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By Greg Standerfer

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Sponsored by the LAN/MAN Standards Committee

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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

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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

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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

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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

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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

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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

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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

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J. M. Peha, B. E. Gilden, R. J. Savage, S. Sheng, B. L. Yankiver

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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

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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

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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

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SYED HUSSAIN ALI, KI-DONG LEE, AND VICTOR C. M. LEUNG THE UNIVERSITY OF BRITISH COLUMBIA

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OFDMA Orthogonal Frequency-Division Multiple Access a physical layer specification for wireless MANs support 2-11 GHz non-line-of-sight operation mesh operation

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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)

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Resource Allocation problems Capacity planning (CP) Call admission control (CAC) dynamic subcarrier assignments (DSA) adaptive power allocation(APA)

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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

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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

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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

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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.

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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

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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)

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Mehri Mehrjoo, Mehrdad Dianati, Xuemin (Sherman) Shen, Kshirasagar Naik

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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

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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

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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

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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

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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