “Procedure related to EPS Bearer Context”. Network also includes PTI IE with same value, so that UE can correlate to ongoing “Procedure relate to transaction”. Once network invokes the “Procedure related to EPS Bearer Context”, then at UE side, the “Procedure relate to transaction” is declared/assumed as completed. These both categories of procedures are in sequence. Thus, indirectly UE can also invoke EPS procedure !!! Once, the “Procedure relate to transaction” is completed, then PTI IE is discarded. Then UE and network, both start using, EBI, which is allocated by the network to that particular (default or dedicated) bearer. If network itself initiates “Procedure related to EPS Bearer Context”, then PTI IE is absent and EBI IE is mandatory. The examples of such procedures are (1) EPS bearer context modification (2) EPS bearer context deactivation. As mentioned earlier, LBI IE is used in “Procedure related to dedicated EPS Bearer Context” to point to default bearer for that particular PDN.

This table provides a relationship among UE initiated “Procedures related to transaction” and network initiated “Procedures related to EPS Bearer Context”

Procedures related to EPS Bearer Cxt -->
Default EPS bearer context activation
Dedicated EPS bearer context activation
EPS bearer context modification
EPS bearer context deactivation
Procedures related to Transaction
PDN connectivity


PDN disconnect

Bearer resource allocation


Bearer resource modification

ESM information request


ESM status message

As one can see at above table, generally “transaction related procedures” are invoked by UE with two exceptions. (1) ESM Status message. It can be sent by both UE and network. (2) “ESM information request” is always sent from network to UE. UE responds with “ESM information response”.

5.     Summary

The author has put his best efforts to describe NAS concepts with correct information in lucid language. Any comments, suggestions are welcome. The author is thankful to his colleagues, supervisors and friends for all supports and encouragement to write this article. Let all the software professionals and telecom professionals use this article as reference material.