Wild Card : Metropolitan Area Networks

Wild Card :Metropolitan Area Networks By Greg Standerfer

IEEE Standard for Local andMetropolitan Area Networks:Overview and Architecture Sponsored by the LAN/MAN Standards Committee

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 havemoderate-to-high data rates • packet-based communication capabilities

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)

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)

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

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

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 • OUI’s = 24 bits and assigned by IEEE • Last 24 assigned by organization

IEEE 802.16* WirelessMAN* Specification Accelerates WirelessBroadband Access D.J. Johnston

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 it’s too expensive

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

802.16 standard • 2400 ISP’s 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 ISP’s carriers • Can handle 60 businesses in one area with T1-type connectivity

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

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

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

Finding an Effective Sustainable Model for a WirelessMetropolitan-Area Network: Analyzing the Case of Pittsburgh J. M. Peha, B. E. Gilden, R. J. Savage, S. Sheng, B. L. Yankiver

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.

Considerations • To maximize the area • Maximize competition for better prices • Minimize subsidies • To ensure it is financially worth it, and can make a profit

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 ISP’s people have a free for all for who gets interconnectivity

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

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

Projected Revenues

Projected Costs

Model Comparisons

What Pittsburgh should do? • Have a WMAN • vertically integrated monopoly • Or a citywide wholesaler with competing retailers

DYNAMIC RESOURCE ALLOCATION IN OFDMAWIRELESS METROPOLITAN AREA NETWORKS SYED HUSSAIN ALI, KI-DONG LEE, AND VICTOR C. M. LEUNG THE UNIVERSITY OF BRITISH COLUMBIA

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

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)

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

Capacity planning • Process of determining the production capacity needed by an network • static optimization problem • Each base station is allocated a bandwidth based on it’s 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

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 SS’s to new BS

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

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.

Optimization solutions • assumed continuous data rates and an infinite number of subcarriers • Problems: • SS’s closest to the BS’s dominate the time • Different APA’s have performance improvements are marginal compared to SNR

Practical Solutions • Assume finite number of subcarriers and discrete data rates • APA is the same for all SS’s • Hungarian method -O(n^3) • iterative heuristic method - O(N)

Opportunistic Fair Scheduling for the Downlink of IEEE 802.16WirelessMetropolitan Area Networks MehriMehrjoo, MehrdadDianati, Xuemin (Sherman) Shen, KshirasagarNaik

PMP • Deals with problems with the second mode of networks in WMAN • In PMP, BS coordinates with more than SS’s downlink and uplink directions • IEEE does not specify how a BS should schedule its transmissions • Need effective scheduler

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

How network works • cross layer design - sends packets based on its maximum capacity • Message postponed if bad channel of communication • Causes SS’s closer to BS’s to dominate • Need a fairness model to prevent SS’s 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

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

Testing • BS placed in center of equally spaced SS’s • 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

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

Wild Card : Metropolitan Area Networks