Transcript Application Requirements - University of Engineering and

The Propagation Factor in Mobile Wireless
Networks
Syed Aun Abbas
LUMS SSE
7/17/2015
The Propagation Factor
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Structure of the Talk
Aims to look at Mobile networks from numerous
perspectives
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Business considerations
Inter cell considerations
Intra cell considerations
System considerations
The focus is to understand issues and design
considerations
Identify issues that still need attention and could
form basis for future research
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Business Considerations
Mobile operators own limited Bandwidth and limited
Transmission Power.
They pay heftily for these resources
Want to sell services to the customers
Typical Services/Applications

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Voice
Data
Real/Non-real time Video
Application Requirements are
1. Data Rate
- symmetric or asymmetric
2. Latency – ( delay)
3. Bit Error Ratio
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Business Considerations
Systems need to be designed to transform bandwidth
and power in bits/sec of voice video and data that
meets latency and bit error requirements
Do it in a manner that number of customers who can
use these resources for payable applications should
be maximized.
There are different dimensions to the last statement
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Design a system that provides maximum useable bits per
second for the whole system
This maximum capacity should be available to the subscriber
base
A lot many time this capacity is not usable by the customers
Researchers continually try to find ways and means to
improve upon system capacity and its utilization
Message to take home; System capacity is nearing
limits but is utilization too?
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INTERCELL CONSIDERATIONS:
Maximizing Capacity of the Mobile Systems;
How can we achieve the objective?

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Use Frequencies repeatedly
Use Digital Communication
 Allows Compression
 Allows easier multiplexing of the different tribes of services

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Triple play > Voice/Data/video
Use Intelligent Control Techniques
 Dynamic Channel Assignment uses resources smartly
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Use Trunking
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INTERCELL CONSIDERATIONS:
Cellular Concept:
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Use Frequencies repeatedly
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INTERCELL CONSIDERATIONS:
Frequency Reuse - Cellular Concept
System capacity is co-channel interference limited
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Carrier-to-Interference ratio (C/I) is the parameter of interest
Isolation derives from distance between cells using the same
frequency group
Frequency planning
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Split total bandwidth in N sets of k channels each
Allocate one channel set per cell without gaps and repeat
N increases, so does D and co-channel interference decreases
N increases, the number of channels per cell decrease and so does
the system capacity
Problem is to find an optimum layout for an initial service that
should be able to scale as system usage changes
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INTERCELL CONSIDERATIONS:
Frequency Reuse – Scaling the network
Cell splitting

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Reduce antenna heights and transmit power
Do not upset the channel assignment scheme
Do not upset the SIR
Generally, reduce the radius to half
Practical implications remain
 More handoffs,
CELL SECTORING
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Use directional Antennas; Propagation can be in 120 or 60 degree
sectors
Sectoring improves SIR by reducing the interference
More handoffs, however, as long as Base station handles handoff,
MSC may be spared
Trunking efficiency may be reduced
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INTERCELL CONSIDERATIONS:
Frequency Reuse – Scaling the network
CELL ZONING > Kind of distributed base station > Still under active
considerations

Addresses Trunking Inefficiency in Cell Sectoring
 While 10 trunked channel with 0.01 GOS can support 4.46 Erlangs of Traffic, 2
groups of 5 trunked channels support 2.72 Erlangs of Traffic

Conclusion; It is desirable to have smaller cluster sizes with more channels/cell to
maximize capacity
 Any base station channel may be assigned to any zone

Making zones in a cell reduces the R in D/R and thus increases D/R while
reducing Tx. power of the Cell
Radio Channel Assignment
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Dynamic vs. Fixed
Fixed Channel Assignment – Calls blocked when all channels in use
Dynamic Channel Assignment does not allocate channel for cells
permanently
Dynamic channel allocation takes into account likelihood of future blocking
in the cells, the frequency of use, the reuse distance of the channel and
other cost functions
Requires real time data on channel occupancy, traffic distribution and radio
signal strength indications
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INTRACELL CONSIDERATIONS: Maximize
bits/sec/user/GPS coordinate
Transceiver Design Issues
Transmit Signal Design - BW, Framing, Data Rate, Modulation
Signal Receiver Design - Coding, Interleaving, Diversity,
Equalization etc.
All of the above have implications on how the radio waves are
received at the receiver and what kind of issues are associated
with them.
Signal Propagation Issues
Path Loss Prediction - Large Scale Issues > Determine the
receive signal strength
Other Channel Impairments: Fading, Doppler Frequency Shift
and Delay Spread - Small Scale Issue
We know what are characteristics of the ideal transmission
channel. Same loss at all frequencies and linear phase charter.
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INTRACELL CONSIDERATIONS: Received Radio Signal
at a Mobile
It has loss and variability in the loss
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INTRACELL CONSIDERATIONS: Signal Propagation Path Loss
Mobile cellular environment

Outdoor Environment
 Macro, Micro and Pico Cells
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Indoor Environment
 Pico cells
Propagation Mechanism in Real Environments
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Multipath Propagation
 Reflection;
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from the ground, building walls etc.
Reflection coefficient
 Refraction;
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through walls etc.
 Diffraction;
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because of edges of the buildings, hills etc.
 Scattering;
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because of Rough reflecting surfaces
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INTRACELL CONSIDERATIONS: Different types of
Fading and transmission rate/reach limitation
Symbol
duration, T
FAST
FLAT
FAST
SELECTIVE
SLOW
FLAT
SLOW
SELECTIVE
Tc
Bc
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Signal Bandwidth
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INTRACELL CONSIDERATIONS:
From where all these impairments come from
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Physics and environment geometry
Multipath propagation is the culprit (or hero in some cases;
e.g., MIMO)
How can we get rid of these environments?
Can we really?
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YES
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INTRACELL CONSIDERATIONS:
Yes! WE CAN…
Antennas with adaptive beam forming can help
If we can reduce the beam width sufficient small; it
virtually becomes free space path loss, fading due to
multipath vanishes; ISI due to multipath vanishes,
MIMO will not yield gains anymore; But do we need
them anymore?
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Modulation and other radio interface are barely any
different
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SYSTEM CONSIDERATIONS; RF Coverage Optimization
Issues Remain; Automate them further…
Focus Cell power resources where the users are;
Know the location of your users
Know the spatial distribution of the users
Know the temporal distribution of users per beam
footprint
Beams should follow users temporal movement
How do we get the information from the users
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Architectural and legal issues
Give rise to a new paradigm
May need overlaid open network management
How to ensure timely delivery with reliability? May need a
complete new approach
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SYSTEM CONSIDERATIONS:
Mobile Network Architecture; GSM Networks
VLR
HLR
Um
PSTN
MAPn
MS
Voice
Abis
MAPn
BTS
EIR
A
ISDN
MS
BSC
HLR- Home Location Register
VLR - Visitor Location register
MSC - Mobile Switching Center
BTS
BSC - Base Station Controller
BTS - Base Transceiver Station
AC - Authentication Center
EIR - Equipment Identity Register
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AC
The Propagation Factor
MSC
Voice/
Data
Data
Internet
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SYSTEM CONSIDERATIONS: GSM System - Protocol
Architecture
Base Station System - BSS
MS
BTS
CM
MM
RR
LAPDm
TDMA
RR
LAPDm
TDMA
Um
BSC
MSC
DTAP, BSSMAP
SCCP
BTSM
MTP3
LAPD
MTP2
T1/E1 or L1
MTP1
BTSM
LAPD
T1/E1 or L1
Abis
CM
MM
BSSMAP, DTAP
SCCP
MTP3
MTP2
MTP1
A
To from other
MSCs
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MAPn
Q.931+
ISUP
TUP
MTP3
MTP2
MTP1
To from other
MSCs and
networks
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3rd Gen. Mobile Networks - IMT 2000
MS
BTS
BSC
MSC
CM
BSCM
SCCP
CM
MM RR
LAC
TDMA
Um
CM
BSM
CM
MTP3
RR BSM
Q.2140
LAC
Q.SAAL
AAL/ATM/PHY
RELAY
LAC
Q.SAAL
PHY AAL/ATM/PHY
Abis
RELAY
LAC
Q.SAAL
PHY AAL/ATM/PHY
A
APPLICATION
MAP(HLR)
SCCP
MTP3
Q.2140
Q.SAAL
AAL/ATM/PHY
MAPn
To from other
MSCs
TCAP
BSM
To from other
MSCs and
networks
TCAP TCP/UDP
Convergence
TCP
UDP
IP
PHY
HLR
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SYSTEM CONSIDERATIONS: 4G LTE IP based
System Architecture
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THANKS and GOOD LUCK
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ABSTRACT
The mobile communication services market is now
focused on delivering data services which have come
a long way from short messaging and paging
services. WiMax and LTE are leading contenders to
proliferate the mobile data networks market. With
most of the technology feature being very similar, the
winning attributes of the two technologies are not
related to their own technical virtues but are
elsewhere. In this talk, we would provide a
perspective on how propagation plays a significant
role in that determination. We would also attempt to
identify some areas of continuing research that
should be most useful to impact the future of mobile
data networks.
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