LTE and 1x/EV-DO networks use different terminology and concepts despite providing similar high-speed packet data services. While LTE is based on OFDMA and uses flexible standards defined by 3GPP, 1x/EV-DO uses CDMA and optimized standards defined by 3GPP2. Key terms related to the air interface, access network, core network, and operations are defined for both networks, showing similarities and differences between the two evolving mobile technologies.

1. LTE and 1x/1xEV-DO
Terminology and Concepts
By Don Hanley, Senior Consultant
2/2009

2. LTE and 1x/1xEV-DO Terminology and Concepts
1xEV-DO and LTE networks are surprisingly similar in many respects, but the terms, labels and acronyms
they use are very different. How can a 1xEV-DO operator make sense of this new jargon?
Introduction
As 4G technologies like Mobile WiMAX and Long Term Evolution (LTE) move closer to commercial reality,
operators are beginning to understand the differences and the similarities between what they have
currently deployed and what is coming down the road. Service providers who are contemplating the
transition from 1xEV-DO to LTE will have to contend not only with new radio technologies and new network
architectures, but with a whole new set of terms and concepts as well.
Both 1xEV-DO and LTE are designed to offer high-speed packet data services to mobile subscribers, so it
should not be surprising that they have taken similar approaches to solving some of the challenges they
both face. An engineer familiar with 1xEV-DO can get a head start with understanding LTE simply by
learning the meaning of key LTE terms and associating them with their 1xEV-DO counterparts.
The following sections take various LTE concepts, grouped into related categories, and provide a brief
explanation of each, along with the corresponding 1xEV-DO equivalent. In some cases, there is a one-to-
one match between LTE and 1xEV-DO; in others, there simply is no equivalent concept. In most cases,
however, there is generally something within 1xEV-DO that does the same thing as its LTE counterpart,
under a different name or in a different location. We will identify the similarities and differences of LTE-EPC
and 1x/1xEV-DO networks in various categories, including Air Interface, Access and Core Networks,
Identities and Operations.
General
LTE is an evolution of the UMTS system defined by the 3G Partnership Project (3GPP), which is an offshoot
of the European Telecommunications Standards Institute (ETSI). 1xEV-DO, on the other hand, is designed
by the 3G Partnership Project 2 (3GPP2), which is associated with the North American Telecommunications
Industry Association (TIA). Both 3GPP and 3GPP2 have mandates to develop specifications for wireless
networks, but they have adopted rather different design philosophies, which are reflected in the resulting
standards:
a) Flexibility versus optimization: In general, 3GPP prefers to create standards which are very open
and flexible, allowing them to incorporate a variety of options, and to easily extend the interfaces to
accommodate new features and capabilities. In contrast, 3GPP2 tends to define very optimized
interfaces, which perform specific tasks as efficiently as possible. 1xEV-DO, for example, takes far
fewer (and much shorter) messages to set up a data session than UMTS requires, but new features
tend to require new sets of messages.
b) Authentication and security: 3GPP takes privacy very seriously, and very little information is sent
over the air in its original form; encryption, temporary identifiers, message integrity checking, and
user verification are basic elements of LTE signaling. 3GPP2 also includes security functions in the
definition of 1xEV-DO, but they are optional extensions to the basic operation of the system.
c) User information: 3GPP makes extensive use of the Subscriber Identity Module (SIM), which stores
user subscription data and related information separately from the phone itself. This allows a user
to make use of a different device without losing their features and contacts. In 3GPP2 systems, the
subscriber’s identity and the phone’s identity are usually tightly linked.
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3. LTE and 1x/1xEV-DO Terminology and Concepts
Despite the different mindsets behind the specifications, however, both 1xEV-DO and LTE do what they
were designed to do quite well: deliver high-speed packet data to mobile users.
Air Interface
Not surprisingly, the greatest differences between LTE and 1xEV-DO lie in the air interface. 1xEV-DO is a
CDMA-based system, using fixed 1.25 MHz channels, while LTE is a scalable OFDMA system, capable of
using anywhere between 1.4 MHz and 20 MHz, divided into 15 kHz subcarriers. 1xEV-DO devices are
assigned timeslots for downlink traffic, but can transmit at any time on the uplink (the hallmark of a CDMA
system); LTE terminals must be explicitly allocated uplink and downlink non-overlapping resources to send
and receive traffic. The Physical Layer descriptions of these two technologies are as different as night and
day.
Nonetheless, they must both be capable of supporting multiple users simultaneously, of allowing new
users to access the network, of tracking the terminal’s location and redirecting traffic as the user moves.
Key LTE terms relating to the air interface, and their 1xEV-DO equivalents, are listed here.
LTE Term Meaning and Usage 1xEV-DO Equivalent
Orthogonal Frequency Division Multiple Access,
OFDMA CDMA
physical layer of LTE Downlink
Single Carrier Frequency Division Multiple Access,
SC-FDMA CDMA
physical layer of LTE Uplink
Subcarrier A single 15 kHz radio channel Radio channel
Symbol A single 66.67 µs time period Chip (0.81 µs)
The smallest unit of radio resources, one subcarrier
Resource Element n/a
for one symbol
The smallest block of resources that can be
Resource Block allocated, 12 subcarriers for 7 symbols (84 n/a
resource elements) 1
Timeslot 7 consecutive symbols1 Slot
Subframe 2 consecutive timeslots n/a
10 consecutive subframes, the basic transmission
Frame Frame
interval
Synchronization Periodic signal for synchronizing with and
Sync message
Signal identifying cells
Periodic signal for transmission quality
Reference Signal Pilot Channel
measurements
PBCH Physical Broadcast Channel Control Channel
Forward Traffic
PDSCH Physical Downlink Shared Channel
Channel
Preambles + MAC
PDCCH Physical Downlink Control Channel
channels
PCFICH Physical Control Format Indicator Channel DO Session
PHICH Physical Hybrid ARQ Indication Channel ARQ Channel
PRACH Physical Random Access Channel Access Channel
Reverse Traffic
PUSCH Physical Uplink Shared Channel
Channel
PUCCH Physical Uplink Control Channel MAC Channels
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Assumes short Cyclic Prefix (CP)
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4. LTE and 1x/1xEV-DO Terminology and Concepts
Access Network
Figure 1 illustrates an LTE eUTRAN, the radio access network. The eUTRAN has a flat architecture, with no
centralized controller; instead each eNode B manages its own radio resources, and collaborates with other
eNode B’s over the X2 interface. The eNode B’s connect to the core network over the S1 interface, to allow
users to register with the network and send and receive traffic.
Key LTE terms relating to the access network, and their 1xEV-DO equivalents, are listed here:
LTE Term Meaning and Usage 1xEV-DO Equivalent
eUTRAN Evolved Universal Terrestrial Radio Access Network AN
eNode B Evolved Node B Base station + RNC
Physical Layer Cell ID Unique cell identifier Pilot PN offset
UE User Equipment AT
X2 eNode B <-> eNode B interface A13/A16/A17/A18
S1 eNode B <-> core network interface A10/A11/A12
Specified per 3GPP2
Uu LTE air interface
C.S0024 (IS-856)
A configured signaling path between the UE and the
Attach DO Session
eNode B
Radio Bearer A configured and assigned radio resource DO Connection
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5. LTE and 1x/1xEV-DO Terminology and Concepts
Core Network
The LTE and 1xEV-DO core networks are more similar than they are different; Figure 2 shows a view of the
LTE Evolved Packet Core (EPC). Both are based on IP protocols, and support seamless access to packet-
based services; both make use of Mobile IP to redirect traffic as the user moves through the network.
Key LTE terms associated with the core network, and their 1xEV-DO equivalents, are listed here:
LTE Term Meaning and Usage 1xEV-DO Equivalent
EPC Evolved Packet Core Packet Data Network
RNC + PDSN + AN-
MME Mobility Management Entity
AAA
S-GW Serving Gateway PDSN + PCF
PDN-GW Packet Data Network Gateway HA
HSS Home Subscriber System AAA
PCRF Policy Charging Rule Function PCRF
MIP Mobile IP MIP
A configured traffic path between the eNode B and
S1 Bearer A10 + R-P Session
the S-GW
A configured traffic path between the S-GW and the
S5/S8 Bearer MIP
PDN-GW
A configured end-to-end traffic path between the UE
EPS Bearer Service and the PDN-GW (Radio Bearer + S1 Bearer + PPP + MIP
S5/S8 Bearer)
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6. LTE and 1x/1xEV-DO Terminology and Concepts
Operational Terms and Identifiers
When a mobile device arrives in the network, it must be recognized, configured and assigned resources,
and its services must be maintained as it moves from cell to cell. Various terms associated with LTE
operational functions, and their 1xEV-DO equivalents, are listed here:
LTE Term Meaning and Usage 1xEV-DO Equivalent
UE User Equipment (the mobile device) Access Terminal (AT)
IMSI [Mobile Country
Code (MCC), Mobile
Network Code (MNC)
and Mobile
IMSI International Mobile Subscriber Identity
Identification Number
(MIN) or
Mobile Directory
Number (MDN)]
Mobile Serial Number
(MSN) or Mobile
IMEI International Mobile Equipment Identity
Equipment Identity
(MEID)
Downlink (DL) Transmissions from the network to the mobile Forward Link (FL)
Uplink (UL) Transmissions from the mobile to the network Reverse Link (RL)
Ciphering Over-the-air privacy Encryption
UATI Assignment +
DO Session
Attach Initial registration process
Establishment + MIP
Registration
Quick Config + Sector
Master Information Block and System Information Parameters + Access
MIB, SIB
Block Parameters + DO
Session
Downlink Control Information and Uplink Control Traffic Channel
DCI, UCI
Information Assignment
C-RNTI Cell Radio Network Temporary Identifier MAC Index
CQI Channel Quality Indicator DRC value
HARQ Hybrid ARQ HARQ
Redirection of traffic from one base station to
Handover Handoff
another
Measurement Control Pilot Add, Pilot Drop,
events A1, A2, A3, A4, Thresholds for cell selection and handover Dynamic (Soft Slope)
A5, B1, B2 Thresholds
Conclusion
A simple description in a table does not convey the full complexity of a concept; a detailed understanding
of LTE’s technologies, architectures and interfaces is needed to fully appreciate both the similarities and
the differences it has with 1xEV-DO. Nevertheless, the fact that LTE and 1xEV-DO concepts can be laid out
side-by-side in this way should help to reassure 1xEV-DO operators that the step from 3G to 4G is not as
big a leap as they may have thought.
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7. LTE and 1x/1xEV-DO Terminology and Concepts
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