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This course consist on introduction to wireless communication, evolution of wireless communication systems, medium access techniques, propagation models, error control techniques, cellular systems, emerging networks. This lecture inlcudes: Mac, Layer, Scalibility, Channel, Research, Issue, idea, Routing, Multi, Channel, Standards
Typology: Slides
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Scalability
Single Channel
Multi-Channel
Some Ideas
Research Issues
Routing
Wish List
Route Optimization Criteria
Routing fairness
Routing – Cross-layer design
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Central coordination point
Reasonable time synchronization
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Improving existing MAC protocol ►
By changing parameters of CSMA/CA based MACs like contentionwindow size and backoff procedures for multi-hop.
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Contention based approaches are not scalable and throughputdegrades with increase in contention.
Cross-layer design with advanced physical layer. ►
MAC based on directional antenna and power control
Innovative solutions ►
Need new ideas to overcome low end-end throughput for multi-hop adhoc environment.
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TDMA or CDMA based MAC needs to be explored.
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Compatibility, cost and complexity are the important factors indesigning new protocols
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B = bandwidth of a channel
User bandwidth = B/
Ch- Ch-
User bandwidth = B
Ch- Ch-
Chain bandwidth = B
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One channel active at a time
Different nodes may operate on different times.
Hence, coordination is required
A radio includes multiple parallel RF chips and basebandprocessing modules to support several simultaneous channels.
On top of multiple channel in physical layer, only single MAC tocoordinate operations.
A node has multiple radios each with its own MAC andphysical.
A virtual MAC protocol such as a multi-radio unified MACprotocol is required to coordinate communication among all.
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classified into three types depending on its status of allocation.
Negotiations are done through a pre-defined channel known toall nodes.
The criterion is to use a channel with the lowest count ofsource–destination pairs that have selected the channel.
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Scalability issue in multi-hop ad hoc network has not been solvedyet.
CSMA/CA based MAC protocols solve partial problems
A distributed TDMA or CDMA MAC can be the solution.
Mesh routers and clients hold different characteristics like mobility,power consumption etc.
A single solution may not be applicable for both.
Some Mesh routers integrate various wireless networkingtechnologies and require advance bridging functions
Existing research focuses on capacity, throughput and fairness.But many applications may require broadband multimediacommunication in WMNs.
MAC developed with QoS metrics
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Scalability ►
Overhead is an issue inmobile WMNs.
Fast route discovery andrediscovery ►
Essential for reliability.
Mobile user support ►
Seamless and efficienthandover
Flexibility ►
Work with/without gateways,different topologies
QoS Support ►
Consider routes satisfyingspecified criteria
Multicast ►
Important for someapplications (e.g.,emergency response)
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Well known and trusted
Designed on theassumption of seldom linkchanges
Without significantmodifications areunsuitable for WMNs inparticular or for ad hocnetworks in general.
Newcomers bycomparison with theInternet protocols
Designed for high rates oflink changes; henceperform well on WMNs
May be further optimizedto account for WMNs’particularities
Ad HocNetworks Wireless MeshNetworks
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Routing – Physical ►
Link quality feedback isshown often to help inselecting stable, highbandwidth, low error rateroutes.
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Fading signal strength cansignal a link about to fail
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preemptive route requests.
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Cross-layer design essentialfor systems with smartantennas.
Routing – MAC ►
Feedback on link loads canavoid congested links
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enables load balancing.
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Channel assignment androuting depend on eachother.
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MAC detection of newneighbors and failed routesmay significantly improveperformance at routing layer.
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Choosing routes withlow error rates mayimprove TCP’sthroughput.
Especially importantwhen multiple routesare used
Freezing TCP when aroute fails.
Especially with respect ofsatisfying QoS constraints
