Modern Wireless Networks

Cellular Networks
ICEN 574– Spring 2019
Prof. Dola Saha
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 Cellular Generations

Universally
accepted single
technology

~1980 ~1990 ~2000 ~2010 ~2020

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The Next Generation – 5G/NR
Ø Discussions on fifth-generation (5G) mobile
communication began around 2012.
Ø The term 5G is often used to refer to specific new 5G
radio-access technology.
Ø 5G Use Cases:
§ enhanced mobile broadband (eMBB),
§ massive machine-type communication (mMTC), and
§ ultra-reliable and low-latency communication (URLLC)
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5G Use Case Classification
Examples?

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 5G Use Case Classification

Virtual Reality
4K video

Massive number of
Traffic Safety
remote
Factory Automation
sensors/actuators

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NR – The New 5G Radio-Access Technology
Ø All requirements were not met by LTE
Ø 3GPP initiated the development of a new radio-access
technology known as NR (New Radio)

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5G Wireless Access
Ø More Spectrum
Ø Tight interworking with LTE
Ø Not restricted to be
backward compatible
Ø Standalone mode
Ø 5G Core Network (5GCN) is
under development
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Standardization
Ø Coordinated international effort by wireless industry
Ø Depends on Global & Regional regulations
Ø Interoperability of the products
Ø Multiple organizations involved in creating technical
specifications and standards as well as regulation
§ Standards Developing Organizations (SDOs)
§ Regulatory bodies and administrations
§ Industry Forums
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Standards Developing Organizations (SDOs)
Ø Develop and agree on technical standards for mobile
communications systems
Ø Protocol to communicate is standardized
Ø Proprietary solutions possible (like scheduling)
Ø Usually nonprofit industry organizations and not
government controlled
Ø Example: 3GPP

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Regulatory bodies and administrations
Ø Government-led organizations that set regulatory and
legal requirements for selling, deploying, and operating
mobile systems and other telecommunication products.
Ø Spectrum allocation, amount of emisions from a Tx.
Ø International Telecommunications Union (ITU) handles
spectrum regulation on a Global level.
Ø Federal Communications Communications (FCC) for USA.

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Industry Forums
Ø Industry-led groups promoting and lobbying for specific
technologies or other interests
Ø Mostly led by network operators
Ø Examples: Next Generation Mobile Networks (NGMN), 5G
Americas

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Organizations in Cellular Network

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Requirements
Ø ITU-R is the radio communications sector of the
International Telecommunications Union (ITU).
Ø ITU-R defines the spectrum for different services in the RF
spectrum
Ø International Mobile Telecommunications (IMT) –
requirements issued by ITU-R.
Ø The framework and objective for IMT-2020 is outlined in
ITU-R Recommendation M.2083.
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Workplan for IMT-2020 in ITU-R

World Radiocommunication Conference (WRC) 15

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Recommendation ITU-R M.2083 - Capabilities

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Capabilities – IMT 2020
Ø Peak data rate
§ = System bandwidth x Peak spectral efficiency
Ø The user experienced data rate
§ the data rate that can be achieved over a large coverage area for a majority of the
users
Ø Spectrum efficiency
§ the average data throughput per Hz of spectrum and per “cell” (or TRP)
Ø Area traffic capacity
§ = Spectrum efficiency x BW x TRP density
TRP- Transmission/Reception Point 18
Capabilities – IMT 2020
Ø Network energy efficiency
§ Energy consumed per bit of data (Tx & Rx)
Ø Latency (10 fold reduction compared to IMT Advanced)
Ø Mobility (500Km/hr)
Ø Connection Density

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Additional Capabilities – IMT 2020
Ø Spectrum and bandwidth flexibility
Ø Reliability (very high level of availability)
Ø Resilience (operate correctly after disturbance)
Ø Security & Privacy
Ø Operational lifetime (example, machine-type devices
requiring a very long battery life > 10 years)

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3GPP Standardization
Ø Requirements: what is to be achieved by the specification.
Ø Architecture: the main building blocks and interfaces are decided.
Ø Detailed specifications: every interface is specified in detail.
Ø Testing and verification: the interface specifications are proven to work
with real-life equipment.

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3GPP Technical Specifications Groups
Ø RAN
Ø Services & System Aspects
Ø Core Network & Terminals

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Spectrum for LTE
Ø Paired bands
§ separated frequency ranges are assigned for uplink and downlink
§ used for Frequency Division Duplex (FDD) operation
Ø Unpaired bands
§ single shared frequency range for both uplink and downlink
§ used for Time Division Duplex (TDD) operation
Ø Unpaired downlink only bands
§ used for carrier aggregation for supplemental downlink
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Bands allocated above 1GHz for LTE

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Bands Allocated below 1GHz for LTE

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Spectrum for 5G (All bands in LTE + More)
Ø Bands to be studied already Ø Bands to be studied not assigned to
assigned to the mobile service the mobile service on a primary
on a primary basis basis
§ 24.25-27.5 GHz § 31.8-33.4 GHz (aeronautical and shipborne
§ 37-40.5 GHz radar)
§ 42.5-43.5 GHz § 40.5-42.5 GHz (satellite)
§ 45.5-47 GHz § 47-47.2 GHz (amateur satellite radio)
§ 47.2-50.2 GHz
§ 50.4-52.6 GHz
§ 66-76 GHz
§ 81-86 GHz
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Bands for 5G NR in FR1 (below 6 GHz)

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Bands for 5G NR in FR2 (24.2-52.6 GHz.)

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RF Exposure Limits
Ø Mandated
§ Recommended by International Commission on Non-Ionizing Radiation (ICNIRP)
§ Specified by the Federal Communications Commission (FCC) in the US
Ø Set with wide safety margins to protect against excessive heating of
tissue due to energy absorption
Ø Energy absorption in tissue becomes increasingly superficial with
increasing frequency, and thereby more difficult to measure
Ø To be compliant with ICNIRP at the higher frequencies, the transmit
power might have to be up to 10 dB below the power levels used for
current cellular technologies
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LTE Releases

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LTE Core Network Architecture
Ø RAN: Radio Access Network
Ø S-GW: Serving Gateway
Ø P-GW: Packet Data Network Gateway
Ø MME: Mobility Management Entity
Ø HSS: Home Subscriber Service
Ø EPC: Evolved Packet Core
Ø EPC and LTE RAN is together termed
EPS (Evolved Packet Service)
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Path to Internet
Ø User Equipment (UE) to the Internet

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Evolved Packet System (EPS)
Ø RAN: Radio related functionalities
§ scheduling, radio-resource handling, retransmission protocols, cod- ing,
and various multi-antenna schemes
Ø EPC: functionalities needed for providing a complete
mobile-broadband network
§ authentication, charging functionality, and setup of end-to-end
connections
Ø Why two separate entities?
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Modules of EPC
Ø MME
§ Control-plane node of the EPC.
§ Handles connection/release of bearers to a device, handling of IDLE to ACTIVE
transitions, and handling of security keys.
Ø S-GW
§ User-plane node connecting the EPC to the LTE RAN.
§ The S-GW acts as a mobility anchor when devices move between eNodeBs.
§ Collection of information and statistics necessary for charging is also handled by the S-
GW.

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Modules of EPC
Ø P-GW
§ connects the EPC to the internet
§ Allocation of the IP address for a specific device
§ quality- of-service (QoS) enforcement
Ø HSS
§ a database containing subscriber information
Ø Other modules:
§ Multimedia Broadcast Multicast Services (MBMS)
§ The Policy Control and Charging Rules Function (PCRF) 35
Radio Access Network Interfaces

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eNodeB
Ø eNodeB:
§ logical representation
§ physical implementation can be a three-sector BS
§ can be a BBU pool, where RRH are connected remotely
Ø Interfaces:
§ S1: connection between eNB and EPC (S1-U and S1-C)
§ X2: connecting eNBs for active mode mobility, multi-cell radio resource
management (RRM)

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5G Core Network Architecture

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Modules of 5G
Ø User Plane Function (UPF):
§ Gateway between the RAN and external networks such as the Internet.
§ Handles packet routing and forwarding, packet inspection, quality-of-
service handling and packet filtering, and traffic measurements.
§ Serves as an anchor point for (inter-RAT) mobility when necessary.
Ø Session Management Function (SMF):
§ Handles IP address allocation for the UE, control of policy enforcement,
and general session-management functions.

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Modules of 5G
Ø The Access and Mobility Management Function (AMF):
§ handles control signaling between the core network and the device, security for user
data, idle-state mobility, and authentication.
Ø Other functions:
§ the Policy Control Function (PCF) responsible for policy rules,
§ the Unified Data Management (UDM) responsible for authentication credentials and
access authorization
§ the Network Exposure Function (NEF)
§ the NR Repository Function (NRF)
§ the Authentication Server Function (AUSF) handing authentication functionality
§ the Application Function (AF). 40
Combinations of Core Networks and RATs
Ø eNodeB – evolved Node B
Ø gNodeB – generalized Node B

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RAN Protocol Architecture

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Protocol

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Protocol Entities of the RAN
Ø Packet data convergence protocol (PDCP)
§ performs IP header compression, ciphering, and integrity protection.
§ handles in-sequence delivery and duplicate removal in case of handover.
Ø Radio-link control (RLC)
§ responsible for segmentation/concatenation, retransmission handling,
duplicate detection, and in-sequence delivery to higher layers.
§ provides services to the PDCP.

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Protocol Entities of the RAN
Ø Medium-access control (MAC)
§ handles multiplexing of logical channels, hybrid-ARQ retransmissions,
and uplink and downlink scheduling.
§ The scheduling functionality is located in the eNodeB for both uplink
and downlink.
§ The hybrid-ARQ protocol part is present in both the transmitting and
receiving ends of the MAC protocol.
§ The MAC provides services to the RLC in the form of logical channels.

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Protocol Entities of the RAN
Ø Physical layer (PHY)
§ coding/decoding, modulation/demodulation, multi-antenna mapping,
and other typical physical-layer functions.
§ The physical layer offers services to the MAC layer in the form of
transport channels.

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LTE Data Flow

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