status of next generation cellular and wireless local area networks and current research activities...
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Status of Next Generation Cellular and Wireless Local Area Networks and Current
Research Activities
Mohsen GuizaniComputer Science DepartmentWestern Michigan University
Western Michigan University
• WMU is located in Kalamazoo, Michigan• WMU is one of 15 Michigan state schools• WMU has more than 28,000 students• The Computer Science is home to about
400 students• CS has 18 faculty members, 5 full
professors, 7 associate professors, and 6 assistant professors.
Outline Introduction Cellular Coverage in the United States Current Problems in the Telecommunications
Industry Review of Cellular Technologies Wi-Fi: Competing or Complementary
Technology? The Future Current Research Activities Conclusions
Current Research Activities Research Goal 1x EV-DV Architecture Resource Allocations Techniques Cross Layer Design Overview Intelligent Network QoS Protocols Intelligent Network QoS Validation Protocol Wireless QoS Based Routing Protocol
Introduction A combination of factors has led to the current
wireless situation in the US, which is rather poor in many respects Rapid technological change Rapid change in way people use technology Poor business and investment decisions Unrealistic expectations for new technologies Competition on features and packages rather
than underlying infrastructure More thinking and intelligent decision making in
future should enable vastly improved wireless service
Cellular Coverage in the US: Reason for Poor Coverage
Coverage is similar (often poor) because all providers use the same antenna towers
Much of the engineering behind tower placement is done in the old days of 3 watt cell phones at 800 MHz in cars with external antenna; in this day and age, the is much lower-powered units inside buildings or cars with no external antennas
NIMBY (“not in my backyard”) syndrome: Wealthy neighborhoods refuse to allow unsightly antenna towers
Cellular Coverage in the US (Continued) Call by one of the authors from Baltimore, MD to
Washington DC Dulles International Airport interrupted seven times due to coverage gaps—partly ascribed to the fact that there are five major cellular providers each of which has to build an entire network
The Yankee Group estimates that it would take $50B to $100B to bring cellular system up to snuff Carriers do not have that kind of money Would not solve political problems
Convenience trumps service quality Relatively few people have abandoned landline
phones
Cellular Coverage in the US (Continued)
0
5
10
15
20
25
30
35
40
45
50
MCI Pre-Bankruptcy
$41.0
MCI Post-Bankruptcy
$5.5 *
Verizon
$45.4
Sprint
$19.2
SBC
$17.9
Qwest
$17.5BellSouth
$15.0
AT&T
$14.4
0
5
10
15
20
25
30
35
40
45
50
MCI Pre-Bankruptcy
$41.0
MCI Post-Bankruptcy
$5.5 *
Verizon
$45.4
Sprint
$19.2
SBC
$17.9
Qwest
$17.5BellSouth
$15.0
AT&T
$14.4
Source: Wall Street Journal,
4/15/04
Cost Constraints Minimal revenue per minute of air time
Brutal competition Availability of free airtime and long distance
packages No “killer app” has ever materialized
Not cameras and ability to send photos People want dependable voice communications
Cellular phones unsuitable as wireless modems Promoters did not consider human factors E-mail already well-served by dedicated devices
such as the popular Blackberry by RIM
Cost Constraints (cont.) Access to the Internet is done while at
rest Coverage problems would interrupt most
operations if in motion Cannot really do anything while driving or
walking Screen is too small
Competing technologies such as Wi-Fi are much better
Problems
Problem Reasons
Telecommunications firms are deeply in debt (or out of business) because of
two miscalculations stemming from over-estimating revenue
potential of fiber optics
Poor understanding of human factors—how quickly people will change their way of doing things
The difficulty of solving the “last mile” problem—aging copper plant; coaxial system designed for one-way transmission
Technology provided capacity far in excess of
users to absorb
$100M will buy a fiber from US to UK With WDM technology this could be >2
Tbits per second—few users
No “killer app” has materialized
The only one is sight is HDTV (video on demand)—may well happen, as HDTV is slowly being adopted; however widespread demand is still 3 to 5 years in the future
Will not be from low-bandwidth devices such as videophones
Problems (Continued)Problem Reasons
Telecommunications companies rested on their
laurels
Did not upgrade “last mile” Rollout of DSL was initially slow—many
areas could not be served; has limits in any case
Pressure built as CATV companies began to offer broadband
Only recently have telecommunications companies begun to move out on POE
Infatuation with technology and disregard of human factors has led
to other telecommunications
company fiascos, such as Iridium and Global Star
Proponents underestimated speed at which conventional cellular systems would be deployed
Never showed that a large base of users would pay $5 per minute—not enough Antarctic explorers, oil drilling rigs, Sahara desert trekkers, Mt. Everest climbers; village chief in third world country could not afford it
Problems (continued)Problem Reasons
Other: Narrowband Integrated Services Digital
Network (ISDN) (2B+D)
Developed in the late 1970s Supposed to be vehicle to convert telephony
worldwide in the 1980s Priced very high Few could see any real benefits—calls
connected faster, but audio quality about the same
128 Kbits per second was enormous by 300 bd standards in the 1980s—few places to dial-up then
By the time “killer app” arrived, the Internet, ISDN was wrong paradigm
Connection-oriented service (pay by minute) for connections protocol
56K modems were extremely cost-effective and not that much slower
Problems (continued)Problem Reasons
Other: DSL
technologies offer much higher
bandwidth than ISDN at lower cost for typical usage
Rollout delayed by ISDN push Now a successful service
Other: Telecommunication
s companies overbid for 3G
wireless spectrum to the tune of
billions of dollars
Supposed to provide great advantages, unfortunately based on several assumptions
Technology was proven Users had need for features it offered, such as video
1G Cellular Technology
Advanced Mobile Phone Service (AMPS) Analog Widest coverage, much wider than digital systems Phased out by 2008
Of concern to users of OnStar, which employs it—digital systems’ coverage poor by comparison
Being phased out because newer systems can support more customers per unit of bandwidth—bandwidth is most precious resource
2G: GSM, CDMA, IS-95-a, iDEN
Global System Mobile (GSM) Initially Group Speciale Mobile; renamed Global System
Mobile to give it an international flavor Combined TDMA/FDMA system Offered by AT&T, T-Mobile, and Cingular in the US Advantage: With unlocked tri-band phone, users can
have cellular service worldwide Problem: Outside the US, reciprocal agreements with US
providers expensive—$~4 per minute for airtime Better solutions: Get subsidy unlock code for phone used
in US—buy SIM card when abroad from kiosk; buy cheap tri-band phone in the US, then buy SIM card when abroad
2G (Continued)
Coded Division Multiple Access (CDMA) Offered by Sprint and Verizon in the US Verizon recently launched high-speed
data service based on Phase 1 Evolution Data Only (1xEV-DO) in Washington, DC and San Diego, CA
Can handle the largest number of users per unit BW; most economically attractive
2G (continued)
Time Division Multiple Access (TDMA) Use declining Offered by AT&T and Cingular in the US
Integrated Digital Enhanced Network (iDEN) Developed by Motorola Based on TDMA Offered by Nextel in the US Likely to be phased out in favor of CDMA-2000
2.5G
So-called 2.5 or 3rd generation wireless technologies unlikely to be profitable, especially given prices paid for spectrum Main thrust is higher speed data Cannot compete with Wi-Fi Nextel is planning to bypass altogether What is needed is data rate of >2 Mbps
Beyond Various generations of cellular telephony more important
to providers than users Maximize revenue per unit bw Users care more about features, cost, dependability Many features being pushed are of dubious value
Multimedia Messaging Service (MMS) Short Messaging Service (SMS) Walkie-talkie feature
Reduces connect time to ~2 second versus 15 second dial time
Games Downloadable ring tones Replaceable covers
Wi-Fi: Is It Really a Good Idea?
IEEE 802.11b Caught on very fast; manufacturers
incorporate Wi-Fi chips in laptops; hopes are that this will be the new “killer app”
Wireless LAN equipment sales have been growing—Gartner Group says 2002 spending on all vendors is ~$2.3B; end-user spending increasing by about 50 percent for the last two years
Wi-Fi: Security Issues Algorithm is used, Wired Equivalent
Privacy (WEP) discredited Encryption key length too short Initialization vector implementation flawed Scheme can be cracked quickly Successor, WPA, is patch—not a fix
Vulnerable to broadband jamming, unless it uses frequency hopping as does Bluetooth
Wi-Fi: Security Issues(Continued)
Users do not seem to care 70 percent of installations have not even
implemented what little security measures there are
Incompatibilities among vendor equipment mean that Wi-Fi hot spots must implement lowest common denominator, i.e., no security
Wi-Fi user sitting next to “me” at Starbuck’s can intercept all transmissions to/from my computer Doctor files in “my” computer Impersonate “me” after “I” have logged off
Wi-Fi: Security Issues(Concluded)
Lack of scalability PKI has not provided desired solution Efficiently and rapidly propagating
information about revoked encryption keys through large networks
Problem of where to store private or secret key safely in a manner that hacking cannot compromise
Smart cards may be the only viable solution, but most laptops have no smart card reader Could be added through USB port
Wi-Fi: Business Model No clear business model Nobody making money off of Wi-Fi
Not a cost center, but a gimmick to attract customers
Issue of illegal use of Wi-Fi connectivity—who is liable? Maryland homeowner recently held liable when
someone used his hot spot for an illegal act Airports and other such places look to Wi-Fi to recoup
money no longer received from pay phones Travelers unlikely to agree to open yet another
account unless all places they frequent use same account
Wi-Fi: Setup Difficulties and Network Incompatibilities Complex Windows’ network setup menus and options to
set the SSID for each hotspot provider’s Access Point Most non-technical laptop users are disinclined to do so
Technical help from kid behind counter at Starbuck’s, etc., is a losing proposition
Proliferation of different Wi-Fi hotspot providers means that users must open a separate account for each
T-Mobile account at 2,100 Starbuck’s or Kinko’s Cometa account at MacDonald’s FatPort account in Canada Surf & Sip account at Foley’s Irish pubs Toshiba account at Arizona’s Circle K stores Waypoint account at a few select hotels
Wi-Fi: User Fees and Speed Problems User fees
Disinclination of users to pay more access fees Many feel they are already paying their
Internet dues through home subscriptions Lots of free Wi-Fi access points
From businesses that want to attract customers for their main product
Speed problems Chips implementing 802.11b with WEP force
all users to speed of slowest user at the hotspot
Wi-Fi: Incompatibilities and Spectrum Shortage Incompatibilities between WEP and WPA
Problem has not received much press because commercial hotspots have not enabled either—due to vendor incompatibilities
Spectrum shortage 802.11a has more spectrum allocated to it
(which allows it to accommodate more concurrent users)—however has not yet caught on
Dual 802.11b/a access points and especially client user’s PCMCIA cards are very expensive; suffers from the same security vulnerabilities
Wi-Fi: Standards and Scalability Standards
802.11i, 802.11x, and 802.11e “standards” waiting in wings in various levels of agreement as to their final specs
Problem is that millions of deployed laptops and hotspots may make upgrade to better standards impossible
Scalability Inherently not scalable Operates in crowded unlicensed band with baby
monitors, cordless phones, Bluetooth devices, microwave ovens
Limited number of channels—3 versus 8 for 802.11a
Wi-Fi: Summary Wi-Fi has not really taken anything away
from cellular Cell phones are not as practical as wireless
modems at 3 Kbps to 8 Kbps Some CDMA systems (Sprint) encouraged
use of cell phone itself for e-mail and messaging; however not practical due to the small size of the keyboard
Human factors: do people really want to make coffee shops another extension of their office?
The Future Despite problems, wireless is here to stay
Convenience dictates that it users will demand it Problems of “last mile” access Need to set up and tear down networks quickly
Mobile ad hoc networks (MANETs) for military and for emergency responder use
Sets the stage for determining who will emerge victorious in future Go beyond solving current problems and
anticipate and solve future problems—foregoing; societal preferences, economics, scalability, and regulatory issues
The Future (Continued) Realities of wireless solutions
Must be commercialized within months Cannot hope for any regulatory protection given
in the past to telecommunications monopolies Will have to compete fiercely with other
technologies for customer dollars—and hence for survival
Three issues of importance Spectrum Technology available to address problems Socio-political issues
The Future (Continued)
Really is not a spectrum shortage Even in areas such as Washington,
DC, only about 20 percent of available cell phone spectrum used during peak hours
Real problem is more intelligent and efficient use of available spectrum
Technology Available to address Problems
Ultra-wideband Wi-Max Wireless mesh networks Smart antennae Software radios
Technology Available to address Problems (cont.)
Ultra-wideband Uses short (~1 nsec) pulses which correspond
to about 1 GHz bandwidth Such pulses with 1 W peak power and repetition
rate of 108 have average power of 100 mW spread over 1 GHz
Interference in a 1 kHz channel ~ 0.1 mW
FCC has allocated 3.1-10.6 GHz band Currently in use by satellite uplinks and downlinks
Data rates up to 500 Mbits per second can be accommodated versus 700 kbps for Bluetooth
Technology Available to address Problems (cont.)Ultra-wideband (Concluded) UBW likely to become
standard of choice for home networks
IEEE standard is 802.15.3a Uses TDMA Wireless Personal Area
Network (WPAN) 245 devices up to 90 m Data rates 11 – 55 Mbps,
declining with distance AES encryption Discussions now about
dividing
Expected shipments of UWB equipment
Technology Available to address Problems (cont.)
Wi-Max Another emerging technology
Intended for distances up to 50 km at data rates up to 70 Mbps
Intended to provide broadband service to replace “last mile” where this is not cost-effective with conventional technology
May also take up some of the functions of Wi-Fi
Technology Available to address Problems (cont.)Wireless mesh networks Low-powered systems that pass messages from node to
node on their way to their destination, not unlike what Internet nodes do with e-mail and other Transmission Control Protocol/Internet Protocol (TCP/IP) traffic
Any one node’s RF power output needs to be no more than what is required to close the link to the next nearest nodes
Redundant paths enhance the likelihood of end-to-end message integrity
Inherent is frequency reuse Similar to old Ricochet network which went bankrupt
because high costs of installation could not be recouped with small base of users
Technology Available to address Problems (cont.)Smart antennae Two stations communicating by wireless have
absolutely no excuse for using omni-directional antennas
If each end could beam all of its RF energy towards the direction of the intended receiver, the RF spectrum would experience a massive increase in availability with no new frequency allocations
Beam forming can be computer-controlled for adaptive beam forming
In case of cellular base stations can be fast enough to accommodate vehicular users
In case of Wi-Fi can extend range; SF startup, Vivato, working on 128 beam implementation
Technology Available to address Problems (cont.)
Software radios Software-configurable cell phones To handle multiple systems, also
Wi-Fi Eliminate need to buy new cell
phones every year or so
Socio-Political Issues Diverging international standards—China adopting
its own wireless LAN standard, basically Wi-Fi with improved security
Ad hoc implementations—Some locations installing their own area-wide Wi-Fi to deal with problem of multiple accounts (Cerritos, CA)
Voice over IP Currently a major trend, or at least major hyped
trend Promises many benefits But many legal and regulatory issues unresolved,
especially related to emergency response and USF
Conclusion Rate of change in telecommunications has been
unprecedented International cellular and wireless LAN industries have
had two decades of gross miscalculations Multibillion dollar bankruptcies Endless miles of unused fiber optic cables Digital cellular coverage in the US which is poor even
by third world country standards Wireless LAN standards whose lack of security has
been an embarrassment Hodge-podge of mutually incompatible cellular
standards
Conclusion (continued) Industry now has the opportunity to
plan wisely ahead Forego the short-term gimmickry of
downloadable ringing tones and designer-face-plates
Use US technological prowess in evolving technologies such as software radios, ultra-wideband, and smart antennas to forge standards that will with-stand the test of time and of consumer acceptance
Current Research Activities Research Goal 1x EV-DV Architecture Resource Allocations Techniques Cross Layer Design Overview Intelligent Network QoS Protocols Intelligent Network QoS Validation Protocol Wireless QoS Based Routing Protocol
Motivations
High bit-rate applications (www, file transfer, full motion video) impose strong requirements/needs on the system capacity
Studies confirm a productive gain of between 7-8 hours a week when business users are equipped with mobile PCs and wireless access.
All-IP applications: end to end packet-switched network
Goals To develop a new dynamic and
intelligent resource allocation technique for optimizing the average throughput of the wireless system.
Maximize the spectral efficiency and the number of users supported.
Develop QoS based protocol in the upper layer to assure the level of service required.
Block Diagram
Physical Layer
MAC Layer
MAC/Network QoS Mapping Layer
Intelligent Network QoS Validation Protocol Engine
Res. Alloc.
Network QoS
Competing technologies
CDMA Family
cdmaOne - IS-95A (2G) - IS-95B (2.5G)
CDMA 2000 1x (3G) 2000 CDMA 2000 3x MC (3G) 2001 1xED-DO (3G) 2002 1xEV-DV (3.5G) 2003
IS-95A
2G – 1995 Upto 14.4 kbps data rates Used exclusively for circuit-switched
voice Used Convolutional channel coding Used BPSK (fixed) modulation technique * BPSK: Binary Phase Shift Keying
IS-95B
2.5G – 1999 MAC layer enhanced over IS-95A Up to 115 kbps data rates (64 kbps) Up to 8 forward or reverse code channels
can be simultaneously assigned to a MSU using Walsh codes and PN sequence masks
Code channels are transmitted at full data rates during a data burst.
Used Convolutional channel coding Used BPSK modulation technique
CDMA 2000 1x 3G – 2000 Up to 307 kbps data rates (144 kbps) Q-PCH enables to monitor F-CCCH and Paging
Channel => improve battery life Radio Configurations (RC) => additional data
rates Quality and Erasure indicator bit (QIB and EIB)
on the reverse power control sub-channel. Code channels are transmitted at full data
rates during a data burst. Used Convolutional and Turbo channel coding Used QPSK modulation technique
CDMA 2000 3x MC
3G – 2001 Up to 2 Mbps data rates Using 3 standard 1.25 MHz Chs
within a 5 MHz band Used Convolutional and Turbo
channel coding Used QPSK modulation technique
1xEV-DO 3G – 2002 1st Evolution phase of CDMA2000 Up to 2.4 Mbps data rates No backward-compatibility with CDMA 2000 2 inter-operable modes: 1x and 1xEV modes Adaptive Rate Operation with respect to
channel conditions Adaptive Modulation and Coding (AMC) Macro diversity via radio selection Always-on operation of 1xEV-DO terminals in
the active state Multi-level modulation format (QPSK, 8-PSK, 16-
QAM)
1xEV-DV 3.5G 2003 Forward peak data rate: 3.072 Mbps Reverse peak data rate: 451.2 kbps 3 new Chs to the forward link for the packet data
operation (F-PDCH, F-PDCCH0, F-PDCCH1) 3 new Chs to the reverse link to support operation
of F-PDCH (R-RICH, R-CQICH, R-ACKCH) Adaptive Modulation and Coding on the forward link
in real time to adapt to the RF environment (QPSK, 8-PSK, 16-QAM)
Variable RF frame duration (1.25, 2.5 and 5 ms) Fast selection of base station to serve forward link No soft handoff on F-PDCH or F-PDCCH0 and F-
PDCCH1
Tracing the DR Evolution
14.4 115307
20002400
3072
0
500
1000
1500
2000
2500
3000
3500
Data Rates Evolution
Data Rate (kbps)
IS-95A IS-95B CDMA2000 1x CDMA2000 3x 1xEV-DO 1xEV-DV
CDMA Evolution Path
1xEV-DV Architecture
Logical and Physical Channels
Physical Layer Interface Control Information
MAC Layer User’s control Bearer Data
Other Layers No new service interfaces
Forward Packet Data Channel Traffic channel combinations
operate in both mixed voice and data services and data-only services in the forward and reverse links.
New Physical Channels
Forward Link Traffic Channel
F-PDCH Control Channel
F-PDCCH
Reverse Link Control Channel
R-ACKCH RCQICH
Adaptive Modulation and Coding
Adaptive Modulation and Coding
Base Station (Tx)Modulation and Coding Scheme
Mobile Station (Rx)Channel Quality
Reverse Link Feedback (R-CQICH)
CHANNEL
The base station assigns users the best modulation and coding rate for the instantaneous channel conditions (SINR).
Adaptive Modulation and Coding
Provides higher data rate services by varying The RF frame duration (1.25, 2.5 or 5
milliseconds) The number of bits per RF frame (between
408 and 3864 bits) The coding algorithm
QPSK (Quadrature Phase Shift Keying) 8-PSK (8-states Phase Shift Keying) 16-QAM (16-state Quadrature Amplitude
Modulation) .
F-PDCH Data Rates Data rates depending on F-PDCH packet size
and RF frame duration. The RF frame duration
“Number of Slots per Sub-packet” (1 slot = 1.25 ms)
Hybrid ARQ Automatic Repeat reQuest (ARQ)
Immigrates from MAC layer to Physical layer for improving performance
A mechanism supporting retransmission of frames received in error
Hybrid ARQ Chase combining, each retransmission
repeats the first transmission or part of it. Incremental redundancy (IR), each
retransmission provides new code bits from the mother code to build a lower rate code
AMC and hybrid ARQ On a single carrier, 1xEV-DV can
efficiently serve both data and legacy services (e.g., voice) by combining of Fast AMC and Hybrid ARQ Fast AMC is a link adaptation scheme where
the base station assigns users the best modulation and coding rate for the instantaneous channel conditions.
Hybrid ARQ improves throughput and enables fast AMC by making the initial modulation and code rate selection process tolerant to selection error.
F-CPCCH
R-PICH
F-PICH
(F-DCCH/FCH/SCH)
(R-DCCH/FCH/SCH)
F-CPCCH
F-PICH
R-PICH
R-CQICH
F-PDCCH
F-PDCH
R-ACKCH
(F-DCCH/FCH/SCH)
(R-DCCH/FCH/SCH)
BTS 1 BTS 2MOBILE
Cell Selection
The mobile station selects one base station from its active set
The selection based on the RF quality measured (SINR) by the mobile station
Flexible TDM/CDM Multiplexing 1xEV-DV was designed to support all
services Services that use large packets Services that use small packets
To reach the goal, TDM and CDM are included into the 1xEV-DV specifications
TDM/CDM multiplexing allows the selection of both the number of timeslots and the number of Walsh codes allocated to a user.
TDM/CDM
The TDM/CDM in 1xEV-DV system maximizes system throughput by providing optimal modulation and coding rate assignments to all services while maintaining frame fill efficiency.
A small packet may receive a few of the Walsh codes, and the remaining Walsh codes can be used by another user, improving overall system capacity
WasteUsed by other
traffic
TDM TDM/CDM
Required Required
Cod
e S
pace
Frame Duration
Modulation and Coding Schemes (MCS)
Rate (kbps) Slots Per Packet
Packet size (Bits)
Turbo Code Rate
Modulation Effective Code Rate
38.4 16 1,024 1/5 QPSK 1/48 76.8 8 1,024 1/5 QPSK 1/24 153.6 4 1,024 1/5 QPSK 1/12 307.2 2 1,024 1/5 QPSK 1/6 614.4 1 1,024 1/3 QPSK 1/3 307.2 4 2,048 1/3 QPSK 16/99 614.4 2 2,048 1/3 QPSK 16/49 1,228.8 1 2,048 1/3 QPSK 2/3 921.6 2 3,072 1/3 8-PSK 16/49 1,843.2 1 3,072 1/3 8-PSK 2/3 1,228.8 2 4,096 1/3 16-QAM 16/49 2,457.6 1 4,096 1/3 16-QAM 2/3
AMC Fixed Threshold Method
AMC has a set of n MCS levels
MCS set has a corresponding throughput vs. av. Channel SINR denoted by
These throughput values can be graphically represented, where the curves intersect with each other.
SINR at intersection points are threshold values, denoted by
}1,...,0),({ niTi
},,...,,{ 110 nn
},...,{ 10 nMM
AMC Fixed Threshold Method These threshold points partition the
range of SINR into n regions, denoted by
The kth MCS, namely Mk is assigned to the region
if the following condition is satisfied
1,...,0 ),[ 1 niforii
),[ 1ii
).,[,),()( 1 iijk kjTT
AMC Fixed Threshold Method
With this corresponding between the MCS’s and the average SINR, Mk is selected for the next frame if the average channel SINR in the current frame lies in the region ),[ 1ii
Channel Estimate
SINR
γi
MCSi
}
Threshold values, fixed
Disadvantages of TM Error in the estimation of average
channel SINR can cause inappropriate selection of MCS resulting in a degradation of the performance
The threshold values associated with the MCSs are not jointly optimized based on the overall stochastic behavior of the users’ SINR degrade the efficiency of the overall system resources.
Optimized Method
The threshold values associated with the MCSs are jointly optimized based on the overall stochastic behavior of the users’ SINRs The goal is:
Higher overall throughput
Channel Estimate
SINR
γi
MCSi
}
Threshold values, optimized
Percentage of users served by a MCSi
P1 + P2 + + PN = 1 The SINR is a random variable (r.v.)
achieved by an arbitrary user at a given instant
We prove ordinarily that Pi is a discrete random function that is dependent on the users’ joint SINR cumulative distribution function (CDF) and data rate granularity (N).
)},,[Pr{ 1 iii SINRSINRSINRP
Throughput Optimization Consider the event {SINR x} where x is a
real number in the interval [0,). We write the probability of this event as
The function F(x) is the CDF of the r.v. SINR. In
our case, F(0) ≡ F() = 0 and F(SINRN+1) ≡ F() = 1. Thus, we can rewrite Pi as
)Pr()Pr()Pr()Pr(
)Pr()Pr()Pr(
11
11
iiii
iiiii
SINRSINRSINRSINRSINRSINRSINRSINR
SINRSINRSINRSINRSINRSINRSINRP
.0),Pr()( xxSINRxF
In terms of discrete CDF functions, Pi is expressed as
)Pr()Pr()()( 11 iiiii SINRSINRSINRSINRSINRFSINRFP
Throughput Optimization
SINRi thresholds:
,/TNDRRii CpCi
,ii CpC
CHIP
ip NDR
N
R
WG
iii PLTCC RRR /
CHIPPLi
CiPTCiiobi NR
NDRNESINR
/
SINRi thresholds for variable bit rates: The SINRi threshold associated with a MCSi is determined by
p
iobi G
NESINR
)/(
Bit rate can be calculated
GP can be calculated
RCi is given by
Throughput calculations:
N
iiiii
PL
CTCTSP SINRSINRSINRSINRSINRFSINRFR
NR
T
ND
i
ii
111 )Pr()Pr()()(
,TSii NR
,_ iiieff P
i represents the throughput that can be transmitted by a base station
Let also eff_i represents the effective throughput that can be received by the users who can achieve an SINR in the range [SINRi, SINRi+1)
Simulation Model
Assume there are M possible users’ realizations over a certain period of time, then P is a member in an M-size set {Pj: j = 1, 2, … , M}.
We consider 19 3-sector cells located on a hexagonal grid and used the SINR calculations as shown
1 2
34
5
6 7
8
9
101112
13
14
15
16 17 18
19
Effective throughput
Effective aggregate throughput for 100 different realizations for users’ locations selected at random within the cell range
User Data Rate vs. Users Density
Effective aggregate throughput as a function of the users density. Here the radius was changing inversely proportional to the users density.
Physical Layer
MAC Layer
MAC/Network QoS Mapping Layer
Intelligent Network QoS Validation Protocol Engine
Res. Alloc.
Network QoS
Intelligent Network QoS Validation Protocol
Interaction between the Physical/MAC layers and the Network QoS validation protocol
Intelligent Network QoS Validation Protocol (contd.)
Bandwidth Delay Jitter Loss
MAC/Network QoS mapping
MCS1
Application
MCS2
…MCSi
MCSi candidates
other
QoS classes
Traffic class Characteristics
Conventional Low delay, low date rate, sensitive
to delay variations, e.g. video conferencing
Streaming Less sensitive to delay, may
require high bandwidth, e.g. live coverage of sports
InteractiveBursty, variable bandwidth
requirement, moderate data loss, e.g. email, Telnet
BackgroundHigh tolerant to delay and data loss, high variable bandwidth, background file downloading
Intelligent Network QoS Validation Protocol (contd.)
At the MAC layer Network resources are allocated based
on the MAC QoS
At the network layer Network resources are validated based
on the network QoS requirements, which are traffic type dependent
Cross Layer Design Goal
Provide efficient methods of allocating network resources and applications
QoS support in all layers Dynamic protocol design Jointly optimize the network performance
Tradeoff Performance versus complexity and
scalability
Cross Layer Design (contd.)
Why? There exists direct coupling between
physical layer and upper protocol layers
Several upper layer protocols do not get advantage of the wireless medium information available within the physical and MAC layer.
Intelligent Network QoS Protocols
At the network layer
Intelligent network QoS validation protocol
Wireless QoS based routing protocol
Intelligent Network QoS Validation Protocol (contd.) Approach
Model the system as an objective function to be maximized based on network QoS parameters
Not to violate the MAC QoS constraints. Optimizing the objective function is an NP-
Complete problem Use heuristic techniques
Genetic algorithms Fuzzy logic Simulated annealing Etc.
Wireless QoS Based Routing Protocol
Features Low overhead control traffic On demand operation Optimal route computation Network configuration change Distributed operation
Communication
An optimum size of the protocol update control messages
The frequency of neighbor update messages
Modified version of the route discovery protocol implemented by most of the distance vector routing protocol
Wireless QoS Based Routing Protocol (contd.)
High Level Protocol Design QoS based routing protocol suite high
level design Optimization of resource usage
Advertise resource information to all neighboring nodes
Graceful network performance degradation Restrict the update message flooding to the
neighboring nodes only New neighboring information exchange policy
techniques using some heuristic algorithms
Adaptive routing protocol In case of a change in the network or node
resources, update messages will be triggered based on our neighboring information exchange policy
Granularity of the routing decision Source and destination-based routing
approach: the traffic between a given source and destination will be routed over the same route.
On the fly determination of feasible paths
High Level Protocol Design (contd.)
Performance objectives while computing QoS-based paths
Achieve better network throughput by achieving low route-request blocking probability while providing QoS based paths
Optimum routing overhead during the computation, communication, and routing information storage
Minimize the routing overhead caused by the rapid change of some of the network resources as well as the call setup frequency
High Level Protocol Design (contd.)
Route computation Use Kalman-filter or equivalent heuristic
techniques in order to determine the best path
Routing information storage Maintain a partial routing table
High Level Protocol Design (contd.)
Conclusion Improve the overall throughput of the
wireless network SINR AMC MCS Compute the best
threshold Use cross layer design technique Design a new protocol at the network layer
to assure better QoS based on the traffic type
Design a new QoS based routing protocol Less control message overhead Improve call blocking probability
Future Work
Simulation study using OPNET Performance evaluation of the
developed protocols (control message overhead, CBP, etc.)
Comparison study of the proposed QoS routing protocol with the existing protocols