Transcript Wireless 101 - dannenclasses

Wireless 101:
Cellular Network
Basics
© Paul Bedell 2010
Copyright (c) Paul Bedell 2010
Cellular Technology Defined:
 A communications system which serves users via radio
waves (a “radio air interface”) by connecting the user’s
mobile terminal to the antennas at the nearest “cell base
station”. The cell base station antennas can be tower
mounted; rooftop mounted; mounted on water tanks; or
hidden from sight for aesthetic purposes. Average base
station coverage area today: 2-5 miles radius.
 The system functions by re-using frequencies at the low-
powered cell base stations throughout a cellular market
area, and handing off calls in progress from one cell base
station to another as users move throughout the market
area.
Copyright (c)
Paul Bedell
2010
Call Base
Station Photos
Copyright (c)
Paul Bedell
2010
 Mobile Telephone (Cellular Technology)
 Wireless service is founded on one key concept
known as “frequency re-use”



Cellular service launched in Chicago in 1983
Traditionally, to engineer a cell network to support millions
of users in a metropolitan area, or thousands in a rural
area, markets are broken down into cells. Cells are
geographic areas that use their own sets of
frequencies (channels) to support dozens of users
simultaneously.
Frequency re-use is accomplished by breaking down all
available frequencies into groups of 7 (N=7).
 Each cell base station has its own transmission
system (antennas) and set of assignable channels.
Copyright (c)
Paul Bedell
2010
N=7 Frequency Re-Use Cluster. Each hexagon represents a
base station with distinct set of frequencies. Note how identical
frequency sets are laid out symmetrically. This facilitates design
and engineering. This concept isn’t used much anymore, as the
majority of system design is now done via complex software
programs.
Copyright (c)
Paul Bedell
2010
Five Key Components To Every
(Macro) Wireless Network:
 Mobile phone, aka “UE” (user equipment) or




“mobile terminal”
Cell Base Station
Fixed network, aka “backhaul network”
Mobile Switching Center (MSC) (aka “MTSO”)
Interconnection to PSTN and Internet
Copyright (c)
Paul Bedell
2010
(2)
(4)
(3)
Mobile Switching Center
(Location of Switch and
System Peripherals
(5)
(1)
(1) The Mobile Unit
(2) The Cell Base Station
(3) The Backhaul
Network (aka “Fixed
Network”
(4) The Mobile Switching
Center
(5) Interconnection to
PSTN and Internet (“other
networks”)
Copyright (c)
Paul Bedell
Internet
2010
PSTN
(Landline)
Key design and engineering concepts that drive
cellular technology:
 Frequency Re-Use – supports simultaneous use of
hundreds or thousands of frequencies (channels) to
exponentially increase system capacity
 Call Handoffs – seamless transfer of a call /
transmission in progress from one base station to an
adjacent (neighbor) base station
 Frequency Agility: in handsets / terminals – ability of
cell phones to operate on any one of dozens or
hundreds of possible frequencies. Call handoff
cannot occur without this ability.
Working together, these concepts support basic
cellular operation.
Copyright (c)
Paul Bedell
2010
Radio Spectrum: Industry Gold
Range
Band
Code
30 to 300 Hz
300 to 3,000 Hz
3 kHz to 30 kHz
30 kHz to 300 kHz
300 kHz to 3,000 kHz
3 MHz to 30 MHz
30 MHz to 300 MHz
300 MHz to 3,000 MHz
Extremely Low Frequency
Voice Frequency
Very Low Frequency
Low Frequency
Medium Frequency
High Frequency
Very High Frequency
Ultra High Frequency
ELF
VF
VLF
LF
MF
HF
VHF
UHF
3 GHz to 30 GHz
Super High Frequency
SHF
30 GHz to 300 GHz
Extremely High Frequency EHF
Copyright (c)
Paul Bedell
2010
Applications
Commercial power transmission
Telecommunications speech
Sonar, submarine communications
WWV, radio navigation
AM radio
Amateur radio
Amateur radio, TV
GPS, cellular, PCS, MW, UHF TV,
military search radar, ATC
transponder, space telemetry,
microwave heating
Airport search radar, microwave relay,
satellite communications, STL microwave
relay, police radar (C & K band), airborne
FC radar
Experimental, military, satellit
e
communications
RF Propagation defines how well a radio wave travels
through a given medium, which can be air, water, cable,
or optical fiber. Three things can impact RF propagation
in the cellular world:
 Free space loss – any radio signal will fade over
distance. This is especially true at higher frequencies.
The higher the frequency, the greater the degree of
free space loss.
 Rayleigh Fading – any signal propagating from one
point to another will reflect off many objects in its
path, which can weaken the signal and cause multiple
“reflected” signals. If reflected signals combine with
the strongest signal, they can weaken the composite
signal entering the antenna.
 Absorption: all radio signals can be absorbed by
objects in the path of propagation. This is especially
true of organic entities and anything that is waterbased (i.e. plants, trees)
Copyright (c)
Paul Bedell
2010
Rayleigh Fading
Reflected Signal (Indirect)
House
ro n
nal (St
g
i
S
t
c
D i re
gest)
Cell Base Station
Food Mart
Convenience store
Reflected Signals (Indirect)
Lake
Copyright (c)
Paul Bedell
2010
Tower Types
1.Monopole: single tubular structure
2.Free Standing, aka “Lattice”: 3 or 4sided structure with cross-arm sections
(lattice design). Self sustaining (no guy
cables). Looks like an elongated pyramid.
Seen at many toll plazas. Red and white.
3.Guyed Towers: tallest tower type. Held
up by guyed cables that are 80% of the
tower’s height. Can reach heights of 2000
feet !!
Copyright (c)
Paul Bedell
2010
Free Standing Tower. Note the parabolic
reflector microwave radio antennas
Copyright (c)
Paul Bedell
2010
Guyed Tower
Copyright (c)
Paul Bedell
2010
Monopole Towers
Copyright (c)
Paul Bedell
2010
Stealth Cell Sites
Copyright (c)
Paul Bedell
2010
Cell On Wheels
“COW”
Copyright (c)
Paul Bedell
2010
Free-Standing Tower In
Colorado Subjected To
“Rime Ice”, which is
when fog crystallizes and
freezes.
Copyright (c)
Paul Bedell
2010
Generations Of Wireless Technology
 Wireless Service(s)
 Cellular service first launched in 1983 in Chicago,
Illinois by Illinois Bell.
 First generation (1G) service:





All analog, more prone to noise, crosstalk, call drops
Limited system capacity
Used 850 Mhz frequency spectrum
1983 – 1994
KEY DIFFERENTIATOR: first instance of frequency re-use
to exponentially increase capacity over previous mobile
systems
 Second generation (2G) service:




Also known as “PCS” (Personal Communication Service)
Co-existed with analog service for 15 years
Used different frequency spectrum (1900 Mhz / 1.9 Ghz)
KEY DIFFERENTIATOR: all digital service
Copyright (c)
Paul Bedell
2010
Generations Of Wireless Technology
 Wireless Service(s) Continued:
 Third generation (3G) service:





All digital
“Always On” Internet access
High-speed access and transmission (> 384 Kbps)
Technologies: UMTS (GSM-based), CDMA 1X-EVDO
KEY DIFFERENTIATOR: supports sustainable multimedia
transmissions (i.e. voice, video, text, image, video)
 Fourth generation (4G)



Launching in 2009 with Clearwire WiMax launch
Key technologies: WiMax (802.16) and LTE (Long Term
Evolution)
KEY DIFFERENTIATOR: super-fast access and
transmissions – tens of Megabits. Technology built into
laptops.
Copyright (c)
Paul Bedell
2010
RF SIGNAL FLOW THROUGH A CELL SITE:
DOWNLINK (Forward Channel)
Radio / Transceiver
RX 0
antenna
RX 1
TX
Duplexer: allows
for TX and
RX over one
antenna
duplexer
Power Amp:
Boosts Signal
Combiner
Combiner:
wireless
“mux”
Copyright (c)
Paul Bedell
2010
Incoming
Transmission
RF SIGNAL FLOW THROUGH A CELL SITE:
UPLINK (Reverse Channel)
RX-O
RX-1
Bandpass Filter
Bandpass Filter
Low Noise Amp
(LNA)
DIVERSITY
RECEIVE
ANTENNAS
filters out all
frequencies
except RCV freq.
Low Noise Amp
(LNA)
Boosts RX signal
level for separation
Radio / Transceiver
Multicoupler
(Wireless “Demux”
Multicoupler
(Wireless “Demux”
TX
RX 1
RX 0
To Other Transceivers
Copyright (c)
Paul Bedell
2010
To MTSO /
Core Network
Two Antenna Types:

Omnidirectional: propagates radio signal
equally 360 degrees, aka “omni”. Also
called “stick” antennas. (Lamp With No
Shade)

Directional: radio energy is focused in a
specific direction at a specific beamwidth,
based on a reflector within the antenna
housing. (Flashlight)
Copyright (c)
Paul Bedell
2010
Omni Antenna
Copyright (c)
Paul Bedell
2010
Directional “Panel” Antennas
Copyright (c)
Paul Bedell
2010
Why LTE?
LTE’s Key Radio Access Network (RAN) Capabilities:
Peak Data Rate
• Instantaneous downlink peak data rate of 100 Mbps within a 20
MHz downlink spectrum allocation (5 bps/Hz)
• Instantaneous uplink peak data rate of 50 Mbps within a 20MHz
uplink spectrum allocation (2.5 bps/Hz)
Control-Plane Capacity
• At least 200 users per cell should be supported in the active state
(for spectrum allocations up to 5 MHz). 200 simultaneous
transmissions per cell !!
User Throughput
• Downlink: average user throughput per MHz, 3 to 4 times Release 6
HSDPA
• Uplink: average user throughput per MHz, 2 to 3 times Release 6
Enhanced Uplink
• Improved cell edge throughput performance – more consistent
performance
Copyright (c)
Paul Bedell
2010
LTE’s Key RAN Capabilities:
Spectrum efficiency
• Downlink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 3
to 4 times Release 6 HSDPA )
• Uplink: In a loaded network, target for spectrum efficiency (bits/sec/Hz/site), 2 to
3 times Release 6 Enhanced Uplink
Spectrum flexibility
• E-UTRA (LTE physical layer) shall operate in spectrum allocations of different
sizes, including 1.4 MHz, 3 MHz, 5 MHz, 15 MHz, and 20 MHz in both the uplink
and downlink. Operation in paired and unpaired spectrum shall be supported
• Improved system latency
Modulation
• Downlink would use Orthogonal Frequency Division Multiplexing (OFDM) and
the uplink would use Single Carrier – Frequency Division Multiple Access (SCFDMA).
• Supported downlink data-modulation schemes are QPSK, 16QAM, and 64QAM.
The possible uplink data-modulation schemes are BPSK, QPSK, 8PSK and
16QAM.
• The use of the Multiple Input Multiple Output (MIMO) scheme, with possibly
up to four antennas at the mobile side, and four antennas at the Cell site.
Copyright (c)
Paul Bedell
2010
4G Building Blocks
Core
Network
•
•
•
•
IP-Based Core Network
Packet Voice Solutions
Reduced Cost
Scalable Design
• Distributed, IP-Based
Architecture
• Reduced Latency
• Scalable Design
Access Network
• OFDMA
• Multiple Antenna Techniques
• Very High Radio Efficiency
Air Interface
Copyright (c)
Paul Bedell
2010
High Level LTE Network Architecture
E-UTRAN: Evolved Universal
Terrestrial Radio Access
Network
eNodeB
Backhaul Network
eNodeB
EPC: Evolved Packet Core
MME
S-GW
HSS
P-GW
eNodeB:
S-GW:
P-GW:
MME:
HSS:
UE (User Equipment)
Evolved Node B
Serving Gateway
Packet Gateway
Mobility Management Entity
Home Subscriber Server
= Main Logical Nodes
Copyright (c)
Paul Bedell
2010
Mobility Management Entity
(MME):
• Device Registration and
Tracking
• Bearer Management
EPC Architecture
Home Subscriber System (HSS)):
• Subscription Data
• Security Information
EPC
MME
S-GW
HSS
P-GW
Serving Gateway (SGW):
• Packet Data Routing
• Mobility Anchor
IP
Network
PDN Gateway (PGW):
• Default Gateway
• Packet Filtering
• QOS Enforcement
Copyright (c)
Paul Bedell
PCRF
2010
Policy Charging
and Rules
Function (PCRF):
• QOS
Decisions
LTE Downlink Modulation Scheme: OFDM:
(Orthogonal Frequency Division Multiplexing)
• Orthogonal frequency-division multiplexing (OFDM) is a method of
digital modulation in which a signal is split into several narrowband channels
at different frequencies. In some respects, OFDM is similar to conventional
frequency-division multiplexing (FDM). The difference lies in the way in
which the signals are modulated and demodulated. Priority is given to
minimizing the interference, or crosstalk, among the channels and symbols
comprising the data stream.
• The basic principle of OFDM is to split a high-rate data stream into a
number of lower rate streams that are transmitted simultaneously, in parallel,
over a number of subcarriers. OFDM splits the transmission bandwidth
(channel) into many narrow subchannels which are transmitted in parallel.
• OFDM is present in:
• LTE
• Mobile WiMax IEEE 802.16e
• xDSL
• Wireless LAN IEEE 802.11a,g,n
Copyright (c)
Paul Bedell
2010
Major Challenges For Wireless Industry:
– 1983 – Present: The “NIMBY” phenomenon. “Not In My
Backyard”. Wireless subscribers desire – demand – great cellular
coverage but protest when base station towers are installed in
areas where “ugly towers” are not desired.
– 2006 – Present: Backhaul network congestion and bottlenecking
due to proliferation and popularity of wireless data technologies
and services, based on 3G rollouts.
• Traditionally, base station-to-MSC (switch) connections have
been one or two DS-1 circuits. This traditional model is
quickly becoming outmoded as the backhaul network now has
huge potential to become a bottleneck. Adding more and
more DS-1 circuits becomes expensive. Solution? Ethernet in
the backhaul network: simple, known technology. Ultimately
less expensive than multiple DS-1 circuits.
– 2010: Radio spectrum is becoming a precious and increasingly
scarce commodity. Also, data traffic vs. revenue dichotomy.
Copyright
(c) Voice
Paul Bedell
2010
TDC-425
/ Data Network
Fundamentals
For More Information………
Available On Amazon.com
and other fine Internet outlets.
Copyright (c)
Paul Bedell
2010