LAN vs. MAN LAN Local Area Network MAN metropolitan area
network Single building, lab, etc Run and operated by single
organization Couple of blocks to whole city Run by multiple
organizations Both are peer to peer communication networks Both
have moderate-to-high data rates packet-based communication
capabilities
Slide 4
Standards for IEEE Follow the Open Systems Interconnection
(OSI) Basic Reference Model (OSI/RM) And cover the lowest two
layers : data layer and application layer Data layer is divided
into two parts : LLC (logical link control) and MAC (medium access
control)
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LLC Layer Connected to MAC layer through a single MAC service
access point (MSAP) Communicates in three different ways :
unacknowledged connectionless-mode (type 1), connection-mode (type
2) acknowledged connectionless-mode (type 3)
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MAC Layer Communicates through the use of packets called MAC
frames Primary functions are: frame delimiting and recognition
Addressing of destination stations, transparent data transfer of
LLC error protection direct access to the physical layer
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interconnection layer devices Need to have all interconnection
devices operate correctly and transparently for large amounts of
end to end systems physical layers have repeaters or hubs MAC layer
has bridges Connect multiple access domains Network layer has
routers
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Unique Identifiers LAN/MAN networks allow for unique MAC
addresses,group addresses, and protocol identifiers This is done by
assigning Organizationally Unique Identifiers (OUIs) to each end
system OUIs = 24 bits and assigned by IEEE Last 24 assigned by
organization
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D.J. Johnston
Slide 10
Broadband access Has been huge delays in the US to get
broadband access. In 2002, the US only held 17 percent of the total
broadband subscribers Reasons: Are out of reach of DSL services Are
not part of a residential cable infrastructure Think its too
expensive
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WirelessMAN Designed to fix all these problems and get more
broadband to the US customers Benefits: Do not need towers, (can be
put on tall buildings Easy to install Easy for customer to link up
with Base station Scalable Cheaper than wires. Phone companies are
slower
Slide 12
802.16 standard 2400 ISPs in the United States serving 6000
markets all with their own standards and expensive setup Makes it
very expensive to setup large wireless networks in this type of
market Need a common ground of technologies. 802.16 sought to
combine the same technologies throughout all wireless ISPs carriers
Can handle 60 businesses in one area with T1-type connectivity
Slide 13
802.16 (continued) This new technological advance allows for a
whole new set of opportunities to arrise standard 802.16a has been
developed with a frequency of 2-11 Ghz non-line-of-sight operation
Mesh network Mesh network allows subcarriers to forward messages
through other subcarriers to a base station Allows users
mobility
Slide 14
WiMax Worldwide Interoperability for Microwave Access fixed and
fully mobile internet access and refers to implementation of 802.16
Created in June 2001 Was created closely with the IEEE and European
Telecommunications Standards Institute (ETSI) The ETSI version is
HIPERMAN
Slide 15
Hopes There is a lot of hope for this new WirelessMAN
technology to decrease the costs of having broadband internet
Several companies are starting to make larger pushes with this
technology. (CLEAR) Only time may tell
Slide 16
J. M. Peha, B. E. Gilden, R. J. Savage, S. Sheng, B. L.
Yankiver
Slide 17
WMAN Becoming cheap enough and financially logical enough for
cities to implement. Cities have a lot of issues to balance in
order to decide whether or not to have a WMAN network and how
implement it.
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Considerations To maximize the area Maximize competition for
better prices Minimize subsidies To ensure it is financially worth
it, and can make a profit
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Models Monopoly One for the whole city Facilities based
competition separate entities running their own networks that
compete against each other, and overlap Wholesale-retail one
network for the city, with wholesale in charge, and allows
retailers to sign up users, manage accounts and payers while user
the services the wholesale provides Open-competition done by
default where all ISPs people have a free for all for who gets
interconnectivity
Slide 20
City Policies Policies to affect first year - One time cash
payment for the first year for the initial construction and
infrastructure needs Policies to affect annually reducing annual
costs or revenue for the vendors City can be the biggest default
subscriber. Need to have to the city utilize the network as much as
possible to ensure it will not fail
Slide 21
Revenue and Cost projections Need to compare the city to other
cities that are in similar situations Can make estimates based on
that mean cost of a WMAX is $111,000 per square mile Pittsburgh =
55.5 miles Around $6.5 million for first year
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Projected Revenues
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Projected Costs
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Model Comparisons
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What Pittsburgh should do? Have a WMAN vertically integrated
monopoly Or a citywide wholesaler with competing retailers
Slide 26
SYED HUSSAIN ALI, KI-DONG LEE, AND VICTOR C. M. LEUNG THE
UNIVERSITY OF BRITISH COLUMBIA
Slide 27
OFDMA Orthogonal Frequency-Division Multiple Access a physical
layer specification for wireless MANs support 2-11 GHz
non-line-of-sight operation mesh operation
Slide 28
Mesh Operation Allow subscriber stations (SS) to use other
subscriber stations as relay station to relay station to a base
station Done when a base station channel is in poor condition
Lowers the cost of communication Complicates the network resources
multihop routing (MHR)
Slide 29
Resource Allocation problems Capacity planning (CP) Call
admission control (CAC) dynamic subcarrier assignments (DSA)
adaptive power allocation(APA)
Slide 30
Capacity planning Process of determining the production
capacity needed by an network static optimization problem Each base
station is allocated a bandwidth based on its previous usage Done
with system offline and very time consuming Problems: effect of
group mobility users on QoS the effect of fluctuation in channel
gains on QoS Note: that blocking a new call is more favorable that
dropping one
Slide 31
Call admission control When each call from a subscriber comes
in, it allocates bandwidth based on how much CP has allocated for
the base station Done in real time Trouble occurs at edges of
stations Hard to determine when to pass off SSs to new BS
Slide 32
Slide 33
Dynamic subcarrier assignments/ adaptive power allocation OFDMA
assigns subcarrier time slots for each carrier to a base station =
DSA allocates the carriers of the frame APA = how much power goes
into the frame at the time when the connection is made Both need to
occur at the same time and in real time Most important resource
allocation problems
Slide 34
Network Types 1. PMP mode= point to multipoint base station has
a central role controls CAC and DSA/APA since it is in charge of
the bandwidth allocation 2. Mesh mode More difficult since it is
not centralized DSA may be implemented to change or reuse
frequencies APA can be implemented to not interfere with other
subscribers.
Slide 35
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Optimization solutions assumed continuous data rates and an
infinite number of subcarriers Problems: SSs closest to the BSs
dominate the time Different APAs have performance improvements are
marginal compared to SNR
Slide 37
Practical Solutions Assume finite number of subcarriers and
discrete data rates APA is the same for all SSs Hungarian method -
O(n^3) iterative heuristic method - O(N)
PMP Deals with problems with the second mode of networks in
WMAN In PMP, BS coordinates with more than SSs downlink and uplink
directions IEEE does not specify how a BS should schedule its
transmissions Need effective scheduler
Slide 40
Good Scheduler BS that forwards real time and non real time
messages Prevents the bottleneck that occurs at the BS for downlink
(downlink has much higher demands) Needs to non real time
downloads, which are delay tolerant Allows for real time to work
more effectively which are not delay tolerant
Slide 41
How network works cross layer design - sends packets based on
its maximum capacity Message postponed if bad channel of
communication Causes SSs closer to BSs to dominate Need a fairness
model to prevent SSs from starving SS associates with BS, and BS
assigns it a timeframe UL and DL are done with time division
multiplexing And share the same bandwidth
Slide 42
Slide 43
Scheduler solution Fairness is key SNR can be random and fade
But too much fairness will cause all time to be spent on the ones
that do not work. Need utility function Adds quality of service
into the allocation equation utility function for non real time
service is concave function while real time is delay-based
function
Slide 44
Slide 45
Testing BS placed in center of equally spaced SSs Three models
performed demonstrating low amount of traffic to heavy traffic
Three models Round robin Just basic sharing Opportunistic -
Straight picking the best connections Opportunistic fair
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Conclusion Yes Opportunistic had the best throughput which was
expected, but Opportunistic fair had a better throughput than round
robin on both sides. Opportunistic is also much more fair than the
other two algorithms, especially at a