Vishal joined Award Solutions in 2006, bringing his
telecom industry expertise in wireline and wireless systems design and
development, end-to-end system integration and testing and support. His
experience is in leading and participating in multi-site, cross-functional technical
teams in all stages of product development from
original concept through delivery including requirements definition,
architecture, design, development, testing, integration and support. He has demonstrated
capacity for technical leadership and organizational abilities, by
coordinating, mentoring, motivating and providing analytical guidance to
multi-site teams working on
concurrent projects. Vishal has over 15 years of experience in the wireless telecom industry.
Vishal began his career working on real-time embedded
software development for Nortel. He worked on complete life cycle of product
design to deployment and support and provided technical leadership and advice
in area of project planning, software release ownership, configuration
management, requirements for design/simulation tools and a technical liaison
for the 1xRTT/1xEV-DO BSC product. As a product architect for CDMA2000
development, Vishal lead multi-site teams that developed and delivered the 2nd
generation of Nortel's CDMA 1xRTT BSC.
As a Senior Consultant at Award Solutions, Vishal
specializes in 3G and 4G wireless systems as well as IP convergence
technologies, focusing on LTE, UMTS, HSPA, 1x/1xEV-DO, GPRS/EDGE, IP/MPLS
networks. He has developed and delivered Air Interface, Protocols and Signaling
courses on LTE and UMTS/HSPA as well as planning/design, deployment and
troubleshooting, operation and optimization workshops based on hands-on
Vishal received his Bachelor's degree in Electrical
Engineering from Bangalore University, Bangalore, India. He has a Master's
degree in Electrical Engineering from University of Texas, Arlington, Texas and
an MBA in Corporate Finance from University of Dallas, Irving, Texas.
consistently exhibited Award Solutions' core values of expertise, flexibility,
my previous blog I had motivated the idea behind the Registered
State/Deregistered State and the Connected Mode/Idle Mode. I would like to
continue to build on those ideas and briefly talk about five key Identifiers
assigned to the UE by different entities during the UEs lifetime. This is not a
comprehensive list of all the identifiers but their discussion broadly covers
the end to end data connectivity concepts in LTE.
IMSI (International Mobile Subscriber Identity) and IMEI (International Mobile
Equipment Identity) are permanent identifiers assigned to the USIM card and the
Mobile Equipment, respectively. They are permanently associated with the
subscriber and stored in a permanent provider database like the HSS (Home Subscriber
Server) and will be used by other nodes in the network to identify the user. Similar
to 2G and 3G technologies, for reasons of security, efficiency and practicality
- the LTE network minimizes the exchange of these two identifiers with the UE.
the Initial Attach procedure between the UE and the LTE Network the UE is
assigned three additional dynamic identifiers by different LTE Network nodes that
have varying scopes of use.
eNodeB (Evolved Node B) assigns the UE a C-RNTI (Cell Radio Network Temporary
Identifier) to identify the UE during exchange of all information over the air.
The C-RNTI is assigned during the setup of the RRC Connection (Idle Mode à Connected Mode transition) between a
UE and an eNodeB and is valid only for that RRC Connection. Once the UE leaves
the coverage area of an eNodeB the RRC Connection must be moved (Inter-eNodeB
Handover) and the "new" eNodeB will assign a "new" C-RNTI to the UE. The C-RNTI
is an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) specific
identifier and the EPC (Evolved Packet Core) Network has no visibility to it.
MME (Mobility Management Entity) assigns the UE a GUTI (Globally Unique
Temporary Identifier) to identify the UE during all message exchanges and
procedures with the EPC. The GUTI is assigned during the Attach procedure (Deregistered
Registered State transition) between the UE and the MME and is valid only as
long as the UE is attached to the MME that assigned the GUTI. Once the UE
leaves the Tracking Area(s) of an MME the "Attachment" has to be moved (Inter-MME
handover) and the "new" MME will assign a "new" GUTI to the UE. Embedded within
the GUTI are the PLMN ID of the service provider and the MME Identity. Thus,
the GUTI uniquely and globally identifies a UE attached to a specific MME in a
specific Service Providers LTE Network in a specific Country. The MME may
choose to periodically re-assign a "fresh" GUTI to a UE that is attached to it.
PGW (Packet Data Network Gateway) assigns the UE an IP address to facilitate
data connectivity between the UE and any internal or external PDN (Packet Data
Network). This could be an IPv4, IPv6 or Dual Stack IP address and the PGW
could use a variety of IP address allocation schemes associated with the type
of IP Address. The UE may set up PDN Connections with more than one PGW and may
be assigned more than one IP address. The first IP address is assigned to the
UE during the Initial Attach procedure and it stays with the UE as long as the
UE is attached to the LTE Network. Unlike the other temporary identifiers the
IP address is more "persistent" or "sticky" and does not change as long as the
UE is attached - thus uninterrupted IP connectivity is provided to the UE. For
all practical purposes, the UE is assigned an IP address when it powers on and
loses its IP connectivity when it powers off. It is important to recognize that
the eNodeB, MME and the SGW do not have any use for this UE IP address for
connectivity purposes. It is used for IP forwarding decisions by the PGW and
all nodes "north" (between the PGW and the PDN) of the PGW.
These ideas have been
captured in the picture below.
1. IMSI - International Mobile
2. IMEI - International Mobile Equipment
3. C-RNTI - Cell Radio Network Temporary
4. GUTI - Globally Unique Temporary
5. IP Address